Antifouling Composition

Field of the Invention

The present invention relates to marine antifouling coating compositions, more specifically to marine antifouling coating compositions comprising a particular class of polyoxalate binder as well as to the binder itself. The invention further relates to kits for the preparation of the antifouling coating compositions or a "one pot" anti-foul ing coating composition comprising the new polyoxalate binder. The invention also relates to surfaces coated with the antifouling coating compositions.

Background

Surfaces that are submerged in seawater are subjected to fouling by marine organisms such as green and brown algae, barnacles, mussels, tube worms and the like. On marine constructions such as vessels, oil platforms, buoys, etc. such fouling is undesired and has economical consequences. The fouling may lead to biological degradation of the surface, increased load and accelerated corrosion. On vessels the fouling will increase the friction a I resistance which will cause reduced speed and/or increased fuel consumption. It can also result in reduced manoeuvrability.

To prevent settlement and growth of marine organisms antifouling paints are used. These paints general ly comprise a film-forming binder, together with different components such as pigments, fillers, solvents and biologically active substances.

The most successful antifouling coating system on the market until 2003 was a tributyltin (TBT) self-pol ishing copolymer system. The binder system for these antifouling coatings was a linear acrylic copolymer with tributyltin pendant groups. In seawater the polymer was gradually hydrolysed releasing tributyltin, which is an effective biocide. The remaining acrylic copolymer, now containing carboxylic acid groups, became sufficiently soluble or dispersible in seawater to be washed out or eroded away from the coating surface. This self-polishing effect provided a controlled release of the biologically active compounds in the coating resulting in excellent antifouling efficiency and smooth surfaces and hence reduced frictional resistance. The I MO Convention " International Convention on the Control of Harmful Anti-fouling Systems on Ships" of 2001 prohibited the appl ication of new TBT containing ant i foul ing coatings from 2003 and TBT containing antifouling coatings were prohibited on ship hulls from 2008.

In recent years new antifouling coating systems have been developed and introduced as a consequence of the TBT ban. One broad group of biocidal antifouling coatings on the market today is the self-polishing antifoul ing coatings which mimic the TBT self-polishing copolymer coatings. Those antifouling coatings are based on (meth )acryl ic copolymers hav ing pendant hydrolysable groups without biocidal properties. The hydrolysis mechanism is the same as in the TBT containing

copolymers. This gives the same controlled dissolution of the polymers and thereby the controlled release of antifouling compounds from the coating film, resulting in similar performance as the TBT containing antifouling coating systems. The most successful self-polishing antifouling systems today are based on silyl ester functional

(meth)acryiic copolymers. These coating compositions are for example described in, EP 0 646 630, EP 0 802 243, EP 1 342 756, EP I 479 737, EP 1 641 862, WO 00/77102, WO 03/070832 and WO 03/080747.

The above mentioned antifouling coating systems degrade by hydrolysis of pendant groups on the polymer backbone, which results in a water erodable polymer. The hydrolysis of the pendant groups on the polymer backbone results in the formation of carboxylic acid salts which make the polymer hydrophiiic and thereby erodable. A certain amount of hydrolysable groups are needed to get sufficient hydroph ilicity and an erodable polymer after hydrolysis. Silyl ester copolymer technology is expensive.

Another way of obtaining water erodable polymers is by introducing hydrolysable groups in the polymer backbone, resulting in degradation of the polymer structure, which gives erosion of the polymer film or coating film. Polyanhydrides are a class of polymers that degrade by backbone hydrolysis. The polyanhydrides are wel l documented for their surface degradation properties. Surface degradation is one of the most important factors for obtaining a successful antifouling coating. The use of specific aromatic polyanhydrides as binders in antifouling coating compositions is, for example, described in WO 2004/096927. However, the anhydride group is extremely labile in the presence of moisture and it is therefore difficult to design a coating system based on polyanh yd rides that exhibits a slow, controlled hydrolysis for use in ant i fouling coatings. Accordingly, the polyanh yd rides used for antifoul ing coating compositions generally have a high content of aromatic units in order to control the hydrolysis.

In recent years, polyoxalates have emerged as a class of polymers that are well suited for use as binders in antifouling coatings. Backbone hydrolysis in these compounds is more control led than for the polyanh yd rides but because of the two adjacent carbonyl groups in the oxalate unit, the ester group is activated and labile towards hydrolysis. Polyoxalates also have better solubility in common organic solvents than polyanhydrides.

The use of self pol ishing binders which hydroiyse in the polymer backbone make it possible to obtain erodable crossl inked polymers and high molecular weight polymers. One of the greatest advantages of the po I vox a I ate technology over the current commercial solution, the silyl technology, is that the cost of the binder is much lower. Furthermore, solvents levels, and consequently VOC (volatile organic compounds) levels, can be reduced when using polyoxalates compared with silyl copolymers. Legislation controlling levels of VOC is now enforced in many countries. Due to this, it is highly preferred that any antifouling coating has a VOC content of less than 400 g/L.

Polyoxalates arc not new compounds. In EP-A- 1 505097 various polyoxalates are mentioned as being suitable for the formation of shaped articles or films. Moreover, the use of polyoxalates as self-polishing binders in anti-fouling coating compositions is reported in WO 2009/100908. Although these compounds have shown promise in this area of technology, problems still exist in developing a polymer of this class which possesses both good polishing properties and acceptable film hardness.

It is important for a binder used in an antifouling coating composition to have good pol ishing properties in order to prevent fouling. If the binder displays no polishing, there is very little hydrolysis or release of the biocide and it is ineffective in an antifouling coating. It is, however, also important that the pol ishing is not too rapid and does not display exponential hydrolysis behaviour since this is indicative of bulk hydrolysis rather than pol ishing. Bulk hydrolysis causes unwanted swel ling of the coating. A linear polishing rate is desirable in order for the antifouling coating to last and for its properties to be predictable during the sailing interval of the vessel.

Moreover, it is necessary that the coating composition is resistant to swel l ing as this will lead to eventual col lapse of the paint film. In this regard, the inventors have found that the use of an oxalate monomer alone increases the risk of such swelling.

It is also important that antifouling coating compositions have good shelf-life, in particular that they have acceptably low levels of thickening during storage. EP 1 033 392 describes resin compositions which use metal compounds such as ZnO to form metal carboxylate links within the resin. These compositions also require the presence of an external chelating agent, which does not form part of the polymer resin, to reduce the thickening effect of the metal ion. EP 1 033 392 requires the resin to have an acid value of more than lOmg KOH/g. The present invention does not rely on metal carboxylate binders and does not therefore suffer from the same thickening mechanism Binders according to the present invention do not need the addition of chelating agent.

Furthermore, the coating needs a sufficient hardness in order to be resistant to the mechanical impact to which vessels and other marine constructions are often exposed. Developing a polyoxalate binder which fulfils some or all of these criteria has proved challenging. Ideally, a good balance of al l these properties is desirable.

The object of the present invention is to prov ide an antifouling coating composition which comprises a polyoxalate binder, which combines good polishing properties, in particular a linear polishing rate, with acceptable film hardness.

Surprisingly, some or all of these objectives may be attained by the use of a specific class of polyoxalates, prepared using a particular diol monomer, as the binder in an antifouling coating composition.

The present inventors also unexpectedly found that coating compositions comprising the polyoxalate binder of the invention display an attractive balance of properties without the need for curing. This offers the additional advantage of being able to formulate a "one-pot" paint, which reduces application times since no premixing is required. It also el iminates the problem of l imited pot life and the risk of using incorrect mixing ratios associated with two componentpaint compositions.

Summar of the Invention Thus, viewed from one aspect the invention prov ides a binder for a marine antifouling coating composition comprising:

a polyoxalate polymer with a Mw of at least 4000 g mol, wherein said polyoxalate polymer comprises:

(i) a residue of an oxalate monomer selected from oxalic acid or a diester derivative thereof;

(ii) a residue of a second monomer selected from a cyclic diester or cyclic diacid; and

(iii) a residue of a third monomer which is hydrogenated bisphenol A.

