U.S. patent application number 10/305400 was filed with the patent office on 2003-07-03 for micronized barium sulfate.
This patent application is currently assigned to Solvay Barium Strontium GmbH. Invention is credited to Engels, Tanja, Gabel, Hans, Glas, Joerg, Hardinghaus, Ferdinand, Koehler, Karl, Park, Jai-Won.
Application Number | 20030124048 10/305400 |
Document ID | / |
Family ID | 7644100 |
Filed Date | 2003-07-03 |
United States Patent
Application |
20030124048 |
Kind Code |
A1 |
Hardinghaus, Ferdinand ; et
al. |
July 3, 2003 |
Micronized barium sulfate
Abstract
Micronized barium sulfate (BaSO.sub.4) and methods for the
production and use thereof. The micronized barium sulfate of the
invention is particularly suitable for use as an additive or filler
for adhesives, colorants, rubber articles and/or cosmetics.
Inventors: |
Hardinghaus, Ferdinand; (Bad
Hoenningen, DE) ; Engels, Tanja; (Sankt Katharinen,
DE) ; Park, Jai-Won; (Goettingen, DE) ;
Koehler, Karl; (Diekholzen, DE) ; Gabel, Hans;
(Kasbach-Ohlenberg, DE) ; Glas, Joerg;
(Rheinbrohl, DE) |
Correspondence
Address: |
CROWELL & MORING LLP
INTELLECTUAL PROPERTY GROUP
P.O. BOX 14300
WASHINGTON
DC
20044-4300
US
|
Assignee: |
Solvay Barium Strontium
GmbH
Hannover
DE
|
Family ID: |
7644100 |
Appl. No.: |
10/305400 |
Filed: |
November 27, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10305400 |
Nov 27, 2002 |
|
|
|
PCT/EP01/06031 |
May 26, 2001 |
|
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Current U.S.
Class: |
423/554 |
Current CPC
Class: |
C01P 2004/62 20130101;
C01P 2004/64 20130101; A61K 8/23 20130101; C01F 11/462 20130101;
C08L 21/00 20130101; A61Q 17/04 20130101; C08K 3/30 20130101; A61Q
19/00 20130101; C01P 2006/12 20130101; C09C 1/027 20130101; B82Y
30/00 20130101; C08K 3/30 20130101; A61K 2800/412 20130101 |
Class at
Publication: |
423/554 |
International
Class: |
C01F 011/46 |
Foreign Application Data
Date |
Code |
Application Number |
May 31, 2000 |
DE |
100 26 791.2 |
Claims
What is claimed is:
1. A method for producing particulate barium sulfate in which at
least 90% of the particles have a primary grain diameter of less
than 0.1 .mu.m, said method comprising: combining a barium salt
solution with an alkali sulfate salt solution to form a reaction
mixture in a continuously operating mixing reactor, in which shear,
displacement and frictional forces of intermeshing tools act at
high relative speed on the reaction mixture formed, whereby
resulting barium sulfate is precipitated, and after passage of the
reaction mixture through the reactor, separating and drying the
resulting barium sulfate; wherein the concentration of barium salt
and sulfate in the salt solutions is at least 80% of the maximum
possible concentration.
2. A method according to claim 1, wherein the concentration of
barium salt and sulfate in the salt solutions is at least 90% of
the maximum possible concentration.
3. A method according to claim 1, further comprising washing the
separated barium sulfate at least once with water before
drying.
4. A method according to claim 1, wherein the barium sulfate is
precipitated at a temperature between 0.degree. C. and 100.degree.
C.
5. A method according to claim 4, wherein the barium sulfate is
precipitated at a temperature between 20.degree. C. and 50.degree.
C.
6. A method according to claim 1, wherein at least some of said
intermeshing tools are mounted on at least one rotor which rotates
at a rotational speed of from 2000 rpm to 8000 rpm.
7. A method according to claim 1, wherein the reaction mixture has
a residence time in the mixing reactor in the millisecond
range.
8. A method according to claim 1, wherein said barium salt solution
and said alkali sulfate solution are aqueous solutions.
9. A method according to claim 1, wherein the barium salt solution
is a solution of barium chloride.
10. A method according to claim 9, wherein the barium chloride
solution has a BaCl2 concentration of at least 0.9 mole/liter.
11. A method according to claim 1, wherein the alkali sulfate
solution is a solution of sodium sulfate.
