Airbag fabric and method for producing the same

Abstract

In the conventional weaving method, the tension of the warp yarns at the end portions in the width direction during weaving is generally insufficient, resulting in a difference in the curling rate between the center in the width direction and the end portions in the width direction of the fabric. The difference in the curling rate causes unevenness in the woven fabric in the width direction. As a solution, the present invention uses an additional yarn having a smaller boiling water shrinkage than the base yarn, thereby suppressing the shrinkage of the fabric at the end portions in the width direction and thus reducing the difference in the curling rate between the center in the width direction and the end portions in the width direction of the fabric. This makes it possible to produce a fabric for an airbag having high uniformity in the width direction.

Description

Technical Field

[0001] This invention relates to fabrics for airbags and methods for producing fabrics for airbags. Background Technology

[0002] Airbags are installed in vehicles to protect occupants by instantly expanding high-temperature, high-pressure gases during a collision. To withstand the instantaneous expansion caused by these gases in a collision, the fabric used in airbags must have high strength and low permeability.

[0003] A high-strength, low-permeability fabric for airbags is woven using high-strength yarns to achieve a high density. To further increase the density after weaving, the resulting fabric is typically subjected to scouring and shrinking processes to produce a high-quality fabric. In this invention, the scouring and shrinking fabric is referred to as "fabric for airbags".

[0004] Flaring (also known as "wavy selvage" and "loose selvage") occurs on both sides of the width of a conventional high-density woven fabric for airbags. Flaring is a defect caused by defects on both sides of the width of the woven fabric, and is caused by other defects such as thick selvage and wrinkles when the woven fabric is rolled up. Flaring is caused by the difference in crimp (tightening of the yarn; the wavy state of the yarn in cross-section) between the center of the warp yarns constituting the airbag fabric and the sides of the fabric in the width direction.

[0005] When cutting as described above, multiple fabric pieces are typically stacked to cut off the tassels formed during weaving and the sides with numerous defects in the width direction. An increased flaring rate requires cutting off more, leading to increased waste. Furthermore, because the height of the cutting machine's inlet is limited, the sides of the stacked fabric pieces in the width direction may become too large to fit into the machine's inlet, resulting in a reduced number of pieces that can be cut at once and consequently decreased work efficiency.

[0006] List of citations

[0007] Patent documents

[0008] PTL 1: JP 2014-181430 Summary of the Invention

[0009] Technical issues

[0010] Although Patent Document (PTL) 1 specifies the desired boiling water shrinkage rate of the yarns constituting the fabric, PTL 1 does not disclose a technique for improving the uniformity of the woven fabric by adding yarns with different boiling water shrinkage rates; therefore, the uniformity between the center and sides of the fabric in the width direction is unsatisfactory. The present invention provides a technique that improves the uniformity of the woven fabric by using a specific additional yarn having a different boiling water shrinkage rate than the base yarn constituting the airbag fabric, thereby reducing the difference in crimp rate between the warp yarns at the center and sides of the fabric in the width direction.

[0011] Solution to the problem

[0012] As a result of extensive research, the inventors discovered that the above-mentioned objectives can be achieved through the following embodiments. This completes the present invention.

[0013] Specifically, the present invention includes the following embodiments.

[0014] (1) A fabric for an airbag, comprising unremoved fringe at two sides in the width direction of the fabric.

[0015] The fabric includes at least two additional yarns on each side in the width direction.

[0016] in

[0017] The crimp rate of the warp yarns arranged in the center of the fabric's width direction ranges from 7% to 20%.

[0018] The crimp rate of the warp yarns arranged on the sides in the width direction of the fabric is less than 3% to 15%, and

[0019] The difference in crimp rate between the warp yarns arranged on the sides and the warp yarns arranged in the center is less than 5.0%.

[0020] (2) The fabric for an airbag according to item (1), wherein the additional yarn has a smaller boiling water shrinkage rate than the base yarn constituting the fabric for the airbag, and the difference in boiling water shrinkage rate between the additional yarn and the base yarn is more than 0.8%.

[0021] (3) A method for producing the fabric for airbags of item (1), comprising:

[0022] At least two additional yarns are incorporated into each side of the fabric in the width direction, wherein the boiling water shrinkage rate of the base yarn is greater than that of the additional yarns, and the difference in boiling water shrinkage rate between the base yarn and the additional yarns is greater than 0.8%.

