Organopolysiloxane depolymerization

Abstract

The present invention relates to a process for preparing cyclic polysiloxanes by reactive distillation of at least one organopolysiloxane in the presence of an alkali salt catalyst selected from salts of K, Na, Rb, or Cs and a multidentate complexing agent.

Description

[Technical field]

[0001] The present invention relates to cyclic organopolysiloxanes, and more particularly to a process for preparing cyclic organopolysiloxanes by depolymerization of organopolysiloxanes in the presence of a catalyst system comprising an alkaline catalyst and a multidentate complexing agent. [Background technology]

[0002] Recycling of industrial and used silicone products is an ongoing concern. Recycling silicone polymers could reduce the gas emissions (CO, CO2) associated with the silicone industry by 75% and silicone waste by 65%.

[0003] One envisioned recycling route is the depolymerization of organopolysiloxanes to produce cyclic organopolysiloxanes (or cyclosiloxanes).

[0004] The depolymerization of silanol-terminated polydimethylsiloxanes (PDMS) in the presence of strong alkaline hydroxides or quaternary hydroxides is known, in particular from US 5,670,689. The reaction is carried out at 140° C. to achieve a 90% yield of the mixture of cyclic organopolysiloxanes. However, a high loading of catalyst is required, in particular at least 2% by weight relative to the weight of PDMS-OH.

[0005] There is therefore an interest in providing an optimized process that makes it possible to efficiently depolymerize organopolysiloxanes and obtain good yields of cyclic siloxanes, in particular D3 (hexamethylcyclotrisiloxane), D4 (octamethylcyclotetrasiloxane) and D5 (decamethylcyclopentasiloxane). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] US5670689 Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, one object of the present patent application is to provide a depolymerization method for efficiently depolymerizing organopolysiloxanes, which makes it possible to obtain good yields of cyclic organopolysiloxanes, in particular D3, D4 and D5.

[0008] Another object of the present application is to provide a catalyst system for carrying out this method.

[0009] Yet another object of the present application is to provide a catalyst system which is simple and gives good reaction kinetics, thus making it suitable for industrialization of the process.

[0010] Other objects will become apparent from a reading of the following description of the invention. [Means for solving the problem]

[0011] These objects are achieved in the present patent application, which relates to a process for preparing cyclic organopolysiloxanes CO by reactive distillation of at least one organopolysiloxane O in the presence of a catalyst of alkali salt type selected from salts of K, Na, Rb or Cs and a multidentate complexing agent. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The organopolysiloxane O of the invention may be any type of organopolysiloxane and may in particular be chosen from linear organopolysiloxanes, such as oils or gums, or branched organopolysiloxanes.

[0013] The organopolysiloxane O may in particular be oily or rubbery and preferably has a dynamic viscosity at 25° C. of 50 to 600,000 mPa.s or a consistency at 25° C. between 200 and 2000 (expressed in tenths of a millimeter).

[0014] All viscosities mentioned in this description correspond to so-called "Newtonian" dynamic viscosity values ​​at 25°C, i.e. dynamic viscosities measured in known manner using a Brookfield viscometer at shear rate gradients that are sufficiently low that the measured viscosity is independent of the velocity gradient.

[0015] The term "gum" is typically used for organopolysiloxane compounds having a viscosity greater than 600,000 mPa.s, which corresponds to a molecular weight greater than 260,000 g / mol.

[0016] The consistency or penetrometer of the gums is determined at 25° C. using a penetrometer of type PNR12 or equivalent model, which makes it possible to apply a cylindrical head to the sample under standardized conditions.

[0017] These organopolysiloxanes O contain one or more functional units, such as -OH, -H, alkenyl, especially containing 2 to 6 carbon atoms, preferably vinyl; O-Alk, where Alk represents an alkyl group containing 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, - 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 (O-Alk), x ; x represents an integer between 2 and 200. an amino group, in which Alk represents alkyl containing 1 to 5 carbon atoms, in particular (Alk)-NH2 or (Alk)-NH-(Alk)-NH2, - Cyclic amines, e.g. -(CH2) z -O-piperidine, where z represents an integer from 1 to 5, preferably 3, which may be substituted, in particular by one or more alkyl groups containing from 1 to 3 carbon atoms, preferably methyl, preferably the substituted piperidine is

[0018] [ka]

[0019] embedded image

[0020] Preferably, the organopolysiloxane O may contain one or more functional units, such as H, OH, as defined above, alkenyl (preferably vinyl), aryl, cyclic amine.

[0021] The organopolysiloxane O of the present invention may be partially crosslinked.

[0022] The organopolysiloxane O of the present invention may in particular be a waste (used) organopolysiloxane, for example one used as a heat transfer fluid and to be recycled, and thus the method of the present invention makes it possible to obtain cyclic organopolysiloxane CO, which can then be directly used in industrial processes, in particular in new polymerization processes. For example, the organopolysiloxane O of the present invention may be a silicone oil, in particular one with terminal trimethylsilyl, dimethylhydroxysilyl or dimethylvinylsilyl units, or indeed a silicone gel. If waste organopolysiloxane O is repurposed, the organopolysiloxane may contain other elements such as additives, pigments, etc. The inventors have thus shown that the presence of these other elements does not interfere with the depolymerization reaction and the formation of the cyclic organopolysiloxane CO.

