Radiation-curable coating composition, method of coating a substrate and coated substrate

Abstract

A radiation-curable coating composition comprising: a) one or more butenolide monomer A of general formula (I) wherein: n is 0 or an integer of from 1 to 5; R1 is alkyl or aryl; X is any one of -C(O)-, -C(O)O-, -C(O)NR2-, -S(O)-, -S(O2)-, -C(O)S-, -C(S)S- and - C(S)NR2-; wherein R2 is hydrogen, alkyl or aryl; or wherein, when n is 0 and X is -C(O)NR2- or -C(S)NR2-, R1 and R2 together with the nitrogen atom through which they are linked form a nitrogen-containing heterocyclic group or nitrogen-containing heteroaryl group; and b) one or more vinyl monomer B comprising one or more vinyl groups wherein at least one vinyl group has a difference in 13C chemical shift between the α-C and β-C of a vinyl group of at least 25 ppm; wherein at least one monomer of A and B comprises at least two vinyl groups; and to coated substrates.

Description

[0001] RADIATION-CURABLE COATING COMPOSITION, METHOD OF COATING A SUBSTRATE AND COATED SUBSTRATE

[0002] Field of the Invention

[0003] The present invention relates to a radiation-curable coating composition, a method of coating a substrate comprising applying and curing such coating composition, and a coated substrate obtainable by such method.

[0004] Background of the Invention

[0005] Radiation-curable coating compositions containing double bonds that can be activated by actinic radiation, such as UV light or electron beam radiation, are well known in the art. Reference herein to actinic radiation is to electromagnetic, ionizing radiation, in particular electron beam radiation, UV light and visible light. Radiation-curable coating compositions typically cross-link through radical polymerization of monomers with an ethylenically unsaturated group, such as an acryloyl, methacryloyl, or vinyl group. Examples of such monomers include acrylic acid, methacrylic acid, alkyl esters of (meth)acrylic acid, styrene, alkyl-substituted styrene, vinyl esters, and vinyl ethers. The monomers are usually prepared from petrochemical raw materials.

[0006] There is an increasing demand for chemical products prepared from renewable feedstock. Binder polymers at least partly prepared from renewable feedstock are known in the art. Alkyd resins for example comprise a relatively high content of fatty acids obtained from vegetable oil.

[0007] In US 4,954,593 is disclosed a copolymer for use as a protective coating that is prepared by combining a furanone monomer and a vinyl ether monomer in a molar ratio of about one. The copolymer may be prepared by photopolymerization or by solution polymerization in the presence of a free-radical initiator.

[0008] Butenolides are ethylenically unsaturated furanoic compounds that can be prepared from carbohydrates, i.e. a renewable feedstock. Carbohydrate feedstock such as starch, cellulose or carbohydrate-containing bio-waste can be converted into furfural, hydroxymethylfurfural, or related furan derivatives by dehydration and can then be oxidized into furanones. Preparation of alkoxylated furanones is for example described in Chapter II of J.C. de Jong, Asymmetric Diels-Alder reactions with 5-menthyloxy- 2(5H)-furanones, Thesis University of Groningen, 2006, accessible via https: / / www.rug.nl / research / portal / en / publications / asymmetric-dielsalder-reactions- With-5menthyloxy25hfuranones(f0ab6c00-8c6c-4ccc-90aa-3ef05f759fa4).html.

[0009] Poskonin et al. have disclosed in Russian Journal of Organic Chemistry 35 (1999) 721- 726 copolymers prepared by radical polymerization of 5-alkoxy-2(5H)-furanone and styrene, methyl methacrylate, or vinyl acetate. Use of such copolymers for synthesis of physiologically active substances is suggested. Poskonin et al. have further disclosed in Russian Journal of Organic Chemistry 35 (1997) 520-523 oligomers prepared by radical polymerization of 4-acetoxy-2-butenolide (5-acetoxy-2(5H)-furanone) and styrene, methyl methacrylate, or vinyl acetate. Number average molecular weights of from 1860 to 6460 were achieved.

[0010] W02021 / 084066 describes copolymerization of 5-alkoxy-2(5H)-furanones with selected vinyl ethers or vinyl esters and the use of the resulting copolymers as a binder in a polymer coating composition.

[0011] WO2021 / 259819 describes a radiation-curable copolymer coating composition comprising a 5-hydroxy or 5-alkoxy-2(5H)-furanone compound and a compound with two or more vinyl ether or vinyl ester groups.

[0012] Trost and Toste have disclosed in J. Am. Chem. Soc. 2003, 125, 3090-3100 two butenolide compounds: 2-tert-Butoxycarbonyloxy-5-oxo-2,5-dihydrofuran and 2- benzoyloxy-5-oxo-2,5-dihydrofuran with application in introducing chirality into synthesis of aflatoxins.

[0013] Parijat Ray et al. “Synthesis of Bioacrylic Polymers from Dihydro-5-hydroxyl furan-2-one (2H-HBO) by Free and Controlled Radical Polymerization”, ACS OMEGA, vol. 3, no. 2, 20 February 2018 (2018-02-20), pages 2040-2048 describes the reaction of dihydro-5- hydroxyl furan-2-one with methacrylic anhydride to form a methacrylic-dihydro-5- hydroxyl furan-2-one monomer. Subsequent homo- and co-polymerisation is carried out. There is a need for radiation-curable coating compositions that can at least partially be obtained from renewable feedstock.

