WO2024110325A1

WO2024110325A1 - Yellow methine dyes and their use for dyeing plastics

Info

Publication number: WO2024110325A1
Application number: PCT/EP2023/082174
Authority: WO
Inventors: Hans-Ulrich Borst; Frank Linke
Original assignee: Lanxess Deutschland Gmbh
Priority date: 2022-11-24
Filing date: 2023-11-17
Publication date: 2024-05-30

Abstract

The present invention relates to the use of substituted m-toluidines of formula (I), wherein R1 represents methyl or ethyl, and R2 represents methyl, ethyl or methyl or ethyl, each of which is substituted by a group of formula (A), as thermostable methine dyes in plastics or polymers.

Description

Thermostable methine dyes

The present invention relates to the use of substituted m-toluidines of formula (I)

wherein

R ¹ and R ² are the same or different and each represent optionally substituted alkyl, R ³ and R ⁴ are the same or different and each represent hydrogen or optionally substituted alkyl and R ⁵ represents oxygen or sulfur as thermostable methine dyes and their use for coloring plastics.

Although there are already a large number of yellow dyes on the market for coloring plastics, there is still a need for new dyes with improved properties. In particular, there is still a need to improve the existing dyes with regard to the two properties of color strength and thermal stability. This is particularly true for the use of dyes for the mass coloring of polyamide.

The mass coloring of synthetic polyamides places higher demands on the colorants used than the mass coloring of other plastics. The melting points of synthetic polyamides are significantly higher and the chemical reactivity of the melted polyamides, especially polyamide 6.6, is also significantly greater, so that the heat stability of the colorants used must be extremely good. There are few colorants that meet these high requirements, especially when high light resistance is also required.

EP-A 0 225553 describes azo color lakes that can be used to color polyamide in yellow shades. The use of Pigment Yellow 192 is also known. EP-A 0 074 515 discloses nickel azobarbituric acid complexes that can also be used to produce yellow colorations of polyamide. Although these known pigments have good thermal stability, they cannot be used to produce transparent colors for plastics. Pigments can also impair the mechanical properties of polymers.

It is also known from the state of the art to use solvent dyes to color plastics in transparent yellow shades. The mechanical properties of the polymers are generally not negatively affected by these dyes.

A well-known soluble yellow dye is Solvent Yellow 93 (C.l. 48160; CAS No. 4702-90-3) from the class of methine dyes, but with two 3H-pyrazol-3-one groups in the molecule.

In order to improve the light sensitivity in the visible range, in JP H10 48824 A, at least one methine dye based on substituted m-toluidines is added to a photopolymerizable composition.

EP 0 415 535 A1 relates to colored photothermographic emulsions containing, inter alia, benzylidene leuco dyes based on an m-toluidine structure.

In B. Jedrzejewska et al, Highly Effective Sensitizers Based on Merocyanine Dyes for Visible Light Initiated Radical Polymerization, Polymers 2020, 12(6), 1242, 5-(4-substituted arylidene)-1,3-dimethylpyrimidine-2,4,6-triones are tested as visible light sensitizers for phenyltrialkylborate salts, which in turn are used to initiate polymerization processes.

Finally, DE 31 50 266 A1 describes an electrophotographically sensitive material with an electrophotographically sensitive layer containing a charge-generating material and a charge-transfer material, wherein the charge-generating material comprises a barbituric acid derivative or thiobarbituric acid derivative, each of which may optionally be substituted with an m-toluidine group.

However, the properties of these yellow colorants, which are known from the state of the art, are not sufficient for the technical requirements that now exist and still need to be improved, particularly with regard to their fastness properties, such as light and heat resistance.

Surprisingly, it was found that substituted m-toluidines of the formula (I)

wherein

R ¹ and R ² are the same or different and each represent optionally substituted alkyl,

R ³ and R ⁴ are the same or different and each represent hydrogen or optionally substituted alkyl and

R ⁵ stands for oxygen or sulfur, thermostable methine dyes are obtained which are suitable for use in polymers or plastics.

With the substituted m-toluidines of the formula (I) to be used according to the invention, yellow colorations of plastics, in particular of polyamides, can be achieved which are surprisingly characterized by improved light fastness and improved thermal stability compared to the known yellow dyes used for these purposes.

With the substituted m-toluidines of formula (I) to be used according to the invention, it is possible to significantly exceed the property profiles of known yellow dyes for plastic coloring that have been achieved to date.

For the sake of clarity, it should be noted that the scope of the present invention includes all of the definitions and parameters listed in general or preferred areas in any combination. This particularly applies to the quantities and parameters of the individual components to be used in the processes and uses claimed in the context of the present application. The standards mentioned in the context of this application refer to the version applicable on the filing date of this invention. The terms thermostable and heat-stable are synonymous in the context of this invention. Alkyl in the meaning of R ¹ to R ⁴ represents a straight-chain or branched saturated hydrocarbon radical which is optionally mono- or polysubstituted by identical or different substituents. The alkyl radicals mentioned preferably contain 1 to 6 carbon atoms, particularly preferably 1 to 4 carbon atoms. The alkyl radicals mentioned are in particular methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl and tert-butyl, each of which is optionally mono- or polysubstituted by identical or different substituents.

