JPH0872659A - Manufacture of module cover for storing air bag - Google Patents

Abstract

PURPOSE: To realize the molding where the filler is uniformly dispersed in a module cover by injecting the kneaded material of the measured thermoplastic material and the filler into a mold after the melting/kneading and the measurement are made in a heated cylinder. CONSTITUTION: In an injection molding machine 1, the thermoplastic material is fed from a first material feeding part 4 provided at the rear part of an injection molding equipment 2, and the filler is fed from a second material feeding part 7 provided approximately at the center of the injection molding equipment 2. In addition, in the melting/kneading and measurement process of the injection molding, a screw 10 of the injection molding equipment 2 is rotated to transfer the kneaded material to a measuring part 11 at the tip of a heated cylinder 3 while the material is melted and kneaded. In the process to measure the prescribed amount, the feeding of the thermoplastic material and the filler of the following one shot is simultaneously started, and the respective materials are fed at the specified speed so that the ratio of mixture of these materials may be constant, and the feeding is simultaneously completed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an airbag storage for storing an airbag for protecting an occupant, which is mounted on a steering wheel of a driver's seat, an instrument panel in front of a passenger seat, a door trim, etc. in a vehicle such as an automobile. A module cover for an air bag, characterized in that a kneading material composed of at least a thermoplastic material and a filler is directly molded without preliminarily kneading with an extruder or the like. It is about the method.

[0002]

2. Description of the Related Art An airbag system which is arranged on a steering wheel, an instrument panel, a door trim or the like of a vehicle such as an automobile for the purpose of protecting an occupant has been widely put into practical use. BACKGROUND ART An airbag system generally forms an air cushion between a driver and a steering wheel, etc., which inflates an airbag formed of a bag and cushions the impact when the vehicle undergoes an unexpected impact or a sudden deceleration. .
The airbag system is generally configured as an in-vehicle unit called an airbag module or an airbag unit, and is configured with an inflator (gas generator) that generates relatively high-pressure gas and a device in a folded state. An airbag housed inside and a module cover facing the vehicle interior are provided.

Module covers are generally called pad covers, storage pads, lids, cover doors or deployment doors, etc.
It functions as a case, a housing, or a cushioning material for accommodating the airbag, and when the airbag is deployed, the airbag is torn and deployed relatively easily due to the inflation of the airbag, thereby ensuring a smooth inflation of the airbag. In order to ensure the reliable and quick tearing and unfolding of the module cover, a tearing portion that promotes relatively easy tearing of the module cover, that is, a tear line is provided at a predetermined portion of the module cover. The tear line is generally formed by forming a slit or groove for cleaving on the back surface of the module cover and locally thinning the module cover. As a conventionally known module cover for accommodating an air bag, one using a urethane foam with a three-layer structure in which a reinforcing material such as a net or a base cloth is embedded as an insert material, a skin layer of a soft resin and a hard resin. There is a two-layer structure in which a resin core layer is integrally injection-molded.
As such a module cover, for example, Japanese Patent Laid-Open No.
JP-A-202550 discloses a module cover in which a skin layer and a hard resin core layer are integrally injection-molded by a two-color molding method, and a tear line is formed in the core layer.
Is disclosed. However, in the airbag-cover module cover made of urethane foam, it takes time and difficulty to embed the reinforcing material at a desired position, so that not only the productivity is low but also the reinforcing material is desired. There is a problem that the non-defective rate of the airbag-covered module cover buried in the position is low. In addition, the module cover for storing an air bag by the two-color molding method has a problem that it takes time to mold and a mold for a skin layer and a core layer is required, resulting in an increase in manufacturing cost. It was

On the other hand, recently, a module cover for accommodating an airbag having a one-layer structure obtained by injection molding a single material such as an olefin type thermoplastic elastomer or a polyester type thermoplastic elastomer is also known. There is. This module
Since the weight of the lumber is determined by the specific gravity of the material itself, there is a problem in weight reduction. Further, when these module covers are manufactured by injection molding, thin tear lines having a thickness of 0.4 to 1.4 mm for promoting the cleavage are provided on the central portion and side portions of the top surface of the module cover. Had to be formed.

