CN101255944A - Polyester inflatable bag - Google Patents

Abstract

The invention relates to a polyester plain woven fabric construction, wherein the fabric has a unit weight between 150g/m<2> to 300g/m<2> and a tongue sample tearing intensity equal to or bigger than a nylon air bag with same construction and weight. The invention relates to coated and uncoated polyester fibril woven fabric. The uncoated fabric cab be used in industry, and the fabric has a tongue sample tearing intensity of at least 0.75N/g/m<2> when the unit weight of the fabric is between 150g/m<2> to 300g/m<2>. Optional uncoated polyester fibril yarn has a linear density between 200 dtex to 800 dtex, toughness of at least 65cN/T, a tensile figure of at least 350. The fabric can be coated by using chloroprene, chloroprene rubber, polyurethane, siloxane and other organic coatings to decrease air permeability. The invented fabric can also be composed of chaine and/or weft with an aspect ratio between 1.2 and 1.6.

Description

Polyester inflatable bag

This application is a divisional application of an invention patent application with an application date of May 15, 2003, an application number of 03826463.3, and an invention title of "Polyester Filament Woven Fabric for Inflatable Bags".

technical field

This invention relates to polyester inflatable bags.

The invention relates to an uncoated polyester filament woven fabric for an air bag. More particularly, the present invention relates to an uncoated polyester woven fabric having a tear strength comparable to or exceeding that of nylon filament woven airbag fabric. The fabric has a warp tongue tear strength of at least 0.75 N/g/ ^m2 . These fabrics can optionally be further improved with coatings which reduce the air permeability of the fabric. Furthermore, these fabrics can be manufactured with straight yarns (oval or rectangular cross-section), which also reduce the air permeability of the fabric.

Background technique

Polyester industrial filament yarn has high tenacity (greater than 70 cN/tex), high modulus (greater than 170 cN/tex), low elongation (10-15%) and excellent dimensional stability. These yarns are mainly used in rubber reinforcements such as in tires and conveyor belts and v-belts. Higher elongation industrial filament yarns can be obtained by relaxing the stretched yarn at the expense of tenacity and modulus. For example, for applications such as air bags requiring high strength and elongation, polyester industrial filament yarns are lacking and polyamide (nylon) yarns are used. The analysis of the failed polyester inflatable bags showed that the main mode of failure was the tearing of the fabric. The tearing occurs early in the inflation step, as the high pressure gas first enters the folded bag and before the bag is fully inflated. Therefore, there is a need to develop polyester fabrics with tongue tear strength comparable to nylon.

US Patent 5,540,965 to Nishimura et al. discloses a woven polyester air bag obtained by a shrink-set process. This patent discloses that the preferred tensile elongation at break is between 9 and 18%. Said patent discloses that if the tensile elongation at break is less than 9%, the tensile toughness of the resulting woven fabric is not satisfactory even after the shrink-setting process is performed. The patent also states that if the tensile elongation at break is greater than 18%, the woven fabric may exhibit insufficient dry shrinkage and it may be difficult to control the air permeability of the fabric.

US Patents 4,977,016, 5,010,633 and 5,073,418 to Thornton et al. disclose a calendered polyester air bag fabric having specific fabric properties, but do not disclose the properties of the polyester yarns. They do disclose a fabric having an elongation at break greater than 25% and a trapezoidal tear strength greater than 40 lbs (178N) in no more than 8.25 ounces per square yard of fabric (280 g/ ^m2 ). These various fabric (rather than yarn) properties can be obtained through special weaving techniques and the like. It is not possible to say whether the properties of the fabric are a direct result of the yarn or fabric treatment, or how they compare to nylon fabrics.

Japanese Unexamined Patent Publications 2000-27028 and 27029 by Hisao et al. disclose various methods of obtaining tough polyester yarns, but do not give fabric properties. These publications do disclose relaxation rates of 12% or higher. The draw ratio and the temperature of the various rolls employed in the draw stage are important in obtaining the yarn properties of the disclosed invention.

