JPH05213139A - Lightweight and compact air bag - Google Patents

Abstract

PURPOSE:To provide a compact air bag which is composed of lightweight cloth not covered with elastomer, and can bear hot blast and flame at the time of a collision. CONSTITUTION:A continuous long fiber bundle A composed of thermoplastic fiber such as polyester fiber of 5de or less in single yarn fineness, 6g/de or more in strength, and 1,300kg/mm<2> or less in Young's modulus is positioned at the core part, around which a short fiber bundle B composed of heat resistant fiber which can bear thermal decomposition temperature of 300 deg.C or more such as para-aromatic polyamido fiber of 2de or less in single yarn fineness is wound and held. The long and short composite yarn whose nonuniforming degree coefficient in the lengthwise direction of the thread is 1.3 or less used as warp and weft to be woven so that ventilation degree may be 0.3cc/sec.cm<2> or less, and to sew the finished cloth into a bag.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lightweight and compact airbag. More specifically, it is a lightweight compact that is sewn into a bag body with a high packing density that has flame resistance, is lightweight and thin, and has uniform breathability in every part, and has low breathability. Regarding airbags.

[0002]

2. Description of the Related Art Conventional airbags are produced by weaving high-strength filament yarns having a total fineness of 400 to 1,000 denier made of thermoplastic synthetic fibers such as nylon 6, nylon 66, and polyester into plain weave fabrics or ripstop fabrics.
The woven fabric is coated or impregnated with a chloroprene or silicone elastomer and sewn into a bag body as shown in FIG. 1 is used, which is also put to practical use as a device as shown in FIG. Kosho 48-3029
No. 3, gazette 48-81543 gazette, gazette 51 gazette.
-17936 publication). That is, all of these airbag fabrics have heat resistance and flame resistance, and when a collision accident occurs in an aircraft or an automobile, a current flows through the power cord H of the inflator F, and When the explosive burns and the airbag A expands into a spherical shape, it is designed to withstand the high temperature blast and flame ejected from the combustion gas injection holes G.

That is, in order to meet the safety standard for airbags, the elastomer is coated with a considerably high basis weight, which makes the airbag heavy and coarse and stiff, and significantly reduces the handleability during sewing. In addition, the volume when folded is large, which is an obstacle when mounting on a vehicle. In other words, due to the nature of the airbag device with the built-in airbag, it is necessary to place it in the front part of the driver.On the other hand, there is no space in the front part such as the steering wheel, various instruments and windows, and even a little. A compact airbag device is desired. In addition, when attached to a steering wheel or the like, an airbag that is as light as possible is desirable in terms of operability.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems in the prior art, and is a lightweight and compact airbag, that is, a cloth which is not covered with an elastomer such as chloroprene or silicone. In addition, it is an object of the present invention to provide an airbag in which a woven fabric is sewn into a bag body that can withstand a high temperature blast and a flame ejected from an inflator in the event of a collision.

[0005]

According to the present invention, the single yarn fineness is 5 de or less, the strength is 6 g / de or more, and the Young's modulus is 1,30.
A continuous long fiber bundle a made of a thermoplastic synthetic fiber of 0 kg / mm ² or less is located in the core part, and a pyrolysis temperature of 300 is provided around the core part.
A short fiber bundle b consisting of heat-resistant fibers having a single yarn fineness of 2 de or less at a temperature of ℃ or more is wound around the fibers of the core portion and bound at a weight ratio a / b = 90/10 to 50/50. And a long-short composite yarn having a nonuniformity coefficient of 1.3 or less in the longitudinal direction of the yarn is used for the warp and the weft, and the fabric has an air permeability of 0.3 cc / sec · cm ^2. Provided is a lightweight and compact airbag characterized in that a woven and finished fabric is sewn into a bag shape as described below.

In the present invention, the thermoplastic synthetic fiber means
It is a fiber made of a normal thermoplastic synthetic resin having heat shrinkability, and specific examples thereof include nylon fiber, acrylic fiber, polypropylene fiber, polyethylene fiber and the like.

These thermoplastic synthetic fibers must have a single yarn fineness of 5 de or less, preferably 2.5 de or less. When the single yarn fineness exceeds 5 de, it is essential that the airbag is flexible because it is originally necessary to fold it into a small size, but the obtained airbag becomes extremely coarse and hard, which is no different from the one coated with an elastomer. It will be gone. In addition, the number of constituent yarns is reduced, and it is difficult to obtain uniform entanglement of the heat resistant fibers. Further, there is a problem that the breathability of the woven fabric becomes too large, which is not preferable.

