"PHOTORETICULATING COMPOSITION AND ITS COMPONENTS FROM SOURCES OF RENEWABLE ORIGIN, FOR THREE-DIMENSIONAL PRINTING PROCESSES"

DESCRIPTION

FIELD OF THE INVENTION

The present invention relates to various aspects of the three-dimensional printing processes, and in particular a photo-crosslinkable composition and its components from renewable sources and having similar performances, if not better, in particular as regards both the tensile strength and the flexibility / deformability, compared to the currently available formulations of fossil origins, so as to provide a more ecologically acceptable alternative from the point of view of environmental impact.

STATE OF THE TECHNIQUE

Additive manufacturing commonly known as three-dimensional printing (3D Printing), is a technique that allows the construction of three-dimensional objects with predefined shape, color and size through a computerized virtual model, which is sent to the printer. The product is constructed by layer-by-layer addition of material by selecting the thickness in microns and, based on the printing technique and the printer performance, high resolution and large objects are obtained relatively quickly. Additive manufacturing, compared to the more traditional techniques of subtractive manufacturing and molding, has many advantages, in particular allows a targeted production, very fast and customized in function of the needs of the end user. In recent years such technology has found ever wider applications, both in large-scale industrial manufacturing and in electronics, fashion, jewelry and the biomedical sector, for example for the production of dental prostheses and consumer items.

In 2009, the American Society for Testing Materials (ASTM) (https://compass.astm.org/Standards/WITHDRAWN/F2792.htm) classified the different three-dimensional printing technologies in seven main categories:

(1 ) Material Extrusion: includes techniques called Fused Deposition Modeling (FDM) and Direct Ink Writing (DIW). It is a process that can also be used at the level domestic and low- cost, in which a material is extruded through a fixed support by means of a movable arm. In the first case (FDM) melted thermoplastics polymers are used while in the second (DIW) thixotropic fluids are used; (2) Direct Energy Deposition (DED): a metal or ceramic powder is used, which is fused by a high intensity energy source, in particular a laser or a plasma torch, and deposited layer by layer;

(3) Sheet Lamination: layers of material are folded together layer by layer, generating three-dimensional structures; it is a technique not suitable for structural uses, and it is appreciated above all for the aesthetic aspect of the printed product;

(4) Powder Bed Fusion (PBF): includes Direct Metal Laser Sintering (DMLS), Electron Bean Melting (EBM), Selective Heat Sintering, (SHS), Selective Laser Melting (SLM), and Selective Laser Sintering (SLS), and involves the use of a laser radiation which causes the sintering of polymeric, metallic or ceramics particles, forming three-dimensional objects without the need to provide supports and with minimal waste of material;

(5) Material Jetting (MJ): Like a common inkjet printer, the material is deposited on a platform on which it solidifies thanks to UV irradiation, building the piece layer by layer

(6) Binder Jetting (BJ): is based on the combination of a dusty material that acts as a filler, and a liquid material which acts as an adhesive between the particles of dust; metals, ceramics or polymeric materials can be used.

(7) Vat Photopolymerization, also known as Stereolithography (SLA) in which one layer of light-curing resin is selectively cured with ultraviolet light. Depending on the technology used to produce ultraviolet light it differs in: i) Digital-Light Processing (DLP) when the radiation is produced by a DLP projector, ii) Laser Stereolithography (commonly known simply as L-SLA) when the radiation comes from a UV laser and iii) LCD Stereolithography (LCD-SLA or simply LCD, Liquid Crystal Display) when radiation is generated by a liquid crystal screen.

In Vat photopolymerization according to Digital Light Processing technology (DLP), in the printer a source of UV radiation (with varying powers widely depending on the manufacturing company and wavelengths generally between 360 and 420 nm) is selectively masked by a system of small mirrors known as digital micromirror device (DMD) to harden a thin layer of a liquid and viscous formulation (resin) (the layer can be set with thickness usually around 50-100 pm) placed in a transparent container which contains molecules or polymers having functional groups capable of photopolymerization. At the end of exposure to UV radiation, the printing plate (called "stage") is raised vertically allowing the detachment of the printed layer from the bottom of the vessel. The cycle is then repeated for the subsequent layers, so as to produce the desired object three-dimensional. As opposed to other printing techniques for photopolymerization, in the DLP technique the polymerization takes place simultaneously throughout the illuminated layer, ensuring uniformity to the final object. The DLP printing technique offers the best resolutions and the ability to print very small details, and finds applications in goldsmithing (through the lost wax method) and in the dental prosthetics sector.

The principle of operation of printers for L-SLA is very similar to that of printers for DLP, as mentioned it is based in both cases on the hardening of a liquid resin by photopolymerization of the components inside the formulation. Unlike DLP, however, the formation of the hardened material layer does not occur simultaneously on the entire surface of the layer, but rather occurs in a timely manner because the light source used is a ultraviolet laser directed by suitable mirrors that direct the light in correspondence of the areas to be irradiated, and therefore hardened. Compared to DLP, where the print resolution is directly determined by the pixel size that the projector is capable of generating and is inversely proportional to the size of the printed object due to the radial nature of the source, in SLA the resolution is determined by the ultimate dimensions of the laser beam (generally between 50 and 200 pm) and is independent of the size of the printing area.

Recently, SLA printers using an LCD-LED (Liquid Crystal Display - Light Emitting Diode) screen have also been introduced to the market. This printing technology is more similar to DLP, but light radiation is generated by an array of LEDs shielded by a liquid crystal mask that reveal only the pixels necessary for hardening of the required layer. Unlike DLP, however, light travels in a parallel and non-radial way, so the resolution is not a function of the size of the printed object but only the resolution in pixels of the employed LCD screen.

Compared to L-SLA technology, both DLP and LCD offer a great advantage in terms of print speed. This is because L-SLA technology requires the time necessary for the laser to irradiate the entire portion of resin to be hardened and consequently the printing speed is a function not only of the number of layers to harden (and therefore from the size of the object along the vertical z axis) but also from the xy dimensions of the single layer. DLP and LCD, on the other hand, radiate at the same time all points of each layer, whereby the printing speed is mainly determined by the size of the object along the z axis.

Photo-crosslinkable compositions for printing are known on the market and in the literature for three-dimensional printing. For example, formulations for both DLP or LCD and L-SLA are commercially available including: a) blends of low molecular weight polymers, in particular diacrylates of polyethyleneglycol (PEG), polypropyleneglycol (PPG) or polyurethanes (PU) b) one or more photo-crosslinking components, generally consisting of acrylic monomers or polyfunctional methacrylates such as pentaerythritol tetraacrylate c) a photopolymerization initiator, i.e. a substance that triggers the photopolymerization by absorbing light radiation d) a photo-absorber (i.e. a substance that increases the portion of light absorbed by blocking its excessive diffusion in the resin) which increases the resolution of 3D printing e) a radical inhibitor (terminator), useful for stopping the polymerization after the irradiation.

The Applicant has however found that the components of said formulations are normally obtained from raw materials of fossil origin, therefore not responding principles of the green economy in the chemical field, i.e. maximizing the use of products from renewable and nonpetroleum sources, oil and gas.

SUMMARY OF THE INVENTION

Therefore, the object of the present invention is to provide a new composition for 3D printing, in particular via L-SLA, DLP or LCD, comprising derivatives from sources of renewable origin and having similar, if not better performance, in particular as regards both the tensile strength and the flexibility / deformability compared to the currently available formulations of origin fossil, so as to provide an ecologically more acceptable alternative than the latter from the point of view of environmental impact.

In accordance with the present invention, the Applicant has surprisingly found that it is possible to pursue this and other beneficial purposes through a appropriate and specific selection of the components of the composition for 3D printing.

In particular, the present invention relates in a first aspect to a photo cross-linkable composition comprising:

(A) at least one unsaturated photo-crosslinkable polyester comprising as constituent units:

- at least one polyol unit, - at least one carboxylic unit selected from the group consisting of: one dicarboxylic unit and one hydroxycarboxylic unit, and

- at least one unsaturated functionalizing unit deriving from an unsaturated acid selected in the group consisting of: itaconic acid, tiglic acid, and unsaturated fatty acids, or resulting from a mixture of unsaturated fatty acids and saturated fatty acids;

(B) at least one photo-crosslinkable monomeric compound selected from the group consisting of: 2-hydroxyethyl methacrylate, a 2-hydroxyethyl methacrylate diester of a linear dicarboxylic acid C4-C10 and a 2-hydroxyethyl methacrylate monoester of a saturated or unsaturated linear carboxylic acid C4-C24; and

(C) at least one photopolymerization initiator.

The Applicant has in fact surprisingly found that through a suitable and specific selection of at least one unsaturated light cross-linked polyester (A), at least one monomeric light crosslinking compound (B) and at least one light curing initiator (C), wherein said components (A) and (B) advantageously comprise components from sources of renewable origin, it is possible to obtain a photo cross-linkable composition for printing 3D, especially for L-SLA, DLP or LCD, having similar, if not better performances, in particular as regards both the tensile strength and the flexibility/deformability compared to the currently available formulations of fossil origin, so as to provide an ecologically more alternative than the latter acceptable from the point of view of environmental impact.

In its further aspects, the present invention also relates to a photo-crosslinked resin obtainable by photopolymerization of the light crosslinkable composition according to the first aspect of the invention and a molded product made with said photo-crosslinked resin.

The advantages and characteristics of said further aspects have already been highlighted with reference to the first aspect of the invention and are not repeated here.

Furthermore, the present invention relates in its still further aspects to a unsaturated crosslinkable polyester (A), to a 2-hydroxyethyl methacrylate diester of a saturated linear dicarboxylic acid C4-C10 and a 2-hydroxyethyl methacrylate monoester of a saturated or unsaturated linear carboxylic acid C4-C24.

Said unsaturated photo-crosslinkable polyester (A), said 2-hydroxyethyl methacrylate diester of a linear dicarboxylic acid C4-C10 and said 2-hydroxyethyl methacrylate monoester of a saturated or unsaturated linear carboxylic acid C4-C24, are in fact produced from components from renewable sources that they can advantageously find use in a 3D printing process and offer, individually or in combination, an environmentally more acceptable alternative from the point of view of environmental impact compared to similar components of fossil origin.

Finally, in a still further aspect, the present invention also relates to the use of the photo- crosslinkable composition according to the first aspect of the invention, of the unsaturated light cross-linked polyester (A), of the aforementioned diesters, in a 3D stereolithography process (vat photopolymerization).

The advantages of this use have already been highlighted with reference to the other aspects aspect of the invention and are not repeated here.

