Liquid mixtures of propoxylated para-toluidines

Abstract

To provide a propoxylated 4-toluidine that does not have the disadvantage of N,N-bis(2-hydroxypropyl)-p-toluidine, but can be used at least just as well or better as a polymerization accelerator or as a vulcanization accelerator or as a hardener component for epoxy resins in the polymer systems in which N,N-bis(2-hydroxypropyl)-p-toluidine can be used.SOLUTION: The invention relates to mixtures of propoxylated 4-toluidines containing two or more different di- or tri-propoxylated or higher propoxylated p-toluidines in specific weight ratios, to methods for preparing them and to their use as polymerization accelerators or vulcanization accelerators or as hardener components in epoxy resins.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to mixtures of propoxylated 4-toluidines (para-toluidines) containing two or more different di- or tri-propoxylated or more highly propoxylated p-toluidines in specific ratios, to processes for their preparation, and to their use as polymerization accelerators or as vulcanization accelerators or as hardener components for epoxy resins. [Background technology]

[0002] Crosslinked polymers can be produced by free radical polymerization. This includes, for example, the use of unsaturated polyesters. The polymerization process is also called curing. The polymerization is initiated by what are called curing agents for this group of polymers. They are generally free radical initiators, such as peroxides. The best known and most widely used curing agent is dibenzoyl peroxide. This also includes the use of polymerization accelerators that accelerate the polymerization process and have a beneficial effect on the curing process and / or the properties of the polymer product. Some polymerization accelerators are advantageously incorporated into the polymer via additional functional groups. Tertiary amines in the form of N,N-disubstituted toluidines are an important group of such polymerization accelerators, because of their low volatility, especially in the group of ethoxylated and propoxylated toluidines, and also because of their favorable toxicological profile.

[0003] Individual compounds such as N,N-bis(2-hydroxypropyl)-p-toluidine [N,N-bis(2-hydroxypropyl)-4-toluidine, N,N-dipropoxy-p-toluidine, 1,1'-(p-tolylimino)dipropan-2-ol, CAS RN 38668-48-3; diisopropanol-p-toluidine, N,N-di(2-hydroxypropyl)-p-toluidine], i.e. "dipropoxylated" para-toluidine, are known. Their higher homologues have so far only been disclosed in general terms.

[0004] In (Patent Document 1) ethoxylated p-toluidines and a specific preparation method from 4-toluidine and 3-4 moles of ethylene oxide per mole of 4-toluidine at 80±5°C without the addition of solvent and without the addition of catalyst are described. This gives a liquid mixture of ethoxylated 4-toluidines, but no further description of its composition is given. From the chemical yield it can be deduced that the average degree of ethoxylation (number of ethylene oxide units per molecule of 4-toluidine) is between 2 and 2.5. There is no information about the distribution of the individual homologs.

[0005] Patent Document 2 describes the general homologues of N,N-bis(2-hydroxyalkyl)-p-toluidines, which contain less than 0.2% by weight of alkoxylated 3-toluidine, based on the alkoxylated 4-toluidine. Specifically disclosed is a process for their preparation from 4-toluidines containing less than 0.2% by weight of 3-toluidine and 2.2 to 5 moles, preferably 2.3 to 4 moles, more preferably 2.3 to 3.5 moles, especially 2.5 to 2.6 moles of alkylene oxide per mole of 4-toluidine.

[0006] For example, when 4-toluidine containing less than 0.2% by weight of 3-toluidine, based on 4-toluidine, was reacted with 2.5 moles of ethylene oxide per mole of 4-toluidine used at 120° C. without the addition of solvent and without the addition of catalyst, an ethoxylated 4-toluidine was obtained which no longer contained 4-toluidine (detection limit: 100 ppm), but which consisted of a mixture of less than 0.1% N-hydroxyethyl-4-toluidine, 50.1% N,N-bis(hydroxyethyl)-4-toluidine, and 43.7% N-oxyethyl-N-(hydroxyethyloxyethylene)-4-toluidine, 5.4% tetraoxyethyl-4-toluidine, 0.7% pentaoxyethyl-4-toluidine, and traces of hexaoxyethyl-4-toluidine.

[0007] When 4-toluidine containing less than 0.2% by weight of 3-toluidine based on 4-toluidine is reacted with 2.58 moles of ethylene oxide per mole of 4-toluidine used without the addition of solvent and using 30% sodium methoxide solution as catalyst at 120°C, an ethoxylated 4-toluidine is obtained, which is composed of 47.4% N,N-bis(hydroxyethyl)-4-toluidine, 43.4% N-oxyethyl-N-(hydroxyethyloxyethyl)-4-toluidine, and a mixture of traces of more highly ethoxylated compounds. The document also contains further examples, but does not describe the distribution of homologues in them.

