Are the new Tyvek 2FS and peelable resin films for you?

Pharmaceutical & Medical Packaging News staff

A lighter Tyvek, paired with cleaner-peeling resin-based films, offers opportunities for substantial savings over traditional materials.

by Jenevieve Blair Polin

The first new style of Tyvek for medical packaging in 15 years, along with new companion films designed to seal to its uncoated form, is a windfall for medical device manufacturers, who may reduce the cost of packaging by as much as 40% by converting from traditional packaging. For those who are buying premade pouches, there is the opportunity to save even more by switching to in-house form-fill-seal equipment running the new materials. Medical device manufacturers and equipment and materials suppliers are encouraging packaging engineers to learn whether the new materials are right for their companies' applications and whether they stand to profit, given their product volume.

A LIGHTER TYVEK

In January of this year, DuPont (Wilmington, DE) rolled out Tyvek 2FS, a medical-grade Tyvek brand spunbonded olefin with a lower basis weight (1.65 oz per sq yd) than either 1073B (2.2 oz per sq yd) or 1059B (1.9 oz per sq yd). Device manufacturers whose products are lightweight and free of sharp edges, and therefore require less puncture and tear resistance, may be able to use Tyvek 2FS at considerable cost savings. Some who are using paper as a top web now have the option of changing to Tyvek 2FS. Tyvek 2FS, which is half the weight of paper and stronger than the heaviest grades of medical papers, also generates far fewer airborne particulates.

Multivac's R330 FFS machine can run 15 to 25 cycles per minute.
 

In addition to lowering the basis weight, DuPont has made a few other improvements in creating Tyvek 2FS. With 1073B or 1059B, it was possible to transparentize the seal area at the upper end of the sealing temperature window, a phenomenon that "appeared to the end-user as a defect," but really is acceptable, explains Robert Hagood, DuPont Tyvek medical packaging marketing specialist. DuPont eliminated this perception by adding an opacifier, titanium dioxide, to Tyvek 2FS. The opacifier gives manufacturers additional savings in terms of efficiency, because they can seal at higher temperatures and therefore run at faster speeds. Dwell time is also reduced, Hagood points out, since "you get a little better conductivity of the heat through Tyvek 2FS because it is thinner." The opacifier also makes the surface of Tyvek 2FS look whiter and more uniform. The enhanced contrast increases the readability of bar codes and print.

Another change is that Tyvek 2FS is differentially bonded. "We more heavily bond the side that is used for sealing to try to minimize any fiber tear," Hagood says.

DuPont advises users to verify that they are heat sealing the rough side of the sheet of Tyvek 2FS to minimize fiber tear. Both coating and sealing should be done on the rough side. Slits should not be made in the heat-seal area. Also, an unsealed area should be left around the circumference of the package to minimize fiber tear.

Tyvek 2FS is already available in pouches from many converters. As rollstock, it is available coated, just like 1073B and 1059B, for use with traditional films. Oliver Products Co. (Grand Rapids, MI), for instance, offers the new Tyvek 2FS with its 10MP adhesive, a hot-melt, heat-seal, white, dot-patterned coating. Tolas Health Care Packaging (Feasterville, PA) also converts Tyvek 2FS and applies its own TPT-0268 heat-seal coating to it. The greatest cost savings, however, may be achieved by using uncoated Tyvek 2FS rollstock with one of the new peelable resin-based films developed specifically to partner with it.

POLYMERIC SEALANT SYSTEMS

Converters have been quick to take advantage of Tyvek 2FS by developing resin-based coextruded forming webs for heat sealing to uncoated Tyvek 2FS. Perfecseal Inc. (Philadelphia), Rexam Medical Packaging (Mundelein, IL), and Rollprint Packaging Products Inc. (Addison, IL) all offer such films, which are currently being evaluated and tested by medical device manufacturers.

All-film packages made with materials from Rexam exit Multivac's FFS machine.

When a traditional package marrying a formable film to coated Tyvek is peeled, some of the adhesive coating remains on the Tyvek, and some is transferred to the film, where it is visible as a white area of transfer. The new polymeric sealant systems work differently. Coextruded forming webs of this type consist of at least three layers: the carrier layer, the intermediate layer(s), and an "adhesive" outer layer. Their peelability is achieved through cohesive failure in one of the polymer layers. In systems such as depicted in Figure 1, the outer layer splits cohesively, with some of it remaining on the Tyvek and the balance remaining on the film. In Rexam's Core-Peel system, the outermost layer permanently bonds to the Tyvek, and the cohesive peel occurs in an intermediate peel layer.