[0005]

By the way, in the air bag device using the module cover as described above, the time required for the complete deployment of the air bag at a low temperature such as in winter is at room temperature in other seasons. It is pointed out that it will be significantly delayed compared to the full deployment time of. The inventors of the present invention have developed an injection-molded air bag storage module that is relatively easy to manufacture.
As a result of earnest studies on the complete deployment time in the lunar cover, the cause is that the factor that the gas generation rate of the inflator is slow at a low temperature is insignificant, rather, the tear line part is mainly urethane foam or olefin type. Since it is composed only of the soft resin composed of the thermoplastic elastomer, the material strength of the material itself constituting the module cover is increased, so that the strength of the tear line portion is increased, and the strength of the tear line portion is increased by the temperature. As a result, it was found that the influence of the factor that the cleavage takes time at low temperature is very strong as a result of being easily affected by. As a result of further earnest studies, the present inventors have found that at least the cleavage portion of a module cover made of a thermoplastic material and a filler has a true specific gravity of 0.28 to 0.70,
1 lightweight filler with pressure resistance of 50 kgf / cm ² or more
-50% by volume blended at least 100% tensile strength
By using a thermoplastic elastomer of f / cm ² or more or a module cover made of a thermoplastic resin, occupant protection performance can be stabilized by rapid and reliable tearing and deployment regardless of changes in environmental temperature. We have completed an airbag device that can be used for this purpose.

The module cover used in the airbag device of the present invention should satisfy the above conditions,
It does not depend on the one-layer structure or the two-layer structure. In order to obtain the module cover, a method has been used in which a thermoplastic material and a filler are preliminarily melt-kneaded and pelletized by an extruder or the like and injection-molded in a mold.

However, in the method of preliminarily melt-kneading and pelletizing the thermoplastic material and filler, the thermoplastic material is subjected to the heat history by the extruder and is again subjected to the heat history by the injection molding. Thermoplastic material,
In particular, a decrease in strength has occurred due to a decrease in the molecular weight of a thermoplastic resin such as a urethane type, a polyamide type, a polyester type or a thermoplastic elastomer. Further, when a hollow lightweight filler as a filler was blended with a thermoplastic material, the lightweight filler had its shape destroyed due to the shearing force of a screw of an extruder or the like. As a result, the molded airbag-cover module cover has a high specific gravity, which is problematic in terms of weight reduction. Therefore, for molding without heat history by the extruder, and for rapid and reliable cleavage and deployment of the airbag that is not affected by the temperature environment, the lightweight filler is uniformly dispersed in the molding module cover, Moreover, from the viewpoint of improving production efficiency, there has been a strong demand for a method capable of injection molding. Further, from the viewpoint of energy saving, it has been desired to eliminate the extrusion process economically.

By the way, in normal injection molding, a hopper
In the production of the present module cover, when a filler having a hollow shape is mixed, the diameter is 1.5 to 2.5 mm and the height is 4.5 to 2.5 mm.
5.5 mm cylindrical or 1.5-2.5 mm in diameter
Of a spherical shape and a specific weight of about 0.9 to 1.1, a pellet of thermoplastic elastomer, and a hollow light weight filler having an average particle diameter of 60 μm and a true specific gravity of 0.28 to 0.70, Since the materials having significantly different shapes and specific gravities are used, even if the materials are weighed and mixed in advance and stored in the hopper, the materials are separated from each other and the mixing ratio gradually changes. Therefore, the present invention solves various problems in the conventional manufacturing method of the module cover provided with the tear line that promotes cleavage as described above, and does not require preliminary kneading and pelletization by an extruder. The present invention provides a method for manufacturing a modular cover for accommodating an air bag, which is capable of molding in which a filler is uniformly dispersed in the modular cover.

