Preparation And Application Of Lignin-Urea-Formaldehyde Resin

It is well known that the black liquor in paper industry contains 50 million tons / year of lignin.Most of lignin are burned in addition to 2%.How to disposing and application of lignin is still a prob lem to be solved in the development of this area,and our nation has repeatedly set up a special project to solve this difficult problem.This paper realized the application of lignin.Lignin-urea-formaldehyde resin adhesive(LUF),Lignin-urea-formaldehyde resin based carbon microspheres(LUFC)and Lignin-urea-formaldehyde resin based activated carbon(LUFAC)were in situ synthesized by the ternary(lignin,formaldehyde and urea)copolymerization method step by step with alkali lignin as raw material.And the application performance of adhesive and porous carbon materials were also studied separately in this paper.The main research results are as follows:1.According to the structural characteristics of lignin,the hydroxymethyl lignin was modified by formaldehyde firstly,and then lignin-urea-formaldehyde resin adhesive was prepared by adding formaldehyde and urea to the lignin-methyl group in situ in batches.Lignin instead of the proportion of formaldehyde(0wt%~60wt%)on the properties of the adhesives was studied systematically.The LUF has the greatest bonding strength of 1.42 MPa as the replacement rate is 10 wt%,which is better than that of pure urea-formaldehyde resin of 0.89 MPa.When the replacement rate is 30wt%,the comprehensive performance of LUF is the best,with the bonding strength of 0.94 MPa,the free formaldehyde content 0.3%,the solid content 56.7% and p H 9.15,that achieves the national standard requirements of type Ⅱplywood.2.The lignin-urea-formaldehyde resin microspheres with good uniformity and dispersibility were prepared by polymeric reaction and acid catalytic curing.The pyrolysis processes of the lignin-urea-formaldehyde resin microspheres with different lignin replacement rate(0wt%~60wt%)were studied systematically,and the optimum carbonization temperature was 500 oC.In order to maintain the morphology of the carbon microspheres,0.5oC/min heating rate was selected for the preparation of LUFC,because the temperature 220 oC ~ 350 oC was a rapid weight loss.3.LUFAC was prepared with LUFC as raw material and sodium hydroxide as activator.The effects of activation conditions on the electrochemical performance of LUFAC were studied.The results showed that LUF AC had the best performance when the activation temperature was 750 oC,the time was 1.5h,the ratio of carbon to alkali was 1: 3 and the replacement rate of lignin was 30 wt %.The specific surface area of LUFAC up to 3342m2g-1,with high mesoporosity(83%).In the electrochemical tests,the specific capacitance of LUF AC is as high as 305Fg-1 in 6M KOH,and have a good characteristics of electric double-layer capacitor under different current density and scan rate,as well as a better cycle stabilitythe specific capacitance retention rate is still as high as 96.3% after 10000 times charging and discharging cycles.