Depolymerization of silicone polymers from which organopolysiloxanes are obtained

Abstract

The present invention relates generally to the reuse, reprocessing or recycling of silicone polymers. More specifically, the process of the invention relates to a process for the preparation of organopolysiloxanes OR by the depolymerization reaction of at least one silicone S in the presence of an acid catalyst and at least one chain blocking agent Bc having at least one siloxane function. These organopolysiloxanes OR may then be used in polymerization reactions or directly in various formulations.

Description

Technical Field

[0001] The present invention generally relates to the reuse, reprocessing or recycling of organosilicon polymers. More specifically, the method of the present invention relates to the depolymerization of organosilicon polymers to obtain lower molecular weight organopolysiloxanes OR, which can then be used in polymerization reactions or directly in various formulations. Background Art

[0002] A major challenge facing society and industry in the coming years is the ecological transition. Therefore, from an economic perspective, the so-called "linear" economic model (collect - make - use - discard) should ultimately be replaced by a so-called circular model.

[0003] The circular economy describes an economic system based on a model that replaces the concept of “end-of-life” products with the reduction, alternative reuse, recycling and recovery of these materials in the production / distribution and consumption processes to achieve sustainable development for the benefit of present and future generations.

[0004] As the silicone market continues to grow and the applications of these materials expand, the recycling of used silicone products has become a major challenge for the silicone industry. Recycling silicone can reduce gas (CO, CO2) emissions associated with the silicone industry by 75% and reduce silicone waste by 65%.

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

[0006] Therefore, in 2018, European regulations limited the content of D4 and D5 in rinse-off cosmetics to 0.1% by mass. These regulations will soon apply to other cosmetic products, as well as other application areas of silicones.

[0007] Therefore, there is a need to provide a process which enables the provision of silicone products which are free of cyclic silicones or at least have a low content of cyclic silicones.

[0008] In the prior art, the depolymerization of organopolysiloxanes has been described by various methods.

[0009] In 2002, patent application JP2002348407A disclosed a method for chemically converting silicone products (such as silicone resins or silicone molds) into linear polysiloxanes. However, this method required a large amount of acid catalyst (12%), and the resulting product was a mixture of cyclic compounds formed by a reverse cleavage reaction. This reaction is commonly known as "back-biting."

[0010] More recently, in 2020, patent application US20200377686 describes a process that enables the recycling of silicones (silicone oils, resins) by chemical conversion to obtain α,ω-diacetoxypolydimethylsiloxanes. However, this process requires heating the reaction medium and an excess of acetic anhydride.

[0011] Furthermore, the α,ω-diacetoxypolydimethylsiloxane can subsequently be chemically modified to obtain polydimethylsiloxanes having hydroxyl or acetoxy end groups, which can be used in adhesive compositions or sealing products.

[0012] In 2022, patent application US2022119617 described a similar method. The obtained α,ω-diacetoxypolydimethylsiloxane is reused to obtain α,ω-diisopropoxypolydimethylsiloxane or polydimethylpolysiloxane-polyoxyalkylene block polymer.

[0013] It would therefore be of interest to provide an alternative method for depolymerizing organosilicones into organopolysiloxanes that can be directly reused in subsequent formulations. It would be particularly interesting to provide a catalytic system that allows this depolymerization to be carried out at lower temperatures, limiting the amount of catalyst used and allowing for a robust, selective, and flexible process. It would also be of interest to be able to reliably control the molecular weight of the resulting products. This possibility would increase the potential for applications and uses of such polymers. Summary of the Invention SUMMARY OF THE INVENTION

[0015] One object of the present application is therefore to provide a process for the depolymerization of organosilicones which makes it possible to control the molecular weight of the final product while at the same time varying the chemical nature of the terminal groups.

[0016] Another object of the present application is to provide a catalytic system for implementing this method.

[0017] Another object of the present application is to provide a catalytic system that is simple, non-hazardous and compatible with the industrialization of the process.

[0018] A further object of the present application is to provide a process which is satisfactory from an industrial point of view and belongs to so-called environmentally friendly chemistry.

[0019] A further object of the present application is to obtain organopolysiloxanes OR having a low content of cyclic organopolysiloxanes at the end of the process.

[0020] Other objects may also emerge from reading the following description of the invention.

[0021] Surprisingly, the Applicant has developed a catalytic system that meets these expectations. The present invention therefore relates to a catalytic system for the synthesis of siloxanes by reacting an acid catalyst with at least one chain-capping agent (bloqueur de ) Bc, the acid catalyst is selected from the benzenesulfonic acid derivatives of formula (VIa) alone or as a mixture:

[0022]

[0023] Either R1 and R2 represent hydrogen atoms and R3=C n H 2n+1 , wherein 5≤n≤20, preferably 10≤n≤20,

[0024] Either R1 and R3 represent hydrogen atoms and R2=C n H 2n+1 , wherein 5≤n≤20, preferably 10≤n≤20,

[0025] or either R2 and R3 represent hydrogen atoms and R1=C n H 2n+1 , wherein 5≤n≤20, preferably 10≤n≤20.

[0026] In this case, the acid catalyst and the chain-capping agent Bc make it possible to control the molecular weight of the final product during the depolymerization reaction while making it possible to modify the chemical nature of the terminal groups.

[0027] Detailed description of the invention :

[0028] Silicones, also known as organopolysiloxanes, are polymeric materials containing alternating silicon and oxygen atoms with various organic groups bonded to the silicon.

[0029] For the purposes of the present invention, the term "organosilicon" or "organosilicon product" or "organosilicon polymer" or "organopolysiloxane" is understood to mean a polymer comprising a siloxane backbone (Si-O-Si) having alternating silicon and oxygen atoms with various organic groups bonded to the silicon. These organosilicon polymers can be liquid or solid, depending on the molecular weight and the degree of crosslinking.

[0030] The silicones S of the present invention may be of any type; they may 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 these compounds.

[0031] The organopolysiloxane O may in particular be an oil and preferably have a dynamic viscosity at 25°C of from 10 000 to 600 000 mPa·s, preferably from 30 000 to 600 000 mPa·s at 25°C.

[0032] All viscosities mentioned in this description correspond to so-called "Newtonian" dynamic viscosity values ​​at 25° C., ie dynamic viscosities measured in a manner known per se using a Brookfield viscometer at a shear rate gradient low enough to make the measured viscosity independent of the rate gradient.

[0033] The term "gum" is typically used for organopolysiloxane compounds having a viscosity of typically greater than 600 000 mPa·s, which corresponds to a molecular weight of greater than 300 000 g / mol.

[0034] These organopolysiloxanes O may contain one or more functional units, for example:

[0035] -OH;

[0036] -H;

[0037] -alkenyl, in particular containing 2 to 6 carbon atoms, preferably vinyl;

[0038] -O-Alk, wherein Alk represents an alkyl group containing 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;

[0039] -(O-Alk) x, wherein 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 from 2 to 200; - a linear or branched alkyl group comprising 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, which is substituted by at least one fluorine atom, for example 1 to 10 fluorine atoms, for example (C1-C5)alkyl-CF3, the alkyl group being linear or branched.

[0040] Preferably, the functional unit is selected from:

[0041] -OH;

[0042] -H;

[0043] -alkenyl, in particular containing 2 to 6 carbon atoms, preferably vinyl;

[0044] a linear or branched alkyl group containing 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, which is substituted by at least one fluorine atom, for example 1 to 10 fluorine atoms, such as (C1-C5)alkyl-CF3, the alkyl group being linear or branched.

