Thermoplastic elastomer composition, injection molded product and airbag storage cover

Abstract

To provide a thermoplastic elastomer composition which enables excellent molding that is excellent in designability while maintaining low temperature impact resistance.SOLUTION: A thermoplastic elastomer composition contains the following components (A) to (C), wherein a die swell ratio (test temperature 210°C, and shear rate of 243 / s) in capillary rheometer (JIS K 7199) is 1.10 or more, glossiness when a test piece for glossiness measurement composed of the thermoplastic elastomer composition is measured at an incident angle of 60° according to ISO 2813 is 50% or less, and a bending modulus of elasticity when a test piece for bending modulus of elasticity measurement composed of the thermoplastic elastomer composition is measured according to ISO 178 (2010) is 100-700 MPa. Component (A): propylene-based block copolymer, component (B): ethylene-α-olefin copolymer having α-olefin having 4 or more carbon atoms, and component (C): ethylene-propylene-non-conjugated diene copolymer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a thermoplastic elastomer composition, and an injection-molded article and an airbag storage cover made from this thermoplastic elastomer composition. [Background technology]

[0002] Automotive airbag systems protect drivers and passengers in the event of a collision, and consist of a device that detects the impact of a collision and an airbag device. The airbag device is installed in the steering wheel, the instrument panel in front of the passenger seat, the driver's and passenger's seats, the front and side pillars, etc.

[0003] Various proposals have been made regarding the structure and material of the airbag storage cover in an airbag device so that it will tear as designed when the airbag inflates.

[0004] As an airbag storage cover made of an olefin-based thermoplastic elastomer, for example, Patent Document 1 proposes a thermoplastic elastomer composition obtained by dynamically heat-treating a composition containing a specific propylene-based polymer, a specific olefin-based block copolymer, and a specific amount of a styrene-conjugated diene block copolymer and / or a hydrogenated product thereof in the presence of an organic peroxide. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-186041 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, due to concerns about damage to airbag storage covers at low temperatures caused by increased airbag deployment power, materials with excellent low-temperature impact resistance are desired from the perspectives of improved safety, design freedom, etc. Furthermore, airbag storage covers have traditionally been manufactured through a painting process, but there are cost issues associated with the painting process, such as the installation of additional painting lines, so in recent years, materials that can be manufactured without painting have been desired for cheaper production. Furthermore, compared to unpainted airbag storage covers, molded products with low gloss and improved flow mark resistance are desired from the perspective of design.

[0007] According to detailed studies by the present inventors, it has been found that the thermoplastic elastomer composition described in Patent Document 1 has problems such as poor flow mark resistance and insufficient appearance. The present invention has been made in view of the problems of the prior art. That is, an object of the present invention is to provide a thermoplastic elastomer composition that can be used to form molded articles with excellent design while maintaining low-temperature impact resistance. [Means for solving the problem]

[0008] As a result of extensive investigations into solving the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by a thermoplastic elastomer composition containing a propylene-based block copolymer, an ethylene-α-olefin copolymer, and an ethylene-propylene-non-conjugated diene copolymer, wherein the thermoplastic elastomer composition has a die swell ratio (test temperature: 210°C, shear rate: 243 / s) of 1.10 or more as measured with a capillary rheometer (JIS K7199) (test temperature: 210°C, shear rate: 243 / s), a gloss of 50% or less as measured at an incident angle of 60°, and a flexural modulus of 100 to 700 MPa.

[0009] That is, the gist of the present invention lies in the following [1] to [8].

[0010] [1] A thermoplastic elastomer composition comprising the following components (A) to (C): a die swell ratio (test temperature 210°C, shear rate 243 / s) of 1.10 or more as measured with a capillary rheometer (JIS K7199), a gloss of 50% or less as measured at an incident angle of 60° in accordance with ISO 2813 on a gloss measurement specimen made of the thermoplastic elastomer composition, and a flexural modulus of 100 to 700 MPa as measured in accordance with ISO 178 (2010) on a flexural modulus measurement specimen made of the thermoplastic elastomer composition: Component (A): Propylene block copolymer Component (B): Ethylene-α-olefin copolymer in which the α-olefin has 4 or more carbon atoms Component (C): Ethylene-propylene-non-conjugated diene copolymer

[0011] [2] The thermoplastic elastomer composition according to [1], wherein the α-olefin of component (B) has 4 to 8 carbon atoms.

[0012] [3] The thermoplastic elastomer composition according to [1] or [2], wherein the ethylene-α-olefin copolymer of component (B) is an ethylene-α-olefin block copolymer.

[0013] [4] The thermoplastic elastomer composition according to [3], wherein the ethylene-α-olefin block copolymer is an ethylene-α-olefin block copolymer containing a polymer block composed of ethylene and an ethylene-α-olefin copolymer block.

[0014] [5] The thermoplastic elastomer composition according to [4], wherein the ethylene-α-olefin block copolymer has a crystalline melting peak at 110 to 125°C and a heat of crystalline melting of 20 to 60 J / g.

[0015] [6] The thermoplastic elastomer composition according to any one of [1] to [5], wherein the component (C) is an oil-extended ethylene-propylene-non-conjugated diene copolymer.

[0016] [7] An injection-molded article obtained by injection molding the thermoplastic elastomer composition according to any one of [1] to [6].

[0017] [8] An airbag storage cover using the thermoplastic elastomer composition according to any one of [1] to [6]. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide a thermoplastic elastomer composition that can be used to form molded articles with excellent design while maintaining low-temperature impact resistance. The airbag storage cover made of the molded product of the present invention can be suitably used as any of a driver's seat airbag storage cover, a passenger seat airbag storage cover, a pedestrian airbag storage cover, a knee airbag storage cover, a side airbag storage cover, a curtain airbag storage cover, etc. DETAILED DESCRIPTION OF THE INVENTION

[0019] The present invention will be described in detail below, but the present invention is not limited to the following description and can be modified as desired without departing from the gist of the present invention. In this specification, when a numerical value or physical property value is enclosed by "~", the value before and after the "~" is used to include the values ​​before and after the "~"

[0020] In the present invention, the term "airbag storage cover" refers to the container in general that stores an airbag, and is, for example, the opening in a container that stores an airbag when the airbag is deployed, or the entire container that is integrated with this opening.

[0021] [Thermoplastic elastomer composition] The thermoplastic elastomer composition of the present invention is a thermoplastic elastomer composition containing the following components (A) to (C): a die swell ratio (test temperature: 210°C, shear rate: 243 / s) (hereinafter sometimes simply referred to as the "die swell ratio") measured using a capillary rheometer (JIS K7199) of 1.10 or more, a gloss (hereinafter sometimes simply referred to as the "gloss") measured at an incident angle of 60° in accordance with ISO 2810 on a gloss measurement specimen made of the thermoplastic elastomer composition of 50% or less, and a flexural modulus (hereinafter sometimes simply referred to as the "flexural modulus") measured at an incident angle of 60° in accordance with ISO 178 (2010) on a flexural modulus measurement specimen made of the thermoplastic elastomer composition of 100 to 700 MPa. Component (A): Propylene block copolymer Component (B): Ethylene-α-olefin copolymer in which the α-olefin has 4 or more carbon atoms Component (C): Ethylene-propylene-non-conjugated diene copolymer

[0022] In order to set the die swell ratio, gloss, and flexural modulus within the above-specified ranges, the thermoplastic elastomer composition of the present invention is preferably produced by dynamically heat treating a composition containing the above-mentioned components (A), (B), and (C) in the presence of the following components (D) and (E). Component (D): Organic peroxide Component (E): Crosslinking aid

[0023] <Die swell ratio> It has been found that the thermoplastic elastomer composition of the present invention tends to exhibit good flow mark resistance when the die swell ratio is 1.10 or higher. It is believed that when the thermoplastic elastomer composition of the present invention has a die swell of 1.10 or higher, the flow front in the mold during injection molding becomes stable, improving the flow mark resistance. The die swell ratio of the thermoplastic elastomer composition of the present invention is preferably 1.13 or higher, and more preferably 1.15 or higher. There is no upper limit to the die swell ratio of the thermoplastic elastomer composition, but it is usually 2.00 or lower.

[0024] In the present invention, the die swell ratio in a capillary rheometer (JIS K7199) is a value measured during the extrusion process of a sample using a Capillograph 1D (JIS K7199) manufactured by Toyo Seiki Seisaku-sho, Ltd. under the following conditions, and is calculated by the following calculation formula (I). Test temperature: 210℃ L / D: 10 (D=1mm) Shear rate: 243 / s St=Dm / Dt (I) St, Dm, Dt indicate the following: St: Die swell ratio Dm: diameter of the extruded sample measured at the test temperature at a position 10 mm below the die exit (mm) Dt: diameter of the capillary die measured at the test temperature (mm)

[0025] In order to make the die swelling ratio of the thermoplastic elastomer composition containing the above-mentioned components (A), (B) and (C) 1.10 or more, it is preferable to take the following measures, for example. From the viewpoint of manufacturing method, it is preferable to dynamically heat-treat a mixture of a portion of component (A), component (B), component (C), component (D) and component (E) described below, and, if necessary, component (F) and component (G) described below to partially crosslink the mixture, and then add the remainder of component (A). By doing so, the later-added component (A) is less susceptible to molecular chain scission by radicals, allowing the composition to maintain high tensile strength and control the die swell ratio to 1.10 or higher. Note that the portion of component (A) and the remainder of component (A) may be one or more types as long as they correspond to the component (A) described below, and the portion of component (A) and the remainder of component (A) may be the same or different. Furthermore, as components to be added after partial crosslinking by dynamic heat treatment, it is believed that the die swell ratio can also be increased by adding components (B), (C), (F), and (G) in addition to component (A). Therefore, with regard to components (B), (C), (F), and (G), one or more of these may be partially added and mixed before partial crosslinking by dynamic heat treatment, and the remainder may be added after partial crosslinking by dynamic heat treatment.

