A yellowing-resistant UV-LED-curable coating composition

Abstract

The present invention relates to a yellowing-resistant UV-LED-curable coating composition, which comprises: (a) an amine-modified polyether acrylate; (b) a (meth)acrylate polymer different from (a); (c) a multifunctional thiol compound; and (d) an acylphosphine oxide as a photoinitiator. In addition, the present invention also relates to an article, which comprises a substrate partially or completely coated with the UV-LED-curable coating composition.

Description

Technical Field

[0001] The present invention relates to a UV-LED curable coating composition and also relates to a product comprising the UV-LED curable coating composition. Background Art

[0002] Ultraviolet curing technology (UV) has the advantages of environmental protection, energy saving, fast curing, and controllable curing. It has achieved rapid development in the past 20 years and has been widely used in the fields of coatings, inks, adhesives, microelectronic materials, etc. Compared with the high-energy UV curing technology using conventional mercury lamps, UV-LED has the advantages of low energy consumption, easy portability, and long service life. Therefore, UV-LED curing has received widespread attention in recent years.

[0003] Conventional UV-LED-curable coatings have a single wavelength of curing light source (usually 395nm single wavelength initiation), and oxygen inhibition is serious when the coating is thin, which is manifested as poor surface drying of the coating and low surface strength of the paint film. Usually, it can only be used as a primer, which greatly limits the application of UV-LED-curable coatings. Although thioxanthone photoinitiators are very helpful for surface drying of 395nm wavelength curing, the paint film is seriously yellowed, and the hardness and adhesion of the paint film after curing are reduced, so its application is also greatly limited.

[0004] Therefore, there is still a need in the coatings industry for UV-LED-curable coating compositions that have both yellowing resistance and high curing rate. Summary of the invention

[0005] The present invention provides a UV-LED curable coating composition, comprising:

[0006] (a) amine-modified polyether acrylate;

[0007] (b) a (meth)acrylate polymer different from (a);

[0008] (c) a polyfunctional thiol compound; and

[0009] (d) Acylphosphine oxides, as photoinitiators.

[0010] In an embodiment according to the present invention, the multifunctional thiol compound comprises 3 or more thiol groups.

[0011] In an embodiment of the present invention, the coating composition further comprises a co-initiator, and the co-initiator comprises one or more selected from alkylhydroxylamines, dimethylaminobenzoic acid esters and amine-modified acrylate monomers or prepolymers.

[0012] According to another aspect of the present invention, there is provided a UV-LED curable coating composition, wherein, relative to the total weight of the coating composition, the coating composition comprises:

[0013] (a) 10-30 wt % of amine-modified polyether acrylate;

[0014] (b) 30-60 wt. % of a (meth)acrylate polymer different from (a);

[0015] (c) 0.5-2 wt % of a multifunctional thiol compound;

[0016] (d) 3 to 6% by weight of acylphosphine oxide;

[0017] (e) 15-30% by weight of a reactive diluent;

[0018] (f) 0.5-2 wt% of a coinitiator; and

[0019] (g) 0.1-1 wt % of additional additives, wherein the additional additives include thickeners, surfactants, defoamers, bactericides or any combination thereof.

[0020] In an embodiment of the present invention, the coating formed by curing the UV-LED-curable coating composition of the present invention on a BYK white coating test card has a color difference value ΔE<2.0 with respect to the BYK white coating test card.

[0021] According to another aspect of the present invention, there is provided an article comprising a substrate partially or fully coated with the UV-LED curable coating composition according to the present invention.

[0022] In the present invention, the applicant utilizes a specific multifunctional thiol compound in combination with a specific amine-modified polyether acrylate, which, in addition to inhibiting surface oxygen inhibition, can also utilize the "click" chemical reaction of thiol and double bonds to increase the crosslinking degree of the paint film, thereby improving the performance of the paint film and locking the thiol in the paint film to prevent the thiol from migrating to the surface and causing odor emission. On this basis, by adjusting the combination of film-forming resin and initiator, avoiding the use of yellowing initiator, while ensuring the appearance of the paint film, the co-initiator can be used to further improve the curing reaction efficiency, reduce the required curing energy, and achieve rapid curing.

[0023] The details of one or more embodiments of the invention are set forth in the following description. Other features, objects, and advantages of the invention will become apparent from the description and claims.

[0024] definition

[0025] As used herein, "a", "the", "at least one" and "one or more" and the absence of quantifiers are used interchangeably. Thus, for example, a component containing "a" additive can be interpreted to mean that the component contains "one or more" additives.

[0026] As used herein, "acrylate" is a general term for esters of acrylic acid and its homologues, such as methyl acrylate, ethyl acrylate, methyl 2-methacrylate, and ethyl 2-methacrylate, etc. Therefore, unless otherwise specified, "acrylate" includes both acrylate and methacrylate.

