CN1320090A - Low-permeability airbag cushions with a film coating of exceptionally thin thickness - Google Patents

Abstract

The present invention provides coated inflatable fabrics (26), and more particularly airbags to which very low add-on amounts of coating have been applied, which have very low air permeability. Such fabrics were originally used in automotive cushions that required low permeability characteristics (e.g., side curtain airbags). Such fabrics use inexpensive, very thin coatings to provide the required low level of breathability. Thus, the coated airbag of the present invention has a coating of at most 2.5 ounces per square yard, and most preferably about 0.8 ounces per square yard, and exhibits a drop-back time of at least 7 seconds. All coatings meeting these criteria, particularly elastomers, non-silicon containing coatings and coated airbags, are intended to fall within the scope of the present invention.

Description

Low-permeability airbag cushions with a film coating of exceptionally thin thickness

field of invention

This invention relates to coated inflatable fabrics, and in particular to air bag cushions, which have minimal additional coating and which exhibit exceptionally low air permeability. The inflatable fabric of the present invention is mainly used in automobile cushions (such as side window air bags) requiring low air permeability characteristics. Typically, heavy and expensive coatings such as mixtures of neoprene, silicone, etc. have been used to provide this required low air permeability. The fabrics of the present invention utilize inexpensive, very thin coatings to provide this necessary low level of air permeability. Accordingly, the coated inflatable air bag of the present invention comprises a film overlying at least a portion of the surface of the target fabric, wherein the film has a tensile strength of at least 2,000 and an elongation at break of at least 180%. The film provides a low air permeability airbag cushion with a fallback time of at least 5 seconds with an amount of film on the surface of at most 2.5 ounces per square yard of fabric.

Background technique

Automotive air bags have been known and used for quite some time. Commonly used air bag construction materials are polyester or nylon fabric coated with a layer of elastomer such as neoprene or silicone. The fabrics used in these air bags are typically woven fabrics made from synthetic fiber meshes by weaving operations known in the art.

It has been found that the material of the existing coating is acceptable because it acts as a barrier which does not allow penetration of the aeration medium. The inflation medium is usually nitrogen gas produced by a gas generator or inflator. This gas is transported into the cushion at a higher temperature. The coating prevents the fabric from breathing through these hot gases, allowing the cushion to inflate quickly without excessive decompression during a crash event.

Air bags may also consist of uncoated fabrics woven in such a way as to form a product with low air permeability, or fabrics which have been treated, for example by calendering, to reduce air permeability. Fabrics that are calendered or otherwise mechanically treated after weaving to reduce air permeability are disclosed in US Patent Nos. 4,921,735, 4,977,016 and 5,073,418 (hereby incorporated by reference in their entirety).

Silicone coatings typically use solvent-based or two-component reaction systems. For both front and rear panels of side curtain air bags, the dry coat weight of silicone is in the range of about 3 to 4 ounces per square yard or greater. As will be appreciated by those of ordinary skill in the art, the high add-on weight substantially increases the cost of the airbag base fabric and is difficult to package within a small airbag module. Additionally, silicone has very low tensile strength and elongation at break properties, making it difficult to withstand high pressure inflation without the use of very thick coatings.

U.S. Patent No. 5,110,666 to Menzel et al. (incorporated herein by reference) discloses the use of certain polyurethanes as coatings, which are reported to allow low add-on weights in the range of 0.1 to 1 ounce per square yard. However, the material itself is relatively expensive, and due to the characteristics of the coating material, it is believed that a relatively complicated mixing and coating process is required. However, the patentees fail to disclose any relevant elastic and/or tensile strength properties of their particular polyurethane coating materials. Also, there is no discussion of the importance of this polyurethane material's ability to coat at low add-on weight (and the associated low air permeability) on side curtain air bag fabrics used on the driver or passenger side Upholstered. All air bags must be able to inflate very quickly; in fact, once a crash is sensed, the air bag typically reaches peak air pressure within 10 to 20 milliseconds. Conventional driver-side and passenger-side air bags are designed to withstand this enormous inflation pressure; however, they also deflate very quickly in order to effectively absorb the energy from a car occupant hitting the air bag. So this kind of driver and passenger side cushions (air bags) are made of low air permeability fabric, but they also deflate quickly at the connecting seam (there is no coating to prevent air leakage here) or quickly through the vent holes Deflation. Additionally, the low add-on coatings disclosed in the Menzel patent and in U.S. Patent No. 5,945,186 to Li et al. do not provide long-term gas retention; 2 seconds of prolonged and continuous pressure. The low air permeability of these airbag fabrics therefore contributes little to the continued gas retention within the driver and passenger airbag cushions that would have the desired effect of deflating the cushion to prevent a sufficient crash. These airbag fabrics do not work well as side curtain airbags, at least because the connecting seams (discussed in more detail below) which form the pillow-like, cushion-like structure in these airbags are not coated. Since these areas leak considerably during and after inflation, the aforementioned patented low-coat, low-permeability airbag fabrics will not work properly in side curtain airbags.

