Note: Descriptions are shown in the official language in which they were submitted.
63~
:
BACKGROUND OF THE INVE~TION
Bismuth vanadate occurs in nature in an ortho-
rhombic form commonly called pucherite. Pucherite is a
dull yellow-brown mineral, which is not useful as a pig-
ment. Pucherite is slmilar in color to limonite, a dull
yellow-brown iron oxide, which has never been produced as
a bright, high intensity pigment despite repeated
attempts.
Various references have described the synthetic
preparation of bismuth vanadate, for example,
I. M. Gottlieb and C. R. Rowe, "Preparation and Thermal
Properties of Bismuth Orthovanadate", Thermal Analysis~
Vol. 2, Proceedings Third ICTA DAVOS (1971), pp. 303-311;
R. S. Roth and J. ~. Waring, "Synthesis and~Stability of ~;
Bismutotantalite, Stibiotantalite and Chemically Slmilar
AB04 Compounds", The American Mineralogist, Vol. 48
(Nov. - Dec., 1963)g pp. 1348-56; H. E. Swanson et al.,
"Standard X-Ray Diffraction Powder Patterns", National
Bureau of Standards Report, No. 7592 (Aug., 1962);
Eduard Zintl and Ludwig Vanino, "Process For The Manu-
facture Of Pure Bismuth Vanadate"; German Patent
No. 422,947 (1925). However, as in the case of yellow
iron oxide, none of the above references provide a process
which is successful for use in the preparation of bis-
muth vanadate which is useful as a bright yellow pigment.
SU~ARY OF THE INVENTION
The present invention relates to a process ~or
preparing pigmentary bismuth vanadate which process com-
prises mixing a solution of Bi(N03)3 5H20 in nitric acld
30 with a solution of alkall vanadate in an aqueous base ~
..... . ' . '
- 2 ~
~ '' ' ~." .
.. . . . . . . . . . ..
. . ~ , . ...
.,. : - . . . : . : .
0 ::
selected from sodium hydroxide and potassium hydroxide, :~
to precipitate a bismuth vanadate gel suspended in a
solution containing dissolved alkali nitrate, wherein the
molar ratio of Bi3 to V043 is from about 0.90:1.00 to
about 1.10:1.00 and wherein the normalities of the acid
and base solutions are adjusted prior to mixing so that
the pH of the mixture will be from about 1.0 to about ~ .
11.0~ preferably from about 1.5 to 4.0; adjusting the pH
of the suspension to about 2.2-6.0 with an aqueous base . ~
10 selected from sodium hydroxide and potassium hydroxide ~ . .
if the pH is less than about 2.2, or with an acid :
selected from nitric acid or sulfuric acid if the pH is
greater than about 6.o; removing the gel from the sus- .. ....... ..
pension; washing the gel with water until it contains
about 10 percent or less alkali nitrate, based on the
theoretical yield of bismuth vanadate; heating the gel in
water at about 60-200C. for at least 0.2 hour; holding
the pH within the range of from about 2.2 to 6.o with an
aqueous base selected from sodium hydroxide and potassium
20 hydroxide if the pH is less than about 2.2 or with an .
acid selected ~rom nitric acid, hydrochloric acid~ hydro- ~ :
bromic ac.id, sul~uric acid or phosphoric acid if the pH
is greater than about 6.3 to convert it to pigmentary
monoclinic bismuth vanadate; ad~usting the pH of the . . .
suspension to 8.o to 9.5 with an aq.ueo~base selected .~.
from sodium hydroxide or potassium hydroxide and main~
taining the suspenslon at this pH at a temperature of
50-100C. ~or 15 to 30 minutes; and filtering, washing
and drying the pigment. .. .
DETAILED DESCRIPTION OF_T~IE INVENTION
.. :. ~,
- 3 - : . :
i3~3
:
ThiS ln~entlon rel~tes to ~ proce~ ~or the
preparation of pigmentary monoclinic b~gmuth v~nadate.
By "pi~mentary~' iæ meant a bi~muth vanadate ~hich i8
bright prlmr~se yellow, sin~le ph~3e monoclinlc cryætal-
line a~ detexmined by X-ray di~fractiony having high
intensity, good strength and good light~a~tness. ~-
A6 indicated, pigm~nt~ry bi~muth ~anadate i~
en~irely ln the monoclinlc crystal phase a~ determined
u~g X-ray dif~raction. ~-ray di~action mea~urement~
are made wlth a Debye~Scherrer* powder camera using C ~
radiation ~rom a Norelco* Type l2045B unit at ~0 kV/~OmA
and a 6-hour exposure.
The bismuth vanadate o~ the present invention
exhibits a large increa~e in re~lectance in the range o~
the vislble spectrum ~rom 450 to 525nm which showA th~t
it iæ primrose yellow in color and has high intenælty
and good strength. Reflectanre iæ used herein as a com-
parison of the specular and di~u~e re~lect~nce o~ a
kno~n st~n~rd with the sample to be te~ted using Type I
illumin~tionO Re~lectance i8 measured on a Cary* Model l~
spectrophotometer equipped with an lntegrating sphere,
palnted with Eastm~n* white re~lectanQe paint No~ 6080.
