SILICONE COMPOSITION FOR THREE-DIMENSIONAL PRINTING OF AN OBJECT

Abstract

The present invention relates to a silicone composition for three-dimensional printing of an object by crosslinking said silicone composition via photohydrosilylation. The composition is mainly characterized in that it comprises:a) one or more polysiloxanes containing carbon-carbon multiple bonds and Si-H bonds between a hydrogen atom and a silicon atom,b) at least one photoactivatable platinum complex hydrosilylation catalyst,c) at least one crosslinking inhibiting agent,d) at least one optical absorbing agent capable of absorbing electromagnetic radiation in a wavelength range of ultraviolet and / or visible light. Figure for abstract: Fig. 4

Description

Title of the invention: SILICONE COMPOSITION FOR THREE-DIMENSIONAL PRINTING OF AN OBJECT Technical field of the invention

[0001] The present invention relates to a silicone composition for three-dimensional printing of an object by crosslinking said silicone composition by photohydrosilylation.

[0002] The invention also relates to a method for three-dimensional printing of an object by crosslinking such a silicone composition by photohydrosilylation. Technological background

[0003] Three-dimensional printing, or more simply "3D printing", is now widespread, and makes it possible to design more or less complex volume objects, by successively stacking and crosslinking layers of material, in particular silicone in the case of 3D printing of silicone polymers.

[0004] The object to be manufactured is first modeled with computer-aided design software (CAD acronym), before being sent to the 3D printer equipped with specific software which cuts the model into a plurality of layers necessary for the production of the object.

[0005] 3D printing encompasses stereolithography and digital light processing.

[0006] 3D printing by stereolithography, or "stereolithography" in English (acronym SLA), consists of irradiating a liquid polymer resin with a beam of light, a laser, or a projector, in order to crosslink the polymers that compose it, and obtain a final object in solid plastic.

[0007] 3D printing by digital light processing, or "digital light processing" in English (acronym DLP), differs from stereolithography by the nature of the light source. It uses a digital screen projector which projects an image of the layer onto the entire manufacturing platform, thus polymerizing all the points of the layer simultaneously.

[0008] Among the various existing 3D printing techniques, hydrosilylation is particularly advantageous for generating silicone elastomers by crosslinking silicone polymers, called polysiloxanes.

[0009] In particular, hydrosilylation by photoirradiation, i.e. the irradiation of a silicone-based composition by a light beam, leads to rapid and moderate formation of crosslinked silicone elastomers, and therefore constitutes a good alternative to hot crosslinking.

[0010] Hydrosilylation is a chemical reaction that occurs between a silicon-hydrogen Si-H bond and a multiple bond, for example a carbon-carbon double bond or a carbon-carbon triple bond. A general hydrosilylation reaction scheme using an example of an alkene and a silane is shown below (S), in which R3 and R' represent alkyl groups. The most commonly used catalysts are two platinum complex catalysts, namely the Karstedt catalyst and the Speier catalyst.

[0011] [Chem.l] Catalyst

[0012] Silicone elastomers crosslinked by hydrosilylation generally exhibit better chemical and temperature resistance, as well as improved mechanical properties, such as tensile strength, tear strength, and gas permeability, compared to polymers obtained by other crosslinking techniques, for example by radical cross-linking.

[0013] In addition, hydrosilylation formulations offer the advantage of being chemically safe and odorless. They also exhibit no shrinkage (polyaddition reaction without release of molecules).

[0014] To illustrate recent advances in the field of crosslinking silicone polymers by hydrosilylation, mention may be made, for example, of document US 10155884, in the name of Dow Corning Corporation, which describes a 3D printing process using a photocurable, i.e. photoretic, silicone composition. This document describes in particular examples of silicone formulations which can be crosslinked by the reaction of a thiol group with a vinyl group in the presence of a radical initiator, as well as examples of silicone formulations crosslinked by hydrosilylation in the presence of photoactivatable catalysts: platinum (II) acetylacetonate and trimethyl(methylcyclopentadienyl)platinum (IV).

[0015] Document US10471653, in the name of Wacker Chemie AG, describes a 3D printing process, which uses polysiloxane formulations comprising vinyl and Si-H groups which can participate in crosslinking in the presence of a photoactivatable platinum catalyst, namely trimethyl(methylcyclopentadienyl)platinum(IV). 3D printing is carried out by controlled deposition of droplets followed by UV irradiation ensuring crosslinking of the deposited material.

