WO2024033289A1 - A photocurable oligomer containing uretdione groups, method of preparing the oligomer and dual-cure resin composition containing the oligomer thereof - Google Patents

Abstract

A photocurable oligomer having at least one uretdione group and at least one ethylenically unsaturated group, derived from a compound (A) having an active hydrogen-containing group and at least one ethylenically unsaturated group and a uretdione precusor compound (B) having at least one isocyanate group. A dual-cure resin composition, comprising (a) the aforesaid oligomer; (b) a photo-polymerizable compound which is different from the oligomer (a); and (c) a photoinitiator.

Description

A photocurable oligomer containing uretdione groups, method of preparing the oligomer and dual-cure resin composition containing the oligomer thereof

Technology Field

The present invention relates to the technical field of chemical materials for three-dimensional (hereinafter referred to as “3D”) printing, and in particular relates to a photocurable oligomer containing uretdione groups, to a method of preparing the oligomer, to a dual-cure resin composition containing the oligomer.

Background

Traditional unsaturated urethane (meth)acrylate oligomers offer a wide range of mechanical properties, from which ones with high performance usually have high viscosity. This issue could limit the portion of such oligomers and also urethane content in curable resin compositions and therefore impede the optimization of overall properties. Dual-cure functionalized urethane (meth)acrylate oligomers, which contain both unsaturated (meth)acrylate groups and residual active isocyanates, can afford improved properties when formulating with resins having active hydrogen-containing groups.

U.S. Pat. No. 9,175,117 invented a composition containing polyuretdiones, polyols, and free radical curable monomers to enable the production of prepreg materials for composites. After thermal curing the crosslinked polyurethanes and polyacrylates are formed as inter-penetrating networks in principle.

U.S. Pat. No. 9,453,142 described urethane (meth)acrylate compositions containing a reacitve blokced prepolymer based on a dual-cure mechanism for additive manufacturing applications.

However, the mechnical properties of current dura-cure composition containing functionalized urethane (meth)acrylate oligomers are still not satisfied. They suffer the common disadvantage of polymer materials used in 3D printing that good toughness and stiffness can not be aquired at the same time.

Therefore there is a strong need to develop a new liquid oligomer having the capability to further improve mechanical properties and being storage-stable for 1 K system as well, which could benefit a variety of applications such as 3D printing, adhesives, coatings, composites, etc.

Summary of the invention

The photocurable oligomer according to the present invention is a new liquid oligomer having low viscosity and high urethane content which can be used for the photopolymerized composition. The free isocyanate groups released at thermal treatment would react with the active hydrogen-containing groups to form urethanes/ureas to tune mechanical properties. Furthermore, the composition containing the photocurable oligomer shows excellent storage stability and excellent printing accuracy, and meanwhile good printability and improved mechanical properties, especially improved Young’s modulus and impact strength to enable the development of 3D objects.

It has been surprisingly found that above advantages can be achieved by following embodiments:

A photocurable oligomer having at least one uretdione group and at least one ethylenically unsaturated group, derived from a compound (A) having an active hydrogen-containing group and at least one ethylenically unsaturated group and a uretdione precusor compound (B) having at least one isocyanate group.

In one embodiment, the photocurable oligomer has the structure ( I ) and/or the structure (II)

wherein n is an integer of 1 to 5; m is an integer of 1 to 8; each R¹ is independently selected from alkylene groups having 1 to 18 carbon atoms, arylene groups having 6 to 18 carbon atoms, and arylalkylene and alkylarylene groups having 7 to 18 carbon atoms, wherein alkylene groups, alkylene portions of arylalkylene groups, and alkyl portions of alkylarylene groups may be linear, branched, or cyclic;

X is independently a radical derived from the compound (A) by abstracting a hydrogen atom of an active hydrogen-containing group; and Y is a moiety derived from a chain extender compound (C) having at least one active hydrogen-containing group by abstracting at least one hydrogen atom of active hydrogencontaining groups. In a preferred embodiment, the compound (A) of the photocurable oligomer is an ester of an aliphatic or aromatic polyol or epoxy and an acrylic or methacrylic acid, an amide of an amino alcohol and an acrylic or methacrylic acid, or an unsaturated polyetherol or polyesterol or polyacrylate polyol.

In a preferred embodiment, the uretdione precusor compound (B) of the photocurable oligomer is uretdione precusor momomer Bi having the structure (III) when the photocurable oligomer has the structure ( I )

In a preferred embodiment, the uretdione precusor compound (B) of the photocurable oligomer is uretdione precusor prepolymer B2 having the structure (IV) when the photocurable oligomer has the structure ( II )

In a more preferred embodiment, the compound (C) of the photocurable oligomer is nucleophile chain extender including multifunctional alcohols, thiols, or amines, and/or functional chain extender including hydrophilic chain extender.

Another object of the present invention is to provide a process for the production of the photocurable oligomer having structure ( I ) which comprises ( i ) reacting the uretdione precusor monomer (B1) with the compound (A) so that both terminal isocyanate groups of compound (B1) are reacted, optionally with the presence of a catalyst; optionally (ii) adding a radical inhibitor.

A further object of the present invention is to provide a process for the production of the photocurable oligomer having structure ( II) which comprises (ia) reacting the uretdione precusor monomer (B1) with compound (A) so that one side of terminal isocyanate groups of compound (B1) are reacted, which forms the uretdione precusor prepolymer (B2); ( i ) reacting the uretdione precusor prepolymer (B2) with compound (C) so that another side of terminal isocyanate groups of compound (B2) are reacted , optionally with the presence of a catalyst; and optionally (ii) adding a radical inhibitor.

A still further object of the present invention is to provide a dual-cure resin composition containing the photocurable oligomer thereof, wherein the dual-cure composition comprises (a) at least one photocurable oligomer; (b) at least one photo-polymerizable compound which is different from the oligomer (a); and (c) at least one photoinitiator.

A yet further object of the present invention is to provide 3D objects formed by using the dualcure composition.

Embodiment of the invention

Unless defined otherwise, all technical and scientific terms used herein have the meaning commonly understood by a person skilled in the art to which the invention belongs. As used herein, the following terms have the meanings ascribed to them below, unless specified otherwise.

As used herein, the articles "a", "an" and “the” refer to one or more of the species designated by the term following said article.

In the context of the present disclosure, any specific values mentioned for a feature (comprising the specific values mentioned in a range as the end point) can be recombined to form a new range.

Photocurable oligomer (a)

One aspect of the present invention is directed to a photocurable oligomer having at least one uretdione group and at least one ethylenically unsaturated group, derived from a compound (A) having an active hydrogen-containing group and at least one ethylenically unsaturated group and a uretdione precusor compound (B) having at least one isocyanate group.

In one embodiment, the oligomer has the structure ( I )

wherein n is an integer of 1 to 5, each R¹ is independently selected from alkylene groups having 1 to 18 carbon atoms, arylene groups having 6 to 18 carbon atoms, and arylalkylene and alkylarylene groups having 7 to 18 carbon atoms, wherein alkylene groups, alkylene portions of arylalkylene groups, and alkyl portions of alkylarylene groups may be linear, branched, or cyclic;

X is independently a radical derived from the compound (A) by abstracting a hydrogen atom of an active hydrogen-containing group.

In another embodiment, the oligomer has the structure ( II )

wherein m is an integer of 1 to 8;

Y is a moiety derived from a chain extender compound (C) having at least one active hydrogencontaining group by abstracting at least one hydrogen atom of active hydrogen-containing groups.

In a further embodiment, the oligomer has the structure ( I ) and the structure ( II ).

When the oligomer has the structure ( I ), the uretdione precusor compound (B) is uretdione precusor momomer (Bi) having the structure (III)

When the oligomer has the structure ( II ), the uretdione precusor compound (B) is uretdione precusor prepolymer (B2) having the structure (IV)

In certain embodiment, X is the radical of structure (V) or structure (VI)

wherein

R² is divalent alkyl, aryl, alkylaryl or arylalkyl having up to 12 carbon atoms,

R³, R⁴ and R⁵ are each independently H or a radical of structure (VII), and at least one of R³, R⁴ and R⁵ are selected from structure (VII),

(VII), wherein

R⁶ is hydrogen or Ci-Ce alkyl,

R⁷ is selected from divalent C1-C20 alkyl group, C1-C20 alkoxy group or C2-C20 carbonyl group.