BRIEF DESCRIPTION OF THE FIGURES

In the drawings:

Figure 1 shows the 1 H-NMR spectrum (600 MHz, CDCI3) of the photo-crosslinkable polyester (Lin-2MA2-DD-I) according to example 4 with corresponding integration of the main peaks;

Figure 2 shows the 1 H NMR spectrum (600 MHz, CDCI3) of the photo-crosslinkable polyester (Lim-2ME2-DDO-I) according to example 5 with corresponding integration of the main peaks;

Figure 3 shows the 1 H NMR spectrum (600 MHz, CDCI3) of the photo-crosslinkable polyester poly(Myr-lt-BDO-l) according to example 6 with corresponding integration of the main peaks;

Figure 4 shows the 1 H NMR spectrum (400 MHz, CDCI3) of Sorb-PCL-Te according to example 7 with corresponding integration of the main peaks;

Figure 5 shows the 1 H NMR spectrum (400 MHz, CDCI3) of BH-Seb according to example

8 with corresponding integration of the main peaks;

Figure 6 shows the 1 H NMR spectrum (400 MHz, CDCI3) of L-HEMA according to example

9 with corresponding integration of the main peaks;

Figure 7 shows the 1 H NMR spectrum (400 MHz, CDCI3) of O-HEMA according to example

10 with corresponding integration of the main peaks; Figure 8 shows the 1 H NMR spectrum (400 MHz, CDCH) of Do-Me-lt according to example 11 with corresponding integration of the main peaks;

Figure 9 shows the 1 H NMR spectrum (400 MHz, CDCI3) of BDO-2Pr-lt according to example 12 with corresponding integration of the main peaks;

Figure 10 shows the ATR-FTIR spectrum of the photo-crosslinkable composition 1.1 according to example 13;

Figure 11 shows the ATR-FTIR spectrum of the photo-crosslinkable composition 2 according to example 14;

Figure 12 shows the ATR-FTIR spectrum of the photo-crosslinkable composition 3 according to example 15;

Figure 13 shows the ATR-FTIR spectra of the photo-crosslinkable compositions 4.1(a) and 4.2(b) according to example 16;

Figure 14 shows the ATR-FTIR spectrum of the photo-crosslinkable composition 5 according to example 17;

Figure 15 shows the ATR-FTIR spectrum of the photo-crosslinkable composition 6 according to example 18;

Figure 16 shows the ATR-FTIR spectrum of the photo-crosslinked resin 1.1 according to example 19 obtained from the photo-crosslinkable composition 1.1 ;

Figure 17 shows the ATR-FTIR spectrum of the photo-crosslinked resin 2 according to example 19 obtained from the photo-crosslinkable composition 2;

Figure 18 shows the ATR-FTIR spectrum of the photo-crosslinked resin 3 according to example 19 obtained from the photo-crosslinkable composition 3;

Figure 19 shows the ATR-FTIR spectra of the photo-crosslinked resins 4.1(a) and 4.2(b) according to example 19 obtained from the respective photo-crosslinkable compositions 4.1 and 4.2.

Figure 20 shows the ATR-FTIR spectrum of the photo-crosslinked resin 5 according to example 19 obtained from the photo-crosslinkable composition 5;

Figure 21 shows the ATR-FTIR spectrum of the photo-crosslinked resin 6 according to example 19 obtained from the photo-crosslinkable composition 6; DETAILED DESCRIPTION OF THE INVENTION the present invention relates in a first aspect to a photo cross-linkable composition comprising:

(A) at least one unsaturated photo-crosslinkable polyester comprising as constituent units:

- at least one polyol unit,

- at least one carboxylic unit selected from the group consisting of: one dicarboxylic unit and one hydroxycarboxylic unit, and

- at least one unsaturated functionalizing unit deriving from an unsaturated acid selected in the group consisting of: itaconic acid, tiglic acid, and unsaturated fatty acids, or resulting from a mixture of unsaturated fatty acids and saturated fatty acids;

(B) at least one photo-crosslinkable monomeric compound selected from the group consisting of: 2-hydroxyethyl methacrylate, a 2-hydroxyethyl methacrylate diester of a linear dicarboxylic acid C4-C10 and a 2-hydroxyethyl methacrylate monoester of a saturated or unsaturated linear carboxylic acid C4-C24; and

(C) at least one photopolymerization initiator.

The Applicant has in fact surprisingly found that through a suitable and specific selection of at least one unsaturated light cross-linked polyester (A), at least one monomeric light crosslinking compound (B) and at least one light curing initiator (C), wherein said components (A) and (B) advantageously comprise components from sources of renewable origin, it is possible to obtain a photo cross-linkable composition for printing 3D, especially for L-SLA, DLP or LCD, having similar, if not better performances, in particular as regards both the tensile strength and the flexibility/deformability compared to the currently available formulations of fossil origin, so as to provide an ecologically more alternative than the latter acceptable from the point of view of environmental impact.

Within the scope of the present description and in the subsequent claims, all numerical quantities indicating quantities, parameters, percentages, and so on are from to be understood preceded in all circumstances by the term "about" unless otherwise indicated. Furthermore, all ranges of numerical quantities include all possible combinations of the maximum and minimum numerical values and all possible intermediate intervals, in addition to those specifically indicated below. The present invention may present in one or more of its aspects one or more of the preferred features listed below, which can be combined according to the application needs.

The photo-crosslinkable composition according to the present invention comprises at least an unsaturated photo-crosslinkable polyester (A). Said photo-crosslinkable polyester comprises as a constituent at least one unit polyol.

In one embodiment, said polyol unit is derived from a thiol-ene reaction product of at least one a,u)-mercaptoalcohol with at least one terpene compound.

Preferably, said a,w-mercaptoalcohol is selected in the group consisting of: 2- mercaptoethanol and 6-mercaptohexanoL Preferably, said terpene compound is selected from the group consisting of: linalool, geraniol, limonene, a-terpinene, y-terpinene, and myrcene.

In a preferred embodiment, said thiol-ene reaction product of at least one a,a)- mercaptoalcohol with at least one terpene compound is selected in the group which consists of the compounds of formula (I) - (XII):

In a further embodiment, said polyol unit of said photo-crosslinkable polyester derives from a polyol comprising from 2 to 6 hydroxyl groups.

Preferably, said polyol is selected from the group consisting of: ethylene glycol, 1 ,3- propanediol, propylene glycol, 1 ,4-butandiol, 1 ,6-hexandiol, 1,12-dodecandiol, glycerol, erythritol, xylitol, arabitol, sorbitol, mannitol, and galactitol, even more preferably from sorbitol.

The unsaturated light cross-linkable polyester (A) comprises as a constituent at least one carboxylic unit selected from the group consisting of: one dicarboxylic unit and one hydroxycarboxylic unit.

Preferably, said dicarboxylic unit derives from a compound selected in the group consisting of: a C4-C12 saturated linear dicarboxylic acid, a product of thiol-ene reaction between a a,w- mercaptoester and a terpene compound, and a Diels-Alder cycloaddition reaction product between an unsaturated diester and a terpene compound. Preferably, said C4-C12 saturated linear dicarboxylic acid is dodecanedioic acid.

Preferably, in said thiol-ene reaction product between an a,u)-mercaptoester and a terpene compound said a,u)-mercaptoester is selected in the group consisting of: methyl thioglycolate and methyl 3-mercaptopropionate. Preferably, said thiol-ene reaction product between an a,u)-mercaptoester and a terpene compound said terpene compound is selected in the group consisting of: linalool, geraniol, limonene, a-terpinene, y-terpinene, and myrcene.

In a preferred embodiment, said thiol-ene reaction product between an a,u)-mercaptoester and a terpene compound is selected in the group which consists of the compounds of formula (XIII) - (XXIV):

Preferably, said dicarboxylic unit of the photocurable polyester (A) derives from a Diels-Alder cycloaddition reaction product between an unsaturated diester and a terpene compound.

Preferably, in said Diels-Alder cycloaddition reaction product said unsaturated diester is selected from the group consisting of: dimethyl itaconate, dimethyl fumarate and dimethyl maleate.

Preferably, in said Diels-Alder cycloaddition reaction product said terpene compound is selected in the group consisting of: isoprene, myrcene, farnesene and a-terpinene.

In a preferred embodiment, said Diels-Alder cycloaddition reaction product of at least one unsaturated diester with at least one terpene compound is selected from the group consisting of the compounds of formula (XXV) - (XXXII):

(XXV),

(XXVI),

(XXVII),

(XXVIII),

Preferably, said hydroxy carboxylic unit derives from a hydroxy carboxylic acid selected from the group consisting of: glycolic acid, hydroxybutyric acid, hydroxycaproic acid, hydroxyvaleric acid, lactic acid, their lactides and lactones.

The unsaturated photo-crosslinkable polyester (A) further comprises as a constituent at least an unsaturated functionalizing unit deriving from an unsaturated acid selected in the group consisting of: itaconic acid, tiglic acid, and an unsaturated fatty acid, or resulting from a mixture of unsaturated fatty acids and saturated fatty acids.

Preferably, said unsaturated functionalizing unit derives from itaconic acid, from an unsaturated fatty acid or from a mixture of saturated and unsaturated fatty acids.

Preferably, said unsaturated fatty acid is selected from the group consisting of: myristoleic acid, palmitoleic acid, heptadecenoic acid, oleic acid, elaidinic acid, vaccenic acid, asclepic acid, petroselinic acid, petroselaidic acid, gadoleic acid, gondoic acid, cetoleic acid, erucic acid, nervonic acid, acid linoleic, linolenic acid, stearidonic acid, arachidonic acid, timnodonic acid, clupanodonic acid, and cervonic acid.

Preferably, said mixture of unsaturated fatty acids and saturated fatty acids is obtained from a natural oil selected from the group consisting of: safflower oil, castor oil, linseed oil, and palm oil.

Preferaby, said unsaturated functionalizing unit derives from itaconic acid. Preferably, the unsaturated light cross-linkable polyester (A) has an average molecular weight between 1000 and 250000 g/mol.

Said molecular weight can be measured for example by gel permeation (GPC).

Preferably, the photo-crosslinkable polyester (A) has a viscosity equal or lower than 10 Pas, said viscosity being measured at 25°C using a modular compact rheometer (for example Anton-Parr MCR102 with DPP25-SN0 geometry) using double plate geometry with a 25 mm diameter.

In a preferred embodiment, the unsaturated photo-crosslinkable polyester (A) includes as constituent units: at least one polyol unit deriving from a thiol-ene reaction product of at least one a,u>- mercaptoalcohol with at least one terpene compound; at least one dicarboxylic unit derived from a C4-C12 saturated linear dicarboxylic acid; and at least one unsaturated functionalizing unit deriving from a selected unsaturated acid in the group consisting of: itaconic acid, tiglic acid, and an unsaturated fatty acid selected in the group consisting of: myristoleic acid, palmitoleic acid, acid heptadecenoic acid, oleic acid, elaidinic acid, vaccenic acid, asclepic acid, acid petroselinic, petroselaidic acid, gadoleic acid, gondoic acid, cetoleic acid, erucic acid, nervonic acid, linoleic acid, linolenic acid, stearidonic acid, arachidonic acid, timnodonic acid, clupanodonic acid, cervonic acid, or resulting from a mixture of unsaturated fatty acids and saturated fatty acids obtained from an oil natural selected in the group consisting of: safflower oil, castor oil, lineseed oil, and palm oil.

