Method for preparing siloxanes

Abstract

The present invention relates to hexamethylcyclotrisiloxane used in 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. It has been found that a content of at least 0.5% by weight of hexamethylcyclotrisiloxane can reduce the equilibrium reaction time and provide a statistically uniform distribution of SiH functional groups in the poly(methylhydrogen)-polydimethylsiloxane copolymer. Using the produced poly(methylhydrogen)-polydimethylsiloxane copolymer, a polyether polydimethylsiloxane can be produced which can be used as a stabilizer for polymer foams such as polyurethane foams.

Description

[Technical Field]

[0001] The present invention relates to hexamethylcyclotrisiloxane used in 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. It has been found that a content of at least 0.5% by weight of hexamethylcyclotrisiloxane can reduce the equilibrium reaction time and provide a statistically uniform distribution of SiH functional groups in the poly(methylhydrogen)-polydimethylsiloxane copolymer. Using the produced poly(methylhydrogen)-polydimethylsiloxane copolymer, a polyether polydimethylsiloxane can be produced which can be used as a stabilizer for polymer foams such as polyurethane foams.

[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. Polyether polydimethylsiloxanes can be produced by hydrosilylation reactions utilizing poly(methylhydrogen)-polydimethylsiloxane copolymers and polyethers.

[0004] The synthesis of poly(methylhydrogen)-polydimethylsiloxane copolymers can be carried out via so-called equilibrium reactions. In these equilibrium reactions, cyclic polydimethylsiloxanes and poly(methylhydrogen)siloxanes are commonly used.

[0005] It is particularly advantageous when the polyether modification is randomly distributed along the siloxane skeleton. On the other hand, a blocky arrangement is disadvantageous. Therefore, the SiH functional groups should be statistically distributed in the underlying poly(methylhydrogen)-polydimethylsiloxane. The statistical distribution of SiH functional groups in poly(methylhydrogen)-polydimethylsiloxane is generally only achieved after long reaction times, especially when using recycled cyclic polydimethylsiloxanes.

[0006] Therefore, the objective of this application is to shorten the equilibrium reaction time and achieve a statistical distribution of SiH functional groups in the resulting poly(methylhydrogen)-polydimethylsiloxane.

[0007] High-purity cyclic polydimethylsiloxanes are typically obtained from chlorosilanes via the Mueller-Rochow process (hereinafter abbreviated as MR or the 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 production of cyclic polydimethylsiloxanes by the Mueller-Rochow process requires a wasteful amount of energy.

[0008] 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.

[0009] 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 like polydimethylsiloxane is essential for the polymer industry's transition to carbon neutrality. As such, polydimethylsiloxane is widely used in industry, for example, in sealants, adhesives, lubricants, cookware, and equipment for medical applications, heat insulation, and electrical insulation.

[0010] 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 a linear or branched organopolysiloxane 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.

[0011] 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.

[0012] As detailed above, cyclic polydimethylsiloxane is a starting material in the production of polyether polydimethylsiloxane. However, the prior art has considered that cyclic siloxanes must have high purity when subjected to an equilibration reaction, and that the cyclic siloxane composition from a recycling process does not have the purity necessary to enable the production of a suitable polyether polydimethylsiloxane foam stabilizer. Therefore, there is no mention of the production of polyether polydimethylsiloxane derived from cyclic siloxanes from a recycling process.

[0013] Therefore, there remains a need to provide poly(methylhydrogen)-polydimethylsiloxane and polyether polydimethylsiloxane with a reduced carbon footprint based on the product from a recycling process.

[0014] It has been found that the equilibration reaction time can be shortened by utilizing at least 0.5% by weight of hexamethylcyclotrisiloxane in an equilibration reaction. Furthermore, the carbon footprint can be reduced by utilizing recycled cyclic polydimethylsiloxanes such as recycled hexamethylcyclotrisiloxane recycled in the equilibration reaction.

[0015] Summary A manufacturing method is provided. The method includes (a) subjecting a cyclic polydimethylsiloxane-containing composition to an equilibration reaction with at least one poly(methylhydrogen)siloxane in the presence of at least one equilibration catalyst to form a poly(methylhydrogen)-polydimethylsiloxane copolymer, wherein the cyclic polydimethylsiloxane-containing composition includes at least 0.5% by weight of hexamethylcyclotrisiloxane based on the total weight of the cyclic polydimethylsiloxane-containing composition and up to 0.05% by weight of water measured in accordance with DIN 51777:2020-04 based on the total weight of the cyclic polydimethylsiloxane-containing composition.

[0016] Furthermore, the present invention relates to a method for preparing a polymer foam, comprising reacting one or more monomer species in the presence of one or more polyether polydimethylsiloxanes obtained according to the present invention to obtain a polymer foam. Articles comprising the polymer foam obtained according to the present invention are also provided.

[0017] Furthermore, polyether polydimethylsiloxane is used as a foam stabilizer, and polyether polydimethylsiloxane is produced starting from a cyclic polydimethylsiloxane-containing composition that includes recycled hexamethylcyclotrisiloxane.

[0018] Hexamethylcyclotrisiloxane is used in 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, wherein the cyclic polydimethylsiloxane-containing composition comprises at least 0.5% by weight of hexamethylcyclotrisiloxane and up to 0.05% by weight of water, measured according to DIN 51777:2020-04, based on the total weight of the cyclic polydimethylsiloxane-containing composition.

[0019] Detailed explanation Any numerical range enumerated herein is intended to include all subranges contained therein. For example, the range "1 to 10" is intended to include the enumerated minimum value of 1 and the enumerated maximum value of 10 and all subranges containing them, i.e., all subranges beginning with a minimum value of 1 or greater and ending with a maximum value of 10, and all of those subranges, e.g., 1 to 6.3, or 5.5 to 10, or 2.7 to 6.1. Any endpoint of a range and / or numbers within those ranges can be combined within the scope of this disclosure.

[0020] Components that are stated to be present "up to" a specified amount or "up to" a specified amount, without specifying a minimum amount, are not necessarily present in each composition. For example, a cyclic polydimethylsiloxane-containing composition containing up to 40 ppm (by weight) of water may not contain water substantially or not at all.

[0021] All parts, quantities, concentrations, etc., mentioned herein are by weight unless otherwise specified.

[0022] As used herein, the term “comprising” is open-ended and does not exclude the presence 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 presence of any unspecified elements, components, or method steps. While this disclosure describes “comprising,” it also covers “consisting of” or “consisting essentially of.” In this regard, “consisting essentially of” means that any additional compositional components do not substantially affect the relevant properties of the cyclic polydimethylsiloxane-containing composition in the method for producing polyether polydimethylsiloxane.

[0023] As used herein, the singular forms "a," "an," and "the" refer to multiple objects unless otherwise explicitly indicated by the context.

[0024] 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 cyclic 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 cyclic polydimethylsiloxane-containing composition. As used herein, the term “completely absent” means that the material is not present at all in the composition. Therefore, the cyclic polydimethylsiloxane-containing compositions disclosed herein do not have to contain chlorine-containing compounds.

[0025] 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.

[0026] The present invention relates to a method for producing a poly(methylhydrogen)-polydimethylsiloxane copolymer, comprising (a) subjecting a cyclic polydimethylsiloxane-containing composition to an equilibrium reaction with at least one poly(methylhydrogen)siloxane in the presence of at least one equilibrium catalyst, wherein the cyclic polydimethylsiloxane-containing composition comprises at least 0.5% by weight of hexamethylcyclotrisiloxane based on the total weight of the cyclic polydimethylsiloxane-containing composition, and up to 0.05% by weight of water, measured according to DIN 51777:2020-04 based on the total weight of the cyclic polydimethylsiloxane-containing composition.

