FIELD OF THE INVENTION
The present invention relates to a film having a desiccant material incorporated therein. More specifically, the present invention relates to a film structure having a desiccant material within a sealant layer of the film structure wherein said film structure is utilized as a package for a product that may be sensitive to the presence of moisture. In addition, the present invention relates to methods of manufacturing and methods of using the film having a desiccant material incorporated therein.
BACKGROUND OF THE INVENTION
It is generally known to utilize plastic packaging to reduce exposure of products to atmospheric conditions, such as to moisture or oxygen, which may damage the products. For example, packaging for foodstuffs is well known, in that moisture and oxygen may cause the foodstuffs to become spoiled and inedible or otherwise undesirable. In addition, many products in the medical field may also be very sensitive to atmospheric moisture.
Typically, moisture-sensitive products may be encased in thermoplastic material that is relatively impermeable to water molecules. Specifically, many polymeric materials are utilized as barriers to moisture transmission. For example, a film of high density polyethylene (HDPE), or polyvinylidene chloride-methyl acrylate (PVdC-MA) copolymer may be utilized to restrict the movement of water molecules through the film. Oriented polypropylene, metallized oriented polypropylene, or metallized polyester would also be useful as moisture barrier material. In addition, metal foil is known to prevent the transmission of oxygen and/or moisture through polymeric packaging having a layer of metal foil contained therein.
Although these moisture barrier polymers may be useful in restricting the movement of moisture into a package, some moisture molecules can still make their way into the package to deleteriously affect the product contained therein. In addition, even when barrier materials are effective at restricting the transmission of water molecules through a package, certain features of the package may still allow for the transmission of water molecules. For example, where a barrier material is incorporated into a central layer of a film structure and the film structure is sealed to another film structure having a barrier material as a central layer, the edges of the package may not be protected by the barrier layers. This may allow moisture to make its way into a package along the edges of a heat sealed package.
One solution to maintaining a particularly low or virtually nonexistent level of moisture within a package is to incorporate sachets of desiccant material into the internal space of the package to remove the moisture from the headspace of the package. A sachet may effectively maintain a very low level of moisture in inside spaces of packages, but may have difficulty maintaining the same consistent moisture levels after the package has been opened and a product has been removed. For example, a typical package of moisture-sensitive products may contain a plurality of the products. A sachet of desiccant material incorporated into the package may only guarantee that moisture level of the package is maintained at a constant or minimal moisture level until the package is opened and the first product is thereby removed. The remaining products will be instantly exposed to atmospheric moisture when the seal of the package is broken. Although the sachet may remove some moisture from the headspace of the package after the package is opened, the remaining moisture-sensitive products, having already been exposed to moisture, may already be damaged. This may be especially true in bulk packaged materials where sachets are most often used. Desiccant materials are typically incorporated into liddings of jars or in sachets of multi-unite packages.
In addition, sachets of desiccant material may become saturated with atmospheric moisture relatively quickly thereby decreasing or eliminating their effectiveness. Moisture-sensitive products, therefore, stand a greater chance of being damaged by moisture in this case.
Moreover, the desiccant material contained in the sachets is typically in powder or granular form and may leak or otherwise spill from the sachets thereby contaminating the product or products contained within the package. For example, if the desiccant material contacts a food product or medical device, the food product or medical device may become contaminated with the desiccant material, which may be damaging to the health of an individual that consumes the food product or uses the medical device.
Additionally, although desiccant material is generally known to reduce the moisture content within a package, typical desiccant materials are “physical” desiccant materials, such as molecular sieves, that bind water molecules within pore spaces of a material. Typically, physical desiccant materials absorb water at all humidity levels, but will cease to absorb water when interstices of the physical desiccant material are filled. Therefore, physical desiccant materials may be ineffective at high humidity levels.
