Urethane (meth)acrylate and related compositions for higher loading Field of the invention

The present invention relates to a urethane (meth)acrylate obtained by using a specific combination of hydroxylated (meth)acrylates, a diisocyanate and a diol, as well as its manufacturing process. The present invention also relates to a curable composition comprising the urethane (meth)acrylate and to a cured product obtained by curing the urethane (meth)acrylate or the curable composition.

Background of the invention

Urethane (meth)acrylates (including polymers and oligomers) are widely known in photocurable resins to provide mechanical toughness to the system. However, urethane (meth)acrylates typically exhibit very viscous behavior at regular handling temperatures (10-30°C) due to their urethane linkages. The high viscosity is also observed with urethane (meth)acrylates having a moderate molecular weight. Formulators cannot use too much highly viscous component in most applications, in particular flowable process applications like inks and coatings. Accordingly, the loading amount of conventional urethane (meth)acrylates in such formulations is limited and the advantageous effect on mechanical properties cannot be fully obtained. In this sense, it would be advantageous to have urethane (meth)acrylates with low viscosity since higher content could be loaded in applicative formulations thus broadening the freedom of blend design and improving the mechanical properties of the cured products obtained therefrom.

Urethane (meth)acrylates and related reactive resins in general and their uses are well-known from prior art.

W09118033 discloses a reactive liquid resin for hybrid urethane resin network, having a viscosity at 23°C in the range of 1 to 150 mPa.s fa injection molding. Said resin is a mixture of three components a polyisocyanate, a first ethylenically unsaturated monomer bearing an isocyanate-reactive group (OH) with a molecular weight lower than 500 g/mol, preferably lower than 400 g/mol, and a second ethylenically unsaturated monomer copolymerizable with the 1 ^st one. After the cure, a hybrid urethane network is formed by reaction of the polyisocyanate with the isocyanate-reactive groups (OH) of the copolymer, which is formed by radical copolymerization between said first isocyanate-reactive ethylenically unsaturated monomer and said second ethylenically unsaturated monomer, leading to a hybrid network comprising urethane crosslinks. The viscosity of the resin is kept low (1-150 mPa.s at 23 °C) by limiting the molecular weight of the reactive components and, in particular, of the isocyanate-reactive monomer to less than 500 g/mol, preferably less than 400 g/mol. The reactive resin disclosed in W09118033 does not include a polymeric diol and after copolymerization of the ethylenic unsaturations, there are no remaining ethylenic unsaturations in the formed copolymer or in the resulting urethane crosslinked network. As such, W09118033 does not disclose a urethane (meth)acrylate polymer (non-crosslinked structure).

JP4013532 discloses a polyurethane (meth)acrylate component C) for increasing the viscosity and adhesion of curable compositions for optical applications on specific supports, without affecting hardness and transparency. This component C) is obtained from the reaction of a polyisocyanate with a diol having from 1 to 5 alkoxy units in C2-C4 and a monoalcohol bearing at least two (meth)acryloyl groups. The molar ratio of polyisocyanate to diol in said polyurethane (meth)acrylate component is from 3:2 to 21 :20.

None of these prior art documents discloses or suggests the specific urethane (meth)acrylate of the present invention and its effect on lowering viscosity while maintaining its mechanical performances with respect to prior art urethane (meth)acrylate .

So, the main objective of the present invention is finding new UAs with a tailored structure in terms of the location of urethane bonds (repeating units) and their contents with specific repeating and terminal units, so that the viscosity is lower with respect to UA known from prior art not having these specific structural characteristics, while enabling satisfactory mechanical performances for the related UA cured compositions.

After careful study of UA structure, the Applicant has found that a specific range of the urethane linkage position in the UA could provide a significantly low viscosity even with the same chemical components. Controlling the weight percentage of urethane bonds in the structure, and the molecular chain length ratio between the terminal and central moieties provides urethane (meth)acrylates having low viscosity prior to curing and satisfactory mechanical properties once cured.

The low viscosity of the urethane (meth)acrylates of the invention compared to those of the prior art enables formulators to load higher amount into their formulation and/or to facilitate the processing of the formulation. Higher amounts of urethane (meth)acrylate also enables broader freedom in designing formulations and better mechanical performances after curing. Summary of the invention

A first object of the present invention is a urethane (meth)acrylate of formula (I): wherein A, A’, B, D, Ri, R’i, a, a’ and b are as defined herein, and the weight content of urethane bonds in the urethane (meth)acrylate is from 5 to 20% based on the total weight of the urethane (meth)acrylate.

A second object of the present invention is a curable composition comprising the urethane (meth)acrylate of the invention.

Another object of the present invention is a preparation process of the urethane (meth)acrylate of the invention.

Another object of the present invention is the use of the urethane (meth)acrylate of the invention or the curable composition of the present invention.

Yet another object of the present invention is a cured product resulting from the cure of the urethane (meth)acrylate of the invention or the curable composition of the present invention .

Detailed description

Definitions

In the present application, the term “comprise(s) a/an” means “comprise(s) one or more”.

Unless mentioned otherwise, the % by weight in a compound or a composition are expressed based on the weight of the compound, respectively of the composition.

The term « diisocyanate » means a compound bearing two isocyanate groups.

The term « diol » means a compound bearing two hydroxyl groups.

The term « hydroxylated (meth)acrylate » means a compound bearing one hydroxyl group and at least one (meth)acrylate group.

The term « isocyanate group » means a group of formula -N=C=0. The term « hydroxyl group » means a group of formula -OH.

The term “(meth)acrylate group” refers to a group of formula CH ₂ =CR-(C=0)-0- where R is H or methyl.

The term « alkyl » means a monovalent saturated alicyclic hydrocarbon group of formula -C _X H _2X+I wherein x is 1 to 20. An alkyl may be linear or branched. Examples of alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, 2-methylbutyl, 2,2-dimethylpropyl, n-hexyl, 2-methylpentyl, 2,2-dimethylbutyl, n-heptyl, 2-ethylhexyl, and the like.

The term “C2-C12 alkylene” refers to a saturated divalent radical derived from an alkane comprising 2 to 12 carbon atoms.

The term « linker » means a plurivalent group. A linker may connect at least two moieties of a compound together. For example, a linker that connects two moieties of a compound together may be referred to as a divalent linker.

The term « hydrocarbon linker » means a linker having a carbon backbone chain which may optionally be interrupted by one or more heteroatoms selected from N, O, S, Si and mixtures thereof. A hydrocarbon linker may be aliphatic, cycloaliphatic or aromatic. A hydrocarbon linker may be saturated or unsaturated. A hydrocarbon linker may be optionally substituted.

The term « aliphatic compound » or « aliphatic linker » means a compound, respectively a linker, that does not comprise any rings. It may be linear or branched, saturated or unsaturated. It may be substituted by one or more groups, for example selected from alkyl, hydroxyl, halogen (Br, Cl, I), isocyanate, carbonyl, amine, carboxylic acid,-C(=0)-OR’, -C(=0)-0-C(=0)-R’, each R’ being independently a C1-C6 alkyl. It may comprise one or more bonds selected from ether, ester, amide, urethane, urea and mixtures thereof.

The term « cycloaliphatic compound » or « cycloaliphatic linker » means a compound, respectively a linker, comprising a non-aromatic ring. The non-aromatic ring may have only carbon atoms as the ring atoms (i.e. a cycloalkyl) or it may comprise carbon atoms and one or more heteroatoms selected from N, O and S as ring atoms (i.e. an heterocycloalkyl). It may be substituted by one or more groups as defined for aliphatic compounds and linkers. It may comprise one or more bonds as defined for aliphatic compounds and linkers.

The term « aromatic compound » or« aromatic linker » means a compound, respectively a linker, comprising an aromatic ring (i.e. a ring that respects Huckel’s aromaticity rule). The aromatic ring may have only carbon atoms as the ring atoms (i.e. an aryl, such as a phenyl) or it may comprise carbon atoms and one or more heteroatoms selected from N, O and S as ring atoms (i.e. an heteroaryl). It may be substituted by one or more groups as defined for aliphatic compounds and linkers. It may comprise one or more bonds as defined for aliphatic compounds and linkers. Araliphatic compounds and linkers (ie. compounds and linkers comprising both an aromatic moiety and an aliphatic moiety) are encompassed by aromatic compounds and linkers.

The term « saturated » means a compound that does not comprise any double or triple carbon-carbon bonds.

The term « unsaturated » means a compound that comprises a double or triple carbon- carbon bond, in particular a double carbon-carbon bond.

The term « polyol » means a compound comprising at least two hydroxyl groups.

The term « polyether polyol » « polyether diol » or « polyether linker » means respectively a polyol, a diol or a linker comprising at least two ether bonds.

The term « polyester polyol » « polyester diol » or « polyester linker » means respectively a polyol, a diol or a linker comprising at least two ester bonds.

The term « polycarbonate polyol » or « polycarbonate linker » means a polyol, respectively a linker, comprising at least two carbonate bonds.