[0027] Where a composition is described as comprising or including specific components, it is contemplated that optional components not contemplated by the present invention are not excluded from the composition, and that the composition may consist of or be composed of the contemplated components; or where a method is described as comprising or including specific process steps, it is contemplated that optional process steps not contemplated by the present invention are not excluded from the method, and that the method may consist of or be composed of the contemplated process steps.

[0028] For simplicity, only some numerical ranges are explicitly disclosed herein. However, any lower limit can be combined with any upper limit to form an unambiguous range; and any lower limit can be combined with other lower limits to form an unambiguous range, and any upper limit can be combined with any other upper limit to form an unambiguous range. In addition, although not explicitly stated, each point or single value between the range endpoints is included in the range. Thus, each point or single value can be combined with any other point or single value as its own lower limit or upper limit or with other lower limits or upper limits to form an unambiguous range.

[0029] In the context of the present invention, "polyfunctional thiol compound" refers to a polythiol compound containing two or more thiol groups in the molecule. The chemical formula of the thiol group is -SH, which is a negative monovalent functional group composed of a sulfur atom and a hydrogen atom connected.

[0030] When appearing in this description and claims, the terms "comprises" and "includes" and variations thereof do not have a limiting meaning.

[0031] The terms "preferred" and "preferably" refer to embodiments of the present invention that may provide certain benefits in certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. In addition, the recitation of one or more preferred embodiments does not mean that other embodiments are not applicable, and is not intended to exclude other embodiments from the scope of the present invention. DETAILED DESCRIPTION

[0032] An embodiment of the present invention provides a UV-LED curable coating composition, comprising:

[0033] (a) amine-modified polyether acrylate;

[0034] (b) a (meth)acrylate polymer different from (a);

[0035] (c) a polyfunctional thiol compound; and

[0036] (d) Acylphosphine oxides, as photoinitiators.

[0037] (a) Amine-modified polyether acrylate

[0038] In the coating composition of the embodiment of the present invention, the amine-modified polyether acrylate as the film-forming resin is obtained by amine-modifying a polyether acrylate with a high degree of esterification and low viscosity. The curing rate of the amine-modified polyether acrylate is high, and the curing shrinkage is significantly reduced, while still having a low viscosity. The amine-modified polyether acrylate provided by the present invention can effectively reduce odor and amine migration, and has the characteristics of low yellowing.

[0039] Amine-modified polyether acrylate is a commonly used resin in the art, and is available from BASF as, for example, PO 83F, PO 94F, LR8869 and / or LR8889.

[0040] The amine-modified polyether acrylate is present in an amount of 10 to 40 wt %, preferably 10 to 30 wt %, more preferably 15 to 30 wt %, based on the total weight of the UV-LED-curable coating composition.

[0041] (b) a (meth)acrylate polymer different from (a)

[0042] The UV-LED-curable coating composition according to an embodiment of the present invention further comprises a (meth)acrylate polymer different from the above-mentioned amine-modified polyether acrylate as a film-forming resin.

[0043] The (meth)acrylate polymer other than the amine-modified polyether acrylate includes at least one of epoxy (meth)acrylate, polyurethane (meth)acrylate, polyester (meth)acrylate, polyether (meth)acrylate, and acrylate copolymer.

[0044] The epoxy (meth) acrylate polymer is an addition product of an epoxy resin and an unsaturated carboxylic acid (e.g., acrylic acid, methacrylic acid), including epoxy (meth) acrylate of bisphenol A epoxy resin, epoxy (meth) acrylate of phenol or cresol-novolac epoxy resin, or (meth) acrylate of diglycidyl ether.

[0045] The polyurethane (meth) acrylate polymer is a reaction product obtained by reacting a hydroxyl-containing (meth) acrylate with a reaction product of a polyol and an organic polyisocyanate. The hydroxyl-containing (meth) acrylate is a hydroxyalkyl (meth) acrylate, such as 2-hydroxyethyl (meth) acrylate or 2-hydroxypropyl (meth) acrylate. The polyol includes ethylene glycol, propylene glycol or butylene glycol, etc. The organic polyisocyanate includes toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, hexamethylene diisocyanate or isophorone diisocyanate.

[0046] The polyester (meth) acrylate polymer is a dehydration condensation product of polyester polyol and (meth) acrylic acid. The polyester polyol is a reaction product of a polyol and a dibasic acid, wherein the polyol includes ethylene glycol, polypropylene glycol, 1,6-hexanediol or trimethylolpropane, etc., and the dibasic acid includes adipic acid, succinic acid, phthalic acid, hexahydrophthalic acid or terephthalic acid, etc.

[0047] The polyether (meth)acrylate polymer is a polyalkylene glycol di(meth)acrylate, such as polyethylene glycol di(meth)acrylate or polypropylene glycol di(meth)acrylate.

[0048] The acrylic ester copolymer is a type of polymer obtained by free radical polymerization of monomers such as (meth)acrylic acid, (meth)acrylate and styrene under the action of a peroxide initiator (for example, benzoyl peroxide).