As mentioned above, there are three main types of different air bags, each with a different end use. For example, an air bag on the driver's side is typically secured in the steering column tube and exhibits higher air permeability for better cushioning of the driver in the event of an impact. The air bag on the passenger side also includes a higher breathability fabric to allow gas to be released either through it or through vent holes integrated therein. All of these types of air bags are designed to protect occupants in a sudden crash, and typically explode in packaged modules from either the steering column tube or the dashboard (thus having multiple "sides"). However, side window air bags have been primarily designed to protect occupants in rollover crashes by maintaining their inflated state for a relatively long duration, and are generally kept from within the roofline along the side windows of the car ( and therefore only have the rear side and the front side) of the packaging container opened. So the side curtain airbags not only have a cushioning effect, but also protect against broken glass and other debris. Also, as mentioned above, the side curtain airbags must hold a large amount of gas and a very high pressure to remain inflated for an extended period of time throughout a possible rollover condition. To achieve this, the front and rear sides of these side cushions are usually heavily coated with sealing material. Since most side curtain air bag fabrics consist of woven tube stock that is sewn, sealed, or integrally woven together, discontinuities of potentially severe air leakage are prevalent, specifically at and around seams . It has been accepted as a requirement that heavy coatings are required to provide the low air permeability (and thus long fallback times) required for side curtain airbags. Without this heavy coating, these airbags would deflate very easily and quickly and thus would not function properly during a rollover crash. Those of ordinary skill in the art will appreciate that such a heavy coating adds significant cost to the overall production of the targeted side curtain airbag. There is therefore a great need to produce a low-permeability side curtain airbag with an inexpensive coating (most preferably a low coating add-on weight) that does not damage the airbags needed for its own operation once deployed for use. Aging, humidity and air permeability properties. To date, little, if any, of reducing the need for such heavy air bag coatings from side curtain air bags has been achieved.

In addition, there is a current driver that holds such low-permeability side curtain airbags in a cylindrical-shaped module. Since these air pockets are usually housed in the roofline of the car, the available area is rather limited and there is always a pressing need to limit the packing volume of such compressed upholstery to their absolute minimum. However, previously practiced low-permeability side curtain airbags have proven difficult to preserve in such cylindrical containers located on the roofline of the target vehicle. It has been difficult to reduce the actual time and energy required to roll up such a heavy coated low air permeability article and the packaging volume itself. Additionally, with the use of such heavy coatings, the problem of latching (ie, bonding together the different coated parts of the cushion) is amplified when the items are packed together very closely. The chance of delayed deployment during inflation increases when there is a potential latch-up problem. Therefore, there is an urgent need for a very tightly packed, low-volume, low-lock side window low-permeability airbag. Unfortunately, the prior art no longer affords this advantage to the airbag industry.

Summary of the invention

In light of the background above, it has been seen that there is a need for a low-permeability side curtain airbag which uses a smaller and less expensive coating amount and thus is comparable to the standard low-permeability type sidecurtain airbag. Compared with its packaging volume is greatly reduced. Such coated low-permeability airbags must have the required long fall-back time under inflation and after prolonged storage. This novel airbag and novel coating formulation represent a significant improvement over the expensive, high add-on airbag coatings (and resulting airbag articles) used in the past.

It is therefore an object of the present invention to provide a coated air bag in which the coating has a very low added weight and is characterized by a particularly long fall-back time after inflation, whereby a secondary characteristic is low air permeability. Another object of the present invention is to provide an inexpensive side curtain airbag cushion. A further object of the present invention is to provide a highly effective air bag coating formulation which can be used in very low add-on quantities to obtain air bag structures with particularly low air permeability after inflation. Another object of the present invention is to provide an air bag coating formulation that not only provides beneficial and long-term low air permeability, but also exhibits excellent long-term storage stability (by heat aging and humidity aging tests). Yet another object of the present invention is to provide a low air permeability side curtain airbag for storage in the roofline of an automobile, having a very low roll-pack volume and no occlusion characteristics for long-term effective storage.

