Preparation And Appliction Of Straw Enthanol Residue Modified Urea-formaldehyde Resin

Lignin, the most abundant renewable phenolic compounds in the nature, has a complex structure and various active functional groups. Lignin is also the main residue of straw ethanol industry. Except the part utilization as fuel, lignin generally cause the pollution of the environment in most cases.Urea-formaldehyde resin is one of most frequently using adhesives in man-made board industry. However, the feedstocks for the production of urea-formaldehyde resin are primarily originated from petroleum based chemicals, which is regared as a unsustainable process.Therefore, lignin in this paper will be used to replace part of urea in the synthesis of urea-formaldehyde resin and achieve its high value utilization. In addition, the use of lignin also can reduce the production cost of straw ethanol industry and promote the development of biomass energy and materials industry.In this context, lignin model compounds and lundquist lignin were used respectively to investigate the copolymerization theory of lignin-urea-formaldehyde resin and their process of reaction by FT-IR and NMR. It was found that the methylolation of lignin compounds and lundquist lignin were the main reactions under alkali condition at the first stage. At the second stage, polycondensation between methylolated lignin compounds or methylolated lundquist lignin, and methylolated urea occured under acid condition. At the last stage, polycondensation stopped and we obtained final products. By the analyse of the structure of intermediate product, we deduced the mechanism of reaction.The straw ethanol residue modified melamine-urea-formaldehyde(ERMUF) resins were prepared by using straw ethanol residue(ER), melamine(M), urea(U) and formaldehyde as starting material in alkali-acid-alkali process. Effect of the content of ER, M, U on the performance of ERMUF resins and the plywood bonded by them were investigated. And the optimal conditions of reaction are described as follows: n(U)/ n(F) is 1/1.5, n(M)/n(F) is 0.15,m(ER)/m(ER+U) is 0.48. Additionally, effects of the curing agents of ERMUF resin on the performance were also investigated. The results showed that NH4 Cl and H3PO4 were the optimal curing agents. When 1% NH4 Cl and 0.5%H3PO4 were added into ERMUF resin for bonding the plywood, the performance can achieve the best.At the same time, the methylolated straw ethanol residues(HER) were prepared by the reaction between ER and formaldehyde(F), and used to blend with UF resin to prepare HER/UF composite resin. The optimal methylolated condition was described as follows:m(ER)/m(F) is 20 and m(NaOH)/m(HER) is 0.9 %. FT-IR spectra showed that the amount of methylol group in lignin of HER was more than that in lignin of ER. As the increase of the value of m(ER)/m(F), hydroxymethyl group in HER decreased. The composite resin would become more crisper with the increase of the fraction of ER or HER in resin. SEM image revealed that HER have a better dispersity than ER in the UF resin. The three layers ply board bonded by the blend of UF with 30 % HER in resin has the best performance. When UF resin consisted of 10 %~40 % HER, formaldehyde emission of the three- layers ply boards could meet E0 grade and the bonding strength of them could meet the requirement of type ?plywood.The result of DSC measurement showed that the increase of ER would result in the low the curing reaction of ERMUF resin. The application of ERMUF resin was investigated and the scale-up experiment of 30%ERMUF and 50%ERMUF has been performed. The bonding strengths of the plywood with these two ERMUF all reach the requirement of ? plywood and the formaldehyde emission reach the requirement of E0 grade.