JP3020807B2 - Airbag storage cover - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cover for accommodating an inflating and deploying air bag 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 is.

[0002]

2. Description of the Related Art Conventionally, a cover for accommodating an air bag in an air bag apparatus is crushed when the air bag is activated (inflated), and fragments of the cover are scattered to 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 having such a net-like insert, a number of complicated manufacturing steps for inserting a net-like reinforcing material are required.

In order to solve these problems, Japanese Patent Application Laid-Open Nos. Hei 1-2202550 and Hei 2-171362 have been proposed.
And Japanese Patent Application Laid-Open No. 2-200946 propose 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. As a result, there was no need to use a net-like reinforcing material, which had the effect of reducing the number of manufacturing steps, but required a dedicated two-color injection molding machine and used two dies. Therefore, there remains a problem that the molding cycle is long, and that sinks and warpage due to shrinkage during molding and high-temperature heating are large.
Therefore, for the purpose of solving this,
171364, JP-A-2-151348,
JP-A-4-314648, JP-A-5-38996
A method of forming a single-layer injection-molded product as described in Japanese Patent Application Laid-Open No. H10-264, has been proposed.

[0004]

Therefore, according to these proposals, the cover for storing the air bag in the air bag apparatus can be molded by using a usual injection molding machine, and the molding cycle is shortened. . However, sinking and warping due to shrinkage during molding and high-temperature heating have not yet reached a satisfactory level.

[0005]

Means for Solving the Problems [Summary of the Invention] The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, compounded an olefin resin and talc with an olefin copolymer rubber. As a result, the present inventors have found that a molded article with less sink marks and warpage due to shrinkage during molding and secondary shrinkage such as baking of paint can be obtained, and have completed the present invention. That is, the airbag storage cover of the present invention is formed by a single-layer injection-molded article having a fragile structure for easily tearing the airbag storage cover on the inner surface side when the airbag device is operated, in the airbag device. It is composed of the following components A to C and has a flexural modulus according to JIS-K7203 of 500 to 8,000 kg / cm ² . Component A: Olefin-based copolymer rubber 20 to 80 parts by weight Component B: Olefin-based resin 80 to 20 parts by weight Component C: Talc having an average particle size of 1.0 to 6.0 μm Total amount of component A and component B 100 parts by weight 1 to 30 per part
Parts by weight

[Detailed Description of the Invention] [I] Cover for storing airbag (1) Constituent material. The materials constituting the air bag storage cover of the present invention include the following olefin copolymer rubber of component (A), olefin resin of component (B), and component (C) shown below.
It is important to use each essential component of the talc.

Component (A): Olefin copolymer rubber The olefin copolymer rubber used in the present invention includes ethylene / propylene copolymer rubber (EPM), ethylene / butene-1 copolymer rubber (EBM), Examples of the non-conjugated diene include ethylene-propylene-non-conjugated diene copolymer rubber (EPDM) using 5-ethylidene norbornene, 5-methylnorbornene, 5-vinylnorbornene, dicyclopentadiene and the like. The production method and shape of these 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 olefin copolymer rubbers have a weight average molecular weight of 50,000 to 1,000,000, preferably 60,000 to 800,000, particularly preferably 80,000 to 500,000, and a propylene content of 10
It is preferable to use a copolymer rubber having a Mooney viscosity ML _{1 + 4} (100 ° C.) of 5 to 350, preferably 10 to 300% by weight, preferably 15 to 55% by weight.
If the weight average molecular weight of the olefin copolymer rubber is less than the above range, rubber elasticity and mechanical strength tend to be inferior. If the weight average molecular weight exceeds the above range, moldability tends to be inferior.

Component (B): Olefin resin The olefin resin of the component (B) used in the present invention includes propylene resin, ethylene resin, crystalline polybutene-1 resin, ethylene / vinyl acetate copolymer, ethylene Ethylene resins such as (meth) acrylic acid copolymers and ethylene (meth) acrylate copolymers can be mentioned. Among these olefin-based resins, it is preferable to use a propylene-based resin, and particularly preferably, a melt flow rate (JIS-K6758, 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, and an ethylene content of 0 to 1 g / min.
It is a propylene-based resin in the range of 5% by weight, preferably 0 to 13% by weight, particularly preferably 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. If 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. Resin (straight-chain ethylene polymer) or low-density, which is a copolymer of ethylene and α-olefin obtained by a medium-low pressure method,
Medium density and high density polyethylene resins (linear ethylene polymers) can be mentioned. Examples of the linear α-olefin as the comonomer include butene-1, pentene-1,
Hexene-1, 4-methylpentene-1, octene-1
And these may be used in combination of two or more. As specific production conditions, generally, pressure 5 to
A method is employed in which ethylene and an α-olefin are copolymerized under conditions of 2,500 kg / cm ² and a temperature of 50 to 300 ° C. using a catalyst such as a Ziegler catalyst, a vanadium catalyst, or a Kaminski catalyst. To be more specific,
A method described in, for example, Japanese Patent Publication No. -18132 is known.

