COATING COMPOSITION

Abstract: A primer composition for application to a substrate to promote adhesion of a room-temperature-vulcanisable silicone rubber coating comprises (A) an aminosilane material, (B) a chlorinated polyolefin and (C) a room-temperature-curable polydiorganosiloxane. The aminosilane material (A) is a primary amine-functional silane or the reaction product of a primary amine-functional silane with an epoxy-functional silane or an alpha, omega-dihydroxypolydimethylsiloxane oil.

Description: COATING COMPOSITION Field of the inventio This invention relates to a Drimer composition for aoDlication to a substrate to promote adhesion of a room-temperature-vulcanisable (RTV) silicone rubDer coating. RTV silicone rubPer coatings are applied to underwater surfaces, for example ships' hulls. the cooling water inlets and outlets of power stations, fish-farming equip- ment and the underwater and splash-zone surfaces of oil production platforms, to inhibit fouling by aquatic or¬ ganisms such as algae and barnacles. Background of the invention Silicone rubber fouling-resistant coatings are des- cribed for example in GB-A-1307001 , GB-A-1470465, GB-A- 1581727, GB-A-2141436, EP-A-16195 and US-A-3702773. RTV silicone rubber coatings have also been suggested as coatings inhibiting the adhesion of ice, for example on the superstructure and topsides of ships. A problem in the use of such RTV silicone rubber coatings is that it is difficult to make them adhere well to substrates. This problem is discussed in EP-A-16195 which proposes applying the RTV silicone rubber as a cladding on a fabric backing. Various primer compositions have been suggested for room-temperature-vulcanisable silicone rubber antifoulingε. US-A-3702778 proposes a cross!inkable silicone paste. EP- A-89066 proposes a mixture of an epoxysilane and a silane containing an unsaturated hydrocarbon group. JP-A-53- 137231, JP-A-53-137233 and JP-A-53-137234 propose various elastomeric materials such as polyurethane, natural rubber, chloroprene or neoprene rubber or butyral/si 1icone rubber. - EP-A-323906 and EP-A-329375 propose a silicone resin containing an aminosilane. US-A-4070421 describes the use of cnloπnated polyethylene as a primer for improving adhesion of coatings on polyolefin surfaces. Summary of the invention A primer composition according to the invention for application to a substrate to promote adhesion of an RTV silicone rubber coating comprises: (A) an aminosilane material which is (i) a primary amine-functional silane of the formula: (RO) χ R (3 _ χ SiR 1 NHR 2 • (I) where the radicals R, which can be tne same or different, are monovalent hydrocarbon radicals having 1 to 12 carbon atoms and optionally contain¬ ing an ether linkage: R is an alkylene radical having 2 to 4 carbon atoms or a divalent aliphatic 2 ether radical having 3 to 8 carbon atoms; R is hydrogen or an alkylene radical of 2 to 4 carbon atoms tipped with a primary amine group; and x is 2 or 3: or (ii) the reaction product of a primary am ne-functional silane of the formula (I) with an epoxy-functional silane of the formula: A - Si ( B)a a C0B) * (,3-a .) (II) where A is an epoxide-substituted monovalent hydrocarbon radical having 4 to 12 carbon atoms; the radicals B, which can be the same or different, are alkyl radicals having 1 to 4 carbon atoms; and a is 0 or 1 ; or (iii ) the reaction product of a primary amine-functional silane of the formula (I) with an alpha, omega- dihydroxypolydimethylsiloxane oil of the formula: HO ( Si ( CH 3 ) 2 0) v H (III) in which y is 2 to 60: (B) a chlorinated polyolefin: and (C ) a room-temperature-curab e polyαiorganosi loxane. Detailed disclosure In the primary amine-functional silane of formula (Ii the radicals R are preferably alkyl, for example methyl, ethyl, hexyl or octyl , aryl , for example phenyl , or aralkyl, for example benzyl. The alkylene radical R is preferably -(CH 2 )„-, -(CH-).- or methyl-sub¬ stituted trimethylene, or can be -(CH 2 ) --O-fCH,. ).. , -(CH2)„-0-('CH2) ' 3„- or -CH.