WO2012099305A1 - Liquid silicone rubber coating composition and airbag with cured film thereof - Google Patents

Liquid silicone rubber coating composition and airbag with cured film thereof Download PDF

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Publication number
WO2012099305A1
WO2012099305A1 PCT/KR2011/005228 KR2011005228W WO2012099305A1 WO 2012099305 A1 WO2012099305 A1 WO 2012099305A1 KR 2011005228 W KR2011005228 W KR 2011005228W WO 2012099305 A1 WO2012099305 A1 WO 2012099305A1
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WIPO (PCT)
Prior art keywords
silicone rubber
coating composition
liquid silicone
composition according
weight
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Application number
PCT/KR2011/005228
Other languages
French (fr)
Inventor
Ye Jin HONG
Sang Bok Lee
Keun Mook Choi
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Kcc Corporation
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Publication of WO2012099305A1 publication Critical patent/WO2012099305A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
    • B60R21/00—Arrangements or fittings on vehicles for protecting or preventing injuries to occupants or pedestrians in case of accidents or other traffic risks
    • B60R21/02—Occupant safety arrangements or fittings, e.g. crash pads
    • B60R21/16—Inflatable occupant restraints or confinements designed to inflate upon impact or impending impact, e.g. air bags
    • B60R21/20—Arrangements for storing inflatable members in their non-use or deflated condition; Arrangement or mounting of air bag modules or components
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D183/00—Coating compositions based on macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon, with or without sulfur, nitrogen, oxygen, or carbon only; Coating compositions based on derivatives of such polymers
    • C09D183/04—Polysiloxanes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
    • B60R21/00—Arrangements or fittings on vehicles for protecting or preventing injuries to occupants or pedestrians in case of accidents or other traffic risks
    • B60R21/02—Occupant safety arrangements or fittings, e.g. crash pads
    • B60R21/16—Inflatable occupant restraints or confinements designed to inflate upon impact or impending impact, e.g. air bags
    • B60R21/23—Inflatable members
    • B60R21/235—Inflatable members characterised by their material
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
    • C09D7/40—Additives
    • C09D7/60—Additives non-macromolecular
    • C09D7/61—Additives non-macromolecular inorganic
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
    • C08G77/04—Polysiloxanes
    • C08G77/12—Polysiloxanes containing silicon bound to hydrogen
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
    • C08G77/04—Polysiloxanes
    • C08G77/20—Polysiloxanes containing silicon bound to unsaturated aliphatic groups
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/34—Silicon-containing compounds
    • C08K3/36—Silica

Definitions

  • the present invention relates to a liquid silicone rubber-coating composition and an airbag with cured film thereof. More specifically, the present invention relates to a liquid silicone rubber-coating composition which contains an adhesion-imparting agent comprising 1-allyl-3,5-diglycidylisocyanurate and thus can maintain excellent adhesion property even after long-term exposure to high temperature/high humidity conditions as well as immediately after coating, and an airbag with cured film of the composition formed on fabric.
  • an adhesion-imparting agent comprising 1-allyl-3,5-diglycidylisocyanurate
  • Silicone rubbers generally have good heat resistance, electrical insulation, flame resistance and restoration after compression and deformation, and thus are widely used in various fields. For example, if a substrate fabric comprising a synthetic fiber such as nylon or an inorganic fiber such as a glass fiber is coated with a silicone rubber composition, it provides good thermal properties, storage stability, flexibility and abrasion resistance. Thus, such a silicone rubber composition is in the spotlight as a coating material for various articles including car airbags.
  • airbags comprising a nylon bag coated with silicone rubber have been marketed, and they have been recognized as reliable and used as a new type of airbag replacing conventional airbags. Furthermore, as the latest airbag system, a side-curtain shield airbag has been developed for alleviating the impact to passenger(s) from broadside collisions and for preventing driver from being catapulted out of the car during lateral turning.
  • silicone rubber-coating compositions for an airbag comprising as an adhesion-imparting ingredient, organosilane compound having epoxy group or isocyanate group are suggested in Japanese Laid-open Patent Publication Nos. (Hei)5-25435 and (Hei)5-98579, respectively.
  • the airbag using such a composition as a coating material therefor cannot secure it long-term wholesomeness since its long-term exposure to abnormal conditions such as high temperature/high humidity leads to the lowering of adhesion and generation of peeling.
  • the present invention has an object of providing a silicone rubber-coating composition which satisfies the basic properties required for application to an airbag, etc. and can maintain excellent adhesion even under high temperature/high humidity conditions.
  • the present invention provides a liquid silicone rubber-coating composition
  • a liquid silicone rubber-coating composition comprising: (A) polyorganosiloxane containing two or more alkenyl groups per molecule; (B) polyorganohydrogensiloxane containing hydrogen in the side chain of the molecule; (C) reinforcing silica; (D) catalyst for addition reaction; and (E) adhesion-imparting agent comprising 1-allyl-3,5-diglycidylisocyanurate.
  • the other aspect of the present invention provides an airbag having a cured film of the liquid silicone rubber-coating composition formed on airbag fabric.
