Airbag and method of manufacturing the same

Abstract

The present disclosure relates to an airbag formed by using a laminate formed by bonding a base fabric and a multilayer film to each other, wherein the base fabric is formed to have a bag shape, and the multilayer film is formed on a surface of the base fabric, the multilayer film including: an adhesive layer as a side of the multilayer film to be bonded to the base fabric; and a sealing layer bonded to the adhesive layer, wherein the adhesive layer and the sealing layer each contain a thermoplastic polyester-based elastomer, the melting point of the sealing layer is higher than the melting point of the adhesive layer and the difference between them exceeds 20°C, and the melting point of the sealing layer is 180°C or higher, and the ratio of the content of soft segments in the thermoplastic polyester-based elastomer of the adhesive layer to the content of soft segments in the thermoplastic polyester-based elastomer of the sealing layer is 1.2 to 5.

Description

[0001] This application is a divisional application of the invention patent application with application number 201880039337.X, application date June 15, 2018, and title "Multilayer film, laminate, airbag and method for manufacturing laminate". Technical Field

[0002] This invention relates to a multilayer film, a laminate, an airbag, and a method for manufacturing the laminate. Background Technology

[0003] Historically, polymer films bonded to a base fabric have been used as materials for applications such as vehicle airbags, outdoor products, and packaging.

[0004] For example, Patent Document 1 discloses a laminate formed by laminating a thermoplastic elastomer onto a fabric made of thermoplastic resin fibers.

[0005] In addition, Patent Document 2 discloses a technique for applying or laminating a thermoplastic elastomer onto the treated surface by means of an adhesive after performing at least one of the following treatments: electrical discharge treatment or ultraviolet treatment.

[0006] <Prior art documents> <Patent Documents> Patent Document 1: Japanese Patent Application Publication No. 2-114035 Patent Document 2: Japanese Patent Application Publication No. 5-338092 Summary of the Invention

[0007] <Problem to be solved by this invention> However, in the invention of Patent Document 1, the thermoplastic elastomer being laminated is a single layer. Therefore, when laminating the thermoplastic elastomer using heat, it is difficult to adjust the temperature of the elastomer during lamination to a temperature that ensures both the sealing of the elastomer layer and good adhesion to the fabric, which may lead to reduced production stability. On the other hand, if an adhesive is used for lamination, applying the adhesive requires time and cost.

[0008] In addition, the invention in Patent Document 2 also uses an adhesive when bonding thermoplastic elastomers, which also takes time and costs.

[0009] In view of the above-mentioned problems, one aspect of the present invention aims to provide a multilayer film that can achieve high production stability and has low production time and cost when bonded to a base fabric to form a laminate.

[0010] <Methods for solving the above problems> To achieve the above objectives, one aspect of the present invention is a multilayer film bonded to a base fabric, comprising an adhesive layer as the side bonded to the base fabric, and a sealing layer bonded to the adhesive layer, wherein the adhesive layer and the sealing layer comprise a thermoplastic polyester elastomer, and the melting point of the sealing layer is higher than that of the adhesive layer.

[0011] <The Effects of the Invention> According to one aspect of the present invention, a multilayer film can be provided that achieves high production stability and has low production time and cost when bonded to a base fabric to form a laminate. Attached Figure Description

[0012] Figure 1 This is a schematic cross-sectional view of one embodiment of the multilayer film of the present invention.

[0013] Figure 2 This is a schematic cross-sectional view of one embodiment of the stacked body of the present invention.

[0014] Figure 3 This is a schematic cross-sectional view of a laminated body (airbag) of one embodiment of the present invention.

[0015] Figure 4 This is a schematic diagram of an apparatus for manufacturing a laminate of one aspect of the present invention.

[0016] Figure 5 This is a schematic diagram illustrating the lamination of a base fabric and a multilayer film in a manufacturing process of a laminate according to one aspect of the present invention. Detailed Implementation

[0017] (Multilayer film) Figure 1 A schematic cross-sectional view showing the multilayer film 1. One aspect of the invention is as follows. Figure 1 The image shows a multilayer film 1, which includes a sealing layer 2 and an adhesive layer 3 bonded to the sealing layer 2. The multilayer film 1 is bonded to a base fabric, and the adhesive layer 3 is the side bonded to the base fabric. Furthermore, both the adhesive layer 3 and the sealing layer 2 comprise thermoplastic polyester elastomers, with the melting point of the sealing layer 2 being higher than that of the adhesive layer 3.

[0018] In this specification, a sealing layer refers to a layer that prevents the flow of gas between its interior and exterior. An adhesive layer refers to a layer that adheres to the base fabric; this adhesion is achieved by softening or melting the adhesive layer under specified conditions, such as increased temperature and / or pressure. When a multilayer film is bonded to a base fabric to form a laminate, the adhesive layer is directly laminated onto the base fabric, becoming an inner layer sandwiched between the base fabric and the sealing layer in the laminate. Therefore, the adhesive layer can also be described as the layer that bonds the sealing layer to the base fabric.

[0019] This type of multilayer film has a structure of at least two layers, including a sealing layer and an adhesive layer. Therefore, each layer can respectively perform the adhesive function when the film is bonded to the base fabric, and the sealing function of the resulting laminate. Thus, compared to the case of a single-layer film bonded to the base fabric, the use of this type of multilayer film can create a high-quality laminate that guarantees both adhesion to the base fabric (interlayer peel resistance between the base fabric and the multilayer film) and sealing performance.

