Phthalic urea process

Only two techniques have gained commercial importance. The phthalonitrile process, developed in England and Germany, is particularly important in Germany, while the phthalic anhydride/urea process has stimulated more interest in... 

The phthalonitrile process has the particular advantage over the phthalic anhydride process of forming ring-substituted chloro-copper phthalocyanines. Using copper(I)chloride produces so-called semi-chloro Copper Phalocyanine Blue, a pigment which possesses a statistical average of 0.5 chlorine atoms per copper phthalocyanine molecule. Copper(II)chloride, on the other hand, affords a product which comprises an average of one chlorine atom per copper phthalocyanine molecule. A prerequisite for the formation of the chloro substituted compound, however, is the absence of ammonia or urea in the reaction mixture. 

There is an interesting technique which makes it possible to introduce carboxylic acid groups into a copper phthalocyanine structure by an economical route. Carrying out the phthalic anhydride/urea process in the presence of a small amount of trimellitic acid or another benzene polycarboxylic acid will afford a car-boxylated pigment. 

The phthalic anhydride/urea process may also be employed to convert tetra-chloro phthalic anhydride to green copper hexadecachloro phthalocyanine by condensation. In this case, titanium or zirconium dioxides, particularly in the form of hydrated gels, are used instead of the molybdenum salts which are used in the phthalic anhydride process [23]. There is a certain disadvantage to the fact that the products lack brilliance and require additional purification. 

Copper Perbromo Phthalocyanine Green may also be obtained from tetra-bromo phthalic anhydride by the phthalic anhydride/urea process in the presence of titanium or zirconium catalysts. This route has not yet been introduced on a commercial scale. 

Industrial production of copper phthalocyanine usually favors either the phthalic anhydride-urea process or the -phthalodinitrile process. Roth can be carried oul continuously or balchwise in a solvent or bake process of the solid reactants. 

Two processes are commonly used for the production of copper phthalocyanine the phthalic anhydride-urea process patented by ICI [33,34] and the I.G. Farben dinitrile process [48], Both can be carried out continuously or batchwise in a solvent or by melting the starting materials together (bake process). The type and amount of catalyst used are crucial for the yield. Especially effective as catalysts are molybdenum(iv) oxide and ammonium molybdate. Copper salts or copper powder is used as the copper source [35-37] use of copper(i) chloride results in a very smooth synthesis. Use of copper(i) chloride as starting material leads to the formation of small amounts of chloro CuPc. In the absence of base, especially in the bake process, up to 0.5 mol of chlorine can be introduced per mole of CuPc with CuCl, and up to 1 mol with CuCl2. 

As apparatus for the batch process, an enamel or steel reactor with an agitator and pressure steam or oil heating suffices. Apparatuses used in the continuous synthesis in the presence of solvents and in the bake process are described in [50] and [51,52], respectively. The choice of process depends on the availability and cost of the starting materials phthalodinitrile or phthalic anhydride. Although the phthalodinitrile process has certain advantages over the phthalic anhydride process, the latter is preferred worldwide because of the ready accessibility of phthalic anhydride. In this process the molar ratio of phthalic anhydride, urea, and cop-per(i) chloride is 4 16 1, with ammonium molybdate as catalyst. The mixture is heated in a high-boiling solvent such as trichlorobenzene, nitrobenzene, or kerosene. The solvent is removed after the formation of copper phthalocyanine. Fre-... 

The reactants are phthalic anhydride, urea and copper(n) chloride, which are heated in a high-boiling aromatic solvent such as 1,2,4-trichlorobenzene, nitrobenzene or m-dinitrobenzene in the presence of a catalyst, usually ammonium molybdate. The solvent also acts as a heat-transfer medium. On heating to 120 °C an exothermic reaction begins and this temperature is maintained for about an hour. The temperature is then raised to 160-180 °C and kept constant for 6-12 hours. During this time ammonia and carbon dioxide are evolved, together with some solvent the reaction is complete when ammonia evolution ceases. The remaining solvent is then removed by either steam or vacuum distillation. The yield is 90-95%. For many years the solvent process was in almost exclusive use. 