[0027] A cyclic polydimethylsiloxane-containing composition may contain, based on the total weight of the cyclic polydimethylsiloxane-containing composition, at least 0.8% by weight of hexamethylcyclotrisiloxane, preferably at least 1.0% by weight of hexamethylcyclotrisiloxane, more preferably at least 1.5% by weight of hexamethylcyclotrisiloxane, even more preferably at least 2.0% by weight of hexamethylcyclotrisiloxane, and most preferably at least 4.0% by weight of hexamethylcyclotrisiloxane. A cyclic polydimethylsiloxane-containing composition may contain, based on the total weight of the cyclic polydimethylsiloxane-containing composition, up to 20% by weight of hexamethylcyclotrisiloxane, preferably up to 15% by weight of hexamethylcyclotrisiloxane, more preferably up to 13% by weight of hexamethylcyclotrisiloxane, even more preferably up to 10% by weight of hexamethylcyclotrisiloxane, and most preferably up to 8.0% by weight of hexamethylcyclotrisiloxane. A cyclic polydimethylsiloxane-containing composition may contain, based on the total weight of the cyclic polydimethylsiloxane-containing composition, 0.5 to 20% by weight of hexamethylcyclotrisiloxane, preferably 0.8 to 15% by weight of hexamethylcyclotrisiloxane, more preferably 1.0 to 13% by weight of hexamethylcyclotrisiloxane, even more preferably 2.0 to 10% by weight of hexamethylcyclotrisiloxane, and most preferably 4.0 to 8.0% by weight of hexamethylcyclotrisiloxane.

[0028] The equilibrium reaction is desirable to provide a poly(methylhydrogen)-polydimethylsiloxane copolymer having a statistically uniform distribution of SiH functional groups. In other words, the poly(methylhydrogen)-polydimethylsiloxane copolymer after the equilibrium reaction should have a statistically uniform distribution of SiH functional groups. This can be determined by using a polyether polydimethylsiloxane foam stabilizer derived from the poly(methylhydrogen)-polydimethylsiloxane copolymer.

[0029] The method can further comprise (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 with Si-H bonds, preferably in the presence of at least one hydrosilylation catalyst, to obtain a polyether-polydimethylsiloxane. The polyether-polydimethylsiloxane can be used as a foam stabilizer.

[0030] As understood herein, polydimethylsiloxane is a polymer having siloxane units (repeating units), i.e., O 1 / 2 -Si-O 1 / 2 units and methyl substituents (hereinafter abbreviated as "Me") on silicon atoms. Thereby, individual siloxane units are interconnected by oxygen atoms. O 1 / 2 -SiMe2-O 1 / 2 units are conventional and are also denoted herein as D units. A polydimethylsiloxane copolymer, herein, refers to a polymer containing, in addition to the O 1 / 2 -SiMe2-O 1 / 2 repeating unit (D unit), additional repeating units different from O 1 / 2 -SiMe2-O 1 / 2 . Polydimethylsiloxane or a copolymer thereof can contain branched units conventionally and herein denoted as T units and Q units. Thereby, a T unit refers to a Me1SiO 3 / 2 unit, and a Q unit refers to a SiO 4 / 2 unit. Further, an M unit refers to a Me3SiO 1 / 2 unit herein and thus forms a chain end. Branched polydimethylsiloxane refers to polydimethylsiloxane containing T units and / or Q units. A branched polydimethylsiloxane copolymer refers to a copolymer containing T units and / or Q units and / or additional branched units other than T units or Q units in the polymer chain.

[0031] The cyclic polydimethylsiloxane-containing composition used in the process for producing the polyether polydimethylsiloxane of the present invention comprises at least one cyclic polydimethylsiloxane, including hexamethylcyclotrisiloxane. Typically, the cyclic polydimethylsiloxane-containing composition comprises a mixture of different cyclic polydimethylsiloxanes, such as hexamethylcyclotrisiloxane (referred to conventionally and herein as D3), octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), dodecamethylcyclohexasiloxane (D6), tetradecamethylcycloheptasiloxane (D7), and hexadecamethylcyclooctasiloxane (D8), with D4 being typically the most abundant cyclic polydimethylsiloxane in the cyclic polydimethylsiloxane-containing composition. Advantageously, the cyclic polydimethylsiloxane-containing composition has an octamethylcyclotetrasiloxane (D4) content of 40% to 90% (by weight), preferably 45% to 80% (by weight), or more preferably 50% to 80% (by weight), based on the total weight of the cyclic polydimethylsiloxane-containing composition. The above cyclic polydimethylsiloxane-containing composition preferably contains hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, and decamethylcyclopentasiloxane, and more preferably contains hexamethylcyclotrisiloxane and octamethylcyclotetrasiloxane. The content of cyclic polydimethylsiloxane in the cyclic polydimethylsiloxane-containing composition is preferably determined by gas chromatography, for example, according to the method described below. The relative content of cyclic polydimethylsiloxane in a cyclic polydimethylsiloxane-containing composition may depend, in particular, on the conditions in the method steps for obtaining the cyclic polydimethylsiloxane, as detailed below, and may be compensated in the equilibrium reaction by appropriately adjusting, for example, the equilibrium reaction time or other method parameters.

[0032] A typical cyclic polydimethylsiloxane-containing composition according to the present invention contains, based on the total weight of the cyclic polydimethylsiloxane-containing composition, at least 0.5% by weight of hexamethylcyclotrisiloxane and 40-90% by weight of octamethylcyclotetrasiloxane.

[0033] Another typical cyclic polydimethylsiloxane-containing composition according to the present invention comprises 1.0 to 10% by weight of hexamethylcyclotrisiloxane and 60 to 90% by weight of octamethylcyclotetrasiloxane, based on the total weight of the cyclic polydimethylsiloxane-containing composition.

[0034] The term "cyclic polydimethylsiloxane-containing composition" means that the composition contains at least one cyclic polydimethylsiloxane, but the composition may also contain acyclic polydimethylsiloxanes. However, it is preferable that all polydimethylsiloxanes in the cyclic polydimethylsiloxane-containing composition are cyclic polydimethylsiloxanes.

[0035] A cyclic polydimethylsiloxane-containing composition may have a total content of cyclic polydimethylsiloxane exceeding 90% (by weight), preferably exceeding 95% (by weight), or more preferably exceeding 98% (by weight), based on the total weight of the cyclic polydimethylsiloxane-containing composition. A large amount of cyclic polydimethylsiloxane in the composition results in better control of the target properties of the equilibrium reaction.

