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

Abstract

A radiation curable coating composition comprising: a) one or more butenolide monomers A of general formula (I) wherein n is 0 or an integer 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 attached form a nitrogen-containing heterocyclic group or nitrogen-containing heteroaryl group; and b) one or more vinyl monomers B comprising one or more vinyl groups, wherein at least one vinyl group has a 13C chemical shift difference between alpha-C and beta-C of the vinyl group of at least 25 ppm; wherein at least one monomer of A and B comprises at least two vinyl groups; and coating the substrate. # imgabs0 #

Description

Field of the Invention

[0001] The present invention relates to a radiation curable coating composition, a method of coating a substrate, including applying and curing the coating composition, and a coated substrate obtainable by the method. BACKGROUND OF THE INVENTION

[0003] 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. Actinic radiation as mentioned herein is electromagnetic, ionizing radiation, especially electron beam radiation, UV light and visible light. Radiation curable coating compositions are generally crosslinked by free radical polymerization of monomers having ethylenically unsaturated groups, such as acryloyl, methacryloyl or vinyl groups. Examples of such monomers include acrylic acid, methacrylic acid, (meth)acrylic acid alkyl esters, styrene, alkyl substituted styrenes, vinyl esters and vinyl ethers. These monomers are generally prepared from petrochemical raw materials.

[0004] There is an increasing demand for chemical products prepared from renewable raw materials. Binder polymers that are at least partially prepared from renewable raw materials are known in the art. Alkyd resins, for example, contain a relatively high content of fatty acids obtained from vegetable oils.

[0005] In US 4,954,593, a copolymer used as a protective coating is disclosed, which is prepared by combining a furanone monomer and a vinyl ether monomer in a molar ratio of about 1. The copolymer can be prepared by photopolymerization or by solution polymerization in the presence of a free radical initiator.

[0006] Butenolides are ethylenically unsaturated furan compounds that can be prepared from carbohydrates, i.e., renewable raw materials. Carbohydrate raw materials such as starch, cellulose or carbohydrate-containing biowaste can be converted by dehydration into furfural, hydroxymethylfurfural or related furan derivatives and can subsequently be oxidized to furanones. The preparation of alkoxylated furanones is described, for example, in Chapter II of J.C. de Jong, Asymmetric Diels-Alder reactions with 5-menthyloxy-2(5H)-furanones, Thesis University of Groningen, 2006, which is accessible https: / / www.rug.nl / research / portal / en / publications / asymmetric-dielsalder-reactions- with-5menthyloxy25hfuranones(f0ab6c00-8c6c-4ccc-90aa-3ef05f759fa4).html .

[0007] Poskonin et al. have disclosed in Russian Journal of Organic Chemistry 35(1999)721-726 copolymers prepared by free radical polymerization of 5-alkoxy-2(5H)-furanone and styrene, methyl methacrylate or vinyl acetate. The use of such copolymers in the synthesis of physiologically active substances has been proposed. Poskonin et al. have further disclosed in Russian Journal of Organic Chemistry 35(1997)520-523 oligomers prepared by free radical polymerization of 4-acetoxy-2-butenolide (5-acetoxy-2(5H)-furanone) and styrene, methyl methacrylate or vinyl acetate. A number average molecular weight of 1860-6460 has been achieved.

[0008] WO2021 / 084066 describes the copolymerization of 5-alkoxy-2(5H)-furanone with a selected vinyl ether or vinyl ester and the use of the resulting copolymer as a binder in a polymer coating composition.

[0009] WO2021 / 259819 describes a radiation-curable copolymer coating composition comprising a 5-hydroxy- or 5-alkoxy-2(5H)-furanone compound and a compound having two or more vinyl ether or vinyl ester groups.

[0010] Trost and Toste have disclosed in J.Am.Chem.Soc.2003, 125, 3090-3100 two butenolide compounds for introducing chirality into the synthesis of aflatoxins: 2-tert-butoxycarbonyloxy-5-oxo-2,5-dihydrofuran and 2-benzoyloxy-5-oxo-2,5-dihydrofuran.

[0011] 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, February 20, 2018(2018-02-20), pp. 2040-2048 describe the reaction of dihydro-5-hydroxyfuran-2-one with methacrylic anhydride to form the monomer dihydro-5-hydroxyfuran-2-one methacrylate. Subsequently, homopolymerization and copolymerization are carried out.

[0012] There is a need for radiation-curable coating compositions that can be obtained at least in part from renewable raw materials. SUMMARY OF THE INVENTION

[0014] It has now been found that hard and chemically resistant cured coatings can be obtained by radiation curing of a composition comprising a 5-substituted butenolide monomer and a monomer containing one or more vinyl groups, the radiation curing being activated by actinic radiation such as visible light or UV light or electron beam radiation. The coatings formed have properties that make them suitable as protective or decorative coatings.

