首先,研究了不同工艺条件下木质素替代部分苯酚制备的木质素改性酚醛树脂(LPF)胶粘剂的性能;其次,探讨了木质素对苯酚的替代率、氢氧化钠用量、甲醛/木质素质量比及产品固含量等对LPF性能的影响,并对各参数进行了优化;最后,通过DSC分析研究了LPF的热性能.结果表明:麦草碱木质素的碱活化和羟甲基化有利于提高木质素的化学反应活性;优化工艺条件下(木质素对苯酚的替代率为50%、氢氧化钠用量为4.5%,甲醛/木质素质量比为8∶100、固含量为41.4%)制备的胶黏剂其粘结强度可达2.04 MPa,未经分离提纯的胶粘剂的残留甲醛和苯酚都远低于国家标准;相对于酚醛树脂粘剂胶,所制备的木质素改性酚醛树脂胶粘剂的固化温度降低,固化速度增大,克服了酚醛树脂胶粘剂的缺陷.
This paper deals with the properties of lignin-modified phenol-formaldehyde resin(LPF) adhesive synthesized with lignin partially substituting for phenol under various conditions.Then,the influences of such factors as the substitution rate of lignin for phenol,the sodium hydroxide dosage,the formaldehyde-to-lignin mass ratio and the solid content of the product on the properties of LPF were discussed,and the factors were optimized.Finally,the thermal properties of LPF were analyzed by means of DSC.The results show that the alkali activation and hydroxymethylation help to improve the chemical reactivity of the lignin,that the adhesive prepared under the optimal conditions(a substitution rate of 50%,a sodium hydroxide dosage of 4.5%,a formaldehyde-to-lignin mass ratio of 8∶ 100 and a solid content of 41.4%) is of high bond strength(up to 2.04 MPa) as well as low residual formaldehyde and phenol contents(much less than those regulated by the national standard),and that the prepared LPF adhesive is superior to the phenol-formaldehyde resin adhesive because it is of low curing temperature and high curing rate.