Abstract: Before the advent of synthetic dyes, natural dyes had a long history of use and wre very widely used in the world. Black is one of the five normative colors in China. There has been a great demand for successive dynasties, so the black natural dyes are indispensable in China's dyeing history. Oak acorn is one of the most important sources of brown and black dye in China, which is the fruit of Quercus acutissima. Its main component is tannin. Many ancient books, such as Compendium of Materia Medica, Be Capable of General Affairs, and T'ien-kung k'ai-wu, recorded the dyeing process related to oak acorn. With the advent of synthetic dyes, the use of natural dyes fell silent for a long time. However, natural dyeing has regained popularity in recent years due to contemporary consumer interest in environmentally friendly printing and dyeing, as well as the discovery of the many benefits of using natural dyes derived from plants and animals.
In order to explore a faster, more efficient and scientific dyeing process of oak acorn, Response Surface Methodology (RSM) was used to optimize the oak acorn dyeing process, with ferrous sulfate as the mordant, K/S value and Integ value as the response value. In this study, the factors influencing the dyeing process, such as dyeing temperature, dye concentration, mordanting temperature, mordant concentration, dyeing time, mordanting time, and pH, were investigated using the Plackett-Berman experiment to screen the significant influencing factors on oak acorn dyeing. Factors with P-values higher than 0.05 were considered as non-significant. Based on the P-value, the factor of dyeing temperature was found to be the most influential factor on the color depth of oak acorn dyeing, followed by dye concentration and mordanting temperature. After the significant factors were clarified, the response surface methodology (RSM) was carried out using the central composite design (CCD) method. Then, the response surface results were obtained and the response surface model was analyzed, based on which the interaction between oak acorn dyeing results and each dyeing factor was analyzed. Based on the above, K/S value and Integ value as the response value, the optimization model of the oak acorn dyeing process was established and the differences of the obtained response surface models were compared. It was found that the optimal oak acorn dyeing process - the dyeing temperature was 82.9 ℃, the dye concentration was 200% (owf), and the mordanting temperature was 53.5 ℃. The dyeing results showed that increasing the dye concentration and dyeing temperature can improve the K/S and Integ values of acorn-dyed silk, but the mordanting temperature should not exceed 60 ℃. The results of RSM experiments showed that the value of Integ is more suitable as the response value of natural dye oak acorn seed dyeing, which can more accurately reflect the change of color depth, and the validation results are in line with the predicted values, which indicates that the model is reasonable in design, stable and reliable. In addition, the color fastness results of silk showed that the dyed silk fabrics had good resistance to washing, rubbing and sunlight, which were all above grade 3.
The experiments showed that RSM provides a simple and reliable method to optimize the oak acorn dyeing process. It also provides a reference for the subsequent deconstruction of the dyeing methods recorded in ancient documents. In addition, when the dye composition was analyzed in this study, it was found that its up-dyeing components were divided into ellagic acid. Therefore, the experimental design of this study may have important reference significance for the process optimization of tannin-based natural dyes containing ellagic acid.

Key words: natural dyes, Oak acorn, RSM, K/S, Integ value.

摘要： 橡碗子是中国古代最常用的黑色天然染料之一，也可用于现代生态染色。以硫酸亚铁为媒染剂，K/S值和Integ值作为响应值，采用响应面法（Response surface method, RSM）对橡碗子色素在丝绸上的染色工艺进行优化。先采用Plackett-Berman实验筛选出影响染色工艺的显色因素：染色温度、染液浓度和媒染温度；再利用RSM获得橡碗子色素染色丝绸的最优染色工艺条件：染色温度为86.5 ℃、染液浓度为200%(o.w.f)、媒染温度为53.5 ℃。实验结果显示，RSM为橡碗子色素在丝绸上的染色工艺提供了一种简单可靠的优化方法，其中以Integ值为响应值的模型表现出了更优异的交互性。本优化工艺可为天然染料橡碗子的现代染色应用研究提供参考，也可为其他单宁类天然染料的染黑工艺的研究提供借鉴。

关键词: 天然染料, 橡碗子, 响应面法, K/S, Integ值