United States Patent
`[19]
`[11] Patent Number:
`5,911,937
`
`Hekal
`[45] Date of Patent:
`Jun. 15, 1999
`
`U5005911937A
`
`[54] DESICCANT ENTRAINED POLYMER
`
`[75]
`
`Inventor:
`
`Ihab M. Hekal, Stamford, Conn.
`
`[73] Assignee: Capitol Specialty Plastics, Inc.,
`Auburn Ala.
`’
`
`[21] Appl. No.: 08/611,298
`.
`Flled:
`
`Mar. 5, 1996
`
`[22]
`
`Related US. Application Data
`
`[63]
`
`Continuation—in—part of application No. 08/424,996, Apr. 19,
`1995.
`Int. Cl.5 ............................. F26B 25/16; B65B 81/26
`[51]
`[52] US. Cl.
`.................... 264/255; 264/165; 264/173.16;
`264/1761; 264/259; 264/268; 264/299;
`264/250; 264/DIG. 78; 34/95; 34/329; 53/400;
`53/428; 53/111; 206/204; 252/194; 502/402;
`502/405
`
`[58] Field of Search ................................. 206/204; 34/95,
`34/329; 502/402’ 405; 53/400’ 428’ 111;
`264/DIG. 78, 250, 259, 510, 173.16, 268,
`165, 299, 176.1; 252/194
`
`[56]
`
`References Cited
`
`.............................. 252/25
`
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`/
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`’
`’
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`8/1963 Jackson, Jr.
`.............................. 18/47.5
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`11/1964 Dl’lpms ~~~~~~~~~~~~~~~~~~~~~~~ 229/30
`
`""" 360/41
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`3,2 6,441
`6/1966 Grasty ..................................... 2 0/108
`(List continued on next page.)
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`
`0225 593 A3
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`4013799
`
`6/1987 European Pat. Off.
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`5/1994
`France -
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`
`.
`.
`
`Japan ~
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`56'89928
`Japan .
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`62—108019
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`WO 96/29603
`WO 96/33108 10/1996 WIPO .
`PCT/US97/
`03610
`
`5/1997 WIPO .
`
`OTHER PUBLICATIONS
`
`Leaversuch, D., “Desiccant molding technique builds mois-
`“”6 reSIStance ’MOdem P1‘13”“ May’ 1997’ pp‘ 35‘36’
`Primary Examiner—Catherine Timm
`Assistant Examiner—Suzanne E. Mason
`Attorney, Agent, or Firm—Reed Smith Shaw & McCLay
`L.L.P.
`
`ABSTRACT
`[57]
`The present invention includes processes and resulting struc-
`.
`.
`.
`.
`.
`tures for producmg m01sture absorbmg de51ccant entramed
`.
`polymers. A polymer ls caused to assume a molten state,
`typically by applying .heat and melting the polymer. To
`achleve certam results 1n the hardened end product, such as
`rigidity and durability,
`the polymer normally acts as a
`moisture barrier in a solidified state, both before and after
`melting. A desiccating agent is blended into the polymer so
`th 1 th (1
`.
`t.
`t . d.
`t .b t
`(1
`.th.
`th
`1
`a
`e 6.51“” mg 3g“ 15
`15 n u. 6 W1
`1“
`6 P0 ymer'
`A channelmg agent 1s also blended mto the polymer so that
`It IS dlstrlbuted Wlthln the polymefi Together, the Polymer,
`desiccating agent and channeling agent create a blended
`mixture. The mixture is solidified so that the channeling
`agent forms passages in the mixture through Wthh moisture
`is communicable to desiccating agent
`that
`is entrained
`Within the mixture. The solidified mixture may be used to
`form plug type inserts and liners for closed containers, or it
`may be used for producing laminated sheeting employed as
`acka e wra .
`p
`g
`p
`
`0172714 A1
`
`2/1986 European Pat. Off.
`
`.
`
`33 Claims, 3 Drawing Sheets
`
`
`
`CLARIANTX 1018 Page 1
`
`CLARIANTX 1018 Page 1
`
`

`

`5,911,937
`
`Page 2
`
`US. PATENT DOCUMENTS
`
`4,725,393
`
`2/1988 Nasu ....................................... 264/160
`
`............................ 252/194
`224/5
`
`t
`5/1967 B
`3 322 355
`Wan ~
`,
`,
`6/1967 Dolan et al.
