Photocurable silicone rubber coating composition, coated airbag fabric and method for producing same

Abstract

To provide a photocurable silicone rubber coating composition that gives a cured coating film that does not use a large amount of organic solvent, in which blocking is hard to occur in the case of being coated on a base fabric and a surface has low friction properties and excellent flexibility, and which can be compactified when being housed.SOLUTION: A photocurable silicone rubber coating composition contains: (A) linear organopolysiloxane which has a number average polymerization degree of 10 to 1,000, and contains two or more alkenyl groups bonded to silicon atoms in one molecule; (B) organohydrogenpolysiloxane containing two or more hydrogen atoms bonded to silicon atoms in one molecule; (C) talc fine powder having the median diameter (D50) of 0.5 to 20 μm; and (D) platinum group compound catalyst activated by light having the wavelength 200 to 500 nm as a catalyst for hydrosilylation reaction.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a photocurable silicone rubber coating composition and a method for producing a silicone-coated base fabric for airbags that is coated with a cured film of said composition. [Background technology]

[0002] Conventionally, fabrics coated with curable silicone rubber on the surface of a base fabric to form a cured silicone rubber coating on the base fabric have been suitable for use as automotive airbag fabrics due to their excellent heat resistance, airtightness, weather resistance, and flame retardancy. However, because airbags are stored in a folded state, such as inside pillars, undesirable adhesion (blocking) between coating materials on the surface of the base fabric can occur. If such blocking occurs or if the cured coating surface has high friction, the airbag may not deploy properly during a vehicle collision, potentially preventing it from fulfilling its role of preventing injury or death to passengers. In addition, if the coating has high friction, passengers may suffer abrasions from contact with the airbag surface when the airbag deploys. Therefore, there is a need for coating materials that do not cause blocking and have a low surface friction coefficient. Furthermore, when the airbag base fabric is folded and stored in a pillar or the like inside the vehicle, if the flexibility of the base fabric is low, the volume of the airbag base fabric when folded increases, compressing the interior space. Therefore, a highly flexible airbag base fabric is required.

[0003] To address this issue, a low-friction silicone coating composition containing an addition-curable silicone rubber composition, inorganic fillers such as alumina, talc, and silica, and an organic solvent, and a method for forming a silicone rubber coating film using this composition have been disclosed (Patent Document 1). In this method, the organic solvent in the composition is volatilized during heat curing, exposing part of the inorganic filler to the surface of the coating film, achieving low friction and allowing the production of a silicone rubber coating film with low friction and high surface roughness. However, in recent years, concerns have arisen about reducing CO2 emissions and the health hazards caused by volatile organic compounds (VOCs), making this method undesirable as it uses large amounts of organic solvent.

[0004] A heat-curable silicone coating composition containing a polysiloxane having vinyl groups only in the side chains, a polysiloxane having hydrosilyl groups, and talc has been disclosed as a silicone coating agent for airbag fabrics (Patent Document 2). This composition produces airbag fabrics with low friction and excellent blocking resistance. However, because the silicone coating layer is hard, there are concerns that the coated fabrics have poor flexibility and poor foldability.

[0005] Another coating material for airbag fabrics has been disclosed: an anti-blocking coating material containing a blend of fluoropolymer, talc, alumina, aqueous aliphatic polyurethane, a surfactant, and an adhesive (Patent Document 3). This coating material produces a coated fabric with excellent blocking resistance and flame retardancy. However, the only specific example of a resin used to form the coating layer on the fabric is a urethane resin containing an ethylene-vinyl acetate copolymer. Urethane resins generally have poor heat resistance and moist heat resistance, raising concerns about durability in high-temperature, humid environments such as the interior of a car in summer. Additionally, an aqueous coating composition has been disclosed in which talc, chlorite, and other solid lubricants are dispersed in an aqueous solution of sodium polyacrylate, a water-soluble organic polymer (Patent Document 4). This aqueous coating composition can produce a coating with low friction and excellent blocking resistance. However, because it uses a water-soluble organic polymer, the coating swells in humid environments due to moisture, raising concerns about an increase in the coefficient of friction and a decrease in blocking resistance and adhesion. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-098319 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-083946 [Patent Document 3] Japanese Patent Application Laid-Open No. 2016-005953 [Patent Document 4] Special Publication No. 2013-516522 Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, an object of the present invention is to provide a photocurable silicone rubber coating composition that, when applied to a base fabric, provides a cured coating that is resistant to blocking, has a low surface friction, is highly flexible, and can be compacted for storage, without using large amounts of organic solvents. Another object of the present invention is to provide a method for producing a silicone-coated base fabric for airbags that is covered with a cured coating of the silicone rubber coating composition. [Means for solving the problem]

