| 摘要 |
<p>#CMT# #/CMT# A pyrogenically prepared silicon dioxide powder (C1) in the form of aggregated primary particles has statistical thickness surface area (STSA) of 10-500 m 2>/g; thickening action, based on the STSA surface area of 4-8 mPasx g/m 2>; and micropore volume of 0.03-0.07 cm 3>/g. #CMT# : #/CMT# Independent claims are included for following: (1) preparing the pyrogenic silicon dioxide powder (C1) involving, mixing at least one hydrolyzable silicon compounds, oxygen-containing gas and/or primary combustion gas; igniting the mixture in a burner, burnt via pipe into a reaction chamber; passing secondary combustion gas into the reaction chamber and separating powder formed from gaseous substances, where the hydrogen ratio gamma(primary) of the raw material mixture is less than 1 and oxygen ratio lambda(primary) of the raw material mixture is greater than 1, gamma(primary) is defined as the combustion gas fed to the mixing chamber divided by the combustion gas required stoichiometrically and lambda(primary) is the oxygen supplied to the mixing chamber divided by the oxygen required stoichiometrically; and (2) a dispersion containing the pyrogenically prepared silicon dioxide powder (C1). #CMT#USE : #/CMT# In a dispersion for producing polyester films, catalyst supports, as constituent of paints and inks, or for polishing metallic and oxidic surfaces (claimed). #CMT#ADVANTAGE : #/CMT# The silicon dioxide powder has a low thickening effect and shows a statistical thickness surface area (STSA) surface area of 30-300 m 2>/g, thickening action, based on the STSA surface area, of 5-7 mPasx g/m 2>, micropore volume of 0.035-0.065 cm 3>/g, fractal dimension D m of greater than 2.61-2.85; average primary particle diameter of 10-40 nm; and dibutyl phthalate (DBP) absorption of = 300 g/100 g. #CMT#INORGANIC CHEMISTRY : #/CMT# Preferred Process: The hydrolyzable silicon compound is introduced in vapor form. The gamma(primary) is 0.4-0.9, gamma(total) is 1.05-4. The lambda(primary) and lambda(total) is less than 10. Preferred Compositions: The silicon compound selected from silicon halides, silicon organohalides and/or silicon alkoxides. The combustion gas contains hydrogen, methane, ethane, propane, butane, natural gas and/or carbon monoxide. The air or oxygen-enriched air is used as oxygen containing gas. The silicon dioxide fraction in the dispersion is 0.1-50 wt.%, the pH of the dispersion is 2-11.5, and the average diameter of the silicon dioxide particles in the dispersion is less than 500 nm. #CMT#EXAMPLE : #/CMT# Silicon tetrachloride (108 kg/h), hydrogen (primary combustion gas) (14 m 3>/h) and air (140 m 3>/h) were mixed in a burner, and the mixture was ignited and burnt into a reaction chamber, hydrogen (secondary combustion gas) (21 m 3>/h) and secondary air (40 m 3>/h) gamma(primary) (0.50), gamma(total) (1.24), lambda(primary) (4.13) and lambda(total) (1.67) were introduced and the resulting powder was deposited in a downstream filter and then treated countercurrently with air and steam at 520[deg] C, to give a silicon dioxide powder (test), which was dissolved in water to form a dispersion. The thickening property of this dispersion was compared with a dispersion of Aerosil 130 (RTM: silicon dioxide powder). The test/comparative showed thickening of approximately 840/2300 mPas respectively.</p> |
