WO2024117138A1 - Production method for airbag having enhanced internal-pressure retaining performance - Google Patents

Abstract

Provided is a production method for an airbag that has high internal-pressure retaining performance, is low-cost, is highly producible, and is excellent in compactness. The production method according to the present invention is a manufacturing method for an airbag formed by stitching at least one pair of base fabric panels at the peripheral edges thereof. The production method includes: a fusion-bonding step for fusion-bonding the first surface layer to the inner surfaces of the base fabric panels by applying heat or ultrasonic waves from the outside of the pair of base fabric panels while applying a tensile force to a strip-shaped impermeable film type protection material that has been center-folded, comprises a laminated resin film including a first surface layer and a second surface layer, and is located between the inner surfaces of the respective base fabric panels, and while the strip-shaped impermeable film-type protection material is continuously inserted along the linear or curved peripheral edges of the pair of base fabric panels, and in this step, the second surface layer peels when the second surface layer is not fusion-bonded to itself by thermal fusion-bonding or ultrasonic fusion-bonding, or when a strong tensile force is applied to the pair of base fabric panels; and a stitching step for stitching the pair of base fabric panels in the vicinity of a bonding region before, after, or simultaneously with bonding. Said production method also executes, in two stages, the bonding of one of the base fabric panels, the protection material, and the other of the base fabric panels.

Description

Airbag manufacturing method with improved internal pressure retention

The present invention relates to a method for manufacturing an airbag used in an airbag device mounted on a vehicle. More specifically, the present invention relates to a method for manufacturing an airbag in which the outer edges of a pair of base fabric panels are sewn together, and which has improved internal pressure retention performance.

Conventionally, airbags used in airbag devices mounted on vehicles are made by sewing (stitching) the outer edges of a pair of base fabric panels together to form a bag-like shape, into which gas is instantly injected to inflate and deploy. However, because the sewing (stitching) is usually done using sewing thread, gas leakage between the pair of base fabric panels and through the holes in the sewing needle is unavoidable.

Today, various types of airbags are used depending on where they are installed in a vehicle, including PAB (Passenger Airbag), DAB (Driver Airbag), SAB (Side Airbag), KAB (Knee Airbag), CAB (Curtain Airbag), and pedestrian airbags. Airbags absorb impacts on the human body by retaining injected gas. In particular, DABs meet performance requirements if they can handle instantaneous impacts (first impacts). However, for example, CABs must maintain the inflated state of the airbag even during the rotation (rollover) of the vehicle after the first impact, and are required to maintain a constant pressure (e.g., 30 kPa) or higher (i.e., internal pressure maintenance) within the airbag for a long period of time (e.g., six seconds). In addition, pedestrian airbags require internal pressure maintenance for a longer period of time than DABs, because the timing at which a pedestrian lands on the bonnet and hits the vehicle body (e.g., the pillar section) varies.

In order to meet the requirement of maintaining the internal pressure, the following methods have been considered.
One method is to bond the outer edges of a pair of base fabric panels with only an adhesive instead of sewing. Although this method can prevent gas leakage, there is a risk that the adhesive will not be able to withstand the strength required for the airbag to deploy because there is no sewing.

Another method is to manufacture a pair of base fabric panels using the One Piece Woven method and then coat the outside of the base fabric. With this method, there are no stitching and the coating means there is no problem with airtightness, and there are no problems with strength either, but it is difficult to create complex shapes, the coating needs to be applied relatively thickly, and this tends to increase the weight of the airbag, and it is also expensive.

Another method is to bond the outer edges of a pair of base fabric panels with a silicone adhesive and then sew the bonded portion. This method can ensure strength while suppressing gas leakage, but it has problems such as low productivity, thick bonded portions, and poor folding and storage properties of the airbag. In addition, the weight of the silicone adhesive increases the weight of the airbag.
As illustrated in FIG. 2, in this method, the silicone adhesive stretches during airbag deployment, preventing gas from accessing the stitching.
Generally, silicone adhesives are suitable for such applications because of their high adhesive strength with base fabric panels, but the adhesive takes half a day to about a day to harden, resulting in low productivity, and for example, the folded thickness of a pair of base fabric panels is 2.2 mm at the location where there is no adhesive (location where internal pressure does not need to be maintained), whereas the folded thickness at the location where there is adhesive and stitching is 5.2 mm, resulting in a lack of compactness (foldability, storability). Furthermore, silicone adhesives must be separated from the airbag fabric when recycled, and they emit a relatively large amount of GHG (Green House Gas) during production, so they are not environmentally friendly in the manufacture and disposal of airbags.

The following Patent Document 1 describes an airbag device having a protective cloth sewn along a seam where a pair of opposing portions of a base fabric are sewn together, at a position away from the seam so as to cover the seam from the inside where gas from the inflator is introduced (see Figures 2 and 7 of the same document). Patent Document 1 discloses a protective material for the seam, but this protective material is fixed to the base fabric by sewing, not by adhesion. The purpose of this protective material is to prevent the seam from being directly exposed to the high-pressure gas from the inflator and being destroyed, and to distribute tension in the protective material's seam to prevent damage to the seam of the pair of base fabrics, but is not intended to maintain internal pressure without damaging the seam.

Patent Document 2 listed below discloses an airbag having walls including a laminate material, the laminate material including a backing layer having a breathable sheet-like structure made of a woven or knitted fabric, at least two layers of coextruded polymer film, a first polymer layer having a predetermined glass transition temperature on the backing layer side, and a second polymer layer having a predetermined storage modulus on the opposite side to the backing layer, the airbag having walls bonded together such that the second polymer layer is bonded at the edge of the airbag, and a manufacturing method for bonding the first polymer layer and the second polymer layer by applying different thermal energies to them.
The object of the invention described in US Pat. No. 5,399,633 is to provide an airbag which can be produced at low cost and which is easy and reliable to seal (see Figs. 1-3 of the same document).
Patent Document 2 does not disclose any protective material for the seams of the airbag, and the manufacturing method therefor is primarily intended to increase productivity, not to maintain internal pressure.

The following Patent Document 3 describes an airbag in which panels are joined together at joints, the panels having a woven fabric and a synthetic resin film bonded to the woven fabric via an adhesive, the panels are joined together by pressurizing and heating with a hot melt adhesive sheet interposed between the panels, and the synthetic resin film is disposed on the outside of the airbag. The object of the invention described in Patent Document 3 is to provide an airbag in which the strength of the seams between the panels is high, the durability is excellent, gas leakage is prevented, and handling is easy (see Figures 3 and 4).
In the invention described in Patent Document 3, panels are bonded together with a bonding layer made of hot melt adhesive, thereby increasing the strength of the joints between the panels, reducing the thread density of the woven fabric, and a synthetic resin film is placed on the outside of the panel to prevent the woven fabric from coming into direct contact with the inside of the vehicle body, thereby increasing durability. In addition, the stitching of the woven fabric is impregnated with hot melt adhesive to prevent gas leaks from pinholes and stitching threads from coming loose.
Patent Document 3 does not describe a method for preventing gas leakage from stitching holes due to stress being applied to the joints between the panels when the adhesive surface around the outer periphery of the airbag is stressed during deployment, which may cause the adhesive to break.Furthermore, there is no mention of the technical idea of adhering a protective material for the stitching to the base fabric at a location separate from the stitching, and maintaining the adhesion between the protective material and the base fabric to maintain the internal pressure.

In light of the state of the art, an airbag that has excellent internal pressure retention when inflated and deployed, is low cost, highly productive, and has excellent compactness, and a manufacturing method thereof, has not yet been provided.

International Publication No. 2010/122852 US Patent Application Publication No. 2010/0320736 JP 2018-177122 A

Under the level of the conventional technology, the problem that the present invention aims to solve is to provide a highly productive method for manufacturing an airbag in which a pair of base fabric panels are sewn together at their outer periphery to form a bag body, in which an airtight structure is formed by bonding both outer surfaces of a half-folded, strip-shaped, non-breathable protective material to the inner surface of each of the pair of base fabric panels in a bonding region of a predetermined width along the stitching from near the stitching toward the inside of the bag body, the bonding region having a proximal end and a distal end, and which maintains this structure even when the airbag is deployed, thereby improving the internal pressure retention performance, and providing a low-cost, highly productive, and highly compact airbag manufacturing method.

The inventors of the present application conducted intensive research and repeated experiments in order to solve the above-mentioned problems, and unexpectedly discovered that the above-mentioned problems could be solved by using a non-breathable protective material having the structure defined below, which led to the completion of the present invention.
That is, the present invention is as follows.

