Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Patent
1998-04-28
2000-10-17
Moore, Margaret G.
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
428407, 428403, B32B 2714
Patent
active
06132874&
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to hydroxylated inorganic oxide supports, in particular of silica, alumina, titanium oxide and rare-earth metal oxide type, which are functionalized and capable of being used in multiple applications, in particular in the field of functionalized fillers, for example for tyres, anti-adhesive paper, RTVs (room-temperature vulcanizable elastomers), antifoaming agents and pigmentation agents in electronics. The invention also applies, for example, to the preparation of hydrophobic supports or supports for enantiomer separation or for heterogeneous catalysis. Another subject of the invention is a process for their preparation.
The combination of silicones with silica is widely used today.
The silica can serve as inorganic filler intended to improve the mechanical properties of the silicones. This application involves the strong interactions which exist between the silanols of the silica and the Si-O-Si groups. In this case, it is also known to modify these interactions by treating the surface of the silica, for example with the help of Me.sub.3 Si groups, giving a degree of hydrophobicity to the silica which facilitates the incorporation of the filler in the silicone or in polymer matrices.
Attempts have also been made to functionalize the silica with the help of linear silicones, in order to obtain a functionalized silica having specific surface characteristics conferring useful properties on the silica.
T. Suhara et al., Colloids and Surfaces, Physicochemical and Engineering Aspects, 95 (1995), 1-9, thus use a tetramethylcyclotetrasiloxane (TMCTS) to coat the particles of a silica powder. The linear silicone is deposited on the silica by a vapour-phase deposition method at 80.degree. C., which enables covering of the silica by the silicone to be obtained. The Si-H groups of the polymethylsiloxane layer formed at the surface of the silica particles can react with various functional derivatives by a hydrosilylation reaction. It is thus possible to increase the dispersibility by crafting olefins or alcoholic hydroxyl groups, to form a matrix for anion exchange by grafting ionic diethylamino groups or to make the surface of the silica hydrophobic by grafting groups such as diethylamino or octadecyl groups. The writers describe the reaction of the silica, coated with its polymethylsiloxane layer, with p-chloromethylstyrene in the presence of a platinum-based catalyst and then with an N,N-dimethyl-n-alkylamine. Depending on the length of the grafted carbon chain, the final product can be hydrophobic or hydrophilic. This process takes advantage of the volatile nature of TMCTS at high temperature and is not applicable to silicones having a larger number of units.
The article by H. W. Stuurman et al., in Chromatographia, Vol. 25, No. 4, April 1988, relates to the preparation of a stationary silica phase which is useful in enantiomeric separation. The process described provides for a partial hydrosilylation reaction of a siloxane oligomer or polymer (for example having 22 or 35 SiH units on the silicone chain) and of quinine in the presence of a platinum-based catalyst and then for the chemical bonding of the compound obtained above to a silica gel (see also W. Roder et al., Journal of High Resolution Chromatography & Chromatography Communications, Short Communication 10710, Vol. 10, 665-667, December 1987). This process does not allow a homogeneous coating to be obtained and is not necessarily applicable to all types of functionalization, in particular molecules of significant size, without modifying the reactivity of the Si-H units of the silicone, just as it limits the amount of molecules which can be grafted.
Patent Application FR-A-2,666,999 describes a process for obtaining a silica-based support which is useful in analytical or preparative chromatography, in particular in high performance liquid chromatography, in solid/liquid extraction, in heterogeneous catalysis or in capillary electrophoresis. The process comprises the grafting onto the silica of hydrosilanes containing 1 silico
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Fischer Christian
Mignani Gerard
Priou Christian
Moore Margaret G.
Rhodia Chimie
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