Recovery of polyols

Abstract

The invention relates to a method for reducing the content of 2, 6-diaminotoluene and / or 2, 4-diaminotoluene in a polyol, in particular in a recovered polyol, in which a polyol containing 2, 6-diaminotoluene and / or 2, 4-diaminotoluene is reacted with at least one compound selected from the group consisting of a), b) and c), in which the polyol containing 2, 6-diaminotoluene and / or 2, 4-diaminotoluene is reacted with at least one compound selected from the group consisting of a), b) and c), wherein: a) one or more epoxy-functional compounds, preferably dodecyl / tetradecyl glycidyl ethers, b) one or more anhydrides, in particular phthalic anhydrides, and c) one or more aldehydes, preferably benzaldehyde.

Description

[0001] The present invention relates to a method for reducing the content of 2,6-diaminotoluene and / or 2,4-diaminotoluene in a polyol containing 2,6-diaminotoluene and / or 2,4-diaminotoluene by reacting with a suitable compound as described in claim 1.

[0002] For example, when polyurethane and / or polyurethane-polyurea waste is chemically recycled or chemically depolymerized, a polyol containing 2,6-diaminotoluene and / or 2,4-diaminotoluene is obtained. In the context of the present invention, the abbreviation "PU" is also used for polyurethane.

[0003] Many methods for the physical utilization, in particular the depolymerization, of polyurethanes have been described in the literature and have been implemented in pilot-scale and production-scale plants. These are reactions in which the urethane bond is cleaved.

[0004] The most commonly used method is alcoholysis, in which the polyurethane is cleaved with a diol or a mixture of diols to give short-chain urethanes (see, for example, EP 0835901 A2, EP 0899292 A1, EP 0546415 A1, EP 0 771 644A2). Generally, the reaction mixture is reacted with a short-chain urethane which is reactive due to free hydroxyl groups, and then the polyurethane component which is usually cleaved off without further aftertreatment is reacted with an isocyanate component to give a polyurethane compound again. This gives a mixed polyurethane for new, usually lower-performance applications. This also changes the product composition of each recycling operation, which has complex effects on possible uses.

[0005] For example, glycolytic cleavage can be used when the individual components of the polyurethane to be cleaved, such as aromatic amines and polyether polyols, are not recycled.

[0006] Another method for cleaving polyurethanes taking this aspect into account is hydrolysis. The cleavage products formed in the reaction of the polyurethane with water and carbon dioxide are amine and polyether polyol components.

[0007] The advantage of this method is that the amine and polyether polyol components can be returned to polyurethane production, so that, if desired, the same isocyanate or a homogeneous polyurethane can be produced again.

[0008] The hydrolysis of polyurethanes is known from the literature (see, for example, US 4,035,314, US 4,316,992, US 3,441,616, WO2022042909A1, WO2022042910A1). After the reaction, the cleavage components can usually be separated and worked up. Preferably, water, solvents and the amines formed can be fractionated directly from the reaction mixture in a vacuum distillation. The water and solvents can generally be reused in the recovery process without further work-up steps. If desired, the amines can be purified further as required.

[0009] The recovered polyols usually cannot be completely freed of 2,6-diaminotoluene and / or 2,4-diaminotoluene by distillation. Depending on the distillation conditions, polyols, especially polyether polyols, are obtained with different contents of 2,6-diaminotoluene and / or 2,4-diaminotoluene.

[0010] The presence of these amines is critical, especially due to their toxicity and carcinogenicity.

[0011] Therefore, there is a general requirement to further reduce the content of 2,6-diaminotoluene and / or 2,4-diaminotoluene in the corresponding polyols containing 2,6-diaminotoluene and / or 2,4-diaminotoluene, such that preferably a TDA content of at least ≤ 0.03 wt% can be achieved, where the TDA content means the sum of 2,6-diaminotoluene and 2,4-diaminotoluene present.

[0012] In the context of the present invention, "TDA" means the total amount of 2,6-diaminotoluene and 2,4-diaminotoluene. In the context of the present invention, the "TDA content" means the sum of 2,6-diaminotoluene and 2,4-diaminotoluene present. A synonym for 2,6-diaminotoluene (CAS No. 823-40-5) is toluene-2,6-diamine. A synonym for 2,4-diaminotoluene (CAS No. 95-80-7) is toluene-2,4-diamine.

[0013] Thus, for example, if the "TDA polyol" of a polyol is ≤ 0.03 wt%, this means in the context of the present invention that in total 2,6-diaminotoluene and 2,4-diaminotoluene (meaning the sum of 2,6-diaminotoluene and 2,4-diaminotoluene present) can be present in the polyol in question at ≤ 0.03 wt%; the weight percentage here refers to the total amount of the polyol in question plus the 2,6-diaminotoluene and 2,4-diaminotoluene present therein.

[0014] Also included in the context of the present invention are the following possible situations: the polyol contains only 2,4-diaminotoluene but does not contain 2,6-diaminotoluene, or the polyol contains only 2,6-diaminotoluene but does not contain 2,4-diaminotoluene; preferably, 2,6-diaminotoluene and 2,4-diaminotoluene are present.

[0015] It has also been found that in the case of a relatively high TDA content, the presence of 2,6-diaminotoluene and / or 2,4-diaminotoluene can impair the reusability of polyols, especially polyether polyols, in the production of new PU foams, such that, for example, it is no longer possible to achieve the desired foam quality.

[0016] This can be offset in foam production, for example, by highly diluting with a commercially available polyol component.

[0017] In view of this background, the specific problem solved by the present invention is to provide means for reducing the levels of 2,6-diaminotoluene and / or 2,4-diaminotoluene in polyols containing 2,6-diaminotoluene and / or 2,4-diaminotoluene, such as recycled polyols, especially recycled polyether polyols.