[0020] Furthermore, the melting point of the sealing layer is higher than that of the adhesive layer. Therefore, when the adhesive layer of the multilayer film is heated to a temperature lower than the melting point of the sealing layer before bonding to the base fabric, softening of the sealing layer can be suppressed while the adhesive layer softens or melts to a suitable softness for bonding with the base fabric. This ensures that the adhesive function of the adhesive layer is effectively utilized while suppressing softening of the sealing layer to maintain its sealing function. Thus, both strong adhesion to the base fabric and maintenance of the multilayer film's sealing properties can be achieved.

[0021] Even without adhesives, this type of multilayer film can be well bonded to the base fabric by utilizing heat, as described above. Therefore, it can reduce the time and cost of using adhesives. In addition, under long-term use or in high temperature and high humidity environments, it can prevent the adhesive from deteriorating, which could lead to loss of flexibility and interlayer delamination in the laminate.

[0022] In this specification, the melting point of a layer refers to the temperature at which the layer softens as its temperature rises, the polymer molecules within the layer begin to move relative to each other, and the polymer exhibits fluidity. Therefore, the melting points of the adhesive layer and the sealing layer can be considered as the melting points of the polymers (including polymer alloys) in the adhesive layer and the sealing layer, respectively. The melting point of this polymer can be obtained using the peak melting temperature measured by differential scanning calorimeters.

[0023] (Adhesive layer) In this configuration, the adhesive layer comprises a thermoplastic elastomer, specifically a thermoplastic polyester elastomer. The thermoplastic elastomer is preferably a block copolymer comprising hard segments (also known as high-melting-point segments or crystalline segments) and soft segments (also known as low-melting-point segments or amorphous segments). Thermoplastic elastomers can exhibit flowability due to heat softening, but exhibit rubber-like elasticity in their unheated state.

[0024] By using thermoplastic polyester elastomers in the adhesive layer, the interlaminar peel resistance of the resulting laminate can be improved. That is, the adhesion between the adhesive layer and the base fabric, and between the adhesive layer and the sealing layer, can be improved, regardless of whether it is at room temperature or under high temperature and / or high humidity conditions. In addition, the overall flexibility and mechanical strength of the laminate can also be improved.

[0025] Thermoplastic polyester elastomers can be polyester / polyether type, where the hard segment mainly contains aromatic polyesters and the soft segment mainly contains aliphatic polyethers, or polyester / polyether type, where the hard segment mainly contains aromatic polyesters and the soft segment mainly contains aliphatic polyesters.

[0026] The hard segment of the thermoplastic polyester elastomer is preferably a segment containing aromatic polyester, such as a polyester formed from an aromatic dicarboxylic acid component and a diol component.

[0027] Examples of aromatic dicarboxylic acids that can function as aromatic dicarboxylic acid components include terephthalic acid, isophthalic acid, phthalic acid, naphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, anthracene dicarboxylic acid, diphenyl-4,4'-dicarboxylic acid, diphenoxyethane dicarboxylic acid, 4,4'-diphenylether dicarboxylic acid, 5-sulfoisophthalic acid, and sodium 3-sulfoisophthalic acid. Aromatic polyesters may contain two or more of the aforementioned aromatic dicarboxylic acid components, either alone or in combination. Additionally, in the hard segment, a portion of the aforementioned aromatic dicarboxylic acid components may be replaced with alicyclic or aliphatic carboxylic acids.

[0028] Examples of diols that can function as diol components include diols with a molecular weight below 400, such as aliphatic diols like 1,4-butandiol, ethylene glycol, 1,3-propanediol, 1,5-pentanediol, 1,6-hexanediol, neoopentylglycol, and decaethylene glycol; alicyclic diols like 1,1-cyclohexanedimethanol, 1,4-dicyclohexanedimethanol, and tricyclodecanedimethanol; and xylene glycol. Aromatic glycols include glycol, bis(p-hydroxy)diphenyl, bis(p-hydroxy)diphenylpropane, 2,2'-bis[4-(2-hydroxyethoxy)phenyl]propane, bis[4-(2-hydroxyethoxy)phenyl]sulfone, 1,1-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane, 4,4'-dihydroxy-p-terphenyl, and 4,4'-dihydroxy-p-quaterphenyl. Aromatic polyesters may contain two or more of the above-mentioned glycol components, either alone or in combination.

[0029] From the viewpoint of heat resistance and gas barrier properties, the polyester contained in the hard segment is preferably polybutylene terephthalate, polyethylene terephthalate, or polytrimethylene terephthalate, and more preferably polybutylene terephthalate.

[0030] The soft segment of the thermoplastic polyester elastomer preferably comprises an aliphatic polyether and / or an aliphatic polyester. Examples of aliphatic polyethers include poly(ethylene oxide) glycol, poly(propylene oxide) glycol, poly(tetramethylene oxide) glycol (i.e., polytetramethylene ether glycol), poly(hexamethylene oxide) glycol, copolymers of ethylene oxide and propylene oxide, ethylene oxide addition polymers of poly(propylene oxide) glycol, and copolymer diols of ethylene oxide and tetrahydrofuran. In addition, examples of aliphatic polyesters include poly(ε-caprolactone), polyenantholactone, polycaprylolactone, polybutylene adipate, and polyethylene adipate.

