Post-treatment of 3D printed elastomeric silicone articles

Abstract

The present invention relates to a process for the post-treatment of a 3D printed silicone article, said process comprising coating the 3D printed silicone article with a crosslinkable silicone composition comprising a microfiller. The invention further relates to a crosslinkable silicone composition comprising a microfiller, and to the use thereof as a post-treatment composition for post-treating 3D printed silicone articles.

Description

Technical Field

[0001] The present invention relates to a post-treatment method for 3D-printed silicone elastomer articles. More specifically, the present invention relates to a method for post-treating a 3D-printed silicone elastomer article, especially its surface, with a specific post-treatment composition. The present invention also relates to the specific post-treatment composition, the post-treated 3D-printed silicone elastomer article, and an additive manufacturing method comprising the post-treatment method. Background Art

[0002] Three-dimensional (3D) printing is a process in which materials are deposited, joined or solidified under computer control to produce a three-dimensional object in which materials are added together layer by layer. Additive manufacturing technology covers different technologies in which objects are obtained layer by layer through specific techniques such as extrusion, sintering, fusion, photopolymerization, spraying, lamination and deposition.

[0003] Silicone has been used in various medical applications, mainly due to its biocompatibility and thermal stability. Medical grade silicone is used in anatomical models, mannequins, prostheses, drugs, lubricated injection devices, etc. Producing silicone structures by 3D printing is a promising method with high design flexibility.

[0004] However, objects printed by this 3D printing process, while faithful to the geometry of the original electronic file used for printing, may also reflect some surface problems. In fact, 3D printing technology is based on a layer-by-layer printing process. Due to the layer-by-layer printing or deposition in the 3D printing process, the surface or contour of the 3D printed object often has a wrinkled or wavy appearance, which can be called a step effect or sometimes aliasing. The step effect is related to several problems:

[0005] - Step effects can lead to aesthetic issues, which may be unacceptable when the 3D printed article is intended to be used, for example, as a prosthesis. It is highly desirable that the surface of a 3D printed article exhibits a skin-like or soft touch similar to human skin.

[0006] - In addition, depending on the final application, the mechanical and / or physical properties of the 3D printed article may be affected by excessive surface roughness. For example, when the 3D printed article is a 3D printed silicone tracheal patch for repairing tracheal defects, high roughness may trigger an excessive inflammatory response in tracheostomy patients.

[0007] Different methods have been proposed to eliminate the step effect. For metal materials, polishing, anodizing, sandblasting, powder coating and electroplating are usually used to obtain smooth surfaces and contours. For plastic or polymer objects, some mechanical treatments such as sandblasting or polishing can be used for surface finishing (polishing) to remove the step effect. However, when the 3D printed article is a silicone elastomer, these standard methods seem to be inappropriate.

[0008] US patent applications US2020 / 0108548 A1, US2020 / 0316850 A1 and US 2020 / 0238601 A1 disclose the possibility of post-processing 3D printed silicone articles to improve the surface quality of the silicone articles. However, these documents do not disclose any details about the post-processing steps, nor do they disclose any examples.

[0009] International patent application WO 2022 / 141374 A1 discloses a method for post-treatment of the surface of an additively manufactured object, comprising the steps of coating at least a portion of the surface with a curable silicone composition and then curing the coating at room temperature or by heat or UV radiation, characterized in that the viscosity of the curable silicone composition is 300mPa.s to 500000mPa.s. According to the document, this post-treatment method can greatly or completely remove the step effect without compromising the adhesion and mechanical properties of the surface. However, the document does not mention the improvement of the skin touch of the surface. Summary of the invention

[0010] The present invention aims to provide a post-treatment method for 3D printed silicone articles for reducing step effects. The present invention also aims to provide a method for additively manufacturing 3D silicone elastomer articles having a surface with improved skin touch. SUMMARY OF THE INVENTION

[0012] All of these objectives and others are achieved by the present invention, which is directed to a method for post-processing a 3D printed silicone article, the method comprising coating the 3D printed silicone article with a cross-linkable silicone composition comprising microfillers.

[0013] The present invention also relates to a cross-linkable silicone composition comprising microfillers, and use thereof as a post-treatment composition for post-treatment of 3D printed silicone articles.

[0014] The present invention also relates to a method for additively manufacturing a 3D silicone elastomeric article, comprising the steps of a) additively manufacturing a silicone article, and b) coating the 3D printed silicone article with a cross-linkable silicone composition comprising a microfiller.

[0015] Detailed description of the invention

[0016] In the absence of other indications, the viscosity of the silicone compositions described herein and their individual components corresponds to the amount of "Newtonian" dynamic viscosity at the indicated temperature, i.e. the dynamic viscosity measured in a manner known per se using a Haake rheometer at a shear rate gradient that is sufficiently low such that the measured viscosity is independent of the shear rate gradient.

[0017] Unless otherwise stated, contents in % or ppm are by weight.

[0018] As used herein, the term "silicone elastomer" includes the cross-linked product of any cross-linkable silicone composition. The terms "silicone elastomer" and "silicone rubber" are used interchangeably.

[0019] As used herein, the terms "crosslinked" and "cured" are used interchangeably and refer to the reaction that occurs when the components of the crosslinkable silicone composition are combined and allowed to react, resulting in a crosslinked silicone elastomer.

[0020] According to ISO / ASTM standard 52900 (“Additive manufacturing-General principles-Terminology”, 2017), “Additive manufacturing (AM)” is defined as a process of joining materials from 3D modal data, usually layer by layer, to manufacture parts, as opposed to subtractive manufacturing and prototyping manufacturing techniques. Synonyms associated with AM include additive manufacturing, additive process, additive technology, additive layer manufacturing, layer manufacturing, solid freeform manufacturing, and freeform manufacturing. In addition, “3D printing” is defined as the manufacture of objects by depositing material using a print head, nozzle, or another printer technology. It is a term that is often used synonymously with additive manufacturing in non-technical contexts. As used herein, “3D printing” is generally interchangeable with “additive manufacturing” and vice versa. “3D printer” is defined as a machine used for 3D printing.

[0021] The present invention relates to a post-processing method for a 3D-printed silicone article, the method comprising coating the 3D-printed silicone article with a cross-linkable silicone composition containing microfillers.

[0022] The crosslinkable silicone composition according to the present invention comprises a microfiller. The microfiller according to the present invention is a filler material having an average particle size of 1 μm-1000 μm. As used herein, "average particle size", also referred to as "D50", is the particle size value at 50% in the cumulative volume distribution. The particle size can typically be measured by static laser scattering. The average particle size can be measured according to the ISO13320 standard. The microfiller can advantageously be selected from powders containing spherical (or substantially spherical) particles. Spherical particles refer to particles having a spherical shape with one or more nearly spherical diameters spanning the center of mass or geometric center, and may be spherical particles with an uneven surface. In particular, the spherical particles have a ratio of the shortest diameter to the longest diameter of 0.2 to 1, preferably 0.3 to 1 or, for example, 0.4 to 0.5, or 0.6 to 0.9, or 0.7 to 0.9.

[0023] The microfiller may be selected from low-density hollow fillers, silica or glass microfillers and spherical silicone resin particles.

[0024] According to a first preferred embodiment, the crosslinkable silicone composition according to the present invention comprises a low-density hollow filler. The low-density hollow filler may preferably have a true density of less than 1 g / cm 3 (g / cm3), more preferably less than 0.8 g / cm 3 , even more preferably less than 0.5 g / cm 3 According to one embodiment, the low-density hollow filler may have a true density of 0.01 g / cm 3 Up to 1g / cm 3 .

[0025] In this document, the expression "true density" is the value obtained by dividing the mass of a filler sample by the true volume of that mass of filler (measured by a gas densimeter). The "true volume" is the aggregated total volume of the filler, not the bulk volume. The true density (sometimes also referred to as "specific density" or "effective density") is thus the particle density measured by liquid displacement, whereas the bulk density is the weight measured in the container and includes interstitial air.

