Polypropylene resin composition and injection foam molded product thereof

Abstract

To provide a polypropylene-based resin composition having low thermal conductivity and excellent processability of the resulting molded body.SOLUTION: There are provided: a polypropylene-based resin composition which comprises 10 to 70 mass% of a propylene-based polymer(A) based on the total mass of the composition, 10 to 80 mass% of a hollow filler (B) having a pressure resistance strength of 100 to 220 MPa, a true density of 0.3 to 0.7 g / cm3 and an average particle diameter of 10 to 40 μm based on the total mass of the composition and 0.1 to 10 mass% of a foaming agent (E) based on the total amount of (A) and (B), wherein (A) is a polymer only composed of 5 to 40 mass% of a propylene-ethylene copolymer (a1) which is an n-decane soluble part (Dsol) at 23°C and 60 to 95 mass% of a propylene homopolymer (a2), (a1) has an intrinsic viscosity [η] in tetralin at 135°C of 5.0 to 12.0 dl / g and (A) has a melt flow rate of 70 to 500 g / 10 min, as measured at 230°C under a load of 2.16 kg; and an injection foam molded body thereof.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polypropylene resin composition and an injection foam molded article thereof. [Background technology]

[0002] To build a sustainable society, it is essential to make effective use of energy without waste in order to reduce CO2 emissions. Heat control technology is attracting attention in these efforts. For example, with the recent spread of hybrid and electric vehicles (EVs), the impact of air conditioning and heating on automobile fuel efficiency has become an issue. In particular, the fuel energy consumed by heating in winter significantly reduces automobile fuel efficiency, so it is necessary to prevent warm air from inside the vehicle from escaping through vehicle body parts.

[0003] In various fields such as civil engineering, construction, and the vehicle industry, polyolefin resin foams such as polyethylene resin foams and polypropylene resin foams are widely used as basic materials for heat insulating materials, waterproofing agents, heat retaining agents, packing materials, etc. In particular, in the vehicle industry, polyolefin resin foams are used as interior materials such as ceiling materials and door materials. Polyolefin resin foams used for such applications are rarely used alone, and for example, Patent Documents 1 to 3 disclose laminated products in which a skin material made of PVC (polyvinyl chloride), TPO (thermoplastic polyolefin), polyolefin elastomer, etc. is bonded to the surface of a polyolefin resin foam. Patent Document 4 also discloses a polypropylene resin composition that can be used to produce molded articles that have a low brittle temperature and excellent low-temperature impact resistance, in the case of molded articles that are desired to be lightweight. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 62-149431 [Patent Document 2] Japanese Patent Application Laid-open No. 62-18437 [Patent Document 3] Japanese Patent Application Publication No. 1-163225 [Patent Document 4] Japanese Patent Application Laid-Open No. 2013-166817 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the materials described in Patent Documents 1 to 3 cannot be injection molded, and therefore have limited freedom in shape and processability issues, making them unsuitable for automobile parts such as door trims and pillars. Furthermore, no consideration has been given to low thermal conductivity for the injection-molded article made of the polypropylene-based resin composition described in Patent Document 4. Given these circumstances, there is a need for the development of a material that combines processability and low thermal conductivity. An object of one embodiment of the present invention is to provide a propylene-based resin composition that produces a molded article having low thermal conductivity and excellent processability. Another problem to be solved by another embodiment of the present invention is to provide an injection-molded foam having low thermal conductivity and excellent processability. [Means for solving the problem]

[0006] The means for solving the above problems include the following aspects. <1> a propylene polymer (A) in an amount of 10 to 70% by mass based on the total mass of the composition; Pressure resistance: 100-220 MPa, true density: 0.3-0.7 g / cm 3 , and average particle size D 50 10 to 80% by mass of hollow filler (B) having a diameter of 10 to 40 μm relative to the total mass of the composition, and The foaming agent (E) is contained in an amount of 0.1 to 10% by mass based on the total amount of the propylene polymer (A) and the hollow filler (B), the propylene polymer (A) is a polymer consisting of 5 to 40 mass% of a propylene-ethylene copolymer (a1) identified as an n-decane soluble portion (Dsol) at 23°C and 60 to 95 mass% of a propylene homopolymer (a2); the propylene-ethylene copolymer (a1) has an intrinsic viscosity [η] in tetralin at 135°C of 5.0 to 12.0 dl / g; The propylene polymer (A) has a melt flow rate of 70 to 500 g / 10 min as measured at 230°C under a load of 2.16 kg. Propylene-based resin composition. <2> The melt flow rate measured at 190°C under a load of 2.16 kg is in the range of 1 to 40 g / 10 min, and the density is 0.85 to 0.90 g / cm 3 The ethylene copolymer (C) is contained in an amount of 30 mass% or less based on the total mass of the composition. <1> The propylene-based resin composition according to claim 1. <3> The inorganic filler (D) other than the hollow filler (B) is contained in an amount of 30% by mass or less based on the total mass of the composition. <1> or <2> The propylene-based resin composition according to claim 1. <4> <1> ~ <3> 2. An injection foam-molded article obtained by injection foam-molding the propylene-based resin composition according to any one of 1 to 11. [Effects of the Invention]

