FR3145164A1 - Additive manufacturing method for producing a silicone elastomer article - Google Patents

Abstract

The invention relates to an additive manufacturing method for producing a silicone elastomer article, said method comprising the following steps: implementing a photocrosslinkable silicone composition X and an irradiation source, said photocrosslinkable silicone composition X comprising:a ) at least one organopolysiloxane A comprising at least one (meth)acrylate groupb) at least one radical photoinitiator B of formula (I): c) at least one tertiary amine C;ii) Selective irradiation of at least part of the photocrosslinkable silicone composition X by means of the irradiation source to form part of the silicone elastomer article; andiii) Repeating step ii) a sufficient number of times to produce the silicone elastomer article. The invention also relates to a photocrosslinkable silicone composition and its use.

Description

Additive manufacturing method for producing a silicone elastomer article

The present invention relates to an additive manufacturing method for producing an article by 3D printing from a photocrosslinkable composition X comprising at least one organopolysiloxane and at least one type II photoinitiator system. In particular, this method makes it possible to produce an article by 3D printing from a photocrosslinkable composition X comprising at least one organopolysiloxane (meth)acrylate, a radical photoinitiator associated with a co-initiator as defined in the present invention.

Nowadays, additive manufacturing is experiencing very strong momentum and has phenomenal growth potential due to its emergence and the multiple applications of the articles thus obtained.

More recently 3D techniques have been developed with better printing resolution, relatively high printing speed, flexibility in modeling parts while having a low cost during production.

A key element of the progress made in this technological field has been the development of new photoinitiators or new photoinitiator systems. The development of these new photoinitiators allows to reduce the time of the additive manufacturing of the part but also allows by its properties to work at lower energy and to obtain more complex products.

In the field of radical polymerization of acrylic silicone compositions, the commonly used photoinitiator molecules are so-called type I photoinitiators. Under irradiation, these molecules split and produce free radicals. These radicals induce the polymerization initiation reaction which results in the hardening of the compositions and the production of an article with satisfactory mechanical properties.

However, these commonly used type I photoinitiators may have disadvantages. In particular, the solubility of these photoinitiators in silicone compositions is not satisfactory and may lead to a decrease in the reactivity of such photocrosslinkable compositions. In addition, photoinitiators and their degradation products, such as benzaldehyde, pose health risks and may have an unpleasant odor.

Indeed, a commonly used type I photoinitiator such as TPO-L (CAS 88434-11-7) could be banned or heavily regulated due to its toxicity to humans and the environment.

In addition to these toxic properties, TPO-L in the presence of at least 10% of fillers such as silica or other fillers with hydroxyl groups leads to the exponential increase in the viscosity of the photocurable composition. This high viscosity can make the execution of the additive manufacturing method complex or even impossible.

There are also type II photoinitiator systems comprising a radical photoinitiator and a coinitiator. In type II photoinitiator systems, the photoinitiators used are capable of generating polymerization-initiating free radicals by reaction with another compound called a coinitiator, said reaction causing the transfer of a hydrogen from the coinitiator to said photoinitiator. The photoinitiators used in type II photoinitiator systems are designated by the expression “type II photoinitiators”.

These photoinitiators have the advantage of not creating degradation products. On the other hand, they are generally less reactive than type I photoinitiators.

To date, photoinitiators such as isopropylthioxanthone, also known as ITX, are a reference photoinitiator. However, its very low solubility in silicone medium makes its use impossible in photocrosslinkable silicone compositions.

On the other hand, patent application WO2018/234643A1 discloses various type II photoinitiators effective for the polymerization of acrylic silicone compositions. These compositions are intended to provide a method for preparing a film or a coating on a substrate or an additive manufacturing method leading to the formation of a silicone article.

The type II photoinitiators disclosed in WO2018/234643A1 are derivatives of xanthones, thioxanthones or anthraquinones associated with an organohydrogenpolysiloxane comprising one or more Si-H bonds as a co-initiator. However, the additive manufacturing method implemented using this type II radical photoinitiator system requires working at high energies such as 75 mW/cm ² . Furthermore, in order to obtain an article with satisfactory properties, the type II photoinitiators developed in patent application WO2018/234643A1 require crosslinking by radical route and by polyaddition called "dual-cure". This method has the disadvantage of requiring a heating step as well as the addition of additional compounds such as a platinum catalyst and at least one vinylated organopolysiloxane.

In this context, it is therefore essential to develop a new system of photoinitiators that can overcome these disadvantages.

The aim of the present invention is to provide an additive manufacturing method comprising a silicone composition photocrosslinkable by irradiation with a type II photoinitiator having satisfactory properties at low or even very low energy corresponding respectively to the wavelengths 385nm and 405nm.

Another essential objective of the invention is the provision of an additive manufacturing method comprising a silicone composition photocrosslinkable by irradiation with a type II photoinitiator having no toxic properties for humans or for the environment.

Another essential objective of the invention is the provision of an additive manufacturing method comprising a silicone composition photocrosslinkable by irradiation with a type II photoinitiator having satisfactory photochemical properties and compatible with a filler content in the composition which can be up to 35% relative to the total mass of the composition.

Another objective of the present invention is that this photocrosslinkable silicone composition comprising a type I photoinitiator can be used to form non-stick coatings.

Other objectives will become apparent when reading this application.

Surprisingly, the applicant has developed an additive manufacturing method where the developed type II photoinitiator meets the requirements mentioned above.

Thus, the invention relates to an additive manufacturing method for producing a silicone elastomer article, said method comprising the following steps:
i) implementing a photocrosslinkable silicone composition X and an irradiation source, said photocrosslinkable silicone composition X comprising:
a) at least one organopolysiloxane A comprising at least one (meth)acrylate group
b) at least one radical photoinitiator B of the following formula (I):
[Chem 1]

in which,
R ₁ and R ₃ , identical or different, are chosen from the group consisting of: a hydrogen atom, a hydroxyl and a group of formula -OZ with the symbol O being an oxygen atom and the symbol Z being chosen from the group consisting of:
a _C1 - _C20 alkyl group, preferably _C3 - _C20 or _C2 - _C20 alkenyl,
a –(C=O)-R ₈ group, with the radical R ₈ being selected from C ₁ -C ₂₀ alkyl, C ₂ -C ₂₀ alkenyl, C ₃ -C ₂₀ cycloalkyl and C ₆ -C ₁₂ aryl groups, and
a group -Si(R ₉ ) ₃ , where the R ₉ group, which may be identical or different, is chosen from C ₁ -C ₂₀ alkyl, C ₂ -C ₂₀ alkenyl, C ₃ -C ₂₀ cycloalkyl, C ₆ -C ₁₂ aryl, C ₁ -C ₂₀ alkoxyl groups and the hydrogen atom;
R ₂ is selected from the group consisting of: a hydrogen atom, a C ₁ -C ₆ alkyl group, a –(C=O)-R ₁₀ group with the radical R ₁₀ being selected from the C ₁ -C ₂₀ alkyl, C ₂ -C ₂₀ alkenyl, C ₃ -C ₂₀ cycloalkyl, C ₆ -C ₁₂ aryl, OR ₁₁ and –(N-(R ₁₁ ) ₂ radical with the radical R ₁₁ being selected from the C ₁ -C ₁₂ alkyl groups;
R ₄ , R ₅ , R ₆ and R ₇ , identical or different, are chosen from the group consisting of: a hydrogen atom and a C ₁ -C ₆ alkyl group;
and with one of the following conditions:
- at least one of the substituents R ₁ or R ₃ is a group of formula -OZ, or
- the substituent R ₂ is a group of formula –(C=O)-R ₁₀ .
(c) at least one tertiary amine C ;
(ii) selectively irradiating at least a portion of the photocurable silicone composition X using the irradiation source to form a portion of the silicone elastomer article; and
iii) Repeat step ii) a sufficient number of times to produce the silicone elastomer article.

The radical photoinitiator B has good solubility in silicones. It is thus possible to use the pure photoinitiator, without organic solvent, by diluting it directly in the organopolysiloxane A.

The combination of the radical photoinitiator B and the tertiary amine C makes it possible to obtain a type II photoinitiator having good properties in terms of conversion and reaction kinetics. Unlike the systems previously described in the literature, the combination of a radical photoinitiator B and a tertiary amine C in the presence of an organopolysiloxane (meth)acrylate A leads to the production of silicone articles having very satisfactory physical and mechanical properties at low or even very low energy.

In the present application, the term “photocrosslinkable silicone composition” means a silicone composition comprising at least one organopolysiloxane capable of hardening by electronic or photonic irradiation. Among electronic irradiations, mention may be made of exposures to an electron beam. Among photonic irradiations, mention may be made of exposures to radiation with a wavelength between 200 nm and 450 nm, in particular to UV radiation, or exposures to gamma rays.

By “(meth)acrylate” is meant a methacrylate group or an acrylate group.

By “alkyl” is meant a linear or branched alkyl group. The alkyl group preferably comprises 1 to 6 carbon atoms.

By “alkylene” is meant a divalent, linear or branched alkyl group which may have unsaturated bonds. The alkylene group preferably comprises between 1 and 50 carbon atoms, preferably between 1 and 10 carbon atoms and more preferably between 1 and 6 carbon atoms.

In the present application, the “shear rate” or “shear rate” measures the shear applied within the fluid. Thus, cone-plane geometry viscometers allow, from an angular speed of rotation in a sample (proportional to the shear rate), to proportionally deduce the viscosity of this sample.

Unless otherwise stated, all viscosities referred to in this application correspond to a viscosity quantity measured at 25°C according to ASTM D4287.

In this application, all percentages are stated as mass percentages unless otherwise stated.

Additive manufacturing:

In general, all additive manufacturing processes have a common starting point which is a computer data source or a computer program that can describe an object. This computer data source or computer program can be based on a real or virtual object.

For example, a real object can be scanned using a 3D scanner and the obtained data can be used to generate the computer data source or computer program.

Alternatively, the computer data source or computer program can be designed from scratch. The computer data source or computer program is typically converted to a stereolithography (STL) file, however, other file formats can be used. The file is typically read by 3D printing software which uses the file and, possibly, user input, to separate the object into hundreds or thousands of "layers".
Typically, 3D printing software transfers instructions to the machine, for example in the form of G-code, which are read by the 3D printer which then manufactures the objects, usually layer by layer.

Additive manufacturing methods via photopolymerization are a rapidly expanding technology. It is initiated from a photocrosslinkable liquid composition, deposited locally on a surface and then crosslinked. Alternatively, the photocrosslinkable liquid composition is placed in a tank and then selectively crosslinked.

Various additive manufacturing method techniques are known to those skilled in the art, such as laser stereolithography (SLA) printing, digital light processing (DLP), continuous liquid interface production (CLIP), ink deposition or extrusion.

Advantageously, in the context of the present application, the additive manufacturing method is an additive manufacturing method by vat photopolymerization, in particular, by laser stereolithography (SLA) printing, by digital light processing (DLP), or by continuous liquid interface production (CLIP), using a process where the radiation is transmitted through a liquid crystal display (LCD), by ink-jet projection/deposition or by extrusion.

These technologies and the equipment associated with them are well known to those skilled in the art, who will know how to choose the appropriate technique and the corresponding 3D printer.
These technologies and equipment are for example described in the following documents: WO2015/197495, US5236637, WO2016/181149 and WO2014/126837.

The irradiation source may be any irradiation source that enables photocrosslinking of the photocrosslinkable silicone composition X.

Advantageously, the irradiation source is a light source, preferably an ultraviolet (UV), visible, or infrared (IR) light source. In general, UV light sources have a wavelength of between 200 and 400 nm, visible light sources have a wavelength of between 400 and 700 nm, and IR light sources have a wavelength greater than 700 nm, for example between 700 nm and 1 mm, or between 700 and 10,000 nm.

The light source may be a gas vapor lamp, diodes such as light emitting diodes or a laser. Preferably, the irradiation source is selected from UV lamps, UV lasers, visible lamps, visible lasers, IR lamps and IR lasers.
In a particular embodiment of the method, the irradiation source is a block of light emitting diodes (LEDs), preferably a block of light emitting diodes (LEDs) having a wavelength of 355, 365, 385 or 405 nm.

The power of the irradiation source may be at least 1, 10 or 50 mW/cm ² . It may be between 1 and 1,000 mW/cm ² , preferably between 1 and 200 mW/cm ² , preferentially between 1 and 50 mW/cm ² , and more preferentially between 1 and 20 mW/cm ² .

In a particular embodiment, the penetration depth of the irradiation (Dp) is less than 2000 µm for an irradiance of between 1 and 50 mW/cm ² at 385 or 405 nm, preferably the penetration depth of the irradiation is between 100 and 1000 µm, and more preferably between 100 and 500 µm.

