EP3642192A1

EP3642192A1 - Free-radical photoinitiators and uses of same in silicone compositions

Info

Publication number: EP3642192A1
Application number: EP18750239.8A
Authority: EP
Inventors: Christian Maliverney; Perrine Theil; Jean-Marc Frances; Xavier Allonas; Ahmad IBRAHIM
Original assignee: Universite de Haute Alsace; Elkem Silicones France SAS
Current assignee: Universite de Haute Alsace; Elkem Silicones France SAS
Priority date: 2017-06-22
Filing date: 2018-06-21
Publication date: 2020-04-29
Also published as: CN111295379A; KR102458743B1; JP2020524735A; JP6944549B2; CA3067711A1; US20230159706A1; BR112019027471A8; WO2018234643A1; US11629233B2; US20210332191A1; KR20200035004A; CN111295379B; BR112019027471A2

Abstract

The present invention concerns type II photoinitiators for the free-radical crosslinking of silicone compositions, in particular acrylic silicone compositions. The present invention concerns a silicone composition C1 that can be crosslinked by exposure to radiation with a wavelength of between 300 and 450 nm, comprising: - at least one organopolysiloxane A comprising at least one methacrylate group bonded to a silicon atom, - at least one organohydrogenopolysiloxane H comprising at least two, and preferably at least three hydrogen atoms each bonded to different silicon atoms, and - at least one free-radical photoinitiator P. The present invention also concerns the provision of a silicone composition that can be polymerised or crosslinked by free-radical process comprising a type II photoinitiator system suitable for crosslinking silicone compositions, in particular by exposure to radiation, and absorbing light radiation with a wavelength greater than 300 nm.

Description

RADICAL PHOTOUSERS AND THEIR USES IN

The present invention relates to type II photoinitiators for the radical crosslinking of silicone compositions, especially acrylic silicone compositions.

The use of plastic films as support materials for coating silicone coatings in order to create release coatings requires a suitable technology. Indeed, most of these plastic films are heat-sensitive. Thus, a dimensional deformation of the film occurs during the coating and drying in thermal furnaces of the silicone layer under the combined effect of the tensile forces and the temperature imposed on the films. The crosslinking technology of functional silicone oils under ultraviolet (UV) radiation makes it possible to overcome the use of high temperatures and thus to crosslink anti-adhesive layers without impacting the supports. In addition, this technology has the advantage of achieving high productivity without being energy-consuming and without using solvents. Plastic substrates are materials of choice for many applications and their use is constantly growing. Also, an effort of research and innovations is essential in the field of the crosslinking under UV of thin films of silicone.

The silicone compositions are generally crosslinked under UV or visible radiation emitted by doped or non-doped mercury vapor lamps whose emission spectrum extends from 200 nm to the visible (> 400 nm). Light sources such as light-emitting diodes, better known by the acronym "LED" ("Light-Emitting Diodes") which deliver a specific UV or visible light can also be used.

From a general point of view, the crosslinking under irradiation is promoted by a photoinitiator molecule. A large literature describes photoinitiators and their uses. In the field of the radical polymerization of acrylic silicone compositions, the photoinitiator molecules commonly used 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 curing of the compositions. Many efforts have been made to ensure that Type I photoinitiators have characteristics enabling their use in acrylic silicone formulations to obtain release coatings. For the whole of the application, the term "type I photoinitiators" means compounds well known to those skilled in the art, capable of generating free radical initiators of polymerization under UV excitation by intramolecular homolytic fragmentation.

There are also type II photoinitiator systems including a radical photoinitiator and a co-initiator. In photoinitiator systems of type II, the photoinitiators used are capable of generating free radicals initiating polymerization by reaction with another compound called a co-initiator, said reaction causing the transfer of a hydrogen from the co-initiator to said photoinitiator . Photoinitiators used in Type II photoinitiator systems are referred to as "Type II photoinitiators".

To date, there is no type II photoinitiator system, comprising a radical photoinitiator and a co-initiator, effective for the polymerization of acrylic silicone compositions under UV or visible radiation emitted by light sources such as light-emitting diodes, better known by the acronym "LED" (Light-Emitting Diodes) which generate a light beam with a narrow output spectrum centered on a specific wavelength. LEDs with UV or visible radiation exist mainly with an emission band centered on a wavelength of 365, 385, 395 or 405 nm. The object of the present invention is to provide a radically polymerizable or crosslinkable silicone composition comprising a type II photoinitiator system suitable for crosslinking silicone compositions, in particular by exposure to UV or visible radiation emitted by light-emitting diodes. LED lamps are of interest in terms of power consumption, lifetime and electrical safety compared to mercury or xenon lamps commonly used so far. Another advantage of LEDs is the absence of warm-up time which allows productivity gains.

Another object of the present invention is to provide a radically polymerizable or crosslinkable silicone composition comprising a photoinitiator system. of type II adapted for the crosslinking of silicone compositions, in particular by exposure to radiation, and absorbing a light radiation of wavelength greater than 300 nm. The present invention also aims to provide a method for preparing a film or a coating on a substrate from the radical-polymerizable silicone composition according to the invention.

The present invention also aims to provide a substrate coated with a film or a coating obtained from the radical-polymerizable silicone composition according to the invention.

Another object of the present invention is to provide silicone compositions which make it possible to obtain release coatings which crosslink under radiation, and in particular under UV radiation, from organopolysiloxanes comprising (meth) acrylate groups, in particular ester groups ( meth) acrylics or epoxy acrylates or polyether acrylates. ,

The present invention also aims to provide a polymerizable silicone composition or radically crosslinkable by exposure to radiation and by polyaddition. These silicone compositions with a double crosslinking system have the particularity of being able to crosslink partially very rapidly by irradiation and then continue the crosslinking by heating, to obtain a silicone elastomer with good stability and good mechanical properties.

Silicone compositions with a dual crosslinking system are described in US Pat. No. 4,585,669 (GE). Silicone compositions comprising an organohydrogenpolysiloxane, an organopolysiloxane comprising acrylate radicals, an organopolysiloxane comprising vinyl groups, a Pt catalyst and a free radical type photoinitiator are described. The combination of diethoxyacetophenone as photoinitiator and benzophenone as photosensitizer is illustrated.

The silicone compositions with a double crosslinking system have a certain interest for their use in 3D printing because they make it possible to increase the printing speed of silicone elastomeric parts. Irradiation of the layers of silicone compositions as the print is made allows the rapid gelation of part of the composition during production and thus each layer retains its shape without collapsing the printed structure. When the printing is complete, a heating step makes it possible to finish the crosslinking of the composition by polyaddition to obtain a silicone elastomer with good stability and good mechanical properties.

Patent application WO2016 / 134972 discloses a method for producing a silicone elastomer article with a 3D extrusion or inkjet printer. In this patent application is implemented a crosslinked silicone composition both by UV irradiation and by heating. The irradiation leads to the gelation of the layers and the final thermal hardening leads to a silicone elastomer with good stability and mechanical properties. The only photoinitiator described is a commercial type I photoinitiator Irgacure® 651 which corresponds to 2,2-dimethoxy-2-phenylacetophenone. In the examples, UV radiation with a wavelength of 360 nm is used.

The patent application WO2017 / 07952 also describes silicone compositions for additive manufacturing comprising a first reagent polymerizable by irradiation and a second reagent system crosslinkable inter alia by polyaddition. In this patent application, the additive manufacturing is carried out either in tanks by a continuous production of liquid interface (CLIP) or by ink jet. As a photoinitiator, the combination of morpholinone and isopropylthioxanthone is described. In the examples the poor solubility of the photoinitiator is illustrated. A centrifugation step is necessary to separate the photoinitiator which has not dissolved. In addition, morpholinone, by the presence of an amino group, is an inhibitor of the polyaddition reaction. In general, the absorbing photoinitiators at wavelengths between 200 and 500 nm are described. Consequently, there is a need to develop crosslinkable silicone compositions by irradiation with UV or visible radiation of wavelength greater than 300 nm emitted by light-emitting diodes and by polyaddition using a photoinitiator that is soluble in the silicone composition. It is also an object of the present invention to provide a radically radiation-curable and polyaddition-curable radically crosslinkable silicone composition useful for additive manufacturing processes also known as 3D printing methods.

