Addition-curable liquid silicone rubber composition for airbags, and airbag

Abstract

The present invention provides an addition-curable liquid silicone rubber composition for airbags, which is characterized by containing: (A) an organopolysiloxane that has two or more alkenyl groups each bonded to a silicon atom in each molecule and has a degree of polymerization of 50-2,000; (B) an organohydrogenpolysiloxane that has two or more hydrogen atoms each bonded to a silicon atom (two or more hydrosilyl groups) in each molecule; (C) a silica fine powder that has a specific surface area of 50 m2 / g or more as determined by a BET method; (D) a hydrosilylation reaction catalyst; (E) an organosilicon compound that has an adhesiveness-imparting functional group; and (F) one or more selected from among sulfates, sulfonates, phosphates, and carbonates of alkali metals. The present invention thereby provides: an addition-curable liquid silicone rubber composition for airbags, which has excellent flame retardancy and adhesiveness when applied to a base fabric for airbags and cured, and which can be stored for a long period of time; and an airbag.

Description

Addition-curing type liquid silicone rubber composition for airbag and airbag

[0001] The present invention relates to an addition-curing type liquid silicone rubber composition for airbag and an airbag.

[0002] Conventionally, a silicone rubber composition for airbag aimed at forming a rubber coating on the surface of fibers has been proposed. An airbag having a silicone rubber coating is preferably used as an airbag for automobiles and the like because it has excellent internal pressure retention and flame retardancy.

[0003] As such an addition-curing type liquid silicone rubber composition for airbag, an addition-curing type liquid silicone coating composition for airbag using an organohydrogenpolysiloxane containing a T unit or a Q unit as a crosslinking agent has been disclosed (Patent Document 1). The coating base fabric coated with this composition is characterized by excellent strength. In addition, an addition-curing type liquid silicone rubber composition for airbag in which a silicone resin composed of M, D, and Q units and containing a crosslinkable functional group only in the D unit is blended as a flame retardant has been disclosed (Patent Document 2). The silicone coating base fabric for airbag coated with this composition on a nylon base fabric is characterized by excellent flame retardancy.

[0004] On the other hand, in recent years, in order to reduce costs and CO ２ emissions, the switch to a PET base fabric for the airbag base fabric has been progressing, and the development of a silicone coating composition for airbag having the same flame retardancy as that of a nylon base fabric even with a PET base fabric is desired. As a method for improving the flame retardancy of a silicone coating PET base fabric for airbag, a composition in which iron(III) hydroxide monohydrate or α-iron(III) oxide is blended as a flame retardant in a silicone rubber composition has been disclosed (Patent Document 3). However, in the method of blending a large amount of an inorganic salt flame retardant, there is a high possibility that sedimentation of the flame retardant in the silicone rubber composition occurs over time, and there is a problem of poor storage stability in the long term.

[0005] As a method to improve the flame retardancy of other silicone-coated PET base fabrics for airbags, a method of compounding a metal carboxylate salt into a silicone rubber composition has been disclosed (Patent Document 4). This method yields a silicone-coated PET base fabric with less color unevenness during coating and excellent flame retardancy. However, since metal carboxylate salts crack the silicone polymer, there was a problem that the viscosity decreased and the rubber properties deteriorated when the silicone rubber composition containing the metal carboxylate salt was stored for a long period of time.

[0006] Japanese Patent Publication No. 2019-513907, International Publication No. 2018 / 168315, Japanese Patent Publication No. 2022-072086, Japanese Patent Publication No. 2024-078296

[0007] The present invention has been made in view of the above circumstances, and aims to provide an addition-curing liquid silicone rubber composition for airbags, which exhibits excellent flame retardancy and adhesion when coated onto an airbag base fabric and cured, and which can be stored for a long period of time, as well as an airbag.

[0008] To solve the above problems, the present invention provides an addition-curing liquid silicone rubber composition for airbags, comprising: (A) 100 parts by mass of an organopolysiloxane having alkenyl groups bonded to two or more silicon atoms in one molecule and a degree of polymerization of 50 to 2,000; (B) an organohydrogenpolysiloxane having hydrogen atoms (hydrosilyl groups) bonded to two or more silicon atoms in one molecule: an amount such that the hydrosilyl groups contained in the composition are 1 to 10 moles per mole of the total alkenyl groups bonded to silicon atoms contained in the composition; and (C) a specific surface area of ​​50 m² by the BET method. ２Silica fine powder having a BET specific surface area of 1 to 500 m² / g: 1 to 50 parts by mass, (D) catalyst for hydrosilylation reaction: 1 to 500 ppm in terms of the mass of the catalyst metal element with respect to the mass of the component (A), (E) organosilicon compound having an adhesion-imparting functional group: 0.1 to 10 parts by mass, and (F) one or more selected from alkali metal sulfates, sulfonates, phosphates, and carbonates: 100 to 2,000 ppm in terms of the mass of the alkali metal with respect to the mass of the component (A), and an addition-curing type liquid silicone rubber composition for an airbag containing the same is provided.

[0009] Such an addition-curing type liquid silicone rubber composition for an airbag can be stored for a long time, and furthermore, the silicone-coated base fabric for an airbag produced therefrom has excellent flame retardancy and adhesiveness.

[0010] In the present invention, it is preferable that the component (E) contains at least one reactive silyl group selected from an alkoxysilyl group, an alkenyl group-containing silyl group, and a hydrosilyl group in one molecule, and at least one reactive organic group selected from an epoxy group, an isocyanate group, and a (meth)acrylic group.

[0011] Such an addition-curing type liquid silicone rubber composition for an airbag has more excellent adhesiveness of the silicone rubber layer to the base fabric for an airbag.

[0012] In the present invention, it is preferable that the addition-curing type liquid silicone rubber composition for an airbag further contains, as the component (G), one or more condensation catalysts selected from an organic titanium compound, an organic zirconium compound, and an organic aluminum compound, in an amount of 0.05 to 5 parts by mass with respect to 100 parts by mass of the component (A).

[0013] Such an addition-curing type liquid silicone rubber composition for an airbag has more excellent adhesiveness of the silicone rubber layer to the base fabric for an airbag.

[0014] In the present invention, it is preferable that the alkali metal of the component (F) is sodium or potassium.

[0015] With such an addition-curing liquid silicone rubber composition for airbags, the silicone coated base fabric for airbags prepared from it will have superior flame retardancy.

[0016] Furthermore, in the present invention, it is preferable that the addition-curing liquid silicone rubber composition for airbags further contains, as component (H), 0.1 to 100 parts by mass of powdered three-dimensional network organopolysiloxane resin (provided that the organopolysiloxane resin does not contain hydrogen atoms bonded to silicon atoms) per 100 parts by mass of component (A).

[0017] With such an addition-curing liquid silicone rubber composition for airbags, the silicone coated base fabric for airbags prepared from it will have superior flame retardancy.

[0018] Furthermore, the present invention provides an airbag having a cured coating of the above-described addition-curing liquid silicone rubber composition for airbags on an airbag base fabric.

[0019] Such an airbag would have excellent flame retardancy and adhesive properties.

[0020] Furthermore, in the present invention, it is preferable that the base fabric for the airbag is made of polyester fiber.

[0021] If the base fabric is made of polyester fibers, CO2 will be used during manufacturing. ２ Emissions are lower than with nylon base fabric, resulting in a smaller environmental impact.

[0022] As described above, according to the present invention, by coating an airbag base fabric with the silicone coating and curing it, an airbag silicone coating base fabric with excellent flame retardancy and adhesion can be obtained, and an airbag addition-curing liquid silicone rubber composition that can be stored for a long period of time can be obtained.

