WO2023275145A1

WO2023275145A1 - Novel coatings with low adhesion to ice

Info

Publication number: WO2023275145A1
Application number: PCT/EP2022/067900
Authority: WO
Inventors: Morten Martinsen; Jakob Stensgaard DIGET; Kim Oeberg HED
Original assignee: Jotun A/S
Priority date: 2021-06-30
Filing date: 2022-06-29
Publication date: 2023-01-05

Abstract

An ice mitigating coating composition comprising: (I) at least 25 wt% dry weight of one or more curable organic polymers comprising less than 20 wt% polysiloxane monomer residues; (II) 5 to 20 wt% of an ice mitigating copolymer comprising: A) at least 30 wt% of a (meth)acrylate functional, (meth)acrylamide functional or vinyl functional polysiloxane monomer residue or mixture thereof; B) at least 10 wt% of a (meth)acrylate functional, (meth)acrylamide functional or vinyl functional alkyl monomer residue, alkoxy substituted alkyl monomer residue or aryl monomer residue or a mixture thereof and C) 0 to 40 wt% of a (meth)acrylate functional, (meth)acrylamide functional or vinyl functional poly(alkylene glycol) monomer residue or mixture thereof; and (III) one or more curing agents.

Description

153884/01/P1909 Novel coatings with low adhesion to ice

Field of the invention

The invention relates to an ice mitigating copolymer and the use of that copolymer to prepare a coating composition to prevent or reduce the adhesion of ice to a surface.

The invention also relates to a method of preparing such an ice mitigating copolymer and a coating and to a structure coated with such a coating.

Background

Atmospheric icing on industrial structures and infrastructure such as wind turbine blades, radio towers and shipping vessels can lead to operational down-time and pose a serious health and safety risk. This challenge has been addressed using differing approaches. These approaches are generally based on ice-release or ice-removal, or avoiding ice-build up (anti-icing) in the first place.

The strategies for handling icing on horizontal and vertical surfaces can be divided into two categories: active and passive ice removal. The former relies on an external input, which may be heating of the surface to be protected or mechanical and/or chemical removal of ice.

The latter approach involves coatings or surface modifications on the substrate to ensure that ice does not form or to ensure that the adhesion of ice to the surface is sufficiently low that ice on the coated surface is removed under gravity or by wind.

The passive anti-icing approach is the more attractive strategy with regard to complexity, cost and environmental impact. However, the challenge of designing a coating or surface with durable anti-icing properties has proved difficult due to different icing phenomena. The state-of-the-art anti-icing/ice release solutions suffer from a range of draw-backs such as condensation icing issues, depletion of active anti-icing components, problems when exposed to a range of temperature and mechanical durability.

The state-of-the-art low ice adhesion coatings described in the literature utilize the low surface energy of silicone materials and/or the low elastic modulus of the bulk material. The low surface energy decreases the adhesion of ice and the low elastic modulus of the coating works as a crack initiator for the solid ice when a shear force is applied on the ice. This too reduces the ice adhesion. The challenge with this approach is that the low elastic modulus coatings, typically a silicone, do not meet the industry-demand for toughness. Such coatings suffer from irreversible damage by weathering and poor erosion resistance.

Slippery infused porous surfaces (SLIPS) represent another approach with low adhesion to ice, but the oil lubricant required depletes from the coating over time, thus increasing the adhesion of ice over time. Furthermore, when mixing typical lubricant oils, such as unreactive silicones, with commercially available non-porous organic coatings, such as acrylic polyurethane coatings, several critical issues emerge such as loss of adhesion, fisheyes or other non-wetting phenomena and oily surfaces.

The present inventors sought therefore to improve upon state of the art passive ice mitigation solutions. The inventors have found a copolymer which reduces the ice adhesion in a cured coating comprising that copolymer. The copolymer is compatible with other typical components of such an ice preventing composition, e.g. curable organic polymers based on hydroxyfunctional (meth)acrylate polymers.

In one embodiment, the ice mitigating copolymer of the invention has a “bottle brush” structure comprising a polydimethylsiloxane (PDMS) monofunctional (meth)acrylate macromonomer and a low molecular weight alkyl (meth)acrylate and optionally a (methoxy) polyethylene glycol mono(meth)acrylate macromonomer.

We have found that the ice mitigating copolymers of the invention decrease the ice adhesion of cured organic polymer coatings by stratifying to the surface and thus have a small effect of the bulk properties of the coating formulation as demonstrated by the uniaxial elongation results in Table 6 and curves in Figure 2. This enables coatings with low ice adhesion without compromising desirable mechanical properties such as elastic modulus of the cured coating composition. Furthermore, the ice mitigating copolymers have good compatibility with organic polymers such as polyacrylics, polyesters, polycarbonates, polyethers, polyvinyl and polyaspartics and curing agents such as poly iso cyan ate curing agents.

Similar polymers have been disclosed in W02019/101912 in the context of antifouling and fouling release compositions however there is no suggestion that these polymers might have utility in ice mitigation. We have now found however that with an increase in the methyl (meth)acrylate content and/or decrease the PEG content, these copolymers offer ice mitigation properties.

In W02020018768, a dirt mitigating coating is described comprising a first film forming polymer with hydrophobic groups (e.g. PDMS) and reactive functional groups, a second film forming composition with hydrophobic groups, and a curing agent.

The first film forming composition is a free radical polymerized copolymer which in example A-C contains low molecular weight (meth) acrylic monomers including OH- functional (meth) acrylic monomers, and a hydrophobic acrylic monomer where example A contains 4.8wt% PDMSMA, example B contains fluorinated methacrylate and example C contains carboxyl modified PDMS (12.5wt%).

Example D is described as the second film forming composition and contains 23wt% PDMSMA along with hydroxy-functional methacrylate and other (meth)acrylate monomers. There is no disclosure of a minimum of 30 wt% of a (meth)acrylate functional or vinyl functional polysiloxane monomer or mixture thereof.

Summary of the invention

Viewed from one aspect the invention provides an ice mitigating copolymer comprising, such as consisting of:

A) at least 30 wt%, preferably at least 60 wt%, of a (meth)acrylate functional, (meth)acrylamide functional or vinyl functional polysiloxane monomer residue or mixture thereof;

B) at least 10 wt%, such as 20 wt% or more, of a (meth)acrylate functional, (meth)acrylamide functional or vinyl functional alkyl monomer residue, alkoxy substituted alkyl monomer residue or aryl monomer residue or a mixture thereof; and

C) 0 to 40 wt%, preferably 0 to 25 wt% of a (meth)acrylate functional, (meth)acrylamide functional or vinyl functional poly(alkylene glycol) monomer residue or mixture thereof.

Viewed from one aspect the invention provides an ice mitigating copolymer comprising, preferably consisting of:

A) 30 wt% or more, preferably 60 wt% or more, of one or more monomer residues of formula A1 and A2:

in formula (A1) and (A2)

R is selected from H and methyl;

X² is selected from COOR³ or CONHR³;

R³ is selected from substituted or unsubstituted, linear or branched, C1-8 alkylene; 0 is 0 or 1 , preferably 1 ; each R⁴ is independently selected from CM_O alkyl and C_5-10 aryl; and in formula (A1) q is an integer from 1 to 160; and in formula (A2) q is 0 or an integer from 1 to 80,

R⁵ is selected from CMO alkyl, C5-10 aryl or 0-Si(R⁶)3, wherein R⁶ is independently selected from CMO alkyl and C5-10 aryl.

B) 10 wt% or more, such as 20 wt% or more, of one or more monomer residues of formula B

in formula (B)

R is selected from H and methyl;

X³ is selected from R⁷, COOR⁷, CONHR⁷; R⁷ is selected from alkoxy substituted or unsubstituted, linear or branched, Ci-e alkyl or aryl; and

C) 0 to 40 wt%, such as 0 to 25 wt% of one or more monomer residues of formula (C):

wherein in formula (C)

R is selected from H and methyl;

X¹ is selected from COO or CONH; m is 0 or 1 , preferably 1 ;

R¹ is selected from substituted or unsubstituted, linear or branched, Ci-₈ alkylene; n is 0 or 1 ; preferably 1 ; and R² is poly(alkylene oxide).

The term “consisting of’ is used herein to require that the ice mitigating copolymer contains one or more comonomers A), one or more comonomers B) and optionally one or more comonomers C) only. Comonomers such as of 2-(1-pyrrolidonyl))ethyl methacrylate are excluded.

Viewed from another aspect the invention provides an ice mitigating copolymer, preferably non-curable copolymer, comprising:

A) at least 30 wt%, such as at least 60 wt%, of a (meth)acrylate functional, (meth)acrylamide functional or vinyl functional polysiloxane monomer residue or mixture thereof;

B) at least 10 wt% of a (meth)acrylate functional, (meth)acrylamide functional or vinyl functional alkyl monomer residue, alkoxy substituted alkyl monomer residue or aryl monomer residue or a mixture thereof; and

C) 1 to 25 wt% of a (meth)acrylate functional, (meth)acrylamide functional or vinyl functional poly(alkylene glycol) monomer residue or mixture thereof. It is preferred if the ice mitigating copolymer of the invention is non-curable, i.e. it does not react with the curing agent.

Viewed from another aspect the invention provides ice mitigating coating composition comprising:

(I) at least 25 wt% (dry weight) of one or more curable organic polymers comprising less than 20 wt% polysiloxane monomer residues;

(II) an ice mitigating copolymer, e.g. 5 to 20 wt% of an ice mitigating copolymer, comprising, preferably consisting of:

B) at least 10 wt% of a (meth)acrylate functional, (meth)acrylamide functional or vinyl functional alkyl monomer residue, alkoxy substituted alkyl monomer residue or aryl monomer residue or a mixture thereof;

C) 0 to 40 wt%, such as 0 to 25 wt% of a (meth)acrylate functional, (meth)acrylamide functional or vinyl functional poly(alkylene glycol) monomer residue or mixture thereof; and

(III) one or more curing agents.

Viewed from another aspect the invention provides ice mitigating composition comprising:

(I) at least 40 wt% of one or more curable organic polymers;

(II) one or more ice mitigating co-polymers, e.g. 5 to 20 wt% of an ice mitigating copolymer, as hereinbefore defined; and

(III) one or more curing agents.

(I) at least 40 wt% of one or more curable poly(siloxane) free organic polymers; and

(III) one or more curing agents. Viewed from another aspect the invention provides ice mitigating composition comprising:

(I) at least 40 wt% of one or more curable poly(siloxane) free (meth)acrylate polymers; and

(II) one or more ice mitigating co-polymers, e.g. 5 to 20 wt% of an ice mitigating copolymer, as herein before defined; and

(III) one or more curing agents.

Viewed from another aspect, the invention provides a substrate coated with a coating composition as defined herein.

Viewed from another aspect, the invention provides a process for coating a substrate with a coating composition as defined herein comprising spraying the coating composition onto said substrate. The substrate may already have an undercoat such as an epoxy layer undercoat.

Viewed from another aspect, the invention provides a kit for preparing a coating composition as defined herein, comprising:

(i) a first container containing the curable organic polymer or mixture thereof;

(ii) a second container containing a curing agent;

(iii) optionally a third container containing a catalyst if not present within components (i) or (ii); and

(iv) optionally instructions for combining the contents of said containers; wherein the ice mitigating copolymer as defined herein is present in one of containers 1 to 3.

Viewed from another aspect, the invention provides the use of the coating composition of the invention to prevent or reduce the build-up of ice on a substrate.

Viewed from another aspect, the invention provides a method for the prevention or reduction of ice build-up on a substrate comprising applying to said substrate, a coating composition as hereinbefore defined.

Definitions

As used herein the term “polysiloxane” refers to a polymer comprising siloxane, i.e. -Si-O- repeat units.

As used herein the term “bulk polymer” refers to the polymer that forms the bulk of the binder in the ice resistant polymer composition. The bulk polymer of the composition is the main polymer in the composition, i.e. it preferably forms at least 25 wt% dry weight of the composition. It is curable. The curable organic polymer of the invention ideally acts as a “bulk polymer”.

