JP2977661B2 - Airbag storage case - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is applied to an automobile or the like,
The present invention relates to a case for storing an airbag that inflates at a predetermined time immediately before a collision or the like.

[0002]

2. Description of the Related Art Development of an air bag system has been promoted as one of safety measures for a vehicle, and some air bag systems have been recently mounted. This airbag system basically consists of a sensor that senses abnormalities, a gas generator that generates gas based on signals from the sensor, an airbag that inflates with jetted gas to protect occupants, and a small airbag during normal times. It consists of a storage bag that is folded and stored.

[0003] The air bag storage case must have excellent mechanical and thermal characteristics like other interior parts, but must be easily broken by the force when the bag is inflated. In order to prevent occupants from being injured due to the scattering of air, generally, it is made of urethane foam in which a net made of polyamide fiber is inserted.

[0004] A non-reinforcing portion (line shape) without a net must be provided so that the case can be easily broken by the smooth deployment of the airbag, which complicates the molding operation and lowers productivity. have. In addition, since the net is included, the appearance is inferior due to waving or pinholes on the surface.

[0005] Therefore, by using a soft thermoplastic polymer (styrene-based elastomer) as a skin layer and an olefin-based rubber as a core layer, a polyamide net insert is not required, and a new proposal has been made with improved productivity. (Japanese Unexamined Patent Publication (Kokai) Nos. 1-2202550 and 2-17).
Nos. 1362 and 2-220946). However, the tear line for unfolding and rupture is a thin weak portion for facilitating rupture. Since the airbag storage case also plays a role as an interior component, poor appearance significantly reduces commercial value.

[0006] Further, a case in which a conventional urethane foam is used as the skin layer and a styrene or olefin elastomer is used for the core layer has been studied, but the adhesion between the skin layer and the core layer is not sufficient. Poor deployment performance. In addition, the risk to the occupant due to the scattering of the debris is increased.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in view of the above-mentioned problems, and as a result, have found that urethane foam is used as a skin layer and a specific composition is used as a core layer or a backside layer. The case is found to be significantly superior in productivity, appearance, deployability and danger prevention compared to the conventionally used cases and conventionally proposed cases,
The present invention has been reached.

That is, the present invention provides a skin layer made of urethane foam, 10 to 90% by weight of a rubber-reinforced styrene resin based on a rubbery polymer having a glass transition temperature of minus 40 ° C. or less, and a Crashberg temperature of minus 10. 1
Productivity, appearance, deployability, characterized by being formed from a core layer or a back layer made of a resin composition comprising 90 to 10% by weight of a thermoplastic urethane elastomer having a temperature of 0 ° C. or less.
An object of the present invention is to provide an airbag storage case excellent in danger prevention. Hereinafter, the airbag storage case of the present invention will be described in detail.

The urethane foam constituting the skin layer is not particularly limited in its raw material, production method and the like, and known urethane foam can be used. Generally, it is obtained by reacting a polyol, a hydroxyl group-containing short-chain compound and diisocyanate in the presence of a blowing agent and a catalyst.

The polyol is a polyether polyol having a molecular weight of 2,000 to 8,000 having 2 to 3 hydroxyl groups, and the hydroxyl group-containing short-chain compound is 1,4-butane having 2 to 3 hydroxyl groups. Examples include diol, ethylene glycol, diethylene glycol, glycerin, and triethanolamine.

Further, examples of the diisocyanate include diphenylmethane diisocyanate, tolylene diisocyanate, naphthalene diisocyanate, and polyisocyanates obtained by adding diisocyanate to a polyhydric alcohol.

Water (reaction with isocyanate to generate carbon dioxide), Freon (CFC-11, H
CFC-22), methylene dichloride, pentane,
Air and the like can be mentioned. Examples of the catalyst include amines represented by triethylenediamine, organic tin compounds (such as dibutyltin dilaurate), and the like.

If necessary, a foam stabilizer, a flame retardant, a light stabilizer, a pigment and the like can be added.

Examples of the method for producing urethane foam include a one-shot method and a prepolymer method. From the viewpoint of productivity, the RIM process (reaction injection molding) is preferred.

