BR112019027471B1 - SILICONE COMPOSITIONS, USES OF COMPOSITIONS, METHODS FOR PREPARING SILICONE FILMS AND FOR PREPARING ARTICLES, SILICONE ELASTOMERS, COMPOUNDS AND USE OF COMPOUNDS - Google Patents

Abstract

The present invention relates to type II photoinitiators for the radical crosslinking (by free radicals) of silicone compositions, particularly acrylic silicone compositions. The present invention relates to a C1 silicone composition that can be crosslinked by exposure to radiation with a wavelength between 300 and 450 nm, comprising: - at least one organopolysiloxane A comprising at least one (meth) acrylate group linked to a silicon atom; - at least one organohydrogenpolysiloxane H comprising at least two, and preferably at least three, hydrogen atoms, each bonded to different silicon atoms; and - at least one radical photoinitiator P. The present invention also aims to provide a radical polymerizable or crosslinkable silicone composition comprising a type II photoinitiator system suitable for crosslinking silicone compositions, in particular by exposure to radiation and absorption of light radiation with a wavelength greater than 300 nm.

Description

[001] The present invention relates to type II photoinitiators for cross-linking via radical reaction of silicone compositions, particularly acrylic silicone compositions.

[002] The use of plastic films as support materials for coating silicone coatings in order to create non-stick coatings (release coating) requires appropriate technology. In fact, most of these plastic films are sensitive to heat. Thus, dimensional deformation of the film occurs during the coating and drying of the silicone layer in heating ovens under the combined effect of traction forces and temperature to which the films are subjected. The technology for cross-linking functional silicone oils under ultraviolet (UV) radiation makes it necessary to use high temperatures so that the non-stick layers can be cross-linked without affecting the substrates. Furthermore, this technology offers the advantage of achieving high productivity without consuming energy and without the use of solvents. Plastic substrates are materials of choice for countless applications and their use is constantly increasing. Therefore, research and innovation efforts are indispensable in the field of crosslinking silicone thin films under UV.

[003] In general, silicone compositions are crosslinked under UV or visible radiation emitted by mercury vapor lamps, doped or undoped, whose emission spectrum extends from 200 nm to the visible wavelength (> 400 nm ). Light sources such as light-emitting diodes, better known by the acronym LEDs, can also be used, which deliver a point source of UV or visible light.

[004] From a general point of view, crosslinking under irradiation is promoted by a photoinitiator molecule. Photoinitiators and their uses are extensively discussed in the literature. In the field of radical polymerization of acrylic silicone compositions, the photoinitiator molecules normally used are the so-called type I photoinitiators. Under irradiation, these molecules decompose and produce free radicals. These radicals induce the polymerization initiation reaction, which leads to the hardening of the compositions. Many efforts have been made to ensure that type I photoinitiators have characteristics that allow their use in acrylic silicone formulations to obtain non-stick coatings. Throughout this application, the expression “type I photoinitiators” denotes compounds well known to those skilled in the art, capable of generating polymerization-initiating free radicals under UV excitation by intramolecular homolytic fragmentation.

[005] There are also type II photoinitiator systems comprising a radical photoinitiator and a co-initiator. In type II photoinitiator systems, the photoinitiators used are capable of generating free radicals that initiate polymerization by reacting with another compound called a co-initiator, said reaction resulting in the transfer of a hydrogen atom from the co-initiator to said photoinitiator. Photoinitiators used in type II photoinitiator systems are indicated by the term “type II photoinitiators”.

[006] To date, there is no type II photoinitiator system comprising a radical photoinitiator and a co-initiator, effective for the polymerization of acrylic silicone compositions under UV or visible radiation emitted by light sources, such as light-emitting diodes, better known by the acronym LEDs, which generate a beam of light with a narrow output spectrum centered on a specific wavelength. LEDs with UV or visible radiation mainly have a mission band centered on the wavelength of 365, 385, 395 or 405 nm.

[007] The objective of the present invention is to provide a silicone composition crosslinkable or polymerizable by radical reaction (free radicals) comprising a type II photoinitiator system suitable for crosslinking silicone compositions, notably by exposure to UV or visible radiation emitted by emitting diodes of light. LED lamps offer advantages in terms of energy consumption, service life and electrical safety compared to lamps with mercury or xenon sources commonly used to date. Another advantage of LEDs is the absence of warm-up time, which provides productivity gains.

[008] Another object of the present invention is to provide a crosslinkable or polymerizable silicone composition by radical reaction (free radicals) comprising a type II photoinitiator system suitable for crosslinking silicone compositions, notably by exposure to radiation, and which absorbs light in the wavelength above 300 nm.

[009] Another object of the present invention is to provide a method for preparing a film or coating on a substrate from the radical polymerizable silicone composition according to the invention.

[010] Another object of the present invention is to provide a substrate coated with a film or a coating obtained from the radical polymerizable silicone composition according to the invention.

[011] Another objective of the present invention is to provide silicone compositions to obtain release coatings that crosslink under radiation and, mainly, under UV radiation, from polyorganosiloxanes comprising (meth)acrylate groups, notably (meth)acrylic ester groups or else epoxy acrylates or polyether acrylates.

[012] Another objective of the present invention is to provide a silicone composition that is polymerizable by free radicals (via radical reaction) or crosslinkable by exposure to radiation and by polyaddition. These silicone compositions with a double crosslinking system have the particular characteristic that they can partially crosslink very quickly by irradiation and then continue crosslinking by heating, to obtain a silicone elastomer with good stability and good mechanical properties.

[013] Silicone compositions with a double crosslinking system are described in US Patent 4,585,669 (GE). Silicone compositions comprising an organohydrogen polysiloxane, a polyorganosiloxane comprising acrylate radicals, a polyorganosiloxane comprising vinyl groups, a Pt catalyst and a radical photoinitiator are described. The combination of diethoxyacetophenone as photoinitiator and benzophenone as photosensitizer is illustrated.

[014] Silicone compositions with a double crosslinking system (“double curing silicone compositions”) are definitely of interest for use in 3D printing, as they allow to increase the printing speed of silicone elastomer items. Irradiation of layers of silicone compositions as printing proceeds allows rapid gelation of a portion of the composition during production and therefore each layer maintains its shape without collapse of the printed structure. When printing is finished, a heating step makes it possible to complete the cross-linking of the composition by polyaddition to obtain a silicone elastomer with good stability and good mechanical properties.

[015] Patent application WO2016/134972 describes a method for producing a silicone elastomer article with an extrusion or inkjet 3D printer. This patent application employs a silicone composition that is cross-linked by both UV irradiation and heating. Irradiation leads to gelation of the layers and final thermal hardening leads to a silicone elastomer with good stability and mechanical properties. The only photoinitiator described is a commercial type I photoinitiator Irgacure® 651, which corresponds to 2,2-dimethoxy-2-phenylacetophenone. UV radiation at wavelength 360 nm is used in the examples.

[016] Patent application WO2017/079502 also describes silicone compositions for additive manufacturing comprising a first reagent polymerizable by irradiation and a second system of reagents crosslinkable, among other things, by polyaddition. In this patent application, additive manufacturing is carried out in a Continuous Liquid Interphase Printing (CLIP) tank or by inkjet. A combination of morpholinone and isopropylthioxanthone is described as a photoinitiator. The poor solubility of the photoinitiator is illustrated in the examples. A centrifugation step is necessary to separate any undissolved photoinitiator. Furthermore, due to the presence of an amino group, morpholinone is an inhibitor of the polyaddition reaction. In general, photoinitiators that absorb at wavelengths between 200 and 500 nm are described.

[017] Consequently, it is necessary to develop crosslinkable silicone compositions by irradiation under UV or visible radiation at a wavelength above 300 nm emitted by light-emitting diodes and by polyaddition using a photoinitiator that is soluble in the silicone composition.

[018] Another objective of the present invention is to provide a silicone composition that is polymerizable by free radicals (radical reaction) or crosslinkable by exposure to radiation and by polyaddition and is useful for additive manufacturing methods, also known as 3D printing processes. .

[019] Thus, the present invention refers to a C1 composition crosslinkable by exposure to radiation with a wavelength between 300 and 450 nm, comprising: - at least one polyorganosiloxane A comprising at least one (meth) acrylate group linked to a silicon atom, - at least one organohydrogenpolysiloxane H comprising at least two and preferably at least three hydrogen atoms, each bonded to different silicon atoms, and at least one free radical photoinitiator P having the following formula ( I): where: - the symbol and R3, which may be the same or different, are selected from the group consisting of: a hydrogen atom, a hydroxyl group and a group of general formula -OZ, with the symbol O being an oxygen atom and the symbol Z being selected from the group consisting of; ■ a C1-C20 alkyl group, preferably C3-C20, or a C2-C20 alkenyl group, ■ a -(C=O)-R5 group, in which the radical R5 is selected from C1-C20 alkyl, alkenyl groups C2-C20, C3-C20 cycloalkyl and C6-C12 aryl; and ■ a -Si(R6)3 group, in which the R6 groups, which may be the same or different, are selected from C1-C20 alkyl, C2-C20 alkenyl, C3-C20 cycloalkyl, C6-C12 aryl groups, C1-C20 alkoxy and the hydrogen atom, - and with the condition that at least one of the substituents R1 or R3 represents a hydroxyl group or a group with the general formula -OZ.

[020] With the aim of obtaining a photocrosslinking bond under radiation, the composition comprises a type II photoinitiator system which, under the effect of absorbing incident light energy, releases free radicals into the medium. These radicals play the role of initiators of the radical polymerization of (meth)acrylic functions. Since this is the hardening vector of the composition, the photoinitiator system is a key point of this application.