  • the liquid silicone rubber-coating composition of the present invention can maintain excellent adhesion property even after long-term exposure to high temperature/high humidity conditions as well as immediately after coating, has good mechanical properties and low viscosity for easy coating and can secure the required function such as air-leak prevention even by a small amount of coating thereof.
  • Such liquid silicone rubber-coating composition of the present invention can be usefully applied for coating the substrate fabric of synthetic fibers, inorganic fibers, etc. ⁇ in particular, for an airbag.
  • liquid silicone rubber-coating composition of the present invention is explained in detail according to each constitutional component below.
  • Polyorganosiloxane (also referred to as “component (A)”) comprised in the composition of the present invention is the main raw material (base polymer) of the addition-curable-type liquid silicone rubber-coating composition. It contains two or more alkenyl groups (concretely, alkenyl groups bound to Si) per molecule in order for the composition of the present invention to be formed into cured silicone rubber film.
  • the curing of the composition proceeds by the crosslinking reaction of said polyorganosiloxane and polyorganohydrogensiloxane as explained below.
  • the polyorganosiloxane may be a linear polyorganosiloxane represented by the following formula 1:
  • the polyorganosiloxane contains alkenyl groups such as vinyl group, allyl group, butenyl group, pentenyl group, hexenyl group, heptenyl group, etc., and vinyl group is particularly preferred.
  • Alkenyl groups may be contained in both terminus and/or side chain of the polyorganosiloxane molecule. Alkenyl groups are contained preferably in a ratio of 0.001 ⁇ 5 mmol per gram of polyorganosiloxane, and more preferably in a ratio of 0.01 ⁇ 3 mmol/g. If the content is less than 0.001 mmol/g, the composition may not be coated smoothly. If the content is greater than 5 mmol/g, there may be a problem of lowered mechanical properties (strength, etc.) of the silicone rubber film.
  • the viscosity of the polyorganosiloxane is preferably 100 ⁇ 150,000 mPa ⁇ s at 25°C. If the viscosity is less than 100 mPa ⁇ s, the mechanical properties (strength, etc.) of the silicone rubber film may be lowered. If the viscosity is greater than 150,000 mPa ⁇ s, the composition may not be coated smoothly.
  • Polyorganohydrogensiloxane (also referred to as “component (B)”) comprised in the composition of the present invention performs the role of a crosslinking agent and contains hydrogen (concretely, hydrogen bound to Si) in the side chain of the molecule.
  • the curing of the composition proceeds by the crosslinking reaction of polyorganosiloxane and polyorganohydrogensiloxane.
  • the polyorganohydrogensiloxane may be represented by the following formula 2:
  • each of R 2 independently represents a saturated aliphatic hydrocarbyl group or aromatic hydrocarbyl group ⁇ for example, methyl, ethyl, butyl, phenyl, etc. (preferably, methyl); and each of m and n independently denotes an integer of 10 ⁇ 100.
  • Hydrogen is contained in the side chain of the molecule preferably in a ratio of 0.1 ⁇ 20 mmol per gram of polyorganohydrogensiloxane. If the content is less than 0.1 mmol/g, the strength of the silicone rubber film may be lowered. If the content is greater than 20 mmol/g, the heat resistance of the silicone rubber film may be lowered.
  • the amount of polyorganohydrogensiloxane in the present composition is preferably 1 ⁇ 30 parts by weight and more preferably 2 ⁇ 25 parts by weight, based on 100 parts by weight of polyorganosiloxane. If the amount is less than 1 part by weight, the composition may not be cured, or the crosslinking density may become lowered. If the amount is greater than 30 parts by weight, foaming by dehydration reaction may occur, or there may be a problem in releasing property.
  • Reinforcing silica (also referred to as “component (C)”) comprised in the composition of the present invention is an ingredient added to improve the strength of the silicone rubber.
  • any silica containing SiO 2 as the main ingredient may be used as the reinforcing silica without special limitation.
  • fumed silica, precipitated silica, diatomite, pulverized quartz, molten quartz or the like is used alone or in a combination of two or more thereof.
  • the above materials may be used without modification as the reinforcing silica, if they are surface-treated with hexamethyldisilazane, octamethylcyclotetrasiloxane or the like during the process and then used, the dispersibility and storage stability may be further improved.
  • the reinforcing silica has a preferable average particle diameter of 20 ⁇ m or less, more preferably 10 ⁇ m or less, and still more preferably 7 ⁇ m or less. If the average particle diameter is greater than 20 ⁇ m, the strength of the silicone rubber may not be improved sufficiently and in some cases, the strength may even be lowered. For the same reason, as the reinforcing silica (for example, fumed silica or precipitated silica), it is advantageous to use those having a primary particle diameter of sufficiently less than 5 ⁇ m (usually about 0.001 ⁇ 1 ⁇ m) and a specific surface area by BET method of 50 m2/g or greater, preferably 50 ⁇ 400 m2/g, and more preferably 100 ⁇ 350 m2/g.
  • the amount of reinforcing silica in the present composition is preferably 10 ⁇ 50 parts by weight and more preferably 15 ⁇ 35 parts by weight, based on 100 parts by weight of polyorganosiloxane. If the amount is less than 10 parts by weight, it may be difficult to obtain sufficient mechanical strength. If the amount is greater than 50 parts by weight, the viscosity may be too high and thus the processability may be lowered.
