Purified polyether siloxanes ii

Abstract

The present invention relates to a polyether siloxane comprising at least one siloxane block and at least one polyether block, characterized in that the polyether siloxane comprises not more than 0.5 wt.-% + / - 10% of at least one short, linear siloxane N2 to N6.

Description

[0001] Purified polyether siloxanes II

[0002] The present invention is in the field of siloxanes, more particular in the field of polyether siloxanes. In particular, the present invention relates to highly pure polyether siloxanes, a composition for use in the preparation of a polyurethane foam article, comprising said polyether siloxane, the use of said polyether siloxane as a foam stabilizer in the preparation of a polyurethane foam article, and the use of said polyether siloxane as an additive in coating formulations.

[0003] Polyether siloxanes are known polymers with outstanding substance properties and are used in many everyday products. They are molecules, especially macromolecules, whose basic structure consists of alternating silicon and oxygen atoms. In more detailed level, polyether siloxanes comprise at least one siloxane block and at least one polyether block. The number of the different blocks can vary. Polyether siloxanes can be linear or branched.

[0004] Formula (a) illustrates a linear polyether siloxane:

[0005] Formula (a): linear polyether siloxane

[0006] R1in formula (a) are, independently of one another, identical alkyl or aryl residues, R1preferably being phenyl or methyl. R2in formula (a) are, each independently of one another, identical or different residues selected from the group consisting of R1and R3, where R3is, independently of one another, identical or different polyether residues. The parameter n is preferably between 2 to 500 for the formula (a), and the parameter m is preferably between 0 and 40 for formula (a).

[0007] However, the siloxane scaffold can also be branched if it contains so-called T or Q units ([RSiOac] or [SiO.4 / 2]). The established M, D, T and Q nomenclature refers to the functionality of the siloxane units. T units accordingly are trifunctional siloxane units and Q units are tetrafunctional siloxane units. For the M, D, T and Q nomenclature see, e.g., W. Noll, Chemie und Technologie der Silicone, Verlag Chemie GmbH, Weinheim (1960), pages 2ff.

[0008] Organomodified siloxanes are usually produced in two steps. First, the siloxane backbone is synthesized and then the organic function is added to the siloxane backbone. The siloxane backbone is usually produced by equilibrium polymerizations. Acidic catalysts, such as H2SO4 or CF3SO3H, can be used for this purpose. Siloxanes with a certain molecular weight distribution are obtained. The molecular weight distribution of the linear siloxane produced during equilibration can be described approximately with the Flory theory of random rearrangement. Depending on the chain length, each product of equilibrium polymerizations contains a certain proportion of shorter siloxane chains. The shorter the average siloxane chain, the higher this percentage.

[0009] However, even with relatively long siloxane chains, considerable quantities of shorter siloxane chains are found to be present in the product. The formation of short linear siloxanes can be avoided if the siloxanes at the ends of the chain are organically modified. The article “Equilibrium Molecular Weight Distribution of Cyclic and Linear Methylsiloxanes” (Jack B. Carmichael and James Heffel, J. Phys. Chem. 1965, 69, 7, 2218-2223) describes the molecular weight distribution of the siloxanes.

[0010] Therefore, technical polyether siloxanes often contain short, linear siloxanes, often also referred as (part of) volatile siloxanes. The group of short, linear siloxanes comprises hexamethyldisiloxane (N2), octamethyltrisiloxane (N3), decamethyltetrasiloxane (N4), dodecamethylpentasiloxane (N5), and tetradecamethylhexasiloxane (N6).

[0011] These compounds are under observation to their evaluation regarding their potentially negative effects on human health and the environment. For example, octamethyltrisiloxane (N3) was included in the Community Rolling Action Plan (CoRAP) in 2015 by the EU in accordance with Regulation (EC) No. 1907 / 2006 (REACH) as part of the evaluation of substances. The effects of the substance on human health and the environment are reassessed and, if necessary, follow-up measures are initiated. The inclusion of octamethyltrisiloxane was due to concerns about consumer use and widespread use, as well as the dangers posed by a possible classification of PBT / vPvB substances.

[0012] Decamethyltetrasiloxane (N4) was also investigated under REACH in 2015 as part of the substance evaluation by the UK because of its potential PBT or vPvB properties as well as its exposure to the environment and its broad dispersive use.

[0013] Accordingly, there is an ongoing demand for polyether siloxanes having a low content of short, linear siloxanes, in particular N2 to N6.

[0014] This requirement is met by the polyether siloxanes according to the present invention.

[0015] One object of the present is therefore a polyether siloxane comprising at least one siloxane block and at least one polyether block, characterized in that the polyether siloxane comprises not more than 0.5 wt.-% + / - 10% of at least one short, linear siloxane N2 to N6. Preferably polyether siloxane comprises not more than 0.2 wt.-% + / - 10%, more preferably not more than 0.1 wt.-% + / - 10%, most preferably not more than 0.05 wt.-% + / - 10%, of at least one short, linear siloxane N2 to N6.