[0045] Preferably, the organopolysiloxane O may contain one or more functional units, such as H, OH, alkenyl (preferably vinyl), aryl, or cyclic amine, as defined above. The organopolysiloxane O may be partially crosslinked. The organopolysiloxane O may in particular be a used organopolysiloxane that has been used, for example, as a heat transfer fluid and is to be recycled. The process of the present invention thus allows the production of an organopolysiloxane OR that can then be directly used in industrial processes. When using used organopolysiloxane O, the organopolysiloxane may contain other components, such as additives, pigments, etc. The inventors have demonstrated that, under these conditions, a depolymerization reaction can be carried out to form the organopolysiloxane OR.

[0046] According to one embodiment of the present invention, the organopolysiloxane O comprises:

[0047] at least 500, preferably at least 700, siloxy units of formula (I):

[0048] R c SiO (4-c) / 2 (I)

[0049] in,

[0050] R, same or different, means:

[0051] - an alkyl group containing 1 to 15 carbon atoms, preferably 1 to 12 carbon atoms, preferably 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, preferably a methyl group,

[0052] or an aryl group containing 6 to 10 carbon atoms, preferably phenyl,

[0053] and c = 0, 1, 2 or 3;

[0054] and optionally, one or more units of formula (II):

[0055] R 1 d R e SiO (4-d-e) / 2 (II)

[0056] in,

[0057] R is as defined above;

[0058] R 1 , the same or different, means:

[0059] - an alkenyl group containing 2 to 6 carbon atoms, preferably a vinyl group,

[0060] - hydroxyl group (OH),

[0061] - a group (O-Alk), wherein Alk represents an alkyl group containing 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,

[0062] - group (O-Alk) x , wherein Alk represents an alkyl group containing 1 to 15 carbon atoms, preferably 1 to 12 carbon atoms, preferably 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, preferably a methyl group, and x represents an integer of 2 to 200,

[0063] a linear or branched alkyl group containing 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, which is substituted by at least one fluorine atom, for example 1 to 10 fluorine atoms, such as (C1-C5)alkyl-CF3, the alkyl group being linear or branched, or

[0064] -hydrogen;

[0065] d=1, 2 or 3, preferably d=1 or 2, more preferably d=1; e=0, 1 or 2; and the sum d+e=1, 2 or 3.

[0066] It will be understood that in the above formulae, if there are multiple R groups or if there are multiple R 1 groups, they may be the same as or different from each other.

[0067] Preferably, in the above formula, R 1 , the same or different, means:

[0068] - an alkenyl group containing 2 to 6 carbon atoms, preferably a vinyl group,

[0069] - hydroxyl group (OH),

[0070] a linear or branched alkyl group containing 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, which is substituted by at least one fluorine atom, for example 1 to 10 fluorine atoms, such as (C1-C5)alkyl-CF3, the alkyl group being linear or branched, or

[0071] -hydrogen.

[0072] In the present invention:

[0073] -Siloxy unit "M" represents a unit having the formula Y3SiO 1 / 2 The siloxy units,

[0074] -Siloxy unit "D" represents a unit having the formula Y2SiO 2 / 2 The siloxy units,

[0075] -Siloxy units "T" represent units having the formula YSiO 3 / 2 The siloxy units,

[0076] -Siloxy unit "Q" represents a unit having the formula SiO 4 / 2 The siloxy units,

[0077] Symbol Y is R or R 1 .

[0078] The organopolysiloxanes O may optionally be linear or branched and comprise, in particular, T and Q units.

[0079] According to a preferred embodiment, the organopolysiloxane O is selected from compounds of formula (III):

[0080] R 1 a R (3-a) SiO-(SiR2O) n1 -(SiR 1 RO) m1 -SiR 1 a R (3-a) (III)

[0081] in:

[0082] R, same or different, means:

[0083] - an alkyl group containing 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, or

[0084] - an aryl group containing 6 to 10 carbon atoms, preferably a phenyl group;

[0085] R 1 , the same or different, means:

[0086] - an alkenyl group containing 2 to 6 carbon atoms, preferably a vinyl group,

[0087] - hydroxyl group (OH),

[0088] - a group (O-Alk), wherein Alk represents an alkyl group containing 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,

[0089] - group (O-Alk) x , wherein Alk represents an alkyl group containing 1 to 15 carbon atoms, preferably 1 to 12 carbon atoms, preferably 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, preferably a methyl group, and x represents an integer of 2 to 200,

[0090] a linear or branched alkyl group containing 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, which is substituted by at least one fluorine atom, for example 1 to 10 fluorine atoms, such as (C1-C5)alkyl-CF3, the alkyl group being linear or branched, or

[0091] -hydrogen;

[0092] a is an integer and represents 0, 1, 2 or 3, preferably 0, 1 or 2, more preferably 0 or 1;

[0093] -n1 represents an integer of 500-10 000, preferably 1 000-5 000, preferably 500-5 000, more preferably 600-2 000;

[0094] -m1 represents an integer of 0-100, preferably 0-50, more preferably 0-30, and preferably m=0.

[0095] Particularly preferably, the organopolysiloxane O is a compound of the formula (III) in which R 1 , the same or different, means:

[0096] - an alkenyl group containing 2 to 6 carbon atoms, preferably a vinyl group,

[0097] - hydroxyl group (OH),

[0098] a linear or branched alkyl group containing 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, which is substituted by at least one fluorine atom, for example 1 to 10 fluorine atoms, such as (C1-C5)alkyl-CF3, the alkyl group being linear or branched, or

[0099] -hydrogen.

[0100] Particularly preferably, the organopolysiloxane O is a compound of the formula (III) in which R 1 , the same or different, represent: -CH3, vinyl, H, (C1-C5)alkyl-CF3 or OH.

[0101] Particularly preferably, the organopolysiloxane O is a compound of the formula (III) wherein

[0102] R, identical or different, represents CH3 or phenyl, preferably CH3;

[0103] R 1 , the same or different, means:

[0104] - an alkenyl group containing 2 to 6 carbon atoms, preferably a vinyl group,

[0105] - hydroxyl group (OH),

[0106] a linear or branched alkyl group containing 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, which is substituted by at least one fluorine atom, for example 1 to 10 fluorine atoms, such as (C1-C5)alkyl-CF3, the alkyl group being linear or branched, or

[0107] -hydrogen.

[0108] Particularly preferably, the organopolysiloxane O is a compound of the formula (III) wherein

[0109] R, identical or different, represents CH3 or phenyl, preferably CH3,

[0110] R 1 , which are the same or different, represent CH3, vinyl, H, (C1-C5)alkyl-CF3 or OH.

[0111] The silicone S according to the invention can also be of the type of crosslinked silicone material, such as a gel or elastomer. Crosslinked silicone materials are well known to those skilled in the art. These materials can be obtained, inter alia, by polycondensation, free-radical polymerization, thermal or UV-irradiation polyaddition. Silicone products have a wide range of applications. For example, they can be found in food applications such as cooking molds, in medical applications and in the pharmaceutical field, in baby bottle nipples, catheters, implants or tubes for medical applications. In technical and industrial applications, silicones are often used as materials for seals or membranes. In the automotive sector, they are used for hoses, cable sheathing or insulation and as a cushioning material.

[0112] Silicone elastomers are cross-linked silicone materials that contain fillers such as silica to achieve good mechanical properties. By varying the silicone oil, fillers, additives, and cross-linking pattern, silicone elastomers can exhibit different properties and colors.

[0113] Silicone elastomers can be divided into three main categories known to those skilled in the art. Heat-vulcanized elastomers (EVC, also known as "high temperature vulcanization (HTV)" or "heat cured rubber (HCR)") are silicone elastomers derived from very high-viscosity silicone compositions containing silicone rubber and fillers. They are vulcanized at high temperatures, typically between 140°C and 200°C. Crosslinking occurs via peroxide-catalyzed free radical crosslinking or via addition reactions in which platinum compounds are used as catalysts.

