U.S. patent application number 14/126226 was filed with the patent office on 2014-05-22 for biocidal foul release coating systems.
This patent application is currently assigned to AKZO NOBEL COATINGS INTERNATIONAL B.V.. The applicant listed for this patent is Andrew Curry, Ian Michael Hawkins, Phillip Keith Jones, Zhiyi Li, John David Sinclair-Day. Invention is credited to Andrew Curry, Ian Michael Hawkins, Phillip Keith Jones, Zhiyi Li, John David Sinclair-Day.
Application Number | 20140141263 14/126226 |
Document ID | / |
Family ID | 44904675 |
Filed Date | 2014-05-22 |
United States Patent
Application |
20140141263 |
Kind Code |
A1 |
Jones; Phillip Keith ; et
al. |
May 22, 2014 |
BIOCIDAL FOUL RELEASE COATING SYSTEMS
Abstract
Structure coated with a biocidal foul release coating system,
the structure being obtained by a. providing a substrate, b.
coating the substrate with a first coating layer, c. applying at
least one subsequent coating layer on top of the first coating
layer, the first coating layer containing a biocide, the subsequent
coating layer(s) containing less biocide than the first coating
layer and which is(are)free or substantially free of biocide, and
wherein the first and the subsequent coating layer(s) form a
biocidal foul release coating system showing a controlled leaching
of the biocide.
Inventors: |
Jones; Phillip Keith; (Tyne
& Wear, GB) ; Hawkins; Ian Michael; (New South
Wales, AU) ; Curry; Andrew; (Tyne & Wear, GB)
; Li; Zhiyi; (Zhejiang, CN) ; Sinclair-Day; John
David; (Tyne & Wear, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Jones; Phillip Keith
Hawkins; Ian Michael
Curry; Andrew
Li; Zhiyi
Sinclair-Day; John David |
Tyne & Wear
New South Wales
Tyne & Wear
Zhejiang
Tyne & Wear |
|
GB
AU
GB
CN
GB |
|
|
Assignee: |
AKZO NOBEL COATINGS INTERNATIONAL
B.V.
ARNHEM
NL
|
Family ID: |
44904675 |
Appl. No.: |
14/126226 |
Filed: |
July 19, 2012 |
PCT Filed: |
July 19, 2012 |
PCT NO: |
PCT/EP2012/061625 |
371 Date: |
December 13, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61499430 |
Jun 21, 2011 |
|
|
|
Current U.S.
Class: |
428/447 ;
427/407.1 |
Current CPC
Class: |
B63B 59/04 20130101;
C09D 5/1675 20130101; Y10T 428/31663 20150401; C09D 5/1693
20130101; C09D 5/1625 20130101 |
Class at
Publication: |
428/447 ;
427/407.1 |
International
Class: |
B63B 59/04 20060101
B63B059/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 21, 2011 |
EP |
11170712.1 |
Claims
1-11. (canceled)
12. A structure coated with a biocidal foul release coating system,
the structure being obtained by a. providing a substrate, b.
coating the substrate with a first coating layer, c. applying at
least one subsequent coating layer on top of the first coating
layer, the first coating layer formed from a coating composition
containing a biocide, the at least one subsequent coating layer
formed from a subsequent coating composition containing less
biocide than the coating composition forming the first coating
layer and which is free or substantially free of biocide, and
wherein the first and the at least one subsequent coating layers
form a biocidal foul release coating system, and wherein at least
one of the first coating layer and the at least one subsequent
coating layer comprise a polyorganosiloxane.
13. The structure according to claim 12, wherein the ratio of the
release rate of biocide from the foul release coating system 5 days
after application of the coating (R.sub.5) and the release rate of
biocide 30 days after application of the coating (R.sub.30)
R.sub.5/R.sub.30.ltoreq.1.5.
14. The structure according to claim 13, wherein the ratio
R.sub.5/R.sub.30.ltoreq.1.33.
15. The structure according to claim 12, wherein at least one of
the first coating layer and the at least one subsequent coating
layer comprises an elastomeric polymer.
16. The structure according to claim 12, wherein the substrate is
coated with an anticorrosion coating and the first coating layer is
used as a tie coat over said anticorrosion coating.
17. The structure according to claim 12, wherein the biocide in the
first coating layer is an organic or metal-organic biocide.
18. The structure according to claim 12, wherein the biocide is one
or more of a 2-trihalogenomethyl-3-halogeno-4-cyano pyrrole
derivative substituted in position 5 and optionally in position 1
or a 1,4-dithiaanthraquinone-2,3-dicarbonitrile.
19. The structure according to claim 12, wherein the at least one
subsequent coating layer comprises an incompatible fluid.
20. The structure according to claim 12, wherein the substrate is a
marine or an aquaculture structure.
21. The structure according to claim 20, wherein the marine or
aquaculture structure is a ship hull, a boat hull, a buoy, a
drilling platform, an oil rig, a floating production storage and
offloading vessel (FPSO), a pipe, a cooling water intake in a power
plant, a fish net or a fish cage.
22. A method of controlling the rate of release of biocide from a
foul release coating system, the method comprising a. providing a
substrate, b. coating the substrate with a first coating layer, c.
applying at least one subsequent coating layer on top of the first
coating layer, the first coating layer formed from a coating
composition containing a biocide, the at least one subsequent
coating layer formed from a subsequent coating composition
containing less biocide than the coating composition forming the
first coating layer and which is free or substantially free of
biocide, wherein the ratio of the release rate of biocide from the
foul release coating system 5 days after application of the coating
(R.sub.5) and the release rate of biocide 30 days after application
of the coating (R.sub.30) R.sub.5/R.sub.30.ltoreq.1.5.
23. The structure according to claim 13, wherein at least one of
the first coating layer and the at least one subsequent coating
layer comprises an elastomeric polymer.
24. The structure according to claim 13, wherein the substrate is
coated with an anticorrosion coating and the first coating layer is
used as a tie coat over said anticorrosion coating.
25. The structure according to claim 13, wherein the biocide in the
first coating layer is an organic or metal-organic biocide.
26. The structure according to claim 15, wherein the biocide in the
first coating layer is an organic or metal-organic biocide.
27. The structure according to claim 13, wherein the biocide is one
or more of a 2-trihalogenomethyl-3-halogeno-4-cyano pyrrole
derivative substituted in position 5 and optionally in position 1
or a 1,4-dithiaanthraquinone-2,3-dicarbonitrile.
28. The structure according to claim 16, wherein the biocide is one
or more of a 2-trihalogenomethyl-3-halogeno-4-cyano pyrrole
derivative substituted in position 5 and optionally in position 1
or a 1,4-dithiaanthraquinone-2,3-dicarbonitrile.
29. The structure according to claim 13, wherein the at least one
subsequent coating layer comprises an incompatible fluid.
30. The structure according to claim 15, wherein the at least one
subsequent coating layer comprises an incompatible fluid.
31. The structure according to claim 13, wherein the substrate is a
ship hull, a boat hull, a buoy, a drilling platform, an oil rig, a
floating production storage and offloading vessel (FPSO), a pipe, a
cooling water intake in a power plant, a fish net or a fish cage.
Description
FIELD OF INVENTION
[0001] The present invention relates to the use of a foul release
coating to control the leaching of biocide from a coating system
comprising said foul release coating and a biocidal underlying
coating. The present invention further relates to such a coating
system, its use in inhibiting fouling on a substrate and a
substrate coated with the coating system.
BACKGROUND ART
[0002] Man-made marine structures such as ship and boat hulls,
buoys, drilling platforms, dry dock equipment, oil production rigs,
and pipes which are immersed in water are prone to fouling by
aquatic organisms such as green and brown algae, barnacles,
mussels, and the like. Such structures are commonly of metal, but
may also comprise other structural materials such as concrete. This
fouling is a nuisance on boat hulls, because it increases
frictional resistance during movement through the water, the
consequence being reduced speeds and increased fuel costs. It is a
nuisance on static structures such as the legs of drilling
platforms and oil production rigs, firstly because the resistance
of thick layers of fouling to waves and currents can cause
unpredictable and potentially dangerous stresses in the structure,
and, secondly, because fouling makes it difficult to inspect the
structure for defects such as stress cracking and corrosion. It is
a nuisance in pipes such as cooling water intakes and outlets,
because the effective cross-sectional area is reduced by fouling,
with the consequence that flow rates are reduced.
