(12) United States Patent
`Haas et a1.
`
`(10) Patent N0.:
`(45) Date of Patent:
`
`US 7,655,296 B2
`Feb. 2, 2010
`
`US007655296B2
`
`(54)
`
`(75)
`
`INK-RECEPTIVE FOAM ARTICLE
`
`Inventors: Christopher K. Haas, Cottage Grove,
`MN (US); Robert D. Taylor, Stacy, MN
`(US); William B. Black, Eagan, MN
`(US); James M. Jonza, Woodbury, MN
`(US); Terrence E. Cooprider,
`Woodbury, MN (US)
`
`(73)
`
`Assignee: 3M Innovative Properties Company,
`St. Paul, MN (US)
`
`Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 361 days.
`
`Appl. N0.: 11/460,436
`
`Filed:
`
`Jul. 27, 2006
`
`Prior Publication Data
`
`3,855,376 A 12/1974 Ono et a1.
`3,884,606 A
`5/1975 Schrenk
`3,889,270 A
`6/1975 Hoffmann et 31.
`4,038,350 A
`7/1977 Jaques
`4,107,247 A
`8/1978 Dukess
`
`(Continued)
`FOREIGN PATENT DOCUMENTS
`
`AU
`
`488652
`
`4/1976
`
`(Continued)
`OTHER PUBLICATIONS
`
`H. C. Lau et a1, “Melt Strength of Polypropylene: Its Relevance to
`Thermoforming”, Polymer Engineering and Science, (Nov. 1998),
`pp. 1915-1923, vol. 38, No. 11.
`(Continued)
`Primary ExamineriBetelhem SheWareged
`(74) Attorney, Agent, or FirmiKent S. Kokko
`
`(21)
`
`(22)
`
`(65)
`
`(63)
`
`(51)
`
`(52)
`
`(58)
`
`(56)
`
`US 2006/0257594 A1
`
`Nov. 16, 2006
`
`(57)
`
`ABSTRACT
`
`Related U.S. Application Data
`Continuation-in-part of application No. 10/502,229,
`?led as application No. PCT/US03/11255 on Apr. 10,
`2003, noW abandoned.
`
`Int. Cl.
`(2006.01)
`B32B 27/00
`U.S. Cl. ............ .. 428/319.3; 428/317.9; 428/319.7;
`428/3148; 428/316.6; 428/131; 428/195.1
`Field of Classi?cation Search ............ .. 428/319.3,
`428/317.9, 319.7, 314.8, 316.6, 131, 195.1
`See application ?le for complete search history.
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`The present invention is directed an oriented, foamed article
`having an ink-receptive surface, and a method of making the
`article. The invention provides a printable substrate compris
`ing at least one high melt-strength, oriented polypropylene
`foam layer having an ink-receptive surface. The high melt
`strength polypropylene having a melt strength of 25 to 60 cN
`at 1900 C. The ink-receptive surface may comprise and oxi
`diZing treatment, such as corona or ?ame-treatment of the
`foam surface, or may comprise an ink-receptive coating, such
`as a primer coating, on the foam surface.
`
`The oriented foam article is particularly useful in the prepa
`ration of printed security documents such as currency, stock
`and bond certi?cates, birth and death certi?cates, land titles
`and abstracts and the like.
`
`3,782,870 A
`
`l/ 1974 Schippers
`
`24 Claims, 2 Drawing Sheets
`
`Page 1 of 23
`
`BOREALIS EXHIBIT 1075
`
`

`
`US 7,655,296 B2
`Page 2
`
`U.S. PATENT DOCUMENTS
`
`4,162,343
`4,206,165
`4,221,624
`4,310,591
`4,379,804
`4,503,111
`4,518,557
`4,536,016
`4,555,437
`4,564,560
`4,613,525
`4,657,811
`4,714,716
`4,747,983
`4,761,256
`4,775,594
`4,844,979
`4,896,901
`4,916,198
`4,937,134
`4,940,736
`5,089,318
`5,126,195
`5,134,198
`5,198,306
`5,215,691
`5,234,729
`5,240,767
`5,264,275
`5,342,688
`5,393,099
`5,429,856
`5,449,200
`5,489,471
`5,536,468
`5,605,936
`5,618,630
`5,660,919
`5,678,863
`5,698,333
`5,716,695
`5,721,806
`5,766,398
`5,824,400
`5,834,098
`5,871,833
`5,879,028
`5,882,774
`5,935,696
`6,001,469
`6,008,286
`6,045,894
`6,062,604
`6,074,747
`6,096,247
`6,096,469
`6,114,022
`6,164,739
`6,288,842
`
`7/1979
`6/1980
`9/1980
`1/1982
`4/1983
`3/1985
`5/1985
`8/1985
`11/1985
`1/1986
`9/1986
`4/1987
`12/1987
`5/1988
`8/1988
`10/1988
`7/1989
`1/1990
`4/1990
`6/1990
`7/1990
`2/1992
`6/1992
`7/1992
`3/1993
`6/1993
`8/1993
`8/1993
`11/1993
`8/1994
`2/1995
`7/1995
`9/1995
`2/1996
`7/1996
`2/1997
`4/1997
`8/1997
`10/1997
`12/1997
`2/1998
`2/1998
`6/1998
`10/1998
`11/1998
`2/1999
`3/1999
`3/1999
`8/1999
`12/1999
`12/1999
`4/2000
`5/2000
`6/2000
`8/2000
`8/2000
`9/2000
`* 12/2000
`9/2001
`
`Wilcox et al.
