Patent Application
20100129575
This invention relates to coated textile fabrics for use in the manufacture of inflatable devices such as air bags, side air curtains or the like, for vehicle occupant restraint systems. More particularly, the invention relates to woven or knitted textile fabrics coated with one or more polymeric layers that impart superior air holding and heat sealable properties to the fabric. Moreover, the coatings are easily applied and more cost effective than those currently employed in the manufacture of these devices. The coatings are suitable for application both to flat one-layer textiles of woven, non-woven or multi-directional construction, as well as to multi-layered woven, non-woven, unidirectional, cross-ply or multi-directional fabrics having preconfigured air-holding cavities and one or more polymeric layers coated thereon.
Presently known restraint systems for vehicles include driver and passenger side air bags, which are housed in the steering wheel and in the dashboard, respectively, in a collapsed, folded condition and are adapted to be deployed instantaneously by introduction of a gas—sometimes referred to herein as “air”—upon the occurrence of a collision. Additionally, the automotive industry has introduced air bags which are housed in the rear supports of the front seats or in the rear seats to protect the cabin occupants in the event of a collision occurring on either side of the vehicle. Moreover, a further safety feature that has been made available for passenger vehicles, especially the so-called sport utility vehicles (SUVs), are air-holding side impact protective inflatable side curtains which are designed to provide a cushioning effect in the event of rollover accidents. These side curtains are housed uninflated in the roof of the vehicle or in one of the main support pillars of the vehicle, and deploy along the interior sidewalls of the cabin of the SUV in the event of a rollover.
In addition to the widely used flat textile fabrics that are coated and then sewn or stitched to form an air bag, there has more recently been introduced into this field one-piece woven fabrics (OPW) that are woven as preformed air bags or side curtains with preconfigured air-holding cavities that require little or no further sewing or stitching in the formation of the bag. These OPW fabrics, mainly used in the construction of side curtains, require only an exterior surface coating to retain air.
Each of these different types of air bags has different design and physical property requirements, such as air holding, air permeability, air pressure and volume, puncture resistance and adhesion of the coating material to a woven fabric. For example, driver side air bags must have little or no permeability and, as a result, are often made from a material having very little or no permeability. Passenger side air bags, on the other hand, require a controlled permeability, and are most often made from materials having some degree of permeability. Furthermore, all such vehicle air restraint devices must have superior packageability and anti-blocking qualities. Packageability refers to the ability for a relatively large device to be packaged (stored) in a relatively small space. Anti-blocking refers to the ability of the device to deploy almost instantaneously from the stored condition without any resistance caused by the material sticking to itself. This is an important consideration in an air bag or side curtain which could remain stored for long periods of time before it is activated.
The air holding capability of side curtains is critical since they must remain inflated for an extended period of time to protect passengers in multiple rollovers. Unlike air bags which are designed to inflate instantaneously, and to deflate almost immediately after inflation in order to avoid injury to the driver and front seat passenger, air curtains used in SUVs, or in ordinary passenger vehicles, must be capable of remaining inflated in the range of from about three (3) to about twelve (12) seconds, depending upon the size of the curtain and the type of vehicle. An average passenger vehicle would require a side curtain of from about 60 inches to about 120 inches in length as measured along the length of the vehicle, while a larger vehicle, such as a minivan, would require an even longer side curtain. The maximum inflation period of a side curtain should be sufficient to protect the cabin occupants during three (3) rollovers, the maximum usually experienced in such incidents.
When such air bags are deployed, depending upon their specific location or application, they may be subjected to pressures within a relatively broad range. For example, air bag deployment pressures are generally in the range of from about 50 kilopascals (kpa) to about 450 kpa, which corresponds generally to a range of from about 7.4 pounds per square inch (psi) to about 66.2 psi. Accordingly, there is a need for fabric products and air bags that can be made to be relatively impermeable to fluids under such anticipated pressures while being of relatively light weight. One such type of fabric has been disclosed in Thornton et al. U.S. Pat. No. 5,073,418, in which a thin, lightweight, flexible air bag fabric of reduced air permeability is made by calendering uncoated woven fabrics, such as nylon or polyester yarn.
