JPH1067890A - Thermoplastic elastomer composition for air bag cover - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compsn. which is suitable for producing an air bag cover which is not broken at other parts than intended parts to be torn when expanded, has a good surface appearance when produced, and is excellent in scratch resistance and fusion by welding. SOLUTION: This compsn. contains 10-40wt.% hydrogenated styrene- conjugated diene block copolymer (A), 10-40wt.% ethylene-α-olefin copolymer rubber (B) having a Mooney viscosity (ML1+4 , 100 deg.C) lower than 80, 5-30wt.% ethylene-α-olefin copolymer rubber (C) having a Mooney viscosity (ML1+4 , 100 deg.C) of 80 or higher, and 30-70wt.% olefin resin (D), the sum of amts. of ingredients A, B, and C being 70-30wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoplastic resin for a cover for accommodating an inflating and deploying airbag which operates by detecting the impact or deformation of a high-speed moving body such as an automobile in the event of a collision or the like. It relates to elastomers.

[0002]

2. Description of the Related Art Conventionally, when an airbag is operated (inflated), a cover containing the airbag is crushed when the airbag is operated (inflated), and fragments of the cover scatter and hit the occupant's face or eyes. Because of the danger of injury, the conventional device generally has a reinforcing material (net or the like) inserted for the purpose of preventing fragments from scattering. However, in order to manufacture an airbag storage cover containing such a net-like insert, a number of complicated manufacturing steps for inserting a net-like reinforcing material were required. So, as an attempt to solve these,
JP-A-1-202550, JP-A-2-117136
No. 2, JP-A-2-200946 proposes a two-color injection molded product comprising a skin layer using a thermoplastic elastomer having a soft feeling and a core layer using a hard thermoplastic resin having shape retention. Was done.

[0003] As a result, the necessity of using a net-like reinforcing material has been eliminated, which has the effect of reducing the number of manufacturing steps. However, a dedicated two-color injection molding machine is required, and two metal molds are required. The problem that the molding cycle is long from the use of the mold remains. Therefore, for the purpose of solving this, JP-A-2-171364, JP-A-4-151348, JP-A-4-314648,
A method of forming a single-layer injection-molded product as described in JP-A-5-38996 has been proposed.

[0004] With these proposals, it has become possible to mold an airbag storage cover in an airbag apparatus by using an ordinary injection molding machine, and the molding cycle has been shortened. However, when the airbag storage cover is inflated and deployed, a low-flow, high-impact material with a large amount of rubber components is used in order to prevent the fragments other than the predetermined cleavage portion from breaking and scattering fragments. The cover obtained by injection molding has a poor surface appearance and has a problem that the surface is easily scratched due to the softness of the rubber component, so it is common to provide a decorative protective layer, that is, a coating film. However, in order to solve this problem, a method using a composition having a specific blending ratio of a styrene-based thermoplastic elastomer, an ethylene-propylene random copolymer, and polypropylene as a material, as described in JP-A-8-2363. Was proposed.

[0005]

Therefore, according to these proposals, it is possible to form the cover for storing the airbag in the airbag apparatus by using an ordinary injection molding machine, and to shorten the cycle. It is no longer necessary to apply a film. However, since the airbag storage cover is provided with a predetermined cleavage portion having a thickness of 0.5 mm to 1.5 mm so as to be easily broken during inflation and deployment, the predetermined cleavage portion becomes an obstacle in the mold during injection molding. By the merged fusion part of the different flow resins, that is,
Welding occurs. The weld part is low in strength compared to the general part because it has a concave shape with a width and depth of several μ, and when it is exposed to a high heat part exposed to direct sunlight, such as the steering wheel part and instrument panel part in the vehicle. The width of the concave shape is widened, which causes a problem in appearance, and in some cases, there is a serious problem that the concave portion is broken.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventor has found that by using a thermoplastic elastomer containing a specific component in a specific ratio, a predetermined cleavage portion can be formed at the time of expansion and deployment. Without breaking without
Further, the present inventors have found that an airbag storage cover having a good surface appearance at the time of molding, and excellent in scratch resistance and weld fusion property can be obtained, thereby completing the present invention. That is, the thermoplastic elastomer composition for an airbag storage cover of the present invention contains the following specific components at specific ratios.

