Airbag base fabric and method for manufacturing same

Abstract

The present invention addresses the problem of providing an airbag base fabric that shows excellent visibility at the time of inspection, has low air permeability even under high temperature and high humidity conditions, and can be recycled. As a solution, provided is an airbag base fabric comprising a film containing a thermoplastic resin laminated on a woven fabric containing a fiber of a thermoplastic resin. The airbag base fabric is characterized in that the fiber and the film contain the same type of thermoplastic resin, and the film is an alignment film having a haze of less than or equal to 10%.

Description

Airbag fabric and manufacturing method thereof

[0001] The present invention relates to an airbag fabric in which a film is laminated on a woven fabric, and a method for manufacturing the same.

[0002] Airbag systems, one of the safety components of automobiles, have seen a rapid increase in installation rates in recent years as passenger safety awareness has improved. In an automobile collision, a sensor detects the impact and an inflator generates high-temperature, high-pressure gas, which rapidly deploys the airbag to protect the passenger, preventing their head from hitting the steering wheel, windshield, door glass, etc., when the passenger's body is thrown in the direction of the collision.

[0003] Conventionally, synthetic rubber or thermoplastic resin-coated base fabrics have been used in airbags because of their excellent properties such as heat resistance, air barrier properties (low air permeability), and flame retardancy (see, for example, Patent Documents 1 and 2). However, since the synthetic rubber or thermoplastic resin used for coating is a resin different from the fibers constituting the base fabric, it is generally difficult to re-use the recovered airbag base fabric as a raw material by thermal melting it again into fibers or woven fabrics. This is because when a different type of thermoplastic resin is used, a large amount of gel is generated during thermal melting, which makes it easy for thread breakage to occur, or the mechanical properties of the airbag base fabric are likely to be insufficient.

[0004] Patent Document 3 proposes a fiber gas bag material in which a thin film is bonded to a fabric layer with a thermoplastic film. It describes a preferred material in which the thermoplastic film is a modified polyolefin and the thin film is a polyether block amide (claims 2 and 4). Therefore, since the laminate is manufactured using materials made of different resins, it is insufficient in terms of recyclability.

[0005] Furthermore, Patent Document 4 proposes a laminate in which an unstretched multilayer film made of a thermoplastic polyester elastomer is bonded to a polyester base fabric. However, unstretched films made of thermoplastic polyester elastomers tend to deteriorate due to hydrolysis when placed under high temperature and high humidity conditions, resulting in increased breathability. As a result, when used as an airbag, inflation is insufficient or cannot be maintained, making it unsatisfactory.

[0006] JP-A-5-16753 Patent No. 4151414 Patent No. 4965757 Patent No. 7236820

[0007] An object of the present invention is to provide an airbag base fabric which has low air permeability under high temperature and high humidity conditions, which makes it easy to check the quality of the base fabric, and which is recyclable, and a method for manufacturing the same.

[0008] The airbag fabric of the present invention, which can achieve the above-mentioned object, has the following configuration. [1] An airbag fabric comprising a woven fabric containing thermoplastic resin fibers and a film containing thermoplastic resin laminated thereon, wherein the fibers and the film contain the same type of thermoplastic resin, and the film is an oriented film having a haze of 10% or less. [2] The airbag fabric according to [1], wherein the thermoplastic resin contained in the fibers and the thermoplastic resin contained in the film are both polyester. [3] The airbag fabric according to [1] or [2], wherein the thermoplastic resin contained in the fibers and the thermoplastic resin contained in the film are obtained by polymerizing monomer components containing 40 mol% to 100 mol% of terephthalic acid as an acid component and 40 mol% to 100 mol% of ethylene glycol as a glycol component. [4] The airbag fabric according to [1] or [2], wherein the oriented film has a thickness of 5 μm to 100 μm. [5] The airbag fabric according to [1] or [2], wherein the oriented film has a laminated structure having an A layer and a B layer, the A layer being an adhesive layer in contact with the woven fabric, and the B layer being a base layer. [6] The airbag fabric according to [1] or [2], wherein the air permeability under a pressure of 20 kPa after treatment at 80°C and 95% RH for 1000 hours is 0.1 L / cm２ The airbag fabric according to [1] or [2], wherein the elongation rate is 1 / min or less.