The person skilled in the art will know how to adapt the photoinitiator content, the power of the irradiation source and the duration of irradiation to obtain the desired depth of penetration suited to the object.

In a preferred embodiment, the method does not implement a dual cure type composition. In particular, the method does not implement a composition crosslinkable by polyaddition.

In one embodiment, the method implements a cleaning step such as a solvent rinse or a post-treatment step such as exposure to an additional radiation source or exposure to heat for a given duration.
In a particular embodiment, the method does not implement a post-processing step.

Preferably, the photocurable silicone composition X is implemented in a tank and the silicone elastomer article is produced on a platen, preferably a movable platen. The platen can be any type of platen.

Advantageously, the plate is a platform of a 3D printer, such as a mobile platform, or a support for one or more layers of the photocrosslinkable silicone composition X initially printed with the desired geometry to be able to be detached and crosslinked under irradiation.

According to a first embodiment of the method, the additive manufacturing method is carried out layer by layer, each layer representing a surface of the photocrosslinkable silicone composition X. This first embodiment is particularly suitable for laser stereolithography (SLA) printing and digital light processing (DLP).

In this first embodiment, step ii) of irradiation may comprise the following sub-steps:
a. Deposit a first layer of the photocrosslinkable silicone composition X on a tray
b. Selectively irradiating the surface of the photocrosslinkable silicone composition X with an irradiation source to form a crosslinked layer of the silicone elastomer article to be produced;
c. Forming an additional layer of photocrosslinkable silicone composition X on the first crosslinked layer produced in step b); and
d. Selectively irradiating the additional layer to form an additional crosslinked layer of the silicone elastomer article to be produced.

The tray on which the layer of photocrosslinkable silicone composition X is deposited during step a) may be any type of tray. Preferably, it is a movable tray.

Advantageously, the tray is a platform of a 3D printer, such as a mobile platform. The support applied to the tray may also comprise the first layer or generally comprise several layers of the photocrosslinkable silicone composition X which are selectively deposited and irradiated.

Preferably, in step d), the additional layer that is formed adheres to the first crosslinked layer of the silicone elastomer article formed in step b).

Advantageously, the thickness of a layer of photocrosslinkable silicone composition X is between 0.1 and 500 µm, preferably between 5 and 400 µm, preferentially between 10 and 300 µm, and more preferentially between 10 and 100 µm.

In a particular embodiment, the irradiation time of the layer of photocrosslinkable silicone composition X is at least 0.001 seconds.

Preferably, the irradiation time is between 0.001 seconds and 10 minutes, preferably between 0.001 seconds and 5 minutes and more preferably between 0.01 seconds and 1 minute.

These different parameters can be adjusted depending on the desired result.

The deposition of a layer of photocrosslinkable silicone composition X can be carried out by moving the support, or using a blade, or scraper, which deposits a new layer of photocrosslinkable silicone composition X.

Preferably, in the case where the irradiation source is a laser (SLA method for example) the laser traces the surface of the layer of the silicone elastomer article to be produced, in order to have selective irradiation, and in the case where the irradiation source is a block of light-emitting diodes (DLP method for example) it is a single image of the crosslinked layer of the object to be printed which is projected onto the entire surface of the photocrosslinkable composition X.

Two variants are possible in this first embodiment: additive manufacturing can be carried out by irradiation from above or irradiation from below. These two variants are described in document US5236637.

In a first variant of this first embodiment, the additive manufacturing is carried out from above: the photocrosslinkable silicone composition X is contained in a tank and the irradiation source is focused on the surface of the photocrosslinkable silicone composition X.
The layer that is irradiated is the one between the plate and the surface of the photocrosslinkable silicone composition X.

In this first variant, the deposition of a layer of photocrosslinkable silicone composition X is carried out by lowering the plate into the tank by a distance equal to the thickness of a layer. A blade, or scraper, can then sweep the surface of the photocrosslinkable silicone composition X , which makes it possible to flatten it.

In a second variant of this first embodiment, the additive manufacturing is from the bottom: the tank comprises a transparent bottom and a non-adhesive surface, and the irradiation source is focused on the transparent bottom of the tank. The layer that is irradiated is therefore the one between the bottom of the tank and the plate.

In this case, the deposition of a layer of photocurable silicone composition X is carried out by raising the plate to allow the photocurable silicone composition X to be inserted between the bottom of the tank and the plate. The distance between the bottom of the tank and the plate corresponds to the thickness of a layer.

Advantageously, the additive manufacturing method is a digital light processing (DLP) vat photopolymerization additive manufacturing method, where additive manufacturing is performed from below: the deposition of a layer of photocurable silicone composition X is performed by raising the plate in the vat to allow the photocurable silicone composition X to be inserted between the bottom of the vat and the plate. The distance between the bottom of the vat and the plate corresponds to the thickness of a layer.

According to a second embodiment, the additive manufacturing method is carried out continuously. This second embodiment is particularly suitable for continuous liquid interface production (CLIP) described in WO2014/126837. In this second embodiment, the irradiation step ii) may comprise the following sub-steps, which take place simultaneously:
a. Selectively irradiating at least a portion of the photocurable silicone composition X with an irradiation source to form a portion of the silicone elastomer article on the platen; and
b. Move the tray and the part of the silicone elastomer article formed in step a) away from the irradiation source, along the irradiation axis.

Advantageously, in step a), the part of the silicone elastomer article is formed on a plate and in step b), it is the plate which is moved simultaneously.
Preferably, in this second embodiment, the additive manufacturing is carried out by bottom irradiation: the tank comprises a transparent bottom and the irradiation source is focused on the transparent bottom of the tank.

Thanks to an oxygen-permeable membrane, photopolymerization only takes place at the interface between the photocrosslinkable silicone composition X and the plate; the photocrosslinkable composition X between the bottom of the tank and the interface does not photopolymerize.

Thus, it is possible to maintain a continuous liquid interface where the silicone elastomer article is formed by irradiating the photocurable composition X and simultaneously moving the portion of the silicone elastomer article formed on the platen out of the tank.

Once the silicone elastomer article is obtained, it is possible to rinse it in order to eliminate the non-crosslinked photocrosslinkable silicone composition X.

Once the silicone elastomer article has been obtained, it is also possible to carry out additional steps to improve the surface quality of the article. The use and application of coatings such as top coats as a final layer can in particular improve the surface quality of the article.

Spraying or coating the silicone elastomer article with a LSR or RTV silicone composition that can be crosslinked by heating or UV radiation can also be used to achieve a smooth appearance. It is also possible to perform a surface treatment of the article obtained with a laser.

For medical applications, it is possible to sterilize the resulting silicone elastomer article. Sterilization of the article can be carried out by heating, for example at a temperature above 100°C, either in a dry atmosphere or in an autoclave with steam. Sterilization can also be carried out by gamma rays, with ethylene oxide, or by electron beams.

The invention also relates to a silicone elastomer article obtained by the method described in the present application.

The resulting silicone elastomer article can be any article with simple or complex geometry. For example, it can be silicone molds, masks, tubes, anatomical models (functional or non-functional) such as a heart, kidney, prostate, models for surgeons or for teaching, orthoses, prostheses, such as dentures, aligners, mouth guards, or implants of different classes, such as long-term implants, hearing aids, stents, laryngeal implants, etc.

The resulting silicone elastomer article can also be a cylinder for robotics, a seal, a mechanical part for the automotive or aeronautical industries, a part for electronic devices, a part for encapsulating components, a vibration insulator, an impact insulator or a sound insulator.

Photocrosslinkable composition

According to one embodiment, the photocrosslinkable silicone composition X has a dynamic viscosity of between 0.01 and 20 Pa.s at a shear rate of 17s ^-1 at 25°C, preferably between 1 and 15 Pa.s, more preferably between 1 and 10 Pa.s at a shear rate of 17s ^-1 at 25°C.

In the present application, according to the method of the invention, the photocrosslinkable silicone compositions X comprise at least one organopolysiloxane A.

Preferably, according to the method of the invention, the photocrosslinkable silicone compositions X comprise at least one organopolysiloxane A comprising at least one (meth)acrylate group, preferably at least 2 (meth)acrylate groups.

As representatives of (meth)acrylate functions carried by the silicone and particularly suitable for the invention, mention may more particularly be made of acrylate derivatives, methacrylates, (meth)acrylate ethers and (meth)acrylate esters linked to the polysiloxane chain by an Si-C bond.

According to one embodiment, organopolysiloxane A comprises:
(a) at least one motif of the following formula (II):
R _a Z _b SiO _(4-ab)/2 (II)
formula in which:
- the symbols R, which may be identical or different, each represent a linear or branched C ₁ to C ₁₈ alkyl group, a C ₆ to C ₁₂ aryl or aralkyl group, said alkyl and aryl groups possibly being optionally substituted, preferably by halogen atoms, or a group -OR ⁵ with R ⁵ being a hydrogen atom or a hydrocarbon group comprising from 1 to 10 carbon atoms,
- the symbols Z are monovalent groups of formula –Y-(Y')n in which:
- Y represents a polyvalent C ₁ -C ₁₈ alkylene or heteroalkylene group, said alkylene and heteroalkylene groups possibly being linear or branched, and possibly being interspersed by one or more cycloalkylene groups, and possibly being extended by bivalent C ₁ to C ₄ oxyalkylene or polyoxyalkylene radicals, said alkylene, heteroalkylene, oxyalkylene and polyoxyalkylene groups possibly being substituted by one or more hydroxy groups,
- Y' represents a monovalent alkenylcarbonyloxy group, 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
(b) possibly patterns of the following formula (III):
R _a SiO _(4-a)/2 (III)
formula in which:
- the symbols R are as defined above in formula (II), and
- a is an integer equal to 0, 1, 2 or 3.

In the formulae (II) and (III) above, the symbols R, which may be identical or different, each represent a linear or branched C ₁ to C ₁₈ alkyl group or a C ₆ to C ₁₂ aryl or aralkyl group. Preferably, the symbol R represents a monovalent group selected from the group consisting of methyl, ethyl, propyl, 3,3,3-trifluoropropyl, xylyl, tolyl and phenyl, and preferably the symbol R represents a methyl.

The organopolysiloxane A may have a linear, branched, cyclic or network structure. Preferably, the organopolysiloxane A has a linear structure.
When it comes to linear organopolysiloxanes, these can essentially consist of:
- siloxyl units “D” chosen from the units of formulas R ₂ SiO _2/2 , RZSiO _2/2 and Z ₂ SiO _2/2 ;
- siloxyl units “M” chosen from the units of formulas R ₃ SiO _1/2 , R ₂ ZSiO _1/2 , RZ ₂ SiO _1/2 and Z ₃ SiO _1/2 , and
- the symbols R and Z are as defined above in formula (II).

According to one embodiment, in formula (II) above, among the aforementioned Y' alkenylcarbonyloxy groups, mention may be made of acryloxy [CH ₂ =CH–CO–O–] and the methacryloxy group: [CH ₂ =C(CH ₃ )–CO–O–]. Advantageously, the organopolysiloxane A comprises at least 2 Y' alkenylcarbonyloxy groups, preferably at least 3 Y' alkenylcarbonyloxy groups.

As an illustration of the symbol Y in the motifs of formula (II), the following groups will be mentioned:
–CH ₂ – ;
–(CH ₂ ) ₂ – ;
–(CH ₂ ) ₃ – ;
–CH ₂ -CH(CH ₃ )-CH ₂ – ;
–(CH ₂ ) ₃ -NR'-CH ₂ -CH ₂ – ; with R' which is a C ₁ -C ₆ alkyl group
–(CH ₂ ) ₃ -OCH ₂ – ;
–(CH ₂ ) ₃ -[O-CH ₂ -CH(CH ₃ )-] _n –; with n = 1 to 25
–(CH ₂ ) ₃ -O-CH _2- CH(OH)(–CH ₂ –);
–(CH ₂ ) ₃ -O-CH ₂ –C(CH ₂ -CH ₃ )[–(CH ₂ -)] ₂ ;
–(CH ₂ ) ₃ -O-CH ₂ –C[–(CH ₂ )-] ₃ and
–(CH ₂ ) ₂ -C ₆ H ₉ (OH)–.

Preferably, the organopolysiloxane A corresponds to the following formula (IV):
[Chem 2]
(IV)
formula in which:
- the symbols R ¹ , which may be identical or different, each represent a linear or branched C ₁ to C ₁₈ alkyl group, an aryl or C ₆ to C ₁₂ alkyl group, said alkyl and aryl groups possibly being optionally substituted, preferably by halogen atoms, or a group –OR ⁵ with R ⁵ being a hydrogen atom or a hydrocarbon group comprising from 1 to 10 carbon atoms,
- the symbols R ² and R ³ , identical or different, each represent either a group R ¹ or a monovalent group of formula Z = –Y-(Y')n in which:
- Y represents a polyvalent C ₁ -C ₁₈ alkylene or heteroalkylene group, said alkylene and heteroalkylene groups possibly being linear or branched, and possibly being interspersed by one or more cycloalkylene groups, and possibly being extended by bivalent C1 to C4 oxyalkylene or polyoxyalkylene radicals, said alkylene, heteroalkylene, oxyalkylene and polyoxyalkylene groups possibly being substituted by one or more hydroxy groups,
- Y' represents a monovalent alkenylcarbonyloxy group,
- 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, preferably a = 0 to 500 and a+b+c+d= 0 to 500,
- provided that at least one symbol R ² or R ³ represents the monovalent group of formula Z, preferably at least two symbols R ² or R ³ represent a monovalent group of formula Z.