[1] A method for manufacturing an airbag having at least one pair of base fabric panels sewn together at their outer periphery, comprising the steps of:
a welding step of continuously sandwiching a semi-folded, band-shaped non-breathable film-like protective material, which is made of a monolayer resin film having a predetermined width with a release paper sandwiched therebetween or a laminated resin film having two or more layers including a first surface layer and a second surface layer, between the inner surfaces of the pair of base fabric panels while applying tension to the material along the linear or curved outer periphery of the pair of base fabric panels, and applying heat or ultrasonic waves from the outside of the pair of base fabric panels to weld a surface of the monolayer resin film or the first surface layer to the inner surface of the base fabric panel in an adhesive region of a predetermined width, wherein although the surfaces of the monolayer resin film on the release paper side are not welded to each other due to the presence of the release paper, or the second surface layers of the laminated resin film are not welded to each other by heat welding or ultrasonic welding, or are welded to each other by heat welding or ultrasonic welding, the second surface layer peels off when a tensile force is applied to the pair of base fabric panels when the airbag is deployed;
a sewing step of sewing the pair of fabric panels together adjacent the bonded areas before, after, or simultaneously with the bonding;
The manufacturing method comprising the steps of:
[2] The method according to [1], wherein the half-folded band-shaped non-breathable film-like protective material is fed from a roll in which it is wound in a half-folded state, and sandwiched between a pair of base fabric panels.
[3] A step of heating a part or the whole of the half-folded, band-shaped, non-breathable film-like protective material before a welding step of welding the half-folded, band-shaped, non-breathable film-like protective material;
The method according to any one of claims 1 to 2, further comprising:
[4] A step of cooling a part or the whole of the half-folded, band-shaped, non-breathable film-like protective material after a welding step of welding the half-folded, band-shaped, non-breathable film-like protective material;
The method according to any one of the above [1] to [3],
[5] In the welding process of welding the half-folded band-shaped non-breathable film-like protective material, a process of heating and/or cooling a part or the whole of the half-folded band-shaped non-breathable film-like protective material while intermittently applying/releasing the pressure of a hot plate and/or a cold plate;
The method according to any one of the above [1] to [4],
[6] The method according to any one of [1] to [5], wherein the melting point of the resin constituting the first surface layer of the laminated resin film which is the half-folded non-breathable film-like protective material is 50°C to 160°C lower than the melting point of the resin constituting the second surface layer.
[7] The method according to any one of [1] to [6] above, wherein the half-folded non-breathable film-like protective material is a single-layer or multilayer film including a first surface layer and a second surface layer of a laminated resin film, and the difference in SP value between any adjacent layers is 2.0 [cal/ ^cm3 ) ^1/2 ] or more.
[8] The method according to any one of [1] to [7] above, wherein the half-folded non-breathable film-like protective material is a single-layer or multilayer film including a first surface layer and a second surface layer of a laminated resin film, and the difference in HSP value between any adjacent layers is 1.0 [cal/ ^cm3 ) ^1/2 ] or more.
[9] The method according to any one of [1] to [8], wherein when a tensile force is applied between the pair of base fabric panels during deployment of the airbag, the length between the distal ends along the folded non-breathable film-like protective material is greater than or equal to the length between the distal ends along the pair of base fabric panels.
[10] a sewing step of sewing the pair of base fabric panels together adjacent to the bonded areas after the bonding;
The method according to any one of the above [1] to [9],
[11] a welding step of applying tension to a semi-folded band-shaped non-breathable film-like protective material having a predetermined width and made of a laminated resin film of two or more layers including a first surface layer and a second surface layer, from below the first fabric panel, continuously along a straight or curved outer periphery of the first fabric panel, thereby welding the first surface layer to an upper surface of the first fabric panel;
a welding step of overlapping another base fabric panel on the welded film-like protective material and applying heat or ultrasonic waves from the upper side of the overlapped base fabric panel to weld the first surface layer to the lower surface of the overlapped base fabric panel, wherein the second surface layers of the laminated resin film are not welded to each other by thermal welding or ultrasonic welding, or are welded to each other by thermal welding or ultrasonic welding, but the second surface layer peels off when a tensile force is applied to the base fabric panels when the airbag is deployed;
a sewing step of sewing the fabric panels together adjacent the areas of the resulting welds after said bonding;
The manufacturing method comprising the steps of:

The method for manufacturing an airbag according to the present invention comprises bonding the outer surfaces of both ends of a folded, strip-shaped, non-breathable protective material to the inner surface of each of at least a pair of base fabric panels in bonding areas of a predetermined width along the seams, having proximal and distal ends from near the seams toward the inside of the bag, and when a tensile force is applied to the pair of base fabric panels when the airbag is deployed, substantially no tensile force is applied to the bonding areas, thereby maintaining an airtight structure.As a result, this method for manufacturing an airbag has high internal pressure retention performance, is low cost, has high productivity, and is also highly compact.
Therefore, the airbag and the manufacturing method thereof according to the present invention can be suitably used for automobile airbags, in particular for CABs and pedestrian airbags which require high internal pressure retention performance.

1 is a plan view of an airbag in which a pair of base fabric panels are sewn together at their outer periphery to form a bag body, which can be manufactured by the manufacturing method of this embodiment. 2 is an explanatory diagram of a state of an airbag when deployed, in a location corresponding to the cross section AA in FIG. 1, in which a portion bonded with a silicone adhesive is sewn. FIG. FIG. 2 is an explanatory diagram of the state of a non-breathable protective material in an airbag that can be manufactured by the manufacturing method of this embodiment when the airbag is deployed. This is an explanatory diagram of a state in which, in an airbag that can be manufactured by the manufacturing method of this embodiment, when a tensile force is applied between the pair of base fabric panels during deployment of the airbag, the length between the distal ends along the half-folded non-breathable protective material is greater than or equal to the length between the distal ends along the pair of base fabric panels, thereby maintaining an airtight structure in the adhesive region. This is an explanatory diagram of a state in which a non-breathable film-like protective material that is folded in half is a laminated resin film of two or more layers including a first surface layer and a second surface layer, and the first surface layer is welded to the base fabric panel, but the second surface layers are not bonded to each other, thereby maintaining an airtight structure in the adhesive area. This is an explanatory diagram of a state in which the half-folded non-breathable film-like protective material is a laminated resin film of two or more layers including a first surface layer and a second surface layer, and the first surface layer is welded to the base fabric panel, while the second surface layers are bonded together.However, when a tensile force is applied to the pair of base fabric panels when the airbag is deployed, the second surface layer peels off, thereby maintaining an airtight structure in the adhesive area. 1 is an explanatory diagram showing the relationship between the resin constituting the first surface layer and the resin constituting the second surface layer of a laminated resin film which is a non-breathable film-like protective material folded in half. FIG. FIG. 2 is an explanatory diagram of an example of a method for producing a half-folded non-breathable film-like protective material (winding up a half-folded film). FIG. 13 is an explanatory diagram of a state in which a wound, half-folded non-breathable film-like protective material is supplied to a heat welding location. This is a diagram explaining the supply state of a half-folded, strip-shaped, non-breathable film-like protective material, which is made of a single-layer resin film with a release paper of a predetermined width sandwiched between the inner surfaces of a pair of base fabric panels, or a laminated resin film of two or more layers including a first surface layer and a second surface layer, is continuously sandwiched along the straight or curved outer peripheral edge of the pair of base fabric panels while applying tension to the material, and then heat or ultrasound is applied from the outside of the pair of base fabric panels to weld the surface of the single-layer resin film or the first surface layer to the inner surface of the base fabric panels. FIG. 1 is an explanatory diagram of a method for winding a multi-layer film in a two-ply state around a 3-inch paper tube by an inflation method using a multi-layer circular die. FIG. 2 is a schematic diagram of a jig (half-folding former) used to fold a film in half. 1 is an explanatory diagram of an example of an airbag (cushion) including an isolated sewn portion (in the center) of a closed space. 10 is an explanatory diagram of one method of adhering a folded film to an isolated sewn portion of a closed space. FIG. FIG. 15 is an explanatory diagram of the sealing state according to the method 1 shown in FIG. 14 . 13A and 13B are explanatory diagrams of another method for adhering a folded film to an isolated sewn portion of a closed space and a sealed state. FIG. 2 is an explanatory diagram of the layer structure of a folded film in terms of the melting point difference (left side) and the interlayer SP value difference (right side).

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
An embodiment of the present invention is a method for manufacturing an airbag having at least one pair of fabric panels sewn together at a periphery thereof, the method comprising the steps of:
a welding step of continuously sandwiching a semi-folded, band-shaped non-breathable film-like protective material, which is made of a monolayer resin film having a predetermined width with a release paper sandwiched therebetween or a laminated resin film having two or more layers including a first surface layer and a second surface layer, between the inner surfaces of the pair of base fabric panels while applying tension to the material along the linear or curved outer periphery of the pair of base fabric panels, and applying heat or ultrasonic waves from the outside of the pair of base fabric panels to weld a surface of the monolayer resin film or the first surface layer to the inner surface of the base fabric panel in an adhesive region of a predetermined width, wherein although the surfaces of the monolayer resin film on the release paper side are not welded to each other due to the presence of the release paper, or the second surface layers of the laminated resin film are not welded to each other by heat welding or ultrasonic welding, or are welded to each other by heat welding or ultrasonic welding, the second surface layer peels off when a tensile force is applied to the pair of base fabric panels when the airbag is deployed;
a sewing step of sewing the pair of fabric panels together adjacent the bonded areas before, after, or simultaneously with the bonding;
The manufacturing method includes the steps of:

[Base fabric panel (panel fabric, main panel)]
The pair of base fabric panels is not particularly limited and may be a plain weave fabric of polyamide or polyester that is normally used as a base fabric for airbags. The fineness of the fibers constituting the base fabric used in this embodiment is preferably 150 to 900 dtex. A fineness of 150 dtex or more can provide the strength required for an airbag, and a fineness of 900 dtex or less can provide a soft base fabric for an airbag.
It is preferable to use a multifilament as the fiber constituting the base fabric used in this embodiment, and the single yarn fineness of the fiber is preferably 0.1 to 10 dtex. When the fiber is in this range, it is flexible when used as a base fabric for an airbag and has a high deployment speed.
In addition, the weaving density of the base fabric used in this embodiment is preferably 30 to 90 threads/inch for both warp and weft, and the cover factor is preferably 1500 to 2500. Within this range, when used as a base fabric for an airbag, it is flexible and can obtain strength sufficient to withstand deployment. However, the cover factor is a value calculated by the following formula.
CF = (number of warp threads per 2.54 cm) × √ (total warp thread size (dtex)) + (number of weft threads per 2.54 cm) × √ (total weft thread size (dtex))

The base fabric panel may be coated with resin on one or both sides or laminated with a single or multi-layer film to reduce breathability. In this case, the resin used for the resin coating may be a silicone or polyurethane coating, or a method of thermal lamination using a flame-retardant thermoplastic resin film, etc. may be used.
When coating with a resin, the coating amount is preferably 5 to 50 g/m ^2. When laminating a film on a base fabric, the thickness of the film is preferably 0.001 mm or more and 0.5 mm or less. Within this range, a base fabric that is flexible and has excellent airtightness when used as a base fabric for an airbag can be obtained.

