Aqueous radiation curable composition

Abstract

An aqueous radiation curable composition comprising: a) 45-80 wt% of at least one ethylenically unsaturated compound (A); and b) 20-55 wt% of at least one ethylenically unsaturated polyurethane polymer (B) obtained by reacting: i. At least one polyisocyanate compound (i); ii. At least one polymeric polyol (ii); iii. At least one hydrophilic compound (iii) comprising at least one reactive group capable of reacting with isocyanate groups, and at least one group capable of dispersing the polyurethane polymer (B) directly in an aqueous medium or after reacting with a neutralizing agent to provide a salt; iv. At least one compound (iv) comprising at least one reactive group capable of reacting with isocyanate groups and further comprising at least one ethylenically unsaturated group; and v. Optionally, at least one compound (v) comprising at least one reactive group capable of reacting with an isocyanate group; wherein compounds (A), (i), (ii), (iii), (iv) and (v) are different from each other, and wherein wt% is based on the total dry content weight of the radiation curable composition.

Description

Technical Field

[0001] The present invention relates to an aqueous radiation-curable composition and a coating composition comprising said aqueous radiation-curable composition. Background Art

[0002] Plastic coatings are an important and high-growth area of the coatings industry, addressing the severe demand for advanced surface treatment technologies for aesthetics as well as additional protective and functional features. Coatings for so-called 3C applications (including computers, communications, and consumer electronics) are particularly difficult to formulate because they use various low-surface-energy substrates, including, for example, polycarbonate and other synthetic polymers or fibers, and these coatings are known to be difficult to adhere to the substrates.

[0003] With the increasingly strict implementation of VOC emission regulations worldwide, the demand for low-VOC coating solutions is growing rapidly. Against this background, aqueous radiation-curable coating compositions are becoming increasingly popular in replacing solvent-based resins. However, it is known that the use of aqueous radiation-curable coating compositions known in the art is limited in high-difficulty plastic applications due to unsatisfactory adhesion performance.

[0004] For example, partial solutions are described in US2020 / 0181451A1 (Su et al.). Without intending to deny the technical advantages of the solutions known in the art, there is still a need for a low-VOC radiation-curable composition that at least partially overcomes the above-mentioned drawbacks. Summary of the Invention

[0005] According to one aspect, the present invention relates to an aqueous radiation-curable composition comprising: a) 45 - 80 wt% of at least one ethylenically unsaturated compound (A); and b) 20 - 55 wt% of at least one ethylenically unsaturated polyurethane polymer (B) obtained by reacting: i. at least one polyisocyanate compound (i); ii. at least one polymeric polyol (ii); iii. at least one hydrophilic compound (iii) comprising at least one reactive group capable of reacting with an isocyanate group and at least one group capable of directly dispersing the polyurethane polymer (B) in an aqueous medium or dispersing it in an aqueous medium after reacting with a neutralizing agent to provide a salt; iv. at least one compound (iv) comprising at least one reactive group capable of reacting with an isocyanate group and further comprising at least one ethylenically unsaturated group; and v. optionally, at least one compound (v) comprising at least one reactive group capable of reacting with an isocyanate group; wherein the compounds (A), (i), (ii), (iii), (iv) and (v) are each different from one another, and wherein the wt% is based on the total dry content weight of the radiation-curable composition.

[0006] According to another aspect, the present invention relates to a coating composition comprising the aqueous radiation-curable composition as described above.

[0007] In yet another aspect of the present invention, there is provided a method for preparing an aqueous radiation-curable composition, which comprises the following steps: a) mixing and reacting the compounds (i), (ii), (iii) as described above and optionally the compound (vi); b) reacting the product of step a) with the compound (iv) as described above to obtain an ethylenically unsaturated polyurethane polymer (B); c) adding at least one ethylenically unsaturated compound (A) as described above; d) optionally, reacting the compound (iii) with a neutralizing agent to convert the hydrophilic group provided by the compound (iii) into an anionic salt; e) dispersing the ethylenically unsaturated polyurethane polymer (B) obtained in step b) or optionally step d) in an aqueous medium; and f) optionally, reacting the ethylenically unsaturated polyurethane polymer (B) obtained in step e) with the compound (v) as described above.

[0008] According to another aspect, the present invention relates to the use of the aqueous radiation-curable composition or coating composition as described above in computer, communication and consumer electronics applications, dual-curing applications or thick color systems. Detailed Description of the Invention

[0009] According to a first aspect, the present invention relates to an aqueous radiation-curable composition, which comprises: a) 45 - 80 wt% of at least one ethylenically unsaturated compound (A); and b) 20 - 55 wt% of at least one ethylenically unsaturated polyurethane polymer (B) obtained by reacting: i. at least one polyisocyanate compound (i); ii. at least one polymeric polyol (ii); iii. at least one hydrophilic compound (iii) comprising at least one reactive group capable of reacting with an isocyanate group and at least one group capable of directly dispersing the polyurethane polymer (B) in an aqueous medium or dispersing it in an aqueous medium after reacting with a neutralizing agent to provide a salt; iv. at least one compound (iv) which comprises at least one reactive group capable of reacting with an isocyanate group and further comprises at least one ethylenically unsaturated group; and v. optionally, at least one (non-polymerizable) compound (v) which comprises at least one (substantially one) reactive group capable of reacting with an isocyanate group; wherein compounds (A), (i), (ii), (iii), (iv) and (v) are all different from one another, and wherein wt% is based on the total dry content weight of the radiation-curable composition.

[0010] In the context of the present invention, it has surprisingly been found that the aqueous radiation-curable compositions as described above have excellent colloidal stability even under severe aging conditions, as well as favorable formulation flexibility.

[0011] It has also surprisingly been found that the aqueous radiation-curable compositions as described above are particularly suitable for forming coatings having excellent properties and performance attributes, including adhesion to difficult-to-adhere plastic substrates (in particular polycarbonate, acrylonitrile butadiene styrene, and any combination thereof), hot water resistance, hydrolysis resistance, visual aesthetics (even in complex formulations such as metallic or matte formulations), abrasion resistance, stain resistance, and low VOC characteristics.

[0012] Without being bound by theory, it is believed that these excellent properties and attributes are particularly attributable to the use of a specific combination of: (a) at least one ethylenically unsaturated compound (A), and (b) at least one ethylenically unsaturated polyurethane polymer (B) obtained as described above; wherein compound (A) and polyurethane polymer (B) are included in the radiation-curable composition in the specific ranges detailed above.

[0013] More specifically, it is believed that the specific combination of the components in the specific weight ranges as described above contributes to providing the aqueous radiation-curable composition with favorable properties, in particular a relatively small particle size and excellent viscosity characteristics, which in turn confer on the coating the excellent properties and performance attributes as described above.

[0014] Still without being bound by theory, it is further believed that the polyurethane polymer (B) obtained as described above, when used in combination with 45 - 80 wt% (based on the total dry content weight of the radiation-curable composition) of at least one ethylenically unsaturated compound (A), formally acts as an effective internal stabilizer (or emulsifier) for the relatively high proportion of ethylenically unsaturated compound (A), which in turn favorably affects the stability of the resulting aqueous radiation-curable composition.

[0015] This is a particularly surprising and counterintuitive finding, considering that aqueous compositions containing such ethylenically unsaturated compounds (A) in amounts greater than 30 wt% are generally considered to have insufficient stability and poor aging resistance.

[0016] The specific ethylenically unsaturated polyurethane polymers (B) as described above also allow for excellent design flexibility, thereby allowing for the obtaining of aqueous radiation-curable compositions with fine-tuned properties and excellent formulation flexibility and coatings obtained therefrom. In addition, the presence of ethylenic unsaturation in the structure of the polyurethane polymer (B) is also believed to prevent (or at least significantly reduce) the presence of free stabilizers (or emulsifiers) after polymerization. In fact, it is known that the presence of these free or mobile stabilizers after curing has an adverse effect on various properties of the resulting coating, especially its (heat) water resistance and hydrolysis resistance, which in turn has a negative impact on its visual appearance, as these free stabilizers migrate unfavorably through the coating to its outer surface.

[0017] Therefore, the aqueous radiation-curable composition of the present invention is very suitable for forming coatings for 3C applications.

[0018] The aqueous radiation-curable composition of the present invention comprises 45 - 80 wt% of at least one (polymerizable) ethylenically unsaturated compound (A) as the first component, based on the total dry content weight of the radiation-curable composition.

[0019] In an advantageous aspect, based on the total dry content weight of the radiation-curable composition, the aqueous radiation-curable composition comprises more than 45 wt%, more than 50 wt%, more than 55 wt%, more than 60 wt%, more than 65 wt%, more than 70 wt%, or even more than 75 wt% of at least one ethylenically unsaturated compound (A).

[0020] In another advantageous aspect of the present invention, based on the total dry content weight of the radiation-curable composition, the aqueous radiation-curable composition comprises 45 - 75 wt%, 45 - 70 wt% or even 50 - 70 wt% of at least one ethylenically unsaturated compound (A).

[0021] The ethylenically unsaturated compound (A) used herein is not particularly limited. Those skilled in the art will readily determine suitable ethylenically unsaturated compounds (A) suitable for use herein according to the present invention.

