The present invention relates to a mixture comprising the components (A) and (B) and optionally the further component (C). Component (A) comprises at least one bismuth- containing catalyst which is defined by the general formula (I) detailed in the subsequent text. The bismuth-containing catalyst comprises at least one radical R ¹ , which comprises a carboxyl fragment according to the general formula (II), wherein a first carbon atom (a-carbon) is bonded to the carbon atom of the carboxyl group, which in turn is directly substituted with at least one aromatic system. Component (B) of the inventive mixture is at least one hydrocarbon compound containing two hydroxyl groups (“diol”). The optionally present component (C) is at least one solvent.

The present invention further relates to a method for preparing such mixture and also to the use of such mixture for preparing compounds comprising a urethane group.

The EP patent application 19155916.0 relates to a bismuth-containing catalyst as such which can be employed as component (A) within the mixture according to the present invention.

WO 2018/069018 relates to a coating composition system comprising the components (A) to (C) and optionally further components. The component (A) is at least one polyhydroxyl group-containing compound and the component (B) is at least one polyisocyanate-containing compound. In contrast, the component (C) is a catalyst comprising at least two salts of an aliphatic monocarboxylic acid having at least four carbon atoms. In this case, the metal component of the first salt is bismuth (Bi), while the second salt comprises magnesium (Mg), sodium (Na), potassium (K) or calcium (Ca) as metal component. The coating composition system according to WO 2018/069018 may be configured according to a first option such that all components are present separately from one another, i.e. the individual components are not mixed with one another, whereas according to a second option of the corresponding coating composition system, the respective components can also be present completely or at least partially mixed with one another.

US-A 4,895,827 discloses a catalyst in the form of a metal salt, in which the catalyst is a constituent of a heat-sensitive color-forming composition which, in addition to the catalyst, comprises a chromogenic material comprising an acidic developer and a suitable binder. The metal salt may comprise different metals as central metal atom/metal ion comprising, for example, zinc, tin, aluminum or nickel. The corresponding metal salt comprises organic compounds as ligands which, in addition to a carboxyl group, also comprise aromatic fragments and vinyl groups. However, bismuth-containing catalysts are not disclosed in US-A 4,895,827. JP-A 58 87 087 discloses the use of a multivalent metal salt of diphenylacetic acid, especially diphenylzinc acetate, as colorants, wherein a water-proof colored picture can be produced. However, bismuth-containing metal salts or the use of metal salts for preparing a compound comprising a urethane bond are not disclosed in JP-A 5887087.

The preparation of compounds comprising a urethane group (urethane bond) has likewise been known for a long time. A compound having a urethane group is generally obtained if a compound comprising an isocyanate group is reacted with a compound comprising an hydroxyl group. The reaction generally takes place in the presence of a catalyst. Although tin-containing catalysts exhibit very high activity in such reactions, the use of such tin-containing catalysts, especially alkyltin compounds, should be avoided owing to their (very high) toxicity.

The object of the present invention, therefore, was to provide a novel mixture based on a bismuth-containing catalyst which can be used for preparing compounds comprising a urethane group. The object is achieved by a mixture comprising components (A) and (B):

(A) at least one bismuth-containing catalyst according to general formula (I) in which the variables are defined as follows:

R ¹ is mutually independently a radical of the general formula (II) and x is 1, 2 or 3;

R ² is mutually independently a radical of the general formula (III) and y is 0, 1 or 2;

X ¹ is mutually independently hydroxyl, halogen, carbonate, hydro- gencarbonate or R ⁷ and z is 0, 1 or 2; wherein the sum total of x, y and z is equal to 3;

R ³ is unsubstituted or at least monosubstituted CrC ₃₀ -alkyl, C ₆ -C ₁₄ -aryl or C ₇ - Cso-aralkyl, wherein the substituents are selected from hydroxyl, halogen, carboxyl, -CF ₃ , -NH ₂ , C Ce-alkoxy, CrC ₃₀ -alkyl or C ₆ -C ₁₄ -aryl and the alkyl and aryl fragments of these substituents may in turn be at least monosubstituted by hydroxyl, halogen, -CF ₃ , -NH ₂ or CrC ₆ -alkoxy, and wherein the carbon atom of the radical R ³ bonded directly to the carbon atom of the carboxyl group of the general formula (III) does not comprise any unsubstituted or at least monosubstituted C ₆ -Ci ₄ -aryl as substituent,

R ⁴ , R ⁵ and R ⁶ are mutually independently unsubstituted or at least monosubstituted CrC ₃₀ -alkyl, C ₆ -C ₁₄ -aryl or C ₇ -C ₃₀ -aralkyl, wherein the substituents are selected from hydroxyl, halogen, carboxyl, -CF ₃ , -NH ₂ , Ci-C ₆ -alkoxy, CrC ₃₀ -alkyl or C ₆ -Ci ₄ -aryl and the alkyl and aryl fragments of these substituents may in turn be at least monosubstituted by hydroxyl, halogen, -CF ₃ , -NH ₂ or CrC ₆ -alkoxy, and wherein at least one of the radicals R ⁴ , R ⁵ or R ⁶ is unsubstituted or at least monosubstituted C ₆ -C ₁₄ -aryl, R ⁷ is unsubstituted or at least monosubstituted C Cso-alkyl, C ₆ -C ₁₄ -aryl or C ₇ -C ₃₀ -aralkyl, wherein the substituents are selected from hydroxyl, halogen, carboxyl, -CF ₃ , -NH ₂ , C Ce-alkoxy, CrC ₃₀ -alkyl or C ₆ -C ₁₄ -aryl and the alkyl and aryl fragments of these substituents may in turn be at least monosubstituted by hydroxyl, halogen, -CF ₃ , -NH ₂ or CrC ₆ -alkoxy,