[0114] Liquid silicone rubber (LSR) is a silicone elastomer obtained from a composition containing a viscous silicone oil and a filler. Crosslinking occurs by an addition reaction at temperatures similar to EVC, but generally occurs much faster.

[0115] The third category is that of silicones obtained by crosslinking silicone compositions at ambient temperature, using silicone oils and fillers as raw materials, crosslinked by polycondensation or polyaddition reactions. These elastomers are known in French as "élastomère silicone vulcanisables à froid" (EVF, or "room temperature vulcanization (RTV)" in English). These compositions are available in one- and two-component systems.

[0116] In the present method, the term "silicone S" is also understood to refer to silicone-based materials, such as materials containing at least 0.1% by mass of silicone relative to the total mass of the silicone-based material. These materials are conventionally found in silicone-coated textiles (airbags or synthetic leather) and silicone coatings (food paper).

[0117] The silicone-based material may contain up to 100% by mass of silicone, preferably up to 99.9% by mass of silicone, relative to the total mass of the silicone-based material. These silicone-based materials may also contain additives or fillers, such as colorants, silica, calcium carbonate, calcium oxide, celite, quartz, titanium oxide, cerium hydroxide, magnesium oxide, mica, and the like.

[0118] According to one embodiment, the organosilicon S comprises silicon dioxide, calcium oxide, quartz, titanium oxide, magnesium oxide, mica and mixtures thereof.

[0119] Within the scope of the present invention, the number of moles of (Si-O) is understood to mean the number of moles of (Si-O) bonds in the organosilicon S. In cases where the chemical formula of the starting organosilicon S is unknown, particularly in the case of formulated commercial products, the number of moles of (Si-O) bonds can be estimated. In practice, those skilled in the art know that the amount of filler in formulated silicone elastomers is between 20 and 40% by mass. Therefore, by estimating the amount of filler to be an average of 30% by mass, a 70% by mass silicone is obtained, which enables the calculation of the number of moles of (Si-O) bonds from the average molar mass of the repeating units.

[0120] Within the scope of the present invention, the term "chain-capping agent Bc" has at least one siloxane function.

[0121] In the process of the present invention, the chain-capping agent Bc is represented by formula (IV):

[0122]

[0123] in,

[0124] R 1 , the same or different, means:

[0125] a linear or branched alkyl radical containing 1 to 12 carbon atoms, preferably 1 to 8 carbon atoms, which is optionally substituted by heteroatoms O, N, S or halides,

[0126] - an alkenyl group containing 2 to 6 carbon atoms,

[0127] - a cycloalkyl group containing 5 to 10 carbon atoms, which is optionally substituted by heteroatoms O, N, S or halides,

[0128] -C6-C 18 aryl groups,

[0129] - a hydroxyl group, or

[0130] -hydrogen,

[0131] R 2 , the same or different, means:

[0132] - an alkenyl group containing 2 to 6 carbon atoms, preferably a vinyl group,

[0133] - hydroxyl group (OH),

[0134] a linear or branched alkyl radical comprising 1 to 12 carbon atoms, preferably 1 to 5 carbon atoms, which is optionally substituted by at least one heteroatom O, N, S or a halide such as a fluorine atom, for example 1 to 10 fluorine atoms, for example (C1-C5)alkyl-CF3, the alkyl radical being linear or branched; or

[0135] - hydrogen; and q is an integer of 1-50, preferably 1-20, more preferably 1-10.

[0136] In another embodiment, the chain-capping agent Bc is represented by formula (IV), wherein:

[0137] R 1 , the same or different, represent CH3 or phenyl, preferably CH3;

[0138] R 2 , the same or different, means:

[0139] - an alkenyl group containing 2 to 6 carbon atoms, preferably a vinyl group,

[0140] - hydroxyl group (OH),

[0141] a linear or branched alkyl group containing 1 to 12 carbon atoms, preferably 1 to 5 carbon atoms, which is optionally substituted by at least one heteroatom O, N, S or a halide such as a fluorine atom, for example 1 to 10 fluorine atoms, for example (C1-C5)alkyl-CF3, the alkyl group being linear or branched,

[0142] - optionally substituted C5-C 10 cycloalkyl groups,

[0143] - optionally substituted C6-C 18 an aryl group, or

[0144] -hydrogen;

[0145] And q is an integer of 1-50, preferably 1-20, more preferably 1-10.

[0146] Particularly preferably, the chain-capping agent Bc is represented by formula (IV), wherein:

[0147] R 1 , which represents CH3 in the same way;

[0148] R 2 , the same or different, means:

[0149] - an alkenyl group containing 2 to 6 carbon atoms, preferably a vinyl group,

[0150] - hydroxyl group (OH),

[0151] - a linear or branched alkyl group containing 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms,

[0152] - optionally substituted C6-C 18 an aryl group, or

[0153] -hydrogen,

[0154] And q is an integer between 1-20, preferably between 1-10, more preferably between 1-5.

[0155] Other siloxane-functional blocking agents according to the invention are described on page 264 of the book “Chemistry and Technology of Silicones”, published by Académie Press in 1968.

[0156] The chain-capping agent Bc may be in a solvent. This is particularly advantageous for dissolving it in the reaction medium. The solvent may in particular be a non-polar solvent such as an organic solvent of the alkane or aromatic hydrocarbon type. Preferably, the solvent is selected from n-hexane, n-heptane, n-decane, n-dodecane, isododecane, EXXSOL D60, xylene, toluene, and mixtures thereof.

[0157] The amount of the chain end capping agent Bc used in the method of the present invention is at least 10 moles relative to the number of moles of (Si-O) bonds in the organosilicon S. -4 mole, preferably 10 -3 to 5×10 -1 mole, more preferably 10 -3 to 10 -2 mole, even more preferably 3×10 -3 to 6×10 -1 mole, for example 5×10 -3 Mole, relative to the moles of (Si-O) bonds in the silicone S.

[0158] These chain-capping agents make it possible to functionalize the organopolysiloxanes OR during the depolymerization reaction. It is thus possible to obtain organopolysiloxanes OR having Si-vinyl or Si-H functionalities, for example.

[0159] In the process according to the invention, mixtures of various chain-capping agents can optionally be used. Organopolysiloxanes OR can thus be obtained which may have different functional groups at the chain ends.

[0160] In an alternative embodiment, the process according to the invention can be carried out without chain-capping agent Bc.

[0161] The acid catalyst used as catalyst in the process of the present invention is selected from Bronsted acids having a pKa of less than or equal to 2, such as trifluoromethanesulfonic acid, benzenesulfonic acid and derivatives thereof, alone or as a mixture.

[0162] Preferably, the acid catalyst is selected from benzenesulfonic acid and its derivatives of formula (Va), alone or as a mixture:

[0163]

[0164] Either R1 and R2 represent hydrogen atoms and R3=C n H 2n+1 , where 1≤n≤20,

[0165] Either R1 and R3 represent hydrogen atoms and R2=C n H 2n+1 , where 1≤n≤20,

[0166] or either R2 and R3 represent hydrogen atoms and R1=C n H 2n+1 , where 1≤n≤20.

[0167] In one embodiment, the acid catalyst is selected from benzenesulfonic acid and its derivatives of formula (Vb), alone or as a mixture:

[0168]

[0169] Where R=H or C n H 2n+1 , where 1≤n≤20.

[0170] More preferably, the acid catalyst is selected from the group consisting of benzenesulfonic acid derivatives of formula (VIa), alone or as a mixture:

[0171]

[0172] Either R1 and R2 represent hydrogen atoms and R3=C n H 2n+1 , wherein 5≤n≤20, preferably 10≤n≤20,

[0173] Either R1 and R3 represent hydrogen atoms and R2=C n H 2n+1 , wherein 5≤n≤20, preferably 10≤n≤20,

[0174] or either R2 and R3 represent hydrogen atoms and R1=C n H 2n+1 , wherein 5≤n≤20, preferably 10≤n≤20.