Alternatively viewed, the invention provides a polyoxalate binder for a marine antifouling coating composition having a Mw of at least 4000 g'mol obtainable by the copolymerisation. of:

(i) an oxalate monomer selected from oxal ic acid or a diester derivative thereof;

(ii) a second monomer w hich is a cyclic diester or cycl ic diacid; and

(iii) a third monomer which is hydrogenated bisphenol A.

Viewed from another aspect the invention prov ides a marine antifouling coating composition comprising:

( I ) a polyoxalate polymer binder with a Mw of at least 4000 g'mol, w herein said polyoxalate polymer comprises:

(i) a residue of an oxalate monomer selected from oxalic acid or a diester derivative thereof;

(ii) a residue of a second monomer selected from a cycl ic diester or cyclic diacid: and

(iii) a residue of a third monomer w hich is hydrogenated bisphenol A; and

( I I ) a marine antifouling agent.

Viewed from another aspect the invention prov ides a process for the preparation of a binder for a marine anti-fouiing coating composition comprising polymerising

(i) an oxalate monomer selected from oxalic acid or a diester derivative thereof;

(ii) a second monomer which is a cyclic diester or cycl ic diacid; and (iii) a third monomer which is hydrogenated bisphenol A so as to form a polyoxalate polymer with a Mw of at least 4000 g/mol .

Viewed from another aspect the invention provides a process for the preparation of a marine anti-fouling coating composition comprising polymerising

(i) an oxalate monomer selected from oxalic acid or a di ester derivative thereof;

(ii) a second monomer which is a cyclic di ester or cycl ic diacid; and

(iii) a third monomer which is hydrogenated bisphenol A so as to form a polyoxalate polymer with a Mw of at least 4000 g/moi; and

combining said polyoxalate polymer with at least one marine ant i foul ing agent to form said anti-foul ing coating composition.

Viewed from another aspect the invention provides a process for protecting an object from fouling comprising coating at least a part of said object which is subject to fouling with an anti-fouling coating composition as hereinbefore described.

Viewed from another aspect the invention provides an object coated with an anti-fouling coating composition as hereinbefore defined.

Definitions

It will be clear that the polyoxalate polymer is formed through the

polymerisation of, at least, the various monomers identified above. Other monomers can also be used in the manufacturing process. The term monomer residue refers to the actual repeating unit present in the polymer backbone which is formed from the monomer during the polymerisation process.

The term cyclic di ester or a cyclic diacid refers to a compound in which two ester groups or two carboxylic acids are directly bound to the same ring system. It does not therefore cover a linear diester in which the terminal ester groups are cyclic for example, such as Ph0 ₂ CCH2CH2C0 ₂ Ph.

Detailed Description

The an ti fou l ing coating composition of the invention comprises a polyoxalate polymer. The polyoxalate performs the role of the binder in the composition. The term binder is a term of this art. The binder is the actual film forming component of an anti- foul ing composition. The binder imparts adhesion and binds the components of the composition together.

Polyoxalate

The polyoxalate which is used in the invention may be a linear or branched polymer. It is a copolymer formed from at least three different monomers, e.g. a random copolymer or block copolymer. It will be appreciated that any polyoxalate of the invention comprises sufficient repeating units in order to achieve a Mw of at least 4000 g/moi.

The polyoxalate of the invention is formed from the polymerisation of an oxalate monomer, selected from oxalic acid or a diester derivative thereof (i) and at least two further monomers. The second monomer (ii) can be a cyclic diacid or a cyclic diester and the third monomer (iii) is hydrogenated bisphenol A.

The polyoxalates of the present invention can be prepared by condensation polymerisation using any of various methods known and used in the art.

Optionally the pol ycondensation is carried out in the presence of a catalyst. The catalyst preferably comprises at least one member selected from compounds of magnesium, calcium, titanium, zirconium, vanadium, manganese, iron, cobalt, zinc, aluminium, germanium, tin, phosphorus and antimony. Among the compounds organometall ic compounds are preferred, more preferably organic titanium compounds and organic tin compounds. Examples of organic titanium compounds include titanium alkoxides, such as tn isopropyl titanate, titanium tetraisopropoxide, titanium glycolates, titanium butoxide, hexyleneglycol titanate and tetraisooctyl titanate. Examples of organic tin compounds include tin 2-ethylhcxanoatc, dibutyltin dilaurate, monobutyitin tris(2-ethylhexanoate), dibutyltin oxide, dioctyltin oxide and monobutyitin oxide.

The oxalate monomer used in the polymerisation reaction is oxalic acid or a diester derivative thereof. Esters may be alky! esters, alkenyl esters, cycloalkyl esters or aryl esters. Examples of suitable diester derivatives of oxalic acid include those of Formula (I) below:

wherein Ri and R ₂ are each independently selected from a straight or branched chain Ci_2o al kyl group, preferably C _1-10 al kyl group, most preferably Ci_ ₆ al ky I group (e.g. methyl or ethyl); a straight or branched chain C ₂ -io al kenyl group, preferably C ₂ -6 alkenyl group; a C ₆ . ₂ o aryl group, preferabl y C ₆ -io aryl group; a C7-.20 arylalkyl group, preferably C ₇ _i ₂ arylalkyl group and a C _3-20 cycloalkyl group, preferably C4 5 cycloalkyl group, especial ly C ₅ _io cycloalkyl group. R| and R ₂ may be the same or di fferent, preferabl y the same. In any arylalkyl group the l ink to the O atom may be from the alkyl port ion or aryl portion of the substituent, preferably therefore forming tolyl or benzyl.

Preferably, the oxalate monomer (i) is selected from the group of oxalic acid and dialkyl oxalates. Dialkyl oxalates are especially preferred such as diC i mal kyl oxalates. Examples of dialkyl oxalates include dimethyl oxalate, diethyl oxalate, di propyl oxalate and dibutyl oxalate, especial ly diethyl oxalate, i .e. the compound of Formula (I) wherein R| and R ₂ are both ethyl .

In al l embodiments of the invention, unless otherwise stated, any alkyl group, al kenyl group, cycl ic group or aryl group may be optional ly substituted with one or more funct ional groups, e.g. ester, acid, am ino or hydroxy! groups. Ideal l y however, no such groups are present.

It is within the scope of the invention for a mixture of oxalate monomers to be used in the preparation of the pol yoxalates of the i nvention . Where a mixture is employed, the use of two dial kyl oxalates is preferred. Ideal ly, however, on ly one oxalate monomer is used in the polymerisation reaction, e.g. a diester derivative of oxalic acid, such as a dialkyl oxalate as hereinbefore defined.

Preferably, the oxalate monomer (i) is present in an amount of greater than 20 mol%, preferably greater than 25 mol% (e.g. 25 to 40 mol%), relative to the amount of monomer(s) in total. In some embodiments, the oxalate monomer is present in an amount of up to 45 mol%, preferably up to 40 mol%, more preferably up to 35 mol%, relative to the amount of monomer(s ) in total. This amount of oxalate monomer reflects the total mol% of al l oxalate monomers (i) present in the polyoxalate of the invention (i.e. summing monomer contents if more than one oxalate is employed ).

If, as preferred, there is only one oxalate monomer then these fi ures apply to that one monomer only.

In addition to a residue of the oxalate monomer (i), the polyoxalate used in the invention comprises a residue of a second monomer (ii) selected from a cyclic diester or a cycl ic diacid. It has surprisingly been found that the use of this specific type of comonomer leads to an increase in hardness of the polyoxalate polymer. Thus, the antifoul ing coating compositions of the invention, and any paint film produced therefrom, possess particularly attractive film hardness properties. The addition of this second monomer is also of value as it decreases the risk of swelling and collapse of the paint film, compared to one prepared using only an oxalate monomer.