Thus, the present invention relates to a silicone composition C1 crosslinkable by exposure to radiation of wavelength between 300 and 450 nm, comprising:

at least one organopolysiloxane A comprising at least one (meth) acrylate group bonded to a silicon atom,

at least one organohydrogenpolysiloxane H comprising at least two, and preferably at least three, hydrogen atoms each bonded to different silicon atoms, and

at least one radical photoinitiator P of formula (I) below:

(I)

in which :

the symbol X is chosen from the group consisting of: an oxygen atom, a sulfur atom, a CH 2 group and a carbonyl radical, the symbols R ² and R ⁴ are hydrogen atoms,

the symbols R ¹ and R ³ , which are 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 C 1 -C 20, preferably C 3 -C 20, alkyl group or alkenyl group

A group - (C = O) ~ R ⁵ , with the radical R ⁵ being chosen from the groups C1-C20 alkyl, C2-C20 alkenyl, C3-C20 cycloalkyl and C6-C12 aryl, and ^■ a group -Si (R ⁶⁾ 3; wherein the same or different R ⁶ groups are selected 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 alkoxy and hydrogen, and with the proviso that at least one of the substituents R ¹ or R ³ is a hydroxyl or a group of formula -OZ.

In order to obtain radiation photocrosslinking, the composition comprises a type II photoinitiator system which, under the effect of the absorption of the incident light energy, releases free radicals into the medium. These radicals act as initiators of radical polymerization of (meth) acrylic functions. Since it is the vector of hardening of the composition, the photoinitiator system is an essential key of this application.

The present invention is therefore based on the use of a specific type II photoinitiator system comprising the combination of a radical photoinitiator P as defined above and an organohydrogenpolysiloxane H as co-initiator.

The silicone composition C1 has the advantage of efficiently crosslinking by exposure to UV or visible radiation. In addition, the free radical photoinitiator P of formula (I) has the advantage of being more soluble in organopolysiloxanes comprising at least one (meth) acrylate group than commercial free radical initiators such as benzophenone or isopropylthioxanthone.

Throughout this document, reference will be made to conventional nomenclature elements to designate siloxyl units M, D, T, Q of the organopolysiloxanes which according to the name widely known in the silicone chemistry represent:

M = siloxyl unit of formula R3S1O1 / 2

- D = siloxyl unit of formula R2S1O2 / 2

- T = siloxyl unit of formula RSiO 3/2 and

- Q = siloxyl unit of formula S1O4 / 2,

where the radicals R, identical or different, are monovalent groups.

All the viscosities referred to herein correspond to a dynamic viscosity quantity at 25 ° C. (except otherwise indicated), known as "Newtonian", ie the dynamic viscosity which is measured, in a manner known in the art. self, with a Brookfield viscometer at a shear rate gradient sufficiently low that the measured viscosity is independent of the velocity gradient.

The crosslinkable silicone compositions C1 according to the invention comprise at least one organopolysiloxane A comprising at least one (meth) acrylate group bonded to a silicon atom. As a representative of (meth) acrylate functions carried by silicone and particularly suitable for the invention, there may be mentioned more particularly the derivatives of acrylates, methacrylates, ethers of (meth) acrylates and esters of (meth) acrylates linked to the chain. polysiloxane via an Si-C bond.

According to one embodiment, the organopolysiloxane A comprises:

a1) at least one unit of formula (A1) below:

RaZ _b SiO (4-ab) / 2 (A1)

formula in which:

the symbols R, which may be identical or different, each represent a linear or branched C1-C18 alkyl group, a C6-C12 aryl or aralkyl group, which is optionally substituted, preferably with halogen atoms, or an alkoxy-OR radical; ⁴ with R ⁴ being a hydrogen atom or a hydrocarbon radical comprising from 1 to 10 carbon atoms

the symbols Z are monovalent radicals of formula -y- (Y ') n in which:

Y represents a linear or branched C ₁ -C ₄ alkylene radical which may be optionally extended by divalent C ₁ -C ₄ oxyalkylene polyoxyalkylene radicals optionally substituted with a hydroxyl radical;

Y 'represents a monovalent alkenylcarbonyloxy radical, and

N is equal to 1, 2 or 3, and

a is an integer equal to 0, 1 or 2, b is an integer equal to 1 or 2 and the sum a + b = 1, 2 or 3; and

a2) optionally units of the following formula (A2):

RaSiO ( _4-a ) / 2 (A2)

formula in which:

the symbols R, which may be identical or different, each represent a linear or branched C 1 -C 18 alkyl group, a C 6 to C 12 aryl or aralkyl group, optionally substituted, preferably with halogen atoms, and

- a is an integer equal to 0, 1, 2 or 3. In formulas (A1) and (A2) above, the symbol R may advantageously represent a monovalent radical chosen from the group consisting of: methyl, ethyl, propyl, 3,3,3-trifluoropropyl, xylyl, tolyl and phenyl.

The organopolysiloxane A may have a linear, branched, cyclic or network structure. In the case of linear organopolysiloxanes, these can essentially consist of:

- Siloxyl "D" units chosen from the units of formulas R2S1O2 / 2, RZS1O2 / 2 and

siloxyl "M" units chosen from the units of formulas R 3 SiO 1/2, R 2 SiO 1/2, R 2 SiO 1/2 and Z 3 SiO 1/2; and

the symbols R and Z are as defined above in formula (A1).

According to one embodiment, in formula (A1) above, among the radicals Y 'alkenylcarbonyloxy mentioned above, there may be mentioned acryloxy [CH2 = CH-CO-O-] and methacryloxy radicals: [(CH ₃ ) CH = CH-CO-O-] and [CH ₂ = C (CH ₃ ) -CO-O-].

As an illustration of the symbol y for said symbol Z in the units of formula (A1), mention will be made of the radicals: - (CH ₂ ) ₂ -;

- (CH ₂ ) ₃ -;

-CH ₂ -CH (CH ₃ ) -CH ₂ -;

- (CH ₂ ) ₃ -NH-CH ₂ -CH ₂ -;

- (CH ₂ ) ₃ -OCH ₂ -;

- (CH ₂ ) ₃ - [O-CH ₂ -CH (CH ₃ ) -] -;

- (CH ₂ ) 3 -O-CH ₂ -CH (OH) (- CH ₂ -);

- (CH 2) ₃ -O-CH 2 -C (CH 2 -CH 3) [- (CH ₂ ) ₂ -] ₂ ; and

Preferably, the organopolysiloxane A corresponds to the following formula (III)

formula in which:

the symbols R ¹ , which are 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, optionally substituted, preferably by halogen atoms, or an alkoxy radical; OR ⁴ with R ⁴ being a hydrogen atom or a hydrocarbon radical comprising from 1 to 10 carbon atoms,

the symbols R ² and R ³ , which are identical or different, each represent either a radical R ¹ or a monovalent radical of formula Z = -w- (Y ') _n in which:

W represents a linear or branched C1-C18 alkylene polyvalent radical optionally extended by divalent oxyalkylene or polyoxyalkylene radicals Ci-C optionally substituted by a hydroxyl radical,

Y 'represents a monovalent alkenylcarbonyloxy radical, and

N is equal to 1, 2 or 3, and

with a = 0 to 1000, b = 0 to 500, c = 0 to 500, d = 0 to 500 and a + b + c + d = 0 to 2500, and

the condition that at least one R ² or R ³ symbol represents the monovalent radical of formula Z.

According to a preferred embodiment, in formula (III) above:

- c = 0, d = 0, a = 1 to 1000, b = 1 to 250, the symbol R ² represents the monovalent radical of formula Z and the symbols R ¹ and R ³ have the same meaning as above.

Even more preferably, in formula (III) above:

- c = 0, d = 0, a = 1 to 500, b = 1 to 100, the symbol R ² represents the monovalent radical of formula Z and the symbols R ¹ and R ³ have the same meaning as above.

According to one embodiment, the organopolysiloxane A according to the invention corresponds to the following formula (IV):

in which :

x is between 1 and 1000;

n is between 1 and 100.

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

By the expression, a hydrogen atom bonded to a silicon atom means an Si-H function or an Si-H bond or a hydrogenosilyl function.

According to a preferred embodiment, the organohydrogenpolysiloxane H comprises:

(i) at least two units of formula (H1),

HdL _e SiO - (d + e (H1)

in which :

L represents a monovalent radical different from a hydrogen atom,

H represents the hydrogen atom,

d and e represent integers, d being 1 or 2, e being 0, 1 or 2 and (d + e) being 1, 2 or 3;

(ii) and optionally other units of formula (H2):

in which :

- L has the same meaning as above, and

f represents an integer equal to 0, 1, 2 or 3.

