JP2021138796A - Thermoplastic elastomer composition for airbag storing cover, and airbag storing cover - Google Patents

Abstract

To provide a thermoplastic elastomer composition for an airbag storing cover, enabling obtaining a molded article excellent in molding appearance, low-temperature impact resistance and rigidity, and to provide an airbag storing cover using the thermoplastic elastomer composition.SOLUTION: A thermoplastic elastomer composition for an airbag storing cover is a dynamic heat-treated product of a mixture which contains a component (A), a component (B), a component (C) and a component (D) as follows. Preferably, the mixture contains 40-50 pts.mass of the component (A) and 50-60 pts.mass of the component (B) in 100 pts.mass of the sum total of the component (A) and the component (B), and contains 0.005-0.3 pt.mass of the component (C), and 0.005-2.0 pts.mass of the component (D) based on 100 pts.mass of the sum total of the component (A) and the component (B). The component (A): a polypropylene block copolymer; the component (B): an ethylene α-olefin copolymer; the component (C): an organic peroxide; and the component (D): a maleimide cross-linking aid.SELECTED DRAWING: None

Description

The present invention relates to a thermoplastic elastomer composition for an airbag storage cover that can provide a molded product having excellent molded appearance, low temperature impact resistance and rigidity, and an airbag storage cover comprising this thermoplastic elastomer composition.

The airbag system for automobiles is a system that protects the driver and passengers in the event of a collision of a car or the like. It has an airbag device that operates to inflate the bag. The airbag device is installed on the steering wheel, the instrument panel in front of the passenger seat, the driver's seat and the passenger seat, the front and side pillars, and the like.

Various proposals have been made for the structure and material of the airbag storage cover in the airbag device so that the airbag storage cover can be cleaved as designed in a wide temperature range from low temperature to high temperature.

Examples of the airbag storage cover made of an olefin-based thermoplastic elastomer include, in Patent Document 1, a specific polypropylene-based polymer, an ethylene-octene copolymer, a styrene-conjugated diene block copolymer, and / or hydrogenation thereof. A thing is disclosed which contains a specific amount of a thing and consists of a thermoplastic elastomer composition obtained by dynamic heat treatment in the presence of an organic peroxide. Further, Patent Document 2 proposes a thermoplastic elastomer composition containing a propylene resin and a specific ethylene / α-olefin block copolymer in a specific amount. In Patent Document 3, a heterophasic polymer material, a propylene block copolymer, and an ethylene / α-olefin copolymer having different MFRs are dynamically subjected to the presence of an organic peroxide and a trimethyl trimethylolpropane cross-linking aid. Disclosed is a thermoplastic elastomer composition obtained by heat treatment.

Japanese Unexamined Patent Publication No. 2016-186041 International Publication No. 2014/046139 JP 2015-193710

In recent years, due to the flexibility of the instrument panel due to the upgrade of automobiles, the airbag storage cover and the instrument panel are deformed during the deployment test, and the airbag storage cover is damaged in the low temperature range due to the improvement of the airbag deployment output. There is concern. In addition, paint-less airbag cover materials are increasing in order to reduce the manufacturing process. Based on the above, the airbag storage cover is required to have bending elasticity as an airbag storage cover from the viewpoint of enhancing safety, design freedom, and cost reduction by reducing the insert molding process of metal plates and nylon raw cloth. It has been desired to further improve the appearance and low temperature impact resistance while maintaining the rigidity such as the modulus.
However, the conventional materials for airbag storage covers are insufficient in material strength, low temperature impact resistance, and molded appearance.

The problem to be solved by the present invention is to use a thermoplastic elastomer composition for an air bag storage cover capable of obtaining a molded product having excellent molded appearance, low temperature impact resistance and rigidity, and the thermoplastic elastomer composition. To provide an elastomer storage cover.

As a result of diligent studies to solve the above problems, the present inventor dynamically changes the polypropylene block copolymer and the ethylene / α-olefin copolymer in the presence of an organic peroxide and a maleimide-based cross-linking aid. It has been found that a molded product having excellent molded appearance, low-temperature impact resistance and rigidity can be obtained from the thermoplastic elastomer composition obtained by heat treatment, and the present invention has been made. That is, the gist of the present invention lies in the following [1] to [7].

[1] A thermoplastic elastomer composition for an airbag storage cover, which is a dynamically heat-treated product of a mixture containing the following components (A), component (B), component (C) and component (D).
Component (A): Polypropylene block copolymer component (B): Ethylene / α-olefin copolymer component (C): Organic peroxide component (D): Maleimide-based cross-linking aid

[2] The thermoplastic elastomer composition for an airbag storage cover according to [1], wherein the component (B) is a saturated ethylene / α-olefin copolymer.

[3] The thermoplastic elastomer composition for an airbag storage cover according to [1] or [2], wherein the α-olefin constituting the component (B) has 4 to 8 carbon atoms.

[4] Described in any one of [1] to [3], wherein the component (B) is an olefin-based block copolymer containing a polymer block made of ethylene and an ethylene / 1-octene copolymer block. A thermoplastic elastomer composition for the airbag storage cover.

[5] The thermoplastic elastomer composition for an airbag storage cover according to any one of [1] to [4], wherein the component (D) is N, N'-m-phenylene bismaleimide.

[6] The mixture contains 40 to 50 parts by mass of the component (A) and 50 to 60 parts by mass of the component (B) in a total of 100 parts by mass of the component (A) and the component (B). [1] to 0.3 parts by mass of the component (C) and 0.005 to 2.0 parts by mass of the component (D) with respect to a total of 100 parts by mass of the component (B) and the component (B). The thermoplastic elastomer composition for an airbag storage cover according to any one of [5].

[7] An airbag storage cover made of the thermoplastic elastomer composition for the airbag storage cover according to any one of [1] to [6].

The molded product made of the thermoplastic elastomer composition for an air bag storage cover of the present invention is excellent in molded appearance, low temperature impact resistance and rigidity. Therefore, the airbag storage cover made of the thermoplastic elastomer composition for the airbag storage cover of the present invention has excellent durability and can be suitably used for high-power airbags.

Hereinafter, the present invention will be described in detail, but the present invention is not limited to the following description, and can be arbitrarily modified and carried out without departing from the gist of the present invention. In addition, in this specification, when a numerical value or a physical property value is put before and after using "~", it is used as including the value before and after that.

