United States Patent [19]
`Eichbauer et al.
`
`US006083611A
`[11] Patent Number:
`[45] Date of Patent:
`
`6,083,611
`Jul. 4, 2000
`
`[54] ROLL WRAP FILM
`
`[75] Inventors: George N. Eichbauer, Conyers, Ga.;
`Robert J. Silver, Macedon, NY.
`
`[73] Assignee: Tenneco Packaging, Inc., Evanston, Ill.
`
`[21] Appl. No.: 08/968,999
`[22] Filed:
`Nov. 12, 1997
`
`[51] Int. Cl.7 .................................................... .. B32B 27/00
`[52]
`428/213; 428/352
`[58] Field of Search ................................... .. 428/352, 354,
`428/355 AC, 355 EN, 515, 516, 520, 213,
`220; 53/399, 441
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`Leaversuch, R., “LPDE, mPE vie in Flexible Film Market”,
`Modern Plastics, Sep. 1994, pp. 23 & 25.
`Product Literature, Dow Chemical Company, “Dow Resins
`for Stretch Film Applications—An Overview”, p. 1.5, Oct.,
`1994.
`Product Literature, Dow Chemical Company, “Dow Skin
`Resins for Cast Stretch Film Applications”, p. 3.1—3.4, Oct.,
`1994.
`Product Literature, Dow Chemical Company, “ENGAGE
`Polyole?n Elastomer for Industrial Collation Packaging”,
`KC 8852, May, 1994.
`Product Literature, To Give Your Customers’ Used Stretch
`Film A New Lease On Life, Turn The Page, Mobil, 4 pgs.
`(1993).
`
`(List continued on next page.)
`
`2/1972 Elston ................................ .. 260/80.78
`3,645,992
`7/1973 Hilkert et 211.
`3,748,962
`3,986,611 10/1976 Dreher .................................. .. 206/386
`
`Primary Examiner—Paul Thibodeau
`Assistant Examiner—D Lawrence TaraZano
`Attorney, Agent, or Firm—Jenkens & Gilchrist
`
`(List continued on next page.)
`
`[57]
`
`ABSTRACT
`
`FOREIGN PATENT DOCUMENTS
`
`0 600 425 11/1993
`WO 92/17539 10/1992
`WO 94/14855
`7/1994
`WO 94/25271 11/1994
`WO 94/26816 11/1994
`
`European Pat. Off. .
`
`WIPO .
`
`WIPO .
`
`WIPO .
`
`WIPO .
`
`OTHER PUBLICATIONS
`
`“Advantages of Metallocene Ethylene Polymer Resin
`Blends in Blown and Cast Films”, Research Disclosure,
`Aug. 1995, pp. 565—573.
`“Advantages of Metallocene Ethylene Polymer Resin
`Blends in Cast Film”, Research Disclosure, Aug. 1995, pp.
`556—557.
`“Advantages of Metallocene Ethylene Polymer Resins in
`Blown and Cast Stretch Films”, Research Disclosure, Aug.
`1995, pp. 539—545.
`Chowdhury, et al., “Polymers by Blueprint: Metallocene
`catalysts, the biggest thing to hit plastics since LLDPE,
`transform workhorse resins into engineering plastics,”
`Chemical Engineering (Apr. 1993), pp. 34—39.
`
`Amultilayer, thermoplastic roll wrap ?lm containing at least
`three polymeric ?lm layers and comprised of an outer cling
`layer, a non-cling outer layer, and at least one inner poly
`meric layer. The roll wrap ?lm has at least one inner
`polymeric layer, located between the outer cling layer and
`then non-cling outer layer. The non-cling outer layer is
`preferably comprised of a high pressure, low density poly
`ethylene resin having a melt index of from about 0.5 to about
`6. The inner polymeric layer comprises a low polydispersity
`polymer. The low polydispersity polymer has a polydisper
`sity of from about 1 to about 4, a melt index (I2) of from
`about 0.5 to about 10 g/ 10 min., and a melt ?ow ratio (120/12)
`of from about 12 to about 22. The roll wrap ?lm has a
`transverse tear resistance of at least 400 grams/mil as
`measured by ASTM D1922, a machine direction tear resis
`tance as measured by ASTM D1922 of at least 150 grams/
`mil and a F-50 dart drop of at least 600 grams. It is
`contemplated that additional layers may be added to the
`present invention.
