WO2025093746A1

WO2025093746A1 - Adhesion-promoting compounds and use thereof

Info

Publication number: WO2025093746A1
Application number: PCT/EP2024/080942
Authority: WO
Inventors: Matthew UNTHANK
Original assignee: Northumbria University
Current assignee: Northumbria University
Priority date: 2023-11-03
Filing date: 2024-11-01
Publication date: 2025-05-08
Anticipated expiration: 2026-05-03
Also published as: GB2635204A; GB202316872D0

Abstract

The present invention relates to novel compounds and their use as adhesion-promoting additives. In particular, the invention relates to additives for promoting adhesion between epoxy-amines and polysiloxanes. The additives have particular use for promoting adhesion between epoxy-amine coatings and polysiloxane coatings in marine and protective coating applications. The invention also relates to methods of promoting adhesion between epoxy-amines and polysiloxanes.

Description

Adhesion-Promoting Compounds and Use Thereof

The present invention relates to novel compounds and their use as adhesion-promoting additives. In particular, the invention relates to additives for promoting adhesion between epoxy-amines and polysiloxanes. The additives have particular use for promoting adhesion between epoxy-amine coatings and polysiloxane coatings in marine and protective coating applications. The invention also relates to methods of promoting adhesion between epoxyamines and polysiloxanes.

Marine coatings are protective coatings which are applied in marine environments to protect predominantly submerged materials from the effects of sea water. Marine coatings are therefore applied to surfaces such as the hulls of ships and other maritime vessels as well as immersed static structures such as oil and gas pipes, water pipes and oil and gas rigs. Typically, marine coating is a three-stage process. In the first stage, a primer or base coat is applied. The primer/base coat is typically used to impart anti-corrosion properties to the exposed surface. Amine-cured epoxide functional polymers are typically used for these primer coats, due to their ability to impart the requisite anti-corrosion properties, while bonding strongly to metallic surfaces such as boat hulls. For submerged surfaces, at least 3 coats of such primer are typically applied.

In addition to the primer/base coat, an anti-fouling top coat is needed to prevent the buildup of slime and the attachment of marine species (barnacles, algae etc.) to the material surface. This prevents increased drag (with resultant fuel inefficiency) and also the crosscontamination of marine species throughout waterways. While previously, biocidal products such as cuprous oxide were added to marine coatings to prevent fouling, due to leaching of these biocides into waterways the use of these compounds is now regulated. Polysiloxanes (silicones) are now the material of choice for anti-fouling/top coats, due to their low surface energy which deters bonding to the surface by marine organisms.

A problem associated with the use of silicone topcoats is that their low surface energy properties, which are crucial for the anti-fouling effect, also prevent adhesion to the primer or base coat. This therefore necessitates the use of an intermediate coat, or "tie-coat", which has good adhesion to both the primer coat and the top coat, and serves to adhere or bind the two coats together. The primary purpose of the tie-coat is to prevent disbondment of the primer and top coats. However, the application of tie-coat typically can account for up to 35% of the cost of coating a marine vessel, taking into account the cost of the formulation, the cost of application, and dry-dock time during which the vessel is out of service.

In summary, while known primer coat and top coat formulations each impart required functionality on marine and protective coatings, their lack of adhesion to each other causes problems from both a cost and an efficiency perspective. It would be advantageous to obviate and/or mitigate one or more of these problems. In particular, it would be beneficial to remove the need for a separate tie-coat to be applied to adhere the primer and top-coat formulations to each other. It would also be useful more generally to provide a method of promoting adhesion between epoxy-amine and polysiloxane coatings.

Summary of the Invention

According to a first aspect of the present invention there is provided compound of formula l(a)(i), l(a)(ii), l(b)(i),(b)(ii), l(c)(i) or l(c)(ii):

in which R¹ and R², which may be the same or different, are each H or alkyl Ci-io; or R¹ and R² together with -O-B-O- form a 5-, 6- or 7-membered ring optionally substituted with one or more C1-C4 alkyl groups; each R³ is independently Ci-C₈ alkyl or phenyl; A¹ and A² are each independently -CH₂ or CHY;

Y, which may be present or absent, is one or more substituents selected from a C1-C20 linear or branched saturated or unsaturated aliphatic hydrocarbon; halogen-substituted C1-C20 linear or branched saturated or unsaturated aliphatic hydrocarbon; halogen; -OR⁴; -NR⁴ ₂; -NO₂; - SO₃H; -C(=O)R⁴; -C(=O)OR⁴; -OC(=O)NR⁴ ₂; -C N; -SR⁴; -P(=O)R⁴ ₂; -OC(=O)OR⁵; -NC(=O)OR⁵; - SO2R⁵; -SOR⁵; in which R⁴ is H, a C1-C20 linear or branched aliphatic hydrocarbon group or PhY; and R⁵ is a C1-C20 linear or branched saturated or unsaturated hydrocarbon group or PhY; or Y is PhY;

PhY is a phenyl group optionally substituted with Y; and m is an integer from 1 to 3; and isomers thereof; wherein formula I is not:

In an embodiment, the compound of formula I is not:

As used herein, the term "alkyl" refers to a fully saturated, branched, unbranched or cyclic hydrocarbon moiety, i.e., primary, secondary, or tertiary alkyl or, where appropriate, cycloalkyl or alkyl substituted by cycloalkyl. Where not otherwise indicated, an alkyl group comprises 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms, or more preferably 1 to 4 carbon atoms. Representative examples of alkyl groups include, but are not limited to, methyl, ethyl, n- propyl, /so-propyl, n-butyl, sec-butyl, /so-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, n- hexyl, 3-methylhexyl, 2,2-dimethylpentyl, 2,3-dimethylpentyl, n-heptyl, n-octyl, n-nonyl and n-decyl.

The compounds of formulae I (a)(i), I (a)(ii), I (b)(i), and I (b)(ii) include isomers thereof, and in particular, constitutional isomers. Thus, as a skilled person would appreciate, while the 1,4- (para) substituted isomers are shown, the formulae explicitly encompass the 1,2- (ortho) and l,3-(meta) substituted compounds.