[0016] In the context of the present invention, the term short, linear siloxane is used as known to the person skilled in the art and in analogy to the aforementioned cyclic siloxanes denotes the corresponding linear siloxanes of comparable size. Specifically, the term short, linear siloxane denotes the siloxanes explicitly mentioned in context with this term, i.e., hexamethyldisiloxane (N2), octamethyltrisiloxane (N3), decamethyltetrasiloxane (N4), dodecamethylpentasiloxane (N5), and tetradecamethylhexasiloxane (N6). In an embodiment the at least one short, linear siloxane N2 to N6 comprises hexamethyldisiloxane (N2), octamethyltrisiloxane (N3), decamethyltetrasiloxane (N4), dodecamethylpentasiloxane (N5), tetradecamethylhexasiloxane (N6), and / or a mixture of any of these.

[0017] The at least one short, linear siloxane N2 to N6 can comprise one short, linear siloxane N2 to N6, two short, linear siloxanes N2 to N6, three short, linear siloxanes N2 to N6, four short, linear siloxanes N2 to N6, or all (five) short, linear siloxanes N2 to N6.

[0018] In an embodiment the polyether siloxane according to the present invention comprises not more than 0.5 wt.-% + / - 10%, preferably not more than 0.2 wt.-% + / - 10%, more preferably not more than 0.1 wt.-% + / - 10%, most preferably not more than 0.05 wt.-% + / - 10% of all short, linear siloxanes N2 to N6.

[0019] In another embodiment the polyether siloxane according to the present invention comprises not more than 0.005 wt.-% of each short, linear siloxane N2 to N6.

[0020] In a further embodiment the polyether siloxane according to the present invention comprises not more than 0.02 wt.-% + / - 10% of all short, linear siloxanes N2 to N6.

[0021] Where at least one of the short, linear siloxanes N2 to N6 is present in the polyether siloxane according to the invention, it is preferred for the polyether siloxane to comprise at least 0.0001 wt.-% + / - 10%, more preferably at least 0.0005 wt.-% + / - 10%, yet more preferably at least 0.001 wt.-% + / - 10%, most preferably at least 0.002 wt.-% + / - 10% of at least one of the short, linear siloxanes N2 to N6. Here, it is particularly preferred for the polyether siloxane to contain at least one of the short, linear siloxanes N2 to N6 in the range of 0.0001 to 0.5 wt.-% + / - 10%, more preferably 0.0005 to 0.2 wt.-% + / - 10%, yet more preferably 0.001 to 0.1 wt.-% + / - 10%, most preferably 0.002 to 0.05 wt.-% + / - 10%. In yet another embodiment the polyether siloxane comprises at least 0.0001 wt.-% + / - 10%, more preferably at least 0.0005 wt.-% + / - 10%, yet more preferably at least 0.001 wt.-% + / - 10%, most preferably at least 0.002 wt.-% + / - 10% all of the short, linear siloxanes N2 to N6.

[0022] In addition to the short, linear siloxanes N2 to N6 as mentioned above, , technical polyether siloxanes often also contain cyclic siloxanes, also known as cyclosiloxanes. Cyclic siloxanes are annular siloxane compounds in which silicon and oxygen are bonded alternately. The group of cyclic siloxanes comprises hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), dodecamethylcyclohexasiloxane (D6), tetradecamethylcycloheptasiloxane (D7), hexadecamethylcyclooctasiloxane (D8), and / or a mixture of any of these.

[0023] Of particular importance within the scope of this invention are the cyclosiloxanes octamethylcyclotetrasiloxane (D4, CAS No.: 556-67-2), decamethylcyclopentasiloxane (D5, CAS No.: 541-02-6) and dodecamethylcyclohexasiloxane (D6, CAS No.: 540-97-6). Octamethylcyclotetrasiloxane meets the criteria for the identification of persistent, bioaccumulative and toxic substances and also very persistent and very bioaccumulative substances. Furthermore, the use of decamethylcyclopentasiloxane is also controversial for environmental reasons. The European Chemicals Agency classifies this substance as persistent and bioaccumulative. Hence, as of 31 January 2020, rinsable cosmetic products with a concentration of decamethylcyclopentasiloxane of 0.1 per cent by weight or higher may not be marketed in the EU.

[0024] Owing to the toxicological classification and potential danger of cyclic siloxanes D3 to D8, there is a desire to provide polyorganosiloxanes which contain as little of cyclic siloxanes D3 to D8, preferably D4 to D6, as possible or are free from them.

[0025] In an embodiment the polyether siloxane according to the present invention comprises not more than 0.02 wt.-% of at least one siloxane D3 to D8, preferably D4 to D6.

[0026] In an embodiment the at least one siloxane comprises hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), dodecamethylcyclo-hexasiloxane (D6), tetradecamethylcycloheptasiloxane (D7), hexadecamethylcyclooctasiloxane (D8), and / or a mixture of any of these.