The term curable means that the material in question reacts with the curing agent. As used herein the term “alkyl” refers to saturated, straight chained, branched or cyclic groups. Alkyl groups may be substituted or unsubstituted.

As used herein the term “alkylene” refers to a bivalent alkyl group.

As used herein the term “aryl” refers to a group comprising at least one aromatic ring. The term aryl encompasses fused ring systems wherein one or more aromatic ring is fused to a cycloalkyl ring. Aryl groups may be substituted or unsubstituted. An example of an aryl group is phenyl, i.e. 0₆H₅. Phenyl groups may be substituted or unsubstituted.

As used herein the term "substituted" refers to a group wherein one or more, for example up to 6, more particularly 1 , 2, 3, 4, 5 or 6, of the hydrogen atoms in the group are replaced independently of each other by the corresponding number of the described substituents. The term "optionally substituted" as used herein means substituted or unsubstituted.

As used herein the term “polyether” refers to a compound comprising two or more - O- linkages interrupted by alkylene units.

As used herein the terms “poly(alkylene oxide)”, “poly(oxyalkylene) and “poly(alkylene glycol)” refer to a compound comprising -alkylene-O- repeat units. Typically the alkylene is ethylene or propylene.

As used herein the term “(meth)acrylate” encompasses both methacrylate and acrylate.

As used herein the term wt% is based on the dry weight of the coating composition, unless otherwise specified (dry weight and solids weight are the same herein).

As used herein the term “volatile organic compound (VOC)” refers to a compound having a boiling point of 250 °C or less.

Typically, the final wt% of monomer residues in the polymer is a reflection of the monomer content in the reaction mixture although the conversion of the monomer is not always 100%. The actual monomer incorporation can be determined through analysis of the final polymer, e.g. using NMR or other analytical techniques.

The polymers of the invention are prepared by polymerising monomers. A monomer residue then becomes incorporated into the polymer. The person skilled in the art will appreciate that disclosure on the nature of monomers used also defines the nature of monomer residues that form the polymer backbone.

As used herein, the weight average molar mass is M_w and molar mass distribution = Mw l Mn, where M_n is the number average molar mass. The molecular weight as used herein refers to the g mol ¹ weight of one molecule (or part of that molecule).

Detailed description

This invention relates to an ice mitigating composition comprising: a) a curable organic polymer; b) an ice mitigating copolymer as herein defined; and c) a curing agent.

Curable organic polymer

The main binder of the invention is a curable organic polymer or mixture of such polymers. The curable organic polymer or polymers must be different from the ice mitigating copolymer of the invention. The curable organic polymer must react with the curing agent. This is readily achieved through the introduction of suitable functional groups in the polymer such as hydroxyl groups or amino groups that react with an isocyanate curing agent.

In one embodiment of the invention the curable organic polymer contains less than 20 wt% polysiloxane monomer residues, especially less than 10 wt% polysiloxane monomer residues. Ideally it does not contain polysiloxane at all.

The polymer backbone of the curable organic polymer may be a polyester, polyether, polycarbonate, polyaspartic, polyvinyl and/or (meth)acrylate back-bone. The backbone may also comprise a mixture of these groups. Preferably, the curable organic polymer is a (meth)acrylate polymer.

Preferably, the curable functional groups present in the curable organic polymer are hydroxyl groups. Preferably, the curable organic polymer comprises two or more hydroxyl groups, i.e. the curable organic polymer is preferably a polyol.

(Meth)acrylate polymer

Preferably, the curable organic polymer is a (meth)acrylate polymer. The curable (meth)acrylate polymer may be a homopolymer or a copolymer based on (meth)acrylate monomers. Ideally, all monomer residues present in the curable organic polymer are (meth)acrylate monomers.

In another embodiment, the curable (meth)acrylate copolymer of the invention may also comprise vinyl monomer residues such as styrene. In one preferred embodiment, the curable (meth)acrylate copolymer comprises styrene monomer residues.

If the curable (meth)acrylate polymer is a homopolymer then the monomer used must be one that contains a reactive functional group such as hydroxyl or amino group.

The use of a hydroxyalkyl or aminoalkyl (meth)acrylate monomer is preferred. The use of a hydroxy alkyl (meth)acrylate is particularly preferred.

The (meth)acrylate polymer preferably comprises at least one alkyl (meth)acrylate monomer and/or alkoxyalkyl (meth)acrylate monomer. The alkyl (meth)acrylate monomer or alkoxyalkyl (meth)acrylate monomer is not one that cures as it does not comprise a reactive functional group, e.g. a hydroxyalkyl or aminoalkyl (meth)acrylate monomer.

It is required that a reactive (i.e. curable) monomer is used in addition to such nonreactive monomer. Curable monomers include ones comprising a hydroxyl or amino group, e.g. a hydroxyalkyl or aminoalkyl (meth)acrylate monomer. Ideally, there is a single hydroxyl or amino group present in the monomer.

The alkyl group present in any (meth)acrylate monomer may comprise 1 to 10 carbon atoms, such as 1 to 6 carbon atoms, especially 1 to 4 carbon atoms. An alkoxy group may comprise 1 to 6 carbon atoms, especially 1 to 4 carbon atoms.

Any amino group may be primary or secondary, preferably primary. A secondary amino group may be of formula -NH(C1 -6-alkyl).

Preferred non-curable monomers present in the (meth)acrylate polymer include methyl acrylate, ethyl acrylate, tert-butyl acrylate, n-butyl acrylate, isobutyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, isooctyl acrylate, 2-methoxyethyl acrylate, methyl methacrylate, ethyl methacrylate, tert-butyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, isooctyl methacrylate, and 2-methoxyethyl methacrylate.

Preferred curable monomers present in the (meth)acrylate polymer include 2- hydroxyethyl acrylate, 4-hydroxylbutyl acrylate, 2-hydroxyethyl methacrylate, 4- hydroxylbutyl methacrylate.

Particularly preferably the monomers present in the alkyl (meth)acrylate present in the coating composition of the invention are selected from ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate and n-butyl methacrylate and a hydroxyalkyl (meth)acrylate such as 2-hydroxyethyl (meth)acrylate. Butyl (meth)acrylate is a particularly preferred monomer.

The amount of the reactive (curable) monomer residues can be varied depending on the required level of curing. More reactive monomer gives more curing. Typically, there is 10 to 45 wt% of the curable monomer(s) residues present in the (meth)acrylate polymer, such as 15 to 25 wt%.

The amount of the non-reactive monomer(s) residues (i.e. non-curable monomers) can be varied depending on the required level of curing. More non-reactive monomer residues give less curing. Typically, there is 55 to 90 wt% of the non-curable monomer(s) residues present in the (meth)acrylate polymer, such as 65 to 85 wt%. There may be one or more types of such non-reactive monomer residues.

It is preferred if the curable organic polymer comprises 65 to 90 wt% of alkyl (meth)acrylate or alkoxyalkyl (meth)acrylate monomer residues and 10 to 35 wt% of hydroxylalkyl (meth)acrylate or aminoalkyl (meth)acrylate monomer residues. Examples of commercially available (meth)acrylate curable organic polymers suitable for use in the present invention are listed below:

Polyacrylic polyols (from Allnex):

MACRYNAL® SM 510n/65BACX, MACRYNAL SM 515/70BAC, MACRYNAL SM 2703/80BACX, MACRYNAL® SM 2810/75BAC, MACRYNAL SM 565/70BAC, MACRYNAL SM 2704/75BACX, MACRYNAL VSM 1509/60LG.

SETALUX D A 160 X, SETALUX D A 163 X

SETALUX 1917 BA-80

SETALUX 1164 XS-65

Setalux 1907

Setalux 1909

SETALUX 1910 BA-75

Setalux 1914

SETALUX 1252 SS-65

SETALUX 1215 BA-68

SETALUX 1753 XS-65

SETALUX® FC 2008 BA-75

SETALUX® FC 1227 BA-67

SETALUX® FC 1922 BA-75

SETALUX® FC 1923 BA-75

SETALUX® FC 1925 BA-75

SETALUX® 27-1592 (oligomer)

Polyacrylic polyols (from Arkema): SYNOCURE 866 EEP 75 SYNOCURE 854 BA80 SYNOCURE® 9256 X 70 MY SYNOCURE 9279 S65 SYNOCURE 9237 S 70

Polyacrylic polyols (from Synres) Uracron CY444 XE-65 Uracron CY127 XS1 E-60 Uracron CY841 E-75 Uracron CY131 S1X-70 Uracron CY129 E-70 Uracron CY130 E-65 Uracron CY135 XS1 E-60 Uracron CY142 XE-65 Uracron CY126 E-60 Uracron CY475 E-60 Uracron CY474 E-70 Uracron CY472 E-57 Uracron CY468 XF-60 Uracron CY467 E-50 Uracron CY464 E-50 Uracron CY465 E2K-50 Uracron CY463 E-50 Uracron CY458 XE Uracron CY451 XE-50 Uracron CY450 S1E Uracron CY433 XE-60 Uracron CY430 E-70 Uracron CY134 E-70 Uracron CY127 S1-60 Uracron CY127 X-60 Uracron CY27 S1-60 Uracron FH28 70BAC Uracron FH28 60SOLA Uracron F2760X Uracron F27 60SOLA Uracron F22 60X Uracron F12 6 OX- B AC Uracron CY499 E-75 Uracron CY455 XK1-51

Polycarbonate polymer

In one embodiment, the curable organic polymer is a polycarbonate. The polycarbonate may be any curable or crosslinkable polycarbonate or a mixture of curable or crosslinkable polycarbonates. By "curable" or "crosslinkable" it is meant that the polycarbonate contains reactive groups, e.g. OH groups, which enable it to be cured or crosslinked. By “polycarbonate polyol” we mean any polycarbonate polymer which contains two or more hydroxyl (OH) moieties. In all embodiments of the invention, it is preferable if the polycarbonate polyol is a diol, i.e. contains two hydroxyl functional groups. More preferably, the two hydroxyl functional groups are terminal groups on the polymer chain, i.e. one at each end of the polymer chain.

Preferably, the polycarbonate polyol comprises a repeating unit with the following structure:

wherein

R is selected from the group consisting of linear or branched C1-20 alkyl groups, C3- 12 cycloalkyl groups, and optionally substituted C₆-2oaryl groups; and n is an integer from 2 to 50.

Preferably, R is a linear or branched C1-20 alkyl group. The term "alkyl" is intended to cover linear or branched alkyl groups such as propyl, butyl, pentyl and hexyl. It will be understood that the “alkyl” group in the context of the polycarbonate is divalent and thus may also be referred to as “alkylene”. In all embodiments, the alkyl group is preferably linear.

In one embodiment, only a single (i.e. one type of) repeating unit is present. In an alternative embodiment, more than one, e.g. two, different repeating units are present. If different repeating units are present they may have a random or a regular distribution within the polycarbonate polyol. It will be understood that where more than one repeating unit is present, these repeating units will contain different R groups.

Particularly preferred cycloalkyl groups include cyclopentyl and cyclohexyl.

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

It is preferable if R does not contain an hydroxyl functional group.

Preferably, n is an integer in the range 2 to 25, such as 2 to 20, e.g. 2 to 15.

The number average molar mass ( _n) of the polycarbonate is preferably between 200 and 20,000, more preferably 300 to 10,000, such as less than 5000, preferably less than 3000 g mol ¹ (determined by GPC). The functionality of the polycarbonate polymer (i.e. the number of hydroxyl groups present per molecule) may range from 2 to 10. Preferably, the functionality is 2.

The polycarbonate polyols of the invention preferably have a hydroxyl number of 30-250 mg KOH/g. The polycarbonate is preferably a liquid-like to waxlike solid around room temperature but when heated, can be reduced in the viscosity and becomes easy to handle. Also, the polycarbonate polyol can be dissolved in an appropriate solvent.

It is, of course, possible to employ a mixture of two or more polycarbonate polyols in the compositions of the invention, however it is preferable if only a single polycarbonate polyol is used.

Examples of commercially available polycarbonate polyols are listed below: Polycarbonate polyols:

Duranol T5651 , T5652, T5650J, T5650E, T6001 , T6002, T4671 , T4672, T4691 , T4692, G3452 and G3450J from Asahi Kasei.