`
`80 Claims, 1 Drawing Sheet
`
`30%
`
`Page 1 of 10
`
`BOREALIS EXHIBIT 1059
`
`

`
`6,083,611
`Page 2
`
`U.S. PATENT DOCUMENTS
`
`428/35
`
`3/1977 Levine et a1. ........................... .. 526/96
`4,011,382
`9/1977 Lancaster, III et a1~
`53/211
`4,050,221
`2/1978 Anderson et a1.
`526/348.6
`4,076,698
`8/1979 6955911 --------- ~-
`526/153
`4,163,831
`5/1980 Morita et a1- --
`525/240
`4,205,021
`4,302,565 11/1981 Goeke et a1. ..
`526/88
`4,302,566 11/1981 Karol 9t 91
`526/125
`4,359,561 11/1982 Fraser et a1.
`526/88
`4,399,173
`8/1983 Anthony 91 a1
`-- 428/212
`4,399,180
`8/1983 Briggs 9t 91- --
`-- 428/218
`4,418,114 11/1983 Briggs 9t 91- --
`-- 525/240
`4,461,873
`7/1984 Bailey et a1- --
`4,511,609
`4/1985 Craver 9t 91- -
`428/35
`428/339
`4,514,465
`4/1985 Schoenberg
`526/106
`4,522,987
`6/1985 Hogan et a1. ..
`428/35
`4,565,720
`1/1986 Yaeo et a1.
`428/220
`4,574,104
`3/1986 Aishima et a1. ..
`428/516
`4,588,650
`5/1986 Mientus 9t 91-
`4,808,561
`2/1989 Welborn,]r
`502/104
`428/323
`4,833,017
`5/1989 Benoit --
`428/220
`4,837,075
`6/1989 Dudley
`423/265
`4,871,523 10/1989 Dana 9M1
`502/117
`4,871,705 10/1989 H991
`502/107
`4,925,821
`5/1990 Chang
`502/309
`4,925,825
`5/1990 Tachi 9t 91
`526/128
`4,937,301
`6/1990 Chang
`526/128
`5,001,205
`3/1991 H991
`502/107
`5,006,500
`4/1991 Chang
`525/127
`5,017,655
`5/1991 K959 9t 91-
`264/171
`5,019,315
`5/1991 Wilson
`526/127
`5,026,798
`6/1991 Canich -
`526/129
`5,032,652
`7/1991 Chang ------ --
`- 428/35-2
`5,049,423
`9/1991 Germanjlr-
`5,079,205
`1/1992 Canich .................................. .. 502/117
`5,084,534
`1/1992 Welborn,]r- e191- ---------------- ~- 526/160
`5,085,927
`2/1992 Dohrer ............... ..
`..
`5,110,663
`5/1992 Nishiyama et a1. .................. .. 428/195
`5,124,418
`6/1992 W6lboin,Ji. .......................... .. 526/114
`5,173,343 12/1992 Arvedson et a1.
`. 428/34.9
`5,183,867
`2/1993 Welborn, Jr. .......................... .. 526/114
`5,206,075
`4/1993 Hodgson, Jr. ......................... .. 428/216
`5,248,547
`9/1993 Wilson
`.. 428/218
`5,272,016 12/1993 R6lpli .................................... .. 428/516
`5,273,809 12/1993 Simmons .............................. .. 428/212
`5,278,272
`1/1994 L6i616l.
`526/3485
`5,279,872
`1/1994 Ralph ................................... .. 428/34.9
`2,5235? Z133: \lsllilhoit ......... ..l ...................... .. gig/2(1);
`5,334,428
`8/1994 DObreSki 616l. .................... .. 428/34.9
`5,358,792 10/1994 M61116 616l. .......................... .. 428/516
`53747459 12/1994 Mumpower e161
`_ 4253/36]
`5,376,439 12/1994 Hodgson et a1. ..................... .. 428/220
`
`,
`
`,
`
`atsunaga et a .
`
`..
`
`5,380,810
`5,382,631
`573957471
`5,397,613
`573977640
`5,399,426
`5,407,732
`574197795
`5,419,934
`574207220
`
`1/1995 Lai et a1. .............................. .. 526/352
`1/1995 Stehling et a1.
`525/240
`3/1995 obijeski et a1_ _________________ __ 156/244“
`3/1995 GeOrgelOS ............................ .. 428/36.7
`3/1995 Georgelos et a1_
`428/349
`3/1995 Koch 6161.
