Polypropylene resin composition and foam molded article

Abstract

One embodiment of the present invention relates to a polypropylene resin composition or a foam molded article containing the polypropylene resin composition, the polypropylene resin composition (X) satisfies the condition (x-1) and contains 20-80 parts by mass (inclusive) of an impact-resistant polypropylene (A) satisfying the conditions (a-1) and (a-2), 10-40 parts by mass (inclusive) of an ethylene-based elastomer (B) satisfying the conditions (b-1) and (b-2), and 10-40 parts by mass (inclusive) of a talc inorganic filler (C). (a-1) The MFR measured at 230 DEG C under a load of 2.16 kg in accordance with ASTM D-1238 is from 60 g / 10 min to 300 g / 10 min (inclusive). (a-2) a propylene-ethylene copolymer containing a decane soluble fraction determined at 23 DEG C, the intrinsic viscosity [eta] of the propylene-ethylene copolymer being 4.1 dl / g to 10 dl / g (inclusive); (b-1) The MFR measured at 190 DEG C under a load of 2.16 kg in accordance with ASTM D-1238 is from 0.5 g / 10 min to 30 g / 10 min (inclusive). (b-2) the density is more than 0.85 g / cm < 3 > and less than 0.875 g / cm < (x-1) The content of a polypropylene component having a molecular weight of 106.5 or more is less than 0.05 mass% with respect to 100 mass% of the polypropylene resin composition (X).

Description

Technical Field

[0001] One embodiment of the present invention relates to a polypropylene-based resin composition or a foamed molded product containing the polypropylene-based resin composition. Background Art

[0002] Polypropylene resin is widely used in various fields including daily necessities, housing, home appliances, automobile components, etc. due to its excellent moldability, physical property balance, recycling characteristics, and cost performance. In the field of automobile interior and exterior decoration components, foamed molded bodies of polypropylene and the like are sometimes used from the perspective of lightweight. As an example of a composition that can be used for the manufacture of such a foamed molded body, Patent Document 1 discloses a polypropylene resin composition for foaming, which comprises a resin composition containing 40 to 95% by mass of a propylene polymer (A) selected from at least one of a propylene homopolymer (A-1) and a propylene-ethylene copolymer (A-2) and 5 to 60% by mass of an ethylene-α-olefin copolymer (B) (wherein the total of (A) and (B) is set to 100% by mass) and a β-crystal nucleating agent. In addition, it is disclosed that the polypropylene resin composition for foaming can provide a foamed molded body with less occurrence of striped appearance defects called silver streaks.

[0003] When manufacturing foamed molded products, a core-back molding method is sometimes used. Regarding a polypropylene resin composition that can be used for the core-back molding method, Patent Document 2 discloses a linear polypropylene resin composition containing a strain-curable linear propylene-ethylene block copolymer and a foaming agent, wherein the linear propylene-ethylene block copolymer has specific physical properties and a specific composition such as a linear propylene polymer portion and a linear ethylene-propylene random copolymer portion and a melt flow rate exceeding 60g / 10min (MFR: 230°C, 2.16kg load). In Patent Document 2, as an effect of using such a linear polypropylene resin composition, it is disclosed that the bubbles at the flow front are not easy to break, the surface of the foamed molded product can be prevented from being uneven, and an injection foamed molded product with excellent surface appearance can be provided.

[0004] Patent document 3 discloses a polypropylene resin composition (X) for foam molding, which contains a polypropylene resin composition (A) and a foaming agent (B), wherein the polypropylene resin composition (A) has a sea-island structure including a polypropylene resin as a sea component and a thermoplastic resin as an island component, and as the polypropylene resin composition (A), a propylene-ethylene block copolymer having an MFR (230° C., 2.16 kg load) of 50 to 300 g / 10 min is exemplified. Patent document 3 discloses that by forming a sea component and an island component in the polypropylene resin composition (A) in such a way as to obtain a specific interfacial area amount of a specific value or more, turbulence and bubble entrainment are less likely to occur at the melt front (resin flow front end), thereby suppressing the generation of dimples on the surface of the injection foam molding.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2008-255191

[0008] Patent Document 2: Japanese Patent Application Publication No. 2010-144133

[0009] Patent Document 3: Japanese Patent Application Publication No. 2014-196398 Summary of the invention

[0010] After in-depth research, the inventors found that the composition described in Patent Document 1 has low impact resistance and is prone to pits (depressions). Although the molded body using the compositions of Patent Documents 2 and 3 can suppress the generation of pits, since the linear propylene-ethylene block copolymer polypropylene component of strain curing property is an essential component in the composition of Patent Document 2, in the composition of Patent Document 3, it is necessary to form the sea component and the island component of the polypropylene resin composition (A) in a manner to obtain a specific interfacial area above a specific value, the compositions described in Patent Documents 2 and 3 are all low in versatility and cannot be easily manufactured. Moreover, the compositions described in Patent Documents 2 and 3 are sometimes not suitable for the molding of components with long flow distances due to the large resistance during flow.

[0011] Since foams have lower impact resistance than non-foams, a resin composition that can be used to manufacture a molded body with excellent impact resistance is needed. In addition, in order to stably manufacture foams, a resin composition that can be easily manufactured and can suppress appearance defects such as flow marks, foaming defects, and pits is needed.

[0012] Therefore, one embodiment of the present invention provides a polypropylene resin composition that can be used to produce a molded body that is less likely to have appearance defects such as pits, foaming defects, and flow marks on the surface of the molded body and has excellent impact resistance, and can be produced relatively easily.

[0013] Technical solutions for solving technical problems

[0014] The configuration examples of the present invention are as follows.

[0015] In addition, in this specification, "A to B" which shows a numerical range means A or more and B or less.

