JPH11207769A - Manufacture of car interior panel with air bag storage section cover - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a car interior panel with an air bag storage section cover of superior heat fusion bonding properties with a decorative skin for the swelling of an air bag and the destruction, scattering and the like of an air bag storage section cover at the time of spreading, uniformizing the wall thickness of a preset opening and tearing line and molding securely reinforcing ribs. SOLUTION: In a manufacturing method for an interior panel, a thermoplastic elastomer material in the molten state composed of original thermoplastic elastomer and/or styrene thermoplastic elastomer as a main component, which is not cut into two in the notched Izod impact test under the conditions of 10 g/10 minutes melt flow rate or more and 50-1000 MPa bending modulus of elasticity at -30 deg.C, is introduced into a cavity of a compression molding die. Then the compression molding is carried out to manufacture the air bag storage section cover integrated with the interior panel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention accommodates an airbag of an airbag device which operates by detecting the impact or deformation of an automobile in the event of a collision or the like, and protects an occupant by inflating and deploying. The present invention relates to a method of manufacturing an automobile interior panel with a cover for an airbag storage unit, which integrally has a cover for the airbag storage unit.

[0002]

2. Description of the Related Art Conventionally, an airbag device installed in an interior panel of an automobile, for example, an instrument panel, includes an instrument panel body having an airbag opening, an airbag storage cover, and an airbag storage. The parts are formed by injection molding in separate steps, and then integrated together with an airbag module. Further, one of the instrument panel body having the opening and the cover for the airbag housing is injection-molded in advance, and it is inserted into a mold, and the other is injection-molded to integrally mold the two. A method for reducing the number of manufacturing steps and man-hours (for example, JP-A-8-192666 and JP-A-9-39706).
No., JP-A-9-109816).

[0003] The structure of the cover for the airbag storage portion is provided with a predetermined cleavage line as a thin fragile portion for easily tearing the cover when the airbag is inflated when the airbag is inflated. A complicated structure is adopted in which a mounting portion for mounting and a frame with a reinforcing rib for preventing breakage due to inflation of the airbag are provided on the outer periphery.

In these conventional methods, since the cover for the airbag accommodating portion is formed by injection molding, there is an inherent problem that the orientation of the material at the time of molding lacks a stable tearing property of a predetermined cleavage line, and the airbag has a problem. Thermoplastic elastomers, which are often used as a material for the cover for the storage section to prevent inflation of the airbag, destruction and scattering during deployment, etc., are generally inferior in melt flowability. However, there are problems such as remaining of the resin and difficulty in forming a complicated rib structure.

On the other hand, in order to solve these problems, a method of stamping and molding a thermoplastic elastomer previously formed into a sheet has been proposed (see, for example, Japanese Patent Application Laid-Open No. Hei 8-1).
However, in recent years, in order to prevent a secondary accident from inflicting occupants on the occupant due to the pressure at the time of inflation and deployment of the airbag, the airbag device has reduced the inflation and deployment pressure and has an airbag storage section. The thickness of the planned tear line of the cover for automobiles has been further reduced, and the frame with ribs for reinforcement has been expanded. For these tendencies, even with the above-described stamping molding, the uniformity of the thickness at the thin planned cleavage line, the moldability of the reinforcing ribs, and the decorative skin At present, it is difficult to say that the requirements of the market can be sufficiently satisfied in terms of heat-fusibility.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned prior art, and therefore, the present invention can eliminate the work of integrating the cover for the airbag housing and the interior panel. At the same time, the airbag is not inflated, the airbag housing cover is not broken or scattered at the time of deployment, of course, the thickness at the predetermined cleavage line is uniform, and the reinforcing ribs can be reliably formed. It is another object of the present invention to provide a method for manufacturing an automobile interior panel with a cover for an airbag storage portion, which is excellent in heat fusion property with a decorative skin.