`428/335
`4/1995 Dokurno
`. 428/213
`5/1995 Wood et a1_
`_ 156/184
`5/1995 Wilson
`428/349
`5/1995 Cheruvu et a_
`_ 5265481
`
`5,431,284
`
`7/1995 Wilson . . . . . . . . . . .
`
`. . . .. 206/597
`
`. 428/220
`9/1995 Erderly 61 61.
`5,451,450
`428/515
`9/1995 s6il6i616l.
`5,451,468
`428/34.9
`5,460,861 10/1995 Vicik 61 61. .
`428/500
`5,462,807 10/1995 H6116 616l. .
`_ 428/339
`574827770
`1/1996
`_ 428/349
`574827771
`1/1996
`_ 428/213
`574917019
`2/1996
`428552
`_
`575237136
`6/1996
`525/240
`5,530,065
`6/1996 F6il6y 61 61.
`.428/349
`5,543,223
`8/1996 sli6li ...... ..
`.428/216
`5,558,930
`9/1996 DiPoto
`. 426/127
`5,576,038 11/1996 Mooi6 6161.
`.. 264/456
`5,591,390
`1/1997 W6l1on 616l. ..
`53/441
`5,595,050
`1/1997 Koch 6161. .
`53/441
`5,617,707
`4/1997 Simmons
`. 264/565
`5,681,523 10/1997 cobl6i616l.
`53/399
`5,749,202
`5/1998 Ei6lib6n6i
`53/399
`5,752,362
`5/1998 Ei6lib6n6i
`. 428/220
`5,814,399
`9/1998 Ei6lib6n6i
`. 428/515
`5,902,684
`5/1999 Bullard 61 61.
`53/441
`5,907,942
`6/1999 Ei6lib6n6i
`53/441
`5,907,943
`6/1999 Ei6lib6n6i
`.428/213
`5,922,441
`7/1999 Ei6lib6n6i
`.428/213
`5,976,682 11/1999 Ei6lil>6n6i
`_ 428/343
`579987017 12/1999 Eichbauer
`6,013,378
`1/2000 Wlii16 616l. .......................... .. 428/516
`
`OTHER PUBLICATIONS
`
`Schut, “Competition for Metallocenes Could Turn Ugly,”
`Plastics World (Jan. 1995), pp. 33—36.
`Product literature, Recycling LOOP For Stretch Film, Mobil,
`2 pages (NO Date)‘
`_
`_
`_
`_
`Product hteramre> Stretch F 11'" Recyclmg> M°b11> 2 Pages
`(N0 Date)
`Product literature, Paper Roll Protection For The Harshest
`Conditions, Mobil, 8 pages (NO Date)
`P1091“ hteramre’ Trance!‘ K/FKm?And Film R0” WmP'
`Pmg System’ Trancel’ 8 Pages (NO Date)
`Product literature, Trancel: Combination Roll Wrapping
`System, Trancel, 8 pages (No Date).
`
`-
`
`_
`
`-
`
`Page 2 of 10
`
`

`
`U.S. Patent
`
`Jul. 4, 2000
`
`6,083,611
`
`30 N
`
`FIG. 1
`
`20 /\_/
`
`2O /\_/
`
`3O /\_,
`
`N 20
`
`FIG. 2
`
`Page 3 of 10
`
`

`
`6,083,611
`
`1
`ROLL WRAP FILM
`
`FIELD OF INVENTION
`
`The present invention is directed to roll Wrap ?lm and
`methods for their use. In particular, the present invention is
`directed to roll Wrap ?lm having higher tensile strength,
`enhanced tear resistance, abrasion resistance, uniform
`stretching characteristics, superior puncture resistance, high
`total energy dart drop, superior optical qualities, and overall
`strength.
`
`BACKGROUND OF THE INVENTION
`The use of thermoplastic roll Wrap ?lms for protecting
`goods, and in particular, large paper roll stock is a signi?cant
`commercially important application of polymer ?lm, includ
`ing generically, polyethylene. HoWever, a factor affecting
`their acceptance is the machine performance of the roll Wrap
`?lms.
`In one commercial application, roll Wrap ?lm of the
`present invention is used as primary protection of a mill roll
`of ?ne paper. In this application, the roll Wrap ?lm is
`typically applied in multiple layers around such ?ne paper.
`These rolls of ?ne paper typically include bar codes Which
`contain information such as product type, purchase order
`number and Weight. Roll Wrap ?lm may be applied in
`conjunction With pre-stretch machines and non pre-stretch
`machines. The use of a pre-stretch machine tends to cause
`severe “tiger striping” in many roll Wrap ?lms because of the
`lack of uniform stretching.
