Patent ID: 8211341

Claim:
A method for making fiber reinforced polypropylene composite pellets comprising: (a) forming synthetic organic fiber pellets by: i) mixing in a solid state in a plow mixer, a tumbler or a ribbon type blender a combination of pre-cut synthetic organic fiber and one or more waxes to form a fiber-wax mixture, ii) feeding the fiber-wax mixture into a pelleting press, iii) forcing the fiber-wax mixture in a solid state through a die of the pelleting press to form synthetic organic fiber strands, and iv) cutting the synthetic organic fiber strands into synthetic organic fiber pellets, (b) feeding into a compounding extruder at least 25 wt % polypropylene based polymer, from 5 to 60 wt % of synthetic organic fiber in the form of the synthetic organic fiber pellets, and from 0 to 60 wt % inorganic filler, based on the total weight of the composition; (c) extruding the polypropylene based resin, the synthetic organic fiber pellets, and the inorganic filler through the compounding extruder to form a fiber reinforced polypropylene composite melt; (d) cooling the fiber reinforced polypropylene composite melt to form a solid fiber reinforced polypropylene composite; and (e) pelletizing the solid fiber reinforced polypropylene composite to form fiber reinforced polypropylene composite pellets; wherein the synthetic organic fiber pellets comprise at least 80 wt % of the pre-cut synthetic organic fiber chosen from polyalkylene terephthalates, polyalkylene naphthalates, polyamides, polyolefins, polyacrylonitrile, and combinations thereof, and from 2 to 20 wt % of the one or more waxes; and wherein an article molded from the composite pellets has a flexural modulus of at least 2.07 GPa and exhibits ductility during instrumented impact testing.