The airbag according to this embodiment can be one in which a pair of base fabric panels are sewn together at their outer periphery to form a bag, as shown in FIG. 1. In FIG. 1, reference numeral 2 indicates the sewn (stitched) portion of the main panel, and reference numeral 4' indicates the position of the inner edge (top of the loop) of a semi-folded non-breathable protective material, which is on the back side of the front base fabric panel and which will be described below. As shown in FIG. 1, an inner tube (reference numeral 23), which is usually made into a cylindrical shape from base panels of the same material, can be inserted into the opening, and when the airbag inflates and deploys, gas is instantly injected into the airbag from inside the inner tube.

[suture]
The stitching is not particularly limited as long as it is not broken when the airbag is inflated and deployed, but it is preferably machine-sewn with sewing thread made of multifilament fiber of the same material as the base fabric panel. As described above, in order to maintain the internal pressure, it is required that the stitching does not break when the airbag is deployed and that there is substantially no gas leakage.
The sewing thread may be a single twisted fiber or a multiple twisted fiber having two or more single twisted fibers twisted together, and the total fineness of the twisted fibers is preferably 700 to 2000 dtex.
The sewing method may be a lock stitch, a chain stitch, etc. The number of stitches (stitch pitch) is preferably 30 to 60 stitches/10 cm.

[Semi-folded non-breathable film-like protective material]
Fig. 2 is an enlarged view of the area corresponding to the A-A cross section in Fig. 1 to prevent gas leakage at the seams, and explains the state of an airbag when it is deployed if it is sewn to the area bonded with silicone adhesive in the conventional technology. When silicone adhesive is used, the silicone adhesive deforms and stretches during deployment to seal in the gas, improving the internal pressure retention, but the thickness of the silicone adhesive after curing increases the thickness of the airbag after folding (when stored), making it difficult to store, and it takes a long time, from half a day to about a day, to cure, reducing the productivity of the airbag.

According to the manufacturing method of this embodiment, instead of using such a silicone adhesive, an airbag can be manufactured with high productivity in which both end outer surfaces of a folded, band-like, non-breathable film-like protective material are bonded to the inner surface of each of a pair of base fabric panels in an adhesive region of a predetermined width along the seam from the vicinity of the seam toward the inside of the bag body, the outer surfaces being bonded in a straight or curved line, the non-breathable film-like protective material being a laminated resin film of two or more layers including a first surface layer and a second surface layer, the first surface layer being welded to the base fabric panel, and the second surface layers being not bonded to each other, or being bonded to each other but causing the second surface layer to peel off when a tensile force is applied to the pair of base fabric panels when the airbag is deployed.
When the airbag is deployed, when a tensile force is applied between a pair of base fabric panels, it is preferable that the length between the distal ends along the folded non-breathable film-like protective material is greater than or equal to the length between the distal ends along the pair of base fabric panels.

The manufacturing method of this embodiment can be used for the entire outer periphery of the airbag, or for a portion of the airbag. Here, a portion means, for example, 50% or more. When using this manufacturing method for a portion of the airbag, a manufacturing method using, for example, silicone adhesive for the stitching that may cause other gas leaks in the airbag can be selected in order to ensure airtightness for the entire airbag. Furthermore, this characteristic structure can be applied to the vicinity of the stitching of any two (a pair) of base fabric panels of an airbag composed of at least two or more base fabric panels. The pair of base fabric panels do not necessarily need to have the same shape, and as long as the airtightness of the adhesive area is not compromised, the pair of base fabric panels may be three-dimensionally sewn with different shapes of stitching lines.

In this specification, the term "an airbag formed by sewing at least one pair of fabric panels together at their outer periphery" refers to an airbag in which the fabric panels are sewn together to form an inflation chamber for the airbag, and in which two or more fabric panels are sewn together at the outer periphery of the chamber. Therefore, the airbag is not limited to an airbag composed of only two fabric panels, which are made by overlapping two fabric panels of the same shape, as shown in Figures 1 and 13, and there is no limit to the number of fabric panels that make up the airbag or the overall structure of the airbag, as long as there is a portion where two or more fabric panels are joined together at the outer periphery of the chamber. Here, there is at least one pair of fabric panels to be sewn together, that is, at least two, and these sewn fabric panels may be made of the same fabric or different fabrics. For example, this broadly includes a single, line-symmetrical base fabric panel that is folded along the line of symmetry and the overlapping portions sewn together, a single, strip-shaped base fabric panel that is rolled into a tube and the overlapping portions sewn together, and three or more base fabric panels that are sewn together, that is, as long as the partial structure has a non-breathable protective material covering the sewn portions of the base fabric panels.

In this specification, the term "non-breathable" refers to the surface property of a protective material that suppresses ventilation to a degree that does not significantly impair the airtightness of the airbag. When a differential pressure of 500 Pa is applied between the front and back of the protective material, the amount of gas passing through the surface is preferably 0.5 L/ ^dm2 /min or less, more preferably 0.1 L/ ^dm2 /min or less, and even more preferably 0.05 L/ ^dm2 /min or less.

Fig. 3 illustrates the state of the semi-folded non-breathable protective material when the airbag is deployed. As can be seen from Fig. 3, the semi-folded non-breathable protective material presents a loop shape toward the inside of the airbag and forms an airtight structure in the bonded area with the base fabric panel, thereby exhibiting internal pressure retention.
In the airbag that can be manufactured by the manufacturing method of this embodiment, the length between the distal ends along the folded non-breathable protective material is preferably greater than or equal to the length between the distal ends along a pair of base fabric panels when the airbag is deployed, thereby maintaining an airtight structure in the adhesive region. That is, as shown in Figures 4(a) and 4(b), since the loop-shaped protective material has a sufficient length, when the airbag is deployed and pulled horizontally from the seam, substantially no force is applied to the adhesive region between the protective material and the base fabric panel, and there is no peeling or destruction in the adhesive region, so that airtightness is maintained. Note that, when the non-breathable film-like protective material has high extensibility, even if the length of the loop of the protective material before the airbag is deployed (when the airbag is housed) is approximately the same as or shorter than the adhesive distance along the base fabric panels, the non-breathable protective material is stretched by the tensile force applied when the airbag is deployed, and if the seam is destroyed first, substantially no force is applied to the adhesive region, resulting in the same result.
The state of the airbag when it is deployed can be simulated by, for example, using the following method. First, the stored airbag is taken out, a part of the protective material and the base fabric panel are cut, and the pair of base fabric panels are spread 180° as shown in the deployed state in Figures 4(a) and (b). When each base fabric panel is grasped and pulled in a direction parallel to the base fabric panel, it is confirmed whether the seam is broken before the protective material. At this time, attention is paid to arranging the seam so that it is approximately perpendicular to the pulling direction. As described above, Figure 4(a) is the first pattern, and Figure 4(b) is the second pattern (loop outside, film folded back and stored). In either pattern, in the state when the airbag is deployed, the length between the distal ends along the half-folded non-breathable protective material is greater than or equal to the length between the distal ends along the pair of base fabric panels, thereby maintaining an airtight structure in the adhesive region.

In this specification, the term "half-folded non-breathable film-like protective material" includes not only a material that is half-folded when housed in an airbag, as shown in the upper part of Figures 4(a) and (b), i.e., a material made by folding a strip-shaped single-layer or multi-layer resin film or laminate base fabric in half, but also a material that is folded multiple times, such as into an accordion-like shape, or a material made by overlapping two strip-shaped (including curved) single-layer or multi-layer resin film or laminate base fabric and bonding one end with an adhesive or welding (i.e., a material made by laminating two sheets). However, from the viewpoint of improving productivity, it is preferable to manufacture protective materials by continuously supplying half-folded strip-shaped films, etc., and heat welding them, as shown in Figures 8 to 10 and 12, rather than by laminating two sheets.

Such a band-shaped, semi-folded, non-breathable film-like protective material is adhered to the base fabric in a straight or curved manner along the seams. In the manufacturing method of the present embodiment, two sheets of a band-shaped non-breathable film-like protective material are used, which are obtained by cutting a resin film into a desired shape, and the outer layers of one end (inner edge side) of the multilayer film are welded together (for example, in the case of a PE (second surface layer)-PA6/12 (first surface layer) multilayer film, a part of the second surface layer is peeled off and the first surface layers are welded together) along the inner edge so that the length from the outer edge is a predetermined length, for example, a width of 5 mm, or the sheets are bonded together with, for example, a cyanoacrylate-based instant adhesive (manufactured by Konishi Co., Ltd.) and thoroughly dried (that is, a method of bonding two protective materials cut into a base fabric panel shape (horseshoe shape) as shown in FIG. 1, rather than a band-shaped protective material), but it is preferable to manufacture the protective material by continuously supplying a band-shaped sheet of resin film folded in half and heat welding it while applying tension, as shown in FIGS. 8 to 10, rather than by manufacturing the protective material by a two-sheet bonding method. This is because, while the two-sheet lamination method requires cutting out the resin film along the sewing shape of the airbag, the use of a half-folded belt-shaped resin film can maximize the efficiency of film utilization, and can increase productivity because there is no need to bond the films together. In addition, since an actual airbag is deployed instantly from a folded state, a part of the airbag may be exposed to a very fast inflator gas flow rate at the initial stage of deployment, etc., but by using a single resin film, the adhesive margin between the resin films is not required, and it is possible to prevent the adhesive margin from being exposed to the gas flow rate and being destroyed. Furthermore, since it is not necessary to bond the resin films together, there is little change in thickness and hardness of the loop-shaped resin film between the distal ends along the half-folded belt-shaped resin film, and even if the airbag is exposed to a fast gas flow rate when it is deployed, stress concentration occurs at the part where the thickness and hardness change at the adhesive interface between the resin films, etc., and the loop-shaped structure is prevented from being destroyed. In addition, by using a single resin film, compared to the two-film lamination method, it is possible to prevent the film from becoming hard due to adhesion between the films, and by eliminating the need for adhesion between the films, it is possible to reduce the weight of the airbag and improve the storability of the airbag.