The alkyl radicals mentioned in the meaning of R ¹ to R ⁴ are unsubstituted or mono- or polysubstituted by identical or different substituents. Possible substituents for the alkyl radicals mentioned are, for example, halogen atoms, in particular fluorine and/or chlorine atoms and/or aryloxy radicals.

Preferred are substituted m-toluidines of the formula (I) in which

R ¹ and R ² independently of one another represent unsubstituted Ci-C ₄ alkyl or represent Ci-C ₄ alkyl which is in each case substituted by a phenoxy or naphthoxy radical which is optionally mono- or disubstituted by identical or different substituents,

R ³ and R ⁴ independently of one another each represent hydrogen or unsubstituted Ci-C ₄ alkyl, and

R ⁵ stands for oxygen or sulfur.

Particularly preferred are substituted m-toluidines of the formula (I) in which

R ¹ represents unsubstituted Ci-C ₄ alkyl,

R ² represents unsubstituted Ci-C ₄ alkyl, or represents Ci-C ₄ alkyl, each of which is monosubstituted by a radical of the formula

wherein

R ⁶ each represents halogen, unsubstituted Ci.C ₄ -alkyl, unsubstituted Cs-Cy-cycloalkyl or unsubstituted phenyl, and and R ⁷ represents hydrogen or unsubstituted Ci-C ₄ -alkoxy,

R ³ and R ⁴ independently represent hydrogen or unsubstituted C1-C4 alkyl, and

R ⁵ stands for oxygen or sulfur.

Very particular preference is given to substituted m-toluidines of the formula (I) in which

R ¹ is methyl, ethyl, n-propyl or iso-propyl,

R ² represents methyl, ethyl, n-propyl or iso-propyl or represents methyl, ethyl, n-propyl or iso-propyl, each of which is monosubstituted by a radical of the formula

wherein

R ⁶ is methyl, ethyl, n-propyl, iso-propyl, cyclopentyl, cyclohexyl or phenyl, and R ⁷ is hydrogen, methoxy or ethoxy,

R ³ and R ⁴ independently represent hydrogen, methyl, ethyl, n-propyl or iso-

Propyl, and

R ⁵ stands for oxygen or sulfur.

Particularly preferred are substituted m-toluidines of the formula (I) in which

R ¹ is methyl or ethyl,

R ² represents methyl, ethyl or methyl or ethyl, each of which is substituted by a radical of the formula

wherein

R ⁶ is methyl, ethyl, cyclohexyl or phenyl, and

R ⁷ is hydrogen or methoxy,

R ³ and R ⁴ independently represent hydrogen, methyl or ethyl, and R ⁵ represents oxygen or sulfur. The essential subject matter of the present invention is the use of substituted m-toluidines of the formula (I) for use as thermostable methine dyes in plastics or polymers, preferably for mass coloring of plastics. The substituted m-toluidines to be used according to the invention can be used individually or in any desired mixture with one another.

The present invention therefore particularly relates to the use of substituted m-toluidines of the formula (I)

where R ¹ is methyl or ethyl,

R ² represents methyl, ethyl or methyl or ethyl, each substituted by a

Rest of the formula

wherein R ⁶ is methyl, ethyl, cyclohexyl or phenyl, and R ⁷ is hydrogen or methoxy,

R ³ and R ⁴ independently of one another each represent hydrogen, methyl or ethyl, and R ⁵ represents oxygen or sulphur, as thermostable methine dyes in plastics or polymers, with the proviso that “thermostable” means a heat stability > 395 °C to be determined on the respective plastic granulate according to DIN EN 12877-2 Method A (“Determination of the fastness of the colour to heat when processing colourants in plastics”).

Methine dyes can be prepared using the substituted m-toluidines of formula (I) used according to the invention and can be used to produce yellow dyes for plastics, in particular polyamides, which surprisingly characterized by improved light fastness and improved thermal stability compared to the known yellow dyes used for these purposes.

With the substituted m-toluidines of formula (I) to be used according to the invention, it is possible to synthesize methine dyes which significantly exceed the property profiles of previously realized yellow dyes for plastic coloring and specifically meet the demand for thermostable yellow dyes.

Mass dyeing refers in particular to processes in which the dye is incorporated into the molten plastic mass, e.g. with the aid of an extruder, or in which the dye is already added to the starting components for producing the plastic, e.g. monomers before polymerization.

Polymers or plastics according to the invention to be colored from the heat- or thermostable methine dyes obtainable from the substituted m-toluidines of the formula (I) are preferably thermoplastics, particularly preferably vinyl polymers, polyesters, polyamides or polyolefins, very particularly preferably polyethylene, polypropylene, polycarbonates, polyamides or polymethyl methacrylates. Polyamides are particularly preferred, especially very particularly preferred are polyamide 6.6 polyamide 6. The invention also includes mixtures of the plastics or polymers listed.

The term polyamide is used in the context of the present invention to refer to synthetic, technically usable thermoplastics and thus distinguishes this class of material from chemically related proteins. Almost all important polyamides are derived from primary amines, because the repeating unit consists of the functional group -CO-NH-. There are also polyamides from secondary amines (-CO-NR-, R = organic residue). The monomers used to produce the polyamides are in particular aminocarboxylic acids, lactams and/or diamines and dicarboxylic acids.

Polyamide 6.6 (CAS No. 32131-17-2) is usually made from hexamethylenediamine (HMD) and adipic acid. It is produced by polycondensation with elimination of water. Polyamide 6 (CAS No. 25028-54-4) is obtained by ring-opening polymerization of ε-caprolactam with water as starter.