[0026] According to a preferred embodiment, the low-density hollow filler according to the present invention is a hollow microsphere, preferably selected from the group consisting of mineral hollow microspheres and organic hollow microspheres.

[0027] As examples of suitable mineral hollow microspheres, mention may be made of hollow glass microspheres or hollow ceramic microspheres.

[0028] Hollow glass microspheres, sometimes also called "hollow glass beads" or "hollow glass bubbles", are small hollow spheres of hardened silica (glass) whose size and density can vary depending on the grade. They have a shell that is thick enough to maintain structural rigidity. Due to their hollow nature, they are very lightweight and the density varies with size and wall thickness. In bulk, they appear as a white powder. The main differences between grades are their size, strength and density, where the strength of the microspheres is expressed in terms of their average isostatic crushing strength.

[0029] According to one embodiment, the hollow glass beads are hollow borosilicate glass microspheres.

[0030] According to one embodiment, the hollow glass microspheres have a true density of 0.10 g / cm 3 Up to 0.75g / cm 3 .

[0031] According to a preferred embodiment, the hollow glass microspheres are selected from:

[0032] 1) 3M TM Glass Bubbles Floated Series (A16 / 500, G18, A20 / 1000, H20 / 1000, D32 / 4500 and H50 / 10,000 EPX glass bubble products) and 3M TM Glass Bubbles K, S, iM and XLD Series (such as, but not limited to, K1, K11, K15, S15, S22, K20, K20HS, K25, S32, S32LD, S35, XLD3000, S28HS, S35, K37, S38, S38HS, S38XHS, S32HS, K46, K42HS, S42XHS, S60, S60HS, iM16K, iM30K glass bubble products) are sold by 3M Company. The glass bubbles exhibit various crushing strengths ranging from 1.72 MPa (250 psi) to 186.15 MPa (27,000 psi), at which a ten percent volume of the first plurality of glass bubbles is broken. Other glass bubbles sold by 3M may also be used according to the present invention, such as 3M TM Glass Bubbles-HGS Series and 3M with Surface Treatment TM Glass bubbles; and

[0033] 2) By product name (such as the following products: 110P8, 60P18, 34P30 and 25P45) or under the trade name Hollow glass microspheres sold by Potters Industries Inc., such as the following products: 6014, 6019, 7019, 6019S, 5020, 5020FPS, 7023, 7028, 2058, 6036, 7037, 7040S, 6042S, 6048, and 5070S.

[0034] Hollow ceramic microspheres, also known as cenospheres, are lightweight, inert hollow spheres filled with inert air or gas, typically produced as a byproduct of coal combustion in thermal power plants. They are made primarily of silicon dioxide and aluminum oxide. The color of cenospheres varies from gray to almost white, and their true density is about 0.4 g / cm 3 -0.8g / cm 3 . It flows like a liquid and has a powdery appearance. Suitable hollow microspheres are unsurface treated or surface treated with a silane-based coupling agent, such as one or more of the following: 3-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-(methacryloyloxy)propyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 4-aminopropylmethyldimethoxysilane or 3-aminopropylmethyldiethoxysilane.

[0035] Commercially available examples of hollow ceramic microspheres are produced by 3M TM Commercialization of Z-Light TM Spheres Microspheres (such as the following products: 3M TM Z-Light TM Spheres G-3125, G-3150 and G-3500).

[0036] As an example of suitable organic hollow microspheres, it can be any organic hollow microspheres as described below, which consist of thermoplastic spheres encapsulating a gas. The thermoplastic polymer can be any organic polymer, such as polyethylene (PE), polyurethane (PU), polysulfide (PS) or polymethyl methacrylate (PMMA). Commercially available examples include those from Akzo Nobel (now Nouryon). Microspheres.

[0037] The low-density hollow filler according to the present invention may preferably have an average particle size of 1 μm-1000 μm. Typically, the hollow glass microspheres used in the composition are substantially homogeneous and substantially uniform in sphericity, and have an average particle size of about 5 μm to 500 μm, for example, about 10 μm to 70 μm. Typically, the organic hollow microspheres used in the composition are substantially homogeneous and substantially uniform in sphericity, and have an average particle size of about 10 μm to 1000 μm, for example, about 10 μm to 70 μm. In the composition according to the present invention, it is preferred to select a low-density hollow filler having an average particle size of less than 600 μm, more preferably less than 400 μm, more preferably less than 200 μm, and even more preferably less than 100 μm.

[0038] According to a second embodiment, the crosslinkable silicone composition according to the invention comprises silica or glass microfillers.

[0039] Silica microfillers can be selected from silica powders having an average particle size greater than 1 μm. These silicas can advantageously be colloidal silica, combustion silica, precipitated silica or mixtures thereof. Silica microfillers can be untreated or treated, in particular, the surface of the silica particles can be rendered hydrophobic. Making the filler particles hydrophobic can be performed before or after the precipitated silica particles are dispersed in the polysiloxane component. This can be achieved by pretreating the silica particles with a hydrophobic agent such as a fatty acid, a reactive silane, a wax or a reactive siloxane. Examples include, but are not limited to, stearic acid, dimethyldichlorosilane, trimethylchlorosilane, hexamethyldisilazane, hydroxyl-terminated or methyl-terminated polydimethylsiloxane, a siloxane resin or a mixture of two or more of these substances. Precipitated silica particles that have been treated to be hydrophobic are commercially available on the market. The most preferred hydrophobic agent is hexamethyldisilazane or polyethylene wax.

[0040] Examples of commercially available silica microfillers are Silica and Silicon dioxide, both from Evonik (products such as: OK 607,

[0041] 3300, 3600, TS100, 30A / B,

[0042] 60A / B, DP-0111, DP-0112 and DP-0115); Aerogel (silicon dioxide aerogel particles) from Cabot (products such as MT1100 and MT1200); and Silicon dioxide, from Grace (products such as C Series: 7000, C906, C907, and ED Series: ED30).

[0043] The glass microfiller may be selected from glass beads having an average particle size greater than 1 μm. Similar to the silica microfiller, the glass beads may be untreated or treated. Examples of commercially available glass microfillers are Potters' Solid glass balls (A-GLASS series or E-GLASS series) and Sovitec's Solid glass beads.

[0044] According to a third embodiment, the crosslinkable silicone composition according to the present invention comprises spherical silicone resin particles. The spherical silicone resin particles may be spherical polysilsesquioxane (preferably polymethylsilsesquioxane) particles and present a substantially spherical shape.

[0045] "Polysilsesquioxane particles" means that the particles contain at least 50 mol% T units, based on the sum of M, D, T and Q units in the molecule. Preferably, the polysilsesquioxane particles contain 60 mol% or more, 70 mol% or more, 80 mol% or more, 90 mol% or more, and can be 100 mol% T units, based on the sum of M, D, T and Q units.

[0046] "Polymethylsilsesquioxane" refers to a polysilsesquioxane in which the substituent groups of the T units are substantially methyl groups.

[0047] An example of commercially available spherical silicone resin particles is Mirasil from Elkem Silicones. TM Micropearl 40, silicone resin powder available from Shin-Etsu Chemical Co., Ltd. (products such as KMP-706, KMP-701, or X-52-1621), and Tospearl supplied by Momentive TM Silicone beads.

[0048] Any microfiller according to the invention can be added directly to the crosslinkable silicone composition as such during the preparation of the mixture, or in the form of a dispersion of particles in a diluent.

[0049] The amount of microfillers in the crosslinkable silicone composition according to the present invention may preferably be 0.1% to 50% by weight, preferably 1% to 20% by weight, more preferably 2% to 15% by weight, even more preferably 5% to 10% by weight, relative to the total weight of the crosslinkable silicone composition.