[0049] The (meth)acrylate polymer other than the amine-modified polyether acrylate is present in an amount of 30 to 70 wt %, preferably 30 to 60 wt %, more preferably 40 to 60 wt %, based on the total weight of the UV-LED curable coating composition.

[0050] (c) Multifunctional thiol compounds

[0051] The polyfunctional thiol compounds used in the embodiments of the present invention are those containing 2 or more mercapto groups in their molecules. The polythiol compounds include aliphatic polythiol compounds, aromatic polythiol compounds and the like.

[0052] Specifically, the aliphatic polythiol compounds include dithiol compounds such as 1,2-ethanedithiol, 1,2-propanedithiol, 1,3-propanedithiol, 1,4-butanedithiol, 1,6-hexanedithiol, 1,7-heptanedithiol, 1,8-octanedithiol, 1,9-nonanedithiol, 1,10-decanedithiol, 1,12-dodecanedithiol, 2,2-dimethyl-1,3-propanedithiol, 3-methyl-1,5-pentanedithiol, 2-methyl-1,8-octanedithiol, 1,4-cyclohexanedithiol, 1,4-bis(mercaptomethyl)cyclohexane, 1,1-cyclohexanedithiol, 1,2-cyclohexanedithiol, bicyclo[2,2,1]heptyl-exo-cis-2,3-dithiol , 1,1-bis(mercaptomethyl)cyclohexane, bis(2-mercaptoethyl) ether, ethylene glycol bis(2-mercaptoacetate) and ethylene glycol bis(3-mercaptopropionate); trithiol compounds such as 1,1,1-tris(mercaptomethyl)ethane, 2-ethyl-2-mercaptomethyl-1,3-propanedithiol, 1,2,3-propanetrithiol, triformylpropane tris(2-mercaptoacetate), triformylpropane tris(3-mercaptopropionate) and tris((mercaptopropionyloxy)-ethyl)isocyanurate; and polythiol compounds containing 4 or more mercapto groups, such as pentaerythritol tetrakis(2-mercaptoacetate), pentaerythritol tetrakis(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptobutyrate) and dipentaerythritol hexa-3-mercaptopropionate.

[0053] In addition, the aromatic polythiol compounds include 1,2-dimercaptobenzene, 1,3-dimercaptobenzene, 1,4-dimercaptobenzene, 1,2-bis(mercaptomethyl)benzene, 1,3-bis(mercaptomethyl)benzene, 1,4-bis(mercaptomethyl)benzene, 1,2-bis(2-mercaptoethyl)benzene, 1,3-bis(2-mercaptoethyl)benzene, 1,4-bis(2-mercaptoethyl)benzene, 1,2-bis(2-mercaptoethyleneoxy)benzene, 1,3-bis(2-mercaptoethyleneoxy)benzene, 1,4-bis(2-mercaptoethyleneoxy)benzene, 1,2,3-trimercaptobenzene, 1,2,4-trimercaptobenzene, 1,3,5-trimercaptobenzene, 1,2,3-tris(mercaptomethyl)benzene, 1,2,4-tris(mercaptoethyl)benzene, 1,3,5-tris(mercaptomethyl)benzene, 1,2,3-tris(2-mercaptoethyl)benzene, 1,2,4-tris(2-mercaptoethyl)benzene, 1,3,5-tris(2-mercaptoethyl)benzene, 1,2,3-tris(2-mercaptoethyleneoxy)benzene, 1,2,4-tris(2-mercaptoethyleneoxy)benzene, 1,3,5-tris(2-mercaptoethyleneoxy)benzene, 1,2,3,4-tetramercaptobenzene, 1,2,3,5-tetramercaptobenzene, 1,2,4,5-tetramercaptobenzene, 1,2,3,4-tetrakis(mercaptomethyl)benzene, 1,2,3,5-tetrakis(mercaptomethyl)benzene, 1,2,4,5-tetrakis(mercaptomethyl)benzene, 1,2,3,4-tetrakis(2-mercaptoethyl)benzene )benzene, 1,2,3,5-tetrakis(2-mercaptoethyl)benzene, 1,2,4,5-tetrakis(2-mercaptoethyl)benzene, 1,2,3,4-tetrakis(2-mercaptoethyleneoxy)benzene, 1,2,3,5-tetrakis(2-mercaptoethyleneoxy)benzene, 1,2,4,5-tetrakis(2-mercaptoethyleneoxy)benzene, 2,2′-dimercaptobiphenyl, 4,4′-thiobis-benzenethiol, 4,4′-dimercaptobiphenyl, 4,4′-dimercaptobitolyl, 2,5-toluenedithiol, 3,4-toluenedithiol, 1,4-naphthalenedithiol, 1,5-naphthalenedithiol, 2,6-naphthalenedithiol, 2,-naphthalenedithiol, 2,4-dimethylbenzene-1,3-dithiol, 4,5-di 1,3-dithiol, 9,10-anthracenedimethanethiol, 1,3-bis(2-mercaptoethylthio)benzene, 1,4-bis(2-mercaptoethylthio)benzene, 1,2-bis(2-mercaptoethylthiomethyl)benzene, 1,3-bis(2-mercaptoethylthiomethyl)benzene, 1,4-bis(2-mercaptoethylthiomethyl)benzene, 1,2,3-tris(2-mercaptoethylthio)benzene, 1,2,4-tris(2-mercaptoethylthio)benzene, 1,3,5-tris(2-mercaptoethylthio)benzene, 1,2,3,4-tetrakis(2-mercaptoethylthio)benzene, 1,2,3,5-tetrakis(2-mercaptoethylthio)benzene, and 1,2,4,5-tetrakis(2-mercaptoethylthio)benzene, and the like.

