COATED PRODUCT TECHNICAL FIELD

[0001]

The present invention relates to a silicone rubber composition containing a block polyisocyanate composition and a curable silicone rubber composition, a manufacturing method of a coated product, and a coated product. According to the present invention, the compatibility between the block polyisocyanate composition and the curable silicone rubber composition is favorable, and the adhesion of the silicone rubber composition does not decrease as time passes.

Furthermore, when the silicone rubber composition is applied onto an unrefined or refined fabric in which the amount of an oil solution is 5% by mass or less relative to the weight of the fabric, the composition strongly adheres to the fabric even when cured. In particular, the present invention relates to a silicone rubber composition, a method for manufacturing a coated product, and a coated product, which are suitable for air bags.

BACKGROUND

[0002] A coated product manufactured by coating a resin or the like with a curable silicone rubber composition and curing the coating is used in various fields. However, there has been a problem that when a large amount of a spinning oil solution used during manufacture remains in fabric, adhesion between the cured product of the silicone rubber composition and the fabric is lost. Therefore, a refining process for removing an oil solution component in a fabric needs to be performed in the manufacture. For example, Patent Literature 1 discloses a method of limiting the component and amount of an oil

solution, and further adding a silicone compound to the oil solution for promoting adhesion with the silicone rubber composition. However, managing the component and amount of an oil solution and the facilities for the refining process took labor and time.

[0003]

On the other hand, it has been a practice to mix an adhesiveness-improving component to a silicone rubber

composition in order to increase the adhesion force thereof. In particular, for use in air bags, it is difficult to suppress the leakage of a high-pressure gas and maintain the persistence of expansion time. Therefore, strong adhesiveness is demanded in order to achieve the object. As such a

component, for example, Patent Literature 2 discloses an isocyanate compound. However, only triallyl isocyanurate can exert the adhesion effect, and there is no description or knowledge regarding the refining state of a fabric and the oil solution. Since triallyl isocyanurate is solid, there has been the drawback that compatibility thereof with the silicone rubber composition is poor, causing difficulty in dispersion. As a result, due to separation and dispersion failure, the silicone rubber composition could not adhere to, in

particular, a fabric which is unrefined or not sufficiently refined to have a large amount of a remained oil solution. As a method for improving compatibility, there is a means of adding an organic solvent. However, from the viewpoint of the environment, addition of an organic solvent is not preferred, and it is required to contain a small amount of a solvent, more preferably to hardly contain a solvent.

[0004]

Also, since an isocyanate group is highly reactive, a reaction proceeds in a silicone rubber composition, thereby resulting in gradually reducing the adhesiveness. Therefore, it was difficult to previously mix an isocyanate compound having an isocyanate group to prepare a composition kit. Even when an isocyanate compound is added at mixing a silicone rubber composition kit for addressing the above-described concern, adhesiveness is lost as time passes, and an available time is short. Thus, the industrial manufacture was

practically impossible. For controlling the reactivity of an isocyanate group, a low-viscosity block polyisocyanate composition not containing a solvent is disclosed in Non- Patent Literature 1. However, there is no description or knowledge regarding mixing such a low-viscosity block

polyisocyanate composition into a silicone rubber composition.

[0005]

As described above, a known silicone rubber composition including a block polyisocyanate composition and a curable silicone rubber composition has a problem in terms that the compatibility between the block polyisocyanate composition and the curable silicone rubber composition is favorable, the adhesiveness of the silicone rubber composition does not decrease as time passes, and when the silicone rubber

composition is applied onto an unrefined or refined fabric in which the amount of an oil solution is 5% by mass or less relative to the weight of the fabric, the silicone rubber composition strongly adheres to the fabric even when cured. Therefore, a silicone rubber composition which can achieve the object has been demanded.

CITATION LIST PATENT LITERATURE

[0006]

Patent Literature 1: Japanese Patent Application Laid- Open No. 2012-177220 Patent Literature 2: Japanese Patent Application Laid- Open No. 2007-186596

NON-PATENT LITERATURE

[0007]

Non-Patent Literature 1: "Technical data sheet (Coating

Times)" 2015, No. 235 (Asahi Kasei Chemicals Corporation)

SUMMARY OF INVENTION TECHNICAL PROBLEM

[0008]

The present invention has been achieved in view of the aforementioned problems, and relates to a silicone rubber composition containing a block polyisocyanate composition and a curable silicone rubber composition. An object of the present invention is to provide a silicone rubber composition in which the compatibility between the block polyisocyanate composition and the curable silicone rubber composition is favorable, and the adhesiveness of the silicone rubber composition does not decrease as time passes; and which, when it is applied onto an unrefined or refined fabric in which the amount of an oil solution is 5% by mass or less relative to the weight of the fabric, can strongly adhere to the fabric even when cured. In particular, the silicone rubber

composition is suitable for air bags. SOLUTION TO PROBLEM

[0009]

The present inventors have intensively conducted studies. As a result, they have found that the object of the present invention can be achieved by using a block polyisocyanate composition, in particular, which has a low viscosity. Thus, the present invention has been completed.

[0010]

That is, the present invention provides a silicone rubber composition including a block polyisocyanate composition and a curable silicone rubber composition, wherein the block

polyisocyanate composition contains a polyisocyanate and a thermally dissociating blocking agent. ADVANTAGEOUS EFFECTS OF INVENTION

[0011]

According to the silicone rubber composition including a block polyisocyanate composition and a curable silicone rubber composition of the present invention, the compatibility

between the block polyisocyanate composition and the curable silicone rubber composition becomes favorable, and the

adhesiveness of the silicone rubber composition does not decrease as time passes. Furthermore, when the silicone rubber composition is applied onto an unrefined or refined fabric in which the amount of an oil solution is 5% by mass or less relative to the weight of the fabric, the composition strongly adheres to the fabric even when cured. Therefore, the workload in a refining process can be drastically reduced, thereby improving productivity.

DESCRIPTION OF EMBODIMENTS

[0012]

Hereinafter, the silicone rubber composition according to the present invention will be described in detail.