  • the catalyst for addition reaction (also referred to as “component (D)”) comprised in the composition of the present invention is an ingredient to promote the addition reaction of components (A) and (B).
  • any catalysts capable of promoting addition reaction of components (A) and (B) such as platinum catalyst, rhodium catalyst, palladium catalyst or the like may be used without special limitation.
  • Platinum compound is preferably used.
  • platinum in the platinum compound acts as a catalyst to crosslink polyorganosiloxane containing alkenyl group (for example, vinyl group) and polyorganohydrogensiloxane.
  • the reactivity and compatibility with a silicone polymer may be improved by using a platinum compound that forms a complex with a vinylsiloxane of low molecular weight and has the oxidation number of 0.
  • Examples of ligand forming a complex with platinum in the platinum compound may include divinyltetramethylsiloxane, tetramethyltertavinyl tetracyclosiloxane and the like, but it is not limited by them.
  • the content of platinum in the platinum compound is preferably 0.5 ⁇ 15% by weight.
  • the amount of catalyst for addition reaction in the present composition is preferably 0.01 ⁇ 1 part by weight and more preferably 0.1 ⁇ 0.5 part by weight, based on 100 parts by weight of polyorganosiloxane. If the amount is less than 0.01 part by weight, the addition reaction of the composition may become significantly slow, or the curing itself may not even occur. If the amount is greater than 1 part by weight, the addition reaction may become faster and thus pot life may become shorter, by which the workability may be lowered.
  • the adhesion-imparting agent (also referred to as “component (E)”) comprised in the composition of the present invention is an ingredient meant to increase the adhesion between the silicone rubber and the woven or non-woven fabric substrate such as an airbag fabric.
  • the present invention uses an adhesion-imparting agent comprising 1-allyl-3,5-diglycidylisocyanurate and not containing silicon. Accordingly, it is possible to provide a silicone rubber film which can maintain excellent adhesion property even upon exposure to high temperature/high humidity conditions as well as immediately after coating.
  • 1-allyl-3,5-diglycidylisocyanurate comprised in the adhesion-imparting agent may be represented by the following formula 3 and structural formula 1, which is obtainable ⁇ for example, as the trade name of MA-DGIC (Shikoku Co. Ltd., Japan).
  • 1-allyl-3,5-diglycidylisocyanurate may be used alone or in combination with another adhesion-imparting component (organosilane compound, organotitanium compound, etc.) conventionally added for silicone rubber.
  • the amount of adhesion-imparting agent in the present composition is preferably 0.01 ⁇ 0.5 part by weight, based on 100 parts by weight of polyorganosiloxane. If the amount is less than 0.01 part by weight, the effect of improving adhesion from its addition may not be expected. If the amount is greater than 0.5 part by weight, excessive increase of viscosity and lowering of storage stability may result.
  • composition of the present invention may further comprise a curing retarder (also referred to as “component (F)”). If a curing retarder is added to the addition-curable type liquid silicone rubber-coating composition together with the catalyst for addition reaction, the curing rate can be controlled smoothly. By properly adjusting the ratio of the catalyst for addition reaction and curing retarder, the workability required for specific application may be secured.
  • a curing retarder also referred to as “component (F)
  • compounds having a double bond including alkenyl or a triple bond such as 1-ethynyl-1-cyclohexanol, 1,1,3,3-tetramethyl-1,3-divinyldisilazane, 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, 2-methyl-3-butyn-2-ol, etc. may be used, but it is not limited by them.
  • the preferable amount of curing retarder in the present composition is 0.02 ⁇ 0.5 part by weight, based on 100 parts by weight of polyorganosiloxane. If the amount is less than 0.02 part by weight, there may be a problem due to an overly high curing rate. If the amount is greater than 0.5 part by weight, the curing itself may not occur.
  • composition of the present invention may further comprise additive(s) generally used for silicone rubber.
  • inorganic filler for improving strength and heat resistance such as fumed titanium dioxide, crystalline silica, calcium silicate, titanium dioxide, ferric oxide and carbon black
  • wetter for improving dispersibility including low molecular weight organosilane compound such as diorganopolysiloxane having terminal hydroxy group, diphenylsilanediol, hexaorganopolysiloxane and organoalkoxysilane
  • heat-resistance promoter including metal oxide such as iron oxide, cerium oxide, zinc oxide and titanium oxide, cerium silanolate and cerium fatty acid salt
  • flame-resistance imparting agent including platinum compound such as complexes of platinum tetrachloride, hydrogen hexachloroplatinate and hydrogen hexachloroplatinate hexahydrate with olefin or divinyldimethylpolysiloxane, alcohol
  • the method for preparing the present liquid silicone rubber-coating composition from the above components is not particularly limited, and the present composition may be prepared by using a conventional method in this field of art.
  • components (A) and (C) may be mixed by using a rubber kneader to prepare a base compounding, and components (B), (D) and (E) and optionally (F) if needed, and other additives may then be added thereto and mixed to prepare the present composition.
