GB2559454B

GB2559454B - A silyl ester copolymer and use thereof in an antifouling composition

Info

Publication number: GB2559454B
Application number: GB1718614.9A
Authority: GB
Inventors: Braendvang Morten; Tobias Boman Kjartan; Dahling Marit
Original assignee: Jotun AS
Current assignee: Jotun AS
Priority date: 2016-11-11
Filing date: 2017-11-10
Publication date: 2019-10-09
Anticipated expiration: 2037-11-10
Also published as: GB201718614D0; KR102634288B1; JP2018109146A; CN108070054B; CN108070054A; KR20230050293A; KR20180053260A; DE102017126335A1; JP7178167B2; GB2559454A

Description

A silyl ester copolymer and use thereof is as sstifoslisg composition

Field of the Invention

The present invention relates to marine antiibuling coating compositions, more specifically to marine antiibuling coating compositions comprising ethyl diethyleneglveol acrylate (EDEGA) and triisopropyisi lyi methacrylate (TISMA) or triisopropyisilyi acrylate (TISA). The invention further relates to a method of protecting objects from fouling, and objects coated with the antifouling composition of the invention.

Background of invention

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 economic consequences. The fouling may lead to biological degradation ofthe surface, increased load and accelerated corrosion. On vessels the fouling will increase the frictional resistance which will cause reduced speed and/or increased foe! consumption, it can also result in reduced manoeuvrability,

Ihe risk of -fouling is higher when a surface io contact with seawater is stationary for an. extended period of time. For instance, during outfitting the vessel is idle for several months which leads to a high risk of fouling. Vessels having long idle periods or low speed during trading also have a high risk of fouling. In these situations an antiibuling coating with high polishing rate is desirable in order to prevent fouling.

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

The most successful self-polishing antifouling systems on the market today are based on silyl ester functional (meth)acrylie copolymers. These coating compositions are for example described in, EP 0 646 630, EP 0 802 243, EP 1 342 756, EP 1 479 737, EP 1 641 862, WO 00/77102, WO 03/070832 and WO 03/080747.

Silyl ester functional (meth)acrylic copolymers are often used together with other binders such as acrylates and rosin or rosin derivatives to adjust the self-polishing properties and the mechanical properties of antifouling coating fdms. A biocide such as copper oxide or an organic biocide such as 4-bromo-2-(4-chlorophenyl)-5-(trifluoromethyl)-lH-pyrrole-3-carbonitrile [tralopyril] may also be included.

Silyl ester copolymers including a hydrophilic acrylate comonomer have been previously described. EP 0 646 630 describes antifouling coatings in which the hydrophilic acrylate comonomer includes 1-25 ethylene glycol repeating units. In an example, ethyl diethyleneglycol acrylate (EDEGA) is used in combination with another hydrophilic acrylate comonomer having 9 repeating glycol units, methyl methacrylate and n-butyl acrylate. In this example the silyl ester comonomer is tri(n-butyl)silyl methacrylate. W02014/096102 describes silyl ester copolymers with a hydrophilic comonomer, in which the silyl ester comonomer includes two non-branched C1/C2 groups attached to silicon and the third group attached to silicon having at least two branches. Thexyldimethylsilyl methacrylate and thexyldimethylsilyl acrylate are exemplified as the silyl ester comonomer. Thexyldimethylsilyl based monomers are not commercially available at this time making them less attractive options for paint binders. Also the combination of thexyldimethylsilyl (meth)acrylate and ethyl diethyleneglycol acrylate (EDEGA) give an antifouling coating with less cracking resistance in comparison to the combination of triisopropyl silyl (meth)acrylate and ethyl diethyleneglycol acrylate (EDEGA). EP 1 016 681 describes silyl ester copolymers with a hydrophilic acrylate or methacrylate comonomer. Many of the polymers exemplified are copolymers of triisopropyl silyl acrylate, methyl methacrylate, with low levels of a hydrophilic acrylate or methacrylate having a hydroxy group in the 2, 4 or 6 position. Also exemplified are copolymers of triisopropyl silyl acrylate, methyl methacrylate and polyethylene glycol methacrylates having 5, 12 or 15 repeating polyethylene glycol units.

The present inventors have now surprisingly established that a silyl ester copolymer incorporating both triisopropyl silyl methacrylate (TISMA) or triisopropylsilyl acrylate (TISA) and ethyl diethyleneglycol acrylate (EDEGA) as comonomers provides a self-polishing antifouling system having an appropriate polishing rate. Moreover, in a preferred embodiment, this is achieved using a low level of the comparatively expensive hydrophilic monomer EDEGA. Compared to non-hydrophilic (meth)acrylates, such as MMA and n-BA, EDEGA and other hydrophilic monomers, such as MEMA and MEA, are relatively expensive. The use of EDEGA in the silyl ester copolymer is however, economically viable compared to other hydrophilic monomers on the scale envisaged by the present inventors.

The object of the present invention is therefore to provide an antifouling coating composition having a polishing rate suitable to prevent fouling under circumstances where an object is in stationary contact with seawater for an extended period of time (e.g. a ship idle for weeks or months at a time), preferably at lower cost than existing coatings.

These objectives are attained through the use of a silyl ester copolymer which includes triisopropylsilyl methacrylate (TISMA) or triisopropylsilyl acrylate (TISA) and ethyl diethyleneglycol acrylate (EDEGA) comonomers.

Summary of invention

In a first aspect the invention provides a silyl ester copolymer comprising as comonomers: (i) ethyl diethyleneglycol acrylate (EDEGA); and (ii) triisopropylsilyl (meth)acrylate; preferably wherein the ratio of (i):(ii) in the copolymer is in the range of 5:95 to 60:40 (mol/mol).