Another aspect of the present invention is directed to a process for the production of the photocurable oligomer having structure ( I ), which comprises ( i ) reacting a uretdione precursor monomer (Bi) with compound (A) so that both terminal isocyanate groups of compound (Bi) are reacted, optionally with the presence of a catalyst.

Further aspect of the present invention is directed to a process for the production of the photocurable oligomer having structure ( II), which comprises (ia) reacting the uretdione precusor monomer (Bi) with compound (A) so that one side of terminal isocyanate (NCO) groups of compound (Bi) are reacted, which forms the uretdione precusor prepolymer (B2); ( i ) reacting the uretdione precusor prepolymer (B2) with compound (C) so that another side of terminal isocyanate groups of compound (B2) are reacted, optionally with the presence of a catalyst. It has to be pointed out that during the process of (ia), it’s inevitable to obtain a mixture of compounds with one side of NCO reacted and both side of NCO reacted. In the reaction of the process, uretdione precursor compound (B) is capped with compound (A) by reacting one mole of compound (B) with equivalent moles of compound (A) so that all terminal isocyanate groups of compound (B) are reacted. The reaction may be carried out under typical conditions for reaction of isocyanate groups with active hydrogen-containing groups with the proviso that uretdione groups do not react under the selected reaction conditions.

In certain embodiments, the reaction is carried out at a temperature of from about 20°C to about 100°C, optionally in the presence of a catalyst. In other embodiments, the reaction may be carried out at a temperature of from about 20°C to about 80°C or at a temperature of from about 50°C to about 80°C, again optionally in the presence of a catalyst. While a temperature above 100°C is generally not preferred, such a temperature may be used if under the reaction conditions, the uretdione groups of the compound (B) do not ring open to any appreciable extent (and preferably does not ring open at all).

Nonlimiting, illustrative examples of suitable catalysts that may be used during the reaction include tertiary amines such as triethylamine, DABCO, and organotin and organobismuth compounds such as dibutyltin dilaurate, dibutyltin oxide, bismuth octoate, and combinations of these. The amount of catalyst, if used, is generally from about 0.01 to about 5 wt.% based on the total weight of compounds (A) and (B). The catalyst in certain embodiments may be from about 0.05 to about 2 wt.% based on the total weight of compounds (A) and (B), or may be from about 0.1 to about 1 wt.% based on the total weight of compounds (A) and (B).

The reaction can be followed by disappearance of free isocyanate groups, which may be determined for example by titration (e.g. reaction with excess secondary amine and titration of the residual amine with acid) or by infrared spectrophotometry (i.e. FTIR). The reaction may be carried out at atmospheric pressure, but higher pressures may also be used. The reaction product oligomer may be isolated before being used for the dual-cure composition or may be used without isolation or purification for the dual-cure composition. The reaction time until completion will vary depending upon the factors the person skilled in carrying out reaction like this should expect, such as presence or absence of catalyst, type of catalyst, reaction temperature, particular reactants selected, and concentration of reactants in the reaction medium.

In a prefered embodiment, the reaction can be occured without solvent when all reactants are low-viscous liquid. In this condition, there is no need to remove extra solvent.

Compounds (A) and (B) are commercially available. The compound (A) from which the radical X is derived are, for example, esters of a, p-unsaturated carboxylic acids, such as acrylic acid, methacrylic acid (referred to below for short as (meth)acrylic acid), crotonic acid, acrylamidogly colic acid, methacrylamidoglycolic acid or vinylacetic acid and polyols having preferably 2 to 20 carbon atoms and at least two hydroxyl groups, such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-propylene glycol, dipropylene glycol, tripropylene glycol, 1 ,4-butanediol, 1 ,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 2- methyl-1,5-pentanediol, 2-ethyl-1,4-butanediol, 1,4-dimethylolicyclohexane, glycerol, trimethylolethane, trimethylol propane, trimethylolbutane, pentaerythritol, ditrimethylolpropane, erythritol and sorbitol, provided the ester has one isocyanate-reactive OH group. Examples are caprolactone acrylate, 2-Methacryloyloxy ethyl 2-hydroxy propyl phthalate, 2-Acryloyloxy ethyl 2-hydroxy propyl phthalate and 2-Hydroxyl-3-phenoxy propylacrylate.

The compound (A) may also be the amides of (meth)acrylic acid with amino alcohols, examples being 2-aminoethanol, 3-amino-1-propanol, 1-amino-2-propanol and 2-(2-aminoethoxy) ethanol, and from the vinyl ethers of the above mentioned polyols, provided they still have one free OH group. Examples of amides of ethylenically unsaturated carboxylic acids with amino alcohols are hydroxyalkyl (meth) acrylamides such as N-hydroxymethyl acrylamide, N-hydroxymethyl methacrylamide, N-hydroxyethyl acrylamide, N-hydroxyethyl methacrylamide, 5-hydroxy-3- oxopentyl (meth)acrylamide, N-hydroxyalkyl crotonamides such as N-hydroxymethyl crotonamide, N-hydroxyalkyl maleimides such as N-hydroxyethyl maleimide.

Further suitable compound (A) are unsaturated polyetherols or polyesterols or polyacrylate polyols having one isocyanate-reactive OH group.

The compound (A) are preferably alcohols such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, 1,4-butanediol mono(meth)acrylate, neopentyl glycol mono(meth)acrylate, glycerol mono- and di(meth) acrylate, trimethylolpropane mono- and di(meth)acrylate, pentaerythritol di- and tri(meth)acrylate, dipentaerythritol pentaacrylate and poly ethoxy(10) ethyl (meth)acrylate. With particular preference the compound (A) are selected from hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxybutyl acrylate, pentaerythritol triacrylate, and poly ethoxy(10) ethyl methacrylate.

Uretdione precursor compound (B) may be made, for example, by dimerization of diisocyanates according to well known methods, for example as described in U.S. patent application Publication No. US 2007/0032594, incorporated herein by reference. Some trimerization of the diisoycanate (to form an isocyanurate) may also occur. Commercial sources of uretdiones may contain 5 to 30% by weight of the corresponding isocyanurate of the diisocyanate. While not necessarily preferred, presence of the trimer compound does not generally cause problems in the reaction, but when a mixture of the uretdione and isocyanurate of a diisocyanate is used, the oligomer product will be expected to also contain the reaction product of the isocyanurate and compound (A).