[0054] In addition, the polyfunctional thiol compounds containing thioether bonds in the molecules also include bis(2-mercaptoethyl) sulfide, bis(2-mercaptoethylthio)methane, 1,2-bis(2-mercaptoethylthio)ethane, 1,3-bis(2-mercaptoethylthio)propane, 1,2,3-tris(2-mercaptoethylthio)propane, tetrakis(2-mercaptoethylthiomethyl)methane, 1,2-bis(2-mercaptoethylthio)propanethiol, 2,5-dimercapto-1,4-dithiane, bis(2-mercaptoethyl) sulfide, 3,4-thiophenedithiol, 1,2-bis(2-mercaptoethyl)thio-3-mercaptopropane, and bis-(2-mercaptoethylthio-3-mercaptopropane) sulfide, etc.

[0055] Particularly preferred polyfunctional thiol compounds are trivalent (containing 3 or more mercapto groups) or higher valent (generally about 8 valent or lower) aliphatic polythiol compounds, and particularly preferred are trimethylolpropane tris(2-mercaptoacetate), triformylpropane tris(3-mercaptopropionate), tris((mercaptopropionyloxy)-ethyl)isocyanurate, pentaerythritol tetrakis(2-mercaptoacetate), pentaerythritol tetrakis(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptobutyrate), and dipentaerythritol hexa-3-mercaptopropionate, and the like.

[0056] In the coating composition according to the present invention, preferably, at least a part of the polyfunctional thiol compounds contained are trivalent or higher-valent (usually about 8-valent or lower-valent) polythiol compounds, and the polyfunctional thiol compounds contained as a whole are trivalent or higher-valent polythiol compounds.

[0057] In an embodiment according to the present invention, the multifunctional thiol compound comprises 3 or more thiol groups, preferably 4 or more thiol groups.

[0058] The multifunctional thiol compound is present in an amount of 0.5 to 4 wt %, preferably 0.5 to 3 wt %, more preferably 0.5 to 2 wt %, based on the total weight of the UV-LED curable coating composition.

[0059] (d) Acylphosphine oxide

[0060] In an embodiment of the present invention, the coating composition comprises an acylphosphine oxide as a photoinitiator having significant absorption under LED light radiation in the wavelength range of 340-420 nm. As a typical cleavage-type photoinitiator, the maximum absorption peak of the acylphosphine oxide is in the range of 340-420 nm, and can effectively absorb light radiated by a light-emitting diode LED.

[0061] The acylphosphine oxide includes a monoacylphosphine oxide, a bisacylphosphine oxide or a combination thereof. The bisacylphosphine oxide may be a compound of formula (I):

[0062]

[0063] Among them, Ar 1 ,Ar 2 and Ar 3 Each of them is independently a substituted or unsubstituted C6-C18 aryl or C1-C6 alkyl.

[0064] The structure of monoacylphosphine oxide is similar to that of bisacylphosphine oxide, except that only one acyl group is directly attached to phosphorus. As an example, the monoacylphosphine oxide may be a compound of formula (II) (Lucirin TPO-L):

[0065]

[0066] Acylphosphine oxides suitable for use in the present invention include, but are not limited to, 2,4,6-trimethylbenzoyldiphenylphosphine oxide (Lucirin TPO, commercially available from BASF), ethyl 2,4,6-trimethylbenzoylphenylphosphonate (Lucirin TPO-L, commercially available from BASF), bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (IRGACURE 819, commercially available from BASF), or any combination thereof.

[0067] Currently, the most successful commercial acylphosphine oxides are IRGACURE 819 and Lucirin TPO, which can absorb ultraviolet light at 385-410 nm.

[0068] The acylphosphine oxide is present in an amount of 2 to 8 wt %, preferably 3 to 8 wt %, more preferably 3 to 6 wt %, based on the total weight of the UV-LED curable coating composition.

[0069] In addition, the UV-LED curable coating composition according to the present invention may further include a co-initiator, wherein the co-initiator includes one or more monomers or prepolymers selected from alkylhydroxylamines, dimethylaminobenzoates, and amine-modified acrylates.

