Cationization Of Cotton Fabric And Its Effect On Dyeing Properties Of Reactive Dyes

The dyeing wastewater discharged in the traditional reactive dye dyeing process has problems such as high inorganic salt concentration and high chroma.This is mainly due to the need to add a large amount of electrolytes such as Na Cl in the traditional process to overcome the electrostatic repulsion between the fiber to be dyed and the dye.Moreover,the utilization rate of reactive dyes in this process is not high,resulting in a large amount of dyes that are not used and are directly discharged into dyeing wastewater.In order to solve the above problems,this paper chose the DMC modification method to cationize the cotton fiber to enhance the positive charge of the fiber in the dye solution and promote the combination of reactive dyes.This modification is a redox initiator composed of K₂S₂O₈-Na HSO₃,which is initiated by free radicals to graft the DMC monomer to the cotton fiber macromolecule,and successfully realizes the cationization of the cotton fiber.The grafting of DMC on cotton fiber was proved by FT-ATR-IR,and the modified fiber was characterized by X-ray diffraction(XRD),X-ray photoelectron spectrometer(XPS)and scanning electron microscope(SEM).The experiment also used three commonly used reactive dyes,reactive yellow M-3RE,reactive red M-3BE and reactive brilliant blue KN-R,to dye the modified cotton without salt,and use the cationic content of the modified cotton and the dye uptake rate E%And fixation rate F%as an index,determined the optimal grafting reaction conditions such as the molar ratio of K₂S₂O₈ to DMC,the amount of DMC,the reaction temperature and the reaction time.Through optimization of conditions,the fixation rate of reactive yellow M-3RE,reactive red M-3BE and reactive brilliant blue KN-R under salt-free conditions can be as high as 95.3%,92.9%and 95.1%,respectively.Salt dyeing can only reach 69.2%,70.3%and 67.8%respectively,and the dye utilization rate has been greatly improved.However,the experiment found that after dyeing DMC modified cotton,the color of the fabric sample will change significantly.GTA is also a good cationic reagent for fiber modification,which can be carried out by impregnation process.It was found that the modified cotton fiber could be dyed without salt by GTA impregnation.By GTA modification,the dyeing rate and color fixation rate of three kinds of reactive dyes of cotton fiber can reach more than 90%without salt,and the color fastness can also meet commercial requirements.At the same time,the colouring properties of raw cotton fiber,GTA modified cotton and DMC modified cotton were studied by the test of fiber's yellowness,whiteness and L*,a*,b*.The results showed that GTA modified cotton also had an effect on the dyeing colouring of cotton fabric.However,the degree of color light change of GTA-modified cotton is lower than that of DMC modified cotton,which may be due to the difference of the functional groups connected by the cationic groups of the two.Moreover,the polymerization of DMC in the graft reaction increases the length of the cationic chain,which has a greater effect on the association behavior of the dye in the dye solution.