FR2655908A1 - Enclosure containing a pneumatic safety cushion for a vehicle - Google Patents

Abstract

The enclosure according to the invention comprises a surface skin layer (1A) made of a thermoplastic polymer containing (A) a hydrogenated derivative of a block copolymer comprising styrene and a conjugated diene; (B) an olefinic resin; (C) a polyisobutylene of viscosity-average molecular mass not greater than 70,000; and (D) a plasticising agent for rubbers of the hydrocarbon series, of kinetic viscosity at 40 DEG C not higher than 500 cSt, and/or polybutene with a number-average molecular mass not exceeding 2500, the ratio of the mixture (by weight) being (A) = 40-80 %, (B) = 5-30 %, (C) = 2-30 %, (D) = 0-20 %, and having a hardness JIS6-A according to JIS-K6301 of 20-90, and a core layer (1B), made of an olefinic resin which has a flexural modulus according to JIS-K7203 of 9.8x10<7> - 6.9x10<8> Pa. The layer (1B) has a hardness greater than that of the layer (1A) and has a part adapted to the easy bursting of the enclosure when the actuation of the cushion begins.

Description

ENVELOPE CONTAINING A PNEUMATIC SAFETY CUSHION FOR
VEHICLE
The present invention relates to a casing for containing a pneumatic air bag, which is actuated to expand and expand upon collision of a vehicle by sensing impact shock, deformation or the like. , caused by the collision.

An envelope of this type, containing a safety pad, is generally provided with a reinforcing material, such as nets (see, for example, Japanese Patent Publications Sho 62-234 764,
Sho 50-127 336, and Utility Model Publications
Japanese Sho 52-80 928, Sho 50-43 454 and Sho 51-25 342)
The shell with the net-like inserts is usually made by preparing an entire shell with a relatively low strength material, such as a foamed polyurethane, and providing the entire shell with reinforcing nets. Lines, not provided by the reinforcing threads, are generally arranged so that the air bag can be developed smoothly during expansion for easy breakage of the casing.

In addition, the Publication of the Utility Model
Japanese Sho 52-76 042 offers an envelope containing a pneumatic cushion, comprising two layers, namely a superficial skin layer, made of rigid urethane foams, to ensure a fine finish of the surface, and a core layer, made of low density urethane foams (high expansion ratio), to soften the entire casing in which slits (lines to smoothly develop the airbag during expansion) are arranged to extend from the core layer up to part of the superficial skin layer.

Among the conventional envelopes containing pneumatic cushions described above, the envelope containing an air cushion, provided with the thread-like inserts, poses the problem that its manufacture requires a number of steps and is inconvenient, than to manufacture at the same time. High precision is difficult even by using, for example, urethane expansion molding (RIM - reactive injection molding process), the manufacturing efficiency is low, and the cost is high, since the reinforcements of type nets are introduced.

In addition, the envelope, as described in the Japanese Utility Model Publication
Sho 52-76 042 has a superficial skin layer made of rigid urethane foams (ASTM-D2240, Shore hardness 30-40) and, therefore, it cannot provide a soft feeling, but gives an unpleasant feeling when A part of a driver's body is in contact with it, for example, while driving the vehicle. In addition, since the urethane-based material has low impact impact resistance and no reinforcing inserts are provided, broken pieces are scattered during the expansion of the airbag. .

The object of the present invention is to provide a solution to the previous problems of the envelope containing a pneumatic cushion of the prior art and to provide an envelope containing an air cushion having characteristics such that the superficial skin layer is flexible and gives a feeling of flexibility, that the core layer retains a shape capable of withstanding external pressure, that the casing is easily broken during the expansion operation of the air bag, but that it does not shatter into pieces broken in a temperature range of -40 C to +80 C, and it also shows satisfactory breaking performance by hardly changing appearance within the temperature range specified above even after being for a long time at an elevated temperature of 1100C and for 1000 hours, having regard to the actual assembly of a vehicle, which can be achieved by means of a simple molding process, such as molding e by injection, in high efficiency, with a method which does not lead to defective products, with high precision, with high productivity, and with satisfactory economic advantages.

The envelope containing a pneumatic cushion according to the present invention comprises - a superficial skin layer, made of a
thermoplastic polymer containing the ingredients
following A, B, C and D
ingredient A: a hydrogenated derivative of a copolymer
block comprising styrene and a
conjugated diene,
ingredient B: an olefinic resin,
ingredient C: a polyisobutylene having a mass
molecular viscosity average no
greater than 70,000, and
ingredient D: a rubber plasticizer of
the series of hydrocarbons, having a
kinetic viscosity at 400C not higher
greater than 500 cSt, and / or polybutene
having an average molecular mass of
number not exceeding 2,500,
in which the mixing ratio is
ingredient A = 40 to 80% by weight,
ingredient B = 5 to 30% by weight,
ingredient C = 2 to 30% by weight,
ingredient D = 0 to 20% by weight, and
having JIS6-A hardness according to JIS-K6301 ranging from 20 to
90, and - a core layer, made of an olefinic resin
having a flexural modulus according to JIS-K7203 ranging from
9.8 x 107 to 6.9 x 108 Pa (1000 to 7000 kg / cm2), wherein said core layer has a hardness greater than that of said surface skin layer, and said core layer is provided with parts adapted for easy bursting or easy tearing of the casing when starting the actuation of the air bag.

