Airbag base fabric and method for manufacturing airbag base fabric

Abstract

In a fabric installed on a conventional loom, there can be a difference in cloth length between the central portion and the end portion of the fabric, and the rate of flaring increases, and in the scouring / shrinking step, the yarn shrinks and the curling rate changes, thereby further increasing the flaring. In the present invention, by using a rod-type temple having a loop function in the weaving process, the bulging is reduced, and in addition, the boiling water shrinkage of the additional yarn inserted is reduced to be lower than the boiling water shrinkage of the base yarn, whereby the shrinkage of the base fabric end portion can be efficiently suppressed.

Description

Technical Field

[0001] This invention relates to a base fabric for airbags and a method for manufacturing a base fabric for airbags. Background Technology

[0002] Airbags are installed in vehicles to protect occupants during a collision by utilizing the instantaneous expansion of high-temperature, high-pressure gas. The base fabric of airbags requires high strength and low permeability to withstand the instantaneous expansion caused by high-temperature, high-pressure gas in the event of a crash.

[0003] To weave a high-strength, low-permeability base fabric for airbags, high-strength yarns are used to weave the base fabric at a high density. In many cases, to further increase the density after weaving, the finished fabric is spun and shrunk, thereby producing a high-quality base fabric. In this invention, the spun and shrunk base fabric is referred to as "airbag base fabric".

[0004] In the base fabric for conventional airbags, which is a high-density fabric, the left and right ends are cut with a cutter; however, the cut weft yarns have low tension, so the weft yarns at both ends of the fabric shrink, thereby increasing the crimp rate. This, in turn, results in a lower crimp rate of the warp yarns at the fabric ends, thus the warp yarns at the selvage have low tension. In this case, a tension difference appears between the central part and the ends of the fabric, which causes a difference in fabric length, resulting in flaring (also known as "wavy edge" or "loose edge"). Flaring is caused by defects at the fabric ends, as well as other defects (such as high selvage and wrinkles when the fabric is rolled up).

[0005] Typically, various airbag base fabrics as described above are laminated and cut into multiple parts using a laser cutter or similar device. Airbag base fabrics with large flares at both ends vary in degree depending on the base fabric; therefore, when multiple sheets are laminated, the overlap of the base fabric near the ends is poor. In other words, because the base fabric expands randomly in three dimensions, the shape of the parts is unstable during laser cutting, which can cause defects, and cutting can proceed several centimeters inward from each end where the base fabric has less expansion, increasing wear at the ends. Furthermore, the height of the cutter's input end is limited. After lamination, the ends of the base fabric become too large to fit the cutter's input end, resulting in a reduced number of sheets that can be cut at once, thus causing a decrease in work efficiency.

[0006] During the fabrication stage, which forms the base fabric for the original airbag, a selvage device is attached near the weft of the fabric on the loom to prevent weaving shrinkage during weaving. Various types of selvage exist, such as rod-type selvage that supports the fabric across its entire width, and disc-type selvage that supports the ends of the fabric to prevent weaving shrinkage in the weft direction.

[0007] Rod-type side braces can support the entire base fabric; however, the holding force at the two ends is not adequately guaranteed compared to the central portion. Therefore, excessive density during weaving creates bulges at the weft insertion points, and the density difference between the central and end portions of the fabric increases, potentially causing flaring. In disc-type side braces, excessive density during weaving eliminates the holding force in the central portion; therefore, the ends of the fabric are pulled towards the central portion, and the fabric detaches from the disc-type side brace. It is difficult to manufacture high-density fabrics for airbags that even have uniform density at the fabric ends and reduced flaring.

[0008] In addition, it has been reported that flaring can be improved by introducing additional yarns (also known as "tightening yarns" and "seam tightening yarns") with a finer density than the base yarns (the warp and weft yarns that form the fabric); however, it cannot be said that sufficient effect has been achieved.

[0009] It has also been reported that flaring can be improved by attaching a dedicated additional yarn device to the outside of the rod-type side brace and introducing additional yarn into the device; however, it cannot be said that this sufficiently improves flaring.

