Multilayer composite for airbag and airbag

Abstract

The present disclosure provides: a multilayer composite for airbags having excellent durability by controlling the softness and the adhesion between the adhesive layer and the base fabric within a specific range; and an airbag using the multilayer composite for airbags. The multilayer composite for airbags of the present invention comprises: a base fabric; and a multilayer film, which includes an outer layer and an adhesive layer bonded to one surface of the base fabric, characterized in that the bonding strength at the interface between the multilayer film and the base fabric is 5 N / cm or more, and the difference in ring stiffness between the multilayer composite for airbags and the base fabric is 130 mN / cm or less, the adhesive layer comprises a first resin having hydrogen bonding ability, and the difference in Hansen solubility parameter (△HSP) between the base fabric and the first resin is 5 MPa 0 . 5 the following.

Description

Technical Field

[0001] The present disclosure relates to a multilayer composite used in an airbag for protecting passengers in a vehicle or the like (hereinafter referred to as a multilayer composite for airbags) and an airbag using the multilayer composite for airbags. More specifically, it relates to a multilayer composite for airbags having excellent airtightness, adhesion and durability, wherein a multilayer film is laminated on the surface of a synthetic fiber, and an airbag using the multilayer composite for airbags. Background Art

[0002] In order to protect passengers from impact, various forms of airbags installed in vehicles and the like have been put into practical use. For example, as airbags for dealing with head-on collisions, there are front airbags and knee airbags for protecting the head and legs of passengers. In addition, as airbags for dealing with collisions from the side, there are side airbags for protecting the torso of passengers. In addition, side curtain airbags for protecting the head of passengers and preventing them from being thrown out of the vehicle when the vehicle rolls over have also been put into use. And, with the increase in awareness of safety, various airbags like these have become popular.

[0003] In addition, the performance required of these airbags varies depending on the assumed dangerous conditions. For example, a front airbag only needs to continue to inflate for a moment during a collision, while a side curtain airbag needs to continue to inflate for a longer period of time to prevent the vehicle from being thrown out of the vehicle during a rollover. Therefore, the multilayer composite for the airbag itself is required to have higher airtightness.

[0004] Generally, a multilayer composite for an airbag is composed of a base fabric (e.g., a synthetic fiber layer composed of synthetic fibers) and an airtight layer. The base fabric is a layer that serves as a support, and is used to maintain a specific three-dimensional structure after the bag-shaped cushion that was previously stored in a folded state during a collision is unfolded. In view of the aspects of softness, strength, heat resistance, and flame retardancy, synthetic fibers made of polyamide fibers or polyester fibers are used in this layer. However, the base fabric composed of these synthetic fibers itself lacks airtightness, and therefore it is difficult for the folded cushion to be quickly unfolded and continuously inflated for the required time. Therefore, in order to make it airtight, it usually has a structure in which an airtight layer is formed on one surface of the base fabric.

[0005] As related technologies of such airtight layers, for example, there are coating-type airbag multilayer composites coated with a thermosetting silicone film and film-laminated airbag multilayer composites coated with a resin film. The present disclosure relates to the latter multilayer film for airbags laminated with a resin film, and related technologies are disclosed in Patent Documents 1 and 2.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2000-296748

[0009] Patent Document 2: European Patent Application Publication No. 1518761 Summary of the invention

[0010] Problems to be solved by the invention

[0011] In the technologies of Patent Documents 1 and 2, a multilayer composite for an airbag is formed by a film laminate coated with a resin film, so that a large and large equipment (such as inflation molding) is not required in the manufacture of the resin film. In addition, even when the base fabric is subjected to a heat lamination process of the resin film, it can be processed with relatively simple equipment and the processing speed is also high, so that the manufacturing from the film manufacturing process to the heat lamination process can be carried out at a low cost.

[0012] However, in the multilayer film consisting of an outer layer and an adhesive layer disclosed in Patent Document 1, an acid-modified polyolefin is used in the adhesive layer. However, the adhesive layer lacks affinity with polyamide fibers or polyester fibers, and the bonding strength at the interface between the adhesive layer and the base fabric is reduced. Therefore, when the airbag is rapidly inflated (also called deployed), the interface between the adhesive layer and the base fabric is easily peeled off.

[0013] In addition, Patent Document 2 discloses a technology for using a low melting point polyamide elastomer composed of polyamide 12 (hard segment) and polyether (soft segment) in the adhesive layer of a multilayer film. This technology improves the affinity between the base fabric and the adhesive layer, but in order to lower the melting point of the adhesive layer (for example, below 150° C.), it is necessary to relatively increase the copolymerization ratio of the polyether, so there is still room for improvement from the perspective of durability.

[0014] As a specific example of durability, for example, when a vehicle is used continuously for more than 10 years, the airbag mounted on the vehicle will be repeatedly subjected to vibration, friction, and thermal shock, which are causes of fatigue. Along with this, the bonding strength between the base fabric and the multilayer film of the multilayer composite for the airbag decreases over time, and there is a tendency to peel off easily during deployment. As one of the evaluation methods for the tolerance of such repeated loads, that is, durability, a scratch test can be cited. The scratch test refers to the following load test method: the number of times the coating layer or resin film (also called multilayer film) is peeled off or damaged from the base fabric is evaluated by repeatedly stretching and rubbing the multilayer composite of the airbag at the same time.

[0015] According to the durability evaluation based on the scratch test, it is difficult to obtain sufficient durability performance in the technologies of Patent Documents 1 and 2, especially in the OPW (One Peace Woven) type multilayer composite for airbags in which the airtight layer is provided on the outer layer of the base fabric. This is considered to be a problem that should be improved.

[0016] An object of the present disclosure is to provide a multilayer composite for an airbag having excellent durability by controlling the flexibility and the adhesion between an adhesive layer and a base fabric within a specific range, and an airbag using the multilayer composite for an airbag.

[0017] Means for solving problems

[0018] The present disclosure was completed in view of the above-mentioned problems. It was surprisingly found that the softness of the multilayer film, as a factor other than adhesion, has a great influence on durability. It was further found that the durability can be improved by balancing the softness of both the multilayer film and the base fabric within a specific range, thereby completing the following present disclosure.

[0019] [1] The present disclosure relates to a multilayer composite for an airbag, comprising a base fabric and a multilayer film, wherein the multilayer film comprises an outer layer and an adhesive layer bonded to one surface of the base fabric, wherein the multilayer composite for an airbag is characterized in that the bonding strength at the interface between the multilayer film and the base fabric is greater than 5 N / cm, and the difference in ring stiffness between the multilayer composite for an airbag and the base fabric is less than 130 mN / cm, and the adhesive layer comprises a first resin having hydrogen bonding ability, and the absolute value of the difference in Hansen solubility parameter (ΔHSP) between the base fabric and the first resin is 5 MPa 0.5 Below. (“△” stands for the Greek letter delta.)

[0020] [2] In the present embodiment, the first resin is preferably a polyamide copolymer of two or more selected from the group consisting of polyamide 6, polyamide 66, polyamide 610, polyamide 11, and polyamide 12 and / or a dimer acid-based polyamide.

[0021] [3] In the present embodiment, it is preferred that the glass transition temperature of the first resin is 20° C. or higher.

[0022] [4] In the present embodiment, the outer layer of the multilayer film preferably contains a second resin having a melting point 20° C. or higher than the melting point of the first resin contained in the adhesive layer.

[0023] [5] In the present embodiment, the second resin is preferably a polyamide-based copolymer or / and a thermoplastic polyamide elastomer, a thermoplastic polyester elastomer, or a thermoplastic polyurethane elastomer.

[0024] [6] In the present embodiment, it is preferred that an intermediate layer is provided between the outer layer and the adhesive layer of the multilayer film, the intermediate layer contains a third resin, and the third resin contains a polar polyolefin-based resin.

[0025] [7] In the present embodiment, the average thickness of the multilayer film is preferably 40 μm or less.

[0026] [8] In this embodiment, the base fabric is preferably made of polyamide fiber.

[0027] [9] The present disclosure relates to an airbag using the multilayer composite for an airbag having a multilayer film joined thereto as described in any one of [1] to [8].

[0028] Effects of the Invention

[0029] According to the present disclosure, by controlling the flexibility and the adhesiveness at the interface between the adhesive layer and the base fabric within a specific range, a multilayer composite for an airbag having excellent durability can be provided.

[0030] According to the present disclosure, by using a multilayer composite for an airbag having excellent durability, it is possible to reduce the weight of the airbag. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a schematic diagram showing a ring stiffness test.

[0032] Figure 2 It is a schematic diagram showing the adhesive strength test.

[0033] Figure 3 This is a schematic diagram showing a method for forming a multilayer film.

[0034] Figure 4 This is a schematic diagram showing a method for producing a multilayer composite for an airbag. DETAILED DESCRIPTION

[0035] Modes for carrying out the present disclosure will be described in detail below, but the present disclosure is not limited to the following embodiments and examples, and can be arbitrarily modified within the scope of the gist and equivalent scope of the present disclosure.

