Title of Invention

ALUMINIUM OXIDE DISPERSION

Abstract Aluminium oxide dispersion, which is stable in a pH range from 5 to 9 and has an aluminium oxide content of at least 40 wt.%, obtainable by dispersing pyrogenically produced aluminium oxide particles in an aqueous phase, wherein one or several at least dibasic hydroxycarboxylic acids present dissolved in the dispersion and at least one salt of a dialkali metal hydrogen phosphate and/or alkali metal dihydrogen phosphate are added to the aqueous phase each mutually independently in a quantity of 0.3 - 3 x 10-6 mol/m2 of aluminium oxide specific surface area.
Full Text Aluminium Oxide Dispersion
The invention relates to a stable, aqueous aluminium oxide
dispersion of high fill factor, a process for production
thereof and use thereof.
From EP-A-1258458, an aqueous dispersion of pyrogenically
produced aluminium oxide with a BET surface area of 100 + /-
15 m2/g is known. The pH of the dispersion can be varied in
a range between 2 and 8 by addition of acids or bases, the
content of aluminium oxide can be about 30 +/- 20 wt.%.
From WO 03/035552, an aqueous dispersion of pyrogenically
produced aluminium oxide with a BET surface area of more
than 115 m2/g and a Sears number of more than 8 ml/2g is
known.
A disadvantage with the said dispersions is their low
stability against sedimentation and reagglomeration. These
dispersions attain their maximal stability at an aluminium
oxide content of less than 30 wt.%, wherein, however,
markedly acidic pH values of In certain use fields, for example in the production of
lacquers, this pH range is as a rule not desirable, since
recipes are often standardised in a pH range around the
neutral point. However in this pH range an Al2O3 dispersion
is no longer stable since the zeta potential is low
(isoelectric point at ca. pH 10).
Furthermore, other particles dispersed in aqueous paint/
lacquer recipes often have a negative surface charge. Such
negatively charged particles would immediately coagulate
with the still positively charged aluminium oxide particles
and make the dispersion unusable.
However, aluminium oxide has interesting properties for
applications in the paint/lacquer field, such as high
hardness and a high refractive index, compared to silicon
dioxide.

Particularly desirable in the field of scratch resistant
lacquers are high fill factors with good workability, i.e.
low viscosity, of the dispersion.
In the polishing field, in particular chemical-mechanical
polishing, aluminium oxide is used as an abrasive material.
Here it is of particular importance that these particles
leave no scratches on the surface to be polished. This can
for example be caused by a few coarse particles in a
dispersion.
There was thus the problem of providing a dispersion which
in a weakly acidic to weakly basic pH range has high
stability, a high solids content, good workability in the
form of low viscosity and is free from coarse particles.
Further, there was the problem of providing a process for
the production of this dispersion.
An object of the invention is an aluminium oxide dispersion
which is stable in a pH range from 5 to 9 and has an
aluminium oxide content of at least 40 wt.%, obtainable by
dispersing one or several aluminium oxide powders with a
specific surface area of 5 to 200 m2/g in an aqueous phase,
wherein one or several at least dibasic hydroxycarboxylic
acids present dissolved in the dispersion and at least one
salt of a dialkali metal hydrogen phosphate and/or alkali
metal dihydrogen phosphate each mutually independently are
added to the aqueous phase in a quantity of 0.3 - 3 x 10-6
mol/m2 specific aluminium oxide surface area.
Stable in the sense of the invention should be understood
to mean stability against sedimentation and reagglomeration
with a period of 1 month, as a rule of at least 6 months.
Preferably, the aluminium oxide dispersion according to the
invention can contain aluminium oxide powder of pyrogenic
origin. Here pyrogenic should be understood to mean that
this aluminium oxide powder is obtained by conversion of a
suitable starting material in a flame. Pyrogenic processes