By using a resin film as the half-folded non-breathable protective material and using the manufacturing method described below of continuously supplying and heat welding while applying tension, even curved sections (including R sections and reverse R sections) can be welded without wrinkles, even if it is a single sheet of non-breathable protective material, making it possible to produce an airbag with excellent airtightness.

There are no particular limitations on the non-breathable film-like protective material, so long as it is not destroyed when the airbag is inflated and deployed, and single-layer or multi-layer resin films can be used. From the viewpoint of reducing the weight and compactness (ease of folding and storage) of the airbag, it is preferable to use single-layer or multi-layer resin films as the non-breathable protective material. When using single-layer or multi-layer resin films as the non-breathable film-like protective material, the adhesive strength can be increased by bonding the same type of single-layer or multi-layer resin film to a laminated base fabric panel, thereby improving the internal pressure retention of the airbag. Furthermore, by using the same type of single-layer or multi-layer resin film (and substrate) used in the non-breathable protective material and the base fabric panel, recyclability can be improved.

In this specification, the term "bonding" includes bonding with an adhesive and welding with ultrasonic waves or heat. As explained in the section on the manufacturing method of the airbag below, if the material of the base fabric panel and the material of the outer layer of the semi-folded non-breathable protective material are the same, the base fabric panel and the protective material can be bonded together by welding using heat or ultrasonic waves to form a bonded area that will not peel off even when the airbag is deployed and can maintain airtightness. Welding without using adhesives is preferable from the standpoint of thickness after folding, productivity, recycling, etc.

As shown in Figures 4(a) and (b), the term "bonded area (5, 5')" has a proximal end (6, 6') and a distal end (7, 7') with respect to the seam (2), respectively. As shown in Figure 4(a), the proximal end (6, 6') may be located on the inside of the airbag from the seam (2) or on the outside of the airbag. In the latter case, the bonded area will extend to the seam allowance.
Furthermore, as shown in Fig. 4(b), the loop structure of the non-breathable protective material folded in half in the adhesive region may be arranged so as to face the outer edge of the airbag (outside of the airbag). In the state when the airbag is deployed, the half-folded non-breathable protective material has a loop shape toward the inside of the airbag, and the length between the distal ends along the half-folded non-breathable protective material is greater than the length between the distal ends along a pair of base fabric panels, so that an airtight structure can be formed in the adhesive region with the base fabric panels as in the case of Fig. 4(a). However, when sewing the outer edge of the airbag after adhering the protective material, in order to prevent the part that contributes to maintaining the internal pressure of the protective material from being damaged by sewing, it is preferable to arrange the loop structure of the non-breathable protective material so as to face the inside of the airbag.
The "bonded region" need only be bonded in such a way that it will not be destroyed or peeled off when the airbag inflates and deploys, and that it maintains airtightness and internal pressure retention.

In the airbag that can be manufactured by the manufacturing method of this embodiment, the thickness of the non-breathable film-like protective material is preferably 0.001 mm or more and 0.5 mm or less, and more preferably 0.001 mm or more and 0.1 mm or less, from the viewpoint of the folded thickness.

In the airbag that can be manufactured by the manufacturing method of this embodiment, the adhesive strength (peel strength) in the adhesive region between the base fabric panel and the non-breathable film-like protective material is preferably 1 N/cm or more, and more preferably 3 N/cm or more, from the viewpoint of airtightness. If the adhesive strength is 3 N/cm or more, the occurrence of leaks caused by the film peeling off from the panel base fabric due to the wind pressure of the gas when the airbag is deployed is significantly reduced.

The tensile modulus of the semi-folded band-shaped non-breathable protective material is preferably 100 to 800 MPa in both MD (machine direction) and TD (transverse direction), more preferably 150 to 600 MPa, and even more preferably 200 to 500 MPa. However, the tensile modulus of the film referred to here is the measurement result when the band-shaped non-breathable film-like protective material is opened from the half-folded state and pulled. When the band-shaped non-breathable film-like protective material is deformed to follow the curved outer edge by applying tension, the above tensile modulus (flexibility) makes it easy to form a curved structure to follow the curved parts (including R parts and reverse R parts) that are usually used in the main fabric of an airbag. By setting the tensile modulus to 100 to 800 MPa, the film has good handleability (balance between ease of deformation at curved parts and handling of the film) due to moderate flexibility. In addition, in terms of the durability required for the film, the tensile breaking strength of the film is preferably 10 to 100 MPa in both MD and TD from the viewpoint of durability, more preferably 15 to 80 MPa, and even more preferably 20 to 60 MPa. By setting the tensile breaking strength to 100 MPa or less, the rigidity is suppressed and the film has good handling properties. Furthermore, when the band-shaped non-permeable and breathable film-like protective material is deformed to follow the curved outer peripheral edge by applying tension, it is preferable to use a thermoplastic resin film, since the film can be easily stretched by applying heat.

The airbag of this embodiment may have, in the adhesive region, an R portion with a curvature radius of 300 mm or less and/or an inverse R portion with a curvature radius of 300 mm or less, as shown in FIG. 1 and FIG.
Here, the R portion is a portion of the seam line along the outer periphery of the base fabric panel that is curved convexly toward the side other than the inflatable portion (chamber) of the airbag. For example, the X portion in FIG. 1 corresponds to this. On the other hand, the reverse R portion is a portion of the seam line along the outer periphery of the base fabric panel that is curved convexly toward the inflatable portion (chamber) of the airbag. For example, the Y portion in FIG. 1 corresponds to this. In curved seams including such R portions and reverse R portions, wrinkles are more likely to occur when the non-breathable protective material is adhered along the seam line than in straight seams, and tension is more likely to be applied to the sewn portion when the airbag is deployed. The degree of wrinkles when the non-breathable protective material is adhered can be confirmed by measuring the step (peak-valley difference) between the wrinkled portion and the normal portion. The step (peak-valley difference) between the wrinkled portion and the normal portion of such R portion is preferably 400 μm or less, more preferably 300 μm or less, even more preferably 200 μm or less, and even more preferably 100 μm or less. By making the surface step (peak-to-valley difference) of the R portion 400 μm or less, the step between the wrinkled portion and the normal portion can be made small, thereby preventing stress concentration, suppressing gas leakage from the adhesive portion, and resulting in an airbag with excellent storage properties.
In addition, the ratio (R portion/straight portion) of the step (peak-valley difference) between the wrinkled portion and the normal portion of the R portion to the step (peak-valley difference) between the wrinkled portion and the normal portion of the approximately straight portion excluding the R portion is preferably 0.6 to 2.0, and more preferably 0.8 to 1.5.

The wrinkle step measurement was performed using a surface roughness measuring instrument (SURFTEST EXTREME SV-3000CNC) manufactured by Mitutoyo Corporation, and the wrinkled area and the surrounding normal area were measured in three-dimensional mode under the following measurement conditions. An arbitrary cross-section extraction function was used in the obtained three-dimensional image to extract a cross-section that included the largest step area, and a baseline was drawn on the extracted cross-section (two-dimensional) connecting the start point and end point of the wrinkled area (step), and the maximum height from the baseline was determined.
(Surface roughness measurement conditions)
Measurement length: 10 mm
Measurement width: 5 mm
Measurement speed: 5 mm/sec
Sampling pitch: 1 μm
Sampling interval: 50 μm
Stylus: radius = 10 μm (Code No. 12AAB415)
(Image processing)
-Trend correction is only performed on the "plane"

As shown in Figures 5 to 7, when a single-layer resin film is used as the protective material during thermal welding by heating the base fabric panel and the protective material, if a release paper is inserted inside the loop, it becomes possible to bond the protective material with a loop length sufficient to maintain airtightness in the bonding area. There are no particular limitations on the material of the release paper, and paper, cloth, film, etc. can be used as long as it can prevent the bonding of the single-layer resin film to each other.
In comparison with the above configuration, a multilayer resin film is used as the half-folded belt-shaped protective material, and a release paper is not used, and the second surface layers on the inside of the loop are not bonded to each other or are welded by heat welding or ultrasonic welding, but when a tensile force is applied to the pair of base fabric panels when the airbag is deployed, the second surface layers are peeled off, which improves the productivity of the airbag in that the process of inserting and/or removing the release paper is not required, the consideration of the material and physical properties of the release paper and its handling are not required, and the tension can be easily adjusted. Furthermore, with this configuration, even if it is difficult to remove the release paper from the sewn airbag in a curved or circular shape due to the sewing shape of the airbag, the release paper does not remain in the airbag, so that the weight of the airbag does not increase and the storability does not deteriorate, and the release paper can be prevented from affecting the deployment speed and deployment behavior of the airbag.

Such a configuration can be achieved, for example, by setting the melting point of the resin constituting the first surface layer of the laminated resin film, which is a non-breathable film-like protective material folded in half, to be 50°C to 160°C, and preferably 60°C to 160°C, lower than the melting point of the resin constituting the second surface layer, so that the second surface layers on the inside of the loop are not welded to each other, or by setting the difference in SP value of the resin constituting the first surface layer, the resin constituting the second surface layer, and the resin constituting the other layer of the laminated resin film, which is a non-breathable film-like protective material folded in half, to be 2.0 [cal/ ^cm3 ) ^1/2 ] or more between adjacent layers, so that delamination occurs between any of the layers, or the second surface layer delaminates from an adjacent layer.

That is, in a multilayer film including a first surface layer and a second surface layer of the laminated resin film which is the half-folded non-breathable film-like protective material, the difference in SP value between any adjacent layers is preferably 2.0 [cal/ ^cm3 ) ^1/2 ] or more, more preferably 2.5 [cal/ ^cm3 ) ^1/2 ] or more, even more preferably 3.0 [cal/ ^cm3 ) ^1/2 ] or more, and even more preferably 4.0 [cal/ ^cm3 ) ^1/2 ] or more.

