Functionalized, structurally modified silicas
View Patent ↗Functionalized, structurally modified silicas with 3-methacryloxypropylsilyl and/or glycidyloxypropylsilyl groups on the surface are prepared by mixing the silicas with the silane and heat-treating, destructuring and grinding the mixture. The silicas are employed in radiation-curing coatings.
1. A functionalized, destructured silica, characterized by functional groups fixed on the surface, the groups being 3-methacryloxypropylsilyl and/or glycidyloxypropylsilyl, with the following physico-chemical characteristic data:
BET surface area
m 2 /g
25–380
Primary particle size
nm
6–45
Tamped density
g/l
50–400
pH
3–10
Carbon content
%
0.1–15
DBP number
%
<200
wherein said silica is produced pyrogenically by flame hydrolysis of SiCl 4 prior to surface modification.
2. The functionalized, destructured silica of claim 1 wherein the BET surface area ranges from 90±15 to 380±15.
3. A process for the preparation of functionalized, destructured silica having functional groups fixed on the surface, the groups being 3-methacryloxypropylsilyl and/or glycidyloxypropylsilyl, with the following physico-chemical characteristic data:
BET surface area
m 2 /g
25–380
Primary particle size
nm
6–45
Tamped density
g/l
50–400
pH
3–10
Carbon content
%
0.1–15
DBP number
%
<200
wherein said silica is produced pyrogenically by flame hydrolysis of SiCl 4 prior to surface modification,
comprising spraying silica first with water or dilute acid and then with a surface modification reagent or a mixture of several surface modification reagents in a mixing vessel, intensively mixing the silica and said reagent, optionally re-mixing the silica for 15 to 30 minutes and then heat-treating at a temperature of 100 to 400° C. over a period of 1 to 6 h, to thereby produce a functionalized silica, then destructuring or compacting said silica and optionally re-grinding said silica in a mill.
4. A coating composition containing the functionalized, destructured silica according to claim 1 in a binder vehicle.
5. A functionalized, structurally modified destructured silica, characterized by functional groups fixed on the surface, the groups being 3-methacryloxypropylsilyl and/or glycidyloxypropylsilyl, with the following physico-chemical characteristic data:
BET surface area
m 2 /g
25–380
Primary particle size
nm
6–45
Tamped density
g/l
50–400
pH
3–10
Carbon content
%
0.1–15
DBP number
%
<200,
said functionalized, destructured silica being produced by spraying pyrogenically produced silica first with water or dilute acid and then with at least one of a surface modification reagent selected from the group consisting of 3-methacryloxypropylsilane, glycidoxypropylsilane and mixtures thereof, in a mixing vessel, intensively mixing the silica and said reagent, optionally re-mixing the silica for 15 to 30 minutes and then heat-treating at a temperature of 100 to 400° C. over a period of 1 to 6 h, to thereby produce said functionalized silica.
6. The functionalized, destructured silica according to claim 5 , which has been additionally subjected to destructuring or compacting and optionally re-grinding said silica in a mill.