[0016] Generally speaking, in photocrosslinking, the aim is to obtain rapid crosslinking of the silicone composition, without any other particularly preponderant criterion.

[0017] On the other hand, in 3D printing by hydrosilylation, one of the main desired effects is to crosslink the silicone composition only at the level of the regions that we come to irradiate, and that the crosslinking stops when we stop irradiating in order to limit the appearance of burrs, which would require carrying out a deburring step at the end of the process. We therefore seek to obtain good selectivity both during irradiation and after irradiation, and that this is controlled over time.

[0018] However, the 3D printing processes by hydrosilylation that currently exist are not entirely satisfactory in this regard. They often lead to final objects whose shape is not entirely faithful to the original CAD file, due to excess polymer resin on the surface of the object, and in particular for objects whose shape is complex. In certain cases, the object of the CAD model may even be impossible to produce, at least in a single iteration of the process, or to use, in the case where the object has complex shapes making the deburring operation delicate or even impossible. Brief description of the invention

[0019] An aim of the invention is to propose a silicone composition for the three-dimensional printing of an object by crosslinking said silicone composition by photohydrosilylation making it possible to obtain a final object of good visual quality, without burrs usually formed from excess resin on the object, the structure of which corresponds to that of the original CAD file, regardless of its structural complexity.

[0020] To this end, the invention provides a silicone composition for three-dimensional printing of an object by crosslinking said silicone composition by photohydrosilylation.

[0021] The composition is mainly characterized in that it comprises: (a) one or more polysiloxanes containing carbon-carbon multiple bonds and Si-H bonds between a hydrogen atom and a silicon atom, b) at least one photoactivatable platinum complex hydrosilylation catalyst, c) at least one crosslinking inhibiting agent, d) at least one optical absorbing agent capable of absorbing electromagnetic radiation in a wavelength range of ultraviolet and / or visible light.

[0022] Surprisingly, the Applicant has noticed that the combination of a photoactivatable platinum complex hydrosilylation catalyst, a crosslinking inhibiting agent, and an optical absorbing agent in the ultraviolet (UV) or visible range, makes it possible to manufacture more or less complex silicone objects of very good structural quality, which conform to the CAD model, and which do not have burrs, which avoids having to carry out deburring in post-treatment.

[0023] Rather than using the crosslinking inhibitor for its known primary function, know how to inhibit the crosslinking of polysiloxanes before carrying out 3D printing, during storage of said polymers, the Applicant has noticed that, surprisingly, during 3D printing, the crosslinking inhibitor allows crosslinking to occur only when the relevant regions of the polysiloxanes are irradiated, and ceases almost immediately when the irradiation of these regions ceases.

[0024] The crosslinking inhibitor thus makes it possible to crosslink the polysiloxanes selectively during irradiation only, with little or no inertia of crosslinking after irradiation.

[0025] This avoids the formation of excess crosslinked polymer resin on the surface of the final object, generally called “burrs”.

[0026] The invention also relates to a method for three-dimensional printing of an object by crosslinking a silicone composition by photohydrosilylation, in which the silicone composition is as defined above.

[0027] Another subject of the invention relates to the use of a crosslinking inhibiting agent in a silicone composition to prevent the appearance of burrs on an object manufactured by three-dimensional printing by crosslinking the silicone composition by photohydrosilylation, said silicone composition comprising one or more polysiloxanes containing carbon-carbon multiple bonds and Si-H bonds between a hydrogen atom and a silicon atom, and at least one photoactivatable platinum complex hydrosilylation catalyst. Preferably, the silicone composition is as described above. More preferably, the silicone composition used comprises at least one photoactivatable platinum complex hydrosilylation catalyst chosen from platinum (II) acetylacetonate Pt(Acac)2, trimethyl(methylcyclopentadienyl)platinum (IV), and a mixture thereof.The use of one and / or the other of these catalysts advantageously makes it possible to do without an optical absorbing agent while maintaining optimal print quality and without smearing.

