Note: Descriptions are shown in the official language in which they were submitted.
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pres~3 il No. B 67402768
(a) Title of Invention
LIQUID ABSORBING PACKET
(b) Background of Invention
1. Field of Invention.
This invention relates to liquid absorbing packets. More
specifically this invention discloses to a packet containing liquid
absorbing granules for immobilizing a liquid wherein the swelling
of the liquid absorbing granules breaks apart the packet at a
predetermined location on the packet thereby quickly releasing the
liquid absorbing granules from the packet to increase the speed of
absorption of the liquid absorbing granules.
2. Prior Art.
Desiccant containers which operate to absorb water vapor,
liquids and the like are known in the art. Generally these
containers are composed of water or water vapor permeable sheets of
fibrous material securely bonded together at their edges containing
a desiccant, such as silica gel. The volume of water or water
vapor capable of being absorbed by the container is determined by
the absorbent capacity of the desiccant material within the
container.
More recently containers containing liquid absorbing materials
for absorbing large quantities of liquid have been designed. These
liquid absorbing materials are capable of absorbing relatively
large amounts of liquids as disclosed, for example in U.S. Patent
No. 3,661,815, which discloses a water insoluble granular solid
comprising alkali metal carboxylate salts of a starch-
polyacrylonitrile graft copolymer. See, also, U.S. Patent No.
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4,224,366 and 4,124,116. Liquid absorbing and immobilizing
granules such as sodium polyacrylate are known in the industry and
are disclosed, for example, in U.S. Patent Nos. 4,853,266,
4,748,069 and 4,749,600.
To achieve greater absorption the liquid absorbing and
immobilizing packets release the liquid absorbing material from
their packets to the surrounding environment. One choice for
enabling this release is disclosed by U.S. Patent Nos. 4,748,069,
4,749,600, 4,853,266, 4,725,465, 4,124,116 and 4,224,366. Each of
these patents discloses a packet whose envelope is composed of a
liquid soluble material. For example, in U.S. Patent No.
4,224,366, upper and lower contiguous sheets, which are bonded
together, are fabricated from a paper which dissolves in the
presence of moisture or a liquid to release the absorbent granules
from the packet. A particular disposable packet manufactured by
Multiform Desiccants, Inc. and disclosed, for example, in U.S.
Patent Nos. 4,748,069, 4,749,600 and 4,853,266, contains sodium
polyacrylate as the absorbent material contained within a
degradable starch paper envelope. When a liquid comes into
contact with such a degradable envelope, the liquid first dissolves
the envelope and then, only after such dissolution, the liquid-
absorbing materials are released from the envelope to absorb the
liquid. A slightly different design of the envelope is disclosed
in U.S. Patent No. 4,725,465 wherein the interior surface of the
water soluble paper which envelopes the absorbent granules is
coated with an adhesive in a grid or dot-like pattern. Once this
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paper is contacted by a liquid, it dissolves to expose the
absorbent granules to the liquid to be absorbed.
While each of these patents discloses products which provide a
means for the absorption of liquids, each requires that the packet
or envelope which encloses the liquid absorbing material degrade or
decompose prior to the release of the liquid absorbing granules
into the environment for full absorption of liquid. Improved
designs for faster and more efficient release of absorbent granules
from such packets are necessary.
Therefore, it is an object of this invention to provide a
liquid absorbing and immobilizing packet which will quickly absorb
and immobilize a relatively large quantity of liquid.
It is another object of this invention to disclose a liquid
absorbing and immobilizing packet which will come apart at its
seams to release quickly the liquid absorbing material into the
contiguous environment.
It is a still further object of this invention to disclose a
liquid absorbing and immobilizing packet wherein the envelope of
the packet is liquid permeable and wherein at least one of the
seams of the packet comes apart upon expansion of liquid absorbing
granular material contained within said envelope to release quickly
the liquid absorbing granular material into the contiguous
environment.
It is a further object of this invention to provide a process
for the production of a liquid absorbing and immobilizing packet
which packet will quickly and efficiently release liquid absorbing
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and immobilizing material contained within a packet into the
contiguous environment.
These and other objects and features of the present invention
will become apparent to those skilled in the art from a
consideration of the following detailed description, drawings and
claims. The description, along with the accompanying drawings,
provides a selected example of construction of the product and the
process to illustrate the invention.
(c) Summary of Invention
In accordance with the present invention there is provided a
packet for immobilizing a liquid, comprised of a liquid permeable
sheet formed into an envelope wherein each of two of the sides of
the sheet are sealed to form a pair of seals, preferably end seals,
wherein the two r~ining sides of the sheet are sealed together to
form a single seal, preferably a center seal running between the
end seals, wherein contained within the envelope is a quantity of
swellable, liquid absorbing granules which swell to a size greater
than the size of those granules in their dry condition, and wherein
as the liquid absorbing granules swell, they break the center seal
to release the liquid absorbing granules into the environment
outside of the packet to absorb liquid. In addition, there is
disclosed a process for forming a packet for absorbing and
immobilizing a liquid comprised of (a) forming an envelope
comprised of a liquid permeable sheet, wherein each of two of the
sides of the sheet are bonded to form a pair of seals, preferably
end seals, and wherein the two remaining sides are bonded together
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to form a seal, preferably a center seal, running between the end
seals and (b) filling the envelope with a quantity of swellable
liquid absorbent granules which swell to a size greater than the
size of those liquid absorbent granules in their dry condition and
wherein as the granules swell, they break the center seal of the
envelope thereby releasing the liquid absorbent granules outside of
the packet to absorb the liquid.
