Copper phthalocyanine blue

Phthalocyanine Blues. a-Copper phthalocyanine blue is a reddish species used primarily in coatings and plastics. Several varieties are marketed. The basic form, the unstable Pigment Blue 15 [147-14-8] (Cl 74160), is used in water-based paints, paints containing weak petroleum solvents, and in certain plastics, eg, PVC, that require mild processing conditions. 

Metal-free copper phthalocyanine blue, ie. Pigment Blue 16 [574-93-6] is one of the eadiest forms of phthalocyanine. Environmental concerns about copper in pigments tended to increase the use of metal-free copper phthalocyanine, but certain shortcomings (greenish hue, lack of stabiHty in aromatic solvents) allowed only specialty uses (109). The stabiH2ed a-NC-type is used in certain automotive coatings. 

Phthalocyanines have been used to incorporate semiconductor properties in polymers (182) or to develop a thin-film transistor (183). Phthalocyanines and their derivatives can act as dyes in color photography (qv) (184) or electrophotography (185). Light-sensitive compositions for use on Hthographic plates are comprised in part of copper phthalocyanine blue (186). Dichlorosilicon phthalocyanine [19333-10-9] has been used in the... 

Conversion of crude blue into copper phthalocyanine blue pigments... 

It has often been observed that the coloristic properties of an organic pigment are a function not only of the size of particles but also of their shape. This is due to the anisotropy of the optical properties in different crystallographic directions within the crystal forms of a pigment. In 1974 [5, 6], it was demonstrated that of the equally sized but differently shaped particles of beta copper phthalocyanine blue, the almost completely cubic, i.e., more or less isometric form produces greenish blue shades, while acicular forms are responsible for reddish blue hues. The optical behavior of ordered pigment particles in systems has been reported in the literature [7, 8]. 

The correlation between rheological data and the most frequent particle diameter Dmf has been studied on a dispersion of the gamma modification of Pigment Violet 19 and various types of copper phthalocyanine blue in an offset vehicle on... 

Copper Phthalocyanine Blue is the copper(II) complex of tetraazatetrabenzo-porphine. As shown below, the mesomeric structures indicate that all of the pyrrole rings simultaneously contribute to the aromatic system ... 

In 1929, Linsted obtained samples of this complex from ICI chemists (Scottish Dyes Ltd was now owned by ICI). ICI had developed two routes leading to the phthalocyanine iron complex. One method started from phthalic anhydride, iron, and ammonia, while the second pathway proceeded from phthalimide, iron sulfide, and ammonia. In 1933/34, elucidation of the phthalocyanine structure was credited to Linstead. The corresponding copper and nickel phthalocyanines had been prepared in the meantime. ICI introduced the first Copper Phthalocyanine Blue to the market as early as 1935, and the Ludwigshafen subsidiary of the IG Farben-industrie followed suit with a corresponding product. 

Copper Phthalocyanine Blue exhibits more than one crystal modification. This is also true for the metal-free ligand whose greenish blue crystal phase was used on a large industrial scale for a certain period of time (Sec. 3.1.2.6). Free-base Phthalocyanine Blue was largely displaced by (3-Copper Phthalocyanine Blue as it became possible to produce the latter more economically (Sec. 3.1.2.3). 

In 1937, Du Pont started producing Copper Phthalocyanine Blue in the USA after it had previously been launched in Great Britain and Germany. Other companies followed. 

Copper Phthalocyanine Blue was no longer open for patent application after it had been described by de Diesbach and von der Weid in 1927. Yet a great many synthetic methods for this important compound were patented. 

Knowledge of the most important types of copper phthalocyanine pigments is useful for the understanding of the processes concepts underlying pigment manufacture. Heading the list are the a- and [i-modil i cations of unsubstituted Copper Phthalocyanine Blue (Sec. 3.1.2.3). The a-modification exhibits an unstabilized and a stabilized form as to change of crystal modification. 

After completion of the reaction, the solvent is removed by filtration. Most often, however, the solvent is separated from the crude Copper Phthalocyanine Blue by distillation. 

This simple one-step route leads to the starting material for the solvent-stabilized a-modification of Copper Phthalocyanine Blue. 

Invariably, the primary product is a crude Copper Phthalocyanine Blue with insufficient properties. It is boiled with dilute hydrochloric acid or aqueous alkali and then rinsed with hot water to remove acid or base before it can be finished. 

The solvent is removed from the solid product by filtration or centrifugation to afford a crude Copper Phthalocyanine Blue of a quality that makes intermediate purification unnecessary. In contrast to the product obtained by the baking process, this material is pure enough to be used directly for further pigment manufacture. Crude Copper Phthalocyanine Blue, on the other hand, which evolves as the solvent is removed by distillation, contains so many impurities that it must be boiled before being utilized further. 

