Synthesis And Characterization Of Aqueous Oil-Modified Urethanes

Water-borne polyurethane (WBPU) are now greatly being favored because of its excellent overall performance and good environmental effect. The conventional method to render polyurethane polymer dispersible in water is to introduce hydrophilic group either ionic type or non ionic type on their backbone; however, the hydrophilic nature of group renders WBPUs, poor water and solvent resistant. As compared to solvent based products, there are other drawback such as slow drying, low gloss and poor weatherability. In this paper, to improve the inferior performance above mentioned, vegetable oils are used the raw materials for the manufacture of polyurethane components such as polyols. A kind of new aqueous oil-modified urethanes dispersion (OMUD), with fast-drying, high gloss and good water resistance, was prepared from vegetable oils.First, alcoholysis intermediates were syntheized based on linseed oil and trimethylol propane at the presence of catalyst. The effects of mole ratio of linseed oil to trimethylol propane, catalyst content, reaction temperature and time on the alcoholysis reaction were investigated. The optimum condition of synthesis was mole ratio of 2.0:1, catalyst content of 0.04 wt%, reaction time of 120 min, reaction temperature of 220℃. The chemical changes of alcoholysis process and the structures of alcoholysis intermediates were characterized by Fourier Transform Infrared Spectrum(FT-IR) and Nuclear Magnetic Resonance (~1H-NMR).A kind of anionic aqueous oil-modified urethanes dispersion was prepared with alcoholysis intermediates of linseed oil, polyether polyol, isophorone diisocyanate (IPDI) and dimethylol butyric acid (DMBA) as anionic cencers. The influences of DMBA content and alcoholysis intermediates content for dry time, gloss and water absorption of flim, and the influenees of alcoholysis intermediates content for the glass transition temperature of flim were studied. FT-IR, Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry(DSC), Thermal Gravimetric Analysis (TGA) and electronic tensile machine were employed to investigate the structure and properties of OMUD and their polymers. Especially, the physical and chemical changes of film-forming process for OMUD were discussed by FT-IR. Meanwhile the performance of OMUD and WBPU were compared.The results showed that The particle morphology of aqueous oil-modified urethanes dispersion and water-borne polyurethane were sphercial, the particle size of the former was larger than that of the latter. Two transition temperature were observed for the film from the aqueous oil-modified urethanes dispersion, one corresponds to the glass transition temperature (Tg) of hard segment, the other corresponds to Tg of soft segment. The optimum condition of synthesis was DMBA content of 7 wt%, alcoholysis intermediates content of 45 wt%. The dry time, gloss, water absorption of the corresponding flim was 17 min, 90% and 20.1%, respectively. The decomposition temperature(Td5) of 5 wt% weight loss was 244℃. The original double bond in the OMUD have been reacted during film curing. The dry time, gloss, water absorption and heat resistance of aqueous oil-modified urethanes film much better than water-borne polyurethane, achieve the desired purpose.