Propylene-based resin composition and its uses

Abstract

The purpose of the present invention is to obtain a propylene-based resin composition that is suitable for obtaining a foam molded body having uniform cell diameter, good appearance and excellent surface impact resistance. The present invention pertains to a propylene-based resin composition characterized by comprising: 50-90 mass% of a propylene-based polymer (A) containing 5-22 mass% of a propylene-ethylene copolymer (a1) that is specified as an n-decane soluble portion, and 78-95 mass% [provided that the total amount (a1)+(a2) is regarded as 100 mass%] of a propylene homopolymer (a2); 5-50 mass% of a copolymer (B) containing an alkenyl aromatic compound-derived unit; and 0-20 mass% [provided that the total amount (A)+(B)+(C) is regarded as 100 mass%] of an ethylene-based copolymer (C) having an MFR of 20-40 g / 10 min.

Description

[Technical field]

[0001] The present invention relates to a propylene-based resin composition suitable for obtaining a foamed molded article having uniform cell diameter, good appearance and excellent surface impact resistance, and to an injection-molded foam. [Background technology]

[0002] One of the important molding methods for polypropylene is foam molding. Various molded products obtained by extrusion foam molding and injection foam molding are used in a wide range of applications, taking advantage of their excellent properties such as heat insulation, sound insulation, cushioning, and energy absorption. It is generally known that the higher the foam expansion ratio of a foam, the better the cushioning and heat insulation properties, and the higher the open cell ratio, the better the sound absorption and the lighter the weight. However, foam molded products have significantly lower surface impact performance than non-foam molded products, and are prone to poor appearance due to foaming, such as swirl marks, so there is a demand in the market for foamable propylene-based resin compositions that combine impact performance and good appearance.

[0003] Methods proposed for improving the impact resistance of injection-molded foams include blending an ethylene-α-olefin copolymer, which has a high melt tension, and an olefin polymer resin, which has a low melt tension, with a polypropylene resin (Patent Document 1), and blending a polyethylene resin, which has a high melt tension, and at least one thermoplastic resin selected from rubber containing alkenyl aromatic compound units and an ethylene-α-olefin copolymer with a polypropylene resin (Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2012 / 043824 Brochure [Patent Document 2] JP 2013-1826 A Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to obtain a propylene-based resin composition suitable for producing a foamed molded article having uniform cell diameter, good appearance and excellent surface impact resistance. [Means for solving the problem]

[0006] The present invention relates to a polymer composition comprising 5 to 22 mass% of a propylene-ethylene copolymer (a1) specified as an n-decane soluble portion, the propylene-ethylene copolymer portion specified as an n-decane soluble portion (Dsol) at 23°C having an intrinsic viscosity [η] in tetralin at 135°C in the range of 4.0 to 9.0 dl / g, and 78 to 95 mass% of a propylene homopolymer (a2) (wherein the total amount of (a1) + (a2) is 100 mass%), and 50 to 90 mass% of a propylene polymer (A) having an MFR in the range of 70 to 150 g / 10 min as measured at 230°C under a load of 2.16 kg in accordance with ASTM D-1238; A copolymer (B) containing a unit derived from an alkenyl aromatic compound having a MFR of 10 to 80 g / 10 min measured at 230° C. in accordance with ASTM D-1238 in the range of 5 to 50% by mass, The present invention relates to a propylene-based resin composition comprising an ethylene-based copolymer (C) having a MFR of 20 to 40 g / 10 min measured at 230° C. in accordance with ASTM D-1238 in a range of 0 to 20 mass % (wherein the total amount of (A)+(B)+(C) is taken as 100 mass %). Effect of the Invention

[0007] The injection foam molded article obtained by injection foam molding of the propylene-based resin composition of the present invention has a uniform cell diameter, good appearance and excellent surface impact resistance, and therefore can be suitably used for various applications such as automobile interior and exterior parts, substitutes for cardboard and the like, electrical appliances, building materials, etc. [Brief description of the drawings]

[0008] [Figure 1]FIG. 2 is a schematic diagram of the injection foamed molded articles obtained in the examples and comparative examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The propylene polymer composition according to the present invention and the injection foam molded article (hereinafter, sometimes simply referred to as "molded article") made of the composition will be specifically described below.