[0014] Summary of the Invention

[0015] It has now been found that a hard and chemically resistant cured coating can be obtained by radiation curing, activated by actinic radiation such as visible or UV light or electron beam radiation, of a composition comprising a 5-substituted butenolide monomer and a monomer comprising one or more vinyl groups. The coatings formed have properties that make them suitable as protective or decorative coatings.

[0016] Accordingly, the invention provides in a first aspect a radiation-curable coating composition comprising: a) one or more butenolide monomer A of general formula (I): wherein: n is 0 or an integer of from 1 to 5;

[0017] R1is alkyl or aryl;

[0018] X is any one of -C(O)-, -C(O)O-, -C(O)NR2-, -S(O)-, -S(O2)-, -C(O)S-, -C(S)S- and - C(S)NR2-; wherein R2is hydrogen, alkyl or aryl; or wherein, when n is 0 and X is -C(O)NR2- or -C(S)NR2-, R1and R2together with the nitrogen atom through which they are linked form a nitrogen-containing heterocyclic group or nitrogen-containing heteroaryl group; and b) one or more vinyl monomer B comprising one or more vinyl groups wherein at least one vinyl group has a difference in13C chemical shift between the a-C and p-C of a vinyl group of at least 25 ppm; wherein at least one monomer of A and B comprises at least two vinyl groups.

[0019] It is an advantage of the coating composition that it can be formulated without organic solvent or with only a small amount of organic solvent, typically less than 20 wt%.

[0020] In a second aspect, the invention provides a method of coating a substrate comprising: providing a substrate applying a coating composition as defined herein to the substrate; and radiation-curing the coating composition to form a cured coating.

[0021] The coating composition and the cured coating formed from it has a relatively high content of furanone, a bio-based material.

[0022] The binder polymer formed upon curing has a polymer backbone with acetal functionality, which advantageously provides possibilities for further crosslinking or modification of the coating, for example with a hydroxyl or thiol functional crosslinker or with a polymer with hydroxyl or thiol functionality.

[0023] In a third aspect, the invention provides a coated substrate obtainable by a method according to the second aspect of the invention.

[0024] Detailed Description

[0025] The radiation-curable coating composition comprises a) one or more butenolide monomer A; and b) one or more vinyl monomer B, wherein at least one monomer of A and B comprises at least two vinyl groups. The presence of a monomer having at least two vinyl groups is necessary to act as a cross-linker in the coating composition.

[0026] A butenolide as described herein is equivalent to a furanone. A 5-substituted butenolide as described herein is equivalent to a 5-substituted furanone. As used herein the term one or more with reference to each of A and B means that multiple different monomers of each of A and respectively B may be present in the coating composition. For example a composition may comprise one butenolide monomer A and one vinyl monomer B. Alternatively, it may comprise one butenolide monomer A and two vinyl monomers B, which vinyl monomers B are different from each other. Alternatively, it may comprise two butenolide monomers A, which butenolide monomers A are different from each other, and one butenolide monomer B.

[0027] A vinyl group has an a-C and p-C determined by proximity to another functional group in the molecule. As used herein difference in13C chemical shift between the a-C and p- C of the vinyl group can be determined from the chemical shift as reported in the Spectral Database for Organic Compounds (https: / / sdbs.db.aist.go.jp / sdbs / cgi- bin / direct frame top.cgi), managed by the National Institute of Advanced Industrial Science and Technology.

[0028] As used herein an alkyl radical may be branched, unbranched, linear or cyclic. The alkyl radical may be saturated or unsaturated. It may be substituted or unsubstituted. An alkyl radical typically comprises from 1 to 20 carbon atoms, in particular from 1 to 12 carbon atoms, 1 to 6 carbon atoms or 1 to 4 carbon atoms. An alkyl radical may comprise from 2 to 20 carbon atoms, in particular from 2 to 12 carbon atoms, 2 to 6 carbon atoms or 2 to 4 carbon atoms. An alkyl radical may contain from 1 to 3 carbon atoms, for example 1 , 2 or 3 carbon atoms. Examples of alkyl radials are methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, sec-butyl, isobutyl, hexyl, lauryl, oleyl and cyclohexyl.

[0029] As used herein, cycloalkyl means a cyclic alkyl radical. Cyclic heteroalkyl means a cyclic heteroalkyl radical wherein at least one carbon in the cycle is substituted with a heteroatom. A heteroatom may be nitrogen, oxygen or another atom other than carbon. A cyclic heteroalkyl radical may be a nitrogen-containing cyclic heteroalkyl.

[0030] As used herein aryl means an aromatic radical. An aryl radical may be substituted or unsubstituted. An aryl radical typically contains 6 or 10 carbon atoms. An aryl radical may be phenyl or naphthyl, in particular phenyl. Heteroaryl means an aryl radical comprising a heteroatom, i.e. an atom other than carbon, in an aromatic ring. A heteroaryl radical may be substituted or unsubstituted. A heteroaryl radical typically contains from 5 to 12 carbon atoms. A typical heteroatom is oxygen or nitrogen.

