Stabilizer for polymer foams based on the regeneration of polydimethylsiloxane

Abstract

This invention relates to polyether polydimethylsiloxane, which can be used as a stabilizer for polymer foams such as polyurethane foams. It is known that polyether polydimethylsiloxane can be produced based on compounds from recycling processes. Therefore, a method for producing polyether polydimethylsiloxane based on recycled linear polydimethylsiloxane is provided. This invention also relates to methods and compositions for preparing polymer foams utilizing polyether polydimethylsiloxane, as well as articles produced therefrom. Furthermore, this invention relates to the use of recycled polydimethylsiloxane-containing compositions and the use of polyether polydimethylsiloxane as a foam stabilizer.

Description

[Technical Field]

[0001] This invention relates to polyether polydimethylsiloxane, which can be used as a stabilizer for polymer foams such as polyurethane foams. It is known that polyether polydimethylsiloxane can be produced based on compounds from recycling processes. Therefore, a method for producing polyether polydimethylsiloxane based on recycled linear polydimethylsiloxane is provided. This invention also relates to methods and compositions for preparing polymer foams utilizing polyether polydimethylsiloxane, as well as articles produced therefrom. Furthermore, this invention relates to the use of recycled polydimethylsiloxane-containing compositions and the use of polyether polydimethylsiloxane as a foam stabilizer.

[0002] Technical background Foam stabilizers are typically used to ensure the formation of a stable foam. These compounds ensure that gases produced during the reaction do not leak from the reaction mixture and that the resulting foam remains stable until the reaction is complete, preventing collapse. Typical polymer foams are polyurethane foams, phenolic resin foams, or polyvinyl chloride foams.

[0003] Frequently used foam stabilizers are selected from polyether polydimethylsiloxanes. Linear polydimethylsiloxanes and cyclic polydimethylsiloxanes such as octamethylcyclotetrasiloxane can be used as starting materials for the production of polyether polydimethylsiloxanes. High-purity cyclic polydimethylsiloxanes are usually obtained from chlorosilanes in the Mueller-Rochow process (hereinafter abbreviated as MR or MR process), followed by hydrolysis. The Mueller-Rochow process is the most common process for preparing organosilicon compounds on an industrial scale directly from natural silicon sources such as sand. In the Mueller-Rochow process, alkyl chlorides react with elemental silicon in a fluidized bed reactor. Unfortunately, the Mueller-Rochow process requires a wasteful amount of energy.

[0004] Therefore, it is desirable to reduce the carbon footprint of the manufacturing process and the polyether polydimethylsiloxane foam stabilizers thus produced, and to provide alternative methods for their preparation.

[0005] On the other hand, the accumulation of large amounts of plastic waste is one of the global challenges currently facing the world. In fact, the serious environmental risks of landfills or the incineration of plastic waste are a growing global concern. Under these conditions, the recycling of polymers such as polydimethylsiloxane (also abbreviated herein as PDMS) is essential for the polymer industry's transition to carbon neutrality. As a result, polydimethylsiloxane is widely used in industry, for example, in sealants, adhesives, lubricants, cookware, and equipment for medical applications, thermal insulation, and electrical insulation.

[0006] Various recycling methods for polydimethylsiloxanes are known. For example, European Patent Application Publication No. 0009202 discloses that waste materials containing polyorganylsiloxanes can be recycled by catalytic depolymerization. For this purpose, a composition of linear organopolysiloxanes consisting of at least 50 mol% dimethylsiloxane units and aqueous sulfuric acid as a catalyst to promote the rearrangement of siloxane bonds is heated to obtain a cyclic dimethylpolysiloxane-containing composition.

[0007] Furthermore, U.S. Patent No. 5,110,972 relates to the recycling of waste silicone by dissolving the silicone in a suitable solvent and converting it to a cyclic siloxane by applying a two-step acid / base catalytic cracking process. Thus, the silicone waste consists of high molecular weight liquid or elastomer materials formed by silicone polymers, typically having short alkyl groups, particularly methyl groups. The cyclic siloxane-containing composition is ultimately obtained in high yield by distillation.

[0008] Canadian Patent Application Publication No. 2737235 discloses a method for preparing equilibrium products of organosiloxanes useful as stabilizers for flexible polyurethane foams. Specifically, the document discloses a first step of producing a hydrogen polysiloxane comprising reacting decamethylcyclopentasiloxane (D5), poly(methyl)hydrogensiloxane and hexamethyldisiloxane (HMDS) using a pre-dried ion-exchange resin. The resulting polyhydrogendimethylsiloxane is then subjected to a central formula CH2=CH-CH2O-(C2H4O)5-(C3H6O) compound having a platinum metal complex. 21 By reacting CH3 with a polyether, a blocked polysiloxane-polyoxyalkylene is formed and used as a stabilizer for flexible polyurethane foam.

[0009] U.S. Patent Application Publication No. 2006 / 0241270 discloses a method for preparing equilibrium products of organohydrogensiloxanes, specifically, the document discloses a first step of mixing a mixture of decaethylcyclopentasiloxane (D5), poly(methyl)hydrogensiloxane PTF1, and hexamethyldisiloxane HMDS with a pre-dried ion exchange resin and subsequently equilibrating to obtain a hydrogensiloxane. In the next step, the hydrogensiloxane is further treated with polyethers of various average formulas to obtain blocked polysiloxanes-polyoxyalkylenes.

[0010] Linear polydimethylsiloxanes can be obtained by polymerizing cyclic polydimethylsiloxanes in the presence of a polymerization catalyst. As detailed above, linear or polydimethylsiloxanes can be used as starting materials in the production of polyether polydimethylsiloxanes. However, the prior art does not address the production of polyether polydimethylsiloxanes derived from linear polydimethylsiloxanes from recycled processes, as it is considered in the art that the siloxanes must be of high purity, and siloxanes from recycled processes do not have the purity necessary to enable the production of suitable polyether polydimethylsiloxane foam stabilizers.

[0011] However, classifying at least some cyclic polydimethylsiloxanes as POPs is a significant issue. POPs (persistent organic pollutants) are organic substances that possess specific properties that can harm humans and the environment. More specifically, POPs are organic compounds characterized by their ability to remain in the environment for extended periods (persistence), accumulate through the food chain (bioaccumulative), be harmful to human health and the environment (ecotoxic), and be transportable over long distances in the environment. These are regulated not only at the EU level by POP regulations but also globally by the Stockholm Convention. The objective is clear: to prohibit or at least restrict the manufacture, marketing, and use of POPs. The cyclosiloxanes octamethylcyclotetrasiloxane (D4, CAS number: 556-67-2), decamethylcyclopentasiloxane (D5, CAS number: 541-02-6), and dodecamethylcyclohexasiloxane (D6, CAS number: 540-97-6) are particularly important in this context. Octamethylcyclotetrasiloxane meets the criteria for POP (Primary Oxide). The POP classification for D4 / 5 remains a subject for future research.

[0012] Therefore, the objective remains to provide polyether polydimethylsiloxanes with a reduced carbon footprint, based on the recycling process and the product from an environmental and health perspective.

[0013] overview A method for producing polyether polydimethylsiloxane has been found to be able to solve or mitigate the drawbacks of the prior art. The method comprises (a) subjecting a recycled polydimethylsiloxane-containing composition, which includes recycled linear polydimethylsiloxane, to an equilibrium reaction with at least one poly(methylhydrogen)siloxane in the presence of at least one equilibrium catalyst to form a poly(methylhydrogen)-polydimethylsiloxane copolymer, and (b) subjecting the poly(methylhydrogen)-polydimethylsiloxane copolymer obtained in step (a) to a hydrosilylation reaction with at least one polyether containing at least one carbon-carbon double bond reactive to the Si-H bond, preferably in the presence of at least one hydrosilylation catalyst, to obtain a polyether polydimethylsiloxane, wherein the recycled linear polydimethylsiloxane is obtained from the recycling of at least one linear polydimethylsiloxane or its copolymer, and at least one linear polydimethylsiloxane or The recycling of the copolymer may include (c) subjecting a polydimethylsiloxane-containing composition containing at least one linear polydimethylsiloxane or its copolymer to catalytic depolymerization in the presence of at least one depolymerization catalyst to form at least one cyclic polydimethylsiloxane in the depolymerization reaction mixture; (d) distilling the depolymerization reaction mixture to obtain a cyclic polydimethylsiloxane-containing composition containing at least one cyclic polydimethylsiloxane; (e) optionally subjecting the cyclic polydimethylsiloxane-containing composition to fractional distillation purification; (f) subjecting the cyclic polydimethylsiloxane-containing composition containing at least one cyclic polydimethylsiloxane to a polymerization reaction in the presence of a polymerization catalyst to obtain recycled linear polydimethylsiloxane in the recycled polydimethylsiloxane-containing composition; and (g) optionally purifying the recycled polydimethylsiloxane-containing composition.

[0014] The present invention also relates to a composition for preparing a polymer foam comprising at least one monomer species and one or more polyether polydimethylsiloxanes obtained according to the method for producing polyether polydimethylsiloxanes disclosed herein, wherein the polymer foam is preferably a polyurethane foam, a phenolic resin foam, or a polyvinyl chloride foam, more preferably a polyurethane foam.

[0015] The present invention also relates to a method for preparing a polymer foam, which comprises reacting one or more monomer species in the presence of one or more polyether polydimethylsiloxanes obtained according to the method for producing polyether polydimethylsiloxanes disclosed herein to obtain a polymer foam.

[0016] The present invention also provides an article comprising a polymer foam obtained according to the method for preparing a polymer foam disclosed herein, or a reaction product of a composition for preparing a polymer foam disclosed herein.

[0017] The present invention further relates to the use of recycled linear polydimethylsiloxane for producing polyether polydimethylsiloxane.

[0018] The present invention further relates to the use of at least one polyether polydimethylsiloxane obtained by the method for producing polyether polydimethylsiloxanes disclosed herein as an additive in a method for producing a polymer foam or a composition for preparing a polymer foam, wherein the polymer foam is preferably a polyurethane foam, a phenolic resin foam, or a polyvinyl chloride foam.

[0019] Advantageously, the method for producing a polyether polydimethylsiloxane as defined in appended claim 1 provides a polyether polydimethylsiloxane having properties suitable for use as a foam stabilizer. At the same time, the polyether polydimethylsiloxane has the advantage of a reduced carbon footprint compared to polyether polydimethylsiloxanes obtained from conventional routes based on the Mueller-Rochow process. The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description.

[0020] Detailed Description Any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of "1 to 10" includes the recited minimum value 1 and the recited maximum value 10 and every sub-range therebetween, i.e., every sub-range beginning with a minimum value of 1 or more and ending with a maximum value of 10, and all sub-ranges thereof, e.g., 1 to 6.3, or 5.5 to 10, or 2.7 to 6.1. Any endpoint and / or number within those ranges can be combined within the scope of the present disclosure.

[0021] Components described as being present "up to" a specified amount or "at most" a specified amount, where a minimum amount is not stated, are not necessarily present in each composition. For example, a recycled polydimethylsiloxane-containing composition containing up to 40 ppm (by weight) of water may contain substantially no water or may contain no water at all.

[0022] All parts, amounts, concentrations, etc. referred to herein are by weight unless otherwise specified.

[0023] As used herein, the term “comprising” is understood to be open-ended and not to exclude the existence of any additional undescribed or unlisted elements, materials, components, or method steps. Terms such as “including” and “containing” are understood to be synonymous with “comprising.” As used herein, the term “consisting of” is understood to exclude the existence of any unspecified elements, components, or method steps. While this disclosure describes “comprising,” “consisting of” or “consisting essentially of” are also within the scope of this disclosure. For example, while this disclosure describes recycled polydimethylsiloxane-containing compositions comprising recycled linear polydimethylsiloxane, recycled polydimethylsiloxane-containing compositions that are essentially and / or consist of recycled linear polydimethylsiloxane are also within the scope of this disclosure. In this context, “essentially derived from” means that any additional compositional components do not substantially affect the relevant properties of the recycled polydimethylsiloxane-containing composition in the method for producing polyether polydimethylsiloxane.