[0023] As described above, there was a need for the development of an addition-curing liquid silicone rubber composition for airbags, and for airbags themselves, that would exhibit excellent flame retardancy and adhesion when coated onto an airbag base fabric and cured, and that could be stored for a long period of time.

[0024] As a result of diligent research into the above-mentioned problems, the present inventors have discovered that an addition-curing liquid silicone rubber composition for airbags containing an alkali metal salt exhibits excellent flame retardancy and adhesion to the coated base fabric when coated onto an airbag base fabric and cured, thus completing the present invention.

[0025] In other words, the present invention relates to an addition-curing liquid silicone rubber composition for airbags, comprising: (A) 100 parts by mass of an organopolysiloxane having alkenyl groups bonded to two or more silicon atoms in one molecule and a degree of polymerization of 50 to 2,000; (B) an organohydrogenpolysiloxane having hydrogen atoms (hydrosilyl groups) bonded to two or more silicon atoms in one molecule: in an amount such that the amount of hydrosilyl groups contained in the composition is 1 to 10 moles per mole of the total amount of alkenyl groups bonded to silicon atoms contained in the composition; and (C) having a specific surface area of ​​50 m² by the BET method. ２ This is an addition-curing liquid silicone rubber composition for airbags, containing: (D) silica fine powder with a concentration of 1 / g or more: 1 to 50 parts by mass; (A) catalyst for hydrosilylation reaction: 1 to 500 ppm in mass of the catalyst metal element relative to the mass of component (A); (E) organosilicon compound having an adhesion-imparting functional group: 0.1 to 10 parts by mass; and (F) one or more alkali metals selected from sulfates, sulfonates, phosphates, and carbonates: 100 to 2,000 ppm in mass of the alkali metal relative to the mass of component (A).

[0026] The present invention will be described in detail below, but is not limited thereto. In this specification, viscosity is the value measured by a rotational viscometer at 25°C using the method described in JIS K 7117-1:1999. The weight-average degree of polymerization is the value obtained as the weight-average molecular weight (weight-average degree of polymerization) in polystyrene terms by GPC (gel permeation chromatography) analysis using tetrahydrofuran (THF) as the developing solvent, measured under the following conditions. [Measurement Conditions] Developing solvent: Tetrahydrofuran Flow rate: 0.35 mL / min Detector: Differential refractive index detector (RI) Column: TSK Guardcolumn SuperH-L TSKgel SuperH4000 (6.0 mm I.D. × 15 cm × 1) TSKgel SuperH3000 (6.0 mm I.D. × 15 cm × 1) TSKgel SuperH2000 (6.0 mm I.D. × 15 cm × 2) (All manufactured by Tosoh Corporation) Column temperature: 40°C Sample injection volume: 10 μL (0.5 wt% tetrahydrofuran solution)

[0027] <Addition-curing liquid silicone rubber composition for airbags> The addition-curing liquid silicone rubber composition for airbags of the present invention comprises: (A) 100 parts by mass of an organopolysiloxane having alkenyl groups bonded to two or more silicon atoms in one molecule and a degree of polymerization of 50 to 2,000; (B) an organohydrogenpolysiloxane having hydrogen atoms (hydrosilyl groups) bonded to two or more silicon atoms in one molecule: an amount such that the hydrosilyl groups contained in the composition are 1 to 10 moles per mole of the total alkenyl groups bonded to silicon atoms contained in the composition; (C) a specific surface area of ​​50 m² by the BET method. ２The mixture contains: (D) silica fine powder with a concentration of 1 to 50 parts by mass, (A) catalyst for hydrosilylation reaction: 1 to 500 ppm in mass of the catalyst metal element relative to the mass of component (A), (E) organosilicon compound having an adhesion-imparting functional group: 0.1 to 10 parts by mass, and (F) one or more alkali metals selected from sulfates, sulfonates, phosphates, and carbonates: 100 to 2,000 ppm in mass of alkali metal relative to the mass of component (A), and is liquid at room temperature (25°C). Each component will be described in detail below.

[0028] [Component (A)] Component (A) is an organopolysiloxane having a weight-average degree of polymerization of 50 to 2,000, containing two or more alkenyl groups bonded to silicon atoms in one molecule, that is, an organopolysiloxane having two or more alkenyl groups bonded to silicon atoms in one molecule and a degree of polymerization of 50 to 2,000, and is the base polymer (main component) of the addition-curing liquid silicone rubber composition for airbags according to the present invention.

[0029] The molecular structure of component (A) is preferably linear, with the main chain consisting of repeating diorganosiloxane units, and both ends of the molecular chain sealed with triorganosiloxy groups, forming a diorganopolysiloxane. Furthermore, the position of the silicon atom to which the alkenyl group is bonded in the molecule of the linear organopolysiloxane of component (A) may be either at the end of the molecular chain (i.e., the triorganosiloxy group) or in the middle of the molecular chain (i.e., a bifunctional diorganosiloxane unit located at the non-terminus of the molecular chain), or both. Particularly preferred as component (A) is a linear diorganopolysiloxane containing alkenyl groups bonded to silicon atoms at at least both ends of the molecular chain.

[0030] (A) Examples of alkenyl groups bonded to silicon atoms in component (A) include those typically having 2 to 8 carbon atoms, preferably 2 to 4 carbon atoms. Specific examples include vinyl groups, allyl groups, propenyl groups, butenyl groups, pentenyl groups, hexenyl groups, cyclohexenyl groups, heptenyl groups, etc., with vinyl groups being particularly preferred.

[0031] (A) The number of alkenyl groups bonded to the silicon atom in component (A) is two or more, preferably 2 to 100, and more preferably 2 to 50.

[0032] (A) Examples of monovalent hydrocarbon groups bonded to silicon atoms other than the alkenyl group of component (A) include monovalent hydrocarbon groups having 1 to 12 carbon atoms, preferably 1 to 10 carbon atoms. Specific examples of monovalent hydrocarbon groups include alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclohexyl, and heptyl groups; aryl groups such as phenyl, tolyl, xylyl, and naphthyl groups; aralkyl groups such as benzyl and phenethyl groups; and halogen-substituted alkyl groups such as chloromethyl, 3-chloropropyl, and 3,3,3-trifluoropropyl groups, with methyl groups being particularly preferred.

[0033] The weight-average degree of polymerization of component (A) is 50 to 2,000, preferably 100 to 1,500, and more preferably 120 to 1,000. If the weight-average degree of polymerization is lower than 50, the mechanical properties of the cured product obtained from the addition-curing liquid silicone rubber composition for airbags of the present invention may be poor. If the weight-average degree of polymerization is greater than 2,000, the viscosity of the resulting addition-curing liquid silicone rubber composition for airbags may be high, resulting in poor coating workability.

[0034] The viscosity of component (A) is preferably 50 to 200,000 mPa·s, more preferably 100 to 150,000 mPa·s, and even more preferably 400 to 100,000 mPa·s at 25°C. If the viscosity of component (A) is 50 mPa·s or higher, the mechanical properties of the cured product obtained from the addition-curing liquid silicone rubber composition for airbags of the present invention will be good, and if it is 200,000 mPa·s or lower, the viscosity of the obtained addition-curing liquid silicone rubber composition for airbags will not be high, and the coating workability will be good.