[0023] According to one embodiment of the present invention, the organopolysiloxane O of the present invention is - Formula R c SiO (4-c) / 2 (In the ceremony R may be the same or different and is any of the following: 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; an aryl group containing 6 to 10 carbon atoms, preferably phenyl; represents where c=0, 1, 2, or 3), and - In some cases, the formula R 1 d R e SiO (4-d-e) / 2 (In the formula: R is as defined above, R 1 may be the same or different and are as follows: alkenyl groups containing 2 to 6 carbon atoms, preferably vinyl, Hydroxyl group (OH), the (O-Alk) group, in which 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, 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, and x represents an integer between 2 and 200 (O-Alk). x basis, an amino group selected from (Alk)-NH2 or (Alk)-NH-(Alk)-NH2, wherein Alk represents an alkyl group containing 1 to 5 carbon atoms; Cyclic amines, e.g. -(CH2) z-O-piperidine, in which z represents an integer from 1 to 5, preferably 3, and which may in particular be substituted by one or more alkyl groups containing 1 to 3 carbon atoms, preferably methyl, preferably the substituted piperidine is

[0024] [ka]

[0025] (which is the basis of Hydrogen, represents one or more units having d=1, 2, or 3, preferably d=1 or 2, more preferably d=1; e=0, 1, or 2; the sum d+e=1, 2, or 3, Includes.

[0026] In the above formula, if multiple R groups are present, or multiple R 1 It is understood that groups, if present, can be the same or different from one another.

[0027] Preferably, in the above formula, R 1 may be the same or different and are as follows: alkenyl groups containing 2 to 6 carbon atoms, preferably vinyl, Hydroxyl group (OH), Cyclic amines, e.g. -(CH2) z -O-piperidine, in which z represents an integer from 1 to 5, preferably 3, and which may in particular be substituted by one or more alkyl groups containing 1 to 3 carbon atoms, preferably methyl, preferably the substituted piperidine is

[0028] [ka]

[0029] (which is the basis of Hydrogen Represents.

[0030] In the present invention: - The siloxyl unit "M" has the formula YSiO 1 / 2 represents a siloxyl unit having the formula - The siloxyl unit "D" has the formula YSiO 2 / 2 represents a siloxyl unit having the formula - The siloxyl unit "T" has the formula YSiO 3 / 2 represents a siloxyl unit having the formula - The siloxyl unit "Q" has the formula SiO 4 / 2 represents a siloxyl unit having the formula The symbol Y is R or R 1 It is.

[0031] Organopolysiloxane O may optionally contain small amounts of T and Q units. Without intending to be bound by any particular theory, the depolymerization method of the invention can be carried out on organopolysiloxane O comprising long chains of consecutive D units. Preferably, organopolysiloxane O according to the invention comprises less than 20%, preferably less than 10%, even more preferentially less than 5%, even more preferentially less than 2% of T or Q units as defined above, relative to the total number of siloxyl units of organopolysiloxane O.

[0032] According to one preferential embodiment, the organopolysiloxane O of the invention preferably has the following formula (I): R 1 a R (3-a) SiO-(SiRO) n -(SiR 1 RO) m -SiR 1 a R (3-a) (I) (In the formula: R may be the same or different and is any of the following: 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; an aryl group containing 6 to 10 carbon atoms, preferably phenyl; represents R 1 may be the same or different and are as follows: alkenyl groups containing 2 to 6 carbon atoms, preferably vinyl, Hydroxyl group (OH), the (O-Alk) group, in which 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, 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, and x represents an integer between 2 and 200 (O-Alk). x base, an amino group selected from (Alk)-NH2 or (Alk)-NH-(Alk)-NH2, wherein Alk represents an alkyl group containing 1 to 5 carbon atoms; Cyclic amines, e.g. -(CH2) z -O-piperidine, in which z represents an integer from 1 to 5, preferably 3, and which may in particular be substituted by one or more alkyl groups containing 1 to 3 carbon atoms, preferably methyl, preferably the substituted piperidine is

[0033] [ka]

[0034] (which is the basis of Hydrogen, represents a is an integer number which is 0, 1, 2 or 3, preferably 0, 1 or 2, more preferably 0 or 1; n is an integer number between 10 and 10,000, preferably between 10 and 5,000, preferably between 50 and 5000, more preferably between 60 and 5000, for example between 70 and 1000; m represents an integer between 0 and 100, preferably between 0 and 50, more preferably between 0 and 30, and preferably m=0. The compound is selected from compounds having the formula:

[0035] The presence of Si-H groups in the organopolysiloxane O can lead to the release of dihydrogen. It can therefore be advantageous for the device for carrying out the method of the invention to provide a device for managing the release of dihydrogen, if the amount of Si-H groups is significant. In order to avoid the need to employ such a device, the amount of Si-H groups is preferably less than 20% by weight, preferably less than 10% by weight, more preferably less than 5% by weight, most preferably less than 2% by weight, relative to the total weight of the organopolysiloxane O.

