2,4,6-三羟甲基苯酚钠改性脲醛树脂的制备与表征

Preparation and Characterization of Urea Formaldehyde Resins Modified by 2,4,6-trimethylol Sodium Phenate

以苯酚和甲醛为原料,在强碱条件下制备中间体2,4,6-三羟甲基苯酚钠,产物经核磁氢谱得到确认;在传统三段工艺条件下(碱-酸-碱工艺),制备了不同2,4,6-三羟甲基苯酚钠/尿素(TMP/U)摩尔比的低游离甲醛释放的脲醛树脂并研究了TMP/U摩尔比对脲醛树脂的性能的影响.结果表明,随着TMP/U摩尔比的增加,脲醛树脂中的游离甲醛含量明显降低,改性树脂的粘度有所提高.当TMP/U摩尔比为1∶40时,脲醛树脂的游离甲醛质量分数小于0.01%;脲醛树脂制备过程中各阶段的游离甲醛含量分析表明,TMP对脲醛树脂中游离甲醛的降低主要发生在碱性阶段和第二批尿素加入阶段后期;随着TMP/U摩尔比的增加,NH4Cl/TMPUF体系的pH值逐渐升高.此外,改性脲醛树脂粘接胶合板的干强度和湿强度都高于参比组,改性脲醛树脂粘接胶合板的游离甲醛释放最低低于1 mg/L.

The intermediate 2, 4, 6-trimethylol sodium phenate（TMP） was synthesized by using phenol andformaldehyde as raw materials under strong alkaline condition, and characterized by1H-NMR spectrosopy. Inaddition, series of TMP-urea-formaldehyde（TMPUF）resins with different TMP/U mole ratios were prepared un-der traditional three step process（alkali-acid-alkali）and their performances were explored. Results showed thatthe free formaldehyde concentration reduced while the viscosity of TMPUF resin increased with the increase ofmole ratio of TMP/U;when the mole ratio of TMP/U was higher than 1/40, the free formaldehyde mass frac-tion in TMPUF resin was less than 0.01%. The analysis of the change of free formaldehyde level during eachsynthesis period of TMPUF resins showed that the reduction of free formaldehyde concentration mainlyhappened during the alkali stage and after the second addition of urea;furthermore, the p H value of NH4Cl-TMPUFsystem gradually increased as the mole ratio of TMP/U rose. In addition, the dry strength and wet strength ofplywood bonded by modified UF adhesives were better than those by pure UF adhesive, and the lowest value offormaldehyde emission of plywood bonded by modified UF adhesive was less than 1 mg/L.