`3,326,810
`37:23:32? @1331)
`112/113:
`‘
`3,687,062
`8/1972 Frank . ..........................................
`3,704,806
`12/1972 PlachenoV et al.
`....................... 220/64
`3,730,372
`5/1973 Komendowski .
`3,750,966
`8/1973 Anderson .
`3,804,282
`4/1974 Komendowski .
`3,833,406
`9/1974 White ........................................ 117/97
`3,926,379
`12/1975 Dryden et al.
`.
`3,929,295
`12/1975 Montalbano .
`4,013,566
`3/1977 Taylor ..................................... 210/502
`4,021,388
`5/1977 Griffin .
`4,029,830
`6/1977 Yamamoto .
`4,036,360
`7/1977 Deffeyes ................................. 206/204
`4,081,397
`3/1978
`252/194
`
`.
`.
`4,153,206
`5/1979
`8/1979 Denning .
`4,165,743
`4,176,755
`12/1979 Winchell .
`4,201,209
`5/1980 LeVeen et al.
`4,205,794
`6/1980 Horton et al.
`4,240,937 12/1980 Allen .
`4,243,767
`1/1981 Kaufman et al.
`4,284,548
`8/1981 Kaufman et al.
`4,340,352
`7/1982 Hayberg.
`4,351,630
`9/1982 Hayberg et al.
`206/204
`4,387,803
`6/1983 Mercil
`............
`55/281
`4,394,144
`7/1983 Aoki ...........
`
`..
`.. 428/516
`4,407,897 10/1983 Farrell et al.
`
`........................... 428/516
`4,425,410
`1/1984 Farrell et al.
`4,447,565
`5/1984 Lula et al.
`.
`4,464,443
`8/1984 Farrell et al.
`4,485,204
`11/1984 Nabors .
`4,527,350
`7/1985 Tockey, Jr.
`.
`4,531,437
`7/1985 Szablak et al.
`4,533,576
`8/1985 Tanahashi et al.
`4,547,536
`10/1985 Nabors .
`4,554,297
`11/1985 Dabi .
`.
`4,573,258
`3/1986 10 et al.
`.
`4,619,409
`10/1986 Harpet et al.
`4,646,914
`3/1987 Gipson ................................. 206/45.34
`4,665,050
`5/1987 Degen et al.
`........................... 502/402
`4,686,093
`8/1987 Flanigen et al.
`.
`
`.
`
`.
`
`.
`.
`
`.
`
`........................... 428/688
`
`
`....................... 43/55
`
`.
`
`5/1988 Forrest et al.
`4,745,073
`7/1988 Griffith et al.
`4,759,508
`9/1988 Farrell et al.
`4,770,944
`9/1988 Cullen et al.
`4,772,300
`11/1988 Abrams .
`4,783,056
`............................. 55/387
`11/1988 Cullen et al.
`4,783,206
`4,792,484 12/1988 Mor1tan1 .................................. 428/323
`4,809,915
`3/1989 Koffsky et al.
`.
`4,834,234
`5/1989 Sacherer et al.
`4,884,756
`12/1989 Pearson -
`4,971,261
`11/1990 SOIOIIIOIIS .
`4,994,312
`2/1991 Maier et al.
`5,030,406
`7/1991 Sorensen .
`5,078,909
`1/1992 Shigeta et al.
`5,096,130
`3/1992 Gulmini .
`5,114,003
`5/1992 Jackisch et al.
`5,118,655
`6/1992 Pedersen .
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`7/1992 Bunker et al.
`5,130,018
`7/1992 Tolman et al.
`5,143,763
`9/1992 Yamada et al.
`5,154,960 10/1992 Mucci et al.
`.
`5,178,336
`1/1993 Lodovico et al.
`5,186,331
`2/1993 Valster .
`5,203,806
`4/1993 Broida .
`5,221,000
`6/1993 Lee ......................................... 206/77.1
`5,242,652
`9/1993 SaVigny
`........................ 264/510
`
`.
`5,267,646
`12/1993 Inoue et al.
