Novel pigmentary form of .beta.-copper phthalocyanine

A .beta.-copper phthalocyanine pigment which consists, to the extent of more than 50% by weight, of flakes which are not less than 10 .mu.m long and 3 .mu.m wide, the length:width ratio being not less than 3.3:1, and which has a reflection maximum between 610 and 640 nm and another between 710 and 740 nm. In surface coatings and printing inks the pigment gives optical effects resembling those of metallic pigments. In a baking finish, reddish brown to bluish gray colorations with a metallic reflectance are obtained.

The present invention relates to a novel pigmentary form of .beta.-copper 
phthalocyanine. 
In this novel pigmentary form of .beta.-copper phthalocyanine (CuPc), the 
pigment consists, to the extent of at least 50% by weight, preferably to 
the extent of 70% by weight or more, of flakes which are not less than 10 
.mu.m long and not less than 3 .mu.m wide, the length:width ratio being 
not less than 3.3:1 and has a reflection maximum between 610 and 640 nm 
and another between 710 and 740 nm. 
Printing inks and surface coatings of the novel pigmentary form give 
optical effects which resemble those of metallic pigments. For example, 
when it is used in a baking finish, a high-hiding coating is obtained 
which shows a reddish brown or bluish gray metallic luster, depending on 
the angle of incidence of the light. 
Surface coatings produced with the novel CuPc pigments of the present 
invention differ significantly, in the reflectance curve of the visible 
region of the spectrum, namely at from 350 to 750 nm, from coatings 
produced with CuPc pigments of the prior art. 
The reflectance curves of high-hiding pure shade colorations employing 
conventional CuPc pigments are virtually straight lines which run parallel 
to the abscissa, ie. virtually all the incident light is absorbed. Only 
4-6% of the light is reflected. Accordingly, the viewer has the impression 
of a dark, blue color. The blue impression is due to a flat reflection 
maximum at 460 nm. This maximum is about 2% above the basic reflection of 
4%. At the end of the visible region, at 710-750 nm, the reflection again 
rises slowly to about 6% at 750 nm. 
In contrast, the novel CuPc pigments show a marked reflectance above 550 
nm. This reaches a maximum at between 610 and 640 nm, the maximum being 
5-7% above the reflection curve of the conventional CuPc pigments. A 
second reflection maximum, of the same height, is found in the region 
between 710 and 740 nm, (FIG. 1, appendix). Accordingly, the colorimetric 
evaluation of the reflectance curves, in accordance with DIN 6174, of 
surface coatings containing the novel CuPc pigments, in terms of the three 
characteristics required to establish the color location, namely lightness 
(L), hue gradation (HGD) and chroma (C) (=purity of hue), reveals novel 
hues. 
The lightness L is .gtoreq.25 and accordingly significantly above the value 
of the prior art CuPc pigments, where L is .ltoreq.20. 
The hue gradation HGD has values of from 15 to 33, indicating the reddish 
hues (blue color locations have an HGD of about 270, the purple range 
corresponds to HGD's of from 270 to 360, and red starts at HGD zero). The 
conventional brownish dark CuPc pigments have an HGD of .ltoreq.10, whilst 
the bluish dark CuPc pigments fall in the purple range, with an HGD of 
about 320. 
The purity of hue (chroma) of the novel CuPc pigments is also superior to 
those of the prior art pigments. For the former, C is .gtoreq.15 and 
accordingly substantially above the values for the prior art CuPc 
pigments, where C is at most 10. 
By varying the reaction conditions, it is possible to obtain pigmentary 
forms which, in the surface coating, give luminous golden brown to dark 
brown, or luminous reddish brown to yellowish brown, metallic effects. 
These results are surprising. It is known to a skilled worker that using 
the conventional .beta.-CuPc, which consists of acicular particles which 
are from 1 to 20 .mu.m in length, only tinctorially worthless dull, almost 
black colorations are obtained. The valuable blue pigmentary forms are 
obtained from these raw pigments only by comminuting the particles and 
conditioning them by a finishing method. 
It is surprising that increasing the crystals of CuPc to above 10 .mu.m 
gives pigmentary forms which produce metallic effects. A skilled worker 
would have expected, from his knowledge, that increasing the size of the 
crystals would give tinctorially worthless pigmentary forms of low color 
strength. 
