Liquid mixture of propoxylated p-toluidine

Abstract

The present invention relates to mixtures of propoxylated 4-toluidines containing two or more different di- or tri- or higher propoxylated p-toluidines in specific weight ratios, to processes for their preparation and to their use as polymerization or cure accelerators or as hardener components in epoxy resins.

Description

Technical Field

[0001] This invention relates to mixtures of propoxylated 4-toluidine (p-toluidine) comprising two or more different dipropoxylated or tripropoxylated or higher propoxylated p-toluidines in a specific ratio, to methods of their preparation, and to their use as polymerization accelerators, curing accelerators, or as curing agent components for epoxy resins. Background Technology

[0002] Crosslinked polymers can be produced through free radical polymerization. This, for example, involves the use of unsaturated polyesters. The polymerization process is also known as curing. Polymerization is initiated by a so-called curing agent for this group of polymers. These are typically free radical initiators, such as peroxides. The most well-known and widely used curing agent is dibenzoyl peroxide. This also often involves the use of polymerization accelerators, which promote the polymerization process and have a favorable effect on the curing process and / or product properties of the polymer. Some polymerization accelerators can advantageously become part of the polymer through other functional groups. Tertiary amines in the form of N,N-disubstituted toluidines are an important group of such polymerization accelerators (for reasons including their low volatility and more favorable toxicological characteristics), particularly the group of ethoxylated and propoxylated toluidines.

[0003] The single compound N,N-bis(2-hydroxypropyl)-p-toluidine [N,N-bis(2-hydroxypropyl)-4-toluidine, N,N-dipropoxy-p-toluidine, 1,1'-(p-toluimido)diprop-2-ol, CAS RN38668-48-3; diisopropanol-p-toluidine, N,N-bis(2-hydroxypropyl)-p-toluidine], i.e., "dipropoxylated" p-toluidine, is known. To date, its higher homologues have only been disclosed generally.

[0004] RU 2063960 A describes ethoxylated p-toluidine, and specifically its preparation at 80 ± 5 °C, without the addition of solvent or catalyst, from 4-toluidine and 3 to 4 mol / mol of ethylene oxide. This provides a liquid mixture of ethoxylated 4-toluidine, the composition of which is not further described. From the chemical yield, it can be inferred that the average degree of ethoxylation (the number of ethylene oxide units per 4-toluidine molecule) is between 2 and 2.5. The distribution of individual homologues is unknown.

[0005] EP 1650184 A1 describes a homologue of N,N-bis(2-hydroxyalkyl)-p-toluidine containing less than 0.2% by weight of alkoxylated 3-toluidine based on alkoxylated 4-toluidine. Specifically, it discloses the preparation of 4-toluidine containing less than 0.2% by weight of 3-toluidine and 2.2 to 5 mol, preferably 2.3 to 4 mol, more preferably 2.3 to 3.5 mol, and particularly 2.5 to 2.6 mol of epoxide / mol of 4-toluidine.

[0006] For example, 4-toluidine containing less than 0.2% 3-toluidine by weight and 2.5 mol ethylene oxide / mol of 4-toluidine, reacted at 120 °C without solvent or catalyst, provides ethoxylated 4-toluidine that no longer contains any 4-toluidine (detection limit: 100 ppm), and constitutes a mixture of <0.1% N-hydroxyethyl-4-toluidine, 50.1% N,N-bis(hydroxyethyl)-4-toluidine and 43.7% N-ethoxy-N-(hydroxyethyloxyethylidene)-4-toluidine, 5.4% tetraethoxy-4-toluidine, 0.7% pentaethoxy-4-toluidine and trace amounts of hexaethoxy-4-toluidine.

[0007] Based on the reaction of 4-toluidine containing less than 0.2% by weight of 3-toluidine with 2.58 mol / mol of ethylene oxide, at 120 °C without solvent addition and using 30% sodium methoxide solution as a catalyst, ethoxylated 4-toluidine is provided, constituting 47.4% N,N-bis(hydroxyethyl)-4-toluidine, 43.4% N-ethoxy-N-(hydroxyethylethoxy)-4-toluidine, and trace amounts of compounds with higher ethoxylation. The document contains descriptions of other examples, but the distribution of homologues is not known.