[0009] In addition to the above-mentioned object, the manufacturing method of the airbag fabric of the present invention, which can achieve low cost, has the following configuration: [7] The manufacturing method of the airbag fabric according to [1] or [2], characterized in that the woven fabric and an oriented film formed by stretching at least uniaxially and then heat-treating are laminated by thermocompression bonding in the manufacturing process of the fabric.

[0010] The airbag fabric of the present invention has low air permeability under high temperature and high humidity conditions, makes it easy to check the quality of the fabric, and is recyclable. Further, according to the present invention, a method for producing the airbag fabric can be provided.

[0011] The airbag fabric of the present invention comprises a woven fabric containing thermoplastic resin fibers and an oriented film containing a thermoplastic resin laminated thereon, and the fibers and the oriented film contain the same type of thermoplastic resin. In other words, since the material constituting the fabric is a monomaterial, it is suitable for recycling. Thus, in the present invention, the term "same type" in "same type of thermoplastic resin" means that the two thermoplastic resins are within a range that allows them to be handled as a monomaterial for recycling. In this regard, the fibers and the oriented film preferably contain the same type of thermoplastic resin at 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, 90% by weight or more, 95% by weight or more, or 98% by weight or more. The airbag fabric of the present invention is preferably a woven fabric substantially composed of thermoplastic resin fibers and an oriented film substantially composed of a thermoplastic resin laminated thereon, and more preferably a woven fabric composed of thermoplastic resin fibers and an oriented film composed of a thermoplastic resin laminated thereon.

[0012] Examples of thermoplastic resins constituting the woven fabric and oriented film include polyester, polyamide, polyethylene, polypropylene, polysulfone, polyurethane, and acrylic. A preferred thermoplastic resin is polyester or polyamide, and from the viewpoint of recyclability, polyester is particularly preferred. As monomer components used in producing polyester, preferred acid components include terephthalic acid and isophthalic acid, and preferred glycol components include ethylene glycol, butylene glycol, cyclohexanone dimethanol, and diethylene glycol.

[0013] More preferred examples of the polyester include polyethylene terephthalate obtained by polymerizing terephthalic acid and ethylene glycol as the main monomer components, and copolymer polyesters obtained by copolymerizing terephthalic acid with other acid components and ethylene glycol with other glycol components. Among these, from the viewpoint of stable production of woven fabrics and stretched films, it is even more preferred that the monomer components contain 40 mol% to 100 mol% of terephthalic acid as the acid component and 40 mol% to 100 mol% of ethylene glycol as the glycol component. Furthermore, it is particularly preferred that the monomer components contain 60 mol% to 90 mol% of terephthalic acid and 50 mol% to 90 mol% of ethylene glycol.

[0014] On the other hand, it is preferable that the oriented film used in the present invention does not use a polyester elastomer obtained by polymerizing a monomer component containing an ether component, because oriented films using the polyester elastomer obtained by polymerizing a monomer component containing an ether component often have a haze of more than 10% and often deteriorate under high temperature and high humidity conditions even after stretch orientation.

[0015] The oriented film used in the present invention has a haze of 10% or less, preferably 5% or less. When the haze of the oriented film is 10% or less, the woven fabric can be visually checked through the oriented film when visually checking the quality of the base fabric laminated by high-temperature pressure bonding of the oriented film to the woven fabric. This makes it easier to check for foreign matter contamination and longitudinal misalignment in the woven fabric, thereby reducing deterioration in productivity such as reduced yield. In the present invention, the haze value is measured in accordance with JIS-K7136.

[0016] The oriented film laminated to the woven fabric in the present invention is produced by melt-extruding thermoplastic resin pellets into a sheet form onto a cooling roll from a T-die, stretching the cooled and solidified unstretched film uniaxially or more with a heating roll and / or tenter, and then heat-treating it. The thickness of the oriented film is preferably 5 μm or more and 500 μm or less. From the viewpoint of suppressing a decrease in the breathability and flexibility of the airbag base fabric, the thickness of the oriented film is more preferably 5 μm or more and 100 μm or less. The ratio of the thickness of the oriented film to the thickness of the woven fabric is preferably 5% or more and 30% or more, more preferably 8% or more and 20% or less. By setting the thickness ratio (oriented film / woven fabric) to 5% or more, a decrease in breathability is suppressed and inflation of the airbag during use is less likely to be hindered. On the other hand, by setting the thickness ratio (oriented film / woven fabric) to 30% or less, the flexibility of the airbag is less likely to be reduced. In the present invention, the thickness of the oriented film is measured using a dial gauge in accordance with JIS K7130-1999 Method A.