--0-(CH ) <.L-. R 2 is Dreferablv hvdroqen or It may be 1 p • referred to seoarate any ether oxygen atom in R and R by at least two carbon atoms from the nearest heteroato . Examples of primary amine-functional si lanes of formula (I) are: (CH 3 0) 3 Si(CH ) 3 NH(CH 2 ),NH 2 ; (CH 3 CH 2 0CH 2 CH 0) 3 Si (CH 2 -NH 2 ; (C 2 H 5 0)^Si (CH 9 ) 3 H 2 ; (CH 3 OCH 2 CH 2 0. ~ \(CH 2 ) 3 NH 2 ; (C 2 H 5 0) 3 Si(CH 2 ) 3 0(CH 2 ) 3 NH 2 : (CgHgO^CgHgS (CH 2 )gNH 2 ; (C..H c 0) SiCH n 0(CH ) / ,NH : (C H K 0)„Si?CH ) 0(CH )-NH • and (C H,-0),-CH„Si (CH ) NH . Mixtures of twc or more primary amine-functional silanes (I) may be used if desired. The primary amine-functional silane (I) is preferably used as such in the primer composition. It can however be replaced wholly or in part by a reaction product of the primary amine-functional silane (I) and an epoxy-functiona! silane (II). The group A in the epoxy-functiona! silane (II) is preferably a glycidoxy-substituted alkyl group, for examole 3-glycidoxypropyl . The epoxy-functiona! silane (II) can for example be 3-glycidoxypropyl trimethoxy silane, 3-glycidoxypropyl diethoxy methoxy silane, 2- glycidoxypropyl trimethoxy silane, 3-(3,4-epoxycyclohexyl )- prcpyl trimethoxy silane or 2-(3,4-epoxy-4-methylcyclo- hexy! )-ethyl trimethoxy silane. Examples of preferred reaction products of an amine-functional silane (I) and an ecoxv-functiona! silane (II) are: C 2 H ε 0) 3 Si (CH,) 3 - NH - CH.-, - CH - CH - 0(CH o . ft ~ .S ' i(0CH '3)'3 OH (CH n 0)„Si(CH )„ - NH - CH„ - CH - CH„ - 0(CH ) Si (0CH OH (CH 0) ^ Si(CH ) - NH-(CH ) -NH-CH -CH-CH -0(CH ),,Si(0CH-.)„ OH The aminosilane (I) and the epoxysilane (II) can be reacted at 20-80°C, preferably using 0.4-1.2 primary amine groups of aminosilane (I) per epoxide group in (II). In a further alternative, the primary amine-functional silane (I) is replaced wholly or in part by a reaction product of the primary am ne-functional silane (I) and an alpha, omega-dihydroxypolydimethylsiloxane (III;. (I) and (III) can be reacted at 20-80°C, preferably using 0.4-1.2 alkoxy groups of aminosilane (I) per silanol group i (III). The chlorinated polyolefin (B) preferably has a molecular weight of 5.000 to 50,000 and a chlorine content cf 15 to 75%, most preferably 17 to 40%. by weight. Chlorinated polyolefins are commercially available. They can be prepared by treating a polyolefin with chlorine in the presence of a peroxide catalyst. The chlorinatior. reaction is preferably carried out in a solvent for the polyolefin starting material. The polyolefin is preferably a Dθly(aloha-olefin) such as Dolvεthvlene or polvproDvlene. " he oclyolefin can be cf high or low Density, amcronous or crystalline. It can be a cooolymer of two or more olefins, oreferably aloha-olefins. SuitaDle cnloπnatεd oolyolefms are described for exa Dle in US-A-35ei965 and US-A-4070421. The chlorinated oclyolefin (B) car, oe used ir. conjunc¬ tion with another chlorinated hydrocarbon resin, for example a chlorinated polyterpeπe resin or cnlcππatec polystyrene. The polystyrene is oreferably of low mole¬ cular weight (less than 5000). Such a chlorinated hyαrc- carbon resin oreferably has a similar degree of chlorina- ticn to the chlorinated polyolefin. The chlorinated hydrocarbon resin can for example be used in an amount cf from 1 to 100% by weight based on the chlorinated polyole¬ fin (B). The aminosilane material (A) is generally used at 0.1 to 50% by weight based on the chlorinated material (chlor¬ inated polyolefin (B) plus any other chlorinated hydrocar¬ bon resin), most oreferably 1 to 20% by weight. The room-temoerature-curable cclydiorganosiloxane (C) is oreferably a oolvdiorganosiloxane of viscosity 700 to 1,000,000 m Pa s at 25°C. It preferably contains siliccn- bonded hydroxyl groups, for example an aloha.omega- dihydroxypo!vdiorganosi loxane, or s licon-bonded hydrolys- able groups, for example a polvdiorganosi loxane tipped with silicon-bonded hydrolysable groups. More oreferably. it is formed of recurring diorgancsi loxy units cf the formula - R 4 ? SiO - where the radicals R4, which can be the same or different, represent hydrocarbon radicals having 1 to 10 carbon atoms. It is preferred that at least 50% of the raαicals R are methyl groups. The dihydroxyoolydior- ganosiloxane may further contain onoorganosi loxy groups cf the formula R SiO„ι .o c and/or siloxv' groups of the formula SιO ? in a maximum proportion of 2% with respect to the • * ■ number of diorganosiloxy groups R SιO. The nydrocarbon radicals represented by the symbol R in the di- and mono-organosi loxy units may suitably be selected from alkyl radicals such as methyl, ethyl, n- prooyl , isooropyl, n-butyl , n-pentyl , n-hexyl , 2-etnyl hexyl or n-octyl , cycloalkyl radicals having frc 4 to 8 carbon atoms such as cyclopentyl , cyclohexyl or methyl- cyclohexyl , alkenyl radicals having from 2 to 4 carbon atoms such as vinyl, allyl or buten-2-yl , and aryl radicals having from 6 to 8 carbon atoms such as phenyl, tolyl or xylyl . As preferred examples cf the groups represented by 4 R Si0 the following formulae are noted: (CH 3 ) 2 SiO CH 3 (CH 2 =CH)SiO CH 6.