[0013]

The curable silicone rubber composition according to the present invention includes one or more composition kits of a silicone rubber composition, and is not particularly limited as long as these composition kits are mixed to initiate a reaction for curing so that a cured product of the silicone rubber composition is finally obtained. Examples of such a curing technique may include peroxide curing, condensation curing, addition curing, UV curing, and electron beam curing. Examples of a suitable curing method according to the present invention may include a method of crosslinking an Si-H group of an organohydrogenpolysiloxane to an organopolysiloxane having an alkenyl group bonded to a silicon atom in one molecule with an addition reaction catalyst or an organic peroxide, and a method of crosslinking an Si-H group of an organohydrogenpolysiloxane to an organopolysiloxane having a hydroxy group or an alkoxy group bonded to a silicon atom at both terminals in the molecular chain with a condensation reaction catalyst.

[0014]

(Component (A) )

Component (A) is the main component of the curable silicone rubber composition, and the main material of the silicone rubber composition for obtaining excellent rubber properties after curing. Component (A-l) is an

organopolysiloxane containing in average 1.8 or more alkenyl groups bonded to a silicon atom in one molecule, and the average composition formula thereof is usually represented by the following general formula (1) :

In the formula (1), R ² ' s are each the same or different, unsubstituted or substituted, monovalent hydrocarbon group with 1 to 18 carbon atoms, and a is 1.7 to 2.1.

[0015]

Here, of the monovalent hydrocarbon groups represented by R ² , at least two monovalent hydrocarbon groups are selected from an alkenyl group such as a vinyl group, an allyl group, a propenyl group, an isopropenyl group, a butenyl group, an isobutenyl group, a hexenyl group, and a cyclohexenyl group. Other groups are a substituted or unsubstituted monovalent hydrocarbon group with 1 to 18 carbon atoms, and specifically selected from: an alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a

neopentyl group, a hexyl group, a 2-ethylhexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, and a dodecyl group; a cycloalkyl group such as a cyclopentyl group, a cyclohexyl group, and a cycloheptyl group; an aryl group such as a phenyl group, a tolyl group, a xylyl group, a biphenyl group, and a naphthyl group; an aralkyl group such as a benzyl group, a phenylethyl group, a phenylpropyl group, and a methylbenzyl group; and a halogen-substituted alkyl group and a cyano-substituted alkyl group in which a portion or the entirety of hydrogen atoms in each of these hydrocarbon groups is substituted with a halogen atom, a cyano group, and the like, such as a chloromethyl group, a 2-bromoethyl group, a 3 , 3 , 3-trifluoropropyl group, a 3-chloropropyl group, and a cyanoethyl group.

[0016]

In selection of R ² , a vinyl group is preferable as the at least two alkenyl groups required, and a methyl group, a phenyl group, and a 3 , 3 , 3-trifluoropropyl group are preferable as other groups. 70 mol% or more of all R ² ' s is preferably a methyl group from the viewpoint of properties of a cured product and economic efficiency. Usually, those having a methyl group in an amount of 80 mol% or more of all R ² ' s are used .

[0017]

The organopolysiloxane of the component (A-l) may be linear or branched. Examples of the molecular structure may include: a dimethylpolysiloxane in which both terminals of the molecular chain are blocked with a dimethylvinylsiloxy group; a dimethylsiloxane-methylphenylsiloxane copolymer in which both terminals of the molecular chain are blocked with a

dimethylvinylsiloxy group; a

dimethylsiloxane-methylvinylsiloxane copolymer in which both terminals of the molecular chain are blocked with a

dimethylvinylsiloxy group; a

dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymer in which both terminals of the molecular chain are blocked with a dimethylvinylsiloxy group; a

dimethylsiloxane-methylvinylsiloxane copolymer in which both terminals of the molecular chain are blocked with a

trimethylsiloxy group; an organopolysiloxane obtained by substituting a portion or the entirety of methyl groups of each of these organopolysiloxanes with an alkyl group such as an ethyl group and a propyl group, an aryl group such as a phenyl group and a tolyl group, and an alkyl halide group such as a 3 , 3 , 3-trifluoropropyl group; and a mixture of two or more of these organopolysiloxanes. Among these, a linear

organopolysiloxane having a vinyl group at both terminals of the molecular chain is preferable in terms of availability.

[0018]

Component (A-2) is an organopolysiloxane having a hydroxy group bonded to a silicon atom at both terminals of the molecular chain, and/or an organopolysiloxane having an alkoxy group bonded to a silicon atom at both terminals of the molecular chain. These organopolysiloxanes may be liner or branched. Examples of the alkoxy group may include a methoxy group and an ethoxy group. Of these, a methoxy group is preferable from the viewpoint of reactivity. Groups other than the hydroxy group and the alkoxy group are preferably the same or different, unsubstituted or substituted, monovalent

hydrocarbon groups with 1 to 18 carbon atoms, and specifically selected from: an alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a

neopentyl group, a hexyl group, a 2-ethylhexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, and a dodecyl group; a cycloalkyl group such as a cyclopentyl group, a cyclohexyl group, and a cycloheptyl group; an aryl group such as a phenyl group, a tolyl group, a xylyl group, a biphenyl group, and a naphthyl group; an aralkyl group such as a benzyl group, a phenylethyl group, a phenylpropyl group, and a methylbenzyl group; and a halogen-substituted alkyl group and a cyano-substituted alkyl group in which a portion or the entirety of hydrogen atoms in each of these hydrocarbon groups is substituted with a halogen atom, a cyano group, and the like, such as a chloromethyl group, a 2-bromoethyl group, a 3 , 3 , 3-trifluoropropyl group, a 3-chloropropyl group, and a cyanoethyl group. Among these, a methyl group is preferable from the viewpoint of properties of a cured product, economic efficiency, and the like. Usually, those having a methyl group in an amount of 80 mol% or more are used.

[0019]

The organopolysiloxane of the component (A) is

manufactured by a method known to those skilled in the art. The viscosity at 25°C thereof is preferably 50 to 1,000,000 mPa-s, and more preferably 200 to 500, 000 mPa-s . In particular, it is preferable to use two or more organopolysiloxanes having different viscosities, in order to facilitate adjustment in the viscosity of a finally obtained silicone rubber

composition. The viscosity may be measured using a rotary viscometer and the like.