[Thermoplastic elastomer composition for airbag storage cover]
The thermoplastic elastomer composition for an air bag storage cover of the present invention is a dynamically heat-treated product of a mixture containing the following components (A), component (B), component (C) and component (D), and at least the component (A). ) And the component (B) are dynamically heat-treated in the presence of the component (C) and the component (D).
Component (A): Polypropylene block copolymer Component (B): Ethylene / α-olefin copolymer
Component (C): Organic peroxide component (D): Maleimide-based cross-linking aid

<Mechanism>
The airbag storage cover made of the thermoplastic elastomer composition for the airbag storage cover of the present invention has excellent low-temperature impact resistance and a molded appearance while maintaining the original rigidity of the thermoplastic elastomer composition by the following mechanism. It has the feature of being good.
In the dynamic cross-linking of the polypropylene block copolymer of the component (A) and the ethylene / α-olefin copolymer of the component (B), the organic peroxide of the component (C) first generates molecular cleavage and radicals. Next, due to the binding effect of the maleimide-based cross-linking aid of the component (D), a high dispersion effect is exhibited, and a fine and uniform sea-island structure of the polypropylene matrix and the rubber domain is formed.

However, when the ethylene / α-olefin copolymer of the component (B) is mainly an unsaturated ethylene / α-olefin copolymer, the crosslinked composition obtained by the dynamic heat treatment forms a highly reactive double bond. Therefore, it is preferable to use a saturated ethylene / α-olefin copolymer as the component (B), and it is saturated. By using an ethylene / α-olefin copolymer, a uniform dispersion can be obtained, and a molded product having excellent molded appearance and low-temperature impact resistance can be obtained. In particular, by using an olefin-based block copolymer containing a polymer block made of ethylene having a low glass transition temperature and an ethylene / 1-octene copolymer block, the strength and low-temperature impact resistance can be further improved. can.

The maleimide-based cross-linking aid of component (D) does not have a double bond that contributes to the reaction at the end and has a bulky maleimide group around the double bond, so that self-reaction between the cross-linking agents is unlikely to occur, and ethylene -The cross-linking efficiency for the α-olefin copolymer is very high, more uniform dispersion can be obtained, and excellent molded appearance and low temperature characteristics can be exhibited. On the other hand, other cross-linking aids such as highly reactive divinylbenzene, methacrylic acid ester type, and acrylic acid ester type have double bonds located at the ends that contribute to the reaction, and self-reaction between the cross-linking agents is likely to occur, and ethylene. -The cross-linking efficiency to the α-olefin copolymer is low, it is difficult to obtain uniform dispersion, and the molded appearance and low temperature characteristics tend to be inferior.

<Ingredient (A)>
The polypropylene block copolymer of the component (A) contained in the thermoplastic elastomer composition for an air bag storage cover of the present invention may be a homopolymer of propylene, or in addition to propylene units, ethylene units, ethylene and It may be a propylene / (ethylene and / or α-olefin) copolymer containing an α-olefin unit other than propylene. Further, it may contain a monomer unit other than ethylene and α-olefin.

When the component (A) is a propylene / α-olefin copolymer having an α-olefin unit other than propylene, the α-olefin unit other than ethylene and propylene includes an α-olefin unit having 4 to 20 carbon atoms. be able to. Examples of α-olefins having 4 to 20 carbon atoms include 1-butene, 1-pentene, 1-hexene, 1-hexene, 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 Examples thereof include -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, and more preferably 1-butene, 1-hexene, or 1-octene.

More specifically, the polypropylene block copolymer of the component (A) includes a propylene homopolymer, a propylene / ethylene copolymer, a propylene / 1-butene copolymer, a propylene / 1-hexene copolymer, and a propylene. 1-octene copolymer, propylene / ethylene / 1-butene copolymer, propylene / ethylene / 1-hexene copolymer, propylene / ethylene / 1-octene copolymer, etc. Examples thereof include a polymer of at least one monomer selected from α-olefin and propylene. Further, a propylene-based polymer composed of a propylene-based polymer component (A1) having a propylene unit content of 90 to 100% by mass and an ethylene / propylene copolymer component (A2), preferably containing propylene units in the first step. Examples of propylene-based block copolymers obtained by polymerizing a propylene-based polymer having an amount of 90 to 100% by mass and then polymerizing an ethylene-propylene copolymer in the second step can be exemplified. Among these, as the component (A), from the viewpoint of low temperature impact resistance and high temperature strength, a propylene-based polymer having a propylene unit content of 90 to 100% by mass was polymerized in the first step, followed by the first step. It is preferably a propylene-based block copolymer obtained by polymerizing an ethylene / propylene copolymer in two steps. Further, a propylene homopolymer (polypropylene) is preferable from the viewpoint of impact resistance, heat resistance, moldability, and mechanical strength.

The content of the propylene unit of the polypropylene block copolymer of the component (A) is preferably 70 to 100% by mass, more preferably 80 to 100% by mass, and further preferably 90 to 100% by mass with respect to the entire component (A). %. When the content of the propylene unit of the component (A) is at least the above lower limit value, the heat resistance and the rigidity tend to be good. The propylene unit content in the component (A) can be determined by infrared spectroscopy.

The component (A) is a propylene-based polymer composed of a propylene-based polymer component (A1) having a propylene unit content of 90 to 100% by mass and an ethylene-propylene copolymer component (A2), preferably the first step. In the case of a propylene-based block copolymer obtained by polymerizing a propylene-based polymer having a propylene unit content of 90 to 100% by mass and then polymerizing an ethylene-propylene copolymer in the second step, the components (A) preferably contains 60 to 95% by mass of the component (A1) with respect to the total amount of the component (A1) and the component (A2). If the content of the component (A1) in the component (A) is less than the above lower limit, the mechanical strength and rigidity tend to decrease, and if it is more than the above upper limit, the impact resistance is improved by containing the component (A2). The effect cannot be fully obtained. The content of the component (A1) in the component (A) is more preferably 65% by mass or more, further preferably 70% by mass or more, and more preferably 80% by mass or less.

The ethylene unit of the ethylene / propylene copolymer of the component (A2) may be such that it satisfies the preferable propylene unit content of the above-mentioned component (A), but is usually about 20 to 80% by mass. The content of the ethylene unit of the component (A) as a whole is preferably 5 to 15% by mass, more preferably 7 to 10% by mass. The content of ethylene units in the component (A) can also be determined by infrared spectroscopy.