The crystalline butene-1 resin is a crystalline resin synthesized from a butene-1 monomer which may contain a small amount (20% by weight or less) of other comonomers such as ethylene and propylene, and has a density of 0.890-0.925
g / cm ³ , preferably 0.893 to 0.923 g / c
m ³ , particularly preferably 0.900 to 0.920 g / cm
³ , melt flow rate (MFR: 190 ° C., 2.16
kg load) is 0.01 to 1,000 g / 10 minutes, preferably 0.05 to 500 g / 10 minutes, and particularly preferably 0.1 to 1,000 g / 10 minutes.
1 to 100 g / 10 min, crystallinity of 30% or more, preferably 30 to 70%, weight average molecular weight of 10,000 to
3,000,000, preferably 50,000 to 2.5
Those having a molecular weight of 00,000 are preferably used.

Component (C): Talc The talc of the component (C) used in the present invention has an average particle size of 1.0 to 6.0 μm, preferably 1.5 to 5.0 μm.
0 μm talc is used, which improves shrinkage, warpage and shrinkage due to shrinkage.

Preferred talc has a specific surface area of 3
7,000 cm ² / g or more, preferably 40,000 c
m ² / g or more, the length is substantially 15 μm or less, preferably 10 μm or less, and the average aspect ratio is 5 or more, preferably 6 or more. Here, the “substantially” length of talc means that most talc particles are in this range. For example, talc is obtained by pulverizing raw talc with an impact-type pulverizer or a micron-type pulverizer.
After finely pulverizing with a jet-type pulverizer, the product is classified and adjusted using a cyclone, micron separator or the like. Here, the measurement of the average particle size is a value measured using a laser light scattering type particle size distribution meter. As such a measuring device, for example, LA-500 manufactured by HORIBA, Ltd. has excellent measurement accuracy. desirable. The diameter, length, and aspect ratio are values measured with a microscope or the like.

Component (D): Softener for Hydrocarbon Rubber The softener for hydrocarbon rubber used as an additional component in the present invention has a weight average molecular weight of 300-2,
000, preferably 500 to 1,500. 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. Oils having a naphthene ring carbon number of 30 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. The paraffinic oil used in the present invention has a kinematic viscosity at 40 ° C of 20 to 800 cst, preferably 5 to 800 cst.
0 to 600 cst, fluidity of 0 to -40 ° C, preferably 0 to -30 ° C, and flash point (COC) of 200 to 40
Oils at 0 ° C, preferably 250-350 ° C, are suitably used. Component A and Component B
1 to 50 parts by weight, preferably 1 to 40 parts by weight, particularly preferably 1 to 30 parts by weight, per 100 parts by weight of the total amount of The softening agent for hydrocarbon rubber is important for adjusting the hardness and the melt fluidity during molding.

Component (E): Additional compounding agent The compounding material of the cover for storing an air bag of the present invention may contain any compounding component according to various purposes within a range that does not significantly impair the effects of the present invention. can do. Specifically, various thermoplastic resins, various elastomers, various plasticizers, antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, neutralizers, lubricants, anti-fog agents, anti-blocking agents, slip agents, Various additives such as a crosslinking agent, a crosslinking aid, a coloring agent, a flame retardant, a dispersant, an antistatic agent, a conductivity-imparting agent, a metal deactivator, a molecular weight regulator, a bactericide, and a fluorescent whitening agent. be able to.

Examples of the thermoplastic resin include styrene resins such as polystyrene, acrylonitrile / styrene copolymer, acrylonitrile / butadiene / styrene copolymer, polyphenylene ether resins, polyamide resins such as nylon 6 and nylon 66, and polyethylene resins. Terephthalate, polyester resins such as polybutylene terephthalate, polyoxymethylene homopolymers, polyoxymethylene resins such as polyoxymethylene copolymers,
Examples thereof include polymethyl methacrylate-based resins. The thermoplastic resin to be used may be one kind or a mixture of plural kinds.

Examples of the elastomer include a hydrogenated product of a styrene / conjugated diene block copolymer. The hydrogenated product of the styrene / conjugated diene block copolymer is obtained by hydrogenating a block copolymer of styrene and a conjugated diene,
Specifically, styrene / ethylene / butylene / hydrogenated styrene / butadiene block copolymer (hereinafter sometimes simply referred to as “hydrogenated SBS”) may be used.
Styrene / ethylene / propylene / styrene (SEBS) or a hydrogenated product of a styrene / isoprene block copolymer (hereinafter sometimes simply referred to as “hydrogenated SIS”). Styrene copolymer (S
EPS), hydrogenated styrene-butadiene-isoprene block copolymer (hereinafter simply referred to as “hydrogenated S-BI-
S ". ).

