Depolymerization of silicone polymers into organopolysiloxanes

Abstract

The present invention relates generally to the reuse, reprocessing, or recycling of silicone polymers. More specifically, the process of the present invention relates to a method for preparing organopolysiloxanes (OR) by depolymerizing at least one silicone (S) in the presence of an acid catalyst and at least one chain blocker (Bc) having at least one siloxane functional group. These OR organopolysiloxanes can then be used in polymerization reactions or directly in various formulations.

Description

Title of the invention: Depolymerization of silicone polymers into or-ganopolysiloxanes technical field

[0001] The present invention relates generally to the reuse, reprocessing, or recycling of silicone polymers. More specifically, the process of the present invention relates to the depolymerization of silicone polymers to obtain lower molecular weight organopolysiloxanes (OR) that can subsequently be used in polymerization reactions or directly in various formulations. Prior art

[0002] A major societal and industrial challenge in the coming years is the ecological transition. Thus, from an economic point of view, the so-called "linear" economic model (take, manufacture, use, discard) must eventually be replaced by a so-called circular model.

[0003] A circular economy describes an economic system based on models that replace the concept of an end-of-life product with the reduction, alternative reuse, recycling and recovery of these materials in the production / distribution and consumption processes, with the aim of achieving sustainable development for the benefit of current and future generations.

[0004] With the ever-increasing growth of the silicone market and the proliferation of applications for such materials, the recycling of used silicone products is a major challenge in the silicone industry. Silicone recycling could reduce gas emissions (CO, CO2) related to the silicone industry by 75% and silicone waste by 65%.

[0005] Furthermore, cyclic silicones or organopolysiloxanes such as octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5) are and will be subject to restrictions on their use. In addition to the fact that these cyclic compounds present environmental risks due to their non-biodegradability, they are also suspected of being endocrine disruptors and potentially carcinogenic.

[0006] In this regard, in 2018 European regulations limited the content of D4 and D5 to 0.1% by mass in rinse-off cosmetic products. This regulation will soon be adopted for other cosmetic products as well as in other areas of silicone application.

[0007] Therefore, there is a need to provide processes for supplying silicone products that are free from, or at least have a low content of, cyclic silicones.

[0008] In the prior art, the depolymerization of organopolysiloxanes has been described by the implementation of different processes.

[0009] In 2002, the contents of patent application JP2002348407A disclosed a process for chemically transforming a silicone product, such as a silicone resin or a silicone mold, into linear polysiloxane. This process, however, requires a significant amount of acid catalyst, 12%, and the resulting product is mixed with cyclic compounds formed by a backbiting reaction. This reaction is commonly referred to as "backbiting."

[0010] More recently, in 2020, US patent application US20200377686 describes a process for recycling silicones (silicone oils, resins) by chemical transformation to obtain α,co-diacetoxypolydimethylsiloxane. However, this process requires heating the reaction medium and operating in excess of acetic anhydride.

[0011] Furthermore, the a,co-diacetoxypolydimethylsiloxane is chemically modifiable further to obtain a polydimethylsiloxane having terminal hydroxyl or acetoxyl groups which can be used in adhesive compositions or in sealants.

[0012] In 2022, US patent application 2022119617 describes a similar process. The α,co-diacetoxypolydimethylsiloxane obtained is re-engaged to obtain α,co-di-isopropoxypolydimethylsiloxane or a block polydimethylsiloxane-polyoxyalkylene polymer.

[0013] There is therefore an advantage to providing an alternative process for depolymerizing silicones into organopolysiloxanes that can be directly reused in subsequent formulations. In particular, there is an advantage to providing a catalytic system that allows this depolymerization to be carried out at lower temperatures, limits the amount of catalyst used, and enables a robust, selective, and flexible process. There is also an advantage to being able to reliably control the molecular mass of the products formed. This capability expands the potential uses and applications of such polymers. Summary of the invention

[0014] One objective of the present application is therefore to propose a silicone depolymerization process which allows control of the molecular mass of the final product while being able to vary the chemical nature of the terminal groups.

[0015] Another objective of the present application is to provide a catalytic system for the implementation of this process.

[0016] Another objective of the present application is to propose a simple and non-hazardous catalytic system compatible with industrialization of the process.

[0017] Another objective of the present application is to propose a satisfactory method for a from an industrial point of view and which is part of a so-called environmentally friendly chemistry.

[0018] Another objective of the present application is to obtain, at the end of this process, an organopolysiloxane OR having a low cyclic organopolysiloxane content.

[0019] Other objectives will become apparent upon reading the description of the invention which follows.

[0020] Surprisingly, the Applicant has developed a catalytic system that meets these expectations. Thus, the present invention relates to a process for preparing organopolysiloxanes OR, by a depolymerization reaction of at least one silicone S in the presence of an acid catalyst and at least one chain blocker Bc having at least one siloxane function.

[0021] In this case, the acid catalyst and the chain blocker Bc allow, during the depolymerization reaction, control of the molecular mass of the final product while allowing variation of the chemical nature of the terminal groups. Description of the implementation methods

[0022] Silicones, otherwise known as organopolysiloxanes, are polymeric materials comprising silicon and oxygen atoms alternating with various silicon-bound organic radicals.

[0023] In the context of the present invention, silicone, silicone products, silicone polymers, or organopolysiloxanes are defined as polymers comprising a siloxane (Si-O-Si) backbone having silicon and oxygen atoms alternating with various silicon-bonded organic radicals. These silicone polymers may be liquid or solid, depending on the molecular weight and the degree of cross-linking.

[0024] The silicones S of the invention can be of any type, they can be for example linear organopolysiloxanes O such as oils or gums, branched organopolysiloxanes O such as resins, crosslinked organopolysiloxanes such as gels or elastomers, or mixtures of such compounds.

[0025] The organopolysiloxane O can in particular be an oil, and preferably has a dynamic viscosity between 10,000 and 600,000 mPa.s at 25°C, preferably between 30,000 and 600,000 mPa.s at 25°C.

[0026] All viscosities referred to in this presentation correspond to a dynamic viscosity quantity at 25°C called “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.

[0027] The term gum is classically used for organopolysiloxane compounds having viscosities classically greater than 600,000 mPa.s, which corresponds with a molecular weight greater than 300,000 g / mol.

[0028] These organopolysiloxanes O may comprise one or more functional motifs such as: -OH; -H; - alkenyl in particular comprising 2 to 6 carbon atoms, preferably vinyl; - O-Alk with Alk represents an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms, preferably from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms, preferably methyl; - (O-Alk)x with Alk represents an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms, preferably from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms, preferably methyl, and x represents an integer between 2 and 200; - a linear or branched alkyl group comprising from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms, substituted by at least one fluorine atom, for example 1 to 10 fluorine atoms, for example (C1-C5) alkyl-CF3, the alkyl being linear or branched.

[0029] Preferably, the functional motifs are chosen from: -OH; -H; - alkenyl in particular comprising 2 to 6 carbon atoms, preferably vinyl; - a linear or branched alkyl group comprising from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms, substituted by at least one fluorine atom, for example 1 to 10 fluorine atoms, for example (C1-C5) alkyl-CF3, the alkyl being linear or branched.

[0030] Preferably, the organopolysiloxanes O may comprise one or more functional groups such as H, OH, alkenyl (preferably vinyl), aryl, cyclic amine, as defined above. The organopolysiloxanes O may be partially cross-linked. Organopolysiloxanes (O) can be, in particular, used organopolysiloxanes, such as those used as heat transfer fluids, which should be recycled. The process of the invention thus makes it possible to generate organopolysiloxanes (OR) that can then be directly used in industrial processes. When using used organopolysiloxanes (O), the resulting organopolysiloxane may contain other elements such as additives, pigments, etc. The inventors have shown that it is possible to carry out the depolymerization reaction and the formation of organopolysiloxanes (OR) under such conditions.