As a skilled person would appreciate, the compounds of formula I (a)(i) and I (a)(ii) are isomers. Any mixtures or additives comprising the compound may comprise a single isomeric form, or a mixture of the two isomers. Similarly, the compounds of formula l(b)(i) and l(b)(ii) are isomers, and mixtures or additives comprising the compound may comprise a single isomeric form or a mixture of the two isomers. Again, similarly, the compounds of formula I (c)(i) and I (c)(ii) are isomers, and mixtures or additives comprising the compound may comprise a single isomeric form or a mixture of the two isomers. The compound may be used as a single isomeric form or as a mixture of isomers.

Advantageously, the inventors have discovered that compounds of formula l(a)(i)-(ii), l(b)(i)- (ii) and l(c)(i)-(ii) are useful as adhesion promoters. In particular, the inventors have demonstrated that compounds of formula l(a)(i)-(ii), l(b)(i)-(ii) and l(c)(i)-(ii) can be used to promote adhesion between epoxy-amine coatings and silicone coatings, such as, but not limited to, those used as primer/base coats and anti-fouling top coats in marine and protective coating applications. The compounds can be used as additives to promote adhesion between these coatings, and in embodiments, eliminate the need for an intermediate tie-coat.

The compounds of formula l(a)(i)-(ii), l(b)(i)-(ii) and l(c)(i)-(ii) can be mono-, di- or trialkoxysilanes.

In an embodiment, m is 2 or 3.

In an embodiment, m is 3.

Trialkoxysilanes are commonly commercially available and may be a useful and cost-effective choice, particularly for large-scale applications.

In an embodiment, each R³ is independently Ci-Cs alkyl.

In an embodiment, each R³ is independently C1-C4 alkyl.

In an embodiment, each R³ is independently methyl or ethyl.

In some embodiments, each R³ may be the same.

In an embodiment, each R³ is ethyl.

R¹ and R², which may be the same or different, are each H or alkyl C1-10; or R¹ and R² together with -O-B-O- form a 5-, 6- or 7-membered ring optionally substituted with one or more C1-C4 alkyl groups.

In an embodiment, when R¹ and R² are each alkyl C1-10, R¹ and R² may be the same. As a skilled person will appreciate, when R¹ and R² are the same, this may have advantages in terms of ease of synthesis. However, it is not essential that R¹ and R² are the same, and compounds in which they are different will function as adhesion promoters as required by the invention.

In an embodiment, R^T and R² are each alkyl C1-6. In an embodiment, R¹ and R² are each alkyl C2-4.

In an embodiment, R¹ and R² are each butyl.

In an embodiment, R¹ and R² are each n-butyl.

Advantageously, when R¹ and R² are each butyl, hydrolysis of the compound during adhesion results in the release of butanol, which is already a common solvent in paint and coating formulations. The use of compounds of formula I in which R^T and R² are each butyl as additives for such known formulations may therefore be advantageous in some cases.

In an embodiment, when the compound is a compound of formula 1(a), and R¹ and R² are each butyl, the compound is a compound of formula l(a)(i)(a) or l(a)(ii)(a):

Formula l(a)(i)(a) Formula l(a)(ii)(a)

In this embodiment, Y may be absent.

When the compound is a compound of formula l(a)(i)(a) or l(a)(ii)(a), m is preferably 3. Each R³ may preferably be ethyl.

In an embodiment, the compound is a compound of formula l(a)(i)(a)(i) or l(a)(ii)(a)(i):

I(a)(i)(a)(i) l(a)(ii)(a)(i)

This compound of formula l(a)(i)(a)(i) or formula l(a)(ii)(a)(i) is hereinafter called LE. As previously noted, any additives may comprise a mixture of these two isomers.

In an embodiment, when the compound is a compound of formula 1(b), and R¹ and R² are each butyl, the compound is a compound of formula l(b)(i)(a) or l(b)(ii)(a):

Formula l(b)(i)(a) Formula l(b)(ii)(a).

In this embodiment, Y may be absent.

When the compound is a compound of formula l(b)(i)(a) or l(b)(ii)(a), m is preferably 3.

Each R³ may preferably be ethyl. In an embodiment, the compound is a compound of formula l(b)(i)(a)(i) or l(b)(ii)(a)(i):

l(b)(i)(a)(i) I(b)(ii)(a)(i)

In an embodiment, when the compound is a compound of formula 1(c), and R¹ and R² are each butyl, the compound is a compound of formula I (c)( i)(a) or l(c)(ii)(a):

In formula I (c)(i)(a). A¹ and A² are each independently -CH₂ or CHY.

In an embodiment, A¹ and A² are not both Y.

In an embodiment, Y is absent. In this embodiment, A¹ and A² are each -CH₂. When the compound is a compound of formula l(c)(i)(a) or l(c)(ii)(a), m is preferably 3.

Each R³ may preferably be ethyl.

In an embodiment, the compound is a compound of formula l(c)(i)(a)(i) or l(c)(ii)(a)(i):

l(c)(ii)(a)(i)

This compound of formula l(c)(i)(a)(i) or formula l(c)(ii)(a)(i) is hereinafter called ALBE. As previously discussed, any additives may comprise a mixture of these two isomers. Alternatively, in the compound of Formula l(a)(i)-(ii), l(b)(i)-(ii) or l(c)((i)-(ii), R¹ and R² may, together with -O-B-O-, form a 5-, 6- or 7-membered ring, which 5-, 6-, or 7-membered ring may be optionally substituted with one or more C1-C4 alkyl groups. Such compounds are shown below as formulae l(a)(i)(b)(i)-l(c)(ii)(b)(iii):

l(a)(i)(b)(ii) I(a)(ii)(b)(ii)

5

l(b)(i)(b)(iii) l(b)(ii)(b)(iii)

l(c)(i)(b)(iii);

l(c)(ii)(b)(iii) in which R⁶ to R²³ may each, independently, be H or C1-C10 alkyl, with the proviso that in formula l(a)(i)(b)(i), when m = 3 and R³ is ethyl, then R⁶, R⁷, R⁸ and R⁹ are not all methyl.

In an embodiment, Y is absent.

In an embodiment, R⁶ to R²³ may each, independently, be H or Ci-Ce alkyl. In an embodiment, R⁶ to R²³ may each be H.

In embodiments, the 5-, 6-, and 7-membered rings may be unsubstituted.

Compounds with 5- or 6-membered rings may be preferred due to their ease of synthesis.

