JP2022149485A - Polypropylene-based resin composition and method for producing the same and injection molded body - Google Patents

Abstract

To provide a method for producing a polypropylene-based resin composition capable of obtaining an injection molded body having a small amount of elution component into n-heptane, having excellent balance of rigidity, surface impact strength, moldability, durability (breaking strain) on a mating surface of an in-mold label, appearance, odor and productivity and a method for producing the same and to provide an injection molded body.SOLUTION: There is provided a polypropylene-based resin composition which comprises: 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 an α-olefin having 3 to 10 carbon atoms; an ethylene-α-olefin copolymer (B) of an optional component which is a copolymer of ethylene and an α-olefin having 4 to 10 carbon atoms; and a nucleating agent (C).SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a polypropylene-based resin composition, a method for producing the same, and an injection-molded article.

Polypropylene is used in various applications because of its excellent physical properties such as impact resistance, rigidity, transparency, chemical resistance and heat resistance. An injection-molded product of a resin composition containing polypropylene as a main component is sometimes required to have an excellent appearance. discloses a resin composition from which an injection-molded article having excellent appearance as well as various mechanical properties can be obtained.

JP 2019-189818 A

Molded articles used as packaging materials such as containers that come into contact with food are required to have components that are less likely to leak into the food. According to the standards established by the government (Ministry of Health and Welfare Notification No. 370), an elution test is performed by immersing a container (test piece) containing polypropylene as the main component in n-heptane, and the amount of eluted components must be less than a predetermined value. is required. Although the predetermined value varies depending on the operating temperature, it can be said that it must be 35 μg/ml or less in order to meet strict standards. On the other hand, it is not assumed that the resin composition disclosed in Patent Document 1 necessarily satisfies the above criteria.

The present invention has few components eluted into n-heptane, and has excellent balance of rigidity, surface impact strength, moldability, durability (breaking strain) on the mating surface of in-mold labels, appearance, odor, and productivity. Provided are a polypropylene-based resin composition from which an injection-molded article is obtained, a method for producing the same, and an injection-molded article.

The present invention has the following aspects.
[1] A polypropylene resin (A) containing a continuous phase comprising a propylene polymer (a1) and a rubber phase comprising a copolymer (a2) of ethylene and an α-olefin having 3 to 10 carbon atoms,
A polypropylene-based resin composition containing an optional ethylene/α-olefin copolymer (B), which is a copolymer of ethylene and an α-olefin having 4 to 10 carbon atoms, and a nucleating agent (C),
The content of the polypropylene resin (A) is 90% by mass or more and less than 100% by mass with respect to the total mass of the polypropylene resin composition,
The content of the ethylene/α-olefin copolymer (B) is 0 to 10% by mass with respect to the total mass of (A) and (B),
The content of the nucleating agent (C) is 0.02 parts by mass or more and 0.5 parts by mass or less with respect to the total mass of 100 parts by mass of the (A) and the (B),
MFR of the polypropylene-based resin composition at a temperature of 230° C. and a load of 2.16 kg is 40 to 120 g/10 minutes,
The ratio ( _Mw / _Mn ) of the weight average molecular weight _Mw to the number average molecular weight _Mn of the propylene polymer (a1) is less than 7,
The content of ethylene-derived units in the propylene polymer (a1) is 1.5% by mass or less with respect to the total mass of the propylene polymer (a1),
The content of the copolymer (a2) is 24 to 43% by mass with respect to the total mass of the polypropylene resin (A),
The content of ethylene-derived units in the copolymer (a2) is 25 to 60% by mass with respect to the total mass of the copolymer (a2),
The xylene-soluble portion of the polypropylene resin (A) has an intrinsic viscosity of 0.5 to 3.0 dl/g in tetrahydronaphthalene at 135°C,
The MFR of the polypropylene resin (A) at a temperature of 230° C. and a load of 2.16 kg is 40 to 120 g/10 minutes.
A polypropylene-based resin composition.
[2] The propylene polymer (a1) and the copolymer (a2) are mixed by polymerization, and the polypropylene resin (A) uses a catalyst containing the following components (a) to (c). The polypropylene-based resin composition according to [1], which is a polymerization mixture produced by
(a) a solid catalyst containing magnesium, titanium, halogen, and a phthalate compound as an electron donor compound; (b) an organoaluminum compound; or (c) an organosilicon compound as an external electron donor compound [3] [1] or In the method for producing a polypropylene resin composition according to [2], using a catalyst containing the following components (a) to (c), in the presence of the propylene polymer (a1), ethylene monomer A method for producing a polypropylene-based resin composition, comprising a step of polymerizing an α-olefin monomer having 3 to 10 carbon atoms to obtain the polypropylene-based resin (A).
(a) Solid catalyst containing magnesium, titanium, halogen, and a phthalate compound as an electron donor compound as essential components (b) Organoaluminum compound (c) Organosilicon compound as an external electron donor compound [4] [ An injection-molded article obtained by injection-molding the polypropylene-based resin composition according to 1] or [2].
[5] The injection molded article according to [4], wherein the thinnest portion has a thickness of 1 mm or less.
[6] The injection-molded article according to [4] or [5], which is molded in the shape of a container, and the sidewall of the container has a thickness of 0.1 to 1 mm.
[7] The injection-molded article according to any one of [4] to [6], which is molded in the shape of a container and provided with an in-mold label on the side wall of the container.
[8] The injection molded article according to any one of [4] to [7], which is used in a low temperature environment of -10°C or lower.
[9] The injection molded article according to any one of [4] to [8], which is used as a container or package in contact with food.

If the polypropylene-based resin composition of the present invention is used, it has excellent food sanitation properties (that is, there are few components eluted into n-heptane), and rigidity, surface impact strength, moldability, and in-mold label mating surfaces An injection-molded article having an excellent balance of durability (breaking strain), appearance, odor, and productivity can be obtained.
Moreover, the polypropylene-based resin composition of the present invention is suitable for thin wall injection molding (TWIM).
The injection molded article of the present invention is particularly suitable for food packaging applications (containers, drink cups, etc.) because it has an excellent balance of the above mechanical properties. In addition to food packaging applications, for example, miscellaneous goods, daily necessities, home appliance parts, electric and electronic parts, automobile parts, housing parts, toy parts, furniture parts, building material parts, packaging parts, industrial materials, distribution materials, agricultural materials, etc. may be used for the purpose of

The container with the in-mold label is placed horizontally inside the compression tester and is just before being compressed. It is a state after the container with the in-mold label is placed horizontally inside the compression tester and compressed.

<Polypropylene resin composition>
The polypropylene-based resin composition of the present invention comprises a continuous phase composed of a propylene polymer (hereinafter also referred to as component (a1)) and a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms (hereinafter referred to as component (a2 ) containing a rubber phase consisting of a polypropylene resin (A) (hereinafter also referred to as component (A)), and further a copolymer of ethylene and an α-olefin having 4 to 10 carbon atoms It contains an optional ethylene/α-olefin copolymer (B) (hereinafter also referred to as component (B)) and a nucleating agent (C) (hereinafter also referred to as component (C)).
Component (B) is an optional component and may or may not be included in the polypropylene-based resin composition of the present invention.

The content of the polypropylene resin (A) is 90% by mass or more and less than 100% by mass with respect to the total mass of the polypropylene resin composition, and the lower limit is preferably 90% by mass or more, and 95% by mass or more. More preferably, 99% by mass or more is even more preferable.
When the content is at least the lower limit of the range, the above-described effects of the present invention can be sufficiently obtained.
If it is less than the upper limit of the range, there is room for containing component (B) or component (C).

The content of the ethylene/α-olefin copolymer (B) is 0 to 10% by mass with respect to the total mass of component (A) and component (B), and the upper limit is preferably 10% by mass or less. % by mass or less is more preferable, and 0% by mass is even more preferable.
When it is at least the lower limit of the range, the plane impact strength of the injection molded article increases.
When it is at most the upper limit of the range, the rigidity of the injection molded article is increased. If it exceeds 10% by mass, the rigidity is lowered and handling becomes difficult.

The content of the nucleating agent (C) is 0.02 parts by mass or more and 0.5 parts by mass or less with respect to 100 parts by mass of the total mass of components (A) and (B).
When it is at least the lower limit of the range, the rigidity of the injection molded body is increased.
If the upper limit of the above range is exceeded, the effect of improving the rigidity of the injection-molded body hits a ceiling, which is uneconomical.

The MFR of the polypropylene resin composition at a temperature of 230° C. and a load of 2.16 kg is 40 to 120 g/10 minutes, and the lower limit is preferably 50 g/10 minutes or more, more preferably 60 g/10 minutes or more. Also, the upper limit is preferably 100 g/10 minutes or less, more preferably 85 g/10 minutes or less. Here, the MFR is a value measured by a method described later.
When it is at least the lower limit of the above range, it is difficult for insufficient filling into the mold to occur even during thin-walled injection molding, and it is possible to cope with high-cycle (high-speed) molding.
When it is at most the upper limit of the above range, the low-temperature impact resistance of the injection molded article can be sufficiently enhanced.