An additional type of desiccant material may be hydrate forming agents such as salts. Typical salts that may be utilized as desiccant material are magnesium sulfate, sodium phosphate di-basic, ammonium chloride, potassium carbonate, potassium aluminum disulfate, magnesium chloride, diammonium sulfate, sodium nitrate, calcium chloride, and calcium sulfate, although many others are known as well. Typically, the drying capacity is greatly influenced by the relative humidity within a package. Generally, no water is taken up by the hydrate-forming agent until the relative humidity reaches a value at which the first hydrate forms. In the case of calcium chloride, for example, the first hydrate occurs at less than about two percent relative humidity (R.H.). Water is then taken up by the hydrate forming salt until the first hydrate is completely formed by the salt. No further water is taken up by the salt until the relative humidity reaches a second level where the second hydrate forms. This process continues through as many hydrates as the agent forms at which point the substance begins to dissolve and a saturated solution is formed. The saturated solution will then continue to take up water.
Although these salts may be effective at removing water molecules from a quantity of gas that may be contained within the headspace of a package, since the salt only binds the water molecules within the salt, the water molecules may easily escape back into the package. This is known as breathing, and may cause deliquescence (water droplets and liquidization) inside the package. Typically, this can happen if the salt becomes saturated and if the temperature of the package increases, or if the pressure of the package decreases, which may occur during shipment or storage of the package.
In addition, salts may not allow moisture levels within a package to fall to a level that is necessary to protect the moisture-sensitive product that may be contained within the package. Typically, since salts typically have different levels of hydration, humidity levels may remain a certain level without decreasing until the level of hydration changes.
However, these salts may be utilized to maintain certain humidity levels within the headspace of a package. For example, certain products may require that a certain level of moisture or humidity be maintained within the package headspace. Headspace humidity control for products can be manipulated by incorporation of the appropriate hydrate forming agents.
Desiccant materials may also be used that form no hydrates, such as common salt (NaCl) or potassium bromide (KBr). For example, common salt will absorb no water at a relative humidity below about 75 percent. When 75 percent relative humidity is reached, a saturated solution is formed which continue to take up water.
The present invention may utilize chemical desiccant technology, which is more preferable because the moisture level within a package may be maintained at an extremely low level. Chemical desiccant materials chemically react with water molecules to form a new product, wherein the water molecules are chemically incorporated into the new product. For example, calcium oxide binds water in the following reaction:
Because the reaction noted above requires very high energy levels to reverse, it is, for all practical purposes, irreversible. Chemical desiccant materials typically absorb water at all humidity levels, and will continue to take up water at high relative humidity levels. These chemical desiccant materials, therefore, may reduce levels of moisture within the package headspace to zero or near zero, which is often desired to maintain maximum dryness of the product.
An example of a moisture-sensitive product that would benefit from the present invention are medical diagnostic testing equipment, such as diagnostic test strips. Medical diagnostic test strips are typically used to test for the presence of particular compounds in a biological fluid, such as blood or urine. For example, diagnostic test strips may detect the presence of narcotics or other substances.
A diagnostic test strip is typically dipped into a sample of the biological fluid and if the individual has traces of narcotics in the sample of the biological fluid then the diagnostic test strip may change colors to indicate the presence of the narcotics.
In addition, diagnostic test strips may be useful to detect particular levels of naturally occurring compounds that may be present within biological fluids. For example, high levels of protein in blood and/or urine may indicate a disease state. Diagnostic strips are useful to test not only for protein levels, but a plurality of other indicators for levels of various disease indicators. Diagnostic strips may also be utilized to detect certain biological conditions, such as pregnancy.
Diagnostic strips, like the ones described above, are typically extremely sensitive to moisture, and must be removed from atmospheric conditions in order to work properly. In the medical field, it is extremely important to get accurate readings using diagnostic testing strips. An inaccurate reading may make it difficult to diagnose a particular disease state, or may make a doctor misdiagnose a particular disease-state entirely. In addition, an inaccurate reading may jeopardize an individual that may test positive for a particular narcotic, especially if the positive result is a false reading. Therefore, it is of utmost importance that diagnostic strips be as accurate as possible.
