PROBLEM TO BE SOLVED: To provide a rubber stopper for use in freeze-drying, of which the top face can be sucked with a rubber stopper suction holder when the stopper is half-plugged into a vial, and does not stick closely to a press board when the stopper is completely plugged in a freeze-drying chamber.;SOLUTION: The rubber stopper comprises legs which are inserted into the mouth of the vial, a flange which is made to come in contact with the upper edge of the mouth of the vial bottle, and the top face. The main composition of the rubber stopper is chiefly composed of at least one of a group of copolymer consisting of butyl rubber, halogenated butyl rubber, and brominated p-methyl stylene isobutylene copolymer. The top face of the stopper has three to eight projections, and three to eight grooves with each one end open at the end edge of the top face.;COPYRIGHT: (C)2004,JPO
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