MARINE COATING AND CERTAIN NEW TERPOLYMERS FOR USE THEREIN

ENDUIT POUR SURFACES IMMERGEES DANS L'EAU, ET TERPOLYMERE ENTRANT DANS SA COMPOSITION

English Abstract

ABSTRACT
Marine coating which comprises units of the following
monomers:
1. <IMG>
R = H or CH3, R" = CH3 or C2H5, n = 1 or 2,
and
2. <IMG>
R' = C1-4 alkyl,
and optionally
3. one or more triorganotin methacrylates or acrylates.
New acrylic terpolymer which contains units of the said
monomers 1-3.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Marine coating comprising a film-forming acrylic polymer
characterised in that the acrylic polymer comprises units of the
following monomers:
1. <IMG>
R = H or CH3, R" = CH3 or C2H5, n = 1 or 2
and
2. <IMG>
R' = C1-4alkyl.
2. Marine coating according to claim 1, characterised in
that the acrylic polymer comprises units of
1. 2-methoxyethyl acrylate, and
2. methyl methacrylate.
3. Marine coating according to claim 1, characterised in
that the acrylic polymer comprises 15-80 percent by weight of
monomer 1 units, and 20-85 percent by weight of monomer 2 units.
4. Marine coating according to claim 1, characterised in
that the acrylic polymer also comprises units of one or more tri-
organotin methacrylates or acrylates.

5. Marine coating according to claim 1, characterised in
that the acrylic polymer comprises units of tributyltin meth-
acrylate.
6. Marine coating according to claim 4 or 5, characterised
in that the acrylic polymer comprises up to 60 percent by weight
of said triorganotin methacrylate or acrylate units.
7. Acrylic terpolymer characterised in that it comprises
units of the following monomers:
1. <IMG>
R = H or CH3, R" = CH3 or C2H5, n = 1 or 2
2. <IMG>
R' = C1-4alkyl, and
3. triorganotin methacrylates or acrylates.
8. Acrylic terpolymer according to claim 7, characterised
in that it comprises units of:
1. 2-methoxyethyl acrylate
2. methyl methacrylate, and
3. tributyltin methacrylate.
9. Acrylic terpolymer according to claim 7 or 8, charac-
terised in that it contains 1-80 percent by weight of monomer 1

units, 20-85 percent by weight of monomer 2 units and up to 60
percent by weight of monomer 3 units.
10. Acrylic terpolymer according to claim 7 or 8, charac-
terised in that it contains 5-40 percent by weight of monomer 1
units, 20-70 percent by weight of monomer 2 units and 1-55 percent
by weight of monomer 3 units.
11. A process for protecting a substrate against marine
corrosion which process comprises applying to the substrate a
marine coating comprising a film-forming acrylic polymer charac-
terised in that the acrylic polymer comprises units of the
following monomers:
1. <IMG>
R = H or CH3, R" = CH3 or C2H5, n = 1 or 2
and
2. <IMG>
R' = C1-4alkyl.
12. A process according to claim 11 wherein the acrylic
polymer comprises units of
1. 2-methoxyethyl acrylate, and
2. methyl methacrylate.

13. A process according to claim 11 wherein the acrylic
polymer comprises 15-80 percent by weight of monomer 1 units, and
20-85 percent by weight of monomer 2 units.
14. A process according to claim 11, 12 or 13 wherein the
acrylic polymer also comprises units of one or more triorganotin
methacrylates or acrylates.
15. A process according to claim 11, 12 or 13 wherein the
acrylic polymer comprises units of tributyltin methacrylate.
16. A process according to claim 11, 12 or 13 wherein the
acrylic polymer comprises up to 60 percent by weight of said
triorganotin methacrylate or acrylate units.

