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

Abstract

To provide an addition-curable liquid silicone rubber composition for airbags that minimizes coating unevenness during the coating process and allows for easy detection of defective products.SOLUTION: The present invention is an addition-curable liquid silicone rubber composition for airbags which comprises (A) a linear organopolysiloxane, (B) a three-dimensional net-like organopolysiloxane resin in powder form, (C) an organohydrogen polysiloxane that contains two or more hydrosilyl groups per molecule, (D) a silica fine powder that has a BET method specific surface area of at least 50 m2 / g, (E) a hydrosilylation reaction catalyst, (F) an organic silicon compound that contains an adhesiveness-imparting functional group, and (G) an expanded graphite powder that has a median diameter of 0.1-50 μm, wherein the content of the component (C) is such that the total of hydrosilyl groups in the composition is 1-10 moles per 1 mole of the total of silicon atom-bound alkenyl groups in the composition.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an addition-curable liquid silicone rubber composition for airbags and to an airbag. [Background technology]

[0002] Silicone rubber compositions for airbags have been proposed for the purpose of forming a rubber coating on the surface of fibers. Airbags having a silicone rubber coating have excellent internal pressure retention and low burning rate, and are therefore suitable for use as airbags for automobiles, etc.

[0003] As such an addition-curing liquid silicone rubber composition for airbags, a silicone rubber composition using an organohydrogenpolysiloxane containing T units or Q units as a crosslinking agent has been disclosed (Patent Document 1). A coated base fabric coated with this composition is characterized by excellent strength. An addition-curing liquid silicone rubber composition for airbags has also been disclosed (Patent Document 2), which contains a silicone resin composed of M, D, and Q units, with only the D units containing crosslinkable functional groups, as a flame retardant. An airbag coated with this composition is characterized by a slow burning rate.

[0004] On the other hand, in recent years, there is a tendency to reduce the coating amount of silicone rubber composition in order to save space and reduce weight. Therefore, there is a demand for the development of a silicone rubber composition for airbags that has the same flame retardancy as conventional compositions even with a low coating amount. A method for improving flame retardancy is to incorporate a flame retardant. For example, compositions incorporating iron (III) oxide monohydrate or α-iron (III) oxide as a flame retardant in a silicone rubber composition (Patent Document 3) and compositions incorporating carbon black (Patent Documents 4 and 5) have been disclosed. However, when a flame retardant such as iron oxide or carbon black, which has a strong coloring power, is incorporated in a silicone rubber composition, coating spots may occur during coating, which may impair the appearance. In addition, the manufacturing process of an airbag base fabric includes many steps such as a step of weaving the base fabric, a step of washing, a step of drying, a step of coating a silicone material, a step of heat curing the silicone material, and a step of winding up the coated base fabric. If defects such as stains, scratches or holes occur in the airbag base fabric during these processes, and the silicone rubber coating on the airbag base fabric is dark in color and has strong hiding power, it may be difficult to detect these defects by visual inspection or image inspection using a camera. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2019-513907 [Patent Document 2] International Publication No. 2018 / 168315 [Patent Document 3] Patent Publication No. 2022-072086 [Patent Document 4] Japanese Patent Application Publication No. 7-300774 [Patent Document 5] Japanese Patent Application Publication No. 7-195990 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in view of the above circumstances, and has an object to provide an addition-curing liquid silicone rubber composition for airbags which is less prone to coating unevenness during coating, and which produces a coated airbag base fabric which has a slow burning rate and allows for easy detection of defects such as stains, scratches and holes, and an airbag having a cured coating of the composition. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides an addition-curable liquid silicone rubber composition for airbags, comprising: (A) a linear organopolysiloxane having a weight average degree of polymerization of 50 to 2,000 and containing two or more alkenyl groups bonded to silicon atoms in each molecule: 100 parts by mass, (B) powdered three-dimensional network organopolysiloxane resin (provided that the organopolysiloxane resin does not contain a hydrosilyl group): 5 to 100 parts by mass, (C) an organohydrogenpolysiloxane containing two or more hydrosilyl groups in one molecule; (D) BET specific surface area is 50m 2 / g or more: 1 to 50 parts by mass of silica fine powder, (E) a hydrosilylation reaction catalyst: 1 to 500 ppm by mass of catalytic metal element based on the total mass of the (A) to (D) components; (F) an organosilicon compound containing an adhesion-imparting functional group: 0.1 to 10 parts by mass, and (G) Expanded graphite powder having a median diameter of 0.1 to 50 μm: 0.1 to 1 part by mass and wherein the component (C) is contained in an amount such that the total amount of hydrosilyl groups contained in the composition is 1 to 10 moles per mole of the total amount of silicon-bonded alkenyl groups contained in the composition.

[0008] A silicone-coated airbag fabric having a cured coating of this type of addition-curable liquid silicone rubber composition for airbags has excellent flame retardancy, is less prone to coating spots, and makes it easy to detect defects such as stains, scratches, and holes.

[0009] Furthermore, in the present invention, it is preferable that the component (H) contains 0.05 to 5 parts by mass of one or more condensation catalysts selected from organic titanium compounds, organic zirconium compounds, and organic aluminum compounds, per 100 parts by mass of the component (A).

[0010] If such an addition-curing liquid silicone rubber composition for airbags is used, the silicone-coated base fabric for airbags produced from the composition will have excellent adhesive properties.

[0011] In the present invention, the component (F) is preferably an organosilicon compound having, in one molecule, one or more reactive silyl groups selected from an alkoxysilyl group, an alkenyl-containing silyl group, and a hydrosilyl group, and one or more reactive organic groups selected from an epoxy group, an isocyanate group, and a (meth)acrylic group.

[0012] Such an addition-curable liquid silicone rubber composition for airbags provides superior adhesion of the silicone rubber layer to the airbag fabric.

[0013] The present invention also provides an airbag having a cured coating of the addition-curable liquid silicone rubber composition for airbags of the present invention on an airbag base fabric, the cured coating surface having an L value of 60 or greater when measured using the L*a*b* color system.