[0027] In another embodiment the polyether siloxane according to the present invention comprises not more than 0.02 wt.-% of all siloxanes D3 to D8, preferably D4 to D6.

[0028] In a further embodiment the polyether siloxane according to the present invention comprises not more than 0.005 wt.-% of each cyclic siloxane D3 to D8, preferably D4 to D6.

[0029] In yet another embodiment the polyether siloxane according to the present invention comprises not more than 0.015 wt.-% of all cyclic siloxanes D3 to D8, preferably D4 to D6.

[0030] Where at least one of the cyclic siloxane D3 to D8 is present in the polyether siloxane according to the invention, it is preferred for the polyether siloxane to comprise at least 0.0001 wt.-%, more preferably at least 0.0005 wt.-%, yet more preferably at least 0.001 wt.-%, most preferably at least 0.002 wt.-% of at least one of the cyclic siloxane D3 to D8, preferably D4 to D6. Here, it is particularly preferred for the polyether siloxane to contain at least one cyclic siloxane of D3 to D8, preferably D4 to D6, in the range of 0.0001 wt.-% to 0.015 wt.-%, more preferably 0.0005 to 0.010 wt.-%, yet more preferably 0.001 to 0.0075 wt.-%, most preferably 0.002 to 0.005 wt.-%.

[0031] In the context of the present invention the entirety of cyclic siloxanes D3 to D8 and short, linear siloxanes N2 to N6 is also referred to as volatile siloxanes.

[0032] In principle, the polyether siloxane according to the present invention is not subject to any limitation regarding a specific structure. In a more detailed presentation, the polyether siloxane can be represented as a compound of the general Formula (1)

[0033] Formula (1) where

[0034] R1= identical or different alkyl or aryl residues with 1 to 16 carbon atoms, preferably phenyl or methyl,

[0035] R2= R1or R3,

[0036] R3= identical or different polyether residues, n = 2 to 500, preferably 4 to 300, in particular 6 to 200, m = 0 to 40, preferably 0 to 25, in particular 1 to 20, with the proviso that when all R2are R1, then m > 1 ,

[0037] In an embodiment of the polyether siloxane according to the present invention the at least one polyether block is connected to the at least one siloxane block through a SiC-bond.

[0038] In another embodiment the polyether siloxane according to the present invention is a compound of the general Formula (1)

[0039] Formula (1) where

[0040] R1= identical or different alkyl or aryl residues with 1 to 16 carbon atoms, preferably phenyl or methyl,

[0041] R2= R1,

[0042] R3= identical or different polyether residues, preferably polyether residues of the general formula A or B, in particular of the Formula A, n = 2 to 500, preferably 4 to 300, in particular 6 to 200, m = 0 to 40, preferably 0 to 25, in particular 1 to 20, with the proviso that when all R2are R1, then m > 1 , with

[0043] -R4-O-(CH2CH2O)a-(CH2CH(CH3)O)b-(CH(CH3)CH2O)c-(CH2CH(R5)O)d-(CH(R5)CH2O)e-R6

[0044] Formula A where

[0045] R4= a divalent hydrocarbon residue, preferably a -CH2-CH2-CH2- residue,

[0046] R5= identical or different alkyl or aryl residues, optionally interrupted by ether groups, preferably ethyl or phenyl,

[0047] R6= residues of the group comprising hydrogen, saturated or unsaturated hydrocarbon residues with 1 to 16 carbon atoms, and residues of the formula C, preferably hydrogen, methyl, butyl, or acetyl,

[0048] Formula C

[0049] R7= saturated or unsaturated hydrocarbon residues with 1 to 16 carbon atoms, a = 0 to 60, preferably 0 to 50, in particular 1 to 40, b = 0 to 60, preferably 0 to 50, in particular 1 to 40, c = 0 to 60, preferably 0 to 50, in particular 0, where a + b + c > 3, d = 0 to 25, preferably 0 to 10, in particular 0, e = 0 to 25, preferably 0 to 10, in particular 0, with

[0050] Formula B where r = 0 to 15, preferably 1 to 10, in particular 1 to 5, s = 0 to 15, preferably 1 to 10, in particular 1 to 5.

[0051] Preferably, the alpha and omega siloxane units of the polyether siloxane according to the present invention only have methyl groups, i.e., R1and R2of the alpha and omega siloxane unit in Formula (1) are all methyl. In that case, the polyether siloxane is end-capped with trimethylsilyl groups.

[0052] In a further embodiment of the polyether siloxane according to the present invention the siloxane backbone is end-capped with trimethylsilyl groups.

[0053] In order to obtain polyether siloxanes with low contents of volatile siloxanes, the cyclosiloxanes and / or short, linear siloxanes are usually removed by distillation after the polyether siloxane has been prepared. Depending on the viscosity of the polyether siloxanes, however, distillation requires long residence times in the vessel, very low pressures, and high temperatures. This leads to a strong thermal load on the compounds, which can have a negative effect on the quality, e.g. the color, of the products. Special equipment such as thin-film evaporators can reduce thermal stress but requires significant equipment and additional process steps. This complicates the cost-effective and thus competitive production of products containing polyether siloxanes.