In an embodiment, R¹ and R² together with -O-B-O- form a 5-membered ring, wherein the 5- membered ring is optionally substituted with one or more C1-C4 alkyl groups. In this embodiment, the compound may have the formula:

l(a)(i)(b)(i) l(a)(ii)(b)(i), with the proviso that in I (a )(i)(b)(i ) when m is 3 and R³ is ethyl, all of R⁶ to R⁹ cannot be methyl. In this embodiment, the compound is a compound of formula l(a)(i)(b)(i) or l(a)(ii)(b)(i). In these compounds, R⁶, R⁷, R⁸ and R⁹ may be the same. In an embodiment, m is 3.

In an embodiment, R³ is a C1-C4 alkyl.

In an embodiment, R³ is a Ci or C2 alkyl.

In an embodiment, R³ is ethyl.

In an embodiment, Y is absent.

In an embodiment, the 5-membered ring is unsubstituted, i.e., R⁶, R⁷, R⁸ and R⁹ are all H and the compound is a compound of formula l(a)(i)(b)(i)(a) or l(a)(ii)(b)(i)(a):

These compounds are hereinafter called CE.

As noted above, the inventors have advantageously determined that compounds of formula l(a)(i)-(ii), l(b)(i)-(ii) and l(c)(i)-(ii) have adhesion promoting properties. In particular, the inventors have demonstrated that the compounds of formula I (a)(i)-(ii), I (b)(i)-(ii) and l(c)(i)- (ii) can be used to promote adhesion between an epoxy-amine and a polysiloxane, such as those generally used in primer coats and top coats, respectively, for marine and protective coating applications. However, the invention is not limited to marine and protective coating applications, and the compounds can be used to promote adhesion between epoxy-amines and silicones in any field of application. The invention therefore relates to these compounds for use in promoting adhesion, in particular adhesion between epoxy-amines and silicones.

In aspects, the invention relates to the use of a compound of formula II as an adhesion promoter:

Formula II wherein in formula II, R¹ and R², which may be the same or different, are each H or alkyl Ci-io; or R¹ and R² together with -O-B-O- form a 5-, 6- or 7-membered ring optionally substituted with one or more C1-C4 alkyl groups; each R³ is independently Ci-Cio alkyl or Phenyl; m is an integer from 1 to 3; and L is a linker group of the formula X¹n-L¹-X²o, wherein:

L¹ is a C1-C20 aliphatic group or C5-C14 aromatic ring group or a C3-C8 cyclic hydrocarbon group; and each of X¹ and X² is a C1-C20 linear or branched saturated or unsaturated aliphatic hydrocarbon group; and wherein each of X¹, X², and L¹ is optionally substituted with Y, wherein Y is a C1-C20 linear or branched aliphatic hydrocarbon; halogen-substituted C1-C20 linear or branched aliphatic hydrocarbon; halogen, -OR⁴; -NR⁴2; -NO2; -SO3H; -C(=O)R⁴; -C(=O)OR⁴; - OC(=O)NR⁴ ₂; -C N; -SR⁴; -P(=O)R⁴ ₂; -OC(=O)OR⁵; -NC(=O)OR⁵; -SO₂R⁵; -SOR⁵; in which R⁴ is H, a C1-C20 branched or straight chain alkyl group or phenyl optionally substituted with Y; and R⁵ is a C1-C20 branched or straight chain alkyl group, and n and o are each independently 0 or 1.

In an embodiment, each X¹ and X², where present, is independently a Ci-C₈ linear or branched saturated or unsaturated aliphatic hydrocarbon group.

In an embodiment, L¹ is a Ci-Cs linear or branched hydrocarbon group or a C5-C14 aromatic ring group.

In an embodiment, L¹ is a C1-C4 linear or branched hydrocarbon group, or is benzene, or naphthalene. In an embodiment, L¹ is a C₂ alkyl group, or is benzene or naphthalene.

In an embodiment, the use relates to a compound of formula II wherein n and o are both 0.

In an embodiment, L¹ is unsubstituted.

In an aspect of the present invention there is provided use of a compound of formula 11 (a)(i)~ (ii), ll(b)(i)-(ii) or I l(c)(i)-(ii) as an adhesion promoter. Compounds of formula 11 (a )(i)-(ii), 11( b)(i )-

(ii) or ll(c)(i)-(ii) have the structure:

ll(c)(i) ll(c)(ii); in which R¹ and R², which may be the same or different, are each H or alkyl Ci-io; or R¹ and R² together with -O-B-O- form a 5-, 6- or 7-membered ring optionally substituted with one or more C1-C4 alkyl groups; each R³ is independently Ci-C₈ alkyl, or phenyl;

A¹ and A² are independently -CH₂ or CY;

PhY is a phenyl group optionally substituted with Y; and m is an integer from 1 to 3.

As before, the compounds of formula ll(a)(i) and ll(a)(ii) are isomers of each other, the compounds of formula I l(b)(i) and 11 (b)(ii) are isomers of each other, and the compounds of I l(c)(i) and 11 (c)(ii) are isomers of each other. The use of the compounds includes the use of the compounds in their single isomeric form, or as a mixture of isomers.

Compounds 1(a), 1(b) and 1(c) have the same structure as compounds 11(a), 11(b) and 11(c), respectively, however compound 1(a) specifically excludes the embodiment in which R¹ and R² together with -O-B-O- form a 5-membered ring (i.e. compound I (a )(i)(b)(i )) where m is 3, R³ is ethyl and which is substituted at R⁶, R⁷, R⁸ and R⁹ with -CH3), whereas this is explicitly encompassed within formula 11(a) The invention therefore relates to compounds of formula l(a)(i)-(ii),l(b)(i)-(ii) and l(c)(i)-(ii) per se, and to the use of compounds of formula II, and in particular of formula 11 (a )(i)-( ii), ll(b)(i)-(ii) and 11 (c) (i)-(ii) as adhesion promoters.

In an embodiment, the invention relates to use of a compound of formula I l(a)(i)-(ii), ll(b)(i)- (ii) or ll(c)(i)-(ii) as an adhesion promoter to promote adhesion between an epoxy-amine and a polysiloxane. Throughout this specification, the terms polysiloxane and silicone are used interchangeably.