[0031] The coating composition comprises one or more butenolide monomer A of general formula (I): wherein: n is 0 or an integer of from 1 to 5;

[0032] R1is alkyl or aryl;

[0033] X is any one of -C(O)-, -C(O)O-, -C(O)NR2-, -S(O)-, -S(O2)-, -C(O)S-, -C(S)S- and - C(S)NR2-; wherein R2is hydrogen, alkyl or aryl; or wherein, when n is 0, R1and R2together with the nitrogen atom through which they are linked form a nitrogen-containing heterocyclic group or nitrogen-containing heteroaryl group.

[0034] In one embodiment for at least one butenolide monomer A, n=0; and wherein at least one vinyl monomer B comprises at least two vinyl groups.

[0035] In one embodiment which comprises at least two butenolide monomers A, for at least one butenolide monomer A, n is an integer of from 1 to 5.

[0036] In one embodiment X is any one of -C(O)-, -C(O)O-, -C(O)NR2-. In this embodiment R2is for example hydrogen. Alternatively, when X is -C(O)-, R1may be C2-C6 alkyl or phenyl. In one embodiment R1is C1-C20 alkyl, C5-C7 cycloalkyl or phenyl. In one embodiment, R1may be C1-C12 alkyl. In another embodiment, R1may be C5-C7 cycloalkyl. In another embodiment R1may be phenyl.

[0037] In one embodiment, R2may be hydrogen or C1-C20 alkyl. In particular, R2may be hydrogen or C1-C12 alkyl, for example R2may be hydrogen.

[0038] If n is an integer with a value in the range of from 1 to 5, butenolide monomer A is an oligomer obtainable by reacting a multifunctional scaffold having in the range of from 2 to 6 reactive groups with 5-hydroxy-2(5H)-furanone. The multifunctional scaffold may for example have from 1 to 40 carbon atoms.

[0039] Examples of suitable multifunctional scaffolds include polyacids such as oxalic acid, malonic acid, succinic acid, maleic acid, fumaric acid, adipic acid, citric acid, propane- 1 ,2,3-tricarboxylic acid, trimesic acid and the corresponding thioacid, isocyanate and thiocyanate counterparts. Other examples of suitable scaffolds include alkyl carbonate of chloroformate derivatives of polyols such as ethylene glycol, propylene glycol, glycerol, cyclohexanedimethanol or pentaerythritol.

[0040] In one embodiment a vinyl monomer B is a vinyl compound of general formula (II) R3CH=CH2(II); wherein R3is any one of:

[0041] -OR4, -OC(O)R4, -N(R5)C(O)R4, -N(R5)C(O)OR4, -NR5C(S)R4, -NR5C(S)OR4, - NR5C(S)SR4and -SC(S)SR4; wherein R4is alkyl or aryl, and wherein R5is hydrogen, alkyl or aryl, or wherein R4and R5together with the atoms through which they are linked form a nitrogen-containing heterocyclic group or nitrogen-containing heteroaryl group.

[0042] In one embodiment R3is -OR4, -OC(O)R4or -N(R5)C(O)R4.

[0043] In one embodiment a vinyl momomer B is a monovinyl ester, a monovinyl ether or a mono N-vinyl compound. In one embodiment a vinyl monomer B is n-butyl vinyl ether, iso-butyl vinyl ether, cyclohexyl vinyl ether, phenyl vinyl ether, 2-ethylhexyl vinyl ether, n-dodecyl vinyl ether, 4-hydroxybutyl vinyl ether, vinyl neodecanoate, vinyl neononanoate, N-vinylpyrrolidone, N-vinyl imidazole, N-vinyl-formamide, N-vinyl-pyrrole or N-vinylcaprolactam.

[0044] In one embodiment, a vinyl compound B is a monovinyl ester, a monovinyl ether, a mono N-vinyl compound and / or a (meth)acryloyl monomer with a molecular weight in the range of from 50 to 800 g / mol, more preferably of from 100 to 500 g / mol.

[0045] In one embodiment a vinyl monomer B has at least two vinyl groups. In the vinyl monomer of formula (II), R3comprises at least one vinyl group. For example, R4comprises at least one vinyl group or R5comprises at least one vinyl group or both R4and R5comprise at least one vinyl group.

[0046] The radiation-curable coating composition may comprise at least two vinyl monomers B. At least one vinyl monomer B may comprise at least two vinyl groups. For example, the radiation-curable coating composition may comprise one vinyl monomer B, which is a monovinyl compound and one vinyl monomer B which is a divinyl compound.

[0047] In one embodiment a vinyl monomer B has at least two vinyl groups and is a divinyl ether, a divinyl ester or a di-N-vinyl compound.

[0048] Examples of a vinyl monomer B with at least two vinyl ester groups include malonic acid divinyl ester, adipic acid divinyl ester, fumaric acid divinyl ester, sebacic acid divinyl ester, phthalic acid divinyl ester, and trimellitic acid trivinyl ester.

[0049] Examples of a vinyl monomer B with two or three vinyl ether groups include divinyl ethers or trivinyl ethers of (poly)ethylene glycol or (poly)propylene glycol such as ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, tetraethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, tripropylene glycol divinyl ether, tetrapropylene glycol divinyl ether; butanediol divinyl ether; hexanediol divinyl ether; 1 ,4-cyclohexanedimethanol divinyl ether; and trimethylol propane trivinyl ether. Examples of a vinyl monomer B with at least two N-vinyl groups are N-vinyl substituted polycarboxamides, for example adipamide, succinamide, terephthalamide, isophthalamide, benzene-tricarboxamides.