[0036] The content of cyclic polydimethylsiloxanes (e.g., D3, D4, D5, D6, D7, and D8) in a cyclic polydimethylsiloxane-containing composition can be determined as follows: The substances are separated according to their boiling points 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, split 40 mL; 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 cyclic polydimethylsiloxane-containing composition may further contain siloxanes (e.g., as impurities) that also contain M, T, and Q units in addition to D units. Therefore, a cyclic polydimethylsiloxane-containing composition may be characterized by its molar content of M, T, and Q units based on the total moles of M, D, T, and Q units in the cyclic polydimethylsiloxane-containing composition. In a preferred embodiment of the present invention, a cyclic polydimethylsiloxane-containing composition contains up to 0.25 mol%, preferably up to 0.15 mol%, or more preferably up to 0.05 mol%, of M units. The sum of T and Q units in a cyclic polydimethylsiloxane-containing composition may be up to 0.75 mol%, preferably up to 0.5 mol%, or more preferably up to 0.25 mol%. The sum of M, T, and Q units in a cyclic polydimethylsiloxane-containing composition may be up to 1.00 mol%, preferably up to 0.65 mol%, or more preferably up to 0.3 mol%. The content of M, D, T, and Q is: 29 It is preferable to determine this using Si NMR spectroscopy.29 In Si NMR spectroscopy, M units yield signals in the range of 6-9 ppm, D units yield signals in the range of -16 to -24 ppm, T units yield signals in the range of -40 to -80 ppm, and Q units yield signals in the range of -95 to -140 ppm. The proportion of each unit is determined by setting the sum of the signal intensities of each unit relative to the sum of the signal intensities of all M, D, T, and Q units. For example, the content of M units is determined by setting the sum of the signal intensities of all M, D, T, and Q units to be between 6 and 9 ppm. 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.

[0038] A cyclic polydimethylsiloxane-containing composition may be further described by the content of components other than cyclic polydimethylsiloxanes, such as water, linear siloxanes, and siloxanes containing hydroxyl or vinyl groups.

[0039] In a preferred embodiment of the present invention, the cyclic polydimethylsiloxane-containing composition contains, as measured according to DIN 51777:2020-04, up to 300 ppm (by weight) of water, or preferably up to 100 ppm (by weight), preferably 50 ppm (by weight), preferably 45 ppm (by weight), or more preferably up to 40 ppm (by weight), or most preferably up to 10 ppm (by weight), based on the total weight of the cyclic polydimethylsiloxane-containing composition. Even more preferably, the cyclic polydimethylsiloxane-containing composition is substantially water-free or completely water-free. The cyclic polydimethylsiloxane-containing composition is preferably 29Based on the total moles of silicon atoms in the cyclic polydimethylsiloxane-containing composition, as determined by Si-NMR spectroscopy, the composition may contain up to 0.2 mol% of hydroxyl-substituted silicon atoms, preferably up to 0.1 mol%, or more preferably up to 0.05 mol%, of which hydroxyl-substituted silicon atoms may be present. For this purpose, regarding the signals corresponding to the hydroxyl-substituted silicon atoms... 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 cyclic 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.

[0040] A cyclic polydimethylsiloxane-containing composition may contain up to 3% (by weight) of linear siloxane, preferably up to 2% (by weight) of linear siloxane, or more preferably up to 1% (by weight), based on the total weight of the cyclic polydimethylsiloxane-containing composition, and is preferably measured by gas chromatography. For this purpose, GC measurement can be used to determine the linear siloxane. A suitable method is also used for determining the cyclic fraction, and is the method described above. More preferably, a cyclic polydimethylsiloxane-containing composition is substantially or completely devoid of linear siloxane. Such linear siloxanes typically have 2 to 6 repeating units. Linear siloxanes introduce M units that affect the chain length of the resulting poly(methylhydrogen)-polydimethylsiloxane copolymer and therefore may require the formulation of an equilibrium reaction mixture that is undesirable from the viewpoint of process efficiency.

[0041] The cyclic polydimethylsiloxane-containing composition contains a maximum of 0.5 mol%, preferably a maximum of 0.2 mol%, or more preferably a maximum of 0.1 mol%, based on the total molar silicon atoms in the cyclic polydimethylsiloxane-containing composition. 29 It may contain vinyl-substituted silicon atoms determined by Si-NMR spectroscopy. For this purpose, the signal corresponding to the vinyl-substituted silicon atom is 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 as the ratio to 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 measurement is advantageous. More preferably, the cyclic 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.

[0042] At least one cyclic polydimethylsiloxane may be at least partially derived from at least one linear or branched polydimethylsiloxane or its copolymer. Preferably, it can be derived from at least one linear or branched polydimethylsiloxane or its copolymer. Thus, at least one cyclic polydimethylsiloxane can be expressed as at least one recycled cyclic polydimethylsiloxane. In particular, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, and decamethylcyclopentasiloxane can be derived from at least one linear or branched polydimethylsiloxane or its copolymer. Preferably, hexamethylcyclotrisiloxane is derived from at least one linear or branched polydimethylsiloxane or its copolymer.

[0043] A cyclic polydimethylsiloxane-containing composition may, for example, include at least one cyclic polydimethylsiloxane derived from at least one linear or branched polydimethylsiloxane or its copolymer in a recycling process as detailed below, i.e., at least one recycled cyclic polydimethylsiloxane, and further include at least one further cyclic polydimethylsiloxane, such as octamethylcyclotetrasiloxane derived from chlorosilane in a conventionally applied Mueller-Rochow process. Thus, a cyclic polydimethylsiloxane-containing composition may, for example, include at least one cyclic polydimethylsiloxane derived from at least one linear or branched polydimethylsiloxane or its copolymer in a recycling process as detailed below, and further include at least one further cyclic polydimethylsiloxane, such as octamethylcyclotetrasiloxane derived from chlorosilane in a conventionally applied Mueller-Rochow process. However, preferably, the cyclic polydimethylsiloxane-containing composition is substantially or completely free of further cyclic polydimethylsiloxanes obtained based on methylchlorosilane from, for example, the Mueller-Rochow process. Therefore, at least one cyclic polydimethylsiloxane in the cyclic polydimethylsiloxane-containing composition is preferably not derived from methylchlorosilane. Therefore, at least one cyclic polydimethylsiloxane in the cyclic polydimethylsiloxane-containing composition is preferably not obtained from a product of the Mueller-Rochow process, such as chlorosilane. Furthermore, at least one linear or branched polydimethylsiloxane or its copolymer to be reused can first be obtained, for example, from chlorosilane from the Mueller-Rochow process. Therefore, the cyclic polydimethylsiloxane-containing composition of the present invention can have a lower content of chlorine-containing compounds than the respective content of cyclic polydimethylsiloxane-containing compositions derived from methylchlorosilane.The chlorine-containing compounds understood herein include inorganic compounds such as chlorine-containing salts such as NaCl, and organic compounds such as chlorosilanes. A cyclic 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, based on the total weight of the cyclic polydimethylsiloxane-containing composition. Preferably, a cyclic polydimethylsiloxane-containing composition is substantially free of chlorine-containing compounds, or most preferably completely free of chlorine-containing compounds.

[0044] At least one cyclic polydimethylsiloxane can be at least partially derived from at least one linear or branched polydimethylsiloxane or its copolymer. Advantageously, at least one linear or branched polydimethylsiloxane or its copolymer 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 the at least one linear or branched polydimethylsiloxane or its copolymer. Preferably, at least one linear or branched polydimethylsiloxane or its copolymer is preferably 29 The 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 or branched 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 or branched polydimethylsiloxane or its copolymer is a linear polydimethylsiloxane homopolymer.

[0045] At least one linear or branched 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 them.

[0046] At least one linear or branched polydimethylsiloxane or its copolymer can correspond to different polydimethylsiloxane polymers or copolymer products. For example, at least one linear or branched 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 or branched polydimethylsiloxane or its copolymer may be a mixture of polydimethylsiloxane oil and polydimethylsiloxane elastomer or rubber. The linear or branched polydimethylsiloxane or its copolymer may, of course, be a mixture of two or more different polydimethylsiloxane oils, each being a polydimethylsiloxane elastomer or rubber. Polydimethylsiloxane oil is preferred. 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, DIN 53019-2:2001-02, DIN 53019-3:2008-09 and DIN 53019-4:2016-10. 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 to ultimately obtain at least a portion of at least one cyclic polydimethylsiloxane.

