HK1092169B - Silyl ester copolymer compositions - Google Patents

Description

Silyl ester copolymer compositions

The present invention relates to silyl ester copolymer solutions and antifouling coating compositions comprising a silyl ester copolymer and an ingredient having biocidal properties for aquatic organisms.

Man-made structures immersed in water, such as boat hulls, floats, drilling platforms, oil production rigs and pipes, are prone to fouling by aquatic organisms such as green and brown algae, nasal clamps, shellfish and the like. Such structures are typically metallic but may also comprise other structural materials such as cement or wood. This fouling can cause damage to the hull of the vessel because it increases the frictional resistance during travel through the water, resulting in reduced speed and increased fuel consumption. It causes damage to stationary structures such as the legs of drilling platforms and oil production rigs, firstly because the resistance of thick layers of scale to waves and currents can cause unpredictable and potentially dangerous stresses in the structure, and secondly because scale makes inspection of structure defects such as stress cracks and corrosion difficult. It causes damage to pipes such as cooling water inlets and outlets because fouling reduces the effective cross-sectional area and as a result, the flow velocity is reduced.

It is known to use antifouling paints, for example as topcoats on ship hulls, to inhibit the deposition and growth of marine organisms such as barnacles and algae, typically by release of marine biocides.

Traditionally, antifouling paints have included relatively inert binders and biocidal pigments that leach out of the paint. Binders that have been used include vinyl resins and rosins. Vinyl resins are seawater insoluble and paints based on them use high pigment concentrations to allow contact between pigment particles to ensure leaching. Rosin is a hard brittle resin that is very slightly soluble in seawater. Rosin-based antifouling paints have been referred to as dissolving binders or corrosive paints. The biocidal pigment leaches out of the rosin binder matrix used very slowly, leaving a rosin matrix which is washed off the hull surface to leach the biocidal pigment deep within the paint film.

Many successful antifouling paints in recent years have been "self-polishing copolymer" paints based on a polymeric binder to which biocidal tri-organotin moieties are chemically attached and from which the biocidal moieties are gradually hydrolysed by seawater. In such adhesive systems, the side groups of the linear polymer units are broken down in a first step by reaction with seawater, so that the remaining polymer skeleton becomes water-soluble or water-dispersible. In a second step, the water-soluble or water-dispersible framework of the paint layer surface of the ship is washed off or eroded. Such paint systems are described, for example, in GB-A-1457590.

Another self-polishing antifouling paint system based on silyl ester copolymers has been developed. Silyl ester copolymers and antifouling compositions comprising these copolymers are described, for example, in WO 00/77102 a1, US 4,593,055 and US 5,436,284. Typically, a solution of the silyl ester copolymer is prepared, which is then used as a component of the coating composition.

EP 1127902 discloses binders for antifouling compositions. The binder comprises a silyl ester copolymer preparable by polyaddition in an organic solvent. The molecular weight of the copolymer prepared was high, i.e., 36,600-59,000.

EP 1127925 discloses a binder for an antifouling composition comprising two types of polymers. One type may be a silyl ester copolymer. The silyl ester copolymer prepared in the examples had a molecular weight of 37,600.

EP 0775733 a1 describes an antifouling coating composition comprising a chlorinated paraffin and a silyl ester copolymer having a weight average molecular weight of 1,000-150,000. The silyl ester copolymer solution may have a viscosity of 30 to 1,000 centipoise at 25 ℃ in a 50 wt.% xylene solution. In the examples, silyl ester copolymer solutions were prepared having a solids content of less than 50 wt.%. Coating compositions prepared from these solutions contain a large amount of volatiles. Coating compositions containing low levels of volatiles are not disclosed or suggested.

EP 0802243A 2 describes antifouling coating compositions comprising silyl ester copolymers having a weight average molecular weight of 1,000-150,000. It is mentioned that the solids content of the silyl ester copolymer solution may be from 5 to 90% by weight. However, in the examples, copolymer solutions were prepared that contained 50 wt% volatile solvents, and coating compositions prepared from these solutions contained significant amounts of volatiles. There is no disclosure in this document of how to obtain a high solids polymer solution. Nor any possible or preferred molecular weight ranges for the copolymer in such high solids solutions. In addition, no specific properties are disclosed which such high solids copolymer solutions should have when used to prepare antifouling coating compositions.

Coating compositions containing high amounts of volatile organic compounds have the disadvantage that large amounts of these substances have to be evaporated, whereas the level of Volatile Organic Content (VOC) is limited by existing legislation in many countries. For example, for an anti-fouling coating, U.S. federal regulations limit the content of volatile organic hazardous gas pollutants (generally synonymous with VOC) to less than 400 g/L. Thus, there is a need for antifouling coatings comprising a relatively low content of volatile organic compounds, preferably having a VOC of less than 400 g/L.

The most common methods of applying antifouling coatings are airless spraying, brushing, and rolling. We have found that to prepare a self-polishing antifouling coating composition comprising a silyl ester copolymer and having a VOC of less than 400g/L, which can be applied by airless spraying, brushing, rolling or other common application methods, a silyl ester copolymer solution having a solids content of at least 55 wt% and a viscosity at 25 ℃ of less than 20 poise or less, preferably 10 poise or less, must be used, otherwise the viscosity of the coating is too high to have satisfactory application properties, or additional solvent must be added at the time of application, which may exceed the VOC limit.

The VOC level of the composition can be determined according to EPA reference method 24 in conjunction with ASTM standard D3960-02 or calculated according to ASTM standard D5201-01. Both methods generally give similar results. A given viscosity value for a copolymer solution or coating composition of the invention refers to a high shear viscosity measured using a cone and plate viscometer according to ASTM standard D4287-00.