[0050] Vinyl monomer B may be a compound with a polymeric backbone and two or more vinyl ether groups, for example a polyurethane, polyester-urethane, polyetherurethane, poly(meth)acrylate-urethane, or polyester with two or more vinyl ether groups. Such compounds may for example be prepared by reacting an isocyanate with a hydroxyl functional vinyl ether and a hydroxyl functional polyester, polyether or poly(meth)acrylate. A polyester with two or more vinyl ether groups can be prepared via a transesterification of a hydroxyl functional vinyl ether with a polyester with two or more ester groups of alcohols with a relatively low boiling point. By using in the coating composition such compound with a polymeric backbone, the properties of the cured coating, in particular mechanical properties, can be tuned by the choice of the backbone.

[0051] Vinyl monomer B may have a molecular weight in the range of from 100 to 3,000 g / mol. If vinyl monomer B is a compound with a polymeric backbone as described above, the molecular weight may be in the range of from 500 to 3,000 g / mol.

[0052] In one embodiment, the weight fraction of monomers comprising at least two vinyl groups in the composition is at most 5 wt.%.

[0053] In one embodiment, the molar ratio of furanone moieties to vinyl moieties is in the range of from 1.5: 1.0 to 1.0: 1.5. For example the molar ratio may be of from 1.2 to 1.0 to 1.0 to 1.2. Vinyl moieties are present in vinyl monomer B. In one embodiment, the coating composition does not comprise any compounds with vinyl moieties other than vinyl monomer B.

[0054] In one embodiment, the radiation-curable coating composition is free of a compound with two or more acryloyl or methacryloyl groups. The presence of such compound may have a negative effect on film formation. The total amount of butenolide monomer A and vinyl monomer B in the radiation- curable coating composition may be in the range of from 70 to 100 wt%, more preferably from 80 to 100 wt%, even more preferably of from 90 to 100 wt%.

[0055] The coating composition is radiation-curable. The coating composition may be cured by photoinitiation, i.e. by radiation with visible light or UV light. In one embodiment, the composition further comprises c) a photo-initiator.

[0056] The photo-initiator may be one photo initiator or a mixture of two or more thereof. Photo-initiators generate free radicals when exposed to radiation energy in the visible light or UV light wavelength range. Any suitable photo-initiator known in the art may be used, depending on the wavelength. Suitable photo-initiators include benzoin derivatives, benzile ketales, a-hydroxyalkylphenones, monoacylphosphine oxide (MAPO) and bisacylphosphine oxides (BAPO), such as diphenyl(2,4,6- trimethylbenzoyl)phosphine oxide, 1-hydroxy-cyclohexyl-phenyl-ketone, bis(2,4,6- trimethylbenzoyl)-phenylphosphineoxide, bis(2,6-dimethoxybenzoyl)-2,4,4- trimethylpentyl-phosphine oxide, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 2-methyl- 1[4-(methylthio)phenyl]-2-morpholono-propan-1-one, a phenyl glyoxylic acid methyl ester. Mixtures of these compounds may also be employed.

[0057] The photo-initiator may be present in an amount of from 0.1 to 10 wt%, for example from 0.5 to 5.0 wt%, based on the total weight of the coating composition.

[0058] Alternatively, the curing of the coating composition may be initiated by electron beam or by gamma radiation. For initiation by electron beam or gamma radiation, no photoinitiator is needed.

[0059] The coating composition may be a powder coating composition or a liquid coating composition, preferably a liquid coating composition. The coating composition preferably is an essentially solvent-free liquid coating composition. Reference herein to an essentially solvent-free coating composition is to a coating composition comprising at most 1 wt% of organic solvent, more preferably at most 0.5 wt%, still more preferably 0 wt%. In case the viscosity of butenolide monomer A and vinyl monomer B is undesirably high the coating composition may comprise some organic solvent to control the viscosity. Preferably, the coating composition comprises at most 30 wt% organic solvent, more preferably at most 20 wt%, even more preferably at most 10 wt%, still more preferably at most 5 wt% or at most 2 wt%.

[0060] Suitable organic solvents are solvents in which butenolide monomer A and vinyl monomer B and the cured polymer dissolve at polymerization conditions. The organic solvent may be an oxygenated organic solvent, for example an alcohol, ketone, ester or ether. In particular, the solvent is a glycol ether, glycol ester or an alkyl acetate, for example 1-methoxy-2-propanol or butyl acetate.

[0061] The coating composition is not a waterborne coating composition, i.e. water is not the liquid medium in which butenolide monomer A and vinyl monomer B are dissolved or dispersed. The coating composition may comprise a small amount of water, for example water that is contained in additives comprised in the coating composition. In one embodiment, the coating composition comprises less than 5 wt% water, more preferably less than 1 wt%.

[0062] The coating composition may comprise further ingredients commonly used in coating compositions such as color pigments, extender pigments, and one or more additives such as for example light stabilizers, other stabilizers, defoaming agents, matting agents, wetting agents, or flow agents.

[0063] Radiation-curing the coating composition may be by exposing the coating composition to visible light or UV radiation, electron beam radiation, or gamma radiation, to form a cured coating.