The strength of the thermoplastic synthetic fiber is 6 g /
It is necessary to be more than de. The high-strength filaments used in conventional airbags are still 6g / de or more, and if the filaments are lower than this, the yarn must be thicker accordingly, and the lightweight and compact airbag which is the object of the present invention can be obtained. Becomes difficult.

The Young's modulus of the thermoplastic synthetic fiber is
It should be 1300 kg / mm ² or less. If the Young's modulus exceeds 1,300 kg / mm ² , since many other components, such as heat resistant fibers, have a high Young's modulus, the Young's modulus of the yarn after mixing is high, and the fabric after weaving is It becomes coarse and hard, which is not preferable.

Further, the thermoplastic synthetic fiber preferably has a boiling water shrinkage of 5% or more, particularly 8% or more.
In order to absorb the impact energy due to the rapid expansion during the operation of the inflator, it is preferable that the fabric has an elongation of about 15% or more. In particular, a low elongation heat-resistant fiber such as para aromatic polyamide is used. When it is contained, it is effective to shrink the cloth by heat so as to obtain the elongation, and for this purpose, the boiling water shrinkage of the thermoplastic synthetic fiber is preferably 5% or more.

Further, the fiber form of the thermoplastic synthetic fiber needs to be a continuous long fiber bundle. In short fiber bundles, not only the sufficient strength of the fibers cannot be utilized, but also the thickness unevenness in the length direction is large, and when forming a woven fabric, minute gaps occur between the yarns, resulting in large ventilation unevenness. , Evenly air permeability 0.3cc
/ Sec · cm ^{2 It} becomes difficult to lower it. If there is a spot where the air permeability is large in spots, a large amount of high-temperature and high-pressure gas flows intensively there, and burnt powder of explosives and the like are also likely to concentrate, which is a problem that melt damage easily occurs, which is not preferable.

On the other hand, heat resistant fibers have a thermal decomposition temperature of 30.
A fiber having a temperature of 0 ° C. or higher, for example, a meta-type or para-type wholly aromatic polyamide fiber, specifically, polymetaphenylene terephthalamide, polyparaphenylene terephthalamide, a para-type aromatic polyamide and a meta-type aromatic polyamide. A para-aromatic polyamide obtained by copolymerizing 3,4′-diaminodiphenyl ether, for example, a fiber made of polyparaphenylene sulfone, polyparaphenylene sulfide, polyether ether ketone, etc. Can be mentioned. Above all,
Para-aromatic polyamide is preferable, and the strength is 20 g / d from the viewpoint of strength and impact resistance of the obtained airbag.
Para-aromatic polyamides of e or higher are particularly preferable.

It is necessary that the single yarn fineness of the heat resistant fiber is 2 de or less. If the single yarn fineness exceeds 2 de, the texture of the woven fabric becomes coarse and hard, which is not preferable. Also,
When the mixing ratio of heat-resistant fibers is constant, the finer the terminal fineness, the larger the number of constituent fibers, the better the flame resistance and the less yarn unevenness,
In addition, the breathability of the woven fabric can be lowered, and also from this point, the single yarn fineness of the heat resistant fiber is preferably 2 de or less.

In the present invention, the cloth is obtained by coating the continuous long fiber bundle a of the thermoplastic synthetic fiber with a short fiber bundle b made of such heat-resistant fibers uniformly in the length direction. And a long-short composite yarn having a non-uniformity coefficient of 1.3 or less, which represents the thickness unevenness in the length direction of the obtained yarn, is used as the warp and the weft, and the air permeability thereof is 0.3 cc / sec.cm. It consists of woven and finished woven fabrics with a weight of ² or less.

Even if the cloth is not covered with an elastomer or the like, it is jetted from the inflator at 500 to 800 ° C.
It does not melt, break or burn up against the above high temperature and high pressure blast and flame.

The short fiber bundle B constituting the long / short composite yarn is
It is preferable that the heat-resistant fiber has an average fiber length of 100 to 800 mm according to the draft method. The stretch-cutting method is preferable because the fiber length can be increased. That is, when the average fiber length is short, the tenacity factor is reduced, and more fluff is produced, which makes it difficult to perform high-density weaving. On the other hand, if the fiber length is long, it becomes filamentous and the supply nip is reduced.

