JP2003502522A - Low permeability airbag cushion with very low coating level - Google Patents

Abstract

SUMMARY OF THE INVENTION The present invention relates to a coated inflatable fabric (26), and more particularly to an airbag having a very low amount of coating applied thereto and exhibiting very low air permeability. The inflatable fabrics of the present invention are used primarily in automotive restraint cushions that require low transmission properties (such as side curtain airbags). Traditionally, coatings of heavy and expensive compounds such as neoprene, silicon have been used to provide low permeability levels. The fabric of the present invention provides such a necessarily low permeability level using inexpensive and very thin coatings. Accordingly, the coated inflatable airbag of the present invention has a coating in an amount of up to 2.5 ounces per square yard, most preferably in an amount of up to 0.8 ounces per square yard, Has a leakdown time of at least 7 seconds (measurement time required for the total amount of gas within the maximum airbag pressure during inflation to release the airbag at 10 psi) All coatings that meet these criteria, especially elastomers, non-silicone coatings and coated airbags, are intended to fall within the scope of the present invention.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD OF THE INVENTION

TECHNICAL FIELD The present invention relates generally to coated inflatable fabrics, and more specifically to airbag cushions that have very low amounts of coating added and exhibit extremely low air permeability. . The inflatable fabric of the present invention is primarily used in automotive restraint cushions that require low permeability properties (such as side curtain airbags). Traditionally, coatings of heavy and expensive compounds such as neoprene, silicone have been used to provide low permeability. The fabrics of the present invention use such inexpensive and very thin coatings to provide such inevitably low permeability levels. Accordingly, the coated inflatable airbag of the present invention has a coating comprising a single (or multiple) elastomeric material coated onto the target fabric, and within the fabric, the elastomeric material Has a tensile strength of at least 2,000 and an elongation of at least 180% at break. The coating is then applied (preferably in film) to the surface of the airbag in an amount of up to 2.5 ounces per square yard. The airbag of the present invention has a leak-down of at least 5 seconds after inflation.
Characterizes time (defined as the ratio of inflated bag volume to bag leakdown volume fraction at 10 psi). The resulting airbag cushions, especially permeable cushions with a very small rolled packing volume, are intended to be within the scope of the present invention.

[0002]

[Prior art]

Airbags for motor vehicles are known and have been used for quite some time. Typical construction materials for airbags were polyester or nylon fabrics coated with an elastomer such as neoprene or silicone. The fabric used in such bags is typically a woven fabric formed from synthetic yarns by spinning methods known in the art. The coated material has been found to be acceptable as it acts as an impermeable barrier to the expansion medium. The expansion medium is typically nitrogen, helium or other similar gas from a gas generator or expander. Such gas is delivered into the cushion at a relatively warm temperature. The coating prevents the permeation of the fabric by such hot gases, thus allowing the cushion to quickly inflate in a crash without excessive vacuum. Airbags can also be formed from uncoated fabrics that have been woven in a manner that creates a product with low permeability, or fabrics that have been treated such as calenders to reduce permeability. Fabrics that have reduced air permeability after weaving by calendering or other mechanical treatment are described in US Pat. No. 4,921.
, 735, U.S. Pat. No. 4,977,016, U.S. Pat. No. 5,073,418.
No., which is incorporated herein by reference in its entirety.

Silicone coatings typically use solvent-based or two-component synthetic reaction systems. Silicone coating weights for conventional driver side bags are typically 0.5 to 1.2 ounces per square yard. Unlike the driver's side, the passenger side airbags and side curtain airbags that emerged in the latter half of the 1990's are aimed at protecting the passengers in the event of a side impact and a crash. Side curtain bags have a higher than normal working pressure and, more importantly, during a length of time two orders of magnitude larger than the inflation time for a driver or passenger side airbag. It must remain expanded within the pressure range. The dry coating weight on silicone was about 3-4 ounces per square yard or more for both the front and back panels of the side curtain airbag. Lower coating weights for side curtain bags could not be achieved without sacrificing performance. As one of ordinary skill in the art will appreciate, adding too much weight adds to the cost of the base fabric for the airbag and makes it very difficult to fit in a small airbag module. Furthermore, the tensile strength and tear resistance properties of silicon are very low and cannot withstand high pressure expansion unless a very thick coating is used.

The use of certain polyurethanes as disclosed in Menzel et al. US Pat. No. 5,110,666 (incorporated herein by reference),
Weight gains reported in the range of 0.1 to 1 per square yard can be avoided, but the materials themselves are relatively expensive and due to the nature of the coating materials, relatively complex formulation and application procedures are required. It is considered necessary. This patentee, however, fails to disclose any suitable elasticity and / or tensile strength properties as a polyurethane coating material. Furthermore, only for fabrics used in the driver's or passenger's side cushions, the coating performance (and thus the interrelated air permeability or There is no comment on the importance of leak-down time characteristics. All airbags must be inflatable immediately and very quickly. In fact, once a collision is sensed, the airbag will typically reach maximum pressure in 10 to 20 milliseconds. Normal driver-side and passenger-side airbags are designed to withstand enormous inflation pressures, but the airbag also quickly deflates to absorb energy from the vehicle occupant, who is the bag. . The driver's and passenger's side cushions (airbags) are thus made of a low permeability fabric, but the airbags also quickly deflate through the vents at the connecting seams. Moreover, the knowledge of minor additive coatings in the Menzel patent and in US Pat. No. 5,945,186 granted to Li et al. Does not provide long term gas retention. That is, the airbag cannot withstand the long continuous pressure supplied by the actuated inflator for up to about 2 seconds or more.

The low permeability of these airbag fabrics is therefore much less than a long-term retention of gas in the driver side and passenger side airbag cushions to provide the contracting shock cushioning effect required for sufficient collision protection. Useless. Such airbag fabrics, which are described in detail below, do not perform well for side curtain airbags because they are minimally uncoated with the connecting seams that create the pillow and cushion structure within the airbag. In these areas, the largest leakdowns occur before and after inflation, so the low-coating low-permeability airbag fabrics of the aforementioned patent are not properly used in side curtain airbags.