In a further preferred embodiment, the unsaturated photo-crosslinkable polyester (A) includes as constituent units: at least one polyol unit deriving from a polyol comprising from 2 to 6 groups hydroxyls selected in the group consisting of: ethylene glycol, 1 ,3-propanediol, propylene glycol, 1 ,4- butanediol, 1 ,6-hexandiol, 1 ,12-dodecandiol, glycerol, erythritol, xylitol, arabitol, sorbitol, mannitol, and galactitol, preferably sorbitol; at least one hydroxy carboxylic unit deriving from a hydroxy carboxylic acid selected from the group consisting of: glycolic acid, hydroxybutyric acid, hydroxycaproic acid, hydroxyvaleric acid, lactic acid, their lactides and lactones; and at least one unsaturated functionalizing unit deriving from a selected unsaturated acid in the group consisting of: itaconic acid, tiglic acid, and an unsaturated fatty acid selected in the group consisting of: myristoleic acid, palmitoleic acid, heptadecenoic acid, oleic acid, elaidinic acid, vaccenic acid, asclepic acid, acid petroselinic, petroselaidic acid, gadoleic acid, gondoic acid, cetoleic acid, erucic acid, nervonic acid, linoleic acid, linolenic acid, stearidonic acid, arachidonic acid, timnodonic acid, clupanodonic acid, cervonic acid, or resulting from a mixture of unsaturated fatty acids and saturated fatty acids obtained from an oil natural selected in the group consisting of: safflower oil, castor oil, lineseed oil, and palm oil.

The unsaturated photo-crosslinkable polyester (A) is advantageously obtainable according to any method known to the skilled in the art for obtaining polyesters; advantageously, the unsaturated photo-crosslinkable polyester (A) can be obtained by means of polymerization by polycondensation.

In addition to the unsaturated light cross-linkable polyester (A), the photo cross-linkable composition according to the present invention further comprises at least one photocrosslinking agent (B) selected from the group consisting of: 2-hydroxyethyl methacrylate, a 2-hydroxyethyl methacrylate diester of a linear dicarboxylic acid C4-C10 and a 2-hydroxyethyl methacrylate monoester of a saturated or unsaturated linear carboxylic acid C4-C24.

Preferably, said saturated linear dicarboxylic acid C4-C10 is sebacic acid.

Preferably, said saturated or unsaturated linear carboxylic acid C4-C24 is selected from the group consisting of: butyric acid, valeric acid, capronic acid, enantic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, myristoleic acid, palmitoleic acid, heptadecenoic acid, oleic acid, elaidinic acid, vaccenic acid, asclepic acid, petroselinic acid, petroselaidic acid, acid gadoleic, gondoic acid, cetoleic acid, erucic acid, nervonic acid, linoleic acid, linolenic acid, stearidonic acid, arachidonic acid, timnodonic acid, clupanodonic acid, and cervonic acid.

The 2-hydroxyethyl methacrylate esters of the light cross-linking compound (B) are advantageously obtainable according to any method known to those skilled in the art for obtaining esters; advantageously they can be obtained by condensation of 2-hydroxyethyl methacrylate with acyl chlorides of fatty acids or with acyl dichlorides of dicarboxylic acids.. In an embodiment described in the present application, the photocrosslinkable composition as defined herein may comprise, in substitution or admixture with the photocrosslinking compound (B), at least one diester of itaconic acid with saturated alcohols or polyols C1-C12, as the photocrosslinking compound.

Said saturated alcohols or polyols C1-C12 may be selected in the group consisting of: methanol, ethanol, 1 -propanol, 2-propanol, 1 -butanol, 2-butanol, 1 -pentanol, 1 -hexanol, 1- heptanol, 1-octanol, 1-nonanol, 1-decanol, 1-undecanol, 1-dodecanol, ethylene glycol, 1 ,3- propanediol, 1 ,4-butanediol, 1 ,6-hexanediol and 1 ,12-dodecanedioL

The esters of itaconic acid according to this embodiment can be obtained according to any method known to the skilled in the art for the obtainment of esters; advantageously they are obtainable by condensation of methyl 3-(chlorocarbonyl)-3-butenoate, methyl 2- (chlorocarbonyl)-3-butenoate or their mixtures with the corresponding alcohol or polyol, or by opening the cyclic anhydride of itaconic acid with a first alcohol followed by the functionalization of the free carboxylic functionality with a second alcohol or polyol.

The photo cross-linkable composition according to the present invention further comprises at least one photopolymerization initiator (C).

As photopolymerization initiating compounds phosphine oxides can be advantageously used such as phenyl bis(2,4,6-trimethylbenzoyl) phosphine oxide, diphenyl (2,4,6- trimethylbenzoyl) phosphine oxide, phenyl ethyl (2,4,6-trimethylbenzoyl) phosphine oxide. Natural products are also employable such as all derivatives of flavones, such as quercetin, chaicones such as curcumin, beta carotene and derivatives, vanillin and derivatives, chlorophyll A and bacterio-chlorophyll, dihydroxyantrachinones and derivatives, camphor and derivatives, products that can also absorb in Near InfraRed (NIR) at wavelengths greater than 700 nm.

Preferred examples of photopolymerization initiators are 2,4,6-trimethylbenzoyl diphenyl phosphine oxide, phenyl bis (2,4,6-trimethylbenzoyl) phosphine oxide, and ethyl phenyl 2,4,6-trimethylbenzoyl phosphine oxide.

Preferably, the photo cross-linkable composition according to the present invention includes, with respect to the total weight of the photo-cross-linkable composition: from 4 to 75% by weight, more preferably from 40 to 60% by weight, of said at least one unsaturated photo-crosslinkable polyester (A); from 24 to 95% by weight, more preferably from 39 to 59% by weight, of said at least one photo-crosslinking compound (B); and from 0.2 to 2% by weight, more preferably from 0.5 to 1% by weight, of said at least one photopolymerization initiator (C).

Preferably, the photo-crosslinkable composition according to the present invention further comprises at least one light-absorbing compound.

As light-absorbing compounds heterocyclic compounds with high absorption in the UV-VIS spectrum can advantageously be used such as isothioxanthones, anthraquinones and bis (benzoxazolyl) thiophenes, or natural products derived from ferulic acid, gallic acid, caffeic acid, coumaric acid and aloin. The photoreticulable composition according to the present invention can also comprise mixtures of said compounds photoabsorbers.

A preferred example of a photoabsorbent is 2-isopropyl thioxanthone.

Preferably, said photo-absorbing compound is present in the photo-crosslinkable composition according to the present invention in an amount ranging from 0.2 to 1% by weight, with respect to the total weight of the photo-crosslinkable composition.

Preferably, the photo cross-linkable composition according to the present invention further comprises at least one photopolymerization terminator.

Examples of photopolymerization terminators usable in the composition are phenolic compounds such as 4-methoxyphenol and 2,6-ditertbutyl-4-methylphenol, or natural products such as tocopherol, ascorbic acid and curcumin.

Preferably, said photopolymerization terminator is present in the photo-crosslinkable composition according to the present invention in quantities ranging from 0.2 to 5% by weight, with respect to the total weight of the photo cross-linkable composition.

In addition to said components, the photo cross-linkable composition according to the present the invention may further comprise one or more other additional components, such as dyes, preferably of natural origin. Examples of natural dyes usable in the photo- crosslinkable composition according to the present invention are for example carotene, chlorophyll A, guaiazulene, morine, quercetin and ellagic acid.

In a preferred embodiment, the photo-crosslinkable composition according to the present invention comprises at least 80% by weight of components from renewable sources. Said percentage by weight of components from renewable sources is easily determined by the skilled in the art on the basis of the quantity of components sourced from renewable source present in the components of the photo-crosslinkable composition, according to the present invention.

In its further aspects, the present invention also relates to a photo-crosslinked resin obtainable by photopolymerization of the photo-crosslinkable composition according to the first aspect of the invention and a printed product made with said photo-crosslinked resin.

The present invention also relates to the use of the photo-crosslinkable composition, in a 3D stereolithography process (vat photopolymerization).

Preferably, said 3D stereolithography process is selected in the group which consists of: Digital-Light Processing (DLP), laser stereolithography (L-SLA), and stereolithography with liquid crystal display (Liquid Crystal Display Stereolithography LCD-SLA).

Said 3D stereolithography processes can be carried out according to the operational conditions known for the purpose to the expert in the sector.

The advantages and characteristics of said further aspects have already been highlighted with reference to the first aspect of the invention and are not repeated here.

In addition to the photo-crosslinkable composition according to the present invention in his complex and the further aspects described up to now, the present invention also relates, in its further and advantageous aspects, even some of the components of the composition cross-linked and also concerns their use for 3D stereolithography, preferably for one of the above mentioned 3D stereolithography techniques.

Said components of the composition are an unsaturated light cross-linked polyester (A), a 2-hydroxyethyl methacrylate diester of a C4-C10 saturated linear dicarboxylic acid and a 2- hydroxyethyl methacrylate monoester of a saturated or unsaturated linear carboxylic acid C4-C24. These are in fact advantageously produced from components from sources of renewable origin and can be advantageously used in a 3D printing process and offer, individually or in combination, an environmentally friendly alternative more acceptable from the point of view of environmental impact than analogue components of fossil origin.

In particular, in a further and advantageous aspect thereof, the present invention therefore refers to an unsaturated photo-crosslinkable polyester comprising as a unit constitutive: - at least one polyol unit deriving from a thiol-ene reaction product of at least an a.ui- mercaptoalcohol with at least one terpene compound or one derived from a polyol comprising 2 to 6 hydroxyl groups selected from the group consisting of: glycol ethylene, 1 ,3-propanediol, propylene glycol, 1 ,4-butanediol, 1 ,6-hexanediol, 1 ,12- dodecandiol, glycerol, erythritol, xylitol, arabitol, sorbitol, mannitol, and galactitol, preferably sorbitol;

- at least one carboxylic unit selected in the group consisting of: one dicarboxylic acid unit derived from a saturated linear dicarboxylic acid C4-C12, one hydroxycarboxylic acid unit resulting from a hydroxycarboxylic acid selected from the group which consists of: glycolic acid, hydroxybutyric acid, hydroxycaproic acid, acid hydroxyvaleric, lactic acid, their lactides and lactones, a dicarboxylic unit derived from a thiol-ene reaction product of at least one a,w-mercaptoester with at least one terpene compound, and a dicarboxylic unit resulting from a Diels-Alder cycloaddition reaction product of at least one unsaturated diester with at least one terpene compound;

- at least one unsaturated functional unit deriving from an unsaturated acid selected in the group consisting of: itaconic acid, tiglic acid, and an unsaturated fatty acid, or resulting from a mixture of unsaturated fatty acids and saturated fatty acids.

The unsaturated photo-crosslinkable polyester according to this aspect of the invention can exhibit one or more of the preferred characteristics described for the unsaturated crosslinkable polyester (A) of the photo-crosslinkable composition according to the first aspect of the invention.

In particular, in the unsaturated photo cross-linkable polyester according to this aspect of the invention said a,u)-mercaptoalcohol is preferably selected in the group that consists of: 2-mercaptoethanol and 6-mercaptohexanoL

In the unsaturated photo crosslinkable polyester according to this aspect of the invention said terpene compound is preferably selected from the group consisting of: linalool, geraniol, limonene, a-terpinene, y-terpinene and myrcene.

In the unsaturated photo-crosslinkable polyester according to this aspect of the invention said thiol-ene reaction product of at least one a,u)-mercaptoalcohol with at least one terpene compound is preferably selected from the group consisting of the compounds of formula (I)- (XII):

In the unsaturated light cross-linkable polyester according to this aspect of the said invention C4-C12 saturated linear dicarboxylic acid is preferably dodecanedioic acid.

In the unsaturated photo-crosslinkable polyester according to this aspect of the invention said polyol comprising 2 to 6 hydroxyl groups is preferably 1 ,12-dodecanediol or 1 ,4- butanediol. In particular, in the unsaturated photo cross-linkable polyester according to this aspect of the invention said a,u)-mercaptoester is preferably selected in the group which consists of: methyl thioglycolate and methyl mercaptopropionate.

