JP7506641B2 - Addition-curable liquid silicone rubber composition for airbags and airbags - Google Patents

Description

The present invention relates to an addition-curable liquid silicone rubber composition for airbags and to an airbag.

Conventionally, silicone rubber compositions for airbags have been proposed with the aim of forming a rubber coating on the surface of fibers. Airbags with silicone rubber coatings have excellent internal pressure retention and low burning rates, and are therefore ideally used as airbags for automobiles, etc.

An example of such an addition-curing liquid silicone rubber composition for airbags is a combination of a crosslinking agent having hydrosilyl groups at both ends of the molecular chain and a crosslinking agent having hydrosilyl groups in the side chain (Patent Document 1). This addition-curing liquid silicone rubber composition for airbags is characterized by its excellent internal pressure retention. In addition, a method is also known in which a resin-like polysiloxane is contained, and the siloxane component is premixed with silica, a surface treatment agent, and water to produce an addition-curing liquid silicone rubber composition for airbags (Patent Document 2). By coating the fiber surface with this composition, an airbag base fabric with excellent low burning rate is obtained. Furthermore, an addition-curing liquid silicone rubber composition for airbags using an organohydrogenpolysiloxane containing T units or Q units as a crosslinking agent has also been disclosed (Patent Document 3). A coated base fabric coated with this composition is characterized by excellent strength. Patent Document 4 discloses an addition-curing liquid silicone rubber composition for airbags that contains a silicone resin composed of M, D, and Q units, with only the D units containing crosslinkable functional groups, as a flame retardant. Airbags coated with this composition are characterized by their excellent low burning rate.

However, the coating base fabric for airbags using conventional addition-curing liquid silicone rubber compositions for airbags showed a significant decrease in adhesion after durability tests such as heat resistance and moist heat resistance. Therefore, the adhesive durability required for airbag base fabrics was not satisfied. Furthermore, in recent years, there has been a trend toward reducing the amount of silicone rubber composition applied to the airbag base fabric in order to reduce weight and save space. Therefore, there is a demand for materials that have excellent adhesive durability and flame retardancy even with a low coating amount.

JP 2013-531695 A JP 2013-209517 A JP 2019-513907 A International Publication No. 2018/168315

The present invention was made in consideration of the above circumstances, and aims to provide an addition-curing liquid silicone rubber composition for airbags that has excellent adhesion durability to airbag base fabrics and flame retardancy, and an airbag.

In order to solve the above problems, the present invention provides an addition-curable liquid silicone rubber composition for airbags, comprising:
(A) an 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) 5 to 100 parts by mass of a boron-atom-containing three-dimensional network organopolysiloxane resin containing monofunctional R ¹ ₃ SiO _1/2 units (M units, in the formula, R ¹ is independently a group selected from an unsubstituted or substituted alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an alkenyl group having 2 to 10 carbon atoms), tetrafunctional SiO _4/2 units (Q units), and a trifunctional boron atom bonded to three oxygen atoms (BO _3/2 units), wherein the ratio of the M units to the Q units is 0.65 to 1.40, the ratio of the trifunctional boron atoms to the silicon atoms of the Q units is 0.05 to 0.4, and the amount of alkenyl groups is 0.01 to 0.30 mol/100 g;
(C) an organohydrogenpolysiloxane containing two or more hydrogen atoms bonded to silicon atoms (hydrosilyl groups) per molecule: the amount of hydrosilyl groups contained in the composition is 1 to 10 moles per mole of the total number of alkenyl groups bonded to silicon atoms contained in the composition;
(D) silica fine powder having a specific surface area of 50 m ² /g or more as measured by the BET method: 1 to 50 parts by mass,
(E) a hydrosilylation reaction catalyst: 1 to 500 ppm by mass of catalytic metal element per 100 parts by mass of component (A); and (F) an organosilicon compound containing an adhesion-imparting functional group: 0.1 to 10 parts by mass,
The present invention provides an addition-curable liquid silicone rubber composition for air bags, comprising:

Such an addition-curing liquid silicone rubber composition is an addition-curing liquid silicone rubber composition that has excellent adhesion durability to airbag base fabrics and flame retardancy.

In addition, in the present invention, it is preferable that the component (G) further contains 0.1 to 5 parts by mass of one or more condensation catalysts selected from an organic titanium compound, an organic zirconium compound, and an organic aluminum compound.

Such an addition-curing liquid silicone rubber composition has superior adhesive properties.

In the present invention, it is also preferable that the adhesion-imparting functional group is one or more groups selected from an epoxy group, an alkoxy group bonded to a silicon atom, a hydrosilyl group, an isocyanate group, an acrylic group, and a methacrylic group.

Such an addition-curing liquid silicone rubber composition can further improve the adhesion of the addition-curing liquid silicone rubber composition to the airbag base fabric.

The present invention also provides an airbag having a cured coating of the above-described addition-curable liquid silicone rubber composition for airbags on an airbag base fabric.

Such an airbag will have excellent adhesion durability to the airbag base fabric and excellent flame retardancy.

As described above, the present invention can provide an addition-curing liquid silicone rubber composition for airbags that has excellent adhesion durability to airbag base fabrics and flame retardancy, and an airbag.

As mentioned above, there was a need to develop an addition-curing liquid silicone rubber composition and airbag that have excellent adhesion durability to airbag fabrics and flame retardancy.

The inventors conducted extensive research to achieve the above object, and discovered that an addition-curing liquid silicone rubber composition containing a specific composition of boron-containing three-dimensional network organopolysiloxane resin is suitable for use in airbags. Specifically, they discovered that an airbag base fabric coated with and cured with the addition-curing liquid silicone rubber composition exhibits excellent adhesion durability to the base fabric and flame retardancy, which led to the invention.