As mentioned above, there are three different types of airbags, each with a different end use purpose. For example, a driver-side airbag is generally mounted on a steering column, exhibits relatively high permeability, and plays a greater role in cushioning the driver when the vehicle is impacted. Passenger side airbags are composed of a fabric or a relatively highly permeable fabric that is capable of releasing gas via vents incorporated into the fabric. These types of airbags
It is designed to protect humans in the event of a sudden crash and generally to rip from the packaging module from the steering column or dashboard (and thus from multiple "sides"). However, the side curtain airbag uniquely protects passengers during a rollover collision by keeping it inflated for an extended period of time, and also in the roofline along the side windows of the vehicle (hence the backside). And has only the front side) designed to be deployed from a stored collapsed container. The side curtain airbags therefore not only provide a shock absorbing effect, but also protect against broken glass and other debris. Therefore, as pointed out above, it is essential that the side curtain airbags retain high pressures as well as large amounts of gas and remain inflated for the entire long term in a substantially capsized condition. To achieve this, these side curtains are typically coated with large amounts of sealant on both the front and back sides. Since most side curtain airbag fabrics consist of woven fabric blanks that are sewn, sealed, or integrally woven together,
There are many discrete areas where large amounts of gas leak, especially in the seam and its surroundings. Thick coatings have been accepted as a requirement to provide the low permeability (and thus short leakdown time) required for side curtain airbags. Without such a thick coating, such airbags would shrink rapidly and would not function properly during a rollover crash. As one of ordinary skill in the art will appreciate, such thick coatings significantly increase the cost of producing the targeted side curtain airbag. Therefore, it does not lose the heat aging, humidity aging, and permeation properties necessary for proper functioning when inflated, and produces a low-cost (preferably low coating weight), low-permeability side curtain airbag. There is a need. To date, few, if any, have met the need for such thick and heavy airbag coatings for side curtain airbags.

Moreover, there is currently a movement to store such low permeability side curtain airbags in a cylindrical module. There is always a great need to maximize the packing volume of the restraining cushions since airbags are typically stored in the roofline of automobiles and the area that can be reserved is very limited. However, the conventionally implemented low-permeability side curtain airbags have proven to be cumbersome to fit in a tubular container at the targeted roofline of the vehicle. It is very difficult to reduce the actual time and energy for folding such a thickly coated, low permeability product, as well as the packaging volume itself. Moreover, such thick coatings used amplify the problem of blocking (ie sticking between differently coated parts of the cushion) when the products are packaged in close proximity to each other. Delays in deployment during inflation can occur when the possibility of blocking exists. Therefore, they are packed too close to each other,
There is a strong need for low permeability airbags that are packaged in a small volume and have a low chance of blocking. Unfortunately, the prior art has not yet responded to advances in the airbag industry.

[0008]

[Problems to be Solved by the Invention]

In view of the above background, there is a need for side curtain airbags that use low permeability, low volume, and therefore inexpensive coatings over standard low permeability side curtain airbags, and thus extremely small packaging volumes. It is easy to see that there is.

[0009]

DISCLOSURE OF THE INVENTION Low-permeability airbags coated in this manner, needless to say, have a high leak-down time when inflated and after long-term storage. Must be provided. Such novel airbag and novel coating formulations offer significant improvements over the more expensive, higher dose additive airbag coatings (and resulting airbag products) used in the past.

Therefore, it is an object of the present invention that the coating has a very low additive weight and has a very special leak-down time after expansion, so that it has a low permeability which is complementary. Is to provide a bag. Another object of the present invention is to provide an inexpensive side curtain airbag cushion. Yet another object of the present invention is to provide a highly efficient coating formulation that can be applied with very low loading to obtain a very low permeability airbag structure after inflation. . Yet an additional object of the present invention is to provide an air bag coating formulation (through heat and humidity aging tests) that exhibits excellent long term storage stability as well as advantageous long term low permeability. is there. Yet another object of the present invention is a low permeability side curtain airbag with very little collapsible packing volume and non-blocking (mutually sticking) characteristics for effective long term storage in the roofline of an automobile. Is to provide.

Accordingly, the present invention relates to an airbag cushion comprising a coated fabric, wherein the fabric is coated with an elastomeric component in an amount of 2.5 ounces per square yard of the largest fabric and the airbag. The cushion exhibits a leakdown time of at least 5 seconds after extended storage. The present invention also relates to an airbag cushion comprising a coated fabric, wherein the fabric is coated with an elastomeric component, wherein the elastomeric component has a tensile strength of at least 1,500 psi and at least 180%. The airbag cushion comprises at least one elastomer having elongation and also exhibits a characteristic leakdown time of at least 5 seconds after extended storage. Further, the scope of the present invention includes coated airbags that exhibit a collapsed packaging volume factor (diameter of the collapsed airbag cushion measured as the length of the unfolded fabric) of at least 17.

The term “characteristic leak down time” is intended to encompass the range of pressure damping characteristics of a side curtain airbag after the bag has been inflated at the highest operating pressure. The pressure decay curve of a side curtain airbag is very similar to the mathematical exponential decay curve in which a simple time constant is used to give the overall curve its characteristics. The characteristic leakdown time used in the present invention is used to act as a time constant in describing the pressure decay of an airbag. The measurement is that it has already been expanded (up to the initial maximum pressure to "open" the weak seam area),
This is done with an airbag cushion that has been deflated following a subsequent re-inflation at a constant pressure of 10 psi. It is known and understood in the airbag art that retention of inflation gas for extended periods of time during a collision is of greatest demand, especially for side curtain airbag cushions. Side curtain airbags are designed to inflate at the same rate as the driver's and passenger side bags, but side curtain airbags contract very slowly to allow for between rollover and side impact. Passengers must be protected. Therefore, it is essential that the bag exerts a very low leakdown rate after it has been subjected to maximum pressure during the momentary rapid inflation. Therefore, the bag coating must be sufficiently resistant to shock and stress when the bag is inflated rapidly. Therefore, a high leakdown time measurement is best for keeping the maximum amount of available gas in the inflated airbag.