Another means of improving air holding capability in vehicle restraint systems has been through coatings, such as chloroprene and silicone rubber coatings, which are applied to the textile substrate. However, these coated air bags are not susceptible to heat sealing and are usually made by stitching, a process that requires the addition of an adhesive sealant in stitched areas. To alleviate this problem there have been developed improved polyurethane, acrylic, polyamide and silicone coatings that are coated singly or in layers on the fabric substrates. It has been disclosed in the art, for example, in Menzel et al., U.S. Pat. No. 5,110,666, to coat a woven nylon substrate with polyurethane to provide the desired permeability to better retain the inflation gas. Certain aqueous silicone emulsion coating compositions that yield a tack-free surface and high mechanical strength to prevent cracking on inflation of the air bag have also been disclosed in the art, such as, for example, in Inoue et al., U.S. Pat. No. 5,254,621.
Wherever coated fabrics are used, however, there exists the problem of insufficiency of adhesion of the coating to the fabric substrate. More particularly, the smoother the substrate surface, generally the more difficult it is to obtain strong adhesion of the coating material to the substrate. Therefore, much attention has been paid to the problems associated with adhesion of coatings to woven substrates, and in particular to multiple coatings of one or more polymeric materials on woven and non-woven fabric substrates of polyesters and polyamide, including combinations as well as mixed deniers of those fabric substrates. Examples of such coated fabric substrates, coating materials and methods of coating such fabrics are disclosed in commonly assigned U.S. Pat. Nos. 6,239,046; 6,350,709; 6,455,449; 6,458,724; 6,641,686; 6,645,565; and 6,734,123, the disclosures of each of which are incorporated by reference herein and made a part of this disclosure.
Despite advances in air bag coating technology, there remain problems related to the controlling of air permeability, air pressure, and volume. In particular, means to accomplish these important functions while at the same time reducing the already high cost of production of air bags and side curtains in a highly cost competitive environment is of paramount concern. In this respect, polysiloxane coatings are very expensive and OPW fabrics often require a second coating of polyurethane to accomplish the sealing effect required for a side curtain. Polyvinyl chloride coatings are much less expensive than polysiloxane coatings, but have not been considered acceptable for use as air bag coatings because of problems of adhesion (sticking) due to the relatively low melting point of polyvinyl chloride (PVC) compared to polyurethane and polysiloxane. Moreover, it was thought that polyvinyl chloride would not work well in air bags as a result of adhesion or sticking during long periods of storage because of its relatively low melting point. The problem of sticking became of increasing concern with the advent of the OPW air bag fabric used in side curtains, which have two interior facing inflation surfaces that must not stick together when the air bag is deployed.
I have invented a product and process by which polyvinyl chloride is used to coat flat woven air bag fabric as well as prefabricated OPW fabric for use in side curtains. The polyvinyl chloride-coated products of this invention are typically used, preferably in conjunction with so-called cold inflators, and can be used alone or in combination with polyurethane coatings, if desired. The polyvinyl chloride coatings of the invention provide substantially equally effective air holding capability and aging characteristics as do the polysiloxane and polyurethane coatings of the prior art and adhere well to polyester woven fabrics commonly used in air bags and side curtains. Moreover, when the polyvinyl chloride coatings are used in combination with polyurethane coatings, additional benefits in terms of air holding capability are obtained.
It has been found that by applying either a single coating of polyvinyl chloride, or a plurality of coating layers that includes polyvinyl chloride, for cut, sew and seal applications, either to flat one-layer textiles of woven, non-woven or multi-directional construction, or to a woven textile fabric substrate having preconfigured air holding cavities (OPW), an air-holding vehicle restraint system is obtained that has superior air holding characteristics, namely, air permeability, volume and air pressure retention. Further, if a multi-layered woven textile fabric substrate having top and bottom surfaces is first coated on both surfaces with an adhesive polyurethane layer and, thereafter, the adhesive polyurethane layer is coated with a layer of polyvinyl chloride, the air bag formed therefrom has superior air holding permeability and volume.
