WORLD INTELLECTUAL PROPERTY ORGANIZATION
`International Bureau
`
`
`
`INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)
`
`(51) International Patent Classification 7 3
`
`(11) International Publication Number:
`
`WO 00/02955
`
`C08J 3/00, 3/03, 3/12, 5/18
`
`A1
`
`.
`(43) International Publication Date:
`
`20 January 2000 (2001.00)
`
`(21) International Application Number:
`
`PCT/US99/15396
`
`(22) International Filing Date:
`
`8 July 1999 (08.07.99)
`
`(30) Priority Data:
`09/113,778
`
`10 July 1998 (l0.07.98)
`
`US
`
`INC.
`KIMBERLY~CLARK WORLDWIDE,
`(71) Applicant:
`[US/US]; 401 North Lake Street, Neenah, WI 54956 (US).
`
`(72) Inventors: WANG, James, H.; 1325 East Overland Road,
`Appleton, WI 54915 (US). TOPOLKARAEV, Vasily; 1730
`South Lee Street, Appleton, WI 54915 (US).
`
`(74) Agents: PRIOR, Kimberly, J.; Jones & Askew, LLP, 2400
`Monarch Tower, 3424 Peachtree Road, Atlanta, GA 30326
`(US) et al.
`
`(81) Designated States: AE, AL, AM, AT, AU, AZ, BA, BB, BG,
`BR, BY, CA, CH, CN, CU, CZ, DE, DK, EE, ES, FI, GB,
`GD, GE, GH, GM, HR, HU, ID, IL, IN, IS, JP, KE, KG,
`KP, KR, KZ, LC, LK, LR, LS, LT, LU, LV, MD, MG, MK,
`MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI,
`SK, SL, TJ, TM, TR, TT, UA, UG, UZ, VN, YU, ZA, ZW,
`ARIPO patent (GH, GM, KE, LS, MW, SD, SL, SZ, UG,
`ZW), Eurasian patent (AM, AZ, BY, KG, KZ, MD, RU, TJ,
`TM), European patent (AT, BE, CH, CY, DE, DK, ES, F1,
`FR, GB, GR, IE, IT, LU, MC, NL, PT, SE), OAPI patent
`(BF, BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE,
`SN, TD, TG).
`
`Published
`With international search report.
`Before the expiration of the time limit for amending the
`claims and to be republished in the event of the receipt of
`amendments.
`
`J___
`(54) Title: WATER SOLUBLE POLYETHYLENE OXIDE FILMS
`
`(57) Abstract
`
`The invention relates to blends of a polyethylene oxide (PEO) resin and a latex emulsion. The blends are formed by mixing or coating
`21 PEO powder resin with a latex emulsion and melt blending the powder. The blends have improved processibility and toughness which
`are beneficial in the manufacture of PEO—based films and fibers. The films composed of the PEO/latex blend have improved toughness,
`breathability, and tear resistance and are useful for the manufacture of disposable, flushable medical and personal care products, such as
`diapers, tampons, feminine napkins, and bladder control pads.
`
`DRL - EXHIBIT 1040
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`DRL001
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`DRL001
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`

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`FOR THE PURPOSES OF INFORMATION ONLY
`
`Codes used to identify States party to the PCT on the front pages of pamphlets publishing international applications under the PCT.