[0036] "Multilayer composite for airbag"

[0037] The multilayer composite for airbags disclosed in the present invention comprises a base fabric and a multilayer film, wherein the multilayer film comprises an outer layer and an adhesive layer bonded to one surface of the base fabric. Furthermore, the adhesive strength at the interface between the multilayer film and the base fabric is 5 N / cm or more, the difference in ring stiffness between the multilayer composite for airbags and the base fabric is 130 mN / cm or less, and the absolute value of the difference in Hansen solubility parameter (ΔHSP) of the first resin having hydrogen bonding ability contained in the adhesive layer between the base fabric and the multilayer film is 5 MPa. 0.5 As follows. Thus, a multilayer composite for airbags having excellent durability can be provided. It should be noted that in this specification, the multilayer composite for airbags is also simply referred to as a "multilayer composite".

[0038] The multilayer composite for airbags of the present embodiment is a film body having a base fabric (eg, synthetic fiber) and a multilayer film coated on one surface of the base fabric. The airbag of the present embodiment is preferably a bag body formed of the multilayer composite for airbags.

[0039] The multilayer film of this embodiment is composed of at least two layers, wherein a layer bonded (or joined) to the base fabric in the multilayer composite for airbags is referred to as an "adhesive layer", and the other layer is referred to as an "outer layer". In addition, the "outer layer" corresponds to a layer exposed on the outside of the airbag. It should be noted that the expression "00 to □□" indicating a range means greater than 00 and less than □□.

[0040] In the multilayer composite for airbags of the present embodiment, by heating the multilayer film on at least one surface of the base fabric (eg, synthetic fiber), the adhesive layer can be melted and firmly bonded to the surface of the base fabric.

[0041] In the present embodiment, the bonding strength at the interface of multilayer film and base cloth is shown as more than a specific value, so that multilayer film is not easy to peel off from base cloth, so the durability as an air bag can be exerted. In this case, the lower limit of the bonding strength at the interface of multilayer film and base cloth is preferably more than 5N / cm, more preferably more than 6N / cm, and further preferably more than 7N / cm. In addition, the upper limit of the bonding strength at the interface of multilayer film and base cloth is not particularly limited, for example, preferably below 20N / cm. About the preferred range of this bonding strength, the above-mentioned lower limit and upper limit can be combined arbitrarily respectively. In addition, because the fracture strength of multilayer film is lower than bonding strength, the thinner the multilayer film is, the more the bonding strength shows the tendency of reduction in appearance.

[0042] The "bonding strength" in this specification refers to the peeling strength when the multilayer film coated on the surface of the base fabric peels off from the base fabric. Specifically, a sample of a multilayer composite for airbags in which the multilayer film and the base fabric are bonded is produced by partially applying a specific temperature, pressure, and time while the base fabric and the multilayer film overlap. A sample with a width of 10 mm and a length of 80 mm is cut out from the multilayer composite for airbags. In a tensile testing machine, the distance between the chucks is set to 30 mm. The multilayer film part and the base fabric part are gripped with chucks in such a way that the bonding part of the sample is in the center of the chucks. The bonding strength is measured at a peeling speed (tensile speed) of 5 mm / min. The bonding strength refers to the 180° T-type peeling strength measured above. The detailed conditions and methods for the bonding strength measurement are as follows: Figure 2 method.

[0043] As the dominant factor of the above-mentioned bonding strength, for example, the chemical combination of (a) base fabric and adhesive layer, (b) contact area of ​​base fabric and adhesive layer, (c) anchoring effect shown by infiltrating into the monofilaments of the fiber bundle constituting the weft and warp, etc. Specifically, about (a), the chemical combination can be controlled by using a resin with hydrogen bonding ability or / and implementing corona treatment, plasma treatment, substrate treatment, etc. In addition, about (b) and (c), the melt viscosity of the hot lamination processing temperature, speed, pressure, and resin can be controlled. By optimizing these conditions, the bonding strength at the interface of multilayer film and base fabric can be shown as more than a specific value. In a preferred example of the present embodiment, as described below, by focusing on various resins with hydrogen bonding ability, limiting the solubility parameters of base fabric and adhesive layer, the difference of bonding strength and ring stiffness is controlled in a specific range.

[0044] In the present embodiment, by making the difference between the hoop stiffness of the overall multilayer composite for airbags and the hoop stiffness of the base fabric used in the multilayer composite for airbags be below a specific value, the softness of the multilayer film to repeated loads is increased, thereby improving the followability of the base fabric to expansion and contraction, resulting in durability that can be used for practical purposes.

[0045] The durability of the multilayer composite for airbags, which is the subject of the present disclosure, has been studied intensively, and the results show that the softness of the multilayer film has a great influence on the durability (scratch resistance). The "softness" mentioned here refers to the relative difference between the multilayer film and the base fabric, and is expressed in the form of the difference between the "ring stiffness value of the multilayer composite for airbags" and the "ring stiffness value of the base fabric alone" obtained by the ring stiffness measurement method described later.

[0046] In addition, the lower limit of the difference in ring stiffness between the multilayer composite for airbags and the base fabric is preferably close to 0, and more preferably, for example, greater than 0 mN / cm. In addition, from the perspective of scratch resistance and flexibility, the upper limit of the difference in ring stiffness between the multilayer composite for airbags and the base fabric is preferably 130 mN / cm or less, more preferably 120 mN / cm or less, and further preferably 110 mN / cm or less.

[0047] The "ring stiffness" in this specification refers to the stress required to compress a sample of a membrane such as a film by a certain amount along the diameter direction of the ring after bending it into a ring. The stiffness of the membrane is evaluated by the value of the ring stiffness. In this specification, a ring stiffness tester (manufactured by Toyo Seiki) is used. The sample width is 20 mm and the sample length is 150 mm. The measurement is performed at a compression speed of 3.3 mm / sec to measure the stress required to flatten the ring by 30 mm. The detailed conditions for the ring stiffness measurement are described in the Examples section and Figure 1 method.

[0048] For example, if the conditions such as the (d) thickness of the multilayer film is 40 μm or less (more preferably 35 μm or less, further preferably 30 μm or less) and the (e) tensile elastic modulus is 500 MPa or less (more preferably 400 MPa or less, further preferably 300 MPa or less) are met, the difference between the ring stiffness of the multilayer composite for airbags as a whole and the ring stiffness of the base fabric used in the multilayer composite for airbags tends to be below a specific value.

[0049] The multilayer film and base fabric constituting the multilayer composite for an airbag will be described in detail below.

[0050] (Multilayer Film)

[0051] The multilayer film may be composed of at least two layers, an outer layer and an adhesive layer. In addition, the multilayer film may also be a three-layer structure of adhesive layer / intermediate layer / outer layer, in which an intermediate layer is provided between the outer layer and the adhesive layer. Alternatively, the multilayer film may be a four-layer or five-layer structure of adhesive layer / glue layer / intermediate layer / glue layer / outer layer, in which a glue layer is further provided between the adhesive layer and the intermediate layer and / or between the outer layer and the intermediate layer.

[0052] It should be noted that, of course, other layers other than the above may be further included.

[0053] In the multilayer film in the present embodiment, at least two layers of the outer layer and the adhesive layer constituting the multilayer film can be the same resin (one kind and two layers), or different resins (two kinds and two layers). In addition, in the embodiment in which an intermediate layer is provided between the outer layer and the adhesive layer, the three layers of adhesive layer / intermediate layer / outer layer can be the same resin, or different resins (three kinds and three layers). In addition, in the case where the embodiment is a five-layer structure of adhesive layer / glue layer / intermediate layer / glue layer / outer layer, the five layers can be the same resin, or different resins (five kinds and five layers).

[0054] It should be noted that as a method for measuring the layer ratio and average thickness of each layer of the above-mentioned multilayer film, in the case of a multilayer film, for example, two sheets formed by coating EVA adhesive on a polypropylene sheet with a thickness of 1 mm (size: 5 mm×10 mm) can be prepared, and the multilayer film can be sandwiched between the above-mentioned two sheets in a manner such that the EVA adhesive surface is on the inner side for integration, and 5μm to 10μm slices are collected using a microtome, the cross-section of the above-mentioned slices is enlarged using a polarizing microscope, and the thickness of the adhesive layer is measured using image analysis software.

[0055] Regarding the layer ratio and average thickness of a multilayer composite for airbags in which a multilayer film is bonded to the surface of a base fabric, the multilayer film is preferably separated from the base fabric and then calculated from the melting peak area (melting energy) of each layer according to the DSC measurement method described below.

[0056] (Adhesive layer)

[0057] The adhesive layer in this embodiment is a layer bonded to the surface of the base fabric, and more specifically, is a layer that is melted by the heat from the heating roller during the thermal lamination process and bonded to the surface of the base fabric. The adhesive layer in this embodiment contains a first resin having hydrogen bonding ability, and the absolute value of the difference in Hansen solubility parameter (ΔHSP) between the base fabric and the first resin is 5 MPa. 0.5 the following.

[0058] This improves the adhesion between the base fabric and the first resin, and thus it is possible to provide a multilayer composite for an airbag having excellent durability.

[0059] In the multilayer composite for airbags of the present embodiment, the absolute value (ΔHSP) of the difference between the Hansen solubility parameter (HSP) of the first resin and the Hansen solubility parameter (HSP) of the synthetic fiber constituting the base fabric is 5 MPa. 0.5 Below, preferably 4.5MPa 0.5 Below, more preferably 4.0MPa 0.5 Below. The unit of △HSP is MPa 0.5 By setting the ΔHSP to the above range, the compatibility between the adhesive layer and the base fabric is good, so that it is easy to satisfy the condition that the bonding strength at the interface between the multilayer film and the base fabric is 5 N / cm or more.