It is understood in formulas (H1) and (H2) above that if several L groups are present, they may be the same or different from each other. In the formula (H1), the symbol d may preferentially be 1. Moreover, in the formula (H1) and in the formula (H2), L may preferably represent a monovalent radical selected from the group consisting of an alkyl group having 1 to 8 carbon atoms, optionally substituted by at least one halogen atom, and an aryl group. L may advantageously represent a monovalent radical chosen from the group consisting of methyl, ethyl, propyl, 3,3,3-trifluoropropyl, xylyl, tolyl and phenyl. Examples of units of formula (H1) are as follows: H (CH ₃₎ ₂ SiO / 2, H (CH ₃₎ Si0 _2/2 and H (C ₆ H ₅₎ Si0 _2/2.

The organohydrogenpolysiloxane H can have a linear, branched, cyclic or network structure. In the case of linear organohydrogenpolysiloxanes, these can essentially consist of:

of siloxyl "D" units chosen from the units of formulas HLS1O2 / 2 (also called D 'unit) and L2S1O2 / 2; and

siloxyl "M" units chosen from the units of formulas HL ₂ SiOi / ₂ (also called M 'unit) and L3S1O2 / 2,

with the symbol L having the same meaning as above and the symbol H denoting a hydrogen atom.

These linear organohydrogenpolysiloxanes H may be oils having a dynamic viscosity at 25 ° C of between 1 mPa.s and 100 000 mPa.s, preferably between 1 mPa.s and 5000 mPa.s, and even more preferably between 1 mPa. s and 2,000 mPa.s.

In the case of cyclic organohydrogenpolysiloxanes, they may consist of siloxyl units "D" chosen from the units of formulas HLS1O2 / 2 and L ₂ ₂ Si0 2, or of siloxyl units of formula HLSi0 _2/2 only . The units of formula L 2 SiO 2/2 may in particular be dialkylsiloxy or alkylarylsiloxy dies. These cyclic organohydrogenpolysiloxanes may have a dynamic viscosity at 25.degree. C. of between 1 mPa.s and 5000 mPa.s.

Examples of organohydrogenpolysiloxane H are:

polydimethylsiloxanes with hydrogenodimethylsilyl ends;

poly (dimethylsiloxane-co-hydrogenomethylsiloxane) with trimethylsilyl ends;

poly (dimethylsiloxane-co-hydrogenomethylsiloxane) with hydrogenodimethylsilyl ends;

polyhydromethylsiloxanes with trimethylsilyl ends; and cyclic hydrogen methylpolysiloxanes. In the case of branched or networked organohydrogenpolysiloxanes H, these may furthermore comprise:

siloxyl "T" units chosen from units of formulas HS1O3 / 2 and siloxyl "Q" units of formula S1O4 / 2,

with the symbol H representing a hydrogen atom and L having the same meaning as above.

According to one embodiment, the organohydrogenpolysiloxane H comprises at least 0.05 mol of Si-H functions per 100 g of polymer, preferably at least 0.08 mol of Si-H functions per 100 g of polymer, more preferably between 0.08 mole and 2.5 moles of Si-H functions per 100 g of polymer, and even more preferably between 0.08 mole and 1.8 moles, of Si-H functions per 100 g of polymer.

The silicone composition C1 comprises a radical photoinitiator P of formula

(I) following:

in which :

^■ a C1-C20, preferably C3-C20, or alkenyl

^■ a group - (C = 0) -R ^5, with the radical R ⁵ is selected from C1-C20 alkyl, C2-C20 alkenyl, C3-C20 cycloalkyl and EC-C12 aryl, and ^■ a group -Si (R ⁶⁾ 3; wherein the same or different R ⁶ groups are selected 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 alkoxy and hydrogen, and with the proviso that at least one of the substituents R ¹ or R ³ is a hydroxyl or a group of formula -OZ.

According to an advantageous embodiment of the invention, in formula (I) above, R ² = R ³ = R ⁴ = H and R ¹ = OH or -OZ as defined above.

According to another embodiment in the formula (I) above, R ¹ = R ² = R ⁴ = H and R ³ = OH or -OZ as defined above.

According to one embodiment, the radical photoinitiator P is chosen from the group consisting of thioxanthone derivatives, of following formula (la):

in which :

the symbol X is a sulfur atom,

the symbols R ² and R ⁴ are hydrogen atoms,

^■ a C1-C20, preferably C3-C20, or alkenyl

^■ a group - (C = 0) -R ^5, with the radical R ⁵ is selected from C1-C20 alkyl, C2-C20 alkenyl, C3-C20 cycloalkyl and C6-C12 aryl, and

^■ a group -Si (R ⁶⁾ 3; wherein the same or different R ⁶ groups are selected 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 alkoxy and hydrogen, and with the proviso that at least one of the substituents R ¹ or R ³ is a hydroxyl or a group of the formula -OZ.

According to an advantageous embodiment of the invention, in the formula (la) above, R ² = R ³ = R ⁴ = H and R ¹ = OH or -OZ as defined above.

According to another embodiment in formula (Ia) above, R ¹ = R ² = R ⁴ = H and R ³ = OH or -OZ as defined above.

By way of examples of free-radical photoinitiators P of formula (Ia), mention will be made in particular of the following compounds:

2-hydroxy-9H-thioxanthen-9-one, RN-CAS = 31696-67-0,

2-methoxy-9H-thioxanthen-9-one, RN-CAS = 40478-82-8,

2-ethoxy-9H-thioxanthen-9-one, RN-CAS = 5543-66-8,

2-hexyloxy-9H-thioxanthen-9-one, RN-CAS = 5596-56-5,

2-octyloxy-9H-thioxanthen-9-one, formula (6) below

2- decyloxy-9H-thioxanthen-9-one, formula (7) below

2-dodecyloxy-9H-thioxanthen-9-one, formula (8) below

2- acetyloxy-9H-thioxanthen-9-one, RN-CAS = 92439-12-8,

2 - [(trimethylsilyl) oxy] -9H-thioxanthen-9-one, formula (17) below

2-propenoic acid 9-oxo-9H-thioxanthen-2-yl ester RN-CAS = 1 13797-58-3,

2-neodecanoic acid 9-oxo-9H-thioxanthen-2-yl ester, formula (20) below

4-neodecanoic acid 9-oxo-9H-thioxanthen-2-yl ester, formula (25) hereinafter and 4-hydroxy-9H-thioxanthen-9-one, formula (23) hereinafter.

According to another embodiment, the radical photoinitiator P is chosen from the group consisting of xanthone derivatives, of following formula (Ib):

in which :

the symbol X is an oxygen atom, the symbols R ² and R ⁴ are hydrogen atoms, the symbols R ¹ and R ³ , which are 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, preferably C3-C20 alkenyl or C2

^■ a group - (C = 0) -R ^5, with the radical R ⁵ is selected from C1-C20 alkyl, C2-C20 alkenyl, C3-C20 cycloalkyl and EC-C12 aryl, and

^■ a group -Si (R ⁶⁾ 3; wherein the same or different R ⁶ groups are selected 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 alkoxy and hydrogen, and with the proviso that at least one of the substituents R ¹ or R ³ is a hydroxyl or a group of formula -OZ.

According to an advantageous embodiment of the invention, in formula (Ib) above, R ² = R ³ = R ⁴ = H and R ¹ = OH or -OZ as defined above.

According to another embodiment in formula (Ib) above, R ¹ = R ² = R ⁴ = H and R ³ = OH or -OZ as defined above.

As examples of free radical photoinitiators P of formula (Ib), mention will be made in particular of the following compounds:

2-hydroxy-9H-xanthen-9-one, RN-CAS = 1915-98-6,

2-methoxy-9H-xanthen-9-one, RN-CAS = 1214-20-6,

2-ethoxy-9H-xanthen-9-one, RN-CAS = 103573-60-0,

2-hexyloxy-9H-xanthen-9-one, formula (1) below

2-octyloxy-9H-xanthen-9-one, formula (2) below

2- decyloxy-9H-xanthen-9-one, formula (3) below

2-dodecyloxy-9H-xanthen-9-one, formula (4) below

2 - [(trimethylsilyl) oxy] -9H-xanthen-9-one, RN-CAS = 32747-67-4, formula (18) below,

2-neodecanoic acid 9-oxo-9H-xanthen-2-yl ester, formula (19) below

4-neodecanoic acid 9-oxo-9H-xanthen-2-yl ester, formula (24) below and

4-hydroxy-9H-xanthen-9-one RN-CAS = 14686-63-6. According to one embodiment, the radical photoinitiator P is chosen from the group consisting of the anthracenone derivatives, of following formula (le):

in which :

the symbol X is a group CH2,

the symbols R ² and R ⁴ are hydrogen atoms,

^■ a C1-C20, preferably C3-C20, or alkenyl

According to an advantageous embodiment of the invention, in formula (Ie) above, R ² = R ³ = R ⁴ = H and R ¹ = OH or -OZ as defined above.

