Method for preparing organopolysiloxanes with (METH)acrylate functions

Abstract

The invention relates to a method for preparing a composition X comprising at least one organopolysiloxane A comprising at least one (meth)acrylate group, said method comprising the following steps: a) reacting at a temperature between 50°C and 130°C, preferably between 70°C and 130°C and even more preferentially between 90°C and 125°C, at least one organopolysiloxane E comprising at least one epoxy group with acrylic acid or methacrylic acid or a mixture of the two, and in the presence: - of a catalyst C which is a complex of chromium in the (III) oxidation state of the following formula (1): [CrL1)3] (1) in which the L1 symbols, which may be identical or different, represent a β-diketonate anion, and - of an inhibitor for the polymerization of acrylic acid or methacrylic acid, b) devolatilizing the reaction medium obtained on conclusion of step a), c) obtaining said composition X comprising at least one organopolysiloxane A.

Description

[0001] TITLE OF THE INVENTION: Process for the preparation of organopolysiloxanes with (meth)acrylate functions

[0002] The present invention relates to a process for preparing organopolysiloxanes with (meth)acrylate functions, preferably acrylates. Throughout the document it should be understood that the (meth)acrylate groups include acrylate groups, methacrylate groups or a mixture of both. These (meth)acrylate functionalities are present only in organic groups linked to the polysiloxane chain by an Si-C bond which may be present in the chain, at the end of the chain or both. These (meth)acrylic acid ester functions are capable of reacting by radical means under thermal activation and / or by radiation according to a polyaddition polymerization mechanism.

[0003] These (meth)acrylate-functional organopolysiloxanes are widely used in radically crosslinkable silicone compositions which can optionally be coated in a thin layer on a flexible support which is made of textile, paper, polyvinyl chloride (PVC), polyester, polypropylene, polyamide, polyethylene, polyethylene terephthalate (PET), polyurethane or non-woven glass fibers, to produce an elastomer.

[0004] The coating of silicone formulations on flexible substrates targets numerous applications. For example, when the flexible substrate is a textile, water-repellent properties are targeted or when the substrate is a paper or a polymer such as PVC or PET, non-stick properties are most often sought.

[0005] Release coatings are useful for many applications where it is necessary to make a surface or material that would normally adhere to them non-stick to other materials. For example, silicone compositions are used as coatings for release papers and can thus be combined with adhesive elements that can be easily released without losing their adhesive properties, these elements being pressure-sensitive adhesives for labels, decorative laminates, transfer tape, etc. Silicone-based release coatings applied to paper, polyethylene, polypropylene, polyester and other such supports are also useful as release surfaces for products for food use and particularly in the industrial packaging sector.There has therefore been a long-standing strong interest in these (meth)acrylate-functional organopolysiloxanes and their preparation can be envisaged in various ways described in the prior art.

[0006] Recently, this interest has been reinforced by the use of such organopolysiloxanes in various additive manufacturing methods by photopolymerization to obtain a silicone elastomer article. Examples include laser stereolithography (SLA) printing, digital light processing (DLP) 3D printing, and continuous liquid interface production (CLIP). The resulting silicone elastomer articles have good mechanical properties.

[0007] It is known that such (meth)acrylate-functional organopolysiloxanes are obtained industrially by reaction between an organopolysiloxane functionalized by epoxy groups and (meth)acrylic acid in the presence of a chromium-based catalyst.

[0008] Patent EP1276825-B 1 teaches us in particular the preparation of organopolysiloxanes with a (meth)acrylate function starting from organopolysiloxanes having epoxy functionalities and acrylic acid in the presence of chromium (III) acetate and two solvents including an alcohol. When implementing this process described in patent EP1276825B 1, these solvents are necessary to solubilize the chromium (III) acetate catalyst. In addition, the yield and selectivity of such a process can be improved. Furthermore, the compositions comprising the organopolysiloxanes with an acrylate function obtained according to the teaching of this title have an unpleasant odor that is bothersome for users of these compositions.

[0009] Recently, patent application WO2017187030 teaches the preparation of organopolysiloxanes with (meth)acrylate functionality from organopolysiloxanes with epoxy functionalities, acrylic acid, chromium (III) acetate, solvent but in the absence of alcoholic solvent. This patent application WO2017187030 has advantageously shown that it makes it possible to obtain an improved yield of organopolysiloxanes with (meth)acrylate functionality. In addition, this process makes it possible to obtain oils without unpleasant odors in times compatible with industrial production. On the other hand, when dealing with organopolysiloxane oils with epoxy functionalities comprising a low level of epoxy functionality, the implementation of this process can become complex. A decrease in the yield and selectivity for such compounds is then observed. This drop in reactivity is explained in particular by the low solubility of the chromium acetate catalyst under such conditions.For the purposes of this application, the epoxy functionality level is measured in moles of epoxy functions per kilogram of polyorganosiloxane oils.

[0010] To limit this drop in reactivity, the reaction medium can be preheated to promote the solubilization of the catalyst or the reagents can be introduced at different stages of the process. However, these adjustments to the process can lead to a drop in kinetics and thus an increase in the reaction time to form organopolysiloxanes with (meth)acrylate function.

[0011] With a view to improving this process, one of the essential objectives of the present invention is to develop a process for preparing organopolysiloxanes with a (meth)acrylate function with satisfactory kinetics and selectivity while avoiding the use of alcoholic solvent.

[0012] Another essential objective of the present invention is to provide a process for preparing robust (meth)acrylate functional organopolysiloxanes from organopolysiloxane oils having different chain lengths and / or different levels of acrylate functionality.