That is, the present invention provides an addition-curable liquid silicone rubber composition for airbags, comprising:
(A) an 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) 5 to 100 parts by mass of a boron-atom-containing three-dimensional network organopolysiloxane resin containing monofunctional R ¹ ₃ SiO _1/2 units (M units, in the formula, R ¹ is independently a group selected from an unsubstituted or substituted alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an alkenyl group having 2 to 10 carbon atoms), tetrafunctional SiO _4/2 units (Q units), and a trifunctional boron atom bonded to three oxygen atoms (BO _3/2 units), wherein the ratio of the M units to the Q units is 0.65 to 1.40, the ratio of the trifunctional boron atoms to the silicon atoms of the Q units is 0.05 to 0.4, and the amount of alkenyl groups is 0.01 to 0.30 mol/100 g;
(C) an organohydrogenpolysiloxane containing two or more hydrogen atoms bonded to silicon atoms (hydrosilyl groups) per molecule: the amount of hydrosilyl groups contained in the composition is 1 to 10 moles per mole of the total number of alkenyl groups bonded to silicon atoms contained in the composition;
(D) silica fine powder having a specific surface area of 50 m ² /g or more as measured by the BET method: 1 to 50 parts by mass,
(E) a hydrosilylation reaction catalyst: 1 to 500 ppm by mass of catalytic metal element per 100 parts by mass of component (A); and (F) an organosilicon compound containing an adhesion-imparting functional group: 0.1 to 10 parts by mass,
The addition-curable liquid silicone rubber composition for air bags comprises:

The present invention will be described in detail below, but the present invention is not limited thereto. 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 calculated as a polystyrene-equivalent weight-average degree of polymerization (weight-average molecular weight) by GPC (gel permeation chromatography) analysis using toluene as a developing solvent, measured under the following conditions.
[Measurement condition]
Developing solvent: toluene Flow rate: 0.35 mL/min
Detector: Refractive index detector (RI)
Column: TSK Guard column Super H-L
TSKgel Super H4000 (6.0 mm I.D. x 15 cm x 1)
TSKgel Super H3000 (6.0 mm I.D. x 15 cm x 1)
TSKgel Super H2000 (6.0 mm I.D. x 15 cm x 2)
(Both manufactured by Tosoh Corporation)
Column temperature: 40°C
Sample injection volume: 10 μL (toluene solution with a concentration of 0.5% by weight)

<Addition-curable liquid silicone rubber composition for airbags>
The addition-curable liquid silicone rubber composition for airbags of the present invention comprises:
(A) an 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) 5 to 100 parts by mass of a boron-atom-containing three-dimensional network organopolysiloxane resin containing monofunctional R ¹ ₃ SiO _1/2 units (M units, in the formula, R ¹ is independently a group selected from an unsubstituted or substituted alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an alkenyl group having 2 to 10 carbon atoms), tetrafunctional SiO _4/2 units (Q units), and a trifunctional boron atom bonded to three oxygen atoms (BO _3/2 units), wherein the ratio of the M units to the Q units is 0.65 to 1.40, the ratio of the trifunctional boron atoms to the silicon atoms of the Q units is 0.05 to 0.4, and the amount of alkenyl groups is 0.01 to 0.30 mol/100 g;
(C) an organohydrogenpolysiloxane containing two or more hydrogen atoms bonded to silicon atoms (hydrosilyl groups) per molecule: the amount of hydrosilyl groups contained in the composition is 1 to 10 moles per mole of the total number of alkenyl groups bonded to silicon atoms contained in the composition;
(D) silica fine powder having a specific surface area of 50 m ² /g or more as measured by the BET method: 1 to 50 parts by mass,
(E) a hydrosilylation reaction catalyst: 1 to 500 ppm by mass of catalytic metal element per 100 parts by mass of component (A); and (F) an organosilicon compound containing an adhesion-imparting functional group: 0.1 to 10 parts by mass,
and is liquid at room temperature (25° C.). Each component will be described in detail below.

[Component (A)]
The organopolysiloxane of component (A) is an 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, and is the base polymer (main component) of the composition of the present invention.

The molecular structure of component (A) may be, for example, linear, cyclic, or branched, but a linear diorganopolysiloxane in which the main chain is basically composed of repeated diorganosiloxane units and both ends of the molecular chain are blocked with triorganosiloxy groups is preferred. In addition, when the molecular structure of the organopolysiloxane of component (A) is linear or branched, the position of the silicon atom to which the alkenyl group is bonded in the organopolysiloxane molecule may be either or both of the molecular chain end (i.e., triorganosiloxy group) and the middle of the molecular chain (i.e., difunctional diorganosiloxane unit or trifunctional monoorganosilsesquioxane unit located at the non-terminal of the molecular chain). Particularly preferred as component (A) is a linear diorganopolysiloxane containing alkenyl groups bonded to silicon atoms at least at both ends of the molecular chain.

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.

The content of alkenyl groups bonded to silicon atoms in component (A) is preferably 0.001 to 10 mol %, and more preferably about 0.01 to 5 mol %, based on the total amount of monovalent organic groups bonded to silicon atoms (i.e., unsubstituted or substituted monovalent hydrocarbon groups).

Examples of the monovalent organic groups bonded to silicon atoms other than the alkenyl groups of component (A) include, for example, the same or different unsubstituted or substituted monovalent hydrocarbon groups, typically having 1 to 12 carbon atoms, preferably 1 to 10 carbon atoms. Specific examples of monovalent organic 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.

The weight average degree of polymerization of component (A) is from 50 to 2,000, preferably from 100 to 1,500, and more preferably from 120 to 1,000. If the weight average degree of polymerization is less than 50, the mechanical properties of the resulting silicone rubber may deteriorate, while if the weight average degree of polymerization is more than 2,000, the viscosity of the resulting silicone rubber composition may increase, deteriorating coating workability.
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.

Specific examples of the organopolysiloxane of component (A) include dimethylsiloxane-methylvinylsiloxane copolymers capped with trimethylsiloxy groups at both molecular chain ends, methylvinylpolysiloxane capped with trimethylsiloxy groups at both molecular chain ends, dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymers capped with trimethylsiloxy groups at both molecular chain ends, dimethylpolysiloxane capped with dimethylvinylsiloxy groups at both molecular chain ends, methylvinylpolysiloxane capped with dimethylvinylsiloxy groups at both molecular chain ends, dimethylsiloxane-methylvinylpolysiloxane capped with dimethylvinylsiloxy groups at both molecular chain ends, dimethylsiloxane copolymer, dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymer capped at both molecular chain terminals with dimethylvinylsiloxy groups, dimethylpolysiloxane capped at both molecular chain terminals with divinylmethylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymer capped at both molecular chain terminals with divinylmethylsiloxy groups, dimethylpolysiloxane capped at both molecular chain terminals with trivinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymer capped at both molecular chain terminals with trivinylsiloxy groups, and mixtures of two or more of these organopolysiloxanes.