[0015] Accordingly, in a first aspect, the present invention provides a radiation curable coating composition comprising:

[0016] a) one or more butenolide monomers A of the general formula (I):

[0017]

[0018] wherein

[0019] n is an integer of 0 or 1 - 5;

[0020] R 1 is alkyl or aryl;

[0021] X is any one of -C(O)-, -C(O)O-, -C(O)NR 2 -, -S(O)-, -S(O2)-, -C(O)S-, -C(S)S- and -C(S)NR 2 -; where R 2 is hydrogen, alkyl or aryl;

[0022] or wherein when n is 0 and X is -C(O)NR 2 - or -C(S)NR 2 -, R 1 and R 2 together with the nitrogen atom to which they are attached form a nitrogen-containing heterocyclic group or a nitrogen-containing heteroaryl; and

[0023] b) one or more vinyl monomers B containing one or more vinyl groups, wherein at least one vinyl group has a 13 C chemical shift difference of at least 25 ppm between the α-C and β-C of the vinyl group; wherein at least one of the monomers A and B contains at least two vinyl groups.

[0024] An advantage of this coating composition is that it can be formulated without organic solvents or with only a small amount, usually less than 20% by weight, of organic solvents.

[0025] In a second aspect, the present invention provides a method of coating a substrate, comprising:

[0026] - providing a substrate,

[0027] - applying a coating composition as defined herein to a substrate; and

[0028] - radiation curing the coating composition to form a cured coating.

[0029] The coating composition and the cured coating formed therefrom have a relatively high content of furanone, a bio-based material.

[0030] The binder polymer formed upon curing has a polymer backbone with acetal functional groups, which advantageously provides the possibility of further crosslinking or modifying the coating, for example, with a hydroxy or thiol functional crosslinker or with a polymer having hydroxy or thiol functional groups.

[0031] In a third aspect, the present invention provides a coated substrate obtainable by the method according to the second aspect of the present invention.

[0032] DETAILED DESCRIPTION

[0033] The radiation-curable coating composition comprises a) one or more butenolide monomers A; and b) one or more vinyl monomers B, wherein at least one of A and B contains at least two vinyl groups. The presence of monomers having at least two vinyl groups is necessary for use as a crosslinker in the coating composition.

[0034] The butenolides described herein are equivalent to furanones. The 5-substituted butenolides described herein are equivalent to 5-substituted furanones.

[0035] The term one or more with respect to each of A and B means that a plurality of different monomers, each respectively of A and 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, the vinyl monomers B being different from each other. Alternatively, it may comprise two butenolide monomers A and one butenolide monomer B, the butenolide monomers A being different from each other.

[0036] A vinyl group has an α-C and a β-C determined by the proximity to another functional group in the molecule. The 13 C chemical shift difference between the α-C and the β-C of a vinyl group used herein can be determined from the chemical shifts reported in the spectral database of 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.

[0037] The alkyl groups used herein can be branched, unbranched, linear or cyclic. The alkyl group can be saturated or unsaturated. It can be substituted or unsubstituted. The alkyl group generally contains 1 to 20 carbon atoms, especially 1 to 12 carbon atoms, 1 to 6 carbon atoms or 1 to 4 carbon atoms. The alkyl group can contain 2 to 20 carbon atoms, especially 2 to 12 carbon atoms, 2 to 6 carbon atoms or 2 to 4 carbon atoms. The alkyl group can contain 1 to 3 carbon atoms, such as 1, 2 or 3 carbon atoms. Examples of alkyl groups are methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, sec-butyl, isobutyl, hexyl, lauryl, oleyl and cyclohexyl.

[0038] The cycloalkyl groups used herein refer to cyclic alkyl groups. The cyclic heteroalkyl groups refer to cyclic heteroalkyl groups in which at least one carbon in the ring is replaced by a heteroatom. The heteroatom can be an atom other than nitrogen, oxygen or carbon. The cyclic heteroalkyl group can be a nitrogen-containing cyclic heteroalkyl group.

[0039] The aryl groups used herein refer to aromatic groups. The aryl group can be substituted or unsubstituted. The aryl group generally contains 6 or 10 carbon atoms. The aryl group can be phenyl or naphthyl, especially phenyl. The heteroaryl group refers to an aryl group containing a heteroatom, that is, an atom other than carbon, in the aromatic ring. The heteroaryl group can be substituted or unsubstituted. The heteroaryl group generally contains 5 to 12 carbon atoms. Typical heteroatoms are oxygen or nitrogen.

[0040] The coating composition comprises one or more butenolide monomers A of general formula (I):

[0041]

[0042] wherein

[0043] n is an integer of 0 or 1 - 5;

[0044] R 1 is an alkyl or aryl group;

[0045] X is one of -C(O)-, -C(O)O-, -C(O)NR 2 -, -S(O)-, -S(O2)-, -C(O)S-, -C(S)S- and -C(S)NR 2 -; wherein R 2 is hydrogen, an alkyl or aryl group;

[0046] or when n is 0, R 1 and R 2 together with the nitrogen atom to which they are attached form a nitrogen-containing heterocyclic group or a nitrogen-containing heteroaryl group.