[0031] According to one embodiment of the invention, the organopolysiloxane O comprises: - at least 500 motifs, preferably at least 700 siloxyl motifs of formula (I): RcSiO(4 C) / 2(I) in which, R, whether identical or different, represents: -an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms, preferably from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms, preferably methyl, or an aryl group comprising 6 to 10 carbon atoms, preferably phenyl, and c = 0, 1, 2 or 3; and possibly one or more formula patterns (II): R1dReSiO(4 of) / 2(H) in which, R is as defined above; R1, whether identical or different, represents: -an alkenyl group comprising 2 to 6 carbon atoms, preferably vinyl, -a hydroxyl group (OH), -an (O-Alk) group, where Alk represents an alkyl group comprising 1 to 15 carbon atoms, preferably 1 to 12 carbon atoms, preferably 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, preferably OCH3 or OC2H5, -an (O-Alk)x group, where Alk represents an alkyl group comprising 1 to 15 carbon atoms, preferably 1 to 12 carbon atoms, preferably 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, preferably methyl, and x represents an integer between 2 and 200, -a linear or branched alkyl group comprising from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms, substituted by at least one fluorine atom, for example 1 to 10 fluorine atoms, for example (Ci-C5)alkyl-CF3, the alkyl being linear or branched, or -a hydrogen; d=l, 2 or 3, preferably d=l or 2, more preferably d=l; e=0, 1 or 2; and the sum d+e=l, 2 or 3.

[0032] It is understood in the above formulas that, if several R groups are present or if several R1 groups are present, they may be identical or different from each other.

[0033] Preferably, in the above formulas R1, identical or different, represents: - an alkenyl group comprising 2 to 6 carbon atoms, preferably vinyl, - a hydroxyl group (OH), - a linear or branched alkyl group comprising from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms, substituted by at least one fluorine atom, by example 1 to 10 fluorine atoms, for example (Ci-C5)alkyl-CF3, the alkyl being linear or branched, or -a hydrogen.

[0034] In the present invention: - a siloxyl motif "M" represents a siloxyl motif with the formula Y3SiOi / 2, - a siloxyl motif "D" represents a siloxyl motif with the formula Y2SiO2 / 2, - a siloxyl motif "T" represents a siloxyl motif with the formula YSiO3 / 2, - a siloxyl motif "Q" represents a siloxyl motif with the formula SiO4 / 2, the symbols Y being R or R1.

[0035] The organopolysiloxane O may optionally be linear or branched and in particular include T and Q motifs.

[0036] According to a preferred method, the organopolysiloxane O is chosen from among the compounds of formula (III): R'aR(3 a)SiO-(SiR2O)nl-(SiR1RO)ml-SiR1aR(3 a) (III) in which: R, whether identical or different, represents: -an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms, preferably from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms, preferably methyl, or -an aryl group comprising 6 to 10 carbon atoms, preferably phenyl; R1, whether identical or different, represents: - an alkenyl group comprising 2 to 6 carbon atoms, preferably vinyl, -a hydroxyl group (OH), -an (O-Alk) group where Alk represents an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms, preferably from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms, preferably OCH3 or OCH2H5, -a (O-Alk)x group where Alk represents an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms, preferably from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms, preferably methyl, and x represents an integer between 2 and 200, -a linear or branched alkyl group comprising from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms, substituted by at least one fluorine atom, for example 1 to 10 fluorine atoms, for example (Ci-C5)alkyl-CF3, the alkyl being linear or branched, or -a hydrogen; a is an integer and represents 0, 1, 2 or 3, preferably 0, 1 or 2, more preferably 0 or 1; -ni represents an integer between 500 and 10,000, preferably between 1,000 and 5,000, preferably between 500 and 5,000, more preferably between 600 and 2,000; -ml represents an integer between 0 and 100, preferably between 0 and 50, more preferably between 0 and 30, preferably m=0.

[0037] In a particularly preferred manner, organopolysiloxane O is a compound of formula (III) in which R1, identical or different, represents: -an alkenyl group comprising 2 to 6 carbon atoms, preferably vinyl, -a hydroxyl group (OH), -a linear or branched alkyl group comprising from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms, substituted by at least one fluorine atom, for example 1 to 10 fluorine atoms, for example (Ci-C5)alkyl-CF3, the alkyl being linear or branched, or -a hydrogen.

[0038] In a particularly preferred manner, organopolysiloxane O is a compound of formula (III) in which R1, identical or different, represents: -CH3, vinyl, H, (Ci-C5)alkyl-CF3 or OH.

[0039] In a particularly preferred manner, organopolysiloxane O is a compound of formula (III) in which, R, identical or different, represents CH3 or phenyl, preferably CH3; R1, whether identical or different, represents: -an alkenyl group comprising 2 to 6 carbon atoms, preferably vinyl, -a hydroxyl group (OH), -a linear or branched alkyl group comprising from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms, substituted or not by at least one fluorine atom, for example 1 to 10 fluorine atoms, for example (Ci-C5)alkyl-CF3, the alkyl being linear or branched, or -a hydrogen.

[0040] In a particularly preferred manner, organopolysiloxane O is a compound of formula (III) in which, R, identical or different, represents CH3 or phenyl, preferably CH3; R1, identical or different, represents CH3, vinyl, H, (C1-C5)alkyl-CF3, or OH.

[0041] The silicones S of the invention may also be of the type of crosslinked silicone material, such as gels or elastomers. Crosslinked silicone materials are well known to those skilled in the art. These materials may, in particular, be obtained by polycondensation, radical polymerization, thermal polyaddition, or UV irradiation.

[0042] Silicone products have a multitude of applications. By way of illustration, they can be found in food applications such as, for example, Silicone is used in baking molds, medical and pharmaceutical applications such as baby bottle teats, catheters, implants, and medical tubing. In technical industrial applications, silicone is often used as a material for seals or membranes. In the automotive sector, it is used for hoses, cable sheathing or insulation, and as a damping material.

[0043] Silicone elastomers are cross-linked silicone materials comprising fillers, such as silica, to obtain good mechanical properties.

[0044] By varying the silicone oils, fillers and additives as well as the crosslinking method, silicone elastomers exhibit different properties and colours.

[0045] Silicone elastomers can be divided into three main groups well known to those skilled in the art. High-temperature vulcanizable rubber (HTV) elastomers are silicone elastomers obtained from silicone compositions with very high viscosity, comprising silicone gums and fillers. They are vulcanized at high temperatures, generally between 140 °C and 200 °C. Crosslinking is either radical-catalyzed by peroxides or achieved by an addition reaction where platinum compounds are used as catalysts.

[0046] Liquid silicone rubber (LSR) is a type of silicone elastomer obtained from compositions comprising viscous silicone oils and fillers. Crosslinking occurs via an addition reaction at temperatures similar to those of viscous silicone rubber (VSR), although crosslinking generally occurs much more rapidly.

[0047] The third group consists of silicones obtained by room-temperature crosslinking of silicone compositions from silicone oils and fillers, crosslinking by polycondensation or polyaddition reactions. These elastomers are known in French as cold-vulcanizable silicone elastomer (EVF, in English room temperature vulcanization (RTV)). These compositions are available in one- and two-component systems.

[0048] In the process of this application, silicone S also means silicone-based materials, for example, materials comprising at least 0.1% by mass of silicone relative to the total mass of silicone-based material. These materials are commonly found in silicone-coated textiles (airbags or synthetic leather) and silicone coatings (food-grade paper).