According to another embodiment in formula (Ie) above, R ¹ = R ² = R ⁴ = H and R ³ = OH or -OZ as defined above.

As examples of free radical photoinitiators P derived from anthracenone of formula (Ic), mention may be made of 2-methoxy-10H-anthracen-9-one (RN-CAS = 53604-95-8) and the 4-methoxy-10H-anthracen-9-one (RN CAS = 7470-93-1) as well as the compounds of formulas (13), (14), (15), (16) and (22) below.

According to one embodiment, the radical photoinitiator P is chosen from the group consisting of the anthraquinone derivatives of the following formula (Id):

in which :

the symbol X is a carbonyl radical,

the symbols R ² and R ⁴ are hydrogen atoms,

^■ a C1-C20, preferably C3-C20, or alkenyl

^■ a group -Si (R ⁶⁾ 3; wherein the same or different R ⁶ groups are selected 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 alkoxy and hydrogen, and with the proviso that at least one of the substituents R ¹ or R ³ is a hydroxyl or a group of formula -OZ. According to an advantageous embodiment of the invention, in the formula (Id) above, R ² = R ³ = R ⁴ = H and R ¹ = OH or -OZ as defined above.

According to another embodiment in the formula (Id) above, R ¹ = R ² = R ⁴ = H and R ³ = OH or -OZ as defined above. As examples of anthraquinone derivative radical photoinitiators of formula (Id), mention may be made of 2-dodecyloxy-10H-anthraquin-9-one (RN-CAS = 218961-85-4) and octanoic acid, 9 , 10-dihydro-9,10-dioxo-2-anthracenyl ester (RN-CAS = 1 10484-84) as well as the compounds of formula (9), (10), (1 1), (12) and (21 ) below.

According to an advantageous embodiment, the radical photoinitiator P is chosen from the thioxanthone derivatives of formula (Ia) and xanthone of formula (Ib) as described above. The xanthone derivatives absorbing at 365 nm and the thioxanthone derivatives absorbing at 395 nm are preferred because they allow their implementation with the LE D.

According to one embodiment, the crosslinkable silicone compositions C1 according to the invention comprise at least 0.0003 moles of radical photoinitiator P per 100 g of composition C1, and preferably at least 0.0005 moles of radical photoinitiator P per 100 g of composition C1. Preferably, the mole content of radical photoinitiator P in the compositions C1 of the invention is between 0.0003 and 0.015 mole per 100 g of composition C1, and even more preferably between 0.0005 and 0.015 mole per 100 g of composition C1. According to one embodiment, the composition C1 does not comprise platinum.

The crosslinkable silicone compositions C1 according to the invention may also comprise at least one additive. As an additive, at least one additive for controlling the release force of a silicone / adhesive interface can be included in the composition which is chosen from:

(i) organic (meth) acrylate derivatives, and

(ii) silicones with (meth) acrylate function (s).

Particularly suitable organic (meth) acrylate derivatives are epoxidized (meth) acrylates, (meth) acryloglyceropolyesters, (meth) acrylouretanes, (meth) acrylopolyethers, (meth) acrylopolyesters, and (meth) acryloacrylic compounds. More particularly preferred are trimethylolpropane triacrylate, tripropylene glycol diacrylate and pentaerythritol tetraacrylate. According to a preferred variant of the invention, the additive used is a silicone with (meth) acrylate function (s). As a representative of (meth) acrylate functional groups carried by silicone and particularly suitable for the invention, mention may be made more particularly of acrylate, methacrylate and meth (meth) acrylate derivatives and meth (acrylate) esters linked to the chain. polysiloxane via an Si-C bond. Such acrylate derivatives are in particular described in patents EP 0 281 718, FR 2 632 960 and EP 0 940 458.

The present invention also relates to the use of the composition C1 according to the invention, for the preparation of silicone films with anti-adherent properties.

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

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

The present invention also relates to a process for preparing silicone films with anti-adhesive properties, comprising a step of crosslinking a composition C1 as defined above. Preferably, in the process for preparing silicone films with antiadhesive properties according to the invention, compositions C1 as defined above are used, in which the ratio between the number of moles of radical photoinitiator P and the number of moles of Si-H functions of organohydrogenpolysiloxane B is between 0.5 and 20, preferably between 1 and 5, said organohydrogenpolysiloxane B preferably comprising at least 0.08 mole, preferably between 0.1 mole and 2.5 mole. moles, of Si-H functions per 100 g of organohydrogenpolysiloxane B.

According to one embodiment of the process of the invention, the crosslinking step is carried out under air or under an inert atmosphere. Preferably, this crosslinking step is carried out under an inert atmosphere. According to one embodiment, the crosslinking step of the process according to the invention is carried out by radiation with a wavelength of between 200 nm and 450 nm, preferably under an inert atmosphere.

According to a preferred embodiment, the crosslinking step of the process according to the invention is carried out by radiation with a wavelength of between 300 nm and 450 nm, preferably under an inert atmosphere. The present invention also relates to a process for preparing a coating on a substrate, comprising the following steps:

the application of a crosslinkable composition C1 as defined above to a substrate, and

the crosslinking of said composition C1 by exposure to radiation of wavelength between 200 nm and 450 nm.

The radiation can be emitted by doped or non-doped mercury vapor lamps whose emission spectrum extends from 200 nm to the visible. Light sources such as light-emitting diodes, better known by the acronym "LED" (Light-Emitting Diodes) which deliver a specific UV or visible light can also be used.

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

The irradiation time can be short and is generally less than 1 minute, preferably less than 10 seconds and can be of the order of a few hundredths of a second for the low coating thicknesses. The crosslinking obtained is excellent even in the absence of any heating.

According to one embodiment, the crosslinking step is carried out at a temperature of between 10 ° C. and 50 ° C., preferably between 15 ° C. and 35 ° C. Of course, the rate of curing can be adjusted in particular by the number of lamps used, the exposure time and the distance between the composition and the lamp or lamps. The composition C1 according to the invention without solvent, that is to say undiluted, can be applied using devices able to deposit, in a uniform manner, small amounts of liquid. For this purpose, for example, the device called "sliding helio" may be used, comprising in particular two superposed cylinders: the role of the lowest placed cylinder, immersed in the coating tank where the compositions are located, is to impregnate into one 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 which it is impregnated, such a dosage is obtained by adjusting the respective speed of the two cylinders which rotate in direction reverse one another. The amounts of composition C1 deposited on the supports are variable and generally range from 0.1 to 5 g / m ² of treated surface. These amounts depend on the nature of the supports and the desired anti-adherent properties. They are most often between 0.5 and 1.5 g / m ² for non-porous supports. This method is particularly suitable for preparing a release-resistant silicone coating on a substrate which is a flexible support made of textile, paper, polyvinyl chloride, polyester, polypropylene, polyamide, polyethylene, polyethylene terephthalate, polyurethane or polyethylene terephthalate. nonwoven glass fibers. These coatings are particularly suitable for their use in the field of anti-adhesion.

The present invention therefore also relates to a coated substrate capable of being obtained according to the process as defined above. As indicated above, the substrate may be a flexible support in textile, paper, polyvinyl chloride, polyester, polypropylene, polyamide, polyethylene, polyethylene terephthalate, polyurethane or nonwoven glass fibers. The coated substrates have a non-stick, water-repellant, or improved surface properties such as slipperiness, stain resistance or softness. Another aspect of the invention relates to a thermally crosslinkable silicone composition C2 and by exposure to radiation of wavelength between 300 and 450 nm comprising:

at least one composition C1 as described above,

at least one organopolysiloxane B comprising at least two alkenyl units bonded to silicon atoms and

at least one hydrosilylation catalyst.

In this composition C2, the organohydrogenpolysiloxane H acts as a radical co-initiator and a crosslinking agent for the hydrosilylation reaction.

For the whole of the application, the term "crosslinking" is used to mean the curing of the composition by polymerization reactions of the meth (acrylate) functional groups, by polyaddition reactions between the Si-H bonds of the organohydrogenpolysiloxanes H and the alkenyl groups of the organopolysiloxanes. B or a combination of both.