[0175] In one embodiment, the acid catalyst is selected from benzenesulfonic acid derivatives of formula (VIb), alone or as a mixture:

[0176]

[0177] Where R = C n H 2n+1 , wherein 5≤n≤20, preferably 10≤n≤20.

[0178] It should be noted that the alkyl groups described in formulae (Va), (Vb), (VIa) and (VIb) may be primary, secondary or tertiary alkyl groups.

[0179] Even more preferably, the acid catalyst is HDBS, also known as 4-dodecylbenzenesulfonic acid (CAS 121-65-3).

[0180] Alternatively, the acid catalyst is selected from Bronsted acids having a pKa less than or equal to 2, such as perfluoroalkanoic acids, for example trifluoromethanesulfonic acid (acid triflique), pentafluoroethanesulfonic acid, heptafluoropropanesulfonic acid, or chlorinated derivatives, alone or as a mixture.

[0181] Depending on the nature of the acid catalyst, it can be dissolved in a solvent. Preferably, the solvent is a non-polar solvent. The solvent may in particular be an organic solvent of the alkane or aromatic hydrocarbon type. Preferably, the solvent is the same as the solvent selected during the depolymerization reaction. Thus, the solvent may in particular be an organic solvent of the alkane or aromatic hydrocarbon type.

[0182] The amount of the acid catalyst used in the method of the present invention is 0.001-3% by mass relative to the mass of the organosilicon S, preferably 0.05-1% by mass, more preferably 0.1-1% by mass, such as 0.4% by mass, relative to the mass of the organosilicon S.

[0183] In one embodiment, the organopolysiloxane OR may have functional groups at the chain ends which are derived from a chain-capping agent, such as vinyl functional groups, Si—H functional groups or Si-aryl functional groups.

[0184] 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 units.

[0185] According to one embodiment of the present invention, the organopolysiloxane OR comprises:

[0186] - at least 2 siloxy units of formula (VII):

[0187] [R 2 R 1 2Si(OSiR 1 2) q ]-O-SiR c O (3-c) / 2 (VII)

[0188] in

[0189] R, same or different, means:

[0190] - an alkyl group containing 1 to 15 carbon atoms, preferably 1 to 12 carbon atoms, preferably 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, preferably a methyl group,

[0191] - an aryl group containing 6 to 10 carbon atoms, preferably a phenyl group,

[0192] c = 1, 2, or 3;

[0193] R 1 , the same or different, means:

[0194] - a linear or branched alkyl radical comprising 1 to 12 carbon atoms, preferably 1 to 8 carbon atoms, which is optionally substituted by heteroatoms O, N, S or halides,

[0195] - an alkenyl group containing 2 to 6 carbon atoms,

[0196] - a cycloalkyl group containing 5 to 10 carbon atoms, which is optionally substituted by heteroatoms O, N, S or halides,

[0197] -C6-C 18 aryl groups,

[0198] - a hydroxyl group, or

[0199] -hydrogen,

[0200] R 2 , the same or different, means:

[0201] - an alkenyl group containing 2 to 6 carbon atoms, preferably a vinyl group,

[0202] - hydroxyl group (OH),

[0203] a linear or branched alkyl group containing 1 to 12 carbon atoms, preferably 1 to 5 carbon atoms, which is optionally substituted by at least one heteroatom O, N, S or a halide such as a fluorine atom, for example 1 to 10 fluorine atoms, for example (C1-C5)alkyl-CF3, the alkyl group being linear or branched,

[0204] - optionally substituted C5-C 10 cycloalkyl groups,

[0205] - optionally substituted C6-C 18 an aryl group, or

[0206] -hydrogen;

[0207] q is an integer of 1-50, preferably 1-20, more preferably 1-10,

[0208] and one or more units of formula (VIII), preferably 10 to 1500 units, more preferably 50 to 1000 units, even more preferably 100 to 500 units:

[0209] SiR 3 d R e O (4-d-e) / 2 (Formula VIII)

[0210] in:

[0211] R, same or different, as defined above;

[0212] R 3 , same or different, as above for R 1 Group defined;

[0213] And d=0, 1, 2, preferably d=0 or 1; e=1, 2 or 3; and the total d+e=1, 2 or 3.

[0214] Preferably, in the above formula, R 3 , the same or different, means:

[0215] - an alkenyl group containing 2 to 6 carbon atoms, preferably a vinyl group,

[0216] - hydroxyl group (OH),

[0217] - a linear or branched alkyl group containing 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, which is optionally substituted by at least one fluorine atom, for example 1 to 10 fluorine atoms, for example (C1-C5)alkyl-CF3, the alkyl group being linear or branched;

[0218] -hydrogen.

[0219] According to one embodiment of the present invention, the organopolysiloxane OR may be a compound of formula (IX):

[0220]

[0221] in

[0222] R, same or different, means:

[0223] - an alkyl group containing 1 to 15 carbon atoms, preferably 1 to 12 carbon atoms, preferably 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, preferably a methyl group,

[0224] - an aryl group containing 6 to 10 carbon atoms, preferably a phenyl group,

[0225] R 1 , the same or different, means:

[0226] - an alkenyl group containing 2 to 6 carbon atoms, preferably a vinyl group,

[0227] - hydroxyl group (OH),

[0228] - a group (O-Alk), wherein Alk represents an alkyl group containing 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,

[0229] - group (O-Alk) x , wherein Alk represents an alkyl group containing 1 to 15 carbon atoms, preferably 1 to 12 carbon atoms, preferably 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, preferably a methyl group, and x represents an integer of 2 to 200, or

[0230] -hydrogen;

[0231] R 2 , the same or different, means:

[0232] - an alkenyl group containing 2 to 6 carbon atoms, preferably a vinyl group,

[0233] - hydroxyl group (OH),

[0234] a linear or branched alkyl group containing 1 to 12 carbon atoms, preferably 1 to 5 carbon atoms, which is optionally substituted by at least one heteroatom O, N, S or a halide such as a fluorine atom, for example 1 to 10 fluorine atoms, for example (C1-C5)alkyl-CF3, the alkyl group being linear or branched,

[0235] - optionally substituted C5-C 10 cycloalkyl groups,

[0236] - optionally substituted C6-C 18 an aryl group, or

[0237] -hydrogen;

[0238] q is an integer of 1-50, preferably 1-20, more preferably 1-10;

[0239] n2 represents an integer of 10-1500, preferably 10-1000, preferably 50-1000, more preferably 100-500;

[0240] m2 represents an integer of 0-100, preferably 0-50, more preferably 0-30, and preferably m=0.

[0241] According to a preferred embodiment of the present invention, the organopolysiloxane OR is a compound of formula (IX):

[0242] in,

[0243] R, identical or different, represents CH3 or phenyl, preferably CH3;

[0244] R 1 , the same or different, means:

[0245] - an alkenyl group containing 2 to 6 carbon atoms, preferably a vinyl group,

[0246] - hydroxyl group (OH),

[0247] a linear or branched alkyl group containing 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, which is optionally substituted by at least one fluorine atom, for example 1 to 10 fluorine atoms, such as (C1-C5)alkyl-CF3, the alkyl group being linear or branched, or

[0248] -hydrogen;

[0249] R 2 , the same or different, means:

[0250] - an alkenyl group containing 2 to 6 carbon atoms, preferably a vinyl group,

[0251] - hydroxyl group (OH),

[0252] a linear or branched alkyl group containing 1 to 12 carbon atoms, preferably 1 to 5 carbon atoms, which is optionally substituted by at least one heteroatom O, N, S or a halide such as a fluorine atom, for example 1 to 10 fluorine atoms, for example (C1-C5)alkyl-CF3, the alkyl group being linear or branched,

[0253] - optionally substituted C5-C 10 cycloalkyl groups,

[0254] - optionally substituted C6-C 18 an aryl group, or

[0255] -hydrogen;

[0256] q is an integer of 1-50, preferably 1-20, more preferably 1-10;

[0257] n2 represents an integer of 10-1500, preferably 10-1000, preferably 50-1000, more preferably 100-500;

[0258] m2 represents an integer of 0-100, preferably 0-50, more preferably 0-30, and preferably m=0.

