Macro Engineering has shipped a "one-of-a-kind" 7-layer, 2.4 meter wide cast barrier film line in June 2003. The customer is a leading Chinese manufacturer of barrier film located in Suzhou in Jiangsu province. The line is designed to produce 2.1 meter wide barrier films from 35 to 250 microns using PP, PA, EVOH and PVDC. Structures containing PVDC are produced using encapsulation to prevent this barrier resin from contacting the metal surfaces of the feed block and die. The line, identified as CXL-7210, includes nine extruders: seven for each of the seven layers plus two for encapsulating the two edges. The melt stream of one of the tie layer extruders is diverted to provide PVDC encapsulation. The CXL-7210 is the first of its kind in the world.

The edge encapsulating resin (usually LDPE) allows trimming and reprocessing of the web edges, which are thicker because of the "draw down" effect in the melt curtain. The rest of web (containing PP, PA, EVOH and/or PVDC) can then be narrowly trimmed, cutting down on scrap. Mirek Planeta, Macro's President, explained that edge encapsulation significantly reduces one of the main drawbacks of cast barrier film, namely, trim waste. "The inexpensive LDPE used for edge encapsulation is reused for the same purpose or in another layer. Only a narrow strip of the coextruded barrier film is trimmed and discarded to ensure that all resins reach the edge of the web. Edge encapsulation makes cast barrier film price competitive," explained Planeta. "In addition, the high melt strength LDPE resin used in the edges reduces curtain neck-in for maximum web width and helps prevent curtain breaks for optimum running speeds."

The CXL-7210 cast barrier film line comes with a newly designed casting unit featuring a wide range of options. It is designed and predrilled for an additional third chill roller and a pressure rubber roller for embossing. An air knife and electrostatic pinning come as a standard features.

A fully automatic Automax T-2400 center-turret winder features a linear lay on roll assembly. The film can be cut in both directions with Macro's special flying knife design, which can cut through the toughest films up to 500 micron thick. Gap winding and a feather pressure secondary lay-on roll provide adjustable gap and precise lay-on pressure. A special design keeps the gap constant even after roll winding interruption. Proprietary tension controls allows the operator to set different tension during roll build-up. The winder has automatic shaft extraction, eliminating handling of heavy shafts.

An automatic gauge control system assures optimal film gauge, maintaining the thickness variation between 1.5 - 2.5% within 2-sigma. The complete line is controlled by Macro's proprietary SUPERCOM 9000 system. This centralized computer system features two 17" touch screens, which allow complete control of the CXL-7210 line.

There are compelling reasons why some barrier film manufacturers opt for having cast film capability. "Our customer in Suzhou, which already manufactures seven layer barrier film by the blown film process, required additional capacity", explains Steven Shi, Area Sales Manager for China. "Our initial discussions revolved around supplying them with a 7-layer blown film line to meet their needs. After carefully analyzing the situation, they decided to go with cast film because their customers were requesting higher quality film for certain applications. Cast film offers superior optical properties (clarity and gloss), unsurpassed gauge uniformity, excellent flatness, and better thermoformability when compared to blown film."

Adolfo Edgar, Area Sales Manager for Latin America explains that Macro has perceived a heightened interest in cast barrier film from customers in the last few months. "Shortly after the sale of our first CXL-7210 to China we sold a second one to an undisclosed customer in Latin America to be delivered during the first quarter of 2004. Emerging markets are looking for the unique capabilities offered by the cast film process. Highly clarity glossy structures with PP in the outer layer for deep draw forming applications are simply unattainable with the blown film process", says Edgar. "Additionally, Macro's CXL-7210 is capable of producing PVDC, and the more traditional PA/EVOH/PA barrier structures."