[0007] According to one embodiment of the present invention, there is provided a propylene-based resin composition which produces a molded article having low thermal conductivity and excellent processability. According to another embodiment of the present invention, an injection-molded foam having low thermal conductivity and excellent processability is provided. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing an example of a test piece used in a thermal conductivity test. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will be described in detail below. The following description of the components may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. In this specification, the use of "to" to indicate a range of values ​​means that the values ​​before and after it are included as the lower and upper limits. In this specification, when a numerical range is indicated by "to", the units written before or after the range indicate the same units unless otherwise specified. As used herein, a combination of two or more preferred embodiments is a more preferred embodiment. The present invention will be described in detail below.

[0010] (Propylene-based resin composition) The propylene-based resin composition according to the present invention contains a propylene-based polymer (A) in an amount of 10 to 70% by mass based on the total mass of the composition, has a compressive strength of 100 to 220 MPa, and a true density of 0.3 to 0.7 g / cm 3 and the composition contains 10 to 80% by mass of hollow filler (B) having an average particle size of 10 to 40 μm, based on the total mass of the composition, and 0.1 to 10% by mass of a blowing agent (E), based on the total amount of the propylene polymer (A) and the hollow filler (B); the propylene polymer (A) is a polymer consisting of 5 to 40 mass% of a propylene-ethylene copolymer (a1) identified as an n-decane soluble portion (Dsol) at 23°C and 60 to 95 mass% of a propylene homopolymer (a2); The propylene-ethylene copolymer (a1) has an intrinsic viscosity [η] in tetralin at 135°C of 5.0 to 12.0 dl / g, The propylene polymer (A) has a melt flow rate of 70 to 500 g / 10 min as measured at 230° C. under a load of 2.16 kg. The propylene-based resin composition according to the present invention has the above-mentioned constitution, and thus the molded article obtained has low thermal conductivity and excellent processability. The reason for this is not clear, but is presumed to be as follows. The propylene-based resin composition contains a propylene-based polymer (A) containing a specific amount of a specific propylene-ethylene copolymer (a1) and a propylene homopolymer (a2), a hollow filler (B) having specific physical properties, and a foaming agent (E), which increases the air space with high thermal insulation properties and reduces thermal conductivity.In addition, the resin viscosity is optimal, which is thought to provide excellent processability.

[0011] <Propylene polymer (A)> The propylene polymer (A) is a polymer consisting of 5 to 40 mass% of a propylene-ethylene copolymer (a1) specified as an n-decane soluble portion (Dsol) at 23°C and 60 to 95 mass% of a propylene homopolymer (a2), and has a melt flow rate of 70 to 500 g / 10 min measured at 230°C under a load of 2.16 kg. As described in the Examples below, the "n-decane soluble portion (Dsol) at 23°C" refers to a component of the polypropylene polymer (A) that is dissolved in the n-decane solution when the temperature is lowered to 23°C after heating and dissolving in n-decane at 150°C for 2 hours. Specifically, the propylene-ethylene copolymer (a1) identified as the n-decane soluble portion at 23°C (Dsol) and the propylene homopolymer (a2) identified as the n-decane insoluble portion at 23°C (Dinsol) described below can be identified by the following method. First, approximately 3 g of propylene-based polymer (A), 500 mL of decane, and a small amount of a decane-soluble heat stabilizer were placed in a glass measuring vessel. Under a nitrogen atmosphere, the vessel was heated to 150°C over 2 hours while stirring with a stirrer to dissolve the propylene-based polymer (A). The vessel was then held at 150°C for 2 hours and then slowly cooled to 23°C over 8 hours. The resulting liquid containing the precipitate of propylene-based polymer (A) was filtered under reduced pressure using a 25G-4 glass filter manufactured by Iwata Glass Co., Ltd. The component dissolved in the filtrate was identified as the n-decane soluble fraction (Dsol) at 23°C, which was identified as propylene-ethylene copolymer (a1). The precipitate remaining on the glass filter was identified as the n-decane insoluble fraction (Dinsol) at 23°C, which was identified as propylene homopolymer (a2).

[0012] <<MFR of propylene polymer (A)>> The propylene polymer (A) has a melt flow rate (MFR) of 70 to 500 g / 10 min measured at 230° C. under a load of 2.16 kg. The MFR can be determined by a measurement method in accordance with ASTM D-1238. The MFR of the propylene polymer (A) is not particularly limited as long as it satisfies the above range. However, the MFR measured in accordance with ASTM D-1238 at a temperature of 230°C under a load of 2.16 kg is usually in the range of preferably 70 to 300 g / 10 min, more preferably 70 to 200 g / 10 min. The MFR of the propylene polymer (A) can be adjusted by the contents of the propylene-ethylene copolymer (a1) and the propylene homopolymer (a2).