[0054] It was found that it is possible to remove cyclosiloxanes and / or short, linear siloxanes from polyether siloxanes by distillation with the use of at least one auxiliary substance, as further described hereinbelow, under particularly mild conditions. In this way, the distillation times can also be significantly reduced.

[0055] Another object of the present invention is therefore a process for preparing the polyether siloxane according to the present invention, comprising the step of removing cyclic siloxanes D3 to D8, preferably D4 to D6, and / or short, linear siloxanes N2 to N6 from compositions comprising at least one polyether siloxane and at least one cyclic siloxane D3 to D8, preferably D4 to D6, and / or at least one short, linear siloxane N2 to N6 by distillation, wherein the distillation takes place in the presence of at least one auxiliary substance selected from the group consisting of glycols.

[0056] Preferably, before the distillation, the composition comprises at least one polyether siloxane in a total amount of 50 wt.-% to 99 wt.-%, preferably 60 wt.-% to 95 wt.-%, more preferably 70 wt.-% to 90 wt.-%, at least one cyclic siloxane D3 to D8, preferably D4, D5 and / or D6, in a total amount of 0.05 wt.-% to 10 wt.-%, preferably 0.1 wt.-% to 7 wt.-%, in particular 0.5 wt.-% to 4 wt.-%, and / or at least one short, linear siloxane N2 to N6 in a total amount of 0.05 wt.-% to 8 wt.-%, preferably 0.1 wt.-% to 5 wt.-%, and in particular 0.5 wt.-% to 3 wt.-%, at least one auxiliary substance selected from the group consisting of carboxylic acids having 1 to 8 carbon atoms and glycols, in a total amount of 0.03 wt.-% to 30 wt.-%, preferably 0.6 wt.-% to 15 wt.-%, in particular 0.9 wt.-% to 10 wt.-%, and optional further components, such as reaction by-products, reactant surpluses or additional solvents in a total amount of less than 50 wt.-%, preferably < 40 wt.-%, especially < 30 wt.-%, in particular < 20 wt.-%, in particular < 10 wt.-%, in particular < 5 wt.-%, based on the total weight of the composition.

[0057] The process according to the present invention allows for a complete or at least partial removal of the at least one cyclic siloxanes D3 to D8, preferably D4 to D6, and / or short, linear siloxanes N2 to N6 from the compositions comprising at least one polyether siloxane and at least one cyclic siloxanes D3 to D8, preferably D4 to D6, and / or short, linear siloxanes N2 to N6.

[0058] In an embodiment of the process according to the present invention the at least one cyclic siloxane D3 to D8, preferably D4 to D6, and / or short, linear siloxanes N2 to N6 is therefore completely removed or at least partially removed from the composition.

[0059] The process according to the present invention also allows for a simple and energy- as well as costefficient removal of cyclic siloxanes D3 to D8, preferably D4 to D6, and / or short, linear siloxanes N2 to N6 from polyether siloxanes. For example, the distillation is carried out at a relative low temperature in the range of only 60 °C to 120 °C. The low temperatures applied according to the present invention also have the benefit to reduce negative impacts on the product quality, e.g., regarding color. Typically, the higher the temperature and thus the thermal load, the more likely decomposition products are formed in the distillation. By comparison, the process according to the present invention is performed at relatively low temperatures. This also reduces any potentially negative impacts on the product quality significantly.

[0060] The distillation in the process according to the present invention can be carried out in any way known to the person skilled in the art. The usual distillation processes and principles can be employed, including for example more complicated processes such as short-path distillation or thin-film evaporators.

[0061] The process according to the present invention is also not subject to any limitation regarding a specific time point at which the at least one auxiliary substance is added to the composition - provided that the distillation has not been finished yet. For example, said at least one auxiliary substance can be added before the distillation, during the distillation or before and during the distillation. In the latter case, said at least one auxiliary substance can be added in portions.

[0062] In a further embodiment the at least one auxiliary substance is added to the composition before and / or during the distillation, where appropriate in portions.

[0063] Glycols which can be used preferably for the purposes of the present invention are in particular those dialcohols (divalent alcohols), which are derived from ethylene glycol, so-called 1 ,2-diols or vicinal diols. Preferred example thereof are ethylene glycol and / or propylene glycol. Examples of further glycols, which can also be used preferably for the purposes of the present invention are a,w-diols which are formed by condensation of ethylene glycol and / or propylene glycol, such as diethylene glycol, dipropylene glycol, triethylene glycol and / or tripropylene glycol. The glycols for the purposes of the present invention preferably have a molar mass of less than 200 g / mol.

[0064] In another embodiment of the process according to the present invention the distillation is carried out in the presence of at least one glycol, wherein said at least one glycol is selected from the group consisting of ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, and / or a mixture of any of these. Preferably, the glycol is propylene glycol, and / or ethylene glycol.

