Conversion of crude phthalocyanine blue from red to green shade in an aqueous environment

A method for converting crude phthalocyanine blue from red to green by milling a dispersion of the crude phthalocyanine and an aqueous medium containing a particulate grinding aid and a surfactant grinding aid composition characterized by employing a surfactant grinding aid composition comprising an acetylenic diol surfactant of the general formulas I and II: ##STR1## where R.sup.1 and R.sup.2, which may be the same or different, are C1-C8 alkyl, R.sup.3 is hydrogen or methyl, R.sup.4 is hydrogen, methyl, ethyl, or any combination thereof, and m+n=an average value from 1 to 100.

TECHNICAL FIELD 
The present invention relates to a process for transforming crude 
phthalocyanine blue in an aqueous composition into a pigmentary state 
using a surfactant grinding aid. 
BACKGROUND OF THE INVENTION 
Organic pigments are, in general, obtained from their synthesis in a 
physical state which is unsuitable for use. These crude pigments have, for 
example, a coarse particle size, a non-uniform or unsuitable crystal 
shape, or an excessive aggregation tendency. Crude pigments are therefore 
comminuted, and the residues of starting materials, undesirable 
by-products and the like are removed. The powders as obtained, however, 
have poor coloristic properties on account of a broad particle-sized 
spectrum. 
Phthalocyanine pigment has been used as a color source in many industries 
including inks, coatings, plastics and textiles. In many cases, the 
desired shade or hue of the phthalocyanine pigment is that of the green 
(.beta. crystal) shade. As synthesized crude phthalocyanine of the .beta. 
form is blue, but, due to its large particle size, poor color strength and 
an inherent dirty red shade, it is typically processed further to the more 
desired green shade via milling, or grinding, with salts and solvents. 
Specially designed additives, such as grinding aids and/or dispersants are 
required for direct conversion of phthalocyanine blue pigment by media 
milling because the conversion includes not only the breaking of 
agglomerates to their primary particle size but also goes one step 
further. The phthalocyanine blue crude starts as a red shade crystal, but 
the milling breaks the crystal structure into the unstable "Y" .alpha. 
crystal and causes a lattice change to produce the green shade .beta. 
crystal. A milling process (media size=0.25 mm) which induces a high 
amount of work and energy into the pigment dispersion is required to 
facilitate pigment crystal fracture, lattice structure shift and 
ultimately, pigment conversion. In addition to providing the properties of 
pigment wetting and stabilization, these additives also need to provide 
the grinding medium and composition with the proper rheology, viscosity 
and temperature stability due to the high energy nature of the process. 
The salt grind process utilizes sodium chloride and glycols such ethylene 
glycol, diethylene glycol, or triethylene glycol, to break down the 
agglomerates and finally change crystal structure of .beta. crude to the 
.alpha. form. The .alpha. crystal, however, is a red shade and it must be 
further reduced in particle size to the more thermodynamically stable 
.beta. crystal via long grind times and high temperatures of &gt;100.degree. 
C. The "salt grind" process for conversion of crude phthalocyanine blue 
typically takes up to 24 hours and produces copious amounts of excess 
solvent and wastewater. 
Thus, the traditional conversion of crude phthalocyanine blue by the salt 
grind process has the following drawbacks: 
______________________________________ 
environmental concerns from wastewater created by the washing of salts 
and solvents 
long processing times of up to 24 hr 
many processing steps-once conversion is complete, it must be 
reprocessed into a sellable/usable form such as finished pigment 
dispersion 
______________________________________ 
U.S. Pat. No. 2,816,115 discloses converting a crude phthalocyanine 
coloring matter in .beta. form to a pigmentary state without converting 
the coloring matter into the .alpha. form by milling it in an aqueous 
environment comprising a comminuted water-insoluble, solid grinding agent 
and a water soluble dispersing agent containing an anionic, water-soluble 
compound having relatively strong dispersing powers. 