12. A method according to claim 11, wherein the sodium sulfate
solution has a Na.sub.2SO.sub.4 concentration of at least 0.9
mole/liter.
13. A method according to claim 1, wherein a wetting agent or a
dispersing agent is added during or after precipitation of the
resulting barium sulfate.
14. A particulate, coated BaSO.sub.4, wherein at least 95% of the
particles have a primary grain diameter .ltoreq.0.1 .mu.m, produced
according to the method of claim 13.
15. A particulate, coated BaSO4 according to claim 14, wherein at
least 99% of the particles have a primary grain diameter
.ltoreq.0.1 .mu.m.
16. A particulate, coated BaSO4 according to claim 15, wherein 100%
of the particles have a primary grain diameter .ltoreq.0.1 .mu.m.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of international patent
application no. PCT/EP01/06031, filed May 26, 2001 designating the
United States of America and published in German as WO 01/92157,
the entire disclosure of which is incorporated herein by reference.
Priority is claimed based on Federal Republic of Germany patent
application no. DE 100 26 791.2, filed May 31, 2000.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a particulate barium
sulfate, its production, and its use.
[0003] Barium sulfate may be used as a pigment in paper production,
for example. Other intended applications, such as an additive for
cosmetics like skin creams and sunscreens, or as a filler in
pigments, adhesives, or rubber articles, however, require extremely
fine particles of BaSO.sub.4.
SUMMARY OF THE INVENTION
[0004] An object of the present invention is to provide a new
effective method for producing a finely dispersed, particulate
micronized barium sulfate.
[0005] Another object of the invention is to provide an improved
micronized barium carbonate which may be used as an additive for
cosmetics or as filler for pigments, adhesives, or rubber
articles.
[0006] These and other objects are achieved in accordance with the
present invention by providing a method for producing particulate
barium sulfate in which at least 90% of the particles have a
primary grain diameter of less than 0.1 .mu.m, said method
comprising combining a barium salt solution with an alkali sulfate
salt solution to form a reaction mixture in a continuously
operating mixing reactor, in which shear, displacement and
frictional forces of intermeshing tools act at high relative speed
on the reaction mixture formed, whereby resulting barium sulfate is
precipitated, and after passage of the reaction mixture through the
reactor, separating and drying the resulting barium sulfate;
wherein the concentration of barium salt and sulfate in the salt
solutions is at least 80% of the maximum possible
concentration.
[0007] In accordance with a further aspect of the invention, the
objects are achieved by providing a particulate, coated BaSO.sub.4,
wherein at least 95% of the particles, preferably 99% of the
particles, and particularly preferably 100% of the particles, have
a primary grain diameter .ltoreq.0.1 .mu.m, produced according to
the method of the invention.
[0008] The method according to the present invention for producing
particulate barium sulfate provides that a barium salt solution is
combined with a sulfate salt solution in a continuously operating
mixing reactor, in which shear, transverse, and frictional forces
of intermeshing tools act in accordance with the rotor-stator
principle, with high relative speed on the reaction mixture formed,
and after the reaction mixture has passed through the reactor, the
resulting barium sulfate is separated out and dried, subject to the
condition that the concentration of barium salt and/or sulfate
corresponds to at least 80%, preferably at least 90%, of the
maximum possible concentration. The shear, transverse, and
frictional forces in the reactor have the effect that the barium
sulfate is produced in extremely finely dispersed form.
[0009] In principle, any arbitrary aqueous barium salt solution
having a correspondingly high concentration may be used. In the
context of the present invention, barium hydroxide is also
understood as a salt that may be used. A barium chloride
(BaCl.sub.2) solution is the most technically expedient. The
concentration of barium salt in the solution advantageously
corresponds to at least 95% of the maximum possible concentration.
For BaCl.sub.2, this is approximately at least 0.9 mole/liter at
60.degree. C.
[0010] As used herein the term "sulfate solutions" includes
solutions of any arbitrary aqueous sulfate salt. In the context of
the present invention, sulfuric acid is also considered a "sulfate
solution." The concentration is preferably at least 95% of the
maximum possible concentration, up to the saturation limit. Aqueous
alkali sulfate solution is preferably used. Alkali preferably
stands for sodium. The concentration of Na.sub.2SO.sub.4 (at
40.degree. C.) is preferably at or above 0.5 mole/liter, up to
saturation concentration.