By including polyisocyanate compounds, compound (B) having an average uretdione ring functionality greater than 1 can be prepared. As used herein, the term “polyisocyanate” means any organic compound that has two or more reactive isocyanate ( — NCO) groups in a single molecule such as, for example, diisocyanates, triisocyanates, tetraisocyanates, and mixtures thereof. Exemplary polyisocyanates that can be used to prepare uretdione-containing compounds include: 1) (cyclo)aliphatic diisocyanates such as 1 ,2-ethylene diisocyanate; 1 ,4- tetramethylene diisocyanate; 1 ,6-hexamethylene diisocyanate; 2,2,4-trimethyl-1 ,6- hexamethylene diisocyanate; 2,4,4-trimethyl-1,6-hexamethylene diisocyanate; 1 ,9-diisocyanato- 5-methylnonane; 1 ,8-diisocyanato-2,4-dimethyloctane; 1 ,12-dodecane diisocyanate; w,w'- diisocyanatodipropyl ether; cyclobutene 1 ,3-diisocyanate; cyclohexane 1 ,3-diisocyanate; cyclohexane 1 ,4-diisocyanate; 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate, IPDI), 1 ,4-diisocyanatomethyl-2,3,5,6-tetramethylcyclohexane; decahydro-8-methyl-(1 ,4-methanol-naphthalen)-2,5-ylenedimethylene diisocyanate; decahydro- 8-methyl-(1 ,4-methanol-naphthalen)-3,5-ylenedimethylene diisocyanate; hexa hydro-4, 7- methanoindan-1 ,5-ylenedimethylene diisocyanate; hexahydro-4, 7-methanoindan-2, 5- ylenedimethylene diisocyanate; hexahydro-4, 7-methanoindan-1 ,6-ylenedimethylene diisocyanate; hexahydro-4, 7-methanoindan-2,5-ylenedimethylene diisocyanate, hexahydro-4, 7- methanoindan-1 ,5-ylene diisocyanate; hexahydro-4, 7-methanoindan-2,5-ylene diisocyanate; hexahydro-4, 7-methanoindan-1 ,6-ylene diisocyanate; hexahydro-4, 7-methanoindan-2,6-ylene diisocyanate; 2,4-hexahydrotolylene diisocyanate; 2,6-hexahydrotolylene diisocyanate; 4,4'- methylenedicyclohexyl diisocyanate; 2,2'-methylenedicyclohexyl diisocyanate; 2,4- methylenedicyclohexyl diisocyanate; 4,4'-diisocyanato-3,3',5,5'-tetramethyldicyclohexylmethane; 4,4'-diisocyanato-2,2',3,3,5,5',6,6'-octamethyldicyclohexylmethane; w,w'-diisocyanato-1 ,4- diethylbenzene; 1 ,4-diisocyanatomethyl-2,3,5,6-tetramethylbenzene; 2-methyl-1 ,5- diisocyanatopentane; 2-ethyl-1 ,4-diisocyanatobutane; 1 ,10-diisocyanatodecane; 1 ,5- diisocyanatohexane; 1 ,3-diisocyanatomethylcyclohexane; 1 ,4-diisocyanatomethylcyclohexane; 2) aromatic diisocyanates such as 2,4-diphenylmethane diisocyanate; 4,4'-biphenylene diisocyanate; 3,3'-dimethoxy-4,4'-biphenyl diisocyanate; 3,3'-dimethyl-4, 4'-biphenyl diisocyanate; 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate; xylene diisocyanate; 3- methyldiphenylmethane-4,4'-diisocyanate; 1 ,1-bis(4-isocyanatophenyl)-cyclohexane; m- or p- phenylene diisocyanates; chlorophenylene-2,4-diisocyanate; 1 ,5-diisocyanatonaphthalene; 4,4'- biphenyl diisocyanate; 3,5'-dimethyldiphenyl-4,4'-diisocyanate; diphenyl ether-4,4'-diisocyanate; and 3) combinations thereof. Triisocyanates which may be used include, for example, trimerized isocyanurate versions of the diisocyanates listed above (e.g., the isocyanurate trimer of 1 ,6- hexamethylene diisocyanate and related compounds such as DESMODUR N 3300 from Covestro LLC, Pittsburgh, Pa.).

Mono-functional isocyanates may also be used (e.g., to vary the uretdione-containing compound average uretdione ring functionality). Examples include vinyl isocyanate; methyl isocyanatoformate; ethyl isocyanate; isocyanato(methoxy)methane; allyl isocyanate; ethyl isocyanatoformate; isopropyl isocyanate; propyl isocyanate; trimethylsilyl isocyanate; ethyl isocyanatoacetate; butyl isocyanate; cyclopentyl isocyanate; 2-isocyanato-2-methyl-propionic acid methyl ester; ethyl 3-isocyanatopropionate; 1-isocyanato-2,2-dimethylpropane; 1- isocyanato-3-methylbutane; 3-isocyanatopentane; pentyl isocyanate; 1-ethoxy-3- isocyanatopropane; phenyl isocyanate; hexyl isocyanate; 1-adamantyl isocyanate; ethyl 4- (isocyanatomethyl)cyclohexanecarboxylate; decyl isocyanate; 2-ethyl-6-isopropylphenyl isocyanate; 4-butyl-2-methylphenyl isocyanate; 4-pentylpheny isocyanate; undecyl isocyanate; 4-biphenylyl isocyanate; 4-phenoxyphenyl isocyanate; 2-benzylphenyl isocyanate; 4- benzylphenyl isocyanate; diphenylmethyl isocyanate; 4-(benzyloxy)phenyl isocyanate; hexadecyl isocyanate; octadecyl isocyanate; and combinations thereof. Preferred compound (B) include, for example, uretdione-containing compounds derived from hexamethylene diisocyanate.

The conversion of compound (B) having a single uretdione ring to having at least 2 uretdione rings (i.e. , a polyuretdione) may be accomplished by reaction of the free NCO groups with hydroxyl-containing compounds, which include monomers, polymers, or mixtures thereof. Examples of such compounds include, but are not limited to, polyesters, polythioethers, polyethers, polycaprolactams, polyepoxides, polyesteramides, polyurethanes or low molecular mass di-, tri- and/or tetraols as chain extenders, and if desired, mono-ols as chain terminators, for example, as described in EP 0 669 353, EP 0 669 354, DE 30 30 572, EP 0 639 598, EP 0 803 524, and U.S. Pat. No. 7,709,589. Useful compound (B) may optionally contains isocyanurate, biuret, and/or iminooxadiazinedione groups in addition to the uretdione groups. For example, compound (B) may include a uretdione of hexamethylene diisocyanate (HDI- dimer), a uretdione of isophorone diisocyanate (IDI-dimer), a uretdione of methylene dicyclohexyl diisocyanate (MDI-dimer), a uretdione of hydrogenated methylene dicyclohexyl diisocyanate (HMDI-dimer), and/or a uretdione of toluene diisocyanate (TDI-dimer). Further, compound (B) may include an isocyanaurate of hexamethylene diisocyanate (HDI-trimer), an isocyanaurate of isophorone diisocyanate (I Dl-trimer), an isocyanaurate of methylene dicyclohexyl diisocyanate (MDI-trimer), an isocyanaurate of hydrogenated methylene dicyclohexyl diisocyanate (HMDI-trimer), and/or an isocyanaurate of toluene diisocyanate (TDI- trimer). The chain extender (C) are low-molecular weight compound having at least two active hydrogens which react with isocyanate groups to build polyurethane/polyurea backbone and increase the block length of the hard segment. The chain extender can be selected from nucleophile chain extender and other functional chain extender used in polyurethane coating which is known to the person skilled in the art, such as hydrophilic chain extender.

The nucleophile chain extender are usually exemplified by multifunctional alcohol, thiol, or amine. Specific examples of alcohol include straight chain diols such as ethylene glycol, diethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1 ,5-pentanediol, 1,6-hexanediol, 2,4- heptanediol, 1,8-octanediol, 1 ,4-dimethylol hexane, 1,9-nonanediol, and 1,12-dodecanediol, dimerdiol; diols having branched chains such as 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3- propanediol, 2,2-diethyl-1 ,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2-ethyl-1 ,3- hexanediol, 2,2,4-trimethyl-1 ,3-pentanediol, 2-methyl-1,8-octanediol, and 2-butyl-2-ethyl-1 ,3- propanediol; diols having a ring group such as 1 ,4-cyclohexanediol, 1,4-cyclohexanedimethanol, and 1,4-dihydroxyethylcyclohexane; diols having aromatic group such as xylylene glycol, 1,4- dihydroxyethyl benzene, and 4,4'-methylenebis(hydroxyethyl benzene; polyols containing at least three hydroxyl groups such as glycerin, trimethylolpropane, pentaerythritol, sorbitol, xylitol, and mannitol which can be used to prepare branched uretdione precusor prepolymer so that produce branched photocurable oligomer containing uretdione groups of the invention. Amine such as N-methylethanolamine, and N-ethylethanolamine; polyamine such as ethylene diamine, 1 ,3-propane diamine, hexamethylenediamine, triethylenetetramine, diethylene triamine, isophoronediamine, 4,4'-diaminodicyclohexylmetane, 2-hydroxyethylpropylene diamine, di-2- hydroxyethylethylene diamine, di-2-hydroxyethylpropylene diamine, 2-hydroxypropylethylene diamine, di-2-hydroxypropylethylene diamine, 4,4'-diphenylmethanediamine, methylenebis(o- chloroaniline), xylylenediamine, diphenyldiamine, tolylenediamine, The use of diamine chain extenders such as polyoxypropylenediamine (Jeffamine D-230), 4,4'-diaminodibenzyl (MDA) and 3,5-diethyltoluene-2,4-diamine/3,5-diethyltoluene-2,4-diamine (Ethacure 100) results in a urea linkage that results in bidentate hydrogen bonding.

The hydrophilic chain extender can improve hydrophilicity of the oligomer. Examples of hydrophilic chain extenders are dimethylolpropionic acid, dimethylol butyric acid, dihydroxy half ester, N-methyl diethanolamine (N-MDEA), N-butyldiethanolamine, 2,2'-iminodiethanol or trishydroxyethylamine, preferably dimethylolbutanoic acid (DMBA), N-methyl diethanolamine (N- MDEA).