In particular, in the unsaturated photo-crosslinkable polyester according to this aspect of the invention said thiol-ene reaction product between a a,u)-mercaptoester and a terpene compound, said terpene compound is preferably selected in the group consisting of: linalool, geraniol, limonene, a-terpinene, y-terpinene, e myrcene.

In the unsaturated photo-crosslinkable polyester according to this aspect of the invention said thiol-ene reaction product of at least one a,w-mercaptoester with at least one terpene compound is preferably selected from the group consisting of the compounds of formula

(XIII) - (XXIV):

Preferably, in the unsaturated photo-crosslinkable polyester according to this aspect of the invention said dicarboxylic unit derives from a Diels-Alder cycloaddition reaction product between an unsaturated diester and a terpene compound. In particular, in the unsaturated photo-crosslinkable polyester according to this aspect of the invention said unsaturated diester is preferably selected from the group which consists of: dimethyl itaconate, dimethyl fumarate, dimethyl maleate.

In particular, in the unsaturated photo-crosslinkable polyester according to this aspect of the invention in which in said Diels-Alder cycloaddition reaction product said terpene compound is preferably selected in the group consisting of: isoprene, myrcene, farnesene and a- terpinene.

In the unsaturated photo-crosslinkable polyester according to this aspect of the invention said Diels-Alder reaction product of at least one unsaturated diester with at least one terpene compound is preferably selected from the group consisting of the compounds of formula (XXV) - (XXXII):

(XXV),

(XXVI), (XXVII),

(XXVIII),

(XXIX),

(XXX),

(XXXI), and

(XXXII).

Preferably the unsaturated photo-crosslinkable polyester according to this aspect of the invention has an average molecular weight between 1000 and 250000 g/mol.

Said molecular weight can be measured for example by gel permeation chromatography (GPC).

Preferably, the unsaturated photo-crosslinkable polyester according to this aspect of the invention has a viscosity equal or lower than 10 Pas, said viscosity being measured at25°C using a modular compact rheometer (for example Anton-Parr MCR102 with DPP25-SN0 geometry) using double plate geometry with a 25 mm diameter. In its still further and advantageous aspects, the present invention also refers to a 2- hydroxyethyl methacrylate diester of a C4-C10 saturated linear dicarboxylic acid, and a 2- hydroxyethyl methacrylate monoester of a saturated or unsaturated linear carboxylic acid C4-C24. Said unsaturated photo-crosslinkable polyester, said 2-hydroxyethyl methacrylate diester of a saturated linear dicarboxylic acid C4-C10 and said 2-hydroxyethyl methacrylate monoester of a saturated or unsaturated linear carboxylic acid C4-C24, are in fact produced by components from renewable sources that they can find advantageously use in a 3D printing process and offer, individually or in combination, an environmentally more acceptable alternative from the point of view of environmental impact compared to similar components of fossil origin.

Preferably, in the 2-hydroxyethyl methacrylate diester of a saturated linear dicarboxylic acid C4-C10 according to this invention, said saturated linear dicarboxylic acid C4-C10 is sebacic acid.

Preferably, in the 2-hydroxyethyl methacrylate monoester of a saturated or unsaturated linear carboxylic acid C4-C24 according to this invention, said saturated or unsaturated linear carboxylic acid C4-C24 is lauric acid.

Further features and advantages of the invention will become more evident by the following Examples, intended for illustrative and not limitative purposes.

EXPERIMENTAL PART

PROCEDURES AND METHODS

Preparation of the unsaturated photo-crosslinkable polyester (A) according to the invention

Procedure A: Unsaturated light cross-linkable polyester comprising constituent units deriving from a polyol having from 2 to 6 hydroxyl units

The following procedure is suitable for the preparation of various polyesters comprising constituent units deriving from a polyol having from 2 to 6 hydroxyl units.

The carboxylic unit of the polyester can derive from a hydroxy carboxylic acid or a dicarboxylic acid; the hydroxycarboxylic acid can be, for example, hydroxycaproic acid (PCL) or lactic acid (PLA), also using the respective caprolactone or L-lactide in the synthesis.

As for the polyol, it can have from 2 to 6 hydroxyl units and specifically:

- in the case of polyols with 2 hydroxyl units: diols can be used such as ethylene glycol (EG), 1 ,3-propanediol (PDO), propylene glycol (PG), 1 ,4-butane diol (BDO), 1 ,6- hexandiol (HDO), 1 ,12-dodecandiol (DDO) (30 mmol). In in this case, the polyesters obtained are indicated in the present application respectively as EG-Polyester-OH2, PDO-Polyester-OH ₂ , PG-Polyester-OH ₂ , BDO-Polyester-OH ₂ , HDO-Polyester- OH ₂ and DDO-Polyester-OH ₂ , - in the case of polyols with 3 hydroxyl units: triols can be used such as glycerol (Gly) (20 mmol). In this case, the obtained polyester is indicated in the present application as Gly-Polyester-OHs,

- in the case of polyols with 4 hydroxyl units: tetraols can be used such as erythritol (Ery) (15 mmol). In this case, the obtained polyester is indicated in the present application as Ery-Polyester-OI-U,

- in the case of polyols with 5 hydroxyl units: pentaols can be used such as xylitol (Xyl), arabitol (Ara) (12 mmol). In in this case, the polyesters obtained are indicated in the present application respectively as Xyl-Polyester-OHs and Ara Polyester-OHs, and

- in the case of polyols with 6 hydroxyl units: hexaols can be used such as sorbitol (Sorb), mannitol (Man), galactitol (Gal) (10 mmol). In in this case, the polyesters obtained are indicated in the present application respectively as Sorb-Polyester-OH ₆ , Man-Polyester-OH ₆ and Gal-Polyester-OH ₆ .

The usable procedure is as follows: in an anhydrous 100 mL flask and under nitrogen atmosphere, the polyol (60 mmol of OH groups) and the carboxylic acid are added, for example the lactone (180 mmol) or lactide (90 mmol) in 40 mL of anhydrous anisole. Subsequently, 730 mg (1.8 mmol) of tin (II) 2-ethylhexanoate are added and the mixture is heated under reflux (180°C) for 4 hours. The mixture is then cooled and the product and the mixture is directly subjected to the process of functionalization with acyl chlorides.

The polyesters thus obtained are then functionalized so as to include at least one unsaturated functionalizing unit, such as various natural compounds such as fatty acids (FA), itaconic acid (I) or tiglic acid (T). The corresponding acyl chlorides can be used for this purpose, according to the following procedure: At the end of the polymerization reaction described above, the mixture is allowed to cool to 0°C by means of an ice bath, then 9.06 mL of anhydrous triethylamine (6.58 g, 65 mmol) are then added and the acyl chloride(s) (65 mmol) is slowly added dropwise. Once the addition is complete, the ice bath is removed and the reaction is left at room temperature for 4 hours. At this point the mixture is filtered on celite to remove the insoluble triethylammonium chloride and most of the organic solvent is removed by rotavapor. The product is precipitated by adding an excess of a mixture of petroleum ether / ethyl ether 1 : 1 in a separating funnel, which causes separation of the product as a viscous liquid in the lower phase. Precipitation is repeated 3 times and solvent residues are removed in high vacuum. In detail, using hydroxy-caproic acid as carboxylic acid or its lactone the obtained polyesters are indicated with the abbreviation Polyol-PCL-OH _n :

- for n = 2: using the diols ethylene glycol (EG), 1 ,3-propanediol (PDO), propylene glycol (PG), 1 ,4-butanediol (BDO), 1 ,6-hexanediol (HDO), 1 ,12-dodecanediol (DDO) the obtained polyesters are respectively indicated in this application as EG-PCL- OH ₂ , PDO-PCL-OH ₂ , PG-PCL-OH2, BDO-PCL-OH2, HDO-PCL-OH2 or DDO-PCL- OH2 (150 mmol);

- for n = 3: using the triol glycerol (Gly) the obtained polyester is indicated in this application as Gly-PCL-OHa (100 mmol);

- for n = 4: using the tetraol erythritol (Ery) the obtained polyester is indicated in this application as Ery-PCL-OhU (75 mmol);

- for n = 5: using the pentaols xylitol (Xyl) and arabinol (Ara), the obtained polyesters are respectively indicated in this application as Xyl PCL-OH5 and Ara-PCL-OH ₅ (60 mmol); and

- for n = 6: using the hexaoles sorbitol (Sorb), mannitol (Man) and galactitol (Gal) the obtained polyesters are respectively indicated in this application as Sorb-PCL-OH ₆ , Man-PCL-OH ₆ and Gal-PCL-OH ₆ (50 mmol).

Using, for example, lactic acid (or a lactide thereof), the notation would be analogous with PI_A instead of PCL.

For the functionalization of the polyesters, for example, acyl chlorides of unsaturated acids can be used:

• methyl 3-(chlorocarbonyl)-3-butenoate, methyl 2-(chlorocarbonyl)-3-butenoate or mixtures thereof (65 mmol, 10.6 g). The obtained polyesters which can be obtained using this acyl chloride are indicated in this application as Polyol-polyester-l _n according to the abovementioned notation for polyol and carboxylic acid units and in which the index n indicates the number of unsaturated functionalizing units present in the chain. For example, using ethylene glycol and hydroxycaproic acid, the obtained polyester is indicated in this application as EG-PCL-fe;

• trans-2-methyl-2-butenoyl chloride (65 mmol, 7.72 g) and the obtainable polyesters using this acyl chloride are indicated in the present application as Polyol-polyester- T _n according to the above notation for polyol and carboxylic units and in which the index n indicates the number of unsaturated functionalizing units present in the chain; • Acyl chlorides of fatty acids (65 mmol) such as lauroyl (L) chloride, oleoyl (O) chloride, palmitolyl (P) chloride, stearoyl (Ste) chloride, linoleoyl (Lin) chloride, arachidoneoyl (Ara) chloride and myristoyl (Mir) chloride, or mixtures of saturated and unsaturated fatty acids derived directly from natural oils such as oil safflower (Saff), castor oil (Cast), linseed oil (Lins), palm oil (Palm). The polyesters obtainable using these acyl chlorides are indicated in the present application with the acronym Polyol-polyester- FA _n if according to the above notation for polyol and carboxylic units, in which the index n indicates the number of unsaturated functionalizing units present in the chain and in which FA indicates the abbreviation for the different fatty acids or their mixtures deriving from the aforementioned natural oils;

• A mixture of methyl 3-(chlorocarbonyl)-3-butenoate, methyl 2-(chlorocarbonyl)-3- butenoate or mixtures thereof (32.5 mmol, 5.28 g) and acyl chlorides of fatty acids (32.5 mmol) as described in the previous paragraph. The polyesters obtainable using these acyl chlorides are indicated in the present application with the acronym Polyol- polyester-FA _n /2-l _n /2 se according to the above notation for polyol and carboxylic units, in which the index n indicates the number of unsaturated functionalizing units present in the chain and in which FA indicates the abbreviation for the different fatty acids or their mixtures deriving from the aforementioned natural oils;

• A mixture of trans-2-methyl-2-butenoyl chloride (32.5 mmol, 3.86 g) and acyl chlorides of fatty acids (32.5 mmol) as described in the previous point. The polyesters obtainable using these acyl chlorides are indicated in the present application with the acronym Polyol-polyester-FA _n /2-T _n /2 according to the notation reported above for polyol and carboxylic units, in which the index n indicates the number of unsaturated functionalizing units present in the chain and where FA indicates the abbreviation for the different fatty acids or or their mixtures deriving from the aforementioned natural oils;

The effective functionalization is verifiable by 1 H-NMR spectroscopy (CDCh, 600 MHz) according to the method described in the paragraph “1 H-NMR” below, which also allows to confirm the presence of itaconic acid, tiglic acid, and/or inserted fatty functionalities and their effective ratio in case acyl chlorides are used in blend.

