Silicone coatings

Abstract

This disclosure relates to an unscoured airbag fabric hydrosilylation curable silicone rubber coating composition, a method for coating an unscoured airbag fabric with said composition and an unscoured airbag fabric coated with said composition.

Description

[0001] SILICONE COATINGS

[0002] This disclosure relates to an unscoured airbag fabric hydrosilylation curable silicone rubber coating composition, a method for coating an unscoured airbag fabric with said composition and an unscoured airbag fabric coated with said composition.

[0003] Inflatable safety restraint devices, especially airbags are widely used to cushion vehicle occupants in the event of collisions and accidents. They are designed to protect drivers and passengers from being injured between an initial impact and further impacts, by their inflation in within 0.02-0.12 seconds of the initial impact during a traffic accident. They generally consist of a textile or fabric (hereafter referred to as a fabric) bag (sometimes referred to as a cushion), a sensor and a means of inflation. In the event of an accident, a sensor within a vehicle identifies an abnormal deceleration and triggers the inflator causing an effectively immediate inflation of the airbag. Expanding gases travel through conduits and inflate the airbag(s), to cushion the vehicle occupant (driver or passenger) to protect them from any further harmful impact within the interior of the vehicle, e.g., a car.

[0004] The airbags may be made from flat fabric pieces which are coated and then sewn together to provide sufficient mechanical strength or may be woven in one piece (generally referred to as “one-piece woven” or OPW) with integrally woven seams.

[0005] Airbag fabric is typically made from woven polyester yarns such as polyethylene terephthalate (PET) or woven polyamide yams such as nylon-6, 6. Prior to weaving the airbag fabric, the e.g., polyester or polyamide yarn is coated with one or more sizing and / or spin finishing agents to aid in high-speed weaving processes.

[0006] Sizing agents are applied to tire polyester or polyamide yarn prior to tire weaving process to function as a protective coating to change the absorption and wear' characteristics of initially the yarn and subsequently the woven fabric. Spin finishing agents are utilised on, for example, polyester and / or polyamide yarns and fibres at the last stage of the fibre production. They are used to form thin uniform coatings on the fibre surface to e.g., reduce surface friction and flexural rigidity of the, in the present case, airbag fabric material. Spin finishing agents may include a variety of ingredients such as, but not limited to, lubricants, emulsifiers, antistatic agents, bactericides and antioxidants.

[0007] Traditionally once the airbag fabric has been woven the sizing agents and spin finishing agents are removed from the yarn surfaces by a scouring process (sometimes referred to as a de-sizing process). The scouring process involves the fabric being washed and heated in a process to remove the sizing agents and spin finishing agents. Scouring removes soluble and insoluble impurities found in fabrics as natural, added and adventitious impurities: for example, oils, waxes, fats, vegetable matter, as well as dirt. Removing these contaminants through scouring prepares the fabric for additional processes, in particular in the case of airbag materials coating processes.

[0008] Airbags and / or airbag fabrics benefit from the application of silicone coatings in a number of ways. These include:

[0009] 1) improved thermal protection from hot gases and particulates (600°C to l,000°C) generated during airbag expansion using for pyrotechnic generators; 2) improved flame-resistance of fabric;

[0010] 3) improved resistance to bag deflation;

[0011] 4) improved resistance to stresses when airbag cushions deployed; and

[0012] 5) the softness and lightness of silicone coating provide airbags with very good flexibility, enabling them to be folded into a more compact module.

[0013] Silicone coatings used on airbags are not only designed to prevent air leakage but are also designed to keep the airbags flexible and resistant to temperature fluctuations, aging and abrasion. They need such properties because, for example, an airbag may remain unused for an extended period of time before a collision triggers deployment. This requires the silicone coating to be very stable over time in order to prevent the airbag from becoming stuck and to ensure smooth deployment even after many years.

[0014] Furthermore, in order to remain functional throughout the lifetime of the vehicle in which they are stored they need to be strongly adhered to the textile and / or fabric with which the airbag is made.

[0015] Ideally, the scouring step would be eliminated completely because it is resource (water, energy, and time) intensive and has negative environmental and economic consequences. However, the sizing and / or spin finishing agents with which the yarn is treated before weaving are typically detrimental to adhesion of the silicone coating(s) onto the resulting airbag fabric.

[0016] However, the adhesion of silicone coatings to unscoured airbag fabric i.e., with a surface covered in residual spinning and sizing agents is poor and unable to meet airbag safety requirements, as necessitated by industry standards e.g., scrub resistance test methods for coatings, particularly after prolonged exposure to heat and humidity.

[0017] Sewn flat fabric airbags are generally assembled with tire coated fabric surface at tire inside of the airbag but may be coated on tire insider and / or outside. One-piece woven airbags are coated on the outside of the airbag. Some airbags are designed to retain gas pressure after deployment, so they remain inflated for longer periods of time after a collision or the like, e.g., side-curtain airbags. These tend to be, but are not exclusively, one-piece woven airbags.

[0018] Today, it is generally compulsory to have several airbags in vehicles as a means of providing safety to the occupants in the event of a collision. They include frontal airbags, front-centre airbags, side airbags, side-curtain airbags, thorax airbags, and / or knee airbags. Typically, the airbags are concealed within the vehicle trim to be invisible during normal vehicle operation.

[0019] For example, frontal airbags may be installed in the steering wheel on the driver's side of car and in the dashboard on the passenger side of a car. They are provided to function as a cushion at a point of impact especially in collisions with the front or back of the vehicle. They exhibit relatively high air permeabilities to allow the expanded airbag to quickly deflate after the initial impact. Typically, these airbags are flat fabric pieces sewn together.

[0020] Side-curtain airbags are increasingly utilized and are most often mounted within the headliner above the doors and windows and deploy along the side window from the vicinity of the ceiling to protect vehicle occupants from a side collision and consequent rollover incidents (where the vehicle tips over onto its side or upside-down or flips over more than once). Because of this, side -curtain airbags, are designed to retain their inflated state for a long duration (for example, exhibiting a retention of at least 50% of the initial pressure after 5 seconds subsequent to high pressure inflation) i.e., they need to retain large amounts of gas, as well as high gas pressures, throughout the longer time periods of the entire potential rollover. They generally unroll from packing containers stored within the roofline along the side windows of an automobile (and thus have a back and front side only). Side-curtain airbags therefore not only provide cushioning effects but also provide protection from broken glass and other debris.

[0021] One-piece woven type airbags are usually (but not exclusively) used for side-curtain airbags in order to provide the low permeability (and thus longer gas escape times) necessary for side-curtain airbags. Consequently, hydrosilylation curable silicone rubber coating compositions for treating textiles and fabrics often contain adhesion promoters to enhance adhesion between the coating and the textile / fabric to which they have been applied.

[0022] Development of new adhesion packages for liquid silicone rubber airbag coatings that maintain strong adhesion to unscoured fabrics even after exposure to heat and humidity would bring both economic and environmental benefits.

[0023] There is provided herein an unscoured airbag fabric hydrosilylation curable silicone rubber coating composition comprising:

[0024] a) an organopolysiloxane polymer having a zero-shear viscosity of between 100 and 200,000mPa.s inclusive at 25 °C, and at least two unsaturated groups per molecule, which unsaturated groups are selected from alkenyl groups, alkynyl groups or a mixture thereof;

[0025] b) optionally one or more fillers;

[0026] c) an organosilicon compound having at least two, or at least three Si-H groups per molecule;

[0027] d) a hydrosilylation cure catalyst;

[0028] e) an adhesion promoter comprising or consisting of an organosiloxane having (i) at least two epoxy groups, (ii) at least two alkenyl groups and (iii) at least two alkoxy groups; and

[0029] f) a chelated metal condensation catalyst wherein the metal is selected from one or more of titanium, zirconium, aluminum, vanadium, chromium, scandium, manganese, iron, cobalt, nickel, copper and zinc. There is also provided herein a coated unscoured airbag fabric comprising a unscoured airbag fabric coated with the cured product of an unscoured airbag fabric hydrosilylation curable silicone rubber coating composition comprising:

[0030] a) an organopolysiloxane polymer having a zero-shear viscosity of between 100 and 200,000mPa.s inclusive at 25 °C, and at least two unsaturated groups per molecule, which unsaturated groups are selected from alkenyl groups, alkynyl groups or a mixture thereof;

[0031] b) optionally one or more fillers;

[0032] c) an organosilicon compound having at least two or at least three Si-H groups per molecule;

[0033] d) a hydrosilylation cure catalyst;

[0034] e) an adhesion promoter comprising or consisting of an organosiloxane having (i) at least two epoxy groups, (ii) at least two alkenyl groups and (iii) at least two alkoxy groups; and f) a chelated metal condensation catalyst wherein the metal is selected from one or more of titanium, zirconium, aluminum, vanadium, chromium, scandium, manganese, iron, cobalt, nickel, copper and zinc. There is also provided herein a method of coating unscoured airbag fabric with an unscoured airbag fabric hydrosilylation curable silicone rubber coating composition comprising the steps of mixing the components of the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition: comprising

[0035] a) an organopolysiloxane polymer having a zero-shear viscosity of between 100 and 200,000mPa.s inclusive at 25 °C, and at least two unsaturated groups per molecule, which unsaturated groups are selected from alkenyl groups, alkynyl groups or a mixture thereof;

[0036] b) optionally one or more fillers;

[0037] c) an organosilicon compound having at least two or at least three Si-H groups per molecule;

[0038] d) a hydrosilylation cure catalyst;

[0039] e) an adhesion promoter comprising or consisting of an organosiloxane having (i) at least two epoxy groups, (ii) at least two alkenyl groups and (iii) at least two alkoxy groups; and

[0040] f) a chelated metal condensation catalyst wherein the metal is selected from one or more of titanium, zirconium, aluminum, vanadium, chromium, scandium, manganese, iron, cobalt, nickel, copper and zinc; by applying tire unscoured airbag fabric hydrosilylation curable silicone rubber coating composition onto an unscoured airbag fabric and curing tire composition to form an unscoured airbag fabric.

[0041] There is also provided a use of

[0042] e) an adhesion promoter comprising or consisting of an organosiloxane having (i) at least two epoxy groups, (ii) at least two alkenyl groups and (iii) at least two alkoxy groups; and

[0043] f) a chelated metal condensation catalyst wherein the metal is selected from one or more of titanium, zirconium, aluminum, vanadium, chromium, scandium, manganese, iron, cobalt, nickel, copper and zinc; in an unscoured airbag fabric hydrosilylation curable silicone rubber coating composition for coating an unscoured airbag fabric which composition otherwise comprises:

[0044] a) an organopolysiloxane polymer having a zero-shear viscosity of between 100 and 200,000mPa.s inclusive at 25 °C, and at least two unsaturated groups per molecule, which unsaturated groups are selected from alkenyl groups, alkynyl groups or a mixture thereof;

[0045] b) optionally one or more fillers;

[0046] c) an organosilicon compound having at least two or at least three Si-H groups per molecule;

[0047] d) a hydrosilylation cure catalyst;

[0048] to enhance adhesion of the coating onto the surface of an unscoured airbag fabric.