[021] Consequently, the present invention is based on the use of a specific type II photoinitiator system comprising the combination of a free radical photoinitiator P, as defined above and an organohydrogen polysiloxane H as co-initiator.

[022] The C1 silicone composition has the advantage of efficiently crosslinking upon exposure to UV or visible radiation. Furthermore, the free radical photoinitiator P of formula (I) has the advantage of being more soluble in polyorganosiloxanes comprising at least one (meth) acrylate group than commercial radical photoinitiators such as benzophenone or isopropylthioxanthone.

[023] Throughout this document, we will refer to elements of conventional nomenclature to denote the siloxy units M, D, T, Q of polyorganosiloxanes which, according to the widely known designations in silicone chemistry, represent: - M = unit siloxy with formula R3SiO1/2 - D = siloxy unit with formula R2SiO2/2 - T = siloxy unit with formula RSiO3/2; and - Q = siloxy unit with the formula SiO4/2, where the radicals R, which can be identical or different, are monovalent groups.

[024] All viscosities discussed in the present description correspond to a quantity of dynamic viscosity at 25 °C (unless otherwise indicated) called "Newtonian", that is, the dynamic viscosity that is measured, in a way known per with a Brookfield viscometer at a sufficiently low shear rate gradient so that the measured viscosity is independent of the shear rate gradient.

[025] The C1 crosslinkable silicone compositions according to the invention comprise at least one polyorganosiloxane A comprising at least one (meth) acrylate group linked to a silicon atom. As a representative of the (meth)acrylate functions brought by silicone and very particularly suitable for the invention, one can more particularly mention the acrylate derivatives, methacrylates, (meth)acrylate ethers and (meth)acrylate esters linked to the polysiloxane chain by a Si-C bond.

[026] According to an example embodiment, organopolysiloxane A comprises:

[027] a1) at least one unit of the following formula (A1): RaZbSiO(4-a-b)/2 (A1) where: - the symbols R, which may be the same or different, each represent an alkyl group linear or branched C1 to C18, a C6 to C12 aralkyl or aryl group, optionally substituted, preferably with halogen atoms, or an alkoxy radical -OR4, with R4 being a hydrogen atom or a hydrocarbon radical comprising from 1 to 10 carbon atoms. carbon, - the symbols Z are monovalent radicals of formula -y-(Y')n where: • Y represents a straight or branched chain polyvalent C1-C18 alkylene radical optionally extended by bivalent C1 to C4 oxyalkylene or polyoxyalkylene radicals, optionally substituted by a hydroxy radical, • Y' represents a monovalent alkenylcarbonyloxy radical, and • n is equal to 1, 2 or 3, and - “a” is an integer equal to 0, 1 or 2, b is an integer equal to a 1 or 2 and the sum a+b = 1, 2 or 3; and a2) optionally, units of the following formula (A2): RaSiO(4-a)/2 (A2) where: - the symbols R, which may be the same or different, each represent an alkyl group chain C1 to C18, linear or branched, a C6 to C12 aralkyl or aryl group, optionally substituted, preferably by halogen atoms, and - “a” is an integer equal to 0, 1, 2 or 3.

[028] In formulas (A1) and (A2) above, the symbol R can advantageously represent a monovalent radical chosen from the group consisting of: methyl, ethyl, propyl, 3,3,3-trifluoropropyl, xylyl, tolyl and phenyl .

[029] Organopolysiloxane A can have a linear, branched, cyclic or network structure. When it comes to linear organopolysiloxanes, they can essentially be made up of: - “D” siloxyl units chosen from the formula units R2SiO2/2, RZSiO2/2 and Z2SiO2/2; - siloxy units “M” chosen from the formula units R3SiO1/2, R2ZSiO1/2, RZ2SiO1/2 and Z3SiO1/2, and - the symbols R and Z are as defined above for formula (A1).

[030] According to an embodiment example, in formula (A1) above, among the alkenylcarbonyloxy radicals Y' mentioned above, the acryloxy radical [CH2=CH-CO-O-] and the methacryloxy radicals can be mentioned: [ (CH3)CH=CH- CO-O-] and [CH2=C(CH3)-CO-O-].

[031] By way of illustration of the symbol y for said symbol Z in the units of formula (A1), the radicals are mentioned: - CH2-; - (CH2)2-; - (CH2)3-; - CH2-CH(CH3)-CH2-; - (CH2)3-NH-CH2-CH2-; - (CH2)3-OCH2-; - (CH2)3-[O-CH2-CH(CH3)-]-; - (CH2)3-O-CH2-CH(OH)(-CH2-); - (CH2)3-O-CH2-C(CH2-CH3)[-(CH2)2-]2; and - (CH2)2-C6H9(OH)-.

[032] Preferably, organopolysiloxane A corresponds to formula (III) below: wherein: - the symbols R1, which may be the same or different, each represent a linear or branched C1 to C18 alkyl group, a C6 to C12 aralkyl or aryl group, optionally substituted, preferably with halogen atoms, or a alkoxy radical -OR4, with R4 being a hydrogen atom or a hydrocarbon radical comprising from 1 to 10 carbon atoms, - the symbols R2 and R3, identical or different, each represent a radical R1 or a monovalent radical of formula Z = -w-(Y')n, in which: • w represents a straight-chain or branched polyvalent C1-C18 alkylene radical optionally extended by bivalent C1 to C4 oxyalkylene or polyoxyalkylene radicals, optionally substituted by a hydroxy radical, • Y' represents a monovalent alkenylcarbonyloxy radical, and • n is equal to 1, 2 or 3, and - with a = 0 to 1000, b = 0 to 500, c = 0 to 500, d = 0 to 500 and a+b+c +d= 0 to 2500, and - with the proviso that at least one symbol R2 or R3 represents the monovalent radical of formula Z.

[033] According to a preferred embodiment, in formula (III) above: - c=0, d=0, a= 1 to 1000, b= 1 to 250, the symbol R2 represents the monovalent radical of formula Z and the symbols R1 and R3 have the same meaning as given above.

[034] Even more preferably, in formula (III) above: - c=0, d=0, a= 1 to 500, b= 1 to 100, the symbol R2 represents the monovalent radical of formula Z and the symbols R1 and R3 have the same meaning as given above.

[035] According to an example embodiment, organopolysiloxane A, according to the invention, has the following formula (IV): where: - x is between 1 and 1000; - n is between 1 and 100.

[036] The organohydrogenpolysiloxane H comprises at least two and preferably at least three hydrogen atoms, each bonded to different silicon atoms.

[037] The expression “a hydrogen atom bonded to a silicon atom” means a Si-H function or a Si-H bond or a hydrogen-silyl function.

[038] According to a preferred embodiment, organohydrogenpolysiloxane H comprises: (i) at least two units of formula (H1), HdLeSiO(4 -(d+e))/2 (H1) where: - L represents a monovalent radical other than a hydrogen atom, - H represents the hydrogen atom, - d and e represent integers, where d has a value of 1 or 2, e e has a value of 0, 1 or 2 and (d + e) has a value of 1, 2 or 3; (ii) and optionally other units of formula (H2): LfSiO(4-f)/2 (H2) where: - L has the same meaning as above, and - f represents a number with a value of 0, 1, 2 or 3.

[039] It is understood that in formulas (H1) and (H2) above, if several L groups are present, they may be identical or different from each other. In formula (H1), the symbol d may preferably be 1. Furthermore, in formula (H1) and formula (H2), L may preferably represent a monovalent radical chosen from the group consisting of an alkyl group having from 1 to 8 carbon atoms, optionally replaced by at least one halogen atom, and an aryl group. L may advantageously represent a monovalent radical chosen from the group consisting of methyl, ethyl, propyl, 3,3,3-trifluoropropyl, xylyl, tolyl and phenyl. Examples of units of formula (H1) are the following: H(CH3)2SiO1/2, H(CH3)SiO2/2 and H(C6H5)SiO2/2.

[040] The organohydrogenpolysiloxane H can have a linear, branched, cyclic or network structure. When it comes to linear organohydrogenopolysiloxanes, they can essentially be made up of: - “D” siloxyl units selected from the formula units HLSiO2/2 (also called D’ unit) and L2SiO2/2; and - siloxyl units “M” chosen from the formula units HL2SiO1/2 (also called M’ unit) and L3SiO2/2, with the symbol L having the same meaning given above and the symbol H designating a hydrogen atom.

[041] These linear H organohydrogen polysiloxanes can be oils with a dynamic viscosity at 25 ° C comprised between 1 mPa.s and 100,000 mPa.s, preferably between 1 mPa.s and 5,000 mPa.s, and even more preferably between 1 mPa. s and 2,000 mPa.s.

[042] When it comes to cyclic organohydrogen polysiloxanes, they can be made up of “D” siloxyl units chosen from the units with the formulas HLSiO2/2 and L2SiO2/2, or only siloxyl units with the formula HLSiO2/2. The units of the formula L2SiO2/2 may in particular be dialkylsiloxy or alkylarylsiloxy. These cyclic organohydrogen polysiloxanes can have a dynamic viscosity at 25 °C of between 1 mPa.s and 5,000 mPa.s.