[0047] In one embodiment, for at least one butenolide monomer A, n = 0; and wherein at least one vinyl monomer B contains at least two vinyl groups.

[0048] In one embodiment including at least two butenolide monomers A, for at least one butenolide monomer A, n is an integer from 1 to 5.

[0049] In one embodiment, X is any one of -C(O)-, -C(O)O-, -C(O)NR 2 -. In this embodiment, R 2 is, for example, hydrogen. Alternatively, when X is -C(O)-, R 1 can be C2-C6 alkyl or phenyl.

[0050] In one embodiment, R 1 is C1-C 20 alkyl, C5-C7 cycloalkyl or phenyl. In one embodiment, R 1 can be C1-C 12 alkyl. In another embodiment, R 1 can be C5-C7 cycloalkyl. In another embodiment, R 1 can be phenyl.

[0051] In one embodiment, R 2 can be hydrogen or C1-C 20 alkyl. R 2 In particular, it can be hydrogen or C1-C 12 alkyl, for example R 2 can be hydrogen.

[0052] If n is an integer having a value in the range of 1-5, the butenolide monomer A is an oligomer that can be obtained by reacting a multifunctional scaffold having a reactive group in the range of 2-6 with 5-hydroxy-2(5H)-furanone. The multifunctional scaffold can have, for example, 1-40 carbon atoms.

[0053] 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, trimellitic acid and the corresponding thioacids, isocyanate and thiocyanate counterparts. Other examples of suitable scaffolds include alkyl carbonate or chloroformate derivatives of polyols such as ethylene glycol, propylene glycol, glycerol, cyclohexanedimethanol or pentaerythritol.

[0054] In one embodiment, the vinyl monomer B is a vinyl compound of the general formula (II):

[0055] R 3 CH=CH2 (II);

[0056] wherein R 3is -OR 4 、 -OC(O)R 4 、 -N(R 5 )C(O)R 4 、 -N(R 5 )C(O)OR 4 、 -NR 5 C(S)R 4 、 -NR 5 C(S)OR 4 、 -NR 5 C(S)SR 4 and -SC(S)SR 4 any one of;

[0057] wherein R 4 is alkyl or aryl, and wherein R 5 is hydrogen, alkyl or aryl, or wherein R 4 and R 5 together with the atoms to which they are attached form a nitrogen - containing heterocyclic group or a nitrogen - containing heteroaryl.

[0058] In one embodiment, R 3 is -OR 4 、 -OC(O)R 4 or -N(R 5 )C(O)R 4 .

[0059] In one embodiment, the vinyl monomer B is a mono - vinyl ester, a mono - vinyl ether or a mono - N - vinyl compound.

[0060] In one embodiment, the vinyl monomer B is n - butyl vinyl ether, isobutyl vinyl ether, cyclohexyl vinyl ether, phenyl vinyl ether, 2 - ethylhexyl vinyl ether, n - dodecyl vinyl ether, 4 - hydroxybutyl vinyl ether, vinyl neodecanoate, vinyl neodecanoate, N - vinylpyrrolidone, N - vinylimidazole, N - vinylformamide, N - vinylpyrrole or N - vinylcaprolactam.

[0061] In one embodiment, the vinyl compound B is a mono - vinyl ester, a mono - vinyl ether, a mono - N - vinyl compound and / or a (meth) acryloyl monomer having a molecular weight in the range of 50 - 800 g / mol, more preferably 100 - 500 g / mol.

[0062] In one embodiment, the vinyl monomer B has at least two vinyl groups. In the vinyl monomer of formula (II), R 3 contains at least one vinyl group. For example, R 4 contains at least one vinyl group or R 5 contains at least one vinyl group or R4 and R 5 Both contain at least one vinyl group.

[0063] The radiation-curable coating composition may comprise at least two vinyl monomers B. At least one vinyl monomer B may contain at least two vinyl groups. For example, the radiation-curable coating composition may comprise a vinyl monomer B that is a mono-vinyl compound and a vinyl monomer B that is a di-vinyl compound.

[0064] In one embodiment, vinyl monomer B has at least two vinyl groups and is a divinyl ether, a divinyl ester, and a di-N-vinyl compound.

[0065] Examples of vinyl monomer B having at least two vinyl ester groups include divinyl malonate, divinyl adipate, divinyl fumarate, divinyl sebacate, divinyl phthalate, and trivinyl trimellitate.

[0066] Examples of vinyl monomer B having two or three vinyl ether groups include di-vinyl ethers or tri-vinyl 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 trimethylolpropane trivinyl ether.