[0026] <Glossiness> The gloss of the thermoplastic elastomer composition of the present invention measured at an incident angle of 60° is 50% or less. If the gloss is equal to or less than the above upper limit, the desired design can be obtained without painting. The upper limit of the gloss is preferably 40% or less, and more preferably 35% or less.

[0027] The gloss level in the present invention is a value measured in accordance with ISO 2813 at an incident angle of 60° using a test piece for gloss measurement (a sheet having a thickness of 2 mm, a width of 120 mm, and a length of 80 mm) molded from the thermoplastic elastomer composition using an in-line screw type injection molding machine at an injection speed of 30 mm / s, a cylinder temperature setting of 220°C, and a mold temperature of 40°C.

[0028] In the present invention, in order to make the gloss of the thermoplastic elastomer composition equal to or less than the above upper limit, it is preferable to subject a composition containing components (A), (B), and (C) to dynamic heat treatment in the presence of components (D) and (E) described below.

[0029] <Flexural modulus> The thermoplastic elastomer composition of the present invention has a flexural modulus of 100 to 700 MPa. In the present invention, the flexural modulus is correlated with low-temperature impact resistance, and by setting the flexural modulus within the above range, excellent low-temperature impact resistance can be achieved while maintaining the shape retention of the molded article. From the viewpoint of low-temperature impact resistance, the upper limit of the flexural modulus is preferably 600 MPa or less, more preferably 500 MPa or less. From the viewpoint of shape retention of the molded article, the lower limit of the flexural modulus is preferably 150 MPa or more, more preferably 200 MPa or more.

[0030] The flexural modulus in the present invention is a value measured at a speed of 2 mm / min using a Pentograph B-2 manufactured by Toyo Seiki Co., Ltd., in accordance with ISO 178 (2010), using a multipurpose evaluation test piece A (180 mm long dumbbell) in accordance with ISO 3167 (2002) molded from the thermoplastic elastomer composition of the present invention using an in-line screw type injection molding machine at an injection speed of 30 mm / s, a cylinder set temperature of 220°C, and a mold temperature of 40°C, and then cutting off the ends of the dumbbell to prepare a flexural modulus measurement test piece (4 mm thick × 10 mm wide × 80 mm long).

[0031] In the present invention, in order to set the flexural modulus of the thermoplastic elastomer composition within the above range, it is preferable to use components (A), (B) and (C) as materials and blend them in the preferred ranges described below.

[0032] <Component (A)> The thermoplastic elastomer composition of the present invention contains a propylene-based block copolymer as component (A). The propylene unit content of the propylene-based block copolymer of component (A) is usually 50% by mass or more, and preferably 70 to 99% by mass, based on the total mass of component (A). When the propylene unit content of component (A) is equal to or greater than the above-mentioned lower limit, heat resistance and rigidity tend to be good. When the propylene unit content of component (A) is equal to or less than the above-mentioned upper limit, low-temperature impact resistance tends to be good. When component (A) is composed of a mixture of two or more propylene-based polymers with different compositions, the propylene unit content of component (A) as a whole may be within the above-mentioned numerical range.

[0033] The propylene unit content and the α-olefin unit content described below in component (A), and the ethylene unit content and the α-olefin unit content described below in component (B) can each be determined by infrared spectroscopy.

[0034] Component (A) contains propylene units in the above-mentioned preferred content relative to the total of component (A), and also contains ethylene units other than propylene units, units of α-olefins other than propylene (hereinafter sometimes referred to as "other α-olefins"), monomer units other than ethylene and α-olefins, etc. Examples of the propylene-based block copolymer of component (A) include propylene-ethylene block copolymers, propylene-other α-olefin block copolymers, propylene-ethylene-other α-olefin block copolymers, and other propylene-based block copolymers.

[0035] The total content of ethylene units other than propylene units, other α-olefin units and other monomer units in component (A) is preferably 1 to 30% by mass.

[0036] When component (A) is a propylene-other α-olefin block copolymer, the α-olefin units other than propylene can be α-olefin units having 4 to 20 carbon atoms. Examples of α-olefins having 4 to 20 carbon atoms include 1-butene, 1-pentene, 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-octadecene, 1-nonadecene, 1-eicosene, 3-methyl-1-butene, 3-methyl-1-pentene, 4-methyl-1-pentene, 2-ethyl-1-hexene, and 2,2,4-trimethyl-1-pentene. The α-olefin other than propylene is preferably an α-olefin having 4 to 10 carbon atoms, more preferably 1-butene, 1-hexene, or 1-octene. Component (A) may contain only one type of these other α-olefin units, or may contain two or more types.

[0037] Examples of the propylene-based block copolymer of component (A) include a propylene-ethylene block copolymer, a propylene-1-butene block copolymer, a propylene-1-hexene block copolymer, a propylene-1-octene block copolymer, a propylene-ethylene-1-butene block copolymer, a propylene-ethylene-1-hexene block copolymer, a propylene-ethylene-1-octene block copolymer, and a propylene-based block copolymer obtained by polymerizing a propylene homopolymer in a first step and subsequently polymerizing a propylene-ethylene block copolymer in a second step.

[0038] Preferred are block copolymers of propylene and at least one monomer selected from ethylene and α-olefins having 4 to 10 carbon atoms, and propylene-based block copolymers obtained by polymerizing a propylene homopolymer in a first step and subsequently polymerizing a propylene-ethylene copolymer in a second step. Among these, from the viewpoints of low-temperature impact resistance and high-temperature strength, component (A) is particularly preferably a propylene-based block copolymer obtained by polymerizing a propylene homopolymer in a first step and subsequently polymerizing a propylene-ethylene copolymer in a second step.

[0039] The melt flow rate (230°C, load 21.18N) of component (A) is not limited, but is usually 0.1 g / 10 min or more. From the viewpoint of the appearance of the molded product, it is preferably 10 g / 10 min or more, more preferably 20 g / 10 min or more, and even more preferably 30 g / 10 min or more. The melt flow rate (230°C, load 21.18N) of component (A) is usually 200 g / 10 min or less. From the viewpoint of tensile strength, it is preferably 150 g / 10 min or less, more preferably 100 g / 10 min or less. The melt flow rate (MFR) of component (A) is measured according to ISO 1133 (2011) at 230°C and a load of 21.18 N. A plurality of components (A) having a melt flow rate (230°C, load 21.18N) in the range of 0.1 to 200 g / 10 min may be used.

[0040] The propylene-based block copolymer of component (A) can be produced by a known polymerization method using a known olefin polymerization catalyst. For example, a polymerization method using a Ziegler-Natta catalyst can be used. The polymerization method can be a slurry polymerization method, a solution polymerization method, a bulk polymerization method, a gas phase polymerization method, or the like, or a combination of two or more of these methods.

[0041] Component (A) may be commercially available. Examples of commercially available products of component (A) include "PrimPolypro (registered trademark)" manufactured by Prime Polymer Co., Ltd., "Sumitomo Noblen (registered trademark)" manufactured by Sumitomo Chemical Co., Ltd., "Polypropylene Block Copolymer" manufactured by SunAllomer Co., Ltd., "Novatec (registered trademark) PP" manufactured by Japan Polypropylene Corporation, "Moplen (registered trademark)" manufactured by LyondellBasell, "ADFLEX (registered trademark)" manufactured by LyondellBasell, "Hifax (registered trademark)" manufactured by LyondellBasell, "ExxonMobil PP" manufactured by ExxonMobil, "Formolene (registered trademark)" manufactured by Formosa Plastics, and B Examples of such polypropylene include "Borealis PP" manufactured by Borealis, "SEETEC PP" manufactured by LG Chemical, "ASIPOLYPROPYLENE" manufactured by A. Schulman, "INEOS PP" manufactured by INEOS Olefins & Polymers, "Braskem PP" manufactured by Braskem, "Hanwha Total" manufactured by Hanwha Total Petrochemicals, "Sabic (registered trademark) PP" manufactured by Sabic, "TOTAL PETROCHEMICALS Polypropylene" manufactured by Total Petrochemicals, and "YUPLENE (registered trademark)" manufactured by SK Chemicals.

[0042] The propylene-based block copolymer of component (A) may be used alone or in combination of two or more types having different copolymer component compositions, physical properties, etc.