include flame oxidation and flame hydrolysis. For the
large-scale industrial production of aluminium oxide, the
flame hydrolysis of aluminium chloride in a hydrogen/oxygen
flame is mainly used. As a rule, aluminium oxide particles
produced in this way are in the form of aggregated primary
particles, wherein the primary particles are free from
pores and bear hydroxyl groups on their surface. In the
conversion of aluminium chloride to aluminium oxide, hydro-
chloric acid is formed as a by-product, and adheres to the
aluminium oxide particles. Usually, a major part of the
hydrochloric acid is removed from the particles by a steam
treatment. An aluminium oxide powder in a 4 percent
dispersion in water then as a rule exhibits a pH value of
3 to 5. Suitable aluminium oxide powders can be AEROXIDE®
Alu C, AEROXIDE® Alu 65, AEROXIDE® Alu 130, all Degussa
AG, SpectrAl™ 100 Fumed Alumina, SpectrAl™ 51 Fumed
Alumina, SpectrAl™ 81 Fumed Alumina, all Cabot Corp..
Further, it can be advantageous if the aluminium oxide
particles in the dispersion according to the invention have
a mean aggregate diameter of less than 100 nm.
Further, it can be advantageous if the dispersion according
to the invention is free from particles with a diameter of
more than 1 µm.
Preferably, the aluminium oxide content can be 40 to
60 wt.%. With a high solids content, the dispersion
according to the invention in this range shows a low
viscosity with at the same time high stability.
Further, the pH of the dispersion according to the
invention can preferably be 6 to 8. In this range, the
dispersion displays a low viscosity with at the same time
high stability of the dispersion.
The zeta potential of the dispersion according to the
invention is preferably lower than -15 mV. Particularly
preferable is a zeta potential in the range from -25 to

-40 mV. The zeta potential is a measure of the surface
charge of the particles, which can be shifted by substances
which deposit on the surface. Zeta potential should be
understood to mean the potential at the shear plane within
the electrochemical double layer aluminium oxide particles/
electrolyte in the dispersion. An important quantity in
connection with the zeta potential is the isoelectric point
(IEP). The IEP states the pH value at which the zeta
potential is zero. With aluminium oxide, the IEP is at a pH
of ca. 9 to 10. The greater the difference between the pH
of the dispersion and the IEP, the more stable is the
dispersion. The zeta potential can for example be
determined by measurement of the colloid vibration current
(CVI) of the dispersion or by determination of the
electrophoretic mobility.
The at least dibasic hydroxycarboxylic acids added to the
aqueous phase, and present dissolved in rhe dispersion, can
preferably be citric acid or tartaric acid.
A further object of the invention is a process for the
production of the dispersion according to the invention
wherein
one or several at least dibasic hydroxycarboxylic
acids, present dissolved in the dispersion and at
least one salt of a dialkali metal hydrogen phosphate
and/or alkali metal dihydrogen phosphate and in a
quantity of 0.3 - 3 x 10-6 mol/m2 specific surface area
are first placed in water,
the aluminium oxide particles, corresponding to the
desired quantity in the dispersion are added all at
once in portions or continuously,
and dispersed by an energy input of more than
1000 KJ/m3.
Suitable dispersion units can be: planet kneaders, rotor-
stator machines, an agitating ball mill or a cylinder mill.

A process wherein the dispersion is first performed with an
energy input of less than 1000 kJ/m3 with the formation of
a predispersion, the predispersion is divided into at least
two part streams, these part streams are placed in a high
energy mill under a pressure of at least 500 bar, released
via a nozzle and allowed to impinge on one another in a
gas- or liquid-filled reaction chamber, and the high energy
grinding is optionally repeated once or several times, has
been found to be particularly suitable.
A further object of the invention is the use of the
dispersion for the coating of glass, ceramic and metal
surfaces and for the production of lacquers.

Examples
Analytical Procedures:
The viscosity is determined with an MCR300 instrument with
CC27 measuring system, Parr-Physica Co., with which the
measurements are made at shear rates of 0.01 to 1000 sec-1
and 23°C. The viscosity values at 10 sec-1 and 100 sec-1 are
stated.
The zeta potential and the isoelectric point is determined
with an instrument of the DT-1200 type from Dispersion
Technology Inc., by the CVI procedure. The titration is
performed with KOH/HNO3.
The mean particle size d50 of the aluminium oxide particles
in the dispersion is determined by laser diffraction. The
instrument Horiba LA-910 (Horiba, Ltd., Japan) is used.
The volume-weighted median value from the peak analysis is
stated.
The specific surface area is determined as per DIN 66131.
Examples
Example 1 (according to invention): 34.7 kg of deionised
water are placed in a 60 1 stainless steel batch vessel.
Next, 7.0 kg of AEROXIDE® Alu 65 (BET 65 m2/g), Degussa Co.
are sucked in by means of the suction pipe of the Ystral
Conti-TDS 3 (stator slits: 4 mm annulus and 1 mm annulus,
rotor/stator gap ca. 1 mm) under shear conditions. Further,
13.3 kg of a solution of 1.80 kg of anhydrous citric acid,
1.4 9 kg of disodium hydrogen phosphate dihydrate and 10 kg
of water are added and a further 65.0 kg of AEROXIDE® Alu
65 are sucked in. After completion of the suction, the
suction connector is closed and shearing at 3000 RPM is
continued for a further 10 mins. After the grinding, 108 g
of Acticide® MV, THOR Co., are added as a preservative.
This predispersion is passed in two passages through the
high energy mill Sugino Ultimaizer HJP-25050 at a pressure