The novel pigmentary form can contain 10% by weight, or more, of flakes of 
from 100 to about 150 .mu.m length. The third dimension, namely the 
thickness, of the novel pigmentary form is low, being about 1 .mu.m. 
The width of the flakes is from 33 to 100% of the length, pigments with a 
length:width ratio of from 1:033 to 1:0.6 occurring most frequently. 
According to the result of other conventional methods of characterizing 
pigments, such as elementary analysis, X-ray diffraction and infrared 
spectrum, the product is a CuPc in the .beta.-modification. 
The novel pigmentary form has a bulk density of .ltoreq.300 g/l, in 
particular of .ltoreq.200 g/l. 
The novel CuPc pigment is obtained direct from the method of synthesis. In 
the latter, a finely divided copper powder is reacted with 
o-phthalodinitrile in nitrobenzene in the presence of ammonia and of 
molybdic acid anhydride (molybdenum oxide) as the catalyst. 
In order to obtain the pigmentary form according to the invention, the 
starting materials must conform to the criteria given below, and the 
reaction conditions stipulated below must be observed. 
The copper powder used must be sufficiently fine to pass an 0.1 mm mesh 
screen without any retention. Furthermore, more than 98% by weight of the 
powder must consist of copper. 
The most important condition, however, is that the o-phthalodinitrile used 
is sufficiently pure. It must be soluble, without residue, in aromatic 
solvents, such as xylene, chlorobenzene or nitrobenzene, and must not 
contain more than 1.5, and preferably not more than 1, % by weight of its 
isomers, namely terephthalodinitrile and/or isophthalodinitrile, and/or of 
other nitriles, such as tolunitrile. The purer the o-phthalodinitrile 
used, the more easily is the novel pigmentary form of CuPc obtained. Thus, 
o-phthalodinitrile of purity .gtoreq.99.9% by weight gives a flaky CuPc 
pigment which contains more than 80% by weight of particles of .gtoreq.20 
.mu.m in length. In contrast, an o-phthalodinitrile which contains from 2 
to 4% by weight of isomeric dinitriles and/or other nitriles gives a CuPc 
which in addition to flakes of less than 10 .mu.m length contains 
substantial proportions of acicular .beta.-CuPc crystals. If the 
o-phthalodinitrile contains more than 4% by weight of isomeric dinitriles 
and/or other nitriles, the .beta.-CuPc produced is essentially all in the 
(known) acicular form. 
The purity of the other materials required to prepare the pigment is not so 
critical. The commercial technical-grade products are sufficiently pure. 
The ratio of o-phthalodinitrile to solvent is as a rule from 1:2.5 to 1:10, 
preferably about 1:3.5 to 1:6.0, by weight. 
The amount of copper powder used is not more than the stoichiometrically 
required amount, ie. 0.25 equivalent per mole of o-phthalodinitrile. 
Preferably, however, excess phthalodinitrile is used, so that the product 
ultimately isolated is free from copper powder. As a rule, therefore, up 
to 10%, preferably 2-6%, excess of dinitrile is employed. 
The amount of molybdic acid anhydride is from 0.001 to 0.15, preferably 
from 0.01 to 0.1, % by weight, based on o-phthalodinitrile, and is 
accordingly less than the amount of molybdic acid anhydride conventionally 
used in the preparation of CuPc from o-phthalodinitrile. 
To prepare the novel pigmentary form, the mixture of o-phthalodinitrile and 
copper powder with solvent, preferably nitrobenzene, is saturated with 
ammonia at from 70.degree. to 100.degree. C. and then heated to 
180.degree.-210.degree. C., preferably to 145.degree.-205.degree. C., and 
the molybdic acid anhydride required as a catalyst is only added 30-60 
minutes after the reaction temperature has been reached. Excessively 
vigorous stirring during the reaction should be avoided. The reaction 
mixture is only stirred just sufficiently to prevent the copper powder 
from settling out. During the reaction, all measures which form numerous 
crystal nuclei and accordingly favor the formation of acicular .beta.-CuPc 
should be avoided. For the same reason, the reaction mixture should also 
not contain a reaction accelerator, such as a copper-I salt or ammonium 
salt. 