[0013] Another essential objective of the present invention is to provide a catalytic system suitable for the process of the present invention.

[0014] Another essential objective of the present invention is to provide a process for preparing robust (meth)acrylate-functional organopolysiloxanes by a so-called "one-pot" reaction.

[0015] For the purposes of the present invention, the term "one-pot" means the introduction of all the reactants into the reactor at the initial time of said reaction, also called to.

[0016] For the purposes of the present invention, the term “mass percentage of a compound A” means the mass percentage of this chemical species A relative to the total mass of the mixture.

[0017] Thus, surprisingly, the Applicant has developed a process which relates to a process for the preparation of a composition X comprising at least one organopolysiloxane A comprising at least one (meth)acrylate group, said process comprising the following steps: a) At least one organopolysiloxane E comprising at least one epoxy group is reacted at a temperature of 50 to 130°C, preferably 70 to 130°C and even more preferably 90 to 125°C, with acrylic acid or methacrylic acid or a mixture of the two, and in the presence of:

[0018] - a catalyst C which is a chromium complex in the oxidation state (III) of the following formula (1) [Cr(L x )3] (1) in which the symbols L 1identical or different represent a P-diketonate anion, and

[0019] - of an acrylic acid or methacrylic acid polymerization inhibitor, b) The reaction medium obtained at the end of step a) is devolatilized c) Said composition X is obtained comprising at least one organopolysiloxane A.

[0020] Step a) of the process for preparing composition X according to the invention is preferably carried out in the presence of a solvent S which is not an alcohol.

[0021] Thus, preferably, the invention is carried out in the absence of alcohol and in particular in the absence of butanol.

[0022] For the purposes of the present invention, the term solvent means a non-reactive solvent. Therefore, solvent S is different from organopolysiloxane E, acrylic acid and methacrylic acid.

[0023] The process for preparing composition X according to the invention has the advantages of obtaining a satisfactory yield and selectivity for organopolysiloxane A. It is to the credit of the inventors to have identified that implementing the process in the presence of chromium (III) P-diketonate complexes, such as chromium (III) acetylacetonate, makes it possible to obtain better selectivity for organopolysiloxane A. In addition, this process has the advantage of having a process that can be adapted to the industrial scale for organopoly siloxanes E of different degrees of polymerization and / or different levels of epoxy functionality without having to adapt the implementation of the process. Thus, the process according to the invention can be implemented "one-pot" from composition X prepared upstream such as premixes of composition X prepared, for example, the day before. This significant advantage makes it easier to implement said process on an industrial scale.

[0024] The above-mentioned advantages are justified by the improvement of the solubility of the catalyst in the reaction medium. Thus, this catalyst is perfectly soluble in composition X and will not precipitate during storage of composition X prepared upstream of the implementation of said process or during its implementation.

[0025] Other advantages of said process may be cited, such as the composition X obtained which does not have an unpleasant odor. Or, obtaining a conversion rate of the epoxy groups greater than 98% in less than six hours in step a) of said process. According to a preferred embodiment of the invention, the duration of step a) is between one and five hours when the temperature of step a) is between 90 and 125°C.

[0026] The organopolysiloxane A obtained by the process of the invention comprises siloxyl units (I), (II), and optionally (III) of the following formulae: in which:

[0027] -a=1 or 2, b=0, 1 or 2 and a+b= 1, 2 or 3,

[0028] -c= 0,1,2 or 3,

[0029] -d=1 or 2, e=0, 1 or 2 and d+e= 1,2 or 3

[0030] -the symbols Y, identical or different, represent an organic group comprising an epoxy group and optionally further comprising one or more heteroatoms such as an oxygen atom, said organic group Y preferably having from 2 to 20 carbon atoms inclusive, and, more preferably still, Y is chosen from the group consisting of an alkylglycidyl ether, a linear, branched or cyclic epoxyalkyl, a linear, branched or cyclic epoxyalkenyl and a carboxylic acid glycidyl ester,

[0031] - the Z symbols 1 and Z 2, identical or different, represent a monovalent organic group having from 1 to 30 carbon atoms and preferably chosen from the group consisting of alkyl groups having from 1 to 8 carbon atoms and aryl groups of 6 to 12 carbon atoms, and even more preferably chosen from the group consisting of a methyl, ethyl, propyl, 3,3,3-trifluoropropyl, xylyl, toluyl and phenyl group, -the symbols V, identical or different, represent an organic group comprising a (meth)acrylate group, said organic group V preferably having from 5 to 23 carbon atoms inclusive, and,

[0032] -said organopolysiloxane A comprises, per molecule, at least two silicon atoms and at least one siloxyl unit (III).