[0067] Examples of vinyl monomer B having at least two N-vinyl groups are N-vinyl-substituted polycarboxamides, such as adipamide, succinamide, terephthalamide, isophthalamide, and benzotricarboxamide.

[0068] Vinyl monomer B may be a compound having a polymer backbone and two or more vinyl ether groups, such as polyurethane, polyester-polyurethane, polyurea-polyurethane, poly(meth)acrylate-polyurethane, or a polyester having two or more vinyl ether groups. Such compounds can be prepared, for example, by reacting an isocyanate with a hydroxyl-functional vinyl ether and a hydroxyl-functional polyester, polyether, or poly(meth)acrylate. The polyester having two or more vinyl ether groups can be prepared by transesterification of a hydroxyl-functional vinyl ether with a polyester having two or more ester groups of a relatively low-boiling alcohol. By using such a compound having a polymer backbone in the coating composition, the properties of the cured coating, especially the mechanical properties, can be adjusted by selecting the backbone.

[0069] The vinyl monomer B may have a molecular weight in the range of 100 - 3,000 g / mol. If the vinyl monomer B is a compound having a polymer backbone as described above, the molecular weight may be in the range of 500 - 3,000 g / mol.

[0070] In one embodiment, the weight fraction of the monomer containing at least two vinyl groups in the composition is at most 5 wt%.

[0071] In one embodiment, the molar ratio of the furanone moiety to the vinyl moiety is in the range of 1.5:1.0 - 1.0:1.5. For example, the molar ratio can be 1.2:1.0 - 1.0:1.2. The vinyl moiety is present in the vinyl monomer B. In one embodiment, the coating composition does not contain any compound having a vinyl moiety other than the vinyl monomer B.

[0072] In one embodiment, the radiation-curable coating composition does not contain a compound having two or more acryloyl or methacryloyl groups. The presence of such a compound may have an adverse effect on film formation.

[0073] The total amount of the butenolide monomer A and the vinyl monomer B in the radiation-curable coating composition may be in the range of 70 - 100 wt%, more preferably 80 - 100 wt%, even more preferably 90 - 100 wt%.

[0074] The coating composition is radiation-curable. The coating composition can be cured by photoinitiation, i.e., by irradiation with visible light or UV light. In one embodiment, the composition further comprises c) a photoinitiator.

[0075] The photoinitiator can be a single photoinitiator or a mixture of two or more thereof. The photoinitiator generates free radicals upon exposure to radiant energy in the visible light or UV light wavelength range. Depending on the wavelength, any suitable photoinitiator known in the art can be used. Suitable photoinitiators include benzoin derivatives, benzoyl ketals, α-hydroxyalkyl phenyl ketones, monoacylphosphine oxides (MAPO) and bisacylphosphine oxides (BAPO), such as diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, 1-hydroxycyclohexyl phenyl ketone, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, methyl phenylglyoxylate. Mixtures of these compounds can also be used.

[0076] The photoinitiator may be present in an amount of 0.1 - 10 wt%, for example 0.5 - 5.0 wt%, based on the total weight of the coating composition.

[0077] Alternatively, curing of the coating composition can be initiated by electron beam or gamma radiation. For initiation by electron beam or gamma radiation, no photoinitiator is required.

[0078] The coating composition can be a powder coating composition or a liquid coating composition, preferably a liquid coating composition. The coating composition is preferably a substantially solvent-free liquid coating composition. A substantially solvent-free coating composition as referred to herein is a coating composition containing at most 1% by weight, more preferably at most 0.5% by weight, still more preferably 0% by weight of organic solvent.

[0079] In the case where the viscosities of the butenolide monomer A and the vinyl monomer B are undesirably high, the coating composition can contain some organic solvent to control the viscosity. Preferably the coating composition contains at most 30% by weight, more preferably at most 20% by weight, even more preferably at most 10% by weight, still more preferably at most 5% by weight or at most 2% by weight of organic solvent.

[0080] Suitable organic solvents are solvents in which the butenolide monomer A and the vinyl monomer B and the cured polymer are soluble under the polymerization conditions. The organic solvent can be an oxygen-containing organic solvent such as an alcohol, a ketone, an ester or an ether. The solvent is especially a glycol ether, a glycol ester or an alkyl acetate such as 1-methoxy-2-propanol or butyl acetate.

[0081] The coating composition is not an aqueous coating composition, i.e. water is not the liquid medium in which the butenolide monomer A and the vinyl monomer B are dissolved or dispersed. The coating composition can contain a small amount of water, such as the water contained in the additives included in the coating composition. In one embodiment, the coating composition contains less than 5% by weight, more preferably less than 1% by weight of water.

[0082] The coating composition can contain other ingredients commonly used in coating compositions, such as color pigments, extender pigments and one or more additives such as light stabilizers, other stabilizers, defoamers, matting agents, wetting agents or flow agents.