Hereinafter, such a configuration will be described with reference to FIG.
For example, the melting point of PA6/12 is 128°C, that of TPEE is 216°C, that of PA6/66 is 194°C, that of PA12 elastomer is 176°C, that of PO (acid-modified polyethylene) is 120°C, and that of PE (LDPE) is 110°C. Therefore, by using a TPEE (second surface layer)-PA6/12 (first surface layer) multilayer film, a TPEE-PO-PA6/12 multilayer film, or a PA6/66-PO-PA6/12 multilayer film as the protective material, the difference in melting point between the resin constituting the first surface layer and the resin constituting the second surface layer can be made 50°C or more.
Here, the preferred range of the melting point difference is 50°C to 160°C, more preferably 60°C to 160°C, and even more preferably 80°C to 160°C. By making the melting point difference 50°C or more, the adhesive strength with the base fabric panel can be increased and the range of adhesion temperatures at which fusion between the second surfaces can be made difficult to occur can be widened, improving production stability. In addition, by making the melting point difference 160°C or less, for example, when producing a film by inflation molding, flow unevenness and melt tension are appropriately maintained, improving film formation stability.
The melting point of the resin constituting the protective material is preferably 90° C. or higher, more preferably 100° C. or higher, and even more preferably 110° C. or higher. By making the melting point 90° C. or higher, sufficient adhesive strength can be maintained even when the temperature inside the vehicle becomes high.

For example, the SP value of PE is 8.1 [cal/cm ³ ) ^1/2 ], the SP value of PA6/66 is 13.6 [cal/cm ³ ) ^1/2 ], the SP value of PA6/12 is 13.6 [cal/cm ³ ) ^1/2 ] and the SP value of PET is 10.7 [cal/cm ³ ) ^1/2 ], so if PE (second surface layer)-PA6/66 (release layer side of the first surface layer, which is a multilayer film) or PE (second surface layer, release layer)-PET (first surface layer) is used as the protective material, the difference in SP value with the PA base fabric or PET base fabric, respectively, can be made 2.0 [cal/cm ³ ) ^1/2 ] or more.

For example, in the case of the diagram on the right side of Fig. 17 (SP value difference), the first surface layer (fabric panel side) can be considered to be composed of an adhesive layer (PA6/12), while the second surface layer (inside the loop) can be considered to be composed of four layers including a release layer (PE), an intermediate layer (acid-modified PE), and a high melting point layer (PA6/66). It should be noted that the release effect can be achieved not only when the SP value difference between the high melting point layer (PA6/66) and the release layer (PE) is greater than or equal to 2.0 [cal/cm3)1/2], but also when the SP value difference between any of the adjacent layers constituting the first surface layer, the adhesive layer (PA6/12), the X layer (e.g., the intermediate layer (acid-modified PE)), and the high melting point layer (PA6/66), is greater than or equal to 2.0 [cal/ ^cm3 ) ^1/2 .

The above-mentioned configuration based on the SP value difference is preferable to the above-mentioned configuration based on the melting point difference. The reason for this is that the fusion (processing) temperature can be raised above the melting point of the film, making it possible to strengthen the adhesion between the base fabric panel and the film, and by increasing the processing speed, productivity can be improved.

The SP value (Hildebrand solubility parameter) is a physical property defined as the square root of the cohesive energy density, and indicates the solubility behavior of a solvent. Therefore, the inventors of this application used combinations with large differences in SP value as indicators for selecting the release layer. The SP values of various resins are listed, for example, in "Guide to Various Standards and Usage: Plastic Material Test Methods, Comparisons, Evaluations, and Results" p. 32 (2nd edition, May 10, 2011) by Sangyo Gijutsu Center Co., Ltd., and a reference for calculating the SP value is "Practical Polymers for Engineers" by Kodansha, August 1, 1989.

In addition to the SP value, the Hansen solubility parameter (HSP) is also a commonly used parameter. The HSP value is also shown in the examples, but the peeling effect can be achieved by making the HSP value difference 1.0 (cal/ ^cm3 ) ^1/2 or more.
Here, HSP is a predicted value by Winmostar (V9.3.0) manufactured by CrossAbility Co., Ltd., and is calculated by the dispersion term (δD), polarization term (δP), and hydrogen bond term (δH) between certain substances. In addition, the HSP calculation for the copolymer composition is a value obtained by calculating the HSP of each homopolymer and multiplying it by the composition ratio (volume ratio) to obtain a total value.

In addition, in order to avoid tacking in a high-temperature environment and ensure internal pressure retention after aging, the glass transition temperature (Tg) of the second surface layer (inside of the loop) is preferably 0°C or higher, more preferably 20°C or higher, and even more preferably 30°C or higher. On the other hand, in terms of flexibility, the upper limit of the glass transition temperature is 80°C or lower, more preferably 70°C or lower, and even more preferably 60°C or lower.

By using the above-described manufacturing method, in an airbag in which a pair of base fabric panels are sewn together at their outer periphery to form a bag body,
An airbag can be provided with high productivity in which both end outer surfaces of a folded, band-like, non-breathable film-like protective material are bonded to the inner surface of each of the pair of base fabric panels in an adhesive region of a predetermined width along the seam from near the seam toward the inside of the bag body, the outer surfaces being bonded in a straight or curved line, the folded, non-breathable film-like protective material being a laminated resin film of two or more layers including a first surface layer and a second surface layer, the first surface layer being welded to the base fabric panel, and the second surface layers being not bonded to each other, or being bonded to each other but causing the second surface layer to peel off when a tensile force is applied to the pair of base fabric panels when the airbag is deployed.

In the manufacturing method of this embodiment, for the ease of welding the film into a curved shape (R processability), the tensile modulus of the film is preferably 100 to 800 MPa in both MD (machine direction) and TD (transverse direction), more preferably 150 to 600 MPa, and even more preferably 200 to 500 MPa. However, the tensile modulus of the film referred to here is the measurement result when the band-shaped non-air-permeable and breathable film-like protective material is opened from a half-folded state and pulled. When the band-shaped non-air-permeable and breathable film-like protective material is deformed to fit the curved outer edge by applying tension, the above tensile modulus (flexibility) makes it easy to form a curved structure that fits the curved part that is usually used in the main fabric of an airbag. By setting the tensile modulus to 100 to 800 MPa, the film has a moderate flexibility and good handleability (balance between ease of deformation at curved parts and handling of the film). In addition, in terms of the durability required for the film, the tensile breaking strength of the film is preferably 10 to 100 MPa in both MD and TD from the viewpoint of durability, more preferably 15 to 80 MPa, and even more preferably 20 to 60 MPa. By setting the tensile breaking strength to 100 MPa or less, the rigidity is suppressed and the film has good handling properties. Furthermore, when the band-shaped non-permeable and breathable film-like protective material is deformed to follow the curved outer peripheral edge by applying tension, it is preferable to use a thermoplastic resin film, since the film can be easily stretched by applying heat.

In the manufacturing method of this embodiment, methods for sandwiching a strip-shaped non-breathable film-like protective material along the straight or curved outer peripheral edges of a pair of base fabric panels include a method of preparing a roll of half-folded film in advance and feeding the strip-shaped non-breathable film-like protective material from the wound roll to the welding point by heat welding or ultrasonic welding, as exemplified in Figures 8 to 10, a method of preparing a roll of the half-folded strip-shaped non-breathable film-like protective material in an unfolded state and feeding the strip-shaped non-breathable film-like protective material from the wound roll to the welding point by heat welding or ultrasonic welding, folding it in half during the process of feeding it to the welding point by heat welding or ultrasonic welding, and then feeding it to the welding point, and a method of folding in half a strip-shaped non-breathable film-like protective material that has been cut in advance to the length of the straight or curved outer peripheral edges of a pair of base fabric panels, and feeding it to the welding point by heat welding or ultrasonic welding, with the first method being preferred. By winding the film that has already been folded in half onto a roll, the pleats in the folded portion can be firmly fixed, and by continuously feeding the film from the wound roll, the folded portion of the film is less likely to shift, and warping (curling) of the folded film is suppressed (as the film structure is symmetrical between the top and bottom), which is expected to have the further effect of suppressing the occurrence of wrinkles (improving quality).

In this manufacturing method, the method of applying tension to the half-folded film (tape) is not particularly limited, but for example, as shown in Figure 17, a method can be used in which the tape is held down with one hand and the base fabric with the other while the tape is pulled while adjusting the tension applied to it so that it conforms to the shape of the outer periphery of the airbag. Alternatively, a roll of half-folded film may be prepared in advance, and a tension control mechanism may be provided during the process of sending the band-shaped non-breathable film-like protective material from the roll to the welding location by heat welding or ultrasonic welding.

Also, for example, as shown in Fig. 10, the base fabric is sandwiched between upper and lower conveyor belts at the welding location, and while the base fabric is transported by the conveyor belt, it is sandwiched between upper and lower hot plates and heat is applied, so that continuous welding can be performed. In the vicinity of the welding location, the tape (sandwiched between the base fabrics) is in a heated state, and the tape is stretched to fit the shape of the outer periphery of the airbag by applying tension, so that the non-air-permeable and breathable film-like protective material can be bonded without wrinkles even in curved parts including R parts and reverse R parts. Furthermore, before welding by heat welding or ultrasonic welding, a part or the whole of the non-air-permeable and breathable film-like protective material can be preheated by a method such as a hot plate or hot air, so that the tape can be easily stretched to fit the shape of the outer periphery of the airbag.
As shown in Fig. 10, a cooling section using a cooling plate may be provided immediately after welding. By providing a cooling section, the adhesiveness of the non-permeable, breathable film-like protective material is improved. In addition, by intermittently applying and releasing the pressure of the hot plate and the cooling plate, the welding workability of the curved section can be improved.

However, the method of continuously sandwiching the half-folded film (tape) along the straight or curved outer periphery of the pair of base fabric panels while applying tension to the film and applying heat or ultrasonic waves from the outside of the pair of base fabric panels to bond the panels together may lead to misalignment of the base fabrics, as the upper and lower base fabrics are bonded together continuously and simultaneously. Also, in the final stages of bonding or depending on the sewing shape of the airbag, there may be a small space, which may make it difficult to insert the tape under the upper base fabric.

