Synthesis And Properties Of Silicone Modified Polyurethane Coating Agent For Synthetic Leather

Silicone possesses excellent properties such as low surface energy, thermal stability, oxidation resistance and biocompatibility. But the mechanical and adhesive performance is poor. However, polyurethane has superior mechanical properties but not-so-good thermal stability. Silicone modified polyurethane(Si-PU)combines the advantages of both, overcome the disadvantage. It's a promising polymeric material.Synthetic leather is a kind of plastic product, which imitates the physical structure and applied properties of leather and has partially taken place of the leather materials. As the development of environmental protecting, now synthetic leather has been widely used for clothing, portfolio, sofa etc. Coating can effectively improve synthetic leather's physical and mechanical performances, color and luster of the surface properties.Solvent type Silicone Modified Polyurethane (Si-PU) block polymers were synthesized with isophorone diisocyanate (IPDI), Polyoxypropyleneglycol (PPG), hydroxy-terminated poly-dimethylsiloxane(DHPDMS), 14-Butanediol(BDO), trimethylolpropane(TMP). The FT-IR spectroscopy showed that the silicone chain segment was incorporated into PU macromolecule. The influence of reaction conditions on reaction and Si-PU solvent was studied. Results showed that the optimal temperature is 65℃, the solvent is mixed MEK and BA, the quantity of catalyst is about 0.54wt% of all reactants. The influence of the ratio of the materials on the properties of Si-PU solution and film was explored.The results showed that Si-PU film possess similar mechanical properties with PU film when the content of poly-dimethylsiloxane (PDMS) segment is below 16wt%. It had good solvent resistance without obvious loss of mechanical property when the content of TMP is 7wt%. It had relatively small viscosity and better storage stability and similar mechanical property with PU film when the ratio of n(OH)/n(NCO) in all is about 1.05 and the ratio of n(OH)/n(NCO) is about 0.25 in the prepolymerization stage. The thermal stability is improved. Si-PU solution was applied on synthetic leather as coating agnet. The influence of the mass fraction of PDMS on the property and adhesion of Si-PU coating was explored. The results showed that the water contact angle of the coating surface was increased from 66o to 102o when the mass fraction of PDMS was increased from 0 to 10wt% without obvious loss of mechanical property. Meanwhile, the oil resistance level is increased from grade 2 to grade 5 (AATCC118-2002). The water and oil resistance of coating can be kept when the content of PDMS is over 10wt%. Adhesion level can be kept on grade 2 when the content of PDMS is 10-16wt%. The study on the influence of finishing process showed that the optimum diluent is BA, dilution ratio is 2.0-2.5, the usage of finishing agent is 7g/m2, cure temperature is 150℃, cure time is 2.5 hours, cure method is hot blast.