The melt flow rate (MFR) (230 ° C., load 21.2 N (= 2.16 kg)) of the component (A) is usually 0.1 g / 10 minutes or more, and is usually 0.1 g / 10 minutes or more, from the viewpoint of the appearance of the molded product. It is preferably 10 g / 10 minutes or more, and more preferably 20 g / 10 minutes or more. The melt flow rate (MFR) (230 ° C., load 21.2 N) of the component (A) is usually 200 g / 10 minutes or less, preferably 150 g / 10 minutes or less from the viewpoint of tensile strength, and further. It is preferably 100 g / 10 minutes or less. The melt flow rate of the component (A) is measured according to JIS K7210 (1999) under the conditions of a measurement temperature of 230 ° C. and a measurement load of 21.2 N.

The flexural modulus of the component (A) is not limited, but is usually 1000 MPa or more, preferably 1100 MPa or more, and more preferably 1200 MPa or more from the viewpoint of the appearance, rigidity and strength of the molded product. The flexural modulus of the component (A) is 1800 MPa or less, more preferably 1700 MPa or less, from the viewpoint of low temperature impact resistance. The flexural modulus of the component (A) is measured at a span spacing of 64 mm and a bending speed of 2 mm / min in accordance with JIS K7203.

The density of the component (A) is not limited, but is usually 0.87 to 0.92 g / cm ³ . The density of the component (B) is a value measured in accordance with JIS K6760, but a catalog value can also be adopted for a commercially available product.

The melting temperature of the component (A) is not limited, but is preferably 150 ° C. or higher, more preferably 155 ° C. or higher, from the viewpoint of heat resistance. The melting temperature of the component (A) can be determined by the differential scanning calorimetry method (DSC method).

As the component (A), one of the above-mentioned polypropylene block copolymers may be used alone, or two or more of them may be mixed and used, but when two or more of them are mixed and used, as a mixture. It is preferable that the component (A) of (A) satisfies the above-mentioned physical properties such as the propylene unit content and the melt flow rate.

As a method for producing the polypropylene block copolymer of the component (A), a known polymerization method using a known catalyst for olefin polymerization is used. For example, a polymerization method using a Ziegler-Natta catalyst can be mentioned. As the polymerization method, a slurry polymerization method, a solution polymerization method, a massive polymerization method, a gas phase polymerization method and the like can be used, and two or more of these may be combined.

Further, as the component (A), a commercially available applicable product can be used. Specifically, it can be procured from the manufacturers listed below, and can be appropriately selected. Available commercial products include Prime Polymer Co., Ltd.'s Prim Polypro®, Sumitomo Chemical's Sumitomo Noblen®, SunAllomer's polypropylene block copolymers, Japan Polypropylene's Novatec® PP, and Lyondell Basell. Moplen (registered trademark), ExxonMobile PP from ExxonMobile, Polymerene (registered trademark) from Polymera Plastics, Borealis PP from Borealis, SEETEC PP from LG Chemical, A.M. Schulman's ASI POLYPROPYLENE, INEOS Olefins & Polymers, Inc. of INEOS PP, Braskem's Braskem PP, SAMSUNG TOTAL PETROCHEMICALS's Sumsung Total, Sabic's Sabic (registered trademark) PP, TOTAL PETROCHEMICALS company of TOTAL PETROCHEMICALS Polypropylene, SK Corporation of YUPLENE ( Registered trademark), etc.

<Ingredient (B)>
The component (B) used in the thermoplastic elastomer composition for the airbag storage cover of the present invention is an ethylene / α-olefin copolymer.

Examples of the α-olefin constituting the ethylene / α-olefin copolymer include propylene, 1-butene, 2-methylpropylene, 1-pentene, 3-methyl-1-butene, 1-hexene and 4-methyl-1-. Penten, 1-octene and the like can be exemplified, but as described above, from the viewpoint of strength and low-temperature impact resistance, a polymer block made of ethylene having a low glass transition temperature and an ethylene / 1-octene copolymer block are used. It is preferable to use an olefin-based block copolymer containing the mixture. As for the α-olefin in the component (B), only one kind may be copolymerized with ethylene, or two or more kinds may be copolymerized with ethylene.

As described above, when the component (B) has an unsaturated bond, the crosslinked structure formed by the dynamic heat treatment becomes non-uniform. Therefore, the component (B) is a saturated ethylene / α-olefin copolymer. It is preferable to have. That is, it is preferable that the component (B) does not contain a diene component as a copolymerization component.

The content of the ethylene unit of the ethylene / α-olefin copolymer of the component (B) is preferably 20% by mass or more and 80% by mass or less. The content of the ethylene unit of the component (B) is preferably large in order to improve the low temperature impact resistance when the thermoplastic elastomer composition of the present invention is molded, and when the thermoplastic elastomer composition of the present invention is molded. From the viewpoint of appearance, it is preferable that the amount is small. The content of the ethylene unit of the component (B) is more preferably 25 to 75% by mass, still more preferably 30 to 70% by mass.

The content of ethylene units in the component (B) and the content of α-olefin units such as 1-butene can be determined by infrared spectroscopy, respectively.

The melt flow rate (MFR) of the ethylene / α-olefin copolymer of the component (B) is not limited, but is usually less than 10 g / 10 minutes, preferably 8 g / 10 minutes or less from the viewpoint of strength, and more. It is preferably 5 g / 10 minutes or less, and more preferably 3 g / 10 minutes or less. The MFR of the component (B) is usually 0.01 g / 10 minutes or more, preferably 0.05 g / 10 minutes or more, and more preferably 0.10 g / 10 minutes or more from the viewpoint of fluidity. be. The MFR of the component (B) is measured according to JIS K7210 (1999) under the conditions of a measurement temperature of 190 ° C. and a measurement load of 21.2 N (2.16 kg).

Further, the density of the ethylene · alpha-olefin copolymer component (B) from the viewpoint of low-temperature impact resistance, and at 0.90 g / cm ³ or less, preferably 0.88 g / cm ³ or less. On the other hand, the lower limit thereof is not particularly limited, but is 0.85 g / cm ³ or more. The density of the component (B) is a value measured in accordance with JIS K6760, but a catalog value can also be adopted for a commercially available product.

