Multi-layer composite for airbags

Abstract

The object of the present invention is to provide a multilayer composite for airbags that combines scratch resistance and flexibility. The multilayer composite for airbags of the present invention comprises a base fabric and a multilayer film including an outer layer and an adhesive layer bonded to one surface of the base fabric. The multilayer composite for airbags is characterized in that the ratio (Sdr1 / Sdr2) of the interfacial unfolded area ratio Sdr1 of the multilayer film side surface to the interfacial unfolded area ratio Sdr2 of the base fabric side surface of the multilayer composite for airbags is 0.986 to 1.1.

Description

Technical Field

[0001] This invention relates to multilayer composites for airbags. Background Art

[0002] A representative application of airbags is in vehicle use. In this application, the inflator deploys instantaneously upon impact, inflating the folded airbag to absorb the kinetic energy of the passenger, thereby preventing serious injury. In recent years, due to increased vehicle safety regulations and awareness, the number of vehicles equipped with airbags has been increasing.

[0003] Among vehicle airbags, the front airbag, which is designed for frontal collisions, is representative. Other types include side airbags and side curtain airbags, designed for side collisions and rollovers, as well as external airbags for pedestrian protection. The required performance characteristics for these airbags include flexibility for compact placement in confined spaces, strength to withstand pressure during inflation, scratch resistance to withstand friction during placement and inflation, and airtightness to maintain inflation for a certain period. Side curtain airbags, in particular, require a longer inflation time and higher airtightness to protect passengers from side collisions and associated vehicle rollovers.

[0004] As the material constituting the airbag, a synthetic fiber fabric (also referred to as "base fabric" in this specification) is used as the support layer, and a barrier material is covered on its surface to ensure airtightness. This barrier material may be silicone rubber (coating method) or a multilayer film (thermal lamination method), depending on the required properties.

[0005] In the multilayer film used in the above-mentioned thermal lamination, the layer that is bonded to the base fabric is used as the adhesive layer, and the layer on the opposite side of the adhesive layer is used as the outer layer. Each layer is formed using resins with different melting points and glass transition points.

[0006] As for the aforementioned multilayer films, Patent Document 1 discloses related technologies for multilayer films containing a high-melting-point resin layer and a low-melting-point resin layer. According to this document, a modified polyolefin with a melting point of 85 to 105°C is used in the low-melting-point resin layer bonded to the base fabric. Furthermore, Patent Document 2 discloses related technologies for multilayer films composed of resin layers with different glass transition temperatures. According to this document, a copolyamide, copolyester, or polyamide elastomer with a glass transition temperature of -10°C or lower is used in the first resin layer bonded to the base fabric. Additionally, Patent Document 3 discloses related technologies for multilayer films in which the adhesive layer is an adhesive layer containing a resin with a glass transition temperature and melting point within a specific range, and the outer layer is a layer containing a resin with a melting point 20°C higher than that of the resin contained in the adhesive layer.

[0007] Existing technical documents

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent No. 4965757

[0010] Patent Document 2: European Patent Application Publication No. 1518761

[0011] Patent Document 3: International Publication No. 2020 / 032032 Summary of the Invention

[0012] The problem that the invention aims to solve

[0013] However, in Patent Document 1, a modified polyolefin is used in the adhesive layer bonded to the base fabric. Therefore, the affinity with the base fabric, which is composed of polyamide fibers and polyester fibers, is insufficient, and the adhesive strength cannot be considered adequate. In addition, due to the insufficient adhesive strength, there is a risk that the multilayer film may peel off from the base fabric during airbag inflation, thus failing to perform its full function.

[0014] Furthermore, in the barrier material of Patent Document 2, the use of any of the copolyamide, polyamide elastomer, or polyester elastomer with a glass transition temperature below -10°C in the adhesive layer results in excellent softness and adhesion, but the molecular structure lacks stereoregularity, leading to low crystallinity and a tendency to adhere (weld). Therefore, for example, a blow-blowing method with high productivity is employed in the production method of the barrier material. Figure 3 In cases where the films are blown together, adhesion occurs on the pinch rollers after inflation, making it difficult to separate the two stacked films individually during the subsequent peeling process. This can result in wrinkles or winding misalignment due to film breakage or changes in the peeling position, making stable production difficult. Furthermore, in products made by winding films prone to adhesion, adhesion can occur depending on the winding tension, storage temperature and humidity conditions, etc., posing problems with storage where the film cannot be pulled out.

[0015] In the multilayer film of Patent Document 3, although the adhesion problem is solved, high pressure is required during lamination to obtain sufficient adhesive strength, which increases equipment costs. Alternatively, if lamination is performed at low pressure, long-term heating and low-speed lamination are necessary, resulting in poor productivity. In addition, there are problems in balancing scratch resistance and flexibility (packing).

[0016] The purpose of this invention is to provide a multilayer composite for airbags that combines scratch resistance and flexibility.

[0017] Methods for solving problems

[0018] That is, the present invention is as follows. [1]

[0020] A multilayer composite for airbags, comprising a base fabric and a multilayer film including an outer layer and an adhesive layer bonded to one surface of the base fabric, characterized in that the ratio (Sdr1 / Sdr2) of the interfacial unfolded area ratio Sdr1 of the multilayer film side surface of the multilayer composite for airbags to the interfacial unfolded area ratio Sdr2 of the base fabric side surface of the multilayer composite for airbags is 0.986 to 1.1. [2]

[0022] As described in [1], the multilayer composite for airbags has a thickness of 10 to 30 μm. [3]

[0024] The multilayer composite for airbags as described in [1] or [2], wherein the gap length between the multilayer film and the base fabric is less than 6 μm. [4]

[0026] A method for manufacturing a multilayer composite for airbags, characterized by comprising the following steps:

[0027] The hot lamination process involves laminating a base fabric and a multilayer film comprising an outer layer and an adhesive layer onto one surface of the base fabric using a heat lamination process; and

[0028] The post-heating process involves heating again after the heat lamination process.

[0029] The effects of the invention

[0030] According to the present invention, a multilayer composite for airbags that combines scratch resistance and flexibility can be provided. Attached Figure Description

[0031] Figure 1 This is a cross-sectional view showing an example of the multilayer composite for airbags according to this embodiment. (a) is a photograph of the cross-section, and (b) is a schematic diagram of the cross-section.

[0032] Figure 2 This is a schematic diagram obtained by enlarging the junction of the base fabric and the multilayer film of an example of the multilayer composite for the airbag in this embodiment.

[0033] Figure 3 This is a schematic diagram of an example of the inflation method.

[0034] Figure 4 This is a schematic diagram illustrating an example of a method for manufacturing a multilayer composite for an airbag according to this embodiment.

[0035] Figure 5 This is a schematic diagram illustrating a ring stiffness test.

[0036] Figure 6This is a schematic diagram illustrating the cross-section used to measure the void length of a composite. The A-A' section is a section cut in a manner that includes both warp and weft yarns, while the B-B' section is a section cut in a manner that includes only warp yarns. Even for fibers with other weaves (such as twill weave), the cross-sections cut using the above definitions are defined as the A-A' and B-B' sections. Detailed Implementation

[0037] The specific embodiments of the present invention will be described in detail below, but the present invention is not limited to the embodiments and examples shown below, and can be modified arbitrarily within the scope and equivalent scope of the present invention.