The term "thermally crosslinkable silicone composition" refers to a silicone composition capable of curing by heating at a temperature generally between 60 and 220 ° C, preferably between 80 and 180 ° C.

The term "radiation-curable silicone composition" refers to a silicone composition capable of curing by exposure to radiation.

According to one embodiment of the invention, the organopolysiloxane B comprises: (i) at least two siloxyl units (I.5) of the following formula

\ NJJ3 \ Q,,,,

² (I.5)

in which :

- a = 1 or 2, b = 0, 1 or 2 and a + b = 1, 2 or 3; W represents independently an alkenyl group, preferably having from 2 to 6 carbon atoms and, more preferably still, a vinyl or allyl group, and

Z is independently a monovalent hydrocarbon group having from 1 to 30 carbon atoms and preferably selected from the group consisting of alkyl groups having 1 to 8 carbon atoms inclusive, and even more preferably selected from the group consisting of a radical methyl, ethyl, propyl and 3,3,3-trifluoropropyl ₇

(ii) and optionally other siloxyl units (1.6) of the following formula

ZcSiO (4-c) / 2 (1.6)

in which :

Z has the same meaning as above, and

c represents an integer equal to 0, 1, 2 or 3.

The organopolysiloxane B can have a linear structure, possibly cyclic. These linear organopolysiloxanes have a dynamic viscosity at 25 ° C of between 100 mPa.s and 1000000 mPa.s and more preferably between 1000 mPa.s and 120000 mPa.s.

When the organopolysiloxane B has a linear formula, in the formula (1.5), a = 1 and a + b = 2 or 3 and in the formula (I.6) c = 2 or 3. It is understood in the formulas ( 1.5) and (1.6) above that, if several radicals W and Z are present, they may be identical or different from each other.

In the case of linear organopolysiloxanes, these may be chosen from the group consisting of:

polydimethylsiloxanes with dimethylvinylsilyl ends;

poly (vinylmethylsiloxane-co-dimethylsiloxane) with dimethylvinylsilyl ends;

poly (dimethylsiloxane-co-vinylmethylsiloxane) with trimethylsilyl ends and

cyclic polymethylvinylsiloxanes.

Organopolysiloxane B may have a branched structure. This is called silicone resin. Advantageously, these are silicone resins comprising from 0.1 to 20% by weight, preferably from 4 to 20% by weight, of C2-C6 alkenyl groups bonded to silicon atoms. The alkenyl groups may be located on M, D or T siloxyl units. These resins may be prepared, for example, according to the process described in US Pat. U.S. Patent 2 676 1820.1 at 20%. The alkenyl groups are preferably chosen from vinyls, allyls and hexenyls.

In a preferred embodiment of the invention, the silicone resin comprises at least two vinyl radicals and is chosen from the group consisting of the following silicone resins:

- D ⁱ Q, where the vinyl groups are included in the units D,

- MD ^Vi TQ where the vinyl groups are included in the D patterns,

- MM ^Vi Q where the vinyl groups are included in part of the patterns M,

- MM ^Vi TQ, where the vinyl groups are included in one of the units M, - ^ MM DD ^ Q, where the vinyl groups are included in a part of the M and D units,

- and their mixtures,

with:

- = siloxyl unit of formula (R) 2 (vinyl) SiOi / 2

- D ^{V |} siloxylated unit of formula (R) (vinyl) SiO 2/2

and the groups R, which may be identical or different, are monovalent hydrocarbon-based groups chosen from alkyl groups having from 1 to 8 carbon atoms inclusive, such as methyl, ethyl, propyl and 3,3,3-trifluoropropyl groups, and aryl groups such as as xylyl, tolyl and phenyl. Preferably, the R groups are methyls.

Preferably, the silicone resin has the formula MD 2 or MIW 2 as described above.

Polyaddition catalysts K are well known. The platinum and rhodium compounds are preferably used. In particular, platinum complexes and an organic product described in US-A-3 159 601, US-A-3 159 602, US-A-3,220,972 and European patents can be used. A-0 057 459, EP-A-0 188 978 and EP-A-0 190 530, the complexes of platinum and vinyl organosiloxanes described in US-A-3,419,593, US-A-3,715,334. , US-A-3,377,432 and US-A-3,814,730, platinum complexes with carbene ligands as described in EP1235836, diene platinum complexes as described in US6605734 and US20170057980. Photoactivatable hydrosilylation catalysts as described in WO2016044547 may also be used. Other polyaddition catalysts based on non-noble metal complexes such as iron, nickel and cobalt may also be employed. According to a preferred embodiment of the invention, the catalyst K is platinum-based. In this case, the weight amount of catalyst K, calculated as weight of platinum-metal, is generally between 2 and 400 ppm, preferably between 5 and 200 ppm based on the total weight of the composition C2.

Advantageously, the platinum metal content of the composition C2 is between 10 and 120 ppm, preferably between 10 and 95 ppm, more preferably between 0 and 70 ppm and even more preferably between 10 and 60 ppm by weight based on the total weight of the composition. C2.

The silicone compositions C2 may further contain at least one of the following compounds:

An inhibitor I,

• F loads and

Adhesion promoters G. As filler F can be used reinforcing mineral fillers or semi-reinforcing mineral fillers or stuffing. The reinforcing mineral fillers may be chosen from siliceous materials. The reinforcing siliceous fillers are chosen from colloidal silicas, silica powders of combustion and precipitation or their mixture. These powders have an average particle size generally less than 0.1 μm and a BET specific surface area greater than 50 m ² / g, preferably between 150 and 350 m ² / g. These silicas can be incorporated as such or after being treated with organosilicon compounds usually used for this purpose. Among these compounds include methylpolysiloxanes such as hexamethyldisiloxane, octamethylcyclotetrasiloxane, methylpolysilazanes such as hexamethyldisilazane, hexamethylcyclotrisilazane, chlorosilanes such as dimethyldichlorosilane, trimethylchlorosilane, methylvinyldichlorosilane, dimethylvinylchlorosilane, alkoxysilanes such as dimethyldimethoxysilane dimethylvinylethoxysilane, trimethylmethoxysilane. Semi-reinforcing siliceous fillers such as diatomaceous earth or ground quartz can also be used.

In addition to or instead of reinforcing silicas, semi-reinforcing mineral fillers or stuffing may be added. Examples of these non-siliceous fillers that can be used alone or as a mixture are calcium carbonate, optionally surface-treated with an organic acid or with an ester of an organic acid, clay calcined, titanium oxide of the rutile type, oxides of iron, zinc, chromium, zirconium, magnesium, the various forms of alumina (hydrated or not), boron nitride, lithopone, metaborate of barium, barium sulfate and glass microbeads. These fillers are coarser with generally an average particle diameter greater than 0.1 μηι and a surface area generally less than 30 m ^{2 /} g. These fillers may have been surface-modified by treatment with the various organosilicon compounds usually employed for this purpose. .

Conductive fillers such as nano-based graphene or carbon nanotube objects can also be used.

According to one embodiment of the invention, a reinforcing filler F is used which is a fumed silica having a specific surface area measured according to the BET method of between 100 and 400 m ² / g. Even more advantageously, the reinforcing filler F is a fumed silica having a specific surface area measured according to the BET method of between 100 and 400 m ² / g and having been treated with organosilicon compounds.

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

The crosslinking inhibitor I (or retarder of the polyaddition reaction) may, for its part, be chosen from the following compounds:

an organopolysiloxane, advantageously cyclic, and substituted by at least one alkenyl, tetramethylvinyltetrasiloxane being particularly preferred, phosphines and organic phosphites,

unsaturated amides,

the alkylated maleates

and acetylenic alcohols.

These acetylenic alcohols (see FR-B-1,528,464 and FR-A-2,372,874), which form part of the preferred hydrosilylation reaction heat blockers, have the formula (11):

(11) - R ² is a hydrogen atom, a linear or branched alkyl radical, or a phenyl radical;

- The radicals R ¹ , R ² and the carbon atom located alpha of the triple bond may optionally form a ring; and

the total number of carbon atoms contained in R 1 and R 2 being at least 5, preferably from 9 to 20.

Said alcohols are preferably chosen from those having a boiling point greater than 250 ° C. Examples of the following products that are commercially available include:

ethynyl-1-cyclohexanol 1;

3-methyl-1-dodecyn-3-ol;

3,7-trimethyl-1-dodecyn-3-ol;

1,1-diphenylpropyne-2-ol;

3-ethyl-6-ethyl nonyne-1-ol-3;

3-methylpentadecyn-1-ol-3.

