Component Analysis Of The Color Stains On Polyester Or Polyester/Spandex Knit Blends And The Low-Cost Corresponding Solution

The demand for new fabrics made of fiber blended, intertexture and composite textile is growing greatly. Polyester/spandex knit blend is one of the typical new fabrics. However, color stains of polyester/spandex knit blends is easy to occur when dyeing with disperse dyes of brilliant blue color. The color stains on the finished fabric will lead to a very negative effect for economic efficiency of an enterprise. Therefore, it is essential to reduce or eliminate color stains during dyeing process.In order to solve the problem of color stain on polyester/spandex knit blend and find a reasonable and economic solution, the samples of Shanghai Challenge Textile Company Limited (SCT) were studied in detail in this paper. Firstly, the position and the morphology of color stains on the fabric were observed by Scanning Electron Microscope (SEM). Then, the suitable organic solvents were selected to dissolve color stains on the fabric. The solution mixtures were separated by using Thin Layer Chromatography (TLC). The ingredients of color stains were roughly identified by the spots numbers and Rf value. The melting point of the purified solid residue was measured by using melting point apparatus. Finally, the related functional groups of solid residue were characteristiced by means of Fourier Transform Infrared Spectroscopy (FT-IR).In addition, the impact factors for the formation of color stain were investigated by concerning the physical and chemical properties of the dyes and the auxiliaries. Dispersibility of disperse dyes and auxiliaries were tested by double filter paper method. K/S values of grey fabric and dyed fabric after migration were measured by color matching instrument. The migration rate of dyestuff was calculated based on the K/S values. The heating coherence of disperse dyes were determined by staining method. The formation of color stains were obtained by observing the dye particles appearance with optical microscope under different heating processes.The improvement for the process, including tank washing, pre-treatment and dyeing recipe are aimed at low-cost corresponding solution for reducing or avoiding color stains.The main results are summarized as following:(1) The color stains on fabric can be dissolved effectively in ethyl acetate by heating reflux extraction. The main composition of color stains is dyestuff, which comes from the aggregation of dyestuff or the sedimentation of solid residue, such as pre-treatment oils, dyes caking, and oligomer.(2) The dispersibility and the diffusivity of Blue S-R and Blue S-RWF are mean level. But their migration are poor. Blue S-R together with auxiliaries at high temperature appears punctuate condensate occasionally. But its heating coherence is related to crystalline state during heating. The formation of color stains can be avoided by rapid heating from90oC to120oC. However, heating too fast causes the color difference. The heating coherence of Blue S-RWF is independent with crystalline state.(3) The formation of color stains can be avoided if the dispersant and the leveling agent are selected rightly. As for the dispersibility, HS-2085and DMB are better than WS. If concerning the migration, DMB is the best. While the degree of improvement for migration property with HS-2085or WS will be different when used for different dyestuffs. The migration property of Blue S-R and Blue S-RWF can be improved greater by WS than HS-2085.(4) During actual production, the color stains often form on the fabric, which made of superfine (0.5D) or extra-fine (ID) yarns when dyed by Blue S-R or Blue S-RWF. The color stain is also appeared frequently in dye vat D27, D28and D60. Therefore, periodic cleaning of the dye vat is very important. Moreover, the formation of color stains are closely related to the consumption of dyestuff. Usually, the color stains will appear when consumption of Blue S-RWF is above0.58%o.w.f.(5) The color stains can be avoided if HS-2085was substituted by WS when dyeing polyester with Blue S-RWF, and the production cost can be reduced by75%.