[0259] According to a particularly preferred embodiment of the present invention, the organopolysiloxane OR of the present invention is a compound of formula (IX) in which:

[0260] R, identical or different, represents CH3 or phenyl, preferably CH3;

[0261] R 1 , the same or different, represent CH3, vinyl, H, (C1-C5)alkyl-CF3 or OH;

[0262] R 2 , the same or different, means:

[0263] - an alkenyl group containing 2 to 6 carbon atoms, preferably a vinyl group,

[0264] - hydroxyl group (OH),

[0265] - a linear or branched alkyl group containing 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms,

[0266] - optionally substituted C6-C 18 an aryl group, or

[0267] -hydrogen;

[0268] q is an integer of 1-20, preferably 1-10, more preferably 1-5;

[0269] n2 represents an integer of 10-1500, preferably 10-1000, preferably 50-1000, more preferably 100-500;

[0270] m2 represents an integer of 0-100, preferably 0-50, more preferably 0-30, and preferably m=0.

[0271] In one embodiment, the organopolysiloxane OR of the present invention is a compound of formula (X):

[0272]

[0273] in,

[0274] R, same or different, means:

[0275] - an alkyl group containing 1 to 15 carbon atoms, preferably 1 to 12 carbon atoms, preferably 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, preferably a methyl group,

[0276] - an aryl group containing 6 to 10 carbon atoms, preferably a phenyl group,

[0277] R 1 , the same or different, means:

[0278] - an alkenyl group containing 2 to 6 carbon atoms, preferably a vinyl group,

[0279] - hydroxyl group (OH),

[0280] - a group (O-Alk), wherein Alk represents an alkyl group containing 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,

[0281] - group (O-Alk) x , wherein Alk represents an alkyl group containing 1 to 15 carbon atoms, preferably 1 to 12 carbon atoms, preferably 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, preferably a methyl group, and x represents an integer of 2 to 200,

[0282] a linear or branched alkyl group containing 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, which is optionally substituted by at least one fluorine atom, for example 1 to 10 fluorine atoms, such as (C1-C5)alkyl-CF3, the alkyl group being linear or branched,

[0283] - Hydrogen, or

[0284] -CH2CH2(R3SiO) n3 A group, wherein R is as defined above and n3 represents an integer of 0-1000, preferably 0-500, more preferably 0-200;

[0285] R 2 , the same or different, means:

[0286] - an alkenyl group containing 2 to 6 carbon atoms, preferably a vinyl group,

[0287] - hydroxyl group (OH),

[0288] a linear or branched alkyl group containing 1 to 12 carbon atoms, preferably 1 to 5 carbon atoms, which is optionally substituted by at least one heteroatom O, N, S or a halide such as a fluorine atom, for example 1 to 10 fluorine atoms, for example (C1-C5)alkyl-CF3, the alkyl group being linear or branched,

[0289] - optionally substituted C5-C 10 cycloalkyl groups,

[0290] - optionally substituted C6-C 18 an aryl group, or

[0291] -hydrogen;

[0292] q is an integer of 1-50, preferably 1-20, more preferably 1-10;

[0293] n2 represents an integer of 10-1500, preferably 10-1000, preferably 50-1000, more preferably 100-500;

[0294] m2 represents an integer of 0-100, preferably 0-50, more preferably 0-30, and preferably m=0.

[0295] n3 represents different or identical integers of 0-1000, preferably 0-500, more preferably 0-200;

[0296] a represents different or identical integers equal to 0 or 1.

[0297] In the meaning of the present invention, the degree of polymerization is understood to be an integer number of siloxy repeating units.

[0298] According to one embodiment of the process according to the invention, the organopolysiloxane OR thus obtained has a degree of polymerization which is at least halved compared to the degree of polymerization of the organosilicon S introduced, preferably at least divided by three compared to the degree of polymerization of the organosilicon S introduced, preferably at least divided by five compared to the degree of polymerization of the organosilicon S introduced.

[0299] According to one embodiment of the process according to the invention, the organopolysiloxane OR thus obtained has a degree of polymerization which, compared to the degree of polymerization of the organosilicon S introduced, is at least divided by ten.

[0300] In the meaning of the present invention, the weight average molecular weight and number average molecular weight (respectively M w and M n , (denoted by) can be determined by size exclusion chromatography (SEC) in a solvent such as toluene at 40°C using polystyrene standards.

[0301] According to one embodiment of the process of the invention, the organopolysiloxane OR thus obtained has a weight-average molecular weight M w The weight average molecular weight of the organic silicon S is at least halved, preferably halved compared to the weight average molecular weight M of the organic silicon S introduced. w Compared to the weight average molecular weight M of the introduced organosilicon S divided by at least three, preferably w Compare that to at least divided by five.

[0302] According to one embodiment of the process according to the invention, it is also conceivable that the organopolysiloxane OR thus obtained has a weight-average molecular weight M w The weight average molecular weight of the organic silicon S introduced is divided by at least ten, or the weight average molecular weight M of the organic silicon S introduced is divided by at least ten. w Compare that to at least divided by fifteen.

[0303] According to one embodiment of the process according to the invention, the organopolysiloxane OR according to the invention is characterized in that its weight-average molecular weight M wIt may be from 500 to 300 000 g / mol, preferably from 1000 to 150 000 g / mol, preferably from 1000 to 100 000 g / mol, even more preferably from 5000 to 40 000 g / mol.

[0304] According to one embodiment of the process according to the invention, the organopolysiloxane OR thus obtained has a number average molecular weight M n The number average molecular weight of the organic silicon S introduced is at least halved, preferably halved compared to the number average molecular weight of the organic silicon S introduced. n Compared to the number average molecular weight M of the introduced organosilicon S divided by at least three, preferably n Compare that to at least divided by five.

[0305] According to one embodiment of the process according to the invention, it is also conceivable that the organopolysiloxane OR thus obtained has a number average molecular weight M n At least divided by ten compared to the number average molecular weight of the introduced organosilicon S, or the number average molecular weight M of the introduced organosilicon S n Compare that to at least divided by fifteen.

[0306] According to one embodiment of the process according to the invention, the organopolysiloxane OR according to the invention is characterized in that its number-average molecular weight M n It is from 500 to 300 000 g / mol, preferably from 1000 to 150 000 g / mol, preferably from 1000 to 70 000 g / mol, even more preferably from 2500 to 30 000 g / mol.

[0307] According to one embodiment of the process according to the invention, the organopolysiloxanes OR according to the invention are characterized by a dynamic viscosity of 100 to 100 000 mPa.s at 25°C, preferably 1000 and 80 000 mPa.s at 25°C, even more preferably 10 000 to 70 000 mPa.s at 25°C.

[0308] In one embodiment, the organopolysiloxane OR of the present invention has an amount of chain-terminal (Si-OH) bonds of less than or equal to 15%, preferably less than or equal to 10%, preferably less than or equal to 5%, even more preferably less than or equal to 1%, relative to the total amount of chain-terminal silicon atoms of the organopolysiloxane OR of the present invention.

