Study of the Dyeing Properties of Annatto and Ultrafiltrated Annatto as Colourants for Natural Fibres

ABSTRACT

Cotton and wool fabrics have been dyed in the absence of mordants with annatto and ultrafiltrated annatto powder. Τhe optimum dyeing conditions were determined as far as the quantity of salt and dyebath pH are concerned. The dyeing properties of annatto and ultrafiltrated annatto were studied by monitoring the dye uptake in various time intervals and temperatures of dyeing. The adsorption isotherms for both annatto and ultrafiltrated annatto were studied. It was found that adsorption of annatto on cotton follows a BET-type adsorption isotherm indicating a multilayer formation of molecules onto cotton, whereas the adsorption of ultrafiltrated annatto follows a Freundlich-type monolayer adsorption. Adsorption of both annatto and ultrafiltrated annatto on cotton occurs through the formation of Van der Waals forces between annatto molecules and cotton substrate. The adsorption on wool of both annatto and ultrafiltrated annatto follows a Freudlich-type adsorption isotherm indicating a monolayer formation occurring between the positively-charged wool substrate and the negatively-charged annatto molecules. The dyeing behavior of natural annatto resembles that of the synthetic direct and acid dyes commonly applied for dyeing cotton and wool. Thus, annatto and ultrafiltrated annatto can successfully replace the synthetic yellow dye component in the dyeing of cotton and wool fibers.

摘要

棉和羊毛织物在没有媒染剂的情况下用红木和超滤红木粉进行染色. 就盐的用量和染浴pH值确定了最佳染色条件. 通过监测不同时间间隔和染色温度下的上染率，研究了红木和超滤红木的染色性能. 研究了红木和超滤红木的吸附等温线. 发现红木在棉花上的吸附遵循BET型吸附等温线，表明分子在棉花上形成多层结构，而超滤红木的吸附遵循Freundlich型单层吸附. 红木和超滤红木在棉花上的吸附都是通过红木分子和棉花基质之间形成范德华力来实现的. 红木和超滤红木在羊毛上的吸附遵循Freudlich型吸附等温线，表明带正电的羊毛基质和带负电的红木分子之间形成单层. 天然红木的染色性能类似于通常用于染色棉花和羊毛的合成直接染料和酸性染料. 因此，红木和超滤红木可以成功地替代合成黄色染料成分用于棉和羊毛纤维的染色

KEYWORDS 关键词:

• natural dyes, 天然染料
• annatto, 红木
• 、ultrafiltration, 超滤
• coloration isotherms, 染色等温线
• wool, 羊毛
• cotton, 棉花

Abbreviations:

• UF, ultrafiltration; o.w.f., on weight of fiber.

Disclosure statement

The authors declare that there is no conflict of interest in the present piece of research work.