DESC:FIELD OF THE INVENTION
The present invention relates to preparing pigments, particularly copper phthalocyanine.

BACKGROUND OF THE INVENTION
Copper phthalocyanine, (CI 74160) is obtained by the reaction of phthalic anhydride, urea, CuCl and catalyst such as ammonium molybdate. It is also one of the most important blue pigments incorporated in paints and dyes.

As per the most widely employed process for the manufacture of CI 74160, phthalic anhydride, a copper salt and urea are heated in an high boiling solvent at a temperature in the range of 150-260°c in the presence of a catalyst, this method is known as a urea method or Wyler method.

In the aforesaid process, phthalic anhydride is reacted with urea compounds and a metal (I) salt in the presence of a catalyst, in general ammonium molybdate, in a solvent such as nitrobenzene, nitrotoluenes , chlorinated toluenes such as chlorotoluene,dichlorotoluene,chlorinated benzene such as trichlorobenzene, dichlorobenzene, linear alkyl benzene, kerosene, hysolve, sulfolane, dimethylformamide, alkyl benzenes, alkylnaphthalenes, aromatic hydrocarbons tetralin, alkyl cyclohexane, decalin, alicyclic hydrocarbons such as alkyl decalin, decane, aliphatic hydrocarbons dodecane, chloronaphthalene, halogenated hydrocarbons such as hexachlorobutadiene, dimethyl sulfolane, sulfur compounds such as dimethyl sulfoxide, quinolone, methylnaphthalene, naphthalene, alkyl toluene, alkyl xylene, paraffin, naphthene, at temperature between 150° and 260°C. The solvent is removed by filtration or distillation under vacuum, and the crude copper phthalocyanine is heated with dilute mineral acid.

The above process for production of copper phthalocyanine requires the use of high boiling solvents which is expensive.

Furthermore, important characteristics of crude copper phthalocyanine specific to purity, strength, shade, particle size are not satisfactory when the process was carried out by using the aforesaid solvents.

Also, copper phthalocyanine obtained by using the above solvents decomposes at 240°C.

These traditional routes suffer from the disadvantages of high cost of the solvents, low purity, strength, shade, particle size of crude copper phthalocyanine, which decomposes at 240°C.

There is a need for cost effective process for preparing copper phthalocyanine which gives better yield and quality of copper phthalocyanine.

SUMMARY OF THE INVENTION
An aspect of the present invention relates to an improved process for preparation of copper phthalocyanine. The process comprises of reacting phthalic anhydride, urea, CuCl and catalyst such as ammonium molybdate in the presence of nitroalkyl benzene selected from 3-nitro-orthoxylene, 4-Nitro-orthoxylene , 3,4-dinitro-o-xylene, 3,5-dinitro-o-xylene, 3,6-dinitro-o-xylene , 4,5-dinitro-o-xylene, 3,5-dinitro-o-xylene, nitrocumene, mixture of nitrocumenes or combinations thereof.

DETAILED DESCRIPTION OF THE INVENTION
The present invention provides an improved process for the manufacture of copper phthalocyanine used in dyes and paint preparations using specific high boiling low cost solvent such as nitroalkyl benzenes. More specifically, the present invention provides a process for the manufacture of copper phthalocyanine while ensuring the important characteristics of copper phthalocyanine such as strength, shade, and particle size are retained.

A process for preparing copper phthalocyanine comprises of treating phthalic anhydride with urea, copper chloride (CuCl), catalyst such as ammonium molybdate and solvent such as nitroalkyl benzenes selected from 3-nitro-orthoxylene, 4-Nitro-orthoxylene , 3,4-dinitro-o-xylene , 3,5-dinitro-o-xylene, 3,6-dinitro-o-xylene , 4,5-dinitro-o-xylene, 3,5-dinitro-o-xylene , nitrocumene, mixture of nitrocumenes or combinations thereof. The temperature is maintained up to 180°C.

The unreacted solvent is recovered and recycled back to the reaction. This saves the wastage of the solvent and makes the process economical.