[0028] It is specified that, within the framework of the invention, 3D printing includes stereolithography (SLA) and digital light processing (DLP). Description of the figures

[0029] Other advantages and characteristics of the invention will appear on reading the following description given by way of illustrative and non-limiting example, with reference to the following appended figures:

[0030] [Fig-1] is a photograph of a rectangular object obtained by a process 3D printing by photohydrosilylation according to the invention, according to example 1;

[0031] [Fig.2] is a photograph of a rectangular object obtained by a process 3D printing by photohydrosilylation not in accordance with the invention, according to the counter- example 1;

[0032] [Fig.3] is a photograph of a rectangular object obtained by a 3D printing process by photohydrosilylation not in accordance with the invention, according to counter-example 2;

[0033] [Fig.4] is a photograph of a cat-shaped object obtained by a 3D printing process by photohydrosilylation according to the invention, according to example 2;

[0034] [Fig.5] is a photograph of a rectangular object obtained by a 3D printing process by photohydrosilylation according to the invention, according to example 3;

[0035] [Fig.6] is a photograph of a rectangular object obtained by a 3D printing process by photohydrosilylation according to the invention, according to example 4;

[0036] [Fig.7] is a photograph of a rectangular object obtained by a 3D printing process by photohydrosilylation not in accordance with the invention, according to counter-example 3;

[0037] [Fig.8] is a photograph of a rectangular object obtained by a 3D printing process by photohydrosilylation according to the invention, according to example 5;

[0038] [Fig.9] is a photograph of a rectangular object obtained by a 3D printing process by photohydrosilylation not in accordance with the invention, according to counter-example 4;

[0039] [Fig. 10] is a photograph of a rectangular object obtained by a 3D printing process by photohydrosilylation according to the invention, according to example 6;

[0040] [Fig. 11] is a photograph of a rectangular object obtained by a 3D printing process by photohydrosilylation not in accordance with the invention, according to counter-example 5.

[0041] [Fig. 12] describes the UV visible spectrum of the two optical absorbers preferred within the framework of the invention.

[0042] Detailed description of embodiments of the invention

[0043] The composition of the invention comprises one or more polysiloxanes, that is to say polymers whose main chains are formed from alternating sequences of oxygen and silicon atoms substituted by organic groups.

[0044] Polysiloxanes contain carbon-carbon multiple bonds and Si-H bonds between a hydrogen atom and a silicon atom. This means that the polysiloxanes contain carbon-carbon bonds, which may be double or triple, preferably at least double bonds, as well as Si-H bonds. It is specified that the multiple bond (double or triple) is carried by a silicon atom, i.e. by the carbon atoms of the side chains linked to the silicon, and not included in the main chain of the polysiloxane.

[0045] The same polysiloxane may comprise both carbon-carbon multiple bonds and Si-H bonds. Alternatively, a polysiloxane may comprise carbon-carbon multiple bonds, and another polysiloxane may include Si-H bonds.

[0046] Preferably, the polysiloxane(s) are chosen from: polysiloxanes with bis-vinyl termination, polysiloxanes with dimethyl Si(CH3)2H termination, and mixtures thereof.

[0047] The polysiloxanes are preferably chosen from the following compounds: bis(dimethylvinylsilyl)-polydimethylsiloxane (p1), bis(trivinylsilyl)-polydimethylsiloxane (p2), bis(divinylmethylsilyl)-polydimethylsiloxane (p3), bis(dimethylsilyl)-polydimethylsiloxane (p4), bis(dimethylvinylsilyl)-poly(dimethylsiloxane-co-vinylmethylsiloxane) (p5), poly(dimethylsiloxane-co-methyl-hydrogensiloxane) (p6), poly(methyl-hydrogensiloxane) (p7), and mixtures thereof.

[0049] The photoactivatable platinum complex hydrosilylation catalyst makes it possible, in a manner known per se, to carry out the hydrosilylation reaction by UV and / or visible light activation.

[0050] In practice, we first witness an induction step corresponding to the complexation of the metal, for example platinum by the carbon-carbon multiple bond. Then, an oxidative addition of a hydrogenosilane function on the metal increases its oxidation state by two units. For platinum, its oxidation state goes from state 2 to state 4.

[0051] Preferably, the photoactivatable platinum complex hydrosilylation catalyst is chosen from: platinum di-ketonate complexes, platinum cyclodienyl complexes, and mixtures thereof.