The ethylene / α-olefin copolymer of the component (B) was measured in the same manner as in the description of the olefin block copolymer containing the polymer block made of ethylene and the ethylene / α-olefin copolymer block described later. As for the crystal melting peak temperature and the glass transition temperature, the crystal melting peak temperature is preferably 50 to 130 ° C., particularly preferably 100 to 125 ° C., and the glass transition temperature is preferably −55 ° C. or lower, particularly preferably −60 ° C. or lower. The crystal melting peak temperature of the ethylene / α-olefin copolymer is preferably not more than the above lower limit from the viewpoint of heat resistance characteristics, and is preferably not more than the above upper limit from the viewpoint of low temperature impact resistance. The lower the glass transition temperature, the better, but in general, it is −70 ° C. or higher due to the characteristics of the chemical structure.

As a method for producing the ethylene / α-olefin copolymer of the component (B), a known polymerization method using a known catalyst for olefin polymerization is used. For example, as a catalyst for olefin polymerization, a Ziegler-Natta catalyst, a complex catalyst such as a metallocene complex or a non-metallocene complex can be used, and as a polymerization method, a slurry polymerization method, a solution polymerization method, a massive polymerization method, or a ki Examples include a phase polymerization method. It is also possible to use a commercially available applicable product. Examples of commercially available applicable products include Tuffmer (registered trademark) manufactured by Mitsui Chemicals, Inc., and Engage (registered trademark) manufactured by Dow Chemicals.

A polymer block in which the ethylene / α-olefin copolymer of the component (B) used in the thermoplastic elastomer composition for an air bag storage cover of the present invention is made of ethylene, and an ethylene / 1-octene copolymer block or the like. In the case of an olefin-based block copolymer containing an α-olefin copolymer block, the thermoplastic elastomer composition of the present invention is an olefin containing a polymer block made of ethylene and an ethylene / α-olefin copolymer block. It may contain only one kind of system block copolymer, or may contain two or more kinds of those having different monomer unit composition, physical properties and the like. An olefin-based block copolymer containing a polymer block made of ethylene and an ethylene / α-olefin copolymer block has a crystal melting peak at 110 to 125 ° C., and the amount of heat of crystal melting thereof is 20 to 60 J / g. It is preferable to have. Here, in the component (B), the fact that the amount of heat of crystal melting at the peak of crystal melting at 110 to 125 ° C. is 20 to 60 J / g includes a polymer block made of ethylene and an ethylene / α-olefin copolymer block. It is an index showing that the olefin-based block copolymer has a polymer block made of crystalline ethylene. Further, the olefin-based block copolymer containing a polymer block made of ethylene and an ethylene / α-olefin copolymer block is an ethylene / α-olefin copolymer in addition to the crystallinity based on the polymer block made of ethylene. It preferably has block-based amorphous properties. Since the olefin-based block copolymer containing a polymer block made of ethylene and an ethylene / α-olefin copolymer block has such a structure, the thermoplastic elastomer composition of the present invention has high-temperature strength and low-temperature impact resistance. A sexual effect is given. The calorific value of crystal fusion of an olefin-based block copolymer containing a polymer block made of ethylene and an ethylene / α-olefin copolymer block is preferably 20 J / g or more, more preferably 30 J / g or more from the viewpoint of high temperature strength. On the other hand, from the viewpoint of low temperature impact resistance, it is preferably 60 J / g or less, more preferably 50 J / g or less.

The values of the crystal melting peak, the heat of crystal melting, and the glass transition temperature of the olefin-based block copolymer containing the polymer block made of ethylene and the ethylene / α-olefin copolymer block are the differential scanning calorimetry methods. It can be obtained by (DSC method). The crystal melting peak temperature is the top temperature of the melting peak obtained by the differential scanning calorimeter (DSC), and the crystal melting calorie can be obtained from the area of the melting peak obtained by the differential scanning calorimeter. The glass transition temperature is the intersection of the baseline and the tangent at the inflection point obtained by the differential scanning calorimeter. The specific measurement conditions for obtaining these values are as follows.
That is, a sample amount of 10 mg was taken, melted from 25 ° C. to 200 ° C. at a heating rate of 100 ° C./min using DSC, held at 200 ° C. for 1 minute, and then lowered to −130 ° C. at a rate of 10 ° C./min. Crystallize with, hold at −130 ° C. for 10 minutes, and then measure to 200 ° C. at a heating rate of 10 ° C./min.

When the ethylene / α-olefin copolymer of the component (B) of the present invention is an olefin-based block copolymer containing a polymer block made of ethylene and an ethylene / α-olefin copolymer block, a weight made of ethylene is used. The coalesced block is mainly composed of ethylene, but may have other monomer units in addition to ethylene. Here, "mainly" means to occupy 50% by mass or more of the whole, particularly 60 to 100% by mass. Other monomers of other monomeric units include propylene, 1-butene, 2-methylpropylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, An α-olefin such as 1-octene can be exemplified. Preferably, it is an α-olefin having 3 to 8 carbon atoms having an intercarbon double bond at the terminal carbon atom such as propylene, 1-butene, 1-hexene, 1-octene and the like. When the polymer block made of ethylene in the olefin-based block copolymer containing a polymer block made of ethylene and an ethylene / α-olefin copolymer block contains an α-olefin unit, only one type of α-olefin is ethylene. It may be copolymerized with ethylene, or two or more kinds may be copolymerized with ethylene.

The ethylene / α-olefin copolymer block of an olefin-based block copolymer containing a polymer block composed of ethylene and an ethylene / α-olefin copolymer block contains propylene and 1 as an α-olefin unit in addition to the ethylene unit. Examples of those having an α-olefin unit such as −butene, 2-methylpropylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene as a constituent unit are exemplified. be able to. The α-olefin is preferably an α-olefin having 4 to 8 carbon atoms having an intercarbon double bond at the terminal carbon atom such as 1-butene, 1-hexene, 1-octene and the like. Only one type of α-olefin in the ethylene / α-olefin copolymer block of an olefin-based block copolymer containing a polymer block made of ethylene and an ethylene / α-olefin copolymer block is copolymerized with ethylene. However, two or more of them may be copolymerized with ethylene.