[0038] [Multi-layer composite for airbags]

[0039] The multilayer composite for airbags in this embodiment is a composite consisting only of a base fabric and a multilayer film including an outer layer and an adhesive layer bonded to one surface of the base fabric.

[0040] In the multilayer composite for airbags of this embodiment, the ratio (Sdr1 / Sdr2) of the interfacial unfolded area ratio Sdr1 of the multilayer film side surface of the multilayer composite for airbags to the interfacial unfolded area ratio Sdr2 of the base fabric side surface of the multilayer composite for airbags is 0.986 or more.

[0041] In this specification, the multilayer composite for airbags in this embodiment is sometimes simply referred to as the "composite".

[0042] In addition, the aforementioned multilayer film consists of at least two layers, wherein the layer bonded to the base fabric (i.e., the layer containing the surface of the base fabric) is the adhesive layer, and the layer exposed on the outside of the multilayer composite for airbags, containing the surface of the composite, is the outer layer.

[0043] The multilayer film of this embodiment will be described below.

[0044] (Multilayer film)

[0045] The aforementioned multilayer film can be a two-layer structure (adhesive layer / outer layer) formed by laminating an adhesive layer and an outer layer, or a three-layer structure (adhesive layer / intermediate layer / outer layer) or a five-layer structure (adhesive layer / glue layer / intermediate layer / glue layer / outer layer). Additionally, it may include other layers besides those mentioned above. It should be noted that the adhesive layer and the outer layer are preferably the surface layers of both surfaces of the multilayer film.

[0046] Among the aforementioned multilayer films, those with excellent preservation properties due to suppressed adhesion and excellent adhesion to the base fabric are further preferred. By using such multilayer films, multilayer composites for airbags with more stable quality and higher reliability can be obtained.

[0047] -Adhesive layer-

[0048] It is known that crystallinity (crystallization rate) dominates the adhesiveness of crystalline resins, but previous research by the inventors has shown that adhesiveness can also be suppressed by adjusting the glass transition temperature. Further previous research has demonstrated that by using resins with glass transition temperatures and melting points within a specific range in the adhesive layer, a multilayer film for airbags with a superior balance between anti-adhesion and adhesiveness can be obtained.

[0049] The adhesive layer preferably comprises a resin with a glass transition temperature of -80 to 80°C and a melting point of 100 to 160°C (sometimes referred to as "resin A" in this specification). In addition to resin A, the adhesive layer may also contain other resins (sometimes referred to as "resin B" in this specification). Resin A and resin B may be one type or two or more types.

[0050] The adhesive layer described above may consist of resin A alone, may further include resin B and the additives described below, may consist of resin A, resin B and the additives alone, or may consist of resin A and the additives alone.

[0051] The glass transition temperature of the aforementioned resin A is preferably -80 to 80°C, more preferably 0 to 80°C, even more preferably 10 to 70°C, and particularly preferably 20 to 60°C. The range of glass transition temperature is determined from the perspective of adhesion resistance and melting point. When the glass transition temperature is above 0°C, adhesion resistance is further suppressed. By keeping the glass transition temperature below 80°C, the melting point (described later) can be within an appropriate range.

[0052] It should be noted that the glass transition temperature described above can be determined by the method described in the embodiments below.

[0053] When there are two or more types of resin A, the glass transition temperatures of each resin A can be the same or different.

[0054] The melting point of resin A is preferably 100–160°C, more preferably 110–150°C, and even more preferably 120–140°C. By setting the melting point to 100°C or higher, the adhesion strength to the base fabric can be maintained even in high-temperature operating environments, and the range of conditions such as temperature, pressure, and time during lamination processing (also known as the process window) can be expanded, resulting in a multilayer film with stable quality. On the other hand, by setting the melting point to 160°C or lower, moderate flexibility can be obtained.

[0055] It should be noted that the above melting point can be determined by the method described in the following examples.

[0056] When two or more resins A are included, the melting points of each resin A may be the same or different. In addition, when two or more resins A are included and there are two or more melting peaks, the melting peak temperature of the high-temperature side of resin A is preferably 100 to 160°C, more preferably 110 to 150°C, and even more preferably 120 to 140°C.

[0057] The above-mentioned resin A and resin B can be individual resins or mixtures of two or more resins.

[0058] As for the aforementioned resin A, a polyamide-based resin is preferred from the perspective of minimal changes in properties such as softness and adhesion relative to changes in temperature and humidity in the usage environment. Among the aforementioned polyamide-based resins, copolyamide (a-1), dimer acid-based polyamide (a-2), and thermoplastic polyamide elastomer (a-3) are preferred, and copolyamide (a-1) is more preferred from the perspectives of softness, adhesion, and cost.

[0059] As the aforementioned copolyamide (a-1), examples of copolyamides can be made by copolymerizing two or more monomer components known as monomer components constituting aliphatic polyamides (e.g., monomer components constituting polyamide 6, polyamide 66, polyamide 610, polyamide 11, and polyamide 12), such as polyamide 6 / 66, polyamide 6 / 12, polyamide 6 / 11, and polyamide 6 / 66 / 11.

[0060] As an example of the dimer acid polyamide (a-2) mentioned above, a polyamide obtained by dimerizing natural vegetable oil fatty acids (18 carbon unsaturated fatty acids, such as oleic acid, linoleic acid, etc.)) can be cited.

[0061] Examples of thermoplastic polyamide elastomers (a-3) include those containing polyether in the soft segment (amorphous phase) and polyamide in the hard segment (crystalline phase) (including dimer acid-based thermoplastic polyamide elastomers).

[0062] Among them, polyamide 6 / 12 is preferred due to its particularly excellent softness and adhesion.

[0063] The adhesive layer described above can be a mixed resin layer containing resin B in addition to resin A. In this case, resin B is preferably an acid-modified polyolefin, an ionomer, or a thermoplastic polyamide elastomer. From the perspective of flexibility and adhesion at low temperatures, a glass transition temperature of less than 0°C and a melting point of 80–160°C are preferred.

[0064] The aforementioned adhesive layer may suitably contain various additives such as anti-blocking agents, lubricants, nucleating agents, flame retardants, antistatic agents, antioxidants, ultraviolet absorbers, light stabilizers, colorants, and fillers, without compromising its practical properties such as adhesion. Specifically, to further improve the adhesive layer's resistance to caking, it is preferable to include anti-blocking agents, nucleating agents, and / or lubricants; more preferably, it includes anti-blocking agents and / or nucleating agents; and even more preferably, it includes both anti-blocking agents and nucleating agents.

[0065] Examples of anti-blocking agents include organic particles such as cross-linked polystyrene, cross-linked acrylic (PMMA) resin, and fluorine (PTFE) particles, as well as inorganic particles such as silica particles, kaolin, and calcium carbonate.

[0066] Examples of nucleating agents for crystallization include talc, alumina, kaolin, and high-melting-point polyamides (e.g., polyamides with a melting point greater than 160°C).