[0064] The coating composition may be applied to the substrate by conventional techniques, including spraying, rolling, blade-coating, pouring, brushing or dipping. After evaporation of any organic solvent and / or water, if present, the coating composition results in a coating that is from dust-dry to very tacky. Curing is then induced by means of radiation. Any suitable source of radiation can be used. In particular, radiation curing may be by electron beam radiation, UV radiation or visible light radiation. In one embodiment, the coating composition further comprises c) a photo-initiator and the coating composition is cured by exposing the coating composition to visible light or UV radiation, for example to visible light with a wavelength in the range of from 400 to 600 nm or to UV radiation with a wavelength in the range of from 200 to 400 nm, in particular to UV radiation with a wavelength in the range of from 280 to 400 nm, or preferably of from 320 to 400 nm (UV-A radiation).

[0065] For UV radiation, Hg lamps, metal halide lamps, xenon lamps, or UV-LED lamps may for example be used. It is preferred to use UV-LED lamps.

[0066] Radiation curing of the coating composition can be done at ambient conditions, e.g. room temperature and atmospheric pressure. Reference herein to room temperature is to a temperature in the range of from 15 to 30 °C. The curing may be accelerated by post-heating, for example post-heating to a temperature in the range of from 40 to 100 °C, preferably of from 50 to 80 °C.

[0067] The substrate may be any suitable substrate, such as for example wood, polymer, composite, metal, glass, or other mineral substrate. The substrate may be a primed or bare substrate.

[0068] The coating composition can be used as a single layer applied directly to the substrate, or in multilayer systems, e.g. as a primer, a basecoat, a clearcoat, or a topcoat. The coating composition can be used for various applications, such as coating of wood, electronic appliances, plastic automotive components, food can, or as architectural coating.

[0069] The invention is further illustrated by means of the following non-limiting examples.

[0070] The following butenolide compounds were used:

[0071] 5-methoxy-2(5H)-furanone (Methoxy butenolide) MeOBut

[0072] 5-acetoxy-2(5H)-furanone (Acetoxy butenolide) AcOBut 5-isobutyroxy-2(5H)-furanone (Isobutyroxy butenolide) iBrOBut

[0073] 5-pivaloyloxy-2(5H)-furanone (Pivaloyloxy butenolide) PivOBut

[0074] 5-succinyloxy-2(5H)-furanone methyl ester (Succinyloxy butenolide methyl ester) MeOSuccOBut

[0075] The following mono-functional vinyl compounds were used: ethylene glycol vinyl ether EGVE

[0076] / V-vinylpyrrolidone NVP

[0077] The following di-functional butenolide compound was used:

[0078] Bis(5-oxo-2,5-dihydrofuran-2-yl) succinate (Succinyloxy bis-butenolide) SuccOBut2

[0079] The following di-functional vinyl compounds was used: diethylene glycol divinyl ether DEGDVE

[0080] Preparation of butenolide monomers

[0081] Methoxy butenolide

[0082] 5-methoxy-2(5H)-furanone

[0083] Chemical Formula: C5H5O3

[0084] Molecular Weight: 114.1000

[0085] This product and its synthesis were previously described in: Hermens et al., Sci. Adv. 2020; 6: eabe0026. 5-Hydroxy-2(5H)-furanone (100.0 g, 1 mol) was dissolved in 500 mL dry methanol and heated at reflux for 20 h. The conversion was followed by1H NMR until all 5-hydroxy-2(5H)-furanone was consumed. The solvent was evaporated under reduced pressure and the crude was distilled under reduced pressure (70 °C, 1.0x1 O'2mbar) yielding 5-methoxy-2(5H)-furanone (86.5 g, 0.76 mol, 76%) as a slightly yellow oil.

[0086] Acetoxy butenolide

[0087] 5-oxo-2 , 5-d i hyd rof uran-2-y I acetate

[0088] Chemical Formula: C6H5O4

[0089] Molecular Weight: 142.1100 This product and its synthesis were previously described in: G.C. Resende, E.S. Alvarenga, J.C.G. Galindo, F.A. Macias, J. Braz. Chem. Soc. 2012, 23 (12), 2266-2270. In a flask under N2 atmosphere, hydroxy butenolide (1 eq., 500 mg, 5.00 mmol, grey solid) was dissolved in dry DCM (25 mL) and cooled to 0°C with an ice bath. Acetic anhydride (1.6 eq., 754 (1 L, 7.99 mmol) was added, followed by a solution of DMAP (0.3 eq., 183 mg, 1.50 mmol) in dry DCM (1.5 mL). The mixture was stirred at 0°C for 1 h and then allowed to warm up to RT. TLC (25% AcOEt / hexanes, rev. KMnO4) showed formation of a new product at Rf = 0.37. The clear solution was washed with water (25 mL). After phase separation, the aqueous layer was further extracted with DCM (25 mL). The combined organic extracts were dried with sodium sulfate, filtered on cotton and concentrated under reduced pressure. The residue was purified by automatic column chromatography (15g SiO2 cartridge, 10 — 40% AcOEt / pentane over 20 column volume (CV), using DCM for liquid injection. Concentration of the collected fraction afforded pure acetoxy butenolide as a colorless liquid (506 mg, 3.56 mmol, 71 % yield).