In one embodiment of the invention, a one-piece woven (OPW) multi-layered textile fabric having first and second opposed outer surfaces and preconfigured air-holding cavities therein, is coated with at least a first coating layer of adhesive polyurethane on a first surface, and at least a second coating layer of polyvinyl chloride on the first coating layer. In one preferred embodiment, the OPW comprises at least a first coating layer of adhesive polyurethane and a second coating layer of a polymeric material of adhesive polyurethane or polyvinyl chloride.
The multi-layer textile fabric is preferably a fabric constructed from synthetic material, preferably selected from the group consisting of polyamides and polyesters. In the preferred or mixed denier polyester nylon embodiment, the coated textile substrate is a woven nylon fabric, and the first coating layer is selected from the group consisting of aromatic or aliphatic polyester, polyether and polycarbonate polyurethanes. The second coating layers are polyvinyl chloride. Preferably, one of the first coating layers is coated with a second coating layer of elastomeric polyurethane and the other first coating layer is coated with a second coating layer of polyvinyl chloride.
In a preferred embodiment, a coated textile fabric for an air-holding vehicle restraint system is disclosed, which comprises a multilayered woven fabric substrate having first and second opposed outer surfaces and preconfigured air holding woven cavities defined between the fabric layers, at least a first coating layer of adhesive polyurethane coated on both the first and second outer surfaces of the textile fabric, at least a second coating layer of elastomeric polyurethane or polyvinyl chloride, and at least a third coating layer of a polymeric material coated on at least one of the second coating layers.
The coated woven textile substrate is preferably a fabric constructed from synthetic material, wherein the synthetic material is a synthetic filamentary material selected from the group consisting of polyamides and polyesters and/or mixed deniers or synthetic filaments. Also, the woven textile fabric is preferably comprised of woven nylon filaments. The first coating layers are preferably selected from the group consisting of aromatic or aliphatic polyester, polyether and polycarbonate polyurethanes. The first coating layers are preferably coated with a second coating layer of elastomeric polyurethane or first layer of polyvinyl chloride and second layer of polyurethane. One of the first coating layers may be coated with a second coating layer of elastomeric polyurethane or coated with a second coating layer of polyvinyl chloride. The second coating layer of polyvinyl chloride may also be coated with a third coating layer of elastomeric polyurethane, and the second coating layer of polyvinyl chloride may itself be coated with a third coating layer of polyvinyl chloride. The second coating layer of polyurethane is preferably coated with a third coating layer of elastomeric polyurethane, and the second coating layer of polyvinyl chloride is preferably coated with a third coating layer of polyvinyl chloride. As disclosed herein, the fabric substrate also may be coated either with a single coating layer of polyvinyl chloride or with a first coating layer of polyvinyl chloride together with a second coating layer of polyvinyl chloride as a top coat. The polyvinyl chloride base coat layer disclosed herein can be made of a very low weight PVC coating, if desired in the final product. Where a low weight coating layer of polyvinyl chloride is to be used, a coating weight of from about 0.3 ounces/sq. yd. to about 5.0 ounces/sq. yd. may be used under the conditions specified herein. Similarly, a single coating of low weight silicone sealants of the same weight range as that of polyvinyl chloride, such as Wacker Chemical's silicone 6291 product or Dow Chemical's silicone 3615 product, can be coated on the textile fabric. In general, low weight coatings are on the order of from about 15 to about 30 grams/sq. yd. (0.5 to 1.0 ounces/sq. yd.) of textile fabric.
