Study On Blue Light Curable Pigment Inkjet Printing Of Textiles

Textile inkjet printing is a revolutionary innovation compared to conventional textileprintings. However, dye-based inks still suffer from water and energy consumption, adaptabilitylimitation to fabrics. Substituting pigment-based inks for dye-based inks in textile inkjet printingis an effective way to solve these problems. Nevertheless, pigment-based inks usually sufferfrom the nozzle clogging problem, which has been hindering their applications in textile inkjetprinting. Exploitation of a new textile pigment inkjet printing technology with security, efficient,environmental and broad fabric adaptability properties has important academic significance andapplication value.Compared with thermal curing technology, the blue light curing technology, based on thereaction of excited molecules, presents unique advantages such as high efficiency, low cost, safeand low curing temperature. In this study, the integration of photocuring technology with textileinkjet printing was proposed by substituting oligomers and monomers for polymeric binder.During the inkjet printing process, oligomers and monomers are stable with excellent fluidity forink ejection. Once under the light irradiation, the oligomers and monomers are able topolymerize and form a tough film in situ on the fabric surface, achieving an expected colorfastness. To achieve this goal, some works have been carried out including the optimization ofthe blue light photoinitiating system, the construction of the low viscosity photocurablecomponents, the compatibility between colorant and photocurable ink, the performance of inkjetprinting, and the evaluation of the printing effect on fabrics. Beneficial theories andtechnological achievements have been obtained as guidances for preparation of the blue lightcurable ink for textile inkjet printing.1. The kinetics studies of CQ/EDMAB blue light photoinitiating system indicated that,Rp,maxof TMPTA is proportional to [PI]0.5and [I0]0.5, and would decreased under a highconcentration of CQ/EDMAB because of the “filter effect”. Therefore, a suitable photoinitiatorconcentration should be considered in applications. The initiating process of CQ/EDMABcombination demonstrated that, a high efficient hydrogen donating reaction occurred betweenCQ and EDMAB leading to the destruction of the conjugated double-ketone structure and the“Photo-bleaching” phenomenon. UV-vis spectra of CQ/EDMAB were recorded during the blue light initiating process. By comparison the spectra variations of CQ/EDMAB and the theoreticalspectral information calculated by time dependent density functional theory, the intermediatestructure CQ·-in the blue light initiating process was affirmed.2. Based on CQ/EDMAB photoinitiating system, a four-component efficient blue lightphotoinitiating system was exploited. The addition of the photosensitive synergistic agent DPI inCQ/EDMAB can improve the utilization rate of CQ, generate new active species andsignificantly increase the photoinitiating efficiency. The addition of the anti-oxygen inhibitionagent TTMSS can effectively convert the peroxy radicals to new active species, and obviouslydecrease the oxygen inhibition. Due to the synergistic effect of DPI and TTMSS, there was nosignificant induction period of oxygen inhibition in the optimized CQ/EDMAB/TTMSS/DPI (1wt%/0.5wt%/0.5wt%/0.25wt%) system, and its polymerization rate was higher than that ofCQ/EDMAB initiating systems in nitrogen atmosphere over50%.3. A low viscosity urethane acrylate oligomer was synthesized under optimized synthesisconditions using IPDI, HEA and a specially selected low molecular weight polyether diol, andthe synthesis process and the reaction endpoint were monitored by FT-IR spectroscopy. Thesynthesis conditions in the first step (without catalyst,80oC, n(PPG-1000): n(IPDI)=1:2) is thekey point to reduce side reactions and prepare a low viscosity product. The rheologymeasurements verified that the self-synthesized urethane acrylate oligomer behaved as a classicalNewtonian fluid with low viscosity property (0.884Pa·s) at25oC; the photopolymerizationperformance indicated that the self-synthesized urethane acrylate oligomer acted as a typicaldi-functional acrylate oligomer following a bimolecular termination mechanism. Rp,maxof theurethane acrylate oligomer is proportional to [PI]0.5and [I0]0.5; the surface tension of the urethaneacrylate oligomer is34N·m-1, and can be adjusted by mixing with different kinds andproportions monomers to meet the wettability requirement of different substrates.4. Compared with the typical commercial oligomers, the self-synthesized urethane acrylateoligomer showed obvious low viscosity property, which can be further decreased by monomerregulation or increasing the temperature. The viscosity of the photopolymerizable system(PUA/HEA=60wt%/40wt%) can be decreased to0.0302Pa·s at65oC, which satisfies the basicviscosity requirements of the inkjet printing process. By realizing the structure-activity relationship between the structure of monomers and the physical and mechanical properties ofthe copolymer film, a soft, elastic and strong copolymer film was obtained based onPUA/IBOA/HEA=60wt%/30wt%/10wt%. The physical and mechanical properties of thecopolymer film basically met the requirements of the textiles wearability.5. The application performance of the blue light curable pigment ink for textile inkjetprinting were carried out and the results demonstrated that, the dispersing agent Tech6270canimprove the dispersion stability of pigments in ink through three-dimensional protective effect;due to the physical shielding of the incident light, the blue light polymerization performance ofthe blue light curable pigment ink decreased to a certain extent, and can be improved byincreasing the concentration of the photoinitiators or light intensity. The basic performance of theprinted fabrics indicated that, an ideal apparent color depth obtained at a relatively low pigmentconcentration using textile inkjet printing technology. The increase of the photoinitiatorconcentration, light intensity and the optimization of the photopolymerization system werebenificial to increasing the fabric rubbing fastness. The handle of the printed fabrics mainlydepended on the physical and mechanical properties of the cured film.6. With the optimized blue light curable pigment ink formulation CQ/EDMAB/TTMSS/DPI(1wt%/0.5wt%/0.5wt%/0.25wt%), PUA/IBOA/HEA=60wt%/30wt%/10wt%，Tech62701.5wt%，pigment0.1-2wt%, the ejection behavior was smooth in the simulating jet printing process,and the printed fabrics showed bright color, sharp outline and soft handle. The dry and wetrubbing fastness of the printed fabrics reached grade4-5and3-4in nitrogen and air atmosphere,respectively.