基于光谱分析技术的宣纸用铝盐施胶沉淀剂作用机理研究

摘要

为了明确铝盐沉淀剂在书画宣纸表面施胶过程中的作用机理,利用Ferron逐时络合分光光谱、高场27Al核磁共振波谱(27 Al-NMR)以及衰减全反射红外光谱技术(ATR-FTIR)研究了明矾(Alum)、聚合氯化铝(PAC)及聚合硫酸铝(PAS)三种常用铝盐施胶沉淀剂的水解聚合铝形态、与胶料混合后在宣纸表面施胶时的铝形态分布变化.(1)Ferron逐时络合分光光谱和27Al-NMR分析表明,明矾及聚合硫酸铝的水解产物主要为单核铝Al(H2O)3+6(Al1),AlSO+4和多核铝[Al30O8(O H)56(H2O)24]18+(Al30);聚合氯化铝除 Al1, Al30外,还存在笼式结构的多核铝[AlO4Al12(OH)24(H2O)12]7+(Al13);(2)27Al-NMR分析表明,铝盐与明胶混合后单核铝、多核铝形态的共振峰强度均有所降低,结合A T R-FT IR分析结果可知,降低的各正价态水解聚合产物很可能与明胶微粒中羟基(—O H)或羧基(—COO H)产生了键合,形成了网状络合物,将原本带负电的明胶粒子转化为带正电的明胶粒子,促使明胶微粒沉淀在带负电的纤维表面,起到施胶沉淀剂的作用.施胶后,明胶胶原蛋白的羟基、一部分氨基和羧基与植物纤维表面的非离子区域的羧基能形成众多的分子间的氢键,提高宣纸抗水性.因此,Ferron逐时络合分光光度法、高场27Al-NMR及ATR-FTIR技术相结合可迅速判断各类铝盐沉淀剂在宣纸表面施胶过程中的化学形态变化,是研究施胶机理的有效手段.%In order to investigate the action mechanism of aluminum salts in the process of surface sizing of Xuan paper used in painting and calligraphy,the aluminum species distribution of Alum,polyaluminum chloride(PAC)and polyaluminum sulfate (PAS),which were commonly used as sizing precipitant,in aqueous solution and mixed with gelatin on the surface of Xuan pa-per were studied by Al-Ferron complex timed spectrophotometric method(Al-Ferron),high-field 27Al-NMR spectroscopy(27 Al-NMR)and attenuated total reflection infrared spectroscopy(ATR-FTIR)for the first time.(1)Al-Ferron and 27Al-NMR analy-sis showed that the hydrolysis products of alum and PAS solution were mainly monomeric aluminum Al(H2O)3+6(Al1),AlSO+4 and polymeric aluminum[Al30O8(OH)56(H2O)24]18+(Al30);except for Al1and Al30,polymeric aluminum[AlO4Al12(OH)24 (H2O)12]7+(Al13)was also existed in PAC solution;(2)27Al-NMR analysis showed that the peaks of monomeric and polymeric aluminum were weakened significantly with the combination of aluminum salt and gelatin,and the results of ATR-FTIR showed that the reduced positive hydrolyzed products were probably bonded with hydroxyl(—OH)or carboxyl(—COOH)from gelati-n.The tight network structure they formed could improve the crosslinking and water-resistance of the glue.Meanwhile,as a role of precipitants,aluminum hydrolyzed products could transform negative gelatin particles into positive charge,prompting ge-latin particles deposited on the negatively charged fibers.After sizing,the hydroxyl groups,some amino and carboxyl groups of gelatin collagen could form many hydrogen bonds with the carboxyl groups in the non ionic region of the plant fibers,so the wa-ter resistance of the Xuan paper was improved obviously.In summary,as an effective means to study sizing mechanism,the combination of Al-Ferron,high-field 27Al-NMR and ATR-FTIR technology can rapidly reveal the chemical structure changes of aluminum salts in paper sizing process.