[0007]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have achieved the above object by molding by a specific method using a thermoplastic elastomer material having specific physical properties. It has been found that the present invention has been completed and the present invention has been completed, that is, the present invention comprises an olefin-based thermoplastic elastomer and / or a styrene-based thermoplastic elastomer as a main component and has a melt flow rate of 15 g / 10
Min, bending elastic modulus is 50 ~ 1000MPa, -30 ℃
In a notched Izod impact test, a thermoplastic elastomer material that does not break is supplied into the cavity of the compression molding die in a molten state, and then compression molded to produce an airbag storage unit cover and interior panel integrally. To manufacture an automobile interior panel with an airbag storage section cover.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, as an olefin-based thermoplastic elastomer which is a main component constituting a thermoplastic elastomer material, for example, ethylene and propylene, butene-1, hexene-1, octene-1, etc. Binary or more copolymer rubber with α-olefin having about 3 to 8 carbon atoms, ternary or more copolymer rubber obtained by copolymerizing non-conjugated diene thereto, and propylene-based resin and these copolymers Typical examples thereof include a mixture with a coalesced rubber, and a high rubber copolymerized polypropylene having a rubber content of 25% by weight or more as measured by boiling point extraction of xylene.

In the present invention, the styrene-based thermoplastic elastomer which is a main component of the thermoplastic elastomer material includes, for example, styrene, butadiene,
Typical examples thereof include block copolymers with conjugated dienes such as isoprene and hydrogenated products thereof.

In the present invention, the thermoplastic elastomer material contains, as a main component, any one of the olefin-based thermoplastic elastomer and the styrene-based thermoplastic elastomer, or a mixture of both, and a hydrocarbon-based rubber softener. , Fillers, waxes, additives such as antioxidants and light stabilizers, etc., which are commonly used in thermoplastic elastomers. Further, as for the olefin-based thermoplastic elastomer, those obtained by adding an organic peroxide or a crosslinking assistant to the elastomer, melt-kneading with a Banbury mixer, an extruder, or the like and dynamically cross-linking the same are also included in the present invention. And

The thermoplastic elastomer material of the present invention is one of the thermoplastic elastomer materials described above, which is JIS K
It is essential that the melt flow rate (MFR) measured at 230 ° C. under a load of 2.16 kg according to 7210 is 10 g / 10 min or more, preferably 12 to 100 g / 10 min, and more preferably 15 to 80 g. / 10 minutes is particularly preferred. If the MFR is less than the above range, the thickness of the airbag storage portion cover at the predetermined cleavage line becomes non-uniform, and it cannot follow a complicated reinforcing rib structure, so that satisfactory molding cannot be performed.

Further, the thermoplastic elastomer material according to the present invention is one of the thermoplastic elastomer materials described above.
The flexural modulus measured according to SK7203 is 50 to
It is essential that the pressure be 1000 MPa, and 100 to 90
The pressure is preferably 0 MPa, particularly preferably 150 to 850 MPa. If the flexural modulus is less than the above range, the rigidity of the car interior panel will be insufficient. If the flexural modulus is more than the above range, the airbag will be used as a cover for the airbag storage part, particularly when the airbag is inflated at low temperatures, broken or scattered when deployed. Problem occurs.

Further, the thermoplastic elastomer material according to the present invention is a thermoplastic elastomer material as described in JI.
In a notched Izod impact test at −30 ° C. in accordance with SK7110, it is essential that the test be performed without both ends. In the case where the airbag is divided into two parts, problems such as breakage and scattering occur when the airbag is inflated and deployed at a low temperature, particularly as the cover for the airbag storage portion.

According to the method for manufacturing an automobile interior panel with a cover for an airbag storage portion of the present invention, the thermoplastic elastomer material is supplied in a molten state into a cavity of a compression molding die, and then compressed and molded. The cover for the storage section and the interior panel are manufactured integrally.

Here, the method of compression-molding after supplying the molten state into the cavity of the compression-molding mold is described in the so-called injection compression molding method, in which the molten metal is supplied into the mold cavity by injection and then compression-molded. In addition, a conventionally known method such as a so-called injection compression molding method, in which the resin is supplied into the mold cavity with no or low pressure and then subjected to compression molding, may be used. Inside,
In the present invention, the injection compression molding method is preferable, and as the compression molding conditions, the material temperature is preferably 130 to 3.
50 ° C, particularly preferably 150 to 300 ° C, compression pressure is preferably 1 to 30 MPa, particularly preferably 2 to 25 MPa
a, The mold temperature is preferably 20 to 80 ° C.