[043] Examples of organohydrogenpolysiloxanes H are: - polydimethylsiloxanes with hydrogendimethylsilyl ends; - poly(dimethylsiloxane-cohydrogenmethylsiloxane) with trimethylsilyl ends; - poly(dimethylsiloxane-cohydrogenmethylsiloxane) with hydrogendimethylsilyl ends; - polyhydrogenmethylsiloxanes with trimethylsilyl ends; and cyclic hydrogenmethylpolysiloxanes.

[044] When it comes to branched or networked H organohydrogen polysiloxanes, they may also comprise: - “T” siloxyl units chosen from the units of formulas HSiO3/2 and LSiO3/2; - “Q” siloxyl units of formula SiO4/2, with the symbol H representing a hydrogen atom and L having the same meaning previously provided.

[045] According to an example embodiment, the organohydrogenmethylpolysiloxane H comprises at least 0.05 mol of SiH functions per 100 g of polymer, preferably 0.08 mol and Si-H functions per 100 g polymer, even more preferably between 0.08 mol and 2.5 mol of Si-H functions per 100 g of polymer, and even more preferably between 0.08 mol and 1.8 mol of Si-H functions per 100 g of polymer.

[046] The silicone composition C1 comprises a free radical photoinitiator P of the following formula (I): where: - the symbol and R3, which may be the same or different, are selected from the group consisting of: a hydrogen atom, a hydroxyl group and a group of general formula -OZ, with the symbol O being an oxygen atom and the symbol Z being selected from the group consisting of; ■ a C1-C20 alkyl group, preferably C3-C20, or a C2-C20 alkenyl group, ■ a -(C=O)-R5 group, with the radical R5 being selected from C1-C20 alkyl, C2 alkenyl groups -C20, C3-C20 cycloalkyl and C6-C12 aryl; and ■ a -Si(R6)3 group, in which the R6 groups, which may be the same or different, are selected from C1-C20 alkyl, C2-C20 alkenyl, C3-C20 cycloalkyl, C6-C12 aryl groups, C1-C20 alkoxy and the hydrogen atom, - and with the condition that at least one of the substituents R1 or R3 represents a hydroxyl group or a group with the general formula -OZ.

[047] According to an advantageous embodiment of the invention, in formula (I) above, R2 = R3 = R4 = H and R1 = OH or -OZ, as defined above.

[048] According to another embodiment, in formula (I) above, R1 = R2 = R4 = H and R3 = OH or -OZ, as defined above.

[049] According to an exemplary embodiment, the free radical photoinitiator P is selected from the group consisting of thioxanthone derivatives of the following formula (Ia): where: - the symbol X is a sulfur atom; - the symbols R2 and R4 are hydrogen atoms, - the symbols R1 and R3, which may be the same or different, are selected from the group consisting of: a hydrogen atom, a hydroxyl group and a general formula group - OZ, with the symbol O being an oxygen atom and the symbol Z being selected from the group consisting of; ■ a C1-C20 alkyl group, preferably C3-C20, or a C2-C20 alkenyl group, ■ a -(C=O)-R5 group, with the radical R5 being selected from C1-C20 alkyl, C2 alkenyl groups -C20, C3-C20 cycloalkyl and C6-C12 aryl; and ■ a -Si(R6)3 group, in which the R6 groups, which may be the same or different, are selected from C1-C20 alkyl, C2-C20 alkenyl, C3-C20 cycloalkyl, C6-C12 aryl groups, C1-C20 alkoxy and the hydrogen atom, - and with the condition that at least one of the substituents R1 or R3 represents a hydroxyl group or a group with the general formula -OZ.

[050] According to an advantageous embodiment of the invention, in formula (Ia) above, R2 = R3 = R4 = H and R1 = OH or -OZ, as defined above.

[051] According to another embodiment, in formula (Ia) above, R1 = R2 = R4 = H and R3 = OH or -OZ, as defined above.

[052] As examples of P-radical photoinitiators of formula (Ia), we can specifically mention the following compounds: 2-hydroxy-9H-thioxanthen-9-one, RN-CAS= 31696-67-0, 2-methoxy-9H- thioxanthen-9-one, RN-CAS= 40478-82-8, 2-ethoxy-9H-thioxanthen-9-one, RN-CAS= 5543-66-8, 2-hexyloxy-9H-thioxanthen-9-one, RN-CAS= 5596-56-5, 2-octyloxy-9H-thioxanthen-9-one, formula (6) below 2-decyloxy-9H-thioxanthen-9-one, formula (7) below 2-dodecyloxy-9H- thioxanthen-9-one, formula (8) below 2-acetyloxy-9H-thioxanthen-9-one, RN-CAS= 92439-12-8, 2-[(trimethylsilyl)oxy]-9H-thioxanthen-9-one, formula (17) below 9-oxo-9H-thioxanthen-2-yl 2-propenoic acid ester RN-CAS= 113797-58-3, 9-oxo-9H-thioxanthen-2-yl 2-neodecanoic acid ester, formula (20) below 9-oxo-9H-thioxanthen-2-yl 4-neodecanoic acid ester, formula (25) below and 4-hydroxy-9H-thioxanthen-9-one, formula (23) below.

[053] According to another embodiment, the free radical photoinitiator P is selected from the group consisting of xanthone derivatives of the following formula (Ib): where: - the symbol X is an oxygen atom; - the symbols R2 and R4 are hydrogen atoms, - the symbols R1 and R3, which may be the same or different, are selected from the group consisting of: a hydrogen atom, a hydroxyl group and a general formula group - OZ, with the symbol O being an oxygen atom and the symbol Z being selected from the group consisting of; ■ a C1-C20 alkyl group, preferably C3-C20, or a C2-C20 alkenyl group, ■ a -(C=O)-R5 group, with the radical R5 being selected from C1-C20 alkyl, C2 alkenyl groups -C20, C3-C20 cycloalkyl and C6-C12 aryl; and ■ a -Si(R6)3 group, in which the R6 groups, which may be the same or different, are selected from C1-C20 alkyl, C2-C20 alkenyl, C3-C20 cycloalkyl, C6-C12 aryl groups, C1-C20 alkoxy and the hydrogen atom, - and with the condition that at least one of the substituents R1 or R3 represents a hydroxyl group or a group with the general formula -OZ.

[054] According to an advantageous embodiment of the invention, in formula (Ib) above, R2 = R3 = R4 = H and R1 = OH or -OZ, as defined above.

[055] According to another exemplary embodiment, in formula (Ib) above, R1 = R2 = R4 = H and R3 = OH or -OZ, as defined above.

[056] As examples of P-radical photoinitiators of formula (Ib), we can specifically mention the following compounds: 2-hydroxy-9H-xanthen-9-one, RN-CAS= 1915-98-6, 2-methoxy-9H- xanthen-9-one, RN-CAS= 1214-20-6, 2-ethoxy-9H-xanthen-9-one, RN-CAS= 103573-60-0, 2-hexyloxy-9H-xanthen-9-one, formula (1) below 2-octyloxy-9H-xanthen-9-one, formula (2) below 2-decyloxy-9H-xanthen-9-one, formula (3) below 2-dodecyloxy-9H-xanthen-9-one , formula (4) below 2-[(trimethylsilyl)oxy]-9H-xanthen-9-one, RN-CAS= 32747-67-4, formula (18) below, 9-oxo-9H-xanthen- acid ester 2-yl 2-neodecanoic acid, formula (19) below 9-oxo-9H-xanthen-2-yl 4-neodecanoic acid ester, formula (24) below and 4-hydroxy-9H-xanthen-9-one RN-CAS = 14686-63-6.

[057] According to an example embodiment, the photoinitiator free radical P is selected from the group consisting of anthracenone derivatives of the following formula (Ic): where: - the symbol X is a CH2 group; - the symbols R2 and R4 are hydrogen atoms, - the symbols R1 and R3, which may be the same or different, are selected from the group consisting of: a hydrogen atom, a hydroxyl group and a general formula group - OZ, with the symbol O being an oxygen atom and the symbol Z being selected from the group consisting of; ■ a C1-C20 alkyl group, preferably C3-C20, or a C2-C20 alkenyl group, ■ a -(C=O)-R5 group, with the radical R5 being selected from C1-C20 alkyl, C2 alkenyl groups -C20, C3-C20 cycloalkyl and C6-C12 aryl; and ■ a -Si(R6)3 group, in which the R6 groups, which may be the same or different, are selected from C1-C20 alkyl, C2-C20 alkenyl, C3-C20 cycloalkyl, C6-C12 aryl groups, C1-C20 alkoxy and the hydrogen atom, - and with the condition that at least one of the substituents R1 or R3 represents a hydroxyl group or a group with the general formula -OZ.

[058] According to an advantageous embodiment of the invention, in formula (Ic) above, R2 = R3 = R4 = H and R1 = OH or -OZ, as defined above.

[059] According to another exemplary embodiment, in formula (Ic) above, R1 = R2 = R4 = H and R3 = OH or -OZ, as defined above.

[060] As examples of P-radical photoinitiators derived from anthracenone of formula (Ic), we can mention 2-methoxy-10H-anthracen-9-one (RN-CAS = 53604-95-8) and 4-methoxy-10H-anthracenone -9-one (RN CAS = 747093-1), as well as compounds of formula (13), (14), (15), (16) and (22) below.