Examples of cyclic dicarboxyiic acids include those of Formula II shown below:

wherein R is a saturated, unsaturated or aromatic CVC* ring, preferably a C -CV, ring, optional ly comprising one or more heteroatoms selected from the group consisting of N, O and S. Examples of heterocycl ic rings include furan (e.g. giving the compound fu ra n -2 , 5 - d i c a rbo x y I i c acid ). Most preferably R is a phenyl group. The two carboxylic acid groups may occupy any position on the ring. For example, where R is a C ₆ ring, the two carboxylic acid groups may be ortho, meta or para with respect to each other. The two carboxyl ic acid groups should not bind to the same carbon atom.

Examples of cyclic diesters include those of Formula III shown below: wherein R is a saturated, unsaturated or aromatic CVC* ring, preferably a CVCV, ring, optionally comprising one or more heteroatoms selected from the group consisting of N, O and S. It will be appreciated that if a heteroatom is present in the ring that the two ester groups bind on carbon atoms in the ring. The two ester groups may occupy any position on the ring. For example, where R is a C ₆ ring, the two ester groups may be ortho, meta or para with respect to each other, preferably meta. R > and R ₄ in Formula ( I I I ) are each independently a straight or branched chain C _1-20 alkyl group, preferably a CMO alkyl group, more preferably C _1-6 alkyl group, more preferably a C _1-4 alkyl group, especial ly methyl; a straight or branched chain C _2-10 alkenyl group, preferably C ₂ -6 alkenyl group; a C ₆ .20 aryl group, a C ₇ _ ₂ o aryl alkyl group, preferably C ₇ „i ₂ arylalkyi group, preferably Ce-io aryl group; and a C3.20 cycloalkyl group, preferably C _4-15 cycloalkyl group, especially C _5-10 cycloalkyl group. R « and R ₄ may be the same or different, preferably the same.

Preferably, the cycl ic diester is an aromatic di ester, such as one of Formula IV shown below:

wherein R ₅ and R ₆ are each independently a straight or branched chain Ci„ ₂ o alkyl group, preferably a CMO alkyl group, more preferably C , alkyl group, more preferably a C ₁ .4 alkyl group, especial ly methyl. R5 and R(, may be the same or different, preferably the same. A particularly preferred cyclic diester is dimethyl isophthalate. Analogues of compounds of Formula IV. wherein the two ester groups on the phenyl ring are ortho or para to each other are equally applicable for use in the present invention. As discussed above, in al l embodiments of the invention, unless otherwise stated, any alkyl group, alkenyl group, cyclic group or aryl group may be optional ly substituted with one or more functional groups, e.g. ester, acid, amino or hydroxy! groups. Ideally however, no such groups are present. It is particularly preferred if the second monomer (ii) does not contain an hydroxy! functional group in addition to a carboxylic acid functional group.

In a most preferred embodiment, the second monomer (ii) is dimethyl isophthalate.

As noted above, there can be one or more than one monomer fitting the requirements of the second monomer. The figures which follow are based on the total content of second monomers in the polyoxalate. Preferably, the second monomer(s) (ii) is present in an amount of greater than 5 mol%, preferably greater than 8 mol%, more preferably greater than 1 0 mol% (e.g. at least 15 mol%) relative to the total amount of monomers in the polyoxalate as a whole. In some embodiments, the second monomer

(ii) is present in an amount of up to 35 mol%, preferably up to 30 mol%, more preferably up to 25 mol% relative to the total amount of monomers in the polyoxalate as a whole. It is preferred that the mol% of the second monomer does not exceed these upper values as too high a level of this component may lead to diminished polishing properties.

The polyoxalate of the invention further comprises a residue of a third monomer

(iii) which is hydrogenated bisphenol A (4,4'-isopropyiidenedicyclohexanol). It has the following structure:

This cycl ic diol gives polyoxalates with surprisingly high glass transition temperatures, Tg. Moreover, the present inventors have surprisingly found that the use of this specific cycl ic diol leads to polyoxalates which, when used in antifouling coating compositions, produce paints which do not need to be cured in order to attain sufficient hardness and polishing properties. In a preferred embodiment, therefore, the antifoul ing coating compositions of the invention do not comprise a curing agent. Similarly, it is preferred if the antifouling coating compositions of the invention are not cured.

The absence of the need for a curing agent means that, in a preferable embodiment, the antifouling coating composition of the invention is a single pot coating. This avoids many additional costs and inconveniences.

Preferably, hydogenated bisphenol A (iii) is present in an amount of greater than 0. 1 mol%, preferably greater than 0.5 mol%, more preferably greater than 2 mol% (e.g. at least 5 mol%) relative to the amount of monomer(s) in total . In some embodiments, hydogenated bisphenol A (iii) is present in an amount of up to 30 mol%, preferably up to 25 mol%, more preferably up to 20 mol% relative to the amount of monomer(s) in total . A relatively high amount of hydrogenated bisphenol A (iii) may be present without giving rise to a partially crystalline polyoxalate.

It will be appreciated that in addition to the oxalate monomer (i), the second monomer (ii) and the third monomer (iii), the polyoxalate used in the antifoul ing coating compositions of the invention may further comprise additional monomers. It is firstly appreciated that there might be more than one monomer (i) or (ii). Any additional monomers may have a different structure such as those defined below.

Additional monomers may include diacids, diesters or, more preferably, diols.

It is preferred therefore if the polyoxalate of the invention comprises not only the residue of hydrogenated bisphenol A but the residue of a further different diol monomer (iv). Examples of diols include saturated aliphatic and saturated

cycloaliphatic diols, unsaturated aliphatic diols or aromatic diols. It is preferred if the polyoxalate comprises a saturated aliphatic and the hydrogenated bisphenol A.

Preferred diols include C3.20 aliphatic or C^n-cycloal iphatic diols such as 1 ,3- propancdiol , 1 ,2-butanediol , 1.3-butanediol, 1 ,4-butanediol, 2,3-butanediol, 1 ,2- pentanedioi, 1 ,4-pentancdiol, 1 ,5-pentanediol, 2,4-pentanediol, 1 ,2-hexanediol, 1 ,5- hexancdioi, 1 ,6-hexanediol, 2,5-hexanedioi, 1 ,7-heptanedioi, 1 ,2-octanediol, 1 ,8- octancdiol, ,9-nonanediol, 1 , 10-decanediol, 1 ,2-dodecanediol, 1 , 1 2-dodecanediol, 1 .14-tetradecanediol, 1 ,2-hcxadecanediol, 1 , 16-hexadecanediol, 2,2-dimethyi-l ,3- propanediol (neopentyl glycol ), 3-methy - 1 ,3-butanediol, 3-methyl- 1 .5-pentanediol, 2- methyl-2,4-pentanediol, 2,3-dimethyl-2,3-butanedioi, 2,2-diethyl- 1 .3-propanediol, 2,4- dimethyi-2,4-pentanedioi, 2-methyl-2-propyl- 1 ,3-propanediol, 2.2,4-trimethyl- 1 ,3- pentanediol, 2,5-dimethyl-2,5-hexanediol, 2-cthyl- l ,3-hexandiol, 2-butyl-2-ethyl- l ,3- propanediol, 2,2-dibutyl- 1 ,3-propanediol, 2-butyl-2-cthyl- l ,3-propanediol, 1 ,2- cyciohexanediol, 1 ,3-cyclohexanediol, 1 ,4-cyclohexandioi, 1 ,2-cyciohexanedimethanol,

1 .3- cycloh.exanedimethanol, 1 ,4-cyclohexanedimethanol, cyclododecancdiol,

dipropylene glycol. Methylene glycol, pentaethylene glycol, hexaethylene glycol, hydroxypivalyl hydroxypivalate, 3,9-bis( 1 , 1 -dimethyl-2-hydroxyethyl)-2,4,8, 10- tetraoxaspiro[5.5]undecane (spiroglycol ), 2,2,4.4-tetramcthyi- 1 ,3-cyclobutanediol and isohexides, such as l ,4:3,6-dianhydro-D-glucitol (isosorbide), l ,4:3,6-dianhydro-D- mannitol (isomannide) and 1 .4 : 3 , 6-d i a n h yd ro- L - i d i to I (isoidide), and mixtures thereof. Preferred diols are C _3-10 aliphatic or C ni-cycloalipliatic diols such as 1 ,6-hexanedioi,

1.4- cyclohexanedimethanoi and 2-butyl-2-ethyl- l ,3-propanediol .