[0052] The platinum complex photoactivatable hydrosilylation catalyst is preferably a platinum cyclopentadienyl complex or platinum bis(acetylacetonate).

[0053] More preferably, the photoactivatable platinum complex hydrosilylation catalyst is chosen from the following compounds: trimethyl(cyclopentadienyl) platinum (IV) (c1), trimethyl(methylcyclopentadienyl) platinum (IV) (c2), (1,5-cyclooctadiene)dimethyl platinum (II) (c3), platinum (II) acetylacetonate (c4).

[0055] The optical absorbing agent makes it possible to absorb a portion of the electromagnetic energy resulting from light irradiation, in the wavelength range corresponding to ultraviolet radiation and / or visible light. The permissible range of irradiated energy relative to the thickness of the thin layer of silicone to be crosslinked is thus extended. It becomes possible, depending on the content of absorbing agent in the composition, to adjust and standardize the depth of penetration of the electromagnetic energy into the silicone composition, the latter generally being contained in the tank of the printing device.

[0056] This results in obtaining uniform layers of hardened polymer material during the manufacture of the object, and thus in a final object of better visual quality, whose dimensions are accurate and repeatable and whose reliefs are precise.

[0057] It is specified that, in a manner known per se, the range of wavelengths corresponding to ultraviolet radiation is approximately 100 nm to 400 nm (nanometers). The range of wavelengths corresponding to visible light is approximately 400 nm to 800 nm.

[0058] Preferably, the optical absorbing agent is capable of absorbing electromagnetic radiation in a wavelength range of ultraviolet and visible light, said wavelength range being between 100 nm and 405 nm.

[0059] Preferably, the optical absorbing agent is the 2,5-Bis(5-tert-butyl-benzoxazol-2-yl)thiophene (BBOT) or its derivatives.

[0060] The crosslinking inhibiting agent usually makes it possible to improve the shelf life of the silicone composition during its storage, before proceeding with 3D printing.

[0061] Indeed, the crosslinking inhibitor agent prevents any untimely hydrosilylation reaction. Its inhibition function can be deactivated by UV light, so that it does not prevent hydrosilylation from taking place during the 3D printing process.

[0062] According to the invention, when the crosslinking inhibiting agent is used in a process for three-dimensional printing of an object by crosslinking said silicone composition via photohydrosilylation, it allows the crosslinking of the polysiloxanes to take place only in the irradiated regions, and only during the irradiation. Thus, when said regions cease to be irradiated, the crosslinking also ceases, which avoids the appearance of burrs on the final object and the need for a deburring step at the end of the process.

[0063] In other words, the Applicant has noticed that the crosslinking inhibiting agent can be used to prevent the appearance of burrs on the final object obtained after crosslinking of the silicone composition.

[0064] This improves the quality of the object obtained, while accelerating the production rate and reducing production costs.

[0065] When the crosslinking inhibiting agent is used in the silicone composition according to the invention, as described above, 3D printing leads to objects of very good quality, having little or no burrs, and whose shape and dimensions are controlled and conform to the original CAD file.

[0066] Preferably, the crosslinking inhibiting agent is chosen from the compounds having the following formulas (I), (II), (III) and (IV):

[0067] [Chem.4] ! , „,CK ,c< , Rt AK , Ri ^R2 R1X ,R2 R1 P' R2 'P' R2 P' OR OR OR I R3 "'R3 "R3 ^R3 (i) (ii) (m) (iv)

[0068] In which: - Ri, R2, Ri are, independently of each other, alkyl (methyl, ethyl, propyl etc.) or aryl (phenyl; p-toluyl; 2,4-di-tert-butylphenyl etc.).

[0069] Preferably, the crosslinking inhibiting agent is triphenylphosphine or one of its derivatives.

[0070] The composition may further comprise one or more fillers, preferably silicon dioxide and / or carbon black.

[0071] Said composition may also comprise one or more colorants and / or one or several pigments. Examples

[0072] Several examples of manufacturing objects by 3D printing by photohydrosi-lylation are described below.

