Carbazole dioxazine pigments

Abstract

The present disclosure relates to a benzoyl substituted carbazole-dioxazine pigment and its preparation. The process involves benzoylation of 3-nitro-N-ethylcarbazole in monochlorobenzene using benzoylchloride and ferric chloride to yield 3-nitro-6-benzoyl-N-ethyl carbazole, which on catalytic hydrogenation and subsequent condensation with chloranil and cyclization yields benzoyl substituted carbazole-dioxazine pigment.

Claims

1. A process for the synthesis of a carbazole-dioxazine pigment of Formula I; ##STR00007## wherein, R is C.sub.1-C.sub.8 alkyl group, R.sub.1 is a chloro group, and R.sub.2 is a benzoyl group, said process comprising the following steps: a) reacting 3-nitro-N-ethyl carbazole with benzoylchloride in the presence of monochlorobenzene and ferric chloride to obtain 3-nitro-6-benzoyl-9N-ethyl carbazole; b) hydrogenating said 3-nitro-6-benzoyl-9N-ethyl carbazole in a solvent in the presence of Raney nickel catalyst and sodium phosphate dibasic to obtain 6-benzoyl-3-amino-9N-ethyl carbazole; c) condensing 6-benzoyl-3-amino-9N-ethyl carbazole with chloranil in the presence of a solvent and sodium acetate to obtain an intermediate of formula II; and ##STR00008## wherein, R is C.sub.1-C.sub.8 alkyl group, R.sub.1 is a chloro group, and R.sub.2 is a benzoyl group, d) cyclizing the intermediate using a cyclizing agent to obtain carbazole-dioxazine pigment of formula I.

2. The process as claimed in claim 1, wherein the cyclizing agent is benzene sulfonyl chloride.

3. The process as claimed in claim 1, wherein the solvent is selected from the group consisting of ortho-dichlorobenzene, monochlorobenzene and a combination thereof.

4. The process as claimed in claim 1, wherein the step (a) is carried out at a temperature ranging from 90 to 120 C.

5. The process as claimed in claim 1, wherein the step (b) is carried out at a temperature ranging from 120 to 140 C. and at a pressure ranging from 10 to 16 kg/cm.sup.2.

6. The process as claimed in claim 1, wherein the step (c) is carried out at a temperature ranging from 45 to 70 C.

7. The process as claimed in claim 1, wherein the step (d) is carried out at a temperature ranging from 140 to 180 C.

8. A carbazole-dioxazine pigment of formula I; ##STR00009## wherein, R is C.sub.1-C.sub.8 alkyl group, R.sub.1 is a chloro group; and R.sub.2 is a benzoyl.

9. The carbazole-dioxazine pigment of formula I as claimed in claim 8, wherein said pigment is characterized by surface area of from 50 m.sup.2/g to 80 m.sup.2/g.

10. The process as claimed in claim 1, wherein R is an ethyl group.

11. The carbazole-dioxazine pigment as claimed in claim 8, wherein R is an ethyl group.

Description

DESCRIPTION

(1) The present disclosure provides a variant of known carbazole-dioxazine pigment, namely Pigment Violet-23. Particularly, the present disclosure provides a novel benzoyl substituted variant of Pigment Violet-23 which is represented by formula I.

(2) ##STR00005## wherein, R is C.sub.1-C.sub.8 alkyl group, preferably R is an ethyl group, R.sub.1 is a chloro group, and R.sub.2 is a benzoyl group.

(3) In accordance with the present disclosure benzoyl substituted Pigment Violet 23 also herein referred as PV-23 homologue-I, is prepared using 3-nitro-6-benzoyl-N-ethyl carbazole. 3-nitro-N-ethylcarbazole in monochlorobenzene is benzoylated using benzoylchloride and ferric chloride to yield 3-nitro-6-benzoyl-N-ethyl carbazole, which on catalytic hydrogenation in the presence of a promoter in a chlorinated benzene solvent and subsequent condensation with chloranil and cyclisation yields benzoyl substituted Pigment Violet 23 homologue-I.

