JP2020158668A - Thermoplastic elastomer composition, molded article and airbag housing cover - Google Patents

Abstract

To provide a thermoplastic elastomer composition having excellent flexibility while achieving low temperature impact resistance and high temperature strength required for an airbag housing cover and to provide a molded article and an airbag housing cover composed of the thermoplastic elastomer composition.SOLUTION: There is provided a thermoplastic elastomer composition which comprises the following components (A) and (B) and further may comprise the following component (C): a component (A) a polyamide-based thermoplastic elastomer, a component (B) an olefin-based block copolymer containing a polymer block composed of ethylene and an ethylene/α-olefin copolymer block, which has a crystal melting peak at 110 to 125°C and a crystal melting heat quantity of 20 to 60 J/g and a component (C): an acid-modified ethylene/α-olefin copolymer.SELECTED DRAWING: None

Description

The present invention comprises a thermoplastic elastomer composition having excellent flexibility, low temperature impact resistance, high temperature strength, etc., a molded product obtained by injection molding the thermoplastic elastomer composition, and an airbag comprising the thermoplastic elastomer composition. Regarding the storage cover.

An automobile airbag system is a system that protects a driver and a occupant in the event of a collision of an automobile or the like, and includes a device that detects an impact in the event of a collision and an airbag device. This airbag device is installed on the steering wheel, the instrument panel in front of the passenger seat, the driver's seat and the passenger's 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 as to prevent the airbag from being split or scattering other parts as designed when the airbag is inflated.

As a material for an airbag storage cover, for example, in Patent Document 1, a material containing a hydrogenated additive of a styrene-conjugated diene block copolymer, a plasticizer for rubber, an olefin resin and an additive has been proposed. Further, in Patent Documents 2 to 4, those containing a propylene resin, an ethylene / α-olefin copolymer and a styrene elastomer are proposed. Further, Patent Document 5 proposes an olefin-based thermoplastic elastomer obtained by a multi-step polymerization method, a propylene-based resin, and an ethylene / α-olefin copolymer.

Japanese Unexamined Patent Publication No. 5-38996 Japanese Unexamined Patent Publication No. 10-265628 Japanese Unexamined Patent Publication No. 2001-279030 Japanese Unexamined Patent Publication No. 2001-206183 JP-A-2002-194098

In recent years, it has been desired to develop a material having improved flexibility as well as high-temperature strength and low-temperature impact resistance from the viewpoint of strengthening safety corresponding to an improvement in airbag deployment output and design freedom. ..
However, according to a detailed study by the present inventors, the conventional materials for airbag storage covers as described in Patent Documents 1 to 5 have all of flexibility, low temperature impact resistance and high temperature strength. It was difficult to meet.

The present invention has been made in view of the above problems of the prior art.
That is, an object of the present invention is to provide a thermoplastic elastomer composition having excellent flexibility while achieving the low temperature impact resistance and high temperature strength required for the airbag storage cover, and from the thermoplastic elastomer composition. To provide an elastomer and an airbag storage cover.

As a result of diligent studies to solve the above problems, the present inventors have found that a thermoplastic elastomer composition containing a polyamide-based thermoplastic elastomer and a specific olefin-based block copolymer has flexibility, low-temperature impact resistance, and high-temperature strength. We have found that it can be suitably used for an airbag storage cover, and have arrived at the present invention.

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

[1] A thermoplastic elastomer composition containing the following component (A) and component (B).
Component (A): Polyamide-based thermoplastic elastomer Component (B): A polymer block made of ethylene having a crystal melting peak at 10 to 125 ° C. and having a heat of crystal melting of 20 to 60 J / g, and ethylene. Olefin block copolymer containing α-olefin copolymer block

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

[3] The thermoplastic according to [1] or [2], wherein the component (B) is an olefin-based block copolymer containing a polymer block made of ethylene and an ethylene / 1-octene copolymer block. Polymer composition.

[4] The thermoplastic elastomer composition according to any one of [1] to [3], which further contains the following component (C).
Component (C): Acid-modified ethylene / α-olefin copolymer

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

[6] Any of [1] to [5] containing 10 to 150 parts by mass of the component (B) and 0 to 100 parts by mass of the component (C) with respect to 100 parts by mass of the component (A). The thermoplastic elastomer composition described.

[7] A molded product obtained by injection molding the thermoplastic elastomer composition according to any one of [1] to [6].

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

The thermoplastic elastomer composition of the present invention is excellent in flexibility, low temperature impact resistance, high temperature strength and the like. Therefore, the thermoplastic elastomer composition of the present invention can be used for automobile interior parts such as airbag storage covers, instrument panels, center panels, center console boxes, door trims, pillars, assist grips, steering wheels, and automobile exteriors such as mudguards and chromets. It can be suitably used as parts, home appliance parts, building materials, furniture and the like.

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 invention, 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.

In the present invention, the "airbag storage cover" means a container for storing an airbag in general. For example, in a container in which an airbag is stored, an opening when the airbag is deployed, or the opening thereof. The entire container that is integrated with the opening.