[0010] Citation List

[0011] Patent documents

[0012] Patent Document 1: WO2015 / 129684

[0013] Patent Document 2: JP2014-181430A Summary of the Invention

[0014] Technical issues

[0015] One object of the present invention is to reduce the occurrence of flaring in the base fabric for airbags where the fabric has unremoved fringes at both ends.

[0016] Solution to the problem

[0017] As a result of in-depth and meticulous research, the inventors discovered that the above-mentioned objectives could be achieved through the following means, and thus completed the present invention.

[0018] Specifically, the present invention is as follows.

[0019] (1) A base fabric for an airbag, the base fabric for an airbag including an unremoved tassel edge at the end of the base fabric, wherein the base fabric has a flare ratio of less than 1.5% and a flare ratio change slope of less than 0.1%.

[0020] (2) A base fabric for an airbag, wherein the difference between the warp and weft densities of the base fabric for the airbag is less than 1.5 yarns / 2.54cm.

[0021] (3) A base fabric for an airbag, wherein the crimp rate of the ends of the base fabric is more than 80% relative to the crimp rate of the center of the base fabric.

[0022] (4) A method for manufacturing a base fabric for an airbag, the method comprising weaving using a rod-type side support device with a ring function.

[0023] The rod-type side brace device includes an annular weft clamp portion on each end of the inner rod of the rod-type side brace.

[0024] (5) A method for manufacturing a base fabric for an airbag, the method comprising:

[0025] A rod-type edge support device with a ring function is used for weaving by introducing at least two additional yarns at each end of the base fabric, 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%. The rod-type edge support device includes an annular weft clamp portion at each end of the inner rod of the rod-type edge support, and

[0026] Then, refine and shrink the product.

[0027] Beneficial effects of the invention

[0028] Specifically, by weaving the base fabric using a side support device (hereinafter referred to as a "rod-type side support with ring function") having rings at both ends of the inner rod connected to the rod-type side support, the holding force at the ends of the base fabric can be increased while maintaining the weave width and conventional workability. This makes the warp tension uniform in the width direction during weaving on the loom and contributes to the balance of warp and weft density throughout the fabric. Therefore, the difference between warp and weft density can be reduced even up to the ends of the fabric. In addition, the uniform warp tension in the width direction reduces the difference in warp crimp between the center and ends of the base fabric, which reduces the difference in base fabric elongation between the center and ends of the fabric, thus reducing flaring. As a result, high-quality, high-density airbag base fabrics with smaller flaring can be consistently manufactured.

[0029] Furthermore, the introduction of an additional yarn with a different boiling water shrinkage rate than the base yarn (the boiling water shrinkage rate of the base yarn > the boiling water shrinkage rate of the additional yarn) suppresses deformation at the ends of the base fabric caused by shrinkage, because even if the base yarn shrinks due to wastewater, the shrinkage of the adjacent additional yarn is less than that of the base yarn. This thus reduces the flaring rate.

[0030] During the weaving stage, the use of rod-type side braces with loop function reduces the density difference between warp and weft yarns, which significantly contributes to a reduction in the flaring rate. By utilizing a combination of techniques involving the use of specific additional yarns, it is possible to manufacture airbag base fabrics with further improved performance, where the structure can be highly controlled even down to the ends of the base fabric. Attached Figure Description

[0031] Figure 1 A rod-type side brace with a ring function is shown.

[0032] Figure 2 A method for measuring the flaring ratio is shown. Detailed Implementation

[0033] The airbag base fabric according to the present invention is a fabric formed from synthetic fiber multifilaments. The total fineness of the synthetic fiber multifilaments constituting the airbag base fabric is preferably 200 dtex or more and 600 dtex or less, and more preferably 300 dtex or more and 550 dtex or less. A total fineness of 200 dtex or more reduces the excessive increase in the bonding force between warp and weft yarns by eliminating the need for excessively increasing the weave density, thereby making it easier to keep the airbag module's packability within an appropriate range. A total fineness of 600 dtex or less makes it easier to reduce the excessive increase in the stiffness of the yarns constituting the 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 an airbag base fabric with moderate flexibility and therefore excellent packability in the module.

