| 摘要 |
PURPOSE: To provide an ink reverse flow-preventing element for a water-based ink ballpoint pen which is scarcely deformed by an impact, etc., and has excellent follow-up performance. CONSTITUTION: An ink reverse flow preventing element for a water-based ink ballpoint pen comprises base oil made of silicone oil having viscosity of 4 to 8Pa.s at 25 deg.C, viscosity improver and polyester plasticizer in such a manner that the plasticizer of 0.3 to 0.8wt.% is contained. |