[0024] As used herein, the singular forms "a," "an," and "the" refer to multiple objects unless otherwise explicitly indicated by the context.

[0025] As used herein, the term “substantially absent” means that the material being discussed is present, if present, in the composition as an incidental impurity. In other words, the material does not affect the properties of the composition. Therefore, the material may be present in an amount of less than 1 weight percent, preferably less than 0.5 weight percent, or more preferably less than 0.1 weight percent. This means, for example, that a recycled polydimethylsiloxane-containing composition contains less than 1 weight percent of a chlorine-containing compound, or possibly less than 0.05 weight percent of a chlorine-containing compound, where such weight percent is based on the total weight of the recycled polydimethylsiloxane-containing composition. As used herein, the term “completely absent” means that the material is not present at all in the composition. Therefore, the recycled polydimethylsiloxane-containing compositions disclosed herein do not have to contain chlorine-containing compounds.

[0026] Furthermore, the term "polymer" refers to oligomers, homopolymers (e.g., those prepared from a single monomer species), copolymers (e.g., those prepared from at least two monomer species, such as three or more monomer species), and graft polymers.

[0027] As already stated, the present invention is a method for producing polyether polydimethylsiloxane, (a) A recycled polydimethylsiloxane-containing composition, comprising recycled linear polydimethylsiloxane, is subjected to an equilibrium reaction with at least one poly(methylhydrogen)siloxane in the presence of at least one equilibrium catalyst to form a poly(methylhydrogen)-polydimethylsiloxane copolymer. (b) The poly(methylhydrogen)-polydimethylsiloxane copolymer obtained in step (a) is subjected to a hydrosilylation reaction with at least one polyether containing at least one carbon-carbon double bond that is reactive to the Si-H bond, preferably in the presence of at least one hydrosilylation catalyst, to obtain a polyether polydimethylsiloxane. The recycled linear polydimethylsiloxane is obtained from the recycling of at least one linear polydimethylsiloxane or its copolymer, and the recycling of at least one linear polydimethylsiloxane or its copolymer is (c) A polydimethylsiloxane-containing composition comprising at least one linear polydimethylsiloxane or its copolymer is subjected to catalytic depolymerization in the presence of at least one depolymerization catalyst to form at least one cyclic polydimethylsiloxane in the depolymerization reaction mixture, (d) Distilling the depolymerization reaction mixture to obtain a cyclic polydimethylsiloxane-containing composition comprising at least one cyclic polydimethylsiloxane, (e) Depending on the circumstances, the cyclic polydimethylsiloxane-containing composition may be subjected to fractional distillation and purification. (f) A cyclic polydimethylsiloxane-containing composition comprising at least one cyclic polydimethylsiloxane is subjected to a polymerization reaction in the presence of a polymerization catalyst to obtain recycled linear polydimethylsiloxane in the recycled polydimethylsiloxane-containing composition, (g) A method is provided which may include purifying a recycled polydimethylsiloxane-containing composition.

[0028] In silicone recycling, cyclic siloxanes are produced as an intermediate. As mentioned above, at least some cyclic siloxanes are classified as persistent organic contaminants, which is why their presence in the final product is avoided or legally prohibited. A further problem is that aromatic and aliphatic contaminants are frequently found in recycled siloxanes. The aromatic or aliphatic contaminants can be used as additives in the recycling process, for example, as solvents, or to improve phase separation. Alternatively, they may arise from the waste stream used in the recycling process or be formed during the recycling process. For example, benzene may be formed during the heat treatment of phenylsiloxane. However, impurities such as alkanes or benzene cannot be separated from D4 / D5 by distillation. However, it has been found that these impurities can be separated by distillation after the contaminated cyclic siloxane has been converted to a higher molecular weight PDMS oil. An example of this application involves the use of a cyclic organosiloxane-containing composition derived from a recycling process. The aforementioned composition contained cyclic organosiloxanes D3-D6, but also contained different alkanes and benzenes as impurities. It was not possible to completely remove the impurities from the composition. However, if the cyclic organosiloxanes were first converted to polydimethylsiloxane oil, it was possible to remove the impurities. The advantage is that cycles from a lower purity recycling process can be used. The impurities present can be separated at the PDMS oil level. A further advantage is that PDMS oil as a raw material is less toxicologically harmful than cyclic siloxanes and can be transported or stored more easily. The POP classification of D4 / 5 is a future challenge.

[0029] As understood herein, polydimethylsiloxane is a siloxane unit (repeating unit), namely O 1 / 2 -Si-O 1 / 2 It is a polymer having methyl substituents (hereinafter abbreviated as "Me") on its units and silicon atoms. As a result, individual siloxane units are interconnected by oxygen atoms. 1 / 2 -SiMe2-O 1 / 2The units are the same as in the prior art and are also denoted as D units in this specification. The polydimethylsiloxane copolymer, in this specification, refers to a polymer containing, in addition to the repeating unit (D unit), a further repeating unit different from 1 / 2 -SiMe2-O 1 / 2 In addition to the repeating unit (D unit), a polymer containing a further repeating unit different from 1 / 2 -SiMe2-O 1 / 2 Polydimethylsiloxane or its copolymer may contain branched units conventionally and in this specification denoted as T units and Q units. Thus, the T unit refers to the Me1SiO 3 / 2 unit, and the Q unit refers to the SiO 4 / 2 unit. Further, the M unit refers to the Me3SiO 1 / 2 unit in this specification and thus forms the chain ends. Branched polydimethylsiloxane refers to polydimethylsiloxane containing T units and / or Q units. Branched polydimethylsiloxane copolymer refers to a copolymer containing T units and / or Q units and / or further branched units other than T units or Q units in the polymer chain.

[0030] Recycled linear polydimethylsiloxane as understood in this specification refers to linear polydimethylsiloxane obtained from the recycling of waste materials. As waste materials, for example, used, wide-spec, expired, surplus materials, or any mixture or combination thereof can be utilized. In a preferred embodiment of the present invention, the recycled linear polydimethylsiloxane is obtained from the recycling of at least one linear polydimethylsiloxane or its copolymer, as will be further detailed below.

[0031] The recycled polydimethylsiloxane-containing composition of the present invention can have a total content of recycled linear polydimethylsiloxane of more than 90% (by weight), preferably more than 95% (by weight), or even more preferably 98% (by weight) based on the total weight of the recycled polydimethylsiloxane-containing composition.

[0032] <000014o>A recycled polydimethylsiloxane-containing composition may also be characterized by its molar content of M, D, T, and Q units based on the total moles of M, D, T, and Q units in the recycled polydimethylsiloxane-containing composition. In a preferred embodiment of the present invention, a recycled polydimethylsiloxane-containing composition contains up to 7.5 mol%, preferably up to 4 mol%, or more preferably up to 2.5 mol%, of M units based on the total moles of M, D, T, and Q units in the recycled polydimethylsiloxane-containing composition. A recycled polydimethylsiloxane-containing composition may contain at least 0.15 mol%, preferably at least 0.25 mol%, or more preferably at least 1.5 mol%, of M units based on the total moles of M, D, T, and Q units in the recycled polydimethylsiloxane-containing composition. The sum of T and Q units in the recycled polydimethylsiloxane-containing composition may be up to 0.75 mol%, preferably up to 0.5 mol%, or more preferably up to 0.25 mol%, based on the total moles of M, D, T, and Q units in the recycled polydimethylsiloxane-containing composition. 29 In Si NMR spectroscopy, M units yield signals in the range of 6–9 ppm, D units in the range of -16–24 ppm, T units in the range of -40–80 ppm, and Q units in the range of -95–140 ppm. For example, the proportion of M units is determined by setting the sum of the signal intensities of signals from 6–9 ppm to the sum of the signal intensities of all M, D, T, and Q units. 29 Appropriate parameters for recording Si-NMR can be found in the following literature: M. Cypryk, K. Kazmierski, W. Fortuniak, and J. Chojnowski, Macromolecules 2000, 33, 5, 1536-1545.

[0033] A recycled polydimethylsiloxane-containing composition may be further described by the content of water, cyclic siloxanes, and other components that are not recycled linear polydimethylsiloxanes, such as siloxanes containing hydroxyl or vinyl groups.

[0034] In a preferred embodiment of the present invention, the recycled polydimethylsiloxane-containing composition contains, as measured according to DIN 51777:2020-04, up to 0.05% (by weight), preferably up to 100 ppm (by weight), more preferably up to 40 ppm (by weight), or most preferably up to 10 ppm of water, based on the total weight of the recycled polydimethylsiloxane-containing composition. Even more preferably, the recycled polydimethylsiloxane-containing composition is substantially water-free or completely water-free. The recycled polydimethylsiloxane-containing composition may contain up to 0.2 mol%, preferably up to 0.1 mol%, or more preferably up to 0.05 mol%, of hydroxyl-substituted silicon atoms, based on the total moles of silicon atoms in the recycled polydimethylsiloxane-containing composition, preferably 29 This is determined based on Si-NMR spectroscopy. For this purpose, the signal corresponding to the hydroxyl-substituted silicon atom is determined. 29 The peak area of ​​the Si-NMR spectrum is calculated. The sum of the peak areas of all silicon atom signals without a standard is determined and set to a ratio with the peak area of ​​the hydroxyl-substituted silicon atom to obtain the molar content of the hydroxyl-substituted silicon atom. A measurement frequency of at least 400 MHz for NMR measurement is advantageous. More preferably, the recycled polydimethylsiloxane-containing composition is substantially or completely free of hydroxyl-substituted silicon atoms. Water and hydroxyl-substituted siloxanes lead to hydrolysis of the SiH functional group in the equilibrium reaction step, thus ultimately resulting in a structurally altered polyether polydimethylsiloxane, which can degrade the applicability of the polymer foam. Water also leads to solubilization of the equilibrium catalyst, thereby potentially slowing or completely stopping the equilibrium reaction, and as a result, a sufficient statistical distribution of SiH units in the resulting poly(methylhydrogen)-polydimethylsiloxane copolymer cannot be achieved.

[0035] A recycled polydimethylsiloxane-containing composition may contain up to 20% (by weight), or preferably up to 15% (by weight), of cyclic siloxanes, based on the total weight of the recycled polydimethylsiloxane-containing composition, and is preferably measured by gas chromatography, for example, according to the method described below. More preferably, the recycled polydimethylsiloxane-containing composition is substantially or completely free of cyclic siloxanes. Such cyclic siloxanes may have 2 to 8 repeating units, such as hexamethylcyclotrisiloxane (conventionally denoted as D3 herein), octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), dodecamethylcyclohexasiloxane (D6), tetradecamethylcycloheptasiloxane (D7), and hexadecamethylcyclooctasiloxane (D8).

[0036] The content of cyclic polydimethylsiloxanes (e.g., D3, D4, D5, D6, D7, and D8) in recycled polydimethylsiloxane-containing compositions can be determined as follows: The substances are separated according to their boiling point and detected by a thermal conductivity detector (TCD). Aliquots of the sample to be tested are analyzed by GC without further dilution. This is performed in a gas chromatograph equipped with a split / splitless injector, capillary column, and thermal conductivity detector under the following conditions: Injector: 290°C, 40 mL split; Injection volume: 1 μL; Column: 5 m × 0.32 mm HP5 1 μm; Carrier gas: Hydrogen, constant flow rate 2 mL / min; Temperature program: 80°C for 1 min, then 80°C-300°C for 30°C / min, then 300°C for 10 min conditioning; Detector: TCD at 320°C; Makeup gas flow rate: 8 mL / min; Reference gas flow rate: 22 mL / min. Cyclic siloxanes are separated according to their boiling points. The mass fraction of each substance is determined as the percentage of the peak area determined for each substance compared to the total area of ​​all detected substances (area % method).