[0083] The coating composition can be radiation-cured by exposing the coating composition to visible light or UV radiation, electron beam radiation or gamma radiation to form a cured coating.

[0084] The coating composition can be applied to a substrate by conventional techniques including spraying, roll coating, knife coating, pouring, brushing or dipping. After evaporation of any organic solvent and / or water (if present), the coating composition results in a non-dusting dry to very tacky coating. Curing is then initiated by means of radiation. Any suitable radiation source can be used. Radiation curing can especially be by electron beam radiation, UV radiation or visible light radiation.

[0085] In one embodiment, the coating composition further comprises c) a photoinitiator and the coating composition is cured by exposing the coating composition to visible light or UV radiation, such as visible light in the range of 400 - 600 nm or UV radiation in the range of 200 - 400 nm, especially UV radiation in the range of 280 - 400 nm or preferably 320 - 400 nm (UV-A radiation).

[0086] For UV radiation, mercury lamps, metal halide lamps, xenon lamps or UV-LED lamps can be used. UV-LED lamps are preferably used.

[0087] The radiation curing of the coating composition can be carried out under ambient conditions, such as room temperature and atmospheric pressure. The room temperature mentioned herein is a temperature in the range of 15 - 30 °C. Curing can be accelerated by post-heating, such as post-heating to a temperature in the range of 40 - 100 °C, preferably 50 - 80 °C.

[0088] The substrate can be any suitable substrate, such as wood, polymer, composite material, metal, glass or other mineral substrates. The substrate can be a substrate coated with a primer or a bare substrate.

[0089] The coating composition can be used as a single layer applied directly to the substrate, or in a multi-layer system, such as a primer layer, a base coat, a clear coat or a top coat. The coating composition can be used for various applications, such as coating wood, electronic devices, plastic automotive components, food cans, or as an architectural coating.

[0090] The present invention is further illustrated by the following non-limiting examples. Examples

[0091] The following butenolide compounds were used:

[0092]

[0093] The following monofunctional vinyl compounds were used:

[0094] - Ethylene glycol vinyl ether EGVE

[0095] - N-Vinylpyrrolidone NVP

[0096] The following difunctional butenolide compounds were used:

[0097] - Di(5-oxo-2,5-dihydrofuran-2-yl) succinate (succinyloxy-di-butenolide)

[0098] SuccOBut2

[0099] The following difunctional vinyl compounds were used:

[0100] - Diethylene Glycol Divinyl Ether DEGDVE

[0101] Preparation of Butenolide Monomers

[0102] Methoxybutenolide

[0103] 5 - Methoxy - 2(5H) - furanone

[0104] Chemical formula: C5H5O3

[0105] Molecular weight: 114.1000

[0106] The 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 of anhydrous methanol and heated under reflux for 20 hours. The conversion was monitored by 1 1H NMR until all 5 - hydroxy - 2(5H) - furanone was consumed. The solvent was evaporated under reduced pressure and the crude product was distilled under reduced pressure (70 °C, 1.0×10 -2 mbar) to give 5 - methoxy - 2(5H) - furanone as a pale yellow oil (86.5 g, 0.76 mol, 76%).

[0107] Acetoxybutenolide 5 - Oxo - 2,5 - dihydrofuran - 2 - yl acetate

[0108] Chemical formula: C6H5O4

[0109] Molecular weight: 142.1100

[0110] The 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, hydroxybutenolide (1 equivalent, 500 mg, 5.00 mmol, gray solid) was dissolved in anhydrous DCM (25 mL) and cooled to 0 °C with an ice bath. Acetic anhydride (1.6 equivalents, 754 μL, 7.99 mmol) was added, and then a solution of DMAP (0.3 equivalent, 183 mg, 1.50 mmol) in anhydrous DCM (1.5 mL) was added. The mixture was stirred at 0 °C for 1 h and then allowed to warm to room temperature. TLC (25% AcOEt / hexane, visualized with KMnO4) showed the 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 over sodium sulfate, filtered through cotton, and concentrated under reduced pressure. The residue was purified by automated column chromatography (15 g SiO2 column, 10 - 40% AcOEt / pentane, over 20 column volumes (CV)) using DCM injection for the liquid. The collected fractions were concentrated to give pure acetyloxybutenolide (506 mg, 3.56 mmol, 71% yield) as a colorless liquid.