`
`AL
`AM
`AT
`AU
`AZ
`BA
`BB
`BE
`
`BG
`13.1
`BR
`BY
`CA
`CF
`CG
`CH
`CI
`CM
`CN
`CU
`CZ
`DE
`DK
`EE
`
`Albania
`Armenia
`Austria
`Australia
`Azerbaijan
`Bosnia and Herzegovina
`Barbados
`Belgium
`Burkina Faso
`Bulgaria
`Benin
`Brazil
`Belarus
`Canada
`Central African Republic
`Congo
`Switzerland
`Cote d’Ivoire
`Cameroon
`China
`Cuba
`Czech Republic
`Germany
`Denmark
`Estonia
`
`ES
`FI
`FR
`GA
`GB
`GE
`GH
`GN
`GR
`HU
`IE
`IL
`IS
`IT
`JP
`KE
`KG
`KP
`
`KR
`KZ
`LC
`LI
`LK
`LR
`
`Spain
`Finland
`France
`Gabon
`United Kingdom
`Georgia
`Ghana
`Guinea
`Greece
`Hungary
`Ireland
`Israel
`Iceland
`Italy
`Japan
`Kenya
`Kyrgyzstan
`Democratic People’s
`Republic of Korea
`Republic of Korea
`Kazakstan
`Saint l.ucia
`Liechtenstein
`Sri Lanka
`Liberia
`
`LS
`LT
`LU
`LV
`MC
`MD
`MG
`MK
`
`ML
`MN
`MR
`MW
`MX
`NE
`NL
`N0
`NZ
`PL
`PT
`R0
`RU
`SD
`SE
`SG
`
`Lesotho
`Lithuania
`Luxembourg
`Latvia
`Monaco
`Republic of Moldova
`Madagascar
`The fornrer Yugoslav
`Republic of Macedonia
`Mali
`Mongolia
`Mauritania
`Malawi
`Mexico
`Niger
`Netherlands
`Norway
`New Zealand
`Poland
`Portugal
`Romania
`Russian Federation
`Sudan
`Sweden
`Singapore
`
`SI
`SK
`SN
`SZ
`TD
`TG
`TJ
`TM
`TR
`TT
`UA
`UG
`US
`UZ
`VN
`YU
`ZW
`
`Slovenia
`Slovakia
`Senegal
`Swaziland
`Chad
`Togo
`Tajikistan
`Turkmenistan
`Turkey
`Trinidad and Tobago
`Ukraine
`Uganda
`United States of America
`Uzbekistan
`Viet Nam
`Yugoslavia
`Zimbabwe
`
`DRL - EXHIBIT 1040
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`WATER SOLUBLE POLYETHYLENE OXIDE FILMS
`
`FIELD OF THE INVENTION
`
`The present invention relates generally to polymeric films.
`processes for their manufacture, and their use in flushable medical and
`personal care products. More specifically.
`the invention relates to the
`modification and processing of polyethylene oxide (PEO) resins to make
`films for
`the production of such flushable products which have the
`advantages of improved toughness, softness, and tear resistance.
`
`BACKGROUND OF THE INVENTION
`
`such as panti-liners.
`Disposable personal care products,
`diapers, and tampons, are a great convenience, as are disposable medical
`care products, such as drapes, gowns, head coverings, and face masks.
`These products provide the benefit and convenience of one time, sanitary
`use. However. disposal of many of these products is a concern due to
`limited landfill space.
`Incineration of such products is not desirable
`because of increasing concerns about air quality and because of the costs
`and difficulty associated with separating these products from other disposed
`articles that cannot be incinerated. Consequently.
`there is a need for
`disposable products which may be quickly and conveniently disposed of
`without dumping or incineration.
`It has been proposed to dispose of such products in municipal
`and private sewage systems.
`Ideally, the products would be degradable in
`conventional sewage systems.
`Products suited for disposal
`in sewage
`systems which can be flushed down conventional toilets and are dispersed
`or disintegrated in water are termed "flushable." Disposal in this manner
`is simple, convenient, and sanitary.
`Personal care and medical care products must have sufficient
`strength to maintain integrity under the environmental conditions in which
`they will be used. They must also be able to withstand the elevated
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`temperature and humidity conditions encountered during use and storage
`
`and still lose integrity upon contact with water in the toilet. Therefore, a
`
`water—disintegrable material which is capable of thermal processing into a
`
`thin film having mechanical integrity is desirable.
`
`Currently, thin films are typically made from water—insoluble
`
`polymers or polymer blends.
`
`Frequently used polymers
`
`include
`
`amorphous
`
`polymers,
`
`epoxy resins,
`
`and
`
`semicrystalline
`
`polymers.
`
`Examples of
`
`amorphous
`
`polymers
`
`are
`
`polystyrene
`
`(PS),
`
`styrene-
`
`acrylonitrile copolymers, polycarbonate, and poly(vinyl chloride) (PVC).