`Tiger striping is a condition in the stretched ?lms Where
`bands or patterns across the ?lms have not been stretched as
`compared to a remainder of the roll Wrap ?lm. This condi
`tion is caused by the high strain on the stretched roll Wrap
`?lm. This non-uniform stretching results in a “wrinkling”
`pattern in the roll Wrap ?lm Which can cause distortion in the
`scanned reading on the above-described bar codes. In
`addition, the tiger-striped ?lm has less effective cling prop
`erties and may even cause damage to the Wrapped product.
`Some of the properties desired of a good roll Wrap ?lm are
`as folloWs: good cling or cohesion properties, high puncture
`resistance, good machine direction tear resistance, good
`transparency, loW haZe, loW stress relaxation With time, high
`resistance to transverse tear especially When under machine
`direction tension, loW speci?c gravity and thus high yield in
`area per pound, good tensile toughness, high machine direc
`tion ultimate tensile strength, high machine direction ulti
`mate elongation, and loW modulus of elasticity.
`A need exists to develop superior roll Wrap ?lms having
`excellent machine performance With excellent stretched
`clarity and uniform stretched gauge, While still maintaining
`other important roll Wrap ?lm properties.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`SUMMARY OF THE INVENTION
`
`The present invention is a multilayered roll Wrap ?lm
`Which has excellent machine performance, excellent punc
`ture resistance, higher tensile strength, enhanced tear
`resistance, abrasion resistance, uniform stretching
`characteristics, good cling properties, good optical qualities,
`and overall strength.
`The inventive ?lm comprises a cling layer, at least one
`inner polymeric layer and a non-cling layer. The cling layer
`may be constructed of ole?n polymer resins. The cling layer
`is preferably constructed With a ethyl methyl acrylate
`copolymer.
`The inner polymeric layer, located at a position betWeen
`the cling layer and the non-cling layer, comprises a polymer
`
`55
`
`60
`
`65
`
`2
`having a loW polydispersity. The loW polydispersity polymer
`has a polydispersity of from about 1 to about 4, a melt index
`(I2) of from about 0.5 to about 10 g/ 10 min., and a melt ?oW
`ratio (120/12) of from about 12 to about 22. The inner
`polymeric layer(s) are preferably produced utiliZing metal
`locene catalyst polymeriZation techniques. The inner poly
`meric layer may comprise the loW polydispersity polymer
`With other resins.
`The non-cling layer is located as an outer layer adjacent
`to the inner polymeric layer. The non-cling layer is prefer
`ably comprised of a high pressure, loW density polyethylene
`(HPLDPE) having a density in the range of from about 0.88
`to about 0.935 With a melt index of from about 0.5 to about
`6, and preferably from about 1 to about 3 g/10 min.
`The ?lm is constructed With at least three layers; addi
`tional layers are contemplated. For instance, additional inner
`polymeric layers may be incorporated into the ?lm betWeen
`the cling layer and the non-cling layer, Where such layers are
`constructed With the same or different metallocene
`catalyZed polyethylene resins as the ?rst inner polymeric
`layer.
`The multilayer ?lm of the present invention has a trans
`verse tear resistance of at least 400 grams/mil as measured
`by ASTM D1922, a machine direction tear resistance as
`measured by ASTM D1922 of at least 150 grams/mil, and a
`F-50 dart drop of at least 600 grams as measured by ASTM
`D1709.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 shoWs a three layer ?lm constructed according to
`one embodiment of the present invention; and
`FIG. 2 shoWs a ?ve layer ?lm constructed according to
`one embodiment of the present invention.
`
`DESCRIPTION OF ILLUSTRATIVE
`EMBODIMENTS
`
`The multilayer roll Wrap ?lms of the present invention are
`constructed With a cling layer, at least one inner polymeric
`layer and a non-cling layer. The multilayer roll Wrap ?lms of
`the present invention can be prepared as cast ?lms by
`conventional coextrusion techniques.
`Cling Layer
`The cling layer of the roll Wrap ?lms of the present
`invention may be constructed of ole?n polymer resins.
`Suitable polyethylene resins are those ethylenic copolymers
`that comprise a major proportion by Weight of ethylene
`copolymeriZed With a minor proportion by Weight of an
`alpha ole?n monomer containing about 3 to about 12,
`preferably about 4 to about 10, and more preferably about 4
`to about 8 carbon atoms. These resins have a polydispersity
`Which is preferably in the range of from about 3 to about 7.