(2) Mixing ratio The mixing ratio of each component of the material constituting the cover for storing an air bag of the present invention is such that component A is 20 to 80% by weight, preferably 20 to 80% by weight based on the total amount of component A and component B. It is 25 to 75% by weight, particularly preferably 30 to 70% by weight. When the compounding ratio of the component A is less than the above range, the obtained cover has inferior low-temperature impact resistance. That is, the expandability at low temperatures is poor, and when it exceeds the above range, the expandability at high temperatures is poor. The compounding ratio of the component B is also 80 to 20% by weight, preferably 75 to 25% by weight, particularly preferably 70 to 30% by weight based on the total amount of the components A and B. If it exceeds the above range, the low-temperature impact resistance is poor, that is, the expandability at low temperatures is poor, and if it is less than the above range, the expandability at high temperatures becomes poor. Further, the amount of the component C is 1 to 30 parts by weight based on 100 parts by weight of the total of the components A and B. Therefore, when the amount is less than 1 part by weight, the formability, particularly warpage and rib sink is conspicuous, and the shrinkage is poor. If the amount of component C exceeds the above range, the low-temperature impact resistance is poor, that is, the expandability at low temperatures is poor.

[II] Molded Article The molded article of the present invention, which is molded from the above constituent components, is a single-layer injection molded article having a fragile structure on the inner surface side so as to be easily cleaved when the airbag device is operated. JIS-K
The flexural modulus according to 7203 is 500 to 8,000 kg /
cm ² , preferably 500 to 7,000 kg / cm ² ,
An airbag storage cover preferably having a weight of 500 to 6,500 kg / cm ² . Specifically, FIGS. 1 and 2
And a shape as shown in FIG. Reference numeral 1 denotes a cover for storing an air bag.
Are provided with ribs 1b and 1c on the back side of the flat plate portion 1a for attachment to a container portion for storing the airbag.
The b is provided with a mounting hole 3 for being fixed to the container portion with rivets, bolts or the like. The flat portion 1a is formed with a fragile portion 2 for easy tearing when the airbag device is operated. When the airbag device is operated, a part of the airbag storage cover 1 is opened to inflate the airbag. Is available.

As a method for manufacturing such a cover for storing an air bag, a normal injection molding method can be used.
If necessary, various molding methods such as a gas injection molding method and a short-sit foam molding method can be used. If the flexural modulus is less than the above range, the strength of the mounting portion particularly at high temperatures is inferior, and a problem arises in the airbag deployability. If it exceeds the above range, the airbag deployability at low temperatures becomes poor. Injection molding conditions are generally 100
Molding temperature of ~ 300 ° C, preferably 150-280 ° C,
50-1,000 kg / cm ³ , preferably 50-8
Injection pressure of 00kg / cm ^3, 20~80 ℃, are molded preferably at a mold temperature of 20 to 60 ° C.. Furthermore, the average thickness of the airbag storage cover of the present invention is 1 to 5 mm. However, it is necessary to provide a fragile structure in order to easily cleave when the airbag device is operated, and it is necessary to design the cleave portion to have a small thickness, preferably 50% or less of the average thickness. Appropriate.

[III] Coating It is preferable to apply a coating on the surface of the cover of the present invention in view of the design of the interior of the room, or for the purpose of preventing dust and dirt from sticking and preventing damage. As the coating, various coatings conventionally applied to this type of cover can be used.

[IV] Applications The airbag storage cover of the present invention obtained in this way operates when a high-speed moving body such as an automobile detects a shock or a change in a collision accident or the like. , A cover for storing the inflating and deploying 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.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to describe the air bag storage cover of the present invention in more detail, an experimental example will be described below in detail. [I] Raw materials In the examples and comparative examples, the following raw materials were used.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

[0028]

[Table 4]

[0029]

[Table 5]

[II] Evaluation Methods Various evaluations in these Examples and Comparative Examples were performed by the following methods. However, the measurement sample in (1) to (3) was measured using an in-line screw type injection molding machine (small injection molding machine manufactured by Toshiba Machine Co., Ltd .: IS170) at an injection pressure of 500 kg / cm ² and an injection temperature of 210.
℃, mold temperature 40 ℃, 120mm × 120mm × 3
A sheet formed into a size of mm was used. Also, (4)
The measurement sample in (5) to (5) was an in-line screw type injection molding machine (a small injection molding machine manufactured by Toshiba Machine Co., Ltd .: I
Using S220), evaluation was performed with an airbag storage cover formed at the temperature of 220 ° C. into the shape shown in FIGS. 1, 2, and 3.

