But, because phosgene is virulent, strong caustic chemical, make MDI development got restrict, but very great progress already was obtained since abroad is not phosgene law craft 25 years.

• 但是,由于光气是剧毒、强腐蚀性的化学品,使MDI发展受到了限制,但国外非光气法工艺25年以来已取得了很大进展。