[0049] Components (e) and (f) enhance adhesion of the coating onto the surface of an unscoured airbag fabric. The unscoured airbag fabric hydrosilylation curable silicone rubber coating compositions comprise the following components:

[0050] Component (a)

[0051] Component (a) of the unscoured airbag fabric hydrosilylation curable silicone rubber coating compositions is one or more organopolysiloxane polymers having a zero-shear viscosity of between 100 and 200,000mPa.s inclusive at 25 °C, and at least two unsaturated groups per molecule, which unsaturated groups are selected from alkenyl groups, alkynyl groups or a mixture thereof. Each organopolysiloxane polymer of component (a) comprises multiple siloxy units, of formula (I):

[0052] R’aSiO(4-aV2 (I)

[0053] The subscript “a” is 0, 1, 2 or 3.

[0054] Siloxy units may be described by a shorthand (abbreviated) nomenclature, namely - " M," " D," " T," and " Q", when R’ is as described above, alternatively an alkyl group, typically a methyl group. The M unit corresponds to a siloxy unit where a = 3, that is R’aSiOin; the D unit corresponds to a siloxy unit where a = 2, namely R’^SiC, the T unit corresponds to a siloxy unit where a = 1, namely R’iSiOsn; the Q unit corresponds to a siloxy unit where a = 0, namely SiO4 / 2. The organopolysiloxane polymer of component (a) is substantially linear but may contain a proportion of branching due to the presence of T units (as previously described) within the molecule, hence the average value of a in structure (I) is about 2.

[0055] The unsaturated groups of component (a) may be positioned either terminally or pendently on the organopolysiloxane polymer, or in both locations. The unsaturated groups of component (a) may be alkenyl groups or alkynyl groups as described above. Each alkenyl group, when present, may comprise for example from 2 to 30, alternatively 2 to 24, alternatively 2 to 20, alternatively 2 to 12, alternatively 2 to 10, and alternatively 2 to 6 carbon atoms. When present tire alkenyl groups may be exemplified by, but not limited to, vinyl, allyl, methallyl, propenyl, isopropenyl, butenyl, and hexenyl and cyclohexenyl groups. Each alkynyl group, when present, may also have 2 to 30, alternatively 2 to 24, alternatively 2 to 20, alternatively 2 to 12, alternatively 2 to 10, and alternatively 2 to 6 carbon atoms. Examples of alkynyl groups may be exemplified by, but not limited to, ethynyl, propynyl, and butynyl groups. Preferred examples of the unsaturated groups of component (a) include vinyl, propenyl, isopropenyl, butenyl, allyl, and 5-hexenyl.

[0056] In formula (I), each R’, other than tire unsaturated groups described above, is independently selected from an aliphatic hydrocarbyl group, a substituted aliphatic hydrocarbyl group, an aromatic group or a substituted aromatic group. Each aliphatic hydrocarbyl group may be exemplified by, but not limited to, alkyl groups having from 1 to 20 carbons per group, alternatively 1 to 15 carbons per group, alternatively 1 to 12 carbons per group, alternatively 1 to 10 carbons per group, alternatively 1 to 6 carbons per group or cycloalkyl groups such as cyclohexyl. Specific examples of alkyl groups may include methyl, ethyl, propyl, pentyl, octyl, undecyl, and octadecyl groups, alternatively methyl and ethyl groups. Substituted aliphatic hydrocarbyl group are preferably non-halogenated substituted alkyl groups.

[0057] The aliphatic non-halogenated organyl groups are exemplified by, but not limited to alkyl groups as described above with a substituted group such as suitable nitrogen containing groups such as amido groups, imido groups; oxygen containing groups such as polyoxyalkylene groups, carbonyl groups, alkoxy groups and hydroxyl groups. Further organyl groups may include sulfur containing groups, phosphorus containing groups, boron containing groups. Examples of aromatic groups or substituted aromatic groups are phenyl groups and substituted phenyl groups with substituted groups as described above. Component (a) may, for example, be selected from polydimethylsiloxanes, alkylmethylpolysiloxanes, alkylarylpoly siloxanes or copolymers thereof (where reference to alkyl means any suitable alkyl group, alternatively an alkyl group having two or more carbons) providing each polymer has a zero-shear viscosity of organopolysiloxane polymer (a) should be between 100 and 200,000mPa.s inclusive at 25 °C. Hence component (a) may, for the sake of example, be:

[0058] a dialkylalkenyl terminated polydimethylsiloxane, e.g., dimethylvinyl terminated polydimethylsiloxane; a dialkylalkenyl terminated dimethylmethylphenylsiloxane, e.g., dimethylvinyl terminated dimethylmethylphenylsiloxane; a trialkyl terminated dimethylmethylvinyl polysiloxane; a dialkylvinyl terminated dimethylmethylvinyl polysiloxane copolymer; a dialkylvinyl terminated methylphenylpolysiloxane, a dialkylalkenyl terminated methylvinylmethylphenylsiloxane; a dialkylalkenyl terminated methylvinyldiphenylsiloxane; a dialkylalkenyl terminated methylvinyl methylphenyl dimethylsiloxane; a trimethyl terminated methylvinyl methylphenylsiloxane; a trimethyl terminated methylvinyl diphenylsiloxane; or a trimethyl terminated methylvinyl methylphenyl dimethylsiloxane.

[0059] In each case component (a) The zero-shear viscosity of organopolysiloxane polymer (a) should be between 100 and 200,000mPa.s inclusive at 25 °C, alternatively from 1000 to 150,000mPa.s at 25 °C, alternatively, from lOOOmPa.s to 125,000mPa.s, alternatively from lOOOmPa.s to 100,000mPa.s at 25 °C. Unless otherwise indicated all viscosity measurement given are zero-shear viscosity (i]0) values, obtained by extrapolating to zero the value taken at low shear rates (or simply taking an average of values) in the limit where tire viscosity-shear rate curve is rate-independent, which is a test-method independent value provided a suitable, properly operating rheometer is used. For example, the zero-shear viscosity of a substance at 25 °C may be obtained by using commercial rheometers such as an Anton-Parr MCR-301 rheometer or a TA Instruments AR-2000 rheometer equipped with cone-and-plate fixtures of suitable diameter to generate adequate torque signal at a series of low shear rates, such as 0.01 s’1, 0.1 s'1and 1.0 s’1while not exceeding the torque limits of the transducer.

[0060] Typically, the alkenyl and / or alkynyl content, e.g., vinyl content of the polymer is from 0.01 to 3 % for each organopolysiloxane polymer containing at least two silicon-bonded alkenyl groups per molecule of component (a), alternatively from 0.01 to 2.5 % of component (a), alternatively from 0.001 to 2.0 %, alternatively from 0.01 to 1.5 % of component (a) of the or each organopolysiloxane polymer containing at least two unsaturated groups per molecule, which unsaturated groups are selected from alkenyl groups, alkynyl groups or a mixture thereof per molecule of component (a). The alkenyl / alkynyl content of component (a) is determined using quantitative infra-red analysis in accordance with ASTM E168. Component (a) may be present in the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition in an amount of from 40 wt. % to about 80 wt. % of the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition, alternatively from 45 to 80 wt. % of the composition, alternatively from 50 to 80 wt. % of the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition. Typically, component (a) is present in an amount which is the difference between 100 wt. % and the cumulative wt. % of the other components / ingredients of the composition.

[0061] Optional Component (b)

[0062] Component (b) of the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition is optional and when present is one or more fillers. When present, the fillers may comprise one or more reinforcing fillers, one or more non-reinforcing fillers, one or more flame retardant fillers or a mixture thereof.

[0063] When present, component (b) may comprise one or more reinforcing fillers, the reinforcing fillers may comprise fumed silica, precipitated silica or a mixture thereof. Finely divided forms of silica are preferred. Reinforcing silica fillers typically have a relatively high surface area, typically at least 50 m2 / g (BET method in accordance with ISO 9277: 2010) are utilized. For example, fillers, (e.g., fumed silica) having surface areas of from 50-450m2 / g, alternatively, 50 -400m2 / g m2 / g, alternatively from 50 to 300 m2 / g, alternatively 100 - 300m2 / g (BET method in accordance with ISO 9277: 2010) are typically used. Typically, such reinforcing filler(s) is / are naturally hydrophilic (e.g., untreated) silica fillers, and are therefore treated with a treating agent to render it / them hydrophobic. These surface modified reinforcing fillers do not clump and can be homogeneously incorporated into organopoly siloxane polymer (a), as tire surface treatment makes the fillers easily wetted by organopoly siloxane polymer (a).

[0064] Typically, said reinforcing fillers may be surface treated with any low molecular weight organosilicon compounds disclosed in the art applicable to prevent creping of organosiloxane compositions during processing. For example, they may be heated with organosilanes, polydiorganosiloxanes, organosilazanes, short chain siloxane diols, fatty acids or fatty acid esters such as stearates. Once heated the fillers are rendered hydrophobic and consequently easier to handle and to obtain a homogeneous mixture with hie other ingredients, particularly component (a). Specific examples of heating agents include but are not restricted to silanol terminated trifluoropropylmethyl siloxane, silanol terminated vinylmethylsiloxane, tetramethyldi(trifluoropropyl)disilazane, tetramethyldi vinyl disilazane, hexamethyl disilazane (HMDZ), silanol terminated MePh siloxane, liquid hydroxyl-terminated polydiorganosiloxane containing an average from 2 to 20 repeating units of diorganosiloxane in each molecule, hexaorganodisiloxane, hexaorganodisilazane. A small amount of water can be added together with the silica heating agent(s) as a processing aid.

[0065] The reinforcing silica fillers may be pre-heated prior to introduction into the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition r may be heated in situ (i.e., in the presence of at least a portion of the other ingredients of the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition herein by blending these ingredients together at room temperature or above until the filler is completely treated. Typically, when present untreated reinforcing filler is treated in situ with a treating agent in the presence of organopolysiloxane polymer (a) which results in the preparation of a silicone rubber base material which can subsequently be mixed with other ingredients.

[0066] When present in or as component (b), Hie reinforcing filler(s) is / are present in the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition in an amount of from 1.0 to 50wt. %. of the composition, alternatively of from 1 to 30wt. %. of the composition, alternatively of from 2.5 to 30wt. %. of tire composition, alternatively of from 3.5 to 25 wt. %. of the composition.

[0067] The one or more fillers of component (b) may alternatively or also include one of more non-reinforcing fillers such as, for example, crushed quartz, diatomaceous earths, barium sulphate, iron oxide, precipitated calcium carbonate, ground calcium carbonate, titanium dioxide and carbon black, talc and wollastonite. Other fillers which might be used alone or in addition to the above include aluminite, calcium sulphate (anhydrite), gypsum, calcium sulphate, magnesium carbonate, clays such as kaolin, magnesium hydroxide e.g., brucite, graphite, copper carbonate, e.g., malachite, nickel carbonate, e.g., zarachite, barium carbonate, e.g., witherite and / or strontium carbonate e.g., strontianite.

[0068] Other non-reinforcing fillers may include silicates from the group consisting of olivine group; garnet group; aluminosilicates; ring silicates; chain silicates; and sheet silicates. The olivine group comprises silicate minerals, such as but not limited to, forsterite and Mg2SiO4. The garnet group comprises ground silicate minerals, such as but not limited to, pyrope; Mg3Al2Si3O12; grossular; and Ca3Al2Si3O12.

