ExxonMobil Chemical (Houston) has launched a four-grade suite of its Vistamaxx propylene-based elastomers for use in films, saying the material has a positive impact on everything from package seal integrity to line speeds. Carol Fitzpatrick, global development manager for Vistamaxx in films, said the material is helping processors react to a changing market, noting that equipment manufacturers are increasingly offering higher-speed packaging equipment, with some systems capable of rates as high as 80 m/minute. "There are few films in the market today that can run at those speeds or anywhere near them," Fitzpatrick says, adding that Vistamaxx's ability to lower seal-initiation temperatures and broaden the hermetic sealing window have allowed converters to better match their output with the new machine capacities.

Conversely, if a converter has spare capacity, Fitzpatrick says Vistamaxx can allow them to lower the temperature that horizontal form-fill-and-seal machines, for example, run at to reduce the line's overall energy usage. The company has seen this benefit within the cast polypropylene (PP) film market for products like confectionary, among others, with seal-initiation temperatures typically 10-15°C lower.

The Vistamaxx suite's impact on films and how they interact with processing and converting equipment has actually prompted a five-company collaboration among ExxonMobil Chemical, a brand owner, a packaging equipment manufacturer, a cast-PP film extruder, and a laminator to work on high-speed film.

The amount of Vistamaxx added to the film depends on the application, with use as a cling agent requiring very low levels, while an elastic film would be composed primarily from Vistamaxx. In general for packaging films, less than 20% is typically used.

The primary differences among the four grades-Vistamaxx 6202FL, Vistamaxx 6102FL, Vistamaxx 3980FL, and Vistamaxx 3020FL-center on ethylene content and melt flow rate (MFR), according to Brent Johnson, Vistamaxx films market developer.

Vistamaxx 6202FL has an ethylene content of about 16%, a MFR of 20 using a 230°C test, and is designed for extrusion coating and lamination applications, with aggressive adhesion to the substrate it's bonding to a common characteristic.

Vistamaxx 6102FL also has an ethylene content of around 16% but a MFR of 3. Designed for elastic-film applications, Johnson notes that it's turning into "a real multipurpose product," with additional application as an "elastic engine" in personal-care elastic hygiene applications and as a cling additive in stretch films. Both 6102FL and 6202FL are also used as the adhesive layer of surface-protective films.

Vistamaxx 3980FL has ethylene content of 9% and a MFR of 8. Designed as a cast-film grade, Johnson said its predominant use would be for seal-layer modification. Vistamaxx 3020, has ethylene content of 11% and the highest molecular weight of the group, resulting in the lowest MFR: 2. Designed for blown-film applications, it's intended to give as much melt strength as possible. A potential application would be the core of a stretch hood.

At this point in time, Vistamaxx is made at an ExxonMobil Chemical site in Baton Rouge, LA, but a new site for the production of specialty elastomers, including Vistamaxx, is set to open in 2011 in Singapore with nameplate capacity of 300,000 tons/yr, expanding the materials availability in response to strong market demand. "I can tell you that [Vistamaxx's growth rate] is one of the most significant growth rates that we've ever seen in launching a new polymer," Fitzpatrick says.