[0033] Organopolysiloxane E comprises siloxyl units (I) and (II) of the following formulas: in which:

[0034] -a=l or 2, b= 0, 1 or 2 and a+b=l, 2 or 3

[0035] -c= 0, 1, 2 or 3 -the symbols Y, identical or different, represent an organic group comprising an epoxy group and optionally further comprising one or more heteroatoms such as an oxygen atom, said organic group Y preferably having from 2 to 20 carbon atoms inclusive, and, more preferably still, Y is chosen from the group consisting of an alkyldiglycidyl ether, a linear, branched or cyclic epoxyalkyl, a linear, branched or cyclic epoxyalkenyl and a carboxylic acid glycidyl ester;

[0036] -the Z symbols 1 and Z 2, identical or different, represent a monovalent organic group having from 1 to 30 carbon atoms and preferably chosen from the group consisting of alkyl groups having from 1 to 8 carbon atoms and aryl groups having from 6 to 12 carbon atoms, and even more preferably chosen from the group consisting of a methyl, ethyl, propyl, 3,3,3 trifluoropropyl, xylyl, toluyl and phenyl group, and

[0037] - said organopolysiloxane E comprises, per molecule, at least two silicon atoms and at least one siloxyl unit (I)

[0038] Preferably, for the siloxyl unit (I) the symbol Y is chosen from the group consisting of the organic groups (IV) to (VIII) of the following formulas:

[0039] According to a particularly preferred embodiment, in the siloxyl unit (I) the symbol Y is the organic group (VII) of the following formula:

[0040] These organopolysiloxanes E can have a linear, branched or cyclic structure and their degree of polymerization is between 2 and 5000, preferably between 2 and 1000 and even more preferably between 2 and 500.

[0041] Preferably, the organopolysiloxane E has a linear structure and comprises siloxyl units (I) and (II) of the following formulas: in which:

[0042] -a=1 or 2, b= 0, 1 or 2 and a+b= 2 or 3,

[0043] -c= 2 or 3,

[0044] -the symbols Y, identical or different, represent an organic group comprising an epoxy group and optionally further comprising one or more heteroatoms such as an oxygen atom, said organic group Y preferably having from 2 to 20 carbon atoms inclusive, and, more preferably still Y is chosen from the group consisting of an alkylglycidyl ether, a linear, branched or cyclic epoxyalkyl, a linear, branched or cyclic epoxyalkenyl and a carboxylic acid glycidyl ester;

[0045] -the Z symbols 1 and Z 2, identical or different, represent a monovalent organic group having from 1 to 30 carbon atoms and preferably chosen from the group consisting of alkyl groups having from 1 to 8 carbon atoms and aryl groups having from 6 to 12 carbon atoms, and even more preferably chosen from the group consisting of a methyl, ethyl, propyl, 3,3,3-trifluoropropyl, xylyl, touyl and phenyl group, and

[0046] -said organopolysiloxane E comprising, per molecule, at least two silicon atoms and at least one siloxyl unit (I).

[0047] When it is a linear polymer, the organopolysiloxane E is essentially made up of siloxyl units “D” chosen from the group consisting of the siloxyl units Y2SiO2 / 2, YZ^iO^ and Z 2 2SiO2 / 2 and siloxyl units “M” chosen from the group consisting of the siloxyl units YsSiOia, YZ'2SiOi / 2, Y2Z 1 SiOi / 2etZ 2 3SiOi / 2. The symbols Y, Z1 and Z 2 are as described above. According to a preferred embodiment of the invention, the organopoly siloxane E is essentially composed of siloxyl units “D” chosen from the group consisting of the YZ siloxyl units 1 SiO2 / 2 and Z 2 2SiO2 / 2 and siloxyl units “M” chosen from the group consisting of the siloxyl units YZ^SiOia, and Z 2 3SiOi / 2. The symbols Y, Z 1 and Z 2 are as described above.

[0048] Organopolysiloxane E has a dynamic viscosity at 25°C of between 1 and 100,000 mPa.s, preferably between 10 and 50,000 mPa.s and even more preferably between 10 and 10,000 mPa.s, even more preferably between 10 and 5,000 mPa.s.

[0049] All the viscosities referred to in the present application correspond to a dynamic viscosity quantity at 25°C known as “Newtonian”, that is to say the dynamic viscosity which is measured, in a manner known per se, with a Brookfield viscometer at a shear rate gradient sufficiently low so that the measured viscosity is independent of the rate gradient.

[0050] According to a preferred embodiment of the invention, the organopoly siloxane E contains per molecule from 1 to 300 siloxyl units (I) carrying at least one organic group comprising an epoxy group. According to a preferred embodiment of the invention, the organopoly siloxane E contains per molecule from 2 to 250 siloxyl units (I) and more preferably the organopoly siloxane E contains per molecule from 20 to 300 siloxyl units (I).

[0051] According to another embodiment, the organopoly siloxane E contains from 0.5 to 30% by mass of organic groups Y comprising an epoxy group, preferably from 1 to 20% by mass and even more preferably from 1 to 10% by mass relative to the total mass of the organopoly siloxane E.

[0052] According to one embodiment, the content of organic groups Y comprising an epoxy group is from 0.05 to 3 mol per kilogram of organopoly siloxanes E, preferably from 0.1 to 1.5 mol, preferentially from 0.1 to 1 mol per kilogram of organopoly siloxane E.

[0053] According to a preferred embodiment of the process according to the invention, the organopoly siloxane E is chosen from the compounds of formulae (EI) to (E-IV) following: (EI) in which R is an alkyl group comprising from 2 to 5 carbon atoms, a is between 2 and 50 and preferably between 2 and 15 and b is between 20 and 400.

[0054] (E-II) in which n is between 0 and 250.

[0055] (E-III) in which x is between 10 and 300 and y is between 2 and 30, preferably between 2 and 15, and

[0056] (E-IV) in which x is between 0 and 250.

[0057] Depending on the applications envisaged for organopolysiloxane A, a conversion rate of the epoxy functions of the total or partial organopolysiloxane E may be sought. It is thus possible to obtain an organopolysiloxane A comprising epoxy functions and (meth)acrylate functions which can be used for example as an adhesion modulator or as an adhesion promoter or an organopolysiloxane A comprising only or essentially (meth)acrylate functions used for example as an essential constituent of radically crosslinkable silicone compositions to produce an elastomer. The molar ratio R between the (meth)acrylic acid and the epoxy functions of the organopolysiloxane E used in the process will be adapted accordingly.