`The cling layer is preferably comprised of ethyl methyl
`acrylate (EMA). EMA has a melt index of from about 2 to
`about 7, and preferably from about 3 to 5 g/10 min. as
`measured by ASTM D1238. The EMA resins have a density
`of from about 0.88 to about 0.94 g/cm3 and preferably from
`about 0.90 to about 0.92 g/cm3. These EA polymers gener
`ally have an acrylate content betWeen about 2 to about 40%,
`preferably betWeen about 10 to about 35%, by Weight of the
`EA polymer. The acrylates useful in these polymers are
`those generally knoWn in the art, preferably methyl, ethyl,
`and n-butyl acrylate. Ethylene-acrylate (EA) polymer ?lms
`as shoWn in US. Pat. No. 5,049,423, Which is incorporated
`herein by reference in its entirety, are contemplated for the
`cling layer. It is also contemplated that resins such as ethyl
`vinyl acetate (EVA) copolymer, high pressure loW density
`
`Page 4 of 10
`
`

`
`6,083,611
`
`10
`
`15
`
`3
`polyethylene (HPLDPE) may be used in forming the cling
`layer of the roll Wrap ?lms of the present invention.
`Other examples of ethylenic copolymers Which may be
`used are those commonly referred to as linear loW density
`polyethylenes (LLDPE) and very loW density polyethylenes
`(VLDPE) may also comprise the cling layer. Preferably the
`ethylenic copolymers employed are those having from about
`1 to about 20, preferably from about 1 to about 10 Weight
`percent of said higher alpha ole?n monomer copolymeriZed
`therein. In addition, the alpha ole?n monomer employed in
`the ethylenic copolymer is selected from the group consist
`ing of 1-butene, 3-methyl-1-butene, 3-methyl-1-pentene,
`1-hexene, 4-methyl-1-pentene, 3-methyl-1-hexene, 1-octene
`and 1-decene. Particularly preferred are the 1-hexene alpha
`ole?ns. The LLDPE resins are prepared at relatively loW
`pressures employing coordination-type catalysts. Reference
`may be made to Us. Pat. Nos. 3,645,992, 4,076,698,
`4,011,382, 4,163,831, 4,205,021, 4,302,565, 4,302,566,
`4,359,561 and 4,522,987 for more details of the manufacture
`and properties of LLDPE resins including those Which are
`particularly useful herein.
`Common LLDPE resins that may be used to form such a
`cling layer include those having a relatively high Weight
`percentage of n-hexane extractibles, as measured by the
`n-hexane extractibles method of 21 C.F.R. 177.1520.
`Generally, the LLDPE used in the cling layer herein Will
`contain from about 2 to about 10, preferably from about 2 to
`about 8, more preferably from about 2.5 to about 5, Weight
`percent of n-hexane extractibles.
`The LLDPE resins that can be used in the cling layer
`herein have a density ranging from about 0.890 to about
`0.940 g/cm3, more commonly from about 0.90 to about 0.93
`g/cm3, and a melt index (I2) of from about 1 to about 10 g/ 10
`min., as determined by ASTM D1238. Preferred LLDPE
`resins possessing densities Within the range from about
`0.917 to about 0.920 gm/cm3 and a melt index of from about
`2.0 to about 5.0 g/10 min., as determined by ASTM D1238.
`Examples of such LLDPE resins include those set forth in
`US. Pat. No. 5,273,809, Which is incorporated herein by
`reference in its entirety.
`The VLDPE resins that may be used in the cling layer
`herein have a density ranging from about 0.875 to about
`0.912 g/cm3, more commonly from about 0.89 to about 0.91
`g/cm3, and a melt index of from about 0.5 to about 5 g/10
`min., preferably from about 1 to about 3 g/10 min.
`The LLDPE and VLDPE resins that can be used in the
`cling layer herein may also contain knoWn and conventional
`cling additives to augment the cling property that, at least in
`the case of the particularity preferred resins, is inherently
`exhibited. Examples of useful cling additives include poly
`isobutylenes having a number average molecular Weight in
`the range from about 1,000 to about 3,000, preferably about
`1,200 to about 1,800, as measured by vapor phase
`osmometry, amorphous atactic polypropylenes, e.g., those
`having an average molecular Weight of about 2000, and
`polyterpenes and ethylene-vinyl acetate copolymers con
`taining from about 5 to about 15 Weight percent copolymer
`iZed vinyl acetate. The optional cling additive can be present
`in the cling layer in a concentration of from about 0.5 to
`about 10 Weight percent of the resin. Of course, other
`conventional ?lm additives such as antioxidants, UV
`60
`stabiliZers, pigments, dyes, etc., may be present in the usual
`amounts.