[0043] <Ingredient (B)> The thermoplastic elastomer composition of the present invention contains, as component (B), an ethylene-α-olefin copolymer in which the α-olefin has 4 or more carbon atoms. The ethylene-α-olefin copolymer of component (B) preferably has an ethylene unit content of 50 to 80 mass% and an α-olefin unit content of 20 to 50 mass%, where the sum of the ethylene unit content and the α-olefin unit content is 100 mass%. When the ethylene unit content is within the above ranges, affinity with other components is good, and the fine dispersibility of the thermoplastic elastomer composition tends to be improved. The content of each structural unit of component (B) can be determined by infrared spectroscopy.

[0044] The α-olefin constituting the ethylene-α-olefin copolymer of component (B) is not limited, but specific examples include 1-butene, 3-methyl-1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, and 1-decene. Component (B) may contain only one type of these α-olefin units, or two or more types. Among these, α-olefins having 4 to 8 carbon atoms are preferred, with 1-octene being more preferred. The inclusion of 1-octene units as α-olefin units in the ethylene-α-olefin copolymer improves tensile strength.

[0045] Examples of the ethylene-α-olefin copolymer of component (B) include ethylene-α-olefin random copolymers and ethylene-α-olefin block copolymers. Among these, ethylene-α-olefin block copolymers, particularly ethylene-α-olefin block copolymers containing a polymer block composed of ethylene and an ethylene-α-olefin copolymer block, are preferred.

[0046] Ethylene-α-olefin block copolymers have crystalline ethylene polymer blocks, as well as amorphous α-olefin-containing blocks. Component (B) with this structure helps impart high-temperature strength and low-temperature impact resistance to the resulting airbag storage cover. Furthermore, it is believed that the polymer block made of ethylene is dynamically heat treated in the presence of an organic peroxide, component (D) described below, thereby reducing gloss and improving appearance.

[0047] The ethylene-α-olefin block copolymer of component (B) preferably has a crystalline melting peak at 110 to 125°C and a crystalline heat of fusion of 20 to 60 J / g. Here, the fact that component (B) has a crystalline melting peak at 110 to 125°C and a crystalline heat of fusion of 20 to 60 J / g calculated from the crystalline melting peak is an indicator that component (B) contains a polymer block made of crystalline ethylene. From the viewpoint of high-temperature strength, the crystalline heat of fusion of component (B) is more preferably 30 J / g or more. Furthermore, from the viewpoint of low-temperature impact resistance, the crystalline heat of fusion of component (B) is more preferably 50 J / g or less.

[0048] The amorphousness due to the α-olefin-containing blocks of the ethylene-α-olefin block copolymer of component (B) can be expressed by the glass transition temperature. The glass transition temperature of component (B) measured by the DSC method is preferably −80°C or higher, more preferably −75°C or higher, and is preferably −50°C or lower, more preferably −60°C or lower.

[0049] The crystalline melting peak temperature, heat of crystalline melting, and glass transition temperature of component (B) can be determined by differential scanning calorimetry (DSC). The crystalline melting peak temperature is the top temperature of the melting peak obtained by a differential scanning calorimeter (DSC), and the heat of crystalline melting can be determined from the area of ​​the melting peak obtained by a differential scanning calorimeter. The glass transition temperature is the intersection of the tangent line at the inflection point and the baseline obtained by a differential scanning calorimeter. The specific measurement conditions for determining these values ​​are as follows: That is, a 10 mg sample is taken and melted using a DSC at a heating rate of 100°C / min from 25°C to 200°C, held at 200°C for 1 minute, crystallized at a heating rate of 10°C / min to -130°C, held at -130°C for 10 minutes, and then measured at a heating rate of 10°C / min up to 200°C.

[0050] The polymer block of ethylene in the ethylene-α-olefin block copolymer of component (B) is primarily composed of ethylene units, but may contain other monomer units in addition to ethylene. Here, "primarily composed" refers to a ratio of 50% by mass or more, particularly 60 to 100% by mass, of the total. Examples of other monomer units include propylene units, 1-butene units, 2-methylpropylene units, 1-pentene units, 3-methyl-1-butene units, 1-hexene units, 4-methyl-1-pentene units, and 1-octene units. Preferred are α-olefin units having 3 to 8 carbon atoms and a carbon-carbon double bond at the terminal carbon atom, such as propylene units, 1-butene units, 1-hexene units, and 1-octene units. The polymer block of ethylene in component (B) may be composed of only one α-olefin copolymerized with ethylene, or two or more α-olefins copolymerized with ethylene. When the polymer block made of ethylene contains propylene units, the content of propylene units in the entire ethylene-α-olefin block copolymer of component (B) is preferably 5% by mass or less from the viewpoint of high-temperature strength.

[0051] The α-olefin-containing block in the ethylene-α-olefin block copolymer of component (B) may be one having α-olefin units such as 1-butene, 2-methylpropylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, or 1-octene as structural units. Preferred are α-olefin units having 4 to 8 carbon atoms and a carbon-carbon double bond at the terminal carbon atom, such as 1-butene, 1-hexene, or 1-octene. From the viewpoint of low-temperature impact resistance, the α-olefin-containing block in component (B) preferably contains ethylene units in addition to α-olefin units. In this case, the α-olefin-containing block may be one in which only one α-olefin is copolymerized with ethylene, or two or more α-olefins may be copolymerized with ethylene.

[0052] The α-olefin-containing block in the ethylene-α-olefin block copolymer of component (B) may contain, in addition to the α-olefin units and ethylene units described above, other monomer units such as monomer units based on non-conjugated dienes (non-conjugated diene units). Examples of the non-conjugated diene unit include linear non-conjugated diene units such as 1,4-hexadiene unit, 1,6-octadiene unit, 2-methyl-1,5-hexadiene unit, 6-methyl-1,5-heptadiene unit, and 7-methyl-1,6-octadiene unit; and cyclic non-conjugated diene units such as cyclohexadiene unit, dicyclopentadiene unit, methyltetrahydroindene unit, 5-vinylnorbornene unit, 5-ethylidene-2-norbornene unit, 5-methylene-2-norbornene unit, 5-isopropylidene-2-norbornene unit, and 6-chloromethyl-5-isopropenyl-2-norbornene unit. Among these, dicyclopentadiene unit and 5-ethylidene-2-norbornene unit are preferred.

[0053] When the ethylene-α-olefin block copolymer of component (B) contains other monomer units such as non-conjugated diene units, the content thereof is usually 10% by mass or less, preferably 5% by mass or less, based on the total mass of component (B).

[0054] The ethylene-α-olefin block copolymer of component (B) used in the thermoplastic elastomer composition of the present invention may, for example, be an ethylene-α-olefin block copolymer having a polymer block composed of ethylene and an ethylene-α-olefin copolymer block. Specific examples include block copolymers containing a polymer block composed of ethylene and an ethylene-α-olefin copolymer block such as an ethylene-1-butene copolymer, an ethylene-1-hexene copolymer, an ethylene-1-octene copolymer, an ethylene-propylene-1-butene copolymer, an ethylene-propylene-1-hexene copolymer, or an ethylene-propylene-1-octene copolymer. Among these, it is preferable from the viewpoint of tensile strength that component (B) is an ethylene-1-octene block copolymer containing a polymer block made of ethylene and an ethylene-1-octene copolymer block.

[0055] The melt flow rate (190°C, load 21.18N) of component (B) is not limited, but is usually 10 g / 10 min or less. From the viewpoint of strength, it is preferably 8.0 g / 10 min or less, more preferably 5.0 g / 10 min or less, and even more preferably 3.0 g / 10 min or less. The melt flow rate (190°C, load 21.18N) of component (B) is usually 0.01 g / 10 min or more. From the viewpoint of fluidity, it is preferably 0.05 g / 10 min or more, more preferably 0.10 g / 10 min or more. The melt flow rate of component (B) is measured according to ASTM D1238 under conditions of 190°C and load 21.18 N.

[0056] From the viewpoint of low-temperature impact resistance, the density of component (B) is preferably 0.880 g / cm 3 or less, more preferably 0.870 g / cm 3 On the other hand, the lower limit is not particularly limited, but is usually 0.850 g / cm 3 The density of component (B) can be measured according to ASTM D792.

[0057] The ethylene-α-olefin block copolymer of component (B) can be synthesized according to the methods disclosed in JP-A Nos. 2007-529617, 2008-537563, and 2008-543978. For example, it can be produced by preparing a composition containing a mixture or reaction product obtained by combining a first olefin polymerization catalyst with a second olefin polymerization catalyst capable of preparing a polymer having different chemical or physical properties from the polymer prepared by the first olefin polymerization catalyst under equivalent polymerization conditions, and a chain shuttling agent, and then contacting the composition with the ethylene and an α-olefin under additional loading conditions.

[0058] The polymerization of component (B), an ethylene-α-olefin block copolymer, is preferably carried out by a continuous solution polymerization method. In a continuous solution polymerization method, catalyst components, a chain shuttling agent, monomers, and optionally a solvent, an auxiliary, a scavenger, and a polymerization aid are continuously supplied to a reaction zone, and a polymer product is continuously removed therefrom. In this case, the length of each block of the ethylene-α-olefin block copolymer can be varied by controlling the ratio and type of the catalyst, the ratio and type of the chain shuttling agent, the polymerization temperature, etc.