The present inventors have made serious researches to achieve the foregoing object and, as a result, they have accomplished the present invention, on the basis of the finding that the above-mentioned object can be achieved by using a layer of specific surface skin and a specific core layer and providing the core layer with easily burst portions, for example, with weakened shapes.

In the casing containing the airbag according to the present invention, since the relatively stiff core layer is covered by the soft surface skin layer, it provides flexibility and does not give an unpleasant feeling when the body of a conductor is in contact with the casing. In addition, since the core layer is rigid, the casing is neither deformed nor broken, even when some external force is exerted.

In the casing according to the present invention, when the pneumatic bag of the casing is expanded, for example during a collision of a vehicle, in a temperature range from -40 C to +80 C, the casing bursts along the weakened forms of bursting of the envelope, previously arranged at the level of the core layer. Upon bursting of the casing, since the rigid core layer is covered by the soft surface skin layer in close contact with it, the broken pieces of an envelope upon bursting are not scattered .

In addition, the casing according to the present invention exhibits satisfactory breaking performance and hardly shows any change in appearance in the above-mentioned temperature range (-40 C - +80 C) even after 500 hours have elapsed at 110 C, such conditions being taken into account as actual conditions of assembly of a vehicle.

- Figure 1 of the accompanying drawing is a schematic view
in front elevation, partially in cross section
versale, representing an envelope containing a
air cushion as an embodiment
preferred according to the present invention, in the
position attached to an air bag, and - Figure 2 is a rear elevational view of
the envelope containing the pneumatic cushion.

The present invention will now be described in more detail.

In the drawing, there is shown an envelope 1 containing an air bag, an air bag 2, an inflator 3, an annular retainer 4, a base retainer 5, a plate 6, a rivet 7, a diaper of superficial skin 1A, a core layer 1B, and continuous puncture type slits 1C,
As shown in the drawing, the envelope containing an airbag according to the present invention uses, as the surface layer 1A, a surface skin layer, made of a thermoplastic polymer (thermoplastic elastomer) containing the following ingredients AD, in the ratio of following mixture and having JIS-A hardness according to JIS-K630 ranging from 20 to 90
Ingredient A: a hydrogenated derivative of a block copolymer
comprising styrene and a conjugated diene =
48 to 80% by weight;
Ingredient B: an olefinic resin = 5 to 30% by weight,
Ingredient C: a polyisobutylene having a mass
molecular viscosity average no
greater than 70,000 = 2 to 30 by weight,
Ingredient D: a plasticizer for the rubbers of
series of hydrocarbons, having a viscosity
kinetics at 400C not greater than 500 cSt
and / or a polybutene having a mass
molecular number average not exceeding
2500 = 0 to 20% by weight.

Furthermore, a core layer, made of an olefinic resin, having a flexural modulus in accordance with
JIS-K7203 ranging from 9.8 x 107 to 6.9 x 108 Pa (1000 to 7000 kg / cm2), is used as the core layer 1B.

The core layer 1B has a higher hardness than the surface skin layer 1A, and the core layer 1B has weakened shapes 1C, for example, notch-type reduced thickness shapes or shapes. puncture-like slits, as easy bursting parts when starting the actuation of the air bag.

In the present invention, as ingredient A of the thermoplastic elastomer used as a constituent material of the surface skin layer 1A, there may be mentioned a hydrogenated derivative of a styrenic block copolymer, typically represented for example by the general formula
XY,
X-CY-X), or
X (-YX) nY where: - X represents a polymer block of styrene, - Y represents an elastomeric polymer block of diene
conjugated, and - n is an integer ranging from 1 to 5.

As the monomer of the conjugated diene for the polymer block Y in each of the formulas, butadiene or isoprene are suitable, and a mixture thereof can also be used. In addition, the ratio of ingredient A of the styrene polymer block X in the entire block copolymer is usually 5 to 40% by weight and preferably 10 to 35% by weight. If the ratio is less than 5% by weight, the surface skin layer has a reduced mechanical strength, it breaks easily during the expansion of the air bag, and it is deformed by the external pressure to leave traces thereof. . On the other hand, if it exceeds 40% by weight, it is not practically feasible since the feeling of suppleness of the surface skin layer is poor.

It is preferred that the number average molecular weight of polymer block X is in a range of 5000 to 125,000, and that the number average molecular weight of polymer block Y is in a range of 15,000 to 250. 000.

Various processes have been proposed for the preparation of the hydrogenated derivative of the styrenic block copolymer represented by the general formula described above, and typical processes can be mentioned, as described, for example, in the Patent Publications.
Japanese Sho 42-8704 and 43-6636.

In the present invention, a hydrogenated derivative in which at least 50%, preferably more than 80% of the olefinic double bonds of the polymer block Y are hydrogenated and less than 25% of the double bonds of the polymer Y block are hydrogenated upon Preparation, is preferred as ingredient A. As block copolymers, commercially available polymers can be used, for example, KRATON-G (Shell Chemical Co.), KL (Kurare Co.) and TAFTEC. (Asahi Kasei Co.).

As ingredient B, preferred is a homopolymer or copolymer of an α-olefin, such as ethylene, propylene and butene-1.