Optionally radical inhibitor of 100-1000 ppm equivalent can be added in the process for improving storage stability. Examples of the radical inhibitor can be phenolic based inhibitors such as hydroquinone (HQ), 4-methoxyphenol (MEHQ), , butylhydroxytoluene (BHT), hydroquinone monomethyl ether, 2,6-di-tert-butyl-p-cresol, 2,2-methylene-bis-(4-methyl-6-tert- butylphenol), and 1,1 ,3-tris-(2-methyl-4-hydroxy-5-tert-butylphenyl) butane, amine compounds such as phenothiazine, nitrosophenylhydroxylamine (NPHA) and its salts, aromatic amine stabilizers such as diphenylamine (DPA) and phenylenediamine (PPD), metal deactivators such as benzotriazole, Alkoxylamine (NOR) HALS stabilizers such as derivatives of 2, 2,6,6- tetramethyl piperidine, Nitroxyl stabilizers, including mixtures or combinations thereof.

Dual-cure resin composition

Another aspect of the present invention is directed to a dual-cure resin composition, which comprising at least the photocurable oligomer (a), at least a photo-polymerizable compound (b) and a photoinitiator (c).

The amount of component (a) can be in the range from 1 to 50 wt.%, for example 2 wt.%, 5 wt.%, 10 wt.%, 15 wt.%, 20 wt.%, 25 wt.%, 30 wt.%, 35 wt.%, or 40 wt.%, preferably from 2 to 40 wt.%, more preferably from 5 to 30 wt.%, based on the total weight of the dual-cure resin composition.

Photo-polymerizable compound (b)

According to a preferred embodiment of the invention, the functionality of the photo- polymerizable compound can be in the range from 1 to 30, for example 1.2, 1.5, 1.8, 2, 2.2. 2.5, 3, 3.5,4, 5, 6, 7, 8, 9, 10, 11 , 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, preferably 1 to 8, or 1.5 to 6, or 1.5 to 4.

According to the present invention, component (b) can comprise at least one monomer and/or oligomer containing one or more ethylenically unsaturated functional groups. A person skilled in the art could understand that the ethylenically unsaturated functional group in the context of the present disclosure is a radiation-curable group.

The amount of component (b) can be in the range from 10 to 95 wt.%, for example 15 wt.%, 20 wt.%, 30 wt.%, 40 wt.%, 50 wt.%, 60 wt.%, 70 wt.%, 80 wt.%, or 90 wt.%, preferably from 15 to 80 wt.%, more preferably from 20 to 70 wt.%, based on the total weight of the dual-cure resin composition.

The monomer can include (meth)acrylamides, (meth)acrylates, vinylamides, vinyl substituted heterocycles, di-substituted alkenes and mixtures thereof.

Examples of suitable (meth)acrylamides can include acryloylmorpholine, methacryloylmorpholine, N-(hydroxymethyl) (meth)acrylamide, N-hydroxyethyl (meth)acrylamide, N-isopropyl (meth)acrylamide, N-tert-butyl (meth)acrylamide, N,N'-methylene bis(meth)acrylamide, N-(isobutoxymethyl) (meth)acrylamide, N-(butoxymethyl) (meth)acrylamide, N-[3-(dimethylamino)propyl] (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N-hydroxymethyl (meth)acrylamide, N- hydroxyethyl (meth)acrylamide, N-isopropyl (meth)acrylamide and mixtures thereof. Examples of suitable (meth)acrylates can include monofunctional (meth)acrylates, such as isobornyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, ethoxylated phenyl (meth)acrylate, cyclohexyl(meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, octyl (meth)acrylate, isodecyl (meth)acrylate, tridecyl (meth)acrylate, caprolactone (meth)acrylate, nonyl phenol (meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate, methoxy polyethyleneglycol (meth)acrylates, methoxy polypropyleneglycol (meth)acrylates, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, glycidyl (meth)acrylate; bifunctional (meth)acrylates, such as 1 ,3- butylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, diethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, alkoxylated hexanediol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, 3-methyl-1 ,5-pentanediol di(meth)acrylate, dimethylol-tricyclodecane di(meth)acrylate; trifunctional (meth)acrylates, such as trimethylolpropane tri(meth)acrylate; tetrafunctional (meth)acrylates, such as bistrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)crylate, tetramethylolmethane tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, propoxylated pentaerythritol tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, ethoxylated dipentaerythritol tetra(meth)acrylate, propoxylated dipentaerythritol tetra(meth)acrylate, aryl urethane tetra(meth)acrylates, aliphatic urethane tetra(meth)acrylates, melamine tetra(meth)acrylates and mixtures thereof.

Examples of suitable vinylamides can include N-(hydroxymethyl)vinylamide, N-hydroxyethyl vinylamide, N-isopropylvinylamide, N-isopropylmethvinylamide, N-tert-butylvinylamide, N,N'- methylenebisvinylamide, N-(isobutoxymethyl)vinylamide, N-(butoxymethyl)vinylamide, N-[3- (dimethylamino)propyl]methvinylamide, N,N-dimethylvinylamide, N,N-diethylvinylamide, N- methyl-N-vinylacetamide and mixtures thereof.

Examples of suitable vinyl substituted heterocycles can include monovinyl substituteted heterocycles, wherein the heterocycle is a 5- to 8-membered ring containing 2 to 7 carbon atoms, and 1 to 4 (preferably 1 or 2) heteroatoms selected from N, O and S, such as vinylpyridines, N-vinylpyrrolidone, N-vinylmorpholin-2-one, N-vinyl caprolactam and 1- vinylimidazole, vinyl alkyl oxazolidinone such as vinyl methyl oxazolidinone. Particularly preferred are N-vinyloxazolidinone (VOX) and N-vinyl-5-methyl oxazolidinone (VMOX), most preferred is VMOX.

Di-substituted alkene refers to an alkene in which two of the substituents directly attached to the double-bonded carbon atoms are substituents that are other than hydrogen, preferably a hydrocarbyl group, more preferably straight or branched chain alkyl, straight or branched chain alkenyl, straight or branched chain alkynyl, cycloalkyl, alkyl substituted cycloalkyl, aryl, aralkyl, or alkaryl, wherein the hydrocarbyl groups may contain one or more heteroatoms in the backbone of the hydrocarbyl group. Both of the substituents can be attached to the same carbon of the carbon-carbon double bond. Alternatively, one substituent can be attached to each of the double-bonded carbons. Examples of suitable di-substituted alkenes can include 1 ,1 -disubstituted alkenes, preferably a-methylstyrene, 2-methyl-1-butene, 2-methylhept-1-ene, and 1,2-disubstituted alkenes, preferably cyclohexene or 2-methylhept-2-ene.

In one embodiment of the invention, the oligomer contains a core structure linked to the ethylenically unsaturated functional group, optionally via a linking group. The linking group can be an ether, ester, amide, urethane, carbonate, or carbonate group. In some instances, the linking group is part of the ethylenically unsaturated functional group, for instance an acryloxy or acrylamido group. The core group can be an alkyl (straight and branched chain alkyl groups), aryl (e.g. phenyl), polyether, polyester, siloxane, urethane, or other core structures and oligomers thereof. Suitable ethylenically unsaturated functional group may comprise carboncarbon double bond such as methacrylate, acrylate, vinyl ether, allyl ether, acrylamide, methacrylamide, or a combination thereof. In some embodiments, suitable oligomer comprise mono- and/or polyfunctional acrylate, such as mono (meth)acrylate, di(meth)acrylate, tri(meth)acrylate, or higher, or combination thereof. Optionally, the oligomer may include a siloxane backbone in order to further improve cure, flexibility and/or additional properties of the dual-cure resin composition for creation of objects with single or multiple layers.

In some embodiments, the oligomer can be selected from the following classes: urethane (i.e. a urethane-based oligomer containing ethylenically unsaturated functional group), polyether (i.e. an polyether-based oligomer containing ethylenically unsaturated functional group), polyester (i.e. an polyester-based oligomer containing ethylenically unsaturated functional group), polycarbonate (i.e. an polycarbonate-based oligomer containing ethylenically unsaturated functional group), polyestercarbonate (i.e. an polyestercarbonate-based oligomer containing ethylenically unsaturated functional group), epoxy (i.e. an epoxy-based oligomer containing ethylenically unsaturated functional group), silicone (i.e. a silicone-based oligomer containing ethylenically unsaturated functional group), polybutadiene (i.e. a polybutadiene-based oligomer containing ethylenically unsaturated functional group) or any combination thereof. Preferably, the reactive oligomer containing at least one ethylenically unsaturated functional group can be selected from the following classes: a urethane-based oligomer, an epoxy-based oligomer, a polyester-based oligomer, a polyether-based oligomer, a urethane acrylate-based oligomer, a polyether urethane-based oligomer, a polyester urethane-based oligomer, a silicone-based oligomer or a polybutadiene-based oligomer, as well as any combination thereof.