The block of ethylene / α-olefin copolymer in the olefin-based block copolymer containing the polymer block composed of ethylene and the ethylene / α-olefin copolymer block is non-conjugated in addition to the ethylene unit and α-olefin unit. It may have other monomeric units such as a diene-based monomeric unit (non-conjugated diene unit). Examples of the non-conjugated diene include 1,4-hexadiene, 1,6-octadene, 2-methyl-1,5-hexadiene, 6-methyl-1,5-heptadiene, and 7-methyl-1,6-octadien. Chain non-conjugated diene; cyclohexadiene, dicyclopentadiene, methyltetrahydroinden, 5-vinylnorbornene, 5-ethylidene-2-norbornene, 5-methylene-2-norbornene, 5-isopropyridene-2-norbornene, 6- Cyclic non-conjugated diene such as chloromethyl-5-isopropenyl-2-norbornene and the like can be mentioned. Preferably, it is 5-ethylidene-2-norbornene, dicyclopentadiene.
When the olefin-based block copolymer containing the polymer block made of ethylene and the ethylene / α-olefin copolymer block has another monomer unit such as a non-conjugated diene unit, the content thereof is from ethylene. 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less, based on the entire olefin-based block polymer containing the polymer block and the ethylene / α-olefin copolymer block. It is particularly preferably 1% by mass or less, and as described above, a saturated ethylene / olefin copolymer containing no non-conjugated diene unit is preferable in order to obtain uniform dispersion. The content of non-conjugated diene units can also be determined by infrared spectroscopy.

The content of ethylene units in an olefin-based block copolymer containing a polymer block composed of ethylene and an ethylene / α-olefin copolymer block is the total amount of the content of ethylene units and the content of α-olefin units. On the other hand, it is preferably 50% by mass or more and 80% by mass or less. The content of the ethylene unit of the olefin-based block copolymer containing the polymer block made of ethylene and the ethylene / α-olefin copolymer block is the same as that of the polymer block made of ethylene and the ethylene / α-olefin copolymer block. It is preferable that the amount is large in order to prevent fusion due to blocking of the olefin block copolymer containing the above, and it is preferable that the amount is small from the viewpoint of low temperature impact resistance when the thermoplastic elastomer of the present invention is molded. The content of ethylene units in an olefin-based block copolymer containing a polymer block made of ethylene and an ethylene / α-olefin copolymer block is more preferably 55% by mass or more, still more preferably 60% by mass or more. Is. The ethylene unit content is more preferably 75% by mass or less. The content of ethylene units and the content of α-olefin units in an olefin-based block copolymer containing a polymer block made of ethylene and an ethylene / α-olefin copolymer block are determined by infrared spectroscopy, respectively. be able to.

An olefin system in which the ethylene / α-olefin copolymer of the component (B) used in the thermoplastic elastomer composition for an air bag storage cover of the present invention contains a polymer block made of ethylene and an ethylene / α-olefin copolymer block. In the case of a block copolymer, specifically, a polymer block composed of ethylene, an ethylene / 1-butene copolymer, an ethylene / 1-hexene copolymer, an ethylene / 1-octene copolymer, and an ethylene / propylene An example is a block copolymer containing an ethylene / α-olefin copolymer block such as a 1-butene copolymer, an ethylene / propylene / 1-hexene copolymer, and an ethylene / propylene / 1-octene copolymer. be able to. These may be used alone or in combination of two or more. Among these, the component (B) is most preferably an olefin-based block copolymer containing a polymer block made of ethylene and an ethylene / 1-octene copolymer block.

An olefin-based block copolymer containing a polymer block made of ethylene and an ethylene / α-olefin copolymer block has a polymer block made of ethylene having crystallinity, and usually also contains ethylene / α-olefin. It has amorphousness due to the polymer block. This amorphous property can be expressed by the glass transition temperature, and the glass transition temperature by the DSC method is preferably −80 ° C. or higher, more preferably −75 ° C. or higher, while preferably −50 ° C. or lower. , More preferably −60 ° C. or lower.

Regarding the preferable range of melt flow rate (MFR) and density of the olefin-based block copolymer containing the polymer block made of ethylene and the ethylene / α-olefin copolymer block, the above-mentioned component (B) of ethylene / α -Similar to the melt flow rate and density of olefin copolymers.

Olefin-based block copolymers containing a polymer block made of ethylene and an ethylene / α-olefin copolymer block are described in JP-A-2007-528617, JP-A-2008-537563, and JP-A-2008-543978. It can be synthesized according to the method disclosed in. For example, 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 the same polymerization conditions as the first olefin polymerization catalyst. , A composition containing a mixture or reaction product obtained in combination with a chain shutling agent is prepared, and the above ethylene and α-olefin are produced through a step of contacting the composition under addition polymerization conditions. be able to.

A continuous solution polymerization method is preferably applied to the polymerization of an olefin-based block copolymer containing a polymer block made of ethylene and an ethylene / α-olefin copolymer block. In the continuous solution polymerization method, the catalyst component, the chain shuttling agent, the monomers, and optionally the solvent, the auxiliary agent, the scavenger and the polymerization aid are continuously supplied to the reaction zone, and the polymer product is continuously supplied from the reaction zone. Taken out. Further, the length of the block can be changed by controlling the ratio and type of the catalyst, the ratio and type of the chain shuttling agent, the polymerization temperature and the like.

In the method for synthesizing an olefin block copolymer of an olefin block copolymer containing an ethylene polymer block and an ethylene / α-olefin copolymer block, other conditions are described in JP-A-2007-528617. , 2008-537563, and 2008-543978.

Further, as the olefin-based block copolymer containing a polymer block made of ethylene and an ethylene / α-olefin copolymer block, a commercially available applicable product can be used. For example, Engage (registered trademark) manufactured by Dow Chemical Co., Ltd.- Examples include the XLT series and the INFUSE (registered trademark) series.

In the present invention, only one type of ethylene / α-olefin copolymer may be used as the component (B), or two or more types having different physical characteristics, types of copolymerization components, composition, etc. may be used in combination. ..