Preferred unsaturated aliphatic diols are C ₄ _ ₂ o unsaturated aliphatic diols such as 2-butene- l ,4-diol, 3-butene- l ,2-diol, 3-hexene-l ,6-dioi and monoolein.

Preferred aromatic diols are C ₆ -2o aromatic diols such as hydroquinone,

methyl hydroq u i none, resoreinol, 2 -methyl reso rc i no 1 , pyrocatechol, 1 ,2- benzenedimethanol, 1 ,3-benzenedimethanol, 1 .4-benzenedimetlianol, bisphenol A, bisphenol E, bisphenol F, bisphenol M, bisphenol P, bisphenol S, bisphenol Z, bisphenol AF, bisplienol AP, 4,4'-dihydroxybenzophenone, 4.4'-biphenol, 2,2'-biphenoi, 1 ,2-dihydroxynaphthalene, 1 ,4-d i h yd rox ynapli t Ii a I en e, 1 ,5-dihydroxynaphthalene, 1 ,6- dihydroxynaphthalene, 1 ,7-dihydroxynaphthaiene, 2 , 3 -d i h yd rox yn aph t ha I en e, 2,6- dihydroxynaphthaiene, 2.7-diliydroxynaphttialene, and 1 ,8-naphthalenedimethanol.

Thus, in a preferred embodiment, the po!yoxalates of the invention comprise at least one further diol (iv) which is different to hydrogenated bisphenol A. The use of 2- butyi-2-ethyl-l ,3-propanediol, 1 ,4-Cyciohexanedimethanol and

1 ,6-Hexancdiol along with the hydrogenated bisphenol A (iii) is preferred.

The starting materials for the preparation of the poiyoxaiates are preferably used in a molar ratio between the oxalate monomer (i) and the second monomer (ii) of 4: 1 to 1 :2, preferably 3 : 1 to 1 : 1, e.g. 2: 1 . Preferably, the oxalate monomer is in excess relative to the second monomer. In some embodiments, the second monomer is in excess. Preferable, the molar ratio between the total amount of monomers (i) and (ii) and total amount of diol monomers (component (iii) plus any optional additional diols) is 90: 100 to 100:90, preferably 95 : 100 to 100:95, most preferably 100: 100. The polyoxalate polymer architecture will influence the polymer properties. Branching in polymers and "star" shaped polymers are examples of useful structural variables that can be used advantageously to modify polymer properties such as solubility in organic solvents, miscibility in polymer blends, reduce crystal I in ity of the polymer and mechanical properties.

In order to obtain branching or star structure in the poiyoxalates, the

polycondensation may be carried out in the presence of a compound with more than two functional groups, e.g. three functional groups that can take part in the

polymerisation reaction . Examples of suitable compounds include polyols, e.g. C3_ ₂ o polyols such as glycerol, t r i m e t h y I o I m e t h a n e , trimethyiolethanc, trimethylolpropane, 1 ,2,4-butanetriol, 1 ,2,6-hexanetrioi, erythritoi, pentaerythritol, d i ( t r i m e t h y I o 1 p ro pane ) 1 ,2,7,8-octanetetrol triglycerol, dipentaerythritol, pyrogallol and phloroglucinol;

poiycarboxylic acids, e.g. C4.20 poiycarboxylic acids such as trimellitic acid, trimesic acid and pyromeliitic acid;

alkyl esters of poiycarboxylic acid such as tri methyl trimellitate; and anhyd ides of poiycarboxyl ic acid such as trimel l itic anhydride and pyromeliitic dianhydride. The term "poly" is used in relation to these branching monomers to mean the presence of 3 or more functional groups ( i.e. acid groups, hydroxy! groups etc) in the molecule.

Examples of other suitable polyfunctional compounds include mal ic acid, tartaric acid and citric acid.

Polyols with more than two hydroxy! groups are the preferred compounds for obtaining branched and star-shaped poiyoxalates. The amount of any branching reactant, e.g. polyol should preferably be 1 0 mol% or less of the total amount of that reactant type, e.g. of the diols/polyols combined. Too much branching leads to gel l ing and a composition which cannot be applied to an object.

Optional ly, other functional compounds can be included as comonomers to adjust the polymer properties of the poiyoxalates. Such compounds can be used to adjust parameters such as hydrolysis rate and mechanical properties. These functional compounds preferably possess two reactive functional groups e.g. two ester, acid, amino or hydroxy! groups or mixtures thereof and will be called Afunctional compounds. These compounds can form additional monomers in the polymerisation process. Examples of suitable bifunctional compounds include:

a Iky I esters of dicarboxyl ic acids such as dimethyl terephthalatc, dimethyl isophthalatc, dimethyl phthalate.dimcthyl malonate, dimethyl isobutyl malonate, dimethyl succinate, dimethyl glutarate. dimethyl ad i pate, dimethyl pimelate. dimethyl suberate. dimethyl azelate, dimethyl sebacate, dimethyl brassylate, dimethyl glutaconate, diethyl malonate, diethyl methyl malonate, diethyl succinate, diethyl glutarate, diethyl ad i pate, diethyl pimelate, diethyl suberate, diethyl azelate, diethyl sebacate, di butyl succinate, dibutyl ad i pate and dibutyl sebacate;

dicarboxylic acids such as terephthalic acid, isophthal ic acid, phthalic acid, 1 ,4- phcnylenediacetic acid, 1 ,3-phenylcnediacetic acid, 1 .2-phenylenediacetic acid, c yc I oh ex a n ed i c a rbo x y I i c acid, maleic acid, fumaric acid, ma Ionic acid ,

isobutylmalonic acid , succinic acid , glutaric acid , ad i pic acid, pimci ic acid , suberic acid , azelaic acid , sebacic acid , dodecanoic acid, brassylic acid, glutaconic acid and dimer fatty acids;

dicarboxyl ic acid anhydrides such as succinic anhydride, maleic anhydride, citraconic anhydride, glutaric anhydride, diglycolic anhydride, phthalic anhydride, tetrahydrophthal ic anhydride, hexahydrophthalic anhydride, 5-norbornene-2,3- dicarboxyl ic anhydride and 1 ,8-naphthalic anhydride;

alkyl esters of hydroxy! funct ional carboxyl ic acids such as, methyl 3- hydroxybenzoate. methyl 4-h yd rox y ben zoat e, methyl vanillate, methyl 4- hydroxyphenylacetate. ethyl 3 -h yd rox yben zoat e, ethyl 4-h yd rox yben zoat e, methyl 3- hydroxybutyrate. methyl 2 -h yd ro x y i so b u t y ra t e , methyl 10-h ydro.x ydecanoate, ethyl 3- hydroxybutyrate, ethyl 2 - h yd ro x y i so b u t y ra t e , ethyl 2-h ydro.x yhcxanoate and ethyl fill yd rox y h ex a n oa t e ;

hydroxy I functional carboxylic acids such as salicylic acid, 3-hydroxybenzoic acid, 4-h yd rox ybenzo i c acid, vanill ic acid, 2-h yd rox yphen y 1 acet i c acid, 3- h yd rox yphen y I acet i c acid, 4-hyd rox yph en y 1 acet i c acid, glycol ic acid, 3-hydroxybutyric acid, 2 - h y d ro x y i so b u t y r i c acid and ricinoleic acid;

diamines such as 1 .2-ethanediamine, 1 ,2-propanediamine. 1 .3-propanediamine, 1 ,4-butanediamine, 1 .5-pentanediamine, 1 .6-he.xanediamine, 1 ,7-heptanediamine, 1 ,8- octanediamine, 1 .9-nonanediamine, 1 . 10-dccanediamine, 1 .12-dodecanediamine. 2- methyl- 1 ,5-pentanediamine, 2-butyl-2-ethyl- 1 ,5-pentanediamine, 2,2,4- and 2,4,4- trimetliyl- 1 ,6-hexanediamiiie, 0,0'-bis(3-aminopropyl)ethylene glycol, 0,0'-bis(3- aminopropyl)di ethylene glycol, 1 ,2-diaminocyclohexane, 1 ,4-diaminocyclohexane, 1 ,2-phenylenediamine, 1 ,3-phenylenediamine, 1 ,4-phenylenediamine, 1 ,3- bis(aminomethyl)benzene, 1 ,4-bis(aminomethyl)benzene, 1 ,4-diaminonaphthalene, 1 ,5- diaminonaphthalene, 1 ,8-diaminonaphthalene, 4,4'-methylenedianiline, 4,4'- oxydianiline and l ,l , l-tris(aminomethyl)ethane.