[0008] Since the reaction of 4-toluidine with ethylene oxide is almost quantitative, at least when a catalyst is used, the average degree of ethoxylation (the sum of m and n in general formula (I) in the document) can be estimated from the chemical mass yield to be close to the molar ratio between ethylene oxide and 4-toluidine.

[0009] N,N-Bis(hydroxyethyl)-4-toluidine (CAS RN 3077-12-1) is marketed by LANXESS Deutschland GmbH / Saltigo GmbH as a black to yellow / brown liquid or cured product, used as a curing agent component for epoxy resins.

[0010] Also sold by Lanxess Germany GmbH / Cyto is "over-ethoxylated N,N-bis(hydroxyethyl)-4-toluidine", which contains less than 0.2% by weight of ethoxylated 3-toluidine, named Accelerator PT25E / 2. It is a colorless to pale yellowish-brown viscous liquid used as a curing agent component of epoxy resins.

[0011] CN 101200432 A discloses simpler N,N-bis(hydroxypropyl)aniline and its higher homologues. These are obtained by reacting N,N-bis(hydroxypropyl)aniline at a temperature of 145 to 165 °C in the presence of catalysts such as alkali metal hydroxides or mixed metal cyanides, and in the presence of 3 to 3.6 mol ethylene oxide / mol aniline.

[0012] N,N-bis(2-hydroxypropyl)-p-toluidine (CAS RN 38668-48-3) is known and marketed by suppliers such as Lanxess GmbH / Cetor GmbH as a pale yellow curing melt used as a curing agent component in epoxy resins.

[0013] Depending on the application and epoxy resin system, experience suggests that ethoxylated aniline, ethoxylated toluidine, or N,N-bis(2-hydroxypropyl)-p-toluidine are more advantageous. However, a disadvantage of N,N-bis(2-hydroxypropyl)-p-toluidine is that it exists as a solidified melt at room temperature, therefore it must be melted by heating the container containing the product before use. Various isomers of N,N-bis(2-hydroxypropyl)-p-toluidine have been found to have different melting points. This results in lower-melting-point isomers accumulating in the liquid phase during partial melting of the product, and the melting point of the remaining solid increases further after the liquefied portion is removed. In this respect, this phenomenon constitutes "unintentional melt refining." To avoid this, N,N-bis(2-hydroxypropyl)-p-toluidine must be heated to a temperature significantly higher than, for example, N,N-bis(hydroxyethyl)-p-toluidine, which constitutes a performance disadvantage. Because the middle carbon atom in the propylene oxide used as a reactant is asymmetric, and because two R- or S-propylene oxide molecules react with one 4-toluidine molecule, N,N-bis(2-hydroxypropyl)-p-toluidine takes the form of a mixture of different isomers, such as RR, SS, or meso. Furthermore, the epoxy ring of 4-toluidine can be attacked and opened at the major CH2 end group or the middle CH group.

[0014] A. Zoltanski et al., Current Applied Polymer Science, 2018, 2(2), 89-93, The Structure of Propoxylated p-Toluidine, Used as a Polymerization Accelerator or in Unsaturated Polyester Resin Curing, elucidated the different structures formed by the reaction of 4-toluidine with two racemic propylene oxide molecules.

[0015] Internal analysis of different melt fractions of N,N-bis(2-hydroxypropyl)-p-toluidine revealed that, for example, the optically inactive meso isomer melts at higher temperatures than the optically active isomer. This implies a technical disadvantage for N,N-bis(2-hydroxypropyl)-p-toluidine, which presents itself as a complex mixture in the form of a solidified melt, meaning it can only be introduced into industrial applications as a homogeneous mixture of single components in a complex manner. Summary of the Invention

[0016] Therefore, the technical problem to be solved is to provide a propoxylated form of 4-toluidine that does not have the disadvantages of N,N-bis(2-hydroxypropyl)-p-toluidine, but at least can be used or better used as a polymerization accelerator or as a curing accelerator or as a curing agent component of epoxy resins in polymer systems, wherein N,N-bis(2-hydroxypropyl)-p-toluidine can be used.

[0017] This objective is unexpectedly achieved by providing a mixture of two or more different compounds containing general formula (I).