As ingredient C, preferred is a polyisobutylene of high molecular weight, having hardly any double bonds in the molecular chain and having the linking structure.

Polyisobutylene for ingredient C has a viscosity average molecular weight of not more than 70,000 and preferably not more than 50,000. If the viscosity average molecular weight exceeds 70,000, this is not preferred, since this leads to the disadvantage that the resulting surface skin layer exhibits poor soft feeling and poor moldability. As the polyisobutylene suitable for ingredient C, a commercially available polymer can be used, for example TETRAX (Nippon Petrochemical Co.) and BISTANEX (Exon Chemical Co.).

Ingredient D is a rubber plasticizer of the hydrocarbon series, having a kinetic viscosity at 40 ° C not exceeding 500 cSt, specifically a diluent oil or a paraffinic or naphthenic plasticizing oil and / or a polybutene having a mass. Number average molecular weight not exceeding 2500, preferably not exceeding 2000, suitably comprising mainly isobutylene and n-butene partially copolymerized therewith.

If the kinetic viscosity of the plasticizer of the hydrocarbon series rubbers for ingredient D exceeds 500 cSt, this leads to the disadvantage that the moldability of the surface skin layer material is decreased. On the other hand, if the molecular weight of the polybutene exceeds 2500, this also leads to the disadvantage of poor moldability.

Ingredient D can be a mixture of a hydrocarbon series rubber plasticizer and a polybutene.

In the present invention, the mixing ratio of AD ingredients is as shown below
Ingredient A = 40 to 80% by weight, preferably
60 to 75% by weight,
Ingredient B = 5 to 30% by weight, preferably
10 to 20% by weight,
Ingredient C = 2 to 30% by weight, preferably
5 to 20% by weight,
Ingredient D = 0 to 20% by weight, preferably
0 to 15% by weight.

If the styrenic block polymer of ingredient A is present in an amount of less than 40% by weight, the resulting surface skin layer fails to exhibit the feeling of flexibility. On the other hand, if it is present in an amount of more than 80% by weight, the resulting thermoplastic elastomer exhibits poor moldability.

If the olefinic resin of ingredient B is present at less than 5% by weight, the molding stability of the resulting thermoplastic elastomer and the adhesion between the surface skin layer and the core layer are poor. On the other hand, if it is present in an amount of more than 30% by weight, the feeling of suppleness of the resulting surface skin layer is poor.

If the polyisobutylene as ingredient C is present at less than 2% by weight, the soft feeling and moldability are poor. If it is present in an amount of more than 30% by weight, this is not preferred since the surface becomes sticky and the physical strength is lowered.

If the plasticizer of hydrocarbon series rubbers and / or polybutene as ingredient D is (or are) present in an amount of more than 20% by weight, this leads to an undesirable appearance (deformation ) or the like, after 1000 hours has elapsed at 110 C, and causes failure in breaking, in other words, rupture of parts other than the predetermined weakened parts or scattering of the broken pieces during breaking. expansion of the air bag to -40 C.

In the present invention, a thermoplastic polymer is chosen constituting the surface skin layer 1A, with a JIS-A hardness ranging from 20 to 90.

If the hardness is less than the range specified above, the moldability (for example, injection moldability) and mechanical strength are poor, which leads to easy destruction, although the flexibility is. satisfactory. On the other hand, if the hardness exceeds the above-mentioned range, it is not practically achievable since the soft feeling is poor, although there are no moldability problems. The hardness chosen within a range of 20 to 90, although varying depending on the thickness of the surface skin layer, is preferably in a range of 30 to 70, and, more preferably 40 to 65.

The thermoplastic elastomer comprising the ingredients A-D for the surface skin layer 1A of the present invention can be prepared by mechanical melt kneading. Specifically, conventional melt kneading devices, such as Banbury mixers, various kinds of kneaders and extruders, can be used. In the present invention, the constituent materials of the surface skin layer can comprise, in addition to the AD ingredients, various kinds of other resins, elastomers, various kinds of fillers, such as glass fibers, talc, carbonate of calcium, silica and mica, pigments and stabilizers charged by a usual method, as long as the hardness is kept within the range mentioned above.

The thickness of the surface skin layer 1A usually varies depending on the parts of the shell 1, and it is not completely uniform over the entire surface. In the present invention, it is preferred that parts of more than 70%, preferably more than 80% of the surface of the superficial skin layer 1A, have a thickness of more than 0.5 mm. Although there is no particular restriction for the upper limit of the thickness, it is suitable to keep the thickness at a value less than about 10mm, for example, considering the model, economic properties, the soft feeling, running performance and moldability of the air bag.

Further, for the purpose of improving the feeling of flexibility and reducing the weight of the surface skin layer 1A, expansion in a ratio of less than about 3.0 times can be applied.

In the present invention, the olefinic resin used as a constituent material for the core layer 1B and having a flexural modulus according to JIB-K7203 of 9.8 x 107 to 6.9 x 108 Pa (1000 to 7000 kg / cm2 ) and having a thickness greater than that of the thermoplastic polymer of the surface skin layer 1A, is preferably a homopolymer or a copolymer of α-olefins, for example, ethylene and propylene. They can be used alone or as a mixture of two or more of them. In addition, an elastomer, for example, an olefinic rubber, comprising ethylene and an α-olefin, can be added to the olefinic resin for the purpose of improving flexibility, impact resistance to cold impact. or the like, provided that the flexural modulus and hardness are within the range specified above. In addition, various kinds of other resins, elastomers, various kinds of fillers, such as talc, Calcium carbonate, silica or mica, pigments and stabilizers, can be loaded by a usual method, as long as the modulus and hardness are within the ranges mentioned above.