Perfecseal's PerfecFlex CPT (clean-peel transfer technology) is available in several types, including EVA/Surlyn/CPT and PP/Nylon/CPT. Rollprint offers FlexForm T for sealing to uncoated Tyvek. Likewise, Rexam's FM peel system is available as Integra Form PC and Integra Form PSP, which both use a copolymer with polybutylene blended in for peelability. Rexam is also introducing Core-Peel film this year.

One trade-off for some manufacturers switching from coated Tyvek with a traditional formable film to uncoated Tyvek with a new peelable film may be a narrowing of the operating window. With the caveat that this phenomenon depends greatly on the equipment used, Rexam's global marketing director, Jerry Bennish, warns that in some situations the new resin-based systems may yield an operating window "30% less than the window with a coated system." He adds, "It is important to validate the process over the range of sealing temperature variations to ensure that seal quality or machine speed is not compromised." When Core-Peel is launched as a forming film, however, he anticipates that it will have the same window as traditional films with coated Tyvek.

Chris Heezen, product manager, film, for Perfecseal, explains that traditional films used with uncoated Tyvek had a very narrow operating range, "10° maximum, because with technologies that work by adhesive failure you're trying to get two dissimilar materials to separate at a consistent rate, which is very difficult."

However, there is some disagreement as to whether there will be a narrower operating window for the new combinations. Craig Livingston, vice president of sales for Rollprint, reports that the operating window for FlexForm T with uncoated Tyvek is about the same as that for traditional materials, about 50° ±25°. And Heezen reports a 60° operating window range for CPT.

Ron Reichert, senior R&D project manager for BD Infusion Therapy Systems (BD; Sandy, UT), is part of a team collaborating with manufacturers to do extensive testing of these new materials. His facility works closely with the packaging Center for Excellence within BD, so the decisions this center makes will affect the packaging of billions of units at 60 different BD manufacturing sites around the world. He reports that with the new combinations, he's seeing an operating window that is actually a little more open, in terms of both formability and seal process parameters, than with his traditional materials, coated Tyvek of various thicknesses sealed to EVA/K resin/EVA (4 mil to 12 mil).

Another challenge for converters developing peelable films has been to equal the whiteness of the area of transfer in peeled packages employing coated Tyvek. In a best-case scenario, says Heezen, "if we are able to work with customers on the machines and the type of gaskets that are used, we can achieve about 75–80% of the visual whitening" in the area of peel. Similarly, Livingston estimates that with FlexForm T the area is about 90% as white as with coated Tyvek.

Figure 1. Polymeric sealant systems are based on cohesive film failure during the peel process. Because a thin layer of film remains on the Tyvek, fiber tear is eliminated. Shown is the cohesive failure of Perfecseal's CPT.
 

One option for enhancing the visibility of the seal and peel is to add a tint to the outside layer. Rexam, for instance, is promoting the use of a blue tint in Core-Peel, so that the layer left on the Tyvek at the time of peel is blue. Some manufacturers, Bennish says, have embraced this option as a way to differentiate their product. Others, however, want to ensure that any change in packaging materials is unnoticeable to the end-user, so they prefer a white indicator.

Not only reduced cost but also a cleaner peel is promised by converters offering these new materials. "Any kind of fiber generation as the package is opened is a problem," stresses BD's Reichert. "Some of these fibers can become or are nonsterile and if they are flying around and land on, say, the tip of a needle or catheter prior to insertion into the patient, that would not be a good thing."

Because the new peel systems leave a layer of film on the Tyvek, rather than peeling an adhesive coating off the Tyvek, fiber pickoff is significantly reduced. Nevertheless, points out Bennish, "On a microscopic level you still stress fibers with those films." Rexam expects to be able to reduce stress on the fibers even further, he says, with Core-Peel technology (Figure 2).

Figure 2. Surface-scanning electron micrograph of a peeled, Core-Peel-to-Tyvek heat seal. Visible on the Tyvek are the retained seal layer and part of the peel layer from Rexam's Core-Peel film. Magnification is 250x.
 

Resin-based peel systems also reduce quarantine times. "You can improve porosity by going from a coated Tyvek to an uncoated Tyvek, so that's when you can really reduce your outgassing time," explains DuPont's Hagood.

FILM-TO-FILM SEALING

While much of the excitement in form-fill-seal packaging has been generated by the launch of Tyvek 2FS, converters point out that for some manufacturers even greater savings are possible with another packaging option: sealing film to film. Eliminating Tyvek is a possibility for manufacturers who are sterilizing by gamma or E-beam.