[0020]

(Component (B) )

A block polyisocyanate composition of component (B) is an essential component of the present invention for enabling strong adhesion of the silicone rubber composition to an unrefined or refined fabric containing an oil solution in an amount of 5% by mass or less relative to the weight of the fabric. A conventionally known block polyisocyanate compound includes as a raw material a polyisocyanate and a blocking agent which are reacted to generate a urethane group and a urea group. Since a strong intramolecular hydrogen bond in the urethane group and the urea group significantly increases viscosity, there has been the drawback that handling is not easy. Also, since an isocyanate content in the molecule is small, the mixing amount of the block polyisocyanate compound needed to be increased so that the composition is caused to strongly adhere to a base cloth. However, the high viscosity causes the difficulty in handling, as well as incompatibility with a curable silicone rubber composition causes separation or dispersion failure. Thus, sufficient adhesiveness could not be obtained. The present inventors have intensively conducted studies, and found a surprising effect as follows. That is, a block polyisocyanate composition includes a polyisocyanate obtained from at least one diisocyanate selected from the group consisting of an aliphatic diisocyanate and an alicyclic diisocyanate, and a thermally dissociating blocking agent. The block polyisocyanate composition substantially contains no organic solvent, and has a low viscosity at 60°C of 100,000 mPa-s or less. The use of such a block polyisocyanate

composition can drastically improve compatibility with a curable silicone rubber composition as compared to a

conventional block polyisocyanate compound. As a result, the dispersion of the block polyisocyanate composition becomes favorable, and the adhesiveness of the silicone rubber

composition does not decrease as time passes. Furthermore, even when the silicone rubber composition is applied onto an unrefined or refined fabric containing an oil solution in an amount of 5% by mass or less relative to the weight of the fabric, the silicone rubber composition strongly adheres to the fabric.

[0021]

Examples of the aliphatic diisocyanate may include butane diisocyanate, pentane diisocyanate, hexamethylene

diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate. Among these, hexamethylene diisocyanate is preferable from the viewpoint of industrial availability. One of these aliphatic diisocyanates may be used alone, or two or more thereof may also be used in combination. Examples of the alicyclic diisocyanate may include isophorone diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated

diphenylmethane diisocyanate, and 1 , 4-cyclohexane

diisocyanate. Among these, isophorone diisocyanate is

preferable from the viewpoint of industrial availability. One of these alicyclic diisocyanates may be used alone, or two or more thereof may also be used in combination.

[0022]

One of the aliphatic diisocyanate and the alicyclic diisocyanate may be used alone, or two or more of the aliphatic diisocyanate and the alicyclic diisocyanate may also be used in combination.

[0023]

The blocking agent is not particularly limited, as long as it has thermally dissociating properties and does not impair the object of the invention. The blocking agent can protect an isocyanate group, prevent the deactivation of an isocyanate group caused by moisture and the like, and suppress the poisoning of a curing catalyst by an isocyanate group.

Therefore, the blocking agent can stabilize and maintain the isocyanate group even in the silicone composition. As

described herein, "thermally dissociating" properties means that the blocking agent bonded to the isocyanate group is dissociated by heating. Although the temperature necessary for the dissociation varies depending on the structure of the blocking agent, it is, for example, 40°C to 300°C. The

isocyanate group from which the blocking agent has been dissociated can immediately exert adhesion effect.

The blocking agent to be used is preferably one or more selected from an oxime-based compound, an acid amide-based compound, an amine-based compound, an active methylene-based compound, and a pyrazole-based compound, for reasons of industrial availability. Examples thereof may include methyl ethyl ketoxime, acetoxime, methanol, ethanol, acetanilide, amide acetate, ε-caprolactam, diphenylamine, aniline, ethylacetoacetate, 3-methylpyrazole, and 3 , 5-dimethylpyrazole .

[0024]

The block polyisocyanate composition according to the present invention substantially contains no organic solvent. As described herein, "substantially contains no organic solvent" means that the content of an organic solvent in the block polyisocyanate composition is 5% by mass or less, and preferably 3% by mass or less, more preferably 1% by mass or less, from the viewpoint of reduction in a load on the

environment. The viscosity is preferably as low as possible for improving compatibility. Specifically, the viscosity at 60°C is preferably 100,000 mPa-s or less from the viewpoint of facilitating handling, more preferably 30,000 mPa-s or less from the viewpoint of facilitating mixing. The viscosity may be measured using an E-type viscometer for not more than

25, 600 mPa-s, and a rheometer (RS-1 manufactured by HAAKE GmbH) for more than 25, 600 mPa-s . A rotor can be selected depending on the viscosity to be measured.

[0025]

The mixing amount of the component (B) relative to 100 parts by mass of the component (A) is preferably 0.01 to 5 parts by mass, and more preferably 0.02 to 3 parts by mass. When the mixing amount is 0.01 parts or less, the ratio of an initially exposed isocyanate group increases, thereby deactivating the isocyanate group by moisture and the like. Therefore, effect of the adhesiveness is unlikely to be obtained. The amount of 5 parts by mass or more is not

preferably because the curing unfavorably becomes slow.

[0026]

(Component (C) )

The curing catalyst according to the present invention is not particularly limited, as long as it is used for curing the curable silicone rubber composition. As a catalyst used for an addition reaction, there is used any catalyst known to those skilled in the art which promotes an addition curing reaction between an alkenyl group and a hydrogen atom bonded to a silicon atom. Specific examples thereof may include platinum group metal such as platinum, rhodium, palladium, osmium, iridium, and ruthenium, and a product obtained by fixing the platinum group metal to a particulate carrier material (for example, activated carbon, aluminum oxide, and silicon oxide) , and a platinum compound such as platinum halide, a platinum- olefin complex, a platinum-alcohol complex, a platinum- alcoholate complex, a platinum-vinylsiloxane complex,

dicyclopentadiene-platinum dichloride, cyclooctadiene-platinum dichloride, and cyclopentadiene-platinum dichloride.