[0018] In the context of the present invention, "polyol" is especially a polyether having two or more, preferably three or more isocyanate-reactive groups, especially OH groups, preferably a polyether polyol (i.e., a polyether having at least two hydroxyl groups reactive with isocyanate groups), preferably obtained by the depolymerization, especially hydrolysis, of polyurethanes.

[0019] "Recycled polyol" and "recycled polyether polyol" in the context of the present invention refer to polyols and polyether polyols obtained by the depolymerization, especially hydrolysis, of polyurethanes, especially PU foams. Most preferably, the recycled polyols are those obtainable, for example, according to the teachings of document WO2022042909A1 or document WO2022042910A1.

[0020] Document WO 2023 / 275033 A1 discloses a method for producing a PU foam by reacting (a) at least one polyol component containing recycled polyol with (b) at least one isocyanate component in the presence of: (c) one or more catalysts that catalyze the isocyanate-polyol and / or isocyanate-water reaction and / or isocyanate trimerization reaction, (d) at least one foam stabilizer, and (e) optionally one or more chemical or physical blowing agents, and the recycled polyol contains toluene 2,4-diamine, toluene 2,6-diamine, 2,2'-diaminodiphenylmethane, 2,4'-diaminodiphenylmethane, and / or 4,4'-diaminodiphenylmethane. In the examples of this document, a foam was prepared from a recycled polyol having a 2,4-diaminotoluene content of 0.00389% by weight.

[0021] Document DE 4215014 A1 discloses a method for reducing the amount of amine by-products in the production of polyols by alcoholysis of polyurethanes and / or polyureas, which uses a reagent that reacts with the by-products. The amine by-products include toluene diamine, and the reagent is an epoxy resin.

[0022] Document EP 1229071A1 discloses a method for removing amines from amine-containing polyols produced by the decomposition of polyurethanes. In the examples, the method involves a step in which a polyol containing toluene diamine is reacted with maleic anhydride at 120 °C, where maleic anhydride is present in an amine / anhydride ratio of 1.

[0023] Now it has surprisingly been found that, in the context of the present invention, the reaction with many suitable compounds as specifically defined in claim 1 can reduce the TDA content of polyols containing 2,6-diaminotoluene and / or 2,4-diaminotoluene as required, preferably even to a TDA content ≤ 0.03% by weight, where the TDA content refers to the sum of 2,6-diaminotoluene and 2,4-diaminotoluene present. It has also surprisingly been found that the polyols resulting from the present invention can also be successfully used in the production of PU foams.

[0024] The above object is achieved by the subject matter of the present invention. The present invention provides a method for reducing the content of 2,6-diaminotoluene and / or 2,4-diaminotoluene, preferably 2,6-diaminotoluene and 2,4-diaminotoluene, in polyols containing 2,6-diaminotoluene and / or 2,4-diaminotoluene, preferably 2,6-diaminotoluene and 2,4-diaminotoluene, wherein these polyols containing 2,6-diaminotoluene and / or 2,4-diaminotoluene, preferably 2,6-diaminotoluene and 2,4-diaminotoluene, are reacted with at least one compound selected from a), b), and c),

[0025] where a), b), and c) are defined as follows:

[0026] a) one or more epoxy-functional compounds selected from: 1-butene oxide, 1,2-epoxypentane, 1,2-epoxyhexane, 1-octene oxide, 1-dodecene oxide, 1,2-epoxytetradecane, cyclohexene oxide, styrene oxide

[0027] and glycidyl ethers of general formula (I):

[0028]

[0029] wherein R1 = phenyl, cyclohexyl, methylcyclohexyl, benzyl, isopropyl, hexadecyl, octyl / decyl (corresponding to C8-10 alkyl glycidyl ether in formula (I), CAS: 68609-96-1) or dodecyl / tetradecyl (corresponding to dodecyl / tetradecyl glycidyl ether in formula (I), CAS: 68609-97-2), more preferably octyl / decyl (corresponding to C8-10 alkyl glycidyl ether in formula (I), CAS: 68609-96-1) or dodecyl / tetradecyl (corresponding to dodecyl / tetradecyl glycidyl ether in formula (I), CAS: 68609-97-2), especially dodecyl / tetradecyl (corresponding to dodecyl / tetradecyl glycidyl ether in formula (I), CAS: 68609-97-2),

[0030] b) one or more acid anhydrides selected from: acetic anhydride, propionic anhydride, butyric anhydride, valeric anhydride, hexanoic anhydride, heptanoic anhydride, octanoic anhydride, adipic anhydride, maleic anhydride, dodecenyl succinic anhydride, trimellitic anhydride, pivalic anhydride, citraconic anhydride, itaconic anhydride, benzoic anhydride, glutaric anhydride, phthalic anhydride, isophthalic anhydride, terephthalic anhydride, cyclohexanoic anhydride, malonic anhydride, succinic anhydride, polymaleic anhydride, acid anhydrides based on adducts of maleic acid and styrene, dodecenyl succinic anhydride and acid anhydrides of maleic acid with any olefin, among which the following are particularly preferably used: acetic anhydride, dodecenyl succinic anhydride and / or phthalic anhydride, especially phthalic anhydride,

[0031] c) one or more aldehydes preferably selected from: valeraldehyde, n-hexanal, octanal, nonanal, decanal, citral, salicylaldehyde, benzaldehyde, cinnamaldehyde and anisaldehyde, particularly preferably benzaldehyde.