Description

~2~
Marine coating and certain new terpolymers for use
therein.
The present invention rela-tes to new marine coatings
and certain new terpolymers which are useful components
therein.
There are known marine coatings in which an essenti-
al component is a copolymer containing units of alkyl
acrylates and methacrylates and units of triorganotin
esters of acrylic and methacrylic acid. The alkyl
acrylate and methacrylate units impart hardness to the
film obtained when the marine coating is applied to a
substrate, and the triorganotin ester units impart
biocidal as well as self-polishing effect. During use
the triorganotin units are split off from the polymer
by hydrolysis and/or ion exchange, whereby the film of
the marine coating exerts a desired biocidal effect.
At the same time the film is degraded, and this results
in the self-polishing effect.
Thus, to obtain a satisfactory self~polishing effect,
a certain amount of triorganotin units must be present
in the copolymer used in the marine coating, since the
self-polishing effect is a consequence of the cleavage
of said units. On the other hand, it is desired to
keep the amount of triorganotin units as low as poss-
ible, with due regard to the desired biocidal and self-
polishing effect, since the triorganotin monomers are
rather expensive and also have a softening effect on
the copolymer. ~
Copolymers of the above type are disclosed i.a. in
British Patent No. l 457 590.
In British Patent No. 2087415 it ~s
suggested to replace some or all of the triorganotin
ester units by methyl acrylate and/or ethyl acrylate
units. The marine coating may contain some additional
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biocide, particularly if the copolymer does not contain
any trior~anotin ester units. Said methyl acrylate and
ethyl acryla-te wnits will to some extent be hydrolysed
in wa-ter, and will impar-t a selfpolishing effect to the
final coating. However, due -to the low rate of hydro-
lysis of the resulting copolymer, the selEpolishing
effect will not be entirely satisfactory~
According to the present invention there is provid-
ed a marine coating which in addition to ordinary paint
components such as pi.gments, dyes, solvents, etc.
contain a copolymer unit~ of the following monomers:
1. CH2=C-COO(CH2)n-0-R"
R
R = H or CH8' R" = CH3 or C2H5' n = 1 or 2
and
2. CH2=C-COOR'
CH3
R = Cl 4 alkyl
The units of.monomer no. 1 are readily hydrolysed to
form free carboxyl groups, resulting in a polymer which
is gradually degraded to provide a self-polishing
effect.
Monomer No. 2 is present to impart sufficient hard-
ness:to the film.
The copolymer used in the marine coatings of the
present invention usually contain from 15 to 80
percent by weight of monomer No. 1 and from 20 to 85
percent by weight of monomer No. 2.
A preferred representative of monomer No. 1 is 2-
methoxyethyl acrylate, and a preferred representative
of monomer No. 2 is methyl methacrylate.
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As pointed out above, a marine coating which compris-
es a copolymer containing units of the abo~e -two mono-
mers No. 1 and No. 2, may also contain biocidal compo-
nents -to obtain the desired biocidal effect, such as
cuprous oxide, dithiocarbamates and triorganotin com-
pounds as known in the state of art.
In addition to the two types of monomer disclosed
above, the copolymers used in the marine coatings of
the present invention may also contain units of tri-
organotin acryla-tes and methacrylates. Examples of
such triorganotin monomers are tributyltin methacryl-
ate and acrylate, tripropyltin methacrylate and acryl-
ate and triphenyltin methacrylate and acrylate. The
triorganotin monomers may constitute up to 60, parti-
cularly 1-55, percent by weight of the copolymer
(terpolymer). Monomer No. 1 is then normally present
in an amount of 1-80 percent by weight, particularly
5-40 percent by weight, and monomer No. 2 is then
normally present in an amount of 20-85, particularly
20-70 percent by weight.
Such terpolymers are new and represent a further
feature of the invention.
The copolymers containing monomers No. 1 and 2 may
be prepared by ordinary polymerisation of the suitable
monomers, using suitable initiators and polymerisation
conditions. When it is desired to prepare a copolymer
~terpolymer) which also contains triorganotin meth-
acrylate or acrylate units, this may be done either
by polymerising monomers No. 1 and 2 together with the
desired triorganotin methacrylate or acrylate monomer,
or monomers No. 1 and 2 may be polymerised with meth-
acrylic~or acrylic acid, and the carboxyl groups on
the resulting polymer are then esterified with tri-
organotin groups in a per se known manner.
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.8~i
Exam~
Methyl methacrylate (300 g; 3.00 mole) and 2-methoxy-
ethyl acrylate (200 g; 1.54 mole) were dissolved in
xylene 750 g). Azobisisobu-tyronitrile (4 g; 0.024 mole)
was added and the solution heated to 75C, with stirring
and under ni-trogen.
The polymerisation was carried ou-t at the above temp-
erature for a period of 5 hours and was monitored by the
change in refractive index.
The temperature was raised to 100C for 30 minutes to
destroy any residual activity of the initiator.
The solution obtained was that of a copolymer of
methyl methacrylate - 2-methoxyethyl acrylate (60:40 by
weight).
Example 2
Tributyltin methacrylate (150 g; 0.40 mole), methyl
methacrylate (250 g; 2.50 mole) and 2-methoxyethyl
acrylate (100 g; 0.77 mole) were dissolved in xylene
(7S0 g).
Azobisisobutyronitrile (4 g; 0.02 mole) was added
and polymerisation was carried out in a similar manner
as in example 1.
The solution obtained was that of a terpolymer of
tributyltin methacrylate - methyl methacrylate - 2-
methoxyethyl acrylate (30:50:20 by weight).
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~xample 3
Tribu~yltin methacrylate (275 g; 0.73 mole), methyl
methacrylate (210 g; 210 mole) and 2-methoxyethyl
acrylate (15 g; 0.12 mole) were dissolved in xylene
(750 g~.
Azobisisobutyronitrile l4 g; 0,02 mole) was added
~ and polymerisation was carried out in a similar manner
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as in exampl.e 1.
The solution ob-tained was that of a -terpolymer of
-tributyltin methacrylate - methyl methacrylate ~ 2-
methoxyethyl acrylate (55:42:3 by weight).
Example 4
409.2 g of the copolymer solution from example 1 was
mixed with cuprous oxide (365.4 g), zinc oxide (151.2
g), Aerosil~ (colloidal silica) (4.0 g), Bentone~
(thickening agent) (8.0 g), denaturated ethanol (4.8 g)
and xylene (57.4 g), and milled overnight to produce
a paint with a cuprous oxide - zinc oxide ratio of
70:30 by volume.
Example 5
409.2 g of the terpolymer solution from example 2
was mixed with cuprous oxide (365.4 g), zinc oxide
(151.2 g), Aerosil~ (4.0 g), Bentone~ ~8~0 g), dena-
turated ethanol (4.8 g) and xylene (57.4 g) and milled
overnight to produce a paint with a cuprous oxide -
zinc oxide ratio of 70:30 by volume.
Example 6
As Example 4, with the exception that the polymer
of Example 1 was replaced by that of Example 3.
The paints described in Example 4, 5 and 6 were
tested for polishing using a rotor apparatus with a
peripheral speed of 17 knots ~about 31 km/h), in sea
water, at an average temperature of 23~.
A commercially successful selfpolishing paint con-
taining organotin polymer (X) was used as reference.
The test was carried out over a period of 90 days and
the thickness of the paint film was determined by
electromagnetic induction.
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Paint Polishing Rate (~m/year~
X 60
Example 4 52
Example 5 72
Example 6 80
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