  • composition of the present invention comprises polyorganosiloxane, polyorganohydrogensiloxane and reinforcing silica in an appropriate amount, and thus can form silicone rubber film having excellent mechanical properties and can be coated easily on an airbag fabric, etc. since the viscosity is usually 80 Pa ⁇ s or less.
  • the other aspect of the present invention provides an airbag characterized in having a cured film of the present liquid silicone rubber-coating composition formed on an airbag fabric.
  • the liquid silicone rubber-coating composition of the present invention may be usefully applied for coating a substrate fabric of synthetic fibers, inorganic fibers, etc., in particular, for coating an airbag installed in vehicles or the like.
  • the composition may be coated and cured by a conventional method in this field of art to form cured film on an airbag fabric.
  • the coating amount of the composition may be adjusted properly according to the kind, use and structure of the airbag, and the curing of the composition is generally conducted at 80 ⁇ 250°C for 30 seconds ⁇ 10 minutes.
  • composition of the present invention comprises the adhesion-imparting agent containing 1-allyl-3,5-diglycidylisocyanurate as the main ingredient, its excellent adhesion property can be maintained even after long-term exposure to high temperature/high humidity conditions as well as immediately after coating.
  • liquid silicone rubber-coating compositions prepared in the Examples and Comparative Examples were cured in a press at 170°C for 10 minutes to prepare rubber sheet samples with a thickness of 2 mm.
  • the prepared samples were tested for various mechanical properties by the below methods, the results of which are provided in the following Table 1.

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  • Wood Science & Technology (AREA)
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Abstract

The present invention relates to a liquid silicone rubber-coating composition and an airbag with cured film thereof. More specifically, the present invention relates to a liquid silicone rubber-coating composition which contains an adhesion-imparting agent comprising 1-allyl-3,5-diglycidylisocyanurate and thus can maintain excellent adhesion property even after long-term exposure to high temperature/high humidity conditions as well as immediately after coating, and an airbag with cured film of the composition formed on fabric.

Description

LIQUID SILICONE RUBBER COATING COMPOSITION AND AIRBAG WITH CURED FILM THEREOF
The present invention relates to a liquid silicone rubber-coating composition and an airbag with cured film thereof. More specifically, the present invention relates to a liquid silicone rubber-coating composition which contains an adhesion-imparting agent comprising 1-allyl-3,5-diglycidylisocyanurate and thus can maintain excellent adhesion property even after long-term exposure to high temperature/high humidity conditions as well as immediately after coating, and an airbag with cured film of the composition formed on fabric.
Silicone rubbers generally have good heat resistance, electrical insulation, flame resistance and restoration after compression and deformation, and thus are widely used in various fields. For example, if a substrate fabric comprising a synthetic fiber such as nylon or an inorganic fiber such as a glass fiber is coated with a silicone rubber composition, it provides good thermal properties, storage stability, flexibility and abrasion resistance. Thus, such a silicone rubber composition is in the spotlight as a coating material for various articles including car airbags.
Recently, airbags comprising a nylon bag coated with silicone rubber have been marketed, and they have been recognized as reliable and used as a new type of airbag replacing conventional airbags. Furthermore, as the latest airbag system, a side-curtain shield airbag has been developed for alleviating the impact to passenger(s) from broadside collisions and for preventing driver from being catapulted out of the car during lateral turning.
Such a side-curtain shield airbag requires better adhesion of coating material than conventional airbag coating materials since it must maintain internal pressure generated by the explosion of an inflation agent for a given time after its unfolding.
To increase adhesion, silicone rubber-coating compositions for an airbag comprising as an adhesion-imparting ingredient, organosilane compound having epoxy group or isocyanate group are suggested in Japanese Laid-open Patent Publication Nos. (Hei)5-25435 and (Hei)5-98579, respectively. However, the airbag using such a composition as a coating material therefor cannot secure it long-term wholesomeness since its long-term exposure to abnormal conditions such as high temperature/high humidity leads to the lowering of adhesion and generation of peeling.
Accordingly, there is a need to develop a silicone rubber-coating composition which satisfies the basic properties such as adhesion enduring high elongation, elasticity, air-leakage blocking, easy and economical coating, etc. required for application to an airbag, etc. and can maintain excellent adhesion even under high temperature/high humidity conditions as well as immediately after coating.
[PRIOR ART PUBLICATIONS]
<PATENT PUBLICATIONS>
Japanese Laid-open Patent Publication No. (Hei)5-25435
Japanese Laid-open Patent Publication No. (Hei)5-98579
To resolve the problems of prior arts as explained above, the present invention has an object of providing a silicone rubber-coating composition which satisfies the basic properties required for application to an airbag, etc. and can maintain excellent adhesion even under high temperature/high humidity conditions.
To achieve the object as explained above, the present invention provides a liquid silicone rubber-coating composition comprising: (A) polyorganosiloxane containing two or more alkenyl groups per molecule; (B) polyorganohydrogensiloxane containing hydrogen in the side chain of the molecule; (C) reinforcing silica; (D) catalyst for addition reaction; and (E) adhesion-imparting agent comprising 1-allyl-3,5-diglycidylisocyanurate.
The other aspect of the present invention provides an airbag having a cured film of the liquid silicone rubber-coating composition formed on airbag fabric.