U.S. Pat. No. 3,593,927 discloses a process of comminution of an aqueous 
suspension of .beta. copper phthalocyanine, by vigorous agitation in a 
grinding mill, with a particulate grinding aid, in the presence of an 
alkyl glycol ether having at least one ethylene glycol unit in the 
molecule and of one or more amine salts bearing at least one alkyl 
substituent having 12 or more carbon atoms in the chain. 
U.S. Pat. No. 4,158,572 discloses a process for producing a phthalocyanine 
pigment comprising dry grinding a crude phthalocyanine, stirring the 
ground product with an aqueous medium containing a nonionic surfactant and 
isolating the pigmentary product, the preferred nonionic surfactant being 
ethoxylated alkyl phenols. 
U.S. Pat. No. 4,427,810 discloses a method for producing an aqueous 
dispersion of phthalocyanine blue pigment comprising mixing in water a 
phthalocyanine crude pigment with a surfactant and grinding the mixture. 
Useful surfactants have an HLB value greater than 8 and include 
water-soluble, nonionic, cationic and anionic types. 
GB 2,039,290 discloses converting crude copper phthalocyanine into an 
easily dispersible deeply colored pigmentary form without the use of 
organic solvents by dry milling the crude pigment in the absence of 
chemical milling assistants until the milled material consists of 
agglomerates which are composed of primary particles of &lt;0.1 .mu.m in 
size, followed by admixing the milled material with water and heating the 
mixture in the presence of at least 3 wt % surfactant but in the absence 
of shear forces effective to comminute the primary pigment particles, 
thereby recrystallizing the pigment, and isolating the recrystallized 
pigment. The milled material which is mixed with water is obtained by 
milling a mixture of crude copper phthalocyanine and 0.5 to 15 wt % acid 
which has a pK of &lt;4.9 and is non-oxidizing under the milling conditions. 
U.S. Pat. No. 5,852,179 discloses the use of alkoxylated acetylenic diol 
surfactants in aqueous synthesis of dispersed azo dyes to provide a simple 
process for improving the filtration properties of dyestuff. The 
surfactants may be added prior to the coupling steps of the synthesis or 
prior to heat treatment of the dye slurry. For azo dyes that are 
synthesized as non-heat-stable crystal modifications, the presence of 
alkoxylated acetylenic diol surfactants in the dye slurry is effective in 
promoting the conversion of the dye to the desired thermally stable 
crystal modification. 
SUMMARY OF THE INVENTION 
The present invention pertains to a process for converting crude 
phthalocyanine blue from red to green by milling an aqueous dispersion of 
the crude material and a surfactant grinding aid composition. The 
inventive process incorporates an acetylenic diol surfactant into the 
surfactant grinding aid composition. Suitable acetylenic diol surfactants 
include those of the general formulas I and II: 
##STR2## 
where R.sup.1 and R.sup.2, which may be the same or different, are C1-C8 
alkyl, R.sup.3 is hydrogen or methyl, R.sup.4 is hydrogen, methyl, ethyl, 
or any combination thereof, and m+n=an average value from 1 to 100. Since 
alkoxylation of the acetylenic alcohol affords a distribution of alkoxy 
groups, m+n typically is reported as an average value. Acetylenic diol II 
is merely the alkoxylated product of diol I. 
Incorporation of the acetylenic diol surfactants into a surfactant grinding 
aid composition in the milling process for converting phthalocyanine blue 
affords the following advantages compared to the salt grind process: 
shorter processing times 
more environmentally friendly process--significantly reduces wastewater 
(washing of salts and solvents not required) 
a finished, sellable product in the form of an aqueous dispersion 
easy further processing to other end uses such as presscake, dry 
toner/pigment or flush color. 
Additional advantages of the present invention over the use of traditional 
grinding aids and surfactants are the following: 
high temperature stability 
high viscosity stability (80.degree. C.+) 
high ph stability 
high cloud point and no saponification of resinous material 
improved hue, clarity, and gloss 
improved/complete conversion to later form. 
DETAILED DESCRIPTION OF THE INVENTION 
The crude beta-phthalocyanine pigment for use in the present invention can 
be prepared by any of the synthetic routes typically used in the art such 
as that disclosed in U.S. Pat. No. 5,859,237 which is incorporated by 
reference. Of the phthalocyanine pigments suited for use in the process, 
the metal phthalocyanine pigments are preferred, especially the copper 
phthalocyanine pigment. 