[0037] A recycled polydimethylsiloxane-containing composition may contain up to 0.5 mol%, preferably up to 0.2 mol%, or more preferably up to 0.1 mol%, of vinyl-substituted silicon atoms based on the total molar silicon atoms in the recycled polydimethylsiloxane-containing composition, preferably 29 This is determined based on Si-NMR spectroscopy. For this purpose, the signal corresponding to the vinyl-substituted silicon atom is determined. 29 The peak areas of the Si-NMR spectrum are calculated. The sum of the peak areas of all silicon atom signals without a standard is determined and set to the ratio with the peak area of ​​the vinyl-substituted silicon atoms to obtain the molar content of vinyl-substituted silicon atoms. A measurement frequency of at least 400 MHz for NMR measurements is advantageous. More preferably, the recycled polydimethylsiloxane-containing composition is substantially or completely free of vinyl-substituted silicon atoms. Vinyl-substituted siloxanes provide crosslinking sites for the polymer chain in subsequent hydrosilylation reactions, which can lead to an undesirable increase in the viscosity of the resulting polyether polydimethylsiloxane.

[0038] A recycled polydimethylsiloxane-containing composition may contain recycled linear polydimethylsiloxane and at least one further non-recycled polydimethylsiloxane. The at least one further non-recycled polydimethylsiloxane may be added to the recycled polydimethylsiloxane-containing composition before being subjected to the equilibrium reaction. For example, a recycled polydimethylsiloxane-containing composition may contain a non-recycled cyclic polydimethylsiloxane such as octamethylcyclotetrasiloxane. Such a non-recycled cyclic polydimethylsiloxane, such as octamethylcyclotetrasiloxane, can be derived, for example, from chlorosilanes of the conventionally applied Mueller-Rochow process. However, preferably, the recycled polydimethylsiloxane-containing composition is substantially or completely free of further non-recycled polydimethylsiloxanes obtained, for example, based on methylchlorosilanes from the Mueller-Rochow process. Therefore, the recycled polydimethylsiloxane-containing composition of the present invention may have a lower content of chlorine-containing compounds than the respective content of polydimethylsiloxane-containing compositions having polydimethylsiloxane derived from methylchlorosilane. Chlorine-containing compounds as understood herein include inorganic compounds such as chlorine-containing salts such as NaCl, as well as organic compounds such as chlorosilane. Based on the total weight of the recycled polydimethylsiloxane-containing composition, the recycled polydimethylsiloxane-containing composition may contain less than 100 ppm of chlorine-containing compounds, preferably less than 50 ppm, more preferably less than 25 ppm, and most preferably less than 10 ppm. Preferably, the recycled polydimethylsiloxane-containing composition is substantially free of chlorine-containing compounds, or most preferably completely free of chlorine-containing compounds.

[0039] By utilizing recycled linear polydimethylsiloxane, the carbon footprint of recycled polydimethylsiloxane-containing compositions used in the implementation of the present invention can be reduced compared to the use of unrecycled polydimethylsiloxane, which is obtained directly from the products of the Mueller-Rochow process and has been conventionally used in the preparation of polyether polydimethylsiloxane. Thus, recycled linear polydimethylsiloxane can have a carbon footprint of less than 4 kg CO2 equivalent / kg of recycled linear polydimethylsiloxane, or preferably less than 2 kg CO2 equivalent / kg of recycled linear polydimethylsiloxane, as determined according to DIN EN ISO standard 14067:2018.

[0040] As already stated, recycled linear polydimethylsiloxane is obtained in a preferred embodiment of the present invention from the recycling of at least one linear polydimethylsiloxane or copolymer.

[0041] Advantageously, at least one linear polydimethylsiloxane or copolymer subjected to the recycling process contains at least 50% (by weight), preferably at least 90% (by weight), or more preferably at least 99% (by weight), of dimethylsiloxane units (D units) based on the total weight of at least one linear polydimethylsiloxane or copolymer. Preferably, at least one linear polydimethylsiloxane or copolymer is preferably 29The ratio of M units to D units is at least 1:500, preferably at least 1:750, or more preferably at least 1:1000, as determined by Si-NMR spectroscopy. In a preferred embodiment of the present invention, at least one linear polydimethylsiloxane is not a copolymer and therefore consists only of dimethylsiloxane (D) repeating units and M units. In a preferred embodiment of the present invention, at least one polydimethylsiloxane or its copolymer is a linear polydimethylsiloxane. In a more preferred embodiment of the present invention, at least one linear polydimethylsiloxane or its copolymer is a linear polydimethylsiloxane homopolymer.

[0042] At least one linear polydimethylsiloxane or its copolymer corresponds to, for example, waste polydimethylsiloxane polymer or copolymer material, wide-spec polydimethylsiloxane polymer or copolymer material, used polydimethylsiloxane polymer or copolymer material, expired polydimethylsiloxane polymer or copolymer material, surplus polydimethylsiloxane polymer or copolymer material, or any mixture or combination thereof, or derived from there.

[0043] At least one linear polydimethylsiloxane or its copolymer can correspond to different polydimethylsiloxane polymers or copolymer products. For example, at least one linear polydimethylsiloxane or its copolymer may be a polydimethylsiloxane material from a lubricant or heat transfer oil. The polydimethylsiloxane polymer or copolymer may be polydimethylsiloxane oil, polydimethylsiloxane rubber, polydimethylsiloxane elastomer, or any mixture thereof. Polydimethylsiloxane oil refers to the state of aggregation at 25°C and standard pressure (i.e., 1 atm). For example, at least one linear polydimethylsiloxane or its copolymer may be a mixture of polydimethylsiloxane oil and polydimethylsiloxane elastomer or rubber. The linear polydimethylsiloxane or its copolymer may, of course, be a mixture of two or more different polydimethylsiloxane oils, each a polydimethylsiloxane elastomer or rubber. Polydimethylsiloxane oil is preferred. The polydimethylsiloxane oil preferably has a viscosity of at least 1000 mPa·s at 20°C, as measured according to DIN 53019-1:2008-09. If the viscosity is less than 1000 mPa·s, the proportion of M units acting as a chain stopper in the equilibrium reaction is undesirably high. Advantageously, the polydimethylsiloxane elastomer or rubber is shredded before further processing.

[0044] Typically, at least one linear polydimethylsiloxane or its copolymer is included in a polydimethylsiloxane-containing composition used to produce recycled linear polydimethylsiloxane.

[0045] A polydimethylsiloxane-containing composition may be characterized by the weight fraction of at least linear polydimethylsiloxane or its copolymer. Therefore, a polydimethylsiloxane-containing composition preferably contains at least 50% (by weight), preferably at least 70% (by weight), or more preferably at least 90% (by weight), of at least one linear polydimethylsiloxane or its copolymer, based on the total weight of the polydimethylsiloxane-containing composition. A polydimethylsiloxane-containing composition may also essentially consist of, or be composed of, at least one linear polydimethylsiloxane or its copolymer.

[0046] Polydimethylsiloxane-containing compositions can be further characterized by their silicon content. Preferably, polydimethylsiloxane-containing compositions have a silicon content of 19% to 38% (by weight), or more preferably 26% to 38% (by weight), or more preferably 34% to 38% (by weight), based on the total weight of the polydimethylsiloxane-containing composition. The silicon content is preferably measured according to the method described in "Determination of Silicon in Organosilicon Compounds," JAMcHard, PCServais, and HAClark, Analytical Chemistry, 1948, 20(4), 325-328.

[0047] Linear polydimethylsiloxane polymers or copolymer products often contain additives such as fillers, colorants, waxes, crosslinking catalysts, or catalytic residues. Therefore, such additives may be present in the polydimethylsiloxane-containing composition and, if not completely removed from the recycled polydimethylsiloxane-containing composition, may affect the method steps for obtaining the recycled polydimethylsiloxane-containing composition and subsequent reaction steps. The polydimethylsiloxane-containing composition may be characterized by its filler content. Therefore, the polydimethylsiloxane-containing composition contains, based on the total weight of the polydimethylsiloxane-containing composition, preferably less than 50% (by weight), preferably less than 25% (by weight), or more preferably less than 5% (by weight) of fillers. The polydimethylsiloxane-containing composition may also be substantially or completely filler-free.

[0048] Polydimethylsiloxane-containing compositions can also be characterized by the content of colorants that may be contained in the linear polydimethylsiloxane polymer or copolymer product. Therefore, a polydimethylsiloxane-containing composition contains, based on the total weight of the polydimethylsiloxane-containing composition, preferably less than 5% (by weight), preferably less than 3% (by weight), or more preferably less than 1% (by weight) of colorants. A polydimethylsiloxane-containing composition may also be substantially colorant-free or completely colorant-free.

[0049] A polydimethylsiloxane-containing composition may also be characterized by the content of polymers other than polydimethylsiloxane or its copolymers. In a typical embodiment of the present invention, a polydimethylsiloxane-containing composition is substantially or completely polyamide-free. A polydimethylsiloxane-containing composition may contain up to 5% (by weight) of polypropylene and / or polyethylene based on the total weight of the polydimethylsiloxane-containing composition. In a preferred embodiment of the present invention, a polydimethylsiloxane-containing composition is substantially or completely polypropylene and / or polyethylene-free.

[0050] The polydimethylsiloxane-containing composition may contain a total amount of polymers other than polydimethylsiloxane or its copolymers, up to 10% (by weight), preferably up to 5% (by weight), or more preferably up to 2% (by weight), based on the total weight of the polydimethylsiloxane-containing composition.

[0051] A polydimethylsiloxane-containing composition may contain further components that are intentionally or unintentionally added to the composition. A polydimethylsiloxane-containing composition may contain, for example, one or more solvents that can help dissolve at least one linear polydimethylsiloxane or its copolymer. Suitable solvents include, for example, organic solvents such as cyclopentane, hexane, dimethylbenzene, toluene, xylene, ether, chloroform, and tetrahydrofuran. However, a polydimethylsiloxane-containing composition may also be substantially or completely devoid of solvents.

[0052] As already stated, recycled linear polydimethylsiloxane is obtained in a preferred embodiment of the present invention from the recycling of at least one linear polydimethylsiloxane or copolymer. In a particularly preferred embodiment of the present invention, the recycling of at least one linear polydimethylsiloxane or its copolymer may include: (c) subjecting a polydimethylsiloxane-containing composition comprising at least one linear polydimethylsiloxane or its copolymer to catalytic depolymerization in the presence of at least one depolymerization catalyst to form at least one cyclic polydimethylsiloxane in the depolymerization reaction mixture; (d) distilling the depolymerization reaction mixture to obtain a cyclic polydimethylsiloxane-containing composition comprising at least one cyclic polydimethylsiloxane; (e) optionally subjecting the cyclic polydimethylsiloxane-containing composition to fractional distillation purification; (f) subjecting the cyclic polydimethylsiloxane-containing composition comprising at least one cyclic polydimethylsiloxane to a polymerization reaction in the presence of a polymerization catalyst to obtain recycled linear polydimethylsiloxane in the recycled polydimethylsiloxane-containing composition; and (g) optionally purifying the recycled polydimethylsiloxane-containing composition. The distillation in step (d) may be carried out at least partially during catalytic depolymerization. Purifying the recycled polydimethylsiloxane-containing composition in step (g) is intended to reduce the amount of undesirable compounds in the recycled polydimethylsiloxane-containing composition that may interfere with subsequent equilibrium and / or hydrosilylation reactions or should not be present in the resulting polyether polydimethylsiloxane material. For example, cyclic siloxanes can be removed from the recycled polydimethylsiloxane-containing composition, for example, by distillation.