`.
`................... 252/188.28
`5,286,407
`2/1994 Inoue et al.
`4/1994 Shores ............................... 428/355
`5,304,419
`
`6/1994 Miksic et al.
`.
`5,320,778
`5,344,589
`9/1994 Miksic et al.
`........................... 252/392
`5,346,142
`9/1994 Miller et al.
`5,373,971
`12/1994 Laffy et al.
`5,389,347
`2/1995 Hall .
`5,393,457
`2/1995 Miksic et al.
`5,399,609
`3/1995 Moss .
`5,415,907
`5/1995 Inoue et al.
`5,432,214
`7/1995 Lancesseur .
`5,437,414
`8/1995 Hall .
`5,486,380
`1/1996 Enniss et al. .
`5,494,155
`2/1996 Evans et al.
`.
`5,518,761
`5/1996 Hatsuda et al.
`5,551,141
`9/1996 De’Ath et al.
`5,580,369
`12/1996 Belding et al.
`
`.......................... 436/518
`
`.
`
`.
`
`............................. 55/387
`
`........................ 206/204
`
`.......................... 252/194
`
`........................ 206/204
`
`......................... 428/34.3
`.
`
`........................ 428/36.2
`
`.
`
`........................... 252/194
`
`.
`
`.
`
`.
`
`.
`
`.
`
`.
`
`.
`
`CLARIANTX 1018 Page 2
`
`CLARIANTX 1018 Page 2
`
`

`

`US. Patent
`
`Jun. 15, 1999
`
`Sheet 1 0f 3
`
`5,911,937
`
`”FIG. 2
`
`
`
`CLARIANTX 1018 Page 3
`
`CLARIANTX 1018 Page 3
`
`
`

`

`US. Patent
`
`Jun. 15, 1999
`
`Sheet 2 0f 3
`
`5,911,937
`
`FIG. 5
`
`FIG. 6
`
`gill/I’lllll/i.’
`
`52
`
`
`
`.w5uazgwwzfafiigE\\\\\h\\\\\3§\\\\\\\\\\\
`
`:\\\\\\\\\\\V\s.\\\n\.\.\;§§w\\
`
`
`ww\QZMWuN.w%mm%./amnwmfiflmw&mwfl\%w“o5aa“é732\WOa“5fi\.2.a\
`5w.“Cm“
`
`IO55I506O
`
`5
`
`FIG. 8
`
`45
`
`CLARIANTX 1018 Page 4
`
`56
`
`1w
`
`VMA
`193
`
`CLARIANTX 1018 Page 4
`
`
`

`

`US. Patent
`
`Jun. 15,1999
`
`Sheet 3 0f3
`
`5,911,937
`
`FIG. 9
`/20
`45
`0
`3
`45
`wwwa‘mmwxfi r 75
`mm
`
`
`
`
`4/”80
`
`25
`
`30
`
`5
`
`3
`
`
`
`25
`
`25
`
`FIG. 10
`
`30
`
`35
`
`30
`
`/20
`45
`45
`$§§z§é§£fix¥§£§§§é§§s “' 75
`W F 80
`
`
`
`25
`
`FIG. 11
`
`
` CHANNELING
`
`
`
`MELTED
`
`POLYMER
`MATRIX
`BASE
`
`AGENT
`
`
`
`DESICCATING
`AGENT
`
`BLENDED POLYMERIC
`MIXTURE
`
`SOLIDIFIED, DESICCANT
`ENTRAINED AND
`CHANNELED BOY
`
`
`
`
`
`CLARIANTX 1018 Page 5
`
`CLARIANTX 1018 Page 5
`
`

`

`5,911,937
`
`1
`DESICCANT ENTRAINED POLYMER
`
`RELATED APPLICATIONS
`
`This application is a continuation-in-part of US. patent
`application entitled DESICCANT MATERIAL INCLUDED
`IN A CLOSED CONTAINER having Ser. No. 08/424,996
`filed on Apr. 19, 1995.