[0017] The oriented film may have a single layer structure made of a single thermoplastic resin, but preferably has a laminate structure including layers A and B. Layer A is an adhesive layer that contacts the woven fabric, and layer B is a base layer, and a laminate structure having adhesive layer A and base layer B is preferred. An oriented film having a laminate structure (hereinafter referred to as a laminate film) is preferably produced by a co-extrusion method. When a laminate film having layers A and B is laminated such that layer A contacts the woven fabric, a base fabric having good adhesion between the woven fabric and the laminate film and low breathability is obtained.

[0018] The oriented film is produced by stretching at least uniaxially and then heat-treating. Biaxially stretched films are particularly preferred, which are produced by stretching biaxially and then heat-treating. The stretching method preferably includes at least stretching by a tenter method. Molecular orientation occurs through stretching, and the crystalline structure is fixed through heat treatment. Therefore, even if easily hydrolyzed polyester is used as the raw material, deterioration under high temperature and humidity conditions is suppressed, and the breathability of the base fabric can be reduced.

[0019] In the present invention, the method for laminating the woven fabric and the oriented film can be any known technique, among which a method in which the base fabric and the stretched film are pressed together between heated rolls to bond them together is preferred.

[0020] The fibers or oriented films may contain various known additives to improve processability and properties in the yarn production process and post-processing process, as long as the effects of the present invention are not impaired. Examples of such additives include antioxidants, heat stabilizers, UV inhibitors, smoothing agents, antistatic agents, thickeners, flame retardants, inorganic fillers, and crosslinking agents. The fibers may be spun-dyed or dyed after spinning. Furthermore, the cross section of the single yarn (the fibers) may be a circular cross section or a modified cross section.

[0021] It is desirable to adopt a plain weave weave for the woven fabric constituting the airbag base fabric, taking into consideration the uniformity of the base fabric properties. The yarns used are preferably, for example, yarns made of the above-mentioned fibers. The warp and weft yarns constituting the woven fabric do not have to be the same. For example, they may have different finenesses, number of yarns, or fiber types. Known looms can be used to weave the woven fabric. For example, water jet looms, air jet looms, rapier looms, etc. are suitable.

[0022] The total fineness of the fibers used to weave the woven fabric is preferably 100 to 700 dtex, more preferably 110 to 580 dtex. By making the total fineness 100 dtex or more, the tensile strength and tear strength of the woven fabric are improved. On the other hand, by making the total fineness 700 dtex or less, the flexibility of the woven fabric can be improved while maintaining its strength. As a result, a decrease in packability is prevented, and the surface of the woven fabric becomes hard, making it less likely to injure the human skin when the airbag is deployed.

[0023] The single yarn fineness of the fibers is preferably 6 dtex or less, more preferably 4 dtex or less. By making the single yarn fineness 6 dtex or less, the softness of the woven fabric can be improved. On the other hand, the single yarn fineness is preferably 1 dtex or more. By making the single yarn fineness 1 dtex or more, it is possible to prevent insufficient strength of the single yarn, deterioration in productivity due to breakage of single warp yarns during weaving, and deterioration in the quality of the woven fabric.

[0024] The airbag fabric of the present invention has an air permeability of 0.1 L / cm under a pressure of 20 kPa. ２ / min or less, more preferably 0.04 L / cm ２ / min or less. These air permeabilities can be measured, for example, using a high-pressure air permeability measuring instrument manufactured by Kyoto Seiko Co., Ltd. The air permeability of the airbag fabric of the present invention can be achieved by satisfying the technical requirements described in the present invention.

[0025] Furthermore, the airbag fabric of the present invention has an air permeability of 0.1 L / cm under a pressure of 20 kPa even after being placed in a high temperature and high humidity environment (80°C x 95% RH x 1000 hours). ２ / min or less, more preferably 0.08 L / cm ２ / min or less, more preferably 0.04 L / cm ２ / min or less, which is necessary for the airbag to function even in harsh environments.