The sample to be te~ted 15 prepared by mixing lO weight
percent of the bismuth vanadate o~ the presen~ lnvention
wlth 90 weight pereent o~ barium ~ul~ate~ Eastman
Re~lectance Standard No~ 6091, until a uniform powder
ls obtained. Then the r~Mectance o~ the known standard
Eastman Re~lectance Standard No. 6091, is compared with
that o~ the ~ampleO In the range Or the Yi~ible spectrum ` ~ -
from 450 to 525nm~ th~ ~ample conta~nlng the biæmuth
* denotes trade m~rk
. . . , : . .......... .. . . . ....... ~, . .
... . . . . . , ............ ., . ,~ . ............. . .
., .. : ,, ,, , . . . . , . , , . ' , ', ' ' ' ' : ', . . .: ' .
1~3~ 30 : ~
. , .
~anadate o~ the present lnvention exh1bits an increa~e o~
at least about 65 re~lectance units on a scale in which
the Eastman Reflectance Standard No. 6091 exhibitæ a
re~lectance of 100 units over the entire vi~ible spectrum~
In ~act, many o~ the sampleæ exhibit increases in re~lec-
tance o~ at least about 70 units or greater~ The greater
the mag~itude o~ the change in re~lectance within the
speci~ied æpectral range, the greater the intensity and
~trength o~ the sample.
The lntensity and light~a~tne~s o~ pigmentary
bismuth vanadate in a paint are measured ~rom palnt dr~w-
down~ made to complete hiding~ The paint ls made by dis-
per~ing the pigment into a binder in a 2:1 ratio by -:
weight of pigment to binder using a Hoover* muller. The
binder is compo~ed o~ 98.9 weight percent #2 transparent
,
varnish made by Superior Varnish and Drler Company, -:
MerchantsvillQ, ~ew Jersey; 1 weight percent~ a~ lead,
o~ lead Nuodex~ drier (contain~ 24% lead), and 0~1 weight :
percent, as manganese~ of m~nganese Nuode~ drler (con-
tains 6% mangane~e)0 The drawdownæ are dried ~or about ~ ~
72-120 hour~ ~n A well-ventilated room at 25C. and leæs : .:
than about 50% humldlty. ~ .
Intensity i~ determlned by the green ~ilter
re~lectanc~ o~ a masstone drawdown. Inten~ity is expres~ed ~ .
as a percent o~ green ~ilter re~lectance me~sured with a ~ : :
Gardinar* Multipurpose Re~lectometerg Ser~al No. 40
(Gardiner Laboratory, Inc., Bethesda, Maryland)l using a
white re Msct&nce ~t~ndard at a ~etting o~ 86.1 and light
from a General Electric* CVS pro~eetor lamp passed throu~h
the green tristimulu~ ~ilter ~upplied with the Gardiner
* denote~ trade mark
~, ~
~..... 1,. ............. ..
.. ,, - .
3~
~eflectometer. The Gardiner Multipurpose Reflectometer
is described in National Bureau of Standards ~esearch
Paper RP 1345, dated Nov., 1940, by Richard S. Hunter,
and National Bureau of Standards Circular C429, dated
July 30, 1942, by Richard S. Hunter. The higher the
percent reflectance of the drawdown, the more intense the
color. The intensity of the bismuth vanadate of the
present invention is such that it has a green filter
reflectance of at least about 60 percent.
,: :
Lightfastness is determined after the dried
paint drawdowns have been continuously exposed for 44
hours in an Atlas Color Fade-Ometer~ Type FDA P. A ~ -
Gardiner Multipurpose Reflectometer is used as described
above to measure green filter reflectance before and after
exposure. Measurements are taken within one hour prior
to exposure and again within one hour after exposure.
The percent lowering of reflectance after exposure based
on initial reflectance is percent Fade-Ometer~ darkening. -
The lower the percent Fade-Ometer~ darkening, the better
the lightfastness of the pigment. The bismuth vanadate
of the present invention will generally exhibit a percent
Fade-Ometer~ darkening of about 11 percent or less,
preferably about 7 percent or less, after 44 hours of
exposure.
The surface area of the bismuth vanadate is
about 2-22 m2/g. For use in film forming compositions, ~ -
such as paints and inks, a surface area of about a-22 m2/g.
is preferred. For use in plastic compositions, a surface
area of about 2-4 m2/g. is preferred because of increased
30 heat stability. The surface area is measured on a ~ ;
- 6 - ~
: .
.. : , . . , : , , ,. ~
v : :
Perkin-Elmer Shell* Model 212C Sorptometer using the
technique recommended b~ the manufacturer.
According to the process o~ thi~ in~ention
pigmentary bismuth vanadate i5 prepared by mixln~ a
solution of up to about 0.8M BitN03)3 5H20 in up to about
4.oN nitric acid, preferably about O.~M Bl(~03)3'5H20 in
about l.ON nitric acid, with a ~olution of alkali vana-
date (sodium ~anadate or potassium vanadate)~ preferably
up to about 0.32M ~a3V04, in up to about 1.6N aqueous
baæe selected ~rom sodium hydroxide or potaæ~ium hydro- -
xide, more preferably about O.~M Na3V04 in about l.ON
sodium hydroxide. Upper concentration limits for the
re~ctant solutions are determined by solubility; however,
control o~ equimolar incremental mixing is easier with
more dilute solutions. The temperature o~ mlxing is not
critic~l and mixing can be carried out at temperatures
of ~rom lO to 100C~ but it is preferred that the
~olution~ be mixed at 20 to 30C.