`FIELD OF THE INVENTION
`
`This invention relates generally to the use of desiccant
`material in packaging; more particularly, the present inven-
`tion relates to packaging material having a desiccant con-
`tained therein. Still more particularly, the present invention
`relates to polymers having desiccating agents applied to or
`blended or mixed therein. The invention further relates to
`
`desiccant entrained polymers that include means by which
`desiccant located within interior portions of the polymer
`structure are exposed to moisture that is exterior to the
`polymer body. The desiccant entrained polymer of the
`present invention is particularly useful in the manufacture of
`containers and packaging for items requiring moisture
`reduced environments.
`
`BACKGROUND OF THE INVENTION
`
`There are many articles that are preferably stored, shipped
`and/or utilized in an environment that is as moisture free as
`possible. Therefore, containers having the ability to absorb
`excess moisture trapped therein have been recognized as
`desirable. One application in which moisture absorbing
`containers are desired is for the shipment and storage of
`medications whose efficacy is compromised by moisture.
`The initial placement of medicines into a sealed moisture
`free container is usually controllable. Furthermore, the con-
`tainer for the medicine is selected so that it has a low
`
`the medication will
`permeability to moisture. Therefore,
`normally be protected from moisture until it reaches the end
`user. Once the medicine is received by the consumer,
`however,
`the container must be repeatedly opened and
`closed to access the medication. Each time the container is
`
`opened and unsealed, moisture bearing air will most likely
`be introduced into the container and sealed therein upon
`closure. Unless this moisture is otherwise removed from the
`
`it may be
`atmosphere or head space of the container,
`detrimentally absorbed by the medication. For this reason, it
`is a well known practice to include a desiccating unit
`together with the medication in the container.
`Other items, such as electronic components, may require
`reduced moisture conditions for optimal performance. These
`components may be sealed in containers, but excess mois-
`ture that
`is initially trapped therein must be removed.
`Furthermore, the housings may not be completely moisture
`tight, and moisture may be allowed to seep into the con-
`tainer. This moisture must also be retained away from the
`working components. For these reasons, it is important to
`include a desiccating agent within the housing for absorbing
`and retaining excess moisture. Because of the delicacy of
`many of the components that are to be protected from the
`moisture, it is important that the desiccant used not be of a
`“dusting” nature that may contaminate and compromise the
`performance of the components. Therefore,
`it has been
`recognized as advantageous to expose a desiccating agent to
`the interior space of such containers, while at the same time
`shielding the working components from actual contact with
`the desiccating material, including desiccant dust that may
`be produced therefrom.
`In other instances, moisture may be released from items
`that have been placed in containers or sealed in packaging
`
`2
`wrap for shipping and/or storage. Prime examples of such
`items are food stuffs that release moisture during shipping
`and storage. In the instance of containers that are sealed and
`substantially impermeable to moisture, the released moisture
`will remain within the container about the product. If not
`removed, this released moisture may have ill effects on the
`very item that released the moisture. It has been found that
`a substantial amount of moisture is released from certain
`
`food products within the first forty-eight (48) hours after
`manufacture and packaging. This released moisture will
`remain about the product until removed. If the moisture is
`not removed shortly after its release, it may cause the food
`to degrade into a condition that is not saleable. In these
`cases, desiccants may be included together with the con-
`tained items to continually absorb the released moisture until
`the product
`is unpacked.
`In this way, a relatively dry
`environment is maintained about the stored item.
`The need to eliminate moisture from within sealed con-
`
`tainers has been previously recognized. Early attempts to
`achieve these goals included the provision of desiccant
`materials in fabric or similar bags that are placed in the
`containers, together and commingled with the matter being
`shipped or stored. A consumer related problem, however,
`exists when the desiccant is loose and commingled together
`with consumable items. If not carefully and thoroughly
`processed upon unpacking, the desiccant may not be sepa-
`rated from the consumables and could harm a person if
`unknowingly ingested.
`Several inventions have been patented that include both
`structures and processes that provide means for absorbing
`moisture by way of a desiccant that is included in various
`forms of packaging. A most basic example is found in the
`disclosure of US. Pat. No. 3,326,810 issued Jun. 20, 1967
`to Dolan et al for a DESICCANT PACKAGE. That patent
`includes disclosure of a non-dusting silica gel desiccant bag.
`The bag is created from two sheet of nylon mesh that are
`bonded into a bag within which the silica gel is contained.