of 2500 bar and diamond nozzles of 0.3 mm diameter and
thereby intensively further ground.
The pH value measured directly after the grinding is 6.0.
After ca. 48 hrs, a stable pH value of 7.7 is reached. The

solids content of the dispersion is 60 wt.%. Figure 1 of the accompanying drawing shows
the viscosity in mPas as a function of the shear rate in
sec-1. Figure 2 shows the occurrence of the aluminium oxide
particles as a function of their size in nm. The mean
particle size d50 is 84 nm. The zeta potential of the
dispersion is -28 mV at pH 7.7. The dispersion shows no
sign of gelling even after 6 months.
Example 2 (according to invention): 41.1 kg of deionised
water are placed in a 60 1 stainless steel batch container.
Next, 5,8 kg of AEROXIDE® Alu C (BET 100 m2/g), Degussa Co.
are sucked in by means of the suction pipe of the Ystral
Conti-TDS 3 (stator slits: 4 mm crown and 1 mm crown,
rotor/stator gap ca. 1 mm) under shear conditions. Further,
9.80 kg of a solution of 1.70 kg of anhydrous citric acid,
1.42 kg of disodium hydrogen phosphate dihydrate and
6.70 kg of water are added and a further 28.2 kg of
AEROXIDE® Alu C are sucked in. After completion of the
suction, the suction connector is closed and shearing at
3000 RPM is continued for a further 10 mins. After the
grinding, 77 g of Acticide® MV (THOR Co.) are added as
preservative. This predispersion is passed in two passages
through the high energy mill Sugino Ultimaizer HJP-25050 at
a pressure of 2500 bar and diamond nozzles of 0.3 mm and
thus intensively further ground.
The pH value measured directly after the grinding is 5.8.
After ca. 48 hrs, a stable pH value of 7.5 is reached. The
solids content of the dispersion is 40 wt.%. Figure 3 shows
the zeta potential in mV as a function of the pH value in
the range 3.5 to 7.5. Figure 4 shows the zeta potential in
mV as a function of the pH value in the range 7 to 10.5.
The mean particle diameter in the dispersion is 86 nm. The
viscosity is about 26 mPas at a shear rate of 10 sec-1 and

about 24 mPas at 100 sec-1. The dispersion shows no sign of
gelling even after 6 months.
Example 3 (Comparison Example): 61.0 kg of deionised water
are placed in a 60 1 stainless steel batch vessel. Next,
26.6 kg of AEROXIDE® Alu C are sucked in by means of the
suction pipe of the Ystral Conti-TDS 3 (stator slits: 4 mm
crown and 1 mm crown, rotor/stator gap ca. 1 mm) under
shear conditions. Further, 0.8 9 kg of a 50 percent aqueous
acetic acid solution are added. After completion of the
aspiration, the suction connector is closed and shearing is
continued at 3000 RPM for a further 10 mins. After the
grinding, 79 g of Acticide® MV (THOR Co.) are added as a
preservative. This predispersion is passed in two passages
through the high energy mill Sugino Ultimaizer HJP-25050 at
a pressure of 2500 bar and diamond nozzles of 0.3 mm
diameter and thus intensively further ground.
The pH value measured directly after the grinding is 4.1
and is adjusted to 4.0 with 133 g of 50 percent aqueous
acetic acid solution. The solids content of the dispersion
is 30 wt.%. The zeta potential shows positive values in the
claimed pH range. The mean particle size d50 is 8 6 nm. The
viscosity is about 7 mPas at a shear rate of 10 sec-1 and
about 7 mPas at 100 sec-1. The dispersion shows no sign of
gelling even after 6 months.
Example 4 (Comparison Example): 52.0 kg of deionised water
and 1.19 kg of citric acid monohydrate are placed in a 60 1
stainless steel batch vessel and adjusted to a pH of 5.6
with 25 percent caustic soda solution (2.04 kg). Next,
25.5 kg of AEROXIDE® Alu C, Degussa Co. are sucked in by
means of the suction pipe of the Ystral Conti-TDS 3 (stator
slits: 4 mm crown and 1 mm crown, rotor/stator gap
ca. 1 mm) under shear conditions. After completion of the
suction, the suction connector is closed and shearing
continued at 3000 RPM for a further 10 mins. After the
grinding, 85 g of Acticide® MV (THOR Co.) are added as