[0073] The silicone compositions used, also called resins, are as follows:

[0074] - Composition A: 60% by weight of bis-terminated polydimethylsiloxanes vinyls (vinyl content of 0.3 mmol / g), 8.7% by weight of Si(CH3)2H-terminated polydimethylsiloxanes (Si-H content of 1.3 mmol / g), 1.9% by weight of polydimethylsiloxanes containing SiH groups on the main chain (Si-H content of 2.3 mmol / g), 17% by weight of fumed silica, and 12% by weight of non-reactive silicone oil.

[0075] - Composition B: 45.9% by weight of bis-terminated polydimethylsiloxanes vinyls (vinyl content of 0.3 mmol / g), 16% by weight of bis-vinyl terminated polydimethylsiloxanes (vinyl content of 1.08 mmol / g), 18.3% by weight of Si(CH3)2H terminated polydimethylsiloxanes (Si-H content of 1.4 mmol / g), 2% by weight of polydimethylsiloxanes containing SiH groups on the main chain (Si-H content of 4.3 mmol / g), 17.8% by weight of fumed silica.

[0076] For each example, the platinum complex-based photoactivatable hydrosilylation catalyst, the crosslinking inhibiting agent, and the optical absorbing agent are dissolved in chloroform. A defined quantity of the resulting solution is mixed with one of compositions A and B. The resulting composition is mixed using a centrifugal mixer (model Speedmixer™ DAC 400.1 FVZ) for approximately 1 minute at 2500 rpm.

[0077] The 3D printing device used is the Titan 3 model from the company Kudo3d, equipped with a polymer resin tank with dimensions of 109*66*30 mm. The resolution is set to 25 pm, and the LED current to 600*5.86 mA / unit.

[0078] The different examples, in accordance with the invention, are compared with counter-examples not in accordance with the invention.

[0079] The UV spectra illustrating the absorbance (A) on the ordinate as a function of the wavelength (X) of the radiation on the abscissa (solution in chloroform CHCl3 at 1 mg / L) for BBOT (B) and curcumin (C), two optical absorbing agents, are illustrated for information purposes in [Fig. 12].

[0080] Example 1

[0081] 25 mg of platinum (II) acetylacetonate catalyst Pt(Acac)2, 5 mg of triphenyl- phosphine (crosslinking inhibitor), and 5 mg of 2,5-Bis(5-tert-butyl-benzoxazol-2-yl)thiophene (BBOT - optical absorbing agent) are dissolved in 0.5 ml of chloroform. The resulting solution is mixed with 50 g of com position A. The resulting composition is poured into the tank of the 3D printing device, and 8 rectangular layers (3 mm * 40 mm) of 0.5 mm thickness are printed with an exposure time of 180 seconds per layer, and 30 seconds delay after each exposure. The resulting rectangular sample, illustrated in [Fig.l], has no burrs (absence of excess resin), and therefore does not require a deburring operation.

[0082] Counterexample 1

[0083] 25 mg of Pt(Acac)2 are dissolved in 0.5 ml of chloroform. The solution obtained is mixed with 50g of composition A. The resulting composition is poured into the tank of the 3D printing device, and 4 rectangular layers (3 mm * 40 mm) of 0.5 mm thickness are printed with an exposure time of 120 seconds per layer. The resulting rectangular sample, illustrated in [Fig.2], has burrs, is wider and has an irregular shape due in particular to the numerous burrs.

[0084] Counterexample 2

[0085] 25 mg of Pt(Acac)2 and 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (D4Vi - crosslinking inhibitor agent) are dissolved in 0.5 ml of chloroform. The resulting solution is mixed with 50g of composition A. The resulting composition is poured into the tank of the 3D printing device, and 4 rectangular layers (3 mm * 40 mm) of 0.5 mm thickness are printed with an exposure time of 120 seconds per layer, and 240 seconds of delay after each exposure. The resulting sample, illustrated in [Fig.3], is larger and has excess crosslinked resin on its surface.

[0086] Example 2

[0087] 25 mg of Pt(Acac)2, 5 mg of triphenylphosphine, and 5 mg of BBOT are dissolved in 0.5 ml of chloroform. The resulting solution is mixed with 50g of composition A. The resulting composition is poured into the tank of the 3D printing device, and a cat model (28 layers of 0.5 mm thickness) is printed with an exposure time of 180 seconds per layer, and a 30-second delay after each exposure. The resulting cat-shaped sample is shown in [Fig.4]. The contours and reliefs are perfectly clear and precise, and the sample has no burrs.