"In most packaging applications where the breathability of Tyvek is not required for either sterilization or processing of the product, film-to-film packaging can offer considerable cost savings," says Rollprint's Livingston.

Table I. Cost comparisons for Rollprint's FlexForm bottom webs and coated and uncoated top webs of Tyvek or peelable film. Cost comparisons from other converters are also available.

Resin-based peelable films may be sealed to thermoforming films, such as EVA/Surlyn/EVA or a nylon-based product. For instance, in 1996 Rexam introduced the use of Integra Peel FM with Integra Form C. Another option, Livingston offers, is to couple a traditional nonpeelable film as the bottom web and an extrusion-coated peelable film top web (see Table I).

Even cheaper, says Perfecseal's Heezen, is to use a top and bottom web of the same material, such as an all-polyethylene package. This option is suitable only for lightweight, high-volume products, such as gauze, sponges, and surgical gloves.

EQUIPMENT

Manufacturers need not necessarily switch to in-house form-fill-seal systems to take advantage of the cost savings generated by the availability of peelable films that seal to uncoated Tyvek 2FS. Converters have been quick to offer premade pouches constructed of these materials.

Nevertheless, a manufacturer whose product volume justifies the investment will maximize cost savings with the use of in-house form-fill-seal systems. But what is that product volume? According to BD's Reichert, "If you get up over a million units or so, or not even there depending on the application and the size of the pouch of Tyvek or whatever you're using, it's very cost-justified to switch over to form-fill-seal."

Equipment costs are dictated by the maximum width of the machine, the maximum cutoff length or index length of the machine, and the maximum depth, as well as the speed (cycles per minute). A supplier of form-fill-seal machines for medical device manufacturers, Multivac Inc. (Kansas City, MO), offers three machines—the R230, R330, and R530. Cost ranges from $80,000 to $300,000, depending on how the machine is configured. Cutting devices, for instance, can dramatically affect the price of the machine.

In considering such a purchase, says Joe Martin, Multivac's executive vice president, medical division, "You have to ask, 'What is my internal rate of return?' Some people look at simple paybacks and simple ROIs, but you have to consider other difficult-to-quantify factors." Multivac's regional managers and project managers, in fact, use a rigorous model to work with customers on the economic evaluation simultaneously with the technical evaluation. (For a detailed analysis of the model, consult the upcoming September 1999 issue of PMP News.)

An important consideration in equipment selection is the ease and speed of retooling. "In our highly automated plants," says BD's Reichert, "it's a nonissue since we have lines dedicated that never change over. But in our lower-volume operations around the world, tooling changes are required fairly often."

Multivac's Martin explains that the time required for retooling depends on the extent of the package change. The easiest change, requiring as little as five minutes, is a change in the depth of the package. This change requires simply changing spacer plates, and in fact, Multivac has customized some units by adding a stepper motor into the bottom of the forming die so that an operator may vary the depth from a control panel. The most extensive change, a change in cutoff length, requires complete retooling and may take 45 minutes to an hour.

Doyen Medipharm, Inc. (Lakeland, FL), offers fully flexible machines for thermoforming and pouching. For instance, the 4SS form-fill-seal machine is a rapid changeover machine for creating bags and pouches in-house or packaging online. With this machine, says Martin Beriswell, Doyen's general manager, a user can "make a total three-dimensional pack-size change in about five minutes." Doyen is currently working with DuPont to qualify the new Tyvek 2FS on its full range of machinery.

The next wave of change may be equipment modifications to accommodate quirks of the new materials. For instance, "Some of the nylon-based structures are more difficult to cut," points out BD's Reichert, "so we may need to replace some cutting systems and tighten up the tolerances."

Using in-line printers, Perfecseal's Heezen adds, is another way in which manufacturers with in-house form-fill-seal systems reduce costs. But Multivac's Martin warns that it's not unusual for a top web to be run through as many as four devices—a thumbhole punch, a knurling device, a flexographic printer, and an ink-jet or thermal transfer printer—before it reaches the seal die. While nip rollers, cluster rollers, or dancer rollers may control the tension in the top web immediately before the sealing stage, they cannot control the variable tension that may cause it to stretch out of register as it passes through all of these other devices upstream.

TAKING THE PLUNGE

As a welcome surprise, the new packaging materials available offer improved performance while actually lowering costs. Taking advantage of these cost savings requires revalidation but also requires manufacturers to consider equipment investments, changes in sterilization methodology, and more. But even those with mature high-volume commodity products are considering this leap, says Martin. "They really don't have much choice, because if they don't do it, their competitor will, which will force them into it."