[0090] Isobutyroxy butenolide

[0091] 5-isobutyroxy-2(5H)-furanone

[0092] (5-oxo-2,5-dihydrofuran-2-yl isobutyrate)

[0093] Chemical Formula: C8H10O4 Molecular Weight: 170.1640

[0094] In a flask under N2 atmosphere, hydroxy butenolide (90 wt% pure, 1.50 eq., 6.67 g, 4.00 mmol) was dissolved in anhydrous DCM (40 mL, [acid] = 1 M). Isobutyric acid (1.00 eq., 3.70 mL, 40.0 mmol) and DMAP (5 mol%, 244 mg, 2.00 mmol) were added. The clear mixture (blue due to hydroxy butenolide) was cooled to 0°C with an ice bath. N,N'- Dicyclohexylcarbodiimide (DCC) (1.20 eq., 9.90 g, 48.0 mmol) was dissolved in anhydrous DCM (5 mL) and added dropwise at 0°C over 5 min. After the addition, the ice bath was removed, and the mixture was stirred at room temperature for 1 h. The mixture turned from blue to dark brown with a precipitate. The reaction mixture was filtered on cotton wool, rinsing with DCM, affording a brown solid (urea) and a clear brown filtrate, which was concentrated in vacuo to a dark brown oil. The crude residue was purified by automatic column chromatography (80 g SiO2 cartridge, 5-30% AcOEt / pentane over 15 CV), using DCM for liquid injection. Concentration of the collected fraction afforded pure isobutyroxy butenolide as a yellow oil (4.84 g, 28.4 mmol,

[0095] 71% yield).

[0096] Pivaloyloxy butenolide

[0097] 5-pivaloyloxy-2(5H)-furanone

[0098] (5-oxo-2, 5-di hydrofuran-2-yl pivalate)

[0099] Chemical Formula: C9H12O4 Molecular Weight: 184.1910

[0100] Hydroxy butenolide (1 eq., 5.00 g, 50.0 mmol) was dissolved in dry DCM (25 mL) and cooled to 0°C with an ice bath. This caused hydroxy butenolide to (partially) precipitate. Pivalic anhydride (1.2 eq., 12.2 mL, 60.0 mmol) was added, followed by a solution of DMAP (0.1 eq., 610 mg, 5.00 mmol) in dry DCM (2.5 mL). The mixture was first stirred at 0°C for 30 min and was then allowed to warm up to RT, thereby causing full dissolution of the solids. The homogeneous mixture was further stirred at room temperature overnight (20 h in total). Over the course of the reaction, the initially blue mixture turned to dark green / brown. The reaction mixture was concentrated. The residue was purified by automatic column chromatography (80 g SiO2 cartridge, 5-30% AcOEt / pentane over 15 CV), using DCM for liquid injection. Concentration of the collected fraction afforded pure pivaloyloxy butenolide as a pale-yellow oil (6.74 g, 36.6 mmol, 73% yield).

[0101] Succinyloxy butenolide 4-oxo-4-((5-oxo-2,5-dihydrofuran-2-yl)oxy)butanoic acid Chemical Formula: CsHsOe Molecular Weight: 200.1460

[0102] Hydroxybutenolide (1 eq., 1.00 g, 9.99 mmol) was dissolved in dry DCM (20 mL) and cooled to 0°C with an ice bath. Succinic anhydride (1.6 eq., 1.60 g, 16.0 mmol) was added, followed by a solution of DMAP (0.3 eq., 366 mg, 3.00 mmol) in dry DCM (1 mL). The mixture was first stirred at 0°C, during which it turned from light blue to light green, and was then allowed to warm up to room temperature overnight. In the morning the mixture had darkened even more. Thin layer chromatography (50% AcOEt / hexanes + 1 vol% AcOH, rev. KMnCL) showed formation of a new, polar spot at Rf = 0.25. The reaction mixture was concentrated. The residue was purified by automatic column chromatography (40 g SiC>2 cartridge, 10-60% AcOEt / pentane over 25 CV, then 60-100% over 5 CV), using DCM as solvent for liquid injection and adding 1 vol% AcOH in AcOEt. Concentration of the collected fraction afforded succinyloxy butenolide as a white solid (1.37 g) which still contained traces of succinic anhydride. Another purification by column chromatography (25 g SiC>2 cartridge, 10-60% AcOEt / pentane over 25 CV, then 60 — 100% over 5 CV), using solid injection (adsorbed in SiCh) and adding 1 vol% AcOH in AcOEt, afforded pure succinyloxy butenolide (1.13 g, 5.63 mmol, 56% yield) as a white solid.

[0103] Succinyloxy butenolide methyl ester

[0104] 5-succinyloxy-2(5H)-furanone methyl ester

[0105] (methyl (5-oxo-2,5-dihydrofuran-2-yl) succinate) Chemical Formula: C9H10O6 Molecular Weight: 214.1730

[0106] In a flask under N2 atmosphere, succinyloxy butenolide (1.00 eq., 200 mg, 1.00 mmol) was dissolved in anhydrous DCM (5 mL, [SM] = 0.2 M). Methanol (3.00 eq., 121 pL, 3.00 mmol) and DMAP (5 mol%, 6 mg, 0.05 mmol) were added. The hazy mixture was cooled to 0°C with an ice bath. DCC (1.10 eq., 227 mg, 1.10 mmol) was added at once at 0°C. The mixture was stirred at 0°C for 30 min and then at room temperature for 30 min.