According to a preferred embodiment, in formula (IV) above:
- c=0, d=0, a= 1 to 1000, b= 1 to 250, the symbol R ² represents the monovalent group of formula Z and the symbols R ¹ and R ³ have the same meaning as above.

Even more preferably, in formula (V) above:
- c=0, d=0, a= 1 to 500, b= 2 to 100, the symbol R ² represents the monovalent group of formula Z and the symbols R ¹ and R ³ have the same meaning as above.

According to one embodiment, the organopolysiloxaneHASaccording to the invention corresponds to one of the following formulas (Va), (Vb), (Vc) or (Vd):
[Chem 3]

in which:
R identical or different represents a hydrogen atom or a hydroxyl group;
-x₁is an integer between 1 and 1000; preferably x₁is between 1 and 500;
-n₁is an integer between 1 and 100, preferably n₁is between 2 and 50;
-x₂is an integer between 1 and 1000, preferably x₂is between 1 and 500;
-n₂is an integer between 0 and 100, preferably n₂is between 0 and 50;
-x₃is an integer between 1 and 1000, preferably x₃is between 1 and 500;
-n₃is an integer between 0 and 100, preferably n₃is between 0 and 50;
-x₄is an integer between 1 and 1000, preferably x₄is between 1 and 500;
-n₄is an integer between 0 and 100, preferably n₄is between 0 and 50;
-m₁, m₂, m₃and m₄are integers between 1 and 8.

According to one embodiment, the organopolysiloxane A according to the invention corresponds to one of the following formulas (VIa), (VIb), (VIc) or (VId):
[Chem 4]

in which:
- x ₁ is an integer between 1 and 1000; preferably x ₁ is between 1 and 500,
- n ₁ is an integer between 0 and 100, preferably n ₁ is between 0 and 50,
- x ₂ is an integer between 1 and 1000, preferably x ₂ is between 1 and 500
- n ₂ is an integer between 0 and 100, preferably n ₂ is between 0 and 50,
- x ₃ is an integer between 1 and 1000, preferably x ₃ is between 1 and 500,
- n ₃ is an integer between 1 and 100, preferably n ₃ is between 1 and 50,
- x ₄ is an integer between 1 and 500, preferably x ₄ is between 1 and 200,
- n ₄ is an integer between 0 and 100, preferably n ₄ is between 0 and 50.

According to the method of the invention, the photocrosslinkable silicone composition X can comprise from 10 to 99.9% by mass of organopolysiloxane A , relative to the total mass of the photocrosslinkable silicone composition X.

Preferably, the photocrosslinkable silicone composition X may comprise from 10 to 99.5% by weight of organopolysiloxane A , relative to the total weight of the photocrosslinkable silicone composition X. Of course, according to the variants of the invention, the organopolysiloxane A may be a mixture of compounds meeting the definition of organopolysiloxane A.

Radical photoinitiator B:

The photocrosslinkable silicone composition X of the invention comprises a radical photoinitiator B chosen from the group consisting of thioxanthone derivatives.

According to one embodiment, the photocrosslinkable silicone composition X of the invention comprises a radical photoinitiator B of the following formula (VII):
[Chem 5]

in which,
R ₁ and R ₃ , identical or different, are chosen from the group consisting of: a hydrogen atom, a hydroxyl and a group of formula -OZ with the symbol O being an oxygen atom and the symbol Z being chosen from the group consisting of:
a _C1 - _C20 alkyl group, preferably _C3 - _C20 or _C2 - _C20 alkenyl,
a –(C=O)-R ₈ group, with the radical R ₈ being selected from C ₁ -C ₂₀ alkyl, C ₂ -C ₂₀ alkenyl, C ₃ -C ₂₀ cycloalkyl and C ₆ -C ₁₂ aryl groups, and
a group -Si(R ₉ ) ₃ , where the R ₉ group, which may be identical or different, is chosen from C ₁ -C ₂₀ alkyl, C ₂ -C ₂₀ alkenyl, C ₃ -C ₂₀ cycloalkyl, C ₆ -C ₁₂ aryl, C ₁ -C ₂₀ alkoxyl groups and the hydrogen atom;
R ₂ is selected from the group consisting of: a hydrogen atom, a C ₁ -C ₆ alkyl group, a –(C=O)-R ₁₀ group with the radical R ₁₀ being selected from the C ₁ -C ₂₀ alkyl, C ₂ -C ₂₀ alkenyl, C ₃ -C ₂₀ cycloalkyl, C ₆ -C ₁₂ aryl, OR ₁₁ and –(N-(R ₁₁ ) ₂ radical with the radical R ₁₁ being selected from the C ₁ -C ₁₂ alkyl groups;
R ₄ , R ₅ , R ₆ and R ₇ , identical or different, are chosen from the group consisting of: a hydrogen atom and a C ₁ -C ₆ alkyl group;
and with one of the following conditions:
- at least one of the substituents R ₁ or R ₃ is a group of formula -OZ, or
- the substituent R ₂ is a group of formula –(C=O)-R ₁₀ .

According to one embodiment, the photocrosslinkable silicone composition X of the invention comprises a radical photoinitiator B of the following formula (VIII):
[Chem 6]

in which,
R ₁ and R ₂ , identical or different, are chosen from the group consisting of: a hydrogen atom, a hydroxyl and a group of formula -OZ with the symbol O being an oxygen atom and the symbol Z being chosen from the group consisting of:
a _C1 - _C20 alkyl group, preferably _C3 - _C20 or _C2 - _C20 alkenyl,
a –(C=O)-R ₈ group, with the radical R ₈ being selected from C ₁ -C ₂₀ alkyl, C ₂ -C ₂₀ alkenyl, C ₃ -C ₂₀ cycloalkyl and C ₆ -C ₁₂ aryl groups, and
a group -Si(R ₉ ) ₃ , where the R ₉ group, which may be identical or different, is chosen from C ₁ -C ₂₀ alkyl, C ₂ -C ₂₀ alkenyl, C ₃ -C ₂₀ cycloalkyl, C ₆ -C ₁₂ aryl, C ₁ -C ₂₀ alkoxyl groups and the hydrogen atom;
R ₄ , R ₅ , R ₆ and R ₇ , identical or different, are chosen from the group consisting of: a hydrogen atom and a C ₁ -C ₆ alkyl group;
and with one of the following conditions:
- at least one of the substituents R ₁ or R ₃ is a group of formula -OZ
- the substituent R ₂ is a group of formula –(C=O)-R ₁₀ .

The photocrosslinkable silicone composition X of the invention comprises a radical photoinitiator B of the following formula radical photoinitiator B of the following formula (IX):
[Chem 7]

in which,
R ₁ and R ₂ , identical or different, are chosen from the group consisting of: a hydrogen atom, a hydroxyl and a group of formula -OZ with the symbol O being an oxygen atom and the symbol Z being chosen from the group consisting of:
a _C1 - _C20 alkyl group, preferably _C3 - _C20 or _C2 - _C20 alkenyl group
a –(C=O)-R ₃ group, with the radical R ₃ being selected from C ₁ -C ₂₀ alkyl, C ₂ -C ₂₀ alkenyl, C ₃ -C ₂₀ cycloalkyl and C ₆ -C ₁₂ aryl groups, and
a group -Si(R ₄ ) ₃ , where the identical or different R ₄ groups are chosen from C ₁ -C ₂₀ alkyl, C ₂ -C ₂₀ alkenyl, C ₃ -C ₂₀ cycloalkyl, C ₆ -C ₁₂ aryl, C ₁ -C ₂₀ alkoxyl groups and the hydrogen atom,
and with the condition that at least one of the substituents R ₁ or R ₂ is a group of formula -OZ.

As examples of radical photoinitiators B of formula (IX), the following compounds will be cited in particular: 2-methoxy-9H-thioxanthen-9-one (RN -CAS = 40478-83-8), 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 (RN-CAS 2259316-46-4), 2-decyloxy-9H-thioxanthen-9-one (RN-CAS 2259316-47-5), 2-dodecyloxy-9H-thioxanthen-9-one (RN-CAS 2258641-35-7), 2-acetoxy-9H-thioxanthen-9-one (RN-CAS 92439-12-8), 2-[(trimethylsilyl)oxy]-9H-thioxanthen-9-one (RN-CAS= 32747-67-4), 2-propenoic acid-9-oxo-9H thioxanthen-2-yl ester (RN-CAS = 113797-58-3), 2-neodecanoic acid 9-oxo-9H-thioxanthen-2-yl ester, 4-methoxy-9H-thioxanthen-9-one (RN -CAS = 57275-18-0), 4-ethoxy-9H-thioxanthen-9-one (RN-CAS = 57275-11-3), 4-propoxy-9H-thioxanthen-9-one (RN-CAS 106221-19-6), 4-hexyloxy-9H-thioxanthen-9-one,, 4-octyloxy-9H-thioxanthen-9-one, 4-decyloxy -9H-thioxanthen-9-one, 4-dodecyloxy-9H-thioxanthen-9-one, 4-acetyloxy-9H-thioxanthen-9-one, 4-[(trimethylsilyl)oxy]-9H-thioxanthen-9-one, 4-propenoic acid-9-oxo-9H thioxanthen-2-yl ester, 2,4-Diethyl-9H-thioxanthen-9-one (RN-CAS 82799-44-8), 4-neodecanoic acid 9-oxo-9H-thioxanthen-2-yl ester, and mixtures thereof. These compounds have been synthesized and described in international application WO 2018/234643.

According to one embodiment of the invention, the radical photoinitiator B is chosen from the group consisting of thioxanthone derivatives of the following formula (Xa):
[Chem 8]

in which the symbol Z being chosen from the group consisting of: a C ₁ -C ₂₀ alkyl group, preferably C ₃ -C ₂₀ or C ₂ -C ₂₀ alkenyl group, a –(C=O)-R ₃ group, with the radical R ₃ being chosen from the C ₁ -C ₂₀ alkyl, C ₂ -C ₂₀ alkenyl, C ₃ -C ₂₀ cycloalkyl and C ₆ -C ₁₂ aryl groups.

According to one embodiment of the invention, the radical photoinitiator B is chosen from the group consisting of thioxanthone derivatives of the following formula (Xb):
[Chem 9]

in which the symbol Z being chosen from the group consisting of: a C ₁ -C ₂₀ alkyl group, preferably C ₃ -C ₂₀ or C ₂ -C ₂₀ alkenyl group, a –(C=O)-R ₃ group, with the radical R ₃ being chosen from the C ₁ -C ₂₀ alkyl, C ₂ -C ₂₀ alkenyl, C ₃ -C ₂₀ cycloalkyl and C ₆ -C ₁₂ aryl groups.

According to an advantageous embodiment of the invention, the radical photoinitiator B is chosen from the group consisting of thioxanthone derivatives, of the following formula (XIa):
[Chem 10]

in which, R is selected from C ₁ -C ₂₀ alkyl, C ₂ -C ₂₀ alkenyl, C ₃ -C ₂₀ cycloalkyl and C ₆ -C ₁₂ aryl groups.

According to an advantageous embodiment of the invention, the radical photoinitiator B is chosen from the group consisting of thioxanthone derivatives, of the following formula (XIb):
[Chem 11]

in which, R is selected from C ₁ -C ₂₀ alkyl, C ₂ -C ₂₀ alkenyl, C ₃ -C ₂₀ cycloalkyl and C ₆ -C ₁₂ aryl groups.

According to an advantageous embodiment of the invention, the radical photoinitiator B is chosen from the group consisting of thioxanthone derivatives, of the following formula (XIIa):
[Chem 12]

in which, R represents a C ₂ -C ₁₈ alkyl group, preferably C ₄ -C ₁₈ , preferentially C ₈ -C ₁₈ .

According to an advantageous embodiment of the invention, the radical photoinitiator B is chosen from the group consisting of thioxanthone derivatives, of the following formula (XIIb):
[Chem 13]

in which, R represents a C ₂ -C ₁₈ alkyl group, preferably C ₄ -C ₁₈ , preferentially C ₈ -C ₁₈ .