[0069] Aluminosilicates comprise ground silicate minerals, such as but not limited to, sillimanite; Al2SiO5 mullite; 3Al2O3·2SiO2; kyanite; and AhSiOs. Ring silicates may be utilized as non-reinforcing fillers, these include silicate minerals, such as but not limited to, cordierite and Al3(Mg, Fe)2[Si4AlO18]. The chain silicates group comprises ground silicate minerals, such as but not limited to, wollastonite and Ca[SiO3]. Sheet silicates may alternatively or additionally be used as non-reinforcing fillers where appropriate group comprises silicate minerals, such as but not limited to, mica; KAl2[Si3AlO10](OH)2 pyrophyllite; Al2[Si4O10](OH)2; talc; Mg3[Si4O10](OH)2 serpentine for example, asbestos; Kaolinite; Al4[Si4O10](OH)8; and vermiculite. Such non-reinforcing may be hydrophobically treated in a similar' fashion to the reinforcing fillers described above if desired or required.

[0070] A small amount of water can be added together with the treating agent(s) as a processing aid.

[0071] Component (c)

[0072] Component (c) of the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition functions as a cross-linker and is provided in the form of an organosilicon compound having an average of at least two or an average of at least three Si-H groups per molecule. The molecular configuration of the organosilicon compound having an average of at least two or an average of at least three Si-H groups per molecule (c) is not specifically restricted, and it can be a silane or a straight chain, branched (a straight chain with some branching through the presence of T units) or cyclic siloxane polymer or be silicone resin based.

[0073] Component (c) is typically a linear or branched siloxane or a silicone resin. Component (c) normally contains an average of three or more silicon-bonded hydrogen atoms so that the silicon bonded hydrogen atoms can react with the unsaturated groups (alkenyl and / or alkynyl groups) of component (a) and / or the rest of the composition to form a network structure therewith and thereby cure the composition. Some or all of Component (c) may alternatively have an average of two silicon bonded hydrogen atoms per molecule. However, such a molecule is only used as the sole cross-linker when e.g., polymer (a) has greater than two unsaturated groups per molecule in which case a network can be produced during the cure process. Otherwise, when component (c) partially comprises molecules having an average of two silicon bonded hydrogen atoms per molecule, said molecules may function as a chain extender.

[0074] While the molecular weight of component (c) is not specifically restricted, the viscosity may be measured as described above in respect to component (a). However, in the case of very low viscosities they may be measured using a glass capillary viscometer in accordance with ASTM D-445.

[0075] Silicon-bonded organic groups used in component (c) may be exemplified by alkyl groups such as methyl, ethyl, propyl, n-butyl, t-butyl, pentyl, hexyl; aryl groups such as phenyl tolyl, xylyl, or similar aryl groups; 3-chloropropyl, 3, 3,3 -tri fluoropropyl, or similar halogenated alkyl group, preferred alkyl groups having from 1 to 6 carbons, especially methyl ethyl or propyl groups or phenyl groups.

[0076] Preferably the silicon-bonded organic groups used in component (c) are alkyl groups, alternatively methyl, ethyl or propyl groups.

[0077] Examples of the organosilicon compound having an average of at least two or at an average of least three Si-H groups per molecule (c) include but are not limited to:

[0078] (a’) trimethylsiloxy-terminated methylhydrogenpolysiloxane,

[0079] (b’) trimethylsiloxy-terminated polydimethylsiloxane-methylhydrogensiloxane,

[0080] (c’) dimethylhydrogensiloxy-terminated dimethylsiloxane-methylhydrogensiloxane copolymers, (d’) dimethylsiloxane-methylhydrogensiloxane cyclic copolymers,

[0081] (e’) copolymers and / or silicon resins consisting of (Cl Ohl ISiOi / i units, (Cl Ij SiO n units and SiO4 / 2 units,

[0082] (f’) copolymers and / or silicone resins consisting of (CH; )4HS i 01 / 2 units and SiO4 / 2 units,

[0083] (g’) Methylhydrogensiloxane cyclic homopolymers having between 3 and 10 silicon atoms per molecule;

[0084] (h’) an Si-H terminated methylhydrosiloxane-phenylmethylsiloxane co-polymer having a zero-shear viscosity of from 50 to 300 cSt and 30 to 75 mol % of phenylmethylsiloxane units.

[0085] alternatively, component (c), the cross-linker, may be a filler, e.g., silica treated with one of the above, and mixtures thereof.

[0086] In one embodiment the Component (c) is selected from a methylhydrogenpolysiloxane capped at both molecular terminals with trimethylsiloxy groups; a copolymer of a methylhydrogensiloxane and a dimethylsiloxane capped at both molecular terminals with trimethylsiloxy groups; dimethylsiloxane capped at both molecular terminals with dimethylhydrogensiloxy groups; a copolymer of a methylhydrogensiloxane and a dimethylsiloxane capped at both molecular terminals with dimethylhydrogensiloxy groups.

[0087] The cross-linker (c) is generally present in the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition such that the molar ratio of the silicon-bonded hydrogen atoms in component (c) to the total unsaturated groups selected from alkenyl and / or alkynyl groups in the composition is from 0.5:1 to 20:1. When this ratio is less than 0.5:1, a well-cured composition will not be obtained. When the ratio exceeds 20:1, there is a tendency for the hardness of the cured unscoured airbag fabric hydrosilylation curable silicone rubber coating composition to increase when heated. The molar ratio of silicon-bonded hydrogen atoms of component (c) to total unsaturated groups selected from alkenyl and / or alkynyl groups in the organopolysiloxane (a) is preferably at least 1:1 and can be up to 8:1 or 10:1. Most preferably the molar ratio of Si-H groups to aliphatically unsaturated groups is in the range from 1.1:1 to 5:1.

[0088] The silicon-bonded hydrogen (Si-H) content of component (c) is determined using quantitative infra-red analysis in accordance with ASTM E 168. In die present instance the silicon-bonded hydrogen to alkenyl (vinyl) and / or alkynyl ratio is important when relying on a hydrosilylation cure process. Generally, this is determined by calculating the total weight % of alkenyl groups in the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition e.g., vinyl [V] and the total weight % of silicon bonded hydrogen [H] in the composition and given the molecular weight of hydrogen is 1 and of vinyl is 27 the molar ratio of silicon bonded hydrogen to vinyl is 27[H] / [V].

[0089] Typically, dependent on the number of unsaturated groups in component (a) and the rest of the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition as well as the number of Si-H groups in component (c), component (c) will be present in an amount of from 0.1 to 15 wt. % of the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition, alternatively 0.1 to 12.5 wt. % of the composition, alternatively 0.25 to 12.5wt. %, further alternatively from 2.5 wt. % to 12.5 wt. % of the composition, alternatively from 2.5 wt. % to 10 wt. % of the composition.

[0090] (d) Hydrosilylation catalyst

[0091] Component (d) of the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition is a hydrosilylation catalyst comprising or consisting of a platinum group metal or a compound thereof. These are usually selected from catalysts of tire platinum group of metals (platinum, ruthenium, osmium, rhodium, iridium and palladium), or a compound of one or more of such metals.

[0092] Alternatively, platinum and rhodium compounds are preferred due to tire high activity level of these catalysts in hydrosilylation reactions, with platinum compounds most preferred. In a hydrosilylation (or addition) reaction, a hydrosilylation catalyst such as component (d) herein catalyses tire reaction between an unsaturated group, usually an alkenyl group e.g., vinyl with Si-H groups.

[0093] The hydrosilylation catalyst of component (d) can be a platinum group metal, a platinum group metal deposited on a carrier, such as activated carbon, metal oxides, such as aluminum oxide or silicon dioxide, silica gel or powdered charcoal, or a compound or complex of a platinum group metal. Preferably the platinum group metal is platinum.

[0094] Examples of preferred hydrosilylation catalysts of component (d) are platinum based catalysts, for example, platinum black, platinum oxide (Adams catalyst), platinum on various solid supports, chloroplatinic acids, e.g., hexachloroplatinic acid (Pt oxidation state IV) (Speier catalyst), chloroplatinic acid in solutions of alcohols e.g., isooctanol or amyl alcohol (Lamoreaux catalyst), and complexes of chloroplatinic acid with ethylenically unsaturated compounds such as olefins and organosiloxanes containing ethylenically unsaturated silicon-bonded hydrocarbon groups, e.g., tetra-vinyl-tetramethylcyclotetrasiloxane-platinum complex (Ashby catalyst). Soluble platinum compounds that can be used include, for example, the platinumolefin complexes of the formulae (PtCl2.(olefin))2 and H(PtCl3. olefin), preference being given in this context to the use of alkenes having 2 to 8 carbon atoms, such as ethylene, propylene, isomers of butene and of octene, or cycloalkanes having 5 to 7 carbon atoms, such as cyclopentene, cyclohexene, and cycloheptene. Other soluble platinum catalysts are, for the sake of example a platinum-cyclopropane complex of the formula (PtCl₂C₃H₆)₂, the reaction products of hexachloroplatinic acid with alcohols, ethers, and aldehydes or mixtures thereof, or the reaction product of hexachloroplatinic acid and / or its conversion products with vinyl-containing siloxanes such as methylvinylcyclotetrasiloxane in the presence of sodium bicarbonate in ethanolic solution. Platinum catalysts with phosphorus, sulfur, and amine ligands can be used as well, e.g., (Ph₃P)₂PtCl₂ and complexes of platinum with vinylsiloxanes, such as sym-divinyltetramethyldisiloxane (Karstedt’s catalyst).

[0095] Hence, specific examples of suitable platinum-based catalysts of component (d) include:

[0096] (i’) complexes of chloroplatinic acid with organosiloxanes containing ethylenically unsaturated hydrocarbon groups are described in US 3,419,593;

[0097] (if) chloroplatinic acid, either in hexahydrate form or anhydrous form;

[0098] (iii’) a platinum-containing catalyst which is obtained by a method comprising reacting chloroplatinic acid with an aliphatically unsaturated organosilicon compound, such as divinyltetramethyldisiloxane;

[0099] (iv’) alkene-platinum-silyl complexes as described in US Pat. No. 6,605,734 such as (COD)Pt(SiMeC12)2 where “COD” is 1,5 -cyclooctadiene;

[0100] (v’) Karstedt’s catalyst is a Pt₂(divinyl tetramethyl disiloxane)₃ complex typically containing from 30 to 50 wt. % platinum metal in tire complex. It is typically introduced into a silicone rubber composition in a premix with a vinyl siloxane polymer. The combination being from about from 0.25 to 2.0 wt. % of the catalyst complex in 99.75 wt. % to 98 wt. % of the vinyl siloxane polymer which usually has a zero-shear viscosity of from about 200 to 750 mPa.s. Solvents such as toluene and the like organic solvents have been used historically as alternatives but the use of vinyl siloxane polymers by far the preferred choice. These are described in US3, 715, 334 and US3, 814, 730. Alternatively, photo-activated hydrosilylation catalysts (vi’) may be utilised. These may include but are not limited to platinum (II) P-diketonate complex catalysts such as Pt(II) bis(2,4-pentanedionate), Pt(II) bis(2,4-hexanedionate), Pt(II) bis(2,4-heptanedionate), Pt(II) bis(3,5-heptanedionate), Pt(ll) bis(l-phenyl-l,3-butanedionate), Pt(ll) bis(l,3-diphenyl-l,3-propanedionate), and the like; (η-diolefin) (σ-aryl)platinum complexes (η⁵-cyclopentadienyl)tri(σ-alkyl)platinum(IV) complexes and cyclopentadienylplatinum (IV) compounds, such as (methylcyclopentadienyl) trimethylplatinum (IV), and the complexes that derive therefrom; platinum(II) acetylacetonate (Pt(acac)₂, as well as other known photo-activated hydrosilylation catalysts for catalysing curing reactions upon exposure to radiation such as ultraviolet (UV) radiation. In one preferred embodiment component (d) may be selected from co-ordination compounds of platinum. In one embodiment hexachloroplatinic acid and its conversion products with vinyl-containing siloxanes, Karstedt’s catalysts and Speier catalysts are preferred.

