Woven polypropylene (PP) began to replace jute in primary carpet backings during the early 1960s. James Lees Carpet Company applied for the first patent using PP because of its processability, low cost, stability in sourcing, and good physical properties. PP ribbon yarns for primary carpet backing are produced by slit-die extrusion. In 1975, Amoco introduced fabric with a PP ribbon yarn warp and a spun PP filling yarn in a two end leno weave for secondary carpet backing. Hercules and, later, Amoco developed PP yarn for the carpet face in lines such as Genesis.