分段醇解均相缩合生产聚乙烯醇缩丁醛

以聚醋酸乙烯(PVAc)和丁醛为原料,采用分段醇解-缩合均相法生产聚乙烯醇缩丁醛(PVB)。系统讨论了反应温度、催化剂用量和物料配比等因素对醇解反应和缩合反应的影响。结果表明:醇解反应较适宜的工艺条件为w(PVAc)=20%(相对于甲醇质量而言),n(NaOH)∶n(PVAc)=0.005∶1,反应温度40℃;缩醛化反应较适宜的工艺条件为m(HCl)∶m聚乙烯醇(PVA)]=0.3∶1,n(丁醛)∶n(羟基)=1.1∶2,缩醛化反应温度50℃。各阶段最佳反应时间为第一阶段醇解15 min,缩合45 min;第二阶段醇解30 min,缩合60 min;第三阶段醇解50 min,缩合90 min。在最佳工艺条件下生产的PVB,其缩醛基分布均匀,并且其w(缩醛基)≈75%(相对于PVB质量而言)。

Homogeneous PVB produced by stages alcoholysis-polycondensation

With polyvinyl acetate(PVAc) and butyraldehyde as raw materials,so a homogeneous PVB(polyvinyl butyral) was produced by stages alcoholysis-polycondensation.The influences of reaction temperatures,catalyst contents,materiel ratio and other factors were discussed on alcoholysis reaction and polycondensation.The results showed that the optimum process conditions of alcoholysis reaction were obtained when mass fraction of PVAc in methanol was 20%,molar ratio of n(NaOH)∶n(PVAc) was 0.005∶1,and reaction temperature was 40 ℃.The optimum process conditions of polycondensation were obtained when mass ratio of m(HCl)∶mPVA(polyvinyl alcohol)] was 0.3∶1,molar ratio of n(butyraldehyde)∶n(-OH) was 1.1∶2,and reaction temperature was 50 ℃.The optimum reaction time were obtained when the alcoholysis reaction time and polycondensation time were 15 min and 45 min in the first stage,30 min and 60 min in the second stage,50 min and 90 min in the third stage respectively.The distribution of aldehyde acetal group was homogeneous,and mass fraction of aldehyde acetal group was 75% about in PVB which was produced under the optimum process conditions.