The automobile interior panel with a cover for an airbag housing manufactured according to the present invention is, for example, a body such as an instrument panel, a door panel, a center panel, a pillar panel, or a panel formed separately. It has a desired shape as a surface material of the main body and the like, and its average thickness is about 1 to 5 mm, and the planned cleavage line of the cover for the airbag storage part is 50% of the average thickness.
Hereinafter, for example, it is formed by forming a continuous line having a thickness of about 0.3 to 1.5 mm, or by providing a perforated discontinuous through hole.

Further, the method for manufacturing an automobile interior panel with a cover for an airbag storage portion of the present invention is preferably a method in which, for example, a decorative skin having a soft feeling of woodgrain, fabric, soft material, foam or the like is previously molded in a mold. Even when a thermoplastic elastomer material is supplied and compression-molded after the insertion into the cavity to be fused and integrated, the heat-fusibility is excellent. When these decorative skins are provided, it is preferable to provide the same scheduled cleavage lines as those provided on the cover for the airbag storage section also on the decorative skins.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist of the present invention. Test sample thermoplastic elastomer material ethylene - propylene copolymer rubber 35% by weight of propylene - a mixture of 65 wt% ethylene block copolymer resin, MFR is 27 g / 10 min, a flexural modulus of 700 MPa, - An olefin-based elastomer material having physical properties that is not incompatible in a notched Izod impact test at 30 ° C. An olefin elastomer having a rubber content of 50% by weight, a propylene-ethylene block copolymer having an MFR of 30 g / 10 minutes, a flexural modulus of 350 MPa, and a notched Izod impact test at -30 ° C. material. To a mixture of 10% by weight of ethylene-propylene copolymer rubber and 90% by weight of a propylene-ethylene block copolymer having a rubber content of 40% by weight, 5 parts by weight of a softening agent for hydrocarbon rubber, and an organic peroxide And a crosslinking aid, which are melt-kneaded and dynamically crosslinked, and have an MFR of 2
An olefin-based elastomer material having physical properties of 1 g / 10 min, a flexural modulus of 300 MPa, and a notched Izod impact test at −30 ° C.

Ethylene-propylene copolymer rubber 45
% By weight and propylene-ethylene block copolymer resin 5
5% by weight, having an MFR of 8 g / 10 min.
An olefin elastomer material having a physical property such that a flexural modulus is 500 MPa and a notched Izod impact test at −30 ° C. does not cause cross-section. A mixture of 30% by weight of an ethylene-propylene copolymer rubber and 70% by weight of a propylene-ethylene block copolymer resin mixed with 10 parts by weight of a softening agent for a hydrocarbon rubber, and having an MFR of 25 g / 10 An olefin elastomer material having physical properties such that a bending elastic modulus is 350 MPa and a notched Izod impact test at −30 ° C. and the impact strength is 20 KJ / m ² . A mixture of 50% by weight of a hydrogenated styrene-butadiene block copolymer and 50% by weight of a propylene homopolymer resin, having an MFR of 30 g / 10 minutes, a flexural modulus of 450 MPa, and a notch at -30 ° C. A styrenic elastomer material that has physical properties that are compatible with the Izod impact test.

A mixture of 80% by weight of a propylene-based resin propylene-ethylene block copolymer resin and 20% by weight of an ethylene-propylene copolymer rubber, and 10 parts by weight of talc,
MFR is 18g / 10min, flexural modulus is 1200MP
a, A propylene-based resin having both physical properties of a notched Izod impact test at −30 ° C. and an impact strength of 8 KJ / m ² . On a decorative propylene resin foam sheet with a decorative skin thickness of 2.5 mm,
A laminated decorative skin having a 0.35 mm-thick olefin-based thermoplastic elastomer skin whose surface is subjected to graining.