The molar ratio o~ Bi3+ to V043 can be about -;~
0~90:1.00 to 1.10:1.00, preferably about 0~98:1.00 to
1,05:1.00, which indicates that e~ther an eæces~ of B~3~
or ~0~3 i8 allowable. me symbol vo~3 is used herein to
denote a pentavalent ~ranadium species in an a~ueou~
~olution, but lt doeæ not mean a speci~ic pentavalent
~nadium ~pecies pre~ent at a glven p~ and vanadium
concentrationO
The normalitie~ o~ the acid and base solution~
~re adJu~ted prior to mixing ~o that the p~ o~ the reaction
mixture will be about l~O-lloO~ A pH o~ about 1.5-4,0
is preferred because it yield~ a gel ~rom which a
* denotes trade m~rk
- 7 -
, ~ . .
.
9630
plgmentary monoclinic bismuth vanadate product having
optimum intensity and/or light~astness can be
obtained.
The preferred method of mixing the solutions
is in a ~low reactor which gives a very rapid incre-
mental combination under high turbulence conditions.
Incremental combination means that small, essentially
stoichiometric quantities are reacted at one time.
This prevents relatively large gradients and stoichio-
10 metric imbalance that result when large quantities of ~;
reactants are mixed at once. Such imbalance results in
undesirable side reactions. Apparatus which conveniently
achieve this result are tee mixers or flow reactors.
When the solutions of Bl(N03)3 5H20 and alkallvanadate are mixed under the above conditions, a suspen-
sion of bismuth vanadate gel in alkali nitrate (sodium
nitrate, potassium nitrate, or both) solution is ~ormed.
Bismuth vanadate gel as used herein means a hydrous,
. .
X-ray amorphous bismuth vanadate precipitate containing
o~cluded water.
The gel should not be removed from the suspen-
slon until the pH o~ the suspension has been stabllized
at about ~.2-6.0, pre~erably about 3.0-3.5. Thus, i~ the
pH Or the suspension is less than about 2.2, it may be
ad~usted upward with aqueous sodium hydroxide or potassium -
hydroxide, and if it is greater than about 6.0, it may
be ad~usted downward with an acid selected ~rom nitrlc
acid or sulfuric acid. Prompt ad~ustment of the pH of
the suspension to the final range listed above is
advisable, although under certain circumstances the
: .
- 8
. . .
~: .: .. : ; . ... . :
: . ~ . . . . :. ~ ~
bismuth vanadate gel is stable for up to several hours
at room temperature prior to pH adjustment.
The gel is then removed ~rom the suspension, -
preferably by filtration. The gel is collected and, if
it contains more than about 10 percent alkali nitrate
based on the theoretical yield of bismuth vanadate, the
gel must be washed with water until it contains about 10
percent or less.
When an excess of vanadium is used in the forma- -
tion of the gel, the gel must be washed prior to the above
aqueous digestion to remove any alkali nitrate in excess
of 10 percent by weight based on the theoretical yield
of bismuth vanadate. The suspension containing the gel
is then heated at a temperature of ~rom about 60C. to
about 200C. for at least 0.2 hour, and preferably at
a temperature of ~rom 90C. to about 100C. ~or about
one to two hours to convert the gel to pigmentary mono-
clinic bismuth vanadate. Durlng the aqueous digestion
the pH of the suspension must be maintalned at a pH
of from 2.2 to 6.o, and pre~erably ~rom a pH of 3.0 to
3.5, by adding a suitable acid or base as needed. Acids
suitable ror use lnclude nitric, sulfuric, hydrochloric,
hydrobromic or phosphoric. Bases sultable for use
include aqueous sodium hydroxide or potassium hydroxide.
It wlll be understood that if temperatures above about
100C. are used, the heating must Oe carried out undçr
pressure. In additlont when the ratio of Bi to V04 is
0.9:1 to 1.0:1.0, the digested pigment must be washed
a~ter the heatln~ step by suspending it in water for 15
to 30 minutes at 50C. to 100C. while holdlng the pH
_ g _
.,: ', ' ' ' ' ' :,
. ~ , , , , .:
6~ -
at 8.o to 9.5 with an aqueous base selected from sodium
hydroxide and potassium hydroxide. Pre~erably the digested
pigment will be washed in wa~er for 15 minutes at 70C.
while holding the pH at 9.0 with an aqueous base selected
from sodium h~droxide and potassium hydroxlde. When a
molar excess of bismuth is used in the formation of the -~
gel, it is not necessary to reduce the alkali nitrate~ -
content of the gel prior to digestion, although removal or
reduction of the alkali nitrate from the gel prior to
digestion is ~ermissible.