[0067] Examples of such lubricants include aliphatic amides and metallic soaps.

[0068] From the perspective of adhesive strength and flexibility, the average thickness of the above-mentioned adhesive layer is preferably 0.5 to 20 μm, more preferably 1 to 15 μm, and even more preferably 2 to 10 μm.

[0069] -Outer layer-

[0070] The outer layer preferably comprises resin, and more preferably is formed solely of resin.

[0071] The resin used in the outer layer is preferably a resin with a higher melting point than resin A. Furthermore, the resin used in the outer layer is preferably a resin with a higher melting point than the adhesive layer.

[0072] The melting point of the resin used in the outer layer is preferably 20°C or more higher than that of resin A, more preferably 25°C or more higher, and even more preferably 30°C or more higher. The melting point of the resin used in the outer layer is determined by the ease of welding (attachment) to the heated roller used in the lamination process with the base fabric. By using a resin with a melting point 20°C or more higher than that of resin A, welding to the heated roller is less likely to occur, thus achieving stable lamination.

[0073] The melting point of the resin used in the outer layer is preferably 150–240°C, more preferably 160–230°C, and even more preferably 170–220°C. By setting the melting point to 150°C or higher, welding between rollers during hot lamination can be suppressed, and pinholes can be prevented.

[0074] It should be noted that when the adhesive layer contains two or more resins A, and / or when the outer layer contains two or more resins, the above-mentioned melting point of the mixed resin can be the melting peak temperature that appears on the highest temperature side among the melting peak temperatures of the mixed resins contained in the layer.

[0075] From the perspective of flexibility, the glass transition temperature of the resin used in the outer layer is preferably 80°C or less, more preferably 70°C or less, and even more preferably 60°C or less.

[0076] The resins used in the outer layer are preferably polyamide resins or polyester resins, considering that they can produce an outer layer with excellent properties such as airtightness, abrasion resistance, softness, strength, crease resistance (referring to resistance to stress generated during folding), flame retardancy, and slip resistance.

[0077] As the polyamide resins mentioned above, examples of polyamide resins (a-1, a-2, a-3) as resin A included in the adhesive layer can be used, and individual components or compositions of two or more components can be used appropriately.

[0078] As the aforementioned polyester resin, thermoplastic polyester elastomers are preferred, such as those using polyether components in the soft chain segment (polyether-polyester type) and those using polyester components in the soft chain segment (polyester-polyester type).

[0079] In the aforementioned multilayer film, examples of methods for determining the components contained in each layer, such as the adhesive layer and the outer layer, include methods using infrared analysis and NMR. Furthermore, as other methods for determining the melting point and crystallization temperature, in the case of two-layer films consisting of an adhesive layer and an outer layer, the multilayer film can be sampled at the desired size, and the melting point can be determined using the aforementioned melting point determination method. In the case of three or more multilayer films with an intermediate layer between the adhesive layer and the outer layer, the film can be immersed in a solvent (such as hexafluoro-2-propanol) that can only extract the adhesive layer, and the resulting solution can be separated into solvent and solid components using an evaporator. The melting point of the solid components can then be determined using the aforementioned melting point determination method.

[0080] From the perspectives of durability, flexibility, and pinhole suppression during hot lamination, the average thickness of the outer layer is preferably 0.5 to 20 μm, more preferably 1 to 15 μm, and even more preferably 2 to 10 μm.

[0081] -Middle Layer-

[0082] As an example of the aforementioned intermediate layer, a layer formed by a composition consisting of one or more of the following components, namely: linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, high-density polyethylene, polypropylene and other polyolefin resins, acid-modified polyolefin resins, polyolefin copolymer resins, polyolefin thermoplastic elastomers, acid-modified polyolefin elastomers, etc. From the perspective of flexibility, it is preferable to include acid-modified polyolefin resins (preferably acid-modified polyethylene), polyolefin copolymer resins and / or polyolefin thermoplastic elastomers, more preferably formed only of acid-modified polyolefin resins, polyolefin copolymer resins and / or polyolefin thermoplastic elastomers, and even more preferably formed only of acid-modified polyolefin resins.

[0083] From the perspective of flexibility and mechanical strength, the average thickness of the above-mentioned intermediate layer is preferably 1 to 30 μm, more preferably 2 to 28 μm, and even more preferably 3 to 25 μm.

[0084] -Glue layer-

[0085] The aforementioned adhesive layer is used to bond the various layers together. Examples of such layers include those formed from acid-modified polyolefin resins with polar functional groups, such as acid-modified polyethylene and acid-modified polypropylene, and / or polyolefin thermoplastic elastomers. It is preferable to select the adhesive layer based on the requirements for heat resistance and other properties in the intended application.

[0086] The aforementioned adhesive layer can be a layer formed from only one type of resin, or it can be a layer containing two or more types of resin.

[0087] -characteristic-

[0088] The characteristics of the above-mentioned multilayer films are described below.

[0089] The aforementioned multilayer film is a film with at least two layers. The total average thickness of the aforementioned multilayer film is preferably 5 to 100 μm, more preferably 10 to 80 μm, and even more preferably 15 to 40 μm. These ranges are determined based on a balance between film strength, scratch resistance, and flexibility. A thickness of 5 μm or more provides good strength, 100 μm or less provides good flexibility, and 40 μm or less provides an excellent balance between scratch resistance and flexibility.

[0090] In the above-mentioned multilayer film, from the perspective of balancing flexibility and scratch resistance, the ratio of the average thickness of the outer layer to the average thickness (100%) of the adhesive layer is preferably 20 to 500%, more preferably 50 to 400%.

[0091] Furthermore, when the aforementioned multilayer film has a 5-layer structure of outer layer / adhesive layer / intermediate layer / adhesive layer / adhesive layer, the ratio of the average thickness of each layer to the average thickness (100%) of the adhesive layer is preferably 10 to 500%, the intermediate layer is preferably 50 to 10000%, and the outer layer is preferably 10 to 5000%.

[0092] To exhibit high adhesion to the base fabric, the multilayer film preferably has chemical bonds (e.g., hydrogen bonds) with the monofilaments constituting the base fabric and a large contact area. If the contact area is small, the adhesive strength based on the chemical bonds may not withstand the internal pressure generated when the airbag is deployed using the multilayer composite, and the required functions of the airbag may not be fully realized.

[0093] From the perspective of obtaining sufficient adhesive strength between the multilayer film and the base fabric, the lower limit of the thickness ratio of the adhesive layer relative to 100% of the average thickness of the multilayer film is preferably 1%, more preferably 5%, and even more preferably 10%. Furthermore, from the perspective of flexibility, the upper limit of the thickness ratio of the adhesive layer is preferably 50%, more preferably 40%, and even more preferably 30%.

[0094] Furthermore, relative to the average thickness of the multilayer film (100%), the lower limit of the thickness ratio of the outer layer is preferably 5%, more preferably 10%, and even more preferably 20%. Additionally, from the perspective of flexibility, the upper limit of the thickness ratio of the outer layer is preferably 50%, more preferably 40%, and even more preferably 30%.

