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HENRY, Donald, Lindley (3788 Elliott Street #6, San Diego, California, 92106, US)
The claims defining the invention are as follows:
1. A thermal packaging assembly including: a moisture impervious inner layer for location adjacent a refrigerant; and a condensate dispersal layer disposed on a side of said inner layer opposing the refrigerant.
2. A thermal packaging assembly according to claim 1 , wherein the condensate dispersal layer includes a hydrophilic material.
3. A thermal packaging assembly according to claim 1 or claim 2, wherein the condensate dispersal layer includes a non-woven fabric.
4. A thermal packaging assembly according to claim 3, wherein the non-woven fabric is impregnated with a surfactant.
5. A thermal packaging assembly according to claim 3 or claim 4, wherein the non-woven fabric comprises spunbond polypropylene.
6. A thermal packaging assembly substantially as described herein with reference to Figure 3. |
A FABRIC FOR REDUCING FREE WATER DUE TO CONDENSATION AND THERMAL PACKAGING INCORPORATING SAME
TECHNICAL FIELD
The present invention relates to the elimination or reduction of free water due to condensation associated with cold packing material. The invention finds particular application where a cold pack is required that will have improved resistance to the formation of free water.
BACKGROUND
Cold packages are frequently used, for example to assist in the transportation of goods that must be kept at a reduced temperature to avoid spoilage, or in the treatment of athletic injuries.
In U.S. patent No. 4,931 ,333 to the present inventor there is described a reusable thermal packaging assembly. The packaging assembly is comprised of a plurality of pouches, each having a flexible outer skin containing a thermal controlling agent. The pouches may be provided in a continuous sheet in bubble pack form to be laid upon an item to be packed.
A problem that occurs in relation to the cold packaging system described above, and also in relation to most other cold packing systems, is that of free water forming due to condensation.
Condensation may occur over a wide range of temperatures, for example where room temperature atmosphere contacts refrigerator temperature packaging. The temperature range most susceptible to production of condensation is 0° C. to 1O 0 C, which is considered the standard refrigerator temperature. Production of condensation, particularly where the ambient atmosphere has a high humidity content, may result in substantial free water that can be deleteriously affect packaging and in some circumstances damage the very goods that are packed.
One method of reducing damage due to free water is to include absorbent paper towels about the cold packaging to prevent the free water pooling.
A variety of dehumidifying materials may also be used to combat the problem of free water. These dehumidifying agents include silica gel and soda powder for example. However, such agents are usually insufficient to overcome the problem of free water formation.
It is an object of the present invention to provide a means for addressing the above problem.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention there is provided a thermal packaging assembly including: a moisture impervious inner layer for location adjacent a refrigerant; and a condensate dispersal layer disposed on a side of said inner layer opposing the refrigerant. Preferably the condensate dispersal layer includes a hydrophilic material.
In the preferred embodiment the condensate dispersal layer includes a non-woven fabric.
It is preferable that the non-woven fabric is impregnated with a surfactant.
The non-woven fabric may comprise spunbond polypropylene.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed Description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any way. The Detailed Description will make reference to a number of drawings as follows:
Figure 1 is a perspective view of a prior art cold packaging blanket. Figure 2 is a cross-section of the blanket of Figure 1. Figure 3 is cross-section of a blanket similar to Figure 1 incorporating a preferred embodiment of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Figure 1 is a perspective view of a prior art thermal blanket comprised of a continuous sheet of pillow-shaped pouches. The blanket is typically made with polyethylene walls 4 enclosing a refrigerant 6.
Figure 2 is a cross section through two pouches of the same blanket. Each of the pouches is filled with a suitable refrigerant 6 as detailed in the previously mentioned U.S. patent No. 4,931 ,333 for example. The polyethylene walls 4 present a moisture impervious inner layer adjacent refrigerant 6.
As previously discussed, a problem with cool packaging such as the thermal blanket depicted in Figures 1 and 2 is that condensation may form which can then poo! as free water.
Figure 3 is a cross section through a blanket according to an embodiment of the present invention. It will be noted that dispersal layer 8 has been incorporated. In the present embodiment the dispersal layer is provided in the form of a hydrophilic material being a non-woven hydrophilic fabric treated with a surfactant. The inventor has identified a suitable material for dispersal layer 8 being a non-woven spunbond polypropylene fabric with incorporated surfactant available from Jen-Coat, Inc. of 132 North Elm Street, Westfield, MA 01086 U.S.A.
Due to its hydrophilic nature the non-woven cloth absorbs condensate on the outside of the blanket. The surfactant acts to disperse the condensate into a thin film on the outside of the non-woven cloth which is then more easily evaporated before it can pool to form free water globules. Other mechanisms
which achieve the same dispersal effect might also be employed. For example micro roughening of the outer surface of the non-woven fabric may also provide for a sufficiently large surface to reduce free water formation.
Test Results
Tests were performed to determine the moisture and free water production of a prior art product similar to that of Figure 1 with each pouch holding a refrigerant volume of approximately 12 milliliters. A comparison test was preferred on a corresponding product incorporating dispersal layer 8, similar to that depicted in Figure 3.
A blot test was used to measure the moisture on the surface of the alternative products. Frozen sheets, 21.6cm x 10.2cm of cooling blanket with and without the dispersal layer were laid on a granite sink top for 30 minutes at ambient temperature of 25°C and a relative humidity of 82% prior to the blot test.
At 30 minutes the surface of each sheet was given a blot test and its surface temperature was measured. The blot test placing a double folded absorbent tissue on the top surface of each frozen sheet and gently pressing it on to the surface. The tissue was then weighed on an electronic scale calibrated to measure in grams. The weights shown below are the average of ten replicated tests.
Results: Without Dispersal Layer
Temp: 1°C to 3°C
Free water: 0.76 gm
Results: With Dispersal Layer Temp: 2°C to 3°C Free water: 0.37 gm
The above test results show a 51 % reduction in moisture absorbed by the tissue due to the presence of the hydrophilic surfactant impregnated dispersal layer.
It appears that the dispersal layer allows the surface moisture to evaporate more readily, due in part, to the much larger moisture surface made possible by the surfactant. As the reader will be aware, the surfactant reduces the surface tension of a liquid allowing it to spread out without forming globules of water as would otherwise be the case.
In short, condensation formed by ambient air coming in contact with the cold surface 4 of blanket 5 is absorbed by the non-woven hydrophilic cloth 8. In turn the surfactant impregnated within cloth 8 causes the condensation to disburse into a thin film of water that will more readily evaporate.
From a manufacturing perspective, a cooling blanket, or similar product incorporating the laminate may be most efficiently produced by operation of a Lane W-18 pouch making machine. Such a machine is available from Winpak Ltd of 100 Saulteaux Crescent, Winnipeg, MB R3J3T3 Canada.
A surfactant is described in U.S. patent No. 6,608,124 whilst European patent application EP1522620A1 , in the name of Kuraray Co. Ltd, provides an example of a non-woven fabric.
The word "comprises" and its variations is used herein, both in the description and claims, in its inclusive sense and not to the exclusion of any additional integers. In particular, "comprises" and its variations is not used synonymously with the phrase "consisting of.
In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of
its forms or modifications within the proper scope of the appended claims appropriately interpreted by those skilled in the art.
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