Process for surface modification of particulate solids
Improved utilization of organosilicon compounds in hydrophobicizing finely divided particulate solids is accomplished by metering a partial amount of unreacted solids with organosilicon containing offgases derived from admixing and reacting a major portion of solids with organosilicon compounds and admixing the offgas-treated solids with the major portion of solids to be treated.
1. A process for producing surface modified particulate finely divided solid F having a BET surface area of from 0.1 m 2 /g to 1000 m 2 /g, comprising the steps of:
(A) mixing a first amount of unmodified finely divided solid F1 with organosilicon compound(s) to form a first mixture of F1 and organosilicon compound(s) and producing an offgas comprising organosilicon compound(s);
(B) reacting the mixture of unmodified finely divided solid F1 with organosilicon compound(s) to produce surface modified finely divided solid F with or without an offgas comprising organosilicon compound(s);
(C) freeing the surface modified finely divided solid F from step (B) of adsorbed byproducts and unconverted organosilicon compound(s) which are obtained as offgas;
(D) metering a second amount of unmodified finely divided solid F1 into the offgas obtained in process steps (A), (C) or (B) putting in upstream of a filter to mix the solid F1 with organosilicon compound(s) in the offgas to form a second mixture of F1 and organosilicon compound(s); and
(E) feeding the second mixture obtained in process step (D) to process step (A) to augment the first mixture of unmodified finely divided solid F1 and organosilicon compound(s).
2. The process of claim 1 , wherein at least one organosilicon compound is an organosilane of formula (I)
X 1+x′ —SiR 4 2−x′ —(CH 2 ) v —Y (I),
where
X each independently represents halogen, nitrogen, OR 3 or OCOR 3 ,
R 3 each independently represents C—O bonded C 1 -C 15 hydrocarbyl or acetyl,
R 4 each independently represents a hydrogen atom or optionally NC—, OCN—, 2R 2 N—, HOOC—, R 2 OOC—, halogen-, acryloyl-, epoxy-, HS—, HO— or 2R 2 NOC-substituted Si—C bonded C 1 -C 20 hydrocarbyl or C 1 -C 15 hydrocarbyloxy, wherein in each of which one or more nonadjacent methylene units are optionally replaced by —O—, —CO—, —COO—, —OCO—, or —OCOO—, —S—, or —NR 2 — groups and in which one or more mutually nonadjacent methine units are optionally replaced by —N═ or —P=groups,
Y each independently represents hydrogen, unsaturated or mono- or polyunsaturated C 1 -C 20 hydrocarbyl, —OC(O)C(R)═CH 2 , -vinyl, -hydroxyl, -halogen, phosphonato, —NCO, —NH—C(O)—OR 1 , -glycidoxy, —SH, or acid anhydride,
R, R 1 each, independently represent C 1 -C 15 hydrocarbyl,
v is from 0 to 10, and
x′ is 1 or 2.
3. The process of claim 1 , wherein at least one organosilicon compound is an organosiloxane comprising of A units of formula (IIa) and one or more B units of formulae (IIb-d)
(R 5 3 SiO 1/2 ) (IIa),
(R 5 2 SiO 2/2 ) (IIb),
(R 5 SiO 3/2 ) (IIc),
(SiO 4/2 ) (IId),
where the organosiloxanes may contain 1 or 2 —X groups attached to silicon atoms, where X each independently is halogen, nitrogen, OR 3 , or OCOR 3 wherein R 3 each independently is C—O bonded C 1-15 hydrocarbyl or acetyl, and organosiloxanes may contain ≡SiX or ═SiX 2 groups in a number C, and A, B and C are subject to the following condition:
1≦B≦5000, with the proviso that B≧A+C, where A+C=0 is subject to the condition 10≦B≦100, while the ratio of A to C is freely choosable, and
R 5 each independently represents an optionally mono- or polyunsaturated, monovalent, optionally halogenated Si—C bonded hydrocarbyl of 1 to 18 carbon atoms.
4. The process of claim 2 , wherein at least one organosilicon compound is an organosiloxane comprising of A units of formula (IIa) and one or more B units of formulae (IIb-d)
(R 5 3 SiO 1/2 ) (IIa),
(R 5 2 SiO 2/2 ) (IIb),
(R 5 SiO 3/2 ) (IIc),
(SiO 4/2 ) (IId),
where the organosiloxanes may contain 1 or 2 —X groups attached to silicon atoms, where X each independently is halogen, nitrogen, OR 3 , or OCOR 3 wherein R 3 each independently is C—O bonded C 1-15 hydrocarbyl or acetyl, and organosiloxanes may contain ≡SiX or ═SiX 2 groups in a number C, and A, B and C are subject to the following condition:
1≦B≦5000, with the proviso that B≧A+C, where A+C=0 is subject to the condition 10≦B≦100, while the ratio of A to C is freely choosable, and
R 5 each independently represents an optionally mono- or polyunsaturated, monovalent, optionally halogenated Si—C bonded hydrocarbyl of 1 to 18 carbon atoms is also present.
5. The process of claim 1 , wherein process step (B) is conducted in an atmosphere containing less than 2.5% by volume of oxygen.
6. The process of claim 1 , which is a continuous process.
7. The process of claim 1 , wherein the organosilicon compound(s) are admixed in process step (A) as a finely divided aerosol.
8. The process of claim 1 , wherein the mixing with the organosilicon compound(s) in process step (A) and the reacting in process step (B) are effected under mechanical or gasborne fluidization.
9. The process of claim 1 , wherein from 1 to 50 parts by weight of solid F1 are metered into the offgas in process step (D) per 100 parts by weight of solid F1 used in process step (A).
10. The process of claim 1 , wherein the solids F1 are selected from metal oxides, silicates, aluminates, titanates and aluminum sheet-silicates.
11. The process of claim 10 , wherein the solids F1 are selected from precipitated silicas and pyrogenically produced silicas.