| Waterborne polyurethane (WPU) is generally used in the industry of leather, spinning, building, adhesive, coating, etc, as its characteristics of polyurethane material and environmentally friendly. The higher solid content of WPU emulsion is demanded as taken the economical efficiency of transportation and energy conservation into consideration, therefore, high solid content emulsion has becoming one of the mainly development direction of WPU. In this paper, research is aimed at the WPU emulsion’s defects such as low solid contents, bad stability, etc. The high solid content, stability WPU emulsion was prepared out from the appropriate raw materials with designed the formula under the controlled synthesis condition, the properties of the emulsion and film with different formula and under different prepare condition were investigated as well.In this paper, the WPU emulsion was designed to be prepared through stepwise polymerization of the2,4-toluene diisocyanate (TDI) and propylene glycol polyether (N210, Mn=1000) as the main raw materials, the dimethylol propionic acid(DMPA) as the hydrophillic chain extender, the diethylene glycol (DEG) as micro molecular chain extender, triethylamine (TEA) and sodium hydroxide (NaOH) mixing to a scale as neutralizer. The effects of the formula factors such as R value(n-NCO/n-OH), the contents of DMPA and DEG, molar ratio of TEA and NaOH, mass ratio of DMF and DMPA, the degree of neutralization, chain extension methods, the process factors such as pre-polymerization temperature, time, and chain extension methods on the WPU emulsion properties and the film properties were studied. The experimental results showed that the suitable formula was with the R value between1.5-1.7,5.0%of DMPA,1.0-1.3%of DEG, the molar ratio of TEA and NaOH was7:3, the mass ratio of DMF and DMPA was2.00:1,and100%of the degree of neutralization. The exact preparation process was divided into three steps. The first step was the mixing of TDI and N210in60℃for2.5h. The second step was the reaction with DMPA at75℃for2h. The final step was the reaction with DEG at75℃for1h. The WPU emulsion preparation process was the neutralization, chain extension by DEG, and the dispersing into water, the produced WPU emulsion could be with the solid content of60.84%, average grain diameter of207.2nm at bimodal distribution, low viscosity, and high stability.Following conclusions were got from this research:1. Contents of hydrophillic monomer DMPA decisively influenced the emulsion particle size and viscosity. The level of DMPA should be as low as possible in the premise of the stability of the emulsion. In this paper, the suitable content of DMPA was5.0%.2. The kind of neutralizer also influenced the emulsion particle size and viscosity. The stronger of the neutralizer’s alkaline, the smaller and narrower of the emulsion average particle size and distribution, such as, TEA and NaOH.3. The amount, kind and content influenced the emulsion particle size and viscosity. Bimodal distribution, low viscosity, high solid content and good stability WPU emulsion was prepared by two kind of neutralizer with different alkaline, The experimental results showed that the emulsion solid content beyond60%was prepared while the the molar ratio of TEA and NaOH was7:3.4. Particle size analyzer (PCS), Transmission Eletron Microscope (TEM) test results revealed that the emulsion had an average particle diameter207.2nm with a bimodal distribution.5. Mechanical property and thermogravimetric analysis test results played that the WPU film got good mechanical property and heat stability. |
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