Desmophen C1100, C1200 and CXP 2716 from Covestro.

Sovermol® 920 from BASF.

Eternacoll UH-50, UH-100, UH-200, UH-300, PH-50, PH-100, PH-200, and PH-300, UHC- 50-100, UHC-50-200, UC, UM-90 (3/1), UM-90 (1/1), UM-90 (1/3), and UT-200 from UBE.

Polyester polymer

The curable organic polymer may also be a polyester polymer. The polyester polymer may be any polymer which contains more than one ester functional group. Moreover, the polyester preferably contains at least two hydroxyl (OH) functional groups, i.e. it can be described as a polyester polyol. The functionality of the polyester polyol (i.e. the number of hydroxyl groups present per molecule) may range from 2 to 10.

Preferably, the polyester polyol is one comprising the following repeating unit:

wherein R³ is selected from the group consisting of linear or branched C1-20 alkyl groups, C3-12 cycloalkyl groups, and optionally substituted C₆-2oaryl groups; and p is an integer from 2 to 50.

Preferably, R³ is a linear or branched C1-20 alkyl group. The term "alkyl" is intended to cover linear or branched alkyl groups such as propyl, butyl, pentyl and hexyl. Particularly preferable alkyl groups are pentyl and hexyl. In all embodiments, the alkyl group is preferably linear. It will be understood that the “alkyl” group in the context of the polyester polyol is divalent and thus may also be referred to as “alkylene”.

In one particularly preferred embodiment, R³ is Ci-₆alkyl.

Particularly preferred cycloalkyl groups include cyclopentyl and cyclohexyl.

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

Preferably, p is an integer in the range 2 to 25, such as 2 to 20, e.g. 3 to 15.

The number average molar mass ( _n) of the polyester polyol is preferably between 100 and 20,000, such as 200 to 10,000 g mol ¹, (determined by GPC).

The polyester polyols of the invention preferably have a hydroxyl number of 50- 350, such as 100-300, e.g. 150-300 mg KOH/g (calculated on non-volatiles).

The viscosity of the polyester polyol at 23°C may range from 10 to 20,000 cP, such as 100 to 15,000 cP, such as 500 to 10000 cP.

Examples of commercially available polyester polyols are listed below.

URALAC SY942 F-65, Uralac SY946, Uralac SY944, all from DSM (now Covestro). Sovermol® 1006 (BASF, polyester diol).

In some curable organic polymers of the invention, the polyester contains a polyether in the backbone of the polymer, such as a polyalkylene glycol monomer residue. Hybrid polyether/polyester polyols may also be used as the curable organic polymer therefore. Suitable polyether/polyester hybrid polyols include: Sovermol® 750, Sovermol® 760, Sovermol 780, Sovermol® 805, Sovermol® 810, Sovermol® 815, Sovermol® 1083, Sovermol® 1092, Sovermol® 1093, Sovermol® 1102 from BASF.

Polyether polymer

The curable organic polymer may also be a polyether polymer which polymer contains more than one ether functional group. Moreover, the polyether preferably contains at least two hydroxyl (OH) functional groups, i.e. it can be described as a polyether polyol.

Any suitable polyether diol may be used. The polyether diol preferably is a polyethylene diol, polypropylene diol, or polytetrahydrofurane (poly(tetramethylene ether) glycol). The diol may have any suitable molecular weight, typically a _n in the range of from 100 to 15,000 g mol ¹. Examples of commercially available Polyether polyols such are listed below. Sovermol® 1052 (polyether, diol), Sovermol® 100 (branched polyether, triol) andSovermol® 320 (branched polyether, polyol) from BASF.

Aliphatic polyols such as Sovermol® 860, Sovermol® 908 (diol) from BASF may also be used as the organic curable polymer.

Polyaspartic ester polymer

The curable organic polymer of the invention may be a polyaspartic ester polymer comprising sterically hindered secondary amines and ester groups. Suitable polyaspartic esters are described in W02016/049104 A1. The polyaspartic ester may include one or more polyaspartic esters corresponding to formula:

wherein: n is an integer of 2 to 6; Z represents an aliphatic residue; and R¹ and R² represent organic groups that are inert to isocyanate groups under reaction conditions and that may be the same or different organic groups.

In the formula above, the aliphatic residue Z may correspond to a straight or branched alkyl and/or cycloalkyl residue of an n-valent polyamine that is reacted with a dialkylmaleate in a Michael addition reaction to produce a polyaspartic ester.

For example, the residue Z may correspond to an aliphatic residue from an n-valent polyamine including, but not limited to, ethylene diamine; 1 ,2-diaminopropane; 1 ,4- diaminobutane; 1 ,6-diaminohexane; 2,5-diamino-2,5-dimethylhexane; 2,2,4- and/or 2,4,4- trimethyl- ,6-diaminohexane; 1 ,11-diaminoundecane; 1 ,12-diaminododecane; 1-amino- 3,3,5-trimethyl-5-amino- methylcyclohexane; 2,4'- and/or 4,4'- diaminodicyclohexylmethane; 3,3'- dimethyl-4, 4'-diaminodicyclohexylmethane; 2,4,4'- triamino-5- methyldicyclohexylmethane; polyether polyamines with aliphatically bound primary amino groups and having a number average molar mass ( _n) of 148 to 6000 g mol ¹ ; isomers of any thereof, and combinations of any thereof.

In certain embodiments, the residue Z may be obtained from 1 ,4- diaminobutane;

1 ,6-diaminohexane; 2,2,4- and/or 2,4, 4-trimethyl-1 , 6- diaminohexane; 1 -amino-3, 3,5- trimethyl-5-aminomethylcyclohexane; 4,4'- diaminodicyclohexylmethane; 3,3'-dimethyl- 4,4'-diaminodicyclohexylmethane; or 1 ,5-diamine-2-methyl-pentane. In certain embodiments, the polyaspartic ester comprises one or more compounds corresponding to formula (I) in which n is an integer from 2 to 6, in some embodiments n is an integer from 2 to 4, and in some embodiments n is 2.

Examples of commercially available polyapspartic polymers are Desmophen NH1220, NH1420, NH1422, NH1423, NH1520, NH1521 and NH1720 from Covestro.

Amount

The curable organic polymer (or polymers) may form at least 25 wt% (dry weight) of the coating composition, such as at least 30 wt%, preferably at least 50 wt%, especially at least 65 wt% of the coating composition. There may be up to 95 wt% of the curable organic polymer in the coating composition (based on the weight of the coating composition as a whole), such as 70 to 80 wt%.

The amount of curable organic polymer (or polymers) in the coating composition as a whole is markedly affected by the amount of pigment that might be present. Pigments can be heavy and hence make up a large weight percentage of the overall coating composition thus reducing the weight contribution of the curable organic polymer (or polymers). The skilled person in this field will be able to formulate a coating composition with suitable levels of pigment and curable organic polymer (or polymers) as desired. If there are two curable organic polymers present then these wt% refer to the combination of curable organic polymers.

Ice Mitigating copolymer

The ice mitigating copolymer of the present invention may comprise functional groups that react with the curing agent in the coating composition or it may be free of such functional groups that can react with the curing agent in the coating composition. In one preferred embodiment the ice mitigating copolymer (i.e. the polysiloxane containing copolymer) is one that does not react with the curing agent in the coating composition of the invention. Ideally therefore the ice mitigating polysiloxane copolymer should not contain any free hydroxyl or amine groups.

In this embodiment therefore, if monomer C) is present then any alkylene oxide chain is preferably end capped so that there is no -OH group present.

In another embodiment the ice mitigating copolymer comprises free hydroxyl or amine groups and reacts with the curing agent in the coating composition.

The ice mitigating copolymer of the invention is prepared by reacting certain comonomers. The weight percentage of the components present in the monomer mixture used to prepare the ice mitigating copolymer preferably translates into the weight percentage of monomer residues in the final copolymer. However, the actual comonomer content can be determined by measuring the residual unreacted monomers after the polymerisation is complete or by analytical techniques such as NMR.

The first monomer is a (meth)acrylate functional, (meth)acrylamide functional or vinyl functional polysiloxane monomer, preferably a (meth)acrylate functional polysiloxane monomer, more preferably a (meth)acrylate functional or vinyl polydimethylsiloxane monomer, especially a (meth)acrylate functional polydimethylsiloxane monomer.

It is preferred if the (meth)acrylate functional, (meth)acrylamide functional or vinyl functional polysiloxane monomer gives rise to a monomer residue (or repeating unit) of formula A1 or A2:

in formulae (A1) and (A2)

R is selected from H and methyl;

X² is selected from COOR³ , or CONHR³;

R³ is selected from substituted or unsubstituted, linear or branched, Ci-e alkylene; o is 0 or 1 , preferably 1 ; each R⁴ is independently selected from CM_O alkyl and C_5-10 aryl; and in formula (A1) q is an integer from 1 to 160; and in formula (A2) q is 0 or an integer from 1 to 80,

R⁵ is selected from CM_O alkyl, C5-10 aryl or 0-Si(R⁶)₃, wherein R⁶ is independently selected from CMO alkyl and C5-10 aryl.

The X² group is preferably oriented such that the R³ group binds the Si.

In one embodiment the R³ group may comprise longer carbon chains (C™ - C₃o) comprising polyurethane linkages.

Preferably, the ice mitigating copolymer does not react with the curing agent whereas the curable organic polymer does react. Without being bound to any theory it is believed that the ice mitigating copolymer that is not covalently attached to the curable organic polymer can migrate to the surface of the coating and that the flexible carbon backbone in the copolymer will give the polysiloxane groups which are pendant on the copolymer backbone, the opportunity to arrange in the most favourable manner and “face outwards” from the coating to the air. The co-polymer backbone, having a similar surface energy as the curable organic polymer will function as an anchor entangled within the curable organic polymer. The organic co-polymer backbone improves the compatibility of the co-polymer with the curable organic polymer compared with pure polysiloxane polymers which generally have poor compatibility with organic polymers.

It is preferred if the polysiloxane monomer gives rise to a monomer residue of formula:

in formulae (A1) and (A2)

R is selected from H and methyl;

X² is selected from COOR³;

R³ is selected from substituted or unsubstituted, linear or branched, C1-8 alkylene;, preferably unsubstituted, linear or branched, Ci-₆ alkylene;

0 is 1 ; each R⁴ is independently selected from Ci-₆ alkyl, especially methyl; and in formula (A1) q is an integer from 1 to 160; and in formula (A2) q is 0 or an integer from 1 to 80,

R⁵ is selected from C_MO alkyl, C5-10 aryl or 0-Si(R⁶)₃, wherein R⁶ is independently selected from C_MO alkyl and C5-10 aryl, especially R⁵ is methyl.

An advantage of the ice mitigating copolymer of the present invention is that by carefully choosing the monomers and the chain lengths of the monomers, the properties of the copolymer, such as glass transition temperature (Tg), can be adjusted. The use of a monomer residue of formula (A1) is preferred.

The ice mitigating copolymer of the invention also comprises a monomer residue (B) selected from a (meth)acrylate functional, (meth) acrylamide functional or vinyl functional alkyl, alkoxy substituted alkyl monomer residue or aryl monomer residue or a mixture thereof. Monomer (B) is different from monomer (A). Monomer (B) should not contain polysiloxane groups. Monomer (B) is also different from monomer (C). Monomer (B) should not contain polyalkylene glycol groups

Aryl monomer residues of interest as monomer residue (B) might derive from styrene. Alkoxy substituted alkyl monomer residues of interest might derive from a monomer in which an alkoxy substituted alkyl is carried on a vinyl group or an alkoxy substituted alkyl group is carried on a (meth)acrylate.

Preferably the monomer residue (B) is a (meth)acrylate functional alkyl, alkoxy substituted alkyl monomer residue or aryl monomer residue.

The ice mitigating copolymer of the invention preferably comprises a (meth)acrylate monomer residue of formula B

wherein in formula (B)

R is selected from H and methyl;

X³ is selected from R⁷, COOR⁷, CONHR⁷

R⁷ is selected from alkoxy substituted (e.g. Ci-₈ alkoxy) or unsubstituted, linear or branched, Ci-₈ alkyl, or aryl.