[0016] [1] A polypropylene resin composition (X) comprising:

[0017] 20 parts by mass or more and 80 parts by mass or less of impact-resistant polypropylene (A) satisfying the following conditions (a-1) and (a-2);

[0018] 10 parts by mass or more and 40 parts by mass or less of an ethylene-based elastomer (B) satisfying the following conditions (b-1) and (b-2); and

[0019] 10 parts by mass or more and 40 parts by mass or less of an inorganic filler (C), wherein the inorganic filler (C) is talc (wherein the total amount of the impact-resistant polypropylene (A), the ethylene-based elastomer (B) and the inorganic filler (C) is 100 parts by mass),

[0020] The polypropylene resin composition (X) satisfies the following condition (x-1):

[0021] (a-1) MFR measured at 230°C and 2.16 kg load in accordance with ASTM D-1238 is 60 g / 10 min or more and 300 g / 10 min or less;

[0022] (a-2) a propylene-ethylene copolymer containing a decane-soluble portion at 23°C, wherein the intrinsic viscosity [η] of the propylene-ethylene copolymer measured in decalin at 135°C is 4.1 dl / g or more and 10 dl / g or less;

[0023] (b-1) MFR measured at 190°C and 2.16 kg load in accordance with ASTM D-1238 is 0.5 g / 10 min or more and 100 g / 10 min or less;

[0024] (b-2) Density: 0.85 g / cm 3 Above 0.875g / cm 3 the following;

[0025] (x-1) relative to 100% by mass of the polypropylene resin composition (X) above, the molecular weight is 106.5 The content of the above polypropylene component is less than 0.05 mass %.

[0026] [2] The polypropylene resin composition (X) according to [1], wherein the impact polypropylene (A) further satisfies at least one of the following conditions (a-1-1), (a-2-1) and (a-5),

[0027] (a-1-1) MFR measured at 230°C and 2.16 kg load in accordance with ASTM D-1238 is 77 g / 10 min or more and 200 g / 10 min or less;

[0028] (a-2-1) the propylene-ethylene copolymer contains a decane-soluble portion at 23°C, wherein the intrinsic viscosity [η] of the propylene-ethylene copolymer measured in decalin at 135°C is 4.2 dl / g or more and 5.9 dl / g or less;

[0029] (a-5) When the mass of the above-mentioned impact-resistant polypropylene (A) is set to 100 mass%, the content of the propylene-ethylene copolymer contained in the above-mentioned impact-resistant polypropylene (A), which is determined as the decane-soluble portion (Dsol) at 23°C, is 5 to 30 mass%.

[0030] [3] The polypropylene resin composition (X) as described in [1] or [2], wherein the content of the propylene-ethylene copolymer in the polypropylene resin composition (X) is not less than 5 parts by mass and not more than 30 parts by mass (wherein the total amount of the impact-resistant polypropylene (A), the ethylene-based elastomer (B) and the inorganic filler (C) is set to 100 parts by mass).

[0031] [4] The polypropylene resin composition (X) according to any one of [1] to [3], wherein the ethylene elastomer (B) is a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms.

[0032] [5] The polypropylene resin composition (X) according to any one of [1] to [4], wherein the content of the impact polypropylene (A) is 25 parts by mass or more and 74 parts by mass or less,

[0033] The content of the ethylene-based elastomer (B) is 10 parts by mass or more and 40 parts by mass or less,

[0034] The content of the inorganic filler (C) is 16 parts by mass or more and 35 parts by mass or less (assuming that the total amount of the impact polypropylene (A), the ethylene-based elastomer (B) and the inorganic filler (C) is 100 parts by mass).

[0035] [6] A foamed molded product comprising the polypropylene resin composition (X) according to any one of [1] to [5], obtained by molding using a foaming agent (D).

[0036] [7] An automobile interior and exterior member comprising the polypropylene resin composition (X) according to any one of [1] to [5].

[0037] [8] An arch molding comprising the polypropylene resin composition (X) according to any one of [1] to [5].

[0038] [9] A door sill molding comprising the polypropylene resin composition (X) according to any one of [1] to [5].

[0039]

[10] A method for producing a foamed molded article, comprising the step of foaming the polypropylene resin composition (X) according to any one of [1] to [5].

[0040]

[11] The method for producing a foamed molded article according to

[10] , wherein the method is performed by injection foam molding or core-back injection molding.

[0041] Effects of the Invention

[0042] According to one embodiment of the present invention, a polypropylene resin composition can be provided that can be used to produce a molded body that is not prone to appearance defects such as pits, foaming defects, flow marks, etc. on the surface of the molded body and has excellent impact resistance, and can be produced relatively easily. DETAILED DESCRIPTION

[0043] 《Polypropylene resin composition (X)》

[0044] A polypropylene resin composition (X) (hereinafter also referred to as "resin composition (X)") according to one embodiment of the present invention contains an impact polypropylene (A) satisfying prescribed conditions, an ethylene elastomer (B) satisfying prescribed conditions, and may further contain an inorganic filler (C).

[0045] <Impact-resistant polypropylene (A)>

[0046] The impact polypropylene (A) used in the resin composition (X) satisfies the following conditions (a-1) and (a-2), and preferably further satisfies one or more of the following conditions (a-3) to (a-5).

[0047] [Condition(a-1)]

[0048] The melt flow rate (hereinafter also referred to as MFR) measured at 230°C and a load of 2.16 kg in accordance with ASTM D-1238 is 60 to 300 g / 10 min, preferably 60 to 250 g / 10 min, more preferably 60 to 200 g / 10 min or less, further preferably 70 to 180 g / 10 min, particularly preferably 77 to 160 g / 10 min, and particularly preferably 90 to 155 g / 10 min.

[0049] When the MFR of the impact-resistant polypropylene (A) is within the above range, the appearance of a molded product obtained from the resin composition (X) containing the impact-resistant polypropylene (A) becomes good, and the moldability and physical properties of the resin composition (X) are good.

[0050] [Condition (a-2)]

[0051] The impact-resistant polypropylene (A) comprises a propylene-ethylene copolymer determined as a decane-soluble portion (Dsol) at 23°C, and the intrinsic viscosity (135°C, decalin) [η] of the propylene-ethylene copolymer is 4.1 to 10 dl / g, preferably 4.1 to 8.0 dl / g, more preferably 4.2 to 7.0 dl / g, and further preferably 4.5 to 5.9 dl / g.

[0052] When the intrinsic viscosity [η] of the propylene-ethylene copolymer is within the above range, the appearance of a molded article obtained from the resin composition (X) containing the impact polypropylene (A) is good, and the moldability of the resin composition (X) is also good.

[0053] [Condition (a-3)]

[0054] The impact polypropylene (A) preferably comprises a propylene homopolymer determined as a decane insoluble portion (Dinsol) at 23°C, and the MFR (230°C, 2.16 kg load) of the propylene homopolymer is preferably 200 to 800 g / 10 min, more preferably 250 to 600 g / 10 min, and further preferably 310 to 550 g / 10 min. When the MFR of the propylene homopolymer is within the above range, the appearance of the molded article becomes good. It should be noted that the method for measuring the MFR of the propylene homopolymer is as described in the examples described below.