[0309] In the context of the present application, the weight percentage of D4 in the product obtained according to the process of the present invention can be determined by quantitatively 29 SiNMR spectroscopy measurement Alternatively, the weight percentage of D4 in the product obtained according to the process of the present invention can be measured by chromatograms analyzed by size exclusion chromatography (SEC).

[0310] In the meaning of the present invention, the term "cyclic organopolysiloxane" refers to a compound of formula (XI):

[0311]

[0312] Where n represents a natural number from 1 to 5.

[0313] Typically, cyclic organopolysiloxanes within the meaning of the present invention consist of compounds of formula (XI) in which n is equal to 2 or 3 or 4.

[0314] In other words, octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), dodecamethylcyclohexasiloxane (D6) or a mixture thereof.

[0315] 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%, even more preferably less than or equal to 1.5%, relative to the total mass of the organopolysiloxane OR according to the invention.

[0316] 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%, even more preferably less than or equal to 1.5%, relative to the total mass of the organopolysiloxane OR according to the invention.

[0317] Preferably, the process of the invention is carried out in a solvent. The process of the invention is preferably carried out in a non-polar solvent. The solvent may in particular be an organic solvent of the alkane or aromatic hydrocarbon type.

[0318] Preferably, the solvent is selected from n-hexane, n-heptane, n-decane, n-dodecane, isododecane, EXXSOL D60, xylene, toluene and mixtures thereof.

[0319] In one embodiment, the process according to the invention is characterized in that the mass ratio of the mass of organosilicon S to the mass of the solvent used is from 0.01 to 15, preferably from 0.1 to 5, preferably from 0.1 to 2.

[0320] In one embodiment, the process according to the invention is characterized in that the depolymerization reaction is carried out in the absence of a solvent.

[0321] This embodiment is particularly advantageous since it makes it possible to dispense with the use of solvents and their disposal or recycling once used, while at the same time achieving satisfactory results when carrying out the process according to the invention.

[0322] Advantageously and preferably, the reaction is carried out at a temperature of 0°C to 100°C, preferably 0°C to 50°C, more preferably 10°C to 35°C, for example at ambient temperature.

[0323] According to the method of the present invention, the reaction time is 2-72 hours, preferably 5-24 hours, more preferably 8-24 hours, for example 24 hours.

[0324] A person skilled in the art will know how to adjust these parameters according to the nature of the reactor and the materials used.

[0325] The method of the present invention may further comprise a step of neutralizing the acid catalyst. This neutralization step prevents the occurrence of side reactions and deactivates the acid catalyst.

[0326] Advantageously, this neutralization step is carried out by adding a base to the reaction medium or by thermal degradation of the acid catalyst.

[0327] According to the process of the present invention, the base is selected from amines, alkali metal hydroxides, alkaline earth metal hydroxides, carbonates, bicarbonates and mixtures thereof.

[0328] Preferably, the base is selected from a tertiary amine or a bicarbonate.

[0329] Alternatively, the neutralization step is performed by "thermal degradation".

[0330] The term "thermal degradation" is understood to mean heating at a temperature above 120° C. for a duration of 10 minutes to 3 hours. A person skilled in the art will know how to adjust the operating conditions to optimize this thermal degradation step. This step allows the catalyst to be degraded and the depolymerization reaction to be stopped.

[0331] The process according to the invention may also include a filtration step to extract the neutralized catalyst and / or excess base from the reaction medium. This step may also allow the extraction of possible fillers originating from the organosilicon S depolymerized according to the process according to the invention. A person skilled in the art will know how to adapt the filtration process to the size and composition of the reactor used in the process according to the invention.

[0332] According to a preferred embodiment of the present invention, the method of the present invention comprises the following three steps:

[0333] - carrying out a process for preparing organopolysiloxanes OR by depolymerization of at least one organosilicon S in the presence of an acid catalyst and at least one chain-capping agent Bc having at least one siloxane functional group;

[0334] - 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

[0335] - Filtration of the reaction medium obtained at the end of step 2.

[0336] The present application also relates to the use of the organopolysiloxanes OR obtained by the process according to the invention as a directly usable ingredient in various organosilicon formulations that can be used in various sectors such as cosmetics, household care products, motor vehicles, energy.

[0337] The organopolysiloxanes OR derived from silicones S as described in detail above in this application can be reused in various formulations to prepare new silicones S.

[0338] Therefore, the present application also relates to the use of the organopolysiloxanes OR obtained by the process according to the invention for preparing silicones S, for example for preparing silicone oils, resins, gums, gels or elastomers.

[0339] The present application also relates to a method for preparing silicone, in particular silicone oil, resin or glue, comprising the following steps:

[0340] 1) implementing the method for preparing organopolysiloxane OR according to the present invention;

[0341] 2) Preparing an organosilicon S, in particular an oil, a resin, a gum or an elastomer, from the organopolysiloxane OR obtained in step 1).

[0342] In one embodiment, the process for preparing organosilicon S is characterized in that step 2 is carried out by a polyaddition or polycondensation reaction via a cationic or free radical mechanism.

[0343] Step 2 may in particular consist in producing a liquid silicone elastomer (LSR), an thermally vulcanized silicone elastomer (EVC) or an ambient temperature vulcanized silicone elastomer (RTV).

[0344] According to another embodiment, step 2 can consist in particular in preparing silicones S which can be used in the fields of cosmetics, health, household products, technical technical formulations (seals, films, tubes), transport, such as motor vehicles or air transport, or in the energy sector. DETAILED DESCRIPTION

[0345] Example :

[0346] Silicone used in the examples :

[0347] In the following: Me = methyl;

[0348] Silicone S1:

[0349] n = 943; M n =70 000g / mol

[0350] Silicone S2:

[0351]

[0352] Where n = 81 (M n =6000g / mol)、n=943(M n =70 000 g / mol) and n=1080 (M n =80 000 g / mol), a mixture of three silicone oils,

[0353] Silicone S3:

[0354] Silicone S3 is an RTV2 gel formulated by ELKEM. This silicone is obtained by a polyaddition reaction.

[0355] Silicone S4:

[0356] Commercially available silicone tubing of unknown composition cut into small pieces.

[0357] Silicone S5:

[0358]

[0359] Silicone S5 is ELKEM under the name BLUESIL TM PDMS glue sold by FB Organic Silicone.

[0360] The acid catalyst is HDBS, also known as 4-dodecylbenzenesulfonic acid (CAS 121-65-3).

[0361] The solvent used in the examples is a non-polar solvent, preferably toluene or heptane.

[0362] Chain-capping agents used in the examples :

[0363] Chain end capping agent Bc1: divinyltetramethyldisiloxane (CAS 2627-95-4)

[0364] Chain capping agent Bc2: hexamethyldisiloxane (CAS107-46-0)

[0365] Chain capping agent Bc3: Tetramethyldisiloxane (CAS 3277-26-7)

[0366] Chain capping agent Bc4:

[0367]

[0368] Where n = 13 (M n =977 g / mol).

[0369] Example 1: General scheme of the method:

[0370] Organosilicon S and 120 ml of toluene were added to a 250 ml round bottom flask along with variable amounts of acid catalyst and chain end capping agent Bc. The reaction medium was left at ambient temperature for 24 hours under stirring. A large excess of inorganic or amine base was then added to the reaction medium. Samples were taken and passed through 1 H NMR and 29 Analyze by Si NMR.

[0371] In the context of the examples described below, the mass percentage of D4 relative to the total mass in the organopolysiloxane OR obtained according to the process of the invention can be determined by size exclusion chromatography (SEC) in a solvent such as toluene at 40° C. using polystyrene standards.