Accordingly, the present invention relates to an airbag cushion comprising a coated fabric, wherein a film is overlaid on said fabric, wherein said film is present in an amount of at most 2.5 ounces per square yard of fabric; and wherein said airbag cushion Exhibits a characteristic fallback time of at least 5 seconds after prolonged storage. Likewise, the present invention relates to an airbag cushion comprising a coated fabric, wherein said fabric is coated with a multilayer film, wherein said multilayer film has a tensile strength of at least 2,000 and an elongation of at least 180%; And wherein said airbag cushion exhibits a characteristic fall-back time of at least 5 seconds after long-term storage.

The term "characteristic fallback time" refers to the total amount introduced in an already inflated (to the highest initial air pressure that "opens" the weak seal area) and deflated airbag cushion when subsequently reinflated at a constant pressure of 10 psi The inflation gas contained in the required measurement time. In the field of airbags, particularly with respect to side curtain (low air permeability) airbag cushions, it is known and well understood that long-term retention of inflation gas during a crash is of paramount importance. Side window air bags are designed to inflate as quickly as driver-side and passenger-side air bags, but they must deflate very slowly in order to protect occupants during rollovers and side impacts. Therefore, the leakage rate of the air bag must be very low after the air bag reaches the peak pressure during the continuous rapid inflation. Therefore, the coating on the airbag must be strong enough to withstand the impact and pressure when the airbag is inflated so rapidly. Therefore, the long characteristic fall-back time measurement is very important in order to maintain the maximum amount of gas in the inflated air bag that contributes to the cushioning. Air bag leakage after inflation (and after reaching peak pressure) is therefore closely related to the actual air pressure retention characteristics. The air pressure retention characteristics of inflated and deflated side curtain airbags (hereinafter referred to as "fallback time") can be described by the characteristic fallback time t, where:

*SCFH: standard cubic feet per hour

It should be understood that the constant 10 psi is not a limitation of the invention; the fallback time is simply measured at this constant pressure. Therefore, even if the pressure is higher or lower than this value during actual inflation or after the initial pressurization of the bag, the only limitation is if one of ordinary skill in the art is prepared to measure the bag volume and divide it by the bag volume. Time is obtained as volumetric leak rate (measured by the amount of target bag leak during steady state inflation at 10 psi). The resulting measured time will be at least 5 seconds. Preferably, the time is greater than about 9 seconds; more preferably, greater than about 15 seconds; and most preferably, greater than about 20 seconds.

Also, in the case of measurements using uninflated side curtain airbags, the term "fallback time" can be measured as the time required to release half of the introduced inflation gas from the target airbag after the initial peak pressure is reached quantity. Thus, the measurement begins immediately after peak initial pressure is reached when inflated using a standard inflation pattern (e.g., typically about 30 psi) that continuously pumps gas during and after reaching peak initial pressure. Pump into target air bag. It will be appreciated that the pressure of the gas pushed into the air bag after reaching the peak initial pressure will not remain steady (it decreases during the subsequent introduction of inflation gas), and that the target air bag will inevitably deplete a certain amount of air in the process. The overflow of inflation gas. The main task of such side curtain airbags (as described above) is to remain inflated for as long as possible, thereby providing sufficient cushion protection to the vehicle occupants during a rollover accident. The greater the amount of gas that is retained, the better the cushioning effect is provided to the passenger. Therefore, the longer the air bag retains a large amount of inflation gas, the longer the resulting characteristic fallback time, and thus the better the cushioning effect achieved. Regardless, the air bag of the present invention must hold at least half of its inflated gas volume for 5 seconds after reaching peak initial pressure. Preferably, this time is 9 seconds, more preferably 15 seconds, and most preferably 20 seconds.

Likewise, the term "after a long period of storage" includes actual storage of the airbag cushion of the present invention in an inflator assembly (module) in an automobile, and/or waiting for inflation in a storage facility. Such measurements are generally acceptable, well understood and understood by those of ordinary skill in the art, and can be made by comparative analysis after typical heat and humidity aging tests. These tests typically include 16 days of aging in a 107°C oven followed by 16 days at 83°C and 95% relative humidity, and are generally considered to be a correct estimate of the long-term storage conditions of the airbag cushion. Accordingly, the term includes these measurement tests. The airbag fabric of the present invention must exhibit the correct characteristic fallback time after this rigorous simulated storage test.