[0088] Example 3

[0089] 25 mg of Pt(Acac)2, 8.8 mg of tris(2,4-di-tert-butylphenyl)phosphite (Irgafos 168 - crosslinking inhibitor agent), and 5 mg of BBOT are dissolved in 0.5 ml of chloroform. The resulting solution is mixed with 50 g of composition A. The resulting composition is poured into the tank of the 3D printing device, and 8 rectangular layers (3 mm * 40 mm) of 0.5 mm thickness are printed with an exposure time of 360 seconds per layer. The rectangular sample, shown in [Fig.5], has no excess resin, i.e. no burrs.

[0090] Example 4

[0091] 25 mg of trimethyl(methylcyclopentadienyl)platinum (IV), 40 mg of triphenyl- phosphine, and 5 mg of BBOT are dissolved in 0.5 ml of chloroform. The resulting solution is mixed with 50 g of composition A. The resulting composition is poured into the tank of the 3D printing device, and 8 rectangular layers (3 mm * 40 mm) of 0.5 mm thickness are printed with an exposure time of 240 seconds per layer, and 60 seconds of delay after each exposure. The rectangular sample, illustrated in [Fig.6], has no excess resin, i.e. no burrs.

[0092] Counterexample 3

[0093] 25 mg of trimethyl(methylcyclopentadienyl)platinum (IV) and 40 mg of triphenyl- Phosphine are dissolved in 0.5 ml of chloroform. The resulting solution is mixed with 50g of composition A. The resulting composition is poured into the tank of the 3D printing device, and 4 rectangular layers (3 mm * 40 mm) of 0.5 mm thickness are printed with an exposure time of 240 seconds per layer, and a 5-second delay after each exposure. The resulting sample is shown in [Fig.7]. It is wider and has excess crosslinked resin on its surface.

[0094] Example 5

[0095] 25 mg of trimethyl(methylcyclopentadienyl)platinum (IV), 40 mg of triphenyl- phosphine, and 5 mg of curcumin (optical absorbing agent) are dissolved in 0.5 ml of chloroform. The resulting solution is mixed with 50 g of composition A. The resulting composition is poured into the tank of the 3D printing device, and 8 rectangular layers (3 mm * 40 mm) of 0.5 mm thickness are printed with an exposure time of 120 seconds per layer, and 120 seconds of delay after each exposure. The rectangular sample, illustrated in [Fig.8], has no excess resin, i.e. no burrs.

[0096] Counterexample 4

[0097] 25 mg of Pt(Acac)2 and 5 mg of BBOT are dissolved in 0.5 ml of chloroform. The resulting solution is mixed with 50g of composition A. The resulting composition is poured into the tank of the 3D printing device, and 8 rectangular layers (3 mm * 40 mm) of 0.5 mm thickness are printed with an exposure time of 120 seconds per layer, and a 30-second delay after each exposure. The resulting rectangular sample is shown in [Fig.9]. It has burrs, is wider, and has an irregular shape.

[0098] Example 6

[0099] 25 mg of Pt(Acac)2, 5 mg of triphenylphosphine, and 5 mg of BBOT are dissolved in 0.5 ml of chloroform. The resulting solution is mixed with 50g of composition B. The resulting composition is poured into the tank of the 3D printing device, and 8 rectangular layers (3 mm * 40 mm) of 0.5 mm thickness are printed with an exposure time of 120 seconds per layer. The rectangular sample, illustrated in [Fig.10], shows no excess resin, i.e. no smearing.

[0100] Counterexample 5

[0101] 25 mg of Pt(Acac)2 and 5 mg of triphenylphosphine are dissolved in 0.5 ml of chloroform. The resulting solution is mixed with 50g of composition B. The resulting composition is poured into the tank of the 3D printing device, and 8 rectangular layers (3 mm * 40 mm) of 0.5 mm thickness are printed with an exposure time of 60 seconds per layer, and a 30-second delay after each exposure. The resulting rectangular sample is shown in [Fig. 11]. It has burrs, is wider, and has an irregular shape.