[0070] Examples of alkylhydroxylamines as co-initiators are triethanolamine, triisopropanolamine, methyldiethanolamine, etc. Examples of dimethylaminobenzoic acid esters as co-initiators are ethyl 4-dimethylaminobenzoate, isooctyl 4-dimethylaminobenzoate, etc.

[0071] The amine-modified acrylate monomer or prepolymer used as a co-initiator is a reaction product obtained by a nucleophilic substitution reaction between an amine compound (e.g., ethylenediamine) and an acrylate monomer or prepolymer (e.g., trimethylolpropane triacrylate), including diethylamine-modified trimethylolpropane triacrylate and the like.

[0072] The co-initiator is present in an amount of 0 to 4 wt %, preferably 0.5 to 3 wt %, more preferably 0.5 to 2 wt %, based on the total weight of the UV-LED curable coating composition.

[0073] The inventors found that the introduction of multifunctional thiol compounds into the coating composition, in addition to inhibiting surface oxygen inhibition, can also increase the crosslinking degree of the paint film by utilizing the "click" chemical reaction between the thiol group and the double bond, thereby improving the performance of the paint film, and locking the thiol in the paint film to prevent the thiol from migrating to the surface and causing odor emission. On this basis, by selecting amine-modified polyether acrylate as a film-forming resin and acylphosphine oxide as a photoinitiator, the chemical stability of the acylphosphine oxide can be ensured, and the use of a yellowing initiator can be avoided, significantly improving the surface curing performance and yellowing resistance of the paint film. Adding a co-initiator further improves the reaction efficiency and reduces the required curing energy, thereby achieving rapid curing.

[0074] In addition, the UV-LED curable coating composition according to the present invention may further include a reactive diluent. The reactive diluent may be preferably used for viscosity adjustment and / or physical property adjustment.

[0075] Reactive diluents include (meth)acrylic monomers. Examples of monofunctional (meth)acrylic monomers include, but are not limited to, butylene glycol mono(meth)acrylate, cyclohexyl(meth)acrylate, dicyclopentanyl(meth)acrylate, dicyclopentenyl(meth)acrylate, dicyclopentenyloxyethyl(meth)acrylate, N,N-diethylaminoethyl(meth)acrylate, 2-ethoxyethyl(meth)acrylate, 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, caprolactone-modified 2-hydroxyethyl(meth)acrylate, isobornyl(meth)acrylate, lauryl(meth)acrylate, acryloylmorpholine, N-vinylcaprolactam, nonylphenoxypolyethylene glycol(meth)acrylate, nonylphenoxypolypropylene glycol(meth)acrylate, phenoxyethyl(meth)acrylate, phenoxyhydroxypropyl(meth)acrylate, phenoxydiglycol(meth)acrylate, polyethylene glycol(meth)acrylate, polypropylene glycol(meth)acrylate, and tetrahydrofurfuryl(meth)acrylate, and the like.

[0076] The multifunctional (meth)acrylic monomers include, but are not limited to, 1,4-butylene glycol di(meth)acrylate, dicyclopentane di(meth)acrylate, ethylene glycol di(meth)acrylate, dipentaerythritol hexa(meth)acrylate, caprolactone-modified dipentaerythritol hexa(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol tri(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate and its alkoxylates, tri(acryloyloxyethyl)isocyanurate, caprolactone-modified tri(acryloyloxyethyl)isocyanurate, tri(methacryloyloxyethyl)isocyanurate, and tricyclodecane dimethanol di(meth)acrylate, etc.

[0077] These monofunctional (meth)acrylic monomers and polyfunctional (meth)acrylic monomers may be used alone or in combination of two or more monomers, or the monofunctional and polyfunctional monomers may be used in combination.

[0078] As a component used in combination, a monofunctional (meth)acrylic monomer is preferably used for viscosity adjustment and / or physical property adjustment. In a specific application, an alicyclic (meth)acrylate compound such as isobornyl acrylate is preferred.

[0079] In a preferred embodiment according to the present invention, the reactive diluent is selected from at least one of dipropylene glycol di(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate, 1,6-hexanediol di(meth)acrylate, (ethoxylated) trimethylolpropane tri(meth)acrylate, (propoxylated) trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate and isobornyl(meth)acrylate.

[0080] The reactive diluent is present in an amount of 10 to 40 wt %, preferably 10 to 30 wt %, more preferably 15 to 20 wt %, based on the total weight of the UV-LED curable coating composition.

