CN106319720B

CN106319720B - Fabric for airbag, method for producing same, and airbag

Info

Publication number: CN106319720B
Application number: CN201510368890.6A
Authority: CN
Inventors: 山本美保
Original assignee: Toyobo Co Ltd
Current assignee: Toyobo Co Ltd
Priority date: 2015-06-29
Filing date: 2015-06-29
Publication date: 2021-02-09
Anticipated expiration: 2035-06-29
Also published as: CN111155219B; CN111155219A; CN106319720A

Abstract

The present invention relates to a fabric for an uncoated airbag which is excellent in dynamic low air permeability characteristics and also excellent in internal pressure retention characteristics. The high-density fabric for an airbag is characterized by being formed from a synthetic fiber multifilament yarn, having a tensile strength in a twill direction of 400-700N, an Average Dynamic Air Permeability (ADAP) of 500mm/s or less as measured by ASTM D6476, and a dynamic air permeability curve index (Exponent) of 1.5 or less as measured by the above specification.

Description

Fabric for airbag, method for producing same, and airbag

Technical Field

The present invention relates to an airbag, and a fabric for an airbag and a method for manufacturing the same.

Background

In recent years, with the increase of awareness of traffic safety, various airbags have been developed to secure safety of passengers in the event of an automobile accident, and the effectiveness of the airbags has been recognized and rapidly put into practical use.

An airbag is a substance that inflates and expands in a vehicle in a very short time after a vehicle collision, thereby blocking a passenger moving in reaction to the collision and absorbing the impact to protect the passenger. In this effect, the amount of ventilation of the fabric constituting the airbag needs to be small. In recent years, for the purpose of further improving the occupant restraint performance, the requirement for preventing gas from leaking from the fabric when the gas hits the fabric has been increasing, because the internal pressure of the airbag is maintained at a constant level or higher when the airbag is inflated and deployed to stop the occupant.

Conventionally, as means for reducing the air permeability of a woven fabric, a method of coating a resin on a woven fabric for an airbag, and a method of attaching a film to a woven fabric for an airbag have been proposed.

However, application of resin or attachment of a film increases the thickness of the fabric and deteriorates the tightness during storage, and is not suitable as a fabric for an airbag. In addition, since such a resin coating step or a film sticking step is added, there is a problem that the production cost is increased.

In order to solve such problems, recently, a non-coated fabric has been proposed in which synthetic filament yarns (filament yarns) such as polyamide fibers and polyester fibers are woven at a high density without resin processing to reduce the air permeability of the fabric, and for example, as a means for achieving low air permeability, a means for weaving at a high density using synthetic filament yarns having a total fineness of 350 to 470dtex has been disclosed (see patent document 1). According to this means, 0.5L/cm was achieved under a test differential pressure of 20kPa²Ventilation volume below/min.

However, the low air flow amount achieved by these means is a so-called static ventilation characteristic in a state where the differential pressure is kept constant, and the actual inflation/ventilation behavior of the fabric when the airbag functions is determined by or greatly influenced by the high-pressure gas instantaneously touched or the contact of the occupant, and it is considered that there is a characteristic that cannot be sufficiently evaluated among the static ventilation characteristics such as the internal pressure retention property. The internal pressure retention is important in terms of protecting the occupant by absorbing the energy of a collision even after the occupant comes into contact with the airbag.

Thus, an evaluation method concerning dynamic aeration characteristics was determined in ASTM D6476.

However, the above-mentioned means are not sufficient for dynamic ventilation characteristics.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2008-81873

Disclosure of Invention

Problems to be solved by the invention

The purpose of the present invention is to provide a fabric for an airbag that has excellent dynamic low-permeability characteristics and also has excellent internal pressure retention characteristics. In particular, it is an object to provide an airbag fabric and an airbag that can maintain a predetermined ventilation degree even in a dynamic change of a cloth during deployment.

Means for solving the problems

An airbag fabric and an airbag according to the present invention, which can solve the above problems, include the following configurations.

(1) A fabric for an airbag, characterized in that it is a fabric for an airbag formed from a synthetic fiber multifilament yarn (multifilment yarn), the tensile strength in the bias (bias) direction is 400 to 800N, the Average Dynamic Air Permeability (ADAP) measured according to ASTM D6476 is 500mm/s or less, and the dynamic air permeability curve index (Exponent) measured according to the specification is 1.5 or less.

(2) The fabric for an airbag according to (1), characterized in that a bias (CV%) of bias strength is 15% or less.