The reaction is carried out under such conditions that the exothermic 
formation of CuPc extends over a lengthy period. For example, at 
200.degree. C. a reaction time of from 4 to 20 hours has proved 
advantageous. After 4 hours, the novel pigmentary form is already present, 
but the yield is occasionally only about 80% of theory. A yield above 90% 
by theory is reliably achieved after 16-20 hours at 200.degree. C. 
The shape, size and particle size distribution can be influenced to a 
certain degree, during the reaction, by varying the temperature, adding 
small amounts of a lower alcohol, preferably methanol, whilst heating-up 
the reaction mixture, and/or varying the amount of molybdic acid anhydride 
used. By these measures, it is possible to obtain pigmentary forms 
exhibiting different shades in paints and printing inks. Thus, it is 
possible to prepare pigmentary forms which in surface coatings give 
luminous golden brown to dark brown effects or luminous reddish brown to 
yellowish brown effects. 
The largest flakes, having edge lengths of about 100 .mu.m and an almost 
square shape (length:width ratio=from 1:1 to 1:0.6) are obtained, under 
the above optimum conditions, after a reaction time of about 4 hours. 
These flakes give surface coatings exhibiting golden brown metallic 
effects. The powder as such has a reddish glitter. On using higher 
concentrations of the reactants in the reaction mixture, increasing the 
rate of stirring or adding larger amounts of molybdic acid anhydride, 
crystal growth is reduced. The addition of small amounts of a lower 
alcohol, preferably methanol, to the reaction mixture during heating-up 
also influences the shape of the flakes, even though the alcohol distills 
off again before the actual reaction starts. In the surface coatings, the 
golden hue and metallic effect progressively disappear, and the hue shifts 
to reddish violet. 
If the reaction is carried out in the presence of accelerators, such as 
copper-I salts, or is carried out with insufficiently pure 
o-phthalodinitrile, needles having a width of about 1 .mu.m or less are 
obtained under the conditions stated above. This CuPc gives dull brownish 
blue to dark blue surface coatings. Evidently, the light is no longer 
subjected to mirror-like reflection if the particle width decreases below 
a critical value of about 1 .mu.m. 
The conventional acicular CuPc products do not give metallic effects even 
if the 1 .mu.m wide needles have lengths of up to 100 .mu.m. 
After completion of the reaction, the pigment is isolated in a conventional 
manner. The flaky product is very easy to filter off, and the mother 
liquor can easily be completely removed from the pigment by washing. To 
remove the high-boiling solvent, the filter residue is washed with a 
low-boiling solvent, such as methanol, ethanol, acetone or the like, and 
is then dried gently. 
The CuPc obtained by the process is very pure. The flaky CuPc can, after 
comminution, also be converted to conventional finely divided pigmentary 
forms by means of the usual finishing methods.

The Examples which follow illustrate the invention. Percentages are by 
weight. 
DETERMINATION OF TICLE SIZE DISTRIBUTION 
The distribution of the particle sizes in the CuPc pigments obtained was 
determined by 2 methods: 
(1) by wet sieving and 
(2) by the diffraction counting process. 
Process (1) is very time-consuming and labor-intensive. The diffraction 
counting process is rapid but has the disadvantage that it only copes with 
the range of from 2 to 170 .mu.m and accordingly the weight of particles 
of &lt;2 .mu.m and &gt;170 .mu.m is not taken into account. Nevertheless, the 
two methods gave distribution curves which agreed very well. 
The measured size distribution of the samples is shown in Table 1 (wet 
sieve analysis) and 2 (diffraction counting). 
EXAMPLE 1 
(a) 108 g of isomer-free o-phthalodinitrile (99.8% pure according to gas 
chromatography), 12.6 g of finely divided copper powder (from Schlenk) and 
400 g of nitrobenzene are introduced into a 1 liter three-neck flask 
fitted with a thermometer, paddle stirrer, reflux condenser and a short 
gas inlet tube which does not dip into the liquid. A slight stream of 
ammonia, at the rate of 1-2 bubbles per second, is introduced, via a 
glycol-filled washbottle, into the apparatus, whilst stirring the mixture, 
and the air is thus displaced. The reflux condenser is connected to a 
second glycol-filled washbottle, so that the apparatus is sealed from the 
atmosphere and air cannot enter. After the air has been displaced, the 
mixture is saturated with ammonia at 70.degree.-100.degree. C. whilst 
stirring at 250 rpm, and is then gradually and uniformly heated to 
200.degree. C. internal temperature in the course of 3 hours, and kept at 
this temperature for 30 minutes. 50 mg of molybdic acid anhydride are then 
added and the mixture is stirred at 200.degree. C. After about 3 hours, a 
thick reaction mixture has formed, which is only just stirrable and shows 
a reddish bronze effect in light. The mixture is kept at 200.degree. C. 