[0036] In a particularly preferred manner, the organopolysiloxane O of the invention has the formula (I) (In the formula, R 1 may be the same or different and are as follows: alkenyl groups containing 2 to 6 carbon atoms, preferably vinyl, Hydroxyl group (OH), Cyclic amines, e.g. -(CH2) z -O-piperidine, in which z represents an integer from 1 to 5, preferably 3, and which may in particular be substituted by one or more alkyl groups containing 1 to 3 carbon atoms, preferably methyl, preferably the substituted piperidine is

[0037] [ka]

[0038] (which is the basis of Hydrogen It is a compound having the formula:

[0039] In a particularly preferred manner, the organopolysiloxane O of the invention has the formula (I) (In the formula, R 1 may be the same or different and represent CH3, vinyl, H, or OH.

[0040] In a particularly preferred manner, the organopolysiloxane O of the invention is a compound having the formula (I) (In the ceremony R, which may be the same or different, represents CH3 or phenyl, preferably CH3; R 1 may be the same or different and are as follows: alkenyl groups containing 2 to 6 carbon atoms, preferably vinyl, Hydroxyl group (OH), Cyclic amines, e.g. -(CH2) z -O-piperidine, in which z represents an integer from 1 to 5, preferably 3, and which may in particular be substituted by one or more alkyl groups containing 1 to 3 carbon atoms, preferably methyl, preferably the substituted piperidine is

[0041] [ka]

[0042] (which is the basis of Hydrogen (represents).

[0043] In a particularly preferred manner, the organopolysiloxane O of the invention is a compound having the formula (I) (In the ceremony R, which may be the same or different, represents CH3 or phenyl, preferably CH3; R 1 may be the same or different and represent CH3, vinyl, H, or OH).

[0044] In an advantageous manner, the method of the invention may be carried out with organopolysiloxanes O having a dynamic viscosity of between 3 and 20,000,000 mPa.s, preferably between 3 and 6,000,000 mPa.s, for example between 3 and 1,000,000 mPa.s, at 25° C. In a particularly advantageous manner, the method of the invention may be carried out with organopolysiloxanes O or mixtures of organopolysiloxanes O having a dynamic viscosity of between 3 and 1,000,000 mPa.s, preferably between 100 and 60,000 mPa.s, at 25° C. It should therefore be understood that in an advantageous manner, in order to facilitate the implementation of the method, in the context of a mixture of organopolysiloxanes, the organopolysiloxanes O may have a variable viscosity, within the range in which the viscosity of the mixture is as stated above.

[0045] In addition, the process of the invention may be carried out in the presence of a solvent. The solvent should be selected from among the solvents that solubilize the organopolysiloxane O. The solvent may be an alcohol or an n-paraffin. Preferably, the alcohol is selected from among fatty alcohols, such as n-lauryl alcohol, n-myristyl alcohol, n-palmityl alcohol, n-stearyl alcohol, n-docosanol, or Guerbet alcohols, such as 2-octyl 1-dodecanol, 2-decyl 1-tetradecanol. Preferably, the n-paraffin is selected from among the compounds C. 16 H 34 , C 18 H 38 , C 20 H 42 , C 22 H 46 , or C 24 H 50In the case where a solvent is employed in the process of the invention, the amount of solvent added is preferably between 5 and 50% by weight, preferably between 10 and 20% by weight, relative to the weight of organopolysiloxane O. In a particularly advantageous manner, the use of a solvent to facilitate the implementation of the process serves to facilitate the implementation of the process of the invention with more viscous organopolysiloxanes O (for example having a viscosity of between 1,000,000 and 20,000,000 mPa.s at 25° C.), whereby the mixture (organopolysiloxane O+solvent) has a viscosity of between 3 and 1,000,000 mPa.s, preferably between 100 and 60,000 mPa.s at 25° C.

[0046] The alkali salt catalyst is an alkali metal salt comprising a metal M, where the metal M is selected from K, Na, Rb, or Cs, preferably K, Rb, or Cs.

[0047] Preferably, said alkali metal salts are selected from among silanolates, hydroxides, alkoxides and siliconates, preferably silanolates.

[0048] In the context of the present invention, when the term "alkali metal salt" is mentioned, the following terms should be understood as follows: A "silanolate" is a salt derived from a silanol group, which is a functional group containing at least one Si-OH group. Silanolates generally have the formula MOSi(R')3, where M is as defined above, and R', which may be the same or different, represents a linear or branched alkyl group containing 1 to 6 carbon atoms, or an alkenyl group containing 2 to 6 carbon atoms, preferably R', which may be the same or different, represents methyl or vinyl. "Siliconate" is a compound of the formula M(OSi(R 3 )2) p -OSi(R 3 )2, where M is as defined above, R3 represents an alkyl group containing 1 to 6 carbon atoms, preferably methyl, and p represents an integer between 1 and 20, preferably between 1 and 10. A "hydroxide" is a group having the formula MOH, where M is as defined above. An "alkoxide" is a compound having the formula MOAlk, where M is as defined above and Alk represents a linear or branched alkyl group containing 1 to 22 carbon atoms, preferably 1 to 15 carbon atoms, and more preferably 1 to 12 carbon atoms.

