Stabilisierte Suspensionen von SiO2-Partikeln

(A1) Die vorliegende Erfindung betrifft eine Suspension von SiO2-Partikeln, umfassend oder bestehend aus: (a) einer aeusseren Phase, umfassend oder bestehend aus: (a1) polymerisierbaren Monomeren, Oligomeren und/oder Prepolymeren und (a2) einer oder mehreren co-polymerisierbaren oder nicht co-polymerisierbaren organischen Saeuren und (b) einer dispergierten Phase, bestehend aus: oberflaechenmodifizierten und/oder nicht oberflaechenmodifizierten SiO2-Partikeln, wobei die SiO2-Partikel mittels eines Sol-Gel-Verfahrens herstellbar sind und eine mittlere Teilchengroesse von maximal 100 nm besitzen, wobei die Art und die Menge der co-polymerisierbaren oder nicht co-polymerisierbaren organischen Saeure bzw. Saeuren so ausgewaehlt ist, dass die oberflaechenmodifizierten und/oder nicht oberflaechenmodifizierten SiO?2?-Partikel nach Vermischen von 1 Gewichtsteil Hexamethylendiisocyanat-Biuret mit 1 Gewichtsteil der Suspension gegen Zusammenballung zu Partikeln einer mittleren Teilchengroesse von zumindest 1000 nm stabilisiert sind.

DE 102007003622 A1 UPAB: 20081023 NOVELTY - A novel suspension (I) of silicon dioxide particles (SDOP's) comprises (a) an external phase comprising (a1) polymerizable monomers, oligomers and/or prepolymers and (a2) copolymerizable or other organic acid(s) and (b) a dispersed phase consisting of optionally surface modified SDOP's. The acid (a2) stabilizes the SDOP's against agglomeration in presence of hexamethylene diisocyanate biuret. DETAILED DESCRIPTION - A novel suspension (I) of silicon dioxide particles (SDOP's) comprises: (a) an external phase comprising (a1) polymerizable monomers, oligomers and/or prepolymers and (a2) copolymerizable or other organic acid(s); and (b) a dispersed phase consisting of optionally surface modified SDOP's, prepared by a sol-gel process and having average particle size at most 100 nm. The amount and nature of the acid(s) (a2) are such that the SDOP's are stabilized against agglomeration to particles of average size at least 1000 nm after mixing equal weights of hexamethylene diisocyanate biuret and (I). INDEPENDENT CLAIMS are included for: (1) the preparation of (I), by forming a pre-suspension containing an external phase and (b), then mixing with the organic acid(s) (a2) (optionally in anhydride form); (2) the use of the organic acid(s) (a2) for stabilizing suspended, optionally surface modified SDOP's against agglomeration; and (3) a partially or completely hardened dispersion, obtained by polymerization of components (a1) in (I). USE - (I) is specifically a clear or pigmented lacquer system (claimed), especially for use in the automobile sector. The SDOP's are included in (I) to increase the fracture resistance, impact strength, modulus, scratch resistance and abrasion resistance and reduce the shrinkage on hardening and thermal expansion, and in comparison with conventional reinforcing fillers cause a lesser increase in viscosity and can be incorporated in larger amounts. ADVANTAGE - Inclusion of the organic acid component (a2) greatly reduces agglomeration, aggregation and flocculation of the SDOP's in (I), even when (I) is treated with other binders, solvents, additives and/or reactants (specifically isocyanates).