[Thermoplastic Elastomer Composition]
The thermoplastic elastomer composition of the present invention contains the following components (A) and (B), preferably further contains the component (C), and is preferably a component (preferably with respect to 100 parts by mass of the component (A)). It is characterized by containing 10 to 150 parts by mass of B) and 0 to 100 parts by mass of the component (C).
Component (A): Polyethylene-based thermoplastic elastomer Component (B): A polymer block made of ethylene having a crystal melting peak at 10 to 125 ° C. and a heat of crystal melting of 20 to 60 J / g, and ethylene. Olefin-based block copolymer containing α-olefin copolymer block Component (C): Acid-modified ethylene / α-olefin copolymer

<Mechanism>
The thermoplastic elastomer composition of the present invention has the effects of being superior in flexibility, low-temperature impact resistance, high-temperature strength, and the like, as compared with conventional thermoplastic elastomers.
This is because, in the thermoplastic elastomer composition of the present invention, the component (A) and the component (B) provide high-temperature strength, and the component (B) improves flexibility and low-temperature impact resistance. This is because the compatibility effect of the component (A) and the component (B) by C) further improves the high temperature strength and the low temperature impact resistance.

<Ingredient (A)>
The polyamide-based thermoplastic elastomer of the component (A) in the thermoplastic elastomer composition of the present invention is a heat composed of a polyamide block as a semi-crystalline hard segment and a polyether block as an amorphous soft segment. It is a plastic elastomer. As the polyether block, polyethylene polyol, polypropylene polyol, polytetramethylene polyol, polyoxyethylene polyoxypropylene polyol and the like can be used. These polyether polyols may be used alone or in combination of two or more. Among these, polyethylene polyol, polypropylene polyol, and polytetramethylene polyol are preferably used from the viewpoint of flexibility, strength, and water resistance.

Further, as the polyamide block, generally known aromatic polyamides and aliphatic polyamide blocks can be used, but aliphatic polyamides are preferably used.

Examples of the aliphatic polyamide block include a polymer containing a ring-opened polymer of ε-caprolactam as a main component, lactam such as ω-laurolactam, 6-aminocaproic acid, 11-aminoundecanoic acid, and 12-aminododecane, if necessary. Examples thereof include those obtained by copolymerizing one or more aliphatic dicarboxylic acids such as aminocarboxylic acids such as acids, succinic acid, adipic acid, sebacic acid, and azelaic acid.

In addition, a ring-opening polymer containing one or more lactams such as ω-laurolactam as a main component, and one aminocarboxylic acid such as 6-aminocaproic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid. Or a polycondensate containing two or more kinds of main components, or one or more kinds of aliphatic diamines such as hexamethylenediamine, nonamethylenediamine, undecamethylenediamine, and dodecamethylenediamine, and succinic acid and adipic acid. , A block composed of a polycondensate containing one or more aliphatic dicarboxylic acids such as sebacic acid and azelaic acid as main components.

The melt flow rate of the component (A) is not limited, but is usually 100 g / 10 minutes or less, preferably 80.0 g / 10 minutes or less, and more preferably 70.0 g / 10 minutes or less from the viewpoint of strength. Yes, more preferably 60.0 g / 10 minutes or less. The melt flow rate of the component (A) is usually 0.1 g / 10 minutes or more, preferably 0.5 g / 10 minutes or more, and more preferably 1 g / 10 minutes or more from the viewpoint of fluidity. is there. The melt flow rate (MFR) of the component (A) is measured according to ISO1133 under the conditions of a measurement temperature of 230 ° C. and a measurement load of 21.18N.

The density of component (A) (based on ISO 1183) is not limited, but is usually 0.98 to 1.03 g / cm ³ .

The flexural modulus (ISO178 compliant) of the component (A) is preferably 50 MPa or more, particularly preferably 75 MPa or more, and particularly preferably 100 MPa or more from the viewpoint of high temperature strength. Alternatively, from the viewpoint of low temperature impact resistance and flexibility, 600 MPa or less is preferable, and 400 MPa or less, particularly 300 MPa or less is particularly preferable.

The melting point of the component (A) (based on ISO11357) is preferably 120 ° C. or higher, particularly preferably 130 ° C. or higher, and particularly preferably 140 ° C. or higher from the viewpoint of heat resistance. The upper limit of the melting point of the component (A) is not particularly limited, but is usually 180 ° C. or lower.

As the polyamide-based thermoplastic elastomer as the component (A) in the present invention, a commercially available product can be used. For example, it can be appropriately selected and used from those commercially available as the "Pevax (registered trademark)" (manufactured by ARKEMA) series and the like.

The thermoplastic elastomer composition of the present invention may contain only one type of the component (A), or may contain two or more types having different monomer unit compositions, physical properties, and the like.

<Ingredient (B)>
The component (B) used in the thermoplastic elastomer composition of the present invention is an olefin-based block copolymer containing a polymer block made of ethylene and an ethylene / α-olefin copolymer block.

Further, the component (B) 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. Here, in the component (B), the amount of heat of crystal melting at the peak of crystal melting at 110 to 125 ° C. is 20 to 60 J / g, which means that the component (B) has a polymer block made of crystalline ethylene. It is an index to represent. Further, the component (B) preferably has an amorphous property based on an ethylene / α-olefin copolymer block in addition to a crystallinity based on a polymer block made of ethylene. When the component (B) has such a structure, the thermoplastic elastomer composition of the present invention is imparted with the effects of high temperature strength and low temperature impact resistance. The amount of heat of crystal melting of the component (B) is preferably 20 J / g or more, and more preferably 30 J / g or more from the viewpoint of high temperature strength. The amount of heat of crystal melting of the component (B) is preferably 60 J / g or less, and more preferably 50 J / g or less from the viewpoint of low temperature impact resistance.

The respective values of the crystal melting peak of the component (B), the heat of crystal melting, and the glass transition temperature described later can be obtained by the differential scanning calorimetry (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 point at the inflection point obtained by the differential scanning calorimeter. Specific measurement conditions for obtaining these values are obtained as follows. That is, a sample amount of 10 mg was taken, melted using DSC at a heating rate of 100 ° C./min from 25 ° C., held at 200 ° C. for 1 minute, and then lowered to −130 ° C. It is a value obtained by crystallizing at −130 ° C., holding at −130 ° C. for 10 minutes, and then measuring to 200 ° C. at a heating rate of 10 ° C./min.