Further, the long / short composite yarn has an appropriate mixing ratio (weight ratio) of thermoplastic synthetic fiber B and heat resistant fiber B / B of 90.
/ 10 to 50/50, preferably 80/20 to 60/4
The range is 0. If a / b exceeds 90/10, heat resistance and flame contact resistance will be insufficient. On the other hand, I / R is 50/5
If it is less than 0, the amount of short fibers composed of heat-resistant fibers increases, so that the yarn becomes hard and the thickness unevenness in the length direction becomes large, and the asymmetry coefficient easily exceeds 1.3, and the ventilation unevenness of the fabric is increased. Increases and it becomes difficult to lower the air permeability. Further, the heat shrinkage force of the long-short composite yarn becomes small, the heat shrinkage of the woven fabric is limited, and it is difficult to obtain a dense woven fabric having low air permeability. Furthermore, most heat resistant fibers are generally expensive, and the cost increases as the mixing ratio increases.

Further, the long-short composite yarn needs to have an asymmetry coefficient of 1.3 or less, which represents a thickness unevenness in the length direction of the yarn. When the asymmetry coefficient exceeds 1.3, the thickness unevenness of the yarn in the length direction becomes large, the ventilation unevenness of the obtained woven fabric becomes large, and the airbag is apt to be damaged, which is not preferable. In the present invention, the asymmetry factor (I) is given by the following equation (1). Asymmetry coefficient (I) = measured u% × √ (N / 80) ... (1) [where u% is the yarn speed of 50 m on an Evenestaster manufactured by Nippon Keisokuki Kogyo Co., Ltd.] / Min, u when measured under normal conditions
%, N represents the total number of long fibers and short fibers in a constant cross section of the yarn. ]

The heat-resistant fibers used in the present invention are more difficult to spin than ordinary synthetic fibers, and the asymmetry coefficient (I) should be made uniform to 1.3 or less in the ordinary spinning process. Is a difficult technique. That is, it can be achieved only by forming a long-short composite yarn as in the method of the present invention.

In the present invention, such a long / short composite yarn is a continuous length in a tension or constant length state made of thermoplastic synthetic fiber having a single yarn fineness of 5 de or less, a strength of 6 g / de or more and a Young's modulus of 1,300 kg / mm ² or less. A continuous long fiber bundle composed of heat-resistant fibers having a thermal decomposition temperature of 300 ° C. or more and a single yarn fineness of 2 de or less is used as a fiber bundle by using a shooter between a supply roller and a cut-off roller to prevent disorder of the fibers and an average fiber length. 50:50 to 90: 1 for continuous long fiber bundles while tearing to 100 mm or more or after tearing
A yarn obtained by aligning the short fiber bundles at a weight ratio of 0 and tying them up with an air nozzle is preferable.

The woven fabric using the long-short composite yarn as the warp and the weft needs to be woven and finished so that its air permeability (JIS L-1096 Frazier method) is 0.3 cc / sec · cm ² or less. Is. When the obtained fabric has an air permeability of more than 0.3 cc / sec · cm ² , a defect such as a burnt powder of explosive that penetrates the airbag and pollutes the air inside the vehicle is likely to occur during inflation.

Further, it is desirable that the cloth has flame contact resistance of 5 seconds or more. If the flame resistance is less than 5 seconds, a practical airbag cannot be obtained. In the present invention, the flame resistance refers to the time until the fabric attached to the frame is horizontal and a flame of 780 ° C. is applied from the bottom to burn to open holes.

The airbag of the present invention is a lightweight and compact one made by sewing the above-mentioned cloth into a bag shape.

Next, one example of a method for producing a long / short composite yarn in which continuous long fiber bundles (a) made of thermoplastic synthetic fibers and short fiber bundles (b) made of heat resistant fibers are uniformly wound and bound will be described with reference to the drawings.

FIG. 3 shows a long-short compound device. In the figure, a is a continuous thermoplastic synthetic fiber bundle, b is a continuous heat resistant fiber bundle, 11 is a supply nip roller, 12 is a shooter, 1
3 is a drafting nip roller, 14 is a suction air nozzle, 1
5 is a tying nozzle by a swirling flow, 16 is a delivery roller, and 17 is a long / short composite yarn.

The continuous heat-resistant fiber bundle (b) passes through the tension and weaving adjusting guide 18 and the feed nip roller 11 and then, with the help of the shooter 12 between the feed roller and the drafting nip roller 13, It is uniformly torn while preventing turbulence as much as possible, aligned with the continuous thermoplastic fiber bundle a supplied from the drafting nip roller 13 via the tension load guide 19, and then the suction air nozzle 14 and the swirling flow tie nozzle. After being entangled and wound by 15 and imparted with tying property, it is taken out by a delivery roller 16 and becomes a long-short composite yarn 17 in which short fibers are uniformly entangled and wound around a continuous long fiber.