Such a crosslinking inhibitor I is present at a maximum of 3000 ppm, preferably at 100 to 2000 ppm relative to the total weight of the composition C2.

As adhesion promoters G, it will be possible to use the adhesion promoters usually used in the field. For example, we can use:

a vinylated silane or organopolysiloxane alone or partially hydrolysed, as well as one of its reaction products,

a silane or organopolysiloxane functionalized with a single or partially hydrolyzed epoxy functional group and one of its reaction products,

an organopolysiloxane comprising at least one SiH function and at least one functional group chosen from the group consisting of: epoxy functions, (meth) acrylate functions, alkoxy functions and vinyl functions,

a metal alkoxide or a metal chelate such as Ti, Zr, Al, for example tert-butyl titanate.

The invention also relates to a silicone elastomer obtained by crosslinking a composition C2 as defined above. These silicone elastomers can be used in multiple applications, for example in the medical field, the care and treatment of wounds or wounds in English "woundcare" (coating of dressings, manufacture of external prostheses, anti-scar cushions), or for the encapsulation of electronic components or as coatings, in particular for the coating of flexible films made of paper or plastic as well as for textile coating, in particular of airbag airbag inflatables.

Another aspect of the invention relates to a process for preparing articles made of silicone elastomer, comprising a step of crosslinking a composition C2 as defined above by exposure to radiation of wavelength between 300 nm and 450 nm.

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

The process for preparing silicone elastomer articles according to the invention may also comprise a heating step, preferably at a temperature of between 60 and 220 ° C., more preferably between 80 and 180 ° C.

The present invention also relates to the use of the composition C2 according to the invention for the preparation of silicone elastomer articles by additive manufacturing processes also known as 3D printing processes.

This description generally includes ASTM designation F2792-12a, "Standard Terminology for Additive Manufacturing Technologies". According to this ASTM standard, a "3D printer" is defined as "a machine used for 3D printing" and "3D printing" is defined as "the manufacture of objects through the deposition of a material to the using a printhead, nozzle, or other printer technology. "

Additive manufacturing "AM" is defined as a process of joining materials to make objects from 3D model data, usually layer on layer, as opposed to subtractive manufacturing methods. The synonyms associated with 3D printing and encompassed by 3D printing include additive manufacturing, additive processes, additive techniques and layer manufacturing. Additive manufacturing (AM) can also be called rapid prototyping (RP). As used herein, "3D printing" is interchangeable with "additive manufacturing" and vice versa.

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

The silicone compositions C2 according to the invention allow to increase the printing speed of the silicone elastomer parts. Irradiation of the layers of silicone compositions as the print is made allows the rapid gelation of part of the composition during production and thus each layer retains its shape without collapsing the printed structure. When the printing is complete, a heating step makes it possible to finish the crosslinking of the composition by polyaddition to obtain a silicone elastomer with good stability and good mechanical properties. Advantageously, the silicone compositions C2 according to the invention can be used for 3D printing processes using photopolymerization in the tank, the extrusion of material or the deposition of material by adapting the viscosity of the silicone composition C2 to the technology. employee.

Photopolymerization in the tank is an additive manufacturing process in which a curable liquid resin present in a tank is selectively cured when the polymerization of its molecular chains is triggered by ultraviolet light. In-vat photopolymerization can employ a lamp or light-emitting diodes (LEDs) as a source of UV energy. For use in additive manufacturing processes such as photopolymerization in tanks, the viscosity of the silicone composition C2 will be between 10 mPa.s and 100000 mPa.s, preferably between 100 and 10,000 mPa.s and even more preferably between 100 and 100 mPa.s. and 2000 mPa.s. A "3D in the tank" printer is a printer as described in the application WO2017 / 055747 where a UV-visible lighting device comprising an LED light source and a mask adapted to transmit or block irradiation in a pattern display to create a projection image. The mask thus comprises an array of pixels configured to assume an on state and a blocking state of the irradiation. The passing state results in a transmission of the irradiation towards the corresponding point of the projection image. The blocking state results in an absence of transmission of the irradiation towards the corresponding point of the projection image. The display pattern corresponds to the distribution of the states of said pixels.

The manufacturing system of the tank printer thus comprises an irradiation system preferably with UV-visible LEDs, a mask adapted to close the UV-visible radiation emitted by the LEDs in a display pattern to create a projection image emitted by the irradiation device. The printer comprises a system for moving the projection image on a work surface which is arranged in a receptacle called a tank. The tank contains the silicone formulation having a working surface exposed to the projection image emitted by the irradiation device.

The tank manufacturing system can correspond to a working and irradiation surface of silicone formulation layer open side from above but also another possible configuration is irradiation from below through a bottom transparent to the irradiation. In this case the work surface is the surface in contact with the transparent bottom. It avoids sticking of the work surface directly in contact with the transparent bottom by creating an inhibition layer in contact with the transparent bottom by oxygenation of the surface of the transparent bottom. An example of a printer and method according to a method of projection from below is described in the patent application US7052263.

Material extrusion is an additive manufacturing process in which a filament of material is extruded and selectively distributed through a nozzle. The flow rate of extruded material can be controlled inter alia via the pressure exerted on the nozzle or the temperature.

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

For use in additive manufacturing processes such as extrusion or deposition of material, the viscosity of the silicone composition C2 will be between 100 mPa.s and 1000000 mPa.s, preferably between 1000 mPa.s and 300000 mPa. .s and even more preferably between 3000 and 200000 mPa.s. For this use, the silicone compound C2 must exhibit a thixotropic behavior (decrease in viscosity under shear and increase in viscosity after shearing).

A "3D extrusion" printer is a 3D printer where the material is extruded through a nozzle, syringe or orifice during the additive manufacturing process. Material extrusion generally operates by extruding material through a nozzle, syringe, or orifice to print a cross section of an object, which can be repeated for each subsequent layer. The extruded material binds to the layer beneath it during curing of the material. In a preferred embodiment, the method of printing a three-dimensional silicone elastomer article uses an extrusion 3D printer. The silicone compositions are extruded through a nozzle. The nozzle may be heated to facilitate dispensing of the addition-crosslinking silicone composition. The average diameter of the nozzle defines the thickness of the layer. In one embodiment, the diameter of the layer is between 50 and 2000 μm, preferably between 100 and 800 μm, and the most preferably between 100 and 500 μιη. The distance between the nozzle and the substrate is an important parameter to ensure a good shape. It must be between + to / - 30% of the average diameter of the nozzle. The dual cure radical-crosslinking and polyaddition silicone composition to be dispensed through the nozzle may be provided from a cartridge-type system. The cartridge may include a nozzle or nozzles with a fluid reservoir or associated fluid reservoirs. It is also possible to use a coaxial system of two cartridges with a static mixer and a single nozzle. The pressure will be adapted to the fluid to be dispensed, the average diameter of the associated nozzle and the printing speed.

Because of the high shear rate that occurs during extrusion of the nozzle, the viscosity of the silicone compositions is greatly reduced and thus allows the printing of thin layers. The pressure of the cartridge may vary from 1 to 20 bar, preferably from 2 to 10 bar and most preferably from 4 to 7 bar. When nozzle diameters less than 00 m are used, the pressure of the cartridge must be greater than 20 bar to obtain a good extrusion of the material. Suitable equipment using aluminum cartridges must be used to withstand such pressure. The platform of nozzles and / or platform moves in the X-Y (horizontal plane) to complete the cross section of the object, before moving in the plane of the Z axis (vertical) a once a layer is finished. The nozzle has high XYZ motion accuracy. Once each layer is printed in the work plane X, Y, the nozzle is moved in the direction Z only sufficiently large so that the next layer can be applied in the workplace X, Y. In this way, the object that becomes the 3D article is built one layer at a time from the bottom up.

As previously described, the distance between the nozzle and the previous layer is an important parameter to ensure a good shape. It must be between + to / - 30% of the average diameter of the nozzle. The printing speed is between 1 and 50 mm / s, preferably between 5 and 30 mm / s in order to obtain the best compromise between the good precision and the speed of manufacture.

