New-generation LLDPE film resins.

With its new 650-million-lb/yr PE plant in Taft, La., now starting up, Union Carbide Corp., Danbury, Conn., will be able to deliver commercial quantities of new LLDPE film resins made with its Unipol II second-generation gas-phase process. The new technology reportedly allows more precise control of molecular-weight and comonomer (branching) distributions. The first of the Unipol II resins is called Easy Flow. The plant will also boost production of Tuflin and Super Tuflin grades, which are made with standard Unipol technology.

LLDPE RUNS LIKE LDPE 

Easy Flow, which is now available in pilot-plant quantities, is aimed at industrial liners, bags, and construction and agricultural films. These resins have a broader molecular-weight distribution than conventional LLDPEs. At densities of 0.920-0.921 g/cc, they are designed to process as easily as LDPEs in unmodified LDPE extruders with narrow die gaps. Carbide is not revealing what comonomer is used in their composition.

"Field trials are fully validating the concept of an easier-processing LLDPE," says marketing manager Frank Maccarone, adding that Easy Flow can permit substantial down-gauging relative to LDPE.

Initial commercial introductions will include an Easy Flow for replacing 1-MI liner-grade LDPE. Versions with different slip and antiblock levels will be offered. In addition, there will be high-molecular-weight Easy Flow for replacing fractional-melt (0.2 to 0.7 MI) LDPE. These HMW-LLDPEs give higher film strength and excellent bubble stability, resulting in improved throughput. Optical properties of current Easy Flow grades are typical of hazy LLDPE. Later on, clear Easy Flow grades will also be offered to compete with industrial clear LDPE (6-9% haze) and higher-clarity LDPE with under 5% haze.

Although Carbide has not released exact product details, processability and properties of experimental versions were reported previously (see PT, April '93, p. 83).

TOUGH AND TOUGHER

The new plant will also make Tuflin hexene copolymers and Super Tuflin, the high-performance hexene copolymer launched in late 1993. Super Tuflin grades, soon to be more widely available, include ST-2030 for cast films such as [TABULAR DATA OMITTED] stretch wrap that require clarity and superior toughness at very thin gauges. It's said to be stronger than standard higher-alpha-olefin (HAO) LLDPEs.

Super Tuflin ST-2005 and ST-2001 (with slip and anti-block) for blown film reportedly outperform conventional HAO LLDPEs in Elmendorf-tear and dart-impact strengths. They are said to be highly puncture resistant. Both can be used in a wide variety of gauges for shipping sacks, can liners, trash bags, and stretch wrap.

Carbide has also made HMW Super Tuflin with MIs from 0.3 to 1.0 and densities from 0.917 to 0.923 g/cc. A 0.5-MI HMW grade provide better tear and dart impact and modestly improve tensile properties, compared with a standard 1-MI grade.

In the future (Carbide will not say when), the new plant will use Unipol II to make Ultra Tuflin hexene LLDPE for high-performance films such as heavy-duty shipping sacks and ice bags. Certain grades of these HMW resins are designed to run on existing LLDPE film lines, while others are tailored for long-stalk HMW-HDPE equipment. Ultra Tuflin films reportedly will outperform films made with the company's standard Tuflin hexene grades, particularly in tear strength and dart drop.