The mole ratio of phthalic anhydride to urea is 1:3.5 to 1:4.

The mole ratio of phthalic anhydride to CuCl is 1:0.2 to 1:0.35

The mole ratio of phthalic anhydride to ammonium molybdate is 1:0.01 to 1:0.02.

The mole ratio of phthalic anhydride to solvent is 1:2.5 to 1:3.

The crude copper phthalocyanine prepared by the above process is further treated with an acid such as sulphuric acid to obtain wet cake of copper phthalocyanine and an acidic effluent. The wet cake is dried to obtain the product.

An embodiment of the present invention also discloses a process to obtain copper by treating the acidic effluent with iron.

The solvents mentioned above are easily available and are of the low cost. Copper phthalocyanine prepared by using such solvents decomposes above 255°C as compared to 240°C as known from the conventional processes.

Examples
The following examples illustrate the invention and are not limiting thereof.

Example 1: Process for preparing of copper phthalocyanine
One mole of phthalic anhydride, cuprous (I) chloride (0.2 mole), ammonium molybdate (0.01 mole) and four moles of urea were heated to 180°C in 2.5 moles of 3-nitro-orthoxylene. The final reaction mass was maintained for 2-3 hrs followed by recovery of the solvent using vacuum distillation to obtain crude copper phthalocyanine (CPC) blue. The recovered solvent was recycled back to the reaction mass.

Example 2: Acid Process
The crude CPC blue of Example 1 was added slowly into 98% sulphuric acid maintaining temperature below 85°C till complete dissolution of crude CPC blue. The clear solution was stirred for 2 hours at 90°C and cooled to the room temperature. The reaction mass was filtered to get CPC blue wet cake (Alfa blue) and an acidic effluent.

Example 3: Pigmentation Process
The wet cake obtained was charged to a reactor along with fresh water. The PH of aqueous slurry was adjusted to 8-8.5 using ammonia solution and caustic lye and stirred with emulsifier at 70°C for 2 hrs. The slurry was filtered and wet cake washed with large amount of fresh water. The wet cake was dried and pulverized to get the final dry product. Yield of the product was 92% and purity was 99.3%.

Example 4: Treatment of acidic effluent to obtain copper
500gm of acidic effluent of Example 2 was added in a reactor followed by addition of 10gm iron .The reaction mass was stirred and maintained at 35°C for 5 hrs followed by filtration and recovery of 16 gm of copper. The filtrate (493gm) was concentrated upto 50% and cooled to room temperature followed by filtration.

Example 5:
The process of Example 1 was repeated with 2.5 moles of mixture of ortho-nitrocumene and para-nitrocumene instead of 3-nitro-orthoxylene.

Example 6:
The process of Example 1 was repeated individually with each of 3 moles of 4-nitro-orthoxylene, 3,4-dinitro-o-xylene, 3, 5-dinitro-o-xylene, 3,6-dinitro-o-xylene, 4,5-dinitro-o-xylene, 3,5-dinitro-o-xylene and nitrocumene instead of 3-nitro-orthoxylene.
,CLAIMS:
1. A process for preparing copper phthalocyanine , the process comprising treating phthalic anhydride with urea, cuprous chloride , ammonium molybdate in the presence of solvent such as nitroalkyl benzene selected from 3-nitro-orthoxylene, 4-Nitro-orthoxylene , 3,4-dinitro-o-xylene , 3,5-dinitro-o-xylene, 3,6-dinitro-o-xylene, 4,5-dinitro-o-xylene, 3,5-dinitro-o-xylene, nitrocumene, mixture of nitrocumenes or combinations thereof.

2. The process as claimed in claim 1 further comprising recovering and recycling the solvent.

3. The process as claimed in claim 1 comprising treating copper phthalocyanine with an acid to obtain wet cake of copper phthalocyanine and an acidic effluent.

4. The process as claimed in claim 3 comprising drying the wet cake.

5. The process as claimed in claim 3, wherein the acid is sulphuric acid.

6. A process for obtaining copper, the process comprising treating the acidic effluent as claimed in claim 3 with iron.