[0035] (A) Specific examples of organopolysiloxanes include: dimethylsiloxane / methylvinylsiloxane copolymer with trimethylsiloxy groups sealed at both ends of the molecular chain, methylvinylpolysiloxane with trimethylsiloxy groups sealed at both ends of the molecular chain, dimethylsiloxane / methylvinylsiloxane / methylphenylsiloxane copolymer with trimethylsiloxy groups sealed at both ends of the molecular chain, dimethylpolysiloxane with dimethylvinylsiloxy groups sealed at both ends of the molecular chain, methylvinylpolysiloxane with dimethylvinylsiloxy groups sealed at both ends of the molecular chain, and dimethylsiloxane / methylvinyl Examples include nylsiloxane copolymers, dimethylsiloxane / methylvinylsiloxane / methylphenylsiloxane copolymers with dimethylvinylsiloxy groups sealed at both ends of the molecular chain, dimethylpolysiloxane with divinylmethylsiloxy groups sealed at both ends of the molecular chain, dimethylsiloxane / methylvinylsiloxane copolymers with divinylmethylsiloxy groups sealed at both ends of the molecular chain, dimethylpolysiloxane with trivinylsiloxy groups sealed at both ends of the molecular chain, dimethylsiloxane / methylvinylsiloxane copolymers with trivinylsiloxy groups sealed at both ends of the molecular chain, and mixtures of two or more organopolysiloxanes thereof.

[0036] (A) The organopolysiloxane component may be used alone or in combination of two or more types.

[0037] [Component (B)] Component (B) is an organohydrogenpolysiloxane having two or more hydrogen atoms (hydrosilyl groups) bonded to silicon atoms in one molecule, and acts as a crosslinking agent for this composition.

[0038] The molecular structure of component (B), the organohydrogenpolysiloxane, may be linear, cyclic, branched, or three-dimensional network structure. In this case, the number of silicon atoms (or degree of polymerization) in one molecule is 2 to 300, and a liquid at 25°C with approximately 4 to 200 silicon atoms is preferably used. The number of hydrosilyl groups contained in one molecule is 2 to 200, preferably 2 to 150, and more preferably 2 to 100. Note that the hydrosilyl groups may be located at the end of the molecular chain, in the side chain (middle of the molecular chain), or both.

[0039] As the substituent bonded to the silicon atom of the component (B), for example, a monovalent hydrocarbon group having usually 1 to 12 carbon atoms, preferably 1 to 10 carbon atoms is generally mentioned. Specific examples of the monovalent hydrocarbon group include alkyl groups such as methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, cyclohexyl group, heptyl group; aryl groups such as phenyl group, tolyl group, xylyl group, naphthyl group; aralkyl groups such as benzyl group, phenethyl group; halogen-substituted alkyl groups such as chloromethyl group, 3-chloropropyl group, 3,3,3-trifluoropropyl group, etc. Particularly, it is preferably a methyl group or a phenyl group.

[0040] As such an organohydrogenpolysiloxane, for example, 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, methylhydrogen cyclopolysiloxane, methylhydrogen siloxane / dimethylsiloxane cyclic copolymer, tris(dimethylhydrogensiloxy)methylsilane, tris(dimethylhydrogensiloxy)phenylsilane, both ends trimethylsiloxy group-blocked methylhydrogenpolysiloxane, both ends trimethylsiloxy group-blocked dimethylsiloxane / methylhydrogen siloxane copolymer, both ends dimethylhydrogensiloxy group-blocked dimethylpolysiloxane, both ends dimethylhydrogensiloxy group-blocked dimethylsiloxane / methylhydrogen siloxane copolymer, both ends trimethylsiloxy group-blocked methylhydrogen siloxane / diphenylsiloxane copolymer, both ends trimethylsiloxy group-blocked methylhydrogen siloxane / diphenylsiloxane / dimethylsiloxane copolymer, cyclic methylhydrogenpolysiloxane, cyclic methylhydrogen siloxane / dimethylsiloxane copolymer, cyclic methylhydrogen siloxane / diphenylsiloxane / dimethylsiloxane copolymer, (CH ３ ) ２ HSiO １／２ units and SiO ４／２ units and a copolymer composed of (CH [[ID=!2]] ３ ) ２ HSiO １／２ units and SiO ４／２ units and (C６ H ５ ) SiO ３／２ Examples include copolymers consisting of units, and in each of the above example compounds, some or all of the methyl groups are substituted with other alkyl groups such as ethyl groups and propyl groups, or aryl groups such as phenyl groups. Specifically, examples of such organohydrogenpolysiloxanes include compounds with the following structural formulas.

[0041] (In the formula, e is an integer between 2 and 200, and f, g, and h are integers between 0 and 200.)

[0042] The organohydrogenpolysiloxane of component (B) preferably has a viscosity of 0.5 to 10,000 mPa·s at 25°C, and is particularly preferably 1 to 300 mPa·s.

[0043] The amount of component (B) is such that, for every 1 mole (or individual) of alkenyl groups bonded to silicon atoms in the composition containing component (A), the hydrosilyl groups contained in the composition containing component (B) are 1 to 10 moles (or individual), preferably 1.2 to 8 moles (or individual), and more preferably 1.5 to 6 moles (or individual). If the amount of hydrosilyl groups contained in the composition containing component (B) is less than 1 mole for every 1 mole of alkenyl groups bonded to silicon atoms in the composition containing component (A), the addition-curing liquid silicone rubber composition for airbags will not cure sufficiently. If this amount exceeds 10 moles, the heat resistance of the cured silicone rubber product obtained from the addition-curing liquid silicone rubber composition for airbags may be extremely poor.

[0044] (B) The organohydrogenpolysiloxane may be used alone or in combination of two or more types.

[0045] [Component (C)] The specific surface area of ​​component (C) calculated by the BET method is 50 m². ２Silica fine powder with a specific surface area of ​​50 m² / g or more acts as a reinforcing filler. That is, it imparts strength to the cured silicone rubber obtained from the addition-curing liquid silicone rubber composition for airbags according to the present invention. By using silica fine powder as a reinforcing filler, it is possible to form a coating film that satisfies the strength required by the present invention. Such silica fine powder has a specific surface area of ​​50 m² by the BET method. ２ The amount is 50 to 400 mg / g or more, preferably 50 to 400 mg / g. ２ / g, more preferably 100 to 300m ２ It is / g. The specific surface area is 50 m². ２ Below a certain concentration ( / g), it is not possible to impart satisfactory mechanical strength properties as an airbag coating agent.

[0046] Such silica fine powder has a specific surface area of ​​50 m². ２ The specified amount is 1 / g or more, and it can be any known material that has been conventionally used as a reinforcing filler for cured silicone rubber, such as fumed silica or precipitated silica. The specific surface area can be measured using the BET method as described in JIS Z 8830:2013.

[0047] The silica fine powder used may be silica fine powder whose surface has been hydrophobized with a surface treatment agent such as a (usually hydrolyzable) organosilicon compound such as chlorosilane, alkoxysilane, or organosilazane. In this case, the silica fine powder may be used that has been directly surface-hydrophobized with a surface treatment agent in its powder form beforehand. Alternatively, the silica fine powder may be used that has been surface-hydrophobized by adding a surface treatment agent during kneading with silicone oil (for example, an organopolysiloxane containing the alkenyl group of component (A) above).

[0048] (C) Component can be treated by known techniques. For example, the untreated silica fine powder and the surface treatment agent can be placed in a sealed mechanical kneading apparatus or fluidized bed at atmospheric pressure and mixed at room temperature (25°C) or under heat treatment (heating) in the presence of an inert gas as needed. In some cases, water or a catalyst (such as a hydrolysis accelerator) may be used to accelerate the surface treatment. After kneading, the surface-treated silica fine powder can be produced by drying. The amount of surface treatment agent to be added should be equal to or greater than the amount calculated from the coverage area of ​​the surface treatment agent.