[0047] Typically, at least one linear or branched polydimethylsiloxane or its copolymer is included in a polydimethylsiloxane-containing composition used to produce at least one cyclic polydimethylsiloxane.

[0048] A polydimethylsiloxane-containing composition may be characterized by the weight fraction of at least linear or branched 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 or branched 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 or branched polydimethylsiloxane or its copolymer.

[0049] 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.

[0050] Linear or branched 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 cyclic polydimethylsiloxane-containing composition, may affect the method steps for obtaining the cyclic polydimethylsiloxane-containing composition and subsequent reaction steps. The polydimethylsiloxane-containing composition can 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.

[0051] Polydimethylsiloxane-containing compositions can also be characterized by the content of colorants that may be contained in the linear or branched 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.

[0052] 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.

[0053] 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.

[0054] 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 or branched 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.

[0055] At least one cyclic polydimethylsiloxane can be at least partially derived from at least one linear or branched polydimethylsiloxane or its copolymer. Advantageously, at least one cyclic polydimethylsiloxane can be at least partially derived from one linear or branched polydimethylsiloxane or its copolymer by subjecting a polydimethylsiloxane-containing composition containing at least one linear or branched 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, and by distilling the depolymerization reaction mixture to obtain a cyclic polydimethylsiloxane-containing composition containing at least one cyclic polydimethylsiloxane. Distillation may be at least partially performed during catalytic depolymerization. The catalytic depolymerization and distillation described herein constitute one process for recycling linear or branched polydimethylsiloxane or its copolymer. It is particularly preferred to obtain at least one cyclic polydimethylsiloxane using the catalytic depolymerization and distillation described herein. In some cases, the cyclic polydimethylsiloxane-containing composition may be subjected to additional fractional distillation and purification before being subjected to the equilibrium reaction of the method of the present invention.

[0056] 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 cyclic polydimethylsiloxane-containing composition before subjecting it to an equilibrium reaction. Therefore, the content of linear siloxane, water, M units, T units, Q units, Si-hydroxyl, and Si-vinyl in the cyclic polydimethylsiloxane-containing composition is selected as described above. The cyclic polydimethylsiloxane-containing composition should be purified by distillation purification, such as fractional distillation, before subjecting it to an equilibrium reaction.

[0057] By utilizing at least one cyclic polydimethylsiloxane from the recycling of linear or branched polydimethylsiloxanes or their copolymers, the carbon footprint of the at least one cyclic polydimethylsiloxane used in the implementation of the present invention can be reduced compared to cyclic polydimethylsiloxanes conventionally used in the preparation of polyether polydimethylsiloxanes, such as those derived from the Mueller-Rochow process. Thus, the at least one cyclic polydimethylsiloxane can have a carbon footprint of less than 4 kg CO2 equivalent / kg of at least one cyclic polydimethylsiloxane, or preferably less than 2 kg CO2 equivalent / kg of at least one cyclic polydimethylsiloxane, as determined according to DIN EN ISO standard 14067:2018.

[0058] It is preferable that the cyclic polydimethylsiloxane in the cyclic polydimethylsiloxane-containing composition has a carbon footprint of at least one cyclic polydimethylsiloxane with a CO2 equivalent / kg of less than 4 kg, or preferably at least one cyclic polydimethylsiloxane with a CO2 equivalent / kg of less than 2 kg, as determined according to DIN EN ISO standard 14067:2018.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] Catalytic depolymerization can also be carried out as a two-step process combining treatment with an acidic depolymerization catalyst (e.g., as referred to above herein) and subsequent treatment with a basic depolymerization catalyst (e.g., as referred to above herein).

[0063] If necessary, additional components such as solvents can be added to the depolymerization reaction mixture.

[0064] 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.

[0065] The catalytic depolymerization step can be carried out in a batch, semi-continuous, or continuous process.

[0066] A cyclic polydimethylsiloxane-containing composition is subjected to an equilibrium reaction with at least one poly(methylhydrogen)siloxane in the method of the present invention in the presence of at least one equilibrium catalyst, forming a poly(methylhydrogen)-polydimethylsiloxane copolymer in the equilibrium reaction mixture. As used herein, the equilibrium reaction refers to the reorganization of a cyclic polydimethylsiloxane and a 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.

[0067] 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 present in the cyclic 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 both 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.

[0068] Poly(methylhydrogen)siloxane is given by formula 2: [ka] It may have a molecular structure due to the following:

[0069] 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.

[0070] 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.

[0071] 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 cyclic polydimethylsiloxane-containing composition.

[0072] 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.

[0073] 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. The equilibrium reaction time may be less than 5 hours, preferably 4 hours or less. 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, for example, when used as a foam stabilizer in a polyurethane flexible foam system, often leads to significant foam collapse, sometimes resulting in foam decay.

[0074] 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.

[0075] The balancing step can be performed in batches, semi-continuously, or continuously.

[0076] 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 back into the feed of the cyclic polydimethylsiloxane composition, for example, when the equilibrium reaction step is carried out as a continuous process.

[0077] 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.

[0078] 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].

[0079] 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.

[0080] A poly(methylhydrogen)-polydimethylsiloxane copolymer can be subjected 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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 only in small amounts, for example, at most 15 mol%, or preferably at most 10 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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 to 8000 mPa·s at 25°C, as determined preferably according to DIN 53019-1:2008-09, DIN 53019-2:2001-02, DIN 53019-3:2008-09 and DIN 53019-4:2016-10.

[0090] 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.

[0091] 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, in addition to the polyether polydimethylsiloxanes obtained according to the methods disclosed herein, comprise at least one further polyether polydimethylsiloxane not obtained by the methods disclosed herein, for example, 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.

[0092] 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.

[0093] 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 that is not obtained by the methods disclosed herein and is obtained, for example, based on cyclic polydimethylsiloxanes from the Mueller-Rochow process.

[0094] A method for preparing a polyurethane foam may include providing a composition comprising at least one isocyanate-reactive compound having on average at least two isocyanate 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; contacting the composition with a polyisocyanate or a mixture of polyisocyanates having on average at least two isocyanate groups per molecule; and curing the composition under conditions of forming a polyurethane foam.

[0095] 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.

[0096] The present invention further relates to the use of polyether polydimethylsiloxane as a foam stabilizer for polyether polydimethylsiloxane produced from a cyclic polydimethylsiloxane-containing composition comprising recycled hexamethylcyclotrisiloxane. Preferably, the recycled cyclic polydimethylsiloxane, such as recycled hexamethylcyclotrisiloxane, is derived from linear or branched polydimethylsiloxane or its copolymers. Preferably, the recycled hexamethylcyclotrisiloxane is used in an amount of at least 0.5% by weight, based on the total weight of the cyclic polydimethylsiloxane-containing composition. The polyether polydimethylsiloxane may have a carbon footprint of less than 4 kg CO2 equivalent / kg of recycled cyclic polydimethylsiloxane, or preferably less than 2 kg CO2 equivalent / kg of recycled cyclic polydimethylsiloxane, as determined in accordance with DIN EN ISO standard 14067:2018. The recycled cyclic 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.

