Study Of The Preparation Technology Of Materials For Parylene HT Coating Film

Parylene HT is one of the newest parylene films. It has a variety of useful properties such as the thermal properties and anti-salt spray. Therefore, it was widely used in the field of electronics, military weapons, mechanical systems and cultural relic protection.1,1,2,2,9,9, 10,10-octafluoro [2.2] parylene is the mainly chemical vapor deposition precursor of Paylene HT polymer. According to the literature research and the laboratory existing conditions, 1,4-phthalaldehyde was selected as the raw material. Then, numbers of important intermediates during the synthesis process were obtained and optimized the synthesis technology. Finally completed the synthesis of 1,1,2,2,9,9,10,10-octafluoro [2.2] parylene and confirmed their structure through FT-IR as well as (H NMR. The total yield of the compound could reach 11.4%.Firstly, a, a, a’, a’-tetrachloro-p-xylene was synthesized. Many aspects on its yield were investigated. The optimized reaction conditions were as follows:the molar ratio of 1, 4-phthalaldehyde to thionyl chloride being 1:2.5, dimethylformamide as catalyst, reacted at 75℃ for 1 h, and then reacted at 95℃ for 2 h. The crude product was recrystallized by methanol. Under these conditions, a yield of 89.5% and a purity of 99.5% were expressed.Secondly, microwave-assisted synthesis of a, a, a’, a’-tetrafluoro-p-xylene by chlorine/ fluorine exchange using KF as the fluorine sources was studied. The optimized conditions were as follows:N-methyl pyrrolidone as solvent, the molar ratio of KF to a, a, a’, a’-tetrachloro-p-xylene being 8:1, the mixture being put in microwave for 20 minutes, tetraphenylphosphoniumchloride and 18-Crown-6 being mixed at the weight ratio of 2:1 as catalyst, KF being added by three times, reacted at 190℃ for 9 h. Under these conditions, the yield could reach 41.2% and the purity could reach 96.1%.Thirdly, synthesized 1,4-bis-(chlorodifluoromethyl) benzene through using a, a, a’, a’-tetrafluoro-p-xylene and chlorine as material. The optimized conditions were as follows: carbon tetrachloride as solvent, using 0.12 g benzoyl peroxide per gram of a, a, a’, a’-tetrafluoro-p-xylene, reacted at 80℃ for 12 h. The yield of 1,4-bis-(chlorodifluoro-methyl) benzene was 94.5% and the purity was up to 97.8%.Lastly, the synthesis of 1,1,2,2,9,9,10,10-octafluoro [2.2] parylene was researched. Based on the investigated aspects, the optimized conditions were achieved. In a nitrogen atmosphere, dimethylacetamide was the solvent, and per gram of 1,4-bis-(chlorodifluoro-methyl) benzene needed 9.48 g solvent. The molar ratio of 1,4-bis-(chlorodifluoromethyl) benzene to zinc dust was 1:4. The reaction was performed at 110 ℃ for 12 h. Under these conditions, the yield could reach 43.3%. The final product was 1,1,2,2,9,9,10, 10-octafluoro [2.2] parylene whose purity could be above 98.5%.