[0032] The method according to the invention makes it possible to reduce the content of 2,6-diaminotoluene and / or 2,4-diaminotoluene in a polyol containing 2,6-diaminotoluene and / or 2,4-diaminotoluene to a preferably TDA content ≤ 0.03% by weight, where the TDA content means the sum of 2,6-diaminotoluene and 2,4-diaminotoluene present. As has been further elucidated, this also includes the possibility that only one of the two diaminotoluenes is present, but preferably both are present.

[0033] Before applying the method according to the invention, the polyol containing 2,6-diaminotoluene and / or 2,4-diaminotoluene has a relatively high TDA content, for example in the range of not less than, preferably greater than 0.1% by weight to at most for example 5% by weight or at most for example 7% by weight or at most for example 3% by weight. Applying the method according to the invention then results in a reduction of the previously relatively high TDA content, in particular to a value ≤ 0.03% by weight. The possible lower limit of the TDA content after applying the method according to the invention can preferably be for example 0.0001% by weight, where the TDA content in each case means the sum of 2,6-diaminotoluene and 2,4-diaminotoluene. As has been further elucidated, this also includes the possibility that only one of the two mentioned diaminotoluenes is present; preferably, both are present.

[0034] The method according to the invention has excellent applicability for the purification of so-called recycled polyols, since these recycled polyols usually have a relatively high TDA content. The method according to the invention can simply reduce the relatively high TDA content of the recycled polyols, where the TDA content means the sum of 2,6-diaminotoluene and 2,4-diaminotoluene present.

[0035] In a preferred embodiment of the invention, the polyol containing 2,6-diaminotoluene and / or 2,4-diaminotoluene is a polyether polyol.

[0036] In a further preferred embodiment of the invention, the polyol containing 2,6-diaminotoluene and / or 2,4-diaminotoluene is those polyols which have been obtained by the depolymerization of polyurethanes, preferably PU foams, in particular by hydrolysis depolymerization, preferably polyether polyols.

[0037] In another preferred embodiment of the invention, the reaction according to the invention is carried out until the polyol has a TDA content ≤ 0.03% by weight, where the TDA content means the sum of 2,6-diaminotoluene and 2,4-diaminotoluene present. The weight percentage is here based on the total amount of the polyol under discussion plus the 2,6-diaminotoluene and 2,4-diaminotoluene present therein.

[0038] According to option a), the TDA content in the polyol containing 2,6-diaminotoluene and / or 2,4-diaminotoluene can be reduced as required by reacting with one or more epoxy-functional compounds as defined in claim 1 in a).

[0039] The reaction is preferably carried out at a temperature of 80 °C to 150 °C, preferably 120 °C to 140 °C. The usage amounts are preferably calculated such that the molar ratio of the epoxy-functional compound as defined in a) to the sum of the 2,6-diaminotoluene and 2,4-diaminotoluene present is from 5:1 to 2:1, preferably 4:1.

[0040] Optionally, a solvent such as propylene glycol and / or ethylene glycol etc. can be used for dilution; preferably no solvent is used.

[0041] To accelerate the reaction, a catalyst can preferably be optionally used. The optionally present catalyst used can preferably be a Lewis acid such as in particular zinc chloride, tin dichloride and / or iron(III) chloride, most preferably zinc chloride. Based on the total TDA, they can preferably be used in a total amount of 1 mol% to 20 mol%, preferably 8 mol% to 15 mol%, where the total TDA refers to the sum of the 2,6-diaminotoluene and 2,4-diaminotoluene present.

[0042] The reaction with the epoxide-functional compound preferably ends after two to eight hours, more preferably after three to seven hours, and particularly preferably after three to six hours.

[0043] To optionally remove the optionally present catalyst particles from the polyol, any known method for filtration or sedimentation can be used. The optional removal can preferably be carried out at a temperature of 10 °C to 100 °C, preferably at 20 °C to 80 °C. The optionally applied pressure difference can preferably be from 0.001 bar to 200 bar, more preferably from 0.1 bar to 100 bar, and particularly preferably from 0.1 bar to 25 bar, where the pressure difference used depends on the equipment used.

[0044] It has surprisingly been found that if desired, the content of 2,6-diaminotoluene and / or 2,4-diaminotoluene can be reduced to such an extent that a polyol, preferably a polyether polyol, with a TDA content of ≤ 0.03 wt% can be obtained, where the TDA content refers to the sum of the 2,6-diaminotoluene and 2,4-diaminotoluene present. The resulting polyol can be reused without difficulty as a polyol component for the production of polyurethanes, preferably PU foams, especially flexible PU foams.

[0045] In the case of option b), a polyol containing 2,6-diaminotoluene and / or 2,4-diaminotoluene, preferably a polyether polyol, is reacted with one or more acid anhydrides as defined in claim 1 under b), in particular phthalic anhydride, whereby a polyol, preferably a polyether polyol, with a reduced total TDA content, for example preferably ≤ 0.03 wt%, can be obtained, where the TDA content means the sum of 2,6-diaminotoluene and 2,4-diaminotoluene present.

[0046] The acid anhydrides used can preferably be acetic anhydride, propionic anhydride, butyric anhydride, valeric anhydride, hexanoic anhydride, heptanoic anhydride, octanoic anhydride, adipic anhydride, fumaric anhydride, dodecenyl succinic anhydride, trimellitic anhydride, pivalic anhydride, citraconic anhydride, itaconic anhydride, benzoic anhydride, glutaric anhydride, phthalic anhydride, isophthalic anhydride and / or terephthalic anhydride, cyclohexane carboxylic anhydride, malonic anhydride, succinic anhydride, polymaleic anhydride, acid anhydrides based on adducts of maleic acid and styrene, dodecenyl succinic anhydride and / or acid anhydrides of maleic acid and any olefin.

[0047] Particularly preferred are acetic anhydride, dodecenyl succinic anhydride and / or phthalic anhydride, particularly preferably phthalic anhydride.

