CA2078144C - Coating composition - Google Patents

Abstract

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

Description

.,..
~0'~~~. ~4 COATING COMPOSITION
r= ~ a : o= the i nvent i on This invention relates to a primer composition for application to a substrate to promote adhesion of a room-temperature-vulcanisable (RTf) silicone rubaer COatln~.
RTV silicone rubber coatinGS are applied to underwater suri=aces, for example ships' hulls. the cooling water inlets and outlets of power stations, fish-f arming eaui~-1G 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 coatin4s are des cribed for example in GB-A.-1307001. GB-A-1470465. GB-A
1581727. GB-A-214143,6: EP-A-16195 and US-A-3702772. RTV
silicone rubber coatings have also been suggested as coatings inhibiting the adhesion of ice. for example on the superstructure ahd 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 claCCing on a fabric backing.
Various primer compositions have been suggested for room-temperature-vulcani able silicone rubber antifoulinas.
US-A-3702778 proposes a crosslinkable silicone paste. EP-A-89066 proposes a mixture of, an epoxysiiane and a silane containing an unsaturated hydrocarbon group. JP-A-53 3C 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/silicone rubber.

~D'7~14~
EP-R-323905 and EP-A-329375 propose a silicone resin containing an aminosilane.
US-A-4070421 describes the use of chlorinated 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:
1G (A) an aminosilane material which is (i) a primary amine-functional silane of the formula:
(RG)xR(3-x)SiRINHR2 (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-ina an ether linkage: R1 is an alkylene radical having 2 to 4 carbon atoms or a divalent aliphatic ether radical having 3 to 8 carbon atoms: R2 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 amine-functional silane of the formula (I) with an epoxy-functional s i 1 ane of the f ormu 1 a A - SifB)a(OB)(3-a~ (II) where A is an epoxide-substituted monovalen~
hydrocarbon radical having 4 to 12 carbon a:,oms;
the radicals 9, which can be the same or different.
are alkyl radicals having 1 to 4 carbon atoms: and a is 0 or 1: or v.J
(iii) the reaction product of a primary amine-i=unctiona'~
siiane of the formula (I) with an aloha, ome4a-dihydroxy~olvdimethylsiloxane oil of the formula:
HO(Si(CH3)2v)vH iIT_~) in which v is 2 to 6G:
(.B) a chlorinated polyolefin; and (C) a room-temperature-curable,polydiorganosiloxane.
Detailed disclosure In the primary amine-functional siiane of formula ;I;~
the radicals R are preferably alkyl, for example methyl, ethyl, hexyl or octyi, aryl,. for example phenyl, or aralkyl, for example benzyl. The alkylene radical R1 is preferably -(CH2)3-, -(CH2)4- or methyl-sub-stituted trimethvlene, or can be -(CH2)3-0-(CH2)2.
1~~ -tCH2)J-0-l.CH2)3- or -CH2-p,-lCH2)2-. R2 is prei=erably any ether oxygen atom in R and Rl by at least two carbon atoms from the nearest heteroatom. Examples of primary amine-functional silanes of formula (I) are:
(CH30)3Si(CH")3NH(CH2)'NH2: (CH3CH~OCH2t;H'0)3Si(CH2).'NH':
(C2H~0)zSi(OH')3NH2: (CH~OCH2CH20)3Si(CH2)3NH2;
(C2HS0)jSi(CH')30(CH2)3NH2; (C2HSp)~C6H~gi(CH2)3NH2:
(C,.,H~O)VSiCH~O(CH2)'NH2: (C2HS0)3Si(CH2)30(CH2)2NH2; and tC2H50)GCH3Si(CH2)3NH2. Mixtures of twc or more primary 2~ amine-functional siianes (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-functional silane (II). The group A in the epoxy-functional silane (II) is preferably a glycidoxy-substituted alkyl croup. far example 3-giycidoxypropyl. The epoxy-functional silane hydrogen or -CH2CH2NHG. It may be preferred to separate IIi can for example be ~-glycidoxypropyl trimethexy silane. ~-glycidoxypropyl diethoxy methoxy silane. 2-glycidoxypropyl .trimethoxy silane. ~-(3.4-epoxycyciohexyli oronvl trimethoxy silane or 2-(2.4-epoxy-4-methylcyclo hexyl)-ethyl trimethoxy silane. Examples of preferred reaction products of an amine-functional silane (I) and an e~oxv-functional siiane (II) are:
(C2H~0)3Si(CH~)3 - NH - CH.~ - CH - CHI - 0(.CH2)~Si(0~2H,~)~
OH
(CH~O)3Si(CH')3 - NH =,rH~ - CH - CHI - 0(CH.~)3Si(OCH,~~v ,,.,., :v pH
(CH~O)~Si(CH2)~ - NH-(CHI)2-NH-CH2-iH-CH2-0(CH2)SSi(OCHJ)3 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 react~cn croduct of the primary amine-functional silane cI) and an alpha, omega-dihydroxypolydimethylsiloxane (TIIi. (L) and (III) can be .reacted at 20-80°C, preferably using 0.4-1.2 alkoxy groups of amincsilane (I) per silancl group in (III).
The chlorinated polyolefin (Bi preferably has a mol~,:uiar weight of 5.000 to 50.000 and a chlorine content of 1 5 to 75~, most preferabl y 1 7 to 409. by we i ghT;..
Chlorinated polyolefins are commercially available. They can be prepared by treating a polyolefin with chlorine ir:
the presence of a peroxide catalys;,. The chicrinatior, 3C reaction is preferably carried out in a solvent for the polyolefin starting material. The polyolefin is pref~rab-y a poly(alpha-olefin) such as polyethylene or poiyprcpyiene.