[0031] Among these aliphatic polyethers and / or aliphatic polyesters, from the viewpoint of elasticity and formability, poly(tetrahydrofuran) glycol, ethylene oxide addition polymers of poly(propylene oxide) glycol, copolymer diols of ethylene oxide and tetrahydrofuran, poly(ε-caprolactone), polybutylene adipate, polyvinyl adipate, etc., are preferred, and poly(tetrahydrofuran) glycol (polytetramethylene ether glycol), ethylene oxide addition polymers of poly(propylene oxide) glycol, and copolymer diols of ethylene oxide and tetrahydrofuran are particularly preferred.

[0032] The number average molecular weight of the soft segment is preferably in the range of 300 to 6000 in the copolymerization state.

[0033] Here, the aforementioned thermoplastic polyester elastomer can be modified by unsaturated carboxylic acids or their derivatives, such as acrylic acid, maleic acid, and fumaric acid, in the presence of a radical initiator. The amount of unsaturated carboxylic acid or its derivative added for modification is preferably 0.1 to 30 parts by weight relative to 100 parts by weight of the thermoplastic polyester elastomer. The type and amount of this modification component can be appropriately selected depending on the material of the base fabric being bonded and its intended use.

[0034] The content of hard segments in the thermoplastic polyester elastomer of the adhesive layer is preferably 10 to 60% by weight, more preferably 20 to 40% by weight, relative to 100% by weight of the thermoplastic polyester elastomer. Setting it to 10% by weight or more improves the mechanical strength, heat resistance, and durability under high temperature and humidity conditions of the multilayer film and the resulting laminate. Furthermore, setting it to 60% by weight or less ensures adequate elasticity, flexibility, and formability of the multilayer film and the resulting laminate.

[0035] The content of soft segments in the thermoplastic polyester elastomer of the adhesive layer is preferably 50 to 90% by weight, more preferably 60 to 80% by weight, relative to 100% by weight of the thermoplastic polyester elastomer. Setting it to 50% by weight or more ensures adequate elasticity, flexibility, and formability of the multilayer film and the resulting laminate. Furthermore, setting it to 90% by weight or less improves the mechanical strength of the multilayer film and the resulting laminate.

[0036] The proportion of soft segments in thermoplastic polyester elastomers affects their melting point and softening point. Generally, a higher proportion of soft segments in a thermoplastic polyester elastomer results in a lower melting point and softening point. Therefore, by adjusting the proportion of soft segments in the thermoplastic polyester elastomer of the adhesive layer, the melting point of the thermoplastic polyester elastomer can be adjusted, thereby adjusting the melting point of the adhesive layer.

[0037] The melting point of the thermoplastic polyester elastomer used in the adhesive layer is preferably 80°C or higher, more preferably 100°C or higher, and even more preferably 130°C or higher. Furthermore, the upper limit of the melting point of the thermoplastic polymer used in the adhesive layer is not particularly limited as long as it is below the melting point of the sealing layer, but it is preferably 250°C or lower, more preferably 200°C or lower, and even more preferably 170°C or lower.

[0038] The adhesive layer may contain two or more of the aforementioned thermoplastic polyester elastomers. In addition to thermoplastic polyester elastomers, it may also contain other non-polyester thermoplastic elastomers, such as one or more of polyamide elastomers, polyolefin elastomers, polyurethane elastomers, polystyrene elastomers, and polybutadiene elastomers. Furthermore, it may contain other non-elastomer polymers, such as one or more of polyester resins, polyamide resins, polyolefin resins, polystyrene-based resins, and ethylene-vinyl acetate copolymers.

[0039] Commercially available thermoplastic polyester elastomers include "Hytrel (registered trademark)" manufactured by Toray-DuPont, "Primalloy (registered trademark)" manufactured by Mitsubishi Chemical Corporation, "PELPRENE (registered trademark)" manufactured by Toyobo Corporation, and "Arnitel (registered trademark)" produced by DSM NV, among others.

[0040] Other components besides polymers can also be added to the adhesive layer. Examples of such other components include additives such as pigments, fillers, antioxidants, hydrolysis stabilizers, and antiblocking agents.

[0041] The overall thickness of the adhesive layer is preferably 5 to 50 μm, more preferably 5 to 30 μm.

[0042] (Sealing layer) The sealing layer comprises a thermoplastic elastomer, specifically a thermoplastic polyester elastomer. The thermoplastic polyester elastomer used in the sealing layer can be selected from the thermoplastic polyester elastomer materials described above for the adhesive layer.

[0043] In this embodiment, by using a thermoplastic elastomer in the sealing layer, the elasticity, flexibility, and tear strength of the resulting laminate can be improved. Furthermore, it can enhance resistance to high-temperature and / or high-humidity environments.

[0044] Like the adhesive layer, the sealing layer also comprises a thermoplastic polyester elastomer. As described above, the sealing layer and adhesive layer of this embodiment use the same thermoplastic elastomer; that is, both the sealing layer and adhesive layer use polyester elastomers. Therefore, the bond between the sealing layer and adhesive layer is strong, allowing the two layers to be integrated and improving the overall mechanical strength of the multilayer film. Furthermore, when bonded to a base fabric to form a laminate, the overall mechanical strength of the laminate is improved. The interlayer bonding strength between the sealing layer and adhesive layer also increases at room temperature, after long-term storage, and / or after high temperature and humidity storage.

