Desiccants Enhance Package Performance
Changes to desiccant forms streamline the packaging process and simplify the package.
by Annie Gorton, Senior Associate Editor
A desiccant has an important job: to keep a moisture-sensitive pharmaceutical or medical device effective for the duration of its shelf life. While a package remains unopened, the desiccant maintains the humidity level required to keep the drug or device efficacious. Although the "sachet in a bottle" has been the familiar choice for decades, desiccant manufacturers are making changes to the forms their products take. These changes simplify and streamline the packaging process as well as create a better-looking finished package.
What hasn't changed is how desiccants work.
"Desiccants adsorb moisture," says Ed Stasen, marketing manager of Engelhard Corp. (Iselin, NJ). Adsorption occurs when the desiccant captures and holds water vapor; the process differs from that of absorption, which happens when water is integrated into another substance.
"Usually a packet of clay or silica gel is put into the container to protect products that are sensitive to moisture; otherwise, the water vapor within the package could degrade the product," Stasen says. Desiccants may also protect pharmaceuticals from oxygen and odor, depending upon the type used. The length of the shelf life depends upon the specific desiccant included in the package.
"There are three basic types of desiccants," says Greg Morgan, market segment manager at Süd-Chemie Performance Packaging (formerly United Desiccants; Albuquerque). "They include activated clay, silica gel, and molecular sieve. All three types are used in pharmaceutical and medical applications. They have different adsorption capacities under different environments. Some pull down the humidity quickly; others adsorb moisture over a long period of time."
A very hygroscopic (water-attracting) pharmaceutical product, such as a powder pressed into tablet form, will require an aggressive desiccant such as molecular sieve to protect the integrity of the product. A product with moderate hygroscopic characteristics may be well protected with the use of a clay desiccant.
Stasen says: "Typically the main desiccant used in pharmaceuticals is silica gel." A small amount of this desiccant is enough to protect the contents of a package.
In addition, says Chip Skop, marketing group leader at Multisorb Technologies Inc. (Buffalo, NY), "Silica gels are acceptable for many FDA applications." Sometimes, molecular sieve is used for pharmaceutical packages, he adds. "It adsorbs a lot of moisture, and it works well in low relative humidity environments," he says.
Sometimes a company will use a silica desiccant within a bottle, but will use a clay desiccant in a larger package. "Clay desiccants are used more in higher-volume or larger containers. They tend to be less expensive, so when you have a big container, you can use clay," Stasen says.
A humidity indicator is not required with a desiccant, but is recommended by some desiccant manufacturers. "If a medical device may be compromised by the presence of humidity, it would be helpful to have an indicator placed inside the package," says Morgan. "That way when the package arrives, you can see that the humidity never reached above 50%, for example."
Wyntek Diagnostics Inc. (San Diego) does not use indicators in its products, however. Bruce Gardner, the company's vice president, sales and marketing, explains, "We don't use an indicator because we monitor our products in house for stability and shelf life. Also, it might be confusing to consumers to check the humidity."
Multisorb has an indicating silica gel, according to Skop. "The color will change from blue to pink and will tell you when the silica gel has adsorbed nearly its capacity," he explains. Whether or not an indicator is needed depends upon the product.
CLEANLINESS IS ESSENTIAL
The most widely used forms of desiccants are the sachet and the canister. These may be placed inside a bottle or inside the film wrapper containing a medical device. Because they are in direct contact with the product, these desiccant packages must be clean as well as effective.
Lori Gettelfinger, market segment manager for Tyvek Industrial Packaging at DuPont (Wilmington, DE), says that packaging used for desiccant materials "must be porous to allow activation to occur, and it must contain the product both before and after activation."
"The best package for a pharmaceutical desiccant is Tyvek or a capsule," says Ron Tabat, vice president of marketing, planning, and development at Phoenix Health Care Products LLC (Milwaukee). "The material must be porous, but not so porous that dust can go through the material."
Süd-Chemie's desiccant plastic, 2AP, can be injection-molded into a variety of container shapes.
