# Patent

## Title
Surface-modified indium-tin oxides

## Abstract

Surface-modified indium-tin oxides are produced by mixing the oxides with the surface-modifying agent in liquid or vapor form and heat treating the mixture.

    
    
        They can be used to produce coating systems.

## Background
The invention concerns surface-modified indium-tin oxides, a process for their production and their use.
Indium-tin oxides are known from DE 101 29 376. They are produced by mixing a solution of an indium salt with a solution of a tin salt, atomising this solution mixture and pyrolysing the atomised solution mixture.
The invention provides surface-modified indium-tin oxides, which are characterised by:















BET specific surface areas:
0.1-299 m2/g



pH:
2.5-9.5



C content:
0.1 to 15%









The invention also provides a process for producing the surface-modified indium-tin oxides, which is characterised in that the oxides are sprayed with the surface-modifying agent whilst being mixed and the mixture is then heat treated at a temperature of 50 to 400° C. for a period of 1 to 6 hours.
The invention also provides another process for producing the surface-modified indium-tin oxides according to the invention, which is characterised in that the oxides are treated with the surface-modifying agent in vapour form and the mixture is then heat treated at a temperature of 50 to 800° C. for a period of 0.5 to 6 hours.
The heat treatment can take place under protective gas, such as nitrogen for example.
The surface modification can be performed in heatable mixers and dryers with sprayers, continuously or in batches. Suitable devices can be, for example: ploughshare mixers, plate dryers, fluidised-bed or flash dryers.
The indium-tin oxides known from DE 101 29 376 can be used as oxides.
An indium-tin oxide which is characterised by the following physico-chemical parameters can be used according to the invention:
















Average primary particle size
1 to 200
nm



determined by TEM





BET surface area (DIN 66131)
0.1 to 300
m2/g










XRD structure
cubic indium oxide,




tetragonal tin oxide











Mesopores according to
0.03 ml to 0.30
ml/g



BJH method (DIN 66134)





Macropores (DIN 66133)
1.5 to 5.0
ml/g



Bulk density (DIN-ISO 787/XI)
50 to 2000
g/l









The indium-tin oxide for use according to the invention can be doped with the following substances in the form of oxides and/or of elemental metals:















aluminium,
yttrium,



magnesium,
tungsten,



silicon,
vanadium,



gold,
manganese,



cobalt,
iron,



copper,
silver,



palladium,
ruthenium,



nickel,
rhodium,



cadmium,
platinum,



antimony,
osmium,



cerium,
iridium,



zirconium
calcium



titanium
zinc









wherein the corresponding salts can be used as the starting substance.

The indium-tin oxide for use according to the invention can be produced by mixing a solution of an indium salt with a solution of a tin salt, optionally adding a solution of at least one doping component, atomising this solution mixture, pyrolysing the atomised solution mixture and separating the product obtained from the waste gases.
Inorganic compounds such as chlorides, nitrates, for example, and organometallic precursors such as acetates, alcoholates, for example, can be used as salts.
The solution mixture can additionally contain a dispersion of a pyrogenically produced silica, which can optionally be hydrophobed, or a silica sol. It must be borne in mind here that the silica acts as a nucleus of crystallisation and as such the maximum particle size of the silica is predetermined by the maximum particle size of the end product.
The solution can optionally contain water, water-soluble organic solvents such as alcohols, for example ethanol, propanol, and/or acetone.
The solution can be atomised using an ultrasonic nebuliser, ultrasonic atomiser, two-fluid nozzle or three-fluid nozzle.
If an ultrasonic nebuliser or ultrasonic atomiser is used, the aerosol obtained can be mixed with the carrier gas and/or N2/O2 air which is supplied to the flame.
If a two-fluid or three-fluid nozzle is used, the aerosol can be sprayed directly into the flame.
Non-water-miscible organic solvents such as ethers can also be used.
Separation can be carried out with a filter or cyclone.
Pyrolysis can be carried out in a flame generated by burning hydrogen/air and oxygen. Methane, butane and propane can be used in place of hydrogen.
Pyrolysis can also be carried out using an externally heated oven.
A fluidised-bed reactor, a revolving tube or a pulsed reactor can also be used.