[0010] <Propylene-based polymer (A)> The propylene polymer (A), which is one of the components contained in the propylene resin composition of the present invention, contains 5 to 22 mass %, preferably 5 to 15 mass %, more preferably 5 to 13 mass % of a propylene-ethylene copolymer (a1) specified as an n-decane soluble portion (Dsol) at 23°C, the propylene-ethylene copolymer portion having an intrinsic viscosity [η] in tetralin at 135°C of 4.0 to 9.0 dl / g, preferably 5.0 to 8.0 dl / g, more preferably 6.0 to 8.0 dl / g, and 78 to 95 mass %, preferably 85 to 95 mass %, more preferably 87 to 95 mass % of a propylene homopolymer (a2) (wherein the total amount of (a1)+(a2) is 100 mass %). The MFR measured in accordance with ASTM D-1238 at a temperature of 230° C. under a load of 2.16 kg is in the range of 70 to 150 g / 10 min, preferably 73 to 130 g / 10 min, and more preferably 75 to 110 g / 10 min.

[0011] The propylene polymer (A) according to the present invention may be a single polymer or two or more polymers.

[0012] When the content of the propylene-ethylene copolymer (a1) in the propylene-based polymer is less than 5% by mass, the impact resistance of a molded article obtained from the composition may be deteriorated. On the other hand, when the content of the propylene-ethylene copolymer (a1) in the propylene-based polymer is more than 22% by mass, the viscosity of the composition is significantly reduced, so that the appearance of the molded article obtained may be poor.

[0013] When the propylene-ethylene copolymer (a1) content falls within the above range, a molded article obtained from the propylene polymer (A) has good appearance and excellent surface impact resistance.

[0014] When the propylene-based polymer (A) contains the propylene-ethylene copolymer (a1) having an intrinsic viscosity [η] that falls within the above range, the viscosity of the resulting composition falls within the optimum range, and a molded product having a uniform cell size, good appearance, and excellent surface impact resistance can be obtained.

[0015] Propylene polymers (A) with an MFR of less than 70 g / 10 min have high viscosity and therefore generate large shear heat during resin filling. As a result, the amount of gas generated increases, and there is a risk that the appearance of the resulting molded article may deteriorate. On the other hand, when the MFR exceeds 150 g / 10 min, the viscosity is low and the foaming property is poor, and there is a risk that a molded article having uniform cells cannot be obtained. Propylene polymers (A) with an MFR that satisfies the above range can form uniform cell diameters and can obtain molded articles with good appearance and excellent surface impact resistance.

[0016] <Propylene-ethylene copolymer (a1)> The propylene-ethylene copolymer (a1) contained in the propylene polymer (A) according to the present invention generally contains structural units derived from ethylene in a range of 20 to 60 mol %, preferably 30 to 60 mol %, 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 %).

[0017] The propylene-ethylene copolymer (a1) according to the present invention may contain a biomass-derived monomer (propylene, ethylene). The monomers constituting the polymer may be only biomass-derived monomers, or may contain both biomass-derived monomers and fossil fuel-derived monomers. The biomass-derived monomer is a monomer obtained from any renewable natural raw material or its residue, such as a plant-derived or animal-derived monomer, including fungi, yeast, algae, and bacteria, and contains 10 14C isotopes as carbon. -12The biomass carbon concentration (pMC) measured in accordance with ASTM D-6866 is about 100 (pMC). The biomass-derived monomer is obtained by a conventionally known method.

[0018] It is preferable that the propylene-ethylene copolymer (a1) according to the present invention contains a biomass-derived monomer from the viewpoint of reducing the environmental load (mainly reducing greenhouse gases). If the polymer production conditions such as the polymerization catalyst, polymerization temperature, etc. are the same, even if the raw material monomer contains a biomass-derived monomer, the 14C isotope can be decomposed into 10 -12 ~10 -14 Other than the proportion of ethylene in the polymer, its molecular structure is the same as that of propylene-ethylene copolymers made from monomers derived from fossil fuels. Therefore, its performance is said to be the same.

[0019] The propylene-ethylene copolymer (a1) according to the present invention may contain a monomer derived from chemical recycling (propylene, ethylene). The monomers constituting the polymer may be only the monomer derived from chemical recycling, or may contain the monomer derived from chemical recycling and the monomer derived from fossil fuel and / or the monomer derived from biomass. The monomer derived from chemical recycling is obtained by a conventionally known method. It is preferable that the propylene-ethylene copolymer (a1) according to the present invention contains the monomer derived from chemical recycling from the viewpoint of reducing the environmental load (mainly reducing waste). Even if the raw material monomer contains the monomer derived from chemical recycling, the monomer derived from chemical recycling is a monomer obtained by depolymerizing or pyrolyzing a polymer such as waste plastic back to a monomer unit such as ethylene, and a monomer produced using the monomer as a raw material. Therefore, if the polymer production conditions such as the polymerization catalyst, polymerization process, and polymerization temperature are the same, the molecular structure is the same as that of a propylene-ethylene copolymer made of a monomer derived from fossil fuel. Therefore, the performance is said to be the same.