The obtained long-short composite yarn has a large friction between woven fabrics and is less likely to cause seam slip, as compared with continuous filaments and mixed yarns thereof, because of the relation of yarn form, especially fluff. Further, as compared with conventional spun yarn, since it is combined with continuous long fibers, the thickness unevenness in the length direction is extremely small, and the short fiber portion also has a high degree of fiber arrangement, and is stretched to the limit. In addition, since the fiber length is longer, it becomes a high-strength yarn, which is extremely suitable for airbags.

The obtained long-short composite yarn was used as a warp and a weft, and was woven into a plain weave with a high weave density such that the cover factor was 2,000 or more, and subjected to scouring, heat setting, relaxing and calendering. After that, a bag as shown in FIG. 1 is sewn into an airbag A. In the figure, B indicates an inflator insertion hole and C indicates an inflator combustion gas exhaust hole. Here, the cover factor is a value calculated by the following equation (2). Cover factor = warp density (pieces / inch) x √ (warp de) + weft density (pieces / inch) x √ (weft de) (2)

[0029]

EXAMPLES The present invention will be described in more detail with reference to the following examples. In the examples, each evaluation item was evaluated according to the following methods. The fabric was woven with inflator combustion test X / Y combined filament yarn sewn into the air bag as shown in FIG. 1, which is burned to mounting the inflator to the airbag apparatus shown in FIG. 2, when the Evaluation was made based on whether or not the airbag was damaged. ○: There is no damaged part. Δ: Micro-damaged (to the extent that several micro holes having a diameter of 1 to 2 mm are formed in the woven fabric). X: Large breakage (larger hole diameter, larger number of holes than the above Δ, or large breakage that tears the woven fabric).

Flame contact test : The fabric sample attached to the frame was leveled, a flame of about 780 ° C. was applied from the bottom, and the time until burning and opening of holes was measured. Air permeability ; measured by JIS L-1096 Frazier method.

The storability; Figure 4 an air bag (a), (b)
5 was folded along the dotted line D shown in FIG. 3 to form the shape shown in FIG. 5C, and a load E of 5 kg was applied to the shape as shown in FIG. Feeling : Regarding the feel and flexibility of the surface of the fabric, a sensory evaluation was performed on the assumption that the airbag hits the face strongly in the event of a collision. ◯: Soft touch, flexibility, and texture that can be used as clothing. Δ: A slightly rougher texture than the above level. ×: Rigid and rough, with a texture equivalent to tents and canvas. Tensile strength and elongation Measured by JIS L-1096 strip method.

Example 1 Using the apparatus shown in FIG. 3, 0.3 g / de was measured by the guide 19.
Single yarn fineness under tension of 1.4de, strength 8g / d
e, boiling water shrinkage 8%, total fineness 200 de polyester fiber a, single yarn fineness 0.75 de, strength 28 g / de,
A para-aromatic polyamide fiber having a total fineness of 1,500 de [Technora (registered trademark), manufactured by Teijin Ltd.] is 5 mm wide at the tip between the supply nip roller 11 and the cut-off nip roller 13 with a roller distance of 150 cm. While preventing the fibers from being disturbed by the shooter 12 of No. 1, the fiber bundle (B) having a total fineness of 100 de, which is cut at a draft ratio of 15 times, is aligned with a draft roller, and then a suction nozzle having both suction performance and swirling performance. 14 and a tying nozzle 15 having a strong swivel performance in the opposite swirling direction, at a speed ratio of 100: 97 between the drafting nip roller 13 and the delivery roller 16,
A short woven fiber bundle (b) of para-aromatic polyamide fiber was entangled and wound around the continuous polyester fiber (a) to obtain a long / short composite yarn 17 of 300 de.

The weight ratio of the polyester fiber (a) and the para aromatic polyamide fiber (b) of the obtained long / short composite yarn was 67:
33, u% is 5.4%, I coefficient is 1.15, average fiber length of short fibers is 49 cm, and strength is 9.3 g / de (400
T / M twisted yarn measurement), the boiling water shrinkage was 7%. Next, apply 400T / M twist to this yarn, and warp 67 yarns / in
ch, 64 lines / inch (cover factor 2,26
A plain weave having a density of 9) was woven, subjected to scouring, heat setting, calendering, and then sewn into an airbag bag body as shown in FIG. Table 1 shows the evaluation results of the obtained bag.