Airbag leakdown after inflation (and after maximum pressure is reached) is therefore closely linked to the actual pressure holding characteristics. The pressure retention characteristics of a side curtain airbag that has already been inflated and deflated (hereinafter referred to as "leakdown time") can be explained by the leakdown time t of the following equation. t (sec) = {volume of bag (ft ³ ) / 10 volume leakdown rate at 10 Psi (SCFH ^* )} × 3600 where SCFH is standard cubic feet per hour. The 10 psi constant is not meant to limit the invention and is simply taken to be the constant pressure at which the leakdown time measurement is made. Thus, even if the pressure rises and falls this amount during actual inflation or after initial airbag pressurization, the limitation is that one skilled in the art would measure the volume of the bag to determine the volume leakdown rate (10 ps).
Divided by (measured by the targeted airbag leak-down amount during a stable inflated state at i), the current measurement given as the answer is at least 5 seconds. If possible, this time is preferably about 9 seconds or more. Still more preferably, it is greater than about 15 seconds, and most preferably it is greater than about 20 seconds.

Alternatively, and also in the method of measurement with an uninflated side curtain airbag, the term “leakdown time” is targeted at half the inflation gas introduced after the initial maximum pressure is reached. It can be measured as the time required to escape from an existing airbag. Therefore, the measurement is started at the moment after the initial maximum pressure (about 30 psi conventional) is reached with the standard expansion module. The pressure of the gas pushed into the airbag after reaching the initial maximum pressure does not remain stable,
(The pressure decreases during the next introduction of inflation gas) Also from the targeted airbag,
It is well understood that it is not possible to prevent a certain amount of inflation gas from escaping during the introduction. The primary focus of such side curtain airbags (as pointed out above) is to remain inflated for as long as possible to provide sufficient impact cushioning protection to vehicle passengers during a rollover accident. Is. The more gas that is retained, the better the impact cushioning effect is provided to the passenger. Therefore, the longer the air bag holds a large amount of inflation gas, the greater the characteristic leakdown time, and thus the better impact cushioning results. At a minimum, the initial airbag must hold at least 25%, preferably 50% or more inflation gas volume for 5 seconds following the initial maximum pressure. Preferably the time is 9 seconds, even more preferably 15 seconds and most preferably 20 seconds.

Similarly, the term "after extended storage" refers to a storage facility awaiting actual inflator assembly (module) storage or installation of the airbag cushion of the present invention in a vehicle. Extended to. The measurements carried out by comparative analysis after a typical heat aging and humidity aging test (ASTM D 5427) are generally accepted and understood by the person skilled in the art. In these tests used in the industry, 16 days of in-furnace aging at 107 ° C followed by 16 days of aging at 83 ° C and 95% relative humidity led to long-term storage of airbag cushions. It is generally accepted as a correct assessment of the stability conditions. Fabrics for airbags of the present invention must exhibit the correct characteristic leakdown time after the rigorous simulated storage test as described above.

[0016]

DETAILED DESCRIPTION OF THE INVENTION

DETAILED DESCRIPTION OF THE INVENTION The components of the elastomer coating of the present invention must consist of at least one elastomer having a tensile strength of at least 1,500 psi and an elongation at break of about 180% or greater. If possible, the tensile strength should be at least 300
It is preferably at 0 psi, preferably about 4,000, most preferably about 5,000. The best is, in fact, the best to create something that can still stick to the surface of the fabric. The preferred elongation at break is about 200%
It is above, and more preferably about 300% or more. These properties of elastomers are both very strong (and therefore capable of withstanding huge pressures both after and after expansion and not easily ruptured) and can be stretched to such a large size. Correct expansion and pressure. Therefore, with the seam of the side curtain airbag,
Also, when applied to the rest of the airbag structure, the coating forms the most preferred continuous film, although not necessarily required. The coating serves to fill the individual holes between the yarns and / or the seams being woven and at the same time to "fix" the individual yarns in place. Then, during swelling, the coating helps prevent leakage down through the interstices between the yarns and prevents the yarns from moving, which can create large spaces for gas to escape.

The use of such high tensile strength and high elongation to break components allows the use of surprisingly low added weights of such coating formulations. Usually, the added weight of coating required on a side curtain airbag is very high, at least 1 on both sides.
It is 3.0 ounces per square yard (standard is actually higher than this, about 4.0 or more).
The airbag cushion of the present invention has a maximum of 2.5 ounces per square yard on each side at most 2.5 ounces per square yard (preferably as low as 2.0 and more preferably 1.8, Further coatings of 1.5 and most preferably as low as 0.8) provide the desired high leakdown times (low permeability). Furthermore, coatings of the past have required excellent temperature and humidity aging stability. Surprisingly, even with such low loadings, and especially with coating materials that have been problematic in the prior art (eg polyurethane), the coating of the invention, and consequently the airbag cushion of the invention, has excellent thermal aging properties. Exhibits humidity aging characteristics. Therefore, coating components and coated airbags show a clear improvement with certain airbag technologies.

Of particular note, the elastomeric component of the elastomeric composition of the present invention may include polyamides, polyurethanes, acrylics, elastomers, hydrogenated nitrogen rubbers
That is, a hydrated NBR), a butyl rubber, an EPDEM rubber, a fluorinated elastomer (that is, a fluoropolymer and a copolymer-containing fluoromonomer), an ethylene-vinyl acetate copolymer, and an ethylene-acrylic copolymer. Also, such elastomers may or may not be cross-linked to the airbag surface. Preferably the elastomer is polyurethane, most preferably a polycarbonate polyurethane elastomer. The compound is commercially available from Bayer Corporation, Im
It is available under the tradename Impranil®, which includes pranil 85® UD, ELH and EHC-01. Other acceptable polyurethanes include Bayhydrol® 123 from Bayer, both S
Ru 41-710, EX 51-550 and Ru from tahl USA
40-350. In the present case, all polyurethanes or elastomers that exhibit the same tensile strength and elongation at break properties as pointed out above are in the coating formulation of the invention and therefore in the coated airbag of the invention. It is available. However, the added weight of other available elastomers may be higher than others to provide the desired leakdown time for long term storage. However, for the purposes of this invention, the upper limit of 2.5 ounces per square yard should not be exceeded. If desired, the desired elastomer can be added in multiple layers, as long as the thickness for the overall coating is not exceeded. Alternatively, a multi-layer coating system can be used, at least as long as the elastomer has the desired tensile strength and elongation at break.