[0065] In principle, the process according to the present invention is not subject to any limitations regarding specific conditions, in particular with respect to temperature and / or pressure, under which the distillation is carried out. Rather, the temperature and / or pressure depend on the boiling point of the chosen auxiliary substance, the boiling point of the composition comprising at least one polyether siloxane and at least one cyclic siloxanes D3 to D6 and / or short, linear siloxanes N2 to N6, and / or the boiling point of the mixture of said composition with the auxiliary substance in question.

[0066] For the purposes of the present invention, it was found that the distillation is preferably carried out at a (reduced) pressure in the range of 0 mbar to 100 mbar and a temperature in the range of 60 °C to 150 °C.

[0067] For the distillative separation of the cyclic siloxanes D3 to D6 and / or short, linear siloxanes N2 to N6, the composition is preferably heated to temperatures between 40 °C and 150 °C, preferably between 60 °C and 145 °C and in particular preferably between 70 °C and 135 °C and the pressure is preferably reduced to the range of 0 mbar to 100 mbar, preferably 2 mbar to 50 mbar. The distillate containing cyclic siloxanes, short, linear siloxanes and preferably the auxiliary substance is then taken off, e.g., withdrawn from the head of the distillation apparatus.

[0068] In another embodiment the distillation is carried out a pressure in the range of 0 mbar to 100 mbar and a temperature in the range of 60 °C to 145 °C, preferably at a pressure of 2 mbar to 50 mbar and a temperature of 80 °C to 140 °C. Deviations for the values specifically mentioned herein, such as the end points of ranges, and the upper and / or lower end point of an open-ended range, are still comprised by the scope of the present invention, provided that those values deviating from the values specifically mentioned herein still provide for the benefits of the present invention.

[0069] The process according to the present invention allows for providing a polyether siloxane having either no content of cyclic siloxanes D3 to D8, preferably D4 to 6, and / or short, linear siloxanes N2 to N6 as low as possible.

[0070] A further object of the present invention is therefore a polyether siloxane obtained by the process according to the present invention.

[0071] The polyether siloxane according to the present invention and / or the polyether siloxane obtained by the process according to the present invention can be used in the preparation of a polyurethane foam article, either as such, in particular as a foam stabilizer, or as part of a composition for use in the preparation of a polyurethane foam article.

[0072] Another object of the present invention is therefore a composition for use in the preparation of a polyurethane foam article, characterized in that it comprises the polyether siloxane according to the present invention and / or the polyether siloxane obtained by the process according to the present invention.

[0073] A further object of the present invention is the use of the polyether siloxane according to the present invention and / or the polyether siloxane obtained by the process according to the present invention as a foam stabilizer in the preparation of a polyurethane foam article.

[0074] Examples:

[0075] I. Chemicals used:

[0076] Propylene glycol (>99.5%) and diethylene glycol (99%) were purchased from Sigma-Aldrich.

[0077] II. Methods:

[0078] 1. Determination of the numerical mean molar mass by means of GPC measurement:

[0079] GPC measurements were performed to determine polydispersity and numerically mean molar masses Mw under the following measurement conditions: Colum combination SDV 1 ,000 / 10,000 A (length 65 cm), temperature 30 °C, THF as mobile phase, flow rate 1 mL / min, sample concentration 10 g / L, Rl detector, evaluation of the polyether siloxanes was made against polystyrene standard (162-2 520 000 g / mol).

[0080] 2. Determination of the content of cyclic siloxane and short, linear siloxanes: All percentages (%) given are mass percentages, unless otherwise specified.

[0081] The mass fraction of the short, linear siloxanes, i.e., hexamethyldisiloxane (N2), octamethyltrisiloxane (N3), decamethyltetrasiloxan (N4), dodecamethylpentasiloxane (N5), and tetradecamethylhexasiloxane (N6), and the mass fraction of cyclic siloxanes, i.e., octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) in polyether siloxanes was determined using the GC method described below after prior matrix removal by extraction and column chromatographic purification of the extracts.

[0082] For analysis, 200 mg of the sample was dissolved in 2 ml of a solution of 0.2 mg / mL n-dodecane in acetonitrile. The volatile methylsiloxanes were extracted by adding 8 mL of a 98 / 2 (v / v) mixture of petroleum ether (boiling range 40 - 60 °C, purchased from Sigma Aldrich; 77399-1 L) and methyl tert-butyl ether (MTBE) (99.5%, purchased from Merck; 1 .01849.1000) followed by intense shaking. A part of the clear petroleum ether / MTBE phase was then flushed over a solid phase column at a flow rate of 1 - 2 mL / min.

[0083] The solid phase column contained 800 mg of an activated magnesium silicate adsorbent (Florisil, purchased from FLUKA; 46385-500G-F; activated at 140 °C for 12 h), which was filled into a suitable glass column (glass pipette, approx. 8 x 0.6 cm) and coated with 100 mg of anhydrous magnesium sulfate (magnesium sulfate heptahydrate, purchased from Merck; 1.05886.100; dried at 550 °C). The column was pre-cleaned with 5 mL of a 98 / 2 (v / v) mixture of petroleum ether and methyl-tert-butyl ether.