[0020] <Propylene homopolymer (a2)> The propylene homopolymer (a2) contained in the propylene polymer (A) according to the present invention is not particularly limited in MFR as long as the MFR of the propylene polymer (A) satisfies the above range. Generally, the MFR measured in accordance with ASTM D-1238 at a temperature of 230° C. under a load of 2.16 kg is in the range of 50 to 1000 g / 10 min, preferably 100 to 800 g / 10 min, more preferably 200 to 800 g / 10 min.

[0021] The propylene homopolymer (a2) according to the present invention may contain biomass-derived propylene. The propylene constituting the polymer may be only biomass-derived propylene, or may contain both biomass-derived propylene and fossil fuel-derived propylene. Biomass-derived propylene is propylene obtained from any renewable natural raw material, such as fungi, yeast, algae, and bacteria, or from the residues of such raw material, and contains 10C isotopes as carbon. -12 The biomass carbon concentration (pMC) measured in accordance with ASTM D-6866 is about 100 (pMC). Biomass-derived propylene is obtained by a conventionally known method.

[0022] It is preferable that the propylene homopolymer (a2) according to the present invention contains biomass-derived propylene from the viewpoint of reducing the environmental load (mainly reducing greenhouse gases). If the polymer production conditions such as the polymerization catalyst, polymerization process, and polymerization temperature are the same, even if the raw propylene contains biomass-derived propylene, the propylene homopolymer (a2) according to the present invention can be produced without the use of 14C isotopes. -12 ~10 -14 Other than the proportion of propylene in the polymer, its molecular structure is the same as that of propylene homopolymers made from fossil fuel-derived propylene, and therefore its performance is said to be the same.

[0023] The propylene homopolymer (a2) according to the present invention may contain chemically recycled propylene. The propylene constituting the polymer may be only chemically recycled propylene, or may contain chemically recycled propylene and fossil fuel-derived propylene and / or biomass-derived propylene. Chemically recycled propylene can be obtained by a conventionally known method.

[0024] It is preferable that the propylene homopolymer (a2) according to the present invention contains chemically recycled propylene from the viewpoint of reducing environmental load (mainly reducing waste). Even if the raw material monomer contains a chemically recycled monomer, the chemically recycled monomer is a monomer obtained by depolymerizing or pyrolyzing a polymer such as waste plastic back to a monomer unit such as propylene, and a monomer produced using the monomer as a raw material. Therefore, if the polymer production conditions such as the polymerization catalyst, polymerization process, and polymerization temperature are the same, the molecular structure is the same as that of a propylene homopolymer made of a monomer derived from a fossil fuel. Therefore, the performance is said to be the same.

[0025] The propylene polymer (A) according to the present invention can be produced by various known methods, for example, 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) within the above-mentioned ranges to obtain the propylene polymer (A), or 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.

[0026] The propylene polymer (A) according to the present invention is commercially available under the name of a block copolymer produced by a known production method.

[0027] <Copolymer (B) containing units derived from an alkenyl aromatic compound> Copolymer (B) containing units derived from an alkenyl aromatic compound, which is one of the components contained in the propylene-based resin composition of the present invention (hereinafter, may be referred to as "copolymer (B)"), has an MFR measured at a temperature of 230°C in accordance with ASTM D-1238 in the range of 10 to 80 g / 10 min, preferably 11 to 75 g / 10 min, more preferably 12 to 73 g / 10 min.

[0028] The copolymer (B) according to the present invention preferably has a density of 0.88 to 0.98 g / cm 3 and is preferably produced by a method of bonding an alkenyl aromatic compound to an olefin copolymer or a conjugated diene polymer by polymerization, reaction, or the like. Examples of such block copolymers include block copolymers consisting of a vinyl aromatic compound polymer block and a conjugated diene polymer block, and block copolymers in which the double bonds of the conjugated diene portion of the block copolymer have been hydrogenated. More preferably, the block copolymers consist of a vinyl aromatic compound polymer block and a conjugated diene polymer block, and the double bonds of the conjugated diene portion of the block copolymer have been hydrogenated. Even more preferably, the block copolymers have been hydrogenated in 80% or more of the double bonds of the conjugated diene portion of the block copolymer. Even more preferably, the block copolymers have been hydrogenated in 85% or more of the double bonds of the conjugated diene portion of the block copolymer.

[0029] More specifically, the copolymer (B) according to the present invention may be a block copolymer such as styrene-ethylene-butene-styrene rubber (SEBS), styrene-ethylene-propylene-styrene rubber (SEPS), styrene-butadiene rubber (SBR), styrene-butadiene-styrene rubber (SBS), styrene-isoprene-styrene rubber (SIS), or a block copolymer obtained by hydrogenating these rubber components. Among them, it is preferable to use styrene-ethylene-butene-styrene rubber (SEBS) because of its good compatibility with the propylene polymer (A).