`The nylon mesh has micro-porous polyurethane bonded to it
`and through which moisture passes while at the same time
`containing the desiccating silica gel within the bags interior.
`It is explained that the micro porous structure of the poly-
`urethane allows the moisture to be transmitted thereacross,
`but is nonpermeable to desiccant dust that may be produced
`by the silica gel.
`Another known method by which a desiccant is included
`in a container is to provide a special side-compartment
`having limited exposure to the interior of the container.
`Within the side-compartment, desiccating materials or dry-
`ing agents are held for the purpose of absorbing moisture
`that is present within the primary portion of the container.
`Examples of such inventions are found in US. Pat. No.
`4,834,234 issued May 30, 1989 to Sacherer et al for a
`CONTAINER FOR TEST STRIPS. Sacherer provides a
`drying agent cell or compartment within the cap portion of
`a container for test strips that are used in the analysis of body
`fluids. Those strips must be maintained in a moisture
`reduced environment for which Sacherer’s invention is
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`intended. It is disclosed that the drying agent cell is covered
`by a water vapor-permeable cardboard disc that separates
`that cell from the interior of the container. It is the cardboard
`
`60
`
`disc that provides a barrier between the desiccant or drying
`agent and the container’s interior space. A similar example
`is found in US. Pat. No. 5,114,003 issued May 19, 1992 to
`Jackisch et al for a TABLET VIAL WITH DESICCANT IN
`BOTTOM. Jackisch includes disclosure of a desiccant can-
`ister that is secured to the bottom inside of a container’s
`
`65
`
`base. The desiccant canister within which the desiccating
`
`CLARIANTX 1018 Page 6
`
`CLARIANTX 1018 Page 6
`
`

`

`5,911,937
`
`3
`material is contained is initially sealed to prevent the absorp-
`tion of moisture. Immediately prior to use, the desiccant
`canister is punctured and communication of moisture across
`the container is allowed to the desiccant.
`
`Oftentimes, separate capsules of desiccant that are expen-
`sive to produce are provided within the packaging. US. Pat.
`No. 4,783,206 issued Nov. 8, 1988 to Cullen et al for an
`ADSORBENT CARTRIDGE describes an elongated hollow
`cylindrical body fabricated of polyethylene, polyester or
`polypropylene. It is intended that the sides of the body
`member of the cartridge be moisture impermeable and that
`membrane disc coverings be provided as end caps to the
`cartridge’s body through which moisture, odors and other
`gases are permeable. A desiccating agent is enclosed within
`the cartridge thereby maintaining the desiccant separate
`from other items commonly contained within the common
`container. By the cartridge’s construction, it is intended that
`moisture pass only through the end caps constructed of
`spun-bonded polyolefin, and not
`the rigid, high density
`plastic side walls of the cartridge.
`A DRYING CAPSULE is disclosed in US. Pat. No.
`
`2,638,179 issued May 12, 1953 to Yard. The drying capsule
`of Yard includes a desiccant that is encapsulated within a
`moisture permeable skin. The desiccant, which is contained
`within the capsule, absorbs moisture from the skin, and not
`directly from the outside atmosphere. The gelatin capsule is
`used as a regulator for governing the rate at which moisture
`is absorbed by the desiccating agent. In some instances, the
`desiccating agent may be very vigorous in its action and
`would absorb moisture too quickly if not coated by the
`prescribed capsule or skin. It is also the capsule that provides
`a barrier between the desiccant agent and the items to be
`stored together therewith.
`The patented inventions described above each provide a
`compartment within which a desiccating agent is contained
`and separated from a primary storage compartment of a
`container by a physical barrier. The compartment within
`which the desiccant is carried may, or may not be fixed to
`prevent relative movement between it and the storing con-
`tainer. An important and primary function of the enclosure
`about
`the desiccant
`is to provide a barrier between the
`desiccant agent and the primary storage compartment while
`at the same time permitting the transmission of moisture
`thereacross. In each instance, there is no means for prevent-
`ing the formation of desiccant dust, but instead a means for
`keeping it separate and apart from the other products is
`provided. The potential for the barrier being compromised is
`ever present and the possibility of desiccant dust contami-
`nating the stored items is possible.
