Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2003-01-13
2004-03-23
Pezzuto, Helen L. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S515000, C524S516000, C524S530000, C524S533000
Reexamination Certificate
active
06710117
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to marine anti-fouling (AF) paints generally used as topcoat paints for ships' hull, particularly to marine anti-fouling paints that polish at a predetermined rate and to a polymeric composition for a marine anti-fouling paint that hydrolyses at a predetermined rate in the presence of sea water.
The performance of a ship falls off, when marine organisms grow on the submarine part of the hull.
Applying to the hull a topcoat paint comprising anti-fouling agents controls the extent of marine fouling. The anti-fouling agents are biocides that are freed from the paint surface at a rate such that their concentration is lethal to marine organisms.
The use of self polishing copolymer (SPC) systems is nowadays the leading technology to protect ship hulls against fouling: in these systems the interaction with sea water produces soluble species but bulk hydrophobicity confines reaction to sea-water interface (ca 5 &mgr;m). This ~5 &mgr;m leach layer is maintained throughout coating lifetime. This results in a zero order release rate and so the lifetime is directly related to film thickness.
The best known SPC antifoulings are based on tributyltin (TBT) (meth)acrylate copolymers. EP-A-51930 is a milestone patent disclosing such TBT copolymers. The “self-polishing” action (rate is dependent on TBT content) leads to decrease in hull roughness during service. TBT systems have dominated the antifouling market for the last 20 years.
By 1987, tributyltin (TBT) had been shown to leach into the water (it is indeed a potent marine biocide which gives an enhanced anti-fouling effect), harming sea life, possibly entering the food chain, and causing deformations in oysters and sex changes in whelks. Its use was banned for use on vessels with hulls of 25 m or less, but the 1987 ruling left an essential exemption for larger vessels until alternatives were found. In addition, many countries have implemented a maximum limit for the TBT release of antifoulings used on vessels with hulls that are longer than 25 m. The most frequently used limit is that of 4 &mgr;g/cm
2
/day determined according ASTM D 5108-90.
These restrictions have resulted in new developments such as described for example in European patent EP-B-0,218,573 that discloses a marine paint comprising a film-forming polymer, prepared by polymerisation of monomer units A of at least one triorganotin salt of an olefinically unsaturated carboxylic acid and at least one comonomer B selected from the group comprising vinylpyrrolidone, vinylpiperidone and vinylcaprolactam, the balance being at least one C1-C4 alkylmethacrylate and/or styrene comonomer C.
The ban on TBT in Japan will become world wide in the near future and has lead to many TBT-free developments as well:
EP-B-289 481 and EP-B-526 441 discloses marine paint compositions based on rosin or its copper or zinc derivatives and a copolymer of alkyl methacrylates and/or styrene with comonomers which are cyclic tertiary amides or imides having an alkenyl group.
EP-A-342 276 relates to the preparation of metal (preferably zinc or copper) containing resin composition which is characterised by having hydrolysable metal ester bonding at the end portion of pendant chain. GB 2 311 070 also describes a composition comprising a resin having at least one metal carboxylate.
EP-B-0131 626 describes antifouling paints based on film-forming water insoluble, seawater erodible, polymeric binders containing trialkylsilyl (meth)acrylates; EP-A-755 733 discloses antifouling coating compositions based on such a trialkylsilyl esters containing copolymer and a chlorinated paraffin.
There is however still a need in the art for improved erodible anti-fouling paint compositions.
SUMMARY OF THE INVENTION
An object of the present invention is to provide such improved self-polishing and anti-fouling paint compositions for use as topcoat paints for ships' hull.
Another object of the invention is to provide improved polymeric binders for a marine anti-fouling paint that hydrolyses at a predetermined rate in the presence of seawater.
A yet further object of the present invention is to provide an anti-fouling marine paint composition with a high solids content.
Accordingly, the present invention provides a marine paint comprising essentially:
a first polymer comprising from 20 to 70 wt % of monomer units A of at least one hydrolysable either tin or silicium ester of an olefinically unsaturated carboxylic acid or salt of copper, zinc, calcium of an olefinically unsaturated carboxylic acid, the balance of the monomer units being monomer units C selected from the group consisting of the esters of ethylenically unsaturated carboxylic acids with C1-C18 alcohols, styrene, alpha-methyl styrene, vinyl toluenes, and mixtures thereof.
a second polymer comprising from 5 to 40 wt % of at least one comonomer B selected from the group consisting of the N-vinyl lactam monomers of general formula CH2═CH—NR′″″—CO—R′, the N-vinyl amides of general formula CH2═CH—N—CO—R″, the monomers of general formula CH2═CR′″—COO—R″″—NR′″″—CO—R′, the monomers of general formula CH2═CR′″—COO—R″″—N—CO—R″, 2-pyrrolidone-1-isoprenyl ketone, and mixtures thereof, wherein
R′ is a n-alkylidene radical having 2 to 8 carbon atoms,
R″ is selected from the group consisting of alkyl, cycloalkyl, aryl, alkylaryl and arylalkyl radicals having a maximum of 18 carbon atoms,
R′″ is H or CH3,
R″″ is a n-alkylidene radical having from 1 to 8 carbon atoms,
R′″″ is H or R″,
and the balance of the monomer units being monomer units C selected from the group consisting of the esters of ethylenically unsaturated carboxylic acids with C1-C18 alcohols, styrene, alpha-methyl styrene, vinyl toluenes, and mixtures thereof.
At least one antifoulant.
The relative ratio of the first polymer comprising monomer units A to the second polymer comprising monomer units B is from 95:5 to 10:90.
Whilst not wishing to be bound by a theory, it is believed that the two polymeric binders are sufficiently compatible to produce a stable paint composition but sufficiently incompatible to give such structure to the paint that it can be applied in desired layer thicknesses. There will thus be less need to add thixotropic agents in order to obtain a suitable structure. It is known in the art that the solids content of a paint composition decreases when the amount of thixotropic agent increases; the paint compositions of the present invention will thus keep a high solids content.
The applicant has now unexpectedly found that placing monomer units A and monomer units B respectively on two separate binders that are marginally compatible, produces a paint composition with an improved compromise of the following properties:
a suitable structure indicated by the thixotropic factor;
a high solids content;
a suitable polishing rate;
little or no blistering or flaking or detachment;
good can stability.
DETAILED DESCRIPTION OF THE INVENTION
In a first embodiment, the monomer units A used in the first polymer are of the formula R
3
SnOOCCR′═CH
2
or R
3
SiOOCCR′═CH
2
, wherein each R is an alkyl radical containing from 2 to 8 carbon atoms, or an aryl or aralkyl radical, R′ is H or CH
3
. The groups R can be different but are preferably the same.
The first polymer comprises from 20 to 70 wt % of monomer units A, preferably from 30 to 65 wt %, and more preferably from 50 to 60 wt %, the balance being monomer units C.
In another embodiment of the present invention, the first polymer comprising monomer units A is a metal containing resin composition that can be obtained as described in EP-A-342276 by reacting a mixture of
an acid group containing base resin, comprising essentially monomer units C and olefinically unsaturated carboxylic acids monomer units corresponding to monomer unit A;
a metallic salt of low boiling organic basic acid and
a hig
Gillard Michel
Prinsen Jos G. M.
Vos Marcel
Goodwin & Procter LLP
Pezzuto Helen L.
Sigma Coatings B.V.
LandOfFree
Marine paint compositions does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Marine paint compositions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Marine paint compositions will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3271908