In a preferred aspect the invention provides a silyl ester copolymer comprising as comonomers: (i) ethyl diethyleneglycol acrylate (EDEGA); and (ii) triisopropylsilyl methacrylate (TISMA); preferably wherein the ratio of (i):(ii) in the copolymer is in the range of 5:95 to 60:40 (mol/mol).

The amount of (i) in the silyl ester copolymer is preferably in the range of 2 to 40 mol%. The amount of (ii) in the silyl ester copolymer is preferably in the range of 5 to 60 mol%.

In an embodiment the silyl ester copolymer further comprises one or more hydrophilic comonomers of Formula (I):

wherein R is H or CH3, and R is a C3-C18 substituent with at least one oxygen or nitrogen atom, preferably at least one oxygen atom, with the proviso that the hydrophilic comonomer is not EDEGA.

In an embodiment the silyl ester copolymer further comprises one or more non-hydrophilic comonomers of Formula (II):

wherein R is H or CH3, and R is a C1-C8 hydrocarbyl substituent, preferably a Cl-8 alkyl substituent, most preferably methyl, ethyl, n-propyl, 2-ethylhexyl or n-butyl.

In a preferred embodiment the silyl ester copolymer includes methyl methacrylate (MMA) as a comonomer in an amount of 10 to 70 mol%.

The invention also provides an antifouling coating composition comprising a copolymer as described herein dispersed in a solvent. The antifouling coating may further comprise an antifouling agent, preferably cuprous oxide and/or copper pyrithione.

The invention also provides a process for protecting an object from fouling, said process comprising coating at least a part of said object which is subject to fouling with an antifouling coating composition as defined herein.

The invention also relates to objects coated with the antifouling coating composition as defined herein.

Definitions

The term “marine antifouling coating composition”, “antifouling coating composition” or simply “coating composition” refers to a composition which is suitable for use in marine environments. The antifouling coating composition requires an antifouling agent, e.g. a biocide.

The term hydrocarbyl group refers to any group containing C atoms and H atoms only and therefore covers alkyl, alkenyl, aryl, cycloalkyl, arylalkyl groups and so on.

The term “(meth)acrylate” means a methacrylate or acrylate.

The term “rosin” used in the text which follows is being used to cover “rosin or derivatives thereof’.

The term “binder” defines part of the composition which includes the silyl ester copolymer and any other components which together form a matrix giving substance and strength to the composition. Typically the term “binder” used herein means the silyl ester copolymer along with any rosin which may be included.

Detailed description of invention

The antifouling coating composition of the invention comprises a silyl ester copolymer which includes the comonomers ethyl diethyleneglycol acrylate (EDEGA) and triisopropyl silyl (meth)acrylate, i.e. TISMA or TISA, preferably TISMA. Additional silyl (meth)acrylate comonomers, hydrophilic (meth)acrylate comonomers and/or non-hydrophilic (meth)acrylate comonomers may additionally be present, these terms being defined herein.

Silyl ester copolymer

The silyl ester copolymer includes at least the comonomers triisopropylsilyl (meth)acrylate, e.g. TISMA, and ethyl diethyleneglycol acrylate (EDEGA), but may contain additional silyl (meth)acrylate comonomers, hydrophilic (meth)acrylate comonomers and/or non-hydrophilic (meth)acrylate comonomers as described herein.

Where a mol% of a given comonomer in the silyl ester copolymer is given, the mol% is relative to the sum total (mol) of each comonomer present in the copolymer. Thus if TISMA and EDEGA are the only comonomers in the silyl ester copolymer, the mol% of TISMA is calculated as (TISMA (mol) / (TISMA (mol) + EDEGA (mol))) x 100%. If only TISMA, EDEGA and methyl methacrylate (MMA) are present, the mol% of TISMA is calculated as (TISMA (mol) / (TISMA (mol) + EDEGA (mol) + MMA (mol))) x 100%. Percentages by weight of the copolymer are calculated analogously. Preferably the copolymer is >90 wt%, preferably >95 wt%, especially >98 wt% of silyl (meth)acrylate, hydrophilic (meth)acrylate and non-hydrophilic (meth)acrylate comonomers.

Component (i) is ethyl diethyleneglycol acrylate (EDEGA) which has the structure below:

Component (i) preferably forms 2 to 40 mol% of the copolymer, preferably 2 to 30 mol% of the copolymer, especially 5 to 30 mol% of the copolymer, more especially 5 to 25 mol%.

The EDEGA used to prepare the silyl ester copolymer is preferably employed at a purity of > 90 %, preferably > 95 % or especially > 97%. It is believed that the use of a higher purity EDEGA offers certain advantages in terms of the end properties of the dried composition.

Component (ii) is triisopropylsilyl (meth)acrylate, preferably (TISMA), which preferably forms 5 to 60 mol% of the copolymer, preferably 15 to 50 mol%, especially 20 to 45 mol%.

The ratio (i);(ii) (mol/mol) is preferably in the range of 5:95 to 60:40, preferably in the range of 10:90 to 50:50, especially in the range of 20:80 to 50:50, most preferably in the range of 30:70 to 50:50. In one embodiment, it is preferred that the molar amount of (ii) in the copolymer is the same as or greater than the molar amount of (i) in the copolymer.

The amount of (i)+(ii) in the copolymer is preferably at most 85 wt%, such as at most 80 wt%, especially at most 78 wt%. The amount of (i)+(ii) in the copolymer may be in the range of 30-85 wt% or 40-80 wt%.

The amount of (i)+(ii) in the copolymer is preferably at most 75 mol%, such as at most 70 mol%, especially at most 65 mol%. The amount of (i)+(ii) in the copolymer may be in the range 30-75 mol%, such as 35-70 mol%, or especially 35-65 mol%.

