Functionalization of oxidic particle surfaces, particles thus obtained, and the use thereof
A method for the surface modification of particles containing oxidic compounds of metals and/or semimetals M having M-O—H groups on the surface thereof. The particles are contacted with silicon-halogen compounds under conditions such that the M-O—H groups react with the silicon-halogen compounds. The particles thus produced can have Si—OH, Si-Halogen, and/or Si-Organic Radical groups in a density of at least two such groups per nm 2 surface and/or have at least four carbon atoms corresponding to the Si-Organic Radical groups per nm 2 of surface.
1 . A process for modifying the surface of particles of oxidic compounds of metals and/or semimetals M, having M-O—H groups on the surface thereof, and which do not exclusively comprise silicon as the metal or semimetal M, said process comprising a reaction step b) wherein particles are brought into contact with one or more silicon-halogen compounds under conditions such that the M-O—H groups react with the one or more silicon-halogen compounds to afford M-O—Si—X groups (X=halogen).
2 . A process according to claim 1 , wherein the particles of oxidic compounds of metals and/or semimetals M, prior to the reaction step b), are contacted in a reaction step a) with a strong acid.
3 . A process according to claim 1 , wherein the particles, after the reaction step b), are brought into contact in a further reaction step c) with water under conditions such that the M-O—Si—X groups react to form M-O—Si—OH groups.
4 . A process according to claim 3 , wherein the particles, after the reaction step c), are reacted in a further reaction step d) with an organosilicon compound Z (4-n) SiR n ,
in which Z represents a hydrolyzable group;
n means a number in the range 1 to 3; and
R represents an organic group, bonded to the Si through a carbon atom, wherein when n is a number greater than 1 the R groups in the molecule are the same or different;
under such reaction conditions that M-O—Si—O—SiR n groups are formed by cleavage of the Z group from the M-O—Si—OH groups.
5 . A process according to claim 3 , wherein the particles, after the reaction step c), are brought into contact in a further reaction step d) with silicon-halogen compounds under conditions such that the —O—Si—OH groups react with the silicon-halogen compounds to form —O—Si—O—Si—X groups (X=halogen).
6 . A process according to claim 1 , wherein the particles of oxidic compounds of metals and/or semimetals M, prior to the reaction step b), are contacted in a reaction step a) with a strong acid and wherein the particles, after the reaction step b), are brought into contact in a further reaction step c) with water under conditions such that the M-O—Si—X groups react to form M-O—Si—OH groups.
7 . A process according to claim 6 , wherein the particles, after the reaction step c), are reacted in a further reaction step d) with an organosilicon compound Z (4-n) SiR n ,
in which Z represents a hydrolyzable group;
n means a number in the range 1 to 3; and
R represents an organic group, bonded to the Si through a carbon atom, wherein when n is a number greater than 1 the R groups in the molecule are the same or different;
under such reaction conditions that M-O—Si—O—SiR n groups are formed by cleavage of the Z group from the M-O—Si—OH groups.
8 . A process according to claim 6 , wherein the particles, after the reaction step c), are brought into contact in a further reaction step d) with silicon-halogen compounds under conditions such that the —O—Si—OH groups react with the silicon-halogen compounds to form —O—Si—O—Si—X groups (X=halogen).
9 . A process according to claim 1 , wherein after reaction step b) the particles are brought into contact in a further reaction step e) with at least one organic compound or a hydride source under conditions such that Si—X bonds are cleaved and, instead, bonds between Si and the organic compound or to a group thereof or to a hydrogen atom are formed.
10 . A process according to claim 9 , wherein the organic compound is selected from R—OH, RNH 2 , R 2 NH, RPH 2 , R 2 PH, R—Mg—X, Li—R, wherein X represents a halogen atom and R an organic or organosilicon group and, when there are a plurality of R groups in the molecule, said R groups can be the same or different.
11 . A process according to claim 10 , wherein at least one R group possesses at least one C═C double bond or at least one epoxy group.
12 . A process according to claim 9 , wherein the particles of oxidic compounds of metals and/or semimetals M, prior to the reaction step b), are contacted in a reaction step a) with a strong acid.
13 . A process according to claim 9 , wherein the particles of oxidic compounds of metals and/or semimetals M, after reaction step b) and before reaction step e) are contacted with water in a further reaction step c) under conditions such that the M-O—Si—X groups react to form M-O—Si—OH groups and reacted in a further reaction step d) with at least one compound selected from the group consisting of silicon-halogen compounds and organosilicon compounds Z (4-n) SiR n ,
in which Z represents a hydrolyzable group;
n means a number in the range 1 to 3; and
R represents an organic group, bonded to the Si through a carbon atom, wherein when n is a number greater than 1 the R groups in the molecule are the same or different.
14 . Particles of oxidic compounds of metals and/or semimetals M that do not contain exclusively silicon as the metal or semimetal M, and whose surfaces are modified such that said surfaces carry —Si—OH groups, —Si—X groups (X=halogen) and/or —Si—Y groups (wherein Y is an organic group that can be linked to the Si through a carbon atom or a heteroatom) in a density of at least 2 such groups per nm 2 of surface and/or said surfaces carry —Si—Y groups (wherein Y is an organic group that comprises carbon atoms and which can be linked to the Si through a carbon atom or a heteroatom) in such a density per nm 2 of surface that at least 4 carbon atoms of the organic groups Y are present per nm 2 of surface.
15 . Particles according to claim 14 , wherein said particles carry —Si—Y groups on the surface where the organic group Y possesses at least one C═C double bond or at least one epoxy group.
16 . A catalyst comprising one or more catalytically active components and a support containing particles according to claim 14 .
17 . A composition comprising a matrix of one or more organic polymers and particles according to claim 14 .
18 . A ferrofluid comprising a carrier liquid and particles according to claim 14 , wherein said particles have magnetic properties.
19 . A method of grinding or polishing a surface, said method comprising using a grinding or polishing agent containing particles according to claim 14.