It is also possible to use mixtures of different acyl chlorides (such that the sum of the quantity is however equal to 65 mmol): in this way functionalized polyesters can be obtained in which the ratio between the substituents is variable. Procedure B: Unsaturated photo-crosslinkable polyester comprising constituent units deriving from a polyol which is a thiol-ene reaction product of at least one a, j- mercaptoalcohol with at least one terpene compound

1 . (optional) preparation of the polyol by thiol-ene reaction

For the preparation of these polyesters, the polyols of the polyol unit can be optionally prepared by adding a,u)-mercaptoalcohols (xMA) with x carbon atoms such as 2- mercaptoethanol (2MA) and 6-mercaptohexanol (6MA) on terpenic compounds such as linalool (Lin), geraniol (G), limonene (Lim), a-terpinene (aT), y-terpinene (yT) and myrcene (Myr). The obtained polyol is indicated in the present application with the abbreviation Terp- xMA _y where Terp is replaced with the abbreviations given for the different terpenes, x is the number carbon atoms of the a,u)-mercaptoalcohol and y is the number of double bonds in the starting terpene.

In detail, for example: Lin-2MA2, G-2MA2, Lim-2MA2, aT-2MA2, yT-2MA2 and Myr-2MAs.

A usable procedure is as follows: in a flat-bottomed flask equipped with magnetic stir bar is added the terpene compound (1 mol) and an excess of a,u)-mercaptoalcohol (2.5 mol), together with 0.001 mol (0.418 g) of phenyl bis(2,4,6-trimethylbenzoyl) phosphine oxide as a radical initiator. The thiol addition reaction to double bonds of the terpene compound occurs by stirring the reaction mixture in a blue light reactor (LED, 450 nm) for a variable time ranging from 4 to 48 hours. The reaction is stopped when complete conversion of the terpene compound is reached, that can be detected by the disappearance of vinyl signals (1 H-NMR, CDC ) of the unsaturated reagent The neutralization of the excess of thiol occurs by adding 1 M NaOH in water up to pH = 10, and the product is recovered from the aqueous emulsion by extraction with ethyl acetate. After removing residual moisture with sodium sulfate, the solvent is removed in the rotavapor leading to the obtainment of the Terp-xMA _y polyol as a colorless viscous liquid.

2. Preparation of the polyester

The polyesters are then synthesized by polycondensation of the polyols with a carboxylic acid (e.g. itaconic acid (I) and dodecanedioic acid (DD)) using the corresponding dimethyl esters. The obtained polyester is indicated in this application as Poly(Terp-xMA _y -Diacid-l) where Terp-xMAy is replaced with the abbreviations given for the different polyol monomers from thiol-ene reaction and Diacid is replaced with the abbreviations given for the different dicarboxylic acids. For example: Poly(Lin-2MA2-DD-l) indicates polyester comprising the polyol unit deriving from the diol obtained by the thiol-ene reaction of linalool (Lin) and 2- mercaptoethanol (2MA) and the carboxylic unit derived from acid dodecandioic (DD) and itaconic acid (I).

The procedure is as follows: in a 500 mL flask equipped with magnetic stirrer e under nitrogen flow are added 129.1 g (0.5 mol) of dimethyl dodecanedioate, 79.0 g (0.5 mol) of dimethyl itaconate and 1 mol of polyol. To these, 2.49 g (10 mmol) of catalyst (dibutyltin oxide, DBTO) are added. A distillation system with water condensation is placed on the reaction flask, and polymerization is carried out at 190 ° C for 5 hours, continuously separating the methanol produced by the transesterification reaction. At the end of the reaction the mixture is cooled at room temperature, diluted with a small amount of ethyl acetate and the polyester is precipitated by the addition of cold methanol. The process of redissolution-precipitation is repeated 3 times in order to remove small oligomers and residues of unreacted monomers.

Procedure C: Unsaturated photo-crosslinkable polyester comprising constituent units deriving from a diester which is a thiol-ene reaction product of at least one a,u)~ mercaptoester with at least one terpene compound

1 . (optional) Preparation of the diester by thiol-ene reaction

For the preparation of these polyesters, the diesters can optionally be prepared by adding a,w-mercaptoesters (xME) with x carbon atoms, such as methyl 2-mercaptoacetate (2ME) and methyl 3-mercaptopropionate (3ME), on terpenic compounds such as linalool (Lin), geraniol (G), limonene (Lim), a-terpinene (aT), y-terpinene (yT) and myrcene (Myr). The obtained diester is indicated in the present application with the abbreviation Terp-xME _y where Terp is replaced with the abbreviations given for the different terpenes, x is the number of carbon atoms of the a,u)-mercaptoester and y the number of double bonds in the starting terpene.

In detail, for example: Lin-2ME2, G-2ME2, Lim-2ME2, QT-2ME2, yT-2ME2 and Myr-2ME3. One procedure that can be used in this regard is the following: in a flat-bottomed flask equipped with a magnetic stir bar, the terpene compound (1 mol) and an excess are added of a,u)-mercaptoester (2.5 mol), together with 0.001 mol (0.418 g) of phenyl bis(2,4,6- trimethylbenzoyl) phosphine oxide as a radical initiator. The thiol addition reaction to the double bonds of the terpene compound occurs by stirring the mixture of reaction in a blue light reactor (LED, 450 nm) for a time ranging from 4 to 48 hours. The reaction is stopped when complete conversion of the terpene compound is reached, that can be detected by the disappearance of vinyl signals (1 H-NMR, CDCh) of the unsaturated reagent The neutralization of the excess of thiol occurs by adding 1 M NaOH in water up to pH = 10, and the product is recovered from the aqueous emulsion by extraction with ethyl acetate. After removing residual moisture with sodium sulfate, the solvent is removed in the rotavapor leading to the obtainment of the Terp-xME _y diester as a colorless viscous liquid.

2. Preparation of the polyester

The polyesters are then synthesized by polycondensation of the polyol with such diesters from thiol-ene reaction.

The obtained polyester is indicated in the present application as Poly(Terp-xME _y -Polyol-l) where Terp-xME _y is replaced with the abbreviations given for the different diester monomers from thiol-ene reaction and Polyol is replaced with the abbreviations given for the different polyols bearing 2 to 6 hydroxyl units. For example: Poly(Lim-2ME2-DDO-l) indicates a polyester comprising the dicarboxylic unit deriving from itaconic acid (I) and the diester obtained by thiol-ene reaction of limonene (Lim) and methyl 2-mercaptoacetate (2ME), and the polyol unit deriving from 1 ,12-dodecanediol (DDO).

The procedure is as follows: in a 500 mL flask equipped with magnetic stirrer e under nitrogen flow are added 0.5 mol of diester, 79.0 g (0.5 mol) of dimethyl itaconate and 202.3 g (1 mol) of 1,12-dodecanediol. To these, 2.49 g (10 mmol) of catalyst (dibutyltin oxide, DBTO) are added. A distillation system with water condensation is placed on the reaction flask, and polymerization is carried out at 190 ⁰ C for 5 hours, continuously separating the methanol produced by the transesterification reaction. At the end of the reaction the mixture is cooled at room temperature, diluted with a small amount of ethyl acetate and the polyester is precipitated by the addition of cold methanol. The process of redissolution-precipitation is repeated 3 times in order to remove small oligomers and residues of unreacted monomers Procedure D: Unsaturated photo-crosslinkable polyester comprising constituent units deriving from a diester which is a Diels-Alder cycloaddition reaction product of at least one unsaturated diester with at least one terpene compound

1 . (optional) preparation of the diester by Diels-Alder reaction

The diesters of the polyester unit of the unsaturated photo-crosslinkable polyester can be optionally prepared by cycloaddition of unsaturated diesters such as dimethyl itaconate (It), dimethyl fumarate (Fu) and dimethyl maleate (Ma) on terpene compounds such as for example myrcene (Myr), isoprene (Is), farnesene (Fa) or a-terpinene (aT). The obtained diester is indicated in this application with the abbreviation Terp-DE where Terp is replaced with the abbreviations reported for the different terpenes and DE is replaced with the abbreviations reported for the different unsaturated diesters. In detail, for example: Myr-lt, Is-lt, Fa-lt, aT-lt, Myr-Fu, Is-Fu, Fa-Fu, aT-Fu, Myr-Ma, Is-Ma, Fa-Ma, aT-Ma.

In this case, a usable procedure is the following: in a 2 L reactor 3.21 mol of unsaturated diester are dissolved in 1 L of terpene at 60 ⁰ C in an N2 atmosphere. If the terpene used is isoprene the temperature is lowered to 40 ° C. When the dissolution of the unsaturated diester is complete, 64.2 mmol of EtAICh as 1M solution in hexane are added and the mixture is left under stirring for 24 h. The next day, isopropanol is added and the unreacted terpene is removed by evaporation at reduced pressure and the Diels-Alder adduct Terp- DE is then obtained as a yellowish viscous liquid.

2. Preparation of the polyester

The polyesters are then synthesized by polycondensation of a polyol with diesters from Diels-Alder cycloaddition reaction and dimethyl itaconate.

The obtained polyester is indicated in the present application as Poly(Terp-DE-Polyol-l) where Terp-DE is replaced with the abbreviations given for the different diester monomers from Diels-Alder cycloaddition reaction and Polyol is replaced with the abbreviations given for the different polyols bearing 2 to 6 hydroxyl units. For example: Poly(Myr-lt-BDO-l) indicates the polyester comprising the unit dicarboxyl deriving from the diester obtained by the Diels-Alder reaction of myrcene (Myr) and dimethyl itaconate (It), and the polyol unit deriving from 1 ,4-butanediol (BDO).

The procedure is as follows: in a 500 mL flask equipped with magnetic stirrer e under nitrogen flow are added 0.5 mol of diester, 79.0 g (0.5 mol) of dimethyl itaconate and 90 g (1 mol) of 1 ,4-butanediol. To these, 2.49 g (10 mmol) of catalyst (dibutyltin oxide, DBTO) are added. A distillation system with water condensation is placed on the reaction flask, and polymerization is carried out at 190 ° C for 5 hours, continuously separating the methanol produced by the transesterification reaction. At the end of the reaction the mixture is cooled at room temperature, diluted with a small amount of ethyl acetate and the polyester is precipitated by the addition of cold methanol. The process of redissolution-precipitation is repeated 3 times in order to remove small oligomers and residues of unreacted monomers.

Preparation of photo-crosslinking compounds (B) according to the invention

2-hydroxyethyl methacrylate diesters of linear saturated dicarboxylic acids C4-C10 and 2- hydroxyethyl methacrylate monoesters of a linear saturated or unsaturated carboxylic acid C4-C24

2-hydroxyethyl methacrylate esters are obtainable by condensation of 2-hydroxyethyl methacrylate with acyl chlorides of fatty acids or acyl dichlorides of dicarboxylic acids.