[0095] -Manufacturing Method-

[0096] Examples of methods for manufacturing the aforementioned multilayer films include: co-extruding molten resin comprising each layer using a multilayer annular die and manufacturing it by blow molding; T-die method, in which molten resin is co-extruded by a T-die and the film is cooled and solidified using a casting roller; and so on. Among these, blow molding has excellent productivity and is therefore preferred.

[0097] When using the blow-up method, the die head temperature can be 170–280°C. Furthermore, the die lip shape of the annular die head can be 50–500 mm, and the die lip gap can be 0.5–10 mm. Additionally, the blow-up ratio can be 1–10 times, the air ring temperature can be -30–50°C, the distance between the annular die head and the pinch rollers can be 1–100 m, and the traction speed can be 1–200 m / min.

[0098] (Base)

[0099] The aforementioned base fabric is a support for the multilayer membranes in the multilayer composite for airbags, which can maintain a specific three-dimensional structure when the airbag is deployed.

[0100] For the aforementioned base fabric, it is required to have heat resistance, spreadability, strength to withstand rapid expansion or impact, air tightness, and packability, etc., which can withstand high-temperature gas from the inflator. Therefore, it is preferred to be formed of synthetic fibers, and more preferably synthetic fiber fabrics (e.g., fabrics formed only of synthetic fibers).

[0101] The mass percentage of synthetic fibers relative to the total amount (100% by mass) of the base fabric is preferably 20% by mass or more, and more preferably 50 to 100% by mass.

[0102] Examples of synthetic fibers constituting the base fabric or the synthetic fiber fabric include polyamide fibers, polyester fibers, polyolefin fibers, chlorine-containing fibers, fluorine-containing fibers, polyacetal fibers, polysulfone fibers, polyphenylene sulfide (PPS) fibers, polyether ether ketone (PEEK) fibers, fully aromatic polyamide fibers, fully aromatic polyester fibers, polyimide fibers, polyetherimide fibers, poly(p-phenylenebenzodioxazole) fibers (PBO), vinylon fibers, acrylonitrile fibers, cellulose fibers, silicon carbide fibers, alumina fibers, glass fibers, carbon fibers, and steel fibers. Among these, fibers that have hydrogen bonding ability with the resin contained in the adhesive layer (preferably the resin with the highest content in the adhesive layer) are preferred. From the perspectives of strength, specific gravity, cost, and adhesion strength to multilayer films, polyamide fibers or polyester fibers are more preferred.

[0103] The total fineness of the fibers constituting the base fabric is preferably 100 to 1000 dtex, more preferably 210 to 570 dtex, and even more preferably 330 to 490 dtex. By making the total fineness 100 dtex or more, it can withstand the tension during unfolding and expansion. By making the total fineness 1000 dtex or less, the fabric becomes soft, its compressibility is improved, and it can also be unfolded at high speed.

[0104] The fineness of the monofilaments constituting the base fabric is preferably 0.5 to 8 dtex, more preferably 1.5 to 3.7 dtex. By making the fineness of the monofilaments 0.5 dtex or more, warp fuzz during weaving can be suppressed. In addition, by making the fineness of the monofilaments 8 dtex or less, a soft fabric can be produced.

[0105] From the perspective of increasing the bonding area between the multilayer film and the base fabric, the fiber density of the base fabric is preferably 40 to 80 fibers / 2.54 cm. Furthermore, from the perspective of excellent adhesion and tear strength when manufacturing multilayer composites for airbags, it is more preferable to have 50 to 80 fibers / 2.54 cm.

[0106] It should be noted that the above fiber density is a value measured according to JIS L 1096.

[0107] From the perspective of balancing mechanical properties and hardness, the coverage factor (CF) of the aforementioned base fabric is preferably 1800–2400, more preferably 1900–2300, and even more preferably 1900–2200. When the CF is 1800 or higher, the base fabric exhibits excellent strength. On the other hand, as with CF below 2400, the lower the CF, the softer the base fabric. Furthermore, the lower the CF, the lighter the fabric basis weight; therefore, 2300 or lower is preferred.

[0108] Generally, the smaller the CF (fluid density), the more air gaps will be generated between the woven yarns, but air can be suppressed by lamination. It should be noted that CF is represented by the following mathematical formula (1).

[0109] CF=(0.9×d) 1 / 2 ×(2×W) mathematical expression (1)

[0110] (In the above mathematical formula (1), d is the average total fineness (dtex) of the warp and weft fibers constituting the yarn, and W is the average fineness (threads / 2.54cm).)

[0111] The average thickness of the base fabric is preferably 0.15–0.45 mm, more preferably 0.17–0.40 mm, and even more preferably 0.20–0.35 mm. When the average thickness of the base fabric is 0.15 mm or more, it can withstand heat or stress during unfolding and expansion. When the average thickness of the base fabric is 0.40 mm or less, its packability is improved. It should be noted that the thickness is determined according to ISO 5084 at a set pressure of 1 kPa and measured... The values ​​measured below.

[0112] (Properties of the complex)

[0113] The characteristics of the multilayer composite for airbags in this embodiment will be explained.

[0114] In the multilayer composite for airbags of this embodiment, the ratio (Sdr1 / Sdr2) of the interfacial unfolded area ratio Sdr1 of the multilayer film side surface to the interfacial unfolded area ratio Sdr2 of the base fabric side surface of the multilayer composite for airbags is 0.986 to 1.1, with a lower limit of preferably 0.988, more preferably 0.990, and an upper limit of preferably 1.08, more preferably 1.05. By making Sdr1 / Sdr2 within the above range, the durability (scratch resistance) against wear during storage and friction during expansion is improved, and the peeling of the multilayer film from the base fabric can be further suppressed. Furthermore, Sdr1 / Sdr2 can be greater than 1.

[0115] When bonding a multilayer film to a base fabric via thermal lamination, gaps may form between the film and the base fabric due to the unevenness of the base fabric. However, in the case of a composite with many gaps, the ratio of the interfacial unfolded area Sdr1 of the multilayer film side surface to the interfacial unfolded area Sdr2 of the base fabric side surface of the multilayer composite for airbags (Sdr1 / Sdr2) is less than 0.986. Conversely, by reducing the gaps between the film and the base fabric, (Sdr1 / Sdr2) can be increased.

[0116] The rationale is believed to be that, for example, during heat treatment of a porous film, when the voids disappear, the multilayer film is drawn into the void portion, increasing the surface roughness of the heat-treated multilayer film. Therefore, Sdr1 increases relative to Sdr2.

[0117] It should be noted that the ratio of the unfolded area ratio (Sdr1 / Sdr2) can be determined by the method described in the embodiments below.

[0118] If the fiber density of the base fabric is in the range of 40 to 80 (fibers / 2.54 cm), the cutoff values ​​(λc and λf) used in the determination (data processing) of the interfacial unfolded area ratio of the multilayer composite for airbags are preferably λc = 200 μ and λf = 500 μ.