[0053] Exemplary reactions for catalytic depolymerization are disclosed in U.S. Patent No. 5,110,972 under sections D and E. Furthermore, reaction conditions for catalytic depolymerization are disclosed in "Degradation of silicone-based materials as a driving force for recyclability," Buddhima Rupasinghe and Joseph C Furgal, Polym Int 2022;71:521-531, and "Full Circle Recycling of Polysiloxanes via Room-Temperature Fluoride-Catalyzed Depolymerization to Repolymerizable Cyclics," Buddhima Rupasinghe and Joseph C Furgal, ACS Appl. Polym. Mater. 2021, 3,1828-1839. The D3, D4, D5, D6, D7, and D8 content can be adjusted depending on the type of catalytic depolymerization, such as the catalyst, temperature, solvent, and water content. In particular, it is desirable to adjust or control the content of linear siloxane, water, M units, T units, Q units, Si-hydroxyl, and Si-vinyl in the recycled polydimethylsiloxane-containing composition before subjecting it to the equilibrium reaction. Therefore, the content of linear siloxane, water, M units, T units, Q units, Si-hydroxyl, and Si-vinyl in the recycled polydimethylsiloxane-containing composition is selected as described above. The cyclic polydimethylsiloxane-containing composition can be purified by distillation purification, such as fractional distillation, in particular, before subjecting the recycled polydimethylsiloxane-containing composition to the equilibrium reaction.

[0054] Catalytic depolymerization is preferably carried out at a temperature of 40°C to 200°C, or more preferably 50°C to 190°C, or more preferably 80°C to 180°C.

[0055] Catalytic depolymerization can be advantageously carried out at standard pressure (i.e., 10¹³ hPa), reduced pressure (<10¹³ hPa), or under high pressure in a pressure-rated device (>10¹³ hPa) to achieve high heat treatment temperatures up to 200°C. Preferably, the catalytic depolymerization according to the present invention is carried out at a pressure of 10¹³ ± 10 hPa. Advantageously, the catalytic depolymerization is carried out in a reactor resistant to corrosion, temperatures of at least 250°C, and optionally, pressures exceeding standard pressure.

[0056] The depolymerization reaction is advantageously carried out in the presence of at least one depolymerization catalyst. The at least one depolymerization catalyst is preferably selected from Brønsted acids or Brønsted bases. Preferred Brønsted acids are selected from the group consisting of trifluoromethanesulfonic acid, sulfuric acid, hydrochloric acid, and combinations thereof. Preferred Brønsted bases are selected from the group consisting of alkali metal hydroxides, tetraalkylammonium hydroxides, tetraalkylphosphonium hydroxides, phosphazenes, guanidine, and combinations thereof.

[0057] Catalytic depolymerization can also be carried out as a two-step process combining treatment with an acidic depolymerization catalyst (e.g., those mentioned above herein) and subsequent treatment with a basic depolymerization catalyst (e.g., those mentioned above herein).

[0058] If necessary, additional components such as solvents can be added to the depolymerization reaction mixture.

[0059] The depolymerization reaction is typically carried out for 1.5 to 6 hours. It is preferable to stir the depolymerization mixture to ensure that the substances are completely mixed.

[0060] The catalytic depolymerization step can be carried out in a batch, semi-continuous, or continuous process.

[0061] As detailed above, a cyclic polydimethylsiloxane-containing composition comprising at least one cyclic polydimethylsiloxane is typically subjected to a polymerization reaction in the presence of a polymerization catalyst to obtain recycled linear polydimethylsiloxane. The polymerization reaction of at least one cyclic polydimethylsiloxane can be carried out according to any method known in the art, such as that described, for example, in Chojnowski, H. Ring - *Opening Polymerization of Cyclosiloxanes, in Silicon Compounds: Silanes and Silicones 4000A*, Ed. B. Arkles, G. Larson, Geles Inc. 2008, Morrisville, PA, 389-405. The conditions during polymerization are advantageously selected to obtain recycled linear polydimethylsiloxane having the desired viscosity and desired end groups. The polymerization reaction can be carried out as anionic polymerization or cationic polymerization. Suitable polymerization catalysts for anionic polymerization include, for example, strong inorganic or organic bases. Polymerization catalysts suitable for cationic polymerization include strong protic acids such as H2SO4, CF3SO3H, HClO4, CH3SO3H, and CF3SO3H. Chain-blocking agents such as disiloxane or short-chain oligosiloxane end groups can be used to control the molecular weight of recycled linear polydimethylsiloxane and its end groups.

[0062] In a preferred embodiment of the present invention, the recycled linear polydimethylsiloxane has a viscosity of 25 to 2500 mPa·s, preferably 50 to 2000 mPa·s, or more preferably 100 to 1500 mPa·s, at 25°C, as measured according to DIN 53019-1:2008-09.

[0063] A recycled polydimethylsiloxane-containing composition is subjected to an equilibrium reaction with at least one poly(methylhydrogen)siloxane in the presence of at least one equilibrium catalyst in the method of the present invention, forming a poly(methylhydrogen)-polydimethylsiloxane copolymer in the equilibrium reaction mixture. As used herein, the equilibrium reaction refers to the reorganization of recycled linear polydimethylsiloxane and poly(methylhydrogen)siloxane in the presence of at least one equilibrium catalyst, resulting in the formation of a poly(methylhydrogen)-polydimethylsiloxane copolymer in the equilibrium reaction mixture. The poly(methylhydrogen)-polydimethylsiloxane copolymer typically has a general molecular structure according to Formula 1, where units m and n are preferably statistically distributed in the structure. [ka] In the formula, R is independently selected from methyl and hydrogen. Preferably, R is methyl.

[0064] Typically, one or more chain length modifiers are also added to the equilibrium reaction mixture to control the chain length of the resulting poly(methylhydrogen)-polydimethylsiloxane copolymer. The amount of one or more chain length modifiers added to the equilibrium reaction mixture can be adjusted based on the amount of M units contained in the recycled polydimethylsiloxane-containing composition. One typical chain length modifier is hexamethyldisiloxane, which introduces only M units. Alternatively or additionally, 1,1,3,3-tetramethyldisiloxane may be added to the equilibrium reaction mixture, which introduces hydrogen-containing terminal units (HSiMe2-, so-called M' units). Also, the general formula HSiMe2-O-(-SiMe2-O-) introduces D and M' units. q HSiMe2-terminated functional polydimethylsiloxane oil having -SiMe2H may be added. Such oil may have a CAS number of 70900-21-9. Preferably, the HSiMe2-terminated functional polydimethylsiloxane oil has about 5 to 10 dimethylsiloxane units (D units), i.e., q = 5 to 10.

[0065] The chain length, and therefore viscosity, of the resulting poly(methylhydrogen)-polydimethylsiloxane copolymer depends, in particular, on the amount of end groups in the equilibrium reaction mixture, especially M units. Therefore, the amount of chain length modifier added to the equilibrium reaction mixture can be selected based on the amount of end groups already present in the recycled polydimethylsiloxane-containing composition. Thus, a method for producing polyether polydimethylsiloxane according to the present invention may further include measuring the content of end groups, such as M units, in the recycled polydimethylsiloxane-containing composition, and adding, based on the measured content, an amount of at least one chain length modifier, such as those described herein, to achieve the desired viscosity of the poly(methylhydrogen)-polydimethylsiloxane copolymer.

[0066] Poly(methylhydrogen)siloxane is given by formula 2: [ka] It may have a molecular structure due to the following:

[0067] Poly(methylhydrogen)siloxanes may have an SiH content of 4.5 to 16.7 mol / kg, or preferably 10 to 16.5 mol / kg, based on the weight of the poly(methylhydrogen)siloxane. One particularly suitable poly(methylhydrogen)siloxane has an SiH content of about 16 mol / kg and a molar mass of about 2500 g / mol. n It holds.

[0068] As already mentioned, the equilibrium reaction proceeds in the presence of at least one equilibrium catalyst. Typically, at least one equilibrium catalyst is selected from acidic equilibrium catalysts. Suitable acidic equilibrium catalysts include strong protic acids such as sulfuric acid, trifluoromethanesulfonic acid, methanesulfonic acid, and perchloric acid; protic acids and Lewis acids such as HCl+FeCl3 and HCl+SbCl6; acid-activated minerals such as bentonite, montmorillonite, and bleached earth such as Fuller's earth; as well as cation exchange resins such as sulfonic acids and macrocrosslinked cation exchange resins, and mixtures thereof.

[0069] The amount of at least one equilibrium catalyst is preferably 0.02 to 10% (by weight) or more preferably 0.05 to 8% (by weight) based on the total weight of the equilibrium reaction mixture. The amount of at least one equilibrium catalyst in the equilibrium reaction mixture can be adjusted based on the amount of water and hydroxyl-substituted silicon atoms in the recycled polydimethylsiloxane-containing composition.

[0070] The equilibrium reaction can be carried out at a temperature of 10°C to 110°C, or preferably 25°C to 100°C. The equilibrium reaction can be carried out under reduced pressure (<1013 hPa), standard pressure (1013 hPa), or ultra-atmospheric pressure (>1013 hPa). Preferably, the equilibrium reaction is carried out at a pressure of 950 hPa to 1100 hPa, more preferably 1013 hPa.

[0071] The equilibrium reaction can take place over 20 minutes to 20 hours, preferably 30 minutes to 14 hours. However, it is preferable that the equilibrium reaction take place over 20 minutes to 7 hours, preferably 30 minutes to 5 hours. Thus, the equilibrium reaction time should be selected so that the molecular weight distribution, SiH functional group distribution, and molecular structure of the poly(methylhydrogen)-polydimethylsiloxane copolymer reach equilibrium. If equilibrium is not reached, subsequent hydrosilylation reactions using the poly(methylhydrogen)-polydimethylsiloxane copolymer may result in a very turbid polyether-polydimethylsiloxane solution, which, when used as a foam stabilizer in, for example, a polyurethane flexible foam system, often leads to significant foam collapse, sometimes resulting in foam decay.

[0072] If desired, the equilibrium reaction can be carried out in the presence of one or more solvents. Suitable solvents are any solvent that is inert to the equilibrium catalyst, starting materials, and products in the equilibrium reaction. However, it is particularly preferable that the equilibrium reaction be carried out in the absence of a solvent.

[0073] The balancing step can be performed in batches, semi-continuously, or continuously.

[0074] It may be advantageous to separate a portion having a desired boiling point range from the equilibrium reaction mixture. The remaining residue of the equilibrium reaction mixture that does not have the desired boiling point range can be fed back into the equilibrium reaction, for example, for reuse as a starting material. Particularly preferable, especially when the process is carried out continuously, is the portion having the desired boiling point range separated from the equilibrium reaction mixture, and the remaining portion not having the desired boiling point range is fed back into the equilibrium reaction mixture. This separation can be carried out, for example, by simple thermal separation (e.g., by simple distillation or similar means). The fraction having an undesirable boiling point range can be recycled, for example, into the feed of the recycled polydimethylsiloxane-containing composition when the equilibrium reaction step is carried out as a continuous process.

[0075] If necessary, especially if the equilibration step is carried out as a batch process, after equilibrium is achieved, cyclic polydimethylsiloxane and other volatile substances as toxicologically important components are removed from the equilibrium reaction mixture by applying heat and vacuum. The remainder of the equilibrium reaction mixture can be further filtered to remove, for example, the solid-phase equilibrium catalyst, if present. The poly(methylhydrogen)-polydimethylsiloxane copolymer thus obtained can be subjected to the hydrosilylation reaction step without further purification.

[0076] The poly(methylhydrogen)-polydimethylsiloxane copolymer obtained in the equilibrium reaction step can be characterized by its density, viscosity, and SiH value. The poly(methylhydrogen)-polydimethylsiloxane copolymer may have a density of 0.95-0.98 g / mL, preferably 0.96-0.98 g / mL, or more preferably 0.97-0.98 g / mL at 25°C, when preferably determined according to DIN 51757:2011-01. The poly(methylhydrogen)-polydimethylsiloxane copolymer may have a viscosity of 2-2000 mPa·s, preferably 3-1000 mPa·s, or more preferably 10-500 mPa·s at 25°C, when preferably determined according to DIN 53019-1:2008-09. Poly(methylhydrogen)-polydimethylsiloxane copolymers can have an SiH value corresponding to an SiH functional group content of 0.2 to 10 mol / kg, preferably 0.4 to 8 mol / kg, or more preferably 0.6 to 6 mol / kg, as measured preferably by gas volumetric spectroscopy. For this purpose, a weighed sample of poly(methylhydrogen)-polydimethylsiloxane copolymer is decomposed with a sodium butyrate solution to form hydrogen gas. The amount of hydrogen gas is measured and the SiH value is determined using the definition of SiH value: n(H2)[mol] / m(sample)[kg].

