Preparation And Properties Of Lignin Modified Phenolic Resin Adhesive

In this paper,solid lignin,liquid lignin,phenol,formaldehyde,glyoxal were used as raw materials,sodium hydroxide was used as a catalyst,and lignin was treated with phenol under alkaline conditions to prepare two lignin modified Phenolic resin Solid lignin phenol formaldehyde,liquid lignin phenol formaldehyde（S-LPF,L-LPF）adhesive,a lignin formaldehyde-free adhesive lignin phenol glyoxal（LPG）,respectively,Studies on different preparation on conditions on the effect for the properties of the adhesive[such as:lignin substitution,phenol treatment time,phenol treatment temperature,phenol treatment lignin sodium hydroxide dosage（first batch of sodium hydroxide）and phenolic molar ratio（P/F）etc.];its structure was characterized by Fourier Transform Infrared（FT-IR）.The curing properties and thermal properties of S-LPF,L-LPF and LPG were analyzed by means of Thermogravimetric analysis（TG）and Differential Scanning Calorimetry（DSC）.The main result of study is as follows.（1）The lignin modified phenolic resin（S-LPF）adhesive was prepared by using solid lignin,phenol and formaldehyde as raw materials.The results showed that the solid lignin substitution amount was 25%,the phenol treatment time was 2 hours,and the phenol treatment temperature80℃,the first batch of sodium hydroxide was 8%,phenol/formaldehyde molar ratio（P/F）1.0:2.0,the adhesive wet strength of the Prepared S-LPF adhesive is 1.57MPa,compared to the unmodified PF The 1.35MPa of the adhesive was increased by 16.3%,the free phenol 0.58%was reduced by 19.4%compared with 0.72%of the PF adhesive,the free formaldehyde was 0.16%,the solid content was 51.2%,the pH was 11.4,the viscosity was 950 mPa·s,and the storage period was 60 days.The FT-IR analysis showed that the absorption peaks of S-LPF at2893cm^-1 and 1213cm^-1 were significantly weakened,indicating that some methoxy groups in the solid lignin molecules were shed;The absorption peak of L disappeared at 1505cm^-1,1320cm^-1,1114cm^-1 and875cm^-1,indicating that most of the sulfonic acid groups in lignin disappeared during the process of synthesizing the adhesive.The S-LPF absorption peak at 1018cm^-11 was significantly enhanced,indicating the formation of new ether bonds.The TG analysis showed that the final carbon residue rates of PF and S-LPF were 58.72%and 55.71%;The DSC analysis showed that the curing of S-LPF adhesive was exothermic,and the curing temperatures of PF and S-LPF adhesives were 143.8-155℃,133.3-145℃,S-LPF adhesive curing temperature is lower than PF adhesive.（2）The lignin modified phenolic resin（L-LPF）adhesive was prepar-ed by using liquid lignin,phenol and formaldehyde as raw materials.The results showed that the liquid lignin dosage was 50%（solid content is and29%）,the phenol treatment time was 2 hours,and the phenol treatment temperature was 80℃,the first batch of sodium hydroxide was 3%,phenol/formaldehyde molar ratio（P/F）1.0:1.975,reaction temperature was 90℃and the reaction time was 50 min,the adhesive wet strength of the Prepared L-LPF adhesive is 1.36MPa,compared to the unmodified PF The 1.35 MPa of the adhesive was increased by 8.1%,dry strength of the Prepared L-LPF adhesive is 3.15MPa,compared to the unmodified PF The 2.68 MPa of the adhesive was increased by 14.9%,the free phenol0.62%was reduced by 13.9%compared with 0.72%of the PF adhesive,the free formaldehyde was 0.22%,the solid content was 52.8%,the pH was 11.5,the viscosity was 220 mPa·s,and the storage period was 50days.The FT-IR analysis showed that the absorption peaks of L-LPF at2931cm^-1 and 1146cm^-1 were significantly weakened,indicating that some methoxy groups in the liquid lignin molecules were shed;The absorption peak of L disappeared at 1499cm^-1,1412cm^-1,1298cm^-1 and1082cm^-1,indicating that most of the sulfonic acid groups in lignin disappeared during the process of synthesizing the adhesive.The L-LPF absorption peak at 1024cm^-11 was significantly enhanced,indicating the formation of new ether bonds.The TG analysis showed that the final carbon residue rates of PF and L-LPF were 58.72%and 61.23%;The DSC analysis showed that the curing of L-LPF adhesive was exothermic,and the curing temperatures of PF and L-LPF adhesives were 143.8-155℃,145.5-156.3℃,S-LPF and PF adhesive curing temperature the same basic.（3）The lignin formaldehyde-free adhesive（LPG）was prepared by using solid lignin,phenol and glyoxal as raw materials.The results showed that the dosage of lignin was 30%and the phenol treatment temperature was 80℃,phenol treatment time 2h,the first batch of sodium hydroxide dosage 8%,the second batch of sodium hydroxide dosage 6%,phenol and glyoxal（P/G）molar ratio 1.0:1.8,reaction time 3.5h,reaction temperature was 100℃and the mass ratio of glyoxal to lignin is 15%,the bonding strength（dry and wet）of the prepared LPG adhesive was1.81MPa,0.83MPa,and free phenol 0.71%.The viscosity was 126mPa·s,the solid content was 44.25%,the pH was 11.3,and the storage period was 50 days.The FT-IR analysis showed that the absorption peaks of LPG at2932cm^-1 and 1218cm^-1 were significantly weakened,indicating that some methoxy groups in the solid lignin molecules were shed;The absorption peak of L disappeared at 1515cm^-1,1465cm^-1,1329cm^-1 and1123cm^-1,indicating that most of the sulfonic acid groups in lignin disappeared during the process of synthesizing the adhesive.The LPG absorption peak at 1081cm^-11 was significantly enhanced,indicating the formation of new ether bonds.The DSC analysis showed that the curing of LPG adhesive was exothermic,and the curing temperatures of PF and LPG adhesives were143.8-155℃,138.2-150.4℃,LPG adhesive curing temperature is lower than PF adhesive.