[0050] According to one embodiment, the microfiller according to the invention may be an inorganic material. The chemical composition of the microfiller may be silica, silica and alumina, glass (for example of the soda-lime or borosilicate type) or organosilicon.

[0051] The microfillers as described above are contained in the crosslinkable silicone composition.According to a preferred embodiment, the crosslinkable silicone composition is a polyaddition-crosslinkable silicone composition, ie capable of crosslinking by a polyaddition reaction.

[0052] The crosslinkable silicone composition may comprise:

[0053] (A) at least one organopolysiloxane compound A comprising at least two alkenyl groups bonded to silicon atoms per molecule,

[0054] (B) at least one organohydrogenpolysiloxane compound B comprising, per molecule, at least two hydrogen atoms bonded to the same or different silicon atoms,

[0055] (C) at least one polyaddition catalyst C, preferably a polyaddition catalyst consisting of at least one metal or compound from the platinum group,

[0056] (D) at least one microfiller D, wherein the microfiller D is as described above.

[0057] Optionally, the crosslinkable silicone composition may comprise at least one crosslinking inhibitor E.

[0058] Optionally, the crosslinkable silicone composition may further comprise at least one reinforcing filler F.

[0059] Optionally, the crosslinkable silicone composition may further comprise at least one solvent G.

[0060] This silicone composition can be crosslinked by a polyaddition reaction between an organopolysiloxane having at least two unsaturated bonds and an organopolysiloxane having at least two hydrosilyl units.

[0061] Preferably, the organopolysiloxane A has at least two silicon-bonded C 2-12 It may be composed of the following units: at least two siloxy units of the following formula: Y a R 1 b SiO (4-a-b) / 2

[0062] in:

[0063] -Y is C 2-12 Alkenyl, preferably C 2-6 alkenyl, more preferably vinyl,

[0064] -R 1 is a monovalent hydrocarbon group having 1 to 12 carbon atoms, optionally substituted by one or more halogen atoms, preferably selected from an alkyl group having 1 to 8 carbon atoms such as methyl, ethyl or propyl, a cycloalkyl group having 3 to 8 carbon atoms and an aryl group having 6 to 12 carbon atoms,

[0065] - a = 1 or 2, b = 0, 1 or 2 and the sum of a + b = 2 or 3,

[0066] and optionally, units of the formula: R 1 c SiO (4-c) / 2

[0067] Where R 1 has the same meaning as above and c=0, 1, 2 or 3.

[0068] In this disclosure, reference is made to the following nomenclature to represent siloxy units:

[0069] M:R 1 3SiO 1 / 2 Siloxy units,

[0070] M Vi :Selected from YR 1 2SiO 1 / 2 and Y2R 1 SiO 1 / 2 Siloxy units;

[0071] D: R 1 2SiO 2 / 2 Siloxy units,

[0072] D Vi :Selected from Y2SiO 2 / 2 or YR 1 SiO 2 / 2 Siloxy units of siloxy units,

[0073] T: Formula R 1 SiO 3 / 2 The siloxy units of

[0074] Q: Formula SiO 4 / 2 The siloxy units of

[0075] The symbols Y and R 1As mentioned above.

[0076] As examples of terminal "M" units, mention may be made of trimethylsiloxy or dimethylphenylsiloxy.

[0077] As the terminal "M vi As examples of "" units, there may be mentioned dimethylvinylsiloxy or dimethylhexenylsiloxy.

[0078] As examples of the “D” unit, there may be mentioned dimethylsiloxy and methylphenylsiloxy.

[0079] As "D Vi As examples of " " units, there may be mentioned methylvinylsiloxy, methylbutenylsiloxy, methylhexenylsiloxy, methyldecenylsiloxy or methyldecadienylsiloxy.

[0080] As an example of a "T" unit, methylsiloxy may be mentioned.

[0081] The organopolysiloxane A may be a linear organopolysiloxane, a cyclic organopolysiloxane or a resin (ie a branched organopolysiloxane). The crosslinkable silicone composition according to the invention may comprise a mixture of different organopolysiloxanes A.

[0082] According to one embodiment, the organopolysiloxane A may be a linear organopolysiloxane A1. The linear organopolysiloxane exhibits a structure consisting essentially of D or D vi Siloxy unit and terminal M or M vi The linear structure formed by the siloxy units.

[0083] Examples of linear organopolysiloxanes that may be the organopolysiloxane A according to the invention are:

[0084] - poly(dimethylsiloxane) containing dimethylvinylsilyl end groups;

[0085] - poly(dimethylsiloxane-co-methylphenylsiloxane) containing dimethylvinylsilyl end groups;

[0086] - poly(dimethylsiloxane-co-methylvinylsiloxane) containing dimethylvinylsilyl end groups;

[0087] - poly(dimethylsiloxane-co-methylvinylsiloxane) containing trimethylsilyl termini; and

[0088] - Cyclic poly(methylvinylsiloxane).

[0089] According to a preferred embodiment, the organopolysiloxane A1 comprises terminal dimethylvinylsilyl units, and even more preferably, the organopolysiloxane A1 is a poly(dimethylsiloxane) comprising terminal dimethylvinylsilyl groups. The number of dimethylsiloxane units may be 5-1000, preferably 100-600.

[0090] Preferably, the dynamic viscosity of organopolysiloxane A1 at 25° C. may be 100 to 120,000 mPa.s, preferably 100 to 80,000 mPa.s, more preferably 1,000 to 50,000 mPa.s, even more preferably 5,000 to 20,000 mPa.s. The organopolysiloxane A1 may preferably be referred to as organopolysiloxane oil.

[0091] Preferably, the organopolysiloxane A1 has a weight content of alkenyl units of 0.001% to 30%, preferably 0.01% to 10%, preferably 0.02% to 5%.

[0092] According to another embodiment, the organopolysiloxane A may be a branched organopolysiloxane A2 (ie, resin) comprising alkenyl units. It is preferably selected from the organosilicon resins of the following formula:

[0093] -M Vi Q, in which the alkenyl group bonded to the silicon atom is carried by the M group,

[0094] -MM Vi Q, in which the alkenyl group bonded to the silicon atom is carried by a portion of the M unit,

[0095] -MD Vi Q, in which the alkenyl group bonded to the silicon atom is carried by the D group,

[0096] -MDD Vi Q, wherein the alkenyl group bonded to the silicon atom is carried by a portion of the D group,

[0097] -MM Vi TQ, in which the alkenyl group bonded to the silicon atom is carried by a portion of the M unit,

[0098] -MM Vi DD Vi Q, in which the hydrogen atoms bonded to the silicon atoms are carried by a portion of the M and D units,

[0099] - and mixtures thereof,

[0100] According to one preferred embodiment, the crosslinkable silicone composition according to the invention comprises a mixture of at least one linear organopolysiloxane A1 as defined above and at least one branched organopolysiloxane (ie resin) A2 as defined above.

[0101] In the crosslinkable silicone composition according to the present invention, the total amount of the organopolysiloxane compound A containing at least two alkenyl groups bonded to silicon atoms per molecule may preferably be 40% to 95% by weight, preferably 50% to 90% by weight, relative to the total weight of the crosslinkable silicone composition.

[0102] The crosslinkable silicone composition according to the present invention may further comprise at least one organic silicon-containing compound B having at least two and preferably at least three silicon-bonded hydrogen atoms per molecule. The organic silicon-containing compound B is preferably an organohydrogenpolysiloxane compound containing at least two and preferably at least three hydrosilyl functional groups (or Si-H units) per molecule.

[0103] The organic silicon-containing compound B may advantageously be an organopolysiloxane comprising at least two, preferably at least three, siloxy units of the formula: d R 2 e SiO (4-d-e) / 2 ,

[0104] in:

[0105] -Same or different R 2 represents a monovalent group having 1 to 12 carbon atoms,

[0106] - d = 1 or 2, e = 0, 1 or 2 and d + e = 1, 2 or 3;

[0107] and optionally, other units of the formula: R 2 f SiO (4-f) / 2

[0108] Where R 2 has the same meaning as above, and f=0, 1, 2 or 3.