[0060] In this embodiment, the ΔHSP value is calculated using "Winmostar Version 9.3.0". That is, regarding the estimated value of HSP, the HSP value of the first resin (for example, polyamide copolymer (PA6 / 12)) and the HSP value of polyamide 66 fiber most preferably used as the material of the base fabric are estimated using "Winmostar Version 9.3.0" to determine the preferred range of ΔHSP.

[0061] In the present embodiment, the "Hansen Solubility Parameter (HSP) of the first resin" refers to the HSP of the first resin having hydrogen bonding ability.

[0062] The "Hansen Solubility Parameter (HSP) of synthetic fibers" in this specification refers to the HSP of synthetic fibers contained in the base fabric. In addition, when there are multiple types of synthetic fibers in the base fabric, the HSP of each fiber component (totaling 100 mass%) can be multiplied by the component ratio, and the total value can be used as the HSP.

[0063] The adhesive layer in this embodiment is composed of an adhesive layer component. And, the adhesive layer component contains a first resin and, if necessary, contains a resin A described later and / or various additives.

[0064] The glass transition temperature of the adhesive layer in this embodiment is preferably 0° C. to 80° C., more preferably 20° C. to 70° C., and even more preferably 30° C. to 60° C. This can exhibit the effects of blocking resistance and film formation stability.

[0065] In this specification, "the glass transition temperature of the adhesive layer is 0° C. to 80° C. inclusive" means that the glass transition temperature of the resin contained in the adhesive layer components, which is a component constituting the adhesive layer, is 0° C. to 80° C. inclusive. When there are multiple peaks of the glass transition temperature from the resin contained in the adhesive layer components, the peak temperature on the highest temperature side is taken as the glass transition temperature of the adhesive layer (=glass transition temperature of the component constituting the adhesive layer).

[0066] When the glass transition temperature of the adhesive layer is 0°C or higher, the outer layer of the film attached or wound on a roll and the adhesive layer can be prevented from sticking during the film forming process. On the other hand, when the glass transition temperature of the adhesive layer is 80°C or lower, the flexibility of the film and the lamination processing temperature range can be optimized.

[0067] In addition, from the perspective of adhesion to the base fabric, adhesion, and film forming stability of the film, the glass transition temperature of the first resin contained as a component of the adhesive layer is preferably above 0° C. The first resin in this embodiment may be a single resin or a mixture of a plurality of resins, or may be a mixture further blended with other polar components.

[0068] The glass transition temperature of the first resin is preferably 0 to 80° C., more preferably 20 to 70° C., and even more preferably 30 to 60° C. When the first resin having a glass transition temperature of 0° C. or higher is used in the adhesive layer, higher blocking resistance and film forming stability are achieved.

[0069] It should be noted that the above-mentioned glass transition temperature can be measured by the method described in the examples described later. In more detail, in the method for measuring the glass transition temperature of the adhesive layer, after making a sheet with a thickness of 0.9 mm from the adhesive layer components, a dynamic viscoelasticity measuring instrument (Anton-Paar "MCR301") is used to measure the loss tangent tanδ, and the peak temperature of the loss tangent tanδ is used as the glass transition temperature.

[0070] ·Measurement mode: Twist (measurement attachment: SRF10)

[0071] Sample: Thickness = 0.9 mm, Width = 10 mm, Measurement span = 38 mm

[0072] Normal force: -0.3N

[0073] Swing angle: 0.1%

[0074] Frequency: 1Hz

[0075] Heating rate: 2℃ / min

[0076] When there are plural first resins, the glass transition temperatures of the first resins may be approximately the same or different.

[0077] Furthermore, the adhesive layer component may contain a plurality of resins (for example, a polyamide-based resin or resin A described later), or the adhesive layer component may contain various additives.

[0078] The melting point of the first resin is preferably 100°C to 160°C, more preferably 110°C to 150°C, and further preferably 120°C to 140°C. By making the melting point above 100°C, the bonding strength with the base fabric can be maintained even in a high-temperature use environment, and the range of conditions such as temperature, pressure, time, etc. during lamination processing (also called process window) can be expanded, and a multilayer film with stable quality can be obtained. On the other hand, by making the melting point below 160°C, moderate softness can be obtained. It should be noted that the melting point can be measured by the method described in the embodiments described later. When the first resin is a plurality of species, the melting points of each first resin can be the same or different. In addition, when the first resin contains a plurality of species and has a plurality of melting peaks, the melting peak temperature on the high temperature side of the first resin is preferably 100°C to 160°C, and more preferably 110°C to 150°C.

[0079] In addition, the "first resin" in this specification refers to a resin having hydrogen bonding ability (amino group, amide bond, hydroxyl group, etc.).

[0080] In this embodiment, the adhesive layer or adhesive layer component may contain other resins (sometimes referred to as "resin A" in this specification) in addition to the first resin. The first resin and the resin A may be one or more.

[0081] The above-mentioned adhesive layer or adhesive layer component may be composed only of the first resin, or may further contain the above-mentioned resin A and / or the additives described later. Relative to the total amount of 100 mass% of the adhesive layer or the adhesive layer component, the first resin preferably contains 30 mass% or more, more preferably contains 40 mass% or more, further preferably contains 50 mass% to 100 mass%, and further preferably contains 60 mass% or more and 98 mass% or less.

[0082] The glass transition temperature of the above-mentioned first resin is preferably below 80°C, more preferably below 70°C, and further preferably below 60°C, and when it contains 30% by mass or more, more preferably 50% by mass or more, and further preferably 70% by mass or more relative to the adhesive layer (100% by mass), it can exhibit excellent flexibility and adhesive strength.

[0083] In the present embodiment, specific examples of the first resin include polyamide-based resins and polyurethane-based resins. From the viewpoint of hydrolyzability, the polyamide-based resins are preferably used.

[0084] As the polyamide resin, there can be mentioned two or more polyamide copolymers selected from polyamide 4 (hereinafter also referred to as PA4. In addition, other polyamides are also referred to in the form of PA numbers), polyamide 6 (PA6), polyamide 66 (PA66), polyamide 11 (PA11), polyamide 12 (PA12), polyamide 46 (PA46), polyamide 66 (PA66) and polyamide 610 (PA610), and / or dimer acid polyamide obtained using dimer acid as a raw material. From the aspects of flexibility and the temperature range of hot lamination processing, PA6 / 12 (copolymer of polyamide 6 and polyamide 12), PA6 / 66 / 12, PA6 / 66 / 610 / 12, and dimer acid polyamide are more preferred, and PA6 / 12 is more preferred.

[0085] In addition, among the above-mentioned PA6 / 12, from the aspects of adhesive strength, lamination processing suitability, and blocking resistance during film formation, a polyamide-based copolymer composed of 5% to 70% by mass of polyamide 6 and 95% to 30% by mass of polyamide 12 is preferred, and a polyamide-based copolymer composed of 10% to 60% by mass of polyamide 6 and 90% to 40% by mass of polyamide 12 is more preferred.

[0086] Examples of the polyamide-based resin include random copolymers, alternating copolymers, block copolymers, and graft copolymers, and block copolymers and random copolymers are more preferred.

[0087] On the other hand, as the urethane resin, a thermoplastic polyurethane elastomer is preferred from the viewpoint of flexibility, and among them, a polyether-based thermoplastic polyurethane having a relatively good hydrolyzability is preferred.

[0088] The content of each repeating unit in the polyamide resin can be determined by nuclear magnetic resonance ( 1 H-NMR, 13 The calculation is based on the integrated ratio of the spectrum measured by a C-NMR (carbon nanostructured magnetic resonance) measuring device.

[0089] In this embodiment, from the aspect of film forming properties, the viscosity index of the polyamide resin is preferably 50 ml / g to 200 ml / g, more preferably 80 ml / g to 180 ml / g, and further preferably 100 ml / g to 150 ml / g. It should be noted that the above viscosity index is a value obtained in accordance with ISO307, and is a viscosity index when the polyamide resin is dissolved in 96% sulfuric acid aqueous solution at 0.5% by mass.

[0090] In the above-mentioned adhesive layer, the first resin contained in the adhesive layer can be a mixed resin layer containing resin A described later in addition to the above-mentioned polyamide resin or polyurethane resin. The above-mentioned resin A can preferably include acid-modified polyolefins, ionomers, thermoplastic polyamide elastomers, etc. From the perspective of flexibility and adhesion under low temperature environments, it is preferred that the glass transition temperature is less than 0°C and the melting point is in the range of 80°C to 160°C. In addition, as the mass ratio of the above-mentioned resin A in the above-mentioned adhesive layer or adhesive layer component (100% by mass), from the perspective of adhesion, it is preferably 0% by mass to 70% by mass, more preferably 5% by mass to 60% by mass, and further preferably 10% by mass to 50% by mass.

[0091] In this embodiment, the adhesive layer or adhesive layer components may appropriately include various additives such as organic solvents, anti-blocking agents, lubricants, crystal nucleating agents, flame retardants, antistatic agents, antioxidants, ultraviolet absorbers, light stabilizers, colorants, fillers, etc. within a range that does not impair practical properties.