The rubber-reinforced styrenic resin constituting the core layer or the back layer is a thermoplastic rubber-reinforced styrenic resin based on a rubbery polymer having a glass transition temperature of -40 ° C. or lower. A graft polymer obtained by polymerizing an aromatic vinyl compound or an aromatic vinyl compound and another copolymerizable vinyl compound in the presence of a copolymer, or an aromatic vinyl compound and another graft polymer to such a graft polymer. It is a resin containing a copolymer obtained by polymerizing a copolymerizable vinyl compound.

The glass transition temperature of the rubbery polymer is determined by a differential calorimeter (heating rate: 20 ° C./min).

By appropriately changing the composition and composition ratio of the rubbery polymer, the glass transition temperature can be lowered by minus 40.
It is possible to obtain a rubbery polymer having a temperature of not more than ℃.

When the glass transition temperature of the rubber-like polymer is higher than -40 ° C., the low-temperature impact property and the expandability as a storage case are inferior.

Examples of the rubbery polymer having a glass transition temperature of -40 ° C. or lower include various butadiene rubbers obtained by copolymerizing (i) polybutadiene, (ii) other vinyl compounds such as styrene, acrylonitrile, and methyl methacrylate with butadiene. , (Iii) an ethylene-propylene rubber, (iv) an ethylene-propylene-nonconjugated diene rubber into which a non-conjugated diene such as ethylidene norbornene or dicyclopentadiene is introduced, and one or more kinds thereof can be used. .

Examples of the aromatic vinyl compound constituting the rubber-reinforced styrene resin include styrene, α-methylstyrene, p-methylstyrene, bromostyrene and the like, and one or more kinds can be used. Particularly, styrene is preferred.

Other copolymerizable vinyl compounds include:
(i) acrylonitrile, vinyl cyanide compounds such as methacrylonitrile, (ii) unsaturated carboxylic acid alkyl ester compounds such as methyl acrylate, ethyl acrylate, methyl methacrylate, hydroxyethyl acrylate, glycidyl methacrylate, (iii) acrylic acid And unsaturated carboxylic acid compounds such as methacrylic acid, maleic acid and maleic anhydride, and (iv) maleimide compounds such as maleimide, methylmaleimide and N-phenylmaleimide. One or more of them can be used. .

The composition ratio of the rubbery polymer, the aromatic vinyl compound and the other copolymerizable vinyl compound constituting the rubber-reinforced styrene resin is not particularly limited, but is preferably 10 to 80% by weight of the rubbery polymer. %, 90 to 10% by weight of an aromatic vinyl compound and 0 to 80% by weight of another copolymerizable vinyl compound.

The method for producing the rubber-reinforced styrenic resin (graft polymer or a mixture of the graft polymer and the copolymer) is not particularly limited, and may be any of known emulsion polymerization, bulk polymerization,
Solution polymerization, suspension polymerization and the like can be used.

[0024] The thermoplastic polyurethane elastomer is
(i) a molecular weight of about 500 having two or more hydroxyl groups
-2000 compounds, (ii) a compound having at least two active hydrogen groups having a molecular weight of about 500 or less capable of reacting with an isocyanate group, and (iii) an organic diisocyanate,
An elastomer obtained by reacting a pair (ii) at an equivalent ratio of 1: 0.2 to 4, and (i) + (ii) to a pair (iii) at an equivalent ratio of 1: 0.9 to 1.1.

The compound (i) having a molecular weight of about 500 to 2,000 having two or more hydroxyl groups includes a compound having 2 to 2 carbon atoms.
Polyester glycol obtained by condensation of a saturated aliphatic glycol of 8 with a saturated aliphatic dicarboxylic acid or aromatic dicarboxylic acid having 4 to 10 carbon atoms or copolymerization of an alkylene glycol and a lactone can be used. Furthermore, in addition to polyalkylene ether glycols obtained by condensation of alkylene oxides having 2 to 4 carbon atoms, condensation of alkylene oxide with alkylene glycol, ring-opening polymerization of tetrahydrofuran, dihydroxypolyesteramides and dihydroxypolyacetals, Can be used. Among these, polyester glycol, dihydroxy polyethylene adipate, dihydroxy polybutylene adipate and polytetramethylene ether glycol are particularly preferred.