[0009]

Therefore, as a result of intensive studies, in a method of manufacturing a modular cover for accommodating an air bag, which comprises at least a thermoplastic material and a filler, at least two materials of an injection molding device are used. Each of the thermoplastic material and filler individually metered from the supply unit is quantitatively supplied, melt-kneaded, and the kneaded material is injected to uniformly disperse the filler and have a hollow shape. In the case of a filler, it is found that its shape destruction is suppressed to a minimum, so that a lightweight molded airbag-covering modular cover can be manufactured, and in the present invention, as means for solving the above problems, A method for manufacturing an air bag storage module cover according to claim 1, comprising at least a thermoplastic material and a filler,
Module cover for airbag storage with a tear line
The present invention relates to a manufacturing method, wherein the thermoplastic material is quantitatively supplied from a first material supply section provided at a rear portion of a heating cylinder of an injection molding device in which a screw is arranged, and at the same time, a first portion provided at an intermediate portion of the heating cylinder is provided. (2) The filler is quantitatively supplied from the two-material supply unit, melt kneading and measuring are performed in the heating cylinder, and then the measured thermoplastic material and kneading material of the filler are placed in a mold. It is characterized by injection injection. Further, the manufacturing method of the module cover for accommodating an airbag according to claim 2 is characterized in that in claim 1, the thermoplastic material is completely melted in the second material supply section. Furthermore, the manufacturing method of the module cover for storing an airbag according to claim 3 is
The thermoplastic material according to claim 1, wherein the thermoplastic material is at least,
The tensile strength of the thermoplastic elastomer or the thermoplastic resin is 100 kgf / cm ² or more, and the module cover for accommodating the air bag has at least a true specific gravity of 0 as the filler in the thermoplastic elastomer or the thermoplastic resin. 28 ~ 0.70, compressive strength 50kgf / cm ²
It is characterized by being blended with the above lightweight filler. Next, in the method for manufacturing the module cover for accommodating an air bag according to claim 4, in claim 3, the thermoplastic elastomer is a thermoplastic resin containing urethane as a main component or a thermoplastic resin made of polyamide. The light-weight filler is a glass balloon.

[0010]

According to the present invention, with the above-described structure, in the injection molding machine 1, the thermoplastic material is supplied from the first material supply section 4 provided at the rear part of the injection molding apparatus 2, and the filler is the injection molding apparatus 2. It is supplied from the second material supply unit 7 provided at the substantially center. Further, the melt-kneading and measuring step of injection molding, that is, the screw 10 of the injection-molding apparatus 2 rotates, the kneading material is transferred to the measuring section 11 at the tip of the heating cylinder 3 while melt-kneading, and a constant amount is measured. During the process, the next one shot of the thermoplastic material and filler are simultaneously started so that the mixing ratio of these materials becomes constant.
It is desirable to supply each material at a constant rate and complete the supply at the same time, but it suffices that the mixing ratio becomes constant, and the method for supplying the thermoplastic material and the filler is not limited thereto. That is, when the thermoplastic material quantitatively supplied from the first material supply section 4 is transferred to the front by the screw 10 and becomes a molten state, the filler is quantitatively supplied from the second material supply section and kneaded. Then, by injecting into a mold and molding, a modular cover for accommodating an air bag in which a filler is uniformly mixed with a thermoplastic material can be obtained. In this way, the module cover of the present invention does not undergo the pre-melting and kneading step using the extruder, so that it is not necessary to pelletize the thermoplastic material and the damage due to heat history is minimized. It is also economically advantageous, the dispersibility of the filler in the thermoplastic material is uniform and good, and it is fast under a wide range of environmental temperatures from low to high without being affected by environmental temperature. A module cover for accommodating an air bag that is surely cleaved and deployed by the above is provided.