(B) at least one hydrocarbon compound containing two hydroxyl groups and having a molecular weight of < 500 g/mol, wherein the molar ratio of component (B) to component (A) is in the range of 0.1 to 20 [mol/mol]. The inventive mixture based on at least one bismuth-containing catalyst is characterized in that, inter alia, the use of toxic tin-containing catalysts in the production of compounds comprising a urethane group can be avoided. The mixture according to the invention has a comparable catalytic activity as known representatives of the effective, on the one hand catalytically active, but on the other hand toxic, tin- containing catalysts.

Beyond that, the catalytic activity of the mixture according to the present invention is even improved due to the presence of at least one diol according to component (B), compared to the respective catalytic activity of the catalyst according to component (A) as such.

Another advantage of the mixture according to the present invention can be seen in the fact that an improved catalytic activity can be observed at rather low temperatures, such as room temperature (approximately 20°C). In addition, stable and homogeneous mixtures, preferably stable and homogeneous solutions, can be obtained within the present invention. This is especially the case if the inventive mixture component (B) is an aromatic diol based on one or two benzene fragments (such as 2,2-dihydroxy biphenol) or it is an aliphatic diol wherein two hydroxyl groups are in 1,3-position in relation to the respective aliphatic fragment (such as 1,3-propane diol).

Irrespective of that, the catalytic activity of the bismuth-containing catalysts according to component (A) as such is better than the corresponding catalytic activity of the (other) bismuth- or zinc-containing catalysts already known. Moreover, the inventive mixture based on at least one bismuth-containing catalyst exhibits improved hydrolytic stability compared to bismuth-containing catalysts already known. For example, low amounts of water can already be sufficient in order to significantly or fully reduce the catalytic activity of bismuth-containing catalysts based on pure alkyl ligands, such as laurate-containing bismuth catalysts. Whereas such catalysts known from the prior art start to precipitate on contact with water, the mixtures according to the invention are much more stable. Owing to the increased stability to hydrolysis - and thus also storage stability - the inventive mixtures based on at least one bismuth-containing catalyst exhibit their improved catalytic properties over a much longer time period.

Furthermore, in the case of the inventive mixture based on at least one bismuth- containing catalyst, it is also not required that the catalyst must be present as a salt of the corresponding acid. The bismuth-containing catalysts can thus be used without the presence of the corresponding acid at high catalytic activity in order to form compounds having urethane groups.

Advantageous properties are then already obtained in the inventive mixtures if in at least one of the substituents/ligands of the bismuth central atom of the bismuth- containing catalyst according to component (A), at least one aromatic system, especially a phenyl group, is directly substituted on the first carbon atom which is bonded to the carbon atom of the carboxyl group of the corresponding ligands. In accordance with the invention, this first carbon atom is referred to as the a-carbon (or in part also in chemical nomenclature). Known examples for this purpose from chemical nomenclature are a-amino acids, where the a-C atom is the carbon atom to which the amino group and the carboxyl group are attached. Specific examples for this numbering from the field of amino acids are b-alanine and g-aminobutyric acid. In chemical nomenclature, the carbonyl carbon is sometimes also counted and referred to as position 1. Accordingly, said first carbon atom directly adjacent to the carbon atom of the carboxyl group is sometimes also referred to as position 2 in chemical nomenclature. Accordingly, in accordance with the invention, at least one aromatic substituent, especially at least one phenyl substituent, is located on the a-carbon (atom) or in the 2-position, in the latter case based on the respective whole ligands taking carboxyl groups into account.

The said carboxyl group of this substituent is located (spatially speaking) in proximity to the bismuth central atom of the bismuth-containing catalyst. The bismuth-containing catalysts according to component (A) of the invention are represented as salts, wherein the bismuth central atom of the bismuth-containing catalyst according to component (A) of the invention is represented as a (triple positively charged) cation of the corresponding salt (see for example the general formula (I)). The corresponding substituents/ligands of the bismuth-containing catalyst, which are represented by the substituents/radicals R ¹ , R ² and X ¹ in the general formula (I) detailed above, form the corresponding anion components of the bismuth-containing catalyst in this salt representation. Each of these so-called substituents/ligands is singly negatively charged. As detailed below, the two substituents R ¹ and R ² each comprise a carboxyl group. In general, the negative charge in the corresponding substituents/ligands of said carboxyl group is localized and/or the corresponding carboxyl group is located in spatial proximity to the (positively charged) bismuth central atom.