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

[Component (B)]
The boron-containing three-dimensional network organopolysiloxane resin of component (B) is a boron-containing organopolysiloxane resin having a three-dimensional network (resinous) structure, which contains monofunctional R ¹ ₃ SiO _1/2 units (M units, where R ¹ is independently a group selected from unsubstituted or substituted alkyl groups having 1 to 10 carbon atoms, aryl groups having 6 to 10 carbon atoms, and alkenyl groups having 2 to 10 carbon atoms), tetrafunctional SiO _4/2 units (Q units), and a trifunctional boron atom bonded to three oxygen atoms (BO _3/2 units), in which the ratio of the M units to the Q units (M units/Q units) is 0.65 to 1.40, and the ratio of the trifunctional boron atoms to the silicon atoms of the Q units (BO The ratio of boron atoms in Q units to silicon atoms in Q units is _0.05 to 0.4, and the amount of alkenyl groups is 0.01 to 0.30 mol/100 g. If necessary, bifunctional R ¹ ₂ SiO _2/2 units (D units) and trifunctional R ¹ SiO _3/2 units (T units) may be optionally contained. This boron atom-containing three-dimensional network organopolysiloxane resin (herein, the organo group may also include an alkenyl group) can also act as a flame retardant improver and an adhesive durability improver. However, this boron atom-containing three-dimensional network organopolysiloxane resin does not contain hydrogen atoms (hydrosilyl groups) bonded to silicon atoms.

R ¹ in the above formula is independently a substituted or unsubstituted group selected from an alkyl group having 1 to 10 carbon atoms, preferably 1 to 8, and more preferably 1 to 4 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an alkenyl group having 2 to 10 carbon atoms. In this case, it is preferable that R 1 is independently a group selected from an alkyl group having 1 to 10 carbon atoms, preferably 1 to 8, and more preferably 1 to 4 carbon atoms, or an alkenyl group having 2 to 10 carbon atoms. Examples of alkenyl groups and monovalent organic groups (unsubstituted or substituted monovalent hydrocarbon groups) include those similar to those exemplified in component (A) above. Specific examples include alkenyl groups, such as vinyl, allyl, propenyl, butenyl, pentenyl, hexenyl, cyclohexenyl, and heptenyl; 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. Methyl and vinyl groups are particularly preferred.

The content of alkenyl groups bonded to silicon atoms in component (B) is 0.01 to 0.30 mol/100g, preferably 0.03 to 0.20 mol/100g, and more preferably 0.05 to 0.15 mol/100g. If the amount of alkenyl groups is less than 0.01 mol/100g, the mechanical strength required for an airbag coating material may not be obtained, and if it is more than 0.30 mol/100g, the hardness of the cured product may become extremely high, resulting in reduced adhesion and mechanical strength.

The boron-atom-containing three-dimensional network organopolysiloxane resin of component (B) has a ratio of M units to Q units of 0.65 to 1.40, preferably 0.70 to 1.30, and more preferably 0.75 to 1.20. If the ratio of M units to Q units is lower than 0.65, the viscosity may increase when blended into a silicone rubber composition, which may result in poor coating workability, and if it is higher than 1.40, sufficient flame retardancy improvement effect may not be obtained.

The boron-atom-containing three-dimensional network organopolysiloxane resin of component (B) has a ratio of trifunctional boron atoms bonded to three oxygen atoms to silicon atoms in the Q unit of 0.05 to 0.40, preferably 0.08 to 0.30, and more preferably 0.1 to 0.25. If the ratio of trifunctional boron atoms bonded to three oxygen atoms to silicon atoms in the Q unit is less than 0.05, sufficient improvement in adhesion durability cannot be obtained, and if it is greater than 0.40, the compounded silicone rubber composition may become highly thixotropic, resulting in poor coating workability.

Here, as described above, the boron atom-containing three-dimensional network organopolysiloxane resin of component (B) has M units, Q units, and trifunctional boron atoms bonded to three oxygen atoms as essential components, but may also contain D units and T units. In this case, the total content of M units, Q units, and trifunctional boron atoms bonded to three oxygen atoms in the boron atom-containing three-dimensional network organopolysiloxane resin of component (B) is preferably 50 to 100 mol%, and more preferably 80 to 100 mol%. If the total content of M units, Q units, and trifunctional boron atoms bonded to three oxygen atoms in the boron atom-containing three-dimensional network organopolysiloxane resin of component (B) is within the above range, sufficient flame retardancy improvement effect and adhesion durability improvement effect can be obtained, which is preferable.

The weight-average degree of polymerization of the boron-containing three-dimensional network organopolysiloxane resin of component (B) is preferably 2,000 to 50,000, and more preferably 4,000 to 20,000. If the weight-average degree of polymerization is within the range of 2,000 to 50,000, a sufficient flame retardancy improvement effect is obtained, and the viscosity of the liquid silicone rubber coating agent composition is such that coating workability is good.

Specific examples of the boron atom-containing three-dimensional network organopolysiloxane resin of component (B) include a boric acid-organosiloxane copolymer consisting of a siloxane unit represented by the formula: _{R'3SiO1 /2} , a siloxane unit represented by the formula: _R'2R "SiO1 _/ 2, a siloxane unit represented by the formula: SiO4 _/2 , and a trifunctional boron atom unit bonded to three oxygen atoms represented by the formula: BO3 _/2 ; a siloxane unit represented by the formula: _{R'3SiO1 /2} , a siloxane unit represented by the formula: R'2R"SiO1 _{/ 2} , a siloxane unit represented by the formula: SiO4 _/2 , a siloxane unit represented by the formula: R'2SiO2 _{/ 2} , and a trifunctional boron atom unit represented by the formula: BO3/2; a boric acid-organosiloxane copolymer comprising a trifunctional boron atom unit bonded to three oxygen atoms, 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: SiO _4/2, a siloxane unit represented by the formula: R' ₁ R"SiO _2/2 , and a trifunctional boron atom unit bonded to three oxygen atoms, represented by the formula: BO _3/2; a boric acid-organosiloxane copolymer comprising 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 , a siloxane unit represented by the formula: SiO _4/2 , a siloxane unit represented by the formula: R' ₁ SiO _{3/2, and} a trifunctional boron atom unit bonded to three oxygen atoms, represented by the formula: BO Examples of such organosiloxanes include boric acid-organosiloxane copolymers consisting of trifunctional boron atom units bonded to three oxygen atoms, represented by _{the formula 3/2} , and mixtures of two or more of these organopolysiloxanes.