[0008] As a result of extensive research into achieving the above object, the present inventors discovered that the above problems could be solved by the photocurable silicone rubber coating composition described below, which led to the creation of the present invention. [1] (A) 100 parts by mass of a linear organopolysiloxane containing two or more silicon-bonded alkenyl groups per molecule and having a number-average degree of polymerization of 10 to 1,000; (B) an organohydrogenpolysiloxane containing two or more silicon-bonded hydrogen atoms per molecule: an amount such that the number of silicon-bonded hydrogen atoms contained per molecule of this component is 0.4 to 5 per total number of silicon-bonded alkenyl groups in component (A); (C) talc fine powder having a median diameter (D50) of 0.5 to 20 μm: 50 to 150 parts by mass, and (D) an effective amount of a platinum group compound catalyst that is activated by light having a wavelength of 200 to 500 nm as a catalyst for a hydrosilylation reaction; A photocurable silicone rubber coating composition comprising: [2] The photocurable silicone rubber coating composition according to [1], wherein the component (D) is bis(acetylacetonato)platinum(II) or (trimethyl)methylcyclopentadienylplatinum(IV). [3] The photocurable silicone rubber coating composition according to [1] or [2], wherein component (A) is an organopolysiloxane having vinyl groups only at both molecular chain terminals. [4] The photocurable silicone rubber coating composition according to any one of [1] to [3], wherein component (A) is an organopolysiloxane in which 0.1 to 15 mol % of all substituents bonded to silicon atoms are alkenyl groups having 2 to 8 carbon atoms. [5] A coated airbag fabric having, as its outermost layer, a cured layer of the photocurable silicone rubber coating composition according to any one of [1] to [4]. [6] A step of applying the photocurable silicone rubber coating composition according to any one of [1] to [4] to the outermost layer of an airbag fabric; and The coated surface of the photocurable silicone rubber coating composition is irradiated with light at a dose of 100 to 10,000 mJ / cm. 2 A process of irradiating light of A method for producing a coated airbag base fabric having the above structure. [7] [6] A method for producing a silicone rubber-coated base fabric for airbags according to [6], which comprises a curing acceleration step at 40 to 120°C for 5 to 120 seconds following the light irradiation step. [Effects of the Invention]

[0009] The photocurable silicone rubber coating composition of the present invention, when coated on the outermost layer of a base fabric, does not require the use of large amounts of organic solvents and provides a cured coating (cured product layer) that is resistant to blocking, has a low surface friction, is highly flexible, and can be compacted for storage. Therefore, particularly in the production of airbags, using a base fabric coated with this composition can prevent poor deployment of the airbag and abrasions caused by contact between the airbag surface and the occupant. Furthermore, the composition can be easily folded and stored in a compact size inside a vehicle. DETAILED DESCRIPTION OF THE INVENTION

[0010] The photocurable silicone rubber coating composition of the present invention comprises the following components (A) to (D): (A) 100 parts by mass of a linear organopolysiloxane containing two or more silicon-bonded alkenyl groups per molecule and having a number-average degree of polymerization of 10 to 1,000; (B) an organohydrogenpolysiloxane containing two or more silicon-bonded hydrogen atoms per molecule: an amount such that the number of silicon-bonded hydrogen atoms contained per molecule of this component is 0.4 to 5 per total number of silicon-bonded alkenyl groups in component (A); (C) talc fine powder having a median diameter (D50) of 0.5 to 20 μm: 50 to 150 parts by mass, and (D) an effective amount of a platinum group compound catalyst that is activated by light having a wavelength of 200 to 500 nm as a catalyst for a hydrosilylation reaction; Each component is described in detail below.

[0011] [Component (A)] The linear organopolysiloxane of component (A) is an organopolysiloxane having a number-average degree of polymerization of 10 to 1,000 and containing two or more silicon-bonded alkenyl groups per molecule, and is the base polymer (main component) of the composition of the present invention.

[0012] The molecular structure of component (A) is a linear main chain consisting essentially of repeating diorganosiloxane units, and diorganopolysiloxanes in which both molecular chain terminals are blocked with triorganosiloxy groups are particularly preferred. Furthermore, the position of the silicon atom to which the alkenyl group is bonded in the molecule of component (A) may be either or both of the molecular chain terminal (i.e., triorganosiloxy group) and / or midway along the molecular chain (i.e., difunctional diorganosiloxane units located at non-terminal positions of the molecular chain).

[0013] 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, allyl, propenyl, butenyl, pentenyl, hexenyl, cyclohexenyl, and heptenyl groups, with vinyl groups being particularly preferred.

[0014] The content of silicon-bonded alkenyl groups in component (A) is preferably 0.1 to 15 mol %, more preferably 0.5 to 13 mol %, and even more preferably 1.0 to 11 mol % of all silicon-bonded substituents in the organopolysiloxane. If the alkenyl group content is less than 0.1 mol % of all silicon-bonded substituents, the resulting cured coating may not have sufficiently low friction, while if it exceeds 15 mol %, the resulting cured product may become brittle.

[0015] The monovalent organic group bonded to a silicon atom other than an alkenyl group in component (A) is preferably a monovalent hydrocarbon group having 1 to 12 carbon atoms, and more preferably a monovalent hydrocarbon group having 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; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups such as benzyl and phenethyl; and halogen-substituted alkyl groups such as chloromethyl, 3-chloropropyl, and 3,3,3-trifluoropropyl, with methyl being particularly preferred.

[0016] The number-average degree of polymerization of component (A) is 10 to 1,000, preferably 20 to 800, and more preferably 50 to 500. If the number-average degree of polymerization is less than 10, the mechanical properties of the resulting silicone rubber may deteriorate, while if the number-average degree of polymerization is greater than 1,000, the viscosity of the resulting silicone rubber coating composition may increase, resulting in poor coating workability.

[0017] In this specification, the number average degree of polymerization is a value calculated as the number average degree of polymerization from the value of the number average molecular weight obtained by GPC (gel permeation chromatography) analysis using toluene as a developing solvent under the following conditions, converted into polystyrene. [Measurement conditions] Developing solvent: toluene 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 mass toluene solution)

[0018] Component (A) may be liquid at 25° C., and preferably has a viscosity of 10 to 100,000 mPa·s, more preferably 20 to 30,000 mPa·s, and even more preferably 40 to 10,000 mPa·s at 25° C. If the viscosity of component (A) is below 10 mPa·s, the mechanical properties of the resulting silicone rubber may deteriorate, while if it exceeds 100,000 mPa·s, the viscosity of the resulting silicone rubber coating composition may increase, resulting in poor coating workability.