[0097] The present invention also relates to the use of hexamethylcyclotrisiloxane in an equilibrium reaction with at least one poly(methylhydrogen)siloxane in the presence of at least one equilibrium catalyst for forming a poly(methylhydrogen)-polydimethylsiloxane copolymer, wherein the cyclic polydimethylsiloxane-containing composition contains at least 0.5% by weight of hexamethylcyclotrisiloxane based on the total weight of the cyclic polydimethylsiloxane-containing composition. The use of hexamethylcyclotrisiloxane can shorten the equilibrium reaction time, more preferably shortening the equilibrium reaction time and providing a statistically uniform distribution of SiH functional groups in the poly(methylhydrogen)-polydimethylsiloxane copolymer. The equilibrium reaction time can be less than 5 hours. Hexamethylcyclotrisiloxane may be derived from recycled polydimethylsiloxane, and / or hexamethylcyclotrisiloxane is recycled hexamethylcyclotrisiloxane.

[0098] The present invention will be further described according to the following embodiments.

[0099] 1. (a) A method for producing a poly(methylhydrogen)-polydimethylsiloxane copolymer by subjecting a cyclic polydimethylsiloxane-containing composition to an equilibrium reaction with at least one poly(methylhydrogen)siloxane in the presence of at least one equilibrium catalyst, wherein the cyclic polydimethylsiloxane-containing composition contains at least 0.5% by weight of hexamethylcyclotrisiloxane based on the total weight of the cyclic polydimethylsiloxane-containing composition.

[0100] 2. The method according to embodiment 1, further 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.

[0101] 3. The method comprises (c) subjecting a polydimethylsiloxane-containing composition comprising at least one linear or branched 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 hexamethylcyclotrisiloxane, (e) The method according to any one of embodiment 1 or 2, further comprising, optionally, subjecting the cyclic polydimethylsiloxane-containing composition, which optionally contains at least one cyclic polydimethylsiloxane obtained in step (d), to additional fractional distillation and purification before subjecting it to the equilibrium reaction in step (a).

[0102] 4. The method according to any one of embodiments 1 to 3, wherein the cyclic polydimethylsiloxane-containing composition is at least partially derived from at least one linear or branched polydimethylsiloxane or its copolymer, preferably derived from at least one linear or branched polydimethylsiloxane or its copolymer.

[0103] 5. The method according to any one of embodiments 1 to 4, wherein the cyclic polydimethylsiloxane-containing composition contains up to 0.25 mol% of M units, preferably up to 0.15 mol%, or more preferably up to 0.05 mol%, of M units based on the total moles of M, D, T, and Q units of the cyclic polydimethylsiloxane-containing composition.

[0104] 6. The method according to any one of embodiments 1 to 5, wherein the sum of the T and Q units of the cyclic 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 cyclic polydimethylsiloxane-containing composition.

[0105] 7. The method according to any one of embodiments 1 to 6, wherein the sum of the M, T, and Q units of the cyclic polydimethylsiloxane-containing composition is at most 1.00 mol%, preferably at most 0.65 mol%, or more preferably at most 0.3 mol%, based on the total moles of the M, D, T, and Q units of the cyclic polydimethylsiloxane-containing composition.

[0106] 8. The method according to any one of embodiments 1 to 7, wherein at least one cyclic polydimethylsiloxane in the cyclic polydimethylsiloxane-containing composition is not derived from methylchlorosilane.

[0107] 9. The method according to any one of embodiments 1 to 8, wherein the cyclic polydimethylsiloxane-containing composition comprises, based on the total weight of the cyclic polydimethylsiloxane-containing composition, at least 0.8% by weight of hexamethylcyclotrisiloxane, preferably at least 1.0% by weight of hexamethylcyclotrisiloxane, more preferably at least 1.5% by weight of hexamethylcyclotrisiloxane, even more preferably at least 2.0% by weight of hexamethylcyclotrisiloxane, and most preferably at least 4.0% by weight of hexamethylcyclotrisiloxane.

[0108] 10. The method according to any one of embodiments 1 to 9, wherein the cyclic polydimethylsiloxane-containing composition comprises, based on the total weight of the cyclic polydimethylsiloxane-containing composition, up to 20% by weight of hexamethylcyclotrisiloxane, preferably up to 15% by weight of hexamethylcyclotrisiloxane, more preferably up to 13% by weight of hexamethylcyclotrisiloxane, even more preferably up to 10% by weight of hexamethylcyclotrisiloxane, and most preferably up to 8.0% by weight of hexamethylcyclotrisiloxane.

[0109] 11. The method according to any one of embodiments 1 to 10, wherein the cyclic polydimethylsiloxane-containing composition comprises, based on the total weight of the cyclic polydimethylsiloxane-containing composition, 0.5 to 20% by weight of hexamethylcyclotrisiloxane, preferably 0.8 to 15% by weight of hexamethylcyclotrisiloxane, more preferably 1.0 to 13% by weight of hexamethylcyclotrisiloxane, even more preferably 2.0 to 10% by weight of hexamethylcyclotrisiloxane, and most preferably 4.0 to 8.0% by weight of hexamethylcyclotrisiloxane.

[0110] 12. The method according to any one of embodiments 1 to 11, wherein the cyclic polydimethylsiloxane-containing composition further comprises octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, tetradecamethylcycloheptasiloxane and / or hexadecamethylcyclooctasiloxane, preferably octamethylcyclotetrasiloxane and decamethylcyclopentasiloxane, more preferably octamethylcyclotetrasiloxane.

[0111] 13. The method according to any one of embodiments 1 to 12, wherein the cyclic polydimethylsiloxane in the cyclic polydimethylsiloxane-containing composition is not obtained from the Mueller-Rochow process.

[0112] 14. The method according to any one of embodiments 1 to 13, wherein the cyclic polydimethylsiloxane present in the cyclic polydimethylsiloxane-containing composition is recycled cyclic polydimethylsiloxane.

[0113] 15. The method according to any one of embodiments 1 to 14, wherein a cyclic polydimethylsiloxane is at least partially derived from at least one linear or branched polydimethylsiloxane or its copolymer in a recycling process.

[0114] 16. The method according to any one of embodiments 1 to 15, wherein the cyclic polydimethylsiloxane-containing composition is substantially free of chlorine-containing compounds, or most preferably completely free of chlorine-containing compounds, and / or the cyclic polydimethylsiloxane-containing composition contains, based on the total weight of the cyclic polydimethylsiloxane-containing composition, 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.

[0115] 17. The method according to any one of embodiments 1 to 16, wherein the cyclic polydimethylsiloxane-containing composition has a total content of cyclic 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 cyclic polydimethylsiloxane-containing composition.

[0116] 18. The method according to any one of embodiments 1 to 17, wherein the cyclic polydimethylsiloxane-containing composition contains water at a maximum of 0.05% (by weight), preferably at a maximum of 300 ppm, preferably at a maximum of 100 ppm, preferably at a maximum of 50 ppm, preferably at a maximum of 45 ppm, more preferably at a maximum of 40 ppm (by weight), and most preferably at a maximum of 10 ppm, based on the total weight of the cyclic polydimethylsiloxane-containing composition as measured in accordance with DIN 51777:2020-04.

[0117] 19. The method according to any one of embodiments 3 to 18, wherein at least one linear or branched polydimethylsiloxane or its copolymer is a linear polydimethylsiloxane homopolymer.

[0118] 20. A cyclic polydimethylsiloxane-containing composition is determined based on the total moles of silicon atoms in the cyclic polydimethylsiloxane-containing composition. 29 The method according to any one of embodiments 1 to 19, 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.

[0119] 21. A cyclic polydimethylsiloxane-containing composition is determined based on the total moles of silicon atoms in the cyclic polydimethylsiloxane-containing composition. 29 The method according to any one of embodiments 1 to 20, 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.