[Polypropylene resin (A)]
The polypropylene-based resin (A) contained in the polypropylene-based resin composition of the present invention is an aspect of an impact-resistant polypropylene polymer defined in JIS K6921-1, and is a continuation of the propylene polymer (component (a1)). It is composed of two or more phases including a phase and a rubber phase of the ethylene/α-olefin copolymer (component (a2)) present as a dispersed phase in the continuous phase.
The polypropylene resin (A) may be a mixed resin in which the component (a1) and the component (a2) are mixed during polymerization, or the separately obtained component (a1) and the component (a2) are It may be a mixed resin mixed by melt-kneading. Component (a1) and component (a2) are mixed at the time of polymerization, since a product with an excellent balance of rigidity, low-temperature impact resistance and tensile properties (hereinafter also referred to as "mechanical property balance") can be obtained at a lower cost. It is preferred that it is a material (polymerization mixture).
In the polymerization mixture, the component (a1) and the component (a2) can be mixed on the submicron order, so the polypropylene-based resin composition based on the polymerization mixture exhibits excellent mechanical property balance.
On the other hand, when a mere mechanical mixture obtained by melt-kneading separately obtained component (a1) and component (a2) achieves similar uniform mixing to obtain an excellent balance of mechanical properties, storage and storage・Manufacturing costs increase due to the need to go through separate processes such as transfer, weighing, mixing, and melt-kneading. It is also not preferable from the viewpoint of energy cost.
The reason why the polymerization mixture and the mechanical mixture sometimes exhibit different physical properties is presumed to be that the state of dispersion of the component (a2) in the component (a1) is different. At present, no practical means for analyzing the state of dispersion at the molecular level including the state of the interface with (a1) is known. A method for producing the polypropylene-based resin (A) will be described later in detail.

The intrinsic viscosity of the xylene-soluble portion of the polypropylene resin (A) (hereinafter also referred to as “XSIV”) is 0.5 to 3.0 dl / g, and the lower limit is preferably 1.2 dl / g or more. 0.5 dl/g or more is more preferable. Moreover, 2.4 dl/g or less is preferable as an upper limit.
When it is at least the lower limit of the above range, the low-temperature impact resistance of the injection molded article is enhanced. Moreover, when it is less than 0.5 dl/g, it becomes difficult to manufacture the polypropylene-based resin composition.
When it is at most the upper limit of the above range, the low-temperature impact resistance of the injection molded product is enhanced, and poor appearance (exhibition of pimples) can be suppressed.
Here, XSIV is the value measured in tetrahydronaphthalene at 135°C. The xylene solubles are obtained by dissolving a polypropylene resin sample in o-xylene at 135°C, cooling to 25°C, filtering the cooled solution with filter paper, and evaporating the filtrate to dryness. It is a component obtained by

The ratio ( _Mw / _Mn ) between the weight-average molecular weight _Mw and the number-average molecular weight _Mn , which is an index of the molecular weight distribution of the propylene polymer (component (a1)) constituting the polypropylene-based resin (A), is less than 7. is.
If it is less than the upper limit of the range, when a container provided with an in-mold label is formed as an injection-molded article, the strength of the mating surface portion of the in-mold label is improved.
The lower limit of the above ratio is not particularly limited, and an example of a standard is 3 or more.
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 by the method described later.

The ethylene-derived unit content (hereinafter also referred to as “C2”) in the propylene polymer (component (a1)) constituting the polypropylene resin (A) is 1.5 with respect to the total mass of the propylene polymer. % by mass or less, preferably 1.2% by mass or less.
When C2 is equal to or less than the upper limit, the rigidity of the injection molded body increases.
The lower limit of C2 is not particularly limited, and may be 0% by mass.
Therefore, the propylene polymer may be a polypropylene homopolymer consisting only of propylene-derived units, and has 98.5% by mass or more and less than 100% by mass of propylene-derived units and more than 0% by mass and 1.5% by mass or less of ethylene-derived units. Although it may be a copolymer consisting of units, C2 is preferably 0% by mass from the viewpoint of increasing the rigidity of the resulting injection molded article.
C2 is measured by the ¹³ C-NMR method.

The ethylene/α-olefin copolymer (component (a2)) constituting the polypropylene resin (A) is a copolymer having ethylene-derived units and α-olefin-derived units having 3 to 10 carbon atoms.
The content of ethylene-derived units in component (a2) is 25 to 60% by mass relative to the total mass of component (a2), and the lower limit is preferably 30% by mass or more. Moreover, 50 mass % or less is preferable as an upper limit, and 43 mass % or less is more preferable.
When it is at least the lower limit of the above range, the low-temperature impact resistance of the injection molded article is enhanced.
When it is at most the upper limit of the above range, the food sanitation of the injection molded product is enhanced (the amount of elution into n-heptane can be sufficiently reduced).
The ethylene-derived unit content in component (a2) is measured by the ¹³ C-NMR method.

The content of the ethylene/α-olefin copolymer (component (a2)) is 24 to 43% by mass with respect to the total mass of the polypropylene resin (A), and the lower limit is preferably 27% by mass or more. Moreover, 39 mass % or less is preferable as an upper limit.
When it is at least the lower limit of the above range, the low-temperature impact resistance of the injection molded article is enhanced.
If it is equal to or less than the upper limit of the above range, it is possible to reduce the risk of blockage of the flow path on the production facility due to deterioration of powder fluidity during production of the polypropylene resin (A), so that the polypropylene resin (A) can be stably produced. Continuous production is possible.

Examples of α-olefins constituting the ethylene/α-olefin copolymer (component (a2)) include propylene (1-propene), 1-butene, 1-pentene, 1-hexene, and 1-octene.
Specific examples of component (a2) include ethylene/propylene copolymers, ethylene/butene copolymers, ethylene/pentene copolymers, ethylene/hexene copolymers, and ethylene/octene copolymers.
Among these, an ethylene/propylene copolymer is preferable in consideration of improving the productivity of the polypropylene-based resin (A).

The MFR of the polypropylene resin (A) at a temperature of 230° C. and a load of 2.16 kg is 40 to 120 g/10 minutes, and the upper limit is preferably 110 g/10 minutes or less, more preferably 90 g/10 minutes or less. Here, the MFR is a value measured by a method described later.
When it is at least the lower limit of the above range, it is difficult for insufficient filling into the mold to occur even during thin-walled injection molding, and it is possible to cope with high-cycle (high-speed) molding.
When it is at most the upper limit of the range, the low-temperature impact resistance of the injection molded article is enhanced.

[Ethylene/α-olefin copolymer (B)]
The ethylene/α-olefin copolymer (B) is a copolymer of ethylene and an α-olefin having 4 to 10 carbon atoms. α-olefins include 1-butene, 1-pentene, 1-hexene, 1-octene and the like.
Specific examples of the ethylene/α-olefin copolymer (B) include ethylene/butene copolymers, ethylene/pentene copolymers, ethylene/hexene copolymers, and ethylene/octene copolymers.
Among these, an ethylene/butene copolymer or an ethylene/octene copolymer is preferable in consideration of ease of procurement as a raw material, economic efficiency, and the like.

The MFR of the ethylene/α-olefin copolymer (B) at a temperature of 190° C. and a load of 2.16 kg is preferably 1.0 to 40 g/10 minutes. Here, MFR is a value measured based on JIS K6921-2.
When it is at least the lower limit of the range, the fluidity of the polypropylene-based resin composition is enhanced.
If it is at most the upper limit of the range, the occurrence of blocking in the polypropylene resin composition can be suppressed, and the continuous productivity of the composition can be enhanced. It also enhances the low temperature impact resistance and tensile properties of the injection molded article.

[Nucleating agent (C)]
The nucleating agent (C) is also called a crystal nucleating agent. As the nucleating agent (C), known nucleating agents to be contained in conventional polypropylene-based resin compositions can be used, including nonitol-based nucleating agents, sorbitol-based nucleating agents, phosphate ester-based nucleating agents, triaminobenzene derivative nucleating agents, Nucleating agents selected from carboxylic acid metal salt nucleating agents and xylitol-based nucleating agents are preferred. It is also possible to use talc as a nucleating agent. Phosphate ester-based nucleating agents are preferred from the viewpoint of reducing the odor of injection molded articles.
Examples of crystal nucleating agents having nonitol-based structures include 1,2,3-trideoxy-4,6:5,7-bis-[(4-propylphenyl)methylene]-nonitol and crystals having xylitol-based structures. Nucleating agents such as bis-1,3:2,4-(5′,6′,7′,8′-tetrahydro-2-naphthaldehydebenzylidene)1-allylxylitol, bis-1,3:2, 4-(3′,4′-dimethylbenzylidene)1-propylxylitol, nucleating agent having a sorbitol structure such as bis-1,3:2,4-(4′-ethylbenzylidene)1-allyl Sorbitol, bis-1,3:2,4-(3'-methyl-4'-fluoro-benzylidene) 1-propyl sorbitol, bis-1,3:2,4-(3',4'-dimethylbenzylidene) 1'-methyl-2'-propenylsorbitol, 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′-ethyl benzylidene)-1-allyl sorbitol, bis-1,3:2,4-(4'-ethylbenzylidene) 1-allyl sorbitol, bis-1,3:2,4-(3',4'-dimethylbenzylidene) 1-methylsorbitol, bis(p-methylbenzylidene)sorbitol, 1,3:2,4-bis-o-(4-methylbenzylidene)-D-sorbitol and the like.
Examples of commercially available nonitol-based crystal nucleating agents include Millad NX8000 (manufactured by Miliken Japan), and examples of commercially available sorbitol-based crystal nucleating agents include RiKAFAST R-1 (manufactured by Shin Nippon Rika) and Millad 3988 (manufactured by Miliken Japan). , Gelol E-200 (manufactured by Shin Nippon Rika Co., Ltd.), Gelol MD (manufactured by Shin Nippon Rika Co., Ltd.), and the like.
Phosphate-2,2-methylenebis(4,6-di-tert-butylphenyl) sodium salt, phosphate-2,2'-methylenebis(4,6-di-tert- butylphenyl)aluminum salts, phosphate-2,2′-methylenebis(4,6-di-tert-butylphenyl)lithium salts and the like. Examples of commercially available phosphate-based crystal nucleating agents include ADEKA STAB NA-11 (ADEKA), ADEKA STAB NA-21 (ADEKA), and ADEKA STAB NA-71 (ADEKA).
Triaminobenzene derivative crystal nucleating agents include, for example, 1,3,5-tris(2,2-dimethylpropanamido)benzene. Commercially available triaminobenzene derivative crystal nucleating agents include, for example, IRGACLEAR XT386 (manufactured by BASF Japan) and Rikaclear PC1 (manufactured by New Japan Chemical Co., Ltd.).
Carboxylic acid metal salt nucleating agents include 1,2-cyclohexanedicarboxylic acid calcium salt and the like. Examples of commercially available carboxylic acid metal salt nucleating agents include Hyperform HPN-20E (manufactured by Milliken Japan).
These crystal nucleating agents can be used alone or in combination of two or more.