Other possible ingredients in the elastomer coating composition are thickeners, antioxidants, antiblocking agents, crosslinkers, surfactants, flameproofing agents, coalescents, adhesion promoters,
And dye. According to a preferred possible embodiment of the invention, the diffusion of a finely divided elastomeric resin or resin solution (solution or water containing, depending on the elastomer selected) is combined with a flameproofing agent to give a viscosity of about 8000 centipoise or more. Produces a mixed composition of. Most preferred Bay as noted above
Polyurethanes such as polycarbonate polyurethanes such as er and Stahl are preferred. Other available elastomeric resins include W from Witco
itcobond ^™ 253 (35% solids) and B from Cleveland, Ohio
Sancure-like polyurethane from F Goodrich; Chemisat ^™ LC from Goodyear Chemical of Akron, Ohio
Hydrous NBR such as H-7335X (40% solids); EPDM such as EP-603A rubber latex from Lord Corporation, Ely, PA; Butyl rubber latex such as BL-100 from Lord Corporation and butyl rubber latex from Lord Corporation. , And acrylic rubber (elastomer) such as HyCar ^™ from BF Goodrich. This list should not be construed as all inclusive and is only exemplary of possible elastomers. More preferred elastomers include extremely low tensile strength properties (
Silicon is not included, typically below 1500 psi). However, in order to provide effective aging and antiblocking benefits, such components are applied to the elastomeric composition as a topcoat, unless the added weight of the total elastomer exceeds 2.5 ounces per square yard. be able to. In addition, elastomers composed of certain polyester or polyether segments (such as polypropylene oxide) or similar components suffer from stability problems with heat and humidity aging (polyesters readily hydrate, polyethers heat Easily oxidize) Especially very low added weight (ie 0.8-1.2 ounces per square yard)
However, elastomers can be used at high loading weights as long as they do not exceed 2.5 ounces per square yard on each side.

Other particularly preferred additives in this elastomer composition are heat stabilizers, flame retardants, primer adhesives, antiblocking agents, and topcoat materials. A preferred thickener that can be used is Aqualo from Hercules Corporation, which is believed to have a business location in Wilmington, Del.
It is commercially available under the trade name of NATROSOL ^™ 250 HHXR from the N Division. In order to pass the Federal Motor Vehicle Safety Standard 302, flame retardants are preferably added to the compound mixture to meet flame protection requirements for the automotive industry. The preferred flame retardant is Amspe, which is said to have operations in Gloucester, NJ
c AMSP marketed by Chemical Corporation
The ERSE F / R 51. Primer adhesives can be used to facilitate adhesion between the targeted textile surface and the elastomer itself. Therefore, it is preferred that the elastomer be the only component of the elastomeric composition that comes into contact with the surface of the fabric, but targets such as isocyanates, epoxies, functional silanes, and other resins having adhesive properties. Adhesion promoters can be used that do not adversely affect the performance of the elastomer to provide the desired low permeability to the airbag cushion. The adhesive primer coating can be applied directly to the fabric prior to applying the strong elastomeric coating of the present invention to ensure high adhesion.

As pointed out above, silicone topcoat components can also be used to provide suitable antiblocking properties to targeted airbag cushions. Most elastomers, including some grades of silicone or polyurethanes for sealing side curtain structures, tend to block with high surface friction when the temperature rises. High surface friction slows the inflation (opening / deploying) of the airbag, compromising the safety provided by the airbag.
Current side curtain airbags use a non-woven fabric over a silicone coating to provide the anti-blocking benefits as well as the required low friction. However, non-woven fabrics add significantly to packaging volume and overall cost. It has been found that by using an extremely high hardness and high softening point elastomer as the topcoat, antiblocking and low surface friction can be achieved at low cost and improved packing volume. High hardness and softening point can also be achieved by using a cross-linking agent in the top coat. Suitable cross-linking agents include, but are not limited to, melamine-
Formaldehyde resin, polycyanate (bifunctional, trifunctional, and multifunctional), epoxy crosslinker resin, polyazide agent, carbonized diimide crosslinker resin, phenol formaldehyde resin, urea formaldehyde resin and the like. By using a top coat that has extremely high hardness and softening point characteristics, the friction coefficient of friction of about 0.7 or less (
Measured according to ASTM D 4518 Test Method B). The topcoat performs various other functions, including, but not limited to, improved aging of the elastomer coating (such as by silicone), or further reinforcement of the elastomer coating material (with the preferred polycarbonate polyurethane). (Most notably). The topcoat material can therefore be selected from the group of polymeric resins, with the exception of silicone, which have higher softening and hardness points upon coating and optionally curing. Examples of these materials are polyurethanes, polyacrylics, epoxy resins, ethylene-vinyl acetate copolymers, fluoropolymers, polyamides and polyesters.

Airbag fabrics must pass certain tests in order to be used in restraint systems. One of the tests requires a blocking test that shows the force required to separate two pieces of coated fabric (such as an airbag stored) that have been kept in contact with each other for an extended period of time. Laboratory analysis for blocking involves squeezing the 2 "x 2" pieces of coated ends of the airbag fabric together at 5 psi at 100 ° C for 7 days. After this time, the force required to pull the two swatches apart is 50 grams or more, or the time required to separate the fabric hung with a 50 gram weight from the bottom fabric layer,
If it is 10 seconds or longer, the coating fails the blocking test. Of course, the lower the separation shear force, the better the coating. For improved anti-blocking (and therefore also to reduce the possibility of improper adhesion between packaged fabric parts), the added weight of the components of the overall elastomer (including the coating) is 1 Top coats, such as talc, silica, silicates, starches, and the top coat polymeric resins mentioned above, as long as they do not exceed 2.5 ounces per square yard (and preferably at very low levels, for example 1.5). Compounds can be used.

Two other tests that a particular airbag must pass are the oven (heat) aging and humidity aging tests. These tests simulate long-term storage of airbag fabrics by exposure to high temperatures and relatively high humidity. These tests are used to actually analyze various dough properties after long-term storage in hot air ovens (> 100 ° C.) (with or without humidity) for as long as 2 weeks or more. For the purposes of this invention, the test was designed to analyze the air permeability of a basically coated side curtain airbag by measuring the characteristic leakdown time (as detailed above). Was used. The airbag cushion of the present invention, which was first produced and aged, had such a severe characteristic leak-down time of about 5 seconds or less (preliminarily inflated with a maximum pressure of 15 psi or more,
(When it is left to fully deflate and then re-inflated with a gas pressure of 10 psi). Polyurethane, which is the preferred elastomer in the present invention, can be affected by high heat and humidity, although not as much as elastomers containing certain polyesters and polyethers). It is safer to add ingredients that are in the layer and / or the elastomer itself. Antioxidants, anti-aging agents and metal deactivators can be used for this purpose. Although not intended to be limited to this,
As an example, Irganox® 1010 and Irganox® 5 both available from CIBA Specialty Chemicals.
65 can be mentioned. The topcoat may be provided as an additional protection against aging, and the elastomeric composition (including the topcoat) may provide 2.5 ounces per square yard of target fabric add-on weight (per square yard). (Not more than about 1.5 ounces is preferred, but not more than), but not limited to polyamides, NBR rubbers, EPDM rubbers, polyurethanes, melamine formaldehyde resins, urea formaldehyde resins, polyacrylics, Topcoat aging improving materials such as silicone fluoropolymers can be included.