The coating of the present invention, in this case a film, must have a tensile strength of at least 2,000 psi and an elongation at break of greater than about 180%. Preferably, the tensile strength is at least 3,000 psi, more preferably 6,000, and most preferably at least about 8,000 (the upper limit is still substantially the highest that can be produced to adhere to the fabric surface). A preferred elongation at break is greater than about 200%, more preferably greater than about 300%, and most preferably greater than about 600%. These properties of the film translate into a coating that is both strong (and thus withstands the enormous pressure during and after inflation and does not break easily) yet stretchable to compensate for this enormous inflation, pressure, etc. The film is produced prior to contact with the surface of the target airbag cushion or fabric. In order to apply such a film, a lamination process must be performed by simultaneously subjecting the film to heat and hand pressure while in contact with the target surface. The laminate may be adhered to any portion of the target structure, although it is most preferably applied over the entire upholstery or fabric. Likewise, more than one type of multi-layer film may be present on the target pad, where one type of film (with specific tensile strength and stretch properties) is most preferably adhered to specific discrete areas of the target pad, while Another film with different properties can be selected at other locations, such as at the seam. The only requirement is that the final product exhibit the aforementioned long fallback properties. The film appears to work by "sticking" the individual yarns in contact in place and being able to prevent leakage through open areas located between woven yarns and/or stitches. Then during inflation, the coating prevents leakage through the void spaces located between the yarns, helping to prevent yarn deflection (which would create a larger space from which gas could escape).

The use of such high tensile strength and high elongation at break components allows the subsequent use of such films with very low added weight. Typically, the required coating (not a film, but the actual coating formulation that adheres to the surface and then may form a non-delaminated film) on a side curtain airbag is very high, at least 3.5 ounces per square yard (Utilization of the standard is actually higher, around 4.0). The airbag cushions of the present invention require about 2.7 ounces of film coating per square yard (preferably less than, for example, about 2.5, more preferably about 2.2, still preferably less than 2.2 ounces per square yard). The ounce weight per square yard of coating of the present invention is effective to create the desired long fallback characteristics (low air permeability). Additionally, past coatings were required to have excellent thermal and humidity aging stability. Unexpectedly, even at this low add-on, especially with problematic coating materials used in the past (e.g., polyurethane), the coating of the present invention, and subsequently the coating of the present invention with A coated airbag cushion that exhibits excellent heat aging and humidity aging characteristics. Thus, the coating composition and coated airbags represent a significant advance in the specific field of airbags.

Although any of the films mentioned above having equally effective tensile strength and elongation at break properties can be used in the low air permeability airbag cushion of the present invention, it is more interesting to use polyurethane as the desired film. film,. By way of example only, copolymers of polyurethanes, polyamides, etc. may also be used. Also, this film can be cross-bonded or non-cross-bonded on the airbag surface. Preferably, the film is polyurethane, most preferably polycarbonate polyurethane or polyurethane glycol based polyurethane film (available from Deerfield Urethane, Inc., Ivyland, PA available under the trade name Durefiex ^™ PT9400). This particular film exhibited a tensile strength of 8,000 psi and an elongation at break of approximately 600%. This film can be added to the desired cushion in quantities as low as 2.2 ounces per square yard and still provide the desired longer fallback time characteristics. Of course, any other film meeting the characteristics described above may be included in the present invention; however, other available films may have additional weights greater than this preferred value, depending on the actual tensile strength and elongation at break required. However, the upper limit of 2.5 ounces per square yard to satisfy the present invention should not be exceeded. However, if desired, the desired film can be added in multiple layers as long as the thickness required for the overall coating is not exceeded. Alternatively, multiple layer film/coating systems may be used as long as at least one film having the requisite tensile strength and elongation at break is used and exhibits the requisite low air permeability.