[0045] The types of hard segments in the thermoplastic polyester elastomer used in the sealing layer and the types of hard segments in the thermoplastic polyester elastomer used in the adhesive layer can be the same or different. Similarly, the types of soft segments in the thermoplastic polyester elastomer used in the sealing layer and the types of soft segments in the thermoplastic polyester elastomer used in the adhesive layer can be the same or different. Furthermore, the types of hard and soft segments in the thermoplastic polyester elastomer used in the sealing layer, and the types of hard and soft segments in the thermoplastic polyester elastomer used in the adhesive layer, can be the same or different. When the types of segments are the same, the bonding force between the sealing layer and the adhesive layer can be enhanced, interlayer delamination within the multilayer film is less likely to occur, and the mechanical strength of the multilayer film and laminate can be further improved.

[0046] The melting point of the thermoplastic polyester elastomer used in the sealing layer is higher than that of the adhesive layer. Therefore, as described above, when the multilayer film is heated to a temperature lower than the melting point of the sealing layer and bonded to the base fabric, even if the adhesive layer softens or melts and performs its adhesive function, the sealing layer can still be prevented from deforming or deteriorating, thus maintaining its sealing function.

[0047] The content of hard segments in the thermoplastic polyester elastomer of the sealing layer is preferably 40 to 95% by weight, more preferably 60 to 90% by weight, relative to 100% by weight of the thermoplastic polyester elastomer. Setting it to 40% by weight or more improves the mechanical strength, heat resistance, and resistance to high temperature and humidity in the multilayer film and laminate. Furthermore, setting it to 95% by weight or less ensures adequate elasticity, flexibility, and formability of the multilayer film and laminate.

[0048] The content of soft segments in the thermoplastic polyester elastomer of the sealing layer is preferably 5 to 60% by weight, more preferably 10% or more and less than 50% by weight, relative to 100% by weight of the thermoplastic polyester elastomer. Setting it to 5% by weight or more ensures adequate elasticity, flexibility, and formability of the multilayer film and laminate. Setting it to 60% by weight or less improves the mechanical strength, heat resistance, and resistance to high temperature and humidity conditions of the multilayer film and laminate.

[0049] Furthermore, the ratio (Psa / Pss) of the soft segment content (Psa) in the thermoplastic polyester elastomer of the adhesive layer to the soft segment content (Pss) in the thermoplastic polyester elastomer of the sealing layer is preferably 1.2 to 5, more preferably 1.4 to 3.5. By setting it within the above range, production stability can be improved, and multilayer films and laminates that possess both mechanical strength and heat resistance as well as excellent elasticity and flexibility can be obtained.

[0050] As described above, the melting point of the sealing layer is higher than that of the adhesive layer. The difference between the melting points of the sealing layer and the adhesive layer is preferably 10–100°C, more preferably 20–80°C, and most preferably more than 20°C. When bonding the multilayer film to the base fabric using heat, the multilayer film and the base fabric are laminated and heated and pressurized at a temperature lower than the melting point of the sealing layer. If the difference between the melting points of the sealing layer and the adhesive layer is set within the above-mentioned range, the temperature can be easily controlled. This reduces the occurrence of problems such as insufficient softening of the adhesive layer leading to failure to achieve the bonding function, or deformation or deterioration of the sealing layer due to softening, resulting in impaired sealing performance, thereby improving production stability.

[0051] There is no particular limitation on the melting point of the sealing layer, but it is preferably 90°C or higher, more preferably 150°C or higher, and even more preferably 180°C or higher. Furthermore, there is no particular limitation on the upper limit of the melting point of the thermoplastic polymer used in the sealing layer, but considering ease of handling during multilayer film forming, it is preferably 300°C or lower, more preferably 270°C or lower, and even more preferably 230°C or lower.

[0052] The sealing layer may contain two or more of the aforementioned thermoplastic polyester elastomers. Additionally, like the adhesive layer, the sealing layer may also contain other non-polyester thermoplastic elastomers, and may also be combined with non-elastic polymers.

[0053] Similar to the adhesive layer, other components besides the polymer can also be added to the sealing layer. Examples of such other components include additives such as pigments, fillers, antioxidants, hydrolysis stabilizers, and anti-blocking agents.

[0054] The overall thickness of the sealing layer is preferably 5 to 50 μm. More preferably, it is 5 to 30 μm.

[0055] (Layer structure of multilayer films) As described above, the multilayer film has a sealing layer and an adhesive layer. The adhesive layer can be a single layer or multiple layers. When there are multiple adhesive layers, the materials constituting each adhesive layer can be the same or different. Furthermore, the melting points of each of the multiple adhesive layers can be the same or different. Similarly, the sealing layer can also be a single layer or multiple layers. When there are multiple sealing layers, the materials constituting each sealing layer and their melting points can be the same or different.

[0056] As a specific structure, a multilayer film can be formed by stacking two adhesive layers, including a first adhesive layer and a second adhesive layer, and a sealing layer in this order. In this case, pigments such as dyes can be added to either the first adhesive layer or the second adhesive layer. Compared to forming a single adhesive layer with the same volume as the combined volume of the first and second adhesive layers and adding pigments to that adhesive layer as a whole, this structure can reduce the amount of pigment.

[0057] Alternatively, a multilayer film can be formed by stacking three adhesive layers, including a first adhesive layer, a second adhesive layer, and a third adhesive layer, and a sealing layer in that order. Alternatively, a multilayer film can also be formed by stacking two sealing layers, including a first adhesive layer and a second adhesive layer, and the first and second sealing layers in that order.

[0058] (Manufacturing of multilayer films) By bonding the adhesive layer and the sealing layer, a multilayer film can be manufactured. In this case, the adhesive layer and the sealing layer can be pre-formed into separate sheets or films by extrusion molding or the like, and then bonded together to form an integrated film. Examples include methods such as overlapping the sheets or films and melting and pressing them together using a hot press or hot roller, or extrusion lamination methods that press molten material onto the formed sheets or films.