[0372] Similarly, the number average molecular weight (in M) of various organopolysiloxanes OR according to the present invention is n denoted) were determined by the same size exclusion chromatography (SEC) method.

[0373] The QBc value is given in the following example tables. This value represents the number of moles of Bc relative to the number of moles of (Si—O) bonds in the silicone S.

[0374] Example 2: Effect of the properties of organosilicon S on the method of the present invention:

[0375] The protocol of Example 1 was followed, using silicone S (30 g, approximately 404 mmol of (Si—O) bonds in silicone S for S1, S2, S3, and S5), HDBS (4400 ppm by mass, 0.132 g) as the acid catalyst, and Bc1 as the chain-capping agent Bc. The reaction medium was left at ambient temperature with stirring for 24 hours. Silicone S4 was a commercial silicone tube of unknown composition that had been cut into small pieces. For the remainder of this example, it will be assumed that this tube consisted of both a significant amount of filler (30%) and 70% silicone.

[0376] Thus, for 30 g of silicone tube, this test considers the presence of 21 g of silicone S. 0.265 g of chain-capping agent Bc1 and 0.0925 g of HDBS are subsequently introduced into the reaction medium.

[0377] The properties and QBc values ​​of silicone S are given in the table below.

[0378]

[0379] The results show that the method of the invention is general and can be used for all types of silicones, including silicone mixtures and silicones containing fillers.

[0380] Example 3: Effect of the properties of the chain-capping agent Bc on the method of the present invention :

[0381] The protocol of Example 1 was carried out using organosilicon S1 (30 g, 404 mmol of (Si—O) bonds in organosilicon S1), HDBS (4400 ppm by mass, 0.132 g) as acid catalyst and chain-capping agent Bc. The reaction medium was left at ambient temperature for 24 hours.

[0382] The nature of the chain-capping agents and the QBc values ​​are indicated in the table below.

[0383]

[0384] The test was repeated, using RTV2 silicone gel (silicone S3) manufactured by ELKEM instead of silicone S1. The other operating conditions remained unchanged compared to the above. Therefore, this test was conducted using silicone S3 (30 g, 404 mmol of (Si-O) bonds in silicone S3), HDBS (4400 ppm by mass, 0.132 g) as the acid catalyst, and chain-capping agent Bc, as shown in the following table:

[0385]

[0386] These tests demonstrate the versatility and robustness of the process according to the invention. In particular, the nature of the chain-capping agent Bc has an influence on the number-average molecular weight (M) of the organopolysiloxanes OR obtained according to the process according to the invention. n ) has a limited impact. Therefore, the method can be carried out using various organosilicones S and various chain-capping agents Bc. In the context of this embodiment, the D4 percentage of the product obtained according to the method of the present invention is less than or equal to 2% by mass relative to the total mass of the organopolysiloxane OR.

[0387] Example 4: Effect of the amount of chain-capping agent Bc on the method of the present invention :

[0388] The protocol of Example 1 was implemented using organosilicon S1 (30 g, 404 mmol of (Si—O) bonds in organosilicon S1), HDBS (4400 ppm by mass, 0.132 g) as acid catalyst and Bc1 as chain-capping agent. The reaction medium was left at ambient temperature for 24 hours.

[0389] The quality and QBc values ​​of Bc are shown in the table below.

[0390]

[0391] In the context of each test (Tests 1 to 8) of this example, the mass percentage of D4 relative to the total mass of the product OR was less than 2% by mass.

[0392] The test was repeated, using RTV2 silicone gel (silicone S3) manufactured by ELKEM instead of silicone S1. The other operating conditions remained unchanged compared to the above. Therefore, this test was conducted using silicone S3 (30 g, 404 mmol of (Si—O) bonds in silicone S3), HDBS (4400 ppm by mass, 0.132 g) as the acid catalyst, and chain-capping agent Bc.

[0393] The quality and QBc values ​​of Bc are shown in the table below.

[0394]

[0395] These two tests demonstrate that the method according to the invention can be used to determine the number average molecular weight (M n ) is controlled. Variation of the amount of chain-capping agent Bc has an effect on the molecular weight of OR. It can be noted that the product obtained according to the process of the invention has a D4 percentage of less than or equal to 1.3% by mass, relative to the total mass of the organopolysiloxane OR.

[0396] Example 5: Effect of Acid Amount on the Method of the Invention :

[0397] The protocol of Example 1 was carried out using silicone S1 (30 g, 404 mmol of (Si—O) bonds in silicone S1), HDBS (1100 to 17600 ppm by mass) as acid catalyst and chain-capping agent Bc.

[0398] The QBc values ​​and the molar amounts of HDBS are shown in the table below.

[0399]

[0400] It can be noted that at a fixed amount of chain-capping agent QBc, when the amount of acid catalyst is increased, an increase in the percentage of D4 is also observed.

[0401] Therefore, the amount of acid catalyst involved in the reaction has an influence on both the reaction kinetics, the average molecular weight obtained and the amount of undesirable by-products such as D4.

[0402] With the help of the information disclosed in the present invention, a person skilled in the art will know how to adjust these parameters to obtain a desired number average molecular weight M by means of the method of the present invention. n At the same time, polyorganosiloxane OR with controlled ring content.

[0403] Example 6: Comparison with the solution of patent application JP2002348407A :

[0404] 20g of PDMS S4, 47g of toluene and 2.4g of HDBS solution were introduced into a 250ml round-bottom flask equipped with a magnetic stirrer. After stirring with a stirrer for 1 hour at ambient temperature, the organosilicon tube was completely decomposed and dissolved. Next, a solution of 0.54g of calcium hydroxide in 15g of isopropanol was added for neutralization, and 50g of water was added. The obtained mixture was stirred for 10 minutes. After standing for 30 minutes, a sample of the obtained organic phase was extracted, diluted to a suitable concentration, filtered and analyzed by size exclusion chromatography. The number average molecular weight (M) of the organopolysiloxane of 11,000g / mol was then obtained. n ), wherein the amount of undesirable by-products such as octamethyltetrasiloxane (D4) is equal to 15% by mass relative to the total mass of the organopolysiloxane obtained.

[0405] Example 7: Effect of the properties of the acid catalyst :

[0406] The protocol of Example 1 was implemented using organosilicon S1 (30 g, 404 mmol of (Si—O) bonds in organosilicon S1), acid catalyst (4400 ppm by mass) and chain-capping agent Bc. The properties of the acid catalyst and the mass of the catalyst used are shown in the table below.

[0407]

[0408] It can be noted that Tests 2 and 3 have satisfactory results within the meaning of the present invention. However, it can be noted that trifluoromethanesulfonic acid produces 3% by mass of D4 relative to the total mass of the organopolysiloxane OR.

[0409] In contrast, 4-dodecylbenzenesulfonic acid (CAS 121-65-3) exhibits satisfactory performance of the process of the invention, as has already been shown in the preceding examples.

[0410] Example 8: Effect of reaction time on the method of the present invention :

[0411] The protocol of Example 1 was carried out using silicone S1 (30 g, 404 mmol of (Si—O) bonds in silicone S1), HDBS (4400 ppm by mass, 0.132 g) as acid catalyst and chain-capping agent Bc.

[0412] The QBc values ​​and reaction times are shown in the table below.

[0413]

[0414]

[0415] These tests show that the reaction time also enables the number-average molecular weight M of the polyorganosiloxanes OR obtained by the process according to the invention to be controlled. n .

[0416] Example 9: Effect of temperature on the method of the present invention :

[0417] The protocol of Example 1 was carried out using silicone S1 (30 g, 404 mmol of (Si—O) bonds in silicone S1), HDBS (4400 ppm by mass, 0.132 g) as acid catalyst and chain-capping agent Bc.