From a scientific standpoint however, it is also tenable, in place of the salt notation used in the context of the present application for the bismuth-containing catalysts according to component (A) of the invention, to select a notation/representation in which a chemical bond between the bismuth central atom and the three ligands R ¹ , R ² and X ¹ according to general formula (I) is completely or at least partially formed in each case. Expressed in other words, this means that the bismuth central atom is not present as a positively charged cation and the corresponding ligands are also not present as negatively charged anions, but rather the corresponding charge form a chemical bond between the corresponding ligands on the one hand and the bismuth central atom on the other hand. In the context of the present invention, the bismuth- containing catalysts disclosed according to component (A) of the invention therefore also describe such a definition that is not based on a salt.

The catalytic activity and/or stability to hydrolysis/storage stability of the bismuth- containing catalysts according to component (A) of the invention is further improved if at least two aromatic substituents, especially phenyl substituents, are presently directly on the at least one ligand on the first carbon atom (a-carbon atom/2-position), which in turn is bonded to the carbon atom of the carboxyl group. If three aromatic substituents, especially phenyl substituents, are bonded directly to said a-carbon atom, very catalytically active catalysts are also obtained, but their stability to hydrolysis (ostensibly with regard to heat) generally decreases somewhat in comparison to bismuth-containing catalysts according to component (A) of the invention, in which precisely two aromatic systems, especially two phenyl groups, are present on at least one ligand on said a-carbon atom (2-position). The higher the catalytic activity and/or stability to hydrolysis of the bismuth-containing catalysts according to component (A) of the invention, the higher the number of said radicals R ¹ in the bismuth-containing catalyst according to the invention according to general formula (I). The best results are then achieved in this context, if the bismuth-containing catalyst according to component (A) of the invention has three (identical or different) radicals R ¹ according to the definition above, i.e. when the variable x = 3. Particularly preferred catalysts of this kind are also shown below by the general formula (la).

In the context of the present invention, definitions such as CrC ₃₀ -alkyl, such as defined, for example, for the radical R ⁴ in formula (II) above, signifies that this substituent (radical) is an alkyl radical having a carbon atom number of 1 to 30, wherein substituents optionally present are not taken into consideration in the carbon atom number. The alkyl radical may be either linear or branched as well as optionally cyclic. Alkyl radicals having both a cyclic and a linear component also fall under this definition. The same applies to other alkyl radicals such as a C C ₆ -alkyl radical or a CrC ₁₂ -alkyl radical for example. Examples of alkyl radicals are methyl, ethyl, n-propyl, sec-propyl, n-butyl, sec-butyl, isobutyl, 2-ethylhexyl, tertiary-butyl (tert-Bu/t-Bu), pentyl, hexyl, heptyl, cyclohexyl, octyl, nonyl or decyl. In the context of the present invention, the term “aryl" or the term “C ₆ -Ci ₄ -aryl", as defined, for example, for the radical R ⁴ in formula (II) above, signifies that the substituent (radical) is an aromatic system. The corresponding aromatic system has a carbon atom number of 6 to 14, wherein substituents optionally present are not taken into consideration in the carbon atom number. The aromatic system may be a monocyclic, bicyclic or optionally polycyclic aromatic system. In the case of bicyclic or polycyclic aromatic systems, individual rings may optionally be fully or partially saturated. Preferably, all rings of the corresponding aromatic systems are fully unsaturated. Preferred examples of aryl are phenyl, naphthyl or anthracyl, especially phenyl.

In the context of the present invention, the definition “C ₇ -C ₃₀ -aralkyl", as defined for example for the radical R ⁴ in formula (II) above, signifies that the substituent (radical) comprises an alkyl radical (such as C C ₆ -alkyl according to the definitions above), wherein this alkyl radical is in turn substituted by an aryl radical (according to the definitions above). The corresponding aralkyl substituent has a carbon atom number of 7 to 30, wherein substituents optionally present are not taken into consideration in the carbon atom number. The alkyl radical itself present therein may be either linear or branched as well as optionally cyclic. In the context of the present invention, the term “CrC ₆ -alkoxy", as defined for example as (additional) substituent of the radical R ⁴ in formula (II) above, signifies that it is a substituent (radical) in this case which is derived from an alcohol. The corresponding substituent thus comprises an oxygen fragment (-0-), which is in turn linked to an alkyl radical, such as C C ₆ -alkyl (according to the definitions above). The alkyl radical itself may be either linear or branched as well as optionally cyclic. In the context of the present invention, the term “halogen", such as defined for example for the radical X ¹ in formula (I) above, signifies that the substituent (radical) is fluorine, chlorine, bromine or iodine, X ¹ preferably being fluorine or chlorine, particularly preferably chlorine.

In the context of the present invention, the term “unsubstituted or at least monosubstituted CrC ₃₀ -alkyl, C ₆ -C ₁₄ -aryl or C ₇ -C ₃₀ -aralkyl", such as defined for example for the radical R ⁴ in formula (II) above, signifies that each of the in total three substituents (radicals) detailed corresponding to their definitions already specified above may be present either in unsubstituted form or have at least one further substituent (monosubstituted). If one or more substituents are present (for example disubstituted, trisubstituted or even higher substituted), the appropriate substituents are selected independently of one another from the substituent groups specified in each case.

In the case of a disubstituted C ₆ -Ci ₄ -aryl for example, the corresponding aryl unit, such as phenyl for example, may be substituted for example by an hydroxyl and a CrC ₃₀ - alkyl substituent, such as methyl or ethyl. Alkyl or aryl fragments may themselves in turn comprise at least one additional substituent according to the definitions stated. The substitution may be at any desired position of the corresponding fragment.