[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.

[0020] 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-methylpolysiloxanes capped at both molecular chain terminals with dimethylvinylsiloxy groups. Examples include vinyl siloxane copolymers, dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymers terminally blocked with dimethylvinylsiloxy groups, dimethylpolysiloxanes terminally blocked with divinylmethylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers terminally blocked with divinylmethylsiloxy groups, dimethylpolysiloxanes terminally blocked with trivinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers terminally blocked with trivinylsiloxy groups, and mixtures of two or more of these organopolysiloxanes. When the organopolysiloxane of component (A) is an organopolysiloxane having vinyl groups only at both molecular terminals, such as a dimethylpolysiloxane terminally blocked with dimethylvinylsiloxy groups, the hardness of the resulting cured coating is reduced, and airbag fabrics having such cured coatings have excellent flexibility.

[0021] The organopolysiloxane of component (A) may use either a single type alone or a combination of two or more types. In the composition of the present invention, the content of component (A) is preferably 20 to 80 mass %, more preferably 30 to 70 mass %.

[0022] [(B) Component] Component (B) is an organohydrogenpolysiloxane containing two or more silicon-bonded hydrogen atoms (hydrosilyl groups) per molecule, which undergoes a hydrosilylation addition reaction primarily with the alkenyl groups in component (A) above, acting as a crosslinking agent (curing agent).

[0023] The molecular structure of component (B) may be, for example, linear, cyclic, branched, or three-dimensional network (resinous) structure, but is preferably liquid at 25°C. Each molecule is characterized by having two or more silicon-bonded hydrogen atoms (hydrosilyl groups), preferably three or more. More specifically, each molecule typically contains 2 to 300, preferably 3 to 200, and more preferably 3 to 100 hydrosilyl groups. These hydrosilyl groups may be located at either the terminals or midway along the molecular chain, or both.

[0024] As this organohydrogenpolysiloxane, one represented by the following formula (1) as an average composition formula can be used. [ka]

[0025] In the above formula (1), R is independently a monovalent hydrocarbon group having 1 to 10 carbon atoms, such as alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, and decyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups such as benzyl, phenylethyl, and phenylpropyl; and groups in which some or all of the hydrogen atoms have been substituted with halogen atoms such as fluorine, bromine, or chlorine, such as chloromethyl, chloropropyl, bromoethyl, and trifluoropropyl. R is more preferably an alkyl group or an aryl group, and even more preferably a methyl group. R excludes aliphatic unsaturated hydrocarbon groups such as alkenyl groups. Furthermore, it is preferable that a is 0.7 to 2.1, b is 0.001 to 1.0, and a+b is a positive number that satisfies 0.8 to 3.0, and more preferably a is 1.0 to 2.0, b is 0.01 to 1.0, and a+b is a positive number that satisfies 1.5 to 2.5.

[0026] Examples of component (B) include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, tris(hydrogendimethylsiloxy)methylsilane, tris(hydrogendimethylsiloxy)phenylsilane, methylhydrogencyclopolysiloxane, methylhydrogensiloxane-dimethylsiloxane cyclic copolymer, methylhydrogenpolysiloxane terminated at both molecular chain ends with trimethylsiloxy groups, dimethylsiloxane-methylhydrogensiloxane copolymer terminated at both molecular chain ends with trimethylsiloxy groups, dimethylsiloxane-methylhydrogensiloxane-methylphenylsiloxane copolymer terminated at both molecular chain ends with trimethylsiloxy groups, dimethylsiloxane-methylhydrogensiloxane-diphenylsiloxane copolymer terminated at both molecular chain ends with trimethylsiloxy groups, Methylhydrogenpolysiloxanes capped at both molecular chain terminals with dimethylhydrogensiloxy groups, dimethylpolysiloxanes capped at both molecular chain terminals with dimethylhydrogensiloxy groups, dimethylsiloxane-methylhydrogensiloxane copolymers capped at both molecular chain terminals with dimethylhydrogensiloxy groups, dimethylsiloxane-methylphenylsiloxane copolymers capped at both molecular chain terminals with dimethylhydrogensiloxy groups, dimethylsiloxane-diphenylsiloxane copolymers capped at both molecular chain terminals with dimethylhydrogensiloxy groups, methylphenylpolysiloxanes capped at both molecular chain terminals with dimethylhydrogensiloxy groups, diphenylpolysiloxanes capped at both molecular chain terminals with dimethylhydrogensiloxy groups, and compounds in which some or all of the methyl groups have been replaced with other alkyl groups such as ethyl groups or propyl groups, compounds of the formula: R3SiO 1 / 2 Siloxane units represented by the formula: R2HSiO 1 / 2 Siloxane units represented by the formula: SiO 4 / 2 Organosiloxane copolymers consisting of siloxane units represented by the formula: R2HSiO 1 / 2 Siloxane units represented by the formula: SiO 4 / 2 Organosiloxane copolymers consisting of siloxane units represented by the formula: RHSiO 2 / 2 Siloxane units represented by the formula: RSiO 3 / 2Siloxane units or the formula: HSiO 3 / 2 Examples of suitable organosiloxane copolymers include organosiloxane copolymers composed of siloxane units represented by the formula (I) and mixtures of two or more of these organopolysiloxanes. However, preferred examples include methylhydrogenpolysiloxanes end-blocked at both molecular chain terminals with trimethylsiloxy groups, dimethylsiloxane-methylhydrogensiloxane copolymers end-blocked at both molecular chain terminals with trimethylsiloxy groups, methylhydrogenpolysiloxanes end-blocked at both molecular chain terminals with dimethylhydrogensiloxy groups, and dimethylsiloxane-methylhydrogensiloxane copolymers end-blocked at both molecular chain terminals with dimethylhydrogensiloxy groups. Furthermore, the number-average degree of polymerization of component (B) is 5 to 200, more preferably 8 to 100, and even more preferably 10 to 50. A number-average degree of polymerization lower than 5 may result in insufficient film strength, while a number-average degree of polymerization higher than 200 may result in an increase in the viscosity of the composition, resulting in poor coating workability.