According to one embodiment of the invention, the radical photoinitiator B of the invention is chosen from 2-neodecanoic acid 9-oxo-9H-thioxanthen-2-yl ester, 4-neodecanoic acid 9-oxo-9H-thioxanthen-2-yl ester, and mixtures thereof.

In one embodiment of the invention, the mass percentage of the radical photoinitiator B is from 0.1 to 20% relative to the total mass of the photocrosslinkable composition X , preferably from 0.1 to 5%, preferentially from 0.2 to 2%, more preferentially from 0.4 to 1.5% relative to the total mass of the photocrosslinkable composition X.

Tertiary amine C:

The photocrosslinkable silicone composition X of the invention comprises a tertiary amine C. A tertiary amine is an amine where three different hydrogen groups are bonded to the nitrogen atom. For example, trimethylamine is a tertiary amine of formula N(CH ₃ ) ₃ because three methyl groups are bonded to the nitrogen.

Preferably, the tertiary amine C comprises at least one nitrogen atom and alternatively at least two nitrogen atoms.

Examples of acyclic tertiary amines C of formula (XV) include the following compounds: triisopropylamine (CAS 3424-21-3), triisobutylamine (CAS 1116-40-1), triisopentylamine (CAS 645-41-0), triisooctylamine (CAS 25549-16-0), triisononylamine (CAS 38725-13-2), triisodecylamine (CAS 35723-89-8), tripropylamine (CAS 102-69-2), tributylamine (CAS 102-82-9), tripentylamine (CAS 621-77-2), trihexylamine (CAS 102-86-3), triheptylamine (CAS 2411-36-1), trioctylamine (CAS 1116-76-3), trinonylamine (CAS 2044-22-6), tridecan-1-amine (CAS 5910-77-0), tridodecylamine (CAS 102-87-4), N,N-Diisopropylethylamine (CAS 7087-68-5), N,N-Dimethyloctylamine (CAS 7378-99-6), N,N-Dimethyldecylamine (CAS 1120-24-7), Tris(2-ethylhexyl)amine (CAS 1860-26-0), N,N,N',N'-Tetraméthyl-1,6-hexanediamine (CAS 111-18-2), N,N-Diméthyldodécylamine (CAS 112-18-5), N,N,N',N'-Tetraméthyl-1,3-propanediamine (CAS 110-95-2) (3-trimethoxysilyl propyl)-N-methylamine (CAS 31024-70-1), N,N-diethyl-3-aminopropyltrimethoxysilane (CAS 41051-80-3), nN,N-dimethylaminodimethylsilane (CAS 22705-35-4), 3-(N,N-dimethylaminopropyl)trimethoxysilane (CAS 2530-86-1), (N,N-diethylaminomethyl)triethoxysilane (CAS 15180-47-9).

According to one embodiment of the invention, the tertiary amine C is an acyclic tertiary amine of the following formula (XIII):
[Chem 14]

in which,
R ₁ , R ₂ and R ₃ , identical or different, are chosen from:
a _C1 - _C20 alkyl group, preferably _C2 - _C12 , preferentially _C5 - _C12 , or _C2 - _C20 alkenyl substituted or not by at least one group chosen from:
- an aryl group of 6 to 18 carbon atoms
- a heteroatom O, N or S,
- a halogen,
- a hydroxyl group
- a group (O-Alk) with Alk representing an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms,
- an amino-alkyl group of the form N(R ₄ ) ₂ where R ₄ represents a C ₁ -C ₂₀ alkyl group, preferably C ₃ -C ₂₀ ,
- a SiMe ₃ group,
- a Si(O-Alk) ₃ group with Alk representing an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms, preferentially from 1 to 6 carbon atoms.

According to one embodiment of the invention, the tertiary amine C is an acyclic tertiary amine of the following formula (XIV):
[Chem 15]

in which,
R ₁ , R ₂ and R ₃ , identical or different, are chosen from:
a _C1 - _C20 alkyl group, preferably _C2 - _C12 , preferentially _C5 - _C12 , or _C2 - _C20 alkenyl substituted or not by at least one group chosen from:
- an aryl group of 6 to 18 carbon atoms
- a heteroatom O, N or S,
- a halogen,
- a hydroxyl group
- a group (O-Alk) with Alk representing an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms,
- an amino-alkyl group of the form N(R ₄ ) ₂ where R ₄ represents a C ₁ -C ₂₀ alkyl group, preferably C ₃ -C ₂₀ ,
- a SiMe ₃ group,
- a Si(O-Alk) ₃ group with Alk representing an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms, preferentially from 1 to 6 carbon atoms,
and with the condition that at least:
- a group R ₁ , R ₂ or R ₃ represents a C ₅ -C ₁₂ alkyl group
- a group R ₁ , R ₂ or R ₃ represents a C ₁ -C ₂₀ alkyl group substituted by an amino-alkyl group of the form N(R ₄ ) ₂ where R ₄ represents a C ₁ -C ₂₀ alkyl group, preferably C ₃ -C ₂₀ , or
- a group R ₁ , R ₂ or R ₃ represents a C ₁ -C ₂₀ alkyl group substituted by a group Si(O-Alk) ₃ with Alk representing an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms, preferentially from 1 to 6 carbon atoms.

According to one embodiment of the invention, the tertiary amine C is an acyclic tertiary amine of the following formula (XV):
[Chem 16]

in which,
R ₁ , R ₂ and R ₃ , identical or different, are chosen from:
a _C1 - _C20 alkyl group, preferably _C2 - _C12 , preferentially _C5 - _C12 , or _C2 - _C20 alkenyl substituted or not by at least one group chosen from:
- an amino-alkyl group of the form N(R ₄ ) ₂ where R ₄ represents a C ₁ -C ₂₀ alkyl group, preferably C ₃ -C ₂₀ ,
- a SiMe ₃ group,
- a Si(O-Alk) ₃ group with Alk representing an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms, preferentially from 1 to 6 carbon atoms.

According to one embodiment of the invention, the tertiary amine C is an acyclic tertiary amine of the following formula (XVIa):
[Chem 17]

in which,
R ₅ , R ₆ and R ₇ , identical or different, are chosen from:
a _C1 - _C20 alkyl group, preferably _C2 - _C12 , preferentially _C5 - _C12 , or _C2 - _C20 alkenyl substituted or not by at least one group chosen from:
- an aryl group of 6 to 18 carbon atoms
- a heteroatom O, N or S,
- a halogen,
- a hydroxyl group
- a group (O-Alk) with Alk representing an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms,
- an amino-alkyl group of the form N(R ₈ ) ₂ where R ₈ represents a C ₁ -C ₂₀ alkyl group, preferably C ₃ -C ₂₀ ,
- a SiMe ₃ group,
- a Si(O-Alk) ₃ group with Alk representing an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms, preferentially from 1 to 6 carbon atoms,
and with the condition that at least:
- a group R ₅ , R ₆ or R ₇ represents a C ₅ -C ₁₂ alkyl group.

According to one embodiment of the invention, the tertiary amine C is an acyclic tertiary amine of the following formula (XVIb):
[Chem 18]

in which,
R ₅ , R ₆ and R ₇ , identical or different, are chosen from:
- a _C1 - _C20 alkyl group, preferably _C2 - _C12 or _C2 - _C20 alkenyl group substituted or not by at least one group chosen from:
- a heteroatom O, N or S,
- a hydroxyl group
and with the condition that at least:
- a group R ₅ , R ₆ or R ₇ represents a C ₅ -C ₁₂ alkyl group.

According to one embodiment of the invention, the tertiary amine C is an acyclic tertiary amine of the following formula (XVIIa):
[Chem 19]

in which,
R ₉ , R ₁₀ and R ₁₁ , identical or different, are chosen from:
a _C1 - _C20 alkyl group, preferably _C2 - _C12 , preferentially _C5 - _C12 , or _C2 - _C20 alkenyl substituted or not by at least one group chosen from:
- an aryl group of 6 to 18 carbon atoms
- a heteroatom O, N or S,
- a halogen,
- a hydroxyl group
- a group (O-Alk) with Alk representing an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms,
- an amino-alkyl group of the form N(R ₁₂ ) ₂ where R ₁₂ represents a C ₁ -C ₂₀ alkyl group, preferably C ₃ -C ₂₀ ,
- a SiMe ₃ group,
- a Si(O-Alk) ₃ group with Alk representing an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms, preferentially from 1 to 6 carbon atoms,
and with the condition that at least:
- a group R ₉ , R ₁₀ or R ₁₁ represents a C ₁ -C ₂₀ alkyl group substituted by a group Si(O-Alk) ₃ with Alk representing an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms, preferentially from 1 to 6 carbon atoms.

According to one embodiment of the invention, the tertiary amine C is an acyclic tertiary amine of the following formula (XVIIb):
[Chem 20]

in which,
R ₉ , R ₁₀ and R ₁₁ , identical or different, are chosen from:
a _C1 - _C20 alkyl group, preferably _C2 - _C12 , preferentially _C5 - _C12 , or _C2 - _C20 alkenyl substituted or not by at least one group chosen from:
- a heteroatom O, N or S,
-a hydroxyl group
- a SiMe ₃ group,
- a Si(O-Alk) ₃ group with Alk representing an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms, preferentially from 1 to 6 carbon atoms,
and with the condition that at least:
- a group R ₉ , R ₁₀ or R ₁₁ represents a C ₁ -C ₂₀ alkyl group substituted by a group Si(O-Alk) ₃ with Alk representing an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms, preferentially from 1 to 6 carbon atoms.

According to one embodiment of the invention, the tertiary amine C is an acyclic tertiary amine of the following formula (XVIIIa):
[Chem 21]

in which,
R ₁₃ , R ₁₄ and R ₁₅ , identical or different, are chosen from:
a _C1 - _C20 alkyl group, preferably _C2 - _C12 , preferentially _C5 - _C12 , or _C2 - _C20 alkenyl substituted or not by at least one group chosen from:
- an aryl group of 6 to 18 carbon atoms
- a heteroatom O, N or S,
- a halogen,
- a hydroxyl group
- a group (O-Alk) with Alk representing an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms,
- an amino-alkyl group of the form N(R ₁₆ ) ₂ where R ₁₆ represents a C ₁ -C ₂₀ alkyl group, preferably C ₃ -C ₂₀ ,
- a SiMe ₃ group,
- a Si(O-Alk) ₃ group with Alk representing an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms, preferentially from 1 to 6 carbon atoms,
and with the condition that at least:
- a group R ₁₃ , R ₁₄ or R ₁₅ represents a C ₁ -C ₂₀ alkyl group substituted by an amino-alkyl group of the form N(R ₁₆ ) ₂ where R ₁₆ represents a C ₁ -C ₂₀ alkyl group, preferably C ₃ -C ₂₀ .

According to one embodiment of the invention, the tertiary amine C is an acyclic tertiary amine of the following formula (XVIIIb):
[Chem 22]

in which,
R ₁₃ , R ₁₄ and R ₁₅ , identical or different, are chosen from:
a _C1 - _C20 alkyl group, preferably _C2 - _C12 , preferentially _C5 - _C12 , or _C2 - _C20 alkenyl substituted or not by at least one group chosen from:
- a heteroatom O, N or S,
-a hydroxyl group
- an amino-alkyl group of the form N(R ₁₆ ) ₂ where R ₁₆ represents a C ₁ -C ₂₀ alkyl group, preferably C ₃ -C ₂₀
and with the condition that at least:
-a group R ₁₃ , R ₁₄ or R ₁₅ represents a C ₁ -C ₂₀ alkyl group substituted by an amino-alkyl group of the form N(R ₁₆ ) ₂ where R ₁₆ represents a C ₁ -C ₂₀ alkyl group, preferably C ₃ -C ₂₀ .

According to one embodiment of the invention, the acyclic tertiary amineCcomprises two nitrogen atoms and is represented by the formula (XVIIIc):
[Chem 23]

in which R₁₇identical or different, represent:
- a C alkyl group₃-C₁₅,
- a C alkenyl group₂-C₂₀, preferably in C₃-C₁₅, more preferably in C₅-C₁₅;
and n a natural integer between 1 and 20, preferably between 1 and 12, preferably between 1 and 6.

Alternatively, the acyclic tertiary amine C is a so-called “silicone-grafted” acyclic tertiary amine.