Any alky! ester of dicarboxylic acid, dicarboxylic acid anhydrides, diamines, hydroxy! functional carboxyl ic acid, a Iky I ester of hydroxy! functional carboxyl ic acid or dicarboxylic acid used herein may have up to 20 carbon atoms.

Polyoxaiate copolymers are obtained by mixing all starting materials before polymerisation. By mixing all rcaetants, the polyoxaiate which forms is typically a statistical random polymer of ail the monomers used (i.e. the amount of each monomer incorporated essentially reflects the amount of each monomer in the starting mixture). Polyoxaiate block polymers are obtained either by subsequent addition of starting materials during the polymerisation process after an initial polymerisation of only two monomers or preparation of block polymers that are linked together.

The polymerisation conditions can be widely varied although typically temperatures of 100 to 250°C are employed, e.g. 120 to 220°C. During condensation polymerisation a condensate (normally water or an alcohol) is formed. This is preferably removed by distillation as the polymerisation continues. This can be achieved under reduced pressure. The polymerisation is preferable carried out in an inert atmosphere, e.g. nitrogen.

The polyoxalates of the present invention have a weight average molecular weight (Mw) of at least 4000 g/mol, preferably at least 4500 g/mo!, more preferably at least 5000 g/mol, such as at least 5200 g/moi. The weight average molecular weight is preferably up to 30,000 g/mol, preferably up to 20,000 g/mol, such as up to 1 5,000 g mol. There is howev er a trade off here as increasing the Mw too far increases viscosity and means that more solv ent is required to ensure that the coating composition can be applied. More solvent increases volatile organic content which is not desired.

The molecular weight of the polyoxaiate is important in terms of obtaining a film with sufficient hardness. The present inventors have surprisingly found that polyoxalates with weight average molecular weights within the ranges quoted herein possess sufficient hardness, without the need for a curing agent. High molecular weights are associated w ith high viscosities w ich in turn leads to high levels of undesirable volatile organic compounds. The production time required to manufacture < polyoxalate with high molecular weight is also longer. The longer the production time the higher the production cost of the polymer.

The polyoxalate of the invention should preferably have a glass transition temperature (Tg) in the range 0- 100 °C, more preferably 5-60 °C, especial ly 10-50 °C.

In a further preferred embodiment of the invention, the polyoxalate is amorphous. By amorphous is meant that the polyoxalate does not have a discernable melting point, i.e. it is not crystalline. The use of an amorphous polyoxalate increases the solubil ity in the organic solvent typically used in the antifouling composition so the use of amorphous polyoxalates is preferred.

It is preferred that any polyoxalate used in this invention has a solubility of at least 50 wt% in the solvent used in the antifouling composition, preferably at least 75 wt% in the solvent such as at least 95 wt% in the solvent. For example therefore at least 1 kg of polyoxalate should dissolve in 1 kg of solvent. Preferred solvents are discussed below . Xylene is especially preferred.

It is preferred if the polyoxalate forms at least 3 wt%, e.g. at least 5 wt%, perhaps at least 1 0 wt% of the antifoul ing coating composition, such as at least 20 wt% In some embodiments, the polyoxalate binder component may form up to 50 wt% of the anti-foul ing coating composition, preferably up to 40 wt%, especially up to 35 wt% The skil led man will appreciate that the level of polyoxalate binder employed will depend on the amount of antifoul ing compound employed, e.g. the amount of cu rous oxide.

It is preferred that after formation of the polyoxalate, the combined amount of any un reacted monomers in the binder is below 1 wt.%, preferably less than 0.5 wt.%, such as less than 0.2 wt.%.

The solubility of the polyoxalates can, for example, be improved by using flexible building blocks and/or by branching of the polymer by using multifunctional building blocks, in particular the bifunctional building blocks as discussed above. Curing Agent

The polyoxalate binder may be combined with a curing agent in the antifoul ing coating compositions of the invention. However, as stated above, it is preferred if no curing agent is present.

Poiyoxalates have functional end groups that react with curing agents such as chain extenders or cross! inkers. Examples of curing agents wel l known in the art include, for example, monomeric isocyanates, polyisocyanatcs and isocyanate prepolymei's. Polyisocyanatcs are preferred over monomeric isocyanates because of lower toxicity. Pol yisocyanatcs can for example be based on diphenylmethanc diisocyanate (MDI), toluene diisocyanate (TDI), hexamethy ene diisocyanate (HDI) and isophorone diisocyanate (IPDI) chemistry. These are, for example, supplied under the tradename Desmodur by Bayer Material Science and Tolonatc by Vcncorex.

Examples of polyisocyanatcs are Desmodur N3400, Desmodur N75, Desmodur

XP2580, Desmodur Z4470, Desmodur XP2565 and Desmodur VI supplied by Bayer

Material Science.

Polyisocyanatcs can be made with different NCO-functionality. The Myofunctional ity is the amount of NCO-groups per polyisocyante molecule or isocyanate prepolymer molecule. Polyisocyanatcs with different C O - fu n c t i o n a I i t y can be used.

The curing agent is preferably present in an amount of 0.8-1.5 equivalents (equiv) NCO groups relative the amount of hydroxy! groups, preferably 0.9- 1 .4 equiv. more preferably 0.95-1.3 equiv, even more preferably 1-1.2 equiv.

If present, the curing agent is preferably present in an amount of between 0.005 and 0.5 wt% relative to the polyoxalate, preferably 0.01 to 0.2 wt%, more preferably 0.012 to 0.15 wt%.

In addition, a curing catalyst can be used. Examples of such catalysts are tin catalysts, e.g. dibutyltin dilaurate.

It will be appreciated that mixing of the polyoxalate polymer and the curing agent is carried out shortly before application of the coating to an object, e.g. an hour or less before coating. It is preferred therefore if the curing agent is supplied separately to the rest of the anti-fouling coating composition to prevent curing before the coating has been applied to the object. Hence the coating composition of the invention can be supplied as a muitipack (preferably two pack ) formulation.

Thus, viewed from another aspect the invention provides a kit suitable for the preparation of a marine antifouling coating composition comprising a first part (A) ( I ) a polyoxalate polymer with a Mw of at least 4000 g/mol, wherein said polyoxalate comprises:

(i) a residue of an oxalate monomer selected from oxalic acid or a diester derivative thereof;

(ii) a residue of a second monomer selected from a cycl ic diester or cyclic diacid; and

(iii) a residue of a third monomer which is hydrogenatcd bisphenoi A ; and optionally a marine antifoul ing agent; and

a second part (B) comprising a curing agent.

Composition

The antifouling coating composition of the invention should preferably have a solids content above 45 wt%, e.g. above 50 wt%, such as abov e 55 wt%.

Preferably the antifouling coating composition of the inv ention (i.e. containing a curing agent) should have a content of volatile organic compounds (VOC) less than 420 g/L, more preferably less than 410 g/L, such as less than 400 g/L, especially less than 395 g/L. VOC content can be calculated (ASTM D5201-01) or measured, preferably measured.