The term « polybutadiene polyol » or « polybutadiene linker » means a polyol, respectively a linker, comprising at least two units derived from the polymerization of butadiene, in particular at least two units selected from -CH ₂ -CH=CH-CH ₂ - and CH ₂ -CH(CH=CH ₂ )-.

The term « urethane bond » means a -NH-C(=0)-0- or -0-C(=0)-NH- bond.

The term « ester bond » means a -C(=0)-0- or -0-C(=0)- bond.

The term « ether bond » means a -O- bond.

The term « carbonate bond » means a -0-C(=0)-0- bond.

The term « optionally substituted » means a compound, group or linker optionally substituted by one or more groups selected from halogen, alkyl, cycloalkyl, aryl, heteroaryl, alkoxy, aryloxy, aralkyl, alkaryl, haloalkyl, hydroxyl, thiol, hydroxyalkyl, thioalkyl, thioaryl, alkylthiol, amino, alkylamino, isocyanate, nitrile, amide, carboxylic acid, -C(=0)-R’ -C(=0)-0R’, - C(=0)NH-R’, -NH-C(=0)R’, -0-C(=0)-NH-R’, -NH-C(=0)-0-R’, -C(=0)-0-C(=0)-R’ and -S02- NH-R’, each R’ being independently an optionally substituted group selected from alkyl, aryl and alkylaryl.

Urethane (meth)acrylate

The urethane (meth)acrylate of the invention corresponds to the following formula (I): wherein

A and A’ are independently selected from a polyether linker, a polyester linker and combinations thereof;

B is divalent linker;

D is a divalent linker;

Ri and R’i are independently H or methyl; a and a’ are independently from 1 to 5; b is from 1 to 5. The weight content of urethane bonds (-0-C(=0)-NH- and -NH-C(=0)-0-) in the urethane (meth)acrylate is from 5 to 20% based on the total weight of the urethane (meth)acrylate. In particular, the weight content of urethane bonds may be from 5.5 to 17%, from 6 to 15%, from 6.5 to 14.5%, from 7 to 14%, from 7 to 13%, from 7 to 12%, from 7 to 11%, from 7 to 10% or from 7 to 9%, based on the total weight of the urethane (meth)acrylate.

The molecular weight ratios R _A and R _A ’ may both be at least 0.25, wherein

Mn _A

RA Mn _D

Mn _Ai

^Ra ' ⁼ M ¾

MP _A is the number average molecular weight of a hydroxylated (meth)acrylate of formula (II) that may be used to obtain the terminal moiety of formula (III) of the urethane (meth)acrylate: wherein A, FT and a are as defined herein;

MP _A ’ is the number average molecular weight of a hydroxylated (meth)acrylate of formula (IV) that may be used to obtain the terminal moiety of formula (V) of the urethane (meth)acrylate: wherein A’, R’i and a’ are as defined herein;

Mn _D is the number average molecular weight of a diol of formula (VI) that may be used to obtain the central moiety of formula (VII) of the urethane (meth)acrylate:

OH-D-OH (VI) -O-D-O- (VII) wherein D is as defined herein.

In particular, the molecular weight ratios R _A and R _A ’ may both independently be from 0.25 to 2, from 0.26 to 1.9, from 0.27 to 1 .8, from 0.28 to 1.7, from 0.3 to 1.6, from 0.4 to 1 .5, from 0.5 to 1.4 or from 0.6 to 1 .3.

The number average molecular weights MP _A and MP _A ’ may each independently be at least 250 g/mol, preferably from 250 to 3000 g/mol, more preferably from 300 to 2500 g/mol, more preferably still from 340 to 2000 g/mol.

The number molecular weight may be determined according to the method described herein.

The value of a and a’ is independently from 1 to 5. In particular, a and a’ may independently be from 1 to 3, from 1 to 2, or a and a’ may both be 1 . Accordingly, the urethane (meth)acrylate of the invention may bear from 2 to 10, in particular 2 to 6, more particularly 2 to 4, even more particularly 2, (meth)acrylate groups. All of the (meth)acrylate groups of the urethane (meth)acrylate polymer may be carried by residues A and A’. Accordingly, residue D may be free of any (meth)acrylate group. The value of b is from 1 to 5. In particular, b may be from 1 to 4, from 1 to 3, from 1 to 2 or b may be 1 .

A and A’ are independently selected from a polyether linker, a polyester linker and combinations thereof. A and A’ may be identical or different. In one embodiment, A and A’ are identical. In another embodiment, A and A’ are different. For example, A can a polyether linker and A’ can be a different polyether linker. Alternatively, A can be a polyether linker and A’ can be a polyester linker. Alternatively, A can be a polyester linker and A’ can be a different polyester linker.

Part or all of A and A’ may be a polyether linker comprising at least 6 ether bonds. In particular, the polyether linker may comprise from 6 to 50, from 6 to 30 or from 10 to 20 ether bonds. The ether bonds may be comprised in oxyalkylene repeating units. An oxyalkylene repeating unit may correspond to -[0-(CR ₂ R’ ₂ ) _c ]- wherein each R ₂ and R’ ₂ is independently H or methyl and c is 2 to 4. The oxyalkylene repeating units may be selected from oxyethylene (-0-CH ₂ -CH ₂ -), oxypropylene (-0-CH ₂ -CH(CH ₃ )- and/or -0-CH(CH ₃ )-CH ₂ -), oxybutylene (-0- CH ₂ -CH ₂ -CH ₂ -CH ₂ -), and mixtures thereof.

The polyether linker may be the residue, without the OH groups, of an alkoxylated (i.e. ethoxylated, propoxylated and/or butoxylated) polyol POH. Examples of suitable polyols POH include 1 ,2-ethylene glycol, 1 ,2- or 1 ,3-propylene glycol, 1 ,2- 1 ,3- or 1 ,4-butylene glycol, 1 ,5- pentanediol, 1 ,6-hexanediol, 1 ,7-heptanediol, 1 ,8-octanediol, 1 ,9-nonanediol, 1 ,10- decanediol, 1 ,12-dodecanediol, 2-methyl-1 ,3-propanediol, 2, 2-diethyl-1 ,3-propanediol, 3- methyl-1 ,5-pentanediol, 3,3-dimethyl-1 ,5-pentanediol, neopentyl glycol, 2,4-diethyl-1 ,5- pentanediol, cyclohexanediol, cyclohexane-1 ,4-dimethanol, norbornene dimethanol, norbornane dimethanol, tricyclodecanediol, tricyclodecane dimethanol, bisphenol A, B, F or S, hydrogenated bisphenol A, B, F or S, trimethylolmethane, trimethylolethane, trimethylolpropane, di(trimethylolpropane), triethylolpropane, pentaerythritol, di(pentaerythritol), glycerol, di-, tri- or tetraglycerol, polyglycerol, a sugar alcohol, a dianhydrohexitol (i.e. isosorbide, isomannide, isoidide), tris(2-hydroxyethyl)isocyanurate, a polybutadiene polyol, and a polycarbonate polyol.

In particular, the polyether linker may correspond to formula (VIII) or (IX): -(CR ₂ R’ ₂ ) _c -[0-(CR ₂ R’ ₂ )c]d- (VIII)

-[(CR ₃ R ^, 3)e-0]f-(CR4R ^, 4)g-[0-(CR ₅ R ^, 5)e']f- (IX) wherein each R _2J R’ _2J R _3J R’ _3J R _S and R’ ₅ is independently H or methyl; each R ₄ and R’ ₄ is independently H or alkyl; c, e and e’ are independently 2 to 4; d is from 6 to 50, from 6 to 30 or from 10 to 20; f and f are independently 0 to 50, with the proviso that the sum f + f is from 6 to 50, from 6 to 30 or from 10 to 20; g is 2 to 20.

More particularly the polyether linker may be selected from a polyoxyethylene, a polyoxypropylene, a polyoxybutylene, a co-poly(oxyethylene-oxypropylene), a co- poly(oxyethylene-oxybutylene), a co-poly(oxypropylene-oxybutylene), in particular a polyoxypropylene.

The polyether linker may correspond to the residue, without the OH groups, of a polyalkylene glycol. Examples of suitable polyalkylene glycols include a polyethylene glycol, a polypropylene glycol, a polytetramethylene glycol, a polyethylene glycol-co-propylene glycol), a polyethylene glycol-co-tetramethylene glycol) and a poly(propylene glycol-co- tetramethylene glycol). In particular, the polyalkylene glycol may be a polypropylene glycol.

Part or all of A and A’ may be a polyester linker comprising at least 2 ester bonds. In particular, the polyester linker may comprise from 2 to 20, from 2 to 10 or from 2 to 7 ester bonds. The ester bonds may be comprised in repeating units derived from the ring-opening of a lactone, in particular e-caprolactone or d-valerolactone. A repeating unit derived from the ring-opening of a lactone may correspond to -[0-C(=0)-(CH ₂ ) _g ]- wherein g is 3 to 10, in particular 4 to 6, more particularly 5.

The polyester linker may be the residue, without the OH groups, of a polyol POH which is esterified with repeating units derived from the ring-opening of a lactone. Examples of suitable polyols POH are as defined above for the polyether linker.