`Dukess
`Eslinger et a1.
`Lee et a1.
`Eisele et al.
`Jaeger et al.
`Wecker
`Solomon et al.
`Tanck
`Tani et al.
`Miyamoto et al. ........ .. 427/256
`Boyd et al.
`Park
`Colombo
`Hardenbrook et al.
`Desjarlais
`Strobel et al.
`Ekelund
`Scheve et al.
`Schrenk et al.
`Alteepping et a1.
`Shetty et al.
`Light
`Stofko, Jr. et al.
`Kruse
`Bland et al.
`Wheatley et a1.
`UmeZu et al.
`Misuda et a1.
`Kitchin et a1.
`D’Amato
`Krueger et a1.
`Andric et al.
`Inoue et al.
`Leese
`DeNicola, Jr. et al.
`Benoit et al.
`Vallee et al.
`Knight et al.
`Benoit et al.
`Benoit et al.
`Lee
`Cahill et al.
`Petrakis et al.
`Kitamura et al.
`Henbo et al.
`Benoit
`JonZa et al.
`Benoit et al.
`Verardi et a1.
`Groves
`JonZa et al.
`Taylor et al.
`ScholZ et al.
`Ulsh et a1.
`Anderson et al. ......... .. 427/256
`Warner et al.
`Schulz et al. ............. .. 312/406
`FlorcZak et al.
`
`11/2001 Emslander
`6,316,120 B1
`9/2002 Norquist et al.
`6,447,875 B1
`6,468,451 B1 * 10/2002 Perez et al. ................. .. 264/48
`6,495,231 B2 12/2002 Benoit et al.
`6,589,636 B2
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`6,641,910 B1
`11/2003 Bries et al.
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`2001/0021450 A1
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`2003/0072931 A1
`4/2003 Hebrink et a1.
`2004/0053044 A1
`3/2004 Moreno et al.
`
`FOREIGN PATENT DOCUMENTS
`
`CA
`EP
`EP
`GB
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`
`6/1974
`948820
`5/2002
`1 209 518 A2
`5/2002
`1 209 519 A2
`6/1976
`1 439 438
`12/1994
`94/28077 A1
`12/1994
`94/29119 A1
`1/1996
`96/00146 A1
`1/1997
`97/01438 A1
`5/1997
`97/17493 A1
`4/1998
`98/13211 A1
`1/1999
`99/03929 A1
`7/1999
`99/36466 A1
`10/1999
`99/54148 A1
`12/1999
`99/61520 A1
`12/1999
`99/67092 A1
`12/1999
`99/67093 A1
`1/2000
`00/00520 A1
`4/2000
`00/18575 A1
`12/2000
`00/74936 A1
`12/2000
`00/74948 A1
`1/2001
`01/02192 A1
`5/2001
`01/30570 A1
`01/94124 A2 12/2001
`01/96125 A1
`12/2001
`02/00412 A2
`1/2002
`02/00412 A3
`1/2002
`02/00982 A1
`1/2002
`02/051867 A1
`7/2002
`
`OTHER PUBLICATIONS
`
`J. I. Raukola, “A New Technology to Manufacture Polypropylene
`Foam Sheet and BioaXially Oriented Foam Film”, VTT Publications
`361, Technical Research Center of Finland, (1998).
`J. H. Schut, “Foamed Films Find New Niches”, Plastics Technology,
`(Feb. 2002).
