There are many articles that are preferably stored, shipped and/or utilized in an environment that is as moisture free as possible. Therefore, containers and/or packages having the ability to absorb excess moisture trapped therein have been recognized as desirable. One application in which moisture absorbing containers are desired is for the shipment and storage of medications whose efficacy is compromised by moisture. The initial placement of medicines into a sealed moisture free container is usually controllable. Furthermore, the container for the medicine is selected so that is has a low permeability to moisture. Therefore, the medication will normally be protected from moisture until it reaches the end user. Once the medicine is received by the customer, however, the container must be repeatedly opened and closed to access the medication. Each time the container is opened and unsealed, moisture bearing air will most likely be introduced into the container and sealed therein upon closure. Unless this moisture is otherwise removed from the atmosphere or head space of the container, it may be detrimentally absorbed by the medication. For this reason, it is a well known practice to include a desiccating unit together with the medication in the container.
In another example, electronic components may require reduced moisture conditions for optimal performance. These components may be sealed in containers, but excess moisture that is initially trapped therein must be removed. Furthermore, the housings may not be completely moisture tight, and moisture may be allowed to seep into the container. This moisture must also be retained away from the working components. For these reasons, it is important to include a desiccating agent within the housing for absorbing and retaining excess moisture. Because of the delicacy of many of the components that are to be protected from the moisture, it is important that the desiccant used not be of a "dusting" nature that may contaminate and compromise the performance of the components. Therefore, it has been recognized as advantageous to expose a desiccating agent to the interior space of such containers, while at the same time shielding the working components from actual contact with the desiccating material, including desiccant dust that may be produced therefrom.
In other instances, moisture may be released from items that have been placed in containers or sealed in packaging wrap for shipping and/or storage. Prime examples of such items are food stuffs--that release moisture during shipping and storage. In the instance of containers that are sealed and substantially impermeable to moisture, the released moisture will remain within the container. If not removed, this released moisture may have ill effects on the very item that released the moisture. It has been found that a substantial amount of moisture is released from certain food products within the first forty-eight (48) hours after manufacture and packaging. This released moisture will remain until removed. If the moisture is not removed shortly after its release, it may cause the food to degrade into a condition that is not saleable. In these cases, desiccants may be included together with the contained items to continually absorb the released moisture until the product is unpacked. In this way, a relatively dry environment is maintained about the stored item.
The need to eliminate moisture from within sealed containers has been previously recognized. Early attempts to achieve these goals included the provision of desiccant materials in fabric or similar bags that are placed in the containers together and commingled with the matter being shipped or stored. A consumer related problem, however, exists when the desiccant is loose and commingled together with consumable items. If not carefully and thoroughly processed upon unpacking, the desiccant may not be separated from the consumables and could harm a person if unknowingly ingested.
Several inventions have been patented that include both structures and processes that provide means for absorbing moisture by way of a desiccant that is included in various forms of packaging. A most basic example is found in the disclosure of U.S. Pat. No. 3,326,810 issued Jun. 20, 1967 to Dolan et al for a DESICCANT PACKAGE. That patent includes disclosure of a non-dusting silica gel desiccant bag. The bag is created from two sheets of nylon mesh that are bonded into a bag within which the silica gel is contained. Another known method by which a desiccant is included in a container is to provide a special side-compartment having limited exposure to the interior of the container. Examples of such inventions are found in U.S. Pat. No. 4,834,234 issued May 30, 1989 to Sacherer et al for a CONTAINER FOR TEST STRIPS. Sacherer provides a drying agent cell or compartment within the cap portion of a container for test strips that are used in the analysis of body fluids. It is disclosed that the drying agent cell is covered by a water vapor-permeable cardboard disc that separates that cell from the interior of the container. A similar example is found in U.S. Pat. No. 5,114,003 issued May 19, 1992 to Jackisch et al for a TABLET VIAL WITH DESICCANT IN BOTTOM. Jackisch includes disclosure of a desiccant canister that is secured to the bottom inside of a container's base. The desiccant canister within which the desiccating material is contained is initially sealed to prevent the absorption of moisture. Immediately prior to use, the desiccant canister is punctured and communication of moisture across the container is allowed to the desiccant.