(C0-H3-.)SiO (C 6 H 5 ) 2 SiO One example of a suitable alpha, omega-dihydroxy polydi ethylsi loxane is that sold by Rhone Poulenc under the trade name "48V 3500". Alpha, omega-dihydroxypolydiorganosi loxanes can readi¬ ly be prepared by well-known techniαues described, for ex- ample, in FR-A-1134005, FR-A-1198749 and FR-A-1226745. The polvdiorganosiloxanes are preferably separated from vola¬ tile by-products before use, for example by the devolatil- isation process described in US-A-4356116. Preferred alpha, omega-dihydroxypolydimethylsiloxanes consist of successive groups of the formula (CH 3 ) 2 SiO or contain up to 10%, for example 2-10%, by mole of their 4 groups R as phenyl groups, for example in the form of (C e 0H0-.)2„SiO units. Alpha, omega-dihydroxypolydiorganosiloxanes are generally used with a curing agent, for example a compound containing at least two silicon-bonded hydrolysable groups per molecule. Examples of suitable curing agents are ketiminoxvsi lanes. acyloxysi lanes anc alkoxysi lanes, tetraalkyl titanates and aluminium alcoholates. A ketiminoxvsi lane curing agent preferably contains at least two silicon-bonded hvdrolvsable ketiminoxv groups per molecule. Such a curing agent is preferably used at 1 tc 18 parts by weight per 100 parts of alpha,omega-dihycroxy- polydiorganosi loxane. The ketiminoxvsi lane curing agent may have the general formula: γ f SlZ (4-f) in which: Y represents a hydrocarbon radical having 1 to 10 carbon atoms, which may be substituted by halogen or cyano: Z represents a hvdrolysable radical of the formula: 1 1 (2 2 ),C = NO- or E 1 C = NO- ά \ I in which the groups Σ 2, which can be the same or difrerent, represent C,ι-C8 0 hy-drocarbon radica Λ ls and E represents a C 4 .-C 8r alkv-lene radical: the g-roup*s Z' car, be the same cr different: and f represents 0 or 1. Examples of group Y are those listed aPove as ex- amoles of group R 4 in the diorganosiloxy units. Examples of ketiminoxvsi lane curing agents are tnose of the formulae: CH n Si TON = C(CH, CH ^ Si TON = C.CH )C H C " (CH 2. = CH)Si T"ON = C(CH.)C2H0 R ]„ .' C Λ DH5-Si T"'ON = CICHo) 1, CH^Si [ON = C (C 2 H C )(CH 2 ) 3 CH 3 1 3 , (CH 3 ),C = NOSi [ON = C(CH 3 )C 2 H 5 1 3 C ' t--*- * Sl TON = Ci (CtH2)a K 1 " Si [ON = C(C 2 0 H5,)(CHo„)14, or Si TON = C(CH3„)2.l'4. and their mixtures. An acyloxysi lane curing agent can for example have the formula: where R 5 is defined as for group 4 mentioned above, R6 is a monovalent hydrocarbon radical, e.g. of up to 8 carbon atoms, without aliphatic unsaturation and a is 0 or 1. The g radicals R can for example be alkyl such as methyl, ethyl, n-propyl , n-butyl or n-hexyl , cycloalky! such as cyclopenty! or cyclohexyl, or aryl such as phenyl, tolyl or xylyl. Examples of acyloxysilane curing agents are: CH Si ( 0C0CH n ) 3 C 2.H b. Si ( OCOCh 3 ) ύ Λ CH Λ = CHS i ( OCOCH. ) .. C ft H_ Si ( OCOCH ^ ) _ 2 2 o b An acyloxysilane curing agent can for example be used at 2-20 % by weight based on the alpha, o ega- dihvdroxyoolvdiorganosiloxane. An alkoxysilane curing agent can for example be a tetraalkyl orthosi1icate (tetraalkoxysilane) such as tetraethyl orthosi 1icate or an alkyl trialkoxysi lane such as methyl trimethoxysilane, ethyl trimethoxysilane or methyl triethoxysi lane. Alkoxysilane curing agents such as tetraethyl orthosi1icate are particularly preferred for use with moisture-curable polvdiorganosiloxanes. The roo -temoerature-curable polvdiorganosiloxane (C) can be moisture-curable because atmospheric moisture is usually present when coating a marine surface. A moisture- curable oolydiorganosi loxane can for example have hydrolysable end groups. The polvdiorganosi loxane (3) containing silicon-bonded hydrolysable groups is preferaplv formed by combining an alpha,omega-dihydroxypol diorgano¬ siloxane with a compound containing at least two silicon- bonded hydrolysable groups per molecule. Examples of suitable compounds of this type are the ketiminoxvsilanes anc acyloxysilanes described above as curing agents, for example methyl triacetoxy silane. which form colycior- ganosi loxanes