[0022] Compound (A) used herein contains at least one, usually at least two polymerizable ethylenically unsaturated groups per molecule, also referred to herein as "ethylenically unsaturated functional groups" or "ethylenically unsaturated groups". The "polymerizable ethylenically unsaturated groups" in the present invention refer to carbon-carbon double bonds that can undergo free radical polymerization under the influence of radiation. Examples of such groups are (meth)acryloyl, (meth)acrylamide, vinyl, vinyl ether, allyl, styryl, methylstyryl, maleoyl or fumaroyl functional groups. The ethylenically unsaturated groups used herein are generally selected from (meth)acryloyl and / or allyl, preferably (meth)acryloyl, more preferably acryloyl. In the present invention, the term "(meth)acryloyl" should be understood to cover acryloyl and methacryloyl or derivatives and their mixtures.

[0023] The compound (A) used in the present invention can be monomeric, oligomeric and / or polymeric ethylenically unsaturated compounds. Mixtures of monomeric, oligomeric and / or polymeric ethylenically unsaturated compounds (A) can also be used.

[0024] Generally, the ethylenically unsaturated compound (A) is essentially monomeric or oligomeric. Advantageously, the compound (A) used herein is oligomeric. The weight average molecular weight (Mw) of typical monomeric compound (A) measured by conventional gel permeation chromatography (GPC) techniques is 50 - 300 g / mol, 100 - 250 g / mol, or even 100 - 200 g / mol. The weight average molecular weight (Mw) of typical oligomeric compound (A) measured by conventional gel permeation chromatography (GPC) techniques is 300 - 20,000 daltons, 500 - 15,000 daltons, 500 - 10,000 daltons, or even 800 - 5,000 daltons.

[0025] According to an advantageous aspect, the weight average molecular weight (Mw) of the at least one ethylenically unsaturated compound (A) used herein is not greater than 3000 g / mol, not greater than 2500 g / mol, not greater than 2000 g / mol, not greater than 1500 g / mol, not greater than 1200 g / mol, not greater than 1000 g / mol, not greater than 800 g / mol, not greater than 600 g / mol, not greater than 500 g / mol, not greater than 400 g / mol, not greater than 300 g / mol, or even not greater than 200 g / mol.

[0026] In an advantageous aspect, the ethylenically unsaturated compound (A) used herein is a water-insoluble compound. The "water-insoluble compound" in the present disclosure means that the ethylenically unsaturated compound is not self-emulsifying or self-dispersing, but forms an emulsion or dispersion in water or an aqueous solution in the presence of one or more reactive ionic external emulsifiers (B) as defined above. More specifically, according to this advantageous aspect of the present invention, the compound (A) is a non-self-dispersing, non-self-emulsifying, non-water-dilutable compound. Generally, the ethylenically unsaturated compound (A) of the present invention is not a self-dispersing compound. The "self-dispersing compound" in the present disclosure means that the compound can form a stable two-phase system of small particles dispersed in water without the help of an additional emulsifier when mixed with water. The "self-emulsifying compound" in the present disclosure means that the compound can form a stable two-phase system of small droplets dispersed in water without the help of an additional emulsifier when mixed with water. The "stable" herein means that there is substantially no coalescence (droplets) or flocculation (particles) causing phase separation, emulsification, or precipitation of the heterogeneous system after 2 days or longer, usually 4 days or longer, preferably even 10 days at 60 °C. Generally, the compound (A) used herein is not a water-dilutable compound. The "water-dilutable compound" in the present disclosure means that the compound can form a homogeneous single-phase mixture when mixed with water (where the concentration of water in the total mass of water and the compound is 5 - 75 wt%) in the absence of an emulsifier.

[0027] In a typical aspect, the solubility of the ethylenically unsaturated compound (A) of the present invention at 25 °C is less than 50 g / l, less than 40 g / l, less than 30 g / l, less than 25 g / l, less than 20 g / l, less than 10 g / l, less than 5 g / l, or even less than 1 g / l.

[0028] The ethylenically unsaturated compound (A) is generally characterized in that the amount of copolymerizable ethylenically unsaturated groups is at least 1 meq / g, at least 2 meq / g, at least 3 meq / g, at least 4 meq / g, at least 5 meq / g, at least 6 meq / g, at least 7 meq / g, at least 8 meq / g, or even at least 9 meq / g. Generally, this amount of ethylenically unsaturated groups is not greater than 13 meq / g or even 12 meq / g. The amount of ethylenically unsaturated groups is usually measured by nuclear magnetic resonance spectroscopy (NMR) according to techniques well known in the art and is expressed as milliequivalents per gram of solid material (meq).

[0029] In an exemplary aspect, the ethylenically unsaturated compound (A) used herein contains at least 2, at least 4, at least 6, at least 8, or even at least 10 or more ethylenically unsaturated functional groups per molecule.

[0030] Advantageously, compound (A) combines the functionality and unsaturation as described above. Specifically, the preferred compound (A) used herein is characterized by a functionality of having at least 2, at least 4, at least 6, at least 8, or even at least 10 or more ethylenically unsaturated groups per molecule, and an ethylenically unsaturated group of at least 4 meq / g, at least 6 meq / g, at least 8 meq / g, or even at least 9 meq / g.

[0031] According to an exemplary aspect, the ethylenically unsaturated compound (A) for use in the present invention is a (meth)acrylated compound, particularly selected from urethane (meth)acrylate (A1), polyester (meth)acrylate (A2), polyepoxy (meth)acrylate (A3), polycarbonate (meth)acrylate (A4), polyether (meth)acrylate (A5), and polypropylene (meth)acrylate (A6). The exemplary ethylenically unsaturated compound (A) for use herein is described in detail in US Patent Application US2014 / 0377466A1 (Tielemans et al.), the content of which is incorporated herein by reference in its entirety.

[0032] According to a particular aspect of the present invention, the ethylenically unsaturated compound (A) used herein is selected from urethane (meth)acrylate (A1), polyester (meth)acrylate (A2), epoxy (meth)acrylate (A3), (meth)acrylic (meth)acrylate (A4), and any combination or mixture thereof.

[0033] In a preferred aspect, the ethylenically unsaturated compound (A) is selected from urethane (meth)acrylate (A1). It has surprisingly been found that urethane (meth)acrylate provides excellent adhesion properties on difficult-to-adhere plastic substrates (especially polycarbonate, acrylonitrile butadiene styrene, and any combination thereof) particularly used in 3C applications.

[0034] In another preferred aspect, the ethylenically unsaturated compound (A) is selected from (meth)acrylated compounds that do not contain reactive groups capable of reacting with isocyanate groups, particularly selected from (meth)acrylated compounds containing at least two (meth)acryloyl groups.

[0035] In a particularly preferred aspect, the ethylenically unsaturated compound (A) is selected from ethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, glycerol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and their (poly)ethoxylated and / or (poly)propoxylated equivalents, and any combination or mixture thereof.

[0036] In an alternative aspect, the ethylenically unsaturated compound (A) is selected from (meth)acrylated compounds comprising a reactive group capable of reacting with an isocyanate group, in particular from (meth)acrylated compounds comprising at least two (meth)acryloyl groups and one or more additional functional groups (in particular hydroxyl functional groups). These additional functional groups generally aim to provide additional properties to the aqueous radiation-curable composition.

[0037] In another advantageous aspect of the aqueous radiation-curable composition of the present disclosure, the ethylenically unsaturated compound (A) used herein is at least partially bio-based, and in particular its bio-based content is greater than 10 wt%, greater than 20 wt%, greater than 40 wt%, greater than 60 wt%, or even greater than 80 wt% of the total carbon content of the ethylenically unsaturated compound (A), and the bio-based content is determined according to the ASTM D6866 standard test method. Exemplary bio-based ethylenically unsaturated compounds (A) used herein and methods for obtaining them are also described in detail in PCT application WO2022 / 128462 (Tielemans), the content of which is incorporated herein by reference in its entirety.

[0038] The aqueous radiation-curable composition of the present invention comprises at least one (polymerizable) ethylenically unsaturated polyurethane polymer (B) obtained by the reaction of at least one polyisocyanate compound (i) as a second component. The polyisocyanate compound (i) refers to an organic compound comprising at least two isocyanate groups.

[0039] The polyisocyanate compound (i) used herein is not particularly limited. Those skilled in the art will readily recognize suitable polyisocyanate compounds (i) suitable for use herein according to the present invention. The polyisocyanate compound (i) generally comprises no more than three isocyanate groups. Advantageously, the polyisocyanate compound (i) is a diisocyanate.

[0040] In a typical aspect, the at least one polyisocyanate compound (i) is selected from aliphatic and cycloaliphatic polyisocyanates, especially diisocyanates. Examples of aliphatic and cycloaliphatic polyisocyanates are 1,6 - diisocyanatohexane (HDI), 1,1'-methylenebis[4 - isocyanatocyclohexane] (H12MDI), 5 - isocyanato - 1 - isocyanatomethyl - 1,3,3 - trimethylcyclohexane (isophorone diisocyanate, IPDI). Aliphatic polyisocyanates containing more than two isocyanate groups include, for example, derivatives of the diisocyanates described above, such as 1,6 - diisocyanatohexane biuret and isocyanurate. Examples of aromatic polyisocyanates are 1,4 - diisocyanatobenzene (BDI), 2,4 - diisocyanatotoluene (TDI), 1,1'-methylenebis[4 - isocyanatobenzene] (MDI), xylene diisocyanate (XDI), tetramethylxylene diisocyanate (TMXDI), 1,5 - naphthalene diisocyanate (NDI), o - tolidine diisocyanate (TODI), and p - phenylene diisocyanate (PPDI). Particularly preferred are 1,1'-methylenebis[4 - isocyanatocyclohexane] (H12MDI), isophorone diisocyanate (IPDI), and tetramethylxylene diisocyanate (TMXDI).