[0107] The reaction mixture was filtered on a Buchner, rinsing with DCM, leaving a white solid and affording a brown filtrate which was concentrated to a brown murky oil. The residue was purified by automatic column chromatography (15 g SiC>2 cartridge, 10-50% AcOEt / pentane over 20 CV), using DCM for liquid injection. Concentration of the collected fraction afforded pure methyl succinyloxy butenolide (163 mg, 0.761 mmol, 76% yield) as a colorless semi-solid.

[0108] Succinyloxy bis-butenolide

[0109] Bis(5-oxo-2,5-dihydrofuran-2-yl) succinate

[0110] Chemical formula: C12H10O8 Molecular Weight: 282.2040

[0111] In a flask under N2 atmosphere, succinyloxy butenolide (1.00 eq., 500 mg, 2.50 mmol) and hydroxy butenolide (2.00 eq., 500 mg, 5.00 mmol) were dissolved in anhydrous DCM (20 mL, [SM] = 0.125 M). DMAP (5 mol%, 15 mg, 0.13 mmol) was added. The clear mixture was cooled to 0°C with an ice bath. DCC (1.20 eq., 618 mg, 3.00 mmol) was dissolved in anhydrous DCM (2 mL) and added dropwise at 0°C over 5 min. During the addition, the hazy yellowish mixture first became clear yellowish, before turning back to hazy with the precipitation of a solid. The slurry then slowly turned brown over time. After 1 h, the ice bath was removed, and the mixture was stirred at room temperature for 1 h.

[0112] The reaction mixture was filtered, rinsing with DCM, affording a white solid (urea) and a clear brown filtrate, which was concentrated in vacuo to a brown solid. The residue was purified by automatic column chromatography (25 g SiC>2 cartridge, 0-20% AcOEt / pentane over 20 CV), using solid injection with neutralized silica. Concentration of the collected fraction afforded pure succinyloxy bis-butenolide (532 mg, 1.88 mmol, 75% yield) as a white solid.

[0113] Examples 1 to 13 and Comparative Example A

[0114] Coating compositions were prepared by combining a butenolide monomer, a monofunctional vinyl monomer and a di-functional monomer (either a butenolide or vinyl monomer) in various ratios as indicated in Table 1 and adding 1-3 mol% (vs. the most abundant compound) bis(2,4,6-trimethylbenzoyl) phenylphosphine oxide (OmniRad 819 or BAPO) as photo-initiator. All compositions were solvent-free compositions.

[0115] A 100 pm wet film of coating composition was drawn on a glass plate using a drawing bar. The wet film was cured by irradiating the film with UV light using a IIV-A LED irradiation device with 12 LED lamps emitting UV light with a wavelength of 395 nm and a total irradiance of 21 mW / cm2during 5 minutes at a distance of 5 cm. All coatings formed a tack- and defect-free film.

[0116] The UV-cured coatings thus obtained were tested as described below for water resistance, solvent resistance and for hardness, after 4 days of storing at 23 °C and 50 % relative humidity. Results are indicated in Table 1. Dry layer thickness (DFT)

[0117] The dry layer thickness (ISO 2808) of the coatings were measured using the Heidenhain VRZ 402 apparatus calibrated with calibration foil. A spot (10 mm diameter) of curing coating is removed from the glass substrate. The measuring probe was placed on the bare substrate and the measured value was fared, next, three layer thickness measurements are performed. This procedure was performed at three different locations on the substrate (9 measurements in total) and the average value is reported.

[0118] Solvent resistance (methyl ethyl ketone)

[0119] MEK double rub resistances were measured by rubbing the coating back and forth (5 cm) with a cloth soaked in 2-butanone (MEK) applying 10 N downward pressure. The number of double rubs (= 1x back and 1x forth) until the coating failure (dissolution) were counted with a maximum for 200 double rubs. At >200 double rub resistance the film appearance was described (e.g. dulling, staining, or any other change in appearance).

[0120] Water resistance

[0121] Water resistance (ISO 2812-4:2007 part 4) was measured by placing a droplet of demineralized water on the cured coating and covering it with a watch glass. After 60 minutes, the water droplet was wiped off and the effect on the coating was determined visually on a scale of 0 to 5, wherein 5 means that the water droplet had no visible impact on the coating, and 0 means that the water droplet had a detrimental impact.

[0122] Hardness (Knoop)

[0123] Knoop hardness’s (related to ASTM D1474, method A) were measured using the Fischerscope HM 2000 Xyp equipment calibrated using poly(methyl methacrylate) (PMMA). The indentation hardness was determined by measuring the indentation depth after applying a 98 mN (10 gram) load for 18 seconds using a diamond pyramidal shaped indenter (longitudinal angles: 172°30' and transverse angles: 130°) to the dried coating. Five consecutive measurements on different predefined spots were performed making sure the indentation depth does not exceed 75% of the coating thickness. The Knoop hardness was calculated by: Hk= ~^

[0124] C x d2

[0125] Where:

[0126] Hk = Knoop hardness in kg / mm2.

[0127] P = load applied on the indenter in kg.