Comparative Example 1 Using the apparatus shown in FIG. 6, a polyester fiber a having a single yarn fineness of 1.4 de, a strength of 8.0 g / de, a boiling water shrinkage of 8% and a total fineness of 200 de, and a single yarn fineness of 0.75 de , Strength 2
The para-aromatic polyamide fiber (b) having a total fineness of 108 de and 8 g / de was adjusted and aligned so that the tension was the same, and the polyester fiber and the polyester fiber were passed between the supply roller 62 and the delivery roller 64 through the mixed fiber air nozzle 63. A para-aromatic polyamide fiber was uniformly mixed to obtain a yarn 65 of 310 de. The polyester fiber and the para-aromatic polyamide fiber in the obtained yarn had a weight ratio of 65:35, a strength of 9.5 g / de (measured after twisting 400 T / M), and a boiling water shrinkage ratio of 7%. ..

Next, this yarn is twisted at 400 T / M and woven into a plain weave with a weaving density of 67 warps / inch and 64 wefts / inch (cover factor 2,269), scouring, heat setting, and calendering. After processing, the bag was sewn into an airbag bag as shown in FIG. The performance of the obtained bag is shown in Table 1.

COMPARATIVE EXAMPLE 2 Using the tow spinning device shown in FIG. 7, an average fiber length produced by drafting a polyester fiber bundle having a single yarn fineness of 1.5 denier and a total fineness of 72,000 de by a total draft of 7 times. 60 mm,
A sliver with a total denier of 10 000 de and an average fiber length of 50 mm obtained by drafting a bundle of para-aromatic polyamide fibers with a single yarn fineness of 0.7 de and a total fineness of 36,000 de at a total draft of 7 times, A sliver having a total denier of 55,000 and a modulus of 7,100 kg / mm ² was combined and passed through a Gil process, followed by a roving process and a roving process to obtain a weight ratio of polyester fiber to para aromatic polyamide fiber of 67: 33, 17.7 count (300 de) spun yarn was obtained. u% is 7.9, I coefficient is 1.6, and strength is 5 g /
de, the boiling water shrinkage was 6%.

Then, using this spun yarn, the warp density 67
1 / inch, weft density 64 threads / inch (cover factor 2,269), and basis weave into a woven fabric having a basis weight of 215 g / m ² , scouring, heat setting, calendering, and sewing, as shown in FIG. Such a bag body for an airbag is used. The performance of the obtained bag is shown in Table 1.

Comparative Example 3 Nylon 66 having a single yarn fineness of 6.0 de and a total fineness of 840 de
Using the fibers as warps and wefts, plain weaving was performed at 25.4 wefts / inch to obtain a woven fabric having a thickness of 0.380 mm. To this fabric, chloroprene rubber was rolled by AUMA in Germany
er-Head, Continuous vulcan
One side of the woven fabric was calendered with an izing machine to obtain a 0.430 mm-thick base fabric for airbags (vulcanization condition: 180 ° C., 1.5 minutes). The obtained base fabric was sewn into an airbag as shown in FIG. 1 and its performance was evaluated. The results are shown in Table 1.

Comparative Example 4 Single yarn fineness 2.5 de, strength 8.5 g / de, total fineness 50
A polyester filament of 0 de is twisted at 200 T / M and woven into a plain weave at a weave density of 50 warps / inch, weft 49 threads / inch (cover factor 2,214),
After scouring, heat setting and calendering, the bag was sewn into an airbag bag as shown in FIG. The performance of the obtained bag is shown in Table 1.

[0040]

[Table 1]

Examples 2 to 4 and Comparative Examples 5 to 7 As the thermoplastic synthetic fiber a, polyester fiber having a single yarn fineness of 2.1 de, a strength of 7.8 g / de, and a total fineness of 75 de was used as a heat-resistant fiber b. By using para-aromatic polyamide fiber [Technora (registered trademark), manufactured by Teijin Ltd.] having a yarn fineness of 0.75 de, the mixing ratio is changed by changing the number of yarns and the drafting ratio of the thermoplastic synthetic fiber a. A woven fabric with a cover factor of 2,300 was obtained in the same manner as in Example 1 except that the changes were made as shown in Table 2, and an airbag was obtained in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 2.