[Other ingredients]
The polypropylene-based resin composition of the present invention may be added as optional components other than the polypropylene-based resin (A), the ethylene/α-olefin copolymer (B), and the nucleating agent (C) within a range that does not impair the effects of the present invention. agents may be included.
Examples of the additives include antioxidants, neutralizers, nucleating agents other than the nucleating agent, weathering agents, pigments (organic or inorganic), internal and external lubricants, antiblocking agents, antistatic agents, and chlorine absorption. agent, heat stabilizer, light stabilizer, UV absorber, slip agent, anti-fogging agent, flame retardant, dispersant, copper damage inhibitor, plasticizer, foaming agent, anti-foaming agent, cross-linking agent, peroxide, oil exhibitions, etc. Only one kind of these additives may be used, or two or more kinds thereof may be used. The content may be a known amount.

<Method for producing polypropylene resin composition>
As a method for producing the polypropylene-based resin composition of the present invention, the polypropylene-based resin (A), the optional ethylene/α-olefin copolymer (B), and the nucleating agent (C) are mixed and then melted. A method of kneading may be mentioned.
Mixing methods include dry blending using a mixer such as a Henschel mixer, a tumbler, and a ribbon mixer.
Examples of the melt-kneading method include a method of mixing while melting using a mixer such as a single-screw extruder, a twin-screw extruder, a Banbury mixer, a kneader, or a roll mill. The melting temperature for melt-kneading is preferably 160 to 350°C, more preferably 170 to 260°C. After melt-kneading, it may be further pelletized.

[Method for producing polypropylene resin (A)]
The polypropylene resin (A) may be obtained by mixing a propylene polymer (component (a1)) and an ethylene/α-olefin copolymer (component (a2)) during polymerization, or may be obtained by separately producing components. It may be obtained by mixing (a1) and component (a2) by melt-kneading.
The polypropylene-based resin (A) is preferably a polymerization mixture in which the component (a1) and the component (a2) are mixed during polymerization.
Such a polymerization mixture is obtained by polymerizing ethylene monomers and α-olefin monomers in the presence of component (a1). According to this method, the productivity is increased and the dispersibility of the component (a2) in the component (a1) is increased, so that the mechanical property balance of the injection-molded article obtained using this method is improved.

Although the case of using a propylene monomer as the α-olefin monomer will be described below, it can be produced in the same manner when using other α-olefin monomers.

As a method for producing the polymerization mixture, a multistage polymerization method is typically used. For example, in the first-stage polymerization reactor of a polymerization apparatus equipped with two-stage polymerization reactors, a propylene monomer and, if necessary, an ethylene monomer are polymerized to obtain a propylene polymer, and the obtained propylene The polymerization mixture can be obtained by supplying the polymer to the second-stage polymerization reactor and polymerizing the ethylene monomer and the propylene monomer in the second-stage polymerization reactor.
The polymerization conditions may be similar to known polymerization conditions. For example, the polymerization conditions for the first stage include a slurry polymerization method in which propylene is in a liquid phase and the monomer density and productivity are high. As the second-stage polymerization conditions, a gas phase polymerization method is generally used, which facilitates production of a copolymer having high solubility in propylene.
The polymerization temperature is preferably 50 to 90°C, more preferably 60 to 90°C, even more preferably 70 to 90°C. When the polymerization temperature is at least the lower limit of the above range, the productivity and stereoregularity of the obtained polypropylene are more excellent.
The polymerization pressure is preferably 25-60 bar (2.5-6.0 MPa), more preferably 33-45 bar (3.3-4.5 MPa), when carried out in the liquid phase. When carried out in the gas phase, it is preferably 5-30 bar (0.5-3.0 MPa), more preferably 8-30 bar (0.8-3.0 MPa).
Polymerization (polymerization of propylene monomer, polymerization of ethylene monomer, propylene monomer, etc.) is usually carried out using a catalyst. During polymerization, hydrogen may be added for molecular weight adjustment, if necessary. By adjusting the molecular weight of the propylene polymer or the ethylene/propylene copolymer, the MFR of the polypropylene resin (A) and, in turn, the MFR of the polypropylene resin composition can be adjusted.
Prior to polymerization in the first-stage polymerization reactor, propylene may be prepolymerized in order to form polymer chains on the solid catalyst component that will serve as a foothold for subsequent main polymerization. Prepolymerization is usually carried out at 40° C. or lower, preferably 30° C. or lower, more preferably 20° C. or lower.

A known olefin polymerization catalyst can be used as the catalyst.
As the catalyst for polymerizing the ethylene monomer and the propylene monomer in the presence of the propylene polymer, a stereospecific Ziegler-Natta catalyst is preferable, and the following component (a), component (b) and component ( 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 electron donor compound as essential components.
(b) Organoaluminum compounds.
(c) Organosilicon compounds that are external electron donor compounds.

The polypropylene-based resin (A) is obtained by polymerizing an ethylene monomer and an α-olefin monomer (e.g., propylene monomer) in the presence of the propylene polymer using a catalyst (X) to obtain the polypropylene-based resin. It is preferable to manufacture by a method having a step of obtaining By using the catalyst (X), a polypropylene-based resin (A) having physical properties within the above ranges can be easily obtained.
The distribution of the molecular weight and stereoregularity of the propylene polymer obtained differs depending on the catalyst used (especially the electron donor compound of component (a)), and the difference affects the crystallization behavior. details have not been revealed. When trying to clarify this, it is necessary to analyze both the molecular weight distribution and the stereoregularity distribution as the molecular structure. , making the interpretation of the effect of stereoregularity distribution on crystallization behavior more difficult. Furthermore, since actual injection molding is carried out at a very high speed and in a fluid state, it is not easy to grasp the phenomenon even with advanced analytical techniques. Therefore, in a polypropylene resin composition obtained using a specific catalyst, it is almost impossible to specify the difference in crystallization behavior due to the distribution of stereoregularity by numerical values or the like. The molecular weight distribution and the stereoregularity distribution are changed by heat deterioration during melt kneading, peroxide treatment, and the like, in addition to the type of catalyst described above.

Component (a) is prepared using, for example, a titanium compound, a magnesium compound and an electron donor compound.
As a titanium compound used for 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) preferred.
Hydrocarbon groups include methyl, ethyl, propyl, butyl and the like, and halogen groups include Cl, Br and the like.
More specific titanium compounds include titanium tetrahalides such as TiCl ₄ , TiBr ₄ and _{TiI 4} ; Ti(OCH ₃ )Cl ₃ , Ti(OC ₂ H ₅ )Cl ₃ , Ti(On-C ₄ trihalogenated alkoxy titaniums such as _H9 )Cl3, Ti _{( OC2H5} ) _{Br3 ,} Ti(O _{- isoC4H9} ) _Br3 ; Ti ₍ OCH3) _2Cl2 , Ti _{( OC2H} ); ₅ ) _{Dihalogenated} alkoxy titanium such as _{2Cl2 ,} Ti ₍ O _{n -C4H9} ) _{2Cl2 ,} Ti _{( OC2H5} ) _2Br2 ; Ti ₍ OCH3) _3Cl , Ti( _OC2 monohalogenated trialkoxytitanium such as _H5 ) _3Cl , Ti(O _{n -C4H9} ) _3Cl , Ti _{( OC2H5} ) _3Br ; Ti _{( OCH3)4 ,} Ti _{( OC2H5} ) ₄ , tetraalkoxytitanium such as Ti(O _n —C ₄ H ₉ ) ₄ and the like. These titanium compounds may be used individually by 1 type, and may use 2 or more types together.
Among the above titanium compounds, halogen-containing titanium compounds are preferred, titanium tetrahalides are more preferred, and titanium tetrachloride (TiCl ₄ ) is particularly preferred.

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, butylmagnesium hydride and the like. These magnesium compounds can be used, for example, in the form of complex compounds with organoaluminum or the like, and may be liquid or solid. Further suitable magnesium compounds include magnesium halides such as magnesium chloride, magnesium bromide, magnesium iodide, magnesium fluoride; magnesium methoxy chloride, magnesium ethoxy chloride, magnesium isopropoxy chloride, magnesium butoxy chloride, magnesium octoxy chloride; alkoxy magnesium halides; allyloxy magnesium halides such as phenoxy magnesium chloride, methylphenoxy magnesium chloride; alkoxy magnesium halides such as ethoxy magnesium, isopropoxy magnesium, butoxy magnesium, n-octoxy magnesium, 2-ethylhexoxy magnesium; dialkoxymagnesium such as magnesium, diethoxymagnesium, dipropoxymagnesium, dibutoxymagnesium and ethoxymethoxymagnesium; allyloxymagnesium such as ethoxypropoxymagnesium, butoxyethoxymagnesium, phenoxymagnesium and dimethylphenoxymagnesium; . These magnesium compounds may be used individually by 1 type, and may use 2 or more types together.

The electron donor compound used for component (a) preferably contains a phthalate compound as an essential component. When the catalyst (X) containing a phthalate compound as an electron donor is used, a polypropylene resin in which the _Mw / _Mn of the propylene polymer is within the above range can be easily obtained.
Examples of phthalate compounds include monoethyl phthalate, dimethyl phthalate, methyl ethyl phthalate, monoisobutyl phthalate, mono-normal butyl phthalate, diethyl phthalate, ethyl isobutyl phthalate, ethyl normal 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, diphenyl phthalate and the like. Among them, diisobutyl phthalate is particularly preferred.

