酚化木质素制备及在阻燃硬质聚氨酯泡沫中的应用

Preparation of Phenolic Lignin and Its Application on Flame Retardant Rigid Polyurethane Foam

为提高碱木质素羟基含量,对造纸黑液中的碱木质素进行碱溶酸析、液-液萃取、超滤膜过滤、酚化改性处理得酚化改性精制木质素,使用酚化木质素替代部分聚醚多元醇制备硬质聚氨酯泡沫,研究泡沫的阻燃及物理力学性能。采用邻苯二甲酸酐酯化法测定酚化木质素总羟基含量,结果表明,酚化后木质素平均总羟基含量提高6.1177 mgKOH/g。傅里叶变换红外光谱分析表明,820 cm;处为木质素酚化后苯酚苯环上的C—H伸缩振动吸收峰,表明苯酚成功接枝到木质素上,核磁共振氢谱表明化学位移8.13处及7.95处的峰对应木质素酚化改性后α位次甲基上的H,也表明木质素酚化改性成功。以酚化木质素、可膨胀石墨(EG)及水的添加量为三因素,对硬质聚氨酯泡沫极限氧指数(LOI)进行正交实验,发现具有最高LOI(27.6%)的最佳配方为酚化木质素质量分数7.72%,EG质量分数8.98%,水质量分数0.33%。添加酚化木质素可提高泡沫体的力学性能,添加质量分数3.86%酚化木质素,泡沫达到最高压缩强度和拉伸强度,分别为432,486 kPa。

In order to increase the hydroxyl content of alkali lignin,alkali-soluble acid precipitation,liquid-liquid extraction,ultrafiltration membrane filtration,and phenolic modification were performed on the alkali lignin in papermaking black liquor to obtain phenolic modified refined lignin.Rigid polyurethane foams were prepared by replacing part of polyether polyol with the phenolic lignin,and the flame retardancy,physical and mechanical properties of the foams were studied.The total hydroxyl content of lignin was determined by phthalic anhydride esterification method.The results show that the total hydroxyl content of lignin increases by 6.1177 mgKOH/g on average after phenolization.Fourier transform infrared spectrum analysis shows that the peak at 820 cm;is the absorption peak of C—H stretching vibration on the phenolic benzene ring of phenol after phenolization of lignin,indicating that phenol can be successfully grafted to lignin.Proton nuclear magnetic resonance spectroscopy shows peaks at chemical shifts of 8.13 and 7.95 corresponds to H on theα-methine group after phenolic modification of lignin,and the phenolic modification of lignin is successful.The orthogonal test of limited oxygen index(LOI)of the foam with three factors of phenolic lignin,expanded graphite and water additions was carried out.The optimum formulation of the specimen with the highest LOI of 27.6%is phenolic lignin of 7.72 wt%,expandable graphite of 8.98 wt%and water of 0.33 wt%.The addition of phenolic lignin can improve the mechanical properties of the foams,and when adding 3.86 wt%phenolic lignin,the highest compressive strength and tensile strength of the foam are 432,486 kPa respectively.