Alternatively, the polyester linker may be the residue, without the OH groups, of a polyester polyol obtained by reacting a polyol POH with a polycarboxylic acid, a cyclic anhydride or a derivative thereof, in particular a dicarboxylic acid or a cyclic anhydride. Examples of suitable polyols POH are as defined above for the polyether linker. Examples of suitable polycarboxylic acids include adipic acid, succinic acid, oxalic acid, malonic acid, pimelic acid, suberic acid, sebacic acid, dodecanedioic acid, eicosanedioic acid, cyclohexane dicarboxylic acid, hexahydrophthalic acid, itaconic acid, fumaric acid, maleic acid and the like. Aromatic diacids such as phthalic acid and terephthalic acid could also be utilized. Examples of suitable cyclic anhydrides include succinic anhydride, hexahydrophthalic anhydride, maleic anhydride, fumaric anhydride, tetrahydrophthalic anhydride, phthalic anhydride. Derivatives of polycarboxylic acids are compounds that are able to transform in polycarboxylic acid by hydrolysis or transesterification. Suitable examples include dimethylmalonate, diethylmalonate, dimethyladipate, dimethyl glutarate and dimethyl succinate.

In particular, the polyester linker may correspond to formula (X) or (XI):

-[(CH ₂ ) _g -C(=0)-0]h-E-[0-C(=0)-(CH ₂ ) _g ]h- (X)

-[(CR ₇ R’7)j-0-C(=0)-(CR ₈ R’ ₈ )k-C(=0)-0]r(CR ₇ R’7)j- (XI) wherein

E is C2-C20 alkylene or -[(CR6R’6)iO]i -(CR ₆ R’6)i- each Re and R’e is independently H or methyl; each R ₇ , R’ _7J R ₈ and R’ ₈ is independently H or alkyl; g is 3 to 10, in particular 4 to 6, more particularly 5; h and h’ are independently 0 to 20, in particular 2 to 10, more particularly 2 to 7, with the proviso that the sum h + h’ is at least 2; i is 2 to 4, in particular 2; i ^* is 1 to 10, in particular 1 to 5, more particularly 1 to 3; j is 2 to 20, in particular 2 to 12, more particularly 2 to 8; k is 1 to 36, in particular 1 to 20, more particularly 1 to 12;

I is 1 to 20, in particular 2 to 15, more particularly 2 to 10.

More particularly, the polyester linker may correspond to formula (X) and h is 0 and h’ is at least 2 or h is at least 2 and h’ is 0;

E is a C2-20 alkylene, in particular a C2-12 alkylene, more particularly a C2-C6 alkylene.

The terminal moieties of formula (III) and (V) of the urethane (meth)acrylate of the invention: may be the residues, without the hydrogen atom of the hydroxyl group, of hydroxylated (meth)acrylates of formula (II) and (IV): wherein A, A’, Ri, R’i, a and a’ are as defined herein.

In particular, the hydroxylated (meth)acrylates of formula (II) and (IV) bear a single OH group. More particularly, the hydroxylated (meth)acrylates of formula (II) and (IV) bear a single OH group and a single (meth)acrylate group (i.e. a and a’ are both 1). The hydroxylated (meth)acrylates of formula (II) and (IV) may thus be polyethers or polyesters bearing a single OH group and a single (meth)acrylate group. These compounds may be obtained by reacting a polyether diol or a polyester diol with a (meth)acrylate acid or (meth)acryloyl chloride using an appropriate molar ratio so that a single free hydroxyl group remains on the resulting product.

The hydroxylated (meth)acrylates of formula (II) and (IV) may be selected from a polyethylene glycol (meth)acrylate, a polypropylene glycol (meth)acrylate, a polytetramethylene glycol (meth)acrylate, a polyethylene glycol-co-propylene glycol) (meth)acrylate, a polycaprolactone (meth)acrylate and combinations thereof.

In particular, the hydroxylated (meth)acrylates of formula (II) and (IV) may be selected from a hydroxylated polyether (meth)acrylate of formula (XII), a hydroxylated polyester (meth)acrylate of formula (XIII), and combinations thereof: wherein

Rio is H or CH _3J in particular H; each Rg and R’g is independently H or CH ₃ ; each I is independently 2 to 4, in particular 2; m is 6 to 50, in particular 6 to 30, more particularly 10 to 20; wherein

Rii is H or CH ₃ , in particular H;

Li is a linear or branched C2-C12 alkylene, in particular a linear C2-C4 alkylene, more particularly ethylene; o is 2 to 20, in particular 2 to 10, more particularly 2 to 7; even more particularly 2 and n is 3 to 10, in particular 4 to 6, more particularly 5.

A hydroxylated polyether (meth)acrylate of formula (XII) may be prepared by reaction between a polyalkylene glycol (such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol or copolymers thereof, in particular polyethylene glycol or polypropylene glycol) with (meth)acrylic acid or (meth)acryloyl chloride. A hydroxylated polyester (meth)acrylate of formula (XIII) may be prepared by reaction between a hydroxyalkyl (meth)acrylate (such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate or 4-hydroxybutyl (meth)acrylate, in particular 2-hydroxyethyl (meth)acrylate) and a lactone (such as d-valerolactone or e-caprolactone, in particular e-caprolactone). Some of these compounds are commercially available, such as a polyethylene glycol acrylate in the NOF Blemmer ^® AE series, a polypropylene oxide acrylate in the NOF Blemmer AP® series, a polycaprolactone acrylate with 2 units derived from the ring opening e-caprolactone sold under reference SR495 by Sartomer.

B is divalent linker. In particular, B is an aliphatic, cycloaliphatic or aromatic hydrocarbon linker. More particularly, B is a cycloaliphatic hydrocarbon linker B may be the residue, without the NCO groups, of a diisocyanate of formula (XIV): OCN-B-NCO (XIV).

The diisocyanate of formula (XIV) may be an aliphatic, cycloaliphatic or aromatic diisocyanate, in particular a cycloaliphatic diisocyanate.

More particularly, the diisocyanate of formula (XIV) may be selected from the group consisting of isophorone diisocyanate (IPDI - corresponding to 3-isocyanatomethyl-3,5,5- trimethylcyclohexylisocyanate), 2,4- and 2,6-toluene diisocyanate (TDI), tetramethylene diisocyanate, pentamethylene diisocyanate (PDI), hexamethylene diisocyanate (HMDI), dodecane diisocyanate, trimethylhexamethylene diisocyanate (TMDI), 2,2'-, 2,4'- and 4,4'- diphenylmethane diisocyanate (MDI), 2,2'-, 2,4'- and 4,4'-dicyclohexylmethane diisocyanate (H12MDI), m-xylylene diisocyanate, 1 ,5-naphthalene diisocyanate (NDI), 1 ,3- and 1 ,4- phenylene diisocyanate, 1 ,3- and 1 ,4-cyclohexane diisocyanate, 3,3'-dimethyl-4,4'-biphenyl diisocyanate, 1 -methyl-2, 4-diisocyanatocyclohexane, 1 -methyl-2, 6-diisocyanatocyclohexane, dianisidine diisocyanate (1 ,T-biphenyl-3,3’-dimethoxy-4,4’-diisocyanate), dimers of the above-mentioned diisocyanates, and the above-mentioned diisocyanates modified with allophanate, isocyanurate, uretdione or biuret structure.

In a particularly preferred embodiment, the diisocyanate of formula (XIV) is IPDI.

D is divalent linker. In particular, D may be selected from an aromatic, aliphatic or cycloaliphatic hydrocarbon linker, a polyether linker, a polyester linker, a polycarbonate linker, a polybutadiene linker, and combinations thereof.

D may be free of (meth)acrylate groups. D may be free of siloxane groups (i.e. groups comprising a Si-0 bond). D may be a linker that does not comprise any pending groups other than alkyl.

In particular, D may be selected from a polyether linker, a polyester linker and combinations thereof.

The polyether linker may comprise at least 2 ether bonds. In particular, the polyether linker may comprise from 2 to 50, from 4 to 30 or from 6 to 20 ether bonds. The ether bonds may be comprised in oxyalkylene repeating units as defined above.

The polyether linker may be the residue, without the OH groups, of an alkoxylated (i.e. ethoxylated, propoxylated and/or butoxylated) diol DOH. Examples of suitable diols DOH include 1 ,2-ethylene glycol, 1 ,2- or 1 ,3-propylene glycol, 1 ,2- 1 ,3- or 1 ,4-butylene glycol, 1 ,5- pentanediol, 1 ,6-hexanediol, 1 ,7-heptanediol, 1 ,8-octanediol, 1 ,9-nonanediol, 1 ,10- decanediol, 1 ,12-dodecanediol, 2-methyl-1 ,3-propanediol, 2, 2-diethyl-1 ,3-propanediol, 3- methyl-1 ,5-pentanediol, 3,3-dimethyl-1 ,5-pentanediol, neopentyl glycol, 2,4-diethyl-1 ,5- pentanediol, cyclohexanediol, cyclohexane-1 ,4-dimethanol, norbornene dimethanol, norbornane dimethanol, tricyclodecanediol, tricyclodecane dimethanol, bisphenol A, B, F or S, hydrogenated bisphenol A, B, F or S.