[0041] The amount of the polyisocyanate compound (i) used for synthesizing the ethylenically unsaturated polyurethane polymer (B) is generally 5 - 60 wt%, 10 - 50 wt%, 15 - 40 wt%, or even 20 - 30 wt%, based on the total weight of the at least one ethylenically unsaturated polyurethane polymer (B).

[0042] The ethylenically unsaturated polyurethane polymer (B) is obtained by the reaction of at least one additional polymer polyol (ii). In the context of the present invention, the term "polymer polyol" refers to a polymer containing at least two hydroxyl groups and a polymer main chain, where the polymer main chain generally has a weight - average molecular weight (Mw) of at least 500 g / mol.

[0043] The polymer polyol (ii) used herein is not particularly limited. A person skilled in the art can easily determine a suitable polymer polyol (ii) according to the present invention. Advantageously, the polymer polyol (ii) can be selected from high - molecular - weight polyols and low - molecular - weight polyols. Advantageously, the polymer polyol (ii) is selected from high - molecular - weight polyols.

[0044] In a typical aspect, the at least one polymer polyol (ii) has a weight - average molecular weight (Mw) greater than 500 g / mol, greater than 600 g / mol, greater than 700 g / mol, greater than 800 g / mol, greater than 900 g / mol, or even greater than 1000 g / mol.

[0045] Typically, the at least one polymeric polyol (ii) has a weight average molecular weight (Mw) of no greater than 5000 g / mol, no greater than 4000 g / mol, no greater than 3000 g / mol, no greater than 2000 g / mol, no greater than 1500 g / mol, or even no greater than 1000 g / mol.

[0046] According to an exemplary aspect, the at least one polymeric polyol (ii) is selected from polycarbonate polyols, polyester polyols, polyether polyols, fatty dimer diols, polybutadiene polyols, polyacrylate polyols, siloxane polyols, and any combination or mixture thereof.

[0047] Suitable polyacrylate polyols include those prepared by free radical polymerization of (meth)acrylic acid and / or (meth)acrylamide monomers initiated by a thermal free radical initiator in the presence of a hydroxylated thiol and then end-capping transesterification with a short-chain diol (such as 1,4-butanediol).

[0048] Suitable polyether polyols include polyethylene glycol, polypropylene glycol, and polybutylene glycol, or block copolymers thereof. Suitable fatty dimer diols are obtained by hydrogenation of dimer acids (preferably dimer acids containing 36 carbon atoms).

[0049] In an advantageous aspect, the at least one polymeric polyol (ii) is selected from polycarbonate polyols, polyester polyols, and any combination or mixture thereof.

[0050] Suitable polyester polyols are in particular the hydroxyl-terminated reaction products of polyols (preferably diols) with polycarboxylic acids (preferably dicarboxylic acids) or their corresponding acid anhydrides, and those obtained by ring-opening polymerization of lactones. The polycarboxylic acids that can be used to form these polyester polyols can be aliphatic, cycloaliphatic, aromatic, and / or heterocyclic, and they can be substituted, saturated, or unsaturated. The polyols that can be used to prepare polyester polyols include ethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tetraethylene glycol, dibutylene glycol, 2-methyl-1,3-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,4-cyclohexanedimethanol, ethylene oxide adducts or propylene oxide adducts of bisphenol A or hydrogenated bisphenol A. Polyols such as glycerol, trimethylolethane, trimethylolpropane, ditrimethylolethane, ditrimethylolpropane, and pentaerythritol can also be used. Particularly advantageous polyester polyols are those prepared by polycondensation of neopentyl glycol with adipic acid and / or isophthalic acid.

[0051] According to a particularly advantageous aspect of the present invention, the at least one polymeric polyol (ii) is selected from polycarbonate polyols, in particular those obtained by the reaction of diols (such as ethylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol or tetraethylene glycol) with phosgene, dialkyl carbonates (such as dimethyl carbonate), diaryl carbonates (such as diphenyl carbonate) or cyclic carbonates (such as ethylene carbonate and / or propylene carbonate). Particularly advantageous polycarbonate polyols are aliphatic polycarbonate diols, in particular those commercially available from Covestro under the trade name Series.

[0052] It has been found that the use of polycarbonate polyols can provide excellent adhesion properties on difficult-to-adhere plastic substrates (in particular polycarbonate, acrylonitrile-butadiene-styrene, and any combination thereof) especially for 3C applications.

[0053] The amount of the polymeric polyol (ii) used for synthesizing the ethylenically unsaturated polyurethane polymer (B) is generally 2-50 wt%, 3-30 wt%, 5-25 wt% or even 7-25 wt%, based on the total weight of the at least one ethylenically unsaturated polyurethane polymer (B).

[0054] The ethylenically unsaturated polyurethane polymer (B) is obtained by the reaction of at least one additional (non-polymerizable) hydrophilic compound (iii), the hydrophilic compound (iii) comprising at least one reactive group capable of reacting with an isocyanate group, and at least one group capable of directly dispersing the polyurethane polymer (B) in an aqueous medium or dispersing it in an aqueous medium after reaction with a neutralizing agent to provide a salt.

[0055] The hydrophilic compound (iii) used herein is not particularly limited as long as it meets the requirements described above. A person skilled in the art can easily identify suitable hydrophilic compounds (iii) based on the disclosure of the present invention. The hydrophilic compound (iii) is generally a polyol, in particular a diol, containing functional groups that can exhibit ionic or non-ionic hydrophilic properties.

[0056] In an advantageous aspect, the at least one hydrophilic compound (iii) is a non-polymerizable compound (in particular a compound not containing any ethylenically unsaturated groups), in particular selected from polyols containing one or more anionic salt groups (such as carboxylate and sulfonate groups) or acid groups (such as carboxylic acid or sulfonic acid groups) convertible to anionic salt groups.

[0057] In a preferred aspect, the at least one hydrophilic compound (iii) is selected from the general formula (HO) xR(COOH) y The hydroxycarboxylic acids represented, where R represents a straight-chain or branched hydrocarbon residue having 1 to 12 carbon atoms, and x and y are independently integers from 1 to 3. Examples of these hydroxycarboxylic acids include citric acid, malic acid, lactic acid, and tartaric acid. Particularly preferred hydroxycarboxylic acids are α,α-dihydroxymethylalkanoic acids, where in the above general formula x = 2 and y = 1.

[0058] In a more preferred aspect, the at least one hydrophilic compound (iii) is selected from 2,2-dihydroxypropionic acid and 2,2-dihydroxybutyric acid.

[0059] The amount of the hydrophilic compound (iii) used for synthesizing the ethylenically unsaturated polyurethane polymer (B) is generally 1-25 wt%, 2-20 wt%, 3-15 wt% or even 4-10 wt%, based on the total weight of the at least one ethylenically unsaturated polyurethane polymer (B).

[0060] The ethylenically unsaturated polyurethane polymer (B) is obtained by the reaction of at least one additional (polymerizable) compound (iv) which contains at least one (substantially one) reactive group capable of reacting with an isocyanate group and also contains at least one ethylenically unsaturated group.

[0061] The compounds (iv) used herein are not particularly limited as long as they meet the requirements described above. Those skilled in the art can easily identify suitable compounds (iv) based on the disclosure of the present invention.

[0062] Advantageously, the at least one compound (iv) contains substantially one reactive group capable of reacting with an isocyanate group and also contains at least one, particularly at least two, ethylenically unsaturated groups. Generally, the compound (iv) contains at least one nucleophilic functional group capable of reacting with an isocyanate group.

[0063] In a more advantageous aspect, the reactive group of the at least one compound (iv) includes a hydroxyl group, and the ethylenically unsaturated group of the at least one compound (iv) is a (meth)acrylic group. Preferred are (meth)acryloyl monohydroxy compounds, more particularly poly(meth)acryloyl monohydroxy compounds.

[0064] Useful compounds (iv) include the esterification products of aliphatic and / or aromatic polyols with (meth)acrylic acid (residual average hydroxyl functionality of about 1 to 15). Partially esterified products of (meth)acrylic acid with tri-, tetra-, penta- or hexa-hydric polyols or mixtures thereof are preferred. In this case, reaction products of such polyols with ethylene oxide and / or propylene oxide or mixtures thereof, or reaction products of such polyols with lactones, which are added to these polyols by ring-opening reactions, can also be used. Examples of suitable lactones are γ-butyrolactone, and especially δ-valerolactone and ε-caprolactone. These modified or unmodified polyols are generally partially esterified with acrylic acid, methacrylic acid or mixtures thereof until the desired residual hydroxyl functionality is reached. Compounds (iv) obtained by the reaction of (meth)acrylic acid with aliphatic, cycloaliphatic or aromatic compounds having epoxy functional groups and at least one (meth)acrylic acid functional group can also be used. Other suitable compounds are (meth)acrylates of linear or branched polyols in which at least one hydroxyl functionality remains free, such as hydroxyalkyl (meth)acrylates having 1 to 20 carbon atoms in the alkyl group. Preferred molecules in this category are hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate.

