Fuji Photo Film Company, Limited

Yoshihiro Tsukimi

Hideo Nagano

Takayuki Matsumoto

A process for producing microcapsules that have a sufficiently broad particle size distribution to be suitable for use in a pressure measuring films, which process is improved in that it eliminates the need to perform blending and filtering operations while reducing the possible loss in capsule solutions or films or operating efficiency of the capsule applicator. A disperse phase is poured into a disperse medium as the latter is stirred in a preliminary emulsification tank, thereby forming a primary emulsion. The primary emulsion is forced into cylindrical continuous emulsification equipment by means of a metering pump. An emulsion having a broad particle size distribution is produced by lowering stepwise the rotational speed of the inner cylinder of the continuous emulsification equipment in accordance with the following schedule: 3 min and 15 sec at 2900 rpm, 4 min and 15 sec at 2700 rpm, 4 min and 15 sec at 2300 rpm, and 3 min and 15 sec at 2100 rpm. Subsequently, water and a 50% aqueous solution of sodium hydroxide are added to the emulsion in an encapsulation tank 4, where an encapsulation reaction is performed for 3 hours at 72.degree. C. with a stirrer being revolved, thereby producing a capsule solution.

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Shizuoka, Japan

Yoshihiro Tsukimi