[0023] Then it undergoes refining and shrinkage processes.

[0024] Beneficial effects of the invention

[0025] Incorporating an admixture yarn with a different boiling water shrinkage rate than the base yarn (the base yarn's boiling water shrinkage rate > the admixture yarn's boiling water shrinkage rate) suppresses deformation caused by shrinkage at the sides of the fabric in the width direction, because the base yarn's boiling water shrinkage is suppressed by the presence of adjacent admixture yarns (whose shrinkage is less than the base yarn's). This reduces the variation in warp crimp rate at the sides of the warp yarn in the width direction and keeps this crimp rate almost equal to that at the center of the fabric in the width direction, thus reducing the flare rate. Detailed Implementation

[0026] The fabric for airbags according to the present invention is a woven fabric formed from synthetic fiber multifilaments. The total fineness of the synthetic fiber multifilaments constituting the fabric for airbags is preferably 200 to 600 dtex, and more preferably 300 to 550 dtex. A total fineness of 200 dtex or more (due to eliminating the need for excessively increasing weave density) reduces excessive increases in warp and weft binding forces, thus making it easier to bring the packability within the airbag module to an appropriate range. A total fineness of 600 dtex or less makes it easier to reduce excessive increases in the stiffness of the yarns constituting the woven fabric. Synthetic fiber multifilaments with a total fineness in the range of 200 dtex or more and 600 dtex or less are preferred because such synthetic fiber multifilaments make it easier to obtain a fabric for airbags with moderate flexibility and therefore excellent packability within the module.

[0027] In this invention, the total fineness of the synthetic fiber multifilaments constituting the fabric for an airbag is determined as follows. The warp and weft yarns of the fabric obtained through a drying process are removed from the fabric and measured according to JIS L 1013 (2010), 8.3.1. Specifically, a sample of 90 cm in length is accurately removed under initial tension. The absolute dry weight is measured, and the fineness (dtex) based on the corrected weight is calculated using the following formula. The average of five measurements is determined as the total fineness.

[0028] F0=10000×m / 0.9×(100+R0) / 100

[0029] F0: Fineness (dtex) based on calibrated weight

[0030] m: Absolute dry mass of the sample (g)

[0031] R0: Accepted moisture content (%)

[0032] The fabric for airbags according to the invention is woven using base yarns (the warp and weft yarns constituting the fabric for airbags) and further incorporated with additional yarns having specific physical properties. The boiling water shrinkage rate of the additional yarns is preferably less than that of the base yarns constituting the fabric for airbags. In particular, the boiling water shrinkage rate of the additional yarns is preferably less than that of the base yarns (warp yarns).

[0033] To suppress flaring caused by lateral shrinkage in the width direction of the fabric during refining and shrinkage treatments and during drying, the difference in boiling water shrinkage rate between the base yarn and the additional yarn is preferably 0.8% to 20%, more preferably 1.5% to 15%, and particularly preferably 4% to 12%. A difference in boiling water shrinkage rate between the base yarn and the additional yarn of less than 0.8% reduces the effect of suppressing deformation caused by shrinkage, while a difference in boiling water shrinkage rate between the base yarn and the additional yarn of more than 20% adversely affects strength, air permeability, etc., because excessive shrinkage of the base yarn damages the weave structure.

[0034] The boiling water shrinkage rates of the base yarn and the additional yarn used in the fabric for airbags according to the present invention can be such that the boiling water shrinkage rate of the base yarn is greater than that of the additional yarn, and effectively, the difference between them is greater than 0.8%. The additional yarn can be multifilament yarn, monofilament yarn, false twist yarn, or crimped yarn. Its material can be nylon 66 fiber, nylon 6 fiber, polyester fiber, etc. Typically, nylon 66 fiber is often used as the base yarn of airbag fabrics. Since polyester fiber has a lower boiling water shrinkage rate than nylon 66 fiber, it is preferable to use nylon 66 fiber for the base yarn and polyester fiber for the additional yarn.

[0035] In this invention, the weaving density is measured according to JIS L 1096 (2010), 8.6.1.

[0036] More specifically, the sample was placed on a flat surface, and unnatural wrinkles and tension were removed. Then, the number of warp and weft yarns at five different points in a 2.54-cm section was counted, and their respective averages were calculated per unit length to determine the weave density.