[0120] 22. The method according to any one of embodiments 1 to 21, wherein the cyclic polydimethylsiloxane-containing composition has an octamethylcyclotetrasiloxane content of 40% to 90% (by weight), preferably 45% to 80% (by weight), and more preferably 50% to 80% (by weight), based on the total weight of the cyclic polydimethylsiloxane-containing composition.

[0121] 23. The method according to any one of embodiments 1 to 22, wherein the cyclic polydimethylsiloxane-containing composition has a hexamethylcyclotrisiloxane content of 0.1% to 6% (by weight), preferably 0.3% to 5% (by weight), and more preferably 1% to 4% (by weight), based on the total weight of the cyclic polydimethylsiloxane-containing composition.

[0122] 24. The method according to any one of embodiments 1 to 23, wherein the cyclic polydimethylsiloxane in the cyclic polydimethylsiloxane-containing composition has a carbon footprint of at least one cyclic polydimethylsiloxane with a CO2 equivalent / kg of less than 4 kg, or preferably at least one cyclic polydimethylsiloxane with a CO2 equivalent / kg of less than 2 kg, as determined in accordance with DIN EN ISO standard 14067:2018.

[0123] 25. The method according to any one of embodiments 3 to 24, wherein at least one linear or branched polydimethylsiloxane or its 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 or branched polydimethylsiloxane or its copolymer.

[0124] 26. The method according to any one of embodiments 3 to 25, wherein at least one linear or branched 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.

[0125] 27. The method according to any one of embodiments 3 to 26, wherein at least one linear or branched polydimethylsiloxane or its copolymer is included in the polydimethylsiloxane-containing composition.

[0126] 28. The method according to embodiment 27, 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 or branched polydimethylsiloxane or its copolymer, based on the total weight of the polydimethylsiloxane-containing composition.

[0127] 29. The method according to embodiment 27 or 28, 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.

[0128] 30. The method according to any one of embodiments 27 to 29, 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.

[0129] 31. The method according to any one of embodiments 3 to 30, wherein at least one linear or branched 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.

[0130] 32. The method according to any one of embodiments 3 to 31, wherein at least one linear or branched 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.

[0131] 33. The method according to any one of embodiments 3 to 32, wherein at least one linear or branched polydimethylsiloxane or its copolymer 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.

[0132] 34. The method according to any one of embodiments 1 to 33, wherein a further cyclic polydimethylsiloxane obtained from the hydrolysis of chlorosilane is added to the cyclic polydimethylsiloxane-containing composition before being subjected to the equilibrium reaction.

[0133] 35. The method according to any one of embodiments 3 to 34, 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.

[0134] 36. The method according to embodiment 3 or 35, 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.

[0135] 37. The method according to any one of embodiments 3 to 36, wherein catalytic depolymerization is carried out in a reactor that is resistant to corrosion and temperatures of at least 250°C.

[0136] 38. The method according to any one of embodiments 3 to 37, wherein distillation of the depolymerization reaction mixture is carried out at least partially during catalytic depolymerization.

[0137] 39. The method according to any one of embodiments 1 to 38, 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.

[0138] 40. The method according to any one of embodiments 1 to 39, 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.

[0139] 41. The method according to embodiment 40, wherein the amount of at least one chain length adjusting agent is adjusted based on the content of M units in the cyclic polydimethylsiloxane-containing composition, and / or the content of M units in the cyclic polydimethylsiloxane-containing composition is determined before subjecting the cyclic polydimethylsiloxane-containing composition to an equilibrium reaction.

[0140] 42. The method according to any one of embodiments 1 to 41, wherein the equilibrium reaction is carried out at a temperature of 10°C to 110°C, or preferably 25°C to 100°C.

[0141] 43. The method according to any one of embodiments 1 to 42, 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.

[0142] 44. The method according to any one of embodiments 1 to 43, 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.

[0143] 45. The method according to any one of embodiments 1 to 44, 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.

[0144] 46. ​​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 45, 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.

[0145] 47. The method according to any one of embodiments 1 to 46, 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.

[0146] 48. The method according to any one of embodiments 2 to 47, 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.

[0147] 49. The method according to any one of embodiments 2 to 48, wherein at least one hydrosilylation catalyst is a noble metal catalyst, preferably Pt(0) or rhodium.

[0148] 50. The method according to any one of embodiments 2 to 49, 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.

[0149] 51. 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 2 to 50, 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.

[0150] 52. The method according to any one of embodiments 1 to 51, wherein the equilibrium reaction provides a poly(methylhydrogen)-polydimethylsiloxane copolymer having a statistically uniform distribution of SiH functional groups.

[0151] 53. The method according to any one of embodiments 1 to 52, wherein the equilibrium reaction time is 20 minutes to 7 hours, preferably 30 minutes to 5 hours.

[0152] 54. The method according to any one of embodiments 1 to 53, wherein the equilibrium reaction time is less than 5 hours, preferably 4 hours or less.

[0153] 55. A composition for preparing a polymer foam comprising at least one monomer species and one or more polyether polydimethylsiloxanes obtained according to any of the methods of Embodiments 2 to 54, wherein the polymer foam is preferably a polyurethane foam, a phenolic resin foam, or a polyvinyl chloride foam, and more preferably a polyurethane foam.

[0154] 56. A method for preparing a polymer foam, comprising reacting one or more monomer species in the presence of one or more polyether polydimethylsiloxanes obtained according to any of the methods of Embodiments 2 to 54 to obtain a polymer foam.

[0155] 57. An article comprising a polymer foam obtained according to the method described in Embodiment 56, or as a reaction product of the composition of Embodiment 55.

[0156] 58. Use of at least one polyether polydimethylsiloxane obtained by any one of the methods of Embodiments 2 to 54 as an additive (such as a stabilizer) 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.

[0157] 59. Use of polyether polydimethylsiloxanes as foam stabilizers, produced starting from cyclic polydimethylsiloxane-containing compositions containing recycled hexamethylcyclotrisiloxane.

[0158] 60. The use according to aspect 59, wherein the recycled cyclic polydimethylsiloxane has a carbon footprint of less than 4 kg CO2 equivalent / kg of recycled cyclic polydimethylsiloxane, or preferably less than 2 kg CO2 equivalent / kg of recycled cyclic polydimethylsiloxane, as determined in accordance with DIN EN ISO standard 14067:2018.

[0159] 61. The use according to any one of embodiment 59 or 60, wherein recycled hexamethylcyclotrisiloxane is used in an amount of at least 0.5% by weight, based on the total weight of the cyclic polydimethylsiloxane-containing composition.

[0160] 62. Use of hexamethylcyclotrisiloxane in an equilibrium reaction with at least one poly(methylhydrogen)siloxane in the presence of at least one equilibrium catalyst for forming a poly(methylhydrogen)-polydimethylsiloxane copolymer, wherein the cyclic polydimethylsiloxane-containing composition contains at least 0.5% by weight of hexamethylcyclotrisiloxane based on the total weight of the cyclic polydimethylsiloxane-containing composition.

[0161] 63. The use according to embodiment 62, wherein the equilibrium reaction time can be shortened by using hexamethylcyclotrisiloxane, more preferably by using hexamethylcyclotrisiloxane to shorten the equilibrium reaction time and provide a statistically uniform distribution of SiH functional groups in the poly(methylhydrogen)-polydimethylsiloxane copolymer.

