| 摘要 |
<p>The present invention relates to a novel method of recovering and recycling active tannins from spent vegetable tanning liquors. Using a low molecular weight alcohol as the extraction agent produces an alcohol fraction or precipitate containing extracted active tannins, and leaves virtually all non-tannins in the aqueous phase of the spent tanning liquor. The methods and resulting chemical mixtures of the present invention have a variety of uses and applications. The method can be applied to freshly produced or aged spent vegetable tanning liquors. The methods are further applicable to dried forms of spent tanning liquors through aqueous reconstitution of dried ReTan, followed by alcohol extraction. The recovered chemical mixture contains recovered tannins which can be recycled through combination with fresh tanning liquors to form an improved tanning liquor.</p> |