[0055] [Condition (a-4)]

[0056] The molecular weight of the impact-resistant polypropylene (A) is 100% by mass. 6.5 The amount of the above polypropylene component is preferably less than 0.05% by mass, more preferably less than 0.03% by mass, further preferably less than 0.02% by mass, and particularly preferably less than 0.01% by mass. In addition, the impact-resistant polypropylene (A) may not contain a molecular weight of 106.5 The above polypropylene composition.

[0057] When the molecular weight of the impact polypropylene (A) is 10 6.5 When the amount of the above polypropylene component is within the above range, the generation of pits can be effectively suppressed in the foamed molded product obtained from the resin composition (X) containing the impact-resistant polypropylene (A). 6.5 The amount of the above polypropylene component can be adjusted according to, for example, the type of catalyst used in the production of the impact polypropylene (A). 6.5 The method for measuring the amount of the above polypropylene component is as described in the examples given below.

[0058] [Condition (a-5)]

[0059] The content of the propylene-ethylene copolymer determined as the decane-soluble portion (Dsol) at 23°C contained in the impact-resistant polypropylene (A) is not particularly limited as long as the content of the propylene-ethylene copolymer in the resin composition (X) can be adjusted to the range described below. When the mass of the impact-resistant polypropylene (A) is set to 100 mass%, it is preferably 5 to 35 mass%, more preferably 9 to 30 mass%, and further preferably 12 to 25 mass%. In addition, the total of the decane-soluble portion (Dsol) and the decane-insoluble portion (Dinsol) is set to 100 mass%. When the amount of the propylene-ethylene copolymer contained in the impact-resistant polypropylene (A) is within the above range, it is easy to adjust the content of the propylene-ethylene copolymer in the resin composition (X) to the specified range.

[0060] The content of the impact polypropylene (A) in the resin composition (X) is 20 to 80 parts by mass (wherein the total amount of the impact polypropylene (A), the ethylene-based elastomer (B) and the inorganic filler (C) is 100 parts by mass), preferably 25 to 78 parts by mass, more preferably 30 to 78 parts by mass, further preferably 40 to 76 parts by mass, particularly preferably 40 to 74 parts by mass, and particularly preferably 45 to 68 parts by mass. When the content of the impact polypropylene (A) is within the above range, the appearance and physical properties of the molded article obtained from the resin composition (X) are good, and the moldability of the resin composition (X) is good.

[0061] The impact polypropylene (A) can be used alone or in combination of two or more. When two or more impact polypropylenes are used, it is preferred that the various impact polypropylenes (A) used satisfy the above conditions (a-1) to (a-2). In addition, when two or more impact polypropylenes are used, the total amount of the impact polypropylenes (A) used can be adjusted to satisfy the above content range.

[0062] The impact polypropylene (A) may contain at least one or more biomass-derived monomers. The biomass-derived monomers contained in the impact polypropylene (A) may be biomass-derived α-olefins, such as biomass-derived ethylene and biomass-derived propylene. The same monomers constituting the polymer contained in the impact polypropylene (A) may be only biomass-derived monomers, or may include both biomass-derived monomers and fossil fuel-derived monomers. It should be noted that biomass-derived α-olefins such as biomass-derived ethylene and biomass-derived propylene can be obtained by known methods.

[0063] The monomers derived from biomass refer to monomers made from all renewable natural raw materials, including fungi, yeast, algae and bacteria, from plants or animals, and their residues. When all carbons contained in the monomer are taken as 1, the total carbon content is 10. -12 The ratio of about 14 In addition, in biomass-derived monomers, the biomass carbon concentration (pMC, percent Modern Carbon) measured according to ASTM D 6866 is about 100 (pMC).

[0064] From the viewpoint of reducing environmental load, it is preferred that the impact polypropylene (A) contains monomers derived from biomass. When the polymerization catalyst, polymerization temperature and other polymer production conditions are the same, even if the raw material olefin contains olefins derived from biomass, except for 10% of all carbon atoms, -12 The ratio of about 14 The molecular structure other than the C isotope is equivalent to that of the impact polypropylene (A) composed of monomers derived from fossil fuels. Therefore, there is no difference in performance between the impact polypropylene (A) containing monomers derived from biomass and the impact polypropylene (A) composed of monomers derived from fossil fuels.

[0065] The impact polypropylene (A) may contain a monomer derived from chemical recycling. The monomer constituting the polymer may be an α-olefin derived from chemical recycling, for example, ethylene derived from chemical recycling and propylene derived from chemical recycling.

[0066] The same monomers constituting the polymer contained in the impact polypropylene (A) may be monomers derived solely from chemical recycling sources, or may include monomers derived from chemical recycling sources and monomers derived from fossil fuels and / or monomers derived from biomass. Monomers derived from chemical recycling sources can be obtained by existing known methods. From the viewpoint of reducing environmental load (mainly reducing waste), it is preferred that the impact polypropylene (A) involved in the present invention contains monomers derived from chemical recycling sources. Even if the raw material monomers contain monomers derived from chemical recycling sources, since the monomers derived from chemical recycling sources are monomers that recover monomer units such as propylene by depolymerizing, thermally cracking, etc. polymers such as waste plastics, and monomers manufactured using the monomers as raw materials, as long as the polymer manufacturing conditions such as polymerization catalysts, polymerization processes, and polymerization temperatures are the same, the molecular structure is also the same as the impact polypropylene (A) composed of monomers derived from fossil fuels. Therefore, the properties do not change.

[0067] <Ethylene elastomer (B)>

[0068] The ethylene-based elastomer (B) used in the resin composition (X) satisfies the following conditions (b-1) and (b-2), and preferably further satisfies the following condition (b-3).

[0069] [Condition (b-1)]

[0070] The MFR measured at 190°C and 2.16 kg load according to ASTM D-1238 is 0.5 to 30 g / 10 min, preferably 0.9 to 30 g / 10 min, and more preferably 10 to 30 g / 10 min. When the MFR of the ethylene elastomer (B) exceeds 30 g / 10 min, the impact resistance tends to decrease. When the MFR of the ethylene elastomer (B) is within the above range, the moldability of the resin composition (X) containing the ethylene elastomer (B) is good, and the appearance and impact resistance of the molded body obtained from the resin composition (X) are good.