`R. A. RyntZ, “The Effects of Solvent and Thermal History on the
`Adhesion of Coatings to Thermoplastic Ole?ns (TPOs)”,
`Waterborne, High-Solids, and Powder Coatings Symposium, (Feb.
`22-24, 1995), pp. 514-534, Symposium Sponsored by The University
`of Southern Mississippi, Department of Polymer Science, and South
`ern Society for Coatings Technology.
`
`* cited by examiner
`
`Page 2 of 23
`
`

`
`US. Patent
`
`Feb. 2, 2010
`
`Sheet 1 of2
`
`US 7,655,296 B2
`
`FIG. 1
`
`FIG. 2
`
`Page 3 of 23
`
`

`
`US. Patent
`
`Feb. 2, 2010
`
`Sheet 2 of2
`
`US 7,655,296 B2
`
`FIG. 3
`
`100 pm
`
`FIG. 4
`
`429 um
`
`Page 4 of 23
`
`

`
`US 7,655,296 B2
`
`1
`INK-RECEPTIVE FOAM ARTICLE
`
`CROSS REFERENCE TO RELATED
`APPLICATIONS
`
`This application is a continuation-in-part of US. applica
`tion Ser. No. 10/502,229, ?led Jul. 21, 2004 noW abandoned,
`Which is a national stage ?ling under 35 U.S.C. 371 of Inter
`national Application No. PCT/US03/ 11255, ?led Apr. 10,
`2003, Which International Application Was published the
`International Bureau in English on Dec. 24, 2003 as WO
`03/106183, Which in turn claims priority to US. application
`Ser. No. 10/175,020, ?led Jun. 18, 2002, the disclosure of
`Which is herein incorporated by reference.
`
`FIELD OF THE INVENTION
`
`The present invention is directed to an oriented, foamed
`article having an ink-receptive surface, and a method of mak
`ing the article.
`
`BACKGROUND
`
`Many ?lm materials, unlike paper, have no inherent capac
`ity to absorb inks that are commonly used in printing pro
`cesses. Paper hoWever, is not a particularly durable substrate
`and may be damaged by handling, environmental exposure
`and Water.
`The capture of the image-forming ink on polymeric sub
`strates presents a technical challenge because plastic ?lm is
`substantially impervious to liquids. Hydrophilic coatings,
`applied to ?lm materials, are knoWn to provide receptor layers
`for inkj et images. Receptor layers of this type may be porous
`for absorbing ink droplets via capillary action. Such coatings
`are described, for example, in US. Pat. No. 5,264,275. An
`alternative type of absorbent inkjet receptive coating com
`prises polymers that sWell While absorbing image forming ink
`droplets. Such coatings include those described in US. Pat.
`Nos. 3,889,270, 4,503,111, 4,564,560, 4,555,437, 4,379,804,
`5,134,198 and 5,342,688. Hydrophilic inkjet-receptive coat
`ings may also include multilayer coatings as described in US.
`Pat. No. 4,379,804.
`For many applications hoWever, polymeric ?lms do not
`provide the same texture and handling characteristics of paper
`substrates. Polymeric security documents offer several ben
`e?ts over their paper counterparts. In particular, polymeric
`banknotes can offer greatly increased durability and resis
`tance to counterfeiting through the incorporation of security
`features. A requirement for polymeric banknotes is that cer
`tain physical properties are similar to the more commonly
`used paper banknotes. Those properties relate to tactile feel,
`strength, tear resistance, handling, folding, and crumple resis
`tance.
`US. Pat. No. 4,536,016 teaches the use ofa laminate for
`banknotes having biaxially oriented polymeric ?lm and a
`non-printed WindoW for the incorporation of a security fea
`ture. HoWever, US. Pat. Nos. 5,698,333 and 5,935,696 dis
`cuss the shortcomings of banknotes based on the ’01 6 teach
`ings and offers a substrate construction primarily based on a
`polyole?n laminate Which offers improved physical proper
`ties. US. Pat. Nos. 5,393,099 and 5,449,200 offer yet another
`alternative to ’016, in Which a banknote is described that
`includes outer layers of paper laminated to a polymeric core
`as a Way to include paper-like properties.
`Polymeric banknotes offer unique opportunities to incor
`porate security features that are designed to discourage coun
`terfeiting. Many patents relating to banknotes, including
`those cited above, mention the possibility of a transparent
`WindoW someWhere on the banknote, Which offers a quick
`visual check for authenticity and is dif?cult to reproduce With
`
`2
`copying techniques. In most cases, the security feature must
`be added as a separate component With an additional process
`step.