[0049] Specific examples of surface treatment agents include silazanes such as hexamethyldisilazane, silane coupling agents such as methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, dimethyldimethoxysilane, diethyldimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, trimethylmethoxysilane, triethylmethoxysilane, vinyltris(methoxyethoxy)silane, trimethylchlorosilane, dimethyldichlorosilane, divinyldimethoxysilane, and chloropropyltrimethoxysilane, polymethylsiloxane, organohydrogenpolysiloxane, etc. Surface treatment with these agents can be used to produce hydrophobic silica fine powder. Silane coupling agents or silazanes are particularly preferred as surface treatment agents.

[0050] Furthermore, when using silica fine powder of component (C) that has been directly surface-hydrophobized in advance in powder form with a surface treatment agent containing alkenyl groups, the amount of hydrosilyl groups contained in the composition containing component (B) is 1 to 10 moles (or units), preferably 1.2 to 8 moles (or units), more preferably 1.5 to 6 moles (or units), for every 1 mole of alkenyl groups bonded to silicon atoms contained in the composition containing component (A) and the surface treatment agent of component (C).

[0051] This is because, if the amount of hydrosilyl groups is less than 1 mole per mole of alkenyl groups bonded to silicon atoms in the addition-curing liquid silicone rubber composition for airbags, the addition-curing liquid silicone rubber composition for airbags may not cure sufficiently. On the other hand, if the amount of hydrosilyl groups exceeds 10 moles, the heat resistance of the cured silicone rubber product obtained from the addition-curing liquid silicone rubber composition for airbags may deteriorate drastically.

[0052] The amount of component (C) is 1 to 50 parts by mass, preferably 3 to 30 parts by mass, and more preferably 5 to 25 parts by mass, per 100 parts by mass of organopolysiloxane of component (A). If the amount is less than 1 part by mass, a silicone rubber cured product with sufficient strength cannot be obtained, and if the amount exceeds 50 parts by mass, the viscosity of the resulting addition-curing liquid silicone rubber composition for airbags will increase, reducing fluidity and potentially worsening the coating process.

[0053] (C) The silica fine powder of component (C) may be used alone or in combination of two or more types.

[0054] [Component (D)] The catalyst for the hydrosilylation reaction of component (D) mainly promotes the addition reaction between the alkenyl group bonded to the silicon atom in component (A) and the hydrosilyl group in component (B). This catalyst for the hydrosilylation reaction is not particularly limited and includes, for example, platinum group metals such as platinum, palladium, and rhodium; chloroplatinic acid; alcohol-modified chloroplatinic acid; coordination compounds of chloroplatinic acid with olefins, vinylsiloxanes, or acetylene compounds; platinum group metal compounds such as tetrakis(triphenylphosphine)palladium and chlorotris(triphenylphosphine)rhodium, and is preferably a platinum group metal compound.

[0055] The amount of component (D) is 1 to 500 ppm, preferably 5 to 100 ppm, relative to the mass of component (A) in terms of the mass of the catalyst metal element. If the amount is less than 1 ppm, the addition reaction may be significantly delayed, or the addition-curing liquid silicone rubber composition for airbags may not cure. If the amount exceeds 500 ppm, the heat resistance of the cured silicone rubber product may decrease.

[0056] The catalyst for the hydrosilylation reaction of component (D) may be used alone or in combination of two or more types.

[0057] [Component (E)] Component (E) is an organosilicon compound having an adhesion-imparting functional group, and is added to develop and improve the adhesion of the addition-curing liquid silicone rubber composition for airbags to the base fabric for airbags.

[0058] Component (E) can be any organosilicon compound having an adhesion-imparting functional group, but it is preferable that it contains one or more reactive silyl groups selected from alkoxysilyl groups, alkenyl-containing silyl groups, and hydrosilyl groups, and one or more reactive organic groups selected from epoxy groups, isocyanate groups, and (meth)acrylic groups in one molecule.

[0059] Preferably, the alkoxysilyl group is bonded to a silicon atom to form trialkoxysilyl groups such as trimethoxysilyl and triethoxysilyl groups; or alkyldialkoxysilyl groups such as methyldimethoxysilyl, ethyldimethoxysilyl, methyldiethoxysilyl, and ethyldiethoxysilyl groups.

[0060] In alkenyl group-containing silyl groups, it is preferable that the alkenyl group is directly bonded to a silicon atom. Specific examples include vinyltrimethoxysilane and vinyltriethoxysilane.

[0061] The epoxy group is preferably bonded to the silicon atom in the form of a glycidoxyalkyl group such as a glycidoxypropyl group, or an epoxy-containing cyclohexylalkyl group such as a 2,3-epoxycyclohexylethyl group or a 3,4-epoxycyclohexylethyl group.

[0062] The isocyanate group is preferably bonded to a silicon atom via a carbon chain. Specific examples include 3-isocyanate-propyltrimethoxysisilane and 3-isocyanate-propyltriethoxysilane.

[0063] The (meth)acrylic group is preferably bonded to a silicon atom via a carbon chain. Specific examples include 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, and 3-acryloxypropyltriethoxysilane.

[0064] Examples of organosilicon compounds for component (E) include γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, (3,4-epoxycyclohexylethyl)trimethoxysilane, (3,4-epoxycyclohexylethyl)triethoxysilane, (3,4-epoxycyclohexylethyl)methyldimethoxysilane, (3,4-epoxycyclohexylethyl)methyldiethoxysilane, (2,3-epoxycyclohexylethyl)triethoxysilane, (2,3-epoxycyclohexylethyl)methyldimethoxysilane, (2,3-epoxycyclohexylethyl)methyldiethoxysilane, etc. Examples include silane coupling agents containing silane groups (i.e., organoalkoxysilanes containing epoxy functional groups); silane coupling agents containing (meth)acrylic groups such as 3-acryloxypropyltrimethoxysilane and 3-methacryloxypropyltrimethoxysilane; silane coupling agents containing isocyanate groups such as 3-isocyanatetopropyltriethoxysilane and 3-isocyanatetopropyltrimethoxysilane; cyclic organopolysiloxanes containing epoxy groups represented by the following chemical formulas; organosilicon compounds such as linear organopolysiloxanes containing epoxy groups; mixtures of two or more of these, or partial hydrolysis condensates of one or more of these.

[0065] The main examples are listed below. (In the formula, p is an integer between 1 and 40, q is an integer between 0 and 40, and r is an integer between 1 and 40, preferably between 1 and 20.)

[0066] The amount of component (E) is 0.1 to 10 parts by mass, preferably 0.15 to 5 parts by mass, per 100 parts by mass of organopolysiloxane of component (A). If the amount is less than 0.1 parts by mass, the resulting addition-curing liquid silicone rubber composition for airbags may not exhibit sufficient adhesive strength. If the amount exceeds 10 parts by mass, the thixotropy of the addition-curing liquid silicone rubber composition for airbags may increase, reducing fluidity and worsening coating workability.

[0067] Furthermore, if component (E) contains an alkenyl group and / or a hydrosilyl group, the total amount of hydrosilyl groups contained in the composition containing components (B) and (E) is 1 to 10 moles (or groups), preferably 1.2 to 8 moles (or groups), and more preferably 1.5 to 6 moles (or groups), relative to the total amount of alkenyl groups bonded to silicon atoms (or nitrogen atoms) contained in the composition containing components (A), (C), and (E).

[0068] This is because, if the amount of hydrosilyl groups is less than 1 mole per mole of alkenyl groups bonded to silicon atoms in the addition-curing liquid silicone rubber composition for airbags, the addition-curing liquid silicone rubber composition for airbags may not cure sufficiently and may not exhibit sufficient adhesive strength. On the other hand, if the amount of hydrosilyl groups exceeds 10 moles, the heat resistance of the cured silicone rubber product obtained from the addition-curing liquid silicone rubber composition for airbags may be extremely poor.