[0162] 64. The use according to either embodiment 62 or 63, wherein the equilibrium reaction time is less than 5 hours.

[0163] 65. Use according to any one of embodiments 63 to 64, wherein the hexamethylcyclotrisiloxane is derived from recycled polydimethylsiloxane and / or the hexamethylcyclotrisiloxane is recycled hexamethylcyclotrisiloxane. [Examples]

[0164] All quantities mentioned throughout the examples are in parts by weight unless otherwise specified.

[0165] The abbreviation "comp." mentioned in the examples indicates comparison and means a comparative composition or comparative example. The abbreviation "inv." mentioned in the examples indicates invention and means an inventive composition or an example of the invention.

[0166] Example 1: Composition derived from the Mueller-Rochow process Table 1 discloses two cyclic polydimethylsiloxane-containing compositions, one of which comprises a cyclic polydimethylsiloxane derived from the Mueller-Rochow process (MR process), and the other composition according to the present invention comprises a cyclic polydimethylsiloxane derived from the recycling of PDMS. As can be seen from Table 1, the MR process-based composition contains less than 5 ppm of chloride, while the composition derived from PDMS contains no chloride and only small amounts of Si-vinyl, M units, and T units. The main cyclic polydimethylsiloxane in the composition derived from the MR process is octamethylcyclotetrasiloxane (D4).

[0167] [Table 1] 1The sum of D3-D8 was measured by gas chromatography (GC) according to the following method: the substances were separated according to their boiling points and detected by a thermal conductivity detector (TCD). Aliquots of the sample to be examined were analyzed by GC without further dilution. This was done 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 were 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 percentage method). 2 The water content is the amount of water calculated by Karl Fischer's water determination method, in accordance with DIN 51777:2020-04. 3 The acid content was measured according to DIN EN ISO 2114-2002-06. 4 The chloride content was determined by potentiometric titration with silver nitrate solution according to DGF H-III 9, Deutsche Einheitsmethoden zur Untersuchung von Fetten, Fettprodukten, Tensiden und verwandten Stoffen, 2021, 2.Auflage. 5 Si-vinyl 29 The measurement was performed by Si-NMR spectroscopy. The mole fraction of Si-vinyl is determined by setting the sum of the signal intensities of all signals without a standard to -3 to -5 ppm. 29Appropriate 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. 6 The content in M ​​units and T units is: 29 The measurements were taken by Si-NMR. The mole fraction in M ​​units is: 29 This can be determined using Si-NMR. The M unit yields signals in the range of 6–9 ppm, the D unit in the range of -16 to -24 ppm, the T unit in the range of -40 to -80 ppm, and the Q unit in the range of -95 to -140 ppm. The proportion of the M unit is determined by setting the sum of the signal intensities of the signals from 6–9 ppm to the sum of the signal intensities of all the M, D, T, and Q units (no standard). 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.

[0168] Example 2: Composition containing cyclic polydimethylsiloxane Table 2 shows cyclic polydimethylsiloxane-containing compositions used in the production of polyether polydimethylsiloxanes. These compositions contain cyclic polydimethylsiloxanes derived from at least one linear or branched polydimethylsiloxane or its copolymer. More specifically, these compositions were obtained by catalytic depolymerization of a polydimethylsiloxane-containing composition containing at least one linear or branched polydimethylsiloxane or its copolymer, followed by distillation purification. Compositions A, G, H, I, and J of the invention contain more than 0.5% by weight of hexamethylcyclotrisiloxane (D3). Compositions A, G, and H contain increased water content. The "sum" shown in Table 2 refers to the sum of D3 to D6.

[0169] [Table 2] 7 The content of D3, D4, D5, and D6 was measured by gas chromatography (GC) according to the method described in Appendix 1 of Table 1 above in this specification.

[0170] Example 3: Equilibrium Reaction In a 500 mL four-necked flask equipped with a dropping funnel, stirrer, thermometer, gas inlet and reflux condenser, a mixture consisting of 218.3 g of each cyclic organosiloxane-containing composition of Example 2, 21.9 g of poly(methyl)hydrogensiloxane (CAS: 63148-57-2, SiH content: 15.75 mol / kg), and 9.8 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 or 4 hours with constant stirring. Then, 2.5 g of NaHCO3 was added, and the mixture was stirred for a further 2 hours. The mixture was filtered, and then volatile components were removed from the filtrate using a rotary evaporator at 130°C and under reduced pressure of less than 1 mbar. The product was the distillation bottom (i.e., poly(methylhydrogen)-polydimethylsiloxane copolymer).

[0171] Table 3 shows the equilibrium reaction conditions and the resulting poly(methylhydrogen)-polydimethylsiloxane copolymers using each of the cyclic organosiloxane-containing compositions described in Table 2. Since the viscosity of Example H1 was outside the target specifications, the experiment was repeated (Example H2). A larger amount of catalyst was used in Example H2.

[0172] [Table 3] 8 The SiH value was measured according to the following procedure: 15 mL of sodium butyrate solution (5% by weight in butanol) was added to approximately 3 g of hydrogen siloxane sample. The volume of hydrogen formed was determined using a burette. Using the law of ideal gases, the SiH group content was determined and calculated in units of mol / kg. 9 Density was measured according to DIN 51757:2011-1. 10 Viscosity was measured according to DIN 53019-1:2008-09, DIN 53019-2:2001-02, DIN 53019-3:2008-09, and DIN 53019-4:2016-10. 11 The sum of D3 to D6 was measured by gas chromatography (GC) according to the method described in Appendix 1 for Table 1 above. 12 As a comparative example, it was obtained from the MR process.

[0173] [Table 4] 13 Invention H2: An additional amount of catalyst was added 2 hours after the equilibrium reaction.

[0174] Comparative composition MR is a composition derived from the product of the Mueller-Rochow process. The equilibrium reaction times were 4 hours and 6 hours, respectively, and the presence of at least 0.5% by weight of hexamethylcyclotrisiloxane in the composition was sufficient to achieve equilibrium. However, the composition of Example H2 reveals that the second addition of the catalyst was beneficial for the equilibrium reaction. The water content is thought to have an adverse effect on the equilibrium reaction.

[0175] Example 4: Hydrosilylation reaction In a 250 mL four-necked flask equipped with a dropping funnel, stirrer, thermometer, gas inlet, and reflux condenser, add 51.4 g of the average formula: CH2=CHCH2O-(CH2CH2O) 10A mixture consisting of a polyether having (CH2CH(CH3)O)2OH and 43.5 g of each poly(methylhydrogen)-polydimethylsiloxane copolymer from Example 3 was prepared. The mixture was stirred and heated to 90°C. 2.6 ppm of platinum in the form of a Pt(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex solution (CAS: 68478-92-2) was added. An exothermic reaction occurred. The reaction mixture was kept below 100°C by cooling. The reaction mixture was then stirred at 90°C for 2 hours. A clear, homogeneous product was obtained. Finally, 5.0 g of 1,2-propylene glycol and 0.05 g of triisopropanolamine were added. The results of the hydrosilylation reaction are shown in Table 4.