[0048] The reaction is preferably carried out at a temperature of 80 °C to 150 °C, preferably 100 °C to 140 °C.

[0049] The amounts used are preferably calculated such that the molar ratio of total TDA to total acid anhydride is from 1:1 to 1:4, preferably from 1:1.2 to 1:2.5, where total TDA means the sum of 2,6-diaminotoluene and 2,4-diaminotoluene present.

[0050] If appropriate, a solvent capable of dissolving the acid anhydride in solid form can optionally be used; more preferably, no solvent is used.

[0051] The reaction with one or more acid anhydrides according to the invention preferably ends after two to eight hours, more preferably after two to seven hours, particularly preferably after two to five hours.

[0052] In order to optionally separate any precipitated reaction products or solid reactants from the polyol, any known filtration or sedimentation method can be used if required. The optional separation can preferably be carried out at a temperature of 10 °C to 100 °C, further preferably at 20 °C to 80 °C. The pressure difference optionally applied can preferably be from 0.001 bar to 200 bar, more preferably from 0.1 bar to 100 bar, particularly preferably from 0.1 bar to 25 bar, where the pressure difference used depends on the equipment used.

[0053] It has again been found that, in this way, surprisingly, if desired, the TDA content can be reduced to such an extent that polyols, preferably polyether polyols, with a TDA content of preferably ≤ 0.03% by weight can be obtained, where the TDA content is the sum of the 2,6-diaminotoluene and 2,4-diaminotoluene present. The resulting polyols can be reused without difficulty as the polyol component for the production of PU foams, especially flexible PU foams.

[0054] According to option c), the TDA content of the polyol can likewise be reduced as desired by reaction with aldehydes as defined in c) of claim 1, where the TDA content is the sum of the 2,6-diaminotoluene and 2,4-diaminotoluene present.

[0055] This reaction is preferably carried out at a temperature of 40 °C to 130 °C, preferably 50 °C to 120 °C, particularly preferably 50 °C to 100 °C.

[0056] The amounts used are preferably calculated such that the molar ratio of aldehyde to total TDA is 5:1 to 1:1, preferably 4:1 to 2:1, where the total TDA is the sum of the 2,6-diaminotoluene and 2,4-diaminotoluene present.

[0057] Optionally, solvents such as propylene glycol and / or ethylene glycol etc. can be used for dilution; preferably no solvent is used. The reaction preferably ends after one to eight hours, more preferably after two to seven hours, particularly preferably after two to five hours.

[0058] The aldehyde used can be one or more aldehydes, which are preferably selected from: valeraldehyde, n-hexanal, octanal, nonanal, decanal, citral, salicylaldehyde, benzaldehyde, cinnamaldehyde and anisaldehyde, particularly preferably benzaldehyde.

[0059] It has again been found that, in this way, surprisingly, if desired, the TDA content can be reduced to such an extent that polyols, preferably polyether polyols, with a TDA content of preferably ≤ 0.03% by weight can be obtained, where the TDA content is the sum of the 2,6-diaminotoluene and 2,4-diaminotoluene present. The resulting polyols can be reused without difficulty as the polyol component for the production of PU foams, especially flexible PU foams.

[0060] The present invention also provides polyols, preferably polyether polyols, especially those as described in any one of claims 1 - 8, obtained by the method of the present invention, whose TDA content is preferably ≤ 0.03% by weight, where the TDA content is the sum of the 2,6-diaminotoluene and 2,4-diaminotoluene present. The weight percentage is based here on the total amount of the polyol in question plus the 2,6-diaminotoluene and 2,4-diaminotoluene present therein. The preferred lower limit of the TDA content can be, for example, 0.0001% by weight.

[0061] The present invention also provides a process for preparing polyurethanes, preferably PU foams, by reacting polyisocyanates with polyols by using the polyols obtained according to the present invention, in particular the polyols according to claim 9.

[0062] Based on the total amount of polyol used, the polyol obtained according to the present invention can preferably be used in an amount of at least 25% by weight, preferably at least 50% by weight, more preferably at least 75% by weight, especially even 100% by weight.

[0063] The production of polyurethanes (=PU) or PU foams has long been known to those skilled in the art and is described in detail in the technical literature.

[0064] Various different polyurethanes can generally be prepared by reacting polyisocyanates known to those skilled in the art, preferably diisocyanates such as 4,4'-methylenebis(phenyl isocyanate) or toluene-2,4-diisocyanate, with polyols such as preferably polyether polyols and / or polyester polyols. Polyether polyols can be prepared, for example, by alkoxylation of polyhydroxy-functional initiators. Commonly used initiators are, for example, diols, glycerol, trimethylolpropane, pentaerythritol, sorbitol or sucrose. As already mentioned, polyether polyols can also be obtained by depolymerization of polyurethanes. In the production of polyurethane foams, optionally present blowing agents can be used, examples being pentane, dichloromethane, acetone or carbon dioxide. If desired, the chemical blowing agent used can optionally be water. All of this is known to those skilled in the art. Typically, in the production of polyurethane foams, surface-active substances, especially silicone surfactants, can also optionally be used to achieve stabilization. In the preparation of polyurethanes, catalysts can optionally be used. Examples of catalysts that can be used include certain amines or organotin compounds.

[0065] Suitable polyisocyanates, polyols, optionally present blowing agents, optionally present catalysts, optionally present surface-active substances and / or other optionally present additives for the preparation of polyurethanes are known to those skilled in the art and are described in detail in the literature. In the context of the present invention, the term "polyurethane" also encompasses polyurethane-polyureas. Polyurethane foams can be used in a variety of different fields due to their excellent mechanical and physical properties. A variety of different types of PU foams (=polyurethane foams) are known, for example including soft PU foams, rigid PU foams, integral PU foams and other PU foams having properties intermediate between these classifications.