`
`Examples of semicrystalline polymers are polyethylene (PE), polyamide
`
`(PA), polybutadiene (PB), and polypropylene (PP). The most commonly
`
`used polymers are polypropylene, and polyethylene.
`
`The thin films composed of these polymers are formed by
`
`extrusion casting or melt blowing processes. Conventional film extrusion
`
`involves mixing commercially available pellets of the desired polymers at
`
`increased temperatures,
`
`followed by extruding the mixture in a single
`
`screw extruder through a slit die to form a film. The film is then cooled
`
`by passing it through a series of chilled rolls. Films made in this manner
`
`from such water—insoluble polymers are unsuitable for use in “flushable”
`
`personal care and medical care products because they do not possess the
`
`desired characteristics, eg, they will not degrade in conventional sewage
`
`systems and consequently form blockage in the sewer lines.
`
`Polyethylene oxide (hereinafter PEO) is a hydrophilic, water-
`
`soluble polymer,
`
`—(CH2CH20)n—
`
`7
`
`that is produced from the ring opening polymerization of ethylene oxide,
`
`/0\
`CH2—" CH2
`
`It is available in widely varying molecular weights in the form of a powder
`
`from a number of sources, for example, Union Carbide Corp. (Danbury,
`
`CT) PEO is currently used as a flocculant to enhance the deposition of
`
`colloidal particles onto wood pulp fiber in the paper—making process.
`
`It is
`
`also used as an additive to modify such properties as the aggregation state,
`
`sedimentation behavior, and rheology of polymers employed as paints and
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`adhesives. PEO is also used to modify and stabilize polymer lattices, for
`
`example, by grafting PEO chains to a polystyrene lattice.
`
`Due to its unique interaction with water and body fluids, the
`
`present inventors are considering it as a component material for flushable
`
`and personal care products. However, currently available PEO resins are
`
`not practical for the formation of thin films by melt extrusion or for
`
`personal care product applications for a number of reasons.
`
`For example, while low molecular weight PEO resins have
`
`desirable melt viscosity and melt pressure properties
`
`for extrusion
`
`processing, they have low melt strength and low melt elasticity which limit
`
`their ability to be drawn into films having a thickness of less than about 2
`
`mil.
`
`Films produced from low molecular weight PEO also have low
`
`tensile strength, low ductility, and are too brittle for commercial use.
`
`High molecular weight PEO resins, on the other hand, should
`
`produce films having improved mechanical properties compared to those
`
`produced from low molecular weight PEO. High molecular weight PEO,
`
`however, has poor processibility and poor melt drawability due to its high
`
`melt viscosity. Melt pressure and melt temperature must be significantly
`
`elevated during melt extrusion of high molecular weight PEO, resulting in
`
`PEO degradation and severe melt fracture. Therefore, only very thick
`
`films of about 7 mil or greater
`
`in thickness can be made from high
`
`molecular weight PEO. Films this thick are not practical for flushable
`
`applications.
`
`Attempts
`
`to melt
`
`extrude PEO often result
`
`in
`
`severe
`
`degradation of the PEO. Even when a film can be formed,
`
`the PEO
`
`undergoes morphological changes such as crystallization and aging, when it
`
`is cooled from the melt and exposed to the ambient environment. These
`
`changes affect the mechanical properties of the film, resulting in a film that
`
`is weak and brittle, having very low elongation—at—break and tear
`
`resistance, and,
`
`thus, not suitable for
`
`the production of personal care
`
`products. What is needed in the art, therefore,
`
`is a means to overcome the
`
`difficulties in melt processing of PEO resins and to improve the resultant
`
`ductility and toughness of the thin films formed therefrom.
`
`It
`
`is known in the art
`
`to modify water-insoluble polymer
`
`resins,
`
`such as polystyrene and polypropylene, by incorporating soft
`
`rubber particles into the polymeric structure to improve the toughness of
`
`the polymer,
`
`to reduce its modulus, and to improve the softness and
`
`flexibility of the resulting material. The modifier can be a rubber—like
`
`elastomer, a core—shell modifier, or another polymer,
`
`such as styrene
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`butadiene polymers and acrylic polymers.
`
`Incorporation of the modifier
`
`can significantly reduce the elastic modulus of the polymer under tension.