(4) In accordance with exemplary embodiment the process involves the following steps:

(5) In the first step, 3-nitro-N-ethylcarbazole is reacted with benzoylchloride in the presence of monochlorobenzene and ferric chloride to obtain 3-nitro-6-benzoyl-N-ethyl carbazole.

(6) This step of benzoylation is carried out at a temperature ranging from 90 to 120 C.

(7) In the next step, 3-nitro-6-benzoyl-N-ethyl carbazole is hydrogenated in the presence of a catalyst and a promoter in a solvent to obtain 6-benzoyl-3-amino-N-ethyl carbazole. The catalyst employed includes but is not limited to Raney nickel and the solvent is selected from the group consisting of ortho-dichlorobenzene, monochlorobenzene and a combination thereof. The step of hydrogenation is carried out at a temperature ranging from 120 to 140 C. and at a pressure ranging from 10 to 16 kg/cm.sup.2. The promoter employed in the hydrogenation reaction is sodium phosphate dibasic.

(8) The obtained 6-benzoyl-3-amino-N-ethyl carbazole is condensed with chloranil in the presence of a solvent and sodium acetate to obtain an intermediate of formula II.

(9) ##STR00006##

(10) The intermediate of formula II is then cyclized using a cyclizing agent to obtain carbazole-dioxazine pigment of formula I. The cyclizing agent includes but is not limited to benzene sulfonyl chloride. The condensation step is carried out at a temperature ranging from 45 to 70 C., whereas the cyclization is carried out at a temperature ranging from 140 to 180 C.

(11) The obtained pigment is characterized by surface area of from 50 m.sup.2/g to 80 m.sup.2/g. The synthesized pigment is characterized by FTIR spectra, elemental analysis and GC-MS and is found to be in agreement with the molecular formula and molecular weight respectively. The physical properties, fastness properties, and solvent resistance properties of the homologue-1 pigment are also studied and found to be satisfactory. The prepared homologue-1 showed heat stability (upto 280 C.).

(12) The chemical resistance properties (in 5% hydrochloric & 5% sodium hydroxide) are also found to be satisfactory.

(13) Further, solvent fastness (w.r.t. water, xylene, methyethylketone, N-Butanol, PEG, DOP, butyl acetate and mineral turpentine and the like) and the migration fastness property is found to be good to excellent.

(14) The visible absorption spectra of the present pigment (in dimethylformamide) show max at 601 nm, whereas PV-23 shows max at 570 nm.

(15) The study of colour values of the pigment draw-downs is also carried out. The CIE attributes of lightness (L*), chroma (C*), hue (h*) and colour (a*, b*) are determined by colorimetric assessment of pigment drawdown.

(16) The disclosure is further illustrated with the help of following working examples which should not be construed to limit the disclosure in any way.

Example 1

Step: I: Benzoylation of Nitroethylcarbazole

(17) Nitroethylcarbazole (NEC) having purity of 98.8% was crystallized from monochlorobenzene solvent to yield 99.5% pure NEC. 100 gms of purified NEC (0.417 moles) was charged into a reactor vessel containing monochlorobenzene (300 ml) and the mixture was stirred at a temperature of 32 C. for a period of 15 minutes. The temperature of the mixture was then raised to 75 C. and 0.5 gm of ferric chloride (0.031 moles) was added to the mixture followed by drop-wise addition of 77 gm benzoyl chloride (0.548 moles) at a temperature of 100 C. over a period of 5-6 hours. During the benzoylchloride addition, hydrochloric acid was generated. Reaction was continued at a temperature of 115 C. over a period 20 hours till the evolution of the HCl gas ceased. The reacted mixture was then cooled to 90 C., refluxed for 1 hour in the presence of 1N HCl and then further cooled to yield greenish colour benzoylated nitroethylcarbazole (Bz-NEC). Crude benzoylated NEC (Bz-NEC) was then purified by crystallization using monochlorobenzene to yield pure Bz-NEC. Yield of pure Bz-NEC was 60%. The compound Bz-NEC was characterized by FTIR and NMR spectroscopy. The spectroscopic analysis confirms the compound 6-Benzoyl-3-nitro-9N-ethylcarbazole. HPLC and melting point test were also performed to confirm that compound is 6-Benzoyl-3-nitro-9N-ethylcarbazole.