Additional hydrophilic (meth)acrylate comonomer(s)

In certain embodiments the copolymer may include one or more additional comonomers of Formula (I):

wherein R is H or CH3, and R is a C3-C18 substituent containing at least one oxygen or nitrogen atom, preferably at least one oxygen atom, with the proviso that the comonomer of Formula (I) is not EDEGA (this is counted separately as component (i)). As used herein, this structure defines a “hydrophilic” (meth)acrylate comonomer.

As indicated in the above formula, the term “hydrophilic (meth)acrylate” requires the R group in Formula (I) to include at least one oxygen or nitrogen atom, preferably at least one oxygen atom. As explained in detail below, additional non-hydrophilic (meth)acrylate comonomers may also be present, in which the R unit consists of C and H atoms only.

In an embodiment, the silyl ester copolymer contains at least one comonomer of Formula (I) above in which the R group is of formula (CH2CH2O)n-R where R

is a Cl-CIO hydrocarbyl substituent, preferably a Cl-CIO alkyl or C6-C10 aryl substituent, and n is an integer in the range of 1 to 6, preferably 1 to 3. Preferably R is of formula (CH2CH2O)n-R where R is a Cl-CIO alkyl substituent, preferably CH3 or CH2CH3, and n is an integer in the range of 1 to 3, preferably 1 or 2.

In an embodiment, the silyl ester copolymer includes one or more of methoxyethyl methacrylate (MEMA), methoxyethyl acrylate (MEA) and ethoxyethyl methacrylate (EEMA).

In an embodiment, the silyl ester copolymer contains at least one comonomer of Formula (I) above in which the R group is a saturated cyclic group containing at least one oxygen or nitrogen atom, preferably at least one oxygen atom. More preferably, R2 is a group W-R10 wherein R10 is a cyclic ether (such as oxolane, oxane, di oxolane, dioxane optionally alkyl substituted) and W is a C1-C4 alkylene, most preferably tetrahydrofurfuryl acrylate (THFA) having the structure below:

Particularly preferred amounts of hydrophilic (meth)acrylate of Formula (I), where present, are 2 to 25 mol%, preferably 2 to 20 mol%, such as 5 to 15 mol%. Where a mixture of comonomers of Formula (I) are present, these amounts relate to the combined mole fraction of the comonomers of Formula (I) in the copolymer,

Where a comonomer of Formula (I) is present, particularly preferred comonomer(s) include methoxyethyl methacrylate (MEMA), methoxyethyl acrylate (MEA), ethoxyethyl methacrylate (EEMA), tetrahydrofurfuryl acrylate (THFA), tetrahydrofurfuryl methacrylate (THFMA), and ethyl diethyleneglycol methacrylate (EDEGMA).

In a preferred embodiment the copolymer does not contain any significant amount of comonomers of Formula (I), i.e. the copolymer contains less than 10 mol% of such hydrophilic comonomers, especially less than 5 mol% of such comonomers, especially less than 2 mol% of such comonomers.

Additional non-hydrophilic (meth)acrylate comonomer(s)

The silyl ester copolymer may include one or more additional non-hydrophilic (meth)acrylate comonomers of Formula (II)

wherein R is H or CH3, and R is a C1-C8 hydrocarbyl substituent, preferably a Cl-8 alkyl substituent, most preferably methyl, ethyl, n-propyl, n-butyl or 2-ethylhexyl. Comonomers according to Formula (II) are referred to as “non-hydrophilic” comonomers herein.

In all embodiments of the invention the silyl ester copolymer preferably includes at least one additional non-hydrophilic methacrylate and/or non-hydrophilic acrylate comonomer. Where one or more non-hydrophilic (meth)acrylate comonomers are present, the sum of these (meth)acrylate comonomers in the silyl ester copolymer is preferably at most 80 mol%, preferably no more than 70 mol%, such as in the range of 20 to 70 mol%, such as in the range of 30 to 60 mol%, especially in the range of 35 to 60 mol%.

In a preferred embodiment the comonomers TISMA, EDEGA and any non-hydrophilic (meth)acrylate comonomer(s) according to Formula (II) together form >80 mol%, preferably >85 mol%, especially >90 mol% of the comonomers in the silyl ester copolymer.

In a preferred embodiment the silyl ester copolymer includes one or more of the non-hydrophilic comonomers methyl methacrylate (MMA) and/or n-butyl acrylate (n-BA).

In all embodiments of the invention it is preferred that methyl methacrylate (MMA) is included in addition to TISMA and EDEGA. Where present, MMA is preferably present in an amount of 10 to 70 mol%, preferably 30 to 60 mol% of the copolymer. In a preferred embodiment TISMA, EDEGA and MMA together form >80 mol%, preferably >85 mol%, especially >90 mol% of the comonomers in the silyl ester copolymer.

In a particularly preferred embodiment the copolymer includes 20 to 60 mol% of TISMA, 2 to 40 mol% of EDEGA and 10 to 70 mol% of MMA; especially 20 to 50 mol% of TISMA, 5 to 30 mol% of EDEGA, and 30 to 60 mol% of MMA.

In these embodiments additional silyl (meth)acrylate, hydrophilic (meth)acrylate and/or non-hydrophilic (meth)acrylate comonomers may be included.

Where present, n-BA is preferably present in an amount of 2 to 20 mol%, especially 2 to 15 mol%.

In an embodiment the silyl ester copolymer includes the comonomers TISMA, EDEGA, MMA and at least one hydrophilic or non-hydrophilic (meth)acrylate comonomer. In an embodiment the silyl ester copolymer comprises, consists or consists essentially of the monomers: TISMA, EDEGA, MMA; TISMA, EDEGA, MMA and n-BA; or TISMA, EDEGA , MMA, n-BA and THFA.

