Study On Preparation Process Of High-purity Dimer Acid And Its Further Synthesis Of Polyurethane

As one of the most important bio-based chemical raw material intermediates,dimer acid has the advantages of being renewable,wide source,and green and environmental protection.High-purity dimer acid is the basic material of preparation of high-performanced polyamide and other fine chemicals.However,being lack of high-purity dimer acid production,China still needs to import a large number of high-purity dimer acid to meet domestic consumption.Therefore,high purity dimer acid has prosperous development prospect in China.In this paper,based on the researches of dimer acid synthesis at home and abroad,we took the unsaturated oleic acid provided by Tieling Jinduo Technology Co.,Ltd as raw material to explore the technique parameters for dimer acid synthesis,and optimize the reaction conditions using the response surface methodology.Then,the synthetic crude dimer acid was purified by molecular distillation.Subsequently,the polyurethane was synthesized from the purified dimer acid,and its properties were further characterized.The main researches and results were summarized as follows.1.The synthesis conditions of dimer acid were explored with unsaturated oleic acid as raw material and active clay as catalyst.The obtained optimum reaction conditions were: reaction temperature 243 °C,reaction time 6 h,catalyst loading 15.12%,assistant reagent amount 1.17%,under the optimal conditions the highest yield of dimer acid was 72.27%.2.The synthesized crude dimer acid was purified via molecular distillation.The optimum separation conditions of the two-step molecular distillation of dimer acid were investigated.The first step was conducted under the conditions of vacuum degree of the system of 1-1.5Pa,the speed of scraping machine at 150 r/min,the optimum separation temperature of the monomer at 160 °C,and the second step was done under the conditions of vacuum degree of the system of 1-1.5 Pa,the speed of scraping machine at 150r/min,the optimum separation temperature of the monomer at 250 °C.Under the above conditions,the content of dimer acid after being purified was 96.55% and the yield was 50.33%.After a third molecular distillation,the content of dimer acid was up to 99% or more.The acid value of the synthesized dimer acid was 198,the saponification value was 210,and the molecular weight was 589.49,respectively.3.The obtained high-purity dimer acid was employed to synthesize nonisocyanate urethane(NIPU)with ethylene carbonate and 1,6-hexanediamine as the starting materials.The polyurethane material was analyzed via thermogravimetric analysis(TGA)for its decomposition temperature range from 368 °C to 479°C.When the temperature reached 368 °C,the retention rate of polyurethane was 95%,when the temperature was at 455 °C,the decomposition rate of the polyurethane was the largest,when the temperature attained 479°C,the retention rate of the polyurethane was 5%.The differential scanning calorimetry(DSC)analysis revealed that its glass transition temperature was 37.30°C with a good melting property.