EXAMPLES
The process parameters for producing the indium-tin oxides for use according to the invention are set out in the table below:

















Production Exp. no.:














PH04408
PH04410







Metal
Composition
In/Sn/Mg/Al
In/Sn/Au




Type
All chlorides
All chlorides




wt. %
93/5/0.3/1.7
94/5.5/0.5



Solution
Throughput
560
570




g/h






Dissolved in
H2O
H2O




conc. %
3
3



Nebulisation
Ultrasonic
x




Nozzle
2-fluid

x



Gas quantity
H2
1.2
1.2



m3/h
N2/O2
0/0.3
0/0.2




Atomisation
1.5
1.5




Secondary

1.5




Primary
3
1.6




Lambda
2.24
1.93



Reactor
T 1
751
781



temp.
T 2
720
765



° C.
T 3
721
749




Filter
241
240










The physico-chemical parameters of the products obtained are set out in the tables below:










ITO substance data analysis









Exp. no.:












PH04408
PH04410
PH04411
PH04412





XRD phase analysis
cub. In2O3
cub. In2O3
cub. In2O3
cub. In2O3












Particle size by
BET [nm]
31
17
15
15



XRD [nm]
32
20
19
19











Distribution by TEM
homogeneous






distrib. with






spheres















Particle diam.
DN [nm]
21.04





Spec. surf. area
OEM
26.319






[m2/g]






Mol. number dist.
D50 (A)
17.516






[nm]






Mol. weight dist.
D50(g)
32.701






[nm]






90% spec. 
nm
9.87-36.65





number distrib.







90% spec. 
nm
14.67-87.66 





weight distrib.







Overall spread
nm
7.40-116.6





BET spec. 
(m2/g)
26
49
54
55


surface area
















Micropores (de Boer's 
none
none
none
none


t-plot)
















Metal
Compo-
In/Sn/Mg/Al
In/Sn/Au
In/Sn/Au
In/Sn/Au



sition







wt. %
93/5/0.3/1.7
94/5.5/0.5
90/8/1
90/7/3


RFA
%
89/5.1/0.5/3.2
90.9/7.6
89/9
88.7/8.75


Spec. resistance







(ohm)







Compressed
(at 0.5
1.00E+03
1.00E+04
1.00E+04
1.00E+05


density
g/cm3)






Surface analysis
Metal
In/Sn/Au





(XPS)








atom %
25/0.96/0.25






In/Sn
26.04





C content ppm

1000





Cilas d = 50 
without






in μm
US







with US
   1.56
  1.2

  1.1



120 sec.






L/a/b values

85.48/−2.28/22.08
76.15/1.88/20.01
66.31/4.72/11.16
52.2/7.16/0.2


Colour

yellowish
yellow
yellow
violet




green
green
green






orange
pink



Density g/l


150 
280 
253 









The products for use according to the invention display a cubic indium oxide and a tetragonal tin oxide.
Silanes can be used as surface treatment agents. Such silanes can be the following silanes, which can be used both individually and mixed together:

    a) Organosilanes of the type (RO)3Si(CnH2n+1) and (RO)3Si(CnH2n−1)
    
        R=alkyl, such as e.g. methyl, ethyl, n-propyl, i-propyl, butyl
        n=1-20
    
    
    b) Organosilanes of the type R′x(RO)ySi(CnH2n+1) and R′x (RO)ySi (CnH2n−1)
    
        R=alkyl, such as e.g. methyl, ethyl, n-propyl, i-propyl, butyl
        R′=alkyl, such as e.g. methyl, ethyl, n-propyl, i-propyl, butyl
        R′=cycloalkyl
        n=1-20
        x+y=3
        x=1.2
        y=1.2
    
    
    c) Organohalosilanes of the type X3Si(CnH2n+1) and X3Si (CnH2n−1)
    
        X=Cl, Br
        n=1-20
    
    
    d) Organohalosilanes of the type X2(R′)Si(CnH2n+1) and X2 (R′)Si (CnH2n−1)
    
        X=Cl, Br
        R′=alkyl, such as e.g. methyl, ethyl, n-propyl, i-propyl, butyl
        R′=cycloalkyl
        n=1-20
    
    
    e) Organohalosilanes of the type X(R′)2Si(CnH2n+1) and X(R′)2Si(CnH2n−1)
    