Provided that an appropriate radical, such as R ⁴ for example, owing to the definition of, for example, formula (I), may occur two or more times in connection with formula (II), the individual radicals R ⁴ may be selected completely independently of one another according to the respective definitions. For example, if in the general formula (I) the variable x = 3, the radical R ¹ occurs in total three times in the general formula (I). The radical R ¹ , which in turn comprises the radical R ⁴ , can therefore be present three times independently of one another in this scenario. The individual radicals R ¹ can therefore be configured differently according to their basic definition. Thus, it is feasible that a first radical R ¹ , with regard to the constituent of the radical R ⁴ necessarily present therein, has a definition other than the corresponding second and/or third radical R ¹ . Unless otherwise stated in the following text, this logically applies also for all other radicals, such as R ² , R ³ , R ⁵ and/or R ⁶ .

Unless otherwise specified in the following description, the respective definitions of the radicals R ¹ to R ⁷ are in each case the preferred unsubstituted definitions.

The present invention is further specified hereinbelow. The first subject of the present invention is a mixture comprising components (A) and (B) and, optionally, (C), as defined in more detail below.

The mixture according to the present invention comprises as component (A) at least one bismuth-containing catalyst according to general formula (I) as defined below. The bismuth-containing catalyst according to the general formula (I) as such as well as a method for producing such catalyst is described within EP patent application 19155916.0 Component (A) is at least one bismuth-containing catalyst of the general formula (I) in which the variables are defined as follows:

R ¹ is mutually independently a radical of the general formula (II) and x is 1, 2 or 3;

R ² is mutually independently a radical of the general formula (III)

O

R ³ — C — O

(III) and y is 0, 1 or 2; X ¹ is mutually independently hydroxyl, halogen, carbonate, hydrogencarbonate or R ⁷ and z is 0, 1 or 2; wherein the sum total of x, y and z is equal to 3;

R ³ is unsubstituted or at least monosubstituted CrC ₃₀ -alkyl, C ₆ -C ₁₄ -aryl or C ₇ -C ₃₀ -aralkyl, wherein the substituents are selected from hydroxyl, halogen, carboxyl, -CF ₃ , -NH ₂ , CrC ₆ -alkoxy, CrC ₃₀ -alkyl or C ₆ -C ₁₄ -aryl and the alkyl and aryl fragments of these substituents may in turn be at least monosubstituted by hydroxyl, halogen, -CF ₃ , -NH ₂ or CrC ₆ -alkoxy, and wherein the carbon atom of the radical R ³ bonded directly to the carbon atom of the carboxyl group of the general formula (III) does not comprise any unsubstituted or at least monosubstituted C ₆ -C ₁₄ -aryl as substituent.

R ⁴ , R ⁵ and R ⁶ are mutually independently unsubstituted or at least monosubstituted CrC ₃ o-alkyl, C ₆ -Ci ₄ -aryl or C ₇ -C ₃ o ^_ aralkyl, wherein the substituents are selected from hydroxyl, halogen, carboxyl, -CF ₃ , -NH ₂ , CrC ₆ -alkoxy, C C ₃₀ -alkyl or C ₆ -C ₁₄ -aryl and the alkyl and aryl fragments of these substituents may in turn be at least monosubstituted by hydroxyl, halogen, -CF ₃ , -NH ₂ or CrC ₆ -alkoxy, and wherein at least one of the radicals R ⁴ , R ⁵ or R ⁶ is unsubstituted or at least monosubstituted C ₆ -C ₁₄ -aryl,

R ⁷ is unsubstituted or at least monosubstituted C C ₃₀ -alkyl, C ₆ -C ₁₄ -aryl or C ₇ -C ₃₀ -aralkyl, wherein the substituents are selected from hydroxyl, halogen, carboxyl, - _CF 3 _, -NH ₂ , CrC ₆ -alkoxy, C C ₃₀ -alkyl or C ₆ -C ₁₄ -aryl and the alkyl and aryl fragments of these substituents may in turn be at least monosubstituted by hydroxyl, halogen, -CF ₃ , -NH ₂ or CrC ₆ -alkoxy.

In connection with the radicals (substituents/ligands) present in the general formula (I), particularly the necessary radical R ¹ and the optional radical R ² , it should be noted that the further/exact chemical definition of these radicals R ¹ or R ² is a result of the radicals R ⁴ to R ⁶ of the general formula (II) with respect to the radical R ¹ and is a result of the radical R ³ of the general formula (III) with respect to the radical R ² . In accordance with the invention, the radical R ² is chemically always defined differently than the radical R ¹ . Expressed in other words, this signifies that a specific radical R ² or R ³ in accordance with general formula (III) cannot fall under the corresponding definition of a radical R ¹ or the radicals R ⁴ to R ⁶ according to general formula (II). This results in particular from the fact that, in the chemical definition of the radical R ² in accordance with general formula (III), a radical R ³ is present which is defined such that the radical R ³ is directly bonded to the carbon atom of the carbon atom of the corresponding carboxyl group of the general formula (III), no unsubstituted or at least monosubstituted C ₆ -C ₁₄ -aryl, especially no phenyl, can be present as direct substituent. In contrast, such a substituent is necessarily present for at least one of the radicals R ⁴ , R ⁵ or R ⁶ in accordance with the general formula (II) in connection with the radical R ¹ . Accordingly, it is excluded that a substituent falling under the definition of the radical R ² in accordance with general formula (III) can at the same time fall under the corresponding definition of the radical R ¹ in accordance with general formula (II).