In an embodiment, the use of a compound of formula I l(a)(i)-(ii) and/or ll(b)(i)-(ii) and/or I (c)(i)-(i i) as an adhesion promoter may be as an adhesion promoter between an epoxy-amine and a polysiloxane for marine applications. For instance, the use may be as an adhesion promoter between an epoxy-amine primer (or base) coat and a polysiloxane top-coat. The use may negate the need to use a tie-coat between the primer and top coats, particularly in marine applications.

This has significant advantages in terms of reducing dry-dock time, reducing cost and/or reducing labour. As a skilled person would appreciate, the use is not limited to marine applications and the compound can be used as an adhesion promoter between an epoxyamine and a polysiloxane in non-marine applications, such as for buildings, bridges, etc.

However, the use is not limited to applications where the tie-coat is absent, and, as a skilled person would appreciate, the compounds can be used to improve adhesion between a tiecoat and a primer or a base coat, where the tie-coat is based on similar chemistry.

The use of the compound of formula 11 (a )(i )-( ii) or ll(b)(i)-(ii) or 11 (c)(i)-(ii) may be in the form of an additive. The compound may be used in a single isomeric form, or as a mixture of isomers. In this embodiment, the additive may be added to a primer/base coat formulation and/or to a top coat formulation. The additive may be added neat, or may be added as a solution in a solvent. Suitable solvents include, for instance, xylene, toluene, ethyl acetate, propyl acetate, butyl acetate, methylethylketone, methylisobutylketone, propylene glycol methyl ether acetate, mineral spirits, naphtha and turpentine as would be apparent to one skilled in the art.

In an embodiment, the additive is added to the primer or top coat formulation at a concentration of from 0.001 to 15% (w/w) based on the total weight of the formulation.

In an embodiment, the additive is added to the primer or top coat formulation at a concentration of from 0.001 to 7% (w/w) based on the total weight of the formulation.

In an embodiment, the additive is added to the primer or top coat formulation at a concentration of from 0.001 to 4% (w/w) based on the total weight of the formulation. In an embodiment, the additive is added to the primer or top coat formulation at a concentration of from 0.1 to 4% (w/w) based on the total weight of the formulation.

In an embodiment, the additive is added to the primer or top coat formulation at a concentration of from 0.8 to 2.1% (w/w) based on the total weight of the formulation.

In embodiments, the additive may be added to the formulation in lieu of a portion of, or in lieu of all of, a curing agent.

Such curing agents (sometimes referred to as cure catalysts) for polysiloxane coatings are typically based on tetraethyl orthosilicate (TEOS) condensation cure chemistry (including oligomers, polymers and adducts of tetraethyl orthosilicate), and commercially-available silicone coatings are typically provided as a two- or three-part condensation cure formulation made up of the silicone, the curing agent, and optionally other performance additives. The inventors have advantageously determined that the additive of the invention performs a dualfunction, with the siloxane functionality of the additive of formula ll(a)/formula ll(b)/formula 11(c) acting as a curing agent in lieu of TEOS. This means that a portion, or all of, the curing agent can be replaced by additive, so that the properties of the resultant polysiloxane coating are minimally affected by the presence of the additive, but still effectively cure. Beneficially, this allows the compounds of the invention to be simply incorporated into existing, commercially-available formulations.

In an embodiment, the additive may be added to the base coat formulation. When the additive is added to the base coat formulation it can be added to the formulation at a concentration of from 0.001 to 15% (w/w), from 0.001 to 7% (w/w) based on the total weight of the formulation, at from 0.001 to 4% (w/w) based on the total weight of the formulation, from 0.1 to 4% (w/w) based on the total weight of the formulation, or from 0.8 to 2.1% (w/w) based on the total weight of the formulation.

In an embodiment, the additive is added to both the top coat and to the base coat formulation.

In an embodiment, the additive is added to the tie-coat.

According to an aspect of the invention there is provided a method of promoting adhesion between an epoxy-amine coating formulation and a polysiloxane coating formulation, wherein the method comprises adding a compound of formula II (as defined above) to at least one of the coating formulations, and bring the coating formulations into contact.

According to an aspect of the present invention there is provided a method of adhering an epoxy-amine coating formulation and a polysiloxane coating formulation, wherein the method comprises adding a compound of formula I l(a)(i)-(ii) or ll(b)(i)-(ii) or ll(c)(i)-(ii) to at least one of the coating formulations, before bringing the formulations into contact.

In an embodiment, the method comprises adding a compound of formula ll(a)(i)-(ii) or I l(b)(i)- (ii) or I l(c)(i)-(ii) to a polysiloxane coating formulation. In an embodiment, the polysiloxane coating formulation is a multi-part formulation comprising a polysiloxane and a curing agent, and the compound is added in lieu of a portion of the curing agent. The compound can be added at a concentration of from 0.001 to 15% (w/w) based on the total weight of the formulation, or in lieu of from 0.001 to 100 mole% of the curing agent.

As a skilled person will appreciate, the compound of formula l/ll can be added to the silicone formulation at a concentration that provides the formulation with the same concentration of reactive Si-OR³ groups as the original TEOS curing agent. Alternatively, the compound of formula l/ll can be added in addition to the TEOS curing agent.

The invention will now be described by reference to the Figures, in which:

Figure 1 shows the coating of aluminium strips with an epoxy-amine base coat, as described in Example 3;

Figure 2 shows the construction of samples for lap-shear testing as described in Example 4.

Experimental:

All reagents were purchased from Sigma-Aldrich™, Fisher Scientific™, and Fluorochem™, and were used without further purification. A two-component room-temperature curing silicone, silicone moisture cure resin CS25™- was purchased from easycomposites™. Where required, solvents were dried over 3A molecular sieves.

High Resolution Mass Spectrometry (HRMS) HRMS was conducted at the National Mass Spectrometry Facility (NMSF) Swansea. Samples were analysed using the Atmospheric Solids Analysis Probe (ASAP) on the APcI source of the Waters Xevo G2-S QTOF MS. Conditions: Source Temp 80°C. Samples were introduced into the source as a solid or liquid in an open-ended glass capillary held in the ASAP probe. Initial probe T is ~ 40 °C; probe T was then increased until the sample vaporizes (Vap T is sample dependent) and ions formed using a corona discharge current of 4pA. MS Resolving Power: >32,500 FWHM. Mass Range: m/z 50-2000. Mass Accuracy: <3 ppm (using the peptide Leucine enkephalin in solution as the lock mass).

