Within the last year Macro Engineering successfully sold three of its flagship CXL-7210 cast film coextrusion lines. The CXL-7210 is designed to produce 2.1 meter (83”) wide barrier films from 35 to 250 microns (1.4 to 10 mils) using PP, PA, EVOH and PVDC. Structures containing PVDC are produced using encapsulation to insulate this barrier resin from the metal surfaces of the feedblock and die.
The CXL-7210 includes nine MacroPlast extruders which feed a Cloeren feedblock and automatic die. Seven extruders feed each of the seven layers and two are used for encapsulating the two edges. The melt stream of one of the tie layer extruders is diverted to provide PVDC encapsulation. The first CXL-7210 line, shipped in June 2003, was the first of its kind in the world.
Edge Encapsulation
In the cast process beads form in the edges due to the “draw down” effect in the melt curtain. These edges are typically trimmed, reground and fed back into one of the extruders to minimize waste.
Mirek Planeta, Macro’s President, explained that edge encap-sulation dramatically improves the yield and economics by significantly reducing the main drawback of cast barrier film, namely, trim waste. “The problem with barrier films is that the coextruded structure is composed of dissimilar materials, hence a multilayer trim cannot be fed back into the process. With edge encapsulation the web edges are reprocessed as a single material and rest of web (containing PP, PA, EVOH and/or PVDC) is then narrowly trimmed, cutting down on 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. “Additionally, 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.”
Enhanced Line Features
The CXL-7210 line comes with a newly designed casting unit featuring a wide range of options. The unit 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 standard features.
An automatic Automax T-2100 bi-directional, 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. 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 includes automatic shaft extraction.
An automatic gauge control system from NDC assures optimal film gauge uniformity, 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, which features two 17" touch screens, provides complete control of all the operating parameters of the CXL-7210 line.
Cast: The New Frontier
There are compelling reasons why barrier film manufacturers opt for cast film. Steven Shi, Area Sales Manager for China, where the first CXL-7210 was delivered explains, “Our customer in Suzhou, which already manufactures seven layer barrier film by the blown film process, was looking to add capacity. Initial discussions revolved around supplying them with a 7-layer blown film line to meet their needs. After carefully analyzing the situation, they opted for cast film because their customers were requesting specific film properties that blown films were unable to meet. Cast films offer superior optical properties, excellent gauge uniformity, unmatched flatness, and better thermo-formability when compared to blown films.”
Shortly after the sale of the first CXL-7210 to China Macro sold a second one to an undisclosed customer in Latin America. 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. “The market for high end barrier films is moving in the direction of cast. We see the next generation barrier films being produced by cast and not the blown film process. Customers are taking a close look at the unique properties offered by cast barrier films”, says Edgar. “For example, highly clarity, glossy structures with PP in the outer layer for deep draw forming applications are simply unattainable with the blown film process.”
Felix Guberman, Area Sales Manager for Russia, shared some interesting background on the sale of Macro’s third CXL-7210 line to the company Selena Ltd. from the city of Korolev, near Moscow, Russia. The city, named after the famous space scientist Sergey Korolev, is home to Russia’s space program. Korolev is to Russia what Houston is to the U.S.A. “One of the deciding factors for our customer to buy the CXL-7210 line was Macro’s commitment to training,” explained Guberman. “Selena Ltd. has limited expertise in barrier films. The fact that they are located in Korolev allows them to tap a qualified pool of engineers, technicians and operators. These people have aerospace experience but not coextrusion experience. Macro’s successful track record of training customers in the coextrusion of multilayer barrier films was an important selling feature for our line.”