[0111] Isobutyryloxybutenolide

[0112] 5-Isobutyryloxy-2(5H)-furanone (5-oxo-2,5-dihydrofuran-2-yl isobutyrate)

[0113] Chemical formula: C8H 10 O4

[0114] Molecular weight: 170.1640

[0115] In a flask under N2 atmosphere, hydroxymethylenebutyrolactone (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 hydroxymethylenebutyrolactone) 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 minutes. After the addition, the ice bath was removed and the mixture was stirred at room temperature for 1 hour. The mixture turned from blue to dark brown and had a precipitate. The reaction mixture was filtered through cotton wool, rinsed with DCM, to give 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 automated column chromatography (80 g SiO2 column, 5-30% AcOEt / pentane, over 15 CVs) using DCM injection of the liquid. The collected fractions were concentrated to give pure isobutyryloxymethylenebutyrolactone (4.84 g, 28.4 mmol, 71% yield) as a yellow oil.

[0116] Pivaloyloxybutenolide

[0117] 5-Pivaloyloxy-2(5H)-furanone (5-oxo-2,5-dihydrofuran-2-yl pivalate)

[0118] Chemical formula: C9H 12 O4

[0119] Molecular weight: 184.1910

[0120] Hydroxybutenolide (1 eq., 5.00 g, 50.0 mmol) was dissolved in anhydrous DCM (25 mL) and cooled to 0 °C in an ice bath. This caused (partial) precipitation of hydroxybutenolide. 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 anhydrous DCM (2.5 mL). The mixture was first stirred at 0 °C for 30 minutes and then allowed to warm to room temperature, which caused complete dissolution of the solid. The homogeneous mixture was further stirred at room temperature overnight (20 h in total). During the reaction, the initial blue mixture turned dark green / brown. The reaction mixture was concentrated. The residue was purified by automated column chromatography (80 g SiO2 column, 5 - 30% AcOEt / pentane, 15 CVs) with DCM injection liquid. The collected fractions were concentrated to give pure pivaloyloxybutenolide (6.74 g, 36.6 mmol, 73% yield) as a pale yellow oil.

[0121] Succinyloxybutenolide

[0122] 4 - oxo - 4 - ((5 - oxo - 2,5 - dihydrofuran - 2 - yl)oxy)butanoic acid

[0123] Chemical formula: C8H8O6

[0124] Molecular weight: 200.1460

[0125] Hydroxybutenolide (1.00 g, 9.99 mmol, 1.00 eq.) was dissolved in anhydrous DCM (20 mL) and cooled to 0 °C in an ice bath. Succinic anhydride (1.60 g, 16.0 mmol, 1.60 eq.) was added, followed by a solution of DMAP (366 mg, 3.00 mmol, 0.30 eq.) in anhydrous DCM (1 mL). The mixture was first stirred at 0 °C, during which time it changed from light blue to light green, and then allowed to warm to room temperature overnight. In the morning, the mixture had become darker. Thin layer chromatography (50% AcOEt / hexanes + 1% v / v AcOH, visualized with KMnO4) showed the formation of a new polar spot at Rf = 0.25. The reaction mixture was concentrated. The residue was purified by automated column chromatography (40 g SiO2 column, 10 - 60% AcOEt / pentanes, 25 CVs, then 60 - 100%, 5 CVs) using DCM as the eluent and adding 1% v / v AcOH in AcOEt. The collected fractions were concentrated to give succinyloxybutenolide (1.37 g) as a white solid still containing traces of succinic anhydride. Further purification by column chromatography (25 g SiO2 column, 10 - 60% AcOEt / pentanes, 25 CVs, then 60 - 100%, 5 CVs) using solid injection (adsorbed on SiO2) and adding 1% v / v AcOH in AcOEt gave pure succinyloxybutenolide (1.13 g, 5.63 mmol, 56% yield) as a white solid.

[0126] Succinyloxybutenolide Methyl Ester

[0127] 5-Succinyloxy-2(5H)-furanone methyl ester (Methyl succinate (5-oxo-2,5-dihydrofuran-2-yl) ester)

[0128] Chemical formula: C9H 10 O6

[0129] Molecular weight: 214.1730

[0130] Succinyloxybutenolide (200 mg, 1.00 mmol, 1.00 eq.) was dissolved in anhydrous DCM (5 mL, [SM] = 0.2 M) in a flask under a N2 atmosphere. Methanol (121 μL, 3.00 mmol, 3.00 eq.) and DMAP (6 mg, 0.05 mmol, 5 mol%) were added. The cloudy mixture was cooled to 0 °C in an ice bath. DCC (227 mg, 1.10 mmol, 1.10 eq.) was added all at once at 0 °C. The mixture was stirred at 0 °C for 30 minutes and then at room temperature for 30 minutes.

[0131] The reaction mixture was filtered on a Büchner, rinsed with DCM, leaving a white solid and giving a brown filtrate, which was concentrated to a brown turbid oil. The residue was purified by automated column chromatography (15 g SiO2 column, 10 - 50% AcOEt / pentane, over 20 CV) using DCM as the eluent. The collected fractions were concentrated to give pure methyl succinyloxybutenolide as a colorless semi-solid (163 mg, 0.761 mmol, 76% yield).