[0011]

EXAMPLES Examples of the present invention will be described below. (1) Thermoplastic material. The thermoplastic material used in the present invention is not particularly limited as long as it has a tensile strength of 100 kgf / cm ² or more, but preferably a thermoplastic elastomer containing urethane as a main component. -Based elastomers, styrene-based elastomers containing styrene as a main component or hydrogenated products thereof, vinyl chloride-based elastomers containing vinyl chloride as a main component, ester-based elastomers containing polyester as a main component, polyamide-based elastomers containing polyamide as a main component, One type of elastomer or a mixture of two or more types of elastomers selected from the group consisting of olefin elastomers containing polyethylene, polypropylene or the like as a main component can be mentioned. Further, as the thermoplastic resin, nylon 11, nylon 12, nylon 6/12, ABS (acrylonitrile butadiene styrene) resin and the like are preferably used.
Furthermore, these thermoplastic elastomers and thermoplastic resins may be mixed and used at an appropriate ratio. As the urethane-based elastomer, ether-based, ester-based,
A polycarbonate type can be preferably used. In the present invention, the thermoplastic material, if necessary, a flame retardant, an antioxidant, an antistatic agent, a colorant, an ultraviolet absorber, a plasticizer,
Various additives such as a foaming agent can be added. Examples of flame retardants include inorganic flame retardants such as antimony trioxide, aluminum hydroxide, magnesium hydroxide, antimony pentoxide, and zirconium oxide, phosphoric acid ester flame retardants, halogen-containing phosphoric acid ester flame retardants and other phosphorus flame retardants. Examples of the flame retardant include bromine flame retardants, chlorinated paraffin, and chlorine flame retardants such as perchlorocyclodecane. Antioxidants include light stabilizers, metal deactivators, chain initiation inhibitors such as antiozonants, phenolic antioxidants, radical scavengers such as amine antioxidants, sulfur antioxidants, phosphorus. Examples thereof include peroxide decomposers such as system antioxidants. Examples of the antistatic agent include various surfactants and polymers having a functional group. As the colorant, any of pigments and dyes can be used, and usable pigments include azo organic pigments such as poorly soluble azo lakes, phthalocyanine organic pigments such as phthalocyanine blue, and anthraquinone-based slene organic pigments. , Dyeing lake organic pigments such as basic dyes, other organic pigments, oxide inorganic pigments such as titanium, chromic molybdic acid inorganic pigments such as yellow lead,
Examples include sulfides such as cadmium yellow, selenide-based inorganic pigments, ferrocyan-based inorganic pigments such as navy blue, and other inorganic pigments.Dyes that can be used include azo-based, anthraquinone-based, and quinophthalone-based oil-soluble dyes. And water-soluble dyes. As the ultraviolet absorber, salicylate-based, benzophenone-based, benzotriazole-based,
Examples include cyanoacrylate-based and nickel chelate-based UV absorbers. Examples of the plasticizer include phthalic acid plasticizers, fatty acid plasticizers, phosphoric acid plasticizers, adipic acid plasticizers, polyester plasticizers, and epoxy plasticizers.

(2) Filler. The filler used in the present invention has an average particle size of 10
There is no particular limitation as long as it is 0 μm or less, but calcium carbonate (heavy calcium carbonate, chalk, chalk), aluminum silicate (carion clay, wax stone clay), magnesium silicate (talc), silica (silica sand, Diatomaceous earth, amorphous silica, wet white carbon, dry white carbon), basic magnesium carbonate, aluminum hydroxide (alumina hydrate), precipitated barium sulfate, zinc oxide, aluminum oxide, carbon black, mica,
Glass sphere, wood powder, recycled rubber, Evo powder, modified melamine resin, glass fiber, milled fiber, carbon fiber, specific gravity 1
The following lightweight fillers (glass balloons, shirasu balloons, fly ash balloons, pearlite balloons, silica balloons and other silicic acid type inorganic balloons, non-silicic acid type inorganic balloons, thermosetting organic balloons, thermoplastic organic balloons) and the like can be mentioned. . Among them, glass spheres, which are smooth and uniform, and whose particle surface easily wets, and lightweight fillers having a specific gravity of 1 or less are preferable. Further, among these fillers, a lightweight filler having a true specific gravity of 1 or less, which has an effect of reducing the specific gravity of the compound, is preferable. Further, among these lightweight fillers, glass balloons having an excellent effect of reducing specific gravity and excellent pressure resistance are most preferable. Furthermore, the true specific gravity is 0.28 to 0.7
A glass balloon having a porosity of the particle surface of 0, a smooth and uniform particle surface, and a particle surface which is easily wetted can be most preferably used. If the true specific gravity is less than 0.28,
The pressure resistance of glass balloons is often less than 50 kgf / cm ^2, and when melt-kneading with a thermoplastic resin or thermoplastic elastomer, the glass balloon is destroyed in the process and the specific gravity of the module cover for storing the airbag is increased. Is not preferable, and on the other hand, when the true specific gravity exceeds 0.70, the effect of reducing the specific gravity of the airbag-housing module cover is not always sufficient. The average particle diameter of the filler is preferably 100 μm or less. Average particle size is 1
If it exceeds 00 μm, the surface of the module cover, especially the surface of the tear line portion which is a thin portion becomes uneven, which is not preferable in appearance. As the compounding amount of the filler, it is necessary that the compounding amount in the thermoplastic resin or the thermoplastic elastomer is 1 to 50% by volume based on the entire compound.
Below 1% by volume, if the airbag device is used, it is -40
The complete development time at ℃ becomes slower than at room temperature (room temperature), the effect of rapid cleavage expansion is not sufficient, and 50% by volume
In the above cases, the tensile strength of the compound is too low to be practical.