[0049] The silicone-based material may comprise up to 100% silicone by mass, preferably up to 99.9% silicone by mass relative to the total mass of silicone-based material. These silicone-based materials may also comprise additives or fillers such as colorants, silica, or carbonate. calcium, calcium oxide, celite, quartz, titanium oxide, cerium hydroxide, magnesium oxide, mica, etc.

[0050] According to one embodiment, silicone S comprises silica, calcium oxide, quartz, titanium oxide, magnesium oxide, mica and mixtures thereof.

[0051] In the context of the present invention, the number of moles of (Si-O) means the number of moles of (Si-O) bonds of silicone S.

[0052] In the case where the starting silicone S is of unknown formula, particularly in the case of formulated commercial products, it is possible to estimate the number of moles of (Si-O) bonds. Indeed, for formulated silicone elastomers, those skilled in the art know that the amount of filler is between 20 and 40% by mass; thus, estimating the average amount of filler at 30% by mass, we have 70% silicone by mass, which allows us to calculate the number of moles of (Si-O) bonds from the average molar mass of the repeating unit.

[0053] In the context of this application, the chain blocker term Bc has at least one siloxane function.

[0054] In the process of the invention, the chain blocker Bc is represented by formula (IV): [Chem 1] in which, R1, whether identical or different, represents: -a linear or branched alkyl group comprising from 1 to 12 carbon atoms, preferably from 1 to 8 carbon atoms, optionally substituted by an O, N, S heteroatom or a halide, -an alkenyl group comprising 2 to 6 carbon atoms, -a cycloalkyl group of 5 to 10 carbon atoms, possibly substituted by an O, N, S heteroatom or a halide, -an aryl group in C6-Ci8, -a hydroxyl group, or -a hydrogen, R2, whether identical or different, represents: -an alkenyl group comprising 2 to 6 carbon atoms, preferably vinyl, -a hydroxyl group (OH), -a linear or branched alkyl group comprising from 1 to 12 carbon atoms, preferably from 1 to 5 carbon atoms, optionally substituted by at least one O, N, S heteroatom or a halide such as a fluorine atom, for example 1 to 10 fluorine atoms, for example (Ci-C5)alkyl-CF3, the alkyl being linear or branched; or -a hydrogen; and q is an integer between 1 and 50, preferably between 1 and 20, more preferably between 1 and 10.

[0055] In another embodiment, the chain blocker Bc is represented by formula (IV) in which: R1, identical or different, represents CH3 or phenyl, preferably CH3; R2, whether identical or different, represents: -an alkenyl group comprising 2 to 6 carbon atoms, preferably vinyl, -a hydroxyl group (OH), -a linear or branched alkyl group comprising from 1 to 12 carbon atoms, preferably from 1 to 5 carbon atoms, optionally substituted by at least one O, N, S heteroatom or a halide such as a fluorine atom, for example 1 to 10 fluorine atoms, for example (Ci-C5)alkyl-CF3, the alkyl being linear or branched, -a C5-C10 cycloalkyl group, possibly substituted, -an aryl group at C6-Ci8, possibly substituted, or -a hydrogen; and q is an integer between 1 and 50, preferably between 1 and 20, more preferably between 1 and 10.

[0056] In a particularly preferred manner, the chain blocker Bc of the invention is represented by formula (IV), in which: R1, identical, represents CH3 R2, whether identical or different, represents: -an alkenyl group comprising 2 to 6 carbon atoms, preferably vinyl, -a hydroxyl group (OH), -a linear or branched alkyl group comprising from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms, -an aryl group at C6-Ci8, possibly substituted, or -a hydrogen. and q is an integer between 1 and 20, preferably between 1 and 10, more preferably between 1 and 5.

[0057] Other blockers having a siloxane function according to the invention are described in the book Chemistry and Technology of Silicones, published in 1968 by Academy Press, on page 264.

[0058] The chain blocker Bc can be in a solvent. This is particularly advantageous for solubilizing it in the reaction medium. The solvent can be, in particular, a nonpolar solvent such as an organic solvent of the alkane type, or an aromatic hydrocarbon. Preferably, the solvent is chosen from n-hexane, n-heptane, n-decane, n-dodecane, isododecane, EXXSOL D60, xylene, toluene and mixtures thereof.

[0059] The quantity of chain blocker Bc implemented in the process of the invention is at least 10⁴ moles relative to the bonding moles (Si-O), in silicone S, preferably between 10³ and 5x10¹ mol, preferably between 10³ and 10² mol, even more preferably between 3x10³ and 6x10¹ mol, for example 5x10³ mol relative to the bonding moles (Si-O) in silicone S.

[0060] These chain blockers enable the functionalization of the OR organopolysiloxane during the depolymerization reaction. Thus, it is possible to obtain OR organopolysiloxanes having, for example, Si-vinyl or Si-H functional groups.

[0061] In the process according to the invention, a mixture of different chain blockers may optionally be used. Thus, an organopolysiloxane OR may be obtained which may have different functional groups at the end of the chain.

[0062] In an alternative embodiment, the process of the invention can be implemented without chain blocker Bc.

[0063] The acid catalyst used as a catalyst in the process of the present invention is chosen from the group comprising Brønsted acids having a pKa less than or equal to 2 such as trifluoromethanesulfonic acid, benzenesulfonic acid and its derivatives alone or in mixtures.

[0064] Preferably, the acid catalyst is chosen from benzenesulfonic acid and its derivatives of formula (V), alone or in mixtures: [Chem 2] G / OH | I Formula (V) R with R= H or CnH2n+iWHERE l <n<20.

[0065] More preferably, the acid catalyst is chosen from derivatives of benzenesulfonic acid of formula (VI), alone or in mixtures: [Chem 3] C \\ _ / 0H ;s" romtide (VQ R) with R = CnH2n+10 ... <n<20, de préférence 10<n<20.

[0066] Even more preferably, the acid catalyst is HDBS also known as 4-dodecylbenzenesulfonic acid (CAS 121-65-3).

[0067] Alternatively, the acid catalyst is chosen from among the Brønsted acids having a pKa less than or equal to -2 such as perfluoroalkane acids, for example trifluoromethanesulfonic acid (triflic acid), pentafluoroethanesulfonic acid, heptafluoropropanesulfonic acid, or chlorinated derivatives, alone or in mixtures.

[0068] Depending on the nature of the acid catalyst, it is possible to dissolve it in a solvent. Preferably, the solvent is a nonpolar solvent. The solvent may, in particular, be an organic solvent of the alkane or aromatic hydrocarbon type. Preferably, the solvent is the same as that chosen for the depolymerization reaction. Thus, the solvent may, in particular, be an organic solvent of the alkane or aromatic hydrocarbon type.

[0069] The quantity of acid catalyst used in the process of the invention is between 0.001 and 3% by mass relative to the mass of silicone S, preferably between 0.05 and 1%, more preferably between 0.1 and 1%, for example 0.4% by mass relative to the mass of silicone S.

[0070] In one embodiment, the organopolysiloxanes OR which may have at the end of the chain functional groups from the chain blocker such as vinyl functions, Si-H functions, Si-aryl functions for example.

[0071] Depending on the implementation of the process, they may be identical or different. The organopolysiloxane OR as defined above may optionally comprise T and Q motifs.