[0018]

[0019] Where R 1 It is either hydrogen or methyl, but the R on the directly adjacent carbon atom 1 The groups do not all represent hydrogen or methyl groups, and m and n represent integers, characterized in that,

[0020] 4-Toluidine is present in the mixture at a proportion of not more than 2% by weight, preferably from 0.001% to 1% by weight, based on the total mass of all compounds of formula (I) in the mixture, and

[0021] The compounds of formula (I), where the total number of m and n is an integer 2, are present in the mixture at a proportion of no more than 20% by weight, preferably from 0.01% to 20% by weight, and more preferably from 0.01% to 12% by weight, based on the total mass of all compounds of formula (I).

[0022] The compound of formula (I), wherein the total number of m and n is at least an integer 6, is present in the mixture in a proportion of not more than 40% by weight, preferably from 0.01% to 40% by weight, and more preferably from 0.01% to 20% by weight, based on the total mass of all compounds of formula (I).

[0023] The present invention therefore provides mixtures of the present invention comprising two or more different compounds of formula (I). The phrase "comprising two or more different compounds" excludes compounds containing only one homologue, such as N,N-bis(2-hydroxypropyl)-p-toluidine or N,N-bis(2-hydroxypropyloxypropylene)-p-toluidine. Compounds of formula (I) wherein the total number of m and n is the same are homologues of N,N-bis(2-hydroxypropyl)-p-toluidine for the total number of m and n. Therefore, homologues refer to compounds of formula (I) with different total numbers of propylene oxide units.

[0024] The corresponding distribution of propoxylation can be determined, for example, by GC-MS. The weight percentage can even be determined by gas chromatography by calibrating the GC assessment using a calibrating substance.

[0025] Preferably, the mixture of the present invention contains, by weight, a compound of formula (I) in which the total number of m and n is an integer 3, at a ratio of 7% to 49% and particularly preferably 15% to 49% by weight of all compounds of formula (I) based on the total mass of all compounds of formula (I).

[0026] Also preferably, the mixture of the present invention contains, by weight, a compound of formula (I) in which the total mass of all compounds of formula (I) is 10% to 49%, more preferably 10% to 40% by weight, of the mixture.

[0027] In another preferred embodiment, in the mixture of the present invention, each homologue group of compounds of formula (I) is present in the mixture at a weight percentage of less than 50% based on the total mass of all compounds of formula (I) in the mixture. A homologue group of compounds of formula (I) refers to any group of compounds having the same total m and n but which may differ in the combination of m and n. For example, a homologue group of compounds having a total m and n = 4 includes compounds having...

[0028] ·m=0 and n=4 or m=4 and n=0,

[0029] ·m=1 and n=3 or m=3 and n=1 and

[0030] ·m=n=2

[0031] And a single isomer of the compound having the above m and n values.

[0032] The advantage of this is that mixtures of substances are classified as polymers under the chemical laws of a particular region or country, and therefore are subject to different conditions as individual substances under chemical laws.

[0033] In another preferred embodiment, the mixture of the present invention contains less than 0.1% by weight of 4-toluidine based on the total mass of all compounds of formula (I) in the mixture.

[0034] The mixtures of the present invention, as well as the compounds of formula (I), may also contain other components. These may be catalysts, water, or residues of other propylene oxide polymerization products. The total weight percentage of all compounds of formula (I) and the weight percentage of other components shall add up to 100% by weight. Typically, the mixtures of the present invention contain from 96% to 100% by weight of compounds of formula (I).

[0035] The mixtures of the present invention are typically in a liquid state at room temperature and / or at temperatures between 5 and 40°C. Furthermore, the mixtures of the present invention preferably do not contain any solid components. The mixtures of the present invention are preferably not suspensions. Therefore, the mixtures of the present invention can preferably be treated as homogeneous liquids at ambient temperature. This has the advantage that the mixtures of the present invention, when used as polymerization accelerators, curing accelerators, or hardener components, can be easily removed from the container in a precise amount and with a stable and defined composition in a liquid state, and can be used in applications with precise amounts and a stable and defined composition. According to the present invention, the mixtures are in a liquid state when they have a dynamic viscosity of 0.1 to 20000 mPas (millipascal-seconds) at 25°C.