[0058] According to one embodiment of the process according to the invention, in step a) the molar ratio R between the (meth)acrylic acid and the epoxy group(s) carried by the organopolysiloxane E is greater than 1.05 and preferably is between 1.05 and 15, and even more preferably is between 1.05 and 10.

[0059] As a reminder, throughout the document (meth)acrylic acid includes acrylic acid and methacrylic acid.

[0060] According to a preferred embodiment of the process according to the invention, in step a) the molar ratio R between the acrylic acid and the epoxy group(s) carried by the organopolysiloxane E is greater than 1.05 and preferably is between 1.05 and 15, and even more preferably is between 1.05 and 10.

[0061] Catalyst C is a chromium complex in oxidation state (III).

[0062] Catalyst C is a chromium complex of the following formula (1):

[0063] [CrCL s] (1) in which the symbols L 1 are identical or different ligands represent a P-diketonate anion.

[0064] Preferably, catalyst C is a chromium complex of the following formula (1):

[0065] [CrCL s] (1) in which the symbols L 1 are identical or different ligands represent an anion

[0066] P-diketonate represented by the following formula (V): where Ri and R3, identical or different, represent a C1 to C30 hydrocarbon radical, a C6 to C30 hydrocarbon radical comprising an aromatic ring, or Ri and R3 together form, with the atoms to which they are linked, a monocycle consisting of 6 to 10 carbon atoms, and

[0067] R2 is hydrogen or a C1 to C30 hydrocarbon radical, or R1 and R2 together form, with the atoms to which they are attached, a monocycle of 5 to 10 atoms.

[0068] According to a preferred embodiment, the identical or different ligands L1 represent a P-diketonate anion represented by the following formula (2): where R1 and R3, independently of each other, represent a C1 to C30 hydrocarbon radical, or a C6 to C30 hydrocarbon radical comprising an aromatic ring, and R2 is hydrogen or a C1 to C30 hydrocarbon radical. According to one embodiment of the invention, catalyst C is a chromium (III) complex of the following formula (1):

[0069] [CrCL s] (1) in which the symbols L 1are the same or different ligands represent a P-diketonate anion such as pentanedione-2,4; hexanedione-2,4; heptanedione-2,4; octanedione-2,4; nonanedione-2,4; decanedione-2,4; undecanedione-2,4; dodecanedione-2,4; heptanedione - 3,5; ethyl-3-pentanedione-2,4; methyl-5-hexanedione-2,4; octanedione-2,4; octanedione-3,5; dimethyl-5,5-hexanedione-2,4; methyl-6-heptanedione-2,4; dimethyl-2,2-nonanedione-3,5; dimethyl-2,6-heptanedione-3,5; 2-acetylcyclohexanone (Cy-acac ); 2,2,6,6-tetramethyl-3,5-heptanedione (t-Bu-acac ); l,l,l,5,5,5-hexafluoro-2,4-pentanedione (F -acac )]; benzoylacetone; dibenzoyl-methane; 3-methyl-2,4-pentadione; 3-acetyl-pentan-2-one; 3-acetyl-2-hexanone; 3-acetyl-2-heptanone; 3-acetyl-5-methyl-2-hexanone; stearoylbenzoylmethane; 4-t-butyl-4'-methoxy-dibenzoylmethane; 4,4'-dimethoxy-dibenzoylmethane, 4,4'-di-tert-butyl-dibenzoylmethane; 2,2,6,6-tetramethyl-3,5-heptanedione, , a P-diketone stearoylbenzoylmethane or l-phenyl-3-eicosanedione.

[0070] Preferably, catalyst C is a chromium complex of the following formula (1): [CrCL s] (1) in which the symbols L 1 are identical or different ligands represent a P-diketonate anion represented by the following formula (3): where R, identical or different, represent a C1 to C30 hydrocarbon radical, or a C6 to C30 hydrocarbon radical comprising an aromatic ring

[0071] According to a particularly advantageous embodiment, the catalyst C is a chromium P-diketonate with oxidation state (III) chosen from the group consisting of chromium (III) acetylacetonate (2,4-pentanedionate), chromium (III) hexafluoroacetylacetonate (1,1,1,5,5,5-hexafluoro-2,4-pentanedionate (F -acac)) (III), chromium 2,2,6,6-tetramethyl-

[0072] Chromium (III) 3,5-heptanedionate, chromium (III) 3,5-heptanedionate, 2,2,7-trimethyl-

[0073] Chromium (III) 3.5-octanedionate.

[0074] According to another embodiment of the process of the invention, chromium (III) P-diketonate can be generated in situ. According to one embodiment, the concentration of catalyst C expressed in mol% relative to the epoxy groups of organopolysiloxane E is between 0.05 and 1%, preferably between 0.05 and 0.5%, more preferably between 0.05 and 0.3% and even more preferably between 0.05 and 0.25%.

[0075] Another advantage of the process according to the invention is that it is possible to use a small amount of catalyst.

[0076] According to one embodiment of the method of the present invention, said method is carried out without solvent S.

[0077] According to a preferred embodiment of the invention, the process is characterized in that in step a), the composition X further comprises at least one solvent S chosen from the group consisting of methyl isobutyl ketone, methyl ethyl ketone, toluene, xylene, chlorobenzene and mixtures thereof.