[0049] Preferably, the alkaline catalyst of the present invention has the formula MX, M is selected from K, Na, Rb, Cs, preferably K, Rb, Cs, preferably K; X is for OSiR 4 2R 5 (R 4 may be the same or different and represent linear or branched alkyl containing 1 to 6 carbon atoms, preferably methyl; R 5 represents a linear or branched alkyl group containing 1 to 6 carbon atoms, preferably a methyl or vinyl group), OH, OAlk (Alk represents a linear or branched alkyl group containing 1 to 22 carbon atoms, preferably 1 to 15 carbon atoms, preferably 1 to 12 carbon atoms), (OSi(R 3 )2)p-OSi(R 3 ) 2 (wherein M is as defined above, R3 represents an alkyl group containing 1 to 6 carbon atoms, preferably methyl, and p represents an integer between 1 and 20, preferably between 1 and 10), Preferably, X is OSiMe3 (Me represents methyl), OSiMe2Vi (Vi represents vinyl), OH or O-tBu (tBu represents tert-butyl), OSi(Me)2-(OSi(Me)2). p -OSiMe3, where p is as defined above.

[0050] Preferably, M is selected from K, Rb, Cs; X is selected from OSiMe3, OSiMe2Vi (Vi represents vinyl), OH, OSi(Me)2-(OSi(Me)2). p-OSiMe3, where p represents an integer between 1 and 20, preferably between 1 and 10, and O-tBu, where tBu represents tert-butyl. Preferably, the alkaline catalyst is KOSiMe3 (potassium trimethylsilanolate).

[0051] In the context of this patent application, the term "polydentate complexing agent" is used to refer to a complexing agent for the alkali metal of the alkali salt catalyst, in other words a complexing agent for K, Na, Rb, or Cs, preferably a complexing agent for K, Rb, or Cs.

[0052] Preferably, the polydentate complexing agent of the present invention is selected from crown ethers, cryptands which are diamine macrocyclic heterocycles, and OH- or OCH3-terminated polyethylene glycols (PEGs), preferably OCH3-terminated polyethylene glycols, preferably polyethylene glycol dimethyl ether. Preferably, the PEGs are soluble in the reaction medium. Therefore, and preferably, the PEGs have a low number-average molar mass (Mn), for example between 100 and 2000, preferably between 200 and 1000 g / mol. The number-average molar mass (Mn) may be measured by any suitable technique known to the skilled person, for example using steric exclusion chromatography (SEC).

[0053] Preferably, the crown ether contains 2 to 8 oxygen atoms. Crown ethers are cyclic oligomers of ethylene oxide containing the (CH2-CH2-O) group as a repeating unit, and these crown ethers may be substituted or two carbon atoms of the (CH2-CH2-O) unit may be fused to a hydrocarbon ring, in particular cyclohexyl or phenyl.

[0054] Preferably, the multidentate complexing agent is

[0055] [ka]

[0056] (crown ether 18-6),

[0057] [ka]

[0058] From, preferably

[0059] [ka]

[0060] From, preferably

[0061] [ka]

[0062] is selected from.

[0063] Depending on the alkali metal, and particularly its size, a person skilled in the art will know which multidentate complexing agents may be suitable for use.

[0064] The alkali salts are used in catalytic proportions in practice, preferably in amounts between 0.005 and 1.5% by weight, preferably between 0.005 and 0.9% by weight and more preferentially between 0.01 and 0.8% by weight, relative to the weight of the organopolysiloxane (O).

[0065] Preferably, in the context of the present invention, the molar ratio of alkali salt / multidentate complexing agent is between 1 / 100 and 100 / 1, preferably between 1 / 50 and 50 / 1, more preferably between 1 / 25 and 25 / 1, more preferably between 1 / 10 and 10 / 1, more preferably between 1 / 4 and 4 / 1, preferably between 1 / 2 and 2 / 1, preferably greater than or equal to 1, preferably between 1 and 2, for example said ratio being equal to 1.

[0066] The process of the present invention is carried out at a temperature between 50 and 200°C, preferably between 60 and 180°C, more preferably between 120 and 160°C.

[0067] The method of the present invention operationally performs a reactive distillation process.

[0068] As known to those skilled in the art, reactive distillation consists of combining a distillative separation with a chemical reaction. Thus, a device for carrying out reactive distillation is a combination reactor and distillation system.

[0069] The reactive distillation and the method of the present invention may be carried out on a continuous or discontinuous - i.e. batch - process basis.

[0070] Batch reactive distillation combines the advantages of reactive distillation with those of a batch (discontinuous) process: the reaction mixture is charged to a reactor and the reaction products are distilled off as they are formed.