[0109] It should be understood that in the above formula, if there are multiple R 2 groups, they may be the same or different from each other. 2 R may represent a monovalent group selected from an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms and an aryl group having 6 to 12 carbon atoms which is optionally substituted by at least one halogen atom such as chlorine or fluorine. 2 can be advantageously selected from methyl, ethyl, propyl, 3,3,3-trifluoropropyl, xylyl, tolyl and phenyl, and most preferably, R 2 It's methyl.

[0110] The sign d is preferably equal to 1.

[0111] In this disclosure, reference is made to the following nomenclature to represent siloxy units:

[0112] M:R 2 3SiO 1 / 2 Siloxy units,

[0113] M': R 2 2HSiO 1 / 2 Siloxy units,

[0114] D: R 2 2SiO 2 / 2 Siloxy units,

[0115] D': R 2 HSiO 2 / 2 Siloxy units,

[0116] T: R 2 SiO 3 / 2 siloxy units, and

[0117] Q:SiO 4 / 2 Siloxy units,

[0118] Where R 2 Has the same meaning as above.

[0119] The organic silicon-containing compound B may have a linear, branched or cyclic structure. The degree of polymerization is preferably greater than or equal to 2. Typically, it is less than 5,000.

[0120] Preferably, the viscosity of the organic silicon-containing compound B is from 1 mPa.s to 5,000 mPa.s, more preferably from 1 mPa.s to 2,000 mPa.s, and still more preferably from 5 mPa.s to 1,000 mPa.s.

[0121] Examples of organohydrogenpolysiloxanes that may be the organosilicon-containing compound B according to the invention comprising at least two silicon-bonded hydrogen atoms are:

[0122] - poly(dimethylsiloxane) containing hydrodimethylsilyl termini;

[0123] - poly(dimethylsiloxane-co-methylhydrogensiloxane) containing trimethylsilyl termini;

[0124] - poly(dimethylsiloxane-co-methylhydrogensiloxane) containing hydrodimethylsilyl termini;

[0125] - poly(methylhydrogenosiloxane) containing trimethylsilyl termini; and

[0126] - Cyclic poly(methylhydrogensiloxane).

[0127] When the organic silicon-containing compound B has a branched structure, it is preferably selected from the organic silicone resins of the following formula:

[0128] -M'Q, in which the hydrogen atom bonded to the silicon atom is carried by the M group,

[0129] -MM'Q, in which the hydrogen atom bonded to the silicon atom is carried by a part of the M unit,

[0130] -MD'Q, in which the hydrogen atom bonded to the silicon atom is carried by the D group,

[0131] -MDD'Q, in which the hydrogen atom bonded to the silicon atom is carried by a portion of the D group,

[0132] -MM'TQ, in which the hydrogen atoms bonded to the silicon atoms are carried by a portion of the M units,

[0133] -MM'DD'Q, in which the hydrogen atoms bonded to the silicon atoms are carried by a portion of the M and D units,

[0134] - and mixtures thereof.

[0135] Preferably, the organic silicon-containing compound B has a weight content of hydrosilyl Si—H functional groups of 0.2% to 91%, more preferably 3% to 80%, more preferably 15% to 70%.

[0136] Advantageously, the molar ratio of hydrosilyl SiH functional groups of the organic silicon-containing compound B to olefin functional groups of the compound A is from 5 to 100, preferably from 10 to 90, more preferably from 15 to 65, even more preferably from 20 to 55.

[0137] According to a preferred embodiment, the crosslinkable silicone composition according to the invention comprises a mixture of at least one organic silicon-containing compound B1 having at least three silicon-bonded hydrogen atoms per molecule and at least one organic silicon-containing compound B2 having two silicon-bonded hydrogen atoms per molecule. The organic silicon-containing compound B2 preferably contains terminal dimethylhydrogen silyl units, and even more preferably, the organic silicon-containing compound B2 is a poly(dimethylsiloxane) containing terminal dimethylhydrogen silyl groups. The number of dimethylsiloxane units may be from 1 to 200, preferably from 1 to 150, more preferably from 3 to 120. Such an organic silicon-containing compound B2 may be described as a "chain extender" due to its presumed effect of increasing the mesh size of the network when it is crosslinked. In addition, such an organic silicon-containing compound B1 having three or more silicon-bonded hydrogen atoms per molecule may be described as a "crosslinker". Preferably, the organic silicon-containing compound B1 is a poly(dimethylsiloxane-co-methylhydrogen siloxane) containing trimethylsilyl terminals and / or hydrodimethylsilyl terminals.

[0138] In the crosslinkable silicone composition according to the invention, the total amount of organic silicon-containing compounds B having at least two silicon-bonded hydrogen atoms per molecule may preferably be 1% to 20% by weight, preferably 3% to 15% by weight, relative to the total weight of the crosslinkable silicone composition.

[0139] The hydrosilylation catalyst C may be chosen in particular from compounds of platinum and rhodium, but may also be chosen from silicon compounds, such as those described in patent applications WO2015 / 004396 and WO2015 / 004397; germanium compounds, such as those described in patent application WO2016 / 075414; or complexes of nickel, cobalt or iron, such as those described in patent applications WO2016 / 071651, WO2016 / 071652 and WO2016 / 071654. Catalyst C is preferably a compound derived from at least one metal belonging to the platinum group. These catalysts are well known. In particular, complexes of platinum and organic products described in US Pat. Nos. 3,159,601, 3,159,602 and 3,220,972 and in European Patents EP 0057459, EP 0188978 and EP 0190530, or complexes of platinum and vinylated organosiloxanes described in US Pat. Nos. 3,419,593, 3,715,334, 3,377,432 and 3,814,730 may be used. Alternatively, hydrosilylation photocatalysts may be used. The catalysts may be activated by irradiation, preferably by UV radiation. Examples of suitable platinum-based photocatalysts include: bis(acetylacetonate)platinum, trimethyl(acetylacetonate)platinum complex, trimethyl(2,4-pentanedione)platinum complex, trimethyl(3,5-heptanedione)platinum complex, trimethyl(methyl acetoacetate)platinum complex, bis(2,4-pentanedione)platinum complex, bis(2,4-hexanedione)platinum complex, bis(2,4-heptanedione)platinum complex, bis(3,5-heptanedione)platinum complex and bis(1-phenyl-1,3-butanedione)platinum complex.

[0140] Preferably, catalyst C is a compound derived from platinum. Preferably, catalyst C is a Karstedt platinum catalyst.

[0141] The amount of catalyst C in the crosslinkable silicone composition according to the invention may preferably be 2 ppm to 400 ppm, preferably 5 ppm to 200 ppm, calculated as the weight of platinum metal relative to the total weight of the crosslinkable silicone composition.

[0142] Optionally, the crosslinkable silicone composition may contain at least one crosslinking inhibitor E. Crosslinking inhibitors, also known as cure rate controllers, are designed to slow down the cure of compounded silicones when necessary. Crosslinking inhibitors are well known in the art, and examples of such materials can be found in U.S. patents. US 3,923,705 relates to the use of vinyl-containing cyclic siloxanes. US 3,445,420 describes the use of acetylenic alcohols. US 3,188,299 shows the effectiveness of heterocyclic amines. US 4,256,870 describes alkyl maleates for controlling cure. Olefin siloxanes can also be used, as described in US 3,989,667. Polydiorganosiloxanes containing vinyl groups are also used, and this technology can be found in US 3,498,945, US 4,256,870 and US 4,347,346. Preferred inhibitors for use in this composition are 1,3,5,7-tetramethyl-1,3,5,7-tetravinyl-cyclotetrasiloxane, 3-methyl-1-butyn-3-ol and 1-ethynyl-1-cyclohexanol (ECH), with 1-ethynyl-1-cyclohexanol being most preferred.