[0042]

[Table 2]

[0043]

The airbag of the present invention has the following effects as compared with the conventional product. (1) Since it has sufficient heat resistance and strength and can be made to have low air permeability, it is not necessary to coat with an elastomer, and the woven fabric can be made flexible and thin. (2) The woven fabric can be easily folded, and the volume when folded can be reduced. (3) The weight can be reduced. (4) Easy sewing, less slippage of seams, and less reduction in strength due to the sewn portion. (5) It is hard to be damaged by metal pieces or glass pieces. (6) There is little change in the performance of the airbag fabric even after a long period of time.

[Brief description of drawings]

FIG. 1 is a schematic view of an airbag. (A) is a front view,
(B) is a cross-sectional view.

FIG. 2 is a schematic view of an airbag device.

FIG. 3 is a side view of a long-short composite device used for producing a long-short composite yarn.

FIG. 4 is a schematic diagram illustrating how to fold the airbag when evaluating the storability of the airbag. (A), (b)
Indicates folding along the dotted line D. (C) shows a folded airbag.

FIG. 5 is a schematic diagram illustrating a method for measuring the thickness of the airbag folded as shown in FIG.

FIG. 6 is a side view of the filament mixing apparatus used in Comparative Example 1.

7 is a side view of the tow spinning device used in Comparative Example 2. FIG.

[Explanation of symbols]

A Thermoplastic synthetic fiber b Heat resistant fiber A Airbag B Inflator insertion hole C Inflator combustion gas exhaust hole D Folding line E Load weight F Inflator G Combustion gas injection hole H Power cord I Case J Airbag as case and inflator Tightening tool for mounting on A'Shape when air bag A is inflated 11 Supply nip roller 12 Shooter 13 Check-off nip roller 14 Aspirating air nozzle 15 Swirling tie nozzle 16 Delivery roller 17 Mixed fiber yarn 18 Tension Fiber opening adjustment guide 19 Tension load guide 61 Water adhesion roller 62 Nip roller 63 Mixed fiber air nozzle 64 Nip roller 65 Mixed fiber yarn 71 Supply tow 72 Set heater 73 Nip roller 74 Crimper 75 Sliver 76 Storage can t Fold Airbag thickness

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kunio Nishimura 3-4-1 Mihara, Ibaraki City, Osaka Prefecture Teijin Limited Osaka Research Center

Claims (6)

[Claims] 1. A continuous continuous fiber bundle a made of thermoplastic synthetic fiber having a single yarn fineness of 5 de or less, a strength of 6 g / de or more, and a Young's modulus of 1,300 kg / mm ² or less is located in the core part, and a heat is provided around it. Decomposition temperature 300 ° C or higher, single yarn fineness 2 de or less,
The short fiber bundle b consisting of the heat-resistant fiber is a weight ratio a / b = 90
A long-short composite yarn, which is wound and bound at a ratio of / 10 to 50/50, and has a thickness unevenness in the length direction of the yarn with an asymmetry coefficient of 1.3 or less is used as a warp and a weft. A lightweight and compact airbag characterized in that a woven fabric is sewn into a bag shape so that the air permeability of the woven fabric is 0.3 cc / sec · cm ² or less. 2. The lightweight and compact airbag according to claim 1, wherein the shrinkage rate of boiling water of the thermoplastic synthetic fiber is 5% or more. 3. The lightweight and compact airbag according to claim 1, wherein the heat-resistant fiber is a para aromatic polyamide having a strength of 20 g / de or more. 4. The lightweight and compact airbag according to any one of claims 1 to 3, wherein the short fiber bundle (b) is a heat-resistant fiber having an average fiber length of 100 to 800 mm according to a draft method. 5. The lightweight and compact airbag according to claim 1, wherein the fabric has a flame resistance of 5 seconds or more. 6. A continuous or continuous filament bundle in a tension or constant length state, wherein the long-short composite yarn is made of a thermoplastic synthetic fiber having a single yarn fineness of 5 de or less, a strength of 6 g / de or more and a Young's modulus of 1,300 kg / mm ² or less, Pyrolysis temperature 300 ℃ or more, single yarn fineness 2
A continuous long fiber bundle consisting of heat-resistant fibers of de or less is cut between the feeding roller and the drafting roller using a shooter to prevent the fibers from being disturbed, or while being shredded to an average fiber length of 100 mm or more, or after shredded. The yarn obtained by aligning the short fiber bundles at a weight ratio of 50:50 to 90:10 with respect to the continuous long fiber bundles and tying them together with an air nozzle. Lightweight and compact airbag described.