[0011] When the method according to the present invention is
carried out, micronized barium sulfate is obtained in which at
least 90% of the particles have a primary grain diameter smaller
than 0.1 .mu.m, preferably at least 95%, particularly preferably
99%, very particularly preferably 100%.
[0012] Devices in which the rotor rotates at a high speed are
highly suitable for use in the method of the invention. The rotor
speed is preferably 2000 to 8000 rotations/sec. The residence time
of the reaction mixture in the mixing and homogenization device is
preferably in the millisecond range.
[0013] The grain size was assessed via microscopic imagery.
[0014] Before drying, which may advantageously be carried out at a
temperature in the 100 to 120.degree. C. range, the BaSO.sub.4
separated out after passing through the reactor may be washed one
or more times with water. If barium hydroxide/sulfuric acids are
used, this has the advantage that no foreign salts (e.g., NaCl)
arise.
[0015] The precipitation of barium sulfate advantageously may be
carried out at a temperature in the 0 to 100.degree. C. range,
preferably between 20.degree. C. to 50.degree. C.
[0016] Depending on the intended application, a slight excess of
sulfate (up to 5%) may be advantageous.
[0017] According to one embodiment of the method of the invention,
agents that influence the crystallization or the surface properties
are not added.
[0018] A further object of the present invention is the particulate
barium sulfate that is obtainable through the method put forth in
the present invention, in which at least 90% of the primary grain
particles have a diameter in the range of less than 0.1 .mu.m, and
which is free of precipitating agents.
[0019] The BaSO.sub.4 obtainable according to the present invention
in this way may be used for all purposes for which BaSO.sub.4 is
typically used. It is particularly useful as a filler for cosmetics
(it also has reflective, scattering, and light refracting effects).
For this purpose, it is used in appropriate formulations, for
example as a cream. The formulations obtained in this way, which
may be used as sunscreen, for example, are superior to formulations
having TiO.sub.2 as a pigment (UV-light protective agent), since no
visible residues remain after absorption into the skin. If desired,
a sunscreen may be introduced; in this way, the sun protection
factor may be individually adjusted in accordance with its
quantity, and the cream and/or formulation is usable as a
sunscreen.
[0020] The BaSO4 obtainable according to the present invention is
also distinguished by a significant improvement of the skin
feel.
[0021] According to another embodiment, a wetting or dispersing
agent is added to the barium sulfate. This may be performed during
the precipitation, after the precipitation, or both during and
after the precipitation. The wetting and/or dispersing agent leads
to the formation of small crystals, which agglomerate as little as
possible. The wetting and/or dispersing agent also influences the
surface properties of the barium sulfate, i.e., the product
obtained is a coated product.
[0022] Dispersing agents or wetting agents for aqueous and
non-aqueous systems are usable. The dispersing agent is selected so
that it is compatible in regard to the intended use. Hydrophilic
dispersing agents are advantageously used when this property is
desirable, if the base materials of the adhesive, the pigment, or
the cosmetic are also hydrophilic. Otherwise, appropriate
hydrophobic dispersing agents are selected. Therefore, a tailored
adjustment to the desired technical application properties is
possible through the coated particles according to the present
invention, having adjustable surface properties.
[0023] Highly useful dispersing agents in the context of the
present invention include (short chain) polyacrylates, typically in
the form of the sodium salt; polyethers such as polyglycol ether;
ether sulfonates such as lauryl ether sulfonate in the form of the
sodium salt; esters of phthalic acid and its derivatives; esters of
polyglycerol; amines such as triethanolamine; and esters of fatty
acids such as stearic acid ester.
[0024] The quantity of dispersing agent is flexible. A very fine
product having a very high surface area is achieved at a content of
up to 3 weight-percent of the dispersing agent, in relation to the
total weight of dry product. Barium sulfate having a content of 3
weight-percent sodium polyacrylate has, for example, a surface area
of 48 m.sup.2/g; the average particle diameter, determined via wide
angle x-ray diffraction in accordance with modified Warren-Averbach
analysis, was 30 nm in the primary grain. Without adding dispersing
agents, surface areas of 20 m.sup.2/g were achieved. The dispersing
or wetting agent content in the finished product is advantageously
1 to 3 weight-percent on a dry mass basis.
[0025] As noted above, a barium sulfate obtained using a wetting or
dispersing agent is also an object of the present invention.