[0007] Specific essential components constituting the thermoplastic elastomer composition of the present invention include the following components. Component (A): Hydrogenated product of styrene / conjugated diene block copolymer Component (B): Mooney viscosity (ML _{1 + 4} 100 ° C.) is 80
Ethylene / α-olefin copolymer rubber having a Mooney viscosity (ML _{1 + 4} 100 ° C.) of less than 80
The above-mentioned ethylene / α-olefin copolymer rubber Component (D): olefin resin and the composition of the present invention contain these components at the following specific ratios. Component (A) is 10
-40% by weight, 10-40% by weight of component (B), 5-30% by weight of component (C) and components (A), (B)
And the total amount of (C) is 30 to 70% by weight, and the component (D) is 70 to 30% by weight.

[0008] The composition of the present invention comprises Jls-K
Flexural modulus according to 7203: 1,000-6,000k
It exhibits physical properties of g / cm ² and is not coated.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION

[I] Thermoplastic Elastomer Composition for Airbag Storage Cover (1) Constituent Material The constituent materials of the thermoplastic elastomer composition for an airbag storage cover of the present invention include the following component (A)
It is important to use the specific components of (D) to (D).

Component (A): Hydrogenated product of styrene / conjugated diene block copolymer The hydrogenated product of styrene / conjugated diene block copolymer which can be used in the present invention is a block copolymer of styrene and conjugated diene. It is obtained by hydrogenating a polymer, where the preferred conjugated diene is butadiene, isoprene or a mixture thereof. For example, styrene
Styrene / ethylene / butylene / styrene copolymer (SE) which is a hydrogenated product of a butadiene block copolymer (hereinafter sometimes simply referred to as “hydrogenated S-B-S”)
Styrene-ethylene-propylene-styrene copolymer (BS) or a hydrogenated product of a styrene-isoprene block copolymer (hereinafter may be simply abbreviated as "hydrogenated S-I-I-S"). SEPS) and a hydrogenated product of a styrene-butadiene-isoprene block copolymer (hereinafter sometimes simply referred to as “hydrogenated S-BI-S”).

The hydrogenated styrene / conjugated diene block copolymer has a styrene content of 5 to 50% by weight, preferably 8 to 45% by weight, particularly preferably 10 to 45% by weight.
40% by weight, and the 1,2 microstructure is less than 60%, preferably less than 45%,
Further, those having a hydrogenation rate of 95% or more are preferable from the viewpoint of weather resistance. When the conjugated diene is a mixture of isoprene and butadiene, the weight ratio of the mixture (isoprene / butadiene) is 99/1 to 1/99, preferably 90/10.
30/70, particularly preferably 80/20 to 40/60. The weight average molecular weight of the hydrogenated styrene / conjugated diene block copolymer of component (A) is preferably from 50,000 to 150,000, and those less than 50,000 are rubber elasticity, mechanical strength, and scratch resistance. If it exceeds 150,000, the moldability and the surface appearance are inferior. Those having a styrene content of less than 10% by weight are inferior in rubber elasticity and strength, and those having a styrene content of more than 50% by weight are inferior in flexibility. In addition, the above 1,
Those having more than 60% of 21-microstructure are inferior in flexibility.

As a method for producing a hydrogenated product of these styrene / conjugated diene block copolymers, for example, a method described in Japanese Patent Publication No. 23798/1973 is disclosed. A conjugated diene block copolymer is synthesized, and then, for example,
No. 2-8704, JP-B-43-6636, JP-A-59-1984
JP-A-133203, JP-A-60-79005, and a method in which hydrogenation is performed in an inert solvent in the presence of a hydrogenation catalyst. Further, hydrogenated S-BI-S is disclosed in, for example, Japanese Patent Application Laid-Open No. 3-18811.
It was synthesized by the method described in Japanese Patent Publication No.

Component (B): Mooney viscosity (ML _{1 + 4} 10
0 ° C.) Ethylene / α-olefin copolymer rubber of less than 80 Mooney viscosity (ML
The ethylene / α-olefin copolymer rubber having a temperature of ( _{1 + 4} 100 ° C.) less than 80 is a low crystalline or amorphous polymer having a crystallinity of 30% or less as measured by X-ray diffraction. Examples include ethylene / propylene copolymer rubber (EP
M), ethylene-butene-1 copolymer rubber (EBM), ethylene-octene copolymer rubber (EOM), and non-conjugated dienes such as 51-ethylidene norbornene, 5-methylnorbornene, 5-vinylnorbornene, dicyclopentadiene, etc. And ethylene-propylene-non-conjugated diene copolymer rubber (EPDM). The production method and shape of these ethylene / α-olefin copolymer rubbers are not particularly limited. Further, they may be subjected to a heat treatment in the presence of an organic peroxide and crosslinked mainly by radicals. These ethylene / α-olefin copolymer rubbers have an ethylene content of 50 to 90% by weight,
Preferably 55 to 85% by weight, Mooney viscosity (ML _{1 + 4}
(100 ° C.) is preferably less than 1 to 80, preferably 10 to 75. The above ethylene and α
If the Mooney viscosity of the olefin copolymer rubber is less than the above range, rubber elasticity and mechanical strength tend to be inferior, and if the Mooney viscosity exceeds the above range, moldability and surface appearance tend to be inferior.