Although not limited thereto, known techniques such as dyes, UV stabilizers,
Other additives including pigments, crosslinkers / hardeners can be included in the elastomer component. Further, it should be noted that silicone can be applied to some airbags in the present invention, as long as the airbag construction allows for long term characteristic leak down times. The scrape coating method is typically used to apply a standard silicone coating to conventional airbag (driver and passenger airbag) fabrics. Since the scrape coating knife remains in contact with the high points of the target fabric's yarn, it creates a discontinuous film on the surface of the fabric, resulting in variations in the thickness of the finished coating. The resulting thin spots in the coating are vulnerable to failure during expansion, causing high leakdown rates.

However, because of the non-uniformity of the surface texture of the fabric, a coating method that is capable of producing a relatively uniform continuous film with good adhesion on the target fabric is most preferred. The fixed gap coating method gives the best results. The coating method is similar to knife over roll and roll over roll. Transfer roll coating methods (reverse roll, calender roll and gravure roll) can be used as they provide a continuous and uniform coating to the fabric. Extrusion coating and slot die coating methods are also possible as long as they provide good adhesion. Resin solutions or sprays are preferred among the fixed gap coating methods. For the same dry weight, except for the 100% resin system, a very large space reset is used for the resin solution or sparging. Higher spatial settings allow for more uniform coating thickness on the produced film. Most preferred is the use of a resin solution as it provides a good film forming process (resin spraying requires the coalescence of intact resin particles to form a good film).

The substrate onto which the elastomeric coating of the present invention is applied to form a backing fabric for an airbag according to the present invention is preferably a woven fabric formed from a woven yarn of synthetic fibers such as polyamide or polyester. It is preferably cloth. Such yarns preferably have a linear density of about 105 denier to about 840 denier, more preferably about 210 to about 630 denier. Such fibers are formed of a plurality of fibers with a linear density of about 6 denier or less, most preferably about 4 denier or less per fiber, preferably a plurality of fibers. In the most preferred embodiment, the backing fabric is formed of nylon fibers, with the most preferred fibers being nylon 6,6. Polyamide material
It has been found to show particularly good adhesion and resistance to hydrolytic degradation when used in combination with the coating according to the invention. Such substrate fabrics are disclosed, preferably in Bower et al. US Pat. Nos. 5,503,197 and 5,421,378, which are incorporated herein by reference. It is preferably woven on such a solution jet loom. The woven fabric is hereinafter referred to as an airbag base fabric. As pointed out above, the airbag of the present invention must exhibit an extremely low permeability, so the term "side curtain" airbag is given.

As pointed out above and also in detail, side curtain airbags (also known as cushions) provide a large amount of inflated gas during a crash in order to provide the passengers with the correct cushioning during a rollover accident. Must hold. All standard side curtain airbags can be used in combination with low additive coatings to provide a product that exhibits the desired leakdown times noted above. Some side curtain airbags are manufactured by labor intensively stitching together two separate woven fabrics or sewn together (or otherwise) to form an inflatable structure. To be done. Moreover, as those skilled in the art will appreciate, such sewing is performed at strategic locations to form seams (junctions between layers of fabric), but seams also create discrete open areas. During expansion, inflation gas may flow through the region. Such an open area thus provides a larger area during a collision, as a pillow structure in the final inflated airbag cushion, and also provides strength to the bag itself, providing a very high initial inflation. Be able to withstand pressure (and therefore not burst while this expansion occurs). For sewn side curtain airbags, the coating of the present invention applied over a flat fabric and seam provides excellent resistance at the sewn seam and also provides low air flow through both the seam and fabric. Provides a leakdown. Basically, another side curtain airbag cushion is manufactured by co-weaving two layers of fabric that are joined together at certain strategic locations (again forming the desired pillow structure). To do). Such a cushion thus has a connecting seam between the two layers. Due to the large number of seams present (both multi-piece and one-piece woven bags), the gas leak-down problem described above occurs during and after inflation. In particular, the possibility of the yarn slipping as the yarn moves in multiple directions and amounts, thus causing rapid inflation gas escape and rapid bag deflation. Therefore, airbag-based fabrics do little to reduce permeability (and correlated leakdown time, especially at relatively high pressures). This is a seam problem which in the past has given rise to the need to use very thick and therefore expensive coatings in order to give low permeability first.

Recently, apart from multi-piece side curtain airbags (which require a large amount of labor intensive sewing to attach to the woven fabric blank) and traditional one-piece woven cushions, between large weft threads. There is a movement towards a particular one-piece woven fabric that reduces floating and reduces the movement of unbalanced weaving yarns upon expansion, a particular one-piece woven fabric is disclosed in Solar Jr. Application No. 09 / 406,264.
No. 6,096,096, the specification of which is fully incorporated herein.
These one-piece woven bags come in dobby or jacquard (
The one-piece airbags produced and used on the solution jet loom of Jacqard) are preferably made on the Jacquard loom. Such improvements can significantly reduce high leakdown from the seam. These airbags provide a well-balanced woven structure and, compared to traditional one-piece woven airbags,
High pressure expansion reduces the possibility of the yarn moving around the attachment point between the two layers of fabric. This greatly improved substantially float-free and well-balanced seam construction allows for very low elastomer coating loading for low permeability effects in a one-piece woven construction. In fact, these airbags according to the invention work very well with an additive coating of less than 1.5 and even low up to about 0.5 ounces per square yard.