[0081] The UV-LED curable coating composition of the present invention may optionally include additional additives commonly used in coating compositions, which do not adversely affect the coating composition or the cured coating obtained therefrom. Suitable additives include, for example, those reagents that improve the processing properties or manufacturing properties of the composition, enhance the aesthetics of the composition, or improve the specific functional properties or characteristics (such as adhesion to the substrate) of the coating composition or the cured composition obtained therefrom. The additives that may be included are, for example, carriers, film-forming aids, co-solvents, pigments, fillers, anti-migration aids, antibacterial agents, chain extenders, lubricants, wetting agents, biocides, plasticizers, defoamers, colorants, waxes, antioxidants, anticorrosives, flow control agents, thixotropic agents, dispersants, adhesion promoters, UV stabilizers, thickeners, defoamers, pH regulators, or combinations thereof. The content of each optional component is sufficient to achieve its intended purpose, but preferably, such a content does not adversely affect the coating composition or the cured coating obtained therefrom. In a preferred embodiment of the present invention, suitable additional additives include thickeners, surfactants, defoamers, bactericides, mildewicides or any combination thereof.

[0082] The content of the additional additive is in the range of about 0 to about 10 weight %, preferably in the range of about 0.1 to about 5 weight %, and more preferably in the range of about 0.1 to about 1 weight %, relative to the total weight of the UV-LED curable coating composition. In one embodiment of the present invention, the coating composition contains, relative to the total weight of the UV-LED curable coating composition, 0.1 to about 10 weight % of the additional additive. Specifically, the amount of the additional additive contained in the coating composition is from about 0.2 weight %, about 0.3 weight %, about 0.4 weight %, about 0.6 weight %, about 0.7 weight %, about 0.8 weight % or about 0.9 weight % to about 9.0 weight %, about 7.0 weight %, about 6.0 weight %, about 5.0 weight %, about 4.0 weight %, about 2.0 weight % or about 1.0 weight %.

[0083] In one embodiment of the present invention, the UV-LED curable coating composition comprises, relative to the total weight of the UV-LED curable coating composition,

[0084] (a) 10-30 wt % of amine-modified polyether acrylate;

[0085] (b) 30-60 wt % of an acrylate polymer different from (a);

[0086] (c) 0.5-2 wt % of a multifunctional thiol compound;

[0087] (d) 3 to 6% by weight of acylphosphine oxide;

[0088] (e) 15-30% by weight of a reactive diluent;

[0089] (f) 0.5-2 wt% of a coinitiator; and

[0090] (g) 0.1-1 wt % of additional additives, wherein the additional additives include thickeners, surfactants, defoamers, bactericides or any combination thereof.

[0091] As an example of a surfactant, BYK-346 available from BYK can be used. As an example of a thickener, ACRYSOL RM TM As an example of the defoaming agent, BYK-088 available from BYK Company can be used.

[0092] The UV-LED curable coating composition according to the present invention is curable when irradiated with light emitted by a light emitting diode (LED), wherein the wavelength of the light is 340 nm to 420 nm, more preferably 380 nm to 410 nm.

[0093] In the present invention, the UV-LED curable coating composition can be prepared by a method commonly used in the art.

[0094] According to the present invention, the UV-LED curable coating composition can be coated by conventional coating methods known to those skilled in the art, including dip coating, spin coating, spray coating, curtain coating, brush coating, roller coating and other coating methods known in the art.

[0095] The UV-LED curable coating composition according to the present invention can undergo photopolymerization when applied to the surface of a substrate and irradiated by light emitted from a light emitting diode (LED) having a wavelength of about 340 nm to 420 nm, more preferably 380 nm to 410 nm, thereby providing a cured coating on the surface of the substrate.

[0096] The present invention provides a coating composition with high reactivity under LED-UV curing light source, wherein a multifunctional thiol compound is introduced into the formula, which provides excellent anti-surface oxygen inhibition effect, and can also increase the crosslinking degree of the paint film by utilizing the "click" chemical reaction of the thiol group and the double bond, thereby improving the performance of the paint film. On this basis, by adjusting the collocation of the film-forming resin and the initiator, it is ensured that the coating composition will not turn yellow after curing, and the addition of the co-initiator further improves the reaction efficiency.

[0097] Therefore, the coating formed by curing the UV-LED curable coating composition according to the present invention on BYK white coating test card paper has a color difference value of ΔE<2.0 and Δb<1.5 with the BYK white coating test card paper. The color difference value test is described in detail in the embodiment part.

[0098] Due to the above specific composition, the UV-LED curable coating composition according to the present invention can be cured quickly and with high curing efficiency, wherein the curing energy required for the coating composition to be cured to form a coating does not exceed 2000 mJ / cm 2 The UV-LED curable coating composition according to the present invention can provide good surface curing performance after curing. Compared with conventional UV-LED curable coating compositions, the UV-LED curable coating composition according to the present invention can be cured quickly, and after curing, a coating with comparable or even better yellowing resistance is obtained.

[0099] Therefore, the UV-LED curable coating composition according to the present invention can be applied on a fast LED-UV curing line and used as a topcoat or a primer, preferably used as a topcoat, such as a clear topcoat.

[0100] Therefore, the present invention also provides an article, which comprises a substrate partially or fully coated with the UV-LED curable coating composition according to the present invention. A person skilled in the art will select and determine a suitable material as the substrate according to actual needs.