In one embodiment, the ice mitigating copolymer comprises monomer residues of formula (A1) and/or (A2), (B) and optionally (C):

wherein in formula (C)

R is selected from H and methyl;

X¹ is selected from COO- or CONH; m is 0 or 1 , preferably 1 ;

In one embodiment, there is less than 5 wt% of monomer residue (C) present. Monomer (C) is obviously different from monomer (A). Monomer (C) should not contain polysiloxane groups. Monomer (C) is also different from monomer (B). Monomer (B) should not contain polyalkylene glycol groups.

Poly(alkylene oxide) groups may form a hydrogel or hydrogel-type structure from the interaction with the water molecules that helps prevent the deposition of ice onto the coated surface.

Thus in the compositions of the invention the ice mitigating copolymer may comprise monomer residues of formulae (A1) and (B), monomer residues of formulae (A2) and (B), monomer residues of formulae (A1), (B) and (C) or (A2), (B) and (C). Units A1 and A2 could also be in the same polymer. Further preferred compositions of the invention comprise an ice mitigating copolymer having a monomer residue derived from of at least one monomer of each of formula (a1) and/or (a2) and (b), and optionally formula (c):

wherein

R, X¹, X², X³, R¹, R², R³, R⁴, R⁵, R⁶, R⁷, m, n, o and q are as hereinbefore defined.

When monomers (a1), (a2), (b) and (c) are polymerised they produce monomer residues (A1), (A2), (B) and (C) respectively.

Further preferred compositions of the invention comprise an ice mitigating copolymer of formula (Xb1) or (Xb2): wherein

R, X¹, X², X³, R¹, R², R³, R⁴, R⁵, R⁶, Ry, m, n, o and q are as herein defined.

Said ice mitigating copolymer preferably comprises 0-45 wt%, preferably 0-20 wt%, especially 0 to 10 wt% of repeat unit r, 20-70 wt%, preferably 20-50 wt% of repeat unit s and 30-90 wt%, preferably 40-80 wt% of repeat unit t.

A preferred ice mitigating copolymer is of formula

with variables as hereinbefore defined. Ideally, units s and t are the only repeating units present, i.e. the copolymer is free of monomer (C). Said copolymer preferably comprises 20-70 wt%, preferably 20-50 wt% of repeat unit s and 30-90 wt%, preferably 40- 80 wt% of repeat unit t.

The polysiloxane containing monomer ideally has a high molecular weight. For example, a vinyl, (meth)acrylamide or (meth)acrylate functional polysiloxane monomer may have an _n of 900 to 10,000, such as 3,000 to 10,000, such as 4,200 to 6,000 g mol ¹. It has been found that a slightly higher molecular weight improves ice mitigation properties. It is particularly preferred if the Mn is within these ranges when the ice mitigating copolymer of the invention is a random copolymer prepared using a conventional radical polymerisation reaction.

The ice mitigating copolymer of the invention may also be a block-copolymer where the first block is densely grafted polysiloxane monomer such as PDMSMA and the second block being an alkyl (meth)acrylate block such as poly(methyl methacrylate) (PMMA).

Both average Mn of the polysiloxane monomer employed and the weight ratio of the polysiloxane monomer to the alkyl (meth)acrylate, are important for achieving the ice release effect. The best ice release effect is obtained when the copolymer composition contains 60 wt% polysiloxane monomer (A) or more.

When the polysiloxane monomer content in the copolymer is 60 wt% or more, ice shear adhesion is reduced.

Furthermore, the higher _n polysiloxane monomers generally offer the best ice release performance.

It is preferred if the ice mitigating copolymer of the invention consists of:

A) at least 30 wt%, preferably 60 wt% or more, of a (meth)acrylate functional polysiloxane monomer residue; B) at least 10 wt% of an alkyl (meth)acrylate monomer residue or an alkoxy substituted alkyl (meth)acrylate monomer residue or mixture thereof.

In formulae (Xb1-3), the subscripts r, s and t are intended to represent the proportion of the different repeat units present in the polymer and do not necessarily represent the connectivity of the units. The ice mitigating copolymer present in the compositions of the invention may be block copolymers, gradient copolymers or random copolymers.

The ice mitigating copolymer present in the coating composition of the present invention preferably comprises at least 90 wt% (meth)acrylate monomers. Preferred ice mitigating copolymers present in the composition of the present invention comprise 100 wt% (meth)acrylate monomers, i.e. they do not comprise any monomers of another type.

In preferred monomer residues of formula (C), preferred monomers of formula (c), and preferred ice mitigating copolymers of formula (Xb1) and (Xb2), n may be 0 or 1 .

When n is 1 , R¹ is preferably substituted or unsubstituted, linear or branched Ci-₄ alkylene and still more preferably substituted or unsubstituted, linear or branched C1-2 alkylene. Preferably R¹ is unsubstituted. Preferably R¹ is linear. Still more preferably R¹ is unsubstituted, linear Ci-₄ alkylene and yet more preferably R¹ is unsubstituted, linear C1-2 alkylene, e.g. -CH2CH2-. In preferred monomer residues of formula (C), preferred monomers of formula (a), and preferred ice mitigating copolymers of formula (X), however, n is 0.

In preferred monomer residues of formula (C), preferred monomers of formula (c), and preferred ice mitigating copolymers of formula (Xb1) and (Xb2), R² is polyethylene oxide), polypropylene oxide) or a mixture thereof. Preferably R² is of formula (I):

-[(CH₂CH₂0)_U(CH₂CH(CH₃)0)_V]-R⁸ (I) wherein

R⁸ is selected from H, CH₃, CH₂CH₃ and COCH₃; and each u is 0 to 50, each v is 0 to 50 with the proviso that u+v is 2 to 50, preferably 4 to 40, more preferably 4-20 and still more preferably 4-10.

When v is 0, R² is a polyethylene oxide). When u is 0, R² is polypropylene oxide). When both u and v are non-zero, R² is a mixture of polypthylene oxide) and polypropylene oxide). The different alkylene oxide units may be arranged in blocks or randomly and more preferably randomly. Thus formula (I) does not necessarily represent the connectivity of the alkylene oxide units in R².

As used herein the term polypthylene oxide) covers dimers, trimers and oligomers as well as longer polymers. Thus when v is 0, for example, u is preferably 2 to 50 and more preferably 4 to 40. Similarly the term polypropylene oxide) covers dimers, trimers and oligomers as well as longer polymers.

Examples of monomers of formula (c) present in the ice mitigating copolymer present in the coating composition of the present invention include polyethylene glycol) methyl ether methacrylate, polypropylene glycol) methyl ether methacrylate, dipthylene glycol) methyl ether methacrylate, tripthylene glycol) methyl ether methacrylate, polypthylene glycol) methyl ether acrylate, polypropylene glycol) methyl ether acrylate, dipthylene glycol) methyl ether acrylate, tripthylene glycol) methyl ether acrylate, polypthylene glycol) ethyl ether methacrylate, polypropylene glycol) ethyl ether methacrylate, dipthylene glycol) ethyl ether methacrylate, tripthylene glycol) ethyl ether methacrylate, polypthylene glycol) ethyl ether acrylate, polypropylene glycol) ethyl ether acrylate, dipthylene glycol) ethyl ether acrylate, tripthylene glycol) ethyl ether acrylate, polypthylene glycol) methacrylate, polypropylene glycol) methacrylate, polypthylene glycol) acrylate, polypropylene glycol) acrylate and polypropylene glycol) monovinyl ether. Generally monomers referred to as “polyplkylene glycol)-containing” monomers comprise 4-50 alkylene oxide units and monomers referred to as “diplkylene glycol)” and “triplkylene glycol”-containing monomers comprise 2 and 3 alkylene oxide units respectively.

Preferred monomers of formula (c) present in the copolymer present in the coating composition of the present invention include polypthylene glycol)methyl ether methacrylate, polypropylene glycol) methyl ether methacrylate, polypthylene glycol) methyl ether acrylate, polypropylene glycol) methyl ether acrylate, polypthylene glycol) ethyl ether methacrylate, polypropylene glycol) ethyl ether methacrylate, polypthylene glycol) ethyl ether acrylate, polypropylene glycol) ethyl ether acrylate, polypthylene glycol) methacrylate, polypropylene glycol) methacrylate, polypthylene glycol) acrylate and polypropylene glycol) acrylate.

Preferred monomers of formula p) have a number average molar mass ( _n) of 100-3500, more preferably 200-2000 and still more preferably 250-1000.

Representative examples of commercially available monomers include Visiomer MPEG 750 MA W, Visiomer MPEG 1005 MA W, Visiomer MPEG 2005 MA W, Visiomer MPEG 5005 MA W from Evonik, Bisomer PPA6, Bisomer PEA6, Bisomer PEM6, Bisomer PPM5, Bisomer PEM63P, Bisomer MPEG350MA, Bisomer MPEG550MA, Bisomer S10W, BisomerS20Wfrom Geo Speciality Chemicals, SR550 MPEG350MA, SR552 MPEG500MA from Sartomer and RPEG 750 from Ineos Oxide.

In preferred monomer residues of formula (A1) and (A2), preferred monomers of formula p1) and p2), and preferred copolymers of formula (Xb1-3), R³ is substituted or unsubstituted, linear or branched Ci-₆ alkylene and still more preferably substituted or unsubstituted, linear or branched C1-4 alkylene. Preferably R³ is unsubstituted. Preferably R³ is linear. Still more preferably R³ is unsubstituted, linear Ci-₆ alkylene and yet more preferably R³ is unsubstituted, linear Ci-₄ alkylene, e.g. -CH₂CH₂- or -CH₂CH₂CH₂-.

In preferred monomer residues of formula (A1) and (A2), preferred monomers of formula (a1) and (a2), and preferred copolymers of formula (Xb1-3), R⁴ is preferably Ci-₈ alkyl or C5-10 aryl. Preferred alkyl groups are Ci-₄ alkyl, e.g. methyl, ethyl, n-propyl, i- propyl, n-butyl, i-butyl and t-butyl. A preferred aryl group is phenyl. Still more preferably R⁴ is methyl or butyl.

In preferred monomer residues of formula (A1) and preferred monomers of formula (a1), q is 1-160, preferably 10-130, more preferably 10-120 and more preferably 10-80 In preferred monomer residues of formula (A2) and preferred monomers of formula (a2), q is 0-80, preferably 1-70, more preferably 1-60, more preferably 10-40.

In preferred monomer residues of formula (A2), preferred monomers of formula (A2) and preferred copolymers of formula (Xb2), R⁵ is preferably Ci-₈ alkyl orO-Si(R⁶)₃. Preferred alkyl groups include methyl, ethyl, n-propyl and i-propyl. Still more preferably R⁵ is methyl. If R⁵ is aryl, it is preferably phenyl.

In further preferred monomer residues of formula (A2), preferred monomers of formula (a2) and preferred copolymers of formula (Xb2), each R⁶ is preferably Ci-₈ alkyl or C5-10 aryl. Preferred alkyl groups include methyl, ethyl, n-propyl and i-propyl. A preferred aryl group is phenyl. Still more preferably R⁶ is methyl.

Preferred monomers of formula (a1) present in the copolymer present in the coating composition of the present invention include monomethacryloxypropyl terminated polydimethylsiloxane, such as a-methacryloyloxypropyl-co-butyl polydimethylsiloxane, a- methacryloyloxypropyl-co-trimethylsilyl polydimethylsiloxane, a-methacryloyloxyethyl-co- trimethylsilyl polydimethylsiloxane, a-acryloyloxypropyl-co-butyl polydimethylsiloxane, a- acryloyloxypropyl-co-trimethylsilyl polydimethylsiloxane, a-acryloyloxyethyl-co-trimethylsilyl polydimethylsiloxane; monovinyl terminated polydimethylsiloxane, such as a-vinyl-co-butyl polydimethylsiloxane, a-vinyl-co-trimethylsilyl polydimethylsiloxane.