[0077] Poly(methylhydrogen)-polydimethylsiloxane copolymer has the following characteristics: (A) Density of 0.94-0.99 g / mL, preferably 0.95-0.98 g / mL, or more preferably 0.96-0.98 g / mL at 25°C, as measured according to DIN 51757:2011-01; viscosity of 50-70 mPa·s, preferably 52-64 mPa·s, or more preferably 53-63 mPa·s at 25°C, as measured according to DIN 53019-1:2008-09; and SiH value of 1.1-1.60 mol / kg, preferably 1.0-1.50 mol / kg, or more preferably 1.2-1.45 mol / kg, as measured by gas volumetric spectroscopy; or (B) DIN It can have a density of 0.95 to 1.00 g / mL, preferably 0.96 to 0.99 g / mL, or more preferably 0.965 to 0.972 g / mL at 25°C, as measured according to 51757:2011-01; a viscosity of 60 to 85 mPa·s, preferably 64 to 84 mPa·s, or more preferably 67 to 85 mPa·s, at 25°C, as measured according to DIN 53019-1:2008-09; and an SiH value of 1.40 to 1.80 mol / kg, preferably 1.50 to 1.70 mol / kg, or more preferably 1.57 to 1.67 mol / kg, as measured by gas volumetric spectroscopy.

[0078] According to the method of the present invention, a poly(methylhydrogen)-polydimethylsiloxane copolymer is subjected to a hydrosilylation reaction with at least one polyether containing at least one carbon-carbon double bond that is reactive to the Si-H bond, preferably in the presence of at least one hydrosilylation catalyst, to obtain a polyether polydimethylsiloxane.

[0079] The hydrosilylation reaction is described, for example, in European Patent Application Publication No. 1520870. In this reaction, the SiH functional group reacts with the carbon-carbon double bond of the polyether to form a Si-C bond, thereby linking the polyether to the polydimethylsiloxane copolymer. Thus, the resulting polyether polydimethylsiloxane contains dimethylsiloxane units and siloxane units in which the silicon atoms are substituted with polyethers derived from at least one polyether containing a methyl group and at least one carbon-carbon double bond reactive to the Si-H bond. If the at least one polyether containing at least one carbon-carbon double bond reactive to the Si-H bond contains two or more carbon double bonds reactive to the Si-H bond, the polyether portion may be linked to two or more siloxane portions. However, preferably, the at least one polyether containing at least one carbon-carbon double bond reactive to the Si-H bond contains only one carbon-carbon double bond reactive to the Si-H bond.

[0080] As at least one polyether containing at least one reactive carbon-carbon double bond in the Si-H bond, all compounds known in the art can be used. Examples of suitable polyethers containing at least one reactive carbon-carbon double bond in the Si-H bond include: CH2=CH-CH2-O-(CH2-CH2O-) x -(CH2-CH(R')O-) y -R'' CH2=CH-O-(CH2-CH2O-) x -(CH2-CH(R')O-) y -R'' During the ceremony, x = 0 to 100; y = 0 to 100; R' is the same or a different group selected from substituted alkyl groups or phenyl groups having 1 to 4 carbon atoms; R'' is a hydrogen radical or an alkyl group having 1 to 4 carbon atoms; -C(O)-R''' group (wherein R''' is an alkyl radical); -CH2-O-R' group; alkylaryl group such as a benzyl group; -C(O)NH-R' group.

[0081] The at least one polyether containing at least one reactive carbon-carbon double bond in the Si-H bond is preferably selected from the group consisting of polyethers having CAS numbers 27274-31-3, 9042-19-7, 9041-33-2, 27252-80-8, 62744-60-9, 52232-27-6, 27252-87-5, 132935-51-4, and 56090-69-8.

[0082] In addition to at least one polyether containing at least one carbon-carbon double bond reactive to the Si-H bond, at least one compound that is not a polyether and contains at least one carbon-carbon double bond reactive to the Si-H bond may also be present in the hydrosilylation reaction mixture and may participate in the hydrosilylation reaction. However, if such compounds are present, they are preferably present in small amounts, for example, at most 10 mol%, or preferably at most 5 mol%, based on the total moles of the at least one polyether containing at least one carbon-carbon double bond reactive to the Si-H bond and the at least one compound that is not a polyether and contains at least one carbon-carbon double bond reactive to the Si-H bond.

[0083] Suitable hydrosilylation catalysts include noble metals such as Pt(0) or rhodium. A suitable Pt(0) catalyst is disclosed, for example, in European Patent Application Publication No. 1520870.

[0084] The hydrosilylation reaction can be carried out in the presence of one or more solvents that can be separated from the polyether polydimethylsiloxane obtained, for example, by distillation, if necessary.

[0085] The hydrosilylation reaction may be carried out at a temperature of 20°C to 140°C, preferably 40°C to 130°C, and more preferably 60°C to 110°C.

[0086] According to the present invention, the process is preferably carried out at a standard pressure (1013 hPa), but a pressure range deviating from this is also possible if desired.

[0087] Polyether polydimethylsiloxanes can be characterized by their viscosity. Thus, polyether polydimethylsiloxanes can have a viscosity of 100 mPa·s to 12000 mPa·s, or preferably 200 mPa·s to 8000 mPa·s, at 25°C, as determined according to DIN 53019-1:2008-09, DIN 53019-2:2008-09, DIN 53019-3:2008-09, and DIN 53019-4:2008-09.

[0088] Polyether polydimethylsiloxane has a density of 1.030 to 1.060 g / mL, preferably 1.032 to 1.057 g / mL, or more preferably 1.035 to 1.055 g / mL at 25°C, as measured according to DIN 51757:2011-01; and a viscosity of 700 to 1300 mPa·s, preferably 750 to 1250 mPa·s, or more preferably 800 to 1200 mPa·s at 25°C, as measured according to DIN 53019-1:2008-09; or (B) a density of 1.010 to 1.050 g / mL, preferably 1.015 to 1.045 g / mL, or more preferably 1.020 to 1.040 g / mL at 25°C, as measured according to DIN 51757:2011-01; and DIN Measured according to 53019-1:2008-09, it can have a viscosity of 500-1000 mPa·s, preferably 530-900 mPa·s, and more preferably 550-850 mPa·s at 25°C.

[0089] The present invention also provides compositions for preparing polymer foams comprising at least one monomer species and one or more polyether polydimethylsiloxanes obtained according to the methods disclosed herein. The compositions for preparing polymer foams may include, in addition to the polyether polydimethylsiloxanes obtained by the methods disclosed herein, at least one further polyether polydimethylsiloxane, which may not be obtained by the methods disclosed herein and may not be based on recycled products, but may, for example, be based on cyclic polydimethylsiloxanes from the Mueller-Rochow process. In preferred embodiments of the present invention, the polymer foam is a polyurethane foam, a phenolic resin foam, or a polyvinyl chloride foam. Polyurethane foams are particularly preferred. Polyurethane foams may be, in particular, flexible polyurethane foams, rigid polyurethane foams, semi-rigid polyurethane foams, molded polyurethane foams, high-elasticity polyurethane foams, viscoelastic foams, hyper-soft polyurethane foams, or integral foams.

[0090] A composition for preparing a polyurethane foam typically comprises: at least one isocyanate-reactive compound having at least two groups on average per molecule that are reactive to isocyanate groups; at least one polyisocyanate having at least two isocyanate groups on average per molecule; at least one blowing agent; at least one catalyst; at least one polyether polydimethylsiloxane obtained according to a method disclosed herein; and optionally one or more additives selected from the group including dyes, pigments, fillers, antistatic additives, crosslinking agents, chain extenders, cell openers, nucleating agents, thickeners, fragrances, cell expanders, plasticizers, curing accelerators, additives to prevent low-temperature flow, aldehyde scavengers, additives to enhance the resistance of the polyurethane foam to hydrolysis, compatibilizers (emulsifiers), adhesion promoters, and hydrophobic additives.

[0091] The present invention also relates to a method for preparing polymer foams, such as those described herein, comprising reacting one or more monomer species in the presence of one or more polyether polydimethylsiloxanes obtained according to the methods disclosed herein to obtain a polymer foam. Furthermore, there may be at least one additional polyether polydimethylsiloxane, which may not be obtained by the methods disclosed herein and may not be based on recycled products, but may be based on cyclic polydimethylsiloxanes from the Mueller-Rochow process, for example.

[0092] A method for preparing polyurethane foam is: The present invention provides a composition comprising: at least one isocyanate-reactive compound having on average at least two groups reactive to isocyanate groups; one or more polyether polydimethylsiloxanes obtained according to a method disclosed herein; at least one blowing agent; at least one catalyst; and optionally one or more further additives; and the composition comprising: contacting the composition with a polyisocyanate or mixture of polyisocyanates having on average at least two isocyanate groups per molecule; and curing the composition under the formation of a polyurethane foam.

[0093] The present invention also relates to articles comprising polymer foams obtained according to previously disclosed methods for preparing polymer foams, or reaction products of compositions for preparing previously disclosed polymer foams. Articles comprising polyurethane foam as the polymer foam of the present invention may be used for refrigerator insulation, insulation panels, sandwich elements, pipe insulation, spray foams, one-component or 1.5-component can foams, imitation wood, modeling foams, packaging foams, mattresses, furniture cushions, automotive seat cushions, flat or train seat cushions, headrests, armrests, instrument panels, automotive interior trims, automotive ceiling materials, sound-absorbing materials, steering wheels, shoe soles, carpet backing foams, filter foams, sealing foams, sealants, adhesives, coatings, or for use in the manufacture of corresponding products.

[0094] The present invention further relates to the use of recycled linear polydimethylsiloxane for producing polyether polydimethylsiloxane, wherein the recycled linear polydimethylsiloxane is obtained from the recycling of at least one linear polydimethylsiloxane or its copolymer, and the recycling of at least one linear polydimethylsiloxane or its copolymer is (c) subjecting a polydimethylsiloxane-containing composition comprising at least one linear polydimethylsiloxane or its copolymer to catalytic depolymerization in the presence of at least one depolymerization catalyst to form at least one cyclic polydimethylsiloxane in the depolymerization reaction mixture The present invention relates to a method comprising: (d) distilling the depolymerization reaction mixture to obtain a cyclic polydimethylsiloxane-containing composition comprising at least one cyclic polydimethylsiloxane; (e) optionally subjecting the cyclic polydimethylsiloxane-containing composition to fractional distillation; (f) subjecting the cyclic polydimethylsiloxane-containing composition comprising at least one cyclic polydimethylsiloxane to a polymerization reaction in the presence of a polymerization catalyst to obtain recycled linear polydimethylsiloxane in the recycled polydimethylsiloxane-containing composition; and (g) optionally purifying the recycled polydimethylsiloxane-containing composition. The recycled linear polydimethylsiloxane may have a carbon footprint of less than 4 kg CO2 equivalent / kg, or preferably less than 2 kg CO2 equivalent / kg, as determined in accordance with DIN EN ISO standard 14067:2018.

[0095] The present invention also relates to the use of a recycled polydimethylsiloxane-containing composition comprising recycled linear polydimethylsiloxane in an equilibrium reaction for obtaining a poly(methylhydrogen)-polydimethylsiloxane copolymer in a method for producing polyether polydimethylsiloxane. The recycled linear polydimethylsiloxane is preferably obtained from the recycling of at least one linear polydimethylsiloxane or its copolymer. The recycling of at least one linear polydimethylsiloxane or its copolymer is preferably carried out as described above. The use may further include subjecting the poly(methylhydrogen)-polydimethylsiloxane copolymer obtained in the equilibrium reaction to a hydrosilylation reaction with at least one polyether containing at least one carbon-carbon double bond reactive to the Si-H bond, preferably in the presence of at least one hydrosilylation catalyst, to obtain a polyether polydimethylsiloxane. Thereafter, the components and reaction conditions are preferably selected as described above.

