JPH08269244A - Air bag pad for steering wheel - Google Patents

Abstract

PURPOSE: To obtain an air bag pad for a steering wheel which is excellent in feel of softness, can be recycled, and has the surface with an excellent feel to the touch. CONSTITUTION: An air bag pad 7, inside which an air bag mechanism E is installed, is installed at the central part of a steering wheel and is produced from a compsn. comprising 50-80wt.% hydrogenated s tyrene-butadiene rubber having a stryene unit content of 5-35wt.% and a JIS A hardness of 60 or lower and 50-20wt.% propylene copolymer having an ethylene unit content of 2-20wt.%. Such a compsn. gives an air bag pad which is excellent in feel of softness, is recyclable because of its thermoplasticity, and does not exhibit surface stickiness, improving the feel to the touch.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering wheel airbag pad formed in a predetermined shape.

[0002]

2. Description of the Related Art Conventionally, polyurethane has been mainly used as a material for a pad provided in a central portion of a steering wheel, particularly an airbag pad provided with an airbag device inside itself. Such a polyurethane airbag pad is excellent in soft texture and touch, and is applied to many so-called luxury cars.

However, with regard to this polyurethane, the appearance of an alternative material is desired because of its relatively high cost and difficulty in recycling. As materials for airbag pads to meet such demands, thermoplastic polyolefins such as polypropylene and S
Examples thereof include styrene-based thermoplastic elastomers such as EBS (styrene-ethylene-butadiene-styrene copolymer) and compounds containing the same as the main component. According to these materials, the cost can be kept low, and since they are thermoplastic materials, they can be recycled.

[0004]

However, the above-mentioned conventional materials have the following problems.
That is, when a thermoplastic polyolefin is used as a material for an airbag pad, it lacks in a soft texture and has a rugged feel. Therefore, it has been difficult to apply it to a luxury car.

On the other hand, as a material for airbag pads,
When a styrene-based thermoplastic elastomer or a compound containing the same as the main component was used, a sticky feeling on the surface (a sticky feeling peculiar to the styrene-based elastomer) was generated although the softness was excellent. And, in order to wipe off the sticky feeling, a separate coating or the like is required.

The present invention has been made to solve the above problems, and an object thereof is an airbag pad for a steering wheel, which is formed into a predetermined shape, has an excellent soft texture and can be recycled. With
An object of the present invention is to provide an airbag pad for a steering wheel that has an excellent surface feel.

[0007]

In order to achieve the above object, in the invention described in claim 1, the styrene content relative to itself is 5% by weight or more and 35% by weight or less, and JIS
A hydrogenated styrene-butadiene rubber (A) having an A hardness of 60 or less and a polypropylene copolymer (Y) having an ethylene content of 2% by weight or more and 20% by weight or less relative to itself are provided, and the above (X) and (Y ) And the weight ratio is 50: 50-8
The gist is an airbag pad for a steering wheel, which is formed by molding a compound material of 0:20 into a predetermined shape.

Examples of the styrene component (X) used in the present invention include styrene, t-butylstyrene, α-methylstyrene, p-methylstyrene, monochlorostyrene,
Dichlorostyrene, monobromostyrene, dibromostyrene, fluorostyrene, pt-butylstyrene, ethylstyrene, 1,1-diphenylstyrene, N, N-
Diethyl-p-aminostyrene, N, N-diethyl-p
-Aminoethylstyrene and the like, particularly styrene,
α-Methylstyrene is preferably used, and more preferably styrene.

Further, as the butadiene component of (X), 1,3-butadiene and 2,3-dimethyl-1,3-
Butadiene etc. are mentioned and more preferably 1,3-butadiene. (X) is hydrogenated styrene-butadiene rubber composed of the above components, and has a hydrogenation rate of 95% or more, preferably 97% or more.

In the present invention, the styrene content relative to the hydrogenated styrene-butadiene rubber (X) itself is 5% by weight or more and 3
It should be 5% by weight or less. If the styrene content is less than 5% by weight, the surface feel is inferior. Further, when the styrene content is more than 35% by weight, the soft texture is impaired.

The hydrogenated styrene-butadiene rubber (X) used in the present invention must have a JIS A hardness of 60 or less. If the JIS A hardness is greater than 60, good softness may not be ensured. A more preferable JIS A hardness is 50 or less. here,
JIS A hardness is the hardness specified in JIS K-6301.

