油墨的主剂用英语怎么说？

Ink the main agent

直接用base，看看人家怎么写的：

使用前，应将主剂和硬化剂按比例混合搅拌均匀
The base and hardener should be mixed according to
the ratio and stirred thoroughly before using.

main injection of printing ink
或者 main ingredients of printing ink