The Synthesis And Application Of UV-curable Cationic Waterborne Polyurethane Acrylate Adhesives

Textile dyeing and finishing has been the water and energy consumption of consumersand polluters, industry is in urgent need of new technology to satisfy the requirements ofenergy saving and environmental protection. With the application of aliphatic isocyanate andreducing with the use of nitrogenous chain extender, yellowing problems of cationicpolyurethane improved. Cationic waterborne polyurethane is not sensitive to water hardness,suitable for anionic textile and leather processing. Radiation curing technology is differentfrom traditional technology uses energy efficient as the initiation means to achieve rapidcuring coating. The excellent characteristics of water dispersible UV curing technology ofwater dispersion and radiation curing joined at the same time, it overcomes the shortcomingsof high viscosity and low performance of water-based resin, potential skin irritation andother shortage of UV technology while energy saving and environmental friendly, is beingregarded more and more widely.Using4,4’-dicyclohexyl methane diisocyanate (HMDI), polytetramethylene ether glycol(PTMG1000), N-methyl two ethanol amine (MDEA) as the main raw material, hydroxyethylacrylate (HEA) as the blocking agent, A series of stable double-terminated UV reactivecationic waterborne polyurethane dispersions was synthesized, while the structure wasconfirmed by infrared spectroscopy, laser particle size analysis and free NCO root titration;modified by co-monomer hydroxyethyl acrylate with the UV radiation fast curing, theinfluence of hydroxyethyl acrylate proportion and the polyurethane’s nNCO/nOH(R value) tothe thermal properties, mechanical properties and yellowing of the product was investigated.The investigation illustrated the UV-curable cationic waterborne polyurethane acrylate filmeffectively forming a semi-interpenetrating network system to achieve rapid curing coating.The results showed the product cured by WPU dispersion of R=1.5mixed with equimolar HEA obtained low yellowing, the maximum breaking strength, high elongation at break,high thermal decomposition temperature, high crystallization temperature of hard segment,low glass transition temperature of soft segment, high degree of phase separation, betteroverall performance. Water resistance experiment showed that polyurethane in waterswelling consistent with Fick’s diffusion theorem, the smaller R value, PTMG soft segmentcontinuous phase is longer, the greater the saturated water absorption rate.The difficulty of emulsifying process of WPU dispersions increased, stability decreased,WPU particle size increased, the stability of the emulsion decreased when the PDMS isadded into WPU dispersions. The preparation process of PDMS in the whole WPUdispersions in uniform dispersion is very important, if uniform dispersion, the mechanicalproperties reducing of film will significantly delay or even improved by synergistic effect.Because of the hydrophobic component was added, the drying speed is reduced, it is easy toleave the pores after curing, resulting in decreased water resistance. When the content ofPDMS is more than5%, PDMS saturated inside the molecules, PDMS will migrate to themacromolecular surface, improve the water resistance.The application of UV curable cationic waterborne polyurethane-acrylate on the cottonfabric, resin coated on each fiber instead of fabric surface，while have good adhesion, smallyellowing, soft feel, the overall implementation of good adhesive effect as expected.