[0119] When the Sdr1 / Sdr2 ratio is low after heat lamination, it can be increased by performing post-heat treatment or the like. Furthermore, by using a suitable multilayer film as described above and manufacturing under the manufacturing conditions described later, the Sdr1 / Sdr2 ratio can be controlled within the aforementioned range. If the multilayer film is thin, the Sdr1 / Sdr2 ratio is easily 0.986 or higher; therefore, the thickness of the multilayer film is preferably 39 μm or less, more preferably 10 to 30 μm. Additionally, the smaller the total fineness of the base fabric, the smaller the gap between the film and the fibers, thus increasing the Sdr1 / Sdr2 ratio, which is preferable.

[0120] In the composite of this embodiment, by performing a process to give the surface of the multilayer film side unevenness, it is also possible to make Sdr1 greater than Sdr2. As a means of giving unevenness, examples include pressing the surface of the multilayer film with a solid having unevenness.

[0121] In the composite of this embodiment, the fewer the gaps between the multilayer film and the base fabric, the better. Fewer gaps result in superior adhesive strength and improved scratch resistance. Figure 2 )

[0122] The void length of the composite between the multilayer film and the base fabric is preferably 6 μm or less, more preferably 4 μm or less, and even more preferably 2 μm or less. It should be noted that the void length can be measured using the method described in the embodiments below.

[0123] By subjecting the laminate to high temperature, high pressure, long-term heating, or post-heating treatment, voids can be reduced. From a productivity perspective, lamination under low pressure and short-time heating is preferred, followed by post-heating treatment of the composite, thereby reducing voids between the film and the base fabric.

[0124] From the perspective of scratch resistance, the composite of this embodiment is preferably scratched 1,000 to 3,000 times, more preferably 1,500 to 3,000 times.

[0125] The number of scratches described above can be measured using the method described in the embodiments below. Furthermore, the number of scratches can be within the range described above by setting Sdr1 / Sdr2 to the range described above, or by setting the gap between the multilayer film and the base fabric to the range described above.

[0126] The ring stiffness of the composite in this embodiment is preferably 100-300 mN / cm, more preferably 100-250 mN / cm.

[0127] "Ring stiffness" refers to the stress required to compress a specified amount along the diameter of a membrane sample (such as a film) when it is bent into a ring shape. The ring stiffness value is used to evaluate the stiffness of the composite. The ring stiffness can be measured using the method described in the examples below. Furthermore, the ring stiffness can be within the aforementioned range by setting Sdr1 / Sdr2 to the range described above, or by setting the gap between the multilayer film and the base fabric to the range described above.

[0128] In the composite of this embodiment, from the perspective of further improving the adhesion strength between the multilayer film and the base fabric, and further improving the strength of the composite of this embodiment, the average film thickness of the laminated composite can also be made smaller than the average film thickness before lamination. One reason for the reduction in average film thickness can be that the film melts during lamination and fills the voids in the recesses of the base fabric, or penetrates into the fibers of the base fabric. In this case, Figure 6 The resin in section A-A' melts and moves in a way that fills the voids in section B-B', thus increasing the unevenness of the film thickness.

[0129] Regarding the method for determining the average film thickness of the aforementioned composite, the thickness value of the multilayer film is measured every 100 μm in the same number of thickness-direction sections at both the A-A' and B-B' sections, in a direction orthogonal to the thickness direction. This measurement can, for example, be performed at 10 mm in a direction orthogonal to the thickness direction, yielding 100 thickness values. The arithmetic mean of the obtained thickness values ​​(e.g., the 100 thickness values) is then taken as the average film thickness of the composite.

[0130] (Manufacturing method of the composite)

[0131] The manufacturing method of the multilayer composite for airbags according to this embodiment will be described.

[0132] As a method for manufacturing the multilayer composite for airbags according to this embodiment, a heat lamination process is preferred, in which a base fabric and a multilayer film including an outer layer and an adhesive layer are stacked on one surface of the base fabric and the adhesive layer is heat-laminated. More preferably, a post-heating process is also included, in which heating is performed again after the heat lamination process.

[0133] Examples of manufacturing methods for the aforementioned composites include: roller lamination, in which a multilayer film is overlapped with a base fabric and continuously laminated using heated rollers in a roller-to-roll manner; belt lamination, in which a multilayer film is overlapped with a base fabric and then supplied to a pair of heated belts for simultaneous heating and lamination under pressure; vacuum lamination, in which lamination is performed under reduced pressure; lamination based on hot pressing; and so on.

[0134] As for the heating conditions during hot lamination, it is preferable to implement them within a temperature range of melting point to melting point +40°C of the resin contained in the adhesive layer (preferably the resin with the highest content in the adhesive layer).

[0135] For the pressure conditions during hot lamination, the preferred conditions are 1–30 N / cm for roller lamination, 1–20 N / cm for belt lamination, and 1–20 N / cm for hot pressing lamination. 2 More preferably, the resistance is 10–20 N / cm for roller type, and 5–20 N / cm for belt type and hot-press type. 2 .

[0136] Regarding speed conditions, the preferred speeds are 0.1 m / min to 10 m / min for roller type and 0.1 m / min to 30 m / min for belt type, and more preferably 0.1 m / min to 5 m / min for roller type and 0.5 m / min to 10 m / min for belt type.

[0137] The preferred heating time for hot pressing is 1 second to 180 seconds, more preferably 5 seconds to 60 seconds, and even more preferably 10 seconds to 60 seconds.

[0138] The multilayer composite for airbags in this embodiment can be manufactured even without post-heat treatment.

[0139] As an example of a case where no post-heating treatment is performed, in roller lamination, the pressure is preferably 10–20 N / cm, more preferably 10–15 N / cm; the speed is preferably 0.1 m / min–5 m / min, more preferably 0.1 m / min–0.3 m / min; and the temperature is preferably the melting point of the resin contained in the adhesive layer (preferably the resin with the highest content in the adhesive layer) to melting point +40°C, more preferably melting point +10°C to melting point +40°C. In tape lamination and hot pressing lamination, the pressure is preferably 1–30 N / cm.2 More preferably 3-8 N / cm 2 The heating time is preferably 1 to 90 seconds, more preferably 30 to 60 seconds, and the temperature is preferably the melting point of the resin contained in the adhesive layer (preferably the resin with the highest content in the adhesive layer) to melting point +40°C, more preferably melting point +10°C to melting point +40°C.

[0140] The composite in this embodiment is preferably subjected to post-heat treatment. Post-heat treatment can improve the Sdr1 / Sdr2 ratio and reduce the voids between the film and the base fabric.

[0141] Examples of post-heating treatment methods include: methods that continuously contact the composite with hot rollers for treatment; methods that continuously heat-treat the composite in a non-contact manner using hot air or infrared heaters; and so on.

[0142] From the perspective of achieving a stronger bond between the adhesive layer and the base fabric through melting, and reducing the voids between the base fabric and the multilayer film, and from the perspective of ensuring the strength of the multilayer film without melting the outer layer, thereby suppressing pinholes, the preferred post-heat treatment temperature is preferably above and below the melting point of the resin contained in the adhesive layer of the multilayer film (preferably the resin with the highest content in the adhesive layer) and below the melting point of the resin contained in the outer layer (preferably the resin with the highest content in the outer layer). For example, the aforementioned post-heat treatment temperature is preferably below the melting point of the resin contained in the outer layer (preferably the resin with the highest content in the outer layer) and at least 10°C above the melting point of the resin contained in the adhesive layer of the multilayer film (preferably the resin with the highest content in the adhesive layer).