`US. Pat. No. 5,234,729 teaches polymeric laminates hav
`ing a large number of layers and exhibiting optically unique
`properties. The ’729 patent even suggests that the subject of
`that patent could be formed into plastic currency but fails to
`address the physical properties required for that application.
`See additional references US. Pat. Nos. 4,162,343, 4,937,
`134, and 5,089,318. US. Pat. No. 6,045,894 teaches multi
`layered optical ?lms With unique optical properties that can
`be used as security features on certain documents of value but
`also fails to teach the necessary embodiments for such a ?lm
`to be useful as a banknote, particularly having those physical
`properties required of a banknote.
`
`SUMMARY OF THE INVENTION
`
`The invention provides a printable substrate comprising at
`least one oriented, high melt-strength polypropylene foam
`layer having an ink-receptive surface. The ink-receptive sur
`face may comprise an oxidiZing treatment, such as corona or
`?ame-treatment of the foam surface, or may comprise an
`ink-receptive coating, such as a primer coating, on the foam
`surface, or may comprise a laminated or coextruded polymer
`?lm that is ink-receptive.
`The invention further provides a multilayer article com
`prising at least one oriented, high melt strength foam layer
`and at least one non-foam layer. Preferably the non-foam
`layer is a thermoplastic ?lm layer. In such multilayer article
`constructions comprising foam and thermoplastic ?lm
`layer(s), either the foam layer or the ?lm layer may have an
`ink-receptive surface thereon. Preferably, the multilayer con
`struction comprises tWo oriented, high melt strength polypro
`pylene foam layers and a thermoplastic ?lm layer disposed
`betWeen the foam layers. More preferably, the thermoplastic
`?lm layer comprises a thermoplastic polymer that imparts
`stiffness to the multilayer article.
`The invention further provides a method of making the
`printable substrate by the steps of providing an oriented, high
`melt-strength polypropylene foam, and providing an ink-re
`ceptive surface on at least one major surface of the foam
`The present invention also provides a method of preparing
`an ink-receptive, multilayer article comprising at least one
`high-melt strength polypropylene foam layer and at least one
`thermoplastic ?lm layer. Either the foam layer or the ?lm
`layer may have an ink-receptive surface thereon. The multi
`layer article may be prepared by separately preparing the
`foam and ?lm layers, and laminating, bonding or otherWise
`af?xing them together, or the separate layers may be coex
`truded into a multilayer article. If the ?lm layer(s) constitute
`an outermost layer, as in a ?lm/foam/?lm construction, the
`?lm layer(s) may be treated to render them ink-receptive such
`as by corona or an ink-receptive coating, or the thermoplastic
`?lm layer may be inherently ink-receptive.
`The oriented foam article is particularly useful in the
`preparation of printed security documents such as currency,
`stock and bond certi?cates, birth and death certi?cates,
`checks, titles and abstracts and the like.
`Polymeric documents offer several bene?ts over their
`paper counterparts. In particular, polymeric security docu
`ments can offer greatly increased durability and resistance to
`counterfeiting through the incorporation of security features.
`A requirement for some polymeric security documents is that
`certain physical properties are similar to the more commonly
`used paper banknotes. Those properties relate to tactile feel,
`strength, tear resistance, handling, folding, and crumple resis
`tance.
`These foamed articles exhibit improved crumple and
`crease recovery compared to previously knoWn multilayer
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`60
`
`65
`
`Page 5 of 23
`
`

`
`US 7,655,296 B2
`
`3
`optical ?lms, synthetic papers, or currency papers. The proper
`modulus and tear strength, superior folding endurance, and
`crumple and crease recovery properties ?ts the market need
`for increased durability. Advantageously, the articles of the
`present invention may provide security characteristics, such
`as color shifting inks or ?lms, embossments, translucent or
`transparent regions, holographic indicia and the like. These
`articles, When used in security documents, meet or exceed one
`or more of the requirements of the US. Bureau of Engraving
`and Printing including the crumple test, the chemical resis
`tance test and the laundering test. Reference may be made to
`Bureau of Engraving standard test methods 300.002,
`300.004, and 300,005.
`As used in this invention:
`“High melt strength polypropylene” refers to homo- and
`copolymers containing 50 Weight percent or more propylene
`monomer units, and having a melt strength in the range of 25
`to 60 cN at 1900 C.
`“Ink receptive” means a coating, treatment or layer Which
`that is Wetted by the ink and the ink adheres thereto.