Representative examples of commercially available monomers of formula (b1) include X-22-174ASX, X22-174BX, KF-2012, X-22-2426 and X-22-2404 from Shin-Etsu, Silaplane FM-0711 , Silaplane FM-0721 , Silaplane FM-0725 from JNC Corporation, PS560 from United Chemical Technologies and MCR-M07, MCR-M11 , MCR-M17, MCR-M22 and MCR-V41 from Gelest.

Preferred monomers of formula (a2) present in the copolymer present in the coating composition of the present invention include symmetric monomethacryloxypropyl functional polydimethylsiloxane-, such as a,a’-(methyl methacryloyloxypropyl)-bis(co-butyl) polydimethylsiloxanes, 3-tris(trimethylsiloxy)silylpropyl methacrylate; symmetric monovinyl functional polydimethylsiloxane, such as a,a’-(methyl vinyl)-bis(co-butyl) polydimethylsiloxanes. Representative examples of commercially available monomers include MCS-M11 , MCS-MX11 and MCS-V212 from Gelest.

Preferred monomers of formula (a1 and a2) have a _n of 200 to 12000, more preferably a _n of 900 to 12000, more preferably above 4000 g/mol.

Preferred copolymers present in the compositions of the present invention comprise a monomer residue of formula (B). These monomer residues derive from monomers of formula (b).

In preferred monomer residues of formula (B), preferred monomers of formula (b), and preferred copolymers of formula (X), R⁷ is selected from alkoxysubstituted or unsubstituted, linear or branched, Ci-₈ alkyl. Preferably R⁷ is alkoxy substituted or unsubstituted, linear or branched Ci-₄ alkyl and still more preferably alkoxy substituted or unsubstituted, linear or branched C1-2 alkyl. Any alkoxy group may have 1 to 8 carbon atoms, such as 1 to 4 carbon atoms, e.g. methoxy or ethoxy. Preferably R⁷ is unsubstituted. Preferably R⁷ is linear. Still more preferably R⁷ is -CH₃ or-CH₂CH₃.

Preferred monomers of formula (b) present in the copolymer present in the coating composition of the present invention include methyl acrylate, ethyl acrylate, tert-butyl acrylate, n-butyl acrylate, isobutyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, isooctyl acrylate, 2-methoxyethyl acrylate, methyl methacrylate, ethyl methacrylate, tert-butyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, isooctyl methacrylate, and 2- methoxyethyl methacrylate. Particularly preferably the monomers present in the copolymer are selected from ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate and n-butyl methacrylate.

Advantageously the amount and the distribution of polysiloxane, (meth)acrylate and poly(alkylene oxide) modified (meth)acrylate monomers present in the copolymer can be adjusted. This provides the ability to fine tune the properties of the copolymer, e.g. flexibility, surface tension and compatibility with the curable organic polymer.

Preferred ice mitigating copolymers present in the coating composition of the present invention have a weight average molecular weight of 10,000 to 150,000, more preferably 15,000 to 125,000 and still more preferably 20,000 to 100,000, preferably measured according to the method described in the examples section.

A preferred ice mitigating copolymer of the invention comprises, preferably consists of,: A) at least 30 wt%, such as 60 wt% or more, of a (meth)acrylate functional, (meth)acrylamide functional or vinyl functional polysiloxane monomer residue or mixture thereof;

C) 0 to 25 wt% of a (meth)acrylate functional, (meth)acrylamide functional or vinyl functional poly(alkylene glycol) monomer residue or mixture thereof.

A preferred ice mitigating copolymer of the invention comprises, preferably consists of,:

A) at least 30 wt%, preferably 60 wt% or more, of a (meth)acrylate functional, or vinyl functional polysiloxane monomer residue or mixture thereof;

B) at least 10 wt% of a (meth)acrylate functional, or vinyl functional alkyl monomer residue, alkoxy substituted alkyl monomer residue or a mixture thereof; and

C) 0 to 25 wt% of a (meth)acrylate functional, or vinyl functional poly(alkylene glycol) monomer residue or mixture thereof.

A) at least 30 wt%, preferably 60 wt% or more, of a (meth)acrylate functional, (meth)acrylamide functional or vinyl functional polysiloxane monomer residue or mixture thereof;

B) at least 20 wt% of an alkyl (meth)acrylate monomer residue, vinyl functional alkyl monomer residue, an alkoxy substituted alkyl (meth)acrylate monomer residue or alkoxy substituted alkyl vinyl monomer residue or mixture thereof; and

C) 0 to 40 wt% of a (meth)acrylate functional, (meth)acrylamide functional or vinyl functional poly(alkylene glycol) monomer residue or mixture thereof.

A) 30 to 85 wt%, preferably 60 to 70 or 60 to 75 wt% of a (meth)acrylate functional or vinyl functional polysiloxane monomer residue or mixture thereof; B) 10 to 65 wt% of an alkyl (meth)acrylate monomer residue, vinyl functional alkyl monomer residue, an alkoxy substituted alkyl (meth)acrylate monomer residue oralkoxy substituted alkyl vinyl residue or mixture thereof; and

C) 0 to 20 wt% of a (meth)acrylate functional or vinyl functional poly(alkylene glycol) monomer residue or mixture thereof.

A) 30 to 85 wt%, preferably 60 to 70 wt% or 60 to 75 wt%, of a (meth)acrylate functional polysiloxane monomer residue or mixture thereof;

B) 10 to 65 wt% of an alkyl (meth)acrylate monomer residue, an alkoxy substituted alkyl (meth)acrylate monomer residue or mixture thereof; and

C) 0 to 20 wt% of a (meth)acrylate functional poly(alkylene glycol) monomer residue or mixture thereof.

A preferred ice mitigating copolymer of the invention comprises, preferably consists of :

A) 40 to 85 wt%, preferably 60 to 70 wt% or 60 to 75 wt%, of a (meth)acrylate functional or vinyl functional polysiloxane monomer residue or mixture thereof;

B) 10 to 40 wt% of an alkyl (meth)acrylate monomer residue, vinyl functional alkyl monomer residue, an alkoxy substituted alkyl (meth)acrylate monomer residue oralkoxy substituted alkyl vinyl monomer residue or mixture thereof; and

C) 0 to 10 wt% of a (meth)acrylate functional or vinyl functional poly(alkylene glycol) monomer residue or mixture thereof.

A preferred ice mitigating copolymer of the invention comprises, preferably consists of:

A) 40 to 85 wt%, preferably 60 to 70 wt% or 60 to 75 wt%, of a (meth)acrylate functional polysiloxane monomer residue or mixture thereof;

B) 10 to 40 wt% of an alkyl (meth)acrylate monomer residue, an alkoxy substituted alkyl (meth)acrylate monomer residue or mixture thereof; and C) 0 to 10 wt% of a (meth)acrylate functional poly(alkylene glycol) monomer residue or mixture thereof.

The coating composition may comprise one or more (e.g. 1 , 2, 3, 4 or 5) copolymers as hereinbefore described. Preferred coating compositions of the present invention comprise 1 copolymer only.

Preparation of the copolymer of the invention

Suitable copolymers may be prepared using polymerization reactions known in the art. The copolymer may, for example, 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 manner and with controlled polymerization techniques. When preparing a coating composition using the (meth)acrylate polymer as hereinbefore described, 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 to prepare the (meth)acrylate polymer. Examples of suitable polymerization initiators for free radical polymerization include azo compounds such as dimethyl 2,2’-azobis(2-methylpropionate), 2,2'-azobis(2-methylbutyronitrile), 2,2'- azobis(isobutyronitrile) and 1 ,T-azobis(cyanocyclohexane) and peroxides such as tert- butyl peroxypivalate, tert- butyl peroxy-2-ethylhexanoate, tert-butyl peroxydiethylacetate, tert-butyl peroxyisobutyrate, di-tert-butyl peroxide, tert-butyl peroxybenozate, and tert-butyl peroxyisopropylcarbonate, tert-amyl peroxypivalate, tert-amyl peroxy-2- ethylhexanoate, 1 ,1-di(tert-amyl peroxy) cyclohexane and dibenzoyl peroxide. These compounds may be used alone or as a mixture of two or more thereof.

Examples of suitable organic solvent include aromatic hydrocarbons such as xylene, toluene, mesitylene; ketones such as methyl ethyl ketone, methyl isobutyl 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, di ethylene glycol dimethyl ether, dibutyl ether, dioxane, tetrahydrofuran, alcohols such as n-butanol, isobutanol, benzyl alcohol; ether alcohols such as butoxyethanol, 1-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 of the invention may be a random copolymer prepared through the mixture of the relevant monomers in a conventional radical polymerisation reaction. In one embodiment, the copolymers of the invention may be prepared by controlled radical polymerization. This maximises comonomer conversion. Suitable controlled radical polymerization techniques for industrial processes are reverse iodine transfer polymerization (RITP), reversible addition-fragmentation chain-transfer (RAFT), reversible complexation mediated polymerization (RCMP), group transfer polymerization (GTP) and activator regenerated by electron transfer (ARGET) atom transfer radical polymerization (ATRP).

Higher molecular weight polysiloxanes are often difficult to react in a free radical process since a long and flexible dimethyl siloxane chain will randomly coil. The reactivity of the (meth) acrylic active site will thus be diffusion controlled and given the very short lifetime of a propagating radical species, termination will more likely occur prior to incorporation of the polysiloxane-(meth)acrylate material.

This issue is sometimes solved by increasing wt ratio of small molecule (meth)acrylate monomers to act as spacers. That, of course, leads to a reduction in the polysiloxane weight fraction in the copolymer (typically well below 40 wt%). It is thus beneficial to employ controlled radical polymerization techniques such as RITP when preparing copolymers comprising (meth)acrylate functional polysiloxanes. The RITP technique is exemplified below.

The coating composition of the invention preferably comprises 5 to 20 wt% (dry weight) copolymer of the invention, such as 5 to 15 wt%, especially 7.5 to 12 wt% of the copolymer of the invention.

Initial findings have suggested that a minimum of 5 wt% copolymer is valuable to have a significant effect on ice release properties. Additions above 20 wt% of copolymer increase the chances of “oily surfaces” and have a larger impact on the mechanical properties of the “bulk”.

Curing Agent

The curing agent for use in the invention is ideally a polyisocyanate, such as a di or triisocyante.

Suitable poly-isocyanates in the coating composition are well known in the art. Examples of suitable low molecular weight poly-isocyanates, having a molecular weight of 168 to 300 g mol ¹, include: hexamethylene diisocyanate (HDI), 2,2,4- and/or2,4,4- trimethyl-1 ,6-hexamethylene diisocyanate, dodecamethylene diisocyanate, 2,4- diisocyanato-1 -methyl-benzene (toluene diisocyanate, TDI), 2,4-diisocyanato-1- methylbenzene, 1 ,4-diisocyanatocyclohexane, 1-isocyanato-3,3,5-trimethyl-5- isocyanatomethylcyclohexane (IPDI), 2,4'-and/or 4,4'-diisocyanato-dicyclohexyl methane, 2,4-and/or 4,4'-diisocyanato-diphenyl methane and mixtures of these isomers with their higher homologues which are obtained in a known manner by the phosgenation of aniline/formaldehyde condensates, 2,4-and/or2,6- diisocyanatotoluene, and any mixture of these compounds.

In some preferred coating compositions of the present invention the polyisocyanate component a) is selected from aliphatic polyisocyanates, e.g. hexamethylene diisocyanate (HDI), 2,2,4-and/or2,4,4-trimethyl-1 ,6-hexamethylene diisocyanate, dodecamethylene diisocyanate, 1 ,4-diisocyanatocyclohexane, 1-isocyanato-3,3,5-trimethyl-5- isocyanatomethylcyclohexane (IPDI), 2,4'-and/or 4,4'-diisocyanato-dicyclohexyl methane, and 2,4-and/or4,4'-diisocyanato-diphenyl methane.

In other preferred coating compositions of the present invention the polyisocyanate component a) is selected from aromatic polyisocyanates, e.g. 2,4-diisocyanato-1-methyl- benzene (toluene diisocyanate, TDI), 2,4-diisocyanato-1-methyl-benzene and mixtures of these isomers with their higher homologues which are obtained in known manner by the phosgenation of aniline/formaldehyde condensates, 2,4-and/or2,6-diisocyanatotoluene and any mixtures of these compounds.