.:~~,~, The ~clyolefin can be cf high or lcw censitv, ameruhous cr crystalline: It can be a copci~rmer cf two or more olefins.
preferably alpha-olefins. Suitabla chlorinated oolvolefins are descri bed fo;- exar;~ple i n US-A-35~ ; 36:; and US-A-x:070421 .
The ch l on nated pp l yo ; ef i r i B > c, an be used i r , con i unc-tion with another chlorinated hycrocarbon resin, fcr example a chlorinGted polyterpene resin or chicrir~ate~
cclys yrene. The polyst_~rene is preferably of low mole-cu1 ar wei gh t ( 1 ess than 5000 ) . Suc!~ a c;. 1 on hated hvdrc-1 0 carbon res i n prei=erabl y has a s i ~~~ i 1 ar dog roe cf ch i cri na ~icn tc the chlorinated polvolefin. The chlor~nateC
hydrocarbon resin can for examp,ie be used in an amount of from 1 to 1000 by weight based on the chlorinated oolvcie in (B).
15 The aminosilane material (A) is generally used at 0.1 to f0% by weight based on the chlorinated material (chlor-ina~ed oolyolefin (B) plus ahy other chlorinated hvdrocar-bcn resin), most preferably 1 to 20% by weight:
The room-temperature-curable polydiorganosiicxane (C) 2~~ is preferably a polydiorganosiloxane of viscosity 700 to 1.000.000 m Pa s at 2~°C. It creferably contains sii.ccn-bonded hydroxyl groups. for examale an aloha:omeaa-dihydroxypoiydioraanosiloxane, or silicon-bonded hvdrolvs-abla groups. for example a polydioraanosiioxane tiQOed with 25 silicon-bonded hydrolysabie groups. Mcre preferably, it is formed of recurring diorganesiloxy units of the formula - R~2SiG - where the radicals R4, which can be the same or K different. represent hydrocarbon radicals having 1 to 10 carbon atoms. It is preferred that at beast 50% of the 30 radicals R4 are methyl groups. The dihydroxypolydior ganosiloxane may further contain monoorganosiloxy groups cf the formula R4SiC1.5 and%or siloxy groups of the formula SiG2 in a maximum proportion of 2% with respect to the number of dioraanosiloxy groups R4~S~p.

