Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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DARK BROWN PIGMENTS OF PSEUDOBROOKITE 5TRUCTURE
BACKGROUND OF THE INVENTXON
The present invention rela-tes to inorganic
dark brown pigments of pseudobrookite structure.
Pseudobrookite is a solid material of varying
composition in which the unit cell is an orthorhombic
5 arrangement of 20 anions with 12 cations distributed in
interstices between the anions. These materials may be
represented by the general formula:
X2 Yn 2n+3
When n equals 1, the material is said to be
stoichiometric. actual pseudobrookite materials,
however, may deviate to some extent from stoichiometric
composition. In pseudobrookite, the X ions are
primarily trivalent (small amoun-ts of divalent ions may
also be present) and the Y iOIlS are tetravalent. In
15 these materials, cations are present in the
pseudobrookite struc-ture in octahedral coordination.
The starting materials which may be
potentially useful in developing pseudobrookite are
those for which the ionic radius is greater than 0.6
20 Angstroms but less than 1.0 Angstroms. Thus, ions such
as iron, zinc, magnesium, nickel, copper, cohalt,
manganese, titanium, tin, silicon, and vanadium may be
appropriate.
Pigments having a pseudobrookite structure
25 have not been generally described or discussed in the
literature. The specific compound Fe2TiO5 is,
however, discussed in some detail in the scientific
literature (for example, see the book, "The ~lajor
Ternary Structural Families," by 0. Muller and R. Roy,
30 particularly page 232).
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SUMMARY OF THE INVENT ION
It is an object of the present invention to
provide an inorganic dark brown pigment.
It is also an object of the present invention
5 to provide a dark brown pigment with a pseudobrookite
structure having high tinctorial strength, very high
opacity, and excellent color and thermal stability.
These and other objects which will be appaxent
to those skilled in the art are accomplished by
10 calcining a mixture of raw materials which mixture
yields a calcination product corresponding to the
general formula:
X2 Y 2n+3
in which X, Y, and n are as defined below.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to an inorganic
dark brown pigment oE pseudobrookite structure haviny
the general formula:
X2 Yn 2n~3
20 wherein
n is a number from 0.4 to 2.0 and preferably from 0.9
to 1.1;
X represents a trivalent and/or divalent ion selected
from the group consisting of 0.6 to 1.9 mols of iron,
25 0.1 to 1.4 mols of manganese, 0.0 to 0.25 mols of
cobalt, 0.0 to 0.25 mols of zinc, 0.0 to 0.25 mols of
nickel, 0.0 to 0.4 mols of copper, 0.0 to 0.25 mols oE
magnesium, and mixtures thereof, the total amount of
said trivalent and/or divalent ions being 2.0 mols; and
30 Y represents a tetravalent ion selected from the group
consisting of titanium, tin, silicon, and mixtures
thereof. If desired, up to 5~ of the total mols of
tetravalent ion can be vanadium.
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In the most preferred embodiment, X represents
a trlvalent ion selected from the group consisting of
1.3 to 1.8 mols of iron and 0.2 to 0.7 mols of
manganese end Y represents titanium.
When the concentration of iron is less than
0.6 mols, the color is blaek. When the iron
concentration exceeds 1.9 mols, the tinctorial strength
is inadequate. Reverse effects are noted for
manganese. That is, when the concentration ox
10 manganese exceeds 1.4 mols, the color is black rather
than brown, while use of less than 0.1 mols of
manganese results in a medium brown color rather than a
dark brown. Up to 0.25 mols of magnesium or zinc may
replaee iron but when the coneentration of either
15 magnesium or zinc exeeeds 0.25 mols, the product
pigment is a medium brown. The total concentration of
niekel and cobalt should be held to less than 0.25 mols
and the eoncentration ox copper held to less than 0.4
mols to prevent a change of color.
Titanium, tin, silieon, or a eombination
thereof ean be used for the tetravalent ion. The
elarity of eolor when silicon is used is, however,
inferior to that obtained with the other two ionsO
Eeonomie considerations make titanium the most
25 preferred alternative.
Considerable deviation from the pseudobrookite
stoiehiometry can be tolerated in the system of the
present invention. Wevertheless, when the value of "n"
is less than 0.4, the color is blaek rather than
30 brown. When the value of "n" exceeds 2.0, the
tinctorial streng-th is greatly redueed due to the
presenee of substantial rutile in the pigment which
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rutile structure material results in a medium brown
color.
