Process for separating a polysiloxane from a material and process for producing a silane compound

Abstract

A process for separating one or more polysiloxanes from a material which, in addition to the polysiloxane(s), contains at least one further component selected from the group consisting of polyethylene, polypropylene, polyethylene terephthalate, polyamides, polytetrafluoroethylene and perfluoroalkoxy polymers, the process comprising the steps of: (a) providing the material containing the polysiloxane(s); and (b) converting the polysiloxane(s) into one or more fluorosilane compounds by treating the material with a fluoride-containing solution.

Description

The invention relates to a process for separating a polysiloxane from a material. It further relates to a process for preparing a silane.Polysiloxanes are also referred to as poly(organo)siloxanes or silicones. They are polymeric compounds in which silicon atoms are linked via oxygen atoms to form a chain- or network-like skeleton. In this case, a distinction is made between four structural units, which are also referred to as siloxane units: monofunctional units are referred to as M groups or "M", where M is (R 1)3 SiO 1 / 2. An M group forms a chain end. Difunctional moieties are referred to as D groups or "D", where D is (R 1)2 SiO 2 / 2. A D group forms a unbranched section of the framework. Trifunctional units are referred to as T groups or "T", where T is R 1 SiO 3 / 2. A T group forms a branch of the framework. Tetra-functional units that form a crosslinking are referred to as Q groups or "Q", where Q is SiO 4 / 2. A Q group allows the formation of a net-like framework. The four structural units may be linked together to form linear, branched, cyclic and crosslinked polysiloxanes. R 1 in the structural units denotes in each case hydrogen or an organic group. Organic groups of the polysiloxane can be crosslinked. The crosslinking may have been effected, for example, by hydrosilylation reactions, other olefin addition reactions or by condensation reactions. The organic group is often an alkyl group having 1 to 12 carbon atoms, for example, a methyl group.Linear polysiloxanes have the general formula MD n M, where n is an integer equal to or greater than 3. The general formula MD n M corresponds to the following general structural formula of a linear polysiloxane: The radicals R 1 denote hydrogen or identical or different organic groups, for example methyl groups, n is 3 or an integer greater than 3. branched polysiloxanes have a T group instead of a D group, it being possible for a plurality of D groups to be replaced by T groups. Crosslinked polysiloxanes have a T or Q group instead of a D group, it being possible for a plurality of D groups to be replaced by T and / or Q groups.Polysiloxanes are widely used in industry and in numerous all-day applications because of their properties. The silicones used are highly resistant to atmospheric oxygen, water and chemicals. Thus, silicones are not attacked, or are only attacked to a slight extent, by acids or bases. This chemical resistance makes recycling more difficult in such a way that emptied silicone cartridges from home use, which consist of polyethylene (PE) or polypropylene (PP) and are contaminated with residues of polysiloxanes, are considered to be non-recyclable. Furthermore, there are great problems in recycling PET bottles with silicone seals in the cover. Even very small residues of silicone in the PET recyclate cause defects and rejects in refurbished products.In principle, many other fields (electrical appliances, medical products, pharmaceutical products, glass / ceramic industry, textile industry, automotive fields, etc.) are also applicable These may also be used in the form of silicones in the form of composite materials, insulators, mould release agents, membranes, hydrophobicizing agents, etc. Separation is a great challenge today. The prior art is the separation methods of documents U.S. Pat. No. 2018 / 0 171 061 A1 and JP H08-250 400 A.The object of the invention is to eliminate the disadvantages of the prior art. In particular, a process for separating one or more polysiloxanes from a mixture is to be specified. Further, a method for producing a silane compound from the polysiloxane is to be provided.This object is achieved by the features of claims 1 and 14. Practical embodiments of the inventions are evident from the features of the dependent claims.According to the invention, a process for separating one or more polysiloxanes from a material which, in addition to the polysiloxane, comprises at least one further component is provided. The process comprises the steps of: (a) providing the material containing the polysiloxane or polysiloxanes; and (b) reacting the polysiloxane or polysiloxanes to one or more fluorosilane compounds by treating the material with a fluoride-containing solution.The process for separating one or more polysiloxanes from a material which comprises at least one further component in addition to the polysiloxane or polysiloxanes is also referred to below as the first process.The material is a material which comprises at least one further component in addition to one or more polysiloxanes. The further component is a plastic. The material may contain more than one polysiloxane. The material may contain various polysiloxanes. For