Method of preparing polyvinyl alcohol-silver halide photographic emulsions

Claim 1

A METHOD OF PREPARING WASHED POLYVINYL ALCOHOL-SILVER HALIDE PHOTOGRAPHIC EMULSIONS WHICH COMPRISES THE STEPS OF PREPARING A DISPERSION OF SILVER HALIDE IN AN AQUEOUS SOLUTION OF A GELATIN DERIVATIVE WHOSE PRESENCE RENDERS THE SO-OBTAINED DISPERSION COAGULABLE AT A PH WITHIN THE RANGE OF PH 3-4.5, WHICH DERIVATIVE IS SELECTED FROM THE GROUP CONSISTING OF THE AROMATIC SULFONYL CHLORIDE DERIVATIVES OF GELATIN, THE CARBOXYLIC ACID CHLORIDE DERIVATIVES OF GELATIN, THE CARBOXYLIC ACID ANHYDRIDE DERIVATIVES OF GELATIN, THE AROMATIC ISOCYANATE DERIVATIVES OF GELATIN AND THE 1,4 DIKETONE DERIVATIVES OF GELATIN, COAGULATING THE DISPERSION OF SILVER HALIDE IN GELATIN DERIVATIVE BY ADJUSTING TO SAID PH WHEREBY SILVER HALIDE-GELATIN DERIVATIVE GRAINS ARE FORMED, SEPARATING THE THUS-FORMED SILVER HALIDE-GELATIN DERIVATIVE GRAINS FROM THE LIQUID PORTION OF THE MASS AND SUBSEQUENTLY INCORPORATING THOSE GRAINS IN AN AQUEOUS SOLUTION OF POLYVINYL ALCOHOL, THEREBY FORMING A WASHED SILVER HALIDE-POLYVINYL ALCOHOL PHOTOGRAPHIC EMULSION.