There is provided a process for comminution and pigment conversion of an 
aqueous suspension of crude beta phthalocyanine by agitation, or grinding, 
in a grinding mill with a particulate grinding media such as sand or beads 
of porcelain, glass, or insoluble plastic material. The milling is 
performed with an aqueous suspension of the crude phthalocyanine pigment 
containing a surfactant grinding aid composition which comprises an 
acetylenic diol surfactant. 
Suitable concentrations of the crude phthalocyanine suspended in water are 
known in the art, thus 10 to 50 parts by weight (pbw) of pigment, 
particularly 20 to 45 pbw, per 100 pbw of mill charge are suitable. 
Throughout this specification the mill charge means the total ingredients, 
excluding the particulate grinding elements, charged to the mill during 
the grinding process, and all proportions are given by weight, unless 
otherwise stated. 
The particulate grinding elements used in the process of the invention may 
be of any hard nonpliable material which is insoluble in the aqueous 
medium used and may comprise sand, porcelain, glass, plastic, or metal. 
Preferably the particulate grinding aid is in the form of fairly uniform 
spheres about 0.5 mm or less in diameter. 
Suitable means for milling are known in the art and may conveniently be 
carried out in a Zeta mill manufactured by Netzsch, Inc. As desired, the 
apparatus may be arranged to work continuously or discontinuously. When 
disc impellers are used in such an apparatus, they may advantageously 
rotate at a rate such that the peripheral speed of the discs is about 
500-3,000 feet per minute. 
It is preferred to use a mill containing 0.2-0.4 mm beads in order to 
achieve the adequate energy required to break down crude phthalocyanine 
agglomerates and initiate a change in crystal lattice structure from 
.alpha. to .beta. form. Due to the high energy input in this conversion 
process, substantial heat is generated in the milling chamber. Therefore, 
the surfactant grinding aid composition must provide dynamic wetting and 
instantaneous pigment stabilization. In addition, the surfactant 
composition must be temperature stable in order to function properly in 
wetting and dispersing the crude phthalocyanine pigment without pasting up 
during the milling process. The surfactant grinding aid composition of the 
present invention provides for these attributes. 
Completion of the process may readily be recognized by examining particle 
size of the pigment, which should be smaller than 1 micron. Particle sizes 
of the converted beta phthalocyanine pigment of less than 0.13 microns can 
be achieved on commercial milling equipment with milling times ranging 
from 3-6 hours. 
After completion of the milling the particulate grinding aid may be removed 
by conventional means, for example by sieving and the aqueous pigment 
dispersion can be used as is or further treated by a homogenization step 
after which the pigment composition is filtered, washed, dried, and may be 
ground in a known manner until it is a free-flowing powder. 
The surfactant grinding aid composition, which may be used at 0.5-8 wt %, 
preferably 1-6 wt %, of the aqueous pigment dispersion, or mill charge, 
comprises an acetylenic diol surfactant and, optionally, but preferably, 
one or more nonionic and/or anionic surfactants. 
Suitable acetylenic diol surfactants include those of the general formulas 
I and II: 
##STR3## 
where R.sup.1 and R.sup.2, which may be the same or different, are C1-C8 
alkyl, R.sup.3 is hydrogen or methyl, R.sup.4 is hydrogen, methyl, ethyl, 
or any combination thereof, and m+n=an average value from 1 to 100. With 
regard to the alkoxylated acetylenic diols of formula II it preferred that 
R.sup.1 and R.sup.2 are C1-C5, especially C4 (isobutyl), R.sup.3 is 
hydrogen or methyl, R.sup.4 is methyl and m+n=1 to 30. However, the 
preferred acetylenic diols for use in the surfactant grinding aid 
composition are materials of formula I in which R.sup.1 and R.sup.2 are 
C1-C5, especially C4 (isobutyl), and R.sup.3 is methyl. Acetylenic diols 
of formulas I and II are marketed as SURFYNOL.RTM. surfactants by Air 
Products and Chemicals, Inc. 
