Compositions – Humidostatic – water removive – bindive – or emissive
Reexamination Certificate
1999-08-02
2001-05-22
Tung, T. (Department: 1743)
Compositions
Humidostatic, water removive, bindive, or emissive
C204S551000
Reexamination Certificate
active
06235219
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to compositions useful as desiccants and, more specifically, to a composition formed from the combination comprising a hygroscopic material dispersed in an organic polymer such as polyvinyl alcohol, as well as methods relating thereto.
BACKGROUND OF THE INVENTION
There are many materials in need of protection from atmospheric moisture, particularly in the context of specialty goods manufactured by the pharmaceutical, chemical, computer, electronics, military, and food industries. In particular, water vapor in the air is known to have harmful effects on numerous specialty goods, and in the context of frequently opened and resealed products, these harmful effects are often amplified. Accordingly, and in an effort to reduce the damage caused by ambient water vapor, a desiccant typically accompanies those specialty goods in need of moisture protection. For example, pouched or otherwise packaged desiccants routinely accompany specialty goods as part of the product packaging, or in some cases as an integral component of the good itself.
In these types of situations, the accompanying desiccant is able to absorb and hold moisture that would otherwise be in the atmosphere contacting the specialty good (i.e., in the surrounding volume of air) to thereby prevent or reduce the harmful effects that may be caused by ambient water vapor. Although desiccants are of great commercial value, there are, surprisingly, only three major types of desiccants currently available, namely; (1) montmorillonite clay; (2) silica gel; and (3) molecular sieve.
As is known to those skilled in the art, montmorillonite clay is a naturally-occurring calcium aluminum silicate type of hydrous clay; furthermore, it is a non-hazardous material which is typically ground, processed, and bagged prior to use as a desiccant. Similarly, silica gel is a form of sponge-like silica manufactured from sodium silicate and sulfuric acid, and like montmorillonite clay, it is a non-hazardous material which is typically bagged prior to use as a desiccant. Finally, molecular sieve is a manufactured crystalline version of zeolite containing a network of uniform pores and empty cavities, and it too is a non-hazardous material which is typically bagged prior to use as a desiccant.
A common attribute of fresh desiccant is its ability to absorb and hold water. For example, in an atmosphere having 100% humidity, the three commercially available desiccants mentioned above are able to absorb water in an amount ranging from approximately 28% to 40% of their respective masses. Once, however, the desiccant has absorbed its holding capacity of water, it is no longer effective and must be replenished. Although the desiccant may be recharged by removal of the absorbed moisture by, for example, dry heating, this practice is generally not employed because it is considered cost prohibitive; that is, it is usually much cheaper to simply replace the spent desiccant with fresh desiccant.
A significant factor contributing to the high costs associated with desiccant replacement is that the three commercially available desiccants are, as noted above, typically bagged prior to use. In others words, granules of montmorillonite clay, silica gel, or molecular sieve (in selected amounts) are usually placed within a porous pouch or receptacle prior to their accompaniment with the specialty good in need of moisture protection. This practice of desiccant bagging increases the costs of spent desiccant recharging significantly because the bag is generally removed prior to dry heating (thereby making it more economical to simply replace the spent desiccant with new desiccant). A related problem with desiccant bagging is that the resulting bagged desiccant may have a tendency to shift or move about during transportation of the specialty good; such movement may have undesirable consequences.
Accordingly, there is a need in the art for new compositions useful as desiccants, as well as for methods of making and using such new compositions. The present invention fulfills these needs, and provides for further related advantages as disclosed herein.
SUMMARY OF THE INVENTION
In brief, the present invention is directed to compositions useful as desiccants and, more specifically, to one or more compositions comprising (1) a hygroscopic material dispersed in polyvinyl alcohol, (2) a deliquescent material dispersed in an organic polymer, or (3) hygroscopic material and polymeric material both dissolved in solvent, as well as methods relating thereto. In one embodiment, the composition comprises a hygroscopic material dispersed in polyvinyl alcohol, wherein the hygroscopic material is not polyvinyl alcohol. In this embodiment, the hygroscopic material and the polyvinyl alcohol are generally moisture deficient. In addition, the hygroscopic material generally comprises one or more of calcium chloride, phosphorous oxide, sodium silicate, potassium silicate, potassium acetate, bentonite, montmorillonite clay, silica gel, molecular sieve, monohydric compounds, or polyhydric compounds. Preferably, the composition associated with this embodiment is about 25-75 wt % hygroscopic material and about 75-25 wt % polyvinyl alcohol, where the wt % values are based on the total weight of hygroscopic material and polyvinyl alcohol.
In another embodiment, the composition comprises a deliquescent material dispersed in an organic polymer. In this embodiment, the deliquescent material may comprise moisture deficient calcium chloride and/or potassium acetate. In addition, the organic polymer is generally one or more of polyvinyl alcohol, polyvinyl acetate, polyurethane, poly(acrylate), and polystyrene. Preferably, the composition associated with this embodiment is about 25-75 wt % deliquescent material and about 75-25 wt % organic polymer, where the wt % values are based on the total weight of moisture-free deliquescent material and polymer.
In yet another embodiment, the composition comprises hygroscopic material and polymeric material both dissolved in solvent. In this embodiment, the hygroscopic material may comprise a deliquescent material, potassium acetate, and/or calcium chloride, and the polymeric material may comprise polyvinyl alcohol. The solvent may comprise water.
The compositions associated with the first two above-identified embodiments may further comprise a solid support. More specifically, the one or more compositions comprising (1) a hygroscopic material dispersed in polyvinyl alcohol, or (2) a deliquescent material dispersed in an organic polymer, may further include a solid support, wherein a mixture of such materials is distributed across a surface of the solid support.
The present invention is also directed to methods. More specifically, the present invention is also directed to: (1) a method for removing moisture from an enclosed and moisture-containing atmosphere comprising contacting the atmosphere with polyvinyl alcohol, the polyvinyl alcohol being moisture deficient; (2) a method of making a composition useful as a desiccant comprising the steps of admixing components comprising a hygroscopic material and an organic polymer in a solvent to form a solution, and drying the solution to remove solvent and provide a moisture-deficient hygroscopic material dispersed in the organic polymer; and (3) a method of method of making a composition useful as a desiccant comprising the steps of admixing components comprising a hygroscopic material and molten organic polymer to form a fluid admixture, and cooling the fluid admixture to a non-fluid state.
These and other aspects of the present invention will be evident upon reference to the following detailed description.
DETAILED DESCRIPTION OF THE INVENTION
As mentioned above, the present invention relates generally to compositions useful as desiccants and, more specifically, to a composition formed from the combination comprising a hygroscopic material dispersed in an organic polymer such as polyvinyl alcohol, as well as methods relating thereto.
In one embodiment, the composition c
Cross LaToya I.
Seed Intellectual Property Law Group PLLC
Tung T.
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