Additional silyl (meth)acrylate comonomers

The silyl ester copolymer may include additional silyl (meth)acrylate comonomers. Where present, any additional silyl (meth)acrylate comonomer other than triisopropylsilyl (meth)acrylate preferably forms no more than 10 mol% of the copolymer, preferably no more than 5 mol% of the copolymer. Where present, suitable silyl (meth)acrylate comonomers are preferably of Formula (III) wherein

R4 and R5 are each independently selected from linear or branched Cw alkyl groups; 6 V 8 R , R and R are each independently selected from the group consisting of linear or branched C1-C20 alkyl groups, C3-C12 cycloalkyl groups, optionally substituted C6-C20aryl groups and -OSi(R9)3 groups; each R9 is independently a linear or branched C1-C4 alkyl groups, n is an integer from 0 to 5; X is an ethylenically unsaturated group, such as acryloyloxy group, methacryloyloxy group, (methacryloyloxy)alkylenecarbonyloxy group and

(acryloyloxy)alkylenecarbonyloxy group. It will be appreciated that triisopropyl silyl (meth)acrylate should be regarded as excluded from Formula (III) as it is iinherently present in the copolymer..

The term "alkyl" is intended to cover both linear or branched alkyl groups such as methyl, ethyl, isopropyl, propyl and butyl. Particularly preferred cycloalkyl groups include cyclohexyl and substituted cyclohexyl.

Examples of the substituted aryl groups include aryl groups substituted with at least one substituent selected from halogens, alkyl groups having 1 to about 8 carbon atoms, acyl groups, or a nitro group. Particularly preferred aryl groups include substituted and unsubstituted phenyl, benzyl, phenalkyl or naphthyl.

Ideally, preferred silyl ester monomers are based on compounds of Formula (III) in which n is 0, i.e. those of formula X-SiR6R7R8.

Examples of monomers containing silyl ester functionality are well known. Monomers as defined by the general Formula (III) include: silyl ester monomers of acrylic acid and methacrylic acid, such as triethylsilyl (meth)acrylate, tri-n-propylsilyl (meth)acrylate, tri-n-butylsilyl (meth)acrylate, triisobutylsilyl (meth)acrylate, tri-/c/7-butyl silyl (meth)acrylate, tri-sec-butylsilyl (meth)acrylate, tri-n-pentylsilyl (meth)acrylate, triisopentylsilyl (meth)acrylate, tri-n-hexylsilyl (meth)acrylate, tri-n-octylsilyl (meth)acrylate, tri-n-dodecylsilyl (meth)acrylate, triphenyl silyl (meth)acrylate, tri-(p-methylphenyl)silyl (meth)acrylate, tribenzylsilyl (meth)acrylate, ethyldimethylsilyl (meth)acrylate, n-propyldimethylsilyl (meth)acrylate, isopropyldimethylsilyl (meth)acrylate, n-butyldimethylsilyl (meth)acrylate, isobutyldimethylsilyl (meth)acrylate, tert-butyldimethylsilyl (meth)acrylate, n-pentyldimethylsilyl (meth)acrylate, n-hexyldimethylsilyl (meth)acrylate, neohexyldimethylsilyl (meth)acrylate, thexyldimethylsilyl (meth)acrylate, n-octyldimethylsilyl (meth)acrylate, n-decyldimethylsilyl (meth)acrylate, dodecyldimethylsilyl (meth)acrylate, n-octadecyldimethylsilyl (meth)acrylate, cyclohexyldimethylsilyl (meth)acrylate, phenyldimethylsilyl (meth)acrylate, benzyldimethylsilyl (meth)acrylate, phenethyldimethylsilyl (meth)acrylate, (3-phenylpropyl)dimethylsilyl (meth)acrylate, p-tolyldimethylsilyl (meth)acrylate, isopropyldiethylsilyl (meth)acrylate, n-butyldiisopropylsilyl (meth)acrylate, n-octyldiisopropylsilyl (meth)acrylate, methyldi-n-butylsilyl (meth)acrylate, methyldicyclohexylsilyl (meth)acrylate, methyldiphenylsilyl (meth)acrylate, fert-butyldiphenylsilyl (meth)acrylate, nonamethyltetrasiloxy_(meth)acrylate, bis(trimethylsiloxy)methylsilyl (meth)acrylate, tris(trimethylsiloxy)silyl (meth)acrylate_and others as described in W02014/064048 and W003/080747.

Where the silyl ester copolymer comprises triisopropylsilyl acrylate, it may additionally contain triisopropylsilyl methacrylate and vice versa. Formula (III) above is intended to cover the presence of silyl ester comonomers other than triisopropylsilyl acrylate and triisopropylsilyl methacrylate.

Properties of the silyl ester copolymer

The polymer containing organosilyl ester groups can be obtained by polymerizing a monomer mixture in the presence of a polymerization initiator by any of various methods such as solution polymerization, bulk polymerization, emulsion polymerization, and suspension polymerization in a conventional way or by controlled polymerization techniques. In preparing a coating composition using this polymer containing organosilyl ester groups, the polymer is preferably diluted with an organic solvent to give a polymer solution having an appropriate viscosity. From this standpoint, it is desirable to employ solution polymerization.

Examples of the polymerization initiators include azo compounds such as azo compounds such as dimethyl 2,2’-azobis(2-methylpropionate), 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(isobutyronitrile) and 1,1'- azobis(cyanocyclohexane) and peroxides such as fe/7-butyl peroxypivalate, tert-butyl peroxy-2-ethylhexanoate, /c/V-butyl peroxydiethylacetate, fe/7-butyl peroxyisobutyrate, di-fe/7-butyl peroxide, /c/7-butyl peroxybenozate, and /t'/7-butyl peroxyisopropylcarbonate, fe/7-amyl peroxypivalate, /y/y-amyl peroxy-2-ethylhexanoate, l,l-di(fe/7-amyl peroxy)cyclohexane and dibenzoyl peroxide. These compounds are used alone or as a mixture of two or more thereof.