As regards the acyl chlorides of linear saturated or unsaturated carboxylic acids C4-C24, can be used for example lauroyl (L) chloride, oleoyl (O) chloride, palmitolyl (P) chloride, stearoyl (Ste) chloride, linoleoyl (Lin) chloride, arachidoneoyl (Ara) chloride and myristoyl (Mir) chloride, or mixtures of saturated and unsaturated fatty acids derived directly from natural oils such as safflower oil (Saff), castor oil (Cast), linseed oil (Lins), palm oil (Palm).

The 2-hydroxyethyl methacrylate ester thus obtained are indicated in the present application as FA-HEMA, where FA is replaced with the acronyms reported for the different fatty acids or their mixtures deriving from the aforementioned natural oils. In detail: L-HEMA, indicates the 2-hydroxyethyl methacrylate ester of the unsaturated fatty acid lauric acid.

If acyl dichlorides of linear saturated dicarboxylic acids C4-C10 are used, can be used for example succinoyl (Succ) dichloride, adipoyl (Ad) dichloride, fumaroyl (Fu) dichloride, itaconoyl (It) dichloride and sebacoyl (Seb) dichloride. The 2-hydroxyethyl methacrylate ester thus obtained are indicated in the present application as BH-X, where X is replaced with the acronyms reported for the different carboxylic diacids. For example, the acronym BH-Succ indicates the 2-hydroxyethyl methacrylate diester of succinic acid.

A procedure that can be used for the preparation of 2-hydroxyethyl methacrylate esters is the following: in a dry 500 mL 3-necked flask are added 121 mL of 2-hydroxyethyl methacrylate (130.1 g, 1 mol) and 139 mL of anhydrous triethylamine (101.2 g, 1 mol) in 200 mL of 2-methyl THF. The mixture is brought to 0 ° C by means of an ice bath and subsequently a solution of acyl chloride in 200 mL of chloroform is slowly added dropwise. Once the addition is complete, the ice bath is removed and the reaction is left at room temperature for 4 hours. At this point the mixture is filtered on celite to remove insoluble triethylammonium chloride. The solvent then is removed by rotary evaporation and the residue is dissolved in 400 mL of petroleum ether. This solution is then repeatedly washed with water and after removal of the solvent by means of a rotary evaporator, the product is cooled and filtered to remove any solid carboxylic acid formed as a by-product.

In the case of the use of linear saturated or unsaturated carboxylic acids C4-C24, 1 mol of acyl chloride is used.

In the case of the use of linear saturated dicarboxylic acids C4-C10, 0.5 mol of acyl dichloride are used.

Diesters of itaconic acid with saturated alcohols or polyols C1-C12

The diesters of itaconic acid with saturated alcohols or polyols C1-C12 are obtainable by condensation of the respective saturated alcohols or polyols with methyl 3-(chlorocarbonyl)- 3-butenoate, 2-(chlorocarbonyl)-3-butenoate or their mixtures or alternatively by opening the cyclic anhydride of itaconic acid with a first alcohol or polyol, followed by the esterification of the free carboxylic unit with a second alcohol or polyol. Regarding saturated alcohols or polyols C1-C12 may be used for example methanol (Me), ethanol (Et), 1 -propanol (Pr), 2- propanol (2Pr), 1 -butanol (Bu), 2-butanol (2Bu), 1 -pentanol (Pe), 1 -hexanol (Hex), 1 -eptanol (Ep), 1 -octanol (Oc), 1 -nonanol (No), 1 -decanol (De), 1 -undecanol (Un), 1 -dodecanol (Do), ethylene glycol (EG), 1 ,3-propanediol (PDO), 1 ,4-butanediol (BDO), 1 ,6-hexanediol (HDO), and 1 ,12-dodecanediol (DDO).

A procedure that can be used for the preparation of diesters of itaconic acid with saturated alcohols or polyols C1-C12 by condensation of the respective saturated alcohols or polyols with methyl 3-(chlorocarbonyl)-3-butenoate, 2-(chlorocarbonyl)-3-butenoate or their mixtures is the following: in a dry three-necked 1 L flask are added the alcohol or the polyol (0.8 mol of OH groups) and 112 mL (0.8 mol) of dry triethylamine in 500 mL of 2-methyl THF. The mixture is cooled to 0°C using an ice bath and then 100 mL (0.8 mol) of 3- (chlorocarbonyl)-3-butenoate, 2-(chlorocarbonyl)-3-butenoate or their mixtures are slowly added dropwise. At the end of the addition, the ice bath is removed and the reaction is left at room temperature for 4 hours. At this point 500 mL of water are added, the organic solvent is removed by rotary evaporation and the residual is extracted 3 times with ethyl acetate and recovered by rotary evaporation of the organic solvent.

The so-obtained diester of itaconic acid is indicated in the present application as Polyol- Me-lt, where Polyol is replaced with the abbreviations given for the different alcohols or polyols. In details, Do-Me-lt refers to the diester of itaconic acid with methanol and 1- dodecanol.

Alternatively, a procedure that may be used for the preparation of diesters of itaconic acid with saturated alcohols or polyols C1-C12 by opening the cyclic anhydride of itaconic acid with a first alcohol or polyol, followed by the esterification of the free carboxylic unit with a second alcohol or polyol is the following: in a 1 L flask are sequentially added the cyclic anhydride of itaconic acid (168.1 g, 1.5 mol), 300 mL of anisole, 150 pL of sulfuric acid and

1.5 mol of the first alcohol or polyol. The mixture is heated to 100°C under nitrogen atmosphere and reacted under stirring for 1 hour. At the end of the reaction, the mixture is cooled to room temperature and the solvent is removed by evaporation at reduced pressure. The so-obtained monoester of itaconic acid is dissolved in 2 L of the second alcohol or polyol,

28.5 g of p-toluensulfonic acid are added and the mixture is heated to 80°C for 48 hours. At the end of the reaction the mixture is cooled, the solvent is removed at reduced pressure and the product is recovered after neutralization of the mixture with a saturated sodium bicarbonate solution followed by the extraction with ethyl acetate of the product from the aqueous phase. By evaporation of the ethyl acetate the liquid diester is obtained.

The so-obtained diester of itaconic acid is indicated in the present application as Polyoh- Polyok-lt, where Polyoh and Polyoh are replaced with the abbreviations given for the different alcohols or polyols. In details, BDO-2Pr-lt refers to the diester of itaconic acid with 1 ,4-butanediol and 2-propanol.

Preparation of the photo-crosslinkable composition according to the invention

The photo-crosslinkable composition according to the invention can be prepared by simply mixing its components in the appropriate proportions. It is advantageously possible to add a small amount of organic solvent such as ethyl acetate (100 mL per kg of composition) to ensure homogeneity solubilization of the components of the mixture. This is then removed by evaporation at reduced pressure.

1 H-NMR 1 H-NMR spectroscopy was performed using Varian Inova 600 and Varian Mercury 400 spectrometers and deuterated chloroform was employed as solvent at 25 ⁰ C. In all recorded spectra, the chemical shifts are reported in ppm of frequency relative to the signal solvent residue (7.26 ppm for CDCh).

MOLECULAR WEIGHT

The average molecular weight and polydispersity of the analyzed polymers were determined by gel permeation chromatography using a Knauer assembled system with Smartline Pump 1000 and refractive index detector K-2301. The column used was a Shimadzu Shim-Pack GPC-803, 300x8.0 mm equipped with Shimadzu Shim-Pack GPC-800P pre-column filter, 10x4.6 mm. THF was used as the eluent, with a constant flow of 1 mL/min. The system was calibrated with polystyrene standard of known molecular weight (1-50 kDa). Before of the injection, each sample was filtered by a 0.45 pm PTFE filter to remove any dust. For each sample, 50 pL of 3 mg/mL solutions were subjected to the analysis.

ATR-FTIR

Infrared spectroscopy analyses were performed using a Agilent Cary 630 FTIR spectrometer equipped with attenuated total reflectance (ATR) system.

VISCOSITY

Viscosity measurements were performed at 25°C using an Anton-Parr MCR102 modular compact rheometer with DPP25-SN0 geometry, meaning a double plate geometry with a 25 mm diameter.

MECHANICAL CHARACTERIZATION

The mechanical characterization tests of the polymerized compositions were performed using specimens according to ISO37: 2017 type 2 on a tensile strength Remet TC10 machine used using a test speed equal to 50 mm/min with a maximum applicable load of 1 kN. From the stress-strain curve are obtained the elastic modulus, the elongation at break, and the tensile strength. At least 5 specimens were tested for each analyzed composition.

EXAMPLES

Example 1 - preparation of polyols by thiol-ene reaction of terpene compounds with - mercaptoalcohols Following the procedure described in the paragraph " Preparation of the unsaturated photo- crosslinkable polyester (A) according to the invention", procedure B, point 1 (optional) in the "PROCEDURES AND METHODS" section above, the following polyols were prepared, shown in Table 1 below.

Table 1

Example 2 - preparation of diesters by thiol-ene reaction of terpene compounds with - mercaptoesters

Following the procedure described in the paragraph " Preparation of the unsaturated photo- crosslinkable polyester (A) according to the invention", procedure C, point 1 (optional) in the "PROCEDURES AND METHODS" section above, the following polyols were prepared, shown in Table 2 below.

Table 2

Example 3 - preparation of diesters by Diels-Alder reaction of terpene compounds with unsaturated diesters.

Following the procedure described in the paragraph " Preparation of the unsaturated photo- crosslinkable polyester (A) according to the invention", procedure D, point 1 (optional) in the "PROCEDURES AND METHODS" section above, the following were prepared diesters, shown in Table 3 below.

Table 3

Example 4 - preparation of the photo-crosslinkable unsaturated polyester Polv(Lin-2MA2- DD-I)

In a 500 mL flask equipped with magnetic stirring and under nitrogen flow, were added 129.1 g (0.5 mol) of dimethyl dodecanedioate, 79.0 g (0.5 mol) of dimethyl itaconate and 1 mol of

Lin-2MA2 polyol prepared according to Example 1. To these, were added 2.49 g (10 mmol) of catalyst (dibutyltin oxide, DBTO). A distillation system with water condensation is placed on the reaction flask, and polymerization is carried out at 190 ° C for 5 hours, continuously separating the methanol produced by the transesterification reaction. At the end of the reaction the mixture is cooled at room temperature, diluted with a small amount of ethyl acetate and the polyester is precipitated by the addition of cold methanol. The process of redissolution-precipitation is repeated 3 times in order to remove small oligomers and residues of unreacted monomers

The photo-crosslinkable unsaturated polyester Poly(Lin-2MA2-DD-l) thus obtained was characterized to determine the average molecular weight, polydispersity and composition.

In particular, the number average molecular weight, the weight average molecular weight and polydispersity, were determined by gel permeation chromatography as described in the section “PROCEDURES AND METHODS” above, obtaining the following results respectively as 2607 g/mol, 7369 g / mol and 2.83.

In addition, by integration of the NMR signals attributable to the different monomers (Figure 1) it was possible to determine the molar and weight composition of the obtained polyester, summarized in Table 4.

For the calculation of the compositions, the values of the integrals of characteristic signals of each monomer were used.