The acyclic tertiary amine C comprises at least one siloxane function. Preferably, the acyclic tertiary amine C comprises at least one siloxane function having from 1 to 100 units, preferably from 1 to 50 units and more preferably from 1 to 20 units.
According to one embodiment of the invention, amine C is an acyclic tertiary amine of the following formula (XIX):
[Chem 24]

in which,
R ₁₈ is chosen from a C ₁ -C ₂₀ alkyl group, preferably C ₂ -C ₁₂ , preferentially C ₅ -C ₁₂ ;
R ₁₉ is chosen from a C ₁ -C ₁₀ alkyl group, preferably C ₁ -C ₆ , preferentially C ₁ -C ₃ ;
R ₂₀ and R _21, identical or different, are chosen from:
a _C1 - _C20 alkyl group, preferably _C2 - _C12 , preferentially _C5 - _C12 , or _C2 - _C20 alkenyl substituted or not by at least one group chosen from:
- an aryl group of 6 to 18 carbon atoms
- a heteroatom O, N or S,
- a halogen,
- a hydroxyl group
- a group (O-Alk) with Alk representing an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms,
- a SiMe ₃ group,
- a Si(O-Alk) ₃ group with Alk representing an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms, preferentially from 1 to 6 carbon atoms;
n is a natural integer from 0 to 100, preferably from 0 to 50, more preferably from 0 to 25;
x is a natural integer from 0 to 10.

Preferably, the acyclic tertiary amine C has low toxicity in view of its use in photocrosslinkable compositions.

In the context of the present application, the redox potential of tertiary amines C can be measured using a cyclic voltammetry method.

To do this, a glass measuring cell is filled to one third with the support electrolyte solution (tetrabutylammonium hexafluorophosphate 40g/L in acetonitrile) and then sealed tightly while maintaining a flow of argon. A working electrode and a counter-electrode, both made of platinum, are used to take the measurement while a saturated calomel electrode serves as a reference (ECS). A drop or a spatula tip of product is added while stirring, then a potentiostat connected to software is used to measure the current produced in µA when the potential varies from 0 to 2V, then from 2V to 0V. Like a pH jump, we then observe an inflection whose maximum, measured with the derivative method, corresponds to the oxidation potential of the compound studied.

According to one embodiment of the invention, the acyclic tertiary amine C has an oxidation-reduction potential of less than 1.2 V/ECS. Preferably, the acyclic tertiary amine C has an oxidation-reduction potential of 0.4 to 1.1 V/ECS, preferably of 0.7 to 1.1 V/ECS, even more preferably of 0.7 to 0.9 V/ECS or of 0.8 to 1 V/ECS.

According to one embodiment of the invention, the mass percentage of the tertiary amine C is from 0.1 to 20% relative to the total mass of the photocrosslinkable composition X , preferably from 0.1 to 5%, preferentially from 0.2 to 2%, more preferentially from 0.4 to 1.5% relative to the total mass of the photocrosslinkable composition X.

According to one embodiment of the invention, the ratio of molar quantity of tertiary amine C relative to the molar quantity of radical photoinitiator B in the photocrosslinkable composition X is from 1.5 to 13.5, preferably from 2 to 6.5, preferentially from 3 to 5.

Composition without charge:

In one embodiment, the method of the invention is characterized in that the photocrosslinkable silicone composition X comprises:
- from 10 to 99% by mass of at least one organopolysiloxane A comprising at least one (meth)acrylate group;
- from 0.1 to 5% of at least one radical photoinitiator B as defined above;
- from 0.1 to 10% of at least one tertiary amine C as defined above.

For the purposes of the present invention, t _{100 µm} is understood to mean the time required for obtaining a crosslinked layer with a depth of 100 µm.

According to the method of the invention, the photocrosslinkable compositionXshape a cross-linked layer with a depth of 100µm, for a t_100µmbetween 0.1 and 20s, preferably between 0.1 and 15s, preferably between 0.1 and 10s.

Other additives:

In one embodiment, the method of the invention is characterized in that the photocrosslinkable composition X further comprises a photoinitiator chosen from the group consisting of type I radical photoinitiators or type II radical photoinitiators.

Thus, the photocrosslinkable composition X can further comprise a photoinitiator chosen from the group of type I radical photoinitiators such as:
Acyl phosphine oxides, bis-acyl phosphine oxides and their derivatives such as diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), ethyl (2,4,6-trimethylbenzoyl)phenylphosphinate (TPO-L), phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO), benzoin ether, benzoyl oxime, acetophenone & hydroxyacetophenone (HAP), phenylglyoxal, alpha-hydroxyketones, alpha-aminoketones and CPO-1 & CPO-2:
[Chem 25]

Examples of commercial products of such photoinitiators include:

bis(2,4,6-trimethylbenzoyl)phenyl phosphine oxide marketed as OMNIRAD™ 819 by IGM Resin B.V.; liquid mixtures of acylphosphine oxides with at least one other photoinitiator marketed as OMNIRAD™ 1000, OMNIRAD™ 2022, OMNIRAD™ 2100 or OMNIRAD™ 4265 by IGM Resin B.V.; 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl), 2-hydroxy-2-methylpropiophenone marketed as “OMNIRAD™ 1173” by IGM Resin B.V.; 2-benzyl-2-(N,N-dimethylamino)-1-(4-morpholinophenyl)-1-butanone marketed by IGM Resin B.V. under the name OMNIRAD™ 369 or as Irgacure® 369 by Ciba®); 2,2-dimethoxy-1,2-diphenylethan-1-one marketed by Ciba® under the name Irgacure® 651; 2- Methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one marketed by IGM Resin B.V. under the name OMNIRAD™ 907 or as Irgacure® 907 by Ciba®); 2-Hydroxy-2-methyl-1-phenyl-1-propanone marketed by Ciba® under the name Darocure® 1173; 1-hydroxycyclohexyl phenyl ketone type I (Irgacure 184).

Thus, the photocrosslinkable composition X can further comprise a photoinitiator chosen from the group of type II radical photoinitiators such as:
Benzophenones such as 1-hydroxycyclohexyl benzophenone marketed by IGM Resin BV under the name “OMNIRAD™ 184”; thioxanthones such as isopropylthioxanthone, thioxanthone neodecanoate or substituted thioxanthones as disclosed in patent application WO2018/234643; xanthenes such as 9-xanthenone; anthraquinones and hydroxyanthraquinones such as 4-dihydroxyanthraquinone, - 2-methylanthraquinone, 2,2'-bis(3-hydroxy-1,4-naphthoquinone), 2,6-dihydroxyanthraquinone, 1,5-dihydroxyanthraquinone, 2-ethylanthraquinone, 2-methylanthraquinone, 1,8-dihydroxyanthraquinone, -1,3-propanedione, 5,7-dihydroxyflavone.

The photocrosslinkable silicone composition X may also comprise other additives such as polymerization inhibitors, fillers, virucides, bactericides, anti-abrasion additives, adhesion promoters and pigments (organic or mineral). Among the polymerization inhibitors, mention may be made of phenols, hydroquinone, 4-OMe-phenol, 2,4,6-tritertiary-butyl phenol (BHT), phenothiazine, and nitroxyl radicals such as (2,2,6,6-tetramethylpiperidin-1-yl)oxy (TEMPO). Among the adhesion promoters, mention may be made in particular of MEMO (methacryloxypropyltrimethoxysilane) and its derivatives.

The photocrosslinkable silicone composition X may also comprise an organic compound O comprising at least one (meth)acrylate function.

By organic compound O comprising at least one (meth)acrylate function, we mean any compound comprising one or more (meth)acrylate functions.

According to one embodiment, the organic compound O comprising at least one (meth)acrylate function does not comprise a siloxane structure.
Suitable organic compounds O comprising a (meth)acrylate function include, in particular, epoxidized (meth)acrylate compounds, (meth)acryloglyceropolyesters, (meth)acrylo-uretanes, (meth)acrylopolyethers, (meth)acrylopolyesters, and (meth)acrylo-acrylics. More particularly preferred are trimethylolpropane triacrylate, tripropylene glycol diacrylate, hexanediol diacrylate and pentaerythritol tetraacrylate.

As an example of an organic compound O comprising a (meth)acrylate function, we can cite (chemical names in English): ethylhexyl acrylate, stearyl acrylate, tetrahydrofurfuryl acrylate, lauryl acrylate, isodecyl acrylate, 2(2-ethoxyethoxy)ethyl acrylate , cyclohexyl acrylate, isooctyl acrylate, tridecyl acrylate, isobornyl acrylate, caprolactone acrylate, alkoxylated phenol acrylates, 1,3-butylene glycol diacrylate, 1,4-butanediol diacrylate, diethylene glycol diacrylate, neopentyl glycol diacrylate, tetraethylene glycol diacrylate, triethylene glycol diacrylate , dipropylene glycol diacrylate, alkoxylated hexanediol diacrylates, trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, propoxylated glycerol triacrylate, pentarythritol triacrylate, pentaerythritol tetraacrylate, di-trimethylolpropane tetraacrylate, and di-pentaerythritol pentaacrylate.

The photocrosslinkable silicone composition X may comprise from 0 to 50% of organic compound O relative to the total mass of the photocrosslinkable silicone composition X.

According to one embodiment, the photocrosslinkable silicone composition X further comprises a filler D.

The photocrosslinkable silicone composition X may comprise from 0 to 50% by weight of filler D , preferably from 10 to 50% of filler D , preferentially from 10 to 40% of filler D , even more preferentially from 20 to 35% of filler D relative to the total weight of the photocrosslinkable silicone composition X.

According to one embodiment, the photocrosslinkable silicone composition X comprises between 20 and 30% by weight of filler D relative to the total weight of the photocrosslinkable silicone composition X.

This filler is preferably mineral. Filler D may be a very finely divided product with an average particle diameter of less than 0.1 µm.

The filler D may be siliceous in particular. With regard to siliceous materials, they may act as reinforcing or semi-reinforcing fillers. The reinforcing siliceous fillers are chosen from colloidal silicas, combustion and precipitation silica powders or their mixtures. These powders have an average particle size generally less than 0.1 µm (micrometers) and a BET specific surface area greater than 30 m ² /g, preferably between 30 and 350 m ² /g.
Semi-reinforcing siliceous fillers such as diatomaceous earth or crushed quartz can also be used.

These silicas can be incorporated as such or after being treated with organosilicon compounds usually used for this purpose. These compounds include methylpolysiloxanes such as hexamethyldisiloxane, octamethylcyclotetrasiloxane, methylpolysilazanes such as hexamethyldisilazane, hexamethylcyclotrisilazane, tetramethyldivinyldisilazane, chlorosilanes such as dimethyldichlorosilane, trimethylchlorosilane, methylvinyldichlorosilane, dimethylvinylchlorosilane, alkoxysilanes such as dimethyldimethoxysilane, dimethylvinylethoxysilane, trimethylmethoxysilane, and mixtures thereof. As regards non-siliceous mineral materials, they can act as semi-reinforcing or bulking mineral fillers.

Examples of these non-siliceous fillers that can be used alone or in a mixture are calcium carbonate, optionally surface-treated with an organic acid or an ester of an organic acid, calcined clay, rutile-type titanium oxide, iron, zinc, chromium, zirconium and magnesium oxides, the various forms of alumina (hydrated or not), boron nitride, lithopone, barium metaborate, barium sulfate and glass microbeads. These fillers are coarser, 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 surface-modified by treatment with the various organosilicon compounds usually used for this purpose.

Thus, according to one embodiment, the method of the invention is characterized in that the photocrosslinkable silicone composition X comprises:
- from 10 to 89.8% of at least one organopolysiloxane A comprising at least one (meth)acrylate group as defined above;
- from 0.1 to 5% of at least one radical photoinitiator B as defined above;
- from 0.1 to 10% of at least one tertiary amine C as defined above;
- from 10 to 50% load D.

The photocurable silicone composition X may also comprise a photoabsorber E. The photoabsorber E makes it possible to reduce the penetration of the irradiation into the layer of photocurable silicone composition X and thus to improve the resolution of the silicone elastomer article obtained. It makes it possible to control the depth of penetration of the irradiation (Dp) into the layer of silicone elastomer.

According to one embodiment of the invention, the photocrosslinkable silicone composition X comprises from 0 to 5% by weight of photoabsorber E relative to the total weight of the photocrosslinkable silicone composition X , and preferably the photoabsorber E is chosen from the group consisting of TiO ₂ , ZnO, hydroxylphenyl-s-triazines, hydroxylphenyl-benzotriazoles, cyanoacrylates, and mixtures thereof.

The photocrosslinkable silicone composition X may also include a photostabilizer F.

The photostabilizer F makes it possible to reduce or even stop the activity of the photoinitiators, by trapping the radicals still active after the implementation of the method of the present invention. This thus makes it possible to increase the transparency properties of the silicone elastomer article obtained according to the method of the invention.

The photocrosslinkable silicone composition X further comprises from 0 to 2% by weight of photostabilizer F relative to the total weight of the photocrosslinkable silicone composition X , and preferably from 0 to 0.5% by weight of photostabilizer F relative to the total weight of the photocrosslinkable silicone composition X.

Said photostabilizer F is chosen from the group consisting of hindered amines, cyclic amines of 4 to 6 carbon atoms such as for example the commercial compounds Tinuvin® 249, Tinuvin®292, Tinuvin®123 and their mixtures.