[0078] Preferably, there is no solvent in the process according to the invention other than solvent S chosen from the group consisting of methyl isobutyl ketone, methyl ethyl ketone, toluene, xylene, chlorobenzene and their mixtures.

[0079] According to one embodiment of the process according to the invention, the content of solvent S used in step a) of the process as described above is from 0 to 15% by mass, preferably from 2% to 15% by mass, more preferably from 4 to 12% by mass, relative to the total mass of the reaction medium used in step a) of said process.

[0080] On the other hand, if the quantity of solvent S is greater than 15% by mass relative to the total mass of the reaction medium used in step a) of the process according to the invention, the reaction time necessary to achieve a conversion rate of the epoxy groups greater than 98% increases. Thus, it is important to find the right compromise between solubilization of the system and kinetics of the reaction.

[0081] According to one embodiment of the invention in step a) the catalyst C, the (meth)acrylic acid polymerization inhibitor, the solvent S and part or all of the (meth)acrylic acid may be pre-mixed before the addition of the organopolysiloxane E.

[0082] According to a preferred embodiment of the invention in step a) the catalyst C, the (meth)acrylic acid polymerization inhibitor, the solvent S, all of the (meth)acrylic acid and the organopolysiloxane E can be pre-mixed to form a premix before carrying out the process of the invention. For example, this premix can be prepared the day before being used in the process of the invention. This embodiment is particularly advantageous because it makes the process of the invention flexible and particularly suitable for industrial scale.

[0083] In the process according to the invention, in step a), a (meth)acrylic acid polymerization inhibitor is introduced. (Meth)acrylic acid polymerization inhibitors are widely known and, as examples, we can cite phenolic compounds such as 4-methoxyphenol, hydroquinone and methylhydroquinone or alkyldiphenylamines such as phenothiazine. Preferably, the methyl ether of hydroquinone (MEHQ) or 4-methoxyphenol is used as the (meth)acrylic acid polymerization inhibitor. According to a preferred embodiment, the amount of polymerization inhibitor used is between 0.01 and 1% by mass relative to the mass of the organopolysiloxane E and even more preferably between 0.01 and 0.5% relative to the mass of the organopolysiloxane E.

[0084] In step b) of the process according to the invention, the reaction medium obtained at the end of step a) is devolatilized. For this purpose, the reaction medium from step a) is heated to a temperature between 80 and 130°C under reduced pressure. This devolatilization step makes it possible to evaporate the solvent S and the excess (meth)acrylic acid. The solvent S used in the process according to the invention can be recycled.

[0085] According to another embodiment, a filtration step can further be carried out before or after step b). Preferably, if a filtration step is added to the process according to the invention, it takes place after step b).

[0086] According to another embodiment of the invention, the process according to the invention consists of the following steps: a) at least one organopolysiloxane E comprising at least one epoxy group is reacted at a temperature between 70 and 130°C, preferably between 90 and 130°C and even more preferably between 100 and 125°C, with acrylic acid or methacrylic acid or a mixture of the two, in the absence of alcohol and in the presence of:

[0087] - a catalyst C which is a chromium complex with the oxidation state (III) of the following formula (1) [CflL 1 ^] (1) in which the symbols L 1 identical or different represent a P-diketonate anion

[0088] - at least 4% by mass of a solvent S relative to the total mass of the reaction medium of this step a)

[0089] - an acrylic acid or methacrylic acid polymerization inhibitor, b) the reaction medium obtained at the end of step a) is devolatilized, c) optionally the reaction medium obtained at the end of step b) is filtered, and d) said composition X is obtained comprising at least one organopolysiloxane A.

[0090] When implementing the method, it is possible but not necessary to carry out steps a) and b) under an inert atmosphere. According to a preferred embodiment, when using a phenolic compound as an (meth)acrylic acid inhibitor, steps a) and b) of the method will be carried out under air and even more preferably under bubbling dry air.

[0091] Another subject of the invention relates to composition X capable of being obtained by the process described above.

[0092] Another subject of the invention relates to a method for producing a coating on a substrate comprising the following steps: a) a composition X is prepared according to the method as described above, b) a radically crosslinkable silicone composition W is prepared comprising: i. said composition X ii. a photoinitiator, and iii. Optionally at least one additive, c) said composition W is applied to a substrate, and d) said composition W is crosslinked by exposure to radiation.

[0093] Preferably, the substrate is a flexible support made of textile, paper, polyvinyl chloride, polyester, polypropylene, polyamide, polyethylene, polyethylene terephthalate, polyurethane or non-woven glass fibers.

[0094] According to a preferred embodiment of the invention in step d) the radiation is ultraviolet light with a wavelength of less than 420 nm. Mention may in particular be made, as a source of radiation, of light sources such as light-emitting diodes, better known by the acronym “LED” (Light-Emitting Diodes) which deliver point UV or visible light.

[0095] 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 can be between 1 and 1000 mW / cm 2 , preferably between 1 and 200 mW / cm 2 , preferably between 1 and 50 mW / cm 2 , and more preferably between 1 and 20 mW / cm 2The irradiation time can be short and is generally less than 1 second and is of the order of a few hundredths of a second for low coating thicknesses. The crosslinking obtained is excellent even in the absence of any heating.

[0096] According to another embodiment, crosslinking step d) takes place at a temperature between 40 and 100°C.

[0097] Of course, the curing time can be adjusted, in particular, by the number of lamps used, by the duration of UV exposure, by the wavelength of said lamps and by the distance between the composition and the lamp. The quantity of composition W deposited on the substrate is variable and most often ranges between 0.1 and 5g / m 2 of treated surface. This quantity depends on the nature of the support and the non-stick properties sought. It is most often between 0.5 and 1.5g / m 2 .