Nuclear Magnetic Resonance (NMR)

NMR analyses were acquired at 25 °C using a JOEL ECS400 Delta spectrometer at frequencies of 399.78 MHz for ¹H-NMR and 100.53 MHz for ¹³C-NMR. All chemical shifts are quoted as parts per million (ppm) relative to tetramethylsilane (TMS, 6 = 0 ppm) as an internal standard in either deuterated chloroform (CDCI₃) or deuterated dimethyl sulfoxide (DMSO-d⁶). 13^c- NMR assignment was confirmed by DEPT analysis. The spectral data is recorded as chemical shift (6), relative integral, multiplicity (s=singlet, br=broad, d=doublet, t=triplet, q=quartet, quin=quintet, sext=sextet, dd=doublet of doublets, m=multiplet) and coupling constant (J = Hz).

Example 1: Synthesis of Compounds of formula I

1.1. Preparation of vinyl esters

Esterification of 1,4 vinyl phenyl boronic acid (BA) to the corresponding linear and cyclic (5- membered ring) esters, is shown in Scheme 1, and was carried out as follows:

VLE

Scheme 1: Esterification of vinyl phenyl boronic acid (BA) to vinyl cyclic (VCE) and vinyl linear (VLE) esters.

1.1.1 Preparation of vinyl cyclic ester (VCE)

1,4-vinyl phenyl boronic acid (100.0 g, 0.676 mol) was dissolved in dichloromethane (DCM) (1 L) in a 2 L round-bottomed flask, forming a cloudy suspension. To this suspension was added ethylene glycol (42.2 g, 0.678 mol), followed by MgSO₄ (~20 g). The reaction was stirred by use of a magnetic stirrer over 24 hours at room temperature (RT), before filtering to remove MgSO₄. DCM was removed under reduced pressure to produce a solid product (116.71 g, 0.670mol, 99%), which was used in subsequent reactions without further purification.

^XH-NMR (400 MHz, CHLOROFORM-D) 6 7.78 (d, J = 8.2 Hz, 2H), 7.43 (d, J = 8.2 Hz, 2H), 6.74 (dd, J = 17.6, 10.8 Hz, 1H), 5.83 (d, J = 17.4 Hz, 1H), 5.31 (d, J = 10.5 Hz, 1H), 4.38 (s, 4H)

Carbon: ¹³C-NMR (101 MHz, CHLOROFORM-D) 6 140.4, 136.8, 135.1, 125.7, 115.1, 66.0

IR: 2980 w C=C-H, 2915 w B-O-CH₂, 1608 m Ar, 1330 s B-O. 1.1.2 Preparation of vinyl linear ester (VLE)

1,4-vinyl phenyl boronic acid (40.00 g, 0.27 mol) was dissolved in butan-l-ol (371 mL, 300.51 g, 4.05 mol) in a 1 L round bottomed flask which was heated to 30°C and stirred through use of a magnetic stirrer for 4 hours. A vacuum was then applied in a distillation configuration and the temperature was increased to 70°C and distillation continued until no butan-l-ol or water was being distilled. Complete conversion was reached (as characterised by ¹H-NMR) and the resulting liquid was filtered through filter paper and the filtrate was then used in subsequent reactions without further purification. (69.55 g, 0.267 mol, 99%)

^XH-NMR (400 MHz, CHLOROFORM-D) 6 7.57 (br.s, 2H), 7.40 (d, J = 5.5 Hz, 2H), 6.75-6.68 (m, 1H), 5.78 (d, J = 17.4 Hz, 1H), 5.26 (d, J = 10.1 Hz, 1H), 4.02 (br.s, 4H), 1.51 (br.d, J = 74.2 Hz,

8H), 0.93 (br.s, 6H)

¹³C-NMR (101 MHz, CHLOROFORM-D) 6 138.5, 136.9, 134.8, 133.7, 125.5, 114.3, 64.3, 33.9, 19.0, 13.9

IR: 2960 w OC-H2, 2930 w B-O-CH2, 1610 w Ar, 1315 s B-O. 1.2 Preparation of triethoxysilane ester additives

Following the preparation of the vinyl linear and vinyl cyclic esters in Example 1.1 above, hydrosilylation of the esters was carried out to prepare triethoxysilane ester additives according to the invention, as shown in Scheme 2.

Scheme 2: hydrosilylation of vinyl cyclic (VCE) and vinyl linear (VLE) esters to form compounds CE and LE.

1.2.1 Preparation of triethoxysilane cyclic ester (CE)

The vinyl cyclic ester (VCE) prepared in Example 1.1.1 above (20.00 g, 0.115 mol) and platinum(0)-l,3-divinyl-l,l,3,3-tetramethyldisiloxane complex solution (3-3.5% Platinum concentration, 0.219 g) were dissolved in dry xylene (20 mL) in a flame-dried 250 mL round- bottomed flask which had been cooled under a drying tube (CaCI₂ was used as desiccant). The reaction was heated to 60 °C under a drying tube for 20 minutes before the addition of HSi(OEt)s (24.5 g, 0.149 mol). The reaction was stirred for a further 24 hours at 60 °C before ¹H-NMR indicated through the loss of alkene peaks at 6.74 ppm and 5.83 ppm that complete conversion had occurred. The reaction mixture was then filtered through glass wool to remove precipitate that had formed. The resulting solution of CE in xylene was used directly as an additive (see later examples).

High Resolution Mass Spectrometry (APCI) calculates for proposed product Ci6H28BOsSi⁺ (MH⁺) 339.1794 and found 399.1790.

To facilitate solvent-free testing of the additive, removal of the xylene was performed by first replacing the 20 ml of xylene reaction solvent with an equal volume (20 ml) of the lower boiling toluene, and then removing the toluene and xylene under reduced pressure through vacuum distillation in a fume hood. The neat CE was used directly as an additive (see later examples).