A "3D inkjet" printer is defined as an additive manufacturing material in which droplets of silicone formulation are selectively deposited. The silicone formulation is applied by means of a print head in the form of individual droplets, batchwise, at the desired location of the Jetting. It is a 3D apparatus and method for the step-by-step production of 3D structures with a print head arrangement comprising at least one, preferably 2 to 200, printhead nozzles, allowing the selective application of a formulation, if necessary, of a plurality of formulations. The application of silicones by inkjet printing imposes specific requirements on the viscosity of the materials. In a 3D projection printer of the silicone formulation, one or more tanks are subjected to pressure and are connected by a measuring line to a metering nozzle. Upstream or downstream of the tank, there may be devices that make it possible to homogenize and / or evacuate the dissolved gases so that the silicone compositions are homogeneous. One or more independently operated projection apparatuses may be present to construct the elastomeric article from different addition-crosslinked silicone compositions or, in the case of more complex structures, to composite parts of silicone elastomers and other plastics. Due to the high shear rate that occurs in the metering valve during the jet dosing procedure, the viscosity of these addition-crosslinked silicone compositions is considerably lowered and thus allows the delivery of a micro jet. - very fine droplets. Once the microdroplet has been deposited on the substrate, there is a sudden reduction in its shear rate, so that its viscosity rises again. As a result, the deposited drop quickly reaches a very high viscosity and thus allows a precise construction of three-dimensional structures. The individual dosing nozzles can be accurately positioned in the x, y and z directions to allow precise targeted deposition of the silicone droplets on the substrate or, upon subsequent formation of shaped parts, the addition of a crosslinkable silicone composition. It is desirable to use a UV and / or visible irradiation system to initiate curing after printing each layer to prevent collapse of the structure.

Typically, the 3D printer uses one or more dispensers, e.g. a nozzle or a print head for printing the curable silicone composition. Optionally, the dispenser may be heated before, during and after the dispensing of the silicone composition. In one embodiment, this method may utilize material for two different purposes, construct the object, and support overhangs to avoid extruding material into the air. If the object has been printed using support or support structures once the printing process is complete, it is usually eliminated (for example by washing with water) leaving behind the finished object.

After printing, the resulting articles may be subjected to different post-treatment regimes. In one embodiment, the method further comprises the step of heating the silicone elastomer article obtained by 3D printing. The heating can be used to speed up the treatment. In another embodiment, the method further comprises the step of further irradiating the silicone elastomer article obtained by 3D printing. Additional irradiation can be used to speed up the treatment. In another embodiment, the method further comprises the two steps of heating and irradiating the silicone elastomer article obtained by 3D printing. As an option, post-processing steps can significantly improve the surface quality of printed articles. Sanding is a common way to reduce or eliminate visibly distinct layers of the model. Spraying or coating the surface of the elastomeric article with a heat-curable or UV-curable RTV or LSR silicone composition can be used to achieve the appearance of the smooth, straight surface. A surface treatment with a laser can also be done. For medical applications, sterilization of the final elastomeric article can be obtained by heating the object to a temperature greater than 100 ^° C.

Another subject of the invention relates to the following compounds (1) to (25)

Neodecanoic acid is a mixture of carboxylic acids with the common structural formula C10H20O2, a molecular weight of 172.26 g / mol and the CAS number = 26896-20-8. The components of the mixture are acids having the common property of a "trialkylacetic acid" having three carbon-2 alkyl groups, including: 2,2,3,5-tetramethylhexanoic acid, 2,4-dimethyl- 2-isopropylpentanoic acid, 2,5-dimethyl-2-ethylhexanoic acid and 2,2-dimethyloctanoic acid.

For the following structures (19) to (22), (24) and (25), the neodecanoic acid used for the synthesis of photoinitiators is branched with the various acids mentioned above.

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

The examples below are given for illustrative and not limiting. They allow in particular to better understand the invention and bring out all its advantages.

EXAMPLES

In the examples below various photoinitiators, organohydrogenpolysiloxanes and organopolysiloxanes with acrylate functions have been used according to the invention and their structures are indicated in the tables below.

Table 1: Photoamenters

2 Dod-XT (4)

380

Invention

2 neodeca-XT (19)

366

Invention

2 Hex-TX (5)

312

Invention

2 Dod-TX (8)

396

Invention

2 neodeca-TX (20)

382

Invention

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

Synthesis of 2-hydroxyoxanthone (2 QH-XT):

Reagents:

- 2-iodobenzoic acid

4-methoxyphenol

- cesium carbonate

copper chloride (I)

- Tris [2- (2-methoxyethoxy) ethyl] amine (TDA-1)

, 4-Dioxane

Concentrated sulfuric acid In a single-necked flask, add 1 equivalent of 2-iodobenzoic acid, 1.4 equivalents of 4-methoxyphenol and 2.8 equivalents of cesium carbonate in 6 mL of 1,4-dioxane per mmol of 2-iodobenzoic acid. Leave to stir for 10 minutes at room temperature and under argon. Then introduce 0.1 equivalent of copper chloride I and 0.1 equivalent of TDA-1. Let react 20h at reflux under argon.

Once the reaction is complete, the 1,4-dioxane is evaporated on a rotary evaporator. The residue is dissolved with 0% Na 2 CO 3 solution and the solution is filtered. The filtrate is then introduced into a separating funnel and is washed with a 50/50 toluene / ethyl acetate mixture. The aqueous phase is recovered and acidified before filtering to obtain the reaction intermediate. (Yield: 75%)

In a single-necked flask, add 1 equivalent of the intermediate product in 1.25 mL of concentrated sulfuric acid per mmol of reagent. Allow to react until the task of the product with methoxy disappears in TLC (about 3 hours). Once the reaction is complete, the reaction medium is allowed to cool before being poured into 10 times the volume of acid in ice. The solution obtained is then extracted 3 times with ethyl acetate. The organic phases are combined, dried and evaporated. The product obtained is a white solid. It can be recrystallized from acetone (Yield: 48%). The NMR spectrum corresponds to 2-hydroxyxanthone.

Synthesis of 2-hydroxythioxanthone (2 OH-XT):

Reagents:

- Thiosalicylic acid

- Phenol

- Sulfuric acid

In a single-necked flask, slowly add 1 equivalent of thiosalicylic acid in 1 mL of sulfuric acid per mmol of thiosalicylic acid. Leave to shake vigorously for 10 minutes. Then add 5 equivalents of phenol over 30 minutes. Let the mixture react for 1 hour at room temperature, then 2 hours at 80 ° C and let stand overnight at room temperature.

Once the reaction is complete, pour the reaction medium into 10 times the volume of sulfuric acid in boiling water, and boil for 10 minutes. The solution is filtered once cooled. The product obtained is a yellow powder (yield: 62%). The NMR spectrum corresponds to 2-hydroxythioxanthone. Synthesis of xanthone ethers and thioxanthone. compounds (1), (4), (5), (8)

Reagents:

- 2-hydroxyxanthone and 2-hydroxythioxanthone

- lodoalkane (1-lodohexane and 1-lodo-dodecane)

- Potassium carbonate

Dimethylsulfoxide DMSO

Figure 1: synthesis of xanthone ethers and thioxanthone (X = O, S)

Protocol:

In a single-necked flask, add 1 equivalent of 2-hydroxyxanthone (or 2-hydroxythioxanthone) and 2 equivalents of potassium carbonate in 5 mL of DMSO per mmol of product. Leave to stir for 10 min at room temperature under argon. Then introduce the iodoalkane (1-iodohexane or iodododecane) dropwise, then allow to react at 100 ° C under argon for 48h.

Once the reaction is complete, 10 times the volume of the reaction medium is added to water and the mixture is extracted 3 times with n-hexane. The organic phases are then combined, dried and evaporated. The crude product obtained is then purified on silica gel with a 90/10 cyclohexane / ethyl acetate eluent (yield: around 66%).

Synthesis of compounds 2 neodeca-XT (19) and 2 neodeca-TX (20) In a single-necked flask, add 1 equivalent of 2-hydroxyxanthone (or 2-hydroxythioxanthone), 1 equivalent of neodecanoic acid and 1 ml of acid concentrated sulfuric acid per mmol of product. Leave to stir for 2 hours at room temperature under argon. Then allow to react at 120 ° C under argon for 12h.

Once the reaction is complete, 10 times the volume of the reaction medium is added to water and the mixture is extracted 3 times with n-hexane. The organic phases are then combined, neutralized with sodium carbonate, dried and evaporated. The crude product obtained is then purified on silica gel with a 90/10 cyclohexane / ethyl acetate eluent. Table 2: Orqanohydrogenpolysiloxane

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

Acrylic silicones

An organopolysiloxane Acryl 1 of formula

with x = 85 and n = 7 is used in the compositions.

