US2008202385A1PendingUtilityA1
Process for making durable titanium dioxide pigment in the chloride process without wet treatment
Assignee: SUBRAMANIAN NARAYANAN SANKARAPriority: Apr 27, 2000Filed: Apr 24, 2008Published: Aug 28, 2008
Est. expiryApr 27, 2020(expired)· nominal 20-yr term from priority
C01G 23/07C01P 2006/60B82Y 30/00C01P 2004/64C01P 2004/04C09C 1/3661C09C 1/3653
55
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Claims
Abstract
The present invention relates to a process for making durable titanium dioxide pigment by vapor phase deposition of surface treatments on the titanium dioxide particle surface by reacting titanium tetrachloride vapor, an oxygen containing gas and aluminum chloride in a plug flow reactor to form a product stream containing titanium dioxide particles; and introducing silicon tetrachloride into the reactor at a point down stream of the point where the titanium tetrachloride and oxygen were contacted and where at least 97% of the titanium tetrachloride has been converted to titanium dioxide or where the reaction temperature is no greater than about 1200° C., and preferably not more than about 1100° C.
Claims
exact text as granted — not AI-modified1 . A process for making durable titanium dioxide pigment by vapor phase deposition of surface treatments on the titanium dioxide pigment particle surface, the process comprising the steps of:
(a) reacting titanium tetrachloride vapor and aluminum chloride and at least a stoichiometric amount of oxygen in a plug flow reactor to form a product stream containing titanium dioxide particles; and (b) introducing silicon tetrachloride into the reactor at one or more points downstream of the point where the titanium tetrachloride and oxygen were contacted and where at least 97% of the titanium tetrachloride has been converted to titanium dioxide.
2 . The process of claim 1 wherein the silicon tetrachloride is introduced at a point where at least 98% of the. titanium tetrachloride has been converted to titanium dioxide.
3 . The process of claim 1 wherein the silicon tetrachloride is introduced at a point where at least 99% of the titanium tetrachloride has been converted to titanium dioxide.
4 . The process of claim 1 wherein the silicon tetrachloride is introduced in an amount sufficient to provide a silica content of a surface treated titanium dioxide pigment of about at least 1.2% by weight and the aluminum trichloride is added in an amount sufficient to provide an aluminum oxide content of a surface treated pigment of at least about 1% by weight.
5 . The process of claim 1 wherein steam or oxygen is introduced at a point downstream of the point of introduction of silicon tetrachloride or wherein steam or oxygen are introduced along with the silicon tetrachloride.
6 . A durable titanium dioxide pigment wherein at least 85% of the pigment particles are completely covered by a uniform layer formed from a mixture of amorphous aluminum oxide and amorphous silicon dioxide, the pigment produced by:
(a) reacting titanium tetrachloride vapor and aluminum chloride and at least a stoichiometric amount of oxygen in a plug flow reactor to form a product stream containing titanium dioxide particles; and (b) introducing silicon tetrachloride into the reactor at one or more points downstream of the point where the titanium tetrachloride and oxygen were contacted and where at least 97% of the titanium tetrachloride has been converted to titanium dioxide.
7 . The pigment of claim 6 wherein the percent of silicon dioxide is at least about 1.2% of the total weight of the pigment and the aluminum oxide is at least about 1% of the total weight of the pigment.
8 . Durable titanium dioxide pigment particles having a surface treatment layer comprising aluminum oxide and silicon dioxide wherein the at least 85% of the pigment particles are completely covered by a uniform layer formed from a mixture of amorphous aluminum oxide and amorphous silicon dioxide and wherein the pigment particles are free of debris.
9 . The titanium dioxide pigment of claim 8 wherein 95% or more of the pigment particles are completely covered by a uniform layer formed from a mixture of amorphous aluminum oxide and amorphous silicon dioxide.
10 . A method to determine a point of introduction of silicon tetrachloride into a plug flow reactor for the oxidation of a mixture of titanium tetrachloride and aluminum trichloride in a gas containing at least a stoichiometric amount of oxygen to produce titanium dioxide particle having a thin, uniform and complete layer of surface oxides comprising a mixture of amorphous aluminum oxide and silicon dioxide, the steps of the process comprising;
(a) determining the temperature in the reactor where not more than 3% of the titanium tetrachloride remains unreacted using
K
=
[
2
(
100
%
-
u
TiC
l
4
)
+
φ
×
100
%
]
2
u
TiCl
4
(
β
+
u
TiCl
4
)
and
T
<
20733
ln
K
+
6.391
-
273.15
where
μ TiCl4 =unreacted TiCl4 (%)
β=O2 (%) in excess of the stoichiometric amount
φ=feed Cl2 mole ratio (mol/mol TiCl4), and
T=temperature (C);
and
(b) introducing the silicon tetrachloride into the reactor where the temperature is equal to or less than the temperature calculated in step (a).
11 . A process for making durable titanium dioxide pigment by vapor phase deposition of surface treatments on the titanium dioxide pigment particle surface, the process comprising the steps of:
(a) reacting titanium tetrachloride vapor, an oxygen containing gas and aluminum chloride in a plug flow reactor to form a product stream containing titanium dioxide particles; and (b) introducing silicon tetrachloride into the reactor at one or more points downstream of the point where the titanium tetrachloride and oxygen were contacted and where the reaction temperature is no greater than about 1200° C.Join the waitlist — get patent alerts
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