After digestion is complete the pigment is
filtered, washed and dried, e.g., at about 130C. The
product is bright primrose yellow bismuth vanadate which
is entirely in the monoclinic phase as identified by
X-ray dif~raction.
In the process as described above the pH
adJustment can be made a~ter the gel has been removed
from the suspension. However, in order to easily adJust
the pH of the gel, the gel should be resuspended in
water. Once the pH of the gel has been properly
ad~usted, the gel under certain circumstances is stable
for up to about a week at room temperature.
It is possible to prepare the alkali vanadate
solution by dissolving a pentavalent vanadium compound ;
25' Na3vo4~ Na4V2O7~ NaVO3, or K VO4 in an
aqueous base selected from sodium hydroxide and
potassium hydroxide.
After the bismuth vanadate pigment has been
prepared by the process of this inventlon, its light-
3 fastness may be improved by encapsulation in a dense
~. ..:, .- :'
-- 10 --
,.
.. .. , . . . ~ , -, : . -- ~
.. . :. ,., . . . - :
.. : . -, - , ~ . :
.:. : :. : . , . : :,. .
~8~
amorphous coating of silica or a treatment with aluminum
p~rophosphate. Coatings can be applied in accordance
with known processes, such as those taught in Re 27`,818
(reissue of U. S. Patent 3,437,502) to Werner; U. S.
3,639,133 to Linton; U. S. 3,370,971 to Linton; and of
u. s. 3,885,366 to Iler.
EXAMPLE 1
A mixture is prepared by combining the following -
ingredients in a mixing tee:
(i) Bi(NO3)3.5H2O (10.93 lb.) dissolved in
12.78 1. of 4 .ON HN03, then diluted to
51.1 1. with water, and
(ii) V2O5 (2.05 lb.) dissolved ln ~1.94 1. of
water containing 7.210 lb. NaOH, then
diluted to 51.1 1. with water to give a
solution of sodium vanadate plus sodium
hydrDxide.
The mixing tee has inside diameters of 0.118 in. for the
bismuth nitrate opening, 0.192 in. for the sodium vanadate
openlng, and 0.1~2 in. for the exit. The bismuth nitrate
enters on the leg. The solutions are mixed in about 15
minutes when a pressure of about 15 psi is applied across
the tee. Sufficient HNO3 is added to ingredient (i) or
aqueous NaOH to ingredient (ii) so that the pH of the mix-
ture of the two will be about 1.5 to 2Ø The mixture ~-~
is squlrted into a 45 gal. tank containing 7 gal. of water
which has been ad~usted to a pH of 2.2 with HN03. The ~;
contents of the tank are stirred ~or several minutes, and
the pH is ad~usted to 3.2 with 2.0N NaOH. The contents
3n are then stirred for 15 minutes,filtered, and washed with
,
',
. .
.
. . , .: :. ; . , .: :
i3~ :~
20 gal. o~ water and re~iltered. me bismuth vanadate gel
.
is collected ~rom the ~ilter cloth, and is stirred into
a tank containing 70 lb. of water, which ha~ been
adjusted to a pH o~ 3.1 with HN03. The contents of
the tank are heated to 95C. in about 40 minutes and held
at that temperature and a p~ o~ 3.1 ~or 120 minutes. The
product~ pigmentary bismuth vanadate, is isolated by
~iltration, washed twice with 20 gal. o~ water, and dried ~ -
.
~t 1~0~.
The above procedure is repeated four times to -~
yield about 28 lb. o~ pigment, Twenty-five pound~ o~ the -
pi~ment are dispersed in 104 lb. o~ ~ater containing 567 g.
o~ Fi~cher* 28% ~odium silicate æolution (~0-42 ~aume~ by
passing it through a Gaulin* Submicron Homogenizerg first
at 2000 p~i, and again at 5000 psi. me mixture i~ then
heated to ~nd held at 90C. and adJusted to a pH o~ 9.6
w~th 2.0N NaOH. A solution of 14.~97 lb. o~ eher 28%
~odium sllicate in 62.5 lb. o~ water is added to the
mixture over a ~our-hour pcriod. At the same time, a ~
20dilute sulfuric acid solution (2.299 lb. of ~oncentrated -~ -
8ul~uric acld in 71~25 lb. o~ water) iæ added to the
mixture at a rate such that the pH o~ the mixture drops
.
to 9~4 in about 45 mlnutes. The pH o~ the mixture i~
immediately raised to 9.6 wlth 2.0N MaOH. mis pH control
procedure i~ continued over the ~our-hour ~ilicate ;j ~-
addition period.
A~ter the ~our-hour addition period, the pH
i~ reduced to 9.0 wlth H2S04, held ther~ ~or 60 minutes,
and then reduced to 7Ø Then, while the mixture i~
still at 90C~, a solutlon o~ 3.75 lb, of A12(S04~3.18H20
* denotes trade mark
- 12-
,:: ,,' ,.
o
in 15 lb. of water is added over a ten-minute period and
the pH falls to 2.0-3Ø The pH is then raised to 6.o
with 2.ON NaOH in about 20 minutes. The product is
filtered hot, washed twice with 30 gal. of water and
dried at 140C. Chemical analysis and electron micrographs
show that the pigment particles have been coated with
silica. Intensity and lightfastness measurements on the
pigment before and after coating are shown in Table I.