[0036] Dynamic viscosity can be measured by various methods, such as by capillary or rotational viscometer. Unless otherwise specified, dynamic viscosity is measured at a specified temperature using a rotational viscometer according to the principle of the cone-plate measurement system (see DIN 53019-2, Chapter 10.3). The mixtures of the present invention preferably have a dynamic viscosity of 500 to 20000 mPas at 25°C, as measured using a rotational viscometer according to DIN 53019.

[0037] The mixture of the present invention is a product directly produced by the production process of the present invention.

[0038] Therefore, the present invention also provides a mixture of the present invention that can be obtained by the method of the present invention.

[0039] The mixtures of the present invention can be surprisingly produced by a simple and stable method. Given that the detection limit by gas chromatography is 100 ppm, it is preferably no longer possible to detect any unconverted 4-toluidine in the mixtures of the present invention. This is very important because nitrogen-unalkylated toluidine is classified as a serious hemotoxic and carcinogenic substance.

[0040] The method for preparing mixtures according to the present invention includes using a compound of formula (I), wherein R 1 It is either hydrogen or methyl, but the R on the directly adjacent carbon atom 1 The groups do not all represent hydrogen or methyl, and where m and n are integers 1 (N,N-dipropoxy-p-toluidine), reacted in the presence of a catalyst with 1.0 to 4.0 mol, preferably 1.25 to 2.50 mol, of propylene oxide (1,2-propylene oxide) per mole of 4-toluidine.

[0041] N,N-dipropoxy-p-toluidine (i.e., the compound of formula (I)) used as a reactant in the method of the present invention, wherein R 1 It is either hydrogen or methyl, but the R on the directly adjacent carbon atom 1 The groups do not all represent hydrogen or methyl, and m and n are integers. 1) can be commercially available products, or reactants obtained separately through internal production followed by separation, or reactants obtained through internal production without separate separation. In the latter case, the reactants are generated in a reaction vessel in which the method of the present invention is carried out.

[0042] The method of the present invention is preferably carried out at a temperature of 80 to 150°C, more preferably 100 to 150°C. Lower temperatures may lead to incomplete conversion and, in any case, result in an uneconomical long reaction time, which, if the propylene oxide metering rate is not adjusted, can lead to considerable pressure buildup in the reactor and thus dangerous pressure buildup. In contrast, higher temperatures—especially those above the limiting temperature T of N,N-dipropoxy-p-toluidine at 150°C—are more suitable. exo (According to TRAS410) - This can lead to uncontrolled exothermic decomposition and pressure buildup.

[0043] In the method of the present invention, the catalyst used is preferably an alkali metal and alkaline earth metal hydroxide, an alkali metal and alkaline earth metal carbonate, an alkali metal, an alkyl lithium, sodium hydride, a complex hydride such as lithium aluminum hydride, sodium bis(methoxyethoxy)dihydrogen hydride, or an alkali metal alkali ... 1 It is either hydrogen or methyl, but the R on the directly adjacent carbon atom 1The groups do not all represent hydrogen or methyl, and m and n are integers 1 (N,N-dipropoxy-p-toluidine). The method of the present invention preferably uses 0.01 to 0.05 mol, more preferably 0.02 to 0.035 mol of catalyst.

[0044] The N,N-dipropoxy-p-toluidine reactant, i.e., the compound of formula (I), wherein R 1 It is either hydrogen or methyl, but the R on the directly adjacent carbon atom 1 The groups do not all represent hydrogen or methyl, and m and n are integers 1. For example, the method of the present invention can be provided by reacting 4-toluidine with 1.8 to 2.2 mol, preferably 1.9 to 2.1 mol of propylene oxide per mole of 4-toluidine without a catalyst at a temperature of 80 to 150 °C, preferably from 100 to 150 °C, more preferably from 110 to 150 °C.

[0045] This means that the method of the present invention for preparing the mixture of the present invention also includes providing reactants (i.e., compounds of formula (I)) without a catalyst, wherein R 1 It is either hydrogen or methyl, but the R on the directly adjacent carbon atom 1 In the case where the groups do not all represent hydrogen or methyl, and where m and n are integers (1), 4-toluidine is reacted with 1.8 to 2.2 mol, preferably 1.9 to 2.1 mol of propylene oxide per mole of 4-toluidine at a temperature of 80 to 150 °C, preferably 100 to 150 °C, more preferably 110 to 150 °C. The reactants are then reacted with 1.0 to 4.0 mol, preferably 1.25 to 2.50 mol of propylene oxide per mole of 4-toluidine in the presence of a catalyst.