Preferably, the first coating layers of adhesive polyurethane or polyvinyl chloride each have a coating weight of from about 0.3 ounces/sq. yd to about 5.0 ounces/sq. yd. Further, the preferred coating weight is about 0.5 ounces/sq. yd. The second coating layer is preferably an elastomeric aliphatic or aromatic polyether, polyester or polycarbonate polyurethane or polyvinyl chloride having a solids content of from about 25% to about 100% by weight and preferably weighs about 1 ounce/sq. yd to about 8 ounces/sq. yd. and preferably about 2 ounces/sq. yd. The third coating layer is preferably an elastomeric aromatic or aliphatic polyether or polyester polyurethane having a coating weight of from about 0.2 ounces/sq. yd. to about 2.0 ounces/sq. yd.
In one embodiment of the invention, the polyvinyl chloride coatings are applied to the fabric so as to provide either a high or a low coefficient of friction (COF) to an outer surface of the air bag. The purpose of having a lower COF is to increase the lubricity of the surface and enhance the ability of the air bag to slide against the window side of the vehicle, thus enhancing its deployment. Alternatively, or in addition thereto, an opposite side outer surface of the air bag may be made with an increased COF in order to “hold” the head of a vehicle occupant against the protective air bag longer than it otherwise might, to provide increased protection in a collision. The COF of the top coats is adjusted by the addition of lubricious materials such as waxes and oils to the coating composition. Commercially available waxes and oils suitable for use in the invention are Evonik Industries' ACEMATT® TS-100 fumed silica microwax and ACEMATT® HK 450, a silicon dioxide matting agent. A typical COF for the coated textile fabrics of the invention is in the range of from about 0.6 n/n to about 0.8 n/n, while it can be adjusted to as high as from about 0.8 n/n to about 1.2 n/n A COF in the range of from about 0.25 to about 0.4 n/n is considered to be a low COF.
The waxes and oils are prepared by addition, before adding to the coating solution. They are then added to the coating material and mixed therewith. In addition, The “High-Low” COF process and effect can be used with coating combinations other than PVC-PVC. For example, coating combinations such as PVC base coat and PVC low COF top coat; PVC base coat and PVC high COF top coat; PVC base coat and polyurethane low COF or high COF top coat. The COF (static) can be controlled by the amount of the additives added to the solution to achieve a COF as low as about 0.2 n/n to as high as about 1.3 n/n. The desired levels of COF can also be achieved by using liquid silicone rubber both with and without silica.
The High-Low COF values imparted to the coated textile fabrics of this invention are controlled by the amount of lubricating compounds, such as Acematt TS-100 and HK 450, added to the coating solution. By adding a higher amount of silica and waxes, a lower COF is achieved. The higher COFs are produced by reducing the amount of lubricating waxes and oils added to the coating solutions.
A method of coating a textile fabric for an air-holding vehicle restraint system is also disclosed, which comprises coating an adhesive polyurethane or polyvinyl chloride to a first surface of a multi-layered textile fabric having opposed surfaces and drying at an elevated temperature to form a first coating layer, coating an elastomeric polyurethane or polyvinyl chloride to said adhesive polyurethane coating layer and drying at an elevated temperature to form a second coating layer, and coating a polyether, polyester or polycarbonate polyurethane to the second polyurethane coating layer and drying at an elevated temperature to form a third coating layer. The multi-layer textile substrate is a fabric constructed from synthetic fibers selected from the group consisting of polyamides and polyesters, mixed denier or different filament types. The multi-layered textile substrate is a woven multi-layered fabric having opposed layers forming preconfigured pockets having air-holding cavities, the pockets being connected by fabric web connectors formed at least in part of fabric portions of dual thickness and fabric portions of opposed fabric layers stitched together at predetermined locations. The multi-layered textile fabric is preferably woven from nylon filaments or polyester or mixed denier and mixed filament types.