1.2.2 Preparation of triethoxysilane linear ester (LE)

The vinyl linear ester (VLE) prepared in Example 1.1.2 above (20.00 g, 0.077 mol) and platinum(0)-l,3-divinyl-l,l,3,3-tetramethyldisiloxane complex solution (3-3.5% Platinum concentration, 0.146 g) were dissolved in dry xylene (20 mL), in a flame-dried 250 mL round- bottomed flask which had been cooled under a drying tube (CaCl2 was used as desiccant). The reaction was heated to 60 °C for 20 minutes under a drying tube before the addition of HSi(OEt)s (16.440 g, 0.100 mol). The reaction was stirred through use of a magnetic stirrer for 48 hours. The absence of alkene peaks at 6.75-6.68 ppm and 5.78 ppm observed by ¹H-NMR indicated the reaction was complete. The reaction mixture was then filtered through glass wool to remove any precipitate. The resulting LE as a solution in xylene was then used as an additive in silicone-based coatings (see later examples).

To facilitate solvent-free testing of the LE additive, removal of the xylene was performed by first replacing the 20 ml of xylene reaction solvent with an equal volume (20 ml) of the lower boiling toluene, and then removing the toluene and xylene under reduced pressure through vacuum distillation in a fume hood.

High Resolution Mass Spectrometry (APCI) calculates for proposed product C22H42BO₅Si⁺ (MH⁺) 425.2889, and found 425.2885. 1.2.3 Preparation of alkyl linked butyl ester (ALBE)

ALBE was prepared from ethylene butyl boronic ester (EBBE) as shown in Scheme 3.

Alkyl linked butyl ester (ALBE)

Scheme 3: Preparation of alkyl linked butyl ester (ALBE

Ethylene butyl boronic ester (CAS: 6336-45-4, mass = 3 g, 0.0163 mol) and platinum(0)-l,3- divinyl-l,l,3,3-tetramethyldisiloxane complex solution (3-3.5% Platinum concentration, 0.0310 g) were dissolved in xylene (3 g) and stirred in a flame dried round bottom flask fitted with a CaCI₂ guard tube at 60 °C for 20 minutes. Triethoxysilane (3.4855 g, 0.0212 mol) was added dropwise to the mixture and stirred for a further 24 hours at 60 °C. The absence of three alkene peaks between 5.84-6.21 ppm observed by ¹H-NMR indicated the reaction was complete. The reaction mixture was then filtered through glass wool to remove any precipitate. The resulting ALBE as a solution in xylene was then used as an additive in silicone- based coatings (see later examples).

Example 2: Preparation of silicone formulations with CE/LE additives

2.1: Preparation of model primer/base coat formulations

Two model base coating systems were prepared. These model systems were intended to mimic commercially-available epoxy-amine coating formulations, such as those used as a primer or base coat in marine and performance coatings applications.

The first model base coat system (BC1) was prepared by combining a bisphenol A-based commercial epoxide resin (D.E.R. 331), a commercial amine curing agent (1,3- bis(aminomethyl)cyclohexane (also known as 1,3-BAC)) and a catalyst (2,4,6-tris- (dimethylaminomethyl)phenol (also known as DMP-30)) in a formulation that resulted in a 1:1 molar ratio of epoxide groups to NH (amine) groups.

A second model base coat system (BC2) was prepared by combining a bisphenol A-based commercial epoxide resin (D.E.R. 331), a commercial phenalkamine curing agent (Carolite NC 541 LV) and a catalyst (DMP-30) to give a 1:0.75 molar ratio of epoxide groups to NH (amine) groups based on the equivalent molecular weight of Carolite NC 541 LV and D.E.R. 331. Carolite NC 541 LV is a phenalkamine curing agent based on the reaction product of cardanol, formaldehyde and 1,2-ethandiamine, and the model base coat system therefore closely represents commercial epoxy-amine based anticorrosive coating systems, such as those used type used for protection of marine vessels and off-shore oil and gas assets.

Weight percentages of the BC1 and BC2 are shown in Table 1:

Example 2.2: Preparation of silicone topcoat formulations with additive

A silicone top-coat formulation was prepared by combining easycomposite™ silicone rubber base compound and easycomposite™ curing agent, with the CE,LE , or ALBE additive prepared in Examples 1.2.1 to 1.2.3 above. The ingredients were combined in a 20 ml glass sample vial, and manually homogenised for 120 seconds using a spatula before being applied to the top 30 mm of the cured epoxy-amine layer using a 400 pm drawdown bar (see below for details). Samples were prepared as shown in Table 2. Adhesion promoting additives (CE,LE or ALBE) were added as a solution in xylene where CE was a 68/32 (CE/xylene) w/w% solution in xylene, LE was a 66/34 (LE/xylene) w/w% in xylene, and ALBE was a 66/34 (ALBE/xylene) w/w% solution in xylene with the weight% of the additive in the silicone top coat calculated based on the weight of the CE/LE/ ALBE only (i.e., and not counting the xylene). Each formulation also contains trace amounts (0.25 to 2.2 wt%) of xylene depending on the loading of adhesion promotor. The sample shown in Entry 5 was prepared with neat CE additive, i.e., in the absence of added xylene, to assess the effect of solvent on the resulting adhesion.

Table 2: Weight % of components in silicone formulations Example 3: Coating Tests

Aluminium strips were cut to 100 mm x 25 mm, and then roughened with sandpaper, before being washed with deionised water and then with industrial methylated spirits (IMS). The strips were then left to dry for at least 30 minutes.

As illustrated in Figure 1, the aluminium sample strips (1) were coated with an epoxy-amine base coat (2) (either BC1 or BC2 - see Table 1) which was applied using a 400 pm drawdown bar. The epoxy-amine coating was then left to cure under either low temperature (LC) or high temperature (HC) conditions, as set out in table 3 below.

Table 3: Experimental curing conditions

As illustrated in Figure 2, the silicone topcoat (3) (prepared as described above) was then applied to the top 30 mm of the cured epoxy-amine layer at a wet-film thickness of 400 pm using a drawdown bar. A second aluminium strip cut to the same dimensions and also coated in the same epoxy-amine coatings was placed on top of the 30 mm silicone top-coat as shown in Figure 2, giving an overlap distance (O) of 30 mm and then left to cure for 24 hours at room temperature.