The antifouling coating compositions of the invention display an improved balance of hardness and pol ishing properties compared to compositions of the prior art. Surprisingly this can be attained without the need for a curing agent.

In preferred embodiments, the antifouling coating composition of the inv ention has a hardness of at least 20 oscillations, preferably at least 30 oscillations when measured after the paint film has been dried at 50 °C for 72 hours.

The polyoxalates of the present invention will degrade in sea water and release compounds with structural units similar or identical to the starting materials. It will be understood that the degradation reactions which the polyoxalates of the inv ention undergo is an hydrolysis reaction which occurs in the polymer backbone, i.e. the hydrolysablc bonds are present in the polymer backbone. Starting materials which are biologically active towards marine organisms may give polyoxalates which act as anti- foul ing agents themselves. Preferably however, the starting materials are chosen from compounds that give polyoxalates that degrade to components that are not biological ly active towards marine organisms. In such a scenario, the anti-fouling coating composition of the invention may need to contain at least one compound capable of preventing foul ing on an object, e.g. a marine anti-fouling agent (sometimes referred to as a biological ly active agent ) especial ly a biocide.

Therefore, in a preferably embodiment, the antifoul ing coating composition of the present invention further comprises one or more marine anti-fouling agents. Even if the antifouling coating composition of the present invention comprises a biologically active polyoxalatc. it may additionally contain one or more marine anti-fouling agents.

Preferably, therefore, the antifouling coating compositions of the invention further comprise at least one marine anti-foul ing agent, preferably a biocide.

By marine anti-foul ing agent is meant any chemical com ound that prevents the sett lement of marine organisms on a surface, and/or prevents the growth of marine organisms on a surface and/or encourages the dislodgement of marine organisms from a surface. Examples of inorganic marine antifouling agents include copper and copper compounds such as copper oxides, e.g. cuprous oxide and cupric oxide; copper al loys, e.g. copper-nickel alloys; copper salts, e.g. copper thiocyanate. copper sulphide; and barium metaborate.

Examples of organometallic marine antifouling agents include zinc

2-pyridincthiol- 1 -oxide [zinc pyrithione); organocopper compounds such as copper 2-pyridinethiol- 1 -oxide [copper pyrithione], copper acetate, copper naphthenate, copper 8-quinoiinonate [oxine-copper], copper nonylphenolsul fonatc, copper

bis(ethyienediamine)bis(dodecyibenzensulfonate) and copper

bis(pentachlorophenolate); dithiocarbamate compounds such as zinc

b i s ( d i m e t h y I d i t h i o c a r b a m a t e ) [ziram], zinc ethylenebis(dithiocarbamate) [zineb], manganese ethyl eneb is( d ith iocarbamate ) [maneb] and manganese

ethylenebis(dithiocarbamate) complexed with zinc salt [mancozcb]. Examples of organic marine antifouiing agents include heterocyclic compounds such as 2-(tert-butylamino)-4-(cyclopropylamino)-6-(methylthio)-l ,3,5-triazine

[cybutryne], 4,5-dichloro-2-R-octyl-4-isothiazoiin-3-one, 1 , 2 -ben z i sot h i azo I i n -3 -on e [DCOITj, 2-(t iocyanatomet ylthio)-l ,3-benzothiazole [benthiazole], 3-benzo[b]thien- 2-yi-5,6-dihydro-l,4,2-oxathiazine 4-oxide [bethoxazin] and 2,3,5,6-tetrachioro-4- (methyisuiphonyi)pyridine; urea derivatives such as 3-(3,4-dichlorophenyi)-l,l- dimethyiurea [diuron]; amides and imidcs of carboxylic acids, suiphonic acids and suiphenic acids such as A ^L (dichlorofiuoromethyithio)phthalimide, N- dichlorofluoromethyithio-iV'^'-dimethyl-N-phenylsulfamide [dichlofluanid] , N- dichlorofluoromethylthio-A^',N'-dimethyl-N-/7-tolylsulfamide [tolylfluanid] and N- (2,4,6-trichiorophenyi)maieimide; other organic compounds such as pyridine triphcnylborane, amine triphenylborane, 3-iodo-2-propynyl N-butylcarbamate

[iodocarb], 2,4,5, 6-tetrachioroisophthalonitriie [chlorothalonil], /;- ((diiodomethyl ^sulphonyl )toluene and 4-bromo-2-(4-chlorophenyl)-5-(trifluoromethyi)- 1 H -pyrro I e-3 -carbon i t ri I e [tralopyril].

Other examples of marine anti-fouling agents may be t e t ra alkyl h o s h o n i u m halogenides, guanidinc derivatives, imidazole containing compounds such as

4-[ l-(2,3-dimethylphenyl)ethyl j-1 H-imidazole [medetomidine] and derivatives, macrocyclic lactones includes avermectins and derivatives thereof such as ivermectine and spinosyns and derivatives thereof such as spinosad, and enzymes such as oxidase, proteolytically, hemicellulolytically, cellulolytically, lipolytically and amylo!ytieally active enzymes.

Preferred marine anti-fouling agents are cuprous oxide, copper thiocyanate, zinc 2-pyridinethiol- 1 -oxide, copper 2-pyridinethiol-l -oxide, zinc

ethylenebis(dithiocarbamate), 2-( t7V-butylam i no )-4-(cyclopropylam ino )-6- (methyl tli io)-l ,3,5-triazine, 4,5-dichioro-2-«-octyl-4-isothiazoiin-3-one, N- dichlorofluoromethylthio-N',iV'-dimethyl-iV-phenylsulfamide, N- dichiorofluoromethyithio-N',jV'-dimethyi-iV-)-toiylsuifamide and 4-bromo-2-(4- chlorophcnyl )-5-( trifluoromethyl )- 1 H-pyrrole-3-carbonitrilc.

Optionally the marine anti-fouling agents may be encapsulated or adsorbed on an inert carrier or bonded to other materials for controlled release. The marine anti-fouling agents may be used alone or in mixtures. The use of these marine anti-foul ing agents is known in anti-fouling coatings and their use would be familiar to the skilled man.

The total amount of marine anti-foul ing agent in the ant i fouling compositions of the invention may be in the range 0.5 to 80 wt%, such as 1 to 70 wt%. It will be appreciated that the amount of this component will vary depending on the end use and the marine anti-foul ing agent used.

Furthermore, the antifoul ing coating composition according to the present invention opt ional ly comprises one or more components selected among other binders, pigments, extenders and fillers, stabil izers, dehydrating agents and drying agents, additives, solvents and thinners. It is preferred if the composition of the invention does not contain a chelating agent such as a beta-diketone such as acetylacetone,

benzoylacetone, and trifluoroacetylacetone; ester of acetoacetic acid such as methyl acetoacetate, ethyl acetoacetate. and butyl acetoacetate; alpha-dioximes such as dimcthylglyox imes; bipyridyl such as 2,2'-bipyridyl; oxine; salicylic acid and derivatives thereof; lower alkanolamine such as triethanoiamine; glycol such as ethylene glycol ; acetic acid, oxal ic acid and derivativ es thereof, dicarboxylic acid and derivatives thereof.