example, a polysiloxane may be different from another polysiloxane if it has a different sequence of siloxane units.The plastic is a plastic selected from the group consisting of polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyamides (PA), polytetrafluoroethylene (PTFE), and perfluoroalkoxy polymers (PFA). In one embodiment of the invention, the material is a material which contains or consists of polyethylene (PE), polypropylene (PP) and one or more polysiloxanes. This material can be present, for example, in the form of a cartridge which consists of polyethylene (PE) and / or polypropylene (PP) and serves to provide one or more polysiloxanes. In other words, the cartridge is an emptied silicone cartridge which, however, still contains residues of one or more polysiloxanes. These residues can adhere, for example, to the walls of the cartridge. In another embodiment, the plastic is polyethylene terephthalate (PET). The material then contains or consists of a polysiloxane and polyethylene terephthalate (PET). This material can be present, for example, in the form of a bottle made of PET, in the cover of which there is a seal made of polysiloxane.The first method according to the invention can be used in particular in the separation of polysiloxane(s) from materials used in electrical appliances, medical products, pharmaceutical products, textile products and automobiles. It is suitable, for example, for the separation of polysiloxanes which are present as part of a composite material or are present as insulators, as mold release agents, as membranes, as hydrophobicizing agents, etc. together with at least one other component. The first method according to the invention can be used in one embodiment for cleaning the material, for example for cleaning a surface of the material.It can be provided that the material provided in step (a) is a comminuted material. For this purpose, comminution of the material which comprises polysiloxane and the at least one further component can be provided. Comminution is then necessary if the material is not already present as comminuted material. The crushed material preferably has a particle size of not more than 50 mm. The comminution can be effected mechanically, for example. Alternatively, it can be provided that the material in step (b) is rinsed with the fluoride-containing solution. Comminution of the material is not necessary for this purpose.The polysiloxane can be a linear, branched, cyclic or crosslinked polysiloxane. The polysiloxane may have the general formula I wherein m, n, p and r are each 0 or integer of 1 or greater, with the proviso that the sum of m, n, p and r is an integer equal to or greater than 3. It can be provided that the sum of m, n, p and r is not greater than 5000, preferably not greater than 1500, more preferably not greater than 500 and particularly preferably not greater than 100. In the general formula I, M denotes an M group of the formula (R 1)3 SiO 1 / 2, D denotes a D group of the formula (R 1)2 SiO 2 / 2, T denotes a T group of the formula (R 1) SiO 3 / 2 and Q denotes a Q group of the formula SiO 4 / 2, in which the radicals R 1 are hydrogen or identical or different organic groups. Preferably, the R 1 radicals are independently selected at each occurrence from the group consisting of hydrogen, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 12 carbon atoms, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted alkoxy group having 1 to 12 carbon atoms, a substituted or unsubstituted carboxy group having 1 to 12 carbon atoms and a substituted or unsubstituted aryl group. The radicals R 1 are preferably each unsubstituted alkyl groups having 1 to 6 carbon atoms. For example, the radicals R 1 can each be methyl groups. It may be provided that the radicals R 1 have the same meaning on each occurrence. However, it can also be provided that at least one of the radicals R 1 has a different meaning than the other radicals R 1.The material provided in step (a) may comprise one or more polysiloxanes of the general formula I, where the polysiloxanes may be the same or different. The amounts of M, D, T and Q groups can vary widely. The polysiloxane can be a polysiloxane which has no D groups or a polysiloxane which consists exclusively of D and M groups. Organic groups of the polysiloxane can be crosslinked. The crosslinking may have been effected, for example, by hydrosilylation reactions, other olefin addition reactions or by condensation reactions.The polysiloxane may be a polysiloxane elastomer, a silicone resin or a silicone adhesion promoter. The polysiloxane elastomer can also contain significant amounts of M groups and T groups in addition to D groups. In addition to D, M and T groups, it may also contain significant amounts of Q groups. The polysiloxane elastomer may also contain large amounts of SiO 2 as additive. Polysiloxane elastomers can have varying degrees of branching or cross-linking. They may be highly branched or crosslinked.The siloxane units of a polysiloxane are reacted to give the following halosilane compounds: In the reaction of the polysiloxane with the fluoride-containing solution, M groups ((R 1)3 SiO 1 / 2), which comprises the polysiloxane, are reacted to give a halosilane compound of the general formula (R 1)3 SiF, and D groups ((R 1)2 SiO 2 / 2), which comprises the polysiloxane, are