(d) Brief Description of the Drawings
This invention will now be described with references to the
accompanying drawings in which:
Figure 1 is a perspective view of the liquid absorbing packet.
Figure 2 discloses the filling of the packet and forming the
center seal of the packet.
Figure 3 discloses the forming of the end seals of the packet.
(e) Detailed Description of the Preferred Embodiment
Although the invention is adaptable to a wide variety of uses,
it is shown in the drawings for purpose of illustration as embodied
in a packet (10) for absorbing and immobilizing a liquid comprised
of an envelope formed from a sheet of liquid permeable material,
wherein said envelope contains a swellable, liquid absorbing and
immobilizing granular material. The envelope is formed from a
liquid permeable material, wherein the material contains
microperforations for air and water permeability~ Although the
envelope material can be formed from any conventional water
permeable material such as cellulose, polyvinyl alcohol, low
density polyethylene, and nylon, it is preferably formed from a
mixture of cellulose paper pulp and cellulose long fibers. To this
combination may be added synthetic materials such as vinyl acetate,
polyethylene, and other such additives. Other examples of water
permeable films are plain cellophane (not moisture finished),
glassine paper, parchment paper, non-woven fabric films (including
synthetic paper) and the like which permit a liquid to permeate
through said material.
Referring now to Figure 1 the particular absorbent and
immobilizing packet (10) is shown as an elongated, generally
rectangular shaped packet. The envelope is formed from a sheet of
the liquid permeable material as previously disclosed. Although
the sheet may be formed into an envelope by any conventional
method, it is essential that at least one of the seams be formed in
such a manner as to permit breach of that seam of the envelope by
the swelling of absorbent granules contained within the envelope.
Thus, in one preferred embodiment two of the opposite sides of the
sheet are folded onto themselves thus forming two end seals (12,
14). The two remaining opposite sides are joined together to form
a center seal (16) running between the end seals. The end seals
are bonded conventionally while the center seal is bonded under
less pressure and heat to form a weaker seal, such that upon the
expansion of the water swellable absorbent material, the end seals
will retain their seal longer than the center seal. Thus, the
center seal is sealed such that as the absorbent material swells,
it will be easily breached to permit the absorbent material to be
released outside of the packet, thus making such absorbent material
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immediately available to absorb liquid which is present outside of
the packet.
When the preferred cellulose material is used for the liquid
permeable sheet, the two end seals are~sealed by a conventional
sealing operation wherein the edges are heated to a temperature of
from about 200F. to 250F., preferably from about 230F. to about
240F., placed under a pressure of about 15 to 35 psi, preferably
from about 20 to about 30 psi, wherein such pressure is held on
such seals for a dwell time of at least 1 second and preferably
from about 1 to about 5 seconds. In contrast, the center seal is
sealed at a reduced temperature and under a reduced pressure.
Thus, preferably, the center seal is formed at a temperature of
from about 190F. to about 240F. and preferably from about 225F.
to about 235F. and under a pressure of less than 15 psi and
preferably from about 3 to about 10 psi, wherein said pressure is
retained for a dwell time of less than about 5 seconds and
preferably from about 1 to about 3 seconds. As a result of the
reduced temperature and reduced pressure placed upon the center
seal, the center seal is not as secure as are the two end seals.
By reducing the strength of the center seal, it will breach quite
easily when the absorbent material contained within the packet
expands against the center seal.
The liquid absorbent material which is placed within the
packet must swell upon contact with liquid. Suitable materials for
use in the packet will be those normally utilized for the
absorption of liquids. These materials include alkali metal
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carboxylate salts of starch - polyacrylonitrile, graph copolymers
as described in U.S. Patent No. 3,661,815 and products which will
absorb, gel or thicken a particular liquid, such as carboxymethyl
cellulose, cellulose ethers, polyvinyl pyrolidone, starch,
dextrose, gelatin, pectin, and preferably sodium polyacrylate. The
preferred material is a sodium polyacrylate absorbent polymer,
lightly cross-linked produced, for example, by Chemdal Corp. under
the trade name Aridall. The preferred material has the capacity to
absorb or immobilize large volumes of liquids, preferably from
about 180 ml/g to about 220 ml/g of a distilled water solution.
Preferably, the absorbent material will absorb a 1% saline solution
at a capacity of about 33 ml/gm to about 40 ml/gm. It is required
that this material be able to absorb and immobilize liquids
preferably forming a gel-like substance of at least about twice the
volume of the dry material. When the preferred sodium polyacrylate
is used, the majority of the absorbent granules preferably have a
size of no more than about 1000 micron to about 150 microns.