`Alpha-transition temperature, Totc, means to the tempera
`ture at Which crystallite subunits of a polymer are capable of
`being moved Within the larger lamellar crystal unit. Above
`this temperature lamellar slip can occur, and extended chain
`crystals form, With the effect that the degree of crystallinity is
`increased as amorphous regions of the polymer are draWn into
`the lamellar crystal structure.
`“Security document” means a document that might be
`prone to counterfeiting, and may be taken from, but not lim
`ited to the folloWing example: currency, stock and bond cer
`ti?cates, birth and death certi?cates, automobile titles, land
`titles and abstracts and the like.
`“Small-cell foam” means a foam having average cell
`dimensions of less than 100 micrometers (um), preferably 5
`to 50 um (prior to orientation);
`“closed-cell” means a foam that contains substantially no
`connected cell pathWays that extend from one outer surface
`through the material to another outer surface;
`“operating temperature” means the temperature that must
`be achieved in the extrusion process to melt all of the poly
`meric materials in the melt mix;
`“exit temperature” and “exit pressure” mean the tempera
`ture and pressure of the extrudate in the ?nal Zone or Zones of
`the extruder;
`“melt solution” or “melt mixture” or “melt mix” means a
`melt-blended mixture of polymeric material(s), any desired
`additives, and bloWing agent(s) Wherein the mixture is su?i
`ciently ?uid to be processed through an extruder;
`“neat polymer” means a polymer that contains small
`amounts of typical heat-stabiliZing additives, but contains no
`?llers, pigments or other colorants, bloWing agents, slip
`agents, anti-blocking agents, lubricants, plasticiZers, process
`ing aids, antistatic agents, ultraviolet-light stabiliZing agents,
`or other property modi?ers;
`“foam density” means the Weight of a given volume of
`foam;
`“density reduction” refers to a Way of measuring the void
`volume of a foam based on the folloWing formula:
`
`pR=[1-p_fJx100%
`
`A,
`
`where p R is the density reduction, p fis the foam density, and
`p0 is the density of the original material;
`
`4
`“polydispersity” means the Weight average cell diameter
`divided by the number average cell diameter for a particular
`foam sample; it is a means of measuring the uniformity of cell
`siZes in the sample; and is de?ned by the equation:
`
`Zing/Z "i415;
`
`Polydispersity:
`
`“uniform” means that the cell siZe distribution has a poly
`dispersity of 1.0 to 2.0;
`“spherical” means generally rounded; it may include
`spherical, oval, or circular structure;
`“polymer matrix” means the polymeric, or “non-cell,”
`areas ofa foam;
`“(x-ole?n” means an ole?n having three or more carbon
`atoms and having a 4CH:CH2 group.
`“total draW ratio” means the product of the draW ratios in
`the machine and transverse directions, i.e:MD><CD.
`
`BRIEF DESCRIPTION OF THE FIGURES
`
`FIGS. 1 and 2 are digital images of a scanning electron
`micrograph (SEM) of the ink receptive article of Example 1.
`FIG. 3 is a digital image of a scanning electron micrograph
`(SEM) of a cross-section (MD) of the ink receptive article of
`Example 3.
`FIG. 4 is a digital image of a scanning electron micrograph
`(SEM) of a cross-section (CD) of the ink receptive article of
`Example 4.
`
`DETAILED DESCRIPTION
`
`The ink-receptive substrate may be prepared by the steps
`of:
`(1) providing an oriented, high melt-strength polypropy
`lene foam, and
`(2) providing an ink-receptive surface on at least one major
`surface of the foam, Wherein the ink-receptive surface
`may comprise a surface treatment, such as corona or
`?ame treatment, an ink-receptive coating, or a ?lm layer
`that is inherently ink-receptive.
`The oriented, high melt- strength polypropylene foam may
`be prepared by the steps of:
`(l) mixing at least one high melt strength polypropylene
`and at least one bloWing agent in an apparatus having an exit
`shaping ori?ce at a temperature and pressure su?icient to
`form a melt mixture Wherein the bloWing agent is uniformly
`distributed throughout the polypropylene;
`(2) reducing the temperature of the melt mixture at the exit
`of the apparatus to an exit temperature that is no more than
`300 C. above the melt temperature of the neat polypropylene
`While maintaining the melt mixture at a pressure suf?cient to
`prevent foaming;
`(3) passing the mixture through said exit shaping ori?ce
`and exposing the mixture to atmospheric pressure, Whereby
`the bloWing agent expands causing cell formation resulting in
`foam formation, and
`(4) orienting said foam.