reacted to give a compound of the general formula (R 1)2 SiF 2, T groups ((R 1) SiO 3 / 2), which contains the polysiloxane, are reacted to form a halosilane compound of the general formula (R 1) SiF 3 and Q groups (SiO 4 / 2), which contains the polysiloxane, are reacted to form a halosilane compound of the general formula SiF 4. The fluorosilane compound can thus be a compound of the general formula (R 1)z SiF 4-z, in which z is 0, 1, 2 or 3. In the siloxane units and the halosilane compounds, the radicals R 1 have the meanings indicated in connection with the general formula I.The halosilane compound(s) obtained in step (b) can have the general formula S-I in which the radicals X 1 are, independently of one another on each occurrence, fluorine or R 1 with the proviso that at least one of the radicals X 1 is fluorine. The radicals R 1 have the meanings given in connection with the general formula I.The polysiloxane or polysiloxanes can each be a compound which has a repeating unit of the general formula II in which the radicals R 1 have the meanings indicated in connection with the general formula I and n is an integer equal to or greater than 3. It may be provided that n is not greater than 5000, more preferably not greater than 1500, even more preferably not greater than 500 and particularly preferably not greater than 100. The repeating unit of formula I is a D group. If the polysiloxane has two M groups as head groups in addition to D groups, the polysiloxane is a linear polysiloxane of the general formula III in which the radicals R 1 have the meanings indicated in connection with the general formula I.In general formulae I, S-I, II and III, the radicals R 1 are preferably each independently an unsubstituted alkyl group having 1 to 6 carbon atoms. For example, the radicals R 1 can be methyl groups. In this case, the polysiloxane is a compound of the general formula IV wherein n is an integer in a range from 3 to 5000, preferably from 3 to 1500, more preferably from 3 to 500 and particularly preferably from 3 to 100.The fluoride-containing solution is preferably an aqueous solution. The fluoride-containing solution can be, for example, an aqueous solution of hydrofluoric acid or of a fluoride salt. The fluoride-containing solution preferably has a pH of less than 7. It can thus be an acidic solution. The fluoride salt may comprise an inorganic or organic cation. An example of a fluoride salt is ammonium fluoride. The aqueous fluoride-containing solution is preferably an aqueous solution of hydrofluoric acid or ammonium fluoride. The fluoride concentration in the aqueous solution should be in a range of 0.5% by volume and 50% by volume, preferably between 5% by volume and 20% by volume, in each case based on the volume of the fluoride-containing solution.The treatment of the material with the fluoride-containing solution can be carried out at ambient temperature and ambient pressure. For example, the treatment may be carried out at a temperature of 5 to 50°C. The treatment should be for a time sufficient to separate at least 95% polysiloxane by weight from the material. The term "wt%" refers to the weight of the polysiloxane or polysiloxanes contained in the material. It can be provided that the molar amount of siloxane units to the molar amount of fluoride ions in the fluoride-containing solution is in a ratio of 1:2 to 1:4, preferably 1:2 to 1:3.By treating the material with the fluoride-containing solution, the polysiloxane or polysiloxanes contained in the material are converted to one or more halosilane compounds, for example to one or more silane compounds of the general formula S-I. This achieves a separation of polysiloxane(s) from the material. The components which the material contains in addition to the polysiloxane or polysiloxanes remain unchanged. After treatment of the material, the material does not contain polysiloxane or at least a lesser amount of polysiloxane as compared to the material provided in step (a).If the polysiloxane is a compound which has a repeating unit of the general formula II, the reaction in step (b) takes place as indicated in Scheme 1, below. The compound having a repeating unit of the general formula II reacts with fluoride ions in the presence of hydrogen ions to form a fluorosilane compound of the general formula V and water. In the repeating unit of the general formula II and in the compound of the general formula II, the radicals R 1 have the meanings indicated in connection with the general formula I. The fluorosilane compound represented by the general formula V is an example of a fluorosilane compound.If the polysiloxane is a compound of the general formula III, the reaction in step (b) takes place as indicated in Scheme 2, below. The compound of the general formula III reacts with fluoride ions in the presence of hydrogen ions to give halosilane compounds of the general formulae V and VI and water. In the general formulae V and VI, the radicals R 1 have the meanings given in connection with the general formula III, above. The fluorosilane compounds represented by the general formulas V and VI are examples of a fluorosilane compound. It can be seen in Scheme 2 that M groups are converted to halosilane compounds of the general formula VI and D groups are converted to halosilane compounds of the general formula V. Details of the reaction of