[0014] Such an air bag has excellent flame retardancy, is less likely to develop coating spots, and allows easy detection of defects such as stains, scratches, holes, etc. Effect of the Invention

[0015] As described above, according to the present invention, it is possible to provide an addition-curable liquid silicone rubber composition for airbags that, when coated on an airbag base fabric and cured, has excellent flame retardancy, is less likely to cause coating spots, and enables defective products to be easily detected, and also provides an airbag. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] As a result of extensive investigations into the above-mentioned problems, the inventors have discovered that an addition-curable liquid silicone rubber composition for airbags containing expanded graphite powder, when coated onto an airbag base fabric and cured, results in a coated base fabric that is excellent in flame retardancy, is less prone to coating spots, and enables defects such as stains, scratches, and holes to be easily detected, thereby completing the present invention.

[0017] That is, the present invention provides an addition-curable liquid silicone rubber composition for airbags, comprising: (A) a linear organopolysiloxane having a weight average degree of polymerization of 50 to 2,000 and containing two or more alkenyl groups bonded to silicon atoms in each molecule: 100 parts by mass, (B) powdered three-dimensional network organopolysiloxane resin (provided that the organopolysiloxane resin does not contain a hydrosilyl group): 5 to 100 parts by mass, (C) an organohydrogenpolysiloxane containing two or more hydrosilyl groups in one molecule; (D) BET specific surface area is 50m 2 / g or more: 1 to 50 parts by mass of silica fine powder, (E) a hydrosilylation reaction catalyst: 1 to 500 ppm by mass of catalytic metal element based on the total mass of the (A) to (D) components; (F) an organosilicon compound containing an adhesion-imparting functional group: 0.1 to 10 parts by mass, and (G) Expanded graphite powder having a median diameter of 0.1 to 50 μm: 0.1 to 1 part by mass and the composition contains component (C) in an amount such that the total amount of hydrosilyl groups contained in the composition is 1 to 10 moles per mole of the total amount of silicon-bonded alkenyl groups contained in the composition.

[0018] The present invention will be described in detail below, but the present invention is not limited thereto.

[0019] In this specification, the viscosity is a value measured at 25° C. using a rotational viscometer according to the method described in JIS K 7117-1: 1999. The weight-average degree of polymerization is a value determined as a polystyrene-equivalent weight-average molecular weight (weight-average degree of polymerization) by GPC (gel permeation chromatography) analysis using tetrahydrofuran (THF) as a developing solvent measured under the following conditions.

[0020] [Measurement conditions] Developing solvent: Tetrahydrofuran Flow rate: 0.35mL / min Detector: Refractive index detector (RI) Column: TSK Guardcolumn SuperH-L TSKgel SuperH4000(6.0mmI.D.×15cm×1) TSKgel SuperH3000(6.0mmI.D.×15cm×1) TSKgel SuperH2000(6.0mmI.D.×15cm×2) (All manufactured by Tosoh Corporation) Column temperature: 40℃ Sample injection volume: 10 μL (0.5% by weight tetrahydrofuran solution)

[0021] <Addition-curable liquid silicone rubber composition for airbags> The addition-curable liquid silicone rubber composition for airbags of the present invention comprises: (A) a linear organopolysiloxane having a weight average degree of polymerization of 50 to 2,000 and containing two or more alkenyl groups bonded to silicon atoms in each molecule: 100 parts by mass, (B) Powdered three-dimensional network organopolysiloxane resin (provided that the organopolysiloxane resin does not contain a hydrosilyl group): 5 to 100 parts by mass (C) an organohydrogenpolysiloxane containing two or more hydrosilyl groups in one molecule; (D) BET specific surface area is 50m 2 / g or more: 1 to 50 parts by mass of silica fine powder, (E) a hydrosilylation reaction catalyst: 1 to 500 ppm by mass of catalytic metal element based on the total mass of the (A) to (D) components; (F) an organosilicon compound containing an adhesion-imparting functional group: 0.1 to 10 parts by mass, and (G) Expanded graphite powder having a median diameter of 0.1 to 50 μm: 0.1 to 1 part by mass The composition contains component (C) in an amount such that the total amount of hydrosilyl groups contained in the composition is 1 to 10 moles per mole of the total amount of silicon-bonded alkenyl groups contained in the composition, and the composition is liquid at room temperature (25°C).

[0022] Each component will be described in detail below.

[0023] [Component (A)] In the present invention, the organopolysiloxane of component (A) is an organopolysiloxane that contains two or more alkenyl groups bonded to silicon atoms in each molecule and has a degree of polymerization of 50 to 2,000, and is the base polymer (main component) of the addition-curable liquid silicone rubber composition for airbags according to the present invention.

[0024] The molecular structure of component (A) is characterized by being linear. Among these, diorganopolysiloxanes whose main chain is basically composed of repeating diorganosiloxane units and whose molecular chain ends are blocked with triorganosiloxy groups are preferred. The position of the silicon atom to which the alkenyl group is bonded in the linear organopolysiloxane molecule of component (A) may be either or both of the molecular chain ends (i.e., triorganosiloxy groups) and the middle of the molecular chain (i.e., bifunctional diorganosiloxane units located at non-terminal positions of the molecular chain). Particularly preferred as component (A) are linear diorganopolysiloxanes containing alkenyl groups bonded to silicon atoms at least at both molecular chain ends.

[0025] The alkenyl group bonded to the silicon atom in component (A) typically has 2 to 8 carbon atoms, and preferably has 2 to 4 carbon atoms. Specific examples include vinyl groups, allyl groups, propenyl groups, butenyl groups, pentenyl groups, hexenyl groups, cyclohexenyl groups, and heptenyl groups, with vinyl groups being particularly preferred.

[0026] The number of alkenyl groups bonded to silicon atoms in the component (A) is 2 or more, preferably 2 to 100, and more preferably 2 to 50, per molecule.

[0027] Examples of the monovalent substituted or unsubstituted hydrocarbon group bonded to a silicon atom other than an alkenyl group in component (A) include monovalent hydrocarbon groups typically having 1 to 12 carbon atoms, and 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.

[0028] 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 resulting addition-curable liquid silicone rubber composition for airbags may deteriorate, while if the weight average degree of polymerization is greater than 2,000, the viscosity of the resulting addition-curable liquid silicone rubber composition for airbags may increase, resulting in poor coating workability.

[0029] The viscosity of component (A) at 25° C. 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. When the viscosity of component (A) is 50 mPa·s or more, the mechanical properties of the resulting addition-curable liquid silicone rubber composition for airbags will be good, and when it is 200,000 mPa·s or less, the viscosity of the resulting addition-curable liquid silicone rubber composition for airbags will not be high, and coating workability will be favorable.