[0071] [Condition (b-2)]

[0072] The density of the ethylene elastomer (B) is 0.85 to 0.875 g / cm 3 , preferably 0.85 to 0.874 g / cm 3 , more preferably 0.855 to 0.873 g / cm 3 When the density is less than 0.85g / cm 3 When the foaming property is poor, the foaming property is sometimes poor. 3 When the density of the ethylene-based elastomer (B) is within the above range, the moldability and impact resistance of the obtained molded article become good.

[0073] [Condition (b-3)]

[0074] The ethylene-based elastomer (B) is preferably a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms. Specific examples of α-olefins having 3 to 10 carbon atoms copolymerized with ethylene include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-heptene, 1-octene, 1-nonene, and 1-decene. Two or more of these α-olefins may also be used in combination. Among them, 1-butene and 1-octene are particularly preferred because the impact resistance of the resulting molded body is improved.

[0075] The content of the ethylene elastomer (B) in the resin composition (X) is 10 to 40 parts by mass (wherein the total amount of the impact-resistant polypropylene (A), the ethylene elastomer (B) and the inorganic filler (C) is 100 parts by mass), preferably 10 to 35 parts by mass, more preferably 10 to 30 parts by mass, and further preferably 16 to 30 parts by mass. When the content of the ethylene elastomer (B) is within the above range, the moldability of the resin composition (X) is good, and the appearance and impact resistance of the molded article obtained from the resin composition (X) are good.

[0076] The ethylene-based elastomer (B) can be used alone or in combination of two or more. When using two or more, the various ethylene-based elastomers (B) preferably used satisfy the above conditions (b-1) to (b-2). In addition, when using two or more, the total amount of the ethylene-based elastomer (B) used can be adjusted to satisfy the range of the above content.

[0077] <Inorganic filler (C)>

[0078] The inorganic filler (C) used as an embodiment of the present invention is not particularly limited, and examples thereof include heavy calcium carbonate, light calcium carbonate, talc, wollastonite, MOS-HIGE (registered trademark), carbon fiber, glass fiber, magnesium carbonate, mica, kaolin, calcium sulfate, barium sulfate, titanium dioxide, white carbon black, carbon black; metal oxides such as aluminum oxide, magnesium oxide, silicon oxide, zinc oxide; metal hydroxides such as aluminum hydroxide and magnesium hydroxide; metal nitrides such as boron nitride and aluminum nitride; metal nitrogen oxides such as aluminum oxynitride; metal carbides such as silicon carbide; metals or metal alloys such as gold, silver, copper, and aluminum; natural graphite, artificial graphite, and expanded graphite. These fillers can be used alone or in combination of two or more. Among them, talc is most preferably used.

[0079] The shape of talc is not particularly limited, and a product having a number-based particle size distribution D50 (μm) of usually 0.5 to 20 μm, preferably 1.0 to 15 μm, as measured by a laser diffraction scattering method is preferably used.

[0080] The content of the inorganic filler (C) in the resin composition (X) is 10 to 40 parts by mass (wherein the total amount of the impact-resistant polypropylene (A), the ethylene-based elastomer (B) and the inorganic filler (C) is 100 parts by mass), preferably 12 to 35 parts by mass, more preferably 14 to 30 parts by mass, and further preferably 16 to 25 parts by mass. When the content of the inorganic filler (C) is within the above range, the balance between the flexural modulus and the impact resistance of the molded article formed from the resin composition (X) becomes good.

[0081] <Other ingredients>

[0082] The resin composition (X) may further contain various additives as required within the scope not impairing the purpose of the present invention. Specific examples of the additives include nucleating agents, antioxidants, hydrochloric acid absorbers, heat stabilizers, weather stabilizers, light stabilizers, ultraviolet absorbers, lubricants, antistatic agents, flame retardants, pigments, dyes, dispersants, copper inhibitors, neutralizers, plasticizers, crosslinking agents, fluidity improvers (peroxides, etc.), weld strength improvers, natural oils, synthetic oils, waxes, etc.

[0083] <Resin composition (X)>

[0084] The resin composition (X) satisfies the following condition (x-1), and preferably further satisfies the following condition (x-2).

[0085] [Condition (x-1)]

[0086] The molecular weight of the resin composition (X) is 100% by mass. 6.5 The amount of the polypropylene component is less than 0.05% by mass, preferably less than 0.03% by mass, and more preferably less than 0.01% by mass. It should be noted that the resin composition (X) may not contain polypropylene with a molecular weight of 10 6.5 The above polypropylene composition.

[0087] When the molecular weight contained in the resin composition (X) is 10 6.5 When the amount of the polypropylene component is within the above range, the foamed molded article obtained from the resin composition (X) can effectively suppress the generation of pits. 6.5 The amount of the polypropylene component can be adjusted by, for example, using a polypropylene having a molecular weight of 10 6.5 The molecular weight is 10 6.5 The method for measuring the amount of the above polypropylene component is as described in the examples given below.

[0088] [Condition (x-2)]

[0089] The content of the propylene-ethylene copolymer in the resin composition (X), which is determined as the decane-soluble portion (Dsol) at 23°C, is preferably 1 to 30 parts by mass (wherein the total amount of the impact-resistant polypropylene (A), the ethylene-based elastomer (B) and the inorganic filler (C) is set to 100 parts by mass), more preferably 3 to 30 parts by mass, and further preferably 5 to 30 parts by mass. It should be noted that the content of the above-mentioned propylene-ethylene copolymer is a value obtained by the method described in the examples. When the content of the above-mentioned propylene-ethylene copolymer is within the above-mentioned range, the moldability of the resin composition (X) is excellent, and the appearance and impact resistance of the molded body obtained from the resin composition (X) are good.

[0090] <Method for producing resin composition (X)>

[0091] The resin composition (X) can be produced by melt-kneading the impact polypropylene (A), the ethylene-based elastomer (B), the inorganic filler (C), and, if necessary, the other additives mentioned above using a conventionally known mixing device such as a kneader.

[0092] <Foamed Molded Article>

[0093] The foamed molded article according to one embodiment of the present invention is produced using the resin composition (X). That is, the foamed molded article according to one embodiment of the present invention is obtained by adding a foaming agent (D) to the resin composition (X) and molding the resultant.