`
`It can also initiate energy dissipation processes in the polymeric structure
`
`during deformation resulting in increased elongation at break, enhanced
`
`toughness, and improved tear resistance. The efficiency of the modifier
`
`depends upon the specific base polymer/modifier composition, blend
`
`morphology, phase structure, and toughening mechanisms and process
`
`conditions.
`
`The modifier can be incorporated into the base polymer by
`
`several different processes. One such process is conventional melt blending
`
`methods. These methods involve the blending of a base polymer blend
`
`with thermoplastic elastomers or particulate
`
`rubbers.
`
`The highly
`
`dispersive and distributive mixing required is generally achieved with twin
`
`screw extruders or with high shear mixers under high temperature and
`
`high shear conditions. Another such process is to mix liquid rubber with a
`
`monomer of the desired base polymer followed by polymerization of the
`
`mixture under conditions
`
`that
`
`result
`
`in
`
`a controlled rubber—phase
`
`separation.
`
`There are two types of base polymer/modifier systems which
`
`can be formed:
`
`a dispersed system and a network system.
`
`In a dispersed
`
`system,
`
`the base polymer is a matrix throughout which the modifier
`
`particles are dispersed.
`
`In a network system, the base polymer is present in
`
`the form of particles or islands which are surrounded by thin elastomer
`
`layers of the modifier to form a honeycomb—like network. Both types of
`
`systems exhibit very fine, well—dispersed morphologies.
`
`Dispersed
`
`systems
`
`typically
`
`exhibit
`
`two
`
`toughening
`
`mechanisms which provide additional energy absorption in the polymer
`
`under tension. One mechanism is the preferred formation of crazes at the
`
`rubber particles,
`
`i.e.,
`
`stress bearing microcracks with the
`
`stretched
`
`polymer fibrils. This type of energy absorption is observed in high—impact
`
`polystyrene and many grades of acrylonitrile—butadiene—styrene
`
`(ABS)
`
`polymers. Another mechanism is shear deformation between the modifier
`
`particles,
`
`i.e., multiple shearing.
`
`This type of energy absorption is
`
`observed in impact—modified polyamide and polypropylene.
`
`Network or honeycomb systems exhibit a third mechanism of
`
`energy absorption in addition to the two mechanisms exhibited by dispersed
`
`systems.
`
`In this third mechanism there is an intensive yielding of the
`
`thermoplastic particles inside the meshes of the network,
`
`i.e., multiple
`
`particle yielding.
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`PEO cannot be efficiently modified by the prior art methods
`
`described above.
`
`It is difficult to melt process PEO under the conditions
`
`required to incorporate the rubbery modifiers of the prior art
`
`into the
`
`PEO matrix because PEO is very sensitive to high shear and high
`
`temperature. Attempts to modify PEO in this manner result
`
`in poor
`
`thermal
`
`stability and high shear—induced degradation.
`
`Additionally,
`
`conventional melt blend extruders employ a series of water baths to cool
`
`the resulting polymer strands. Because PEO is water—soluble and water-
`
`absorbing, the strands cannot be cooled in this manner.
`
`Polymerization of the PEO monomer/modifier mixture would
`
`require the development of expensive and complex steps. Control of the
`
`morphology of the resulting blend would be significantly limited, and the
`
`success of such a process is unpredictable.
`
`Thus, there is a need in the art for disposable medical and
`
`personal care products that will maintain strength and integrity during use
`
`and will degrade in conventional sewage systems. Further,
`
`there is a need
`
`in the art
`
`for
`
`a process of modifying PEO to improve its melt
`
`processibility and mechanical properties.
`
`Additionally, there is a need in the art for tougher, softer, and
`
`more tear resistant PEO. There is also a need for a PEO resin having
`
`improved melt processing properties. Further,
`
`there is a need in the art
`
`for a PEO resin which is useful for the production of flushable films,
`
`dispersible thin—films, and flushable breathable films.
`
`SUMMARY OF THE INVENTION
`
`Stated generally,
`
`the present
`
`invention comprises water-
`
`dispersible compositions for use in flushable medical and personal care
`
`products
`
`having improved
`
`toughness
`
`and tear
`
`resistance.