[0065] In a preferred aspect, the at least one compound (iv) is selected from the esterification products of aliphatic and / or aromatic polyols with (meth)acrylic acid (residual average hydroxyl functionality of about 1).

[0066] In a more preferred aspect, the at least one compound (iv) is selected from poly(meth)acryloyl monohydroxy compounds, especially selected from glycerol di(meth)acrylate, trimethylolpropane di(meth)acrylate, glycerol di(meth)acrylate, pentaerythritol tri(meth)acrylate, bis-trimethylolpropane tri(meth)acrylate, dipentaerythritol penta(meth)acrylate and their (poly)ethoxylated and / or (poly)propoxylated equivalents, and any combination or mixture thereof. Even more preferably, the at least one compound (iv) is selected from pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, and any combination or mixture thereof.

[0067] The amount of compound (iv) used for the synthesis of the ethylenically unsaturated polyurethane polymer (B) is generally 10 - 60 wt%, 20 - 60 wt%, 15 - 55 wt%, 20 - 55 wt% or even 30 - 50 wt%, based on the total weight of the at least one ethylenically unsaturated polyurethane polymer (B).

[0068] The ethylenically unsaturated polyurethane polymer (B) can be obtained by the reaction of at least one additional optional (non-polymerizable) compound (v) which contains at least one reactive group capable of reacting with an isocyanate group. The compound (v) used herein is not particularly limited and can be readily identified by those skilled in the art according to the present invention.

[0069] In a typical aspect, the at least one compound (v) is a non-polymerizable compound (especially a compound not containing any ethylenically unsaturated groups) which contains at least one reactive group capable of reacting with an isocyanate group.

[0070] Generally, the compound (v) used herein contains at least one nucleophilic functional group capable of reacting with an isocyanate group. More typically, the reactive group capable of reacting with an isocyanate group is capable of reacting with the free (or remaining) isocyanate end groups of the ethylenically unsaturated polyurethane polymer (B), thereby resulting in the chain extension of the polyurethane polymer (B). Therefore, the compound (v) used herein can also be referred to as a chain extender.

[0071] In the context of the present invention, it has surprisingly been found that the chain-extended ethylenically unsaturated polyurethane polymer (B) obtained by using the at least one compound (v) provides enhanced colloidal stability to the waterborne radiation-curable composition, especially relative to those waterborne compositions having a relatively high content of ethylenically unsaturated compound (A) (e.g., typically greater than 55 wt%, greater than 60 wt%, greater than 65 wt%, or even greater than 70 wt% based on the total dry content weight of the radiation-curable composition).

[0072] Without being bound by theory, it is believed that the chain-extended ethylenically unsaturated polyurethane polymer (B) and the relatively high content of ethylenically unsaturated compound (A) present in the waterborne radiation-curable composition ensure excellent compatibility, thereby promoting an improvement in colloidal stability, which in turn improves the aging stability of the resulting composition.

[0073] It is also believed that the chain-extended ethylenically unsaturated polyurethane polymer (B) advantageously affects the abrasion resistance of the coatings obtained from the corresponding waterborne radiation-curable compositions.

[0074] In an advantageous aspect, the at least one compound (v) is selected from the group of compounds containing active amino groups. More advantageously, the at least one compound (v) used herein is selected from (water-soluble) aliphatic, alicyclic, aromatic or heterocyclic primary or secondary polyamines or hydrazines having at most 60, especially at most 12 carbon atoms.

[0075] In a more advantageous aspect, the at least one compound (v) is selected from m-xylylenediamine, ethylenediamine, diethylenetriamine, piperazine, 1,4-butanediamine, 1,6-hexanediamine, 1,8-octanediamine, 1,10-decanediamine, 1,12-dodecanediamine, 2-methylpentanediamine, triethylenetriamine, isophoronediamine (or 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane), bis(4-aminocyclohexyl)methane, bis(4-amino-3-methylcyclohexyl)methane, polyvinylamine, polyoxyethyleneamine and polyoxypropyleneamine, hydrazine, and any combination or mixture thereof.

[0076] In an even more advantageous aspect, the at least one compound (v) is selected from m-xylylenediamine, ethylenediamine, diethylenetriamine, and any combination or mixture thereof.

[0077] In a particularly advantageous aspect of the present invention, the at least one compound (v) is selected as m-xylylenediamine. In the context of the present invention, it has indeed been surprisingly found that the ethylenically unsaturated polyurethane polymer (B) chain-extended with m-xylylenediamine advantageously affects the abrasion resistance and non-yellowing properties of the coatings obtained from the corresponding waterborne radiation-curable compositions.

[0078] When used for the synthesis of the ethylenically unsaturated polyurethane polymer (B), the amount of the compound (v) is generally 0-5 wt%, 0.1-5 wt%, 0.2-3 wt%, 0.5-3 wt%, 0.5-2 wt%, 1-2 wt%, or even 1-1.5 wt%, based on the total weight of the at least one ethylenically unsaturated polyurethane polymer (B).

[0079] The ethylenically unsaturated polyurethane polymer (B) can be obtained by the reaction of at least one additional optional (polymerizable) ethylenically unsaturated polyurethane polymer (B), the additional ethylenically unsaturated polyurethane polymer (B) being obtained by the reaction of at least one additional compound (vi), the compound (vi) containing at least two reactive groups capable of reacting with isocyanate groups and further containing at least two ethylenically unsaturated groups, wherein the compounds (A), (i), (ii), (iii), (iv), (v) and (vi) are all different from each other. The compound (vi) used herein is not particularly limited and can be easily recognized by those skilled in the art according to the present invention.

[0080] Generally, the optional compound (vi) used herein contains at least two nucleophilic functional groups capable of reacting with isocyanate groups and further contains at least two ethylenically unsaturated groups. Advantageously, the at least one compound (vi) contains a hydroxyl group, and the ethylenically unsaturated group is a (meth)acrylic group.

[0081] More preferably, at least one compound (vi) is selected from the reaction products of aliphatic and aromatic diglycidyl compounds with (meth)acrylic acid. Aliphatic diglycidyl compounds derived from α,ω-diols or polyoxyalkylene diols having 4 to 12 carbon atoms (especially polyethylene glycols, polypropylene glycols, or mixtures thereof containing oxyalkylene groups) can be used. Preferred are, for example, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, hydrogenated bisphenol A diglycidyl ether and hydrogenated bisphenol F diglycidyl ether, and their ethoxylated and / or propoxylated equivalents. Diglycidyl esters, such as diglycidyl hexahydrophthalate, can also be used. Aromatic diglycidyl compounds derived from bisphenol A and bisphenol F are advantageous.

[0082] In a particularly advantageous aspect, the at least one compound (vi) is selected from the diacrylates of bisphenol A diglycidyl ether and bisphenol F diglycidyl ether, and their ethoxylated and / or propoxylated equivalents, and any combination or mixture thereof. Diglycidyl esters, such as diglycidyl phthalate, N,N-diglycidylaniline, N,N-diglycidyl-4-glycidyloxyaniline, can also be used. Particularly preferred is the diacrylate of bisphenol A diglycidyl ether.

[0083] When used for the synthesis of the ethylenically unsaturated polyurethane polymer (B), the amount of the compound (vi) is generally 0 - 30 wt%, 0.5 - 30 wt%, 1 - 20 wt%, 2 - 15 wt%, or even 3 - 10 wt%, based on the total weight of the at least one ethylenically unsaturated polyurethane polymer (B).

[0084] According to an advantageous aspect, the aqueous radiation-curable composition of the present invention comprises 25 - 55 wt%, 30 - 55 wt%, or even 30 - 50 wt% of at least one ethylenically unsaturated polyurethane polymer (B), based on the total dry content weight of the radiation-curable composition.

[0085] According to a specific aspect, at least one ethylenically unsaturated polyurethane polymer (B) used herein is obtained by the reaction of: i. 5 - 60 wt%, 10 - 50 wt%, 15 - 40 wt%, or even 20 - 30 wt% of at least one polyisocyanate compound (i); ii. 2 - 50 wt%, 3 - 30 wt%, 5 - 25 wt% or even 7 - 25 wt% of at least one polymeric polyol (ii); iii. At least one hydrophilic compound (iii) in an amount of 1-25 wt%, 2-20 wt%, 3-15 wt% or even 4-10 wt%, said hydrophilic compound (iii) comprising at least one reactive group capable of reacting with an isocyanate group and at least one group capable of directly dispersing the polyurethane polymer (B) in an aqueous medium or, after reaction with a neutralizing agent to provide a salt, dispersing it in an aqueous medium; iv. At least one compound (iv) in an amount of 10-60 wt%, 20-60 wt%, 15-55 wt%, 20-55 wt% or even 30-50 wt%, said compound (iv) comprising at least one (substantially one) reactive group capable of reacting with an isocyanate group and further comprising at least one ethylenically unsaturated group; v. Optionally, at least one (non-polymerizable) compound (v) in an amount of 0-5 wt%, 0.1-5 wt%, 0.2-3 wt%, 0.5-3 wt%, 0.5-2 wt%, 1-2 wt% or even 1-1.5 wt%, said compound (v) comprising at least one (substantially one) reactive group capable of reacting with an isocyanate group; and vi. Optionally, at least one compound (vi) in an amount of 0-30 wt%, 0.5-30 wt%, 1-20 wt%, 2-15 wt% or even 3-10 wt%, said compound (vi) comprising at least two reactive groups capable of reacting with an isocyanate group and further comprising at least two ethylenically unsaturated groups; wherein compounds (i), (ii), (iii), (iv), (v) and (vi) are different from each other, and wherein wt% is based on the total weight of said at least one ethylenically unsaturated polyurethane polymer (B).