[0084] The first 1 .5 mL of the sample eluate was discarded, the fraction 1 .5 mL - 3 mL was collected and analyzed using GC / FID.

[0085] 2.1 Determination of cyclosiloxanes D4 to D6 and short, linear siloxane contents N4 to N6 in polyether siloxanes:

[0086] The volatile siloxanes contents in polyether siloxanes were determined by CG analysis according to the method below.

[0087] Injector: 290 °C, split 40 mL

[0088] Injection volume: 1 pL

[0089] Column: 30 x 0.32 mm HP-5, 0.25 pm

[0090] Carrier gas: hydrogen, const, flow 2 mL / min

[0091] Temperature program: 2 min at 60 °C, then 60 °C to 150 °C at 8 °C / min, then conditioning at 250 °C for

[0092] 10 minutes

[0093] Detector: FID at 30 °C

[0094] Hydrogen 35 mL / min

[0095] Air 240 mL / min

[0096] Make up gas 12 mL / min Octamethylcyclotetrasiloxane (D4), decamethyltetrasiloxane (N4), decamethylcyclopentasiloxane (D5), dodecamethylpentasiloxane (N5), dodecamethylcyclohexasiloxane (D6), and tetradecamethylhexasiloxane (N6) as well as n-dodecane as an internal standard were separated. The mass fractions of the volatile siloxanes were determined by evaluating their peak areas in comparison to the peak areas of the n-dodecane, which was added as an internal standard. For this purpose, the GC system was calibrated by measuring mixtures of the substances to be tested and the internal standard with known composition.

[0097] 2.2 Determination of short, linear siloxane contents N2 to N3 in polyether siloxanes:

[0098] The contents pf short, linear siloxane contents N2 to N3 in polyether siloxanes were determined by CG analysis according to the method below.

[0099] Injector: 280 °C, split 20 mL

[0100] Injection volume: 1 pL

[0101] Column: 50 x 0.32 mm Optima 624-LB, 1 ,8 pm

[0102] Carrier gas: hydrogen, const, flow 2 mL / min

[0103] Temperature program: 2 min at 60 °C, then 60 °C to 150 °C at 8 °C / min, then conditioning at 250 °C for

[0104] 10 minutes

[0105] Detector: FID at 250 °C

[0106] Hydrogen 30 mL / min

[0107] Air 400 mL / min

[0108] Make up gas 12 mL / min

[0109] Hexamethyldisiloxane (N2) and octamethyltrisiloxane (N3) as well as n-dodecane as an internal standard were separated. The mass fractions of hexamethyldisiloxane (N2) and octamethyltrisiloxane (N3) were determined by evaluating their peak areas in comparison to the peak areas of the n-dodecane, which was added as an internal standard. For this purpose, the GC system was calibrated by measuring mixtures of the substances to be tested and the internal standard with known composition.

[0110] III. Example A: Distillation of a polyether siloxane A

[0111] Polyether siloxane A has the structure: wherein n = 18, m = 1 .3, a = 14, b = 7 and R = H.

[0112] Using GPC, the numerical average molar mass Mnand the weight average molar mass Mwof polyether siloxane A were determined as 2880 g / mol (Mn) und 5150 g / mol (Mw).

[0113] Prior to distillation, the polyether siloxane A contained 0.08 wt.-% cycles (sum of D4, D5 and D6) as well as 0.19 wt.-% of short linear siloxanes (N2 to N6).

[0114] 1 . Example A1 : Purification by distillation of a polyether siloxane A without auxiliary substance (not according to the invention)

[0115] 150 g polyether siloxane A were placed into a 250 mL multi-necked flask equipped with KPG-blade-stirrer, distillation bridge, inert gas inlet pipe, and temperature sensor. Initially, the polyether siloxane was distilled at 105 °C and 2 mbar for 15 minutes, and then at 110 °C and 2 mbar for 45 minutes. Subsequently, the content of cyclic siloxanes and short linear siloxanes was determined using GC.

[0116] After distillation, the polyether siloxane A contained 0.023 wt.-% cycles (sum of D4, D5 and D6) as well as 0.073 wt.-% of short linear siloxanes (sum of N2 to N6). 2. Example A2: Purification by distillation of a polyether siloxane A with auxiliary substance (according to the invention)

[0117] 150 g polyether siloxane A and 7.5 g propylene glycol were placed into a 250 mL multi-necked flask equipped with KPG-blade-stirrer, distillation bridge, inert gas inlet pipe, and temperature sensor. Initially, the polyether siloxane was distilled at 105 °C and 2 mbar for 15 minutes, and then at 110 °C and 2 mbar for 45 minutes. Subsequently, the content of cyclic siloxanes and short linear siloxanes was determined using GC.