In addition to the above requirements of the coating composition, the resulting antifouling coating on ships should have a high integrity, i.e. almost no cracks and show good adhesion, especially when applied to those parts of the coating which are alternately wet and dry, such as the water line of a ship. The coating should be hard enough, i.e., not soft or tacky, but should not be brittle. In addition, the coating should exhibit little so-called cold flow or plastic deformation, in other words, the paint film should not wrinkle when the ship is moving in water. Furthermore, the coating composition needs to exhibit a sufficiently short drying time.

In particular, the present invention relates to a silyl ester copolymer-containing solution, a coating composition comprising a silyl ester copolymer, and substrates and structures having a cured coating prepared from the coating composition. It was found that adjusting the weight average molecular weight, polydispersity, glass transition temperature and amount of side chains of the silyl ester copolymer can affect copolymer solution properties, coating composition properties and coating properties.

For the purposes of the present invention, the weight average molecular weights given are weight average molecular weights measured by GPC (gel permeation chromatography) and calculated relative to polystyrene standards. Polydispersity (D), also sometimes referred to as molecular weight distribution, is defined as the ratio of the polymer weight average molecular weight (Mw) to the number average molecular weight (Mn) (D ═ Mw/Mn). Polydispersity can be determined by GPC with Tetrahydrofuran (THF) as solvent and polystyrene as reference.

The present invention relates to silyl ester copolymer solutions having a solids content of at least 55 weight percent, preferably at least 60 weight percent, even more preferably at least 65 weight percent, and a viscosity of less than 20 poise, preferably less than 10 poise, even more preferably less than 5 poise at 25 ℃. Preferably, the solids content of the solution does not exceed 80% by weight. The solids content of the composition can be determined using ASTM standard 1644 or calculated according to ASTM standard D5201-01.

The silyl ester copolymer in solution preferably has a weight average molecular weight greater than 1,500, even more preferably greater than 2,000, preferably less than 20,000, even more preferably less than 15,000.

The polydispersity of the copolymer is preferably greater than 1.1; the polydispersity is preferably less than 3.0, even more preferably less than 2.8. The glass transition temperature of the silyl ester copolymer in solution is preferably higher than 5 ℃, even more preferably higher than 10 ℃; the glass transition temperature is preferably below 90 c, even more preferably below 60 c.

Preferably, more than 10% by weight, even more preferably more than 30% by weight, very preferably more than 40% by weight of the copolymer consists of structural units having a side chain comprising a silyl ester function. Preferably, less than 70% by weight, even more preferably less than 60% by weight, of the copolymer consists of structural units having side chains with silyl ester functionality.

The invention further relates to a stable antifouling coating composition having a VOC of less than 400g/L and a viscosity at 25 ℃ of less than 20 poise, preferably less than 10 poise, even more preferably less than 5 poise. Preferably, the antifouling composition comprises the following components:

-a silyl ester copolymer having a weight average molecular weight preferably greater than 1,500, even more preferably greater than 2,000, preferably less than 20,000, even more preferably less than 15,000; the polydispersity is preferably greater than 1.1, preferably less than 3.0, even more preferably less than 2.8; the glass transition temperature is preferably higher than 5 ℃, even more preferably higher than 10 ℃, the glass transition temperature is preferably lower than 90 ℃, even more preferably lower than 60 ℃; preferably more than 10% by weight, more preferably more than 30% by weight, very preferably more than 40% by weight and preferably less than 70% by weight, more preferably less than 60% by weight of the silyl ester copolymer consists of side chains having a silyl ester function, and

-an ingredient having biocidal properties for aquatic organisms.

Paint films prepared from the coating compositions of the present invention exhibit good integrity and low cold flow.

In preparing the coating composition, the silyl ester copolymer solution is preferably added in an amount of 1 to 60 wt.%, more preferably 5 to 50 wt.%, and even more preferably 15 to 45 wt.%, based on the total weight of the coating composition.

In the coating composition, the ingredient having biocidal properties for aquatic organisms is preferably present in an amount of from 0.1 to 70 wt%, more preferably from 1 to 60 wt%, even more preferably from 2 to 55 wt%, based on the total weight of the coating composition.

The silyl ester copolymer in the silyl ester copolymer solutions and coating compositions of the present invention is a copolymer comprising at least one side chain bearing at least one terminal group of formula (I):

wherein n is 0 or an integer from 1 to 50, and R1, R2, R3, R4 and R5 are each independently selected from optionally substituted C_1-20Alkyl, optionally substituted C_1-20Alkoxy, optionally substituted aryl, and optionally substituted aryloxy. Preferably, at least one of the groups R1-R5 in the silyl ester copolymer is methyl, isopropyl, n-butyl, isobutyl, or phenyl. More preferably, n is 0, and R3, R4 and R5 are the same or different and represent isopropyl, n-butyl or isobutyl.

In the context of the present invention, the term C_1-20Alkyl represents straight, branched and cyclic hydrocarbon groups having 1 to 20 carbon atoms, such as methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, cyclohexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tetradecyl, hexadecyl, octadecyl and eicosyl. The term substituted C_1-20Alkoxy means C_1-20Alkyloxy groups such as methoxy, ethoxy, propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, pentoxy, hexoxy, cyclohexoxy, heptoxy, octoxy, nonoxy, decyloxy, undecyloxy, dodecyloxy, tetradecyloxy, hexadecyloxy, octadecyloxy and eicosyloxy. The term aryl is understood to meanRefers to an aromatic carbocyclic ring or ring system such as phenyl, naphthyl, biphenyl, and xylyl. The term "optionally substituted" is used to indicate that the group may be substituted one or more times, preferably 1 to 5 times, with a substituent. These substituents may be, for example, hydroxyl, alkyl, hydroxyalkyl, alkylcarbonyloxy, carboxyl, alkoxycarbonyl, alkoxy, alkenyloxy, oxy, alkylcarbonyl, aryl, amino, alkylamino, carbamoyl, alkylaminocarbonyl, aminoalkylaminocarbonyl, alkylcarbonylamino, cyano, guanidino, ureido, alkanoyloxy, sulfonyl (sulpho), alkylsulfonyloxy, nitro, sulfanyl (sulphonyl), alkylthio and halogen.