In the above formula, R' is independently a monovalent hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 8 carbon atoms, and more preferably 1 to 4 carbon atoms, and does not include an alkenyl group. Examples of R' include alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclohexyl, and heptyl groups; aryl groups such as phenyl, tolyl, xylyl, and naphthyl groups; aralkyl groups such as benzyl and phenethyl groups; and halogenated alkyl groups such as chloromethyl, 3-chloropropyl, and 3,3,3-trifluoropropyl groups. Of these, the methyl group is preferred. In addition, R" in the above formula is an alkenyl group having 2 to 10 carbon atoms, preferably 2 to 8 carbon atoms, and more preferably 2 to 4 carbon atoms. Examples of R" include vinyl, allyl, butenyl, pentenyl, hexenyl, and heptenyl groups. Of these, the vinyl group is preferred.

The amount of component (B) to be blended is 5 to 100 parts by mass, preferably 5 to 80 parts by mass, and particularly preferably 5 to 50 parts by mass, per 100 parts by mass of the organopolysiloxane of component (A). If the blending amount is outside the range of 5 to 100 parts by mass, sufficient improvement in flame retardancy and adhesion durability cannot be obtained, and the cost-effectiveness is also poor.

The boron-atom-containing three-dimensional network organopolysiloxane resin of component (B) can be used alone or in combination of two or more types.

[Component (C)]
Component (C) is an organohydrogenpolysiloxane that contains two or more silicon-bonded hydrogen atoms (hydrosilyl groups) per molecule, and undergoes a hydrosilylation addition reaction mainly with alkenyl groups in components (A) and (B), thereby acting as a crosslinking agent (curing agent).
The molecular structure of component (C) can be, for example, a linear, cyclic, branched, or three-dimensional network (resinous) structure, and must have at least two, and preferably at least three, hydrogen atoms bonded to silicon atoms (hydrosilyl groups) per molecule, and it is desirable for the component (C) to have typically 2 to 300, preferably 3 to 200, and more preferably 3 to 100 hydrosilyl groups, and the component (C) is liquid at 25° C. Such hydrosilyl groups may be located at either the terminals or midway along the molecular chain, or may be located at both locations.

As the organohydrogenpolysiloxane, one represented by the following average composition formula (1) can be used.

In formula (1), R ² is independently a monovalent hydrocarbon group having 1 to 10 carbon atoms. Examples of R 2 include 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 of these groups have been substituted with halogen atoms such as fluorine, bromine, and chlorine, such as a chloromethyl group, a chloropropyl group, a bromoethyl group, and a trifluoropropyl group. R ² is preferably an alkyl group or an aryl group, and more preferably a methyl group. Note that R ² does not include aliphatic unsaturated hydrocarbon groups such as an alkenyl group. In addition, a is a positive number that satisfies 0.7 to 2.1, b is a positive number that satisfies 0.001 to 1.0, and a+b is a positive number that satisfies 0.8 to 3.0, and preferably, a is a positive number that satisfies 1.0 to 2.0, b is a positive number that satisfies 0.01 to 1.0, and a+b is a positive number that satisfies 1.5 to 2.5.

Examples of such organohydrogenpolysiloxanes of component (C) include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, tris(hydrogendimethylsiloxy)methylsilane, tris(hydrogendimethylsiloxy)phenylsilane, methylhydrogencyclopolysiloxane, methylhydrogensiloxane-dimethylsiloxane cyclic copolymers, methylhydrogenpolysiloxanes capped at both molecular chain terminals with trimethylsiloxy groups, dimethylsiloxane-methylhydrogensiloxane copolymers capped at both molecular chain terminals with trimethylsiloxy groups, dimethylsiloxane-methylhydrogensiloxane-methylphenylsiloxane copolymers capped at both molecular chain terminals with trimethylsiloxy groups, dimethylsiloxane-methylhydrogensiloxane-diphenylsiloxane copolymers capped at both molecular chain terminals with trimethylsiloxy groups, and dimethylsiloxane-methylhydrogensiloxane-diphenylsiloxane copolymers capped at both molecular chain terminals with trimethylsiloxy groups. and compounds of the formula: R ² _{3SiO1 /2} , siloxane units represented by the formula: ^R2 _{2HSiO1 /2,} and siloxane units represented by the formula: SiO4 _/2 ; organosiloxane copolymers comprising siloxane units represented by the formula: ^R2 2HSiO1 _{/ 2} and siloxane units represented by the formula: SiO4 _/2 ; organosiloxane copolymers comprising siloxane units represented by the formula: ^R2HSiO2 _/2 , and siloxane units represented by the formula: ^R2SiO3 _/ 2 or siloxane units represented by the formula: HSiO3 _/2 ; and mixtures of two or more of these organopolysiloxanes.

The amount of component (C) blended is an amount such that the amount of hydrosilyl groups contained in the composition containing component (C) is 1 to 10 moles (or groups), preferably 1.2 to 9 moles (or groups), and more preferably 1.5 to 8 moles (or groups), per 1 mole (or groups) of alkenyl groups bonded to silicon atoms contained in the compositions containing components (A) and (B).
If the composition containing component (C) contains less than 1 mole of hydrosilyl groups per mole of alkenyl groups bonded to silicon atoms in the compositions containing components (A) and (B), the composition will not cure sufficiently. If the amount exceeds 10 moles, the heat resistance of the resulting cured silicone rubber product may be extremely poor.

The organohydrogenpolysiloxane of component (C) may be used alone or in combination of two or more types.

[Component (D)]
The silica fine powder of component (D) having a specific surface area of 50 m ² /g or more as measured by the BET method acts as a reinforcing filler. In other words, it imparts strength to the silicone rubber cured product obtained from the composition of 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. The specific surface area of this silica fine powder as measured by the BET method is 50 m ² /g or more, preferably 50 to 400 m ² /g, and more preferably 100 to 300 m ² /g. If the specific surface area is less than 50 m ² /g, it is not possible to impart mechanical strength properties sufficient for use as a coating agent for airbags.