In particular, the polyether linker may correspond to formula (VIII) or (IX) as defined above.

More particularly the polyether linker may be selected from a polyoxyethylene, a polyoxypropylene, a polyoxybutylene, a co-poly(oxyethylene-oxypropylene), a co- poly(oxyethylene-oxybutylene), a co-poly(oxypropylene-oxybutylene). The polyether linker may correspond to the residue, without the OFI groups, of a polyalkylene glycol. Examples of suitable polyalkylene glycols include a polyethylene glycol, a polypropylene glycol, a polytetramethylene glycol, a polyethylene glycol-co-propylene glycol), a polyethylene glycol- co-tetramethylene glycol) and a poly(propylene glycol-co-tetramethylene glycol).

The polyester linker may comprise at least 2 ester bonds. In particular, the polyester linker may comprise from 2 to 20, from 2 to 10 or from 2 to 7 ester bonds. The ester bonds may be comprised in repeating units derived from the ring-opening of a lactone as defined above.

The polyester linker may be the residue, without the OFI groups, of a diol DOH which is esterified with repeating units derived from the ring-opening of a lactone. Examples of suitable diols DOH are as defined above for the polyether linker.

Alternatively, the polyester linker may be the residue, without the OFI groups, of a polyester polyol obtained by reacting a diol DOH with a polycarboxylic acid functional compound or a derivative thereof, in particular a dicarboxylic acid or a cyclic anhydride. Examples of suitable diols DOH are as defined above for the polyether linker. Examples of suitable polycarboxylic acid functional compounds are as defined above.

In particular, the polyester linker may correspond to formula (X) or (XI) as defined above.

D may be the residue, without the OFI groups, of a diol of formula (VI)

OH-D-OH (VI).

The diol of formula (VI) may be selected from a polyester diol, a polyether diol and mixtures thereof, preferably a polyether diol. The polyester diol may be an aliphatic polyester diol, preferably a polycaprolactone diol.

The polyether diol may be selected from the group consisting of a polyethylene glycol, a polypropylene glycol or polytetramethylene glycol, preferably a polytetramethylene glycol.

Suitable polytetramethylene glycols include a homopolymer of THF (tetrahydrofuran) and its copolymeric form with a THF substituted with an alkyl in C1-C4.

The number average molecular weight Mn _D of the diol of formula (VI) may be from 300 to 3000 g/mol, in particular from 500 to 2500 g/mol, more particularly from 600 to 2000 g/mol.

The urethane (meth)acrylate polymer of the invention advantageously exhibits a Brookfield viscosity at 60°C lower than 4500 mPa.s, in particUar from 50 to 4000 mPa.s, more particularly from 100 to 3500 mPa.s. The viscosity may be measured according to the method disclosed herein.

Process for the preparation of a urethane (meth)acrylate

Another subject-matter of the invention relates to a process of preparing a urethane (meth)acrylate of formula (I) as defined above, wherein the process comprises reacting hydroxylated (meth)acrylates of formula (II) and (IV), a diol of formula (VI) and a diisocyanate of formula (XIV) in one or more steps.

OH-D-OH (VI). OCN-B-NCO (XIV) wherein A, A’, B, D, Ri, R’i, a and a’ are as defined above for the urethane (meth)acrylate.

Components of formulae (II), (IV), (VI) and (XIV) may be as defined above for the urethane (meth)acrylate.

The molar ratio NCO/OH may be from 0.95 to 1 .05. The molar ratio NCO/OH corresponds to the molar ratio between the NCO groups of the diisocyanate of formula (XIV) and the OH groups of the hydroxylated (meth)acrylates of formula (II) and (IV) and the diol of formula (VI). According to a first embodiment, the process comprises the step of mixing and reacting components of formulae (II), (IV), (VI) and (XIV) all together.

In a second embodiment, the process comprises the following successive steps: i) reacting a diisocyanate of formula (XIV) with a diol of formula (VI); and ii) adding to the resulting product of step i) hydroxylated (meth)acrylates of formula (II) and (IV).

In a third embodiment, the process comprises the following successive steps: i) reacting a diisocyanate of formula (XIV) with hydroxylated (meth)acrylates of formula (II) and (IV); and ii) adding to the resulting product of step i) a diol of formula (VI).

The process may be carried out in the presence of a catalyst. The catalyst may be selected from compounds based on Sn, Ti, Zn, Zr, Ba, Bi, Co, Pb, Mn, preferably based on Sn, Bi, Zn, Ti, Zr.

More particularly, the catalyst may be selected from:

- inorganic tin compounds such as stannous octoate, stannous oxalate, stannous stearate, stannous naphthenate or stannous chloride dihydrate;

- organotin compounds such as dibutyltin (DBT) compounds, in particular DBT bis-O- phenylphenate, DBT bis-(2,3-dihydroxypropylmercaptide), DBT bis-(2- hydroxyethylmercaptide), DBT bis-(4-hydroxyphenylmercaptide), dioctyltin bis-(2- hydroxyethylmercaptide), dioctyltin bis-(4-hydroxybutylmercaptide), DBT bis-(4- hydroxyphenylacetate), DBT bis-[3-(4-hydroxyphenyl)propionatel, DBT S,S-dibutylthio- carbonate, DBT diacetate, DBT diketanoate, DBT dilaurate, DBT dilauryl mercaptide or DBT malenate; dioctyltin (DOT) compounds, in particular DOT bis-(4-hydroxyphenylacetate), DOT bis-(3-hydroxybutyrate), DOT diacetate, DOT di(ethylhexanoate), DOT dithioglycolate, DOT dilaurate, DOT diketanoate, DOT dicarboxylate or DOT stannoxane; dimethyltin (DMT) compounds, tributyltin (TBT) compounds, trimethyltin (TMT) compounds, triphenyltin (TPhT) compounds, tetrabutyltin (TeBT) compounds, tricyclohexyltin (TCyHT) compounds, trioctyltin (TOT) compounds, tripropyltin (TPT) compounds, monobutyltin (MBT) compounds or monoctyltin (MOT) compounds;

- bismuth compounds such as bismuth carboxylate, bismuth neodecanoate, bismuth stannate or bismuth stearate;

- zinc compounds such as zinc acetate, zinc acetylacetoate, zinc neodecanoate, zinc octoate or zinc oxalate; - titanium compounds such as titanium acetylacetone complex, titanium ethylacetoacetonate complex, titanium tetrabutanolate or titanium triethanol;

- zirconium compounds such as zirconium ethyl acetoacetonate complex or zirconium octoate;

- some additional organometallic compounds suitable as catalysts such as potassium octoate, potassium neodecanoate, amine complexes, copper oleate, copper naphthenate, cerium octoate, iron acetoacetonate, lead stannate, lead stearate, barium nitride.

The curable composition of the invention comprises a urethane (meth)acrylate of formula (I). The curable composition of the invention may comprise a mixture of urethane (meth)acrylates of formula (I).

The curable composition of the invention may further comprise an ethylenically unsaturated compound other than the urethane (meth)acrylate of formula (I).

As used herein, the term “ethylenically unsaturated compound” means a compound that comprises a polymerizable carbon-carbon double bond. A polymerizable carbon-carbon double bond is a carbon-carbon double bond that can react with another carbon-carbon double bond in a polymerization reaction. A polymerizable carbon-carbon double bond is generally comprised in a group selected from acrylate (including cyanoacrylate), methacrylate, acrylamide, methacrylamide, styrene, maleate, fumarate, itaconate, allyl, propenyl, vinyl and combinations thereof, preferably selected from acrylate, methacrylate and vinyl, more preferably selected from acrylate and methacrylate. The carbon-carbon double bonds of a phenyl ring are not considered as polymerizable carbon-carbon double bonds.

In one embodiment, the ethylenically unsaturated compound may be selected from a (meth)acrylate-functionalized monomer, a (meth)acrylate-functionalized oligomer, an amine- modified acrylate and mixtures thereof.

The total amount of ethylenically unsaturated compound (including (meth)acrylate functionalized monomer, (meth)acrylate functionalized oligomer and amine-modified acrylate) in the curable composition may be from 0 to 80%, from 5 to 70%, from 10 to 60%, from 15 to 50% or from 20 to 40%, by weight based on the weight of the composition. In particular, the curable composition of the invention may comprise from 0 to 40%, from 5 to 40%, from 10 to 40%, from 15 to 40% or from 20 to 40%, by weight of ethylenically unsaturated compound based on the total weight of the curable composition. Alternatively, the curable composition of the invention may comprise from 40 to 80%, from 40 to 75%, from or 40 to 70%, from 40 to 65% or from 40 to 60%, by weight of ethylenically unsaturated compound based on the weight of the curable composition.

As used herein, the term “(meth)acrylate-functionalized monomer” means a monomer comprising a (meth)acrylate group, in particular an acrylate group. The term “(meth)acrylate- functionalized oligomer” means an oligomer comprising a (meth)acrylate group, in particular an acrylate group.

