NON-REVERSIBLE HUMIDITY INDICATOR CARD

Abstract

The present invention is directed to methods for preparing and using a substrate having a deliquescent-containing area for a non-reversible humidity indicator card. Embodiments provided herein also are directed to formulations that are utilized with such cards, as well as the approach of dispensing a composition with a deliquescent material in solution upon a card that can be used as a non-reversible humidity indicator.

Claims

1. A method for detecting humidity in an environment, comprising: preparing a composition that contains a deliquescent material in solution; and dispensing the composition within a spot upon an active layer of a card; wherein drying the composition after it is dispensed causes the deliquescent material to precipitate, such that upon subsequent exposure to a predetermined humidity the deliquescent material deliquesces and migrates upon the active layer.

2. The method of claim 1, wherein preparing a composition that contains a deliquescent material in solution comprises adding a modifier to the composition.

3. The method of claim 1, wherein as the deliquescent material migrates upon the active layer, a change occurs outside the spot that can be detected.

4. The method of claim 3, wherein preparing a composition that contains a deliquescent material in solution comprises adding a dye to the composition, such that the change outside the spot is a color change brought about by the dye.

5. A humidity indicator card, comprising: a substrate comprising an active layer; a spot on the substrate comprising a precipitate of deliquescent material; wherein the spot is defined by visual markings forming a border, and wherein exposure of the card to relative humidity above a predetermined level causes the precipitate to deliquesce and migrate beyond the border in an observable manner.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG. 1 depicts a humidity indicator card.

DETAILED DESCRIPTION

[0019] Current embodiments are directed to a non-reversible humidity indicator card. Generally, various starting materials are used in manufacturing the formulations, including deliquescent materials that can be processed into solution. The amounts and weight percentages of the materials will vary from formulation to formulation as desired for a particular end use. The deliquescent materials can be dissolved in water before adding to the mixture. Other solvents as known to formulation chemists can be used to dissolve the deliquescent material. In some embodiments, various modifiers and diluents or additional solvents are incorporated into the formulation as noted below.

[0020] In an embodiment, the card comprises at least one active layer. In some embodiments, the active layer is a thin, generally planar material of any geometry as desired for the end use, e.g., rectangular. Preferably, the active layer is suitable for receiving inks to show words and other markings on its surface such as for delineating respective borders for one or more spots. As desired, such markings might also contain instructions for use. Suitable materials for the active layer include, without limitation, cellulose- or wood pulp-containing materials such as paper and other non-woven materials (e.g., Tyvek or similar spunbonded non-woven materials). Depending on the particular application, a multi-layer card is contemplated by these embodiments, which further comprises a backing that the active layer is adhered or affixed to. The backing provides functional improvements such as structural support, protective coating, and a barrier from direct contact for the card and should be suitable for having the active layer affixed to its surface, as by an adhesive or through laminating processes known in the art. The backing need not possess any particular minimum thickness, and may be very thin, e.g., and without intending to limit as to dimension, 5 mm. Such backing can be permeable or impermeable to RH. If permeable, the RH will be absorbed from both sides of the card, but it is not required to absorb RH from both sides of the card.

[0021] Alternatively, embodiments include a humidity indicator card comprising only an active layer, such as formed from paper. The active layer of the card demonstrates absorbability to retain the deliquescent-containing solution within the material, as by retention within a cellulose matrix for pulp-containing materials. Generally, a paper formed from cellulose is a suitable material for the active layer sufficient to allow the deliquescent material to absorb into the cellulose matrix. A specific, albeit non-limiting example of such a material is blotting paper that conforms to UU-P-63, also referenced with federal logistics item name code 04784. This is an absorbent, porous, spongy paper made from mixtures of cotton fiber and wood pulp. Other suitable materials for the active layer, again without limitation, would include other woven or non-woven materials having absorbent or adsorbent properties as known in the art.

[0022] Upon an active layer of a card, a solution containing the deliquescent material is dispensed. Various ways of dispensing exist, and the scope of embodiments is not limited based on a particular mode of dispensing. In general, the solution with deliquescent material is dispensed so it remains within the particular spot on the active layer of the card. Consequently, if the material deliquesces during use, there will be an indication provided because the deliquescent material will migrate beyond the markings defining the spot. Incorporating a dye in the solution makes the indication visual when the deliquesced solution is colorless.