TABLE I
1 0 - _Befor~ Coatin~ 1~ After Coatin~ lJ
Intensity ~ightfastness Intensity Lightfastnes~
X Green Filter ~ Fade-Omete~D . % Green Filter % Fade-Omete~
Re~lec~ance Darkening Reflectance Darkenin~ :
67.9 6.0 67.4 2.4
)Pcrcent reflectance change after
~4 hours of Fade-Ometer~ exposure ~
This example shows that encapsulating bismuth '
vanadate pigment with silica improves its lightfastness
as determined by Fade-Ometer~ exposures.
EXAMPLE 2
A mixture is prepared by combining the
following ingredients in a 1 mm ID mixing tee at 40 psi
over a period of about two minutes:
(1) Bi(N03~3.5H20 (166.0 g.) dissolved in
800 ml. of 2.ON HN03 and diluted to
1610 ml. with water, and
(li) Na3V04 (60.66 g.) dissolved in 1610 ml.
of l.ON NaOH.
Sufficient HN03 is added to ingredient (i) or aqueous
NaOH to ingredient (ii) so that the pH of the mixture o~
the two will be about 1.5-2Ø The mixture is squirted
3n into a large beaker containing 1200 ml. o~ water adJusted
- 13 -
to a pH of 2.7 with HN03. The contents of the beaker are
stirred and the pH is adjusted to 3.4 with 0.5N NaOH. The
contents are then stirred for 10 minutes, filtered, washed
with 1000 ml. of water, and refiltered. A bismuth
vanadate gel is collected from the filter paper, is stirred
into a beaker containing 3000 ml. of water, is brought to
a boil, is adJusted to a pH of 3.0-3.5 using HN03 or
NaOH and is held at that temperature and pH for 120
minutes. The product, bismuth vanadate pigment, is
isolated by ~iltration, washed by suspendin~ in 1000 ml.
.
of water, refiltering, and ~inally suspended in 2400 ml.
of water.
The suspension is then heated to 85C. and ~ `~
aluminum sulfate (18.0 g. A12(SO4)3.18H2O in 240 ml. water) ~ ~ -
is added. The pH of the suspension is adjusted to 4.0
~ith 1.0N NaOH, and sodillm pyroph~sphate (6.0 g. in 120 ml.
;
of water) and aluminum sulfate (6.o g. A12(SO4)3.18H20 in ~ -
120 ml. of water) are added to the suspension. The pH ;~
is adjusted to 7.0 with aqueous NaOH over a thirty-minute
period. The suspension is filtered, washed and dried at
110C. to yield an aluminum phosphate coated yellow
pigment. Intensit~ and li~htfastness before and after
. : .
coating are shown in Table II. ~`
~ABLE II
_ , Befcre Coatin~ Ir After Coatin~
Intensity LightfastnessIntensity Lightfastness )
Z Green Filter Y. Fade-Ometer~% Green Filter Y Fade-Omete~ -
Reflectance Darkenin~Reflectance Darkenin~
66.1 6.7 64.g 3.9 `~
l)Percent r,eflectance change after
: 44 hours of Fade-Ometer~ exposure
This example shows that treatment o~ bismuth
:;' '`
- 14 -
, . .:
.. .... . . ..
.
.. : . . . : ,
vanadate pigment with aluminum phosphate improves light-
~astness as determined by Fade-Ometer~ exposures.
EXAMPLE 3
A mixture is prepared by combining the following
ingredients in a 1 mm ID mixing tee at 40 psi over a
period of about two minutes: -
(i) Bi(NO3)3.5H2O (40.0 g.) dissolved in 200 ml.of 2.0N HNO3, then diluted to 405 ml. with
water,and
(ii) Na3VO4 (15.16 g.) dissolved in 200 ml. of
2.0N NaOH, then diluted to 400 ml. with
water.
Sufficient HNO3 is added to ingredient (i) or aqueous
NaOH to ingredient (ii) so that the pH of the mixture
of the two will be about 1.5 to 2Ø The mixture is
squirted into a 4 liter beaker containing 1200 ml. of
water which has been ad~usted to a pH of 3.0 with HN03.
The contents of the beaker are stirred for one minute and
the pH is adjusted to 3.4 with 0.5N NaOH. The mixture is
than stirred for 15 minutes, filtered, washed with 500 ml.
of water, and refiltered. A bismuth vanadate gel (Samp].e
A) is collected from the filter paper, and is stir~red into
a beaker containing 1600 ml. of water and the pH o~ the
mixture is ad~usted to 3.3 to 3.4 wlth HBr or NaOH. The
mixture is boiled for 90 minutes while the pH is held at ~
3.3 to 3.4. A bismuth vanadate plgment is isolated by ~;
filtration, washed with 1000 ml.of water, and heated to
130C. until dry.
Sample B is prepared according to the procedure
~0 used for Sam~le A except that 42.0 g., instead of 40.0 g., .~-
, ,
3(~
of Bi(N03)3.5H20 is used.
