Synthesis Of Glycolic Acid And Polyglycolic Acid

Glycolic acid has the properties of alcohol and medium strong acid,and is widely used in the fields of organic synthesis,chemical cleaning,personal care and the like.Polyglycolic acid has excellent biodegradability,heat resistance,gas barrier properties,mechanical strength,etc.,and has been extensively studied as a novel material.In this thesis,the source of rich chloroacetic acid and methyl chloroacetate was used as raw material to obtain higher purity glycolic acid crystals by alkaline hydrolysis and purification,and the polyglycolic acid was directly polymerized by using chloroacetic acid as raw material.The specific work content is as follows:(1)Using chloroacetic acid as a raw material,glycolic acid is obtained by alkaline hydrolysis of sodium hydroxide.The effects of reaction temperature,reaction time,ratio of raw materials and mass fraction of sodium hydroxide on the yield of glycolic acid were investigated by single factor and orthogonal experiments.The optimal reaction conditions were: reaction temperature 100 °C,reaction time 11 h,n(sodium hydroxide): n(chloroacetic acid)= 1.25:1(based on chloroacetic acid 9.45 g),sodium hydroxide mass fraction 40%.Under the optimal conditions,the yield of glycolic acid was 88.63%,and the conversion of chloroacetic acid was more than99.9%.The glycolic acid solution was refined by solvent extraction method and the optimum extractant was determined to be acetonitrile.The obtained glycolic acid crystal has a purity of 99.58%,a yield of 56.23%,and the product purity exceeds the industrially produced 99% high purity glycolic acid crystal standard.The lactic acid crystals were characterized by FTIR and NMR,and the solid product was determined to be glycolic acid.(2)Using chloroacetic acid methyl ester as a raw material,glycolic acid is obtained by alkaline hydrolysis of sodium hydroxide.The effects of reaction temperature,reaction time,ratio of raw materials and mass fraction of sodium hydroxide on the yield of glycolic acid were investigated by single factor and orthogonal experiments.The optimal reaction conditions were: reaction temperature110 °C.,reaction time 9 h,n(sodium hydroxide): n(methyl chloroacetate)=1:1(based on methyl chloroacetate 20 g),sodium hydroxide mass fraction 15%.The yield of glycolic acid under optimal conditions was 81.76%.The glycolic acid solution was refined by solvent extraction method and the optimum extractant was determined to be acetonitrile.The purity of the glycolic acid crystal obtained was96.97%,the yield was 56.15%,and the purity of the product was slightly lower than that of 99% high-purity glycolic acid produced by industrial production.The crystal standard,but provides a theoretical basis and reference for the process of synthesizing glycolic acid crystals from methyl chloroacetate.The lactic acid crystals were characterized by FTIR and NMR,and the solid product was determined to be glycolic acid.(3)The chloroacetic acid is used as a raw material to directly polymerize into polyglycolic acid.The reaction solvent was optimized by the combination of yield and intrinsic viscosity,and the polyglycolic acid obtained by the reaction was characterized by FTIR,XRD,DSC and GPC.The results show that when the reaction solvent is acetonitrile,the synthesized polyglycolic acid has better crystallinity and thermal stability.The reaction temperature,reaction time and material ratio were optimized by single factor and orthogonal phase determination.The results showed that when the reaction temperature was 90 °C and the reaction time was 5 h,n(triethylamine): n(chloroacetic acid)= 1:1(based on chloroacetic acid 15 g),the intrinsic viscosity of the obtained polyglycolic acid reaches 3.8597 dL/g,which exceeds the quality index of domestic polyglycolic acid industrial production.The product was characterized by XRD,DSC and GPC.The results show that the optimized polyglycolic acid has higher crystallinity and thermal stability,the molecular weight and dispersibility are improved.The number average molecular weight is 11183,which has reached the quality index of domestic polyglycolic acid industrial production.