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

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 in the powder state beforehand. Alternatively, the silica fine powder may be one whose surface has been hydrophobized by adding a surface treatment agent when kneaded with silicone oil (for example, the alkenyl-containing organopolysiloxane of component (A) above).

As a method for treating component (D), surface treatment can be performed by known techniques. For example, the untreated silica fine powder and the surface treatment agent can be placed in a mechanical kneading device or fluidized bed sealed at normal pressure, and mixed at room temperature (25°C) or under heat treatment (heating) in the presence of an inert gas as necessary. In some cases, water or a catalyst (hydrolysis promoter, etc.) can be used to promote the surface treatment. After kneading, the surface-treated silica fine powder can be produced by drying. The amount of the surface treatment agent to be added may be equal to or greater than the amount calculated from the coverage area of the surface treatment agent.

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, polymethylsiloxane, organohydrogenpolysiloxane, etc., and the hydrophobic silica fine powder can be used by surface treatment with these. As the surface treatment agent, silane coupling agents or silazanes are particularly preferred.

When the fine silica powder of component (D) has previously been subjected to a surface hydrophobization treatment directly with 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 groups), preferably 1.2 to 9 moles (or groups), and more preferably 1.5 to 8 moles (or groups), per mole of alkenyl groups bonded to silicon atoms contained in the compositions containing the surface treatment agents of components (A), (B), and (D).
This is because if the number of hydrosilyl groups is less than 1 mole per mole of alkenyl groups bonded to silicon atoms in the composition, the composition may not cure sufficiently and may not exhibit sufficient adhesive strength, whereas if the number of hydrosilyl groups exceeds 10 moles, the heat resistance of the resulting cured silicone rubber may be significantly reduced.

The amount of component (D) is 1 to 50 parts by mass, preferably 3 to 40 parts by mass, and more preferably 5 to 30 parts by mass, per 100 parts by mass of the organopolysiloxane of component (A). If the amount is less than 1 part by mass, the strength required for the present invention will not be obtained, and if the amount is more than 50 parts by mass, the viscosity of the resulting silicone rubber composition will increase, reducing flowability and making the coating process more difficult.

The silica fine powder of component (D) may be used alone or in combination of two or more types.

[Component (E)]
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).The hydrosilylation catalyst is not particularly limited, and examples thereof include platinum group metals such as platinum, palladium, and rhodium; chloroplatinic acid; alcohol-modified chloroplatinic acid; coordination compounds of chloroplatinic acid with olefins, vinylsiloxanes, or acetylene compounds; platinum group metal compounds such as tetrakis(triphenylphosphine)palladium and chlorotris(triphenylphosphine)rhodium, and the like, with platinum group metal compounds being preferred.

The amount of component (E) is 1 to 500 ppm, preferably 5 to 100 ppm, by mass of the catalytic metal element per 100 parts by mass of component (A). If the amount is less than 1 ppm, the addition reaction will slow down significantly or the composition will not cure, which is not preferable, and if the amount exceeds 500 ppm, the heat resistance of the cured product may decrease.

The addition reaction catalyst of component (E) may be used alone or in combination of two or more.

[Component (F)]
Component (F) is an organosilicon compound containing an adhesion-imparting functional group, such as one or more groups selected from epoxy groups, alkoxy groups bonded to silicon atoms (alkoxysilyl groups), hydrosilyl groups, isocyanate groups, acrylic groups, and methacrylic groups, and is added to develop and improve the adhesion of the addition-curable liquid silicone rubber composition for airbags to airbag base fabrics.
As the organosilicon compound, any organosilicon compound can be used so long as it has such an adhesion-imparting functional group, but an organosilicon compound having at least one epoxy group and at least one alkoxy group bonded to a silicon atom in one molecule is preferred, and from the viewpoint of adhesion development, an organosilicon compound having at least one epoxy group and at least one alkoxy group bonded to a silicon atom (e.g., a trialkoxysilyl group, an organodialkoxysilyl group, etc.), for example, an organosilane, or a cyclic or linear organosiloxane having 1 to 100, preferably about 1 to 50, silicon atoms, and having at least one epoxy group and at least two alkoxy groups bonded to silicon atoms, is more preferred.

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.
The alkoxy group bonded to the silicon atom preferably bonds with the silicon atom to form, for example, a trialkoxysilyl group, such as a trimethoxysilyl group or a triethoxysilyl group; or an alkyldialkoxysilyl group, such as a methyldimethoxysilyl group, an ethyldimethoxysilyl group, a methyldiethoxysilyl group, or an ethyldiethoxysilyl group.

Component (F) may also have at least one functional group selected from the group consisting of alkenyl groups such as vinyl groups, acrylic groups, (meth)acryloxy groups, isocyanate groups, and hydrosilyl groups as functional groups other than epoxy groups and alkoxy groups bonded to silicon atoms in one molecule.

Examples of the organosilicon compound of component (F) include epoxy group-containing silanes 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 such as silane coupling agents containing a vinyl group (i.e., an epoxy-functional group-containing organoalkoxysilane), vinyl trimethoxysilane, or the like, acrylic group-containing silane coupling agents, such as 3-acryloxypropyltrimethoxysilane, isocyanate group-containing silane coupling agents, such as 3-isocyanate propylethoxysilane, or methoxysilyl-modified triallyl isocyanurate, as well as organosilicon compounds such as cyclic organopolysiloxanes or linear organopolysiloxanes represented by the following chemical formulas, mixtures of two or more of these, or partial hydrolysis condensates of one or more of these.
The main ones are shown below as examples.

（式中、ｈは１～１０の整数、ｋは０～４０の整数、好ましくは０～２０の整数、ｐは１～４０の整数、好ましくは１～２０の整数、ｑは１～１０の整数である。Ｒ^４の少なくとも１つは－ＣＨ_２ＣＨ_２ＣＨ_２Ｓｉ（ＯＣＨ_３）_３である。）

(In the formula, h is an integer of 1 to 10, k is an integer of 0 to 40, preferably an integer of 0 _to 20, p is an integer of 1 to 40, preferably an integer of 1 to 20, and q is an integer of 1 to _10. At least one of ^R4 is _-CH2CH2CH2Si ( _OCH3 ) ₃ .)