As stated, the surfactant grinding aid compositions, optionally, but 
preferably, contain one or more nonionic and/or anionic surfactants. 
Examples of suitable anionic surfactants for use in the process are 
half-esters of sulfuric acid with C6-C20 alkanols, 2-hydroxyalkanesulfonic 
acids of 8 to 20 carbon atoms, sulfuric acid half esters of C6-C20 
alkylphenol polyalkoxylates, and C6-C20 alkylbenzenesulfonic acids, in the 
form of the alkali metal, ammonium, monoethanol-ammonium or diethanol 
ammonium salts; di(C6-C20 alkyl) sodium sulfosuccinates and salts of alkyl 
(unsubstituted or substituted) sulfosuccinamates in the form of alkali 
metal or ammonium salts. The sulfuric acid half esters of C6-C20 
alkylphenol polyalkoxylates are adducts of ethylene oxides and/or 
propylene oxides in which 5-50 moles, preferably 20-40 moles, alkylene 
oxide are present. The preferred anionic surfactants are salts of sulfated 
alkylphenoxy poly(alkyleneoxy) alcohols, for example ammonium salt of 
sulfated nonylphenoxy poly(ethyleneoxy) ethanol and the alkyl 
sulfosuccinamates, for example, 
tetrasodium-N-(1,2-dicarboxyethyl)-N-octadecyl sulfosuccinamate. 
Examples of suitable nonionic surfactants are amides, 
hydroxy-C2-C3-alkylamides and bis-(hydroxy-C2-C3-alkyl)-amides of C8-C20 
fatty acids, C8-C20 alkanols, polyethylene oxide, polyalkylene oxides 
obtained from propylene oxide and ethylene oxide, adducts of ethylene 
oxides and/or propylene oxides with C8-C20 fatty acids, with C8-C20 fatty 
acid amides, with C8-C20 alkanols, with C6-C20 alkylphenols, with C8-C20 
fatty acid ethanolamides, with C8-C20 fatty acid ethanolamine esters, with 
C8-C20 alkyl amines, with oleyl amine, with aliphatic diamines and 
polyamines, with cycloaliphatic monoamines and diamines, and with 
benzene-aromatic monoamines and diamines, or mixtures of the above. The 
preferred nonionic surfactants are the alkylphenoxy polyalkoxylates 
comprising adducts of ethylene oxides and/or propylene oxides in which 
5-50 moles, preferably 20-40 moles, alkylene oxide are present. 
The most preferred anionic surfactants are the sulfuric acid half esters of 
the C8-C12 alkyl phenol polyalkoxylates and the sulfosuccinamates and the 
most preferred nonionic surfactants are the C8-C12 alkylphenol 
polyalkoxylates. 
The surfactant grinding aid composition may comprise the following active 
materials: 
0-70 wt %, preferably 20-60 wt %, salt of sulfated alkylphenoxy 
polyalkoxylate; 
0-70%, preferably 20-60 wt %, salt of alkyl sulfosuccinamate; and 
5-100 wt %, preferably 5-35 wt %, acetylenic diol surfactant. 
The preferred composition comprises 
20-60 wt % salt of sulfated nonylphenoxy poly(ethyleneoxy) ethanol, 
20-60 w t% tetrasodium N-(1,2-dicarboxy ethyl)-N-octadecyl 
sulfosuccinamate, and 
5-35 wt % 2,4,7,9-tetramethyl-5-decyne-4,7-diol. 
To prepare the surfactant grinding aid composition the acetylenic diol and 
the surfactants are simply blended. Since the preferred acetylenic diol, 
namely 2,4,7,9-tetramethyl-5-decyne-4,7-diol, is a solid at room 
temperature, it must be heated up to 50.degree. C., but no greater than 
60.degree. C., before incorporation into the blend of the surfactants. The 
components should be mixed for approximately 15 minutes on a low, shear 
blender in order to ensure complete mixing. 