[061] According to an embodiment, the photoinitiator free radical P is selected from the group consisting of anthraquinone derivatives of the following formula (Id): where: - the symbol X is a carbonyl radical; - the symbols R2 and R4 are hydrogen atoms, - the symbols R1 and R3, which may be the same or different, are selected from the group consisting of: a hydrogen atom, a hydroxyl group and a general formula group - OZ, with the symbol O being an oxygen atom and the symbol Z being selected from the group consisting of; ■ a C1-C20 alkyl group, preferably C3-C20, or a C2-C20 alkenyl group, ■ a -(C=O)-R5 group, with the radical R5 being selected from C1-C20 alkyl, C2 alkenyl groups -C20, C3-C20 cycloalkyl and C6-C12 aryl; and ■ a -Si(R6)3 group, in which the R6 groups, which may be the same or different, are selected from C1-C20 alkyl, C2-C20 alkenyl, C3-C20 cycloalkyl, C6-C12 aryl groups, C1-C20 alkoxy and the hydrogen atom, - and with the condition that at least one of the substituents R1 or R3 represents a hydroxyl group or a group with the general formula -OZ.

[062] According to an advantageous embodiment of the invention, in formula (Id) above, R2 = R3 = R4 = H and R1 = OH or -OZ, as defined above.

[063] According to another embodiment, in formula (Id) above, R1 = R2 = R4 = H and R3 = OH or -OZ, as defined above.

[064] As examples of P-radical photoinitiators derived from anthraquinone of formula (Id), we can mention 2-dodecyloxy-10H-anthraquin-9-one (RN-CAS = 218961-85-4) and acid ester 9, 10-dihydro-9,10-dioxo-2-anthracenyl-octanoic (CAS-RN = 110484-84), as well as the compounds of formula (9), (10), (11), (12) and ( 21) below.

[065] According to an advantageous embodiment, the free radical photoinitiator P is selected from the thioxanthone derivatives of formula (Ia) and xanthone of formula (Ib) as described above. Xanthone derivatives absorbing at 365 nm and thioxantone derivatives absorbing at 395 nm are preferred as they can be used with LEDs.

[066] According to an example embodiment, the crosslinkable silicone compositions C1 according to the invention comprise at least 0.0003 mol of free radical photoinitiator P per 100 g of composition C1, and preferably at least 0.0005 mol of free radical photoinitiator P per 100 g of composition C1. Preferably, the mole content of free radical photoinitiator P in the compositions C1 of the invention is between 0.0003 and 0.015 mol per 100 g of composition C1, and even more preferably between 0.0005 and 0.015 mol per 100 g of composition C1 .

[067] According to an exemplary embodiment, composition C1 does not comprise platinum.

[068] The C1 crosslinkable silicone compositions according to the invention may further comprise at least one additive. As an additive, at least one additive for regulating the detachment force of a silicone/adhesive interface can be included in the composition, which is chosen from: (i) organic derivatives of (meth)acrylates, and (ii) silicones of (meth)acrylate function(s).

[069] Particularly suitable as organic derivatives of (meth) acrylates are the compounds (meth) acrylate epoxides, (meth) acryloglyceropolyesters, (meth) acrylourethanes, (meth) acrylopolyethers, (meth) acrylopolyesters and (meth) acryloacrylics. Particularly preferred are trimethylolpropane triacrylate, tripropylene glycol diacrylate and pentaerythritol tetraacrylate.

[070] According to a preferred variant of the invention, the additive used is a silicone with (meth) acrylate function(s). As a representative of the (meth)acrylate functions brought by silicone and very particularly suitable for the invention, one can more particularly mention the acrylate derivatives, methacrylates, (meth)acrylate ethers and (meth)acrylate esters linked to the polysiloxane chain by a Si-C bond. Such acrylate derivatives are described in particular in patents EP 0 281 718, FR 2 632 960 and EP 0 940 458.

[071] The present invention also relates to the use of composition C1 according to the invention for the preparation of silicone films with non-stick properties.

[072] Preferably, to prepare these silicone films, compositions C1 as defined above are used, in which the proportion between the number of moles of photoinitiator P and the number of moles of Si-H functions in organohydrogenpolysiloxane B is comprised between 0.5 and 20, preferably between 1 and 5, said organohydrogenpolysiloxane B preferably comprising at least 0.08 mole, preferably between 0.1 mole and 2.5 mole, of Si-H functions per 100 g.

[073] The present invention also relates to a silicone elastomer obtained by crosslinking a crosslinkable C1 composition as defined above.

[074] The present invention also relates to a method of preparing silicone films with non-stick properties, comprising a step of cross-linking a cross-linkable C1 composition as defined above.

[075] Preferably, in the method for preparing silicone films with non-stick properties according to the invention, C1 compositions as defined above are used, in which the ratio of the number of moles of free radical photoinitiator P to the number of moles of Si-H functions in organohydrogenpolysiloxane B is comprised between 0.5 and 20, preferably between 1 and 5, and said organohydrogenpolysiloxane B preferably comprising at least 0.08 mole, preferably between 0.1 mole and 2.5 moles of Si-H functions per 100 g of organohydrogen polysiloxane.

[076] According to an example of carrying out the method of the invention, the crosslinking step is carried out under air or under an inert atmosphere. Preferably, this crosslinking step is carried out under an inert atmosphere.

[077] According to an embodiment, the crosslinking step of the method according to the invention is carried out by radiation at a wavelength between 200 nm and 450 nm, preferably under an inert atmosphere.

[078] According to a preferred embodiment, the crosslinking step of the method according to the invention is carried out by radiation at a wavelength between 300 nm and 450 nm, preferably under an inert atmosphere

[079] The present invention also relates to a method of preparing a coating on a substrate, comprising the following steps: - the application of a crosslinkable composition C1 as defined above on a substrate, and - the crosslinking of said composition C1 by exposure to radiation with a wavelength between 200 nm and 450 nm.

[080] UV radiation can be emitted by doped or undoped mercury vapor lamps whose emission spectrum extends from 200 nm to visible. Light sources such as light-emitting diodes, better known under the acronym “LED” (Light-Emitting Diodes), can also be used, which provide punctual UV or visible light.

[081] According to a preferred embodiment of the method according to the invention, the radiation is generated by light-emitting diodes and, even more preferably, the radiation is generated by light-emitting diodes with an emission band centered on the wavelength of 365, 385, 395 or 405 nm.

[082] The duration of irradiation can be short and is generally less than 1 second, preferably less than 10 seconds and can be on the order of a few hundredths of a second for small coating thicknesses. The crosslinking obtained is excellent even in the absence of any heating.

[083] According to an exemplary embodiment, the crosslinking step is carried out at a temperature comprised between 10 °C and 50 °C, preferably between 15 °C and 35 °C.

[084] Naturally, the hardening speed can be regulated in particular by the number of lamps used, the duration of exposure to radiation and the distance between the composition and the lamp or lamps.

[085] Composition C1, according to the invention without solvent, that is, undiluted, can be applied with the aid of devices capable of depositing small amounts of liquids in a uniform manner. To do this, you can use, for example, the device called “Helio glissant” which comprises in particular two overlapping cylinders: the function of the lower cylinder, diving into the impregnation tank where the compositions are located, is to impregnate in a very thin layer the upper cylinder, the function of the latter is then to deposit the desired quantities of the compositions in which it is impregnated onto the paper, this dosage is obtained by regulating the respective speed of the two cylinders that rotate in opposite directions to each other.

[086] The amounts of composition C1 deposited on the supports are variable and are most often between 0.1 and 5 g/m2 of treated surface. These quantities depend on the nature of the substrate and the non-stick properties to be obtained. They are most often between 0.5 and 1.5 g/m2 for non-porous supports.

[087] This method is particularly suitable for preparing a non-stick silicone coating on a substrate that is a flexible backing of textile, paper, polyvinyl chloride, polyester, polypropylene, polyamide, polyethylene, polyethylene terephthalate, polyurethane or non-woven glass fibers .

[088] These coatings are particularly suitable for use in non-stick compounds.

[089] The present invention, therefore, also relates to a coating substrate that can be obtained by the method as defined above. As noted above, the substrate may be a flexible substrate of textiles, paper, polyvinyl chloride, polyester, polypropylene, polyamide, polyethylene, polyethylene terephthalate, polyurethane or non-woven glass fibers.

[090] Coated substrates have a non-stick, water-repellent character, or allow for improved surface properties such as slippery texture, stain resistance or smoothness.

[091] Another aspect of the invention relates to a C2 silicone composition thermally crosslinkable and by exposure to radiation with a wavelength between 300 and 450nm, characterized by comprising: - at least one C1 composition, as described above, - at least at least one organopolysiloxane B comprising at least two alkenyl units linked to silicon atoms, and - at least one hydrosilylation catalyst.

[092] In this C2 composition, organohydrogenpolysiloxane H plays the role of radical co-initiator and crosslinking agent for the hydrosilylation reaction.

[093] Throughout this patent application, “crosslinking” means hardening of the composition by polymerization reactions of the meth (acrylate) functions, by polyaddition reactions between the Si-H bonds of the organohydrogen polysiloxanes H and the alkenyl groups of the polyorganosiloxanes B or a combination of the two.

[094] The term “thermally crosslinkable silicone composition” indicates a silicone composition capable of hardening by heating at a temperature generally between 60 and 220 °C, preferably between 80 and 180 °C.

[095] The term “radiation crosslinkable silicone composition” indicates a silicone composition capable of hardening upon exposure to radiation.