Examples of electron donor compounds in the solid catalyst other than phthalate compounds include succinate compounds and diether compounds.

The succinate-based compound may be an ester of succinic acid, or an ester of substituted succinic acid having a substituent such as an alkyl group at the 1- or 2-position of succinic acid. Specific examples include diethylsuccinate, dibutylsuccinate, diethylmethylsuccinate, diethyldiisopropylsuccinate, and diallylethylsuccinate.

Examples of diether compounds include 2-(2-ethylhexyl)-1,3-dimethoxypropane, 2-isopropyl-1,3-dimethoxypropane, 2-butyl-1,3-dimethoxypropane, 2-sec-butyl -1,3-dimethoxypropane, 2-cyclohexyl-1,3-dimethoxypropane, 2-phenyl-1,3-dimethoxypropane, 2-tert-butyl-1,3-dimethoxypropane, 2-cumyl-1,3 -dimethoxypropane, 2-(2-phenylethyl)-1,3-dimethoxypropane, 2-(2-cyclohexylethyl)-1,3-dimethoxypropane, 2-(p-chlorophenyl)-1,3-dimethoxypropane , 2-(diphenylmethyl)-1,3-dimethoxypropane, 2-(1-naphthyl)-1,3-dimethoxypropane, 2-(p-fluorophenyl)-1,3-dimethoxypropane, 2-(1 -decahydronaphthyl)-1,3-dimethoxypropane, 2-(p-tert-butylphenyl)-1,3-dimethoxypropane, 2,2-dicyclohexyl-1,3-dimethoxypropane, 2,2-diethyl- 1,3-dimethoxypropane, 2,2-dipropyl-1,3-dimethoxypropane, 2,2-dibutyl-1,3-dimethoxypropane, 2,2-diethyl-1,3-diethoxypropane, 2,2 -dicyclopentyl-1,3-dimethoxypropane, 2,2-dipropyl-1,3-diethoxypropane, 2,2-dibutyl-1,3-diethoxypropane, 2-methyl-2-ethyl-1,3 -dimethoxypropane, 2-methyl-2-propyl-1,3-dimethoxypropane, 2-propyl-2-pentyl-1,3-diethoxypropane, 2-methyl-2-benzyl-1,3-dimethoxypropane, 2-methyl-2-phenyl-1,3-dimethoxypropane, 2-methyl-2-cyclohexyl-1,3-dimethoxypropane, 2-methyl-2-methylcyclohexyl-1,3-dimethoxypropane, 2,2- Bis(p-chlorophenyl)-1,3-dimethoxypropane, 2,2-bis(2-phenylethyl)-1,3-dimethoxypropane, 2,2-bis(2-cyclohexylethyl)-1,3-dimethoxy Propane, 2-methyl-2-isobutyl-1,3-dimethoxypropane, 2-methyl-2-(2-ethylhexyl)-1,3-dimethoxypropane, 2,2-bis(2-ethylhexyl) xyl)-1,3-dimethoxypropane, 2,2-bis(p-methylphenyl)-1,3-dimethoxypropane, 2-methyl-2-isopropyl-1,3-dimethoxypropane, 2,2-diisobutyl- 1,3-dimethoxypropane, 2,2-diphenyl-1,3-dimethoxypropane, 2,2-dibenzyl-1,3-dimethoxypropane, 2-isopropyl-2-cyclopentyl-1,3-dimethoxypropane, 2, 2-bis(cyclohexylmethyl)-1,3-dimethoxypropane, 2,2-diisobutyl-1,3-diethoxypropane, 2,2-diisobutyl-1,3-dibutoxypropane, 2-isobutyl-2-isopropyl -1,3-dimethoxypropane, 2,2-di-sec-butyl-1,3-dimethoxypropane, 2,2-di-tert-butyl-1,3-dimethoxypropane, 2,2-dineopentyl-1, 3-dimethoxypropane, 2-isopropyl-2-isopentyl-1,3-dimethoxypropane, 2-phenyl-2-benzyl-1,3-dimethoxypropane, 2-cyclohexyl-2-cyclohexylmethyl-1,3-dimethoxypropane and 1,3-diethers.
Further specific examples of the 1,3-diether compound include the following.
1,1-bis(methoxymethyl)-cyclopentadiene;
1,1-bis(methoxymethyl)-2,3,4,5-tetramethylcyclopentadiene;
1,1-bis(methoxymethyl)-2,3,4,5-tetraphenylcyclopentadiene;
1,1-bis(methoxymethyl)-2,3,4,5-tetrafluorocyclopentadiene;
1,1-bis(methoxymethyl)-3,4-dicyclopentylcyclopentadiene;
1,1-bis(methoxymethyl)indene;
1,1-bis(methoxymethyl)-2,3-dimethylindene;
1,1-bis(methoxymethyl)-4,5,6,7-tetrahydroindene;
1,1-bis(methoxymethyl)-2,3,6,7-tetrafluoroindene;
1,1-bis(methoxymethyl)-4,7-dimethylindene;
1,1-bis(methoxymethyl)-3,6-dimethylindene;
1,1-bis(methoxymethyl)-4-phenylindene;
1,1-bis(methoxymethyl)-4-phenyl-2-methylindene;
1,1-bis(methoxymethyl)-4-cyclohexylindene;
1,1-bis(methoxymethyl)-7-(3,3,3-trifluoropropyl)indene;
1,1-bis(methoxymethyl)-7-trimethylsilylindene;
1,1-bis(methoxymethyl)-7-trifluoromethylindene;
1,1-bis(methoxymethyl)-4,7-dimethyl-4,5,6,7-tetrahydroindene;
1,1-bis(methoxymethyl)-7-methylindene;
1,1-bis(methoxymethyl)-7-cyclopentylindene;
1,1-bis(methoxymethyl)-7-isopropylindene;
1,1-bis(methoxymethyl)-7-cyclohexylindene;
1,1-bis(methoxymethyl)-7-tert-butylindene;
1,1-bis(methoxymethyl)-7-tert-butyl-2-methylindene;
1,1-bis(methoxymethyl)-7-phenylindene;
1,1-bis(methoxymethyl)-2-phenylindene;
1,1-bis(methoxymethyl)-1H-benzindene;
1,1-bis(methoxymethyl)-1H-2-methylbenzindene;
9,9-bis(methoxymethyl)fluorene;
9,9-bis(methoxymethyl)-2,3,6,7-tetramethylfluorene;
9,9-bis(methoxymethyl)-2,3,4,5,6,7-hexafluorofluorene;
9,9-bis(methoxymethyl)-2,3-benzofluorene;
9,9-bis(methoxymethyl)-2,3,6,7-dibenzofluorene;
9,9-bis(methoxymethyl)-2,7-diisopropylfluorene;
9,9-bis(methoxymethyl)-1,8-dichlorofluorene;
9,9-bis(methoxymethyl)-2,7-dicyclopentylfluorene;
9,9-bis(methoxymethyl)-1,8-difluorofluorene;
9,9-bis(methoxymethyl)-1,2,3,4-tetrahydrofluorene;
9,9-bis(methoxymethyl)-1,2,3,4,5,6,7,8-octahydrofluorene;
9,9-bis(methoxymethyl)-4-tert-butylfluorene.

Halogen atoms constituting component (a) include fluorine, chlorine, bromine, iodine and mixtures thereof, with chlorine being particularly preferred.

Examples of the organoaluminum compound of component (a) include trialkylaluminums such as triethylaluminum and tributylaluminum, trialkenylaluminums such as triisoprenylaluminum, and dialkylaluminum alkoxides such as diethylaluminum ethoxide and dibutylaluminum butoxide. , ethylaluminum sesquiethoxide, alkylaluminum sesquialkoxides such as butylaluminum sesquibutoxide, R ¹ _2.5 Al(OR ² ) _0.5 (R ¹ and R ² may be different or the same) partially alkoxylated aluminum alkyls, dialkylaluminum halides such as diethylaluminum chloride, dibutylaluminum chloride, diethylaluminum bromide, ethylaluminum sesquichloride, butyl Aluminum sesquichloride, alkylaluminum sesquihalogenides such as ethylaluminum sesquibromide, alkylaluminum dihalogenides such as ethylaluminum dichloride, propylaluminum dichloride, butylaluminum dibromide, etc. partially halogenated alkylaluminum, diethyl Partially hydrogenated alkylaluminums such as aluminum hydride, dialkylaluminum hydrides such as dibutylaluminum hydride, ethylaluminum dihydride, alkylaluminum dihydrides such as propylaluminum dihydride, ethylaluminum ethoxychloride, butylaluminum butoxychloride , partially alkoxylated and halogenated alkylaluminums such as ethylaluminum ethoxy bromide, and the like. The component (a) may be used alone or in combination of two or more.