[0026] The airbag fabric of the present invention can be manufactured by using the airbag fabric of the present invention, cutting component parts according to the required shape, and sewing these component parts. The sewing method and sewing thread are not particularly limited, and conventionally known methods and threads may be used. It is also preferable to seal the sewn parts using a known sealing means (such as a sealing tape).

[0027] In addition, an airbag device using an airbag produced by cutting and sewing the airbag fabric of the present invention can use conventionally known components (such as an impact sensor, an inflator, and a hose for introducing inflator gas).

[0028] The present invention will be described in detail below based on examples. However, the following examples do not limit the present invention, and all modifications and variations within the scope of the present invention are included within the technical scope of the present invention. Various evaluations in these examples are performed according to the following methods.

[0029] (1) Air Permeability The air permeability of the base fabric is measured under a pressure of 20 kPa using a high-pressure air permeability measuring instrument (manufactured by Kyoto Seiko Co., Ltd.) with a sample size of 20 cm x 20 cm.

[0030] (2) High-Temperature, High-Humidity Treatment Using a thermo-hygrostat (manufactured by ESPEC, PL-2J), the base fabric was left at 80°C and 95% RH for 1000 hours.

[0031] (3) Thickness: Measured using a dial gauge in accordance with JIS K7130-1999 Method A.

[0032] (4) Intrinsic Viscosity: 0.2 g of polyester resin is dissolved in 50 ml of a mixed solvent of phenol / 1,1,2,2-tetrachloroethane (60 / 40 (mass ratio)), and the intrinsic viscosity is measured at 30° C. using an Ostwald viscometer. The unit is dl / g.

[0033] (5) Haze A piece measuring 5 cm in the longitudinal direction and 5 cm in the transverse direction is cut out from the obtained oriented film, and the total haze is measured at 25°C over all wavelengths of visible light using a turbidity meter (NDH5000, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS-K7136.

[0034] (6) Visibility When the orientation film and the woven fabric are overlapped, if the weave of the base fabric can be visually confirmed through the orientation film, it is marked as O; if this is difficult, it is marked as X.

[0035] Example 1 [Preparation of Polyester Woven Fabric] Polyethylene terephthalate multifilament yarns with a fineness of 555 dtx / 144f were used for the warp and weft yarns, and the fabric was woven in a plain weave using a water jet loom. The fabric was then passed through a hot water bath at 90°C without drying. The fabric was then passed through a drying process so that the surface temperature of the fabric at the dryer outlet (measured with a non-contact thermometer) was 120°C. The fabric was then heat-set so that the surface temperature of the fabric at the heat treatment outlet (measured with a non-contact thermometer) was 170°C, resulting in a fabric with a weave density of 51.0 threads / 2.54 cm in the warp direction and 51.0 threads / 2.54 cm in the weft direction.

[0036] [Preparation of Unstretched Film] The monomer composition of the raw material of the adhesive layer A was adjusted so that the acid component was 100 mol% of terephthalic acid (TPA), and the diol component was 66 mol% of ethylene glycol (EG), 10 mol% of butanediol (BD), 22 mol% of neopentyl glycol (NPG), and 2 mol% of diethylene glycol (DEG). Then, an esterification reaction and a polycondensation reaction were carried out to obtain a copolymer polyester A.

[0037] The monomer composition of the raw materials for the base layer B was adjusted to 100 mol % of terephthalic acid (TPA) as the acid component, and 78 mol % of ethylene glycol (EG), 10 mol % of butanediol (BD), 10 mol % of neopentyl glycol (NPG), and 2 mol % of diethylene glycol (DEG) as the diol component. Subsequently, an esterification reaction and a polycondensation reaction were carried out to obtain a copolymer polyester B.

[0038] After the esterification reaction, an ethylene glycol slurry of silicon dioxide particles (Sylysia 310, manufactured by Fuji Silysia Ltd.) was added as a lubricant to the raw material for the base layer B so that the silicon dioxide content was 700 ppm relative to the polyester.

[0039] The copolymer polyesters A and B were charged into separate extruders, mixed and melted at 280°C, and coextruded through a T-die to obtain an unstretched laminate sheet. The intrinsic viscosity of the sheet was 0.71 dL / g. The extrusion ratio was A layer / B layer = 1 / 2.