[0008] Since the reaction of 4-toluidine with ethylene oxide proceeds practically quantitatively, at least when a catalyst is used, it can be inferred, based on chemical mass balance, that the average degree of ethoxylation (the sum of m and n in general formula (I) in this document) is close to the molar ratio between ethylene oxide and 4-toluidine.

[0009] N,N-bis(hydroxyethyl)-4-toluidine (CAS RN 3077-12-1) is commercially available from LANXESS Deutschland GmbH / Saltigo GmbH as a black to tan liquid or solid product for use as a hardener component for epoxy resins.

[0010] Similarly, "over-ethoxylated N,N-bis(hydroxyethyl)-4-toluidine" containing less than 0.2% by weight of ethoxylated 3-toluidine, a colorless to light yellow-brown viscous liquid for use as a hardener component for epoxy resins, is also commercially available under the name Accelerator PT25E / 2 from LANXESS Deutschland GmbH / Saltigo GmbH.

[0011] Patent document 3 discloses the simpler N,N-bis(hydroxypropyl)aniline and its higher homologues, which are obtained by reacting N,N-bis(hydroxypropyl)aniline in the presence of 3-3.6 moles of ethylene oxide per mole of aniline used, in the presence of a catalyst such as an alkali metal hydroxide or mixed metal cyanide, at a temperature of 145-165°C.

[0012] N,N-Bis(2-hydroxypropyl)-p-toluidine (CAS RN 38668-48-3) is known and is sold by suppliers such as LANXESS Deutschland GmbH / Saltigo GmbH as a pale yellow solidified melt for use as a hardener component for epoxy resins.

[0013] In the field of use of epoxy resin systems, experience has shown that ethoxylated aniline, ethoxylated toluidine or N,N-bis(2-hydroxypropyl)-p-toluidine are advantageous. However, N,N-bis(2-hydroxypropyl)-p-toluidine has the disadvantage that at room temperature it is in the form of a solidified melt, so that N,N-bis(2-hydroxypropyl)-p-toluidine must be melted before use by heating the container containing the product. It has been discovered that the various isomers of N,N-bis(2-hydroxypropyl)-p-toluidine have different melting points. The effect of this is as follows: when the product is partially melted, the isomers with the lower melting point collect in the liquid phase, and after removing the already liquefied fraction, the melting point of the remaining solid is higher. In this respect, the phenomenon is a kind of "unintended melt refining method". To avoid this phenomenon, N,N-bis(2-hydroxypropyl)-p-toluidine must be heated to a much higher temperature than, for example, N,N-bis(hydroxyethyl)-p-toluidine, which constitutes a practical disadvantage. Due to the chirality of the central carbon atom in propylene oxide used as a reactant for the preparation, two molecules of R- or S-propylene oxide react with one molecule of 4-toluidine, N,N-bis(2-hydroxypropyl)-p-toluidine, resulting in the formation of a mixture of various isomers, for example RR, SS or meso. In addition, the epoxy ring of 4-toluidine can be opened by bonding at the terminal CH2 group (which is the main one) or at the central CH group.

[0014] (Non-Patent Document 1) reveals that different structures are formed in the reaction of 4-toluidine with two molecules of racemic propylene oxide.

[0015] In-house analysis of the various melting fractions of N,N-bis(2-hydroxypropyl)-p-toluidine has shown that the optically inactive meso isomer melts at a higher temperature than the optically active isomer. This means that N,N-bis(2-hydroxypropyl)-p-toluidine has the technical difficulty of being in the form of a complex mixture in the form of a solidified melt, and can only be introduced into industrial applications in a complex manner as a homogeneous mixture of the individual components. [Prior art documents] [Patent documents]

[0016] [Patent Document 1] Russian Patent Application Publication No. 2063960A [Patent Document 2] European Patent Application Publication No. 1650184A1 [Patent Document 3] China Patent Publication No. 101200432A [Non-patent literature]

[0017] [Non-Patent Document 1] 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 Summary of the Invention [Problem to be solved by the invention]