[0118] After distillation, the polyether siloxane A contained < 0.005 wt.-% cycles of D4, D5 and D6 each, as well as < 0.005 wt.-% of short linear siloxanes (sum of N2 to N6).

[0119] 3. Example A3: Purification by distillation of a polyether siloxane A without auxiliary substance (not according to the invention)

[0120] 150 g polyether siloxane A were placed into a 250 mL multi-necked flask equipped with a KPG-blade- stirrer, a distillation bridge, an inert gas inlet pipe, and temperature sensor. Initially, the polyether siloxane was distilled at 120 °C and 2 mbar for 30 minutes, and then at 125 °C and 2 mbar for 1 hour. Subsequently, the content of cyclic siloxanes and short linear siloxanes was determined using GC.

[0121] After distillation, the polyether siloxane A contained 0.018 wt.-% cycles (sum of D4, D5 and D6) as well as 0.068 wt.-% of short linear siloxanes (sum of N2 to N6) and 0.17 wt.-% N7.

[0122] 4. Example A4: Purification by distillation of a polyether siloxane A with auxiliary substance (according to the invention)

[0123] 150 g polyether siloxane A and 7.5 g dipropylene glycol were placed into a 250 mL multi-necked flask equipped with KPG-blade-stirrer, distillation bridge, inert gas inlet pipe, and temperature sensor. Initially, the polyether siloxane was distilled at 120 °C and 2 mbar for 30 minutes, and then at 125 °C and 2 mbar for 1 hour. Subsequently, the content of cyclic siloxanes and short linear siloxanes was determined using GC.

[0124] After distillation, the polyether siloxane A contained < 0.005 wt.-% D4, D5 and D6 each as well as < 0.005 wt.-% of short linear siloxanes (N2 to N6) and 0.05 wt.-% N7. IV. Example B: Distillation of a polyether siloxane B

[0125] Polyether siloxane B has the structure: wherein n = 3, m = 1 , a = 8, b = 0 and R = CH3.

[0126] Using GPC, the numerical average molar mass Mnand the weight average molar mass Mwof polyether siloxane B were determined as 1100 g / mol (Mn) und 1850 g / mol (Mw).

[0127] Prior to distillation, the polyether siloxane B contained 1 .4 wt.-% cycles (sum of D4, D5 and D6) as well as 5.56 wt.-% of short linear siloxanes (N2 to N6).

[0128] 1 . Example B1 : Purification by distillation of a polyether siloxane B without auxiliary substance (not according to the invention)

[0129] 150 g polyether siloxane B was placed into a 250 mL multi-necked flask equipped with KPG-blade-stirrer, distillation bridge, inert gas inlet pipe, and temperature sensor. Initially, the polyether siloxane was distilled at 105 °C and 2 mbar for 15 minutes, and then at 110 °C and 2 mbar for 45 minutes. Subsequently, the content of cyclic siloxanes and short linear siloxanes was determined using GC.

[0130] After distillation, the polyether siloxane B contained 0.01 wt.-% cycles (sum of D4, D5 and D6) as well as 1 .09 wt.-% of short linear siloxanes (N2 to N6). 2. Example B2: Purification by distillation of a polyether siloxane B with auxiliary substance (according to the invention)

[0131] 150 g polyether siloxane B and 7.5 g propylene glycol were placed into a 250 mL multi-necked flask equipped with KPG-blade-stirrer, distillation bridge, inert gas inlet pipe, and temperature sensor. Initially, the polyether siloxane was distilled at 105 °C and 2 mbar for 15 minutes, and then at 110 °C and 2 mbar for 45 minutes. Subsequently, the content of cyclic siloxanes and short linear siloxanes was determined using GC. After distillation, the polyether siloxane B contained < 0.005 wt.-% D4, D5 and D6 each as well as < 0.005 wt.-% of short linear siloxanes (N2 to N5, each) and 0.013 wt.-% of N6.

[0132]

[0133] Table 1 : Results of examples A to B2 (in examples A, A1 , A3, B, and B1 a sum parameter is given for the cycles (D4 to D6) and the short linear

[0134] 5 siloxanes (N2 to N6)).

Claims

Patent claims1 . A polyether siloxane comprising at least one siloxane block and at least one polyether block, characterized in that the polyether siloxane comprises not more than 0.5 wt.-% + / - 10%, preferably not more than 0.2 wt.-% + / - 10%, more preferably not more than 0.1 wt.-% + / - 10%, of at least one short, linear siloxane N2 to N6, where the short, linear siloxanes N2 to N6 are hexamethyldisiloxane (N2), octamethyltrisiloxane (N3), decamethyltetrasiloxane (N4), dodecamethylpentasiloxane (N5), and tetradecamethylhexasiloxane (N6).

2. The polyether siloxane according to claim 1 , wherein the polyether siloxane comprises not more than 0.05 wt.-% + / - 10% of at least one short, linear siloxane N2 to N6.