In one embodiment, the oligomer comprises a urethane-based oligomer comprising urethane repeating units and one or more ethylenically unsaturated functional groups, for example carbon-carbon unsaturated double bond such as (meth)acrylate, (meth)acrylamide, allyl and vinyl groups. Preferably, the oligomer contains at least one urethane linkage (for example, one or more urethane linkages) within the backbone of the oligomer molecule and at least one acrylate and/or methacrylate functional groups (for example, one or more acrylate and/or methacrylate functional groups) pendent to the oligomer molecule. In some embodiments, aliphatic, cycloaliphatic, or mixed aliphatic and cycloaliphatic urethane repeating units are suitable. Urethanes are typically prepared by the condensation of a diisocyanate with a diol. Aliphatic urethanes having at least two urethane moieties per repeating unit are useful. In addition, the diisocyanate and diol used to prepare the urethane comprise divalent aliphatic groups that may be the same or different.

In one embodiment, the oligomer comprises polyester urethane-based oligomer or polyether urethane-based oligomer containing at least one ethylenically unsaturated functional group. The ethylenically unsaturated functional group can be carbon-carbon unsaturated double bond, such as acrylate, methacrylate, vinyl, allyl, acrylamide, methacrylamide, etc., preferably acrylate and methacrylate. The functionality of these polyester or polyether urethane-based oligomer is 1 or greater, specifically about 2 ethylenically unsaturated functional groups per oligomer molecule.

Suitable urethane-based oligomers are known in the art and may be readily synthesized by a number of different procedures. For example, a polyfunctional alcohol may be reacted with a polyisocyanate (preferably, a stoichiometric excess of polyisocyanate) to form an NCO- terminated pre-oligomer, which is thereafter reacted with a hydroxy-functional ethylenically unsaturated monomer, such as hydroxy-functional (meth)acrylate. The polyfunctional alcohol may be any compound containing two or more OH groups per molecule and may be a monomeric polyol (e.g., a glycol), a polyester polyol, a polyether polyol or the like. The urethane-based oligomer in one embodiment of the invention is an aliphatic urethane-based oligomer containing (meth)acrylate functional group.

Suitable polyether or polyester urethane-based oligomers include the reaction product of an aliphatic or aromatic polyether or polyester polyol with an aliphatic or aromatic polyisocyanate that is functionalized with a monomer containing the ethylenically unsaturated functional group, such as (meth)acrylate group. In one embodiment, the polyether and polyester are aliphatic polyether and polyester, respectively. In one embodiment, the polyether and polyester urethane-based oligomers are aliphatic polyether and polyester urethane-based oligomers and comprise (meth)acrylate group.

Epoxy-based oligomer containing at least one ethylenically unsaturated functional group can be epoxy-based (meth)acrylate oligomer. The epoxy-based (meth)acrylate oligomer is obtainable by reacting epoxides with (meth)acrylic acid.

Examples of suitable epoxides include epoxidized olefins, epoxidized unsaturates, aromatic glycidyl ethers or aliphatic glycidyl ethers, especially those of aromatic or aliphatic glycidyl ethers.

Examples of possible epoxidized olefins include ethylene oxide, propylene oxide, isobutylene oxide, 1 -butene oxide, 2-butene oxide, vinyloxirane, styrene oxide or epichlorohydrin, preference being given to ethylene oxide, propylene oxide, isobutylene oxide, vinyloxirane, styrene oxide or epichlorohydrin, particular preference to ethylene oxide, propylene oxide or epichlorohydrin, and very particular preference to ethylene oxide and epichlorohydrin.

Examples of epoxidized unsaturates include epoxidized soybean oil, epoxidized linseed oil, epoxidized castor oil, epoxidized palm oil, epoxidized vegetable oil or epoxidized sucrose soyate.

Aromatic glycidyl ethers are, for example, bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol B diglycidyl ether, bisphenol S diglycidyl ether, hydroquinone diglycidyl ether, alkylation products of phenol/dicyclopentadiene, e.g., 2,5-bis[(2,3- epoxypropoxy)phenyl]octahydro-4,7-methano-5H-indene (CAS No. [13446-85-0]), tris[4-(2,3- epoxypropoxy)phenyl]methane isomers (CAS No. [66072-39-7]), phenol-based novolac epoxy (CAS No. [9003-35-4]), and cresol-based novolac epoxy (CAS No. [37382-79-9]).

Examples of aliphatic glycidyl ethers include 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, 1, 1,2,2- tetrakis[4-(2,3-epoxypropoxy)phenyl]ethane (CAS No. [27043-37-4]), diglycidyl ether of polypropylene glycol (a,w-bis(2,3-epoxypropoxy)poly(oxypropylene), CAS No. [16096-30-3]) and hydrogenated bisphenol A (2,2-bis[4-(2,3- epoxypropoxy)cyclohexyl]propane, CAS No. [13410-58-7]). In one embodiment, the epoxy-based (meth)acrylate oligomer is an aromatic glycidyl (meth)acrylate.

Polycarbonate-based oligomer containing at least one ethylenically unsaturated functional group can comprise polycarbonate-based (meth)acrylates oligomer, which is obtainable in a simple manner by trans-esterifying carbonic esters with polyhydric, preferably dihydric, alcohols (diols, hexanediol for example) and subsequently esterifying the free OH groups with (meth)acrylic acid, or else by transesterification with (meth)acrylic esters, as described for example in EP-A 92 269. They are also obtainable by reacting phosgene, urea derivatives with polyhydric, e.g., dihydric, alcohols.

Also conceivable are (meth)acrylates of polycarbonate polyols, such as the reaction product of one of the aforementioned diols or polyols and a carbonic ester and also a hydroxyl-containing (meth)acrylate.

Examples of suitable carbonic esters include ethylene carbonate, 1 ,2- or 1,3-propylene carbonate, dimethyl carbonate, diethyl carbonate or dibutyl carbonate.

Examples of suitable hydroxyl-containing (meth)acrylates are 2-hydroxyethyl (meth)acrylate, 2- or 3-hydroxypropyl (meth)acrylate, 1 ,4-butanediol mono(meth)acrylate, neopentyl glycol mono(meth)acrylate, glyceryl mono- and di(meth)acrylate, trimethylolpropane mono- and di(meth)acrylate, and pentaerythritol mono-, di-, and tri(meth)acrylate.

Silicone-based oligomer containing at least one ethylenically unsaturated functional group can comprise silicone-based (meth)acrylates oligomer, which is obtainable by addition or condensation of functionalized (meth)acrylate monomers with silicone resin. Examples of the silicone-based (meth)acrylates oligomer include DMS-R18, DMS-R22, DMS-R31, RMS-033, RMS-044, RMS-083 (Gelest); CN990, CN9800 (Sartomer); Miramer SIU2400, Miramer SIP910 (Miwon).

Polybutadiene-based oligomer containing at least one ethylenically unsaturated functional group can comprise polybutadiene-based (meth)acrylates oligomer, which is obtainable by addition of functionalized (meth)acrylate monomers with hydroxyl terminated polybutadiene. Examples of the polybutadiene-based (meth)acrylates oligomer include BR-640D, BR-641 D, BR-643 (Dymax); Hypro 2000X168LC VTB, Hypro 1300X33LC VTBNX, Hypro 1300X43LC VTBNX (CVC), CN301, CN303 (Sartomer), TEAI-1000, TE-2000 (NIPPON SODA CO). Polybutadiene can be hydrogenated, epoxidized, or copolymerized with acrylonitrile. The oligomer preferably has a number-average molar weight Mn of 200 to 20 000 g/mol, more preferably of 200 to 10 000 g/mol, and most preferably of 250 to 3000 g/mol.