[0066] More specific details on the production of PUs, especially PU foams, can be found in "The Polyurethanes Book" by J. Wiley, 1st edition, 2002 and "Kunststoff-Handbuch" [Plastics Handbook], volume VII, Carl Hanser Verlag, 3rd edition, Munich 1993. The preparation methods of PU foams are also described by the examples in the examples section.

[0067] The present invention also provides polyurethanes, preferably PU foams, obtainable by the above methods.

[0068] The present invention further provides the use of at least one compound selected from a), b) and c) as defined in claim 1 respectively for reducing the TDA content in polyols containing 2,6-diaminotoluene and / or 2,4-diaminotoluene, preferably polyether polyols containing 2,6-diaminotoluene and / or 2,4-diaminotoluene, especially those polyols obtained by the depolymerization of polyurethanes, especially PU foams, where the TDA content refers to the sum of 2,6-diaminotoluene and 2,4-diaminotoluene present. For the sake of avoiding repetition, reference is made to the above description in this regard.

[0069] The present invention further provides a method for preparing one or more polyols, preferably polyether polyols, by the depolymerization of polyurethanes, preferably by hydrolysis, where after depolymerization, one or more post-treatment steps are carried out on the reaction mixture from the depolymerization to separate one or more polyols from the reaction mixture, preferably including at least one distillation step and / or extraction step, where the separated polyols are reacted with at least one compound selected from a), b) and c) as defined in claim 1 respectively, where the reaction is preferably carried out until the polyol has a TDA content of ≤0.03 wt%, where the TDA content refers to the sum of 2,6-diaminotoluene and 2,4-diaminotoluene present. The weight percentage is based here on the total amount of the polyol under discussion plus the 2,6-diaminotoluene and 2,4-diaminotoluene present therein. The preferred lower limit of the TDA content can be, for example, 0.0001 wt%. Examples

[0070] Chemicals used:

[0071] 2,6-Diaminotoluene (≥97%), zinc chloride (≥98%, anhydrous), phthalic anhydride (≥99%) and benzaldehyde (≥99%) were purchased from Sigma-Aldrich. Dodecyl / tetradecyl glycidyl ether ( RD 24) was purchased from ipoxchemicals GmbH. The polyol 1104 was purchased from Covestro.

[0072] The contents of 2,4- and 2,6-diaminotoluene were determined by HPLC:

[0073] 2,4- and 2,6-diaminotoluene were determined by reversed-phase HPLC / DAD. For this purpose, an appropriate amount of the sample was weighed out and made up to the mark in a standard flask with a solution of 50 mM (NH4)ClO4 in aqueous solution (pH 9.25) and acetonitrile (8:2 v / v).

[0074] For quantification, 2,4- and 2,6-diaminotoluene (purity > 97%) were weighed out as a reference and mixed with a water / acetonitrile mixture (1:1 v / v) such that the concentration of diaminotoluene was 0.013 mg / ml. This stock solution was used to prepare calibration solutions. For this purpose, an appropriate amount of the stock solution was transferred to a standard flask and made up to the mark with a solution of 50 mM (NH4)ClO4 in aqueous solution (pH 9.25) and acetonitrile (8:2 v / v). The concentration range of the calibration solutions was from 0.004 μg / ml to 13.0 μg / ml.

[0075] Aliquots of the solution were analyzed under the following conditions:

[0076] Column: Luna C18(2) 4.6 mm × 250 mm / 5.0 μm, Phenomenex

[0077] Eluent: A: Water

[0078] B: 50 mM (NH4)ClO4 pH: 9.25, in water

[0079] C: Acetonitrile

[0080] Injection volume: 25.0 μl

[0081] Temperature: 30 °C

[0082] Detector: Diode array detector (DAD), 220 nm

[0083] Gradient:

[0084]

[0085]

[0086] Total: 50 min

[0087] Under the above conditions, 2,4-diaminotoluene was eluted at about 12.0 min and 2,6-diaminotoluene was eluted at about 17.2 min.

[0088] Example A:

[0089] Example A1: Preparation of a Polyol Containing 2,6-Diaminotoluene

[0090] Under an argon atmosphere and with constant stirring, 1400 g The initial feed of 1104 and 11.29 g of 2,6-diaminotoluene was heated to 100 °C in a multi-necked flask equipped with a precision glass paddle stirrer, a reflux condenser, an inert gas inlet, and a temperature sensor. After two hours, a clear light brown solution was obtained. The 2,6-diaminotoluene content determined by HPLC was 0.79 wt%.

[0091] Example A2: Preparation of a Polyol Containing 2,6-Diaminotoluene

[0092] Under an argon atmosphere and with constant stirring, 1400 g The initial feed of 1104 and 11.29 g of 2,6-diaminotoluene was heated to 100 °C in a multi-necked flask equipped with a precision glass paddle stirrer, a reflux condenser, an inert gas inlet, and a temperature sensor. After two hours, a clear light brown solution was obtained. The 2,6-diaminotoluene content determined by HPLC was 0.2 wt%.

[0093] Example B

[0094] Example B1: Preparation of a Low-2,6-Diaminotoluene Polyol by Reaction with Dodecyl / Tetradecyl Glycidyl Ether (Inventive)

[0095] Under an argon atmosphere at 130 °C, the initial feed of 300 g of the polyol from Example A1 (containing 19.6 mmol of 2,6-diaminotoluene), 21.95 g of dodecyl / tetradecyl glycidyl ether (78.4 mmol), and 0.267 g of ZnCl2 (10 mol%, based on 2,6-diaminotoluene) was stirred in a multi-necked flask equipped with a precision glass paddle stirrer, a reflux condenser, an inert gas inlet, and a temperature sensor. After a reaction time of six hours, a turbid solution was obtained. It was cooled to 80 °C and filtered while warm (Seitz K300 filter). The resulting product was a light yellow polyol solution with a 2,6-diaminotoluene content of 0.0004 wt% (determined by HPLC).