[0086] In a typical aspect, the ethylenically unsaturated polyurethane polymer (B) is a (meth)acrylated polyurethane polymer (B), wherein the ethylenically unsaturated functional group is a (meth)acrylic group.

[0087] In another typical aspect, the ethylenically unsaturated polyurethane polymer (B) comprises less than 0.20 meq / g, less than 0.15 meq / g, less than 0.10 meq / g, less than 0.05 meq / g or even less than 0.01 meq / g of allophanate groups.

[0088] According to a typical aspect, the ethylenically unsaturated polyurethane polymer (B) has a weight average molecular weight (Mw) of greater than 3000 g / mol, greater than 5000 g / mol, greater than 8000 g / mol, greater than 10,000 g / mol or even greater than 15,000 g / mol.

[0089] Typically still, the weight-average molecular weight (Mw) of the ethylenically unsaturated polyurethane polymer (B) is 2500 - 25,000 g / mol, 3000 - 20,000 g / mol, 5000 - 20,000 g / mol, 8000 - 20,000 g / mol, 8000 - 15,000 g / mol, or even 10,000 - 15,000 g / mol.

[0090] According to a particular aspect in which the ethylenically unsaturated polyurethane polymer (B) is chain-extended, in particular by reaction with at least one compound (iv) comprising at least one reactive group capable of reacting with an isocyanate group and further comprising at least one ethylenically unsaturated group, the resulting ethylenically unsaturated polyurethane polymer (B) has a weight-average molecular weight (Mw) greater than 20,000 g / mol, greater than 30,000 g / mol, greater than 50,000 g / mol, greater than 80,000 g / mol, greater than 100,000 g / mol, greater than 120,000 g / mol, greater than 150,000 g / mol, greater than 180,000 g / mol or even greater than 200,000 g / mol.

[0091] More specifically, the at least one ethylenically unsaturated (chain-extended) polyurethane polymer (B) has a weight-average molecular weight (Mw) of 25,000 - 300,000 g / mol, 30,000 - 280,000 g / mol, 50,000 - 250,000 g / mol, 50,000 - 230,000 g / mol, 80,000 - 230,000 g / mol, 100,000 - 200,000 g / mol, or even 150,000 - 200,000 g / mol.

[0092] In an advantageous aspect, when determined by DLS measurement according to the test method described in the experimental section, the waterborne radiation-curable composition of the present invention has a particle (droplet) size (particle diameter) not greater than 400 nm, not greater than 350 nm, not greater than 300 nm, not greater than 250 nm, not greater than 200 nm, not greater than 150 nm, or even not greater than 100 nm.

[0093] In another advantageous aspect, when determined by DLS measurement according to the test method described in the experimental section, the waterborne radiation-curable composition has a particle (droplet) size of 80 - 350 nm, 80 - 300 nm, 80 - 250 nm, 85 - 200 nm, 85 - 150 nm or even 90 - 120 nm.

[0094] In yet another advantageous aspect, when determined by the gravimetric method according to the test methods described in the experimental section, the aqueous radiation-curable composition has a solids content of 20 - 50 wt%, 30 - 50 wt%, 30 - 40 wt% or even 35 - 40 wt%.

[0095] According to another advantageous aspect, when determined according to the test methods described in the experimental section, the aqueous radiation-curable composition described herein has a viscosity of no greater than 500 mPa·s, no greater than 400 mPa·s, no greater than 300 mPa·s, no greater than 200 mPa·s, no greater than 150 mPa·s, no greater than 100 mPa·s, or even no greater than 50 mPa·s.

[0096] According to a more advantageous aspect, when determined according to the test methods described in the experimental section, the aqueous radiation-curable composition has a viscosity of 10 - 500 mPa·s, 20 - 400 mPa·s, 50 - 300 mPa·s, 50 - 250 mPa·s, 50 - 200 mPa·s, 50 - 150 mPa·s or even 50 - 100 mPa·s.

[0097] The aqueous radiation-curable composition of the present invention has advantageous properties, particularly a relatively small particle size and a relatively low viscosity, which not only have a favorable impact on its overall stability but also contribute to providing the corresponding coatings and articles with the excellent properties and performance attributes as described above.

[0098] Advantageously, the aqueous radiation-curable composition described herein can be at least partially bio-based, and in particular has a bio-carbon content of greater than 5 wt%, greater than 10 wt%, greater than 15 wt%, or even greater than 20 wt% based on the total carbon content of the composition, with the bio-based content determined according to the ASTM D6866 standard test method.

[0099] In accordance with the practice in the art, the aqueous radiation-curable composition of the present invention may also contain various additional components, depending specifically on the target application and performance of the composition. In a typical aspect, the aqueous radiation-curable composition further contains at least one additive selected from the following: photoinitiators, inhibitors, antioxidants, biocides, UV stabilizers, UV absorbers, nanoparticles, dispersants, slip aids, fillers, plasticizers, flow additives, defoaming additives, rheology modifiers, anti-settling agents, wetting agents, defoamers, flame retardants, leveling agents, slip agents, water removers, matting agents, waxes, pigments, dyes, co-solvents, resin materials dispersed or dissolved in the composition, and any combination or mixture thereof.

[0100] In an advantageous aspect, the aqueous radiation-curable composition may further comprise one or more external thermal crosslinking agents that allow dual curing (radiation and heat). Examples of suitable crosslinking agents are (blocked) polyisocyanates, polyaziridines, polycarbodiimides, polyepoxides, polyalkoxysilanes, and metal salts such as ammonium zirconium carbonate. Particularly suitable are polyisocyanates, especially hydrophilic polyisocyanates commercially available from Covestro AG under the trade name BAYHYDUR.

[0101] The aqueous radiation-curable composition of the present invention can be prepared in various ways according to techniques well known to those skilled in the art. In a typical procedure, the composition is prepared as follows: Compounds (i), (ii), (iii), optionally compound (vi), and possibly other ingredients are stirred and mixed in a suitable solvent at a temperature of 20 - 80 °C and reacted until a suitable isocyanate content is reached. The resulting reaction product is then further reacted with compound (iv) to obtain an ethylenically unsaturated polyurethane polymer (B). The resulting polymer (B) can be chain-extended according to conventional procedures, especially using optionally compound (v).

[0102] The aqueous radiation-curable composition disclosed herein generally contains 25 - 95 wt%, more typically 35 - 60 wt%, of water based on the total weight of the composition. The compositions of the present invention generally contain less than 25 wt%, less than 20 wt%, less than 15 wt%, less than 10 wt%, less than 5 wt%, or even less than 1 wt% of organic solvents and volatile organic compounds (VOCs) based on the total weight of the composition. Advantageously, the aqueous radiation-curable composition of the present invention does not contain organic solvents and volatile organic compounds.

[0103] According to another aspect, the present invention relates to a coating composition comprising the aqueous radiation-curable composition as described above. The aqueous radiation-curable composition disclosed herein is indeed particularly suitable for the preparation of coatings. All specific and preferred aspects, especially those relating to the ethylenically unsaturated compound (A) and the ethylenically unsaturated polyurethane polymer (B) and the content described above in the context of the aqueous radiation-curable composition, apply fully to the coating composition.

[0104] Advantageously, the coatings obtained from the aqueous radiation-curable composition have excellent properties and performance attributes, including adhesion to difficult-to-adhere plastic substrates (especially polycarbonate and acrylonitrile-butadiene-styrene), hot water resistance, hydrolysis resistance, visual aesthetic even in complex formulations (such as metallic or matte formulations), abrasion resistance, stain resistance, and low VOC characteristics.

[0105] In an advantageous aspect, the coating composition is a hard coating composition. Thus, the waterborne radiation-curable composition of the present invention is very suitable for forming coatings for 3C applications, which is of particular interest in the context of the present invention. The product applications in this industrial field are truly endless and are generally associated with consumer electronics (such as mobile phones, computers, televisions, optical discs), automotive interior plastics (such as dashboards, decorative strips) or exterior applications (such as headlights, mirrors, bumpers, wheel covers), and industrial plastics (such as films, labels, boxes, toys, sports equipment, garden furniture).

[0106] The waterborne radiation-curable composition of the present invention is also suitable for overprint varnishes, inks, adhesives, and for coating three-dimensional articles.

[0107] Thus, according to another aspect, the present invention relates to inks (such as inkjet), overprint varnishes, adhesives, or three-dimensional articles comprising the waterborne radiation-curable composition or coating composition as described above.

[0108] Another aspect of the present disclosure relates to articles or substrates at least partially coated, printed, or treated with the waterborne radiation-curable composition, coating composition, ink, overprint varnish, or adhesive as described above.