[0030] Among these copolymers (B), from the viewpoint of the impact resistance of the resulting molded articles such as injection foam molded articles, the composition ratio of the SEBS components is preferably in the range of 19 to 29% by mass for styrene blocks and 71 to 81% by mass for ethylene-butene blocks (where the total amount of blocks is taken as 100% by mass). Specifically, styrene-ethylene-butene-styrene rubber (SEBS) (manufactured by Asahi Kasei Chemicals, product name Tuftec H1052 (density = 890 kg / m 3 , MFR(230°C)=13g / 10min), etc. are preferred.

[0031] Examples of the method for producing the copolymer (B) according to the present invention include a method in which an alkenyl aromatic compound is bonded to an olefin copolymer or a conjugated diene rubber by polymerization, reaction or the like.

[0032] The copolymer (B) according to the present invention containing units derived from an alkenyl aromatic compound can be used alone or in combination of two or more different similar copolymers.

[0033] <Ethylene-based copolymer (C)> The ethylene-based copolymer (C), which may be contained in the propylene-based resin composition of the present invention, is a copolymer mainly composed of ethylene having an MFR measured at 230°C in accordance with ASTM D-1238 in the range of 20 to 40 g / 10 min, preferably 21 to 38 g / 10 min, more preferably 22 to 35 g / 10 min.

[0034] The ethylene copolymer (C) according to the present invention preferably has a density of 0.85 to 0.98 g / cm 3 , more preferably 0.85 to 0.88 g / cm 3 , and more preferably 0.86 to 0.87 g / cm 3 The lower the density of the ethylene copolymer (C), the more improved the impact resistance of the resulting molded article such as an injection foam molded article.

[0035] The ethylene-based copolymer (C) according to the present invention is a copolymer of ethylene and an α-olefin, generally known as a linear low-density polyethylene (LLDPE), a medium-density polyethylene (MDPE) or a high-density polyethylene (HDPE), which is an ethylene-based polymer, an amorphous or low-crystalline ethylene-α-olefin copolymer, and a copolymer mainly composed of ethylene.

[0036] 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. These α-olefins are used alone or in combination of two or more.

[0037] The ethylene copolymer (C) according to the present invention can be used alone or in combination of two or more different ethylene copolymers.

[0038] The ethylene copolymer (C) according to the present invention can be produced by various known production methods.

[0039] <Propylene-Based Resin Composition> The propylene-based resin composition of the present invention is a composition containing the above-mentioned propylene-based polymer (A) in the range of 50 to 90 mass%, preferably 60 to 90 mass%, more preferably 70 to 80 mass%, the above-mentioned copolymer (B) containing a unit derived from an alkenyl aromatic compound in the range of 5 to 50 mass%, preferably 5 to 40 mass%, more preferably 5 to 30 mass%, and the above-mentioned ethylene-based copolymer (C) in the range of 0 to 20 mass%, preferably 1 to 20 mass%, more preferably 10 to 20 mass% (wherein the total amount of (A)+(B)+(C) is 100 mass%).

[0040] The propylene-based resin composition of the present invention contains the above-mentioned copolymer (B) in addition to the above-mentioned propylene-based polymer (A) in the above-mentioned range, and thereby it is possible to obtain a molded article having a uniform cell size, good appearance and excellent surface impact resistance.

[0041] The propylene-based resin composition of the present invention has an MFR of preferably 40 to 120 g / 10 min, more preferably 40 to 100 g / 10 min, as measured at 230° C. in accordance with ASTM D-1238. If the MFR is equal to or higher than the lower limit, a molded product having a good appearance can be obtained.

[0042] The propylene-based resin composition of the present invention also exhibits the same effects when it contains an ethylene-based copolymer (C).

[0043] The propylene-based resin composition of the present invention may contain the following components in addition to the above-mentioned propylene-based polymer (A), copolymer (B) and ethylene-based copolymer (C).

[0044] <Crystal nucleating agent (D)> The crystal nucleating agent is a nucleating agent that preferentially forms α-crystals of the propylene polymer (A). Examples of the α-crystal nucleating agent include a phosphate metal salt nucleating agent, a carboxylate metal salt nucleating agent, a rosin metal salt nucleating agent, a sorbitol nucleating agent, a nonitol nucleating agent, a xylitol nucleating agent, and an amide nucleating agent.

[0045] When the propylene-based resin composition of the present invention contains a crystal nucleating agent (D), the amount of the crystal nucleating agent is 0.5 parts by mass or less, and preferably 0.4 parts by mass or less, per 100 parts by mass of the total amount of (A)+(B)+(C) in the propylene-based resin composition.

[0046] <Foaming agent (E)> There is no particular limitation on the foaming agent to be blended in the propylene-based resin composition of the present invention, and any foaming agent that can be used for the intended foam molding may be selected and used.