In one embodiment, the ethylenically unsaturated compound comprises a (meth)acrylate- functionalized monomer. The ethylenically unsaturated compound may comprise a mixture of (meth)acrylate-functionalized monomers.

The (meth)acrylate-functionalized monomer may have a molecular weight of less than 600 g/mol, in particular from 100 to 550 g/mol, more particularly 200 to 500 g/mol.

The (meth)acrylate-functionalized monomer may have 1 to 6 (meth)acrylate groups, in particular 1 to 3 (meth)acrylate groups.

The (meth)acrylate-functionalized monomer may comprise a mixture of (meth)acrylate- functionalized monomers having different functionalities. For example the (meth)acrylate- functionalized monomer may comprise a mixture of a (meth)acrylate-functionalized monomer containing a single acrylate or methacrylate group per molecule (referred to herein as “mono(meth)acrylate-functionalized compounds”) and a (meth)acrylate-functionalized monomer containing 2 or more, preferably 2 or 3, acrylate and/or methacrylate groups per molecule.

In one embodiment, the (meth)acrylate functionalized monomer comprises a mono(meth)acrylate-functionalized monomer. The mono(meth)acrylate-functionalized monomer may advantageously function as a reactive diluent and reduce the viscosity of the composition of the invention.

Examples of suitable mono(meth)acrylate-functionalized monomers include, but are not limited to, mono-(meth)acrylate esters of aliphatic alcohols (wherein the aliphatic alcohol may be straight chain, branched or alicyclic and may be a mono-alcohol, a di-alcohol or a polyalcohol, provided only one hydroxyl group is esterified with (meth)acrylic acid); mono- (meth)acrylate esters of aromatic alcohols (such as phenols, including alkylated phenols); mono-(meth)acrylate esters of alkylaryl alcohols (such as benzyl alcohol); mono- (meth)acrylate esters of oligomeric and polymeric glycols such as diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol, and polypropylene glycol); mono-(meth)acrylate esters of monoalkyl ethers of glycols and oligoglycols; mono-(meth)acrylate esters of alkoxylated (e.g., ethoxylated and/or propoxylated) aliphatic alcohols (wherein the aliphatic alcohol may be straight chain, branched or alicyclic and may be a mono-alcohol, a di-alcohol or a polyalcohol, provided only one hydroxyl group of the alkoxylated aliphatic alcohol is esterified with (meth)acrylic acid); mono-(meth)acrylate esters of alkoxylated (e.g., ethoxylated and/or propoxylated) aromatic alcohols (such as alkoxylated phenols); caprolactone mono(meth)acrylates; and the like.

The following compounds are specific examples of mono(meth)acrylate-functionalized monomers suitable for use in the curable compositions of the present invention: methyl (meth)acrylate; ethyl (meth)acrylate; n-propyl (meth)acrylate; n-butyl (meth)acrylate; isobutyl (meth)acrylate; n-hexyl (meth)acrylate; 2-ethylhexyl (meth)acrylate; n-octyl (meth)acrylate; isooctyl (meth)acrylate; n-decyl (meth)acrylate; n-dodecyl (meth)acrylate; tridecyl (meth)acrylate; tetradecyl (meth)acrylate; hexadecyl (meth)acrylate; 2-hydroxyethyl (meth)acrylate; 2- and 3-hydroxypropyl (meth)acrylate; 2-methoxyethyl (meth)acrylate; 2- ethoxyethyl (meth)acrylate; 2- and 3-ethoxypropyl (meth)acrylate; tetrahydrofurfuryl (meth)acrylate; alkoxylated tetrahydrofurfuryl (meth)acrylate; 2-(2-ethoxyethoxy)ethyl (meth)acrylate; cyclohexyl (meth)acrylate; glycidyl (meth)acrylate; isodecyl (meth)acrylate; lauryl (meth)acrylate; 2-phenoxyethyl (meth)acrylate; alkoxylated phenol (meth)acrylates; alkoxylated nonylphenol (meth)acrylates; cyclic trimethylolpropane formal (meth)acrylate; isobornyl (meth)acrylate; tricyclodecanemethanol (meth)acrylate; tert-butylcyclohexanol (meth)acrylate; trimethylcyclohexanol (meth)acrylate; diethylene glycol monomethyl ether (meth)acrylate; diethylene glycol monoethyl ether (meth)acrylate; diethylene glycol monobutyl ether (meth)acrylate; triethylene glycol monoethyl ether (meth)acrylate; ethoxylated lauryl (meth)acrylate; methoxy polyethylene glycol (meth)acrylates; hydroxyl ethyl-butyl urethane (meth)acrylates; 3-(2-hydroxyalkyl)oxazolidinone (meth)acrylates; and combinations thereof.

In one embodiment, the (meth)acrylate functionalized monomer may comprise a (meth)acrylate-functionalized monomer containing two or more (meth)acrylate groups per molecule.

Examples of suitable (meth)acrylate-functionalized monomers containing two or more (meth)acrylate groups per molecule include acrylate and methacrylate esters of polyhydric alcohols (organic compounds containing two or more, e.g., 2 to 6, hydroxyl groups per molecule). Specific examples of suitable polyhydric alcohols include C2-20 alkylene glycols (glycols having a C2-10 alkylene group may be preferred, in which the carbon chain may be branched; e.g., ethylene glycol, trimethylene glycol, 1 ,2-propylene glycol, 1 ,2-butanediol, 1 ,3- butanediol, 2,3-butanediol, tetramethylene glycol (1 ,4-butanediol), 1 ,5-pentanediol, 1 ,6- hexanediol, 1 ,8-octanediol, 1 ,9-nonanediol, 1 ,12-dodecanediol, cyclohexane-1 , 4-dimethanol, bisphenols, and hydrogenated bisphenols, as well as alkoxylated (e.g., ethoxylated and/or propoxylated) derivatives thereof), diethylene glycol, glycerin, alkoxylated glycerin, triethylene glycol, dipropylene glycol, tripropylene glycol, trimethylolpropane, alkoxylated trimethylolpropane, ditrimethylolpropane, alkoxylated ditrimethylolpropane, pentaerythritol, alkoxylated pentaerythritol, dipentaerythritol, alkoxylated dipentaerythritol, cyclohexanediol, alkoxylated cyclohexanediol, cyclohexanedimethanol, alkoxylated cyclohexanedimethanol, norbornene dimethanol, alkoxylated norbornene dimethanol, norbornane dimethanol, alkoxylated norbornane dimethanol, polyols containing an aromatic ring, cyclohexane-1 ,4- dimethanol ethylene oxide adducts, bis-phenol ethylene oxide adducts, hydrogenated bisphenol ethylene oxide adducts, bisphenol propylene oxide adducts, hydrogenated bisphenol propylene oxide adducts, cyclohexane-1 ,4-dimethanol propylene oxide adducts, sugar alcohols and alkoxylated sugar alcohols. Such polyhydric alcohols may be fully or partially esterified (with (meth)acrylic acid, (meth)acrylic anhydride, (meth)acryloyl chloride or the like), provided they contain at least two (meth)acrylate functional groups per molecule.

Exemplary (meth)acrylate-functionalized monomers containing two or more (meth)acrylate groups per molecule may include ethoxylated bisphenol A di(meth)acrylates; triethylene glycol di(meth)acrylate; ethylene glycol di(meth)acrylate; tetraethylene glycol di(meth)acrylate; polyethylene glycol di(meth)acrylates; 1 ,4-butanediol diacrylate; 1 ,4- butanediol dimethacrylate; diethylene glycol diacrylate; diethylene glycol dimethacrylate, 1 ,6- hexanediol diacrylate; 1 ,6-hexanediol dimethacrylate; neopentyl glycol diacrylate; neopentyl glycol di(meth)acrylate; polyethylene glycol (600) dimethacrylate (where 600 refers to the approximate number average molecular weight of the polyethylene glycol portion); polyethylene glycol (200) diacrylate; 1 ,12-dodecanediol dimethacrylate; tetraethylene glycol diacrylate; triethylene glycol diacrylate, 1 ,3-butylene glycol dimethacrylate, tripropylene glycol diacrylate, polybutadiene diacrylate; methyl pentanediol diacrylate; polyethylene glycol (400) diacrylate; ethoxylated ₂ bisphenol A dimethacrylate; ethoxylated ₃ bisphenol A dimethacrylate; ethoxylated ₃ bisphenol A diacrylate; cyclohexane dimethanol dimethacrylate; cyclohexane dimethanol diacrylate; ethoxylatedio bisphenol A dimethacrylate (where the numeral following “ethoxylated” is the average number of oxyalkylene moieties per molecule); dipropylene glycol diacrylate; ethoxylated4 bisphenol A dimethacrylate; ethoxylatede bisphenol A dimethacrylate; ethoxylateds bisphenol A dimethacrylate; alkoxylated hexanediol diacrylates; alkoxylated cyclohexane dimethanol diacrylate; dodecane diacrylate; ethoxylated ₄ bisphenol A diacrylate; ethoxylatedio bisphenol A diacrylate; polyethylene glycol (400) dimethacrylate; polypropylene glycol (400) dimethacrylate; metallic diacrylates; modified metallic diacrylates; metallic dimethacrylates; polyethylene glycol (1000) dimethacrylate; methacrylated polybutadiene; propoxylated ₂ neopentyl glycol diacrylate; ethoxylated ₃ o bisphenol A dimethacrylate; ethoxylated ₃ o bisphenol A diacrylate; alkoxylated neopentyl glycol diacrylates; polyethylene glycol dimethacrylates; 1 ,3-butylene glycol diacrylate; ethoxylated ₂ bisphenol A dimethacrylate; dipropylene glycol diacrylate; ethoxylated ₄ bisphenol A diacrylate; polyethylene glycol (600) diacrylate; polyethylene glycol (1000) dimethacrylate; tricyclodecane dimethanol diacrylate; propoxylated neopentyl glycol diacrylates such as propoxylated ₂ neopentyl glycol diacrylate; diacrylates of alkoxylated aliphatic alcohols; trimethylolpropane trimethacrylate; trimethylolpropane triacrylate; tris (2-hydroxyethyl) isocyanurate triacrylate; ethoxylated ₂₀ trimethylolpropane triacrylate; pentaerythritol triacrylate; ethoxylated ₃ trimethylolpropane triacrylate; propoxylated ₃ trimethylolpropane triacrylate; ethoxylatede trimethylolpropane triacrylate; propoxylatede trimethylolpropane triacrylate; ethoxylatedg trimethylolpropane triacrylate; alkoxylated trifunctional acrylate esters; trifunctional methacrylate esters; trifunctional acrylate esters; propoxylated ₃ glyceryl triacrylate; propoxylatedss glyceryl triacrylate; ethoxylatedis trimethylolpropane triacrylate; trifunctional phosphoric acid esters; trifunctional acrylic acid esters; pentaerythritol tetraacrylate; di-trimethylolpropane tetraacrylate; ethoxylated ₄ pentaerythritol tetraacrylate; pentaerythritol polyoxyethylene tetraacrylate; dipentaerythritol pentaacrylate; and pentaacrylate esters.