[0096] Example B2: Preparation of a Low-2,6-Diaminotoluene Polyol by Reaction with Phthalic Anhydride (Inventive)

[0097] Under an argon atmosphere, at 135 °C, an initial feed of 30 g of the polyol from Example A1 (containing 1.96 mmol of 2,6-diaminotoluene) and 435 mg of phthalic anhydride (3.92 mmol) was stirred in a multi-necked flask equipped with a precision glass paddle stirrer, a reflux condenser, an inert gas feed, and a temperature sensor. After a reaction time of five hours, a turbid solution was obtained. It was cooled to room temperature and filtered through a Seitz K300 filter. The resulting product was a light yellow polyol solution containing 0.0115 wt% of 2,6-diaminotoluene (determined by HPLC).

[0098] Example B3: Preparation of low-2,6-diaminotoluene polyol by reaction with benzaldehyde (invention)

[0099] Under an argon atmosphere, at 60 °C, an initial feed of 25 g of the polyol from Example A1 (containing 1.63 mmol of 2,6-diaminotoluene) and 0.7 g of benzaldehyde was stirred in a multi-necked flask equipped with a precision glass paddle stirrer, a reflux condenser, an inert gas feed, and a temperature sensor. After a reaction time of three hours, a clear light brown solution was obtained. The polyol contained 0.028 wt% of 2,6-diaminotoluene (determined by HPLC).

[0100] Production of flexible PU foam:

[0101] To test the polyols with respect to their foaming properties and their influence on the physical foam properties, the following formulations were used to produce flexible PU foams. For example, 1.0 part (1.0 pphp) of a component here means 1 g of this substance per 100 g of polyol.

[0102] Table 1: Formulations for the production of flexible PU foams

[0103]

[0104]

[0105] 1) Polyol: Standard The 1104 polyether polyol is available from Covestro. This is a glycerol-based polyether polyol with a hydroxyl value of 56 mg KOH / g and an average molar mass of 3000 g / mol, or the polyol obtained from Example A2, B1, or B3.

[0106] 2) T9, available from Evonik Industries: Tin(II) salt of 2-ethylhexanoic acid.

[0107] 3) DMEA: Dimethylethanolamine, available from Evonik Industries. An amine catalyst used in the preparation of polyurethane foams.

[0108] 4) Polyether-modified polysiloxane, available from Evonik Industries.

[0109] 5) T 80 Toluene diisocyanate (80% 2,4 isomer, 20% 2,6 isomer), from Covestro, viscosity 3 mPa·s, 48% NCO, functionality 2.

[0110] 6) EF, a metal-free catalyst with no emissions, available from Evonik Industries. Tin (II) salt of ricinoleic acid.

[0111] 7) ZE1: An amine catalyst (with a low emission value), available from Evonik Industries.

[0112] 8) Polyether-modified polysiloxane (with a cyclic siloxane content of <0.03%), available from Evonik Industries.

[0113] General process for the production of flexible PU foams

[0114] Polyurethane foams were prepared manually as hand foams in the laboratory. Foams were prepared at an air pressure of 22 °C and 762 mmHg. Polyurethane foams according to Formulations 1 and 2 were prepared using 150 g and 300 g of polyol, respectively. Other formulation components were adjusted accordingly. For example, 1.0 part (1.0 pphp) of a component means 1 gram of the substance per 100 grams of polyol.

[0115] For the foams according to Formulation 1 or 2, first, a tin catalyst (tin(II) 2-ethylhexanoate or tin(II) ricinoleate), a polyol, water, an amine catalyst, and the corresponding foam stabilizer are charged into a paper cup, and the contents are mixed with a disk stirrer at 1000 rpm for 60 s. After the first stirring, isocyanate is added and the mixture is mixed with the same stirrer at 2500 rpm for 7 s, and then the reaction is immediately transferred to a paper-lined box (for the foam prepared from 300 g of polyol: base area 30 cm × 30 cm and height 30 cm, for the foam made from 150 g of polyol: base area 18 cm × 18 cm, height 18 cm). After pouring the foam, it rises in the foaming box. Ideally, the foam breaks when it reaches its maximum rise height and then settles slightly. This opens the cell membranes of the foam bubbles and an open-cell structure of the foam is obtained.

[0116] These properties are evaluated by determining the characteristic parameters described in the following sections.

[0117] Characterization of the Prepared PU Foams

[0118] The prepared foams are evaluated based on the following physical properties:

[0119] a) Settlement ( = fallback) of the foam at the end of the rise phase:

[0120] The settlement or further rise is calculated from the difference in foam height immediately after rupture and 3 minutes after the foam rupture. The foam height is measured at the maximum value at the center of the top of the foam with the aid of a needle fixed to a centimeter scale. A positive value here describes the settlement of the foam after rupture; a negative value correspondingly describes the further rise of the foam.

[0121] b) Foam height

[0122] This is the height of the freely rising foam formed after 3 minutes. The foam height is reported in centimeters (cm).

[0123] c) Rise time

[0124] The time period between the end of the mixing of the reaction components and the rupture of the polyurethane foam. The rise time is reported in seconds (s).