[0143] The post-heat treatment temperature is more preferably above -40°C and below -10°C of the melting point of the resin contained in the outer layer (preferably the resin with the highest content in the outer layer), and even more preferably above -30°C and below -10°C of the melting point of the resin contained in the outer layer (preferably the resin with the highest content in the outer layer).

[0144] Furthermore, the post-heating treatment temperature is preferably higher than the heating temperature during hot lamination, more preferably 10°C or more above the heating temperature during hot lamination, and even more preferably 20°C or more above the heating temperature during hot lamination.

[0145] From the perspective that the resin contained in the adhesive layer can be melted and the multilayer film can be heated for a long time so that the film resin can penetrate into the base fabric fibers, thereby suppressing the decrease in scratch resistance and suppressing the increase in ring stiffness, the above-mentioned post-heat treatment time is preferably 0.5 to 10 minutes, more preferably 1 to 5 minutes, and even more preferably 2 to 4 minutes.

[0146] (Airbag)

[0147] The multilayer composite for airbags of this embodiment can be used as an airbag. The airbag preferably comprises a composite of the multilayer film and a synthetic fiber fabric (base fabric). In the airbag, it is preferable to laminate the adhesive layer of the multilayer film with the synthetic fiber fabric.

[0148] The aforementioned airbags can be used as front airbags, side airbags, side curtain airbags, and exterior airbags in vehicles. Among these, side curtain airbags, in addition to protecting passengers from the impact of a side collision, also require the function of preventing passengers from being ejected from the side roof panel during a rollover. Therefore, side curtain airbags require the ability to instantly seal the entire side roof panel and maintain an inflated state for a longer period than front airbags. Airtightness is a given, and it is also desirable to further improve the adhesion strength between the barrier material and the base fabric. The multilayer film of this invention is more suitable for use as such barrier material.

[0149] Example

[0150] The present invention will be described below through examples. However, the present invention is not limited to the following examples.

[0151] (raw material)

[0152] The raw materials used in the examples and comparative examples and their markings are shown below. Additionally, the glass transition temperature (sometimes described as Tg) and melting point (sometimes described as Tm) of each raw material are values ​​obtained using a dynamic viscoelasticity analyzer and DSC described later.

[0153] <Adhesive Layer>

[0154] (resin)

[0155] CoPA1: Trade name "Ube Nylon 7128B" (manufactured by Ube Industries) copolyamide 6 / 12 (Tg=47℃, Tm=128℃)

[0156] m-PE: Trade name "Admer NF587" (Mitsui Chemicals) acid-modified polyethylene (Tg = -24℃, Tm = 121℃)

[0157] (additive)

[0158] The additives added to the adhesive layer are shown below. It should be noted that, when adding to the resin, a masterbatch containing 5% by mass of the additive is first melt-blended and granulated using a Toshiba Machine-manufactured twin-screw extruder "TEM-18SS" at 180°C and 100 rpm. This prepared granule (masterbatch) is then dry-blended with the resin. Subsequently, a multilayer film is formed using the method described later via blow molding.

[0159] • Anti-blocking agent (AB agent): Trade name "Silton JC-70" (manufactured by Mizusawa Chemical), ingredient: sodium calcium aluminum silicate, shape: spherical, average particle size: 7μm

[0160] • Crystallization nucleating agent (NA agent): Trade name "Micro Ace P-8" (manufactured by Japanese talc), ingredient: talc, shape: flakes, average particle size: 3.3μm

[0161] <Intermediate Layer>

[0162] m-PE: Trade name "Admer NF587" (Mitsui Chemicals) acid-modified polyethylene (Tg = -24℃, Tm = 121℃)

[0163] <Outer layer>

[0164] TPAE: Trade name "UBESTA XPA 9063F1" (manufactured by Ube Industries, Ltd.) High melting point thermoplastic polyamide elastomer (Tg = 24℃, Tm = 172℃)

[0165] CoPA4: Trade name "NAV503X10" (manufactured by Ube Industries, Ltd.) Copolymer polyamide 6 / 66 (Tg=43℃, Tm=190℃)

[0166] The methods for determining each physical property are explained below.

[0167] (Melting point)

[0168] A 150μm thick sheet was produced using a Toyo Seiki Manufacturing Co., Ltd. compression molding machine, "P2-30T-400". The melting point was determined using a DSC (Perkin Elmer "Diamond DSC") at a heating rate of 10℃ / min. It should be noted that the samples were taken under the following compression molding conditions.

[0169] (Glass transition temperature)

[0170] A 0.9 mm thick sheet was produced using a molding machine “P2-30T-400” manufactured by Toyo Seiki Co., Ltd. The loss tangent tanδ was measured using a dynamic viscoelasticity tester (Anton-Paar “MCR301”), and the peak temperature of the loss tangent tanδ was taken as the glass transition temperature.

[0171] • Measurement mode: Torsion (Measurement accessory: SRF10)

[0172] • Sample: Thickness = 0.9mm, Width = 10mm, Measurement span = 38mm

[0173] • Normal force: -0.3N

[0174] • Swing angle: 0.1%

[0175] • Frequency: 1Hz

[0176] • Heating rate: 2℃ / minute

[0177] (The ratio of the unfolded area of ​​the interface (Sdr1 / Sdr2))

[0178] After measuring the three-dimensional data of the membrane surface and the base fabric surface using a non-contact three-dimensional measuring machine (Hyper Quick Vision: manufactured by Mitutoyo), the corrugation curves of the multilayer membrane surface and the base fabric surface were calculated using cutoff values ​​(λc = 200 μ, λf = 500 μ). Then, the interfacial unfolded area ratio (Sdr1) of the multilayer membrane surface and the interfacial unfolded area ratio (Sdr2) of the base fabric surface were calculated according to JIS B 0681-6 (2014). Sdr1 / Sdr2 was evaluated according to the following criteria.

[0179] It should be noted that the multilayer film surface refers to the surface of the composite material that is opposite to the base fabric side and is a multilayer film. Figure 1 Additionally, the base fabric side refers to the surface of the composite material that is opposite to the multilayer film side and is the base fabric. Figure 1 The more closely the multilayer film follows the shape of the base fabric surface, the closer the values ​​of Sdr1 and Sdr2 will be. Figure 1 (b)). It should be noted that, Figure 1 (a) is a microscopic image obtained by embedding an encapsulant on a cross section of a multilayer composite for airbags in any thickness direction.

[0180] -Benchmark-

[0181] ◎(Excellent): Sdr1 / Sdr2 is above 0.988

[0182] 〇 (Good): Sdr1 / Sdr2 is above 0.986 and less than 0.988

[0183] × (Defective): Sdr1 / Sdr2 < 0.986

[0184] (Scratch resistance)

[0185] The test was conducted according to ISO 5981 using a scratch tester (manufactured by Imoto Manufacturing Co., Ltd.). The number of tests was counted when the multilayer film began to peel off from the multilayer composite of the airbag in the examples and comparative examples. Each sample was tested four times, and the average value was calculated.