20'~~144-The hydrocarbon radicals represented by the symbol R4 in the di- and mono-organosiloxy units may suitably be selected from alkyl radicals such as methyl, ethyl, n-propyl, isopropyl, n-butyl. n-pentyl. n-hexyl. 2-ethyl hexyi or n-octyl, cycloalkyl radicals having frcm 4 to b carbon atoms such as cyclopentyl, cyclohexyl or methyi cyclohexyl, alkenyl radicals having from ~ to 4 carbcn atoms such as vinyl. allyl or buten-2-yl, and aryl radicals having from 6 to 8 carbon atoms such as phenyl, tolyl or xvlvl.
As preferred examples of the groups represented by R'~~SiC~ the following formulae are noted:
(CH3)2Si0 CH3(CH2=CH)Si0 CH3(C6H5)Si0 (C6H5)2Si0 One example of a suitable alpha: omega-dihydroxy polydimethylsiloxane is that sold by Rhone Pouienc under the trade name "48V 3500".
Alpha: omega-dihydroxyoolyd~organosiioxanes can reac--1v be prepared by well-known techniaues described. for ex-ample. in FR-A-1134005. FR-A-1198749 and FR-A-1226745. The pclydiorganosiloxanes are preferably separated from vola-tile by-products before use. for example by the devolatil-isation process described in US-A-4356116.
Pref .erred alpha. omega-dihydroxypolydimethylsiloxanes consist of successive groups of the formula (CH3)2Si0 or contain up to 10~, for example 2-10~. by mole of their groups _ .R4 as phenyl groups, for example in the form of (C6H~)~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 WC? 91/14747 PCT/GB91/00454 ~fl'~~144 ketiminoxysilanes, acyloxysilanes ant alkoxysilanes.
tetraalkyl titanates and aluminium alcoholates.
A ketiminoxysilane curing agent preferably contains at least two silicon-bonded hydrolysable ketiminoxy grouts per molecule. Such a curing agent is preferably used Gt 1 tc 1° parts by weight per 100 parts of alpha.omeaa-dihydrcxy-polydiorganosiloxane. The ketiminoxysilane curing agent may have the 4eneral formula:
Y ~~.SiZi (4-f ) in which:
f1 represents a hydrocarbon radical having i to 10 carbon atoms. which may be substituted by halogen or cyane:
Z1 represents a hydroiysable radical of the formula:
~"'-I
( Z~2 ) 2C = N0- Dr EL1-CI - N
1~ in which the groups Z2. which can be'the same or different.
represent Ci-C8 hydrocarbon radicals and Ei represents a C~-CS alkylene radical: the groups Z' car, be the same cr different: and f represents 0 or 1.
Examples of group Y1 are those listed above as ex-amoles of group Fc4 in the diorganosiloxy units.
Examples of ketiminoxysilane curing agents are those of the formulae:
CHVSi [ON - C(CHj)2]J. CHjSi SON = C(CHj)L2HS~V, (CH2 _ CH)Si tON = C(CH3)C2H5]5, C6H~Si [ON = C(CN3)']3.
CH"Si [ON _ C (C2H=)(CH2)3CHj13.
(CH3)2C NOSi [