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%. 

In the presence of a solvent, the crude pigment generally evolves in much purer form than if it is prepared by baking. Higher degrees of purity, i.e., up to 98%, are achieved by additional alkaline and/or acidic treatment. Commercially available types of crude Copper Phthalocyanine Blue typically contain more than 90% pure pigment. This preliminary product is also commonly supplied to and finished by companies who do not manufacture crude pigment themselves. 

Reaction between phthalic anhydride and urea always affords chlorine-free Copper Phthalocyanine Blue. Chlorinated derivatives are obtained only in the absence of bases (ammonia) or urea. The phase stabilized a-modification is prepared by essentially the same but slightly modified route it is derived from mixed con-... 

Despite the described disadvantages, but due to the high yield, economical production methods, and low-cost starting materials, the phthalic anhydride/urea method is presently the most significant industrial route to Copper Phthalocyanine Blue manufacture. 

The gross reaction equation for the preparation of Copper Phthalocyanine Blue from phthalic anhydride and urea may be written as follows ... 

Unsubstituted Copper Phthalocyanine Blue is polymorphous. X-ray diffraction diagrams point to five different crystal modifications (a, (3, y, 8, e) (Fig. 91). The relative thermodynamic stability of the individual cystal phases decreases in the following order (3>e>8>a = y [13-16],... 

Crude Copper Phthalocyanine Blue which is prepared by the phthalonitrile or urea process typically evolves as the -modification with a coarse particle size. 

Recently, by crystal structure studies the number of different polymorphs of Copper Phthalocyanine Blue has been extended to nine, various of which are differing mainly in herringbone-type interaction [17]. 

Dissolving or swelling of crude Copper Phthalocyanine Blue in sulfuric acid, followed by precipitation in water (hydrolysis) affords the a-modification with a fine particle size. Emulsifiers may be present if desired. Dry milling of the crude (3-crys-tal phase, for instance in the presence of sodium chloride or sodium sulfate, also yields the a-phase. 

The -modification as a rule evolves as a more coarse-grained material than the a-phase. It is prepared by milling the crude Copper Phthalocyanine Blue with salt in the presence of a crystallization stimulating solvent. Aromatic hydrocarbons, esters, or ketones are normally used. 

Crude Copper Phthalocyanine Blue is stirred in 60% sulfuric acid and the thus obtained sulfate hydrolyzed with water. Subsequent filtration affords the 7-phase. It is also possible to knead crude Copper Phthalocyanine Blue with salt (sodium sulfate), concentrated sulfuric acid, and a third agent, which may be an alcohol, a polyalcohol, or one of the corresponding organic esters [19]. A third option is to stir a-Copper Phthalocyanine Blue with 30% sulfuric acid and glycol monobutyl-ester or the corresponding ethyl ester or tetrahydrofuran [20],... 

The S-form can be obtained by treating Copper Phthalocyanine Blue in benzene or toluene with aqueous sulfuric acid in the presence of a surfactant [21], The e-phase is produced by comminution of the a-, 7-, or 8-modification, for instance in a planetary ball mill. The mill base is then aftertreated in an organic solvent at elevated temperature. It is important to realize that the temperature, depending on the solvent, must be kept below the transition temperature at which the e-phase converts to the (3-modification (30 to 160°C). The e-modification is made best from the 7-phase, and the most preferred solvents are alcohols [22], For the industrially hitherto insignificant tt, X, and R-forms of Copper Phthalocyanine Blue (see [1], Vol. II, 34-35). 

Phase- and Flocculation-Stabilized Copper Phthalocyanine Blue Pigments... 

Three dimensional X-ray diffraction analysis has been employed to elucidate the molecular and crystal structure of Copper Phthalocyanine Blue ((3-modifica-tion). In all modifications, the planar and almost square phthalocyanine molecules are arranged like rolls of coins, i.e., in one dimensional stacks. The modifications vary only in terms of how these stacks are arranged relative to each other. One important aspect is the angle between staple axis and molecular plane. The a-phase features an angle of 24.7°, while the stacks in the -modification deviate by as much as 45.8° [13]. 

Copper phthalocyanine pigments also demonstrate good overall stability to organic solvents. A number of solvents, however, especially aromatics, may cause a change of modification in unstable types or overcrystallization in stable varieties. This phenomenon is largely due to the tendency of the stable phase to nucleate. The particle size of the resulting cystals decreases as the number of nuclei rises. (3-Copper Phthalocyanine Blue is the thermodynamically stable modification. 

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