[0013] <<Propylene polymer (A) content>> The content of the propylene polymer (A) is 10 to 70% by mass, preferably 20 to 70% by mass, and more preferably 30 to 70% by mass, based on the total mass of the composition. The propylene polymer (A) may be used alone or in combination of two or more kinds.

[0014] <<Propylene-ethylene copolymer (a1)>> The propylene-ethylene copolymer (a1) is a propylene-ethylene copolymer specified by the n-decane soluble portion (Dsol) at 23°C, and its composition is not particularly limited as long as it has an intrinsic viscosity [η] in tetralin at 135°C (described later) of 5.0 to 12.0 dl / g. The propylene-ethylene copolymer (a1) contains structural units derived from ethylene in a range of preferably 20 to 60 mol %, more preferably 30 to 60 mol %, and even more preferably 35 to 55 mol % (wherein the total amount of structural units derived from propylene and structural units derived from ethylene is 100 mol %). The propylene-ethylene copolymer (a1) contains structural units derived from propylene in a range of preferably 40 to 80 mol %, more preferably 40 to 70 mol %, and even more preferably 45 to 65 mol % (wherein the total amount of structural units derived from propylene and structural units derived from ethylene is 100 mol %).

[0015] [Intrinsic viscosity [η] in tetralin at 135°C] The propylene-ethylene copolymer (a1) has an intrinsic viscosity [η] of 5.0 to 12.0 dl / g in tetralin at 135°C. When the intrinsic viscosity [η] of the propylene-ethylene copolymer (a1) is within the above range, the viscosity of the resulting composition falls within the optimum range, making it possible to obtain a molded article with a uniform cell size. From the above viewpoints, the intrinsic viscosity [η] of the propylene-ethylene copolymer (a1) in tetralin at 135°C is preferably 5.0 to 11.0 dl / g, more preferably 5 to 10.0 dl / g, and even more preferably 5 to 9.0 dl / g. The above-mentioned intrinsic viscosity can be adjusted appropriately by adjusting the content of the structural units derived from ethylene and the structural units derived from propylene contained in the propylene-ethylene copolymer (a1) and the molecular weight of the copolymer.

[0016] The content of the propylene-ethylene copolymer (a1) is 5 to 40 mass % based on the total mass of the polymer (A). When the content of the propylene-ethylene copolymer (a1) satisfies the above range, the propylene-based polymer (A) has good foamability of a molded article obtained from the composition. When the content of the propylene-ethylene copolymer (a1) is 5% by mass or more, the propylene-based polymer provides a molded article having excellent impact resistance. On the other hand, when the content of the propylene-ethylene copolymer (a1) is 40% by mass or less, the viscosity of the composition suitable for injection molding is easily obtained. From the above viewpoints, the content of the propylene-ethylene copolymer (a1) is preferably 5 to 30 mass %, more preferably 8 to 30 mass %, and even more preferably 10 to 30 mass %, based on the total mass of the polymer (A).

[0017] <Propylene homopolymer (a2)> The propylene homopolymer (a2) is preferably specified as an n-decane insoluble fraction (Dinsol) at 23° C. The "n-decane insoluble fraction (Dinsol) at 23° C." means a component of the polypropylene polymer (A) that is not dissolved in the n-decane solution when the temperature is lowered to 23° C. after heating and dissolving in n-decane at 150° C. for 2 hours.

[0018] The MFR of the propylene homopolymer (a2) is not particularly limited as long as the MFR of the propylene polymer (A) satisfies the above range. However, the MFR of the propylene homopolymer (a2) measured in accordance with ASTM D-1238 at a temperature of 230°C under a load of 2.16 kg is preferably in the range of 50 to 1000 g / 10 min, more preferably 100 to 800 g / 10 min, and even more preferably 100 to 700 g / 10 min.

[0019] The content of the propylene homopolymer (a2) is 60 to 95% by mass based on the total mass of the polymer (A). When the content of the propylene homopolymer (a2) satisfies the above range, the propylene polymer (A) has a molded article obtained from the composition with good expandability. From the above viewpoints, the content of the propylene homopolymer (a2) is preferably 70 to 95% by mass, more preferably 70 to 92% by mass, and even more preferably 70 to 90% by mass based on the total mass of the polymer (A).

[0020] The method for producing the propylene polymer (A) according to the present invention is not particularly limited, and various known production methods can be used. Examples of the production method for the propylene polymer (A) include a method of polymerizing a propylene homopolymer (a2) and a propylene-ethylene copolymer (a1) satisfying the above-mentioned physical properties, and then mixing or melt-kneading the propylene homopolymer (a2) and the propylene-ethylene copolymer (a1) in the above-mentioned content ranges to obtain the propylene polymer (A), and a method of polymerizing the propylene homopolymer (a2) and the propylene-ethylene copolymer (a1) satisfying the above-mentioned physical properties in one polymerization system or two or more polymerization systems. The propylene polymer (A) may be a commercially available product, or may be a polymer produced by a known production method and sold commercially under the name of a block copolymer.