A method of forming an air-holding restraint system for a vehicle is also disclosed, which comprises, coating an adhesive polyurethane or polyvinyl chloride to a first surface of a multi-layered textile fabric to form a first coating layer, coating an elastomeric polyurethane or polyvinyl chloride to the first coating layer to form a second coating layer, coating a top-coating of a polyester or polyether polyurethane to form a third coating layer, repeating steps (a), (b), and (c) on a second surface of the multi-layered textile fabric, and sealing the first and second coated textile fabrics together by radio frequency sealing, hot air sealing or ultrasonic sealing.
In addition, a method is disclosed in which the fabric to be coated as described herein is first calendered or “embossed”, so as to produce an extremely light weight air bag (OPW), which when coated as disclosed herein, provides an air bag having exceptional air permeability and surface properties. The embossing process includes passing the fabric substrate, either coated or uncoated, through calenders or heated rollers, which squashes the fabric, spreads it out, and reduces the size of the intersticial spaces in the woven yarn.
It has been found that when woven textile fabric substrates, including those having preconfigured air-holding cavities therein, are coated with multiple layers of polymeric coatings, including polyurethane and/or polyvinyl chloride, such coated fabrics can be used to produce air-holding vehicle safety restraint systems having improved air retention, air permeability and volume properties. Such coated fabric substrates have the additional ability to be joined by means other than, or in addition to, sewing, including such means as heat sealing, radio frequency (RF) welding, and vulcanization. It has also been found that when such textile fabrics are coated with a polyurethane layer and thereafter, with a layer of polyvinyl chloride, or layers of polyvinyl chloride and polyurethane, and converted into an air bag or other vehicle restraint device such as a side air curtain, they exhibit improved air-holding characteristics. Examples of the methods of coating such fabrics are disclosed in U.S. Pat. Nos. 6,239,046 and 6,458,724. In such restraint systems, it has been found that the use of a multi-layered textile fabric substrate which includes layers which are already partially attached, reduces the need for excessive cutting and attaching, this reducing the possibility of air loss upon deployment.
Either natural or synthetic fibers can be employed to form the textile fabric substrate contemplated herein, with polyamide or polyester filaments or fibers being preferred. Such fibers can be in the form of either a woven, knit, or non-woven fabric. Woven multi-layered textiles having preconfigured air-holding cavities, such as those that can be produced on a Jacquard machine or a Dobby loom, particularly are contemplated herein as textile fabric substrates that can be coated in accordance with the present invention. The preconfigured air-holding cavities can be of any size or shape such as, for example, pockets, tubular channels and the like. Woven nylon is the specific textile fabric substrate that is preferred. Any denier size, shape and weaving configuration can be employed to advantage. Generally, the shape or configuration to be employed in the air-holding restraint system will depend upon its ultimate location in the vehicle. For example, driver or passenger air bags will generally be elliptical, spherical or circular in shape, while side air curtains will generally be rectangular or oval in configuration.
The coating of the fabric substrate with the desired layers of polyurethane and/or polyvinyl chloride or silicone takes place on a coating line that has multiple coating stations with driers positioned in sequence. Prior to applying the first adhesive polyurethane coating layer, the fabric substrate is heat-set and stabilized by passing it through an oven or hot cylinders at an elevated temperature(s) of from about 200° F. to about 425° F. Thereafter, the fabric substrate is coated in accordance with the present invention. The multi-layered woven textile fabric is coated in accordance with the methods disclosed herein.
According to one aspect of the present invention, as can be seen by reference to
Preferably, the prime coat layer 14 in
Referring again to
Thereafter, if desired, a third layer or topcoat 18 of an aliphatic or aromatic polyether, polyester or polycarbonate polyurethane is coated onto the second polyvinyl chloride layer 16 as is shown in
As shown in
The laminated or composite structures depicted in
An alternative laminated or composite structure is shown in
In another embodiment, as can be seen by reference to
Preferably, the prime coat layer 14 completely covers the entire surface 12 of the fabric 10, or it can be a partial coating dimensioned to coincide with a particular area of the fabric. Particular patterns, such as stripes, wavy lines, etc., with different coating weights, also can be employed to obtain the level of air permeability desired. The prime coat layer is then dried in an oven at an elevated temperature of from about 225° F. to about 425° F. for about 1.5 minutes to about 3.0 minutes while advancing the fabric at about 850 yds./hr. to about 3,500 yds./hr., with 1,500 yds./hrs. being preferred.