[0034] In this invention, the total fineness of the synthetic fiber multifilaments constituting the base fabric of the airbag is determined as follows. The warp and weft yarns of the base fabric, obtained through a dry-finishing step, are each unwoven from the base fabric and measured according to JIS L 1013 (2010) 8.3.1. Specifically, a sample of 90 cm in length is accurately taken under initial tension. The oven-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.

[0035] F0=10000×m / 0.9×(100+R0) / 100

[0036] F0: Fineness (dtex) based on calibrated weight

[0037] m: Oven-dry mass of the sample (g)

[0038] R0: Official moisture content (%)

[0039] The airbag base fabric of the present invention is woven with base yarn (the warp and weft yarns constituting the airbag base fabric), and is further woven by introducing additional yarns with specific physical properties.

[0040] To suppress flaring at the ends of the base fabric due to shrinkage during scouring and drying, the difference in boiling water shrinkage between the base yarn and the extra 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 between the base yarn and the extra yarn of less than 0.8% reduces the effect of suppressing deformation caused by shrinkage, while a difference in boiling water shrinkage between the base yarn and the extra yarn of more than 20% adversely affects strength, air permeability, etc., because excessive shrinkage of the base yarn damages the weave structure.

[0041] The boiling water shrinkage rate of the base yarn is preferably greater than that of the additional yarn.

[0042] The boiling water shrinkage rates of the base yarn and the additional yarn used in the airbag base fabric of the present invention are such that the base yarn > the additional yarn, and a difference of 0.8% or more between them is effective. The additional yarn can be multifilament yarn, monofilament yarn, or yarn that has been crimped, such as by false twisting. The materials used can be nylon 66 fiber, nylon 6 fiber, polyester fiber, etc. Generally, nylon 66 fiber is usually used as the base yarn for the airbag base fabric. Because the boiling water shrinkage rate of polyester fiber is lower than that of nylon 66 fiber, it is preferable to use nylon 66 fiber as the base yarn and polyester fiber as the additional yarn.

[0043] In this invention, the boiling water shrinkage rate of the raw yarn is measured according to method B of boiling water shrinkage rate 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 are marked 500 mm apart. 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 off with absorbent paper or cloth. The sample is air-dried, and the initial tension is applied again. The length between the two points is measured, and the dimensional change rate (%) due to boiling water is calculated using the following formula. The average of the three measurements is determined as the boiling water shrinkage rate. When the sample shrinks as in this invention, the dimensional change rate (%) due to boiling water is negative, and the absolute value (%) is defined as the boiling water shrinkage rate (%) of this invention.

[0044] Boiling water shrinkage rate (%) = (L - 500) / 500 × 100

[0045] L: Length between two points (mm)

[0046] The materials constituting the synthetic fiber multifilaments of the airbag base fabric according to the present invention are not particularly limited and can be selected from a wide range of materials. In order to satisfy the above characteristics and take into account economic efficiency, the materials are preferably multifilaments made of polyamide resins such as nylon 6, nylon 66 and nylon 46, or multifilaments made of polyester resins mainly containing polyethylene terephthalate.

[0047] The synthetic fiber multifilament constituting the base fabric for airbags according to the present invention may contain a variety of additives typically used to improve productivity or properties during the manufacturing process of the raw yarn or the base fabric. For example, the synthetic fiber multifilament constituting the base fabric for airbags according to the present invention may contain at least one selected from the group consisting of: heat stabilizers, antioxidants, light stabilizers, lubricants, antistatic agents, plasticizers, thickeners, pigments, and flame retardants.

[0048] The base fabric for the airbag of the present invention is woven in the following manner: while incorporating a rod-type side brace with a loop function into the loom and considering the weaving performance, the appropriate tension and the number of weft yarns to be introduced are adjusted. For example... Figure 1 As shown, the rod-type side brace with loop function has a structure in which loop functions c are provided at both ends of an inner rod b in the rod-type side brace cover a. The surface of the inner rod b is smooth or threaded, and the needles in the loop functions c are arranged in one or more rows in the width direction. Furthermore, the inner rod b and the loop functions c are detachable and integrated during weaving. Additional yarn is introduced using a separate winding device or pre-wound onto the loom warp beam for weaving.