[0096] Furthermore, the present invention also relates to the use of at least one polyether polydimethylsiloxane obtained according to the method disclosed herein as an additive in a method for producing a polymer foam or in a composition for preparing a polymer foam, wherein the polymer foam is preferably a polyurethane foam, a phenolic resin foam, or a polyvinyl chloride foam. Polyurethane foam is particularly preferred.

[0097] The present invention is further described according to the following embodiments: 1. (a) A recycled polydimethylsiloxane-containing composition, including recycled linear polydimethylsiloxane, is subjected to an equilibrium reaction with at least one poly(methylhydrogen)siloxane in the presence of at least one equilibrium catalyst to form a poly(methylhydrogen)-polydimethylsiloxane copolymer. (b) The poly(methylhydrogen)-polydimethylsiloxane copolymer obtained in step (a) is subjected to a hydrosilylation reaction with at least one polyether containing at least one carbon-carbon double bond that is reactive to the Si-H bond, preferably in the presence of at least one hydrosilylation catalyst, to obtain a polyether polydimethylsiloxane. A method for producing polyether polydimethylsiloxane. 2. (c) A polydimethylsiloxane-containing composition comprising at least one linear polydimethylsiloxane or its copolymer is subjected to catalytic depolymerization in the presence of at least one depolymerization catalyst to form at least one cyclic polydimethylsiloxane in the depolymerization reaction mixture, (d) Distilling the depolymerization reaction mixture to obtain a cyclic polydimethylsiloxane-containing composition comprising at least one cyclic polydimethylsiloxane, (e) Depending on the circumstances, the cyclic polydimethylsiloxane-containing composition may be subjected to fractional distillation and purification. (f) A cyclic polydimethylsiloxane-containing composition comprising at least one cyclic polydimethylsiloxane is subjected to a polymerization reaction in the presence of a polymerization catalyst to obtain recycled linear polydimethylsiloxane in the recycled polydimethylsiloxane-containing composition, (g) Depending on the circumstances, the recycled polydimethylsiloxane-containing composition may be purified. (a) A recycled polydimethylsiloxane-containing composition, comprising recycled linear polydimethylsiloxane, is subjected to an equilibrium reaction with at least one poly(methylhydrogen)siloxane in the presence of at least one equilibrium catalyst to form a poly(methylhydrogen)-polydimethylsiloxane copolymer. A method for producing a polyether polydimethylsiloxane, comprising: (b) subjecting the poly(methylhydrogen)-polydimethylsiloxane copolymer obtained in step (a) to a hydrosilylation reaction with at least one polyether containing at least one carbon-carbon double bond reactive to the Si-H bond, preferably in the presence of at least one hydrosilylation catalyst, to obtain a polyether polydimethylsiloxane. 3. The method according to any one of embodiments 1 and 2, wherein the recycled linear polydimethylsiloxane has a viscosity of 25 to 2500 mPa·s, preferably 50 to 2000 mPa·s, more preferably 100 to 1500 mPa·s, and most preferably 150 to 1000 mPa·s at 25°C, as measured according to DIN 53019-1:2008-09, DIN 53019-2:2008-09, DIN 53019-3:2008-09 and DIN 53019-4:2008-09. 4. The method according to any one of embodiments 1 to 3, wherein the recycled polydimethylsiloxane-containing composition contains up to 7.5 mol% of M units, preferably up to 4 mol%, or more preferably up to 2.5 mol%, of M units based on the total moles of M, D, T, and Q units of the recycled polydimethylsiloxane-containing composition. 5. The method according to any one of embodiments 1 to 4, wherein the sum of the T and Q units of the recycled polydimethylsiloxane-containing composition is at most 0.75 mol%, preferably at most 0.5 mol%, or more preferably at most 0.25 mol%, based on the total moles of the M, D, T, and Q units of the recycled polydimethylsiloxane-containing composition. 6. The method according to any one of embodiments 1 to 5, wherein the recycled polydimethylsiloxane-containing composition is substantially free of chlorine-containing compounds, or most preferably completely free of chlorine-containing compounds, and / or the recycled polydimethylsiloxane-containing composition contains less than 100 ppm of chlorine-containing compounds, preferably less than 50 ppm of chlorine-containing compounds, more preferably less than 25 ppm of chlorine-containing compounds, and most preferably less than 10 ppm of chlorine-containing compounds, based on the total weight of the recycled polydimethylsiloxane-containing composition. 7. The method according to any one of embodiments 1 to 6, wherein the recycled polydimethylsiloxane-containing composition has a total content of recycled linear polydimethylsiloxane of more than 90% (by weight), preferably more than 95% (by weight), or more preferably 98% (by weight), based on the total weight of the recycled polydimethylsiloxane-containing composition. 8. The method according to any one of embodiments 1 to 7, wherein the recycled polydimethylsiloxane-containing composition contains up to 0.05% (by weight), preferably up to 100 ppm, more preferably up to 40 ppm (by weight), and most preferably up to 10 ppm of water, measured according to DIN 51777:2020-04 based on the total weight of the recycled polydimethylsiloxane-containing composition. 9. Based on the total moles of silicon atoms in the recycled polydimethylsiloxane-containing composition, 29 The method according to any one of embodiments 1 to 8, comprising up to 0.5 mol%, preferably up to 0.2 mol%, and more preferably up to 0.1 mol%, of vinyl-substituted silicon atoms, as determined by Si-NMR spectroscopy. 10. Based on the total moles of silicon atoms in the recycled polydimethylsiloxane-containing composition, 29 The method according to any one of embodiments 1 to 9, comprising up to 0.2 mol%, preferably up to 0.1 mol%, and more preferably up to 0.05 mol%, of hydroxyl-substituted silicon atoms, as determined by Si-NMR spectroscopy. 11. The method according to any one of embodiments 1 to 10, wherein the recycled linear polydimethylsiloxane has a carbon footprint of less than 4 kg CO2 equivalent / kg of recycled linear polydimethylsiloxane, or preferably less than 2 kg CO2 equivalent / kg of recycled linear polydimethylsiloxane, as determined in accordance with DIN EN ISO standard 14067:2018. 12. The method according to any one of embodiments 1 to 11, wherein the recycled linear polydimethylsiloxane is obtained from the recycling of at least one linear polydimethylsiloxane or its copolymer. 13. The method according to any one of embodiments 2 and 12, wherein at least one linear polydimethylsiloxane or copolymer contains at least 50% (by weight), preferably at least 90% (by weight), and more preferably at least 99% (by weight) of dimethylsiloxane units based on the total weight of at least one linear polydimethylsiloxane or copolymer. 14. The method according to any one of embodiments 2, 12, and 13, wherein at least one linear polydimethylsiloxane or copolymer thereof is a linear polydimethylsiloxane homopolymer. 15. The method according to any one of Embodiments 2 and 12 to 14, wherein at least one linear polydimethylsiloxane or its copolymer corresponds to or is derived from waste polydimethylsiloxane polymer or copolymer material, wide-spec polydimethylsiloxane polymer or copolymer material, used polydimethylsiloxane polymer or copolymer material, expired polydimethylsiloxane polymer or copolymer material, surplus polydimethylsiloxane polymer or copolymer material, or any mixture or combination thereof. 16. The method according to any one of Embodiments 2 and 12 to 15, wherein at least one linear polydimethylsiloxane or its copolymer is included in the polydimethylsiloxane-containing composition. 17. The method according to any one of embodiments 2 and 16, wherein the polydimethylsiloxane-containing composition comprises at least 50% (by weight), preferably at least 70% (by weight), or more preferably at least 90% (by weight), of at least one linear polydimethylsiloxane or its copolymer, based on the total weight of the polydimethylsiloxane-containing composition. 18. The method according to any one of embodiments 2, 16, and 17, wherein the polydimethylsiloxane-containing composition has a silicon content of 19% to 38% (by weight), preferably 26% to 38% (by weight), and more preferably 34% to 38% (by weight), based on the total weight of the polydimethylsiloxane-containing composition. 19. The method according to any one of Embodiments 2 and 16 to 18, wherein the polydimethylsiloxane-containing composition contains less than 50% (by weight), preferably less than 25% (by weight), and more preferably less than 5% (by weight), of the filler based on the total weight of the polydimethylsiloxane-containing composition. 20. The method according to any one of embodiments 2 and 12 to 19, wherein at least one linear polydimethylsiloxane or its copolymer has an M-unit to D-unit ratio of at least 1:500, preferably at least 1:750, or more preferably at least 1:1000. 21. The method according to any one of embodiments 2 and 12 to 20, wherein at least one linear polydimethylsiloxane or its copolymer is polydimethylsiloxane oil, polydimethylsiloxane elastomer, polydimethylsiloxane rubber, or a mixture thereof, thereby the polydimethylsiloxane oil preferably has a viscosity of at least 1000 mPa·s at 25°C as measured according to DIN 53019-1:2008-09. 22. The method according to any one of embodiments 2 and 12 to 21, wherein at least one linear polydimethylsiloxane or copolymer thereof is polydimethylsiloxane oil, and the polydimethylsiloxane oil preferably has a viscosity of at least 1000 mPa·s at 25°C as measured according to DIN 53019-1:2008-09. 23. The method according to any one of embodiments 1 to 22, wherein at least one further polydimethylsiloxane that has not been recycled is added to the recycled polydimethylsiloxane-containing composition before it is subjected to the equilibrium reaction. 24. Recycled linear polydimethylsiloxane is obtained from the recycling of at least one linear polydimethylsiloxane or its copolymer, and the recycling of at least one linear polydimethylsiloxane or its copolymer is (c) A polydimethylsiloxane-containing composition comprising at least one linear polydimethylsiloxane or its copolymer is subjected to catalytic depolymerization in the presence of at least one depolymerization catalyst to form at least one cyclic polydimethylsiloxane in the depolymerization reaction mixture, (d) Distilling the depolymerization reaction mixture to obtain a cyclic polydimethylsiloxane-containing composition comprising at least one cyclic polydimethylsiloxane, (e) Depending on the circumstances, the cyclic polydimethylsiloxane-containing composition may be subjected to fractional distillation and purification. (f) A cyclic polydimethylsiloxane-containing composition comprising at least one cyclic polydimethylsiloxane is subjected to a polymerization reaction in the presence of a polymerization catalyst to obtain recycled linear polydimethylsiloxane in the recycled polydimethylsiloxane-containing composition, (g) The method according to any one of embodiments 1 to 23, wherein the recycled polydimethylsiloxane-containing composition is optionally purified. 25. The method according to embodiment 27, wherein catalytic depolymerization is carried out at a temperature of 40°C to 200°C, preferably 50°C to 190°C, or more preferably 80°C to 180°C. 26. The method according to any one of embodiments 2, 27, and 28, wherein at least one depolymerization catalyst is selected from a Brønsted acid or a Brønsted base, the Brønsted acid is preferably selected from the group consisting of trifluoromethanesulfonic acid, sulfuric acid, hydrochloric acid, and combinations thereof, and the Brønsted base is preferably selected from the group consisting of alkali metal hydroxides, tetraalkylammonium hydroxides, tetraalkylphosphonium hydroxides, phosphazenes, guanidine, and combinations thereof. 27. The method according to any one of embodiments 2 to 26, wherein catalytic depolymerization is carried out in a reactor resistant to corrosion and temperatures of at least 250°C. 28. The method according to any one of embodiments 2 to 27, wherein the distillation of the depolymerization reaction mixture is carried out at least partially during catalytic depolymerization. 29. The method according to any one of embodiments 1 to 28, wherein the equilibrium reaction is carried out in the presence of at least one chain length modifier, the at least one chain length modifier is preferably selected from the group comprising hexamethyldisiloxane, 1,1,3,3-tetramethyldisiloxane, HSiMe2-terminated functional polydimethylsiloxane oil, and mixtures thereof. 30. The method according to embodiment 29, further comprising measuring the content of terminal groups such as M units in a recycled polydimethylsiloxane-containing composition, and adding a certain amount of at least one chain length modifier based on the measured content to achieve a desired viscosity of the poly(methylhydrogen)-polydimethylsiloxane copolymer. 31. The method according to any one of embodiments 1 to 30, wherein at least one equilibrium catalyst is selected from acidic equilibrium catalysts, the acidic equilibrium catalyst is preferably selected from the group consisting of strong protonic acids such as sulfuric acid, trifluoromethanesulfonic acid, methanesulfonic acid, and perchloric acid, protonic acids and Lewis acids such as HCl+FeCl3 and HCl+SbCl6, acid-activated minerals such as bleached earth, and cation exchange resins such as sulfonic acid, macrocrosslinked cation exchange resins, and combinations thereof. 32. The method according to embodiment 29, wherein the amount of at least one chain length adjusting agent is adjusted based on the content of terminal groups such as M units in the recycled polydimethylsiloxane-containing composition. 33. The method according to any one of embodiments 1 to 32, wherein the equilibrium reaction is carried out at a temperature of 10°C to 110°C, or preferably 25°C to 100°C. 34. The method according to any one of embodiments 1 to 33, wherein the poly(methylhydrogen)-polydimethylsiloxane copolymer has a density of 0.95 to 0.98 g / mL, preferably 0.96 to 0.98 g / mL, or more preferably 0.97 to 0.98 g / mL, at 25°C, as measured according to DIN 51757:2011-01. 35. The method according to any one of embodiments 1 to 34, wherein the poly(methylhydrogen)-polydimethylsiloxane copolymer has a viscosity of 2 to 2000 mPa·s, preferably 3 to 1000 mPa·s, or more preferably 10 to 500 mPa·s, at 25°C, as measured according to DIN 53019-1:2008-09. 36. The method according to any one of embodiments 1 to 35, wherein the poly(methylhydrogen)-polydimethylsiloxane copolymer has an SiH value of 0.2 to 10 mol / kg, preferably 0.4 to 8 mol / kg, or more preferably 0.6 to 6 mol / kg, as measured by gas volumetric spectroscopy. 37. Poly(methylhydrogen)-polydimethylsiloxane copolymer (A) Density of 0.94-0.99 g / mL, preferably 0.95-0.98 g / mL, or more preferably 0.96-0.98 g / mL at 25°C, as measured according to DIN 51757:2011-01; viscosity of 50-70 mPa·s, preferably 52-64 mPa·s, or more preferably 53-63 mPa·s at 25°C, as measured according to DIN 53019-1:2008-09; and SiH value of 1.1-1.60 mol / kg, preferably 1.0-1.50 mol / kg, or more preferably 1.2-1.45 mol / kg, as measured by gas volumetric spectroscopy; or (B) The method according to any one of embodiments 1 to 36, having a density of 0.95 to 1.00 g / mL, preferably 0.96 to 0.99 g / mL, or more preferably 0.965 to 0.972 g / mL at 25°C, as measured according to DIN 51757:2011-01; a viscosity of 60 to 85 mPa·s, preferably 64 to 84 mPa·s, or more preferably 67 to 85 mPa·s at 25°C, as measured according to DIN 53019-1:2008-09; and an SiH value of 1.40 to 1.80 mol / kg, preferably 1.50 to 1.70 mol / kg, or more preferably 1.57 to 1.67 mol / kg, as measured by gas volumetric analysis. 38. The method according to any one of embodiments 1 to 37, wherein the poly(methylhydrogen)-polydimethylsiloxane copolymer is separated from the cyclic polydimethylsiloxane and other volatile substances by applying heat and vacuum to the equilibrium reaction mixture obtained in step (a) before subjecting the poly(methylhydrogen)-polydimethylsiloxane copolymer to the hydrosilylation reaction. 39. The method according to any one of embodiments 1 to 38, wherein the hydrosilylation reaction is carried out at a temperature of 20°C to 140°C, preferably 40°C to 130°C, or more preferably 60°C to 110°C. 40. The method according to any one of embodiments 1 to 39, wherein at least one hydrosilylation catalyst is a noble metal catalyst, preferably Pt(0) or rhodium. 41. The method according to any one of embodiments 1 to 40, wherein the polyether polydimethylsiloxane has a viscosity of 100 mPa·s to 12000 mPa·s, or preferably 200 to 8000 mPa·s, at 25°C, as determined according to DIN 53019-1:2008-09. 42. Polyether polydimethylsiloxane, (A) Density of 1.030 to 1.060 g / mL, preferably 1.032 to 1.057 g / mL, or more preferably 1.035 to 1.055 g / mL at 25°C, as measured according to DIN 51757:2011-01; and viscosity of 700 to 1300 mPa·s, preferably 750 to 1250 mPa·s, or more preferably 800 to 1200 mPa·s at 25°C, as measured according to DIN 53019-1:2008-09; or (B) The method according to any one of embodiments 1 to 41, having a density of 1.010 to 1.050 g / mL, preferably 1.015 to 1.045 g / mL, or more preferably 1.020 to 1.040 g / mL at 25°C, as measured according to DIN 51757:2011-01; and a viscosity of 500 to 1000 mPa·s, preferably 530 to 900 mPa·s, or more preferably 550 to 850 mPa·s at 25°C, as measured according to DIN 53019-1:2008-09. 43. A composition for preparing a polymer foam comprising at least one monomer species and one or more polyether polydimethylsiloxanes obtained by any one of the methods of Embodiments 1 to 42, wherein the polymer foam is preferably a polyurethane foam, a phenolic resin foam, or a polyvinyl chloride foam, and more preferably a polyurethane foam. 44. A method for preparing a polymer foam, comprising reacting one or more monomer species in the presence of one or more polyether polydimethylsiloxanes obtained by the method described in any one of embodiments 1 to 42 to obtain a polymer foam. 45. An article comprising a polymer foam obtained according to the method of Embodiment 44 or as a reaction product of the composition of Embodiment 43. 46. ​​Use of a recycled polydimethylsiloxane-containing composition containing recycled linear polydimethylsiloxane in an equilibrium reaction for obtaining poly(methylhydrogen)-polydimethylsiloxane copolymer in a method for producing polyether polydimethylsiloxane. 47. The use according to embodiment 46, wherein the recycled linear polydimethylsiloxane is obtained from the recycling of at least one linear polydimethylsiloxane or its copolymer. 48. The use according to any one of embodiments 46 and 47, wherein the recycled polydimethylsiloxane-containing composition is as defined in any one of embodiments 4 to 11. 49. Use according to any one of embodiments 46 to 48, wherein the recycled linear polydimethylsiloxane is as defined in any one of embodiments 3, 11, and 12 to 22. 50. Use according to any one of embodiments 47 to 50, wherein the poly(methylhydrogen)-polydimethylsiloxane copolymer is as defined in any one of embodiments 35 to 38. 51. Use according to any one of embodiments 46 to 50, wherein the polyether polydimethylsiloxane is as defined in any one of embodiments 41 or 42. 52. Use according to any one of embodiments 46 to 51, wherein the equilibrium reaction is carried out as defined in any one embodiment of embodiments 29 to 33. 53. The use according to any one of embodiments 46 to 52, further comprising subjecting the poly(methylhydrogen)-polydimethylsiloxane copolymer obtained by the equilibrium reaction to a hydrosilylation reaction with at least one polyether containing at least one carbon-carbon double bond reactive to the Si-H bond, preferably in the presence of at least one hydrosilylation catalyst, to obtain a polyether polydimethylsiloxane. 54. The use according to embodiment 53, wherein the hydrosilylation reaction is carried out as defined in any one of embodiments 39 and 40. 55. Use of at least one polyether polydimethylsiloxane obtained by any one of the methods of Embodiments 1 to 42 as an additive in a method for producing a polymer foam or in a composition for preparing a polymer foam, wherein the polymer foam is preferably a polyurethane foam, a phenolic resin foam, or a polyvinyl chloride foam, and more preferably a polyurethane foam. 56. Use of recycled linear polydimethylsiloxanes for the production of polyether polydimethylsiloxanes. 57. The use according to aspect 56, wherein the recycled linear polydimethylsiloxane has a carbon footprint of less than 4 kg CO2 equivalent / kg of recycled linear polydimethylsiloxane, or preferably less than 2 kg CO2 equivalent / kg of recycled linear polydimethylsiloxane, as determined in accordance with DIN EN ISO standard 14067:2018. [Examples]

