Preparation of Pigment Red 149

Abstract

The invention provides a process for preparing N,N-di(3,5-dimethylphenyl)perylene bis(dicarboximide), and other pigments having modified properties, by reaction of perylene-3,4,9,10-tetracarboxylic dianhydride with 3,5-dimethylaniline, or a mixture of 3,5-dimethyl aniline and at least one other primary amine, in the presence of a secondary amine or tertiary amine as catalyst, wherein the reaction occurs in an aqueous reaction medium and in the presence of added seed crystals of N,N-di(3,5-dimethylphenyl) perylenebis(dicarboximide), such that the aqueous medium is present at the beginning of the reaction.

Claims

1. A process for preparing N,N-di(3,5-dimethyl phenyl)perylenebis(dicarboximide), the process comprising reacting perylene-3,4,9,10-tetra carboxylic dianhydride with 3,5-dimethylaniline in the presence of a secondary amine as catalyst, wherein: a molar ratio between the 3,5-dimethylaniline and the perylene-3,4,9,10-tetracarboxylic dianhydride ranges from 2:1 to 3:1; the reaction occurs in an aqueous reaction medium and in the presence of added seed crystals of N,N-di(3,5-dimethylphenyl) perylenebis(dicarboximide), wherein the seed crystals are present prior to the beginning of the reaction; the aqueous reaction medium is present at the beginning of the reaction; the reaction occurs at a temperature in the range from 130 C. to 170 C. and at a pressure in the range from 2 bar to 13 bar; and the process provides Pigment Red 149 in the alpha form, such that the Pigment Red 149 comprises less than 5% by weight of a monoimide by-product.

2. The process according to claim 1, wherein the aqueous reaction medium comprises no further organic solvents.

3. The process according to claim 1, wherein the secondary amine is selected from the group consisting of piperazine, N-(2-hydroxyethyl) piperazine, diethanolamine, N-ethylpiperazine, N-methylcyclohexylamine, imidazole and N-methylimidazole.

4. The process according to claim 1, wherein the seed crystals are obtained from at least one preceding charge.

5. The process according to claim 1, wherein aqueous reaction medium remaining after a reaction product is filtered off is reused in the preparation of a subsequent charge.

6. The process according to claim 1, wherein 0.5 to 2.0 mol of the secondary amine are used per mole of the perylene-3,4,9,10-dicarboxylic dianhydride.

7. A process for preparing a perylenebis(dicarboximide), the process comprising reacting perylene-3,4,9,10-tetracarboxylic dianhydride with a primary amine mixture in the presence of a secondary amine as catalyst, wherein the reaction occurs in an aqueous reaction medium and in the presence of added seed crystals of N,N-di(3,5-dimethylphenyl) perylenebis-(dicarboximide), wherein the seed crystals are present prior to the beginning of the reaction, wherein: the aqueous reaction medium is present at the beginning of the reaction; the primary amine mixture comprises 3,5-dimethylaniline and 0% to 10% by weight of a primary amine, based on a total weight of the primary amine mixture; the reaction occurs at a temperature in the range from 130 C. to 170 C. and at a pressure in the range from 2 bar to 13 bar; and a molar ratio between the 3,5-dimethylaniline and the perylene-3,4,9,10-tetracarboxylic dianhydride ranges from 2:1 to 3:1.

8. The process according to claim 1, further comprising converting the N,N-di(3,5-imethylphenyl)perylenebis(dicarboximide) into particles having an average size <0.2 m by at least one of dry and wet grinding, optionally with subsequent recrystallization from a solvent.

9. The process according to claim 7, wherein the aqueous reaction medium comprises no further organic solvents.

10. The process according to claim 7, wherein aqueous reaction medium remaining after a reaction product is filtered off is reused in the preparation of a subsequent charge.

11. A process for preparing a perylenebis(dicarboximide), the process comprising reacting perylene-3,4,9,10-tetracarboxylic dianhydride with a primary amine mixture in the presence of a tertiary amine, wherein: the reaction occurs in an aqueous reaction medium and in the presence of added seed crystals of N,N-di(3,5-dimethylphenyl) perylenebis(dicarboximide), wherein the seed crystals are present prior to the beginning of the reaction; the aqueous reaction medium is present at the beginning of the reaction; the primary amine mixture comprises 3,5-dimethylaniline and 0% to 10% by weight of a primary amine, based on a total weight of the primary amine mixture; the reaction occurs at a temperature in the range from 130 C. to 170 C. and at a pressure in the range from 2 bar to 13 bar; and a molar ratio between the 3,5-dimethylaniline and the perylene-3,4,9,10-tetracarboxylic dianhydride ranges from 2:1 to 3:1.

12. The process of claim 7, wherein the primary amine mixture comprises greater than 0% of the primary amine.

13. The process of claim 11, wherein the primary amine mixture comprises greater than 0% of the primary amine.

14. The process of claim 1, wherein the Pigment Red 149 is obtained as a crude product in greater than 94% yield after a resulting reaction mixture is filtered and washed, and before any additional purification.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) The reaction is preferably carried out in a purely aqueous reaction medium comprising essentially no further organic solvents.