The polymer block made of ethylene in the component (B) is mainly composed of ethylene, but may have other monomer units in addition to ethylene. Here, "mainly" means that it occupies 50% by mass or more of the whole, particularly 60 to 100% by mass. Other monomers of other monomeric units include 1-propylene, 1-butene, 2-methylpropylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-. Α-olefins such as butene and 1-octene can be exemplified. Preferably, it is 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. When the polymer block composed of ethylene in the component (B) contains an α-olefin unit, even if only one α-olefin is copolymerized with ethylene, two or more kinds are copolymerized with ethylene. There may be.

The ethylene / α-olefin copolymer block of the component (B) contains 1-propylene, 1-butene, 2-methylpropylene, 1-pentene, 3-methyl-1-butene as α-olefin units in addition to ethylene units. , 1-Hexene, 4-methyl-1-pentene, 1-octene and the like having an α-olefin unit as a constituent unit can be exemplified. 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-propylene, 1-butene, 1-hexene, and 1-octene. As the α-olefin in the ethylene / α-olefin copolymer block of the component (B), only one kind may be copolymerized with ethylene, or two or more kinds may be copolymerized with ethylene.

The block of the ethylene / α-olefin copolymer in the component (B) is composed of other monomer units such as a monomer unit based on a non-conjugated diene (non-conjugated diene unit) in addition to the ethylene unit and the α-olefin unit. May have. Examples of the non-conjugated diene include 1,4-hexadiene, 1,6-octadien, 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- Examples include cyclic non-conjugated diene such as chloromethyl-5-isopropenyl-2-norbornene. Preferred are 5-ethylidene-2-norbornene and dicyclopentadiene.

The ethylene unit content of the component (B) is preferably 50% by mass or more and 80% by mass or less with respect to the total amount of the ethylene unit content and the α-olefin unit content. The ethylene unit content of the component (B) is preferably high in order to prevent fusion due to blocking of the component (B), and is low from the viewpoint of low temperature impact resistance when the thermoplastic elastomer of the present invention is molded. Is preferable. The content of the ethylene unit of the component (B) is more preferably 55% by mass or more, still more preferably 60% by mass or more. The ethylene unit content is more preferably 75% by mass or less. The ethylene unit content and the α-olefin unit content in the component (B) can be determined by infrared spectroscopy, respectively.

When the component (B) has another monomer unit such as a non-conjugated diene unit, the content thereof is usually 10% by mass or less, preferably 5% by mass or less, based on the whole component (B). .. The content of non-conjugated diene units can also be determined by infrared spectroscopy.

Specifically, the component (B) used in the thermoplastic elastomer composition of the present invention includes a polymer block made of ethylene, an ethylene / 1-butene copolymer, an ethylene / 1-hexene copolymer, and an ethylene / 1-. With ethylene / α-olefin copolymer blocks such as octene copolymer, ethylene / propylene / 1-butene copolymer, ethylene / propylene / 1-hexene copolymer, ethylene / propylene / 1-octene copolymer, etc. The block copolymer containing can be exemplified. 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.

In addition to having a polymer block made of ethylene having crystallinity, component (B) usually has amorphousness due to an ethylene / α-olefin copolymer 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.

The melt flow rate of the component (B) is not limited, but is usually 10 g / 10 minutes or less, preferably 8.0 g / 10 minutes or less, and more preferably 5.0 g / 10 minutes or less from the viewpoint of strength. Yes, more preferably 3.0 g / 10 minutes or less. The melt flow rate 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 from the viewpoint of fluidity. That is all. The melt flow rate (MFR) of the component (B) is measured according to ASTM D1238 under the conditions of a measurement temperature of 190 ° C. and a measurement load of 21.18N.

The density of the component (B) (based on ISO1133) is preferably 0.88 g / cm ³ or less, and more preferably 0.87 g / cm ³ or less from the viewpoint of low temperature impact resistance. On the other hand, the lower limit thereof is not particularly limited, but is usually 0.85 g / cm ³ or more.

The component (B) can be synthesized according to the methods disclosed in JP-A-2007-528617, JP-A-2008-537563, and JP-A-2008-543978. 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 additional polymerization conditions. be able to.

A continuous solution polymerization method is preferably applied to the polymerization of the component (B). 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 the olefin block copolymer of the component (B), other conditions are disclosed in Japanese Patent Publication No. 2007-528617, Japanese Patent Publication No. 2008-537563, and Japanese Patent Application Laid-Open No. 2008-543978. ..

In addition, a commercially available applicable product can be used as the component (B), and examples thereof include the Engage (registered trademark) -XLT series and the INFUSE (registered trademark) series manufactured by Dow Chemical Co., Ltd. Among the components (B), those having an ethylene / octene copolymer block were Dow Chemical in 2007 for the INFUSE (registered trademark) series and in 2011 for the Engage (registered trademark) -XLT series. It was not available as a product until the company started commercial production.

The thermoplastic elastomer composition of the present invention may contain only one type of the component (B), or may contain two or more types having different monomer unit compositions, physical properties, and the like.

