|
In the tanning process, tanning is the key, retanning was known as the "Golden Touch ",so the importance of leather tanning agent can be seen. In modern tanning process, thechrome tanning agent was used most widely. However, chrome tanning agent can causeserious environmental pollution, while the crust of chromium resources are very limited, so itis nerious to seek new imminent leather tanning agents.Lignin is rich in nature as renewable resources, it is green and cheap. Because of itsstructure contains hydroxyl groups, which can cross-link raw skin collagen, so it can be usedto make leather tanning agent.This article aims to synthesize leather tanning agents from black liquor lignin and studythe tanning performance of lignin agents.(1) Lignin was extracted by acid precipitation and purified. The Pd/C was used as catalyst tocatalyze hydrogenation of the purified lignin. The optimum conditions are as follows: thetemperature is90℃, the reaction time is3h, lignin tanninng agents was obtained. Theproduct was analyzed by X-ray spectrometry, Folin-Ciocalteu reagent method, UV-VIS,FTIR and GPC. The results showed that the content of the impurity in purified ligninreduced from31.4%to8.9%; Lignin group was increased after hydrogenation, the contentof phenolic hydroxyl increased30.12%. Lignin molecular weight distribution is uniform.(2) Lignin tanning agent was used to tanning pre-pickling skins. The effects of differentamount of lignin tanning agents on leather physical properties were studied. The resultsshowed that when the amount of lignin was12%, the physical properties were best.Leather was soft and full, grain was tight, shrink temperature was91.6℃, the averagedeviation of the thickness was0.0049mm, tear strength was16.6N mm.(3) Lignin tanning agent was used to retanning positive pig, it was investigated with differentcontent on the effect of re-tanning, The results showed that when the amount of lignin was2%, the physical properties of leather was best, the flexibility and softness were good,good fullness, grain tightness, shrink temperature was94.8℃, tensile strength was14.5N/mm~2, tear strength was19.3N mm. In this article, a new proposal of the synthetic of lignin tanning agents was put forwardand a new idea for further research of lignin structure, application and leather tanning agentsynthesis were provided. Lignin can completely replace the other vegetable tanning agents inthe tanning process. As by-product of paper industry, lignin was used to prepare tanning agent,it can not only reduce the cost of tanning, also have practical significance for environmentalprotection and low-carbon economy.
|