[0027]

Because of economic reasons, a metal compound catalyst other than noble metal may be used. Specific examples thereof may include a hydrosilylation iron catalyst such as an

iron—carbonyl complex catalyst, an iron catalyst having a cyclopentadienyl group as a ligand, an iron catalyst having a terpyridine-based ligand, or a terpyridine-based ligand and a bistrimethylsilylmethyl group, an iron catalyst having a bisiminopyridine ligand, an iron catalyst having

bisiminoquinoline as a ligand, an iron catalyst having an aryl group as a ligand, an iron catalyst having a cyclic or non- cyclic olefin group with an unsaturated group, and an iron catalyst having a cyclic or non-cyclic olefinyl group with an unsaturated group. Other examples may include a cobalt catalyst, a vanadium catalyst, a ruthenium catalyst, an iridium catalyst, a samarium catalyst, a nickel catalyst, and a manganese catalyst, which serve as a hydrosilylation

catalyst .

[0028]

The catalyst may be used in a form of being

microencapsulated into a particulate solid and the like. In this case, examples of a particulate solid which contains a catalyst and is insoluble in organopolysiloxane may include thermoplastic resin (for example, a polyester resin or a silicone resin) . The catalyst may also be used in a form of clathrate compound, for example, in cyclodextrins .

[0029]

The effective mixing amount of the catalyst depends desired curing temperature and curing time. The effective mixing amount of the catalyst relative to a total mass of the silicone rubber composition, in terms of the concentration of a catalyst metal element, may be usually 0.5 to 1,000 ppm, more preferably 1 to 500 ppm, and further preferably 1 to 100 ppm. When the mixing amount thereof is less than 0.5 ppm, the curing becomes significantly slow or may be disabled. On the other hand, when the mixing amount thereof is more than 1,000 ppm, costs increase, thereby unfavorably reducing economic efficiency.

[0030]

Examples of the catalyst used for a reaction by an organic peroxide may include benzoyl peroxide, 2,4- dichlorobenzoyl peroxide, p-chlorbenzoyl peroxide, o- chlorbenzoyl peroxide, p-methylbenzoyl peroxide, o- methylbenzoyl peroxide, 2,4-dicumyl peroxide, 2 , 5-dimethyl- bis (2 , 5-t-butylperoxy) hexane, di-t-butylperoxide, t- butylperbenzoate, and 1 , 1-bis (t-butylperoxycarboxy) hexane . The content of these organic peroxides relative to 100 parts by mass of the component (A-l) is 0.1 to 5 parts by mass.

[0031]

Examples of the catalyst used for a condensation reaction may include an organic tin-based catalyst such as dibutyltin diacetate, bis (acetoxydibutyltin) oxide,

bis (lauroxydibutyltin) oxide, dibutyltin bisacetylacetonate, dibutyltin bismaleic acid monobutyl ester, and dioctyl bismaleic acid monobutyl ester. The content of these

condensation reaction catalysts relative to 100 parts by mass of the component (A-2) is 0.1 to 20 parts by mass.

[0032]

(Component (D) )

Component (D) is an organohydrogenpolysiloxane having in average two or more hydrogen atoms bonded to a silicon atom in one molecule, and functions to react with the component (A) to serve as a crosslinking agent. Specific examples thereof may include methylhydrogenpolysiloxane, a dimethyl

siloxane-methylhydrogenpolysiloxane copolymer, a methyl phenyl siloxane-methylhydrogenpolysiloxane copolymer, cyclic

methylhydrogenpolysiloxane, and a copolymer of a

dimethylhydrogensiloxy unit and a Si0 ₄ /2 unit. The mixing amount of this organohydrogenpolysiloxane is preferably such that the amount of the hydrogen atom bonded to a silicon atom becomes 0.5 to 20 mol relative to a total of an alkenyl group of the component (A-l) . When the mixing amount thereof is less than 0.5 mol, the hardness significantly decreases. When the mixing amount thereof is more than 20 mol, the hardness becomes excessive, causing a cured coating film to unfavorably crack and peel.

[0033]

The viscosity at 25°C of the organohydrogenpolysiloxane of the component (D) is preferably 1 to 100,000 mPa-s, and more preferably 2 to 5, 000 mPa-s . One organohydrogenpolysiloxane of the component (D) may be used alone, or two or more thereof may also be used in combination.

[0034]

In particular, an organohydrogenpolysiloxane having a hydrogen atom bonded to a silicon atom only at both terminals of the molecular chain may be included for enhancing the elongation of a cured product of the silicone rubber

composition to follow a stretchable fabric. The

organohydrogenpolysiloxane is preferably linear. In this case, the high elongation is likely to be obtained by relatively easily increasing the molecular chain length of the

organopolysiloxane having an alkenyl group of the component (A-l) by a curing reaction.

[0035]

From the viewpoint of elongation and adhesiveness, an organohydrogenpolysiloxane having a hydrogen atom at both terminals of the molecular chain and at any portion other than the both terminals may be included. Specific examples thereof may include a linear organohydrogenpolysiloxane represented by the following general formula (2) :

HR ³ ₂ SiO- (HR ³ SiO) _m - (R ³ ₂ SiO) _n -SiR ³ ₂ H (2) .

In the formula (2), R ³ ' s are independently the same or different, unsubstituted or halogen-substituted, monovalent hydrocarbon group with 1 to 10 carbon atoms which does not have an aliphatic unsaturated bond, m is a positive number of 1 to 50, n is 0 or a positive number of 1 to 150, and t indicated by formula: t = m/ (m + n) satisfies 0.01 ≤ t ≤ 1.0. In the formula (2), m is more preferably 1 to 20, n is more preferably 10 to 100, and t is more preferably 0.02 ≤ t ≤ 1.0, further preferably 0.02 ≤ t ≤ 0.2. When m is 50 or more, elongation at break is not enhanced. When n is 150 or more, the hardness of a cured product unfavorably decreases. Thus, these values are not preferable. When t is 0.01 or less, the hardness of a cured product unfavorably decreases. When t is 0.1 or more, the elongation at break of a cured product is unfavorably unlikely to be enhanced. Thus, these values are not preferable.