[0132] Succinyloxy Di-Butenolide

[0133] Di(5-oxo-2,5-dihydrofuran-2-yl) succinate

[0134] Chemical formula: C 12 H 10 O8

[0135] Molecular weight: 282.2040

[0136] In a flask under a N2 atmosphere, succinyloxybutenolide (1.00 equiv, 500 mg, 2.50 mmol) and hydroxybutenolide (2.00 equiv, 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 in an ice bath. DCC (1.20 equiv, 618 mg, 3.00 mmol) was dissolved in anhydrous DCM (2 mL) and added dropwise at 0 °C over 5 minutes. During the addition, the turbid pale yellow mixture first became clear pale yellow and then turned back to turbid with solid precipitation. The slurry then slowly turned brown over time. After 1 hour, the ice bath was removed and the mixture was stirred at room temperature for 1 hour.

[0137] The reaction mixture was filtered, rinsed with DCM, giving a white solid (urea) and a clear brown filtrate, which was concentrated in vacuo to a brown solid. The residue was purified by automated column chromatography (25 g SiO2 column, 0 - 20% AcOEt / pentane, over 20 CV) using silica gel for neutralization as the eluent. The collected fractions were concentrated to give pure succinyloxy-di-butenolide as a white solid (532 mg, 1.88 mmol, 75% yield).

[0138] Examples 1-13 and Comparative Example A

[0139] A coating composition was prepared by combining the butenolide monomer, the monofunctional vinyl monomer, and the difunctional monomer (butenolide or vinyl monomer) in the various ratios shown in Table 1 and adding 1 - 3 mol% (relative to the maximum amount of compound) of bis(2,4,6 - trimethylbenzoyl)phenylphosphine oxide (OmniRad 819 or BAPO) as a photoinitiator. All the compositions were solvent - free compositions.

[0140] A 100 - μm wet film of the coating composition was doctor - bladed onto a glass plate. The wet film was cured by irradiating the film with UV light using a UV - A LED irradiation device having 12 LED lights emitting UV light with a wavelength of 395 nm and a total irradiance of 21 mW / cm 2 at a distance of 5 cm within 5 minutes. All the coatings formed non - sticky and defect - free films.

[0141] After storage at 23 °C and 50% relative humidity for 4 days, the water resistance, solvent resistance, and hardness of the thus - obtained UV - cured coatings were tested as described below. The results are shown in Table 1.

[0142] Dry film thickness (DFT)

[0143] The dry film thickness of the coating (ISO 2808) was measured using a Heidenhain VRZ 402 device calibrated with a calibration foil. A small amount of the cured coating (10 - mm diameter) was removed from the glass substrate. The measurement probe was placed on the bare substrate and balanced for the measurement value, and then three layer - thickness measurements were carried out. This procedure was performed at three different positions on the substrate (9 measurements in total) and the average value was reported.

[0144] Solvent resistance (methyl ethyl ketone)

[0145] The MEK rub resistance was measured by rubbing the coating back and forth (5 cm) with a cloth soaked in 2 - butanone (MEK) under an applied downward pressure of 10 N. The number of double rubs ( = one back - and - forth) was counted up to a maximum of 200 double rubs until the coating failed (dissolved). The appearance of the film (such as loss of gloss, staining, or any other appearance change) was described at > 200 double rubs.

[0146] Water resistance

[0147] The water resistance (ISO 2812 - 4:2007, Part 4) was measured by dropping a drop of softened water onto the cured coating and covering it with a watch glass. After 60 minutes, the water drop was wiped off and the effect on the coating was visually determined on a scale of 0 - 5, where 5 means that the water drop has no visible effect on the coating and 0 means that the water drop has an adverse effect.

[0148] Hardness (Knoop)

[0149] The Knoop hardness (related to ASTM D1474 Method A) was measured using a Fischerscope HM 2000Xyp device calibrated with polymethyl methacrylate (PMMA). The indentation hardness was determined by measuring the indentation depth after applying a 98 mN (10 g) load for 18 seconds to the dry coating using a diamond conical indenter (longitudinal angle: 172°30' and transverse angle: 130°). Five consecutive measurements were made at different pre-determined points, ensuring that the indentation depth did not exceed 75% of the coating thickness. The Knoop hardness was calculated by the following formula:

[0150]

[0151] where

[0152] H k = Knoop hardness, kg / mm 2 .

[0153] P = the load applied to the indenter, kg.

[0154] C = the indenter calibration constant: 65.438.

[0155] d = the indentation depth, mm.

[0156] Glass transition temperature (Tg)

[0157] The glass transition temperature (Tg) was measured using a Q2000 (TA Instruments) differential scanning calorimeter (DSC). The DSC cell filled with 6 + / - 1 mg of the cured lacquer flakes and an empty DSC reference cell were heated in the DSC in a modulated mode (±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 the purge gas. Fourier transform was able to separate the modulated heat flow into a heat capacity component (reversible heat flow) and a kinetic component (irreversible heat flow), which allowed the separation of different simultaneous thermal events.