[096] According to an example of embodiment of the invention, polyorganosiloxane B comprises: (i) at least two siloxy units (I.5) of the following formula wherein: - a = 1 or 2, b = 0, 1 or 2 and a + b = 1, 2 or 3; - W independently represents an alkenyl group, preferably with 2 to 6 carbon atoms, and even more preferably a vinyl or allyl group, and - Z independently represents a monovalent hydrocarbon group containing from 1 to 30 carbon atoms and preferably selected from the group consisting of alkyl groups having from 1 to 8 carbon atoms inclusive, and even more preferably, selected from the group consisting of a methyl, ethyl, propyl and 3,3,3-trifluoropropyl radical, (ii) and optionally other siloxy units (I.6) of the following formula where: - Z has the same meaning as defined above, and - c represents a number with a value of 0, 1, 2 or 3.

[097] Polyorganosiloxane B can have a linear, optionally cyclic, structure. These linear polyorganosiloxanes have a dynamic viscosity at 25 °C of between 100 mPa.s and 1,000,000 mPa.s and preferably between 1,000 mPa.s and 120,000 mPa. s.

[098] When polyorganosiloxane B has a linear formula, in formula (I.5), a=1 and a+b =2 or 3 and in formula (I. 6) c=2 or 3. It is understood that in previous formulas (I.5) and (I.6) if several radicals W and Z are present, they can be identical or different from each other.

[099] In the case of linear polyorganosiloxanes, they can be selected from the group consisting of: - polydimethylsiloxanes with dimethylvinylsilyl ends; - poly(vinylmethylsiloxane-co-dimethylsiloxane)s with dimethylvinylsilyl ends; - poly(dimethylsiloxane-co-vinylmethylsiloxane)s with trimethylsilyl ends; and - cyclic polymethylvinylsiloxanes.

[100] Polyorganosiloxane B can have a branched structure. It is then called silicone resin. Advantageously they are silicone resins comprising from 0.1 to 20% by weight, preferably 4-20% by weight, of C2-C6 alkenyl groups linked to silicon atoms. The alkenyl groups can be located in M, D or T siloxy units. These resins can be prepared, for example, by the method described in US Patent -A- 2,676,182, 0.1 to 20%. Preferably, alkenyl groups are selected from vinyls, allyls and hexenyls.

[101] In a preferred embodiment of the invention, the silicone resin comprises at least two vinyl radicals and is selected from the group consisting of the following silicone resins: - MDViQ, where the vinyl groups are included in the D units, - MDViTQ, where the vinyl groups are included in the D units, - MMViQ where the vinyl groups are included in a proportion of the M units, - MMViTQ where the vinyl groups are included in a proportion of the M units, - MMViDDViQ where the vinyl groups are included in a ratio of M and D units, and mixtures thereof. with: - MVi = siloxy unit of formula (R)2(vinyl)SiO1/2 - DVi = siloxy unit of formula (R)(vinyl)SiO2/2 and the R groups, which can be the same or different, are groups containing monovalent hydrocarbons selected from alkyl groups with 1 to 8 carbon atoms inclusive, such as methyl, ethyl, propyl and 3,3,3-trifluoropropyl groups and aryl groups such as xylyl, tolyl and phenyl. Preferably, the R groups are methyl.

[102] Preferably, the silicone resin has the formula MDViQ or MMViQ as described above.

[103] K polyaddition catalysts are well known. Platinum and rhodium compounds are preferably used. One can, in particular, use the complexes of platinum and an organic product described in patents US -A- 3,159,601, US -A- 3,159,602, US-A- 3,220,972 and the European patents EP-A -0057459, EP-A-0188978 and EP-A-0190530, the complexes of platinum and vinylated organosiloxanes described in patents US-A-3,419,593, US-A-3,715,334, US-A-3,377,432 and US-A-3,814,730, platinum complexes with carbene ligands as described in EP1235836, and platinum-diene complexes as described in US 6,605,734 and US 2017/0057980. Photoactivatable hydrosilylation catalysts, as described in WO2016044547, can also be used. Other polyaddition catalysts based on base metal complexes, such as iron, nickel and cobalt, can also be used. According to a preferred embodiment of the invention, catalyst K is based on platinum. In this case, the amount by weight of catalyst K, calculated as weight of metallic platinum, is generally between 2 and 400 ppm, preferably between 5 and 200 ppm, based on the total weight of composition C2.

[104] Advantageously, the metallic platinum content in composition C2 is between 10 and 120 ppmp, preferably between 10 and 95 ppmp, more preferably between 10 and 70 ppmp and even more preferably between 10 and 60 ppmp based on weight. total composition C2.

[105] In addition, C2 silicone compositions may contain at least one of the following compounds: - an inhibitor I, - fillers F, and - adhesion promoters G

[106] As filler F, we can use reinforcing mineral fillers or semi-reinforcing or filler mineral fillers. Reinforcing mineral fillers can be selected from siliceous materials. Siliceous reinforcing fillers are selected from colloidal silicas, fumed silica powder and precipitated silica or a mixture thereof. These powders have an average particle size generally below 0.1 μm and a BET specific surface area greater than 50 m2/g, preferably between 150 and 350 m2/g. These silicas can be incorporated as is or after being treated with organosilicon compounds generally used for this application. These compounds include methylpolysiloxanes such as hexamethyldisiloxane, octamethylcyclotetrasiloxane, methylpolysilazanes such as hexamethyldisilazane, hexamethylcyclotrisilazane, chlorosilanes such as dimethyldichlorosilane, trimethylchlorosilane, methylvinyldichlorosilane, dimethylvinylchlorosilane, alkoxysilanes such as dimethyldimethoxysilane, dimethylvinyleth oxysilane, trimethylmethoxysilane. Siliceous semi-reinforcing fillers, such as diatomaceous earth or quartz soil, can also be used.

[107] Semi-reinforcement fillers or mineral fillers can be added in addition to or instead of reinforcing silicas. Examples of these non-siliceous fillers, usable alone or mixed, are calcium carbonate, optionally, the surface treated with an organic acid or an ester of an organic acid, baked clay, rutile titanium dioxide, iron oxides, zinc, chromium, zirconium, magnesium, the various forms of alumina (whether or not hydrated), boron nitride, lithopone, barium metaborate, barium sulfate and glass microspheres. These fillers are coarse, generally with an average particle diameter greater than 0.1 μm and a specific surface area generally less than 30 m2/g. These fillers may have been superficially modified by treatment with the various organosilicon compounds commonly used for this application.

[108] Conductive fillers such as nano-objects based on graphene or carbon nanotubes can also be used.

[109] According to an example of embodiment of the invention, a reinforcing filler F is used, which is a fumed silica with a specific surface area, measured by the BET method, comprised between 100 and 400 m2/g. Even more advantageously, the reinforcing filler F is a fumed silica having a specific surface area, measured by the BET method, of between 100 and 400 m2/g and which has been treated with organosilicon compounds.

[110] According to a specific embodiment of the invention, the silicone composition C2 comprises from 1 to 40 parts by weight of filler F, preferably from 1 to 25 parts by weight of filler F and more preferably from 1 to 15 parts of filler F per 100 parts by weight of silicone composition C2.

[111] The crosslink inhibitor I (or polyaddition reaction retardant) can, in turn, be selected from the following compounds: - a polyorganosiloxane, advantageously cyclic, and substituted by at least one alkenyl, and being particularly preferred tetramethylvinyltetrasiloxane, - organic phosphines and phosphites, - unsaturated amides, - alkylated maleates - and acetylenic alcohols.

[112] These acetylenic alcohols (cf. FR-B- 1,528,464 and FR-A- 2,372,874), which are part of the preferred thermal blockers of the hydrosilylation reaction, have the formula (I1): (R1)(R2 )C(OH)-C=CH (I1) where: - R1 is a phenyl radical or linear or branched alkyl radical; - R2 is a hydrogen atom, a phenyl radical or linear or branched alkyl radical; - the radicals R1, R2 and the carbon atom in the alpha position of the triple bond that can optionally form a ring; and - the total number of carbon atoms contained in R1 and R2 being at least 5, preferably 9 to 20.

[113] Said alcohols are preferably selected from those having a boiling point greater than 250 °C. As examples, we can mention the following commercially available products: - ethynyl-1-cyclohexanol-1; - methyl-3-dodecin-1-ol-3; - trimethyl-3,7,11-dodecin-1-ol-3; - diphenyl-1,1-propyn-2-ol-1; - ethyl-3-ethyl-6-nonin-1-ol-3; - methyl-3-pentadecin-1-ol-3.

[114] A cross-linking inhibitor I of this type is present at a rate of at most 3000 ppm, preferably at a rate of 100-2000 ppm relative to the total weight of composition C2.

[115] As G adhesion promoters, it will be possible to use the adhesion promoting agents generally used in this field. For example, it will be possible to use: - a vinylated silane or polyorganosiloxane alone or partially hydrolyzed, as well as a reaction product thereof, - a silane or polyorganosiloxane functionalized with an epoxy functionality alone or partially hydrolyzed, as well as a reaction product thereof , - a polyorganosiloxane comprising at least one SiH functionality and at least one functionality selected from the group consisting of: epoxy, (meth)acrylate, alkoxy and vinyl functionality, - a metal alkoxide or a chelate of such a metal such as Ti, Zr, Al, for example tert-butyl titanate.

[116] The invention also relates to a silicone elastomer obtained by crosslinking a crosslinkable C2 composition as defined above.

[117] These silicone elastomers can be used in various applications, for example, such as in the medical field of “wound care”: the care and treatment of wounds or injuries (covering of dressings, manufacture of external prostheses, cushions for prevention of pressure ulcers), or for encapsulation of electronic components or as coatings, in particular for the coating of paper or flexible plastic films, as well as for the textile coating, in particular, airbags for vehicles.

