Investigation On The New Borate Ester Bonding Agents For The High Energy Hydroxy-Terminated Polybutadiene Propellant

Mixed dibasic acids (DBA), also so-called nylon acids, are byproducts of cyclohexane oxidation. It also names AGS acids for its main components are succinic acid, glutanic acid and adipic acid. The recycle and use of DBA can not only save resources but also protect the environment, which means great economic and social benefit. In this article, a high-boiling-point solvent—mixed dibasic esters(DBE) and Polyester polyol for ployurethane are synthesized with DBA and methanol to achieve the utilization of DBA.First, with sulfuric acid as a catalyst, factors of esterfication such as amount of sulfuric acid, molar ratio of methanol to DBA , reaction time and amount of toluene were studied to ascertain the optimal conditions. The product was tested and the technic conditions were improved to control the acid value and colour of the product. The result showed the optimal reaction conditions as follows: molar ratio of methanol to DBA was 5:1, mass of sulfuric acid was 2 ml,reaction time was 3.5 h , mass of toluene was 50 ml based on 100 g DBA. Under the optimal conditions, DBE was a clear liquid with steady quality and a acid value below 1 mg KOH/ g. The average yield of DBE was 86.3% with a content of mixed dimethyl esters above 95%.Meanwhile, the esterfication of DBA and methanol, with environment- friendly catalyst phosphotungstic acid(PW₁₂)and self-made phosphotungstic acid supported on silicon dioxide(PW₁₂/SiO₂), was also studied. Factors such as amount of catalyst, molar ratio of methanol to DBA , reaction time and amount of toluene were studied to ascertain the optimal conditions. The optimal reaction conditions with PW₁₂ were found as follows: molar ratio of methanol to DBA was 3:1, mass of PW₁₂ was 2% ,reaction time was 4 h , mass of toluene was 50 ml based on 100 g DBA. The optimal reaction conditions with PW₁₂/SiO₂ were found as follows: molar ratio of methanol to DBA was 3.5:1, mass of PW₁₂/SiO₂ was 2% ,reaction time was 4.5 h , mass of toluene was 50 ml based on 100 g DBA. The result showed that under the optimal conditions, the average yields of DBE were 85.2% and 84.7% with a content of mixed dimethyl esters above 98%.The recycle of the catalysts were also reviewed in this article. The result showed that PW₁₂/SiO₂ can be separated from the system by simple filtration and reused by simple activation treatment while PW₁₂ was difficult to be separated. PW₁₂/SiO₂ was steady and the yield of DBE was still above 70% under the optimal conditions after using PW₁₂/SiO₂ f or 5 times.Finally, polyester polyol was synthesized by condensation polymerization of self-made DBE, which was synthesized by DBA and methanol with sulfuric acid as a catalyst, and 1,4-Butanediol with tetrabutyl titanate as a catalyst. The molecular weight of polyester polyol varied from 800 to 2000 and could be controlled.