[0125] d) Porosity

[0126] The air permeability of the foam is determined by dynamic pressure measurement of the foam based on DIN EN ISO 4638:1993-07. The measured dynamic pressure is reported in mm water column, and a lower dynamic pressure value characterizes a more open foam. The measurement values are in the range of 0 to 300 mm water column. The dynamic pressure is measured by a device comprising a nitrogen source, a pressure reducing valve with a manometer, a flow regulating screw, a wash bottle, a flow meter, a T-piece, an applicator nozzle, and a graduated glass tube filled with water. The edge length of the applicator nozzle is 100×100 mm, the weight is 800 g, the inner diameter at the outlet opening is 5 mm, the inner diameter at the lower applicator ring is 20 mm, and the outer diameter at the lower applicator ring is 30 mm.

[0127] The measurement is carried out by setting the nitrogen inlet pressure to 1 bar and the flow rate to 480 l / h by adjusting the pressure reducing valve. Set the amount of water in the graduated glass tube so that no pressure difference is formed and no pressure difference is read out. For a foam made of 300 g of polyol, a specimen with dimensions of 250×250×50 mm is measured, or for a foam prepared from 150 g of polyol, a specimen with dimensions of 150×150×50 mm is measured. The applicator nozzle is applied to the corner of the specimen, flush with the edge, and applied once to the (estimated) center of the specimen (in each case on the side with the largest surface area). The result is read out when a constant dynamic pressure is established. The evaluation is based on the calculated average value of the five measurement values obtained.

[0128] e) Cell count

[0129] The cell count is the number of cells per cm: This is visually determined on the cut surface (measured according to DIN EN 15702:2009-04).

[0130] f) Hardness CLD 40% according to DIN EN ISO 3386-1:1997+A1:2010, the measurement values are reported in kilopascals (kPa).

[0131] g) Tensile strength and elongation at break, according to DIN EN ISO 1798:2008-04, the measurement values of the tensile strength are reported in kilopascals (kPa), and the measurement values of the elongation at break are reported in percentage (%).

[0132] h) Resilience, according to DIN EN ISO 8307:2008-03, the measurement values are reported in percentage (%).

[0133] Table 2: Foaming results of soft PU foams prepared with 150 g of polyol, according to formulation 1 of Table 1, using the inventive polyol from Example B1 and the non-inventive polyol from Example A2, and a conventional polyol 1104

[0134]

[0135] Table 2 compares the properties of foams prepared using the polyol of the present invention from Example B1 and the non-inventive polyol from Example A2 with those of foams prepared with 1104. The inventive polyol from Example B1 contains 0.0004 wt% of 2,6-diaminotoluene, and the non-inventive polyol from Example A2 contains 0.2 wt% of 2,6-diaminotoluene. Only the PU foam prepared with 1104 was used as a reference. Comparison of the properties of Foams #1, #2, and #3 shows that the foam obtained with the inventive polyol (#2) from Example B1 is comparable to the reference Foam #1 prepared with 1104. The reaction with the foam of the non-inventive polyol from Example A2 (#3) starts earlier and more violently, making it impossible to control the reaction. When stirred into the isocyanate, foaming had already started, so that the mixture could not be completely transferred to the box. The foam did not finally break. Therefore, the conventional parameters reported in Table 2 could not be recorded or determined. This result clearly shows that a higher TDA content has a strong effect on foaming and may thus make the process scheme quite complex or interrupted.

[0136] Table 3: Foaming results of flexible PU foams prepared with 150 g of polyol, according to Formulation 2 of Table 1, using the inventive polyol from Example B3 and the non-inventive polyol from Example A2, and a conventional polyol 1104

[0137]

[0138] Table 3 compares the properties of foams prepared using the polyol of the present invention from Example B3 and the non-inventive polyol from Example A2 with those of foams prepared with 1104. The inventive polyol from Example B3 contains 0.028 wt% of 2,6-diaminotoluene, and the non-inventive polyol from Example A2 contains 0.2 wt% of 2,6-diaminotoluene. Only the PU foam prepared with 1104 was used as a reference. Comparison of the properties of Foams #1, #2, and #3 shows that the foam obtained with the inventive polyol (#2) from Example B3 is comparable to the reference foam prepared with The reference foam #1 prepared in 1104 has similar properties and is a comparable foam. The reaction of the foam with the non-invention polyol from Example A2 (#3) starts earlier and more violently, making it impossible to control the reaction. When the isocyanate is stirred in, the foam has already started to form, making it impossible to completely transfer the mixture into the box. The foam did not finally break. Therefore, the conventional parameters reported in Table 3 could not be recorded or determined. This result clearly shows that a higher TDA content has a strong effect on foaming and may thus make the process scheme quite complex or interrupted.

Claims

1. A method for reducing the content of 2,6-diaminotoluene and / or 2,4-diaminotoluene in a polyol containing 2,6-diaminotoluene and / or 2,4-diaminotoluene, characterized in that, React these polyols with at least one compound selected from a), b) and c), where a), b) and c) are defined as follows: a) One or more epoxy-functional compounds selected from: 1-epoxybutane, 1,2-epoxypentane, 1,2-epoxyhexane, 1-epoxyoctane, 1-epoxydodecane, 1,2-epoxytetradecane, cyclohexene oxide, styrene oxide and glycidyl ethers of the general formula (I): where R1 = phenyl, cyclohexyl, methylcyclohexyl, benzyl, isopropyl, octyl / decyl or dodecyl / tetradecyl, preferably octyl / decyl or dodecyl / tetradecyl, especially dodecyl / tetradecyl, b) One or more acid anhydrides selected from: acetic anhydride, propionic anhydride, butyric anhydride, valeric anhydride, hexanoic anhydride, heptanoic anhydride, octanoic anhydride, adipic anhydride, fumaric anhydride, dodecenyl succinic anhydride, trimellitic anhydride, pivalic anhydride, citraconic anhydride, itaconic anhydride, benzoic anhydride, glutaric anhydride, phthalic anhydride, isophthalic anhydride, terephthalic anhydride, cyclohexane carboxylic anhydride, malonic anhydride, succinic anhydride, polymaleic anhydride, acid anhydrides based on adducts of maleic acid and styrene, dodecenyl succinic anhydride and acid anhydrides of maleic acid with any olefin, among which the following are particularly preferably used: acetic anhydride, dodecenyl succinic anhydride and / or phthalic anhydride, especially phthalic anhydride, and c) One or more aldehydes preferably selected from: valeraldehyde, n-hexanal, octanal, nonanal, decanal, citral, salicylaldehyde, benzaldehyde, cinnamaldehyde and anisaldehyde, particularly preferably benzaldehyde.