[0101] The catalytic amount of the hydrosilylation catalyst is generally between 0.01 ppm, and 10,000 parts by weight of platinum-group metal, per million parts (ppm), based on the weight of the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition; alternatively, between 0.1 and 7500ppm; alternatively between 0.1 and 1000 ppm, and alternatively between 1 and 100 ppm of metal based on the weight of the composition and wherein dependent on the form / concentration in which the catalyst is provided e.g., in a polymer or solvent, the amount of component (d) present will be within the range of from 0.001 to 3.0 wt. % of the composition, alternatively from 0.001 to 1.5 wt. % of the composition, alternatively from 0.01-1.5 wt. %, alternatively 0.01 to 1.0 wt. %, of the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition. The catalysts may also be microencapsulated to increase shelf storage stability in 1 part or multi-part packages.

[0102] (e) Adhesion promoter

[0103] As previously indicated component (e) is an adhesion promoter comprising or consisting of an organosiloxane having (i) at least two epoxy groups, (ii) at least two alkenyl groups and (iii) at least at least two alkoxy groups.

[0104] The organosiloxane having (i) (ii) and (iii) may be linear branched or cyclic.

[0105] Each epoxy group (i) may be independently selected from a suitable organic moiety comprising an epoxy group. For example, it may comprise an alkyl epoxide group or an alkyl glycidyl ether of the structures below:

[0106] -(CH2)t- 0

[0107] -(CH2)t- ^0 ^V°

[0108]

[0109] and branched isomers thereof, where in each case subscript t may be the same or is different and is from 2 to 30, alternatively, subscript t is from, from 2 to 20, alternatively, subscript t is from 2 to 15, alternatively, subscript t is from 2 to 10. Alternatively, the organic moiety comprising an epoxy group may be a cycloaliphatic epoxide such as a cyclohexyl epoxide.

[0110] Typically the alkenyl groups of adhesion promoter (e) will be the same as those in component (a), i.e., each alkenyl group, may comprise for example from 2 to 30 carbons, alternatively 2 to 24, alternatively 2 to 20, alternatively 2 to 12, alternatively 2 to 10, and alternatively 2 to 6 carbons. The alkenyl groups may be exemplified by, but not limited to, vinyl, allyl, methallyl, propenyl, isopropenyl, butenyl, and hexenyl and cyclohexenyl groups.

[0111] The two or more alkoxy groups may be any suitable alkoxy groups. Typically the alkoxy groups will be linear or branched and have tire structure -OR6where R6is an alkyl group having from 1 to 15 carbons. Typically, each R6may be the same or different and may include but are not restricted to methyl, ethyl, propyl, isopropyl, n- butyl, isobutyl, tertiary butyl (t-butyl), tertiary amyl (C (C2H5) (01 )2). pentyl or hexyl groups and branched secondary alkyl groups such as 2,4-dimethyl-3-pentyl groups. Alternatively, each R6may be the same or different and may be selected from methyl, ethyl, propyl, isopropyl, n- butyl, isobutyl and t-butyl. Alternatively, each R6may be the same or different and may be selected from methyl, ethyl, propyl and isopropyl.

[0112] The organosiloxane having (i) at least two epoxy groups, (ii) at least two alkenyl groups and (iii) at least at least two alkoxy groups may be a linear and or branched methyl alkenyl siloxane polymer with terminally situated epoxy and / or alkoxy groups, a linear and or branched dimethyl methyl alkenyl siloxane copolymer with terminally situated epoxy and / or alkoxy groups or a linear and or branched dimethyl methyl alkoxy copolymer with terminally situated epoxy and alkenyl groups. Alternatively the organosiloxane having (i) at least two epoxy groups, (ii) at least two alkenyl groups and (iii) at least at least two alkoxy groups may be a linear and or branched methyl alkenyl siloxane polymer with terminally situated epoxy and / or alkoxy groups or a linear and or branched dimethyl methyl alkenyl siloxane copolymer with terminally situated epoxy and / or alkoxy groups, alternatively the organosiloxane having (i) at least two epoxy groups, (ii) at least two alkenyl groups and (iii) at least at least two alkoxy groups may be a linear and or branched dimethyl methyl alkenyl siloxane copolymer with terminally situated epoxy and / or alkoxy groups.

[0113] An example being a methylvinyl siloxane polymer comprising at least two -(Si(Me)(R9) -O)- siloxane units or a dimethylmethylvinyl siloxane copolymer comprising randomly situated -(Si(Me)z -O)- and -(Si(Me)(R9) -O)- siloxane units in each case with R9being an alkenyl group having from 2 to 30 carbons, alternatively 2 to 24, alternatively 2 to 20, alternatively 2 to 12, alternatively 2 to 10, and alternatively 2 to 6 carbons, which polymer or copolymer has a zero-shear viscosity of at least 10 mPa-s at 25 °C with terminal groups comprising at least two alkoxy groups and at least two epoxy groups at least two alkoxy and at least two epoxy terminal groups. An example of the above is depicted below (bearing in mind the siloxane repeating units are randomly positioned and in which R9is a vinyl group (merely for the sake of example).

[0114]

[0115] In which each R6may be tire same or different and is as described above subscript t is zero or an integer, subscript w is an integer which is at least 2 and W is an organic moiety comprising an epoxy group as described above.

[0116] In one embodiment the degree of polymerization of the organosiloxane having (i) at least two epoxy groups, (ii) at least two alkenyl groups and (iii) at least at least two alkoxy groups (e.g. t + w in the above structure has an average value of from 2 to 18, alternatively an average value of from 2 to

[0117] 15, alternatively an average value of from 2 to 12, alternatively an average value of from 2 to

[0118] 10, alternatively an average value of from 2 to 6.

[0119] They may be prepared by way of a reaction between, for example a glycidoxyalkyltrialkoxysilane such as 3-glycidoxypropyltrimethoxy silane or 3-glycidoxypropyltriethoxy silane or a 2-(3,4-Epoxy Cyclohexyl) alkyl Trialkoxysilane such as 2-(3,4-Epoxy Cyclohexyl) Ethyl Trimethoxysilane and a suitable oligomeric random copolymer diol of poly(methylvinylsiloxane-dimethylsiloxane) having a suitable zero-shear viscosity. Said adhesion promoter is typically present in the composition in an amount of from about 0.1 to 6wt. % of the composition; alternatively, 0.1 to 4 wt. % of the composition.

[0120] (f) A chelated metal condensation catalyst Component (f) is any suitable chelated metal condensation catalyst, for example a metal acetylacetonate condensation catalyst, a metal alkylacetylacetonate condensation catalyst e.g. a metal ethylacetylacetonate condensation catalyst, a metal hexafluoroacetylacetonate condensation catalyst or a metal triflouroacetylacetonate condensation catalyst. The metals in the above may be, selected from titanium, zirconium, aluminum, vanadium, chromium, scandium, manganese, iron, cobalt, nickel, copper and zinc, The structure of the acetylacetonate ion is (CH3C(=O)CHC(=O)CH“). It is commonly referred to in the industry as “acac”. Component (f) may be selected from acacs of the following transition metals namely zirconium (Zr(acac)₄), aluminum (Al(acac)3), vanadium (VO(acac)2), chromium (Cr(acac)3), scandium (Sc(acac)3), manganese (Mn(acac)2), iron (Fe(acac)3), cobalt (Co(acac)3), copper ((Cu(acac)₂) and zinc (Zn(acac)₂·H₂O) or any of their alkylacetylacetonate, e.g., ethylacetylacetonate, hexafluoroacetylacetonate or triflouroacetylacetonate equivalents.

[0121] As previously indicated metals in tire above may be, selected from titanium, zirconium, aluminum, vanadium, chromium, scandium, manganese, iron, cobalt, nickel, copper and zinc, alternatively zirconium, aluminum, or scandium, manganese, iron, cobalt, nickel, copper and zinc, alternatively zirconium, aluminum and scandium.

[0122] In one embodiment chelated metal condensation catalyst is one of the above metal acac catalysts.

[0123] Alternatively, component (f) is selected from Zr(acac)4, i.e., zirconium (IV) tetraacetyl acetonate or Al(acac)3, i.e., aluminium (III) triacetyl acetonate.

[0124] Typically, such a catalyst is introduced in an amount of from 0.05 - 2.0 wt.% of the composition, alternatively in an amount of from 0.05 - 1.75 wt.% of the composition, alternatively in an amount of from 0.075 - 1.5 wt.% of the composition alternatively in an amount of from 0.075 - 1.25 wt.% of the composition.

[0125] Components (a) and (c) invariably consist of a mixture of macromolecular species with different degrees of polymerization and therefore of different molecular weights. There are different types of average polymer molecular weight, which can be measured in different experiments. The two most important are the number average molecular weight (Mn) and the weight average molecular weight (Mw). The Mn and Mw of a silicone polymer and / or resin can be determined by Gel permeation chromatography (GPC) using polystyrene calibration standards. This technique is standard and yields Mw, Mn and polydispersity index (PI). The degree of polymerisation (DP) =Mn / Mu where Mn is the number-average molecular weight coming from the GPC measurement and Mu is the molecular weight of a monomer unit.

[0126] PI=Mw / Mn. The DP is linked to the viscosity of the polymer via Mw, the higher the DP, the higher the viscosity. The gel permeation chromatography may employ a triple detector system e.g., light-scattering detector, a refractive index detector, and / or a viscosity detector as well as polystyrene standards.

[0127] Additional optional ingredients

[0128] Additional optional ingredients may be present in the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition as hereinbefore described depending on the intended final use thereof. Examples of such optional ingredients include cure inhibitors, silicone resins, pot life extenders, flame retardants, fire retardant fillers, pigments and / or colouring agents, bactericides, wetting agents, heat stabilizers, compression set additives, plasticizers, and mixtures thereof.

[0129] Cure Inhibitors

[0130] When the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition as hereinbefore described is being cured via an addition / hydrosilylation reaction a cure inhibitor may be utilized to inhibit the cure of the composition. These cure inhibitors are utilized to prevent premature cure in storage and / or to obtain a longer working time or pot life of a hydrosilylation cured composition by retarding or suppressing the activity of the catalyst. Cure inhibitors of hydrosilylation catalysts (d), e.g., platinum metalbased catalysts are well known in the art and may include hydrazines, triazoles, phosphines, mercaptans, organic nitrogen compounds, acetylenic alcohols, silylated acetylenic alcohols, maleates, such as dibutyl maleate; fumarates, ethylenically or aromatically unsaturated amides, ethylenically unsaturated isocyanates, olefinic siloxanes, such as tetramethyltetravinylcyclotetrasiloxane; unsaturated hydrocarbon monoesters and diesters, conjugated ene-ynes, hydroperoxides, nitriles, and diaziridines. Alkenyl-substituted siloxanes as described in US 3,989,667 may be used, of which cyclic methylvinylsiloxanes are preferred.