`It is also known to entrain desiccant directly into plastics
`and rubbers. An example of such entrainment is found in
`US. Pat. No. 3,245,946 issued Apr. 12, 1966 to O’Connor
`et al for RUBBER AND PLASTIC FORMULATIONS
`
`AND PROCESS. Therein, the entrainment of a desiccating
`agent into rubber, plastic, and resin formulations during their
`production is utilized to contain moisture produced during
`the manufacture of those materials that would otherwise
`
`adversely affect the produced material. There is no contem-
`plation that the included desiccant will have residual capa-
`bilities that may be utilized in subsequently manufactured
`products beyond the material’s original production.
`A flexible desiccant body is disclosed in US. Pat. No.
`4,013,566 issued Mar. 22, 1977 to Taylor. Therein, a desic-
`cant material is homogeneously distributed and bound in a
`moisture transmissive aliphatic epoxy polymer matrix.
`Therein,
`it
`is specifically recognized that polypropylene
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`4
`bags are not suited as containment materials because of
`potential attrition problems due to melting or thermoplas-
`ticity of the bags during use. It is explained that an important
`aspect of the Taylor invention is that the polymer be elas-
`tomeric so that it retains flexibility and the capability to
`absorb vibrations and mechanical shocks. Furthermore, it
`should be moisture transmissive so that the desiccant mate-
`
`rial bound within the matrix may receive trapped moisture
`within the solid body. It is explicit from the Taylor disclosure
`that polypropylene, because of its characteristics as a mois-
`ture barrier, would not be used as a moisture transmissive
`polymer matrix of this invention and within which a desic-
`cant agent would be entrained. Furthermore, it is expressly
`stated that such polymers as polyethylene would not be
`utilized because of their rigid nature which may result in
`cracking, attrition and insufficient water absorption capacity.
`Another instance in which desiccant agents have been
`combined with polymers is found in layered plastic sheeting
`in which an interior oxygen impermeable layer must be
`protected against moisture which compromises the oxygen
`barrier characteristics of that interior layer. Examples of
`such utilization of a desiccant in a layered structure may be
`found in United States patents that are assigned to the
`American Can Company of Greenwich, Conn. and to the
`Kuraray Co., Ltd. of Kurashiki, Japan. Those United States
`patents include US. Pat Nos. 4,407,897; 4,425,410; 4,464,
`443 and 4,792,484. In the disclosure of these several patents,
`the laminated structure has an interior layer that serves as an
`oxygen barrier and is manufactured from such polymers as
`ethylene-vinyl alcohol (EVOH); in each instance, the EVOH
`is provided solely as an oxygen barrier. These EVOH layers
`serve as oxygen barriers as long as their moisture content
`remains below certain levels. In at least one application
`described in those patents, the layered packaging is used for
`food products that must be sterilized in a retorting process in
`which the food product, together with the packaging is steam
`treated. During the steam treatment process, the protective
`outer
`layers which are commonly manufactured from
`polypropylene and polyethylene and moisture impermeable
`at lower temperatures, permit the transmission of moisture
`thereacross at the elevated temperatures of the retorting
`process. This moisture must be removed and carried away
`from the EVOH layer after the retorting procedure to regen-
`erate that layer’s oxygen barrier characteristics. To effect the
`removal of moisture from the layer, desiccant is added to the
`adhesive layers adjacent
`to the EVOH layer. The sole
`purpose of the desiccant included in the structure of these
`several patents is to control the moisture levels within the
`oxygen barrier layer within the interior of the layered sheets.
`It
`is not contemplated, nor intended that any desiccant
`included within the laminate structure would have desiccat-
`
`ing abilities outside the exterior moisture barrier layers of
`the laminate;
`those exterior layers typically being con-
`structed from polyethylene, polypropylene, or a blend of the
`two. In any event, the only purpose of the described inven-
`tions of those patents to maintain the interior EVOH layer of
`the laminate at relatively low moisture levels to assure its
`performance as an oxygen barrier.
`An example of a desiccating agent being combined with
`a polymer binding material
`is found in US. Pat. No.