(3) Coating. The surface of the module cover may be coated to improve texture and durability. As the paint, it is preferable to use urethane-based paint.

(4) A method for producing a module cover. As a material supply method in the manufacturing method of the module cover for storing the airbag of the present invention, a pellet-shaped thermoplastic material is introduced from the first material supply section 4 provided at the rear part of the heating cylinder 3 of the injection molding apparatus 2. . The charged thermoplastic material is rotated by the screw 10 in the heating cylinder 3,
It is melted while being transferred to the front, and reaches the second material supply unit 7 provided in substantially the middle portion of the heating cylinder 3 of the injection molding device 2. At this time, a lightweight filler, which is weighed so as to have a desired mixing ratio, is charged from the second material supply unit 7 at a constant speed. The injected lightweight filler is easily wrapped in the molten thermoplastic material, and because shearing force is not applied, destruction of the hollow shape is suppressed to a minimum, and the screw 10 is rotated while being transferred forward, The mixture is uniformly mixed and gradually accumulated in the measuring unit 11 at the front end of the heating cylinder 3. When the set amount of accumulated one shot is reached, the accumulated kneading material is injected and injected into the mold K through the injection nozzle 12 attached to the tip of the heating cylinder 3 by the forward movement of the screw 10. A module cover for storing an airbag is manufactured.

In such a manufacturing method, for example, as compared with the case where the mixed material measured at a desired mixing ratio is simultaneously charged from the first material supply section 4, the light weight filler has a heating cylinder 3.
There is no risk of being pinched or compressed between the inner wall and the screw 10, and because it is not crushed by the pellet-shaped thermoplastic material, the hollow lightweight filler is minimally broken. It is a preferable manufacturing method because it is not necessary to use a screw having a special structure to improve the dispersibility of the lightweight filler.
A preferred airbag bag module cover is manufactured.

The dispersibility and shape destruction rate of the lightweight filler were determined by the following methods. Dispersibility is a molded module
100 rugs were produced, and each was visually inspected.
If there are also individual pieces, they are considered defective products, and if none, they are considered good products. From this result, 100 of the total number of checked non-defective products
Divide by and multiply by 100 to get the percentage of good products. Therefore, if this percentage figure is 100, it means that there are no defective products. As for the shape destruction rate, 10 pieces were sampled from one predetermined module cover from different predetermined locations, the specific gravities of the respective pieces were measured, and the average value of the measured specific gravities was obtained. On the other hand, when the shapes of the thermoplastic elastomer and the lightweight filler do not break, and the specific gravity at the time of breaking is known, and since the blending volume% of the lightweight filler to the thermoplastic elastomer is also known, for example, the lightweight filler The calculated specific gravity and the like of the manufactured product when the hollow shape is not broken at all are required. From the results of these specific gravities, the shape fracture volume% is calculated when the blending volume% of the lightweight filler to the thermoplastic elastomer is regarded as 100 volume%. This shape destruction volume%
The higher the value, the more the shape of the lightweight filler is destroyed.

