PURPOSE: To mate draft angle unnecessary by using an amorphous resin contg. a ring structure combined in its molecular main chain for forming a syringe cylinder and specifying respectively its heat distortion temp., coefficient of thermal expansion, molding shrinkage, water absorption, etc., in resin-made syringe cylinder with no draft angle.
CONSTITUTION: In a syringe cylinder with no draft angle, the free end 22 of a plunger 2 is inserted into the inner side of the cylinder and a piston 3 can be freely advanced to the innermost part of the syringe cylinder, namely a position where the piston is brought into contact with the apex wall and the shapes of seal rings 31-33 of this piston 3 are not changed from the shapes at the inlet. In this case, as a material for forming the syringe cylinder, an amorphous resin contg. a ring structure combined in its molecular main chain is used. In addition, the resin satisfying such properties as heat distortion temp. of at lest 70°C, coefficient of thermal expansion of at most 7×105, molding shrinkage (both in longitudinal and transverse directions) of at most 0.8(%), water absorption or at most 0.01(%) and gas (O2) permeability of at most 60-(g/m2.24H) is used.
KIKUCHI MASAHIKO
HAMAMOTO KEIJI
KOBAYASHI HIDEO
DAIICHI SEIYAKU CO