The piyments of the present invention Jay be
prepared by weighing out appropriate arnounts of
5 conventional ceramic grade oxides and/or carbonates and
carefully blending and passing these materials through
a hammer mill to break up any agglomerates. These
mixtures may then be calcined at temperatures of from
1500 to 2000F (816 to 1093C)~ Calcination fox
10 three to six hours at peak temperature and total cycles
of 18 to 24 hours are preferred.
After calcining, it is generally necessary to
mill the pigments until there is no residue upon a
325-mesh screen.
To Eurther illustrate this inven-tion, the
following examples are presented.
EXAMPLES
The pigments oE the present invention were
evaluated Eor their color properties by dispersing -them
20 in a paint medium. The paints were made by mixing 10.0
grams of the pigment of the present invention with 14.0
grams of soya oil alkyd resin, 16.5 grams of mineral
spirits, 2.4 grams of naphtha, and 0.13 grams of
driers. The mixture was then shaken on a paint shaXer
25 for 30 minutes with 30 grams of beads. The paint was
then strained and 0.3 cc of additional driers were
added. The paint was then drawn down with a 0.006 inch
Bird applicator on a Laneta card that was half white
and half black. The drawdown was allowed to air dry
30 for at least 24 hours. The fineness of the pigment was
evaluated by a drawdown of the Hegman gage (see ASTM
test method ~1210 79). The color proper-ties were then
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measured on a Diano/Hardy visible spectrophotometer,
and are reported in terms of the reflectance Rd and
the color parameters "a" and "b". (For a description
of those parameters, see I. B. Judd ancl G. Wyszecki,
5 "Color in Business, Science and Industry", Wiley, New
York, 1963, pO 296.)
EXAMPLE 1
1,331 grams ox ferric hydroxide, 724 grams of
anatase, and 444 grams of manganese carbonate were
lO weighed out, blended, and passed through a hammer
mill. The mixture was then calcined at 1700F for
three hours. The resulting very dark brown pigment was
then flllid energy milled until there was no residue on
a 325-mesh screen. The resulting pigment had -the
15 formula:
Fel 6MnO . 4TiO5
When placed in a paint as descrihed
previously, a ~legman rearing of 7.5 was obtained. The
paint was a dark brown color which had color readings
20 over a white background of:
Rd 5.3%
a = 2.1%
b = 2.1%
The pigment was fully opaque so that the color
25 properties over a black background were substantially
the same as those over a white background.
EXAMPLE 2
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117.5 grams of ferric hydroxide, 73.1 grams oE
anatase, 44.8 grams of manganese carbonate, and 14.5
30 grams of black copper oxide were weighed out, blen-led,
and passed through a hammer mill. They were then
calcined at 1900F for three hours. The resulting dark
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brown pigment was milled in water until there was no
residue on a 325-mesh screen. The resulting pigment
had the formula:
Fel 4Cu0 2r~no.4TiO5
r~hen incorporated in a paint vehicle as
described above, the Hegman reading was 7.5 and the
color properties over a white background were:
Rd = 5.2%
a = 1.4
b = 2.1~
The pigment was fully opaque so tha-t the color
properties over a black background were substantially
the same as those over a white background.
EXAMPT~S 3-12
Each of the formulations given in rrable 1 was
made by weighing out the raw materials, blending those
raw materials and passing the blend through a hammer
mill. Each blend was then Eired according to the
schedules given in Table 1. After iring, each oE the
20 calcined materials was milled in water until there was
no residue upon a 325-mesh screen. The formula of thy
resulting pigment in each case is given in Table 2.
The pigments were then individually added to the paint
formulation described above in order to obtain a Hegntan
25 reading and evaluation of the color properties over
both white and black backgrounds. In each case, the
readings over the black background were equivalent to
those over the white background because the pigments
were fully opaque. The results are given in Table 2.
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TABLE 2
White Background
Example Pigment Formula Hegman Reading Rd a b
1.8 0.2 5 6.6 4.2 5.7
4 FeMnTiO5 8 5.0 1.0 1.7
Fel 4Co 2Mn0 4TiO5 7.5 5.3 2.1 3.3
6 Fel 6ZnO 2Mno.2Ti5 ~-3 4.1 5.4
7 Fel 2Co0 2Zno 2Mn0-4Ti5 5-4 1.9 2.4
8 Fel 4Mgo 2Mno.4T 5 8 5.9 2.3 4.6
g Fel 6Mn0 4Tio.5O4 8 5.0 1.9 2.8
Fel 6Mno.4Ti2 7 5.8 1.9 3.1
11 Fel 3Mno.7Ti5 5.2 1.8 2.8
12 1.4ZnO.2~no.4TiO5 7.5 6.7 4.0 5.7
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