For example, silyl ester copolymers comprising at least one side chain bearing at least one terminal group of formula (I) above may be obtained by copolymerizing one or more vinyl polymerizable monomers with one or more monomers comprising one or more olefinic double bonds and one or more terminal groups (I) above.

Examples of suitable vinyl polymerizable monomers that can be copolymerized with one or more monomers comprising one or more olefinic double bonds and one or more of the above terminal groups (I) include (meth) acrylates such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate and methoxyethyl methacrylate; maleates such as dimethyl maleate and diethyl maleate; fumaric acid esters such as dimethyl fumarate and diethyl fumarate; styrene, vinyl toluene, alpha-methyl styrene, vinyl chloride, vinyl acetate, butadiene, acrylamide, acrylonitrile, methacrylic acid, acrylic acid, isobornyl methacrylate, maleic acid, and mixtures thereof. It is preferable to use a mixture of methyl (meth) acrylate or ethyl (meth) acrylate with another vinyl polymerizable monomer. The polishing rate can be adjusted by using a mixture of hydrophobic and hydrophilic (meth) acrylates. Optionally, hydrophilic comonomers such as methoxyethyl (meth) acrylate, or higher polyoxyethylene derivatives such as ethoxyethyl (meth) acrylate, propoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, polyoxyethylene glycol monoalkylether (meth) acrylates such as polyoxyethylene (N ═ 8) glycol monomethyl ether methacrylate, or N-alkenyl pyrrolidone are included.

Examples of suitable monomers containing one or more olefinic double bonds and one or more of the above terminal groups (I) which are copolymerizable with one or more vinyl polymerizable monomers include monomers containing one or more terminal groups (I) wherein n ═ 0, and can be represented by formula (II):

wherein R3, R4 and R5 are as defined above, and X is (meth) acryloyloxy, maleoyloxy or fumaroyloxy.

The preparation of the monomers (II) can be carried out, for example, according to the methods described in EP 0297505 or EP 1273589 and the references cited therein. Examples of suitable (meth) acrylic acid derived monomers include: trimethylsilyl (meth) acrylate, triethylsilyl (meth) acrylate, tri-n-propylsilyl (meth) acrylate, triisopropylsilyl (meth) acrylate, tri-n-butylsilyl (meth) acrylate, triisobutylsilyl (meth) acrylate, tri-t-butylsilyl (meth) acrylate, tri-n-pentylsilyl (meth) acrylate, tri-n-hexylsilyl (meth) acrylate, tri-n-octylsilyl (meth) acrylate, tri-n-dodecylsilyl (meth) acrylate, triphenylsilyl (meth) acrylate, tri-p-tolylsilyl (meth) acrylate, tribenzylsilyl (meth) acrylate, dimethylphenylsilyl (meth) acrylate, and mixtures thereof, Dimethylcyclohexylsilyl (meth) acrylate, ethyldimethylsilyl (meth) acrylate, n-butyldimethylsilyl (meth) acrylate, t-butyldimethylsilyl (meth) acrylate, diisopropyl-n-butylsilyl (meth) acrylate, n-octyldi-n-butylsilyl (meth) acrylate, diisopropyl stearyl silyl (meth) acrylate, dicyclohexylphenylsilyl (meth) acrylate, t-butyldiphenylsilyl (meth) acrylate, and lauryl diphenylsilyl (meth) acrylate. Triisopropylsilyl (meth) acrylate, tri-n-butylsilyl (meth) acrylate or triisobutylsilyl (meth) acrylate is preferably used for preparing the silyl ester copolymer.

As noted above, it has been found that by adjusting the properties of the silyl ester copolymer, the copolymer solution properties, coating composition properties and coating properties can be influenced. In addition, preferred ranges for a number of properties found have been listed.

In general, the reaction temperature has an effect on the molecular weight of the polymer. The molecular weight can additionally or alternatively be adjusted by the amount of initiator and/or by the addition of chain transfer agents, such as mercaptans. The type of initiator affects the size of the polydispersity. For example, the polydispersity can be reduced by selecting an azo initiator such as azobisisobutyronitrile or azobismethylbutyronitrile. Alternatively, or additionally, the solvent in which the reaction is carried out may be adjusted to adjust the molecular weight of the copolymer and its polydispersity. The viscosity of the silyl ester copolymer solution and/or the coating composition can be adjusted by adjusting the molecular weight of the copolymer, and/or adjusting its polydispersity and/or adjusting the solids content.

The amount of unreacted unconverted monomers should be as low as possible. This is because the unreacted monomers can act as solvents for the polymer and increase the VOC of the coating composition. The viscosity of the copolymer solution and the coating composition is preferably adjusted using a solvent rather than a monomer, since most solvents are less expensive than monomers. In addition, exposure to the monomer should be kept to a minimum, taking into account health and safety concerns associated with the monomer. Furthermore, free monomers in the coating composition have a negative effect on the final paint film. The monomers can act as plasticizers and/or cause water to enter the paint film due to their hydrophilic properties. The degree of conversion of the reaction can be increased by the addition of a coinitiator (boost initiator), but is not essential. In the process for preparing the copolymer solution of the present invention, a coinitiator is preferably used, and an azo initiator, such as azobisisobutyronitrile or azobismethylbutyronitrile, is more preferably used as coinitiator.

