A desiccant system in which a body of water-vapor-adsorbing desiccant
material is sealed in a bag which is permeable to water vapor, but
not to liquid water or particulates. A humidity indicator is sealed
to the bag, and is sensitive to humidity within the bag, but not
to water or water vapor outside the bag. The indicator changes color
when a predetermined humidity level has been reached within the
bag, and thereby to signal that the bag should be replaced.
What is claimed is:
1. A desiccant system, comprising a bag made of a material which
is permeable to water vapor, and impermeable to liquid water and
particulates, a desiccant material sealed in the bag, and a humidity
indicator secured to the bag to sense humidity within the bag, and
to be insensitive to water vapor outside the bag.
2. The system defined in claim 1 in which the humidity indicator
changes color to signal when a predetermined humidity within the
bag has been reached.
3. The system defined in claim 2 in which the humidity indicator
is cobalt chloride.
4. The system defined in claim 1 in which the material of which
the bag is made is a spun-bonded polyolefin sheet material.
5. The system defined in claim 1 in which the desiccant material
comprises a mixture of calcium chloride, Montmorillonite clay, and
6. The system defined in claim 5 and in which the desiccant material
further comprises scented plastic beads.
7. The system defined in any of the preceding claims, in which
the humidity indicator is secured to an outer surface of the bag.
BACKGROUND OF THE INVENTION
This invention relates to a desiccant bag for adsorbing water vapor
from a surrounding space, and having an integrated humidity indicating
card which changes color when the adsorption capacity of the bag
reaches a level where the bag should be discarded and replaced.
The bag finds particular utility in adsorbing water vapor from spaces
such as boat cabins and storage areas, stored automobiles, closets,
drawers and other home spaces, and storage areas in a seaside location
which are especially susceptible to high humidity and damage-causing
SUMMARY OF THE INVENTION
The desiccant system of this invention comprises a desiccant material
sealed in a bag made of a material, preferably spun-bonded polyolefin
sheet material, which is permeable to water vapor, and impermeable
to liquid water and particulates. A humidity indicator secured to
an outer surface of the bag senses the humidity level within the
bag, and signals, preferably by a color change, when the adsorbing
ability of the desiccant material is exhausted and the moisture-adsorbing
desiccant system should be discarded and replaced. The desiccant
material may include pleasantly scented plastic beads.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a front elevation of a desiccant bag according to the
FIG. 2 is a sectional view on line 2--2 of FIG. 1 and additionally
showing a foil container for storing the bag until it is to be used.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the drawings, a desiccant bag 10 is made of a porous
material which is permeable to, and will pass water vapor, but is
impervious to liquid water, dust, and other particulates. A preferred
plastic sheet material for the bag is a spun-bonded polyolefin marketed
by E. I. duPont under the trademark TYVEK.RTM. with a thickness
in a range of 2.0 to 9.1 mils, and typically of about 5.3 mils.
A humidity indicator 11 is in the form of a self-adhesive rectangular
card which is adhered to an outer surface of the bag. Only the rear
surface of the card facing the bag outer surface senses humidity
within the bag, and the card front surface is covered with a transparent
and impervious plastic sheet to be isolated from the outside environment.
Humidity indicators or markers of this type use a humidity-sensing
color-change material 13 such as cobalt chloride, and are available
from Desiccare, Inc., in Santa Fe Springs, Calif., assignee of the
present invention. This material will change color from, for example,
blue to pink or red when a specific humidity level (e.g., typically
50% or 60% depending on the application) is reached within the bag.
The bag is then discarded, and replaced with a fresh desiccant bag.
The bag is filled with about six to seven ounces (for the illustrated
bag size of about 8 to 9 inches high and about 4 to 41/2 inches
wide) of a desiccant material 15 of the following presently preferred
22% calcium chloride
30% Montmorillonite clay.
Balance of diatomacious earth which absorbs water.
About 5 grams of polyethylene pellets entrained with pleasantly
scented material such as lemon oil are added to this mixture. Scented
plastic beads of the type described above are available from Aroma
Tech in Somerville, N.J., and Polyvel in Hammonton, N.J., and in
a variety of long-life odorants which lend a pleasant aroma to the
space in which the desiccant bag is located.
The bag can be economically assembled and loaded by a known production
device called a "form, fill and seal machine." Humidity
indicator 11 is adhered to a cut flat sheet of the Tyvek Bag material
on a side which will become the bag outer surface. The sheet is
then machine folded along its length to form a tube which is heat
sealed along a side or back edge. The lower end of the bag is similarly
heat sealed, and the bag is then loaded with desiccant material
15 following which the open upper end of the bag is heat sealed
to completely enclose the desiccant. For shipment and storage before
use, the completed bag is sealed in a foil bag 17 (FIG. 2) to be
isolated from the outside environment.
The materials used in the bag and contents are nontoxic, and no
disposal problems are presented when the indicator shows desiccant
exhaustion. The bag is easily stored, handled, and placed in service,
and provides a convenient, effective and economical means for humidity
control and prevention of condensate water in storage areas to be