Curl/Moisture Control: Silicone Coater & Laminator
Steam-Foil® is the only system proven to control curl in silicone release liner and laminated products.
Features/Benefits
- Profilable steam application
- De-coupled curl and moisture control
- Easily retrofitted to existing machines
- Easily linked to any measurement system for automatic control of curl and moisture
- Applies steam through silicone coating; re-moisturizes C2S grade
- Significantly increases final moisture
- Achieves remarkable improvements in product quality
- Flat laminates that stay flat
- High moisture lay-flat
What is Curl?
When converters try to obtain an adequate cure for silicone, they usually end up with an over dried and curled sheet. The problem arises from the laminating of two different paper stocks, which creates an unstable construction that curls upon conditioning. With today's demand for a better quality product, relieving curl is of prime importance.
Curl can be defined as the tendency for a flat piece of paper or laminate to distort in a cylindrical fashion.Curl is caused by the uneven expansion and contraction of fibers, coatings or laminates which makes one side of the product "shrink" more than the other. Once the curl memory state is set, a change in the exhibited curl can usually be attributed to a change in moisture. This is due to the fibers growing with an increase in moisture.
Solving the Problem
The objective of curl control is to reset the curl memory state of the paper so that the paper lies flat under most conditions. When steam is applied to paper, it condenses, imparting both heat and moisture to the paper. This heat and moisture softens the fibers and loosens the fiber bonds. Subsquent evaporation resets the curl memory state of the paper.
The Steam-foil
Technological developments in nozzle and actuator design have led to the development of the Steam-Foil. The Steam-Foil has the capability of efficiently and uniformly applying steam without the problems associated with traditional steam showers. Because steam has the ability to penetrate silicone, the Steam-Foil precisely and predictably controls curl by adding moisture to either the silicone or uncoated side of the release liner. A Steam-Foil mounted on each side of the sheet allows the operator to control curl and moisture independently. By adjusting the ratio of steam applied to each side of the sheet, the curling forces can be counteracted to produce a flat sheet. Maintaining this ratio, the overall volume of steam applied to the sheet can be used to increase or decrease the sheet's moisture.
A Typical System
The control of curl and moisture on silicone release liner is typically accomplished by mounting two Steam-Foils in a clamshell configuration after the silicone dryer and chill rolls (see diagram below); maintaining an incoming web temperature between 80F to 100F. This affords control of the liner from coated, flat, to uncoated side curl, with a re-moisturizing range between 3% - 5%. Additionally, re-moisturization of C2S grades is possible. Control of curl and moisture of laminate product can be accomplished by placing a Steam-Foil on both the liner and face stock sides before lamination, or by mounting two Steam-Foils in a clamshell configuration immediately after lamination. With either solution, the benefit is total control of curl and moisture in your finished product.