Instead of the tensioning and clamping method described above, the following two-step method may be used, in which, rather than clamping the tape between a pair of base fabric panels, one side of the tape is adhered to the first piece of base fabric (1st step), and then a second piece of base fabric is placed on top of the tape and compressed (2nd step).

[2-Step Method]
a welding step of applying heat or ultrasonic waves to a semi-folded band-shaped non-breathable film-like protective material of a predetermined width, which is made of a laminated resin film of two or more layers including a first surface layer and a second surface layer, on one of the base fabric panels, continuously along a straight or curved outer periphery of the one of the base fabric panels from below the one of the base fabric panels while applying tension to the material, thereby welding the first surface layer to an upper surface of the one of the base fabric panels;
a welding step of overlapping another base fabric panel on the welded film-like protective material and applying heat or ultrasonic waves from the upper side of the overlapped base fabric panel to weld the first surface layer to the lower surface of the overlapped base fabric panel, wherein the second surface layers of the laminated resin film are not welded to each other by thermal welding or ultrasonic welding, or are welded to each other by thermal welding or ultrasonic welding, but the second surface layer peels off when a tensile force is applied to the base fabric panels when the airbag is deployed;
a sewing step of sewing the fabric panels together adjacent the areas of the resulting welds after said bonding;
The manufacturing method comprising the steps of:

In the 2-step method, instead of sandwiching the tape between a pair of base fabric panels, first the tape is fed onto one base fabric panel while applying tension, and then the tape is welded onto the first base fabric by heating from below, fixing the tape onto the one base fabric panel without wrinkles (1st step). A second base fabric is then placed on top of the tape, and pressure is applied by heating using thermal welding or ultrasonic welding (2nd step). This eliminates the need to simultaneously operate the upper and lower base fabrics as described above, and only one base fabric is operated, and because the tape is not sandwiched between the base fabrics, there is no problem with the space becoming narrow at the final stage of bonding, etc.

In this manufacturing method, the method of applying tension to the tape is not particularly limited, and a method of pulling the tape while adjusting the tension applied to it so that it conforms to the shape of the outer periphery of the airbag can be used, similar to the above-mentioned tension application and clamping method, while holding the tape with one hand and the base fabric with the other hand. Alternatively, a roll of half-folded film may be prepared in advance, and a tension control mechanism may be provided in the process of sending the band-shaped non-breathable film-like protective material from the roll to the welding point by thermal welding or ultrasonic welding. In this manufacturing method, since the tape is not sandwiched between the base fabrics, there is an advantage that the operation of continuously welding the tape while automatically inserting it into the hot plate part of the welding machine (belt heat pressing machine) is easy to perform. By automatically inserting the tape into the heating part, the occurrence of processing defects due to the positional deviation of the tape caused by manual work is reduced. In addition, when the tape is automatically inserted into the belt heat pressing machine, tension can be indirectly applied to the tape by changing the direction when feeding the base fabric side, and the tape can be stretched near the welding point so as to conform to the shape of the outer periphery of the airbag. In this manufacturing method, like the tension application and clamping methods described above, it is possible to preheat part or all of the tape, provide a cooling section, and apply/release the pressure of the hot plate and cooling plate intermittently. When preheating the tape, for example, the tape can be welded onto the first base fabric by a hot plate from below the belt heat pressing machine, while the tape is heated by the upper hot plate to assist in stretching the tape in the R and reverse R sections.

In this manufacturing method, the method for placing a second base fabric on the tape and heating it by thermal welding or ultrasonic welding is not particularly limited, and it may be continuously welded using a belt heat pressing machine as in the first step, or it may be welded all at once using a heat press machine that can heat the welded parts simultaneously, but from the viewpoint of productivity, it is preferable to use a heat press machine that can heat the welded parts simultaneously. In this manufacturing method, since the welded parts are heated twice, the first step is expected to have the secondary effect of improving the processing speed by temporarily fixing the parts.

[Method of manufacturing an airbag including an isolated sewn portion in a closed space]
In order to ensure the internal pressure of the airbag by applying tension and sandwiching in an isolated sewn area in a closed space as shown in Fig. 13, it is necessary to fabricate the film so that the ends (both the start and end) of the folded strip of film are not open. For this purpose, the following two methods can be adopted.
One method is to cut a strip of film folded in half to a certain length with a margin, and seal both ends in advance (a) (for example, after peeling off the LDPE film of the inner layer, heat-pressure bonding is performed for a sufficient time). Then, one end is left and sandwiched between the base fabric to start adhesion (thermal welding) (b), and finally the other end is overlapped and both ends are adhered to each other (c), and then sewn (d). The sealed state after sewing is shown in Fig. 14.
In the second method, as shown in Fig. 15, instead of sealing both ends of the folded strip film in advance, one end is sandwiched between the base fabric and straddles the dotted line to the right of the sewn part (see the leftmost drawing in Fig. 15), and adhesion (thermal welding) is started, and finally the other end is overlapped, also straddles the dotted line to the right of the sewn part, and both ends are adhered to each other, and then sewn. As shown in the rightmost drawing in Fig. 15, it can be seen that the airbag is sealed by the adhesive area in both A-A'section and C-C'section.
As shown in Fig. 15 and Fig. 16, the half-folded band-shaped non-breathable protective material is adhered to the inner surface of each of the pair of base fabric panels in an overlapping manner, and the end of the non-breathable protective material may be sealed. Here, the non-breathable protective material is "adhered to the overlapping manner" means that a plurality of the non-breathable protective materials are arranged in an overlapping manner, the non-breathable protective materials are adhered to each other, and the non-breathable protective material closest to the base fabric panel is adhered to the inner surface of each of the pair of base fabric panels. For example, as shown in Fig. 15 and Fig. 16, the non-breathable protective materials may be overlapped at the same sewing portion and adhered to each other, or in a sewing shape having a branch point, a half-folded band-shaped non-breathable protective material arranged near one sewing line and a half-folded band-shaped non-breathable protective material arranged near the other sewing line may be partially overlapped and adhered near the sewing branch point. In either case, the multiple non-breathable protective materials are united to form a loop-shaped structure bonded to the inner surface of each of the base fabric panels, and when a tensile force is applied between the pair of base fabric panels, a state can be formed in which the length between the distal ends along the folded non-breathable protective materials is greater than or equal to the length between the distal ends along the pair of base fabric panels.
The term "sealed end portions" of the non-breathable protective material refers to a state in which the end portions of the plurality of non-breathable protective materials are not open to the inflatable portion (chamber) of the airbag. The method for sealing the end portions of the non-breathable protective materials is not particularly limited, and may be adhesion with an adhesive, heat welding, ultrasonic welding, or folding the non-breathable protective material. Also, as shown in FIG. 16, a structure in which the end portions are exposed to the outside of the inflatable portion (chamber) may be used.
This manufacturing method can be used as a method for intentionally providing a joint portion of a band-shaped non-breathable protective material folded in half when welding a band-shaped non-breathable protective material folded in half near a sewing shape having a branch point or a bent sewing shape, when the airbag size is large and the process is divided from the viewpoint of workability, etc. Moreover, regardless of the tension application or clamping method, it can be widely applied to the 2-step method, the two-sheet bonding method, etc.

The present invention will be specifically described below with reference to examples and comparative examples.
First, the materials used in the examples and comparative examples, and the methods for measuring the physical properties will be described.

[(Si) coated (base) fabric]
The Si-coated fabric used as the base fabric panel and/or protective material was a plain weave fabric woven using nylon 66 multifilament fibers as the warp and weft, with one side coated with silicone resin. The total fineness of the weaving yarn constituting the base fabric was 470 dtex, the number of filaments was 136, the weaving density of the coated fabric was 49/inch (2.54 cm), and the amount of silicone resin coated was 25 g/ ^m2 .

(Film Preparation Method)
A film to be used as a protective material was prepared as follows.
As shown in Fig. 11, a multilayer circular die was used to wind a desired multilayer film in a two-ply state around a 3-inch paper tube by the inflation method. At this time, the film was formed so that the inner surface side 3b of the tubular film was the adhesive layer and the outer surface side 3a was the outer layer. The film formation conditions were as follows.
Die temperature setting: 210°C
Circular die: Lip outer diameter = 95 mm, lip clearance = 3 mm
Blow-up ratio: 1.1 times Air ring temperature: 22℃
Film surface temperature just before pinch rolling: 32°C
Distance between circular die and pinch roll: 2.4 m
Take-off speed: 12 m/min

(Film raw material)
(Resin A)
PE: LDPE (manufactured by Asahi Kasei): Trade name "Suntech LD F1920" (MFR = 2.0, Tm = 110°C, SP value = 8.1 (cal/ ^cm3 ) ^1/2 , HSP value = 18.0 (cal/ ^cm3 ) ^1/2 )
(Resin B)
PA6/12: Product name "Ube Nylon 7128B" (manufactured by Ube Industries) mid 6/12 copolymer (Tg = 47°C, Tm = 128°C, SP value = 13.6 (cal/ ^cm3 ) ^1/2 , HSP value = 20.7 (cal/ ^cm3 ) ^1/2 )
(Resin C)
PA6/66: Product name "Ube Nylon NAV503X10" (manufactured by Ube Industries, Ltd.) Polyamide 6/66 copolymer (Tg = 43°C, Tm = 194°C, SP value = 13.6 (cal/ ^cm3 ) ^1/2 , HSP value = 22.8 (cal/ ^cm3 ) ^1/2 )
(Resin D)
m-PE: Product name "Admer NF528" (manufactured by Mitsui Chemicals) acid-modified polyethylene (Tm = 120°C)
(Resin E)
PO elastomer: Product name "Engage EG8100" (Dow Chemical, Japan) (Tm = 60°C, melt index = 1.0g/10min (190°C/2.16kg)

The film configurations used in Examples 1 to 8 are shown in Table 1 below.