`The oriented, high melt- strength polypropylene foam may
`be prepared by using a foamable mixture comprising a major
`amount of a high melt-strength polypropylene and a minor
`amount of second polymer component comprising a semic
`rystalline or amorphous thermoplastic polymer. Polymer
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`60
`
`65
`
`Page 6 of 23
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`

`
`US 7,655,296 B2
`
`10
`
`20
`
`25
`
`30
`
`35
`
`5
`mixtures comprising a high melt-strength polypropylene and
`tWo or more added polymers are also Within the scope of the
`invention.
`The high melt strength polypropylene useful in the present
`invention includes homo- and copolymers containing 50
`Weight percent or more propylene monomer units, preferably
`at least 70 Weight percent, and has a melt strength in the range
`of 25 to 60 cN at 190° C. Melt strength may be conveniently
`measured using an extensional rheometer by extruding the
`polymer through a 2.1 mm diameter capillary having a length
`of41.9 mm at 1900 C. and at a rate of0.030 cc/sec; the strand
`is then stretched at a constant rate While measuring the force
`to stretch at a particular elongation. Preferably the melt
`strength of the polypropylene is in the range of 30 to 55 cN, as
`described in WO 99/61520.
`The melt strength of linear or straight chain polymers, such
`as conventional isotactic polypropylene, decreases rapidly
`With temperature. In contrast, the melt strength of highly
`branched polypropylenes does not decrease rapidly With tem
`perature. It is generally believed that the differences in melt
`strengths and extensional viscosity is attributable to the pres
`ence of long chain branching. Useful polypropylene resins
`are those that are branched or crosslinked. Such high melt
`strength polypropylenes may be prepared by methods gener
`ally knoWn in the art. Reference may be made to US. Pat. No.
`4,916,198 (Scheve et al) Which describes a high melt strength
`polypropylene having a strain-hardening elongational viscos
`ity prepared by irradiation of linear propylene in a controlled
`oxygen environment. Other useful methods include those in
`Which compounds are added to the molten polypropylene to
`introduce branching and/or crosslinking such as those meth
`ods described in US. Pat. No. 4,714,716 (Park), WO
`99/36466 (Moad, et al.) and WO 00/00520 (Borve et al.).
`High melt strength polypropylene may also be prepared by
`irradiation of the resin as described in US. Pat. No. 5,605,936
`(Denicola et al.). Still other useful methods include forming a
`bimodal molecular Weight distribution as described in J. I.
`Raukola, A New Technology To Manufacture Polypropylene
`Foam SheeZAnd Biaxially Oriented Foam Film, VTT Publi
`cations 361, Technical Research Center of Finland, 1998 and
`in US. Pat. No. 4,940,736 (Alteepping and Nebe).
`The foamable polypropylene may be comprised solely of
`propylene homopolymer or may comprise a copolymer hav
`ing 50 Wt % or more propylene monomer content. Further, the
`foamable propylene may comprise a mixture or blend of
`propylene homopolymers or copolymers With a homo- or
`copolymer other than propylene homo- or copolymers.
`Particularly useful propylene copolymers are those of pro
`pylene and one or more non-propylenic monomers. Propy
`lene copolymers include random, block, and grafted copoly
`mers of propylene and ole?n monomers selected from the
`group consisting of ethylene, C3-C8 ot-ole?ns and C4-C10
`dienes. Propylene copolymers may also include terpolymers
`of propylene and ot-ole?ns selected from the group consisting
`of C3-C8 ot-ole?ns, Wherein the ot-ole?n content of such
`terpolymers is preferably less than 45 Wt %. The C3-C8
`ot-ole?ns include 1-butene, isobutylene, 1-pentene, 3-me
`thyl-1-butene, 1 -hexene, 3 ,4-dimethyl- 1 -butene, 1 -heptene,
`3-methyl-1-hexene, and the like. Examples of C4-C10 dienes
`include 1,3-butadiene, 1,4-pentadiene, isoprene, 1,5-hexadi
`ene, 2,3-dimethyl hexadiene and the like.
`Minor amounts (less than 50 percent by Weight) of other
`semicrystalline polymers that may be added to the high melt
`strength polypropylene in the foamable composition include
`high, medium, loW and linear loW density polyethylene, ?uo
`ropolymers, poly(1-butene), ethylene/ acrylic acid copoly
`mer, ethylene/vinyl acetate copolymer, ethylene/propylene
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`copolymer, styrene/butadiene copolymer, ethylene/ styrene
`copolymer, ethylene/ ethyl acrylate copolymer, ionomers and
`thermoplastic elastomers such as styrene/ethylene/butylene/
`styrene (SEBS), and ethylene/propylene/diene copolymer
`(EPDM).