[118] Another aspect of the invention relates to a method for preparing articles made from silicone elastomer, comprising a step of cross-linking a composition C2 as defined above by exposure to radiation with a wavelength between 300 nm and 450 nm.

[119] Advantageously, in the above method, the radiation is generated by light-emitting diodes and, even more advantageously, the radiation is generated by light-emitting diodes with an emission band centered on the wavelength of 365, 385, 395 or 405 nm.

[120] The method for preparing articles made of silicone elastomer according to the invention may further comprise a heating step, preferably at a temperature between 60 and 220 °C, even more preferably between 80 and 180 °C.

[121] The present invention also relates to the use of composition C2 according to the invention for the preparation of articles made from silicone elastomer by additive manufacturing methods, also known as 3D printing processes.

[122] This description generally comprises the designation ASTM F2792-12a, “Standard Terminology for Additive Manufacturing”. According to this ASTM standard, a “3D printer” is defined as “a machine used for 3D printing” and “3D printing” is defined as “the manufacture of objects by depositing a material through a print head, a nozzle or some other printer technology”.

[123] Additive manufacturing “AM” is defined as a process for joining materials to manufacture objects based on data from a 3D model, usually layer by layer, as opposed to subtractive manufacturing methods. Synonyms associated with 3D printing and covered by 3D printing comprise additive manufacturing, additive processes, additive techniques, and layer-by-layer manufacturing. Additive manufacturing (AM) can also be called rapid prototyping (RP). As used herein, the term “3D printing” is interchangeable with “additive manufacturing”.

[124] In general, all 3D printing processes have a common starting point, which is a computer-generated data source or a program that can describe an object. The computer-generated data source or program may be based on a real or virtual object. For example, a real object can be scanned using a 3D scanner and the scan data can be used to create the computer or program generated data source. Alternatively, the computer- or program-generated data source can be designed from scratch. The computer or program generated data source is usually converted into an STL (standard language) file format. However, other file formats can be used. The file is typically read into 3D printing software, which takes the file and, optionally, user input to separate it into “slices,” the number of which can reach several thousand. 3D printing software typically provides machine instructions, which may be in the form of G-code, which is read by the 3D printer to construct each slice. The machine instructions are transferred to the 3D printer, which then builds the object, layer by layer, as a function of this data sequence in the form of machine instructions. The thicknesses of such layers may vary.

[125] The C2 silicone compositions according to the invention make it possible to increase the printing speed of silicone elastomer items. Irradiation of layers of silicone compositions as printing proceeds allows rapid gelation of a portion of the composition during production and therefore each layer maintains its shape without collapse of the printed structure. When printing is finished, a heating step makes it possible to finalize the cross-linking of the composition by polyaddition to obtain a silicone elastomer with good stability and good mechanical properties.

[126] Advantageously, the C2 silicone compositions according to the invention can be used for 3D printing processes using photopolymerization tank, material extrusion or material deposition by adapting the viscosity of the C2 silicone composition to the technology used.

[127] Tank photopolymerization is an additive manufacturing process whereby a hardenable liquid resin contained in a tank is selectively hardened when the polymerization of its molecular chains is triggered by ultraviolet light. Tank photopolymerization can utilize a lamp or light-emitting diodes (LEDs) as a source of UV energy. When used in additive manufacturing processes, such as tank photopolymerization, the viscosity of the C2 silicone composition will be between 10 mPa.s and 100,000 mPa.s, preferably between 100 and 10,000 mPa.s, and even more preferably between 100 and 2,000 mPa.s.

[128] A “tank 3D” printer is a printer, as described in application WO2017/055747, in which a UV-visible illumination device comprises an LED-based light source and a mask adapted to transmit or block the irradiation according to a display pattern to create a projection image. The mask thus comprises an array of pixels configured to assume a conducting state that allows irradiation and a blocking state that blocks irradiation. The conduction state is reflected in the transmission of radiation towards the corresponding point of the projected image. The blocking state is reflected in the absence of radiation transmission towards the corresponding point of the projected image. The display pattern corresponds to the distribution of the states of said pixels.

[129] The tank printer manufacturing system therefore comprises, in a system for preferably irradiating with UV-visible LEDs, a mask adapted to cut off the UV-visible radiation emitted by the LEDs according to a display pattern for the creation of a projection image emitted by the irradiation device. The printer comprises a system for moving the projection image onto a work surface, which is arranged in a container called a tank. The tank contains the silicone formulation which has a working surface exposed to the projection image emitted by the irradiation device.

[130] The tank manufacturing system may correspond to a work surface and irradiation of a layer of silicone formulation with the opening on the top side, but also another possible configuration is irradiation from the bottom portion through a background that is transparent to radiation. In this case, the work surface is the surface in contact with the transparent background. Adhesion of the work surface directly in contact with the transparent bottom is prevented by creating an inhibition layer in contact with the transparent bottom by oxygenating the surface of the transparent bottom. An example of a printer and process according to a projection mode from the bottom is described in US Patent 7,052,263.

[131] Material extrusion is an additive manufacturing process in which a strand of material is extruded and selectively distributed through a nozzle. The material flow velocity can be controlled, among other things, by the pressure exerted on the nozzle or by the temperature.

[132] Material deposition is an additive manufacturing process in which fine droplets of a material are selectively deposited by heads similar to those in paper printers. This process is also known as inkjet.

[133] For use in additive manufacturing processes such as extrusion or material deposition, the viscosity of the C2 silicone composition will be between 100 mPa.s and 1,000,000 mPa.s, preferably between 1,000 mPa.s and 300,000 mPa.s, and even more preferably between 3,000 and 200,000 mPa.s. For this use, the C2 silicone composition must exhibit thixotropic behavior (decrease in viscosity during shear and increase in viscosity after shear).

[134] A “3D extrusion” printer is a 3D printer where material is extruded through a nozzle, a syringe, or an orifice during the additive manufacturing process. Material extrusion generally works by extruding the material through a nozzle, a syringe, or an orifice to print a cross-section of an object, which can be repeated for each subsequent layer. The extruded material adheres to the layer below during the material hardening. In a preferred embodiment, the process for printing a three-dimensional silicone elastomer article uses an extrusion 3D printer. The silicone compositions are extruded through a nozzle. The nozzle may be heated to facilitate distribution of the silicone composition for further cross-linking. The average nozzle diameter defines the layer thickness. In an exemplary embodiment, the diameter of the layer is between 50 and 2000 μm, preferably between 100 and 800 μm, and more preferably between 100 and 500 μm. The distance between the nozzle and the substrate is an important parameter to ensure a good shape. It must be between + to/- 30% of the average nozzle diameter. Dual curing of the radical crosslinking and polyaddition silicone composition to be distributed through the nozzle can be provided from a cartridge type system. The cartridge may comprise a nozzle or nozzles with an associated fluid reservoir or fluid reservoirs. It is also possible to use a two-cartridge coaxial system with a static mixer and a single nozzle. The pressure will be adapted to the fluid to be distributed, the associated average nozzle diameter and the printing speed.

[135] Due to the high shear rate that occurs during extrusion from the nozzle, the viscosity of silicone compositions is considerably reduced, thus allowing the printing of thin layers. The cartridge pressure can vary from 0.1 to 2 MPa (1 to 20 bar), preferably between 0.2 to 1 MPa (2 and 10 bar) and more preferably between 0.4 and 0.7 MPa (4 and 7 Pub). When nozzle diameters below 100 μm are used, the cartridge pressure must be above 2 MPa (20 bar) to obtain good material extrusion. Suitable equipment using aluminum cartridges must be used in order to withstand such pressure. The nozzle platform and/or platform moves in the X-Y planes (horizontal plane) to complete the cross-section of the object, before moving in the Z-axis (vertical) plane once a layer is completed. The nozzle has a high precision of XYZ movement. Since each layer is printed on the X, Y work plane, the nozzle is moved in the Z direction just enough for the next layer to be applied to the X, Y work location. Thus, the object that becomes the 3D article is built one layer at a time from bottom to top.

[136] As described above, the distance between the beak and the previous layer is an important parameter to ensure good shape. It should be within + to/- 30% of the average nozzle diameter. The printing speed is between 1 and 50 millimeters/s, preferably between 5 and 30 millimeters/s, in order to obtain the best compromise between good precision and manufacturing speed.

[137] An “inkjet 3D” printer is defined as additive manufacturing equipment in which droplets of silicone formulation are selectively deposited. The silicone formulation is applied via a print head in the form of individual drops, discontinuously, at the desired location on the work plane (blasting). This is a 3D equipment and process for the step-by-step production of 3D structures with a print head arrangement comprising at least one, preferably 2 to 200 print head nozzles, allowing selective application of a formulation or, if applicable , a plurality of formulations. The application of silicones by inkjet printing places specific demands on the viscosity of the materials. In a 3D printer for spraying the silicone formulation, one or more reservoirs are subjected to pressure and are connected by a measuring line to a measuring nozzle. Upstream or downstream of the reservoir there may be devices that allow homogenizing and/or evacuating dissolved gases, so that the silicone compositions are homogeneous. One or more spray units operating independently of each other may be present for the purpose of constructing the elastomer article from different silicone compositions for addition cross-linking or, in the case of more complex structures, for forming composite parts made of silicone elastomers and other plastics. Due to the high shear rate that occurs at the metering valve in the blasting process, the viscosity of such addition cross-linked silicone compositions is considerably reduced and thus provides a jet of very fine microdroplets. Once the microdroplet has been deposited on the substrate, there is a sudden reduction in its shear rate, so that its viscosity increases again. As a result, the deposited drop quickly reaches a very high viscosity and therefore allows the precise construction of three-dimensional structures. The individual measuring nozzles can be precisely positioned in the x, y and z directions to allow accurate deposition of oriented droplets of silicone onto the substrate or, in the subsequent formation of molded parts, upon the addition of a crosslinkable silicone composition. It is desirable to use a UV and/or visible light irradiation system to initiate hardening after printing each layer in order to avoid collapse of the structure.