(18) Characteristic properties of 6-Benzoyl-3-Nitro-9N-ethylcarbazole:

(19) Melting point: 217-219 C.

(20) FTIR: peak at 1593 cm-1 indicates the presence of carbonyl group.

(21) NMR: peaks at 7-9 cm.sup.1 corresponds to aromatic protons, the quadrate at 4.4-4.5 cm.sup.1 corresponds to 2H of CH.sub.2 and the triplet at 1.5-1.6 cm.sup.1 corresponds to 3H of CH.sub.3.

(22) Response factor for NEC to Benzoyl on HPLC was found as follows:

(23) TABLE-US-00001 Actual Ratio Observed Ratio NEC Benzyolated NEC NEC Benzyolated NEC 75 25 52 48 50 50 26 74 25 75 11 89 2 98 0.9 99.1

Step II: Hydrogenation of Benzoylated Nitroethylcarbazole (Bz-NEC)

(24) 90 gm of Bz-NEC (0.26 moles) as obtained in the first step and ortho-dichlorbenzene (1000 ml) were charged in a 2-lit autoclave, to this mixture, raney nickel catalyst (16 gm-wet) and sodium phosphate dibasic (1.04.gm) was added and the mixture was then hydrogenated at a temperature of 130 C. and at a hydrogen pressure of 10-16 kg for a period of 9-15 hours. The reaction was monitored by TLC, till it showed absence of the starting compound. The product yield was 92%. The product was characterized by NMR and FTIR, which confirmed the product to be 6-Benzoyl-3-amino-9-Nethyl carbazole. Characteristic properties of 6-Benzoyl-3-Amino-9N-ethylcarbazole (Bz-ACE): NMR: The peaks at 7-9 cm.sup.1 corresponds to aromatic protons, the singlet at 2.23 cm.sup.1 corresponds to 2H of NH.sub.2, the quadrate at 3.0 cm.sup.1 corresponds to 2H of CH.sub.2, the triplet at 1.89 cm.sup.1 corresponds to 3H of CH.sub.3. From the NMR it is clear that the carbonyl group is not hydrogenated during the reaction.

(25) FTIR spectra show a peak at 3431 cm.sup.1 which indicates the presence of primary amino group and a peak at 1597 cm.sup.1 which indicates the presence of carbonyl group.

Step III: Condensation and Cyclization

(26) 76 gms Bz-ACE (0.242 moles) and ortho-dichlorobenzene (900 ml) were charged in a reactor vessel to obtain a mixture. To this, sodium acetate 40 gms (0.30 moles) and 45 gm chloranil (0.182 moles) were added at a temperature of 45 C., the mixture was then stirred for a period of 10 minutes and heated further to 65 C. for a period of 5 hours. The reaction was monitored by TLC. After the completion of reaction, acetic acid formed was removed along with ortho-dichlorobenzene by distillation at 90 C. and 640 mmHg vacuum, over a period of 3-5 hours. After the complete removal of acetic acid, the reacted mixture was cyclized by adding 28.8 gms of benzene sulfonyl chloride (0.16 moles). The addition was carried out drop-wise at 140 C. over a period of 1 hr. Temperature was slowly raised to 175 C. and maintained for a period of 6 hours. The product mixture so formed was cooled to 90 C. and the product was isolated by filtration. The filtered product was washed with hot ortho-dichlorobenzene, with methanol and finally with water and then dried in oven at 80 C. to yield 75% of crude carbazole-dioxazine pigment.