[0036]

From the viewpoint of adhesiveness and heat resistance, an organohydrogenpolysiloxane having a trimethylsiloxy group at both terminals of the molecular chain and at least one aromatic group in the molecule may be contained. The aromatic group is preferably a phenyl group for economic reasons.

Furthermore, when this organohydrogenpolysiloxane is used in combination with an organohydrogenpolysiloxane having a trimetylsyloxy group at both terminals of the molecular chain and not having an aromatic group in the molecule with a hydrogen content of 5 mmol/g or more, the adhesiveness is favorably further enhanced.

[0037]

(Component (E) )

A silica of component (E) is a component to serve as a reinforcing material. Examples thereof may include fumed silica, silica fume, precipitated silica, pyrogenic silica, colloidal silica, and diatomaceous earth, which have

hydrophilicity or hydrophobicity. These are preferably micronized (micropowder) , and more preferably have a particle size of 100 μιη or less and a specific surface area of 50 m ² /g or more, and further preferably 150 m ² /g or more. Silica having previously subjected to surface treatment with

organosilane, organosilazane, organocyclopolysiloxane, or the like may also be suitably used. The added amount of the component (E) relative to 100 parts by mass of the component

(A) is usually 0.5 to 50 parts by mass, and preferably 1 to 30 parts by mass. One of these may be used alone, or two or more thereof may also be used in combination. When the mixing amount of the component (E) is small, properties such as desired tear strength cannot be obtained. When the mixing amount thereof is excessively large, the fluidity of the silicone rubber composition decreases. Accordingly, a desired thickness of a cured product cannot be obtained, and coating workability deteriorates.

[0038] When hydrophilic micronized silica is used, it is preferable that the surface of the micronized silica be previously subjected to hydrophobization treatment with a hydrophobization agent as necessary. Examples of the

hydrophobization agent may include organosilazane such as hexamethyl disilazane, silane halide such as methyl

trichlorosilane, dimethyl dichlorosilane, and trimethyl chlorosilane, organoalkoxysilane in which the halogen atom of the aforementioned agents is substituted with an alkoxy group such as a methoxy group and an ethoxy group, and dimethyl silicone oil. Among these, hexamethyl disilazane is

preferable .

[0039]

(Component (F) )

Component (F) is a component to impart a function of improving the strength of a cured product of the silicone rubber composition, and preferably an organopolysiloxane resin containing in the molecule a siloxane unit having a vinyl group, and a siloxane unit having a T siloxane unit

represented by the formula: R ¹ Si03/2 (wherein R ¹ ' s are each the same or different, unsubstituted or substituted, monovalent hydrocarbon group with 1 to 18 carbon atoms) and/or a Q siloxane unit represented by the formula: Si0 ₄ /2- The content of the component (F) relative to 100 parts by mass of the component (A) is preferably 0.1 to 50 parts by mass. When the content thereof is 0.1 parts by mass or less, adhesiveness is not improved as expected. When the content thereof is 50 parts by mass or more, a cured product becomes excessively hard, or tack properties are exerted on the surface of a cured product, resulting in likeliness of blocking.

[0040]

(Component (G) )

An organosilicon compound of component (G) is a component to impart a function of further improving the adhesiveness of the silicone rubber composition according to the present invention, and may be any organosilicon compound as long as the compound has an epoxy group and a silicon atom-bonded alkoxy group in one molecule. However, an organosilicon compound having at least one epoxy group and at least two alkoxy groups bonded to a silicon atom is preferable. Such an epoxy group is preferably bonded to a silicon atom, in a form of a glycidoxyalkyl group such as a glycidoxypropyl group, and an epoxy-containing cyclohexylalkyl group such as a 2,3- epoxycyclohexylethyl group and a 3, 4-epoxycyclohexylethyl group. Two or three epoxy groups may also be contained in one molecule. Examples of the silicon atom-bonded alkoxy group may include a trialkylsilyl group, an alkyldialkoxysilyl group, and the like, such as a trimethylsilyl group, a triethylsilyl group, a methyldimethoxysilyl group, an ethyldimethoxysilyl group, a methyldiethoxysilyl group, and an ethyldiethoxysilyl group. As a functional group to be used other than the above- described groups, a functional group selected from an alkenyl group such as a vinyl group, a (meth) acryloxy group, and a hydrosilyl group (SiH group) may be used.

[0041]

(Component (H) )

Component (H) is a component having a function as a condensation co-catalyst for promoting adhesion, and one or more compounds selected from the group consisting of a metal alkoxide, a metal acid salt, and a metal chelate, which include as a metal atom an element selected from B, Al, Ti, and Zr. Examples of such an organometallic compound may include a boron-based condensation catalyst such as boron isopropoxide ; a titanium-based condensation co-catalyst represented by, for example, an organic titanium alkoxide such as tetraisopropyl titanate, tetranormalbutyl titanate,

tetratertiarybutyl titanate, tetraoctyl titanate, and

tetrastearyl titanate, an organic titanium acylate such as titanium isostearate, and an organic titanium chelate compound such as diisopropoxy (acetylacetonate) titanium,

diisopropoxy (ethylacetoacetate) titanium, tetraacetylacetonate titanium, and titanium-1 , 3-propanedioxybis (ethylacetoacetate) ; a zirconium-based condensation co-catalyst represented by, for example, an organic zirconium alkoxide such as tetraisopropyl zirconate, tetranormalbutyl zirconate, tetratertiarybutyl zirconate, tetraoctyl zirconate, and tetrastearyl zirconate, an organic zirconium acylate such as zirconium isostearate, an organic zirconium chelate compound such as zirconium

diisopropoxy (acetylacetonate) , zirconium

diisopropoxy (ethylacetoacetate) , zirconium

tetraacetylacetonate, zirconium tributoxyacetylacetonate, and zirconium butoxyacetylacetonate, and an oxozirconium compound such as zirconium bis (2-ethylhexanoate) oxide and zirconium acetylacetonate (2-ethylhexanoate) oxide; and an aluminum-based condensation catalyst represented by, for example, an aluminum alkoxide such as aluminum triethylate, aluminum

triisopropylate, and aluminum tri (sec-butyrate) , an aluminum chelate compound such as

diisopropoxyaluminum (ethylacetoacetate) , aluminum

tris (ethylacetoacetate) , and aluminum tris (acetylacetonate) , and an aluminum acyloxy compound such as hydroxyaluminum bis (2-ethylhexanoate) .

