关键词: 水性聚氨酯, 超纤革, 上染速率, 吸附等温线, 动力学模型

Abstract: With the shortage of natural leather resources and the enhancement of people's awareness of environmental protection, the development of artificial leather products that can replace natural leather has become a trend of the industry. In recent years, synthetic leather products have been widely used in household, automobile and other industries. As the artificial leather products are most like natural leather at present, microfiber synthetic leather is often dyed to further expand its application range. In the dyeing process of microfiber synthetic leather, the dyeing properties of microfiber and polyurethane were not consistent, and the problems of levelness and poor color fastness often arise in the dyeing process. For the solvent based polyurethane microfiber leather, the current dyeing methods and technologies can meet the market demand. For the waterborne polyurethane microfiber leather, influenced by hydrophilic monomers, the internal structure of the polyurethane is changed, and the adsorption and diffusion behavior of dyes on waterborne polyurethane microfiber leather are also changed correspondingly. At present, the dyeing mechanism and dyeing properties of waterborne polyurethane microfiber leather are rarely studied. In order to improve the dyeing technology of waterborne polyurethane microfiber leather, it is necessary to study the dyeing behavior theoretically.
In this paper, the adsorption kinetics and dyeing thermodynamics of waterborne polyurethane microfiber leather dyed by weak acid dye blue MD-R and neutral dye isolan grey respectively were studied. The uptake of both kinds of dyes on waterborne polyurethane microfiber leather were improved with the increase of dyeing temperature. The blue MD-R was easily to desorpt from waterborne polyurethane microfiber leather, and the equilibrium dye rate decreased. While the neutral dye was easily to congregate, high dyeing temperature was helpful for dispersion and diffusion, so at 90 ℃ the equilibrium dye rate was increased significantly. During the dyeing process, the adsorption of the two dyes conformed to the quasi-second-order kinetic model. There were many micro interstice between the waterborne polyurethane and polyamide microfibers in the leather. During the dyeing process, the dyes were adsorbed on the surface of the microfiber leather and gradually penetrated into the interstice. The isothermal adsorption of the two dyes on the waterborne polyurethane microfiber leather was consistent with Freunlich adsorption model. The thermodynamic calculation results showed that the dyeing affinity of the two dyes were increased with the increasement of temperature. The dyeing of waterborne polyurethane microfiber leather with the weak acid dye was an exothermic process, while with the neutral dye was an endothermic process.

Key words: waterborne polyurethane, microfiber leather, dyeing rate, adsorption isotherm, dynamic model