The Development And Mechanism Of A Novel Direct Inkjet Thermosensitive Ink For Textile

Thermal sublimation inks are widely used for coloring polyester fiber today.The ink is typically printed on transfer paper first before transferring the inks to the polyester fiber under high-temperature heat and pressure.A more efficient print method,direct printing inkjet technology,was developed to lower production costs and reduce solid waste during the last decades.The ink containing sublimation dye can be printed on fiber directly without generating any transfer paper waste.Direct printing technology requires a pretreatment procedure on the fiber before printing.The pretreatment will prevent ink on the fabric from penetrating,which will cause a fuzzy image on the fiber.After sizing printing color under high temperature,the fiber needs a desizing step to wash out all the pretreatment chemicals,which will generate wastewater.To further shorten the coloring process and reduce chemical waste,we report a novel digital printing technology that can avoid any pretreatment and desizing steps.The copolymer piece,poly(ε-caprolactone-colactide)-b-poly(ethylene glycol)-b-poly(ε-caprolactone-co-lactide)(PCLA-PEG-PCLA)was synthesized and formulated into a dispersion inks for digital inkjet printing application.The inks stay in the liquid sol form in a cartridge at room temperature and can quickly turn to a high viscosity gel stage on the heated fabric.The gel state prevents ink droplets from spreading around,significantly improving printing image sharpness and quality.Compared with the traditional methods,thermosensitive ink is harmless to humans and biodegradable.There are no pretreatment and desizing steps required before or after printing.Certainly,no transfer paper is needed as well.Thermosensitive ink is capable of applying to any polyester fabric.This new technology can significantly shorten the process flow,reduce chemical consumption,eliminate transfer paper needed,and ease the environment’s burden.This novel technology aligns with the green textile manufacturing idea and will offer broad application prospects.The specific work is as follows:(1)Synthesis and characterization of PCLA-PEG-PCLA triblock copolymerThe PCLA-PEG-PCLA triblock copolymer was prepared by a ring-opening polymerization reaction with PEG as the initiator and stannous octoate as a catalyst.Analytic methods,1H-NMR,FT-IR,and gel chromatograph have proven the structure.Transition properties of the sol-gel triblock copolymer were analyzed by rotational viscometer and rheometer methods.The copolymer is in the amorphous stage based on XRD and DSC analysis,which is essential for the subsequent stably dispersed temperature-sensitive ink formulation.(2)Thermosensitive ink preparation and ink physicochemical propertiesBlue,yellow,red and black pastes were first prepared using the non-ionic dispersant LasperseTM8390 to disperse the disperse dyes,which were milled using a nano-scale bedroom sander.Temperature sensitive direct disperse dye inks were then prepared by adding different concentrations of PCLA-PEG-PCLA to the inks to give them sol-gel transition properties.The effect of PCLA-PEG-PCLA on the ink’s physical properties was investigated,including viscosity,mean particle size,conductivity,pH,and surface tension at room temperature.The thermosensitive inks are stable under 4℃ storage conditions.Rheometer test,inverted tube analysis,and rotational viscometer indicate that the inks have excellent sol-gel transition properties at a specific temperature.The higher the PCLA-PEG-PCLA content,the higher the maximum viscosity of the thermosensitive ink and the lower the temperature at which the viscosity increases.(3)Digital printing evaluation of the thermosensitive inkPermeability of the copolymer inks on fiber decrease as the concentration of PCLAPEG-PCLA increases at 24℃ or 55℃.The ink line width printed with thermosensitive inks is very close to the original setup’s ideal line widths.The thermosensitive inks can produce a sharp and distinct image quality with a high concentration of PCLA-PEGPCLA copolymer.The K/S,L*,a*,b*and C*values of the fabrics printed with thermosensitive inks are excellent compared with the commercial product.Wash fastness,dry and wet rubbing fastness of polyester fabrics printed with thermosensitive inks is level 5 for blue and 4 for red,yellow,and black colors.