(3) The fabric for an airbag according to (1) or (2), wherein the synthetic fiber multifilament yarn has a single fiber fineness of 1 to 4dtex, and a value obtained by dividing a weaving density of warp yarns by a weaving density of weft yarns is in a range of 0.95 to 1.05.

(4) The fabric for an airbag according to any one of (1) to (3), wherein a solvent extraction component of the fabric for an airbag is 0.5% by weight or less.

(5) The fabric for an airbag according to any one of (1) to (4), which uses a synthetic fiber multifilament yarn having a boiling water shrinkage of 7% or less as a raw yarn.

(6) A method for producing a fabric for an airbag is characterized in that the moisture content of the fabric after weaving by a water jet loom and before a drying step is adjusted to 4-30%, and then the drying step is performed at a temperature of 80-170 ℃.

(7) The method for producing a fabric for an airbag according to item (6), wherein the drying step has a treatment time of 10 seconds to 180 seconds.

(8) The method for producing a fabric for an airbag according to (5) or (6), wherein heat setting is not performed at the time of the drying step or after the drying step.

(9) An airbag using the fabric for an airbag according to any one of (1) to (4).

Effects of the invention

According to the present invention, a fabric for an airbag excellent in dynamic low air permeability characteristics and also excellent in internal pressure retention characteristics can be obtained.

Drawings

Fig. 1 is a view showing a diagonal direction of a fabric.

Detailed Description

The fabric for an airbag of the present invention is formed of synthetic fiber multifilament yarn. As the synthetic fibers constituting the synthetic fiber multifilament yarn, long fiber multifilament yarns made of polyamide fibers such as nylon 6, nylon 66, and nylon 46, or polyester fibers mainly composed of polyethylene terephthalate can be preferably used. Among these, nylon-based or polyester-based yarns are preferably used, and polyamide-based long-fiber multifilament yarns made of nylon 66 or nylon 46 are particularly preferable from the viewpoint of heat capacity and flexibility. Polyamide-based fibers, polyester-based fibers, aromatic polyamide-based fibers, rayon-based fibers, polysulfone-based fibers, ultra-high molecular weight polyethylene-based fibers, and the like can be used. Among them, polyamide-based fibers and polyester-based fibers are preferable, which are excellent in mass productivity and economy.

In the synthetic multifilament yarn, it is preferable that the total fineness of the synthetic multifilament yarn constituting the fabric is 200 to 500dtex in order to ensure strength characteristics required for an airbag, particularly excellent tensile strength and tear strength.

When the total fineness of the yarn is less than 200dtex, it is difficult to obtain sufficient tensile strength and tear strength, which is not preferable. Further, a fineness of more than 500dtex is not preferable because flexibility as a fabric for an airbag is poor, and not only does the storage property for handling and the like become poor, but also there is a high possibility that the impact on the occupant during the deployment of the airbag becomes large.

The single fiber fineness of the multifilament of synthetic fibers constituting the fabric for an airbag is preferably 1 to 4 dtex. That is, when the synthetic multifilament yarn is composed of many filaments, the filling effect of the fibers is further improved, and not only is low air permeability characteristics obtained, but also when the compressed gas hits the fabric, the monofilament filaments in the multifilament yarn are easily moved, and the multifilament yarn extends flatly on the fabric surface, and not only the fine voids for causing air permeability in the multifilament yarn can be filled, but also the voids in the network part of the fabric can be effectively sealed. The single yarn fineness is in the range of 1 to 4dtex, preferably 2 to 3.5dtex, and more preferably 2.5 to 3.4 dtex.

If the single yarn fineness is less than 1dtex, the single yarn strength is insufficient, and the single yarn is likely to be broken particularly at the time of weaving, and the number of times of stopping the loom is increased, thereby deteriorating the productivity or the quality of the woven fabric. On the other hand, if the single yarn fineness is increased to more than 4dtex, the multifilament yarn is not likely to be stretched flatly on the fabric surface at the time of contact with compressed air, and the air permeability is undesirably high.