Other ingredients that can be present in or on these films are thickeners, antioxidants, flame retardants, binders, adhesion promoters and colorants. According to a potentially preferred practice of the invention, a primer cling coat is first applied to the target pad surface. Once this first layer is dry, the desired film is then superimposed by heat and pressure on selected areas of the target surface for a time sufficient to form a laminate. Preferably, the preferred film (or films) does not include any silicone since this material exhibits very low tensile strength (typically less than about 1,500 psi) properties. However, to provide effective aging and non-blocking benefits, certain compositions may be applied to the film as an overcoat provided the added weight of the entire film and overcoat does not exceed 2.5 ounces per square yard. Furthermore, elastomers comprising polyester or polyether segments or other similar components are undesirable because of stability problems in heat and humidity aging (polyesters are readily hydrolyzed in humid environments and polyethers are readily oxidized in heat) , especially when the add-on weight is very low (ie, 0.8-1.2 oz/yd ² ); however, such elastomers can be used in topcoat formulations as long as they do not exceed 2.5 ounces per square yard.

Other preferred additives in or on the film (or multilayer film) are heat stabilizers, flame retardants, primer binders and materials used to protect the outer coating. A potentially preferred thickener is NATROSOL ^(TM) 250HHXR manufactured by the Aqualon Division of Hercules Corporation, believed to have a distribution point in Wilmington, Delaware. In order to meet the requirements of Federal Motor Vehicle Safety Standard 302 for flame retardants in the automotive industry, it is also preferred to add flame retardants to the compounded mixture. A potentially preferred flame retardant is AMSPERSE F/R51 sold by Amspec Chemical Corporation, which is believed to have a distribution point in Gloucester City, New Jersey. As mentioned above, a primer adhesive can be used to promote adhesion between the surface of the target fabric and the film itself. Therefore, while it is preferred for films that the entire coating in contact with the fabric surface is a monolithic part, adhesion promoters such as isocyanates, epoxies, functional silanes, and others with adhesion properties can be utilized resin without detrimentally affecting the low air permeability that the film provides to the target airbag cushion. The outer coating portion can also be used to achieve the desired non-occlusive properties of the airbag cushion due to the latent silicone mentioned above. Such overcoats can perform a variety of functions including, but not limited to, improving the aging of the film (e.g., with silicone) or providing Latch resistance.

For use in cushioning systems, airbag fabrics must undergo specific tests. One such test is called the occlusion test and represents the force required to separate two parts of a coated fabric from each other after they have been stored in contact with each other for an extended period of time (eg, air bag storage). The test analysis for occlusion entails pressing two 2 inch by 2 inch samples of airbag fabric with the coated side together at 5 psi at 100° C. for 7 days. If after this time the force required to tear the two samples apart is greater than 50 grams, or the time required to separate the fabrics using a 50 gram weight suspended from the fabric base layer is greater than 10 seconds, the coating fails the occlusion test . Obviously, the less shear force required to separate, the better the coating. For improved occlusion resistance (and thereby reducing the chance of unsuitable adhesion between parts of the fabric packaged together), the topcoat portion may use, for example, talc, silica, silicate clay and starch, as long as the overall The added weight of the elastomeric component (including the outer coating) does not exceed 2.5 ounces per square yard (and most preferably occurs at lower values, such as about 1.5).

Two other tests that certain coated airbag cushions must pass are the oven (heat) aging and humidity aging tests. These tests also simulate the storage of airbag fabrics over extended periods of time under high temperature exposure and relatively high humidity. These tests were actually used to analyze the properties of various fabrics after long-term storage of 2 or more weeks in a hot air oven (>100°C) (with or without humid conditions). For purposes of the present invention, this test is primarily used to analyze the breathability of coated side curtain airbags by measuring the characteristic fallback time (as discussed in detail above). Originally produced and stored airbag cushions of the present invention should exhibit a characteristic fallback time of greater than about 5 seconds (when the airbag has been pre-inflated to a peak pressure of about 15 psi and allowed to After fully deflated, refill at 10 psi gas pressure). Since polyurethane, the preferred elastomer in this invention, can be adversely affected (although not as deleteriously as certain polyester and polyether containing elastomers) by high temperature and high humidity, caution should be exercised in adding specific ingredients to In the outer coating and/or in the elastomer itself. Antioxidants, antidegradants and metal deactivators can be used for this purpose. Examples include, but should not be limited to, ^Irganox® 1010 and ^Irganox® 565 available from CIBA Specialty Chemical. Such topcoats may also provide additional protection against aging and may therefore include topcoat weathering modifying materials such as, but not limited to, polyamide, NBR rubber, EPDM rubber, etc., as long as the elastomeric component does not exceed per sq. The added weight of the target fabric is 2.5 ounces (preferably at most much less than about 1.5) yards.