Therefore, diagnostic test strips are typically sealed away from atmospheric conditions. For example, diagnostic test strips are typically wrapped or otherwise contained within a material that is impervious to moisture and oxygen that may cause damage to the diagnostic test strips. A thick plastic or glass plastic package, jar, vial or other container is typically used to house diagnostic test strips prior to use. In addition, sachets of desiccant material are typically incorporated into packaging for diagnostic test strips. However, these packages suffer from the problems as detailed above.
Other examples of typical packages or products that would benefit from desiccant material are electrostatic shielding packaging for electronic parts, such as printer cartridges, circuit boards, televisions, DVDs, printers, modems, personal computers, telecommunications equipment, etc., and in pharmaceutical and/or nutriceutical packaging, such as inside pill bottle caps. Further, other packaging that would benefit from desiccant material is packaging for foods, such as cheese, peanuts, coffee, tea, crackers, spices, flour, bread, etc. In addition, other products that would benefit from desiccant material incorporated into the packaging are shoes, boots, film products and cameras, and products that may be shipped by sea, such as high-value wood like mahogany that would be damaged if exposed to ambient humidity typically found in cargo ships.
A need, therefore, exists for polymeric plastic packaging that may be used in packaging to preserve products that may be sensitive to atmospheric moisture. The packaging may comprise films having a desiccant material incorporated directly into a sealant layer of the film. In addition, films are needed that effectively control the level of moisture within packaging without using sachets or desiccant beads that may become ineffective over time, or that may contaminate products contained within the packaging. Moreover, films, methods of use and manufacture are needed to overcome the additional disadvantages as noted above with respect to sachets, beads or physical desiccants.
SUMMARY OF THE INVENTION
The present invention relates to multilayer plastic polymeric flexible packaging films having a desiccant material incorporated within a layer of the film. More specifically, the present invention relates to a polymeric flexible film having a desiccant material incorporated within a layer of the film that is utilized as a package for a product that may be sensitive to the presence of moisture. In addition, the present invention relates to methods of manufacturing and using the polymeric film having a desiccant material incorporated therein.
It is, therefore, an advantage of the present invention, to provide a polymeric plastic packaging film having a desiccant material incorporated therein for packages that may contain moisture sensitive products. These products may be, for example, foodstuffs and/or other products that may suffer from the deleterious effects of moisture. Specifically, diagnostic strips that are useful in health care may be packaged using a film having a desiccant material contained within a layer of the film to maintain the utility of the diagnostic strip. The desiccant material is utilized to control the moisture level within a package made by the film of the present invention. The desiccant materials may be utilized as an alternative to high cost and marginally effective desiccant sachets or beads that may ruin the product within the package if the desiccant sachet breaks open or is otherwise allowed to contaminate the product within the package.
In addition, it is an advantage of the present invention to provide a film having a desiccant material incorporated therein that would eliminate the need to incorporate into high cost and marginally effective sachets or beads of desiccant material that may contaminate products contained within packages if the sachets accidentally release the desiccant material into the package. Moreover, sachets or beads may be unsightly and may take up space within a package that could otherwise be used for product. If the desiccant material within the sachets or beads are ingested, they may become a health hazard. By the present invention, the desiccant material is incorporated directly into the packaging film in a rigid solid state in the packaging film substrate.
Moreover, it is an advantage of the present invention to provide a film wherein the desiccant material is incorporated into the sealant layer of the film and wherein the film is easily extruded. In addition, many different types of desiccant materials may be utilized, thereby allowing for particular relative humidity levels within the packages.
The present invention further reduces packaging costs by allowing for the use of thinner and, therefore, less expensive barrier materials, such as aluminum foil. For example, many flexible foil packages made using films of the present invention can have barrier layers having thicknesses that may be reduced by about 50% or more. Moisture can enter a package through a film structure where two film structures are heat sealed together. The present invention reduces the moisture absorption by blocking this entry point.
Additional features and advantages of the present invention are described in, and will be apparent from, the detailed description of the presently preferred embodiments and from the drawings.