The curable composition of the invention may comprise from 0 to 80%, from 5 to 70%, from 10 to 60%, from 15 to 50% or from 20 to 40%, by weight of (meth)acrylate-functionalized monomer based on the total weight of the curable composition. In particular, the curable composition of the invention may comprise from 0 to 40%, from 5 to 40%, from 10 to 40%, from 15 to 40% or from 20 to 40%, by weight of (meth)acrylate-functionalized monomer based on the total weight of the curable composition. Alternatively, the curable composition of the invention may comprise from 40 to 80%, from 40 to 75%, from or 40 to 70%, from 40 to 65% or from 40 to 60%, by weight of (meth)acrylate-functionalized monomer based on the total weight of the curable composition. In one embodiment, the ethylenically unsaturated compound comprises a (meth)acrylate- functionalized oligomer. The ethylenically unsaturated compound may comprise a mixture of (meth)acrylate-functionalized oligomers.

The (meth)acrylate-functionalized oligomer may be selected in order to enhance the flexibility, strength and/or modulus, among other attributes, of a cured polymer prepared using the curable composition of the present invention.

The (meth)acrylate functionalized oligomer may have 1 to 18 (meth)acrylate groups, in particular 2 to 6 (meth)acrylate groups, more particularly 2 to 6 acrylate groups.

The (meth)acrylate functionalized oligomer may have a number average molecular weight equal or more than 600 g/mol, in particular 800 to 15,000 g/mol, more particularly 1 ,000 to 5,000 g/mol.

In particular, the (meth)acrylate-functionalized oligomers may be selected from the group consisting of (meth)acrylate-functionalized urethane oligomers (sometimes also referred to as “urethane (meth)acrylate oligomers,” “polyurethane (meth)acrylate oligomers” or “carbamate (meth)acrylate oligomers”), (meth)acrylate-functionalized epoxy oligomers (sometimes also referred to as “epoxy (meth)acrylate oligomers”), (meth)acrylate-functionalized polyether oligomers (sometimes also referred to as “polyether (meth)acrylate oligomers”), (meth)acrylate-functionalized polydiene oligomers (sometimes also referred to as “polydiene (meth)acrylate oligomers”), (meth)acrylate-functionalized polycarbonate oligomers (sometimes also referred to as “polycarbonate (meth)acrylate oligomers”), and (meth)acrylate-functionalized polyester oligomers (sometimes also referred to as “polyester (meth)acrylate oligomers”) and mixtures thereof.

Exemplary polyester (meth)acrylate oligomers include the reaction products of acrylic or methacrylic acid or mixtures or synthetic equivalents thereof with hydroxyl group-terminated polyester polyols. The reaction process may be conducted such that all or essentially all of the hydroxyl groups of the polyester polyol have been (meth)acrylated, particularly in cases where the polyester polyol is difunctional. The polyester polyols can be made by polycondensation reactions of polyhydroxyl functional components (in particular, diols) and polycarboxylic acid functional compounds (in particular, dicarboxylic acids and anhydrides). The polyhydroxyl functional and polycarboxylic acid functional components can each have linear, branched, cycloaliphatic or aromatic structures and can be used individually or as mixtures. Examples of suitable epoxy (meth)acrylates include the reaction products of acrylic or methacrylic acid or mixtures thereof with an epoxy resin (polyglycidyl ether or ester). The epoxy resin may, in particular, by selected from bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, brominated bisphenol A diglycidyl ether, brominated bisphenol F diglycidyl ether, brominated bisphenol S diglycidyl ether, epoxy novolak resin, hydrogenated bisphenol A diglycidyl ether, hydrogenated bisphenol F diglycidyl ether, hydrogenated bisphenol S diglycidyl ether, 3,4-epoxycyclohexylmethyl-3',4'- epoxycyclohexanecarboxylate, 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane-1 ,4- dioxane, bis(3,4-epoxycyclohexylmethyl)adipate, vinylcyclohexene oxide, 4- vinylepoxycyclohexane, bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate,3,4-epoxy-6- methylcyclohexy l-3',4'-epoxy-6'-methylcyclohexanecarboxylate, methylenebis(3,4- epoxycyclohexane), dicyclopentadiene diepoxide, di(3,4-epoxycyclohexylmethyl) ether of ethylene glycol, ethylenebis(3, 4-epoxycyclohexanecarboxylate), 1 ,4-butanediol diglycidyl ether, 1 ,6-hexanediol diglycidyl ether, glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, polyglycidyl ethers of a polyether polyol obtained by the addition of one or more alkylene oxides to an aliphatic polyhydric alcohol such as ethylene glycol, propylene glycol, and glycerol, diglycidyl esters of aliphatic long-chain dibasic acids, monoglycidyl ethers of aliphatic higher alcohols, monoglycidyl ethers of phenol, cresol, butyl phenol, or polyether alcohols obtained by the addition of alkylene oxide to these compounds, glycidyl esters of higher fatty acids, epoxidized soybean oil, epoxybutylstearic acid, epoxyoctylstearic acid, epoxidized linseed oil, epoxidized polybutadiene, and the like.

Suitable polyether (meth)acrylate oligomers include, but are not limited to, the condensation reaction products of acrylic or methacrylic acid or synthetic equivalents or mixtures thereof with polyetherols which are polyether polyols (such as polyethylene glycol, polypropylene glycol or polytetramethylene glycol). Suitable polyetherols can be linear or branched substances containing ether bonds and terminal hydroxyl groups. Polyetherols can be prepared by ring opening polymerization of cyclic ethers such as tetrahydrofuran or alkylene oxides (e.g., ethylene oxide and/or propylene oxide) with a starter molecule. Suitable starter molecules include water, polyhydroxyl functional materials, polyester polyols and amines.

Polyurethane (meth)acrylate oligomers (sometimes also referred to as “urethane (meth)acrylate oligomers”) suitable for use in the curable compositions of the present invention include urethanes based on aliphatic, cycloaliphatic and/or aromatic polyester polyols and polyether polyols and aliphatic, cycloaliphatic and/or aromatic polyester diisocyanates and polyether diisocyanates capped with (meth)acrylate end-groups. Suitable polyurethane (meth)acrylate oligomers include, for example, aliphatic polyester-based urethane di- and tetra-acrylate oligomers, aliphatic polyether-based urethane di- and tetra- acrylate oligomers, as well as aliphatic polyester/polyether-based urethane di- and tetra- acrylate oligomers.