[0143] The content of the crosslinking inhibitor E can vary depending on the desired cure rate. In order to obtain a longer "gel time" (also known as working time or "applicability period"), the amount of the crosslinking inhibitor E is adjusted to achieve the desired "gel time". The concentration of the crosslinking inhibitor E in the present silicone composition is sufficient to delay the curing of the composition at ambient temperature without preventing or excessively prolonging the curing at elevated temperatures. This concentration will vary widely depending on the specific inhibitor used, the nature and concentration of the hydrosilylation catalyst, and the nature of the organohydrogenpolysiloxane. In some cases, an inhibitor concentration as low as one mole of inhibitor per mole of platinum group metal will produce satisfactory storage stability and cure rate. In other cases, an inhibitor concentration of up to 500 or more moles of inhibitor / mole of platinum group metal may be required. The optimal concentration of a specific inhibitor in a given silicone composition can be easily determined by a person skilled in the art.

[0144] Optionally, the crosslinkable silicone composition may further comprise at least one thixotropic agent F. A thixotropic agent is a rheological agent used to adjust shear thinning and thixotropic properties. In the present invention, it was found that the addition of a thixotropic agent can advantageously improve the stability of the crosslinkable silicone composition during storage. The phase separation effect is reduced or can even disappear.

[0145] The optional thixotropic agent F may preferably be a reinforcing silica filler. It may be chosen in particular from colloidal silica, fumed silica and precipitated silica powders or mixtures thereof. These powders have an average particle size of less than 100 nm (nanometers) and a BET specific surface area of ​​more than 30 m 2 / g, preferably greater than 50m 2 / g, more preferably 100m 2 / g to 400m 2 / g.

[0146] This type of reinforcing filler is a very well known material in the field of silicone rubbers. The silica filler may have hydrophilic properties or may be hydrophobized by known methods. The silica reinforcing filler may be untreated or may be subjected to an overall surface treatment, preferably a hydrophobic treatment. The surface treatment may be performed prior to adding the silica to the silicone composition, or alternatively, a surface treatment agent may be added during mixing with the organopolysiloxane compound, thereby treating the silica in situ.

[0147] Alternatively, the optional thixotropic agent F may be an organic or organosilicon-containing compound containing a polar group. Preferably, the thixotropic agent F may be selected from: an organic or organosilicon-containing compound having at least one epoxy group, an organic or organopolysiloxane compound having at least one (poly)ether group, an organic compound having at least one (poly)ester group, an organopolysiloxane having at least one aromatic group, or those having a tetramethylpiperidinyl group (known as "HALS" (hindered amine light stabilizer)), and any combination thereof.

[0148] For example, mention may be made of the following polyorganosiloxane compounds containing, per molecule, at least one siloxy unit substituted with at least one group having one or more sterically hindered piperidinyl functional groups, supplied by the company Elkem Silicones under the name FLD 21645, FLD 21650 or FLD HYDROSOFT.

[0149] According to one embodiment, the thixotropic agent F is an organopolysiloxane having at least one aromatic group, more preferably an organopolysiloxane gum containing an aromatic group. For example, compounds disclosed in international patent application WO 2021 / 211752 may be suitable, in particular diphenylsiloxane-dimethylsiloxane-vinylmethylsiloxane copolymer gum or vinyl dimethyl terminated diphenylsiloxane-dimethylsiloxane copolymer gum.

[0150] According to one embodiment, the thixotropic agent F is an organopolysiloxane-polyoxyalkylene copolymer, also known as a polydiorganosiloxane-polyether copolymer or a polyoxyalkylene-modified polyorganosiloxane, which is an organopolysiloxane comprising siloxy units with an oxyalkylene chain sequence. Preferably, the organopolysiloxane-polyoxyalkylene copolymer is an organopolysiloxane comprising siloxy units with an oxyethylene chain sequence and / or an oxypropylene chain sequence. Examples of organopolysiloxane-polyoxyalkylene copolymers that can be used in the process of the invention correspond to the following formula:

[0151] R a 3SiO[R a 2SiO] t [R a Si(R b -(OCH2CH2) x (OCH(CH3)CH2) y -OH)O] r S i a 3

[0152] in

[0153] - Each R a are independently selected from alkyl groups containing 1 to 8 carbon atoms, and preferably, R a Methyl,

[0154] - Each R b is a divalent hydrocarbon group having 2 to 6 carbon atoms or a direct bond, and preferably, R b It is propyl,

[0155] - x and y are independently integers of 1-40, preferably 5-30 and most preferably 10-30,

[0156] -t is 1-200, preferably 25-150, and

[0157] -r is 2-25, preferably 3-15.

[0158] Advantageously, in one embodiment, the organopolysiloxane-polyoxyalkylene copolymer is:

[0159] Me3SiO[Me2SiO] 75 [MeSi((CH2)3-(OCH2CH2) 22 (OCH(CH3)CH2) 22 -OH)O]7SiMe3.

[0160] In another embodiment, the organopolysiloxane-polyoxyalkylene copolymer is a branched organopolysiloxane-polyoxyalkylene copolymer comprising at least one T and / or one Q siloxy unit, wherein Q corresponds to a siloxy unit SiO 2 / 2 , and T corresponds to the siloxy unit R 1 SiO 3 / 2 , where R 1 Independently selected from hydrocarbyl groups containing 1-30 carbon atoms, preferably selected from alkyl groups containing 1-8 carbon atoms, alkenyl groups containing 2-6 carbon atoms and aryl groups containing 6-12 carbon atoms.

[0161] In another embodiment, the organopolysiloxane-polyoxyalkylene copolymer may further contain other functional groups selected from the group consisting of alkenyl groups having 2 to 6 carbon atoms, hydroxides, hydrogen, (meth)acrylate groups, amino groups, and hydrolyzable groups such as alkoxy groups, alkenyloxy groups, acetoxy groups, or oxime groups.

[0162] According to the present invention, the thixotropic agent F can be used alone or in combination.

[0163] The total amount of thixotropic agent F in the silicone composition is 0.2 to 40 wt %, preferably 0.2 to 20 wt %, more preferably 0.2 to 15 wt %, based on the weight of the total composition.

[0164] When the thixotropic agent F is a reinforcing silica filler, the amount of the thixotropic agent F in the silicone composition may preferably be 0.5 to 40 wt %, preferably 1 to 20 wt %, more preferably 2 to 5 wt %, relative to the total weight of the silicone composition.

[0165] When the thixotropic agent F is an organic or organosilicon-containing compound containing a polar group, the amount of the thixotropic agent F in the silicone composition can be at least 0.2 wt %, preferably at least 0.25 wt %, most preferably 0.25 wt % to 4 wt %, even most preferably 0.25 wt % to 3 wt %, relative to the total weight of the silicone composition.

[0166] Optionally, the crosslinkable silicone composition may further comprise at least one solvent G. The role of the solvent here is to dissolve the crosslinkable silicone composition before coating on the 3D printed silicone object. The solvent G may preferably be selected from non-reactive polyorganosiloxanes such as decamethylcyclopentasiloxane (D5), octamethylcyclotetrasiloxane (D4) or polydimethylsiloxanes of low viscosity (typically below 50 mPa.s), and organic solvents such as DMF, chlorobenzene, xylene, toluene, acetonitrile, ethanol, THF, chloroform, ethyl acetate, cyclohexane, butanone, acetone and petroleum ether.

[0167] When the solvent G is present in the silicone composition, the amount of the solvent G may be preferably 1 wt % to 80 wt %, preferably 10 wt % to 60 wt %, relative to the total weight of the silicone composition.