[0003] Fouling has been inhibited traditionally by antifouling
paints containing a biocide, which biocide is gradually leached
from the paint. The commercially most successful methods of
inhibiting fouling have involved the use of antifouling coatings
containing substances toxic to aquatic life, for example
triorganotin compounds. Such coatings, however, are being regarded
with increasing disfavour because of the damaging effects some such
toxins may have if released into the aquatic environment under
certain circumstances.
[0004] It has been known for many years, for example as disclosed
in GB 1,307,001 and U.S. Pat. No. 3,702,778, that certain coatings,
for example elastomers such as silicone rubbers, resist fouling by
aquatic organisms. Such coatings are non-biocidal, generally
hydrophobic and are believed to present a surface which physically
deters settlement and/or to which the organisms cannot easily
adhere, and they can accordingly be called foul release coatings
rather than anti-fouling coatings. Foul release properties can be
characterised by barnacle adhesion measurements, for example, ASTM
D 5618-94. The following barnacle adhesion values have been
recorded by this method: Silicone surface (0.05 MPa), Polypropylene
surface (0.85 MPa), Polycarbonate surface (0.96 MPa), Epoxy surface
(1.52 MPa) and Urethane surface (1.53 MPa) (J.C. Lewthwaite, A. F.
Molland and K. W. Thomas, "An Investigation into the variation of
ship skin fictional resistance with fouling", Trans. R.I.N.A., Vol.
127, pp. 269-284, London (1984)). As an indication of whether or
not a coating may be considered to be foul-release: a foul-release
coating usually has a mean barnacle adhesion value of less than 0.4
MPa.
[0005] Silicone rubbers and silicone compounds generally have very
low toxicity. A disadvantage of this foul release system when
applied to boat hulls is that although the accumulation of fouling
organisms is reduced, relatively high vessel speeds are needed to
remove all fouling species. Thus, in some instances, it has been
shown that it is necessary to sail with a speed of at least 10
knots to satisfactorily remove fouling from a hull that has been
treated with such a coating. For this reason silicone rubbers have
so far gained only limited commercial success.
[0006] It is also long known that the adhesion of silicone foul
release coatings to anticorrosive coatings is generally poor unless
a suitable tie-coat or link coat is used to ensure adequate
adhesion. Such tie coats often contain a silicone. Examples of
silicone containing tie coats are described in EP521983 and
EP1832630.
[0007] The combination of a suitable tie-coat with a second coating
layer is sometimes referred to as a `duplex` foul release system.
Hitherto, the compositions described in the prior-art for use as
the tie-coat in such duplex systems are generally free of added
biocides and WO2008/013825 explicitly teaches away from using
biocides as part of their systems.
[0008] GB1409048 discloses a marine polyurethane top coat
composition capable of imbibing 30 to 300% of its own weight of
seawater which is applied over a biocidal antifouling coating. The
polyurethane top coat of GB1409048 is not foul release coating
within the context of the present invention (see: `Redefining
antifouling coatings`, Journal of Protective Coatings and Linings,
September 1999, pages 26-35 which discloses that polyurethanes have
extremely high barnacle adhesion strengths in comparison to
silicones). No subsequent foul release coating layer is disclosed
or suggested in GB1409048.
[0009] EP 0 313 233 describes an antifouling marine coating
comprising a first layer of anti-fouling corrosion-resisting marine
paint containing a toxicant to marine organisms and a second layer
of porous organic polymeric membrane adhered to said first layer;
the porous organic polymeric membrane preferably being
polytetrafluoroethylene (EPTFE). A porous organic polymeric
membrane is not a coating in the context of the present invention
since is not applied as a liquid mixture which then dries or cures
to form a dry continuous film. Furthermore, polytetrafluoroethylene
is a material that is unsuitable for use as a foul release surface
(see: the above-noted `Redefining antifouling coatings` which
indicates a high barnacle adhesion strength). The use of a
subsequent foul release coating layer is neither disclosed nor
suggested in EP 0 313 233.
[0010] U.S. Pat. No. 4,129,610 describes a water soluble coating
composition for ship bottoms comprising a vinyl copolymer and a
water-soluble epoxy compound. The water soluble coating composition
is applied on a primer coating layer having a toxic material. The
water soluble coating composition of U.S. Pat. No. 4,129,610 is not
considered a foul release coating within the context of the present
invention (see the above-noted `Redefining antifouling coatings`
article which reports the barnacle adhesion strength of epoxy
coatings is extremely high). The use of a subsequent foul release
coating layer is neither disclosed nor suggested.
[0011] FR2636958 describes a chlorinated adhesion primer for a
silicone elastomer. According to this publication a triorganotin
oxide or halide biocide or copper oxide may be added to the primer.
Tributyl tin oxide or fluoride and copper oxide are the only
mentioned suitable biocide additives to such a system and there is
no example or further description of a primer containing any
biocide. The document is completely silent on leaching of biocide
and there is no enabling teaching of a foul release system with a
primer that contains any biocide.
[0012] WO95/32862 discloses a duplex foul release system which can
be used on a substrate for countering fouling by marine organisms.
The duplex system consists of a bonding layer and a release layer
wherein a 3-isothiazolone biocide is embedded in either the bonding
layer or release layer. The document teaches exclusively that
3-isothiazolones should be used as the biocide and that the
leaching rate of the biocide from the bonding layer is inversely
proportional to the square root of time, and no other factors
control the leaching rate other than potentially the solubility of
the biocide in water. The leaching of biocide is therefore only
poorly controlled in such systems and does not qualify as a
biocidal foul release coating system having a controlled leaching
rate of the biocide within the framework of the present invention.
It was found that substrates coated with systems, like the one
disclosed in WO 95/32862 where the leaching rate of the biocide
from the bonding layer is inversely proportional to the square root
of time, shortly after immersion of the substrate in seawater, the
substrate remains substantially free of fouling and exhibit
superior performance in comparison substrates coated with a
biocide-free foul release coating system. However, the superior
performance is not sustained, the coated substrates become
progressively covered with biofouling, and within 4-6 months the
system of WO 95/32862 shows similar severe fouling as substrates
coated with a biocide-free foul release coating system.
SUMMARY OF THE INVENTION
[0013] Surprisingly it was found that a structure coated with a
biocidal foul release coating system can be made that shows a
controlled leaching of biocide.
[0014] According to the present invention, such structure can be
obtained by [0015] a. providing a substrate, [0016] b. coating the
substrate with a first coating layer, [0017] c. applying at least
one subsequent coating layer on top of the first coating layer,
wherein the first and the subsequent coating layer(s) form a
biocidal foul release coating system, the first coating layer
contains a biocide, the subsequent coating layer(s) contain(s) less
biocide than the first coating layer, and the subsequent coating
layer(s) is(are) free or substantially free of biocide.
[0018] The biocidal foul release coating systems as defined in the
present application shows a controlled leaching of the biocide.
[0019] By showing a controlled leaching of the biocide we mean that
the ratio of the release rate of biocide from the foul release
coating system of this invention, 5 days after application of the
coating (R.sub.5) and the release rate of biocide 30 days after
application of the coating (R.sub.30) R.sub.5/R.sub.30 is less than
or equal to (.ltoreq.) 1.5, preferably .ltoreq.1.33, more
preferably .ltoreq.1.11.
[0020] The biocidal foul release coating systems of the present
invention show excellent fouling resistance both at short time and
longer time after immersion of the substrates in seawater.
[0021] Within the framework of the present invention, a biocidal
foul release coating system is a coating system having a surface
which physically deters settlement and/or to which aquatic/marine
organisms cannot easily adhere and where biocide is released from
the coating system.
[0022] To improve the adhesion of the first coating layer to the
substrate, there might be a tie-coat or adhesion promoter layer
between the substrate and the first coating layer. To improve the
corrosion resistance of the substrate, there might also be an
anticorrosive coating applied on the substrate before the first
coating layer is applied. More in general, there might be one or
more coating layer(s) on the substrate before the first coating
layer, comprising the biocide, is applied to the substrate.