[0059] Component (B) may be commercially available, such as the "Engage (registered trademark)-XLT" series and "INFUSE (registered trademark)" series manufactured by The Dow Chemical Company, the "Solumer (registered trademark)" series manufactured by SK Corporation, and the "Tafmer (registered trademark)" series manufactured by Mitsui Chemicals, Inc.

[0060] The ethylene-α-olefin copolymer of component (B) may be used alone or in combination with two or more copolymers having different copolymer component compositions or physical properties.

[0061] <Component (C)> The ethylene-propylene-non-conjugated diene copolymer of component (C) is a copolymer rubber containing ethylene, propylene, and a non-conjugated diene as copolymerization components. Ethylene-propylene-non-conjugated diene copolymer rubbers include oil-extended types, which are mixtures of ethylene-propylene-non-conjugated diene copolymer rubber and a hydrocarbon-based rubber softener (hereinafter sometimes referred to as "oil-extended ethylene-propylene-non-conjugated diene copolymer rubber"), and non-oil-extended types, which do not contain a hydrocarbon-based rubber softener. In other words, in the present invention, either the oil-extended or non-oil-extended ethylene-propylene-non-conjugated diene copolymer rubber of component (C) can be used. Either the non-oil-extended or oil-extended type may be used alone, or two or more types may be used in any combination and ratio. One or more oil-extended types and one or more non-oil-extended types may also be used in any combination and ratio. In this regard, when component (C) is an oil-extended ethylene-propylene-non-conjugated diene copolymer rubber, the hydrocarbon-based rubber softener contained in this oil-extended ethylene-propylene-non-conjugated diene copolymer rubber is included in the hydrocarbon-based rubber softener as component (G).

[0062] The non-conjugated dienes in component (C) include dicyclopentadiene, 1,4-hexadiene, cyclohexadiene, cyclooctadiene, dicyclooctadiene, 1,6-octadiene, 5-methyl-1,4-hexadiene, 3,7-dimethyl-1,6-octadiene, 1,3-cyclopentadiene, 1,4-cyclohexadiene, 2-methyl-1,5-hexadiene, and 6-methyl-1,5-heptadiene. Examples of the non-conjugated diene include, but are not limited to, 5-isopropylidene-2-norbornene, 5-vinyl-2-norbornene, vinylidene norbornene, ethylidene norbornenes such as 5-ethylidene-2-norbornene (ENB), and methylene norbornenes such as 5-methylene-2-norbornene (MNB). Among these, dicyclopentadiene, ethylidene norbornene, and vinylidene norbornene are preferred, and dicyclopentadiene, 5-ethylidene-2-norbornene, and vinylidene norbornene are more preferred, from the viewpoint of crosslinking ability with a crosslinking agent during dynamic crosslinking. The non-conjugated diene may be used alone or in any combination and ratio of two or more.

[0063] Specific examples of ethylene-propylene-non-conjugated diene copolymer rubbers include, but are not limited to, ethylene-propylene-non-conjugated diene copolymer rubbers (EPDM) such as ethylene-propylene-5-ethylidene-2-norbornene copolymer rubber, ethylene-propylene-dicyclopentadiene copolymer rubber, ethylene-propylene-1,4-hexadiene copolymer rubber, and ethylene-propylene-5-vinyl-2-norbornene copolymer rubber. Among these, ethylene-propylene-non-conjugated diene copolymer rubber (EPDM) is preferred from the viewpoints of crosslinking ability with a crosslinking agent during dynamic crosslinking and suppression of bloomout. The ethylene-propylene-non-conjugated diene copolymer rubber may be used alone or in any combination and ratio of two or more kinds.

[0064] The content of ethylene units in the ethylene-propylene-non-conjugated diene copolymer rubber is not particularly limited, but is preferably 50 to 90 mass%, more preferably 55 to 85 mass%, and even more preferably 60 to 80 mass%. When the content of ethylene units is within the above preferred range, a thermoplastic elastomer composition excellent in mechanical strength and rubber elasticity tends to be easily obtained.

[0065] The content of propylene units in the ethylene-propylene-non-conjugated diene copolymer rubber is not particularly limited, but is preferably 9.5 to 49.5 mass%, more preferably 14 to 44 mass%, and even more preferably 18 to 38 mass%. When the content of propylene units is within the above preferred range, a thermoplastic elastomer composition excellent in mechanical strength, moderate flexibility, and rubber elasticity tends to be easily obtained.

[0066] Furthermore, the content of non-conjugated diene units in the ethylene-propylene-non-conjugated diene copolymer rubber is not particularly limited, but is preferably 0.5 to 30 mass%, more preferably 1 to 20 mass%, and even more preferably 2 to 10 mass%. When the content of non-conjugated diene units is within the above-mentioned preferred range, it becomes easy to adjust crosslinkability and moldability, and a thermoplastic elastomer composition excellent in mechanical strength and low-temperature impact resistance tends to be obtained.

[0067] The content of each structural unit of component (C) can be determined by infrared spectroscopy.

[0068] In the present invention, component (C) is particularly preferably an ethylene-propylene-non-conjugated diene copolymer rubber having an ethylene unit content of 55 to 75 mass%, a propylene unit content of 15 to 40 mass%, and a content of at least one non-conjugated diene unit selected from the group consisting of dicyclopentadiene, 5-ethylidene-2-norbornene, and vinylidene norbornene of 1 to 10 mass%.

[0069] Component (C) can be produced by polymerization methods using known olefin polymerization catalysts, such as slurry polymerization, solution polymerization, bulk polymerization, and gas-phase polymerization using complex catalysts such as Ziegler-Natta catalysts, metallocene complexes, and non-metallocene complexes.

[0070] Among the ethylene-propylene-non-conjugated diene copolymer rubbers of component (C) used in the present invention, the Mooney viscosity (ML 1+4 , 125°C) is usually 45 or more, preferably 50 or more. The Mooney viscosity (ML 1+4 , 125°C) is more preferably 50 to 400, and further preferably 50 to 300. On the other hand, the Mooney viscosity (ML 1+4 , 125°C) is not particularly limited, but is preferably 30 to 100, more preferably 35 to 80. If the Mooney viscosity of component (C) is at least the lower limit, low-temperature impact resistance will be good, and if it is at most the upper limit, it is preferred from the standpoint of moldability.

[0071] In the present invention, the Mooney viscosity (ML ) of the ethylene-propylene-non-conjugated diene copolymer before oil extension and the oil-extended ethylene-propylene-non-conjugated diene copolymer of component (C) is 1+4 , 125°C) is expressed by the following formula as described in JP-A-1-103639. Calculation formula: log(ML1 / ML2)=0.0066(ΔPHR) ML1: Mooney viscosity of ethylene-propylene-non-conjugated diene copolymer rubber before oil extension ML2: Mooney viscosity of oil-extended ethylene-propylene-non-conjugated diene copolymer rubber ΔPHR: Amount of oil extension per 100 parts by mass of ethylene-propylene-non-conjugated diene copolymer rubber

[0072] The density of the ethylene-propylene-non-conjugated diene copolymer rubber of component (C) is not particularly limited, but is preferably 0.850 g / cm 3 It is preferable that the content is equal to or greater than 0.855 g / cm. 3 or more, while 0.900 g / cm 3 It is preferable that the concentration is 0.890 g / cm or less, and more preferably 0.890 g / cm 3 When the density of the ethylene-propylene-non-conjugated diene copolymer rubber of component (C) is within the above-mentioned preferred range, a thermoplastic elastomer composition excellent in processability, moldability, flexibility, etc. tends to be obtained. The density can be measured in accordance with JIS K7112:1999.

[0073] As mentioned above, oil-extended ethylene-propylene-conjugated diene copolymer rubber can also be used as component (C). In the case of oil-extended ethylene-propylene-conjugated diene copolymer rubber, hydrocarbon-based rubber softeners are used to soften the ethylene-propylene-non-conjugated diene copolymer rubber, increasing its flexibility and elasticity, as well as improving the processability and flowability of the resulting thermoplastic elastomer composition.

[0074] Hydrocarbon-based rubber softeners used for oil-extended ethylene-propylene-conjugated diene copolymer rubber include, for example, mineral oil-based rubber softeners and synthetic resin-based rubber softeners. Among these, mineral oil-based rubber softeners are preferred from the viewpoint of compatibility with other components. Mineral oil-based rubber softeners are generally mixtures of aromatic hydrocarbons, naphthenic hydrocarbons, and paraffinic hydrocarbons. Those with a paraffinic hydrocarbon carbon ratio of 50% or more to the total carbon atoms are called paraffinic oils, those with a naphthenic hydrocarbon carbon ratio of 30-45% are called naphthenic oils, and those with an aromatic hydrocarbon carbon ratio of 35% or more are called aromatic oils. Among these, paraffinic rubber softeners (paraffinic oils) are preferred as hydrocarbon-based rubber softeners for component (C), the oil-extended ethylene-propylene-conjugated diene copolymer rubber. Hydrocarbon-based rubber softeners can be used alone or in any combination and ratio of two or more.