        X=Cl, Br
        R′=alkyl, such as e.g. methyl, ethyl, n-propyl, i-propyl, butyl
        R′=cycloalkyl
        n=1-20
    
    
    f) Organosilanes of the type (RO)3Si(CH2)m—R′
    
        R=alkyl, such as methyl, ethyl, propyl
        m=0.1-20
        R′=methyl, aryl (e.g. —C6H5, substituted phenyl radicals)
        
            —C4F9, OCF2—CHF—CF3, —C6F13, —O—CF2—CHF2 
            —NH2, —N3, —SCN, —CH═CH2, —NH—CH2—CH2—NH2, —N—(CH2—CH2—NH2)2 
            —OOC(CH3)C═CH2 
            —OCH2—CH(O)CH2 
            —NH—CO—N—CO—(CH2)5 
            —NH—COO—CH3, —NH—COO—CH2—CH3, —NH—(CH2)3Si(OR)3 
            —Sx—(CH2)3Si(OR)3 
            —SH
            —NR′R′′R′′′ (R′=alkyl, aryl; R′′=H, alkyl, aryl; R′′′=H, alkyl, aryl, benzyl, C2H4NR′′′′R′′′′′ where R′′′′=H, alkyl and R′′′′′=H, alkyl)
        
        
    
    
    g) Organosilanes of the type (R′′)x(RO)ySi(CH2)m—R′
    
        R′′=alkyl x+y=3
        
            =cycloalkyl x=1.2
            
                y=1.2
                m=0.1 to 20
            
            
        
        
        R′=methyl, aryl (e.g. —C6H5, substituted phenyl radicals)
        
            —C4F9, —OCF2—CHF—CF3, —C6F13, —O—CF2—CHF2 
            —NH2, —N3, —SCN, —CH═CH2, —NH—CH2—CH2—NH2, —N—(CH2—CH2—NH2)2 
            —OOC(CH3)C═CH2 
            —OCH2—CH(O)CH2 
            —NH—CO—N—CO—(CH2)5 
            —NH—COO—CH3, —NH—COO—CH2—CH3, —NH—(CH2)3Si(OR)3 
            —Sx—(CH2)3Si(OR)3, where R can be methyl, ethyl, propyl, butyl and x=1 or 2
            —SH
            —NR′R′′R′′′ (R′=alkyl, aryl; R′′=H, alkyl, aryl; R′′′=H, alkyl, aryl, benzyl, C2H4NR′′′′R′′′′′ where R′′′′=H, alkyl and R′′′′′=H, alkyl)
        
        
    
    
    h) Organohalosilanes of the type X3Si(CH2)m—R′
    
        X=Cl, Br
        m=0.1-20
        R′=methyl, aryl (e.g. —C6H5, substituted phenyl radicals)
        
            —C4F9, —OCF2—CHF—CF3, —C6F13, —O—CF2—CHF2 
            —NH2, —N3, —SCN, —CH═CH2, —NH—CH2—CH2—NH2 
            —N—(CH2—CH2—NH2)2 
            —OOC(CH3)C═CH2 
            —OCH2—CH(O)CH2 
            —NH—CO—N—CO—(CH2)5 
            —NH—COO—CH3, —NH—COO—CH2—CH3, —NH—(CH2)3Si(OR)3 
            —Sx—(CH2)3Si(OR)3, where R can be methyl, ethyl, propyl, butyl and x=1 or 2
            —SH
        
        
    
    
    i) Organohalosilanes of the type (R)X2Si(CH2)m—R′
    
        X=Cl, Br
        R=alkyl, such as methyl, ethyl, propyl
        m=0.1-20
        R′=methyl, aryl (e.g. —C6H5, substituted phenyl radicals)
        
            —C4F9, —OCF2—CHF—CF3, —C6F13, —O—CF2—CHF2 
            —NH2, —N3, —SCN, —CH═CH2, —NH—CH2—CH2—NH2, —N—(CH2—CH2—NH2)2 
            —OOC(CH3)C═CH2 
            —OCH2—CH(O)CH2 
            —NH—CO—N—CO—(CH2)5 
            —NH—COO—CH3, —NH—COO—CH2—CH3, —NH—(CH2)3Si(OR)3, where R can be methyl, ethyl, propyl, butyl
            —Sx—(CH2)3Si(OR)3, where R can be methyl, ethyl, propyl, butyl and x=1 or 2
            —SH
        