<Component (C)>
As the organic peroxide used as the component (C) of the thermoplastic elastomer composition for the airbag storage cover of the present invention, either an aromatic organic peroxide or an aliphatic organic peroxide can be used. Is. Specifically, di-t-butylperoxide, t-butylcumylperoxide, dicumylperoxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl. -2,5-di (t-butylperoxy) hexin-3,1,3-bis (t-butylperoxyisopropyl) benzene, 1,1-di (t-butylperoxy) -3,3,5 Dialkyl peroxides such as -trimethylcyclohexane; t-butylperoxybenzoate, t-butylperoxyisopropyl carbonate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,5-dimethyl-2 , 5-Di (benzoyl peroxy) hexins-3 and other peroxyesters; acetyl peroxide, lauroyl peroxide, benzoyl peroxide, p-chlorobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide and other hydropers Examples include oxides. Among these, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane is preferable. These organic peroxides may be used alone or in combination of two or more.

<Component (D)>
The maleimide-based cross-linking aid of the component (D) used in the thermoplastic elastomer composition for the airbag storage cover of the present invention includes monomaleimide, bismaleimide, polyvalent maleimide, and an equivalent mixture of maleic anhydride and a primary amine compound. Can be used.

Examples of monomaleimide include N-phenylmaleimide, N- (2-chlorophenyl) maleimide, N-cyclohexylmaleimide, and N-laurylmaleimide. Examples of bismaleimide include N, N'-m-phenylene bismaleimide, 2,2-bis [4- (4-maleimidephenoxy) phenyl] propane, and N, N'-(4,4'-biphenylmethane) bismaleimide. , Bis (3-ethyl-5-methyl-4 maleimidephenyl) methane, N, N'-ethylenebismaleimide and the like.

Examples of the primary amine compound constituting an equivalent mixture of maleic anhydride and the primary amine compound include ethylenediamine, hexamethylenediamine, phenylenediamine, benzylamine, polyallylamine and the like.

Of these, as the maleimide-based cross-linking aid of the component (D), it is preferable to use N, N'-m-phenylene bismaleimide from the viewpoint of cross-linking efficiency.

In addition, other cross-linking aids such as epoxy compounds, acrylic compounds, urethane compounds, and vinyl compounds may be used together with the maleimide-based cross-linking aids as long as the characteristics of the present invention are not impaired.

<Mixing ratio>
The thermoplastic elastomer composition for an air bag storage cover of the present invention is produced by dynamically heat-treating a mixture of components (A) to (D) and other components described below, which are used as necessary.

As for the content ratio of each component in the mixture to be subjected to the dynamic heat treatment of each component, 40 to 50 parts by mass of the component (A) and 40 to 50 parts by mass of the component (A) in a total of 100 parts by mass of the component (A) and the component (B). B) is contained in an amount of 50 to 60 parts by mass, and the component (C) is 0.005 to 0.3 parts by mass and the component (D) is 0. It is preferable to contain 005 to 2.0 parts by mass. The other components will be described later.

Rigidity is achieved when the component (A) is 40 parts by mass or more and the component (B) is 60 parts by mass or less with respect to a total of 100 parts by mass of the component (A) and the component (B) in the mixture to be subjected to the dynamic heat treatment. Excellent, and when the component (A) is 50 parts by mass or less and the component (B) is 50 parts by mass or more, the low temperature impact resistance is excellent. From this point of view, in order to obtain sufficient rigidity and low temperature impact resistance, the component (A) is 40 to 50 parts by mass, the component (B) is 50 to 60 parts by mass, and particularly the component (A) is 42 to 50 parts by mass. It is preferable that the component (B) is contained in an amount of 50 to 58 parts by mass.

The component (C) is used because the component (C) is 0.005 part by mass or more with respect to a total of 100 parts by mass of the component (A) and the component (B) in the mixture to be subjected to the dynamic heat treatment. The effect of improving the appearance and low-temperature impact resistance can be sufficiently obtained by forming the cross-linked structure by the above method, and when the amount is 0.3 parts by mass or less, the cross-linking reaction can be sufficiently controlled. From this point of view, the component (C) is 0.005 to 0.3 parts by mass, particularly 0.01, based on 100 parts by mass of the total of the component (A) and the component (B) in the mixture to be subjected to the dynamic heat treatment. It is preferably contained in an amount of ~ 0.1 parts by mass.

The component (D) is used because the component (D) is 0.005 part by mass or more with respect to a total of 100 parts by mass of the component (A) and the component (B) in the mixture to be subjected to the dynamic heat treatment. The effect of improving the appearance and low-temperature impact resistance can be sufficiently obtained by forming the cross-linked structure by the above method, and when the amount is 2.0 parts by mass or less, the cross-linking reaction can be sufficiently controlled. From this point of view, the component (D) is 0.005 to 2.0 parts by mass, particularly 0.01, based on 100 parts by mass of the total of the component (A) and the component (B) in the mixture to be subjected to the dynamic heat treatment. It is preferably contained in an amount of up to 1.0 part by mass.

<Other ingredients>
In addition to the above components (A) to (D), the thermoplastic elastomer composition for an air bag storage cover of the present invention contains the following additives according to various purposes within a range that does not significantly impair the effects of the present invention. And components (A), resins other than (B), elastomers (hereinafter referred to as "other resins") and other arbitrary components can be blended.

Optional ingredients include colorants, antioxidants, heat stabilizers, light stabilizers, UV absorbers, neutralizers, lubricants, cloud proofing agents, anti-blocking agents, slip agents, flame retardants, dispersants, antistatic agents. , Conductivity imparting agent, metal inactivating agent, molecular weight adjusting agent, antibacterial agent, fluorescent whitening agent and various other additives. The blending amount of these additives is appropriately set according to the required characteristics and the like. For example, the antioxidant is used in the range of 0.01 to 5 parts by mass per 100 parts by mass of the total amount of the component (A), (B) or the component (A), (B) and other resins.

Examples of other resins that can be contained in the thermoplastic elastomer composition for the airbag storage cover of the present invention include polyethylene-based resins other than the components (A) and (B), polyolefin resins such as polypropylene-based resins, and styrene-based thermoplastic elastomers. , Polyester resin, polyamide resin, styrene resin, acrylic resin, polycarbonate resin, polyvinyl chloride resin, various elastomers other than the above, and the like. The other resins listed above may contain only one type or two or more types. When a styrene-based thermoplastic elastomer is used, a hydrocarbon-based softening agent for rubber can also be used.