In the case where the elastomer is contained in the core layer material 1B, the content is preferably not more than 60% by weight. If the olefin rubber exceeds 60% by weight of the mixture composition of the olefinic resin of the elastomer, there arises a problem in the moldability and the shape retention ability.

In the present invention, if the olefin resin constituting the core layer 1B has a flexural modulus of not more than 9.8 x 107 Pa (1000 kg / cm2) or a hardness lower than that of the thermoplastic elastomer of the layer of surface skin 1A, it cannot provide sufficient shape and is easily deformed by the external pressure and, therefore, it is not suitable as a casing containing an air cushion. On the other hand, if the module in deflection exceeds 6.9 x 108 Pa (7000 kg / cm2), the total flexibility of the shell of the double-layer air bag is poor and a problem is likely to occur when the air bag is actuated at -40 C Accordingly, the flexural modulus is preferably greater than 9.8 x 107 Pa (1000 kg / cm2) and less than 6.9 x 108 Pa (7000 kg / cm2), in particular, 1.9 x 108 to 4.9 x 108 Pa (2000 to 5000 kg / cm2), having regard to the feeling of flexibility, the operating characteristics ent and the ability to retain the shape of the entire envelope.

There is no particular limitation to the thickness of the core layer 1B, and this thickness is generally from about 0.5 to 5 mm and, preferably, from 1 to 3 mm.

In the present invention, the core layer ZB, constituted by such a thermoplastic resin, is provided with weakened shapes, so that the core layer 1B bursts when the actuation of the air bag starts. As the weakened shapes, 1C stitch-type slot shapes can be used, as well as various kinds of shapes, such as notch-type shapes of reduced thickness. In addition, there is no particular limitation on the position or area of formation of these weakened shapes, which can suitably be determined depending on the shape and strength of the core layer. 1B, and the stresses caused during actuation of the air bag.

Next, a description will now be made of the method of manufacturing an envelope containing an air bag according to the present invention.

As the molding process for manufacturing the casing containing the air bag according to the present invention, customary molding processes adopted for thermoplastic resins can be mentioned, and, in particular, the injection molding process is preferred. with respect to the model or the like.

Like the injection molding process, there may be mentioned, for example, a so-called insert injection process, which comprises the pre-molding of a core layer, the placing of the product of the molding on a die leaving a space for the surface skin layer, and the injection molding of a surface skin material comprising a thermoplastic polymer in the surface skin layer portion, or a so-called double injection process, which comprises the molding of a layer core, removing the impression die, placing a new impression die having a space for a surface layer successively, without removing the core casting product from the die, and then removing the core casting product from the die. injection molding of the surface skin material.

In this case, it is necessary that the weakened shapes mentioned above are formed at the level of the core layer 1B, so that the air bag easily bursts when starting the actuation.

As the weakened shapes, there may be mentioned notch-type shapes of reduced thickness, continuous stitch-type slit shapes, etc., as described above.

The shapes can be obtained by molding the product of the molding of the casing using a die having such shapes, or by making a layer having such a shape, then backing it with a surface skin layer afterwards. molding of the envelope.

In the air cushion cover according to the present invention, the surface skin layer 1A can be coated, if necessary, to provide shine in a vehicle interior and improve color matching with others. interior parts, as well as touch. A surface skin layer 1A coating is also preferred with regard to scratch resistance.

As has been specifically described above, since the surface layer of the shell containing the air cushion according to the present invention is flexible, it provides a feeling of comfort due to its flexibility when part of the body of the conductor comes into contact with the casing. In addition, since the core layer is relatively hard, it exhibits excellent shape retaining ability and is very durable. Then, upon actuation of the air bag, the casing bursts rapidly due to the weakened forms of bursting of the casing. In addition, the scattering of the core layer upon bursting of the casing can be securely prevented due to the soft surface skin layer, and the shell exhibits preferable breaking performance and exhibits excellent endurance.

In addition, the envelope containing a cushion according to the present invention can be manufactured, for example, by a streamlined molding process, such as a double injection process, in a simple manner, with high precision, without having to does not present defective products, with a high yield, in an effective and efficient manner, which allows a remarkable reduction in the costs of the resulting products.

The present invention will now be explained more specifically with reference to Examples and Comparative Examples, but it should be emphasized that the present invention is not limited to the following examples, and that modifications can be made without necessarily letting the user know. 'we move away from its frame.

Examples 1-7, Comparative Examples 1-6
A core layer (1.0-3.0mm thick), with burst-stitch type slits (29 slits, each about 0.7cm in length) was molded from each of the core materials shown in Table 1, using an in-line, two-color, screw-type injection molding device with a die clamping pressure of 350 tons. Then, a surface skin layer was injection molded using each of the surface skin materials shown in Table 1, at a predetermined thickness, on the core layer, to obtain a modular shell 1 for one. air bag shown in Figure 1.

In Example 4, a coating was applied to the surface skin layer.

