Note: Descriptions are shown in the official language in which they were submitted.
WO 91/14747 PCT/GB91/00454
.,..
~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.
WO 91/14747 PCT/GB91/00454
~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
WO 91/14747 PCT/GB91/00454
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
WO 91/14747 PCT/GB91/00454
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.
W0 91/14747 PCT/GB91/00454
.:~~,~,
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.
WO 91/14747 PCT/GB91/00454
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
1
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 [ONv= C(CH3)C2N5]3.
WO 91/14747 PCT/GB91/00454
8
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'
W0 91/14747 PCT/GB91/00454
8
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:
R7 R4 R4 R4 R7
\ 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
WO 91/14747 PCT/GB91/00454
~'~~~.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
WO 91/14747 PCT/GB91/00454
~~''~~~.4~'
11
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
WO 91/14747 PCT/GB91/00454
12
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-
WO 91/14747 PCT/GB91/00454
~.p'~~1~4
1J
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
WO 91/14747 PCT/GB91/00454
14
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.
WO 91/14747 PCT/GB91/00454
~~'~~~.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
WO 91/14747 PCT/GB91/00454
16
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.