The liquid silicone rubber-coating composition of the present invention can maintain excellent adhesion property even after long-term exposure to high temperature/high humidity conditions as well as immediately after coating, has good mechanical properties and low viscosity for easy coating and can secure the required function such as air-leak prevention even by a small amount of coating thereof. Such liquid silicone rubber-coating composition of the present invention can be usefully applied for coating the substrate fabric of synthetic fibers, inorganic fibers, etc.―in particular, for an airbag.
The liquid silicone rubber-coating composition of the present invention is explained in detail according to each constitutional component below.
(A) Polyorganosiloxane
Polyorganosiloxane (also referred to as “component (A)”) comprised in the composition of the present invention is the main raw material (base polymer) of the addition-curable-type liquid silicone rubber-coating composition. It contains two or more alkenyl groups (concretely, alkenyl groups bound to Si) per molecule in order for the composition of the present invention to be formed into cured silicone rubber film. The curing of the composition proceeds by the crosslinking reaction of said polyorganosiloxane and polyorganohydrogensiloxane as explained below.
In an embodiment, the polyorganosiloxane may be a linear polyorganosiloxane represented by the following formula 1:
[Formula 1]
R-Si(CH3)2O(R1 2SiO)nSi(CH3)2-R
in which R represents an unsaturated aliphatic hydrocarbyl group (preferably, vinyl); R1 represents a saturated aliphatic hydrocarbyl group, unsaturated aliphatic hydrocarbyl group or aromatic hydrocarbyl group―for example, methyl, ethyl, butyl, vinyl, phenyl, etc. (preferably, methyl or vinyl); and n denotes an integer of 50 ~ 250.
The polyorganosiloxane contains alkenyl groups such as vinyl group, allyl group, butenyl group, pentenyl group, hexenyl group, heptenyl group, etc., and vinyl group is particularly preferred.
Alkenyl groups may be contained in both terminus and/or side chain of the polyorganosiloxane molecule. Alkenyl groups are contained preferably in a ratio of 0.001 ~ 5 mmol per gram of polyorganosiloxane, and more preferably in a ratio of 0.01 ~ 3 mmol/g. If the content is less than 0.001 mmol/g, the composition may not be coated smoothly. If the content is greater than 5 mmol/g, there may be a problem of lowered mechanical properties (strength, etc.) of the silicone rubber film.
The viscosity of the polyorganosiloxane is preferably 100 ~ 150,000 mPa·s at 25℃. If the viscosity is less than 100 mPa·s, the mechanical properties (strength, etc.) of the silicone rubber film may be lowered. If the viscosity is greater than 150,000 mPa·s, the composition may not be coated smoothly.
(B) Polyorganohydrogensiloxane
Polyorganohydrogensiloxane (also referred to as “component (B)”) comprised in the composition of the present invention performs the role of a crosslinking agent and contains hydrogen (concretely, hydrogen bound to Si) in the side chain of the molecule. The curing of the composition proceeds by the crosslinking reaction of polyorganosiloxane and polyorganohydrogensiloxane.
In an embodiment, the polyorganohydrogensiloxane may be represented by the following formula 2:
[Formula 2]
R2-Si(CH3)2O(R2HSiO)m(R2 2SiO)nSi(CH3)2-R2
in which each of R2 independently represents a saturated aliphatic hydrocarbyl group or aromatic hydrocarbyl group―for example, methyl, ethyl, butyl, phenyl, etc. (preferably, methyl); and each of m and n independently denotes an integer of 10 ~ 100.
Hydrogen is contained in the side chain of the molecule preferably in a ratio of 0.1 ~ 20 mmol per gram of polyorganohydrogensiloxane. If the content is less than 0.1 mmol/g, the strength of the silicone rubber film may be lowered. If the content is greater than 20 mmol/g, the heat resistance of the silicone rubber film may be lowered.
The amount of polyorganohydrogensiloxane in the present composition is preferably 1 ~ 30 parts by weight and more preferably 2 ~ 25 parts by weight, based on 100 parts by weight of polyorganosiloxane. If the amount is less than 1 part by weight, the composition may not be cured, or the crosslinking density may become lowered. If the amount is greater than 30 parts by weight, foaming by dehydration reaction may occur, or there may be a problem in releasing property.
(C) Reinforcing silica
Reinforcing silica (also referred to as “component (C)”) comprised in the composition of the present invention is an ingredient added to improve the strength of the silicone rubber.
Any silica containing SiO2 as the main ingredient may be used as the reinforcing silica without special limitation. Preferably, fumed silica, precipitated silica, diatomite, pulverized quartz, molten quartz or the like is used alone or in a combination of two or more thereof. Although the above materials may be used without modification as the reinforcing silica, if they are surface-treated with hexamethyldisilazane, octamethylcyclotetrasiloxane or the like during the process and then used, the dispersibility and storage stability may be further improved.
The reinforcing silica has a preferable average particle diameter of 20 ㎛ or less, more preferably 10 ㎛ or less, and still more preferably 7 ㎛ or less. If the average particle diameter is greater than 20 ㎛, the strength of the silicone rubber may not be improved sufficiently and in some cases, the strength may even be lowered. For the same reason, as the reinforcing silica (for example, fumed silica or precipitated silica), it is advantageous to use those having a primary particle diameter of sufficiently less than 5 ㎛ (usually about 0.001 ~ 1 ㎛) and a specific surface area by BET method of 50 ㎡/g or greater, preferably 50 ~ 400 ㎡/g, and more preferably 100 ~ 350 ㎡/g.