tipped with silicon-bonded hydrolysable ketirmnoxy or acyloxy groups. Reaction between the sili¬ con-bonded hydroxyl groups of the aloha.omega-dihycrcxy- oolvdiorganosi loxane and the silicon-bonded hydrolysable groups of the said compound generally takes place as these materials are combined, so that the polvdiorganosi loxane (C) is at least partially tipped with silicon-bonded hydroxyl groups. An alternative polvdiorganosi loxane (C) tipped with silicon-bonded hydrolysable groups is an amine-tioped polvdiorganosiloxane, for example an aloha,omega-diarmnc- oolvdiorganosiloxane of the formula: 4 where R is defined as above, n is an integer such that the polvdiorganosi loxane has a viscosity of 700-1,000.000 m Pa s at 25°C. and R 7 and R8 each represent hydrogen c- a monovalent hydrocarbon group having 1 to 10 carbon atoms. Most preferably R 7 represents hydrogen and R8 represents an alkyl group having 2 to 6 carbon atoms. for example ethyl. prooyl , isopropyl, n-butyl or sec-butyl (but-2-yl). Examples of amine-tioped polvdiorganosiloxanes are sold under the Trade Marks "Silgan 500" and "Silgan 501J". The room-temperature-curable polydiorganosi loxane (C) is preferably used at 0.1 to 100 parts by weight, more preferably 1 to 50 parts by weight, per part by weight of the chlorinated material (chlorinated polyolefin (B) plus any other chlorinated hydrocarbon resin). The primer composition may contain a catalyst for the room-temperature curing of the polydiorganosi loxane. Examples of catalysts are metallic and organometal 1 ic salts of carboxylic acids. Metallic salts may be salts of tin, lead, nickel, cobalt, iron, chromium, ∑inc or man¬ ganese, for example stannous octoate. Preferred organometal 1 ic salts are diorganotin carboxylate compounds such as dibutyltin dilaurate or dibutyltin acetate. Organic titanium derivatives containing at least one -Ti-O-Si- or -Ti-O-C- linkage, e.g. an alkanolamine titanate, and organic zirconium derivatives can be used as catalyst, as described in US-A-4525565. The primer compositions preferably contain an organic diluent which can for example be an aliphatic, cyclo- aliphatic or aromatic hydrocarbon which is optionally halogenated such as n-heptane, n-octane, cyclohexane, methylcyclohexane, toluene, xylene, mesitylene, cumene, tetrahydronaphthalene, perchloroethylene, trichloroethane, tetrachloroethane, chlorobenzene or orthodichlorobenzene, an aliphatic or cycloaliphatic ketone such as methylethyl- ketone, methylisobutylketone, methylisoamylketone, cyclo- hexanone or isophorone: an ether such as a dialkyl ether of ethylene glycol or propylene glycol, or an ester such as ethyl acetate, butyl acetate or ethoxyethyl acetate. The diluent is preferably a solvent for the chlorinated poly¬ olefin (B), including any other chlorinated hydrocarbon resin present. The weight ratio of diluent to chlorinated polyolefin plus any other chlorinated hydrocarbon resin is preferably in the range 1:3 to 20:1, more preferably 2:3 to 10:1. The weight ratio of diluent to room-temoerature- curable polvdiorganosi loxane is usually 1:50 to 20:1, preferably 1:10 to 3:1. The primer composition can be prepared by mixing the aminosilane material (A) and the chlorinated polyolefin (B) with the room-temperature-curable polvdiorganosi loxane (C). The chlorinated polyolefin (B) and any other chlorinated hydrocarbon resin present are preferably dissolved in an organic solvent before mixing with the aminosilane material (A) and the polydiorganosiloxane (C). The primer composition can also contain additives selected from pigments, mineral fillers, thixotrooic agents, stabilisers, surfactants, antioxidants and plas- ticisers. It may be preferred to include colouring pig- ments in the primer composition so that it can be over- coated by a fouling-resistant layer of clear RTV silicone rubber. When incorporating pigments, it may be necessary to take precautionary steps to avoid any moisture present in the pigment from instigating premature curing of the room-temperature-curable polydiorganosi loxane (C). The simplest precaution is to ensure that any pigments used are thoroughly dry. Alternatively, the pigments can be dis¬ persed in a diluent, preferably a polydiorganosi oxane, which inhibits reaction of any moisture present in the pigment with the room-temperature-curable polydiorgano¬ si loxane (C). The pigment can for example be dispersed in a non-reactive