[0418] The following table shows the temperature, degree of polymerization of the product OR and the mass percentage of D4:

[0419]

[0420] The temperature during the implementation of the process according to the invention makes it possible to control the number-average molecular weight M of the polyorganosiloxane OR obtained according to the process according to the invention. n .

[0421] Example 10: Effect of solvent content on the method of the present invention :

[0422] The protocol of Example 1 was carried out using silicone S1 (30 g, 404 mmol of (Si—O) bonds in silicone S1), HDBS (4400 ppm by mass, 0.132 g) as acid catalyst and chain capping agent Bc and toluene as solvent.

[0423] In this example, five tests were performed using different volumes of solvent.

[0424] This example aims to investigate the possible influence of the volume of solvent introduced into the process of the invention.

[0425] The following table shows the volumes of solvent introduced into each test:

[0426]

[0427] The amount of solvent introduced during the implementation of the process according to the invention has an influence on the number average molecular weight M of the polyorganosiloxane OR obtained according to the process according to the invention. n Furthermore, in the same embodiment, for each test, the mass percentage of D4 relative to the total mass of product OR is less than or equal to 2%.

[0428] Example 11: Reuse of Silicone S2 Depolymerized to Organopolysiloxane OR in New RTV2 Formulations :

[0429] In the context of this example, the ability to prepare RTV2 gels using functional organopolysiloxanes OR (obtained under the conditions of Test 1 in Example 2) was tested. Thus, the recycled product OR containing vinyl functional groups from Test 1 in Example 2 was used in combination with a poly(methylhydrogensiloxane)-co-poly(dimethylsiloxane) crosslinker, where [Si-H] / [Si-vinyl]=2.25. To obtain this RTV2 gel, a hydrosilylation reaction was carried out in the presence of Karstedt's catalyst (275 ppm of a 2% Pt solution) and 1-ethynylcyclohexanol as a moderator ([1-ethynylcyclohexanol] / [Pt]=14.6 ppm). The reaction mixture was then mixed, degassed, and crosslinked at 70°C for 4 hours.

[0430] The attached [ Figure 1 ] shows a photograph of an RTV2 gel obtained under the conditions of this example. This RTV2 formulation was prepared twice under the same conditions, and each test exhibited similar physical properties. Specifically, the RTV2 gel obtained in the first test had a swelling degree of 280% and an extractable fraction of 10%, while the RTV2 gel obtained in the second test had a swelling degree of 285% and an extractable fraction of 10%.

[0431] Therefore, this example shows that the organopolysiloxane OR obtained according to the method of the present invention can be used in a formulation to obtain an RTV2-type silicone gel. In view of the information disclosed in the present invention (more particularly in this example), a person skilled in the art will know how to adjust the operating conditions to use the organopolysiloxane obtained according to the method of the present invention in other silicone formulations (EVC, RTV1, LSR).

Claims

1. A process for preparing organopolysiloxanes OR by depolymerization of at least one organosilicon S in the presence of: - an acid catalyst selected from the group consisting of benzenesulfonic acid derivatives of formula (VIa), alone or as a mixture: Either R1 and R2 represent hydrogen atoms and R3=C n H 2n+1 , wherein 5≤n≤20, preferably 10≤n≤20, Either R1 and R3 represent hydrogen atoms and R2=C n H 2n+1 , wherein 5≤n≤20, preferably 10≤n≤20, or either R2 and R3 represent hydrogen atoms and R1=C n H 2n+1 , wherein 5≤n≤20, preferably 10≤n≤20 and at least one chain-capping agent Bc having at least one siloxane functional group.

2. The process according to claim 1, wherein the acid catalyst is selected from benzenesulfonic acid derivatives of formula (VIb) alone or as a mixture: Where R = C n H 2n+1 , wherein 5≤n≤20, preferably 10≤n≤20.

3. The method according to claim 1 or 2, wherein the chain-capping agent Bc is selected from compounds of formula (IV): in, R 1 , the same or different, means: - a linear or branched alkyl radical comprising 1 to 12 carbon atoms, preferably 1 to 8 carbon atoms, which is optionally substituted by heteroatoms O, N, S or halides, - an alkenyl group containing 2 to 6 carbon atoms, - a cycloalkyl group containing 5 to 10 carbon atoms, which is optionally substituted by heteroatoms O, N, S or halides, -C6-C 18 aryl groups, - a hydroxyl group, or -hydrogen, R 2 , the same or different, means: - an alkenyl group containing 2 to 6 carbon atoms, preferably a vinyl group, - hydroxyl group (OH), a linear or branched alkyl group containing 1 to 12 carbon atoms, preferably 1 to 5 carbon atoms, which is optionally 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 -hydrogen; And q is an integer of 1-50, preferably 1-20, more preferably 1-10.

4. The process according to claim 1, wherein the amount of chain-capping agent Bc used in the process of the invention is at least 10 (Si-O) bonds per mole of organosilicon S. -4 mole, preferably 10 (Si-O) bonds per mole of organosilicon S -3 to 5×10 -1 mole, preferably 10 -3 to 10 -2 mole, even more preferably 3×10 -3 to 6×10 -1 Moore.

5. The method according to any one of claims 1 to 4, wherein the amount of the acid catalyst is 0.001-1% by mass relative to the mass of the organosilicon S, preferably 0.05-1% by mass relative to the mass of the organosilicon S, more preferably 0.1-1% by mass.

6. The method according to any one of claims 1 to 5, wherein the organopolysiloxane OR is characterized by a number average molecular weight M n It is from 500 to 300 000 g / mol, preferably from 1 000 to 150 000 g / mol, preferably from 1 000 to 70 000 g / mol, even more preferably from 2 500 to 30 000 g / mol.

7. The method according to any one of claims 1 to 6, wherein the content of cyclic organopolysiloxane 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 organopolysiloxane OR.

8. The process according to any one of claims 1 to 7, wherein the reaction is carried out at a temperature of 0-100°C, preferably 0-50°C, more preferably 10-35°C.

9. The process according to any one of claims 1 to 8, wherein the reaction is carried out in the presence of a non-polar solvent.

10. The method according to any one of claims 1 to 9, characterized in that The mass ratio of the mass of the organosilicon S relative to the mass of the solvent used is from 0.01 to 15, preferably from 0.1 to 5, more preferably from 0.1 to 2.

11. The method according to any one of claims 1 to 10, characterized in that The process also comprises a neutralization step of the acid catalyst by adding a base to the reaction medium or by thermal degradation of the acid catalyst.

12. The method according to any one of claims 1 to 11, characterized in that The method comprises the following steps: 1) carrying out a process for preparing an organopolysiloxane OR by depolymerization of at least one organosilicon S in the presence of an acid catalyst and at least one chain-capping agent Bc having at least one siloxane functional group; 2) neutralizing 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 medium obtained at the end of step 2.

13. Use of the organopolysiloxanes OR obtained according to any of the preceding claims as a constituent of organosilicon formulations in the fields of cosmetics, health, household products, technical technical formulations, transport, such as motor vehicles or air transport, or in the energy sector.

14. A method for preparing an organosilicon S, in particular an organosilicon oil, resin, glue or elastomer, comprising the following steps: 1) implementing the method for preparing an organopolysiloxane OR according to any one of claims 1 to 12; 2) preparing organosilicon S from the organopolysiloxane OR obtained in step 1).

15. The method for preparing organosilicon S according to claim 14, characterized in that: Step 2 is carried out by a cationic mechanism or a free radical mechanism of polyaddition or polycondensation reaction.

16. Use of the organosilicon S obtained by the process according to claim 14 or 15 in the fields of cosmetics, health, household products, technical technical formulations, transport, such as motor vehicles or air transport, or in the energy sector.

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