[0037] In this invention, the boiling water shrinkage rate of the raw yarn is measured according to the rate of dimensional change caused by boiling water and the rate of filament dimensional change (Method B) as specified in JIS L 1013 (2010). Specifically, the boiling water shrinkage rate is measured as follows: An initial tension is applied to the sample, and two points 500 mm apart are marked. The initial tension is then removed, and the sample is immersed in hot water at 100°C for 30 minutes. The sample is then removed, and the water is gently wiped away with absorbent paper or cloth. The sample is air-dried, and then the initial tension is applied again. The length between the two points is measured, and the rate of dimensional change caused by boiling water (%) is calculated using the following formula. The average of the three measurements is determined as the boiling water shrinkage rate.

[0038] ΔL=(L-500) / 500×100

[0039] ΔL: Boiling water shrinkage rate (%)

[0040] L: Length between the two points (mm)

[0041] There are no particular limitations on the materials used to form the synthetic fiber multifilaments of the fabric for airbags according to the present invention, and a wide range of materials can be selected. In order to satisfy the above-mentioned characteristics, and in view of economic benefits, it is preferred to use multifilaments made of polyamide resins such as nylon 6, nylon 66 or nylon 46, or multifilaments made of polyester resins mainly containing polyethylene terephthalate.

[0042] The synthetic fiber multifilament constituting the fabric for an airbag according to the invention may contain various additives typically used to improve productivity or properties during the production process of the yarn or the fabric. The synthetic fiber multifilament constituting the fabric for an airbag according to the invention may contain, for example, at least one selected from the group consisting of: heat stabilizers, antioxidants, light stabilizers, lubricants, antistatic agents, plasticizers, thickeners, pigments, and flame retardants.

[0043] There is no particular limitation on the number of additional yarns in the fabric for airbags according to the present invention. The effect may increase with increasing quantity. Considering operability, etc., the number of additional yarns is preferably 2 to 12. However, since various production facilities differ, there is no limitation on the number of additional yarns, as long as operability and quality are not compromised.

[0044] There is no particular limitation on the width of the fabric used for airbags according to the present invention; however, the greater the width, the greater the possibility of flaring. Widths of 160 cm and above are effective, and widths of 180 cm and above are particularly effective.

[0045] The flaring reduction technique of the present invention is particularly effective for high-density woven fabrics. The coverage factor of the fabric for airbags according to the present invention is preferably 1800 to 2600, and particularly preferably 2000 to 2500.

[0046] CF is measured using the following formula:

[0047] CF = (A × 0.9) 1 / 2 ×(W1)+(B×0.9) 1 / 2 ×(W2)

[0048] Where A and B represent the thickness (dtex) of the warp and weft yarns, and W1 and W2 represent the warp yarn weaving density and the weft yarn weaving density (yarn / 2.54cm).

[0049] There are no particular limitations on the structure of the woven fabric for the airbag according to the invention, and it can be plain weave, twill weave, satin weave or variations of these weave patterns.

[0050] In the fabric for airbags according to the invention, multiple additional yarns are incorporated into the selvage, the difference between the boiling water shrinkage rate of these additional yarns and that of the base yarn being 0.8% or more (the boiling water shrinkage rate of the base yarn > the boiling water shrinkage rate of the additional yarns). Therefore, in the airbag fabric including unremoved tassels on both sides in the width direction of the fabric, the difference in crimp rate between the warp yarns arranged in the center of the fabric's width direction and the warp yarns arranged on the sides of the fabric's width direction is 5.0% or less, thereby suppressing flaring.

[0051] Furthermore, the fabric for airbags according to the present invention can be further coated with silicone resin or the like as needed, which can further improve its low air permeability. Such a fabric can be effectively used as a fabric for coating airbags.

[0052] Example

[0053] The structure and effects of the present invention will be described in detail below with reference to the embodiments.

[0054] Measurement of curl rate

[0055] The curl rate was measured according to the method specified in JIS L 1096, 8.7, Method B.

[0056] As a sample, ten yarns are taken from the center of the fabric in the width direction. Additionally, ten base yarns (excluding auxiliary yarns) from each side of the left and right portions at the very ends in the width direction are taken. Then, the average value at the center of the fabric in the width direction and the average value at the sides of the fabric in the width direction are determined. The crimp rates are compared between the right side and the center of the fabric in the width direction, and between the left side and the center of the fabric in the width direction, and the larger difference is determined as the difference in crimp rate.