[0059] Alternatively, the materials of each layer of the adhesive layer and sealing layer can be processed into a molten state and then extruded, for example, using inflation molding or T-die molding. Among these methods, inflation molding can achieve large-area production and has superior productivity, therefore it is the preferred method.

[0060] (Kib) This type of multilayer film is a material bonded to a base fabric. In this specification, the base fabric is a sheet-like structure that acts as a support, ensuring the strength of the laminated product formed by stacking the multilayer film and the base fabric. Here, "sheet-like" refers not only to a planar shape but also to cylindrical, bag-like, and balloon-like shapes.

[0061] The base fabric preferably has a fiber-containing structure and can be a textile, woven fabric, or non-woven fabric, and can be a material that is entirely or partially sewn together. Textile fabrics are preferred due to their high mechanical strength, and a two-axis structure combining multiple vertical and horizontal lines is preferred; a three-axis structure combining multiple vertical, horizontal, and diagonal lines is also acceptable. A two-axis structure is preferred for the base fabric, and plain-woven textiles are more preferred considering strength and ease of manufacturing. Furthermore, the base fabric also includes non-planar base fabrics, such as OPW (One Piece Woven), which can be woven into a seamless bag shape with a curved surface according to the shape of the target product.

[0062] The aforementioned OPW is suitable for applications such as airbags that inflate by filling them with air. OPWs used in curtain airbags have complex curved surfaces forming multiple chambers, creating a textured structure after inflation. Typically, when bonding a film to a base fabric with such a textured structure, peeling between the base fabric and the film is more likely compared to bonding a film to a flat base fabric. Therefore, by using this type of multilayer film, even with a textured OPW, multiple layers can be well bonded, preventing interlayer peeling.

[0063] The fibers contained in the base fabric can be synthetic fibers, natural fibers, regenerated fibers, semi-synthetic fibers, inorganic fibers, and combinations thereof (including blends and weaves). Among these, synthetic fibers are preferred, and polymer fibers are particularly preferred. As fibers, composite fibers of core-sheath type fibers, side-by-side type fibers, and split type fibers can also be used.

[0064] Polymers that form fibers include homopolymers such as polyethylene terephthalate (PET) and polybutylene terephthalate (PET), as well as poly(olefin) terephthalates. Examples of homopolymer fibers include polyester fibers copolymerized from the acid components constituting the repeating units of these homopolymers with aliphatic dicarboxylic acids such as isophthalic acid, sodium isophthalate 5-sulfonate, or adipic acid; polyamide fibers copolymerized from nylon 6.6, nylon 6, nylon 12, nylon 4.6, and copolymers of nylon 6 and nylon 6.6; polyamide fibers copolymerized from nylon with polyalkylene glycol, dicarboxylic acids, and amines; aromatic polyamide fibers, represented by copolymers of paraphenylene terephthalamide and aromatic ethers; rayon fibers; ultra-high molecular weight polyethylene fibers; sulfone fibers such as paraphenylenesulfone and polysulfone; and polyetherketone fibers.

[0065] Furthermore, when the base fabric is a textile, it can contain two or more types of fibers. For example, different types of fibers can be used as threads extending in different directions. More specifically, in the case of a biaxial structure including vertical and horizontal threads, the vertical and horizontal threads can be made of different types of fibers. In this case, at least one of the vertical and horizontal threads can be polyester fibers.

[0066] This type of multilayer film is suitable for lamination on a base fabric containing polyester fibers.

[0067] The base fabric is preferably formed using yarn with a total fineness (monofilament fineness × number of strands) of 100 to 700 dtex. Furthermore, the monofilament fineness of the fibers used in the base fabric is preferably 1 to 10 dtex.

[0068] When the base fabric is a plain-woven textile, the preferred weaving density is 5 to 30 strands / cm for both vertical and horizontal threads. 2 .

[0069] The unit weight of the base fabric (per 1m) 2 The weight of the laminate (final product) is preferably 300 g / m³, taking into account the containment capacity and cost of the laminate. 2 The following is more preferably 200g / m 2 The preferred value is 190g / m 2 The preferred value is 150g / m³. 2 The following can be selected: 100g / m 2 The following. Furthermore, from the viewpoint of ensuring mechanical strength, 30 g / m² is preferred. 2 The above, more preferably 50g / m 2 The above, and more preferably 70g / m 2 above.

[0070] (Laminated body) Figure 2 This is a schematic cross-sectional view showing one aspect of the laminated body according to the present invention. The laminated body 5 is formed by bonding a multilayer film 1 having the above-described sealing layer 2 and adhesive layer 3 to a base fabric 4.

[0071] Figure 2 In the example, a multilayer film 1 is disposed on one side of the base fabric 4. Furthermore, multilayer films of this configuration can also be disposed on both sides of the base fabric 4. Additionally, when a seamless, bag-shaped OPW is used as the base fabric, such as... Figure 3 As shown, in the state of stacking after the air in the bag is discharged, a structure in which multiple layers of films 1a and 1b are stacked on the surface of the OPW from the top and bottom respectively. Figure 3 The stack shown can be used for airbags, etc.

[0072] (Manufacturing of laminated structures) One aspect of the present invention relates to a method for manufacturing a laminate having the above-described multilayer film and a base fabric, including a step of bonding the multilayer film to the base fabric at a temperature lower than the melting point of the sealing layer.