[0131] One class of known cure inhibitors of hydrosilylation catalysts, e.g., platinum catalysts (d) include the acetylenic compounds disclosed in US 3,445,420. Acetylenic alcohols such as 2-methyl-3-butyn-2-ol constitute a preferred class of cure inhibitors that will suppress the activity of a platinum-containing catalyst at 25 °C. Compositions containing these cure inhibitors typically require heating at temperature of 70 °C or above to cure at a practical rate.

[0132] Examples of acetylenic alcohols and their derivatives include 1-ethynyl-l -cyclohexanol (ETCH), 2-methyl-3-butyn-2-ol, 3-butyn-l-ol, 3-methyl butynol 3-butyn-2-ol, propargyl alcohol, 2-phenyl-2-propyn-l-ol, 3,5-dimethyl-l-hexyn-3-ol, 1-ethynylcyclopentanol, l-phenyl-2-propynol, 3-methyl-l -pentenM-yn-3-ol, and mixtures thereof, In one alternative the cure inhibitor is selected from one or more of 1-ethynyl-l-cyclohexanol (ETCH), tetramethyltetravinylcyclotetrasiloxane, 3-methyl butynol and / or dibutyl maleate. When present, cure inhibitor concentrations as low as 1 mole of cure inhibitor per mole of the metal of catalyst (d) will in some instances impart satisfactory storage stability and cure rate. In other instances, cure inhibitor concentrations of up to 500 moles of cure inhibitor per mole of the metal of catalyst (d) are required. The optimum concentration for a given cure inhibitor in a given unscoured airbag fabric hydrosilylation curable silicone rubber coating composition herein is readily determined by routine experimentation. Mixtures of the above may also be used. Dependent on the concentration and form in which the cure inhibitor selected is provided / available commercially, when present in the composition, the cure inhibitor is typically present in an amount of from O. OOOl-lOwt. %, alternatively 0.001-5%, cure inhibitor, alternatively 0.0125 to 5wt. % of the composition.

[0133] Silicone Resins

[0134] The unscoured airbag fabric hydrosilylation curable silicone rubber coating composition may also include one or more silicone resins for example, silicone resins containing unsaturated groups selected from alkenyl groups, alkynyl groups or a mixture of alkenyl groups and alkynyl groups. Such silicone resins may be selected from T silicone resins (silsesquioxanes), DT silicone resins, MQ silicone resins, MDT silicone resins, MTQ silicone resins, QDT silicone resins or mixtures thereof. Such resins using the MDTQ notation comprise Q type (SiO₄ / ₂) siloxane units T type (R²₁SiO₃ / ₂) siloxane units; D type (R²₁SiO₃ / ₂) siloxane units and R²₃SiO₁ / ₂ (M) siloxane units as indicated. Typically, the MQ resins when present, comprise SiO₄ / ₂ (Q) siloxane units and R²₃SiO₁ / ₂ (M) siloxane units wherein each R2may be the same or different and denotes a monovalent group selected from hydrocarbon groups, having from 1 to 20 carbon atoms and, alternatively from 1 to 12 carbon atoms. Examples of suitable R2groups include alkyl groups, such as methyl, ethyl, propyl, pentyl, octyl, undecyl and octadecyl; cycloaliphatic groups, such as cyclohexyl; alkenyl groups, having from 2 to 12 carbons, such as vinyl, propenyl, butenyl, pentenyl, hexenyl, and the like; alkynyl groups selected from ethynyl, propynyl, butynyl, pentynyl or hexynyl and the like; aryl groups such as phenyl, tolyl, xylyl, benzyl, alpha-methyl styryl and 2-phenylethyl; alternatively R2groups are vinyl, methyl, ethyl or phenyl groups, e.g., examples of preferred R²₃SiO₁ / ₂ (M) siloxane units include Me₃SiO₁ / ₂, PhMe₂SiO₁ / ₂, ViMe₂SiO₁ / ₂ and Ph₂MeSiO₁ / ₂. where Me hereinafter denotes methyl, Vi is vinyl and Ph hereinafter denotes phenyl. T silicone resins may alternatively be referred to as silsesquioxanes. The silicone resin can be a single silicone resin or a mixture comprising two or more different silicone resins, each as described above. Typically, they are MQ resins comprising ViMe₂SiO₁ / ₂ in combination with Me₃SiO₁ / ₂, and / or PhMe₂SiO₁ / ₂ groups.

[0135] Additionally, the silicone resin may be an MQ resin which may contain residual OZ⁵, where Z⁵ can represent hydrogen or alkyl groups. OZ⁵ groups remain on the Q components after synthesis of silicone MQ resins indicative of incomplete condensation during tire reaction to produce tire MQ resin providing the OZ content meets the above hydroxyl per mole Si requirements. Residual OZ⁵ is inherent to the processes and reactions utilized to make MQ resins.

[0136] The silicone resin when present, is typically delivered in a hydrocarbon or silicone solvent, free from solvent the silicone resin is typically a solid but preferably herein the silicone resin is delivered in a silicone solvent such as a non-functional polydimethylsiloxane or a polydimethylsiloxane comprising two or more alkenyl groups per molecule, such as for example component (a) herein.

[0137] For example, in an MQ resin the molar ratio of M siloxane units to Q siloxane units has a value of from 0.5:1 to 1.2:1, alternatively 0.6:1 to 1.1:1, alternatively 0.8:1 to 1.1:1, alternatively 0.9:1 to 1.1:1. In one embodiment MQ resin includes a resinous portion wherein the M units are bonded to SiO4 / 2 siloxane units (i.e., Q units) and each of Q units is bonded to at least one other SiO4 / 2 siloxane unit. The molar ratio of M units to Q units is from 0.3: 1 to 1.2: 1, alternatively 0.4:1 to 1.1:1, alternatively 0.5:1 to 1:1, alternatively 0.6:1 to 0.9:1. Such an MQ resin suitable may have a number-average molecular weight (Mn) of from 2000 to 50,000g / mol, alternatively from 3,000 to 30,000 g / mol. In one embodiment the silicone resin may be described in the terms of a molar fraction as an MQ silicone resin having the formula:

[0138] (R⁴₃SiO₁ / ₂)ᵤ(SiO₄ / ₂)ᵥ

[0139] wherein R4is a Ci to Cio hydrocarbon group free of aliphatic unsaturation, u is from 0.3 to 0.6, alternatively 0.37 to 0.52, v is from 0.4 to 0.7, alternatively 0.48 to 0.63, and the value of u + v is 1.0. When present, in the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition the resin is in an amount of from 1 - 60wt. %, alternatively 1 - 40wt. %, and is preferably in the form of an MQ resin.

[0140] Preferably, when component (b) is not present, silicone resins as described above may be utilised to reinforce the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition. In such cases when (b) is absent and the silicone resin is present preferably the silicone resin comprises one or more unsaturated groups e.g., vinyl groups, alternatively the silicone resin is a vinylated MQ resin. Preferably component (b) or a silicone resin as described herein, or a mixture of component (b) and the silicone resin(s) is present in the composition.

[0141] Pot life extenders, such as triazole, may be used, but are not considered necessary in the scope of the present invention. The unscoured airbag fabric hydrosilylation curable silicone rubber coating composition may thus be free of pot life extender.

[0142] Examples of flame retardants chlorinated paraffins, hexabromocyclododecane, triphenyl phosphate, dimethyl methylphosphonate, tris(2,3-dibromopropyl) phosphate (brominated tris), and mixtures or derivatives thereof. When present in composition, if required the flame retardant may be present in an amount of from 5 to 50 wt. % of the composition.

[0143] Examples of fire-retardant fillers include aluminium oxide, calcium carbonate, hydromagnesite (Mg5(CO3)4(OH)2-4H2O), (MgjCa COsW or a mixture thereof, in particular a mixture of hydromagnesite and huntite, often referred to as HMH. Again, these fire-retardant fillers may be treated with a suitable hydrophobing agent as defined above to render them hydrophobic. Blends of hydromagnesite, and huntite are commercially available e.g., under tire tradenames UltraCarb™ 1251, UltraCarb™ 1253, and UltraCarb™ LH3C from LKAB Minerals AB of Lulea, Sweden. Such filler blends comprise particles having particle sizes between from 0.5 to 15pm measured using Malvern Laser Diffraction (data sheets). It is understood that typically huntite particles have a particle size of around 1.0 pm or less, much smaller than tire particle size of hydromagnesite particles. In one embodiment herein the hydromagnesite and huntite particles are treated with fatty acids e.g., stearic acid or fatty acid esters such as stearates to render them hydrophobic.

[0144] The composition may also include one or more unchelated titanium containing condensation catalysts (Optional)

[0145] The one or more unchelated titanium containing condensation catalysts, typically one or more tetraalkoxy titanate(s). For the avoidance of doubt, such tetra-alkoxy titanates are sometimes respectively referred to as tetra-alkoxy titanium or as tetra-alkyl titanates.

[0146] Any suitable tetra-alkoxy titanates which function as condensation catalysts may be utilised. The tetra-alkoxy titanates may comprise compounds according to the general formula

[0147] Ti[OR7]4

[0148] Where Ti is titanium and each R7may be the same or different and represents a monovalent, primary, secondary or tertiary aliphatic hydrocarbon group which may be linear or branched containing from 1 to 10 carbon atoms. Typically, each R7may be the same or different and include but are not restricted to methyl, ethyl, propyl, isopropyl, n- butyl, isobutyl, tertiary butyl, tertiary amyl (C (C₂H₅) (CH₃)₂). pentyl or hexyl groups and branched secondary alkyl groups such as 2,4-dimethyl-3-pentyl groups. In some embodiments one or more R7groups may contain partial unsaturation. In one embodiment all the R7are the same alkyl group.

[0149] Examples include the following titanates:

[0150] Ti (OC(CH₃)₂)₄ - tetraisopropyltitanate or tetraisopropoxy titanium (TiPT),

[0151] Ti (OCH₂CH₂CH₂)₄ - tetraisobutyltitanate or tetraisobutoxy titanium (TiBT),

[0152] Ti[OC(CH₃)₃]₄ - tetra tertiary butyl titanate or tetra tertiary butoxy titanium (TtBT)

[0153] Ti (C (C₂H₅) (CH₃)₂)₄ - tetra tertiary amyl titanate

[0154] Ti(OCH₂CH₂CH₂CH₃)₄ - tetra n-butyl titanate or tetra n-butoxy titanium (TnBT); and other suitable tetraalkoxy titanate catalysts such as Tyzor™ 9000 commercially available from Dorf Ketal Speciality Catalysts, LLC which has the formula

[0155] Ti [isopropoxy] a’ [t-butoxy]b

[0156] where tire total number of [isopropoxy] + [tertiary butoxy] groups per Ti atom (a’ + b’) is 4 and wherein, on average there are about 10% [isopropoxy] and 90% [t-butoxy] groups. For tire avoidance of doubt, the one or more tetra-alkoxy titanate(s) of component (g) are not partially or completely chelated.