The radical R ¹ in accordance with general formula (II) is preferably defined according to the invention such that R ⁴ , R ⁵ and R ⁶ are mutually independently unsubstituted or at least monosubstituted CrCi ₂ -alkyl or C ₆ -Ci ₄ -aryl, wherein the substituents are selected from hydroxyl, chlorine, -CF ₃ and C C ₆ -alkyl, and wherein at least one of the radicals R ⁴ , R ⁵ or R ⁶ is unsubstituted or at least monosubstituted C ₆ -Ci ₄ -aryl. C ₆ -Ci ₄ -aryl is preferably phenyl, especially unsubstituted phenyl.

Furthermore, it is preferred in accordance with the invention that the radicals R ⁴ to R ⁶ in the general formula (II) are defined as follows: i) R ⁴ is unsubstituted or at least monosubstituted phenyl, wherein the substituents are selected from hydroxyl, chlorine, -CF ₃ and C C ₆ -alkyl, ii) R ⁵ is unsubstituted or at least monosubstituted phenyl or C C ₁₂ -alkyl, wherein the substituents are selected from hydroxyl, chlorine, -CF ₃ and C C ₆ -alkyl, and iii) R ⁶ is unsubstituted or at least monosubstituted phenyl or C C ₁₂ -alkyl, wherein the substituents are selected from hydroxyl, chlorine, -CF ₃ and C Ce-alkyl.

With respect to the radical R ² according to general formula (III), it is preferable that the radical R ³ present therein is unsubstituted or at least monosubstituted C C ₁₂ -alkyl, wherein the substituents are selected from hydroxyl, chlorine or -CF ₃ . With regard to the radical X ¹ , it is preferred in accordance with the invention that this is hydroxyl, chlorine or R ⁷ and R ⁷ is unsubstituted or at least monosubstituted C C ₁₂ -alkyl or C ₆ -C ₁₄ -aryl, wherein the substituents are selected from hydroxyl, chlorine, -CF ₃ and Ci-C ₆ -alkyl.

In the bismuth-containing catalyst according to general formula (I) according to the invention, the radicals R ¹ , R ² and X ¹ present in each case can be present in each case in any combination. A precondition in this case however is that x is at least 1, i.e. at least one radical R ¹ is present in the bismuth-containing catalyst according to the invention according to general formula (I). Furthermore, the sum total of x, y and z is 3, the total number of ligands or negative charges is 3, so that in total charge neutrality is present with respect to the 3-fold positively charged bismuth central atom. If individual ligands/radicals such as R ¹ , R ² or X ¹ occur repeatedly, these can have the same or different definitions according to the respective basic definition.

In the context of general formula (I), the following scenarios are preferred in accordance with the invention, wherein i) x is equal to 2 or 3, y is equal to 0 or 1 and z is equal to 0 or 1 , or ii) x is equal to 3 and y and z are each equal to 0, or iii) x is equal to 2, y is equal to 0 and z is equal to 1 , or iv) x is equal to 2, y is equal to 1 and z is equal to 0, wherein preferably x is equal to 3 and y and z are each equal to 0.

In a preferred embodiment of the present invention, the bismuth-containing catalyst according to the general formula (I) and (II) is defined as follows: i) R ⁴ is unsubstituted or at least monosubstituted phenyl, wherein the substituents are selected from hydroxyl, chlorine, -CF ₃ and C C ₆ -alkyl, ii) R ⁵ is unsubstituted or at least monosubstituted phenyl or C C ₁₂ -alkyl, wherein the substituents are selected from hydroxyl, chlorine, -CF ₃ and C C ₆ -alkyl, iii) R ⁶ is unsubstituted or at least monosubstituted C C ₁₂ -alkyl, wherein the substituents are selected from hydroxyl, chlorine and -CF ₃ , and iv) x is equal to 3 and y and z are each equal to 0. In a further preferred embodiment of the present invention, the bismuth-containing catalyst is defined as follows: i) R ⁴ and R ⁵ are each phenyl, ii) R ⁶ is Ci-Ci2-alkyl, preferably C ₆ -C ₁₀ -alkyl, especially C ₈ -alkyl, and iii) x is equal to 3 and y and z are each equal to 0.

In a particularly preferred embodiment of the present invention, the bismuth-containing catalyst is defined by the general formula (la): wherein the radicals R ⁴ to R ⁶ mutually independently correspond to the definitions described above. As evident from formula (la) compared to the general formula (I), the catalyst according to the invention in this embodiment has in total three radicals R ¹ according to general formula (I). Each of these in total three radicals R ¹ in each case comprises one radical R ⁴ , one radical R ⁵ and one radical R ⁶ . In each of these three radicals R ¹ , the corresponding definitions of the radicals R ⁴ to R ⁶ can be the same or different from one another. However, it is preferred in accordance with the invention that each of the total of three radicals R ⁴ are the same, each of the total of three radicals R ⁵ are the same and each of the total of three radicals R ⁶ are the same.