[0069] (E) Component may be used alone or in combination of two or more types.

[0070] [Component (F)] Component (F) is one or more selected from alkali metal sulfates, sulfonates, phosphates, and carbonates, and acts as a flame retardant. Specifically, alkali metals include lithium, sodium, potassium, rubidium, cesium, and francium. The amount of component (F) is 100 to 2,000 ppm relative to the mass of component (A) by the mass of alkali metal, preferably 150 to 1,500 ppm, and more preferably 200 to 1,000 ppm. If the amount of component (F) is less than 100 ppm, a sufficient flame retardancy improvement effect may not be obtained, and if it is more than 2,000 ppm, the viscosity of the composition may increase, and the coating workability may deteriorate.

[0071] The alkali metal of component (F) is preferably sodium or potassium. When the alkali metal is sodium or potassium, it is readily available.

[0072] When component (F) is a sulfate, sulfonate, or phosphate, there are no particular restrictions on the organic group it contains, but it is preferably an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 20 carbon atoms. Such sulfates, sulfonates, or phosphates are readily available.

[0073] (F) Specific examples of components include sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sodium nonanesulfonate, potassium nonanesulfonate, sodium decanesulfonate, potassium decanesulfonate, sodium dodecanesulfonate, potassium dodecanesulfonate, sodium tetradecanesulfonate, potassium tetradecanesulfonate, sodium pentadecanesulfonate, potassium pentadecanesulfonate, sodium hexadecanesulfonate, potassium hexadecanesulfonate, sodium dodecylbenzenesulfonate, potassium dodecylbenzenesulfonate, 5- Examples include dimethyl sodium sulfoizophthalate, dimethyl potassium 5-sulfoizophthalate, sodium sulfate, potassium sulfate, sodium dodecyl sulfate, potassium dodecyl sulfate, sodium hexadecylate, potassium hexadecyl sulfate, trisodium phosphate, sodium monododecyl phosphate, sodium didodecyl phosphate, disodium phenyl phosphate, etc., but sodium carbonate, potassium carbonate, sodium dodecylbenzenesulfonate, potassium dodecylbenzenesulfonate, sodium dodecyl sulfate, potassium dodecyl sulfate, and sodium monododecyl phosphate are particularly preferred.

[0074] It is preferable to disperse the alkali metal salt of component (F) in a suitable solvent before incorporating it into the silicone rubber composition. This allows for uniform dispersion of component (F) in the silicone rubber composition, reducing uneven coating when coating the addition-curing liquid silicone rubber composition onto the airbag base fabric. The solvent is not particularly limited as long as it is commonly used, but it is preferable to use a low-boiling point polar solvent such as water, methanol, or ethanol.

[0075] Component (F) may be used alone or in combination of two or more types.

[0076] [Other Components] In addition to components (A) to (F) above, the addition-curing liquid silicone rubber composition for airbags according to the present invention may contain other arbitrary components depending on the purpose. Specific examples include the following. These other components may be used individually or in combination of two or more.

[0077] [Component (G)] In the present invention, it is preferable that the addition-curing liquid silicone rubber composition for airbags further contains one or more condensation catalysts selected from organic titanium compounds, organic zirconium compounds, and organic aluminum compounds as component (G). It is more preferable that component (G) is one or more selected from titanium alkoxide complexes, titanium chelate complexes, zirconium alkoxide complexes, zirconium chelate complexes, aluminum alkoxide complexes, and aluminum chelate complexes, and acts as a condensation catalyst for the adhesion-imparting functional group in component (E) to promote adhesion.

[0078] Specific examples of component (G) include, for example, titanium alkoxide complexes such as titanium tetraisopropoxide, titanium tetran-butoxide, and titanium tetra-2-ethylhexoxide; titanium chelate complexes such as titanium diisopropoxybis(acetylacetonate), titanium diisopropoxybis(ethylacetoacetate), and titanium tetraacetylacetonate; zirconium alkoxide complexes such as zirconium tetran-propoxide and zirconium tetran-butoxide; zirconium chelate complexes such as zirconium tributoxymonoacetylacetonate, zirconium monobutoxyacetylacetonate bis(ethylacetoacetate), and zirconium tetraacetylacetonate; aluminum alkoxide complexes such as aluminum secondary butoxide; and aluminum chelate complexes such as aluminum trisacetylacetonate, aluminum bis-ethylacetoacetate monoacetylacetonate, and aluminum tris-ethylacetoacetate.

[0079] Component (G) is an optional component that is added as needed, and its amount is preferably 0.05 to 5 parts by mass, more preferably 0.1 to 2 parts by mass, per 100 parts by mass of component (A). When the amount added is within the range of 0.05 to 5 parts by mass, the cured product obtained from the addition-curing liquid silicone rubber composition for airbags has excellent adhesion to the base fabric for airbags.

[0080] Component (G) may be used alone or in combination of two or more.

[0081] [Component (H)] Component (H) is an organopolysiloxane resin characterized by a three-dimensional network (resin-like) structure, i.e., a powdered three-dimensional network organopolysiloxane resin. Preferably, a trifunctional R １ SiO ３／２ Unit and tetrafunctional SiO ４／２ It is basically composed of one or more branched siloxane units selected from the units, and monofunctional R as needed. １ ３ SiO １／２ Unit and / or bifunctional R １ ２ SiO ２／２ The components may contain any number of units and act as flame retardant enhancers. However, this organopolysiloxane resin may contain alkenyl groups in its molecule, but it does not contain hydrogen atoms (hydrosilyl groups) bonded to silicon atoms. That is, it is preferable that the addition-curing liquid silicone rubber composition for airbags further contains, as component (H), a powdery three-dimensional network organopolysiloxane resin (however, this organopolysiloxane resin does not contain hydrogen atoms bonded to silicon atoms). Furthermore, this organopolysiloxane resin has a three-dimensional network (resin-like) structure and is in powder form at 25°C, so it is clearly differentiated from component (A), which basically has a linear structure and is liquid at 25°C.

[0082] R in the above formula １These are independently monovalent hydrocarbon groups having 1 to 10 carbon atoms, preferably 1 to 8 carbon atoms, and include the same alkenyl groups and monovalent hydrocarbon groups exemplified in component (A) above. Specifically, examples include alkenyl groups such as vinyl, allyl, propenyl, butenyl, pentenyl, hexenyl, cyclohexenyl, and heptenyl groups; alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclohexyl, and heptyl groups; aryl groups such as phenyl, tolyl, xylyl, and naphthyl groups; aralkyl groups such as benzyl and phenethyl groups; and halogen-substituted alkyl groups such as chloromethyl, 3-chloropropyl, and 3,3,3-trifluoropropyl groups. Methyl and vinyl groups are particularly preferred.

[0083] The content of alkenyl groups bonded to silicon atoms in component (H) is preferably 0 to 10 mol%, and more preferably about 2 to 8 mol%, relative to the total amount of substituents bonded to silicon atoms.

[0084] (H) The organopolysiloxane resin of component (R) １ SiO ３／２ Unit and / or SiO ４／２ It is preferable that the unit be present, and the total amount thereof is preferably 20 to 75 mol%, and more preferably 30 to 65 mol%, of the organopolysiloxane resin of component (H).

[0085] Here, the organopolysiloxane resin of component (H) contains, as described above, R １ ３ SiO １／２ Units and / or R １ ２ SiO ２／２ While units may be included as desired, their total amount is preferably 0 to 80 mol%, more preferably 0 to 70 mol%, and particularly preferably 0 to 50 mol% of the organopolysiloxane resin of component (H).