T groups and Q groups can be found in Table 1, below.The halosilane compound obtained in step (b) may be a gaseous or liquid halosilane compound. If a plurality of halosilane compound(s) are obtained in step (b), a mixture of gaseous halosilane compounds, a mixture of liquid halosilane compounds or a mixture of at least one gaseous halosilane compound and at least one liquid halosilane compound can be obtained. It may be provided that the liquid(s) fluorosilane compound(s) obtained in step (b) are evaporated into a carrier gas. An example of a liquid halosilane compound that can be vaporized into a carrier gas is F 2 Si(CH 3)( C 6 H 13). The halosilane compound obtained in step (b) can be obtained in dissolved form. In this case, the halosilane compound is a soluble halosilane compound.As a rule, in step (b) a plurality of halosilane compounds are formed. In this case, a mixture of halosilane compounds is obtained in step (b). It can thus be provided that the first process according to the invention comprises separating the fluorosilane compounds obtained in step (b) from one another. If step (c) is provided, the separation is carried out before step (c). The separation of the mixture of halosilane compounds into its components can be carried out by distillation, adsorption, extraction, membrane processes, crystallization and other processes. It can thus be provided that in step (b) a mixture of a plurality of fluorosilane compounds is obtained and that the method according to the invention comprises separating at least one of the fluorosilane compounds from the mixture. It may be provided that only the separated halosilane compound(s) is subjected to step (c).It can be provided that the method according to the invention further comprises the step:(c) contacting the halosilane compound(s) with a salt Ca(R 2)2, wherein R 2 radicals are independently at each occurrence R 3- O - or R 3- C(O)O - wherein R 3 is a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms.In this way, a reaction of the halosilane compound(s) with the calcium salt Ca(R 2)2 to form one or more silane compounds which do not contain silicon-fluorine bonds can be achieved. The calcium fluoride (CaF 2) formed in step (c) is solid. Alternatively to step (c), it may be provided that the fluorosilane compound(s) are separated from the reaction mixture obtained in step (c) by extraction or adsorption. The extraction may be a liquid-liquid extraction or a liquid-solid extraction.It may be envisaged that step (c) comprises contacting the fluorosilane compound(s) with a liquid composition containing calcium ions. By contacting the halosilane compound(s) with the liquid composition, the halosilane compound(s) contact the calcium ions contained in the liquid composition. The liquid substance mixture can be a solution or a suspension. Preferably, the calcium ions are present in a non-aqueous solvent. The solution should be anhydrous. More preferably, the calcium ions are present in an organic solvent and most preferably in a non-polar organic solvent. An example of a non-polar organic solvent is hexane. Alternatively, the liquid mixture of matter may be a suspension of a salt containing calcium ions in a non-aqueous solvent. The suspension should be anhydrous. It is preferred that the solution or suspension is anhydrous to prevent condensation or polymerization of the silane compound(s) formed in step (c).To contact the halosilane compound(s) with a liquid composition containing calcium ions, the halosilane compound(s) may be mixed with the liquid composition or introduced into the liquid composition. If the halosilane compound or compounds are halosilane compounds that are gaseous or vaporized in a carrier gas, then it is preferred to introduce this halosilane compound(s) into the liquid substance mixture. If the halosilane compound(s) are liquid halosilane compound(s), mixing this halosilane compound(s) with the liquid substance mixture is preferred.The salt Ca(R 2)2 has the calcium ions as cations and the radicals R 2 as anions. Selection of the salt can be made selectively to produce a particular silane compound or compounds.The silane compound(s) obtained in step (c) may each be a silane compound of the general formula S-II in which the radicals X 2 are, independently of one another on each occurrence, R 1 or R 2' with the proviso that at least one of the radicals X 2 is R 2'. The radicals R 1 have the meanings given in connection with the general formula I, the radicals R 2' correspond to the radicals R 2, except that the radicals R 2' are not anions, but are bonded to the silicon atom via a covalent bond. The radicals R 2' can thus independently of one another be -O-R 3 or -O-C(O)-R 3 where R 3 is a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms.In Table 1, for each of the four siloxane units, the fluorosilane compound obtained in step (b) is indicated, and if step (c) is provided, the silane compound obtained in step (c) by reacting the fluorosilane compound with Ca(R 2)2 is indicated. The radicals R 1 have the meanings indicated in connection with the general formula I, the radicals R 2 have the meanings indicated in connection with Ca(R 2)2 and the radicals R 2' correspond to the radicals R 2, except that the radicals R 2' are not anions but are bonded to the silicon atom via a covalent bond. Table 1 Table 1The