Preferred vinyl polymers are polystyrene, styrene-acrylonitrile copolymers, styrene-butadiene copolymers, styrene-butadiene-acrylonitrile terpolymers, polymethacrylate, polyvinyl chloride, etc. Preferred polyesters are polyethylene terephthalates, polybutylene terephthalates,

Polycarbonates and cellulose esters.

The plastics to be colored can be present individually or in mixtures with one another, as plastic masses or melts.

When used for the mass coloration of plastics, the methine dyes according to the invention based on substituted m-toluidines of the formula (I) are preferably used in finely divided form, wherein dispersants can but do not have to be used.

When used for mass coloring of plastics, the methine dyes according to the invention and based on substituted m-toluidines of formula (I) can be used directly in the process of plastics production after polymerization has taken place. Preferably, at least one methine dye according to the invention and based on substituted m-toluidines of formula (I) is dry mixed or ground with the plastic granulate and this mixture is plasticized and homogenized, for example on mixing rollers or in screws. The methine dyes according to the invention and based on substituted m-toluidines of formula (I) can also be added to the molten mass and distributed homogeneously by stirring. The material pre-colored in this way can then be further processed into molded parts in the usual way, e.g. by spinning, extrusion or injection molding.

For the purposes of the present invention, the term “molded parts” refers to three-dimensional bodies of any spatial shape, in particular bristles, threads, fibers, films and plates.

Since the methine dyes to be used according to the invention and based on substituted m-toluidines of the formula (I) are surprisingly resistant to polymerization catalysts, in particular peroxides, it is also possible to add them to the monomeric starting materials for the production of plastics, e.g. polymethyl methacrylate (PMMA) and then to polymerize them in the presence of polymerization catalysts. For this purpose, these are preferably dissolved in the monomeric components of the plastic to be formed or intimately mixed with them. The methine dyes to be used according to the invention and based on substituted m-toluidines of the formula (I) are preferably used for coloring the said plastics, in particular polyamide, in amounts of 0.0001 to 1 wt. %, in particular 0.01 to 0.5 wt. %, based on the amount of polymer.

By adding pigments that are insoluble in the polymers, especially titanium dioxide, corresponding valuable muted colors can be obtained. In this case, titanium dioxide can be present in an amount of 0.01 to 10% by weight, preferably 0.1 to 5% by weight, based on the amount of polymer.

The present invention further relates to a process for the mass coloring of plastics, wherein at least one methine dye based on substituted m-toluidines of the formula (I) is dry mixed or ground with at least one plastic, preferably in granulate form, and this mixture is plasticized and homogenized, for example on mixing rollers or in screws.

However, the methine dyes based on substituted m-toluidines of formula (I) according to the invention can also be added to the molten mass and distributed homogeneously by stirring. It is also possible to add the methine dyes based on substituted m-toluidines of formula (I) to be used according to the invention to the monomeric starting materials during plastics production and then to polymerize them.

The material pre-colored in this way can then preferably be further processed into bristles, threads, etc. by spinning or by extrusion or injection molding to form molded parts.

These processes produce transparent or opaque brilliant yellow colors with very good heat or thermal stability and high light resistance.

To carry out such processes, mixtures of the methine dyes to be used according to the invention and based on substituted m-toluidines of the formula (I) with other dyes and/or inorganic and/or organic pigments can also be used. The present invention further relates to plastic compositions comprising at least one thermoplastic and at least one thermostable methine dye based on substituted m-toluidines of the formula (I).

Preferably, such plastic compositions contain at least one thermoplastic from the series vinyl polymers, polyesters, polyamides and polyolefins, particularly preferably polyethylene and polypropylene, polycarbonates, polyamides and polyacrylic methacrylate.

Such plastic compositions very particularly preferably contain at least one polyamide, in particular polyamide 6.6 and/or polyamide 6.

These plastic compositions can also contain the thermoplastic in the form of the respective polymerizable monomers.

These plastic compositions contain the thermoplastic in finely distributed form, preferably in the form of granules.

These plastic compositions may contain one or more dyes, organic or inorganic pigments as well as usual auxiliaries and additives in the amounts usual for these substances.

To produce muted colors, the plastic compositions according to the invention preferably contain titanium dioxide in an amount of 0.01 to 10 wt. %, preferably 0.1 to 5 wt. %, based on the amount of thermoplastics.

These plastic compositions can be prepared in a known manner, preferably by mixing or grinding at least one thermoplastic, preferably in granulate form, with at least one methine dye based on substituted m-toluidine of the formula (I).

The methine dyes based on substituted m-toluidines of formula (I) can be prepared in a manner known per se by reacting at least one aldehyde of formula (II) ■ li

wherein

R ¹ and R ² have the general and preferred meanings given for formula (I), with at least one barbituric acid derivative of formula (III)

wherein

R ³ , R ⁴ and R ⁵ have the general and preferred meanings given for formula (I).

The process for preparing the methine dyes based on substituted m-toluidines of the formula (I) by reacting the aldehydes of the formula (II) with the barbituric acid derivatives of the formula (III) can be carried out in a manner known per se.