[0042]

(Component ( I ) )

Component (I) is not particularly limited as long as it is a component to impart a function of further improving the dispersion of the block polyisocyanate composition of the component (B) , and is preferably a powder having a density of 2.0 g/cm ³ or more. Since a larger oil absorption amount improves the dispersion of the block polyisocyanate composition, the oil absorption amount is preferably 15 ml/100 g or more. Also, for facilitating mixing, the average particle size is preferably 100 μιη or less. Specific examples thereof may include a powder such as precipitated barium sulfate and talc.

[0043]

The silicone rubber composition according to the present invention may contain any additive that is publicly known as an additive for silicone rubber as an optional component other than the above-described components (A) to (I), within the range that does not impair the object of the present

invention. Examples of such an additive may include a

viscosity modifier, a reinforcing filler, a non-reinforcing filler, an adhesion-imparting agent, a pigment, a dye, a curing inhibitor, a heat resistance-imparting agent, a flame retardant, an antistatic agent, a conductivity-imparting agent, an airtightness improver, a radiation shielding agent, an electromagnetic wave shielding agent, a preservative, a stabilizer, an organic solvent, a plasticizer, a fungicide, an organopolysiloxane containing one silicon atom-bonded hydrogen atom or one alkenyl group in one molecule and not containing any other functional group, and a non-functional

organopolysiloxane and an organopolysiloxane resin which do not contain a silicon atom-bonded hydrogen atom or an alkenyl group. One of these may be used alone, or two or more thereof may also be used in combination.

[0044]

The viscosity modifier is not particularly limited, as long as it imparts a function of controlling a change in the viscosity of the silicone rubber composition. Specifically, silanes containing at least one silanol group (that is, a hydroxyl group bonded to a silicon atom) in one molecule are preferable. One of these may be used alone, or two or more thereof may also be used in combination. Specific examples may include trimethyl silanol, triethyl silanol, triisopropyl silanol, triphenyl silanol, dimethyl phenyl silanol, vinyl phenyl methyl silanol, and dimethyl vinyl silanol. Among these, from the viewpoint of industrial availability,

trimethyl silanol, triethyl silanol, triisopropyl silanol, and triphenyl silanol are preferable.

[0045]

As the adhesion-imparting agent, a silane-coupling agent not containing an epoxy group may be further mixed. At least one selected from a vinyl group, a methacryl group, an acryl group, and an isocyanate group is preferably contained as an organic functional group. Examples thereof may include a methacryloxysilane such as 3- methacryloxypropyltrimethoxysilane and 3- methacryloxypropyltriethoxysilane, 3-trimethoxysilylpropyl succinic acid anhydride, and a furandione such as dihydro-3- (3- (triethoxysilyl) propyl) -2, 5-furandione . The organic functional group may be bonded to a silicon atom via another group such as an alkylene group. These are particularly preferably used in combination with the component (H) because the effect is further promoted. Specific examples of such a combination may include a combination of a methacryloxy group- containing organoalkoxysilane and a titanium chelate compound, a combination of a methacryloxy group-containing

organoalkoxysilane and a zirconium chelate compound, a

combination of a methacryloxy group-containing

organoalkoxysilane and an aluminum chelate compound, a

combination of dihydro-3- (3- (triethoxysilyl) propyl) -2, 5- furandione and a titanium chelate compound, a combination of dihydro-3- (3- (triethoxysilyl) propyl) -2, 5-furandione and a zirconium chelate compound, and a combination of dihydro-3- (3- (triethoxysilyl) propyl) -2, 5-furandione and an aluminum chelate compound .

[0046]

Examples of the pigment may include titanium oxide, alumina silicic acid, iron oxide, zinc oxide, carbon black, rare earth oxides, chromium oxide, cobalt pigment, ultramarine blue, cerium silanolate, aluminum oxide, aluminum hydroxide, titanium yellow, carbon black, phthalocyanine blue, and mixtures thereof.

[0047] As the curing inhibitor, any compound which is publicly known as a compound having the curing inhibiting effect may be used. Examples thereof may include an acetylene-based

compound, hydrazines, triazoles, phosphines, mercaptans, a phosphorus-containing compound such as triphenylphosphine, a nitrogen containing compound such as tributylamine,

tetramethylethylenediamine, and benzotriazole, a sulfur- containing compound, an acetylene-based compound, a compound having two or more alkenyl groups, a hydroperoxy compound, a maleic acid derivative, and silane and a silicone compound which have an amino group.

[0048]

Further specific examples may include various "ene-yne" systems such as 3-methyl-3-pentene-l-yne and 3 , 5-dimethyl-3- hexene-l-yne; acetylene-based alcohols such as 3, 5-dimethyl-l- hexyne-3-ol, 1-ethynyl-l-cyclohexanol, and 2-phenyl-3-butyne- 2-ol; known dialkyl, dialkenyl, and maleate and fumarate such as dialkoxyalkyl maleate and fumarate; and a substance

containing cyclovinylsiloxane .

[0049]

Examples of the heat resistance-imparting agent may include cerium hydroxide, cerium oxide, iron oxide, fume titanium dioxide, and mixtures thereof.

[0050]

Examples of the flame retardant may include metal hydroxide such as aluminum hydroxide, magnesium hydroxide, and calcium hydroxide, diatomaceous earth, and calcium carbonate.

[0051]

The airtightness improver is not particularly limited as long as it has the effect of reducing the air permeability of a cured product, and can be either an organic substance or inorganic substance. Specific examples thereof may include polyvinyl alcohol, polyisobutylene, an isobutylene-isoprene copolymer, a flat-shaped powder such as mica, glass flake, boehmite, and various metal foils and metal oxides, a silicone rubber powder and a silicone resin powder, and mixtures thereof .