The component (B) includes the above-mentioned polymer block made of ethylene and the ethylene / α-olefin copolymer block, has a crystal melting peak at 110 to 125 ° C., and has a crystal melting calorific value of 20. An olefin-based block copolymer of ~ 60 J / g may be used as an acid-modified product modified with an unsaturated carboxylic acid and / or a derivative thereof. By using the component (B) after acid modification, the compatibility of the component (A) with the polyamide-based thermoplastic elastomer is improved, and high-temperature strength and low-temperature impact resistance can be expected to be improved. The modification treatment with the unsaturated carboxylic acid and / or its derivative can be carried out in the same manner as the method for the modification treatment of the acid-modified ethylene / α-olefin copolymer of the component (C) described later.

<Component (C)>
The thermoplastic elastomer composition of the present invention preferably further contains the acid-modified ethylene / α-olefin copolymer of the component (C) in addition to the above components (A) and (B).

The component (C) functions as a compatibilizer that exhibits high compatibility performance with resins containing polar groups such as the component (A) and the component (B), and maintains low-temperature impact resistance and high-temperature strength. , Can increase flexibility. The ethylene / α-olefin copolymer of the acid-modified ethylene / α-olefin copolymer of the component (C) has a structure different from that of the olefin block copolymer of the above component (B). -It is preferably an α-olefin copolymer.

The modified ethylene / α-olefin copolymer of the component (C) is a modified ethylene / α-olefin copolymer obtained by modifying the ethylene / α-olefin copolymer with an unsaturated carboxylic acid and / or a derivative thereof.

The unmodified ethylene / α-olefin copolymer used for the modified ethylene / α-olefin copolymer of the component (C) is a copolymer containing at least an ethylene unit and an α-olefin unit. Examples of the α-olefin include 1-propylene, 1-butene, 2-methylpropylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene and the like. be able to. Preferably, it is an α-olefin having 3 to 8 carbon atoms having an intercarbon double bond at the terminal carbon atom such as 1-propylene, 1-butene, 1-hexene and 1-octene. In the ethylene / α-olefin copolymer used for the modified ethylene / α-olefin copolymer of the component (C), even if only one type of α-olefin is copolymerized with ethylene, two or more types are copolymerized with ethylene. It may be copolymerized.

The ethylene unit content of the ethylene / α-olefin copolymer used in the modified ethylene / α-olefin copolymer of the component (C) is the total amount of the ethylene unit content and the α-olefin unit content. On the other hand, it is preferably 30% by mass or more and 80% by mass or less. The content of the ethylene unit of the ethylene / α-olefin copolymer used in the modified ethylene / α-olefin copolymer of the component (C) is preferably large in order to prevent fusion due to blocking of the component (C). From the viewpoint of low-temperature impact resistance when the thermoplastic elastomer composition of the present invention is molded, a small amount is preferable. The content of the ethylene unit of the ethylene / α-olefin copolymer used in the modified ethylene / α-olefin copolymer of the component (C) is more preferably 40% by mass or more, still more preferably 50% by mass or more. is there. The ethylene unit content is more preferably 75% by mass or less.
The content of ethylene units in the ethylene / α-olefin copolymer used in the modified ethylene / α-olefin copolymer of component (C), the content of α-olefin units, and other monomers shown below. The content of each unit can be determined by infrared spectroscopy.

The ethylene-α-olefin copolymer of the ethylene / α-olefin copolymer used for the modified ethylene / α-olefin copolymer of the component (C) is based on a non-conjugated diene in addition to the ethylene unit and the α-olefin unit. It may have other monomeric units such as monomeric units (non-conjugated diene units). Examples of the non-conjugated diene include 1,4-hexadiene, 1,6-octadien, 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- One or more of cyclic non-conjugated diene such as chloromethyl-5-isopropenyl-2-norbornene can be mentioned. Preferred are 5-ethylidene-2-norbornene and dicyclopentadiene.

When the ethylene / α-olefin copolymer used for the modified ethylene / α-olefin copolymer of the component (C) contains other monomer units such as the above-mentioned non-conjugated diene unit, the other monomer unit The content is usually 10% by mass or less, preferably 5% by mass or less, based on the total ethylene / α-olefin copolymer used for the modified ethylene / α-olefin copolymer of the component (C).

Specifically, as the ethylene / α-olefin copolymer used for the modified ethylene / α-olefin copolymer of the component (C), ethylene / 1-butene copolymer rubber, ethylene / 1-hexene copolymer rubber, Examples thereof include ethylene / 1-octene copolymer rubber, ethylene / propylene / 1-butene copolymer rubber, ethylene / propylene / 1-hexene copolymer rubber, ethylene / propylene / 1-octene copolymer rubber, and the like. Can be done. Of these, ethylene / 1-octene copolymer rubber is preferable.

As a method for producing the ethylene / α-olefin copolymer used for the modified ethylene / α-olefin copolymer of the component (C), a known polymerization method using a known olefin polymerization catalyst is used. For example, as a catalyst for olefin polymerization, a Cheegler-Natta catalyst, a complex catalyst such as a metallocene complex or a non-metallocene complex can be used, and the polymerization method includes a slurry polymerization method, a solution polymerization method, a massive polymerization method, and Qi. Examples thereof include a phase polymerization method. It is also possible to use a commercially available applicable product. Examples of applicable products on the market include KUMHO's "KEP (registered trademark)" series, JSR's "EP (registered trademark)" series, Dow Chemicals' "Engage (registered trademark)" series, and Mitsui Chemicals' "" Examples include the "Toughmer (registered trademark)" series.

The modified ethylene / α-olefin copolymer of the component (C) is the above-mentioned ethylene / α-olefin copolymer modified with an unsaturated carboxylic acid and / or a derivative thereof.
The ethylene / α-olefin copolymer to be modified may be only one type, or may be two or more types having different monomer unit compositions, physical properties, and the like.