[0018] The technical problem addressed here was therefore to provide a propoxylated 4-toluidine which does not have the disadvantages of N,N-bis(2-hydroxypropyl)-p-toluidine but which can be used at least equally well or better as a polymerization accelerator or as a vulcanization accelerator or as a hardener component for epoxy resins in polymer systems in which N,N-bis(2-hydroxypropyl)-p-toluidine can be used. [Means for solving the problem]

[0019] This object has surprisingly been achieved by providing: Mixtures containing two or more different compounds of general formula (I) [ka] [In the formula, R 1 is hydrogen or methyl, except for R on the immediately adjacent carbon atom. 1 groups are not both hydrogen or both methyl, and m and n are integers, 4-toluidine is present in a proportion of less than or equal to 2% by weight, preferably between 0.001% and 1% by weight, based on the total mass of all compounds of formula (I) in the mixture, and Among them, the compound of formula (I) in which the total sum of m and n is an integer 2 is present in the mixture at a ratio of 20% by weight or less, preferably 0.01% by weight to 20% by weight, more preferably 0.01% by weight to 12% by weight, based on the total mass of all compounds of formula (I); and Among them, compounds of formula (I) in which the total sum of m and n is at least an integer of 6 are present in the mixture at a ratio of 40% by weight or less, preferably 0.01% by weight to 40% by weight, and more preferably 0.01% by weight to 20% by weight, based on the total mass of all compounds of formula (I). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The present invention therefore provides a mixture of the present invention, which comprises two or more different compounds of formula (I). The phrase "comprising two or more different compounds" excludes the presence of only one homologue, such as N,N-bis(2-hydroxypropyl)-p-toluidine or N,N-bis(2-hydroxypropyloxypropylene)-p-toluidine. Compounds of formula (I) in which the total sum of m and n is the same are one homologue of N,N-bis(2-hydroxypropyl)-p-toluidine with respect to the total sum of m and n. Thus, a homologue refers to compounds of formula (I) in which the total number of oxypropylene units is different.

[0021] The distribution corresponding to the degree of propoxylation can be ascertained, for example, by GC-MS. It is also possible to quantitate the weight percent by gas chromatography by calibrating the GC measurement with calibration materials.

[0022] The mixture of the present invention preferably contains compounds of formula (I) in which the total sum of m and n is the integer 3, in a proportion of 7% by weight to 49% by weight, particularly preferably 15% by weight to 49% by weight, based on the total mass of all compounds of formula (I).

[0023] It is also preferred that the mixture of the present invention comprises compounds of formula (I) in which the total sum of m and n is the integer 4 in a proportion of 10% to 49% by weight, more preferably 10% to 40% by weight, based on the total mass of all compounds of formula (I).

[0024] In a further preferred embodiment, in the mixture of the present invention, each homologous group of compounds of formula (I) is present in the mixture in a proportion of less than 50 weight percent, based on the total mass of all compounds of formula (I) in the mixture. A homologous group of compounds of formula (I) refers to various groups of compounds in which the sum of m and n is the same, but the combination of m and n may be different. For example, the group of homologous compounds in which the sum of m and n=4 includes the following compounds: m=0 and n=4, or m=4 and n=0, m=1 and n=3, or m=3 and n=1, and m=n=2 and the individual isomers of the compounds having the above values ​​of m and n.

[0025] This has the advantage that the substance mixture may be classified as a polymer in chemical substance legislation in a particular region or country and therefore be subject to different conditions under chemical substance legislation as individual substances.

[0026] In an equally preferred embodiment, the mixture according to the invention has a proportion of 4-toluidine of less than 0.1% by weight, based on the total mass of all compounds of formula (I) in the mixture.

[0027] The mixture of the present invention may further comprise additional components together with the compound of formula (I). They may be catalyst residues, water, or other polymerization reaction products of propylene oxide. The weight percentages of all the compounds of formula (I) and the weight percentages of the additional components add up to 100 weight percent. Typically, the mixture of the present invention comprises 96 weight percent to 100 weight percent of the compound of formula (I).

[0028] The mixture of the present invention is typically a substance in a liquid state at room temperature and / or at a temperature of 5 to 40°C. In addition, it is preferred that the mixture of the present invention does not contain any solid components. It is preferred that the mixture of the present invention is not a suspension. Therefore, it is preferred that the mixture of the present invention can be handled as a homogeneous liquid at ambient temperature. This is advantageous in that when the mixture of the present invention is used as a polymerization accelerator, vulcanization accelerator, or curing agent component, it can be taken out of a container in a simple manner in a liquid state with a precise amount and a stable, predetermined composition, and can be used in the application with a precise amount and a stable, predetermined composition. In the present invention, the mixture is a substance in a liquid state if it has a dynamic viscosity of 0.1 to 20,000 mPas (milliPascal·second) at 25°C.