The invention also relates to a photocrosslinkable silicone composition X2 comprising:
- from 10 to 99% by mass of at least one organopolysiloxane A comprising at least one (meth)acrylate group;
- from 0.1 to 5% of at least one radical photoinitiator B as defined above;
- from 0.1 to 10% of at least one tertiary amine C as defined above.

The photocrosslinkable silicone composition X2 further comprises at least one additive.
In a preferred embodiment, the additive is a filler, a photoabsorber, or a photostabilizer, and mixtures thereof.

The photocurable silicone composition X2 can be used in a wide variety of technical fields such as printing inks, printing techniques, varnishes, wood coatings, plastic coatings, metal coatings, adhesives, and 3D printing.

It is therefore possible to use it with the coating tools used to prepare non-stick silicone coatings.

The invention also relates to a method for preparing a coating on a support, comprising the following steps:
- application of a photocrosslinkable silicone composition X2 on a support, and
-crosslinking of said composition by electronic or photonic irradiation, preferably by exposure to an electron beam, by exposure to gamma rays, or by exposure to radiation with a wavelength between 200 nm and 450 nm, in particular to UV radiation.

Advantageously, the photoinitiator B of the photocrosslinkable composition X2 is a compound chosen from the compounds of formula: (VII) to (XIIb) and/or their mixtures.

Likewise, the tertiary amine C of the photocrosslinkable composition X2 is a compound chosen from the compounds of formula: (XIII) to (XIX) and/or their mixtures.

A silicone elastomer article can thus be obtained from this photocrosslinkable composition X2 . In other words, this photocrosslinkable composition X2 can be used to obtain a silicone elastomer article

The photocrosslinkable silicone composition X2 according to the invention without solvent, that is to say undiluted, can be applied using devices capable of depositing, in a uniform manner, small quantities of liquids. For this purpose, for example, the device called "Helio sliding" can be used, comprising in particular two superimposed cylinders: the role of the cylinder placed lowest, immersed in the coating tank where the compositions are located, is to impregnate in a very thin layer the cylinder placed highest, the role of the latter is then to deposit on the paper the desired quantities of the compositions with which it is impregnated, such a dosage is obtained by adjusting the respective speed of the two cylinders which rotate in opposite directions to each other.

Crosslinking, which results in curing of the photocurable silicone composition X2 , can be carried out continuously by passing the substrate coated with the composition through irradiation equipment which is designed to provide the coated substrate with sufficient residence time to complete curing of the coating.

Preferably, the curing is carried out in the presence of the lowest possible concentration of oxygen, typically at an oxygen concentration of less than 100 ppm, and preferably less than 50 ppm. The curing is generally carried out in an inert atmosphere, for example nitrogen or argon.

The exposure time required to cure X2 silicone composition varies with factors such as:
- the particular formulation used, the type and wavelength of radiation,
- the dose rate, the energy flux,
- the concentration of radical photoinitiator, and
- the atmosphere and the thickness of the coating.

These parameters are well known to those skilled in the art who will know how to adapt them.

The quantities of photocrosslinkable silicone composition X2 deposited on the supports are variable and most often range between 0.1 and 5 g/m² of treated surface. These quantities depend on the nature of the supports and the non-stick properties sought. They are most often between 0.5 and 1.5 g/m² for non-porous supports.

This photocrosslinkable silicone composition X2 is particularly suitable for preparing a non-stick silicone coating on a support which is a flexible support made of textile, paper, polyvinyl chloride, polyester, polypropylene, polyamide, polyethylene, polyethylene terephthalate, polyurethane or non-woven glass fibers.

Flexible supports coated with a non-stick silicone coating can be, for example:
- a paper or a polymer film of the polyolefin type (polyvinyl chloride (PVC), PolyPropylene or Polyethylene) or of the polyester type (PolyEthyleneTerephthalate or PET),
- an adhesive tape whose inner face is coated with a layer of pressure-sensitive adhesive and whose outer face has the non-stick silicone coating;
- or a polymer film for protecting the adhesive face of a pressure-sensitive adhesive or self-adhesive element.

These coatings are particularly suitable for use in the field of non-stick coatings.

The invention also relates to a coated support obtainable from the composition described above. As indicated above, the support may be a flexible support made of textile, paper, polyvinyl chloride, polyester, polypropylene, polyamide, polyethylene, polyethylene terephthalate, polyurethane or non-woven glass fibers.

Coated substrates have a non-stick, water-repellent character, or allow improved surface properties such as slipperiness, stain resistance or softness.

Another subject of the invention relates to the use of a support at least partially coated with a non-stick coating according to the invention and as defined above in the field of self-adhesive labels, strips including envelopes, graphic arts, medical care and hygiene.

The invention also relates to the method of preparing a coating on a support, comprising the following steps:
- application of a photocrosslinkable silicone composition X2 on a support, and
- crosslinking of said composition by electronic or photonic irradiation, preferably by exposure to an electron beam, by exposure to gamma rays, or by exposure to radiation with a wavelength between 200 nm and 450 nm, in particular to UV radiation.

Organopolysiloxanes A used in the examples:
[Chem 26]
(CAS 193486-79-2)
This silicone acrylate polymer having a specific molecular weight M_wof 7942 g/mol (a = 7.5, b = 80), will be notedpolymer a ₁ in the following examples.

[Chem 27]
(CAS = 125455-52-9)
This silicone acrylate polymer having a specific molecular mass M _w of 19,046 g/mol will be denoted polymer a ₂ in the following examples.

[Chem 28]
(CAS = 155419-56-0)
This silicone acrylate polymer having a specific molecular mass M _w of 7654g/mol, will be noted polymer a ₃ in the following examples.

Photoinitiator systems B used in the examples:
[Chem 29]
System 1 (S1)
This photoinitiator system of the present invention denoted S1 is the association of 2-neodecanoic acid 9-oxo-9H-thioxanthen-2yl-ester (neo-THX) with a molar mass of 382g/mol (where q+n+p = 8) with N,N,N',N'-tetramethylenediamine (TMEDA) with a molar mass of 116 g/mol (CAS = 110-18-9).

[Chem 30]
System 2 ( S2)
This photoinitiator system of the present invention denoted S2 is the association of 2-neodecanoic acid 9-oxo-9H-thioxanthen-2yl-ester (neo-THX) with a molar mass of 382g/mol (where q+n+p = 8) with N,N-Diethyl-3-aminopropyltrimethoxysilane (DEAPTMS) with a molar mass of 235 g/mol (CAS= 41051-80-3).

[Chem 31]
System 3 (S3)
This photoinitiator system of the present invention denoted S3 is the association of 2-neodecanoic acid 9-oxo-9H-thioxanthen-2yl-ester (neo-THX) with a molar mass of 382g/mol (where q+n+p = 8) with Triisopentylamine (TIPA) with a molar mass of 227g/mol (CAS = 645-41-0).
[Chem 32]
System 4 (S4)
This photoinitiator system of the present invention denoted S4 is the association of 2-neodecanoic acid 9-oxo-9H-thioxanthen-2yl-ester (neo-THX) with a molar mass of 382g/mol (where q+n+p = 8) with trihexylamine (THXA) with a molar mass of 270g/mol (CAS = 102-86-3).

[Chem 33]
System 5 (S5)
This photoinitiator system of the present invention denoted S5 is the association of 2-neodecanoic acid 9-oxo-9H-thioxanthen-2yl-ester (neo-THX) with a molar mass of 382g/mol (where q+n+p = 8) with dimethyl-decylamine (DMDA) with a molar mass of 185g/mol (CAS= 1120-24-7).

Photoinitiator C comparisons:

[Chem 34]
Comparative system 1 (S _comp 1) .
This photoinitiator is Ethyl(2,4,6-trimethylbenzoyl)-phenylphosphinate known under the name TPO-L (CAS 84434-11-7) and will be noted S _comp 1 in the following examples. This comparative photoinitiator has a molar mass of 316g/mol.

[Chem 35]
Comparative system 2 (S _comp 2)
This photoinitiator is 2-neodecanoic acid 9-oxo-9H-thioxanthen-2-yl-ester (where q+n+p = 8) and will be denoted S _comp 2 in the following examples. This comparative photoinitiator has a molar mass of 382g/mol.
[Chem 36]

Comparative system 3 (S _comp 3)

This comparative photoinitiator system, denoted S _comp 3, is the association of 2-neodecanoic acid 9-oxo-9H-thioxanthen-2yl-ester with a molar mass of 382g/mol (where q+n+p = 8) with polymethylhydrogensiloxane having a viscosity between 2-5 mPa.s and a molar mass of 402g/mol (n ≈ 4).

Photocrosslinkable compositions:

In the context of the examples of the present invention, when it is desired to have a photocrosslinkable silicone composition which is stable for a long period of up to several months, it is then possible to add to said composition 10 to 1000 ppm of stabilizer such as 4-methoxyphenol.

In the following examples, the composition1a ₁ will designate the systemS1implemented with thepolymer a ₁ as organopolysiloxane A.

Composition 1a ₂ will designate the system S1 implemented with the polymer a ₂ as organopolysiloxane A.

The compositionC ₁ has ₂ will designate the systemS _comp 1implemented with thepolymer has ₂ as organopolysiloxane A. In the specific case where for example the systemS2is in the presence of a mixture of polymershas ₁ Andhas ₃ , the photocrosslinkable composition will then be noted composition2a ₁ +a ₃ .

By analogy, compositions 1, 2 and 3 and C ₁ , C ₂ and C ₃ will be noted as set out above.

Additives used in the examples:

Charge D: Pyrogenic silica treated with SiMe ₃ groups on the surface with a BET specific surface area of approximately 200m ² /g.

Physical and/or mechanical properties:

Viscosity: In this application, viscosity is measured with a Brookfield CAP 2000+ viscometer. These ICI type viscometers with cone-plate geometry and imposed speed allow rapid measurement, at controlled temperature, on small sample volumes. This is a characterization at high shear rate.

The viscosity of the sample is measured at 25°C according to ASTM D4287.

Elongation at break and breaking strength: These two physical quantities of the crosslinked sample are measured at 25°C according to the ASTM D412 standard.

Modulus of elasticity at 100% elongation: This physical quantity of the sample is measured at 25°C according to the ASTM D412 standard.

For the purposes of this application, initiation time, denoted t _amorc , is understood to mean the time required for crosslinking to be initiated.
The maximum polymerization speed (Rp _max in %.s ^-1 ) represents the reactivity of the photocrosslinkable composition, more precisely the maximum percentage of meth(acrylate) functions converted in one second.
The final conversion Conv _max (in %) represents the maximum conversion rate of the meth(acrylate) functions of the organopolysiloxanes A.

Materials and devices:

ASIGA UV-Max 385 Printer is a 3D (DLP) printer: Before adding to the 1L tank of the device (with an XYZ printing volume: 119x67x75 mm ³ ), the photocurable compositions are mixed manually or using a Speedmixer mixer. A test piece with a thickness of 2mm +/- 0.1 consisting of 27 layers (i.e. 75 µm per layer) is then designed by a computer program. Unless otherwise indicated, in the present application the first layer is irradiated for 40s and the following ones were irradiated for a period of 20s for each layer at 385nm and at an energy defined in the examples.

The Anycubic Photon Mono 6K printer is a 3D (LCD) printer: In this case, the light coming from a set of 405nm LEDs is projected through an LCD screen that acts as a mask revealing only the pixels necessary for printing the model. Before adding to the 1L tank of the device (with a XYZ printing volume of 192x120x245 mm ³ ), the photocurable compositions are mixed manually or using a mixer.

Example 1: Study and characterization of photocrosslinkable compositions according to the present invention:

Example 1a: Summary table of photocrosslinkable compositions used:

In this example, organopolysiloxaneHASused in the various photocrosslinkable compositions is the polymerhas ₁ . The molar ratio of the system S mentioned in Table 1 below is the molar ratio of the amount of material of the radical photoinitiatorBrelative to the amount of tertiary amine material involvedC. Photocrosslinkable composition Mass percentage of photoinitiator relative to the total mass of the composition (%) Molar ratio of the S system Comparative composition C ₁ to ₁ S _comp 1 : 0.6% - Comparative composition C ₂ to ₁ S _comp 2 : 0.5% - Comparative composition C ₃ to ₁ S _comp 3 : 0.5% neo-THX and 1% polymethylhydrosiloxane: - Composition 1a ₁ S1: 0.5% neo-THX and 0.5% TMEDA 0.3 Composition 2a ₁ S2: 0.5% neo-THX and 1% DEAPTMS 0.3

Example 1b: Measurements of physical properties at a wavelength of 385nm (at an energy of 11.5mW/cm ² ) of a photocrosslinkable composition according to the process of the invention:

This example aims to compare the initiation time noted t _amorc , the maximum polymerization speed (Rp _max in %.s ^-1 ) and the final conversion Conv _max (in %) of a photocrosslinkable composition according to the present invention ( 1a ₁ , 2a ₁ and 3a ₁ ) and of a comparative photocrosslinkable composition ( C ₁ a ₁ , C ₂ a ₁ ) as described in table 1.