[0109] In still another aspect of the present invention, a method for preparing a waterborne radiation-curable composition is provided, which comprises the following steps: a) Mixing and reacting the compounds (i), (ii), (iii) as described above and optionally the compound (vi); b) Reacting the product of step a) with the compound (iv) as described above to obtain an ethylenically unsaturated polyurethane polymer (B); c) Adding at least one ethylenically unsaturated compound (A) as described above; d) Optionally, reacting the compound (iii) with a neutralizing agent to convert the hydrophilic group provided by the compound (iii) into an anionic salt; e) Dispersing the ethylenically unsaturated polyurethane polymer (B) obtained in step b) or optionally step d) in an aqueous medium; and f) Optionally, reacting the ethylenically unsaturated polyurethane polymer (B) obtained in step e) with the compound (v) as described above.

[0110] If the compound (v) is used as a chain extender, it is generally added after the optional neutralization step of the hydrophilic group provided by the compound (iii) and after the dispersion of the ethylenically unsaturated polyurethane polymer (B). The chain extension of the ethylenically unsaturated polyurethane polymer (B) is carried out according to conventional methods well known to those skilled in the art.

[0111] According to another aspect, the present invention relates to a method for coating an object or a substrate, which comprises the following steps: a) providing an aqueous radiation-curable composition or a coating composition as described above, b) applying the composition to at least a part of the surface of the object or the substrate, and c) curing the composition by subjecting the coated surface to actinic radiation and / or thermal energy.

[0112] Generally, the curing step is preceded by a step of evaporating water. Generally, at least 98% of the water, preferably at least 99% of the water, preferably all of the water is evaporated. The actinic energy rays for curing are preferably ultraviolet rays, electron beams, X-rays, radioactive rays or high-frequency waves. From the economic point of view, ultraviolet rays with a wavelength of 180 - 400 nm are particularly preferred. Thermal curing can be carried out after radiation curing in the presence of a suitable external (thermal) crosslinking agent, or thermal curing can be used instead of radiation curing.

[0113] In a specific aspect of the present invention, the article or the substrate comprises plastic, more specifically, it is made of plastic.

[0114] The aqueous radiation-curable composition or the coating composition as described above is generally cured by ultraviolet irradiation, usually in the presence of a photoinitiator. Alternatively, they can also be cured by electron beam radiation, thus allowing the use of compositions without a photoinitiator. The compositions of the present invention provide extremely rapid curing, with higher reactivity, thus allowing higher line speeds or less radiation energy for curing and increased productivity. Low-energy ultraviolet light sources (LED lamps) can also be used.

[0115] According to another aspect, the present invention relates to the use of the aqueous radiation-curable composition or the coating composition as described above in computer, communication and consumer electronics applications, dual-curing applications or thick coloring systems. Examples

[0116] The following further illustrates the present disclosure by way of examples. These examples are for illustrative purposes only and are not intended to limit the scope of the appended claims.

[0117] Throughout the present disclosure and the examples section, the following test and measurement methods are used to characterize the exemplary aqueous radiation-curable compositions and the coatings obtained therefrom. Test methods A) Particle size

[0118] The hydrodynamic size of the particles in various aqueous compositions was characterized using dynamic light scattering (DLS) measurements. Before performing the DLS measurements, the concentrated composition was diluted with deionized distilled water to obtain a particle concentration of 0.05 w / w%. The diluted composition was then filtered. Subsequently, DLS measurements were performed at 23 °C using a Delsa Nano-c particle analyzer from Beckman-Coulter. The wavelength of the incident monochromatic light used in the DLS measurements was λ = 658 nm. The scattered light was detected at an angle of 165° in the near-backscattering geometry. The z-average particle size and the polydispersity index were determined by second cumulant analysis of the electric field autocorrelation function. Then, the single-particle diffusion coefficient was estimated based on the average decay constant. Thereby, the median particle size d50 was derived using the Stokes relationship. B) Solids content

[0119] The solids content (SC) of various aqueous compositions was determined by the gravimetric method, which included drying at 120 °C for 2 hours. C) Viscosity

[0120] The viscosity of various aqueous compositions was determined at 23 °C using a cone-plate rheometer MCR092 (Paar-Physica) according to the test method DIN EN ISO 3219. A fixed shear rate of 25 s -1 . D) Colloidal stability

[0121] The colloidal stability of various aqueous compositions was evaluated at 23 °C by visual observation of sedimentation and / or phase separation (expressed as a percentage of the total height) on a 20 g sample placed in an oven at 60 °C. The colloidal stability is reported here as the number of days before sedimentation exceeds 2% of the total height of the sample. In the context of the present disclosure, good colloidal stability was obtained if no product deterioration was observed for at least 10 days at 60 °C. E) Molecular weight and polydispersity

[0122] The number average molecular weight (Mn), weight average molecular weight (Mw) and polydispersity (D) were determined by conventional gel permeation chromatography (GPC) using polystyrene standards EasyCal from Polymer Laboratories (molecular weight range: 200-400,000 g / mol). The samples were dissolved (1.0% wt / wt) in tetrahydrofuran (THF) containing 0.5% toluene as a flow rate marker. The analysis was performed using liquid chromatography (Merck-Hitachi L7100) equipped with 3 PLGel Mixed-D LS polystyrene-divinylbenzene GPC columns (300×7.5 mm×5 μm). The components of the sample were separated by the GPC columns according to their molecular size in solution and detected by a refractive index detector. The data were collected and processed by Polymer Laboratories Cirrus GPC software. F) Glossiness

[0123] In formation at Leneta TM The gloss evaluation is carried out on coatings on pure white cards. The gloss values ​​are expressed in gloss units [GU] at an angle of 60° and are determined according to the test method DIN EN ISO 2813. G) Adhesion

[0124] The adhesion properties of the coating to the corresponding substrate surface (initial adhesion ADH) were evaluated using the cross-hatch test according to test method ASTM D3359B. In each case, five parallel cuts with a length of 1 cm and a spacing of 1 mm were first made in the coating with a knife. Then, five parallel cuts with a length of 1 cm and a spacing of 1 mm were made in the transverse direction. Subsequently, the tape was placed Press firmly on the cross-cut coating and quickly peel it off. Damage to the cross-cut surface area of ​​the coating due to loss of adhesion is indicated on a scale of 0B-5B, with 5 points corresponding to the best adhesion. H) Hot water resistance

[0125] Hot water resistance testing was performed only on those coatings that showed excellent initial adhesion (ADH test = 5B). The coatings were immersed in hot water (temperature of 80 or 85°C) for 30 or 60 minutes. The cross-hatch tape adhesion performance on the dried coatings was re-evaluated according to the previous procedure. The hot water resistance test was passed when a score of at least 4B was obtained. I) Hydrolysis resistance

[0126] The hydrolysis resistance test is carried out only for those coatings that exhibit excellent initial adhesion (ADH test = 5B) and in accordance with the industrial test standard VW TL 226 (Volkswagen). The coated substrate is placed in a humidity chamber at 60 °C and 95% relative humidity for 96 hours. Then, after the humidity test, the coating of the coated substrate is evaluated for visual damage, gloss, and cross-hatch adhesion. If the coating shows no visual damage and reaches the same level of gloss and adhesion before and after the test, the hydrolysis resistance test is considered passed. J) Scratch resistance

[0127] The scratch resistance is determined using an abrasion-resistant coating (RCA) abrasion tester - Norman tool tester according to the test method ASTM F-2357. The RCA test is carried out using standard paper as the scratching material. Abrasion is performed by pressing the standard paper against the coated polycarbonate substrate with a specific load (175 g). The paper is brought into contact with the rubber ring on the back. The result is expressed as the number of cycles required before the coated substrate starts to visually show damage, haze, or white areas. The higher the number of cycles, the better the abrasion resistance. K) Stain resistance

[0128] The stain resistance of the coating is evaluated as follows: A 50 µm wet layer is applied on a non-porous substrate (white opaque sheet, Leneta) using a Meyer rod, then dried at 50 °C for 6 minutes and UV-cured under a 80 W / cm mercury lamp at a conveyor speed of 5 m / min. Twenty-four hours after the coating is cured, the stain resistance is evaluated by applying a glass microfiber filter paper saturated with the test substance on the coating, or using a black alcohol marker Artline N70 and placing it in contact with the coating for 16 hours. The test substances used are mustard, coffee, eosin, povidone iodine, methylene blue, and ammonia water (10% aqueous solution). Then, the stain is washed off by wiping several times with a paper towel saturated with water or isopropyl alcohol. The remaining stain is visually evaluated using a 1-5 scale, where 5 = no residual stain. The average stain resistance score is shown below. A high expected stain resistance (at least 4 points) can provide the best coating protection against contamination by any household product. Raw materials