In general, the process is carried out by first introducing the aldehyde (II) and adding the barbituric acid derivative (III) and isolating the dye of formula (I) after the reaction has taken place. The isolation can be carried out by conventional methods, preferably by filtration. The reaction product obtained can optionally be worked up by further process steps such as washing and drying.

The process can be carried out in the presence of at least one solvent. Suitable solvents are, for example, those from the series of alkanecarboxylic acids. The process for preparing the dyes (I) according to the invention is preferably carried out in the presence of at least one alkanecarboxylic acid from the series acetic acid, propanoic acid, butanoic acid. The process can be carried out in the presence of at least one base. Suitable bases are, for example, alkali metal hydroxides and alkali metal alcoholates. Preference is given to using lithium hydroxide, sodium hydroxide, potassium hydroxide and/or potassium tert-butoxide, particularly preferably sodium hydroxide and/or potassium tert-butoxide.

The process is generally carried out at a temperature in the range from -10 to 180 °C, preferably from 0 to 110 °C and particularly preferably from 10 to 100 °C.

The process is conveniently carried out at ambient pressure, but the reaction can also be carried out in the range from 1000 to 10000 hPa, preferably 10 to 5000 hPa. Ambient pressure is understood to mean an air pressure in the range from about 925 hPa to 1070 hPa.

The barbituric acid derivatives of formula (III) are known and can be obtained, for example, as commercial products from Alfa Aesar.

Preferred compounds of formula (III) for carrying out the process are barbituric acid, 1,3-dimethylbarbituric acid, thiobarbituric acid and 1,3-diethyl-2-thiobarbituric acid

The aldehydes of formula (II) used to carry out the process are known and can be prepared in a manner known to the person skilled in the art, for example by the Vilsmeier-Haack reaction known from the literature.

To prepare the compounds of formula (II), at least one substituted m-toluidine of formula (IV)

wherein

R ¹ and R ² have the general and preferred meanings given for formula (I), with at least one formylating reagent.

In general, the reaction is carried out by initially introducing at least one compound of formula (IV) and adding the formylation reagent, optionally in the presence of at least one solvent, and then reacting the aldehyde of formula (II) thus prepared, optionally by adding a suitable Amount of a suitable precipitant, and then isolating the aldehyde of formula (II) by conventional methods, for example by filtration.

A mixture of at least one formamide and at least one phosphoric acid chloride is generally used as the formylation reagent.

Preferred formamides are dimethylformamide, diethylformamide and dibutylformamide. Preferred phosphoric acid chloride is phosphorus oxychloride.

The reaction is generally carried out at a temperature in the range between 10 and 90 °C, preferably from 20 to 80 °C and particularly preferably from 30 to 70 °C.

The process for preparing the compounds (II) is conveniently carried out at ambient pressure, but the reaction can also be carried out in the range from 1000 to 10000 hPa, preferably 10 to 5000 hPa. Ambient pressure is understood to mean an air pressure in the range from about 925 hPa to 1070 hPa.

The reaction can be carried out in the presence of at least one solvent. Suitable solvents are, for example, formamides. Dimethylformamide and diethylformamide are preferred, and the use of dimethylformamide is particularly preferred. When using dimethylformamide, it is particularly preferred to use it in excess, with the dimethylformamide then serving simultaneously as a formylation reagent and as a solvent.

A mixture of dimethylformamide and phosphorus oxychloride is particularly preferably used as the formylation reagent.

In general, at least one mole of formylating reagent is used per mole of compound of formula (IV), preferably 1.1 to 1.5 moles and particularly preferably 1.1 to 1.0 moles.

Suitable precipitants for the precipitation of the compounds of formula (II) are, for example, water and alcohols such as methanol and/or ethanol.

Aniline derivatives of the formula (IV) are known and can be purchased as commercial products, for example from Merk, TCI or Sigma Aldrich.

The invention is illustrated, but not limited, by the following examples. EXAMPLES

Preparation of compounds of formula (I

Example 1

Preparation of a compound of formula (1-1) according to the invention

36.6 g (0.10 mol) of the aldehyde of formula (IIa) prepared according to Example A and 12.8 g (0.10 mol) of barbituric acid were added to 200 ml of acetic acid. 2 g of ammonium chloride were then added and the reaction mixture was heated to a temperature of 100 °C and then stirred for 6 hours. It was then cooled to 25 °C and the reaction product was isolated on a suction filter. The filter cake was washed with approx. 300 ml of methanol and approx. 1000 ml of water at a temperature of 80 °C. The washed product was dried in a vacuum drying cabinet at a temperature of 80 °C and a pressure of 20,000 Pa.

Yield: 42.8 g (corresponds to 90% of theory), melting point 237 °C. Examples 2 to 28

The preparation and work-up of the compounds of Examples 2 to 28 were carried out analogously to Example 1, but with the following deviations:

Example 2

Preparation of a compound of formula (I-2) according to the invention

Instead of the barbituric acid used in Example 1, 14.4 g (0.10 mol) of thiobarbituric acid were used.

Yield: 41.3 g (corresponds to 84% of theory), melting point 198 °C. Example 3

Preparation of a compound of formula (I-3) according to the invention

Instead of the barbituric acid used in Example 1, 15.6 g (0.10 mol) of dimethylbarbituric acid were used. Yield: 40.2 g (corresponds to 80% of theory), melting point 210 °C.

Example 4

Preparation of a compound of formula (I-4) according to the invention

Instead of the barbituric acid used in Example 1, 20.0 g (0.10 mol) of 1,3-diethylthiobarbituric acid were used.