`Minor amounts (less than 50 percent by Weight) of amor
`phous polymers may be added to the high melt strength
`polypropylene. Suitable amorphous polymers include, e.g.,
`polystyrenes, polycarbonates, polyacrylics, polymethacryl
`ics, elastomers, such as styrenic block copolymers, e.g., sty
`rene-isoprene-styrene (SIS), styrene-ethylene/butylene-sty
`rene block copolymers (SEB S), polybutadiene, polyisoprene,
`polychloroprene, random and block copolymers of styrene
`and dienes (e. g., styrene-butadiene rubber (SBR)), ethylene
`propylene-diene monomer rubber, natural rubber, ethylene
`propylene rubber, polyethylene-terephthalate (PETG). Other
`examples of amorphous polymers include, e.g., polystyrene
`polyethylene copolymers, polyvinylcyclohexane, polyacry
`lonitrile, polyvinyl chloride, thermoplastic polyurethanes,
`aromatic epoxies, amorphous polyesters, amorphous polya
`mides, acrylonitrile-butadiene-styrene (ABS) copolymers,
`polyphenylene oxide alloys, high impact polystyrene, poly
`styrene copolymers, polymethylmethacrylate (PMMA), ?u
`orinated elastomers, polydimethyl siloxane, polyetherim
`ides, amorphous ?uoropolymers, amorphous polyole?ns,
`polyphenylene oxide, polyphenylene oxideipolystyrene
`alloys, copolymers containing at least one amorphous com
`ponent, and mixtures thereof.
`In addition to the high melt strength polypropylene, the
`foam layer may contain other added components such as
`dyes, particulate materials, a colorant, an ultraviolet absorb
`ing material, inorganic additives, and the like. Useful inor
`ganic additives include TiO2, CaCO3, or high aspect ratio
`?llers such as Wollastonite glass ?bers and mica.
`One useful means to provide an ink receptive surface is in
`the use of special treatments to change the condition of a
`surface by increasing its surface energy. Surface treatments
`for increased surface energy include oxidiZing pretreatments
`or the use of ink-receptive coatings. OxidiZing pre-treatments
`include the use of ?ame, ultraviolet radiation, corona dis
`charge, plasma, chemical oxidiZing agents and the like.
`An ink receptive surface may be provided by ?rst treating
`the foam (or ?lm if multilayer) substrate by ?ame treatment,
`or corona treatment. These surface treatments are believed to
`provide three characteristics to the foam surface. The three
`unifying characteristics are an increase in the oxygen or
`amino content of the treated surface as compared to the bulk
`material, an increase in the hydrophilicity of the surface, and
`an increase in the acidity of the surface. These treatments to
`the surface of the substrate improve the Wetting and the adhe
`sion of the applied ink.
`Another ink-receptive layer may be derived from poly
`meric coatings. Useful ink-receptive coating can be any poly
`mer from Water-based or organic solvent-based systems that
`can be coated on and adhere to the foam layer. Preferably, the
`ink-receptive coating is Water-resistant, yet can be coated
`from a Water-based dispersion. Nonlimiting examples of such
`ink receptive coatings include ethylene-acrylic acid copoly
`mers and their salts, styrene-acrylic acid copolymers and their
`salts, and other (meth)acrylic moiety containing polymers,
`vinylpyrrolidone homopolymers and copolymers and substi
`tuted derivatives thereof, vinyl acetate copolymers (e. g.,
`copolymers of vinylpyrrolidone and vinyl acetate; copoly
`mers of vinyl acetate and acrylic acid, etc.) and hydrolyZed
`derivatives thereof, polyvinyl alcohol; halogen-substituted
`hydrocarbon polymers, acrylic acid homopolymers and
`copolymers; acrylamide homopolymers and copolymers;
`
`Page 7 of 23
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`US 7,655,296 B2
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`7
`cellulosic polymers; styrene copolymers With allyl alcohol,
`acrylic acid and/or maleic acid or esters thereof, alkylene
`oxide polymers and copolymers; gelatins and modi?ed gela
`tins; polysaccharides; and the like as disclosed in US. Pat.
`Nos. 5,766,398; 4,775,594; 5,126,195; 5,198,306.