halosilane compounds shown in Table 1 are halosilane compounds of the general formula S-I. The silane compounds shown in Table 1 are fluoro-silane compounds of the general formula S-II.Scheme 3 illustrates the reaction of a halosilane compound of general formula III with the compound of general formula Ca(R 2)2 to form a silane compound. In the compound of the general formula V and the compound of the general formula VII, the radicals R 1 have the meanings indicated in connection with the general formula I. In the compound of the general formula VII, the radicals R 2' have the definitions given in connection with the fluorosilane compounds shown in Table 1. The compound of the general formula VII is an example of a silane compound.Step (c) may be performed at ambient temperature and pressure. For example, step (c) may be carried out at a temperature of 5 to 50° C. It can be provided that the substance amount of halosilane compound(s) is in a ratio of 1:1 to 1:2 to the substance amount of calcium ions of the calcium salt, preferably 1:1.5.In order to contact the fluorosilane compound(s) with the calcium salt, the use of a carrier gas may be contemplated. Using the carrier gas, the halosilane compound(s) that are gaseous or vaporized in the carrier gas can be introduced into the substance mixture. The carrier gas should not react with the halosilane compound or compounds. The carrier gas can be, for example, nitrogen, argon or helium, with argon being preferred. Alternatively, another inert gas may be used.If the halosilane compound or compounds are liquids or if the halosilane compound(s) are obtained as a liquid solution, the liquid or the liquid solution can be contacted with the liquid substance mixture comprising the calcium salt.The first process may be a continuous, semi-continuous or batch process.The first process enables the removal of polysiloxane(s) from materials which comprise further components in addition to polysiloxane(s). It thus solves the problems associated with recycling of materials containing polysiloxane(s) or contaminated with polysiloxane(s) according to the prior art.According to the invention there is also provided a process for the preparation of a silane compound of the general formula S-II wherein the X 2 radicals are independently at each occurrence R 1 or R 2' with the proviso that at least one of the X 2 R 2' radicals is; the R 1 radicals are independently selected at each occurrence from the group consisting of hydrogen, a substituted or unsubstituted alkyl group having from 1 to 12 carbon atoms, a substituted or unsubstituted alkenyl group having from 2 to 12 carbon atoms, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted alkoxy group having from 1 to 12 carbon atoms, a substituted or unsubstituted carboxy group having from 1 to 12 carbon atoms and a substituted or unsubstituted aryl group; the R 2' radicals are independently -O-R 3 or -OC(O)-R 3 at each occurrence; and R 3 is a substituted or unsubstituted alkyl group having from 1 to 12 carbon atoms; A polysiloxane comprising the steps of: (a) providing the material containing the polysiloxane; (b) reacting the polysiloxane to one or more halosilane compounds of the general formula S-I wherein the radicals X 1 are independently at each occurrence fluorine or R 1 with the proviso that at least one of the radicals X 1 is fluorine and R 1 has the meanings indicated in connection with the silane compound of the general formula S-II, by treatment of the material with a fluoride-containing solution; and(c) contacting the halosilane compound(s) with a salt Ca(R 2)2, wherein the radicals R 2 are independently at each occurrence -O-R 3 or -OC(O)-R 3 and R 3 have the meanings given in connection with formula S-II, to obtain one or more silane compounds of the general formula S-II.The method for producing one or more silane compounds from a polysiloxane is also referred to as a second method below. The second method enables one or more silane compounds to be prepared from a polysiloxane. The silane compound or compounds are the silane compounds described in connection with the first method. The silane compound(s) do not have a silicon-fluorine bond.Scheme 4 illustrates the preparation of a silane compound of general formula S-II according to the second method of the invention. The siloxane unit is an M group, D group, T group or Q group of the polysiloxane of the general formula I.Further details of the second method according to the invention have already been explained in connection with the first method according to the invention. Reference is made to this explanation.It may be provided that the silane compound(s) obtained in step (c) are converted to a polysiloxane. The invention thus makes it possible to produce a new, second polysiloxane from a first polysiloxane which is provided in step (a) by converting the first polysiloxane into one or more halosilane compound(s) of the general formula S-I, then reacting the halosilane compound(s) of the general formula S-I to form one or more silane compounds of the general formula S-II and finally reacting the silane compound(s) of the general formula S-II to form the second polysiloxane. The reaction of silane compound(s) of the general formula S-II to form the second polysiloxane is known per se. It can be carried out, for example, as in WO 2019 / 200 579 A1 (=US 2021 / 0 238 417 A1).The second process may be a continuous, semi-continuous or batch process.The term "alkyl" refers, unless otherwise indicated, particularly to a monovalent saturated aliphatic hydrocarbon group having a branched or unbranched carbon chain of 1 to 12 carbon atoms, preferably 1 to 8 carbon atoms and more preferably 1 to 6 carbon atoms. Examples of alkyl groups include, but are not limited to, methyl, ethyl, propyl, isopropyl, isobutyl, sec-butyl, tert-butyl, pentyl, n-hexyl, octyl, dodecyl, and the like. The alkyl group may be optionally substituted with one or more substituents, each substituent independently being hydroxy, alkyl, alkoxy, aryl, halogen, haloalkyl, cyano, nitro, amino, monoalkylamino or dialkylamino, unless specifically stated otherwise.The term "alkoxy" refers, unless otherwise indicated, particularly to a group of the formula -OR wherein R is an alkyl group as defined herein. Examples of alkoxy moieties include, but are not limited to, methoxy, ethoxy, isopropoxy, and the like. The alkoxy group may be optionally substituted with one or more substituents, each substituent independently being hydroxy, alkyl, alkoxy, aryl, halogen, haloalkyl, cyano, nitro, amino, monoalkylamino or dialkylamino, unless specifically stated otherwise.The term "carboxy" refers, unless otherwise indicated, particularly to a group of the formula -OC(O)-R wherein R is an alkyl group as defined herein. Examples of carboxy moieties include, but are not limited to, methanoyloxy, acetoxy, propanoyloxy, and the like. The carboxy group may be optionally substituted with one or more substituents, each substituent independently being hydroxy, alkyl, alkoxy, aryl, halogen, haloalkyl, cyano, nitro, amino, monoalkylamino or dialkylamino, unless specifically stated otherwise.The term "cycloalkyl", unless otherwise indicated, refers more particularly to monovalent, saturated carbocyclic groups consisting of mono- or bicyclic rings and having from 3 to 12 ring atoms. The cycloalkyl group may be optionally substituted with one or more substituents, each substituent independently being hydroxy, alkyl, alkoxy, aryl, halogen, haloalkyl, cyano, nitro, amino, monoalkylamino, or dialkylamino, unless specifically stated otherwise. Examples of cycloalkyl moieties include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and the like.The term "aryl" refers, unless otherwise indicated, to a cyclic aromatic hydrocarbon group consisting of a mono-, bi- or tricyclic aromatic ring system having 5 to 10 ring atoms, preferably 5 or 6 ring atoms. The aryl group may optionally be a substituted aryl group. Examples of aryl groups include, but are not limited to, phenyl, naphthyl, anthracenyl, naphthalenyl, phenanthryl, fluorenyl, indenyl, pentalenyl, azulenyl, oxydiphenyl, biphenyl, methylene diphenyl, amino diphenyl, diphenyl sulphideyl, diphenyl isopropylidenyl, benzodioxanyl, benzofuranyl, benzodioxylyl, benzopyranyl, benzoxazinyl, benzoxazinonyl, benzopiperadinyl, benzopiperazinyl, benzopyrrolidinyl, benzomorpholinyl, methylenedioxyphenyl, ethylenedioxythiophene, and the like. The term "substituted aryl group" refers in particular to an aryl group optionally substituted independently with one to four substituents, preferably one or two substituents selected from hydroxy, alkyl, alkoxy, aryl, halogen, haloalkyl, cyano, nitro, amino, monoalkylamino or dialkylamino. Unless otherwise stated, the aryl group can be mono- or polyvalent, for example mono- or bivalent.Unless otherwise indicated, the term "alkenyl" refers more particularly to an unsaturated aliphatic hydrocarbon group having a branched or unbranched carbon chain of 2 to 12 carbon atoms, preferably 2 to 8 carbon atoms, and most preferably 2 to 6 carbon atoms, which has at least one olefinic double bond, and more preferably a single double bond. Examples of alkenyl groups include, but are not limited to, vinyl, allyl, methallyl, 1,1-dimethylallyl, propenyl, butenyl, pentadienyl, hexenyl, octenyl, and the like. An allyl group is preferred. The alkenyl group may be optionally substituted with one or more substituents, each substituent independently being alkyl, alkoxy, aryl, halogen, haloalkyl, cyano, nitro, amino, monoalkylamino or dialkylamino, unless specifically stated otherwise.The term "halogen" refers to fluorine, chlorine, bromine or iodine.The term "polysiloxane(s)" describes both a single polysiloxane and multiple polysiloxanes. The term "halosilane compound(s)" describes both a single halosilane compound and a plurality of halosilane compounds. The term "silane compound(s)" refers to both a single silane compound and multiple silane compounds.The invention is explained in more detail below on the basis of exemplary embodiments, which are not intended to restrict the invention, with reference to the drawings. Figure shows FIG. 1 shows a schematic illustration of an apparatus for separating a polysiloxane from a plastic material; and FIG. 2 shows a diagram showing a gas phase IR spectrum after the dissolution of uncrosslinked and / or cured, i.e. crosslinked, silicone elastomers in hydrofluoric acid.The first method according to the invention was used in one example for separating completely or partially cured polysiloxane elastomer from a contaminated silicone cartridge. The completely or partially cured polysiloxane elastomer contains M