[138] Typically, the 3D printer uses one or more distributors, for example, a nozzle or a print head, to print the hardenable silicone composition. Optionally, the dispenser can be heated before, during and after dispensing the silicone composition. In an exemplary embodiment, this method may use material for two different purposes, construction of the object and support protrusions in order to prevent extrusion of material into the air. If the object was printed using support equipment or support structures after the printing process has finished, it is usually removed (e.g. by washing it with water), leaving the finished object behind.

[139] After printing, the resulting articles may be subjected to various types of post-treatment. In an exemplary embodiment, the method further comprises the step consisting of heating the silicone elastomer article obtained by 3D printing. Heat can be used to speed up the treatment. In another embodiment, the method further comprises the step of additional irradiation of the silicone elastomer article obtained by 3D printing. Additional irradiation can be used to speed up treatment. In another embodiment, the method comprises both the steps of heating and irradiating the silicone elastomer article obtained by 3D printing. As an option, post-treatment steps can greatly improve the surface quality of printed articles. Grinding is a common means of reducing or removing layers that are visibly different from those of the model. It is possible to spray or coat the surface of the elastomer article with a heat- or UV-curable RTV or LSR silicone composition to obtain a smooth, straight surface finish. Laser surface treatment can also be applied. For medical applications, sterilization of the last elastomer article can be achieved by heating the object to a temperature above 100 °C.

[140] The invention also relates to the following compounds from (1) to (25);

[141] Neodecanoic acid is a mixture of carboxylic acids with the common structural formula C10H20O2, a molecular weight of 172.26 g/mol and CAS number = 26896-20-8. The components of the mixture are acids having the common property of a “trial alkyl acetic acid” with three alkyl groups at carbon two, comprising: 2,2,3,5-tetramethylhexanoic acid, 2,4-dimethyl-2-isopropylpentanoic acid, 2 ,5-dimethyl-2-ethylhexanoic acid and 2,2-dimethyloctanoic acid.

[142] For the following structures (19) to (22), (24) and (25), the neodecanoic acid used for the synthesis of photoinitiators is branched with the different acids indicated above.

[143] The invention also relates to the use of compounds (1) to (25) described above as radical photoinitiators, and preferably to the use of compounds (1) to (25) described above as radical photoinitiators for the crosslinking of compositions of silicone.

[144] The following examples are provided for illustrative purposes and are not limiting. They remarkably allow a better understanding of the invention and illustrate all its advantages.

EXAMPLES

[145] In the following examples, different photoinitiators, organohydrogen polysiloxanes and polyorganosiloxanes with acrylate functions were used according to the invention and their structures are indicated in the tables provided below. TABLE 1 PHOTOINITIATORS

[146] Among these photoinitiators, compounds (1), (4), (5), (8), (19) and (20) were synthesized according to the protocols explained below.

SYNTHESIS OF 2-HYDROXYXANTONE (2 QH-XT):

[147] Reagents: - 2-iodobenzoic acid - 4-methoxyphenol - cesium carbonate - - copper(I) chloride - tris [2-(2-methoxyethoxy)ethyl]amine (TDA-1) - 1,4-dioxane - concentrated sulfuric acid

[148] A single-neck flask is charged with 1 equivalent of 2-iodobenzoic acid, 1.4 equivalents of 4-methoxyphenol, and 2.8 equivalents of cesium carbonate in 6 mL of 1,4-dioxane per mmol of acid 2 -iodobenzoic. The mixture is stirred for 10 minutes at room temperature, under an argon atmosphere. Then, 0.1 equivalent of copper(I) chloride and 0.1 equivalent of TDA-1 are added. The mixture is left to react for 20 hours under reflux and atm of argon.

[149] After completion of the reaction, 1,4-dioxane is evaporated in a rotary evaporator. The residue is dissolved with 10% by weight Na2CO3 solution and the solution is then filtered. Then, the filtrate is placed in a separatory funnel and washed with a 50/50 toluene/ethyl acetate mixture. The aqueous phase is recovered and acidified before filtration to obtain the reaction intermediate. (Yield: 75%)

[150] A single-neck flask is charged with 1 equivalent of the intermediate in 1.25 mL of concentrated sulfuric acid per mmol of reagent. The mixture is allowed to react until the methoxy coloration of the product disappears on TLC (about 3 h). Once the reaction is complete, the reaction mixture is cooled before adding 10 times the volume of acid on ice. Then, the solution obtained is extracted 3 times with ethyl acetate. The organic phases are collected, dried and evaporated. The product obtained is a white solid. It is possible to recrystallize it in acetone (Yield: 48%). The NMR spectrum corresponds to 2-hydroxyxanthone.

SYNTHESIS OF 2-HYDROXYTHIOXANTONE (2 OH-XT):

[151] Reagents: - thiosalicylic acid - phenol - sulfuric acid

[152] A single-mouth flask is slowly charged with an equivalent of thiosalicylic acid in 1 mL of sulfuric acid per mmol of thiosalicylic acid. The flask is shaken vigorously for 10 minutes. Then 5 equivalents of phenol are added over 30 minutes. The mixture is then left to react for 1 h at room temperature, then 2 h at 80 °C and then left to rest overnight at room temperature.

[153] Once the reaction has been completed, the reaction is poured into a volume of up to 10 times the volume of sulfuric acid into boiling water, and the mixture is left to boil for 10 minutes. The solution is filtered after it is cold. The product obtained is a yellow powder (Yield: 62%). The NMR spectrum corresponds to 2-hydroxythioxanthone.

SYNTHESIS OF XANTHONE AND THIOXANTHONE ETHERS, COMPOUNDS (1), (4), (5), (8).

[154] Reagents: - 2-hydroxyoxanthone and 2-hydroxythioxanthone - iodoalkane (1-iodohexane and 1-iodododecane) - potassium carbonate - dimethylsulfoxide DMSO BALANCED EQUATION:

[155] Fig. 1: Synthesis of xanthone and thioxanthone ethers (X = O, S)

[156] Protocol:

[157] A single-mouth flask is charged with one equivalent of 2-hydroxyxanthone (or 2-hydroxythioxanthone) and 2 equivalents of potassium carbonate in 5 mL of DMSO per mmol of product. The mixture is stirred for 10 minutes at room temperature, under an argon atmosphere. Next, iodoalkane (1-iodohexane or 1-iodododecane) is added dropwise, and then the mixture is allowed to react at 100 °C under argon for 48 h.

[158] Once the reaction has been completed, 10 times the volume of the reaction mixture is added to water and the mixture is extracted 3 times with n-hexane. The organic phases are collected, dried and evaporated. The crude product obtained is then purified over silica gel with an eluent of 90/10 cyclohexane/ethyl acetate (Yield: about 66%).

SYNTHESIS OF COMPOUNDS 2-NEODECA-XT (19) AND 2-NEODECA-TX (20)

[159] A single-mouth flask is charged with one equivalent of 2-hydroxyxanthone (or 2-hydroxythioxanthone), 1 equivalent of neodecanoic acid and 1 mL of concentrated sulfuric acid per mmol of product. The mixture is stirred for 2 hours at room temperature under an argon atmosphere. It is then left to react at 120°C under argon for 12h.

[160] Once the reaction has been completed, 10 times the volume of the reaction mixture is added to water and the mixture is extracted 3 times with n-hexane. The organic phases are then collected, neutralized with sodium carbonate, dried and evaporated. The crude product obtained is then purified over silica gel with an eluent of 90/10 cyclohexane/ethyl acetate. TABLE 2 ORGANO-HYDROGENOPOLYSYLOXANE

[161] The compounds Hyd 1 and Hyd 2 specified in the table above are linear organohydrogen polysiloxanes with SiH units arranged in the middle and/or at the end of the chain.

ACRYLIC SILICONES

[162] An Acryl 1 polyorganosiloxane of formula with x = 85 and n = 7 is used in the compositions.

SILICONE COMPOSITIONS CROSS-CROSS-CROSSED BY IRRADIATION:

[163] The tests were carried out to illustrate the use of type II photoinitiators according to the invention with an organohydrogen polysiloxane as a photoinitiator to polymerize acrylic silicones. The preparations are carried out as follows: weigh and add 1.2 10-4 mol of the photoinitiator to 2 g of Acryl 1 polyorganosiloxane. Stir the complete mixture for 12 hours. Then add 1% by weight of organohydrogenpolysiloxane Hyd 1.

[164] Two types of irradiation crosslinking were tested: - 90 seconds of UV radiation with a mercury-xenon lamp. The lamp power is fixed at 510 mW/cm2, and - 90 seconds of 365 nm LED radiation with a power of 750 mW/cm2 for xanthone derivatives or under 395 nm LED radiation with a power of 680 mW/cm2 for thioxanthone derivatives.

[165] The manipulations were carried out on laminate in order to avoid any inhibition effect on reactive oxygen species. When manipulations are carried out on laminate, the formulation is placed between two polypropylene sheets and then between two CaF2 tablets.