polydiorganosiloxane oil such as a methyl- tipped polydimethylsiloxane oil before the pigment con¬ tacts the room-temperature-curable polydiorganosiloxane (C) (including any curing agent therefor) and preferably also before the pigment contacts the aminosilane material (A). In an alternative procedure the pigment is dispersed in a liquid hydroxyl-tipped polydiorganosiloxane before the pigment contacts the aminosilane material (A) or any curing agent or material containing silicon-bonded hydrolysable groups which forms part of the room-temperature-curable oolydiorganosiloxane (C). When this alternative procedure is used, the liquid hydroxyl-tipped polydiorganosiloxane used as dispersion medium will generally become co-cured with the room-temperature-curable polydiorganosi loxane (C). It can itself be used as the room-temperature-curable polydiorganosiloxane (C), in conjunction with a curing agent added later. It is generally preferred however that a liquid hydroxyl-tipped polydiorganosiloxane used as dispersion medium for the pigment forms only part of the polydiorganosiloxane (C); for example it can be used with a latei—added moisture-curable polydiorganosiloxane (C) tipped with hydrolysable groups. The primer composition is particularly effective in promoting adhesion to organic resin substrates such as neoprene rubber, chlorinated rubber, block copolymer rubbers such as polystyrene/polybutadiene or polysty- rene/poly(ethylene-butylene) rubbers, polyurethanes, (both elastomers and thermoplastic resins), epoxy coatings, vinyl resins such as vinyl chloride polymers or alkyd resins. These resins may for example be in the form of cladding in the case of neoprene and similar rubbers, or may be pre¬ viously-applied coatings, for example anticorrosive coat¬ ings which are to be covered by a silicone rubber antifoul- ing paint, or old antifouling coatings which are to be overcoated. The primer composition also promotes adhesion to metal substrates such as aluminium or steel. The primer composition can be applied to the substrate by any known coating technique. Usually it is applied by spray, brush or roller. The RTV silicone rubber fouling-resistant coating which is applied over the primer composition can for example be based on an alpha, omega-dihydroxypolydioi— ganosiloxane as described above, used with a curing agent selected from those described above and optionally a catalyst selected from those described above. Alternative- ly, the RTV silicone rubber can be a polydiorganosi loxane tipped with silicon-bonded hydrolysable groups as described above, for example silicon-bonded ketiminoxy or acyloxy groups. It may be preferred that the curing agent or silicon-bonded hydrolysable groups in the room-temoerature- curable diorganopolysi loxane (C) in the primer composition and the curing agent or silicon-bonded hydrolysable groups in the RTV silicone rubber coating are the same. The RTV silicone rubber coating preferably includes a non-reactive silicone oil, for example of the formula: Q Si-0-(SiQ_- 0-)nSiQ-„i. wherein each group Q represents a hydrocarbon radical having 1-10 carbon atoms and n is an integer such that the silicone oil has a viscosity of 20 to 5000 Pa s. At least 10% of the groups Q are generally methyl groups and at least 2% of the groups Q are preferably phenyl groups. Most preferably, at least 25% of the -SiQ ? -0- units are methylphenylsiloxane units. Most preferably the non-reactive silicone oil is a methyl-terminated poly(- methylphenylsiloxane) . The oil preferably has a viscosity of 20 to 1000 m Pa s and is preferably used at 1 to 50%, most preferably 2 to 20%, by weight based on the RTV silicone rubber. An example of a preferred non-reactive silicone oil is that sold under the Trade Mark "Rhodorsil Huile 550". The non-reactive silicone o l improves the resistance of the composition to aquatic fouling. Instead of, or in addition to, the non-reactive silicone oil, the RTV silicone rubber composition can contain a non-reactive fluid organic hydrocarbon, for example a lubricating mineral oil such as white oil, a low molecular weight polvbutene or petrolatum or a liquid paraffin/petrolatum mixture. Such a non-reactive fluid organic hydrocarbon is preferably absent from the primer composition. The primer composition improves the overall adhesion of the RTV silicone rubber to the substrate to a greater extent than can be achieved in the absence of any cf the