        
    
    
    j) Organohalosilanes of the type (R)2X Si(CH2)m—R′
    
        X=Cl, Br
        R=alkyl
        m=0.1-20
        R′=methyl, aryl (e.g. —C6H5, substituted phenyl radicals)
        
            —C4F9, —OCF2—CHF—CF3, —C6F13, —O—CF2—CHF2 
            —NH2, —N3, —SCN, —CH═CH2, —NH—CH2—CH2—NH2,
            —N—(CH2—CH2—NH2)2 
            —OOC(CH3)C═CH2 
            —OCH2—CH(O)CH2 
            —NH—CO—N—CO—(CH2)5 
            —NH—COO—CH3, —NH—COO—CH2—CH3, —NH—(CH2)3Si(OR)3 
            —Sx—(CH2)3Si(OR)3, where R can be methyl, ethyl, propyl, butyl and x=1 or 2
            —SH
        
        
    
    
    k) Silazanes of the type






    
    
        R=alkyl, vinyl, aryl
        R′=alkyl, vinyl, aryl
    
    
    l) Cyclic polysiloxanes of the type D 3, D 4, D 5, wherein D 3, D 4 and D 5 are understood to be cyclic polysiloxanes having 3, 4 or 5 units of the type —O—Si(CH3)2—,
    
        e.g. octamethyl cyclotetrasiloxane=D 4
    
    






    m) Polysiloxanes or silicone oils of the type






    R=alkyl, such as CnH2n+1, wherein n=1 to 20, aryl, such as
    
        phenyl and substituted phenyl radicals, (CH2)n—NH2, H
    
    
    R′=alkyl, such as CnH2n+1, wherein n=1 to 20, aryl, such as
    
        phenyl and substituted phenyl radicals, (CH2)n—NH2, H
    
    
    R′′=alkyl, such as CnH2n+1, wherein n=1 to 20, aryl, such as
    
        phenyl and substituted phenyl radicals, (CH2)n—NH2, H
    
    
    R′′′=alkyl, such as CnH2n+1, wherein n=1 to 20, aryl, such as
    
        phenyl and substituted phenyl radicals, (CH2)n—NH2, H
    
    


The following substances can preferably used as surface-modifying agents:
Octyl trimethoxysilane, octyl triethoxysilane, hexamethyl disilazane, 3-methacryloxypropyl trimethoxysilane, 3-methacryloxypropyl triethoxysilane, hexadecyl trimethoxysilane, hexadecyl triethoxysilane, dimethyl polysiloxane, glycidyloxypropyl trimethoxysilane, glycidyloxypropyl triethoxysilane, nonafluorohexyl trimethoxysilane, tridecafluorooctyl trimethoxysilane, tridecafluorooctyl triethoxysilane, aminopropyl triethoxysilane.
Octyl trimethoxysilane, octyl triethoxysilane and dimethyl polysiloxanes can particularly preferably be used.
The surface-modified indium-tin oxides according to the invention can be used for producing coating systems, for example, which are distinguished by IR protection.
The surface-modified indium-tin oxides according to the invention are distinguished by a pronounced transparency.
Examples
For the purposes of surface modification the oxides are placed in a mixer and sprayed first optionally with water and then with the surface-modifying agent whilst undergoing intensive mixing. On completion of spraying, mixing can be continued for a further 15 to 30 minutes and the mixture is then conditioned for 1 to 4 hours at 50 to 400° C.
The water used can be acidulated with an acid, for example hydrochloric acid, to obtain a pH of 7 to 1. The silanising agent used can be dissolved in a solvent, such as ethanol for example. An indium-tin oxide (VP AdNano ITO R 50) was used to produce the examples. Physico-chemical data for the oxide used (UB PH 13195) can be obtained from Table 1. Details of the method together with data for the surface-modified oxides are set out in Tables 2 and 3.