[0072] According to one embodiment of the invention, the organopolysiloxane OR comprises: - at least 2 siloxyl motifs of formula (VII): [R2R*2Si(OSiR12)q]-O-SiRcO(3_cy2(Vn) in which, R, whether identical or different, represents: -an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms, preferably from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms, preferably methyl, -an aryl group comprising 6 to 10 carbon atoms, preferably phenyl, c = 1, 2 or 3; R1, whether identical or different, represents: -a linear or branched alkyl group comprising from 1 to 12 carbon atoms, preferably from 1 to 8 carbon atoms, optionally substituted by an O, N, S heteroatom or a halide, -an alkenyl group comprising 2 to 6 carbon atoms, -a cycloalkyl group of 5 to 10 carbon atoms, possibly substituted by an O, N, S heteroatom or a halide, -an aryl group in C6-Ci8, -a hydroxyl group, or -a hydrogen R2, whether identical or different, represents: -an alkenyl group comprising 2 to 6 carbon atoms, preferably vinyl, -a hydroxyl group (OH), -a linear or branched alkyl group comprising from 1 to 12 carbon atoms, preferably from 1 to 5 carbon atoms, optionally substituted by at least one O, N, S heteroatom or a halide such as a fluorine atom, for example 1 to 10 fluorine atoms, for example (Ci-C5)alkyl-CF3, the alkyl being linear or branched, -a C5-C10 cycloalkyl group, optionally substituted, -a C6-Ci8 aryl group, optionally substituted, or -a hydrogen; q is an integer between 1 and 50, preferably between 1 and 20, more preferably between 1 and 10. and one or more formula motifs (VIII), preferably from 10 to 1,500 motifs, preferably from 50 to 1,000 motifs and even more preferably from 100 to 500 motifs: SiR3dReO(4-de) / 2(Formula VIII) in which, R, identical or different, is as defined previously; R3, identical or different is such as defined previously by the group R1; and d= 0,1, 2, preferably d=0 or 1; e= 1, 2 or 3; and the sum d+e=1, 2 or 3.

[0073] Preferably, in the above formulas R3, whether identical or different, represents: - an alkenyl group comprising 2 to 6 carbon atoms, preferably vinyl; - a hydroxyl group (OH); - a linear or branched alkyl group comprising from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms, substituted by at least one fluorine atom, for example 1 to 10 fluorine atoms, for example (Ci-C5)alkyl-CF3, the alkyl being linear or branched; -a hydrogen.

[0074] According to one embodiment of the invention, the organopolysiloxane OR can be a compound of formula (IX): [Chem 4] in which, R, identical or different, represents: -an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms, preferably from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms, preferably methyl, -an aryl group comprising 6 to 10 carbon atoms, preferably phenyl, R1, whether identical or different, represents: -an alkenyl group comprising 2 to 6 carbon atoms, preferably vinyl, -a hydroxyl group (OH), -an (O-Alk) group where Alk represents an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms, preferably from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms, preferably OCH3 or OCH2H5, -an (O-Alk)x group where Alk represents an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms, preferably from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms, preferably methyl, and x represents an integer between 2 and 200, or -a hydrogen; R2, whether identical or different, represents: -an alkenyl group comprising 2 to 6 carbon atoms, preferably vinyl, -a hydroxyl group (OH), -a linear or branched alkyl group comprising from 1 to 12 carbon atoms, preferably from 1 to 5 carbon atoms, optionally substituted by at least one O, N, S heteroatom or a halide such as a fluorine atom, for example 1 to 10 fluorine atoms, for example (Ci-C5)alkyl-CF3, the alkyl being linear or branched, -a C5-C10 cycloalkyl group, possibly substituted, -an aryl group at C6-C ^possibly substituted, or -a hydrogen; q is an integer between 1 and 50, preferably between 1 and 20, more preferably between 1 and 10; n2 represents an integer between 10 and 1500, preferably between 10 and 1000, preferably between 50 and 1000, more preferably between 100 and 500; m2 represents an integer between 0 and 100, preferably between 0 and 50, more preferably between 0 and 30, preferably m=0.

[0075] According to a preferred embodiment of the invention, the organopolysiloxane OR is a compound of formula (IX): in which, R identical or different, represents CH3 or phenyl, preferably CH3; R1, whether identical or different, represents: -an alkenyl group comprising 2 to 6 carbon atoms, preferably vinyl, -a hydroxyl group (OH), -a linear or branched alkyl group comprising from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms, substituted by at least one fluorine atom, for example 1 to 10 fluorine atoms, for example (Ci-C5)alkyl-CF3, the alkyl being linear or branched, or -a hydrogen; R2, whether identical or different, represents: -an alkenyl group comprising 2 to 6 carbon atoms, preferably vinyl, -a hydroxyl group (OH), -a linear or branched alkyl group comprising from 1 to 12 carbon atoms, preferably from 1 to 5 carbon atoms, optionally substituted by at least one O, N, S heteroatom or a halide such as a fluorine atom, for example 1 to 10 fluorine atoms, for example (Ci-C5)alkyl-CF3, the alkyl being linear or branched, -a C5-C10 cycloalkyl group, possibly substituted, -an aryl group at C6-Ci8, possibly substituted, or -a hydrogen; q is an integer between 1 and 50, preferably between 1 and 20, more preferably between 1 and 10; n2 represents an integer between 10 and 1500, preferably between 10 and 1000, preferably between 50 and 1000, more preferably between 100 and 500; m2 represents an integer between 0 and 100, preferably between 0 and 50, more preferably between 0 and 30, preferably m=0.

[0076] According to a particularly preferred embodiment of the invention, the organopolysiloxane OR of the invention is a compound of formula (IX) in which, R, whether the same or different, represents CH3 or phenyl, preferably CH3. R1, identical or different, represents CH3, vinyl, H, (C1-C5) alkyl-CF3 or OH; R2, whether identical or different, represents: -an alkenyl group comprising 2 to 6 carbon atoms, preferably vinyl, -a hydroxyl group (OH), -a linear or branched alkyl group comprising from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms, -an aryl group at C6-Ci8, possibly substituted, or -a hydrogen; q is an integer between 1 and 20, preferably between 1 and 10, more preferably between 1 and 5; n2 represents an integer between 10 and 1500, preferably between 10 and 1000, preferably between 50 and 1000, more preferably between 100 and 500; m2 represents an integer between 0 and 100, preferably between 0 and 50, more preferably between 0 and 30, preferably m=0.

[0077] In one embodiment, the organopolysiloxane OR of the invention is a compound of formula (X) in which: [Chem 5] R, identical or different, represents: -an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms, preferably from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms, preferably methyl, -an aryl group comprising 6 to 10 carbon atoms, preferably phenyl, R1, whether identical or different, represents: -an alkenyl group comprising 2 to 6 carbon atoms, preferably vinyl, -a hydroxyl group (OH), -an (O-Alk) group where Alk represents an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms, preferably from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms, preferably OCH3 or OCH2H5, -a (O-Alk)x group where Alk represents an alkyl group comprising from 1 to 15 carbon atoms, preferably from 1 to 12 carbon atoms, preferably from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms, preferably methyl, and x represents an integer between 2 and 200, -a linear or branched alkyl group comprising from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms, substituted by at least one fluorine atom, for example 1 to 10 fluorine atoms, for example (Cl-C5)alkyl-CF3, the alkyl being linear or branched, -a hydrogen, or - a group -CH2CH2(R3SiO)n3 with R as defined previously and n3 represents an integer between 0 and 1000, preferably between 0 and 500, more preferably between 0 and 200; R2, whether identical or different, represents: -an alkenyl group comprising 2 to 6 carbon atoms, preferably vinyl, -a hydroxyl group (OH), -a linear or branched alkyl group comprising from 1 to 12 carbon atoms, preferably from 1 to 5 carbon atoms, optionally substituted by at least one O, N, S heteroatom or a halide such as a fluorine atom, for example 1 to 10 fluorine atoms, for example (Ci-C5)alkyl-CF3, the alkyl being linear or branched, -a C5-C10 cycloalkyl group, optionally substituted, -a C6-Ci8 aryl group, optionally substituted, or -a hydrogen; q is an integer between 1 and 50, preferably between 1 and 20, more preferably between 1 and 10; n2 represents an integer between 10 and 1500, preferably between 10 and 1000, preferably between 50 and 1000, more preferably between 100 and 500; m2 represents an integer between 0 and 100, preferably between 0 and 50, more preferably between 0 and 30, preferably m=0; n3 represents a different or identical integer between 0 and 1000, preferably between 0 and 500, more preferably between 0 and 200; a represents an integer, different from or the same as 0 or 1.