Yield: 44.9 g (corresponds to 82% of theory), melting point 127 °C.

Example 5 Preparation of a compound of formula (I-5) according to the invention

Instead of the aldehyde used in Example 1, 16.3 g (0.1 mol) of the aldehyde of formula (I l-b) prepared according to Example B) were used.

Yield: 21.1 g (corresponds to 77% of theory), melting point 228 °C. Example 6

Preparation of a compound of formula (1-6) according to the invention

Instead of the aldehyde used in Example 1, 16.3 g (0.1 mol) of the aldehyde of formula (I l-b) prepared according to Example B) were used and instead of barbituric acid, 14.4 g (0.1 mol) of thiobarbituric acid were used.

Yield: 25.0 g (corresponds to 86% of theory), melting point 212 °C.

Example 7

Preparation of a compound of formula (I-7) according to the invention

Instead of the aldehyde used in Example 1, 16.3 g (0.1 mol) of the aldehyde of formula (I l-b) prepared according to Example B) were used and instead of barbituric acid, 15.6 g (0.1 mol) of dimethylbarbituric acid were used. Yield: 23.1 g (corresponds to 76% of theory), melting point 206 °C.

Example 8

Preparation of a compound of formula (I-8) according to the invention

Instead of the aldehyde used in Example 1, 16.3 g (0.1 mol) of the aldehyde of formula (I l-b) prepared according to Example B) were used and instead of barbituric acid, 20.0 g (0.1 mol) of 1,3-diethylthiobarbituric acid were used.

Yield: 27.5 g (corresponds to 79% of theory), melting point 198 °C.

Example 9

Preparation of a compound of formula (I-9) according to the invention

Instead of the aldehyde used in Example 1, 19.1 g (0.1 mol) of the aldehyde of formula (II-b) prepared according to Example C) were used.

Yield: 22.8 g (corresponds to 75% of theory), melting point 218 °C. Example 10

Preparation of a compound of formula (1-10) according to the invention

Instead of the aldehyde used in Example 1, 19.1 g (0.1 mol) of the aldehyde of formula (II-c) prepared according to Example C) were used and instead of barbituric acid, 14.4 g (0.1 mol) of thiobarbituric acid were used.

Yield: 25.8 g (corresponds to 81% of theory), melting point 222 °C.

Example 11

Preparation of a compound of formula (1-11) according to the invention

Instead of the aldehyde used in Example 1, 19.1 g (0.1 mol) of the aldehyde of formula (I l-c) prepared according to Example C) were used and instead of barbituric acid, 15.6 g (0.1 mol) of dimethylbarbituric acid were used. Yield: 25.2 g (corresponds to 76% of theory), melting point 162 °C.

Example 12

Preparation of a compound of formula (1-12) according to the invention

Instead of the aldehyde used in Example 1, 19.1 g (0.1 mol) of the aldehyde of formula (I l-c) prepared according to Example C) were used and instead of barbituric acid, 20.0 g (0.1 mol) of 1,3-diethylthiobarbituric acid were used.

Yield: 28.2 g (corresponds to 75% of theory), melting point 188 °C.

Example 13

Preparation of a compound of formula (1-13) according to the invention

Instead of the aldehyde used in Example 1, 29.7 g (0.1 mol) of the aldehyde of formula (II-d) prepared according to Example D) were used.

Yield: 33.1 g (corresponds to 76% of theory), melting point 231 °C. Example 14

Preparation of a compound of formula (1-14) according to the invention

Instead of the aldehyde used in Example 1, 29.7 g (0.1 mol) of the aldehyde of formula (II-d) prepared according to Example D) were used and instead of barbituric acid, 14.4 g (0.1 mol) of thiobarbituric acid were used.

Yield: 34.0 g (corresponds to 80% of theory), melting point 218 °C.

Example 15

Preparation of a compound of formula (1-15) according to the invention

Instead of the aldehyde used in Example 1, 29.7 g (0.1 mol) of the aldehyde of formula (II-d) prepared according to Example D) were used and instead of barbituric acid, 15.6 g (0.1 mol) of dimethylbarbituric acid were used. Yield: 34.6 g (corresponds to 79% of theory), melting point 198 °C.

Example 16

Preparation of a compound of formula (1-16) according to the invention

Instead of the aldehyde used in Example 1, 29.7 g (0.1 mol) of the aldehyde of the formula (II-d) prepared according to Example D) were used and instead of barbituric acid, 20.0 g (0.1 mol) of 1,3-diethylthiobarbituric acid were used.

Yield: 34.6 g (corresponds to 74% of theory), melting point 178 °C.

Example 17

Preparation of a compound of formula (1-17) according to the invention

Instead of the aldehyde used in Example 1, 32.6 g (0.1 mol) of the aldehyde of formula (I l-e) prepared according to Example E) were used.

Yield: 32.4 g (corresponds to 74% of theory), melting point 219 °C. Example 18

Preparation of a compound of formula (1-18) according to the invention

Instead of the aldehyde used in Example 1, 32.6 g (0.1 mol) of the aldehyde of formula (I l-e) prepared according to Example E) were used and instead of barbituric acid, 14.4 g (0.1 mol) of thiobarbituric acid were used.

Yield: 35.4 g (corresponds to 78% of theory), melting point 208 °C.