Examples of the organic solvent include aromatic hydrocarbons such as xylene, toluene, mesitylene; ketones such as methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, methyl isoamyl ketone, cyclopentanone, cyclohexanone; esters such as butyl acetate, tert-butyl acetate, amyl acetate, ethylene glycol methyl ether acetate; ethers such as ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dibutyl ether, dioxane, tetrahydrofuran, alcohols such as n-butanol, isobutanol, benzyl alcohol; ether alcohols such as butoxyethanol, l-methoxy-2-propanol; aliphatic hydrocarbons such as white spirit; and optionally a mixture of two or more solvents. These compounds are used alone or as a mixture of two or more thereof. The copolymer is preferably a random copolymer.

The thus-obtained polymer containing organosilyl ester groups preferably has a weight-average molecular weight of from 5,000 to 70,000, preferably of from 10,000 to 60,000. Mw is measured as described in the examples section.

The silyl ester copolymer may be provided as a polymer solution. The polymer solution is desirably regulated so as to have a solid content of from 30 to 90% by weight, preferably from 40 to 85% by weight, more preferably from 47 to 75% by weight.

The final antifouling coating composition of the invention preferably comprises 0.5 to 45 wt% (dry solids) of the silyl ester copolymer, such as 1.0 to 30 wt%, in particular 5 to 25 wt% based on the total coating composition.

The copolymer preferably has a glass transition temperature (Tg) of at least 15 °C, preferably at least 20 °C, such as at least 22 °C, all values being measured according to the Tg test described in the examples section. Values less than 80°C are preferred, such as less than 75°C, e g. less than 50°C.

An antifouling coating composition of the invention may optionally comprise a mixture of the silyl ester copolymer of the invention and other silyl ester copolymers, for example as described in US 4,593,055, EP 0 646 630, WO 2009/007276 and EP 2 781 567.

Rosin component

Rosin can be used to adjust the self-polishing properties and the mechanical properties of the antifouling coating film. Antifouling coating compositions of the invention preferably comprise at least 0.5 wt% (dry solids) rosin, such as at least 1 wt%. The upper limit for rosin components may be 25 wt%, such as 15 wt%.

The rosin of use in the invention can be a rosin or derivative thereof such as a salt thereof e.g. as described below. Examples of rosin materials include wood rosin, tall oil rosin and gum rosin; rosin derivatives such as hydrogenated and partially hydrogenated rosin, disproportionated rosin, dimerised rosin, polymerised rosin, maleic acid esters, fumaric acid esters, glycerol esters, methyl esters, pentaerythritol esters and other esters of rosin and hydrogenated rosin, copper resinate, zinc resinate, calcium resinate, magnesium resinate and other metal resinates of rosin and polymerised rosin and others as described in WO 97/44401. Preferred are gum rosin and derivatives of gum rosin.

In the present invention, the antifouling composition as a whole preferably comprises 0.5 to 25 wt%, preferably 1 to 15 wt% (dry solids) of a rosin material, preferably 2 to 7 wt% (dry solids).

The properties of the antifouling coating can be tuned by varying the relative amounts of silyl ester copolymer and rosin components.

In a preferred embodiment therefore the invention provides a binder comprising a silyl ester copolymer as hereinbefore defined and a rosin or derivative thereof.

Other Binder components

In addition to the silyl ester copolymer and optionally the rosin, an additional binder can be used to adjust the properties of the antifouling coating film. Examples of binders that can be used in addition to the silyl ester copolymers and rosins of the invention include: 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 hydroxyl residue, for example as described in GB 2 311 070 and EP 0 982 324; or amine for example as described in EP 0 529 693; hydrophilic copolymers for example (meth)acrylate copolymers as described in GB 2 152 947 and poly(7V-vinyl pyrrolidone) copolymers and other copolymers as described in EP 0 526 441; (meth)acrylic polymers and copolymers, in particular acrylate binders, such as poly(7/-butyl acrylate), poly(//-butyl acrylate-co-isobutyl vinyl ether) and others as described in W003/070832 and EP2128208; vinyl ether polymers and copolymers, such as poly(methyl vinyl ether), poly(ethyl vinyl ether), poly(isobutyl vinyl ether), poly(vinyl chloride-co-isobutyl vinyl ether); aliphatic polyesters, such as poly(lactic acid), poly(glycolic acid), poly(2-hydroxybutyric acid), poly(3-hydroxybutyric acid), poly(4-hydroxyvaleric acid), polycaprolactone and aliphatic 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, provided that the metal is not copper; alkyd resins and modified alkyd resins; hydrocarbon resin, e.g. as described in WO2011/092143, such as hydrocarbon resin formed only from the polymerisation of at least one monomer selected from a C5 aliphatic monomer, a C9 aromatic monomer, an indene coumarone monomer, or a terpene or mixtures thereof; polyoxalates as described in W02009/100908 and other condensation polymers as described in WO 96/14362.

If, in addition to the rosin and silyl ester copolymer, a further binder is present, the weight ratio of silyl copolymer(s) : binder may range from 30:70 to 95:5, preferably from 40:60 to 80:20, especially 50:50 to 70:30. These preferred ratios relate to the amount of silyl copolymer(s) and additional binder only, i.e. the rosin is not included.

Especially suitable additional binders are (meth)acrylic polymers and copolymers.