[0078] For the purposes of the present invention, degree of polymerization means the integer representing the number of siloxyl repeat units.

[0079] According to one embodiment of the process of the invention, the organopolysiloxane OR thus obtained has a degree of polymerization at least divided by two compared to the degree of polymerization of the silicone S introduced, preferably at least divided by three, preferably at least divided by five compared to the degree of polymerization of the silicone S introduced.

[0080] According to one embodiment of the process of the invention, the organopolysiloxane OR thus obtained has a degree of polymerization at least divided by ten compared to the degree of polymerization of the silicone S introduced.

[0081] For the purposes of the present invention, the average molecular mass by mass and the mass The number-average molecular weights, denoted respectively Mw and Mn, of the different organopolysiloxanes OR can be determined by size exclusion chromatography (SEC) in the presence of polystyrene standards in a solvent such as toluene at 40°C.

[0082] According to one embodiment of the process of the invention, the organopolysiloxanes OR thus obtained has a mass average molecular weight Mw at least half that of the mass average molecular weight of the silicone S introduced, preferably at least three times, preferably at least five times that of the mass average molecular weight Mw of the silicone S introduced

[0083] It is also conceivable that, according to one embodiment of the process of the invention, the organopolysiloxanes OR thus obtained has a mass average molecular weight Mw at least divided by ten compared to the mass average molecular weight of the silicone S introduced, or at least divided by fifteen compared to the mass average molecular weight Mw of the silicone S introduced

[0084] According to one embodiment of the process of the invention, the organopolysiloxane OR of the invention is characterized in that its mass average molecular mass Mw can be between 500 and 300,000 g / mol, preferably between 1,000 and 150,000 g / mol, preferably between 1,000 and 100,000 g / mol, even more preferably between 5,000 and 40,000 g / mol.

[0085] According to one embodiment of the process of the invention, the organopolysiloxanes OR thus obtained has a number-average molecular weight Mn at least half that of the number-average molecular weight of the silicone S introduced, preferably at least three times, preferably at least five times that of the number-average molecular weight Mn of the silicone S introduced

[0086] It is also conceivable that, according to an embodiment of the process of the invention, the organopolysiloxanes OR thus obtained has a number-average molecular mass (Mn) at least divided by ten compared to the mass-average molecular mass (Mn) of the silicone S introduced, or at least divided by fifteen compared to the number-average molecular mass (Mn) of the silicone S introduced

[0087] According to one embodiment of the process of the invention, the organopolysiloxane OR of the invention is characterized in that its average molecular mass in number Mn is between 500 and 300,000 g / mol, preferably between 1,000 and 150,000 g / mol, preferably between 1,000 and 70,000 g / mol and even more preferably between 2,500 and 30,000 g / mol.

[0088] According to one embodiment of the process of the invention, the organopolysiloxane OR of the invention is characterized in that its dynamic viscosity is between 100 and 100,000 mPa.s at 25 °C, preferably between 1,000 and 80,000 mPa.s at 25 °C, even more preferably between 10,000 and 70,000 mPa.s at 25 °C.

[0089] In one embodiment, the organopolysiloxane of the invention OR has a quantity of (Si-OH) bonding at the end of the chain less than or equal to 15%, preferably less than or equal to 10%, preferably less than or equal to 5% and even more preferably less than or equal to 1% relative to the total quantity of silicon atoms at the end of the chain of the organopolysiloxane of the invention OR.

[0090] In the context of this application, the mass percentage or weight percentage of D4 in the products obtained according to the process of the present invention can be measured via quantitative 29Si NMR spectra. Alternatively, the mass percentage or weight percentage of D4 in the products obtained according to the process of the present invention could be measured via chromatograms obtained from size exclusion chromatography (SEC) analysis.

[0091] For the purposes of the present invention, cyclic organopolysiloxanes are defined as compounds of formula (XI): [Chem 6] in which, n represents a natural number between 1 and 5.

[0092] Generally, in the sense of the present invention, cyclic organopolysiloxanes consist of compounds of formula (XI) where n is equal to 2 or 3 or 4.

[0093] In other words, octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), dodecamethylcyclohexasiloxane (D6) or mixtures thereof.

[0094] In one embodiment, the process according to the invention is characterized in that the content of cyclic organopolysiloxanes is less than 5%, preferably less than or equal to 3%, preferably less than or equal to 2% and even more preferably less than or equal to 1.5% relative to the total mass of the organopolysiloxanes of the invention OR.

[0095] In one embodiment, the process according to the invention is characterized in that the content of octamethylcyclotetrasiloxane (D4) is less than 5%, preferably less than or equal to 3%, preferably less than or equal to 2% and even more preferably less than or equal to 1.5% relative to the total mass of the organopolysiloxanes of the invention OR.

[0096] Preferably, the process of the invention is carried out in a solvent. The process of the invention is preferably carried out in a nonpolar solvent. The solvent may, in particular, be an organic solvent of the alkane or hydrocarbon type. aromatic.

[0097] Preferably, the solvent is chosen from n-hexane, n-heptane, n-decane, n-dodecane, isododecane, EXXSOL D60, xylene, toluene and mixtures thereof.

[0098] In one embodiment, the process of the invention is characterized in that the mass ratio, mass of silicone S relative to the mass of solvent involved is between 0.01 and 15, preferably between 0.1 and 5, preferably between 0.1 and 2.

[0099] In one embodiment, the process of the invention is characterized in that the depolymerization reaction takes place without solvent.

[0100] This embodiment is particularly advantageous because it eliminates the need for solvent, its treatment or recycling once used, while still obtaining satisfactory results when carrying out the process of the present invention.

[0101] Advantageously, and preferably, the reaction is carried out at a temperature between 0 and 100°C, preferably between 0 and 50°C, more preferably between 10 and 35°C, for example at room temperature.

[0102] According to the process of the invention, the duration of the reaction is between 2 and 72h, preferably between 5 and 24h, more preferably between 8 and 24h, for example 24h.

[0103] A person skilled in the art will be able to adapt these parameters according to the nature of the reactors and the species used.

[0104] The process according to the invention may further include a step of neutralizing the acid catalyst. This neutralization step prevents the occurrence of side reactions and deactivates the acid catalyst.

[0105] Advantageously, this neutralization step is carried out by adding a base to the reaction medium or by thermal degradation of the acid catalyst.

[0106] According to the process of the invention, the base is chosen from among amines, alkali metal hydroxides, alkaline earth metal hydroxides, carbonates, hydrogen carbonates, and mixtures thereof.

[0107] Preferably, the base is chosen from the group of tertiary amines or hydrogen carbonates.

[0108] Alternatively, the neutralization step is carried out by "thermal degradation".

[0109] "Thermal degradation" means heating to a temperature above 120°C for a period of between 10 minutes and 3 hours. Those skilled in the art will know how to adapt the operating conditions to optimize this thermal degradation step. This step degrades the catalyst and stops the depolymerization reaction.

[0110] The process according to the invention may further include a filtration step to extract the neutralized catalyst and / or excess base from the reaction medium. This This step can also allow the extraction of any fillers from the depolymerized silicone S according to the process of the present invention. Those skilled in the art will be able to adapt the filtration method according to the size of the reactor and the species used in the process according to the invention.

