PROCESS FOR THE PREPARATION OF AQUEOUS SUSPENSIONS OF ANIONIC COLLOIDAL SILICA HAVING A NEUTRAL PH AND APPLICATIONS THEREOF
The instant invention relates to a process for the preparation of an aqueous suspension of anionic colloidal silica having a neutral pH which is stable over time and comprises individualized particles of colloidal silica which are not bound to one another by siloxane bonds. The instant suspensions show high storage stability and are particularly useful for the clarification of beer, for the preparation of cosmetic formulations, for the production of ink for printers, for paints and for anticorrosive treatments.
1 . A process for the preparation of cosmetic creams and for the production of preparations for protecting the human skin against UV radiation, comprising the steps of:
providing an aqueous suspension of anionic colloidal silica having a neutral pH, which is stable over time and comprising individualized particles of colloidal silica which are not bound to one another by siloxane bonds, where said aqueous suspension of anionic colloidal silica comprises individualized particles of colloidal silica which are not bound to one another by siloxane bonds and has a basic pH which are mixed with an aqueous suspension of anionic colloidal silica comprising individualized particles of colloidal silica which are not bound to one another by siloxane bonds and having an acid pH;
providing a cosmetic cream or a preparation for protecting the human skin against UV radiation: and
contacting said aqueous suspension of anionic colloidal silica having a neutral pH with said cosmetic cream or said preparation for protecting the human skin against UV radiation.
2 . A preparation for protecting the human skin against UV radiation, comprising an aqueous suspension of anionic colloidal silica having a neutral pH, which is stable over time and comprising individualized particles of colloidal silica which are not bound to one another by siloxane bonds, obtained by the process characterized in that an aqueous suspension of anionic colloidal silica comprising individualized particles of colloidal silica which are not bound to one another by siloxane bonds and having a basic pH is mixed with an aqueous suspension of anionic colloidal silica comprising individualized particles of colloidal silica which are not bound to one another by siloxane bonds and having an acid pH.
3 . The preparation according to claim 2 , comprising at least one further component which can scatter, reflect or absorb UV radiation.
4 . The preparation according to claim 2 , comprising, a further component selected from the group consisting essentially of: 2-ethylhexyl p-methoxycinnamate, ethylhexyl salicylate, octocrylene, oxybenzone/benzophenone-3, benzophenone-4, benzophenone-5, ethylhexyl N,N-dimethylaminobenzoate, 4-aminobenzoic acid/PABA, ethyhexyl dimethyl PABA, phenylbenzimidazolesulphonic acid, homomenthyl salicylate, homosalate, isoamyl methoxycinnamate, 4-methylbenzylidenecamphor, 3-benzylidenecamphor, benzene-1,4[bis(3-methylidenecamphormethyl-sulphonic)]acid, camphor benzalkonium methosulphate, phenylbenzimidazole-sulphonic acid, terephthalylidene dicamphor-sulphonic acid, butylmethoxydibenzoylmethane, benzylidenecamphorsulphonic acid, polyacrylamidomethylbenzylidenecamphor, PEG-25 PABA, ethylhexyltriazone, drometrizole trisiloxane, methylenebis-benzotriazolyltetramethylbutylphenol, dioctylbutamidotriazone, disodium phenyl dibenzimidazole tetrasulphonate, bisethylhexyloxyphenol methoxyphenoltriazine, 4-isopropylbenzyl salicylate, terephthalylidenedicamphorsulphonic acid, surface-treated or untreated titanium dioxide, surface-treated or untreated iron oxide, surface-treated or untreated zinc oxide and mixtures thereof.
5 . The preparation according to claim 4 , comprising at least one further component which can scatter, reflect or absorb UV radiation.