[0092] Examples of the anti-blocking agent include organic particles such as cross-linked polystyrene, cross-linked acrylic (PMMA) resin, and fluorine (PTFE) particles, and inorganic particles such as silicon oxide particles, kaolin, and calcium carbonate. Examples of the crystal nucleating agent include talc, alumina, kaolin, and high melting point polyamides (e.g., polyamides with a melting point greater than 160° C.). Examples of the lubricant include aliphatic amides, metal soaps, and ultra-high molecular weight silicones.

[0093] The mass ratio of the additive in the adhesive layer or adhesive layer component (100 mass %) is preferably 20 mass % or less, more preferably 10 mass % or less, and further preferably 5 mass % or less, from the viewpoint of adhesiveness.

[0094] From the viewpoint of adhesive strength and flexibility, the average thickness of the adhesive layer in the present embodiment is preferably 1 μm to 20 μm, more preferably 2 μm to 15 μm, and even more preferably 3 μm to 10 μm.

[0095] As a method for measuring the average thickness of the adhesive layer in this specification, in the case of a multilayer film, for example, two sheets formed by coating an EVA adhesive on a polypropylene sheet (size: 5 mm×10 mm) with a thickness of 1 mm can be prepared, and the multilayer film can be integrated by sandwiching the multilayer film between the two sheets with the EVA adhesive surface facing the inside, and 5 μm to 10 μm slices are collected using a microtome, the cross-section of the slices is enlarged using a polarizing microscope, and the thickness of the adhesive layer is measured using image analysis software.

[0096] In the case of an airbag multilayer composite, the layer ratio in the multilayer film can be determined from the melting point peak area (melting energy) derived from the adhesive layer by the DSC measurement method described below.

[0097] (Outer layer)

[0098] The outer layer in this embodiment is a layer facing the adhesive layer, and is a layer corresponding to the outermost surface of the airbag. In addition, from the perspective of preventing fusion during hot lamination and suppressing pinholes, the outer layer is preferably composed of a resin having a melting point higher than that of the adhesive layer. Specifically, the outer layer in this embodiment preferably contains a second resin having a melting point higher than that of the first resin contained in the adhesive layer by 20°C or more, more preferably 30°C or more, and even more preferably 40°C or more.

[0099] The melting point of the second resin is preferably 170°C to 240°C, more preferably 180°C to 230°C or less, and further preferably 190°C to 220°C. By making the melting point above 170°C, which is 20°C or more higher than the melting point of the adhesive layer or the first resin, welding and pinholes during heat lamination can be suppressed. In addition, by making the melting point of the second resin below 240°C, a moderate melt tension can be obtained during film manufacturing, and stable film making can be achieved. It should be noted that the melting point can be measured by the above method and the method described in the embodiments described below. In addition, the second resin, like the first resin, can be a single resin or a mixture of multiple resins, or a mixture further blended with other polar components. When the second resin is multiple, the melting points of each second resin can be the same or different. When the second resin includes a plurality of types and has a plurality of melting peaks, the melting peak temperature on the high temperature side of the second resin is preferably 170°C to 240°C, more preferably 180°C to 230°C.

[0100] The glass transition temperature of the second resin is more preferably 80°C or less, further preferably 70°C or less, and further preferably 60°C or less. When a second resin having a glass transition temperature of 80°C or less is used in the outer layer, a softness effect can be exerted. It should be noted that the glass transition temperature can be measured by the method described in the embodiments described below. In addition, when the second resin is plural, the glass transition temperatures of each second resin can be the same or different.

[0101] From the aspect of heat resistance and flexibility, the second resin can enumerate polyamide resin and polyester resin, polyurethane resin.As the polyamide resin, preferably polyamide copolymer and / or polyamide elastomer.Can enumerate the polyamide copolymer selected from PA4, PA6, PA11, PA12, PA46, PA66, PA610 and PA1010 that are enumerated in the description of the above-mentioned adhesive layer alone or more than two kinds, dimer acid polyamide, the polyamide elastomer (so-called thermoplastic polyamide elastomer) consisting of polyamide component and polyether component or polyester component and the dimer acid polyamide elastomer consisting of dimer acid polyamide and polyether component.These polyamide resins and thermoplastic polyamide elastomer can also be the mixture that single or a plurality of resins are blended. From the viewpoint of flexibility and heat resistance, PA6 / 66, PA6 / 12, PA6 / 66 / 12, PA1010, thermoplastic polyamide elastomer or dimer acid polyamide elastomer is more preferred, and PA6 / 66, PA6 / 66 / 12, PA1010 or thermoplastic polyamide elastomer is further preferred.

[0102] In addition, as polyester resins, thermoplastic polyester elastomers and thermoplastic ester-ester elastomers having a polyester component in the hard segment and a polyether component or a polyester component in the soft segment can be cited. Polyurethane resins can also be cited. Among them, thermoplastic polyurethane elastomers are preferred from the aspect of flexibility. Polyester-based or polyether-based thermoplastic polyurethane elastomers can be more preferably cited, and polyether-based thermoplastic polyurethane elastomers can be further preferably cited from the aspect of hydrolyzability.

[0103] In this embodiment, from the viewpoint of durability, flexibility, and suppression of pinholes during heat lamination, the average thickness of the outer layer is preferably 2 μm to 20 μm, more preferably 3 μm to 15 μm, and even more preferably 5 μm to 10 μm.

[0104] The average thickness of the outer layer in the present specification can be measured by the same method as in the above-mentioned “method for measuring the thickness of the adhesive layer”.

[0105] (Middle layer)

[0106] The multilayer composite in the present embodiment can be provided with an intermediate layer between the adhesive layer and the outer layer as needed. From the aspect of flexibility, the intermediate layer preferably contains the third resin. The third resin is preferably a polyolefin resin with polarity. As a specific example, polyethylene such as low-density polyethylene (LDPE), high-density polyethylene (HDPE) or linear low-density polyethylene (LLDPE), ethylene vinyl acetate copolymer (EVA), polyolefin block copolymer (OBC), polyolefin thermoplastic elastomer (TPO), ionomer, acid-modified polyolefin resin, thermoplastic polyamide elastomer (TPAE), thermoplastic polyester elastomer (TPEE), thermoplastic polyurethane elastomer (TPUE), thermoplastic styrene elastomer, styrene-butadiene-styrene (SBS), hydrogenated styrene-butadiene-styrene elastomer (SEBS), or hydrogenated styrene-isoprene-styrene elastomer (SEPS), acrylic elastomer and the like third resin can be cited. The third resin can be used in the intermediate layer in the form of a single form or a composition blended in multiple forms.

[0107] The above-mentioned intermediate layer may be composed only of the third resin, or may further contain the above-mentioned resin A and / or the above-mentioned additives. Relative to the total amount of 100 mass% of the intermediate layer, the third resin preferably contains 70 mass% or more, more preferably 80 mass% or more and 100 mass% or less.

[0108] The average thickness of the intermediate layer in this embodiment is preferably 1 μm to 30 μm, more preferably 2 μm to 28 μm, and further preferably 3 μm to 25 μm. By making the average thickness above 1 μm, the flexibility can be improved. In addition, by making it below 30 μm, the thickness of the outer layer and / or the adhesive layer is relatively increased, and the properties such as pinhole resistance and mechanical strength are improved. In the case of a layer structure including an intermediate layer, the thickness of the intermediate layer can be arbitrarily set within a preferred range according to the performance required by the airbag mounting position.

[0109] (Glue layer)

[0110] In the multilayer composite of the present embodiment, a glue layer can be further provided as a layer formed to bond the above-mentioned layers (outer layer, middle layer, adhesive layer). Therefore, the glue layer preferably uses a resin with higher polarity. As the glue layer, for example, a layer containing an acid-modified polyolefin resin containing a polar functional group such as acid-modified polyethylene or acid-modified polypropylene or / and a polyolefin thermoplastic elastomer as the main component, or a layer containing a polyamide thermoplastic elastomer (TPAE) or a polyester thermoplastic elastomer (TPEE) as the main component, etc., can be cited, preferably considering the requirements for heat resistance in the application used. The above-mentioned glue layer can be a layer consisting of only one resin, or it can be a layer containing multiple resins. In addition, the resin used in the glue layer preferably has a heat resistance of more than 100°C.

[0111] The above-mentioned "main component" means that 50% by mass or more is contained relative to 100% by mass of the total amount of the glue layer. In addition, the glue layer may also contain the above-mentioned resin A and / or the above-mentioned additives as needed.

[0112] In a preferred mode of this embodiment, when an intermediate layer is provided between the outer layer and the adhesive layer, a glue layer may be provided as a layer for bonding the outer layer and the intermediate layer or / and the adhesive layer and the intermediate layer.

[0113] The average thickness of the glue layer in the present embodiment is preferably 1 μm to 10 μm, more preferably 1.5 μm to 8 μm, and further preferably 2 μm to 6 μm.