[0046] The method of the present invention is generally carried out in such a manner that, before the reaction begins, the component to be propoxylated (i.e., 4-toluidine or N,N-dipropoxy-p-toluidine) is selected to be in liquid form at a certain temperature. The reactor is then inertized with an inert gas (e.g., nitrogen), and subsequently the internal pressure is reduced to approximately 50 to 700 hectopascals (hPa). In the propoxylation of N,N-dipropoxy-p-toluidine according to the present invention, the catalyst is preferably added before the reactor is shut down. The catalyst of the present invention is preferably added in solid form, for example, in the form of flakes, pellets, or powder. It can also be used as an aqueous solution, in which case the water can be distilled off before further reaction, or this removal of water can be omitted.

[0047] Preferably, any propylene oxide remaining in the reactor after the reaction of 4-toluidine or N,N-dipropoxy-p-toluidine is vented using an inert gas.

[0048] Typically, the reaction of 4-toluidine or N,N-dipropoxy-p-toluidine with propylene oxide is carried out in a closed, pressure-sealed reactor (e.g., an autoclave). During the reaction, starting from a pre-established pressure, pressure typically increases in the range of 400 hPa to 2000 hPa. The absolute pressure in the reactor typically does not exceed 0.3 MPa. However, these pressures may be significantly exceeded when gaseous propylene oxide is completely added to the 4-toluidine or N,N-dipropoxy-p-toluidine component to be propoxylated in the reactor before or after reaching the reaction temperature, or when it is metered into the reactor too rapidly before or after reaching the reaction temperature. For safety reasons, both of these situations should be avoided in practice. Typically, propylene oxide is metered into the reaction mixture formed from the 4-toluidine or N,N-dipropoxy-p-toluidine component to be propoxylated and the propylene oxide component such that the pressure does not exceed approximately 0.2 MPa.

[0049] Propylene oxide is typically used in a commercially available racemic form with a purity of at least 99%. In the method of the present invention, a single enantiomer, i.e., R- and / or S-propylene oxide or any desired mixture thereof, may also be used.

[0050] In this invention, the reaction of N,N-dipropoxy-p-toluidine with propylene oxide is always carried out using a catalyst. In contrast, the propoxylation of 4-toluidine to N,N-dipropoxy-p-toluidine is carried out without a catalyst.

[0051] The method of the present invention is preferably carried out in the absence of solvents.

[0052] In a preferred embodiment of the method of the present invention, the N,N-dipropoxy-p-toluidine reactant is provided by reacting with 4-toluidine having a proportion of 3-toluidine of no more than 0.5% by weight based on 4-toluidine. In an alternative preferred embodiment of the method of the present invention, the N,N-dipropoxy-p-toluidine reactant is provided by reacting with 4-toluidine having a proportion of 3-toluidine of no more than 0.2% by weight based on 4-toluidine.

[0053] In order to obtain specific, especially pure, 4-toluidine with a limited 3-toluidine content, it is necessary to remove 3-toluidine from industrial-grade 4-toluidine by distillation, since the boiling points of the two isomers are close to each other (boiling point of 4-toluidine: 200.5℃; boiling point of 3-toluidine: 203.4℃).

[0054] Another method for preparing 4-toluidine with a maximum 3-toluidine content of 0.2% by weight is recrystallization of industrial-grade N-acetyl-4-toluidine, followed by hydrolysis and distillation. 4-Toluidine with a 3-toluidine content of less than 0.2% by weight is preferably prepared by first nitrifying toluene, and then, by very effectively optimizing the reflux ratio, distilling away the two unwanted 2-nitrotoluene and 3-nitrotoluene isomers from the resulting mixture of 2-nitrotoluene, 3-nitrotoluene, and 4-nitrotoluene isomers to obtain the desired purity. The resulting 4-nitrotoluene is then hydrogenated to form 4-toluidine of the desired purity. In this way, even 4-toluidine with a 3-toluidine content of less than 0.2% by weight, preferably less than 0.1% by weight, can be provided in industrial quantities.