[0071] When performed in continuous mode, reagents are introduced continuously.

[0072] In one embodiment, the process and reactive distillation of the invention are carried out continuously. Preferably, the temperature is between 50 and 200° C., preferably between 60 and 180° C., more preferably between 120 and 160° C. Preferably, the pressure is between 0.01 and 50 mbar, preferably between 0.1 and 35 mbar, more preferentially between 5 and 30 mbar.

[0073] A person skilled in the art will also know how to adapt the pressure and temperature setting pairs, for example in one embodiment the pressure is between 0.01 and 50 mbar for temperatures between 50 and 200° C., preferably between 5 and 30 mbar for temperatures between 120 and 160° C.

[0074] In another embodiment, the process and the reactive distillation of the invention are carried out in batch mode. Preferably, the temperature is between 50 and 200° C., preferably between 60 and 180° C., more preferably between 120 and 160° C. Preferably, the pressure is between 0.01 and 50 mbar, preferably between 0.1 and 35 mbar, more preferentially between 5 and 30 mbar.

[0075] In this embodiment, the reaction and heating is started at atmospheric pressure, then after a period of 10 to 120 minutes, preferably 30 to 60 minutes, after reaching temperature, the reactive distillation is started at a pressure between 0.01 and 50 mbar, preferably between 0.1 and 35 mbar, more preferentially between 5 and 30 mbar.

[0076] The process of the invention may be carried out either in the presence or absence of a solvent, in particular a solvent of alcohol type. Preferably, the alcohol is chosen from fatty alcohols, such as n-lauryl alcohol, n-myristyl alcohol, n-palmityl alcohol, n-stearyl alcohol, n-docosanol, or Guerbet alcohols, such as 2-octyl 1-dodecanol, 2-decyl 1-tetradecanol. The solvent may also be n-paraffins, such as compound C 16 H 34 , C 18 H 38 , C 20 H 42 , C 22 H 46 , C 24 H 50 When a solvent is employed in the process of the present invention, the amount of solvent added is preferably between 5 and 50% by weight, preferably between 10 and 20% by weight, based on the weight of the organopolysiloxane.

[0077] The cyclic organopolysiloxane CO (or cyclic organopolysiloxane) obtained by the method of the present invention is preferably the compound D3, D4 or D5. Preferably, the obtained cyclic organopolysiloxane CO is obtained as a mixture containing more than 95% by mass, preferably 95 to 99% by mass, of the mixture of compounds D3, D4 or D5, based on the total mass of the cyclic organopolysiloxane CO produced.

[0078] Preferably, the predominant compound obtained by the process of the invention is compound D4. Preferably, the process of the invention makes it possible to obtain a yield of D4 of at least 80% by weight.

[0079] Compounds D3, D4 and D5 are preferably compounds having the following formula:

[0080] [ka]

[0081] As mentioned above, the starting organopolysiloxane O is 1 In these cases, at least one of the methyl groups of compounds D3, D4, and / or D5 may include a functional group described by the group R 1 may be substituted by at least one of

[0082] According to one embodiment, in order to facilitate the recycling of compounds D3, D4 and D5 and their reuse in industrial processes, in particular polymerization processes, these compounds preferably comprise less than 10% by weight, preferably less than 5% by weight, preferably less than 2 and even more preferentially less than 0.2% by weight of functional groups as described by the R1 groups as discussed above, relative to the total weight of compounds D3, D4 and D5.

[0083] The process of the invention preferably makes it possible to obtain mass yields of cyclic organopolysiloxanes CO of more than 85% by weight, preferably more than 95% by weight, in some cases up to 99% by weight.

[0084] Optionally, compounds D3, D4 and D5 may be separated, in particular by distillation, for example using a number of theoretical plates.

[0085] In a particularly advantageous manner, the compounds D3, D4 and D5 obtained by the process of the invention can be used directly in other industrial processes, such as to be polymerized, thereby producing novel oils and gums.

[0086] The present invention also relates to the use of a catalyst system comprising an alkali salt selected from salts of K, Na, Rb, or Cs and a multidentate complexing agent for the depolymerization of organopolysiloxane O to produce cyclic organopolysiloxane CO.

[0087] According to one embodiment, the alkaline salt for the above mentioned uses is as defined above.

[0088] According to one embodiment, the multidentate complexing agent for the above mentioned uses is as defined above.

[0089] Preferably, the polydentate complexing agent used for the depolymerization of organopolysiloxane O is selected from crown ethers, cryptands which are diamine macrocyclic heterocycles, and OH- or OCH3-terminated polyethylene glycols (PEG), preferably OCH3-terminated polyethylene glycols, preferably polyethylene glycol dimethyl ether. Preferably, the PEG is soluble in the reaction medium. Therefore, and preferably, the PEG has a low number-average molar mass (Mn), for example between 100 and 2000 g / mol, preferably between 200 and 1000 g / mol.