Component (C): Mooney viscosity (ML _{1 + 4} 10
(0 ° C.) 80 or more ethylene / α-olefin-based copolymer rubber The ethylene / α-olefin-based copolymer rubber that can be used in the present invention has a crystallinity of 30% or less as measured by an X-ray diffraction method. It is a low crystalline or amorphous polymer. Examples include ethylene-propylene copolymer rubber (EPM) and ethylene-butene-1 copolymer rubber (EB
M), ethylene-octene (EOM), ethylene-propylene / non-conjugated diene copolymer rubber (EPDM) using 5-1 ethylidene norbornene, 5-methylnorbornene, 5-vinyl norbornene, dicyclopentadiene, etc. as a non-conjugated diene ). The production method and shape of these ethylene / α-olefin copolymer rubbers are not particularly limited. Further, they may be subjected to a heat treatment in the presence of an organic peroxide and crosslinked mainly by radicals. These ethylene / α-olefin copolymer rubbers have an ethylene content of 50 to 90% by weight,
Preferably 55 to 85% by weight, Mooney viscosity (ML _{1 + 4}
(100 ° C.) is preferably 80 to 400, preferably 85 to 350. Further, these copolymer rubbers may be oil-extended copolymer rubbers containing a softening agent for hydrocarbon rubber as a softening and processability imparting agent. Those having a Mooney viscosity of the ethylene / α-olefin-based copolymer rubber less than the above range tend to be inferior in weld fusion property, and those having a Mooney viscosity exceeding the above range tend to be inferior in moldability and surface appearance. .

Component (D): Olefin resin The olefin resin of the component (D) used in the present invention has a crystallinity of at least 35%, preferably 40 to 80%, as measured by X-ray diffraction. It is an olefin resin. Examples include propylene-based resins, ethylene-based resins, crystalline polybutene-1 resins, ethylene-vinyl acetate copolymers, ethylene (meth) acrylic acid copolymers, ethylene (meth) acrylate copolymers, and the like. Ethylene resins can be mentioned. Among these olefin resins, it is preferable to use a propylene resin, and particularly preferable to use a melt flow rate (Jls-K).
6758, 230 ° C, 2.16 kg load) 0.01 to
100 g / 10 min, preferably 0.05 to 80 g / 10
Min, particularly preferably 0.1 to 60 g / 10 min, ethylene content of 0 to 15% by weight, preferably 0 to 13% by weight,
Particularly preferred is a propylene-based resin in the range of 0 to 10% by weight. Here, the ethylene content is a value measured by an infrared spectrum analysis method or the like.

The propylene resin is a propylene homopolymer or a copolymer resin containing propylene as a main component, and specific examples thereof include a propylene / ethylene random copolymer and a propylene / ethylene block copolymer. be able to. When the melt flow rate is less than the above range, the injection moldability is deteriorated, and the appearance of the obtained injection molded body, particularly, the occurrence of flow marks tends to be remarkable. If the melt flow rate exceeds the above range, the material strength tends to decrease.

Examples of the ethylene resin include a low-density polyethylene resin (branched ethylene polymer) obtained by a high-pressure method and a high-density polyethylene which is an ethylene homopolymer obtained by a medium-low pressure method. Examples include resins (linear ethylene copolymers) and low-, medium-, and high-density polyethylene resins which are copolymers of ethylene and α-olefin obtained by a medium-to-low pressure method. Examples of the straight-chain α-olefin that is the comonomer include butene-1, pentene-1, hexene-1, 4-methylpentene-1, octene-1, and the like. These may be used in combination of two or more. good. As specific production conditions, generally, a pressure of 5 to 2,500 kg /
A method of copolymerizing ethylene and an α-olefin using a catalyst such as a Ziegler type catalyst, a vanadium type catalyst or a Kaminski type catalyst under the conditions of cm ² and a temperature of 50 to 300 ° C. is employed. Specifically, a method described in JP-B-56-18132 is known.