[0027] The amount of component (B) to be added is such that the number of silicon-bonded hydrogen atoms (hydrosilyl groups) contained in component (B) is 0.4 to 5 moles (or units) per mole (or units) of silicon-bonded alkenyl groups contained in component (A). If the number of hydrosilyl groups contained in component (B) is less than 0.4 moles per mole of silicon-bonded alkenyl groups contained in component (A), the composition will not cure sufficiently. If the number of hydrosilyl groups contained in component (B) is more than 5 moles, the heat resistance of the resulting silicone rubber cured product may be significantly reduced. In the photocurable silicone rubber coating composition of the present invention, when the composition contains a component other than component (A) that has an alkenyl group bonded to a silicon atom and / or when the composition contains a component other than component (B) that has a hydrogen atom (hydrosilyl group) bonded to a silicon atom, it is preferable to adjust the amount of each component so that the total number of silicon-bonded hydrogen atoms (hydrosilyl groups) in the composition is 0.4 to 5 moles (or units) per mole (or units) of alkenyl groups bonded to silicon atoms in the entire composition.

[0028] The organohydrogenpolysiloxane of component (B) may use either a single compound, or a combination of two or more different compounds.

[0029] [(C) component] Component (C) is a fine talc powder having a median diameter (D50) of 0.5 to 20 μm, and is added to the composition of the present invention as an inorganic filler to impart low friction to the surface of the resulting cured coating.

[0030] The talc fine powder of component (C) has a median diameter of 0.5 to 20 μm, preferably 1 to 15 μm, and more preferably 2 to 10 μm. The median diameter is measured by laser diffraction. If the median diameter is greater than 20 μm, the surface of the resulting cured coating will be rough, resulting in increased frictional resistance and the desired properties may not be achieved. If the median diameter is less than 0.5 μm, the viscosity of the composition will be high, which may reduce coating workability.

[0031] The amount of component (C) blended is 50 to 150 parts by mass, preferably 60 to 120 parts by mass, and particularly preferably 70 to 100 parts by mass per 100 parts by mass of component (A). If the amount of component (C) blended is less than 50 parts by mass, the surface of the resulting cured coating may not have low friction, while if it is more than 150 parts by mass, the viscosity of the resulting composition may increase, resulting in poor coating workability.

[0032] [(D) component] Component (D) is a platinum group compound catalyst that is activated by light with a wavelength of 200 to 500 nm and is a hydrosilylation catalyst. It is inactive in the absence of light and is activated by irradiation with light with a wavelength of 200 to 500 nm, preferably 300 to 450 nm, to promote the hydrosilylation reaction between the alkenyl groups in component (A) and the silicon-bonded hydrogen atoms in component (B). Here, "activation" of the catalyst refers to a state in which the hydrosilylation reaction proceeds at room temperature (25°C) or above in the presence of alkenyl groups, silicon-bonded hydrogen atoms, and the catalyst.

[0033] Examples of such component (D) include β-diketonato platinum complex compounds, (η 5 -cyclopentadienyl)trialkyl platinum complex compounds or derivatives thereof. Specific examples include trimethyl(acetylacetonato)platinum(IV), trimethyl(3,5-heptanedionato)platinum(IV), trimethyl(methylacetoacetate)platinum(IV), bis(acetylacetonato)platinum(II), bis(2,4-pentanedionato)platinum(II), bis(2,4-hexanedionato)platinum(II), bis(2,4-heptanedionato)platinum(II), bis(3,5-heptanedionato)platinum(II), bis(1-phenyl-1,3-butanedionato)platinum(II), bis(1,3-diphenyl-1,3-propanedionato)platinum(II), bis(hexafluoroacetylacetonato)platinum(II), and the like. (methylcyclopentadienyl)trimethylplatinum(IV), (cyclopentadienyl)trimethylplatinum(IV), (1,2,3,4,5-pentamethylcyclopentadienyl)trimethylplatinum(IV), (cyclopentadienyl)dimethylethylplatinum(IV), (cyclopentadienyl)dimethylacetylplatinum(IV), (trimethylsilylcyclopentadienyl)trimethylplatinum(IV), (methoxycarbonylcyclopentadienyl)trimethylplatinum(IV), (dimethylphenylsilylcyclopentadienyl)trimethylcyclopentadienylplatinum(IV), and the like. Of these, particularly preferred are bis(acetylacetonato)platinum(II) and derivatives in which the hydrogen atom bonded to the carbon atom of the acetylacetonato group is substituted with an alkyl group, and (cyclopentadienyl)trimethylplatinum(IV) and derivatives in which the hydrogen atom bonded to the carbon atom of the cyclopentadienyl group is substituted with an alkyl group, with bis(acetylacetonato)platinum(II) or (trimethyl)methylcyclopentadienylplatinum(IV) being particularly preferred.