`
`More
`
`particularly,
`
`the present
`
`invention comprises,
`
`in one aspect, blends
`
`comprising PEO and latex which provide improved processing and solid
`
`state properties when compared with conventional PEO. The blends of the
`
`invention comprising PEO and latex possess a unique rnicrostructure which
`
`provides a number of advantageous properties when compared to PEO
`
`alone. Additionally,
`
`the water present in the latex forms a molecular
`
`association with the PEO in the blend, acting as a plasticizer for the PEO.
`
`In a second aspect, the present invention comprises processes
`
`for modifying PEO, by forming a blend comprising PEO and latex,
`
`to
`
`improve melt processing and physical properties. The process includes
`
`mixing or coating PEO powder or pellets with a latex emulsion. The
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`amount of emulsion added can vary greatly. Generally, about 60 weight
`
`percent or less of the emulsion based on the blend is added to the PEO.
`
`The mixture is then melt processed, for example, by extrusion with a twin
`
`screw extruder fitted with a strand die. The strands of the blend are
`
`collected on a fan—cooled conveyor belt and cut into pellets.
`
`In another aspect, the present invention comprises PEO—based
`
`films produced from the blend. These films can be produced, for example,
`
`by compression molding or extrusion casting. These films have improved
`
`mechanical properties, such as tensile strength and tear resistance. The
`
`films also exhibit reduced modulus and improved softness, toughness, and
`
`ductility. Due to these improved mechanical properties,
`
`the films of the
`
`invention can be produced at
`
`thicknesses significantly less than those
`
`formed with PEO alone. For example, the films of the invention can have
`
`thicknesses of about 1 mil to about 4 mil. They can be used to thermally
`
`process articles which have improved properties, such as toughness and
`
`dispersibility, over articles similarly processed from PEO alone.
`
`Such
`
`items include, but are not limited to, fabrics, garments and articles, such as
`
`drapes,
`
`towels, covers, overwraps, gowns, head coverings,
`
`face masks,
`
`shoe coverings, CSR wraps, sponges, dressings, tapes, underpads, diapers,
`
`liners, wash cloths, sheets, pillow covers, napkins, clothlike outercovers,
`
`feminine tampons, pads and pantiliners, baffle films, and any woven, non-
`
`woven, or otherwise formed materials. Such products can be employed in
`
`the medical industry, both in hospitals and outpatient facilities, and in home
`
`environments.
`
`Accordingly,
`
`it
`
`is an object of
`
`the invention to modify
`
`commercially available PEO resins
`
`in order
`
`to improve the melt-
`
`processibility of the PEO.
`
`It is another object of the invention to modify PEO in order to
`
`thermally process the PEO into components of useful articles without
`
`adversely affecting the PEO and the properties of the finished article.
`
`It
`
`is yet another object of the invention to modify PEO in
`
`order to thermoform articles having improved mechanical properties over
`
`prior art thermoformed articles comprising conventional PEO.
`
`Another object of the invention is to provide a process for
`
`modifying PEO which is fast, economical, and efficient.
`
`Another object of the invention is to blends comprising PEO
`
`and latex with improved flexibility, toughness, and tear resistance.
`
`Yet another object of the invention is to provide blends
`
`comprising PEO and latex having a unique rnicrostructure of a nanoscale
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`dispersion of fine latex particles in the lamellae structural assembly of the
`
`PEO resin.
`
`It
`
`is a further object of the invention to provide a water-
`
`dispersible blends comprising PEO and latex having a more uniform fine
`
`crystalline morphology than conventional PEO.
`
`Another object of the invention is to provide PEO—based films
`
`with improved elasticity, toughness, and tear resistance.
`
`It
`
`is yet another object of invention to provide PEO—based
`
`films having improved melt rheology over conventional PEO films.
`
`More generally,
`
`the present
`
`invention provides for blends
`
`comprising an emulsion and a polymer or mixture of polymers which are
`
`Water—soluble and/or water-dispersible and films made from these blends.
`
`Accordingly it is an object of the present invention to modify water-soluble
`
`and water-dispersible
`
`polymers
`
`in
`
`order
`
`to
`
`improve
`
`their melt-
`
`processibility.