In preferred coating compositions of the present invention the polyisocyanate component a) is a derivative of the above-mentioned monomeric poly-isocyanates, as is conventional in the art. These derivatives include polyisocyanates containing biuret groups. Examples of particularly preferred derivatives include N,N',N"-tris-(6- isocyanatohexyl)-biuret and mixtures thereof with its higher homologues and N,N',N"-tris- (6-isocyanatohexyl)-isocyanurate and mixtures thereof with its higher homologues containing more than one isocyanurate ring.

Examples of suitable commercially available poly-isocyanates are:

Desmodur N3900 (formerly VP2410), ex. Covestro AG, aliphatic polyisocyanate, aliphatic polyisocyanate, based on HDI

Desmodur N3600, ex. Covestro AG, aliphatic polyisocyanate, HDI trimer Desmodur N3800, ex. Covestro AG, aliphatic polyisocyanate, HDI trimer Tolonate HDT-LV2, ex. Vencorex), aliphatic polyisocyanate Desmodur N3300, Covestro aliphatic polyisocyanate, HDI trimer Desmodur N3390, ex. Covestro, aliphatic polyisocyanate, HDI trimer Tolonate HDT90, ex. Vencorex, aliphatic polyisocyanate Basonat HI 190 B/S, ex. BASF aliphatic polyisocyanate Desmodur N100, Covestro, aliphatic polyisocyanate, HDI biuret Desmodur N 3200, Covestro, aliphatic polyisocyanate, HDI biuret Desmodur N75 BA, ex. Covestro, aliphatic polyisocyanate, HDI biuret Desmodur N75 MPA, Covestro, aliphatic polyisocyanate, HDI biuret Desmodur N75 MPA/X, Covestro, aliphatic polyisocyanate, HDI biuret Bayhydur VP LS 2319, ex. Covestro, aliphatic polyisocyanate Tolonate IDT 70B, ex. Vencorex, aliphatic polyisocyanate Desmodur H, ex Covestro, monomeric aliphatic diisocyanate, HDI.

Desmodur Z 4470 BA, Covestro, aliphatic polyisocyanate, IPDI trimer Basonat HB 175 MP/X BASFaliphatic polyisocyanate

Examples of suitable commercially available aromatic polyisocyanate resins are: Desmodur L67 BA (Covestro), aromatic polyisocyanate, based on TDI Desmodur L 67 MPA/X, Covestro, aromatic polyisocyanate, based on TDI Desmodur L 75, Covestro, aromatic polyisocyanate based on TDI Desmodur VL (Covestro), aromatic polyisocyanate, based on MDI Voratron EC 112 (Dow Chemicals)

Desmodur E23 (Bayer Material Science)

Desmodur E 1660 (Bayer Material Science)

Suprasec 2495 (Huntsman Advanced Materials).

Isocyanate group-containing prepolymers and semi-prepolymers based on the monomeric poly-isocyanates mentioned above, and organic polyhydroxyl compounds, are also preferred for use as poly- iso cyan ate component a). These pre-polymers and semi pre-polymers generally have an isocyanate content of 0.5-30 % by weight, preferably 1-20 % by weight, and are prepared in a known manner by the reaction of the above mentioned starting materials at an NCO/OH equivalent ratio of 1.05:1 to 10:1 preferably 1.1 :1 to 3:1 , this reaction being optionally followed by distillative removal of any un-reacted volatile starting poly-isocyanates still present.

The pre-polymers and semi pre-polymers may be prepared from polyhydroxyl compounds having a molecular weight of 62 to 299 g mol ¹. Examples include ethylene glycol, propylene glycol, trimethylol propane, 1 ,6-di hydroxy hexane; low molecular weight, hydroxyl-containing esters of these polyols with dicarboxylic acids of the type exemplified hereinafter; low molecular weight ethoxylation and/or propoxylation products of these polyols; and mixtures of the afore-mentioned polyvalent modified or unmodified alcohols.

Preferably the pre-polymers and semi pre-polymers are prepared from relatively high molecular weight polyhydroxyl compounds. These polyhydroxyl compounds have at least two hydroxyl groups per molecule and more preferably have a hydroxyl group content of 0.5-17 % by weight, preferably 1-10 % by weight.

Commercially available isocyanate prepolymers:

Desmodur E 40080 MPA, Covestro (Germany), aliphatic IPDI prepolymer (previously named Desmodur XP2406) (2.8±0.4 % NCO by weight on solids).

Desmodur E2863 XP, Covestro (Germany), aliphatic HDI prepolymer (approximately 11 % NCO by weight on solids). DesmodurXP2599, Covestro (Germany), aliphatic HDI prepolymer (6±0.5 % NCO by weight on solids).

Desmodur E 15, Covestro (Germany), TDI prepolymers (approximately 4.4 % NCO by weight on solids).

Desmodur E 14, Covestro (Germany), TDI prepolymers (approximately 3.3 % NCO by weight on solids).

Desmodur E 21 , Covestro (Germany), aromatic polyisocyanate prepolymer based on MDI (approximately 16 % NCO by weight on solids).

Desmodur E XP 2727, Covestro (Germany), aromatic polyisocyanate prepolymer based on MDI (approximately 15.3 % NCO by weight on solids).

ANDUR AL80-5AP, aliphatic polyether from polytetramethylene ether glycol (PTMEG) and H12MDI (3.8-4.2 % NCO by weight on solids).

Versathane D-5QM, polyester from ethylene/propylene adipate and TDI, (approximately 5 % NCO by weight on solids).

Prepolymers from Lanxess:

Adiprene® LFH E520 HDI Polyether, 5.00 - 5.40 % NCO by weight on solids.

Adiprene® LFH E710 HDI Polyether, 6.80 - 7.40 % NCO by weight on solids.

Adiprene® LFH C840 HDI Polycaprolactone, 8.20 - 8.60 % NCO by weight on solids. Adiprene® LFH R600 HDI Polycarbonate, 5.60 - 6.40 % NCO by weight on solids. Adiprene® LW 520 H12MDI Polyether, 4.60 - 4.90 % NCO by weight on solids.

Adiprene® LW 570 H12MDI Polyether, 7.35 - 7.65 % NCO by weight on solids.

Trixene® SC 7902 IPDI Polyether, 3.90 - 4.10 % NCO by weight on solids.

Trixene® SC 7930 HDI Biuret Castor Oil, 9.00 - 12.00 % NCO by weight on solids. Trixene® SC 7931 IPDI Polyether, 2.70 - 3.20 % NCO by weight on solids.

Trixene® DP9A / 997 IPDI Polyether, 3.50 - 4.00 % NCO by weight on solids.

The coating composition of the invention preferably comprises curing agent in an amount of 10 to 80 wt% (dry weight) of the coating composition, such as 10 to 60 wt%, especially 15 to 50 wt%.

Catalyst

In order to assist the curing process, the coating composition of the invention preferably comprises a catalyst. Representative examples of catalysts that can be used include transition metal compounds, metal salts and organometallic complexes of various metals, such as, tin, iron, lead, barium, cobalt, zinc, antimony, cadmium, manganese, chromium, nickel, aluminium, gallium, germanium, titanium, boron, lithium, potassium and zirconium. The salts preferably are salts of long-chain carboxylic acids and/or chelates or organometal salts. Examples of suitable catalysts include for example, dibutyltin dilaurate, dibutyltin dioctoate, dibutyltin diacetate, dibutyl tin 2-ethylhexanoate, dibutyltin dineodecanoate, dibutyltin dimethoxide, dibutyltin dibenzoate, dibutyltin acetoacetonate, dibutyltin acetylacetonate, dibutyltin alkylacetoacetonate, dioctyltin dilaurate, dioctyltin dioctoate, dioctyltin diacetate, dioctyl tin 2-ethylhexanoate, dioctyltin dineodecanoate, dioctyl tin dimethoxide, dioctyltin dibenzoate, dioctyltin acetoacetonate, dioctyltin acetylacetonate, dioctyltin alkylacetoacetonate, dimethyltin dibutyrate, dimethyltin bisneodecanoate, dimethyltin dineodecanoate, tin naphthenate, tin butyrate, tin oleate, tin caprylate, tin octanoate, tin strearate, tin octoate, iron stearate, iron 2-ethylhexanoate, lead octoate, lead 2-ethyloctoate, cobalt-2-ethylhexanoate, cobalt naphthenate, manganese 2- ethylhexanoate, zinc 2-ethylhexanoate, zinc naphthenate, zinc stearate, metal trifiates, triethyltin tartrate, stannous octoate, carbomethoxyphenyl tin trisuberate, isobutyltin triceroate.

Further examples of suitable catalysts include organobismuth compounds, such as bismuth 2-ethylhexanoate, bismuth octanoate and bismuth neodecanoate. Examples of commercial organobismuth catalysts are Borchi Kat 24 and Borchi Kat 315 from Borchers. K-KAT XK-651 from King Industries, Reaxis C739E50 from Reaxis and TIB KAT716 from TIB Chemicals. Further examples of suitable catalysts include organotitanium, such as Tyzor IBAY from Dorf Ketal and TIB KAT 517 from TIB Chemicals, organzirconium, such as TIB KAT 816 from TIB Chemicals and organohafnium compounds and titanates and zirconate esters such as, titanium naphthenate, zirconium naphthenate, tetrabutyl titanate, tetrakis(2- ethylhexyl)titanate, triethanolamine titanate, tetra(isopropenyloxy)-titanate, titanium tetrabutanolate, titanium tetrapropanolate, titanium tetraisopropanolate, tetrabutyl zirconate, tetrakis(2- ethylhexyl) zirconate, triethanolamine zirconate, tetra(isopropenyloxy)-zirconate, zirconium tetrabutanolate, zirconium tetrapropanolate, zirconium tetraisopropanolate and chelated titanates such as diisopropyl bis(acetylacetonyl)titanate, diisopropyl bis(ethylacetoacetonyl)titanate and diisopropoxytitanium bis(ethylacetoacetate).

Preferred catalysts are dibutyltin dilaurate, dibutyltin dioctoate, dibutyltin diacetate and dioctyltin dilaurate.

Preferably the catalyst is present in the coating composition of the invention in an amount of 0.005 to 5 wt% based on the total dry weight of the coating composition, more preferably 0.01 to 3 wt%.

Pigments The coating compositon of the invention preferably comprises one or more pigments. The pigments may be inorganic pigments, organic pigments or a mixture thereof. The pigments may be surface treated.

Representative examples of pigments include black iron oxide, red iron oxide, yellow iron oxide, titanium dioxide, zinc oxide, carbon black, graphite, red molybdate, yellow molybdate, zinc sulfide, antimony oxide, sodium aluminium sulfosil icates, quinacridones, phthalocyanine blue, phthalocyanine green, indanthrone blue, cobalt aluminium oxide, carbazoledioxazine, isoindoline orange, bis-acetoaceto-tolidiole, benzimidazolone, quinaphthalone yellow, isoindoline yellow, tetrachloroisoindolinone, and quinophthalone yellow, metallic flake materials (e.g. aluminium flakes). Preferred pigments are carbon black, red iron oxide, yellow iron oxide, phthalocyanine blue and titanium dioxide. In one preferred embodiment the titanium dioxide is surface treaded with a silicon compound, a zirconium compound or a zinc compound.

The amount of pigment present in the coating composition of the present invention is preferably 0 to 25 wt% and more preferably 0.5 to 15 wt% based on the total dry weight of the coating composition.

Solvent

The coating composition of the present invention preferably comprises a solvent. Suitable solvents for use in the compositions of the invention are commercially available.

Examples of suitable organic solvents and thinners are 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, isoamyl acetate, ethylene glycol methyl ether acetate, propylene 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, 1-methoxy-2-propanol; aliphatic hydrocarbons such as white spirit; and optionally a mixture of two or more solvents and thinners.

The amount of solvent present in the coating compositions of the present invention is preferably as low as possible as this minimizes the VOC content. Preferably solvent is present in the compositions of the invention in an amount of 0-35 wt% and more preferably 1-30 wt% based on the total weight of the composition. The skilled man will appreciate that the solvent content will vary depending on the other components present.