Furthermore, in the context of the general formula (la), it is preferable that i) R ⁴ is unsubstituted or at least monosubstituted phenyl, wherein the substituents are selected from hydroxyl, chlorine, -CF ₃ and C C ₆ -alkyl, ii) R ⁵ is unsubstituted or at least monosubstituted phenyl or C C ₁₂ -alkyl, wherein the substituents are selected from hydroxyl, chlorine, -CF ₃ and C C ₆ -alkyl, and iii) R ⁶ is unsubstituted or at least monosubstituted C C ₁₂ -alkyl, wherein the substituents are selected from hydroxyl, chlorine and -CF ₃ .

In the context of the general formula (la), it is even more preferable that i) R ⁴ and R ⁵ are each phenyl, and ii) R ⁶ is Ci-Ci ₂ -alkyl, preferably C ₆ -C ₁₀ -alkyl, especially C ₈ -alkyl.

The mixture according to the present invention comprises as component (B) at least one hydrocarbon compound containing two hydroxyl groups and having a molecular weight of < 500 g/mol. Both these hydrocarbon compounds according to component (B) as such are known to a person skilled in the art.

Any hydrocarbon compound containing two hydroxyl groups (OH groups or hydroxy groups, respectively) and having a molecular weight of < 500 g/mol known to a person skilled in the art can be employed as component (B). Such compounds can also be named as “diols”. The compound may be based on an aliphatic fragment or an aromatic fragment. However, it is also possible that the respective compound may comprise both (at least) one aliphatic fragment and (at least) one aromatic fragment. It is also possible that the respective compound may comprise further substituents (functional groups) besides the two hydroxyl groups. However, it is preferred that the respective hydrocarbon compound does not have any further substituents besides the two hydroxyl groups. It is preferred that the hydrocarbon compound according to component (B) has a molecular weight of < 300 g/mol, more preferably a molecular weight of < 200 g/mol.

It is also preferred that hydrocarbon compounds are employed as component (B), having (at least) one aliphatic fragment, and each of the two hydroxyl groups is positioned at an individual carbon atom of the respective aliphatic fragment and at least one carbon atom is in between the respective two carbon atoms having each one hydroxyl group as substituent. In other words, the two hydroxyl groups are (at least) in 1,3-position in relation to the respective aliphatic fragment in case of aliphatic diols. This means that a 1,4-position, a 1,5-position etc. in relation to the respective aliphatic fragments are also preferred, but the 1,3-position in relation to the respective aliphatic fragment for an aliphatic diol is even more preferred. In contrast, a 1,2-position in relation to the respective aliphatic fragment or even a 1,1 -position is less preferred.

Preferably, the hydrocarbon compound according to component (B) is an aromatic diol or an aliphatic diol, preferably an aromatic diol based on one or two benzene fragments or an aliphatic diol wherein the two hydroxyl groups are in 1,3-position in relation to the respective aliphatic fragment.

More preferably, the hydrocarbon compound according to according to component (B) is selected from 1,3-butanediol, 1,3-propanediol, 2-ethylhexane-1,3-diol, 2,2-dihydroxybiphenol or 1,2-benzenediol, preferably selected from 1,3-propanediol, 2-ethylhexane-1 ,3-diol or 2,2-dihydroxybiphenol.

In a preferred embodiment of the present invention, hydrocarbon compounds according to component (B) are employed, which provide a clear solution when being mixed with the catalyst according to component (A) and even more preferably when being mixed with the catalyst according to component (A) and the solvent according to component (C) as defined below. Within this embodiment, it is preferred that the hydrocarbon compound according to component (B) is selected from 1,3-propanediol, 2-ethylhexane-1 ,3-diol or 2,2-dihydroxybiphenol.

The molar ratio within the mixture according to the present invention of component (B) to component (A) is in the range of 0.1 to 10 [mol/mol], more preferred in the range of 0.1 to 5 [mol/mol]. .

The mixture according to the present invention may comprise as an optional component (C) at least one solvent. Solvents as such are known to a person skilled in the art. In principle, any solvent known to the skilled person can be employed as component (C). However, it is preferred that the respective solvents have a good solubility behaviour in respect to the hydrocarbon compound according to component (B) and/or the catalyst according to compound (A) of the respective mixture.

Preferably, the solvent is selected from aromatic and/or aliphatic solvents, ketones, esters and ether-esters, xylene or methyl ethyl ketone, most preferably the solvent is xylene.

The solvent according to component (C) may be present within the mixture according to the present invention according to any ratio (and/or amount) in relation to components (A) and/or (B) as known to a skilled person. For example, the molar ratio of component (C) to component (A) is in the range of 1 to 20 [mol/mol].

In a preferred embodiment of the present invention, the mixture comprises at least one catalyst according to component (A) as defined above, at least one hydrocarbon compound according to component (B) as defined above, and at least one solvent according to component (C) as defined above.

It is preferred that the mixture according to the present invention is defined as follows: i) the mixture is homogeneous, and/or ii) at least 90% by weight, preferably at least 95% by weight, more preferably at least 99% by weight, most preferably at least 99.9% by weight of the total weight of the mixture consists of components (A) to (C).