[0157] Alternatively, the unchelated titanium containing condensation catalyst may be a titanium-based reaction product obtained or obtainable from a process comprising the steps of:

[0158] (i) mixing a first ingredient, an alkoxy titanium compound having from 2 to 4 alkoxy groups with a second ingredient, a linear or branched polydiorganosiloxane polymer having at least two terminal silanol groups per molecule;

[0159] (ii) enabling the first and second ingredients to react together by stirring under vacuum to form a reaction product; and

[0160] (iii) collecting the reaction product of step (ii).

[0161] When present, the unchelated titanium containing condensation catalyst is present in the composition in an amount of from 0.075 to 2.5 wt. % of the composition, alternatively 0.1 to 2.0 wt. % of the composition, alternatively from 0.1 to 1.75 wt.% of the composition.

[0162] Examples of colouring agents for which may be utilized in the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition include pigments, vat dyes, reactive dyes, acid dyes, chrome dyes, disperse dyes, cationic dyes and mixtures thereof. The unscoured airbag fabric hydrosilylation curable silicone rubber coating composition as described herein may further comprise one or more pigments and / or colorants which may be added if desired. The pigments and / or colorants may be coloured, white, black, metal effect, and luminescent e.g., fluorescent and phosphorescent. Pigments are utilized to colour the composition as required. Any suitable pigment may be utilized providing it is compatible with the composition herein. Suitable white pigments and / or colorants include titanium dioxide, zinc oxide, lead oxide, zinc sulfide, lithophone, zirconium oxide, and antimony oxide.

[0163] Suitable non-white inorganic pigments and / or colorants include, but are not limited to, iron oxide pigments such as goethite, lepidocrocite, hematite, maghemite, and magnetite black iron oxide, yellow iron oxide, brown iron oxide, and red iron oxide; blue iron pigments; chromium oxide pigments; cadmium pigments such as cadmium yellow, cadmium red, and cadmium cinnabar; bismuth pigments such as bismuth vanadate and bismuth vanadate molybdate; mixed metal oxide pigments such as cobalt titanate green; chromate and molybdate pigments such as chromium yellow, molybdate red, and molybdate orange; ultramarine pigments; cobalt oxide pigments; nickel antimony titanates; lead chrome; carbon black; lampblack, and metal effect pigments such as aluminium, copper, copper oxide, bronze, stainless steel, nickel, zinc, and brass.

[0164] Suitable organic non-white pigments and / or colorants include phthalocyanine pigments, e.g., phthalocyanine blue and phthalocyanine green; monoarylide yellow, diarylide yellow, benzimidazolone yellow, heterocyclic yellow, DAN orange, quinacridone pigments, e.g., quinacridone magenta and quinacridone violet; organic reds, including metallized azo reds and nonmetallized azo reds and other azo pigments, monoazo pigments, diazo pigments, azo pigment lakes, P-naphthol pigments, naphthol AS pigments, benzimidazolone pigments, diazo condensation pigment, isoindolinone, and isoindoline pigments, polycyclic pigments, perylene and perinone pigments, thioindigo pigments, anthrapyrimidone pigments, flavanthrone pigments, anthanthrone pigments, dioxazine pigments, triarylcarbonium pigments, quinophthalone pigments, and diketopyrrolo pyrrole pigments.

[0165] Typically, the pigments and / or colorants, when particulates, have average particle diameters in the range of from 10 nm to 50 pm, preferably in tire range of from 40 nm to 2 pm. The pigments and dyes may be used in form of pigment masterbatch composed of them dispersed in component (a) at the ratio of 25:75 to 70:30.

[0166] The unscoured airbag fabric hydrosilylation curable silicone rubber coating composition may be heat stabilised. Examples of heat stabilizers may include metal compounds such as red iron oxide, yellow iron oxide, ferric hydroxide, cerium oxide, cerium hydroxide, lanthanum oxide, copper phthalocyanine, fumed titanium dioxide, iron naphthenate, cerium naphthenate, cerium dimethylpolysilanolate and acetylacetone salts of a metal chosen from copper, zinc, aluminum, iron, cerium, zirconium, titanium and the like. Other examples of heat stabilizers may include suitable antioxidants or metal scavengers such as salicyloylaminotriazole, l,2-bis(3,5-di-tert-butyl-4-hydroxylhydrocinnamoyl)hydrazine, 2-Hydroxy-N-lH-l,2,4-triazol-3-ylbenzamide, and N’l, N’12-Bis(2-hydroxybenzoyl)dodecanedihydrazide. The amount of heat stabilizer when present in the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition may range from 0.01 to 1.0 % weight of the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition.

[0167] optional additional adhesion promoters (which are different from component (e)),

[0168] The unscoured airbag fabric hydrosilylation curable silicone rubber coating composition may include one or more optional additional adhesion promoters (which are different from component (e)). These may include alkoxysilanes such as epoxyalkylalkoxysilanes, for example, 3-glycidoxypropyltrimethoxysilane and, mercapto-alkylalkoxysilanes, (trimethoxysilyl)ethane and (ineth)acryloxy type adhesion promoters such as methacryloxypropyltrimethoxysilane and reaction products of ethylenediamine with silylacrylates. Isocyanurates containing silicon groups such as 1, 3, 5-tris(trialkoxysilylalkyl) isocyanurates may additionally be used as may short chain siloxane diols such as dimethyl methylvinyl siloxane diols, The adhesion promoter may be present in an amount of from 0.1 to 5.0 wt. % of the composition, alternatively from 0.1 to 3.5 wt. %.

[0169] Hence the unscoured airbag fabric hydrosilylation curable silicone rubber coating compositions comprises:

[0170] a) an organopolysiloxane polymer having a zero-shear viscosity of from In each case for component (a) the zero-shear viscosity of organopolysiloxane polymer (a) is between 100 and 200,000mPa.s inclusive at 25 °C, alternatively from 1000 to 150,000mPa.s at 25 °C, alternatively, from lOOOmPa.s to 125,000mPa.s, alternatively from lOOOmPa.s to 70,000mPa.s at 25 °C, having at least two unsaturated groups per molecule selected from alkenyl and / or alkynyl groups, in an amount of from 40 wt. % to about 80 wt. % of the composition, alternatively from 45 to 80 wt. % of the composition, alternatively from 50 to 80 wt. % of the composition of the composition; with the zero-shear viscosity being measured in the manner described above.

[0171] b) optionally one or more fillers selected from one or more reinforcing fillers, one or more nonreinforcing fillers, or a mixture thereof as hereinbefore described;

[0172] said fillers (b) are typically treated to render them hydrophobic and when present are present in an amount of from 1.0 to 50wt. %. of tire composition, alternatively of from 1 to 30wt. %. of the composition, alternatively of from 2.5 to 30wt. %. of tire composition, alternatively of from 3.5 to 25 wt. %. of the composition;

[0173] c) an organosilicon compound having at least two or at least three Si-H groups per molecule and which functions as a cross-linker; preferably the molar ratio of the silicon-bonded hydrogen atoms in component (c) to the total unsaturated groups selected from alkenyl and / or alkynyl groups in the composition is from 0.5: 1 to 20: 1, alternatively the molar ratio of silicon-bonded hydrogen atoms of component (c) to the total unsaturated groups selected from alkenyl and / or alkynyl groups in the organopolysiloxane (a) is preferably at least 1: 1 and can be up to 8: 1 or 10: 1. Most preferably the molar ratio of Si-H groups to aliphatically unsaturated groups is in the range from 1.1:1 to 5: 1; said organosilicon compound having at least two or at least three Si-H groups per molecule being present in an amount of from 0.1 to 10 wt. % of the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition, alternatively 0.1 to 7.5wt. % of the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition e, alternatively 0.5 to 7.5 wt. %, further alternatively from 0.5% to 5 wt. % of the composition. Component (c) functions as a cross-linker;

[0174] (d) a hydrosilylation cure catalyst wherein the catalytic amount of the hydrosilylation catalyst is between 0.01 ppm, and 10,000 parts by weight of platinum-group metal, per million parts (ppm), based on the weight of the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition; alternatively, between 0.1 and 7500ppm; alternatively between 0.1 and 1000 ppm, and alternatively between 1 and 100 ppm of metal based on the weight of the composition and wherein dependent on the form / concentration in which the catalyst is provided e.g., in a polymer or solvent, the amount of component (d) present will be within the range of from 0.001 to 3.0 wt. % of the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition, alternatively from 0.001 to 1.5 wt. % of the composition, alternatively from 0.01-1.5 wt. %, alternatively 0.01 to 1.0 wt. %, of the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition;

[0175] (e) Adhesion promoter

[0176] As previously indicated component (e) is an adhesion promoter comprising or consisting of an organosiloxane having (i) at least two epoxy groups, (ii) at least two alkenyl groups and (iii) at least at least two alkoxy groups, typically present in the composition in an amount of from about 0.1 to 6wt. % of the composition; alternatively, 0.1 to 4 wt. % of the composition.

[0177] (f) a chelated metal condensation catalyst

[0178] Component (f) is any suitable chelated metal condensation catalyst, for example a metal acetylacetonate condensation catalyst, a metal alkylacetylacetonate condensation catalyst e.g. a metal ethylacetylacetonate condensation catalyst, a metal hexafluoroacetylacetonate condensation catalyst or a metal triflouroacetylacetonate condensation catalyst. The metals in the above may be, selected from titanium, zirconium, aluminum, vanadium, chromium, scandium, manganese, iron, cobalt, nickel, copper and zinc, typically, such a catalyst is introduced in an amount of from 0.05 - 2.0 wt.% of tire composition, alternatively in an amount of from 0.05 - 1.75 wt.% of the composition, alternatively in an amount of from 0.075 - 1.5 wt.% of the composition alternatively in an amount of from 0.075 - 1.25 wt.% of the composition.

[0179] Furthermore, the coated unscoured airbag fabric described herein is an unscoured airbag fabric coated with tire cured product of the above unscoured airbag fabric hydrosilylation curable silicone rubber coating composition.

[0180] Typically, prior to use the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition is stored in two or more parts. Most commonly the composition is stored in two parts, Part A and part B to keep components (c) the organosilicon compound having at least two or at least three Sill groups per molecule which functions as a cross-linker (cross-linker) and (d) the hydrosilylation cure catalyst apart to avoid premature cure.

[0181] Typically, a Part A composition will comprise components:

[0182] (a) polymer,

[0183] (b) the one or more optional fillers as hereinbefore defined and

[0184] (d) hydrosilylation cure catalyst and

[0185] Part B will comprise:

[0186] (a) polymer,

[0187] (b) the one or more optional fillers as hereinbefore defined, (c) the organosilicon compound having at least two or at least three Si-H groups per molecule which functions as a cross-linker and Cure inhibitor when present.

[0188] Component (e) the adhesion promoter is typically stored in the part B composition. Component (f ) the chelated metal condensation catalyst is stored in the Part A composition to avoid the silicone bonded hydrogen and alkoxy groups stored in Part B.

[0189] If desired the composition may be stored prior to use in three or more parts.

[0190] Other additives when present in an unscoured airbag fabric hydrosilylation curable silicone rubber coating composition may be in either Part A or Part B, providing they do not negatively affect the properties of any other components present (e.g., catalyst inactivation).