[0114] By setting the average thickness of the glue layer to be 1 μm or more, the glue layer will not fall off, interlayer peeling can be improved, and the flexibility can be improved. In addition, by setting the average thickness to be 10 μm or less, the thickness of the outer layer and / or the adhesive layer is relatively increased, thereby improving the pinhole resistance and mechanical strength. In the case of a layer structure including a glue layer, the thickness of the glue layer can be arbitrarily set within a preferred range according to the performance required by the airbag mounting part.

[0115] (Base fabric)

[0116] The base fabric in this embodiment is a support for the multilayer film in the multilayer composite for the airbag, and maintains a specific three-dimensional structure after the airbag is deployed. In addition, the base fabric is required to have heat resistance to withstand high-temperature gas from the gas generator, deployability, strength to withstand rapid expansion or impact, airtightness, and storage properties, so the base fabric in this embodiment is preferably formed of synthetic fibers, preferably synthetic fiber fabrics.

[0117] The base fabric preferably contains 20% by mass or more of synthetic fibers, and more preferably contains 50% by mass or more and 100% by mass or less of synthetic fibers, based on the total amount (100% by mass) of the base fabric.

[0118] As synthetic fibers constituting the above-mentioned base cloth or the above-mentioned synthetic fiber fabric, for example, polyamide fibers, polyester fibers, polyolefin fibers, chlorine-containing fibers, fluorine-containing fibers, polyacetal fibers, polysulfone fibers, polyphenylene sulfide fibers (PPS), polyetheretherketone fibers (PEEK), wholly aromatic polyamide fibers, wholly aromatic polyester fibers, polyimide fibers, polyetherimide fibers, polyparaphenylene benzobisoxazole fibers (PBO), vinylon fibers, acrylic fibers, cellulose fibers, silicon carbide fibers, alumina fibers, glass fibers, carbon fibers, steel fibers, etc., among which fibers having hydrogen bonding ability are preferred, and polyamide fibers are more preferred from the perspectives of strength, specific gravity, cost, and bonding strength with a multilayer film.

[0119] In this embodiment, the total fineness of the fibers constituting the base fabric is preferably 100 dtex to 1000 dtex, more preferably 210 dtex to 570 dtex, and further preferably 330 dtex to 490 dtex. By making the total fineness 100 dtex or more, the tension during expansion can be withstood. By making the total fineness 1000 dtex or less, the fabric becomes soft, the storage property is improved, and it can also be expanded at high speed.

[0120] In this embodiment, the fineness of the single yarn constituting the base fabric is preferably 0.5 dtex to 8 dtex, and more preferably 1.5 dtex to 3.7 dtex. By making the fineness of the single yarn 0.5 dtex or more, the warp yarn fuzz during weaving can be suppressed. In addition, by making the fineness of the single yarn 8 dtex or less, a soft fabric can be made.

[0121] In this embodiment, from the perspective of both mechanical properties and hardness, the cover factor (CF) of the base fabric is preferably 1800 to 2400, more preferably 1900 to 2300, and even more preferably 1900 to 2200. When the CF is 1800 or more, the base fabric strength required for the airbag can be obtained. On the other hand, if the CF is 2400 or less, the smaller the CF, the softer the base fabric. In addition, since the smaller the CF, the lighter the fabric basis weight, it is preferably 2300 or less.

[0122] Generally, as CF decreases, air gaps are generated between woven yarns, but air ventilation can be suppressed by providing a laminated coating. CF is represented by the following mathematical formula (1).

[0123] [Number 1]

[0124] CF = (0.g × d) 1 / 2 ×(2×W) (1)

[0125] (In the above mathematical formula (1), d represents the average total fineness (dtex) of the yarn in both warp and weft, and W represents the average weave density (threads / 2.54 cm) in both warp and weft.)

[0126] The average thickness of the base fabric in this embodiment is preferably 0.15 mm to 0.45 mm, more preferably 0.17 mm to 0.40 mm, and further preferably 0.20 mm to 0.35 mm. By making the average thickness of the base fabric greater than 0.15 mm, it can withstand heat or stress during expansion. By making the average thickness of the base fabric less than 0.40 mm, the storage property is improved.

[0127] In addition, regarding the thickness measurement, the thickness is a value measured under the conditions of a set pressure of 1 kPa and a measuring head of 10.5 mm in diameter in accordance with ISO5084.

[0128] (thickness)

[0129] In this embodiment, the softness of the multilayer film has a great influence on the durability (scratch resistance). For example, a multilayer composite for airbags (also called laminated base fabric) formed by laminating a highly soft multilayer film on a base fabric can obtain excellent scratch resistance. The mechanism is not clear, but it is speculated that the resistance of the multilayer film generated when the multilayer composite for airbags is stretched and deformed increases in proportion to the thickness, and the multilayer film is difficult to follow the deformation of the base fabric. The thinner the multilayer film, the better the softness and the improved scratch resistance.

[0130] As described above, the average thickness of the multilayer film in this embodiment is one of the important factors affecting flexibility, and also has a great influence on the results of the scratch test. As a target of scratch resistance, it is required to withstand more than 600 times. From the aspect of scratch resistance, the upper limit of the average thickness of the multilayer film is preferably 40 μm or less, more preferably 35 μm or less, and further preferably 30 μm or less. In addition, from the aspect of adhesive strength described later, the lower limit of the average thickness of the multilayer film is 5 μm or more, more preferably 10 μm or more, and further 15 μm or more.

[0131] The range of the average thickness of the multilayer film in the present embodiment may be any combination of the upper limit value and the lower limit value, and is, for example, preferably 5 μm to 40 μm, and more preferably 10 μm to 35 μm.

[0132] The average thickness of the multilayer composite for airbags in this embodiment can be arbitrarily set in consideration of the characteristics, flexibility, and mechanical strength required by the mounting part, and is preferably 100 μm to 500 μm, more preferably 150 μm to 450 μm or less, and further preferably 200 μm to 400 μm. It should be noted that the thickness is a value measured under the conditions of a set pressure of 1 kPa and a measuring head of Φ10.5 mm according to ISO5084.

[0133] (Ratio of each layer)

[0134] In order to achieve high adhesion to the base fabric, it is not sufficient to utilize only the anchoring effect of the adhesive layer (the anchoring effect is achieved by penetrating into the interior of the multiple monofilament structures composed of the weft and warp yarns constituting the base fabric), and chemical bonding (e.g., hydrogen bonding), intermolecular attraction (van der Waals force), contact area, etc. with the monofilaments are important. Regarding the bonding strength based on chemical bonding, if the contact area is small, it cannot withstand the internal pressure generated when the multilayer composite for airbags is deployed, and pinholes will be generated due to the ductile failure of the film during peeling, and the required functions of the airbags may not be fully realized.

[0135] In the preferred range of the multilayer film disclosed in the present invention, in order to obtain sufficient bonding strength with the base fabric, when the average thickness of the multilayer film is 100%, the lower limit of the layer ratio of the adhesive layer is 1% or more, more preferably 5% or more, and further preferably 10% or more. In addition, from the perspective of flexibility, the upper limit of the layer ratio of the adhesive layer is 50% or less, more preferably 40% or less, and further preferably 30% or less.

[0136] Similarly, from the perspective of durability and prevention of pinholes during lamination, the lower limit of the layer ratio of the outer layer is 5% or more, more preferably 10% or more, and further preferably 20% or more. In addition, from the perspective of flexibility, the upper limit of the layer ratio of the outer layer is 50% or less, more preferably 40% or less, and further preferably 30% or less.

[0137] Therefore, when an intermediate layer or glue layer is provided between the outer layer and the adhesive layer, it can be appropriately set in consideration of the flexibility of the multilayer film, the penetration of the resin into the base fabric during lamination, the film forming properties of the multilayer film, etc.

[0138] More specifically, in the case of a two-layer structure of an outer layer and an adhesive layer, the ratio of the average thickness of each layer is preferably in the range of 5% to 95% for the outer layer and 95% to 1% for the adhesive layer. In addition, in the case of three types of three layers, the ratio of the average thickness of each layer can be set in the range of 5% to 45% for the outer layer, 90% to 5% for the middle layer, and 1% to 90% for the adhesive layer according to the required characteristics. In the case of four types of five layers or five types of five layers, the ratio of the average thickness of each layer can be set in the range of 5% to 20% for the outer layer, 1% to 10% for the glue layer, 40% to 88% for the middle layer, 1% to 10% for the glue layer, and 1% to 20% for the adhesive layer according to the required characteristics.

[0139] (Airbag)

[0140] The airbag of the present embodiment is preferably a bag body formed by the above-mentioned laminated composite for airbags. In other words, the airbag of the present embodiment is preferably a bag-shaped laminated composite for airbags in which the above-mentioned adhesive layer in the above-mentioned multilayer film is bonded to the above-mentioned base fabric and the above-mentioned multilayer film is laminated on at least one surface of the above-mentioned base fabric.

[0141] As a method for manufacturing the airbag, there can be mentioned a heat lamination method (roll lamination method) in which roll-to-roll lamination is continuously performed using a heated roller, a vacuum lamination method in which lamination is performed under reduced pressure, a belt lamination method in which double belts are pressed and lamination is performed simultaneously, etc. Preferably, the adhesive layer of the multilayer film and the synthetic fiber fabric (base fabric) are continuously laminated by a roll lamination method or a belt lamination method at a heating temperature in the range of 120° C. to 190° C., for example.