[0111] According to a preferred embodiment of the invention, the process of the present invention comprises the following three steps: 1) Implementation of the process for preparing organopolysiloxanes OR, by a depolymerization reaction of at least one silicone S in the presence of an acid catalyst and at least one chain blocker Bc having at least one siloxane function; 2) Neutralization of the acid catalyst mentioned in the previous step by adding a base to the reaction medium or by thermal degradation of the acid catalyst; and 3) Filtration of the reaction mixture obtained at the end of step 2.

[0112] This application also relates to the use of the OR organopolysiloxanes obtained according to the process of the present invention as an ingredient that can be directly used in various silicone formulations useful in fields such as cosmetics, household cleaning products, automotive, energy.

[0113] The organopolysiloxanes OR derived from silicone S as detailed earlier in this application, can be re-engaged in various formulations to prepare a new silicone S.

[0114] Thus, the present application also relates to the use of the organopolysiloxanes OR obtained by the process of the present invention for the preparation of silicone S, for example for the preparation of silicone oils, resins, gums, gels or elastomers.

[0115] This application also relates to a process for preparing silicone, in particular silicone oils, resins or gums, comprising the following steps: 1) Implementation of the process for preparing organopolysiloxanes OR according to the invention; 2) Preparation of silicone S, in particular oils, resins, gums, or elastomers from the organopolysiloxanes OR obtained in step 1).

[0116] In one embodiment, the silicone S preparation process is characterized in that step 2 is implemented by a polyaddition reaction, polycondensation reaction, cationic mechanism or radical mechanism.

[0117] Step 2 may in particular consist of manufacturing liquid silicone elastomers (LSR), hot vulcanizable silicone elastomers (EVC) or cold vulcanizable silicone elastomers (RTV).

[0118] According to another embodiment, step 2 may in particular consist of preparing silicones S useful in the fields of cosmetics, health, household products, technical industrial formulations (seals, membranes, tubes), and transportation such as the automotive or aviation industries, or even in the energy sector. Silicones used in the examples:

[0119] In what follows Me = Methyl; SI silicone: [Chem 7] n = 943 Mn = 70,000 g / mol Silicone S2: [Chem 8] Mixture of three silicone oils where n= 81, (Mn = 6000 g / mol) n = 943 (Mn = 70 OOOg / mol) and n = 1080 (Mn = 80 OOOg / mol) Silicone S3: S3 silicone is an RTV2 gel formulated by ELKEM. This silicone was obtained by polyaddition reaction. Silicone S4: A commercial silicone tube of unknown composition, cut into pieces. Silicone S5: [Chem 9] S5 silicone is a PDMS gum, marketed by ELKEM under the name BLUESIL™FB Silicone Gum.

[0120] The acid catalyst is HDBS, also known as 4-dodecylbenzenesulfonic acid (CAS 121-65-3).

[0121] The solvent used in the examples is a nonpolar solvent, preferably toluene or heptane.

[0122] String blockers implemented in the examples: Bel chain blocker: divinyltetramethyldisiloxane (CAS 2627-95-4). Bc2 chain blocker: hexamethyldisiloxane (CAS 107-46-0) Bc3 chain blocker: tetramethyldisiloxane (CAS 3277-26-7) BC4 chain blocker: [Chem 10] -¼. M iM rW ■'uq "0% With n= 13 (Mn = 977 g / mol). Example 1: General protocol of the process:

[0123] In a 250 mL flask, silicone S and 120 mL of toluene are introduced, along with varying amounts of acid catalyst and chain blocker Bc. The reaction mixture is placed at room temperature with stirring for 24 hours. A large excess of inorganic or amine base is then added to the reaction mixture. A sample is taken and analyzed by ¹H NMR and ²⁹Si NMR.

[0124] In the context of the examples described below, the mass percentage of D4 relative to the total mass of the organopolysiloxane OR obtained according to the process of the present invention is measured by size exclusion chromatography (SEC) in the presence of polystyrene standards in a solvent such as toluene at 40°C.

[0125] Similarly, the number-average molecular mass denoted Mn of the different organo-polysiloxanes according to the present invention OR is determined by the same size exclusion chromatography (SEC) method.

[0126] The quantity QBc can be found in the various tables exemplified below. This quantity expresses the number of moles of Bc relative to the moles of bonding (Si-O) in the silicone S.

[0127] Example 2: Influence of the nature of silicone S on the process of the invention:

[0128] The protocol of Example 1 is implemented with silicone S (30 g, approximately 404 mmol of (Si-O) bonding in silicone S for SI, S2, S3 and S5), HDBS (4400 ppm wt., 0.132 g) as an acid catalyst and Bel as a Bc chain blocker. The reaction medium is placed at room temperature under stirring for 24 h.

[0129] S4 silicone is a commercial silicone tube of unknown composition, cut into pieces. In the remainder of this example, this tube will be considered to be composed of both a non-negligible amount of filler, 30%, and an amount of silicone of 70%.

[0130] Thus, for 30g of silicone tube, i.e. this test, we consider that we have 21g of silicone S. We then introduced 0.265g of chain blocker Bel and 0.0925g of HDBS into the reaction medium.

[0131] The nature of the silicone S and the quantity QBc are mentioned in Table 1 below.

[0132] [Tables 1] Test number Silicone S Chain blocker Bc QBc Mn of product OR (g / mol) Degree of polymerization of product OR 1 Silicone SI Bel 0.005 11,400 154 2 Silicone S2 0.005 8,300 112 3 Silicone S3 0.005 16,000 215 4 Silicone S4 0.005 11,200 152 4 Silicone S5 0.005 13,200 178

[0133] The results show that the process of the invention is versatile and can be used on all types of silicone including silicone blends and silicones comprising fillers.

[0134] Example 3: Influence of the nature of the chain blocker Bc on the process of the invention:

[0135] The protocol of Example 1 is implemented with silicone SI (30g, 404 mmol of (Si-O) bonding in silicone SI), HDBS (4400 ppm wt., 0.132g) as an acid catalyst and a chain blocker Bc. The reaction medium is placed at room temperature for a period of 24h.

[0136] The nature of the chain blocker and the quantity QBc are mentioned in Table 2 below.

[0137] [Tables2] Test number Chain blocker Bc QBc mBc (g) Mn of product OR (g / mol) Degree of polymerization of product OR Mass percentage in D4 (%) 1 Bel 0.00 5 0.38 11,400 154 1.4 2 Bc2 0.33 12,200 164 1.7 3 Bc3 0.27 11,300 152 2 4 Bc4 1.56 14,100 191 1.4 5 - - 28,000 377 1.3

[0138] This test was repeated by substituting the SI silicone with an RTV2 silicone gel (S3 silicone) manufactured by ELKEM. The other operating conditions remained unchanged from those described above. Thus, it was carried out with S3 silicone (30g, 404 mmol of bonding (Si-O) in S3 silicone), HDBS (4400 ppm (mass, 0.132g) as an acid catalyst and a Bc chain blocker as shown in Table 3 below: [Tables 3] Test Number Chain Blocker Bc QBc mBc (g) Mn of product OR (g / mol) Degree of polymerization of product OR Mass percentage in D4 (%) 1 Bel 0.00 5 0.38 16,000 215 0.9 2 Bc2 0.33 14,400 194 0.9 3 Bc3 0.27 14,700 198 1.7

[0139] These tests demonstrate the versatility and robustness of the process according to the present invention. Indeed, the nature of the chain blocker Bc has a limited effect on the number-average molecular weight (Mn) of the organopolysiloxane OR obtained according to the process of the invention. This process can therefore be adapted to different silicones S and different chain blockers Bc. In this example, the product obtained according to the process of the invention has a D4 percentage less than or equal to 2% by mass relative to the total mass of the organopolysiloxane OR.