[0023] Accordingly, deliquescent materials are processed into solution and then dispensed upon a surface of the card, and more specifically onto an active layer of the card. In some embodiments, the deliquescent-containing solution is applied within the spot on the surface of the active layer. When dispensed, the deliquescent materials are in solution. Subsequent to dispensing, the active layer(s) is dried so that a substantial amount of the liquid (aqueous or volatile organic) content of the solution is evaporated. Drying can occur through any number of modes, such as but not limited to placement in an oven or direct exposure to hot forced air with a dryer. The temperature of the oven or forced air will depend on the type of liquid solvent used, and can be easily determined with reference to the particular liquids making up the deliquescent-containing solutions.

[0024] Upon sufficient drying, the deliquescent material precipitates from solution and remains in the spot where it was dispensed as a solution. The deliquescent material is thus capable of deliquescing at a predetermined humidity according to the particular formulation that is dispensed onto the card. For example, deliquescent materials formed from metal halides have a crystalline structure that will dissolve again in the presence of sufficient humidity within a container, if the humidity remains above a threshold RH for some minimum period of time. Other kinds of deliquescent materials, including those listed in the Background section, can be used within the scope of these embodiments.

[0025] After the solution is dispensed onto the card and dried, the card is ready to be used by placing it into a container where it detects the occurrence of relative humidity above a threshold. Some commercial goods that are unaffected by relative humidity below 50%, for example, could be ruined if the relative humidity is sustained above 80% for a predetermined period of time. Conversely, some commercial goods are so sensitive that exposure to 30%, 20%, or even 10% relative humidity is sufficient to cause major damage and loss, or to require mitigation such as having to re-bake a semiconductor. Accordingly, a range of solutions with deliquescent materials can be formulated to provide indications across a wide spectrum of possible humidity conditions in a container or storage.

[0026] In view of the teachings contained herein, the following exemplary compositions are suitable for use. Such compositions are dispensed onto a card while the deliquescent materials are in solution, then dried to bring the deliquescent materials out of solution so the card can be used in a container. The example formulations are not limiting, but rather are meant to illustrate how modifiers can be used to further increase the flexibility of the current approach.

Example Formulations (A1-A3)

[0027] In some embodiments, besides water or other known solvents which may be selected, additional modifiers are mixed with the solution, such as without limitation a hydrophilic modifier or a modifier with hydrophobic functionality. Such modifiers change the behavior of the deliquescent materials. For example, a hydrophilic modifier increases the tendency to attract and hold ambient moisture around the deliquescent material, which is in precipitate form after drying. On the other hand, modifiers with hydrophobic functionality have more tendency to repel moisture. Glycerin could be used and serves as one of many suitable examples as a hydrophilic modifier with are known in the art, according to present embodiments. Octylphenoxypolyethoxyethanol could be used and serves as one of many suitable examples as a hydrophobic modifier which are known in the art, according to present embodiments.

[0028] The following example formulations are not meant as limiting, but rather illustrative of the flexible approach available from practicing the present embodiments. The approach herein allows a particular deliquescing material and solvent to produce multiple different solutions that deliquesce along a range of RHs. In this way, when different solutions are dispensed on a card as disclosed herein, a single card can be used to more precisely determine the RH in the container.

TABLE-US-00001 A1. Component Weight (%) MX 44% Water 44% Dye .9% Hydrophilic Modifier 11.1%.sup. Total: 100%

TABLE-US-00002 A2. Component Weight (%) MX 44% Water 44% Dye .9% Hydrophobic Modifier 11.1%.sup. Total: 100%

TABLE-US-00003 A.3 Component Weight (%) MX 49% Water 50% Dye 1% Total: 100%

[0029] As a non-limiting illustration, the humidity indicator card illustrated in FIG. 1 shows that a RH above 60% was reached, but relative humidity above 70% was either not reached or was not sustained for sufficiently long to cause the deliquescent material to dissolve and bleed beyond the border of the spot.

