For processors looking to extrude stronger and tougher films, two firms recently came out with hexene-copolymer LLDPEs based on new catalyst technologies. Both resin families are poised to compete with octene LLDPE and metallocene LLDPE (mLLDPE), as well as other "super-hexene" grades.

Processability plus strength

Using a "next-generation" Ziegler-Natta catalyst system in a Unipol gas-phase reactor, Houston-based Equistar Chemicals, LP is producing new Petrothene Select hexene LLDPE resins for blown film. They are said to produce films with better processability and tear strength than mLLDPE. They also boast higher melt strength and dart impact than competitive "super-hexenes" having comparable modulus and tear strength. With a density of 0.916 g/cc, the two initial grades have MIs of 0.7 and 1.0. Each is offered with or without slip/antiblock additives.

"Fabricators are looking for thinner and thinner films that retain dart impact strength and have improved tear strength, without a penalty to processability," says John Hotz, Equistar v.p. of LDPE/ LLDPE.

Used in 0.7-mil films, Petrothene Select has as much dart impact strength as an mLLDPE but has higher tear strength at the same modulus, higher melt strength, and better processability. Films made with these resins do not require use of a processing aid to eliminate melt fracture. On the other hand, gloss is not as good as mLLDPE.

The new resins are aimed at heavy-duty applications, including downgauged prime liners, commercial and industrial packaging, and also consumer packaging such as retail bags.