[0129] The following raw materials and starting products are used in the examples. H12MDI is 4,4'-methylenebis(cyclohexyl isocyanate) and is commercially available from Covestro. IPDI is isophorone diisocyanate and is commercially available from Evonik. C 2102 is a polycarbonate diol with a molecular weight of 1000 g / mol and is commercially available from Covestro. Hereinafter referred to as PC-1000 for short. DMPA is dimethylolpropionic acid and is commercially available from Geo Specialty Chemicals, Inc. DPHA is a mixture of dipentaerythritol pentaacrylate and hexaacrylate, with an IOH of 45 - 75, and is commercially available from Allnex Germany GmbH. PETIA is pentaerythritol triacrylate and is commercially available from Allnex Germany GmbH. IRR 1094 is a hexa - functional aliphatic urethane acrylate oligomer, obtained from Allnex Germany GmbH. 140 is a bis - trimethylolpropane tetraacrylate and is commercially available from Allnex Germany GmbH. Hereinafter it is simply referred to as E - 140. TMPTA is trimethylolpropane triacrylate and is commercially available from Allnex Germany GmbH. HDDA is 1,6 - hexanediol diacrylate and is commercially available from Allnex Germany GmbH. EOEOEA is ethoxyethoxyethyl acrylate and is commercially available from Rahn USA Corp. under the trade name Miramer M170. MXDA is m - xylylenediamine and is commercially available from Huntsman. 600 is an acrylic adduct of bisphenol A diglycidyl ether and is commercially available from Allnex GmbH. Hereinafter it is simply referred to as E - 600. HDMAP (also known as photoinitiator 1173) is a photoinitiator and is commercially available from Allnex GmbH, Germany. Hereinafter it is simply referred to as A - HDMAP. 349 is a polyether - modified silicone defoamer and is commercially available from BYK. Valikat Bi 2010 is a carboxylic acid bismuth - based PU catalyst and is commercially available from Umicore. Hereinafter it is simply referred to as VB - 2010. BHT is butylated hydroxytoluene and is commercially available from Brenntag. TEA is triethylamine and is commercially available from BASF. PUR40 is a non - ionic polyurethane butyl tri - glycol / water associative thickener and is commercially available from Münzing. Hereinafter it is simply referred to as T - PUR40. PUR65 is a nonionic polyurethane butyltriglycol / water associative thickener, commercially available from Münzing. Hereinafter referred to as T-PUR80. XL 250 is an anionic wetting and dispersing agent phosphine, commercially available from Allnex Germany GmbH. Hereinafter referred to as A-XL250. Omnirad 500 is a photoinitiator, commercially available from IGM Resins. Hereinafter referred to as OMN-500. TPO is a phosphine oxide-based photoinitiator, commercially available from Allnex GmbH, Germany. Hereinafter referred to as A-TPO. NIPSIL E1011 is a matting agent, commercially available from Tosoh, Japan. Hereinafter referred to as N-E1011. SBC AQJ6911 is an aluminum paste, commercially available from Changzhou Yale, China. Butyl cellosolve (BCS) is commercially available from Dow Chemicals. Propylene glycol monomethyl ether (PGME) is commercially available from Dow Chemicals. N,N-Dimethylethanolamine (DMEA) is commercially available from BASF. Example 1: General preparation of exemplary waterborne radiation-curable compositions (Ex. 1 to Ex. 8) and comparative example (Ex. C1).

[0130] In a double-walled glass reactor equipped with a mechanical stirrer, thermocouple, steam condenser, and dropping funnel, add the polymeric polyol (ii), optional compound (vi), hydrophilic compound (iii), polyisocyanate compound (i), acetone, and catalyst (VB-2010 or DBTL). Heat the reaction mixture with stirring at 60 °C and maintain reflux until an appropriate isocyanate content is reached. Then, add compound (iv) to the reactor and maintain the reaction mixture under reflux until the isocyanate content reaches an appropriate value. Then, add the ethylenically unsaturated compound (A) to the reaction mixture and stir until a homogeneous mixture is obtained. Cool the mixture further to 45 °C and add triethylamine with stirring. Then, slowly add the resulting mixture to water at room temperature under high-shear stirring until a stable aqueous composition is obtained. For the waterborne radiation-curable compositions of Examples Ex. 1 to Ex. 7 and comparative example Ex. C1 that include a chain extension step, compound (v) is added rapidly after this stabilization step. Remove acetone under vacuum at a temperature of 50 °C until its content is determined by gas chromatography to be less than 0.15 wt%. Table 1: Formulations of exemplary waterborne radiation-curable compositions (Ex. 1 to Ex. 8) and comparative example (Ex. C1). Components (g) Ex.1 Ex.2 Ex.3 Ex.4 Ex.5 Ex.6 Ex.7 Ex.8 Ex.C1 IPDI 60.2 60.2 40.1 60.2 43.4 43.4 28.4 - - H12MDI - - - - - - - 50.7 130.2 E-600 13.3 13.3 8.8 13.3 8.4 8.4 - 9.5 24.3 PC-1000 27.4 27.4 18.3 27.4 17.4 17.4 24.3 19.6 50.2 DMPA 16.7 16.7 11.2 16.7 12.7 12.7 8.1 11.9 30.6 VB-2010 0.40 0.40 0.26 0.40 0.26 0.26 0.18 0.30 0.78 DPHA 126.8 126.8 84.5 126.8 80.3 80.3 57.6 90.5 232.3 PETIA - - - - - - - 63.8 163.6 BHT 0.17 0.17 0.11 0.17 0.11 0.11 0.08 0.34 0.32 IRR 1094 249.3 373.9 387.8 270.2 392.9 - 261.9 - - E-140 - - - - - 115.5 - 230.6 31.6 TMPTA - - - - - 277.4 - - 75.7 HDDA - - - 38.6 - - - - - EOEOEA - - - 11.7 - - - - - TEA 12.8 12.8 8.5 12.8 9.9 9.9 5.8 8.4 23.11 Acetone 55.1 55.1 36.7 55.1 37.4 37.4 25.1 53.5 137.1 Water 926 1157 1029 1157 1046 1046 697 856 1372 MXDA 2.12 2.12 1.04 2.12 2.06 1.77 1.09 - - Example 2: Properties and stability performance of exemplary waterborne radiation-curable compositions (Ex. 1 to Ex. 8).

[0131] The properties and stability performance of the exemplary waterborne radiation-curable compositions (Ex. 1 to Ex. 8) have been determined according to the test methods described above. The exemplary compositions of Ex. 1 to Ex. 7 all contain an extended ethylenically unsaturated polyurethane polymer (B), while the exemplary composition of Ex. 8 contains an unextended ethylenically unsaturated polyurethane polymer (B). The results are shown in Table 2 below. Table 2: Properties and stability performance of exemplary waterborne radiation-curable compositions (Ex. 1 to Ex. 8). Ex.1 Ex.2 Ex.3 Ex.4 Ex.5 Ex.6 Ex.7 Ex.8 <![CDATA[Content of compound (A) [1] > 50.4 60.4 70.4 56.7 70.7 70.7 68.8 48.3 Particle size (nm) 98 124 213 108 197 186 223 215 Solid content (wt%) 35.3 35.7 35.3 35.1 35.4 35.7 35.4 35.2 Colloid stability at 60°C ＞10D ＞10D ＞10D ＞10D ＞10D ＞10D ＞10D ＞10D [1] The values shown correspond to wt% based on the total dry content weight of the radiation-curable composition.

[0132] As can be seen from the results shown in Table 2, the waterborne radiation-curable compositions (Ex. 1 to Ex. 8) of the present invention have excellent colloidal stability and favorable properties, particularly relatively small particle size and relatively high solids content, even under severe aging conditions. Example 3: General preparation of exemplary transparent coating compositions (EX. 9 to EX. 16) and comparative transparent coating compositions (EX. C2).

[0133] The exemplary transparent coating compositions of EX. 9 to EX. 16 and the comparative transparent coating of EX. C2 were further prepared based on the formulations described in Table 3 below. The comparative transparent coating according to EX. C2 was prepared based on the formulation of comparative example EX. C1, which contains 14.5 wt% of compound (A), based on the total dry content weight of the composition of EX. C1. Table 3: Formulations of exemplary transparent coating compositions (EX. 9 to EX. 16) and comparative transparent coating compositions (EX. C2). Components (g) Ex.9 Ex.10 Ex.11 Ex.12 Ex.13 Ex.14 Ex.15 Ex.16 Ex.C2 Composition # Ex.1 Ex.2 Ex.3 Ex.4 Ex.5 Ex.6 Ex.7 Ex.8 Ex.C1 BYK 349 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 A-HDMAP 2 2 2 2 2 2 2 2 2 T-PUR40 1 1 1 1 1 1 1 1 1

[0134] The transparent coating formulation was applied to a polycarbonate substrate using a drawdown coater to obtain a wet coating of 50 μm. The applied formulation was dried at 50 °C for 6 minutes and then cured under UV light using an 80 W / cm 2 Hg lamp at a curing speed of 5 m / min. The cured coating was then used for further testing. Example 4: General Preparation of Exemplary Metal Coating Compositions (EX.17 to EX.19)

[0135] Further prepare the exemplary metal coating compositions of EX.17 to EX.19 according to the formulations described in Table 4 below. Table 4: Formulations of Exemplary Metal Coating Compositions (EX.17 to EX.19) Components (g) Ex.17 Ex.18 Ex.19 Composition # Ex.1 Ex.2 Ex.4 N-E1011 0.5 0.5 0.5 SBC AQJ911 6 6 6 BCS 6 6 6 PGME 3 3 3 A-XL250 0.25 0.25 0.25 T-PUR80 2 2 2 TPO 1.8 1.8 1.8 OMN-500 1.5 1.5 1.5 DMEA 10% 5 5 5 Water 10 10 10

[0136] Apply the metal coating formulation to a plastic substrate (PC or ABS) using a spraying machine. Dry the applied formulation at 60 °C for 10 minutes to obtain a dry film thickness (DFT) of approximately 10 µm. Subsequently, cure the coating under UV light using an 80 W / cm 2 Hg lamp at a curing speed of 5 m / min. Then use the cured coating for further testing. Example 5: Stain Resistance of Exemplary Transparent Coatings (EX.9 to EX.13)

[0137] Determine the stain resistance of the exemplary transparent coatings (EX.9 to EX.13) according to the test method described above. The results are shown in Table 5 below. Table 5: Stain Resistance of Exemplary Transparent Coatings (EX.9 to EX.13). Ex.9 Ex.10 Ex.11 Ex.12 Ex.13 Stain resistance (average) 4.2 4.3 4.2 4.3 4.4

[0138] As can be seen from the results shown in Table 5, the transparent coatings (EX.19 to EX.13) of the present invention have excellent stain resistance to various types of contaminants. Example 6: Adhesion and Hot Water Resistance Properties of Exemplary Transparent Coatings (EX.11 to EX.16) and Comparative Transparent Coatings (EX.C2).