[0021] In the propylene-based resin composition, the ethylene, propylene, and α-olefin monomers contained in the propylene-based polymer (A) and the ethylene-based polymer (C) described below may be biomass-derived monomers. The biomass-derived monomers may be used alone or in combination of two or more. For example, the monomers constituting the polymer may be composed only of biomass-derived monomers, or may be composed of biomass-derived monomers and fossil fuel-derived monomers. Biomass-derived monomers include monomers derived from any renewable natural raw material, such as plant or animal origin, and their residues, including fungi, yeast, algae, and bacteria. Biomass-derived monomers contain carbon as the raw material. 14 C isotope 1×10 -12 It is preferable that the biomass carbon concentration (pMC: Percentage of Modern Carbon) measured in accordance with ASTM D 6866 is about 100 (pMC).

[0022] The method for producing the biomass-derived monomer is not particularly limited, and known methods can be used. From the viewpoint of reducing the environmental load, the propylene-based resin composition preferably contains a biomass-derived monomer. Even if the raw material monomer in the propylene-based resin composition contains a biomass-derived monomer, the propylene-based resin composition can be produced in the same manner as long as the polymer production conditions, such as the polymerization catalyst and polymerization temperature, are the same. 14 C isotope 1×10 -12 Other than containing about 100% propylene, it is equivalent to a polypropylene resin composition made from a fossil fuel-derived monomer, and since the molecular structure is also equivalent, the performance of the resulting propylene resin composition is said to be unchanged.

[0023] <Hollow filler (B)> The hollow filler (B) has a compressive strength of 100 to 220 MPa and a true density of 0.3 to 0.7 g / cm 3 , and average particle size D 50 is 10 to 40 μm. The hollow filler is not particularly limited as long as it is a filler having a hollow structure, and may be an inorganic filler, an organic filler, or a filler made of an organic and inorganic composite material. The hollow filler (B) is preferably a hollow inorganic filler. The hollow filler (B) is not particularly limited as long as it satisfies the above physical properties, and examples thereof include glass bubbles, hollow alumina, perlite, shirasu, fly ash balloons, and aerogel. Among these, glass bubbles or silica aerogel are preferred from the viewpoint of excellent low thermal conductivity, and glass bubbles are more preferred. The shape of the hollow filler is not particularly limited, and examples thereof include a spherical shape and an oval spherical shape.

[0024] The hollow filler (B) has a pressure resistance of 100 to 220 MPa. If the pressure resistance is 100 MPa or more, the hollow bodies are less likely to be crushed during kneading, and thermal conductivity can be reduced. From the above viewpoints, the pressure resistance is preferably 100 to 200 MPa, and more preferably 100 to 190 MPa. The pressure resistance strength can be determined by the method described in the Examples. The pressure resistance strength of a hollow filler is defined by ASTM D-3102-78, and is determined by the pressure at which an appropriate amount of filler is placed in glycerin and pressurized to destroy 10% by volume.

[0025] The true density of hollow filler (B) is 0.3 to 0.7 g / cm 3 and preferably 0.4 to 0.7 g / cm 3 and more preferably 0.4 to 0.65 g / cm 3 The true density is 0.3 g / cm 3 If the temperature is below this, the hollow body will be prone to cracking. The true density means the density calculated from the volume of a container excluding the gap when the hollow filler (B) is filled in a container of a certain volume. The true density is measured using a pycnometer (a gas-phase displacement true density meter, for example, AccuPycII1340 manufactured by Micromeritics).

[0026] Average particle size D of hollow filler (B) 50 is 5 to 70 μm, preferably 5 to 50 μm, and more preferably 5 to 40 μm. Average particle size D of hollow filler (B) 50 is the median diameter D measured by a laser diffraction particle size analyzer 50It is measured using, for example, a laser diffraction particle size distribution analyzer SALD-2100 manufactured by Shimadzu Corporation, but for commercially available products, the catalog value can be used.

[0027] The content of the hollow filler (B) is 10 to 80% by mass based on the total mass of the composition. If the content of the hollow filler (B) is 10% by mass or more, it can contribute to a decrease in thermal conductivity. From the above viewpoint, the content of the hollow filler (B) is preferably 10 to 50% by mass with respect to the total mass of the composition. The hollow filler (B) may be used alone or in combination of two or more kinds.

[0028] <Foaming agent (E)> The propylene-based resin composition contains a blowing agent (E) in an amount of 0.1 to 10% by mass based on the total amount of the propylene-based polymer (A) and the hollow filler (B). The foaming agent (E) is not particularly limited, and any foaming agent that can be used in foam molding can be appropriately selected and used. The foaming agent (E) may be a chemical foaming agent or a physical foaming agent. Examples of chemical foaming agents include decomposition type foaming agents.