Examples 1 to 6 and Comparative Examples 1 to 5 With the structure shown in Table 1, the decorative skin was inserted into the mold or not, and the mold was placed in a mold cavity set at 50 ° C. After injecting an olefin-based or styrene-based thermoplastic elastomer or propylene-based resin at a material temperature of 230 ° C and an injection pressure of 100 MPa using an injection compression composite molding machine with a clamping force of 500 tons, compression molding is performed with a mold clamping force of 300 tons. As a result, an automobile instrument panel with an airbag housing cover with an average thickness of 3 mm and a wall thickness of 0.5 mm at the predetermined cleavage line of the airbag housing cover was manufactured. About the obtained automobile instrument panel with the cover for the airbag storage unit, in the following method, the moldability of the rib in the cover for the airbag storage unit,
Evaluate the uniformity of the thickness of the planned cleavage line, and the heat-fusibility with the decorative skin, and further perform the inflation and deployment test of the airbag to evaluate the inflation and deployment of the airbag. The results are shown in Table 1.

Formability of the ribs The ribs of the frame on the back surface of the cover for the airbag accommodating section were visually inspected to see whether or not the material was filled up to the tip and formed as designed, and whether the ribs were defective or not was judged. . Uniformity of the thickness of the planned cleavage line The portion of the planned cleavage line on the back of the airbag storage unit cover is cut at right angles to the cleavage line with an ultrasonic cutter, and the thickness of the cleavage line is measured with a 20-fold magnifying glass with a scale. Observation was performed, and the case where the variation was less than 30% of the set thickness was evaluated as good, and the case where the variation was 30% or more was evaluated as poor. Also, at the same time visually observe the presence or absence of deformation such as swelling in the cover body around the cleavage line,
evaluated. The heat-fusible fusion interface with the decorative skin was peeled off, and the case where the propylene-based resin foam material was broken was evaluated as good, and the case where the propylene-based resin foam was peeled off at the fusion interface was evaluated as poor.

Inflating and deploying the airbag The airbag storage section and the airbag module are mounted on the mounting section on the back surface of the cover for the airbag storage section.
After leaving it in a constant temperature bath at 8 ° C for 8 hours, conduct an inflation and deployment test. If the airbag does not deploy properly, the cover is broken and scattered, or the mounting part is broken, it is defective. A case where such a problem did not occur was evaluated as good. Furthermore, the same test and evaluation were carried out after leaving in a constant temperature bath at + 85 ° C. for 8 hours.

Comparative Example 6 A sheet having a thickness of 3.5 mm formed by extruding an olefin-based thermoplastic elastomer from a T-die at an extrusion temperature of 180 ° C. was superimposed on a decorative skin inserted into a mold.
Stamping was performed at 0 ° C. For the obtained instrument panel, in the same manner as described above, the formability of the ribs in the cover for the airbag storage portion, the uniformity of the thickness of the planned cleavage line, and the heat sealability with the decorative skin are measured. The airbag was then evaluated for inflation and deployment by performing an inflation and deployment test. The results are shown in Table 1.

[0025]

[Table 1]

[0026]

According to the present invention, the work of integrating the cover for the airbag storage portion and the interior panel can be omitted, and the cover for the airbag storage portion is broken or scattered when the airbag is inflated and deployed. Of course, there is no airbag storage part that has a uniform thickness at the planned cleavage line, can reliably form the reinforcing ribs, and is also excellent in heat fusion with the decorative skin. And a method for manufacturing an automobile interior panel with a cover.

Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 53/02 C08L 53/02 (C08L 53/00 23:16) B29K 23:00 25:00 B29L 31:30

Claims (3)

[Claims] 1. An olefin-based thermoplastic elastomer and / or a styrene-based thermoplastic elastomer as a main component,
A thermoplastic elastomer material that has a melt flow rate of 10 g / 10 min or more, a flexural modulus of 50 to 1000 MPa, and does not break in a notched Izod impact test at -30 ° C. is supplied in a molten state into the cavity of a compression mold. And then compression molding to integrally manufacture the cover for the airbag storage section and the interior panel. 2. The method for manufacturing an automobile interior panel with a cover for an airbag storage section according to claim 1, wherein the thermoplastic elastomer material is supplied into the mold cavity by injection. 3. The production of an automobile interior panel with a cover for an airbag storage part according to claim 1, wherein a thermoplastic elastomer material is supplied after a decorative skin is inserted into the mold cavity in advance. Method.