The amount of component (F) is 0.1 to 10 parts by mass, and preferably 0.25 to 5 parts by mass, per 100 parts by mass of the organopolysiloxane of component (A). If the amount is less than 0.1 parts by mass, the resulting composition may not exhibit sufficient adhesive strength. If the amount is more than 10 parts by mass, the composition may become highly thixotropic, its flowability may decrease, and coating workability may deteriorate.

When component (F) contains an alkenyl group and/or a hydrosilyl group, the amount of component (F) is such that the total of hydrosilyl groups contained in the composition containing components (C) and (F) is 1 to 10 moles (or groups), preferably 1.2 to 9 moles (or groups), and more preferably 1.5 to 8 moles (or groups), per 1 mole (or groups) of alkenyl groups bonded to silicon atoms (or nitrogen atoms) contained in the composition containing components (A), (B), and (F).
This is because if the number of hydrosilyl groups is less than 1 mole per mole of alkenyl groups bonded to silicon atoms in the composition, the composition may not cure sufficiently and may not exhibit sufficient adhesive strength, whereas if the number of hydrosilyl groups exceeds 10 moles, the heat resistance of the resulting silicone rubber cured product may be extremely poor.

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

[Other ingredients]
In addition to the components (A) to (F), the composition of the present invention may contain any other components according to the object of the present invention. Specific examples thereof include the following. Each of these other components may be used alone or in combination of two or more.

[Component (G)]
The condensation catalyst for component (G) is at least one selected from the group consisting of organotitanium compounds, organozirconium compounds, and organoaluminum compounds, and acts as a condensation catalyst for the adhesion-imparting functional groups in component (F) in order to promote adhesion.

Specific examples of component (G) include titanium-based condensation catalysts (titanium compounds) such as organic titanate esters such as titanium tetraisopropoxide, titanium tetra normal butoxide, and titanium tetra-2-ethylhexoxide, organic titanium chelate compounds such as titanium diisopropoxy bis(acetylacetonate), titanium diisopropoxy bis(ethylacetoacetate), and titanium tetraacetylacetonate, organic zirconium esters such as zirconium tetra normal propoxide and zirconium tetra normal butoxide, and zirconium tributoxy monoacetylacetonate. zirconium-based condensation catalysts (zirconium compounds) such as organic zirconium chelate compounds such as zirconium monobutoxy acetylacetonate bis(ethylacetoacetate) and zirconium tetraacetylacetonate; aluminum-based condensation catalysts (aluminum compounds) such as organic aluminum acid esters such as aluminum sec-butoxide, aluminum trisacetylacetonate, aluminum bisethylacetoacetate monoacetylacetonate and aluminum trisethylacetoacetate.

The organic titanium compound, organic zirconium compound, and organic aluminum compound of component (G) are optional components that are blended as necessary, and their blending amount is preferably 0.1 to 5 parts by mass, and more preferably 0.2 to 4 parts by mass, per 100 parts by mass of component (A). When the blending amount is within the range of 0.1 to 5 parts by mass, the resulting cured product has excellent adhesion to the airbag base fabric.

Component (G) may be used alone or in combination of two or more types.

Reaction inhibitor 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 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.

The degree of the curing inhibition effect of the reaction inhibitor varies depending on the chemical structure of the reaction inhibitor, so 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 composition will have excellent long-term storage stability and curing properties at room temperature.

Non-reinforcing fillers Examples of fillers other than the fine silica powder of component (D) include fillers such as crystalline silica (for example, quartz powder having a BET specific surface area of less than 50 ^m2 /g), organic resin hollow fillers, polymethylsilsesquioxane fine particles (so-called silicone resin powder), fumed titanium dioxide, magnesium oxide, zinc oxide, iron oxide, aluminum hydroxide, magnesium carbonate, calcium carbonate, zinc carbonate, carbon black, diatomaceous earth, talc, kaolinite, and glass fiber; 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.

Other Components Other components that can be blended include, for example, organopolysiloxanes that contain one hydrogen atom bonded to a silicon atom per molecule and no other functional groups, organopolysiloxanes that contain one alkenyl group bonded to a silicon atom per molecule and no other functional groups, non-functional organopolysiloxanes that contain 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, and fungicides.

<Preparation of Addition-Curable Liquid Silicone Rubber Composition>
An addition-curable liquid silicone rubber composition can be prepared by uniformly mixing the above components (A) through (F), component (G), and any other components that may be added as necessary.
The addition-curable liquid silicone rubber composition thus obtained is a liquid composition at 25° C., and has a viscosity at 25° C. measured by the method described in JIS K 7117-1: 1999 of preferably 1 to 1,000 Pa·s, more preferably 5 to 500 Pa·s, and even more preferably 10 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 an airbag base fabric.

<Airbag base fabric>
Generally, a known airbag base fabric (a substrate made of fiber fabric) on which a silicone rubber layer is formed is used, and specific examples thereof 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).

<Airbag>
The airbag of the present invention comprises an airbag base fabric and a cured coating of the above-described addition-curable liquid silicone rubber composition for airbags.

<Airbag manufacturing method>
The addition-curable liquid silicone rubber composition for airbags can be applied to at least one surface, particularly one surface, 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). An airbag can be manufactured using the silicone rubber-coated airbag fabric thus obtained.

The method for coating the airbag base fabric with the addition-curable liquid silicone rubber composition 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 10 to 100 g/ ^m2 , preferably 12 to 90 g/ ^m2 , and more preferably 15 to 80 g/ ^m2 .

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.

When the thus-produced airbag base fabric (airbag silicone rubber-coated base fabric) having a silicone rubber layer on at least one surface is processed into an airbag, the outer periphery of two sheets of plain weave fabric, at least the inner surface of which is coated with silicone rubber, is glued together with an adhesive, and the adhesive layer is sewn together to produce the airbag. Alternatively, a method may be used in which a predetermined coating amount of an addition-curing liquid silicone rubber composition is coated on both outer surfaces of an airbag base fabric that has been previously produced by woven fabric, as described above, and then cured under predetermined curing conditions. Note that any known adhesive may be used as the adhesive used here, but a silicone-based adhesive called a seam sealant is preferred in terms of adhesive strength and adhesion durability.

The present invention will be specifically explained below with preparation examples, examples, and comparative examples, but the present invention is not limited to the following examples.