Example 19

Preparation of a compound of formula (1-19) according to the invention

Instead of the aldehyde used in Example 1, 32.6 g (0.1 mol) of the aldehyde of formula (I l-e) prepared according to Example E) were used and instead of barbituric acid, 15.6 g (0.1 mol) of dimethylbarbituric acid were used. Yield: 35.8 g (corresponds to 77% of theory), melting point 178 °C.

Example 20

Preparation of a compound of formula (I-20) according to the invention

Instead of the aldehyde used in Example 1, 32.6 g (0.1 mol) of the aldehyde of formula (I l-e) prepared according to Example E) were used and instead of barbituric acid, 20.0 g (0.1 mol) of 1,3-diethylthiobarbituric acid were used.

Yield: 37.7 g (corresponds to 74% of theory), melting point 169 °C.

Example 21

Preparation of a compound of formula (1-21) according to the invention

Instead of the aldehyde used in Example 1, 34.1 g (0.1 mol) of the aldehyde of formula (II-f) prepared according to Example F) were used.

Yield: 32.6 g (corresponds to 72% of theory), melting point 207 °C. Example 22

Preparation of a compound of formula (1-22) according to the invention

Instead of the aldehyde used in Example 1, 34.1 g (0.1 mol) of the aldehyde of formula (II-f) prepared according to Example F) were used and instead of barbituric acid, 14.4 g (0.1 mol) of thiobarbituric acid were used.

Yield: 36.2 g (corresponds to 77% of theory), melting point 195 °C.

Example 23

Preparation of a compound of formula (1-23) according to the invention

Instead of the aldehyde used in Example 1, 34.1 g (0.1 mol) of the aldehyde of formula (ll-f) prepared according to Example F) were used and instead of barbituric acid, 15.6 g (0.1 mol) of dimethylbarbituric acid were used. Yield: 38.0 g (corresponds to 79% of theory), melting point 171 °C.

Example 24

Preparation of a compound of formula (I-24) according to the invention

Instead of the aldehyde used in Example 1, 34.1 g (0.1 mol) of the aldehyde of the formula (II-f) prepared according to Example F) were used and instead of barbituric acid, 20.0 g (0.1 mol) of 1,3-diethylthiobarbituric acid were used.

Yield: 40.0 g (corresponds to 76% of theory), melting point 163 °C.

Example 25

Preparation of a compound of formula (I-25) according to the invention

Instead of the aldehyde used in Example 1, 36.0 g (0.1 mol) of the aldehyde of formula (II-g) prepared according to Example G) were used.

Yield: 36.8 g (corresponds to 78% of theory), melting point 213 °C. Example 26

Preparation of a compound of formula (I-26) according to the invention

Instead of the aldehyde used in Example 1, 36.0 g (0.1 mol) of the aldehyde of formula (II-g) prepared according to Example G) were used and instead of barbituric acid, 14.4 g (0.1 mol) of thiobarbituric acid were used.

Yield: 38.5 g (corresponds to 79% of theory), melting point 186 °C.

Example 27

Preparation of a compound of formula (I-27) according to the invention

Instead of the aldehyde used in Example 1, 36.01 g (0.1 mol) of the aldehyde of formula (II-g) prepared according to Example G) were used and instead of barbituric acid, 15.6 g (0.1 mol) of dimethylbarbituric acid were used.

Yield: 40.0 g (corresponds to 80% of theory), melting point 175 °C

Example 28

Preparation of a compound of formula (I-28) according to the invention

Instead of the aldehyde used in Example 1, 36.0 g (0.1 mol) of the aldehyde of formula (II-g) prepared according to Example G) were used and instead of barbituric acid, 20.0 g (0.1 mol) of 1,3-diethylthiobarbituric acid were used.

Yield: 44.0 g (corresponds to 81% of theory), melting point 178 °C.

Production of precursors Example A

Preparation of an aldehyde of formula (ll-a)

a) Preparation of the ether

176.3 g (1.0 mol) of 4-cyclohexylphenol and 197.7 g (1.0 mol) of N-(2-chloroethyl)-N-ethyl-3-methylaniline were added to 500 ml of water. Then 84 g (1.05 mol) of a 50% aqueous sodium hydroxide solution were added. The mixture was then heated to 95 °C over the course of 180 minutes and then stirred for 12 hours. The reaction mixture was then left to stand for 4 hours until phase separation had occurred. The aqueous phase was then separated. Any remaining water was removed from the organic phase under vacuum at 80 °C and 2000 Pa. b) Preparation of the aldehyde

Then 310 g (4.24 mol) of dimethylformamide were added dropwise to the organic phase from step a). Then 160 g (1.04 mol) of phosphorus oxychloride were added over the course of 3 hours at a temperature of 60 °C. The reaction mixture was then stirred for 5 hours. It was then cooled to 20 °C and 160 g of methanol and 400 g of water were added. A pH of approx. 8 was adjusted by adding a 50% aqueous sodium hydroxide solution. The reaction mixture was left to stand for 4 hours until phase separation had occurred. The aqueous phase was then separated off. Any remaining water was removed from the organic phase under vacuum at 80 °C and 2000 Pa.

Yield: 347.2 g (corresponds to 95% of theory).