[0052]

The method for manufacturing the silicone rubber

composition according to the present invention is not

particularly limited, and may be any method known to those skilled in the art. For example, the component (A), the component (B) , the component (C) , and the component (E) , or the component (A) , the component (D) , and the component (E) may be previously mixed using a stirrer, or uniformly kneaded using a two-roll, a kneader mixer, a pressure kneader mixer, a high shear-type mixer such as a Ross mixer, an extruder, a continuous extruder, and the like, to prepare a silicone rubber base. After that, to the obtained silicone rubber base, any of the component (F) to the component (I) may be added to manufacture the silicone rubber composition. Alternatively, the components (A) and (C) or the components (A) and (D) may be previously manufactured with an emulsifier using an

emulsifying agent as in a known method. The silicone rubber composition according to the present invention may be

preserved in an organic solvent such as toluene, xylene, hexane, white spirit, or a mixture thereof.

[0053]

The present invention particularly relates to a silicone rubber composition for fiber base cloths used for airbags of automobiles and the like. An airbag is obtained by sewing an airbag base cloth into a bag shape, and mainly mounted to automobiles. The bag is a device to be inflated in a collision to secure the safety of a driver and a passenger. An airbag base cloth is usually a fabric woven with synthetic fiber such as polyamide and polyethylene terephthalate. The silicone rubber composition according to the present invention is applied onto the synthetic fiber fabric. Specifically, examples of such synthetic fiber fabric may include polyamide fiber fabric such as nylon 6, nylon 66, and nylon 46, aramid fiber fabric, polyester fiber fabric represented by

polyalkylene terephthalate, polyether imide fiber fabric, sulfone-based fiber fabric, carbon fiber fabric, and mixtures thereof. The silicone rubber composition is applied onto a fabric woven with a thread having a size of 10 to 5,000 decitex and having a shape of flat woven, a bag, a hose, and the like. From the viewpoint of processability and economic efficiency, a fabric woven with a thread having a size of 50 to 1,000 decitex is preferable.

[0054]

The fabric may be used in an unrefined or refined state. When in an unrefined state, the fabric may be directly coated, thereby omitting a refining process. The type and component of the oil solution is not particularly limited. However, from the viewpoint of facilitating the manufacture, the amount of the oil solution relative to the weight of the fabric is preferably 5% by mass or less, and more preferably 3% by mass or less.

[0055]

Coating with the silicone rubber composition according to the present invention may be performed by a generally used method. Examples thereof may include immersion and padding, brushing, flow coating, spraying, roller coating, gravure coating, comma coater, fiber printing, knife coating, Meyer bar, air brush, slop padding, and roll coating. One or a combination of these methods may be performed depending on the circumstances. The coating is not necessarily performed once, and may be repeated multiple times until an intended coating state is obtained. Therefore, the number of cured films after coating is not necessarily one, and may be two or more. Furthermore, for the purpose of imparting effects such as fouling prevention, charging prevention, sliding properties, and blocking prevention to the cured coated film surface, an additional intended component may be mixed into the silicone rubber composition, the surface after coating or curing may be processed, or a cured layer having such a function may be further formed.

[0056]

The drying and curing after coating are usually performed in a heating device which can generate heat with an energy source such as hot air, infrared ray, near-infrared ray, a gas burner, and a heat exchanger. Note that other than commonly used heating devices, any heating device capable of achieving an intended purpose may be used. Examples thereof may include a heating roll calendar, a heatable bonding press, a heatable daylight press, a high-temperature kiss roll, a hot air dryer, and a microwave dryer.

[0057]

During curing, it is preferable to set a plurality of temperature zones with different temperatures to a heating device, in order to prevent the formation of bubbles in a cured film. For example, in a first temperature zone,

preliminary drying may be performed at a temperature of 60 to 150°C, preferably 80 to 130°C, and further preferably 90 to 120°C, and in a subsequent second temperature zone, curing may be performed at a temperature of 300°C or lower. However, since most fibers have heat resistance limitation in terms of processing, 250°C or lower is preferable.

[0058]

Even when a plurality of temperature zones is difficult to set in terms of manufacturing processes, it is preferable that preliminary drying be performed such that the temperature of a base material to be cured reaches 170°C or higher at least once. The retention time necessary for curing varies depending on the weight of coating, the thermal conductivity of a fabric and a coated fabric, and the like. However, it is preferably about 0.5 to 30 minutes. At room temperature, a base material may be left to stand for 10 minutes to several hours.

EXAMPLES

[0059]

Hereinafter, the present invention will be specifically described with reference to examples and comparative examples. However, the present invention is not limited to the following examples. It is noted that "part(s)" in each example means "part(s) by mass". The results of the examples and comparative examples are shown in Tables 1 and 2.

[0060]

<Test Base Cloth>

Two polyester plain-woven cloths formed of a 470-decitex thread were used as a test base cloth. One is a base cloth having been refined thereby to adjust an oil solution amount to 0.04% by mass relative to a fabric weight, and the other is a base cloth not having been refined and having an oil

solution amount of 1.2% by mass relative to a fabric weight.

[0061]

<Coating Method>

For confirming the adhesiveness over time, a formulated silicone rubber composition was left to stand at room

temperature for 5 hours or more, and then coating was

performed. The coating was performed with a knife coater. The curing temperature was 190°C, and the curing time was 45 seconds .

[0062]

<Adhesiveness Test Method of Coated Product>

The adhesiveness of the cured product was confirmed in a crease-flex test. The measurement was performed by preparing a coated cloth with a size of 10 cm in length x 5 cm in width, and applying a load of 10 N onto the cured film. The test device used was an INC-1507-A scrub tester (manufactured by Imoto Machinery Co Ltd.), and the test was performed in accordance with ISO 5981.

Measurement was performed for each of a coated cloth having been left to stand at room temperature for 24 hours. The adhesiveness was determined as success if pinholes and peeling were not observed when the cloth was crumpled 1000 times .