[0168] However, according to a preferred embodiment, the crosslinkable silicone composition according to the invention comprises less than 30% by weight, more preferably less than 10% by weight, even more preferably less than 1% by weight of organic solvent. The crosslinkable silicone composition according to the invention may be free or substantially free of organic solvent. Advantageously, the low content of organic solvent or the absence of organic solvent makes the crosslinkable silicone composition more environmentally friendly and less susceptible to bacterial attack. Therefore, the post-treatment method according to the invention and the 3D-printed articles treated thereby are suitable for medical applications, such as additively manufactured medical devices or prosthetic appliances.

[0169] The silicone composition according to the invention may also optionally contain other additives, such as standard semi-reinforcing or filling fillers, other functional silicone resins, such as silicone resins with vinyl or cyclosiloxanes, non-reactive methylpolysiloxanes, pigments and / or colorants, organic solvents or adhesion promoters.

[0170] Pigments and colorants can be appropriately selected by those skilled in the art to simulate the color of human skin. A range of different colors can be provided to meet the needs of consumers.

[0171] As for semi-reinforcing or filling fillers, non-siliceous or siliceous minerals may be included. Examples of these semi-reinforcing or filling fillers that can be used alone or in combination are ground quartz, diatomaceous earth, carbon black, titanium dioxide, aluminum oxide, hydrated aluminum oxide, expanded vermiculite, unexpanded vermiculite, calcium carbonate optionally surface-treated with fatty acids, zinc oxide, mica, talc, iron oxide, barium sulfate and slaked lime. These fillers typically have a particle size of 0.001 μm to 300 μm (micrometers) and a BET surface area of ​​less than 100 m 2 / g.

[0172] An adhesion promoter may be further included in the organosilicon composition according to the present invention. A typical adhesion promoting compound may be an organic silicon-containing compound comprising an adhesion promoting group. In particular, it may be an organic silicon-containing compound as follows: The organic silicon-containing compound comprises:

[0173] - one or more hydrolyzable groups bonded to a silicon atom, typically one or more alkoxy groups bonded to a silicon atom; and

[0174] - one or more organic groups selected from the group consisting of thiol, urea, isocyanurate, (meth)acrylate, epoxy and alkenyl groups.

[0175] As examples of adhesion promoters used alone or in combination, mention may be made of vinyltrimethoxysilane (VTMO), 3-glycidyloxypropyltrimethoxysilane (GLYMO), methacryloxypropyltrimethoxysilane (MEMO), [H2N(CH2)3]Si(OCH2CH2CH3)3, [H2N(CH2)3]Si(OCH3)3, [H2N(CH2)3]Si(OC2H5)3, [H2N(CH2)4]Si(OCH3)3, [H2NCH2CH(CH3)CH2CH2]SiCH3(OCH3)2, [H2NCH2 ... C4H9-HN-CH2]Si(OCH3)3, [H2N(CH2)2NH(CH2)3]Si(OCH3)3, H2N(CH2)2NH(CH2)3]Si(OCH2CH2OCH3)3, [CH3NH(CH2)2NH(CH2)3]Si(OCH3)3, [H(NHCH2CH2)2NH(CH2)3]Si(OCH3)3, HS(CH2)3Si(OCH3)3, NH2CONH2(CH2)3Si(OCH3), or polyorganosiloxane oligomers, containing, for example, 2 to 100 silicon atoms and containing more than 20% of the above-mentioned organic groups. Mention may also be made of organic silicon-containing compounds containing at least one or two alkoxy groups bonded to silicon atoms and at least one epoxy group.

[0176] The adhesion promoter may further be selected from an organic titanium compound, preferably a titanium chelate or a titanium alkoxide of the formula Ti(OR)4, wherein R is selected from a linear or branched C1-C8 alkyl, an alkoxyalkyl and an acyl group. More preferably, the titanium compound may be selected from butyl titanate, isopropyl titanate, methyl titanate and octyl titanate, and even more preferably, the titanium compound is butyl titanate (TBOT).

[0177] According to the invention, advantageous combinations of adhesion promoters are as follows:

[0178] - vinyltrimethoxysilane (VTMO) and / or methacryloxypropyltrimethoxysilane (MEMO),

[0179] -3-glycidyloxypropyltrimethoxysilane (GLYMO), and

[0180] -Butyl titanate.

[0181] Furthermore, the adhesion promoter may be an organopolysiloxane compound as disclosed in WO 2017 / 051084. The adhesion promoter is a linear organopolysiloxane, all siloxy units in the chain of which are functionalized with Si-H units or with Si epoxy units, and the total number of siloxy units is 7-30.

[0182] Other additives may be, for example, preservatives, UV stabilizers, flame retardants, softeners, hardeners, tackifiers, nucleating agents, rheology modifiers, surface additives, flow additives, nanoparticles, antioxidants, toughening agents, thermal insulation particles, conductive particles such as carbon black, graphene, iron, copper, single-walled and multi-walled carbon nanotubes (SWT, MWT), aluminum, nickel, silver, metallized glass, lead, zinc and alloys, electrically insulating particles, and any combination or mixture thereof.

[0183] If the 3D printed silicone object obtained according to the present invention is intended for use in the medical field, all additives may be appropriately selected among those approved for use in the medical field.

[0184] For storage reasons, the crosslinkable silicone composition according to the invention can advantageously be present in the form of at least a two-component system, the mixture of which can be crosslinked by polyaddition. The individual components are then preferably separated into different parts according to the rules known to the person skilled in the art; in particular, the catalyst is separated from the component containing the hydrosiloxane.

[0185] In the post-treatment method according to the present invention, the cross-linkable silicone composition is coated on the 3D printed silicone article.

[0186] As used herein, the term "coating" refers to any form or manner of application that allows the composition to adequately cover the area of ​​the silicone article to be post-treated. Examples of coating include dip coating (e.g., immersion in a treatment bath of the silicone composition), spray coating, curtain coating, spin coating, painting, brushing, or any other means. Suitable coating or transfer means, such as a coating bath, a scraper, a roller coater, a brush, a spray gun, etc., can be selected according to the coating technology and the geometry of the coated 3D printed article. The 3D printed silicone article can be partially or fully coated.

[0187] According to one embodiment, the crosslinkable silicone composition is 50 g / m 2 Up to 1000g / m 2 , preferably 50g / m 2 Up to 500g / m 2 , more preferably 100g / m 2 Up to 300g / m 2 Coating weight of 1000 g was applied.

[0188] The coating step can be carried out at various temperatures, in particular at room temperature.

[0189] After coating, the silicone composition can be crosslinked. The crosslinking step can take place at room temperature without any specific operation. However, it is preferably activated, for example, by heating to a temperature of 50°C-200°C, preferably 100°C-150°C. The maximum heat resistance of the 3D printed silicone article is taken into account by a person skilled in the art. The activation measures are those types known and suitable for this purpose, such as heat or IR radiation. Alternatively, the crosslinking step can be activated by radiation, preferably by UV radiation. In this case, a person skilled in the art can select a suitable hydrosilylation photocatalyst, and optionally a suitable photosensitizer. Any UV light source can be used, such as an LED lamp or a mercury lamp, as long as it can provide sufficient energy to crosslink the silicone composition. UV curing can, for example, be carried out for 0.001 seconds to 30 minutes, in particular 0.1 seconds to 2 minutes.

[0190] According to a preferred embodiment, the post-treatment method according to the invention comprises a step consisting in curing the applied silicone composition by heating to a temperature of 50°C-200°C, preferably 100°C-150°C.

[0191] According to one embodiment, the post-treatment method according to the invention may comprise an intermediate step between the coating step and the curing step by heating, which intermediate step consists in a settling step, during which the coated 3D printed silicone article is kept at room temperature. The intermediate step may promote self-leveling of the coating. Depending on the geometry of the coated 3D printed article and the viscosity of the cross-linkable silicone composition, self-leveling may be advantageous or disadvantageous for the final appearance of the surface of the 3D printed coated silicone article.

