Synthesis, Characterization And Application Of Waterborne Polyurethane Crosslinker

Wpu not only has the excellent properties, such as high strength and high resistance to abrasion, but also wpu is safe, non-toxic, operating-processing convenient, non-ignitable, easy-storage and friendly to the environment, so it has received extensive attention. However, because of the limitations of the synthesis conditions self- emulsifying waterborne polyurethane, the molecular weight of polymer is low, and many hydrophilic groups exist in molecular side chain ,the mechanical properties and water resisting properties of latex films are not good, which limited its applied range. In recent years, many researches showed that crosslinking modification is one of the most direct and effective methods to improve the coating performance of waterborne polyurethane. The physical and chemical properties of latex films of WPU can be modified by introducing ketone carbonyl into the molecular chain of waterborne polyurethane, using the reactivity of ketone carbonyl (ketone hydrazine reaction) to prepare WPU which have crosslinking reaction during film formation.So it is quite a meaningful job to synthesize small dihydroxy compounds that can bring ketone carbonyl into molecule of waterborne polyurethane by using cheap and easy-obtained materials, exploring simple synthetic route and appropriate processing parameters.A double-hydroxylalkyl compound containing ketone carbonyl was synthetized, through nucleophilic substitution reaction of halohydrocarbon; and then introduce the ketone carbonyl into the chain segment of polyurethane, using the reactivity of ketone carbonyl(ketone hydrazine reaction) to synthesize the polyurethane, which can have crosslinking reaction during film formation; the properties of polyurethane before and after crossliking were also studied by experiment comparison.BHAP was synthesized between diethanolamine (DEA) and 5-chloro-2-pentanone (CPE) as the raw materials, Whish can be used as the crosslinking agent of polyurethane. To improve the yield of BHAP, the effects of factors was discussed, such as temperature, acid binding agent, catalyst and solvent. the product separation and purification were done by extraction, reduced pressure distillation, thin layer chromatography, and column chromatography, and the BHAP content was examined by high performance liquid chromatography analysis. high yield and purification of BHAP was obtained.BHAP had been fully characterized by using Infrared (FTIR) and nuclear magnetic resonance (1HNMR,13CNMR,COSY,HMBC,HMQC), the molecular weight and element constitute of BHAP was determined by HRMS, Structure of the product was confirmed that it obtained corresponds to the expected structure of ketone carbonyl dihydroxy compounds (BHAP).BHAP was linked as modified material to the waterborne polyurethane molecules and crosslinked polyurethane aqueous dispersion (CWPU) was synthesized by prepolymer method, using 2,4- toluene diisocynate (TDI) as hard segment, Polyether 210, 220 as soft segment, N,N-dimethylol propionic (DMPA) acid as ion centre, diethylenetriamine (DEA) as chain extender. The viscosity of CWPU was determined, water absorption, toluene absorption, tensile strength, elongation at break, gel content of Crosslinking polyurethane film was done, and the properties of Crosslinked polyurethane film was studied. The effects of different carboxyl contents and crosslinker contents on different properties of modified polyurethane moisture medium was discussed, and properties of WPU before and after crossliking were analyzed.The results showed that the best conditions of the reaction between DEA and CPE were that the solvent was DMF, the acid binding agent was Na2CO3, the catalyst was NaI, reaction temperature was 73℃and the reaction time was 30h. The yield and the purity of BHAP were 90.74% and 89.66, which were examined by high performance liquid chromatography analysis. The characterization of the product separated by chromatography is as below: FT-IR spectrogram showed that, structure of the product has all expected functional groups, nuclear magnetic resonance spectrum (1HNMR,13CNMR,COSY,HMBC,HMQC) showed that, the structure of the purified product by column chromatography corresponds to the structure of the expected BHAP, high resolution mass spectra showed that data obtained is the same as the molecular weight and element constitute of BHAP. Study of property comparison of crosslinked polyurethane film indicated that molar ratio of NCO/OH is 1.28, carboxyl content is 1.9%: When BHAP mass fraction was 8%, compared with noncrosslinked modification polyurethane, the water absorption of CWPU decreased by 18.48% and toluene absorption decreased by 72.54%, while breaking strength increased 14.25MPa, and gel mass fraction increased by 11.92%. when molar ratio of NCO/OH is 1.28 and carboxyl content is 2.1%, and BHAP mass fraction was 7%, compared with noncrosslinked modification polyurethane, the water absorption of CWPU decreased by 64.7% and toluene absorption decreased by 15.12%, while breaking strength increased 11.81MPa, and gel mass fraction increased by 4.43%.