(2) The reaction is carried out in the presence of a secondary or tertiary amine as catalyst. Useful catalysts include aliphatic, cycloaliphatic, arylaliphatic or heterocyclic secondary or tertiary amines. In general, useful secondary amines have the formula RRNH, where R and R may be the same or different and may each be a straight-chain or branched alkyl or cycloalkyl of 1 to 6 carbon atoms, with or without hydroxyl, alkoxy, alkyl, alkylamino or aryl substitution, or where R and R combine with the nitrogen atom to form a 5- or 6-membered heterocyclic ring which can be substituted if appropriate (in the case of tertiary amines) by alkyl, aralkyl or aryl groups. Useful tertiary amines generally comprise 3 of the radicals mentioned.

(3) Preferred secondary or tertiary amines are piperazine, N-(2-hydroxyethyl)piperazine, diethanolamine, N,N-dimethylpiperazine, N-ethylpiperazine, N-methylcyclohexylamine, imidazole and N-methyimidazole.

(4) The reaction is carried out in the presence of seed crystals of C.I. Pigment Red 149. The amount of seed crystals added is in the range from 1% to 25% by weight and preferably in the range from 5% to 10% by weight, based on the reaction product. The seed crystals added can come from one of the preceding charges.

(5) The reaction is generally carried out at a temperature of 120 to 190 C. and a pressure of 2 to 13 bar. The reaction time is generally in the range from 5 to 40 hours. The molar ratio of 3,5-dimethylaniline to perylenebisanhydride is generally in the range from 1.8:1 to 4:1 and preferably in the range from 2:1 to 3:1. The molar ratio of secondary or tertiary amine to perylenebisanhydride is generally in the range from 0.5:1 to 2:1 and preferably in the range from 0.8:1 to 1.4:1. Excess 3,5-dimethylaniline can be distilled off after the reaction has ended. The reaction product, C.I. Pigment Red 149, is generally covered by filtration. The mother liquor comprising the secondary or tertiary amine can subsequently be reused as reaction medium to synthesize further Pigment Red 149.

(6) If desired, up to 10% by weight and preferably up to 5% by weight, for example 0.5 to 5% by weight, of the 3,5-xylidine can be replaced by some other primary amine in the preparation process described in order that pigments having modified properties may be obtained. Useful further primary amines include for example 4-methoxyaniline and 4-ethoxyaniline.

(7) The process of the present invention provides Pigment Red 149 in the alpha form. Generally, it comprises less than 5% by weight and preferably less than 1.5% by weight of the monoimide.

(8) Filtration preferably provides the product in the form of a 30-50% by weight press cake.

(9) The coarsely crystalline pigment is generally converted into a suitable particle size by means of customary fine division and finishing processes before its use in coatings and plastics. Generally, one dry- or wet-grinding operation will be sufficient for this purpose, if appropriate with subsequent controlled recrystallization from solvents, for example water or aqueous-organic solvent mixtures. This converts the Pigment Red 149 to particles having a size of generally <0.2 m.

(10) The pigment provides strong reds of high cleanness of hue and good thermal stability when used for coloration of macromolecular material, for example PVC, LDPE, HDPE, polypropylene or polyamide.

(11) The examples which follow illustrate the invention.

EXAMPLES

Example 1

(12) An autoclave is charged with 423 g of perylenebisanhydride as 50% by weight water-moist press cake, corresponding to 0.54 mol, 940 g of water, 44 g piperazine, corresponding to 0.51 mol, and 18 g of Pigment Red 149 as seed crystals, and this initial charge is efficiently stirred. After addition of 156 g of 3,5-dimethylaniline, corresponding to 1.29 mol, the batch is heated to 145 C. and stirred at 145 C. for 15 hours. The autoclave is subsequently let down and the excess xylidine is completely distilled off.

(13) The batch is filtered and washed colorless. The yield of Pigment Red 149 is 311 g, corresponding to 96.4% of theory.

(14) The crude product thus obtained comprises 97.5% by weight of the perylenediimide and 1.4% by weight of the monoimide (O-semicondensate). The product is present in the alpha form.

(15) 30 g of pigment, 60 g (90 g) of sodium chloride and 750 g of steel balls are ball milled at 80 C. for 20 h. Subsequently, the millbase is stirred up in water and in the presence of 2 g of hydrochloric acid, washed salt-free, dried and ground.

(16) The pigment obtained provides a very strong color when judged in accordance with DIN EN 139900-3 on incorporation in LDPE (Low Density Polyethylene) and provides colorations having high cleanness of hue coupled with good thermal stability.

Comparative Example

(17) If no seed crystals are added, a weak-colored, dull Pigment Red 149 is obtained and it moreover still contains 5% of O-semicondensate. It further comprises portions of the undesired beta- and gamma-forms.

(18) TABLE-US-00001 TABLE Coloristics in LDPE white reduction Color strength in % Hue dH* Chroma dC* Example 1 100 0 0 Comparative 82 0.7 1.7 example *dH and dC = hue difference and chroma difference, respectively, between comparative example and inventive example after color strength equalization in accordance with DIN 6174

Example 2

(19) Example 1 is repeated except that 66 g of N-(2-hydroxyethyl)piperazine, corresponding to 0.51 mol, are used as secondary amine. The yield of crude product is 304 g, corresponding to 94.2% of theory.

Example 3

(20) Example 1 is repeated except that 100 parts by weight of 80% pure diethanolamine, corresponding to 0.76 mol, are used as secondary amine. The yield of crude product is 313 g, corresponding to 97.0% of theory.