The tests were performed with a Vertex 70 infrared spectrometer (Bruker Optics) under laminar conditions. Thus, the formulations were placed between two propylene films with a space of 100 µm and sandwiched with two BaF ₂ pellets. The light source is conducted above the sample by an optical fiber during the 100 s of exposure during which a laser beam passing through the sample records the infrared spectra continuously. Each measurement listed in the table below is performed in triplicate to ensure the repeatability of the results.

Table 2 below shows the values of the initiation time t _amorc , the maximum polymerization speed (Rp _max in %. s ^-1 ) and the final conversion Conv _max (in %) at a wavelength of 385nm.

Photocrosslinkable composition t _primer (s) Rp _max (%.s-1) Conv _max (%) Comparative composition C ₁ to ₁ 5.1 4.5 93 Comparative composition C ₂ to ₁ 11.2 4.8 74 Comparative composition C ₃ to ₁ 5.1 7.1 88 Composition 1a ₁ 1.1 30.1 87 Composition 2a ₁ 1.6 16.4 84

It is noted that at a wavelength of 385nm the initiation time for the comparative compositions is very long (5s to 12s) in comparison with the values obtained with the compositions implementing the method of the present invention.

The photocrosslinkable compositions of the present invention also make it possible to obtain very satisfactory maximum polymerization speeds (Rp _max ) at a wavelength of 385nm as shown by the data in the table above.

Example 1c: Measurements of physical properties at a wavelength of 405nm (at an energy of 11.5mW/cm ² ) of a photocrosslinkable composition according to the process of the invention:

For the purposes of this example, the organopolysiloxane A used in the various photocrosslinkable compositions is polymer a ₁ .

This example aims to compare the initiation time noted t _amorc , the maximum polymerization speed (Rp _max in %.s ^-1 ) and the final conversion Conv _max (in %), of a photocrosslinkable composition according to the present invention ( 1a ₁ , 2a ₁ ) and of a comparative photocrosslinkable composition ( C ₁ a ₁ , C ₂ a ₁ ) as described in table 1.

The tests were performed under laminar conditions. Thus, the formulations were placed between two propylene films with a gap of 100µm and sandwiched with two BaF ₂ pellets. Light was conducted above the sample by an optical fiber during the 100s of exposure. Each measurement listed in the table below was performed in triplicate to ensure the repeatability of the results obtained.

Table 3 below shows the values for initiation time, maximum polymerization speed (Rp_maxin %.s^-1) and the final conversion Conv_max(in %) at 405nm. Photocrosslinkable compositions t _primer (s) Rp _max (%.s ^-1 ) Conv _max (%) Comparative composition C ₁ to ₁ 9.7 2.4 85 Comparative composition C ₂ to ₁ 25.5 2.1 60 Comparative composition C ₃ to ₁ - - - Composition 1a ₁ 2.3 28.2 86 Composition 2a ₁ 1.7 17.4 77

Note that the reactivity at 405nm of the comparative formulation C ₃ a ₁ was too low to be measured.

However, it is noted that at a wavelength of 405 nm the initiation time for the comparative photocrosslinkable compositions is very long (9.7 s to 25.5 s) unlike the values obtained with the photocrosslinkable compositions implementing the process of the present invention.

The photocrosslinkable compositions of the present invention also make it possible to obtain very satisfactory maximum polymerization speeds at 405nm as shown by the data in the table above.

Example 2: Evaluation of the physical and mechanical properties of the test piece obtained according to the method of the invention (without addition of charge) at a wavelength of 385nm:

OrganopolysiloxaneHASused in the various photocrosslinkable compositions is a mixture of the polymerhas ₂ and polymerhas ₃ . In the continuation of Example 2, the organopolysiloxaneHASis made of 87% polymerhas ₂ and 13% polymerhas ₃ relative to the total mass of the organopolysiloxaneHAS.

For the purposes of this example, critical energy Ec (mJ/ ^cm2 ) is the amount of energy required for the photocurable composition to reach the solid state at a depth of 0 microns. Light penetration depth, denoted Dp, is the depth beyond which light no longer penetrates the composition.

These quantities were measured by varying the exposure time from 10 to 40 seconds while having the same power of the UV source for this fixed irradiation time. Once a film is formed, it is measured using a micrometer which allows us to determine the depth of the layer formed as a function of the UV dose for each composition.

Example 2a: Summary table of photocrosslinkable compositions used:

Photocrosslinkable composition Mass percentage of photoinitiator relative to the total mass of the composition (%) Molar ratio of the radical photoinitiator system/amine ( B/C ) Comparative composition C ₁ a ₂ +a ₃ S _comp 1 : 0.6% - Comparative composition C ₂ a ₂ +a ₃ S _comp 2 : 0.5% - Comparative composition C ₃ a ₂ +a ₃ S _comp 3 : 0.5% neo-THX and 1% polymethylhydrosiloxane - Composition 1a ₂ +a ₃ S1 : 0.5% neo-THX and 0.5% TMEDA 0.3 Composition 2a ₂ +a ₃ S2 : 0.5% neo-THX and 1% DEAPTMS 0.3 Composition 3a ₂ +a ₃ S3 : 0.5% neo-THX and 1% TIPA 0.3 Composition 4a ₂ +a ₃ S4 : 0.5% neo-THX and 1% THXA 0.3 Composition 5a ₂ +a ₃ S5 : 0.5% neo-THX and 1% DMDA 0.3

Example 2b: Measurements of the physical properties of photocrosslinkable compositions at wavelengths of 385nm (11.5mW/cm ² ) and 405nm (2.8 mW/cm ² ) :

LED 385nm (11.5mW/ ^cm2 ) 405nm LED (2.8 mW/ ^cm2 ) Photocrosslinkable compositions Ec (mJ/cm²) Dp (µm) t _100µm (s) Ec (mJ/cm²) Dp (µm) t _100µm (s) Comparative composition C ₁ a ₂ +a ₃ 54.9 1098 5.1 98.0 1947 36.9 Comparative composition C ₂ a ₂ +a ₃ 374 73 128 - - - Composition 1a ₂ +a ₃ 33.2 248 4.2 92.2 655 38.7 Composition 2a ₂ +a ₃ 55.3 257 7.1 128.9 600 54.4 Composition 3a ₂ +a ₃ 66.3 426 7.2 126.5 766 51.5 Composition 4a ₂ +a ₃ 74.3 374 8.5 131.8 357 62.3 Composition 5a ₂ +a ₃ 56.2 381 6.4 90.5 725 37.2

For a wavelength of 385nm, the table above shows a difference in effective depth of penetration of rays (Dp) between the comparative photocrosslinkable compositions and those of the invention.

Indeed, the comparative composition C ₁ a ₂ +a ₃ has an effective depth of penetration of rays (Dp) greater than 1000 µm which results in a poor resolution of the printed article.

On the contrary, a too low effective depth of penetration of the rays (Dp) as illustrated by the comparative composition C ₂ a ₂ + a ₃ reflects a low reactivity and the printed object will not have satisfactory physical and/or mechanical properties.

Concerning the compositions described according to the method of the present invention, the values of effective depths of penetration of the rays (Dp) are satisfactory.

The low reactivity of the comparative composition C ₂ a ₂ +a ₃ is also underlined by the high value of the time required (t _{100 µm} ) to obtain a crosslinked layer with a depth of 100 µm.

It should also be noted that at a wavelength of 405nm the comparative photocrosslinkable composition C ₂ a ₂ + a ₃ has low reactivity which does not allow crosslinking under good conditions.

The comparative composition C ₃ a ₂ +a ₃ was tested under the same conditions as the comparative composition C ₂ a ₂ +a ₃ and led to similar results. Indeed, this composition was also little or not reactive at low energy.

Example 2c: Measurements of the mechanical properties of photocrosslinkable compositions at wavelengths of 385nm (11.5mW/cm ² ) :

The mechanical properties of the test pieces produced according to the process of the invention from the photocrosslinkable compositions of example 2a could be tested.

These properties were tested after photocrosslinking at an energy value of 11.5mW/ ^cm2 .

The 3D printer used is the ASIGA UV-Max at a wavelength of 385nm; the first layer is irradiated for 40s and each of the following layers is irradiated for 20s to obtain a test specimen and to be able to carry out the evaluation of the mechanical properties.

Table 6 below mentions the mechanical properties like elongation at break, breaking strength and modulus of elasticity at 100%.

The mechanical property values indicated are an average of results obtained for measurements carried out on 4 separate specimens printed simultaneously.

The test pieces printed according to the present invention have a thickness of 2 mm.

UV-LED (Asiga Max 3D printer) at 385nm 385nm (11.5mW/ ^cm2 ) Elongation at break (%) Composition C ₁ a ₂ +a ₃ Comparative 156 Composition 1a ₂ +a ₃ Invention 196 Composition 3a ₂ +a ₃ Invention 163 Breaking strength MPa Composition C ₁ a ₂ +a ₃ Comparative 0.33 Composition 1a ₂ +a ₃ Invention 0.22 Composition 3a ₂ +a ₃ Invention 0.4 Modulus of elasticity at 100% (%) Composition C ₁ a ₂ +a ₃ Comparative 0.2 Composition 1a ₂ +a ₃ Invention 0.11 Composition 3a ₂ +a ₃ Invention 0.3

Table 6 above shows that the photocrosslinkable compositions 1a ₂ +a ₃ and 3a ₂ +a ₃ , according to the invention, lead to the production of test pieces having satisfactory mechanical properties, just like the test piece resulting from the comparative composition C ₁ a ₂ +a ₃ .

Example 3: Study of the physical and mechanical properties of a 3D printed test specimen formulation with load:

In this example, the organopolysiloxane used in the various photocrosslinkable compositions is a mixture of the polymerhas ₂ and polymerhas ₃ .

This example aims to measure the mechanical properties of a test piece according to the method of the invention containing 22 to 30% of D1 filler.

The formulations prepared under the conditions of Table A0 below were introduced into the Asiga 3D printer equipped with a UV-LED with a wavelength of 385nm.

The 3D printed specimens in this example according to the formulas set out below were produced at an energy of 11.5 mW/ ^cm2 .

The 3D specimen was printed with 27 layers of 75µm thickness each.

Constituents of the formulations Masses and mass percentages of the constituents of the formulations of the present invention Comparative formulation C ₁ a ₂ +a ₃ with 22% D1 Formulation 1a ₂ +a ₃ with 22% D1 Formulation 3a ₂ +a ₃ with 22% D1 Formulation 3a ₂ +a ₃ with 30% D1 % by mass % by mass % by mass % by mass S _comp 1 0.6 - - - S1 - 1 - - S3 - - 1.5 1.5 Polymer a ₂ 67.4 67 66.5 58.5 Polymer a ₃ 10 10 10 10 Load D1 22 22 22 30 Total 100 100 100 100

After manual mixing of these formulations for 5 minutes or using a mixer, the viscosities of these formulations were measured after a rest time of at least one hour by a Brookfield Cap 2000+ viscometer with cone-plate geometry (cone 6) as mentioned in Table 8 below.

Shear rate s ^-1 17 33 66 100 133 Viscosity of compositions comprising 22% silica (mPa.s) Comparative formulation C ₁ a ₂ +a ₃ 19,932 13,233 10,461 9,020 8,250 Formulation 1a ₂ +a ₃ 13,860 9,999 7,937 6,952 6,476 Formulation 3a ₂ +a ₃ 5,214 4,224 3,828 3,520 3,440 Viscosity of formulation including 30% silica (mPa.s) Formulation 3a ₂ +a ₃ 18,348 n.d n.d n.d n.d

n.d = not determined

Table of mechanical properties associated with these formulations:

The table below mentions the mechanical and physical properties such as elongation at break, breaking strength, modulus of elasticity at 100%, from a specimen comprising 22 to 30% of D1 load at an energy of 11.5mW/cm ² .

Each measurement listed in the table below is carried out five times to ensure the repeatability of the results obtained.

UV-LED (Asiga Max 3D printer) at 385nm (t _exp = 40-20s, I = 11.5mW/cm ² ) Formulations with 22% pyrogenic silica treated at ^200m2 /g Formulations with 30% pyrogenic silica treated at ^200m2 /g Comparative formulation C ₁ a ₂ +a ₃ Formulation 1a ₂ +a ₃ Formulation 3a ₂ +a ₃ Formulation 3a ₂ +a ₃ Elongation at break (%) N / A 105 146 176 Breaking strength MPa N / A 1.7 1.3 2.6 Modulus of elasticity at 100% (%) N / A 1.6 0.8 1.2

The acronym “N. A” mentioned in the table above means that this is not applicable for the comparative test piece.C ₁ has ₂ +a ₃ . Indeed, the high viscosity of the comparative formulationC ₁ has ₂ +a ₃ does not allow additive manufacturing of test specimens.