Claims

Claims

1. A silicone composition for three-dimensional printing of an object by crosslinking said silicone composition by photohydrosilylation comprising: a) one or more polysiloxanes containing multiple carbon-carbon bonds and Si-H bonds between a hydrogen atom and a silicon atom, b) at least one photoactivatable platinum complex hydrosilylation catalyst, c) at least one crosslinking inhibiting agent, d) at least one optical absorbing agent capable of absorbing electromagnetic radiation at least in a wavelength range of ultraviolet and / or visible light, characterized in that the crosslinking inhibiting agent is chosen from compounds having the following formulae (I), (II), (III) and (IV): [Chem. 7] . A As. , R^ As., A2 RC A' R! P R2 P R2 P ", OR c, OR A OR i R3 R3 R3 'R5 0) (I!) (!!!) (ÎV) In which: - Rb R2, R3 are, independently of each other, alkyl or aryl.

2. Composition according to claim 1, in which the polysiloxanes are chosen from: bis-vinyl terminated polysiloxanes, dimethyl terminated polysiloxanes Si(CH3)2H, and mixtures thereof.

3. Composition according to claim 1, in which the polysiloxanes are chosen from the following compounds: bis(dimethylvinylsilyl)-polydimethylsiloxane (p 1 ), bis(trivinylsilyl)-polydimethylsiloxane (p2), bis(divinylmethylsilyl)-polydimethylsiloxane (p3), bis(dimethylsilyl)-polydimethylsiloxane (p4), bis(dimethylvinylsilyl)-poly(dimethylsiloxane-co-vinylmethylsiloxane) (p5), poly(dimethylsiloxane-co-methyl-hydrogensiloxane) (p6), poly(methyl-hydrogensiloxane) (p7), and mixtures thereof: [Chem. 5]

4.

5.

6. Composition according to any one of claims 1 to 3, in which the photoactivatable platinum complex hydrosilylation catalyst is chosen from: platinum di-ketonate complexes, platinum cyclodienyl complexes, and mixtures thereof. A composition according to any one of claims 1 to 3, wherein the photoactivatable platinum complex hydrosilylation catalyst is a platinum cyclopentadienyl complex or platinum bis(acetylacetonate). A composition according to any one of the preceding claims, wherein the photoactivatable platinum complex hydrosilylation catalyst is selected from the following compounds: trimethyl(cyclopentadienyl) platinum(IV) (c1), trimethyl(methylcyclopentadienyl) platinum(IV) (c2), (1,5-cyclooctadiene)dimethyl platinum(II) (c3), platinum(II) acetylacetonate (c4): [Chem. 6] (cl) (c2) (c3) (c4)

7. A composition according to any preceding claim, wherein the crosslinking inhibiting agent is triphenyl- phosphine or one of its derivatives.

8. A composition according to any preceding claim, wherein the optical absorbing agent is capable of absorbing electromagnetic radiation in a wavelength range of ultraviolet and visible light, said wavelength range being between 100 nm and 405 nm.

9. A composition according to any preceding claim, wherein the optical absorbing agent is 2,5-Bis(5-tert-butyl-benzoxazol-2-yl)thiophene or a derivative thereof.

10. A composition according to any preceding claim, further comprising one or more fillers, preferably silicon dioxide and / or carbon black.

11. A composition according to any preceding claim, further comprising one or more colorants and / or one or more pigments.

12. Method for three-dimensional printing of an object by crosslinking a silicone composition by photohydrosilylation, characterized in that it uses a silicone composition in accordance with any one of claims 1 to 11.

13. Use of a crosslinking inhibiting agent in a silicone composition for preventing the occurrence of smears on an object manufactured by three-dimensional printing by crosslinking the silicone composition by photohydrosilylation, said silicone composition comprising one or more polysiloxanes containing carbon-carbon multiple bonds and Si-H bonds between a hydrogen atom and a silicon atom, and at least one photoactivatable platinum complex hydrosilylation catalyst.

14. Use according to claim 13, wherein the silicone composition conforms to any one of claims 1 to 11.

15. Use according to claim 13 or claim 14, wherein the silicone composition comprises at least one photoactivatable platinum complex hydrosilylation catalyst selected from platinum (II) acetylacetonate, trimethyl(methylcyclopentadienyl)platinum (IV), and a mixture thereof.

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