A molecular weight of about 5 capable of reacting with an isocyanate group
A compound having at least two active hydrogen groups of
i) includes a saturated aliphatic glycol having 2 to 6 carbon atoms,
Examples thereof include aliphatic glycols such as 1,4-cyclohexylene glycol and aromatic glycols such as 1,4-xylylene glycol and phenylenebis- (β-hydroxyethyl ether), and one or more kinds can be used. . Furthermore, water or trihydric alcohol (trimethylolpropane, hexanetriol, glycerin, etc.)
Can be used in combination with the above glycols in a very small amount. Among these, in particular, 1,4-butylene glycol, paraxylylene glycol, phenylene bis (β-
Hydroxyethyl ether) is preferred.

The organic diisocyanate (iii) may be any of organic diisocyanates generally used in the production of polyurethane resins, such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, phenylene diisocyanate, and 4,4'- Diphenylenemethane diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthylene diisocyanate, 3,3'-dimethylbiphenyl-4,4'-diisocyanate, o-, m
-Or p-xylylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, and the like, and one or more kinds can be used. In particular, 4,4'-diphenylmethane diisocyanate is preferred.

The thermoplastic polyurethane elastomer used in the present invention has a Crashberg temperature of -10.
It is below ° C. Crashberg temperature is determined from a temperature-rigidity curve obtained using a Crashberg flexible temperature tester.

By appropriately changing the composition ratio of the above-mentioned compounds (i), (ii) and (iii) and the composition of each compound, an elastomer having a Crashberg temperature of -10 ° C. or less can be obtained.

The resin composition constituting the core layer or the back layer comprises 10 to 90% by weight of the rubber-reinforced styrene resin and 90 to 10% by weight of the thermoplastic polyurethane elastomer. When the amount of the rubber-reinforced styrene resin is less than 10% by weight, the expandability is poor. On the other hand, when the content exceeds 90% by weight, the rigidity of the core layer is increased, and the adhesiveness to the urethane foam is inferior.

Preferably, rubber-reinforced styrene resin 30
To 70% by weight and 70 to 30% by weight of the thermoplastic polyurethane elastomer, and more preferably the rubbery polymer content in the resin composition is 10 to 40% by weight.

The resin composition can be mixed using a known mixer, for example, a Banbury mixer, a single screw extruder, a twin screw extruder, or the like.

At the time of mixing, if necessary, an antioxidant,
An ultraviolet absorber, a light stabilizer, an antistatic agent, a lubricant, a dye, a pigment, a plasticizer, a flame retardant, a softener and the like can be appropriately compounded.

The method for molding the air bag housing case of the present invention formed from the skin layer and the core layer or the back surface layer is not particularly limited, and the resin layer is used to form the core layer by injection molding or the like. , A method of injecting and foaming urethane foam material by inserting it into a urethane foam mold, and a method of double-injection foaming by injecting and foaming the urethane foam material into the space after slightly forming the backside layer after molding the back layer in advance. No.

In the case of the present invention, it is also possible to provide a slit (groove) in the case in order to facilitate deployment. Also, it can be attached to the base of the airbag in the same manner as a conventional product, and can be mounted on a car as an airbag.

Next, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited by these. The number of parts and percent (%) are shown on a weight basis.

[0037]

【Example】

Examples 1 to 3 and Comparative Example 1 Using the compositions shown in Table 1, slitting was performed using an injection molding machine.
A core layer (average thickness 2.5 mm) containing (slit portion thickness 0.6 mm) is formed. After placing the obtained core layer in the mold of the RIM molding machine, the hydroxyl value was 35 and the molecular weight was 4500.
Polyether polyol, 1,4-butanediol,
Triethylenediamine, CFC-11, diphenylmethane diisocyanate (weight ratio 80/5 / 0.5 / 8/2)
7) was injected and foamed to obtain an airbag cover having a skin layer having a density of 0.5 to 0.8 g / cm ³ . The appearance, deployability and danger prevention of the obtained airbag cover were evaluated by the following methods. Table 2 shows the evaluation results.

Comparative Example 2 A core layer having the same shape as that of Example 1 was molded by a two-color injection molding machine using an olefin elastomer, and then a styrene elastomer was injected to form an airbag having a skin layer of 2.5 mm. Obtained. The appearance, deployability, and danger prevention of the obtained airbag cover were evaluated in the same manner as in Example 1. Table 2 shows the evaluation results. The materials for the core layer and the skin layer used in Examples and Comparative Examples are as follows.