[0090] Preferably, the crown ether contains 2 to 8 oxygen atoms. Crown ethers are cyclic oligomers of ethylene oxide containing the (CH2-CH2-O) group as a repeating unit, and these crown ethers may be substituted or two carbon atoms of the (CH2-CH2-O) unit may be fused to a hydrocarbon ring, in particular cyclohexyl or phenyl.

[0091] Preferably, the multidentate complexing agent used for the depolymerization of the organopolysiloxane O is

[0092] [ka]

[0093] (crown ether 18-6),

[0094] [ka]

[0095] From, preferably

[0096] [ka]

[0097] From, preferably

[0098] [ka]

[0099] is selected from.

[0100] According to one preferred use, the alkali salts used for the depolymerization of the organopolysiloxanes O are used in catalytic proportions in practice, preferably in amounts of between 0.005 and 1.5% by weight, preferably between 0.005 and 0.9% by weight and more preferentially between 0.01 and 0.8% by weight, relative to the weight of the organopolysiloxane (O).

[0101] Preferably, in the abovementioned contexts of use, the molar ratio of alkali salt / multidentate complexing agent is between 1 / 100 and 100 / 1, preferably between 1 / 50 and 50 / 1, more preferably between 1 / 25 and 25 / 1, more preferably between 1 / 10 and 10 / 1, more preferably between 1 / 4 and 4 / 1, preferably between 1 / 2 and 2 / 1, preferably greater than or equal to 1, preferably between 1 and 2, for example said ratio being equal to 1.

[0102] According to one embodiment, the above-mentioned uses are effectively carried out using reactive distillation.

[0103] The present application will now be illustrated using the following examples. Organopolysiloxanes used in the examples: Organopolysiloxane O1:

[0104] [ka]

[0105] n=70 Viscosity 100mPa.s Organopolysiloxane O2:

[0106] [ka]

[0107] n=100 Viscosity 350mPa.s Organopolysiloxane O3:

[0108] [ka]

[0109] n=100 (waste oil used as a heating bath for many years) Viscosity 350mPa.s Organopolysiloxane O4:

[0110] [ka]

[0111] n=180 Viscosity 1000mPa.s Organopolysiloxane O5:

[0112] [ka]

[0113] Viscosity 100mPa.s Organopolysiloxane O6:

[0114] [ka]

[0115] Viscosity 450mPa.s Organopolysiloxane O7:

[0116] [ka]

[0117] Viscosity 100mPa.s Organopolysiloxane O8: 50% by weight of O7 + 50% by weight of O1. The viscosity of the mixture is 100 mPa.s. Organopolysiloxane O9: 50% by weight of O1 + 50% by weight of silicone rubber having the following formula:

[0118] [ka]

[0119] The viscosity of the mixture is less than 60,000 mPa.s Organopolysiloxane O10:

[0120] [ka]

[0121] Viscosity 250mPa.s Organopolysiloxane O11: 50% by weight of O1 + 50% by weight of PDMS

[0122] [ka]

[0123] Contains 5% or less Si-Ph units relative to the total number of units, and has a viscosity of 60,000 mPa.s Organopolysiloxane O12: 50% by weight of O1 + 50% by weight of a mixture of two organopolysiloxanes (of type O5 but with different number of units, one with a viscosity of 10,000 mPa.s and the other with a viscosity of 60,000 mPa.s) and a crosslinking catalyst. Organopolysiloxane O13: a mixture of 50% by weight of O1 + 50% by weight of two organopolysiloxanes (of type O5 but with different number of units, one with a viscosity of 10,000 mPa.s and the other with a viscosity of 60,000 mPa.s) with approximately 5% by weight of silicone oil (containing Si-H units). Organopolysiloxane O14: Crosslinked silicone gel derived from O1+O12 and O13, filler free.

[0124] Alkaline salts employed in the practice of the examples: SA1: KOSiMe3 SA2: KOSiMe2Vi SA3: KOH SA4: KO-tBu SA5: RbOSiMe3 SA6: CsOSiMe3 SA7:

[0125] [ka]

[0126] n=1 to 10 SA8: CsOH

[0127] Multidentate complexing agents employed in the practice of the examples: CM1: Crown ether 18-6:

[0128] [ka]

[0129] CM2:

[0130] [ka]

[0131] CM3:

[0132] [ka]

[0133] CM4:

[0134] [ka]

[0135] CM5:

[0136] [ka]

[0137] CM6:

[0138] [ka] EXAMPLES

[0139] General Protocol for Batch (Non-Continuous) Mode The organopolysiloxane, the alkali salt, and the multidentate complexing agent are introduced into a flask (50 mL) equipped with a Vigreux column on top, and heated for 30 minutes to 1 hour at a temperature T. The reaction mixture is then distilled under reduced pressure for 20 to 25 minutes.