2. The method according to claim 1, characterized in that, The polyol containing 2,6-diaminotoluene and / or 2,4-diaminotoluene is a polyether polyol.

3. The method according to claim 1 or 2, characterized in that, The polyol containing 2,6-diaminotoluene and / or 2,4-diaminotoluene is those polyols that have been obtained by the depolymerization of polyurethanes, preferably PU foams, especially by hydrolysis depolymerization, preferably polyether polyols.

4. The method according to any one of claims 1 to 3, characterized in that, Carry out the reaction until the polyol has a TDA content of ≤0.03 wt%, where the TDA content refers to the sum of 2,6-diaminotoluene and 2,4-diaminotoluene present.

5. The method according to any one of claims 1 to 4, characterized in that Carry out the reaction using one or more epoxy-functional compounds as described in a) of claim 1, where the reaction is carried out at a temperature of 80 °C to 150 °C, preferably 120 °C to 140 °C, and where the total amount of all epoxy-functional compounds used as described in a) of claim 1 is calculated such that the molar ratio of these epoxy-functional compounds to the total TDA is preferably 5:1 to 2:1, more preferably 4:1, where the total TDA refers to the sum of 2,6-diaminotoluene and 2,4-diaminotoluene present, and where the reaction is carried out for a period of preferably two to eight hours, more preferably three to seven hours, especially three to six hours.

6. The method according to claim 5, wherein Additionally use at least one catalyst, which is preferably one or more Lewis acids, especially zinc chloride, stannous dichloride and / or ferric trichloride, which is preferably used in a total amount of 1 mol% to 20 mol%, preferably 8 mol% to 15 mol%, based on the sum of 2,6-diaminotoluene and 2,4-diaminotoluene present.

7. The method according to any one of claims 1 to 4, characterized in that, The reaction is carried out using one or more acid anhydrides as described in b) of claim 1, in particular phthalic anhydride, wherein the reaction is carried out at a temperature of 80 °C to 150 °C, preferably 100 °C to 140 °C, and wherein the total amount of all acid anhydrides used as in b) of claim 1 is calculated such that the molar ratio of total TDA to the total acid anhydrides used as in b) of claim 1 is preferably 1:1 to 1:4, preferably 1:1.2 to 1:2.5, wherein total TDA refers to the sum of 2,6-diaminotoluene and 2,4-diaminotoluene present, and wherein the reaction is carried out for a period of preferably two to eight hours, more preferably two to seven hours, especially two to five hours.

8. The method according to any one of claims 1 to 4, characterized in that, The reaction is carried out using one or more aldehydes as described in c) of claim 1, in particular benzaldehyde, and wherein the reaction is carried out at a temperature of 40 °C to 130 °C, preferably 50 °C to 120 °C, particularly preferably 50 °C to 100 °C, and wherein the amount used is calculated such that the molar ratio of the aldehydes as described in c) of claim 1 to total TDA is preferably 5:1 to 1:1, more preferably 4:1 to 3:1, wherein total TDA refers to the sum of 2,6-diaminotoluene and 2,4-diaminotoluene present, and wherein the reaction is carried out for a period of preferably one to eight hours, more preferably two to seven hours, especially two to five hours.

9. A polyol, preferably a polyether polyol, obtained by the method according to any one of claims 1 to 8, having a TDA content of ≤ 0.03% by weight, wherein the preferred lower limit of the TDA content is 0.0001% by weight, and wherein the TDA content refers to the sum of 2,6-diaminotoluene and 2,4-diaminotoluene present.

10. A method for preparing polyurethane, preferably PU foam, by reacting polyisocyanate with polyol, characterized in that, The method is carried out using the polyol according to claim 9.

11. A polyurethane, preferably a PU foam, obtainable according to claim 10.

12. Use of at least one compound selected from a), b) and c) as defined in claim 1 respectively for reducing the TDA content in a polyol containing 2,6-diaminotoluene and / or 2,4-diaminotoluene, preferably a polyether polyol containing 2,6-diaminotoluene and / or 2,4-diaminotoluene, especially those polyols obtained by the depolymerization of a polyurethane, especially a PU foam, wherein the TDA content refers to the sum of 2,6-diaminotoluene and 2,4-diaminotoluene present.

13. A process for preparing one or more polyols, preferably polyether polyols, by depolymerization of a polyurethane, preferably by hydrolysis, wherein after depolymerization the reaction mixture resulting from the depolymerization is subjected to one or more post-treatment steps to separate one or more polyols from the reaction mixture, preferably including at least one distillation step and / or extraction step, characterized in that, React the separated polyol with at least one compound selected from a), b) and c) as defined in claim 1 respectively.

14. The method according to claim 13, characterized in that, Carry out the reaction until the TDA content of the polyol is ≤ 0.03% by weight, wherein the preferred lower limit of the TDA content is 0.0001% by weight, and wherein the TDA content refers to the sum of 2,6-diaminotoluene and 2,4-diaminotoluene present.

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