[Preparation Example 1]
60 parts by mass of dimethylpolysiloxane (A1) with both ends of the molecular chain blocked with vinyldimethylsiloxy groups, viscosity at 25°C of ^30,000 mPa·s, and average degree of polymerization of 750, 8 parts by mass of hexamethyldisilazane, 2 parts by mass of water, and 40 parts by mass of silica fine powder (D) (Aerosil 300, manufactured by Nippon Aerosil Co., Ltd.) with a specific surface area of 300 m2/g by BET method were put into a kneader and mixed at room temperature for 1 hour. Then, 8 parts by mass of hexamethyldisilazane were put in and mixed for another 1 hour. Then, the temperature was raised to 150°C, and mixing was continued for 2 hours. The temperature was then lowered to room temperature, and 25 parts by mass of dimethylpolysiloxane (A1) having a viscosity of 30,000 mPa·s at 25° C. and capped at both molecular chain terminals with vinyldimethylsiloxy groups, and 5 parts by mass of dimethyl-vinylmethylpolysiloxane (A2) having an average degree of polymerization of 200 and containing 5 mol % of vinylmethylsiloxane units and 95 mol % of dimethylsiloxane units among the bifunctional diorganosiloxane units constituting the main chain, and having a viscosity of 700 mPa·s at 25° C. and both molecular chain terminals capped with trimethylsiloxy groups, were added and mixed until uniform, to obtain base compound (1).

[Example 1]
A mixture of 70 parts by mass of the base compound (1) obtained in Preparation Example 1, 58.6 parts by mass of dimethylpolysiloxane (A3) capped at both molecular chain terminals with vinyldimethylsiloxy groups and having an average degree of polymerization of 200 and a viscosity at 25°C of 1,000 mPa·s, 27.5 parts by mass of dimethylpolysiloxane (A4) capped at both molecular chain terminals with vinyldimethylsiloxy groups and having an average degree of polymerization of 450, and a dimethylpolysiloxane having a structure consisting of ( _CH3 ) _{3SiO1 /2} units, ( _CH3 ) ₂ ( _CH2 =CH)SiO1 _/2 units, SiO4 _/2 units and BO _27.5 parts by mass of a boron-containing three-dimensional network organopolysiloxane resin (B1) having a total of M units and Q units of 0.85, a ratio of boron atoms to silicon atoms in the Q units of 0.11, and an alkenyl group content of 0.010 mol/100 g, and 27.5 parts by mass of a dimethylsiloxane-methylhydrogensiloxane copolymer (C) blocked at both molecular chain terminals by trimethylsiloxy groups as a crosslinking agent, the copolymer having a viscosity of 8 mPa·s at 25° C. and having hydrogen atoms bonded to silicon atoms in its molecular chain side chains. Composition A (hydrosilyl group/vinyl group=4.8 mol/mol in the entire composition, viscosity 35 Pa s) was prepared by mixing 19 parts by mass of 1,2-dimethylphenylsilane (P) having a platinum atom content of 1.0% by mass, 0.50 parts by mass of γ-glycidoxypropyltrimethoxysilane (F), 0.07 parts by mass of 1-ethynylcyclohexanol, 0.32 parts by mass of a dimethylpolysiloxane solution (E) containing a chloroplatinic acid/1,3-divinyltetramethyldisiloxane complex having a platinum atom content of 1% by mass, and 0.60 parts by mass of tetraoctyl titanate (G) for 1 hour.

<Flame Retardancy Test Method>
Composition A was coated on a 66 nylon base fabric (210 denier) for airbags with a knife coater so that the surface coating amount was 25 to 30 g/ ^m2 , and then heat curing was performed for 1 minute in a dryer at 200°C to produce an airbag base fabric coated with a silicone rubber cured product (cured coating). The flame retardancy of the above resin-coated airbag base fabric was evaluated by the method described in FMVSS-302 (Federal Motor Vehicle Safety Standard-302). The resin-coated surface of a test piece of base fabric (width 10 cm x length 35 cm) was placed on top, and the burning distance and burning time until the flame went out when burning by the method described in FMVSS-302 were measured with N=10. The burning rate was calculated from the burning distance and burning time. In this case, the test pieces were judged as passing if they did not ignite or if they self-extinguished just before the A-marked line, if they self-extinguished within a burning distance of 51 mm (and within 60 seconds), and if the burning rate was 102 mm/min or less. Those that passed all N=10 tests were rated as passing, and those that failed even one test were rated as failing.

<Adhesion test>
Composition A was coated on 66 nylon base fabric (210 denier) for airbags with a knife coater so that the surface coating amount was 25 to 30 g/ ^m2 , and then heat curing was performed for 1 minute in a dryer at 200°C to produce an airbag base fabric coated with a silicone rubber cured product. The silicone rubber-coated nylon base fabric was evaluated for adhesion using a Scott rub tester (device name: Scott rub-resistance abrasion tester, manufactured by Toyo Seiki Seisakusho Co., Ltd.) according to the method described in JIS K 6404-6:1999. After performing a rub test 500 times with a pressing force of 19.6 N, the destruction state of the coating part was visually confirmed, and the case where the silicone rubber layer was not peeled off from the coating surface was evaluated as pass, and the case where it was peeled off was evaluated as fail.

<Adhesion durability test method>
Composition A was coated on 66 nylon base fabric (210 denier) for airbags so that the surface coating amount was 25 to 30 g/ ^m2 , and then heat curing was performed for 1 minute in a dryer at 200°C to produce an airbag base fabric coated with a silicone rubber cured product. The above silicone rubber-coated nylon base fabric was subjected to a heat resistance test for 400 hours in a dryer at 120°C, and a moist heat resistance test for 400 hours in a thermohygrostat at a temperature of 70°C and a humidity of 95%. Next, the silicone rubber-coated nylon base fabric after the durability test was evaluated for adhesion using a Scott rubbing tester (device name: Scott rubbing abrasion tester, manufactured by Toyo Seiki Seisakusho Co., Ltd.) according to the method described in JIS K 6404-6:1999. After performing a rubbing test 500 times with a pressing force of 19.6 N, the destruction state of the coating part was visually confirmed, and the case where the silicone rubber layer was not peeled off from the coating surface was evaluated as pass, and the case where it was peeled off was evaluated as fail.