[0140] In the results reported in the tables of the Examples: - the yield of cyclosiloxanes is determined by the mass ratio between the mass of the distilled product and the mass of the starting organosiloxane O, and - The ratio of D3 / D4 / D5 / others was determined between the integrated intensities of the signals (D3 / D4 / D5 / others) in the 29Si-NMR spectrum; this ratio corresponds to the mass ratio. EXAMPLES

[0141] Temperature and pressure effects The protocol described in Example 1 is carried out with KOSiMe3 (SA1) used as the alkali salt, and crown ether 18-6 (CM1). The reaction mixture is heated for 30 minutes, followed by reactive distillation (temperature and pressure as described above).

[0142] The organopolysiloxane used is organopolysiloxane O1.

[0143] The results are summarized in Table 1 below.

[0144] [Table 1]

[0145] These results show that the method of the present invention effectively allows the depolymerization and formation of cyclic organopolysiloxanes, and that the method exhibits selectivity in particular towards compound D4. In an advantageous manner, the method of the present invention requires a small amount of catalyst. EXAMPLES

[0146] Effect of the anion X of the alkaline salt The protocol described in Example 1 is carried out with KX used as the alkali salt and crown ether 18-6 (CM1). The reaction mixture is heated for 1 h, after which reactive distillation is carried out at a temperature of 140 °C and a pressure of 10 mbar for 20-25 min.

[0147] The organopolysiloxane is O1.

[0148] The results are summarized in Table 2 below.

[0149] [Table 2]

[0150] These results indicate that the method of the present invention can be performed with a variety of alkaline salts while at the same time maintaining selectivity towards the production of D4. EXAMPLES

[0151] Effect of multidentate complexing agents The protocol described in Example 1 is carried out with KOSiMe3 (SA1) used as the alkali salt and the polydentate complexing agent. The reaction mixture is heated for 1 h, after which reactive distillation is carried out at a temperature of 140 °C and a pressure of 10 mbar for 20-25 min.

[0152] The organopolysiloxane is O1.

[0153] The results are summarized in Table 3 below.

[0154] [Table 3]

[0155] These results indicate that the process of the present invention can be carried out in good yields with a variety of complexing agents. EXAMPLES

[0156] Effect of organopolysiloxane The protocol described in Example 1 is carried out with KOSiMe3 (SA1) used as the alkali salt, and crown ether 18-6 (CM1). The reaction mixture is heated for 1 h, after which reactive distillation is carried out at a temperature of 140 °C and a pressure of 10 mbar for 20-25 min.

[0157] The results are summarized in Table 4 below.

[0158] [Table 4]

[0159] The results show that the method of the present invention makes it possible to process a variety of organopolysiloxanes while at the same time achieving good yields and high selectivity, especially high selectivity towards D4. This example also shows that the method of the present invention makes it possible to process waste (used) silicone oils, rubbers, and crosslinked silicone gels. EXAMPLES

[0160] Effect of the alkali salt / multidentate complexing agent ratio The protocol described in Example 1 is carried out using various catalysts / catalyst systems at a temperature of 140° C. The reaction mixture is heated for 30 minutes, after which the reactive distillation is carried out at a temperature of 140° C. and a pressure of 10 mbar for 20-25 minutes.

[0161] The organopolysiloxane is O1.

[0162] The results are summarized in Table 5 below.

[0163] [Table 5]

[0164] These results demonstrate that the catalyst system of the present invention makes it possible to obtain extremely high yields of cyclosiloxanes. EXAMPLES

[0165] Example using oil derived from chlorosilane hydrolysis by-products The protocol described in Example 1 is carried out with different catalyst systems. The reaction mixture is heated to 150° C. for 30 min, after which the reactive distillation is carried out at a temperature of 150° C. and a pressure of 5 mbar for 30 min.

[0166] The organopolysiloxane is an oil derived from at least 95% organopolysiloxane containing approximately 2% Si-H groups, and other reaction products such as chlorosilane hydrolysis by-products including reaction product residues, catalysts, etc.

[0167] The results are summarized in Table 6 below.

[0168] [Table 6]

[0169] These results show that the catalyst system of the present invention makes it possible to obtain cyclosiloxanes using oils derived from industrially produced by-products and therefore of complex composition.

Claims

1. 1. A process for preparing cyclic organopolysiloxanes CO by reactive distillation of at least one organopolysiloxane O in the presence of an alkali salt type catalyst selected from salts of K, Na, Rb, or Cs and a multidentate complexing agent.

2. 2. The method according to claim 1, wherein the organopolysiloxane O is selected from linear organopolysiloxanes, such as oils or gums, or branched organopolysiloxanes.