Biocide

The antifouling coating additionally comprises a compound capable of preventing or removing marine fouling on or from a surface. Traditionally an antifouling coating composition contains copper biocides such as metallic copper, cuprous oxide, copper thiocyanate and the like.

The cuprous oxide material has a typical particle diameter distribution of 0,1 -70 μι» and an average particle size (d50) of 1--25 um. The cuprous oxide material may content a stabilizing agent (to prevent surface oxidation). Examples of commercial available cuprous oxide include Nordox'i' Cuprous Oxide Red Paint Grade, Nordox® XLT froraNordox AS, Cuprous oxide from Furukawa Chemicals Co., Ltd.; Red Copp 97N, Purple Copp. Lolo Tint 97N, Chemet CDC, Chemet LD from American Chemet Corporation; Cuprous Oxide Red from Spiess-LJrania; Cuprous oxide Roast, Cuprous oxide Electrolytic froinTaixing Smelting Plant Co., Ltd. A series of organic biocides can be used instead of copper biocides such as 4- [l ~(2,3~dimethylphenvl)ethyl ]-1 Fi-imidazole [medetomidine] and 4-bromo-2-(4-chlorophenyl)-5-(triiluoromethyl)’ I H-pyrrole-3-carbonitriie [tralopyrii]. Any known biocide can be used in the invention. The terms antifouling agent, antifoulant, biocide, toxicant are used in the industry to describe known compounds that act to prevent marine fouling on a surface. The antifouling agents of the invention are marine antifouling agents.

The coating composition may include a copper biocide, preferably cuprous oxide (CU2O) and/or copper pyrithione. The coating, compositions of the invention may contain other biocides such as described in WO201 -4/0640-18. Preferred biocides are cuprous oxide, copper thiocyanate, zinc pyrithione, copper pyrithione, zinc ethylenebis(dithiocarbamate) [zineb], 2-(/e/7-butvlamino)-4- icyclopropylarainoJ“6-(methylthio)-U,5'triaz.iue [cubuirynej, 4.5-dichloro-2-n-octyl-4-isothiazolin-3-one [DCOIT], N-dicblorofluoromethyi{hio-N',Ni-dimetbyl.-N-phenylsulfamide [dlcblorofluanidl. N-dSchk»rotluoromethyiihio-N!,N'-dimethyl-N-p-tolyIsulfamide itolyliluanid 1. 4 11 -{2.3-dimethyIpbeny 1 lethyi]-1 id-imidazole [medetomidine], triphenvlborane pyridine [TPBP] and 4-bromo-2~(4-ehlorophenyl)« 5- (t.rifluoromethylI-1 H-pyrroie-e-earbonitrile [tralopyrii]. A mixture of biocides can be used as is known in the art as different biocides operate against different marine fouling organisms. in an alternative embodiment the antiibuling coating is copper free, In this embodiment, a preferred biocide combination involves a combination of tralopyrii and one or more selected from zinc pyrithione, 4,5-dichloro-2-octyl-4-isothiazolin-3-one.

Where present, the combined amount of biocides may form up to 70 wt% of the coating composition, such as 4 to 60 wt%, e.g. 5 to 60 wt%. Where copper is present, a suitable amount of biocide might be 20 to 60 wt% in the coating composition. Where copper is avoided, lower amounts might be used such as 0.1 to 20 wt%, e.g. 0.2 to 15 wt%. It will be appreciated that the amount of biocide will vary depending on the end use and the biocide used.

Some biocides may be encapsulated or adsorbed on an inert carrier or bonded to other materials for controlled release. These percentages refer to the amount of active biocide present and not therefore to any carrier used.

Other components

In addition to the silyl ester copolymer and any of the optional components described above, the antifouling coating composition according to the present invention may optionally further comprise one or more components selected among other binders, inorganic or organic pigments, extenders and fillers, additives, solvents and thinners.

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

Examples of extenders and fillers are minerals such as dolomite, plastorite, calcite, quartz, barite, magnesite, aragonite, silica, wollastonite, talc, chlorite, mica, kaolin and feldspar; synthetic inorganic compounds such as calcium carbonate, magnesium carbonate, barium sulphate, calcium silicate and silica; polymeric and inorganic microspheres such as uncoated or coated hollow and solid glass beads, uncoated or coated hollow and solid ceramic beads, porous and compact beads of polymeric materials such as poly(methyl methacrylate), poly(methyl methacrylate-co-ethylene glycol dimethacrylate), poly(styrene-co-ethylene glycol dimethacrylate), poly(styrene-co-divinylbenzene), polystyrene, poly(vinyl chloride).

Examples of additives that can be added to an antifouling coating composition are reinforcing agents, thixotropic agents, thickening agents, antisettling agents, wetting and dispersing agents, plasticizers and solvents.

Examples of reinforcing agents are flakes and fibres. Fibres include natural and synthetic inorganic fibres such as silicon-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, polyhydrazide 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 pm and an average thickness of 1 to 50 pm 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 cellulose, aluminium stearates and mixtures thereof.

Examples of plasticizers are chlorinated paraffins, phthalates, phosphate esters, sulphonamides, adipates and epoxidized vegetable oils.

Examples of dehydrating agents and drying agents include anhydrous calcium sulphate, calcium sulphate hemihydrate, anhydrous magnesium sulphate, anhydrous sodium sulphate, anhydrous zinc sulphate, molecular sieves and zeolites; orthoesters such as trimethyl orthoformate, triethyl orthoformate, tripropyl orthoformate, triisopropyl orthoformate, tributyl orthoformate, trimethyl orthoacetate and triethyl orthoacetate; ketals; acetals; enolethers; orthoborates such as trimethyl borate, triethyl borate, tripropyl borate, triisopropyl borate, tributyl borate and tri-terZ-butyl borate; silicates such as trimethoxymethyl silane, tetraethyl silicate and ethyl polysilicate; and isocyanates, such as p-toluenesulfonyl isocyanate.