[0040] [Preparation of Stretched Sheet] The unstretched sheet obtained was stretched 4.0 times in the machine direction at 90°C, and biaxially stretched 4.0 times in the transverse direction at 100°C, followed by heat treatment. In the final heat treatment zone, the sheet was relaxed 3% in the transverse direction at 115°C to obtain a biaxially oriented film having a thickness of 30 µm.

[0041] [Fabric Preparation] The laminated film was placed so that the adhesive layer A was in contact with the woven fabric, and the woven fabric and the laminated film were thermally bonded together using a thermal bonding roller under the following thermal bonding conditions: a) temperature: 190°C, b) linear pressure: 51 kg / cm, c) speed: 1 m / min, d) roll diameter: 250 mmφ

[0042] Example 2 A base fabric was obtained in the same manner as in Example 1, except that cyclohexanedimethanol (CHDM) was used instead of neopentyl glycol (NPG) used as the raw material monomer for the adhesive layer A and the base layer B. The intrinsic viscosity of the unstretched sheet before stretching the film was 0.70 dl / g.

[0043] Comparative Example 1 In Example 1, no laminated film was used, and only a polyester woven fabric was used.

[0044] Comparative Example 2 An attempt was made to produce a laminated film similar to that in Example 1 of Patent Document 4, but since it was difficult to carry out the experiment under exactly the same conditions, the following procedure was carried out.

[0045] [Preparation of Unstretched Sheet] As the raw material for adhesive layer A, a polyester / polyether block copolymer (PBT / PTMEG=25 / 75; mass ratio) having polybutylene terephthalate (PBT) as a hard segment and polytetramethylene ether glycol (PTMEG) having a number average molecular weight of 2000 as a soft segment was used.

[0046] The raw material for the base layer B was a polyester / polyether block copolymer (PBT / PTMEG=58 / 42; mass ratio) having polybutylene terephthalate as a hard segment and polytetramethylene ether glycol with a number average molecular weight of 2000 as a soft segment.

[0047] An unstretched sheet was prepared in the same manner as in Example 1, except that the extrusion temperatures were changed to 200°C for Layer A and 230°C for Layer B.

[0048] [Preparation of Stretched Film] The unstretched sheet was simultaneously biaxially stretched four times in the machine and transverse directions at 120°C using a small batch-type stretching machine (manufactured by Toyo Seiki Seisaku-sho), and then heat-treated at 130°C for 30 seconds to obtain a biaxially stretched film. Note that Example 1 of Patent Document 4 uses an unstretched multilayer film.

[0049] [Preparation of Laminate] A laminate of a woven fabric and a laminate film was obtained in the same manner as in Example 1.

[0050]

Claims

1. An airbag fabric in which a film containing a thermoplastic resin is laminated to a woven fabric containing fibers of a thermoplastic resin, the fibers and the film containing the same type of thermoplastic resin, and the film is an oriented film with a haze of 10% or less.

2. The airbag fabric according to claim 1, wherein the thermoplastic resin contained in the fibers and the thermoplastic resin contained in the film are both polyester.

3. The airbag fabric according to claim 1 or 2, wherein the thermoplastic resin contained in the fibers and the thermoplastic resin contained in the film are obtained by polymerizing monomer components containing 40 mol % or more and 100 mol % or less of terephthalic acid as an acid component and 40 mol % or more and 100 mol % or less of ethylene glycol as a glycol component.

4. The airbag fabric according to claim 1 or 2, wherein the film has a thickness of 5 μm or more and 100 μm or less.

5. The airbag fabric according to claim 1 or 2, wherein the film has a laminated structure having an A layer and a B layer, the A layer being an adhesive layer in contact with the woven fabric, and the B layer being a base layer.

6. After 1000 hours of treatment at 80°C and 95% RH, the air permeability under a pressure of 20 kPa is 0.1 L / cm ２ The airbag fabric according to claim 1 or 2, wherein the airbag fabric has a stretchability of 100% or less.

7. A method for producing an airbag fabric as described in claim 1 or 2, characterized in that the woven fabric and an oriented film formed by stretching the fabric in at least one axial direction and then heat-treating the fabric are laminated by thermocompression during the production process of the fabric.

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