[0186] <Specifications and test conditions of the scratch tester>

[0187] • Test load foot (fatted) (10mm wide) = 5N, additional load = 10N

[0188] • Round trip speed: 2.3 times / second

[0189] • Sample conditioning: 23℃-50%RH-24 hours or more

[0190] • Test environment: 23℃-50%RH

[0191] Criteria for determining the number of scratches (average)

[0192] × (Range): 0 or more, less than 500

[0193] △ (Difference): More than 500 times but less than 1000 times

[0194] 〇 (Good): More than 1000 times but less than 1500 times

[0195] ◎(Excellent): 1500 times or more

[0196] The more times it is scratched, the less likely the base fabric and the multilayer film are to peel off during friction, and the better the abrasion resistance.

[0197] (Length of the gap between the membrane and the base fabric)

[0198] The composites obtained in the examples and comparative examples were subjected to [the following conditions] along the thickness direction. Figure 6 Cuttings were made at positions A-A' and B-B' as shown, and the cross-sections were observed using SEM. The length of the gap between the multilayer film and the base fabric in the cross-section was evaluated based on the following criteria.

[0199] -Benchmark-

[0200] The average of the void lengths at section A-A' and section B-B' is taken as the void length of the composite.

[0201] ◎(Excellent): The pore length of the complex is less than 2μm

[0202] 〇 (Good): The porosity of the complex is greater than 2 μm and less than 6 μm.

[0203] × (Difference): The porosity of the complex is greater than 6 μm.

[0204] In addition, the gap length between the multilayer film and the base fabric was determined by the above-mentioned cross-section using the following method.

[0205] The distance in the thickness direction between the base fabric and the multilayer film at the interface between the base fabric and the adhesive layer ( Figure 2The length of the gap 4 between the multilayer film 2 and the base fabric 3 was measured. That is, when there is no gap, the distance is 0; when there is a gap, only the length of the gap in the thickness direction is measured. For a length of 10 mm in the direction orthogonal to the thickness direction of the cross section, the above distance was measured continuously, and the arithmetic mean was taken as the gap length between the multilayer film and the base fabric. The gap length in the A-A' section and the gap length in the B-B' section were measured. Furthermore, the average of the gap length in the A-A' section and the gap length in the B-B' section was taken as the gap length of the composite. The results are recorded in Tables 1 and 2.

[0206] (Ring stiffness)

[0207] Five samples of the multilayer composite for airbags obtained in the examples and comparative examples were taken, each with a TD direction (weft direction of Ny66 base fabric) of 20 mm and an MD direction (warp direction of Ny66 base fabric) of 120 mm. These samples were placed on the sample stage in a ring stiffness tester (Toyo Seiki) with the multilayer film side as the outer side of the ring, and the flattening stress of the 30 mm ring was measured (refer to...). Figure 5 It should be noted that the ring stiffness value is calculated by taking the average value of the 5 pieces measured at different positions and converting it to a width of 1 cm.

[0208] <Measurement Conditions>

[0209] • Sample conditioning: 23℃, 50%RH, for more than 24 hours

[0210] • Test environment: 23℃, 50% RH

[0211] Sample dimensions: 20mm wide × 120mm long

[0212] Measurement speed: 3.3 mm / second

[0213] <Evaluation Criteria>

[0214] ◎(Excellent): Less than 250mN / cm

[0215] 〇 (Good): Above 250mN / cm and less than 300mN / cm

[0216] △(Difference): Above 300mN / cm and less than 350mN / cm

[0217] × (Poor): Above 350mN / cm

[0218] [Membrane 1]

[0219] The layer structure is a multilayer film consisting of three layers: outer layer / intermediate layer / adhesive layer = 20 / 70 / 10. The adhesive layer uses CoPA1 mixed with the above-mentioned additives, the intermediate layer uses m-PE, and the outer layer uses CoPA4. It is extruded using a multilayer annular die and blown into shape. Figure 3 Three types of three-layer multilayer films with thicknesses ranging from 10 to 40 μm were obtained. The film preparation conditions are as follows.

[0220] • Die head temperature setting: 210℃

[0221] • Annular die head: Die lip outline = 95mm, die lip gap = 3mm

[0222] • Blow-up ratio: 1.1 times

[0223] • Ambient air temperature: 22℃

[0224] • Film surface temperature near the pinch roller: 32℃

[0225] • Distance between the annular die head and the pinch rollers: 2.4m

[0226] • Traction speed: 12m / min

[0227] [Membrane 2]

[0228] The layer is composed of two types of two-layer multilayer films with "outer layer / adhesive layer = 20 / 80". Here, the adhesive layer uses m-PE mixed with the above-mentioned additives, and the outer layer uses TPAE. The two types of two-layer multilayer films with a thickness of 30μm are obtained by extrusion using a multi-layer annular die and by blow molding.

[0229] [Base 1]

[0230] Base fabric material (Nylon 66), total fineness 470 dtex, fiber density (50 threads / inch in diameter, 50 threads / inch in weft), cover factor 2060

[0231] [Kibb 2]

[0232] Base fabric material (Nylon 66), total fineness 230 dtex, fiber density (72 threads / inch in diameter, 72 threads / inch in weft), cover factor 2070

[0233] [Base 3]

[0234] Base fabric material (polyester), total fineness 550 dtex, fiber density (51 threads / inch in diameter, 51 threads / inch in weft), cover factor 2270

[0235] [Example 1]

[0236] Using the above-described film 1 (10 μm thick) and the above-described base fabric 1, they are overlapped such that the surface of the base fabric is opposite to the adhesive layer of the above-described film 1, and then laminated using a hot roller laminator. Figure 4 The multilayer film is bonded to the silicone rubber roller side to obtain a laminate. The thermal lamination conditions at this time are as follows.

[0237] Temperature: 160℃

[0238] Linear voltage: 15N / cm

[0239] Roller speed: 3m / min

[0240] Next, after cooling the obtained laminate to room temperature, it was subjected to post-heat treatment at 190°C for 3 minutes in a precision fine oven (DH62: manufactured by YamatoScience) to obtain a multilayer composite, which was then evaluated. The results are shown in Table 1.

[0241] [Example 2]

[0242] Except for using a 20 μm thick membrane 1, a multilayer composite was obtained in the same manner as in Example 1.

[0243] [Example 3]

[0244] Except for using a 30 μm thick membrane 1, a multilayer composite was obtained in the same manner as in Example 1.

[0245] [Example 4]

[0246] In addition to using a 30 μm thick membrane 2, a multilayer composite was obtained in the same manner as in Example 1.

[0247] [Comparative Example 1]

[0248] Except for not performing post-heating treatment, a multilayer composite was obtained in the same manner as in Example 1.

[0249] [Comparative Example 2]

[0250] Except for not performing post-heating treatment, a multilayer composite was obtained in the same manner as in Example 2.