[0047] As the foaming agent, a chemical foaming agent or a physical foaming agent can be used.

[0048] Chemical foaming agents include decomposition type foaming agents, and physical foaming agents include solvent type foaming agents and gaseous foaming agents.

[0049] One type of blowing agent can be used alone, or two or more types of blowing agents can be used in combination.

[0050] Specific examples of decomposition type blowing agents include the following compounds: (1) Inorganic blowing agents: sodium bicarbonate, sodium carbonate, ammonium bicarbonate, ammonium carbonate, ammonium nitrite. (2) Organic blowing agents: (a) N-nitroso compounds: N,N'-dinitrosoterephthalamide, N,N'-dinitrosopentamethylenetetramine. (b) Azo compounds: azodicarbonamide, azobisisobutyronitrile, azocyclohexylnitrile, azodiaminobenzene, barium azodicarboxylate. (c) Sulfonyl hydrazide compounds: benzenesulfonyl hydrazide, toluenesulfonyl hydrazide, p,p'-oxybis(benzenesulfenyl hydrazide), diphenylsulfone-3,3'-disulfonyl hydrazide. (d) Azide compounds: calcium azide, 4,4'-diphenyldisulfonyl azide, p-toluenesulfonyl azide.

[0051] 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.

[0052] As the solvent-based blowing agent, various liquefied gases can be used. Specific examples include low-boiling point aliphatic hydrocarbons such as propane, butane, neopentane, heptane, isohexane, hexane, isoheptane, and heptane, and low-boiling point fluorine-containing hydrocarbons such as chlorofluorocarbon gases.

[0053] Gaseous blowing agents include inert gases such as carbon dioxide, nitrogen, argon, helium, neon, astatine, etc. Gaseous blowing agents may be used in a supercritical state.

[0054] The mixing ratio of the foaming agent is in the range of 0.1 to 10 parts by mass, preferably in the range of 0.1 to 5 parts by mass, and more preferably in the range of 0.1 to 3.0 parts by mass, relative to 100 parts by mass of the total amount of (A)+(B)+(C) of the propylene-based resin composition.

[0055] <Other Ingredients> The propylene-based resin composition of the present invention may contain various additives as necessary within a range that does not impair the purpose. 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, neutralizers, plasticizers, crosslinking agents, flow improvers such as peroxides, weld strength improvers, natural oils, synthetic oils, and waxes. These may be used alone or in combination of two or more.

[0056] <<Method for producing propylene-based resin composition>> The propylene-based resin composition of the present invention can be produced by various known production methods, for example, by mixing the above-mentioned propylene-based polymer (A), the above-mentioned copolymer (B) and the above-mentioned ethylene-based copolymer (C), and optionally a crystal nucleating agent (D), a foaming agent (E) and the like in predetermined amounts by a conventional method such as dry blending or melt kneading in an extruder.

[0057] <<Method for producing injection foamed product>> An embodiment of the production of an injection foamed molded article using the propylene-based resin composition of the present invention will be described below.

[0058] One embodiment of a method for producing an injection foam molded article includes the steps of filling a mold for injection foam molding with a propylene-based resin composition, and foaming and solidifying the propylene-based resin composition in the mold to obtain an injection foam molded article.

[0059] The mold for injection foam molding, the method for filling the propylene-based resin composition into the molding mold, and the foam molding conditions may be selected depending on the shape and physical properties of the desired foam molded product.

[0060] By using an injection molding method in which a propylene-based resin composition is injected into a molding die, an injection foam molded article can be obtained.

[0061] The foaming agent may be mixed with components of the propylene-based resin composition other than the foaming agent and then introduced into a mold for molding, or may be injected and mixed into the resin material in the introduction path of the resin material into the mold for molding, for example, in the cylinder during injection molding or in the flow path from the cylinder to the cavity.

[0062] For the formation of an injection foam-molded article having a thin-walled portion with a thickness of about 1.0 to 5.0 mm, a core-back molding method can be suitably used.

[0063] 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 die into which the propylene-based resin composition is injected and filled can be increased by moving the movable die back (core-back) to expand the cavity. The timing of operating the movable die after the injection and filling is completed can be determined according to the desired foaming rate, foam shape, various physical properties of the injection foam molded product, etc.

[0064] The moving speed of the movable mold during core-back can be selected depending on conditions such as the thickness of the injection foamed article, the composition of the propylene-based resin composition, the type and amount of foaming agent, the mold temperature, and the resin temperature.

[0065] 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 the foaming agent, etc. For example, the temperature of the resin material to be injected can be in the range of 170 to 250°C, preferably 180 to 220°C. The mold temperatures of the fixed and movable molds can be in the range of 10 to 100°C, preferably 30 to 80°C. The injection pressure can be selected from the range of 10 to 250 MPa, 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.