[0139] Determine the adhesion of the exemplary transparent coatings (EX.11 to EX.16) and the comparative transparent coating (EX.C2) to a polycarbonate substrate and their hot water resistance properties according to the test method described above. The results are shown in Table 6 below. Table 6: Adhesion and Hot Water Resistance Properties of Exemplary Transparent Coatings (EX.11 to EX.16) and Comparative Transparent Coatings (EX.C2). Ex.11 Ex.12 Ex.13 Ex.14 Ex.15 Ex.16 Ex.C2 Adhesion / PC 5B 5B 5B 5B 5B 5B 5B Hot water resistance (80°C, 60 min) 5B 5B 5B 5B 5B 5B 0B

[0140] As can be seen from the results shown in Table 6, even under severe conditions, the transparent coatings according to the present invention (EX.11 to EX.16) have excellent performance attributes in terms of adhesion to polycarbonate substrates and hot water resistance. In contrast, it can be seen that the performance and characteristics obtained using the comparative transparent coating (Ex.C2) not according to the present invention are less favorable. In particular, the comparative transparent coatings generally have defects in hot water resistance. Example 7: Hydrolysis resistance performance of exemplary transparent coatings (Ex.14 and Ex.16) and comparative transparent coating (Ex.C2)

[0141] The adhesion of the exemplary transparent coatings (Ex.14 and Ex.16) and the comparative transparent coating (Ex.C2) to the polycarbonate substrate and the hydrolysis resistance performance were determined according to the test methods described above. The results are shown in Table 7 below. Table 7: Hydrolysis resistance performance of exemplary transparent coatings (Ex.14 and Ex.16) and comparative transparent coating (Ex.C2). Ex.14 Ex.16 Ex.C2 Hydrolysis resistance (60°C / 95% relative humidity, 96 hours) 5B 5B 0B

[0142] As can be seen from the results shown in Table 7, even under severe conditions, the transparent coatings according to the present invention (Ex.14 and EX.16) have excellent hydrolysis resistance performance. In contrast, it can be seen that the hydrolysis resistance performance obtained using the comparative transparent coating (Ex.C2) not according to the present invention is not satisfactory. Example 8: Performance attributes of exemplary metal coatings (EX.17 to EX.19).

[0143] The various performance attributes of the exemplary metal coatings (EX.17 to EX.19) were determined according to the test methods described above, particularly the adhesion to polycarbonate substrates, scratch resistance, and glossiness. The results are shown in Table 8 below. Table 8: Performance attributes of exemplary metal coatings (EX.17 to EX.19). Ex.17 Ex.18 Ex.19 Adhesion / PC 5B 5B 5B Scratch resistance (RCA cycle number) 70 40 95 Glossiness (gloss unit number at 60° angle) 15.1 15.1 15.4

[0144] As can be seen from the results shown in Table 8, the metal coatings according to the present invention (EX.17 to EX.19) have excellent performance attributes in terms of adhesion to polycarbonate substrates, scratch resistance, and glossiness.

Claims

1. An aqueous radiation-curable composition, comprising: a) 45 - 80 wt% of at least one ethylenically unsaturated compound (A); and b) 20 - 55 wt% of at least one ethylenically unsaturated polyurethane polymer (B) obtained by reacting: i. at least one polyisocyanate compound (i); ii. at least one polymeric polyol (ii); iii. at least one hydrophilic compound (iii) comprising at least one reactive group capable of reacting with an isocyanate group and at least one group capable of directly dispersing the polyurethane polymer (B) in an aqueous medium or, after reaction with a neutralizing agent to provide a salt, dispersing it in an aqueous medium; iv. at least one compound (iv) comprising at least one reactive group capable of reacting with an isocyanate group and further comprising at least one ethylenically unsaturated group; and v. optionally, at least one compound (v) comprising at least one reactive group capable of reacting with an isocyanate group; wherein the compounds (A), (i), (ii), (iii), (iv) and (v) are all different from each other, and wherein the wt% is based on the total dry content weight of the radiation-curable composition.

2. The composition according to claim 1, comprising more than 45 wt%, more than 50 wt%, more than 55 wt%, more than 60 wt%, more than 65 wt%, more than 70 wt%, or even more than 75 wt% of at least one ethylenically unsaturated compound (A), wherein the wt% is based on the total dry content weight of the radiation-curable composition.

3. The composition according to any one of claims 1 or 2, wherein the at least one ethylenically unsaturated compound (A) is selected from monomers, oligomers, polymers (especially oligomers), and any combination or mixture thereof.

4. The composition according to any one of the preceding claims, wherein the at least one ethylenically unsaturated compound (A) is selected from urethane (meth)acrylate (A1), polyester (meth)acrylate (A2), epoxy (meth)acrylate (A3), (meth)acrylic (meth)acrylate (A4), and any combination or mixture thereof.

5. The composition according to any one of the preceding claims, wherein the at least one polymeric polyol (ii) has a weight average molecular weight (Mw) of greater than 200 g / mol, greater than 300 g / mol, greater than 400 g / mol, greater than 500 g / mol, greater than 600 g / mol, greater than 800 g / mol or even greater than 1000 g / mol.

6. The composition according to any one of the preceding claims, wherein the at least one polymeric polyol (ii) is selected from polycarbonate polyols, polyester polyols, polyether polyols, fatty dimer diols, polybutadiene polyols, polyacrylate polyols, siloxane polyols, and any combination or mixture thereof.

7. A composition according to any one of the preceding claims, wherein the at least one hydrophilic compound (iii) is a non-polymerizable compound, in particular a polyol selected from those containing one or more anionic salt groups.

8. A composition according to any one of the preceding claims, wherein the at least one compound (iv) contains substantially one reactive group capable of reacting with an isocyanate group and further contains at least one, in particular at least two, ethylenically unsaturated groups.

9. A composition according to any one of the preceding claims, wherein the at least one compound (v) is selected from aliphatic, cycloaliphatic, aromatic or heterocyclic primary or secondary polyamines or hydrazines having at most 60, in particular at most 12, carbon atoms.

10. A composition according to any one of the preceding claims, wherein the at least one ethylenically unsaturated polyurethane polymer (B) is obtained by reaction of at least one further compound (vi) containing at least two reactive groups capable of reacting with an isocyanate group and further containing at least two ethylenically unsaturated groups, where compounds (A), (i), (ii), (iii), (iv), (v) and (vi) are all different from one another.

11. A composition according to any one of the preceding claims, which comprises 25 - 55 wt%, 30 - 55 wt% or even 30 - 50 wt% of at least one ethylenically unsaturated polyurethane polymer (B), based on the total dry content weight of the radiation-curable composition.

12. A composition according to any one of the preceding claims, having a particle size of not greater than 400 nm, not greater than 350 nm, not greater than 300 nm, not greater than 250 nm, not greater than 200 nm, not greater than 150 nm or even not greater than 100 nm, determined by DLS measurement according to the test method described in the experimental section.

13. A coating composition comprising the aqueous radiation-curable composition according to any one of claims 1 - 12.

14. A method for preparing an aqueous radiation-curable composition, which comprises the following steps: a) mixing and reacting the compounds (i), (ii), (iii) and optionally the compound (vi) according to any one of claims 1 - 10; b) reacting the product of step a) with the compound (iv) according to any one of claims 1 - 10, thereby obtaining a (blocked) ethylenically unsaturated polyurethane polymer (B); c) adding at least one ethylenically unsaturated compound (A) according to any one of claims 1 - 10; d) optionally reacting the compound (iii) with a neutralizing agent to convert the hydrophilic groups provided by the compound (iii) into anionic salts; e) dispersing the ethylenically unsaturated polyurethane polymer (B) obtained in step b) or optionally step d) in an aqueous medium; and f) optionally reacting the ethylenically unsaturated polyurethane polymer (B) obtained in step e) with the compound (v) according to any one of claims 1 - 10.

15. Use of the aqueous radiation-curable composition or coating composition according to any one of claims 1 to 13 in computer, communication and consumer electronics applications, dual-curing applications or thick colorant systems.