[0034] When using these catalysts, if they are solid catalysts, they can be used in a solid state, but in order to obtain a more uniform cured product, it is preferable to use them dissolved in an appropriate solvent.

[0035] The amount of component (D) added should be an effective amount as an addition reaction catalyst, and is preferably in the range of usually 0.5 to 1,000 ppm, preferably 1 to 500 ppm, and more preferably 10 to 100 ppm, calculated as the mass of platinum group metal element relative to the total mass of components (A) and (B). By adding this amount appropriately, the addition reaction can proceed more efficiently after irradiation with light.

[0036] [Other ingredients] In addition to the above components (A) to (D), other components may be blended into the composition of the present invention as needed.

[0037] [Fine silica powder] To reinforce the cured coating, the composition of the present invention has a specific surface area of ​​50 m2 by the BET method. 2 The silica fine powder may be blended with a specific surface area of ​​50 m / g or more as measured by the BET method. 2 / g or more, preferably 50 to 400m 2 / g, more preferably 100 to 300m 2 / g.

[0038] Such silica fine powder may be any known material that has been conventionally used as a reinforcing filler for cured silicone rubber, provided that its specific surface area is within the above-mentioned range, such as fumed silica and precipitated silica (wet silica).

[0039] The silica fine powder may be one 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 one whose surface has been hydrophobized directly with a surface treatment agent while still in powder form. Alternatively, the silica fine powder may be one whose surface has been hydrophobized by adding a surface treatment agent during kneading with silicone oil (e.g., the alkenyl-containing organopolysiloxane of component (A)).

[0040] The surface of the silica fine powder can be hydrophobized by known techniques. For example, the untreated silica fine powder and the surface treatment agent are placed in a mechanical mixer or fluidized bed sealed at atmospheric 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, water or a catalyst (such as a hydrolysis promoter) may be used to accelerate the surface treatment. After mixing, the mixture is dried to produce the surface-treated silica fine powder. The amount of the surface treatment agent to be added may be equal to or greater than the amount calculated from the surface area covered by the surface treatment agent.

[0041] Specific examples of surface treatment agents include silazanes such as hexamethyldisilazane, methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, dimethyldimethoxysilane, diethyldimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, trimethylmethoxysilane, triethylmethoxysilane, vinyltris(methoxyethoxy)silane, trimethylchlorosilane, dimethyldichlorosilane, divinyldimethoxysilane and chloropropyltrimethoxysilane, silane coupling agents such as polymethylsiloxane, organohydrogenpolysiloxane, etc., and can be surface-treated with these and used as hydrophobic silica fine powder. As the surface treatment agent, silane coupling agents or silazanes are particularly preferred.

[0042] The amount of silica fine powder added is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 15 parts by mass, and even more preferably 1 to 10 parts by mass per 100 parts by mass of the organopolysiloxane of component (A).

[0043] [Adhesion promoter] If it is necessary to further improve the adhesiveness of the composition of the present invention, an adhesion promoter can be added. Examples of adhesion promoters include epoxy group-containing organopolysiloxanes such as epoxy group-containing organopolysiloxanes having alkoxy groups and vinyl groups, epoxy group-containing organopolysiloxanes having silicon-bonded hydrogen atoms, and epoxy group-containing organopolysiloxanes having silicon-bonded hydrogen atoms and alkoxy groups; alkoxy group-containing organopolysiloxanes having silicon-bonded hydrogen atoms; and silane coupling agents such as γ-glycidoxypropyltrimethoxysilane, 3,4-epoxycyclohexylethyltrimethoxysilane, and vinyltrimethoxysilane.

[0044] When an adhesion promoter is added to the composition of the present invention, the amount added is preferably 0.1 to 20 parts by mass, and more preferably 0.2 to 10 parts by mass, per 100 parts by mass of component (A).

[0045] [Heat resistance improver] When it is necessary to further improve the heat resistance of the composition of the present invention, it is preferable to add a heat resistance improver to the composition, such as carbon, iron oxide, titanium oxide, or cerium oxide.

[0046] When a heat resistance improver is added, the amount added is preferably 0.1 to 30 parts by mass, and more preferably 0.3 to 10 parts by mass, per 100 parts by mass of component (A).

[0047] [Hydrosilylation Reaction Control Agent] In addition to the above components, the composition of the present invention may also contain a hydrosilylation reaction inhibitor, if necessary. Specific examples of hydrosilylation reaction inhibitors include triallyl isocyanurate and acetylene alcohols such as 1-ethynylcyclohexanol.

[0048] [Other ingredients] In addition, the composition of the present invention may contain, for example, organopolysiloxanes containing one silicon-bonded hydrogen atom per molecule and no other functional groups, organopolysiloxanes containing one silicon-bonded alkenyl group per molecule and no other functional groups, non-functional organopolysiloxanes containing no silicon-bonded hydrogen atoms, silicon-bonded alkenyl groups, or 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.