Japanese Unexamined Patent Publication 8-269818 by Masataka et al. discloses tough polyester fibers for energy absorbing safety belts, these polyester fibers have a tensile strength of 8 g/denier (71 cN/tex) or greater, elongation at break rate of 30% or higher. Finally, this reference discloses a relaxation ratio of 10% or more. This reference does not give information on tearing of woven fabrics.

Japanese Unexamined Patent Publication 7-11512 by Hideharu et al. discloses a polyester fiber containing silica fine particles therein. An additive is also incorporated to lower the glass transition temperature, all with the aim of improving flex fatigue properties. The literature has no fabric tear strength data and no comparison with nylon fabrics.

Japanese Patent No. 2289115 to Yoshihiko discloses a polyester fiber having a tenacity of at least 10 g/denier (88.2 cN/tex) and an elongation at break of at least 15%. The highest elongation reported was 18.8%. Fabric properties are not disclosed.

Japanese application 7-186858 by Kozauro et al. discloses a lightweight polyester airbag fabric woven from polyester filament yarn having a tenacity of 9 g/denier (79.4 cN/tex) and an elongation at break of 15%.

European Patent 0 442 373 to Swoboda et al. discloses a polyester air bag fabric using low denier yarns. Its yarn tenacity was 66 cN/tex, elongation at break was 19%, and hot air shrinkage at 200°C was 4.7%. The breaking strength of 26×26 threads/cm 1/1 plain weave fabric is 255×265daN, and the elongation is 34%×26% (the values shown on both sides of × represent the properties expressed in the form of warp × weft). No fabric tear properties were reported.

US Patent 5,236,775 to Swoboda et al. discloses an uncalendered, uncoated polyester air bag fabric. No fabric tear data is given, nor is there a comparison to nylon airbag fabric.

US Patent 5,637,114 discloses an uncoated polyester air bag fabric. A 470 decitex, 100 filament yarn was woven in a ripstop construction (5 mm) using 22/22 threads/cm. The tenacity of the yarn was 66.8 cN/tex, the elongation at break was 21.5%, and the hot-air shrinkage at 200° C. was 7.4%. The fabric had a basis weight of 229 g/m ² before washing and drying, breaking strength/elongation in warp and weft directions of 297 daN/32% and 325 daN/24%, respectively, and tear strength in warp and weft directions, respectively It is 25/24daN. Ripstop fabrics are known to have higher tear strength than plain weave fabrics.

US Patent 5,902,672 to Swoboda et al. discloses an uncoated polyester air bag fabric using a modified poof or crepe fabric. A ripstop fabric with 28 threads/cm woven from 315 dtex, 100 filament yarn had a basis weight of 197 g/m ² and a tongue specimen tear of 14 daN in both warp and weft directions. No comparison with nylon fabric.

Japanese application 7-90747 to Nibo et al. discloses weaving nylon and polyester fabrics after heat setting and calendering to produce an uncoated air bag fabric. The tear strength of the fabric was measured in accordance with JIS K63285.3.6. Direct fabric controls woven with 467 dtex, 216 filament polyester and nylon yarns were performed. This document shows that a polyester fabric woven with 66×66 ends/inch (26×26 ends/cm) has comparable tensile strength to a nylon fabric woven with 55×55 ends/inch (21.7×21.7 ends/cm). Tensile strength and elongation, but compared with the 42×40kg tear strength of nylon fabric, its tear strength is poor at 38×36kg. The basis weight of this fabric is not disclosed (values shown on both sides of x indicate properties in the form of warp x weft).

US Patents 6,037,047 and 6,147,017 to Fasteneau et al. disclose industrial fibers with non-circular cross-sections that impart improved cover to fabrics. The non-circular cross-section of the filament is determined by the aspect ratio. These patents disclose aspect ratios in the range of 2-6.

Japanese application 2002-309462 by Tomomichi et al. discloses a nylon inflatable bag fabric woven from flat cross-section yarns, which has relatively low air permeability. No comparison with polyester air bags is given.

None of the prior art documents teach how to achieve the desired balance of properties for an uncoated fabric having tongue tear strength and Tear strength of trapezoidal specimen. In fact, Japanese application 7-90747 exemplifies the poorer fabric tear strength of polyester fabrics compared to nylon fabrics. Moreover, none of the prior literature discloses that uncoated fabrics with comparable or better tear strength than nylon can be improved with coatings or with fibers having a flat cross section (compared to standard round cross section fibers) ( reduced air permeability).