essential components (A), (B) and (C). The aminosilane material (A) and chlorinated polyolefin (B) ensure strong adhesion of the primer to the RTV silicone rubber and to the organic resin substrate respectively. We have however found that when a composition comprising aminosilane material (A), chlorinated polyolefin (B) and solvent is applied to many organic resin substrates it is rapidly absorbed by the substrate, so that adhesion of a subse¬ quently applied RTV silicone rubber coating is poor unless it is applied very soon. The room-temperature-curable polydiorganosi loxane (C) counteracts the tendency for the primer composition to be absorbed by the substrate, allow¬ ing a much longer time period, for example up to a week or even longer, within which overcoating with an RTV silicone rubber composition can be achieved with good adhesion. The primer composition according to the invention has much greater adhesion to many substrates, in particular neoprene, chloroprene or hydrocarbon rubbers, than a composition which does not contain chlorinated polyolefin. On all substrates, including those such as epoxy resin where the simple combination of room-temperature-curable polydiorganosi oxane and aminosilane material gives good adhesion, the chlorinated polyolefin improves the resis¬ tance to sea water immersion: good adhesion of the primer composition to the substrate and of the RTV silicone rubber top coat to the primer composition is maintained even after 18 months or more of immersion in sea water. The invention is illustrated by the following Examples in which parts and percentages are by weight. Exa p1e 1 25 parts of a 40% solution in xylene of a chlorinated polyethylene (chlorine content 22%) was mixed with 2 parts N-(2-aminoethyl )-3-aminopropyl trimethoxy silane and diluted with 73 parts xvlene. 14 parts of the resulting composition was mixed with 61 parts of a room-temperature-curable oolydiorganosi loxane composition and 25 parts methyl isoamyl ketone solvent. The room-temperature-curable polydiorganosi loxane composi- tion comprised an alpha, omega-dihydroxypoly- di ethylsi oxane used with a ketiminoxvsi lane curing agent. The resulting primer composition was applied to a neoprene rubber substrate, and also to substrates coated with epoxy resin, polvurethane, vinyl resin and alkyc resin anticorrosive paints, and to a substrate having the residue of an old antifouling paint based on rosin, a vinyl chloride copoly er and cuprous oxide. In all cases the coating of primer composition could be overcoated with an RTV silicone rubber foul ing-resistant composition oased on an alpha, omega-dihydroxypolydiorganosi loxane with a ketiminoxvsi lane curing agent and a non-reactive ooly(- methyl phenyl si loxane) oil about 10 minutes after applica¬ tion of the primer composition with good adhesion of the RTV composition, and could also be overcoated with the RTV composition 24 hours later with good adhesion. The overcoated materials were immersed in sea water. Adhesion between the primer composition and the substrates, and between the RTV silicone rubber foul ing-resistant coating and the primer composition, remained strong after 18 months immersion in sea water. Example 2 29.7 parts of pigments and fillears (barytes, titanium dioxide, fumed silica and black iron oxide) and 0.1 cart of dibutyltin dilaurate curing catalyst were dispersed by milling in 6.7 parts of non-reactive methyl-tipped oolydi- methylsi loxane oil and 10.6 parts of methyl isoamyl ketone solvent. The resulting pigment dispersion was mixed with 36.4 parts of room-temperature-curable polydimethylsi loxane tipped with ketiminoxy groups, 8.3 parts of the solution of chlorinated polyethylene and N-(2-aminoethyl )-3-aminopropy1 trimethoxy silane described in Example 1 and 8.2 parts of methyl isoamyl ketone. The resulting primer composition was applied to epoxy resin, neoprene rubber and urethane rubber substrates. These samples were overcoated after 16 to 48 hours with the RTV silicone rubber of Example 1. The overcoated materials were immersed in sea water. Adhesion between the primer composition and the substrates, and between the RTV silicone rubber fouling-resistant coating and the primer composition, remained strong after 16 months' immersion in sea water. Example 3 28.1 parts of pigments and fillers (titanium dioxide, barytes, black iron oxide and fumed silica) were dispersed by milling in 11.5 