Example B

Preparation of an aldehyde of formula (ll-b)

310 g (4.24 mol) of dimethylformamide were initially charged and 135.2 g (1.0 mol) of N,N-dimethyl-3-methylaniline were added dropwise. 160 g (1.04 mol) of phosphorus oxychloride were then added at 60 °C over the course of 3 hours. The reaction mixture was then stirred for 5 hours. It was then cooled to 20 °C and 160 g of methanol and 400 g of water were added. A pH of approx. 8 was then adjusted by adding a 50% aqueous sodium hydroxide solution. The reaction mixture was left to stand for 4 hours until phase separation had occurred. The aqueous phase was then separated off. Residual water was removed from the organic phase under vacuum at 80 °C and 2000 Pa.

Yield: 150.1 g (corresponds to 92% of theory).

Example C

Preparation of an aldehyde of formula (ll-c)

310 g (4.24 mol) of dimethylformamide were initially charged and 163.5 g (1.0 mol) of N,N-diethyl-3-methylaniline were added dropwise. Then 160 g (1.04 mol) of phosphorus oxychloride were added at 60 °C over the course of 3 hours. The reaction mixture was stirred for 5 hours. It was then cooled to 20 °C and 160 g of methanol and 400 g of water were added. A pH of approx. 8 was then adjusted with approx. 240 g of a 50% aqueous sodium hydroxide solution. The reaction mixture was left to stand for 4 hours until phase separation had occurred. The aqueous phase was then separated off. Any remaining water was removed from the organic phase under vacuum at 80 °C and 2000 Pa.

Yield: 177.1 g (corresponds to 93% of theory).

Example D

Preparation of an aldehyde of formula (ll-d)

a) Preparation of the ether

500 ml of water were added and 108.1 g (1.0 mol) of p-phenylphenol and 197.7 g (1.0 mol) of N-(2-chloroethyl)-N-ethyl-3-methylaniline were added. Then 84 g (1.05 mol) of a 50% aqueous sodium hydroxide solution were added. The mixture was then heated to 95 °C over the course of 180 minutes and then stirred for 12 hours. The reaction mixture was then left to stand for 4 hours until phase separation had occurred. The aqueous phase was then separated. Remaining water was removed from the organic phase under vacuum at 80 °C and 2000 Pa. b) Preparation of the aldehyde

310 g (4.24 mol) of dimethylformamide were added dropwise to the organic phase from stage a). 160 g (1.04 mol) of phosphorus oxychloride were then added over the course of 3 hours at a temperature of 60 °C. The reaction mixture was then stirred for 5 hours. It was then cooled to 20 °C and 160 g of methanol and 400 g of water were added. A pH of approx. 8 was then adjusted by adding a 50% aqueous sodium hydroxide solution. The reaction mixture was left to stand for 4 hours until phase separation had occurred. The aqueous phase was then separated off. Any remaining water was removed from the organic phase under vacuum at 80 °C and 2000 Pa.

Yield: 279.6 g (corresponds to 94% of theory)

Example E

Preparation of an aldehyde of formula (ll-e)

a) Preparation of the ether

500 ml of water were introduced and 136.2 g (1.0 mol) of 2-isopropylphenol and 197.7 g (1.0 mol) of N-(2-chloroethyl)-N-ethyl-3-methylaniline were added. Then 84 g (1.05 mol) of a 50% aqueous sodium hydroxide solution were added. The mixture was then heated to 95 °C over the course of 180 minutes and then stirred for 12 hours. The reaction mixture was then left to stand for 4 hours until phase separation had occurred. The aqueous phase was then separated. Remaining water was removed from the organic phase under vacuum at 80 °C and 2000 Pa. b) Preparation of the aldehyde:

310 g (4.24 mol) of dimethylformamide were added dropwise to the organic phase from step a). 160 g (1.04 mol) of phosphorus oxychloride were then added over the course of 3 hours at a temperature of 60 °C. The reaction mixture was then stirred for 5 hours. It was then cooled to 20 °C and 160 g of methanol and 400 g of water were added. A pH of approx. 8 was then adjusted by adding a 50% aqueous sodium hydroxide solution. The reaction mixture was left to stand for 4 hours until phase separation had occurred. The aqueous phase was then separated off. Any remaining water was removed from the organic phase under vacuum at 80 °C and 2000 Pa.

Yield: 309.2 g (corresponds to 95% of theory).

Preparation of an aldehyde of formula (ll-f)

a) Preparation of the ether

500 ml of water were introduced and 152.2 g (1.0 mol) of 2-methoxy-4-ethylphenol and 197.7 g (1.0 mol) of N-(2-chloroethyl)-N-ethyl-3-methylaniline were added. Then 84 g (1.05 mol) of a 50% aqueous sodium hydroxide solution were added. The mixture was then heated to 95 °C over the course of 180 minutes and then stirred for 12 hours. The reaction mixture was then left to stand for 4 hours until phase separation had occurred. The aqueous phase was then separated. Remaining water was removed from the organic phase under vacuum at 80 °C and 2000 Pa. b) Preparation of the aldehyde

310 g (4.24 mol) of dimethylformamide were added dropwise to the organic phase obtained in step a). 160 g (1.04 mol) of phosphorus oxychloride were then added over the course of 3 hours at a temperature of 60 °C. The reaction mixture was then stirred for 5 hours. It was then cooled to 20 °C and 160 g of methanol and 400 g of water were added. A pH of approx. 8 was then adjusted by adding a 50% aqueous sodium hydroxide solution. The reaction mixture was left to stand for 4 hours until phase separation had occurred. The aqueous phase was then separated off. Any remaining water was removed from the organic phase under vacuum at 80 °C and 2000 Pa.

