LLDPE is produced by the addition of alpha-olefins - butene, hexene or octene - during the polymerisation of ethylene to give a resin with a similar density to LDPE but the linearity of HDPE. Solution, slurry or gas phase processes are used to make LLDPE but the licensing of low-cost gas phase technology by Union Carbide (now Univation) and later BP Chemicals (INEOS) has contributed to the popularity of this resin. Many processes can swing between LLDPE and HDPE production although many plants tend to be dedicated to one of the two resins.