[0023] To prepare a coating layer, a coating composition is applied
to the surface (e.g. to the substrate or another coating layer) as
a liquid mixture; the coating composition then dries or cures to
form a dry continuous coating film/layer over that surface.
[0024] The present inventors have realised that the rate of biocide
leaching from the biocidal foul release coating system can be
controlled by applying a subsequent coating layer or layers on top
of a first coating layer, wherein the first coating layer contains
a biocide, the subsequent coating layer(s) containing less biocide
than the first coating layer and being free or substantially free
of biocide. The advantage of this is that the biocide leaching rate
can be tuned, made less dependent on time and indeed maintained in
a more linear relationship with time. Therefore a desired and more
constant rate of biocide leaching can be attained. This is
advantageous as it leads to extended performance lifetimes, more
efficient use of the biocide, and reduced environmental impact.
Furthermore, biocide leaching can be controlled such that the
ability of the fouling release coating system to prevent fouling
under low speed or static conditions is especially enhanced.
[0025] In the context of the present invention biocide leaching
(sometimes known as biocide release) and biocide leaching rate
(biocide release rate) should be clearly differentiated from foul
release. Leaching rate is the rate at which the biocide is released
by the coating system into the surrounding waters and is typically
expressed as mass of biocide per unit area per unit time. Foul
release is concerned with prevention of fouling and/or its ease of
removal from the surface of an immersed substrate by non-biocidal
means. For example foul release properties can be characterised by
barnacle adhesion measurements that can be carried out using ASTM D
5618-94, Standard test method for measurement of barnacle adhesion
strength in shear, or a related method. Both are complementary
mechanisms to control fouling but are independent of each
other.
[0026] More particularly, the present inventors have realised that
the leaching rate can be controlled by varying the composition of
the subsequent coating layer(s). The first coating layer behaves as
a reservoir of biocide which contains a ready supply of biocide to
be released. The leaching rate of the biocide can be controlled by
varying certain attributes of the first and subsequent coating
layer(s). These attributes include, but are not limited to: pigment
volume concentration, cross link density, pigment size and shape,
molecular weight of the polymer, the presence and amount of an
incompatible fluid, the cross linking chemistry of the subsequent
coating layer(s) and film thickness.
[0027] The reservoir of biocide, combined with the control
mechanism of the subsequent coating layer(s), allows the biocide
leaching rate to be tailored to the end use.
[0028] Within the framework of the present invention a coating
systems that shows a controlled leaching of biocide is a system
where the release rate of biocide 30 days after immersion in water
(R.sub.30) is at least 67% of the release rate 5 days after
immersion in water (R.sub.5). In other words, a coating systems
showing a controlled leaching of biocide is a system where
R.sub.5/R.sub.30.ltoreq.1.5.
[0029] In one embodiment of the present invention,
R.sub.5/R.sub.30.ltoreq.1.5. In a further embodiment of the present
invention, R.sub.5/R.sub.30.ltoreq.1.33. In an even further
embodiment of the present invention
R.sub.5/R.sub.30.ltoreq.1.11.
[0030] In WO95/32862 the duplex foul release system is described as
having a leaching rate of the biocide from the bonding layer that
is inversely proportional to the square root of time, and no other
factors control the leaching rate other than potentially the
solubility of the biocide in water. For this system, the release
rate of the biocide is described as F(t).about.36/t.sup.0.5, where
F is the leach rate in .mu.g/cm.sup.2/day (.mu.g cm.sup.-2
day.sup.-1) and t is the time in days. For this system,
R.sub.5/R.sub.30=F(5)/F(30)=30.sup.0.5/5.sup.0.5=2.45. WO95/32862
fails to teach that a biocidal foul release coating system, wherein
the substrate is first coated with a coating layer containing a
biocide, which is then over-coated with subsequent layer(s)
containing substantially no biocide would result in a more gradual
and sustained release profile of biocide from the foul release
coating surface.
[0031] According to the present invention, the subsequent coating
layer(s) that are applied on top of the first coating layer
contains less biocide than the first coating layer. Further, the
subsequent coating layer(s) is(are) free or substantially free of
biocide. Substantially free of biocide means that the subsequent
coating layer(s) contains less than 1.0 wt % (based on the total
weight of the coating composition) of biocide. Preferably the
subsequent coating layer(s) contain less than 0.5 wt % of biocide,
more preferably less than 0.1 wt %. For the avoidance of doubt,
weight percent (wt %) is the weight percent, based on the total
weight of the coating composition.
[0032] In one embodiment the subsequent coating layer(s) further
comprises an incompatible fluid.
[0033] The incompatible fluid in the subsequent coating layer(s)
helps to achieve an improved foul release performance. Without
wishing to be bound by theory it is believed that the fluid may
have an effect upon transportation of the biocide.
[0034] In a further embodiment the biocide is either partially or
wholly encapsulated or adsorbed or supported or bound.
[0035] Encapsulation or absorption or supporting or binding of the
biocide can provide a secondary mechanism for controlling biocide
leaching from the coating system in order to achieve an even more
gradual release and long lasting effect.
[0036] The present invention relates to (i) a biocidal foul release
coating system, and to (ii) a structure coated with the biocidal
foul release coating system, the biocidal foul release coating
system comprising
[0037] a. a substrate,
[0038] b. a first coating layer,
[0039] c. at least one subsequent coating layer on top of the first
coating layer, the first coating layer containing a biocide, the
subsequent coating layer(s) containing less biocide than the first
coating layer, and the subsequent coating layer(s) being free or
substantially free of biocide. The biocidal foul release coating
system shows a controlled leaching of the biocide.
[0040] One embodiment of the present invention is a structure
coated with the biocidal foul release coating system defined
above.
DETAILED DESCRIPTION
First Coating Layer Containing a Biocide
[0041] The composition of the first coating layer is not especially
limiting but preferably the first coating layer composition
comprises a polymer. The polymer preferably forms an elastomer.
More preferably this is a polyorganosiloxane. Even more preferably
this is a polydimethylsiloxane. Furthermore, the polyorganosiloxane
may also comprise two or more polyorganosiloxanes of different
viscosity.
[0042] Preferably the polyorganosiloxane has one or more, more
preferably two or more reactive functional groups such as hydroxyl,
alkoxy, acetoxy, carboxyl, hydrosilyl, amine, epoxy, vinyl or oxime
functional groups.
[0043] Preferably the polymer is present in an amount of 5 to 50 wt
% based on the total weight of the coating composition. More
preferably this is present in an amount of 8 to 20 wt %.
[0044] Preferably the polymer is crosslinkable. Depending on the
type of crosslinkable polymer, the coating composition may require
a cross-linker. The necessity for the presence of cross-linker will
depend on the type and number of functional groups that are present
in said polymer. If the polymer comprises alkoxy-silyl groups, the
presence of a small amount of water, and optionally, a condensation
catalyst is generally sufficient to achieve full cure of the
coating after application. For these compositions, atmospheric
moisture is generally sufficient to induce curing, and as a rule it
will not be necessary to heat the coating composition after
application.
[0045] The optionally present cross-linker can be a cross-linking
agent comprising a functional silane and/or one or more of any of
acetoxy, alkoxy, amido, alkenoxy and oxime groups. Examples of such
cross-linking agents are presented in WO 99/33927, page 19, line 9,
through page 21, line 17. Mixtures of different cross-linkers can
also be used.
[0046] Preferably the crosslinking agent is present in an amount of
0.1% to 20 wt % based on the total weight of the coating
composition.
[0047] The first coating layer contains a biocide. By
"contains"/"containing", we mean that the biocide is present within
the body of the coating layer (in the sense that it was mixed in
the coating composition prior to curing/drying).