groups and D groups. It may additionally contain T groups and / or Q groups. The silicone cartridge was a cartridge which consists of polyethylene and / or polypropylene and contains residues of completely or partially cured polysiloxane elastomer. These residues represent an impurity.The contaminated silicone cartridge is a material which, in addition to the completely or partially cured polysiloxane elastomer, contains further plastics, namely polyethylene and / or polypropylene. The material is also referred to below as plastic material. Polyethylene and / or polypropylene, which form the cartridge, are not attacked by hydrofluoric acid and fluoride-containing acidic solutions.The apparatus shown in FIG. 1 has a first reaction vessel 11. Disposed within the reaction vessel 11 is a vessel 12 having a bottom 13 and side walls 14. The bottom 13 and the side walls 14 have a plurality of openings 15 through which a liquid 2 can pass. In the container 12 is the crushed material 1 obtained by crushing the contaminated silicone cartridge. The container 12 serves as a carrier for the comminuted material 1. the liquid 2 which is located in the reaction container 11 is hydrofluoric acid. Hydrofluoric acid is an aqueous solution of HF and thus represents a fluoride-containing solution. The term "F-ISE" denotes an ion selective electrode for measuring the concentration of fluoride ions in the fluoride-containing solution.The separation of the fully or partially cured polysiloxane elastomer from the plastic material is illustrated below using the example of poly(dimethylsiloxane) (PDMS). PDMS 2 contained in the crushed plastic material and containing 2 M groups and n D groups (where n has the meaning given in connection with the general formula II) is reacted by the contact with hydrofluoric acid 1 to give difluorodimethylsilane 3 and monofluorotrimethylsilane 4, as shown in Scheme 5.Difluorodimethylsilane 3 and monofluorotrimethylsilane 4 are gaseous halosilane compounds. Difluorodimethylsilane 3 and monofluorotrimethylsilane 4 are formed in the first reaction vessel as a mixture in the form of gas bubbles 3. the gas bubbles 3 are led out of the first reaction vessel 11 at its ceiling 11o by means of a carrier gas introduced into the first reaction vessel 11 at the bottom 11u of the same. The carrier gas is argon in this example.At the ceiling 11o of the reaction vessel 11, the gaseous mixture consisting of the carrier gas, difluorodimethylsilane 3 and monofluorotrimethylsilane 4 enters a conduit 31. The gaseous mixture is fed by means of the line 31 into a second reaction vessel 21 (arrow A). In the second reaction vessel 21 there is a suspension 4 of calcium acetate in hexane. Hexane is the suspending agent. The line 31 extends in the second reaction vessel 21 as far as into the calcium acetate suspension 4.In the second reaction vessel 21, difluorodimethylsilane 3 and monofluorotrimethylsilane 4 are reacted with calcium acetate (Ca(Ac) 2) to give diacetoxydimethylsilane 5 and monoacetoxytrimethylsilane 6, as shown in Scheme 6. Ac thereby identifies an acetate group. Diacetoxydimethylsilane 5 may alternatively be represented by the formula: The carrier gas leaves the second reaction vessel 21 at the ceiling 21o thereof. CaF 2, which is obtained as a solid, precipitates at the bottom 21 uof the second reaction vessel 21. Diacetoxydimethylsilane 5 and monoacetoxytrimethylsilane 6 are obtained as a mixture in liquid form. CaF 2 can be separated by filtration. Diacetoxydimethylsilane 5 and monoacetoxytrimethylsilane 6 can be separated from the suspension medium by distillation and also separated from one another in the process.The obtained diacetoxydimethylsilane 5 and monoacetoxytrimethylsilane 6 can be used as precursors for the re-production of PDMS. Mono-, tri- and tetraalkoxysilanes and analogous acetoxysilanes can be used in the same way as precursors for the production of a polysiloxane elastomer.The first reaction vessel has an overflow collar. The overflow collar enables continuous mixing and flow of the liquid 2, so that educts (e.g. hydrofluoric acid), products (e.g. difluorodimethylsilane and monofluorotrimethylsilane) and the carrier gas (argon) can be transported well to and from the material surface.Example 1A silicone cartridge of polyethylene and polypropylene contaminated with uncrosslinked and / or cured, i.e., crosslinked, silicone elastomers was comminuted to obtain 20 g of a comminuted material. The crushed material had a particle size in a range of 10 mm to 50 mm. The crushed material was treated with 250 ml of 20% hydrofluoric acid in a first recirculating reaction vessel. The treatment was carried out at room temperature (20° C.) and ambient pressure for a period of 60 minutes. The resulting mixture of gaseous halosilane compounds was analyzed by infrared spectroscopy in the argon carrier gas stream (see FIG. 2 ) and introduced into a suspension of 20 g of calcium acetate in 250 ml of hexane. The liquid phase was separated from the precipitated calcium fluoride by filtration. The resulting diacetoxydimethylsilane was separated from the hexane by distillation.List of reference characters1 Material 2 Fluoride-containing solution 3 Halosilane gas bubble 4 Suspension 11 First reaction vessel 11 u 11 o Decke 12 Vessel 13 Boden 14 Sidewall 15 Opening 21 Second reaction vessel 21 u 21 o 31 Pipe