For the modification treatment with an unsaturated carboxylic acid and / or a derivative thereof, any commonly used method can be adopted, and the method is not particularly limited. For example, as a solution modification method, an ethylene / α-olefin copolymer, an unsaturated carboxylic acid and / or a derivative thereof and, if necessary, a radical initiator or the like are added to an organic solvent, and the temperature is usually 60 to 350 ° C. A method of reacting at a temperature of 80 to 190 ° C., usually for 0.5 to 15 hours, preferably 1 to 10 hours can be mentioned. Further, as a melt modification method, an ethylene / α-olefin copolymer and an unsaturated carboxylic acid and / or a derivative thereof are subjected to a temperature equal to or higher than the melting point of the ethylene / α-olefin copolymer using an extruder or the like (for example). A method of melting at 170 to 290 ° C.) and usually reacting for 0.5 to 10 minutes can be mentioned. Among these, from the viewpoint of hygiene, a melt modification method that does not require the use of a solvent is preferable, and modification using an extruder is more preferable. For efficient modification, it is preferable to modify in the presence of a radical initiator.

Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid, and endocis-bicyclo [2.2.1] hept-5-ene. Examples thereof include -2,3-dicarboxylic acid. Examples of the unsaturated carboxylic acid derivative include acid anhydrides, esters, amides, imides, and metal salts. Specifically, maleic anhydride, hymic anhydride, itaconic anhydride, citraconic anhydride, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, glycidyl acrylate, monoethyl maleate ester, diethyl maleate. Ester, itaconic acid monomethyl ester, itaconic acid diethyl ester, acrylamide, methacrylicamide, maleic acid monoamide, maleic acid diamide, maleic acid-N-monoethylamide, maleic acid-N, N-diethylamide, maleic acid-N, N- Monobutylamide, maleic acid-N, N-dibutylamide, fumaric acid monoamide, fumaric acid diamide, fumaric acid-N-monobutylamide, fumaric acid-N, N-dibutylamide, maleimide, Nbutylmaleimide, N-phenyl Maleimide, sodium acrylate, sodium methacrylate, potassium acrylate, potassium methacrylate and the like can be mentioned. Only one type of unsaturated carboxylic acid and / or a derivative thereof can be used alone, or two or more types can be used in any combination and ratio. Among these, maleic acid and maleic anhydride are particularly preferable.

The radical initiator is not particularly limited, but an organic peroxide or an azo compound is preferable, and an organic peroxide is particularly preferable. Specifically, di-t-butyl peroxide, t-butyl cumyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butyl peroxy) hexane, 2,5-dimethyl. -2,5-di (t-butylperoxy) hexin-3,1,4-bis (t-butylperoxyisopropyl) benzene, 1,1-bis (t-butylperoxy) cyclohexane, n-butyl- 4,4-bis (t-butylperoxy) ballet, 2,2-bis (4,5-t-butylperoxycyclohexyl) propane, 2,2-bis (t-butylperoxy) butane, 1,1 Dialkyl peroxides such as -bis (t-butylperoxy) cyclododecane; t-butylperoxyacetate, t-butylperoxy-2-ethylhexanoate, t-butylperoxypivalate, t-butylper Oxylaurate, t-butylperoxybenzoate, t-butylperoxyisopropyl carbonate, t-butylperoxymaleic acid, di-t-butylperoxyisophthalate, 2,5-dimethyl-2,5-di ( Peroxyesters such as benzoylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexin-3, 2,5-dimethyl-2,5-di (toluylperoxy) hexane; Diacyl peroxides such as di-3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, dibenzoyl peroxide; t-butylhydroperoxide, cumenehydroperoxide, diisopropylbenzenehydroperoxide, p- Hydroperoxides such as mentan hydroperoxide and 2,5-dimethyl-2,5-di (hydroperoxy) hexane; ketone peroxides such as methyl ethyl ketone peroxide and cyclohexanone peroxide can be mentioned. There is no particular limitation. Only one type of radical initiator may be used alone, or two or more types may be used in any combination and ratio.

As the radical initiator, among the above-mentioned examples, a radical initiator having a half-life of 1 minute and a decomposition temperature of 100 ° C. or higher is preferable from the viewpoint of denaturation efficiency. Specifically, di-t-butyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (). Dialkyl peroxides such as t-butylperoxy) hexin-3, or t-butylperoxybenzoate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,5-dimethyl-2 , 5-Di (benzoyl peroxy) hexin-3 and other peroxy esters are preferred. The amount of the radical initiator used is not particularly limited, but is preferably 0.001 part by mass or more and 1 part by mass or less with respect to 100 parts by mass of the ethylene / α-olefin copolymer as a raw material.

Content ratio of unsaturated carboxylic acid and / or its derivative (constituent unit derived from unsaturated carboxylic acid and / or its derivative) in the modified ethylene / α-olefin copolymer (hereinafter, may be referred to as "modification rate". ) Is not particularly limited, but is preferably 0.20% by mass or more and 2.0% by mass or less, more preferably 0.30% by mass, based on the total amount of the modified ethylene / α-olefin copolymer. % Or more and 1.90% by mass or less, more preferably 0.50% by mass or more and 1.70% by mass or less. When the modification rate is out of the range of the preferable content ratio, the compatibility tends to be insufficient. The bonding position of the unsaturated carboxylic acid and / or its derivative in the modified ethylene / α-olefin copolymer is not particularly limited, and at least one of the main chain end and the side chain of the ethylene / α-olefin copolymer. It should be introduced in.