[0048] The biocide of the present invention can be one or more of
an inorganic, organometallic, metal-organic or organic biocide for
marine or freshwater organisms. Examples of inorganic biocides
include copper salts such as copper oxide, copper thiocyanate,
copper bronze, copper carbonate, copper chloride, copper nickel
alloys, and silver salts such as silver chloride or nitrate;
organometallic and metal-organic biocides include zinc pyrithione
(the zinc salt of 2-pyridinethiol-1-oxide), copper pyrithione,
bis(N-cyclohexyl-diazenium dioxy) copper, zinc
ethylene-bis(dithiocarbamate) (i.e. zineb), zinc dimethyl
dithiocarbamate (ziram), and manganese
ethylene-bis(dithiocarbamate) complexed with zinc salt (i.e.
mancozeb); and organic biocides include formaldehyde,
dodecylguanidine monohydrochloride, thiabendazole, N-trihalomethyl
thiophthalimides, trihalomethyl thiosulphamides, N-aryl maleimides
such as N-(2,4,6-trichlorophenyl) maleimide,
3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron),
2,3,5,6-tetrachloro-4-(methylsulphonyl) pyridine,
2-methylthio-4-butylamino-6-cyclopopylamino-s-triazine,
3-benzo[b]thien-yl-5,6-dihydro-1,4,2-oxathiazine 4-oxide,
4,5-dichloro-2-(n-octyl)-3(2H)-isothiazolone,
2,4,5,6-tetrachloroisophthalonitrile, tolylfluanid, dichlofluanid,
diiodomethyl-p-tosylsulphone, capsciacin,
N-cyclopropyl-N'-(1,1-dimethylethyl)-6-(methylthio)-1,3,5-triazine-2,4-di-
amine, 3-iodo-2-propynylbutyl carbamate, medetomidine,
1,4-dithiaanthraquinone-2,3-dicarbonitrile (dithianon), boranes
such as pyridine triphenylborane, a
2-trihalogenomethyl-3-halogeno-4-cyano pyrrole derivative
substituted in position 5 and optionally in position 1, such as
2-(p-chlorophenyl)-3-cyano-4-bromo-5-trifluoromethyl pyrrole
(tralopyril), and a furanone, such as
3-butyl-5-(dibromomethylidene)-2(5H)-furanone, and mixtures
thereof, macrocyclic lactones such as avermectins, for example
avermectin B1, ivermectin, doramectin, abamectin, amamectin and
selamectin, and quaternary ammonium salts such as
didecyldimethylammonium chloride and an alkyldimethylbenzylammonium
chloride. In one embodiment, the biocide may be a 3-isothiazolone,
however the inventors have found that this biocide should
preferably be in an encapsulated, adsorbed or bound form. In
another embodiment, the biocide is not a 3-isothiazolone.
[0049] Preferably the biocide is organic or metal-organic. Without
wishing to be bound by theory, it is believed that leaching of the
biocide involves physical diffusion of the biocide from the first
coating layer through the subsequent coating layer(s) by passive
transport processes. The flux of biocide from the coating system
will therefore be controlled in part by the diffusion of the
biocide through, and compatibility with, the subsequent coating
layer(s). If the diffusion or compatibility are inherently high, as
would be anticipated for organometallic biocides such as organotins
and the like, then the resulting leaching rate will also be
inherently high and difficult to control, such that the lifetime of
the coating will be reduced and undesirable environmental impact
may result. If the diffusion or compatibility are inherently low,
as would be anticipated for inorganic biocides such as the
inorganic salts of copper and the like, then the leaching rate will
also be inherently low and fouling may result. In general, the use
of an organic or metal-organic biocide allows the leaching rate to
be suitably controlled through use of the coating system of the
present invention and unacceptable environmental damage to be
avoided.
[0050] In the context of the present invention, an inorganic
biocide is a biocide whose chemical structure comprises a metal
atom and which is free of carbon atoms; an organometallic biocide
is a biocide whose chemical structure comprises a metal atom, a
carbon atom, and a metal-carbon bond; a metal-organic biocide is a
biocide whose chemical structure comprises a metal atom, a carbon
atom, and which is free of metal-carbon bonds; and an organic
biocide is biocide whose chemical structure comprises a carbon atom
and which is free of metal atoms.
[0051] Preferably, for excellent antifouling properties the biocide
is one or more of a 2-trihalogenomethyl-3-halogeno-4-cyano pyrrole
derivative substituted in position 5 and optionally in position 1,
such as tralopyril, 1,4-dithiaanthraquinone-2,3-dicarbonitrile
(dithianon), copper pyrithione, zinc pyrithione, tolylfluanid,
dichlofluanid, and
N-cyclopropyl-N'-(1,1-dimethylethyl)-6-(methylthio)-1,3,5-triazine-2,4-di-
amine.
[0052] Preferably the biocide(s) is(are) present in the first
coating layer composition in an amount of 0.05 to 50 wt %, more
preferably 3 to 30 wt %, and most preferably 10 to 20 wt % based on
the total weight of the composition of the first coating layer. In
any case, the amount of biocide present in the first coating layer,
must be more than the amount of biocide in the at least one
subsequent coating layer(s) at the time the coating layers are
applied to the substrate.
[0053] Furthermore, the biocide may optionally be wholly or
partially encapsulated, adsorbed or supported or bound. Certain
biocides are difficult or hazardous to handle and are
advantageously used in an encapsulated or absorbed or supported or
bound form. Additionally, encapsulation, absorption or support or
binding of the biocide can provide a secondary mechanism for
controlling biocide leaching rate from the coating system in order
to achieve an even more gradual release and long lasting
effect.
[0054] The method of encapsulation, adsorption or support or
binding of the biocide is not particularly limiting for the present
invention. Examples of ways in which an encapsulated biocide may be
prepared for use in the present invention include mono and dual
walled amino-formaldehyde or hydrolysed polyvinyl acetate-phenolic
resin capsules or microcapsules as described in EP1791424. An
example of a suitable encapsulated biocide is encapsulated
4,5-dichloro-2-(n-octyl)-3(2H)-isothiazolone marketed as by Dow
Microbial Control as Sea-Nine CR2 Marine Antifoulant Agent.
[0055] Examples of ways in which an absorbed or supported or bound
biocide may be prepared include the use of host-guest complexes
such as clathrates as described in EP0709358, phenolic resins as
described in EP0880892, carbon-based adsorbents such as those
described in EP1142477, or inorganic microporous carriers such as
the amorphous silicas, amorphous aluminas, pseudoboehmites or
zeolites described in EP1115282.
[0056] Where the polymer of the biocidal first coating layer
composition is crosslinkable, the composition may optionally
comprise a catalyst. Examples of suitable catalysts are the
carboxylic acid salts of various metals, such as tin, zinc, iron,
lead, barium, and zirconium. The salts preferably are salts of
long-chain carboxylic acids, for example dibutyltin dilaurate,
dibutyltin dioctoate, iron stearate, tin (II) octoate, and lead
octoate. Further examples of suitable catalysts include
organobismuth and organotitanium compounds and organo-phosphates
such as bis(2-ethyl-hexyl) hydrogen phosphate. Other possible
catalysts include chelates, for example dibutyltin acetoacetonate.
Further, the catalyst may comprise a halogenated organic acid which
has at least one halogen substituent on a carbon atom which is in
the [alpha]-position relative to the acid group and/or at least one
halogen substituent on a carbon atom which is in the
[beta]-position relative to the acid group, or a derivative which
is hydrolysable to form such an acid under the conditions of the
condensation reaction.
[0057] Alternatively, the catalyst may be as described in any of
WO2007122325A1, WO2008055985A1, WO2009106717A2, WO2009106718A2,
WO2009106719A1, WO2009106720A1, WO2009106721 A1, WO2009106722A1,
WO2009106723A1, WO2009106724A1, WO2009103894A1, WO2009118307A1,
WO2009133084A1, WO2009133085A1, WO2009156608A2, and
WO2009156609A2.
[0058] The catalyst of the biocidal first coating layer composition
is preferably present in an amount of 0.01 to 4 wt %, based on the
total weight of the coating composition.
[0059] Preferably, the biocidal first coating layer composition
according to the invention also comprises one or more fillers,
pigments, additional catalysts, and/or solvents. Examples of
suitable fillers are barium sulphate, calcium sulphate, calcium
carbonate, silicas or silicates (such as talc, feldspar, and china
clay), aluminium paste/flakes, bentonite or other clays. Some
fillers such as fumed silica may have a thixotropic effect on the
coating composition. The proportion of fillers may be in the range
of from 0 to 25 wt %, based on the total weight of the coating
composition. Preferably the clay is present in an amount of from 0
to 1 wt % and preferably the thixotrope is present in an amount of
from 0 to 5 wt %, based on the total weight of the coating
composition.