[0066] The injection foam molded article according to the present invention can be suitably used for various applications such as automobile interior and exterior parts, substitutes for cardboard, electrical appliances, building materials, etc. Such injection foam molded articles can be particularly suitably used for automobile interior parts, such as door trims, rear side trims, luggage trims, roof trims, back door trims, deck side trims, etc. EXAMPLES

[0067] The present invention will be further described below with reference to examples, although the present invention is not limited thereto.

[0068] As the polymer contained in the propylene-based resin composition used in the examples and comparative examples, the following polymers were used. (1) Propylene polymer (A) (1-1) Propylene-based polymer (A-1) As the propylene polymer (A), a propylene polymer (A-1) was used, which had an MFR of 75 g / 10 min measured at 230°C according to ASTM D-1238, a propylene-ethylene copolymer (a1-1) [room temperature n-decane soluble portion]: intrinsic viscosity [η] = 7.0 dl / g, content = 10.4 mass%, and a propylene homopolymer (a2-1) [room temperature n-decane insoluble portion]: MFR = 198 g / 10 min, content = 89.6 mass%. (1-2) Propylene polymer (A-2) As the propylene polymer (A), a propylene polymer (A-2) was used, which had an MFR of 90 g / 10 min measured at 230°C according to ASTM D-1238, a propylene-ethylene copolymer (a1-2) [room temperature n-decane soluble portion]: intrinsic viscosity [η] = 7.0 dl / g, content = 11.0 mass%, and a propylene homopolymer (a2-2) [room temperature n-decane insoluble portion]: MFR = 382 g / 10 min, content = 89.0 mass%. (2) Copolymers containing units derived from alkenyl aromatic compounds (2-1) Copolymer (B-1) Copolymer (B): MFR = 13 g / 10 min, density = 0.89 g / cm 3 A copolymer (B-1) of SEBS (manufactured by Asahi Kasei Corporation, product name Tuftec H-1052) with a styrene block / ethylene-butene block ratio of 20 / 80 (mass ratio) was used. (2-2) Copolymer (B-2) As copolymer (B), a copolymer (B-2) of SEPS (manufactured by Kuraray, product name Septon 2002) with MFR = 70 g / 10 min (measured at 230 °C) and styrene block / ethylene-propylene block = 30 / 70 (mass ratio) was used. (2-3) Copolymer (H-1) The copolymer used was a copolymer (H-1) of SEPS (manufactured by Kuraray, product name Septon 2063) with MFR = 7 g / 10 min (measured at 230°C) and styrene block / ethylene-propylene block = 13 / 87 (mass ratio). (3) Ethylene-based copolymer (C) (3-1) Ethylene-based copolymer (C-1) As an ethylene copolymer (C), density = 0.864 g / cm 3 An ethylene-1-octene copolymer having a molecular weight of 26 g / 10 min and an ethylene content of 80 mol% (ENGAGE (registered trademark) 8137, manufactured by The Dow Chemical Company) was used as the ethylene copolymer (C-1). (4) Propylene polymer (F) (4-1) Propylene polymer (F-1) As the propylene-based polymer (F), a propylene-based polymer (F-1) was used, which had an MFR of 66 g / 10 min measured at 230°C according to ASTM D-1238, a propylene-ethylene copolymer (f1-1) [room temperature n-decane soluble part]: intrinsic viscosity [η] = 7.0 dl / g, content = 10.0 mass%, and a propylene homopolymer (f2-1) [room temperature n-decane insoluble part]: MFR = 166 g / 10 min, content = 90.0 mass%. (4-2) Propylene polymer (F-2) As the propylene-based polymer (F), a propylene-based polymer (F-2) was used, which had an MFR of 60 g / 10 min measured at 230 °C according to ASTM D-1238, a propylene-ethylene copolymer (f1-2) [room temperature n-decane soluble part]: intrinsic viscosity [η] = 2.7 dl / g, content = 23.0 mass%, and a propylene homopolymer (f2-2) [room temperature n-decane insoluble part]: MFR = 220 g / 10 min, content = 77.0 mass%. (5) Ethylene-based copolymer (G) (5-1) Ethylene-based copolymer (G-1) As an ethylene copolymer (G), density = 0.87 g / cm 3 An ethylene-1-octene copolymer having a molecular weight of 60 g / 10 min and a molecular weight of 60 g / 10 min (ENGAGE (registered trademark) 8407, manufactured by The Dow Chemical Company) was used as the ethylene copolymer (G-1).