Yet another method of avoiding PCB formation in the solvent process is to dispense with the need for urea as a reactant by using the more expensive phthalonitrile instead of phthalic anhydride. 

The technical importance of the phthalonitrile process is only second to the phthalic anhydride/urea technique, of which two varieties are commercially used (Sec. 3.1.2.2). BASF is the primary European user of the phthalonitrile method. 

Likewise, this process [12] may also be carried out either as a solvent-free (baking) method or in the presence of solvents. Although initially performed as a solvent-free technique, it is the solvent version that currently dominates the field of copper phthalocyanine production from phthalic anhydride and urea. It should be mentioned, however, that this trend has been reversed in the very recent past and that solvent-free methods are gaining interest, especially for ecological reasons. 

The first commercial copper phthalocyanine synthesis, a baking process, involved melting phthalic anhydride with urea at 150°C in the presence of boric acid. Cop-per(II)chloride was then added and the temperature increased to approximately 200°C until the copper phthalocyanine production was completed. The reaction mixture was cooled and the crude product milled. After being washed, first with dilute sodium hydroxide solution and then with dilute sulfuric acid, the material was filtered off and dried. The crude copper phthalocyanine obtained was then... 

The baking process has remained much the same until the present day at a stoichiometric ratio of 1 4, phthalic anhydride or phthalic acid reacts with an ammonia releasing compound. The reaction may also start from other suitable materials, such as phthalic acid derivatives, including phthalic acid esters, phthalic acid diamide, or phthalimide. Appropriate ammonia releasing agents include urea and its derivatives, such as biuret, guanidine, and dicyanodiamide. The fact that a certain amount of urea decomposes to form side products makes it necessary to use excess urea. Approximately 0.2 to 0.5, preferably 0.25 equivalents of copper salt should be added for each mole of phthalic anhydride. 0.1 to 0.4 moles of molybdenum salt per mole of phthalic anhydride is sufficient. The reaction temperature is between 200 and 300°C. 

Phthalic anhydride and urea, together with copper(I)chloride and ammonium molybdate, are heated to 200°C in trichlorobenzene. The ratios between the components are the same as in the baking process. Carbon dioxide and ammonia are released to yield Copper Phthalocyanine Blue. The reaction is complete after 2 to 3 hours, producing a yield between 85% and more than 95%. 

Phthalic anhydride initially reacts with ammonia, which in turn is liberated, for instance, by decomposition of urea. Diiminophthalimide is then produced via phthalimide and monoiminophthalimide. Subsequent self-condensation (as in the phthalonitrile process) under cleavage of ammonia affords polyisoindolenines, which form complexes with copper ions. Ring closure is achieved through further release of ammonia, and copper phthalocyanine is finally obtained by reduction. 

Only a minor amount of chlorinated copper phthalocyanine, for instance, especially in the 4-position of the copper phthalocyanine molecule, prevents a change of modification from a to (3. Approximately 3 to 4% chlorine is commonly used, which corresponds to the formula CuPc-Cl0.5, also referred to as semi-chloro-CuPc . The phthalic anhydride/urea synthesis, for instance, affords a partially chlorinated product if 4-chlorophthalic anhydride is added to the reaction mixture. Copper chlorides in the phthalonitrile process have the same effect. 

Phthalocyanines or tetrabenzoporphyrazines are prepared by the Wyler-Riley process (37BRP464126, 37BRP476243) via condensation of phthalic anhydride and urea in the presence of copper(I) chloride or by reaction of phthalonitrile with copper salts. Metal-free phthalocyanine, no longer of commercial importance, is prepared by reaction of phthalonitrile with sodium amylate, followed by demetallization in methanol. 

Some references covet direct preparation of the different crystal modifications of phthalocyanines in pigment form from both the nitrile-urea and phthalic anhydridc-urca process. Mctal-free phthalocyanine can be manufactured by reaction of o-phthalodinitrile with sodium amylate and alcoholysis of the resulting disodium phthalocyanine. The phthalic anhydridc-urca process can also be used. Other sodium compounds or an electrochemical process have been described. Production of the different crystal modifications has also been discussed. 