<Embodiment 1> As operating conditions of the injection molding machine 1 shown in FIG. 1, the temperatures of the first material supply section 4 to the second material supply section 7 of the heating cylinder 3 are 180 to 200 ° C. and the second material. The temperature of the supply unit 7 to the metering unit 11 is 200 to 210 ° C., the screw driving device 13 provided with the screw rotation driving motor 14 sets the rotation speed of the screw to 50 rpm, and the in-line screw is set. From the hopper 6 of the first material supply section 4 which communicates with the rotating screw 10 inside the heating cylinder 3 through the drop port 5 at the rear of the automatic injection device 2, the Shore indentation hardness 79A, the specific gravity 1.09 and the tensile strength 290 kgf.
A pellet type urethane-based thermoplastic elastomer (ether type) having a pressure of / cm ² is supplied, and the inside of the heating cylinder 3 is filled with the urethane-based thermoplastic elastomer. The filled urethane-based thermoplastic elastomer is transferred by the screw 10, and is accumulated and measured in the measuring unit 11 in a molten state.
The measured urethane-based thermoplastic elastomer is ejected from the injection nozzle 12 by the forward movement of the screw 10. Next, the screw 10 starts to move backward while rotating, and at the same time, one shot of each urethane-based thermoplastic elastomer is weighed so that the compounding amount of the glass balloon with respect to the air bag accommodating module cover 15 is 19% by volume. At the same time when the supply of the first material from the hopper 6 of the first material supply section 4 is started, the screw 10 of the second material supply section 7
A true specific gravity of 0.
38, supply of a glass balloon having a pressure resistance of 281 kgf / cm ² is started. Each of the materials that have been started to be supplied is continuously supplied at a constant rate, and at the same time, the supply is completed. At this time, the urethane-based thermoplastic elastomer transferred in the second material supply section 7 was in a semi-molten state. Rotating screw-1
By 0, the kneaded material which is gradually and uniformly mixed is forwardly transferred, accumulated in the measuring unit 11, and measured. Then, this kneaded material is injected into the injection nozzle 1 at a maximum pressure of 80 kgf / cm ^2.
It is injected from 2 and filled in the mold K. This series of operations is repeated several times until the mixing ratio of the materials becomes stable. As a result, as shown in FIG. 2, the wall thickness is 0.6 mm.
Overall top surface 17 having groove 16 for the tear line of
A module cover 15 for storing an air bag having a thickness of 4.0 mm was molded. Furthermore, the surface was painted with urethane paint. In this way, the specific gravity of the obtained molded product was 1.01, the dispersity of the glass balloon was 100%, and the shape destruction rate of the glass balloon was 7%. As a result of visual observation of the tear line grooves 16 and the top surface portion 17 with a magnification of 350 using an electron microscope, the glass balloons were uniformly dispersed. Further, the melt-kneaded material was sampled from the injection nozzle 12, and the molecular weight distribution of the urethane-based thermoplastic elastomer was measured by a general-purpose molecular weight measuring device. As a result, almost no molecular breakage of urethane was confirmed.

<Embodiment 2> As the operating conditions of the injection molding machine 1 shown in FIG. 1, the temperature of the first material supply section 4 to the second material supply section 7 of the heating cylinder 3 is 180 to 230 ° C. and the second material is supplied. According to the same manner as in Example 1, except that the temperature of the supply unit 7 to the measuring unit 11 was 220 to 230 ° C. and the urethane-based thermoplastic elastomer transferred in the second material supply unit 7 was in a molten state. A molded product of the bag cover module cover 15 was obtained. The specific gravity of this molded product was 1.00, the dispersity of the glass balloon was 100%, and the shape destruction rate was 5%.
Met. As a result of visual observation of the tear line grooves 16 and the top surface portion 17 with a magnification of 350 using an electron microscope, the glass balloons were uniformly dispersed.

