The Synthesis And Application Of Phosphite Antioxidant In Continuous Flow

Phosphite antioxidants are used as stabilizers for polymers,such as polyethylene,polypropylene,polystyrene,polyvinyl chloride and synthetic rubber.The aging of polymers can be inhibited effectively by adding phosphite antioxidants into the polymers.Besides,the transparency of polymers could be improved significantly by using them as additives.In this paper,a novel method for the synthesis of phosphite antioxidant and its derivatives has been developed in continuous flow.The research was focused on the preparation of antioxidant 168.The optimal reaction conditions of antioxidant 168 were obtained through the investigation of various reaction parameters in continuous flow.The synthesis of antioxidant 168 has been studied through the reaction of 2,4-diterbutylphenol with phosphorus trichloride,triethylamine used as acid binding agent.First,the reaction conditions were optimized in batch reactor by exploring the effects of temperature,solvent,different kinds and loadings of acid binding agents.After the completion of optimization study in batch reactor,we set out to explore antioxidant 168 in the continuous-flow system.The optimum ratio of 2,4-di-tert-butylphenol,phosphorus trichloride and TEA(acid binding agent)was 3.0:1.0:3.3,the reaction was performed at 70 0C for 20 s,the yield of antioxidant 168 was over 91%.The desired product was characterized by melting point,GC,1H NMR,13C NMR and HRMS.It is obvious that the reaction time was significantly shortened by contrast with batch conditions.The method also has the advantages of' simple operation and process security.Moreover,the reactants were employed in the stoichiometric ratio,which makes the reaction more efficient,economic,and environmental friendly.In this paper,23 different phosphite derivatives were produced by using the obtained metho d for the synthesis of antioxidant 168 in continuous flow.And the app licability of this method to different phosphite derivatives was discussed.Meanwhile,the antioxidant performances of tris(2-(tert-butyl)-4-methylphenyl)phosphite.tri([1,1'-biphenyl]-4-yl)phosphite and tris(4-(2-phenylpropan-2-yl)phenyl)phosphite in polypropylene were also investigated.The three phosphite derivatives were compounded with antioxidant 1010 respectively,and then the melt flow rate.oxidation induction period,and torque rheological property of polypropylene were measured after extrusion processing.The results showed that the synthesized antioxidant 168 has the similar ability of homogenization,plasticization performance and thermal stability compared to the commercial antioxidant 168.In addition,tri([1,1'-biphenyl]-4-yl)phosphite has the best antioxidant performance among the three phosphite derivatives,the antioxidant performance of tris(2-(tert-butyl)-4-methylphenyl)phosphite and tris(4-(2-phenylpropan-2-yl)phenyl)were slightly worse.