[0094] The foaming agent (D) used in the manufacture of the foamed molded article according to one embodiment of the present invention is not particularly limited, and known chemical foaming agents and physical foaming agents can be used. The amount of the foaming agent (D) added is preferably 0.1 to 10 parts by mass, more preferably 0.2 to 8 parts by mass, relative to 100 parts by mass of the resin composition (X).

[0095] The chemical foaming agent may be an inorganic compound or an organic compound, and two or more kinds of compounds may be used. Examples of inorganic compounds used as chemical foaming agents include bicarbonates such as sodium bicarbonate. Examples of organic compounds used as chemical foaming agents include polycarboxylic acids such as citric acid, azo compounds such as azodicarbonamide (ADCA), and the like.

[0096] Examples of physical foaming agents include inert gases such as nitrogen and carbon dioxide, volatile organic compounds, etc. Among them, carbon dioxide, nitrogen or a mixture thereof in a supercritical state is preferably used. Two or more physical foaming agents may be used in combination, or a chemical foaming agent and a physical foaming agent may be used in combination.

[0097] When a physical foaming agent is used, it is preferred to place the physical foaming agent in a supercritical state and mix it with the molten resin composition (X). Since the physical foaming agent in a supercritical state has high solubility in the resin and can be uniformly diffused into the molten polypropylene resin composition in a short time, a foamed molded article having a high foaming ratio and a uniform foamed cell structure can be obtained.

[0098] The step of mixing the physical foaming agent with the polypropylene resin composition in a molten state includes a step of injecting the physical foaming agent into a nozzle or a cylinder of an injection molding device.

[0099] Specific examples of the method for foam-molding the resin composition (X) include known methods such as injection foam molding, press foam molding, extrusion foam molding, and press foam molding.

[0100] The foam molded body according to one embodiment of the present invention can be formed into a decorative foam molded body by attaching a skin material to the surface of the foam molded body by insert molding, bonding, or the like.

[0101] The molding die used for injection foam molding is preferably composed of a fixed mold and a movable mold, and they are in a clamped state when the injection-filled resin composition (X) is injected. In addition, the mold cavity can be expanded by retreating the movable mold (retracting the core) to increase the volume of the mold cavity. Preferably, after injection filling, it is placed for a suitable time to increase the volume of the mold cavity. The core movement speed during the core withdrawal can be appropriately determined according to the thickness of the molded body, the type of resin, the type of foaming agent, the mold temperature, and the resin temperature.

[0102] The temperature of the resin composition (X) and the mold temperature during injection molding of the resin composition (X) vary depending on the thickness of the molded body to be manufactured, but the temperature generally used in the molding of polypropylene resins can be appropriately applied. Specifically, for example, the temperature of the resin composition (X) during injection is generally 180 to 250° C., preferably 200 to 220° C. The surface temperature of the fixed mold and the movable mold is generally 10 to 100° C., preferably 30 to 80° C.

[0103] In the foamed molded body obtained by foaming the resin composition (X), by adjusting the balance between the viscosity of the polypropylene component and the viscosity of the ethylene-based elastomer, it is not easy to produce appearance defects such as pits, foaming defects, and flow marks on the surface of the molded body formed by the resin composition (X). In addition, when the resin composition (X) is filled into the mold cavity, the pressure change at the flow front of the resin composition (X) (the front end of the flow of the molten resin composition (X)) is small, so it is not easy to pulsate or bend the flow front. Therefore, it can be inferred that: bubbles are not easy to be generated due to pressure changes, the orientation difference of the ethylene-based elastomer becomes smaller, pits and foaming defects are not easy to be generated, and flow marks are not easy to be generated.

[0104] The molded article produced by the resin composition (X) can be applied to various applications such as automotive interior and exterior decoration components, substitutes for corrugated cardboard, electrical appliances, building materials, etc. As automotive interior and exterior decoration components, for example, arch molding, rocker molding, side sill protector, vehicle body back door, etc. can be cited, and arch molding and rocker molding are preferred.

[0105] Example

[0106] Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

[0107] <Raw materials>

[0108] The raw materials used in the following Examples and Comparative Examples are as follows.

[0109] [Impact-resistant polypropylene (A)]

[0110] “Impact polypropylene (A-1)”: MFR (230° C., 2.16 kg load) = 97 g / 10 min, ratio of room temperature decane soluble portion = 14.3% by mass, intrinsic viscosity [η] of room temperature decane soluble portion = 5.0 dl / g.

[0111] “Impact polypropylene (A-2)”: MFR (230° C., 2.16 kg load) = 144 g / 10 min, ratio of room temperature decane soluble portion = 13.4% by mass, intrinsic viscosity [η] of room temperature decane soluble portion = 4.8 dl / g.

[0112] “Impact polypropylene (A-3)”: MFR (230° C., 2.16 kg load) = 128 g / 10 min, ratio of room temperature decane soluble portion = 14.3% by mass, intrinsic viscosity [η] of room temperature decane soluble portion = 5.0 dl / g.

[0113] “Impact-resistant polypropylene (A-4)”: MFR (230° C., 2.16 kg load) = 79 g / 10 min, ratio of room temperature decane soluble portion = 12.9% by mass, intrinsic viscosity [η] of room temperature decane soluble portion = 4.4 dl / g.

[0114] In addition, in both the impact-resistant polypropylene (A) and the impact-resistant polypropylene (CA) described below, the room temperature decane-soluble portion is a decane-soluble portion at 23°C.

[0115] [Impact-resistant polypropylene (CA) used in comparative example]

[0116] “Impact polypropylene (CA-1)”: MFR (230° C., 2.16 kg load) = 129 g / 10 min, ratio of room temperature decane soluble portion = 14.4% by mass, intrinsic viscosity [η] of room temperature decane soluble portion = 2.7 dl / g.

[0117] “Impact polypropylene (CA-2)”: MFR (230° C., 2.16 kg load) = 107 g / 10 min, ratio of room temperature decane soluble portion = 15.9% by mass, intrinsic viscosity [η] of room temperature decane soluble portion = 3.3 dl / g.

[0118] “Impact polypropylene (CA-3)”: MFR (230°C, 2.16 kg load) = 56 g / 10 min, ratio of room temperature decane soluble portion = 12.2 mass %, intrinsic viscosity [η] of room temperature decane soluble portion = 4.9 dl / g.