The polyurethane (meth)acrylate oligomers may be prepared by reacting aliphatic, cycloaliphatic and/or aromatic polyisocyanates (e.g., diisocyanate, triisocyanate) with OH group terminated polyester polyols, polyether polyols, polycarbonate polyols, polycaprolactone polyols, polyorganosiloxane polyols (e.g., polydimethylsiloxane polyols), or polydiene polyols (e.g., polybutadiene polyols), or combinations thereof to form isocyanate- functionalized oligomers which are then reacted with hydroxyl-functionalized (meth)acrylates such as hydroxyethyl acrylate or hydroxyethyl methacrylate to provide terminal (meth)acrylate groups. For example, the polyurethane (meth)acrylate oligomers may contain two, three, four or more (meth)acrylate functional groups per molecule. Other orders of addition may also be practiced to prepare the polyurethane (meth)acrylate, as is known in the art. For example, the hydroxyl-functionalized (meth)acrylate may be first reacted with a polyisocyanate to obtain an isocyanate-functionalized (meth)acrylate, which may then be reacted with an OH group terminated polyester polyol, polyether polyol, polycarbonate polyol, polycaprolactone polyol, polydimethylsiloxane polyol, polybutadiene polyol, or a combination thereof. In yet another embodiment, a polyisocyanate may be first reacted with a polyol, including any of the aforementioned types of polyols, to obtain an isocyanate-functionalized polyol, which is thereafter reacted with a hydroxyl-functionalized (meth)acrylate to yield a polyurethane (meth)acrylate. Alternatively, all the components may be combined and reacted at the same time.

Suitable acrylic (meth)acrylate oligomers (sometimes also referred to in the art as “acrylic oligomers”) include oligomers which may be described as substances having an oligomeric acrylic backbone which is functionalized with one or (meth)acrylate groups (which may be at a terminus of the oligomer or pendant to the acrylic backbone). The acrylic backbone may be a homopolymer, random copolymer or block copolymer comprised of repeating units of acrylic monomers. The acrylic monomers may be any monomeric (meth)acrylate such as C1- C6 alkyl (meth)acrylates as well as functionalized (meth)acrylates such as (meth)acrylates bearing hydroxyl, carboxylic acid and/or epoxy groups. Acrylic (meth)acrylate oligomers may be prepared using any procedures known in the art, such as by oligomerizing monomers, at least a portion of which are functionalized with hydroxyl, carboxylic acid and/or epoxy groups (e.g., hydroxyalkyl(meth)acrylates, (meth)acrylic acid, glycidyl (meth)acrylate) to obtain a functionalized oligomer intermediate, which is then reacted with one or more (meth)acrylate- containing reactants to introduce the desired (meth)acrylate functional groups.

The curable composition of the invention may comprise from 0 to 80%, from 5 to 70%, from 10 to 60%, from 15 to 50% or from 20 to 40%, by weight of (meth)acrylate-functionalized oligomer based on the total weight of the curable composition. In particular, the curable composition of the invention may comprise from 0 to 40%, from 5 to 40%, from 10 to 40%, from 15 to 40% or from 20 to 40%, by weight of (meth)acrylate-functionalized oligomer based on the total weight of the curable composition. Alternatively, the curable composition of the invention may comprise from 40 to 80%, from 40 to 75%, from or 40 to 70%, from 40 to 65% or from 40 to 60%, by weight of (meth)acrylate-functionalized oligomer based on the total weight of the curable composition.

In one embodiment, the ethylenically unsaturated compound comprises an amine-modified acrylate. The ethylenically unsaturated compound may comprise a mixture of amine-modified acrylates.

An amine-modified acrylate is obtained by reacting an acrylate-functionalized compound with an amine-containing compound (aza-Michael addition). The amine-modified acrylate comprises at least one remaining acrylate group (i.e. an acrylate group that has not reacted with the amine-containing compound during the aza-Michael addition) and/or at least one (meth)acrylate group (which may not be reactive towards primary or secondary amines).

The acrylate-functionalized compound may be an acrylate-functionalized monomer and/or acrylate-functionalized oligomer as defined above.

The amine-containing compound comprises a primary or secondary amino group and optionally a tertiary amino group. The amine-containing compound may comprise more than one primary and/or secondary amino groups. The amine-containing compound may be selected from monoethanolamine (2-aminoethanol), 2-ethylhexylamine, octylamine, cyclohexylamine, sec-butylamine, isopropylamine, diethylamine, diethanolamine, dipropylamine, dibutylamine, 2-(methylamino)ethano-1 ,2-methoxyethylamine, bis(2- hydroxypropyl)amine, diisopropylamine, dipentylamine, dihexylamine, bis(2-ethylhexyl)amine, 1 ,2,3,4-tetrahydroisoquinoline, N-benzylmethylamine, morpholine, piperidine, dioctylamine, and di-cocoamine, dimethylaminopropylamine, dimethylaminopropylaminopropylamine, 1 ,4- bis(3-aminopropyl)piperazine, 1 ,3-bis(aminomethyl)cyclohexane, 1 ,4-bis(3- aminopropyl)piperazine, aniline and an optionally substituted benzocaine (ethyl-4- aminobenzoate).

Examples of commercially available amine-modified acrylates include CN3705, CN3715, CN3755, CN381 and CN386, all available from Arkema. Polymeric or multi-amino versions are also suitable.

The curable composition may comprise from 0% to 25%, in particular 2.5% to 20%, more particularly 5 to 15%, by weight of amine-modified acrylate based on the total weight of the curable composition.

The curable composition may be radiation-curable, peroxide-curable, amine-curable or curable by a method combining the afore-mentioned methods of cure.

The curable composition may be a radiation-curable composition. A radiation-curable composition may be at least partially cured by exposing the composition to radiation, such as heat, a light source (in particular visible, UV, near-UV or infrared light source) and/or electron beam. For cure with a light source, at least one photoinitiator is present while for electron-beam cure no photoinitiator is required.

The photoinitiator may be a radical photoinitiator, in particular a radical photoinitiator having Norrish type I activity and/or Norrish type II activity, more particularly a radical photoinitiator having Norrish type II activity.

Non-limiting types of radical photoinitiators suitable for use in the curable compositions of the present invention include, for example, benzoins, benzoin ethers, acetophenones, a-hydroxy acetophenones, benzyl, benzyl ketals, anthraquinones, phosphine oxides, acylphosphine oxides, a-hydroxyketones, phenylglyoxylates, a-aminoketones, benzophenones, thioxanthones, xanthones, acridine derivatives, phenazene derivatives, quinoxaline derivatives, triazine compounds, benzoyl formates, aromatic oximes, metallocenes, acylsilyl or acylgermanyl compounds, camphorquinones, polymeric derivatives thereof, and mixtures thereof.

Examples of suitable radical photoinitiators include, but are not limited to, 2- methylanthraquinone, 2-ethylanthraquinone, 2-chloroanthraquinone, 2-benzyanthraquinone, 2-t-butylanthraquinone, 1 ,2-benzo-9,10-anthraquinone, benzyl, benzoins, benzoin ethers, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, alpha- methylbenzoin, alpha-phenylbenzoin, Michler’s ketone, acetophenones such as 2,2- dialkoxybenzophenones and 1-hydroxyphenyl ketones, benzophenone, 4,4’-bis-(diethylamino) benzophenone, acetophenone, 2,2-diethyloxyacetophenone, diethyloxyacetophenone, 2- isopropylthioxanthone, thioxanthone, diethyl thioxanthone, 1 ,5-acetonaphthylene, benzil ketone, a-hydroxy keto, 2,4,6-trimethylbenzoyldiphenyl phosphine oxide, benzyl dimethyl ketal, 2,2-dimethoxy-1 ,2-diphenylethanone, 1-hydroxycylclohexyl phenyl ketone, 2-methyl-1-[4- (methylthio) phenyl]-2-morpholinopropanone-1 , 2-hydroxy-2-methyl-1 -phenyl-propanone, oligomeric a-hydroxy ketone, benzoyl phosphine oxides, phenylbis(2,4,6- trimethylbenzoyl)phosphine oxide, ethyl(2,4,6-trimethylbenzoyl)phenyl phosphinate, anisoin, anthraquinone, anthraquinone-2-sulfonic acid, sodium salt monohydrate, (benzene) tricarbonylchromium, benzil, benzoin isobutyl ether, benzophenone/1-hydroxycyclohexyl phenyl ketone, 50/50 blend, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 4- benzoylbiphenyl, 2-benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone, 4,4'- bis(diethylamino)benzophenone, 4,4'-bis(dimethylamino)benzophenone, camphorquinone, 2- chlorothioxanthen-9-one, dibenzosuberenone, 4,4'-dihydroxybenzophenone, 2,2-dimethoxy-2- phenylacetophenone, 4-(dimethylamino)benzophenone, 4,4'-dimethylbenzil, 2,5- dimethylbenzophenone, 3,4-dimethylbenzophenone, diphenyl(2,4,6- trimethylbenzoyl)phosphine oxide /2-hydroxy-2-methylpropiophenone, 50/50 blend, 4'- ethoxyacetophenone, 2,4,6-trimethylbenzoyldiphenylphophine oxide, phenyl bis(2, 4,6- trimethyl benzoyl)phosphine oxide, ferrocene, 3'-hydroxyacetophenone, 4'- hydroxyacetophenone, 3-hydroxybenzophenone, 4-hydroxybenzophenone, 1- hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methylpropiophenone, 2-methylbenzophenone, 3-methylbenzophenone, methybenzoylformate, 2-methyl-4'-(methylthio)-2- morpholinopropiophenone, phenanthrenequinone, 4'-phenoxyacetophenone,

(cumene)cyclopentadienyl iron(ii) hexafluorophosphate, 9,10-diethoxy and 9,10- dibutoxyanthracene, 2-ethyl-9,10-dimethoxyanthracene, thioxanthen-9-one and combinations thereof.