3. The organopolysiloxane O is selected from the group consisting of: - Formula R c SiO (4-c) / 2 (In the ceremony R may be the same or different and is any of the following: - alkyl groups containing 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 containing 6 to 10 carbon atoms, preferably phenyl represents where c=0, 1, 2, or 3), and - In some cases, the formula R 1 d R e SiO (4-d-e) / 2 (In the formula: R is as defined above, R 1 may be the same or different and are as follows: alkenyl groups containing 2 to 6 carbon atoms, preferably vinyl; - hydroxyl group (OH), - Alk is 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 OCH 3 Or O.C. 2 H 5 an (O-Alk) group, - Alk represents an alkyl group, preferably methyl, containing 1 to 15 carbon atoms, preferably 1 to 12 carbon atoms, preferably 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms; x represents an integer between 2 and 200 (O-Alk) x base, - (Alk)-NH, where Alk represents alkyl containing 1 to 5 carbon atoms. 2 or (Alk)-NH-(Alk)-NH 2 an amino group selected from - Cyclic amines, e.g. -(CH 2 ) z -O-piperidine, where z represents an integer from 1 to 5, preferably 3, which may be substituted, in particular by one or more alkyl groups containing 1 to 3 carbon atoms, preferably methyl, preferably the substituted piperidine is 【Chemistry 1】 (which is the basis of - Hydrogen represents - one or more units with d=1, 2 or 3, preferably d=1 or 2, more preferably d=1 and e=0, 1 or 2, the sum d+e=1, 2 or 3, The method according to claim 1 or 2, comprising:

4. At least one organopolysiloxane O has the following formula (I): R 1 a R (3-a) SiO-(SiR 2 O) n -(SiR 1 RO) m -SiR 1 a R (3-a) (I) (In the formula: R may be the same or different and is any of the following: - alkyl groups containing 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 containing 6 to 10 carbon atoms, preferably phenyl, represents R 1 may be the same or different and are as follows: an alkenyl group containing 2 to 6 carbon atoms, preferably vinyl, - hydroxyl group (OH), - Alk is 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 OCH 3 Or O.C. 2 H 5 an (O-Alk) group, - Alk represents an alkyl group, preferably methyl, containing 1 to 15 carbon atoms, preferably 1 to 12 carbon atoms, preferably 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, and x represents an integer between 2 and 200 (O-Alk) x basis, - (Alk)-NH, where Alk represents alkyl containing 1 to 5 carbon atoms. 2 or (Alk)-NH-(Alk)-NH 2 an amino group selected from - Cyclic amines, e.g. -(CH 2 ) z -O-piperidine, where z represents an integer from 1 to 5, preferably 3, which may be substituted, in particular by one or more alkyl groups containing 1 to 3 carbon atoms, preferably methyl, preferably the substituted piperidine is 【Chemistry 2】 (which is the basis of - Hydrogen, represents a is an integer number which is 0, 1, 2 or 3, preferably 0, 1 or 2, more preferentially 0 or 1; n represents an integer between 10 and 10,000, preferably between 10 and 5,000, preferably between 50 and 5000, more preferentially between 60 and 5000, for example between 70 and 1000, m represents an integer between 0 and 100, preferably between 0 and 50 and more preferentially between 0 and 30, preferably m=0. The method according to any one of claims 1 to 3, wherein

5. 5. The method according to any one of claims 1 to 4, wherein the alkali salt is selected from alkali silanolates, alkali hydroxides, alkali alkoxides and alkali siliconates, preferably alkali silanolates.

6. The alkali salt is a potassium salt, preferably KOSiMe 3 6. The method according to claim 1, wherein

7. Polydentate complexing agents include crown ethers, cryptands which are diamine macrocyclic heterocycles, and OH- or OCH 3 7. The method according to claim 1, wherein the -terminal polyethylene glycol is selected from the group consisting of .alpha.-, .alpha.- and .alpha.-.

8. The polydentate complexing agent is a crown ether and an OCH having a weight average molar mass between 100 and 2000 g / mol, preferably between 200 and 1000 g / mol. 3 8. The method according to claim 1, wherein the aryl group is selected from the group consisting of aryl, aryloxy ...

9. 9. The process according to any one of claims 1 to 8, wherein the reactive distillation is carried out at a temperature between 50 and 200°C, preferably between 60 and 180°C, preferably between 120 and 160°C.

10. 10. The method according to claim 1, wherein the amount of alkali salt used is between 0.005 and 1.5% by weight, preferably between 0.005 and 0.9% by weight and more preferentially between 0.01 and 0.8% by weight, relative to the weight of organopolysiloxane (O).

11. More than 95% by weight of compounds D3, D4, or D5 based on the total weight of the cyclic organopolysiloxanes CO produced 【Chemistry 3】 11. The process according to claim 1 , wherein a mixture of cyclic organopolysiloxanes CO is obtained, the mixture comprising:

12. The multidentate ligand is 【Chemistry 4】 From, preferably 【Chemistry 5】 From, preferably 【Chemistry 6】 12. The method according to any one of claims 1 to 11, wherein the method is selected from the group consisting of:

13. 13. The process according to claim 1, wherein the mass yield of cyclic organopolysiloxane CO is greater than 85%.

14. 2. Use of a catalyst system comprising an alkali salt selected from salts of K, Na, Rb, or Cs and a multidentate complexing agent for depolymerizing an organopolysiloxane O to produce a cyclic organopolysiloxane CO.

15. 15. Use according to claim 14, in which the alkali salt is as defined in claim 5 or 6 and / or the multidentate complexing agent is as defined in any one of claims 7, 8 or 12.

Images