[0176] [Table 5]

[0177] [Table 6]

[0178] Example 5: Preparation of rigid polyurethane foam The Bosch lance mold was cleaned and sprayed with a release agent. A water bath for the mold was set up with a temperature of 50°C. 195.50 g of isocyanate was added to an 8 ounce polycoated paper cup. A second composition was prepared and added to a 44 ounce polycoated paper cup. The second composition contained 2.6 g of water, 1.5 g of DMCHA, 1.5 g of each of the polyether polydimethylsiloxanes from Example 4, and 13.0 g of cyclopentane (foaming agent). The second composition was mixed for 30 seconds at 1000 rpm using a stirring blade. The first composition containing the isocyanate was then transferred from the 8 ounce cup to the 44 ounce cup containing the mixed second composition and mixed for 7 seconds using a stirring blade at 2500 rpm. This composition was then poured into the Bosch lance mold for 5 seconds at the designated injection point to evaluate its fluidity (the injection point was marked with tape on the side of the mold). After 10 minutes of curing, the foam was demolded. Table 5 shows the specific amounts of the polyether polydimethylsiloxane-containing components and the properties of the resulting foams for each example. According to Table 5, it is possible to shorten the equilibrium reaction time from 6 hours to 4 hours in the production of the foam stabilizer without degrading the properties of the resulting foam. Since the foam properties are desirable, a statistically uniform distribution of SiH functional groups in the poly(methylhydrogen)-polydimethylsiloxane copolymer after the equilibrium reaction was successful.

[0179] [Table 7] 15 N,N-dimethylcyclohexylamine (DMCHA) 16 Polyether polyol: Daltolac R-471, Huntsman International LLC 17 Mondur MR, Aromatic Polymer Isocyanate Based on Diphenylmethane-Diisocyanate (MDI), Covestro AG, Leverkusen, Germany

[0180] [Table 8]

Claims

1. A manufacturing method, (a) A method comprising subjecting a cyclic polydimethylsiloxane-containing composition 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, wherein the cyclic polydimethylsiloxane-containing composition comprises at least 0.5% by weight of hexamethylcyclotrisiloxane based on the total weight of the cyclic polydimethylsiloxane-containing composition, and up to 0.05% (by weight) of water, measured according to DIN 51777:2020-04 based on the total weight of the cyclic polydimethylsiloxane-containing composition.

2. The method described above is The method according to claim 1, further comprising (b) subjecting the poly(methylhydrogen)-polydimethylsiloxane copolymer obtained in step (a) to a hydrosilylation reaction with at least one polyether having 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 described above is (c) A polydimethylsiloxane-containing composition comprising at least one linear or branched 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 containing hexamethylcyclotrisiloxane, (e) The method according to any one of claims 1 or 2, further comprising, optionally, subjecting the cyclic polydimethylsiloxane-containing composition, which includes the at least one cyclic polydimethylsiloxane obtained in step (d), to additional fractional distillation and purification before subjecting it to the equilibrium reaction in step (a).

4. The method according to any one of claims 1 to 3, wherein the cyclic polydimethylsiloxane-containing composition is at least partially derived from at least one linear or branched polydimethylsiloxane or its copolymer, preferably from at least one linear or branched polydimethylsiloxane or its copolymer.

5. The method according to any one of claims 1 to 4, wherein the cyclic polydimethylsiloxane-containing composition comprises, based on the total weight of the cyclic polydimethylsiloxane-containing composition, at least 0.8% by weight of hexamethylcyclotrisiloxane, preferably at least 1.0% by weight of hexamethylcyclotrisiloxane, more preferably at least 1.5% by weight of hexamethylcyclotrisiloxane, even more preferably at least 2.0% by weight of hexamethylcyclotrisiloxane, and most preferably at least 4.0% by weight of hexamethylcyclotrisiloxane.

6. The method according to any one of claims 1 to 5, wherein the cyclic polydimethylsiloxane present in the cyclic polydimethylsiloxane-containing composition is recycled cyclic polydimethylsiloxane.

7. The method according to any one of claims 1 to 6, wherein the cyclic polydimethylsiloxane-containing composition further comprises octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, tetradecamethylcycloheptasiloxane and / or hexadecamethylcyclooctasiloxane, preferably octamethylcyclotetrasiloxane and decamethylcyclopentasiloxane, more preferably octamethylcyclotetrasiloxane.

8. The method according to any one of claims 1 to 7, wherein the cyclic polydimethylsiloxane-containing composition has a total content of cyclic 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 cyclic polydimethylsiloxane-containing composition.

9. The cyclic polydimethylsiloxane in the cyclic polydimethylsiloxane-containing composition is determined according to DIN EN ISO standard 14067:2018, and is 4 kg CO ２ Less than equivalent / kg of at least one cyclic polydimethylsiloxane, or preferably 2 kg CO ２ The method according to any one of claims 1 to 8, wherein the carbon footprint of the at least one cyclic polydimethylsiloxane is less than equivalent / kg.

10. The cyclic polydimethylsiloxane-containing composition contains, based on the total moles of M, D, T, and Q units of the cyclic polydimethylsiloxane-containing composition, up to 0.25 mol% of M units, preferably up to 0.15 mol% of M units, or more preferably up to 0.05 mol% of M units, and / or The sum of T and Q units of the cyclic 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 cyclic polydimethylsiloxane-containing composition, and / or The method according to any one of claims 1 to 9, wherein the sum of the M, T, and Q units of the cyclic polydimethylsiloxane-containing composition is at most 1.00 mol%, preferably at most 0.65 mol%, or more preferably at most 0.3 mol%, based on the total moles of the M, D, T, and Q units of the cyclic polydimethylsiloxane-containing composition.

11. The aforementioned cyclic polydimethylsiloxane-containing composition Based on the total weight of the cyclic polydimethylsiloxane-containing composition, as measured according to DIN 51777:2020-04, a maximum of 300 ppm (by weight), preferably a maximum of 100 ppm, preferably a maximum of 50 ppm (by weight), preferably a maximum of 45 ppm (by weight), more preferably a maximum of 40 ppm (by weight), most preferably a maximum of 10 ppm of water; and / or Based on the total moles of M, D, T, and Q units in the cyclic polydimethylsiloxane-containing composition, ２９ When determined based on Si-NMR spectroscopy, up to 0.25 mol%, or preferably up to 0.15 mol%, or more preferably up to 0.05 mol% in M ​​units; and / or Based on the total moles of silicon atoms in the cyclic 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 cyclic polydimethylsiloxane-containing composition, ２９ A maximum of 0.2 mol%, preferably a maximum of 0.1 mol%, and more preferably a maximum of 0.05 mol%, of hydroxyl-substituted silicon atoms, as determined by Si-NMR spectroscopy. The method according to any one of claims 1 to 10, including the method described in any one of claims 1 to 10.

12. 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 11, comprising:

13. 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 2 to 12 to obtain a polymer foam.

14. An article comprising a polymer foam obtained by the method described in claim 13.

15. The use of the aforementioned polyether polydimethylsiloxane as a foam stabilizer for polyether polydimethylsiloxane, which is produced starting from a cyclic polydimethylsiloxane-containing composition containing recycled hexamethylcyclotrisiloxane.

16. Use of hexamethylcyclotrisiloxane in an equilibrium reaction with at least one poly(methylhydrogen)siloxane in the presence of at least one equilibrium catalyst for forming a poly(methylhydrogen)-polydimethylsiloxane copolymer, wherein the cyclic polydimethylsiloxane-containing composition contains at least 0.5% by weight of hexamethylcyclotrisiloxane based on the total weight of the cyclic polydimethylsiloxane-containing composition, preferably the hexamethylcyclotrisiloxane is used to reduce the equilibrium reaction time, more preferably the hexamethylcyclotrisiloxane is used to reduce the equilibrium reaction time, and provides a statistically uniform distribution of the SiH functional value of the poly(methylhydrogen)-polydimethylsiloxane copolymer.

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