[0086] (H) R in organopolysiloxane resin １ SiO ３／２ Unit and / or SiO ４／２A sufficient flame retardancy improvement effect can be obtained when the total amount of units is within the range of 20 to 75 mol%, which is preferable.

[0087] Furthermore, the weight-average molecular weight in polystyrene terms of the organopolysiloxane resin of component (H) in GPC (gel permeation chromatography) analysis using tetrahydrofuran (THF) as the developing solvent is preferably in the range of 2,000 to 50,000, and particularly preferably in the range of 4,000 to 20,000. When the weight-average molecular weight is within the range of 2,000 to 50,000, a sufficient flame retardancy improvement effect is obtained, and the viscosity of the addition-curing liquid silicone rubber composition for airbags with good coating workability is obtained. Note that this weight-average molecular weight is the value obtained by GPC analysis under the same conditions as those used to determine the degree of polymerization of component (A) above.

[0088] A specific example of the organopolysiloxane resin of component (H) is given by formula: R' ３ SiO １／２ The siloxane units and formula shown are: R' ２ R"SiO １／２ The siloxane units and formula shown are: R' ２ SiO ２／２ Siloxane units and formula shown: SiO ４／２ An organosiloxane copolymer consisting of siloxane units represented by the formula: R' ３ SiO １／２ The siloxane units and formula shown are: R' ２ R"SiO １／２ Siloxane units and formula shown: SiO ４／２ An organosiloxane copolymer consisting of siloxane units represented by the formula: R' ２ R"SiO １／２ The siloxane units and formula shown are: R' ２ SiO ２／２ Siloxane units and formula shown: SiO ４／２ An organosiloxane copolymer consisting of siloxane units represented by R'R''SiO, formula: R'R''SiO ２／２ Siloxane units and formula shown: R'SiO ３／２ The siloxane unit or formula shown is: R''SiO ３／２Examples include organosiloxane copolymers consisting of siloxane units represented by and organopolysiloxanes, and mixtures consisting of two or more of these organopolysiloxanes.

[0089] In the above formula, R' is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 8 carbon atoms, other than an alkenyl group, and examples include alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclohexyl, and heptyl groups; aryl groups such as phenyl, tolyl, xylyl, and naphthyl groups; aralkyl groups such as benzyl and phenethyl groups; and halogenated alkyl groups such as chloromethyl, 3-chloropropyl, and 3,3,3-trifluoropropyl groups, with methyl groups being particularly preferred. In addition, R'' in the above formula is an alkenyl group, and examples include vinyl, allyl, butenyl, pentenyl, hexenyl, and heptenyl groups, with vinyl groups being particularly preferred.

[0090] The amount of component (H) is preferably 0.1 to 100 parts by mass, more preferably 2.5 to 90 parts by mass, and particularly preferably 5 to 80 parts by mass, based on 100 parts by mass of organopolysiloxane (A). An amount within the range of 0.1 to 100 parts by mass provides a sufficient flame retardancy improvement effect and is cost-effective.

[0091] Furthermore, if component (H) contains an alkenyl group, the amount of hydrosilyl groups contained in the composition is 1 to 10 moles per mole of total alkenyl groups bonded to silicon atoms in the composition. For example, component (H) can be set to an amount such that the amount of hydrosilyl groups contained in components (B) and (E) is 1 to 10 moles (or groups), preferably 1.2 to 8 moles (or groups), and more preferably 1.5 to 6 moles (or groups) per mole of total alkenyl groups bonded to silicon atoms in components (A), (C), (E), and (H) in the composition. If the total amount of hydrosilyl groups is less than 1 mole per mole of total alkenyl groups bonded to silicon atoms in the composition, the addition-curing liquid silicone rubber composition for airbags may not cure sufficiently and may not exhibit sufficient adhesive strength. On the other hand, if the amount of hydrosilyl groups exceeds 10 moles, the heat resistance of the cured silicone rubber product obtained from the addition-curing liquid silicone rubber composition for airbags may be extremely poor.

[0092] Thus, in the present invention, each component is blended in such a way that the total number of moles of hydrosilyl groups per mole of total alkenyl groups of each component in the addition-curing liquid silicone rubber composition for airbags is 1 to 10 moles.

[0093] The powdered, three-dimensional network organopolysiloxane resin of component (H) can be used alone or in combination of two or more types.

[0094] • Curing Control Agent The curing control agent is not particularly limited as long as it is a compound that has a curing inhibitory effect on the catalyst for the hydrosilylation reaction of component (D), and known compounds can be used. Specific examples include phosphorus-containing compounds such as triphenylphosphine; nitrogen-containing compounds such as tributylamine, tetramethylethylenediamine, and benzotriazole; sulfur-containing compounds; acetylene-based compounds such as acetylene alcohols; compounds containing two or more alkenyl groups; hydroperoxy compounds; and maleic acid derivatives.

[0095] The degree of curing inhibition by a curing control agent varies depending on the chemical structure of the curing control agent; therefore, it is preferable to adjust the amount of curing control agent added to the optimal amount for each curing control agent used. By adding the optimal amount of curing control agent, the addition-curing liquid silicone rubber composition for airbags will have excellent long-term storage stability and curing properties at room temperature.

[0096] - Non-reinforcing filler (C) A filler other than silica fine powder of component (C) may be used, for example, crystalline silica (for example, with a specific surface area of ​​50 m² by the BET method). ２ Examples include fillers such as quartz powder (less than 1g / g), hollow organic resin fillers, polymethylsilsesquioxane fine particles (so-called silicone resin powder), fumed titanium dioxide, magnesium oxide, zinc oxide, iron oxide, aluminum hydroxide, magnesium carbonate, calcium carbonate, zinc carbonate, carbon black, diatomaceous earth, talc, kaolinite, and glass fibers; fillers obtained by surface hydrophobizing these fillers with organosilicon compounds such as organoalkoxysilane compounds, organochlorosilane compounds, organosilazane compounds, and low molecular weight siloxane compounds; silicone rubber powder; and silicone resin powder.

[0097] Other ingredients may also be included, for example, organohydrogenpolysiloxanes containing one hydrogen atom bonded to a silicon atom per molecule and no other functional groups, organopolysiloxanes containing one alkenyl group bonded to a silicon atom per molecule and no other functional groups, non-functional organopolysiloxanes (so-called dimethyl silicone oil) that do not contain hydrogen atoms bonded to a silicon atom, alkenyl groups bonded to a silicon atom, or other functional groups, organic solvents, creep hardening inhibitors, plasticizers, thixotropic agents, pigments, dyes, and antifungal agents.

[0098] <Preparation of addition-curing liquid silicone rubber composition for airbags> An addition-curing liquid silicone rubber composition for airbags can be prepared by uniformly mixing components (A) to (F) above, as well as components (G) and (H), and other components that may be added as needed.

[0099] The resulting addition-curing liquid silicone rubber composition for airbags is liquid at 25°C, and its viscosity at 25°C is preferably 1 to 500 Pa·s, more preferably 2 to 400 Pa·s, and even more preferably 5 to 300 Pa·s. Within this viscosity range at 25°C, the composition is suitable for application to the airbag base fabric because it is less likely to result in uneven coating or insufficient adhesion to the base fabric after curing.

[0100] <Airbag base fabric> Generally, known materials are used as the airbag base fabric (substrate made of fiber cloth) on which the silicone rubber layer is formed. Specific examples include woven fabrics of various synthetic fibers such as 6,6-nylon, 6-nylon, aramid fibers, polyethylene terephthalate (PET), and polybutylene terephthalate (PBT). However, in this invention, CO2 is used during the manufacturing of the base fabric. ２ From the viewpoint of emissions, it is preferable that the base fabric for the airbag be made of polyester fiber.