[0030] Specific examples of organopolysiloxanes of component (A) include dimethylsiloxane-methylvinylsiloxane copolymers capped at both molecular chain terminals with trimethylsiloxy groups, methylvinylpolysiloxanes capped at both molecular chain terminals with trimethylsiloxy groups, dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymers capped at both molecular chain terminals with trimethylsiloxy groups, dimethylpolysiloxanes capped at both molecular chain terminals with dimethylvinylsiloxy groups, methylvinylpolysiloxanes capped at both molecular chain terminals with dimethylvinylsiloxy groups, and dimethylsiloxane-methylvinylpolysiloxanes capped at both molecular chain terminals with dimethylvinylsiloxy groups. and mixtures of two or more of these organopolysiloxanes.

[0031] The organopolysiloxane of the component (A) may use either a single compound, or a combination of two or more different compounds.

[0032] [(B) Component] The powdered three-dimensional network organopolysiloxane resin of component (B) (provided that the organopolysiloxane resin does not contain hydrosilyl groups) acts as a flame retardancy improver. Component (B) preferably contains a trifunctional R 1 SiO 3 / 2 Units and tetrafunctional SiO 4 / 2 The copolymer is essentially composed of one or more branched siloxane units selected from the group consisting of monofunctional R 1 3 SiO 1 / 2 Units and / or bifunctional R 1 2 SiO 2 / 2 However, this organopolysiloxane resin does not contain any hydrogen atoms bonded to silicon atoms (hydrosilyl groups) in the molecule. In addition, this organopolysiloxane resin has a three-dimensional network (resinous) structure and is in powder form at 25°C, so it is clearly distinguished from the aforementioned component (A) which has a linear structure.

[0033] Above R 1 are independently a monovalent substituted or unsubstituted hydrocarbon group having 1 to 10, and preferably 1 to 8, carbon atoms, and examples thereof include the same alkenyl groups and monovalent hydrocarbon groups as exemplified in component (A) above. Specific examples thereof include alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclohexyl, and heptyl groups; alkenyl groups such as vinyl, allyl, propenyl, butenyl, pentenyl, hexenyl, cyclohexenyl, and heptenyl 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. In particular, methyl and vinyl groups are preferred.

[0034] The content of alkenyl groups bonded to silicon atoms in component (B) is preferably 0 to 10 mol %, and particularly preferably 2 to 8 mol %, based on the total number of substituents bonded to silicon atoms.

[0035] The organopolysiloxane resin of component (B) is R 1 SiO 3 / 2 Units and SiO 4 / 2 The total amount of the siloxane units in the organopolysiloxane resin of component (B) is preferably 20 to 75 mol %, and more preferably 30 to 65 mol %. If the amount is within this range, a sufficient effect of improving flame retardancy can be obtained, which is preferable.

[0036] As described above, the organopolysiloxane resin of component (B) contains R 1 3 SiO 1 / 2 Units and / or R 1 2 SiO 2 / 2 The total content of these units in the organopolysiloxane resin of component (B) is preferably 0 to 70 mol %, and more preferably 0 to 50 mol %.

[0037] Furthermore, the polystyrene-equivalent weight average molecular weight of the organopolysiloxane resin of component (B) as determined by GPC (gel permeation chromatography) analysis using tetrahydrofuran (THF) as a developing solvent is preferably in the range of 2,000 to 50,000, and particularly preferably 4,000 to 20,000. If the weight average molecular weight is within the range of 2,000 to 50,000, sufficient flame retardancy improvement effect is obtained, and the viscosity of the addition-curable liquid silicone rubber composition for airbags is good in coating workability. Note that this weight average molecular weight is a value determined by GPC analysis under the same conditions as those used to determine the degree of polymerization of component (A) above.

[0038] Specific examples of the organopolysiloxane resin of component (B) include those represented by the formula: R' 3 SiO 1 / 2 A siloxane unit represented by the formula: R' 2 R”SiO 1 / 2 A siloxane unit represented by the formula: R' 2 SiO 2 / 2 Siloxane units represented by the formula: SiO4 / 2 and an organosiloxane copolymer having a siloxane unit represented by the formula: R' 3 SiO 1 / 2 A siloxane unit represented by the formula: R' 2 R”SiO 1 / 2 Siloxane units represented by the formula: SiO 4 / 2 and an organosiloxane copolymer having a siloxane unit represented by the formula: R' 2 R”SiO 1 / 2 A siloxane unit represented by the formula: R' 2 SiO 2 / 2 Siloxane units represented by the formula: SiO 4 / 2 and an organosiloxane copolymer having a siloxane unit represented by the formula: R'R"SiO 2 / 2 Siloxane units represented by the formula: R'SiO 3 / 2 or a siloxane unit represented by the formula: R″SiO 3 / 2 and mixtures of two or more of these organopolysiloxanes.

[0039] R' in the above formula is independently a group selected from an alkyl group having 1 to 10 carbon atoms, preferably 1 to 8 carbon atoms, an aryl group having 6 to 10 carbon atoms, preferably 1 to 8 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms, preferably 7 or 8 carbon atoms. Examples of the group include alkyl groups such as methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, cyclohexyl group, and heptyl group; aryl groups such as phenyl group, tolyl group, xylyl group, and naphthyl group; aralkyl groups such as benzyl group and phenethyl group; and halogenated alkyl groups such as chloromethyl group, 3-chloropropyl group, and 3,3,3-trifluoropropyl group. Of these, methyl group is particularly preferred. R" in the above formula is an alkenyl group having 2 to 10 carbon atoms, preferably 2 to 8 carbon atoms. Examples of the group include vinyl group, allyl group, butenyl group, pentenyl group, hexenyl group, and heptenyl group. Of these, vinyl group is particularly preferred.

[0040] The blending amount of the (B) component is 5 to 100 parts by mass, preferably 8 to 90 parts by mass, and particularly preferably 10 to 80 parts by mass, per 100 parts by mass of the (A) component organopolysiloxane. When the blending amount is within the range of 5 to 100 parts by mass, a sufficient flame retardancy improving effect is obtained, and it is excellent in cost-effectiveness.

[0041] The three-dimensional network organopolysiloxane resin of component (B) may use either a single type alone or a combination of two or more different types.

[0042] [(C) component] Component (C) is an organohydrogenpolysiloxane that has two or more hydrogen atoms bonded to silicon atoms (hydrosilyl groups) in each molecule, and acts as a crosslinking agent for the composition.