(Film Tensile Elongation at Break)
The tensile elongation at break of the film was measured in accordance with ASTM D-882. The measurement was performed in an atmosphere of 23°C and 50% RH. The tensile elongation at break in the MD and TD directions was measured using an autograph AG-IS (manufactured by Shimadzu Corporation). The width of the sample film was 10 mm, the chuck distance was 50 mm, and the tensile speed was 50 mm/min (strain rate = 100%/min). The tensile elongation at break of a sample cut into a length of 150 mm and a width of 10 mm in the MD or TD direction was measured. However, the tensile elongation at break of the film is the measurement result when a band-shaped non-permeable and breathable film-like protective material is opened from a half-folded state and pulled. If the length of the measurement sample is short and the chuck distance cannot be satisfied, the chuck distance may be narrowed. In this case, a tensile speed at which the strain rate is 100%/min is selected.

(Film Melting Point (Tm))
A film prepared by the inflation method according to the above-mentioned "Film Preparation Method" was measured in accordance with JIS K 7121.

(Glass Transition Temperature (Tg) of Second Surface Layer of Film)
A film prepared by the inflation method according to the above-mentioned "Film Preparation Method" was measured in accordance with JIS K 7244-2.
・Normal force: -0.3N
Swing angle: 0.1%
Frequency: 1Hz
Heating rate: 1.5°C/min

The obtained film was cut along the MD direction to make a strip film 40 mm wide, and wound into a roll.

[Sewing thread]
Airbag sewing thread manufactured by Gunze Ltd. (total fineness 1880 dtex, nylon 66 multifilament fiber 940 dtex two-ply twist) was used for the upper and lower threads.

[sewing machine]
Each part of the airbag was sewn using LU-2210W-7 manufactured by JUKI Corporation.

[Heat welding]
The protective material and the main panel were welded using a continuous feed type small hot plate device LHP-PP1 (welding machine (belt heat pressing machine)) manufactured by Quinlite Electronics Co., Ltd. The upper heater temperature was 230°C, the lower heater temperature was 190°C, and the feed speed was 0.3 m/min, and the main panel was sandwiched from above and below. As shown in FIG. 10, by using such a device, efficient heat conduction is possible through the upper and lower (heating) plates and cooling plates, and by temperature control, it is possible to form a bonded part of sufficient strength while applying heat to the bonded part while avoiding melting damage to the panel base fabric.

[Heat welding (2 steps)]
First, the upper heater temperature of the belt thermocompression machine was set to 100°C, the lower heater temperature to 230°C, and the feed speed was set to 1.0 m/min, and the entire film was heated to 100°C on one main panel using a Ryobi hot air gun (HAG-1551), and the tape was fed out while applying tension, and the tape was welded onto the first base fabric by heating from below (step 1). After that, a second base fabric was placed on top of the tape, and the tape was pressed for 3 seconds at a pressure temperature of 190°C using a hot plate jig having a shape that matches the bonded portion in step 1 (step 2).

[Half-fold former (tape bending jig)]
The tape was folded in half immediately before welding using the tape bending jig shown in Fig. 12. The ends of the film folded in half through the half-folding former may shift, so the shifted ends had to be aligned by hand after the film left the half-folding former.

[Preparation of a belt-shaped folded film (heat tension method)]
In Examples 1 to 8, the above-mentioned strip-shaped film having a width of 40 mm was folded into a film having a width of 20 mm using the folding device shown in FIG. 8, and then wound into a roll.

[Preparation of a belt-shaped folded film (room temperature fixing method)]
In Comparative Example 1, the coated fabric or laminate base fabric previously folded in half was wound into a roll, and a length equal to the sewing length of the outer edge of the airbag was cut and used.

[Making the main (base fabric) panel]
Two pieces of base fabric cut into the shape shown in Fig. 1 were stacked together to form the bag-shaped inflatable portion (main panel) of the airbag, with the uncoated surfaces facing each other. After inserting and welding the protective material described below, the outer periphery was sewn with the sewing machine using the sewing thread described above at a stitch count of 50 stitches/10 cm with a seam allowance of 10 mm. Three backstitches were used at the beginning and end of the stitching.

[Preparation of inner tube]
To form an inner tube to be inserted inside the air inlet of an airbag, two pieces of the Si-coated fabric cut into the shape shown in Fig. 1 were used, overlapped with the coated surfaces facing each other, and both ends were sewn together with the sewing machine using the sewing thread at a stitch count of 50 stitches/10 cm with a seam allowance of 10 mm. Note that three backstitches were used at the beginning and end of the stitching.

(1) Internal pressure retention rate after 6 seconds (%)
An inner tube was inserted through the mounting opening of the main panel sewn to each of the specifications described below, and the relative positions of the main panel and the inner tube were adjusted to prepare an airbag for evaluation. The airbag was filled with room temperature helium in a 0.22 liter tank so that the internal pressure was 8800 kPa, and the tank was connected to the tip of the tank via a metal pipe (inner diameter 21.3 mm). An electromagnetic valve attached near the tip of the tank was instantly opened and closed, and then the change in the internal pressure of the airbag over time was examined using a pressure sensor (PGMC-A-1 MPa, manufactured by Kyowa Electric Industry Co., Ltd.) attached near the connection between the pipe and the airbag.
The internal pressure of the airbag 6 seconds after the solenoid valve was opened was divided by the maximum internal pressure of the airbag after the solenoid valve was opened, and the value was recorded. The test was performed once for each of the three airbags, and the average of the three measurements was calculated as the internal pressure retention rate after 6 seconds, expressed as a percentage.

(2) Thickness after folding (mm)
The straight stitched portion (part B in FIG. 1) of the main panel sewn according to each specification described below was cut to obtain a 60 mm x 30 mm sample piece for thickness evaluation. The cut sample piece was folded in half perpendicular to the straight stitching to produce a folded sample of 30 mm x 30 mm. Using a digital caliper (ABS Digimatic Caliper CD-20APX) manufactured by Mitutoyo Corporation, the measurement part of the caliper was used to pinch the stitched portion 10 mm from the fold and press it with a force of 300 gf, and the value was recorded. The test was performed once for each of the three airbags, and the average value of the three measurements was taken as the thickness after folding.

(3) Elastic modulus of film in MD and TD directions (MPa)
The tensile modulus of the film was measured using an autograph AG-IS (manufactured by Shimadzu Corporation) in an atmosphere of 23°C and 50% RH. In accordance with the method described in ASTM-D-882, a sample cut from the film in the MD or TD direction was displaced from 0.05% to 0.25% under the conditions of a tensile speed of 5 mm/min (strain speed = 5%/min) and a chuck distance of 100 mm, and the tensile modulus was calculated from the stress when the sample was displaced from 0.05% to 0.25%. However, the tensile modulus of the film referred to here was the measurement result when a strip-shaped non-permeable and breathable film-like protective material was opened from a half-folded state and pulled. In addition, if the length of the measurement sample is short and the chuck distance cannot be satisfied, the chuck distance may be narrowed. In this case, a tensile speed at which the strain rate is 5%/min is selected.

(4) Evaluation of handling during R section processing When manufacturing airbags with each of the specifications described below, in the film welding process, workers performing the bonding work were asked to evaluate the ease of deformation at curved sections and handling of the film (whether the film shifts or curls, and whether the film is soft and difficult to hold) on a four-point scale (A: very easy to work with, B: easy to work with, C: somewhat difficult to work with, D: difficult to work with, E: not possible to work with). A total of five workers were asked to evaluate, and the most common answer was taken as the evaluation result for handling during R section processing.

(5) Manufacturing time per bag The time required from the process of cutting sample pieces from the sample fabric to the production of three bags sewn according to each specification described below was divided by 3 to obtain the manufacturing time per bag, which was expressed as an index with Example 1 set as the standard of 100. However, the process of producing the protective material was carried out and prepared in advance.

[Examples 1 to 8, Comparative Example 1]
In Examples 1, 2, 4, 7, and 8 and Comparative Example 1, the protective material used had a layer structure of "adhesive layer/intermediate layer/resin layer 1/resin layer 2", and was a multilayer film made of PA6/12 for the adhesive layer, POm-PE for the intermediate layer, PA6/66 polymer for resin layer 1, and PE (LDPE) for resin layer 2, which were extruded from a multilayer circular die and made into a 30 μm-thick four-type four-layer film by the inflation method. By changing the layer ratio of each resin layer, films with different film elastic moduli in the MD and TD directions were obtained.
In Example 3, the layer structure of the protective material used was a multilayer film consisting of "adhesive layer/resin layer 1/intermediate layer/resin layer 1/resin layer 2/resin layer 3", in which PA6/12 was used for the adhesive layer, PO for resin layer 1, PO elastomer for the intermediate layer, PA6/66 polymer for resin layer 2, and PE (LDPE) for resin layer 3, and the film was extruded from a multilayer circular die and made into a 5-type 6-layer film with a thickness of 30 μm by the inflation method.
In Examples 5 and 6, the layer structure of the protective material used was a multilayer film consisting of "adhesive layer/intermediate layer/resin layer 1", with PA6/66 polymer used for the adhesive layer, POm-PE for the intermediate layer, and PA6/66 polymer used for the resin layer 1, which were extruded from a multilayer circular die and made into a 30 μm thick two-kind three-layer film by the inflation method.
The physical properties of the multilayer films obtained and the evaluation results of airbag test pieces using these films as protective materials are shown in Table 1 below.

In Example 1, a four-type, four-layer multilayer resin film was used as the non-breathable film-like protective material. The elastic modulus of this film in the MD direction was 245 MPa, and the elastic modulus in the TD direction was 250 MPa. When making the airbag, the method of sandwiching the band-shaped non-breathable film-like protective material along the straight or curved outer periphery of a pair of base fabric panels was to prepare a roll of half-folded film in advance, and send the band-shaped non-breathable film-like protective material from the roll to the welding point by heat welding. This method allowed for good handling during processing of the R section, and the obtained airbag had a high internal pressure retention rate and good compactness.