The ingredient having biocidal properties for aquatic organisms present in the coating composition of the present invention may be a pigment or a mixture of pigments having biocidal properties. Examples of suitable biocides are inorganic biocides such as copper oxide, copper thiocyanate, bronze, copper carbonate, copper chloride, copper nickel alloys; organometallic biocides such as zinc pyrithione (i.e., the zinc salt of 2-pyridinethiol-1-oxide), copper pyrithione, bis (N-cyclohexyldiazeniumdioxy) copper (bis (N-cyclohexoxyl-diazeniumdioxy) copper), zinc ethylenebisdithiocarbamate (i.e., zineb), and manganese ethylenebis (dithiocarbamate) (i.e., mancozeb) complexed with zinc salts; and organic biocides, such as formaldehyde, dodecylguanidine hydrochloride, thiabendazole, N-trihalomethylthiophthalimide, trihalomethylthiosulfamide, N-arylmaleimide, 2-methylthio-4-butylamino-6-cyclopropylamino-s-triazine, 3-benzo [ b ] thienyl-5, 6-dihydro-1, 4, 2-oxathiazine-4-oxide, 4, 5-dichloro-2-N-octyl-3 (2H) -isothiazolone, 2, 4,5, 6-tetrachloroisophthalonitrile, 3-iodo-2-propynylbutylcarbamate, pyrimidylbenzane, 2-trihalomethyl-3-halo-4-cyanopyrrole derivatives substituted in the 5-and optionally 1-position, such as 2- (p-chlorophenyl) -one 3-cyano-4-bromo-5-trifluoromethylpyrrole, and furanones such as 3-butyl-5- (dibromomethylene) -2(5H) -furanone, and mixtures thereof.

In addition to the silyl ester copolymer and the ingredient having biocidal properties for aquatic organisms, the antifouling coating composition of the invention optionally comprises other resins or mixtures of other resins and/or one or more non-biocidal pigments and/or additives such as one or more thickeners or thixotropic agents, one or more wetting agents, fillers, liquid carriers such as organic solvents, organic non-solvents or water and the like.

Examples of resins other than silyl ester copolymers that can be used in the antifouling coating composition of the invention include polymers that do not contain triorganosilyl ester groups and triorganotin groups but are reactive in seawater, materials that are sparingly soluble or sensitive to water in seawater, and materials that are insoluble in seawater.

As examples of suitable polymers which are free of triorganosilyl ester groups and triorganotin groups but are reactive in seawater, several resins may be mentioned. Examples of suitable polymers are, for example, acid-functional film-forming polymers in which the acid groups are blocked by quaternary ammonium groups or quaternary phosphonium groups. This is described, for example, in WO 02/02698. Alternatively, the seawater-reactive polymer may be a film-forming polymer containing quaternary ammonium groups and/or quaternary phosphonium groups bound (pendant) to the polymer backbone. These quaternary ammonium groups and/or quaternary phosphonium groups are neutralized, in other words blocked or capped with counter ions. The counter-ion consists of the anionic residue of an acid having an aliphatic, aromatic or alkaryl hydrocarbon group comprising at least 6 carbon atoms. Such systems are described, for example, in EP 02255612.0.

Other examples of suitable seawater-reactive polymers are acid-functional film-forming polymers in which the acid groups are blocked by groups capable of hydrolysis or dissociation to leave a polymer soluble in seawater, the blocking groups being selected from divalent metal atoms bound to monovalent organic residues, divalent metal atoms bound to hydroxyl groups and monoamine groups forming an organic solvent-soluble amine salt of the polymer, as described in WO 00/43460. For example, such seawater-reactive, acid-functional film-forming polymers whose acidic groups are blocked may be polymers having at least one side chain with at least one terminal group of the formula:

wherein X representsOr

M is a metal selected from the group consisting of zinc, copper and tellurium, n is an integer of 1 to 2, R represents a metal selected from the group consisting of-O-R1, -S-R1 orOrganic residue of (A), R₁Are monovalent organic residues as described in EP-A-204456. Such a hydrolysable polymer is preferably one in which X representsM is copper and R representsThe acrylic polymer of (a). having-COOH groups other than-X- [ O-M-R]_nThe parent acrylic polymer of (A) preferably has an acid value of from 25 to 350mg KOH/g. Most preferably, the hydrolysable polymer has a copper content of 0.3-20 wt% and R1 is the residue of a high boiling organic monobasic acid. Such hydrolysable polymers can be prepared by the processes disclosed in EP 0204456 and EP 0342276. The copper-containing film-forming polymer is preferably a copolymer comprising an acrylate or methacrylate ester in which the alcohol residue comprises a bulky hydrocarbon group or soft segment, for example a branched alkyl ester having 4 or more carbon atoms or a cycloalkyl ester having 6 or more atoms, a polyalkylene glycol monoacrylate or polyalkylene glycol monomethacrylate optionally having terminal alkyl ether groups, or an adduct of 2-hydroxyethyl acrylate or 2-hydroxyethyl methacrylate with caprolactone, as described in EP 0779304.

Alternatively, the seawater-reactive, acid-functional film-forming polymer in which such acidic groups are blocked may be a carboxylic acid functional polymer. For example, it may be a copolymer of acrylic or methacrylic acid with one or more alkyl acrylates or methacrylates, at least part of the acidic groups having been converted to groups of the formula-COO-M-OH, wherein M is a divalent metal such as copper, zinc, calcium, magnesium or iron, as described in GB2,311,070.

Another example of a seawater-reactive, acid-functional film-forming polymer with blocked acid groups is an amine salt polymer. Preferably, it is a salt of an amine containing at least one aliphatic hydrocarbon group of 8 to 25 carbon atoms as described in EP 0529693 with an acid-functional film-forming polymer, preferably an addition copolymer of an ethylenically unsaturated carboxylic acid, such as acrylic acid or methacrylic acid, a sulphonic acid, an acid sulphate ester, a phosphonic acid or an acid phosphonate ester with at least one ethylenically unsaturated comonomer, and the film-forming polymer is preferably an amine sulphonate copolymer containing organic cyclic ester units as described in WO 99/37723.