An organosilicon compound is used as the external electron donor compound of component (c).
Preferred organosilicon compounds include, for example, trimethylmethoxysilane, trimethylethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diisopropyldimethoxysilane, t-butylmethyldimethoxysilane, t-butylmethyldiethoxysilane, t-amylmethyldiethoxysilane. Silane, diphenyldimethoxysilane, phenylmethyldimethoxysilane, diphenyldiethoxysilane, bis-o-tolyldimethoxysilane, bis-m-tolyldimethoxysilane, bis-p-tolyldimethoxysilane, bis-p-tolyldiethoxysilane, bisethylphenyldimethoxysilane , dicyclopentyldimethoxysilane, dicyclohexyldimethoxysilane, cyclohexylmethyldimethoxysilane, cyclohexylmethyldiethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, vinyltrimethoxysilane, methyltrimethoxysilane, n-propyltriethoxysilane, decyltri Methoxysilane, decyltriethoxysilane, phenyltrimethoxysilane, γ-chloropropyltrimethoxysilane, methyltriethoxysilane, vinyltriethoxysilane, t-butyltriethoxysilane, thexyltrimethoxysilane, n-butyltriethoxysilane , iso-butyltriethoxysilane, phenyltriethoxysilane, γ-aminopropyltriethoxysilane, chlorotriethoxysilane, ethyltriisopropoxysilane, vinyltributoxysilane, cyclohexyltrimethoxysilane, cyclohexyltriethoxysilane, 2-norbornane Trimethoxysilane, 2-norbornanetriethoxysilane, 2-norbornanemethyldimethoxysilane, ethyl silicate, butyl silicate, trimethylphenoxysilane, methyltriallyloxysilane, vinyltris(β-methoxyethoxysilane), vinyltriacetoxysilane Silane, 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-butylsilane Toxydimethoxysilane, isobutyltrimethoxysilane, cyclohexylisobutyldimethoxysilane, di-sec-butyldimethoxysilane, isobutylmethyldimethoxysilane, bis(decahydroisoquinolin-2-yl)dimethoxysilane, diethylaminotriethoxysilane, dicyclopentyl-bis( ethylamino)silane, tetraethoxysilane, tetramethoxysilane, isobutyltriethoxysilane, t-butyltrimethoxysilane, i-butyltrimethoxysilane, i-butylsec-butyldimethoxysilane, ethyl(perhydroisoquinolin-2-yl)dimethoxysilane Silane, tri(isopropenyloxy)phenylsilane, i-butyl i-propyldimethoxysilane, cyclohexyl i-butyldimethoxysilane, cyclopentyl i-butyldimethoxysilane, cyclopentylisopropyldimethoxysilane, phenyltriethoxysilane, p-tolylmethyldimethoxysilane etc.
Among these, ethyltriethoxysilane, n-propyltriethoxysilane, n-propyltrimethoxysilane, t-butyltriethoxysilane, t-butylmethyldimethoxysilane, t-butylmethyldiethoxysilane, t-butylethyldimethoxysilane Silane, t-butylpropyldimethoxysilane, t-butyl t-butoxydimethoxysilane, t-butyltrimethoxysilane, i-butyltrimethoxysilane, isobutylmethyldimethoxysilane, i-butylsec-butyldimethoxysilane, ethyl (perhydroisoquinoline 2-yl)dimethoxysilane, bis(decahydroisoquinolin-2-yl)dimethoxysilane, tri(isopropenyloxy)phenylsilane, thexyltrimethoxysilane, vinyltriethoxysilane, phenyltriethoxysilane, phenyltrimethoxysilane, vinyltributoxysilane, diphenyldimethoxysilane, diisopropyldimethoxysilane, diisobutyldimethoxysilane, i-butyl i-propyldimethoxysilane, cyclopentyl t-butoxydimethoxysilane, dicyclopentyldimethoxysilane, cyclohexylmethyldimethoxysilane, cyclohexyl i-butyldimethoxysilane, Cyclopentyl i-butyldimethoxysilane, cyclopentylisopropyldimethoxysilane, di-sec-butyldimethoxysilane, diethylaminotriethoxysilane, tetraethoxysilane, tetramethoxysilane, isobutyltriethoxysilane, phenylmethyldimethoxysilane, phenyltriethoxysilane, bisp -tolyldimethoxysilane, p-tolylmethyldimethoxysilane, dicyclohexyldimethoxysilane, cyclohexylethyldimethoxysilane, 2-norbornanetriethoxysilane, 2-norbornanemethyldimethoxysilane, diphenyldiethoxysilane, methyl (3,3,3-trifluoro -n-propyl)dimethoxysilane, ethyl silicate and the like are preferred.
The component (c) may be used alone or in combination of two or more.

Organosilicon compounds play an important role, especially in controlling the amount of xylene insolubles. When the other catalyst components are the same, the amount of the xylene-insoluble matter depends on the type and amount of the organosilicon compound and the polymerization temperature. When the amount of silicon compound is below a certain value, it greatly decreases. Therefore, when the polymerization temperature is 75° C., the lower limit of the molar ratio between the organosilicon compound and the organoaluminum compound (organosilicon compound/organoaluminum) is preferably 0.015, more preferably 0.018. The upper limit of the ratio is preferably 0.30, more preferably 0.20, and even more preferably 0.10.
When a phthalate-based compound is used as the internal electron donor compound, the xylene-insoluble matter increases as the polymerization temperature is raised. lower limit. Specifically, when a phthalate compound is used for polymerization at 80° C., 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.

As catalyst (X), component (a) is trialkylaluminum such as triethylaluminum and triisobutylaluminum, and component (c) is organic silicon such as dicyclopentyldimethoxysilane, cyclohexylmethyldimethoxysilane, diisopropyldimethoxysilane. Compounds are preferred.

The method for obtaining the polymerization mixture by the multi-stage polymerization method is not limited to the above method, and the propylene polymer (component (a1)) may be polymerized in a plurality of polymerization reactors, or the ethylene/α-olefin copolymer may be The polymer (component (a2)) may be polymerized in multiple polymerization reactors.
As a method of obtaining the polymerization mixture, there is also a method of using a polymerization vessel having a gradient of monomer concentration and polymerization conditions. Such a polymerizer may, for example, use at least two joined polymerization zones to polymerize the monomers in a gas phase polymerization.
Specifically, in the presence of a catalyst, a monomer is supplied and polymerized in a polymerization region composed of an ascending pipe, a monomer is supplied and polymerized in a descending pipe connected to the ascending pipe, and the ascending pipe and the descending pipe are used. is circulated to recover the polymerized product. The method comprises means for wholly or partially preventing the gas mixture present in the riser from entering the downcomer. Also, a gas and/or liquid mixture is introduced into the downcomer having a different composition than the gas mixture present in the riser. For this polymerization method, for example, the method described in JP-T-2002-520426 can be applied.

(Method for producing ethylene/α-olefin copolymer (B))
The ethylene/α-olefin copolymer (B) can be produced by a known method (for example, the method described in International Publication WO2006/102155) using a metallocene catalyst or half-metallocene catalyst during polymerization.
Known molecular weight regulators such as chain transfer agents (eg, hydrogen or diethylzinc) may be used during the polymerization.

<Injection molding>
The injection molded article of the present invention can be produced by injection molding the polypropylene resin composition.
The molding temperature is generally 150-350°C, preferably 170-250°C. When the molding temperature exceeds 350°C, it causes deterioration of the resin composition and molding defects. The mold temperature is preferably in the range of 10 to 60°C. If the mold temperature exceeds 60° C., the surface finish of the molded article is excellent and a molded article excellent in rigidity can be obtained, but the molding cycle is lengthened and the productivity is lowered. Conversely, if the mold temperature is set below 10°C, warping and shrinkage become noticeable, making it difficult to obtain a satisfactory molded product. cause it to It is also unsuitable from the viewpoint of energy costs related to cooling.

The polypropylene resin composition of the present invention is suitable for thin injection molding. For example, it is possible to form an injection molded article having a thickness of 1 mm or less, preferably 0.7 mm or less, more preferably 0.5 mm or less at the thinnest portion. A guideline for the lower limit of the thickness of the thin portion is about 0.1 mm. The thickness of the thin portion is measured by observing the cross section of the measurement location with a known means such as a measuring microscope.

The shape of the injection-molded article of the present invention is not particularly limited, and it is suitable for containers because it has an excellent balance of various mechanical properties and can be made thin. The thickness of the sidewall of the container can be, for example, 0.1-1 mm, preferably 0.1-0.7 mm, more preferably 0.1-0.5 mm. The thickness of the side wall is measured by observing the cross section of the measurement location with a known means such as a measuring microscope.

When the injection-molded article of the present invention is a container, the side wall of the container may be provided with an in-mold label. The in-mold label is wrapped around the side wall and has a joint portion where the starting edge and the terminal edge are overlapped. The main body of the in-mold label is usually made of a resin different from the polypropylene-based resin composition forming the container main body. The thickness of the in-mold label can be, for example, 10-100 μm. The thickness of the in-mold label shall be included in the thickness of the sidewall of the container. The in-mold label may be printed with letters, pictures, symbols, numbers, or other arbitrary figures or design images.

Since the injection molded article of the present invention is excellent in low-temperature impact resistance, it can be used in a low-temperature environment of -10°C or lower, preferably -20°C or lower, more preferably -30°C or lower.

Since the injection-molded article of the present invention is formed from a polypropylene-based resin composition having excellent food sanitation properties, it is suitable for use as a container or package that comes into contact with food.
Regarding the injection molded article made of the polypropylene-based resin composition, the amount of the evaporation residue determined by the n-heptane elution test described later is preferably 35 μg/ml or less, more preferably 30 μg/ml or less, and 25 μg/ml or less. More preferred.

The tensile modulus of the injection molded article of the present invention is preferably 900 MPa or more, more preferably 1000 MPa or more.
The higher the tensile modulus, the more rigid the injection-molded article, which is advantageous for the production of injection-molded articles having thin-walled portions.

When the injection-molded article of the present invention is a container provided with an in-mold label, the compression distance (breaking strain) measured by the test method described below is preferably 50 mm or more.
A longer compression distance indicates that the container can withstand greater deformation and is less likely to crack.

Examples and comparative examples are shown below, but the present invention is not limited only to the following examples.

<Preparation of copolymer 1>
A solid catalyst of TiCl ₄ and diisobutyl phthalate as an internal donor on MgCl ₂ was prepared by the method described in EP 728 769, Example 5, lines 46-53. Specifically, it was carried out as follows.