[0101] The substrate can be a non-heat-sensitive substrate, such as glass, ceramic, fiber, cement board or metal (such as aluminum, copper or steel), or a heat-sensitive substrate. Considering that the UV-LED curable coating composition of the present invention can be cured using an LED radiation source with lower radiation energy, it is particularly suitable for providing a coating for a heat-sensitive substrate (preferably wood).

[0102] Suitable heat-sensitive substrates include wood substrates, for example solid wood, such as: hardwood, softwood, plywood; veneer, particle board, low-density fiberboard, medium-density fiberboard and high-density fiberboard, OSB (oriented structural board), wood laminate, chipboard and other substrates in which wood is an important component, such as metal foil-coated wooden substrates, composite wood flooring, plastic-modified wood, plastic substrates or wood-plastic composites (WPC); substrates with cellulose fibers, such as cardboard or paper substrates.

[0103] The following examples more specifically describe the disclosure of the present invention, which are intended for illustrative purposes only, as various modifications and variations within the scope of the disclosure of the present invention are apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by weight, and all reagents used in the examples are commercially available and can be used directly without further treatment.

[0104] Example

[0105] Test Method

[0106] Adhesion

[0107] Adhesion testing is performed to evaluate the adhesion of the coating to the coated substrate. The adhesion test is performed according to ASTM D 3359 - Test Method B. Adhesion is generally rated on a scale of 0-5B, with 5B indicating optimal adhesion.

[0108] Glossiness

[0109] This test is used to measure the gloss of a cured coating. A Sheen small hole gloss meter is used to evaluate 60° gloss according to ASTM D523.

[0110] Characterization of yellowing resistance

[0111] On BYK white film test card, UV-LED curable coating composition is applied by knife with a coating amount of 10-12 g / m 2 ; Cured under 395nm LED-UV light source, curing energy is 1000-1500mJ / cm 2 After curing, use a colorimeter to test and calculate (the formula is as follows) the color difference between the coated area and the original white cardboard.

[0112] △E=[(△L*) 2 +(△a*) 2 +(△b*) 2 ] 1 / 2

[0113] Where ΔL = L sample - L standard (brightness difference); Δa = a sample - a standard (red / green difference); Δb = b sample - b standard (yellow / blue difference).

[0114] △E represents the magnitude of total color difference;

[0115] A large △L indicates whiteness, and a small △L indicates blackness.

[0116] A large △a indicates a reddish color, and a small △a indicates a greenish color.

[0117] A larger △b indicates a yellowish color, and a smaller △L indicates a bluish color.

[0118] Characterization of solvent resistance

[0119] Resistance to solvents (such as methyl ethyl ketone or alcohol) is performed to evaluate the "cure" or crosslinking of the coating. This test is performed as described in ASTM D 5402 93. The integrity of the coating is determined after a certain number of double-sided rubs (i.e., a back and forth motion) (usually 50 times). Solvent resistance is usually rated on a scale of 0-5, where 5 = coating is intact with no scratches (best), 4 = coating scratches are barely noticeable, 3 = coating scratches can be clearly identified, 2-1 = coating gloss is lost due to scratches, and 0 = coating peels off to the substrate (worst).

[0120] Characterization of curing effect

[0121] The rubbing test is performed to evaluate the curing degree of the topcoat: press the dry linen cloth with your thumb, rub it in both directions 10 times on the cured paint surface, and then determine the integrity of the paint surface. The rubbing test results are divided into 0-5 levels, where 5 = the coating is intact and without scratches (best), 4 = the coating scratches are almost unnoticeable, 3 = the coating can be clearly confirmed to have scratches, and 2-0 = the gloss of the coating disappears due to scratches.

[0122] Material

[0123] The materials used are listed in Table 1 below.

[0124] Table 1: Materials used and related information

[0125]

[0126] Formulation of UV-LED curable coating compositions

[0127] A UV-LED curable coating composition was prepared according to the ingredients shown in Table 2. A film-forming resin, a multifunctional thiol compound, a photoinitiator, a co-initiator and additional additives were added to a reactive diluent under stirring to form a coating composition.

[0128] Table 2: Composition of UV-LED curable coating composition

[0129]

[0130] The coating composition thus formed was applied as a topcoat on a log-colored cherry veneer MDF board (the board was pre-rolled with a UV-LED special primer and polished with 400-mesh sandpaper) to form a 15-micron coating. The coating thus formed was then subjected to UV-LED curing. The LED ultraviolet lamp used was purchased from Shenzhen Renwei Optoelectronics Co., Ltd., which emitted light with a wavelength of 395 nm and a power of 4500-5000 mW / cm 2 .

[0131] The curing was performed at different line speeds, and the distance between the LED lamp and the sample was 5 cm during curing. The properties of the cured coating were measured according to the methods listed in the test methods, and the results are shown in Table 3.