`
`It is another object of the invention to modify water-soluble
`
`and/or water-dispersible polymers in order
`
`to thermally process
`
`the
`
`polymers into components of useful articles without adversely affecting the
`
`polymers and the properties of the finished article.
`
`It
`
`is yet another object of the invention to modify water-
`
`soluble and/or water-dispersible polymers in order to thermoform articles
`
`having improved mechanical properties over prior art
`
`thermoformed
`
`articles.
`
`Another object of the invention is to provide a process for
`
`modifying water-soluble and/or water-dispersible polymers which is fast,
`
`economical, and efficient.
`
`Another object of
`
`the
`
`invention is
`
`to provide
`
`blends
`
`comprising an emulsion and a polymer or mixture of polymers which are
`
`water-soluble and/or water-dispersible which have improved flexibility,
`
`toughness, and tear resistance.
`
`Yet another object of the invention is to provide blends
`
`comprising an emulsion and a polymer or mixture of polymers which are
`
`water-soluble and/or water-dispersible having a unique rnicrostructure of a
`
`dispersion of fine particles in the structural assembly of the polymer.
`
`It
`
`is a further object of the invention to provide blends
`
`comprising an emulsion and a polymer or mixture of polymers which are
`
`water-soluble and/or water-dispersible having a more uniform fine
`
`crystalline morphology than the conventional water-soluble and water-
`
`dispersible polymers.
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`Another object of the invention is to provide films made from
`
`blends comprising an emulsion and a polymer or mixture of polymers
`
`which are water—soluble and/or water—dispersible that have improved
`
`ductility, toughness, and tear resistance.
`
`It
`
`is yet another object of invention to provide films made
`
`from blends comprising an emulsion and a polymer or mixture of
`
`polymers which are water—soluble
`
`and/or water—dispersible
`
`having
`
`improved melt rheology over conventional films.
`
`These and other objects of the invention are achieved by
`
`forming blends comprising an emulsion and a polymer or mixture of
`
`polymers which are water—soluble and/or water—dispersible which are
`
`processible into films that are useful
`
`in the manufacture of disposable
`
`personal care products. More particularly, these and other objects of the
`
`invention are achieved by blends comprising PEO and latex which are
`
`processible into PEO—based films that are useful
`
`in the manufacture of
`
`disposable personal care products.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`Figure 1 demonstrates the rubber particle size distribution in
`
`the PEO/latex (90/10) blend.
`
`Figure 2 is a scanning electron micrograph which illustrates
`
`the approximately uniform dispersion of the latex particles in the PEO
`
`resin.
`
`Figure 3 is an atomic force micrograph demonstrating the
`
`unique rnicrostructure of a nanoscale dispersion of fine latex particles in
`
`the PEO resin.
`
`Figure 4 illustrates the reduction in spherulite size by the
`
`addition of latex particles to the PEO resin.
`
`DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
`
`In order to overcome the problems in the art associated with
`
`forming polymer films composed of water—soluble or water—dispersible
`
`polymers,
`
`the present inventors have developed a process for modifying
`
`polymers, such as PEO, with an emulsion, such as a latex emulsion. The
`
`resulting blends possess improved processing properties and produce films
`
`having superior properties to those produced from the water—soluble or
`
`water—dispersible polymer alone.
`
`The particular embodiments of the present invention will be
`
`described in terms of the preferred blend comprising PEO and latex.
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`However,
`
`it
`
`should be understood that any water—soluble or water-
`
`dispersible polymer and any emulsion as defined herein may be employed
`
`in
`
`the
`
`invention
`
`in
`
`a
`
`similar manner
`
`and
`
`that
`
`the
`
`resulting
`
`polymer/emulsion blends will have similarly advantageous properties over
`the polymers alone.
`
`The blend of the invention comprising PEO and latex has a
`
`unique rnicrostructure which can be observed by scanning electron
`
`microscopy and atomic force microscopy. The PEO resin of the blend
`
`possesses a lamellae structural assembly in which there is an approximately
`
`uniform nanoscale dispersion of fine latex particles.
