Preparation method of polypropylene foaming beads

Abstract

The invention provides a preparation method of polypropylene foaming beads. Homo-polypropylene as base resin and ammonium polyphosphate as a fire retardant undergo foaming in the presence of a foaming agent so that the polypropylene foaming beads are prepared. The preparation method comprises that two or more stages of propylene homopolymerization reactions occur in two or more reactors connected in series, wherein external electron donors used in the two or more stages of reactions respectively comprise silane and diether compounds. The preparation method utilizes the wide-molecular weight distribution high-melt strength polypropylene as a raw material, realizes polypropylene raw material stabilization, effectively enlarges a foaming window, has easily adjustable processes and a low cost, can prepare the polypropylene foaming beads having uniform foam pore diameters, compact foam pores, uniform pore size distribution and a closed pore structure and can be widely used in occasions of automobile parts, electronic packaging and building decoration having high flame-retardation requirements on foamed plastic products.

Description

technical field [0001] The invention relates to the field of macromolecules, in particular to a preparation method of halogen-free flame-retardant polypropylene foam beads. Background technique [0002] Since the development of expanded polypropylene beads (EPP) began in foreign countries in the 1980s, it has been widely used in cushioning packaging, food packaging, auto parts, thermal insulation and building materials, and has become a substitute for expanded polystyrene. New environmentally friendly foam materials of ethylene and foamed polyurethane. EPP beads have uniform size and stable expansion ratio, and are suitable for making molded foamed products. [0003] However, EPP beads are flammable substances. When burning, they generate a large amount of heat and are accompanied by molten droplets. They are very easy to spread flames, and their application in flame-retardant applications is limited. At present, most of the flame retardant modification of polypropylene us...

AI Technical Summary

Problems solved by technology

However, polypropylene is a non-polar polymer material that hardly forms charcoal when burned, so it is necessary to add more flame retardants to achieve the UL94V0 flame retardant grade. In addition, the polypropylene flame retardant composite material obtained by this method, after passing The flame retardant grade often drops after kettle impregnation and intermittent foaming, and the oxygen index drops from 35 to 45 of the flame retardant polypropylene microparticles to below 28, which cannot meet the application fields that require higher flame retardant grades

In order to improve the flame retardant effect, the number of flame retardants added is often increased, which will increase the cost of the product and affect the preparation and subsequent molding of EPP beads

Images