Synthesis, Characterization And Application Of Waterborne Polyurethane Crosstinker-Chain Extender5,6-dihydroxyhexan-2-one

A new crosslinker for waterborne polyurethane (WPU),5,6-dihydroxyhexan-2-one(DHO), was synthesized by nucleophilic substitution and hydrolysis from acetylacetone (ACA) and epichlorohydrin (ECH), the effects of reaction conditions on the yield of DHO were investigated, and characterized by means of FTIR, NMR and MS. The results showed that under the optimal reaction conditions of ethanol as the solvent,sodium ethylate as catalyst,reaction temperature60℃, reaction time15h, the yield of5,6-epoxy-2-hexanone(EHO) was34.2%,5-(acetyloxy)-6-hydroxy-2-hexanone was prouduced in synthesis of EHO,the yeild is29.68%.Hydrolysis rection condition as follow:perchloric acid as catalyst, reaction temperature90℃, reaction time8h, the yield of DHO was69.5%.The optimal reaction conditions of5-(acetyloxy)-6-hydroxy-2-hexanone hydrolysis was sodium hydroxide as catalyst,reaction temperature80℃, reaction time8h, the yield of DHO was50.4%.The pure DHO was obtained by preparative HPLC systems, The purity of the DHO, obtained by preparative HPLC systems, was95.96%.The process reaction of nucleophilic substitution from ACA and ECH was tracked by UV,The result showed that keto-acetylacetone react with ECH to produce EHO.The structure of DHO contains two hydroxyl groups and one carbonyl group,so it can be used as crosslinker for water-borne polyurethane. There was no tertiay amines groups of DHO,so avoided its catalytic effect to ammonia ester bond,and the small molacular weight of DHO also make the water dispersion process easy. In this experiment a series of WPU,which contained different DHO,were prepared by Acetone method,using2,4-toluene diisocynate(TDI),N,N-dimethylol propionic (DMPA) gly col,poly ether210and220as base material,triethylamine as neutralizing agent,diethylenetriamine as chain extender.Then those WPU films were tested and studied in water absorption, toluene absorption, tensile strength and elongation at break. The result showed that molar ratio of NCO/OH is1.28, carboxyl content is2.04%: When DHO content is7%, compared with non-crosslinked modification polyurethane, the crosslinked one’s water absorption decreased by68.13%and toluene absorption decreased by50.97%, while breaking strength increased6.211MPa, elongation at break decreased138.32%and gel mass fraction increased by3.78%.