An additional binder can be used to adjust the self-pol ishing properties and the mechanical properties of the antifoul ing coating film. Examples of binders that can be used in addition to the polyoxalate in the antifoul ing coating composition according to the present invention include rosin materials such as wood rosin, tall oil rosin and gum rosin;

rosin derivatives such as hydrogenated and partially hydrogenated rosin, disproportionated rosin, dimeriscd rosin, polymerised rosin, maleic acid esters, fumaric acid esters, glycerol esters, pentaerythritol esters and other esters of rosin and hydrogenated rosin, copper resinate, zinc resinate, calcium resinate, magnesium resinate and other metal resinatcs of rosin and polymerised rosin and others as described in WO 97/44401 ;

resin acids and derivatives thereof such as copal resin and sandarach resin; other carboxyl ic acid containing compounds such as abietic acid, neoabietic acid, dehydroabietic acid, dihydroabietic acid, tetrahydroabietic acid, secodeh yd roab i et i c acid, pimaric acid, paramatrinic acid, isoprimaric acid, levoprimaric acid,

agathenedicarboxylic acid, sandaracopimalic acid. I auric acid, stearic acid, isostearic acid, oleic acid, l inoleic acid, linolenic acid, isononanoic acid, versatie acid, naphthenic acid, tall oil fatty acid, coconut oil fatty acid, soyabean oil fatty acid and derivatives thereof;

hydrocarbon resins, aliphatic, aromatic or dicyciopentadiene based hydrocarbon resins;

silyl ester copolymers, for example as described in US 4,593,055, EP 0 646 630 and NO 2007 3499;

acid functional polymers of which the acid group is blocked with divalent metals bonded to a monovalent organic residue, for example as described in EP 0 204 456 and EP 0 342 276; or divalent metals bonded to a hydroxy! residue, for exam le as described in GB 2 31 1 070 and EP 0 982 324; or amine for example as described in EP 0 529 693;

hydrophi lic copolymers for example (mcth )acrylatc copolymers as described in GB 2 1 52 947 and poly(N-vinyl pyrrolidone) copolymers and other copolymers as described in EP 0 526 441 ;

(meth )acrylic polymers and copolymers, such as poiy(«-butyi acrylate), po I >'(/?- butyl acryiate-c -isobiityi vinyl ether);

v inyl ether polymers and copolymers, such as poly( methyl vinyl ether), polyi ethyl v inyl ether), poly ^' sobuty vinyl ether), poly( vinyl chloride-co-isobutyl vinyl ether);

aliphatic polyesters, such as po I y( lactic acid ), poiy(glycoiic acid ), poly(2- hydroxybutyric acid), po I y( 3 -h yd rox y bu t yri c acid ), po I y(4-h yd rox y va I eri c acid ), polycaprolactone and al iphatic polyester copolymer containing two or more of the units selected from the above mentioned units;

metal containing polyesters for example as described in EP 1 033 392 and EP 1 072 625;

alkyd resins and modified alkyd resins; and

other condensation polymers as described in WO 96/ 14362.

Dehydrating agents and d ying agents contribute to the storage stability of the antifoul ing coating composition by removing moisture introduced from raw materials. such as pigments and solvents, or water formed by reaction between carboxylic acid compounds and bivalent and tri va lent metal compounds in the antifouling coating composition. The dehydrating agents and drying agents that may be used in the antifouling coating composition according to the present invention include organic and inorganic compounds. Examples of dehydrating agents and drying agents include anhydrous calcium sulphate, anhydrous magnesium sulphate, anhydrous sodium sulphate, anhydrous zinc sulphate, molecular sieves and zeolites; orthoesters such as trimethyl orthoformate, triethyl orthoformate, tri propyl orthoformate, triisopropyl orthoformate, tributyl orthoformate, trimethyl orthoacetate and triethyl orthoacetate; kctals; acetals; enolethers; orthoborates such as trimethyl borate, triethyl borate, tripropyl borate, triisopropyl borate, tributyl borate and tri-tert-butyl borate.

Other stabilizers that contribute to the storage stabil ity of the antifoul ing coating composition are monomeric and polymeric carbodiimide compounds, such as bis(2,6- diisop ro p y I h e n y I ) c a r bo d i i m i d c and poly(l ,3,5-triisopropylphenylene-2,4- carbodi imide) and others as described in patent application EP 12189636.7.

Carbodiimides is preferred as stabil izer. Polymeric carbodiimides is most preferred. Acid scavengers can generally be used.

Examples of pigments are inorganic pigments such as titanium dioxide, iron oxides, zinc oxide, zinc phosphate, graphite and carbon black; organic pigments such as phthalocyanine compounds and azo pigments.

Examples of extenders and fillers are minerals such as dolomite, piastorite, calcite, quartz, barite, magnesitc, aragonite. silica, wollastonite, talc, chlorite, mica, kaolin and feldspar; synthetic inorganic compounds such as calcium carbonate, magnesium carbonate, barium sulphate, calcium sil icate and sil ica; polymeric and inorganic microspheres such as uncoated. or coated hollow and solid glass beads, uncoated or coated hol low and sol id ceramic beads, porous and compact beads of polymeric materials such as polyimethyl methacrylate), polyimethyl methacrylatc-co- ethylene glycol dimethacrylate), po I y ( s t yren e-co-e th y I en e glycol di methacrylate), poly(styrene-co-divinylbenzene), polystyrene. poly( vinyl chloride).

Examples of additives that can be added to an antifoul ing coating composition are reinforcing agents, thixotropic agents, thickening agents, anti-settl ing agents, plasticizers and solvents. Examples of reinforcing agents are flakes and fibres. Fibres include natural and synthetic inorganic fibres such as si I icon -containing fibres, carbon fibres, oxide fibres, carbide fibres, nitride fibres, sulphide fibres, phosphate fibres, mineral fibres; metallic fibres; natural and synthetic organic fibres such as cellulose fibres, rubber fibres, acrylic fibres, polyamide fibres, polyimide, polyester fibres, polyhydrazidc fibres,

polyvinylchloride fibres, polyethylene fibres and others as described in WO 00 77102. Preferably, the fibres have an average length of 25 to 2,000 urn and an average thickness of 1 to 50 iim with a ratio between the average length and the average thickness of at least 5.

Examples of thixotropic agents, thickening agents and anti-settling agents are silicas such as fumed silicas, organo-modified clays, amide waxes, polyamide waxes, amide derivatives, polyethylene waxes, oxidised polyethylene waxes, hydrogenated castor oil wax, ethyl cel lulose, aluminium stearates and mixtures of thereof.

Examples of plasticizers are chlorinated paraffins, phthalates, phosphate esters, sulphonamides, ad i pates and epoxidised vegetable oils.

In general, any of these optional components can be present in an amount ranging from 0. 1 to 50 wt%, typical ly 0.20 to 20 wt%, preferably 0.50 to 1 5 wt% of the ant i foul ing composition. It will be appreciated that the amount of these optional components will vary depending on the end use.

It is highly preferred if the ant i fouling composition contains a solvent. This solvent is preferably volatile and is preferably organic. It may have an evaporation rate of more than 0.05 (n-BuAc = 1). Examples of organic solvents and thinners are aromatic hydrocarbons such as xylene, toluene, mesity ene; ketones methyl ethyl ketone, methyl isobutyl ketone, methyl isoamyl ketone, cyclopentanone,

cyclohe anone; esters such as butyl acetate, tert-butyl acetate, amy! acetate, isoamyl acetate, ethylene glycol methyl ether acetate; ethers such as ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dibutyl ether, dio ane, tetrahydrofuran, alcohols such as benzyl alcohol: ether alcohols such as l -methoxy-2-propanol; al iphatic hydrocarbons such as white spirit; and optionally a mixture of two or more solvents and thinners.

Preferred solvents are aromatic solvents, optionally together with butylacetate, especial ly xylene and mixtures of aromatic hydrocarbons. The amount of solvent is preferably as low as possible but is preferably sufficient to dissolve the polyoxaiate. The solvent content may be up to 50 wt% of the composition, preferably up to 45 wt% of the composition, such as up to 40 wt% but may be as low as 1 5 wt% or less. e.g. 10 wt% or less. Again, the skilled man will appreciate that the solvent content will vary depending on the other components present and the end use of the coating composition.

Alternatively the coating can be dispersed in an organic non-solv ent for the fil m-forming components in the coating composition or in an aqueous dispersion.