`
`In the blend, both
`
`individual latex particles, approximately 100 nm to 200 nm in diameter,
`
`and clusters of the particles, approximately a few microns in size, are
`
`embedded in the PEO lamellae structural assembly.
`
`Atomic force
`
`microscopy illustrates the unique microstructure of a nanoscale dispersion
`
`of fine latex particles in the lamellae structure of the PEO resin. Some of
`
`the particles form clusters. The particles in the clusters are not tightly
`
`packed and do not appear to be coupled. (See Figure 3) Scanning electron
`
`microscopy illustrates the approximately uniform dispersion of the latex
`
`particles in the PEO resin.
`
`(See Figure 2)
`
`Analysis of thermal properties using Differential Scanning
`
`Calorimetry (DSC) demonstrates that the blend can exhibit an increased
`
`crystallinity over PEO alone.
`
`This increase may be due to enhanced
`
`molecular mobility of the PEO chains in the presence of the emulsion as
`
`well as additional nucleation sites provided by the rubber.
`
`The DSC data also indicate that water of the emulsion is
`
`structurally bonded with the PEO because water—melting transition does not
`
`occur during the cooling/heating cycle. The bound water functions as a
`
`plasticizing agent for the PEO,
`
`improving its processing and solid state
`
`properties.
`
`The blend comprising PEO and latex also exhibits a lower
`
`melt viscosity, as determined by capillary rheometer, than PEO alone. For
`
`example, blends having a 70/30 ratio of PEO/latex have demonstrated a
`
`30% reduction in melt viscosity. This reduction in viscosity is exhibited
`
`over a broad range of shear rates and provides for improved processing of
`
`the blend over conventional PEO.
`
`It allows the blend to be processed at
`
`lower
`
`temperatures,
`
`reducing PEO degradation.
`
`Lower processing
`
`temperatures provide a reduced temperature gradient during melt cooling
`
`which allows for a higher processing rate.
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`Any polymer resin that is water—soluble, water—dispersible, or
`
`both which can form association compounds with water may be used in the
`
`invention. The invention also contemplates the use of mixtures or more
`
`than one of such polymers. Nonlimiting examples of such polymer resins
`
`are
`
`hydroxypropyl
`
`cellulose, polyvinyl
`
`alcohol,
`
`polyethyloxazoline,
`
`polyvinyl pyrolidone, polyvinyl pyridine,
`
`gelatinized starch,
`
`nylon
`
`copolymers, polyacrylic acid, polyesters or mixtures
`
`thereof.
`
`The
`
`preferred polymer resin is polyethylene oxide (PEO).
`
`The selection of
`
`PEO as the preferred resin for the invention is based upon PEO’s water
`
`solubility and melt processibility. The selection is also based upon the
`
`availability of PEO resins in a wide range of molecular weights.
`
`PEO and other such polymers useful in the present invention
`
`have very distinct properties from the water—insoluble polymers used in the
`
`prior art. These polymers form a molecular association with water. For
`
`example, water molecules form specific hydrogen bonded complexes with
`
`the ether oxygens of the PEO chain. This association affects the local
`
`motion of
`
`the polymeric
`
`chain to provide
`
`a plasticization effect.
`
`Additionally,
`
`the formation of PEO—water
`
`complexes
`
`results
`
`in the
`
`formation of a distinct state of the water in the PEO matrix. The bound
`
`water does not exhibit a detectable phase transition over the range of
`
`temperatures normally associated with bulk water.
`
`In other words,
`
`the
`
`bound water does not freeze or boil. This allows the use of water—based
`
`emulsions,
`
`having
`
`finally
`
`dispersed
`
`latex particles
`
`of
`
`controlled
`
`morphology and size, to modify the PEO or other polymer.
`
`The water—insoluble polymers of the prior art cannot be
`
`modified by the methods of the instant invention because they do not have
`
`the ability to form a molecular association with water. Therefore,
`
`the
`
`water present in the emulsions of the present invention would exists as
`
`“free” water rather
`
`than “bound” water
`
`in any composition formed
`
`between the water—insoluble polymers of the prior art and the emulsions
`
`used in the present
`
`invention.