The amount of reinforcing silica in the present composition is preferably 10 ~ 50 parts by weight and more preferably 15 ~ 35 parts by weight, based on 100 parts by weight of polyorganosiloxane. If the amount is less than 10 parts by weight, it may be difficult to obtain sufficient mechanical strength. If the amount is greater than 50 parts by weight, the viscosity may be too high and thus the processability may be lowered.
(D) Catalyst for addition reaction
The catalyst for addition reaction (also referred to as “component (D)”) comprised in the composition of the present invention is an ingredient to promote the addition reaction of components (A) and (B).
As the catalyst for addition reaction, any catalysts capable of promoting addition reaction of components (A) and (B) such as platinum catalyst, rhodium catalyst, palladium catalyst or the like may be used without special limitation. Platinum compound is preferably used. In this case, platinum in the platinum compound acts as a catalyst to crosslink polyorganosiloxane containing alkenyl group (for example, vinyl group) and polyorganohydrogensiloxane. In an embodiment, the reactivity and compatibility with a silicone polymer may be improved by using a platinum compound that forms a complex with a vinylsiloxane of low molecular weight and has the oxidation number of 0. Examples of ligand forming a complex with platinum in the platinum compound may include divinyltetramethylsiloxane, tetramethyltertavinyl tetracyclosiloxane and the like, but it is not limited by them. The content of platinum in the platinum compound is preferably 0.5 ~ 15% by weight.
The amount of catalyst for addition reaction in the present composition is preferably 0.01 ~ 1 part by weight and more preferably 0.1 ~ 0.5 part by weight, based on 100 parts by weight of polyorganosiloxane. If the amount is less than 0.01 part by weight, the addition reaction of the composition may become significantly slow, or the curing itself may not even occur. If the amount is greater than 1 part by weight, the addition reaction may become faster and thus pot life may become shorter, by which the workability may be lowered.
(E) Adhesion-imparting agent
The adhesion-imparting agent (also referred to as “component (E)”) comprised in the composition of the present invention is an ingredient meant to increase the adhesion between the silicone rubber and the woven or non-woven fabric substrate such as an airbag fabric. The present invention uses an adhesion-imparting agent comprising 1-allyl-3,5-diglycidylisocyanurate and not containing silicon. Accordingly, it is possible to provide a silicone rubber film which can maintain excellent adhesion property even upon exposure to high temperature/high humidity conditions as well as immediately after coating.
Concretely, 1-allyl-3,5-diglycidylisocyanurate comprised in the adhesion-imparting agent may be represented by the following formula 3 and structural formula 1, which is obtainable―for example, as the trade name of MA-DGIC (Shikoku Co. Ltd., Japan).
[Formula 3]
C12H15N3O5
[Structural formula 1]
Figure PCTKR2011005228-appb-I000001
As the adhesion-imparting agent, 1-allyl-3,5-diglycidylisocyanurate may be used alone or in combination with another adhesion-imparting component (organosilane compound, organotitanium compound, etc.) conventionally added for silicone rubber.
The amount of adhesion-imparting agent in the present composition is preferably 0.01 ~ 0.5 part by weight, based on 100 parts by weight of polyorganosiloxane. If the amount is less than 0.01 part by weight, the effect of improving adhesion from its addition may not be expected. If the amount is greater than 0.5 part by weight, excessive increase of viscosity and lowering of storage stability may result.
In addition to the above components, the composition of the present invention may further comprise a curing retarder (also referred to as “component (F)”). If a curing retarder is added to the addition-curable type liquid silicone rubber-coating composition together with the catalyst for addition reaction, the curing rate can be controlled smoothly. By properly adjusting the ratio of the catalyst for addition reaction and curing retarder, the workability required for specific application may be secured.
As the curing retarder, compounds having a double bond including alkenyl or a triple bond such as 1-ethynyl-1-cyclohexanol, 1,1,3,3-tetramethyl-1,3-divinyldisilazane, 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, 2-methyl-3-butyn-2-ol, etc. may be used, but it is not limited by them.
The preferable amount of curing retarder in the present composition is 0.02 ~ 0.5 part by weight, based on 100 parts by weight of polyorganosiloxane. If the amount is less than 0.02 part by weight, there may be a problem due to an overly high curing rate. If the amount is greater than 0.5 part by weight, the curing itself may not occur.
In addition to the above components, the composition of the present invention may further comprise additive(s) generally used for silicone rubber. For example, inorganic filler for improving strength and heat resistance such as fumed titanium dioxide, crystalline silica, calcium silicate, titanium dioxide, ferric oxide and carbon black; wetter for improving dispersibility including low molecular weight organosilane compound such as diorganopolysiloxane having terminal hydroxy group, diphenylsilanediol, hexaorganopolysiloxane and organoalkoxysilane; heat-resistance promoter including metal oxide such as iron oxide, cerium oxide, zinc oxide and titanium oxide, cerium silanolate and cerium fatty acid salt; flame-resistance imparting agent including platinum compound such as complexes of platinum tetrachloride, hydrogen hexachloroplatinate and hydrogen hexachloroplatinate hexahydrate with olefin or divinyldimethylpolysiloxane, alcohol solution of hydrogen hexachloroplatinate hexahydrate, etc., titanium oxide and nitrogen-containing organic compound; reaction-controlling agent for the reaction of platinum catalyst such as vinylmethylcyclopolysiloxane and acetylene alcohol; and pigment may be added in an appropriate amount as needed.