[0128] C = indenter correction constant: 65.438. d = indentation depth in mm.

[0129] Glass transition temperature (Tg)

[0130] Glass temperatures (Tg) were measured with a Q2000 (TA Instruments) Differential Scanning Calorimeter (DSC). A DSC cup filled with 6 + / - 1 mg cured paint chips and an empty DSC reference cup were heated in the DSC in a modulated way (+ / - 1°C every 40 seconds) from -80°C to 200°C at 5°C / min in three consecutive runs using Helium (50 ml / min) as purge gas. Fourier transformation enabled the separation of the modulated heat flow into a heat capacity component (reversing heat flow) and a kinetic component (non-reversing heat flow) allowing to separate different thermal events occurring at the same time.

[0131] At the materials Tg (observed in the reversing heat flow curve) the heat capacity of the material changed rapidly resulting in a strong decrease of the reversing heat flow curve over a certain transfer area. The Tg is calculated at the point of inflection (Tg(l)) and at half width (Tg(W)), the Tg(W) measured in the second run is reported.

[0132]

Claims

CLAIMS A radiation-curable coating composition comprising: a) one or more butenolide monomer A of general formula (I):wherein: n is 0 or an integer of from 1 to 5;R1is alkyl or aryl;X is any one of -C(O)-, -C(O)O-, -C(O)NR2-, -S(O)-, -S(O2)-, -C(O)S-, -C(S)S- and -C(S)NR2-; wherein R2is hydrogen, alkyl or aryl; or wherein, when n is 0 and X is -C(O)NR2- or -C(S)NR2-, R1and R2together with the nitrogen atom through which they are linked form a nitrogen-containing heterocyclic group or nitrogen-containing heteroaryl group; and b) one or more vinyl monomer B comprising one or more vinyl groups wherein at least one vinyl group has a difference in13C chemical shift between the a-C and p-C of a vinyl group of at least 25 ppm; wherein at least one monomer of A and B comprises at least two vinyl groups; and wherein the difference in13C chemical shift between the a-C and p-C of the vinyl group is determined from the chemical shift reported in the Spectral Database for Organic Compounds (https: / / sdbs.db.aist.go.jp / sdbs / cqi- bin / direct frame top.cqi), managed by the National Institute of Advanced Industrial Science and Technology.A radiation-curable coating composition according claim 1 , wherein for at least one butenolide monomer A, n=0; and wherein at least one vinyl monomer B comprises at least two vinyl groups. A radiation-curable coating composition according to claim 1 or claim 2, which comprises at least two butenolide monomers A, wherein for at least one butenolide monomer A, n is an integer of from 1 to 5. A radiation-curable coating composition according to any one of claims 1 to 3, wherein the weight fraction of monomers comprising at least two vinyl groups in the composition is at most 5 wt.%. A radiation-curable coating composition according to any one of claims 1 to 4, wherein X is any one of -C(O)-, -C(O)O-, -C(O)NR2-. A radiation-curable coating composition according to any one of claims 1 to 5, wherein R1is C1-C20 alkyl, C5-C7 cycloalkyl or phenyl. A radiation-curable coating composition according to any one of claims 1 to 6, wherein a vinyl monomer B is a vinyl compound of general formula (II)R3CH=CH2(II); wherein R3is any one of:-OR4, -OC(O)R4, -N(R5)C(O)R4, -N(R5)C(O)OR4, -NR5C(S)R4, -NR5C(S)OR4, - NR5C(S)SR4and -SC(S)SR4; wherein R4is alkyl or aryl, and wherein R5is hydrogen, alkyl or aryl, or wherein R4and R5together with the atoms through which they are linked form a nitrogen-containing heterocyclic group or nitrogen-containing heteroaryl group. A radiation-curable coating composition according to claim 7, wherein R3is - OR4, -OC(O)R4or -N(R5)C(O)R4.A radiation-curable composition according to any one of claims 1 to 8, wherein a vinyl momomer B is a monovinyl ester, a monovinyl ether or a mono N-vinyl compound. A radiation-curable coating composition according to claim 9, wherein a vinyl monomer B is n-butyl vinyl ether, iso-butyl vinyl ether, cyclohexyl vinyl ether, phenyl vinyl ether, 2-ethylhexyl vinyl ether, n-dodecyl vinyl ether, 4-hydroxybutyl vinyl ether, vinyl neodecanoate, vinyl neononanoate, N-vinylpyrrolidone, N-vinyl imidazole, N-vinyl-formamide, N-vinyl-pyrrole, N-vinylcaprolactam or a mixture of two or more thereof. A radiation-curable coating composition according to any one of claims 1 to 10, wherein a vinyl monomer B has at least two vinyl groups and which is a divinyl ether, a divinyl ester or a di-N-vinyl compound. A radiation-curable coating composition according to any one of claims 1 to 11, wherein the molar ratio of furanone moieties to vinyl moieties is in the range of from 1.5: 1.0 to 1.0: 1.

5. A radiation-curable coating composition according to any one of claims 1 to 12, wherein the composition further comprises c) a photo-initiator. A method of coating a substrate comprising: providing a substrate; applying a coating composition as defined in any one of the preceding claims to the substrate; and radiation-curing the coating composition to form a cured coating. A coated substrate obtainable by a method according to claim 14.

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