In one embodiment, the oligomer has a glass transition temperature in the range from -130 °C to 350 °C, for example -120 °C, -70 °C, 0 °C, 100 °C, 200 °C, 250 °C, 300 °C, preferably from -70 to 300 °C, more preferably from 0 to 250 °C.

In another embodiment, the viscosity of the oligomer at 60 °C can be in the range from 100 to 20000 mPa s, for example 100 mPa s, 200 mPa s, 500 mPa s, 800 mPa s, 1000 mPa s, 2000 mPa s, 3000 mPa s, 4000 mPa s, 5000 mPa s, 6000 mPa s, 7000 mPa s, 8000 mPa s, 10000 mPa s, 20000 mPa s.

In a further embodiment, component (b) comprises at least one monomer and oligomer containing one or more ethylenically unsaturated functional groups and the weight ratio of the monomer to the oligomer in component (b) can be in the range from 10:90 to 90:10, for example 15:85, 20:80, 25:75, 30:70, 35:65, 40:60, 45:55, 50:50, 55:45, 60:40, 65:35, 70:30, 75:25, 80:20, 85:15, preferably from 30:70 to 70:30, more preferably from 40:60 to 60:40.

Photoinitiator (c)

The dual-cure resin composition comprises at least one photoinitiator as component (c). For example, the photoinitiator component (c) may include at least one free radical photoinitiator and/or at least one ionic photoinitiator, and preferably at least one (for example one or two) free radical photoinitiator. For example, it is possible to use all photoinitiators known in the art for use in compositions for 3D-printing, e.g., it is possible to use photoinitiators that are known in the art use with SLA, DLP or PPJ (Photo polymer jetting) processes.

Exemplary photoinitiators may include benzophenone, acetophenone, chlorinated acetophenone, dialkoxyacetophenones, dialkylhydroxyacetophenones, dialkylhydroxyacetophenone esters, benzoin and derivative (such as benzoin acetate, benzoin alkyl ethers), dimethoxybenzion, dibenzylketone, benzoylcyclohexanol and other aromatic ketones, alpha-aminoketone compounds, phenylglyoxylate compounds, oxime ester, acyloxime esters, acylphosphine oxides, acylphosphonates, ketosulfides, dibenzoyldisulphides, diphenyldithiocarbonate, mixtures thereof and mixtures with alpha-hydroxy ketone compounds, or alpha-alkoxyketone compounds.

Examples of suitable acylphosphine oxide compounds are of the structure (XII),

(XII), wherein

R50 is unsubstituted cyclohexyl, cyclopentyl, phenyl, naphthyl or biphenylyl; or is cyclohexyl, cyclopentyl, phenyl, naphthyl or biphenylyl substituted by one or more halogen, C1-C12 alkyl, Ci- 012 alkoxy, C1-C12 alkylthio or by NR53R54; or R50 is unsubstituted C1-C20 alkyl or is C1-C20 alkyl which is substituted by one or more halogen, C1-C12 alkoxy, C1-C12 alkylthio, NR53R54 or by -(CO)-O-Ci-C24 alkyl;

R51 is unsubstituted cyclohexyl, cyclopentyl, phenyl, naphthyl or biphenylyl; or is cyclohexyl, cyclopentyl, phenyl, naphthyl or biphenylyl substituted by one or more halogen, C1-C12 alkyl, Ci- 012 alkoxy, C1-C12 alkylthio or by NR53R54; or R51 is -(CO)R’s2; or R51 is C1-C12 alkyl which is unsubstituted or substituted by one or more halogen, C1-C12 alkoxy, C1-C12 alkylthio, or by NR53R54;

R52 and R’52 independently of each other are unsubstituted cyclohexyl, cyclopentyl, phenyl, naphthyl or biphenylyl, or are cyclohexyl, cyclopentyl, phenyl, naphthyl or biphenylyl substituted by one or more halogen, C1-C4 alkyl or C1-C4 alkoxy; or R52 is a 5- or 6-membered heterocyclic ring comprising an S atom or N atom;

R53 and R54 independently of one another are hydrogen, unsubstituted C1-C12 alkyl or C1-C12 alkyl substituted by one or more OH or SH wherein the alkyl chain optionally is interrupted by one to four oxygen atoms; or R53 and R54 independently of one another are C2-C12 alkenyl, cyclopentyl, cyclohexyl, benzyl or phenyl.

Specific examples of photoinitiators can include 1 -hydroxycyclohexyl phenylketone, 2-methyl-1- [4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-N,N-dimethylamino-1-(4- morpholinophenyl)-1-butanone, combination of 1 -hydroxycyclohexyl phenyl ketone and benzophenone, 2,2-dimethoxy-2-phenyl acetophenone, bis(2,6-dimethoxybenzoy 1 -(2,4,4- trimethylpentyl)phosphine oxide, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, bis(2,4,6-trimethyl benzoyl) phenyl phosphine oxide, 2-hydroxy-2-methyl-1-phenyl-1 -propane, combination of

2.4.6-trimethylbenzoyldiphenyl-phosphine oxide, 2-hydroxy-2-methyl-1-phenyl-propan-1-one,

2.4.6-trimethylbenzoyldiphenylphosphinate and 2,4,6-trimethylbenzoyldiphenyl-phosphine oxide and also any combination thereof.

In a particularly preferred embodiment, the photoinitiator (c) is a compound of the structure (XII), such as, for example, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide; 2,4,6- trimethylbenzyl- diphenyl-phosphine oxide; ethyl (2,4,6-trimethylbenzoyl phenyl) phosphinic acid ester; (2,4,6- trimethylbenzoyl)-2,4-dipentoxyphenylphosphine oxide and bis(2,6-dimethoxybenzoyl)-2,4,4- trimethylpentylphosphine oxide.

The amount of the photoinitiator (c) can be in the range from 0.1 to 10 wt.%, for example 0.2 wt.%, 0.5 wt.%, 0.8 wt.%, 1 wt.%, 2 wt.%, 3 wt.%, 5 wt.%, 8 wt.%, or 10 wt.%, preferably from 0.1 to 5 wt.%, more preferably from 0.5 to 3 wt.%, based on the total weight of the composition.

Auxiliaries

The dual-cure composition of the present invention may further comprise one or more auxiliaries.

As auxiliaries, mention may be made by way of preferred example of surface-active substances, flame retardants, nucleating agents, lubricant wax, adhesion promoters, rheology modifiers, dyes, pigments, catalyst, UV absorbers and stabilizers, e.g. against oxidation, hydrolysis, light, heat or discoloration, inorganic and/or organic fillers, reinforcing materials and plasticizers. As hydrolysis inhibitors, preference is given to oligomeric and/or polymeric aliphatic or aromatic carbodiimides. To stabilize the material cured of the invention against aging and damaging environmental influences, stabilizers are added to system in preferred embodiments.

If the composition of the invention is exposed to thermo-oxidative damage during use, in preferred embodiments antioxidants are added. Preference is given to phenolic antioxidants. Phenolic antioxidants such as Irganox® 1010 from BASF SE are given in Plastics Additive Handbook, 5th edition, H. Zweifel, ed., Hanser Publishers, Munich, 2001 , pages 98-107, page 116 and page 121.

If the composition of the invention is exposed to UV light, it is preferably additionally stabilized with a UV absorber. UV absorbers are generally known as molecules which absorb high-energy UV light and dissipate energy. Customary UV absorbers which are employed in industry belong, for example, to the group of cinnamic esters, diphenylcyan acrylates, formamidines, benzylidenemalonates, diarylbutadienes, triazines and benzotriazoles. Examples of commercial UV absorbers may be found in Plastics Additive Handbook, 5th edition, H. Zweifel, ed, Hanser Publishers, Munich, 2001 , pages 116-122.