[0049] The diameter of the inner rod b is preferably 5 mm to 50 mm, and the surface is preferably smooth or threaded (at least one thread and at most three threads). The material can be selected from POM (polyacetal), PET (polyethylene terephthalate), and metals with high corrosion and rust resistance (brass, aluminum, etc.). Furthermore, the rod-type side brace can be coated to reduce damage to the original yarn (for anti-pilling).

[0050] The number of extra yarns in the base fabric for the airbag according to the present invention is not particularly limited; however, the effect may be improved as the number increases. Considering ease of handling, the number of extra yarns is preferably 2 to 12. However, since handling performance and quality vary depending on the manufacturing equipment, the number of extra yarns is not limited, as long as it does not impair handling performance and quality.

[0051] The width of the base fabric for airbags according to the present invention is not particularly limited; however, the greater the width, the more likely flaring will occur. Base fabrics for airbags with a width of 160 cm or more are effective, and widths of 180 cm or more are particularly effective.

[0052] The flaring reduction technology of the present invention works particularly effectively for high-density base fabrics. The coverage factor of the base fabric for airbags according to the present invention is preferably 1800 to 2600, and particularly preferably 2000 to 2500.

[0053] CF is measured using the following formula:

[0054] CF = (A × 0.9) 1 / 2 ×(W1)+(B×0.9) 1 / 2 ×(W2)

[0055] 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).

[0056] The fabric of the airbag base fabric according to the invention can be plain weave, twill weave, satin weave or variations of these weaving patterns; however, the structure is not particularly limited.

[0057] By introducing an additional yarn with a boiling water shrinkage rate difference of 3% or more (base yarn > additional yarn) into the selvage of the airbag base fabric according to the present invention, the flaring rate of the airbag base fabric is reduced to 1.5% or less, and the flaring rate change slope is reduced to 0.1 or less. Furthermore, the warp and weft density difference can be reduced to 1.5 yarns / 2.54 cm or less.

[0058] Furthermore, the airbag base fabric according to the present invention can be further coated with silicone resin or the like as needed, which can improve low air permeability. Such a base fabric can be effectively used as a base fabric for coated airbags.

[0059] Example

[0060] The structure and effects of the present invention will be explained in detail using examples.

[0061] Measurement of flaring ratio

[0062] The flare ratio represents the ratio of the length of the end portion of the base fabric to the length of the central portion of the base fabric.

[0063] Prepare a full-width fabric with a central section length of 100cm, and cut the fabric along the weft yarns at the front and rear ends of the central section (100cm section) until both ends. Additionally, as... Figure 2 As shown, the following sample is cut from the end.

[0064] A1: A 1cm wide sample cut from a point 1cm from one end.

[0065] A2: A sample with a width of 2cm cut from a position 2cm from one end.

[0066] A3: A 2cm wide sample cut from a point 4cm from one end.

[0067] A4: A sample with a width of 6cm cut from a position 6cm from one end.

[0068] A5: A 10cm wide sample cut from a position 12cm from one end.

[0069] B1: A 1cm wide sample cut from a point 1cm from the other end.

[0070] B2: A 2cm wide sample cut from a point 2cm from the other end.

[0071] B3: A 2cm wide sample cut from a point 4cm from the other end.

[0072] B4: A 6cm wide sample cut from a point 6cm from the other end.

[0073] B5: A 10cm wide sample cut from a point 12cm from the other end.

[0074] After cutting, the length of the central portion of each cut sample is measured, and the measurement result is substituted into the following formula. Because there are flares in the base fabric at both ends, the higher of F1 or F2 is taken as the flare ratio of the base fabric for the airbag. Similarly, the higher of X1 or X2 is taken as the slope of the flare ratio change.