[0055] The mixtures of the present invention cannot be prepared in one step starting from 4-toluidine because the required total amount of propylene oxide and catalyst, or the required total amount of propylene oxide in the absence of a catalyst, is added to the initial feed of 4-toluidine. In this case, unwanted byproducts may form to varying degrees and / or the 4-toluidine used may be incompletely converted.

[0056] In carrying out preferred embodiments of the method of the present invention, it is crucial to observe narrow limitations on parameters relating to the molar ratio between propylene oxide and 4-toluidine and / or the catalyst and 4-toluidine and / or the reaction temperature, in order to achieve the desired narrow distribution of a single homologue of propoxylated 4-toluidine of formula (I). Because these parameters interact, all of the above-described limits of the parameters, or combinations of all of the following limits, can be associated with other parameters (e.g., stoichiometric rate, mixing of the liquid reaction phase of 4-toluidine, stoichiometric catalyst, and gaseous propylene oxide) and may produce, in some cases, non-inventory mixtures of propoxylated 4-toluidine. However, those skilled in the art will be able to determine, without particular difficulty, a suitable combination of parameters within the above-described ranges to obtain the mixtures of the present invention by adjusting these parameters according to the experimental setup or reactor size.

[0057] The yield of propoxylation in this invention is almost quantitative and is limited only by operational losses, such as the case of transferring the residue adhering to the reactor wall. After propoxylation, it has been found useful to cool the reaction mixture to a temperature in the range of 60 to 100°C and pass nitrogen through the reaction mixture for a period of time to completely remove any present propylene oxide from the system.

[0058] The reaction mixture can be prepared by methods known to those skilled in the art or used directly.

[0059] Using propylene oxide as a propoxylating agent has advantages over other reagents (such as 1-chloropropan-2-ol, 1-bromopropan-2-ol, or 1-iodopropan-2-ol), namely, it eliminates the need for auxiliary reagents (such as a stoichiometric amount of base as a hydrogen halide scavenger) and correspondingly avoids the formation of salts that must be removed in a separate step. Another disadvantage of using halopropanols is, for example, corrosion of the metal equipment used.

[0060] The present invention further provides the use of the mixtures of the invention as polymerization or curing accelerators, preferably in the polymerization of polyesters, particularly unsaturated polyesters, or as a curing agent component in epoxy resins. It has been found useful to use the mixtures of the invention in amounts of 0.1% to 5% by weight. Polymerization using the mixtures of the invention is preferably free radical polymerization.

[0061] In polymerization systems (where N,N-dipropoxy-p-toluidine is known to be advantageously used compared to ethoxylated or other alkylated 4-toluidines), the mixtures of the present invention have improved operation and / or better processability and / or lower required dosage and / or higher reactivity. In the free radical polymerization of polyesters, particularly unsaturated polyesters, or as a curing agent component of epoxy resins, replacing N,N-dipropoxy-p-toluidine, which is known to exist in solid melt form, with the liquid mixtures of the present invention can advantageously affect the physicochemical and / or physicomechanical properties of the polymers produced therewith.

[0062] In alternative embodiments, the mixtures of the present invention containing a small proportion of propoxylated 3-toluidine are characterized by their particularly advantageous use as polymerization or curing accelerators in the production of colorless polymers, as their use does not cause any discoloration of the polymer. This can be very important, depending on the desired use of the polymer, and may not be achievable with all the polymerization and curing accelerators of the prior art.

[0063] The present invention also provides polymer products obtained by polymerization, preferably the polymerization of polyesters, particularly unsaturated polyesters, in the presence of the mixture of the present invention as a polymerization or curing accelerator or as a curing agent component of an epoxy resin. Polymerization using the mixture of the present invention is preferably free radical polymerization. Detailed Implementation

[0064] Examples:

[0065] Examples 1a to 1e: Production of propoxylated toluidines starting from N,N-dipropoxy-p-toluidine Example 1a