If the composition of the invention is liable to degrade thermally at thermal treatment, it is preferably additionally to accelerate with a catalyst. Catalysts for urethanes have been proven to reduce reaction temperature and/or time efficiently. Examples of catalysts that can be used here are organometallic compounds, such as complexes of tin, of zinc, of titanium, of zirconium, of iron, of mercury, or of bismuth, preferably organotin compounds, such as stannous salts of organic carboxylic acids, e.g. stannous acetate, stannous octoate, stannous ethylhexanoate, and stannous laurate, and the dialkyltin(IV) salts of carboxylic acids, e.g. dibutyltin diacetate, dibutyltin dilaurate (DBTL), dibutyltzin maleate, and dioctyltin diacetate, and also phenylmercury neodecanoate, bismuth carboxylates, such as bismuth(lll) neodecanoate, bismuth 2- ethylhexanoate, and bismuth octanoate, or a mixture. Other possible catalysts are basic amine catalysts. Examples of these are amidines, such as 2,3-dimethyl-3,4,5,6-tetrahydropyrimidine, tertiary amines, such as triethylamine, triethylenediamine, tributylamine, dimethylbenzylamine, N-methyl, N-ethyl, N-cyclohexylmorpholine, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'- tetramethylbutanediamine, N,N,N',N'-tetramethylhexanediamine, pentamethyldiethylenetriamine, tetramethyldiaminoethyl ether, bis(dimethylaminopropyl)urea, dimethylpiperazine, 1 ,2-dimethylimidazole, 1-azabicyclo[3.3.0]octane, and preferably 1,4- diazabicyclo[2.2.2]octane,1,8-diazabicyclo[5.4.0]-undecen-7-ene, and alkanolamine compounds, such as triethanolamine, triisopropanolamine, N-methyl- and N-ethyldiethanolamine, and dimethylethanolamine. The catalysts can be used individually or in the form of a mixture.

Further details regarding the abovementioned auxiliaries may be found in the specialist literature, e.g. in Plastics Additive Handbook, 5th edition, H. Zweifel, ed, Hanser Publishers, Munich, 2001.

According to the present invention, the auxiliary can be present in an amount of from 0 to 50% by weight, from 0.01 to 50% by weight, for example from 0.5 to 30% by weight, based on the total weight of the dual-cure resin composition.

Examples

The present invention is further illustrated by the following examples, which are set forth to illustrate the present invention and is not to be construed as limiting thereof. Unless otherwise noted, all parts and percentages are by weight.

Materials

Component (a)

HEA: hydroxyethyl acrylate, supplied by Sigma Aldrich; Desmodur N-3400: hexamethylene diisocyanate (HDI) dimer from Covestro; Tin catalyst: Dibutyltin dilaurate (DBTDL), supplied by Sigma Aldrich;

Glycerol, supplied by Sigma Aldrich;

2,2-bis(hydroxymethyl)butyric acid, supplied by Sigma Aldrich.

Component (b)

ACMO: acryloyl morpholine, manufactured by KJ Chemicals; I BOA: Isobornyl acrylate, manufactured by Sartomer;

G4247: aliphatic urethane methacrylate, Genomer 4247, manufactured by RAHN AG; BR-541 MB: difunctional aliphatic polyether urethane methacrylate, manufactured by Dymax Corporation;

Component (c)

TPO: 2,4,6-trimethylbenzoyldiphenylphosphine oxide, Omnirad TPO, manufactured by IGM Resins.

Methods

(1) Viscosity

The viscosity of liquid resin was determined at 100 s^-1 shear rate with an Anton Paar Rheometer (Physica MCR 302) with a cone plate CP50 at 60 °C.

(2) 1 H NMR spectra was obtained in CDC and d-DMSO using a 600 MHz Bruker Avance Neo.

(3) Tensile test

Tensile tests were carried out according to ISO 527-5A:2009 with Zwick, Z050 Tensile equipment, wherein the parameters used include: Start position: 50 mm; Pre-load: 0.02 MPa; Test speed: 10 mm/min. The calculated results were based on 6 replicates

(4) impact strength notched

Izod notched impact strength was measured according to the standard ASTM D256 on Zwick Roell HIT25P testing machine. The calculated results were based on 6 replicates.

Preparation of photocurable oligomer

Photocurable oligomer 1 (N3400XL)

1. Synthesis

HDI uretdione (Desmodur N-3400, 19.3g, 50% by weight in acetone) was charged to a reaction vessel under nitrogen and agitated. HEA (11.6g, NCO:OH ratio =1 :1) was added dropwise to the HDI uretdione solution. Catalyst DBTDL (1000ppm based on the weight of N-3400) was then added. The temperature of the reaction was maintained between 20 and 40°C. The completion of reaction was determined by the disappearance of the N=C=O stretch signal (between 2250 and 2285 cm-1) in infrared spectroscopy. Free-radical inhibitor MEHQ (1000ppm based on the total weight of N-3400 and HEA) was added, followed by vacuumed evaporation to remove acetone below 60°C.

Desmodur N3400 HEA N3400XL 2. Characterization

1 H NMR spectrum (600 MHz, CDCI3) as shown in Figure 1 verifies the identity of N3400XL. b(ppm) = 6.27 (1 H, =CH2), 6.0-6.01 (1H, -CH=), 5.74 (1H, =CH2), 5.23 (1H, NH), 4.18 (2H, OCH2), 4.15 (2H, OCH2), 3.05 (NCH2), 1.47 (2H, CH2), 1.37 (2H, CH2), 1.21 (2H, CH2). The peak around 5.23 ppm was assigned to -NH-C=O- indicating successful reaction of -NCO and - OH.

The viscosity of the obtained N3400XL is measured as 1000 mPa s at 60°C.

Photocurable oligomer 2 (N3400XL-G)

1. Synthesis

HDI uretdione (Desmodur N-3400, 19.3g, 50% by weight in acetone) was charged to a reaction vessel under nitrogen and agitated. HEMA (9.76g, NCO:OH ratio =1:0.75) was added dropwise to the HDI uretdione solution. Catalyst DBTDL (1000ppm based on the weight of N-3400) was then added. The temperature of the reaction was maintained between 0 and 20°C. The completion of this reaction step was determined by the stablization of the C=O stretch signal from urethane group (between 2250 and 2285 cm-1) in infrared spectroscopy. Glycerol (0.77g, NCO:OH ratio =1:0.25) was added dropwise to the solution and allowed reacting at the same temperature. The completion of reaction was determined by the disappearance of the N=C=O stretch signal (between 2250 and 2285 cm-1) in infrared spectroscopy. Free-radical inhibitor MEHQ (1000ppm by the total weight of N-3400, HEMA and Glycerol) was added, followed by vacuumed evaporation to remove acetone below 60°C.

2. Characterization

1 H NMR spectrum (600 MHz, d-DMSO) as shown in Figure 2 verifies the identity of N3400XL-G. b(ppm) = 6.03 (1 H, =CH2), 5.68 (1 H, =CH2), 4.90 (1 H, OCH), 4.25 (2H, OCH2), 4.19 (2H, OCH2), 4.08 (2H, OCH2), 3.14 (2H, NCH2), 2.95 (2H, NCH2), 1.88 (3H, CH3). The peaks around 4.08 ppm (2H, OCH2) and 4.90 (1 H, OCH) showed significant peak assignment shift indicating the successful reaction of Glycerol.

The viscosity of the obtained N3400XL-G is measured as 3100 mPa-s at 60°C.

Photocurable oligomer 3 (N3400XL-D)

1 . Synthesis

HDI uretdione (Desmodur N-3400, 19.3g, 50% by weight in acetone) was charged to a reaction vessel under nitrogen and agitated. HEMA (9.76, NCO:OH ratio =1 :0.75) was added dropwise to the HDI uretdione solution. Catalyst DBTDL (1000ppm based on the weight of N-3400) was then added. The temperature of the reaction was maintained between 0 and 20°C. The completion of this reaction step was determined by the stabilization of the C=O stretch signal from urethane group (between 2250 and 2285 cm-1) in infrared spectroscopy. DMBA (1.85g, NCO:OH ratio =1 :0.25, 50% by weight in N, N-dimethylformamide) was added dropwise to the solution and allowed reacting at the same temperature. The completion of reaction was determined by the disappearance of the N=C=O stretch signal (between 2250 and 2285 cm-1) in infrared spectroscopy. Free-radical inhibitor MEHQ (1000ppm by the toal weight of N-3400, HEMA and DBMA) was added, followed by vacuumed evaporation to remove solvent below 60°C.

2. Characterization

1 H NMR spectrum (600 MHz, d-DMSO) as shown in Figure 3 verifies the identity of N3400XL-D. b(ppm) = 6.03 (1 H, =CH2), 5.69 (1 H, =CH2), 4.24 (2H, OCH2), 4.19 (2H, OCH2), 4.04 (2H.