[0075] Expansion rate F1 = (A1 - 100) / 100 * 100

[0076] Expansion rate F2 = (B1 - 100) / 100 * 100

[0077] The higher of F1 and F2 values ​​represents the flare rate of the airbag base fabric.

[0078] The slope of the change in the flaring ratio, X1 = (A1 - A5) / 15.5

[0079] The slope of the change in the flaring ratio, X2, is calculated as (B1 - B5) / 15.5.

[0080] The distance between the measurement locations of samples A1 and A5 is 15.5 cm.

[0081] The higher of X1 and X2 is the slope of the flare rate change of the airbag base fabric.

[0082] Weave density of the base fabric

[0083] Measurements were performed according to JIS L 1096 (2010) 8.6.1. More specifically, the sample was placed on a platform, and unnatural curls and tension were removed. The number of warp and weft yarns in the 2.54-cm segment was counted and determined as density. Measurements were performed at least n=35 times at 5-cm intervals from the selvage reference, and both warp (longitudinal) and weft (transverse) densities were measured, with the difference between them calculated at each measurement point.

[0084] Measurement of curl rate

[0085] The curl rate was measured according to the method described in JIS L1096(1999)8.7.2B.

[0086] As a sample, 10 warp yarns were extracted from the center of the base fabric, and 10 base yarns (excluding extra yarns) located at the very end in the warp direction were extracted from each of the left and right ends of the base fabric, and the average value of the center and ends of the base fabric was determined.

[0087] Then, by substituting the crimp rate of the center of the base fabric and the crimp rate of the ends that have a larger difference from the center of the base fabric, the difference in warp crimp rates between the center and the ends of the base fabric can be determined.

[0088] The difference in warp crimp between the center and ends of the base fabric = warp crimp at the ends of the base fabric / warp crimp at the center of the base fabric × 100

[0089] Example 1

[0090] Using nylon 66 filament yarns (circular cross-section) with a fineness of 470 dtex / 144f and a boiling water shrinkage rate of 5.5% in both the weft and warp directions of the base yarn, the fabric is woven in a plain weave pattern using a water-jet loom equipped with a rod-type side brace (15-mm diameter, flat inner rod surface) with a loop function, by introducing two additional yarns with a boiling water shrinkage rate of -1.3% and the weft and warp yarns, resulting in a weave density of 49.0 yarns / 2.54cm for both the weft and warp. The base fabric is then passed through a hot water shrink bath at 98°C without drying, followed by a continuous dry finishing process using a two-step suction tube dryer, where the first step is adjusted to a temperature T1 of 130°C and the second step to a temperature T2 of 135°C.

[0091] Example 2

[0092] Using nylon 66 filament yarns (circular cross-section) with a fineness of 470 dtex / 144f and a boiling water shrinkage rate of 5.5% in both the weft and warp directions, the fabric is woven in a plain weave pattern using a water-jet loom equipped with rod-type side braces (15-mm diameter, flat inner rod surface) with a loop function, resulting in a weave density of 49.0 yarns / 2.54cm for both the weft and warp. The base fabric is then passed through a hot water shrink bath at 98°C without drying, followed by a continuous dry finishing process using a two-step suction tube dryer, where the first step is set at 130°C (T1) and the second step at 135°C (T2).

[0093] Example 3

[0094] Using nylon 66 filament yarns (circular cross-section) with a fineness of 470 dtex / 144f and a boiling water shrinkage rate of 5.5% in both the weft and warp directions of the base yarn, the fabric is woven in a plain weave pattern using a water-jet loom equipped with a rod-type side brace (15-mm diameter, flat inner rod surface) with a loop function, by introducing two additional yarns with a boiling water shrinkage rate of -1.3% and using a water-jet loom. The weft and warp yarn densities are both 53.0 yarns / 2.54 cm. The base fabric is then passed through a hot water shrink bath at 98°C without drying, followed by a continuous dry finishing process using a two-step suction tube dryer, where the first step is set at a temperature T1 of 130°C and the second step at a temperature T2 of 135°C.