[0066] A 3-liter autoclave (stainless steel) equipped with a stirrer, internal thermometer, immersion inlet tube for propylene oxide, and riser for removal was initially charged with 1425 g of molten 98% N,N-dipropoxy-p-toluidine [a compound of formula (I), where m and n are each integers 1; 6.25 mol] and 10.9 g of approximately 90% potassium hydroxide flakes (0.175 mol). The autoclave was shut off, inertized by injecting nitrogen, and the pressure was reduced and evacuated to approximately 670 hPa (absolute pressure). The contents were heated to >80°C to substantially melt the N,N-dipropoxy-p-toluidine. The melt was then heated to the desired reaction temperature (120°C). At this temperature, the envisioned propylene oxide (690.1 g = 11.88 mol, equivalent to 1.9 molar equivalents based on N,N-dipropoxy-p-toluidine, i.e., a total of 3.9 molar equivalents based on 4-toluene) was metered at a rate of approximately 163 g / h, reaching a pressure of 0.18 MPa (absolute pressure) within a short time. In other instances, this pressure was typically not exceeded. Approximately 90 minutes after the metered addition, the total pressure dropped to approximately 800 hPa and was then held constant for approximately 15 minutes. The mixture was then stirred at the reaction temperature for another 60 minutes, cooled to 40°C, and the pressure was reduced by nitrogen compensation. Any remaining propylene oxide was purged with nitrogen, and the mixture was partitioned through a clarifying filter. 2109.3 g (yield: 99.2% of the amount used) of product was obtained, having the following distribution (by weight percentage) of the homologues of formula (I):

[0067]

[0068] Examples 1b through 1e were carried out in a similar manner—if applicable, in a 0.5 L autoclave. Examples 1b through 1e were not the quantities envisioned in Example 1a, but were carried out using the data specified in Table 1.

[0069] Table 1: Reaction data for Examples 1b to 1e

[0070]

[0071] 1) 1 mol%: Based on 0.01 mol base of 1 mol N,N-dipropoxy-p-toluidine used

[0072] 2) x moleq.: Based on x mol propylene oxide used in 1 mol N,N-dipropoxy-p-toluidine.

[0073] Examples 2a to 2e: Production of propoxylated toluidines starting from 4-toluidine

[0074] Example 2a

[0075] A 3-liter autoclave (stainless steel) equipped with a stirrer, internal thermometer, immersion inlet tube for propylene oxide, and riser for removal was initially charged with 672.1 g of molten 99.7% 4-toluidine (6.25 mol). The autoclave was shut off, inertized by injecting nitrogen, and the pressure was reduced and evacuated to approximately 670 hPa (absolute). The contents were heated to >45°C, initially without stirring, to allow the 4-toluidine to completely melt. The melt was then further heated to the desired reaction temperature (120°C). At this temperature, 726.4 g of propylene oxide (12.49 mol) was metered at approximately 163 g / h without a catalyst, reaching a maximum pressure of 0.27 MPa (absolute) within a short time. In other instances, this pressure was typically not exceeded. Approximately 3.5 h after the metered addition was completed, the total pressure dropped to approximately 770 hPa and was then held constant for approximately 15 minutes. The mixture was then stirred for another 60 minutes at the reaction temperature, and then cooled to 80 to 100°C under reduced pressure using nitrogen. Sampling was then performed to verify whether the typical composition of N,N-dipropoxy-p-toluidine had been achieved.

[0076] Subsequently, approximately 90% potassium hydroxide (based on 2.8 mol% of 4-toluidine used) in solid form was added, and the autoclave was shut off again, inertized as described above, evacuated, and heated to the desired reaction temperature of 120 °C. Then, an additional 690.1 g (11.88 mol) of propylene oxide was metered at approximately 163 g·h, and a pressure increase of approximately 760 hPa to approximately 0.143 MPa (absolute) was observed at the end. Approximately 50 minutes after the metered addition, the total pressure dropped to the original pressure of 670 hPa. The mixture was then stirred at the reaction temperature for another 60 minutes, cooled to 40 °C, and the pressure was reduced by nitrogen compensation. Any remaining propylene oxide was purged with nitrogen, and the mixture was partitioned through a clarifying filter. 2087.4 g (yield: 99.4% of the amount used) of product was obtained, which had the following distribution (by weight percentage) of the homologues of formula (I):

[0077]

[0078] Examples 2b through 2e were carried out in a similar manner—if applicable, in a 0.5L autoclave. Examples 2b through 2e were not the quantities envisioned in Example 2a, but were carried out using the data specified in Table 2.

[0079] Table 2: Reaction data for Examples 2b to 2e

[0080]

[0081]

[0082] 1)1 mol%: Based on 0.01 mol base of 1 mol 4-toluidine used.