However, when the thermoplastic elastomer composition for the airbag storage cover of the present invention contains the above-mentioned other resins and elastomers, the content thereof is the heat of the present invention in which the components (A) to (D) are essential components. In order to effectively obtain the effect of the thermoplastic elastomer composition, it is preferably 50 parts by mass or less with respect to 100 parts by mass of the total of the components (A) and (B) from the viewpoint of appearance, low temperature impact resistance, and rigidity.

<Manufacturing method of thermoplastic elastomer composition for airbag storage cover>
The thermoplastic elastomer composition for an air bag storage cover of the present invention is obtained by dynamically heat-treating a raw material mixture containing the above components (A) to (D) and other components used as needed in a predetermined ratio. It is what you get.

In the present invention, "dynamic heat treatment" means kneading in a molten state or a semi-molten state in the presence of the component (C) and the component (D). This dynamic heat treatment is preferably performed by melt-kneading, and as a mixing-kneading device for that purpose, for example, a non-open type Banbury mixer, a mixing roll, a kneader, a twin-screw extruder or the like is used. Among these, it is preferable to use a twin-screw extruder. A preferred embodiment of the manufacturing method using this twin-screw extruder is to supply each component to a raw material supply port (hopper) of a twin-screw extruder having a plurality of raw material supply ports to perform dynamic heat treatment.

The temperature at which the dynamic heat treatment is performed is usually 80 to 300 ° C, preferably 100 to 250 ° C. The time for performing the dynamic heat treatment is usually 0.1 to 30 minutes.

<Physical characteristics>
The thermoplastic elastomer composition for an air bag storage cover of the present invention moves the component (A) and the component (B), and other components used as necessary in the presence of the component (C) and the component (D). By being heat-treated, it is excellent in molded appearance, low-temperature impact resistance, rigidity and the like.

(Charpy impact strength)
In the present invention, the fracture type of the notched Charpy impact test at a temperature of −40 ° C. according to JIS K7111 is used as an index of low temperature impact resistance.
C: Complete destruction (test piece breaks into two or more pieces)
H: Hinge fracture (incomplete fracture in which only the thin hinge-like surface layer with low bending strength is integrated into a test piece that does not separate)
P: Partial destruction (incomplete destruction that does not meet the definition of hinge destruction)
NB: Non-destructive The fracture type of the thermoplastic elastomer composition for the airbag storage cover of the present invention in the Charpy impact test is preferably H or more, more preferably P or more, and further preferably NB.

(Flexural modulus)
The thermoplastic elastomer composition for an air bag storage cover of the present invention preferably has a flexural modulus of 600 MPa or less, particularly 200 to 600 MPa, particularly 200 to 550 MPa, measured in accordance with JIS K7203. If the flexural modulus of the thermoplastic elastomer composition is larger than the above upper limit, the low temperature impact resistance tends to decrease, and if it is smaller than the above lower limit, the rigidity and strength tend to be insufficient.

<Molding method>
The thermoplastic elastomer composition for an airbag storage cover of the present invention can be molded by a known method as needed and used as various molded bodies. Examples of the molding method include a molding method used for a thermoplastic elastomer, for example, an injection molding method, an extrusion molding method, a hollow molding method, a compression molding method, a molding method described in the following section of the airbag storage cover, and the like. Be done. Further, after that, secondary processing such as laminating molding and thermoforming may be performed. The thermoplastic elastomer composition of the present invention may be used alone as a molded product, or may be combined with other materials to form a laminated body or the like.

[Airbag storage cover]
Using the thermoplastic elastomer composition for an air bag storage cover of the present invention, generally, various injection molding methods, or, if necessary, a gas injection molding method, an injection compression molding method, a short shot foam molding method, etc. It can be used as an airbag storage cover by forming a molded product by using a molding method. In particular, the molding conditions for injection molding the airbag storage cover are as follows.

The molding temperature for injection molding the airbag storage cover is usually 150 to 300 ° C, preferably 180 to 280 ° C. The injection pressure is usually 5 to 100 MPa, preferably 10 to 80 MPa. The mold temperature is usually 0 to 80 ° C, preferably 20 to 60 ° C.

The airbag storage cover of the present invention obtained by molding the thermoplastic elastomer composition for the airbag storage cover of the present invention senses the impact and deformation of a high-speed moving object such as an automobile in the event of a collision. It is used as an airbag storage cover for airbag systems that operate by operating and protect occupants by expanding and deploying.

Hereinafter, the content of the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples as long as the gist of the present invention is not exceeded. The values of various production conditions and evaluation results in the following examples have meanings as preferable values of the upper limit or the lower limit in the embodiment of the present invention, and the preferable ranges are the above-mentioned upper limit or lower limit values and the following. It may be in the range specified by the value of Examples or the combination of the values of Examples.

[material]
<Ingredient (A)>
(A-1) A polypropylene block copolymer (a propylene homopolymer (component (A1)) is polymerized in the first step, and then an ethylene / propylene copolymer (component (A2)) is polymerized in the second step. What was obtained)
Content of propylene unit: 91% by mass
Ethylene unit content: 9% by mass
Density: 0.90 g / cm ³
MFR (230 ° C, load 21.2N): 30g / 10 minutes Flexural modulus: 1350MPa
Melting temperature: 165 ° C

<Ingredient (B)>
(B-1): Ethylene / 1-butene copolymer Crystal melting peak temperature: 58 ° C.
Density: 0.861 g / cm ³
MFR (190 ° C, load 21.2N): 0.5g / 10 minutes Glass transition temperature (DSC method): -60 ° C

(B-2): Olefin-based block copolymer containing a polymer block made of ethylene and an ethylene / 1-octene copolymer block Crystal melting peak temperature: 119 ° C.
Crystal melting heat: 37 J / g
Density: 0.870 g / cm ³
MFR (190 ° C, load 21.2N): 0.5g / 10 minutes Glass transition temperature (DSC method): -65 ° C

<Component (C)>
(C-1): A mixture of 40% by mass of 2,5-dimethyl-2,5-di (t-butylperoxy) hexane and 60% by mass of calcium carbonate.