CH3Si fON = C (CH2)~l_3 CHJSi [ON - i (CH2)51S
Si~ON - C(C~H5)(CHS)14 or SifON - C(CHJ)'14 and their mixtures.
An acyloxysilanE curing agent can for example have the formula:
R5aSi(OCOR6)4-a where RS is defined as for group R4 mentioned above. R0 is a monovalent hydrocarbon radical, e.g. of up to 8 carbon atoms, without aliphatic unsaturation and a is 0 or 1. The radicals R6 can for example be alkyl such as methyl.
ethyl. n-propyl, n-butyl or n-hexyl. cycloalkyl such as cyclopentyl or cyclohexyl, or aryl such as phenyl, tolyl or xvlvl. Examples of acyloxysilane curing agents are:
CHjSi(OCOCHS)3 ~C2H~Si(OCOCH3)J
C6HvSi(OCOCHC)3 CH ,, - CH S i ( OCOCH f ) ,..
CH3Si(OCOCH(C2Hv)fCH2).VCHS)3 CFVCH2CH2Si(OCCC6H5)3 An acyloxysilane curing agent can for example be used at 2-20 ~ by weight based on the aloha, omega dihydroxypolydiorganosiloxane.
An alkoxysilane curing agent can for example be a tetraalkyl orthosilicate (tetraalkoxysilane) such as tetraethyl orthosilicate or an alkyl trialkoxysilane such as methyl trimethoxysilane, ethyl trimethoxysilane or 2~ methyl triethoxysilane. Alkoxysilane curing agents such as tetraethyl orthosilicate are particularly preferred for use with moisture-curable polydiorganosiloxanes.
The room-temperature-curable polydiorganosiloxane (C' can be moisture-curable because azmosoheric moisture is usually present when coating a marine surf ace. A moisture-curable poiydioraanosiloxane can for examt~le have hydrolysable end group : The polydiorgahosiioxane (r ) containing silicon-bonded hydrolysable groups is preferably formed by combining an alpha,omega-dihydroxypoiydicraano-siioxane with a compound containing at least two silicon-bonded hydrolysabie groups per molecule. Examples of suitable compounds of this type are the ketiminoxvsilar,es ane acyloxysilanes described above as curing agents, for example methyl triacetoxy silane, which form colvcior-ganosiloxanes tipped with silicon-bonded hvdrolvsable ketiminoxy or acyloxy 4roups: Reaction between the sili-con-bonded hydroxyl- groups of the alpha, omega-dihycrcxy-1~ oolydiorganosiloxane and the silicon-bonded hvdrolvsable groups of the said compound generall.v takes d ace as these materials are combihed, so that the oolydiorganosiioxane (C) is at least partia3ly tipped with silicon-bonded hydroxyl groups.
An alternative polydiorganosilcxane (c:) tipped with silicon-bohded hydrolysable grcups is an amine-tiobe poiydiorganosiloxane, for example an aipha,omega-diaminc-polydiorganosiloxane of the formula:

\ i 1 .l /
N - Si - O Si - 0 Si - N
R8 R4 ~4 n R4 P8 R
where R4 is defined as above, n is an integer such that the polydioraanosiloxane has a viscosity of 7Q0-1.000.000 m Pa s at 25°C, and R7 and RB each represent hyCroger, cr a monovalent hydrocarbon group having 1 to 10 carbon atoms.
Most preferably R7 represents hydrogen and R8 represents ar alkyl group having 2 to 6 carbon atoms. for example ethyl.
propyl, isopropyl, n-butyl or sec-butyl (but-2-vi).
Examples of amine-tipped polydiorganosiioxanes are sold ~'~~~.44 under the Trade Marks "Silgan 500" and "Silgan 501J".
The room-temperature-curable poiydiorganosiloxane (C) is preferably used at 0.1 to 700 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 conrain a catalyst for the room-temperature curing of the polydiorganosiioxane.
Examples of catalysts are metallic and organometallic salts of carboxylic acids.,',Metallic salts may be salts of tin, lead, nickel, cobaht, iron: chromium, zinc or man-ganese, for exampie~ stannous octoate. Preferred oraanometallic salts are diorganotin carboxylate compounds such as dibutyltin dilaurate or dibutyltin acetate. Organic titanium derivatives containing at least one -Ti-0-Si- or -Ti-0- .C- linkage, e.9. 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 halo4enated such as n-heptane, n-octane, cyclohexane.
methylcyclohexanetoluene, xylene, mesityiene, cumene, tetrahydronaphthalene, perchloroethylene. trichioroethane, tetrachloroethane, chlorobenzene or orthodichlorobenzene, an aliphatic or cycloaliphatic ketone such as methylethyl-ketone. methylisobutyiketone, 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 oolvolefin plus any other chlorinated hydrocarbon resin is preferably in the range 1:3 to 20:1, more preferably 2:3 to ~~''~~~.4~' 10:1. The weight ratio of diluent to room-tem~erature-curable polydioraanosiloxane is usually 1:50 to 20:1.
preferably 1:10 to 3:7.
The primer composition can be prepared by mixing the aminosilane material (A) and the chlcrinated ao'lyolefi-n (8) with the room-temperature-curable polydiorganosiloxane (C).
The chlorinated polyolefin (B) and any other chlorinated hydrocarbon resin present are preferably dis dived in an organic solvent before mixing with the aminosilane material (A) and the polydiorganosiloxane (C).
The primer composition can also contain adaitives selected from pigments, mineral fillers, thix~trooic agents,. stabilisers, surf actants, antioxidants and. nlas-ticisers. It may be preferred to include colouring pia-merits in the primer composition so that it can be over-coated by'a fouling-resistant layer of clear RTV silicone rubber. When incorporating pi4menirs, it may be necessary to take precautionary steps to avoid any moistura present in the pigment from instigating premature curing of the ~0 room-temperature-curable oolyd',ioraanosiloxane (C): The simplest precaution is to ensure that any pigments used are thoroughly dry. Altornatively, the aigments can be dis-persed in a dilvent. preferably a. nolydior4anosiloxane.
which inhibiis reaction .of any moisture pre er,t in the pigment with the room-temperature-curable oolydiorgano-siloxane (C). The pigment can f or exampla be disaersed in a non-reactive polvdioraanosiloxane oil such as a methvl-tipped poiydimethyisiloxane 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 ah alternative procedure the,pigment is dispersed in a liouid hydroxyl-tipped polydiorganosiloxane before the pigment contacts the aminosilane material (A) or any curing agent or material containing silicon-bonded hydrolysahle groups which forms part , of the room-tems~erature-curable Dolvdiorganosiloxane (C). When this alternative procedure is used; the lieuid hydroxyl-tipped polydiorganosiloxane used as dispersion medium will generally become co-cured with the room-temperature-curable polydiorganosiloxane (C).
It can itself be used as the room-temperature-curable oolvCiorgancsiloxane (C), in con.iunction with a curing agent added later. It is generally preferred however that liauid hydroxyl-tipped polydiorganosiloxane used as dispersion mediuym for the pigment forms only part of the polydioraanosilAx~ane (C): for example it can be used with a later-addedv,' 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. chiorinated 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 anv known coating technioue. Usually it is applied by spray, brush or roller.
The RTV- silicone rubber fouling-resistar;t coating whit h is applied over the primer compositicn can for example be based on an alpha, omega-dihydroxypolydior-ganosiloxane .as described above, used with a curing agent selected from those described above and optionally a catalyst selected from those described above. Alternative-~.p'~~1~4 1y, the RTV silicone rubber can be a polydiorganosiloxane tipped with silicon-bonded hydrolysabie groups as described above, for example silicon-bonded ketiminoxy or' acyloxy groups. It may be preferred that the curing scent or silicon-bonded hydrolysable groups in the room-temperature curable diorganopolysiloxane (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: ~avSi-0-tSiC~2-0-?nSiQJ. 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 m Pa s.
At least 10% of the- groups Gr are generally methyl groups and at least 2~ of ; the groups Q are preferably phenyl groups. Most preferably, at least 25% of the -SiC~2-0-uni s are methylghenylsiloxane units. Most preferably the non-reactive silicone oil is a methyl-terminated poly(-methylphenylsiloxahe}: The oil preferably has a viscositv_ 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 Huila 550". The non-reactive silinone oft improves the 2~ resistance of the compositioh to aauatic fouling.
Instead of, or in addition to, the non-reactive silicone oii, 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 polybutene 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 of the essential components (A), (8) and (C). The aminosilana material (A) and chlorinated polyolefin (B) ensure strong adhesion of the primer to the RTV silicone rubber and to the or4anic 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 pcor unless it is applied very soon,. The room-temperature-curable polydiorganosiloxane (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 RT'v silicone rubber composition can be achieved with good adhesion.
The primer composition according to the wvenL~on nas 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 polydiorganosiloxane _and aminosilane material gives good adhesion. the chlorinated polyolefin improves the resis-tance .to sea water ~mmer-s vUW : Nvuu QUIICa 1 Vi, v, ~,.c composition to the substrate and of the RTV silicone rubber too 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.

3~ Example 1 25 Darts of a 40~ solution, in xylene of a chlorinated polyethylene (chlorine content 220) was mixed with 2 Darts N-(2-aminoethyl)-3-aminopropyl trimethoxy silane and diluted with 73 parts xylene.