[Example 2]
A composition B (hydrosilyl group/vinyl group=4.8 mol/mol, _viscosity 30 _Pa.s ) was prepared in the _same manner as in Example ₁ , except that the boron-containing _three -dimensional network organopolysiloxane resin (B1) in Example 1 was replaced with the same parts by mass of a boron-containing _{three-dimensional} network organopolysiloxane resin ( _B2 ) consisting of ( _CH3 )3SiO1 _/2 units, (CH3)2(CH2=CH)SiO1/2 units, SiO4/2 units, and BO3/2 units, in which the ratio of the sum of M units to Q units is 0.85, the ratio of boron atoms to silicon atoms in the Q units is 0.05, and the amount of alkenyl groups is 0.010 mol/100 g. The composition B was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[Example 3]
A composition C (hydrosilyl group/vinyl group= _4.8 mol _/ mol, viscosity _{45 Pa.s )} was prepared in the _same manner as in Example 1, except that the boron atom-containing _three -dimensional network organopolysiloxane resin ( _B1 ) in Example 1 was replaced with the same parts by mass of a boron atom-containing _three -dimensional network organopolysiloxane resin ( _B3 ) consisting of (CH3)3SiO1/2 units, (CH3)2(CH2=CH)SiO1/2 units, SiO4/2 units, and BO3/2 units, the ratio of the sum of M units to Q units being 0.85, the ratio of boron atoms to silicon atoms in the Q units being 0.35, and the amount of alkenyl groups being 0.010 mol/100 g. The results are shown in Table 1.

[Comparative Example 1]
A composition D (hydrosilyl group/vinyl group=4.8 mol _/ mol, _{viscosity 25 Pa.s} ) _was prepared in the _same manner as in Example 1, except _that the boron-containing _three -dimensional network organopolysiloxane resin ( _B1 ) in Example 1 was replaced by the same parts by mass of a boron-containing _three -dimensional network organopolysiloxane resin having a three-dimensional network structure composed of (CH3)3SiO1/2 units, (CH3)2(CH2=CH)SiO1/2 units, SiO4/2 units, and BO3/2 units, the ratio of the sum of M units to Q units being 0.85, the ratio of boron atoms to silicon atoms in the Q units being 0.01, and the amount of alkenyl groups being 0.010 mol/100 g. The results are shown in Table 1.

[Comparative Example 2]
A composition E (hydrosilyl group/vinyl group= _4.8 mol _/ mol, viscosity _{1,200 Pa.s} ) was prepared according to the same recipe as in Example 1, except that the boron-containing _three -dimensional network organopolysiloxane resin ( _B1 ) in Example 1 was replaced by the same parts by mass of a boron-containing _three -dimensional network organopolysiloxane resin consisting of ( _CH3 ) _3SiO1 /2 units, (CH3)2(CH2=CH)SiO1/2 units, SiO4/2 units, and BO3/2 units, the ratio of the sum of M units to Q units being 0.50, the ratio of boron atoms to silicon atoms in the Q units being 0.11, and the amount of alkenyl groups being 0.010 mol/100 g. The results are shown in Table 1.

[Comparative Example 3]
A composition F (hydrosilyl group/vinyl group= _4.8 mol _{/mol, viscosity 15 Pa.s} ) was prepared according to the _same recipe as in Example 1, except that the boron-containing _three -dimensional network organopolysiloxane resin ( _B1 ) in Example 1 was replaced by the same parts by mass of a boron-containing three-dimensional network organopolysiloxane resin consisting of ( _CH3 ) _3SiO1 /2 units, (CH3)2(CH2=CH)SiO1/2 units, and SiO4/2 units, in which the ratio of the sum of M units to Q units was 1.60, the ratio of boron atoms to silicon atoms in the Q units was 0.11, and the amount of alkenyl groups was 0.010 mol/100 g. The results are shown in Table 1.

As can be seen from Table 1, Examples 1 to 3, which used the addition-curing liquid silicone rubber composition for airbags of the present invention, exhibited excellent adhesion durability to the airbag base fabric and flame retardancy.

On the other hand, Comparative Examples 1 to 3, which did not use the addition-curing liquid silicone rubber composition for airbags of the present invention, were unable to achieve both adhesion durability to the airbag base fabric and flame retardancy.

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 within the technical scope of the present invention.

Claims (4)

An addition-curable liquid silicone rubber composition for airbags, comprising:
(A) an 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) 5 to 100 parts by mass of a boron-atom-containing three-dimensional network organopolysiloxane resin containing monofunctional R ¹ ₃ SiO _1/2 units (M units, in the formula, R ¹ is independently a group selected from an unsubstituted or substituted alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an alkenyl group having 2 to 10 carbon atoms), tetrafunctional SiO _4/2 units (Q units), and a trifunctional boron atom bonded to three oxygen atoms (BO _3/2 units), wherein the ratio of the M units to the Q units is 0.65 to 1.40, the ratio of the trifunctional boron atoms to the silicon atoms of the Q units is 0.05 to 0.4, and the amount of alkenyl groups is 0.01 to 0.30 mol/100 g;
(C) an organohydrogenpolysiloxane containing two or more hydrogen atoms bonded to silicon atoms (hydrosilyl groups) per molecule: the amount of hydrosilyl groups contained in the composition is 1 to 10 moles per mole of the total number of alkenyl groups bonded to silicon atoms contained in the composition;
(D) silica fine powder having a specific surface area of 50 m ² /g or more as measured by the BET method: 1 to 50 parts by mass,
(E) a hydrosilylation reaction catalyst: 1 to 500 ppm by mass of catalytic metal element per 100 parts by mass of component (A); and (F) an organosilicon compound containing an adhesion-imparting functional group: 0.1 to 10 parts by mass,
1. An addition-curable liquid silicone rubber composition for airbags, comprising: The addition-curable liquid silicone rubber composition for airbags according to claim 1, further comprising, as component (G), 0.1 to 5 parts by mass of one or more condensation catalysts selected from organic titanium compounds, organic zirconium compounds, and organic aluminum compounds. The addition-curable liquid silicone rubber composition for airbags according to claim 1 or 2, characterized in that the adhesion-imparting functional group is one or more groups selected from an epoxy group, an alkoxy group bonded to a silicon atom, a hydrosilyl group, an isocyanate group, an acrylic group, and a methacrylic group. An airbag characterized in that a cured coating of the addition-curing liquid silicone rubber composition for airbags according to any one of claims 1 to 3 is provided on an airbag base fabric.