As examples of suitable polymers or resins which are sparingly soluble or sensitive to water in seawater, the following compounds may be mentioned: polyvinyl methyl ether, polyvinyl ethyl ether, alkyd resins, modified alkyd resins, polyurethanes, saturated polyester resins, poly-N-vinylpyrrolidone and rosin materials. The rosin material is preferably rosin, in particular wood rosin or may be tarry (tau rosin) or gum rosin. The main chemical component of rosin is abietic acid. The rosin may be any grade sold commercially, preferably the rosin sold as WW (water white) rosin. Alternatively, the rosin material may be a rosin derivative, such as a maleated or fumarated rosin, a hydrogenated rosin, a formylated rosin or a polymerized rosin, or a rosin metal salt such as a calcium, magnesium, copper or zinc salt of pinoresinoic acid.

As examples of suitable polymers or resins that are insoluble in seawater, the following compounds may be mentioned: modified alkyd resins, epoxy polymers, epoxy esters, epoxy urethanes, polyurethanes, linseed oil, castor oil, soybean oil and derivatives of these oils. Other examples of suitable seawater-insoluble polymers or resins are: vinyl ether polymers, for example poly (vinyl alkyl ethers) such as polyvinyl isobutyl ether, or copolymers of vinyl alkyl ethers with vinyl acetate or vinyl chloride, acrylate polymers such as homopolymers or copolymers of one or more alkyl acrylates or methacrylates in which the alkyl group preferably contains from 1 to 6 carbon atoms and may also contain comonomers such as acrylonitrile or styrene, and vinyl acetate polymers such as polyvinyl acetate or vinyl acetate/vinyl chloride copolymers. Alternatively, the seawater-insoluble polymer or resin may be a polyamine, particularly a polyamide having a plasticising effect, such as a polyamide of a fatty acid dimer or a polyamide sold under the trade mark "Santiciser".

If the coating composition comprises, in addition to the silyl ester copolymer and the ingredient having biocidal properties for aquatic organisms, another resin or a mixture of other resins, this/these other resin(s) can constitute 99% of the total amount of resins in the coating composition. Preferably, the other resin is a rosin material and is present in an amount of 20% of the total resin in the coating composition to obtain a high quality self-polishing coating. Alternatively, it is preferred that the other resin is a rosin material and is present in an amount of 50-80% of the total resin in the coating composition to obtain a so-called controlled depletion coating (hybrid coating).

In another embodiment, the other resin is a mixture of a rosin material and a seawater insoluble resin. In this case, the rosin material constitutes from 20% to at most 80% or 95% by weight of the total amount of resins in the coating composition. The rosin material preferably constitutes at least 25 wt%, more preferably at least 50 wt%, most preferably at least 55 wt% of the total amount of resins in the coating composition. The silyl ester preferably constitutes at least 30 wt%, most preferably at least 50 wt%, up to 80 wt% or 90 wt%, of the total weight of the non-rosin resins, the remainder being seawater insoluble resin.

Examples of non-biocidal pigments that can be added to a composition comprising a silyl ester copolymer and an ingredient having biocidal properties for aquatic organisms are: non-biocides which are sparingly soluble in seawater, such as zinc oxide and barium sulfate, and non-biocides which are insoluble in seawater, such as fillers and coloring pigments, such as titanium dioxide, iron oxide, phthalocyanine compounds and azo pigments.

Examples of additives that may be added to the composition comprising the silyl ester copolymer and the ingredient having biocidal properties for aquatic organisms are reinforcing agents, stabilizers, thixotropic or thickening agents, plasticizers and liquid carriers.

Examples of suitable reinforcing agents are fibers such as carbide fibers, silicon-containing fibers, metal fibers, carbon fibers, sulfide fibers, phosphate fibers, polyamide fibers, aromatic polyhydrazide fibers, aromatic polyester fibers, cellulose fibers, rubber fibers, acrylic fibers, polyvinyl chloride fibers, and polyethylene fibers. Preferably, the fibers have an average length of 25 to 2,000 μm and an average thickness of 1 to 50 μm, and the ratio of the average length to the average thickness is at least 5. Examples of suitable stabilizers are moisture scavengers, zeolites, aliphatic or aromatic amines such as dehydroabietylamine, tetraethylorthosilicate, and triethyl orthoformate.

Examples of suitable plasticizers are phthalic acid esters such as dibutyl phthalate, butyl benzyl phthalate or dioctyl phthalate, phosphoric acid triesters such as tris (tolyl) phosphate or tris (isopropylphenyl) phosphate, or chlorinated paraffins and sulfonamides such as N-substituted toluenesulfonamides. Examples of suitable liquid carriers are organic solvents, organic non-solvents and water. Examples of suitable organic solvents are aromatic hydrocarbons such as xylene, toluene or trimethylbenzene, alcohols such as n-butanol, ether alcohols such as butoxyethanol or methoxypropanol, esters such as butyl acetate or isoamyl acetate, ether esters such as ethoxyethyl acetate or methoxypropyl acetate, ketones such as methyl isobutyl ketone or methyl isoamyl ketone, aliphatic hydrocarbons such as white spirit, or mixtures of two or more of these solvents. The coating can be dispersed in an organic non-solvent for the film-forming components of the coating composition. Alternatively, the coating may be water-based; for example, it may be based on an aqueous dispersion.

The invention will be illustrated with reference to the following examples. These examples are intended to illustrate the invention, but are not to be construed as limiting its scope in any way.

Examples

The copolymers and coating compositions of the present invention were prepared and compared.

The following abbreviations are used:

TBSMA tributylsilyl methacrylate

TiPSA acrylic acid triisopropylsilyl ester

MMA methyl methacrylate

NVP N-vinylpyrrolidone

MEA methoxy ethyl acrylate

TBPEH tert-butyl peroxy ethyl hexanoic acid

AIBN azobisisobutyronitrile

AMBN azo dimethyl butyronitrile

High shear viscosity is expressed in poise. The solids content is expressed in weight percent. The number average molecular weight (Mn) and weight average molecular weight (Mw) are given relative to polystyrene.