[0075] The paraffinic oil used in the oil-extended ethylene-propylene-non-conjugated diene copolymer rubber of component (C) is not particularly limited, but has a kinematic viscosity at 40°C of typically 20 cSt (centistokes) or more, preferably 50 cSt or more, and typically 800 cSt or less, preferably 600 cSt or less. Furthermore, a paraffinic oil having a pour point of typically -40°C or more, preferably -30°C or more, and typically 0°C or less is preferably used. Furthermore, a paraffinic oil having a flash point (COC) of typically 200°C or more, preferably 250°C or more, and typically 400°C or less, preferably 350°C or less is preferably used.

[0076] When an oil-extended ethylene-propylene-non-conjugated diene copolymer rubber is used as component (C), the content ratio of the ethylene-propylene-non-conjugated diene copolymer rubber to the hydrocarbon-based rubber softener is not particularly limited, but the content of the hydrocarbon-based rubber softener per 100 parts by mass of the ethylene-propylene-non-conjugated diene copolymer rubber is usually 10 parts by mass or more, preferably 20 parts by mass or more, and on the other hand, is usually 200 parts by mass or less, preferably 160 parts by mass or less, more preferably 120 parts by mass or less.

[0077] The method for preparing the oil-extended ethylene-propylene-non-conjugated diene copolymer rubber (oil extension method) is not particularly limited, and known methods can be used. Examples of oil-extending methods include a method in which the ethylene-propylene-non-conjugated diene copolymer rubber and a hydrocarbon-based rubber softener are mechanically kneaded and extended using a mixing roll or Banbury mixer; a method in which a predetermined amount of hydrocarbon-based rubber softener is added to the ethylene-propylene-non-conjugated diene copolymer rubber and the solvent is then removed by a method such as steam stripping; and a method in which a mixture of crumb-like ethylene-propylene-non-conjugated diene copolymer rubber and hydrocarbon-based rubber softener is stirred and impregnated using a Henschel mixer or the like. From the perspective of preparing a high-molecular-weight oil-extended ethylene-propylene-non-conjugated diene copolymer rubber, a method in which a predetermined amount of hydrocarbon-based rubber softener is added to a polymerization reaction solution or suspension of the ethylene-propylene-non-conjugated diene copolymer rubber (component (C))) and the solvent is then removed is preferred.

[0078] The ethylene-propylene-non-conjugated diene copolymer rubber of component (C) is commercially available in a wide variety of grades from manufacturers both in Japan and overseas, and these commercially available products can be used. Examples of commercially available products include JSR EPR manufactured by JSR Corporation, Mitsui EPT manufactured by Mitsui Chemicals, Esprene® manufactured by Sumitomo Chemical Co., Ltd., Keltan® manufactured by ARLANXEO, NORDEL® manufactured by Dow Chemical, and KEP manufactured by Kumho Polychem.

[0079] <Ingredient (D)> As described above, the thermoplastic elastomer composition of the present invention is preferably produced using an organic peroxide as component (D). The organic peroxide as component (D) acts as a crosslinking agent in the dynamic heat treatment. This dynamic heat treatment can reduce the gloss of molded articles such as airbag storage covers made from the thermoplastic elastomer composition of the present invention, resulting in particularly good appearance.

[0080] As the organic peroxide of component (D), either an aromatic organic peroxide or an aliphatic organic peroxide can be used. Specific examples include dialkyl peroxides such as di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexyne, 1,3-bis(t-butylperoxyisopropyl)benzene, and 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane; peroxy esters such as t-butyl peroxybenzoate, t-butylperoxyisopropyl carbonate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, and 2,5-dimethyl-2,5-di(benzoylperoxy)-3-hexyne; and hydroperoxides such as acetyl peroxide, lauroyl peroxide, benzoyl peroxide, p-chlorobenzoyl peroxide, and 2,4-dichlorobenzoyl peroxide. Among these, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane is preferred. These may be used alone or in combination of two or more.

[0081] <Ingredient (E)> As described above, the thermoplastic elastomer composition of the present invention is preferably produced using the crosslinking aid of component (E) together with component (D). Component (E) acts as a crosslinking aid in dynamic heat treatment.

[0082] Examples of the crosslinking aid of component (E) include peroxide aids such as sulfur, p-quinone dioxime, p-dinitrosobenzene, and 1,3-diphenyl guanidine; polyfunctional vinyl compounds such as divinylbenzene, triallyl cyanurate, triallyl isocyanurate, and diallyl phthalate; and polyfunctional (meth)acrylate compounds such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and allyl (meth)acrylate. These may be used alone or in combination of two or more.

[0083] <Component (F)> The thermoplastic elastomer composition of the present invention may contain a styrene-conjugated diene block copolymer and / or a hydrogenated product thereof as component (F).

[0084] Suitable conjugated dienes for component (F), the styrene-conjugated diene block copolymer and / or its hydrogenated product, are butadiene, isoprene, or a mixture thereof. Examples of component (F) include styrene-butadiene block copolymers and / or their hydrogenated products. Examples of hydrogenated styrene-butadiene block copolymers include partially hydrogenated styrene-butadiene-butylene-styrene copolymer (SBBS) and substantially fully hydrogenated styrene-ethylene-butylene-styrene copolymer (SEBS). Other examples of component (F) include hydrogenated styrene-isoprene block copolymers, such as styrene-ethylene-propylene-styrene copolymer (SEPS), and hydrogenated styrene-butadiene-isoprene block copolymers.

[0085] The styrene unit content of the styrene-conjugated diene block copolymer and / or its partially hydrogenated or fully hydrogenated product is not particularly limited, but from the viewpoints of strength and heat resistance, it is preferably 5% by mass or more, more preferably 8% by mass or more, and even more preferably 10% by mass or more. From the viewpoints of flexibility and impact resistance, the styrene unit content is preferably 70% by mass or less, more preferably 55% by mass or less, and even more preferably 40% by mass or less.

[0086] The conjugated diene in component (F) preferably has a 1,2-microstructure of 60 mol % or less, more preferably 45 mol % or less, as analyzed by NMR. A 1,2-microstructure of no more than the above upper limit is preferred from the viewpoints of moldability and flexibility, and is also preferred from the viewpoint of preventing excessive crosslinking reactions due to dynamic heat treatment. From the viewpoint of utilizing the crosslinking reaction in component (F), when component (F) is a hydrogenated styrene-conjugated diene block copolymer, the hydrogenation rate is preferably 95% or less, more preferably 90% or less, and even more preferably 85% or less.

[0087] When the conjugated diene in component (F) is a mixture of isoprene and butadiene, the mass ratio (isoprene / butadiene) is generally 99 / 1 to 1 / 99, preferably 90 / 10 to 30 / 70, and more preferably 80 / 20 to 40 / 60.

[0088] From the viewpoint of releasability, the weight average molecular weight (Mw) of component (F) is preferably 50,000 or more, more preferably 80,000 or more, and even more preferably 100,000 or more. From the viewpoint of fluidity and dispersibility, the weight average molecular weight (Mw) of component (E) is preferably 500,000 or less, more preferably 450,000 or less, even more preferably 400,000 or less, and particularly preferably 350,000 or less.

[0089] The weight average molecular weight (Mw) of the component (F) is measured by gel permeation chromatography (GPC), and can be measured, for example, under the following conditions. Equipment: Tosoh Corporation "HLC-8220GPC(R)" Column: Tosoh Corporation "TSKgel Super HM-M (6.0 mm I.D. x 15 cm x 2+G)" Detector: Differential refractive index detector (RI / built-in) Solvent: Chloroform Temperature: 40℃ Flow rate: 0.25mL / min Injection volume: 0.1 mass% x 20 μL Calibration sample: monodisperse polystyrene Calibration method: Polystyrene equivalent Calibration curve approximation: cubic (hyperbolic) Exclusion limit setting time: 12 minutes

[0090] Examples of methods for producing component (F) styrene-conjugated diene block copolymers include the method described in Japanese Patent Publication No. 40-23798, in which a styrene-conjugated diene block copolymer is synthesized in an inert solvent using a lithium catalyst. Examples of methods for producing hydrogenated styrene-conjugated diene block copolymers include the method described above, in which a styrene-conjugated diene block copolymer is synthesized, and then hydrogenated in an inert solvent in the presence of a hydrogenation catalyst, as described in Japanese Patent Publication Nos. 42-8704, 43-6636, 59-133203, and 60-79005.

[0091] The styrene-conjugated diene block copolymer and / or its hydrogenated product as component (F) may be commercially available. Examples of commercially available styrene-conjugated diene block copolymers include "Kraton® D" manufactured by Kraton Polymers and "Globalprene®" manufactured by LCY. Examples of partially hydrogenated styrene-conjugated diene block copolymers include "Tuftec® P" manufactured by Asahi Kasei Corporation. Examples of fully hydrogenated styrene-conjugated diene block copolymers include "Kraton® G" manufactured by Kraton Polymers, "Septon®" manufactured by Kuraray Co., Ltd., and "Tuftec®" manufactured by Asahi Kasei Corporation.