Microprolate MgCl ₂ .2.1C ₂ H ₅ OH was prepared as follows. Into a 2 L autoclave equipped with a turbine stirrer and a suction pipe were placed 48 g of anhydrous MgCl ₂ , 77 g of anhydrous C ₂ H ₅ OH, and 830 mL of kerosene under inert gas at ambient temperature. Heating the contents to 120° C. with stirring resulted in an adduct between the MgCl ₂ and the alcohol which was melted and mixed with the dispersant. The nitrogen pressure inside the autoclave was maintained at 15 atmospheres. The suction pipe of the autoclave was externally heated to 120°C using a heating jacket. The suction pipe had an inner diameter of 1 mm and a length of 3 m from one end of the heating jacket to the other. The mixture was passed through this pipe at a speed of 7 m/sec. At the outlet of the pipe, the dispersion was taken with stirring into a 5 L flask containing 2.5 L of kerosene and externally cooled by a jacket maintaining an initial temperature of -40°C. The final temperature of the dispersion was 0°C. The spherical solid product, which constituted the dispersed phase of the emulsion, was allowed to settle, separated by filtration, washed with heptane and dried. All these operations were performed in an inert gas atmosphere. MgCl ₂ .3C ₂ H ₅ OH in the form of solid spherical particles with a maximum diameter of less than 50 μm was obtained. Yield was 130 g. The product thus obtained was freed of alcohol by gradually increasing the temperature from 50° C. to 100° C. in a stream of nitrogen until the alcohol content was reduced to 2.1 moles per mole of MgCl ₂ .

A 500 mL cylindrical glass reactor equipped with a filtration barrier was charged at 0° C. with 225 mL of TiCl ₄ and 10.1 g (54 mmol) of the microprolongated MgCl ₂ .2.1C ₂ H ₅ OH obtained as described above. was added over 15 minutes while stirring the contents. After that, the temperature was raised to 40° C. and 9 mmol of diisobutyl phthalate was added. The temperature was increased to 100° C. over 1 hour and stirring was continued for an additional 2 hours. TiCl ₄ was then removed by filtration and 200 mL of TiCl ₄ was added while stirring at 120° C. for an additional hour. Finally, the contents were filtered and washed with n-heptane at 60° C. until the chloride ions completely disappeared from the filtrate. The catalyst component thus obtained contained Ti=3.3% by weight and diisobutyl phthalate=8.2% by weight.

Next, using the solid catalyst, triethylaluminum (TEAL) as an organoaluminum compound, and dicyclopentyldimethoxysilane (DCPMS) as an external electron donor compound, the mass ratio of TEAL to the solid catalyst is 20, and the mass ratio of TEAL/DCPMS was 10 (0.05 when converted to the above-described organosilicon compound/organoaluminum molar ratio), and the contact was carried out at 12° C. for 24 minutes.
Prepolymerization was carried out by keeping the obtained catalyst (X) in suspension 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-stage 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 the polymerization, temperature and pressure were controlled and hydrogen was used as a molecular weight regulator.
As for the ratio of polymerization temperature and reactants, in the first-stage reactor, the polymerization temperature and hydrogen concentration were 70° C. and 2.32 mol %, respectively, and in the second-stage reactor, the polymerization temperature, hydrogen concentration, ethylene and propylene were The ratio of ethylene to the total of and was 80° C., 3.62 mol %, and 0.35 mol ratio, respectively. Also, the residence time distribution in the first stage and the second stage was adjusted so that the amount of the ethylene-propylene copolymer was 28% by mass. The target copolymer 1 was obtained by the above method.
The obtained copolymer 1 is a polymerization mixture of component (a1), which is a propylene polymer constituting the continuous phase, and component (a2), which is an ethylene/propylene copolymer constituting the rubber phase, and It is a polypropylene resin (A).
Regarding copolymer 1, molecular weight distribution Mw/Mn of component (a1), ethylene-derived unit content of component (a1), mass ratio component (a2)/[component (a1) + component (a2)], component (a2 ), the XSIV of component (a1) + component (a2), and the MFR of component (a1) + component (a2) were as shown in Table 1.
In Table 1, the catalyst (X) containing a phthalate compound as component (a) is represented as "Pht", and the catalyst (X) containing a succinate compound as component (a) is represented as "Suc".

<Production of copolymer 2-7>
The residence time distribution in the first stage and the second stage is changed so that the mass ratio of component (a2) / [component (a1) + component (a2)] is the ratio shown in Table 1, and component (a1) +Component (a1) and component (a1) and component ( An attempt was made to produce a copolymer 2-7 composed of the polymerization mixture of a2), and the target copolymer was obtained for the copolymer 2-6. Regarding copolymer 7, the mass ratio of component (a2)/[component (a1) + component (a2)] was large (45% by mass), and the reactor was clogged, so the target copolymer could not be obtained. rice field.
The obtained copolymer was measured in the same manner as the copolymer 1. Table 1 shows the measured values (target values in the case of copolymer 7).

<Production of copolymers 8-9 and 11-12>
Except that the ratio of ethylene to the total of ethylene and propylene in the second-stage reactor was changed to the value shown in Table 1 so that the ethylene-derived unit content of component (a2) was the ratio shown in Table 1. , Copolymers 8-9 and 11-12 each comprising a polymerized mixture of component (a1) and component (a2) were obtained in the same manner as in the case of copolymer 1.
These copolymers were measured in the same manner as for copolymer 1. Table 1 shows the measured values.

<Production of copolymer 10>
The sum of the hydrogen concentration, ethylene and propylene in the second-stage reactor so that the XSIV of component (a1) + component (a2) and the ethylene-derived unit content of component (a2) are the values shown in Table 1. The ratio of ethylene to the copolymer was changed to the value shown in Table 1, and the hydrogen concentration in the first stage was changed to the value shown in Table 1 to adjust the MFR of component (a1) + component (a2). A copolymer 10 composed of a polymerization mixture of the component (a1) and the component (a2) was obtained by the same manufacturing method as in the case of coalescence 1. This copolymer was measured in the same manner as for copolymer 1. Table 1 shows the measured values.

<Preparation of copolymer 13-18>
The hydrogen concentration in the second-stage reactor was changed to the value shown in Table 1 so that the XSIV of component (a1) + component (a2) became the ratio shown in Table 1, and component (a1) + component (a2) Polymerization of component (a1) and component (a2) in the same production method as for copolymer 1, except that the hydrogen concentration in the first stage was changed to the value shown in Table 1 in order to adjust the MFR of ) Attempts were made to produce copolymers 13 to 18 consisting of mixtures, and the desired copolymers were obtained with the exception of copolymer 15. Regarding copolymer 15, the XSIV of component (a1)+component (a2) was small (0.4), and production was difficult, so the desired copolymer could not be obtained.
The obtained copolymer was measured in the same manner as the copolymer 1. Table 1 shows the measured values (target values in the case of copolymer 15).

<Preparation of copolymer 19-23>
Same as for copolymer 1 except that the hydrogen concentration in the first-stage reactor was changed to the value shown in Table 1 so that the MFR of component (a1) + component (a2) was the value shown in Table 1. Copolymer 19-23 consisting of a polymerization mixture of component (a1) and component (a2) was obtained by the production method of .
These copolymers were measured in the same manner as for copolymer 1. Table 1 shows the measured values.

<Preparation of copolymers 24 and 25>
In order to adjust the MFR of component (a1) + component (a2) while changing the ethylene concentration in the first stage reactor so that the ethylene-derived unit content of component (a1) is the ratio shown in Table 1 Copolymer 24 consisting of a polymerization mixture of component (a1) and component (a2) was prepared in the same manner as in the case of copolymer 1, except that the hydrogen concentration in the first stage was changed to the value shown in Table 1. 25 was obtained.
These copolymers were measured in the same manner as for copolymer 1. Table 1 shows the measured values.

<Production of copolymer 26>
A solid catalyst was prepared by the following procedure according to the preparation method described in the example of JP-T-2011-500907.
Into a nitrogen-purged 500 mL four-necked round bottom flask, 250 mL of _TiCl4 was introduced at 0°C. With stirring, 10.0 g of microspherical MgCl ₂ .1.8C ₂ H ₅ OH (prepared according to the method described in Example 2 of USP-4,399,054, but running at 3000 rpm instead of 10000 rpm ), and 9.1 mmol of diethyl-2,3-(diisopropyl)succinate were added. The temperature was increased to 100°C and held for 120 minutes. Agitation was then stopped, the solid product was allowed to settle, and the supernatant liquid was siphoned off. The following procedure was then repeated twice: 250 mL of fresh TiCl ₄ was added, the mixture was allowed to react at 120° C. for 60 minutes, and the supernatant was siphoned off. The solid was washed six times with anhydrous hexane (6 x 100 mL) at 60°C.
The solid catalyst was contacted with TEAL and DCPMS in amounts such that the mass ratio of TEAL to solid catalyst was 18 and the mass ratio of TEAL/DCPMS was 10 at room temperature for 5 minutes. Prepolymerization was carried out by keeping the resulting catalyst system in suspension in liquid propylene at 20° C. for 5 minutes. The obtained prepolymer is introduced into a liquid phase polymerization reactor of a polymerization apparatus equipped with a liquid phase polymerization reactor and a gas phase polymerization reactor in series, and propylene is converted into propylene in a liquid phase state in the first stage polymerization reactor. A polymer was produced, and an ethylene/propylene copolymer was produced in a second-stage gas-phase polymerization reactor. During the polymerization, the polymerization temperature is set at 80° C., the polymerization pressure and the amount of catalyst added are adjusted, and ethylene is supplied in the second stage so that the content of ethylene-derived units in the component (a2) is a predetermined amount. The amount and propylene feed rate were adjusted to provide a 0.27 molar ratio of ethylene to total ethylene and propylene. In addition, using hydrogen as a molecular weight modifier, the hydrogen concentration was adjusted to 1.51 mol% in the first stage and 2 in the second stage so that the MFR and XSIV of component (a1) + component (a2) were predetermined values. 0.69 mol %. In addition, the residence time distributions in the first and second stages were adjusted so that the mass ratio of component (a2)/[component (a1)+component (a2)] was a predetermined amount. The target copolymer 26 was obtained by the above method.
The resulting copolymer 26 is a polymerization mixture of component (a1), which is a propylene polymer constituting the continuous phase, and component (a2), which is an ethylene/propylene copolymer constituting the rubber phase. It is a polypropylene resin (A).
Regarding copolymer 26, molecular weight distribution Mw/Mn of component (1), ethylene-derived unit content of component (1), mass ratio component (a2)/[component (a1) + component (a2)], component (a2 ), the XSIV of component (a1) + component (a2), and the MFR of component (a1) + component (a2) were as shown in Table 1.