In particular, the doublets at 5.7 and 6.3 ppm for itaconic acid (signals relating to the methylene protons), the multiplet at 2.25 ppm for dodecanedioic acid (signal related to the protons in the positions in alpha to the groups ester) and the signals at 0.92 ppm for the polyol Lin-2M 2 (signals related to isopropylic methyls).

Table 4

Example 5 - preparation of the photo-crossl inkable unsaturated polyester Polv(Lim-2ME2- DDO-I)

Example 4 was repeated, using Lim-2ME2 in place of dimethyl dodecanedioate and 1.12- dodecanediol instead of Lin-2MA2.

The photo-crosslinkable unsaturated polyester Poly(Lim-2ME2-DDO-l) thus obtained was characterized to determine the average molecular weight, polydispersity and composition. In particular, the number average molecular weight, the weight average molecular weight and polydispersity, were determined by gel permeation chromatography as described in the section “PROCEDURES AND METHODS” above, obtaining the following results respectively as 3011 g/mol, 7648 g/mol and 2.54.

In addition, by integration of the NMR signals attributable to the different monomers (Figure 2) it was possible to determine the molar and weight composition of the obtained polyester, summarized in Table 5.

For the calculation of the compositions, the values of the integrals of characteristic signals of each monomer were used.

In particular, the doublets at 5.7 and 6.3 ppm for itaconic acid (signals relating to the methylene protons), the multiplet at 4.1 ppm for 1.12-dodecanediol (signal related to protons in alpha positions to alcohol groups) and signals at 0.92 ppm and 0.97 ppm for the Lim- 2ME2 diester (signals related to methyl groups).

Table 5

Example 6 - preparation of the photo-crosslinkable unsaturated polyester Polv(Myr-lt-BDO- D

Example 4 was repeated, using the Myr-lt diester in place of dimethyl dodecandioate and 1 ,4-butanediol in place of Lin-2MA2.

The photo-crosslinkable unsaturated polyester Poly(Myr-lt-BDO-l) thus obtained was characterized to determine the average molecular weight, polydispersity and composition.

In particular, the number average molecular weight, the weight average molecular weight and polydispersity, were determined by gel permeation chromatography as described in the section “PROCEDURES AND METHODS” above, obtaining the following results respectively as 1587 g/mol, 3428 g/mol and 2.16. In addition, by integration of the NMR signals attributable to the different monomers (Figure 3) it was possible to determine the molar and weight composition of the obtained polyester, summarized in Table 6.

For the calculation of the compositions, the values of the integrals of characteristic signals of each monomer were used.

In particular, the doublets at 5.7 and 6.3 ppm for itaconic acid (signals relating to the methylene protons), the multiplet at 4.1 ppm for 1 .4- butanediol (signal related to protons in alpha positions to alcohol groups) and signals at 5.0 ppm and 5.3 ppm for the Myr-lt diester (signals related to the protons of the two double bonds).

Table 6

Example 7 - preparation of the unsaturated photo-crosslinkable polyester Sorb-PCL-Te

In a dry 100-mL round-bottomed flask under nitrogen atmosphere were added sorbitol (60 mmol of OH groups) and caprolactone (180 mmol) in 40 mL of anhydrous anisole. Subsequently, 730 mg (1.8 mmol) of tin (II) 2-ethyl hexanoate were added and the mixture was heated under reflux (180 ° C) for 4 hours.

The reaction mixture was allowed to cool to 0°C with an ice bath. Then 9.06 mL of anhydrous triethylamine (6.58 g, 65 mmol) were added and trans-2-methyl-2-butenoyl chloride (65 mmol) was slowly added dropwise. When the addition was complete, the ice bath was removed and the mixture was allowed to heat to room temperature for 4 hours. At this point the product was filtered on celite to remove the insoluble triethylammonium chloride and most of the organic solvent was removed by rotary evaporation. The product was precipitated by the addition of an excess of a mixture of petroleum ether / ethyl ether 1 : 1 in a separatory funnel, which caused the separation of the product as a viscous liquid in the lower phase. The precipitation was repeated 3 times and the solvent residues were removed with high vacuum. The photo-crosslinkable unsaturated polyester Sorb-PCL-Te thus obtained was characterized to determine the average molecular weight, polydispersity and composition.

In particular, the number average molecular weight, the weight average molecular weight and polydispersity, were determined by gel permeation chromatography as described in the section “PROCEDURES AND METHODS” above, obtaining the following results respectively as 3757 g/mol, 6763 g/mol and 1 .8.

In addition, by analyzing the 1 H-NMR spectrum of the obtained product (Figure 4) as described in the "PROCEDURES AND METHODS" section above it was possible to confirm the effective functionalization with trans-2-methyl-2-butenoyl chloride.

Also, by integration of NMR signals it was possible to estimate the average number of monomers for arm, which is equal to 5. This corresponds to an average molecular weight of 4000 g/mol, in accordance with what was determined via gel permeation chromatography.

For the calculation of the compositions, the values of the integrals of characteristic signals of each monomer were used. In particular, the multiplet at 6.8 ppm for tiglic acid (signals related to the proton of the double bond), and the multiplets at 2.3 ppm and 4.0 ppm for sorbitol and 6-hydroxyhexanoate (signal related to protons in the positions in alpha to alcohol groups).

Example 8 - preparation of the cross-linking compound BH-Seb

In a dry 3-necked 500 mL flask were added 121 mL (130.1 g, 1 mol) of 2-hydroxyethyl methacrylate and 139 mL (101 .2 g, 1 mol) of anhydrous triethylamine in 200 mL of 2-methyl THF. The mixture was brought to 0 ° C with an ice bath and subsequently a solution of sebacoyl dichloride (0.5 mol) in 200 mL of chloroform was added dropwise. When the addition was complete, the ice bath was removed and the mixture was allowed to heat to room temperature for 4 hours. At this point the product was filtered on celite to remove the insoluble triethylammonium chloride and most of the organic solvent was removed by rotary evaporation then the residue was dissolved in 400 mL of petroleum ether. This solution was then repeatedly washed with water and, after removal of the solvent by means of a rotary evaporator, the product was cooled and filtered to remove any carboxylic acid formed as a by-product. Yield 87% (185 g, 0.435 mol).

The cross-linking compound BH-Seb thus obtained was characterized by 1 H-NMR as described in the "PROCEDURES AND METHODS" section above to determine efficacy of the synthesis and the purity of the product obtained (Figure 5), which was possible through the following attributions:

5 6.12 (s, 2H), 5.58 (s, 2H), 4.46 - 4.14 (m, 8H), 2.32 (t, 4H), 1.94 (dd, 6H), 1.61 (m, 4H), 1.40 - 1.10 (m, 8H).

Example 9 - preparation of the cross-linking compound L-HEMA

Example 8 was repeated, using a solution of lauroyl chloride (1 mol) in place of the sebacoyl dichloride solution (0.5 mol). Yield 82% (256 g, 0.82 mol).

The cross-linking compound L-HEMA thus obtained was characterized by 1 H-NMR as described in the “PROCEDURES AND METHODS” section above to determine efficacy of the synthesis and the purity of the product obtained (Figure 6), which was possible through the following attributions:

5 6.12 (dq, 1 H), 5.58 (dq, 1 H), 4.33 (m, 4H), 2.32 (t, 2H), 1.94 (dd, 3H), 1.61 (m, 2H), 1.40 - 1.10 (m, 16H), 0.88 (t, 3H).

Example 10 - preparation of the cross-linkinq compound O-HEMA

Example 8 was repeated, using a oleoyl chloride solution (1 mol) in place of the sebacoyl dichloride solution (0.5 mol). Yield 87% (343 g, 0.87 mol).

The cross-linking compound O-HEMA thus obtained was characterized by 1 H-NMR as described in the section "PROCEDURES AND METHODS" above to determine the efficacy of the synthesis and the purity of the product obtained (Figure 7), which was possible through the following attributions:

5 6.12 (dq, 1 H), 5.58 (dq, 1 H), 5.35 (m, 2H), 4.32 (m, 4H), 2.31 (t, 2H), 2.00 (m, 4H),

1.93 (dd, 3H), 1.62 (m, 2H), 1.45 - 1.15 (m, 20H), 0.88 (t, 3H).

Example 11 - preparation of the cross-linking compound Do-Me-lt

In a dry 1 L three-necked flask, 180 mL of 1 -dodecanol (0.8 mol) and 112 mL of triethylamine (0.8 mol) were added to 500 mL of 2-methyl THF. The mixture was brought to 0°C using an ice bath and then 100 mL (0.8 mol) of methyl 3-(chlorocarbonyl)-3-butenoate were slowly added dropwise. At the end of the addition, the ice bath is removed and the reaction is left at room temperature for 4 hours. At this point 500 mL of water are added, the organic solvent is removed by rotary evaporation and the residual is extracted 3 times with ethyl acetate and recovered by rotary evaporation of the organic solvent. The cross-linking compound Do-Me-lt thus obtained was characterized by 1 H-NMR as described in the section "PROCEDURES AND METHODS" above to determine the efficacy of the synthesis and the purity of the product obtained (Figure 8), which was possible through the following attributions:

5 6.31 (m, 1 H), 5.69 (m, 1 H), 4.13 (t, 2H), 3.68 (s, 3H), 3.34 (s, 2H), 1.64 (m, 2H),

1.25 (m, 18H), 0.88 (t, 3H).

Example 12 - preparation of the cross-linking compound BDO-2Pr-lt

In a 1 L flask are sequentially added the cyclic anhydride of itaconic acid (168.1 g, 1 .5 mol), 300 mL of anisole, 150 pL of sulfuric acid and 1.65 mol (146 mL) of 1 ,4-butanedioL The mixture is heated to 100°C under nitrogen atmosphere and reacted under stirring for 1 hour. At the end of the reaction, the mixture is cooled to room temperature and the solvent is removed by evaporation at reduced pressure. The so-obtained monoester of itaconic acid is dissolved in 2 L of isopropanol, 28.5 g of p-toluensulfonic acid are added and the mixture is heated to 80°C for 48 hours. At the end of the reaction the mixture is cooled, the solvent is removed at reduced pressure and the product is recovered after neutralization of the mixture with a saturated sodium bicarbonate solution followed by the extraction with ethyl acetate of the product from the aqueous phase. By evaporation of the ethyl acetate the liquid diester is obtained.

The cross-linking compound BDO-2Pr-lt thus obtained was characterized by 1 H-NMR as described in the section "PROCEDURES AND METHODS" above to determine the efficacy of the synthesis and the purity of the product obtained (Figure 9), which was possible through the following attributions:

5 6.25-6.24 (m, 1 H), 5.6-5.84 (m, 1 H), 5.03 (sep, 1 H), 4.15 (m, 2H), 3.68 (m, 2H), 3.27-3.42 (m, 2H), 1.68 (m, 4H), 1.25 (d, 6H).