The theoretical solids content (expressed as weight percent or non-volatile volume percent) was calculated from the formulation of each composition according to ASTM standard D5201-01. The actual solids content (expressed as weight percent) was determined in accordance with ASTM standard 1644.

Theoretical VOC levels (g/L) were calculated from the formulation of each composition according to ASTM standard D5201-01. The determined VOC level (g/L) was determined according to EPA reference method 24 in conjunction with ASTM standard D3960-02.

Copolymer solution

Comparative examples 1a and 1b

Example 10 of EP 1127902 was repeated to prepare comparative copolymer solution 1a (CSol 1a), to which another sample, to which reference was made in part, gave comparative copolymer solution 1 b. The ingredients of the composition are listed in table 1.

TABLE 1 composition of comparative copolymer solutions 1a and 1b

		CSol 1a and CSol 1b	CSol 1a	CSol 1b
						Components	Monomer component (% by weight)	Parts by weight	Parts by weight
Monomer	TBSMA	45	23.32	23.32
						MMA	50	25.91	25.91
	NVP	5	2.59	2.59
					Primary initiator	TBPEH		1.04	1.04
Initiator aid	TBPEH		0.10 times 5	0.10 times 5
					Solvent (xylene)	Reactor charging		27.89	27.89
	Premix addition		4.24	4.24
						Cosolvent		-	-
	Diluting solvent		14.50	-

According to the procedure of example 10 of EP 1127902, a pre-mixture of monomers, initiator and solvent (xylene) was prepared in the specified proportions and a further quantity of solvent (xylene) was added to a temperature-controlled reactor equipped with a stirrer, reflux condenser, nitrogen inlet and pre-mixture feed inlet. The reactor was heated and maintained at 90 ℃ and the premix was added to the reactor at a constant rate over 3 hours under a nitrogen atmosphere. After a further 30 minutes, five postadditions of TBPEH as coinitiator were added at 45 minute intervals. After a further 15 minutes, the temperature of the reactor was raised to 120 ℃ over 1 hour and then cooled.

A sample of the product was diluted with styrene in proportions to give comparative copolymer solution 1a (CSol 1a) as described in example 10 of EP 1127902. The other sample was not diluted; comparative copolymer solution 1b (CSol 1b) was obtained. The properties of the resulting copolymer solution are shown in Table 2.

TABLE 2 Properties of comparative copolymer solutions 1a and 1b

	CSol 1a	CSol 1b
			Nominal solids content (% theoretical, weight)	53.4	62.4
Actual solid content (% by weight, measurement value)	52.3	61.6
			Viscosity (poise)	14.4	＞40
Number average molecular weight (g/mol)	13,145	13,145
			Weight average molecular weight (g/mol)	38,560	38,560
Polydispersity (Mw/Mn)	2.93	2.93
			Glass transition temperature (. degree. C.)	43	43

This example shows that merely lowering the amount of solvent to obtain a high solids solution can have a very large effect on the viscosity of the copolymer solution.

Example 2

Copolymer solution 2(Sol 2) was prepared using the same type and amount of monomers as in comparative examples 1a and 1 b. Copolymer solution 2 is the solution obtained according to the invention. The ingredients of the composition are listed in table 3.

TABLE 3 composition of copolymer solution 2

	Components	Monomer component (% by weight)	Parts by weight
				Monomer	TBSMA	45	26.14
	MMA	50	29.04
					NVP	5	2.90
Primary initiator	AIBN		1.34
				Initiator aid	AIBN		0.29 time 2
Solvent (xylene)	Reactor charging		26.00
					Premix addition		12.00
	Cosolvent		2 times 1.00

Diluting solvent

-

A premix of monomer, initiator and solvent (xylene) was prepared in the specified proportions and a further quantity of solvent (xylene) was added to a temperature controlled reactor equipped with a stirrer, reflux condenser, nitrogen inlet and premix feed inlet. The reactor was heated and maintained at 100 ℃ and the premix was added to the reactor at a constant rate over 3 hours under a nitrogen atmosphere. After a further 30 minutes, two post-additions of AIBN as co-initiator were added at 45 minute intervals as xylene slurry. The temperature of the reactor was maintained at 100 ℃ for another 1 hour and then cooled. The properties of the resulting copolymer solution are shown in Table 4.

TABLE 4 Properties of copolymer solution 2

	Sol 2
		Nominal solids content (% theoretical, weight)	60
Actual solid content (% by weight, measurement value)	60.5
		Viscosity (poise)	11.4
Number average molecular weight (g/mol)	5810
		Weight average molecular weight (g/mol)	12345
Polydispersity (Mw/Mn)	2.12
		Glass transition temperature (. degree. C.)	43

Compared to example 1b, copolymer solution 2 has a higher solids content, a lower viscosity, a lower weight average molecular weight and a lower polydispersity. In addition, it is evident from the small difference in theoretical and measured solids content that more monomer is converted.

Examples 3a to 3d

Using another set of monomers, four copolymer solutions of the present invention were prepared. The ingredients of the composition are listed in tables 5a and 5b.