Although not preferred in the present invention, the coating composition of the present invention is a non-silicone coating of high tensile strength, high elongation, especially in the low addition amount of the present invention, which is a standard one-piece woven air. It has been found to provide similar low permeability benefits to the bag. However, the amount of coating required for high leakdown times is as described in Solars Jr. Much higher than for Therefore,
Amount of 1.2 per square yard, and 2.2 for other woven airbags
Additions up to ounces are needed to achieve the correct, low level of air permeability. Even with such high loading coatings, the coatings of the present invention themselves compare to standard, commercially available prior art coatings such as silicon (at least 3.0 ounces per square yard must be present). do it,
Provides obvious notable improvements.

Furthermore, it has been found that the components of the coating of the present invention, such as the loadings of the present invention, provide the same type of advantages in the sewn or sewn side curtain airbags described above. While this construction is not quite preferred as it has the potential for high leakdown at the mounting seam, the coatings of the present invention have a permeability that correlates with the lower loadings of standard silicone and neoprene rubber coating formulations. It has been found to result in a significant reduction (in fact to the acceptable leakdown time level). Such additions approach 2.5 ounces per square yard, but are lower due to the use of targeted elastomeric composition components on the dough surface that are sufficiently high in tensile strength and sufficiently stretchable. Amount (eg, 1.
5 ounces) have proven effective. Also, the ability to reduce the amount of coating material (usually expensive) reduces the permeability to the targeted airbag structure while at the same time providing high moisture resistance and also effective aging stability. The coating composition, and also the coated airbag of the present invention, is clearly a huge improvement over conventional airbag technology.

Surprisingly, there is the advantage that the coating according to the invention can be applied to side curtain airbags of unobstructed construction. Conventional woven side curtain bags use a very tightly woven fabric to reduce the likelihood and stress of seam bonding on the applied coating. For example, a typical 420 denier jacquard one-piece woven bag has 54 to 57 per square inch. In contrast, typical driver and passenger side airbag fabrics are 39 to 49 threads per square inch using the same 420 denier yarn. The coatings of the present invention provide very low permeability on less than 54 coarser texture fabrics using 420 denier per square inch. Combining the high tensile strength coatings of the present invention with a lower structure results in faster weaving speeds, less fiber usage, more flexible fabrics, smaller packing volume of coated fabrics, and lower packing. Airbags can be made by weight and at a lower overall cost. Higher tensile strengths or higher coating weights are required to achieve the required low overall permeability or characteristic leakdown times for coarser textured fabrics.

Of particular importance in the present invention is that the airbag cushion can be folded as small as possible into the tubular containment in the targeted roofline of the vehicle. In the collapsed configuration (to fit snugly within the tubular container itself, and thus to inflate completely downward in a collision to provide sufficient protection for passengers), the air of the present invention The bag can be a tubular structure having a diameter of up to 23 millimeters with an unfolded fabric length of 43 centimeters. In such an example, with a 2 meter roofline containment vessel, the required volume of the vessel would be approximately 8
Equal to 30 cm ³ (with volume calculated as length [π] radius ² ). The collapsed packaging diameter of a standard commercial side curtain airbag cushion is at least 25 mm (due to the thickness of the coating required to provide low permeability properties). Therefore, the required tubular container volume is at least 980 cm ³ . Preferably, the collapsed diameter during storage of the airbag cushion of the present invention is up to 20 mm, which clearly deviates from the standard packaging volume (resulting in a packaging volume of 628 cm ³ ). Thus, with respect to the depth of the airbag cushion when inflated (i.e., the length of the airbag extending from the roofline to the lowest point along the window, such as inside the targeted vehicle), the airbag of the present invention. Bag cushion depth (approx. 1 standard)
The quotient for the folded and packed diameter of 7 inches or 431.8 mm) must be at least 18.8. Preferably, this index is approximately 21.6 (
20 mm diameter) and its maximum about 24 (with a minimum diameter of about 18 mm). Needless to say, the range of this index is the standard 17
It need not be an inch deep and is uniquely a function of the coating thickness and thus the weight added.

Another advantage of the side curtain airbag of the present invention is that a low pressure inflator can be used. In the past, the applied coating (ie, relatively thick, eg, 4.0 ounces per square yard of a silicone-based formulation) provided an effective seal and thus sufficient gas retention for the side curtain airbag. But only when the inflation pressure was extremely high. The initial maximum pressure rapidly introduces a large volume of inflation gas into the targeted airbag, thus achieving the amount of time that the targeted airbag remains inflated at a level sufficient to cushion the impact. did it. Unfortunately, even when the desired level of expansion time and the volume of gas retained are met, these are basically very low, only somehow reaching the minimum desired level of properties. The side curtain airbag of the present invention provides a positive improvement in terms of gas retention and inflation time (ie, characteristic leakdown time) as compared to conventional silicon coated airbags. The final user may use significantly lower inflation pressures (ie, may be 15-20 psi or less), but will still be inflated to maximize impact during long rollover collisions. Provided is a side curtain airbag that remains inflated to provide a relief benefit. The performance of using a smaller inflator (lower output is less likely to cause serious injuries and safer for car passengers when inflated), cheaper inflator, lower volume Makes the inflator, and bags and fabrics that need to respond to low physical requirements when inflated, safer. Although the present invention has been described and disclosed in some preferred embodiments and methods, the present invention is not limited to the specific examples, but can be defined in the claims and their equivalents. It is intended to encompass structures, structural equivalence and all alternative embodiments and modifications.

Detailed Description of the Invention and Preferred Embodiments Surprisingly, at 2.5 ounces per square yard on both sides of the surface of the side curtain airbag fabric, and preferably between 0.8 and 2.0. , More preferably 0.8
To about 1.5, even more preferably 0.8 to about 1.2, and most preferably at least 1,500 psi coated at about 0.8 ounces per square yard.
All elastomers with a tensile strength of at least 180% and an elongation at break of at least 180%
It has been found to provide a coated airbag cushion that has very low long term permeability upon and after inflation and that passes long term blocking and long term oven aging tests. The type and amount of coating that outperforms this expectation easily expands after long-term storage and remains expanded for a sufficient period of time to ensure maximum safety within the restraint system. Provide airbag cushion to secure the level. Moreover, it goes without saying that the cost of the final product is lower if less coating ingredients are required. Further, the low content of the coating reduces the storage volume of the airbag within the airbag device. The advantage is improved capacity for airbag fabrics.