The boiling water shrinkage of the base yarn before weaving is preferably 7% or less. In the high density fabric it can be observed that: when the interval between adjacent yarns is already close to the closest packing and shrinkage occurs in a refining process or the like, the yarns move not only in the plane direction of the fabric, that is, so that the interval between adjacent yarns becomes smaller, but also in the direction in which the movement of the yarns is not suppressed, that is, in the thickness direction. If the boiling water shrinkage ratio is more than 7%, the yarn moves greatly in the thickness direction, so the crimp (crimp) ratio becomes too large, and a gap is likely to occur in a portion where the warp and weft overlap in the thickness direction. It is thus assumed that: even if the multifilament yarn extends flatly on the fabric surface when touched by the compressed gas, the fine voids in the multifilament yarn or the voids in the network part of the fabric cannot be narrowed effectively. This tendency becomes more remarkable as the force, i.e., the pressure, with which the compressed gas collides becomes larger, and therefore the dynamic permeability curve index described later becomes larger. Preferably 6.5% or less, more preferably 6% or less. The lower limit is not particularly limited, but if it is considered that a high-strength raw yarn is actually used, the lower limit is 3% or more, preferably 4% or more, and more preferably 4.5% or more.

The weave density of the airbag fabric of the present invention is preferably set to a value obtained by dividing the weave density of warp yarns by the weave density of weft yarns, the value being in the range of 0.95 to 1.05. This is due to: when the weaving density is within this range, a woven fabric having isotropy can be obtained, and the multifilament yarn, which is stretched in an equal direction when touched by compressed gas and extends flatly on the fabric surface, can more effectively fill the voids in the network portion of the woven fabric. If this value is less than 0.95, the woven fabric becomes non-isotropic, and it is not only difficult to fill the voids in the network part of the woven fabric, but also the productivity is not good because the weft density needs to be increased. When the value is more than 1.05, the woven fabric becomes non-isotropic, and it is difficult to fill the gaps in the mesh part of the woven fabric, and the warp density is high, which causes friction between warps at the time of weaving the opening, generates pile, and deteriorates the quality, which is not preferable.

The fabric preferably has a Coverage Factor (CF) of 1900 to 2300, which is determined by the following formula. The cover factor is an index representing the air permeability of the fiber in a woven fabric state by the total fineness of the warp and weft and the density of each of them, and can be said to represent the woven density, and the larger the value, the smaller the gap between the yarns and the higher the air tightness. However, the softness as a fabric is reduced and the weight is increased. That is, as the cover factor becomes smaller, the fabric becomes soft and lightweight, but the airtightness is more decreased. Therefore, in order to ensure both appropriate flexibility and sufficient airtightness (low air permeability), it is necessary to determine an appropriate CF value, and the present inventors have confirmed this, and as a result, they have found that: the CF value is in the range of 1900 to 2300. By setting the cover factor to 1900 or more, low air permeability can be obtained. Further, by setting the cover factor to 2300 or less, the tight storage property can be improved.

CF ═ total denier of untwisted warp (dtex) × 9/10)^1/2X warp yarn Density (root/2.54 cm) + (Total denier of untwisted weft yarns (dtex). times. 9/10)^1/2X weft yarn Density (root/2.5 cm)

The weaving method is not particularly limited, and plain weaving is preferable in consideration of uniformity of fabric physical properties, and the weaving machine is not particularly limited to Air Jet Loom (AJL), Rapier Loom (RL), Water Jet Loom (WJL), and the like, and a water jet loom is preferable in consideration of weaving efficiency.

The tensile strength in the diagonal direction (hereinafter also referred to as diagonal strength) of the airbag fabric of the present invention is preferably in the range of 400 to 800N. Here, the twill direction is a direction in which the warp yarns are interlaced at an angle of half of an angle formed by the warp yarns and the weft yarns of the fabric. In the case of a fabric, since the angle formed by the warp and weft is about 90 degrees, the twill direction is a direction deviated from the warp by about 45 degrees. The tensile strength in the twill direction indicates the strength at which the multifilament yarns constituting the woven fabric are intertwined with each other, and if the tensile strength in the twill direction is within this range, only the monofilament filaments move when touched by compressed gas, and the multifilament yarns themselves do not move, and the multifilament yarns, which are flat to the woven fabric, effectively seal the fine voids in the multifilament yarns and the voids in the network part of the woven fabric. When the tensile strength in the twill direction is less than 400N, the multifilament yarns are less entangled with each other, and the multifilament yarns move when they are touched by compressed gas, which is not preferable because the voids in the network part of the fabric become large. On the other hand, if the tensile strength in the twill direction is greater than 800N, the multifilament yarns are strongly entangled with each other, and the movement of the monofilament filaments is hindered, which is not preferable. More preferably 450 to 700N.