Step IV: Finishing

(27) The dried crude pigment was salt kneaded in a kneader in the presence of diethyl glycol (DEG) in the ratio (1 part pigment:10 part salt:4 parts DEG) for a period of 10 hrs at 50 C. The kneaded product was heated to 80 C. in water and further treated with 5% concentrated HCL for a period of 1-2 hrs at 70 C. The treated product was filtered, washed with water till it was salt free and had neutral pH, with conductivity less than 500 micron. The wet cake was further refluxed with isobutyl alcohol in the presence of caustic lye at a temperature of 90 C. for a period of 3-4 hours, the isobutyl alcohol water mixture was removed by distillation and the residue was washed with water till pH was adjusted to 7 and then further washed with distilled water till the conductivity was less than 500 micron. The washed residue was than dried at 80-90 C. and then pulverized.

(28) The product was characterized by elemental analysis, GCMS, IR spectra which was in agreement with the structure. The XRD Peak profile was found to be different than that of PV 23.

(29) Testing of the pigment as obtained in step IV:

(30) The pigment PV-23 homologue-1 showed high blue colour than existing PV-23 in aqueous, air dried paint and also in muller test.

(31) Physical Characterization of the pigment PV-23 homologue-1:

(32) XRD analysis: Peak profile is different from that of PV 23.

(33) Surface area: 69.91 m.sup.2/gm

(34) Coloristic Results:

(35) VisualReddish blue color with good transparency and tinting strength.

(36) Instrumental:

(37) Lab ValuesPlastic

(38) TABLE-US-00002 Illum* L* a* b* C* h PV 23 D65 34.22 10.55 49.92 51.03 281.94 Homologue # CWF_2 28.66 11.58 59.72 60.84 280.98 9A PVC FT A 29.10 1.86 58.05 58.08 268.16 PV 23 D65 47.45 3.15 36.76 36.90 274.90 Homologue # CWF_2 43.23 4.34 44.35 44.57 275.59 9A PVC RN A 44.08 3.34 41.80 41.94 265.44

(39) Lab ValuesPaint

(40) TABLE-US-00003 Illum* L* a* b* C* h PV 23 D65 20.424 0.083 0.001 0.083 180.7 Homologue CWF_2 20.423 0.289 0.157 0.329 151.545 # 9A SPFS A 20.44 0.21 0.16 0.26 322.01 PV 23 D65 48.722 0.663 31.244 31.251 271.215 Homologue CWF_2 45.66 1.675 36.918 36.956 272.598 # 9A SPRN A 45.79 6.22 35.55 36.09 260.08 Illuminants* D65Day light, CWF_2Fluorescent, ATungsten

(41) Paint Application Properties:

(42) TABLE-US-00004 Properties Result 1. Chemical Resistance (1-5 gray scale) 1.1. Acid (2%) 4 1.2. Alkali (2%) 3 2. Resistance to solvents (1-5 gray scale) 2.1. Water 5 2.2. Mineral Turpentine oil 5 2.3. n-Butanol 5 2.4. Butyl acetate 4 2.5. Xylene 4 2.6. MEK 4 2.7. PEG 5 2.8. DOP 5 3. Heat stability-Alkyd/Melamine paint- 130 C. full shade @ 30 minutes baking 4. Heat stability-Alkyd/Melamine paint- 180 C. reduction @ 30 minutes baking 5. Weather fastness (1-5 gray scale) 5.1. Alkyd/Melamine-FS 1 5.2. Alkyd/Melamine-1/3SD 2-3 5.3. Alkyd/Melamine-1/25SD 2 6. Over coating fastness (1-5 gray scale) 5

(43) Plastic Application Properties:

(44) TABLE-US-00005 Properties Result 1. Chemical Resistance (1-5 Gray scale) 1.1. Acid (2%) 4 1.2. Alkali (2%) 3 2. Heat stability-HDPE reduction 280 C. (Violet @ 5 minutes dwelling. patches seen on chips) 3. Migration fastness-PVC (1-5 Gray scale) 4

(45) Throughout this specification the word comprise, or variations such as comprises or comprising, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

(46) The use of the expression at least or at least one suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results.

(47) Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the invention as it existed anywhere before the priority date of this application.

(48) While considerable emphasis has been placed herein on the preferred embodiment, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.