Study On Dyeing Technology Of Disperse Dye On Bi-component Sheath-core Polyester Fiber With Low Melting Point

Low melting point polyester is a new type of modified polyester with low melting point. It can be produced by adding a number of modified components which can change the molecular structure of PET and reduce its crystallinity. Bi-component sheath-core polyester fiber with low melting point can be obtained with low melting point polyester and conventional polyester. This bi-component fiber can be blended with wool to improve the dimensional stability and anti-pilling property of wool fabrics. Now the study of synthesis, structure and properties of low melting polyester and application to improve the dimensional stability and anti-pilling property of wool fabrics are universal, but its dyeing technology has not been reported. Therefore, study on dyeing technology of bi-component sheath-core polyester fiber with low melting point is very impotant.In this paper, the bi-component sheath-core polyester fiber with low melting point was taken as main research object and the conventional polyester fiber as reference object. Chemical structure, crystal property, thermal property, physical and mechanical property of these two types of polyester fibers were studied by modern analytical methods. The result showed that bi-component sheath-core polyester fiber with low melting point was made of low melting point polyester and conventional polyester. The sheath is low melting polyester and the core is conventional polyester. The ratio of sheath to core is about 50:50. Compared with conventional polyester fiber, bi-component fiber's chemical structure is no significant different and thermal performance is slight poor. The glass transition temperature of low melting point polyester is 72.66℃and the melting point is 130.06℃. The arrangement of molecular chains is relatively orderless and the integrity of crystallization is poor. The breaking strength is almost as the conventional polyester fiber. The extension and breaking time is increased for a certain degree.The optimum dyeing process with disperse red SE-GFL, disperse yellow M-4GL and disperse blue 2BLN1% ( o.w.f.)for bi-component sheath-core polyester fiber with low melting point was determined through the single factors and orthogonal experiments: T=85℃, t=60min, pH=5.5 and liquor ratio is 1:30. The results showed that some indexes such as color depth and color fastness of the fiber dyed with the optimum dyeing process were close to or above those indexes of conventional polyester fiber dyed at high temperature and pressure. However, its dyeing permeability is poor and disperse dyes remain in the cortex of the low melting point polyester fiber.Two typical disperse dyes such as Disperse Red SE-GFL ( azo ) and Disperse Blue 2BLN (anthraquinone) were used to dye the fiber. The dyeing kinetics and dyeing thermodynamics of disperse dye on the bi-component sheath-core fiber with low melting point were studied as well. The results showed that the type of adsorption isotherm of disperse dye on bi-component sheath-core fiber with low melting point was the same as that on conventional polyester fiber, both of which are conforming with Nernst distribution mechanism. Compared with dyeing with disperse dye on the conventional polyester fiber, dyeing with disperse dye on the bi-component sheath-core fiber has some features, i.e. the dyeing rate increase greatly, half-dyeing time decrease, diffusion coefficient and dyeing affinity enhance, absolute value of dyeing heat and dyeing entropy reduce.Then the better one-bath dyeing process with disperse dyes and Lanaset dyes for bi-component sheath-core polyester fiber with low melting point/wool fiber was determined through the optimizing the low temperature dyeing process of wool fiber, studying the staining of dyes and compatibility of agents: dispersant NNO 2g/L, effective compound penetrant 1g/L, dyeing temperature 85℃, dyeing time 60min, pH value 5.0~5.5, liquor ratio 1:30. The results showed that color depth and color fastness of the fiber dyed with the better one-bath dyeing process basically meet the production requirements.