Contents of the invention

The present invention is an improvement over polyester filament fabrics known in the art in that these polyester woven fabrics have trapezoidal tear strength and tongue tear resistance equal to or better than nylon woven fabrics strength.

In its broadest sense, the invention includes a flat woven fabric composed of a polyester homopolymer having a warp tongue tear strength of at least 0.75 N/g/ ^m2 .

The broadest scope of the invention also includes a balance of yarn properties wherein said yarn has a tenacity of at least 65 cN/tex and a tensile index of at least 350.

In its broadest sense, the present invention includes fabrics comprising an uncoated polyester woven fabric having a tear strength comparable to or exceeding that of nylon filament woven airbag fabric.

The broadest scope of the present invention includes an improved uncoated polyester filament plain weave fabric woven from polyester yarns having a dtex of from about 200 to about 800, at least about A tenacity of 65 cN/tex and a tensile index of at least about 350.

In its broadest sense, the present invention includes a flat woven fabric having a tear strength equal to or exceeding that of a nylon filament flat woven air bag of the same construction or of a similar fabric construction and weight, wherein Both polyester and nylon use warp and/or weft filaments with non-circular cross-sections (their aspect ratios are greater than 1.2).

Polyethylene terephthalate (PET) homopolymer is prepared by one of two methods, namely: 1) transesterification method and 2) direct esterification method. In the transesterification method, dimethyl terephthalate (DMT) and ethylene glycol are reacted (transesterified) to obtain bis(2-hydroxyethyl)terephthalate (mono body) and small amounts of other reaction products (oligomers), and methanol. Since the reaction is reversible, methanol must be removed for complete conversion of the feedstock to monomer. It is known to use magnesium and/or cobalt and/or zinc in transesterification reactions. The catalyst activity is then deactivated at the end of the transesterification reaction by introducing phosphorus, for example in the form of polyphosphoric acid (PPA). Then carry out condensation treatment (polycondensation) on the monomer, and polymerize the monomer into PET. When the monomers are polycondensed, the most commonly used catalyst is antimony. Without the catalyst employed in the phosphorous chelation transesterification reaction, the resulting polymer is susceptible to degradation (thermal degradation) and has a very unacceptable yellow color.

The second method of making PET is to obtain bis(2-hydroxyethyl) terephthalate, oligomer and water. This reaction is also reversible and thus can be brought to completion by removing water during the reaction. The direct esterification step does not require a catalyst and is not conventionally employed. As in the DMT process, the monomers are polycondensed to produce PET. Polycondensation reactions typically use antimony as a catalyst, however, titanium in the form of titanium compounds is also considered a typical catalyst.

The polyester homopolymers of the present invention are spun, drawn, relaxed, and wound onto bobbins as described in US Patent 6,471,906 to DeBenedictis et al. This patent is incorporated herein by reference to describe a suitable method for making the fibers of the present invention. Other known methods for relaxing fibers may be used with the present invention as long as the method results in a minimum 8% relaxation.

The present invention contemplates the use of polyester homopolymers. However, other ingredients may also be present in minor amounts, typically comprising no more than 2% by weight of the polyester homopolymer, such as processing aids, e.g. _TiO2 , permanent yarn coatings, which will e.g. Reduce its coefficient of friction, or increase its adhesion to other substances such as rubber, or make it more UV stable and less prone to breakage.

In order to achieve the claimed fabric properties, it is important to note that if the yarn tenacity is too low, the fabric strength will also be too low. The minimum tenacity of the yarn is about 65 cN/tex. It is important to treat the polyester yarn to provide a tensile index greater than about 350. The through-air shrinkage of polyester yarns is generally less than about 6%, and the present invention does not rely on high fabric shrinkage to achieve high tear strength.