parts of liquid hydroxyl-tipped polydi¬ methylsi loxane with 0.5 part of wetting aid and 11.4 parts of methyl isoamyl ketone. The resulting pigment dispersion was mixed with 7.6 parts of the solution of chlorinated polyethylene and N-(2-aminoethyl )-3-aminopropyl trimethoxy silane described in Example 1, 30.9 parts of room-tempera¬ ture-curable polydimethylsi loxane tipped with ketiminoxy groups, 0.03 part of dibutyltin dilaurate and 10.0 parts of methyl isoamyl ketone. The resulting primer composition was applied to substrates of epoxy resin, aluminium, urethane rubber, neoprene rubber, a substrate having a residue of old antifouling paint as described in Example 1, polystyrene/polybutadiene block copolymer rubber and polystyrene/polyfethylene-butylene) block copolymer rubber. These samples were overcoated after 16 to 48 hours with the RTV silicone rubber of Example 1. The overcoated materials were immersed in sea water. Adhesion between the primer composition and the substrates, and between the RTV silicone rubber foul ing-resistant coating and the primer composition, remained strong after 6 months' immersion in sea water.

Claims: CLAIMS 1. A primer composition for application to a suostrate to promote adhesion of a room-temperature-vulcanisable silicone rubber coating, which primer composition com- prises: (A) an aminosilane material which is (i) a primary amine-functional silane of the formula: (RO) χ R (3 _ χ) SiR 1 NHR 2 (I) where the radicals R, which can be the same or different, are monovalent hydrocarbon radicals having 1 to 12 carbon atoms and optionally contain¬ ing an ether linkage; R is an alkylene radical having 2 to 4 carbon atoms or a divalent aliphatic ~ ether radical having 3 to 8 carbon atoms: R" is hydrogen or an alkylene radical of 2 to 4 carbon atoms tipped with a primary amino group: and x is 2 or 3: or Hi) the reaction product of a primary amine-functional silane of the formula (I) with an epoxy-functiona! silane of the formula: A- Si(B)a a (OB)(, ό-.-a a .,) (II) where A is an epoxide-substituted monovalent hydrocarbon radical having 4 to 12 carbon atoms; the radicals B, which can be the same or different, are alkyl radicals having 1 to 4 carbon atoms; and a is 0 or 1 ; or (iii) the reaction product of a primary amine-functional silane of the formula (I) with an alpha, omega- dihydroxypolydimethylsiloxane oi! of the formula: HO(Si(CH 3 ) 2 0) y H (III) in which v is 2 to 60: (B) a chlorinated polyolefin; and (C) a room-temperature-curable polydiorganosi loxane. 2. A primer composition according to claim 1, charac¬ terised in that the room-temperature-curable polydior- ganosiloxane (C) is an alpha, omega-dihy roxypolydiorgano¬ si loxane used in conjunction with a ketiminoxvsi lane curing agent. 3. A primer composition according to claim 1, cnarac- terised in that the room-temperature-curable polydior- ganosi loxane (C) is an alpha, omega-dihydroxypolydiorgano¬ si loxane used in conjunction with an acyloxysi lane curing agent. 4. A primer composition according to claim 1, charac¬ terised in that the room-temperature-curable polydior- ganosiloxane (C) is an alpha, omega-dihydroxypolydiorgano¬ si loxane used in conjunction with an alkoxysilane curing agent. 5. A primer composition according to claim 1, charac¬ terised in that the room-temperature-curaPle polydioi— ganosi loxane (C) is a polydiorganosiloxane tipped with silicon-bonded hydrolysable groups. 6. A primer composition according to claim 5, charac¬ terised in that the silicon-bonded hydrolysable groups are ketiminoxy, acyloxy or amine groups. 7. A primer composition according to any of claims 1 to 6, characterised in that the chlorinated polyolefin (B) has a chlorine content of 17 to 40% by weight. 8. A primer composition according to any of claims 1 to 7. characterised in that the composition contains another chlorinated hydrocarbon resin in an amount of 1 to 100% by weight based on the chlorinated polyolefin (B). 9. A primer composition according to any of claims 1 to 8, character sed in that the aminosilane material (A) is used at 1 to 20% by weight based on the weight of chlorin¬ ated polyolefin (B) plus any other chlorinated hydrocarbon resin present in the composition. 10. A primer composition according to any of claims 1 to 9, characterised in that the weight ratio of the room- temperature-curable polydiorganosiloxane (C) to the chlor¬ inated polyolefin (B) plus any other chlorinated hydrocar— bon resin present in the composition is 1:1 to 50:1. 