[0098] This process is particularly suitable for preparing a non-stick silicone coating on a substrate which is a flexible support made of textile, paper, polyvinyl chloride, polyester, polypropylene, polyamide, polyethylene, polyethylene terephthalate, polyurethane or non-woven glass fibers. These coatings are particularly suitable for their use in the field of non-stick.

[0099] To polymerize organopolysiloxanes having (meth)acrylate functions, a person skilled in the art will be able to choose a suitable radical photoinitiator absorbing light radiation with a wavelength of less than 420 nm. Examples of radical photoinitiators include: α-hydroxyketones, benzoin ethers and aromatic α-amino ketones. Examples of radical photoinitiators include the following: isopropylthioxanthone, benzophenone, camphorquinone, 9-xanthenone, anthraquinone, 1-4 dihydroxyanthraquinone, 2-methylanthraquinone, 2,2-bis(3-hydroxy-1,4-naphthoquinone), 2-6-dihydroxyanthraquinone, 1-hydroxycyclohexylphenylketone, 1,5-dihydroxyanthraquinone, 1,3-diphenyl-1,3-propanedione, 5,7-dihydroxyflavone, dibenzoylperoxide, 2-benzoylbenzoic acid, 2-hydroxy-2-methylpropiophenone, 2-phenylacetophenone, 2,4,6-trimethylbenzenoyldiphenphosphine oxide and its derivatives, anthrone, bis(2,6-trimethylbenzenoyldiphenphosphine oxide) and its derivatives. dimethylbenzoyl)-2,4,4-trimethylpentylphosphine, 4,4'- dimethoxybenzoin, phenantrenequinone, 2-ethylanthraquinone, 2-methylanthraquinone, 1,8- dihydroxyanthraquinone, dibenzoylperoxide, 2,2-dimethoxy-2-phenylacetophenone, benzoin, 2-hydroxy-2-methylpropiophenone, benzaldehyde, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-methylpropyl) ketone, benzoylacetone, ethyl(2,4,6- trimethylbenzoyl)phenylphosphinate and mixtures thereof. Examples of commercial radical photoinitiator products include the products marketed by CIBA-GEIGY: Irgacure ® 369, Irgacure ® 651, Irgacure ® 907, Darocure ® 1173, etc.,

[0100] The amount of photoinitiator in composition W is generally between 0.001 and 5%, most often between 0.005 and 3% by mass relative to the total mass of composition W.

[0101] As an additive, at least one additive for regulating the detachment force of a silicone / adhesive interface may be included in the composition, which additive is chosen from:

[0102] (i) organic (meth)acrylate derivatives, and

[0103] (ii) silicones with (meth)acrylate functions.

[0104] Suitable organic (meth)acrylate derivatives include, in particular, epoxidized (meth)acrylate compounds, (meth)acryloglyceropolyesters, (meth)acrylouretanes, (meth)acrylopoly ethers, (meth)acrylopolyesters, (meth)acrylo-acrylics.

[0105] More particularly preferred are trimethylolpropane triacrylate, tripropylene glycol diacrylate and pentaerythritol tetraacrylate.

[0106] According to a preferred variant of the invention, the additive used is a silicone with (meth)acrylate function(s). 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. Such acrylate derivatives are described in particular in patents EP 281718, FR2632960 and EP940458.

[0107] Other additives such as thiols or aromatic amines can be added to accelerate the crosslinking of composition W.

[0108] Thus, another object of the invention relates to a substrate comprising at least one coating capable of being obtained according to the method as described above.

[0109] Another subject of the invention relates to a method for producing an elastomer article by additive manufacturing comprising the following steps: a) preparing a composition X according to the method as described above, b) using an irradiation source and a photocrosslinkable silicone composition W2 comprising: i. said composition X ii. a photoinitiator, and iii. Optionally at least one additive, c) selectively irradiating at least a portion of the photocrosslinkable silicone composition W2 using the irradiation source to form a portion of the silicone elastomer article; and d) repeating step ii) a sufficient number of times to produce the silicone elastomer article.

[0110] Advantageously, the additive manufacturing method is a vat photopolymerization additive manufacturing method, in particular, by laser stereolithography (SLA) printing, by digital light processing (DLP), or by continuous liquid interface production (CLIP). These technologies and the equipment associated therewith are well known to those skilled in the art, who will be able 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.

[0111] Among the irradiation sources that can be used, mention may be made of mercury lamps which are commonly used in photopolymerization reactions of silicone compositions. In a particular embodiment of the method, the irradiation source is an LED lamp, preferably an LED lamp having a wavelength of 355, 365, 385 or 405nm.

[0112] Concerning, the nature of the photoinitiators and any additives used in the photocrosslinkable composition W2 are identical to those previously set out for the composition W. However, the photocrosslinkable silicone composition W2 may comprise a filler D. The filler D makes it possible to improve the mechanical properties of the silicone elastomer article obtained at the end of the method, while retaining good elastomeric properties. In particular, the filler D makes it possible to improve the modulus at break of the silicone elastomer article obtained, while retaining a high elongation at break.

[0113] A final object of the invention concerns the silicone elastomer article obtained according to said additive manufacturing process.

