酰化单宁的制备及其鞣制性能

Preparation and tanning properties of acylated tannin

以单宁为原料,制得酰化单宁。优化反应条件,并以酰化单宁为鞣剂进行皮革鞣制,测定皮革的性能并推断鞣制机理。结果表明,将1 g单宁溶于6 g三氟乙酸中,添加1.5 g乌洛托品,在100℃下回流反应1.5 h,制备得到醛基含量为2.33 mmol/g的酰化单宁。以酰化单宁为鞣剂,鞣制皮革的收缩温度可达(85.3±2.5)℃,撕裂强度为(47.7±1.3)N/mm,抗张强度为(10.2±1.1)MPa,断裂伸长率为97.9%±2.0%,优于未改性单宁鞣制的皮革。此外,鞣制的皮革还具有较强的抗紫外性能。酰化单宁保留了其原有的活性基团,在鞣制过程中与皮革胶原纤维分子形成氢键交联作用,引入的醛基可以和胶原纤维分子中的氨基发生反应形成稳定的化学键。在两种作用力的共同影响下,使得皮革的性能得到显著提高。

Acylated tannin was prepared from tannin, the reaction conditions were optimized and the acylated tannin was used as tanning agent for leather tanning. The properties of the tanned leather were measured and the tanning mechanism was inferred. The results showed that by dissolving 1 g of tannin in 6 g of trifluoroacetic acid, adding 1.5 g of hexamethylenetetramine, and reflux reaction for 1.5 h at 100 ℃, the acylated tannin with aldehyde group content of 2.33 mmol/g was prepared. The shrinkage temperature of leather tanned with acylated tannin was(85.3±2.5) ℃, the tear strength was(47.7±1.3) N/mm, the tensile strength was(10.2±1.1) MPa, and the elongation at break was 97.9%±2.0%, which were better than those of unmodified tannin tanned leather. In addition, the tanned leather also had strong anti-ultraviolet capability.Acylated tannin retained their original active groups, which could form hydrogen bond cross-linking with leather collagen fiber molecules during the tanning process. The introduced aldehyde groups could react with the amino groups in the collagen fiber molecules to form stable chemical bonds. The combined influence of the two forces made the properties of tanned leather significantly improved.