In the second manufacturing process for copper phthalocyanine, phthalonitrile, copper(II) acetate and ammonium acetate are heated in the presence of a base, with or without a solvent such as pyridine. The mechanism of this has been less studied than that of the phthalic anhydride/urea reaction. It is, however, significant that metal-free phthalocyanine is manufactured by heating phthalonitrile with the sodium derivative of a high-boiling alcohol in an excess of the alcohol. This reaction is believed148 to occur by the route outlined in Scheme 7, which is supported by the isolation of compounds of types (223) and (224). If this or a related mechanism operates in the... 

Process Economics Program Report SRI International. Menlo Park, CA, Isocyanates IE, Propylene Oxide 2E, Vinyl Chloride 5D, Terephthalic Acid and Dimethyl Terephthalate 9E, Phenol 22C, Xylene Separation 25C, BTX, Aromatics 30A, o-Xylene 34 A, m-Xylene 25 A, p-Xylene 93-3-4, Ethylbenzene/Styrene 33C, Phthalic Anhydride 34B, Glycerine and Intermediates 58, Aniline and Derivatives 76C, Bisphenol A and Phosgene 81, C1 Chlorinated Hydrocarbons 126, Chlorinated Solvent 48, Chlorofluorocarbon Alternatives 201, Reforming for BTX 129, Aromatics Processes 182 A, Propylene Oxide Derivatives 198, Acetaldehyde 24 A2, 91-1-3, Acetic Acid 37 B, Acetylene 16A, Adipic Acid 3 B, Ammonia 44 A, Caprolactam 7 C, Carbon Disulfide 171 A, Cumene 92-3-4, 22 B, 219, MDA 1 D, Ethanol 53 A, 85-2-4, Ethylene Dichloride/Vinyl Chloride 5 C, Formaldehyde 23 A, Hexamethylenediamine (HMDA) 31 B, Hydrogen Cyanide 76-3-4, Maleic Anhydride 46 C, Methane (Natural Gas) 191, Synthesis Gas 146, 148, 191 A, Methanol 148, 43 B, 93-2-2, Methyl Methacrylate 11 D, Nylon 6-41 B, Nylon 6,6-54 B, Ethylene/Propylene 29 A, Urea 56 A, Vinyl Acetate 15 A. 

Preparation of t-butykmine. t-Butylurea, obtained from Eastman or Fisher or prepared from t-butanol, urea, and coned, sulfuric acid, is heated with phthalic anhydride to produce t-butylphthalimide, which is cleaved by refluxing with aqueous-alcoholic hydrazine to phthalhydrazidc and t-butylamine. After cooling, the mixture is made acid (HCI) and the heterocyclic product removed by filtration. Suitable processing of the filtrate affords pure t-butylamine hydrochloride. 

Mg, Be, Ag, Fe(II), Sb(III), Mn(II), Sn(II), alkali metals, alkaline earth metals, rare earths, Cd, Hg, and Pb 19, 21, 54, 119, 226). The rate of demetallation varies considerably 19) (see Section VI,B). The phthalo-cyanines of Cu, Zn, Co(II), Ni, Pt, Pd, VO, Al, Ga, and In resist demetallation in concentrated sulfuric acid at room temperature 10, 21, 56, 57). Phthalocyanine may also be prepared by the condensation of phthalonitrile or 1,3-diiminoisoindoline in hydrogen-donor solvents 10, 81, 86, 346), and by the catalytic condensation of phthalonitrile in the dry with platinum metal 10). Processes involving intermediates such as phthalic acid and urea have also been developed 380). 

The reaction of urea, CuCl and phthalic anhydride is carried out at ca.200 °C in a process lasting 2 to 3 hours, using ammonium molybdate as a catalyst nitrobenzene, trichlorobenzene or kerosene can be used as solvents. When phthalodinitrile is used, the reaction is carried out without catalyst at ca. 200 °C as a baking process or in solution. When the crude phthalocyanine has been produced, it is conditioned to suitable crystal modifications, e.g. by dissolving in sulfuric acid and subsequent hydrolysis, or treatment with organic solvents. 

---