[0142] The above-mentioned airbags can be used as front airbags, side airbags, side curtain airbags, distal side airbags, exterior airbags and other vehicle airbags. Among them, the side curtain airbags, in addition to protecting the occupants from the impact during a side collision, are also required to have the function of preventing the occupants from being thrown out of the side roof panel during rollover. In addition, the distal side airbag is arranged between the occupant and other occupants to mitigate the impact during rollover. As described above, for the above-mentioned side curtain airbags and the above-mentioned distal side airbags, since it is assumed that the vehicle will roll over, they need to be inflated for a longer period of time than the front airbag. Needless to say, airtightness is required, and it is also desired to further improve the bonding strength between the barrier material and the base fabric. The multilayer composite for airbags of this embodiment can be more suitably used for the above-mentioned barrier material.

[0143] Example

[0144] The present embodiment will be specifically described below by way of examples, but the present embodiment is not limited to the examples described below.

[0145] 1. "Raw materials"

[0146] The raw materials and their symbols used in Examples and Comparative Examples are as follows: The glass transition temperature (sometimes referred to as Tg) and melting point (sometimes referred to as Tm) of each raw material are values ​​obtained using a dynamic viscoelasticity measuring instrument and DSC described later.

[0147] <Raw Materials Used in Adhesive Layer>

[0148] (Resin component)

[0149] The resin components added to the adhesive layer are as follows.

[0150] Co-PA1: Trade name "Ube Nylon 7128B" (manufactured by Ube Industries) polyamide copolymer (PA6 / 12) (Tg = 47°C, Tm = 128°C, viscosity index = 117 ml / g)

[0151] · Co-PA2: trade name "Griltex 2A" (manufactured by EMS Chemie) polyamide copolymer (PA6 / 66 / 12) (Tg = 40°C, Tm = 118°C)

[0152] ·L-TPAE: Trade name "Ubesta XPA9040F1" (manufactured by Ube Industries) low melting point thermoplastic polyamide elastomer (Tg = -43°C, Tm = 136°C)

[0153] Co-PA1 / m-PE1=49 mass% / 51 mass% (corresponding to the resin composition of Example 4) (Tg=29°C, Tm=125°C)

[0154] (additive)

[0155] The additives added to the adhesive layer are as follows.

[0156] AB (anti-blocking agent (AB agent)): Trade name "Silton JC-70" (manufactured by Mizusawa Chemical), ingredient name: sodium calcium aluminum silicate, shape: spherical, average particle size: 7 μm

[0157] NA (crystal nucleating agent (NA agent)): trade name "Micro Ace P-8" (manufactured by Nippon Talc), ingredient name: talc, shape: flaky, average particle size: 3.3 μm

[0158] It should be noted that when adding the additive to the above resin component, a masterbatch containing 5% by mass of the additive was melt-kneaded and granulated using a twin-screw extruder "TEM-18SS" manufactured by TOSHIBA MACHINE at a temperature of 180° C. and a screw speed of 100 rpm, and the granules (masterbatch) prepared in this way were dry-mixed with the resin component. Thereafter, a multilayer film was made by an inflation method using the method described below.

[0159] <Raw materials used in glue layer>

[0160] m-PE1: Trade name "Admer NF587" (Mitsui Chemicals), acid-modified polyethylene (Tg = -24°C, Tm = 121°C)

[0161] <Raw materials used in the middle layer>

[0162] ·LLDPE: Trade name "Umerit 3570FC" (produced by Ube Maruzen Polyethylene) metallocene polyethylene (Tg <-70°C, Tm = 122°C)

[0163] OBC: Trade name "INFUSE 9500" (manufactured by Dow Chemical) polyolefin block copolymer (Tg = -51°C, Tm = 120°C)

[0164] m-PE1: Trade name "Admer NF587" (Mitsui Chemicals), acid-modified polyethylene (Tg = -24°C, Tm = 121°C)

[0165] <Raw materials used in outer layer>

[0166] PA6 / 66: Trade name "Ube Nylon NAV503X10" (manufactured by Ube Industries) polyamide copolymer (PA6 / 66) (Tg = 43°C, melting point = 190°C, viscosity index = 249 ml / g)

[0167] ·H-TPAE: Trade name "Ubesta XPA9063F1" (manufactured by Ube Industries) high melting point thermoplastic polyamide elastomer (Tg = 22°C, Tm = 172°C)

[0168] The following is a description of the methods for measuring various physical properties.

[0169] <Raw materials used in base fabric>

[0170] The following synthetic fibers (Ny66 base fabric) were used as the base fabric used in the examples and comparative examples.

[0171] ·Base fabric material = Polyamide (also known as nylon) 66 fiber

[0172] · Denier = 235dtex,

[0173] ·Number of single filaments = 72

[0174] Fiber density: warp = 76 strands / inch, weft = 74 strands / inch

[0175] 2. "Method for producing a multilayer composite for airbags"

[0176] (1) Method for preparing multilayer film

[0177] Use a multi-layer annular die, through Figure 3 The inflation method shown above is to wind the desired resin film in a 3-inch paper tube in a state of overlapping two sheets. At this time, the film is formed in such a way that the inner layer 1b of the tubular film is the adhesive layer and the outer layer 1a is the outer layer. The film forming conditions are as follows.

[0178] <Multilayer Film Formation Conditions>

[0179] Die head temperature setting: 220℃

[0180] Annular die: Die lip profile = 95mm, Die lip gap = 3mm

[0181] Inflation ratio: 1.1 times

[0182] Air ring temperature: 25℃

[0183] ·Film surface temperature near the tensioning roller: 35℃

[0184] Distance between annular die head and tensioning roller: 2.4m

[0185] The pulling speed can be changed according to the thickness of the multilayer film. For example, when the thickness is 40 μm, the pulling speed is 12 m / min. On the other hand, when the thickness is 20 μm, the pulling speed is 24 m / min.

[0186] (2) Method for manufacturing multilayer composite for airbag

[0187] Refer to the following Figure 4 The method for producing the multilayer composite for airbags used in Examples and Comparative Examples will be described.

[0188] The multilayer film 1c is placed on the base fabric 2 between a pair of rollers consisting of a heating roller 17 and a pressure roller 16 covered with silicone rubber in such a manner that the multilayer film 1c is in contact with the surface of the pressure roller 16, and is sandwiched between the rotating rollers 16 and 17, and a lamination process is performed under specific temperature, pressure, and speed conditions in such a manner that one surface of the base fabric is substantially entirely covered with the multilayer film. The specific method is described in detail below.

[0189] (Multilayer composite for scratch resistance evaluation, multilayer composite for ring stiffness measurement)

[0190] In the case of a sample for scratch resistance evaluation and an airbag multilayer composite for ring stiffness measurement, the dimensions of the base fabric 2 and the multilayer film 1c (1a, 1b) are as follows. For the multilayer film 1c (1a, 1b), the dimensions are 250 mm in the MD (Mashine Derection) direction and 110 mm in the TD (Transverse Direction). For the base fabric, the dimensions are 260 mm in the warp direction and 120 mm in the weft direction.

[0191] Thereafter, the MD direction of the collected multilayer film is made the same as the warp direction of the base fabric, and the adhesive layer 1b of the multilayer film is overlapped in a manner that it is in contact with the base fabric 2. Next, in a laminator set to specific conditions, the TD direction (the weft direction of the base fabric 2) of the multilayer film 1c (1a, 1b) is overlapped in a manner that it is parallel to the surface length direction (the direction of the width of 540 mm) of the heating roller 17 and the pressure roller 16, and the multilayer film 1c (1a, 1b) is oriented to be in contact with the pressure roller 16, and is clamped between the pressure roller 16 and the heating roller 17 of the laminator, and a lamination process is performed, thereby preparing a sample.

[0192] (Multilayer composite for bonding strength measurement)

[0193] In addition, for the sample for bonding strength (180° T-shaped bonding strength), under the above conditions, at the stage of lamination processing of about 5 cm from the front end of the multilayer film 1c (1a, 1b) and the base cloth 2, the pressure roller 16 and the heating roller 17 are opened and extracted to prepare the sample.

[0194] <Roll Laminator Specifications>

[0195] ·Metal heating roller diameter: Φ100mm Roller surface length: 540mm Surface: mirror finish

[0196] ·Pressure roller diameter: Φ100mm Roller surface length: 540mm Surface: Silicone rubber lining processing

[0197] Pressure cylinder diameter: Φ50mm×2

[0198] <Lamination Processing Conditions>

[0199] Temperature 160℃

[0200] Linear pressure 15N / cm (set gauge pressure = 0.2MPa)

[0201] Processing speed: 0.3m / min

[0202] 3. “Evaluation Method”

[0203] The evaluation methods used in Examples and Comparative Examples are as follows.

[0204] (1) Composition analysis of multilayer films and evaluation methods of thermal properties

[0205] (Glass transition temperature Tg)

[0206] Using a compression molding machine "P2-30T-400" manufactured by Toyo Seiki Seisaku-sho, a 0.9 mm thick sheet was made using the components of each layer constituting the multilayer film, and the loss tangent tanδ was measured using a dynamic viscoelasticity tester ("MCR301" manufactured by Anton-Paar), and the peak temperature of the loss tangent tanδ was taken as the glass transition temperature.