The modification rate of the modified ethylene / α-olefin copolymer can be measured by, for example, the following method. That is, first, a sheet-shaped press sample having a thickness of 0.1 to 0.4 mm is prepared from the modified ethylene / α-olefin copolymer using a compression molding machine or the like. Next, a spectrum of 2000 to 1600 cm ^-1 of the press sample was measured with a Fourier transform infrared spectrophotometer, and the absorption peculiar to unsaturated carboxylic acid and / or its derivative (C = O stretching vibration band, that is, carbonyl) was measured. It can be obtained from characteristic absorption). More specifically, the obtained spectrum, pull the baseline between 1950cm ^-1 and 1665 cm ^-1, calculates the peak area S between 1827~1665cm ^-1. Using the obtained peak area S, the content Xm of the structural unit derived from the unsaturated carboxylic acid and / or its derivative is calculated based on the following formula (1). In the modification of the ethylene / α-olefin copolymer, an unsaturated carboxylic acid and / or a derivative thereof that has not reacted with the ethylene / α-olefin copolymer may remain, but what is the modification rate in the present specification? As described above, it means the value when the modified ethylene / α-olefin copolymer is measured by the above method.
Xm = k ・ S / t ・ ρ ・ ・ ・ (1)
(In the formula, k represents a coefficient obtained based on the NMR quantitative value of the methyl esterified product of the ethylene / α-olefin copolymer containing an unsaturated carboxylic acid, and t (mm) represents the thickness of the sample. , Ρ represents the sample density (g / cm ³ ).)

The melt flow rate (MFR) of the acid-modified ethylene / α-olefin copolymer of the component (C) is not particularly limited, but is 0.1 to 50 g / 10 as measured at 190 ° C. and a load of 21.18 N according to ISO1183. Minutes are preferred, more preferably 0.2-40 g / 10 minutes, still more preferably 0.3-30 g / 10 minutes.

The density of the acid-modified ethylene / α-olefin copolymer of the component (C) (based on ISO1133) is not particularly limited, but is preferably 0.850 to 0.930 g / cm ³ , more preferably 0.851 to 0. It is 925 g / cm ³ .

In addition to having a polymer block made of ethylene having crystallinity, the component (C) usually has amorphousness due to an ethylene / α-olefin copolymer 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 −40 ° C. or lower. , More preferably −45 ° C. or lower.

The thermoplastic elastomer composition of the present invention may contain only one type of the component (C), or may contain two or more types having different monomer unit compositions, physical properties, and the like.

<Mixing amount>
The thermoplastic elastomer composition of the present invention contains 10 to 150 parts by mass of the olefin-based block copolymer of the component (B) and the modified ethylene / α- of the component (C) with respect to 100 parts by mass of the component (A). It is preferable to contain 0 to 100 parts by mass of the olefin copolymer.
When the content of the component (B) is at least the above lower limit, the effect of improving the high temperature strength and the low temperature impact resistance by containing the component (B) can be effectively obtained. Further, when the content of the component (B) is not more than the above upper limit, the effect of improving the high temperature strength can be effectively obtained. The preferable content of the component (B) is 10 to 150 parts by mass, more preferably 20 to 100 parts by mass with respect to 100 parts by mass of the component (A).

As described above, the component (C) functions as a compatibilizer that exhibits high compatibility performance with resins containing polar groups such as the component (A) and the component (B), and by containing this, the temperature is low. It is possible to increase the flexibility while maintaining the impact resistance and the high temperature strength, but if the content is too large, the high temperature characteristics tend to deteriorate, so that the upper limit or less is preferable. When the thermoplastic elastomer composition of the present invention contains the component (C), the content of the component (C) is based on 100 parts by mass of the component (A) in order to sufficiently obtain the blending effect of the component (C). It is preferably 0 to 100 parts by mass, and more preferably 1 to 30 parts by mass.

<Other ingredients>
Further, the thermoplastic elastomer composition of the present invention includes the following additives, inorganic fillers, organic fillers and components (A) according to various purposes within a range not significantly impairing the effects of the present invention other than the above components. -Any component such as a resin other than the component (C) (hereinafter, referred to as "other resin") can be blended.

Additives 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 agents, metal inactivating agents, molecular weight regulators, antibacterial agents, fluorescent whitening agents, and other various additives can be mentioned. These additives can be used by blending each additive in the range of 0.01 to 2 parts by mass with respect to a total of 100 parts by mass of the usual components (A) to (C).

Other resins that can be contained in the thermoplastic elastomer composition of the present invention include polypropylene-based resins, polyethylene-based resins, polyester-based elastomers, urethane-based elastomers, polystyrene-based elastomers, acrylic-based elastomers, polyester resins, polyurethane resins, and styrene resins. , Acrylic resin, polypropylene resin, polyvinyl chloride resin, and various other elastomers. The other resins listed above may contain only one type or two or more types.
However, when the thermoplastic elastomer composition of the present invention contains these other resins, in order to effectively obtain the effect of the present invention by containing the components (A) to (C), the components (A) to The content of the resin other than (C) is preferably 30% by mass or less in 100% by mass of the thermoplastic elastomer composition of the present invention.

<Manufacturing method of thermoplastic elastomer composition>
The thermoplastic elastomer composition of the present invention comprises a component (A), a component (B) or, if necessary, a component (C) and other components in a conventional extruder, Banbury mixer, roll, lavender plastograph, kneaderb. It can be produced by kneading with a conventional method using lavender or the like. Among these manufacturing methods, it is preferable to use an extruder, particularly a twin-screw extruder. When the thermoplastic elastomer composition of the present invention is kneaded and kneaded with an extruder or the like, it can be produced by melt-kneading while heating to 160 to 240 ° C., preferably 180 to 220 ° C. Further, the thermoplastic elastomer composition of the present invention may be partially crosslinked by blending the following crosslinking agent or crosslinking aid and dynamically heat-treating.