[0029] The dynamic viscosity can be measured by various methods, for example by means of a capillary viscometer or a rotational viscometer. Unless otherwise specified, the dynamic viscosity is measured using a rotational viscometer according to the principle of the cone-plate measuring system (reference: DIN 53019-2, chapter 10.3) at a given temperature according to DIN 53019. It is preferred that the mixture of the present invention has a dynamic viscosity of 500 to 20,000 mPas, measured by means of a rotational viscometer according to DIN 53019 at a temperature of 25°C.

[0030] The mixture of the present invention is a reaction product obtained directly from the manufacturing process of the present invention.

[0031] The present invention therefore also provides the mixtures according to the invention obtainable by the process according to the invention.

[0032] The mixture of the present invention can surprisingly be produced by a simple and stable process.When the detection limit by gas chromatography is 100 ppm, it is preferable that no unconverted 4-toluidine is detected in the mixture of the present invention.This is very important because toluidine that is not alkylated on the nitrogen is classified as a severe hemotoxin and carcinogenic.

[0033] The process of the invention for preparing such mixtures includes the step of preparing a compound of formula (I) 1 is hydrogen or methyl, provided that R on the immediately adjacent carbon atom 1 The method includes reacting N,N-dipropoxy-p-toluidine, in which m and n are not both hydrogen or both methyl and in which m and n are the integer 1, with 1.0 to 4.0 moles, preferably 1.25 to 2.50 moles, of propylene oxide (1,2-epoxypropane) per mole of 4-toluidine used, in the presence of a catalyst.

[0034] The N,N-dipropoxy-p-toluidine used as a reactant in the process of the present invention, i.e., 1 is hydrogen or methyl, provided that R on the immediately adjacent carbon atom 1 The compounds of formula (I), in which the radicals are neither both hydrogen nor both methyl, and in which m and n are the integer 1, are either commercially available as products or are reactants which are separately obtained by in-house preparation and subsequent isolation, or are reactants which are separately obtained by in-house preparation and subsequent isolation, in the latter case being prepared in the reaction vessel in which the process of the invention is carried out.

[0035] The process of the invention is preferably carried out at temperatures between 80 and 150° C., preferably between 100 and 150° C. At lower temperatures, the conversion may be incomplete and in any case lead to lengthy reactions which are cost-prohibitive and which, if the metering rate of propylene oxide is not regulated, may result in a significant and therefore dangerous pressure build-up in the reactor. In contrast, at higher temperatures (in particular the limiting temperature T exo Temperatures exceeding those specified by TRAS410 may result in destruction due to uncontrolled heating accompanied by pressure build-up.

[0036] In the process 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)aluminum dihydride, or an alkali metal alkoxide. More preferably, the catalyst used is an alkali metal hydroxide, an alkali metal and alkaline earth metal carbonate, most preferably sodium hydroxide or potassium hydroxide. In the process of the present invention, 1 is hydrogen or methyl, but R on the immediately adjacent carbon atom 1 Preferably, 0.01 to 0.05 moles, more preferably 0.02 to 0.035 moles, of the catalyst are used per mole of the compound of formula (I) (N,N-dipropoxy-p-toluidine) in which the radicals are not both hydrogen or both methyl, and in which m and n are the integer 1.

[0037] For the process of the present invention, the N,N-dipropoxy-p-toluidine reactant, i.e., 1 is hydrogen or methyl, but the R on the immediately adjacent carbon atom 1The compound of formula (I), in which the groups are neither both hydrogen nor both methyl, and in which m and n are the integer 1, can be obtained by reacting 4-toluidine with 1.8 to 2.2 moles, preferably 1.9 to 2.1 moles, of propylene oxide per mole of 4-toluidine used, at a temperature of 80 to 150° C., preferably 100 to 150° C., more preferably 110 to 150° C., in the absence of a catalyst.

[0038] This means that the inventive process for preparing the inventive mixture further comprises reacting 4-toluidine with 1.8-2.2 moles, preferably 1.9-2.1 moles, of propylene oxide per mole of 4-toluidine used, at a temperature of 80-150° C., preferably 100-150° C., more preferably 110-150° C., in the absence of a catalyst, to obtain a reactant, i.e., 1 is hydrogen or methyl, but the R on the immediately adjacent carbon atom 1 The method includes obtaining a compound of formula (I), wherein the radicals are not both hydrogen or both methyl, and wherein m and n are the integer 1, and then reacting the reactant with 1.0 to 4.0 moles, preferably 1.25 to 2.50 moles, of propylene oxide per mole of 4-toluidine used, in the presence of a catalyst.