[0057] Fabric weaving density

[0058] Measurements were performed according to JIS L 1096 (2010), 8.6.1. More specifically, the sample was placed on a flat surface, and unnatural wrinkles and tension were removed. The number of warp and weft yarns in the 2.54-cm section was calculated and determined as density. Measurements were performed at least n = 35 times (at 5-cm intervals from the base of the selvage), and both vertical and horizontal densities were measured. The difference between them was calculated at each measurement point.

[0059] Example 1

[0060] Using nylon 66 filament yarn with a fineness of 470 dtex / 144f and a boiling water shrinkage rate of 8.4% in both warp and weft directions (circular monofilament cross-section), the fabric was woven in a plain weave pattern using a water-jet loom, with two additional yarns (0.3% boiling water shrinkage rate) added to each side (a total of four additional yarns). This resulted in a weave density of 53.0 yarns / 2.54 cm for both the weft and warp yarns. The fabric was then passed through a hot water shrinkage bath at 98°C without drying, followed by a continuous drying process using a two-step suction drum dryer, where the first step was adjusted to a temperature T1 of 130°C and the second step to a temperature T2 of 135°C.

[0061] Example 2

[0062] Using nylon 66 filament yarn with a fineness of 470 dtex / 144f and a boiling water shrinkage rate of 8.4% in both warp and weft directions (circular monofilament cross-section), the fabric was woven in a plain weave pattern using a water jet loom, incorporating 10 additional yarns with a boiling water shrinkage rate of 0.3% on each side (a total of 20 additional yarns). This resulted in a weave density of 53.0 yarns / 2.54 cm for both the weft and warp yarns. The fabric was then passed through a hot water shrinkage bath at 98°C without drying, followed by a continuous drying process using a two-step suction drum dryer, where the first step was adjusted to a temperature T1 of 130°C and the second step to a temperature T2 of 135°C.

[0063] Example 3

[0064] Using nylon 66 filament yarn with a fineness of 470 dtex / 144f and a boiling water shrinkage rate of 8.4% in both warp and weft directions (circular monofilament cross-section), the fabric was woven in a plain weave pattern using a water jet loom, incorporating 10 additional yarns with a boiling water shrinkage rate of 6.8% on each side (a total of 20 additional yarns). This resulted in a weave density of 53.0 yarns / 2.54 cm for both the weft and warp yarns. The fabric was then passed through a hot water shrinkage bath at 98°C without drying, followed by a continuous drying process using a two-step suction drum dryer, where the first step was adjusted to a temperature T1 of 130°C and the second step to a temperature T2 of 135°C.

[0065] Comparative Example 1

[0066] Using nylon 66 filament yarn with a fineness of 470 dtex / 144f and a boiling water shrinkage rate of 8.4% in both warp and weft directions (circular monofilament cross-section), the fabric was woven in a plain weave pattern on a water jet loom, resulting in a weave density of 53.0 yarns / 2.54 cm for both weft and warp. The fabric was then passed through a hot water shrink bath at 98°C without drying, followed by a continuous drying process using a two-step suction drum dryer, wherein the first step was adjusted to a temperature T1 of 130°C and the second step to a temperature T2 of 135°C.

[0067]

[0068] Industrial applicability

[0069] This invention improves the quality of fabrics used in airbags by reducing the difference in crimp rate between the center and the sides of the fabric in the width direction, and helps to reduce the cost of airbag manufacturing.

Claims

1. A fabric for an airbag, the fabric comprising unremoved tassels at two sides in the width direction of the fabric, each side in the width direction comprising at least two additional yarns. in The crimp rate of the warp yarns arranged in the center of the width direction of the fabric is in the range of 7% to 20%. The crimp rate of the warp yarns arranged on the sides in the width direction of the fabric is 3% to 15% or less, and The difference in crimp rate between the warp yarns arranged on the sides and the warp yarns arranged in the center is less than 5.0%, and The boiling water shrinkage rate of the additional yarn is less than that of the base yarn constituting the fabric for the airbag, and the difference in boiling water shrinkage rate between the additional yarn and the base yarn is greater than 0.8%.

2. A method for producing a fabric for an airbag according to claim 1, the method comprising: At least two additional yarns are incorporated at each side of the fabric in the width direction, wherein the boiling water shrinkage rate of the base yarn is greater than that of the additional yarns, and the difference in boiling water shrinkage rate between the base yarn and the additional yarns is greater than 0.8%. Then it undergoes refining and shrinking.

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