The coating was applied by rubbing the superficial skin layer with isopropanol after injection molding of the casing, spray application of a primer made by Sakai Kagaku Co (MEX5440 and methyl ethyl ketone in a ratio of 1: 1), to a thickness of 7-10 Mm, drying it at room temperature for 10 minutes, then applying a layer of urethane top coating, made by Sakai
Kagaku Co. (MEX6047: Curing Agent F-3L: Thinner 58u = 100: 10: 50), to a thickness of 20-25 µm, drying it at room temperature for 10 minutes, then applying a cooking at 800C for 30-45 minutes.

The resulting products were evaluated by the method to be described below, and the results are shown in Table 2.

The materials used, presented in the
Table 1, and the manufacturing methods are as follows.

(Core Material) Propylene-ethylene block copolymer resin
(SPX 9800, manufactured by Mitsubishi Yuka Co.)
MFR (230 C, 2.16 kg) = 1 g / 10 min,
Flexural modulus = 4.4 x 108Pa (4500 kg / cm2) P-2: Propylene-ethylene block copolymer resin
(BC-8, manufactured by Mitsubishi Yuka Co.)
MFR (230 C, 2.16 kg) = 1.8 g / 10 min,
Flexural modulus = 10.6 x 108 Pa (10800 kg / cm2) P-3: Ethylene-propylene rubber
(Ep07p, manufactured by Nippon Synthetic Rubber Co.)
ML (100 C) = 70
Propylene content = 27% P-4: Low pressure polyethylene resin
(JX-20, manufactured by Mitsubishi Yuka Co.)
MFR (190 C, 2.16 kg) = 5.5 g / 10 min,
Flexural modulus: 8.8 x 108 Pa (9000 kg / cm2) (Process for manufacturing the core material)
100 parts by weight of the core material having the blend composition as set forth in
Table 1 were kneaded with the addition of 0.2 part of Illuganox 1010, manufactured by Ciba Geigy Co., as stabilizer, and 0.5 part by weight of carbon black, in a twin-screw extruder, at 200 vs.

(Surface skin material)
Ingredient A
Al: Hydrogenated derivative of styrene block copolymer
butadiene
Styrene content: 33% by weight
Number average molecular mass: 180,000
A-2: Hydrogenated derivative of styrene isoprene block copolymer
Styrene content: 13% by weight
Number average molecular mass: 60,000
Ingredient B
Bl: The same material as P-1 used for the core material
B-2: Propylene-ethylene block copolymer (BC1, manufactured
by Mitsubishi Yuka Co.)
MFR (230 "C, 2.16 kg) = 30 g / 10 min
Flexural modulus = 9.8 x 108 Pa (10,000 kg / cm2)
Ingredient C
C-1: Polyisobutylene (TETRAX 3T, manufactured by Nippon
Petrochemical Co.)
Viscosity average molecular mass = 30,000
C-2: Polyisobutylene (TETRAX 5T, manufactured by Nippon
Petrochemical Co.)
Viscosity average molecular mass = 50,000
C-3: Polyisobutylene (VISTANEX MML-100, manufactured by Exon
Chemical)
Viscosity average molecular mass = 90,000
D-1: Plasticizing agent for paraffinic-type rubbers
(oil) (pw380, manufactured by Idemitsu Kosan Co.)
Kinetic viscosity at 40 "C = 380 cSt
D-2: Polybutene (Nisseki Polybutene HV-100, manufactured by
Nippon Petrochemical Co.)
Number average molecular mass = 970 (Manufacturing process of the superficial skin material)
100 parts by weight of each of the ingredients of a mixture composition shown in Table 1 were kneaded with the addition of 0.2 part by weight of Illuganox 1010 and 0.5 part by weight of carbon black used for the material. soul, in a mixer type
Banbury, at 1800C, for 20 minutes, in a sheet-like shape, which was then made into square pellets using a sheet cutter.

Comparative Example 7
For comparison, an envelope containing an air cushion comprising two layers, i.e., a surface skin layer, made of high density urethane foam and a low density urethane core layer, was fabricated and evaluated. .

The molding was carried out by molding and pre-curing a core layer to a low expansion density by a urethane molding process.
RIM, placing the latter in a die intended for the formation of a surface skin layer, then application of an insert molding process to mold a surface skin layer according to the same process. Freon gas was used as a blowing agent for molding the surface skin layer. The process required two curing steps and the productivity was poor.

The resulting casing containing an airbag was evaluated by the same method as in Example 1, and the results are shown in Fig.
Table 2.

Comparative Example 8
For still further purposes of comparison, a casing containing an air cushion, provided with reinforcing nets, was manufactured and evaluated.

In this RIM urethane molding with the incorporation of netting, polyester fibers were braided in the shape of a net, which was cut by welding according to the burst shape of the casing, and metal fasteners (hooks ) were fixed for two-layer molding in the same way as in Example
Comparison 7. They were placed in a RIM die, and a RIM molding was conducted with urethane. In this case, a gaseous Freon was used as the blowing agent, and, after demolding, curing was carried out at 1000C for 30 min. This method has the disadvantages that the preparation of a layer of safety skin by the insertion of nets is difficult and that the molding cycle is not efficient.

The resulting casing containing an airbag was evaluated according to the same method as in Example 1, and the results are shown in Fig.
Table 2.

