The Degradation Of Lignin And Synthesis Of Epoxy Resin

Lignin is a kind of renewable biomass resource with abundant content,but its molecular structure is complex,physical and chemical properties are not active,extraction is difficult,so that it can not be fully rational use.By exploring the structural characteristics of lignin,the chemical structure of lignin can be changed by chemical degradation,so as to enhance the activity of lignin.This not only makes full use of lignin resources,but also has an important practical significance to China’s papermaking effluent,environmental management,energy utilization.In this paper,the structural characteristics of lignin and epoxy resin were introduced,and the method for synthesizing epoxy resin using lignin as raw material was also introduced.On the basis of previous researchers,the chemical degradation of lignin(LG)was carried out by the method of ionic liquid([BMIm]Cl)and hydrochloric acid in this paper,and the degradation lignin(DLG)was prepared,the content of hydroxyl in lignin was increased,then under alkaline conditions,the degradation of lignin and epichlorohydrin(ECH)epoxidation reaction occurs to lignin based epoxy resin(LGEP).Firstly,DLG was synthesized by the chemical degradation of LG by ionic liquid and hydrochloric acid.Taking the content of hydroxyl in DLG as index,L9(34)orthogonal experiment was designed to investigate the effects of ionic liquid dosage,hydrochloric acid dosage,reaction temperature and reaction time on the degradation reaction.The results showed that the optimum degradation conditions of LG(corresponding to 0.5g lignin):the dosage of hydrochloric acid was 3mL,the ionic liquid dosage was 3mL,the degradation temperature was 100℃,the degradation time was 4h,under the optimum conditions,the content of phenolic hydroxyl in DLG was 6.72%.Under the alkaline condition,the epoxidation reaction of DLG and ECH was obtained by LGEP.Taking the epoxy value of LGEP as index,L9(34)orthogonal experiment was designed to investigate the effects of ECH content,NaOH content,reaction temperature and reaction time on the epoxy value of LGEP.The results showed that the optimum reaction conditions of LGEP:m(ECH):m(DLG)=3.5:1,m(NaOH):m(DLG)=1:1,the reaction time was 5h,the reaction temperature was 90℃,under the optimum conditions,the epoxy value of LGEP was 0.380.The performance of LGEP was also tested.the results show that the solid content of LGEP was 55.3%,the softening point was 30.5℃,the viscosity was 7.43P,and the water absorption was 0.42.Finally,phthalic anhydride was used as curing agent and three ethylamine was used as accelerator to cure LGEP,and the reaction kinetics of LGEP was analyzed.The results show that the three characteristic temperatures of LGEP curing reaction:Curing gel temperature Ti0=440.12 K,Curing temperature Tp0=491.56 K,Post treatment temperature Tf0=586.37 K.When the curing temperature was 491.56 K,Curing degree of alpha was 95%,the curing time of t was 36.5 min can be obtained.The curing degree was 99%,and the curing time was 119.7 min.In order to achieve the curing effect,the curing time of LGEP should be 120 min.