[166] Polymerization kinetics monitoring is carried out using Real-Time Fourier Transform Infrared (RT-FTIR, Vertex 70 from Brucker Optik). This spectroscopic technique consists of exposing the sample simultaneously to light and an infrared ray in order to monitor changes in the IR spectrum at 1636 cm-1, which is a characteristic range of the C=C bond of acrylic functions.

[167] The degree of conversion of C=C to C-C during polymerization is directly related to the decrease in the calculated area under the 1636 cm-1 peak according to the following equation: conversion (%)=(A0-At) /A0 x100, where A0 is the area under the peak before irradiation and At is the area under the peak at each time t of irradiation

[168] For the tests carried out with the mercury-xenon lamp, the results were plotted as a function of time, making it possible not only to find the final degree of conversion, but also other important parameters, such as the maximum conversion speed Rp expressed in the following tables as Rp/[M]0)x100 where [M]0 is the initial concentration of the acrylate function. The maximum conversion rate Rp is determined from the slope of the curve conversion (%) = f(time) at its inflection point.

[169] The results are summarized in Table 3 and 4 below. TABLE 3 UV-LED RADIATION *-: low solubility <50%; + : partial solubility > 50%, ++ : soluble.

[170] Observations made after stirring for 12 h with a magnetic stirrer

[171] The photoinitiators according to the invention give a better degree of conversion after 90s of irradiation with LEDs. TABLE 4 RESULTS WITH HG-XE LAMPS

[172] The photoinitiators according to the invention give a better degree of conversion after 90s of irradiation with a Hg-Xe lamp.

[173] Irradiation and thermally crosslinked silicone compositions:

[174] The formulations tested are detailed in Table 5 below.

[175] Formulations are prepared by simply mixing all constituents in a high-speed mixer, mixing at 1000 rev/min for one minute.

[176] In addition to the compounds already described above, the following compounds are used: - Vinyl oil 1: polydimethylsiloxane oil blocked at each end of the chain with a (CH3)2ViSiO1/2 unit, with a viscosity of 60,000 mPa.s. - Vinyl Resin 2: polyorganosiloxane of formula MMViQ containing 1.1% by weight of vinyl groups. - Hydrosilylation catalyst: platinum metal, added in the form of an organometallic complex to 10% by weight of metallic platinum, known as Karstedt's catalyst, - Inhibitor: ethynyl-1-cyclohexanol-1 or ECH, - Filler: Aerosil® 200 from Evonik, - Polydimethylsiloxane PDMS with viscosity 50 mPa.s. TABLE 5: SILICONE COMPOSITIONS WITH FREE RADICAL AND POLYADDITION CROSSLINKING

[177] Two compositions are obtained: - Composition 1 mixing A1+ B, which is a comparative example. - Composition 2 mixing A2+B, which is an example according to the invention. At 23°C, the dynamic viscosity of composition 2 equals 15,400 mPa.s.

3D PRINTING TEST

[178] 100 g of composition is placed in the reservoir of a 3D printer using tank photopolymerization with LEDs at 365 nm. A Prodway® DLP 3D printer with a dual-cartridge system equipped with a static mixer was used. The bath life or “storage limit” (potlife) of the composition obtained in the dark (away from light) is 24 hours before undergoing gelation.

[179] The results for the conditions necessary for crosslinking for the first layer with a thickness of 250 μm deposited on a plate and exposed for 5.5 s to 365 nm LED UV radiation with an intensity of 75.5 mW/cm2 are presented in table 6 below. TABLE 6 ENERGY REQUIRED FOR RADIATION CROSSCLICKING OF A 250 MM LAYER OF SILICONE COMPOSITIONS Optical properties Composition 1 Comparative Composition 2 Invention

[180] In the following table, Ec represents the critical surface energy measured in mJ/cm2.

[181] The composition according to the invention has a lower critical surface energy. Less energy will need to be supplied to it to reach the gel point. Therefore, this composition offers the advantage of requiring less energy for crosslinking and consequently it will be possible to print successive layers more quickly.

[182] E4 is the energy to be supplied to obtain crosslinking with a thickness of 100 micrometers, E8 to reach 200 micrometers and E10 to reach 250 micrometers. TABLE 7 MECHANICAL PROPERTIES ACCORDING TO THE NF EN ISO 527 STANDARD ON SILICONE ELASTOMERS OBTAINED AFTER IRRADIATION AND THERMALLY CROSS-CROSSING

Claims (16)

1. SILICONE COMPOSITION C1, crosslinkable by exposure to radiation with a wavelength between 300 and 450 nm, characterized by comprising: - at least one polyorganosiloxane A comprising at least one (meth) acrylate group linked to a silicon atom, - at least at least one organohydrogenpolysiloxane H comprising at least two and, preferably, at least three hydrogen atoms, each bonded to different silicon atoms, and - at least one free radical photoinitiator P having the following formula (I): wherein: - the symbol X is selected from the group consisting of: an oxygen atom, a sulfur atom and a CH2 group; - the symbols R2 and R4 are hydrogen atoms; - the symbols R1 and R3, which may be the same or different, are selected from the group consisting of: a hydrogen atom, a hydroxyl and a group of general formula -OZ, with the symbol O being an oxygen atom and the symbol Z being selected from the group consisting of: - a C1-C20, preferably C3-C20, alkyl group, or a C2-C20 alkenyl group; - a -(C=O)-R5 group, with the R5 radical being selected from C1-C20 alkyl, C2-C20 alkenyl, C3-C20 cycloalkyl and C6-C12 aryl groups; and - a -Si(R6)3 group, in which the R6 groups, which may be the same or different, are selected from C1-C20 alkyl, C2-C20 alkenyl, C3-C20 cycloalkyl, C6-C12 aryl groups, C1-C20 alkoxy and the hydrogen atom, - and with the condition that at least one of the substituents R1 or R3 represents a hydroxyl or a group with the general formula -OZ. 2. COMPOSITION, according to claim 1, characterized in that the free radical photoinitiator P is selected from the compounds of formula (I), in which the symbol X is an oxygen atom or sulfur atom. 3. COMPOSITION, according to any one of claims 1 to 2, characterized by the polyorganosiloxane A comprising: a1) at least one unit of the following formula (A1): RaZbSiO(4-a-b)/2 (A1) wherein: - the R symbols, which may be the same or different, each represent a linear or branched C1 to C18 alkyl group, a C6 to C12 aralkyl or aryl group, optionally substituted, preferably with halogen atoms, or an alkoxy radical -OR4, with R4 being a hydrogen atom or a hydrocarbon radical comprising 1 to 10 carbon atoms; - the symbols Z are monovalent radicals of formula -y- (Y')n, where: • Y represents a polyvalent C1-C18 alkylene radical, with a straight or branched chain, optionally extended by bivalent C1 to C4 oxyalkylene or polyoxyalkylene radicals, optionally substituted with a hydroxy radical; • Y' represents a monovalent alkenylcarbonyloxy radical; and • n is equal to 1, 2 or 3, and - “a” is an integer equal to 0, 1 or 2, b is an integer equal to 1 or 2 and the sum a + b = 1, 2 or 3; and a2) optionally, units of the following formula (A2): RaSiO(4-a)/2 (A2) where: - the symbols R, which may be the same or different, each represent an alkyl group chain C1 to C18, linear or branched, a C6 to C12 aralkyl or aryl group, optionally substituted, preferably with halogen atoms, and - “a” is an integer equal to 0, 1, 2 or 3. 4. COMPOSITION, according to any one of claims 1 to 3, characterized in that the concentration of the free radical photoinitiator P is between 0.0003 and 0.015 mol per 100 g of composition C1. 5. USE OF COMPOSITION C1, as defined in any one of claims 1 to 4, characterized in that it is for the preparation of silicone films with non-stick properties. 6. METHOD FOR PREPARING SILICONE FILMS, with non-stick properties, characterized by comprising a step of cross-linking a composition C1, as defined in any one of claims 1 to 4, by exposure to radiation with a wavelength between 300 nm and 450nm. 7. METHOD, according to claim 6, characterized in that the radiation is generated by light-emitting diodes. 8. C2 SILICONE COMPOSITION, thermally crosslinkable and by exposure to radiation with a wavelength between 300 and 450nm, characterized by comprising: - at least one C1 composition, as defined in any one of claims 1 to 4; - at least one organopolysiloxane B comprising at least two alkenyl groups, each bonded to a silicon atom; and - at least one hydrosilylation catalyst. 9. COMPOSITION, according to claim 8, characterized by additionally comprising at least one additive chosen from the group consisting of: ■ an inhibitor I; ■ a load F; and ■ an adhesion promoter G. 10. SILICONE ELASTOMER, characterized in that it is obtained by cross-linking a composition C1 or C2, as defined in any of claims 1 to 4 or 8 to 9, respectively. 11. USE OF COMPOSITION C2, as defined in any one of claims 8 to 9, characterized in that it is for the preparation of articles made from silicone elastomer by an additive manufacturing process. 12. METHOD FOR PREPARING ARTICLES, made of silicone elastomer, characterized by comprising a step of cross-linking a composition C2, as defined in any one of claims 8 to 9, by exposure to radiation with a wavelength between 300 nm and 450nm. 13. METHOD, according to claim 12, characterized in that the radiation is generated by light-emitting diodes. 14. METHOD according to any one of claims 12 to 13, characterized in that it additionally comprises a heating step. 15. COMPOUNDS, from (1) to (8), (13) to (17), (19), (20) and (22) to (25), characterized by the following formulas: 16. USE OF COMPOUNDS, as defined in claim 15, characterized by being photoinitiating free radicals.