The elastomeric components of the present invention are preferably prepared according to the following table: Table 1 Standard water-floating elastomeric composition component parts by weight (vs total composition) Resin (30-40% in water) Solid content) 100 Natrosol® 250 HHXR (thickener) 10 Irganox® 1010 (stabilizer) 0.5 DE-83R (flame retardant) 10 (this particular resin is in Table 2 below) And the amounts listed are simply added into this standard composition to form the coating formulations of the examples of the invention).

The viscosity of the composition being synthesized is determined by Brookfield
) Of about 15,000 centipoise. Once the synthesis is complete, the fixed gap method (maximum distance is about 1 as described in the Solar Jr application above).
The formulation was applied to both sides of a one-piece jacquard woven air bag (with a 420 denier nylon 6,6 thread in it) by means of a gap between the 00 micron coating and the surface of the bag. The bag was then dried at elevated temperature (about 300 ° F for about 3 minutes) and cured to form the required thin coating. As pointed out above, the scraper coating can also provide the desired film coating, but with a fixed gap coating, it can maintain the surface uniformity of the bag for the desired film width. The method is preferred. Scrape coating in this sense is not limited to this,
It consists of a knife coating of a specific knife overgap table, float knife, and knife overform pad method. The final dry weight of the coating is preferably about 0.6 to 2.5 ounces per square yard or less,
Most preferably, it is 0.8 to 1.2 ounces per square yard or less. The resulting airbag cushion is substantially substantially impermeable to air as measured according to ASTM test D737, "Air Permeability of Textile Fabrics" standard. Table 2 Standard water-floating elastomer component component parts by weight (vs total composition) Resin (25-40% solids in solvent) 100 Irganox® 1010 (stabilizer) 0.5 DE-83R ( Flame Retardant 10 The resulting coating is applied in the same manner as indicated above for elastomers that float on water.

To further illustrate the present invention, some non-limiting examples are given in Table 3 below. These examples are provided for the purpose of illustrating some preferred embodiments and should not be construed as limiting the scope of the invention in any way. For these examples, within the ranges of Tables 1 and 2 of the above formulation,
It incorporates the preferred elastomers shown below. Each of the coated bags undergoes rapid inflation up to a maximum pressure of 30 psi. Then the air leakage (SCFH) of the inflated bag is 10ps
measured at i. Characteristic leakdown time (sec) was calculated based on leak rate and bag volume.

[Table 3]

As mentioned above, Examples 1-6 worked very well within the scope of the invention. Examples 10 and 11 show some limitations and show that polyester-based elastomers (
Witcobond 290H) showed excellent thermal aging (oxidation) stability, but it tends to hydrolyze easily at high humidity. The polyester-based elastomer (Sancure 861) showed excellent resistance to hydrolysis, but poor oxidation. However, it has been demonstrated that these elastomers have acceptable permeability which reduces high loading weights to less than 2.5 ounces per square yard. Furthermore, although silicon showed heat resistance and hydrolysis resistance (humidity aging), tensile strength and tear resistance were limited. Natural rubber, SBR, chloroprene rubber and other unsaturated carbon double bonds exhibited excellent hydrolysis resistance. However, the unsaturated carbon double bonds that give elastic oxidation oxidize immediately and the properties of the rubber change after aging. Elastomers with good physical properties and hydrolysis and oxidation resistance properties are preferred for this application. A polyurethane base on a soft segment of polycarbonate is preferred for this application. The airbag of Example 3 exhibited a slip coefficient with a friction constant of about 0.6. A relatively thick silicon-based coated side curtain airbag consisting of a nonwoven layer showed a constant of about 0.8.

(Detailed Description Based on the Drawings) As shown in FIG. 1, the inside of the vehicle 10 before inflation of a side curtain airbag (not shown) is shown. Vehicle 10 has a front seat 1
2, a back seat 14, a front side window 16, a back side window 18, and a roof in which a tubular container 22 containing a side curtain airbag (not shown) of the present invention is stored. It consists of line 20. Also in the roofline 20 is an inflator assembly 24 that ignites upon impact and pushes gas into the side curtain airbag (26 in FIG. 2). FIG. 2 shows the side curtain airbag 26 inflated. As pointed out above, the airbag 26 is coated with a coating formulation (not shown) at a maximum of 2.5 ounces per square yard, preferably polyurethane polycarbonate. The airbag 26 of the present invention has a minimum of 5 seconds,
Most preferably, it remains fully expanded for 20 seconds.

FIG. 3 shows a container 2 formed into a roofline tubular shape in an unexpanded state.
2 shows a side curtain airbag 26 stored in No. 2. As pointed out above, the thickness of the airbag 26, measured as the diameter of the collapsed package (
(As shown in FIG. 5), the container 22 formed into a cylindrical shape of the roof line is removed from the airbag 2
6 to the bottom lowest point 28 of at least 17 and up to 29 when compared to the depth of the airbag in either the uninflated or inflated state.

4 and 5 show the folded airbag 26 in line 2 when stored in the container 22.
Along the way you can understand this concept. The measured diameter of the airbag 26 of Example 3 described above is approximately 20 millimeters. A standard side curtain airbag has a depth of about 17 inches or 431.8 millimeters. Therefore,
The preferred packing volume factor is about 21.6. The coating add-on weight for the comparative silicon base thickness is 4.0 ounces per square yard given about 25 millimeters for a factor of about 17.3. There are, of course, numerous alternative embodiments and variations of the present invention that are intended to be within the spirit and scope of the appended claims.

[Brief description of drawings]

FIG. 1 is a side view and an inner view of a vehicle before inflation of a side curtain airbag of the present invention.

FIG. 2 shows a side view and an inside view of the vehicle after the side curtain airbag of the present invention is inflated.

[Figure 3]   The side view of a side curtain airbag is shown.

[Figure 4]   The side view of the container of a side curtain airbag is shown.