[0039] The process of the invention is typically carried out in such a way that, before starting the reaction, a temperature is selected at which the components to be propoxylated, i.e. 4-toluidine or N,N-dipropoxy-p-toluidine, are in liquid form. The reactor is then inerted with an inert gas, for example nitrogen, and then the internal pressure is reduced to a pressure of about 50 to 700 hectopascals (hPa). In the propoxylation of N,N-dipropoxy-p-toluidine of the invention, it is preferred to add a catalyst before closing the reactor. The catalyst of the invention is preferably added in solid form, for example in the form of flakes, beads or powder. It is also possible to use it as an aqueous solution, in which case the water can be distilled off before the further reaction or this removal of water can be dispensed with.

[0040] Preferably, propylene oxide is still present in the reactor after purging the 4-toluidine or N,N-dipropoxy-p-toluidine reactants with an inert gas.

[0041] Typically, the reaction of 4-toluidine or N,N-dipropoxy-p-toluidine with propylene oxide is carried out in a closed pressure-resistant reactor, such as an autoclave. In the reaction, the pressure increases, proceeding from a preset pressure, until a pressure is reached that typically ranges from 400 hPa to 2000 hPa. An absolute pressure in the reactor of more than 0.3 megapascals (MPa) is typically not reached. However, these pressures can be significantly exceeded if gaseous propylene oxide is added in its entirety to the 4-toluidine or N,N-dipropoxy-p-toluidine component to be propoxylated in the reactor, either before or after the reaction temperature is reached, or if it is metered too quickly into the reactor, either before or after the reaction temperature is reached. Both of these should be avoided in practice from a safety standpoint. Typically, propylene oxide is metered into the reaction mixture formed from the 4-toluidine or N,N-dipropoxy-p-toluidine to be propoxylated and the propylene oxide components, while ensuring that the pressure does not exceed about 0.2 MPa.

[0042] Propylene oxide is typically used in the form of its commercially available racemate, having a purity of at least 99%. In the process of the invention, it is also possible to use the individual enantiomers, i.e., R- and / or S-propylene oxide, or any desired mixtures thereof.

[0043] The reaction of N,N-dipropoxy-p-toluidine with propylene oxide according to the present invention is always carried out using a catalyst, in contrast to the propoxylation of 4-toluidine to give N,N-dipropoxy-p-toluidine, which is carried out in the absence of a catalyst.

[0044] It is preferred to carry out the process of the present invention in the absence of a solvent.

[0045] In a preferred embodiment of the process of the invention, the N,N-dipropoxy-p-toluidine reactant is obtained by reacting 4-toluidine having a ratio of 3-toluidine of not more than 0.5% by weight, based on 4-toluidine.In an alternative preferred embodiment of the process of the invention, the N,N-dipropoxy-p-toluidine reactant is obtained by reacting 4-toluidine having a ratio of 3-toluidine of not more than 0.2% by weight, based on 4-toluidine.

[0046] To obtain a specific, particularly pure, 4-toluidine with a limited 3-toluidine content, it is necessary to remove 3-toluidine from technical grade 4-toluidine by careful distillation, since the boiling points of the two isomers are close to each other (boiling point of 4-toluidine: 200.5° C.; boiling point of 3-toluidine: 203.4° C.).

[0047] Another method for preparing 4-toluidine with a 3-toluidine content of at most 0.2% by weight is to recrystallize technical grade N-acetyl-4-toluidine, followed by hydrolysis and distillation.In a preferred method, 4-toluidine with a 3-toluidine content of less than 0.2% by weight is prepared by first nitrating toluene, removing the two undesirable 2- and 3-nitrotoluene isomers from the thus obtained isomeric mixture of 2-, 3- and 4-nitrotoluene by distillation with a reflux ratio optimized very efficiently to obtain the desired purity, and then subjecting the obtained 4-nitrotoluene to hydrogenation to form 4-toluidine with the desired purity.In this way, it is possible to obtain 4-toluidine with a 3-toluidine content of less than 0.2% by weight, preferably less than 0.1% by weight, even in industrial quantities.

