Preparation and properties of reactive disperse dyes for nylon printing
Nylon,also known as aliphatic polyamide fiber,exhibits excellent performance,such as light weight,elasticity,good thermal stability,and mechanical property.Nylon has been widely used in the manufacturing of sportswear,stockings,conveyor belts,tents,industrial fabrics,and others.Nylon can be dyed by using acid dyes,reactive dyes,or disperse dyes.Nylon fabrics dyed with acid dyes offer vibrant color shades.However,their wet fastness is relatively poor.By employing reactive dyes,the dye molecules can form covalent bonds with nylon fibers by reacting with the amino end groups.Therefore,good color fastness to wet treatment can be achieved.However,reactive dyes usually display limited deep dyeing on nylon.And,the deeper the color,the more noticeable the reduction in color fastness.Dyeing of nylon with disperse dyes provides good levelness and penetration,while exhibits poor color fastness property due to the low affinity between dyes and fibers.Reactive disperse dyes,which are constructed by attaching reactive groups to hydrophobic chromophores,combine the advantages of disperse dyes and reactive dyes.Currently,the most common approach to design reactive disperse dyes involves combining triazine and azo structures.This design concept is simple,effective,and allows for easy synthesis.However,reported molecular designs often directly combine the triazine structure with the primary amino group on the azo structure,greatly impacting the electronic effect of the azo chromophore and consequently affecting the color of the dye.This paper aimed to design seven reactive disperse dyes,E1—E7,by introducing dichlorotriazine moiety onto the hydroxyethyl group of the azo chromophore,and to synthesize the designed dyes by using a two-step method including condensation reaction and coupling reaction.The structures of these dyes were characterized and confirmed by nuclear magnetic resonance spectroscopy,Fourier infrared spectroscopy,and high-resolution mass spectrometry.Nylon fabrics were dyed with reactive disperse dyes with a printing process.The composition for the printing paste was as follows:dye x%,Na2 SO4 3%,NaHCO3 2%,urea 8%,sodium alginate 2.2%,and water.The printing process was performed under the condition of drying at 60℃and steaming at 102℃.The properties of the dyed nylon fabrics,such as levelness,color depth,fixation value,color fastness,migration value,and breaking strength were tested.The results indicate that the colors of nylon fabrics dyed with dyes E1—E7 show various colors of yellow,red,purple,and blue,respectively,with a color difference ΔE ranging from 0.16 to 0.28,which indicates good level dyeing performance.Nylon fabrics dyed with E1—E7 exhibit excellent resistance to organic solvent extraction.In comparison,the color of conventional disperse dye Disperse Blue SE-3RT on dyed nylon fabric can be completely stripped off by DMF.As calculated,dye E1 has the highest fixation value,reaching over 90%,while dye E5 has the lowest color fixation value of 74%.The other five dyes exhibit fixation values of above 80%.Due to the covalent bonding between reactive disperse dyes and fibers,the dyed nylon fabric demonstrates a good color fixing property.The nylon fabrics dyed with dyes E1—E7 exhibit color fastnesses to washing,rubbing,and sublimation of grade 4 or above.The dye migration values of dyed nylon fabrics are less than 5%.The breaking strengths of the nylon fabrics dyed with dyes E1—E7 range from 416 to 446 N,with a decrease in strength of only 1%to 7.6%,as compared with the original nylon fabric.This indicates that the dyeing of nylon fabric using dyes E1—E7 will not significantly damage the mechanical property.The above results provide a new approach for the molecular design of azo-type reactive disperse dyes and their application in dyeing of nylon fabrics.
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