[0140] Example 4: Influence of the quantity of chain blocker Bc on the process of the invention:

[0141] The protocol of Example 1 is implemented with silicone SI (30 g, 404 mmol of (Si-O) bonding in silicone SI), HDBS (4400 ppm wt., 0.132 g) as an acid catalyst, and Bel as a chain blocker. The reaction medium is placed at room temperature for 24 hours.

[0142] The mass of Bc and the quantity QBc are mentioned in Table 4 below.

[0143] [Tables4] Test number QBc mBc (g) Product Mn OR (g / mol) Product polymerization degree OR 1 0.000 0.00 28,000 377 2 0.002 0.15 17,700 239 3 0.003 0.23 15,200 205 4 0.005 0.38 11,400 154 5 0.007 0.53 9,600 129 6 0.008 0.60 8,000 108 7 0.009 0.68 7,200 97 8 0.010 0.75 6,500 87

[0144] In each test (test 1 to 8) of this example, the mass percentage of D4 is less than 2% by mass relative to the total mass of the OR product.

[0145] This test was repeated by substituting the silicone SI with an RTV2 silicone gel (silicone S3) formulated by ELKEM. The other operating conditions remained unchanged from those mentioned above. Thus, it was carried out with silicone S3 (30g, 404mmol of bonding (Si-O) in silicone S3), HDBS (4400ppm wt., 0.132g) as an acid catalyst and a chain blocker Bc.

[0146] The mass of Bc and the quantity QBc are given in Table 5 below. [Tables5] Test number QBc mBc (g) Mn of product OR (g / mol) Degree of polymerization of product OR Mass percentage in d4 (%) 1 0.001 0.026 33,500 451 1.3 2 0.003 0.08 22,000 296 1.0 3 0.005 0.15 16,000 215 0.9 4 0.007 0.23 14,500 195 1.3 5 0.009 0.30 11,500 155 0.9

[0147] These two tests demonstrate the control of the number-average molecular weight (Mn) of the organopolysiloxane OR according to the process of the invention. Varying the amount of substance of the chain blocker Bc affects the molecular weight of OR.

[0148] It can be noted that the product obtained according to the process of the invention has a percentage of D4 less than or equal to 1.3% by mass relative to the total mass of the organopolysiloxane OR.

[0149] Example 5: Influence of the quantity of acid on the process of the invention:

[0150] The protocol of Example 1 is implemented with SI silicone (30g, 404mmol of (Si-O) bonding in SI silicone), HDBS (110ppm to 17,600ppm mass) as acid catalyst and a Bc chain blocker.

[0151] The quantity QBc and the molar quantity of HDBS are mentioned in Table 6 below. [Tableauxô] Test Number Silicon eS Chain Blocker Bc QBc Quantity HDBS (mass) Mn of product OR (g / mol) Degree of polymerization of product OR Mass percentage in D4 (%) 1 Silicon eSl Bel 0.00 5 1100 ppm (0.033 g) 31,000 418 nd 2 2200 ppm (0.066 g) 21,600 291 nd 3 4400 ppm (0.132 g) 11,400 154 1.7 4 6600 ppm (0.132 g) 8,500 115 3.5 5 8800 ppm (0.132 g) 8,100 109 4.5 6 17,600 ppm (0.132 g) 6,500 88 11

[0152] It can be noted that at a fixed quantity of chain blocker QBc, increasing the quantity of acid catalyst also results in an increase in the percentage of D 4*

[0153] Thus, the amount of acid catalyst involved in the reaction has an impact on both the reaction kinetics, the average molecular masses obtained, and also on the amount of undesirable co-products such as D4.

[0154] Using the information disclosed in the present invention, a person skilled in the art will be able to adapt these parameters to obtain, using the process of the present invention, an OR polyorganosiloxane with the number-average molecular mass Mn desired while controlling the cyclic content.

[0155] Example 6: Comparative according to the protocol of patent application JP2002348407A

[0156] In a 250 mL round-bottom flask equipped with a magnetic stirrer, 20 g of PDMS S4, 47 g of toluene, and 2.4 g of HDBS solution were introduced. After stirring for 1 hour at room temperature using a stirrer, the silicone tube was completely decomposed and dissolved. Next, a solution of 0.54 g of calcium hydroxide in 15 g of isopropanol was added for neutralization, along with 50 g of water. The resulting mixture was stirred for 10 minutes. After 30 minutes of rest, a sample of the resulting organic phase was taken, diluted to the appropriate concentration, filtered, and analyzed by size-exclusion chromatography. We then obtain the number average molecular mass (Mn) of the organopolysiloxane of 11,000 g / mol and an amount of undesirable co-products such as octamethyltetrasiloxane (D4) equal to 15% by mass relative to the total mass of the organopolysiloxane obtained.

[0157] Example 7: Influence of the nature of the acid catalyst:

[0158] The protocol of Example 1 is implemented with silicone SI (30g, 404mmol of (Si-O) bonding in silicone SI), an acid catalyst (4400 ppm mass) and a chain blocker Bc. The nature of the acid catalyst and the mass of catalyst involved are mentioned in Table 7 below. [Tables 7] Test number Chain blocker Bc QBc Nature of acid catalyst Mass of acid catalyst (g) Mn of product OR (g / mol) Degree of polymerization of product OR Mass percentage in D4 (%) 1 Bel 0.00 5 - - 70,000 943 - 2 HDBS 0.132 11,400 154 1.3 3 Trifluoromethanesulfonic acid (CAS 1493-13-6) 0.061 9,800 132 3.0

[0159] It may be noted that tests 2 and 3 have satisfactory results within the meaning of the present invention. However, it may be noted that trifluoromethanesulfonic acid leads to 3% by mass of D4 relative to the total mass of the organopolysiloxane OR.

[0160] On the other hand, 4-dodecylbenzenesulfonic acid (CAS 121-65-3) presents a satisfactory implementation of the process of the present invention as has already been shown in the preceding examples.

[0161] Example 8: Influence of reaction time on the process of the invention:

[0162] The protocol of Example 1 is implemented with SI silicone (30g, 404mmol of (Si-O) bonding in SI silicone), HDBS (4400ppm wt, 0.132g) as acid catalyst and a Bc chain blocker.

[0163] The quantity QBc and the duration of the reaction are mentioned in Table 8 below.

[0164] [Tables8] Test Number Chain Blocker Bc QBc Reaction Time (h) Product Mn OR (g / mol) Product Polymerization Degree OR Mass Percentage of D4 (%) 1 Bel 0.00 5 0 70,000 943 0.06 2 2 32 200 434 0.2 3 4 22,400 302 0.2 4 6 16,800 226 0.3 5 8 14,500 195 0.40 6 10 13,000 175 0.5 7 24 11,400 154 1.3

[0165] These tests demonstrate that the reaction time also allows control of the average molecular mass in number Mn of the polyorganosiloxane OR obtained according to the process of the invention.

[0166] Example 9: Influence of temperature on the process of the invention:

[0167] The protocol of Example 1 is implemented with SI silicone (30g, 404mmol of (Si-O) bonding in SI silicone), HDBS (4400ppm wt, 0.132g) as acid catalyst and a Bc chain blocker.

[0168] Table 9 below shows the temperature, the degree of polymerization of the OR product and the mass percentage of D4: [Tables 9] Test Number Chain Blocker Bc QBc Temperature (°C) Product Mn OR (g / mol) Product Polymerization Degree OR 1 Bel 0.005 RT 11,400 154 2 50 16,000 216 3 70 19,000 256 4 100 17,700 239

[0169] The temperature during the implementation of the process of the invention makes it possible to control the average molecular mass in number Mn of the polyorganosiloxane OR obtained according to the process of the invention.