[0063]

<Example 1>

The component (A-l) was obtained by mixing 8 parts of a dimethylpolysiloxane containing a vinyl group at both

terminals and having a viscosity of about 100,000 mPa-s, 7.8 parts of a dimethylpolysiloxane containing a vinyl group at both terminals and having a viscosity of about 1,000 mPa-s, and 0.5 parts of a dimethylpolysiloxane containing a vinyl group at both terminals and in the molecule (vinyl group content: 3 mmol/g) and having a viscosity of about 10 mPa-s, into 60 parts of a dimethylpolysiloxane containing a vinyl group at both terminals and having a viscosity of about 20, 000 mPa-s . To the component (A-l), there were added 0.3 parts of Duranate X2252 (manufactured by Asahi Kasei Corp.), as the component (B) , having a viscosity at 60°C of 20, 000 mPa-s, and 0.3 parts of a dimethylpolysiloxane solution, as the component (C) ,

containing a platinum-divinyl tetramethyldisiloxane complex in an amount of 1% in terms of a platinum content. The mixture was thoroughly mixed using a stirring and mixing device to prepare a rubber base.

[0064]

To 77 parts of the rubber base, there were added 5.9 parts of fumed silica, as the component (E) , having a specific surface area of 300 m ² /g measured by a BET method, and 0.1 parts of ethynyl cyclohexanol as a curing inhibitor. The mixture was thoroughly mixed using a stirring and mixing device. To the resultant product, there were further added, as the component (D) , 0.6 parts of a methylhydrogenpolysiloxane (hydrogen content: 1.6%) in which both terminals were blocked with a trimethylsiloxy group, and the viscosity at 25°C was 30 mPa-s, 3 parts of a methylhydrogenpolysiloxane (hydrogen content: 0.8%) in which both terminals were blocked with a trimethylsiloxy group, and the viscosity at 25°C was 70 mPa-s, 0.2 parts of a methylphenylhydrogenpolysiloxane (hydrogen content: 0.8%) in which both terminals were blocked with a trimethylsiloxy group, and the viscosity at 25°C was 40 mPa-s, 5 parts of an organohydrogenpolysiloxane (hydrogen content: 0.05%) in which only both terminals have a hydrogen atom bonded to a silicon atom, and the viscosity at 25°C was 50 mPa-s, and 0.3 parts of trimethylsilanol . The mixture was thoroughly mixed using a stirring and mixing device.

[0065]

To the resultant product, there were further added 0.8 parts of 3-glycidoxypropyltrimethoxysilane as the component

(G) , and 0.5 parts of diisopropoxy (ethylacetoacetate) titanium as the component (H) . The mixture was thoroughly mixed using a stirring and mixing device to prepare a silicone rubber composition according to Example 1. The molar ratio between all Si-H groups and all vinyl groups in this silicone rubber composition was 5.9. The obtained silicon rubber composition was left to stand at room temperature for 5 hours, and then applied onto a refined polyester cloth with about 36 g/m ² , and cured An adhesion test was performed after it was left to stand at room temperature for 24 hours.

[0066]

The coated cloth of Example 1 had several pinholes at 2,000 times. However, it had no pinholes and peeling until 1,800 times, and exhibited favorable adhesiveness with the judgment of adhesiveness being success.

[0067]

<Example 2>

The silicone rubber composition in Example 1 having been left to stand at room temperature for 5 hours was applied onto an unrefined polyester cloth with 36 g/m ² to prepare a coated cloth in the same manner as that in Example 1. Even with the cloth of Example 2 having an increased amount of an oil solution, pinholes and peeling were not observed until 1,800 times with the judgment of adhesiveness being success.

[0068]

<Example 3>

A silicone rubber composition of Example 3 was prepared by: further adding, to the formulation of the silicone rubber composition of Example 1, 6 parts of an organopolysiloxane resin having a vinyl group unit and a Q siloxane unit in the molecule as Component (F) , and 0.3 parts of a precipitated barium sulfate powder (density: 4.0 g/cm ³ , oil absorption: 18 ml/100 g, average particle size: 0.3 μιη) as Component (I); and thoroughly mixing the mixture using a stirring and mixing device. The obtained silicon rubber composition was left to stand at room temperature for 5 hours, and applied onto a refined or unrefined polyester cloth with about 35 g/m ² . The coating was cured to prepare a coated cloth. In Example 3, adhesiveness was further improved. Pinholes and peeling were not observed even at 2,000 times, and the judgment of

adhesiveness was success.

[0069]

<Comparative Example 1>

A silicone rubber composition which did not include a block polyisocyanate composition as the component (B) in the formulation of Example 3 was prepared as Comparative Example 1. Then, the silicone rubber composition having been left to stand at room temperature for 5 hours was applied onto a refined polyester cloth with 35 g/m ² to prepare a coated cloth in the same manner as that in Example 1. In Comparative

Example 1, pinholes and peeling were not observed until 600 times. However, since peeling was found at 800 times, the test was stopped. Accordingly, the judgment of adhesiveness was failure .

[0070] <Comparative Example 2>

The mixed liquid prepared in Comparative Example 1 having been left to stand at room temperature for 5 hours was applied onto an unrefined polyester cloth with 35 g/m ² to prepare a coated cloth in the same manner as that in Example 1. In

Comparative Example 2, pinholes and peeling were not observed even at 200 times. However, since peeling was found at 400 times, the test was stopped. Accordingly, the judgment of adhesiveness was failure.

[Table 1]

[0072]

[Table 2]

INDUSTRIAL APPLICABILITY

[0073]

According to the silicone rubber composition including a block polyisocyanate composition and a curable silicone rubber composition of the present invention, the compatibility between the block polyisocyanate composition and the curable silicone rubber composition becomes favorable, and the

adhesiveness of the silicone rubber composition does not decrease as time passes. Furthermore, when the silicone rubber composition is applied onto an unrefined or refined fabric in which the amount of an oil solution is 5% by mass or less relative to the weight of the fabric, it strongly adheres to the fabric even when cured. Therefore, the work load in a refining process can be drastically reduced, thereby improving productivity.