[0095] Example 4

[0096] Using nylon 66 filament yarns (circular cross-section) with a fineness of 470 dtex / 144f and a boiling water shrinkage rate of 5.5% in both the weft and warp directions of the base yarn, the fabric is woven in a plain weave pattern using a water-jet loom equipped with rod-type side braces (15-mm diameter, flat inner rod surface) with a loop function, by introducing two additional yarns with a boiling water shrinkage rate of 4.5% and using a water-jet loom. The weft and warp yarns are both woven at a density of 53.0 yarns / 2.54 cm. The base fabric is then passed through a hot water shrink bath at 98°C without drying, followed by a continuous dry finishing process using a two-step suction tube dryer, where the first step is set at a temperature T1 of 130°C and the second step at a temperature T2 of 135°C.

[0097] Example 5

[0098] Using nylon 66 filament yarns (circular cross-section) with a fineness of 470 dtex / 144f and a boiling water shrinkage rate of 7.0% in both the weft and warp directions of the base yarn, the fabric is woven in a plain weave pattern using a water-jet loom equipped with rod-type side braces (15-mm diameter, flat inner rod surface) with a loop function, by introducing two additional yarns with a boiling water shrinkage rate of 7.0% and using a water-jet loom. The weft and warp yarns are both woven at a density of 53.0 yarns / 2.54 cm. The base fabric is then passed through a hot water shrink bath at 98°C without drying, followed by a continuous dry finishing process using a two-step suction tube dryer, where the first step is adjusted to a temperature T1 of 130°C and the second step to a temperature T2 of 135°C.

[0099] Comparative Example 1

[0100] Using nylon 66 filament yarns (circular cross-section) with a fineness of 470 dtex / 144f and a boiling water shrinkage rate of 5.5% in both the weft and warp directions, the fabric is woven in a plain weave pattern using a water-jet loom equipped with rod-type selvedges, by introducing two additional yarns with a boiling water shrinkage rate of 5.0%. This results in a weft and warp yarn density of 53.0 yarns / 2.54 cm. The base fabric is then passed through a hot water shrink bath at 98°C without drying, followed by a continuous dry finishing process using a two-step suction tube dryer, where the first step is set at a temperature T1 of 130°C and the second step at a temperature T2 of 135°C.

[0101] Comparative Example 2

[0102] Using nylon 66 filament yarns (circular cross-section) with a fineness of 470 dtex / 144f and a boiling water shrinkage rate of 7.0% in both the weft and warp directions, two additional yarns with a boiling water shrinkage rate of 7.0% are introduced. The fabric is woven in a plain weave pattern on a water-jet loom equipped with rod-type selvedges, resulting in a weave density of 53.0 yarns / 2.54 cm for both the weft and warp. The base fabric is then passed through a hot water shrink bath at 98°C without drying, followed by a continuous dry finishing process using a two-step suction tube dryer, where the first step is set at a temperature T1 of 130°C and the second step at a temperature T2 of 135°C.

[0103]

[0104] Industrial applicability

[0105] According to the present invention, specifying the flaring ratio can improve the quality of the base fabric for airbags and contribute to cost reduction in the airbag manufacturing industry.

Claims

1. A base fabric for an airbag, the base fabric including an unremoved tassel edge at an end of the base fabric, the end of the base fabric having one or more rows of pinholes in the width direction, wherein the base fabric has a flare rate of less than 1.01% and a flare rate change slope of less than 0.1%, and having at least two additional yarns at each end of the base fabric, 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 more than 0.8%.

2. The base fabric for airbags according to claim 1, wherein the difference between the warp and weft densities of the base fabric is less than 1.5 yarns / 2.54 cm.

3. The base fabric for an airbag according to claim 1, wherein the warp crimp rate at the ends of the base fabric is 80% or more relative to the warp crimp rate at the central portion of the base fabric.

4. A method for manufacturing a base fabric for an airbag according to claim 1, the method comprising weaving using a rod-type side support device with a loop function. The rod-type side support device has one or more rows of needles arranged in the width direction, and includes an annular weft clamp portion on each end of the inner rod of the rod-type side support.

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