[0092] The styrene-conjugated diene block copolymer and / or its hydrogenated product as component (F) may be used alone or in combination with two or more different copolymer component compositions and physical properties.

[0093] <Ingredients (G)> From the viewpoint of improving moldability, the thermoplastic elastomer composition of the present invention preferably contains a hydrocarbon-based rubber softener as component (G).

[0094] Examples of hydrocarbon-based rubber softeners for component (G) include mineral oil-based softeners and synthetic resin-based softeners, with mineral oil-based softeners being preferred in terms of compatibility with other components. Mineral oil-based softeners are generally mixtures of aromatic hydrocarbons, naphthenic hydrocarbons, and paraffinic hydrocarbons. Those in which 50% or more of the carbon atoms are paraffinic hydrocarbons are called paraffinic oils, those in which 30-45% of the carbon atoms are naphthenic hydrocarbons are called naphthenic oils, and those in which 35% or more of the carbon atoms are aromatic hydrocarbons are called aromatic oils. Of these, paraffinic oils are preferred in the present invention.

[0095] The kinematic viscosity (ASTM D 445 / JIS K2283) of the hydrocarbon rubber softener of component (G) at 40°C is not particularly limited, but is preferably 20 cSt or more, more preferably 50 cSt or more, and is preferably 800 cSt or less, more preferably 600 cSt or less. The flash point (COC method) of the hydrocarbon rubber softener is preferably 200°C or more, more preferably 250°C or more.

[0096] The hydrocarbon rubber softener of component (G) may be commercially available, such as the Nippon Oil Polybutene (registered trademark) HV series manufactured by JX Nippon Oil & Energy Corporation and the Diana (registered trademark) Process Oil PW series manufactured by Idemitsu Kosan Co., Ltd., from which an appropriate product may be selected and used.

[0097] The hydrocarbon-based rubber softeners of component (G) may be used alone or in combination of two or more.

[0098] <Mixing ratio> The blending ratio of the raw materials for the thermoplastic elastomer composition of the present invention will be explained below.

[0099] The content of component (B) in the thermoplastic elastomer composition of the present invention is usually 40 parts by mass or more, preferably 50 parts by mass or more, more preferably 60 parts by mass or more, per 100 parts by mass of component (A) from the viewpoint of low-temperature impact resistance, and usually 200 parts by mass or less, preferably 150 parts by mass or less, more preferably 120 parts by mass or less, from the viewpoint of rigidity and tensile strength of the molded article.

[0100] The content of component (C) in the thermoplastic elastomer composition of the present invention is usually 1 part by mass or more, preferably 5 parts by mass or more, more preferably 10 parts by mass or more, per 100 parts by mass of component (A) from the viewpoint of low-temperature impact resistance, and usually 100 parts by mass or less, preferably 70 parts by mass or less, more preferably 50 parts by mass or less, from the viewpoint of rigidity and tensile strength of the molded article.

[0101] When component (D) is used in the thermoplastic elastomer composition of the present invention, the content of component (D) is usually 0.01 part by mass or more, preferably 0.05 part by mass or more, and more preferably 0.10 part by mass or more, relative to 100 parts by mass of the total of components (A), (B), and (C), from the viewpoint of low gloss, while it is usually 1.00 part by mass or less, preferably 0.80 part by mass or less, and more preferably 0.60 part by mass or less, from the viewpoints of low-temperature impact resistance and flow mark resistance. When the thermoplastic elastomer composition of the present invention further contains component (F) and / or component (G), the content of component (D) described above may be applied to 100 parts by mass of the total of components (A), (B), (C), (F), and (G).

[0102] When component (E) is used in the thermoplastic elastomer composition of the present invention, the content of component (E) is usually 0.01 part by mass or more, preferably 0.05 part by mass or more, and more preferably 0.10 part by mass or more, from the viewpoint of low gloss, relative to 100 parts by mass of the total of components (A), (B), and (C), while from the viewpoint of flow mark resistance, it is usually 1.00 part by mass or less, preferably 0.80 part by mass or less, and more preferably 0.60 part by mass or less. When the thermoplastic elastomer composition of the present invention further contains component (F) and / or component (G), the content of component (E) described above may be applied to 100 parts by mass of the total of components (A), (B), (C), (F), and (G).

[0103] When the thermoplastic elastomer composition of the present invention contains component (F), the content thereof is usually 1 part by mass or more, preferably 5 parts by mass or more, and more preferably 10 parts by mass or more per 100 parts by mass of component (A) from the viewpoint of low-temperature impact resistance, and usually 100 parts by mass or less, preferably 80 parts by mass or less, and more preferably 60 parts by mass or less from the viewpoint of rigidity and tensile strength of the molded article.

[0104] When the thermoplastic elastomer composition of the present invention contains component (G), the content thereof is usually 1 part by mass or more, preferably 5 parts by mass or more, and more preferably 10 parts by mass or more per 100 parts by mass of component (A) from the viewpoints of low-temperature impact resistance, fluidity, and flow mark resistance. Also, from the viewpoints of rigidity, tensile strength, and oil bleeding of the molded article, the content thereof is usually 100 parts by mass or less, preferably 80 parts by mass or less, and more preferably 60 parts by mass or less.

[0105] <Other ingredients> The thermoplastic elastomer composition of the present invention may contain other components as required, provided that the effects of the present invention are not impaired.

[0106] Examples of other components include resins such as thermoplastic resins and elastomers other than components (A), (B), (C), and (F), as well as various additives such as antioxidants, fillers, heat stabilizers, weathering aids, light stabilizers, ultraviolet absorbers, neutralizing agents, lubricants, antifogging agents, antiblocking agents, slip agents, dispersants, colorants, flame retardants, antistatic agents, conductivity imparting agents, metal deactivators, molecular weight modifiers, antibacterial agents, antifungal agents, and fluorescent brighteners. These may be used alone or in combination of two or more.

[0107] Examples of thermoplastic resins other than component (A) include polyphenylene ether resins, polyamide resins such as nylon 6 and nylon 66, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polyoxymethylene resins such as polyoxymethylene homopolymers and polyoxymethylene copolymers, polymethyl methacrylate resins, and polyolefin resins (excluding those corresponding to components (A) to (C)). Examples of elastomers other than components (B), (C), and (F) include styrene elastomers (excluding those corresponding to component (F)), polyester elastomers, and polybutadiene.

[0108] Examples of antioxidants include phenol-based antioxidants, phosphite-based antioxidants, and thioether-based antioxidants. When an antioxidant is used, it is generally used in an amount of 0.01 to 3.0 parts by mass per 100 parts by mass of the total of components (A), (B), (C), and optionally components (F) and (G).

[0109] Examples of fillers include glass fiber, hollow glass spheres, carbon fiber, talc, calcium carbonate, mica, potassium titanate fiber, silica, metal soap, titanium dioxide, and carbon black. When a filler is used, it is typically used in an amount of 0.1 to 50 parts by mass per 100 parts by mass of the total of components (A), (B), (C), and optionally components (F) and (G).

[0110] [Method of producing thermoplastic elastomer composition] The thermoplastic elastomer composition of the present invention is preferably produced by subjecting a composition containing predetermined amounts of component (A), component (B), component (C), and optionally component (F), component (G), and other components, to dynamic heat treatment in the presence of component (D) and component (E).

[0111] In the present invention, "dynamic heat treatment" refers to kneading components (D) and (E) in a molten or semi-molten state in the presence of the components. This dynamic heat treatment is preferably carried out by melt kneading, and the mixing and kneading device used therefor may be, for example, a non-open Banbury mixer, a mixing roll, a kneader, or a twin-screw extruder. Among these, it is preferable to use a twin-screw extruder.

[0112] In a preferred embodiment of the twin-screw extruder production method, a mixture containing a portion of component (A), components (B), (C), (D), (E), optional components (F), (G), and other components is fed into a cylinder through a more upstream feed port (hopper) (hereinafter sometimes referred to as the "first hopper") of a twin-screw extruder having multiple feed ports, melt-kneaded, and the remaining amount of component (A) is fed into the cylinder through a separate feed port (hopper) (hereinafter sometimes referred to as the "second hopper") located further downstream from the first hopper and further heat-treated to produce a partially crosslinked thermoplastic elastomer. Here, the second hopper to which the remaining amount of component (A) is fed is preferably located downstream of L / 2, where L is the distance from the most upstream feed port (usually the first hopper) to the most upstream mixture outlet. However, if the second hopper is located too far downstream, the component (A) supplied from the second hopper will not be sufficiently dispersed, and therefore, the second hopper is preferably located at least 1 / 10 L upstream of the outlet for the mixture. Furthermore, the raw material supplied from the second hopper may be at least a portion of component (B), component (C), component (F), and component (G) in addition to the remainder of component (A).

[0113] In this way, by dynamically heat treating a mixture of a part of component (A), component (B), component (C), component (D), component (E), component (F), and component (G) to partially crosslink them, and then adding the remainder of component (A), component (A) added later is less susceptible to molecular chain scission by radicals, and the resulting thermoplastic elastomer composition has increased tensile strength and an improved die swell ratio.