[0119] [Ethylene elastomer (B)]

[0120] “Ethylene elastomer (B-1)”: ethylene-1-octene copolymer (EOR), manufactured by The Dow Chemical Company, ENGAGE (registered trademark) 8137, MFR (190° C., 2.16 kg load) = 13 g / 10 min, density = 0.864 g / cm 3 .

[0121] “Ethylene elastomer (B-2)”: ethylene-1-octene copolymer (EOR), manufactured by The Dow Chemical Company, ENGAGE (registered trademark) 8100, MFR (190° C., 2.16 kg load) = 1.0 g / 10 min, density = 0.870 g / cm 3 .

[0122] “Ethylene elastomer (B-3)”: ethylene-1-octene copolymer (EOR), manufactured by The Dow Chemical Company, ENGAGE (registered trademark) 8407, MFR (190° C., 2.16 kg load) = 30 g / 10 min, density = 0.870 g / cm 3.

[0123] [Ethylene-based elastomer (CB) used in comparative example]

[0124] “Ethylene-based elastomer (CB-1)”: ethylene-1-butene copolymer (EBR), LF675 manufactured by LG Chemical Co., Ltd., MFR (190°C, 2.16 kg load) = 14 g / 10 min, density = 0.877 g / cm 3 .

[0125] “Ethylene-based elastomer (CB-2)”: ethylene-1-butene copolymer (EBR), Tafmer (registered trademark) A-35050S manufactured by Mitsui Chemicals, Inc., MFR (190°C, 2.16 kg load) = 35 g / 10 min, density = 0.863 g / cm 3 .

[0126] “Ethylene-based elastomer (CB-3)”: ethylene-1-butene copolymer (EBR), Tafmer (registered trademark) A-35070S manufactured by Mitsui Chemicals, Inc., MFR (190°C, 2.16 kg load) = 35 g / 10 min, density = 0.870 g / cm 3 .

[0127] [Inorganic filler (C)]

[0128] “Inorganic filler (C-1)”: talc (manufactured by Asada Flour Mill Co., Ltd., trade name JM-209, number-based particle size distribution D50 (laser diffraction): 4 to 5 μm.

[0129] [Foaming agent (D)]

[0130] “Masterbatch of organic foaming agent (D-1)”: a masterbatch containing 10 to 20% by mass of ADCA (azodicarbonamide), manufactured by Eiwa Chemicals Co., Ltd., Polythlene EE206.

[0131] [additive]

[0132] “Nucleating agent”: a phosphate metal salt-based nucleating agent, manufactured by ADEKA Corporation, ADK STAB NA-11 (sodium 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate).

[0133] The composition and physical properties of each component used in Examples and Comparative Examples were measured by the following methods.

[0134] <Content of n-decane soluble fraction at 23°C>

[0135] Add 2.0000 g of impact-resistant polypropylene (A-1), 500 ml of decane and a heat-resistant stabilizer soluble in decane (a small amount) to a glass measuring container, stir with a stirrer under a nitrogen atmosphere and heat up to 150°C in two hours to dissolve the impact-resistant polypropylene (A-1). After maintaining the temperature at 150°C for 2 hours, slowly cool to 23°C in 8 hours. Filter the slowly cooled sample under reduced pressure with a glass filter. Collect 100 ml of the filtrate, dry the collected filtrate under reduced pressure to obtain a portion of the decane-soluble portion, and measure the mass. The proportion of the n-decane-soluble portion (Dsol) is determined by the following formula. It should be noted that in the following formula, a is the mass of the decane-soluble portion obtained by reduced pressure drying, and b is the mass of the impact-resistant polypropylene (A-1) added to the measuring container.

[0136] Ratio (mass %) of n-decane soluble part (Dsol) = (500×a) / (100×b)×100

[0137] The amount of the propylene-ethylene copolymer in the composition containing the impact-resistant polypropylene (A-1) is the product of the amount of the impact-resistant polypropylene (A-1) contained and the ratio of the n-decane-soluble portion.

[0138] The ratio of the n-decane soluble portion at 23° C. was determined for other impact polypropylenes in the same manner as for the impact polypropylene (A-1), and the content (parts by mass) of the propylene-ethylene copolymer in each composition of Examples and Comparative Examples was calculated using the obtained value.

[0139] <Intrinsic viscosity [η]>

[0140] The intrinsic viscosity [η] of the propylene-ethylene copolymer, which is determined as the n-decane soluble portion (Dsol), is measured in decalin at 135°C according to a conventional method. That is, about 20 mg of the decane soluble portion obtained by vacuum drying when determining the content of the n-decane soluble portion at 23°C is dissolved in 15 ml of decalin, and the specific viscosity ηsp is measured in an oil bath at 135°C. 5 ml of decalin solvent is added to the decalin solution for dilution, and the specific viscosity ηsp is measured in the same manner. This dilution operation is repeated twice, and the ηsp / C value when the concentration (C) is extrapolated to 0 is obtained as the intrinsic viscosity [η].

[0141] [η] = lim(ηsp / C)(C→0)

[0142] <Melt Flow Rate (MFR)>

[0143] The MFR of the impact polypropylenes (A-1) to (A-4) and (CA-1) to (CA-3) was measured at 230°C and a load of 2.16 kg in accordance with ASTM D-1238.

[0144] The MFR of the ethylene-based elastomers (B-1) to (B-3) and the ethylene-based elastomers (CB-1) to (CB-3) was measured under the conditions of 190°C and a load of 2.16 kg in accordance with ASTM D-1238.

[0145] The propylene homopolymer contained in the impact polypropylene (A-1) to (A-4) and the impact polypropylene (CA-1) to (CA-3) was separated from the impact polypropylene by the following separation treatment, and then the MFR was measured. The MFR of the propylene homopolymer was measured in accordance with ASTM D-1238 at 230°C and a load of 2.16 kg.

[0146] (Separation and treatment of propylene homopolymer)

[0147] 2.0000 g of the impact polypropylene (A-1), 500 ml of decane and a heat-resistant stabilizer soluble in decane (a small amount) were placed in a glass measuring container, and the temperature was raised to 150° C. over 2 hours while stirring with a stirrer in a nitrogen atmosphere to dissolve the impact polypropylene (A). After maintaining the temperature at 150° C. for 2 hours, the mixture was filtered under reduced pressure using a glass filter. The residue remaining on the glass filter was taken as the n-decane insoluble portion (Dinsol), i.e., the propylene homopolymer in the impact polypropylene (A-1).