Example 13 - preparation of the photo-crosslinkable composition 1

1 Kg of photo-crosslinkable composition was prepared by mixing at a temperature of 25 ° C in a dark container the photo-crosslinkable polyester Poly(Lin-2MA2-DD-l) according to example 4, BH-Seb according to example 8, L-HEMA according to example 9, diphenyl 2,4,6-trimethylbenzoyl phosphine oxide, and 4-methoxy phenol in different ratios according to what shown in Table 7. Table 7

The compositions were characterized by infrared spectroscopy as described in the "PROCEDURES AND METHODS" section above. In Figure 10 the ATR-FTIR spectrum of the photo-crosslinkable composition 1.1 . No substantial differences were found between the spectra of the three compositions 1.1 , 1.2 and 1.3. In the spectrum of Figure 10 and in the spectra of compositions 1.2 and 1.3, the signal at 1630 cm ^-1 confirms the presence of the photo-crosslinkable functionalities. Also, the spectra were dominated by the most intense and characteristic peaks, in particular the peak related to the stretching of the C=O bond (1720 cm ^-1 ) and the one relative to the C-O-C bond (1150 cm ^-1 ), characteristic of abundant ester groups, the one relative to the long aliphatic chains of dodecanedioic acid, L-HEMA and BH-Seb (2860 and 2930 cm ^-1 ) and the one relative to the tertiary hydroxy groups on the of Lin-2MA2 monomers.

The viscosity of the compositions 1.1 , 1.2 and 1.3 was evaluated as described in the "PROCEDURES AND METHODS" section above, obtaining as results 1.52, 1.48 and 1.43 Pas, respectively.

Example 14 - preparation of the photo-crosslinkable composition 2

1 Kg of photo-crosslinkable composition was prepared by mixing at a temperature of 25 ° C in a dark container 500 g of the photo-crosslinkable polyester (Lim-2ME2-DDO-I) according to example 5, 388 grams of BH-Seb according to example 8, 100 grams of dimethyl itaconate, 5 grams of phenyl ethyl 2,4,6-trimethylbenzoyl phosphine oxide, and 7 grams of 4-methoxy phenol. The composition was characterized by ART-FTIR infrared spectroscopy (Figure 11) as described in the "PROCEDURES AND METHODS" section above. The presence of the signal at 1630 cm ^-1 confirms the presence of the photo-crosslinkable functionalities. Also, the spectra were dominated by the most intense and characteristic peaks, in particular the peak related to the stretching of the C=O bond (1720 cm ^-1 ) and the one relative to the C-O- C bond (1150 cm ^-1 ), characteristic of abundant ester groups, and the one relative to the long aliphatic chains of dodecanediol and BH-Seb (2860 and 2930 cm ^-1 ).

The viscosity of composition 2 was evaluated as described in the "PROCEDURES AND METHODS" section above, obtaining as results 1.89 Pas.

Example 15 - preparation of the photo-crosslinkable composition 3

1 Kg of photo-crosslinkable composition was prepared by mixing at a temperature of 25°C in a dark container 500 grams of the photo-crosslinkable polyester Sorb-PCL-Te according to example 7, 387 grams of BH-Seb according to example 8, 100 grams of L-HEMA according to example 9, 5 grams of phenyl ethyl 2,4,6-trimethylbenzoyl phosphine oxide, 4 grams of 2-isopropyl thioxanthone and 5 g of 4-methoxy phenol.

The composition was characterized by ART-FTIR infrared spectroscopy (Figure 10) as described in the "PROCEDURES AND METHODS" section above. The presence of the signal at 1630 cm ^-1 confirms the presence of the photo-crosslinkable functionalities. Also, the spectra were dominated by the most intense and characteristic peaks, in particular the peak related to the stretching of the C=O bond (1720 cm ^-1 ) and the one relative to the C-O- C bond (1150 cm ^-1 ), characteristic of abundant ester groups, and the one relative to the long aliphatic chains of oleic acid residues, BH-Seb, L-HEMA and poly (6-hydroxy hexanoate) (2860 and 2930 cm' ¹ ).

The viscosity of composition 3 was evaluated as described in the "PROCEDURES AND METHODS" section above, obtaining as results 2.75 Pas

Example 16 - preparation of the photo-crosslinkable composition 4

1 Kg of photo-crosslinkable composition was prepared by mixing at a temperature of 25°C in a dark container the photo-crosslinkable polyester Poly(Myr-lt-BDO-l) according to example 6, L-HEMA according to example 9, 2-hydroxyethyl methacrylate (HEMA), diphenyl 2,4,6-trimethylbenzoyl phosphinoxide, phenyl bis(2,4,6- trimethylbenzoyl) phosphine oxide and 4-methoxy phenol in different ratios according to what is shown in Table 8. Table 8

The compositions were characterized by ART-FTIR infrared spectroscopy as described in the "PROCEDURES AND METHODS" section above. Figure 13 shows the ATR-FTIR spectra of the light crosslinkable compositions 4.1 (a) and 4.2 (b).The presence of the signal at 1630 cm ^-1 confirms the presence of the photo-crosslinkable functionalities in both compositions. Also, the spectra were dominated by the most intense and characteristic peaks, in particular the peak related to the stretching of the C=O bond (1720 cm ^-1 ), the one relative to the C-O-C bond (1150 cm ^-1 ), characteristic of abundant ester groups, the one relative to the long aliphatic chains of L-HEMA (2860 and 2930 cm ^-1 ). In the spectrum relative to composition 4.1 the band relative to the stretching of the alcoholic OH bond of HEMA (3500 cm ^-1 ) is also marked.

The viscosity of the compositions 4.1 and 4.2 was evaluated as described in the "PROCEDURES AND METHODS" section above, obtaining as results 2.95 and 2.71 Pas, respectively.

Example 17 - preparation of the photo-crosslinkable composition 5

1 Kg of photo-crosslinkable composition was prepared by mixing at a temperature of 25°C in a dark container 470 grams of the photo-crosslinkable polyester Poly(Myr-BDO-l) according to example 6, 250 grams of Do-Me-lt according to example 11 , 250 grams of BH- Seb according to example 8, 20 grams of phenyl ethyl 2,4,6-trimethylbenzoyl phosphine oxide, 3 grams of 2-isopropyl thioxanthone and 7 g of 4-methoxy phenol. The composition was characterized by ART-FTIR infrared spectroscopy (Figure 14) as described in the "PROCEDURES AND METHODS" section above. The presence of the signal at 1630 cm ^-1 confirms the presence of the photo-crosslinkable functionalities. Also, the spectra were dominated by the most intense and characteristic peaks, in particular the peak related to the stretching of the C=O bond (1720 cm ^-1 ) and the one relative to the C-O- C bond (1150 cm ^-1 ), characteristic of abundant ester groups, and the one relative to the long aliphatic chains of Myr-lt, BH-Seb and Do-Me-lt (2860 and 2930 cm ^-1 ).

The viscosity of composition 5 was evaluated as described in the "PROCEDURES AND METHODS" section above, obtaining as results 3.02 Pas.

Example 18 - preparation of the photo-crosslinkable composition 6

1 Kg of photo-crosslinkable composition was prepared by mixing at a temperature of 25°C in a dark container 500 grams of the photo-crosslinkable polyester Poly(Myr-BDO-l) according to example 6, 470 grams of BDO-2Pr-lt according to example 11 , 20 grams of phenyl ethyl 2,4,6-trimethylbenzoyl phosphine oxide, 3 grams of 2-isopropyl thioxanthone and 7 g of 4-methoxy phenol.

The composition was characterized by ART-FTIR infrared spectroscopy (Figure 15) as described in the "PROCEDURES AND METHODS" section above. The presence of the signal at 1630 cm ^-1 confirms the presence of the photo-crosslinkable functionalities. Also, the spectra were dominated by the most intense and characteristic peaks, in particular the peak related to the stretching of the C=O bond (1720 cm ^-1 ) and the one relative to the C-O- C bond (1150 cm ^-1 ), characteristic of abundant ester groups, and the one relative to the long aliphatic chains of Myr-lt (2860 and 2930 cm ^-1 ).

The viscosity of composition 6 was evaluated as described in the "PROCEDURES AND METHODS" section above, obtaining as results 3.27 Pas.

Example 19 - 3D stereolithography of the photo-crosslinkable compositions 1-6

The stereolithography prints were made using a Peopoly Moai 130 SLA printer equipped with a 150 mW 405 nm laser with a 70 pm spot size. Photo-crosslinkable compositions 1.1 , 1.2, 1.3, 2, 3, 4.1 , 4.2, 5 and 6 were printed with the same g-code, generated using the Ultimaker Cura 2.0 software for slicing the specimen (with the geometry specified in ISO37:2017 type 2) according to the parameters shown in Table 9. Table 9

For each different composition, 100 g of photo-crosslinkable composition were poured into the transparent vat of the printer. At the end of the printing process, each specimen was removed from the printing plate, washed with a 1 : 1 mixture of isopropanol and acetone and subjected to a post-crosslinking process by exposure to UV radiation for 2 minutes, using a 120 W Sharebot CURE UV oven equipped with 405 nm LEDs.

Example 20 - characterization of photo-crosslinked resins according to example 19 The photo-crosslinked resins were subjected to a tensile test in order to quantify their mechanical properties in terms of elastic modulus, elongation at break and load a rupture as described in the "PROCEDURES AND METHODS" section above. The results obtained for the different compositions are shown in Table 10.

Table 10

Furthermore, the effective and effective crosslinking of the printed specimens was evaluated by infrared spectroscopy (Figures 16-21) as described in the section “PROCEDURES AND METHODS” above, highlighting for all resins the absence of signals from the photopolymerizable unsaturations by comparison with the IR spectra of the photo- crosslinkable compositions according to examples 13-18.

Figure 16 shows the ATR-FTIR spectrum of the photo-crosslinked resin 1.1 obtained from the photo-crosslinkable composition 1.1. No substantial differences can be observed with respect to the spectrum of the photopolymerizable composition 1.1 (Figure 10) except for the disappearance from the peak at 1630 cm ^-1 which confirms the complete and effective crosslinking of the composition.

Figure 17 shows the ATR-FTIR spectrum of the photo-crosslinked resin 2 obtained from the photo-crosslinkable composition 2. No substantial differences can be observed with respect to the spectrum of the photopolymerizable composition 2 (Figure 11) except for the disappearance from the peak at 1630 cm ^-1 which confirms the complete and effective crosslinking of the composition.

Figure 18 shows the ATR-FTIR spectrum of the photo-crosslinked resin 3 obtained from the photo-crosslinkable composition 3. No substantial differences can be observed with respect to the spectrum of the photopolymerizable composition 3 (Figure 12) except for the disappearance from the peak at 1630 cm ^-1 which confirms the complete and effective crosslinking of the composition.

Figure 19 shows the ATR-FTIR spectra of the photo-crosslinked resin 4.1 (a) and 4.2 (b) obtained from the photo-crosslinkable compositions 4.1 and 4.2 respectively. No substantial differences can be observed with respect to the spectrum of the photopolymerizable compositios 4.1 and 4.2 (Figure 13) except for the disappearance from the peak at 1630 cm- ¹ which confirms the complete and effective crosslinking of the composition.

Figure 20 shows the ATR-FTIR spectrum of the photo-crosslinked resin 5 obtained from the photo-crosslinkable composition 5. No substantial differences can be observed with respect to the spectrum of the photopolymerizable composition 5 (Figure 14) except for the disappearance from the peak at 1630 cm ^-1 which confirms the complete and effective crosslinking of the composition.

Figure 21 shows the ATR-FTIR spectrum of the photo-crosslinked resin 6 obtained from the photo-crosslinkable composition 6. No substantial differences can be observed with respect to the spectrum of the photopolymerizable composition 6 (Figure 15) except for the disappearance from the peak at 1630 cnr ¹ which confirms the complete and effective crosslinking of the composition.