[0191] Part A and part B of the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition described herein are mixed together shortly prior to use to initiate cure of the full composition into a silicone elastomeric material. The Part A and part B compositions can be designed to be mixed in any suitable weight ratio e.g., part A: part B may be mixed together in weight ratios of from 100:1 to 1:100, alternatively from 10:1 to 1:10, alternatively from 5:1 to 1:5, but most preferred is a weight ratio of 1:1.

[0192] Ingredients in each of Part A and / or Part B may be mixed together individually or may be introduced into tire composition in pre -prepared combinations for, e.g., ease of mixing the final composition. For example, components (a) and (b) are often mixed together to form an LSR polymer base or masterbatch prior to addition with other ingredients. Similarly, component (e) may also be premixed with component (a), if desired. These may then be mixed with the other ingredients of the Part being made directly or may be used to make pre-prepared concentrates commonly referred to in the industry as masterbatches. In this instance, for ease of mixing ingredients, one or more masterbatches may be utilized to successfully mix the ingredients to form Part A and / or Part B compositions. For example, a “fumed silica” masterbatch may be prepared. This is effectively an LSR silicone rubber base with silica treated in situ. Parts A and B of the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition may be prepared by combining all of their respective components at ambient temperature. Any mixing techniques and devices described in the prior art can be used for this purpose. The particular device to be used will be determined by the viscosities of components and the final composition. Suitable mixers include but are not limited to paddle type mixers e.g., planetary mixers and kneader type mixers. Cooling of components during mixing may be desirable to avoid premature curing of the composition.

[0193] Prior to use the respective Part A and Part B compositions are mixed together in the desired ratio.

[0194] As part of the method herein the coating composition as hereinbefore described may be applied on to a fabric substrate, typically a one-piece woven or flat fabric airbag substrate by any suitable known technique. These include spraying, gravure coating, bar coating, knife coating, e.g., coating by knife-over-roller, coating by knife -over-air; padding, dipping and screen-printing.

[0195] The unscoured airbag fabric hydrosilylation curable silicone rubber coating composition can be applied onto one or both sides of fabric material substrate, e.g., an airbag fabric which is to be cut into pieces and sewn to assemble an airbag or may be applied onto a one-piece woven airbag. Curing of the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition herein applied onto the woven fabric is typically conducted by heating the composition at a temperature of from 150 to 200°C for 45 seconds to 2 minutes which can be accomplished using a suitable oven or through drying tunnel of circulating hot-air ovens.

[0196] Although it is not preferred, it is possible to apply the composition in multiple layers, which together have a pre-determined mean dry coat weight which can be measured in accordance with ISO 3801, It is also possible to apply onto the coating composition a further compatible coating, e.g., of a material providing e.g., low friction, if deemed necessary.

[0197] Any suitable desired coat weight may be applied on the fabric material such as an airbag, e.g., from 15 to 150 g / m2, alternatively from 15 to 100 g / m2, alternatively from 20 to 75 g / m2determined in accordance with ISO 3801. The thickness of coating layer ranges from of 20 to 80pm depending on the coating weight.

[0198] The unscoured airbag fabric substrate

[0199] The unscoured airbag fabric substrate onto which the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition is applied may be made from any suitable woven unscoured airbag fabric, particularly a plain weave unscoured airbag fabric, but can for example be a knitted or nonwoven unscoured airbag fabric. The unscoured airbag fabric may be made from synthetic fibres or blends of natural and synthetic fibres, for example polyamide fibres such as Nylon-6, Nylon-6, 6 and Nylon-4, 6; polyester fibres such as polyethylene terephthalate and polybutylene terephthalate; polyimide, polyethylene, polypropylene, polyester-cotton, polyacrylonitrile fibre fabric, aramid fibre fabric, polyether imide fibre fabric, polysulfone fibre fabric, carbon fibre fabric, rayon fibre fabric and / or glass fibres.

[0200] When treating an airbag of unscoured fabric, the airbag may be a one-piece woven airbag or may be flat fabric pieces which after coating are sewn together to provide sufficient mechanical strength. Such airbags are generally made from polyamide fibre fabric or polyester fibre fabric for applications requiring high strength, especially in the case of automotive one-piece woven airbags. Prior to coating with the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition described herein, the woven fabric is preferably washed with water and dried.

[0201] For use as an airbag fabric, the fabric should be sufficiently flexible to be able to be folded into relatively small volumes, but also sufficiently strong to withstand deployment at high speed, e.g., under the influence of an explosive charge. Polyamide and polyester fibres are particularly preferred for making airbag fabrics; however, it can be difficult to get coatings to adhere to polyamide and polyester airbags, especially when unscoured, hence the need for adhesion promoters such as component (e) herein.

[0202] The airbag obtained by coating an unscoured airbag fabric with the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition described herein has at least one coating layer formed of a cured product from the unscoured airbag fabric hydrosilylation curable silicone rubber coating composition described herein. If necessary, however, one or more additional layers may be provided on the coated woven fabric. Such additional layers are applied typically for improving the tactile sensation of the surface of a coated woven fabric, for improving abrasion resistance of tire surface of a coated woven fabric, and / or for improving the strength of a coated woven fabric. The additional coating layer may be exemplified by a plastic film, a woven fabric, a non-woven fabric, or a coating layer formed of an elastic coating material other than the cured silicone rubber disclosed herein. Preferably no additional layers are required or desired.

[0203] This technology can be used in any suitable fabric application but is particularly suited for airbags applications particularly in the automobile market but also for e.g., escape chutes from aircraft.

[0204] Examples

[0205] In the following examples, the compositions are defined in weight % (wt. %) unless otherwise stated. Vinyl group and Si bonded hydrogen content was measured by Infrared spectroscopy in accordance with ASTM E168 using standards of the carbon double bond stretch and silicon-hydrogen bond stretch respectively.

[0206] All flex abrasion, or “scrub resistance” testing was carried out as described in accordance with ISO 5981:2007 test method A and the values provided in tire Tables below are an average of three results in each case.

[0207] A series of compositions were prepared and were analysed for their suitability as coatings for unscoured airbag fabrics. Whilst any suitable method can be used, unless the composition is to be used immediately it is prepared in two parts, part A and part B with a view to preventing premature curing. The liquid silicone rubber compositions prepared were prepared as two-part compositions, part A and part B. Two standard airbag compositions were first prepared using the compositions identified as Ref. 1 and Ref. 2 in Table 1.

[0208] Table 1: Airbag coating compositions (wt. %)

[0209] Ref. 1 Part A Ref. 1 Part B Ref. 2 Part A Ref. 2 Part B Fumed Silica 19.71 19.66 19.71 19.66

[0210] Polymer 1 79.96 72.90 44.93 48.30

[0211] Polymer 2 35.03 21.10

[0212] Adhesion Promoter 1 0.00 1.19 0.00 1.19

[0213] Zirconium (iv) acac 0.30 0.00 0.30 0.00

[0214] Adhesion Promoter 2 0.00 0.16 0.00 0.16

[0215] Tetramethyldivinyldisilazane 0.02 0.19 0.02 0.19

[0216] Cross -linker 1 0.00 5.75 0.00 0.00

[0217] Cross -linker 2 9.25

[0218] Karstedt Catalyst 0.004 0.00 0.004 0.00

[0219] ETCH 0.00 0.07 0.00 0.07

[0220] Polymer 3 0.002 0.08 0.002 0.08

[0221]

[0222] In the above,

[0223] Fumed Silica was CAB-O-SIL™ MS-75D fumed silica which is commercially available from Cabot Corporation.

[0224] Polymer 1 Vinyldimethylsiloxy terminated polydimethylsiloxane having a zero-shear viscosity of 40,000 mPa.s at 25 °C;

[0225] Polymer 2 was Vinyldimethylsiloxy terminated polydimethylsiloxane having a zero-shear viscosity of 10,000 mPa.s at 25 °C;

[0226] Adhesion Promoter 1 was Glycidoxypropyltrimethoxysilane;

[0227] Zirconium (iv) acac was zirconium(IV) acetylacetonate;

[0228] Adhesion Promoter 2 was Dimethyl Methylvinyl Diol;

[0229] Cross-linker 1 is a trimethyl terminated dimethyl methylhydrogen siloxane having a degree of polymerization of 11 and 0.457% silicon bonded hydrogen (Si-H);

[0230] Crosslinker 2: a trimethyl terminated dimethyl methylhydrogen siloxane having a degree of polymerization of 11 and 0.3% silicon bonded hydrogen (Si-H); and

[0231] Polymer 3 was Hydroxydimethylsiloxy terminated polydimethylsiloxane having viscosity of approximately 25 mPa.s at 25°C.

[0232] The Ref. 1 airbag compositions when Parts A & B are mixed together in a 1: 1 weight ratio and is cured forms a 10 Shore A (70 Shore 00) elastomer as defined in ASTM D2240-15. Ref. 2 airbag composition when Parts A & B are mixed together in a 1: 1 weight ratio and is cured forms a 65 Shore 00 elastomer as defined in ASTM D2240-15.

[0233] In a first step for making the composition an in-situ treated fumed silica masterbatch was prepared in a Kneader mixer by mixing tire masterbatch ingredients depicted in Table 1 and the stripping off residual water and treatment agents. The part A and part B compositions were then prepared by mixing the identified ingredients together using a speed mixer. The resulting part A and part B compositions were then stored separately until shortly before use. Prior to use the adhesion promoters identified in Table 2a were introduced into the Ref. 1 part B composition and the modified Part B composition resulting therefrom. To make the final compositions the modified Part B composition and the part A composition were intermixed before cure in a 1: 1 weight ratio.

[0234] Table 2a: Modified Ref. 1 Part B Compositions with adhesion promoter in parts by weight per 100 parts by weight of the Ref. 1 Part B Composition

[0235] Ref. 1 C. 1 Ex. 1 Ex. 2

[0236] Ref. 1 Part B Composition 100 100 100 100

[0237] Comp Adhesion Promoter 1 1.0

[0238] AP - 1 1.0

[0239] AP-2 1.0

[0240]

[0241] The comparative adhesion promoter used had the following structure with n = average of about 7 and is depicted below.

[0242] H,

[0243] 0.

[0244]

[0245] AP-1 was the ‘reaction product of 2-(3,4-Epoxy Cyclohexyl) Ethyl Tri methoxy silane and an oligomeric random copolymer diol of poly(methylvinylsiloxane-dimethylsiloxane) having a zero-shear viscosity of 15 mPa-s at 25 °C and vinyl content of 6 wt.% Vi.”

[0246] AP-2 was the reaction product of 3-glycidoxypropyltrimethoxysilane and an oligomeric random copolymer diol of poly(methylvinylsiloxane-dimethylsiloxane) having a zero-shear viscosity of 15 mPa-s at 25 °C and vinyl content of 6 wt.% Vi.

[0247] The resulting airbag coating compositions after the modified part B and the part A compositions had been mixed together, were coated onto flat unscoured polyethylene terephthalate (PET) fabric using a lab scale Mathis blade coater. The target coat weight for each coating was from 60-70 g / m2and once the fabric was coated, tire resulting coated polyethylene terephthalate (PET) fabric samples were cured for 90 seconds (s) at 190 °C. The airbag fabric was then top coated with talc in a commercial topcoat sold under tire tradename SILASTIC™ 3715 Topcoat which is a low-friction, low-soiling topcoat for cured liquid silicone rubber elastomers commercially available from Dow Silicones Corporation.