[Figure 5]     FIG. 5 shows a perspective sectional view of an airbag stored in the container of FIG. 4.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) D03D 1/02 D03D 1/02 (31) Priority claim number 09/501, 467 (32) Priority date 2000 February 9, 2000 (29 February 2000) (33) Priority claiming countries United States (US) (81) Designated countries EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE), OA (BF, BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG) , AP (GH, GM, KE, LS, MW, MZ, SD, SL, SZ, TZ, UG, ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, CA, CH, CN, CU, CZ, DE, DK, EE, ES, FI, GB, GD, GE, GH, GM, HR, HU , ID, IL, IN, IS, JP, KE, KG, KP, KR, KZ, LC, LK, LR, LS, LT, LU, LV, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, UA, UG, UZ, VN, YU, ZW F terms (reference) 3D054 AA07 AA18 CC26 CC29 FF18 4F100 AK45A AK46B AK48B AK51A BA02 DD31 DG11B DG12B GB32 JA02 JA13B JD01 YY00A YY00B 4L033 AA08 AB05 AC15 CA47 CA50 4L048 AA24 AA34 AA48 AB07 AB11 BA02 CA01 CA25 DA01 Scope of invention Is intended.

Claims (39)

[Claims] 1. An airbag cushion comprising a coated fabric, the fabric being coated with an elastomeric composition in an amount of at most 2.5 ounces per square yard of fabric, the airbag being inflated. An airbag cushion that later shows a characteristic leakdown time of at least 5 seconds. 2. The airbag cushion of claim 1, wherein the elastomeric composition does not include silicone. 3. The airbag cushion of claim 1, wherein the elastomeric composition comprises polyurethane. 4. The airbag cushion according to claim 1, wherein the coating material is woven with a polyamide weaving thread. 5. The airbag cushion according to claim 4, wherein the polyamide weaving yarn is formed of nylon 6,6 fibers. 6. The polyamide yarn is a multifilament yarn, comprising 210
The airbag cushion according to claim 4, having a linear density of 630 denier. 7. The airbag cushion of claim 6, wherein the multi-fiber woven yarn is a plurality of fibers having a linear fiber density of about 4 denier or less per single fiber. 8. The airbag cushion of claim 1, wherein the elastomeric composition is present in the form of an aqueous solution or solvent solution. 9. The airbag cushion of claim 3, wherein the elastomeric polyurethane composition comprises polycarbonate polyurethane. 10. The elastomer composition is at most 2. per square yard.
The airbag cushion of claim 1, wherein the airbag fabric surface is coated with an amount of 0 ounces. 11. The elastomeric composition is at most 1. per square yard.
11. The airbag cushion of claim 10, wherein the airbag fabric surface is coated in an amount of 5 ounces. 12. The elastomeric composition has at most 1. per square yard.
The airbag cushion of claim 11, wherein the airbag fabric surface is coated in an amount of 2 ounces. 13. The elastomeric composition is at most 1. per square yard.
13. The airbag cushion of claim 12, wherein the airbag fabric surface is coated in an amount of 0 ounces. 14. The elastomeric composition is at most 0. 2 per square yard.
14. An airbag cushion according to claim 13, characterized in that the airbag fabric surface is coated in an amount of 8 ounces. 15. An airbag cushion having a coated fabric, the fabric being coated with an elastomeric composition, the elastomeric composition having a tensile strength of at least 1,500 and an elongation of at least 180%. An airbag cushion comprising an elastomer and exhibiting a leakdown time of at least 7 seconds after inflation. 16. The airbag cushion of claim 15, wherein the elastomeric composition comprises polyurethane. 17. The airbag cushion according to claim 15, wherein the coating material is woven with a polyamide weaving thread. 18. The airbag cushion according to claim 17, wherein the polyamide weaving yarn is formed of nylon 6,6 fibers. 19. The polyamide yarn is a multifilament yarn, comprising about 21
19. The airbag cushion according to claim 18, having a linear density of 0 to 630 denier. 20. The airbag cushion of claim 19, wherein the multifilament yarn has a linear fiber density of about 4 denier or less per filament. 21. The airbag cushion of claim 15, wherein the elastomeric composition is in the form of a latex. 22. The airbag cushion of claim 16, wherein the elastomeric polyurethane composition comprises polycarbonate polyurethane. 23. The airbag cushion of claim 15, wherein the elastomer of the elastomeric composition is polyurethane polycarbonate. 24. The elastomeric composition is at most 2. per square yard.
The airbag cushion of claim 15, wherein the airbag fabric surface is coated in an amount of 5 ounces. 25. The elastomeric composition is at most 2. per square yard.
The airbag cushion of claim 24, wherein the airbag fabric surface is coated with an amount of 0 ounces. 26. The elastomeric composition is at most 1. per square yard.
26. The airbag cushion of claim 25, wherein the airbag fabric surface is coated in an amount of 5 ounces. 27. The elastomeric composition is at most 1. per square yard.
27. The airbag cushion of claim 26, wherein the airbag fabric surface is coated in an amount of 2 ounces. 28. The elastomeric composition is at most 1. per square yard.
28. The airbag cushion of claim 27, wherein the airbag fabric surface is coated with an amount of 0 ounces. 29. The elastomeric composition is at most 0. 2 per square yard.
29. The airbag cushion of claim 28, wherein the airbag fabric surface is coated in an amount of 8 ounces. 30. A coated side curtain airbag exhibiting a collapsed packing volume ratio of about 18.8 to about 29, having a leakdown time of at least 5 seconds after inflation. Side curtain airbag. 31. The airbag cushion of claim 30, wherein the roll packing volume ratio is about 21.6. 32. An airbag cushion comprising a coated fabric, wherein the fabric is coated with an elastomeric composition, the elastomeric composition having at least 80% non-silicone material, the airbag cushion being accelerated aging. An airbag cushion characterized by exhibiting a characteristic leak-down time of at least 5 seconds after inflation before and after deployment. 33. The airbag of claim 32, wherein the elastomeric composition comprises at least one polyurethane. 34. The airbag of claim 33, wherein the mixture of polyurethanes is polycarbonate polyurethane. 35. The airbag of claim 32, wherein the characteristic change in leakdown time between the airbag before aging and the airbag after aging is about 50% or less. 36. The airbag of claim 32, wherein the elastomeric component has a coating add-on weight of at most 2.5 ounces per square yard. 37. The airbag of claim 32, wherein the elastomeric construction comprises at least one non-silicone elastomer having a tensile strength of 1500 pounds per square inch. 38. The airbag of claim 32, wherein the airbag has a coefficient of friction of 0.7 or less. 39. The airbag of claim 32, wherein the airbag has a packing volume ratio of about 18.8 to about 29.