Process for producing hydrophobized silicon oxide-coated metal oxide particles comprising primary and secondary hydrophobizing steps
View Patent ↗Hydrophobized silicon oxide-coated metal oxide particles excellent in dispersibility in fluororesins, durability to fluorinated compounds and ultraviolet-shielding properties, and a fluororesin film excellent in transparency, weather resistance and ultraviolet-shielding properties comprising the hydrophobized silicon oxide-coated metal oxide particles, the hydrophobized silicon oxide-coated metal oxide particles being obtained by a process including a primary and a secondary hydrophobizing treatment.
1. A process for producing hydrophobized silicon oxide-coated metal oxide particles, which comprises:
(a) adding a silicon oxide precursor to a dispersion of metal oxide particles to form a silicon oxide film on the surface of metal oxide particles thereby to obtain a dispersion of silicon oxide-coated metal oxide particles,
(b) adding a compound represented by the following formula (1) or (2) and a silicon oxide precursor to the above dispersion of silicon oxide-coated metal oxide particles thereby to obtain a dispersion of primarily hydrophobized silicon oxide-coated metal oxide particles,
R 1 4-n Si(OR 2 ) n (1)
R 3 3 Si—NH—SiR 3 3 (2)
in the above formulae (1) and (2), R 1 is a C 1-9 alkyl group, each of R 2 and R 3 which are independent of each other, is an alkyl group, and n is an integer of from 1to 3,
(c) adding a silanol-protective agent to the above dispersion of primarily hydrophobized silicon oxide-coated metal oxide particles thereby to obtain a dispersion of secondarily hydrophobized silicon oxide-coated metal oxide particles, and
(d) drying the above secondarily hydrophobized silicon oxide-coated metal oxide particles thereby to obtain the hydrophobized silicon oxide-coated metal oxide particles.
2. The process for producing hydrophobized silicon oxide-coated metal oxide particles according to claim 1 , wherein in the dispersion of metal oxide particles, the 90% particle size of the metal oxide particles is from 10 to 100 nm.
3. The process for producing hydrophobized silicon oxide-coated metal oxide particles according to claim 1 , wherein in the dispersion of metal oxide particles, the 90% particle size of the metal oxide particles is from 20 to 80 nm.
4. The process for producing hydrophobized silicon oxide-coated metal oxide particles according to claim 1 , wherein the silicon oxide film in the hydrophobized silicon oxide-coated metal oxide particles has a thickness of from 1 to 20 nm.
5. The process for producing hydrophobized silicon oxide-coated metal oxide particles according to claim 1 , wherein the metal oxide particles are zinc oxide particles.
6. The process for producing hydrophobized silicon oxide-coated metal oxide particles according to claim 1 , wherein the silicon oxide precursor is tetraethoxysilane.
7. The process for producing hydrophobized silicon oxide-coated metal oxide particles according to claim 1 , wherein R 2 in the formula (1) is a methyl group.
8. The process for producing hydrophobized silicon oxide-coated metal oxide particles according to claim 1 , wherein the compound represented by the formula (1) is added and is isobutyltrimethoxysilane or hexyltrimethoxysilane.
9. The process for producing hydrophobized silicon oxide-coated metal oxide particles according to claim 1 , wherein the compound represented by the formula (2) is added and is hexamethyldisilazane.
10. The process for producing hydrophobized silicon oxide-coated metal oxide particles according to claim 1 , wherein the silanol-protective agent is hexamethyldisilazane.
11. The process for producing hydrophobized silicon oxide-coated metal oxide particles according to claim 1 , wherein the metal oxide particles are present in the dispersion at a concentration of from 1 to 20 mass %.
12. The process for producing hydrophobized silicon oxide-coated metal oxide particles according to claim 1 , wherein the amount of silanol-protective agent is from 1 to 200 parts by mass, based on 100 parts by mass of the primarily hydrophobized silicon oxide-coated metal oxide particles.
13. Hydrophobized silicon oxide-coated metal oxide particles obtained by the process as defined in claim 1 .
14. The hydrophobized silicon oxide-coated metal oxide particles according to claim 13 , which have a methanol hydrophobizing degree being from 45 to 75%.
15. A fluororesin film comprising hydrophobized silicon oxide-coated metal oxide particles obtained by the process as defined in claim 1 and a fluororesin.
16. The fluororesin film according to claim 15 , which has a light transmittance at 360 nm being at most 5%, and further has a haze value being at most 15%.
17. The fluororesin film according to claim 15 , which has a light transmittance at 300 nm being at most 5%, and further has a haze value being at most 15%.
18. The fluororesin film according to claim 15 , wherein the fluororesin is an ethylene/tetrafluoroethylene type copolymer.