| Pigment coatings for textiles in dyeing and printing have many advantages, such as a simple and short product process, little wastewater, and low production cost. However, organic pigments are insoluble in the water-based media used for application, they are commonly used as dispersions with the addition of dispersing agents. They have no affinity for fabrics; therefore, a binder is required to fix pigment particles on the fiber surface to give colorfastness. Pigment and polymer latex are the most important ingredients in water-based paint and ink formulations. Thermal curing process may be required to polymerise binder molecules with each other resulting in adhering the pigments to textile. Thermal curable pigment printed textile must be dried and then cured with heat to convert the binders to a tough polymer leading to consuming large amounts of energy. UV curing was performed at ambient temperature, in addition, UV technology is also known for space saving, fast curing speed and short start-up period. It could eliminate the drying steps and drastically reduce consumption of energy during curing process to print with UV-curable pigment paste, where pigments were dispersed in UV-curable formulations containing oligomers and photoinitiators, and be cured with ultraviolet radiation.Different from the UV ink & coating with high demands on hardness and strength of the cured film, pigment printing has very high requirements on the softness, flexibility and water resistance. Design one kind of UV-curable polyurethane acylate with softness, good flexibility, low cross-linking density, low shrinkage rate. Bifunctional polyurethane acrylate was synthesized by two steps from toluene diisocyanate(TDI), polyethylene glycol(PEG) and 2-hydroxyethyl acrylate(HEA) via solution polymerization, use ethylene glycol or 1,3-butanediol as the chain extenders. The effects of reaction temperature, catalysts, inhibitive substance were discussed and the most suitable reaction conditions of every reaction were acquired. The quantity ratio of four monomers was n(TDI):n(PEG):n(HEA):n(chain extender)=4:2:2:1. Firstly, TDI and HEA reacted at room temperature(25?) for an hour, then added the chain extender and reacted at 25~30? for 15 min. At last, added HEA and reacted at 40? for 5h. The appropriate quantity of DBTDL was 0.3% and the proper dosage of quinol was 0.15%. The effects of molecular weight of PEG and chain extenders on curing rate, the cured film's properties were discussed in detail. With the increase of PEG weight the cured film's properties of hardness, acid resistance, solvent resistance would reduce and the property of wearing resistance flexility and adhesion to glass would be enhanced.Compared with common PUA, chain-extended PUA, which are synthesized from the same PEG, the latter's curing rate is much slower than the former's. As the consequence, the latter's cured film would have a serious problem of yellowing. Chain extension has no relationship with the cured film's properties of water resistance, acid resistance, alkali resistance and hardness. But after chain extension the cured PUA film's flexility and adhesion to glass are enhanced.Because of high viscosity of oligomers, plenty of monomers are added to the paste to attain a feasible viscosity, and too much monomer would decrease the density of the film of the oligomers which contributes to bad crockfastness. Lack of thixotropic property restricts applications of UV-curable paste in textile printing, as well. The waterborne UV technology, using water as diluent, could solve the problems mentioned above.Anionic and non-ionic oligomer O/W emulsions were produced by ultrasonic dispersion of the usual oligomer respectively in SDBS or Boltorn? W3000 aqueous solutions. The present work studies various factors affecting the stability and droplet size of the oligomer-in-water emulsion stabilised by SDBS or Boltorn? W3000. The optimal SDBS concentration was 2.5%, under which condition the stability of the emulsion increased as the emulsifier content increased, with a subsequent decrease in the droplet size of the emulsion, while above which emulsion agglomeration occurred. Similarly, the optimal Boltorn? W3000 concentration was 5.5%. Increasing the power and duration of ultrasonic dispersion resulted in increased emulsion stability and decreased droplet size, while increases in the oligomer content reduced the emulsion stability. When the ultrasonic power was 1000 W, the particle size of emulsion obtained by ultrasonic emulsification 20 min was small and narrow distributed. Compared with anionic oligomer emulsion, non-ionic oligomer emulsions has better storage stability.The emulsifier will affect the water resistance of the cured PUA film, self-emulsified PUA contains hydrophilic group in the polyurethane chain to give the polyurethane acrylate good water dispersibility, avoid the use of emulsifiers. Self-emulsified PUA was prepared by using dimethylolpropionic acid(DMPA) as hydrophilic chain extender in the introduction of hydrophilic groups in the molecular chain of PUA. Hydroxyl active hydrogen in hydroxyl silicone oil can react with isocyanate, hydroxyl silicone oil can be introduced into the polyurethane acrylate to improve the water resistance of PUA cured film.UV-curable waterborne polyurethane emulsion modified with PDMS was prepared by using isophorone diisocyanate(IPDI), hydroxyl silicone oil(PDMS1000), polyethylene glycol(PEG600), dimethylopropionic acid(DMPA), hydroxyethyl methacrylate(HEMA) as the main raw materials, finally neutralized with triethylamine(TEA) and emulsified in deionized water. The reaction rate of-NCO is closely related with the concentration of PMDS. When the concentration of PMDS was less than 10%, the reaction rate of- NCO was very high. With the increase of concentration of PMDS, reaction rate reduces gradually.With the increase of concentration of PDMS, the pencil hardness, water resistance, chemical resistance of UVcurable waterborne polyurethane curing membrane were improved, but beyond a certain concentration, the performances were no longer increased, the best concentration of PDMS is between 10%-20%.Color of pigment will be affected by lattice structure, organic pigment arrangement, crystallinity, crystal type and particle size and distribution, fundamentally there were great difference in UV light refraction, reflection and absorption of the pigment with different crystal type, particle size, scattering, crystal. Single crystal type of phthalocyanine blue pigment were prepared by controlling the process of organic pigments, alpha phthalocyanine blue with smaller crystal size and regular arrangement, the effect on the UV absorption, reflection and refraction were minimum. Ball milling processing rely on the powerful role of mechanical impact and the friction shear stress change the crystal type and particle size, compared to the kneading phthalocyanine blue, phthalocyanine blue ball milling method has a more regular crystal shape, the three edges of the cell edge length gap smaller, so the crystal arrangement will be more Compact and neat. Introduction of halogen in the CuPc molecule in the crystal plane arrangement affects the convergence in the crystalline molecular plane of the accumulation, inhibition of molecule beta type lattice forms compact, piled up, will make the pigment crystal more pure, reflecting more bright colors. Due to the single pure crystal. P.R.254 pigment with smaller particle size has higher UV light transmittance.Using chain extender PUA emulsion and hydroxyl silicone oil modified PUA as pigment printing binder, selecting of high UV light transmission pigment as coloring material, UV curable pigment printing has good properties of printed fabrics. Curing speed is very fast, high definition, hydroxy silicone oil modification improves the wet rubbing fastness of printed fabric using waterborne polyurethane acrylate as binder. |
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