TABLE 5a monomer composition of copolymer solutions 3a-3d

		Sol 3a	Sol 3b	Sol 3c	Sol 3d
							Components	Monomer component (% by weight)	Monomer component (% by weight)	Monomer component (% by weight)	Monomer component (% by weight)
Monomer	TIPSA	60	60	60	60
							MMA	33	33	33	40
	MEA	7	7	7	-

TABLE 5b composition of copolymer solutions 3a-3d

		Sol 3a	Sol 3b	Sol 3c	Sol 3d
							Components	Parts by weight	Parts by weight	Parts by weight	Parts by weight
Monomer	TIPSA	34.7	34.35	37.21	34.75
							MMA	19.11	18.89	20.47	23.17
	MEA	4.05	4.01	4.34	-
						Primary initiator	AMBN	1.51	2.18	2.36	1.51
Initiator aid	AIBN	0.29 time 2	0.29 time 2	0.31 time 2	0.29 time 2
						Solvent (xylene)	Reactor charging	26.00	26.00	24.50	26.00
	Premix addition	12.00	12.00	8.75	12.00
							Cosolvent	2 times 1.00	2 times 1.00	0.88	2 times 1.00

Copolymer solutions 3a-3d were obtained following the general procedure used to prepare example 2. The properties of the resulting copolymer solution are shown in Table 6.

TABLE 6 Properties of copolymer solutions 3a-3d

	Sol 3a	Sol 3b	Sol 3c	Sol 3d
					Nominal solids content (% theoretical, weight)	60	60	65	60
Actual fixationBody content (measured value,% by weight)	59.2	59.3	64.6	59.5
					Viscosity (poise)	1.41	1.29	3.13	2.44
Number average molecular weight (g/mol)	3,635	3,095	3,315	3,865
					Weight average molecular weight (g/mol)	8,775	6,705	7,465	3,520
Polydispersity (Mw/Mn)	2.42	2.2	2.23	2.5
					Glass transition temperature (. degree. C.)	42	42	42	55

Comparative examples 4a and 4b

The preparation of the polymer PA4 described in EP 1127925 was repeated, prepared as described in examples S-1 to S-6 of EP 0775733, to prepare comparative copolymer solution 4 a. Another experiment was performed using less solvent to give CSol 4 b. The ingredients of the composition are listed in table 7.

TABLE 7 composition of comparative copolymer solutions 4a and 4b

		CSol 4a and CSol 4b	CSol 4a	CSol 4b
						Components	Monomer component (% by weight)	Parts by weight	Parts by weight
Monomer	TBSMA	57	28.50	33.79

	MMA	43	21.50	25.49
					Primary initiator	AIBN		0.60	0.71
Initiator aid	(none)		-	-
					Solvent (xylene)	Reactor charging		49.40	40.00
	Premix addition		-	-
						Cosolvent		-	-
	Diluting solvent		-	-

According to the description of the preparation of polymer PA4 in EP 1127925, i.e.as described in EP 0775733, a premix of monomers and initiator was prepared in the specified proportions and a further quantity of solvent (xylene) was added to a temperature-controlled reactor equipped with a stirrer, reflux condenser, nitrogen inlet and premix feed inlet. The reactor was heated and maintained at 90 ℃ and the premix was added to the reactor at a constant rate over 4 hours under a nitrogen atmosphere. The temperature of the reactor was maintained at 90 ℃ for another 4 hours and then cooled. The preparation of polymer PA4 was carried out as described in EP 1127925, i.e.as described in EP 0775733, without addition of coinitiator.

A larger amount of solvent was used to prepare comparative copolymer solution 4a (CSol 4a) than for CSol 4 b. The properties of the resulting copolymer solution are shown in Table 8.

TABLE 8 Properties of comparative copolymer solutions 4a and 4b

	CSol 4a	CSol 4b
			Nominal solids content (% theoretical, weight)	50	60
Actual solid content (% by weight, measurement value)	46.1	55.8
			Viscosity (poise)	0.93	4.95
Number average molecular weight (g/mol)	9,630	10,030
			Weight average molecular weight (g/mol)	20,020	22,345
Polydispersity (Mw/Mn)	2.08	2.22
			Glass transition temperature (. degree. C.)	33	33

The conversion was low for both samples, probably due to the fact that no co-initiator was used in the preparation. Coating composition

Some of the above copolymer solutions were used to prepare coating compositions. These coating compositions were used to prepare coated substrates and the coated substrates were tested for their performance.

Hardness test

Test coating films were prepared by pouring the coating composition onto degreased glass plates (about 15 cm. times.10 cm) using a bar coater having a gap width of 500. mu.m. The coating film was dried under ambient conditions for 3 days before testing. Described subsequently by ISO 1522And measuring the hardness of the coating by using a swing rod damping method. The quantification of hardness is the number of pendulum swings decaying from 6 ° to 3 °.

Mechanical Property (crack resistance) test

Test samples were prepared by pouring the paint on steel or aluminum panels (15.2cm x 10.2cm) pre-coated with a commercially available anti-corrosive coating (Intertuf 203, International Coatings Ltd.) using a rod coater (gap width of 500 μm). The panels were dried at ambient conditions for 3 days and subsequently immersed in natural seawater at 23 ℃ for 24 hours. The panels were then removed from the seawater and dried for 8 hours. The plates were then immersed in natural seawater at 23 ℃ for a further 16 hours, removed and dried for 8 hours. This cycle was repeated 4 times. After wet-dry cycling, the mechanical properties of the coatings, in particular the resistance to cracking, were evaluated according to the following board rating scheme.

Plate rating:

5: without cracks or other visible defects

4: hairline cracks just visible to the naked eye

3: slight cracking

2: moderate cracking

1: severe cracking

0: coarse cracks

Comparative example 5

A comparative coating composition (CCoat5) was prepared by mixing the ingredients with a high speed disperser. The ingredients of CCoat5 are listed in table 9, and the properties of the composition and coatings prepared from the composition are listed in table 10.

TABLE 9 Components of comparative coating composition 5

Components		Parts by weight
			Silyl ester copolymers	CSol 1b	34.18
Biocide	Copper oxide	34.18
				Copper pyrithione	2.93
Soluble pigments	Zinc oxide	6.84

Coloured pigments	Iron oxide	0.98
			Filled pigments	Talc	9.77
Thixotropic agent	Polyamide wax	1.50
			Solvent(s)	Xylene	9.62

TABLE 10 Properties of comparative coating composition 5

This example shows that high solids paints with a VOC of 400g/L and a viscosity of less than 20 poise are not readily prepared from comparative copolymer solution 1 b.