As a cross-linking agent for partially cross-linking the thermoplastic elastomer composition of the present invention, it is preferable to use an organic peroxide, and 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) Examples thereof include 3,5,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di (peroxybenzoyl) hexin-3, and dicumyl peroxide.

Examples of the cross-linking aid used when partially cross-linking with these organic peroxides include compounds having N, N'-m-phenylene bismaleimide, toluylene bismaleimide, P-quinonedioxime, nitrobenzene, and the like. Compounds with radically polymerizable carbon-carbon double bonds such as diphenylguanidine, trimethylolpropane, divinylbenzene, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, and allyl methacrylate, and the component (B). Examples thereof include compounds having a functional group that reacts with a carbon linear moiety.

<Physical properties / applications>
In the present invention, the fracture type of the notched Charpy impact test at a temperature of −40 ° C. with reference to ISO180 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 destruction type of the Charpy impact test of the thermoplastic elastomer composition of the present invention is preferably H or more, and more preferably P or more.

In the present invention, the tensile fracture strength at 85 ° C. with reference to ISO37-1A is used as an index of high temperature strength. The high-temperature strength of the molded product of the thermoplastic elastomer composition of the present invention is preferably 10 MPa or more, more preferably 11 MPa or more, and even more preferably 12 MPa or more. When the tensile breaking strength at 85 ° C. is less than the above lower limit, the high temperature strength tends to be inferior, so that the high temperature deployability of the airbag storage cover tends to decrease. The present invention is characterized in that it is excellent in high-temperature strength while maintaining low-temperature impact resistance, as compared with the conventional thermoplastic elastomer composition for airbag storage covers. Therefore, in the present invention, it is particularly important to increase the high temperature strength.

The thermoplastic elastomer composition of the present invention uses the flexural modulus with reference to ISO178 as an index of flexibility. The thermoplastic elastomer composition of the present invention preferably has a flexural modulus of 50 to 250 MPa, particularly 80 to 180 MPa, and particularly preferably 100 to 150 MPa. 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 the airbag may not be broken or completely opened when the airbag is deployed. Further, if it is smaller than the above lower limit, the rigidity and strength tend to be insufficient.

Using the thermoplastic elastomer composition of the present invention, generally, by using an ordinary injection molding method or, if necessary, various molding methods such as a gas injection molding method, an injection compression molding method, and a short shot foam molding method. By forming a molded body, it can be used as an airbag storage cover. In particular, it is preferable that the thermoplastic elastomer of the present invention is injection-molded to form a molded product, and the molding conditions for injection molding are as follows. The molding temperature for injection molding the thermoplastic elastomer composition 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 thermoplastic elastomer composition of the present invention is excellent in low temperature impact resistance, high temperature strength, flexibility, mold releasability, injection moldability, etc., and can be suitably used for various applications. The thermoplastic elastomer composition of the present invention includes, for example, automobile interior parts such as airbag storage covers, instrument panels, center panels, center console boxes, door trims, pillars, assist grips, and steering wheels, and automobile exterior parts such as mudguards and chromets. It is useful as home appliances, building materials, furniture, etc. Among these, the thermoplastic air stomacher composition of the present invention is particularly useful as an airbag storage cover, and among these airbag storage covers, for example, when a high-speed moving body such as an automobile collides, the impact or deformation thereof occurs. It is suitable as an airbag storage cover for an airbag system that operates by sensing and protects 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.

<Raw materials>
[Component (A)]
(A-1): Polyamide-based thermoplastic elastomer ARKEMA Pevacs 5533SP01
MFR (ISO1133): 24 g / 10 minutes (230 ° C, 21.18N)
Density (ISO1183): 1.01 g / cm ³
Melting point (ISO11357): 159 ° C
Flexural modulus (ISO178): 186 MPa

[Component (B)]
(B-1): Olefin-based block copolymer XLT8677 manufactured by Dow Chemical Co., Ltd. (having a crystalline polymer block made of ethylene and a block of ethylene 1-octene copolymer)
Crystal melting peak temperature: 119 ° C
Crystal melting heat: 37 J / g
MFR (ASTM D1238): 1.3 g / 10 minutes (190 ° C, 21.18N)
Density (ISO1133): 0.87 g · cm ³
Glass transition temperature (DSC method): -67 ° C

[Component (C)]
(C-1): Modified ethylene / α-olefin copolymer Ethylene / 1-octene copolymer and maleic anhydride are melt-reacted by a twin-screw extruder Density (ISO1133): 0.88 g / cm ³
MFR (ISO1183): 10 g / 10 minutes (190 ° C, 21.18N)
Glass transition temperature (DSC method): -50 ° C
Maleic acid denaturation rate: 1.1% by mass

[Component (D)]
(D-1): Polypropylene block copolymer (obtained by polymerizing a propylene homopolymer in the first step and then polymerizing an ethylene / propylene copolymer in the second step).
Content of propylene unit: 91% by mass
Ethylene unit content: 9% by mass
Density (ISO1133): 0.90 g / cm ³
MFR (ISO1183): 30 g / 10 minutes (230 ° C, load 21.18 N)
Flexural modulus (ISO178): 1350 MPa
Melting point (ISO11357): 165 ° C
Crystal melting peak temperature: 165 ° C
Crystal melting heat: 105 J / g

