| 摘要 |
PCT No. PCT/EP97/03304 Sec. 371 Date Dec. 30, 1998 Sec. 102(e) Date Dec. 30, 1998 PCT Filed Jun. 24, 1997 PCT Pub. No. WO98/01414 PCT Pub. Date Jan. 15, 19981,4-Dibenzothiazine-comprising crude acrylic acid is purified by crystallization by raising its diacrylic acid content to at least 1% by weight prior to the crystallization step. |