`Preferably the ink receptive layer is permanently adhered
`to the foam layer and may be hydrophilic, ink sorptive, coat
`ing material. The ink receptive layer may be visually trans
`parent, translucent or opaque. The image-transparent, ink
`receptive layer may be prepared from a Wide variety of hydro
`philic, ink sorptive, coating materials. In current industry
`practice, the ink receptive layer typically is formulated to
`provide suitable ink receptivity tuned for a particular printing
`technique and related ink used therein. In general, suitable
`formulations for the ink receptive layer are disclosed in Des
`jarlais, US. Pat. No. 4,775,594; Light, US. Pat. No. 5,126,
`195; and Kruse, US. Pat. No. 5,198,306.
`The ink receptive layer may comprise at least one hydro
`philic polymer or resin that also may be Water-soluble. Suit
`able hydrophilic polymers or resins include polyvinyl alco
`hols, including substituted polyvinyl alcohols; polyvinyl
`pyrrolidones, including substituted polyvinyl pyrrolidones;
`vinyl pyrrolidone/vinyl acetate copolymer; vinyl acetate/
`acrylic copolymers; acrylic acid polymers and copolymers;
`acrylamide polymers and copolymers; cellulosic polymers
`and copolymers; styrene copolymers of allyl alcohol, acrylic
`acid, maleic acid, esters or anhydride, and the like; alkylene
`oxide polymers and copolymers; gelatins and modi?ed gela
`tins; polysaccharides; and the like. Preferred hydrophilic
`polymers include poly(vinyl pyrrolidone); substituted poly
`(vinyl pyrrolidone); poly(vinyl alcohol); substituted poly(vi
`nyl alcohol); vinyl pyrrolidone/vinyl acetate copolymer;
`vinyl acetate/acrylic copolymer; polyacrylic acid; polyacry
`lamides;
`hydroxyethylcellulose;
`carboxyethylcellulose;
`gelatin; and polysaccharides.
`A particularly useful ink-receptive coating includes
`copolymers of ethylene vinyl acetate, carbon monoxide and
`methyl acrylate; copolymers of acid and/or acrylate modi?ed
`ethylene and vinyl acetate; and terpolymers of ethylene and
`any tWo polar monomers, for example vinyl acetate and car
`bon monoxide. Commercially available modi?ed ole?n res
`ins that are useful as ink-receptive coating sinclude: BYNEL
`3101, an acid-acrylate modi?ed ethylene vinyl acetate
`copolymer; ELVALOY 741, a terpolymer of ethylene/vinyl
`acetate/carbon monoxide; ELVALOY 4924, a terpolymer of
`45
`ethylene/vinyl
`acetate/carbon monoxide; ELVALOY
`1218AC, a copolymer of ethylene and methyl acrylate; and
`FUSABOND MG-423D, a modi?ed ethylene/acrylate/car
`bon monoxide terpolymer. All are available from E.l. duPont
`De Nemours, Wilmington Del.
`The ink receptive layer may also contain other Water
`insoluble or hydrophobic polymers or resins to impart a suit
`able degree of hydrophilicity and/or other desirable physical
`and chemical characteristics. Suitable polymers or resins of
`this class include polymers and copolymers of styrene, acryl
`ics, urethanes, and the like. Preferred polymers and resins of
`this type include a styrenated acrylic copolymer; styrene/allyl
`alcohol copolymer; nitrocellulose; carboxylated resin; poly
`ester resin; polyurethane resin; polyketone resin; polyvinyl
`butyral resin; or mixtures thereof.
`Other useful ink-receptive coatings include those
`described in US. Pat. Nos. 5,721,806, 6,316,120, 5,240,767,
`5,834,098, 6,495,231, 6,800,341, 6,793,859 and 6,589,636.
`In addition to the polymeric or resin components, the ink
`receptive layer may contain other added components such as
`a dye mordant, a surfactant, particulate materials, a colorant,
`an ultraviolet absorbing material, an organic acid, an optical
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`brightener, antistatic agents, antiblocking agents and the like.
`Dye mordants that may be used to ?x the printed ink to the ink
`receptive layer may be any conventional dye mordant. e.g.
`such as polymeric quaternary ammonium salts, poly(vinyl
`pyrrolidone), and the like. Surfactants that are used as coating
`aids for the ink receptive layer may be any nonionic, anionic,
`or cationic surfactant. Particularly useful, are ?uorosurfac
`tants, alkylphenoxypolyglycidols, and the like.
`The ink receptive layer may also contain