[0158] The heat capacity of the material changes rapidly at the Tg of the material (observed in the reversible heat flow curve), resulting in a significant drop in the reversible heat flow curve within a certain transition region. The Tg was calculated at the inflection point (Tg(I)) and the half-width (Tg(W)), and the Tg(W) measured in the second run was reported.

[0159]

Claims

1. A radiation-curable coating composition comprising: a) one or more butenolide monomers A of the general formula (I): wherein n is an integer of 0 or 1 - 5; R 1 is an alkyl or aryl group; X is -C(O)-, -C(O)O-, -C(O)NR 2 -, -S(O)-, -S(O2)-, -C(O)S-, -C(S)S- and -C(S)NR 2 either of; wherein R 2 is hydrogen, alkyl or aryl; or wherein when n is 0 and X is -C(O)NR 2 - or -C(S)NR 2 - then R 1 and R 2 together with the nitrogen atom to which they are attached form a nitrogen-containing heterocyclic group or a nitrogen-containing heteroaryl group; and b) one or more vinyl monomers B containing one or more vinyl groups, wherein at least one vinyl group has a 13 chemical shift difference of at least 25 ppm between the α-C and β-C of the vinyl group; wherein at least one of the monomers A and B contains at least two vinyl groups; and Among them, the 13 chemical shift difference between the α-C and β-C of the vinyl group is determined by the chemical shifts reported in the spectral database of organic compounds managed by the National Institute of https: / / sdbs.db.aist.go.jp / sdbs / cgi-bin / direct_frame_top.cgi Advanced Industrial Science and Technology.

2. The radiation-curable coating composition according to claim 1, wherein for at least one butenolide monomer A, n = 0; and wherein at least one vinyl monomer B contains at least two vinyl groups.

3. The radiation-curable coating composition according to claim 1 or 2, comprising at least two butenolide monomers A, wherein for at least one butenolide monomer A, n is an integer of 1 - 5.

4. The radiation-curable coating composition according to any one of claims 1 - 3, wherein the monomer containing at least two vinyl groups has a weight fraction of at most 5% by weight in the composition.

5. The radiation-curable coating composition according to any one of claims 1-4, wherein X is any one of -C(O)-, -C(O)O-, -C(O)NR 2 -.

6. The radiation-curable coating composition according to any one of claims 1-5, wherein R 1 is C1-C 20 alkyl, C5-C7 cycloalkyl or phenyl.

7. The radiation-curable coating composition according to any one of claims 1 - 6, wherein the vinyl monomer B is a vinyl compound of the general formula (II): R 3 CH=CH2 (II); wherein R 3 is -OR 4 、-OC(O)R 4 、-N(R 5 )C(O)R 4 、-N(R 5 )C(O)OR 4 、-NR 5 C(S)R 4 、-NR 5 C(S)OR 4 、-NR 5 C(S)SR 4 and -SC(S)SR 4 or any one of them; wherein R 4 is an alkyl or aryl group, and wherein R 5 is hydrogen, an alkyl or aryl group, or wherein R 4 and R 5 together with the atom to which they are attached form a nitrogen-containing heterocyclic group or a nitrogen-containing heteroaryl group.

8. The radiation curable coating composition according to claim 7, wherein R 3 is -OR 4 , -OC(O)R 4 or -N(R 5 )C(O)R 4 .

9. The radiation-curable composition according to any one of claims 1 - 8, wherein the vinyl monomer B is a mono-vinyl ester, mono-vinyl ether or mono-N-vinyl compound.

10. The radiation-curable coating composition according to claim 9, wherein the vinyl monomer B is n-butyl vinyl ether, isobutyl vinyl ether, cyclohexyl vinyl ether, phenyl vinyl ether, 2-ethylhexyl vinyl ether, n-dodecyl vinyl ether, 4-hydroxybutyl vinyl ether, vinyl neodecanoate, vinyl neodecanoate, N-vinylpyrrolidone, N-vinylimidazole, N-vinylformamide, N-vinylpyrrole, N-vinylcaprolactam or a mixture of two or more thereof.

11. The radiation-curable coating composition according to any one of claims 1 - 10, wherein the vinyl monomer B has at least two vinyl groups and is a divinyl ether, divinyl ester or di-N-vinyl compound.

12. The radiation-curable coating composition according to any one of claims 1 - 11, wherein the molar ratio of the furanone structural moiety to the vinyl structural moiety is in the range of 1.5:1.0 - 1.0:1.

5.

13. The radiation-curable coating composition according to any one of claims 1 - 12, wherein the composition further comprises c) a photoinitiator.

14. A method of coating a substrate, comprising: - providing a substrate; - applying the 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.

15. A coated substrate obtainable by the method according to claim 14.

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