[0098] Starting materials: In Example 1, a cyclic organosiloxane-containing composition A was used, which was obtained from recycling and contained 0.9 wt% D3, 67.7 wt% D4, 23.0 wt% D5, and 3.4 wt% D6, as well as different alkanes and 130 ppm benzene as impurities. The cyclic organosiloxane-containing composition A was converted to recycled linear polydimethylsiloxane.

[0099] The recycled linear polydimethylsiloxane was used in the equilibrium reaction of Example 2b according to the present invention to obtain a SiH-functionalized siloxane, which was further treated in the hydrosilylation reaction of Example 3b according to the present invention to obtain a polyether polydimethylsiloxane.

[0100] In Example 2a, which does not conform to the present invention, a SiH-functionalized siloxane was obtained by using cyclic organosilixane-containing composition A as is, and this was further treated with the hydrosilylation reaction of Example 3a, which does not conform to the present invention, to obtain a polyether polydimethylsiloxane.

[0101] The content of individual cyclic organosiloxanes in Composition A and the products of the examples was determined using the following GC method "cyclics". The benzene content was determined using the method of DIN 51405:2004-01.

[0102] GC method "Cyclics": The mass fraction of cyclic siloxanes was determined by GC, which first separates the substances according to their boiling points and then detects them using a thermal conductivity detector. Aliquots of the samples under test were analyzed by GC without further dilution. This was performed in a gas chromatograph equipped with a split / splitless injector, capillary column, and thermal conductivity detector under the following conditions. Injector: 290℃, 40ml split Injection volume: 1μl Column: 5m x 0.32mm HP5 1μm Carrier gas: Hydrogen, constant flow rate 2 mL / min Temperature program: 80°C for 1 minute, then 80°C-300°C at 30°C / minute, then conditioning at 300°C for 10 minutes. Detector: TCD at 320°C Makeup gas 8 mL / min Standard gas flow rate: 22 mL / min

[0103] The SiH value was determined by gas volumetric analysis. For this purpose, weighed samples of poly(methylhydrogen)-polydimethylsiloxane copolymer were decomposed with a sodium butyrate solution to form hydrogen gas. The amount of hydrogen gas was measured, and the SiH value was determined using the definition of SiH value: n(H2)[mol] / m(sample)[kg].

[0104] Example 1 (according to the present invention): Structure of recycled cyclic organosiloxane-containing composition A Me3SiO[SiMe2O] 98 Conversion to recycled linear polydimethylsiloxane containing SiMe3 A mixture consisting of 293.4 g of cyclic organosiloxane-containing composition A and 6.6 g of hexamethyldisiloxane (CAS: 107-46-0) was prepared in a 500 ml four-necked flask equipped with a stirrer, thermometer, gas inlet, and reflux condenser. 0.30 g of trifluoromethanesulfonic acid (CAS: 1493-13-6, purity >99%) was added. The mixture was stirred at 35°C for 6 hours, then 3.0 g of NaHCO3 was added, and the mixture was stirred for a further 2 hours. The mixture was filtered. The product was a filtrate. The volatile components were then removed from the product using a rotary evaporator at 130°C and under reduced pressure of less than 1 mbar for 2 hours. The viscosity of the product was 141 mPa·s, and the benzene content was 5 ppm.

[0105] Example 2a (not according to the present invention): Structure Me3SiO[SiMe2O] 51 Equilibrium reaction of a cyclic organosiloxane-containing composition A to a SiH-functionalized siloxane having [SiMeHO]7SiMe3 In a 500 ml four-necked flask equipped with a stirrer, thermometer, gas inlet, and reflux condenser, a mixture consisting of 216.6 g of cyclic organosiloxane-containing composition A, 26.3 g of poly(methyl)hydrogensiloxane (CAS: 63148-57-2, SiH content: 15.25 mol / kg), and 7.1 g of hexamethyldisiloxane (CAS: 107-46-0) was prepared, and 0.25 g of trifluoromethanesulfonic acid (CAS: 1493-13-6, purity >99%) was added. The mixture was stirred at 35°C for 6 hours, then 2.5 g of NaHCO3 was added, and the mixture was stirred for a further 2 hours. The mixture was filtered. The product was the filtrate (equilibrium reaction mixture 2a).