[0170] Example 10: Influence of solvent content on the process of the invention:

[0171] The protocol of Example 1 is implemented with SI silicone (30g, 404mmol of (Si-O bonding in silicone SI), HDBS (4400ppm mass, 0.132g) as an acid catalyst and a Bc chain blocker and toluene as a solvent.

[0172] In this example, five tests with different volumes of solvents were carried out.

[0173] This example aims to study a possible influence on the volume of solvent introduced into the process of the invention.

[0174] Table 10 below shows the volume of solvent introduced in the different tests [Tables 10] Test number Chain blocker Bc QBc Solvent volume (mL) Product Mn OR (g / mol) Product polymerization degree OR 1 Bel 0.005 120 11 400 154 2 60 10 600 143 3 30 13 100 177 4 15 13 600 183 5 0 15 200 205

[0175] The quantity of solvent introduced during the implementation of the process of the invention has a small influence on the variation of the average number molecular mass Mn of the polyorganosiloxane OR obtained according to the process of the invention.

[0176] Moreover, in this same example, the mass percentage of D4 by mass relative to the total mass of the OR product is less than or equal to 2% for each of the tests.

[0177] Example 11: Reuse of depolverterized S2 silicone as organopolvsiloxane OR in a new RTV2 formulation:

[0178] In this example, the ability to use the functional organopolysiloxane OR (obtained under the conditions of trial 1 of example 2) to prepare an RTV2 gel was tested.

[0179] Thus the recycled OR product of Example 2, Test 1 comprising vinyl functions was used in combination with a poly(methylhydrogenosiloxane)-co-poly(dimethylsiloxane) type crosslinker where [Si-H] / [Si-vinyl] = 2.25.

[0180] In order to obtain this RTV2 gel, the hydrosylilation reaction was carried out in the presence of a Karstedt catalyst (275 ppm of a 2% Pt solution) and 1-ethynylcyclohexanol used as a moderator ([1-Ethynylcyclohexanol] / [Pt] = 14.6 ppm).

[0181] Next, the reaction mixture was mixed, degassed and crosslinked for 4h at 70°C.

[0182] Figure 1 in the appendix illustrates a photograph of the RTV2 gel obtained in the conditions of this example. This RTV2 formulation was prepared twice under the same conditions, and each of these trials has similar physical characteristics. Indeed, the RTV2 gel obtained in the first trial has a swelling rate of 280% and an extractable fraction of 10%, while the RTV2 gel obtained in the second trial has a swelling rate of 285% and an extractable fraction of 10%.

[0183] Therefore, this example demonstrates that the OR organopolysiloxanes obtained according to the process of the invention can be reused in formulations to obtain RTV2 type silicone gels.

[0184] In view of the information disclosed in the present invention and more particularly in this example, a person skilled in the art will be able to adapt the operating conditions to use the organopolysiloxanes obtained according to the process of the invention in other silicone formulations (EVC, RTV1, LSR).

Claims

Demands

1. Method for preparing organopolysiloxanes OR, by a depolymerization reaction of at least one silicone S in the presence of: - of an acid catalyst chosen from the derivatives of benzenesulfonic acid of formula (VI), alone or in mixtures: [Chem 3] U 3 O Formula (VI) with R = CnH2n+10 ... <n<20, et - of at least one chain blocker Bc chosen from the compounds of formula (IV): [Chem 11] pi Formula (IV) in which, R1, whether identical or different, represents: - a linear or branched alkyl group comprising from 1 to 12 carbon atoms, preferably from 1 to 8 carbon atoms, optionally substituted by an O, N, S heteroatom or a halide, - an alkenyl group comprising 2 to 6 carbon atoms, - a cycloalkyl group of 5 to 10 carbon atoms, possibly substituted by an O, N, S heteroatom or a halide, - an aryl group in C6-Ci8, - a hydroxyl group, or - hydrogen R2, whether identical or different, represents: -an alkenyl group comprising 2 to 6 carbon atoms, preferably vinyl, -a hydroxyl group, -a linear or branched alkyl group comprising from 1 to 12 carbon atoms, preferably from 1 to 5 carbon atoms, possibly substituted by at least one heteroatom O, N, S or a halide such as a fluorine atom, for example 1 to 10 fluorine atoms, or -a hydrogen; and q is an integer between 1 and 50, preferably between 1 and 20, more preferably between 1 and 10.

2. Method according to claim 1, wherein the amount of chain blocker Bc implemented in the process of the invention is at least 10⁴ mol per mole of bonding (Si-O) in silicone S, preferably between 10³ and 5x10¹ mol, preferably between 10³ and 10² mol, even more preferably between 3x10³ and 6x10¹ mol per mole of bonding (Si-O) in silicone S.

3. Method according to any one of claims 1 or 2, wherein the amount of acid catalyst is between 0.001 and 1% by mass relative to the mass of silicone S, preferably between 0.05 and 1%, more preferably between 0.1 and 1% relative to the mass of silicone S.

4. A method according to any one of claims 1 to 3, wherein the organopolysiloxane OR is characterized in that its number-average molecular weight, denoted Mn, is between 500 and 300,000 g / mol, preferably between 1,000 and 150,000 g / mol, preferably between 1,000 and 70,000 g / mol and even more preferably between 2,500 and 30,000 g / mol.

5. A method according to any one of claims 1 to 4, wherein the cyclic organopolysiloxane content is less than 5% by mass, preferably less than or equal to 3% by mass, preferably less than or equal to 2% by mass and even more preferably less than or equal to 1.5% by mass relative to the total mass of the OR organopolysiloxanes.

6. A method according to any one of claims 1 to 5, wherein the reaction is carried out at a temperature between 0 and 100°C, preferably between 0 and 50°C, more preferably between 10 and

7. JJ. Method according to any one of claims 1 to 6, wherein the reaction is carried out in the presence of a nonpolar solvent.

8. Method according to any one of claims 1 to 7, characterized in that the mass ratio, mass of silicone S relative to the mass of solvent involved, is between 0.01 and 15, preferably between 0.1 and 5, preferably between 0.1 and 2.

9. Method according to any one of claims 1 to 8, characterized in that it further comprises a step of neutralizing the acid catalyst carried out by adding a base to the reaction medium or by thermal degradation of the acid catalyst.

10. A method according to any one of claims 1 to 9, characterized in that it comprises the following steps: 1) Carrying out the process for preparing organopolysiloxanes OR, by a depolymerization reaction of at least one silicone S in the presence of an acid catalyst and at least one chain blocker Bc having at least one siloxane function; 2) Neutralization of the acid catalyst mentioned in the preceding step by adding a base to the reaction medium or by thermal degradation of the acid catalyst; and 3) Filtration of the reaction medium obtained at the end of step 2.

11. Use of the organopolysiloxane OR obtained according to any one of the preceding claims as an ingredient in silicone formulations in the fields of cosmetics, health, household products, technical industrial formulations, transport such as automotive or aviation, or even in the energy sector.

12. A process for preparing silicone S, in particular silicone oils, resins, gums or elastomers, comprising the following steps: 1) Carrying out the process for preparing organopolysiloxanes OR according to any one of claims 1 to 10; 2) Preparing silicone S from the organopolysiloxanes OR obtained in step 1).

13. A method for preparing silicone S according to claim 12, characterized in that step 2 is carried out by a poly-addition reaction, polycondensation reaction, cationic mechanism or radical mechanism.

14. Use of silicone S obtained by the process according to claim 12 or 13 in the field of cosmetics, health, household products, technical industrial formulations, transport such as automobiles or aviation, or even in the energy field.