[0148] The impact polypropylenes (A-2) to (A-4) and the impact polypropylenes (CA-1) to (CA-3) were also treated in the same manner as the impact polypropylene (A-1) to separate propylene homopolymers.

[0149] [Example 1]

[0150] <Preparation of resin composition (X1)>

[0151] A resin composition (X1) was obtained by mixing 61 parts by weight of impact polypropylene (A-1), 18.5 parts by weight of ethylene elastomer (B-1), and 20.5 parts by weight of inorganic filler (C-1). Thereafter, the resin composition (X1) was granulated to obtain pellets of the resin composition (X1).

[0152] <Determination of content of high molecular weight polypropylene component>

[0153] The molecular weight distribution of the sample for measurement was measured by gel permeation chromatography (GPC) under the following measurement conditions, and the molecular weight distribution of 10 6.5 The molecular weight of the resin composition (X1) is calculated by calculating the amount of the component composed of the homopolypropylene having a molecular weight of 6.5 The above polypropylene content.

[0154] GPC measurement equipment

[0155] Column: Two TOSO GMHHR-H(S)HT

[0156] Detector: RI detector for liquid chromatography WATERS150C

[0157] Measurement conditions

[0158] Solvent: 1,2,4-trichlorobenzene

[0159] Measurement temperature: 145°C

[0160] Flow rate: 1.0ml / min

[0161] Sample concentration: 5mg / 10ml

[0162] Injection volume: 300μl

[0163] Calibration Curve: Universal Calibration

[0164] Analysis program: HT-GPC (Ver.1.0)

[0165] <Impact Resistance Evaluation>

[0166] A non-foamed molded article was prepared by molding pellets of the resin composition (X1), and a test piece (with a notch) was prepared from the obtained non-foamed molded article in accordance with ISO 179. The obtained test piece was subjected to a Charpy impact test at a temperature of 23° C. in accordance with ISO 179. The obtained Charpy impact value was evaluated according to the following impact resistance evaluation criteria.

[0167] (Impact resistance evaluation standard)

[0168] ○: Charpy impact value exceeds 30kJ / m 2 .

[0169] ×: Charpy impact value is 30kJ / m 2 the following.

[0170] <Injection Foam Molding>

[0171] 2 parts by weight of a masterbatch of an organic foaming agent (D-1) are added to 100 parts by weight of pellets of the resin composition (X1). It should be noted that the numerical value of the column of the organic foaming agent (D-1) in the following Table 1 is the amount of the organic foaming agent (D-1) calculated as a product containing 20% ​​by weight of ADCA in the masterbatch of the organic foaming agent (D-1). After the pellets and the masterbatch of the organic foaming agent (D-1) are fully mixed, injection foaming molding is performed using an injection molding machine (J350ADS-460H model (mold clamping force 3440 kN) manufactured by Nippon Steel Works, Ltd.) under the following conditions.

[0172] <Injection Foam Molding Conditions>

[0173] Mould

[0174] Cavity dimensions: length 350mm, width 100mm, thickness 2.0mm.

[0175] Gate: Side gate thickness 1mm, width 6mm.

[0176] Barrel setting temperature: The temperatures of the 8 thermocouples were set to 190°C, 190°C, 205°C, 205°C, 190°C, 180°C, 160°C and 50°C from the nozzle side.

[0177] Mould surface temperature: 40℃.

[0178] Injection speed: 80mm / s.

[0179] Foaming molding conditions

[0180] Mold cavity gap during injection: 2.0mm

[0181] Gap between molds after foaming process: 3.0mm

[0182] Core withdrawal setting time: 0.05 seconds

[0183] Delay time for core removal after resin filling: 0 seconds

[0184] <Appearance Evaluation of Injection Molded Article>

[0185] [Flow mark evaluation]

[0186] The core-removing surface of the foamed molded article obtained by the above-mentioned injection foam molding method was visually confirmed to see whether flow marks (continuous gloss change) occurred. The confirmation results were evaluated according to the following evaluation criteria.

[0187] (Flow mark evaluation standard)

[0188] ○: No flow mark occurs between the gate position and the position 100 mm away from the gate.

[0189] ×: Flow marks occurred between the gate position and the position 100 mm away from the gate.

[0190] [Pit Evaluation]

[0191] Visually check whether a pit is formed between the gate position and the position 100 mm away from the gate. The check result is evaluated according to the following evaluation criteria.

[0192] (Pit Evaluation Standard)

[0193] ○: No visually observable pit was generated between the gate position and the position 100 mm away from the gate.

[0194] ×: A visually recognizable pit was generated between the gate position and a position 100 mm away from the gate.

[0195] [Foaming defect evaluation]

[0196] The foaming defect (large dent) at a position 100 mm from the end of the molded product was visually confirmed.

[0197] (Evaluation criteria for foaming defects)

[0198] ○: There is no depression of 10 mm or more between the end of the molded article and a position 100 mm away from the end.

[0199] ×: A depression of 10 mm or more occurred between the end of the molded article and a position 100 mm away from the end.

[0200] [Examples 2 to 4, Comparative Examples 1 to 6]

[0201] The types and amounts of the raw materials used are shown in Tables 1 and 2. The resin compositions used in the examples or comparative examples were prepared, and the obtained resin compositions were used instead of the resin composition (X1) to produce samples for impact resistance evaluation and foamed molded products. The impact resistance evaluation and foamed molded product evaluation were performed in the same manner as in Example 1. The obtained results are shown in Tables 1 and 2.

[0202] [Table 1]

[0203]

[0204] Dsol: Propylene-ethylene copolymer determined as the decane soluble fraction at 23°C.

[0205] Dinsol: Propylene homopolymer determined as the decane insoluble fraction at 23°C.

[0206] *The content of the propylene-ethylene copolymer in the composition is a value when the total amount of the impact polypropylene (A), the ethylene-based elastomer (B) and the inorganic filler (C) is 100 parts by mass.

[0207] **Molecular weight is 10 6.5 The above content of the polypropylene component is a value when the resin composition (X) is taken as 100 mass %.

[0208] [Table 2]

[0209]

[0210] Dsol: Propylene-ethylene copolymer determined as the decane soluble fraction at 23°C.

[0211] Dinsol: Propylene homopolymer determined as the decane insoluble fraction at 23°C.