Example 6

The coating composition of the present invention (Coat6) was prepared by mixing the ingredients using a high speed disperser. The ingredients of Coat6 are listed in Table 11, and the properties of the composition and coatings prepared from the composition are listed in Table 12.

TABLE 11 Components of coating composition 6

Components		Parts by weight
			Silyl ester copolymers	Sol2	34.41
Biocide	Copper oxide	34.41
				Copper pyrithione	2.95
Soluble pigments	Zinc oxide	6.88
			Coloured pigments	Iron oxide	0.98
Filled pigments	Talc	9.83
			Thixotropic agent	Polyamide wax	1.51
Solvent(s)	Xylene	9.00

TABLE 12 Properties of coating composition 6

Properties of Coat6 composition
		Viscosity (poise)	4.6
Nominal solids content (% of theory, volume)	53.9

This example shows that high solids paints with a VOC of 400g/L and a viscosity of less than 20 poise can be readily prepared from copolymer solution 2.

Example 7

The coating composition of the present invention (Coat7) was prepared by mixing the ingredients with a high speed disperser. The ingredients of Coat7 are listed in Table 13, and the properties of the composition and coatings prepared with the composition are listed in Table 14.

TABLE 13 Components of coating composition 7

Components		Parts by weight
			Silyl ester copolymers	Sol 5	29.30
Co-existing resins	Methyl methacrylate/n-butyl methacrylate copolymer solution1	4.00
				Gum rosin solution2	5.76
Biocide	Copper oxide	33.07
				Copper pyrithione	2.83
Soluble pigments	Zinc oxide	6.61
			Coloured pigments	Iron oxide	0.94
Filled pigments	Talc	9.45
			Thixotropic agent	Bentonite clay	0.96
	Amorphous silica	0.77
			Solvent(s)	Xylene	6.3

¹) Degalan LP64/12 (from Rohm Chemische Fabrik); 45 wt% xylene solution

²) Natural rosin, 65% by weight xylene solution

TABLE 14 Properties of comparative coating composition 7

Properties of Coat7 composition
		Viscosity (poise)	3.7
Nominal solids content (% of theory, volume)	59.7
		VOC level (theoretical value, g/L)	349

Comparative example 8

For comparison, the performance of a commercially available silyl ester copolymer antifouling paint, Sea Quantum Plus (CCoat8) from Jotun paints was determined. The properties of CCoat8 and coatings prepared from the composition are listed in table 15.

TABLE 15 Properties of comparative coating composition 8

³) Published in technical data sheet for the antifouling paint Sea Quantum Plus available from Jotun Paints, 3 months and 17 days 2003

This example shows that the mechanical properties (hardness and crack resistance) of a commercial silyl ester copolymer antifouling paint CCoat8 are similar to Coat6 and Coat 7.

Claims (11)

1. Use of a silyl ester copolymer solution having a solids content of at least 55 wt.% and a viscosity of less than 20 poise at 25 ℃ in an antifouling coating composition, the silyl ester copolymer solution comprising a silyl ester copolymer having a weight average molecular weight of less than 20,000.

2. Use of a silyl ester copolymer solution according to claim 1 in an antifouling coating composition, wherein the solids content of the silyl ester copolymer solution is no more than 80 wt%.

3. Use of a silyl ester copolymer solution according to claim 1 in an antifouling coating composition, characterized in that the silyl ester copolymer solution comprises a silyl ester copolymer having a weight average molecular weight of less than 20,000, a polydispersity of less than 3.0 and a glass transition temperature of less than 90 ℃, wherein less than 70% by weight of said silyl ester copolymer consists of side chains having silyl ester functionality.

4. Use of a silyl ester copolymer solution according to any of claims 1 to 3 in an antifouling coating composition, characterized in that the silyl ester copolymer is a copolymer containing at least one side chain bearing at least one end group of formula:

wherein n is 0, R3, R4 and R5 are identical or different and represent methyl, isopropyl, n-butyl, isobutyl or phenyl.

5. Use of a silyl ester copolymer solution according to claim 4 in an antifouling coating composition, wherein n-0, R3, R4 and R5 are the same or different and represent isopropyl, n-butyl or isobutyl.

An antifouling coating composition having a VOC of less than 400g/L and a viscosity at 25 ℃ of less than 20 poise comprising a silyl ester copolymer solution having a solids content of at least 55 weight percent and an ingredient having biocidal properties for aquatic organisms, characterized in that the silyl ester copolymer is a silyl ester copolymer having a weight average molecular weight of less than 20,000, a polydispersity of less than 3.0, and a glass transition temperature of less than 90 ℃, wherein less than 70 weight percent of said silyl ester copolymer consists of side chains having silyl ester functionality.

7. An antifouling coating composition according to claim 6, characterised in that the silyl ester copolymer is a copolymer containing at least one side chain bearing at least one terminal group of the formula:

wherein n is 0, R3, R4 and R5 are identical or different and represent methyl, isopropyl, n-butyl, isobutyl or phenyl.

8. An antifouling coating composition according to claim 7, wherein n-0, R3, R4 and R5 are the same or different and represent isopropyl, n-butyl or isobutyl.

9. An antifouling coating composition according to any of claims 6 to 8, characterised in that the composition further comprises one or more polymers or resins selected from: compounds that are free of triorganosilyl ester groups and triorganotin groups but are reactive in seawater, materials that are sparingly soluble or sensitive to water in seawater, and materials that are insoluble in seawater.

10. An antifouling coating composition according to claim 9, characterised in that the composition comprises a rosin material which is slightly soluble or sensitive to water in seawater.

11. A substrate or structure coated with an antifouling coating composition according to any of claims 6 to 10.