TABLE 1








Specific surface area (BET)
m2/g
48



pH, 4% in water

3.3



Compacted bulk density
g/l
195



Loss on drying
%
0.9
















TABLE 2







Production of the surface-modified oxides














Parts







SMA*/
Parts H2O/
Cond.
Cond.



Surface-
100 parts
100 parts
temp.
time


Example
modifying agent
oxide
oxide
[° C.]
[h]















1
A
6
0.5
120
2


2
A
4

120
2


3
B
5

120
2


4
C
4
0.5
120
2


5
D
4
0.5**
120
2





*SMA = Surface-modifying agent


**0.001n HCl were used in place of H2O


Surface-modifying agents:


A = octyl trimethoxysilane


B = 3-methacryloxypropyl trimethoxysilane


C = hexamethyl disilazane


D = hexadecyl trimethoxysilane













TABLE 3







Physico-chemical data for the surface-modified oxides













BET specific






surface area





Example
[m2/g]
pH
C content [%]






1
41
3.3
2.4



2
45
3.3
1.7



3
44
3.3
1.7



4
47
4.7
0.2



5
40
3.2
3.2

## Claims

1. Surface-modified particles containing pyrogenically produced indium-tin oxides, characterised by















BET specific surface areas:
0.1-299 m2/g



pH:
2.5-9.5



C content:
0.1 to 15%








obtained by treating pyrogenically produced oxides with silanes as surface-modifying agents whilst being mixed and heating the mixture at a temperature of 50 to 400° C. for a period of 1 to 6 hours.

2. Process for producing the surface-modified particles containing indium-tin oxides as defined in claim 1, comprising spraying pyrogenically produced indium-tin oxides with silanes as surface-modifying agents whilst being mixed and heat treating the mixture at a temperature of 50 to 400° C. for a period of 1 to 6 hours.

3. Process for producing the surface-modified particles containing indium-tin oxides as defined in claim 1, comprising spraying pyrogenically produced indium-tin oxides with silanes as surface-modifying agents in vapour form whilst being mixed and heat treating the mixture at a temperature of 50 to 800° C. for a period of 0.5 to 6 hours.

4. A coating composition comprising the surface-modified particles containing indium-tin oxides of claim 1 and a carrier.

5. The surface-modified particles containing pyrogenically produced indium-tin oxides according to claim 1, wherein the silane is selected from the group consisting of octyl trimethoxysilane, octyl triethoxysilane, hexamethyl disilazane, 3-methacryloxypropyl trimethoxysilane, 3-methacryloxypropyl triethoxysilane, hexadecyl trimethoxysilane, hexadecyl triethoxysilane, dimethyl polysiloxane, glycidyloxypropyl trimethoxysilane, glycidyloxypropyl triethoxysilane, nonafluorohexyl trimethoxysilane, tridecafluorooctyl trimethoxysilane, tridecafluorooctyl triethoxysilane, and aminopropyl triethoxysilane.

6. The process according to claim 3, wherein the silane is selected from the group consisting of octyl trimethoxysilane, octyl triethoxysilane, hexamethyl disilazane, 3-methacryloxypropyl trimethoxysilane, 3-methacryloxypropyl triethoxysilane, hexadecyl trimethoxysilane, hexadecyl triethoxysilane, dimethyl polysiloxane, glycidyloxypropyl trimethoxysilane, glycidyloxypropyl triethoxysilane, nonafluorohexyl trimethoxysilane, tridecafluorooctyl trimethoxysilane, tridecafluorooctyl triethoxysilane, and aminopropyl triethoxysilane.

7. The process according to claim 4, wherein the silane is selected from the group consisting of octyl trimethoxysilane, octyl triethoxysilane, hexamethyl disilazane, 3-methacryloxypropyl trimethoxysilane, 3-methacryloxypropyl triethoxysilane, hexadecyl trimethoxysilane, hexadecyl triethoxysilane, dimethyl polysiloxane, glycidyloxypropyl trimethoxysilane, glycidyloxypropyl triethoxysilane, nonafluorohexyl trimethoxysilane, tridecafluorooctyl trimethoxysilane, tridecafluorooctyl triethoxysilane, and aminopropyl triethoxysilane.