The method for preparing the present liquid silicone rubber-coating composition from the above components is not particularly limited, and the present composition may be prepared by using a conventional method in this field of art. For example, components (A) and (C) may be mixed by using a rubber kneader to prepare a base compounding, and components (B), (D) and (E) and optionally (F) if needed, and other additives may then be added thereto and mixed to prepare the present composition.
The composition of the present invention comprises polyorganosiloxane, polyorganohydrogensiloxane and reinforcing silica in an appropriate amount, and thus can form silicone rubber film having excellent mechanical properties and can be coated easily on an airbag fabric, etc. since the viscosity is usually 80 Pa·s or less.
The other aspect of the present invention provides an airbag characterized in having a cured film of the present liquid silicone rubber-coating composition formed on an airbag fabric. The liquid silicone rubber-coating composition of the present invention may be usefully applied for coating a substrate fabric of synthetic fibers, inorganic fibers, etc., in particular, for coating an airbag installed in vehicles or the like. The composition may be coated and cured by a conventional method in this field of art to form cured film on an airbag fabric. The coating amount of the composition may be adjusted properly according to the kind, use and structure of the airbag, and the curing of the composition is generally conducted at 80 ~ 250℃ for 30 seconds ~ 10 minutes.
Examples of the airbag fabric on which the composition of the present invention is coated include substrate fabrics (woven, non-woven or knitted) comprising fabric of synthetic fiber such as polyamide fiber, e.g., nylons 6, 66, 46, etc.; aramid fiber; polyester fiber, e.g., polyethyleneterephthalate; vinylon fiber; rayon fiber; polyolefin fiber; and polyetherimide fiber, or fabric of inorganic fiber such as glass fiber, carbon fiber, etc. In particular, the composition may be preferably applied for coating a nylon 66 fiber.
Since the composition of the present invention comprises the adhesion-imparting agent containing 1-allyl-3,5-diglycidylisocyanurate as the main ingredient, its excellent adhesion property can be maintained even after long-term exposure to high temperature/high humidity conditions as well as immediately after coating.
The present invention is explained in more detail by the following Examples and Comparative Examples. However, the scope of the present invention is not limited by them.
Examples 1 ~ 3 and Comparative Examples 1 ~ 3
Liquid silicone rubber-coating compositions were prepared through the following procedure (for Example 1) by using the components and amounts as shown in the following Table 1.
To obtain the base compounding, 100 parts by weight of polyorganosiloxane component (A), 32 parts by weight of reinforcing silica component (C), 8 parts by weight of hexamethyldisilazane and 2.3 parts by weight of water were mixed at room temperature for 30 minutes and then refluxed at 90 ~ 100℃ for 1 hour. After normal and reduced pressure recovery process at 140 ~ 160℃ for 2 hours, a cooling process was conducted. To the obtained silicone rubber base, 13.9 parts by weight of polyorganohydrogensiloxane component (B) as a crosslinking agent was mixed. Subsequently, adhesion-imparting agent (E) (which was not added in Comparative Example 1), 0.13 part by weight of catalyst component (D) for addition reaction and 0.08 part by weight of curing retarder component (F) were added thereto, and the mixture was agitated for 15 minutes to prepare a liquid silicone rubber-coating composition.
Evaluation of mechanical properties and adhesion
The liquid silicone rubber-coating compositions prepared in the Examples and Comparative Examples were cured in a press at 170℃ for 10 minutes to prepare rubber sheet samples with a thickness of 2 mm. The prepared samples were tested for various mechanical properties by the below methods, the results of which are provided in the following Table 1.
(1) Viscosity: Measured at 25℃ by using a Cone & Plate type viscometer
(2) Hardness: Measured according to ASTM D 2240
(3) Specific gravity: Measured according to ASTM D 792
(4) Tensile strength and elongation: Measured according to ASTM D 412
(5) Tearing strength: Measured according to ASTM D 624B
Meanwhile, in order to evaluate the adhesion to an airbag fabric, the compositions were coated on an airbag fabric of nylon 66 by using a coating bar. After curing at 150℃ for 2 minutes, flex abrasion and peel resistance directly after the coating and after aging were measured by the below methods, the results of which are provided in the following Table 1. The aging was conducted by keeping the samples under the high temperature/high humidity conditions of 80℃ and 95％ relative humidity for 240 hours.
(1) Flex abrasion: Measured according to ISO 5981
(2) Peel resistance: Measured according to ASTM D 1876
Table 1
Figure PCTKR2011005228-appb-T000001
As can be seen from the above Table 1, in case of the Examples, mechanical properties such as tensile strength and elongation generally required for silicone rubbers and low viscosity were satisfied, and excellent adhesion to the airbag fabric was maintained immediately after the coating and even after the high temperature/high humidity test. To the contrary, in case of the Comparative Examples, the adhesion to the airbag fabric was significantly lowered after the high temperature/high humidity test.