[0060] Examples of suitable pigments are black iron oxide, red iron
oxide, yellow iron oxide, titanium dioxide, zinc oxide, carbon
black, graphite, red molybdate, bismuth vanadate yellow, yellow
molybdate, zinc sulfide, antimony oxide, cobalt/zinc titanium oxide
greens, zinc/tin titanate oranges, lanthanide sulphide oranges and
reds, manganese pyrophosphate violets, sodium aluminium
sulfosilicates, quinacridones, phthalocyanine blue, phthalocyanine
green, black iron oxide, indanthrone blue, cobalt aluminium oxide,
carbazoledioxazine, chromium (III) oxide, isoindoline orange,
bis-acetoaceto-tolidiole, benzimidazolone, quinaphthalone yellow,
isoindoline yellow, tetrachloroisoindolinone, and quinophthalone
yellow. The proportion of pigments may be in the range of from 0 to
10 wt %, based on the total weight of the coating composition.
Suitable solvents include aromatic hydrocarbons, alcohols, ketones,
esters, and mixtures of the above with one another or an aliphatic
hydrocarbon. Preferable solvents include methyl isoamylketone
and/or xylene. Preferably the solvent is present in an amount of 10
to 40 wt % based on the total weight of the composition.
[0061] The composition optionally includes an adhesion promoting
material, typically in an amount of 0.01-0.5 wt % based on the
total weight of the composition. Examples of suitable adhesion
promoters include silanes such as aminosilanes, epoxysilanes,
methacryoyloxypropylsilanes and mercaptosilanes.
[0062] Preferably the adhesion promoter is an aminosilane of the
type:
(RO).sub.xR.sub.3-xSiR.sup.1N(R.sup.2).sub.2
wherein each R independently is selected from C1-8 alkyl (e.g.
methyl, ethyl, hexyl, octyl, etc.), C1-4 alkyl, 0, C2-4 alkyl; aryl
(e.g. phenyl) and aryl C1-4 alkyl (e.g. benzyl); R.sup.1 is
selected from (CH.sub.2).sub.1-4, methyl-substituted trimethylene
and (CH2).sub.2-3, O, (CH.sub.2).sub.2-3; R.sup.2 is selected from
hydrogen, an alkyl, cycloalkyl, arakyl or aryl group or
(CH.sub.2).sub.2-4--NH.sub.2.
[0063] Alternatively, the adhesion promoter is a "dipodal" silane
as mentioned in WO2010018164 of the type
(R.sup.3O).sub.3SiR.sup.1NHR.sup.2Si(OR.sup.4).sub.3 or
(R.sup.3O).sub.3SiR.sup.1NHR.sup.5NHR.sup.2Si(OR.sup.4).sub.3
where R.sup.1, R.sup.2 and R.sup.5 independently are C1 to C5
alkylene groups and R.sup.3 and R.sup.4 independently are selected
from methyl or ethyl.
[0064] Alternatively, the adhesion promoter is an epoxysilane of
the type:
A-Si(R).sub.a(OR).sub.(3-a)
where A is an epoxide substituted monovalent hydrocarbon radical
having 2 to 12 carbon atoms; and each R independently is selected
from C1-8 alkyl (e.g. methyl, ethyl, hexyl, octyl, etc.),
C1-4-alkyl-, O--, C2-4-alkyl; aryl (e.g. phenyl) and aryl C1-4
alkyl (e.g. benzyl); and a is 0 or 1.
[0065] The group A in the epoxysilane is preferably a
glycidoxy-substituted alkyl group, for example 3-glycidoxypropyl.
The epoxysilane can for example be
3-glycidoxypropyltrimethoxysilane,
3-glycidoxypropyltriethoxysilane,
3-glycidoxypropyldiethoxymethoxysilane,
2-glycidoxypropyltrimethoxysilane,
2-(3,4-epoxy-4-methylcyclohexyl)-ethyltrimethoxysilane,
5,6-epoxy-hexyltriethoxysilane; or their oligomers.
[0066] More preferably the adhesion promoter is
N-2-aminoethyl-3-aminopropyltrimethoxysilane. Additional optional
additives include dispersants such as an unsaturated polyamide acid
ester salt.
Subsequent Coating Layer(s), Foul-Release Layer
[0067] The composition of the subsequent coating layer(s) is not
especially limiting but the composition preferably comprises a
polymer. Preferably the polymer forms an elastomer. More preferably
this is a polyorganosiloxane. Even more preferably this is a
polydimethylsiloxane. Furthermore, the polyorganosiloxane may also
comprise two or more polyorganosiloxanes of different
viscosity.
[0068] The polyorganosiloxane has one or more, preferably two or
more reactive functional groups such as hydroxyl, alkoxy, acetoxy,
carboxyl, hydrosilyl, amine, epoxy, vinyl or oxime functional
groups.
[0069] Alternatively, the polymer may be as described in
WO2008132196, wherein the polymer is a polyorganosiloxane
polyoxyalkylene block copolymer of the form PS-(A-PO-A-PS)n,
wherein PS represents a polyorganosiloxane block, PO represents a
polyoxyalkylene block, A represents a divalent moiety, and n has a
value of 1 or more than 1.
[0070] The polymer has two or three reactive groups X on a
polyorganosiloxane block per molecule which may self-condense and
crosslink in the presence or absence of a catalyst (as defined
earlier in this document) which can, optionally, be crosslinked
with another organosilicon crosslinking agent containing two or
more groups Y which are reactive with the said groups X.
[0071] Preferably the polyorganosiloxane(s) polymer(s) is(are)
present in an amount of 30 to 90 wt %, based on the total weight of
the coating composition.
[0072] Preferably the polymer is crosslinkable. Depending on the
type of crosslinkable polymer, the coating composition may require
a cross-linker. The presence of a cross-linker is only necessary if
the curable polymer cannot be cured by condensation. This will
depend on the type and number of functional groups that are present
in said polymer. If the polymer comprises alkoxy-silyl groups, the
presence of a small amount of water, and optionally a condensation
catalyst is generally sufficient to achieve full cure of the
coating after application For these compositions, atmospheric
moisture is generally sufficient to induce curing, and as a rule it
will not be necessary to heat the coating composition after
application.
[0073] The optionally present cross-linker can be a cross-linking
agent comprising a functional silane and/or one or more of any of
acetoxy, alkoxy, amido, alkenoxy and oxime groups. Examples of such
cross-linking agents are presented in WO 99/33927, page 19, line 9,
through page 21, line 17. Mixtures of different cross-linkers can
also be used.
[0074] Preferably the crosslinking agent is present in an amount of
1 to 25 wt % based on the total weight of the coating
composition.
[0075] Where the polymer of the subsequent coating layer
composition is crosslinkable, the composition may optionally
comprise a catalyst. Examples of suitable catalysts are the
carboxylic acid salts of various metals, such as tin, zinc, iron,
lead, barium, and zirconium. The salts preferably are salts of
long-chain carboxylic acids, for example dibutyltin dilaurate,
dibutyltin dioctoate, iron stearate, tin (II) octoate, and lead
octoate. Further examples of suitable catalysts include
organobismuth and organotitanium compounds and organo-phosphates
such as bis(2-ethyl-hexyl) hydrogen phosphate. Other possible
catalysts include chelates, for example dibutyltin acetoacetonate.
Further, the catalyst may comprise a halogenated organic acid which
has at least one halogen substituent on a carbon atom which is in
the [alpha]-position relative to the acid group and/or at least one
halogen substituent on a carbon atom which is in the
[beta]-position relative to the acid group, or a derivative which
is hydrolysable to form such an acid under the conditions of a
condensation reaction.
[0076] Alternatively, the catalyst may be as described in any of
WO2007122325A1, WO2008055985A1, WO2009106717A2, WO2009106718A2,
WO2009106719A1, WO2009106720A1, WO2009106721 A1, WO2009106722A1,
WO2009106723A1, WO2009106724A1, WO2009103894A1, WO2009118307A1,
WO2009133084A1, WO2009133085A1, WO2009156608A2, and
WO2009156609A2.