[0043] The molecular structure of the organohydrogenpolysiloxane of component (C) may be any of linear, cyclic, branched, and three-dimensional network structures. In this case, the number of silicon atoms (or degree of polymerization) in one molecule is preferably 2 to 300, particularly 4 to 200, and is liquid at 25°C. The number of hydrosilyl groups contained in one molecule is 2 or more, preferably 2 to 200, more preferably 2 to 150, and even more preferably 2 to 100. The hydrosilyl groups may be present at the molecular chain terminals, side chains (in the middle of the molecular chain), or both.

[0044] Examples of the substituent bonded to the silicon atom of component (C) include monovalent substituted or unsubstituted hydrocarbon groups usually having 1 to 12 carbon atoms, and preferably 1 to 10 carbon atoms. Specific examples of the monovalent hydrocarbon group 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 and phenyl groups being particularly preferred.

[0045] Examples of such organohydrogenpolysiloxanes include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, methylhydrogencyclopolysiloxane, methylhydrogensiloxane-dimethylsiloxane cyclic copolymer, tris(dimethylhydrogensiloxy)methylsilane, tris(dimethylhydrogensiloxy)phenylsilane, methylhydrogenpolysiloxane capped at both ends with trimethylsiloxy groups, dimethylsiloxane-methylhydrogensiloxane copolymer capped at both ends with trimethylsiloxy groups, and dimethylhydrogensiloxane-methylhydrogensiloxane copolymer capped at both ends with dimethylsiloxy groups. Hydrogensiloxy-capped dimethylpolysiloxane, copolymer of dimethylhydrogensiloxy-capped dimethylsiloxane and methylhydrogensiloxane at both ends, copolymer of methylhydrogensiloxane and diphenylsiloxane at both ends with trimethylsiloxy-capped methylhydrogensiloxane, copolymer of methylhydrogensiloxane, diphenylsiloxane and dimethylsiloxane at both ends with trimethylsiloxy-capped methylhydrogensiloxane, cyclic methylhydrogenpolysiloxane, copolymer of cyclic methylhydrogensiloxane and dimethylsiloxane, copolymer of cyclic methylhydrogensiloxane, diphenylsiloxane and dimethylsiloxane, (CH 3 ) 2 HSiO 1 / 2 Units and SiO 4 / 2 A copolymer consisting of (CH 3 ) 2 HSiO 1 / 2 Units and SiO 4 / 2 Units and (C 6 H 5 )SiO 3 / 2 and copolymers consisting of units, and the above-listed compounds in which some or all of the methyl groups have been substituted with other alkyl groups such as ethyl groups, propyl groups, etc., or aryl groups such as phenyl groups, etc. Specific examples of such organohydrogenpolysiloxanes include compounds of the following structural formula:

[0046] [ka] (In the formula, e is an integer from 2 to 200, and f, g, and h are each an integer from 0 to 200.)

[0047] The organohydrogenpolysiloxane preferably has a viscosity at 25° C. of 0.5 to 10,000 mPa·s, and more preferably 1 to 300 mPa·s.

[0048] The amount of component (C) is such that the total of hydrosilyl groups contained in the composition of the present invention is 1 to 10 moles per mole of the total of silicon-bonded alkenyl groups contained in the composition of the present invention, preferably 1.2 to 9 moles (or units), and more preferably 1.5 to 8 moles (or units). If the composition containing component (C) contains less than 1 mole of hydrosilyl groups per mole of the total of silicon-bonded alkenyl groups contained in components (A) and (B), the addition-curable liquid silicone rubber composition for airbags will not cure sufficiently, and if it exceeds 10 moles, the heat resistance of the cured silicone rubber obtained from the addition-curable liquid silicone rubber composition for airbags may be extremely poor.

[0049] The organohydrogenpolysiloxane of the component (C) may use either a single compound, or a combination of two or more different compounds.

[0050] [(D) component] (D) Component BET specific surface area is 50m 2 The silica fine powder having a specific surface area of ​​50 m2 or more as measured by the BET method acts as a reinforcing filler. In other words, it imparts strength to the cured silicone rubber obtained from the addition-curable liquid silicone rubber composition for airbags according to the present invention, and by using the silica fine powder as a reinforcing filler, it becomes possible to form a coating film that satisfies the strength required for the present invention. Such silica fine powder has a specific surface area of ​​50 m2 as measured by the BET method. 2 / g or more, preferably 50 to 400m 2 / g, more preferably 100 to 300m 2 / g. The specific surface area can be 50m 2If the molecular weight is less than 1 / g, it is not possible to impart mechanical strength properties sufficient for use as an air bag coating agent.

[0051] Such silica fine powder may be any known type that has been conventionally used as a reinforcing filler for cured silicone rubber, provided that the specific surface area is within the above-mentioned range, such as fumed silica and precipitated silica (wet silica).

[0052] The silica fine powder may be a silica fine powder whose surface has been hydrophobized with a surface treatment agent such as a (usually hydrolyzable) organic silicon compound, such as chlorosilane, alkoxysilane, or organosilazane. In this case, the silica fine powder may be directly surface-hydrophobized in a powder state. The silica fine powder may also be surface-hydrophobized by adding a surface treatment agent when kneading with silicone oil (for example, the organopolysiloxane containing alkenyl groups, which is the component (A) and is in an oil state).

[0053] The surface of component (D) can be treated by a known technique. For example, the untreated silica fine powder and the surface treatment agent are placed in a mechanical mixer or fluidized bed device sealed at normal pressure, and mixed at room temperature (25°C) or under heat treatment (heating) in the presence of an inert gas, if necessary. In some cases, the surface treatment may be accelerated by using water or a catalyst (such as a hydrolysis promoter). After mixing, the mixture is dried to produce a surface-treated silica fine powder. The amount of the surface treatment agent may be equal to or greater than the amount calculated from the area covered by the surface treatment agent.

[0054] As the surface treatment agent, specifically, silazane such as hexamethyldisilazane, methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, dimethyldimethoxysilane, diethyldimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, trimethylmethoxysilane, triethylmethoxysilane, vinyltris(methoxyethoxy)silane, trimethylchlorosilane, dimethyldichlorosilane, divinyldimethoxysilane and chloropropyltrimethoxysilane, silane coupling agent, polymethylsiloxane, organohydrogenpolysiloxane, etc. can be mentioned, and can be surface-treated with these and used as hydrophobic silica fine powder.As the surface treatment agent, silane coupling agent or silazane is particularly preferred.

