Ciba-geigy Corporation

Werner Preiswerk

Beat Bruttel

The invention relates to a process for preventing the gelation of concentrated aqueous photoactivator solutions containing sulfonated zinc or aluminium phthalocyanines. The process comprises passing a crude solution containing these compounds, when preparing the solutions, through a semipermeable asymmetrical membrane having a pore diameter of 1 to 500 .ANG.. This membrane consists of a basic structure of cellulose acetate, polyacrylonitrile or a copolymer of acrylonitrile and other ethylenically unsaturated monomers. This basic structure is modified in specific manner with ionic groups. The concentrated photoactivator solutions so obtained have excellent storage stability, do not gel, and contain exceedingly small amounts of inorganic and organic impurities.

Process for preventing the gelation of concentrated aqueous

The invention relates to a process for the preparation of solid photoactivator formulations containing sulfonated zinc or aluminum phthalocyanines. The process comprises passing a crude solution containing these compounds through a semipermeable asymmetrical membrane having a pore diameter of 1 to 500 .ANG. and drying the photoactivator solution obtained under mild conditions. The membrane consists of a basic structure of cellulose acetate, polyacrylonitrile or a copolymer of acrylonitrile and other ethylenically unsaturated monomers. This basic structure is modified in a specific manner with ionic groups. If desired, fillers and/or surfactants customarily employed in the detergent industry may be added to the concentrated solution before it is dried. The solid photoactivator formulations so obtained have excellent storage stability, are substantially non-hygroscopic, and contain exceedingly small amounts of undesirable organic impurities.

Growing community of inventors

Binningen, Switzerland

Werner Preiswerk