二苯基甲烷二异氰酸酯二聚体在制备润滑脂过程中的变化

The Change of Diphenylmethane Diisocyanate Dimer during Preparation of Grease

为了给二苯基甲烷二异氰酸酯(MDI)聚脲润滑脂的制备及质量控制提供参考,研究了MDI二聚体在制备润滑脂过程中随温度的变化情况。用傅里叶变换红外光谱(FT-IR)监测MDI聚脲润滑脂在制备过程中异氰酸酯基团(-N=C=O)的红外特征吸收峰。制备温度为85℃时,聚脲润滑脂中显示有MDI二聚体的特征峰(2294 cm^(-1)),而没有MDI单体的特征峰(2270 cm^(-1)),说明在85℃时MDI单体已反应生成了聚脲。135℃~180℃出现的2281 cm^(-1)吸收峰是MDI二聚体衍生物解聚后产生的吸收峰。165℃,聚脲分子中-N-H基团的吸收峰从3330 cm^(-1)处移到了3308 cm^(-1)处,与脲基相连的苯环骨架振动的特征吸收峰1593 cm^(-1)相对强度的减弱,表明了MDI稠化剂分子间形成了氢键和网络结构。165℃以上可以消除MDI二聚体对MDI聚脲润滑脂性能的影响,得到稠度稳定的MDI聚脲润滑脂。

In order to provide reference for the preparation and quality control of diphenylmethane diisocyanate （MDI） polyurea grease, the changes of MDI dimer during the preparation of grease were studied with temperature.The infrared absorption peaks of the isocyanate groups （-N=C=O） during the preparation of MDI polyurea greases were monitored by Fourier transform infrared spectroscopy （FT-IR）. When the temperature was 85 ℃, the characteristic peaks （2294 cm-1） of MDI dimer was shown in polyurea grease without the characteristic peaks （2270 cm-1） of MDI monomer. This indicated that MDI monomer had reacted to form polyurea at 85 ℃.The 2281 cm-I absorption peak appearing at 135 ℃ to 180 ℃ was the absorption peak after de-polymerization of the MDI dimer derivative. At 165 ℃ ,the absorption peaks of the -N-H groups in the polyurea increased from 3330 cm-1 to 3308 cm-1.The characteristic absorption peak of the benzene ring skeleton connected with urea group was weakened by the relative intensity of 1593 cm-1,and this indicated that the formation of hydrogen bonds and network structures between MDI thickener molecules.During the preparation of MDI polyurea grease,when the temperature was above 165 ℃ ,the influence that MDI dimer on MDI polyurea grease could be eliminated, and could form a polyurea grease with stable consistency.