Sample C is prepared by combining the following
ingredients in a 1 mm ID mixing tee at 40 psi over a
period of about 2 minutes:
(iii) Bi(N~)3 5H2o (88.o g.) dissolved in 52 ml.
of concentrated HNO3 and 400 ml. of water,
then diluted to 800 ml. with water, and
(iv) V2O5 (15.0 g.) dissolved in 600 ml. of
water containing 53.0 g. of NaOH, then
diluted to 800 ml. with water to give a
solution of sodium vanadate plus sodium
hydroxide.
Sufficient HNO3 is added to ingredient (iii) of aqueous
NaOH to ingredient (iv) so that the pH of the mixture of
the two will be about 1.5 to 2Ø The mixture is
squirted into a 4-liter beaker containing 1200 ml. of
water which has been adjusted to a pH of 2.2 with HN03. ; ~ ;
The contents of the beaker are stirred for one minute
and the pH is ad~usted to 3.3 with 0.5N NaOH. The mixture
20 is then stirred for 15 minutes, filtered, washed with -~;-
500 ml. of water, and refiltered. A bismuth vanadate gel
is collected from the filter paper and is stirred into
a beaker containing 500 ml. of water. The pH of the
mixture is ad~usted to 3.3 to 3.4 with HNO3 or NaOH and
is boiled for 90 minutes while the pH is kept constant
at 3.3 to 3.4. A bismuth vanadate pigment is isolated by
filtration, washed with 500 ml. of water, and heated at
130C. until dry.
Sample D is prepared according to the procedure
30 used for Sample A, except that 46.o g., instead of 40.0 g.,
- 16 -
., . . . . ,................ ,.. ,, . .. . .............. :- .
, ,.
~U~630
of Bi(N03)3.5H20 is used.
Sample E is prepared by combining the following
ingredients in a 1 mm ID mixing tee at 40 psi over a
period of 2 minutes.
(v) Bi(N03)3.5H20 (72.0 g.) dissolved in
56 ml. concentrated HN03 and 400 ml.
water, then diluted to 800 ml. with
water, and
(vi) V205 (15.0 g.) dissolved in 600 ml.
water containing 53.30 g. NaOH, then
diluted to 800 ml. with water to give
a solution of sodium vanadate plus
sodium hydroxide.
Sufficient HN03 is added to ingredient (v) or aqueous
NaOH to ingredient (vi) so that the pH of the mixture
o~ the two will be about 1.5 to 2Ø The mixture is
squirted into a 4-liter beaker containing 1200 ml. of
water whlch has been ad;usted to a pH of 2.2 with HN03.
The contents of the beaker are stirred for one minute and
.
20 ~ the pH is ad~usted to 3.3 with 0.5N NaOH. The mixture is
then stirred for 15 minutes and ~iltered. A bismuth
vanadate gel is collected ~rom the filter paper. The gel
is stirred into a beaker containing 500 ml. of water and
the pH o~ the mixture is ad~usted to 3.1 with HN03 or
NaOH. The mixture 1s boiled for 120 minutes while its
pH is held at 3.1. The bismuth vanadate pigment is
.. . .
lsolated by ~iltration and resuspended ln 400 ml.
of water. The temperature is then raised to 50C. and
; the pH raised to 8 . o and held there for 10 minutes. A
.
3 bismuth vanadate pigment is isolated by filtration,
.
' '
,
.
.. .. .: : .
1~18~t~30
washed with 500 ml. of water9 and heated to 130C. until
dried.
TABLE III
3~ 3_ Intensity Lightfastness
Bi ~o VO4 Z Green Fi.].ter % Fade-Om~te~
Samples Molar R~tio Reflect~nceDarlccning
Aq~eous .
A 1.00/1.00 71.2 4.5
B 1.05/1.00 69.0 . 6.4
C 1.10/1.00. 73.9 8.0 : :
D 1.15/1.00 74.2 l4.5 .:
E 0.90/].. 00 61.7 4.7 -~:
1 0 , ~ ,,
reflectance chan~e after ;
44 hour3 of Fade-Ometer~ exposure
- EXAMPLE 4
A mixture is prepared by combining the ~ollowing-~
ingredients in a mixing tee: -
(i) Bi(N03)3.5H20 (10.731 lbs.) dissolved in
12.78 liters of 4.oN HN03, then diluted
to 51.1 liters with water, and
(ii) V205 (2.049 lb.) dissolved in 31.94 liters
of water containing 7.210 lb. NaOH, then
diluted to 51.1 liters with water, to give -
a solution of sodium vanadate plus
sodium hydroxide.
The mixing tee has inside diameters of 0.118 in. ~or the
bismuth nitrate opening, 0.192 in. ~or the sodium vanadate
opening, and 0.192 in. for the exit. The bismuth
nitrate enters on the leg. The solutions are mixed in
about 15 minutes when a pressure of about 15 psi is
applied across the tee. Su~ficient HN03 is added to
ingredient (i) or aqueous NaOH to ingredient (ii) so
that the pH of the mixkure of the two will be about
- 18 -
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~18~363V
1.5 to 2Ø The mixture is squirted into a 45 gal. tank
containing 7 gal. of water which has been ad;usted to
a pH of 2.2 with HNO3. The contents of the tank are
stirred for several minutes, and the pH is adjusted to
3.2 with 2.ON NaOH. The contents are then stirred for
15 minutes, filtered and washed with 20 gal. of water
and refiltered.