Desiccants have been designed with pharmaceuticals in mind. Silica gel, one of the preferred desiccants, is unlikely to create dusting problems, says Stasen. In addition, the materials used for sachets keep any dust from contaminating the product. Canisters have micropores, tiny holes that contain the desiccant and prevent leaks. And the newest desiccant products are designed to be clean as well as effective.
DuPont has created a new Tyvek suitable for packaging desiccants. Tyvek 1025BL is a thinner, lighter-weight style designed for less stringent applications where less strength is required. "For smaller packages, such as desiccant packages, Tyvek 1025BL may be more cost-effective," Gettelfinger says. "The 1025BL has higher permeability and greater moisture vapor transmission, enabling the desiccant to act more quickly if manufacturers have that requirement. We are anticipating that we'll see more manufacturers investigating the possibility of using 1025BL instead of kraft paper for packaging desiccants, because the two are similar in cost."
Some new forms besides the sachet and canister are gaining increased use as desiccant manufacturers strive to improve their products. Morgan believes that the "bag in a bottle" will eventually be replaced. "Desiccants are becoming performance oriented," he says. "They can be placed in the packaging material or in the cap so the consumer can't see them, which makes a more aesthetic package."
Wyntek Diagnostics manufactures rapid diagnostic test kits for human fertility and infectious disease. The company uses desiccants from Süd-Chemie Performance Packaging to adsorb moisture. "One product we use is the desiccant tablet contained in the cap," says Gardner. The tablet form of desiccant is well suited for use in packages containing effervescent products or diagnostic kits. Not only is this form less obvious to the user, it can also speed up the packaging process.
For Lakeland Biomedical (Eden Prairie, MN), a company that makes diagnostic kits, replacing a desiccant sachet with a tablet increased packaging speeds from 6 to 200 kits per minute. The tablet was glued to the cap of the package, which meant that the extra step of inserting the desiccant sachet before closing the package was eliminated.
Other forms of desiccants include coatings and plastics. Tabat says: "The desiccant market has recently been diversifying. Manufacturers are now looking for new ways to incorporate the desiccant into coatings. Instead of having a loose desiccant in the package, the package itself can adsorb moisture."
Süd-Chemie has developed a way to implant the desiccant into plastic, creating a product called 2AP. The 2AP material combines precise amounts of a desiccant, such as molecular sieve or silica gel, with a polymer. With the desiccant incorporated into the packaging material itself, there is no need to add the desiccant in a separate step on a packaging line. The 2AP can be customized to control the moisture adsorption rate. The material is dustless and recyclable, according to the company.
Capitol Specialty Plastics Inc. (Auburn, AL) also combines a desiccant with a channeling agent into a polymer that can be molded or extruded into many shapes. Almost any type of polymer can be used. The company's desiccant plastic allows the entire package to act as the moisture adsorber. Roger Moore, Capitol's vice president of sales and marketing, says that use of the desiccant plastic "eliminates costly sourcing, handling, placement, and inspection of desiccant beads, packets, canisters, lozenges, and pouches."
DuPont Tyvek offers a clean, porous material for packaging desiccant products.
Moore adds, "Although the desiccant plastic is slightly more expensive than other plastics, when you eliminate the step of adding a desiccant to a container, the desiccant plastic is cost-effective." The company can design the desiccant plastics to meet production requirements as well as to control the rate of adsorption.
Capitol's plastic vial contains a sleeve of desiccant plastic that lines the vial's bottom and sides. This sleeve places the desiccant over a large surface area within the vial.
PACKAGERS DIRECT THE FUTURE
Desiccants will continue to develop and change as the needs of packagers change. Their essential function remains the same, but the shapes, forms, and sizes will diversify. Packaging engineers may have more say about the future of desiccants than they think.
Engelhard's Stasen explains: "Instead of a desiccant manufacturer offering three types of sachets to choose from, the package engineer may tell the manufacturer the exact needs of their product. The manufacturer can then design the best desiccant package for the application."
Opening photo by Roni Ramos