[0106] Example 2b (according to the present invention): Structure Me3SiO[SiMe2O] 51 Equilibrium reaction of recycled linear polydimethylsiloxane to SiH-functionalized siloxane having [SiMeHO]7SiMe3 In a 500 ml four-necked flask equipped with a stirrer, thermometer, gas inlet and reflux condenser, a mixture consisting of 221.4 g of recycled linear polydimethylsiloxane from Example 1, 26.3 g of poly(methyl)hydrogensiloxane (CAS: 63148-57-2, SiH content: 15.25 mol / kg), and 2.3 g of hexamethyldisiloxane (CAS: 107-46-0) was prepared, and 0.25 g of trifluoromethanesulfonic acid (CAS: 1493-13-6, purity >99%) was added. The mixture was stirred at 35°C for 6 hours, then 2.5 g of NaHCO3 was added, and the mixture was stirred for a further 2 hours. The mixture was filtered. The product was the filtrate (equilibrium reaction mixture 2b).

[0107] Table 1 summarizes the results of equilibrium reactions using cyclic organosiloxane-containing compositions and recycled linear polydimethylsiloxanes.

[0108] [Table 1]

[0109] Example 3a (not according to the present invention): Hydrosilylation reaction In a 250 ml four-necked flask equipped with a stirrer, thermometer, gas inlet and reflux condenser, the average formula is: CH2=CHCH2O-(CH2CH2O) 10 A mixture consisting of 70 g of polyether containing (CH2CH(CH3)O)2OH and 55 g of poly(organyl hydrogen)-polyorganosiloxane from Example 2a was prepared. The mixture was stirred and heated to 90°C. 5 ppm of Pt in the form of platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex solution (CAS: 68478-92-2) was added. An exothermic reaction occurred. The reaction was maintained below 100°C by cooling. The reaction mixture was then stirred at 90°C for 2 hours. A clear and homogeneous product was obtained.

[0110] Next, volatile components were removed from the product using a rotary evaporator at 130°C and under reduced pressure of less than 1 mbar for 2 hours. The benzene content of the product was 11 ppm.

[0111] Example 3b (according to the present invention): Hydrosilylation reaction In a 250 ml four-necked flask equipped with a stirrer, thermometer, gas inlet and reflux condenser, the average formula is: CH2=CHCH2O-(CH2CH2O) 10 A mixture consisting of 70 g of polyether containing (CH2CH(CH3)O)2OH and 55 g of poly(organyl hydrogen)-polyorganosiloxane from Example 2b was prepared. The mixture was stirred and heated to 90°C. 5 ppm of Pt in the form of platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex solution (CAS: 68478-92-2) was added. An exothermic reaction occurred. The reaction was maintained below 100°C by cooling. The reaction mixture was then stirred at 90°C for 2 hours. A clear and homogeneous product was obtained. The volatile components were then removed from the product using a rotary evaporator at 130°C and under reduced pressure of less than 1 mbar for 2 hours. The benzene content of the product was 1 ppm.

[0112] [Table 2]

[0113] The examples demonstrate that it is advantageous to first convert a cyclic organosiloxane-containing composition into linear polydimethylsiloxanes, then distill them at this stage, and then convert only those into SiH-functionalized siloxanes or polyethersiloxanes. In this way, volatile contaminants such as aromatic or aliphatic hydrocarbons can be removed more easily. This is thought to be because the viscosity of linear polydimethylsiloxanes is lower than that of polyethersiloxanes. Furthermore, siloxane oils have a less critical toxicological classification because they have fewer toxicologically questionable cycles. This makes transportation and storage easier.

Claims

1. A method for producing polyether polydimethylsiloxane, (a) A recycled polydimethylsiloxane-containing composition, including recycled linear polydimethylsiloxane, is subjected to an equilibrium reaction with at least one poly(methylhydrogen)siloxane in the presence of at least one equilibrium catalyst to form a poly(methylhydrogen)-polydimethylsiloxane copolymer, (b) The poly(methylhydrogen)-polydimethylsiloxane copolymer obtained in step (a) is subjected to a hydrosilylation reaction with at least one polyether containing at least one carbon-carbon double bond that is reactive to the Si-H bond, preferably in the presence of at least one hydrosilylation catalyst, to obtain a polyether polydimethylsiloxane. The recycled linear polydimethylsiloxane is obtained from the recycling of at least one linear polydimethylsiloxane or its copolymer, and the recycling of at least one linear polydimethylsiloxane or its copolymer is (c) A polydimethylsiloxane-containing composition comprising at least one linear polydimethylsiloxane or a copolymer thereof is subjected to catalytic depolymerization in the presence of at least one depolymerization catalyst to form at least one cyclic polydimethylsiloxane in the depolymerization reaction mixture, (d) Distilling the depolymerization reaction mixture to obtain a cyclic polydimethylsiloxane-containing composition comprising at least one cyclic polydimethylsiloxane, (e) Depending on the circumstances, the cyclic polydimethylsiloxane-containing composition may be subjected to fractional distillation and purification. (f) A cyclic polydimethylsiloxane-containing composition comprising at least one cyclic polydimethylsiloxane is subjected to a polymerization reaction in the presence of a polymerization catalyst to obtain recycled linear polydimethylsiloxane in the recycled polydimethylsiloxane-containing composition, (g) A method comprising, if applicable, purifying the recycled polydimethylsiloxane-containing composition.

2. The method according to claim 1, wherein the recycled linear polydimethylsiloxane has a viscosity of 25 to 2500 mPa·s, preferably 50 to 2000 mPa·s, more preferably 100 to 1500 mPa·s, and most preferably 150 to 1000 mPa·s at 25°C, as measured according to DIN 53019-1:2008-09.

3. The recycled polydimethylsiloxane-containing composition contains, based on the total moles of M, D, T, and Q units of the recycled polydimethylsiloxane-containing composition, up to 7.50 mol% of M units, preferably up to 4 mol% of M units, or more preferably up to 2.50 mol% of M units, ... up to 1% The sum of T and Q units of the recycled polydimethylsiloxane-containing composition is at most 0.75 mol%, preferably at most 0.5 mol%, or more preferably at most 0.25 mol%, based on the total moles of M, D, T, and Q units of the recycled polydimethylsiloxane-containing composition. The method according to any one of claims 1 and 2.

4. The recycled polydimethylsiloxane-containing composition is - Based on the total weight of the recycled polydimethylsiloxane-containing composition, measured according to DIN 51777:2020-04, a maximum of 0.05% (by weight), preferably a maximum of 100 ppm, more preferably a maximum of 40 ppm (by weight), and most preferably a maximum of 10 ppm of water; and / or - Based on the total moles of silicon atoms in the recycled polydimethylsiloxane-containing composition, ２９ As determined by Si-NMR spectroscopy, up to 0.5 mol%, preferably up to 0.2 mol%, more preferably up to 0.1 mol%, of vinyl-substituted silicon atoms; and / or - Based on the total moles of silicon atoms in the recycled polydimethylsiloxane-containing composition, ２９ The method according to any one of claims 1 to 3, comprising up to 0.2 mol%, preferably up to 0.1 mol%, and more preferably up to 0.05 mol% of hydroxyl-substituted silicon atoms as determined by Si-NMR spectroscopy.

5. The method according to any one of claims 1 to 4, wherein the recycled linear polydimethylsiloxane is obtained from the recycling of at least one linear polydimethylsiloxane or a copolymer thereof.

6. The method according to claim 5, wherein the at least one linear polydimethylsiloxane or its copolymer corresponds to or is derived from waste polydimethylsiloxane polymer or copolymer material, wide-spec polydimethylsiloxane polymer or copolymer material, used polydimethylsiloxane polymer or copolymer material, expired polydimethylsiloxane polymer or copolymer material, surplus polydimethylsiloxane polymer or copolymer material, or any mixture or combination thereof.

7. The at least one linear polydimethylsiloxane or its copolymer is contained in the polydimethylsiloxane-containing composition, and the polydimethylsiloxane-containing composition is - Based on the total weight of the polydimethylsiloxane-containing composition, the composition comprises at least 50% (by weight), preferably at least 70% (by weight), or more preferably at least 90% (by weight), of at least one linear polydimethylsiloxane or its copolymer; and / or - Having a silicon content of 19% to 38% (by weight), preferably 26% to 38% (by weight), and more preferably 34% to 38% (by weight), based on the total weight of the polydimethylsiloxane-containing composition; and / or - The method according to any one of claims 5 and 6, comprising less than 50% (by weight), preferably less than 25% (by weight), and more preferably less than 5% (by weight), of the total weight of the polydimethylsiloxane-containing composition, as a filler.

8. The aforementioned poly(methylhydrogen)-polydimethylsiloxane copolymer Density of 0.95–0.98 g / mL, preferably 0.96–0.98 g / mL, or more preferably 0.97–0.98 g / mL, at 25°C, as measured according to DIN 51757:2011-01; Viscosity measured according to DIN 53019-1:2008-09, of 2 to 2000 mPa·s, preferably 3 to 1000 mPa·s, or more preferably 10 to 500 mPa·s at 25°C; and / or The SiH value measured by gas volumetric spectroscopy is 0.2 to 10 mol / kg, preferably 0.4 to 8 mol / kg, or more preferably 0.6 to 6 mol / kg. The method according to any one of claims 1 to 7, comprising:

9. A composition for preparing a polymer foam comprising at least one monomer species and one or more polyether polydimethylsiloxanes obtained by the method according to any one of claims 1 to 8, wherein the polymer foam is preferably a polyurethane foam, a phenolic resin foam, or a polyvinyl chloride foam, and more preferably a polyurethane foam.

10. A method for preparing a polymer foam, comprising reacting one or more monomer species in the presence of one or more polyether polydimethylsiloxanes obtained by the method described in any one of claims 1 to 8 to obtain a polymer foam.

11. An article comprising a polymer foam obtained by the method described in claim 10, or as a reaction product of the composition described in claim 9.

12. The use of recycled linear polydimethylsiloxane for the production of polyether polydimethylsiloxane, wherein the recycled linear polydimethylsiloxane is obtained from the recycling of at least one linear polydimethylsiloxane or its copolymer, and the recycling of at least one linear polydimethylsiloxane or its copolymer is (c) A polydimethylsiloxane-containing composition comprising at least one linear polydimethylsiloxane or a copolymer thereof is subjected to catalytic depolymerization in the presence of at least one depolymerization catalyst to form at least one cyclic polydimethylsiloxane in the depolymerization reaction mixture, (d) Distilling the depolymerization reaction mixture to obtain a cyclic polydimethylsiloxane-containing composition comprising at least one cyclic polydimethylsiloxane, (e) Depending on the circumstances, the cyclic polydimethylsiloxane-containing composition may be subjected to fractional distillation and purification. (f) Subjecting a cyclic polydimethylsiloxane-containing composition containing at least one cyclic polydimethylsiloxane to a polymerization reaction in the presence of a polymerization catalyst to obtain recycled linear polydimethylsiloxane in the recycled polydimethylsiloxane-containing composition, (g) Use, which may include purifying the recycled polydimethylsiloxane-containing composition.

13. The recycled linear polydimethylsiloxane is determined according to DIN EN ISO standard 14067:2018, 4 kg CO2 ２ The recycled linear polydimethylsiloxane in an equivalent / kg or, preferably, 2 kg CO ２ The use according to claim 12, wherein the recycled linear polydimethylsiloxane has a carbon footprint of less than equivalent / kg.

14. Use of at least one polyether polydimethylsiloxane obtained by the method of any one of claims 1 to 8 as an additive in a method for producing a polymer foam or a composition for preparing a polymer foam, wherein the polymer foam is preferably a polyurethane foam, a phenolic resin foam, or a polyvinyl chloride foam, and more preferably a polyurethane foam.

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