`4,665,050 issued May 12, 1987 to Degen et al for SELF-
`SUPPORTING STRUCTURES CONTAINING IMMOBI-
`LIZED INORGANIC SORBENT PARTICLES AND
`METHOD FOR FORMING THE SAME. Therein,
`it
`is
`explained that sorbent particles are mixed into a softened,
`but not melted thermoplastic material such as polyethylene
`or polypropylene. By only softening the polymer medium,
`
`CLARIANTX 1018 Page 7
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`5,911,937
`
`5
`“blinding” of the sorbent material is prevented. That is,
`exterior portions of the sorbent material must be exposed
`and not blocked by the surrounding polymer. In this manner,
`moisture is transmitted into the sorbent material at those
`
`locations that are not covered by the binding polymer. It is
`explained that the polymer should only be softened to an
`extent that it becomes slightly tacky and does not become so
`viscous as to flow.
`The combination of a moisture-absorbent substance with
`
`a thermoplastic resin is disclosed in US. Pat. No. 5,078,909
`entitled MOISTURE-ABSORBENT COMPOSITIONS
`
`AND MOLDED ITEMS that issued Jan. 7, 1992 to Shigeta
`et al. Therein, it is contemplated that a thermoplastic resin,
`which may include polyethylene, polypropylene, as well as
`others may be employed in the formation of the composi-
`tion. The inclusion of various additives are contemplated in
`the Shigeta disclosure which may include color indicators
`that respond to the moisture content of the composition, as
`well as foaming agents that may be mixed together with the
`other substances to produce a composition that is light in
`weight and has high moisture absorption properties both in
`its outer and inner parts.
`Prior to the present invention, the establishment of chan-
`nels throughout a desiccant entrained polymer has not been
`known. The present
`invention, has been developed in
`response to a recognized need for structures constructed
`from polymers that normally act as moisture barriers in their
`solid, rigid state, but when produced according to the present
`invention have a desiccant entrained therein which is
`
`capable of absorbing moisture exterior to the polymer.
`
`SUMMARY OF THE INVENTION
`
`The apparatus and method of the present invention makes
`it possible to provide a polymer matrix within which a
`desiccant agent is entrained in the structure of the product
`itself or in an appropriate insert therefore. In each instance,
`a means is provided by which moisture is communicable to
`most, if not all of the entrained desiccant, including that
`which is located most internally within the matrix. As has
`been described above with respect to previously patented
`inventions,
`it
`is known to entrain a desiccant within a
`polymer base for the purpose of fixing the desiccant with
`respect to the polymer and then using the combination in the
`manufacture of other items. The sole purpose of the earlier
`combinations was to reduce, if not eliminate, desiccant dust
`that may precipitate from desiccant particles confined in
`other ways. Many types of packaging and containers are
`manufactured from plastics and are selected based on the
`properties and performance characteristics of the plastic in
`each application. In some instances, flexibility is important
`when the packaging is utilized as plastic wrap for articles or
`in the construction of pouch or bag-type containers. In these
`cases, plastic sheeting is often utilized that may be folded or
`otherwise positioned about an object and then sealed to
`prevent foreign matter from contaminating the enclosed
`items. In some instances, the housed item may be moisture
`sensitive and for that reason it is desirable to have packaging
`with desiccating abilities that will absorb moisture trapped
`within the interior of the package and retain it within its
`structure away from the item so that the item is protected and
`preserved.
`In other applications, containers may be desirably con-
`structed from a rigid material that maintains its form and
`resists breakage and deformation of the container. Like the
`plastic wrap, items may be stored within the rigid containers
`that also require minimized moisture conditions. For that
`
`6
`reason, it is desirable to similarly entrain or combine des-
`iccating agents within these plastics which harden and form
`a rigid structure or container. Many of the plastic or polymer
`matrixes within which the desiccant agent will be entrained
`is substantially moisture impermeable so that desiccant
`entrained within the interior of the plastic, and not exposed
`at the surface of the plastic body, will be unable to absorb
`and retain moisture. One solution has been to locate the
`
`desiccant at the polymer’s surface. This, however, has not
`proved to be entirely satisfactory in that greater amounts of
`desiccant may be required to remove sufficient amounts of
`moisture to protect the items that are to be packaged. For that
`reason, the present invention has been developed as a result
`of desiring to entrain desiccating agent throughout a greater
`portion of a rigid plastic body or container, while at the same
`time providing means by which moisture may be commu-
`nicated to most, if not all of the desiccant that has been
`entrained therein. To do so will permit a plastic structure to
`be more greatly loaded with desiccant thereby enhancing
`absorption capacities.