<Example 3> As the thermoplastic elastomer, an olefinic thermoplastic elastomer having a Shore indentation hardness of 80 A, a specific gravity of 0.97 and a tensile strength of 117 kgf / cm ² was used, and the module cover 1 for storing an air bag was used.
A molded article of the airbag-containing module cover 15 was obtained in the same manner as in Example 2 except that the compounding amount of the glass balloon with respect to 5 was 12% by volume. The specific gravity of this molded product was 0.91, the degree of dispersion of the glass balloon was 100%, and the shape destruction rate thereof was 7%. As a result of visual observation of the tear line grooves 16 and the top surface portion 17 with a magnification of 350 using an electron microscope, the glass balloons were uniformly dispersed.

Example 4 As a thermoplastic material, Shore indentation hardness 57D, specific gravity 1.15 and tensile strength 527 kg.
Urethane-based thermoplastic elastomer (f-cm ²⁾
A molded article of an air bag containing module cover was obtained in the same manner as in Example 2 except that the tel type was used. The specific gravity of this molded product was 1.04, the degree of dispersion of the glass balloon was 100%, and the shape destruction rate thereof was 5%. As a result of visual observation of the tear line grooves 16 and the top surface portion 17 with a magnification of 350 using an electron microscope, the glass balloons were uniformly dispersed.

Example 5 As a thermoplastic material, Rockwell indentation hardness 80, specific gravity 1.02 and tensile strength 400
A molded article 15 of a module cover for storing an airbag was obtained in the same manner as in Example 2 except that nylon 12 having kgf / cm ² was used. The specific gravity of this molded product is 0.94
The glass balloon had a dispersity of 100% and a shape destruction rate of 5%. As a result of visual observation of the tear line grooves 16 and the top surface portion 17 with a magnification of 350 using an electron microscope, the glass balloons were uniformly dispersed.

Comparative Example 1 A urethane type thermoplastic elastomer (ether type) having a Shore indentation hardness of 79 A, a specific gravity of 1.09 and a tensile strength of 290 kgf / cm ² and a true specific gravity of 0.3.
8. Measure the compounding amount of the glass balloon having a pressure resistance of 281 kgf / cm ² into the molded air bag module cover 15 to be 19% by volume, and set the cylinder temperature to 1
The mixture was fed to a general-purpose twin-screw extruder (not shown) at 60 to 210 ° C and a screw rotation speed of 50 rpm, melt-kneaded, and pellets were prepared. The temperature of the heating cylinder 3 is 1
80 to 200 ° C, the rotation speed of the screw 10 is 50 rp
m, the maximum injection pressure is 80 kgf / cm ² and is supplied from the material supply section of an injection molding machine (not shown) having one general-purpose material supply section under operating conditions. As shown, the overall top surface 17 having tear groove 16 with a wall thickness of 0.6 mm has a thickness of 4.0 m.
The module cover 15 for storing an airbag of m was molded. Furthermore, the surface was painted with urethane paint. The specific gravity of this molded product was 1.09, the degree of dispersion of the glass balun was 100%, and the shape destruction rate thereof was 30%. Since the pellets were produced by the twin-screw extruder, the production efficiency was poor. Further, the molten kneaded material was sampled from the injection nozzle 12, and the molecular weight distribution of the urethane-based thermoplastic elastomer was measured by a general-purpose molecular weight measuring device.
Urethane molecular cleavage was confirmed.

<Comparative Example 2> Using the material used in Example 1, the temperature of the heating cylinder is 180 to 200 ° C, the rotation speed of the screw 10 is 50 rpm, and the maximum injection pressure is 80 kgf.
General-purpose injection molding machine under operating conditions of / cm ² (not shown)
From the material supply section in the rear part, urethane thermoplastic elastomer (ether system) and glass balloon, which are weighed for one shot, are simultaneously supplied, and the supply is continued at a constant speed, and At the same time, the supply is completed and, as in the general injection molding method, as shown in FIG. 2, the overall top surface portion 17 having the groove portion 16 for the tear line having a wall thickness of 0.6 mm has a thickness of 4. A module cover 15 for storing a 0 mm airbag was molded. Furthermore, the surface was painted with urethane paint. In addition, at the time of supplying the material, the compounding amount of the glass balloon with respect to the airbag-containing module cover 15 was measured to be 19% by volume. In this way, the specific gravity of the obtained molded product was 1.04, the dispersity of the glass balloon was 98%, and the shape destruction rate of the glass balloon was 13%.