As the crystalline butene-1 resin, other comonomers such as ethylene and propylene may be used in a small amount (for example,
20% by weight or less) A crystalline resin synthesized from a butene-1 monomer which may have a density of 0.890 to
0.9259 / cm ^3, preferably from 0.893 to 0.9
239 / cm ³ , particularly preferably 0.900 to 0.92
09 / cm ³ , melt flow rate (MFR: 190
° C, 2.16 kg load) 0.01 to 1,000 g / 1
0 min, preferably 0.05 to 500 g / 10 min, particularly preferably 0.1 to 100 g / 10 min, crystallinity of 30%
Above, preferably 30-70%, weight average molecular weight of 1
0000-3,000,000, preferably 50,000
Those having a size of from 00 to 2,500,000 are preferably used.

In the constituent materials of the composition of the present invention, in addition to the above essential components, optional components can be added according to various purposes within a range that does not significantly impair the effects of the present invention. In particular, since the airbag storage cover of the present invention is used without painting, it is necessary to unify the color with other interior parts, so the coloring agent and the antioxidant for preventing deterioration and discoloration, the heat stability, Agents, light stabilizers and UV absorbers are important components.

Further, the above-mentioned constituent materials may be those obtained by blending the following crosslinking agent or crosslinking assistant and dynamically heat-treating to partially crosslink. As a crosslinking agent for partially crosslinking, an organic peroxide is preferable, and 2,5-dimethyl-
2,5-di (t-butylperoxy) hexane, 2,5
-Dimethyl-2,5-di (t-butylperoxy) hexine-3,1,3-bis (t-butylperoxyisopropyl) benzene, 1,11-di (t-butylperoxy) 3,5,5 Examples include monotrimethylcyclohexane, 2,5-dimethyl-2,5-di (peroxybenzoyl) hexine-3, and dicumyl peroxide. Examples of a crosslinking assistant at the time of partial crosslinking with an organic peroxide include N, N'-m-phenylenebismaleimide, toluylenebismaleimide, P-quinonedioxime, nitrobenzene, diphenylguanidine, trimethylolpropane, divinylbenzene, and ethylene. There are functional compounds such as glycol dimethacrylate, polyethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, allyl methacrylate.

Further optional components include softeners for various hydrocarbon rubbers, various inorganic fillers, various thermoplastic resins, various elastomers, neutralizing agents, lubricants, cloud-proofing agents, anti-blocking agents, slip agents, Various additives such as a flame retardant, a dispersant, an antistatic agent, a conductivity imparting agent, a metal deactivator, a molecular weight regulator, a bactericide, and a fluorescent brightener can be exemplified.

The softening agent for hydrocarbon rubber has a weight average molecular weight of 300 to 2,000, preferably 500
~ 1,500 are preferred. Generally, such a softening agent for hydrocarbon rubber is a mixture of an aromatic ring, a naphthene ring and a paraffin ring in which the number of carbon atoms in the paraffin chain accounts for 50% or more of the total carbon. It is called paraffinic oil and has a naphthene ring carbon number of 30.
Those having a carbon number of up to 45% are called naphthenic oils, and those having an aromatic carbon number of more than 30% are called aromatic oils. Among them, it is preferable to use paraffin oil from the viewpoint of weather resistance. As the paraffinic oil, the kinematic viscosity at 40 ° C is 20 to 800 cst, preferably 50 to 600 cst, and the pour point is 0 to 140 ° C.
Preferably from 0 to 130 ° C. and a flash point (COC) of 2
Oils at 00-400 ° C, preferably 250-350 ° C, are suitably used. The softening agent for hydrocarbon rubber is mainly blended in order to adjust the hardness and the melt fluidity during molding.

As the inorganic filler, talc, mica,
Glass fiber, whisker, carbon fiber, calcium carbonate,
Glass balloons and the like can be mentioned.

Examples of the thermoplastic resin include styrene resins such as polystyrene, acrylonitrile / styrene copolymer, and acrylonitrile / butadiene / styrene copolymer.
Polyphenylene ether resins, polyamide resins such as nylon 6 and nylon 66, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polyoxymethylene resins such as polyoxymethylene homopolymer and polyoxymethylene copolymer, and polymethyl methacrylate Resins and the like can be mentioned.