[0077] Preferably the catalyst is present in an amount of 0.05 to 4
wt % based on the total weight of the coating composition.
[0078] Preferably, the subsequent coating layer composition
according to the invention also comprises one or more fillers,
pigments, catalysts, and/or solvents.
[0079] Examples of suitable fillers are barium sulphate, calcium
sulphate, calcium carbonate, silicas or silicates (such as talc,
feldspar, and china clay), aluminium paste/flakes, bentonite or
other clays. Some fillers such as fumed silica may have a
thixotropic effect on the coating composition. The proportion of
fillers may be in the range of from 0 to 25 wt %, based on the
total weight of the coating composition. Preferably the clay is
present in an amount of from 0 to 1 wt % and preferably the
thixotrope is present in an amount of from 0 to 5 wt %, based on
the total weight of the coating composition.
[0080] Examples of suitable pigments are black iron oxide, red iron
oxide, yellow iron oxide, titanium dioxide, zinc oxide, carbon
black, graphite, red molybdate, yellow molybdate, zinc sulfide,
antimony oxide, sodium aluminium sulfosilicates, quinacridones,
phthalocyanine blue, phthalocyanine green, black iron oxide,
indanthrone blue, cobalt aluminium oxide, carbazoledioxazine,
chromium oxide, isoindoline orange, bis-acetoaceto-tolidiole,
benzimidazolone, quinaphthalone yellow, isoindoline yellow,
tetrachloroisoindolinone, and quinophthalone yellow.
[0081] The proportion of pigments may be in the range of from 0 to
25 wt %, based on the total weight of the coating composition.
Suitable solvents include aromatic hydrocarbons, alcohols, ketones,
esters, and mixtures of the above with one another or an aliphatic
hydrocarbon. Preferable solvents include methyl isoamyl ketone
and/or xylene. Preferably the solvent is present in an amount of
0-40 wt %, based on the total weight of the composition.
[0082] The foul release properties of the coating system of the
present invention are generally improved when the subsequent
coating layer(s) composition forms a generally hydrophobic or
amphiphilic foul release coat when dried or cured. The bulk and
surface hydrophobicity of the subsequent coating layer(s) can be
characterised by various means, for example, by seawater uptake
measurements or surface contact angle measurements. Preferably, the
seawater uptake of the subsequent coating layer(s) is less than 30%
by mass, more preferably less than 25% by mass. Preferably the
equilibrium water contact angle of the subsequent coating layer(s)
is greater than 30 degrees at 23.degree. C.
[0083] In a preferred embodiment the subsequent coating layer(s)
composition comprises an incompatible fluid or grease. In the
context of the present invention an incompatible fluid means a
silicone, organic or inorganic molecule or polymer, usually a
liquid, but optionally also an organosoluble grease or wax, which
is immiscible (either wholly or partly) with (the elastomer network
of) the subsequent coating layer(s). Once the first coating layer
and subsequent coating layers have cured, the fluid will form
become enriched at the surface of the subsequent coating layer(s)
and augment its foul release properties. An example of an
incompatible fluid is provided in WO2007/10274. In WO2007/10274,
the incompatible fluid is a fluorinated polymer or oligomer in a a
polysiloxane coating; the process of enrichment of the fluorinated
polymer/oligomer at the surface of the cured polysiloxane coating
layer is thermodynamically driven due to the difference in surface
energy. The low surface energy provided by the fluorinated polymer
or oligomer in combination with the elastic properties provided by
the cured polysiloxane improves the fouling release properties of
the coating.
[0084] Examples of suitable fluids are: [0085] a) Linear and
trifluoromethyl branched fluorine end-capped perfluoropolyethers
(eg Fomblin Y.RTM., Krytox K.RTM. fluids, or Demnum S.RTM. oils);
[0086] b) Linear di-organo (OH) end-capped perfluoropolyethers (eg
Fomblin Z DOL.RTM., Fluorolink E.RTM.); [0087] c) Low MW
polychlorotrifluoroethylenes (eg Daifloil CTFE.RTM. fluids)
[0088] In all cases the fluorinated alkyl-or alkoxy containing
polymer or oligomer does not substantially take part in any
cross-linking reaction. Other mono- and diorgano-functional
end-capped fluorinated alkyl- or alkoxy-containing polymers or
oligomers can also be used (eg carboxy-, ester-functional
fluorinated alkyl- or alkoxy-containing polymers or oligomers).
[0089] Alternatively, the fluid can be a silicone oil, for example
of the formula:
Q.sub.3Si--O--(SiQ.sub.2--O--).sub.nSiQ.sub.3
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 Q are
generally methyl groups and at least 2% of the groups Q are phenyl
groups. Most preferably, at least 10% of the --SiQ.sub.2-O-- units
are methyl-phenylsiloxane units. Most preferably the silicone oil
is a methyl terminated poly(methylphenylsiloxane). The oil
preferably has a viscosity of 20 to 1000 m Pa s. Examples of
suitable silicone oils are sold under the trademarks Rhodorsil
Huile 510V100 and Rhodorsil Huile 550 by Bluestar Silicones. The
silicone oil improves the resistance of the coating system to
aquatic fouling.
[0090] The fluid may also be an organosilicone as shown:
##STR00001##
wherein: [0091] R1 may be the same or different and is selected
from alkyl, aryl, and alkenyl groups, optionally substituted with
an amine group, an oxygen-containing group of the formula OR5,
wherein R5 is hydrogen or a C1-6 alkyl, and a functional group
according the formula (I):
[0091] --R6-N(R7)-C(O)--R8-C(O)--XR3 [0092] wherein: [0093] R6 is
selected from alkyl, hydroxyalkyl, carboxyalkyl of 1 to 12 carbon
atoms, and polyoxyalkylene of up to 10 carbon atoms; [0094] R7 is
selected from hydrogen, alkyl, hydroxyalkyl, carboxyalkyl of 1 to 6
carbon atoms, and polyoxyalkylene of 1 to 10 carbon atoms; R7 may
be bonded to R8 to form a ring; [0095] R8 is an alkyl group with
1-20 carbon atoms; [0096] R9 is hydrogen or an alkyl group with
1-10 carbon atoms, optionally substituted with oxygen- or
nitrogen-containing groups; [0097] X is selected from 0, S and NH;
[0098] provided that at least one R1-group in the organosilicone
polymer is a functional group according to the above formula (I) or
a salt derivative thereof; [0099] R2 may be the same or different
and is selected from alkyl, aryl, and aklenyl; [0100] R3 and R4,
which may be the same or different, are selected from alkyl, aryl,
capped or uncapped polyoxyalkylene, alkaryl, aralkylene, and
alkenyl; [0101] a is an integer from 0 to 50,000; [0102] b is an
integer from 0 to 100; and [0103] a+b is at least 25.
[0104] In one embodiment [0105] R2, R3 and R4 are independently
selected from methyl and phenyl, more preferably methyl. [0106] R6
is an alkyl group with 1-12, more preferably 2-5 carbon atoms.
[0107] R7 is hydrogen or an alkyl group with 1-4 carbon atoms.
[0108] R8 is an alkyl group with 2-10 carbon atoms. [0109] R9 is
hydrogen or an alkyl group with 1-5 carbon atoms. [0110] X is an
oxygen atom. [0111] a+b ranges from 100 to 300.
[0112] In one embodiment the fluid is present in 0.01 to 10 wt %,
based on the total weight of the coating composition. Most
preferably the fluid is present in the range of 2 to 7 wt %.
Method of Controlling the Rate of Release of Biocide
[0113] According to the present invention, there is provided a
method of controlling the rate of release of biocide from a foul
release coating system wherein the ratio of the release rate of
biocide from a foul release coating system wherein the ratio of the
release rate of biocide from the foul release coating system 5 days
after application of the coating (R.sub.5) and the release rate of
biocide 30 days after application of the coating (R.sub.30)
R.sub.5/R.sub.30.ltoreq.1.5, the method comprising [0114] a.
providing a substrate, [0115] b. coating the substrate with a first
coating layer, [0116] c. applying at least one subsequent coating
layer on top of the first coating layer, the first coating layer
containing a biocide, the subsequent coating layer(s) containing
less biocide than the first coating layer and being free or
substantially free of biocide.