Silicone compositions crosslinking by irradiation:

Attempts have been made to illustrate the use of type II photoinitiators according to the invention with an organohydrogenpolysiloxane as photoinitiator for polymerizing acrylic silicones. The preparations are carried out as follows: 1.2 × 10 -4 mol of the photoinitiator are weighed into 2 g of Acryl 1 organopolysiloxane. The mixture is stirred for 12 hours. Then 1% by weight of the organohydrogenpolysiloxane Hyd 1 is introduced.

Two types of radiation crosslinking are tested:

- 90 seconds of UV radiation with a Mercury-Xenon lamp. The power of the lamp is fixed at 510mW / cm ² and - 90 seconds of 365 nm LED radiation with a power of 750 mW / cm ² for Xanthone derivatives or under 395 nm LED radiation with a power of 680 mW / cm ² for Thioxanthone derivatives. The manipulations were carried out in laminate in order to overcome any action of inhibition of the reactive species by oxygen. When the manipulations are made of laminate, the formulation is placed between two sheets of polypropylene, then between two pellets of CaF2. The monitoring of polymerization kinetics is carried out by Real-Time Fourier Transform Infra-Red (RT-FTIR, Vertex 70 from Brucker Optik). This spectroscopic technique consists of exposing the sample simultaneously to light and an infra-red ray in order to follow the changes in the IR spectrum at 1636 cm ^-1, which is a characteristic band of the C = C bond of the acrylic functions.

The degree of conversion of C = C to CC during the polymerization is directly related to the decrease in the area calculated under the peak at 1636 cnr ¹ according to the following equation: conversion (%) = (Ao-A _t ) / Ao * 100 with Ao the area under the peak before irradiation and A _t the area under the peak at each instant t of irradiation. For tests carried out with the Mercure-Xenon lamp, the plot as a function of time allows access to the final conversion rate, but also to other important parameters, such as the maximum conversion speed Rp expressed in the tables below. as R _p / [M] ox100 where [M] ₀ is the initial acrylate function concentration. The maximum conversion rate Rp is determined by the slope of the conversion curve (%) = f (time) at its point of inflection.

The results are shown in Tables 3 and 4 below.

Table 3 UV Radiation -LED

* -: low solubility <50%; +: partial solubility> 50%, ++: soluble

Observations made after 12 hours of stirring with a magnetic stirrer

The photoinitiators according to the invention make it possible to obtain a better conversion rate after 90s of irradiation with LEDs.

Table 4 / Results with Hq-Xe lamp

The photoinitiators according to the invention make it possible to obtain a better conversion rate after 90 s of irradiation with a Hg-Xe lamp. Silicone compositions crosslinking by irradiation and thermally:

The formulations tested are detailed in Table 5 below.

The formulations are prepared by simply mixing all the constituents in a speed mixer and mixing at 1000 rpm for one minute. In addition to the compounds already described above, the following compounds are used:

Vinyl oil 1: polydimethylsiloxane oil blocked at each end of the chains by a (CH 3) 2ViSiOi / 2 unit, having a viscosity of 60000 mPa.s. - Vinyl Resin 2: Organopolysiloxane of formula MM ^ Q containing 1.1% by weight of vinyl groups.

- Hydrosilylation catalyst: platinum metal, introduced in the form of an organometallic complex containing 10% by weight of platinum metal, known under the name of Karstedt catalyst,

Inhibitor: ethynyl-1-cyclohexanol-1 or ECH,

Polydimethylsiloxane PDMS with a viscosity of 50 mPa.s

Table 5: Radical Crosslinking and Polyaddition-Based Silicone Compositions

We obtain two compositions:

Composition 1 by mixing A1 + B which is a comparative example.

Composition 2 by mixing A2 + B which is an example according to the invention. At 23 ° C., the dynamic viscosity of composition 2 is equal to 15400 mPa.s.

3D printing test

100 g of composition is introduced into the tank of a 3D printer using photopolymerization in the tank with LED 365 nm. It is a Prodway® DLP 3D printer with a dual-cartridge system equipped with a static mixer. The bathing time or "potlife" of the composition obtained in the dark (protected from light) is 24 hours before gelation. The results of the crosslinking conditions required for the first layer of 250 μm thick deposited on a plate and exposed for 5.5 s to UV LED radiation of 365 nm and an intensity of 75.5 mW / cm ² are presented in Table 6 below.

Table 6 Energy required to radiation crosslink a 250 μm layer of silicone compositions

In the table below Ec represents the surface critical energy measured in mJ / cm ² .

The composition according to the invention has a lower critical surface energy. It will have to provide him with less energy to reach the freezing point. This composition therefore has the advantage of requiring less energy to crosslink and therefore it will be possible to print the successive layers more quickly.

E4 is the energy to be supplied to achieve the crosslinking to a thickness of 100 microns, E8 to reach 200 microns and E10 to reach 250 microns.

Table 7 / Mechanical properties measured according to the NF EN ISO 527 standard on the silicone elastomers obtained after irradiation and thermal crosslinking

Properties Compositionl Composition 2 mechanical Comparative Invention

Resistance to

1.65 1.65 rupture (MPa)

Lengthening to

65 65 break (%)

Traction module

2.54 2.54

(MPa)

Claims

C1-silicone composition crosslinkable by exposure to radiation of wavelength between 300 and 450 nm, comprising:

at least one radical photoinitiator P of formula (I) below:

in which :

^■ a C1-C20, preferably C3-C20, or alkenyl

^■ a group -Si (R ⁶⁾ 3; wherein the same or different R ⁶ groups are selected 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 alkoxy and hydrogen, and with the proviso that at least one of the substituents R ¹ or R ³ is a hydroxyl or a group of formula -OZ. 2 - Composition C1 according to claim 1 wherein the photoinitiator P is selected from compounds of formula (I) wherein the symbol X is an oxygen atom or a sulfur atom.

3 - Composition C1 according to any one of the preceding claims, wherein the organopolysiloxane A comprises:

a1) at least one unit of formula (A1) below:

RaZ _b SiO (4-ab) / 2 (A1)

formula in which:

the symbols R, which may be identical or different, each represent a linear or branched C1-C18 alkyl group, a C6-C12 aryl or aralkyl group, which is optionally substituted, preferably with halogen atoms, or an alkoxy-OR radical; ⁴ with R ⁴ being a hydrogen atom or a hydrocarbon radical comprising from 1 to 10 carbon atoms,

the symbols Z are monovalent radicals of formula -y- (Y ') n in which:

Y represents a linear or branched C 1 -C 18 alkylene polyvalent radical optionally extended by bivalent oxyalkylene or C 1 -C 4 polyoxyalkylene radicals optionally substituted by a hydroxyl radical,

Y 'represents a monovalent alkenylcarbonyloxy radical, and

N is equal to 1, 2 or 3, and

a2) optionally units of the following formula (A2):

RaSiO (4-a) / 2 (A2)

formula in which:

- a is an integer equal to 0, 1, 2 or 3.

4- Composition C1 according to any one of the preceding claims, wherein the concentration of radical photoinitiator P is between 0.0003 and 0.015 mole per 100 g of composition C1. 5 - Use of the composition C1 according to any one of claims 1 to 4, for the preparation of silicone films with non-stick properties.

6 - Process for preparing silicone films with anti-adhesive properties, comprising a step of crosslinking a composition C1 according to any one of claims 1 to 4 by exposure to radiation of wavelength between 300 nm and 450 nm.

7 - Process according to claim 6, wherein the radiation is generated by light emitting diodes.

8 - A thermally crosslinkable silicone composition C2 and by exposure to radiation of wavelength between 300 and 450 nm comprising:

at least one composition C1 according to any one of claims 1 to 4,

at least one organopolysiloxane B comprising at least two alkenyl groups each bonded to a silicon atom, and

at least one hydrosilylation catalyst.

9 - silicone composition C2 according to claim 8 further comprising at least one additive selected from the group consisting of:

An inhibitor I,

· A load F, and

• an adhesion promoter G.

10 - silicone elastomer obtained by crosslinking a composition C1 or C2 according to any one of claims 1 to 4 and 8 to 9.

11 - Use of the composition C2 according to claims 8 or 9, for the preparation of silicone elastomer articles by an additive manufacturing process. 12 - Process for the preparation of silicone elastomer articles, comprising a step of crosslinking a composition C2 according to any one of claims 8 to 9 by exposure to radiation of wavelength between 300 nm and 450 nm.

13 - The method of claim 12, wherein the radiation is generated by light emitting diodes.

14 - The method of claim 12 or 13 further comprising a heating step.

Compounds (1) to (25) of the following formulas:

(17)

16 - Use of the compounds according to claim 15 as radical photoinitiators.