[0192] The crosslinkable silicone composition disclosed in the present invention can be used for post-processing any 3D printed silicone elastomer article. The 3D printed silicone elastomer article can be obtained by any additive manufacturing method known to those skilled in the art. It can be obtained from a silicone composition that can be crosslinked by a polyaddition reaction or by a polycondensation reaction. Preferably, the 3D printed silicone elastomer article is obtained from a silicone composition that can be crosslinked by a polyaddition reaction.

[0193] Without wishing to be bound by any theory, it is believed that the crosslinkable silicone composition according to the invention which can be crosslinked by polyaddition is particularly suitable for the post-processing of 3D-printed silicone elastomeric articles obtained from silicone compositions which can be crosslinked by polyaddition reactions. The similarity between the coating material and the building material of the article makes it possible to achieve good adhesion properties and good mechanical properties.

[0194] The present invention also relates to a method for additively manufacturing a 3D silicone elastomer article, comprising the following steps:

[0195] a) Additive manufacturing of silicone products, and

[0196] b) coating the 3D printed silicone article with a cross-linkable silicone composition comprising a microfiller as defined above.

[0197] The additive manufacturing technique used in step (a) may be any technique generally known to those skilled in the art, and may preferably be an extrusion technique, a spraying technique or a photopolymerization technique.

[0198] According to a preferred embodiment, the step of additively manufacturing an organosilicon article comprises the following steps:

[0199] 1) printing a first addition-curable liquid silicone composition on a substrate with a 3D printer selected from an extrusion-type 3D printer or a material jetting-type 3D printer to form a first layer,

[0200] 2) printing a second addition-curable liquid silicone composition on the first layer or a previous layer with the 3D printer to form a subsequent layer,

[0201] 3) optionally, repeating step 2) with an independently selected addition-curable liquid silicone composition for any desired additional layers, and

[0202] 4) Crosslinking the first and subsequent layers, optionally by heating, to obtain the silicone elastomeric article.

[0203] Some implementation examples are disclosed in international patent applications WO 2020 / 082359 and WO 2021 / 211752.

[0204] According to another embodiment, the additive manufacturing technology used in step (a) can be a photopolymerization technology. 3D printing technologies based on photopolymerization are now receiving more and more attention. They start with liquid materials, either deposited locally and cured, or selectively cured from a liquid tank (vat). Examples of such technologies are UV-stereolithography (SLA), UV-digital light processing (DLP), continuous liquid interface production (CLIP), UV-extrusion and inkjet deposition.

[0205] UV-stereolithography (SLA) is disclosed, for example, in WO 2015 / 197495. For example, UV-stereolithography (SLA) uses a laser beam that is usually moved in an XY (horizontal) plane by a scanning system. A motor guided by information from a generated data source drives a mirror that sends the laser beam on a surface.

[0206] UV-digital light processing (DLP) is disclosed in, for example, WO 2016 / 181149 and US2014-0131908. In UV-digital light processing (DLP), a 3D model is sent to a printer and a liquid polymer tank is exposed to light from a DLP projector under safelight conditions. The DLP projector displays an image of the 3D model onto the liquid polymer. The DLP projector can be mounted under a window, which can be made of a transparent elastic film, through which UV light from the DLP projector is transmitted.

[0207] Continuous Liquid Interface Production (CLIP, originally Continuous Liquid Interphase Printing) is disclosed in, for example, WO 2014 / 126837 and WO 2016 / 140891, which uses, for example, photopolymerization to produce smooth-sided solid objects of a wide variety of shapes.

[0208] UV-extrusion 3D printing process is disclosed in, for example, WO 2015 / 107333, WO 2016 / 109819 and WO 2016 / 134972. For example, in this process, material is extruded through a nozzle to print a cross section of an object, and this operation is repeated for each layer. An energy source can be directly attached to the nozzle so that it is then extruded for immediate curing, or can be separated from the nozzle for delayed curing. The nozzle or building platform is usually moved in the XY (horizontal) plane, and then in the Z-axis (vertical) plane once each layer is completed. UV curing can be performed immediately after deposition, or the plate is moved under UV light to give a delay between deposition and UV curing. Support materials can be used to avoid extruding the main wire material into the air. Some post-processing treatments can be used to improve the quality of the printed surface.

[0209] Finally, inkjet deposition is disclosed, for example, in WO 2017 / 40874, WO 2016 / 071241, WO 2016 / 134972, WO 2016 / 188930, WO 2016 / 044547 and WO 2014 / 108364, which for example use a material jetting printer having a print head that moves around a printing area, jetting a specific liquid curable composition, for example by UV polymerization. The ability of the inkjet nozzle to form droplets, as well as their volume and their speed, is affected by the surface tension of the material.

[0210] According to this embodiment, the step of additively manufacturing the silicone article comprises the following steps:

[0211] 1) providing a photocurable composition;

[0212] 2) exposing the photocurable composition to actinic radiation to form a cured cross-section on a plate or support, and

[0213] 3) Repeat steps 1) and 2) with new layers on the previously solidified cross section to build a three-dimensional printed article.

[0214] The photocurable composition may be a photocurable liquid silicone composition, preferably a polyaddition-curable silicone composition in combination with a photoactivatable catalyst.

[0215] Advantageously, mechanical surface treatments such as sandblasting or polishing for making the surface uniform or removing step effects may not be required in the 3D printing or additive manufacturing method according to the present invention.

[0216] Also provided herein is the use of a post-processed 3D printed silicone article obtained by the method of the present invention.

[0217] In some embodiments, the post-processed 3D printed silicone article according to the present invention can be used in the field of medical materials and / or medical devices. For example, the article can be applied to various drug delivery devices, implantable devices, medical tubes, gastric catheters, medical balloons, catheter balloons, artificial dialysis machines, hemodialysis machines, implant components, chemical plugs, O-rings, pipes in peristaltic drug delivery pumps, check valves, resuscitator balloons, diaphragms, and prosthetic suction cups for limb connections.

[0218] Also provided is the use of a post-treated 3D printed silicone article according to the present invention in an article and / or product (such as a medical device or electronic device as described herein). DETAILED DESCRIPTION

[0219] Various embodiments of the present invention may be better understood by reference to the following examples which are provided by way of illustration.The present invention is not limited to the examples given herein.

[0220] Example

[0221] Reference Examples

[0222] 3D printing was performed using a Delta Tower 3D printer comprising a two-component Viscotec metering system equipped with a static mixer for the two-component silicone composition. The average nozzle diameter used (equal to the layer thickness) was 400 μm. The pressure used was 4 bar. The printing speed was adjusted to 5-10 mm / s. There was no pause between each layer printing. No heat or radiation was applied.

[0223] Addition-crosslinking silicone compositions for additive manufacturing: 20501-50TRS (commercialized by Elkem Silicones). It is a two-component silicone-based raw material suitable for the additive manufacturing of customized and complex silicone elastomer technical parts. It crosslinks via a polyaddition reaction.

[0224] The 3D printed nose (approximate size = 4.1 x 6.6 x 2.4 cm) was obtained, with a clear step effect on the surface (see Figure 1 ).

[0225] A post-treated silicone composition (Comp. 1) was prepared having the composition disclosed in Table 1 below.

[0226]

[0227] Table 1

[0228] The 3D printed nose was immersed at room temperature in a bath of the post-treated silicone composition Comp. 1. The post-treated object was subjected to thermal curing at 150°C for 5 minutes.

[0229] The obtained post-treatment coating (thickness of about 50-100 μm) successfully adhered to the 3D printed nose. However, the coating was not sufficient to cover up the step effect.

[0230] After 3 consecutive coats, the visual appearance of the object improved, but the feel was still not good or soft enough to be considered skin-touch.

[0231] Examples 1-14

[0232] To the comparative post-treated silicone composition (Comp. 1) disclosed above were added several additives according to Table 2:

[0233]

[0234] Table 2

[0235]

[0236] Table 2 (continued)

[0237] *Pigment is manufactured by Smooth-On under the name Silc Skin color pigment distributed by Flesh (reference number 488C). Addition of 5% pigment did not affect the cure speed of comparative composition Comp. 1.