The substrate to which the film coating is applied to form the airbag base fabric of the present invention is most preferably a woven fabric formed from yarns comprising synthetic fibers such as polyester or polyether. Such yarns preferably have a linear density of from about 105 denier to about 840 denier, more preferably from about 210 to about 630 denier. Such yarns are preferably formed from a plurality of filaments, wherein the filaments each have a linear density of about 7 denier or less, more preferably about 6 denier or less, and most preferably about 4 denier or smaller. In a more preferred embodiment, this base fabric should be formed from nylon fibers, and most preferably nylon 6,6. Such polyester materials have been found to exhibit particularly good adhesion and retention against hydrolysis when used in conjunction with the coatings of the present invention. Such base fabrics are most preferably spun using the flow air-jet looms disclosed in US Patent Nos. 5,503,197 and 5,421,378 to Bower et al. This woven fabric is hereinafter referred to as an airbag base fabric. As mentioned above, the airbag of the present invention must exhibit a particularly low air permeability and must be a so-called "side window" airbag. As already described in detail, in order to provide adequate long-term cushion protection to the occupants during a rollover accident, such side curtain airbags (also called cushions) must retain a substantial amount of inflation gas during the crash. Any standard side curtain airbag can be used in combination with a low add-on coating to provide a product that exhibits the desired fallback time as described above. Most side curtain air bags are made by joining together two separate blanks of woven fabric to form an inflatable structure through laborious, intensive sewing or seaming (or otherwise). Additionally, as understood by those of ordinary skill in the art, such sewing is done at strategic locations to create seams (joint points between the various layers of fabric) that in turn form the inflation gas during inflation. Discrete open areas into which flow can flow. These open areas thus form a pillow-shaped structure in the final inflated airbag cushion to provide more surface area during a crash, as well as provide strength to the airbag itself to withstand very high internal inflation pressures (and Hence no explosion during such an inflation event). Other side curtain airbag cushions come in different one-piece weaves. In general, some inflatable airbags are formed by simultaneously weaving together two separate layers of cloth at specific strategic locations (again, forming the desired pillow-shaped structure). These pads therefore have seams connecting the two layers. The presence of so many seams (in both multi-piece and single-piece woven airbags) creates the aforementioned problem of gas loss during or after inflation. The yarns may be deflected, especially where the yarns are deflected in many different ways and amounts, thereby producing a rapid deflation of the air bag by a rapid escape of the inflation gas. Therefore, the airbag base fabric does not provide much assistance in reducing air permeability (and associated fallback time, especially at relatively high air pressures). Previously this seam problem had primarily dictated the need to use very heavy and expensive coatings to provide the requisite low air permeability.

Recently, advances have been made in either multi-piece side curtain airbags (which require a very large amount of labor intensive sewing to join woven fabric blanks) or traditionally made single-piece woven upholstery , for a more special single-piece woven fabric, the floating filaments between the woven yarns are greatly reduced, thereby fundamentally reducing the deviation of the yarn imbalance in the inflated state, such as in Sollars, Jr. Ser. No. 09/406,264, the specification of which is incorporated herein in its entirety. These monolithic woven airbags are usually made on dobby looms or Jacquard fluid jet looms, preferably the monolithic airbags used are made by the Jacquard weaving process. With this improvement, the possibility of higher leaks at seams is greatly reduced. These airbags provide a balanced woven structure at and around the junction point between the two layers of fabric such that the yarns become deflected under high pressure inflation compared to standard single piece woven airbags Ability to decrease. Unfortunately, the single piece woven airbag of this invention still presents a problem in that the woven intersections may move under high pressure inflation such that leaks may still occur at a high rate for proper functioning. As a result, there remains a need to coat monolithic woven structures of fabrics with materials that reduce and/or eliminate this effect. However, this single piece woven structure allows for a very low add-on of elastomeric coating for low air permeability effects. In fact, the airbags of the present invention work extremely well with a low add-on coating of less than 1.5 and as low as about 0.8 ounces per square yard.

In addition, although it is not preferred in the present invention, it has been found that the coating composition of the present invention provides similar low air permeability advantages for standard monolithic woven airbags, especially with the low add-on high resistance of the present invention. Tensile strength, high elongation at break, and silicone-free coatings; however, the number of coatings required to create a longer fallback time is much higher than the aforementioned Sollars, Jr. invention of the single-piece woven structure. Thus, for these other monolithic woven airbags, an additional amount of 1.5 or even up to about 2.7 ounces per square yard may be required to achieve an appropriately low level of breathability. Even with such a high add-on coating, the coating of the present invention compares itself to standard, commercially available prior art coatings such as silicone, which must be present in an amount of at least 3.0 ounces per square yard. , obviously providing significant progress.

