Stock material or miscellaneous articles – Hollow or container type article – Nonself-supporting tubular film or bag
Reexamination Certificate
1999-01-25
2001-09-18
Dye, Rena L. (Department: 1772)
Stock material or miscellaneous articles
Hollow or container type article
Nonself-supporting tubular film or bag
C428S193000, C428S196000, C428S361000, C383S003000, C383S117000, C139S38400B, C442S183000, C442S184000, C280S728100, C280S743100, C280S743200, C427S372200
Reexamination Certificate
active
06291040
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an air bag which absorbs impact when a motor vehicle collides, thus affording passenger protection. In more detail, the invention relates to a fabric for use as a base fabric in an air bag, an air bag comprising the fabric, a method of producing it and its use as a base fabric in an air bag so as to provide an air bag having low air permeability and less susceptible to fraying.
BACKGROUND OF THE INVENTION
Conventional air bags are produced by coating or laminating a plain weave fabric, formed by weaving nylon 66 or nylon 6 filament yarns of 300 to 1000 deniers (330 to 1100 dtex), with an elastomer resin such as a synthetic rubber, for example chloroprene, chlorosulfonated olefin or silicone, to provide a base fabric with improved heat resistance, flame resistance, gas interceptability, etc., and cutting and sewing the base fabric into bags.
When the plain weave fabric is coated or laminated with such an elastomer resin, a coating process such as knife coating, roll coating or reverse coating, is generally adopted. If the plain weave fabric made from filaments is coated with a chloroprene elastomer resin, to make the base fabric, the resin is applied to the surface of the base fabric in an amount of 90 to 120 g/m
2
, and the air bag produced is very heavy, hard and coarse in appearance. If the air bag is inflated to contact the face of the passenger, he/she can be scratched. Furthermore, also when it is folded into a compact standby style, it is hard to fold. If the base fabric is coated with silicone elastomer resin, the air bag is considerably more heat resistant and cold resistant than an air bag having a base fabric coated with chloroprene elastomer resin. Moreover, the amount of resin coated is only 40 to 60 g/m
2
, thus allowing a reduction in weight and an improvement in appearance and foldability. However, as yet, such improvement is not regarded as sufficient. Furthermore, the coating or lamination with an elastomer resin requires a complicated process, with attendant problems in productivity.
In addition, it is also demanded that the base fabric for air bags be less expensive and more easily folded for reducing the size of the module cover. Thus, air bags using non-coated base fabrics have attracted attention. In particular, high density non-coated air bags formed from woven fabrics of polyamide fibers such as nylon 66 and nylon 6, and polyester fibers have been tested and found to have improved mechanical properties and foldability as compared with air bags formed from coated base fabrics. However, they become frayed during sewing and are not low enough in air permeability, i.e., not high enough in gas interceptability, and intensive studies are being made to solve these problems. For example, JP-A-64-070247 proposes a pressure-compressed base fabric. However, this does not sufficiently prevent fraying, even though it is lower in air permeability. Furthermore, JP-A-07-040798 and JP-A-0-503763 propose a base fabric formed from a urethane resin. In particular JP-A-07-040798 discloses an air bag having a base fabric coated by dipping into an emulsion of a urethane resin and subsequently treated with a fireproof agent. However, even though such air bags are highly improved from the point of view of prevention of fraying, they are not low enough in air permeability, especially since the air permeability is increased by thermal deterioration, so that maintenance of air permeability at a stable, low level cannot be assured.
SUMMARY OF THE INVENTION
The present invention seeks to overcome the above mentioned disadvantages of conventional air bags, so as to provide a base fabric for air bags which is prevented from being frayed during sewing, excellent in foldability and low in air permeability while retaining the mechanical properties required for air bags.
The present invention enables the above problems to be solved by providing, according to one aspect, a fabric for a base fabric for air bags, which fabric comprises a fibrous substrate and a covering layer, which covering layer is made of a thermoplastic synthetic resin and of 10 &mgr;m or less in average thickness and which covering layer is adhered to a surface of a fibrous substrate such that interstices between the fibers are filled with the resin, and also by providing, according to another aspect, an air bag comprising such a fabric. According to yet another aspect, the invention provides a process for producing a base fabric for air bags, comprising the steps of applying a solution or dispersion, in a liquid, preferably aqueous, medium, of a thermoplastic synthetic resin to a fibrous substrate; and heat-treating.
Basically, in accordance with the invention, a covering layer made of a thermoplastic synthetic resin is formed in such a way that the covering layer adheres to a fibrous substrate used in a fabric for air bags, and without this configuration, the present invention cannot be achieved. The process of the present invention can provide a fabric for air bags which does not fray during sewing, and from which air bags can be constructed which are excellent in foldability and low in air permeability while retaining the mechanical properties required for air bags.
The fibrous substrate of a fabric in accordance with the present invention can be a woven fabric, knitted fabric or non-woven fabric formed from polyamide fibers of nylon 6.6, nylon 6, nylon 12, nylon 4.6, nylon 6-nylon 6.6 copolymer, or any of copolymers of nylon with, for example, a polyalkylene glycol, dicarboxylic acid or amine, polyester fibers of a homopolyester such as polyethylene terephthalate or polybutylene terephthalate, or any copolymer thereof additionally containing units derived from another acid component of a polyester, such as an aliphatic dicarboxylic acid, for example, isophthalic acid, 5-sodiumsulfoisophthalic acid or adipic acid, aramid fibers of, for example, any copolymer formed from paraphenyleneterephthalamide and an aromatic ether, rayon fibers, sulfone based fibers, ultrahigh molecular weight polyethylene fibers, and high polymer fibers arranged within an islands-in-sea structure mainly composed of the above synthetic fibers. As the fabric of the fiber substrate, a woven fabric is preferable. As for the weave, a plain weave, twill weave, satin weave, modified weaves of these types or a multi-axial weave, can be used, but among them a plain weave, is preferable because it is excellent in mechanical properties and thin. Among these woven fabrics, a plain weave of polyamide fibers or polyester fibers is capable of providing an air bag having excellent properties. The fibers can contain various additives usually used for improving productivity and properties in the production and processing of raw filaments. For example, a thermal stabilizer, antioxidant, photo stabilizer, smoothing agent, antistatic agent, plasticizer, thickening agent, pigment or flame retarder, can be present
The strength of the mono-filaments constituting the woven fabric is not especially limited, but is preferably 6 g/denier (6.7 g/dtex) or more, more preferably 7 g/denier (7.8 g/dtex) or more. The thickness of each of the mono-filaments and the thickness of each of the filament yarns respectively constituting the woven fabric are not especially limited as far as the mechanical properties required as air bags can be satisfied. However, it is preferable that the thickness of each of the mono-filaments is at least 0.1 denier (0.11 dtex), more preferably at least 0.5 denier (0.55 dtex) up to 7 deniers (7.8 dtex) inclusive, and that the thickness of each of the filament yarns is 200 to 500 deniers (220 to 550 dtex). Furthermore, the cover factor of the woven fabric is preferably 1700 to 2500 denier
0.5
in
−1
[(0.9 dtex)
0.5
(2.54 cm.)
−1
]. The cover factor referred to here is expressed by (D1)×N1+(D2)×N2, where D1 is the thickness (denier) (0.9 dtex) of each of the warp filament yarns, N1, the density of the warp filament yarns (number per inch) (number per 2.54
Fujiyama Tomomichi
Kano Susumu
Moriwaki Yoshitsugu
Dye Rena L.
Morrison & Foerster / LLP
Toray Industries Inc.
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