In another example, separate capsules of desiccant that are expensive to produce are provided within the packaging. U.S. Pat. No. 4,783,206 issued Nov. 8, 1988 to Cullen et al for an ADSORBENT CARTRIDGE describes an elongated hollow cylindrical body fabricated of polyethylene, polyester or polypropylene. A desiccating agent is enclosed within the cartridge thereby maintaining the desiccant separate from other items commonly contained within the common container. By the cartridge's construction, it is intended that moisture pass only through the end caps constructed of spun-bonded polyolefin, and not the rigid, high density plastic side walls of the cartridge. A DRYING CAPSULE is disclosed in U.S. Pat. No. 2,638,179 issued May 12, 1953 to Yard. The drying capsule of Yard includes a desiccant that is encapsulated within a moisture permeable skin. The desiccant, which is contained within the capsule, absorbs moisture from the skin, and not directly from the outside atmosphere. The gelatin capsule is used as a regulator for governing the rate at which moisture is absorbed by the desiccating agent.
Another instance in which desiccant agents have been combined with polymers is found in layered plastic sheeting in which an interior oxygen impermeable layer must be protected against moisture which compromises the oxygen barrier characteristics of that interior layer. Examples of such utilization of a desiccant in a layered structure may be found in United States patents that are assigned to the American Can Company of Greenwich, Conn. and to the Kuraray Co., Ltd. of Kurashiki, Japan. Those United States patents include numbers U.S. Pat. Nos. 4,407,897; 4,425,410; 4,464,443; 4,770,944 and 4,792,484. In the disclosure of these several patents, the laminated structure has an interior layer that serves as an oxygen barrier and is manufactured from such polymers as ethylene vinyl alcohol (EVOH); in each instance, the EVOH is provided solely as an oxygen barrier. These EVOH layers serve as oxygen barriers as long as their moisture content remains below certain levels. In at least one application described in those patents, the layered packaging is used for food products that must be sterilized in a retorting process in which the food product, together with the packaging is steam treated. During the steam treatment process, the protective outer layers which are commonly manufactured from polypropylene and polyethylene and moisture impermeable at lower temperatures, permit the transmission of moisture thereacross at the elevated temperatures of the retorting process. The EVOH layer loses its oxygen barrier characteristics above a certain moisture level. Desiccant is therefore added to the adhesive layers adjacent to the EVOH layer to control the moisture levels within the oxygen barrier layer within the interior of the layered sheets so that the oxygen barrier layer can maintain its oxygen barrier properties. The only purpose of the described inventions of those patents is to maintain the interior EVOH layer of the laminate at relatively low moisture levels to assure its performance as an oxygen barrier.
An example of a desiccating agent being combined with a polymer binding material is found in U.S. Pat. No. 4,665,050 issued May 12, 1987 to Degen et al for SELF-SUPPORTING STRUCTURES CONTAINING IMMOBILIZED INORGANIC SORBENT PARTICLES AND METHOD FOR FORMING THE SAME. Therein, it is explained that sorbent particles are mixed into a softened, but not melted thermoplastic material such as polyethylene or polypropylene. By only softening the polymer medium, "blinding" of the sorbent material is prevented. That is, exterior portions of the sorbent material must be exposed and not blocked by the surrounding polymer. In this manner, moisture is transmitted into the sorbent material at those locations that are not covered by the binding polymer. It is explained that the polymer should only be softened to an extent that it becomes slightly tacky and does not become so viscous as to flow.
The combination of a moisture-absorbent substance with a thermoplastic resin is disclosed in U.S. Pat. No. 5,078,909 entitled MOISTURE-ABSORBENT COMPOSITIONS AND MOLDED ITEMS that issued Jan. 7, 1992 to Shigeta et al. Therein, it is contemplated that a thermoplastic resin, which may include polyethylene, polypropylene, as well as others may be employed in the formation of the composition. The inclusion of various moisture absorbing agents are required in order to obtain absorbtion by the desiccating agent.
It is also known to entrain desiccant directly into plastics and rubbers. An example of such entrainment is found in U.S. Pat. No. 3,245,946 issued Apr. 12, 1966 to O'Connor et al for RUBBER AND PLASTIC FORMULATIONS AND PROCESS. Therein, the entrainment of a desiccating agent into rubber, plastic, and resin formulations during their production is utilized to contain moisture produced during the manufacture of those materials that would otherwise adversely affect the produced material.
A flexible desiccant body is disclosed in U.S. Pat. No. 4,013,566 issued Mar. 22, 1977 to Taylor. Therein, a desiccant material is homogeneously distributed and bound in a moisture transmissive aliphatic epoxy polymer matrix. Therein, it is specifically recognized that polypropylene bags are not suited as containment material because of potential attrition problems due to melting or thermoplasticity of the bags during use.
Prior to the present invention, the establishment of channels throughout a desiccant entrained polymer has not been known. The present invention, has been developed in response to a recognized need for structures constructed from polymers that normally act as moisture barriers in their solid, rigid state, but when produced according to the present invention have a desiccant entrained therein which is capable of absorbing moisture exterior to the polymer.