Study On The Preparation Process Of Materials For Parylene-D Film

Parylene films, synthesized through Chemical vapor deposition of the paracyclophane and its derivatives, were a kind of high quality conformal coating materials. Owing to they had the characteristic of great chemical stability, biocompatibility, they were widely used in the field of aerospace, microelectronics, semiconductor, sensors, magnetic materials, medical equipment, cultural relic’s protection and it likes.Two hydrogen atoms linking with benzene were substituted by chlorine atoms. The groups were introduced to improve the insulation properties and heat resistance of parylene film. By the introduction of chlorine atoms, the density of the material is increased, and its ability of standing against heat is improved. As a coating material, it has a better protective capability.The synthesis of materials for Parylene D films (tetrachloroparacyclophane) was investigated. By selecting the appropriate process route and optimizing the synthesis process, the synthesis yield of tetracholorparacyclophane was improved which was available for the large-scale industrialization of the Parylene D monomer.Firstly,2,5-dichloro-p-xylent as raw material, several kinds of different halogen agents was studied on the effect of benzyl halide. The advantages and disadvantages of these methods were compared. We optimized the processing conditions for bromination of 2,5-dichloro-p-xylent with NBS, HBr/H2O2 which was prepared in high yield. The influences of molar ratio of raw materials, solvent, inhibitor content, and reaction time on the yield of bromine substitute were investigated. The better reaction conditions were:When using NBS as a bromine agent, with trichloromethane as solvent, benzoyl peroxide as inhibitor, at reflux temperature for 3 hours reaction. Under these conditions, the 2,5-dichloro-4-methyl-benzylbromide yield could reach 77%, the 1,4-bis (bromomethyl)-2,5-dichloro-benzene yield could reach 8%. When using UBT/H2O2 as a bromine agent, with trichloromethane as solvent, the molar ratio of 2,5-dichloro-p-xylent to bromine hydride and hydrogen peroxide being 1:1.2:2, 40W incandescent lamp as inhibitor, at reflux temperature for 12 hours reaction. Under these conditions, the 2,5-dichloro-4-methyl-benzylbromide yield could reach 75%, the 1,4-bis (bromomethyl)-2,5-dichloro-benzene yield could reach 10%.Secondly, process conditions for the generation of quaternary ammonium salt with bromined compound and tertiary amine were studied. The influences of molar ratio of raw materials, reaction time on the yield of bromine substitute were investigated. The better reaction conditions for the preparing of quaternary ammonium salt were:0.2-fold excess of the tertiary amine and bromine substitute reacting in an ice bath for 1.5 hours. Under these conditions, the yield of quaternary ammonium salt could reach 93.5%.At last, we worked on the process conditions for preparing tetracholor-paracyclophane using the quaternary ammonium salt as raw material. The influences of molar ratio of raw materials, solvent, polymerization inhibitor (0.8% mass fraction), reaction temperature and reaction time on the yield of tetrachloroparacyclophane were investigated. The better reaction conditions for preparing tetrachloroparacyclophane were:the molar ratio of NaOH and PBA being 5:1, phenothiazine(0.8% mass fraction) as inhibitor, reaction temperature 110℃and reaction time 10 h and the yield of tetrachloroparacyclophane could reach 48.7% whose purity could reach 75.6%.