To minimize air permeability of the air bag fabric, a flat, 1 x 1 weave is preferred. Depending on the type of air bag desired, a yarn having a linear density of about 200 to about 800 dtex is used. Higher dtex yarns are woven for larger passenger airbags compared to lower dtex yarns for side curtains. The filaments in the textile yarn can be non-circular, flat type filaments. Typically, the straightness of the filaments is determined by the aspect ratio. The aspect ratio is the ratio of the length and width of the filaments (the aspect ratio for a circular cross-section is 1.0). The larger the aspect ratio, the flatter the yarn. A preferred aspect ratio is between 1.2 and 6. Flat filaments make the fabric more impermeable. But there are practical limitations in that filaments with aspect ratios above about 6 do not produce any significant improvement and are more difficult to weave. Fibrils with aspect ratios less than about 1.2 do not provide any significant improvement over round fibrils.

The fabric can be coated with neoprene, neoprene, polyurethane, silicone or other organic coatings to reduce breathability and act as an insulating cover, especially in the driver's side air bag.

Detailed ways

Test Methods

Yarn Physical Properties

ASTM D885-02: Tenacity and elongation, using a 254 cm gauge length and a 120% strain rate. Free shrinkage (no load) was measured at 177°C for 30 minutes. Linear Density (dtex) is measured using Test Method D1907, Option 1.

The tensile index is the product of the tenacity and the square root of the elongation at break.

Fabric Strip Physical Properties

ASTM D5035-95

fabric grab properties

ASTM D5034-95

Fabric tongue tear

ASTM D2261-96

Tear of fabric trapezoidal specimen

ASTMD5587-96

fabric breathability

Static air permeability is measured in accordance with ASTM D737-96 using a differential pressure of 125Pa. Dynamic air permeability is measured according to ASTM D6476-02.

Yarn Intrinsic Viscosity (IV)

The relative viscosity (RV) of a 3% polyester solution in o-chlorophenol was measured at 25°C with an Ubbelohde viscometer. Intrinsic viscosity (IV) is calculated by the following relationship:

RV＝1+IV×C+0.305×IV ² ×C ² +1.85×10 ^-5 ×exp ^(4.5*IV) ×C ⁴

where C is the solution concentration in gm/100ml.

Example 1-3

A polyester polymer containing 0.08% _TiO2 was spun and drawn by a conventional spin-draw machine to obtain a yarn with an IV of 0.89. Treatment conditions are listed in Table 1.

Table 1

Example Tensile speed (m/min) stretch ratio Relaxation ratio (%) 1 3705 5.56 93 2 3000 6.18 12.0 3 3000 6.18 15.5

These examples are listed in Table 2 along with the physical properties of the yarns of a commercial polyester yarn (KoSa T781) and two commercial nylon yarns (DuPont T725 and T743).

Table 2

sample Ftex Toughness (cN/tex) Elongation(%) tensile index Hot air shrinkage (%) Polyester T781 493 78.6 13.2 285 7.25 Example 1 489 69.8 18.8 303 4.25 Example 2 493 71.9 23.6 349 3.00 Example 3 487 67.5 28.4 360 2.75 Nylon T725 463 76.8 23.0 368 5.35 Nylon T743 467 84.7 20.0 379 5.50

The yarns were woven in a plain weave at 48 x 43 ends/inch (18.9 x 16.9 ends/cm) and a fabric weight of 176 g/ ^m2 . T743 has a slightly higher fabric weight of 183g/m ² . The fabrics were scoured and their physical properties were measured and the results are listed in Table 3.

table 3

sample direction Strip strength (N) Strip elongation (%) grabbing strength (N) Grab sample elongation (%) Trapezoidal specimen tearing force (N) Tongue-shaped specimen tearing force (N) Polyester T781 warp weft 14111263 29.625.7 15981573 29.526.7 391387 116119 Example 1 warp weft 11741161 30.730.8 15921618 34.134.6 456418 135130 Example 2 warp weft 11871245 36.837.3 16171733 41.842.0 553545 152131 Example 3 warp weft 11561116 45.743.4 17071642 48.949.4 589518 151139 Nylon T725 warp weft 13381210 42.637.6 18631686 46.342.9 560464 119123 Nylon T743 warp weft 17301536 37.532.3 22821890 43.034.2 423329 143138

Although the yarn tenacity of the Examples was reduced (Table 2), the fabric grab strength (Table 3) was higher than the commercial T781 polyester fabric. Even more surprising was the fact that the key tear properties (trapezoid and tongue strength) matched and, in the case of Example 3, exceeded the nylon control.