The curable composition may be a peroxide-curable composition. A peroxide-curable composition may be at least partially cured by decomposition of a peroxide, in particular a hydroperoxide (R-O-O-H), a dialkyl peroxide (R-O-O-R) a peroxyacid (RC(O)-O-O-H), a peroxyester (RC(O)-O-O-R’), a diacyl peroxide (RC(0)-0-0-C(0)-R’), a peroxyketal and mixtures thereof, R and R’ being aliphatic, cycloaliphatic or aromatic groups. The peroxide may be decomposed by heating or using an activator at room temperature (20-25°C). The activator may be selected so as to promote the decomposition of the peroxide at room temperature such that curing is achieved without having to heat or bake the curable composition. In particular, the activator may be selected from an amine or a red/ox system, in particular a tertiary amine or red/ox system comprising a metallic salt or a potassium salt, more particularly a tertiary amine selected from N,N-dimethyl-p-toluidine (DMPT), N,N-dihydroxyethyl-p-toluidine (DHEPT), N,N-diethyl-p-toluidine (DEPT) and para-toluidine ethoxylate (PTE), or a red/ox system comprising a metallic salt selected from an iron salt, a copper salt, a cobalt salt, a manganese salt, a vanadium salt and mixtures thereof.

The curable composition may be an amine-curable composition. An amine-curable composition may be at least partially cured by Michael addition of an amine having free NH groups on a (meth)acrylate group of the urethane (meth)acrylate thus forming an aminoacrylate bond.

The method combining the afore-mentioned methods of cure means any binary or ternary combination said afore-mentioned cure methods.

According to a specific option of the invention, said curable composition is a radiation-curable composition selected from the group consisting of UV-curable, electron beam-curable.

According to a preferred option, said curable composition is a coating composition selected from a paint, varnish, ink, including inkjet ink and screen ink, adhesive, sealant or resist, composition or said curable composition is a composite material composition or a 3D-printing composition.

The present invention also relates to a cured product, which results from the cure of at least one urethane (meth)acrylate according to the present invention or from the cure of at least one curable composition according to the present invention.

Preferably, the cured product is a coating selected from a paint, a varnish, an ink, including inkjet ink and screen ink, an adhesive, a sealant or a resist or it is a composite material or a 3D printed article.

Uses

Another subject-matter of the present invention relates to the use of the urethane (meth)acrylate of the invention in a coating composition selected from a paint, a varnish, an ink, an adhesive, a sealant or a resist compositions, in a composite material composition or in a 3D article printing compositions. More particularly, the urethane (meth)acrylate of the invention may be used to obtain compositions having a lower viscosity compared to that of a composition comprising a urethane (meth)acrylate that is not according to the present invention in equivalent amounts.

The following examples are given by way of illustrating the present invention and its performances and do not in any way limit its coverage, the latter being defined by the claims.

Examples

Methods

The following methods were used herein:

Viscosity

The viscosity was measured at 60 °C using Brookfield viscometer RVDVII+ at 100 rpm with spindle 27 or at 6 rpm with spindle18.

Urethane bond content

The %wt of urethane bonds (%U) is based on the number average molecular weight of the urethane (meth)acrylate and was calculated with the following equation: a x 59

% U = x 100

Mn wherein a is the number of urethane bonds -0-(C=0)-NH- or -NH-(C=0)-0- in the urethane (meth)acrylate;

59 corresponds to the molecular weight of one urethane bond;

Mn is the number average molecular weight of the urethane (meth)acrylate obtained by calculation using the number average molecular weight of the components used to form the urethane (meth)acrylate.

For example, for a urethane (meth)acrylate of formula (I) obtained by reacting hydroxylated (meth)acrylates of formula (II) and (IV), a diol of formula (VI) and a diisocyanate of formula (XIV): (I)

OH-D-OH (VI).

OCN-B-NCO (XIV) the %wt of urethane bonds (%U) may be obtained with the following equation: wherein b is the number of repeating units -[D-0-C(=0)-NH-B-NH-C(=0)-0]-;

MP _A is the number average molecular weight of the hydroxylated (meth)acrylate of formula (II);

MP _A ’ is the number average molecular weight of the hydroxylated (meth)acrylate of formula (IV);

MPB is the number average molecular weight of the diisocyanate of formula (XIV);

Mn _D is the number average molecular weight of the diol of formula (VI). Number average molecular weight

The number average molecular weight of the components used to form the urethane (meth)acrylate (i.e. the hydroxylated (meth)acrylates of formula (II) and (IV), the diol of formula (VI) and the diisocyanate of formula (XIV)) were obtained from the suppliers of each component (technical data sheet of the component). The number average molecular weight of the urethane (meth)acrylate may be measured by gel permeation chromatography (GPC) using polystyrene standards. The measurement conditions of GPC are given below:

Model: Hitachi High-Technologies Corporation made by high-performance liquid chromatogram LaChrom Elite® Column: SHODEX GPC KF-G/-401 HQ/-402.5HQ/-403HQ (4.6 x 250 mm)

Eluent: THF

Flow rate: 0.45 mL/min Temperature : 40 C

Injection volume and concentration of sample. : 5 pL, 10 mg/mL Detection: Rl (differential refractometer)

System to gather and process data: Hitachi EZChrome Elite

Materials

The following materials were used in the examples:

IPDI: isophorone diisocyanate (M = 222 g/mol) from Bayer HEA: hydroxyethyl acrylate from Nippon Shokubai (Mn = 116 g/mol)

AP-800 (BLEMMER ^® AP-800): polypropylene glycol acrylate (Mn = 826 g/mol) from NOF Corporation

SR495: polycaprolactone acrylate (Mn = 344 g/mol) from Sartomer PolyTHF® 650: polyoxytetramethylene diol (Mn = 650 g/mol) from BASF PTG-L 1000: polyoxytetramethylene diol (Mn = 1222 g/mol) from Hodogaya Chem PTG-L 3500: polyoxytetramethylene diol (Mn of 3772 g/mol), from Hodogaya Chem

25.8 grams of isophorone diisocyanate (IPDI), 0.2 gram of (BHT) and 0.2 gram of dibutyltin dilaurate (DBTDL) were charged into a 1000 ml reactor and agitated at 25°C for 15 min. 14.8 grams of HEA were added drop-wise over 80 min with dry air sparge, allowing the batch to exotherm to 60°C, over the first 30 min to control remaining %NCO around 3.2% ~ 3.7%. The mixture was then heated to 75°C and 41 .5 grams of RclyTHF® 650 were slowly added over 30 min, allowing the batch to exotherm to 90°C over the first 30 min. The mixture was then maintained at 90°C until confirming appropriate %NOO consumption (<0.06%).

Example 1 was reproduced using 43.8 grams of SR495 instead of HEA (SR495 replacing HEA in same molar amount).

Example 3 (invention) Example 1 was reproduced using 115.4 grams of AP-800 instead of HEA (AP-800 replacing HEA in same molar amount).

25.8 grams of isophorone diisocyanate (IPDI), 0.2 gram of (BHT) and 0.2 gram of dibutyltin dilaurate (DBTDL) were charged into a 1000 ml reactor and agitated at 25°C for 15 min. 14.8 grams of HEA were added drop-wise over 80 min with dry air sparge, allowing batch to exotherm to 60°C over the first 30 min to control emaining %NCO around 3.2% ~ 3.7%. The mixture was then heated to 75°C and 58.4 grams of PTG-L 1000 over 30 min, allowing the batch to exotherm to 90°C over the first 30 min. The mixture was then maintained at 90°C until confirming appropriate %NCO consumption (<0.06%).

Example 7 was reproduced using 43.8 gram of SR495 instead of HEA (SR495 replacing HEA in same molar amount).

Example 5 was reproduced using 115.4 grams of AP-800 instead of HEA (AP-800 replacing HEA in same molar amount).

25.8 grams of isophorone diisocyanate (IPDI), 0.2 gram of (BHT) and 0.2 gram of dibutyltin dilaurate (DBTDL) were charged into a 1000 ml reactor and agitated at 25°C for 15 min. 14.8 grams of HEA were added drop-wise over 80 min with dry air sparge, allowing the batch to exotherm to 60°C over the first 30 min to control emaining %NCO around 3.2% ~ 3.7%. The mixture was then heated to 75°C and 192.1 grams ofPTG-L 3500 were slowly added over 30 min, allowing the batch to exotherm to 90°C over the first 30 min. The mixture was then maintained at 90°C until confirming appropriate %NOO consumption (<0.06%).

Example 7 was reproduced using 43.8 grams of SR495 instead of HEA (SR495 replacing HEA in same molar amount). Example 9 (comparative)

Example 7 was reproduced using 115.4 grams of AP-800 instead of HEA (AP-800 replacing HEA in same molar amount).

Example 10 : Applicative properties The characteristics of the urethane (meth)acrylates of Examples 1 -9 are presented in the table below.

The urethane (meth)acrylates of the invention have a significantly reduced viscosity compared to that of the comparative examples.