Further, in the present invention, the variation (CV%) of the tensile strength in the diagonal direction is preferably 15% or less, and more preferably 10% or less. The deviation (CV%) described herein is a value calculated by dividing the standard deviation of the measured values at 10 points of the sample at which the twill strength was measured by the average value and multiplying the result by 100 times. If CV (%) is larger than 15%, bias of the bias strength becomes large, and as a result, stress concentrates on a portion where the bias strength is low during unrolling, and therefore, there is a possibility that the needle hole of the sewn portion may be displaced or opened, which is not preferable.

Further, it was found that: in order to set the tensile strength in the bias direction within a predetermined range, conditions for refining and drying the fabric are important. That is, the tensile strength in the twill direction is considered to be a degree of "ease of movement of the yarn" by the interaction between the warp yarn and the weft yarn, and is influenced not only by the total fineness, the single fiber fineness, and the weave density but also by the solvent extraction component amount and the conditions of the tension at the time of shrinkage of the warp and weft yarns, and the present invention was achieved.

In the present invention, the water content of the cloth before drying is required to be in the range of 4% to 30%. By setting the moisture content in this range, the cloth is uniformly dried during drying, and therefore, the entire fabric can be uniformly dried and shrunk, and a balanced cloth can be obtained. When the moisture content is less than 4%, the cloth is not uniformly dried by the heat in the dryer. In particular, since the drying is performed before the fabric edge side, the crimp ratio in the weft direction becomes large, which results in a reduction in twill strength. Preferably 4.5% or more, more preferably 5% or more. When the moisture content is more than 30%, not only a large amount of heat is required to sufficiently dry the sheet, but also drying becomes uneven, which may result in a reduction in bias strength. Preferably 25% or less, more preferably 20% or less.

The moisture content of the fabric before drying can be achieved by adjusting the moisture content of the fabric after the WJL weaving and refining treatment. When the moisture content is insufficient, the adjustment can be performed by supplying water, and when the moisture content is large, the adjustment can be performed by blowing water or sucking moisture by an air flow. In addition, the method of removing water by the treatment using the padder which is often used in resin processing has a problem of generation of wrinkles, and the pressure of the padder is not uniform in reinforcing the intersection of the woven fabric, and the bias strength is not uniform, which is not preferable.

For the purposes of the present invention, the temperature of the dryer is preferably relatively low. However, if it is too low, drying cannot be sufficiently performed, and therefore, it is preferably 80 ℃ or higher. More preferably 100 ℃ or higher, and still more preferably 110 ℃ or higher. If the drying temperature is too high, uneven drying occurs particularly at the fabric edge side in the dryer, and the strength of the diagonal is reduced. Preferably 170 ℃ or lower, more preferably 160 ℃ or lower, and still more preferably 150 ℃ or lower. The treatment time is not particularly limited as long as the cloth is dried at the drying temperature × the treatment time, but is not preferable because the twill strength of the cloth is reduced when the treatment is performed at a high temperature for a long time. The time for passing through the dryer is 180 seconds or less, more preferably 120 seconds or less, and still more preferably 90 seconds or less.

By setting the moisture content of the web before drying to a predetermined range, the entire web can be dried uniformly. Due to this phenomenon, since the yarns constituting the fabric contract and stretch in the width direction at the same time, the yarns themselves are arranged at the optimum positions. This has the effect of increasing the bias strength of the fabric itself, and the present invention has been achieved.

In the case of woven fabrics, the airbag of the invention preferably does not carry out heat setting which is usually carried out on uncoated base fabrics. When heat setting is performed, the yarns constituting the fabric shrink by heat, and the fiber bundle itself is collected to generate a fiber-fiber gap, which is not preferable in terms of low air permeability. Further, since heat setting is not performed, the manufacturing process can be simplified, and there is an advantage that the manufacturing cost can be reduced. The refining step may be performed after weaving, but the refining step is preferably performed in a warm water bath at 20 to 100 ℃.

The solvent extraction component of the airbag fabric of the present invention is preferably 0.5 wt% or less. If the amount is more than 0.5% by weight, the above-mentioned bias strength is reduced by the lubricating effect, which is not preferable. Preferably 0.3% by weight or less, more preferably 0.1% by weight or less.