The tear properties normalized to the basis weight of the fabric are listed in Table 4.

Table 4

samples direction Tear of trapezoidal specimen (N/g/m ² ) Tongue-shaped specimen tearing (N/g/m ² ) Polyester T781 warp weft 2.222.20 0.660.68 Example 1 warp weft 2.592.37 0.770.74 Example 2 warp weft 3.143.10 0.860.75 Example 3 warp weft 3.352.94 0.860.79 Nylon T725 warp weft 3.182.64 0.670.70 Nylon T743 warp weft 2.321.80 0.780.75

Polyester T781, Example 3 and Nylon T743 fabrics were coated with silicone rubber (40 g/m ² ).

The physical properties of the coated fabrics are listed in Table 5.

table 5

sample Weight(g/m ² ) direction grabbing strength (N) Grab sample elongation (%) Tongue-shaped specimen tearing force (N) Tongue-shaped specimen tearing (N/g/m ² ) Polyester T781 221 warp weft 19292058 27.332.1 251259 1.131.17 Example 3 210 warp weft 18901792 32.038.0 293316 1.391.50 Nylon T743 214 warp weft 22412116 33.749.2 263227 1.231.06

Even after coating, the fabric of Example 3 of the present invention exhibits tear properties superior to nylon and existing polyester fabrics.

Example 4-7

Higher dtex yarns (720 dtex) were produced with different filament counts and cross-sections as in Examples 1-3. The aspect ratio is the ratio of the length and width of the filaments (a circular cross-section has an aspect ratio of 1.0). Oval cross-sections are obtained by using rectangular spinnerets. Treatment conditions are listed in Table 6.

Table 6

Example Filament count aspect ratio Tensile speed (m/min) stretch ratio Relaxation ratio (%) 4 140 1.0 3000 5.95 12.5 5 192 1.0 3650 5.62 12.75 6 200 1.8 3218 5.55 13.0 7 200 1.8 4265 4.80 13.0

Physical properties are listed in Table 7.

Table 7

Example Ftex Toughness (cN/tex) Elongation(%) tensile index Hot air shrinkage (%) 4 720 69.9 28.1 371 2.5 5 728 69.9 26.6 360 3.0 6 722 74.0 27.5 388 3.5 7 720 68.1 22.9 325 4.0

These yarns are woven in a flat weave into commercial air bag fabrics. Fabrics 4, 5 and 6 used the yarn of Example 4 as the warp and the yarns of Examples 4, 5 and 6 as the weft. Both the warp and the weft of fabric 7 used the yarn of Example 7. The fabric properties, compared to established specifications for nylon fabrics, are listed in Table 8.

Table 8

test unit Nylon Min/Max Fabric 4 Fabric 5 Fabric 6 Fabric 7 Structure: warp and weft Example 4 Example 4 Example 4 Example 5 Example 4 Example 6 Example 7 Example 7 Fabric unit weight g/ ^m2 220/270 238 241 246 262 Structure: warp and weft line/dm 152/168152/168 165157 161157 164161 165161 Tensile strip strength: Warp and weft N 22242224 38123432 38143411 37683464 23352482 Tensile bar elongation: Warp and weft % 25/5525/55 3041 3037 3235.5 3243.5 Grab Tensile Strength: Warp and Weft N 22242224 27902860 27442526 27362655 -- Grab elongation: Warp and weft % 25/5525/55 3850 4047 3951 -- Tear strength of tongue-shaped sample: warp and weft N 200200 219217 230237 230216 228231 Tear strength of tongue-shaped sample: warp and weft N/g/ ^m2 0.740.74 0.920.91 0.950.98 0.930.88 0.870.88 Static air permeability 1/dm ² /minute 0/10 30 22.5 10 5.7 Dynamic air permeability mm/sec 300/700 1490 1310 670 515

These fabric examples show that polyester yarns made according to the present invention generally meet air bag specifications established for nylon fabrics. Fabrics made with higher dtex/filament weft yarns (Example 5) and with oval cross-section weft yarns (Example 6) and 720 dtex 140 filament warp yarns all maintained their excellent tongue tear Strength while reducing the breathability of the fabric. The fabric (Example 7) made from both the warp and fill yarns of the lower tensile index (325) oval cross-section yarn met not only the tear strength specification, but also the static and dynamic air permeability specifications.