Example 4: Lap Shear Testing

Lap shear testing was performed using an Instron tensile tester equipped with a 3 kN load cell at an extension rate of 1 mm/min and the maximum tensile force (N) was measured in each case. Each coating system was tested 5 times. The failure method of the sample was recorded using the following code:

Table 4: Failure codes

4.1: Effect of CE Concentration (BC1)

The effect of CE concentration in the silicone top coat, was evaluated by preparing silicone top coat 1 with concentrations of CE additive ranging from 0.5 % to 2.5% w/w (see Table 2, Entries 2-5). Sample 1 was a control sample which did not contain any CE additive. Samples were prepared as described in Example 2.2 above. The base coat was the model system BC1 (Table 1) which was prepared using high temperature cure conditions (HC). The results are shown in Table 5.

Lap-sheer testing of Sample# 1 (control) showed an average force of adhesion loss of 245 N and adhesion failure mechanism 'A', when no additive was included in the silicone top coat. When CE was added, all silicone top coats showed improved adhesion to the base coat, with optimal results obtained when 1.5 wt% of CE was included. At this concentration, adhesion loss did not occur until 1,351 N, representing a 550% increase in adhesion strength versus control sample #1, where no CE additive was included. Example 4.2: Effect of LE concentration (BC1)

The experiments of Example 4.1 were repeated, but with the LE additive instead of CE (corresponding to samples, 6, 7, 8 and 9 from Table 2, with sample 1 again representing a control). The results are shown in Table 6.

Table 6: Effect of LE additive concentration on adhesion

Sample #1 in Table 6 again shows the adhesive strength of the control system with no additive (245 N) for comparison with the coating formulations which contained the LE additive at 0.6, 1.3, 1.9 and 3.1 wt.%. The best performing coating was Sample #3 (1.3% LE, 1318 N) and adding LE at all levels from 0.6-3.1 wt% had a significant positive impact on adhesion between the silicone top-coat and the epoxy-amine base coat.

Example 4.3: Effect of CE concentration (BC2)

The experiments of Example 4.1 were repeated using Base Coat 2 (BC2, formulation shown in

Table 1) under low temperature (LC) curing conditions. The results are shown in Table 7.

Table 7: Effect of CE concentration on adhesion, BC2 Table 7 shows the results of introducing the CE additive at 0.5 and 2.5 w/w as a solution in xylene (68/32 CE/xylene w/w%), compared to a control additive-free silicone topcoat (sample #1, 102 N). Sample #2 and sample # 3 both show significant improvement in adhesion when compared to the control sample #1. Sample #2 (0.5wt% CE) showed adhesion of 563 N, whilst sample #3 (2.5wt% CE) showed adhesion of 947 N. Both examples showed a large and significant improvement in adhesion versus the control sample in which no CE additive was included.

4.4: Effect of LE concentration (BC2)

The experiments of Example 4.1 were repeated using Base Coat 2 (BC2, formulation shown in Table 1) which was prepared using both high (HC, 60 °C) and low (LC, room temperature) cure conditions. The effect of LE concentration in the silicone top coat, was evaluated by preparing silicone top coat 1 with concentrations of LE additive ranging from 1.3 % to 3.1% w/w as described in Example 2.2 above. The results are shown in Table 8.

Table 8: Effect of LE additive concentration on adhesion to BC2

Sample # 1 is a control sample where no adhesion promoter is present while samples 2-5 show the effect of introducing LE adhesion promoter in xylene at a range of different levels (66/34 LE/xylene w/w%). Sample #4, which contained the highest concentration of LE adhesion promotor (3.1% w/w) was found to have the greatest adhesion performance (1026 N), in comparison to the control sample #1 which contained no LE additive (adhesion of 102 N). The sample containing 3.1 wt% LE was tested under both high (HC) and low (LC) temperature cure conditions to assess the impact of the cure conditions on the adhesion promotion. The results (samples 4 and 5) demonstrate that significant adhesion improvement is seen regardless of the conditions under which the base coat is cured. When the LC cure type (i.e., room temperature, table 3) cure conditions were used, a substantial improvement in adhesion versus the control sample was observed, at 856 N (versus 102 N for the control). This suggests that the additives will be useful for the promotion of adhesion at ambient temperatures.

4.5: Effect of ALBE concentration (BC2)

The experiments of Example 4.1 were repeated using Base Coat 2 (BC2, formulation shown in Table 1) which was prepared using low (LC, room temperature) cure conditions. The effect of ALBE concentration in the silicone top coat, was evaluated by preparing silicone top coat 3 with concentrations of ALBE additive ranging from 0.6 % to 2.7% w/w (see Table 2, Entries 10- 11). Sample 1 was a control sample which did not contain any ALBE additive. The results are shown in Table 9.

Table 9: Effect of ALBE additive concentration on adhesion to BC2

Lap-sheer testing of Sample# 1 (control) showed an average force of adhesion loss of 102 N and adhesion failure mechanism 'A', when no additive was included in the silicone top coat. When ALBE was added, all silicone top coats showed improved adhesion to the base coat, with optimal results obtained when 2.7 wt% of ALBE was included. At this concentration, adhesion loss did not occur until 1025 N, representing a 1005 % increase in adhesion strength versus control sample #1, where no ALBE additive was included.

Further tests carried out with commercially available base and top coat formulations confirm that the improved adhesion between the coats resulting from the addition of the additive is sufficient to negate the need for a tie-coat to be used.

Claims

Claims:

1. A compound of formula 1(a)(1), I (a )(i i), I (b) (i), I (b)(ii ) or I (c)(i)-(i i) :

1(c)(1) l(c)(ii) in which R¹ and R², which may be the same or different, are each H or alkyl Ci-io; or R¹ and R² together with -O-B-O- form a 5-, 6- or 7-membered ring optionally substituted with one or more C1-C4 alkyl groups; each R³ is independently Ci-C₈ alkyl or phenyl;

A¹ and A² are independently -CH₂ or CHY;

Y, which may be present or absent, is one or more substituents selected from a C1-C20 linear or branched saturated or unsaturated aliphatic hydrocarbon; halogen- substituted C1-C20 linear or branched saturated or unsaturated aliphatic hydrocarbon; halogen; -OR⁴; -NR⁴ ₂; -NO₂; -SO₃H; -C(=O)R⁴; -C(=O)OR⁴; -OC(=O)NR⁴ ₂; -C N; -SR⁴; - P(=O)R⁴ ₂; -OC(=O)OR⁵; -NC(=O)OR⁵; -SO₂R⁵; -SOR⁵; in which R⁴ is H, a C1-C20 linear or branched aliphatic hydrocarbon group or PhY; and R⁵ is a C1-C20 linear or branched saturated or unsaturated hydrocarbon group or PhY; or Y is PhY; PhY is a phenyl group optionally substituted with Y; and m is an integer from 1 to 3; and isomers thereof; wherein formula I is not:

2. A compound of formula l(a)(i)-(ii),l(b)(i)-(ii) or I (c)(i)-(ii) as claimed in claim 1, wherein m is 2 or 3.

3. A compound of formula l(a)(i)-(ii),l(b)(i)-(ii) or 1(c) (i)-(ii) as claimed in claim 2, wherein m is 3.

4. A compound of formula I (a )(i )-(i i), l( b)(i)-(ii) or I (c)(i)-(ii) as claimed in any preceding claim, wherein each R³ is independently Ci-Cs alkyl.

5. A compound of formula l(a)(i)-(ii),l(b)(i)-(ii) or 1(c) (i)-(ii) as claimed in claim 4, wherein each R³ is independently C1-C4 alkyl.

6. A compound of formula l(a)(i)-(ii),l(b)(i)-(ii) or I (c)(i)-(ii) as claimed in claim 5, wherein each R³ is methyl or ethyl.

7. A compound of formula 1 1 (a )(i)-( ii),l (b)(i)-(ii) or I (c)(i)-(i i) as claimed in claim 6, wherein each R³ is ethyl.

8. A compound of formula I (a )(i )-(i i), l( b)(i)-(ii) or I (c)(i)-(ii) as claimed in any preceding claim, wherein R¹ and R² are each independently C1-C10 alkyl.

9. A compound of formula l(a)(i)-(ii),l(b)(i)-(ii) or I (c)(i)-(ii) as claimed in claim 8, wherein R¹ and R² are the same.

10. A compound of formula l(a)(i)-(ii),l(b)(i)-(ii) or I (c)(i)-(i i) as claimed in claim 8 or claim 9, wherein R¹ and R² are Ci-C₆ alkyl.

11. A compound of formula l(a)(i)-(ii),l(b)(i)-(ii) or I (c)(i)-(i i) as claimed in any of claims 8 to 10, wherein R¹ and R² are butyl.

12. A compound of formula l(a)(i)-(ii),l(b)(i)-(ii) or I (c)(i)-(i i) as claimed in any of claims 1 to 7 wherein R¹ and R² together with -O-B-O- form a 5-, 6- or 7-membered ring optionally substituted with one or more C1-C4 alkyl groups.

13. A compound of formula l(a)(i)-(ii),l(b)(i)-(ii) or I (c)(i)-(i i) as claimed in claim 12 wherein R¹ and R² together with -O-B-O- form a 5- or 6-membered ring optionally substituted with one or more C1-C4 alkyl groups.

14. A compound of formula l(a)(i)-(ii),l(b)(i)-(ii) or I (c)(i)-(i i) as claimed in claim 12 or claim 13, wherein R¹ and R² together with -O-B-O- form a 5-, 6- or 7-membered unsubstituted ring.

15. A compound of formula l(a)(i)-(ii),l(b)(i)-(ii) or 1(c) (i)-(ii) as claimed in any preceding claim, wherein Y is absent.

16. A compound of formula l(a)(i)-(ii),l(b)(i)-(ii) or l(c)(i)-(ii) as claimed in any preceding claim, wherein the compound is selected from:

Si (OEt)₃

17. Use of a compound of formula II as an adhesion promoter:

Formula II wherein in formula II, R¹ and R², which may be the same or different, are each H or alkyl Ci-io; or R¹ and R² together with -O-B-O- form a 5-, 6- or 7-membered ring optionally substituted with one or more C1-C4 alkyl groups; each R³ is independently C1-C10 alkyl or Phenyl; m is an integer from 1 to 3; and L is a linker group of the formula X¹n-L¹-X²o, wherein:

L¹ is a C1-C20 aliphatic group or C5-C14 aromatic ring group or a C3-C8 cyclic hydrocarbon group; and each of X¹ and X² is a C1-C20 linear or branched saturated or unsaturated aliphatic hydrocarbon group; and wherein each of X¹, X², and L¹ is optionally substituted with Y, wherein Y is a C1-C20 linear or branched aliphatic hydrocarbon; halogen-substituted C1-C20 linear or branched aliphatic hydrocarbon; halogen, -OR⁴; - NR⁴ ₂; -NO₂; -SO3H; -C(=O)R⁴; -C(=O)OR⁴; -OC(=O)NR⁴ ₂; -C N; -SR⁴; -P(=O)R⁴ ₂; - OC(=O)OR⁵; -NC(=O)OR⁵; -SO₂R⁵; -SOR⁵; in which R⁴ is H, a C1-C20 branched or straight chain alkyl group or phenyl optionally substituted with Y; and R⁵ is a C1-C20 branched or straight chain alkyl group, and n and o are each independently 0 or 1.

18. Use of a compound of formula II as claimed in claim 17, wherein X¹ and X², where present, is each independently a Ci-Cs linear or branched saturated or unsaturated aliphatic hydrocarbon group.

19. Use of a compound of formula II as claimed in claim 17 or claim 18, wherein L¹ is a Ci- Cs linear or branched hydrocarbon group or a C5-C14 aromatic ring group.

20. Use of a compound of formula II as claimed in claim 19, wherein L¹ is a C1-C4 linear or branched hydrocarbon group, or is benzene, or naphthalene.

21. Use of a compound of formula II as claimed in claim 19, wherein L¹ is a C2 alkyl group, or is benzene or naphthalene.

22. Use of a compound of formula II as claimed in any of claims 17 to 21, wherein n and o are both 0.

23. Use of a compound of formula II as claimed in any of claims 17 to 22, wherein L¹ is unsubstituted.

24. Use of a compound of formula II as claimed in any of claims 17 to 23 wherein the compound of formula II is selected from:

,

25. A method of promoting adhesion between an epoxy-amine coating formulation and a polysiloxane coating formulation, wherein the method comprises adding a compound of formula II as defined in any of claims 17 to 24 to at least one of the coating formulations, and bringing the formulations into contact.