As evident from Table 2, the envelopes containing air cushions according to the present invention shown in Examples 1-7 were excellent in soft feeling, shape retention ability. , development test at -40 C, endurance test at 1100C for 500 hours, and productivity.

(Evaluation Process) (1) Feeling of Flexibility
As shown in Figure 1, a modular envelope comprising an air bag 2, a casing 1 to contain the air bag, retainers (metal fasteners) 4, 5, and an inflator 3, or a casing 1 alone. were left at -20 C-80 C, so that the temperature of the sample reached atmospheric temperature, and the envelopes were evaluated using touch with the hands by 10 people. by the number of people who felt a feeling of flexibility and indicated by o if ten people out of the ten felt this feeling of flexibility and "" if 8 people out of the 10 felt a feeling of flexibility. "x" means that the number of people who felt a sense of flexibility was less than 8.

(2) Aptitude for Conservation of Form.

A modular envelope comprising the air bag 2, the envelope 1 to contain the air bag, the retainers (metal fasteners) 4, 5, and the inflation device, as shown in Figure 1, or the envelope 1 alone , were left in the following thermal cycles, namely
1000C x 4 h <-40 C x 4 h -
850C x 98% (Relative humidity) 4h <-40C, 4h for 10 cycles, and the deformation state during or after the test was observed. (o) indicates suitability as a casing containing an air bag with almost no deformation, and (x) means unsuitability as an casing containing an air bag with significant deformation.

(3) Development Test at -40 C
The module assembled in (1) and (2) above was attached to a flywheel, left at -40 C for a period of time sufficient to reach the temperature of the atmosphere, and the development test was applied within a minute. (x) signifies inappropriateness as an air bag, not functioning normally as an air bag, such that the modular casing cracked and scattered or the casing tore into sharp shapes to tear the cushion, and (o) means a suitability showing that the airbag has operated normally.

(4) Endurance test at 1100C for 1000 hours
After aging of the modular shell under the conditions mentioned above by a transmission type thermal aging device, a development test at -40 C was applied according to the test method of paragraph (3) below. above, then the appearance of the modular envelope was compared between before and after aging. "x" means a significant change, such as warping, deformation or migration of the plasticizer to the core material, while (o) means that there have been no such changes.

(5) Productivity
20 products were produced successively and checked with regard to moldability (for example, moldability, or direct injection), size and weight and, in particular, the appearance of the products for the superficial skin layer (tackiness, delamination in the area of the injection point, appearance of the weld, surface depressions, melt marks, grain appearance, uneven gloss, warping, or the like). "o" means that the test was positive for all products, "A" means that the test was positive for more than 90% of the products, and "x" means that the test was positive for less than 90% d 'between them.