[0048] The mixtures of the present invention cannot be prepared in one step starting from 4-toluidine, such that either the entire amount of propylene oxide required and catalyst, or the entire amount of propylene oxide required without catalyst, is added to an initial charge of 4-toluidine, in which case undesirable by-products are formed to a significant extent and / or the conversion of the 4-toluidine used is incomplete.

[0049] In carrying out the preferred embodiment of the process of the present invention, in order to achieve the desired narrow distribution of the individual homologues of the propoxylated 4-toluidine of formula (I), it is very important to pay attention to the narrow limits of the parameters related to the molar ratio between propylene oxide and 4-toluidine and / or between the catalyst and 4-toluidine, and / or the reaction temperature. These parameters influence each other, so that combinations of these parameters above or below all the limits, also in conjunction with other parameters such as the metering rate, the reaction phase of the liquid 4-toluidine, the catalyst, and the mixture of the metered gaseous propylene oxide, may result in the formation of a mixture of propoxylated 4-toluidine that is not according to the invention in individual cases. However, a person skilled in the art will be able to determine in a simple manner, without any particular difficulty, the suitable combination of parameters by adjusting these parameters within these strict limits depending on the experimental configuration or the size of the reaction vessel, thereby obtaining the mixture of the present invention within the above-mentioned limits.

[0050] The yield of the propoxylation of the present invention is virtually quantitative and is limited only by losses in handling, such as those caused by adhesion of residual amounts to the walls of the reactor during transfer. After the propoxylation is complete, it has been found useful to cool the reaction mixture to a temperature in the range of 60-100°C and pass nitrogen through the reaction mixture for a period of time to completely remove any propylene oxide present from the system.

[0051] The reaction mixture can be worked up by methods known to those skilled in the art or can alternatively be used directly in a further step.

[0052] The use of propylene oxide as a propoxylation agent has the advantage over other reactants (e.g., 1-chloropropan-2-ol, 1-bromopropan-2-ol, or 1-iodopropan-2-ol) in that it does not require the use of auxiliary reactants (e.g., stoichiometric amounts of base as a hydrogen halide scavenger) and therefore does not produce salts that must be removed in a separate step. Another disadvantage of using halopropanols is, for example, the corrosion of the metallic equipment used.

[0053] The present invention further provides the use of the mixtures according to the invention as polymerization accelerators or vulcanization accelerators, preferably in the polymerization of polyesters, in particular unsaturated polyesters, or as hardener components for epoxy resins. It has been found useful to use the mixtures according to the invention in amounts of 0.1 to 5% by weight. The polymerizations in which the mixtures according to the invention can be used are preferably free radical polymerizations.

[0054] In polymerization systems in which the known N,N-dipropoxy-p-toluidine is used more advantageously than ethoxylated or other alkylated 4-toluidines, the mixtures of the invention have improved handling properties and / or better processability and / or lower dosage and / or higher reactivity. By replacing N,N-dipropoxy-p-toluidine, known to be in the form of a solid melt in the free radical polymerization of polyesters, especially unsaturated polyesters, or as a hardener component for epoxy resins, with the liquid mixtures of the invention, the physicochemical and / or physicomechanical properties of the polymers produced therewith can be advantageously influenced.

[0055] In an alternative embodiment, a feature of the mixtures according to the invention, which contain only small proportions of propoxylated 3-toluidine, is that they can be used particularly advantageously as polymerization or vulcanization accelerators in the preparation of colorless polymers, since their use does not result in any discoloration of the polymer. Depending on the desired use of the polymer, this is of great importance and is not achievable with any of the polymerization and vulcanization accelerators of the prior art.

[0056] The present invention further provides polymeric reaction products obtainable by polymerizing preferably polyesters, in particular unsaturated polyesters, in the presence of the mixtures of the present invention as polymerization or vulcanization accelerators or as hardener components for epoxy resins. The polymerizations in which the mixtures of the present invention can be used are preferably free-radical polymerizations. EXAMPLES

