Synthesis And Performances Of UV-curable Polysiloxane-polyether Block Polyurethane Acrylates For PVC Leather Finishing Agents

As necessary leather auxiliary used for leather surface coating, leather finishing agents can not only protect the leather from damaging, but also beautify the leather surface, thereby covering the shortage of the artificial leathers. The leather finishing agents cooperating with photopolymerization technique exhibit unique advantages, such as fast-curing, low energy consumption, solvent-free formulations and high efficiency, compared with traditional leather finishing agents with the problem of environmental pollution and poor efficiency. Polysiloxane-modified polyurethane acrylate prepolymers can effectively combine excellent performances of polysiloxane and polyurethane. The products based on the prepolymers have good wear-resistance, high ductility, good flexibility, excellent mechanical property, resistance to high and low temperatures and perfect biological compatibility. Generally, the introducing polyether chains into the silicone-containing polyurethane acrylate prepolymer can effectively enhance the compatibility between soft segments and hard segments of the prepolymer molecule and improve the properties of the prepolymers. Besides, the cost is dramatically reduced without compromising to other excellent performances. Hence, the photopolymerizable polysiloxane-polyether block polyurethane acrylate prepolymers would exhibit great advantages in improving product performance, modifying production processes and reducing the cost. In this work, eight novel photopolymerizable polysiloxane-polyether block polyurethane acrylate prepolymers (DSi5E5PUA, TSi1E9PUA, TSi3E7PUA, TSi5E5PUA, TSi7E3PUA, TSi9E1PUA, TSi5E5PUAl and TSi5E5PUA2) were synthesized. The effect of the degree of functionality, polysiloxane chains content and molecular weight on the performance of prepolymer was investigated. Furthermore, the performances of leather finishing agents for PVC leather based on the polysiloxane-polyether block polyurethane acrylate prepolymers were also studied in ditail. The specific work and study results are as follows:1、Eight novel polysiloxane-polyether block polyurethane acrylates with different degree of functionality, gradual increase of polysiloxane chains content and different molecular weight were synthesized based on hydroxyalkyl-terminated polysiloxane, polypropylene glycol (PPG-2000), isophorone diisocyanate (IPDI), diethanol amine and 2-hydroxyethyl acrylate (HEA). And their structures were confirmed by Fourier transform infrared (FTIR), gel permeation chromatography (GPC), proton nuclear magnetic resonance (1H NMR) and silicon nuclear magnetic resonance (29Si NMR).2、The effect of degree of functionality on the viscosities and photopolymerization kinetics of prepolymers, and the physical and chemical properties of the UV-cured films was investigated. The results show that the increase of degree of functionality improved the photopolymerization efficiency of prepolymers, but it had no effect on the viscosities. Furthermore, the water repellency, tensile strength, glass transition temperature and thermostability of the UV-cured films were also enhanced by cooperated with multifunctional prepolymers and monomers.3、The effect of polysiloxane chains content in prepolymer molecules on the viscosities and photopolymerization kinetics of prepolymers, the physical and chemical properties of the UV-cured films was investigated. It was found that the increase of polysiloxane chains content improved the viscosities, but it had no effect on the photopolymerization efficiency, the yellowing resistance, gel yield and water absorption of UV-cured films. The UV-cured films had a good yellowing resistance and their volume shrinkage during the photopolymerization process was less than 6%. Besides, when the prepolymer contained more polysiloxane segments, the corresponding UV-cured film had relatively good thermal stability, elongation at break and surface hydrophobicity.4、The effect of molecular weight of prepolymer molecules on the viscosities and photopolymerization kinetics of prepolymers, and the physical and chemical properties of the UV-cured films was investigated. The increase of molecular weight dramatically increased the viscosities of the prepolymers. TSi5E5PUAl had the best photopolymerization kinetics resulted from its suitable viscosity among TSi3E PUA, TSi E^PUAl and TSi5E5PUA2. The UV-cured films had good yellowing resistance, and their water absorption was 3.9%-4.4%. The corresponding contact angle and dispersion surface energy were 74 °-76 ° and 85 mN/m-90 mN/m. Moreover, the increase of molecular weight enhanced the tensile strength and elongation at break of UV-cured films, and reduced the volume shrinkage.5. DSi5E5PUA, TSi5E5PUA, TSi7E3PUA, TSi9E1PUA, TSi5E5PUA1 and TSi5E5PUA2 can all be applied to leather finishing agents and exhibited excellent comprehensive performances. The coating that had outstanding adhesion to PVC leather was smooth and dry. And coating appearance did not change after being boiled in deionized water for 360h at 80℃, being folded for 6×104 times at room temperature as well as being scrubbed 2000 times with alcohol.