[0026] If the dispersing agent or wetting agent is added after the
precipitation, it is advantageous to knead it into the freshly
precipitated barium sulfate "dough," for example through
corresponding kneading apparatus or extruders having mixing
sections or something similar. This is also true if dispersing
agent is to be worked in during and after the precipitation.
[0027] The resulting coated barium sulfate, which is redispersable
into particles having a particle size below 100 nm, preferably
below 50 nm, is particularly suitable for use as a filler for
adhesives (such as reactive, melt, and dispersion adhesives), for
rubber articles, for pigments (such as coating varnish, base
varnish, or primer) and for cosmetics (such as for the purpose of
UV absorption, or for skin care or lip care products).
[0028] The coated barium sulfate is inert, transparent, and
provides rheological properties advantageous to the application
matrix. It is redispersable in solvents and/or the base materials
for adhesives, pigments, cosmetics, or rubber articles. Through
selection of the suitable dispersing agent, it is also compatible
with the material used. The tailored coating adjustment is
therefore easily possible.
[0029] The following examples are intended to illustrate the
present invention in further detail, without limiting its
scope.
EXAMPLE 1
[0030] Preparation of sub-micron BaSO.sub.4 without a dispersing
agent.
[0031] A mixing reactor having a rotor with a speed of 6,650 rpm
was used; the rotor exerted corresponding shear, displacement and
frictional forces on the mixture of the reactants.
[0032] Sodium sulfate solution (40.degree. C., 0.96 mole/liter, 400
liters/hour) and barium chloride solution (15.degree. C., 0.96
mole/liter, approximately 400 liters/hour) were each introduced
into the mixing reactor using a metering pump. The suspension
exiting from the mixing reactor was filtered, washed using
demineralized water, dried at 110.degree. C. in a drying cabinet,
and deagglomerated. Virtually 100% of the particles had a primary
grain diameter <0.1 .mu.m.
EXAMPLE 2
[0033] Preparation of a vanishing cream having 5 weight-percent
BaSO.sub.4 added.
[0034] 2.1 Preparation of a base material for an oil/water type
vanishing cream.
1 a) Lanette N.sup.R 3.0% Stearin 9.0% Vitamin F ethyl ester 3.0%
Carrot oil 3.0% Arnica oil 3.0% Preservative (Phenonip .TM.) 0.5%
b) H.sub.2O, distilled 74.5% Miglyol .TM. 4.0% Triethanolamine
0.5%
[0035] Melt a) and heat to approximately 80.degree. C. Heat b) to
approximately 80.degree. C. and add to part a) while stirring. Stir
further using dissolver (rapid stirrer), until the emulsion is
cooled to approximately 40.degree. C. (approximately 1 hour, 15
minutes). The resulting vanishing cream is creamy and absorbs into
the skin without residues.
[0036] 2.2 Adding the BaSO.sub.4
[0037] After the heated components listed under 2.1 b) were added
to the components listed under 2.1 a), blanc fixe (BaSO.sub.4)
produced according to example 1 was added while stirring. The
quantity added was 5 weight-percent BaSO.sub.4, in relation to the
base material from example 1, set as 100 weight-percent.
[0038] This cream, which contained BaSO.sub.4, was also creamy and
absorbed into the skin without residues. There was also no
formation of agglomerates to be detected.
[0039] By adding a precisely calculated quantity of a sunscreen,
the sun protection factor may be individually adjusted. The cream
is then also usable as a sunscreen.
EXAMPLE 3
[0040] Preparation of coated BaSO.sub.4.
[0041] Example 1 was repeated. The Na.sub.2SO.sub.4 solution,
however, had sodium polyacrylate (product Dispex N40, Ciba) added
to it. The quantity was selected in such a way that 3
weight-percent of the dispersing agent was contained in the
finished dried product.
[0042] The resulting coated barium sulfate had a specific surface
area of 48 m.sup.2/g (BET method) and an average particle diameter
of 30 nm (wide angle x-ray diffractometry, modified Warren-Averbach
method) in the primary grain (measurement without
redispersion).
[0043] This product is particularly suitable for use as an additive
for pigments, rubber articles, and adhesives, because the
dispersing agent acts as a binding mediator.
[0044] The foregoing description and examples have been set forth
merely to illustrate the invention and are not intended to be
limiting. Since modifications of the described embodiments
incorporating the spirit and substance of the invention may occur
to persons skilled in the art, the invention should be construed
broadly to include all variations falling within the scope of the
appended claims and equivalents thereof.
* * * * *