Synthesis Of Photosensitive Polyurethane Oligomer And Its Application In Imitation Leather Coating

Polyurethane imitation leather coating fabric based on textiles can fill the market shortage of natural leather.However,solvent coating processing technology is often used in conventional imitation leather fabrics,which not only causes environmental pollution,but also seriously endangers the health of employees and can not meet the requirements of national and social sustainable development of the environment.In this paper,a flexible photosensitive polyurethane acrylate(PUA)oligomer was designed and prepared by UV-LED light curing technology,aiming at the special requirements of imitation leather fabric on flexibility,hand feeling and other properties.The comprehensive requirements of coating on processing rheological properties,photopolymerization properties and coating film properties were met through the structural regulation of oligomer and the compounding of monomer components,which provided a useful exploration for the development of flexible photocuring PUA coating and imitation leather coating products.(1)Dicyclohexylmethane 4,4'-diisocyanate(HMDI),Polyether diol(PTMG),1,4-butanediol(BDO),N-methyldiethanolamine(MDEA)and hydroxyethyl acrylate(HEA)were used as the main raw materials to design and synthesize photosensitive PUA oligomers.The reaction process,end point and PUA structure were detected and characterized by dibutylamine titration,online FTIR and ~1H NMR spectroscopy.The optimal synthesis process was:prepolymerization stage:200 ppm catalyst triethylenediamine(DABCO),temperature 80°C,time 2?2.5 h;Chain extension stage:chain extender MDEA/BDO ratio of 1/1.5(mass ratio),temperature 70°C,time 2h;end-capping:temperature 65°C,time 6?7 h.(2)The structure-activity relationship of coating polymerization system showed that:appropriately reducing the oligomer R value can increase the molecular weight of the oligomer,increase the chain length between adjacent crosslinking points of the cured film,and improve the flexibility of the coating film;multifunctional end-capped PUA and multifunctional monomer have branched structure and more reactive groups,which can improve the photopolymerization performance of the polymerization system,the crosslinking density of the cured film and the wear resistance of the coating film;the monomer component can effectively adjust the rheological properties of polymerization system and affect its polymerization performance.Based on rheological,photopolymerization and mechanical properties,the optimal polymerization system was as follows:the ratio of PUA oligomer/HEA/EOTMPTA912 was 60%/32%/8%,the R value of PUA oligomer was 1.3,and the ratio of HEA/PETA was 2/1.(3)Using UV-LED as irradiation source,the suitable high efficient photoinitiator system and additives were selected to construct a light-cured skin-like coloring coating agent.The optimized coating processing conditions are:coating thickness 0.2 mm,scraping speed 2 m/min;irradiation intensity 24?36 m W/cm~2,irradiation time 30?60s.The photocured imitation leather colored coating fabric prepared by curing and bonding processes has excellent dry and wet rubbing fastness(grade 4?5 and above),soft handle,excellent wear resistance(50000 times in Martindale)and aging resistance.