3. The polyether siloxane according to claim 1 or 2, wherein the polyether siloxane comprises not more than 0.5 wt.-% + / - 10%, preferably not more than 0.2 wt.-% + / - 10%, more preferably not more than 0.1 wt.-% + / - 10%, of all short, linear siloxanes N2 to N6.

4. The polyether siloxane according to any of claims 1 to 3, wherein the polyether siloxane comprises not more than not more than 0.05 wt.-% + / - 10%, of all short, linear siloxanes N2 to N6.

5. The polyether siloxane according to any of claims 1 to 4, wherein the polyether siloxane comprises not more than 0.005 wt.-% of each short, linear siloxane N2 to N6.

6. The polyether siloxane according to any of claims 1 to 5, wherein the polyether siloxane comprises not more than 0.02 wt.-% + / - 10% of all short, linear siloxanes N2 to N6.

7. The polyether siloxane according to any of claims 1 to 6, wherein the polyether siloxane comprises not more than 0.02 wt.-% of at least one siloxane D3 to D8, preferably D4 to D6, where D3 to D8 are hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), dodecamethylcyclohexasiloxane (D6), tetradecamethylcycloheptasiloxane (D7), hexadecamethylcyclooctasiloxane (D8).

8. The polyether siloxane according to any of claims 1 to 7, wherein the polyether siloxane comprises not more than 0.02 wt.-% of all siloxanes D3 to D8, preferably D4 to D6, with D3 to D8 defined as in claim 5.

9. The polyether siloxane according to any of claims 1 to 8, wherein the polyether siloxane comprises not more than 0.005 wt.-% of each cyclic siloxane D3 to D8, preferably D4 to D6, with D3 to D8 defined as in claim 5.

10. The polyether siloxane according to any of claims 1 to 9, wherein the polyether siloxane comprises not more than 0.015 wt.-% of all cyclic siloxanes D3 to D8, preferably D4 to D6, with D3 to D8 defined as in claim 5.11 . The polyether siloxane according to any of claims 1 to 10, wherein the at least one polyether block is connected to the at least one siloxane block through a SiC-bond.

12. The polyether siloxane according to any of claims 1 to 11 , wherein the polyether siloxane is a compound of the general Formula (1)Formula (1) whereR1= identical or different alkyl or aryl residues with 1 to 16 carbon atoms, preferably phenyl or methyl,R2= R1,R3= identical or different polyether residues, preferably polyether residues of the general formula A or B, in particular of the Formula A, n = 2 to 500, preferably 4 to 300, in particular 6 to 200, m = 0 to 40, preferably 0 to 25, in particular 1 to 20, with the proviso that when all R2are R1, then m > 1 , with-R4-O-(CH2CH2O)a-(CH2CH(CH3)O)b-(CH(CH3)CH2O)c-(CH2CH(R5)O)d-(CH(R5)CH2O)e-R6Formula A whereR4= a divalent hydrocarbon residue, preferably a -CH2-CH2-CH2- residue,R5= identical or different alkyl or aryl residues, optionally interrupted by ether groups, preferably ethyl or phenyl,R6= residues of the group comprising hydrogen, saturated or unsaturated hydrocarbon residues with 1 to 16 carbon atoms, and residues of the formula C, preferably hydrogen, methyl, butyl, or acetyl,Formula CR7= saturated or unsaturated hydrocarbon residues with 1 to 16 carbon atoms, a = 0 to 60, preferably 0 to 50, in particular 1 to 40, b = 0 to 60, preferably 0 to 50, in particular 1 to 40, c = 0 to 60, preferably 0 to 50, in particular 0, where a + b + c > 3, d = 0 to 25, preferably 0 to 10, in particular 0, e = 0 to 25, preferably 0 to 10, in particular 0, withFormula B where r = 0 to 15, preferably 1 to 10, in particular 1 to 5, s = 0 to 15, preferably 1 to 10, in particular 1 to 5.

13. The polyether siloxane according to any of claims 1 to 12, wherein the siloxane backbone is end-capped with trimethylsilyl groups.

14. A process for preparing the polyether siloxane according to the present invention, comprising the step of removing short, linear siloxanes N2 to N6 and / or cyclic siloxanes D3 to D8, preferably D4 to D6, from compositions comprising at least one polyether siloxaneand at least one short, linear siloxane N2 to N6 and / or at least one cyclic siloxane D3 to D8, preferably D4 to D6, by distillation, wherein the distillation takes place in the presence of at least one auxiliary substance selected from the group consisting of glycols, with N2 to N6 defined as in claim 1 and D3 to D8 defined as in claim 5.

15. A polyether siloxane obtained by the process according to claim 14.

16. A composition for use in the preparation of a polyurethane foam article, characterized in that it comprises the polyether siloxane according to any of claims 1 to 13 and / or the polyether siloxane according to claim 15.

17. Use of the polyether siloxane according to any of claims 1 to 13 and / or of the polyether siloxane according to claim 15 as a foam stabilizer in the preparation of a polyurethane foam article.

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