[0057] Examples 1a-1e: Preparation of propoxylated toluidine starting from N,N-dipropoxy-p-toluidine Example 1a A 3 liter autoclave (stainless steel) equipped with a stirrer, an internal thermometer, an immersion-type inlet tube for propylene oxide, and a riser tube 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 integers 1; 6.25 moles] and 10.9 g of about 90% potassium hydroxide flakes (0.175 moles). The autoclave was closed and inerted by injecting nitrogen, depressurizing, and venting to about 670 hectopascals (hPa) (absolute pressure). The contents were heated to a temperature above 80° C. to mostly melt the N,N-dipropoxy-p-toluidine. The melt was then heated to the desired reaction temperature (120° C.). At this temperature, the expected amount of propylene oxide (in this case 690.1 g = 11.88 moles, corresponding to 1.9 molar equivalents based on N,N-dipropoxy-p-toluidine, i.e. 3.9 molar equivalents in total based on 4-toluene) was metered in at a rate of about 163 g / h, which within a short time reached a pressure of 0.18 MPa (absolute pressure). Typically, this pressure was not exceeded, also in the other examples. Approximately 90 minutes after the end of the metering, the total pressure dropped to a pressure of about 800 hPa, which remained constant for about 15 minutes thereafter. This was followed by stirring for a further 60 minutes at reaction temperature, then cooling to 40°C, compensating the vacuum with nitrogen, expelling any remaining propylene oxide with nitrogen and dispensing the mixture through a clarification filter. 2109.3 g (yield: 99.2%, based on the amount used) of reaction product were obtained, which had the following distribution of homologues of formula (I) (units, weight percent):

[0058] [Table 1]

[0059] Examples 1b-1e were similarly carried out in 0.5 liter autoclaves where appropriate. Rather than the volumes assumed in Example 1a, Examples 1b-1e were carried out using the data specified in Table 1.

[0060] [Table 2]

[0061] Examples 2a-2e: Preparation of propoxylated toluidine starting from 4-toluidine Example 2a A 3 liter autoclave (stainless steel) equipped with stirrer, internal thermometer, immersion-type inlet tube for propylene oxide and riser tube for removal was initially charged with 672.1 g of 99.7% 4-toluidine (6.25 mol) in the molten state. The autoclave was closed and inerted by injecting nitrogen, depressurizing and venting to about 670 hPa (absolute pressure). The contents were heated, initially without stirring, to a temperature above 45° C. to completely melt the 4-toluidine. The melt was then further heated to the desired reaction temperature (120° C.). At that temperature, in the absence of catalyst, 726.4 g of propylene oxide (12.49 mol) were metered in at a rate of about 163 g / h, reaching a maximum pressure of 0.27 MPa (absolute pressure) within a short time. Typically, this pressure was not exceeded, also in the other examples. Approximately 3.5 hours after the end of the metered addition, the total pressure dropped to a pressure of approximately 770 hPa, which remained constant for approximately 15 minutes afterwards. Stirring was then continued for a further 60 minutes at reaction temperature, after which the mixture was cooled to 80-100° C. and the vacuum was replaced with nitrogen. By means of sampling it was possible to verify whether N,N-dipropoxy-p-toluidine of typical composition was obtained.

[0062] The expected amount of solid potassium hydroxide at about 90% (2.8 mol %, based on the 4-toluidine used) was then added, the autoclave was closed again and inerted, degassed and heated to the desired reaction temperature of 120° C. Afterwards, a further 690.1 g (11.88 mol) of propylene oxide were metered in at about 163 g / h, and a pressure increase was observed from about 760 hPa to a final pressure of about 0.143 MPa (absolute). About 50 minutes after the end of the metered addition, the total pressure dropped back to the original pressure of 670 hPa. This was followed by stirring for a further 60 minutes at reaction temperature, then cooling to 40° C., compensating the vacuum with nitrogen, driving off any remaining propylene oxide with nitrogen and dispensing the mixture through a clarification filter. 2087.4 g (yield: 99.4%, based on the amount used) of reaction product was obtained, which had the following distribution of homologues of formula (I) (units, weight percent):

[0063] [Table 3]

[0064] Examples 2b-2e were similarly carried out in 0.5 liter autoclaves where appropriate. Rather than the volumes assumed in Example 2a, Examples 2b-e were carried out using the data specified in Table 2.

[0065] [Table 4]

Claims

1. A mixture comprising two or more different compounds of general formula (I), 【Chemistry 1】 [In the formula, R １ is hydrogen or methyl, except for R on the immediately adjacent carbon atom. １ the groups are not both hydrogen or both methyl, and m and n are integers; 4-toluidine is present in a proportion of less than or equal to 2% by weight, preferably between 0.001% and 1% by weight, based on the total mass of all compounds of formula (I) in the mixture; and The compound of formula (I), in which the total sum of m and n is the integer 2, is present in the mixture in a proportion of 20% by weight or less, preferably 0.01% by weight to 20% by weight, more preferably 0.01% by weight to 12% by weight, based on the total mass of all compounds of formula (I); and the compound of formula (I) in which the sum of m and n is at least an integer of 6 is present in the mixture in a proportion of not more than 40% by weight, preferably from 0.01% to 40% by weight, more preferably from 0.01% to 20% by weight, based on the total mass of all compounds of formula (I); A mixture comprising:

2. 2. The mixture according to claim 1, characterized in that the compound of formula (I), in which the sum of m and n is the integer 3, is present in the mixture in a proportion of from 7% to 49% by weight, preferably from 15% to 49% by weight, based on the total mass of all compounds of formula (I).