[0069] The compounding agents contained in the propylene-based resin compositions used in the Examples and Comparative Examples were as follows. (6) Nucleating Agent (D) A phosphate metal salt-based nucleating agent (trade name Adeka STAB NA-11 (manufactured by ADEKA Corporation)) was used as the crystal nucleating agent (D-1). (7) Foaming agent (E) A sodium bicarbonate type foaming agent (trade name Polysurene EE65C (manufactured by Eiwa Kasei Co., Ltd.)) was used as the foaming agent (E-1). [Injection foam molding method] The injection foamed molded articles of the propylene-based resin compositions obtained in the Examples and Comparative Examples were molded by the following method.

[0070] 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: 200℃ Mold surface temperature: 40℃ Injection speed: 120mm / s Foam molding conditions: Mold clearance after foaming process: 3.0mm Core back time: 0.2s Delay time after filling composition to start foaming: 0s Injection mold cavity clearance (L0): 1.5mm The physical properties of the injection foamed articles were measured by the following methods. [Puncture Energy Value] In accordance with ISO 6603-2, puncture energy values ​​were measured using 100 mm x 100 mm test pieces cut from injection foam molded products under the following conditions: measurement temperature: 23°C, striker diameter: 20 mm, support table inner diameter: 40 mm, impact speed: 4.4 mm / s.

[0071] 〇: Puncture energy value is 8.0J or more.

[0072] ×: Puncture energy value is less than 8.0 J. [Cell diameter] An observation sample was prepared by cutting a thin section perpendicular to the flow direction at the center of the injection foam molded article at a position 100 mm from the gate with a razor blade.

[0073] The observation sample was observed under a microscope, binarized by light and dark, and the average cell perimeter was measured. The larger the value, the coarser the cell diameter. The smaller and more uniform the cell diameter, the better the physical properties of the foam. The cell size was judged as follows.

[0074] The average cell perimeter is less than 190 μm.

[0075] An average cell perimeter of 190 μm or more was considered defective. [Appearance of injection foamed product] The appearance of the injection foam molded article was visually observed, and the presence or absence of avatars and swirl marks was visually judged and the appearance was evaluated. If both avatars and swirl marks could be visually confirmed, it was rated as ×, and if they could not be confirmed, it was rated as ◯.

[0076] Example 1 76% by mass of the propylene polymer (A-1) and 24% by mass of the copolymer (B-1) were mixed and granulated to obtain a polypropylene resin composition for foam molding.

[0077] Next, 3 parts by mass of the foaming agent (E-1) was mixed (added) to 100 parts by mass of the obtained composition, and injection foam molding was carried out by the method described above to obtain an injection foam molded article.

[0078] The obtained injection foamed molded articles were evaluated by the methods described above, and the results are shown in Table 1.

[0079] Example 2 The same procedure as in Example 1 was carried out to obtain an injection foamed molded article, except that the propylene polymer (A-1) used in Example 1 was replaced with 74 mass% of the propylene polymer (A-2), 26 mass% of the copolymer (B-1), and 0.2 mass parts of the crystal nucleating agent (D-1) per 100 mass parts of the total amount of (A) + (B).

[0080] The obtained injection foamed molded articles were evaluated by the methods described above, and the results are shown in Table 1.

[0081] Example 3 An injection foam-molded product was obtained in the same manner as in Example 1, except that the polypropylene resin composition for foam molding used in Example 1 was replaced with 76 mass% of propylene-based polymer (A-1), 6 mass% of copolymer (B-1), and 18 mass% of ethylene-based copolymer (C-1).

[0082] The obtained injection foamed molded articles were evaluated by the methods described above, and the results are shown in Table 1.

[0083] Example 4 The procedure of Example 1 was repeated, except that the polypropylene resin composition for foam molding used in Example 1 was replaced with 76 mass% of the propylene polymer (A-1) and 24 mass% of the copolymer (B-2), to obtain an injection foam molded article.

[0084] The obtained injection foamed molded articles were evaluated by the methods described above, and the results are shown in Table 1.

[0085] Comparative Example 1 The procedure of Example 1 was repeated, except that the polypropylene resin composition for foam molding used in Example 1 was replaced with 76 mass% of a propylene polymer (A-1) and 24 mass% of an ethylene copolymer (G-1), to obtain an injection foam molded article.

[0086] The obtained injection foamed molded articles were evaluated by the methods described above, and the results are shown in Table 1.

[0087] Comparative Example 2 The procedure of Example 1 was repeated, except that the polypropylene resin composition for foam molding used in Example 1 was replaced with 76 mass% of the propylene polymer (F-1) and 24 mass% of the copolymer (B-1), to obtain an injection foam-molded product.

[0088] The obtained injection foamed molded articles were evaluated by the methods described above, and the results are shown in Table 1.