[0248] Once cured flex abrasion testing (also referred to as scrub resistance) were measured by in accordance with ISO 5981:2007 (test method A) using both newly coated bags and bags after a period of aging (7 days at 95% relative humidity and 80 °C). Samples of fabric were cut and loaded into the instrument and visually assessed for failure indicated by the presence of a pinholes and / or blistering. The values reported were the last successful scrub resistance measurement and the results are provided in Table 2b below.

[0249] Table 2b: Scrub resistance results for coated unscoured PET fabric test pieces in accordance with ISO 5981:2007 (Test method A) _

[0250] Initial scrub resistance Aged scrub resistance

[0251] (Unscoured PET) (Unscoured PET)

[0252] C. 1 1000 400

[0253] C.2 1000 200

[0254] Ex. 1 1200 900

[0255] Ex. 2 1100 1100

[0256]

[0257] Sustained adhesion to unscoured fabric after prolonged exposure to heat and humidity is the most challenging adhesion metric to satisfy. Airbag safety requirements specify that airbag coatings must resist at least 600 scrubs without pin hole formation or delamination. The aged samples were assessed after aging using a typical accelerated heat and humidity aging protocol used in the industry of exposing samples to 80 °C heat and 95% relative humidity for 7 days.

[0258] In Table 2b, Ref. 1 was the product of an LSR airbag coating which when cured forms a 10 Shore A (70 Shore 00) elastomer as defined in ASTM D2240-15. It was found that Ref. 1 reached 1000 scrubs on unscoured PET initially but fell below the scrub resistance requirement after aging. As a result, Ref. 1 has insufficient adhesion on unscoured fabric.

[0259] C. 1 incorporated comparative adhesion promoter 1 that contains at least 2 epoxides, but no alkoxy groups and contains silicone bonded hydrogen (Si-H) rather than vinyl groups. No improvement was seen in the scrub resistance performance for C. 1 examples. Ex. 1 and Ex. 2 incorporate adhesion promoters that contain at least 2 epoxide groups, at least 2 alkoxy groups, and at least 2 vinyl groups. Both Ex. 1 and Ex. 2 display significantly improved scrub resistance performance after heat-and-humidity aging, exceeding the 600-scrub resistance requirement. Ex. 1 uses cyclohexene oxide as the epoxide source and ethoxy as the alkoxy source. Ex. 2 uses glycidyl ether as the epoxide source and methoxy as the alkoxy source.

[0260] A second set of examples were undertaken, in this case using Ref. 2 Part B Composition and having the ingredients indicated in Table 3a added to the Ref. 2 Part B Composition and then having the modified part B composition and tire Ref. 2 Part A Composition mixed together in a 1: 1 weight ratio.

[0261] Compositions were prepared in the same manner as above. Compositions used in Ref. 2 and Ex. 3 and 4 are depicted in Table 3a in parts weight per 100 parts by weight of the Part B composition of the Ref. 2 composition depicted in Table la above.

[0262] Table 3a: Modified Ref. 2 Part B Compositions with adhesion promoter in parts by weight per 100 parts by weight of the Ref. 2 Part B Composition

[0263] Ref. 2 Ex. 3 Ex. 4

[0264] Ref. 2 Part B Composition 100 100 100

[0265] AP-1 1.0

[0266] AP-2 1.0

[0267] Cross -linker 3 1.5 1.5

[0268]

[0269] In the above,

[0270] Cross-linker 3 was a commercially available cross-linker from Gelest Inc. sold under the HPM-502 tradename which is defined as an Si-H terminated methylhydrosiloxane-phenylmethylsiloxane copolymer having a viscosity of between 75 and 110 cSt, and a 45-50 mol % of phenylmethylsiloxane (both values taken from supplier website). Samples were prepared in the same way as above and coated on PET fabrics as described above. The same scrub resistance tests were undertaken for initial and aged samples (aged in the same manner as previously described). The scrub resistance results for Ref. 2 and Ex. 3 and 4 are provided in Table 3b.

[0271] Table 3b: Scrub resistance results for Ref. 2 and Ex. 3 & 4in accordance with ISO 5981:2007 Test method A

[0272] Initial scrub resistance Aged scrub resistance (Unscoured PET) (Unscoured PET)

[0273] Ref. 2 400 400

[0274] Ex. 3 800 1000

[0275] Ex. 4 1000 733

[0276]

[0277] In Table 3b, Ref. 2 gave poor scrub resistance performance before and after aging on unscoured PET. Incorporation of cross-linker 2 in combination with tire adhesion promoter added in Ex. 3 and Ex. 4 provides good initial and heat and humidity aged scrub resistance performance.

Claims

CLAIMS1. An unscoured airbag fabric hydrosilylation curable silicone rubber coating composition comprising:a) an organopolysiloxane polymer having a zero-shear viscosity of between 100 and 200,000mPa.s inclusive at 25 °C, and at least two unsaturated groups per molecule, which unsaturated groups are selected from alkenyl groups, alkynyl groups or a mixture thereof;b) optionally one or more fillers;c) at least one organosilicon compound having at least two, or at least three Si-H groups per molecule; d) a hydrosilylation cure catalyst;e) an adhesion promoter comprising or consisting of an organosiloxane having (i) at least two epoxy groups, (ii) at least two alkenyl groups and (iii) at least two alkoxy groups; andf) a chelated metal condensation catalyst wherein the metal is selected from one or more of titanium, zirconium, aluminum, vanadium, chromium, scandium, manganese, iron, cobalt, nickel, copper and zinc.

2. An unscoured airbag fabric hydrosilylation curable silicone rubber coating composition in accordance with claim 1 in which component (f) is selected from a metal acetylacetonate condensation catalyst, a metal alkylacetylacetonate condensation catalyst, a metal hexafluoroacetylacetonate condensation catalyst or a metal triflouroacetylacetonate condensation catalyst.

3. An unscoured airbag fabric hydrosilylation curable silicone rubber coating composition in accordance with claim 1 or 2 in which component (f) is selected from Zr(acac)4, Al(acac)3, VO(acac)2, Cr(acac)3, Sc(acac)3, Mn(acac)2, Fe(acac)3, Co(acac)3, Cu(acac)2and Zn(acac)2·H2O, wherein acac stands for acetylacetonate.

4. An unscoured airbag fabric hydrosilylation curable silicone rubber coating composition in accordance with claim 1, 2 or 3 in which component (f) is selected from Zr(acac)4, Al(acac)3, Sc(acac)3, wherein acac stands for acetylacetonate.

5. An unscoured airbag fabric hydrosilylation curable silicone rubber coating composition in accordance with claim 1, 2, 3 or 4 wherein component (e) is selected from a methylvinyl siloxane polymer comprising at least two -(Si(Me)(R9)-O)- siloxane units or a dimethylmethylvinyl siloxane copolymer comprising randomly situated -(Si(Me)2-O)- and -(Si(Me)(R9)-O)- siloxane units in which in each case(i) R9is an alkenyl group having from 2 to 30 carbons,(ii) having a zero-shear viscosity of at least 10 mPa-s at 25 °C and(iii) terminal groups comprising at least two alkoxy groups and at least two epoxy groups.

6. An unscoured airbag fabric hydrosilylation curable silicone rubber coating composition in accordance with any one of claims 1 to 5 wherein each epoxy group is the same or different and are selected from an alkyl epoxide group, an alkyl glycidyl ether and a cycloaliphatic epoxide.

7. An unscoured airbag fabric hydrosilylation curable silicone rubber coating composition in accordance with any one of claims 1 to 6 component (c) comprises or consists of an Si-H terminatedmethylhydrosiloxane-phenylmethylsiloxane co-polymer having a zero-shear viscosity of from 50 to 300 cSt and 30 to 75 mol % of phenylmethylsiloxane units.

8. An unscoured airbag fabric hydrosilylation curable silicone rubber coating composition in accordance with any one of claims 1 to 7 which composition additionally comprises one or more cure inhibitors, pot life extenders, flame retardants, lubricants, pigments and / or colouring agents, bactericides, wetting agents, heat stabilizers, compression set additives, plasticizers, and mixtures thereof.

9. A coated unscoured airbag fabric comprising an unscoured airbag fabric coated with the cured product of an unscoured airbag fabric hydrosilylation curable silicone rubber coating composition in accordance with any one of claims 1 to 8.

10. A coated unscoured airbag fabric in accordance with claim 9 wherein the unscoured airbag fabric is a woven fabric or nonwoven fabric made from synthetic fibres or blends of natural and synthetic fibres.

11. A coated unscoured airbag fabric in accordance with claim 9 or 10 made from polyamide fibres; polyester fibres; polyimide, polyethylene, polyethylene terephthalate, polypropylene, polyester-cotton, polyacrylonitrile fibre fabric, aramid fibre fabric, polyether imide fibre fabric, polysulfone fibre fabric, carbon fibre fabric, rayon fibre fabric and / or glass fibres.

12. A method of coating an unscoured airbag fabric with an unscoured airbag fabric hydrosilylation curable silicone rubber coating composition in accordance with one of claims 1 to 8 comprising the steps of mixing the components of tire unscoured airbag fabric hydrosilylation curable silicone rubber coating composition, applying tire unscoured airbag fabric hydrosilylation curable silicone rubber coating composition onto an unscoured airbag fabric surface and curing tire composition to form a coated unscoured airbag fabric.

13. A method of coating an unscoured airbag fabric with an unscoured airbag fabric hydrosilylation curable silicone rubber coating composition coated in accordance with claim 12 wherein the unscoured airbag fabric is made from polyamide fibres; polyester fibres; polyimide, polyethylene, polyethylene terephthalate, polypropylene, polyester-cotton, polyacrylonitrile fibre fabric, aramid fibre fabric, polyether imide fibre fabric, polysulfone fibre fabric, carbon fibre fabric, rayon fibre fabric and / or glass fibres.

14. A use ofe) an adhesion promoter comprising or consisting of an organosiloxane having (i) at least two epoxy groups, (ii) at least two alkenyl groups and (iii) at least two alkoxy groups; andf) a chelated metal condensation catalyst wherein the metal is selected from one or more of titanium, zirconium, aluminum, vanadium, chromium, scandium, manganese, iron, cobalt, nickel, copper and zinc; in an unscoured airbag fabric hydrosilylation curable silicone rubber coating composition for coating an unscoured airbag fabric which composition otherwise comprises:a) an organopolysiloxane polymer having a zero-shear viscosity of between 100 and 200,000mPa.s inclusive at 25 °C, and at least two unsaturated groups per molecule, which unsaturated groups are selected from alkenyl groups, alkynyl groups or a mixture thereof;b) optionally one or more fillers;c) an organosilicon compound having at least two or at least three Si-H groups per molecule;d) a hydrosilylation cure catalyst.

15. Use in accordance with claim 14 wherein components (e) and (f) enhance adhesion of the coating onto the surface of an unscoured airbag fabric.

16. Use of an unscoured airbag fabric hydrosilylation curable silicone rubber coating composition in accordance any one of claim 1 to 8 as an airbag coating composition.

Images