[0049] [Coat airbag base fabric and its manufacturing method] The coated airbag fabric of the present invention has, as its outermost layer, a cured layer of the photocurable silicone rubber coating composition of the present invention. In a preferred embodiment, the coated airbag fabric of the present invention has a cured layer of a base coating agent formed by applying a silicone rubber coating composition or the like as a base coating agent to the surface of a known airbag fabric, and also has a cured layer of a top coating agent formed by applying the photocurable silicone rubber coating composition of the present invention as a top coating agent on the surface of the cured layer of the base coating agent. The coated airbag fabric of the present invention can be produced, for example, by applying the photocurable silicone rubber coating composition of the present invention to the outermost surface of the airbag fabric, and irradiating the surface coated with the photocurable silicone rubber coating composition with light at a dose of 100 to 10,000 mJ / cm. 2 In particular, the coated airbag fabric of the present invention can be produced by a method comprising the steps of applying a silicone rubber coating composition or the like as a base coating agent to the surface of a known airbag fabric, curing the composition to form a cured layer of the base coating agent, applying the photocurable silicone rubber coating composition of the present invention as a top coating agent to the surface of the cured layer of the base coating agent, and irradiating the surface coated with the photocurable silicone rubber coating composition with a light dose of 100 to 10,000 mJ / cm. 2 It is preferable to produce the film by a method including a step of irradiating the film with light of the formula (I).

[0050] Coating process Known base fabrics can be used for airbags, and specific examples include woven fabrics of various synthetic fibers such as 6,6-nylon (PA66), 6-nylon (PA6), aramid fiber, various polyamide fibers, and various polyester fibers. PA66 base fabric or PET base fabric is preferred. The airbag fabric may be formed into a bag shape in advance by sewing or the like, depending on the embodiment.

[0051] Base coat agent The base coating agent applied to the surface of a known airbag fabric is a composition different from the photocurable silicone rubber coating composition of the present invention, particularly a silicone rubber coating composition. Known compositions used for airbag fabrics can be used. For example, a heat-addition-curable liquid silicone rubber coating composition containing a silicone oil having a vinyl group, a silicone oil having a hydrosilyl group, a platinum catalyst, reinforcing silica, an adhesive aid, etc., an ultraviolet-curable liquid silicone rubber coating composition in which the platinum catalyst is replaced with a platinum catalyst activated by light of a specific wavelength, and an organic peroxide-curable silicone rubber coating composition in which an organic peroxide is added instead of the platinum catalyst are used (for example, JP 2019-019196 A, JP 2018-003194 A, etc.). The silicone rubber coating composition used as a base coat agent does not contain the talc fine powder, which is component (C) of the photocurable silicone rubber coating composition of the present invention, and is different from the photocurable silicone rubber coating composition of the present invention, but the main organopolysiloxane component (silicone oil having a vinyl group, silicone oil having a hydrosilyl group, etc.) contained in the silicone rubber coating composition of the base coat agent can be exemplified by the same as components (A) and (B) described above for the photocurable silicone rubber coating composition of the present invention. In order to improve the airtightness and flame retardancy of the airbag base fabric, it is preferable that the silicone rubber coating composition used as a base coat agent contains reinforcing silica and an adhesion promoter.

[0052] The silicone rubber coating composition of the base coat agent can be applied to both sides of the airbag base fabric by a known method such as knife coating, and the thickness (or surface coating amount) of the silicone rubber coating material for airbags is preferably 30 to 200 g / m 2 and more preferably 40 to 150 g / m 2 , and more preferably 50 to 100 g / m 2 is. After applying the silicone rubber coating composition of the base coat agent to the base fabric for an airbag, the silicone rubber coating composition of the base coat agent is cured by heating or irradiating with light in a conventional manner in accordance with the curing type of the silicone rubber coating composition of the base coat agent, thereby forming a cured layer of the silicone rubber coating composition of the base coat agent.

[0053] Next, the photocurable silicone rubber coating composition of the present invention is applied to the cured layers of the silicone rubber coating composition of the base coat agent formed on both sides of the airbag fabric by a conventional method such as knife coating. The coating amount (thickness) of the photocurable silicone rubber coating composition is preferably 1 to 30 g / m. 2 and more preferably 3 to 25 g / m 2 , and more preferably 5 to 20 g / m 2is.

[0054] ·Light irradiation process After the coating step, the coated surfaces of the photocurable silicone rubber coating composition formed on the cured layer of the silicone rubber coating composition of the base coat agent formed on both sides of the airbag base fabric are irradiated with light. Light sources useful for curing the photocurable silicone rubber coating composition of the present invention include ordinary mercury vapor lamps, metal halide lamps, and light-emitting diode (LED) elements designed to emit light energy in various wavelength bands. For example, a useful light wavelength range is 200 to 500 nm, preferably 300 to 450 nm. Furthermore, the light irradiation dose useful for curing is not particularly limited as long as it is sufficient for curing, but is preferably 100 to 10,000 mJ / cm. 2 and more preferably 200 to 5,000 mJ / cm 2 , and more preferably 300 to 3,000 mJ / cm 2 This light irradiation step can be carried out in air or in an inert gas atmosphere, but is preferably carried out in an inert gas atmosphere since curing is less inhibited by oxygen, and more preferably in a nitrogen gas or argon gas atmosphere.

[0055] ·Curing acceleration process The photocurable silicone rubber coating composition of the present invention can be cured by irradiation with light even at room temperature (25°C). However, the curing can be further accelerated by heating in a drying oven or the like after light irradiation. The method for producing a coated airbag fabric of the present invention may optionally include a curing acceleration step. The acceleration temperature is preferably 40 to 120°C, more preferably 60 to 100°C, and the acceleration time is preferably 5 to 120 seconds, more preferably 10 to 90 seconds. If the acceleration temperature is too high, wrinkles may form in the airbag fabric due to the difference in thermal shrinkage between the cured coating of the photocurable silicone rubber coating composition, the cured layer of the silicone rubber coating composition of the base coat agent, and the airbag fabric. [Example]

[0056] The present invention will be specifically explained below with reference to Preparation Examples, Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[0057] The following components were used as component (A): (A-1): A linear dimethylpolysiloxane (alkenyl groups: 1.30 mol%) with both molecular chain terminals capped with vinyldimethylsiloxy groups, a number average degree of polymerization of 75, and a viscosity of 100 mPa·s. (A-2): A linear dimethyl-vinylmethylpolysiloxane (alkenyl groups: 10.8 mol%), with both molecular chain ends capped with trimethylsiloxy groups, a number-average degree of polymerization of 170, a viscosity of 650 mPa·s, and containing 20 mol% vinylmethylsiloxane units and 80 mol% dimethylsiloxane units among the bifunctional diorganosiloxane units that make up the main chain.