On the other hand, as the polypropylene copolymer (Y), a block or random copolymer of propylene and ethylene can be used. In the present invention, the ethylene content based on the polypropylene copolymer (Y) itself needs to be 2% by weight or more and 20% by weight or less. If the ethylene content is less than 2% by weight, it may be difficult to obtain good inflation characteristics at low temperatures. Further, when the ethylene content is more than 20% by weight, the heat resistance may be deteriorated and the shape retention may be deteriorated.

Further, in the compound material molded into a predetermined shape in the present invention, the weight ratio of the hydrogenated styrene-butadiene rubber (X) and the polypropylene copolymer (Y) is 50:50 to 80:20. Composed of something. Here, hydrogenated styrene-butadiene rubber (X)
If the weight ratio is less than 50%, the air bag pad may be inferior in softness. The weight ratio of hydrogenated styrene-butadiene rubber (X) is 8
If it is more than 0%, the airbag pad may become too soft, which may cause molding failure during molding.

Further, in the invention described in claim 2,
In the airbag pad for a steering wheel according to claim 1, the gist is that the compound material contains 0.1 to 5% by weight of a lubricant with respect to the compound material.

Here, examples of the lubricant to be added include oleic acid amide, bisamide, silicone lubricants such as silicone oil, polyethylene wax and the like. Of these, oleic acid amide is preferable. The amount of lubricant added is preferably 0.1% by weight or more and 5% by weight or less. If the addition amount is less than 0.1% by weight, the effect of improving the surface stickiness may be small. On the other hand, if the addition amount is more than 5% by weight, the moldability may be deteriorated.

By adding such a lubricant, further prevention of stickiness on the surface, releasability and texture can be achieved.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the steering wheel airbag pad of the present invention will be described below with reference to FIGS.

As shown in these figures, an airbag pad (hereinafter simply referred to as "pad") 7 is provided at the center of the steering wheel. An airbag mechanism E is provided inside the pad 7.
The airbag mechanism E includes a metal bag holder 1, an inflator 2, an airbag 3 and the like. The bag holder 1 has a main body portion 1a having an opening in the center and a side wall portion 1b extending downward in the figure, and is substantially box-shaped as a whole. The bag holder 1 is fixed to a boss of a steering wheel (not shown). An inflator 2 containing a gas generating agent is disposed inside the opening. An airbag 3 and a ring retainer 4 made of cloth are attached to the upper surface of the bag holder 1. More specifically, the ring retainer 4 is integrally formed with a plurality of leg portions 5 protruding downward. Then, the leg portions 5 are inserted into the through holes of the airbag 3 and the bag holder 1, and the nuts 6 are fastened to the screw portions of the leg portions 5 projecting from the lower side of the bag holder 1, whereby the air The bag 3 and the ring retainer 4 are attached and fixed to the bag holder 1.

The pad 7 is made of a material to be described later, and the pad main body 8 covering the upper side of the bag holder 1 and a direction substantially perpendicular to the bag holder 1 side from the substantially end edge of the pad main body 8 (downward in the figure). The pad side wall 9 extends. The pad body 8 has a flat H-shaped groove 1 for facilitating the expansion of the pad 7 when the airbag 3 is inflated.
0 (see FIG. 1) is formed.

In the present embodiment, the side wall portion 1 of the bag holder 1
Through holes 11 and 12 are formed in b and the pad side wall 9, respectively. The through holes 11 and 12 are aligned such that the pad side wall 9 contacts the side wall portion 1b of the bag holder 1, and the both sides 1b and 9 are caulked and fixed by the rivet 13.

When a predetermined impact or the like occurs, a large amount of gas is generated from the inflator 2 and the airbag 3 inflates. Due to this expansion, a crack is formed along the groove 10 of the pad body 8, the pad 7 is expanded, and the expanded airbag 3 is interposed between the occupant and the steering wheel.

Next, the material forming the pad 7 in this embodiment will be described. A predetermined compound material is used for the pad 7 in this embodiment. That is, this compound material has a styrene content of 5% by weight or more and 35% by weight or less based on JIS A
Hydrogenated styrene-butadiene rubber (X) having a hardness of 60 or less
And a polypropylene copolymer (Y) having an ethylene content relative to itself of 2% by weight or more and 20% by weight or less. The weight ratio of (X) to (Y) is 50: 5.
It is 0 to 80:20. The pad 7 is formed by molding this compound material into the shape shown in FIG. 1 by a known injection molding method. However, in the present embodiment, 0.
A lubricant of 1% by weight or more and 5% by weight or less is added.