The an ti fou ling coating composition of the invention can be applied to a whole or part of any object surface which is subject to fouling. The surface may be permanently or intermittently underwater (e.g. through tide movement, different cargo loading or swel l ). The object surface will typically be the hul l of a vessel or surface of a fixed marine object such as an oil platform or buoy. Appl ication of the coating composition can be accomplished by any convenient means, e.g. via painting (e.g. with brush or roller) or spraying the coating onto the object. Typically the surface w ill need to be separated from the seawatcr to al low coating. The application of the coating can be achiev ed as conventionally know n in the art.

The invention will now be defined with reference to the following non limiting examples and figures.

Figure 1 show s that the antifoul ing coating compositions containing

hydrogenated bisphenol A as a diol component display good pol ishing properties, even when not cured. Good hardness is also observed.

Figure 2 shows polishing rates for inventive, cured compositions C6-C10.

Figure 3 shows polishing properties of inventive, cured compositions C 1 1 -C 1 5

Fig re 4 shows pol ishing properties of comparative composition CC 1.

Figure 5 shows pol ishing properties of comparative composition CC2.

Determination of polymer solution viscosity

The viscosity of the polymers are determined in accordance with ASTM D2196- 10 using a Brook field DV-I viscometer with LV-2 or LV-4 spindle at 1 2 rpm. The polymers are temperated to 23.0 C ± 0.5°C before the measurements. Determ ination of solids content of the polymer solutions

The solids content in the polymer solutions are determined in accordance with ISO 3251 :2008. A test sample of 0.6 g ± 0. 1 g are taken out and dried in a ventilated oven at 150°C for 0 minutes. The weight of the residual material is considered to be the non- volatile matter (NVM ). The non- volatile matter content is expressed in weight percent. The value given is the average of three parallels.

Determination of polymer average molecular weights distribution

The polymers are characterised by Gel Permeation Chromatography (GPC) measurement. The molecular weight distribution (MWD) was determined using a Polymer Laboratories PL-GPC 50 instrument with two PLgel 5 iim Mixed-D columns (300 x 7.5 mm ) from Polymer Laboratories in series, tetrahydrofuran (THF) as eluent at ambient temperature and at a constant flow rate of I mL min and with a refractive index (R l ) detector. The columns were calibrated using polystyrene standards Easivials PS-H from Polymer Laboratories. The data were processed using Cirrus software from Polymer Labs.

Samples were prepared by dissolving an amount of polymer solution corresponding to 25 mg dry polymer in 5 ml , THF. The samples were kept for minimum 3 hours at room temperature prior to sampling for the GPC measurements.

The weight-average molecular weight (Mw), the number-average molecular weight (Mn) and the polydispersity index (PDI), equivalent to Mw/Mn, are reported in the tables.

Determination of the glass transition temperature

The glass transition temperature (Tg) is obtained by Differential Scanning Calorimetry ( DSC ) measurements. The DSC measurements were performed on a TA Instruments DSC Q200. Samples were prepared by transfering a smal l amount of polymer solution to an aluminium pan and dry the samples for minimum 10 h at 50°C and 3 h at 150°C. The samples of approx. 10 mg dry polymer material were measured in open aluminum pans and scans were recorded at a heating and cool ing rate of I O 'C'm in with an empty pan as reference. The data w ere processed using Universal Analysis software from TA Instruments. The inflection point of the glass transition range, as defined in ASTM El 356-08, of the second heating is reported as the Tg of the polymers.

Coating film hardness - Koni pendulum hardness

Pendulum hardness tests were performed according to ISO 1522:2006.

Each of the antifouling coating compositions was applied to a transparent glass plate (100 ^χ 200 ^χ 2 mm ) using a film applicator with 300 μηα gap size. The coating films were dried for 24 h (or 72 h ) at 23°C and then 72 h at 50°C. The coating film hardness of the dry coating film was measured at a temperature of 23°C and relative humidity of 50% using a Erich sen 299/300 pendulum hardness tester. The hardness is quantified as the number of pendulum swings to damp the ampl itude from 6° to 3°.

Determ ination of polishing rates of antifouling coating films in sea water

The polishing rate is determined by measuring the reduction in film thickness of a coating film over time. For this test PVC disc are used. The coating compositions are appl ied as radial stripes on the disc using a film applicator with a gap size of 300 urn. The thickness of the dry coating fi lms are measured by means of a contact surface profiler. The PVC discs are mounted on a shaft and rotated in a container in which seawater is flowing through. atural seawatcr which has been filtered and temperature- adjusted to 25°C ± 2°C is used. The PVC discs are taken out at regular intervals for measuring the film thickness. The discs are rinsed and al lowed to dry overnight at room temperature before measuring the film thickness.

Polymer synthesis

Synthesis of the poiyoxaiates used in the Examples were made using the following general procedure.

Monomers and catalyst are added in the amounts indicated in the Table to a 250- m L temperature controlled reaction vessel equipped with a mechanical stirrer, nitrogen inlet and distillation equipment. The mixture is slowly heated to 1 90 C under nitrogen atmosphere while the condensate is distilled off. The heating rate is controlled so the temperature off the distillate does not exceed the boiling point of the condensate. The temperature is kept at 190°C until 80-90% of the theoretical amount of condensate has been removed. The nitrogen inlet is closed and vacuum is applied. The vacuum is gradually decreased to the values shown in the Tables. The temperature is increased to 200°C. The stirring speed is gradually increased. The vacuum is applied for 1 -5 hours. The polymer is cooled to 150°C under vacuum. The vacuum is removed and xylene is added to obtain the desired non-volatile matter. The polymer solution is cooled to room temperature.

The amount of hydroxyl groups present in the polymer is calculated from the number-average molecular weight (M _n ). It is assumed that one end of the polymer chain consists of a hydroxyl group when a 1 : 1 molar ratio between diesters and diols are used. Based on this the amount of curing agent needed can be calculated. 50 ppm of curing catalyst relative the amount of hydroxyl groups is used.

Calculation example - amount of curing agent and curing catalyst:

PO-1 (Polymer 1)

M _N = 3137 g/mol, wt% solid = 67.3%

If 1 g of polymer solution is used in the paint

noH = (wt% solid x m _po iymer) / ( Mn x 1 ) (as a 1 : 1 molar ratio between diesters and diols is used in PO-1) n _0H = (0.673 x l) / (3137 x 1 ) mol

If 1 equiv of curing agent is used→ n ₀ H = n _NC o = (0.673 x 1) / (3137 x 1) mol

If Desmodur XP2580 is used, NCO content = 19.5 wt%, M _{w NC0} = 42.02 g/mol m _XP 258o = (n _N co x MW CO) / NCO content

m _X P2580 = (((0.673 x 1) / (3 137 x 1)) x 42.02 ) / 0.195 = 0.046 g

Table 1 . Information of the curing agents used in the e amples.

Curing agent Type NCO- Form NCO- content supplied functionality approx.. (%)

Desmodur i PD I 19.5 100% 2.0 < F < 2.8

XP2580 Allophanate

Desmodur N75 HDI Biuret 16.5 75% in F > 3.6 butylacetate

Five inventive (PO-1 to PO-5) and four comparative (POC-1 to POC-4) polyoxalate polymers were prepared according to the above method. Data is shown in Table 2. The inventive polymers were used to prepare an ti foil ling coating compositions C 1 to C 1 5, shown in Tables 3 and 4. Comparative composition examples CC-1 to CC-2 are shown in Table 5.

Table 2: Inventive and Comparative Polyo.xalate Polymers

POC-3 and OC-4 use bisphenol A. The Tg data show that hydrogenated bisphenol A gives a polymer with higher Tg than bisphenol A.

Table 3 : Inventive Ant i fouling Compositions - No curing agent present

Table 4: Inventive A nti fouling Compositions - Curing agent present

Table 5: Comparative Antifouling Compositions

Polishing Properties

The polishing rates of the inventive and comparative antifouling coating compositions were measured and compared. Results are shown in Figures 1 to 5.

Figure 1 shows that the antifouling coating compositions containing hydrogenated bisphenol A as a diol component display good polishing properties, when not cured. Good hardness is also observed.