[0114] From the viewpoint of improving the mechanical strength and die swell ratio of the resulting composition, the initial charge amount of component (A) (amount charged from the first hopper) is preferably 90 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 70 parts by mass or less, where the total amount of component (A) is 100 parts by mass. On the other hand, from the viewpoint of production stability during production, the initial charge amount of component (A) (amount charged from the first hopper) is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and even more preferably 30 parts by mass or more. When components (B), (C), (F), and (G) are fed in portions, they are preferably fed in portions in the same proportions as component (A).

[0115] The temperature when the dynamic heat treatment is carried out is usually 80 to 300° C., and preferably 100 to 250° C. The time for which the dynamic heat treatment is carried out is usually 0.1 to 30 minutes.

[0116] When the thermoplastic elastomer composition of the present invention is produced by dynamic heat treatment using a twin-screw extruder, it is preferable to perform extrusion while maintaining the relationship of the following formula (1) among the barrel radius R (mm), screw rotation speed N (rpm), and discharge rate Q (kg / h) of the twin-screw extruder, and it is more preferable to perform extrusion while maintaining the relationship of the following formula (2). 2.6 <NQ / R 3 <22.6 …(1) 3.0 <NQ / R 3 <20.0 …(2)

[0117] For efficient production of a thermoplastic elastomer composition, it is preferable that the above relationship between the barrel radius R (mm), screw rotation speed N (rpm), and throughput rate Q (kg / h) of the twin-screw extruder be greater than the above lower limit, while it is preferable that the above relationship be smaller than the above upper limit to suppress heat generation due to shear and to reduce the generation of foreign matter that causes poor appearance.

[0118] [Molded products] <Ingredient method> A molded article can be obtained by molding the thermoplastic elastomer resin composition of the present invention. The thermoplastic elastomer composition of the present invention can be molded into a molded article by a conventional injection molding method or, if necessary, by various molding methods such as gas injection molding, injection compression molding, short shot foam molding, etc. Among these, it is preferable to produce a molded article by injection molding, and the molding conditions for injection molding are as follows. The molding temperature when injection molding a molded product is generally 150 to 300°C, preferably 160 to 280°C. The injection pressure is generally 5 to 100 MPa, preferably 10 to 80 MPa. The mold temperature is generally 0 to 80°C, preferably 20 to 60°C.

[0119] <Application> The molded article thus obtained can be used, for example, as an airbag storage cover, which is suitably used as an airbag storage cover for an airbag system that is activated and inflates upon sensing impact or deformation in the event of a collision or other accident involving a high-speed moving object such as an automobile. The airbag storage cover of the present invention can be suitably used as a driver's seat airbag storage cover, a passenger seat airbag storage cover, a pedestrian airbag storage cover, a knee airbag storage cover, a side airbag storage cover, a curtain airbag storage cover, etc.

[0120] [Physical properties of thermoplastic elastomer compositions and molded products] <mfr> The thermoplastic elastomer composition of the present invention also has excellent moldability. Specifically, the melt flow rate (MFR) according to ISO 1133 (2011) at a temperature of 230°C and a measuring load of 21.18 N is usually 0.5 to 50 g / 10 min, preferably 1 to 40 g / 10 min, and more preferably 2 to 30 g / 10 min.

[0121] <Tensile strength at break> The thermoplastic elastomer composition of the present invention also has excellent tensile strength. Specifically, the tensile strength at break measured using a 1A dumbbell according to ISO 37 (2011) at a pulling rate of 500 mm / min in an atmosphere of 23°C is typically 10 MPa or more, preferably 13 MPa or more, and more preferably 14 MPa or more.

[0122] <Elongation at break> The thermoplastic elastomer composition of the present invention also has excellent elongation at break. Specifically, the elongation at break measured using a 1A dumbbell according to ISO 37 (2011) at a tensile speed of 500 mm / min in an atmosphere of 23°C is typically 500% or more, preferably 600% or more, and more preferably 700% or more.

[0123] <Low temperature impact resistance> The thermoplastic elastomer composition of the present invention has excellent low-temperature impact resistance. In the present invention, the low-temperature impact resistance is evaluated by the Izod impact strength at -45°C according to the method shown in the Examples below. In the present invention, the Izod impact strength at -45°C is 50 kJ / m 2 It is preferable that the concentration is 60 kJ / m or more. 2 More preferably, it is 70 kJ / m or more. 2 More preferably, it is equal to or greater than this.

[0124] <Flow mark resistance> Molded articles obtained from the thermoplastic elastomer composition of the present invention are excellent in terms of flow mark resistance, with almost no flow marks being observed. As mentioned above, the thermoplastic elastomer composition of the present invention tends to exhibit good resistance to flow marks when the die swell ratio is large. That is, a large die swell ratio of 1.10 or more is thought to contribute to the stability of the flow front in the mold during injection molding, thereby improving the resistance to flow marks. [Example]

[0125] The present invention will be described in more detail below using examples, but the present invention is not limited to the following examples as long as it does not deviate from the gist of the invention. The values ​​of various production conditions and evaluation results in the following examples represent preferred upper or lower limit values ​​in the embodiments of the present invention, and preferred ranges may be defined by combining the above-mentioned upper or lower limit values ​​with the values ​​in the following examples or values ​​between the examples.

[0126] [Raw materials for manufacturing thermoplastic elastomer compositions] <Component (A)> A-1: Propylene block copolymer (obtained by polymerizing propylene homopolymer in the first step, followed by polymerizing propylene-ethylene copolymer in the second step) Novatec (registered trademark) PP BC06NCA manufactured by Japan Polypropylene Corporation MFR (ISO 1133 (2011)): 60 g / 10 min (measurement conditions: 230°C, load 21.18 N) Propylene unit content: 96% by mass Ethylene unit content: 4% by mass

[0127] <Ingredient (B)> B-1: Ethylene-1-octene block copolymer (a block copolymer having a polymer block consisting of ethylene and a block of ethylene-1-octene copolymer) Dow Chemical Company Engage® XLT8677 Crystal melting peak temperature: 119℃ Heat of crystal fusion: 37J / g MFR (ASTM D1238): 0.5 g / 10 min (measurement conditions: 190°C, load 21.18 N) (catalog value) Glass transition temperature (DSC method): -67℃ Density (ASTM D792): 0.870g / cm 3 (catalog value)

[0128] B-2: Ethylene-1-octene random copolymer Dow Chemical Company Engage® 8180 Crystal melting peak temperature: No peak between 110 and 125°C Heat of crystal fusion: 0 MFR (ASTM D1238): 0.5 g / 10 min (measurement conditions: 190°C, load 21.18 N) (catalog value) Density (ASTM D792): 0.863g / cm 3 (catalog value)

[0129] <Component (C)> C-1: Non-oil-extended ethylene-propylene-5-ethylidene-2-norbornene terpolymer rubber Mitsui Chemicals, Inc. Mitsui EPT3092PM Mooney viscosity ML(1+4)125℃(ASTM D1646):61(catalog value) Ethylene unit content (ASTM D3900): 65% by mass (catalog value) 5-Ethylidene-2-norbornene unit content (ASTM D6047): 4.6% by mass (catalog value)

[0130] (C-2): Oil-extended ethylene-propylene-5-ethylidene-2-norbornene terpolymer rubber (mixture of 100 parts by mass of component (C) and 40 parts by mass of component (G)) Mitsui Chemicals, Inc. Mitsui EPT3072EPM Mooney viscosity ML(1+4)125℃(ASTM D1646):51(catalog value) Ethylene unit content (ASTM D3900): 64% by mass (catalog value) 5-Ethylidene-2-norbornene unit content (ASTM D6047): 5.4% by mass (catalog value)

[0131] <Ingredient (D)> D-1: Trigonox 101-40C (a mixture of 40% by mass of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane and 60% by mass of calcium carbonate) manufactured by Nouryon Chemical Industries, Ltd.

[0132] <Ingredient (E)> E-1: Mitsubishi Chemical Acryester TMP (trimethylolpropane trimethacrylate) E-2: Divinylbenzene (a mixture of 55% by mass of divinylbenzene and 45% by mass of ethylvinylbenzene) manufactured by Wako Pure Chemical Industries, Ltd.

[0133] <Component (F)> F-1: Styrene-butadiene-styrene block copolymer Kraton Polymers, Inc. Kraton (registered trademark) D1101J Weight average molecular weight (Mw): 160,000 Styrene unit content: 31% by mass (catalog value) Conjugated diene unit content: 69% by mass (catalog value) 1,2-microstructure of conjugated diene component: 12 mol% Hydrogenation rate: 0%

[0134] <Ingredients (G)> G-1: Paraffin oil Idemitsu Kosan Diana (registered trademark) Process Oil PW90 Kinematic viscosity at 40°C: 95.54 cSt Pour point: -15℃ Flash point: 272℃

[0135] [Method for evaluating thermoplastic elastomer compositions] 1) Melt flow rate (MFR) Measured in accordance with ISO 1133 (2011) at 230°C and a load of 21.18 N.