Example 8

Lower dtex, circular cross-section yarns (380 dtex, 70 filaments) were produced as in Examples 1-3 and compared to KoSa's commercial polyester industrial yarns T787 and T781. Use of lower dtex yarns in side curtain inflatable bags. Treatment conditions are listed in Table 9.

Table 9

Example Tensile speed (m/min) stretch ratio Relaxation ratio (%) 8 2000 6.2 20 781 type polyester 3500 5.2 2.5 787 type polyester 3750 5.4 13

Physical properties are listed in Table 10.

Table 10

Example Ftex Toughness (cN/tex) Elongation(%) tensile index Hot air shrinkage (%) 8 378 66.2 32.5 377 2.2 781 type polyester 378 77.7 16.1 312 6.0 787 type polyester 378 71.5 22.6 340 3.0

The yarn was flat-woven into a commercial air bag fabric. Their fabric properties are listed in Table 11 below.

Table 11

test unit Example 8 Polyester T781 Polyester T787 fabric weight g/ ^m2 170 160 166 Structure: warp and weft Line/cm 5745 5446 5951 Tensile strength: Warp and weft N 22201978 27672055 23962124 Tensile bar elongation: Warp and weft % 58.848.0 30.022.2 38.530.8 Grab Tensile Strength: Warp and Weft N 18521650 18551243 17741427 Grab elongation: Warp and weft % 57.543.1 31.520.6 39.529.0 Tear strength of tongue-shaped sample: warp and weft N 136121 116108 109104 Tear strength of tongue-shaped sample: warp and weft N/g/ ^m2 0.800.71 0.730.68 0.660.63 Tear strength of trapezoidal sample: warp and weft N 390462 392274 407366 Tear strength of trapezoidal sample: warp and weft N/g/ ^m2 2.292.72 2.451.71 2.452.20

The higher stretch index of Example 7 (see Table 10) again gives the polyester fabric superior tensile tear properties over existing polyester fabrics.

Therefore, it is evident that according to the present invention there is provided a yarn, a method of making the same and a fabric made from the same which fully satisfy the above objects, objects and advantages. Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art from the foregoing description. Accordingly, the present invention intends to embrace all such substitutions, modifications and variations within the spirit and broad scope of the present invention.

Claims (8)

CLAIMS 1. An uncoated polyester air bag comprising a flat woven polyester fabric air bag, wherein said fabric has a warp and weft tongue tear strength of at least 0.7 N/g/ ^m2 . 2. The polyester air bag of claim 1, wherein the fabric has a basis weight of between 150 and 300 g/ ^m2 . 3. A polyester air bag having a plain weave fabric construction, wherein said fabric has a basis weight between 150 and 300 g/ ^m2 and is equal to or better than a nylon air bag of the same construction and weight The tear strength of the tongue-shaped specimen. 4. The air bag of claim 3, wherein said fabric is coated and said tongue test piece tear strength is equal to or better than the tongue of a similarly coated nylon air bag of the same construction and weight The tear strength of the shaped specimen is better. 5. The air bag of claim 3 wherein said fabric is constructed of non-circular yarns and said nylon air bag is similarly constructed. 6. A polyester air bag woven from polyester yarn having a tenacity of at least about 65 cN/tex, a tensile index of at least about 300, and a linear density between 200 and 800 dtex, said The yarn is woven into a plain weave fabric having a tear strength of at least 0.75 N/g/ ^m2 on the warp tongue. 7. The polyester air bag of claim 6, wherein the fabric has a basis weight of between 150 and 300 g/ ^m2 . 8. The polyester air bag of claim 6, wherein the fabric has a warp and weft tongue tear strength of at least 0.7 N/g/ ^m2 .