The Average Dynamic Air Permeability (ADAP) of the fabric for an airbag of the present invention is preferably 500mm/s or less as measured by ASTM D6476. More preferably 400mm/s or less, and still more preferably 300mm/s or less. If the amount is set within this range, the leakage of gas from the fabric is suppressed as much as possible when the airbag inflates and deploys to stop the occupant, and the internal pressure of the airbag can be maintained. In this measurement, a sample in which the compressed air filled in the test head is instantaneously discharged to touch the fabric is measured, the air permeability (dynamic air permeability) corresponding to the pressure which gradually changes is measured, and the average air permeability of the dynamic air permeability in the range between the UPPER LIMIT pressure (UPPER LIMIT) and the LOWER LIMIT pressure (LOWER LIMIT) after the maximum pressure is reached is calculated. The method of measuring the leakage of air after the maximum pressure is reached shows the internal pressure retention from the time when the airbag is deployed to the time when the restraint of the occupant is completed, and is completely different from the static ventilation in which the ventilation at a certain point pressure is measured. The measurement conditions for the Average Dynamic Air Permeability (ADAP) of the present invention are set in a range in which the internal pressure of the airbag at the time of actual occupant restraint is calculated such that the maximum pressure reaches 100 ± 5kPa and the lower limit pressure of the average dynamic air permeability is 30kPa and the upper limit pressure is 70 kPa.

The fabric for an airbag of the present invention has a dynamic air permeability curve index (exposure) of 1.5 or less, preferably 1.4 or less, and more preferably 1.3 or less, as measured by ASTM D6476. The dynamic permeability curve index (exposure) is a curve index E obtained from a pressure-dynamic permeability curve obtained by the measurement of the average dynamic permeability, and can be calculated by using an air bag specific permeability tester FX3350 available from TEXTEST corporation. The present inventors have conducted intensive studies on the relationship between the dynamic permeability curve index and the retention of the internal pressure of the airbag when the occupant is stopped after the airbag is inflated and deployed, and as a result, have found that it is important for the retention of the internal pressure of the airbag that the dynamic permeability curve index is 1.5 or less.

The dynamic ventilation curve index is explained in detail below. If the dynamic permeability curve index is 1.0, a constant permeability is exhibited regardless of the change in the internal pressure of the airbag. If the dynamic permeability curve index is greater than 1.0, the permeability increases as the internal pressure of the airbag increases. If the dynamic permeability curve index is less than 1.0, it shows a decrease in the permeability as the internal pressure of the airbag increases. Generally, the smaller the average dynamic ventilation, the larger the dynamic ventilation curve index. That is, if a flow path through which air can pass is provided, the flow path expands as the internal pressure of the airbag increases, meaning that the ventilation degree increases. When the airbag is deployed so that the inflating airbag touches the occupant, the pressure inside the airbag increases, and the pressure increases to increase the permeability, so that the loss of inflator gas (inflator gas) of the fabric having a high dynamic permeability curve index becomes larger than that of the fabric having a low dynamic permeability curve index.

The fabric for an airbag of the present invention is characterized in that: although the average dynamic ventilation is small, the dynamic ventilation curve index is small. If the dynamic permeability curve index is larger than 1.5, the permeability is increased when the pressure inside the airbag is increased by the occupant touching the airbag, and the loss of the inflator gas becomes excessively large, which is not preferable.

The tensile strength of the fabric for an airbag of the present invention is preferably 500N/cm or more in both the warp direction and the weft direction. Preferably 550N/cm or more, more preferably 600N/cm or more. When the airbag is broken due to the strength of the fabric during operation of the airbag, stress concentrates on the portion having the lowest strength, and the airbag tends to break. In other words, as long as the minimum strength of the fabric satisfies the required strength, breakage can be prevented.

By using the fabric of the invention of the present application, the deployment performance when making an airbag can be improved. That is, the dynamic air permeability at the time of deployment of the airbag is not hindered by movement of the yarns (single yarns) and the multifilaments are arranged in a flat shape, and the voids of the fabric-knotted portion can be effectively sealed. The improvement of the unfolding performance as described herein means: the improvement of the burst pressure of the fabric during the deployment, the shortening of the deployment time, and even when a high-pressure inflator is used, the airbag using the raw yarn having the same strength as the conventional one can be dealt with, instead of the airbag using the high-strength raw yarn.

Examples

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the examples described below, and it goes without saying that the present invention can be carried out by modifying the examples within the scope conforming to the gist of the context, and all of them are included in the technical scope of the present invention. Further, the test methods of various properties employed in the following examples are as follows. JIS used the 1999 year edition.

Boiling water shrinkage of raw yarn: the sample was sampled in the form of a sugar cane (Japanese text: カセ), and the sample was conditioned at 20 ℃ and 65% RH in a temperature/humidity conditioning chamber for 24 hours or longer, and a load of 0.045cN/dtex was applied to the sample to measure the length L0. Subsequently, the sample was immersed in boiling water in a tensionless state for 30 minutes, and then air-dried in the temperature/humidity adjustment chamber for 4 hours, and a load corresponding to 0.045cN/dtex was applied again to the sample, thereby measuring the length L1. The boiling water shrinkage was determined from the lengths L0 and L1 according to the following equation.