[0073] In this method of manufacturing the laminate, "film" refers to a flexible thin film, and its temperature, hardness, and other properties are not limited. That is, the provided multilayer film can be a material below room temperature or a material above room temperature. Furthermore, it can be a material that, after softening, at least a portion of it is in a state where it can perform adhesive functions. Therefore, for example, by using a heating element to heat the supplied multilayer film below room temperature at a temperature below the melting point of the sealing layer while bonding it to a base fabric, the laminate of this form can be manufactured. Alternatively, for example, by bonding a film-like polymer heated and extruded by an extruder to a base fabric, the laminate can also be manufactured.

[0074] Figure 4 The schematic representation shows a laminate manufacturing apparatus 20 for implementing the manufacturing method of the laminate of this form. Figure 4 The lieutenant general describes an apparatus for manufacturing a laminated body in which multiple films are stacked on both sides of a base fabric 4. The laminated body manufacturing apparatus 20 includes a heating unit 22 and a cooling unit 24.

[0075] In use Figure 4 In the manufacturing method of the laminate manufacturing apparatus 20, firstly, the base fabric 4 and the multilayer films 1a and 1b pre-wound on a roll or the like are unwound, and the multilayer films 1a and 1b are overlapped on both sides (top and bottom) of the base fabric 4. Specifically, as shown in the figure, the multilayer film 1a having a sealing layer 2a and an adhesive layer 3a is stacked with the adhesive layer 3a facing the base fabric 4. Furthermore, the multilayer film 1b having a sealing layer 2b and an adhesive layer 3b is stacked with the adhesive layer 3b facing the base fabric 4. Then, the overlapped multilayer film 1b, the base fabric 4, and the multilayer film 1a are fed to a heating unit 22, where they are heated and pressurized.

[0076] The heating unit 22 includes pressure elements, such as a pair of opposing rollers (clamping rollers, etc.) or a pair of opposing belts as illustrated in the figure. Thus, by passing the overlapping multilayer film 1b, the base fabric 4, and the multilayer film 1a between the pair of pressure elements, heating and pressure can be applied. Here, the melting point of the adhesive layer of the multilayer film is lower than the melting point of the sealing layer. Therefore, by setting the heating temperature of the heating unit 22 to a temperature lower than the melting point of the sealing layer, the adhesive layer can be pressed onto the base fabric while it is sufficiently softened. Thus, multilayer films 1a and 1b can be bonded to both sides of the base fabric 4, forming a laminate 5 including multilayer film 1b, the base fabric 4, and multilayer film 1a.

[0077] Next, the laminate 5, passing through the heating section 22, is conveyed to the cooling section 24. In the cooling section 24, the temperature of the laminate 5 can be reduced to a preferred ambient temperature. The cooling section 24 may include a cooling element containing a cooling medium and a suction element, etc. Furthermore, in the cooling section 24, as illustrated in the figure, pressure can be applied using a pressure element consisting of a pair of opposing strips, but pressure is not always necessary.

[0078] In addition, Figure 4 In the manufacturing apparatus, by omitting either of the multilayer films 1a and 1b, such as Figure 2 As shown, it is possible to manufacture a laminate with multiple layers of film 1 stacked on one side of the base fabric 4.

[0079] Additionally, seamless woven tubular or bag-shaped OPW can also be used as the base fabric 4. This allows for the manufacture of products such as... Figure 3 The laminated body is shown. In this case, the base fabric 4, which has become a sheet after the air inside the bag-shaped base fabric 4 is expelled, is pre-wound onto a roll or the like and then loosened before being overlapped. Then, multilayer films 1a and 1b are stacked on the top and bottom of the base fabric 4 respectively as described above. In this case, the base fabric 4 is bag-shaped, so both the top and bottom of the base fabric 4 become the surface of the base fabric 4.

[0080] Figure 5 This diagram schematically illustrates the state in which multilayer films 1a and 1b are stacked on top of and below a base fabric 4, which is placed in a flat state into the laminate manufacturing apparatus 20. (See diagram for example.) Figure 5 As shown, in the heating section 22, a pair of pressure-applying elements apply pressure to both sides of the overlapping multilayer film 1a, the base fabric 4, and the multilayer film 1b. Thus, as... Figure 3 As shown, multilayer films 1a and 1b are bonded to the upper and lower surfaces of the base fabric 4, respectively, and the edges of multilayer films 1a and 1b are bonded together by heating or the action of an adhesive, thereby obtaining a laminated body (airbag) 6. Excess edges can be removed. In this manner, an airbag can be manufactured in which the base fabric is formed into a bag shape, and a multilayer film is formed on at least one of the inner and outer surfaces of the base fabric.

[0081] The temperature during manufacturing of the laminate only needs to be below the melting point of the sealing layer; there are no particular limitations. The heating temperature can be set to a temperature below the melting point of the sealing layer, and also a temperature that softens the adhesive layer. Specifically, 120–250°C is preferred. Furthermore, the applied pressure, while depending on the structure of the multilayer film and the base fabric, can be set to 5–700 N / cm. 2 Preferably, it is 10–500 N / cm 2 Furthermore, the strength can be set to 5–50 N / cm based on the operating conditions during the manufacturing of the laminate. 2 .

[0082] (use) This type of multilayer film and laminate is suitable for use in vehicle airbags, outdoor products, packaging, etc., and is particularly suitable for vehicle airbags, especially for manufacturing curtain airbags. A curtain airbag is an airbag installed on the roofline above the side window, which can deploy vertically downwards like a curtain under high loads during an impact.