[0117] In one embodiment, the method of the invention is capable of
controlling the rate of release of biocide from a foul release
coating system such that the ratio R.sub.5/R.sub.30 is less than or
equal to (.ltoreq.) 1.33, and preferably less than or equal to
(.ltoreq.)1.11.
[0118] Suitably, the first coating layer and/or the subsequent
coating layer(s) comprises an elastomeric polymer. The elastomeric
polymer is as described in all preceding paragraphs.
[0119] Suitably, the first coating layer and/or the subsequent
coating layer(s) comprise a polyorganosiloxane. The subsequent
coating layer(s) are as described in all preceding paragraphs.
[0120] Suitably, the substrate is coated with an anticorrosion
coating and the first coating layer is used as a tie coat over said
anticorrosion coating.
[0121] Suitably, the biocide in the first coating layer is an
organic or metal-organic biocide. The biocide is as described in
all preceding paragraphs.
[0122] Suitably, the biocide is one or more of any of the biocides
previously mentioned, and most suitably a
2-trihalogenomethyl-3-halogeno-4-cyano pyrrole derivative
substituted in position 5 and optionally in position 1 or
1,4-dithiaanthraquinone-2,3-dicarbonitrile.
[0123] Suitably, the subsequent coating layer(s) comprises an
incompatible fluid such as a silicone, organic or inorganic
molecule or polymer, which is immiscible with the subsequent
coating layer(s).
Application
[0124] The coating system according to the present invention can be
applied to a substrate by normal techniques, such as brushing,
roller coating, dipping or spraying (airless and conventional).
[0125] After the subsequent coating layer(s) has cured, it can be
immersed immediately and gives immediate anti-fouling and
fouling-release protection. The resulting coating system has very
good anti-fouling and fouling-release properties. This makes the
coating system according to the present invention very suitable for
use in preventing fouling in marine and freshwater applications.
The coating system can be used for both dynamic and static
structures, such as ship and boat hulls, buoys, drilling platforms,
oil rigs, floating production storage and offloading vessels
(FPSOs), pipes, cooling water intakes in power plants, fish nets,
fish cages and other aquaculture and marine apparatus/structures
and the like which are wholly or partially immersed in water. The
coating system can be applied on any substrate that is used for
these structures, such as metal e.g. steel, aluminium, concrete,
wood, plastic or fibre-reinforced resin.
[0126] In addition to the coating system according to the present
invention having a controlled rate of release of biocide from a
foul release coating system such that the ratio of the release rate
of biocide from the foul release coating system 5 days after
application of the coating (R.sub.5) and the release rate of
biocide 30 days after application of the coating (R.sub.30)
R.sub.5/R.sub.30 is less than or equal to (.ltoreq.) 1.5
(preferably .ltoreq.1.33), it has also been found to be effective
against a broader range of fouling-types including (i) slime
fouling, (ii) weed fouling, (iii) soft bodied fouling and (iv) hard
bodied fouling, particularly on slow moving aquatic vessels,
compared to systems which do not comprise a biocide or a
foul-release coating layer.
[0127] The coating system may be applied directly to a non-treated
substrate. Alternatively, the coating system of the present
invention may be applied to a substrate to which surface treatments
or other coating layers have been previously applied. Examples of
such surface treatments and other coating layers include
anticorrosion coatings, biocidal antifouling coatings, sealer
coats, tie-coats, adhesion promoting layers, and the like.
[0128] For application to ship and boat hulls at newbuilding, the
system would typically be applied directly over a substrate having
one or more anticorrosive coatings. At maintenance and repair or
recoat, the scheme would typically be applied optionally over the
existing coating scheme (with optional link coat) or directly over
the substrate after removal of the existing coating scheme and
reapplication of one or more anticorrosive coatings.
[0129] The substrate for which fouling is to be inhibited is not
especially limited and includes any of steel, plastic, concrete,
wood, fibre-reinforced resin and aluminium.
[0130] In a typical situation, for application on ships and boat
hulls, the first coating layer would be applied to result in a dry
film thickness in the range of 100-200 .mu.m, and the subsequent
coating layer(s) would be applied to result in a dry film thickness
in the range of 100-200 .mu.m. Where a greater dry film thickness
is required, the required film thickness may be produced by
successive applications, each with a dry film thickness of 100-200
.mu.m. On other substrates, the first coating layer would be
applied to result in a dry film thickness in the range of 50-500
.mu.m, and the subsequent coating layer(s) would be applied to
result in a dry film thickness in the range of 50-500 .mu.m.
[0131] The invention will now be elucidated with reference to the
following examples. These are intended to illustrate the invention
but are not to be construed as limiting in any manner the scope
thereof.
EXAMPLES
Examples 1 to 8
[0132] Eight different coating systems according to the present
invention (Examples 1-8) were prepared.
[0133] The biocide leaching rate for each coating system was
experimentally determined. In summary, duplicate panels coated with
each coating system were immersed in a holding tank of synthetic
seawater. The panels were periodically transferred to a leaching
rate measuring container of fresh synthetic seawater and gently
agitated for a fixed period. At the end of this period, the panels
were returned to the holding tank and the amount of biocide that
had leached into the container was determined by chemical analysis.
From knowledge of the determined amount of leached biocide, the
exposed surface area of the coated panel, and the period of
immersion in the leaching rate measuring container, the biocide
leaching rate can be determined and expressed as .mu.g cm.sup.-2
d.sup.-1.
Artificial Seawater
[0134] Commercial Instant Ocean Sea Salt was used to prepare
artificial seawater by mixing 33 g of salt per litre of deionised
water.
Panel Preparation
[0135] 15.times.10 cm polycarbonate panels were masked to give a
known surface area (typically about 100 cm.sup.2). 125 .mu.m dry
film thickness of a 2 pack epoxy anticorrosive paint (Intershield
300, International Paint) was applied via draw down bar, followed
by application of the biocide containing coating layer via draw
down bar at 100 .mu.m dry film thickness. Following drying the
final `finish` coat was applied to the film via draw down bar at 15
.mu.m dry film thickness (excluding example 5 where 100 .mu.m dry
film thickness was used). The masking tape was removed and the
edges of the coated panels were sealed, using a brush, with a
2-pack epoxy anticorrosive paint (Intershield 300, International
Paint). Each coat was allowed to cure under ambient conditions
before application of a subsequent coating layer(s) and before
immersion in the holding tank.
Holding Tank
[0136] The panels were fully immersed in 40 litres of artificial
seawater in a rigorously clean glass tank and the water was
constantly circulated through an activated carbon filter to avoid
build up of the biocide or its degradation products. The
temperature of the holding tank was maintained at around
22-23.degree. C. All panels remained immersed in the holding tank
for the duration of the experiment, except during leaching rate
measurements which took place on predefined measurement days using
the leaching rate measuring container.
Leaching Rate Measuring Container
[0137] On predetermined measurement days, panels were transferred
to individual rigorously clean lidded polypropylene containers
(15.times.8.times.8 cm, l.times.w.times.h) containing 100 ml of
artificial seawater at a temperature of around 22-23.degree. C. The
containers were gently agitated using an orbital mixer for 2 hours
and the panels were then returned to the holding tank.
Leaching Rate Determination--General
[0138] The concentration of biocide in the leaching rate measuring
container may be determined using standard analytical methods known
to one skilled in the art, for example high performance liquid
chromatography (HPLC). The concentration of biocide in the leaching
rate measuring container can then be used to determine the leaching
rate R using the equation below.
R = C .times. V .times. 24 t .times. A .mu. g cm - 2 d - 1
##EQU00001##
[0139] Where C is the equivalent concentration of the biocide in
the leaching rate measurement container, V is the volume of
artificial seawater in the leaching rate measuring container
(litres), t is period of immersion of the panel in the leaching
rate measuring container (hours), and A is the exposed surface area
of the coating system on the panel (cm.sup.2).
Leaching Rate Determination of Examples 1-8--Tralopyril
[0140] Approximately 12 ml of artificial seawater from each
leaching rate measuring container was transferred to a glass vial
at the end of the agitation period. This vial was held at
45.degree. C. overnight to ensure quantitative conversion of the
leached tralopyril to
3-bromo-5-(4-chlorophenyl)-4-cyano-1H-pyrrole-3-carboxylic acid
(BCCPCA).