[0114] Examples:

[0115] Organopolysiloxanes E used in the examples: Organopoly siloxane El:

[0116] Organopolysiloxane E3: Organopolysiloxane E4:

[0117] Table 1: Summary of the different organopolysiloxanes E used in the examples

[0118] Example 1: Preparation of compositions comprising polyorganosiloxanes containing acrylate groups

[0119] In an IL reactor equipped with mechanical stirring, a refrigerant, an air inlet and a thermodynamic sheath are loaded under stirring:

[0120] - 68.4g of acrylic acid

[0121] - 0.332g of chromium (III) acetylacetonate (Cr(acac)s)

[0122] - 0.6g of 4-methoxyphenol (MEHQ)

[0123] - varying amounts of solvent (see table 1)

[0124] -500g of a polydimethylsiloxane oil E1, E2, E3 or E4 functionalized by epoxy groups with a dynamic viscosity at 25°C defined above.

[0125] Stirring is adjusted to 600 rpm, then the reactor is heated to 120°C with an aluminum hot plate while a depleted air flow of approximately (4L / h / kg of oil) is maintained. Samples are taken over time to measure the conversion rate of the epoxy groups by potentiometry. After the reaction times indicated in the table below, the mixture is devolatilized under vacuum (gradually up to 20mbar) while maintaining air bubbling to evaporate the acrylic acid that has not been consumed and the reaction solvents. After cooling, the composition obtained is filtered under pressure on a cellulose filter. The acrylate functions are determined by 1H NMR.

[0126] The acrylate yield is calculated as the ratio between the number of moles of acrylate dosed in the composition and the number of moles of theoretical acrylate calculated multiplied by 100. Thus, the time for the 96% acrylate yield is the reaction time required to achieve such a yield, noted t96% acrylate in Table 2 below.

[0127] In the table below, the comparative catalyst is Cr(OAc)3 introduced at 0.5mol% relative to the epoxide concentration for comparative tests 3 and 4. The comparative catalyst concentration is equal to 0.25mol% relative to the epoxide concentration for comparative tests 1 and 2.

[0128] Acrylation selectivity, denoted SA, is equal to the acrylation yield over the conversion rate of epoxy groups. The objective is to obtain the highest possible selectivity. The results are presented in the following table. *For comparative test 3, the conditions had to be drastically adapted in order to guarantee the solubility of the catalyst. Thus, on the one hand the catalyst content had to be reduced to guarantee its solubility and a premix containing acrylic acid, the solvent, the catalyst and the polymerization inhibitor had to be heated for 2 hours at 45 °C. Heating the reaction medium to 45 °C is necessary to guarantee the homogeneity of the reaction medium after the addition of one third of the total mass of epoxy oil 2. Then, the reaction medium is heated to 120 °C and the oil is added by pouring over a period of one hour. The subsequent steps of the process are identical to those of the process of the present invention.

[0129] **For comparative test 4, the conditions were also adapted as detailed above to allow for catalyst solubility and homogeneity of the reaction medium.

[0130] The various tests mentioned in the table above show that the process according to the invention makes it possible to obtain satisfactory yields and selectivity from very different organopolysiloxanes E. In addition, the operating conditions implemented in the tests of the present invention facilitate implementation on an industrial scale. This thus demonstrates the robustness and versatility of the process described according to the invention.

[0131] The comparative test in the presence of chromium acetate and n-butanol shows an acrylate selectivity of less than 95% (comparative test 1). Furthermore, as mentioned previously in the present application, the presence of n-butanol leads to the production of a product with an unpleasant odor.

[0132] Comparative tests in the presence of chromium acetate without butanol with the chromium (III) acetate catalytic system face implementation difficulties (comparative test 2) with certain organopoly siloxane E oils. This is explained in particular by poor solubility of the catalyst in these oils.

[0133] Thus, the process according to the present invention makes it possible to obtain very good yields and selectivities in acrylate from all types of organopolysiloxane E oils under conditions suitable and adaptable to industrial scale.

[0134] Example 2: Adaptability of the method of the present invention:

[0135] The operating conditions of the previous example were adapted to a 3L reactor with organopolysiloxane oil E2.

[0136] The table below implements the method of the present invention according to three different routes.

[0137] In test 1, the organopolysiloxane oil E2 was introduced by pouring into the reaction medium containing the other constituents at a temperature of 60°C and then the reactor was heated to 120°C under conditions similar to those described previously.

[0138] In test 2, the organopolysiloxane oil E2 was introduced into the reactor heated to 45°C, then the other constituents were added to the reactor which was then heated to 120°C under conditions similar to those previously explained.

[0139] In test 3, a premix made the day before consists of: - the dissolution of the catalyst Cr(acac)3 and the inhibitor 4-methoxyphenol (MeHQ) in acrylic acid in the presence of MIBK solvent at room temperature (21°C) for a period of 5 minutes.

[0140] - introduction of the mixture formed above into a reactor at room temperature (21°C), - addition of the E2 oil in its entirety and stirring for a period of 10 minutes at room temperature.

[0141] -stop stirring and let the reaction medium rest for 18 hours -then heat the reaction medium to 120°C to carry out the acrylate reaction.

[0142] The satisfactory miscibility of the catalytic system used in the context of the present invention allows the production of homogeneous premixes at room temperature which are directly introduced in a "one-pot" into the reactor to implement the process of the present invention. This flexibility makes it easier to implement such a process on an industrial scale by eliminating the need for pouring reactants, fractional heating or other obstacles to the industrialization of such a process.