Alternatively, at a second coating station, a polyvinyl chloride layer 16 is then coated onto the surface of the polyurethane layer 14 in overlying relationship thereto as shown in
In still another embodiment, there is illustrated in
In still further embodiments of the invention, a textile fabric to be used in the formation of a panel of an air bag or an air curtain such as that shown in
The High/Low values of COF are produced by the addition of more or less lubricious materials, such as the waxes and oils referred to above, to the coating material. The ACEMATT® TS 100 and HK 450 materials are added in amounts of from 0.25 to 4.0 PUR (polyurethane resin powder) to provide a relatively low COF on the order of from about 0.25 n/n to about 0.6 n/n, to achieve the desired low COF in the air bag of the invention. The low COF provides enhanced deployment of the air bag as it slides along the window glass, for example. By comparison, a COF of from about 0.8 n/n to about 1.2 n/n is considered a high COF for the air bags and is useful in “holding” the head of a vehicle occupant on the air bag for a sufficient amount of time to provide increased protection in case of a collision. In the case of a multi-layered woven textile fabric (OPW), the opposed outer surfaces of the air bag could be adjusted during the coating process so that one outer surface has a high COF relative to the other outer surface. For example only, one such outer surface could have a COF of about 0.3 n/n, which would be relatively low compared with the other outer surface which could have a COF of 1.0 n/n. It is apparent that these comparative ranges can be adjusted to fit any situation requiring a low COF of one outer surface relative to a high COF on the opposite outer surface.
One embodiment of the present invention involves coating multi-layered woven textile fabrics, such as those formed on Jacquard machines or Dobby looms. Further, such multi-layered textile fabrics are preferably woven of nylon filamentary materials and are made to have preconfigured air-holding pockets defining internal cavities without the need to join separate panels of fabric together by sewing, heat sealing, RF welding, etc., as discussed hereinabove. Alternative materials such as other polyamides, polyethers or other known air-holding pockets can be, for example, in the shape of tubular channels, or other geometric shapes, such as square, circular or oval in design. One such shape is shown in
Referring again
Referring now to
Referring again to
Referring again to
Referring now to
As noted, when the multi-layered woven fabric substrate of the present invention is coated in a process of the types described herein, it will have the same type of coating layers thereon as shown in the examples given in
These coated multi-layered textile fabrics with preconfigured air-holding cavities will have the superior air-holding and other properties as the fabric substrates referred to in the commonly-assigned patents referred to herein and in the co-pending parent patent application of which this application is a continuation-in-part. The woven textile fabrics of the invention are coated and prepared as “roll goods”, i.e. they are manufactured as a continuous roll of coated fabric. The fabrics are later cut into predetermined lengths, sewn, heat sealed or RF welded, or combinations thereof, into the appropriate size and shape desired for installation into a particular automotive vehicle. These shapes may also include sealed “dead air” zones in which no inflation will occur, such as where seat backs or other automotive structures require no impact protection. After the safety device is prefabricated and adapted for installation in a particular vehicle, it is fitted with inflation tubes (not shown) through which it will receive the inflation gas that is generated by the inflator when the device is deployed. The inflation tube is typically sewn or clamped into the device at either or both of its ends, depending upon the size of the side air curtain. The inflation tubes will deliver the inflation gas to the individual air-holding pockets or tubular air-holding channels shown in the examples of the figures herein, to produce a fully operational automotive vehicle safety restraint device.
This is a continuation-in-part of co-pending U.S. patent application Ser. No. 12/202,227, filed Aug. 30, 2008.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12202227 | Aug 2008 | US |
| Child | 12634949 | US |