Example 2 was the same as Example 1, except that the elastic modulus of the film in the MD direction was 200 MPa and the elastic modulus in the TD direction was 200 MPa. This method provided excellent handling during processing of the R section, and the airbag obtained had a high internal pressure retention rate and good compactness.

Example 3 was the same as Example 1, except that the elastic modulus of the film in the MD direction was 300 MPa and the elastic modulus in the TD direction was 290 MPa. With this method, the film was somewhat hard and difficult to deform, which slightly worsened the handling properties during processing of the R section, but the airbag obtained had a high internal pressure retention rate and good compactness.

Example 4 was the same as Example 1, except that the elastic modulus of the film in the MD direction was 150 MPa and the elastic modulus in the TD direction was 125 MPa. With this method, the film was soft and sometimes difficult to handle, and the handling properties during processing of the R section were slightly worse, but the airbag obtained had a high internal pressure retention rate and good compactness.

In Example 5, a two-type, three-layer multilayer resin film was used as the non-breathable film-like protective material. In producing the airbag, a roll of half-folded film was prepared in advance to sandwich the band-shaped non-breathable film-like protective material along the straight or curved outer periphery of a pair of base fabric panels, and a 20 mm wide PE film (thickness 50 μm) was sandwiched inside the fold of the half-folded film as a release paper. The band-shaped non-breathable film-like protective material was sent from the roll to the welding point by heat welding. With this method, the release paper may be misaligned, making it difficult to handle, and the handling during processing of the R section was slightly deteriorated, but the obtained airbag had a high internal pressure retention rate and good compactness.

In Example 6, the same film as in Example 5 was used, but a roll of strip-shaped film was prepared in advance without being folded in half, and a strip-shaped non-breathable film-like protective material was folded in half using a half-folding former in the process of sending it from the roll to the welding point by heat welding, and then a 20 mm wide PE film (thickness 50 μm) was sandwiched as release paper inside the fold of the half-folded film and sent to the welding point. With this method, the release paper and film were prone to shifting, making them difficult to handle, and handling during processing of the R section was impaired, but the resulting airbag had a high internal airbag pressure retention rate and good compactness.

In Example 7, the same film as in Example 1 was used, but a roll of strip-shaped film was prepared in advance without being folded in half, and in the process of sending the strip-shaped non-breathable film-like protective material from the roll to the welding location by heat welding, the material was folded in half using a half-folding former, and then sent to the welding location. With this method, the film was prone to shifting and curling, making it difficult to handle, and the handling properties during processing of the R section were somewhat worse, but the resulting airbag had a high internal airbag pressure retention rate and good compactness.

In Example 8, the same film as in Example 1 was used, but when making the airbag, instead of sandwiching a strip-shaped non-air-permeable, breathable film-like protective material along the straight or curved outer periphery of a pair of base fabric panels, a tape was fed onto one main panel while applying tension, and the tape was welded onto the first base fabric by heating from below (step 1). After that, a second base fabric was placed on top of the tape and pressed onto it (step 2). This method allowed for good handling during processing of the R-section, the manufacturing time per bag was short, and the resulting airbag had a high airbag internal pressure retention rate and good compactness.

In Comparative Example 1, the same film as in Example 1 was used, but when the airbag was made, the film-like protective material was sandwiched between two panels of cloth so as to form a loop on the inside of the airbag, and the panels of cloth were sewn together, and then the protective material and the laminated surface of the panel cloth were heat-sealed inside the stitching. Because the protective material was fixed by sewing when bonding, it was bonded without applying tension to the protective material. With this method, the film was prone to shifting and wrinkling, which could make it difficult to handle, and the handling during processing of the R section was poor. In addition, the manufacturing time per bag was long, and the resulting airbag had a low internal pressure retention rate and was not very compact.

The method for manufacturing an airbag according to the present invention comprises bonding the outer surfaces of both ends of a folded, strip-shaped, non-breathable protective material to the inner surface of each of at least a pair of base fabric panels in bonding regions of a predetermined width along the seams from near the seams toward the inside of the bag, the bonding regions having proximal and distal ends. This method is highly productive for producing an airbag which has high internal pressure retention performance, is low cost, has high productivity, and is also highly compact.
Therefore, the airbag manufacturing method according to the present invention can be suitably used for automobile airbags, CABs and pedestrian airbags which particularly require high internal pressure retention performance.

1. Base fabric panel (panel fabric, main panel)
1' Base fabric panel (panel fabric, main panel)
Reference Signs List 2: Sewn (stitched) portion 2': Isolated sewn (stitched) portion 3: Silicone adhesive 4: Non-breathable (film-like) protective material 4': Inner edge of non-breathable (film-like) protective material 4": Half-folded strip-shaped non-breathable (film-like) protective material 5: Adhesive area 5': Adhesive area 6: Proximal end of adhesive area 6': Proximal end of adhesive area 7: Distal end of adhesive area 7': Distal end of adhesive area 8: End (sealed) portion of non-breathable (film-like) protective material 8': End (sealed) portion of non-breathable (film-like) protective material 10: Bag-shaped airbag with outer edge sewn A-A: Cross section 11: Multilayer film 11a: Multilayer film (outer layer)
11b Multilayer film (adhesive layer)
12 Multi-layer die 13 Air ring 14 Deflator (free roll)
15 First pinch drive roll 16 Guide roll (free roll)
17 Second pinch drive roll 18 Touch roll (free roll)
19 Winding drive roll 20 Nylon 66 base fabric 21 Pressure roll (silicon rubber lining)
22 Heating roll (chrome plated)
23 Inner tube 24 Sewing part of inner tube

Claims (11)

1. A method for manufacturing an airbag having at least one pair of fabric panels sewn together at a peripheral edge, the method comprising the steps of:
   a welding step of continuously sandwiching a semi-folded, band-shaped non-breathable film-like protective material, which is made of a monolayer resin film having a predetermined width with a release paper sandwiched therebetween or a laminated resin film having two or more layers including a first surface layer and a second surface layer, between the inner surfaces of the pair of base fabric panels while applying tension to the material along the linear or curved outer periphery of the pair of base fabric panels, and applying heat or ultrasonic waves from the outside of the pair of base fabric panels to weld a surface of the monolayer resin film or the first surface layer to the inner surface of the base fabric panel in an adhesive region of a predetermined width, wherein although the surfaces of the monolayer resin film on the release paper side are not welded to each other due to the presence of the release paper, or the second surface layers of the laminated resin film are not welded to each other by heat welding or ultrasonic welding, or are welded to each other by heat welding or ultrasonic welding, the second surface layer peels off when a tensile force is applied to the pair of base fabric panels when the airbag is deployed;
   a sewing step of sewing the pair of fabric panels together adjacent the bonded areas before, after, or simultaneously with the bonding;
   The manufacturing method comprising the steps of:
2. The method according to claim 1, wherein the semi-folded band-shaped non-breathable film-like protective material is fed from a roll wound in a semi-folded state and sandwiched between a pair of base fabric panels.
3. a step of heating a part or the whole of the half-folded band-shaped non-breathable film-like protective material before a welding step of welding the half-folded band-shaped non-breathable film-like protective material;
   The method of claim 1 or 2, comprising:
4. a step of cooling a part or the whole of the semi-folded, band-shaped, non-breathable film-like protective material after a welding step of welding the semi-folded, band-shaped, non-breathable film-like protective material;
   The method of claim 1 or 2, comprising:
5. a step of heating and/or cooling a part or the whole of the half-folded band-shaped non-breathable film-like protective material while intermittently applying/releasing the pressure of a hot plate and/or a cold plate in a welding step of welding the half-folded band-shaped non-breathable film-like protective material;
   The method of claim 1 or 2, comprising:
6. The method according to claim 1 or 2, wherein the melting point of the resin constituting the first surface layer of the laminated resin film, which is the half-folded non-breathable film-like protective material, is 50°C to 160°C lower than the melting point of the resin constituting the second surface layer.
7. The method according to claim 1 or 2, wherein the half-folded non-breathable film-like protective material is a single-layer or multilayer film including a first surface layer and a second surface layer of a laminated resin film, and the difference in SP value between any adjacent layers is 2.0 [cal/ ^cm3 ) ^1/2 ] or more.
8. The method according to claim 1 or 2, wherein the half-folded non-breathable film-like protective material is a single-layer or multilayer film including a first surface layer and a second surface layer of a laminated resin film, and the difference in HSP value between any adjacent layers is 1.0 [cal/ ^cm3 ) ^1/2 ] or more.
9. The method according to claim 1 or 2, wherein when a tensile force is applied between the pair of base fabric panels during deployment of the airbag, the length between the distal ends along the folded non-breathable film-like protective material is greater than or equal to the length between the distal ends along the pair of base fabric panels.
10. a sewing step of sewing the pair of base fabric panels together adjacent the bonded areas after the bonding;
    The method of claim 1 or 2, comprising:
11. a welding step of applying heat or ultrasonic waves to a semi-folded band-shaped non-breathable film-like protective material of a predetermined width, which is made of a laminated resin film of two or more layers including a first surface layer and a second surface layer, on one of the base fabric panels, continuously along a straight or curved outer periphery of the one of the base fabric panels from below the one of the base fabric panels while applying tension to the material, thereby welding the first surface layer to an upper surface of the one of the base fabric panels;
    a welding step of overlapping another base fabric panel on the welded film-like protective material and applying heat or ultrasonic waves from the upper side of the overlapped base fabric panel to weld the first surface layer to the lower surface of the overlapped base fabric panel, wherein the second surface layers of the laminated resin film are not welded to each other by thermal welding or ultrasonic welding, or are welded to each other by thermal welding or ultrasonic welding, but the second surface layer peels off when a tensile force is applied to the base fabric panels when the airbag is deployed;
    a sewing step of sewing the fabric panels together adjacent the areas of the resulting welds after said bonding;
    The manufacturing method comprising the steps of:

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