In addition, it has been found that the film coating compositions of the present invention have the same advantages as the aforementioned sewn, seamed side curtain airbags in the additional amounts of the present invention, etc. Although the potential high leakage of this construction at these connecting seams is highly undesirable, it has been found that the breathability of the coatings of the present invention is improved with lower add-ons than standard silicone neoprene coating formulations. Significantly reduced (actually to an acceptable fallback time). This additional amount will reach the limit of 2.7 ounces per square yard, but has been shown to be more effective based on the use of an elastomeric composition of sufficiently high tensile strength and sufficient elongation capability in a film coating composition that is in direct contact with the target fabric surface. Low amounts (eg, 2.2 ounces per square yard) are effective. Also, with the possibility to reduce the amount of coating material (which is usually always very expensive), at the same time, to make the target air bag structure has a rather low air permeability, a high resistance to humidity and a particularly effective aging stability, the present The inventive coating composition and the coated airbag itself of the present invention are clearly a significant improvement over prior art airbag coatings.

The main focus in the present invention is to be able to pack the coated airbag cushion with the smallest possible volume in a cylindrical storage container located at the roofline of the target vehicle. In a rolled-up configuration (for optimal fit within the cylindrical container itself, and thus for optimal inflation in the event of a crash, to provide adequate protection to the occupants), the airbag of the present invention can Defined as cylindrical with a diameter of at most 23 mm. In this example, with a 2 meter long cylindrical roof profile holding container, such a container would require a volume approximately equal to 830 cubic centimeters (this volume is calculated as 2π(radius) 2 ). For commercially available side curtain airbag cushions, the standard rolled package diameter is at least 25mm (due to the thickness of the coating required to provide the low air permeability characteristics). Therefore, the desired volume of the cylindrical vessel should be at least 980 ^cm3 . Preferably, the rolled diameter of the airbag cushion of the present invention during storage is at most 20 mm (resulting in a packaged volume of about 628 cm ³ ), which is significantly lower than the standard package volume. Also, relative to the depth of the inflated airbag cushion (i.e., the length extending from the roofline down to the lowest point along a side of the target vehicle such as a window), the depth of the airbag cushion of the present invention (in The ratio of substantially 17 inches (or 431.8 mm) to its rolled, packaged diameter in standard cases should be at least about 18.8. Preferably the ratio should be about 21.6 (20 mm diameter) and its maximum should be about 24 (with a minimum diameter of about 18 mm). Of course, the range of ratios need not be the standard depth of 17 inches and is essentially a function of coating thickness and such added weight.

Although the invention has been described and disclosed in connection with specific preferred embodiments and practices, the invention is not limited to these specific embodiments but rather covers equivalent structures, structural equivalents and all varied embodiments and modifications , and may be defined by the scope of the appended claims and equivalents.

Detailed description of the preferred embodiment

Delightfully, there have been disclosed films having a tensile strength of at least 2,000 psi and an elongation at break of at least 180%, at most 2.7 ounces per square yard, preferably less than about 2.5, more preferably about 2.2, and most preferably less than about 2.2 ounces per square yard, coated on both surfaces of side curtain air bag fabric, providing a coated fabric with very low and prolonged air permeability during and after inflation. Airbag cushion. This unexpectedly multiple beneficial film coatings thus form an air pocket cushion that is easily inflated after prolonged storage and remains inflated long enough to guarantee an optimal level of safety within the cushioning system . In addition, it goes without saying that the fewer film coating components required, the cheaper the final product. Furthermore, the reduction in the amount of film coating components required will translate into a reduction in the packing volume of the air bag fabric within the air bag device. So this helps to improve the packing ability of the air bag fabric.