[0029] Specific examples of decomposition type foaming agents include the following compounds: (1) Inorganic foaming agents: sodium bicarbonate, sodium carbonate, ammonium bicarbonate, ammonium carbonate, ammonium nitrite. (2) Organic foaming agents: (a) N-nitroso compounds: N,N'-dinitrosoterephthalamide, N,N'-dinitrosopentamethylenetetramine. (b) Azo compounds: azodicarbonamide, azobisisobutyronitrile, azocyclohexylnitrile, azodiaminobenzene, barium azodicarboxylate. (c) Sulfonylhydrazide compounds: benzenesulfonylhydrazide, toluenesulfonylhydrazide, p,p'-oxybis(benzenesulfenylhydrazide), diphenylsulfone-3,3'-disulfonylhydrazide. (d) Azide compounds: calcium azide, 4,4'-diphenyldisulfonyl azide, p-toluenesulfonyl azide.

[0030] The decomposition type foaming agent may be used in combination with a foaming assistant, such as an organic acid such as citric acid or an organic acid metal salt such as sodium citrate, which induces the generation of gas by decomposition.

[0031] Physical blowing agents include solvent-based blowing agents and gaseous blowing agents. Examples of solvent-type blowing agents include various liquefied gases, and specific examples include low-boiling aliphatic hydrocarbons such as propane, butane, neopentane, heptane, isohexane, hexane, isoheptane, and heptane, and low-boiling fluorine-containing hydrocarbons such as chlorofluorocarbons.

[0032] Examples of gaseous blowing agents include inert gases such as carbon dioxide, nitrogen, argon, helium, neon, astatine, etc. The gaseous blowing agent may be used in a supercritical state.

[0033] The blowing agent (E) may be one type alone or two or more types may be used in combination. The blending ratio of the foaming agent is in the range of 0.1% by mass to 10% by mass, preferably 0.1% by mass to 5.0% by mass, and more preferably 0.1% by mass to 3.0% by mass, based on the total amount of the propylene polymer (A) and the hollow filler (B).

[0034] <Ethylene polymer (C)> The propylene resin composition may contain an ethylene polymer (C). The ethylene copolymer (C) is not particularly limited and may be an ethylene homopolymer or a copolymer of ethylene and an α-olefin. Examples of the ethylene copolymer (C) include ethylene polymers generally known as linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE), as well as amorphous or low-crystalline ethylene-α-olefin copolymers and copolymers mainly composed of ethylene.

[0035] The α-olefin copolymerized with ethylene is preferably an α-olefin having 3 to 20 carbon atoms, specifically propylene, 1-butene, 4-methyl-1-pentene-1, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-nonadecene, 1-eicosene, 9-methyl-1-decene, 11-methyl-1-dodecene, and 12-ethyl-1-tetradecene. Among these α-olefins, 1-butene and 1-octene are particularly preferred. The above α-olefins may be used alone or in combination of two or more.

[0036] The melt flow rate (MFR) of the ethylene polymer (C) measured at 190°C under a load of 2.16 kg is preferably 1 to 40 g / 10 min in accordance with ASTM D-1238. When the MFR is in the above range, the foamability is excellent and the amount of air in the molded article increases, making it possible to suppress thermal conductivity. From the above viewpoints, the melt flow rate (MFR) of the ethylene polymer (C) measured at 190°C is more preferably 1 to 35 g / 10 min, and even more preferably 2 to 35 g / 10 min. The melt flow rate (MFR) measured at 190°C is determined by a measurement method in accordance with ASTM D-1238.

[0037] The ethylene copolymer (C) preferably has a density of 0.85 to 0.90 g / cm from the viewpoint of improving impact resistance that is reduced by foaming from the foaming agent (E). 3 , more preferably 0.85 to 0.88 g / cm 3 is in the range. The density of the ethylene copolymer (C) is determined by a method in accordance with ASTM D792.

[0038] The content of the ethylene polymer (C) is preferably 30% by mass or less, more preferably 0 to 30% by mass, and even more preferably 0 to 25% by mass, based on the total mass of the composition. The ethylene copolymer (C) may be one type alone or a combination of two or more different ethylene copolymers.

[0039] From the viewpoint of low thermal conductivity and excellent moldability, the propylene-based resin composition has a melt flow rate measured at 190°C under a load of 2.16 kg in the range of 1 to 40 g / 10 min and a density of 0.85 to 0.90 g / cm 3 The ethylene copolymer (C) preferably comprises 30% by mass or less of the total mass of the composition.

[0040] The method for producing the ethylene copolymer (C) is not particularly limited, and it can be produced by various known production methods.

[0041] <<Inorganic filler (D)>> The propylene-based resin composition may contain an inorganic filler (D) other than the hollow filler (B) according to the desired physical properties of the foamed molded article. The inorganic filler (D) is not particularly limited, and examples thereof include heavy calcium carbonate, light calcium carbonate, talc, glass fiber, magnesium carbonate, mica, kaolin, calcium sulfate, barium sulfate, titanium white, white carbon, carbon black, aluminum hydroxide, and magnesium hydroxide.