[0055] When the fine silica powder of component (D) has previously been subjected to a surface hydrophobization treatment directly using a surface treatment agent containing an alkenyl group while in a powder state, the amount of hydrosilyl groups contained in the composition containing component (C) is 1 to 10 moles (or units), preferably 1.2 to 8 moles (or units), and more preferably 1.5 to 6 moles (or units), per 1 mole (or units) of alkenyl groups bonded to silicon atoms contained in the compositions containing the surface treatment agents of components (A), (B), and (D).

[0056] This is because if there is less than 1 mole of hydrosilyl groups per mole of alkenyl groups bonded to silicon atoms in the addition-curable liquid silicone rubber composition for airbags, the addition-curable liquid silicone rubber composition for airbags will not cure sufficiently and may not exhibit sufficient adhesive strength, whereas if there are more than 10 moles of hydrosilyl groups, the heat resistance of the cured silicone rubber obtained from the addition-curable liquid silicone rubber composition for airbags may be significantly reduced.

[0057] The amount of component (D) 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 the organopolysiloxane of component (A). If the amount is less than 1 part by mass, a silicone rubber cured product with sufficient strength will not be obtained, while if the amount exceeds 50 parts by mass, the viscosity of the resulting addition-curable liquid silicone rubber composition for airbags will increase, decreasing its flowability and making the coating process more difficult.

[0058] The fine silica powder of component (D) may use either a single type alone or a combination of two or more types.

[0059] [(E) component] The hydrosilylation catalyst of component (E) mainly promotes the addition reaction between the alkenyl groups bonded to silicon atoms in components (A) and (B) and the hydrosilyl groups in component (C). This hydrosilylation catalyst is not particularly limited, and examples thereof include platinum group metals such as platinum, palladium, rhodium, etc.; 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, etc., and platinum group metal compounds are preferred.

[0060] The amount of component (E) is 1 to 500 ppm, preferably 5 to 100 ppm, calculated as the mass of the catalytic metal element relative to the total mass of components (A) to (D). If the amount is less than 1 ppm, the addition reaction will be significantly slowed down and the addition-curable liquid silicone rubber composition for airbags will not cure, which is undesirable, whereas if the amount is more than 500 ppm, the heat resistance of the cured silicone rubber product may decrease.

[0061] The hydrosilylation reaction catalyst of the component (E) may use either a single compound, or a combination of two or more different compounds.

[0062] [Component (F)] Component (F) is an organosilicon compound having an adhesion-imparting functional group, which is added to develop and improve the adhesion of the addition-curable liquid silicone rubber composition for airbags to the airbag base fabric.

[0063] Any organosilicon compound having an adhesion-imparting functional group can be used as component (F), but it is preferable for the compound to be an organosilicon compound having, in one molecule, one or more reactive silyl groups selected from an alkoxysilyl group, an alkenyl-containing silyl group, and a hydrosilyl group, and one or more reactive organic groups selected from an epoxy group, an isocyanate group, and a (meth)acrylic group.

[0064] The alkoxy group (alkoxysilyl group) bonded to the silicon atom is preferably bonded to the silicon atom to form, for example, a trialkoxysilyl group such as a trimethoxysilyl group or a triethoxysilyl group; an alkyldialkoxysilyl group such as a methyldimethoxysilyl group, an ethyldimethoxysilyl group, a methyldiethoxysilyl group, an ethyldiethoxysilyl group, etc. The epoxy group is preferably bonded to the silicon atom in the form of, for example, a glycidoxyalkyl group such as a glycidoxypropyl group; an epoxy-containing cyclohexylalkyl group such as a 2,3-epoxycyclohexylethyl group or a 3,4-epoxycyclohexylethyl group; or the like.

[0065] Examples of the organosilicon compound of component (F) include epoxy group-containing silicon compounds such as 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, and (2,3-epoxycyclohexylethyl)methyldiethoxysilane. Examples of the silane coupling agent include silane coupling agents (i.e., organoalkoxysilanes containing epoxy functional groups), (meth)acrylic group-containing silane coupling agents such as 3-acryloxypropyltrimethoxysilane and 3-methacryloxypropyltrimethoxysilane, and isocyanate group-containing silane coupling agents such as 3-isocyanatepropyltriethoxysilane and 3-isocyanatepropyltrimethoxysilane, and organosilicon compounds such as cyclic organopolysiloxanes containing epoxy groups represented by the following chemical formulas, and linear organopolysiloxanes containing epoxy groups, and mixtures of two or more of these, and partial hydrolysis and condensation products of one or more of these.

[0066] The main ones are listed below as examples.

[0067] [ka] (In the formula, p is an integer of 1 to 40, q is an integer of 0 to 40, and r is an integer of 1 to 40, preferably an integer of 1 to 20.)

[0068] The amount of component (F) is 0.1 to 10 parts by mass, preferably 0.15 to 5 parts by mass, based on 100 parts by mass of the organopolysiloxane of component (A). If the amount is less than 0.1 part by mass, the resulting addition-curable liquid silicone rubber composition for airbags may not exhibit sufficient adhesive strength. If the amount is more than 10 parts by mass, the thixotropy of the addition-curable liquid silicone rubber composition for airbags may increase, the flowability may decrease, and the coating workability may deteriorate.

[0069] When component (F) contains an alkenyl group and / or a hydrosilyl group, the total number of hydrosilyl groups contained in the composition containing components (C) and (F) per 1 mole (or units) of alkenyl groups bonded to silicon atoms contained in the composition containing components (A), (B), (D), and (F) is 1 to 10 moles (or units), preferably 1.2 to 8 moles (or units), and more preferably 1.5 to 6 moles (or units).

[0070] This is because if there is less than 1 mole of hydrosilyl groups per mole of alkenyl groups bonded to silicon atoms in the addition-curable liquid silicone rubber composition for airbags, the addition-curable liquid silicone rubber composition for airbags will not cure sufficiently and may not exhibit sufficient adhesive strength; on the other hand, if there are more than 10 moles of hydrosilyl groups, the heat resistance of the cured silicone rubber obtained from the addition-curable liquid silicone rubber composition for airbags may be extremely poor.

[0071] The component (F) may use either a single type alone, or a combination of two or more types.