In the following examples all the aqueous dispersions of the crude 
phthalocyanine blue were prepared using the following formulations 
containing a surfactant grinding aid composition and the mill procedure 
(pigment conversion process) unless otherwise stated. 
______________________________________ 
DISPERSION FORMULATION (pbw) 
1 2 
______________________________________ 
Crude Phthalocyanine Pigment 
40 40 
Water 43.5 44.9 
Surfactant Grinding Aid Composition 
3.5 4.1 
AMP 95 1 1 
DEG 12 10 
______________________________________ 
MILLING PROCEDURE 
Premix on Cowles Blade for 15 min 
Horizontal shot mill (Eiger M100 or Netzsch Mini Zeta) 
0.4 mm zirconium shot 
50 to 75 vol % charge 
Mill speed 4500 RPM 
Milling temperature .about.80.degree. C. 
Surfynol 104E surfactant added as needed to control foam 
Make-up water was added to compensate for evaporation 
Milling time varied according to abilities of grind aid 
Table A shows the surfactant grind aid compositions used in the following 
examples, components in wt %: The wt % amounts in the table are based on 
active material (other than for the glycols and water). 
TABLE A 
______________________________________ 
Grind Aid 
Composition 1 2 3 4 5 6 7 
______________________________________ 
Aerosol NPES 3030P 
12 15 7.1 15 12 12 -- 
Surfynol 104 
10 8 7.6 10 -- -- 8 
Aerosol 22 12.2 -- -- -- 12.2 12.2 17.5 
Igepal W-730 
-- 27 25.6 -- -- -- 27 
SMA 1440H -- -- 7.9 -- -- -- -- 
Disperbyk 190 
-- -- -- 20 -- -- -- 
Emulgen HP-60 
-- -- -- -- 10 -- -- 
Ethylene Glycol 
-- 11 -- -- -- -- 11 
Diethylene Glycol 
-- -- 5 -- -- -- -- 
Water 65.8 39 46.8 55 65.8 75.8 36.5 
______________________________________ 
The following materials were used in the examples: 
Crude phthalocyanine blue pigment from Phthalchem 
AMP 95 aminomethyl propanol from Angus Chemicals 
DEG--diethylene glycol 
Aerosol NPES 3030P surfactant--ammonium salt of sulfated nonylphenoxy 
poly(ethyleneoxy) ethanol (30 moles EO) from Cytec Industries. 
Surfynol 104 surfactant--tetramethyl decynediol from Air Products and 
Chemicals, Inc. 
Surfynol 104E surfactant--50 wt % S-104 in ethylene glycol 
Aerosol 22 surfactant--tetrasodium N-(1,2-dicarboxyethyl)-N-octadecyl 
sulfosuccinamate from Cytec Inds. 
Igepal CO-730=Igepal W-730 nonylphenol ethoxylate (15 moles EO) from Rhodia 
SMA 1440H surfactant is styrene maleic anhydride polymer from Elf Atochem 
Disperbyk 190 polymeric dispersant from BYK Chemie 
Emulgen HP-60 alcohol alkoxylate from High Point Chemical 
Percent conversion, or tinctorial strength, is conveniently measured by 
comparing the color of one pigment (the experimental batch), mixed with a 
specified amount of white base, with the color of another pigment (the 
standard) mixed with an equal amount of the same white base. In the 
following examples the conversion of crude phthalocyanine pigment was 
determined by color analysis comparing the experimental sample with a 
standard dispersion. 
Procedure for Color Analysis 
Standard Dispersion: 
40% salt ground converted phthalocyanine blue pigment Color analysis: 
1. Into a 50 ml container pour 25.00 g of bleach white (flat interior 
paint) and 0.50 g of dispersion 
2. Mix until homogeneous and agitate on a paint shaker for 15 minutes. 
3. On Leneta chart, make a draw down using a #20 wire wound rod. 
4. Allow the draw down to dry over night. 
5. Measure the color using a spectrophotometer. 
6. The "a" value of the Standard Dispersion (STD) is taken to be 100%, 
Therefore, % conversion =(("a" value trial) / ("a" value STD)).times.100