[0101] <Airbag> The airbag of the present invention has a cured coating of the above-described addition-curing liquid silicone rubber composition for airbags on an airbag base fabric.

[0102] <Method for Manufacturing Airbags> The above-mentioned addition-curing liquid silicone rubber composition for airbags can be applied to one or both sides, or more particularly only one side, of an airbag base fabric (a substrate made of fiber cloth), and then heated and cured in a drying oven or the like to form a silicone rubber layer (cured film). An airbag can be manufactured using the silicone rubber coated base fabric for airbags obtained in this way.

[0103] Here, a conventional method can be used to coat the airbag base fabric with the addition-curing liquid silicone rubber composition for airbags, but coating by knife coater is preferred. The thickness of the coating layer (or surface coating amount) is usually 5 to 100 g / m². ２ Preferably 8 to 90 g / m ２ More preferably 10 to 80 g / m２ It can be done this way.

[0104] The addition-curing liquid silicone rubber composition for airbags can be cured under known curing conditions and by known curing methods. Specifically, for example, the composition can be cured by heating at 100 to 200°C for 1 to 30 minutes.

[0105] When processing an airbag base fabric (airbag silicone rubber coated base fabric) having a silicone rubber layer on one or both sides, manufactured in this manner, into an airbag, one method is to bond the outer edges of two of the above-mentioned airbag silicone rubber coated base fabrics together with an adhesive, with the silicone rubber coated side facing inward, and then sew the adhesive layer together. Alternatively, one may coat both outer surfaces of an airbag base fabric that has been pre-woven into a bag with an addition-curing liquid silicone rubber composition for airbags in a predetermined coating amount, as described above, and then cure it under predetermined curing conditions. While known adhesives can be used here, silicone-based adhesives called seam sealants are preferred in terms of adhesive strength and adhesive durability.

[0106] The present invention will be specifically described below using preparation examples, examples, and comparative examples, but the present invention is not limited to these.

[0107] The following components were used as component (A): (A-1): A linear dimethylpolysiloxane with vinyldimethylsiloxy groups sealed at both ends of the molecular chain, a weight-average degree of polymerization of 700, and a viscosity of 30,000 mPa·s. (A-2): A linear dimethylpolysiloxane with vinyldimethylsiloxy groups sealed at both ends of the molecular chain, a weight-average degree of polymerization of 520, and a viscosity of 10,000 mPa·s. (A-3): A linear dimethylpolysiloxane with vinyldimethylsiloxy groups sealed at both ends of the molecular chain, a weight-average degree of polymerization of 450, and a viscosity of 5,000 mPa·s.

[0108] The following component was used as component (B): (B): A linear dimethylsiloxane-methylhydrogensiloxane copolymer in which both ends of the molecular chain are sealed with trimethylsiloxy groups, has a weight-average degree of polymerization of 64, and a viscosity of 45 mPa·s (hydrosilyl group content 0.011 mol / g).

[0109] (C) The following component was used as component (C): Specific surface area of ​​300 m² by the BET method ２ Silica fine powder at / g (product name: Aerosil 300, manufactured by Nippon Aerosil Co., Ltd.)

[0110] The following component was used as component (D): (D): Dimethylpolysiloxane solution containing 1% by mass of chloroplatinic acid / 1,3-divinyltetramethyldisiloxane complex as the platinum atom content.

[0111] The following component was used as component (E): (E): γ-glycidoxypropyltrimethoxysilane

[0112] The following components were used as component (F). The aqueous solutions were prepared using deionized water. (F-1): 25% aqueous solution of sodium carbonate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (F-2): 25% aqueous solution of potassium carbonate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (F-3): 25% aqueous solution of sodium dodecyl sulfate (manufactured by Tokyo Chemical Industry Co., Ltd.) (F-4): 5% aqueous solution of sodium monododecyl phosphate (manufactured by Tokyo Chemical Industry Co., Ltd.) (F-5): 67% water-wet product of sodium dodecylbenzenesulfonate (soft type) (mixture) (manufactured by Tokyo Chemical Industry Co., Ltd.) (F-6): 50% aqueous solution of potassium 2-ethylhexanoate (manufactured by Tokyo Chemical Industry Co., Ltd.) (for comparative example) (F-7): 2-ferrous ethylhexanoate (III) mineral spirit solution (containing 6% iron) (manufactured by Nippon Chemical Industrial Co., Ltd.) (for comparative example)

[0113] (G) The following component was used as component (G): Titanium tetraacetylacetonate (product name: TC-401, manufactured by Matsumoto Fine Chemical Co., Ltd.)

[0114] The following component was used as the (H) component: (H): (CH ３ ) ３ SiO １／２Units and (CH ３ ) ２ (CH ２ =CH)SiO １／２ Units and SiO ４／２ A powdery, three-dimensional network organopolysiloxane resin consisting of units, with a weight-average molecular weight of 5,500, a Q unit content of 56 mol%, and an alkenyl group content of 6.7 mol% relative to the total substituents to which silicon atoms are bonded.

[0115] The following component was used as a curing control agent: (Curing control agent): 1-ethynylcyclohexanol

[0116] [Preparation Example 1] 60 parts by mass of base oil (A-1), 8 parts by mass of hexamethyldisilazane, 2 parts by mass of water, and 40 parts by mass of silica fine powder (C) were placed in a kneader and mixed at room temperature for 1 hour. Then, another 8 parts by mass of hexamethyldisilazane were added and mixed at room temperature for 1 hour. After that, the temperature was raised to 150°C and mixed for a further 2 hours. After this, 30 parts by mass of base oil (A-1) were added and mixed until homogeneous to obtain a base compound.

[0117] [Examples and Comparative Examples] Two-component addition-curing liquid silicone rubber compositions for airbags were prepared by mixing each component in the proportions shown in Tables 1 to 3 in a mixer at room temperature for 15 minutes, followed by mixing under reduced pressure for 15 minutes.

[0118] <Method for preparing silicone rubber coated base fabric> Mix the two-component addition-curing liquid silicone rubber compositions for airbags prepared in Tables 1 to 3 in a 1:1 mass ratio, then coat a 470 denier PET base fabric with 20 g / m² of the mixture. ２ The material was knife-coated using a Mathis lab coater (product name: LTE-S) to achieve the desired result. Subsequently, the material was placed in a 180°C dryer for 90 seconds to cure the addition-curing liquid silicone rubber composition for airbags, thereby preparing a silicone rubber coated base fabric.

[0119] <Flame Retardancy Test Method> Flame retardancy was evaluated using the method described in FMVSS-302 (Federal Motor Vehicle Safety Standard-302). Specifically, each silicone rubber coated base fabric prepared earlier was cut to a size of 10 cm wide x 35 cm long. Then, with the silicone rubber coated side facing upwards, the burning distance and burning time until the flame extinguished were measured using the method described in FMVSS-302. The burning rate was calculated from this burning distance and burning time. At this time, a sample was evaluated as passing the flame retardancy test if any of the following conditions were met: (1) the test piece did not ignite or self-extinguished (SE) before the A mark, (2) the test piece self-extinguished (SE) within a burning distance of 51 mm (and within 60 seconds), or (3) the burning rate was 102 mm / min or less. The test was conducted with N=10 samples, and it was evaluated as "pass" if all samples passed, and "fail" if even one sample failed. The results are shown in Tables 1-3. In addition, the self-extinguishing rate (SE rate) was calculated using the following formula, and the results are also listed in Tables 1-3. Note that a higher SE rate indicates better flame retardancy. SE rate (%) = [((1) Number of test pieces that did not ignite or self-extinguished before mark A + (2) Number of test pieces that self-extinguished within a burning distance of 51 mm (and within 60 seconds)) / 10] × 100

[0120] <Adhesion Test Method> The silicone rubber coated base fabric prepared above was evaluated for adhesion using a scrub tester (manufactured by SERVONETIC Control Instruments) according to the method described in ISO 5981. After 600 scrub tests, the condition of the coating was visually checked. A sample was judged as pass if the silicone rubber layer did not peel off the coating surface, and as fail if it had peeled off. The results are shown in Tables 1 to 3.