<Component (D)>
(D-1): N, N'-m-phenylene bismaleimide

<Ingredient (E)>
(E-1): Trimethylolpropane trimethacrylate

<Ingredient (F)>
(F-1): Mixture of 60% by mass of divinylbenzene and 40% of ethylvinylbenzene

[Evaluation method]
1) Molding appearance Using the obtained thermoplastic elastomer composition, an in-line screw type injection molding machine (“SE180DU” manufactured by Sumitomo Heavy Industries, Ltd.) has a cylinder temperature of 210 ° C., a mold temperature of 40 ° C., and an injection speed of 80 mm / s. A sheet having a thickness of 3 mm, a width of 100 mm, and a length of 400 mm (front surface: textured, back surface: mirror surface) was molded at an injection pressure of 50 MPa, and the appearance of the obtained molded sheet was visually confirmed and evaluated according to the following criteria. bottom.
⊚: No flow mark on the mirror surface ○: No flow mark on the textured surface ×: Flow mark on the textured surface It is preferable that there is no flow mark on the textured surface, and it is most preferable that there is no flow mark on the mirror surface.

2) Flexural modulus (unit: MPa)
Using the obtained thermoplastic elastomer composition, flexural modulus was measured by an in-line screw type injection molding machine (“IS130” manufactured by Toshiba Machine Co., Ltd.) at an injection pressure of 50 MPa, a cylinder temperature of 220 ° C., and a mold temperature of 40 ° C. The test piece is molded into a test piece (thickness 4 mm x width 10 mm x length 80 mm), and the flexural modulus of this test piece is determined at a span spacing of 64 mm and a bending speed of 2 mm / min in accordance with JIS K7203. It was measured. The flexural modulus is preferably in the range of 200 to 600 MPa.

3) Low temperature impact resistance (Charpy impact test fractured state)
Using the obtained thermoplastic elastomer composition, the Charpy impact strength was measured by an in-line screw type injection molding machine (“IS130” manufactured by Toshiba Machine Co., Ltd.) at an injection pressure of 50 MPa, a cylinder temperature of 220 ° C., and a mold temperature of 40 ° C. A test piece for use (a test piece having a thickness of 4 mm, a width of 10 mm, and a length of 80 mm) was formed. The obtained test piece was notched with a notch processing machine (manufactured by Toyo Seiki Co., Ltd. Notching Tool A4). This test piece was subjected to a Charpy impact test at a temperature of −40 ° C. according to JIS K7111, and the fracture type of the Charpy impact test was used as an index of low temperature impact resistance.
C: Complete destruction (test piece breaks into two or more pieces)
H: Hinge fracture (incomplete fracture in which only the thin hinge-like surface layer with low bending strength is integrated into a test piece that does not separate)
P: Partial destruction (incomplete destruction that does not meet the definition of hinge destruction)
NB: Non-destructive The fracture type of the thermoplastic elastomer composition of the present invention in the Charpy impact test is preferably H or more, and more preferably P or more.

[Example / Comparative example]
<Example 1>
(A-1) 50 parts by mass, (b-1) 50 parts by mass, (c-1) 0.2 parts by mass, (d-1) 1.0 parts by mass, and antioxidant (pentaerythritol tetrakis [3] -(3,5-di-t-butyl-4-hydroxyphenyl) propionate) 0.1 part by mass and 1.5 parts by mass of colored master batch (40% carbon-containing LLDPE) were blended with a Henshell mixer for 1 minute. It is charged into a twin-screw extruder in the same direction (Kobe Steel "TEX30α", L / D = 45, number of cylinder blocks = 13) at a speed of 20 kg / h, and the temperature is raised in the range of 180 to 210 ° C. for melt kneading. This was done to produce pellets of the thermoplastic elastomer composition. The pellets of the obtained thermoplastic elastomer composition were evaluated in 1) to 3) above. The evaluation results are shown in Table 1.

<Examples 2-9, Comparative Examples 1-5>
Pellets of the thermoplastic elastomer composition were obtained in the same manner as in Example 1 except that the formulation of the thermoplastic elastomer composition was the formulation shown in Table 1, and the evaluations of 1) to 3) were evaluated in the same manner as in Example 1. went. The evaluation results are shown in Table 1.

[Discussion]
From Table 1, it can be seen that Examples 1 to 9 corresponding to the present invention are excellent in molded appearance and flexural modulus, and excellent in low temperature impact resistance.
On the other hand, Comparative Example 1 which does not contain the component (C) and the component (D), Comparative Example 2 which uses only the component (C) and does not contain the component (D), or only the component (D) is used and the component. Comparative Examples 3 not containing (C) and Comparative Examples 4 and 5 using the cross-linking aid components (E) and (F) other than the component (C) and the component (D) have a poor molded appearance. Comparative Example 4 corresponds to the technique of Patent Document 3 using trimethylolpropane trimethacrylate as a cross-linking aid.

The thermoplastic elastomer composition for an airbag storage cover of the present invention is excellent in molding appearance, low temperature impact resistance, rigidity, etc., and is very useful as a molding material for an airbag storage cover or the like.

Claims (7)

A thermoplastic elastomer composition for an airbag storage cover, which is a dynamically heat-treated product of a mixture containing the following components (A), component (B), component (C) and component (D).
Component (A): Polypropylene block copolymer component (B): Ethylene / α-olefin copolymer component (C): Organic peroxide component (D): Maleimide-based cross-linking aid The thermoplastic elastomer composition for an airbag storage cover according to claim 1, wherein the component (B) is a saturated ethylene / α-olefin copolymer. The thermoplastic elastomer composition for an airbag storage cover according to claim 1 or 2, wherein the α-olefin constituting the component (B) has 4 to 8 carbon atoms. The air bag according to any one of claims 1 to 3, wherein the component (B) is an olefin-based block copolymer containing a polymer block made of ethylene and an ethylene / 1-octene copolymer block. Thermoplastic elastomer composition for storage covers. The thermoplastic elastomer composition for an airbag storage cover according to any one of claims 1 to 4, wherein the component (D) is N, N'-m-phenylene bismaleimide. The mixture contains 40 to 50 parts by mass of the component (A) and 50 to 60 parts by mass of the component (B) in a total of 100 parts by mass of the component (A) and the component (B). Claims 1 to 5 include 0.005 to 0.3 parts by mass of the component (C) and 0.005 to 2.0 parts by mass of the component (D) with respect to 100 parts by mass in total with B). The thermoplastic elastomer composition for an airbag storage cover according to any one of the above. An airbag storage cover made of the thermoplastic elastomer composition for the airbag storage cover according to any one of claims 1 to 6.