[0042] The shape and particle size of the inorganic filler (D) are not particularly limited and can be selected depending on the desired physical properties of the foamed molded article. The blending ratio of the inorganic filler (D) is preferably 30% by mass or less, more preferably 0% by mass to 30% by mass, even more preferably 0% by mass to 25% by mass, and particularly preferably 0% by mass to 21% by mass, relative to the total mass of the composition. The inorganic filler (D) can be used alone or in combination of two or more kinds.

[0043] <<Other ingredients>> The propylene-based resin composition may contain various additives other than the above (A) to (D) as necessary, provided that the purpose of the composition is not impaired. Examples of 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, neutralizing agents, plasticizers, crosslinking agents, flow improvers such as peroxides, weld strength improvers, natural oils, synthetic oils, and waxes. The additives may be used alone or in combination of two or more.

[0044] <<Method for producing propylene-based resin composition>> The method for producing the propylene-based resin composition is not particularly limited, and various known production methods can be used. Examples of the method for producing the propylene-based resin composition include a production method in which the propylene-based polymer (A), the hollow filler (B), the foaming agent (E), and the ethylene-based polymer (C), the inorganic filler (D), and additives, which are contained as needed, are mixed in predetermined amounts by a conventional method such as dry blending or melt-kneading in an extruder.

[0045] (Injection foam molding) The injection foam molded article according to the present invention is produced by injection foam molding the above propylene-based resin composition. Hereinafter, one embodiment of the production of an injection foamed molded article using the propylene-based resin composition according to the present invention will be described.

[0046] [Method for producing injection-molded foam] The method for producing an injection foam molded article preferably includes the steps of filling a mold for injection foam molding with the propylene-based resin composition, and foaming and solidifying the propylene-based resin composition in the mold to obtain an injection foam molded article.

[0047] The mold for injection foam molding, the method for filling the propylene-based resin composition into the mold, and the foam molding conditions may be selected depending on the shape and physical properties of the desired foam molded article. An injection-molded foam can be obtained by using an injection molding method in which a propylene-based resin composition is injected into a mold.

[0048] The method for filling the propylene-based resin composition into a molding die is not particularly limited. The foaming agent (E) may be mixed with components of the propylene-based resin composition other than the foaming agent (E) and then introduced into the molding die, or the foaming agent (E) may be injected and mixed with the resin material in an introduction path for the resin material into the molding die, for example, in the cylinder during injection molding or in a flow path from the cylinder to the cavity.

[0049] The core-back molding method can be suitably used to form an injection-molded foam having a thin-walled portion with a thickness of about 1.0 to 5.0 mm. One form of molding die used in the core-back molding method has a fixed die and a movable die. These dies are preferably in a clamped state when the propylene-based resin composition is injected and filled. The volume of the cavity in the mold into which the propylene-based resin composition is injected and filled can be increased by retracting (core-backing) the movable die to expand the cavity. The timing for operating the movable die after injection and filling is complete can be determined depending on the desired expansion rate, foam shape, various physical properties of the injection-molded foam, etc. The moving speed of the movable mold during core back can be selected depending on conditions such as the thickness of the injection foam molded article, the composition of the propylene-based resin composition, the type and amount of foaming agent added, the mold temperature, and the resin temperature.

[0050] The temperature of the propylene-based resin composition to be injected and the mold temperature can be selected depending on the thickness of the molded article, the composition of the propylene-based resin composition, the type and amount of foaming agent added, and the like. For example, the temperature of the resin material to be injected can be set preferably in the range of 170 to 250°C, more preferably 180 to 230°C. The mold temperatures of the fixed and movable dies can be set preferably in the range of 10 to 100°C, more preferably 30 to 80°C. The injection pressure can be selected from the range of preferably 10 to 250 MPa, more preferably 12 to 200 MPa. In order to obtain good foaming properties, the temperature of the propylene-based resin composition injected and filled into the mold is preferably higher than the mold temperature.

[0051] The injection foam molded article according to the present invention can be suitably used in various applications requiring heat insulating properties for containers, such as automobile interior parts and electrical appliances. [Example]

[0052] The present invention will be further described below with reference to examples, although the present invention is not limited to these examples.

[0053] The following polymers were used as the polymers contained in the propylene-based resin compositions used in the Examples and Comparative Examples. <(1) Propylene-based polymer (A)> <<(1-1) Propylene Polymer (A-1)>> As the propylene polymer (A), a propylene polymer (A-1) was used, which had a MFR of 120 g / 10 min measured at 230°C under a load of 2.16 kg in accordance with ASTM D-1238 and contained the following propylene-ethylene copolymer (a1-2) and propylene homopolymer (a2-2).