[0058] The following components were used as component (B): (B-1): A linear methylhydrogenpolysiloxane (in the formula (1) above, a = 1.10, b = 0.95, and R = CH3) in which both molecular chain terminals are blocked with trimethylsiloxy groups, the number average degree of polymerization is 40, and the viscosity is 20 mPa s. (B-2): A linear dimethylsiloxane-methylhydrogensiloxane copolymer (in the formula (1) above, a = 1.33, b = 0.70, R = CH3) with both molecular chain ends capped with trimethylsiloxy groups, a number-average degree of polymerization of 64, and a viscosity of 45 mPa·s.

[0059] The following components were used as component (C): (C): Talc fine powder with a median diameter of 8.0 μm (product name: MicroAce K-1, manufactured by Nippon Talc Co., Ltd.)

[0060] The following components were used as component (D): (D-1): A toluene solution containing bis(acetylacetonato)platinum(II) at a platinum atom content of 0.5% by mass. (D-2): A toluene solution containing 0.5% by mass of (trimethyl)methylcyclopentadienyl platinum as a platinum atom content. (D-3): Dimethylpolysiloxane solution containing 1% by mass of chloroplatinic acid / 1,3-divinyltetramethyldisiloxane complex as platinum atom content (platinum group compound catalyst not activated by light with a wavelength of 200 to 500 nm, for comparison)

[0061] The following components were used as reaction inhibitors: (Reaction inhibitor): 1-ethynylcyclohexanol

[0062] The following components were used as the reinforcing silica fine powder. (Silica fine powder): R-974 (manufactured by Nippon Aerosil Co., Ltd., BET specific surface area 170 g / m 2 )

[0063] [Examples and Comparative Examples] The components in the amounts shown in Tables 1 and 2 were mixed in a mixer at room temperature (25°C) for 30 minutes to prepare silicone rubber coating compositions.

[0064] <Dynamic friction coefficient> To evaluate the frictional properties of the cured coating surface, the dynamic friction coefficient of the cured coating surface was measured in accordance with the standard JIS P8147:2010. Specifically, the silicone rubber coating composition was applied to a PET film at a rate of 20 g / m. 2 After coating so that the silicone rubber coating composition was uniform, it was cured under the conditions listed in Tables 1 and 2 to prepare measurement samples with a cured film of the silicone rubber coating composition on the surface. A UV-LED irradiator HLUV-504UV365 (manufactured by CCS Inc., wavelength 365 nm) was used for light irradiation. The dynamic friction coefficient of the obtained samples was measured under a load of 100 g using an automatic friction and wear analyzer TSF-503 (manufactured by Kyowa Interface Science Co., Ltd.). N=5 measurements were taken, and the median values ​​are shown in Tables 1 and 2.

[0065] <Blocking resistance> To evaluate the blocking resistance of the cured coating surface, the following test was conducted in accordance with JIS K 6404-3:2020. First, a sample was prepared with a cured coating of silicone rubber coating composition on its surface, similar to the sample for measuring the dynamic friction coefficient described above. Two 150 mm × 150 mm pieces were cut from this sample with a cured coating on its surface. The cured coatings on the two pieces were then bonded together and sandwiched between smooth plates (metal, glass, etc.) of the same size. A 5 kgf weight was placed on the cured coating so that a uniform force was applied to the cured coating. The sample was then left to stand in an oven at 70°C for 3 hours, after which the weight was removed, the sample was removed from the oven, and the sample was allowed to cool naturally. This yielded a sample with PET films on the top and bottom, with two layers of cured coating bonded together. Then, a region of the sample extending parallel to one side and extending about 20 mm from the sample was manually peeled off together with the PET film so that the bonded surfaces of the cured coatings peeled off. One edge of the peeled PET film was fixed during the peeling, and a 50 gf weight was hung from the other edge of the PET film to measure the time until the entire bonded surface peeled off. Cases in which the time until peeling was within 30 seconds (including cases in which peeling had already occurred before measurement) were evaluated as passing, and cases in which it exceeded 30 seconds were evaluated as failing.