`
`Such free water would undergo phase
`
`transitions during melt processing, resulting in microscopic holes and weak
`
`spots
`
`in the
`
`film.
`
`Films produced from such polymer/emulsion
`
`compositions would have reduced tensile strength and reduced fracture
`
`resistance, the very problems solved by the present invention.
`
`The PEO resins useful in the practice of this invention can be
`
`of any molecular weight. Preferred PEO resins have an average molecular
`
`weight ranging from about 100,000 g/mol to about 8,000,000 g/mol. High
`
`molecular weight PEO resins are desirable for enhanced liquid stability,
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`mechanical strength, and ductility, while low molecular weight resins
`
`provide better melt flow and film—forming properties. Based upon these
`
`considerations, especially preferred PEO resins of the invention have a
`
`molecular weight between 200,000 g/mol and 4,000,000 g/mol.
`
`Such PEO resins are commercially available. For example,
`
`PEO resins are available from Union Carbide Corporation (Danbury, CT)
`under the trade designations Polyox® WSR N—80 (MW = 200,000), WSR
`
`N—750 (MW=300,000), WSR N—3000 (MW = 400,000), and WSR 205
`
`(MW = 600,000).
`
`Other PEO resins available from Union Carbide
`
`Corporation within the above average molecular weight range are sold
`
`under the trade designations WSR—3333, WSR—N—l2K, WSR—N—60K, WSR-
`
`30l, WSR Coagulant, WSR—303.
`
`The emulsions useful in the practice of the present invention
`
`may be any organic polymer emulsion or
`
`any inorganic particulate
`
`dispersion and/or suspension. These emulsions can provide a number of
`
`different modifying properties, such as softness, ductility, toughness, and
`
`tear resistance, to the PEO.
`
`There are basically two types of organic polymer emulsions,
`
`polybutadiene and acrylic—based polymers. Each type can be synthesized
`
`through emulsion polymerization techniques which are known in the art.
`
`The particle size of the rubber (latex) particles in the emulsions can be
`
`controlled during polymerization. For the present invention, an average
`
`particle size of about 10 nanometers to a few microns is preferred. The
`
`emulsions can also be produced in a variety of particle morphologies, such
`
`as rubbery—spherical,
`
`rubbery—core/glassy—shell, and multilayered.
`
`The
`
`morphology can be tailored to provide modifier particles with controlled
`
`compliance and surface properties.
`
`Organic polymer emulsions useful
`
`in the present
`
`invention
`
`include, but are not
`
`limited to,
`
`styrene butadiene polymers, acrylics,
`
`styrene
`
`acrylics,
`
`polyvinyl
`
`acetate,
`
`acrylonitrile—butadiene—styrene,
`
`acrylonitrile, and acrylonitrile butadiene. Especially preferred polymer
`emulsions
`are
`styrene
`butadiene GOOD—RITE® 1168
`latex
`and
`acrylonitrile—butadiene—styrene HYCAR® latex, each available from BF
`GOODRICH® Company having offices in Cleveland,Ohio.
`In
`particular,
`inorganic
`particulate
`dispersions
`
`and/or
`
`suspensions useful in the invention include, but are not limited to, stabilized
`
`silica gel dispersions, nanoscale spherical silica dispersions, and dispersions
`
`of swellable clays. The invention is not limited to these compounds but
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`includes any organic or inorganic particulate emulsion/stable dispersion in
`
`the form of discrete particulates in a stabilizing fluid.
`
`The amount of emulsion may be varied based upon the
`
`particular polymer to be modified, the particular modifier chosen, and the
`
`particular properties to be enhanced. For example, modifiers for
`
`low
`
`molecular weight PEO may be selected and used in amounts that improve
`
`mechanical properties,
`
`such as softness,
`
`tensile strength, and ductility.
`
`Similarly, modifiers for high molecular weight PEO may be selected and
`
`used in amounts that lower melt viscosity and improve drawability.
`
`In
`
`general, the percentage of emulsion employed is from about 10 to about 60
`
`weight percent of the blend, preferably about 10 to about 50 weight
`
`percent, more preferably about 15 to about 35 weight percent of the blend.
`
`Two other parameters which affect the properties of the blend
`
`are the diameter