[0136] 2) Tensile strength at break and elongation at break Using an inline screw-type injection molding machine (Sumitomo Wiring Systems, Ltd., "SE100DU"), the thermoplastic elastomer composition was molded into test specimens for tensile testing (2 mm thick x 120 mm wide x 80 mm long sheets) at an injection speed of 30 mm / s, a cylinder temperature of 220°C, and a mold temperature of 40°C. These test specimens were then punched out using a 1A dumbbell in accordance with ISO 37 (2011). The tensile strength at break (unit: MPa) and elongation at break (unit: %) of these punched test specimens were measured using a Shimadzu Corporation Autograph Precision Universal Testing Machine "AGS-H" at a tension speed of 500 mm / min in an atmosphere of 23°C.

[0137] 3) Flexural modulus Using an inline screw-type injection molding machine (SE100DU manufactured by Sumitomo Wiring Systems, Ltd.), the thermoplastic elastomer composition was molded into multipurpose evaluation specimens A (180 mm long dumbbells) conforming to ISO 3167 (2002) at an injection speed of 30 mm / s, a cylinder temperature of 220 °C, and a mold temperature of 40 °C. The ends of the dumbbells were cut off to prepare specimens for measuring flexural modulus (4 mm thick x 10 mm wide x 80 mm long). The flexural modulus was measured at a speed of 2 mm / min using a Pentograph B-2 manufactured by Toyo Seiki Co., Ltd., according to ISO 178 (2010).

[0138] 4) Die swell ratio Measurement was carried out during the extrusion process of the thermoplastic elastomer composition using a Capillograph 1D (JIS K7199) manufactured by Toyo Seiki Seisakusho Co., Ltd. under the following conditions. Test temperature: 210℃ L / D: 10 (D=1mm) Shear rate: 243 / s The die swell ratio was calculated by the following formula (I). St=Dm / Dt (I) St, Dm, Dt indicate the following: St: Die swell ratio Dm: diameter of the extruded sample measured at the test temperature at a position 10 mm below the die exit (mm) Dt: diameter of the capillary die measured at the test temperature (mm)

[0139] 5) Glossiness Using an in-line screw-type injection molding machine (SE100DU manufactured by Sumitomo Wiring Systems, Ltd.), a gloss measurement test piece (a sheet having a thickness of 2 mm, a width of 120 mm, and a length of 80 mm) was molded from the thermoplastic elastomer composition at an injection speed of 30 mm / s, a cylinder temperature of 220°C, and a mold temperature of 40°C. The gloss measurement was performed at an incident angle of 60° in accordance with ISO 2813.

[0140] 6) Low temperature impact resistance (Izod impact strength) The thermoplastic elastomer composition was molded into a thickness of 4 mm, width of 10 mm, and length of 80 mm as a test piece for Izod impact strength using an inline screw-type injection molding machine (SE100DU manufactured by Sumitomo Wiring Systems, Ltd.) at an injection speed of 30 mm / s, a cylinder temperature setting of 220°C, and a mold temperature of 40°C. After that, a notch was made in the dumbbell (the notch dimensions and evaluation method were in accordance with ISO 180 (2013)), and measurements were made at -45°C.

[0141] 7) Flow mark resistance The flow mark resistance was evaluated by molding a gloss measurement test piece (a sheet having a thickness of 2 mm, a width of 120 mm, and a length of 80 mm) from the thermoplastic elastomer composition using an in-line screw type injection molding machine (SE100DU manufactured by Sumitomo Wiring Systems, Ltd.) at an injection speed of 30 mm / s, a cylinder temperature setting of 220°C, and a mold temperature of 40°C. The appearance of the test piece was visually observed and evaluated according to the following criteria. Judgment criteria 1: Flow marks are noticeable and the appearance is very poor. 2: Flow marks are noticeable and the appearance is poor. 3: Flow marks are observed. 4: A few flow marks are visible. 5: No flow marks observed.

[0142] [Example 1] A portion of component (A-1): 20 parts by mass, component (B-1): 45 parts by mass, component (C-1): 5 parts by mass, component (D-1): 0.40 parts by mass, and component (E-1): 0.40 parts by mass, and 0.1 parts by mass of an antioxidant (trade name Irganox (registered trademark) 1010 manufactured by BASF Japan Ltd.) and 2 parts by mass of a black pigment (carbon concentration 40% by mass product) per 100 parts by mass in total of component (A-1), component (B-1), component (C-1), component (D-1), and component (E-1) were added. The mixture was blended for 1 minute in a well mixer and then fed into a co-rotating twin-screw extruder (Kobe Steel, Ltd., "TEX30α", L / D=45, number of cylinder blocks: 13) through the first feed port at a rate of 14 kg / hr. The temperature was raised to 180-210°C and melt-kneaded. Simultaneously, the remaining component (A-1), 30 parts by mass, was fed through the second feed port installed midway through the extruder cylinder at a rate of 6 kg / hr and kneaded. The mixture was then pelletized to produce a thermoplastic elastomer composition. The evaluation results of the resulting thermoplastic elastomer composition are shown in Table 1. The first supply port is provided in the cylinder block on the most upstream side of the co-rotating twin-screw extruder, and the second supply port is provided in the cylinder block that is ninth from the upstream side.

[0143] [Examples 2 to 5, Comparative Examples 1 to 9] Pellets of a thermoplastic elastomer composition were obtained in the same manner as in Example 1, except that the raw material compositions were as shown in Tables 1 and 2. The obtained thermoplastic elastomer compositions were evaluated in the same manner as in Example 1. The evaluation results are shown in Tables 1 and 2.

[0144] In Tables 1 and 2, "A-1 (*1)" is the amount of component (A-1) added from the first supply port, and "A-1 (*2)" is the amount of component (A-1) added from the second supply port. Also, "-" in the raw material composition column indicates that the component was not used.

[0145] [Table 1]

[0146] [Table 2]

[0147] [Consideration] From Tables 1 and 2, the following can be seen: The thermoplastic elastomer compositions of Examples 1 to 5, which contain components (A) to (C) and have die swell ratios, gloss levels, and flexural moduli within the ranges specified by the present invention, have low gloss levels, good flow mark resistance, and excellent design properties. They also have excellent low-temperature impact resistance.

[0148] In contrast, Comparative Examples 1 and 2 have a large die swell ratio, but have high gloss and poor design properties. In Comparative Examples 3 to 6 and 8 to 9, the die swell ratio was less than 1.10, flow marks were observed, and the design was poor. In Comparative Example 7, the die swell ratio was 1.10 or more, and the flow mark resistance was excellent, but the gloss level was high and the design was poor. [Industrial Applicability]

[0149] The thermoplastic elastomer composition of the present invention maintains low-temperature impact resistance while also exhibiting excellent design properties, making it suitable for a variety of applications. For example, the thermoplastic elastomer composition of the present invention is useful for automotive interior parts such as airbag storage covers, instrument panels, center panels, center console boxes, door trims, pillars, assist grips, and steering wheels; automotive exterior parts such as mudguards and grommets; home appliance parts; building materials; and furniture. Among these, the thermoplastic elastomer composition of the present invention is particularly useful as an airbag storage cover, and particularly suitable as an airbag storage cover for an airbag system that senses impact or deformation in the event of a collision or other accident involving a high-speed moving object such as an automobile, activates, and inflates to protect occupants.< / mfr>

Claims

1. A thermoplastic elastomer composition obtained by subjecting a composition containing the following components (A) to (C) to dynamic heat treatment in the presence of the following components (D) and (E): The die swell ratio (test temperature 210°C, shear rate 243 / s) measured using a capillary rheometer (JIS K7199) is 1.10 or more, A gloss measurement specimen made of the thermoplastic elastomer composition has a gloss of 50% or less as measured at an incident angle of 60° in accordance with ISO 2813; and a flexural modulus of 100 to 700 MPa as measured in accordance with ISO 178 (2010) using a test piece for flexural modulus measurement made of the thermoplastic elastomer composition. Component (A): Propylene-based block copolymer Component (B): Ethylene / α-olefin copolymer in which the α-olefin has 4 or more carbon atoms Component (C): Ethylene-propylene-non-conjugated diene copolymer Component (D): Organic peroxide Component (E): Crosslinking aid

2. 2. The thermoplastic elastomer composition according to claim 1, wherein the α-olefin of component (B) has 4 to 8 carbon atoms.

3. 3. The thermoplastic elastomer composition according to claim 1, wherein the ethylene / α-olefin copolymer of component (B) is an ethylene / α-olefin block copolymer.

4. The thermoplastic elastomer composition according to claim 3, wherein the ethylene / α-olefin block copolymer is an ethylene / α-olefin block copolymer comprising a polymer block composed of ethylene and an ethylene / α-olefin copolymer block.

5. The thermoplastic elastomer composition according to claim 4, wherein the ethylene / α-olefin block copolymer has a crystalline melting peak at 110 to 125°C and a heat of crystalline melting of 20 to 60 J / g.

6. The thermoplastic elastomer composition according to any one of claims 1 to 5, wherein the component (C) is an oil-extended ethylene-propylene-non-conjugated diene copolymer.

7. An injection-molded article obtained by injection molding the thermoplastic elastomer composition according to any one of claims 1 to 6.

8. An airbag storage cover using the thermoplastic elastomer composition according to any one of claims 1 to 6.

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