(1) Flexural modulus (kg / cm ² ): JIS-K-7203 compliant (2) Shrinkage after heating: 120 mm × with brushed lines (100 mm intervals) applied to the design surface of the mold After heating a 120 mm x 3 mm sheet in an oven (120 ° C x 1 hour) and allowing it to cool, measure the distance between the bristle lines on the molded sheet and calculate the shrinkage after heating by the following formula. Was determined according to the following criteria. Criteria 基準: Shrinkage after heating (%) ≦ 2 ×: Shrinkage after heating (%)> 2

(3) Formability (degree of warp or rib sink mark) In the cover molded body, the degree of warp or rib sink mark is easily observed with naked eyes. Was evaluated as poor (x). (4) Deployment test The deployment test temperature (−40 ° C., 80
(C) for 1 hour, and then a development test was performed. If the cover was broken and scattered, or was broken into a sharp shape and could not be deployed normally, or if it was torn off from the mounting part, it was determined to be defective (x), and the deployment was free from the above-mentioned problems. The case where it was performed was evaluated as good (（).

[III] Experimental Examples Examples 1 to 13 and Comparative Examples 1 to 6 The raw materials shown in Tables 1 to 5 were used and blended in the composition (parts by weight) shown in Tables 6 to 8; 0.1 parts 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 8, and 6 parts at a temperature of 170 ° C. beforehand using a Banbury mixer. After kneading for a minute, the sheet is cut to obtain pellets, L / D = 33,
The mixture was melted and kneaded at a temperature of 200 ° C. with a twin screw extruder having a cylinder diameter of 45 mm to obtain TPE composition pellets. The pellet was injection molded as described above to form a sheet, and the above evaluation was performed. Tables 6 to 8 show these evaluation results. In Example 13, 0.1 part by weight of a phenolic antioxidant (trade name “Irganox 1010”) was added to 100 parts by weight of the total composition shown in Table 7 at the time of melt-kneading. 2,5-dimethyl-
0.3 parts by weight of 2,5-di (t-butylperoxy) hexane (trade name “Kayahexa AD”) and 0.2 parts by weight of divinylbenzene as a crosslinking aid were added, and L / D = 3
3. Heat treatment (crosslinking treatment) at a temperature of 220 ° C. using a twin-screw extruder with a cylinder diameter of 45 mm to perform partial crosslinking T
PE composition pellets were obtained. The pellet was injection molded as described above to form a sheet, and the above evaluation was performed. Table 7 shows the evaluation results.

[0034]

[Table 6]

[0035]

[Table 7]

[0036]

[Table 8]

[0037]

The cover for storing an air bag according to the present invention is
Molding can be performed using a normal injection molding machine, and the molding cycle can be shortened.Furthermore, the molded product has a good appearance due to small sink marks and warpage due to shrinkage during molding and high temperature heating. Therefore, in the event of a collision of a high-speed moving body such as an automobile or the like, it is extremely useful industrially as a cover for sensing an impact or deformation and storing an inflating and deploying airbag.

[Brief description of the drawings]

FIG. 1 is a perspective view of an airbag storage cover according to an embodiment of the present invention.

FIG. 2 is a diagram showing the air bag storage cover A- of FIG. 1;
It is A sectional drawing.

FIG. 3 is a view showing the air bag storage cover B- of FIG. 1;
It is B sectional drawing.

[Explanation of symbols]

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

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-5-38996 (JP, A) JP-A-4-314648 (JP, A) JP-A-2-171362 (JP, A) JP-A-2- 220946 (JP, A) JP-A-5-320483 (JP, A) JP-A-5-311018 (JP, A)

Claims (3)

(57) [Claims] A cover for storing an airbag in an airbag device is formed by a single-layer injection-molded article having a fragile structure on an inner surface side of the airbag device, which is easily ruptured when the airbag device is operated. A cover for storing an air bag, comprising a constituent material of Component C and exhibiting a physical property value of 500 to 8,000 kg / cm ² according to JIS-K7203. Component A: Olefin-based copolymer rubber 20 to 80 parts by weight Component B: Olefin-based resin 80 to 20 parts by weight Component C: Talc having an average particle size of 1.0 to 6.0 μm Total amount of component A and component B 100 parts by weight 1 to 30 per part
Parts by weight 2. The airbag storage cover comprises:
The cover for storing an airbag of the airbag device according to claim 1, comprising the following component D. Component D: softener for hydrocarbon rubbers 1 to 50 based on 100 parts by weight of the total of components A and B
Parts by weight 3. The cover for storing an airbag of an airbag device according to claim 1, wherein the surface of the cover for storing an airbag is coated.