<Comparative Example 3> Using the materials used in Example 4 and using a general-purpose injection molding machine (not shown) under the same operating conditions as in Comparative Example 2, the same as in Comparative Example 2 was performed. As shown in FIG. 2, according to the material supplying procedure and the injection molding method, the entire top surface portion 17 having the groove portion 16 for the tear line having a thickness of 0.6 mm has a thickness of 4.0 mm for accommodating the airbag. A module cover 15 was molded. Further, the surface was treated with a primer and then coated with a urethane-based paint. The specific gravity of the obtained molded product was 1.18, the dispersity of the glass sphere was 100%, and the shape destruction rate of the glass sphere was 64%.

[0025]

As described above in detail, in the present invention, in the method for manufacturing the airbag-covered module cover having the tear line for promoting the tearing, at least a thermoplastic material and a filler are used, In the method of manufacturing a modular cover for storing an air bag provided with a tear line, at the same time as quantitatively supplying the thermoplastic material from the first material supply unit provided at the rear of the heating cylinder of the injection molding device,
The filler is quantitatively supplied from a second material supply unit provided in the middle portion of the heating cylinder, melt kneading and weighing are performed, and then the measured thermoplastic material and filler are measured.
Since the resin was injected and injected into the mold for molding, a module cover in which the filler was uniformly blended with the thermoplastic material was obtained. As described above, in the method for manufacturing the airbag-cover module cover of the present invention, since the preliminary melt-kneading step using the extruder is not performed, it is not necessary to pelletize the thermoplastic material, and the thermal history is not required. It is possible to minimize the damage due to, and it is lightweight and economically advantageous, and the dispersibility of the filler in the thermoplastic material is uniform and good. (EN) Provided is a modular cover for accommodating an air bag which can be rapidly and surely cleaved and deployed even under a wide range of environmental temperatures up to high temperatures.

[Brief description of drawings]

FIG. 1 is a partial schematic cross-sectional view of an injection molding machine according to the present invention.

FIG. 2 is a schematic cross-sectional view of an airbag storing module cover according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Injection molding machine 2 Injection molding apparatus 3 Heating cylinder 4 First material supply part 5,8 Drop opening 6,9 Hopper 7 Second material supply part 10 Screw 11 Measuring part 12 Injection nozzle 13 Screw drive device 14 Screw Rotation drive motor 15 Air bag storage module cover 16 Groove 17 Top surface K Mold

Claims (4)

[Claims] 1. At least a thermoplastic material and a filler.
In the method of manufacturing a modular cover for storing an air bag provided with a tear line, the thermoplastic material is quantitatively supplied from the first material supply unit provided at the rear of the heating cylinder of the injection molding device, and at the same time, Quantitatively supplying the filler from the second material supply unit provided in the middle of the heating cylinder,
After performing melt-kneading and measuring in the heating cylinder, the measured thermoplastic material and the kneading material of the filler are injection-injected into a mold to produce a module cover for storing an air bag. Method. 2. The thermoplastic material is completely melted in the second material supply section.
A method for manufacturing the module cover for storing an airbag according to. 3. The thermoplastic material is made of a thermoplastic elastomer or a thermoplastic resin having a tensile strength of 100 kgf / cm ² or more, and the airbag-covering module cover is made of the thermoplastic elastomer or the thermoplastic resin. The filler is a lightweight filler having a true specific gravity of 0.28 to 0.70 and a compressive strength of 50 kgf / cm ² or more.
A method for manufacturing the module cover for storing an airbag according to. 4. The thermoplastic elastomer is a thermoplastic elastomer containing urethane as a main component, the thermoplastic resin is a polyamide, and the lightweight filler is a glass balloon. A method of manufacturing the airbag-cover module cover according to claim 3.