Claims

A process for separating one or more polysiloxanes from a material containing, in addition to the polysiloxane or polysiloxanes, at least one further component selected from the group consisting of polyethylene, polypropylene, polyethylene terephthalate, polyamides, polytetrafluoroethylene and perfluoroalkoxy polymers, the process comprising the steps of: (a) providing the material containing the polysiloxane or polysiloxanes; and (b) reacting the polysiloxane or polysiloxanes to one or more halosilane compounds by treating the material with a fluoride-containing solution.Process according to Claim 1, characterized in that the polysiloxane is a compound of the general formula I M m D n T p Q r in which M is an M group of the formula (R 1)3 SiO 1 / 2, D is a D group of the formula (R 1)2 SiO 2 / 2, T is a T group of the formula (R 1) SiO 3 / 2 and Q is a Q group of the formula SiO 4 / 2, R 1 is hydrogen or identical or different organic groups and m, n, p and r are each 0 or integer of 1 or greater, with the proviso that the sum of m, n, p and r is an integer equal to or greater than 3.The process according to claim 2, wherein the radicals R 1 are selected independently of one another at each occurrence from the group consisting of hydrogen, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 12 carbon atoms, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted alkoxy group having 1 to 12 carbon atoms, a substituted or unsubstituted carboxy group having 1 to 12 carbon atoms and a substituted or unsubstituted aryl group.A process according to claim 2 or claim 3, wherein R 1 are identical or different unsubstituted alkyl groups having 1 to 6 carbon atoms.Process according to one of the preceding claims, characterized in that the fluorosilane compound is a compound of the general formula S-I in which the radicals X 1 are, independently of one another on each occurrence, fluorine or R 1 with the proviso that at least one of the radicals X 1 is fluorine.Method according to one of the preceding claims, characterized in that in step (a) the material is provided as comminuted material.Process according to one of the preceding claims, characterized in that the fluoride-containing solution is an aqueous solution.Method according to one of the preceding claims, characterized in that the fluoride-containing solution is a solution of hydrofluoric acid or ammonium fluoride.Process according to any of the preceding claims, characterized in that in step (b) a mixture of a plurality of fluorosilane compounds is obtained and in that the process comprises separating at least one of the fluorosilane compounds from the mixture.A process according to any preceding claim, characterised in that it further comprises the step of: (c) contacting the fluorosilane compound with a salt Ca(R 2)2, wherein R 2 radicals are independently at each occurrence R 3- O - or R 3- C(O)O - wherein R 3 is a substituted or unsubstituted alkyl group having from 1 to 12 carbon atoms.The method of claim 10, wherein step (c) comprises introducing the halosilane compound into a liquid composition containing the salt Ca(R 2)2.Process according to Claim 11, characterized in that the liquid substance mixture is a solution or suspension of the salt in a nonaqueous solvent.The method according to any one of claims 10 to 12, characterized in that the salt is calcium acetate.A process for the preparation of a silane compound of the general formula S-II from a polysiloxane, wherein the radicals X 2 are independently of one another at each occurrence R 1 or R 2' with the proviso that at least one of the radicals X 2 R is 2'; the R 1 radicals are independently selected at each occurrence from the group consisting of hydrogen, a substituted or unsubstituted alkyl group having from 1 to 12 carbon atoms, a substituted or unsubstituted alkenyl group having from 2 to 12 carbon atoms, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted alkoxy group having from 1 to 12 carbon atoms, a substituted or unsubstituted carboxy group having from 1 to 12 carbon atoms and a substituted or unsubstituted aryl group; and the R 2' radicals are independently -O-R 3 or -OC(O)-R 3 at each occurrence; and R 3 is a substituted or unsubstituted alkyl group having from 1 to 12 carbon atoms; comprising the steps of: (a) providing the material containing the polysiloxane; (b) reacting the polysiloxane to one or more halosilane compounds of the general formula S-I wherein the radicals X 1 are, independently of one another at each occurrence, fluorine or R 1 with the proviso that at least one of the radicals X 1 is fluorine, and R 1 has the meanings indicated in connection with the silane compound of the general formula S-II, by treating the material with a fluoride-containing solution; and (c) contacting the halosilane compound(s) with a salt Ca(R 2)2, in which the radicals R 2 are, independently of one another on each occurrence, R 3- O - or R 3- C(O)O - and R 3 have the meanings indicated in connection with formula S-II, to give one or more silane compounds of the general formula S-II.The process according to claim 14, wherein step (b) gives a mixture of a plurality of fluorosilane compounds, and wherein the process comprises separating at least one of the fluorosilane compounds from the mixture.

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