Boiling water shrinkage [ (L0-L1)/L0] × 100 (%)

Total denier of the constituent yarns: : measured according to JIS L1096, appendix 14-A.

Number of filaments constituting the yarn: the yarn section was enlarged and photographed by a stereomicroscope, and the number of filaments was counted from the sectional photograph.

Single yarn fineness: the value obtained by removing the number of filaments from the total fineness was used.

The weave density: based on JIS L1096: 19998.6.1 were measured. The sample was placed on a flat table, the unnatural wrinkles and tension were removed, the number of warp yarns and weft yarns in a 1-inch (2.54cm) section was counted at 5 different positions, and the average value of each was calculated.

Coverage Factor (CF): the following formula is shown.

(7) Strength of the fabric: according to JIS L1096: 19998.12.1A (test for the elongation of the fabric), the warp direction and the weft direction were measured. Taking 5 test pieces, removing yarns from two sides of a cloth width, wherein the cloth width is 50mm, stretching the test pieces by using a constant-speed traction strength tester at a clamp interval of 200mm and a stretching speed of 200mm/min until the test pieces are broken, measuring the maximum load until the test pieces are broken, and respectively calculating the average value in the longitudinal direction and the transverse direction.

(8) Twill strength: the straight line interwoven with the warp yarns of the fabric at an angle of 45 degrees was set to a twill direction, and the width was cut to 30mm and the length was cut to 150mm along the twill direction. The maximum load was measured on the sample at a jig interval of 50mm and a tensile speed of 50mm/min using a constant-speed traction tester. Further, 10-point samples were randomly taken from the entire width (weft direction) × warp direction 1m of the cloth, and the average value and the variation (CV%) thereof were calculated. In addition, CV% was calculated by dividing the standard deviation of 10 measurement values by the average value and multiplying by 100 times.

(9) Average dynamic ventilation-dynamic ventilation curve index: determined based on ASTM D6476. The air-bag ventilation tester FX3350 manufactured by TEXTEST company is used, and a test pressure head is 200cm³. The pressure (START PRESS URE) of the compressed air charged in the test head was adjusted so that the maximum pressure applied to the fabric became 100. + -.5 kPa.

The compressed air charged in the test head was released and brought into contact with the fabric sample, and the pressure and the air permeability were measured with time, and the average value of the dynamic air permeability in the range of the UPPER LIMIT pressure (UPPER LIMIT: 70kPa) to the LOWER LIMIT pressure (LOWER LIMIT: 30kPa) after the maximum pressure was reached in the obtained pressure-dynamic air permeability curve was determined as the Average Dynamic Air Permeability (ADAP). In addition, a dynamic ventilation curve index (exposure) was calculated from the obtained pressure-dynamic ventilation curve.

(10) Moisture percentage before dryer:

the cloth to be put into the dryer was cut, and measured according to JIS L10968.9 using the cut cloth. Further, 3 points (center portion 1 point, selvage end 2 point) at different positions in the cloth width direction were measured.

(11) Solvent extraction composition of fabric:

measured according to JIS L10968.36. In addition, n-hexane was used as an extraction solvent.

(12) Airbag deployment test:

airbag sewing: an airbag described in international publication No. 99/28164 is sewn. However, 2 rows of double lock stitches with a stitch of 1470dtex and a needle count of 5.0 needles/cm were used for peripheral sewing. No vent holes are provided. The airbag obtained was folded according to the method described in the pamphlet of international publication No. 01/9416, and attached to the deployment opening while maintaining a state in which the airbag was folded by a commercially available rubber ring.

As a deployment test using an inflator, an airbag test apparatus (an eatingmachine) having a nitrogen gas filling capability was used. In addition, when the 60L airbag is used, the airbag is unfolded under the condition that the maximum pressure is between 60-70 kPa, and the state of the sewing part of the unfolded airbag is confirmed.

Very good: the needle eye deviation of the sewing part is within 1 mm.

O: the sewed part has a part with a needle hole of 1 mm-3 mm.

And (delta): the sewed part has a part with 3 mm-5 mm needle eye opening.

X: the shape of the airbag is not maintained after deployment, or there is a portion where a pinhole deviation of more than 5mm occurs in the sewn portion.