Table 1

<SEP> Example <SEP> Example <SEP> Comparison
<tb><SEP> 1 <SEP> 2 <SEP> 3 <SEP> 4 <SEP> 5 <SEP> 6 <SEP> 7 <SEP> 1 <SEP> 2 <SEP> 3 <SEP> 4 <SEP> 5 <SEP> 6 <SEP> 7 <SEP> 8
<tb><SEP> Mixture <SEP> P <SEP>#<SEP> - <SEP> 1 <SEP> - <SEP> 40 <SEP> - <SEP> - <SEP> - <SEP> - <SEP> - <SEP> 50 <SEP> - <SEP> - <SEP> - <SEP> - <SEP>
<SEP> Urea- <SEP> Urea
<SEP> of <SEP> d- <SEP> P <SEP>#<SEP> - <SEP> 2 <SEP> 40 <SEP> - <SEP> 50 <SEP> 40 <SEP> 40 <SEP> 40 <SEP> 40 <SEP> - <SEP> 80 <SEP> 40 <SEP> 40 <SEP> 40 <SEP> 40
<tb><SEP> sine <SEP> of <SEP> thanne <SEP> thanne
<tb><SEP> P <SEP>#<SEP> - <SEP> 3 <SEP> 40 <SEP> 40 <SEP> 30 <SEP> 40 <SEP> 40 <SEP> 40 <SEP> 40 <SEP> 50 <SEP> - <SEP> 40 <SEP> 40 <SEP> 40 <SEP> 40
<tb><SEP> poly
<SEP> olefin <SEP> P <SEP>#<SEP> - <SEP> 4 <SEP> 20 <SEP> 20 <SEP> 20 <SEP> 20 <SEP> 20 <SEP> 20 <SEP> 20 <SEP > - <SEP> 20 <SEP> 20 <SEP> 20 <SEP> 20 <SEP> 20
<tb><SEP> (pp)
<tb><SEP> Hardness <SEP> (JIS <SEP> - <SEP> A) <SEP> 98 <SEP> 96 <SEP> 99 <SEP> 98 <SEP> 98 <SEP> 98 <SEP> 98 <SEP> 88 <SEP> 99 <SEP> 98 <SEP> 98 <SEP> 98 <SEP> 98
<tb><SEP> 3.8 <SEP> 2.05 <SEP> 6.4 <SEP> 3.8 <SEP> 3.8 <SEP> 3.8 <SEP> 3.8 <SEP> 0, 78 <SEP> 9.8 <SEP> 3.8 <SEP> 3.8 <SEP> 3.8 <SEP> 3.8
<tb><SEP> Module <SEP> in <SEP> (kg / cm) <SEP> (3900) <SEP> (2100) <SEP> (6500) <SEP> (3900) <SEP> (3900) <SEP> (3900) <SEP> (3900) <SEP>(<SEP> 800 <SEP>) <SEP> (10000) <SEP> (3900) <SEP> (3900) <SEP> (3900) <SEP> (3900)
<tb><SEP> Bending <SEP> 10 <SEP> Pa
<tb><SEP> Ingr- <SEP> A <SEP> - <SEP> 1 <SEP> 20 <SEP> 20 <SEP> 20 <SEP> 20 <SEP> 20 <SEP> 20 <SEP> 20 <SEP > 20 <SEP> 20 <SEP> 20 <SEP> - <SEP> 20 <SEP> 25
<tb><SEP> dient
<tb><SEP> A <SEP> A <SEP> - <SEP> 2 <SEP> 45 <SEP> 43 <SEP> 43 <SEP> 45 <SEP> 35 <SEP> 45 <SEP> 50 <SEP> 45 <SEP> 45 <SEP> 45 <SEP> 45 <SEP> 20 <SEP> 20
<tb><SEP> Degree <SEP> B <SEP> - <SEP> 1 <SEP> 10 <SEP> - <SEP> 7 <SEP> 10 <SEP> - <SEP> 10 <SEP> 10 <SEP> 10 <SEP> 10 <SEP> 10 <SEP> 5 <SEP> - <SEP> 20
<tb><SEP> dient
<tb><SEP> B <SEP> B <SEP> - <SEP> 2 <SEP> - <SEP> 12 <SEP> - <SEP> - <SEP> 20 <SEP> - <SEP> - <SEP> - <SEP> - <SEP> - <SEP> - <SEP> 40 <SEP>
<SEP> Ingre- <SEP> C <SEP> - <SEP> 1 <SEP> 15 <SEP> 15 <SEP> 20 <SEP> - <SEP> 15 <SEP> 15 <SEP> 20 <SEP> 15 <SEP> 15 <SEP> - <SEP> 40 <SEP> - <SEP> 10
<tb><SEP> dient
<tb><SEP> C <SEP> - <SEP> 2 <SEP> - <SEP> - <SEP> - <SEP> 15 <SEP> - <SEP> - <SEP> - <SEP> - <SEP> - <SEP> - <SEP> - <SEP> 5 <SEP>
<SEP> C
<tb><SEP> C <SEP> - <SEP> 3 <SEP> - <SEP> - <SEP> - <SEP> - <SEP> - <SEP> - <SEP> - <SEP> - <SEP> - <SEP> 15 <SEP> - <SEP> - <SEP>
<SEP> Ingné- <SEP> D <SEP> - <SEP> 1 <SEP> 10 <SEP> 10 <SEP> 10 <SEP> 10 <SEP> 10 <SEP> - <SEP> - <SEP> 10 <SEP> 10 <SEP> 10 <SEP> 10 <SEP> 15 <SEP> 25
<tb><SEP> dient
<tb><SEP> D <SEP> D <SEP> - <SEP> 2 <SEP> - <SEP> - <SEP> - <SEP> - <SEP> - <SEP> 10 <SEP> - <SEP> - <SEP> - <SEP> - <SEP> - <SEP> - <SEP>
<SEP> (JIS <SEP> - <SEP> A) <SEP> 52 <SEP> 61 <SEP> 43 <SEP> 55 <SEP> 75 <SEP> 57 <SEP> 60 <SEP> 52 <SEP> 52 <SEP> 60 <SEP> 17 <SEP> 92 <SEP> 54
<tb><SEP> Notes <SEP> (1) <SEP> (2) <SEP> (3)
<tb> pp = parts by weight (1): Coated surface skin - (2) RIM foaming (3) with reinforcing mesh Table 2

<SEP> Example <SEP> Example <SEP> Comparison
<tb><SEP> 1 <SEP> 2 <SEP> 3 <SEP> 4 <SEP> 5 <SEP> 6 <SEP> 7 <SEP> 1 <SEP> 2 <SEP> 3 <SEP> 4 <SEP> 5 <SEP> 6 <SEP> 7 <SEP> 8
<tb><SEP> Sensation <SEP> of <SEP> O <SEP> O <SEP> O <SEP> O <SEP> O <SEP> O <SEP> O <SEP> O <SEP> x <SEP> O <SEP> O <SEP> x <SEP> O <SEP>#<SEP>#
<tb><SEP> flexibility
<tb><SEP> Aptitude <SEP> to <SEP> the <SEP> con- <SEP> O <SEP> O <SEP> O <SEP> O <SEP> O <SEP> O <SEP> O <SEP > x <SEP> O <SEP> x <SEP> x <SEP> O <SEP> O <SEP> O <SEP> O
<tb><SEP> servation <SEP> of <SEP> the <SEP> form
<tb><SEP> Test <SEP> of <SEP> development <SEP> O <SEP> O <SEP> O <SEP> O <SEP> O <SEP> O <SEP> O <SEP> O <SEP > x <SEP> O <SEP> O <SEP> O <SEP> O <SEP> x <SEP> O
<tb><SEP> pement <SEP> to <SEP> -40 C
<tb><SEP> Test <SEP> Development
<SEP> pement <SEP> O <SEP> O <SEP> O <SEP> O <SEP> O <SEP> O <SEP> O <SEP> O <SEP> x <SEP> O <SEP> O <SEP > O <SEP> x <SEP> O <SEP> O
<tb><SEP> from extended- <SEP> to <SEP> -40 C
<tb><SEP> rance <SEP> Aspect <SEP> of <SEP> O <SEP> O <SEP> O <SEP> O <SEP> O <SEP> O <SEP> O <SEP> O <SEP> O <SEP> O <SEP> O <SEP> O <SEP> x <SEP> x <SEP> O
<tb><SEP> product
<tb><SEP> Productivity <SEP> O <SEP> O <SEP> O <SEP> O <SEP> O <SEP> O <SEP> O <SEP> O <SEP> O <SEP> x <SEP> x <SEP> O <SEP> O <SEP> O <SEP> x
<tb>