[0132] Table 3: Coating properties

[0133]

[0134] It can be seen from the above results that the UV-LED curable coating composition according to the present invention achieves good curing and has excellent yellowing resistance. Moreover, the combination of a specific multifunctional thiol compound and a specific amine-modified polyether acrylate, in addition to inhibiting surface oxygen inhibition, can also increase the crosslinking degree of the paint film by utilizing the "click" chemical reaction of the thiol group and the double bond, thereby improving the performance of the paint film. The addition of a co-initiator further improves the curing reaction efficiency, achieves rapid curing, and reduces the required curing energy. The UV-LED curable coating composition according to the present invention can obtain a coating with excellent surface properties in a short curing time.

[0135] All patents, patent applications and publications cited herein and all disclosures of electronically available materials are incorporated herein by reference. The aforementioned detailed description of the invention and embodiments are provided only for clear understanding. It is not to be understood therefrom as unnecessary limitations. The present invention is not limited to the precise details shown and described, and obvious changes to those skilled in the art will be included in the present invention defined by the claims. In some embodiments, the present invention disclosed illustratively herein can be implemented in the absence of any element not clearly disclosed herein.

[0136] Although the invention has been described with reference to a number of embodiments and examples, those skilled in the art will recognize, based on the present disclosure, that other embodiments can be designed without departing from the scope and spirit of the invention.

Claims

1. A UV-LED curable coating composition comprising: (a) amine-modified polyether acrylate; (b) a (meth)acrylate polymer different from that of (a); (c) a polyfunctional thiol compound; and (d) acylphosphine oxides, as photoinitiators; wherein the multifunctional thiol compound is present in an amount of 0.5 to 4 wt % based on the total weight of the UV-LED curable coating composition; The acylphosphine oxide is present in an amount of 2 to 8 wt % based on the total weight of the UV-LED curable coating composition; The amine-modified polyether acrylate is present in an amount of 10 to 40 wt % based on the total weight of the UV-LED-curable coating composition; and The (meth)acrylate polymer other than the amine-modified polyether acrylate is present in an amount of 30 to 70 wt %, based on the total weight of the UV-LED-curable coating composition.

2. The UV-LED curable coating composition according to claim 1, wherein The multifunctional thiol compound contains 3 or more thiol groups.

3. The UV-LED curable coating composition according to any one of claims 1 to 2, wherein: The (meth)acrylate polymer is selected from at least one of epoxy (meth)acrylate, polyurethane (meth)acrylate, polyester (meth)acrylate, and polyether (meth)acrylate.

4. The UV-LED curable coating composition according to any one of claims 1 to 2, wherein: The (meth)acrylate polymer is selected from acrylate copolymers.

5. The UV-LED curable coating composition according to any one of claims 1 to 2, wherein: The coating composition further comprises a co-initiator, which comprises one or more monomers or prepolymers selected from alkylhydroxylamines, dimethylaminobenzoates and amine-modified acrylates.

6. The UV-LED curable coating composition according to any one of claims 1 to 2, wherein: The coating composition also includes a reactive diluent.

7. The UV-LED curable coating composition according to claim 6, wherein: The active diluent is selected from at least one of dipropylene glycol di(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate, 1,6-hexanediol di(meth)acrylate, (ethoxylated) trimethylolpropane tri(meth)acrylate, (propoxylated) trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, and isobornyl(meth)acrylate.

8. The UV-LED curable coating composition according to any one of claims 1 to 2, wherein: Relative to the total weight of the coating composition, the coating composition comprises: (a) 10-30 wt % of the amine-modified polyether acrylate; (b) 30-60 wt % of a (meth)acrylate polymer different from (a); (c) 0.5-2 wt % of the multifunctional thiol compound; (d) 3-6 wt % of the acylphosphine oxide; (e) 15-30% by weight of a reactive diluent; (f) 0.5-2 wt % of a co-initiator; and (g) 0.1-1 wt % of additional additives, wherein the additional additives include a thickener, a surfactant, a defoaming agent, a bactericide or any combination thereof.

9. The UV-LED curable coating composition according to any one of claims 1 to 2, which is used as a topcoat or a primer.

10. The UV-LED curable coating composition according to any one of claims 1 to 2, which is used as a topcoat.

11. The UV-LED curable coating composition according to any one of claims 1 to 2, wherein: The curing energy required for the coating composition to be cured to form a coating is no more than 2000 mJ / cm 2 .

12. The UV-LED curable coating composition according to any one of claims 1 to 2, wherein: The coating formed by curing the coating composition on BYK white coating test card paper has a color difference value ΔE<2.0 with respect to the BYK white coating test card paper.

13. An article comprising a substrate partially or fully coated with the UV-LED curable coating composition according to any one of claims 1 to 12.

14. The article of claim 13, wherein: The substrate is one or more of wood, glass, ceramic, metal, plastic and cement board.

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