The measurement results in Table 1 are values measured by the following measurement method.

<Mw/Mn of component (a1)>
A 2.5 g sample obtained by collecting the component (a1) polymerized in the first stage reactor is used as a measurement sample, and the number average molecular weight (Mn) and weight average molecular weight (Mw) are measured as follows. The molecular weight distribution (Mw/Mn) was obtained by dividing (Mw) by the number average molecular weight (Mn).
PL GPC220 manufactured by Polymer Laboratories was used as an apparatus, 1,2,4-trichlorobenzene containing an antioxidant was used as a mobile phase, and UT-G (1) and UT-807 (1) manufactured by Showa Denko were used as columns. ) and UT-806M (two) connected in series, and a differential refractometer was used as a detector. In addition, the same solvent as the mobile phase was used for the sample solution, and the sample concentration was 1 mg/mL, and the solution was dissolved with shaking at a temperature of 150° C. for 2 hours to prepare a measurement sample. 500 μL of the sample solution thus obtained was injected into the column and measured at a flow rate of 1.0 mL/min, a temperature of 145° C., and a data acquisition interval of 1 second. A polystyrene standard sample (Shodex STANDARD, manufactured by Showa Denko KK) with a molecular weight of 5,800,000 to 7,450,000 was used for calibrating the column using a cubic approximation. The Mark-Houwink-Sakurada coefficients are K = 1.21 × 10 ^-4 and α = 0.707 for polystyrene standard samples, and for polypropylene homopolymer, propylene random copolymer, and polypropylene-based polymer, K=1.37×10 ⁻⁴ and α=0.75 were used.

<Total ethylene content of copolymer, ethylene-derived unit content of component (a1)>
A copolymer sample dissolved in a mixed solvent of 1,2,4-trichlorobenzene/deuterated benzene was measured using a Bruker AVANCE III HD400 ( ¹³ C resonance frequency of 100 MHz) at a measurement temperature of 120° C. and a flip angle of 45°. A ¹³ C-NMR spectrum was obtained under the conditions of a pulse interval of 7 seconds, a sample rotation speed of 20 Hz, and an accumulation number of 5000 times.
Using the spectrum obtained above, the total ethylene Amount (% by mass) was determined.
When measuring the component (a1) as a sample, the total ethylene amount (% by mass) obtained by the above method is the ethylene-derived unit content (% by mass) of the component (a1).

<Ethylene-derived unit content in component (a2)>
The same as the total ethylene content except that the integrated intensity T'ββ obtained by the following formula was used instead of the integrated intensity of Tββ obtained when measuring the total ethylene content of the copolymer by the method described in the above document. The ethylene-derived unit content (% by mass) of the component (a2) was determined by the method of .
T′ββ=0.98×Sαγ×A/(1−0.98×A)
Here, A=Sαγ/(Sαγ+Sαδ), which is calculated from Sαγ and Sαδ described in the above literature.
In the copolymer consisting of the component (a1) and the component (a2), when the component (a1) contains an ethylene unit, the content of ethylene-derived units in the component (a2) is the mass ratio component (a2)/[ When the component (a1)+component (a2)] is clear from the polymerization conditions (the above-mentioned copolymers 24 and 25 correspond), it was determined by the following formula.
Ethylene-derived unit content of component (a2) (unit: % by mass) =
[Total amount of ethylene in the copolymer - content of ethylene-derived units in component (a1) x content of component (a1) in copolymer]
/ (Content ratio of component (a2) in copolymer)

<Mass ratio component (a2)/[component (a1) + component (a2)]>
It was obtained by the following formula.
Component (a2)/[Component (a1)+Component (a2)] (Unit: % by mass)=Total amount of ethylene in the copolymer/(Content of ethylene-derived units in Component (a2)/100)

<XSIV of Component (a1) + Component (a2)>
A xylene-soluble component of the copolymer was obtained by the following method, and the intrinsic viscosity (XSIV) of the xylene-soluble component was measured.
A 2.5 g sample of the copolymer is placed in a flask containing 250 mL of o-xylene (solvent), and is completely dissolved by stirring at 135° C. for 30 minutes using a hot plate and a reflux apparatus while purging with nitrogen. After that, it was cooled at 25° C. for 1 hour. The resulting solution was filtered using filter paper. 100 mL of the filtrate after filtration was collected, transferred to an aluminum cup or the like, evaporated to dryness at 140° C. while purging with nitrogen, and allowed to stand at room temperature for 30 minutes to obtain xylene solubles.
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.).

<MFR of Component (a1) + Component (a2)>
To 5 g of the copolymer sample, 0.05 g of H-BHT manufactured by Honshu Chemical Industry Co., Ltd. was added, and after homogenization by dry blending, according to JIS K6921-2, the temperature was 230 ° C. and the load was 2.16 kg. It was measured.

[Examples 1 to 20, Comparative Examples 1 to 12]
Components (A) to (C) are blended with the composition shown in Table 2, and the total amount of components (A) to (C) is 100 parts by mass, and 0.2 parts by mass of BASF B225 as an antioxidant, medium 0.05 parts by mass of calcium stearate manufactured by Tannan Kagaku Kogyo Co., Ltd. was added as a solubilizing agent, and stirred and mixed for 1 minute with a Henschel mixer. The mixture was melt-kneaded and extruded at a cylinder temperature of 200° C. using a co-rotating twin-screw extruder TEX-30α manufactured by JSW Co., Ltd. After cooling the strand in water, it was cut with a pelletizer to obtain pellets of the polypropylene composition. Various physical properties were evaluated for the polypropylene-based resin compositions thus produced and the injection-molded articles obtained using them. Table 2 shows the results.

Each component in Table 2 is as follows.
Component (A) is copolymers 1-26 in Table 1.

Component (B) is the following ethylene/α-olefin copolymer.
B-1: Dow Chemical Co., Engage 8100, ethylene/octene copolymer, MFR (190°C, load 2.16 kg) = 1.0 g/10 minutes

Component (C) is the following nucleating agent.
C-1: Adekastab NA11 manufactured by ADEKA Co., Ltd. (phosphate ester-based nucleating agent)
C-2: Neotalc UNI05 manufactured by Neolite Kosan Co., Ltd. (talc with a volume average particle size of 5 μm measured by a laser diffraction method)
C-3: Millad 3988 manufactured by Miliken Japan Co., Ltd. (sorbitol-based nucleating agent)

Other ingredients are the following additives.
Antioxidant: B225 manufactured by BASF
Neutralizing agent: Calcium stearate manufactured by Tannan Chemical Industry Co., Ltd.

The measurement results and evaluation results in Tables 2A and 2B are values measured and evaluated by the following methods.

<Liquidity MFR>
The MFR of the polypropylene resin composition was measured under conditions of a temperature of 230° C. and a load of 2.16 kg based on JIS K6921-2.

<Rigidity Tensile modulus>
According to JIS K6921-2, using an injection molding machine (FANUC ROBOSHOT S2000i manufactured by FANUC CORPORATION), the molten resin temperature is 200 ° C., the mold temperature is 40 ° C., the average injection speed is 200 mm / sec, the pressure holding time is 40 seconds, and the total cycle time is A multi-purpose test piece (type A1) defined in JIS K7139 was injection molded from the polypropylene resin composition under conditions of 60 seconds to obtain a test piece for measurement. According to JIS K7161-2, a precision universal testing machine (Autograph AG-X 10 kN) manufactured by Shimadzu Corporation was used to measure the tensile modulus under the conditions of a temperature of 23° C., a relative humidity of 50%, and a test speed of 1 mm/min.

<Low temperature impact resistance, plane impact strength>
Using a puncture impact tester (Hydroshot HITS-P10 manufactured by Shimadzu Corporation), the surface impact strength of the test piece for measurement was measured at −20° C. according to JIS K7211-2. The larger the face impact strength value, the better the impact resistance.

<Food hygiene n-heptane elution test evaporation residue>
A press sheet having a length × width × thickness of 80 × 80 × 0.5 mm is pressed using a 36t press molding machine manufactured by Shoji Co., Ltd. under the conditions of a hot plate temperature of 230 ° C., a cooling plate temperature of 30 ° C., and a pressure of 5 MPa. Obtained. Using this pressed sheet as a test piece, it was immersed in 250 ml of n-heptane (25° C.) and allowed to stand for 1 hour. Next, n-heptane (test solution) obtained by removing the test piece was transferred to an eggplant-shaped flask, concentrated under reduced pressure to a few ml, and the flask was washed twice with about 5 ml of heptane. was placed in a heat-resistant glass evaporating dish of known weight that had been previously dried at 105° C., and evaporated to dryness on a water bath. Next, it was dried at 105° C. for 2 hours, allowed to cool in a desiccator, and weighed to determine the weight difference between the front and back of the evaporating dish to calculate the amount of evaporation residue (unit: μg/ml). The above tests were conducted according to the method described in Notification No. 370 of the Ministry of Health and Welfare.
When the calculated amount of evaporation residue was 35 μg/ml or less, it was determined that the standard was met. The smaller the amount, the better.