[0072] [(G) component] The (G) component is an expanded graphite powder, which acts as a flame retardant improving agent. The expanded graphite powder is obtained by inserting a chemical such as sulfuric acid between the layers of graphite powder such as scaly graphite, and then evaporating the chemical by heating to spread the gap between the graphite layers, and then pulverizing the mixture into a powder. A conventional method can be used for pulverization, and examples of the method include a method in which an expanded graphite sheet formed into a sheet by dry molding is pulverized in a bead mill, a jet mill, a roll mill, a ball mill, a disk mill, or a hammer mill. The graphite powder is obtained by burning out impurities from charcoal or carbon black at an ultra-high temperature of 2,000 to 3,000°C while blocking off air, thereby increasing the crystallization rate, and is clearly different from carbon black.

[0073] The volume average particle diameter D50 of the expanded graphite powder as measured by a laser diffraction scattering method is preferably 0.1 to 50 μm, more preferably 0.5 to 40 μm, and even more preferably 1 to 30 μm. If the median diameter is 0.1 or less, the composition becomes highly thixotropic, which may deteriorate the coating workability, whereas if it is 50 μm or more, it may cause the occurrence of coating spots when coated on a base fabric.

[0074] The amount of component (G) is 0.1 to 1 part by mass, preferably 0.25 to 1 part by mass, based on 100 parts by mass of the organopolysiloxane (A). If the amount is less than 0.1 part by mass, sufficient flame retardancy improvement effect may not be obtained. If the amount is more than 1 part by mass, the black color of the addition curing liquid silicone rubber composition for airbags becomes stronger and the brightness of the silicone-coated base fabric decreases, which may make it difficult to detect defective products in the inspection process after the production of the airbag base fabric.

[0075] The component (G) may use either a single type alone, or two or more types in combination.

[0076] [Other ingredients] In addition to the components (A) to (G), the addition-curable liquid silicone rubber composition for airbags according to the present invention can contain any other components depending on the purpose. Specific examples include the following. Each of these other components may be used alone or in combination of two or more.

[0077] [(H) component] Furthermore, the composition may contain, as component (H), one or more condensation catalysts selected from organic titanium compounds, organic zirconium compounds, and organic aluminum compounds. Component (H) is preferably one or more selected from titanium alkoxide complexes, titanium chelate complexes, zirconium alkoxide complexes, and zirconium chelate complexes, which act as condensation catalysts for the adhesion-imparting functional groups in component (F) to promote adhesion.

[0078] Specific examples of the component (H) include titanium alkoxide complexes such as titanium tetraisopropoxide, titanium tetra normal 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 tetra normal propoxide and zirconium tetra normal butoxide; and zirconium chelate complexes such as zirconium tributoxy monoacetylacetonate, zirconium monobutoxy acetylacetonate bis(ethylacetoacetate), and zirconium tetraacetylacetonate.

[0079] Component (H) is an optional component that is blended as necessary and is present in an amount of preferably 0.05 to 5 parts by mass, more preferably 0.1 to 5 parts by mass, and particularly preferably 0.08 to 2 parts by mass, per 100 parts by mass of component (A). When the blended amount is within the range of 0.05 to 5 parts by mass, the cured product obtained from the addition-curable liquid silicone rubber composition for airbags has excellent adhesion to airbag fabrics.

[0080] The component (H) may use either a single type alone, or two or more types in combination.

[0081] [Reaction control agent] The reaction inhibitor is not particularly limited as long as it is a compound that has a curing inhibitory effect on the hydrosilylation catalyst of component (E), and known compounds can be used. Specific examples thereof 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.

[0082] Since the degree of cure inhibition effect of the reaction inhibitor varies depending on the chemical structure of the reaction inhibitor, it is preferable to adjust the amount of reaction inhibitor added to an optimal amount for each reaction inhibitor used. By adding an optimal amount of reaction inhibitor, the addition-curable liquid silicone rubber composition for airbags has excellent long-term storage stability and cure properties at room temperature.

[0083] [Non-reinforcing filler] As a filler other than the fine silica powder of component (D) and the expanded graphite powder of component (G), for example, crystalline silica (for example, a specific surface area of ​​50 m by the BET method) 2 / g or less quartz powder), organic resin hollow filler, polymethylsilsesquioxane fine particles (so-called silicone resin powder), fumed titanium dioxide, magnesium oxide, zinc oxide, aluminum hydroxide, magnesium carbonate, calcium carbonate, zinc carbonate, diatomaceous earth, talc, glass fiber, and other fillers; fillers obtained by subjecting these fillers to surface hydrophobic treatment with organosilicon compounds such as organoalkoxysilane compounds, organochlorosilane compounds, organosilazane compounds, and low molecular weight siloxane compounds; silicone rubber powder; and silicone resin powder.

[0084] [Other ingredients] In addition, for example, organopolysiloxanes 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 containing no hydrogen atoms bonded to silicon atoms, no alkenyl groups bonded to silicon atoms, and no other functional groups (so-called dimethyl silicone oil), organic solvents, creep hardening inhibitors, plasticizers, thixotropy-imparting agents, pigments, dyes, anti-fungal agents, and the like can be blended.

[0085] <Preparation of Addition-Curable Liquid Silicone Rubber Composition for Airbags> An addition-curable liquid silicone rubber composition for airbags can be prepared by uniformly mixing the above components (A) to (G), component (H), and any other components that may be added as necessary.

[0086] The addition-curable liquid silicone rubber composition for airbags thus obtained is a liquid composition at 25° C., and preferably has a viscosity at 25° C. of 1 to 500 Pa·s, more preferably 2 to 400 Pa·s, and even more preferably 5 to 300 Pa·s. If the viscosity is within the above range at 25° C., it is suitable for use because it is less likely to cause uneven coating or insufficient adhesion to the base fabric after curing when applied to the airbag base fabric.

[0087] <Airbag fabric> Generally, the airbag base fabric (substrate made of fiber fabric) on which the silicone rubber layer is formed is made of a known material, and specific examples of this include woven fabrics of various synthetic fibers, such as various polyamide fibers such as 6,6-nylon, 6-nylon, and aramid fiber, and various polyester fibers such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT).

[0088] <Airbag> The airbag of the present invention has a cured coating of the above-mentioned addition-curable liquid silicone rubber composition for airbags on an airbag base fabric, and is characterized in that the L value of the cured coating surface measured using the L*a*b* color system is 60 or greater.