preservative. This predispersion is passed in two passages
through the high energy mill Sugino Ultimaizer HJP-25050 at
a pressure of 2500 bar and diamond nozzles of 0.3 mm
diameter and thus intensively further ground.
The pH value is adjusted to 7.5 with 110 g of 25 percent
caustic soda solution. Even after 48 hrs, the pH was
unchanged. The Al2O3 content of the dispersion is
31.5 wt.%. The mean particle size d50 is 89 nm. The
viscosity is about 1245 mPas at a shear rate of 10 sec-1
and about 243 mPas at 100 sec-1. The dispersion gels after
a few days.

WE CLAIM:
1. Aluminium oxide dispersion, which is stable in a pH range from 5 to 9
and has an aluminium oxide content of 40 to 60 wt.%, obtainable by
dispersing one or several aluminium oxide powders with a specific
surface area of 5 to 200 m2/g in an aqueous phase, wherein one or
several at least dibasic hydroxycarboxylic acids present dissolved in the
dispersion and at least one salt of a dialkali metal hydrogen phosphate
and/or alkali metal dihydrogen phosphate are added to the aqueous
phase each mutually independently in a quantity of 0.3 - 3 x 106
mol/m2 of aluminium oxide specific surface area.
2. Aluminium oxide dispersion as claimed in claim 1, wherein the
aluminium oxide powder is of pyrogenic origin.
3. Aluminium oxide dispersion as claimed in any one of claims 1 or 2,
wherein the aluminium oxide powder in a 4 percent dispersion exhibits
a pH value of 3 to 5.
4. Aluminium oxide dispersion as claimed in any one of claims 1 to 3,
wherein the aluminium oxide particles have a mean aggregate diameter
d50 of less than 100 nm.
5. Aluminium oxide dispersion as claimed in any one of claims 1 to 4,
wherein it is free from particles with a diameter of more than 1 µm.
6. Aluminium oxide dispersion as claimed in any one of claims 1 to 5,
wherein the aluminium oxide content is 40 to 60 wt.%.
7. Aluminium oxide dispersion as claimed in any one of claims 1 to 6,
wherein the pH value is 6 to 8.

8. Aluminium oxide dispersion according to Claims 1 to 7,
characterized in that the zeta potential is less than
-15 mV.
9. Aluminium oxide dispersion according to Claims 1 to 8,
characterized in that the at least dibasic hydroxy-
carboxylic acid present dissolved in the dispersion is
citric acid or tartaric acid.
10.Process for the production of the aluminium oxide
dispersion according to Claims 1 to 9, characterized
in that
one or several at least dibasic hydroxycarboxylic
acids present dissolved in the dispersion and at
least one salt of a dialkali metal hydrogen
phosphate and/or alkali metal dihydrogen phosphate
and in a quantity of 0.3 - 3 x 10-6 mol/m2 specific
surface area are first placed in water,
the aluminium oxide particles, corresponding to the
desired quantity, in the dispersion are added all
at once in portions or continuously,
- and dispersed by an energy input of more than
1000 KJ/m3.
11.Process according to Claim 10, characterized in that
the dispersion is firstly performed with an energy
input of less than 1000 kJ/m3 with the formation of a
predispersion, the predispersion is divided into at
least two part streams, these part streams are placed
in a high energy mill under a pressure of at least
500 bar, released via a nozzle and allowed to impinge
on one another in a gas- or liquid-filled reaction
chamber and the high energy grinding is optionally
repeated one or several times.

12.Use of the aluminium oxide dispersion according to
Claims 1 to 9 for the coating of glass, ceramic and
metal surfaces and for the production of lacquers.

Aluminium oxide dispersion, which is stable in a pH range
from 5 to 9 and has an aluminium oxide content of at least
40 wt.%, obtainable by dispersing pyrogenically produced
aluminium oxide particles in an aqueous phase, wherein one
or several at least dibasic hydroxycarboxylic acids present
dissolved in the dispersion and at least one salt of a
dialkali metal hydrogen phosphate and/or alkali metal
dihydrogen phosphate are added to the aqueous phase each
mutually independently in a quantity of 0.3 - 3 x 10-6
mol/m2 of aluminium oxide specific surface area.

