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PRODUCT OF THE MONTH

The use of inorganic additives to reinforce Teflon® is not new; the author published his first article on the subject in Machine Design in1958. However, to manufacture a roll cover of reinforced Teflon® for the Paper Industry was not commercially successful until the late 1990’s.

Fig.1. The U. S. Patent office has issued a Patent Number 6,471,627 on this Roll Cover for the paper industry

There are two big advantages of a roll cover made of Teflon® reinforced with carbon. First: The reinforced cover outwears an unreinforced roll cover by ten fold. Second: A conductive form of carbon eliminates the “static build-up” that has been a shock hazard in some dryer roll applications. The good news is that the reinforcement does not affect the outstanding release characteristics of Teflon®.

In the early 1990’s DuPont experimented with a development grade of static-dissipative Teflon® resin, and Bunnell Plastics extruded some small diameter roll covers with the compound and advertised the roll cover called NS2. There were several successful applications of the product. This created considerable interest in the industry, but a lack of uniformity in the product and the high cost of extrusion of a single roll cover, led to the product’s demise and the development was discontinued.

Fluoron, Inc. was challenged by several customers to offer such a product. Randall & Frank Chapman, the founders of Fluoron picked up the challenge. They discovered they could make ultra-high melt viscosity polymers such as ultra-high molecular weight polyethylene and the homopolymer Teflon® PTFE heat shrinkable and with the addition of the right form of carbon it could be made static-dissipative. They were able to solve the economics by manufacturing production quantities of carbon reinforced sheet with the less expensive homopolymer. Then, from this inventory of sheet, they could custom manufacture any size roll cover utilizing their butt weld seaming technology. Their efforts were rewarded in October 2002 when the U. S. Patent office issued Patent Number 6,471,627.

1st Installation - After the two-year development Randall Chapman installed the first static-dissipative roll cover on a bowed roll that had such severe static build-up that it blew holes in a standard Teflon® FEP roll cover in 60 days. The new roll cover completely eliminated the static problem. Fluoron’s new carbon reinforced roll covers were marketed under the tradename “Fluoro-Stat”.

Teflon® is the registered Trademark of DuPont for its fluoropolymer resins with the best release properties. Fluoron Inc. certifies that it uses only virgin DuPont Teflon® in its roll cover products..

To overcome the quality problems, the Chapman’s scrutinized the blending of the carbon with virgin DuPont Teflon® and then Fluoron saw to it that the manufacturing process variables were held under extremely tight control to provide the highest quality sheet product possible and designated it “Sheet Product 102”.

The other critical technology was to make a uniform weld in the tube that would not mark the sheet in the most critical of paper mill applications. In 95% of the roll cover applications the seam is so good that the seam does not have to be ground and Fluoron Inc. will guarantee it. However, if required the roll cover can be ground.

Fig. 2. Close up of a seamed “Fluoro-Wear” 102 roll cover finished for a critical application

Fluoro-Wear™
Wear testing of the 102 formulation indicated it provided greatly improved life for a roll cover. There had been a number of installations of standard .060" thick heat shrinkable roll covers of unreinforced Teflon® on felt rolls where there were severe build up problems. The release characteristics eliminated the problem, but in most cases, the wear life was not good enough to satisfy the paper machine superintendent. One mill in the Mid-West with a large machine, and a big build-up problem on the stretch roll of the 1st felted section, had tried a coating and found that while it provided release, it wore off. In 1999, they installed one of the then new 102 roll covers. The long lasting roll cover was called “Fluoro-Wear” 102. The roll cover has been in this severe wear application providing excellent release for 3 1/2 years.

Since then that same mill has purchased “Fluoro-Wear” 102 roll covers ranging in diameter from 16" to 30.3" up to 342" long.

Fig. 3. This “Fluoro-Wear” 102 cover has been in service 3 1/2 years and wear measurements indicate that it will have greater than a ten-year life.

Fluoron Inc. technicians install the roll covers in the Paper Mill with the bearings setting on horses or faster with the bearings removed and rotated in a lathe. Or the rolls can be sent to roll shops like Western Machine in Portland, Oregon who are experienced with these installations. Most of the bowed roll manufacturers are also experienced with installing the “Fluoro-Stat” and “Fluoro-Wear” roll covers. The installations are relatively simple. One end of the roll is supported on a beam and the roll cover is first put on the beam and then pulled off the beam onto the roll. The roll cover is bonded to the roll with stripes of adhesive.

 

 

 

 

 

Fig. 4. This “Fluoro-Wear” roll cover was installed on the 24" diameter x 342" face roll in 3 hours.

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