[0089] Because the airbag of the present invention uses expanded graphite powder (component (G)) as a flame retardant improving agent, the addition-curing liquid silicone rubber composition for airbags has a weak black color and the silicone-coated base fabric has a high brightness, making it easy to detect defective products during the inspection process after the airbag base fabric is manufactured.

[0090] In the airbag of the present invention, the L value of the silicone-coated surface of the silicone-coated base fabric was measured using a spectrophotometer CM-700d (manufactured by Konica Minolta, Inc.) The L value was measured using the L*a*b* color system.

[0091] <Airbag manufacturing method> The addition-curing liquid silicone rubber composition for airbags can be applied to one or both sides, particularly only one side, of an airbag fabric (a substrate made of fiber fabric), and then the composition can be cured by heating in a drying oven or the like to form a silicone rubber layer (cured coating). Airbags can be manufactured using the silicone rubber-coated airbag fabric thus obtained.

[0092] Here, the method for coating the addition-curable liquid silicone rubber composition for airbags onto the base fabric for airbags can be any conventional method, but coating with a knife coater is preferred. The thickness of the coating layer (or the amount of coating on the surface) is usually 5 to 100 g / m 2 , preferably 8 to 90 g / m 2 , more preferably 10 to 80 g / m 2 It can be said that:

[0093] The addition-curable liquid silicone rubber composition for airbags can be cured by a known curing method under known curing conditions. Specifically, the composition can be cured, for example, by heating at 100 to 200° C. for 1 to 30 minutes.

[0094] When the thus-produced airbag base fabric (airbag silicone rubber coated base fabric) having a silicone rubber layer on one or both sides is processed into an airbag, the outer periphery of two sheets of the above-mentioned airbag silicone rubber coated base fabric is bonded together with an adhesive with the silicone rubber coated side as the inner side, and then the adhesive layer is sewn together to produce the airbag. Alternatively, the airbag base fabric may be woven in advance and coated with a predetermined coating amount of the addition curing liquid silicone rubber composition for airbags on both outer sides thereof, as described above, and cured under a predetermined curing condition. The adhesive used here may be a known one, but a silicone adhesive called a seam sealant is preferable in terms of adhesive strength and adhesive durability. EXAMPLES

[0095] The present invention will be specifically described below with reference to Preparation Examples, Examples, and Comparative Examples, but the present invention is not limited to the following Examples. Note that the following viscosity, weight average molecular weight (weight average degree of polymerization), and median diameter are values ​​determined under the above-mentioned conditions.

[0096] The following components were used as component (A): (A-1): A linear dimethylpolysiloxane whose molecular chain is terminated at both ends with vinyldimethylsiloxy groups, with a weight-average degree of polymerization of 750 and a viscosity of 30,000 mPa s. (A-2): A linear dimethylpolysiloxane whose molecular chain is terminated at both ends with vinyldimethylsiloxy groups, with a weight-average degree of polymerization of 450 and a viscosity of 5,000 mP·s. (A-3): A linear dimethylpolysiloxane whose molecular chain is terminated at both ends with vinyldimethylsiloxy groups, with a weight-average degree of polymerization of 200 and a viscosity of 1,000 mP·s.

[0097] The following components were used as component (B): (B):(CH 3 ) 3 SiO 1 / 2 Units and (CH 3 )(CH 2 =CH)SiO 2 / 2 Units and SiO 4 / 2 A powdered three-dimensional network organopolysiloxane resin having a weight average molecular weight of 5,500, a Q unit content of 56 mol %, and an alkenyl group content of 6.7 mol % based on the total number of silicon-bonded substituents.

[0098] The following components were used as component (C): (C): A linear dimethylsiloxane-methylhydrogensiloxane copolymer with both ends of the molecular chain capped with trimethylsiloxy groups, a weight-average degree of polymerization of 20, an average of 9 hydrosilyl groups per molecule, and a viscosity of 8 mPa s (hydrosilyl group content: 0.0089 mol / g).

[0099] The following components were used as component (D): (D): Specific surface area is 300m by BET method 2 / g of silica fine powder (product name: Aerosil 300, manufactured by Nippon Aerosil Co., Ltd.)

[0100] The following components were used as component (E): (E): Dimethylpolysiloxane solution containing chloroplatinic acid / 1,3-divinyltetramethyldisiloxane complex at 1% by mass of platinum atom content

[0101] The following components were used as component (F): (F): γ-glycidoxypropyltrimethoxysilane

[0102] The following components were used as component (G): (G-1): Expanded graphite powder (product name: CS-5, manufactured by Marutoyo Foundry Manufacturing Co., Ltd., median diameter: 7 μm) according to the present invention (G-2): Scaly graphite powder (product name: MT-4, manufactured by Marutoyo Foundry Manufacturing Co., Ltd., median diameter: 4 μm) not according to the present invention. (G-3): Carbon fiber (product name: XN-500, manufactured by Nippon Graphite Fiber Co., Ltd., average length: 50 μm) not according to the present invention. (G-4): Diamond powder (product name: BRM, manufactured by Besco Superabrasives, median diameter: 10 μm) not according to the present invention. (G-5): Carbon black (product name: Denka Black, manufactured by Denka Co., Ltd., median diameter: 0.35 μm) not according to the present invention.

[0103] The following components were used as component (H): (H): Zirconium tetraacetylacetonate (product name: ZC-162, manufactured by Matsumoto Fine Chemical Co., Ltd.)

[0104] The following components were used as reaction control agents: (Reaction inhibitor): 1-ethynylcyclohexanol

[0105] [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 (D) were put into a kneader and mixed at room temperature for 1 hour. Then, 8 parts by mass of hexamethyldisilazane were further put in and mixed at room temperature for 1 hour. Next, the temperature was raised to 150°C and mixed for 2 hours. After this, 30 parts by mass of base oil (A-1) was added and mixed until uniform, to obtain a base compound.

[0106] [Examples 1 to 5 and Comparative Examples 1 to 7] The components in the compounding ratios shown in Tables 1 and 2 were mixed in a mixer at room temperature for 30 minutes to prepare an addition-curable liquid silicone rubber composition for airbags.

[0107] [Table 1]

[0108] [Table 2]

[0109] <Preparation method of silicone rubber coated base fabric> Each of the silicone rubber coating compositions for airbags prepared in Tables 1 and 2 was applied at 20 g / m to a 210 denier PA66 base fabric. 2 The silicone rubber coating composition was then cured by placing the cloth in a 200°C dryer for 1 minute to prepare a silicone rubber-coated fabric.