[Component (E)]
(E-1): Ethylene 1-octene copolymer rubber Dow Chemical Co., Ltd. Engage (registered trademark) 8150
Density (ISO1133): 0.86 g / cm ³
MFR (ISO1183): 0.5 g / 10 minutes (190 ° C, 21.18N)
Glass transition temperature (DSC method): -52 ° C
Crystal melting peak temperature: 60 ° C
Crystal melting heat: 0 J / g

<Evaluation method>
1) Low temperature impact resistance (Charpy impact test fracture 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 shown below 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

2) High temperature strength (tensile strength 85 ° C)
Using the obtained thermoplastic elastomer composition, an in-line screw type injection molding machine (“IS130” manufactured by Toshiba Machine Co., Ltd.) is used for a tensile test at an injection pressure of 50 MPa, a cylinder temperature of 220 ° C., and a mold temperature of 40 ° C. After molding the test piece (thickness 2 mm × width 120 mm × length 80 mm sheet), the ISO37-1A dumbbell was punched out. With reference to ISO37-1A, the tensile fracture strength (unit: MPa) of this punched test piece was measured at a tensile speed of 500 mm / min and an atmosphere of 85 ° C. It was evaluated that the larger the value of tensile fracture strength, the better the high temperature strength.

3) Flexibility (flexural modulus)
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. Molded into a test piece (thickness 4 mm x width 10 mm x length 80 mm), and the flexural modulus was measured for this test piece at a span spacing of 64 mm and a bending speed of 2 mm / min in accordance with ISO178. did.

<Example / Comparative example>
[Example 1]
Antioxidant for 100 parts by mass of (a-1), 43 parts by mass of (b-1), and 100 parts by mass of the components (A) and (B) (trade name: Irganox (registered trademark) manufactured by BASF Japan). 1010) 0.1 parts by mass and 1.5 parts by mass of black pigment (carbon concentration 40% by mass) were blended with a Henchel mixer for 1 minute, and a twin-screw extruder in the same direction (Kobe Steel "TEX30α", L / D. = 45, number of cylinder blocks: 13), and the mixture was charged at a rate of 20 kg / h, heated in the range of 180 to 210 ° C. and melt-kneaded to produce pellets of a 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 to 4 and Comparative Examples 1 to 3]
Pellets of the thermoplastic elastomer composition were obtained in the same manner as in Example 1 except that the formulations shown in Table 1 were used (however, the antioxidant was added to a total of 100 parts by mass of the components (A) to (E). 0.1 part by mass and 1.5 parts by mass of the black pigment were blended. The description of these blending amounts was omitted in Table 1). The pellets of the obtained thermoplastic elastomer composition were evaluated in 1) to 3) above in the same manner as in Example 1. The evaluation results are shown in Table-1.

[Discussion]
From Table 1, it can be seen that all of Examples 1 to 4 corresponding to the present invention are excellent in flexibility, low temperature impact resistance, and high temperature strength.
On the other hand, Comparative Example 1 does not contain the component (B) and the component (C), and therefore has poor low temperature impact resistance. In Comparative Example 2, since the component (B) was not used and the component (E) of the ethylene / 1-octene copolymer rubber was used instead, the low temperature impact resistance was poor. In Comparative Example 3, since the component (A) was not used and the polypropylene block copolymer component (D) was used instead, it can be seen that the high temperature strength and flexibility are insufficient.

The thermoplastic elastomer composition of the present invention is excellent in flexibility, low temperature impact resistance, high temperature strength and the like, and can be suitably used for various applications. The thermoplastic elastomer composition of the present invention includes, for example, automobile interior parts such as airbag storage covers, instrument panels, center panels, center console boxes, door trims, pillars, assist grips, and steering wheels, and automobile exterior parts such as mudguards and chromets. It is useful as home appliances, building materials, furniture, etc. Among these, the thermoplastic air stomacher composition of the present invention is particularly useful as an airbag storage cover, and among these airbag storage covers, for example, when a high-speed moving body such as an automobile collides, the impact or deformation thereof occurs. It is suitable as an airbag storage cover for an airbag system that operates by sensing and protects occupants by expanding and deploying.

Claims (8)

A thermoplastic elastomer composition containing the following component (A) and component (B).
Component (A): Polyamide-based thermoplastic elastomer Component (B): A polymer block made of ethylene having a crystal melting peak at 10 to 125 ° C. and having a heat of crystal melting of 20 to 60 J / g, and ethylene. Olefin block copolymer containing α-olefin copolymer block The thermoplastic elastomer composition according to claim 1, wherein the α-olefin has 4 to 8 carbon atoms in the ethylene / α-olefin copolymer block of the component (B). The thermoplastic elastomer composition according to claim 1 or 2, wherein the component (B) is an olefin-based block copolymer containing a polymer block made of ethylene and an ethylene / 1-octene copolymer block. The thermoplastic elastomer composition according to any one of claims 1 to 3, further containing the following component (C).
Component (C): Acid-modified ethylene / α-olefin copolymer The thermoplastic elastomer composition according to claim 4, wherein the α-olefin of the component (C) has 4 to 8 carbon atoms. The thermoplastic elastomer according to any one of claims 1 to 5, which contains 10 to 150 parts by mass of the component (B) and 0 to 100 parts by mass of the component (C) with respect to 100 parts by mass of the component (A). Composition. A molded product obtained by injection molding the thermoplastic elastomer composition according to any one of claims 1 to 6. An airbag storage cover comprising the thermoplastic elastomer composition according to any one of claims 1 to 6.