(2) Compounding ratio The compounding ratio of each component constituting the thermoplastic elastomer composition for an airbag storage cover of the present invention is as follows: Component (A) hydrogenated product of styrene / conjugated diene block copolymer
40% by weight, component (B) Mooney viscosity (ML _{1 + 4} 100
C) 10 to 40% by weight of an ethylene / α-olefin copolymer rubber of less than 80, component (C) Mooney viscosity (ML _{1 + 4}
100 ° C.) 5 to 30% by weight of an ethylene / α-olefin-based copolymer rubber of 80 or more, and the total amount of components (A), (B) and (C) is 30 to 70% by weight; D) The olefin-based resin is 30 to 70% by weight, and the following problems occur when each component is out of the above range. That is, if the blending ratio of the hydrogenated product of the component (A) styrene / conjugated diene block copolymer is less than 10% by weight, the scratch resistance is poor, and if it exceeds 40% by weight, the developability at low temperature is poor. Inferior. Component (B) An ethylene / α-olefin copolymer rubber having a Mooney viscosity (ML _{1 + 4} 100 ° C.) of less than 80 and a compounding ratio of less than 10% by weight is inferior in low-temperature expandability and 40% by weight. Those exceeding are inferior in weldability. Component (C) If the blending ratio of an ethylene / α-olefin copolymer rubber having a Mooney viscosity (ML _{1 + 4} 100 ° C.) of 80 or more is less than 5% by weight, the weldability is inferior, and more than 30% by weight. Is inferior in deployability at low temperatures. If the proportion of the component (D) olefin-based resin is less than 30% by weight,
Weldability and expandability at high temperatures are inferior, and those exceeding 70% by weight are inferior in expandability at low temperatures.

[II] Molding The average thickness of the airbag storage cover using the thermoplastic elastomer composition of the present invention is 1 to 5 mm. However,
It is necessary to provide a fragile structure to easily cleave when the airbag device is activated.
Preferably, it is appropriate to design the thickness to be 50% or less of the average thickness. As a method of manufacturing the airbag storage cover, a normal injection molding method, or, if necessary, a gas injection molding method, an injection compression molding method, various molding methods such as a short shot foam molding method can be used, The injection molding conditions are generally a molding temperature of 100 to 300 ° C., preferably 150 to 280 ° C., and 50 to 1,000 k.
g / cm ^2, preferably injection pressure of 100~800kg / cm ^2, 20~80 ℃, can preferably be adopted a mold temperature of 20 to 60 ° C..

[III] Applications The cover for airbag storage obtained in this manner operates and senses the impact or deformation of a high-speed moving body such as an automobile in the event of a collision or the like, and is inflated and deployed. This is a cover for storing the airbag. Specifically, the cover is an airbag storage cover used for a driver's seat, a passenger seat, a rear seat, and the like of an automobile.

[0028]

EXAMPLES In order to describe the thermoplastic elastomer composition for an airbag storage cover of the present invention in more detail, experimental examples will be specifically described below. [I] Raw materials In the examples and comparative examples, the following raw materials were used.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

[Table 3]

[0032]

[Table 4]

[II] Evaluation method Various evaluations in these examples and comparative examples were performed by the following methods. However, the measurement samples in (1) and (2) were obtained by using an in-line screw type injection molding machine (injection molding machine manufactured by Nippon Steel Works Co., Ltd .; N100B) at an injection pressure of 500 kg / cm ² , an injection temperature of 220 ° C.
At a mold temperature of 40 ° C, a thickness of 4 mm and a width of 1 for bending elastic modulus
0mm, length 90mm, thickness 4mm, width 10mm, length 80mm with notch for Izod impact strength
A piece molded into a piece was used. Further, the measurement sample in (3) was a flat piece having a 3 mm-thick weld fusion portion shown in FIG. 1 using the same injection molding machine and conditions as the measurement sample in (1), and FIG. A flat piece without a weld fusion part shown in FIG. Further, as the measurement sample in (4), the flat piece of FIG. 2 which is the measurement sample in (3) was used. The measurement samples in (5) and (6) were measured at 220 ° C. using an in-line screw type injection molding machine (Injection molding machine manufactured by Toshiba Machine Co., Ltd .; IS220).
The evaluation was performed using the airbag storage cover molded at the temperature shown in FIGS. 3, 4 and 5.