For the packet to effectively and efficiently absorb liquid by
breaching the center seal of the envelope, it is preferable that
the liquid absorbing material occupy at least about 30 percent and
preferably at least about 50 percent of the volume of the packet
when the packet is empty. As the preferred sodium polyacrylate
material can absorb up to at least about 200 times its weight in
water and about 30 to about 40 times its weight of a one percent
saline solution, upon contact with a liquid the liquid absorbing
material will immediately swell and breach the center seal thereby
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releasing the liquid absorbing material to the surrounding
environment without first requiring the envelope to be dissolved.
It is anticipated that the packets will be manufactured by
first forming the sheet of the envelope into a tube, preferably
around a fill tube using a single running sheet of the envelope
material. See Figure 2. The tube will be formed by folding the
sheet upon itself inwardly and then heat sealing the edges to form
a seal, preferably the center seal. As previously discussed, the
strength of the center seal is closely monitored as it must be
breachable upon swelling of the absorbent material. The center
seal (16) is then formed by sealing opposite sides of the packet
together under heat and pressure, for example, by use of
conventional spring loaded rollers (20) under the heat and pressure
limitations previously discussed. It is critical that the heat and
pressure that is used to form the center seal be less than the heat
and the pressure that is used to form the end seals as has been
previously discussed. The general process for the formulation of
this seal is disclosed in Figures 2 and 3. As the tube is formed,
the liquid absorbing material is funneled into the tube to fill it
to the extent previously discussed, which is at least about one-
third of the space and preferably at least one-half of the space of
the envelope when empty. The center seal can be formed by bringing
the sides of the packet together around a fill tube (18). See
Figure 2. While the size of the packet can be any conventional
size, preferably it is approximately 50 to about 65 millimeters in
width and about 120 to about 135 millimeters in length. The width
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of the center seal can vary, but should be in the range of about 2
to about 8 millimeters and preferably about 3 to about S
millimeters. Once the center seal is formed, the end seals are
formed in a continuous forming process as is shown in Figure 3.
Once again, conventional spring loaded heat seal rollers (22) are
used which are placed at a higher heat and pressure than was used
for forming the center seal. On the surface of those rollers are
heated mandrels (24) which extend from the body of the roller and
which press together to form the end seals. By the adjustment of
the location of the spring loaded heat seal rollers and the
distance of extension of the mandrels, sufficient pressure and heat
are brought to bear upon the end seals to result in a stronger bond
for those seals than for the center seal, as has previously been
discussed. The width of these seals is not particularly critical
but should be at least about 5 millimeters and preferably at least
about 8 millimeters in width. After the center seal and the end
seals are formed, the continuous roll of packets is cut to form
individual packets by a conventional cutting process.
The packet must contain a sufficient quantity of the liquid
absorbing material. Preferably the material fills at least about
1/3 of the interior space of the packet and more preferably, at
least about 1/2 of that space.
The packet can be utilized in a variety of ways to contain
liquid spills. As a preventative or precautionary manner, the
packet can be placed in secondary containers, such as shipping
cases to immobilize liquids from broken or damaged primary
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containers such as bottles or cans. As an after spill measure, the
packets can be placed in or surrounding a spilled chemical or
liquid to control flow and/or spreading.
Upon being placed in liquid, the liquid will immediately pass
through the liquid permeable envelope material to contact the
absorbent material. That absorbent material will immediately swell
and breach the center seal of the packet within a matter of a few
seconds, preferably no more than about 5 seconds, thus releasing
the absorbent material outside of the packet to permit full
utilization of the absorbent material. This provides a quick and
efficient packet for the absorption of a liquid.
(f) Examples
Comparative Example 1
A liquid absorbing packet manufactured by Multiform
Desiccants, Inc. called DriMop, which is 32.8 mm. in length and
32.8 mm. in width, is used as the comparison product. 50
milliliters of a 1% saline solution is placed within a 500 ml
container. The Multiform packet is dropped into the saline
solution. Approximately 10-20 seconds after exposure to the saline
solùtion, the envelope containing the Multi-Form absorbent material
dissolves to release the absorbent material contained within the
packet. Full absorption of the liquid occurs within 180 seconds.
Example 2
A packet of approximately the same size as the Multiform
packet but formed by the process of the instant invention
containing approximately the same amount of liquid absorbent
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material as was utilized in comparative example 1 is prepared. The
composition of the envelope is HDPE, i.e., a poly vinyl chloride,
vinyl acetate, cellulose composition. The liquid absorbing
material is a sodium polyacrylate absorbent polymer, lightly cross-
linked and supplied by Chemdal Corp. under the name Aridall, ASAP
No. 1100. The packet containing the liquid absorbing material is
placed in a 500 ml container containing 50 milliliters of a 1%
saline solution. Within 2 seconds the center seal is breached,
thus exposing the saline solution to the liquid absorbent material
contained within the packet. Within 30 seconds the entire amount
of the liquid is absorbed.
As is apparent from the above examples, the product of the
instant invention absorbs liquids, especially saline solutions,
more quickly than that of the comparative example product formed by
conventional procedures.