[0054] The physical properties of the propylene-ethylene copolymer (a1-2) and the propylene homopolymer (a2-2) are as follows: Propylene-ethylene copolymer (a1-2) specified by n-decane soluble portion at 23°C [n-decane soluble portion at 23°C]: Intrinsic viscosity [η] in tetralin at 135°C is 7.5 dl / g, (a1-2) content = 11.0 mass% Propylene homopolymer (a2-2) which is an n-decane insoluble portion at 23°C [n-decane insoluble portion at 23°C]: MFR measured in accordance with ASTM D-1238 at a temperature of 230°C and a load of 2.16 kg = 500 g / 10 min, (a2-2) content = 89.0 mass%

[0055] <<(1-2) Propylene Polymer (A-2)>> As the propylene polymer (A), a propylene polymer (A-2) was used, which had a MFR of 60 g / 10 min measured at 230°C under a load of 2.16 kg in accordance with ASTM D-1238 and contained the following propylene-ethylene copolymer (a1-1) and propylene homopolymer (a2-1).

[0056] Propylene-ethylene copolymer (a1-1) (room-temperature n-decane soluble portion) that is n-decane soluble at 23°C: Intrinsic viscosity [η] in tetralin at 135°C = 6.0 dl / g, (a1-1) content = 11% by mass Propylene homopolymer (a2-1) which is an n-decane insoluble portion at 23°C [room temperature n-decane insoluble portion]: MFR = 210 g / 10 min, (a2-1) content = 89% by mass

[0057] [Intrinsic viscosity [η]] The intrinsic viscosity [η] (dl / g) of propylene-ethylene copolymers (a1-1) and (a1-2) measured in decalin at 135°C was measured as follows. First, approximately 25 mg of sample was dissolved in 25 mL of decalin, and the specific viscosity ηsp was measured in an oil bath at 135°C. This decalin solution was diluted with 5 mL of additional decalin solution, and the specific viscosity ηsp was measured in the same manner. This dilution procedure was repeated two more times, and the value of ηsp / C when the concentration (C) was extrapolated to 0 was determined as the intrinsic viscosity. This value was used as the intrinsic viscosity [η] (dl / g) of the sample measured in decalin at 135°C.

[0058] <(2) Hollow filler (B)> (B-1): Glass bubbles, Glass Bubbles (product name), 3M "Model: iM30K" (compression strength 186 MPa, true density 0.60 g / cm 3 , and average particle size 16 μm)

[0059] The compounding agents contained in the propylene-based resin compositions used in the Examples and Comparative Examples were as follows.

[0060] <(3) Foaming agent (E)> (E-1): Sodium bicarbonate foaming agent: Trade name Polythrene EE65C (manufactured by Eiwa Chemical Industry Co., Ltd.)

[0061] The injection foamed molded articles of the propylene-based resin compositions obtained in the Examples and Comparative Examples were formed by the following method, and the obtained injection foamed molded articles were evaluated according to the following evaluation methods.

[0062] Injection molding machine: Japan Steel Works J350ADS-460H (mold clamping force 350t) Mold: Cavity size: length: 400mm, width: 200mm, thickness: 1.5mm Gate: Direct gate (installed at the center of the molded product) Injection cylinder temperature setting: 220℃ Mold surface temperature: 40℃ Injection speed: 120mm / s Foam molding conditions: Mold clearance after foaming process: 3.0 mm Core back time: 0.2 seconds Delay time after filling foaming composition: 0 seconds Injection mold cavity clearance (L0): 1.5 mm

[0063] [Workability] The foam cross section of the injection foamed molded article formed by the above method was visually inspected and evaluated according to the following evaluation criteria. + It can be said that an injection foamed molded article that satisfies the above condition is excellent in processability. -Evaluation criteria- A + : No voids with a width of 0.5 mm or more were observed. A: Voids less than 0.5 to 1 mm in width are observed. B: Voids with a width of 1 mm or more are observed.

[0064] [Low thermal conductivity] The injection foam molded article was cut out to a size of 200 mm x 400 mm, and test pieces were cut from the position shown in Figure 1 to have the following shape. Using this test piece, a thermal conductivity test was carried out under the following measurement conditions, with reference to ASTM E1530. The thermal conductivity (W / mK) of the measured test piece (t3.0 mm molded body) was evaluated according to the following evaluation criteria; the lower the thermal conductivity, the better the low thermal conductivity.

[0065] Test equipment: GH-1 (manufactured by Alpac Riko Co., Ltd.) Set temperature: 30℃ Set air pressure for holding sample: 0.3 MPa Test piece shape: diameter φ: approx. 50 mm x thickness: 3.0 mm

[0066] -Evaluation criteria- A: The thermal conductivity was less than 0.09 W / mK. B: Thermal conductivity was 0.09 W / mK or higher.