[0066] [Preparation Example 1] Both molecular chain ends are blocked with vinyldimethylsiloxy groups, and the viscosity at 25°C is 30,000 mPa·s. The average degree of polymerization is 750. 60 parts by mass of dimethylpolysiloxane, 8 parts by mass of hexamethyldisilazane, 2 parts by mass of water, and a specific surface area of ​​300 m2 measured by the BET method are contained in the polymer. 2 40 parts by mass of silica fine powder (Aerosil 300, manufactured by Nippon Aerosil Co., Ltd.) having a viscosity of 1 / g was added to a kneader and mixed at room temperature for 1 hour. 8 parts by mass of hexamethyldisilazane was then added to the mixture and mixed at room temperature for 1 hour. The mixing temperature of the mixture was then raised to 150°C and mixed for a further 2 hours. The mixture was then cooled to room temperature, and 30 parts by mass of dimethylpolysiloxane, both molecular chain terminals of which were capped with vinyldimethylsiloxy groups and had a viscosity of 30,000 mPa·s at 25°C, was added and mixed until uniform, to prepare a base compound. The resulting base compound (128 parts by mass) was mixed with 50 parts by mass of a dimethylpolysiloxane with a viscosity of 30,000 mPa·s and an average degree of polymerization of 750, 4.1 parts by mass of a dimethylsiloxane-methylhydrogensiloxane copolymer (average degree of polymerization: 16, SiH group content: 0.0031 mol / g) in which both molecular chain terminals are blocked with dimethylhydrogensiloxy groups and the molecular chain side chains have an average of two hydrogen atoms bonded to silicon atoms, and 4.1 parts by mass of a methylhydrogenpolysiloxane (average polymerization: 16, SiH group content: 0.0031 mol / g) in which both molecular chain terminals are blocked with trimethylsiloxy groups and the molecular chain side chains have an average of 38 hydrogen atoms bonded to silicon atoms. A silicone rubber coating composition for airbags was prepared by mixing for one hour 0.25 parts by mass of γ-glycidoxypropyltrimethoxysilane (polymerizable copolymer of γ-glycidoxypropyltrimethoxysilane, 0.3 parts by mass of γ-glycidoxypropyltrimethoxysilane, 0.36 parts by mass of an isopropanol solution of titanium tetraacetylacetonate (product name: TC-401, manufactured by Matsumoto Fine Chemical Co., Ltd.), 0.05 parts by mass of 1-ethynylcyclohexanol as a reaction inhibitor, and 0.2 parts by mass of a dimethylpolysiloxane solution containing chloroplatinic acid / 1,3-divinyltetramethyldisiloxane complex with a platinum atom content of 1% by mass.

[0067] <Base fabric stiffness test> To evaluate the stiffness and flexibility of the airbag fabric, the following test was carried out in accordance with the standard ASTM D4032. Specifically, the silicone rubber coating composition for airbags prepared in Preparation Example 1 was applied as a base coat to a 210 denier PA66 fabric at a rate of 80 g / m. 2 The base coating was then placed in a dryer at 200°C for 1 minute to cure the base coating. Then, 15 g / m of each of the silicone rubber coating compositions in Tables 1 and 2 was applied as a top coating agent to the surface of the cured base coating. 2 The coated airbag fabrics were knife coated to a thickness of 102 mm x 204 mm and cured under the conditions shown in Tables 1 and 2. The resulting coated airbag fabrics were cut to a size of 102 mm x 204 mm and tested for stiffness using a SASD-672-1 stiffness tester (manufactured by JAKING) with N = 3. The median values ​​are shown in Tables 1 and 2.

[0068] [Table 1]

[0069] [Table 2]

[0070] As can be seen from Table 1, in Examples 1 to 8, which used the photocurable silicone rubber coating composition of the present invention, the cured coating had a low coefficient of dynamic friction, excellent blocking resistance, and the coated airbag fabric had low stiffness and flexibility.

[0071] On the other hand, as can be seen from Table 2, in Comparative Examples 1 to 7, which did not use the photocurable silicone rubber coating composition of the present invention, the coatings were either uncured or had higher dynamic friction coefficients and poorer blocking resistance than the Examples, and the stiffness and flexibility of the coated airbag fabrics were also high.

Claims

1. A photocurable silicone rubber coating composition used to form a cured layer on the outermost surface of a base fabric for coated airbags, comprising: (A) 100 parts by mass of a linear organopolysiloxane containing two or more silicon-bonded alkenyl groups per molecule and having a number-average degree of polymerization of 10 to 1,000; (B) an organohydrogenpolysiloxane containing two or more silicon-bonded hydrogen atoms per molecule: an amount such that the number of silicon-bonded hydrogen atoms contained per molecule of this component is 0.4 to 5 per total number of silicon-bonded alkenyl groups in component (A); (C) talc fine powder having a median diameter (D50) of 0.5 to 20 μm: 50 to 150 parts by mass, and (D) an effective amount of a platinum group compound catalyst that is activated by light with a wavelength of 200 to 500 nm as a hydrosilylation reaction catalyst; A photocurable silicone rubber coating composition comprising:

2. 2. The photocurable silicone rubber coating composition according to claim 1, wherein component (D) is bis(acetylacetonato)platinum(II) or (trimethyl)methylcyclopentadienylplatinum(IV).

3. 2. The photocurable silicone rubber coating composition according to claim 1, wherein component (A) is an organopolysiloxane having vinyl groups only at both molecular chain terminals.

4. 2. The photocurable silicone rubber coating composition according to claim 1, wherein component (A) is an organopolysiloxane in which 0.1 to 15 mol % of all substituents bonded to silicon atoms are alkenyl groups having 2 to 8 carbon atoms.

5. 5. A coated airbag fabric having a cured product layer of the photocurable silicone rubber coating composition according to claim 1 as the outermost layer.

6. A step of applying the photocurable silicone rubber coating composition according to any one of claims 1 to 4 to the outermost layer of an airbag fabric; and The coated surface of the photocurable silicone rubber coating composition is irradiated with light at a dose of 100 to 10,000 mJ / cm. 2 A process of irradiating light of A method for producing a coated airbag base fabric having the above structure.

7. The method for producing a coated airbag fabric according to claim 6, further comprising a curing acceleration step at 40 to 120 ° C. for 5 to 120 seconds following the light irradiation step.

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