The preferred dehydrating agents and drying agents are silicates and the inorganic compounds.

Examples of stabilizers that contribute to the storage stability of the antifouling coating composition are carbodiimide compounds, such as bis(2,6- dii sopropylphenyl)carbodiimide and poly(1,3,5 -trii sopropylphenylene-2,4-carbodiimide) and others as described in patent EP 2725073.

In general, any of these optional components can be present in an amount ranging from 0.1 to 20 wt%, typically 0.5 to 20 wt%, preferably 0.75 to 15 wt% of the antifouling 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 antifouling composition contains a solvent. This solvent is preferably volatile and is preferably organic. Examples of organic solvents and thinners are aromatic hydrocarbons such as xylene, toluene, mesitylene; ketones such as methyl ethyl ketone, methyl isobutyl ketone, methyl isoamyl ketone, methyl amyl ketone, diisobutyl ketone, methyl propyl ketone, cyclopentanone, cyclohexanone; esters such as butyl acetate, tert-butyl acetate, amyl acetate, isoamyl acetate, ethylene glycol methyl ether acetate, propyl propionate, butyl propionate; ethers such as ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dibutyl ether, dioxane, tetrahydrofuran; alcohols such as //-butanol, isobutanol, benzyl alcohol; ether alcohols such as butoxy ethanol, l-methoxy-2-propanol; aliphatic hydrocarbons such as white spirit; and optionally a mixture of two or more solvents and thinners.

Preferred solvents are aromatic solvents, especially xylene and mixtures of aromatic hydrocarbons.

The amount of solvent is preferably as low as possible. 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 15 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-solvent for the fdm-forming components in the coating composition or in an aqueous dispersion.

The antifouling coating composition of the invention should preferably have solids content above 40 vol%, e.g. above 45 % by volume, such as above 50 vol%, preferably above 55 vol%.

More preferably the antifouling coating composition should have a content of volatile organic compounds (VOC) below 500 g/L, preferably below 400 g/L, e.g. below 390 g/L. VOC content can be calculated (ASTM D5201-01) or measured, preferably measured.

The antifouling 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 swell). The object surface will typically be the hull of a vessel or surface of a fixed marine object such as an oil platform or buoy. Application 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 will need to be separated from the seawater to allow coating. The application of the coating can be achieved as conventionally known in the art.

When applying the antifouling coating to an object (e.g a ship hull) the surface of the object is typically not protected solely by a single coat of antifouling. Depending on the nature of the surface the antifouling coating can be applied directly to an existing coating system. Such a coating system may comprise several layers of paint of different generic types (e.g. epoxy, polyester, vinyl or acrylic or mixtures thereof). If the surface is a clean and intact antifouling coating from a previous application, the new antifouling paint can be applied directly, typically as one or two coats with more in exceptional cases.

Alternatively, the artisan may start with an uncoated surface (e.g. steel, aluminium, plastic, composite, glass fiber or carbon fiber). To protect such a surface, the full coating system will typically comprise one or two layers of an anticorrosive coating, one layer of tie-coat and one or two layers of antifouling paint. The person skilled in the art will be familiar with these coating layers.

In exceptional cases additional antifouling paint layers may be applied.

In a further embodiment therefore the invention provides a substrate having coated thereon an anticorrosive coating layer such as an epoxy primer, a tie layer and an antifouling coating composition as herein defined.

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

Materials and methods

.Qenemiprocedum A quantity of solvent is charged to a temperature-controlled reaction vessel equipped with a stirrer, a condenser, a nitrogen inlet and a .feed inlet The reaction vessel is heated and maintained at. the reaction temperature given in Table 1. A pre-mix of monomers, initiator and solvent is prepared. The pre-mix is charged to the reaction vessel at a constant rate over 2 hours under a nitrogen atmosphere. After a further I hour the reaction vessel is maintained at or heated to the boost reaction temperature given in Table 1. Then a post-addition of a boost initiator solution is added to the reaction mixture. T he reaction is kept at the given temperature for a further 2 hours and is then cooled to room temperature.

Dctcrminniion of polymer solution viscosity

The viscosity of the polymers arc determined in accordance with ASTM D2196-15 Test method A using a Brookfield® DV-I viscometer with LV-2 or I..V-4 spindle at 12 rpm. The polymers are tempered to 23.0c'C ± 0.5°C before the measurements.

Determination of non-volatile matter content of the polymer solutions

The non-volatile matter content of the polymer solutions are determined in accordance with ISO 3251. A test sample of 0.5 g ± 0.1 g are taken out and dried in a ventilated oven at 150°C for 30 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 pm Mixed-D columns from Polymer Laboratories in series, tetrahydrofuran (THF) as eluent at ambient temperature and at a constant flow rate of 1 mL/min and with a refractive index (RI) 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. Before analysis the samples were filtered through 0.45 pm Nylon filters. The weight-average molecular weight (Mw), the number-average molecular weight (Mn) and the polydispersity index (PDI), given as 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 transfer of a small amount of polymer solution to an aluminium pan and dry the samples for minimum 10 h at 50°C with subsequent 3 h at 150°C The samples of approx. 10 mg dry polymer material were measured in open aluminium pans and scans were recorded at a heating rate of 10°C/min and cooling rate of 10°C/min with an empty pan as reference. The data were processed using Universal Analysis software from TA

Instruments. The inflection point of the glass transition range, as defined in ASTM El 3 56-08, of the second heating is reported as the Tg of the polymers.