[0083] 2) x moleq.: Based on x mol of propylene oxide used in 1 mol of 4-toluidine.

Claims

1. A method for preparing a mixture comprising two or more different compounds of general formula (I), Where R 1 It is either hydrogen or methyl, but the R on the directly adjacent carbon atom 1 The groups do not all represent hydrogen or methyl groups, and m and n represent integers, characterized in that, 4-Toluidine is present in the mixture at a proportion not exceeding 2% by weight, based on the total mass of all compounds of formula (I). Furthermore, the total number of m and n is an integer of 2, and the compounds of formula (I) are present in the mixture at a proportion not exceeding 20% ​​by weight based on the total mass of all compounds of formula (I). Furthermore, the total number of m and n is an integer of 3, and the compounds of formula (I) are present in the mixture in proportions of 7% to 49% by weight based on the total mass of all compounds of formula (I). Furthermore, the total number of m and n is an integer of 4, and the compounds of formula (I) are present in the mixture in proportions of 10% to 49% by weight based on the total mass of all compounds of formula (I). Furthermore, the total number of m and n is at least an integer of 6, and the compounds of formula (I) are present in the mixture in a proportion not exceeding 40% by weight based on the total mass of all compounds of formula (I). The method includes: a) Prepare a compound of formula (I), wherein R 1 It is either hydrogen or methyl, but the R on the directly adjacent carbon atom is... 1 The groups do not all represent hydrogen or methyl, and m and n are integers 1. The preparation of the compound of formula (I) is carried out by reacting 4-toluidine with 1.8 to 2.2 mol of propylene oxide per mole of 4-toluidine at a temperature of 80 to 150 °C without a catalyst. b) React the compound of formula (I) with 1.25 to 4.0 mol of propylene oxide per mole of 4-toluidine in the presence of a catalyst, wherein R 1 It is either hydrogen or methyl, but the R on the directly adjacent carbon atom is... 1 The groups are not all hydrogen or methyl, and m and n are integers 1. The catalyst is selected from: alkali metal and alkaline earth metal hydroxides, alkali metal and alkaline earth metal carbonates, alkali metals, alkyl lithium, sodium hydride, complex hydrides or alkali metal alkoxides.

2. The method according to claim 1, characterized in that, Each homologue of the compounds of formula (I) is present in the mixture at a weight percentage of less than 50% based on the total mass of all compounds of formula (I) in the mixture.

3. The method according to claim 1 or 2, characterized in that, The mixture comprising two or more different compounds of general formula (I) contains less than 0.1% by weight of 4-toluidine based on the total mass of all compounds of formula (I) in the mixture.

4. The method according to claim 1 or 2, characterized in that, The mixture of two or more different compounds containing general formula (I) is in a liquid state at a temperature of 5 to 40°C.

5. The method according to claim 1 or 2, characterized in that, The mixture of two or more different compounds containing general formula (I) has a dynamic viscosity of 500 to 20,000 mPas at 25°C, as measured by a rotational viscometer according to DIN 53019.

6. The method according to claim 1 or 2, characterized in that, The mixture of two or more different compounds comprising general formula (I) contains 96% to 100% by weight of the compound of formula (I).

7. The method according to claim 1, wherein, In step b), the reaction is carried out at a temperature of 80 to 150°C.

8. The method according to claim 1, wherein, In step b), the reaction is carried out in the presence of 0.01 to 0.05 mol catalyst / molar of compound of formula (I) used, in which R 1 It is either hydrogen or methyl, but the R on the directly adjacent carbon atom 1 The groups do not all represent hydrogen or methyl groups, and m and n are integers of 1.

9. The method according to any one of claims 1, 7, and 8, characterized in that, The reaction was carried out in the absence of a solvent.

10. The method according to any one of claims 1, 7, and 8, wherein, The 4-toluidine contains 3-toluidine in a proportion of no more than 0.2% by weight of 4-toluidine.

11. The method according to any one of claims 1, 7, and 8, wherein, The catalyst is selected from lithium aluminum hydride and sodium bis(methoxyethoxy)aluminum hydride.

12. The method according to any one of claims 1, 7, and 8, wherein, The catalyst is selected from sodium hydroxide and potassium hydroxide.

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