[0207] ·Measurement mode: Twist (measurement attachment: SRF10)

[0208] Sample: Thickness = 0.9 mm Width = 10 mm Measurement span = 38 mm

[0209] Normal force: -0.3N

[0210] Swing angle: 0.1%

[0211] Frequency: 1Hz

[0212] Heating rate: 2℃ / min

[0213] (Melting point Tm)

[0214] Using a compression molding machine "P2-30T-400" manufactured by Toyo Seiki Seisaku-sho, a 150 μm thick sheet was prepared using the components of each layer constituting the multilayer film, and a weight of 10 mg was collected. Using DSC ("Diamond DSC" manufactured by Perkin Elmer), the melting peak temperature obtained at a heating rate of 10°C / min according to JIS K 7121 was taken as the melting point. It should be noted that, regarding compression molding conditions, samples were collected under the following conditions.

[0215] (2) Evaluation method of bonding strength

[0216] In the measurement of the bonding strength (180° T-peel strength), an airbag multilayer composite prepared according to the (Multilayer composite for bonding strength measurement) in the column "Method for preparing a multilayer composite for airbags" was used. In the measurement of the bonding strength of the sample, in order to suppress the elongation of the film as much as possible during the measurement, "Super Strong LineTape for Business Use, Model: RM-605" sold by Shinfuji burner Co., Ltd. was adhered to the outer surface of the film for reinforcement, and the multilayer film was cut into 10 mm in the TD direction (the weft direction of the base fabric), and was cut into 80 mm in the MD direction (the warp direction of the base fabric) of the multilayer film so that the end 20 mm was the bonding part. Five samples for bonding strength measurement were prepared respectively, and five T-shaped 180° peel tests were carried out using a tensile testing machine ("Autograph AG-IS" manufactured by Shimadzu Corporation) (refer to Figure 2 ), and the average of their respective maximum values ​​was taken as the bonding strength.

[0217] <Adhesion Strength Measurement Conditions>

[0218] Sample conditioning: Store at 23°C-50%RH for 2 days

[0219] Peel test: 23℃-50%RH

[0220] · Between chucks: 30 mm (install so that the bonding part is at the center between the chucks)

[0221] Peeling speed: 5mm / min

[0222] (3) Evaluation method of ring stiffness

[0223] In the measurement of ring stiffness, a multilayer composite for airbags prepared according to the "Method for producing a multilayer composite for airbags" column (Multilayer composite for measuring ring stiffness) was used. Five samples of the multilayer film with a TD direction (weft direction of Ny66 base fabric) of 20 mm and a MD direction (warp direction of Ny66 base fabric) of 120 mm were collected from the multilayer composite for airbags, and placed on a sample stand with the multilayer film side as the outer side of the ring using a ring stiffness tester (Toyo Seiki), and the ring crushing stress was measured (refer to Figure 1 ). In addition, the ring stiffness of the Ny66 base fabric was measured by collecting a sample with the same size in an untreated state without undergoing the history of heat and pressure by a laminator.

[0224] In addition, the value of the loop rigidity was calculated by averaging the values ​​of five pieces measured at different locations and converting them into a 1 cm width.

[0225] It should be noted that when measuring the ring stiffness of the multilayer composite for airbags, the ring stiffness can be obtained by using a portion without deformation or damage and collecting a sample in the same manner as described above. In addition, the ring stiffness of the base fabric in the multilayer composite may be lower than that of the untreated base fabric due to the history of heat and pressure during lamination and the mesh of the base fabric caused by peeling the multilayer film. In this case, the ring stiffness of the base fabric itself is calculated using the following procedures (a) to (d).

[0226] (a) The composition of the base fabric in the multilayer composite for an airbag was determined by infrared spectroscopy (FT-IR).

[0227] (b) The cross section of the multilayer composite is analyzed using SEM to determine the fiber structure (basis weight, thickness, fineness, fiber density).

[0228] (c) A base fabric having the same composition and fiber structure (basis weight, thickness, fineness, fiber density) as those determined in (a) and (b) above is separately prepared.

[0229] (d) The ring stiffness of the so-called replica base fabric prepared separately in the above (c) was measured.

[0230] Thereby, the difference in the ring stiffness between the multilayer composite for airbags and the base fabric can be obtained.

[0231] <Ring stiffness measurement conditions>

[0232] Sample condition adjustment: 23℃-50%RH-24 hours or more

[0233] Test environment: 23℃-50%RH

[0234] Sample size: 20mm width × 120mm length

[0235] ·Measurement speed: 3.3mm / sec

[0236] (4) Evaluation method of scratch resistance

[0237] The test was conducted using a scratch tester (manufactured by Imoto Seisakusho) in accordance with ISO5981, and the number of times the film began to peel off from the multilayer composite for airbags of Examples and Comparative Examples was counted. The test was repeated 4 times for each sample, and the average value was calculated.

[0238] <Specifications and test conditions of the scratch tester>

[0239] Test load base (10mm width) = 5N Additional load = 10N additional

[0240] Round trip speed: 2.3 times / second

[0241] · Sample condition adjustment 23℃-50%RH-24 hours or more

[0242] Test environment: 23℃-50%RH

[0243] · Criteria for judging the number of scratches (average value)

[0244] Number of peeling starts: 1 to 299 times: ×

[0245] Number of peeling starts: 300 to 599 times: △

[0246] Number of peeling starts: 600 to 999 times: ○

[0247] Number of peeling starts: 1000 times or more: ◎

[0248] (5) Evaluation method of layer ratio and film thickness

[0249] The thickness of the multilayer film was measured using a dial gauge (SM-1201 manufactured by Teclock, measuring head Φ2).

[0250] In addition, regarding the ratio of each layer of the multilayer film, two sheets of polypropylene sheets (size: 5mm×10mm) with a thickness of 1mm are prepared, and the multilayer film is sandwiched between the above two sheets in a manner that the EVA adhesive surface is on the inner side for integration. For its cross-section, a slicer can be used to collect slices with a thickness of 5μm to 10μm, and the cross-section of the slices can be enlarged using a polarizing microscope, and the thickness of each layer can be measured using image analysis software.

[0251] (6) Composition analysis and thermal property measurement methods of multilayer films

[0252] As an example of a method for determining the components contained in the adhesive layer in a multilayer film having an adhesive layer and an outer layer, methods for determining by infrared spectroscopy (FT-IR) and NMR methods can be cited. In addition, as other methods for determining the melting point and crystallization temperature, in the case where the multilayer film is a two-layer film consisting of a bonding layer and an outer layer, the multilayer film can also be directly sampled into a desired size and determined according to the above-mentioned melting point determination method. In the case where the multilayer film is a three-layer or more multilayer film having an intermediate layer between the adhesive layer and the outer layer, it can also be immersed in a solvent (hexafluoro-2-propanol, etc.) that can only extract the adhesive layer, and the obtained solution is separated into a solvent and a solid component using an evaporator, and the solid component is determined according to the above-mentioned melting point determination method.

[0253] (7) Calculation of △HSP value

[0254] The HSP of the first resin and other resins contained in the adhesive layer used in the examples and comparative examples and the HSP of the base fabric were analyzed by NMR and FT-IR, and calculated using "Winmostar Version 9.3.0" based on the obtained composition ratios. The results are shown in Table 1.

[0255] [Example 1]

[0256] A multilayer film of 4 types and 5 layers with a thickness of 20 μm was obtained, which was composed of an outer layer (20%) / glue layer (10%) / intermediate layer (50%) / glue layer (10%) / adhesive layer (10%), and a polyamide copolymer composed of CoPA1 (PA6 / 12) was used in the above adhesive layer. Here, the numerical values ​​in the above brackets represent the layer ratio. The multilayer film was laminated on a nylon 66 (Ny66) base cloth at a temperature of 160°C, a linear pressure of 15 N / cm (set gauge pressure = 0.2 MPa), and a speed of 0.3 m / min to produce a multilayer composite (1) for airbags, and the performance was evaluated. Table 1 shows the composition of the multilayer film and the multilayer composite for airbags, and the evaluation results. According to the results of Table 1, the multilayer composite for airbags of Example 1 obtained good results in softness, adhesion, and scratch resistance.

[0257] It should be noted that in the resin composition column in Table 1, "symbol = number" means "the symbol represents the resin name described in the above "raw material" column, and Y represents the content of the resin". Therefore, for example, "PA6 / 66 = 100" corresponding to the outer layer of Example 1 in Table 1 means "a raw material (product) containing 80% by mass or more of a polyamide copolymer of PA6 and PA66 is used, and the raw material contains 100% by mass". In addition, in the resin composition column in Table 1, "-" means that the layer is not set.

[0258] [Example 2]

[0259] In Example 1, the layer ratio of the adhesive layer was increased from 10% to 20%, and the intermediate layer was reduced from 50% to 40%, thereby obtaining four types of five-layer films with a thickness of 15 μm. Using this multilayer film, a multilayer composite for airbags (2) was prepared in the same manner as in Example 1, and the performance was evaluated. Table 1 shows the composition of the multilayer film and the multilayer composite for airbags and the evaluation results. From the experimental results of the multilayer composite for airbags (2), it was confirmed that the softness (difference in ring stiffness) was improved compared with the multilayer composite for airbags (1) of Example 1, thereby improving the scratch resistance.