On the contrary, the formulations defined according to the process of the invention allow the production of 3D printed test pieces with satisfactory mechanical properties as demonstrated by the data in table 9 above.

Furthermore, it is observed that the presence of filler makes it possible to considerably improve the mechanical and physical properties of the test pieces obtained according to the process of the invention (Formulations 1a ₂ +a ₃ and 3a ₂ +a ₃ ) .

In particular, it is observed that at 30% of load D1 the test piece (Formulation 3a ₂ +a ₃ ) obtained according to the method of the invention has properties of resistance to rupture doubled compared to that having 22% of load D1 . This mechanical property is satisfactory to allow to envisage new fields of application and thus to print functional articles according to the method of the invention.

Claims (20)

Additive manufacturing method for producing a silicone elastomer article, said method comprising the following steps:
i) implementing a photocrosslinkable silicone composition X and an irradiation source, said photocrosslinkable silicone composition X comprising:
a) at least one organopolysiloxane A comprising at least one (meth)acrylate group
b) at least one radical photoinitiator B of the following formula (I):
[Chem 37]

in which,
R ₁ and R ₃ , identical or different, are chosen from the group consisting of: a hydrogen atom, a hydroxyl and a group of formula -OZ with the symbol O being an oxygen atom and the symbol Z being chosen from the group consisting of:
- a _C1 - _C20 alkyl group, preferably _C3 - _C20 or _C2 - _C20 alkenyl group,
-a group –(C=O)-R ₈ , with the radical R ₈ being chosen from the groups C ₁ -C ₂₀ alkyl, C ₂ -C ₂₀ alkenyl, C ₃ -C ₂₀ cycloalkyl and C ₆ -C ₁₂ aryl, and
- a group -Si(R ₉ ) ₃ , where the R ₉ group, which may be identical or different, is chosen from C ₁ -C ₂₀ alkyl, C ₂ -C ₂₀ alkenyl, C ₃ -C ₂₀ cycloalkyl, C ₆ -C ₁₂ aryl, C ₁ -C ₂₀ alkoxyl groups and the hydrogen atom;
R ₂ is selected from the group consisting of: a hydrogen atom, a C ₁ -C ₆ alkyl group, a –(C=O)-R ₁₀ group with the radical R ₁₀ being selected from the C ₁ -C ₂₀ alkyl, C ₂ -C ₂₀ alkenyl, C ₃ -C ₂₀ cycloalkyl, C ₆ -C ₁₂ aryl, OR ₁₁ and –(N-(R ₁₁ ) ₂ radical with the radical R ₁₁ being selected from the C ₁ -C ₁₂ alkyl groups;
R ₄ , R ₅ , R ₆ and R ₇ , identical or different, are chosen from the group consisting of: a hydrogen atom and a C ₁ -C ₆ alkyl group;
and with one of the following conditions:
- at least one of the substituents R ₁ or R ₃ is a group of formula -OZ, or either
- the substituent R ₂ is a group of formula –(C=O)-R ₁₀ .
(c) at least one tertiary amine C ;
(ii) selectively irradiating at least a portion of the photocurable silicone composition X using the irradiation source to form a portion of the silicone elastomer article; and
iii) Repeat step ii) a sufficient number of times to produce the silicone elastomer article. Method according to claim 1, wherein the radical photoinitiator B is a compound of formula (IX)
[Chem 38]

in which,
R ₁ and R ₂ , identical or different, are chosen from the group consisting of: a hydrogen atom, a hydroxyl and a group of formula -OZ with the symbol O being an oxygen atom and the symbol Z being chosen from the group consisting of:
a _C1 - _C20 alkyl group, preferably _C3 - _C20 or _C2 - _C20 alkenyl group,
a –(C=O)-R ₃ group, with the radical R ₃ being selected from C ₁ -C ₂₀ alkyl, C ₂ -C ₂₀ alkenyl, C ₃ -C ₂₀ cycloalkyl and C ₆ -C ₁₂ aryl groups, or
a group -Si(R ₄ ) ₃ , where the identical or different R ₄ groups are chosen from C ₁ -C ₂₀ alkyl, C ₂ -C ₂₀ alkenyl, C ₃ -C ₂₀ cycloalkyl, C ₆ -C ₁₂ aryl, C ₁ -C ₂₀ alkoxyl groups and the hydrogen atom,
and with the condition that at least one of the substituents R ₁ or R ₂ is a group of formula -OZ. A method according to any preceding claim, wherein the tertiary amine C is an acyclic tertiary amine. Method according to any one of the preceding claims, characterized in that the tertiary amine C is an acyclic tertiary amine of the following formula (XIV):
[Chem 39]

in which,
R ₁ , R ₂ and R ₃ , identical or different, are chosen from:
a _C1 - _C20 alkyl group, preferably _C2 - _C12 , preferentially _C5 - _C12 , or _C2 - _C20 alkenyl substituted or not by at least one group chosen from:
- an aryl group of 6 to 18 carbon atoms
- a heteroatom O, N or S,
- a halogen,
- a hydroxyl group
- a group (O-Alk) with Alk representing an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms,
- an amino-alkyl group of the form N(R ₄ ) ₂ where R ₄ represents a C ₁ -C ₂₀ alkyl group, preferably C ₃ -C ₂₀ ,
- a SiMe ₃ group,
- a Si(O-Alk) ₃ group with Alk representing an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms, preferentially from 1 to 6 carbon atoms,
and with the condition that at least:
- a group R ₁ , R ₂ or R ₃ represents a C ₅ -C ₁₂ alkyl group
- a group R ₁ , R ₂ or R ₃ represents a C ₁ -C ₂₀ alkyl group substituted by an amino-alkyl group of the form N(R ₄ ) ₂ where R ₄ represents a C ₁ -C ₂₀ alkyl group, preferably C ₃ -C ₂₀ , or
- a group R ₁ , R ₂ or R ₃ represents a C ₁ -C ₂₀ alkyl group substituted by a group Si(O-Alk) ₃ with Alk representing an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms, preferentially from 1 to 6 carbon atoms. Method according to any one of the preceding claims, characterized in that the tertiary amine C is an acyclic tertiary amine of the following formula (XV):
[Chem 40]

in which,
R ₁ , R ₂ and R ₃ , identical or different, are chosen from:
a _C1 - _C20 alkyl group, preferably _C2 - _C12 , preferentially _C5 - _C12 , or _C2 - _C20 alkenyl substituted or not by at least one group chosen from:
- an amino-alkyl group of the form N(R ₄ ) ₂ where R ₄ represents a C ₁ -C ₂₀ alkyl group, preferably C ₃ -C ₂₀ ,
- a SiMe ₃ group,
- a Si(O-Alk) ₃ group with Alk representing an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms, preferentially from 1 to 6 carbon atoms. Method according to any one of the preceding claims, characterized in that the tertiary amine C is an acyclic tertiary amine of the following formula (XVIa):
[Chem 41]

in which,
R ₅ , R ₆ and R ₇ , identical or different, are chosen from:
a _C1 - _C20 alkyl group, preferably _C2 - _C12 , preferentially _C5 - _C12 , or _C2 - _C20 alkenyl substituted or not by at least one group chosen from:
- an aryl group of 6 to 18 carbon atoms
- a heteroatom O, N or S,
- a halogen,
- a hydroxyl group
- a group (O-Alk) with Alk representing an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms,
- an amino-alkyl group of the form N(R ₈ ) ₂ where R ₈ represents a C ₁ -C ₂₀ alkyl group, preferably C ₃ -C ₂₀ ,
- a SiMe ₃ group,
- a Si(O-Alk) ₃ group with Alk representing an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms, preferentially from 1 to 6 carbon atoms,
and with the condition that at least:
- a group R ₅ , R ₆ or R ₇ represents a C ₅ -C ₁₂ alkyl group. Method according to one of claims 1 to 4, in which the tertiary amine C is an acyclic tertiary amine of the following formula (XVIIa):
[Chem 42]

in which,
R ₉ , R ₁₀ and R ₁₁ , identical or different, are chosen from:
a _C1 - _C20 alkyl group, preferably _C2 - _C12 , preferentially _C5 - _C12 , or _C2 - _C20 alkenyl substituted or not by at least one group chosen from:
- an aryl group of 6 to 18 carbon atoms
- a heteroatom O, N or S,
- a halogen,
- a hydroxyl group
- a group (O-Alk) with Alk representing an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms,
- an amino-alkyl group of the form N(R ₁₂ ) ₂ where R ₁₂ represents a C ₁ -C ₂₀ alkyl group, preferably C ₃ -C ₂₀ ,
- a SiMe ₃ group,
- a Si(O-Alk) ₃ group with Alk representing an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms, preferentially from 1 to 6 carbon atoms,
and with the condition that at least:
- a group R ₉ , R ₁₀ or R ₁₁ represents a C ₁ -C ₂₀ alkyl group substituted by a group Si(O-Alk) ₃ with Alk representing an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms, preferentially from 1 to 6 carbon atoms. Method according to one of claims 1 to 4, in which the tertiary amine C is an acyclic tertiary amine of the following formula (XVIIIa):
[Chem 43]

in which,
R ₁₃ , R ₁₄ and R ₁₅ , identical or different, are chosen from:
a _C1 - _C20 alkyl group, preferably _C2 - _C12 , preferentially _C5 - _C12 , or _C2 - _C20 alkenyl substituted or not by at least one group chosen from:
- an aryl group of 6 to 18 carbon atoms,
- a heteroatom O, N or S,
- a halogen,
- a hydroxyl group,
- a group (O-Alk) with Alk representing an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms,
- an amino-alkyl group of the form N(R ₁₆ ) ₂ where R ₁₆ represents a C ₁ -C ₂₀ alkyl group, preferably C ₃ -C ₂₀ ,
- a SiMe ₃ group,
- a Si(O-Alk) ₃ group with Alk representing an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms, preferentially from 1 to 6 carbon atoms,
and with the condition that at least:
- a group R ₁₃ , R ₁₄ or R ₁₅ represents a C ₁ -C ₂₀ alkyl group substituted by an amino-alkyl group of the form N(R ₁₆ ) ₂ where R ₁₆ represents a C ₁ -C ₂₀ alkyl group, preferably C ₃ -C ₂₀ . Method according to any one of the preceding claims, in which the tertiary amine C has an oxidation-reduction potential of 0.4 to 1.1 V/ECS, preferably of 0.7 to 1.1 V/ECS, even more preferably of 0.8 to 1 V/ECS. Method according to any one of the preceding claims, characterized in that the mass percentage of the tertiary amine C is from 0.1 to 20% relative to the total mass of the photocrosslinkable composition X , preferably from 0.1 to 5%, preferentially from 0.2 to 2%, more preferentially from 0.4 to 1.5% relative to the total mass of the photocrosslinkable composition X. Method according to any one of the preceding claims, characterized in that the ratio of molar quantity of tertiary amine C relative to the molar quantity of radical photoinitiator B in the photocrosslinkable composition X is from 1.5 to 13.5, preferably from 2 to 6.5, preferentially from 3 to 5. Method according to any one of the preceding claims, characterized in that the photocrosslinkable composition X further comprises a filler D. Method according to any one of the preceding claims, characterized in that the photocrosslinkable composition X further comprises a photoabsorber E , or a photostabilizer F , and their mixtures. Method according to any one of the preceding claims, characterized in that the additive manufacturing is a technology selected from the group consisting of laser stereolithography (SLA), digital light processing (DLP), liquid crystal display (LCD), continuous liquid interface production (CLIP), ink-jet or extrusion printing. Silicone elastomer article obtained according to any one of the preceding claims. Photocrosslinkable silicone composition X2 comprising:
- from 10 to 99% by mass of at least one organopolysiloxane A comprising at least one (meth)acrylate group;
- from 0.1 to 5% of at least one radical photoinitiator B as defined according to claim 1 or 2;
- from 0.1 to 10% of at least one tertiary amine C as defined according to claim 3 to 8. Silicone elastomer obtained by crosslinking a photocrosslinkable composition X2 according to claim 16. Use of a photocrosslinkable silicone composition X2 according to claim 16 for the manufacture of a silicone elastomer article. Use of a photocrosslinkable silicone composition X2 according to claim 16 for the preparation of silicone films with non-stick properties. Process for preparing a coating on a support, comprising the following steps:
- application of a photocrosslinkable silicone composition X2 on a support, and
- crosslinking of said composition by electronic or photonic irradiation, preferably by exposure to an electron beam, by exposure to gamma rays, or by exposure to radiation with a wavelength between 200 nm and 450 nm, in particular to UV radiation.