Preparation Of High Melt Index Polypropylene Plastic As Injection Molding Material

Polypropylene has excellent chemical stability,physical and mechanical properties and processing performance,and is therefore one of the most widely used general-purpose plastics.With the rapid development of polypropylene industry in recent years in China,coupled with the successive operation of COAL-TO-OLEFINS and propane dehydrogenation installation,the capacity of polypropylene production capacity will further increase and may be in surplus,which may weaken the profitability of polypropylene enterprise.But the domestic new devices are mainly for the production of low-end materials,and the high-end products still depend on massive importation.How to increase the proportion of special production and improve the enterprise profitability will be the most important issue faced by the polypropylene producers.At present,in injection products market,domestic materials just occupy the low-end market,while imported materials exclusively take up high-end market,such as market much-needed special material of thin-walled injection molding.Thin-walled injection molding market has great market potential with the consumption of 1.5 million tons in 2008,and most of them need to be imported.To this end,by using the polypropylene plant of Qingdao Refining and Chemical Company,high melt index injection molding materials have been successfully produced via a hydrogen adjustment method,and all the product quality indicators meet the requirements.New grades ofproducts have made use of hydrogen adjustment method for the first time among the same type of devices in China.For the production of new grades of products,this thesis attempted to have solved the series of basic process problems of production.First,the corresponding relation between hydrogen addition amount and melt index.Second,the influence of hydrogen addition amount on the catalytic activity.Third,the influence of hydrogen addition amount on product isotacticity.Fourth,how to adjust the key equipment when producing high melt index products.Through analysis in this study,it was found that when the reaction temperature and pressure were set at 70^oC,and 3.45MPa respectively,by increasing the amount of hydrogen addition to 5500×10^-6mol/mol,decreasing the Al-Si ratio to 12.4mol/mol,and adding an appropriate amount of the additive,the product melt index was finally increased to 60g/10min or higher,with the product isotacticity at 95%,the product impact strength up to 2.1kJ/m²,the elastic modulus of 1680MPa,and the heat distortion temperature of up to 110?or higher.The products have the advantages of high transparency,good gloss,excellent toughness,high processing flow,and small buckling deformation,with part of performance indice better than similar products on the market,and thus the products have got user's full acceptance.The new products can bring nearly a million RMB/year as economic benefits for the company.