General procedure for preparation of antifouling coating compositions

The components were mixed in the proportions given in Table 2. The mixture was dispersed in the presence of glass beads (approx. 2mm in diameter) in a paint can of 250 ml using a vibrational shaker for 15 minutes. The glass beads were filtered of before testing.

Determination of paint viscosity using Cone and Plate viscometer

The viscosity of the antifouling paint compositions are determined according to ISO 2884-1:1999 using a digital Cone and Plate viscometer set at a temperature of 23°C, working at a shear rate of 10000 s'1 and providing viscosity measurement range of 0-10 P. The result is given as the average of three measurements.

Calculation of the volatile organic compound (VOC) content of the antifouling coating composition

The volatile organic compound (VOC) content of the antifouling coating composition is calculated in accordance with ASTM D5201.

Determination of the polishing rates of antifouling coating films on rotating disc in seawater

The polishing rate is determined by measuring the reduction in film thickness of a coating film over time. For this test PVC discs are used. The coating compositions are applied as radial stripes on the disc using a film applicator. The thickness of the dry coating films are measured by a surface profiler. The PVC discs are mounted on a shaft and rotated in a container in which seawater is flowing through. The speed of the rotated shaft are giving an average simulated speed of 16 knots on the disc. Natural seawater 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 allowed to dry overnight at room temperature before measuring the film thickness.

Table 1. Details of the silyl ester copolymer solutions Si to Si 1 and Cl to C5. Ingredients are given in parts by weight. The monomer compositions are also given in parts by mol [in brackets].

Claims

Claims

1. A silyl ester copolymer comprising as comonomers: (i) ethyl diethyleneglycol acrylate (EDEGA); and (ii) triisopropyl silyl (meth)acrylate; preferably wherein the ratio of (i):(ii) in the copolymer is in the range of 5:95 to 60:40 (mol/mol).
2. A silyl ester copolymer as claimed in claim 1 wherein component (ii) is triisopropyl silyl methacrylate (TISMA).
3. A silyl ester copolymer according to any of claims 1 to 2 wherein the amount of (i) in the silyl ester copolymer is in the range of 2 to 40 mol%, preferably in the range of 2 to 30 mol%, more preferably in the range of 5 to 25 mol%.
4. A silyl ester copolymer according to any of claims 1 to 3 wherein the amount of (ii) in the silyl ester copolymer is in the range of 5 to 60 mol% of the copolymer, preferably 15 to 50 mol%, especially 20 to 45 mol%.
5. A silyl ester copolymer according to any of claims 1 to 4 wherein the silyl ester copolymer further comprises one or more hydrophilic comonomers of Formula (I):

wherein R is H or CH3, and R is a C3-C18 substituent with at least one oxygen or nitrogen atom, preferably at least one oxygen atom, with the proviso that the hydrophilic comonomer of formula (I) is not EDEGA.
6. A silyl ester copolymer according to claim 5 wherein one or more of said 2 3 3 hydrophilic comonomers includes an R group of formula (CH2CH2O)n-R where R

is a Cl-CIO alkyl or C6-C10 aryl substituent and n is an integer in the range of 1 to 6. preferably 1 to 3, with the proviso that the comonomer is not EDEGA.
7. A silyl ester copolymer according to claim 5 or 6 wherein one or more hydrophilic comonomer(s) are present and have an R group of formula (CH2CH2O)n-R where R is an alkyl substituent, preferably CH3 or CH2CH3, and n is an integer in the range of 1 to 3, preferably 1 or 2, with the proviso that the comonomer is not EDEGA.
8. A silyl ester copolymer according to any preceding claim further comprising one or more of methoxy ethyl methacrylate (MEMA), methoxy ethyl acrylate (MEA), ethoxyethyl methacrylate (EEMA) and tetrahydrofurfuryl acrylate (THFA).
9. A silyl ester copolymer according to any preceding claim further comprising one or more non-hydrophilic comonomers of Formula (II):

wherein R is H or CH3, and R is a C1-C8 hydrocarbyl substituent, preferably an C1-C8 alkyl substituent, most preferably methyl, ethyl, n-propyl, 2-ethylhexyl or n-butyl.
10. A silyl ester copolymer according to claim 9 comprising one or more of methyl methacrylate (MMA) and n-butyl acrylate (n-BA).
11. A silyl ester copolymer according to any of claims 1 to 10 including MMA as a comonomer in an amount of 10 to 70 mol%, preferably 30 to 60 mol%.
12. A silyl ester copolymer according to any of claims 1 to 11 including n-butyl acrylate (n-BA) as a comonomer in an amount of 2 to 20 mol%, preferably 2 to 15 mol%.
13. A silyl ester copolymer according to any of claims 1 to 12 wherein said silyl ester copolymer comprises, consists essentially of, or consists of the comonomers TISMA, EDEGA and: a. MMA; b. MMA and n-BA; or c. MMA, n-BA and THFA.
14. A binder for an anti-fouling coating composition comprising a silyl ester copolymer as claimed in any of claims 1 to 13 and a rosin or derivative thereof.
15. An antifouling coating composition comprising a copolymer according to any of claims 1 to 13 and at least one antifouling agent.
16. An antifouling coating composition according to claim 15, wherein said antifouling agent comprises cuprous oxide and/or copper pyrithione.
17. A process for protecting an object from fouling, said process comprising coating at least a part of said object which is subject to fouling with an antifouling coating composition as claimed in any of claims 15 to 16.
18. An object coated with the antifouling coating composition as claimed in any of claims 15 to 16.
19. An object as claimed in claim 18 wherein the object is coated with an anticorrosive coating layer, a tie layer and an antifouling coating composition as claimed in claim 15 to 16.
20. An object as claimed in claim 18 wherein the object is coated with an antifouling coating composition as claimed in claims 15 or 16 which covers a preexisting antifouling coating composition on the substrate.