for a total of 5 hours after addition of the molybdic acid anhydride. The 
reaction mixture is then cooled to 150.degree. C. and filtered on a coarse 
glass suction filter, and the filter residue is washed with nitrobenzene 
until the filtrate is pale, and thereafter with methanol until free from 
nitrobenzene. The filter cake thus obtained is dried at 70.degree. C. 107 
g of copper phthalocyanine, in the .beta.-modification, are obtained in 
the form of a glistening loose powder with a reddish sheen, having a bulk 
density of 200 g/l. The product can be used direct for the production of 
metallic effect finishes. 
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C.sub.32 H.sub.16 N.sub.8 Cu (molecular weight 575.5) 
C H N Cu 
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calculated 66.8 2.78 19.5 11.04% 
found 66.2 3.0 18.9 11.2% 
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A sample of about 1 mg is triturated with one drop of linseed oil on a 
microscope slide and a cover slip is placed on top; under the microscope, 
at 100-fold magnification, the crystals show up as coarse flakes, some of 
which are almost square in appearance. The proportion of particles of 
.ltoreq.10 .mu.m is very low. 
More than half of the particles are more than 50 .mu.m long and about 10-40 
.mu.m wide. If the incident light is allowed to impinge at an angle, a 
brownish glitter or sheen is discerned, and the peculiar structure of the 
flakes, interlocked at the edges, is noted. 
The particle size distribution is determined on a sample of the CuPc 
pigment both by wet sieve analysis and by diffraction counting. The 
results are summarized in Tables 1 and 2. More than 90% of the particles 
are larger than 20 .mu.m. 
(b) 8 g of the pigment obtained according to (a) are dispersed in 92 g of 
an alkyd-melamine baking finish (35% solids) by stirring, using a 
dissolver. The colored finish thus obtained is sprayed onto an aluminum 
sheet or bonderized steel sheet until the substrate has been covered. 
After air-drying for 15 minutes, the coating is oversprayed with a clear 
acrylate-melamine baking finish (about 35% solids content) and the coating 
is air-dried for 30 minutes and then baked at 130.degree. C. for 30 
minutes. A very glossy coating, whose character resembles a metallic 
effect, is obtained. Depending on the angle of incidence of light, the 
viewer sees luminous golden brown to bluish gray or brown colors having a 
marked yellowish cast. 
The reflectance curve of the coating, recorded with visible light, of 
standard light type D, in the range of from 350 to 750 nm (Spectronic 505; 
Bausch & Lomb, Rochester, N.Y.) shows, from about 570 nm onward, a 
reflectance of from 7 to 12%, with two slight maxima at 630 and 720 nm 
(cf. curve B1 in the Figure). 
The colorimetric evaluation of the reflectance curve by the CIELAB method 
(DIN 6174) gives the following values: 
Lightness L=27.0 
hue gradation; HGD=33.3.degree. 
Chroma C=20.5, 
which corresponds to a yellowish warm brown shade. 
EXAMPLE 2 
The procedure described in Example 1 is followed, except that 75 mg of 
molybdic acid anhydride are added. Yield: 105 g of a flaky reddish blue 
glistening .beta.-copper phthalocyanine, which has similar properties to 
those of the product of Example 1. The result of the particle size 
distribution analysis is shown in Tables 1 and 2. More than 80% of the 
particles are larger than 20 .mu.m. 
When used in a baking finish, the pigment gives a bluish red coating which 
by reflected light shows an intense bronzy glitter. The reflectance curve 
of the coating, recorded with light of standard light type D on a 
spectrograph (Spectronic from Bausch & Lomb, Rochester, N.Y.) shows 7-12% 
reflectance from about 570 nm onward, with 2 slight maxima at 630 and 720 
nm, these maxima being somewhat flatter than those observed on a coating 
containing the pigment of Example 1 (cf. curve B2 of the Figure). 