Claims (19)

1 - Envelope containing a pneumatic safety cushion, comprising - a superficial layer of skin, made of a thermoplastic polymer containing the ingredients following A, B, C and D ingredient A: a hydrogenated derivative of a copolymer block comprising styrene and a conjugated diene, ingredient B: an olefinic resin, ingredient C: a polyisobutylene having a mass molecular viscosity average no greater than 70,000, and ingredient D: a rubber plasticizer of the series of hydrocarbons, having a kinetic viscosity at 400C not higher greater than 500 cSt, and / or polybutene having an average molecular mass of number not exceeding 2,500, in which the mixing ratio is ingredient A = 40 to 80% by weight, ingredient B = 5 to 30% by weight, ingredient C = 2 to 30% by weight, ingredient D = 0 to 20% by weight, and having JIS6-A hardness according to JIS-K6301 ranging from 20 to 90, and - a core layer, made of an olefinic resin having a flexural modulus according to JIS-K7203 ranging from 9.8 x 107 to 6.9 x 108 Pa (1000 to 7000 kg / cm2), wherein said core layer has a hardness greater than that of said surface skin layer, and said core layer has a portion adapted to the easy bursting of the casing when the actuation of the pneumatic cushion is started. 2 - Envelope according to claim 1, characterized in that the part adapted to the easy bursting of the envelope is constituted by thin-walled areas of the notch type or by puncture-type slots arranged linearly. 3 - Envelope according to claim 1, characterized in that ingredient A is a hydrogenated derivative of a styrenic block copolymer, typically represented, for example, by the general formula X-Y, X * YX) n or X-CY-XY or - X represents a polymer block of styrene, - Y is an elastomeric polymer block of diene conjugated, and - n is an integer ranging from 1 to 5. 4 - Envelope according to claim 3, characterized in that the conjugated diene monomer for the polymer block Y of each of the formulas described above is butadiene or isoprene. 5 - Envelope according to claim 3, characterized in that the ratio of the styrenic block polymer X in the totality of the block copolymer of ingredient A ranges from 5 to 40% by weight. 6 - Envelope according to claim 3, characterized in that the number-average molecular weight of the polymer block X ranges from 5000 to 125,000, and the number-average molecular weight of the polymer block Y ranges from 15,000 to 250,000. 7 - Envelope according to claim 1, characterized in that ingredient B is a homopolymer or a copolymer of an a-olefin, for example, ethylene, propylene and butene-1. 8 - Envelope according to claim 1, characterized in that ingredient C is a high molecular weight polyisobutylene, hardly having double bonds in the molecular chain and having a linking structure

9 - Envelope according to claim 1, characterized in that the plasticizer of rubbers of the hydrocarbon series for ingredient D is a diluent oil or a paraffinic or naphthenic plasticizing oil. 10 - Envelope according to claim 1, characterized in that the polybutene having the number average molecular weight not exceeding 2500 for ingredient D mainly comprises isobutylene and partly n-butene copolymerized therewith. 11 - Envelope according to claim 1, characterized in that the surface skin layer (1A) has a thickness ranging from 0.5 mm to 10 mm, for more than 70% of the surface area of the skin layer superficial (1A). 12 - Envelope according to claim 1, characterized in that the surface skin layer (1A) is provided with foaming at a ratio of less than about 3.0 times, in order to improve the feeling of flexibility and weight reduction. 13 - Envelope according to claim 1, characterized in that the olefinic resin for the core layer is a homopolymer or a copolymer of an α-olefin, for example, ethylene and propylene. 14 - Envelope according to claim 1, characterized in that the core layer further contains an elastomer. 15 - Cover according to claim 14, characterized in that the elastomer is an olefinic rubber comprising ethylene and an α-olefin. 16 - Envelope according to claim 14, characterized in that the ratio of the elastomer to the total amount of the olefin resin and of the elastomer is less than 60% by weight. 17 - Envelope according to claim 1, characterized in that the thickness of the core layer ranges from 0.5 to 5 mm. 18 - Envelope according to claim 1, characterized in that the surface of the superficial skin layer is provided with a coating. 19 - A pneumatic safety cushion device, comprising - a base retainer (5), to which a air cushion is intended to be fixed - a folded air cushion (2), fixed to said device base retainer - an inflator (3) attached to said retainer base restraint, so as to inject a gas into the pneumatic cushion, in order to rapidly develop said air bag; and - an envelope (1) as defined in the resale cation 1, enveloping the airbag and fixed to the basic restraint.