Bio-based material PDI can replace the traditional isocyanate used in water-based polyurethane

Keywords: bio-based, methyl isocyanate, water-based polyurethane
background: In recent years, with countries on new materials, new energy areas of increasing attention. In the field of water-based polyurethane, the study of bio-based methyl dichloride (PDI) has gradually become a hot spot for many scientists. PDI is made from 1,5-diamine, and 1,5-diamine is obtained through environmentally friendly biochemical methods, such as fermentation, enzyme catalysis and other methods

. PDI is similar in physical and chemical properties to HDI, but when PDI is used as a hard segment in WPU synthesis, it has a lower raw material consumption due to the higher isocyanate ratio in PDI molecules.
many international industry giants, such as BASF, Covestro and Mitsui Chemical of Japan, have invested a lot of human and material resources in PDI research. Cosco is a leader in research, announcing on January 15, 2015 that it is using biotechnology to prepare lysine from non-food-obtained starch sugar biofermentation, lysine biodexylase catalysis to prepare 1,5-diamine, and then to prepare methyl diocyanate (PDI). Cosco has since launched a range of PDI-based water-based polyurethane products, including water-based two-group crosslinkers. The first PDI-based product was announced in April 2015 with a production capacity of 20,000 t/a in 2016.
Jiao Feng of Nanjing University of Technology and others prepared a series of water-based polyurethane (WPU) dispersions using a pre-polyester process of NCO/OH molar ratio and 1,6-hexiol (HDO)/DMPA) molar ratio, using five methylene 1,5-disocyanates as raw materials. The findings were published in Frontiers of ChemicalScience and Engineering.
the content of the
1. The synthesis of water-based polyurethane dispersion
water-based polyurethane dispersion is synthesized in a four-mouth round bottom burner (500 ml) equipped with a mechanical agitator, thermometer, condenser and argon intake. First, add the PDI and N210 to the cans placed in the oil bath (80 degrees C). In argon, stir about 2h at a medium speed (150-200r/min) to obtain the pre-polymer at the NCO seal end by reacting the active hydroxyl hydroxyl of N210 with the isocyanate base of PDI through a pro-nuclear addition. A certain amount of DMPA is then dissolved in the DMF as a hydro-water-based group, DBTDL as a catalyst, and HDO (chain expansion) is added to the can. After 2 hours, the remaining NCO content reaches the required value. Cool the prejudes to < 50 degrees C and add TEA to medium the acid reaction for 30 minutes. During the process of saling, add acetone to reduce viscosity. Then, disperse the prejudging in ionized water for 30 minutes (scenario 1). Finally, steam for 30 minutes at 50 degrees C to remove acetone in order to obtain WPU. The composition of the WPU dispersion is shown in Table 1.
preparation of the 2.WPU curing film
pours the water-based polyurethane dispersion into a Teflon disc and dries it at room temperature for 24 hours to prepare the film. The coating film is then vacuum-dried at 2 h at 45 degrees C and stored in a vacuum dryer at room temperature.
and performance testing, the authors
series of symptoms and performance tests on the synthetic materials.
effects of 1.NCO/OH molar ratio
(1) Chemical mortification of WPU curing membranes: FTIR spectra of
Figure 1 (a) polyethers, PDI and prejudes, (b) different NCO/FTIR spectra of WPU cured membranes under OH molar ratio conditions, FTIR spectra
(2) WPU curing membranes under OH molar ratio conditions:
Figure 2 Under different NCO/OH molar ratio conditions (a) TGA curve of WPU curing film, (b) DSC curve, (c) XRD Figure
2.HDO/DMPA mormon ratio effect
(1) Chemical characterization of WPU curing film:
(2) thermal properties of WPU curing membranes:
Conclusion:
successfully synthesized a series of WPU dispersions with different NCO/OH molar ratios and HDO/DMPA molar ratios with PDI as a hard segment. The chemical properties, thermal stability, crystallization and physical properties of these dispersions were studied. FTIR results show that increasing the NCO/OH molar ratio or HDO/DMPA molar ratio can improve the degree of orderly hydrogen bonding, while the NCO group can generate arbond bonds during the expansion of the prejudge chain. The improvement of thermal stability is related to higher HDO/DMPA molar ratio or lower NCO/OH molar ratio. An increase in the NCO/OH molar ratio or the increase in the amount of DMPA in the HDO/DMPA molar ratio will reduce the glass transition temperature, possibly due to the increased phase separation in PUs. Finally, due to the fatty family nature of PDI, all WPU curing membranes show a lower stretch strength, of which WPU3.0-2.4 has the greatest stretch strength and shear strength.
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FengJ, Lu Q, Tan W, et al. The influence of the NCO/OH ratio and the1,6-hexanediol/dimethylol propionic acid molar ratio on the properties ofwaterborne polyurethane dispersions based on 1,5-pentamethylenediisocyanate[J]. Frontiers of Chemical Science and Engineering,2019,13(1):80-89.
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