[0067] Example 1 50% by mass of the propylene polymer (A-1) and 50% by mass of the hollow filler (B-1) were mixed and granulated, and then 3 parts by mass of the blowing agent (E) was blended (added) to a total of 100 parts by mass of the propylene polymer (A-1) and hollow filler (B-1) to prepare a polypropylene resin composition. The obtained polypropylene resin composition was injection foam molded using the method described above to form an injection foam molded article. The obtained injection-molded foams were evaluated by the above-mentioned methods, and the results are shown in Table 1.

[0068] Example 2 A polypropylene resin composition was prepared in the same manner as in Example 1, except that the propylene polymer (A-1) was used in an amount of 70% by mass and the hollow filler (B-1) was used in an amount of 30% by mass. The polypropylene resin composition was then used to form an injection-molded foam. The injection-molded foam was evaluated according to the methods described above. The results are shown in Table 1.

[0069] Example 3 A polypropylene resin composition was prepared in the same manner as in Example 1, except that the propylene polymer (A-1) was used in an amount of 80% by mass and the hollow filler (B-1) was used in an amount of 20% by mass. The polypropylene resin composition was then used to form an injection-molded foam. The injection-molded foam was evaluated according to the methods described above. The results are shown in Table 1.

[0070] Example 4 A polypropylene resin composition was prepared in the same manner as in Example 1, except that the propylene polymer (A-1) was used in an amount of 90% by mass and the hollow filler (B-1) was used in an amount of 10% by mass. The polypropylene resin composition was then used to form an injection-molded foam. The injection-molded foam was evaluated according to the methods described above. The results are shown in Table 1.

[0071] Comparative Example 1 A polypropylene resin composition was prepared in the same manner as in Example 1, except that the propylene polymer (A-1) was used in an amount of 95% by mass and the hollow filler (B-1) was used in an amount of 5% by mass. The polypropylene resin composition was then used to form an injection-molded foam. The injection-molded foam was evaluated according to the methods described above. The results are shown in Table 1.

[0072] Comparative Example 2 A polypropylene resin composition was prepared in the same manner as in Example 1, except that the propylene polymer (A-2) was used in an amount of 50% by mass and the hollow filler (B-1) was used in an amount of 50% by mass. The obtained polypropylene resin composition was used to form an injection-molded foam, which was then evaluated by the above-mentioned method. The results are shown in Table 1.

[0073] [Table 1]

[0074] In Table 1, "-" in the composition column means that the component is not included, and "-" in the low thermal conductivity column means that the component could not be measured.

[0075] As shown in Table 1, the molded articles obtained from the polypropylene resin compositions of Examples 1 to 4 have thermal conductivities of less than 0.09 W / mK, and are superior in low thermal conductivity and processability compared to the molded articles obtained from the polypropylene resin compositions of Comparative Examples 1 and 2. In contrast, the polypropylene resin composition of Comparative Example 1 had a hollow filler (B) content of less than 10% by mass relative to the total mass of the composition, and therefore the thermal conductivity of the resulting molded article was high. The polypropylene resin composition of Comparative Example 2 had a propylene polymer (A-2) with an MFR of less than 70 g / 10 min measured at 230°C under a load of 2.16 kg, and therefore the viscosity of the resin composition was high, and processability was poor, making it impossible to produce an injection-molded foam. From the above, it is clear that the polypropylene resin composition according to the present invention has excellent thermal conductivity and processability for the molded article obtained.

Claims

1. 10 to 70% by mass of a propylene polymer (A) relative to the total mass of the composition, Compression strength: 100 to 220 MPa, true density: 0.3 to 0.7 g / cm ３ , and average particle size D ５０ 20 to 50% by mass of hollow filler (B) having a diameter of 10 to 40 μm relative to the total mass of the composition, and a foaming agent (E) is contained in an amount of 0.1 to 10% by mass based on the total amount of the propylene polymer (A) and the hollow filler (B); the propylene polymer (A) is a polymer consisting of 5 to 40 mass% of a propylene-ethylene copolymer (a1) identified as an n-decane soluble portion (Dsol) at 23°C and 60 to 95 mass% of a propylene homopolymer (a2); the propylene-ethylene copolymer (a1) has an intrinsic viscosity [η] in tetralin at 135°C of 5.0 to 12.0 dl / g; the propylene polymer (A) has a melt flow rate of 70 to 500 g / 10 min as measured at 230°C under a load of 2.16 kg; Propylene-based resin composition.

2. The melt flow rate measured at 190°C under a load of 2.16 kg is in the range of 1 to 40 g / 10 min, and the density is 0.85 to 0.90 g / cm ３ The propylene-based resin composition according to claim 1, wherein the ethylene-based copolymer (C) is in an amount of 30 mass % or less based on the total mass of the composition.

3. The propylene-based resin composition according to claim 1 or 2, further comprising an inorganic filler (D) other than the hollow filler (B) in an amount of 30 mass % or less based on the total mass of the composition.

4. An injection foam molded article obtained by injection foam molding the propylene-based resin composition according to any one of claims 1 to 3.

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