11. A primer composition according to any of claims 1 to 10, characterised in that a pigment is dispersed in the composition. 12. A process for preparing a primer composition in which (A) an aminosilane material which is (i) a primary amine-functional silane of the formula: (RO) χ R (3 _ χ SiR 1 NHR 2 (I) where the radicals R, which can be the same or different, are monovalent hydrocarbon radicals having 1 to 12 carbon atoms and optionally contain¬ ing an ether linkage; R is an alkylene radical having 2 to 4 carbon atoms or a divalent aliphatic ether radical having 3 to 8 carbon atoms; R 2 is hydrogen or an alkylene radical of 2 to 4 carbon a . tomε tipped with a primary amino group; and x is 2 or 3; or (ii) the reaction product of a primary amine-functional silane of the formula (I) with an eooxy-functiona! silane of the formula: A - Si ( B) a (OB) (3 _ a) (II) where A is an epoxide-substituted monovalent hydrocarbon radical having 4 to 12 carbon atoms; the radicals B, which can be the same or different, are alkyl radicals having 1 to 4 carbon atoms; and a is 0 or 1 ; or (iii) the reaction product of a primary amine-functional silane of the formula (I) with an alpha, omega- dihydroxypolydimethylsi loxane oil of the formula: H0(Si ( CH 3 ) 2 0) y H (III) in which y is 2 to 60; and (B) a chlorinated polyolefin; are mixed with (C) a room-temperature-curable polydiorganosi loxane. 13. A process according to claim 12, characterised in that a pigmented primer composition is prepared by dispers¬ ing a pigment in a non-reactive polydiorganosiloxane oil and mixing with the aminosilane material (A), the chlorin- ated polyolefin (B) and the room-temperature-curable polydiorganosi loxane (C), said step of dispersing the pigment in polydiorganosiloxane oil being carried out before the pigment contacts the aminosilane material (A) or the room-temperature-curable polydiorganosi loxane (C). 14. A process according to claim 12, characterised in that a pigmented primer composition is prepared by dispers¬ ing a pigment in a liquid hydroxyl-tipped polydiorgano¬ siloxane and mixing it with the aminosilane material (A), the chlorinated polyolefin (B) and the room-temperature- curable polydiorganosiloxane (C), said step of dispersing the pigment in a liquid polydiorganosiloxane being carried out before the pigment contacts the aminosilane material (A) or any curing agent or material containing silicon- bonded hydrolysable groups which forms part of the room- temperature-curable polydiorganosi loxane (C). 15. A process according to claim 12, characterised in that a pigmented primer composition is formed by dispersing a pigment in a liquid hydroxyl-tipped polydiorganosi loxane and mixing it with the aminosilane material (A), the chlorinated polyolefin (B) and a curing agent which together with the liquid hydroxyl-tipped polydiorgano¬ siloxane forms the room-temperature-curable polydiorgano¬ siloxane (C), said step of dispersing the pigment in a liquid polydiorganosiloxane being carried out before the pigment contacts the aminosilane material (A) or the said curing agent. 16. A process for coating a substrate with a room- temperature-vulcanisable silicone rubber, characterised in that the substrate is coated with a primer composition according to any of claims 1 to 11 and the room-tempera- ture-vulcanisable silicone rubber composition is applied over the said primer composition. 17. A process according to claim 16, characterised in that the primer composition is as defined in any of claims 2 to 4 and the room-temperature-vulcanisable silicone rubber composition comprises an alpha,omega-dihydroxypoly¬ diorganosi loxane used in conjunction with a curing agent of the same type as is used in the primer composition. 18. • A process according to claim 16, characterised in that the primer composition is as defined in claim 5 or claim 6 and the room-temperature-vulcanisable silicone rubber composition comprises a polydiorganosiloxane tipped with silicon-bonded hydrolysable groups of the same type as those in the room-temperature-curable polydiorganosiloxane (C).

Inventors: BROOKS RODNEY RALPH, WINTER MICHAEL JOHN, BROOKS, RODNEY, RALPH, WINTER, MICHAEL, JOHN
Applicants: COURTAULDS COATINGS HOLDINGS, COURTAULDS COATINGS (HOLDINGS) LIMITED
Application year: 1991
Main classification: C09D183
IPC codes: C09D123, C09D183