(example 1): 475dtex/140 multifilament yarns (boiling water shrinkage of 5.7%) made of nylon 66 were used as warp and weft yarns in a state of no twist, and a plain fabric was woven by a Water Jet Loom (WJL), and the fabric was refined and dried to produce 53.4 warps/inch, 52.8 wefts/inch and a Cover Factor (CF) 2196. The web before drying was blown with high-pressure air to remove water, and the moisture content was adjusted to 7%. The physical properties of the obtained fabric are shown in table 1. As is clear from table 1: the fabric is excellent in dynamic low air permeability and internal pressure retention, and is a very excellent fabric for an airbag.

(example 2): 353dtex/192 multifilament yarn (boiling water shrinkage of 6.2%) made of nylon 66 was used as warp and weft yarns in a state of no twist, and a flat fabric was woven from WJL, and then refined and dried to produce a fabric having 63.0 warps/inch, 60.5 wefts/inch, and a Cover Factor (CF) 2201. The web before drying was subjected to suction by a vacuum apparatus to remove water, and the moisture content was adjusted to 15%. The physical properties of the obtained fabric are shown in table 1. As is clear from table 1: the fabric is excellent in dynamic low air permeability and internal pressure retention, and is a very excellent fabric for an airbag.

(example 3): 470dtex/144 multifilament yarn (boiling water shrinkage 5.2%) made of nylon 66 was used as warp and weft yarns in a state of no twist, and a flat fabric was woven from WJL, and then refined and dried to produce a fabric having 49.0 warp yarns/inch, 49.0 weft yarns/inch, and a Cover Factor (CF) 2016. The web before drying was subjected to suction by a vacuum apparatus to remove water, and the moisture content was adjusted to 8%. The physical properties of the obtained fabric are shown in table 1. As is clear from table 1: the fabric is excellent in dynamic low air permeability and internal pressure retention, and is a very excellent fabric for an airbag.

(example 4): 225dtex/108 multifilament yarns (boiling water shrinkage of 6.5%) made of nylon 66 were used as warp and weft yarns in a state of no twist, and a flat fabric was woven from WJL, and then refined and dried to produce a fabric having 73.4 warp yarns/inch, 73.8 weft yarns/inch, and a Cover Factor (CF) 2095. The web before drying was subjected to suction by a vacuum apparatus to remove water, and the moisture content was adjusted to 4.7%. The physical properties of the obtained fabric are shown in table 1. As is clear from table 1: the fabric is excellent in dynamic low air permeability and internal pressure retention, and is a very excellent fabric for an airbag.

(comparative example 1): 481dtex/144 multifilament yarn (boiling water shrinkage 9.5%) made of nylon 66 was used as warp and weft yarns in a state of no twist, and a flat fabric was woven from WJL, and then refined and dried to produce a fabric having 53.2 warps/inch, 52.9 wefts/inch, and a Cover Factor (CF) 2208. The physical properties of the obtained fabric are shown in table 1. As is clear from table 1: in this woven fabric, since the boiling water shrinkage ratio of the raw yarn is high and the moisture percentage before drying is as high as 33%, the heat applied to the woven fabric during drying becomes uneven, and as a result, the shrinkage of the woven fabric becomes uneven, and the variation becomes large. As a result: since the bias becomes excessively large although the average value of the bias strength is high, the stress concentrates on the portion where the bias strength is low in the spread test, and the eyelet deviation of the sewn portion of 3.6mm at maximum occurs.

(comparative example 2): 472dtex/72 pieces of multifilament yarn (boiling water shrinkage 9.8%) made of nylon 66 was used as warp and weft yarns in a state of no twist, and a flat fabric was woven from WJL, and then refined and dried to produce a fabric having 55.5 pieces/inch of warp yarns, 54.5 pieces/inch of weft yarns, and a Cover Factor (CF) 2267. The physical properties of the obtained fabric are shown in table 1. As is clear from table 1: the multifilament yarn constituting the fabric has a large single yarn fineness, so that the air permeability of the fabric is high, and a high shrinkage ratio, a reduction in bias strength due to a high temperature during drying, and an increase in variation in bias strength occur, and in a development test, a needle eye deviation of a sewn portion of 4.8mm at maximum occurs.