[0030] It will be appreciated that the use of solutions having different modifiers, or no modifiers, allows a single card to present a range of sensitivities to RH inside a container. To illustrate with the above examples, each contains at least a water solvent, MX or a salt that is hydrophilic and soluble in water, and a dye. The above non-limiting examples are identified as A1 (hydrophilic modifier), A2 (hydrophobic modifier), and A3 (no modifier). If the three were placed at distinct spots on a single card, that card can be used to detect RH conditions in a container along a range of possible RHs. For example, A1 (with a hydrophilic modifier) would deliquesce at a lower RH than the other two because hydrophilic compounds have greater tendency to absorb moisture from the air.

[0031] In other words, the tendency of a hydrophilic modifier to attract moisture from the surrounding environment means a solution with this modifier requires less RH to produce deliquescence than a solution which is identical except that it lacks this modifier. By comparison, the absence of a hydrophilic modifier, A3 (no modifier) would deliquesce at a higher RH than A1. However, compositions with added hydrophobic or amphiphilic modifiers, such as but not limited to A2, would tend to deliquesce at even higher RHs because of non-polar functional groups. In other words, having a modifier with hydrophobic functionality tends to repel moisture from the surrounding environment, as compared to a solution with a hydrophilic modifier, or no modifier. Thus, a solution with a hydrophobic modifier requires a higher RH to produce deliquescence than a solution which is identical except it lacks this modifier.

[0032] Further deliquescent at a particular spot on a card can be controlled not only by selection of modifier, but by the amount of modifier used. Thus, although Examples A1-A3 all list a specific percentage, for illustrative purposes only, the scope of present embodiments would encompass a range of possible weight percentages. Accordingly, changing Example A1 by reducing the hydrophilic modifier to 35% would reduce the RH at which deliquescence occurs compared to A1. Likewise, raising the hydrophilic modifier to 55% would increase the RH at which deliquescence occurs compared to A1. Moreover, changing Example A2 by reducing the hydrophobic modifier to 35% would increase the RH at which deliquescence occurs compared to A2. Likewise, changing Example A2 by raising the hydrophobic modifier to 55% would reduce the RH at which deliquescence occurs compared to A2. In this respect, modifier content can be chosen outside of the ranges set forth or suggested in this paragraph, without departing from the scope of present embodiments.

[0033] Accordingly, based on the teachings provided herein, a wide array of compositions could be formed with deliquescent materials in solution for ready dispensing based on the teachings herein. In some embodiments, an aqueous solution of metal halide is mixed with additional water, a dye, with the dye facilitating visual detection. Alternative forms of detection, such as an optical reader or fluorescent dyes, are likely more expensive, but would be within the same kinds of operating principles described herein.

[0034] In general, the starting materials for these compositions are mixed in any order, and at a suitable temperature and level of agitation sufficient to place the deliquescent materials in solution, and the compositions are expected to be applied to the card while the deliquescent materials are still in solution. Described herein are a number of exemplary (i.e., non-limiting) deliquescent-containing solutions and formulations. These illustrate the wide range of embodiments for processing deliquescent materials into a solution, which is then dispensed onto an active layer to form a humidity indicator card. Also described are various modes for applying the formulations and preparing a card that contains these deliquescing materials.

[0035] It will be understood that the embodiments described herein are not limited in their application to the details of the teachings and descriptions set forth, or as illustrated in the accompanying figures. Rather, it will be understood that the present embodiments and alternatives, as described and claimed herein, are capable of being practiced or carried out in various ways. Also, it is to be understood that words and phrases used herein are for the purpose of description and should not be regarded as limiting. The use herein of such words and phrases as including, such as, comprising, e.g., containing, or having and variations of those words is meant to encompass the items listed thereafter, and equivalents of those, as well as additional items.

[0036] Accordingly, the foregoing descriptions of embodiments and alternatives are meant to illustrate, rather than to serve as limits on the scope of what has been disclosed herein. The descriptions herein are not meant to limit the understanding of the embodiments to the precise forms disclosed. It will be understood by those having ordinary skill in the art that modifications and variations of these embodiments are reasonably possible in light of the above teachings and descriptions.