[0121] <Long-term storage test method> Each of the two-component addition-curing liquid silicone rubber compositions for airbags prepared according to Tables 1 to 3 was filled into 100 mL glass bottles and stored in a 70°C dryer for 504 hours, after which the viscosity was measured. Furthermore, silicone rubber coated base fabrics were prepared using the same method as described above for each of the two-component addition-curing liquid silicone rubber compositions for airbags that had been stored at 70°C for 504 hours, and the adhesion was tested using the method described above. The results are shown in Tables 1 to 3.

[0122]

[0123]

[0124]

[0125] As can be seen from Tables 1 and 2, in Examples 1 to 9 using the addition-curing liquid silicone rubber composition for airbags of the present invention, airbag base fabrics with excellent flame retardancy and adhesion were obtained. Furthermore, no thickening or decrease in adhesion was observed in the 70°C / 504-hour storage test. On the other hand, as can be seen from Tables 1 and 3, Comparative Examples 1 and 2, which did not contain component (F), showed inferior flame retardancy. Also, as can be seen from Table 3, Comparative Example 3, in which the metal content of component (F) was 10 ppm relative to component (A), showed inferior flame retardancy. Furthermore, in Comparative Examples 4 and 5, which contained carboxylates, although flame retardancy was excellent, adhesion decreased, and a decrease in viscosity and adhesion due to cracking of the silicone polymer was observed in the 70°C / 504-hour storage test.

[0126] This specification includes the following embodiments: [1]: Addition-curing liquid silicone rubber composition for airbags, comprising: (A) 100 parts by mass of an organopolysiloxane having alkenyl groups bonded to two or more silicon atoms in one molecule and a degree of polymerization of 50 to 2,000; (B) an organohydrogenpolysiloxane having hydrogen atoms (hydrosilyl groups) bonded to two or more silicon atoms in one molecule: an amount such that the hydrosilyl groups contained in the composition are 1 to 10 moles per mole of the total alkenyl groups bonded to silicon atoms contained in the composition; (C) a specific surface area of ​​50 m² by the BET method. ２An addition-curing liquid silicone rubber composition for airbags, characterized in that it contains: (D) silica fine powder having a concentration of 1 to 50 parts by mass, (A) catalyst for hydrosilylation reaction: 1 to 500 ppm in terms of the mass of the catalyst metal element relative to the mass of component (A), (E) organosilicon compound having an adhesion-imparting functional group: 0.1 to 10 parts by mass, and (F) one or more selected from alkali metal sulfates, sulfonates, phosphates, and carbonates: 100 to 2,000 ppm in terms of the mass of alkali metal relative to the mass of component (A). [2]: The addition-curing liquid silicone rubber composition for airbags according to [1] above, characterized in that component (E) contains one or more reactive silyl groups selected from alkoxysilyl groups, alkenyl group-containing silyl groups, and hydrosilyl groups, and one or more reactive organic groups selected from epoxy groups, isocyanate groups, and (meth)acrylic groups in one molecule. [3]: The addition-curing liquid silicone rubber composition for airbags according to [1] or [2] above, characterized in that the addition-curing liquid silicone rubber composition for airbags further contains, as component (G), one or more condensation catalysts selected from organic titanium compounds, organic zirconium compounds, and organic aluminum compounds in an amount of 0.05 to 5 parts by mass per 100 parts by mass of component (A). [4]: ​​The addition-curing liquid silicone rubber composition for airbags according to any one of [1] to [3] above, characterized in that the alkali metal of component (F) is sodium or potassium. [5]: The addition-curing liquid silicone rubber composition for airbags according to any one of [1] to [4] above, characterized in that the addition-curing liquid silicone rubber composition for airbags further contains, as component (H), 0.1 to 100 parts by mass of powdered three-dimensional network organopolysiloxane resin (provided that the organopolysiloxane resin does not contain hydrogen atoms bonded to silicon atoms) per 100 parts by mass of component (A). [6]: An airbag characterized in that it has a cured film of the addition-curing liquid silicone rubber composition for airbags according to any one of [1] to [5] above on an airbag base fabric.[7]: The airbag according to [6] above, characterized in that the base fabric for the airbag is made of polyester fiber.

[0127] It should be noted that the present invention is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of the present invention and achieves similar effects is included within the technical scope of the present invention.

Claims

1. An addition-curing liquid silicone rubber composition for airbags, comprising: (A) 100 parts by mass of an organopolysiloxane having alkenyl groups bonded to two or more silicon atoms in one molecule and a degree of polymerization of 50 to 2,000; (B) an organohydrogenpolysiloxane having hydrogen atoms (hydrosilyl groups) bonded to two or more silicon atoms in one molecule: an amount such that the hydrosilyl groups contained in the composition are 1 to 10 moles per mole of the total alkenyl groups bonded to silicon atoms contained in the composition; (C) a specific surface area of ​​50 m² by the BET method. ２ An addition-curing liquid silicone rubber composition for airbags, characterized by containing: (D) silica fine powder with a concentration of 1 to 50 parts by mass, (A) catalyst for hydrosilylation reaction: 1 to 500 ppm in mass of catalyst metal element relative to the mass of component (A); (E) organosilicon compound having an adhesion-imparting functional group: 0.1 to 10 parts by mass; and (F) one or more selected from alkali metal sulfates, sulfonates, phosphates, and carbonates: 100 to 2,000 ppm in mass of alkali metal relative to the mass of component (A).

2. The addition-curing liquid silicone rubber composition for airbags according to claim 1, characterized in that component (E) contains in one molecule one or more reactive silyl groups selected from alkoxysilyl groups, alkenyl group-containing silyl groups, and hydrosilyl groups, and one or more reactive organic groups selected from epoxy groups, isocyanate groups, and (meth)acrylic groups.

3. The addition-curing liquid silicone rubber composition for airbags according to claim 1, characterized in that the addition-curing liquid silicone rubber composition for airbags further contains, as component (G), one or more condensation catalysts selected from organic titanium compounds, organic zirconium compounds, and organic aluminum compounds in an amount of 0.05 to 5 parts by mass per 100 parts by mass of component (A).

4. The addition-curing liquid silicone rubber composition for airbags according to claim 1, characterized in that the alkali metal of component (F) is sodium or potassium.

5. The addition-curing liquid silicone rubber composition for airbags according to claim 1, characterized in that the addition-curing liquid silicone rubber composition for airbags further contains, as component (H), 0.1 to 100 parts by mass of powdered three-dimensional network organopolysiloxane resin (provided that the organopolysiloxane resin does not contain hydrogen atoms bonded to silicon atoms) per 100 parts by mass of component (A).

6. An airbag characterized in that it has a cured coating of an addition-curing liquid silicone rubber composition for airbags described in any one of claims 1 to 5 on an airbag base fabric.

7. The airbag according to claim 6, characterized in that the base fabric for the airbag is made of polyester fiber.

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