[0141] The concentration of BCCPCA in the treated sample was
determined by high performance liquid chromatography (HPLC) by
direct injection using an Agilent 1100 HPLC system equipped with a
Pursuit UPS 2.4 .mu.m C18 column (50.times.3 mm) and using a
mixture of acetonitrile, water, and orthophosphoric acid at a ratio
of 50:49.95:0.05 parts by volume as mobile phase.
[0142] A minimum of 6 calibration standards covering the range from
10 to 500 .mu.g litre.sup.-1 were freshly prepared each day by
appropriate dilution with artificial seawater of a 1000 .mu.g
litre.sup.-1 stock solution of BCCPCA in tetrahydrofuran.
Artificial seawater blanks were analysed before and after the
standards and after each sample set. Check standards were run after
every 5 samples to check for reproducibility of the analytical
method. At every time point, the analytical method was proven to be
reproducible.
[0143] The equivalent concentration of tralopyril in the leaching
rate measuring container at the end of the agitation period is
calculated by multiplying the determined BCCPCA concentration by
the relative molar masses of tralolopyril and BCCPCA, and the
leaching rate of tralopyril, R, is then calculated according to the
following equation:
R = C tralopyril .times. V .times. 24 t .times. A .mu. g cm - 2 d -
1 ##EQU00002##
[0144] Where C.sub.tralopyril is the equivalent concentration of
tralopyril in the leaching rate measurement container, V is the
volume of artificial seawater in the leaching rate measuring
container (litres), t is period of immersion of the panel in the
leaching rate measuring container (hours), and A is the exposed
surface area of the coating system on the panel (cm.sup.2).
[0145] Table 3 shows the leaching rate results collected on
measurement days 5 (R.sub.5) and 30 (R.sub.30), and
R.sub.5/R.sub.30. In each case, the results are the mean results of
duplicate panels for each coating system.
[0146] As can be seen, each coating systems demonstrates controlled
leaching as defined within the framework of the present invention
and none of the coatings shows biocide leaching rate behaviour that
corresponds to the biocide leaching rate being proportional to the
square root of time. Moreover, by varying particular parameters of
the subsequent coating layer, control can be exercised over the
biocide leaching rate behaviour, which can be made to fall, rise or
remain essentially constant over time.
[0147] Furthermore, different mean rates of biocide leaching can be
attained and, by varying particular parameters of the subsequent
coating layer, the biocide leaching rate can be controlled such
that a higher or lower biocide leaching rate can be obtained at any
given point in time.
TABLE-US-00001 TABLE 1 First coating layer formulation - Examples
1-8 Material % weight Polydimethyl siloxane 13.8 Surfactant based
on salts of long chain unsaturated 0.6 polyaminoamides and high
molecular weight acid esters Tralopyril 13.6 Titanium dioxide 6.7
Fumed silica 0.6 Methyl iso-amyl ketone 18.6 Oxime-cured silicone
mastic 37.2 Xylene 7.8 Chlorinated Polyolefin 0.8
N-2-aminoethyl-3-aminopropyltrimethoxysilane 0.2
Dioctyltindilaurate 0.1
TABLE-US-00002 TABLE 2 formulation details second coating layer.
(Ingredients in vol. % based on total volume of the composition)
Example Ingredient 1 2 3 4 5 6 7 8 Short chain 59.5 Poly Dimethyl
siloxane (viscosity of 7.5 stokes) Silicone 78.6 polyether block
copolymer* Poly Dimethyl 65.6 59.5 59.5 59.5 59.5 siloxane
(viscosity of 35 strokes) Fumed silica 1.5 1.8 1.5 1.5 1.5 1.5
(Hydrophobic) Red iron oxide 13.2 Micaceous iron 7.9 oxide
Disparlon 6500 2 amide (commercial product) Titanium 6.5 6.5 6.5
6.5 dioxide Carbon black 1.4 1.4 1.4 1.4 Xylene 18.4 20.5 18.4 18.4
23.6 18.4 Tetra-ethyl 2.7 3 2.7 2.7 2.7 2.7 ortho silicate
polymethyl 5.2 5.7 5.2 5.2 5.2 phenylsiloxane oil 2,4- 4.3 3.9 4.7
4.3 4.3 4.3 4.3 Pentanedione Dioctyltin 0.5 0.5 0.5 0.5 0.5 0.5 0.5
dilaurate Intersleek 970 100 commercial product *Corresponds to
Example 12 of WO 2008/132236
TABLE-US-00003 TABLE 3 Leaching rate results - Examples 1-8 Mean
leaching rate (.mu.g cm.sup.-2 d.sup.-1) Example Primary
Variable(s) R.sub.5.sup.1) R.sub.30.sup.2) R.sub.5/R.sub.30 1
Cross-link density 8.4 8.4 1.00 2 Subsequent coating layer(s) 5.6
7.0 0.80 chemistry 3 Pigmentation presence 9.7 7.3 1.32 4 Pigment
hydrophobicity 10.7 8.5 1.25 5 Thickness of subsequent 9.0 7.0 1.28
coating layer(s) 6 Fluid type 9.0 11.0 0.81 7 Presence of fluid 9.6
8.4 1.14 8 Pigment morphology 9.3 10.1 0.92 .sup.1)release rate of
biocide 5 days after immersion .sup.2)release rate of biocide 30
days after immersion
Examples 9 to 12
[0148] As shown in Table 4, further coating systems in accordance
with the present invention (Examples 9 to 12) were prepared for
comparison with a commercial biocide-free foul release coating
system (all Examples).
TABLE-US-00004 TABLE 4 First coating layer formulations for
Examples 9-12: Material % weight Polydimethyl siloxane 12.80
Surfactant based on salts of long chain unsaturated 0.55
polyaminoamides and high molecular weight acid esters Biocide 20.00
Methyl iso-amyl ketone 23.91 Oxime-cured silicone mastic 34.56
Xylene 6.07 Chlorinated Polyolefin 1.88
N-2-aminoethyl-3-aminopropyltrimethoxysilane 0.16
Dibutyltindilaurate 0.03 Example Biocide 9 Tralopyril 10 Dithianon
11 Copper Pyrithione (CPT) 12 Zinc Pyrithione (ZPT)
[0149] Test panels were prepared in order to determine the ability
of each coating system to control the leaching of biocide from the
first coating layer and inhibit fouling. The coating systems of
Examples 9 to 12 were applied to 60.times.60 cm marine plywood
panels by roller to give a dry film thicknesses for the first
coating layer and subsequent coating layer of about 100 and 150
.mu.m respectively. The boards had been pre-primed with one coat of
a 2 pack epoxy anticorrosive paint (Intershield 300, International
Paint) with a DFT of about 125 .mu.m per coat. One half of each
panel (the left hand side) was coated with a coating system
corresponding to one of the Example 9 to 12 coating systems and, as
a control, the other half of the panel (right hand side) was coated
with a commercial foul release tie-coat (Intersleek 737,
International Paint). Both sides then had a standard foul-release
finish coat applied (Intersleek 757, International paint). Each
coat was allowed to cure fully under ambient conditions before
application of a subsequent coating layer(s) and the start of
testing.
[0150] Test panels were simultaneously immersed in natural tropical
marine waters at a depth of 0.5 to 1.0 m in Changi, Singapore where
fouling growth is known to be severe. The panels were periodically
removed from the water, photographed and the growth of fouling on
the coating systems was assessed prior to re-immersion of the
panels.
[0151] The coating systems containing tralopyril (Example 9) and
dithianon (Example 10) remained substantially free of fouling even
after immersion for 8 months. The coating systems containing copper
pyrithione (Example 11) and zinc pyrithione (Example 12) exhibited
more severe fouling growth than Examples 9 and 10 after 8 months
than but less severe fouling growth than the control coatings.
[0152] In all cases, the coating systems of Examples 9 to 12 were
free of blisters, and cracks after 8 months immersion.
[0153] These results clearly show that the ability of the coating
systems according to the present invention to inhibit fouling over
an extended period is significantly improved over the standard
commercial foul release coating system.
* * * * *