(1) Flexural modulus (kg / cm ² ) Measured at a span of 64 mm and a bending speed of 2 mm / min in accordance with JIS-1K-17203. (2) Izod impact strength (kg / cm / cm) Measured at 140 ° C using a notched specimen in accordance with JIS-K-7110. If the test piece did not break after the measurement, a cover for storing an airbag was molded and a low-temperature deployment test was performed at 140 ° C. If the test piece was broken and the test piece broke, the low-temperature deployment test was not performed. (3) Weld strength The breaking strength measured at a tensile speed of 200 mm / min by punching out a JLS-1K-6301,3 dumbbell from a predetermined position (FIG. 2) of a flat plate having a weld fusion part in FIG. From the flat plate having no weld-welded portion, the one having less than 50% of the breaking strength measured with a dumbbell having the same shape as the above was regarded as defective, and the one having 50% or more as good. (4) Scratchability A flat piece was scratched with a tip of 25R and a cutting edge having a shear angle of 22 ° at a rotation speed of 0.5 rpm (Taber-type scratch tester manufactured by Toyo Seiki Seisaku-sho, Ltd.), and formed on the surface of the piece. Scars are observed with a 7x magnifier and naked eye, and those that are markedly scratched and conspicuous are defective,
In addition, those with less conspicuousness were evaluated as good. (5) Weld appearance After the formed airbag storage cover is heat-treated for 48 hours in a hot-air dryer at 110 ° C., the weld formed by the fusion of the molten resin is visually evaluated with the cover before the heat treatment, and after the heat treatment. Those with remarkable welds were evaluated as poor, and those without such welds were evaluated as good. (6) Deployment Test After the airbag device set in which the airbag device and the storage cover were assembled was allowed to stand for 1 hour in a thermostat at a deployment test temperature (140 ° C., 80 ° C.), a deployment test was performed.
When the cover is broken and scattered, when it is broken into a sharp shape and normal deployment cannot be performed, or when the cover is torn off from the mounting portion, it is regarded as defective, and the normal deployment is performed without the above-described trouble. Was good.

[III] Experimental Examples Examples 1 to 3 and Comparative Examples 1 to 10 The raw materials shown in Tables 1 to 4 were used and blended in the composition (parts by weight) shown in Tables 5 to 6. 0.1 part by weight of a phenolic antioxidant (trade name "Irganox 1010") was added to 100 parts by weight of the total amount of the composition shown in No. 6, and a biaxial with L / D = 33 and a cylinder diameter of 45 mm was added. The mixture was melted and kneaded at an extruder (PCM45 manufactured by Ikegai Seisakusho) at a temperature of 200 ° C. to obtain pellets. The pellets were injection molded as described above and evaluated as described above. Tables 5 and 6 show the results of these evaluations.

[0036]

[Table 5]

[0037]

[Table 6]

[0038]

[Table 7]

[0039]

The thermoplastic elastomer composition for an airbag storage cover of the present invention can be molded using a usual injection molding machine, and can be scratched and weld-fused without a coating film. As a storage cover with excellent wearability can be obtained, it is used as a cover material to store airbags that expand and deploy by sensing the impact and deformation of a high-speed moving object such as automatic grass in the event of a collision. It is useful.

[Brief description of the drawings]

FIG. 1 is a schematic view of a flat plate-shaped piece with a weld for evaluation of weld strength.

FIG. 2 is a schematic view of a flat piece without weld for evaluating weld strength.

FIG. 3 is a perspective view of the airbag storage cover of the embodiment.

FIG. 4 is a cross-sectional view of the airbag storage cover taken along line AA of FIG. 3;

FIG. 5 is a cross-sectional view of the airbag storage cover of FIG. 3 taken along line B-B.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Airbag storage cover 1a Flat plate part 1b Rib 2 Fragile part 3 Mounting hole

Claims (1)

[Claims] 1. Component (A): a hydrogenated product of a styrene / conjugated diene block copolymer, and component (B): an ethylene / α-olefin copolymer rubber having a Mooney viscosity (ML _{1 + 4} 100 ° C.) of less than 80. Component (C): ethylene / α-olefin copolymer rubber having a Mooney viscosity (ML _{1 + 4} 100 ° C.) of 80 or more, and Component (D): containing an olefin resin, wherein component (A) is 10 to 40. % By weight, component (B) 10-4
0% by weight, the component (C) is 5 to 30% by weight, and the total amount of the components (A), (B) and (C) is 30 to 70% by weight.
Wherein the component (D) is 70 to 30% by weight of the thermoplastic elastomer composition for an airbag storage cover.