[0238] 3D printed noses were coated using the post-treated silicone compositions of Ex. 1, Ex. 2 and Ex. 5 by brushing in 3 to 5 layers at room temperature. The post-treated objects were subjected to thermal curing at 150°C for 5 minutes. In all cases, the adhesion between the substrate and the coating was successful. Visual evaluation of the step effect: The step effect of Ex. 1, Ex. 2 and Ex. 5 was improved when compared to the substrate coated with the comparative composition (Comp. 1). Figure 2A 3D printed nose with the post-treated silicone composition of Ex. 2 is shown.

[0239] Silicone slab (9.2cm*6.6cm*2mm) is used by casting method LSR 4310 composition was prepared, which is a liquid silicone rubber composition commercially available from Elkem Silicones. Liquid Silicone Rubber (LSR) is a two-component, platinum-catalyzed silicone elastomer designed for use in healthcare and medical devices.

[0240] The silicone sheet was painted with the post-treatment silicone composition using a brush at room temperature. The post-treated object was subjected to heat curing at 150° C. for 5 minutes.

[0241] For all post-treatment compositions 1-14, adhesion between the substrate and the coating was successful.

[0242] Visual evaluation of step effect: When compared to the substrate coated with the comparative composition (Comp. 1), the step effect of all Examples 1-14 was improved. From a visual point of view, the step effect of all Examples 1-14 was improved when compared to the substrate coated with the comparative composition (Comp. 1). TM Glass Bubbles S22 (Ex. 1-4 and 11-14) and The results obtained with 6019S (Ex. 5-7) are preferred because the Z-Light Sphere G-3500 filler provides some gray color to the coating, taking away from the appearance of natural skin.

[0243] The addition of Silica Aerosil 200 (Ex. 11-14) prevented phase separation of the coating composition during storage.

[0244] In addition, the dynamic friction coefficient (K) was measured according to the following method: d ): Place the coated sheet on the paper. The loading surface area is 40cm 2 The force F required to maintain this setup at a displacement speed of 100 mm / min is d The coefficient of kinetic friction is the ratio of this force to the applied weight, or K d =F d / mg. The peak force results are recorded in Table 3.

[0245] <![CDATA[K d ]]> Uncoated sheet 2.85 Comp.1 post-treatment coating 1.50 Ex.2 post-treatment coating 0.98 Ex.3 post-treatment coating 0.99 Ex.12 post-treatment coating 1.10 Ex.13 post-treatment coating 1.12

[0246] Table 3

[0247] When the aftertreatment according to the invention is carried out, the dynamic friction coefficient is significantly reduced.

[0248] Although the difference in dynamic friction coefficient between the post-treatment coatings of Ex. 2 / 3 vs Ex. 12 / 13 was not significant, the addition of silica filler in Ex. 12 & 13 significantly reduced the phase separation of the coating compositions.

[0249] Examples 15-16

[0250] A 3D printed object was produced according to the reference example disclosed above, except that the final object was not a nose but a plate (6×12 cm).

[0251] Post-treated silicone compositions (Ex. 15 and Ex. 16) were prepared having the compositions disclosed in Table 4 below.

[0252]

[0253] Table 4

[0254] The 3D printed plates were coated by brushing (1 layer) at room temperature using the post-treatment silicone compositions of Ex. 15 and Ex. 16. The post-treated objects were subjected to heat curing at 150°C for 3 minutes.

[0255] Qualitative evaluation of the post-treated panels showed that the coating (thickness of about 60 μm) adhered firmly to the substrate. No erasure (100%) and no changes in the integrity of the coating after stretching were recorded.

[0256] The coefficient of friction (CoF) was measured with a texture analyzer equipped with a CoF slide according to standard ASTM D1894 / ISO 8295. The results of peak force and sliding force are reported in Table 5.

[0257] Peak force(kg) Sliding force(kg) Untreated plate 2.48 0.5 Ex.15 post-treatment coating 0.6 0.5 Ex.16 post-treatment coating 0.85 0.5

[0258] Table 5

Claims

1. A post-processing method for a 3D-printed silicone article, the method comprising coating the 3D-printed silicone article with a cross-linkable silicone composition comprising a microfiller having an average particle size of 1 μm to 1000 μm, wherein the microfiller is selected from a low-density hollow filler, a silica or glass microfiller, and a spherical silicone resin particle.

2. The post-treatment method according to claim 1, wherein the microfiller is selected from powders comprising substantially spherical particles.

3. The post-treatment method according to any one of claims 1 or 2, wherein the crosslinkable silicone composition comprises a low-density hollow filler, which preferably has a true density of less than 1 g / cm 3 , more preferably less than 0.8 g / cm 3 , even more preferably less than 0.5 g / cm 3 , even more preferably 0.01 g / cm 3 Up to 1g / cm 3 .

4. The post-treatment method according to claim 3, wherein the low-density hollow filler is a hollow microsphere, preferably selected from mineral hollow microspheres and organic hollow microspheres.

5. The post-processing method according to claim 3 or 4, wherein the low-density hollow filler is hollow glass microspheres.

6. The post-treatment method according to any one of claims 1 to 5, wherein the amount of microfiller in the crosslinkable silicone composition is 0.1 wt % to 50 wt %, preferably 1 wt % to 20 wt %, more preferably 2 wt % to 15 wt %, even more preferably 5 wt % to 10 wt %, relative to the total weight of the crosslinkable silicone composition.

7. The post-treatment method according to any one of claims 1 to 6, wherein the cross-linkable silicone composition comprises: (A) at least one organopolysiloxane compound A comprising at least two alkenyl groups bonded to silicon atoms per molecule, (B) at least one organohydrogenpolysiloxane compound B comprising, per molecule, at least two hydrogen atoms bonded to the same or different silicon atoms, (C) at least one polyaddition catalyst C, preferably a polyaddition catalyst consisting of at least one metal or compound from the platinum group, (D) at least said microfiller D; (E) optionally, at least one cross-linking inhibitor E; (F) optionally, at least one reinforcing filler F; (G) Optionally, at least one solvent G.

8. The post-treatment method according to any one of claims 1 to 7, wherein the cross-linkable silicone composition is coated on the 3D printed silicone article by dip coating, spray coating, curtain coating, spin coating, painting or brushing.

9. The post-treatment method according to any one of claims 1 to 8, wherein the cross-linkable silicone composition is 50 g / m 2 Up to 1000g / m 2 , preferably 50g / m 2 Up to 500g / m 2 , more preferably 100g / m 2 Up to 300g / m 2 Coating weight of 1000 g was applied.

10. A method for additively manufacturing a 3D silicone elastomer product, comprising the following steps: a) Additive manufacturing of silicone products, and b) coating the 3D printed silicone article with a cross-linkable silicone composition comprising a microfiller having an average particle size of 1 μm to 1000 μm, wherein the microfiller is selected from low-density hollow fillers, silica or glass microfillers and spherical silicone resin particles.

11. The method for additive manufacturing of 3D silicone elastomer products according to claim 10, wherein the additive manufacturing technology used in step (a) is extrusion technology, injection technology or photopolymerization technology.

12. A 3D silicone elastomeric article obtained or obtainable by the process according to claim 10 or 11, wherein the 3D silicone elastomeric article comprises a coating with a crosslinkable silicone composition comprising microfillers.

13. The 3D silicone elastomer article according to claim 12, wherein the 3D silicone elastomer article is a medical material and / or a medical device.

14. Use of a cross-linkable silicone composition comprising a microfiller having an average particle size of 1 μm to 1000 μm as a post-treatment composition for post-treatment of 3D printed silicone articles, wherein the microfiller is selected from low-density hollow fillers, silica or glass microfillers and spherical silicone resin particles.

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