EXAMPLE 3 
The procedure described in Example 1(a) is followed, but the mixture is 
stirred at 400 rpm, 18 g of methanol are additionally introduced as a 
solvent, and the temperature of the reaction mixture is kept at 70.degree. 
C. until the mixture has been saturated with ammonia (which requires about 
1 hour). The mixture is then heated as described in Example 1(a), in the 
course of which the methanol distils off. The temperature in the reaction 
mixture is set to 190.degree. C. 30 minutes after reaching this 
temperature, 100 mg of molybdic acid anhydride are added and thereafter 
the procedure described in Example 1(a) is followed. Yield: 106 g of 
.beta.-CuPc, in the form of finer flakes than those obtained in Example 1 
or 2 (cf. Tables 1 and 2). 
In a baking finish, a reddish violet hue, with a suggestion of 
transparency, and a gentle glitter effect, is obtained. The reflectance 
curve of the coating, in the visible region of the spectrum, shows a rise 
at 550 nm, and two flat maxima, with 10% reflectance, at 630 and 720 nm 
(curve B3 in the Figure). 
The colorimetric evaluation by the CIELAB method, DIN 6174, gives L=26.5, 
HGD=16.7.degree. and C=16.5, corresponding to a relatively dark red hue, 
which, however, is lighter and purer than that obtained with the pigments 
of Examples 4 and 5. 
EXAMPLE 4 
The procedure described in Example 1 is followed, but 98.2% pure 
o-phthalodinitrile containing 0.1% of benzonitrile, 0.5% of tolunitrile 
and 1.2% of isophthalodinitrile and terephthalodinitrile, is used. 
Yield: 99 g of .beta.-CuPc, essentially consisting of acicular crystals. 
According to particle size distribution analysis, fewer than 50% of the 
particles are larger than 20 .mu.m (cf. Tables 1 and 2). 
In a baking finish, dull bluish dark brown colorations are obtained, which 
no longer glitter by reflected light. The reflectance curve of the 
coloration is virtually a straight line between 350 and 750 nm, with a 
reflectance of from 4 to 6%. The colorimetric evaluation by the CIELAB 
method gives L=18.3, HGD=9.5 and C=5.4, corresponding to a markedly darker 
and duller hue than those of the colorations with the pigments of Examples 
1, 2 and 3 (curve B4 in the Figure). 
EXAMPLE 5 
For comparison, .beta.-CuPc was prepared by the process described in German 
Patent No. 1,569,636, Example 4. The particle size distribution was 
determined on the crude CuPc obtained. The result is shown in Tables 1 and 
2. Fewer than 20% of the particles are larger than 20 .mu.m. 
In a baking finish, dark blue, high-hiding colorations are obtained. These 
show no maximum in reflectance between 550 and 750 nm. The CIELAB 
colorimetric evaluation gives L=19, HGD=321.degree. and C=8.55, and 
amounts to the colorimetric description of a dull, dark purple hue (curve 
B5 in the Figure). 
TABLE 1 
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Particle size distribution in percent by weight, according 
to wet sieve analysis 
Particle 
Example Example Example 
Example 
Example 
size 1 2 3 4 5 
range [% by [% by [% by [% by [% by 
[.mu.m] weight] weight] weight] 
weight] 
weight] 
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0-10 1 5 32 47 64 
10-20 6 9 43 7 14 
20-50 26 35 21 19 12 
50-100 43 41 3 25 6 
&gt;100 24 10 1 2 4 
Propor- 99 95 68 53 36 
tion &gt;10 
Propor- 93 86 25 46 22 
tion &gt;20 
Propor- 67 51 4 27 10 
tion &gt;50 
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TABLE 2 
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Particle size distribution in percent by weight by the 
diffraction counter analysis method 
Particle 
Example Example Example 
Example 
Example 
size 1 2 3 4 5 
range [% by [% by [% by [% by [% by 
[.mu.m] weight] weight] weight] 
weight] 
weight] 
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0-10 2 8 27 35 53 
10-20 7 10 35 17 29 
20-50 32 41 38 29 16 
50-100 45 32 0 16 2 
&gt;100 14 9 0 3 0 
Propor- 98 92 73 65 47 
tion &gt;10 
Propor- 91 82 38 48 18 
tion &gt;20 
Propor- 59 51 0 19 2 
tion &gt;50 
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