高压均质预分散制备聚乙烯醇缩丁醛粉体

摘要

以聚乙烯醇(PVA)和正丁醛为原料,利用高压均质技术进行预分散,沉淀法制备聚乙烯醇缩丁醛(PVB)粉体,缩丁醛基的质量分数可达77.11%.产物过160目筛通过率达80%以上.利用激光粒度分析仪与场发射扫描电镜对产物进行分析.此外,考察pH值、正丁醛用量、分散剂种类和用量对缩醛化反应的影响,并用自动视频接触角测量仪对产物洗液进行表面张力刺定,考察不同洗涤方法的效果.结果表明:PVB粉末由粒径为3～7μm的椭球状初始颗粒团聚而成,过筛后的粉末平均粒径和中值粒径(d50)分别为35.28、29.29μm.缩醛反应较适宜的工艺务件为:pH=2,低温加料、梯度升温10℃/h,最终反应温度70℃,反应总时间6 h,分散荆十二烷基苯磺酸钠(SDBS)用量为1.83g/L,正丁醛加入量为PVA羟基完全反应所需量的90%.产物用m(H2O):m(PVB)=2:1的水洗涤15次或用m(H2O):m(PVB)=20:1的水洗涤4次,洗液的表面张力值基本与纯水相同,分散剂基本除尽.%The fine powder of polyvinyl butyral (PVB) was synthesized via high pressure homogenously predispersing the butyraldehyde into the aqueous solution of polyvinyl alcohol (PVA).The mass fraction of butyral group content of final product reached to 77.11％, and more than 80％ of the powder passed through 160 mesh sieve.The products were analyzed by laser particle size analyzer and field emission scanning electron microscopy.The pH value and dosage of butyraldehyde as well as the effect of dispersant were investigated.The results showed that the PVB powder was an aggregate of ellipsoids which had a similar size of 3～7 μm.The mean size and the median size (d50) of the screened powder was 35.28, 29.29 μm.The optimized parameters were as follow: pH= 2, the reaction temperature raised from 2 ℃ to 70 ℃ with a gradient heating rate 10 ℃/h,the mass concentration of sodium dodecyl benzene sulfonate (SDBS) was 1.83 g/L, the dosage of butyraldehyde was the theoretic value at 90％ of acetal degree.When the PVB powder was washed 15 and 4 times at respective with solution of 2∶1 and 20∶ 1 in mass ratio of H2O and PVB in each frequency, the surface tension of washing water was similar to that of the pure water, which proved that the dispersant was washed away.