[0212] *The content of the propylene-ethylene copolymer in the composition is a value when the total amount of the impact polypropylene (A), the ethylene-based elastomer (B) and the inorganic filler (C) is 100 parts by mass.

[0213] **Molecular weight is 10 6.5 The above content of the polypropylene component is a value when the resin composition (X) is taken as 100 mass %.

[0214] As shown in Table 1, in any of Examples 1 to 4, the impact resistance of the obtained foamed molded product is excellent. In addition, no flow marks or pits were confirmed on the surface of the foamed molded product, and no pits larger than 10 mm were generated. The results are inferred to be: due to the good viscosity balance between the polypropylene component and the ethylene-based elastomer component contained in the resin composition (X) molded in Examples 1 to 4, the pressure change at the flow front (the front end of the flow of the molten resin composition (X)) is small, and it is not easy to pulsate or bend the flow front. That is, it is inferred that: when the resin composition (X) is used, since the pressure change at the flow front is small, it is not easy to generate bubbles due to pressure changes. Moreover, it is inferred that: due to the good viscosity balance between the polypropylene component and the ethylene-based elastomer component, in the resin composition (X), the orientation difference of the ethylene-based elastomer at the flow front is small, and as a result, the generation of pits, the generation of foaming defects and the generation of flow marks are suppressed. Furthermore, it is inferred that in the resin composition (X), since the viscosity ratio between the polypropylene component and the ethylene elastomer component is good, the dispersion effect of the ethylene elastomer is good, and as a result, the foamed molded product obtained from the resin composition (X) has excellent impact resistance.

[0215] On the other hand, in Comparative Examples 1 and 2, the intrinsic viscosity of the propylene-ethylene copolymer component contained in the impact-resistant polypropylene is low, so the evaluation results of impact resistance and flow mark evaluation are poor. The density of the ethylene-based elastomer (CB-1) in Comparative Example 3 is high, and the dispersibility of the ethylene-based elastomer (CB-1) is poor, so the impact resistance is poor. Comparative Examples 4 and 5 have poor impact resistance and foaming defects due to the high MFR of the ethylene-based elastomer. In Comparative Example 6, since the MFR of the impact-resistant polypropylene is low, turbulence at the flow front is easily generated, resulting in pits on the surface of the molded body and foaming defects.

Claims

1. A polypropylene resin composition (X), characterized in that: contain: 20 parts by mass or more and 80 parts by mass or less of impact-resistant polypropylene (A) satisfying the following conditions (a-1) and (a-2); 10 parts by mass or more and 40 parts by mass or less of an ethylene-based elastomer (B) satisfying the following conditions (b-1) and (b-2); and 10 parts by mass or more and 40 parts by mass or less of an inorganic filler (C), wherein the inorganic filler (C) is talc, The total amount of the impact-resistant polypropylene (A), the ethylene-based elastomer (B) and the inorganic filler (C) is 100 parts by mass. The polypropylene resin composition (X) satisfies the following condition (x-1): (a-1) MFR measured at 230°C and 2.16 kg load in accordance with ASTM D-1238 is 60 g / 10 min or more and 300 g / 10 min or less; (a-2) a propylene-ethylene copolymer comprising a decane-soluble portion at 23°C, wherein the intrinsic viscosity [η] of the propylene-ethylene copolymer as measured in decalin at 135°C is 4.1 dl / g or more and 10 dl / g or less; (b-1) MFR measured at 190°C and 2.16 kg load in accordance with ASTM D-1238 is 0.5 g / 10 min or more and 30 g / 10 min or less; (b-2) Density: 0.85 g / cm 3 Above 0.875g / cm 3 the following; (x-1) relative to 100% by mass of the polypropylene resin composition (X), the molecular weight is 10 6.5 The content of the above polypropylene component is less than 0.05 mass %.

2. The polypropylene resin composition (X) according to claim 1, characterized in that: The impact-resistant polypropylene (A) further satisfies at least one of the following conditions (a-1-1), (a-2-1) and (a-5), (a-1-1) MFR measured at 230°C and 2.16 kg load in accordance with ASTM D-1238 is 77 g / 10 min or more and 200 g / 10 min or less; (a-2-1) the propylene-ethylene copolymer contains a decane-soluble portion at 23°C, and the intrinsic viscosity [η] of the propylene-ethylene copolymer measured in decalin at 135°C is 4.2 dl / g or more and 5.9 dl / g or less; (a-5) When the mass of the impact-resistant polypropylene (A) is set to 100 mass%, the content of the propylene-ethylene copolymer contained in the impact-resistant polypropylene (A), which is determined as the decane-soluble portion Dsol at 23°C, is 5 to 30 mass%.

3. The polypropylene resin composition (X) according to claim 1, characterized in that: The content of the propylene-ethylene copolymer in the polypropylene resin composition (X) is 5 parts by mass or more and 30 parts by mass or less, wherein the total amount of the impact polypropylene (A), the ethylene elastomer (B) and the inorganic filler (C) is 100 parts by mass.

4. The polypropylene resin composition (X) according to claim 1, characterized in that: The ethylene-based elastomer (B) is a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms.

5. The polypropylene resin composition (X) according to claim 1, characterized in that: The content of the impact-resistant polypropylene (A) is 25 parts by mass or more and 74 parts by mass or less, The content of the ethylene-based elastomer (B) is not less than 10 parts by mass and not more than 40 parts by mass, The content of the inorganic filler (C) is 16 parts by mass or more and 35 parts by mass or less, The total amount of the impact-resistant polypropylene (A), the ethylene-based elastomer (B) and the inorganic filler (C) is 100 parts by mass.

6. A foamed molded article, characterized in that: This is a foamed molded product containing the polypropylene resin composition (X) according to any one of claims 1 to 5, obtained by molding using a foaming agent (D).

7. A component for interior and exterior decoration of an automobile, characterized in that: A polypropylene resin composition (X) according to any one of claims 1 to 5.

8. An arch plate molding, characterized in that: A polypropylene resin composition (X) according to any one of claims 1 to 5.

9. A door sill molding, characterized in that: A polypropylene resin composition (X) according to any one of claims 1 to 5.

10. A method for producing a foamed molded article, characterized in that: The method comprises the step of foaming the polypropylene resin composition (X) according to any one of claims 1 to 5.

11. The method for producing a foamed molded article according to claim 10, wherein: Carry out injection foam molding or core-retracting injection molding.

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