Rubber-reinforced styrene resin (ABS-1) 1,3-butadiene 100% is polymerized by an emulsion polymerization method, and polybutadiene rubber latex having a glass transition temperature minus 85 ° C. (particle diameter 0.43 μm, gel 93%) is obtained. Obtained.
50 parts (solid content) of polybutadiene rubber latex, 35 parts of styrene and 15 parts of acrylonitrile were graft-polymerized by a known emulsion polymerization method. On the other hand, in another reactor, 70 parts of styrene and 30 parts of acrylonitrile were polymerized by a known emulsion polymerization method. After mixing the obtained polymer latex, salting out, dehydration and drying were performed to obtain a resin having a rubber content of 40%.

Rubber-reinforced styrene resin (AES) Ethylene-propylene-ethylidene norbornene rubber
(Ethylene / propylene ratio = 1/1, Iodine value 15, Mooney viscosity 65) (Glass transition temperature minus 48 ° C.) 50
Parts, 35 parts of styrene and 15 parts of acrylonitrile were subjected to graft polymerization based on a known suspension polymerization method, followed by dehydration and drying. On the other hand, the styrene-acrylonitrile copolymer used in ABS-1 was solely salted out and dried. Both were mixed to obtain a resin having a rubber content of 40%.

Rubber-reinforced styrene resin (ABS-2) 65% of 1,3-butadiene and 35% of styrene are polymerized by an emulsion polymerization method, and a butadiene-styrene rubber latex having a glass transition temperature of -30 ° C. (particle diameter 0.35 μm) is obtained. , Gel 81%). A resin having a rubber content of 40% was obtained in the same manner as in ABS-1 described above.

Thermoplastic polyurethane elastomer TPU-1: Commercially available thermoplastic polyurethane elastomer using polyester glycol as compound (i)
(Crushburg temperature minus 48 ° C) TPU-2: Commercially available thermoplastic polyurethane elastomer using polytetramethylene ether glycol as compound (i) (Crushburg temperature minus 66 ° C) TPU-3: Polyester as compound (i) Commercially available thermoplastic polyurethane elastomer using glycol
(Crashburg temperature minus 17 ° C)

Styrene-based elastomer Styrene-based elastomer manufactured by Mitsubishi Yuka Co., Ltd. (trade name: Lavalon SJ4400)

Olefin-based elastomer Ethylene-propylene block polymer (trade name: BC-8) manufactured by Mitsubishi Yuka Co., Ltd.

Appearance The surface of the skin layer of the obtained airbag cover was visually observed to judge the quality. Good: The surface is smooth and free from distortion, and there is no floating of the slit pattern. Poor: Distortion or lifting of a strip pattern over the entire surface.

The air bag system using the obtained air bag cover is operated in an environment of -40 ° C. and + 80 ° C., and the air bag cover is ruptured and the fragments are scattered. Judged from the situation. Good deployability: rupture along the entire slit line. Poor: no rupture, part of slit remaining, or rupture over the entire surface but not along the slit. Danger prevention Good: No sharp debris. Poor: sharp fragments are observed.

[0047]

[Table 1]

[0048]

[Table 2]

[Brief description of the drawings]

FIG. 1 is a front view of a steering wheel provided with an airbag cover according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the airbag cover according to the embodiment of the present invention.

FIG. 3 is a sectional view of an airbag cover according to another embodiment of the present invention.

FIG. 4 is a cross-sectional view of an airbag cover according to another embodiment of the present invention.

FIG. 5 is a cross-sectional view of an airbag cover according to another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... skin layer, 2 ... core layer or back surface layer, 3 ... slit, 4
... A broken part.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-202550 (JP, A) JP-A-2-171362 (JP, A) JP-A-2-220946 (JP, A) JP-A-3-202 189252 (JP, A) JP-A-3-258634 (JP, A) JP-A-2-220946 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B60R 21/16-21 / 32 B32B 1/00-35/00

Claims (1)

(57) [Claims] 1. A skin layer comprising urethane foam, 10 to 90% by weight of a rubber-reinforced styrenic resin based on a rubbery polymer having a glass transition temperature of -40 ° C. or lower, and a Crushberg temperature of -10 ° C. or lower. An airbag storage case formed from a core layer or a back layer made of a resin composition comprising a thermoplastic urethane elastomer of 90 to 10% by weight.