Another subject of the present invention is a method for producing a mixture as described above. Any method known to a person skilled in the art for obtaining a mixture can be employed. The method for producing a mixture as defined above can be carried out by a method wherein components (A) and (B) and also optionally present component (C) are provided separately from one another and subsequently mixed with one another.

Preferably, a mixture is provided comprising components (A) to (C), wherein components (A) and (C) are mixed beforehand and component (B) is added afterwards, more preferably components (A) and (C) are mixed in order to obtain a homogeneous mixture and component (B) is added afterwards.

For the sake of completeness, it is mentioned here that the catalyst according to component (A) as such can be prepared by a method as described in EP patent application 19155916.0.

The method for preparing a bismuth-containing catalyst of the general formula (I) or of the general formula (la) according to component (A) as defined above can be carried out for example, in which i) at least one compound of the general formula (I la) or a corresponding salt thereof, wherein the radicals R ⁴ to R ⁶ are defined according to the embodiments/definitions above, ii) optionally at least one compound of the general formula (Ilia) o

R ³ ,— C II— OH

(Ilia) or a corresponding salt thereof, wherein the radical R ³ is defined according to the embodiments/definitions above, iii) is reacted with at least one bismuth-containing compound selected from Bi ₂ 0 ₃ , bismuth carbonate, bismuth hydrogencarbonate, bismuth halide, Bi(C ₆ -Ci4-aryl) ₃ ,

Bi(C C ₁₂ -alkyl) ₃ or metallic bismuth.

The reactants listed above, i.e. the acids according to the general formulae (I la) or (Ilia) or the appropriate corresponding salts as such, are known to those skilled in the art. The corresponding salts used can be, for example, sodium, potassium or calcium salts. Optionally, instead of the aforementioned acids according to the general formulae (lla) or (Ilia) or corresponding salts thereof as reactants, it is also possible to use corresponding carboxylic esters, for example a methyl or ethyl ester. Such carboxylic esters can be prepared by reacting the aforementioned acids or a corresponding salt thereof with a suitable alcohol, for example methanol or ethanol, optionally in the presence of a catalyst. The appropriate preparation methods of such carboxylic esters are known to a person skilled in the art.

In principle, any bismuth-containing compound can be used in the method according to the invention, which is suitable for the purpose of forming the bismuth central atom in the bismuth-containing catalyst of the general formula (I) according to component (A), by reaction with the appropriate compound according to the general formula (lla) or optionally (Ilia). Bismuth-containing compounds as such are known to those skilled in the art. If, in accordance with the invention, a bismuth halide is used as bismuth- containing compound, it is preferably a chlorine-containing compound, especially BiCI ₃ . Any specific substituents/substitution patterns, such as the radicals R ⁴ to R ⁶ for example, may already be present in the corresponding reactant. Optionally, such substituents/substitution patterns can also be attached or completed even after the preparation process of a bismuth-containing catalyst according to the general formula (I) described above. Preferably, the bismuth-containing compound is selected from Bi ₂ 0 ₃ , BiCI ₃ , Bi(C ₆ H ₅ ) ₃ or metallic bismuth.

The bismuth-containing catalysts according to the general formula (I) according to component (A) are preferably prepared by reacting at least one compound of the general formula (I la) and optionally at least one compound of the general formula (Ilia) with at least one bismuth-containing compound, wherein i) the reaction is carried out under a protective atmosphere and/or in the presence of at least one solvent, especially toluene or tetrahydrofuran, and/or ii) the reaction is conducted for at least 10 hours and/or at a temperature of at least 100°C, and/or iii) following the reaction, volatile constituents are removed, the bismuth-containing catalyst is dried under reduced pressure and/or a recrystallization is carried out.

Furthermore, it is preferred in accordance with the invention that the at least one compound of the general formula (lla) used as reactant in the method according to the invention is prepared from a corresponding compound according to the general formula (lib), wherein the compounds according to the general formula (lla) only differ from the corresponding compounds of the general formula (lib) in that one or at most two radicals selected from R ⁴ , R ⁵ and R ⁶ is defined as H (hydrogen) in place of the definitions listed for the compounds according to general formula (lla). This is preferably effected by reacting a corresponding compound (lib), but in which R ⁵ and/or R ⁶ is H, with a lithium-containing compound, especially with n-butyllithium, and the intermediate obtained in this case is subsequently reacted with a haloalkane to introduce the radicals R ⁵ and R ⁶ to obtain a compound according to the general formula (lla). Haloalkanes used can be, for example, 1-bromooctane or 1-bromo- propane. This method variant is thus used in particular if a catalyst according to the invention in accordance with general formula (I) is intended to be prepared in which at least one of the radicals R ⁴ to R ⁶ , preferably precisely one of these radicals, is a Ci-Ci2-alkyl. Alternatively, it is also conceivable that, instead of a haloalkane, an appropriate haloaryl or haloaralkyl compound is used if, in the context of this method step, a fully or partially aromatic substituent is intended to be introduced into the corresponding compound (lib). Preferably, the compound according to the general formula (lib) used is 2-arylacetic acid, 2,2-diarylacetic acid, particularly 2-phenylacetic acid or 2,2-diphenylacetic acid, particularly preferably 2,2-diphenylacetic acid. The present invention further relates to the use of at least one mixture according to the definitions above for preparing compounds comprising a urethane group.

The invention is illustrated hereinafter by examples.