Preferred airbag cushions of the present invention were produced according to the following examples.

example

First, an adhesion primer formulation is produced with the following ingredients:

Composition Weight Ratio

Desmoderm 43195 (Bayer Corporation, polyurethane) 25 grams

Dimethylformamide (Aldrich, solvent) 75 g

Desmodur CB-75N (Bayer, polyisocyanate adhesion promoter) 4 grams

The primer coat was adhered to both sides of a 2.5 liter sized Jacquard woven nylon air bag (440 denier fiber) serial number No. 09/ 406,264 U.S. Patent Application Figures and Preferred Embodiments. The primer coat was dried at about 160°C for about 2 minutes to give a dry coat weight of about 0.25 ounces per square yard per side. Next, apply a pressure of approximately 80 psi at approximately 188° C. using a heat press for a duration of approximately 1 minute, and then overlap a 2 mil thick polyurethane film on both sides of the primer-coated air bag (Dureflex ^™ PT9400). The total polyurethane film add-on weight per side of the air bag is approximately 2.2 ounces per square yard. The air bag is then rapidly inflated to 30 psi atmospheric pressure. More than 28 seconds elapsed before the gas pressure decreased to 8 psi. Thus the leak velocity measured at 10 psi is about 4 SCFH. The characteristic fallback time is a surprising value, greater than 80 seconds.

Description of drawings

Figure 1 shows a side, interior view of a vehicle prior to the use of the side curtain airbag of the present invention.

Figure 2 shows a side, interior view of a vehicle after using the side curtain airbag of the present invention.

Detailed description of the drawings

As shown in FIG. 1 , the interior of the vehicle 10 before the side curtain air bag (not shown in the figure) is inflated is shown. The vehicle 10 includes front seats 12 and rear seats 14, front side windows 16 and rear side windows 18, a roofline 20 on which a cylindrical container 22 containing the side curtain air bag (not shown) of the present invention is held. Inside. In the roofline 20 there is also an inflator element 24 which is activated in the event of a crash and feeds gas into the side curtain airbags ( 26 in FIG. 2 ).

FIG. 2 shows the side curtain air bag 26 after inflation. As noted above, the air bag 26 is coated with up to 2.5 ounces per square yard of a coating formulation (not shown), preferably polyurethane polycarbonate. The air bag 26 of the present invention will remain sufficiently inflated for at least 5 seconds, preferably more, and most preferably for at least 20 seconds.

Of course, the present invention may have various altered embodiments and modifications within the concept or scope defined by the appended claims.

Claims (17)

1. airbag cushion that comprises the fabric of coating, wherein said fabric is with every square yard of fabric quantity coating multiple film of 2.7 ounces at the most; And distinctive time of at least 5 seconds fallen the time after wherein said airbag cushion had inflation.

2. airbag cushion according to claim 1, wherein said film is not contain silicone resin.

3. airbag cushion according to claim 1, wherein said thin film composition comprises polyurethane.

4. airbag cushion according to claim 1, the fabric of wherein said coating forms by polyester yarn is woven.

5. airbag cushion according to claim 4, wherein said polyester yarn is made by 6,6 nylon fibers.

6. airbag cushion according to claim 4, wherein said polyester yarn are the polyfilament yarns with the linear density feature at about 210-630 dawn.

7. airbag cushion according to claim 6, wherein said polyfilament yarn are characterised in that every about 7 dawn of filament or thin silk thread density still less.

8. airbag cushion according to claim 1, wherein said film with every square yard at the most 2.5 ounces quantity be present on the described air-bag fabric surface.

9. airbag cushion according to claim 8, wherein said film with every square yard at the most 2.2 ounces quantity be present on the described air-bag fabric.

10. airbag cushion that comprises the fabric of coating, wherein said fabric is coated with multilayer film; Wherein said film has at least 2,000 tensile strength and at least 180% elongation at break; And distinctive time of at least 5 seconds fallen the time after wherein said airbag cushion had inflation.

11. airbag cushion according to claim 9, wherein said film comprises polyurethane.

12. airbag cushion according to claim 10, the fabric of wherein said coating forms by polyester yarn is woven.

13. airbag cushion according to claim 11, wherein said polyester yarn is made by 6,6 nylon fibers.

14. airbag cushion according to claim 12, wherein said polyester yarn are the polyfilament yarns with the linear density feature at about 210-630 dawn.

15. airbag cushion according to claim 13, wherein said polyfilament yarn are characterised in that every about 7 dawn of filament or thin silk thread density still less.

16. airbag cushion according to claim 10, wherein said film with every square yard at the most 2.5 ounces quantity be present on the described air-bag fabric surface.

17. airbag cushion according to claim 16, wherein said film with every square yard at the most 2.2 ounces quantity be present on the described air-bag fabric.

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