According to the pad 7 having the component composition of this embodiment, a predetermined amount of hydrogenated styrene-butadiene rubber (H-SBR) (X) having a JIS A hardness of 60 or less is contained, and polypropylene Combined with the fact that the ethylene component of the polymer (Y) is contained in a predetermined amount, the soft feel is excellent and the surface is less sticky. Further, since (X) is well compatible with (Y), rubber elasticity is imparted to (Y), and touch feeling can be improved. Also, since all the materials are made of thermoplastic materials, they can be recycled.

Further, in this embodiment, a predetermined amount of lubricant is added to the compound material. For this reason, it is possible to further prevent the stickiness of the surface and improve the releasability and the texture during molding.

Next, in order to confirm the above effects, the following experiment was conducted. That is, various materials were used to mold pads by an injection molding method, and various performances were evaluated. Table 1 shows the evaluation results at that time.

In the table, PP-1 indicates a homopolymer of polypropylene, PP-2 indicates a block copolymer of polypropylene, and PP-3 indicates a random copolymer of polypropylene. However, the ethylene content in the block copolymer is 7.0% by weight, and the ethylene content in the random copolymer is 2.5% by weight.

Also, as H-SBR, manufactured by Nippon Synthetic Rubber Co., Ltd., trade name: Dynaron 1320P (styrene content: 10% by weight, JIS A hardness: 39, hydrogenation rate: 99
%), And SEBS (corresponding to conventional technology: styrene-
As the ethylene-butadiene-styrene copolymer), trade name: Kraton G1657 (styrene content ... 13% by weight, JIS A hardness ... 65, hydrogenation rate ... 99%) manufactured by Shell Chemical Co., Ltd. was used. Further, oleic acid amide was used as a lubricant.

In addition, the inflation performance is an evaluation of the expansion state of the pad when the airbag mechanism is actually operated.
The fact that the expansion situation is good indicates that the expansion was not successful in some way. The low temperature means-
The performance at 40 ° C. and the high temperature indicate the performance at 90 ° C., respectively.

In addition, the sensory evaluation by five persons regarding the touch was marked with ◯ when the number of persons who felt soft without stickiness was 4 or more, and with X when the number of persons was 3 or less. In addition, the unit of the numerical value of each material is parts by weight.

[0030]

[Table 1]

As shown in Table 1 above, according to the composition of this embodiment, the finally obtained pad has a JIS A hardness of 9
It can be seen that a product having a relatively low value of 0 or less and an excellent soft feel can be obtained. Further, it can be seen that the inflation performance at low temperature and high temperature is not hindered and can be suitably used as a pad for an airbag. Furthermore, it can be seen that the surface feel is excellent.

The present invention is not limited to the above embodiment, but may be configured as follows, for example. (1) In the above embodiment, the lubricant is added to the compound material, but the lubricant may be omitted.

The technical idea which is not described in each claim of the claims and can be grasped from the above-mentioned embodiment will be described below together with its effect. (A) In the airbag pad for a steering wheel according to claim 1 or 2, a compound material having a weight ratio of (X) and (Y) of 70:30 to 80:20 is molded into a predetermined shape. It is characterized by With such a configuration, the soft texture can be further improved.

[0034]

As described in detail above, according to the airbag pad for a steering wheel of the present invention, it has an excellent soft feel, can be recycled, and has an excellent tactile sensation on the surface. It has an unprecedented advantageous effect of being excellent in inflation performance over time.

In particular, according to the invention described in claim 2, there is an excellent effect that the stickiness of the surface can be further prevented, and the releasing property and the texture can be further improved.

[Brief description of drawings]

FIG. 1 is a perspective view showing an airbag pad according to an embodiment.

FIG. 2 is a cross-sectional view showing an airbag pad and the like in one embodiment.

[Explanation of Codes] 7 ... Airbag pad.

Claims (2)

[Claims] 1. The styrene content relative to itself is 5% by weight.
Hydrogenated styrene-butadiene rubber (X) with JIS A hardness of 60 or less and ethylene content of 2 wt% or more and 20 wt% or more
Air for a steering wheel, comprising the following polypropylene copolymer (Y), and a compound material in which the weight ratio of (X) to (Y) is 50:50 to 80:20 is molded into a predetermined shape. Bag pad. 2. The airbag pad for a steering wheel according to claim 1, wherein the compound material contains 0.1% by weight or more and 5% by weight or less of a lubricant with respect to the compound material. The characteristic airbag pad for steering wheel.