(comparative example 3): 353dtex/192 multifilament yarn (boiling water shrinkage of 6.2%) made of nylon 66 was used as warp and weft yarns in a state of no twist, and a flat fabric was woven from WJL, and then refined and dried to produce a fabric having 55.0 warps/inch, 63.0 wefts/inch, and a Cover Factor (CF) 2103. The physical properties of the obtained fabric are shown in table 1. As is clear from table 1: in this woven fabric, the weft yarn density is much higher than the warp yarn density, and therefore isotropy is lost, and it is difficult to fill the gaps in the net part of the woven fabric and the twill strength is also reduced, thereby causing a large needle-eye deviation in the sewn part.

(comparative example 4): 225dtex/108 multifilament yarns (boiling water shrinkage of 6.5%) made of nylon 66 were used as warp and weft yarns in a state of no twist, flat fabrics were woven by WJL, and the fabrics before drying were subjected to blowing of high-pressure air to remove water, and the moisture percentage was adjusted to 8%. As the drying conditions, the fabric was fixed in a state of widening by 0.5% from the weft width of the fabric before drying, passed through a furnace at 180 ℃ for 120 seconds, and subjected to so-called heat setting. The resulting fabric had a weave density of 71.8 ends/inch for the warp yarns and 73.5 ends/inch for the fill yarns, and a Cover Factor (CF) of 2068. The physical properties of the obtained fabric are shown in table 1. The heat setting treatment excessively increases the strength of the twill, and as a result, the air permeability performance is deteriorated. This is due to: the heat setting is a condition for applying excessive tension to the warp and weft. However, the warp and weft yarns themselves do not widen the monofilament due to tension and cannot fill the gaps between the yarns, which results in poor air permeability, and a needle eye deviation of more than 5mm occurs at 2 positions of the sewn portion of the airbag after deployment.

(comparative example 5): 475dtex/140 multifilament yarn (boiling water shrinkage 5.7%) made of nylon 66 was used as warp and weft yarns in a state of no twist, and flat fabric was woven by AJL. The airbag fabric is obtained without refining, drying, heat setting, or the like. The weave density was 52.1 warp yarns/inch, 51.9 weft yarns/inch, and the Cover Factor (CF) was 2150. The physical properties of the obtained fabric are shown in table 1. In this fabric, the yarn oil remains 0.63%, and the intersection between the warp and weft yarns easily slides, resulting in a reduction in twill strength. Thus, the result is: the mean dynamic ventilation (ADAP) is high and the dynamic ventilation curve index (Exponent) exceeds 1.5. In addition, the bias strength is reduced, and this causes a large displacement of the sewn portion of the airbag after deployment.

[ TABLE 1 ]

Industrial applicability

The present invention provides a fabric for an airbag, which has excellent dynamic low air permeability characteristics and excellent internal pressure retention characteristics, by determining the total fineness, single yarn fineness, and boiling water shrinkage of the base yarn constituting the fabric, and further determining the weave density and twill strength of the fabric.

Description of the symbols

1 Fabric for airbag

2 Fabric

3 warp yarn

4 weft yarn

5 lines in the warp direction

6 lines indicating the weft direction

7 lines in diagonal directions

Claims

1. A fabric for an airbag, characterized in that it is a fabric for an airbag formed from a synthetic fiber multifilament yarn, the tensile strength in the twill direction is 643N to 800N, the average dynamic air permeability ADAP measured according to ASTM D6476 is 500mm/s or less, the dynamic air permeability curve index Exponent measured according to the specification is 1.5 or less, and the single fiber fineness of the synthetic fiber multifilament yarn is 2.1dtex to 4 dtex.

2. The fabric for an airbag according to claim 1, wherein a variation CV% of bias strength is 15% or less.

3. The fabric for an airbag according to claim 1 or 2, wherein a value obtained by dividing a weaving density of warp yarns by a weaving density of weft yarns is in a range of 0.95 to 1.05.

4. The fabric for an airbag according to claim 1 or 2, wherein a solvent extraction component of the fabric for an airbag is 0.5 wt% or less.

5. The fabric for an airbag according to claim 1 or 2, which uses a synthetic fiber multifilament yarn having a boiling water shrinkage of 7% or less as a raw yarn.

6. A method for producing a fabric for an airbag according to any one of claims 1 to 5, characterized in that the moisture content of the fabric after weaving by a water jet loom and before a drying step is adjusted to 4% to 15%, and then a drying step is performed at a temperature of 80 ℃ or higher and 170 ℃ or lower, and heat setting is not performed at or after the drying step.

7. The method for producing a fabric for an airbag according to claim 6, wherein a treatment time in the drying step is 10 seconds or more and 180 seconds or less.

8. An airbag using the fabric for an airbag according to any one of claims 1 to 4.