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VCI (Volatile Corrosion Inhibitor) PACKAGING PRODUCTS
Cor-Pak™ Cocooning Stretch Film
"A new low cost procedure to wrap metal coils"
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A new low cost procedure to wrap metal coils in rolling position with bore/eye horizontal is now operational. The process utilizes a semi-automatic stretch wrapper and Cortec’s unique Cor-Pak™ Cocoon VCI Stretch Film specifically designed for applications requiring a strong but soft film. It is now possible to cocoon wrap coils fast and efficiently with packaging that conforms to the metal product.

In 1991, Cortec Corporation patented the inclusion of environmentally friendly vapor corrosion inhibitors (VCI’s) into polyethylene stretch film. This opened the doors for use as packaging wrap for metals. At one time, the steel industry in particular rejected consideration of any plastic contacting metal fearing condensation and ultimately corrosion.

During the process of film development and patenting, Cortec worked with Australian Challenge to produce film for the Coilmaster® joint ventured by BHP Steel and K-C Metal Products in Victoria, Australia. The Coilmaster® wraps coils through the eye and spawned a new era in steel packaging at BHP where corrosion was virtually eliminated using Cortec’s VCI Technology in an environmentally friendly recyclable film. This equipment and wrapping procedure has been adopted at some locations worldwide where the investment could be justified. For some potential users, however, this method proved cost prohibitive.

Following continued interest and growth of VCI stretch film for packaging metals over subsequent years, a low cost method to wrap primary coils in rolling position eluded the industry. The "cocooning" method has been successfully used to wrap large rolls of paper and bales of hay over many years. Strema in Germany engineered and produced a sophisticated automatic cocooning system for steel coils, which has been well received. While requiring less investment than Coilmaster®, it still is economically challenging for many companies.

To properly protect eye horizontal coils against corrosion and handling damage, several packaging components are required. An ID insert to protect the bore/eye, ID edge protector to prevent handling damage when lifting, sidewall protection to avoid damage from C-hook or equivalent when moving coils, and OD protector to prevent edge cuts during wrapping and stacking of coils. However, the manual placement of these necessary components negated goals for reduced labor and investment costs.

Cortec has developed corrosion protection with each of these components required. VCI-350 A&B coating for fibreboard and corrugated, VCI-357 saturation coating for laminated edge protection, VCI-126 films for ID tubes and edge wraps, Eco-Weave‰ where strength is required, and even VCI plastic corrugated for converting as warranted.

We continued to believe in and recommended the potential of the Cocoon Method as the ultimate answer to low cost wrapping of coils. What was needed was a simple way to combine the various packaging components and minimize hand application.

The answer came from Jan Martin and Liberty Distributors, Inc. in West Virginia, USA, when they combined the required components and patented VCEYE Insert® both in US and Internationally. It combines a heavy paper tube containing an outer wrap of Cortec’s VCI-146 kraft with a die-cut V-board ID protector and kraft corrugated doughnut shaped sidewall disc. This insert is slit for ease of insertion and placed one in each side of eye overlapping for complete inside coverage of the coil eye. While Liberty’s insert has made the cocooning method of stretch wrapping very attractive requiring only one operator to place the protection and operate the wrapper, other mills with low cost labor might choose to use the individual components.

Cocoon Wrap Method:
Most manufacturers of stretch wrap equipment offer various size and speed units in their semi-automatic line to cocoon wrap coils. They can either furnish blocker rollers used to roll the coil during wrapping or install over an existing blocker roll system. These wrappers are available with an articulating wrapper arm to move in and out for coil placement and removal. Cost for the wrapper only with 12 to 18 RPM would approximate $20,000 US and compatible blocker rolls would be about $15,000 US installed depending upon desired accessories. These relatively low costs for mill equipment are what make this packaging method available universally. For exceptionally large coils requiring a large diagonal wrapper mounted on four legs, the entire unit could be engineered on tracking to move aside for overhead handling.

Cortec’s high performance Cor-Pak™ VCI Stretch Film is designed for maximum strength and holding force with superior corrosion protection. For the Cocoon Wrap Method, trials found that other characteristics were required leading to the development of the unique Cor-Pak™ Cocoon Stretch Film. This innovative designed film maintains the same advantages as the regular Cortec stretch film while also conforming exceptionally well to the curvature of the coil and clings to prevent slippage and zippering of the film.

Procedure Guidelines:
While there is limited data available at this time, we can recommend some guidelines for consideration by the mills wishing to pursue the advantages offered by this method. While the high speed Strema automatic equipment and Coilmaster® use film widths nearly 10 inches, standard 20 inch US width Cortec film can be used effectively on a semi-automatic wrapper following the cocooning procedure. Film gauge of 2 mil continues to be the norm for both strength and application efficiency. An axiom would be that the higher the speed the larger the number of wraps could be applied in a given time, then the lower the gauge and higher pre-stretch would be possible. All of which should be consistent with the coverage required to hold and protect the product.

For starters, we recommend a Cortec designed corrosion protection be applied to the surface of the packaging components used to protect the coil eye, edges and sidewall followed by wrapping with Cor-Pak™ Cocoon Stretch Film down to the coil eye. An alternative would be to first place a VCI coated tube or insert in the eye and wrap the entire coil covering the coil eye opening and then cut open the eye to place the ID edge protector and sidewall disc in position. A second cocooning wrap of the coil down to the coil eye will secure the packaging components in position. However, this involves lost time shutting down which could be avoided by using Cortec protected products first and then overwrapping.

With this new Cortec film, it will be possible to wrap down to the coil eye without covering it. Some mills may prefer to cocoon the entire coil covering the eye and then slitting the eye open for access by C-hook. With 2 mil film pre-stretched at least 150%, we recommend a minimum of 48 total wraps overlapping approximately 50%. The exact number of wraps and pre-stretch should be determined during evaluation trials based on individual mill conditions and product mix requirements.

Weirton Steel leads again:

They pioneered development of the stretch wrap concept in tinplate packaging beginning in 1993 with the help of Cortec’s Metals Packaging Consultant and the benefit of Cortec Corrosion Protection Technology. Hundreds of thousands of tinplate coils have been shipped by Weirton Steel with Cortec VCI corrosion protection and stretch wrap securing the coils to skids which resulted in substantial cost savings. Now with the help of Jan Martin and Liberty Distributors, they are again leading the way with low cost packaging of cold rolled and galvanized coils.

Weirton’s initial installation involves a Wulftec WRT-150 semi-automatic stretch wrapper positioned over mill installed blocker rolls at their No. 8 Skin Mill packaging area. They are using the VCEYE Insert® and 2 mil Cor-Pak™ Cocoon Stretch Film pre-stretching 120% and applying 36 wraps. They place the protective insert first and then overwrap down to the eye. A major benefit is only one operator is required and the coil can be wrapped in 2 minutes. The logistics enhancement for coil placement and storage will achieve production levels beyond their expectation.

Initial customer reaction has been very favorable and other mills are inquiring about this new application. So confident is Weirton Management of the potential for this cocoon packaging that they have already placed orders for additional 6 wrappers with plans for 5 more in the near future. One feature they cite is the ability to place these small units at locations best suited to wrapping thereby avoiding time and labor in unnecessary coil movement.

Click Here to view a collection of photos related to the cocooning process.

Cortec Corporation is proud to have been a part of bringing this new metals packaging application to the industry. Our Total Corrosion Control commitment with environmentally friendly technology and products enables ideas to become reality!

August 29, 2000

For more information contact
Cortec Corporation


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