Claims

CLAIMS

1. Process for the preparation of a composition X comprising at least one organopolysiloxane A comprising at least one (meth)acrylate group, said process comprising the following steps: a) at least one organopolysiloxane E comprising at least one epoxy group is reacted at a temperature between 50 and 130°C, preferably between 70 and 130°C and even more preferably between 90 and 125°C, with acrylic acid or methacrylic acid or a mixture of the two, and in the presence of: - a catalyst C which is a chromium complex in the oxidation state (III) of the following formula (1) [C^L 1 ^] (1) in which the symbols L 1 identical or different represent a P-diketonate anion, -in the presence of a solvent S which is not an alcohol, and - an acrylic acid or methacrylic acid polymerization inhibitor, b) the reaction medium obtained at the end of step a) is devolatilized c) said composition X is obtained comprising at least one organopolysiloxane A.

2. Process according to claim 1 characterized in that in step a) the molar ratio between the acrylic acid and the epoxy groups carried by the organopolysiloxane E is greater than 1.05 and preferably is between 1.05 and 15, and even more preferably is between 1.05 and 10.

3. Process according to claim 1 or 2 characterized in that in step a), the solvent S is chosen from the group consisting of methyl isobutyl ketone, methyl ethyl ketone, toluene, xylene, chlorobenzene and their mixtures.

4. Process according to claim 3 characterized in that in step a), the content of solvent S is comprised from 0 to 15% by mass, preferably from 2% to 15% by mass, more preferably from 4 to 12% by mass, relative to the total mass of the reaction medium used in said step a) of the process.

5. Process according to any one of the preceding claims, characterized in that the catalyst C is a chromium complex of the following formula (1): [CrCL s] (1) in which the symbols L 1 are identical or different ligands represent a P-diketonate anion represented by the following formula (2): where Ri and R3, identical or different, represent a C1 to C30 hydrocarbon radical, a C6 to C30 hydrocarbon radical comprising an aromatic ring, or Ri and R3 together form, with the atoms to which they are linked, a monocycle consisting of 6 to 10 carbon atoms, and R2 is hydrogen or a C1 to C30 hydrocarbon radical, or R1 and R2 together form, with the atoms to which they are attached, a monocycle of 5 to 10 atoms.

6. Process according to any one of the preceding claims, characterized in that the catalyst C is a chromium P-diketonate in oxidation state (III) chosen from the group consisting of chromium (III) acetylacetonate, chromium (III) hexafluoroacetylacetonate (III), chromium (III) 2,2,6,6-tetramethyl-3,5-heptanedionate, chromium (III) 3,5-heptanedionate, chromium (III) 2,2,7-trimethyl-3,5-octanedionate.

7. Process according to any one of the preceding claims, characterized in that the organopolysiloxane E comprises siloxyl units (I) and (II) of the following formulae: in which: a=1 or 2, b= 0, 1 or 2 and a+b= 1,2 or 3 c=0,1,2 or 3 -the symbols Y, identical or different, represent an organic group comprising an epoxy group and optionally further comprising one or more heteroatoms such as an oxygen atom, said organic group Y preferably having from 2 to 20 carbon atoms inclusive, and, more preferably still, Y is chosen from the group consisting of an alkylglycidyl ether, a linear, branched or cyclic epoxyalkyl, a linear, branched or cyclic epoxyalkenyl and a carboxylic acid glycidyl ester; - the Z symbols 1 and Z 2 , identical or different, represent a monovalent organic group having from 1 to 30 carbon atoms, preferably chosen from the group consisting of alkyl groups having from 1 to 8 carbon atoms and aryl groups having from 6 to 12 carbon atoms, and even more preferably chosen from the group consisting of a methyl, ethyl, propyl, 3,3,3-trifluoropropyl, xylyl, tolyl and phenyl group, and said organopolysiloxane E comprises, per molecule, at least two silicon atoms and at least one siloxyl unit (II).

8. Process according to claim 7, characterized in that in the siloxyl unit (I), the symbol Y is chosen from the group consisting of the organic groups (IV) to (VIII) of the following formulae:

9. Process according to any one of the preceding claims, characterized in that the organopolysiloxane E contains from 0.5 to 30% by mass of organic groups Y comprising an epoxy group, preferably from 1 to 20% by mass and even more preferably from 1 to 10% by mass relative to the total mass of organopolysiloxane E.

10. Composition X obtainable by the process described according to any one of claims 1 to 9.

11. A method for producing a coating on a substrate comprising the following steps: a) a composition X is prepared according to the method of any one of claims 1 to 9, b) a radically crosslinkable silicone composition W is prepared comprising: -said composition X -a photoinitiator, and - optionally at least one additive, c) said composition W is applied to a substrate, and d) said composition W is crosslinked by exposure to radiation

12. A method according to claim 11 wherein in step d) the radiation is ultraviolet light of wavelength less than 420nm.

13. Substrate comprising at least one coating obtainable according to the method of claim 11 or 12.

14. A method for producing an elastomer article by additive manufacturing comprising the following steps: a) preparing a silicone composition X according to the method as described above, b) using an irradiation source and a photocrosslinkable silicone composition W2 comprising: i. said silicone composition X ii. a photoinitiator, and iii. Optionally at least one additive, c) selectively irradiating at least a portion of the photocrosslinkable silicone composition W2 using the irradiation source to form a portion of the silicone elastomer article; and d) repeating step ii) a sufficient number of times to produce the silicone elastomer article.

15. Method according to claim 14, characterized in that the irradiation source is an LED lamp, preferably an LED lamp having a wavelength of 355, 365, 385 or 405nm.

16. Silicone elastomer article obtainable by the method described according to one of claims 14 or 15.

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