~~'~~~.44 1~
14 parts of the resulting composition was mixed with 6l parts of a room-temperature-curable polydioraanosiloxane composition and 25 parts methyl isoamyl ketone scivent.
The room-temperature-curable polydiorganosiloxane comoosi-tion comprised an alpha. omega-dihydroxypoly-dimethyl iloxane used with a ketimihoxysilane curinc_ agent.
The resulting primer composition was applieC to a neoprene rubber substrate, and also to substrates coated 1C with epoxy resin, polyurethane, vinyl resin and alkyC resin anticorrosive paints. an,d to a substrate having the residue of an old antifouling paint based on rosin, a vinyl chloride copolymer and cuprous oxide. In all cases the coating of primer composition could be overcoated with an RTV silicone rubber fouling-resistant composition cased on an , alpha, omega-dihydroxypolydiorganosiloxane with a ketiminoxysilane curing agent and a non-reactive oolv!-methyl phenyl siloxane) oil about 1O minutes after acclica-tion of the prime r compositioh 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 fouling-resistant coat;ihg and the primer composition, remained stronc 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 wart of dib;;tyltin dilaurate curing catalyse were dispersed by milling in 6:7 parts of hop-reactive methyl-tipped ~olydi-methylsiloxane oil and 10.6 parts of methyl isoam_vl ketone solvent. The resulting pigment dispersion was mixed with 36.4 Qarts of room-temt~erature-curable oolvdimethvlsiloxane tipped with ketiminoxy groups. 8.3 parts of the solution of chlorinated polyethylene and N-(2-aminoethyl)-3-aminopropyl trimethoxy silane described in Example 1 and 8.2 parts of methyl isoamvl 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-resistan;.
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.
barvtes, black iron oxide and fumed silica) were dispersed by milling in 11.5 parts of liauid hydroxyl-tipped polydi-methvlsiloxane 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 polydimethylsiloxane tipped with ketiminoxy groups. 0.03 part of dibutyltin dilaurate and 10.0 parts of methyl isoamyl ketone.
The resulting primer composition was applied tc 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/poly(ethylene-butylene) block copolymer rubber.
These samples were overcoated after 16 to 48 hours with the WO 91/14747 PC1'/GB91/00454 1' ,:
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 E
months' immersion in sea water.

Claims (18)

1. A primer composition for application to a substrate 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)x R (3-x) SiR1NHR2 (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; R1 is an alkylene radical having 2 to 4 carbon atoms or a divalent aliphatic ether radical having 3 to 8 carbon atoms; R2 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 (ii) the reaction product of a primary amine-functional silane of the formula (I) with an epoxy-functional 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-dihydroxypolydimethylsiloxane oil of the formula:
HO(Si(CH3)2O)y H (III) in which y is 2 to 60;

(B) a chlorinated polyolefin; and (C) a room-temperature-curable polydiorganosiloxane.

2. A primer composition according to claim 1, charac-terised in that the room-temperature-curable polydior-ganosiloxane (C) is an alpha, omega-dihydroxypolydiorgano-siloxane used in conjunction with a ketiminoxysilane curing agent.

3. A primer composition according to claim 1, charac-terised in that the room-temperature-curable polydior-ganosiloxane (C) is an alpha, omega-dihydroxypolydiorgano-siloxane used in conjunction with an acyloxysilane 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-siloxane used in conjunction with an alkoxysilane curing agent.

5. A primer composition according to claim 1, charac-terised in that the room-temperature-curable polydior-ganosiloxane (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, characterised in that the aminosilane material (A) is used at 1 to 20% by weight based on the weight of chlorin-ated polyolefin (8) 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)x R (3-x) SiR1NHR2 (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; R1 is an alkylene radical having 2 to 4 carbon atoms or a divalent aliphatic ether radical having 3 to 8 carbon atoms; R2 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 (ii) the reaction product of a primary amine-functional silane of the formula (I) with an epoxy-functional 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-dihydroxypolydimethylsiloxane oil of the formula:

HO(Si(CH3)2O)y H (III) in which y is 2 to 60;
and (B) a chlorinated polyolefin;
are mixed with (C) a room-temperature-curable polydiorganosiloxane.

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 polydiorganosiloxane (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 polydiorganosiloxane (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 polydiorganosiloxane (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 polydiorganosiloxane 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-diorganosiloxane 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).