<Moldability>
Injection moldability in high cycle (cycle time: 10 seconds) was evaluated.
Using an injection molding machine (SE230HY, manufactured by Sumitomo Heavy Industries, Ltd.), a polypropylene-based resin composition was molded under the conditions of a cylinder setting temperature of 250°C, a mold temperature of 15°C, and a cycle time of 10 seconds. , 0.5 mm thick drink container (container suitable for holding a liquid for eating and drinking). In order to remove the container from the mold, the bottom of the container was pushed out at a speed of 100 mm/sec with an ejector pin of 15 mmφ. At this time, evaluation was made according to the following criteria.
"◯": Molded without problems.
"Poor": Since the rigidity of the container is too low, it buckles due to the force of the ejector pin when the container is removed from the mold. Alternatively, the fluidity is too low, resulting in short shots and inability to mold perfectly shaped containers.

<Breaking strain of container with in-mold label>
A container having the same shape was formed in the same manner as described above. At this time, a rectangular in-mold label film (thickness: 60 μm, material: PP) is loaded into the mold, and an in-mold label (hereinafter referred to as a label) that wraps around the outer peripheral surface of the container is attached. rice field. On the side surface of the container after molding, the film is wrapped around the side surface of the container from one short side of the rectangular film to the other short side, and the one short side and the other short side overlap each other and are sealed to each other. It is This sealed portion is the mating surface (seam) of the label, and is the location where breakage is likely to occur when the container is crushed.
As shown in FIGS. 1 and 2, using a Hydro Shot (HIPS-P10, manufactured by Shimadzu Corporation) apparatus, the container is placed horizontally on a support table whose temperature is adjusted to 0° C., and a striker (20 mmφ) A cylindrical push rod) was pressed against the label near the center of the side of the container to compress and deform at high speed, and the compression distance (unit: mm) of the striker until breakage occurred along the label mating surface was measured. A longer distance indicates that the container with the label is more resistant to deformation and cracking. FIG. 1 shows the inside of the tester at the start of the test, and FIG. 2 shows the inside of the tester after compressive deformation.
The conditions for pressing the striker were as follows.
Impact velocity: 1m/sec
Maximum reach: 80.5mm
Number of sampling points: 1200 points Sampling time: 50 μsec
Data collection time: 600msec
Number of n: 5

<Appearance>
Using an injection molding machine (α100C, manufactured by Fanuc Co., Ltd.), the polypropylene-based resin composition was molded into a flat plate of 130 mm square and 2 mm thick under the conditions of a cylinder set temperature of 230° C. and a mold temperature of 40° C. Before evaluating the appearance of the flat plate as a test piece, it was conditioned by storing it in a room at a temperature of 23±2° C. and a relative humidity of 50±5% for 48 hours. Next, the test piece was visually observed and evaluated according to the following criteria.
"◯": Good: No appearance defects of the molded product ("Gel": granular surface roughness due to aggregation of the high-viscosity component in the component (a2)) is not observed.
"X": Poor: Poor external appearance of molded product ("Gel": Granular surface roughness due to aggregation of high-viscosity component in component (a2)) is observed.

<Odor>
A container having the same shape was formed in the same manner as described above. The tester smelled the container and evaluated the odor according to the following criteria.
"◯": No odor is generated.
"△": Odor generation is extremely small.
"X": Odor is generated.

<Productivity>
"◯": The manufacturing process of the polypropylene-based resin was stable, and the product could be produced.
"Poor": The manufacturing process of the polypropylene-based resin was not stable, and the production was difficult.

≪Action and effect≫
Since the injection-molded articles (drink containers, etc.) of Examples 1 to 20 use a polypropylene-based resin composition having predetermined physical properties, they have excellent rigidity, surface impact strength, moldability, and durability on the mating surface of the in-mold label. (breaking strain), appearance, odor, and productivity, as well as food hygiene required for food containers and food packaging applications (n-heptane elution test evaporation residue is below the standard value (here, 35 μg / ml).
In order not only to achieve the above-mentioned excellent balance, but also to satisfy food sanitation standards, the present inventors had to review the formulation of the entire composition. In other words, in order to reduce the evaporation residue in the n-heptane elution test, it was necessary to suppress the content of ethylene-derived units in the component (a2) to a predetermined value or less. For example, the content of ethylene-derived units in component (a2) affects the rubbery properties of the composition, so if it is too small, the impact resistance at low temperatures tends to deteriorate. For this reason, by diligently adjusting other parameters such as the XSIV value of component (a1) + component (a2), it is possible to satisfy food sanitation standards and balance other mechanical properties at a high level. completed the invention.

Comparative Example 1 did not contain the component (C), had poor rigidity, and caused problems when removing the injection-molded article from the mold. That is, due to its low rigidity, it buckled when it was pushed out of the mold with an ejector pin.
In Comparative Example 2, the content of component (B) was large, the rigidity was poor, and problems occurred when the injection-molded article was removed from the mold. That is, due to its low rigidity, it buckled when it was pushed out of the mold with an ejector pin.
In Comparative Example 3, the content of component (a2) in component (A) is small, the surface impact strength is weak, and there is concern about use in a low temperature environment.
In Comparative Example 4, the content of component (a2) in component (A) was large, and production was difficult.
Comparative Example 5 had a large content of ethylene-derived units in the component (a2) and did not meet the standards for food sanitation.
In Comparative Example 6, the content of ethylene-derived units of the component (a2) was small, the surface impact strength was weak, and there was concern about use in a low-temperature environment.
In Comparative Example 7, the XSIV of component (a1) + component (a2) was small, and the production of component (A) was difficult.
In Comparative Example 8, the XSIV of component (a1)+component (a2) is large, the surface impact strength is weak, there is concern about use in a low temperature environment, and the appearance of the injection molded product surface is poor.
In Comparative Example 9, the fluidity of component (a1)+component (a2) and the fluidity of the resin composition were low, and moldability was poor. That is, a short shot problem arose.
In Comparative Example 10, the fluidity of component (a1)+component (a2) and the fluidity of the resin composition are high, the surface impact strength is weak, and there is concern about use in a low temperature environment.
In Comparative Example 11, the content of ethylene-derived units of component (a1) was large, the rigidity was poor, and a problem occurred when the injection-molded article was removed from the mold.
In Comparative Example 12, the component (a1) has a wide molecular weight distribution, and there is concern about resistance to compression deformation when an in-mold label is provided.

Claims (9)

A polypropylene resin (A) comprising a continuous phase comprising a propylene polymer (a1) and a rubber phase comprising a copolymer (a2) of ethylene and an α-olefin having 3 to 10 carbon atoms;
A polypropylene-based resin composition containing an optional ethylene/α-olefin copolymer (B), which is a copolymer of ethylene and an α-olefin having 4 to 10 carbon atoms, and a nucleating agent (C),
The content of the polypropylene resin (A) is 90% by mass or more and less than 100% by mass with respect to the total mass of the polypropylene resin composition,
The content of the ethylene/α-olefin copolymer (B) is 0 to 10% by mass with respect to the total mass of (A) and (B),
The content of the nucleating agent (C) is 0.02 parts by mass or more and 0.5 parts by mass or less with respect to the total mass of 100 parts by mass of the (A) and the (B),
MFR of the polypropylene-based resin composition at a temperature of 230° C. and a load of 2.16 kg is 40 to 120 g/10 minutes,
The ratio ( _Mw / _Mn ) of the weight average molecular weight _Mw to the number average molecular weight _Mn of the propylene polymer (a1) is less than 7,
The content of ethylene-derived units in the propylene polymer (a1) is 1.5% by mass or less with respect to the total mass of the propylene polymer (a1),
The content of the copolymer (a2) is 24 to 43% by mass with respect to the total mass of the polypropylene resin (A),
The ethylene-derived unit content in the copolymer (a2) is 25 to 60% by mass with respect to the total mass of the copolymer (a2),
The xylene-soluble portion of the polypropylene resin (A) has an intrinsic viscosity of 0.5 to 3.0 dl/g in tetrahydronaphthalene at 135°C,
The MFR of the polypropylene resin (A) at a temperature of 230° C. and a load of 2.16 kg is 40 to 120 g/10 minutes.
A polypropylene-based resin composition. The propylene polymer (a1) and the copolymer (a2) are mixed by polymerization, and the polypropylene resin (A) is produced using a catalyst containing the following components (a) to (c). 2. The polypropylene-based resin composition according to claim 1, which is a polymerized mixture.
(a) Solid catalysts containing magnesium, titanium, halogen, and phthalate compounds as electron donor compounds (b) Organoaluminum compounds (c) Organosilicon compounds as external electron donor compounds 3. The method for producing a polypropylene-based resin composition according to claim 1 or 2, wherein, in the presence of the propylene polymer (a1), ethylene A method for producing a polypropylene-based resin composition, comprising a step of polymerizing a monomer and an α-olefin monomer having 3 to 10 carbon atoms to obtain the polypropylene-based resin (A).
(a) Solid catalyst containing magnesium, titanium, halogen, and a phthalate compound as an electron donor compound as essential components (b) Organoaluminum compound (c) Organosilicon compound as an external electron donor compound An injection molded article obtained by injection molding the polypropylene resin composition according to claim 1 or 2. 5. The injection molded article according to claim 4, wherein the thinnest portion has a thickness of 1 mm or less. 6. The injection-molded article according to claim 4, wherein the article is molded in the shape of a container, and the thickness of the side wall of the container is 0.1 to 1 mm. The injection molded body according to any one of claims 4 to 6, which is molded in the shape of a container and provided with an in-mold label on the side wall of said container. 8. The injection molded article according to any one of claims 4 to 7, which is used in a low temperature environment of -10°C or lower. 9. The injection molded article according to any one of claims 4 to 8, which is used as a container or package in contact with food.

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