3. 3. The mixture according to claim 1 or 2, characterized in that the compound of formula (I), in which the sum of m and n is the integer 4, is present in the mixture in a proportion ranging from 10% to 49% by weight, preferably from 10% to 40% by weight, based on the total mass of all compounds of formula (I).

4. 4. The mixture according to claim 1, wherein each homologous group of compounds of formula (I) is present in the mixture in a proportion of less than 50 percent by weight, based on the total mass of all compounds of formula (I) in the mixture.

5. 5. The mixture according to claim 1, characterized in that it contains less than 0.1% by weight of 4-toluidine, based on the total mass of all compounds of formula (I) in the mixture.

6. A mixture according to any one of claims 1 to 5, characterized in that it is a substance in the liquid state at temperatures between 5 and 40°C.

7. 7. The mixture according to claim 1, characterized in that it has a dynamic viscosity of from 500 to 20,000 mPas, measured in accordance with DIN 53019 using a rotational viscometer at a temperature of 25° C.

8. The mixture according to any one of claims 1 to 7, characterized in that it contains from 96% to 100% by weight of the compound of formula (I).

9. A process for producing the mixture according to any one of claims 1 to 8, comprising the steps of: １ is hydrogen or methyl, but R on the immediately adjacent carbon atom １ A process comprising reacting a compound of formula (I), wherein the radicals are neither both hydrogen nor both methyl, and in which m and n are the integer 1, with 1.0 to 4.0 moles, preferably 1.25 to 2.50 moles, of propylene oxide per mole of 4-toluidine used, in the presence of a catalyst.

10. 10. The process for producing a mixture according to claim 9, wherein the reaction is carried out at a temperature of from 80 to 150°C, preferably from 100 to 150°C.

11. The reaction is carried out using the compound of formula (I) R １ is hydrogen or methyl, but R on the immediately adjacent carbon atom １ 11. The process for producing a mixture according to claim 9 or 10, which is carried out in the presence of 0.01 to 0.05 moles of a catalyst selected from alkali metal and alkaline earth metal hydroxides, alkali metals, alkyllithiums, sodium hydrides, complex hydrides such as lithium aluminum hydride, sodium bis(methoxyethoxy)aluminum dihydride, or alkali metal alkoxides, preferably selected from alkali metal hydroxides, alkali metal and alkaline earth metal carbonates, per mole of compound of formula (I) (N,N-dipropoxy-p-toluidine), in which the radicals are neither both hydrogen nor both methyl and in which m and n are the integer 1.

12. 4-toluidine is reacted with 1.8 to 2.2 moles, preferably 1.9 to 2.1 moles, of propylene oxide per mole of 4-toluidine used in the absence of a catalyst at a temperature of 80 to 150° C., preferably 100 to 150° C., more preferably 110 to 150° C. to obtain the compound represented by formula (I) R １ is hydrogen or methyl, but R on the immediately adjacent carbon atom １ 10. The process for producing the mixture of claim 9, comprising producing a compound of formula (I) (N,N-dipropoxy-p-toluidine) in which the groups are not both hydrogen or both methyl, and in which m and n are the integer 1.

13. A process for producing a mixture according to any one of claims 9 to 12, characterized in that the reaction is carried out in the absence of a solvent.

14. A process for producing a mixture according to any one of claims 9 to 13, wherein the 4-toluidine contains 3-toluidine in a proportion of no more than 0.2% by weight, based on 4-toluidine.

15. Use of a mixture according to any one of claims 1 to 8 as a polymerization accelerator or vulcanization accelerator, preferably in the free radical polymerization of polyesters, in particular unsaturated polyesters, or as a hardener component for epoxy resins.

16. 9. A polymeric product obtainable by polymerization, preferably by polymerization of polyesters, in particular unsaturated polyesters, in the presence of a mixture according to any one of claims 1 to 8 as a polymerization accelerator or vulcanization accelerator or as a hardener component for epoxy resins.

Images