[0089] Comparative Example 3 The same procedure as in Example 1 was carried out to obtain an injection foam-molded product, except that the polypropylene resin composition for foam molding used in Example 1 was replaced with 90 mass% of the propylene polymer (F-2) and 10 mass% of the copolymer (B-1).

[0090] The obtained injection foamed molded articles were evaluated by the methods described above, and the results are shown in Table 1.

[0091] Comparative Example 4 The procedure of Example 1 was repeated, except that the polypropylene resin composition for foam molding used in Example 1 was replaced with 76 mass% of propylene polymer (A-1) and 24 mass% of copolymer (H-1), to obtain an injection foam molded article.

[0092] The obtained injection foamed molded articles were evaluated by the methods described above, and the results are shown in Table 1.

[0093] [Table 1] As shown in Table 1, the injection foam-molded articles obtained in Examples 1 to 3 had puncture energy values ​​of 8.0 J or more, average cell perimeters of less than 190 μm, and beautiful appearances.

[0094] In contrast, the injection foamed product obtained in Comparative Example 1 did not contain the copolymer (B-1), and therefore had a low puncture energy value of 7.4 J. Moreover, the cell diameter was large, possibly due to the high MFR of the ethylene-based copolymer (G-1).

[0095] The injection foamed article obtained in Comparative Example 2 had a deteriorated appearance due to an increased amount of gas generated by shear heat, probably due to poor fluidity caused by a small MFR of the propylene polymer.

[0096] The injection foamed article obtained in Comparative Example 3 had poor fluidity due to a small MFR of the propylene polymer. Moreover, probably because the intrinsic viscosity [η] of the propylene-ethylene copolymer contained therein was low, the amount of gas generated due to shear heating increased and the cell diameter was large.

[0097] The injection foamed article obtained in Comparative Example 3 had poor fluidity due to a small MFR of the propylene polymer, and had a poor appearance due to an increase in gas generation caused by shear heating. Moreover, the cell diameter was large, possibly due to the low intrinsic viscosity [η] of the propylene-ethylene copolymer contained.

[0098] In addition, the injection foam obtained in Comparative Example 4 had a poor appearance due to an increase in gas generation caused by shear heating, possibly due to the low MFR of the resin and poor fluidity. In addition, the copolymer (H-1) had a low puncture energy value of 7.9 J due to its poor fluidity with an MFR of 7 g / 10 min.

Claims

1. The composition contains 5 to 22 mass% of a propylene-ethylene copolymer (a1) specified as an n-decane soluble portion, the propylene-ethylene copolymer portion specified as the n-decane soluble portion (Dsol) at 23° C. having an intrinsic viscosity [η] in tetralin at 135° C. in the range of 4.0 to 9.0 dl / g, and 78 to 95 mass% of a propylene homopolymer (a2) (wherein the total amount of (a1) + (a2) is 100 mass%), and contains 50 to 90 mass% of a propylene polymer (A) having an MFR in the range of 70 to 150 g / 10 min as measured at 230° C. under a load of 2.16 kg in accordance with ASTM D-1238; 5 to 50% by mass of a copolymer (B) containing units derived from an alkenyl aromatic compound having an MFR in the range of 10 to 80 g / 10 min as measured at 230° C. according to ASTM D-1238, and A propylene-based resin composition comprising 0 to 20 mass % (wherein the total amount of (A)+(B)+(C) is taken as 100 mass %) of an ethylene-based copolymer (C) having an MFR in the range of 20 to 40 g / 10 min as measured at 230° C. in accordance with ASTM D-1238.

2. 2. The propylene-based resin composition according to claim 1, which has an MFR in the range of 40 to 120 g / 10 min as measured at 230° C. in accordance with ASTM D-1238.

3. The copolymer (B) containing units derived from an alkenyl aromatic compound has a density of 0.88 to 0.98 g / cm 3 The propylene-based resin composition according to claim 1, wherein the propylene-based resin composition has a molecular weight of 1:1 or more.

4. The ethylene copolymer (C) is a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms and has a density of 0.85 to 0.98 g / cm 3 The propylene-based resin composition according to claim 1, wherein the propylene-based resin composition has a molecular weight of 1:1 or more.

5. The propylene-based resin composition according to claim 1, further comprising a crystal nucleating agent (D) in an amount of 0 to 0.5 parts by mass per 100 parts by mass of the total amount of (A) + (B) + (C).

6. The propylene-based resin composition according to claim 1, comprising a foaming agent (E) in an amount of 0.1 to 10 parts by mass per 100 parts by mass of the total amount of (A) + (B) + (C).

7. A foam obtained by foaming the propylene-based resin composition according to any one of claims 1 to 6.

8. 7. An automobile interior part obtained by injection foam molding the propylene-based resin composition according to any one of claims 1 to 6.

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