Documents:

00111-kolnp-2008-abstract.pdf

00111-kolnp-2008-claims.pdf

00111-kolnp-2008-correspondence others.pdf

00111-kolnp-2008-description complete.pdf

00111-kolnp-2008-drawings.pdf

00111-kolnp-2008-form 1.pdf

00111-kolnp-2008-form 2.pdf

00111-kolnp-2008-form 3.pdf

00111-kolnp-2008-form 5.pdf

00111-kolnp-2008-international publication.pdf

00111-kolnp-2008-international search report.pdf

00111-kolnp-2008-pct priority document notification.pdf

00111-kolnp-2008-pct request form.pdf

111 -KOLNP-2008-CORRESPONDENCE OTHERS-1.3.pdf

111 -KOLNP-2008-OTHER.pdf

111-KOLNP-2008-ABSTRACT 1.1.pdf

111-kolnp-2008-abstract 1.2.pdf

111-kolnp-2008-amanded claims 1.2.pdf

111-KOLNP-2008-AMANDED CLAIMS.pdf

111-kolnp-2008-correspondence 1.2.pdf

111-KOLNP-2008-CORRESPONDENCE OTHERS 1.1.pdf

111-KOLNP-2008-CORRESPONDENCE OTHERS 1.2.pdf

111-KOLNP-2008-CORRESPONDENCE.pdf

111-KOLNP-2008-DESCRIPTION (COMPLETE) 1.1.pdf

111-kolnp-2008-description (complete) 1.2.pdf

111-KOLNP-2008-DRAWINGS 1.1.pdf

111-KOLNP-2008-EXAMINATION REPORT REPLY RECIEVED.pdf

111-KOLNP-2008-EXAMINATION REPORT.pdf

111-KOLNP-2008-FORM 1-1.1.pdf

111-kolnp-2008-form 1-1.2.pdf

111-kolnp-2008-form 13 1.1.pdf

111-KOLNP-2008-FORM 13.pdf

111-KOLNP-2008-FORM 18.1.pdf

111-kolnp-2008-form 18.pdf

111-KOLNP-2008-FORM 2-1.1.pdf

111-kolnp-2008-form 2-1.2.pdf

111-KOLNP-2008-FORM 3-1.1.pdf

111-kolnp-2008-form 3-1.2.pdf

111-KOLNP-2008-FORM 3.pdf

111-kolnp-2008-form 5-1.2.pdf

111-KOLNP-2008-FORM 5.pdf

111-KOLNP-2008-FORM-27.pdf

111-KOLNP-2008-GPA.pdf

111-KOLNP-2008-GRANTED-ABSTRACT.pdf

111-KOLNP-2008-GRANTED-CLAIMS.pdf

111-KOLNP-2008-GRANTED-DESCRIPTION (COMPLETE).pdf

111-KOLNP-2008-GRANTED-DRAWINGS.pdf

111-KOLNP-2008-GRANTED-FORM 1.pdf

111-KOLNP-2008-GRANTED-FORM 2.pdf

111-KOLNP-2008-GRANTED-SPECIFICATION.pdf

111-kolnp-2008-pa 1.2.pdf

111-KOLNP-2008-PA.pdf

111-KOLNP-2008-PRIORITY DOCUMENT.pdf

111-KOLNP-2008-REPLY TO EXAMINATION REPORT.pdf

111-KOLNP-2008-TRANSLATED COPY OF PRIORITY DOCUMENT.pdf


Patent Number 249846
Indian Patent Application Number 111/KOLNP/2008
PG Journal Number 46/2011
Publication Date 18-Nov-2011
Grant Date 16-Nov-2011
Date of Filing 08-Jan-2008
Name of Patentee EVONIK DEGUSSA GMBH
Applicant Address RELLINGHAUSER STRASSE 1-11 45128 ESSEN, GERMANY
Inventors:
# Inventor's Name Inventor's Address
1 HEINZ LACH IM LOCHSEIF 63 63517 RODENBACH
2 DR. WOLFGANG LORTZ FELDSTR. 9 63607 WÄCHTERSBACH
3 GABRIELE PERLET OBERHAAGSTR. 7A 63538 GROßKROTZENBURG
4 WERNER WILL SCHULSTR. 46 63571 GELNHAUSEN
5 DR. CHRISTOPH BATZ-SOHN RIEDSTR. 10A 63454 HANAU-MITTELBUCHEN
PCT International Classification Number C01F 7/02
PCT International Application Number PCT/EP2006/063047
PCT International Filing date 2006-06-09
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 10 2005 032 427.4 2005-07-12 Germany