Fillers

The coating composition of the present invention optionally comprises fillers. Examples of fillers that can be used in the coating composition according to the present invention are zinc oxide, barium sulphate, calcium sulphate, calcium carbonate, silicas or silicates (such as talc, feldspar, and china clay) including fumed silica, bentonite and other clays, and solid silicone resins, which are generally condensed branched polysiloxanes. Some fillers such as fumed silica may have a thickening effect on the coating composition.

The amount of fillers present in the coating composition of the present invention is preferably 0 to 25 wt%, more preferably 0.1 to 10 wt% and still more preferably 0.15 to 5 wt%, based on the total dry weight of the coating composition.

Additives

The coating composition of the present invention optionally comprises one or more additives. Examples of additives that may be present in the coating composition of the invention include reinforcing agents, thixotropic agents, thickening agents, anti-settling agents, dehydrating agents, dispersing agents, wetting agents, surfactants, binders, plasticizers, and dyes.

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 and mixtures thereof. Preferably thixotropic agents, thickening agents and anti settling agents are each present in the composition of the invention in an amount of 0-10 wt%, more preferably 0.1-6 wt% and still more preferably 0.1 -2.0 wt%, based on the total dry weight of the composition.

The dehydrating agents and desiccants that may be used in the coating compositions include organic and inorganic compounds. The dehydrating agents can be hygroscopic materials that absorb water or binds water as crystal water, often refered to as desiccants. Examples of desiccants include calcium sulphate hemihydrate, anhydrous calcium sulphate, anhydrous magnesium sulphate, anhydrous sodium sulphate, anhydrous zinc sulphate, molecular sieves and zeolites. The dehydrating agent can be a compound that chemically reacts with water. Examples of dehydrating agents that reacts with water include orthoesters such as trimethyl orthoformate, triethyl orthoformate, tripropyl orthoformate, triisopropyl orthoformate, tributyl orthoformate, trimethyl orthoacetate, triethyl orthoacetate, tributyl orthoacetate and triethyl orthopropionate; ketals; acetals; enolethers; orthoborates such as trimethyl borate, triethyl borate, tripropyl borate, triisopropyl borate, tributyl borate and tri-tert-butyl borate; organosilanes such as trimethoxymethyl silane, vinyltrimethoxysilane, phenyltrimethoxysilane, tetraethoxysilane and ethyl polysilicate. Preferably the dehydrating agent is present in the compositions of the invention in an amount of 0-5 wt%, more preferably 0.5-2.5 wt% and still more preferably 1.0-2.0 wt%, based on the total dry weight of the composition.

Composition and Paint

The present invention also relates to a method of preparing the coating composition as hereinbefore described wherein the components present in the composition are mixed. Any conventional production method may be used.

The composition as described herein may be prepared in a suitable concentration for use, e.g. in spray painting. In this case, the composition is itself a paint. Alternatively the composition may be a concentrate for preparation of paint. In this case, further solvent and optionally other components are added to the composition described herein to form paint. Preferred solvents are as hereinbefore described in relation to the composition.

After mixing, and optionally after addition of solvent, the coating composition or paint is preferably filled into a container. Suitable containers include cans, drums and tanks.

The coating composition may be supplied as one-pack, as a two-pack or as a three-pack. Preferably the composition is supplied as a two-pack or as a three-pack and still more preferably as a two-pack

When supplied as a one-pack, the composition is preferably supplied in a ready- mixed or ready to use form. Optionally the one-pack product may be thinned with solvents prior to application.

When supplied as a two pack, the first container preferably comprises a curable organic polymer; and the second container preferably comprises curing agent. The other components can generally be in ether pack. The catalyst is preferably in the first container. Instructions for mixing the contents of the containers may optionally be provided.

When supplied as a three pack, the first container preferably comprises a curable organic polymer; the second container preferably comprises a curing agent; and the third container preferably comprises a catalyst. Instructions for mixing the contents of the containers may optionally be provided. The other components can be in any pack.

The coating composition of the invention preferably has a solids content of 50-99 wt%, more preferably 60-99 wt% and still more preferably 65-99 wt%.

Preferably the coating composition of the invention has a content of volatile organic compounds (VOC) of 50 to 400 g/L, preferably 50 to 350 g/L, e.g. 50 to 300 g/L. VOC content can be calculated (ASTM D5201-05A) or measured (US EPA method 24 or ISO 11890-1). Preferably the coating composition and paint of the invention has a viscosity of 700 to 1100 mPa under a shear rate of 100/s.

The coating composition of the present invention may be applied to any pre-treated coating layers examples of such coating layers are epoxy anticorrosive layers. The coating composition may also be applied directly to the substrate, such as a metal substrate.

The coating composition according to the present invention may be applied in one or two or more layers. Preferably the coating composition according to the present invention is applied in one layer.

The dry film thickness of each of the coating layers of the coating composition of the present invention is preferably 50-500 pm, more preferably 100 - 400 pm, most preferably 150 - 300 pm.

The coating composition of the invention can be applied to a whole or part of any article surface which is subject to icing. The article surface will typically be the hull of a vessel or surface of an object such as an oil platform orbuoy, wind turbine. Application of the coating composition can be accomplished by any convenient means, e.g. via painting (e.g. with brush or roller) or more preferably spraying the coating onto the article. The application of the coating can be achieved as conventionally known in the art. After the coating is applied, it is preferably dried and/or cured.

Applications

The coating of the present invention is typically applied to the surface of structure where ice mitigation is required such as vessels (including but not limited to boats, yachts, motorboats, motor launches, ocean liners, tugboats, tankers, container ships and other cargo ships, submarines, and naval vessels of all types), shore and off-shore machinery, constructions and objects of all types such as piers, pilings, bridge substructures, water power installations and structures etc. Their use on wind turbines is especially preferred.

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

Brief Description of the Figures:

Figure 1 shows ice adhesion measurements by shear stress. Figure 2 shows uniaxial tensile measurements of coatings with and without copolymer additions based on the data in Table 2.

Examples - Determination Methods

Measurement of solid content The measurement of solids content of polymer solutions was measured according to ISO 3251 :2019.

Molar mass

The weight average molar mass ( M_w ) and molar mass distribution {D_M = M_wl M_n, where M_n is the number average molar mass) were determined with gel permeation chromatography (GPC) and was carried out at 30 °C on a Malvern Omnisec GPC system with a 10 (length) x 4.6 (inner diameter) mm guard column (Viscotek),2x PL-gel 5 pm Mixed - D column (Polymer Labs) and a refractive index detector. Tetrahydrofurane (THF) was employed as mobile phase and with a flow of 1 mL/min. Calibration was established with 12 different narrow polystyrene standards ranging from 162- 364,000 g mol ¹ (Agilent).

Polymer molecular structure and unreacted monomers

The amount of unreacted monomers and the chemical structure of the synthesized polymers were determined with ¹H-NMR measurements (e.g. monomer ratios in Tables 3 and 4).

The ¹H-NMR spectra were recorded at 298 K using a 400 MHz Bruker Avance III HD NMR spectrometer in CDCI₃ and solvent signal was used as reference signal relative to tetramethylsilane.

Contact Angle measurements

Contact angle measurements were carried out on a Kriiss DSA100 drop shape analyzer with 2 pL drop size of distilled water or diiodomethane (CH2I2) at 23 °C and 50% relative humidity (RH). Advancing and receding contact angles of water were obtained via the tilted plane method using 20 pL droplets and with a tilt speed of 1° per second. Measurements were carried out on unexposed flat coating-surfaces. Details on coating preparations are given in the coating formulations example section below.

Calculation of surface energies

Surface energies were calculated by the Owens-Wendt-Rabel & Kaeble model (OWRK) using distilled water (72.8 mN/m) and diiodomethane (50.8 mN/m) as liquids, according to ASTM D7490-13.

Mechanical properties

Unaxial tensile measurements were carried out using a universal testing machine (UTM) from Testometrics Co. Ltd. fitted with a 50 kg load cell and using a strain rate of 5 mm/min at 23 °C according to ASTM D882 - 18. Samples were prepared by doctor blading coating solutions onto mylar® film. The coatings were cured for 14 days at 23 °C/50% RH to obtain dry coating thicknesses of approximately 150 pm. The samples were then cut into dumbells as specified in ISO 527-3-2018 (specimen type 2) and removed from the mylar® film prior to uniaxial tensile measurements.

Ice adhesion measurements

Ice shear adhesion strength measurements were carried out using a UTM, fitted with a 50 kg load cell and a climate chamber (temperature range - 40 to 200 °C) both from Testometrics Co. Ltd. and a custom build ice shear adhesion fixture (Martinsen et. al. J Coat Technol Res, 2020). Measurements were carried out on unexposed flat coating- surfaces. Details on coating preparations are given in the coatings formulations example section below.

The following components were used

Methyl isoamyl ketone (MIAK)

Methyl methacrylate (MM A) n-butyl methacrylate (BMA) n-butyl acrylate (BA)

2-hydroxyethyl methacrylate (HEMA)

2-hydroxylethyl acrylate (HEA)

Poly(dimethylsiloxane) monomethacrylate (PDMSMA-1) ( M_n (¹H-NMR) = 4617 g mol ¹, tradename KF-2012 from Shin etsu)

Poly(dimethylsiloxane) monomethacrylate (PDMSMA-2) ( M_n (¹H-NMR) = 984 g mol ¹, tradename ASX-174 from Shin etsu)

Methoxy polyethylene glycol) monomethacrylate (MPEGMA) ( _n = 300 g mol ¹, Sigma- Aldrich)

2,2'-Azodi(2-methylbutyronitrile) (AMBN)

Xylene (isomer mixture)

Toluene

Hexamethylene diisocyanate-biuret (HDI-biuret, tradename Desmodur N 75 MPA/X from Covestro)

Isophorone diisocyanate trimer (IPDI-trimer, tradename Desmodur Z 4470 SN from Covestro)

Dioctyltin dilaurate (DOTDL)

Tetrabutyl ammonium iodide (TBAI)

Iodine ( )

Nitrogen gas (N₂) Example 1 (copolymer 1.1)

MIAK (30 g) in a 250 ml. 3-neck round bottom flask fitted with a condenser was heated to 90 °C under N₂-flow. A mixture of PDMSMA-1 (22.93 g, 5 mmol), MMA (9.36g, 93.5 mmol), AMBN (0.2 g, 1.12 mmol) and MIAK (20 g) was then added dropwise over 2 hours. The reaction mixture was allowed to react for 30 minutes where after a solution of AMBN (0.1 g, 0.56 mmol) and MIAK (1.0 g) was added. The solution was kept at 90 °C for an additional 2 hours and then cooled to ambient temperature. The resulting polymer solution was used without any further purification. Characterization: M_w= 65.1 kg mol ¹, D_M= 3.27. Solids content: 40.1 wt%. Residual, unreacted monomer: PDMSMA = 25 wt%

Example 2 (copolymer 1.2)

A mixture of PDMSMA-1 (23.52, 5 mmol), MMA (9.6 g, 95.9 mmol), AMBN (0.686 g, 3.57 mmol), (0.3, 1.18 mmol) and toluene (35 g) in a 250 mL 3-neck round bottom flask fitted with a condenser was heated to 80 C under N₂-flow and in the absence of light. The mixture was reacted for 7 hours and a clear colourless polymer solution was obtained. The polymer was precipitated in ethanol and dried. Characterization: M_w = 20.1 kg mol ¹, D_M = 1.43, Residual unreacted monomer: PDMSMA = 12 wt%.

Example 3 (copolymer 1.3)

MIAK (40 g) in a 250 mL 3-neck round bottom flask fitted with a condenser was heated to 90 °C under N₂-flow. A mixture of BA (30 g, 234 mmoles), PDMSMA-1 (27 g, 5.87 mmoles), MPEGMA (3 g, 10 mmoles), AMBN (0.5 g, 2.6 mmoles) and MIAK (20 g) was then added dropwise over 2 hours. The reaction mixture was allowed to react for 30 minutes and then added a solution of AMBN (0.1 g, 0.56 mmol) in MIAK (1.0 g). The polymer solution was held at 90 °C for an additional 2 hours and then cooled to ambient temperature. The polymer was precipitated in ethanol and dried. Characterization: M_w= 48.3 kg mol ¹, DM = 4.7. No residual unreacted monomers.