[0251] [Comparative Example 3]

[0252] Except for not performing post-heating treatment, a multilayer composite was obtained in the same manner as in Example 3.

[0253] [Comparative Example 4]

[0254] In addition to using a 40 μm thick membrane 1, a multilayer composite was obtained in the same manner as in Comparative Example 1.

[0255] [Comparative Example 5]

[0256] Using a 40 μm thick film 1, the roller speed during hot lamination was 0.3 m / min, and the post-heat treatment conditions were 150°C for 3 minutes. Otherwise, the multilayer composite was obtained in the same manner as in Example 1.

[0257] [Comparative Example 6]

[0258] Except for using a 30 μm thick membrane 2 and not performing post-heat treatment, a multilayer composite was obtained in the same manner as in Example 5.

[0259] [Comparative Example 7]

[0260] In addition to using a 40 μm thick membrane 1, a multilayer composite was obtained in the same manner as in Example 1.

[0261] [Example 5]

[0262] Using the aforementioned membrane 1 (20 μm thick) and the aforementioned base fabric 1, the layers are overlapped such that the surface of the base fabric is opposite to the aforementioned adhesive layer of the membrane 1, and hot-pressed using a Lab Press (P2-30T-400: Toyo Seiki) to obtain a multilayer composite. The hot-pressing conditions at this time are as follows.

[0263] Temperature: 170℃

[0264] Surface pressure: 5 N / cm 2

[0265] Time: 0.5 minutes

[0266] [Example 6]

[0267] Except for setting the hot-pressing time to 1 minute, a multilayer composite was obtained in the same manner as in Example 5.

[0268] [Example 7]

[0269] Except for using a 30 μm thick membrane 1, a multilayer composite was obtained in the same manner as in Example 5.

[0270] [Example 8]

[0271] In addition to setting the hot pressing conditions to a temperature of 170℃ and a surface pressure of 18 N / cm, 2 In addition to the time of 0.3 minutes, a multilayer composite was obtained in the same manner as in Example 5.

[0272] [Comparative Example 8]

[0273] A 40 μm thick film 1 was used, and the hot-pressing conditions were: temperature 170 °C and surface pressure 5 N / cm². 2 The time was 1 minute, and otherwise the same as in Example 5, a multilayer composite was obtained.

[0274] [Comparative Example 9]

[0275] In addition to setting the hot pressing conditions to a surface pressure of 18 N / cm 2 In addition to a time of 1 minute, a multilayer composite was obtained in the same manner as in Comparative Example 8.

[0276] [Comparative Example 10]

[0277] Except for setting the hot pressing time to 2 minutes, a multilayer composite was obtained in the same manner as in Comparative Example 9.

[0278] [Example 9]

[0279] Except that base fabric 2 is used instead of base fabric 1, a multilayer composite is obtained in the same manner as in Example 2.

[0280] [Example 10]

[0281] Except that base fabric 3 is used instead of base fabric 1, a multilayer composite is obtained in the same manner as in Example 2.

[0282] The multilayer composites obtained in the examples and comparative examples were evaluated, and the results are shown in Tables 1, 2 and 3.

[0283]

[0284]

[0285] [Table 3]

[0286]

[0287] As shown in Tables 1-3, a composite with improved scratch resistance was obtained when the Sdr1 / Sdr2 ratio was in the range of 0.986 to 1.1. Furthermore, a composite that balances scratch resistance and flexibility was obtained when the multilayer film thickness was in the range of 10-30 μm.

[0288] Industrial applicability

[0289] The multilayer composite for airbags of the present invention has excellent scratch resistance and flexibility, and therefore can be appropriately used for airbag applications.

[0290] Explanation of symbols

[0291] 1. Multi-layer composite for airbags

[0292] 2···· Multilayer film

[0293] 21···Outer layer

[0294] 22···Other layers

[0295] 23··· Adhesive Layer

[0296] 3···· Base

[0297] 31··· Monofilament

[0298] 4···· Gap

[0299] 51··· Multi-layer mold head

[0300] 52···Air Ring

[0301] 53···Exhaust Device (Free Roller)

[0302] 54···First pinch drive roller

[0303] 55···Guide Roller (Free Roller)

[0304] 56···Second pinch drive roller

[0305] 57···Contact Roller (Free Roller)

[0306] 58··· Winding drive roller

[0307] 61··· Pressure Roller (Silicone Rubber Lining Processing)

[0308] 62··· Metal heating roller (mirror finish)

[0309] 71··· Pressure Head

[0310] 72···Clipping with Ring Stiffness

[0311] 73···Sample Stage

Claims

1. A multilayer composite for airbags, comprising a base fabric and a multilayer film including an outer layer and an adhesive layer bonded to one surface of the base fabric, characterized in that, The ratio of the interfacial unfolded area ratio Sdr1 of the multilayer membrane side surface of the airbag multilayer composite to the interfacial unfolded area ratio Sdr2 of the base fabric side surface of the airbag multilayer composite, Sdr1 / Sdr2, is 0.986 to 1.

1.

2. The multilayer composite for airbags as described in claim 1, wherein, The thickness of the multilayer film is 10 μm to 30 μm.

3. The multilayer composite for airbags as described in claim 1 or 2, wherein, The void length of the composite between the multilayer film and the base fabric is less than 6 μm.

4. The multilayer composite for airbags as described in claim 1 or 2, wherein, The adhesive layer comprises a polyamide resin.

5. The multilayer composite for airbags as described in claim 1 or 2, wherein, The outer layer comprises a polyamide resin.

6. The multilayer composite for airbags as described in claim 1 or 2, wherein, The ratio of Sdr1 to Sdr2 is 0.988 to 1.

08.

7. The multilayer composite for airbags as described in claim 1 or 2, wherein, The average thickness of the outer layer is 20% to 400% of the average thickness of the adhesive layer.

8. The multilayer composite for airbags as described in claim 1 or 2, wherein, The total fineness of the fibers constituting the base fabric is 100 dtex to 570 dtex.

9. The multilayer composite for airbags as described in claim 1 or 2, wherein, The total fineness of the fibers constituting the base fabric is 210 dtex to 490 dtex.

10. The multilayer composite for airbags as described in claim 3, wherein, The gap length is less than 4 μm.

11. A method for manufacturing a multilayer composite for an airbag according to any one of claims 1 to 10, characterized in that, It includes a heat lamination process, in which a base fabric and a multilayer film comprising an outer layer and an adhesive layer are laminated by heat lamination on one surface of the base fabric, and the adhesive layer is stacked thereon.

12. A method for manufacturing a multilayer composite for airbags, characterized in that, The manufacturing method of the multilayer composite for airbags according to any one of claims 1 to 10 includes the following steps: The hot lamination process involves heat-laminating a base fabric with a multilayer film comprising an outer layer and an adhesive layer, stacking the adhesive layer on one surface of the base fabric; and The post-heating process involves heating again after the heat lamination process.

13. The method for manufacturing a multilayer composite for airbags as described in claim 12, wherein, The temperature of the post-heat treatment is 10°C or higher than the heating temperature during the heat lamination.

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