`As previously stated, a primary drawback of entraining a
`desiccant within a rigid polymer matrix is the creation of a
`moisture impermeable polymer encasement about the indi-
`vidual desiccant particles contained within the structure. The
`present invention discloses both a structure and a method by
`which passages are established throughout
`the polymer
`matrix that communicate the entrained desiccant particles to
`the appropriate areas of the exterior of the plastic body in a
`manner that permits moisture to migrate from outside the
`plastic structure to interior locations where the desiccant
`particles are positioned. Furthermore,
`these channels or
`veins through which the moisture is permitted to travel may
`be occupied by agents or compounds that absorb and trans-
`port moisture at rates even greater than those achieved by the
`desiccant. These transporting agents, however, are unable to
`absorb significant quantities of moisture and retain those
`quantities therein. For that reason, the transporting agents
`are used to act as bridges from the surface of the plastic
`bodies inwardly to the desiccant particles positioned within
`the plastic structure.
`It has been discovered that certain compounds, which are
`referred to herein as channeling agents, may be combined
`with a polymer base matrix that is used in the formation of
`rigid bodies, including at least portions of closeable con-
`tainers. In practice, the polymer base material into which the
`desiccant agent and channeling agent are blended and mixed
`include as examples, polyethylene and polypropylene, each
`of which are particularly suited for use in the construction of
`rigid containers. Most often, these containers will be injec-
`tion or blow molded from molten polymer.
`The desiccant and channeling agent may be added to the
`polymer when the polymer base is in a molten state prior to
`forming it into a container so that these additive agents may
`be blended and thoroughly mixed throughout
`the base
`polymer material. After thoroughly blending the several
`materials together and the mixing process is subsequently
`stopped, the channeling agent will separate from the poly-
`mer base and form veins or channels that act as moisture
`
`communicating passages throughout the polymer. Ethylene-
`vinyl alcohol (EVOH) and polyvinyl alcohol (PVOH) have
`been found to be particularly suited as channeling agents.
`Each of these alcohols may be mechanically mixed with
`base polymers, such as polypropylene and polyethylene, and
`then allowed to separate into domains while still in the
`molten state. The polymer base and channeling agents do not
`separate out into distinct levels or phases, one above the
`other, but instead establish veined domains of channeling
`
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`20
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`5,911,937
`
`7
`agent that extend across the polymer base thereby establish-
`ing channels or passages through the polymer. The channels
`are open at the surface of the polymer structures and thereby
`provide access for moisture to interior portions of the
`polymer matrix.
`Alternatively, the desiccant material may be added on top
`of a polymer base during a thermal forming process of sheets
`of plastic material.
`Various types of desiccating agent are known in the art
`and most may be used in mixtures with polymer bases.
`Similarly, most can also be used in the mixtures of the
`present invention that contain both polymer and channeling
`agents. There are three primary types of desiccating agents.
`The first type comprises chemical compounds that form
`crystals that contain water. Examples of such desiccant are
`anhydrous salts which tend to absorb water or moisture and
`form a stable salt. In this reaction with the moisture, a stable
`compound is formed within which the moisture is held and
`prevented from release. A second type of desiccant com-
`pounds are those which are considered to be reactive. These
`compounds typically undergo a chemical reaction with
`water or moisture and form new compounds within which
`the water is combined. These newly formed compounds are
`generally irreversible at
`low temperature and require a
`significant amount of energy to be regenerated so that they
`may be reused as a desiccant. These reactive type desiccants
`are mainly used in solvent drying and as additives to
`polymers which must themselves be maintained in a mois-
`ture reduced state. One application in which these reactive
`type compounds are particularly suitable was described
`above with respect to the multi-layer sheeting within which
`a layer of EVOH is laminated between two shielding layers
`of what is normally moisture impermeable material such as
`polypropylene or polyethylene. As earlier noted, however,
`these types of sheeting or wrap are used to package fo