Carretti Emiliano, Giorgi Rodorico, Berti Debora, Baglioni Piero
Department of Chemistry and CSGI, University of Florence, via della Lastruccia 3 - Sesto Fiorentino, 50019 Florence, Italy.
Langmuir. 2007 May 22;23(11):6396-403. doi: 10.1021/la700487s. Epub 2007 Apr 25.
A novel class of p-xylene-in-water microemulsions mainly based on nonionic surfactants and their application as low impact cleaning tool in cultural heritage conservation is presented. Alkyl polyglycosides (APG) and Triton X-100 surfactants allow obtaining very effective low impact oil-in-water (o/w) microemulsions as alternatives to pure organic solvents for the removal of polymers (particularly Paraloid B72 and Primal AC33) applied during previous conservation treatments. The ternary APG/p-xylene/water microemulsions have been characterized by quasi elastic light scattering to obtain the hydrodynamic radius and the polydispersity of the microemulsion droplets. Laplace inversion of the correlation function CONTIN analysis provided evidence of acrylic copolymers solubilization into the oil nanodroplets. Contact angle, Fourier transform infrared (FTIR), and scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS) data confirmed that microemulsions were effective in removing polymer coatings. The phase diagram of APG microemulsions showed that a reduction >90% (compared to the conventional cleaning methods) of the organic solvent can be achieved by using o/w microemulsions. The microemulsions were successfully tested in two real cases: (1) the APG based microemulsion was used in a Renaissance painting by Vecchietta in Santa Maria della Scala, Siena, Italy, degraded by the presence of a polyacrylate coating applied during a previous restoration and (2) a Triton X-100 oil-in-water microemulsion containing (NH4)2CO3 in the water continuous phase. The association of ammoniun carbonate to the microemusion led to the swelling of an organic deposit (mainly asphaltenes deposited on the fresco in the Oratorio di San Nicola al Ceppo in Florence, still contamined by the water of the Arno river during the 1966 flood) and a very efficient removal of highly insoluble inorganic deposits (mainly gypsum) strongly associated to asphaltenes. These innovative systems are very attractive for the low amount of organic solvent used to extract the polymers or highly insoluble substances as the asphaltene and the very efficient and mild impact of the cleaning procedure on the fragile painted surfaces.
本文介绍了一类新型的对二甲苯/水微乳液，其主要基于非离子表面活性剂，并阐述了其作为低影响清洁工具在文化遗产保护中的应用。烷基多苷（APG）和吐温X-100表面活性剂能够制备出非常有效的低影响水包油（o/w）微乳液，可替代纯有机溶剂用于去除先前保护处理过程中施加的聚合物（特别是Paraloid B72和Primal AC33）。通过准弹性光散射对三元APG/对二甲苯/水微乳液进行了表征，以获得微乳液滴的流体动力学半径和多分散性。相关函数CONTIN分析的拉普拉斯反演提供了丙烯酸共聚物溶解于油纳米滴中的证据。接触角、傅里叶变换红外光谱（FTIR）和扫描电子显微镜/能谱（SEM/EDS）数据证实微乳液在去除聚合物涂层方面是有效的。APG微乳液的相图表明，通过使用o/w微乳液，有机溶剂的用量可减少>90%（与传统清洁方法相比）。这些微乳液在两个实际案例中得到了成功测试：（1）基于APG的微乳液用于意大利锡耶纳圣玛利亚德拉scala教堂中韦基耶塔的一幅文艺复兴时期绘画，该绘画因先前修复过程中施加的聚丙烯酸酯涂层而受损；（2）一种水连续相中含有（NH4）2CO3的吐温X-100水包油微乳液。碳酸铵与微乳液的结合导致有机沉积物（主要是1966年洪水期间阿诺河水仍污染的佛罗伦萨圣尼古拉阿尔切波祈祷室壁画上沉积的沥青质）膨胀，并非常有效地去除了与沥青质紧密结合的高度不溶性无机沉积物（主要是石膏）。这些创新体系极具吸引力，因为用于提取聚合物或高度不溶性物质（如沥青质）的有机溶剂用量少，且清洁过程对脆弱的绘画表面具有高效且温和的影响。