Yield: 324.3 g (corresponds to 95% of theory).

Example G

Preparation of an aldehyde of formula (ll-g)

a) Preparation of the ether

500 ml of water were added and 170.2 g (1.0 mol) of 4-phenylphenol and 197.7 g (1.0 mol) of N-(2-chloroethyl)-N-ethyl-3-methylaniline were added. Then 84 g (1.05 mol) of a 50% aqueous sodium hydroxide solution were added. The mixture was then heated to 95 °C over the course of 180 minutes and then stirred for 12 hours. The reaction mixture was then left to stand for 4 hours until phase separation had occurred. The aqueous phase was then separated. Remaining water was removed from the organic phase under vacuum at 80 °C and 2000 Pa. b) Preparation of the aldehyde

Then 310 g (4.24 mol) of dimethylformamide were added dropwise to the organic phase from step a). Then 160 g (1.04 mol) of phosphorus oxychloride were added over the course of 3 hours at a temperature of 60 °C. The reaction mixture was then stirred for 5 hours. It was then cooled to 20 °C and 160 g of methanol and 400 g of water were added. A pH of approx. 8 was then adjusted by adding a 50% aqueous sodium hydroxide solution. The reaction mixture was stirred for 2 hours. The reaction product was then isolated on a suction filter at 20 °C. The filter cake was washed with approx. 300 ml of methanol and approx. 1000 ml of water at a temperature of 50 °C. The washed product was dried in a vacuum drying oven at a temperature of 80 °C and a pressure of 20,000 Pa.

Yield: 341.5 g (corresponds to 95% of theory). List of purchased raw materials.-

Spectroscopic measurements

The results of the UVA/IS measurements and absorbance values for the inventive compounds of Examples 1 to 28 are shown in Table 1.

Table 1

¹⁾ The UVA/IS absorption spectra of the compounds of the invention were all determined in

Solvent 1-methoxy-2-propyl acetate (CAS No. 108-65-6) was measured.

²⁾ The E1/1 value given is a fictitious extinction value that would be obtained if a 1 weight percent solution of the respective compound (dissolved in 1-methoxy-2-propyl acetate) were measured in a cuvette with a path length of 1 cm.

Application-related results

Description of the test method “Thermostability” In a tumble mixer, 2 g of the dye to be tested were mixed with 1998 g of a PA6 granulate of the type Durethan B30S (commercial product of Lanxess Deutschland GmbH) with 1% TiO2, which was dried for 4 hours at 80 °C. This mixture was extruded at a maximum melt temperature of 240 °C on a single-screw extruder (Stork, 25 mm screw), cooled with water, granulated with a granulator from Sheer and dried for 8 hours at 80 °C. The heat stability of the plastic granulate obtained was tested according to DIN EN 12877-2 (“Determination of the resistance of the color to heat when processing colorants in plastics”) (Method A) on an injection molding machine. The standard was a sample was prepared at 240 °C with a residence time in the screw of 2.5 minutes. The samples to be determined were coloristically evaluated against this standard sample, which were prepared at a residence time of 5 minutes and temperatures of 240-320 °C. Samples with a total color deviation of DE < 3.0 were considered stable at the temperature used.

The results of the determination of the thermal stability of the compounds according to the invention of Examples 1 to 28 as well as those of the non-inventive compounds of the prior art are shown in Table 2.

Table 2

As can be seen from Table 2, the dyes according to the invention have a significantly increased heat or thermal stability compared to the heat or thermal stability of the prior art dyes that are used for coloring plastics.

Claims

Patent claims:

1 . Use of substituted m-toluidines of formula (I)

where R ¹ is methyl or ethyl,

R ³ and R ⁴ independently represent hydrogen, methyl or ethyl, and

R ⁵ stands for oxygen or sulphur, as thermostable methine dyes in plastics or polymers, with the proviso that “thermostable” means a heat stability > 395 °C to be determined on the respective plastic granulate according to DIN EN 12877-2 Method A.

2. Use according to claim 1, characterized in that the substituted m-toluidines of formula (I) are at least one of the formulae (1-1) to (I-28)

3. Use according to claim 1 or 2, characterized in that the methine dyes based on substituted m-toluidines of the formula (I) are used for the mass coloring of plastics.

4. Use according to claim 3, characterized in that the plastics are thermoplastics.

5. Use according to claim 3 or 4, characterized in that it is a plastics material from the series vinyl polymers, polyesters, polyolefins, polycarbonates, polyamides or polymethyl methacrylates or mixtures thereof.

6. Use according to claim 5, characterized in that the polyamides are polyamide 6 or polyamide 6.6.

7. Use according to one or more of claims 3 to 6, characterized in that the methine dye based on substituted m-toluidines of the formula (I) is used in an amount of 0.0001 to 1 percent by weight, in particular 0.01 to 0.5 percent by weight, based on the amount of plastic.

8. Use according to one or more of claims 3 to 7, characterized in that in mass dyeing the methine dye based on substituted m-toluidines of formula (I) is mixed with at least one plastic, preferably in granular form, is dry mixed or ground and this mixture is melted and homogenized.