Example 4 (curable organic polymer 2.1)

Xylene (86 g) in a 250 mL 3-neck round bottom flask fitted with a condenser was heated to 90 C under N₂-flow. A mixture of BMA (80 g, 563 mmoles), HEMA (20 g, 154 mmoles), AMBN (5 g, 26 mmoles) and xylene (14 g) was added dropwise over 2 hours. The reaction mixture was allowed to react for 30 minutes and then added a solution of AMBN (0.1 g, 0.56 mmol) in xylene (1 .0 g). The polymer solution was held at 90 C for an additional 2 hours and then cooled to ambient temperature. The resulting polymer solution was used and characterized without any further purification. Characterization: M_w= 21.4 kg mol ¹, D_M = 2.24. Solids content: 49.4 wt%.

Example 5 (copolymer 1.4)

A PDMS-I macrotransfer agent was prepared via RITP in the following manner. PDMSMA- 2 (2.0 g, 2.22 mmol), AMBN (30.8 mg, 0.16 mmol) and l₂ (20.3 mg, 0.08 mmol) were dissolved in toluene (3 ml.) in a 25 ml. round bottom flask fitted with a condenser and under N₂- flow. The red mixture was then heated at 80 °C in the dark. After approximately 2 hours, the mixture became clear, indicating end of the inhibition period. After a total reaction time of 5 hours the polymerization was quenched by exposing it to air. The polymer was precipitated in excess methanol and dried under vacuum to yield a clear, viscous oil (1.21 g, 60 % yield). Characterization: M_w= 15.4 kg mol ¹, D_M = 1.21.

The resulting PDMS-I macrotransfer agent (0.5 g) was added MMA (1 ml_, 9.4 mmol) and TBAI (48 mg, 0.13 mmol) and heated at 110 °C for 3 hours under N₂- flow. A yellow gel was obtained and precipitated in methanol to yield a white solid. Characterization: M_w = 25.9 kg mol ¹, D_M = 1.31. The structure of the block copolymer was verified by GPC and ¹H NMR. From ¹H NMR the weight ratio PDMS and MMA in the co-polymer was determined to be 65 parts PDMS to 35 parts MMA by weight. No residual monomer.

Copolymers 1.5 to 1.8

Copolymers 1.5-1.8 were prepared in a similar manner as described in example 2. Residual PDMSMA in copolymer 1.2-1.8 was removed prior to further use by precipitating the copolymer in a mixture of methanol and THF (2 : 1 by volume). Curable organic polymer 2.2 and 2.3 were prepared in the same manner as curable organic polymer 2.1 described in example 4. The monomer feed ratios forthe ice mitigating copolymer 1.1-1.8 and curable organic copolymer 2.1-3. are summarized in table 1 and 2, respectively.

Table 1 : Monomer feed ratios forthe polymerizations to obtain the ice mitigating copolymers

Table 2: Monomer feed ratios for the polymerizations to obtain the curable organic polymers

The composition of the monomer residues of the copolymers 1.1 -1.8 and curable organic polymer 2.1-2.3 were determined using ¹H-NMR and are given in Table 3 and Table 4, respectively, including molar mass distribution of each copolymer.

Table 3: Monomer residues and weight average molar masses of the copolymers given in kg mol ¹.

Table 4: Monomer residues and weight average molar masses of the curable organic polymers given in kg mol ¹.

Coating formulation examples

A typical coating formulation was prepared as follows: Copolymer, curable organic copolymer and catalyst were diluted with solvent (xylene) to obtain a mixture with a spray viscosity of 17 s (DIN cup 4, DIN 53211). Just before application, the premade solution was mixed with a curing agent under stirring and thereafter spraycoated onto an aluminium substrate (panels of 1.5 x 75 x 75 mm). The samples were then allowed to cure for either 14 days at 23°C/50% RH or at ambient temperature for 24 hours followed by 1 hour drying at 80 °C. The coating formulations are summarized in Table 5.

Table 5: Coating formulations given in weight of solids, where the OH-functional curable organic polymer-types are mixed stochiometric to the NCO-functional hardeners, i.e. , the OH:NCO molar ratio is 1 :1.

^*AII amounts given are based on dry weight of the components

Table 5 cont.

Mechanical properties

The mechanical properties of coating formulations with and without copolymer were evaluated by uniaxial tensile measurement of free films. As can be seen from the results in Table 6 and Figure 2, elastic modulus values are similar for copolymer containing coating films and pristine coating films (comparative).

Table 6: Mechanical test-data for coating 1 ,2, 5, 6, 9 and 10.

lce adhesion measurements

Ice adhesion was measured for coatings 1-17. The coatings are described above in table 5, and results from the ice adhesion measurements are given in Figure 1. The comparative examples (coatings 1 , 5 and 9 - copolymer free) have ice adhesion values of approximately 400 kPa. Coating 11 demonstrates the lowest ice adhesion with around 10 kPa. Comparative coating 16 had an oily surface and severe surface defects from the mismatch between the surface tension of silicone and acrylic curable organic polymer.

The advancing (0_aciv) and receding (0_rec)- contact angles, the contact angle hysteresis (CAH) and surface energies (SE) of coatings 9-12 and coating 15 are shown in Table 7. Coating 9 is the pure crosslinked curable organic polymer 2.3 and coatings 10-12 and 15 are modified with copolymers having varying degree of hydrophobic and hydrophilic groups. The CAH is given by 0_adv - 0_rec and is a result of chemical and topographical heterogeneities of the surface. A high advancing contact angle and a low CAH indicates surfaces with low adhesion to ice. The SE is divided into a dispersive and polar component and is a measure of the chemical nature of the components present in the solid- air interphase (i.e. coating surface and surrounding atmosphere). It is evident that the copolymers are surface-active and that the surface energy of the surface can be modified by adjusting the ratio between hydrophobic and hydrophilic groups in the copolymer.

Table 7: Surface energies calculated from contact angle measurements of H2O and CH2I2 applying the OWRK-method. Advancing and receding contact angles were obtained via the tilted plane-method with 20 pL drop size and 1 ⁰ per second tilting speed.

It can also be seen that high amounts of PEG are detrimental to performance (comparative example 15). Lower PEG levels in the copolymers offer lower ice adhesion but copolymer 3 (composition 4) still offers weaker performance than copolymers free of PEG.

It is shown in example 17 that using an ice mitigating copolymer having functional groups that reacts with the curing agent (OH groups) also gives reduced ice adhesion. When the polysiloxane monomer content in the copolymer is 60 wt% or more, ice shear adhesion is reduced. Coatings 4 and 8 (prepared from copolymer 1.3 comprising 51.2 wt% PDMSMA) can be directly compared with coating 14 (prepared from copolymer 1.6 comprising 79 wt% PDMSMA) as both have comparable amounts of MPEGMA. Coating 14 has significantly lower ice shear adhesion than coatings 4 and 8 as shown in Figure 1.

Claims

1. An ice mitigating coating composition comprising:

(I) at least 25 wt% dry weight of one or more curable organic polymers comprising less than 20 wt% polysiloxane monomer residues;

(II) 5 to 20 wt% of an ice mitigating copolymer comprising:

A) at least 30 wt% of a (meth)acrylate functional, (meth)acrylamide functional or vinyl functional polysiloxane monomer residue or mixture thereof;

B) at least 10 wt% of a (meth)acrylate functional, (meth)acrylamide functional or vinyl functional alkyl monomer residue, alkoxy substituted alkyl monomer residue or aryl monomer residue or a mixture thereof and

C) 0 to 40 wt% of a (meth)acrylate functional, (meth)acrylamide functional or vinyl functional poly(alkylene glycol) monomer residue or mixture thereof; and (III) one or more curing agents.

2. An ice mitigating copolymer, preferably non-curable copolymer, consisting A) at least 60 wt% of a (meth)acrylate functional, (meth)acrylamide functional or vinyl functional polysiloxane monomer residue or mixture thereof;

3. An ice mitigating copolymer, preferably non-curable copolymer, as claimed in claim 2 consisting of:

A) 60 wt% or more of one or more monomer residues of formula A1 and/A2:

in formulae (A1) and (A2)

R is selected from H and methyl;

X² is selected from COOR³ or CONHR³;

R³ is selected from substituted or unsubstituted, linear or branched, Ci-e alkylene; o is 0 or 1 , preferably 1 ; each R⁴ is independently selected from C_MO alkyl and C_5-10 aryl; and in formula (A1) q is an integer from 1 to 160; and in formula (A2) q is 0 or an integer from 1 to 80,

R⁵ is selected from CM_O alkyl, C5-10 aryl or O-Si(R⁶)₃, wherein R⁶ is independently selected from CM_O alkyl and C5-10 aryl. B) 10 wt% or more of one or more monomer residues of formula B

wherein in formula (B) R is selected from H and methyl;

X³ is selected from R⁷, COOR⁷, CONHR⁷;

R⁷ is selected from alkoxy substituted or unsubstituted, linear or branched, Ci-₈ alkyl or aryl; and

C) 0 to 25 wt% of one or more monomer residues of formula (C):

wherein in formula (C)

R is selected from H and methyl;

X¹ is selected from COO or CONH; m is 0 or 1 , preferably 1 ; R¹ is selected from substituted or unsubstituted, linear or branched, Ci-e alkylene; n is 0 or 1 ; preferably 1 ; and R² is poly(alkylene oxide).

4. An ice mitigating copolymer as claimed in claim 2 or 3 wherein the monomer residue C) is not present.

5. An ice mitigating copolymer as claimed in claim 2 to 4 wherein the polysiloxane is a polydimethylsiloxane.

6. An ice mitigating copolymer as claimed in claim 2 to 5 wherein the content of the monomer residues B) is 15 to 40 wt%.

7. An ice mitigating copolymer as claimed in claim 2 to 6 wherein the _n of the polysiloxane monomer residue A) is 500-12000 g mol ¹, preferably 4000 g mol ¹ or more.

8. An ice mitigating copolymer as claimed in claim 2 to 7 wherein monomer (B) is ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate and n- butyl methacrylate.

9. An ice mitigating copolymer as claimed in claim 2 to 8 wherein the poly (alkylene glycol) monomer residue C) has an _n between 300-2000 g mol ¹, such as 300 to 1000 g mol ¹.

10. An ice mitigating copolymer as claimed in claim 2 to 9 wherein monomer B) is a (meth)acrylate functional, or vinyl functional alkyl monomer residue especially a (meth)acrylate functional monomer residue.

11. An ice mitigating copolymer as claimed in claim 2 to 9 wherein monomer B) is an alkyl or alkoxyalkyl (meth)acrylate monomer preferably, a Ci-₈ alkyl (meth)acrylate monomer or Ci-₈ alkoxysubstituted Ci-₈ alkyl (meth)acrylate such as MM A, MEMA, EEA or BMA.

12. An ice mitigating composition comprising

(I) at least 25 wt% of one or more curable organic polymers which must be different from the ice mitigating copolymer(s); and

(II) one or more ice mitigating co-polymers as defined in any one of claims 2 to 11 ; and (III) one or more curing agents.

13. A composition as claimed in claim 12 wherein the curing agent comprises a plurality of isocyanate groups.

14. A composition as claimed in claim 12 and 13 comprising a curing catalyst.

15. A composition as claimed in claim 12 to 14 wherein the curable organic polymer is free of polysiloxane.

16. A composition as claimed in claim 12 to 15 wherein the curable organic polymer comprises an alkyl (meth)acrylate monomer residue, such as hydroxyalkyl (meth)acrylate monomer residue, preferably a mixture of one or more alkyl (meth)acrylate monomer residues and one or more hydroxyalkyl (meth)acrylate monomer residues.

17. A substrate coated with a composition as defined in claim 1 , or 12 to 15.

18. Use of the coating composition as defined in claim 1 , or 12 to 15 to prevent or reduce the build-up of ice on a substrate.