[0083] Curtain airbags inflate continuously for several seconds after deployment, for example, 6 to 7 seconds. Therefore, the materials used in curtain airbags must be pressure-resistant. Furthermore, curtain airbags are often stored in a folded or rolled-up state inside a casing for extended periods before deployment, and are frequently exposed to high temperature and humidity environments. This type of multilayer film and laminate is also suitable for such applications.

[0084] Furthermore, when laminates consisting of a membrane and a base fabric are used in vehicle airbags, various performance characteristics are required for safety. Different countries have established safety standards, which are becoming increasingly stringent. For example, in the United States, airbag safety standards have been raised in recent years. Regarding durability under high temperature and humidity conditions, for instance, the previous high temperature and humidity adhesion test requirements of 40°C, 92% relative humidity, and 168 hours have been changed to a more stringent requirement of 70°C, 95% relative humidity, and 408 hours. Therefore, airbag materials are required to withstand such severe high temperature and humidity environments. The multilayer membrane and laminate of this type, when stored under such severe high temperature and humidity conditions, are less prone to interlayer delamination, exhibiting excellent durability.

[0085] Furthermore, cost reduction has always been a requirement in the manufacture of airbags. Historically, polyamide materials such as nylon have been commonly used as the base material for airbags, but now relatively inexpensive polyester base materials are increasingly being used. Therefore, a film material with high adhesion to polyester-containing base materials is needed; however, the adhesion of conventional films to polyester base materials is sometimes insufficient. In response, this type of multilayer film exhibits superior adhesion to polyester-containing base materials.

[0086]

Example

[0087] In this embodiment, a multilayer film having a sealing layer and an adhesive layer was formed, and the multilayer film was bonded to a base fabric to manufacture a laminate, and the results were evaluated.

[0088] [Raw materials for multilayer films] The following materials are used as raw materials for multilayer films. Here, the melting point of each raw material is the peak melting temperature measured using a differential scanning calorimeter.

[0089] Thermoplastic polyester elastomer (PTEE-1): A polyester polyether block copolymer with polybutylene terephthalate as the hard segment and polytetramethylene ether glycol (with a number average molecular weight of 2000) as the soft segment. In the above copolymer, the content of polybutylene terephthalate is 25% by weight, and the content of the polytetramethylene ether glycol segment is 75% by weight (melting point 152°C).

[0090] Thermoplastic polyester elastomer (PTEE-2): A polyester polyether block copolymer with polybutylene terephthalate as the hard segment and polytetramethylene ether glycol (with a number average molecular weight of 2000) as the soft segment. In the above copolymer, the content of polybutylene terephthalate is 35% by weight, and the content of the polytetramethylene ether glycol segment is 65% by weight (melting point 185°C).

[0091] Thermoplastic polyester elastomer (PTEE-3): A polyester polyether block copolymer with polybutylene terephthalate as the hard segment and polytetramethylene ether glycol (with a number average molecular weight of 2000) as the soft segment. In the above copolymer, the content of polybutylene terephthalate is 58% by weight, and the content of the polytetramethylene ether glycol segment is 42% by weight (melting point 207°C).

[0092] Polyamide (PA): "Vestamid (registered trademark)", manufactured by Daicel-Evonik AG. [Evaluation of Multilayer Films and Laminates] <High Temperature and High Humidity Adhesion (Interlayer Peel Resistance under High Temperature and High Humidity)> A 50×150mm test piece was prepared using a laminated body formed by multilayer films and a base fabric. This test piece was placed in a sealed container, and the conditions inside the container were set to a temperature of 70°C and a relative humidity of 95% for 408 hours. While the base fabric portion of the test piece (laminated body) was fixed after being removed from the container, the force required to peel off the multilayer film portion (sealing layer and adhesive layer) in a 180° direction at a traction speed of 100 mm / min was measured. This force was used as the peel force (N / mm). The evaluation criteria are as follows.

[0093] 〇: Peeling force exceeds 0.5N / mm.

[0094] △: Peeling force is 0.3~0.5N / mm.

[0095] ×: Peel force is less than 0.3 N / mm, or interlayer peeling has occurred within the multilayer film.

[0096] Here, to prevent the multilayer film from breaking or stretching during the peel test when measuring the peel force, a 100μm thick polyethylene terephthalate film was bonded to the sealing layer side of the multilayer film with an adhesive to reinforce it.

[0097] [Example 1] (Multilayer film) Multilayer films were manufactured using an inflation extrusion unit (manufactured by Dr. Collin) with three extruders. Thermoplastic polyester elastomer (PTEE-1), thermoplastic polyester elastomer (PTEE-3), and thermoplastic polyester elastomer (PTEE-3) were fed into each extruder, and the raw materials were melted above their melting points to form a three-layer film by inflation.

[0098] The obtained film is a three-layer film formed by laminating a first adhesive layer made of thermoplastic polyester elastomer (PTEE-1), a second adhesive layer made of thermoplastic polyester elastomer (PTEE-1), and a sealing layer made of thermoplastic polyester elastomer (PTEE-3) in this order. The extrusion amount of the first adhesive layer, the second adhesive layer, and the sealing layer is 10 g / m³. 2 .

[0099] (Lamination of multilayer film and base fabric) The base fabric used is a plain weave fabric woven from polyethylene terephthalate fibers. The total fineness of both the vertical and horizontal threads is 470 dtex, and the weaving density of both the vertical and horizontal threads is 22 strands / cm.