Seven 100 g. samples of the gel are respectively
suspended in seven 300 ml. portions of water. The
suspensions are heated to a boil and held at that
temperature for two hours. The pHs of the suspensions
are brought to the values shown in Table IV for samples
A to G by additions of HNO3 or aqueous NaOH, as necessary,
and held there during the two-hour boiling period. All
the samples are then filtered, resuspended in 200 ml.
of water, re~iltered and dried at 130C.
The crystal phase, intensity and lightfastness
for the samples are given in Table IV.
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EXAMPLE 5
A mixture is prepared by combining the following
ingredients in a mixing tee:
(i) Bi(NO3)3 5H2O (277.5 g) dissolved in
694.3 ml of 4.lN HNO3 and diluted to 2750 ml
with water.
(ii) V2O5 (51.6 g) dissolved in 1718 ml of water
containing 178 g of NaOH, then diluted to
2750 ml to give a solution of sodium vanadate
plus sodium hydroxide. ~ -
Sufficient HNO3 is added to ingredient (i) or
aqueous NaOH to ingredient (ii) so that the pH o~ the mix-
ture of the two will be about 1.5-2Ø The mixture is
squirted into a strike jar containing 1500 ml of water
which has been ad~usted to a pH of 2.2 with HNO3. The
mixture is stirred and the pH adjusted to 3.2 with O.5N
NaOH. The stirring is continued for 15 minutes. The pH is
adjusted to 3.1 with lN HNO3 and heated to 95C for 3 hrs.
with pH kept between 2.8 and 3.5 using 0.5N NaOH or l.ON
HNO3. The bismuth vanadate precipitate is filtered, washed
to 2000Q resistance and dried. The product has 66.2% green ~ ~
fllter reflectance and 4.5% Fade-Ometer darkening. ~-
EXAMPLE 6
, .
A mixture is prepared by combining the following ~ -
ingredients in a 1 mm ID mixing tee at a pressure of 40 p5i .
; over about a 2-minute period. - -
(i) Bi(NO3)3 5H2O (82.0g) dissolved in 400 ml of
2N HNO3 then diluted with 400 ml of dis-
tilled water.
3o (ii) Na3VO4 (30.3g) dissolved in 400 ml of 2N NaOH
- 21 -
..
. .. , ~ . , - . . . ... . ... .. ~ . , ,
1~8~3~3~) .
and diluted with 400 ml of distilled water.
These components give a molar ratio of Bi3 to
V043- of 1.025:1.00.
Sufficient HNO3 is added to ingredient (i) or
NaOH to ingredient (ii) so that the pH of the mixture of
the two will be between 1.5 and 2Ø The mixture is
squirted into a 4Q beaker containing 1200 ml of distilled
water which had been adjusted to a pH of 2.7 with HNO3.
The mixture is stirred and adjusted to pH = 3.4 with 0.5N
NaOH and stirred at room temperature for 10 minutes. The
suspension is filtered and washed. The bismuth vanadate
gel is converted to monoclinic bismuth vanadate by hydro-
thermal digestion at pH 3.0 to 3.5 at 100C. Twelve-month
Florida exposure ln thermosetting acrylic lacquer showed
good performance versus commerclal yellow pigment.
EXAMPLE 7
A mixture is prepared by combining the following
ingredients in a 1 mm ID mixing tee at a pressure of 40 psi
over about a 2-minute period.
(i) Bi(NO3~3-5H2O (80.5g) dissolved in 203 ml of ;
4.1N HNO3 and diluted to 800 ml with dis- :-
tilled water.
(ii) V2O5 (14.8g) dissolved in 345 ml of 2.3N -
(NaOH) and diluted to 800 ml with distilled
water.
Sufficient HNO3 is added to ingredient (1) or
NaOH to ingredient (ii) so that the pH of the final mixture
is 3.2. The mlxture is squirted into a 4Q beaker c~n-
taining 1200 ml of distilled water which had a pH = 5.8.
3 The suspension is stirred and pH monitored at 4.o-6.o during
,' ~, ,.
- 22 -
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v ::
most of the strike. Final pH is 3.2. The pH is adjusted
immediately to 3.0 with HN03 and stirred at room tempera-
ture for 30 minutes. The suspension is filtered and
washed. The gel is resuspended at pH = 3.1 and converted
to monoclinic bismuth vanadate at 100C.
Intensity of the product as measured by green
~ilter reflectance is 67.3% and % darkening after 44 hr.
Fade-Ometer exposure is 5.8%.
EXAMPLE 8
A mixture is prepared by combining the following
ingredients in a 1 mm ID mixing tee at 15 psi to give a
molar ratio of Bi3 to V043 of 0.95:1.00.
(i) ~i(NO3)3-5H2O (76.0 g) dissolved in 400 ml
of 2N HN03 and diluted to 800 ml.
(ii) V205 (15.0 g) dissolved in 600 ml of dis-
tilled water containing 52.0 g NaOH and
diluted to 800 ml to give a solution of
sodium vanadate and sodium hydroxide.