[0260] [Example 3]

[0261] In Example 1, the layer ratio of the adhesive layer was increased from 10% to 50%, and the ratio of the intermediate layer was reduced from 50% to 10%, thereby obtaining a 20 μm thick 4-layer film. Using this multilayer film, a multilayer composite (3) for airbags was prepared in the same manner as in Example 1, and the performance was evaluated. Table 1 shows the composition of the multilayer film and the multilayer composite for airbags and the evaluation results. In the experimental results of the multilayer composite (3) for airbags, compared with Example 1, the softness was reduced, and the scratch resistance was also reduced accordingly, but the performance of more than 600 times was still obtained.

[0262] [Example 4]

[0263] A composition blended with 50% by mass of m-PE1 (acid-modified PE) was used in the adhesive layer to obtain a 4-type 5-layer multilayer film with a thickness of 40 μm. Using this multilayer film, a multilayer composite for airbags (4) was prepared in the same manner as in Example 1, and the performance was evaluated. Table 1 shows the composition of the multilayer film and the multilayer composite for airbags and the evaluation results. In the experimental results of the multilayer composite for airbags (4), even if m-PE1 was blended in the adhesive layer, the bonding strength did not decrease, and the scratch resistance also achieved a performance of more than 600 times.

[0264] [Example 5]

[0265] Two types of two-layer multilayer films with a thickness of 20 μm, each consisting of an outer layer and an adhesive layer, were obtained. Using the multilayer film, a multilayer composite for airbags (5) was prepared in the same manner as in Example 1, and the performance was evaluated. Table 1 shows the composition of the multilayer film and the multilayer composite for airbags and the evaluation results. In the experimental results of the multilayer composite for airbags (5), a decrease in softness was confirmed compared with Example 1, and the scratch resistance was also reduced accordingly, but the performance was still more than 600 times.

[0266] [Example 6]

[0267] A multilayer film was prepared in the same manner as in Example 5 except that H-TPAE (high melting point thermoplastic polyamide elastomer) was used in the outer layer. A multilayer composite (6) for airbags was prepared in the same manner as in Example 1 using the multilayer film, and the performance was evaluated. Table 1 shows the composition of the multilayer film and the multilayer composite for airbags and the evaluation results. In the test results of the multilayer composite for airbags (6), the softness, adhesion, and scratch resistance were substantially equivalent to those of Example 5.

[0268] [Example 7]

[0269] A multilayer film with a thickness of 20 μm was prepared, which is a three-layer film consisting of an outer layer (20%) / intermediate layer (70%) / adhesive layer (10%), wherein PA6 / 66 was used in the outer layer, m-PE was used in the intermediate layer, and Co-PA1 was used in the adhesive layer. Using this multilayer film, a multilayer composite for airbags (7) was prepared in the same manner as in Example 1, and the performance was evaluated. Table 1 shows the composition of the multilayer film and the multilayer composite for airbags and the evaluation results. In the experimental results of the multilayer composite for airbags (7), the softness, adhesion, and scratch resistance obtained were equal to or better than those of Example 1.

[0270] [Example 8]

[0271] Three types of three-layer films with a thickness of 20 μm were prepared in the same manner as in Example 7 except that Co-PA2 was used in the adhesive layer. Using the multilayer films, a multilayer composite for airbags (8) was prepared in the same manner as in Example 1, and the performance was evaluated. Table 1 shows the composition of the multilayer film and the multilayer composite for airbags and the evaluation results. In the experimental results of the multilayer composite for airbags (8), the softness of the film was improved compared with that in Example 7, and thus the scratch resistance was good.

[0272] [Comparative Example 1]

[0273] Four kinds of 5-layer multilayer films having the same layer structure as Example 1 were prepared except that the thickness was changed from 20 μm to 40 μm. Using the multilayer films, a multilayer composite (A) for airbags of Comparative Example 1 was prepared in the same manner as Example 1, and the performance was evaluated. Table 1 shows the structure of the multilayer film and the multilayer composite (A) and the evaluation results. In the experimental results of Comparative Example 1, as compared with Example 1, the softness decreased as the thickness increased, and the scratch resistance decreased to 275 times.

[0274] [Comparative Example 2]

[0275] In Example 1, the same multilayer film as in Example 1 was obtained except that the layer ratio of the adhesive layer was increased from 10% to 40% and the thickness was increased from 20 μm to 35 μm. Using the multilayer film, a multilayer composite (B) for airbags of Comparative Example 1 was prepared in the same manner as in Example 1, and the performance was evaluated. Table 1 shows the composition of the multilayer film and the multilayer composite (B) and the evaluation results. In the experimental results of Comparative Example 2, the layer ratio and thickness of the adhesive layer were increased compared to Example 1, so the flexibility was reduced, and the scratch resistance was reduced to 325 times.

[0276] [Comparative Example 3]

[0277] A multilayer film of two kinds of two layers having a thickness of 40 μm consisting of H-TPAE (high melting point thermoplastic polyamide elastomer) and L-TPAE (low melting point thermoplastic polyamide elastomer) was obtained. Using the multilayer film, a multilayer composite (C) for airbags of Comparative Example 3 was prepared in the same manner as in Example 1, and the performance was evaluated. Table 1 shows the composition of the multilayer film and the multilayer composite (C) and the evaluation results. In the experimental results of Comparative Example 3, the softness was poor and the scratch resistance was reduced to 200 times.

[0278]

[0279] As shown in Table 1, scratch resistance depends on the bonding strength and the softness of the film. By making the bonding strength above 5N / cm and the softness of the film (laminated base fabric-base fabric) below 130mN / cm, practical scratch resistance (durability) is obtained.

[0280] Industrial Applicability

[0281] The multilayer composite of the present disclosure is excellent in adhesiveness, airtightness, durability, flexibility, and lightness, and can be manufactured at a low cost, so it can be suitably used in airbag applications, typified by vehicle applications.

[0282] Explanation of symbols

[0283] 1····Multi-layer composite laminate

[0284] 1a···Multilayer film (outer layer)

[0285] 1b···Multilayer film (adhesive layer)

[0286] 1c···Multilayer film

[0287] 2. Base fabric

[0288] 3. Pressure head

[0289] 4·····Chuck of ring stiffness

[0290] 5····Sample stage

[0291] 6····Reinforcement belt

[0292] 7····Chuck of tensile testing machine

[0293] 8····Multilayer die head

[0294] 9····Air Ring

[0295] 10···Exhauster (free roller)

[0296] 11···First pulling drive roller

[0297] 12···Guide roller (free roller)

[0298] 13···Second tensioning driving roller

[0299] 14···Contact roller (free roller)

[0300] 15···Winding drive roller

[0301] 16···Pressure roller (silicone rubber lining processing)

[0302] 17···Metal heating roller (mirror finish)

Claims

1. A multilayer composite for an air bag, comprising: Base fabric; and A multilayer film comprising 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 bonding strength of the interface between the multilayer film and the base fabric is 5 N / cm or more, and the difference in ring stiffness between the multilayer composite for airbags and the base fabric is 130 mN / cm or less, the bonding layer contains a first resin having hydrogen bonding ability, and the difference in Hansen solubility parameter ΔHSP between the base fabric and the first resin is 5 MPa 0.5 the following, The average thickness of the multilayer film is 35 μm or less, The first resin has a glass transition temperature of 20° C. or higher.

2. The multilayer composite for airbags according to claim 1, wherein: The first resin is a polyamide-based copolymer of two or more selected from the group consisting of polyamide 6, polyamide 66, polyamide 610, polyamide 11, and polyamide 12 and / or a dimer acid-based polyamide.

3. The multilayer composite for airbags according to claim 1 or 2, characterized in that: The outer layer includes a second resin, and the second resin has a melting point that is 20° C. or higher than that of the first resin.

4. The multilayer composite for airbags according to claim 3, wherein: The second resin includes a polyamide-based copolymer and / or a polyamide-based elastomer.

5. The multilayer composite for airbags according to claim 1 or 2, characterized in that: An intermediate layer is provided between the outer layer and the adhesive layer. The intermediate layer contains a third resin, and the third resin is a polar polyolefin resin.

6. The multilayer composite for airbags according to claim 1 or 2, characterized in that: The base fabric is polyamide fiber.

7. The multilayer composite for airbag according to claim 1 or 2, characterized in that: The difference ΔHSP between the base fabric and the first resin is 4.0 MPa. 0.5 the following.

8. The multilayer composite for airbags according to claim 1 or 2, characterized in that: The glass transition temperature of the first resin is 20°C to 70°C.

9. The multilayer composite for airbags according to claim 1 or 2, characterized in that: The first resin is selected from the group consisting of PA6 / 12, PA6 / 66 / 12, PA6 / 66 / 610 / 12 and dimer acid-based polyamide.

10. The multilayer composite for airbag according to claim 3, wherein: The second resin is selected from the group consisting of PA6 / 66, PA6 / 66 / 12, PA1010 and thermoplastic polyamide elastomer.

11. The multilayer composite for airbags according to claim 1 or 2, characterized in that: The multilayer film has an average thickness of 10 μm to 40 μm. 12 . An airbag using the multilayer composite for an airbag according to claim 1 .

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