[0100] Using a lamination device (manufactured by Mayer, Twin-belt flat lamination system), the PET base fabric and the three-layer film are laminated with the adhesive layer in contact with the base fabric surface, and heated to 170°C while using clamping rollers at 18 N / cm. 2 While applying pressure, the adhesive layer was softened, and the base fabric and the three-layer film were laminated.

[0101] [Example 2] (Multilayer film) Thermoplastic polyester elastomer (PTEE-1) was replaced with thermoplastic polyester elastomer (PTEE-2), and a three-layer film was prepared under the same conditions as in Example 1. The resulting film is a three-layer film formed by laminating a first adhesive layer composed of thermoplastic polyester elastomer (PTEE-2), a second adhesive layer composed of thermoplastic polyester elastomer (PTEE-2), and a sealing layer composed of thermoplastic polyester elastomer (PTEE-3) in that order. The extrusion amounts of the first adhesive layer, the second adhesive layer, and the sealing layer are each 10 g / m³.2 .

[0102] (Lamination of multilayer film and base fabric) The heating temperature for laminating the base fabric and the multilayer film was set to 200°C. Furthermore, a laminate of the base fabric and the multilayer film was fabricated using the same method as in Example 1. The evaluation was conducted in the same manner as in Example 1. The results are shown in Table 1.

[0103] [Comparative Example 1] (Multilayer film) Polyamide (PA) was used instead of thermoplastic polyester elastomer (PTEE-3), and a three-layer film was prepared under the same conditions as in Example 1. The resulting film is a three-layer film formed by laminating a first adhesive layer made of thermoplastic polyester elastomer (PTEE-1), a second adhesive layer made of thermoplastic polyester elastomer (PTEE-1), and a sealing layer made of polyamide (PA) in that order. The extrusion amounts of the first adhesive layer, the second adhesive layer, and the sealing layer are all 10 g / m³. 2 .

[0104] (Lamination of multilayer film and base fabric) Similar to Example 1, laminates of the base fabric and multilayer film were fabricated and evaluated. The results are shown in Table 1.

[0105] [Table 1] *Interlayer delamination occurred within the multilayer film. The laminates prepared in Examples 1 and 2, which use thermoplastic polyester elastomers in both the adhesive and sealing layers and have a higher melting point than the adhesive layer, exhibit superior production stability. That is, production can proceed stably even if manufacturing conditions such as heating temperature change during the manufacturing process. Furthermore, in Examples 1 and 2, the difference between the melting point of the sealing layer and the adhesive layer exceeds 20°C, thus demonstrating particularly excellent production stability. Additionally, the laminates prepared in Examples 1 and 2 also exhibit excellent adhesion under high temperature and high humidity conditions.

[0106] In contrast, in Comparative Example 1, where the adhesive layer is a thermoplastic polyester elastomer and the sealing layer is polyamide, interlayer delamination is visible between the adhesive layer and the sealing layer. The production stability and adhesion under high temperature and humidity conditions are not as good as in Examples 1 and 2.

[0107] This application claims priority to Japanese Patent Application No. 2017-119099, filed on June 16, 2017 with the Japanese Patent Office, and incorporates the entire contents of that patent application.

[0108] Symbol Explanation 1, 1a, 1b Multilayer films; 2, 2a, 2b Sealing layers; 3, 3a, 3b Adhesive layers; 4. Base fabric; 5. Laminated structures; 6. Laminated structure (airbag); 20. Laminated body manufacturing apparatus; 22. Heating section; 24. Cooling section.

Claims

1. An airbag formed by using a laminated body, the laminated body being formed by bonding a multilayer film to a base fabric, wherein the base fabric is formed in a bag-like shape, and the multilayer film is formed on the surface of the base fabric, the multilayer film comprising: The adhesive layer serves as the side of the multilayer film that is bonded to the base fabric; and A sealing layer that bonds with the adhesive layer, The adhesive layer and the sealing layer each comprise a thermoplastic polyester elastomer. The melting point of the sealing layer is higher than that of the adhesive layer, and the difference between the two exceeds 20°C. Furthermore, the melting point of the sealing layer is 180°C or higher. The ratio of the soft segment content in the thermoplastic polyester elastomer of the adhesive layer to the soft segment content in the thermoplastic polyester elastomer of the sealing layer is 1.2 to 5.

2. The airbag according to claim 1, The hard segments of the thermoplastic polyester elastomer in the adhesive layer comprise aromatic polyesters, and the hard segments of the thermoplastic polyester elastomer in the sealing layer comprise aromatic polyesters.

3. The airbag according to claim 2, The aromatic polyester comprises polybutylene terephthalate.

4. The airbag according to claim 1, The soft segments of the thermoplastic polyester elastomer in the adhesive layer comprise aliphatic polyethers, and the soft segments of the thermoplastic polyester elastomer in the sealing layer comprise aliphatic polyethers.

5. The airbag according to claim 1, The proportion of soft segments in the thermoplastic polyester elastomer of the adhesive layer is 50% to 90% by weight relative to 100% by weight of the thermoplastic polyester elastomer of the adhesive layer.

6. The airbag according to claim 1, The adhesive layer includes a first adhesive layer and a second adhesive layer, and The first adhesive layer or the second adhesive layer contains pigment.

7. The airbag according to claim 1, The base fabric contains polyester.

8. A method for manufacturing an airbag according to any one of claims 1 to 7, the method comprising: The process of bonding the multilayer film to the base fabric at a temperature lower than the melting point of the sealing layer.

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