[0110] <Flame retardancy test method> The flame retardancy was evaluated by the method described in FMVSS-302 (Federal Motor Vehicle Safety Standard-302). Specifically, each silicone rubber-coated base fabric prepared above was cut to a size of 10 cm wide x 35 cm long. Then, the silicone rubber-coated surface was placed on the top, and the burning distance and burning time until the flame went out when burning by the method described in FMVSS-302 were measured. The burning rate was calculated from the burning distance and burning time. In this case, (1) the test piece did not ignite or self-extinguished (SE) before the A-mark line, (2) 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 was evaluated as passing the flame retardancy. N=10 tests were performed, and if all passed, it was evaluated as "passed", and if even one failed, it was evaluated as "failed". The results are shown in Tables 1 and 2. In addition, the self-extinguishing rate (SE rate) was calculated by the following formula, and the results are shown in Tables 1 and 2. In addition, when the SE rate is high, the flame retardancy is said to be better. SE rate (%) = [((1) Number of test pieces that did not ignite or self-extinguished before the A-marked line + (2) Number of test pieces that self-extinguished within a burning distance of 51 mm (and within 60 seconds)) / 10] x 100

[0111] <How to measure L value using a colorimeter> The silicone-coated surface of the prepared silicone rubber-coated base fabric was measured for L value using a spectrophotometer CM-700d (Konica Minolta, Inc.). The median values ​​measured with N=3 are shown in Tables 1 and 2. The L value was measured using the L*a*b* color system.

[0112] As can be seen from Table 1, Examples 1 to 5, which used the addition-curable liquid silicone rubber composition for airbags of the present invention, achieved excellent results in the flame retardancy test. In addition, the L value, which indicates lightness, was high when measured with a colorimeter.

[0113] On the other hand, as can be seen from Table 2, the powders of Comparative Examples 1 to 7, which are mainly composed of carbon like the expanded graphite, either had inferior flame retardancy compared to the Examples or had low L values, which indicate brightness measured by a colorimeter.

[0114] In this way, with the present invention, the lightness (L value) of the cured coating surface of the airbag is high, and the lightness of the silicone-coated base fabric is also high, making it easier to detect defective products during the inspection process after the airbag base fabric is manufactured.

[0115] The present specification includes the following aspects. [1] (A) a linear organopolysiloxane having a degree of polymerization of 50 to 2,000 and containing two or more alkenyl groups bonded to silicon atoms in each molecule: 100 parts by mass, (B) powdered three-dimensional network organopolysiloxane resin (provided that the organopolysiloxane resin does not contain a hydrosilyl group): 5 to 100 parts by mass, (C) an organohydrogenpolysiloxane containing two or more hydrosilyl groups in one molecule; (D) BET specific surface area is 50m 2 / g or more: 1 to 50 parts by mass of silica fine powder, (E) a hydrosilylation reaction catalyst: 1 to 500 ppm by mass of catalytic metal element based on the total mass of the (A) to (D) components; (F) an organosilicon compound containing an adhesion-imparting functional group: 0.1 to 10 parts by mass, and (G) Expanded graphite powder having a median diameter of 0.1 to 50 μm: 0.1 to 1 part by mass an addition-curable liquid silicone rubber composition for airbags, comprising: [2] The addition-curable liquid silicone rubber composition for airbags according to [1], further comprising, as component (H), 0.05 to 5 parts by mass of one or more condensation catalysts selected from organic titanium compounds, organic zirconium compounds, and organic aluminum compounds, per 100 parts by mass of component (A). [3] The addition-curable liquid silicone rubber composition for airbags according to [1] or [2], wherein the component (F) is an organosilicon compound having in one molecule one or more reactive silyl groups selected from an alkoxysilyl group, an alkenyl-containing silyl group, and a hydrosilyl group, and one or more reactive organic groups selected from an epoxy group, an isocyanate group, and a (meth)acrylic group. [4] A cured coating of the addition-curable liquid silicone rubber composition for airbags described in any one of [1] to [3] is provided on an airbag base fabric, and the cured coating surface is L * a * b * An airbag characterized in that its L value measured using a color spacer is 60 or more.

[0116] The present invention is not limited to the above-described embodiment. The above-described embodiment is merely an example, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits similar effects is included in the technical scope of the present invention.

Claims

1. An addition-curable liquid silicone composition for airbags, comprising: (A) a linear organopolysiloxane containing two or more alkenyl groups bonded to silicon atoms in each molecule and having a weight average degree of polymerization of 50 to 2,000: 100 parts by mass, (B) powdered three-dimensional network organopolysiloxane resin (provided that the organopolysiloxane resin does not contain a hydrosilyl group): 5 to 100 parts by mass, (C) an organohydrogenpolysiloxane containing two or more hydrosilyl groups in one molecule; (D) BET specific surface area is 50 m ２ / g or more: 1 to 50 parts by mass of silica fine powder, (E) a hydrosilylation catalyst: 1 to 500 ppm by mass of catalytic metal element based on the total mass of the (A) to (D) components; (F) an organosilicon compound containing an adhesion-imparting functional group: 0.1 to 10 parts by weight, and (G) Expanded graphite powder having a median diameter of 0.1 to 50 μm: 0.1 to 1 part by mass an addition-curable liquid silicone rubber composition for airbags, comprising:

2. The addition-curable liquid silicone rubber composition for airbags according to claim 1, further comprising, as component (H), 0.05 to 5 parts by mass of one or more condensation catalysts selected from organic titanium compounds, organic zirconium compounds, and organic aluminum compounds, per 100 parts by mass of component (A).

3. 2. The addition-curable liquid silicone rubber composition for airbags according to claim 1, wherein said component (F) is an organosilicon compound having in one molecule one or more reactive silyl groups selected from an alkoxysilyl group, an alkenyl-containing silyl group, and a hydrosilyl group, and one or more reactive organic groups selected from an epoxy group, an isocyanate group, and a (meth)acrylic group.

4. A cured coating of the addition-curable liquid silicone rubber composition for airbags according to any one of claims 1 to 3 is provided on a base fabric for airbags, and the cured coating surface is provided on a L ＊ a ＊ b ＊ An airbag having an L value of 60 or more as measured by a color spacer.

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