I) Preparation of catalysts according to component (A) of the invention la) Precursor of example 1: 2,2-Diphenyldecanoic acid (dpdH)

2,2-Diphenylacetic acid (10.6 g; 48 mmol) are dissolved in 75 ml_ of dry tetrahydrofuran (THF) under a protective gas atmosphere (argon or nitrogen) in a 200 ml_ Schlenk flask and cooled to -15°C. A 1.6M solution of n-butyllithium in hexane (60 ml_; 96 mmol) is then added with stirring and over a period of 30 minutes. The reaction solution is stirred at -15°C for one hour and cooled to -78°C for the addition of 1-bromooctane (8.3 ml_; 48 mmol). Subsequently, the reaction solution is slowly warmed to room temperature and stirred for a further 24 hours.

For the work-up and purification of the 2,2-diphenyldecanoic acid, a saturated ammonium chloride solution (60 ml_) is added to the reaction solution and stirred for 30 minutes. The aqueous phase is separated by means of a separating funnel and extracted with 3 x 25 ml_ of diethyl ether. The combined organic phases were dried over magnesium sulfate (MgS04). All volatile solvents are then removed under reduced pressure (1 10-3 mbar) and the resulting solid dried at 140°C under reduced pressure (1 10-3 mbar) for 24 hours.

Characterization by 1H-NMR, 13C-NMR, HRMS (high-resolution mass spectrometry), infra-red spectroscopy. lb) Catalyst according to Example 1: Bi(2,2-diphenyldecanoate) ₃ (Bi(dpd) ₃ )

Triphenylbismuth (1.1 g; 2.5 mmol) and 2,2-diphenyldecanoic acid (2.43 g; 7.5 mmol) are initially charged under a protective gas atmosphere in a 25 mL three-necked flask equipped with stirrer bar, reflux condenser, thermometer and protective gas atmosphere inlet (argon or nitrogen). 12.5 mL of dry tetrahydrofuran or dry toluene (5 mL of solvent per 1 mmol of triphenylbismuth) are added to the reactants and the mixture is heated at 110°C under a protective gas atmosphere for at least 16 hours. The reaction is monitored by 1H-NMR (nuclear magnetic resonance spectroscopy). After complete conversion of triphenylbismuth with formation of benzene, the reaction is terminated and cooled. All volatile solvents are then removed under reduced pressure (1 10-3 mbar) and the resulting solid dried at 60°C under reduced pressure (1 10-3 mbar) for 24 hours. As required, the resulting compound is purified from toluene and hexane at -40 °C or by recrystallization from hot toluene.

Characterization by 1H-NMR, 13C-NMR, C/H/N elemental analysis, infra-red spectroscopy.

II) Determination of the catalytic activity

The activity of the catalyst can be found in the subsequent tables. The activity is determinated through the reaction of an isocyanate functional compound Desmodur LD = 2-ethyl hexyl-(6-isocyanatohexyl)-carbamate (Covestro AG) with n-butanol. For this purpose, 3.3 ml (= 11 mmol) of Desmodur LD are mixed under inert conditions with 2 ml xylene containing 0.1 mmol of BiDPD ₃ and, where mentioned, the diols were added in an amount of 1 mmol. Directly before conducting the reaction via reflective IR- spectroscopy, 1 ml (11 mmol) butanol was added and the mixture thoroughly mixed. The mixture was held at 60°C or at 20°C according to the trial conditions. For each point measured, a drop of the above-mentioned mixture was isolated and measured in IR in times according to table 2.

The isocyanate decrease and thus the formation of a urethane group are investigated by horizontal ATR-IR spectroscopy. For this purpose, 0.05 mL of the reaction solution are withdrawn at defined time intervals and investigated directly by spectroscopy. The conversion is determined by the relative decrease in intensity of the asymmetrical isocyanate stretching vibration at 2250 - 2285 cm ^·1 . The starting content of free isocyanate of the reaction solution at room temperature in the absence of catalyst was determined. All IR spectra were normalized to the bands of the symmetrical and asymmetrical stretching vibrations of the CH ₂ groups (3000 - 2870 cm).

The catalysts used are detailed in Table 1.

V1 Bi(DPD) ₃ . NCO consumption tested at 60°C V2 Bi(DPD) ₃ . NCO consumption tested at 20°C E1 Bi(DPD) ₃ plus 10 equivalents of 1.3-propandiol E2 Bi(DPD) ₃ plus 10 equivalents of 2.2-dihydroxybiphenol [CAS 661-369]

V3 Bi(DPD) ₃ . NCO consumption tested at 20°C. Instead of n-butanol 2.2-di hydroxy- biphenol was used as reaction partner. “V” means comparative example, whereas Έ” means working example.

Table 1 Table 2

As can be seen from table 2, the presence of component (B) according to working examples E1 and E2 provides a clear increase in terms of catalytic activity compared to comparative example V2. Comparative example V3 shows that component (B) as such is not as active forming urethanes from both reaction partners, but component (B) successfully increases the catalytic activity of the catalyst according to component (A) as shown in working example E2. However, the activity of working examples E1 and E2 (carried out at room temperature of 20°C) is comparable to that of comparative example V1 where the reaction is conducted at 60°C showing the real benefit of the diols as activation component (at rather low temperatures such as room temperature).