Suf~icient HNO3 is added to ingredient (i) or ~ ~;
NaOH to ingredient (ii) so that the pH o~ mixture will be
between 1,5 and 2.5. The mixture is squirted under 15 psi ~ -
pressure into a LIQ beaker containing 1200 ml of distilled
water adjusted to pH 2.2 with dilute HN03. The contents -
o~ the beaker are stirred, a~ter 2 minutes the pH is
ad~usted to 3.2 with 2N NaOH and stirred 15 minutes.
. : .
About 1/3 o~ the suspended gel is removed and is
designated Sample A (See Table V). The remainder ls ~ -~
filtered and divided into 2 parts identi~ied as Samples B
and D, respectively. Sample B is filtered only and
Sample D is washed once in 200 ml o~ distilled water.
i ': '
- 23 -
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,, ~ .. . . :
.. ,: .. . .:
- . . :
~9
Sample A's pH is ad~usted to 3.2 and it is heated
to 90-100C with pH maintained between 2.8 and 3.5 at a
volume of 700-800 ml for 2-3 hours. After conversion of
gel to crystalline material the pH is raised to 8.5 for
15 minutes with temperature ~60C. Bismuth vanadate is
then filtered, washed twice and dried at 110C.
Samples B and D are resuspended, respectively,
in 700-800 ml of distilled water and pH adjusted to 3.2.
Samples B and D are converted at the same temperature, time
and pH as Sample A. After conversion, Sample B is divided
in half. One half retains identification as Sample B, is
filtered, washed and dried at 110C. The other half is
identified as Sample C,has pH adjusted to 9.0 at tempera-
ture >60C for 15 minutes, is filtered, washed and dried
at 110C. -~
After conversion, Sample D is divided in half.
One half retains identification as Sample D, is filtered,
washed and dried. The other half is identif~ed as
Sample E and is treated in the same fashion as Sample C.
Sample F is prepared according to the procedure
of Sample A except that 78.5 g of Bi(N03)3-5H20 is used,
givlng a molar ratio of Bi3 to ~043 of 0.98: 1.00. The
gel suspension is filtered and divided in half. One half
retains identification Sample F and the other half is
identi~ied as Sample G and is washed once in 250 ml of dis-
tllled water. i
Sample F is converted according to the procedureof Sample A, is filtered, washed and dried at 110C.
Sample G is converted according to the procedure of
Sample A, is filtered, washed and dried at 110C.
- 2~ -
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This example shows that where the molar ratio
Or Bi3 to V043 is less than 1.00:1.00, NaN03 concentra-
tion must be reduced below 44% and excess vanadium must
be removed by washing the pigmentary bismuth vanadate with
a baslc solution.
EXAMPLE 9
A mixture is prepared by combining the following
ingredients in a 1 mm ID mixing tee at 15 psi to give a
molar ratio of Bi3 to V043 of 1.00:1.00.
(i) Bi(N03)3 5H20 (80.0g) dissolved in 400 ml
of 2N HN03 and diluted to 800 ml with
distilled water.
(ii) Na3V04 (30.3 g) dissolved in 400 ml of
2N NaOH and diluted to 800 ml with distilled
water.
Suf~icient HN03 is added to ingredient (i) or
NaOH to ingredient (ii) so that the pH of the mixture will
be between 1.5 and 2.5. The mixture is squirted under
40 psi pressure into a 4Q beaker containing 1000 ml o~
distilled water which had been adjusted to pH 3.3 with
2N HN03. The gel suspension is stirred for a minute and
the pH adJusted to 3.3 with 0.5N NaOH. The mixture is
stirred for 10 minutes at pH = 3.3. About 1300 ml of the
mixture is removed and identified as Sample H in Table V.
The remainder of the mixture, identified as Sample J~is
filtered and washed twlce with ~500 ml of distilled water.
Sample H is diluted to 2000 ml, pH is adjusted
to 3.3, heated at 100C for 4 hrs. to convert the gel to
crystalline material, ~iltered, washed and dried at 110C.
Sample J is converted according to procedure of
.:.
- 25 -
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: - - . ., . - , , , , :
, . , , . , :.. ,
Sample H except for 3 hrs. instead of 4. The crystalline
material is filtered, washed and dried at 110C.
Sample K is prepared by the procedure of
Sample H except 88.o g Bi(N03)3 5H20 is used and Na3V04
is prepared from V205 and NaOH. This gives a molar ratio
of Bi3 to V043 of 1.10:1.00. The gel suspension is
divided in half. One-half retains identification Sample K;
the other half is identified Sample L.
Sample K gel suspension pH is adjusted to 3.2, :
lOtemperature is raised to 98-100C for 2-1/2 hours, pH is ~-
maintained at 3.3. Product is filtered, washed and dried
at 140C.
Sample L is filtered and resuspended in distilled
water to give 700 ml volume. Sample L is converted,
filtered 3 washed and dried by the procedure of Sample K.
This example shows that where the molar ratio ~;
of Bi3 to V043 is equal to or greater than 1.00:1.00,
NaN03 need not be removed and a basic wash is not required. ~ ;
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