OCH2), 3.14 (2H, NCH2), 2.95 (2H, NCH2), 1.88 (3H, CH3), 0.80 (3H, CH3). The peak around 4.04 ppm (2H. OCH2) shows significant peak assignment shift indicating the successful reaction of DMBA. The viscosity of the obtained N3400XL-D is measured as 2700 mPa s at 60°C.

Preparation of dual-cure resin composition

The dual-cure resin composition of example 1 (E1) , example 2 (E2) and comparative example 1 (C1) were obtained by mixing the components in amounts shown in Table 1. Firstly, component (a) (the photocurable oligomer) was dissolved in component (b) at 60 °C with mechanical stirring at 1000 RPM, until component (b) was completely dissolved. Next, the rest of components were added to the pre-mixture of component (a) and component (b) to mix together uniformly at the same temperature and stirring condition.

Specimen casting

Example 1 , example 2 and comparative example 1 were prepared into test specimens using UV casting method, during which the compositions were poured into a pre-defined Teflon/silicone mould followed by UV irradiation. UV-curing of the compositions was done by using a UV conveyor belt (385 nm and 405 nm wavelengths). The UV dose applied was 3600 mJ/cm² for each side. Then, the specimens were UV post-cured by using a NextDentTM LC 3D Printbox (315 to 550 nm wavelength) for 40 mins. Then, thermal curing was performed by heating specimens in a conventional oven at 80 °C for 24 hours and 160 °C for 18 hours respectively.

The physical properties of the cured specimens obtained at different thermal condition from the dual-cure resin compositions of example 1, example 2 and comparative example 1 were also shown in Table 1.

Table 1

Claims

Claims

1. A photocurable oligomer having at least one uretdione group and at least one ethylenically unsaturated group, derived from a compound (A) having an active hydrogen-containing group and at least one ethylenically unsaturated group and a uretdione precusor compound (B) having at least one isocyanate group.

2. The photocurable oligomer according to claim 1 of the structure ( I ) and/or the structure ( II)

wherein n is an integer of 1 to 5; m is an integer of 1 to 8; each R¹ is independently selected from alkylene groups having 1 to 15 carbon atoms, arylene groups having 6 to 15 carbon atoms, and arylalkylene and alkylarylene groups having 7 to 15 carbon atoms, wherein alkylene groups, alkylene portions of arylalkylene groups, and alkyl portions of alkylarylene groups may be linear, branched, or cyclic;

X is independently a radical derived from the compound (A) by abstracting a hydrogen atom of an active hydrogen-containing group; and Y is a moiety derived from a chain extender compound (C) having at least one active hydrogen-containing group by abstracting at least one hydrogen atom of active hydrogencontaining groups.

3. The photocurable oligomer according to claim 1 or 2, wherein the compound (A) is an ester of an aliphatic or aromatic polyol and an acrylic or methacrylic acid, an amide of an amino alcohol and an acrylic or methacrylic acid, or a unsaturated polyetherol or polyesterol or polyacrylate polyol.

4. The photocurable oligomer according to any of claims 1 to 3, wherein the uretdione precusor compound (B) is uretdione precusor momomer Bi having the structure (III) when the photocurable oligomer has the structure ( I )

5. The photocurable oligomer according to any of claims 1 to 3, wherein the uretdione precusor compound (B) is uretdione precusor prepolymer B2 having the structure (IV) when the photocurable oligomer has the structure ( II )

6. The photocurable oligomer according to claim 2 or 5, wherenin the compound (C) is nucleophile chain extender including multifunctional alcohols, thiols, or amines, and/or functional chain extender including hydrophilic chain extender.

7. The photocurable oligomer according to any of claims 1 to 6, wherein X is the radical of structure (V) or structure (VI)

wherein

R² is divalent alkyl, aryl, alkylaryl or arylalkyl having up to 12 carbon atoms;

R³, R⁴ and R⁵ are each independently H or a radical of structure (VII), and at least one of R³, R⁴ and R⁵ are selected from structure (VII),

wherein R⁶ is hydrogen or C1-C4 alkyl,

R⁷ is selected from divalent C1-C20 alkyl group, C1-C20 alkoxy group, or C2-C20 carbonyl group.

8. The photocurable oligomer according to any of claims 1 to 7, wherein the compound (A) is selected from hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, pentaerythritol triacrylate, or poly ethoxy (10) ethyl methacrylate, preferably hydroxyethyl acrylate, or hydroxyethyl methacrylate

9. The photocurable oligomer according to any of claims 1 to 3 or any of claims 5 to 8, wherein the compound (C) is selceted from ethylene glycol, 1 ,4-butanediol, glycerol, pentaerythritol, 4,4'-diaminodibenzyl, 3,5-diethyltoluene-2,4-diamine, dimethylolbutanoic acid, or N-methyl diethanolamine, preferably glycerol, or 2,2-bis(hydroxymethyl)butyric acid.

10. A process for the production of the photocurable oligomer according to any of claims 1 to 4, which comprises ( i ) reacting the uretdione precusor monomer (Bi) with the compound (A) so that both terminal isocyanate groups of compound (Bi) are reacted, optionally with the presence of a catalyst; optionally (ii) adding a radical inhibitor.

11. The process for the production of the photocurable oligomer according to any of claims 1 to 3 or claim 5, which comprises (ia) reacting the uretdione precusor monomer (Bi) with compound (A) so that one side of terminal isocyanate groups of compound (Bi) are reacted, which forms the uretdione precusor prepolymer (B2); ( i ) reacting the uretdione precusor prepolymer (B2) with compound (C) so that another side of terminal isocyanate groups of compound (B2) are reacted, optionally with the presence of a catalyst; and optionally (ii) adding a radical inhibitor

12. The process according to claim 10 or 11 , wherein the uretdione precursor monomer (Bi) is selected from (1) (cyclo)aliphatic diisocyanates, preferably 1 ,2-ethylene diisocyanate; 1 ,4- tetramethylene diisocyanate; 1 ,6-hexamethylene diisocyanate (HDI-dimer); 2,2,4-trimethyl-1 ,6- hexamethylene diisocyanate; 1 ,9-diisocyanato-5-methylnonane; cyclobutene 1 ,3-diisocyanate; or 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate, I PDI- dimer), more preferably 1 ,6-hexamethylene diisocyanate (HDI-dimer); 3-isocyanatomethyl- 3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate, IPDI-dimer); (2) aromatic diisocyanates such as 2,4-diphenylmethane diisocyanate (MDI-dimer); 3,3'-dimethoxy-4,4 - biphenyl diisocyanate; xylene diisocyanate; toluene diisocyanate (TDI-dimer), preferably toluene diisocyanate (TDI-dimer); and (3) conbinations thereof.

13. Use of the photocurable oligomer according to any of claims 1 to 9, or obtained by the process according to any of claims 10 to 12 for preparing a dual-cure resin composition.

14. A dual-cure resin composition, comprising

(a) the oligomer according to any of claims 1 to 9, or obtained by the process according to any of claims 10 to 12;

(b) a photo-polymerizable compound which is different from the oligomer (a);

(c) a photoinitiator.

15. The dual-cure resin composition according to claim 14, wherein the photo-polymerizable compound (b) comprises at least one monomer and/or oligomer containing one or more ethylenically unsaturated functional groups.

16. The dual-cure resin composition according to claim 14 or 15, wherein the amount of component (a) is in the range from 1 to 50 wt.%, preferably from 2 to 40 wt.%, more preferably from 5 to 30 wt.%, based on the total weight of the dual-cure resin composition.

17. The dual-cure resin composition according to any of cliams 14 to 16, wherein the amount of component (b) is in the range from 10 to 95 wt.%, preferably from 15 to 80 wt.%, more preferably from 20 to 70 wt.%, based on the total weight of the dual-cure resin composition.

18. Use of the dual-cure resin composition according to any of claims 14 to 17 in a photopolymerization 3D printing process, coatings, inks, varnishes, adhesives, composite materials and solder resists.

19. A process of forming 3D objects, comprising following steps:

(i) applying radiation to cure the dual-cure resin composition according to any of claims 14 or 17 layer by layer to form an intermediate 3D object;

(ii) removing the excessive liquid resin from the intermediate object obtained in step (i), optionally followed by radiation post-curing the intermediate 3D object obtained in step (i) as a whole; and

(iii) thermal treating the object obtained in step (ii) as a whole to form a final 3D object.

20. A 3D object formed from the dual-cure resin composition according to any of claims 14 to 17 or obtained by the process according to claim 19.