Claims (12)

  1. A liquid silicone rubber-coating composition comprising:
    (A) polyorganosiloxane containing two or more alkenyl groups per molecule;
    (B) polyorganohydrogensiloxane containing hydrogen in the side chain of the molecule;
    (C) reinforcing silica;
    (D) catalyst for addition reaction; and
    (E) adhesion-imparting agent comprising 1-allyl-3,5-diglycidylisocyanurate.
  2. The liquid silicone rubber-coating composition according to claim 1, wherein the polyorganosiloxane component (A) is a linear polyorganosiloxane represented by the following formula 1:
    [Formula 1]
    R-Si(CH3)2O(R1 2SiO)nSi(CH3)2-R
    in which R represents an unsaturated aliphatic hydrocarbyl group; R1 represents a saturated aliphatic hydrocarbyl group, unsaturated aliphatic hydrocarbyl group or aromatic hydrocarbyl group; and n denotes an integer of 50 ~ 250.
  3. The liquid silicone rubber-coating composition according to claim 2, wherein the polyorganosiloxane component (A) contains alkenyl groups with a ratio of 0.001 ~ 5 mmol/g in one or more of both terminus and side chain.
  4. The liquid silicone rubber-coating composition according to claim 1, wherein the alkenyl group contained in the polyorganosiloxane component (A) is vinyl group.
  5. The liquid silicone rubber-coating composition according to claim 1, wherein the polyorganosiloxane component (A) has a viscosity of 100 ~ 150,000 mPa·s at 25℃.
  6. The liquid silicone rubber-coating composition according to claim 1, wherein the polyorganohydrogensiloxane component (B) is represented by the following formula 2:
    [Formula 2]
    R2-Si(CH3)2O(R2HSiO)m(R2 2SiO)nSi(CH3)2-R2
    in which each of R2 independently represents a saturated aliphatic hydrocarbyl group or aromatic hydrocarbyl group; and each of m and n independently denotes an integer of 10 ~ 100.
  7. The liquid silicone rubber-coating composition according to claim 6, wherein the polyorganohydrogensiloxane component (B) contains hydrogen with a ratio of 0.1 ~ 20 mmol/g in the side chain of the molecule.
  8. The liquid silicone rubber-coating composition according to claim 1, wherein the reinforcing silica (C) has a specific surface area of 50 ~ 400 ㎡/g by BET method.
  9. The liquid silicone rubber-coating composition according to claim 1, wherein the catalyst component (D) for addition reaction is a platinum compound.
  10. The liquid silicone rubber-coating composition according to claim 1, further comprising (F) curing retarder.
  11. The liquid silicone rubber-coating composition according to claim 10, comprising, based on 100 parts by weight of polyorganosiloxane (A):
    (B) 1 ~ 30 parts by weight of polyorganohydrogensiloxane;
    (C) 10 ~ 50 parts by weight of reinforcing silica;
    (D) 0.01 ~ 1 part by weight of catalyst for addition reaction;
    (E) 0.01 ~ 0.5 part by weight of adhesion-imparting agent; and
    (F) 0.02 ~ 0.5 part by weight of curing retarder.
  12. An airbag having a cured film of the liquid silicone rubber-coating composition according to any one of claims 1 to 11 formed on an airbag fabric.
PCT/KR2011/005228 2011-01-20 2011-07-15 Liquid silicone rubber coating composition and airbag with cured film thereof WO2012099305A1 (en)

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JP2021181522A (en) * 2020-05-18 2021-11-25 信越化学工業株式会社 Liquid silicone rubber coating agent composition
US11530333B2 (en) 2016-12-26 2022-12-20 Akzo Nobel Coatings International B.V. Coating composition system, the preparation method, and the use thereof

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JP2002138249A (en) * 2000-11-01 2002-05-14 Dow Corning Toray Silicone Co Ltd Liquid silicone rubber coating material composition
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JP2001287610A (en) * 2000-04-07 2001-10-16 Asahi Kasei Corp Coating composition for air bag, and air bag
JP2002138249A (en) * 2000-11-01 2002-05-14 Dow Corning Toray Silicone Co Ltd Liquid silicone rubber coating material composition
JP2006137800A (en) * 2004-11-10 2006-06-01 Shin Etsu Chem Co Ltd Addition reaction-curable silicone rubber adhesive composition for polymer electrolyte fuel cell and polymer electrolyte fuel cell using the composition
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JP2015110694A (en) * 2013-12-06 2015-06-18 サンユレック株式会社 Silicone resin composition
US11530333B2 (en) 2016-12-26 2022-12-20 Akzo Nobel Coatings International B.V. Coating composition system, the preparation method, and the use thereof
JP2021181522A (en) * 2020-05-18 2021-11-25 信越化学工業株式会社 Liquid silicone rubber coating agent composition
JP7353235B2 (en) 2020-05-18 2023-09-29 信越化学工業株式会社 Liquid silicone rubber coating composition

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