`Other knoWn cling layers are contemplated for the present
`invention. In addition, the above-described resins may be
`blended in forming the cling layer of the present invention.
`The cling layer of the ?lm can be treated by such knoWn
`and conventional postforming operations as corona
`
`4
`discharge, chemical treatment, ?ame treatment, etc., to
`modify the printability or ink receptivity of the surface(s) or
`to impart other desirable characteristics thereto.
`INNER POLYMERIC LAYER
`The multilayer roll Wrap ?lms of the present invention are
`constructed With at least one inner polymeric layer compris
`ing a polymer resin having a loW polydispersity and located
`betWeen the outer layers. The inner polymeric layer com
`prises a polymer having a loW polydispersity. The loW
`polydispersity polymer may be prepared from a partially
`crystalline polyethylene resin that is a polymer prepared
`With ethylene and at least one alpha ole?n monomer, e.g., a
`copolymer or terpolymer. The alpha ole?n monomer gen
`erally has from about 3 to about 12 carbon atoms, preferably
`from about 4 to about 10 carbon atoms, and more preferably
`from about 6 to about 8 carbon atoms. The alpha ole?n
`comonomer content is generally beloW about 30 Weight
`percent, preferably beloW about 20 Weight percent, and more
`preferably from about 1 to about 15 Weight percent. Exem
`plary comonomers include propylene, 1-butene, 1-pentene,
`1-hexene, 3-methyl-1-pentene, 4-methyl-1-pentene,
`1-octene, 1-decene, and 1-dodecene.
`The loW polydispersity polymer generally has the char
`acteristics associated With an LLDPE material, hoWever it
`has improved properties as explained more fully beloW. The
`loW polydispersity polymer de?ned herein Will have a
`density of from about 0.88 to about 0.94 g/cm3, preferably
`from about 0.88 to about 0.93 g/cm3, and more preferably
`from about 0.88 to about 0.925 g/cm3.
`The average molecular Weight of the copolymer can
`generally range from about 20,000 to about 500,000, pref
`erably from about 50,000 to about 200,000. The molecular
`Weight is determined by commonly used techniques such as
`siZe exclusion chromatography or gel permeation chroma
`tography. The loW polydispersity polymer should have a
`molecular Weight distribution, or polydispersity, (MW/Mn,
`“MWD”) Within the range of about 1 to about 4, preferably
`about 1.5 to about 4, more preferably about 2 to about 4, and
`even more preferably from about 2 to about 3. The ratio of
`the third moment to the second moment, MZ/MW, is generally
`beloW about 2.3, preferably beloW about 2.0, and more
`typically in the range of from about 1.6 to about 1.95. The
`melt ?oW ratio (MFR) of these resins, de?ned as I20/I2and as
`determined in accordance to ASTM D-1238, is generally
`from about 12 to about 22, preferably from about 14 to about
`20, and more preferably from about 16 to about 18. The melt
`index (MI), de?ned as the I2 value, should be in the range of
`from about 0.5 to about 10 g/10 min., preferably from about
`1 to about 5 g/ 10 min. If additional resin materials are to be
`incorporated With the loW polydispersity polymer, it is
`preferred to maintain the level of the loW polydispersity
`polymer to at least about 60 Weight percent of the inner
`polymeric layer.
`Useful loW polydispersity polymers are available from,
`among others, DoW Chemical Company and Exxon Chemi
`cal Company Who are producers of single site or constrained
`geometry catalyZed polyethylenes. These resins are com
`mercially available as the AFFINITY and EXXACT poly
`ethylenes (see Plastics World, p.33—36, January 1995), and
`also as the ENHANCED POLYETHYLENE and EXCEED
`line of resins. The manufacture of such polyethylenes,
`generally by Way of employing a metallocene catalyst
`system, is set forth in, among others, US. Pat. Nos. 5,382,
`631, 5,380,810, 5,358,792, 5,206,075, 5,183,867, 5,124,418,
`5,084,534, 5,079,205, 5,032,652, 5,026,798, 5,017,655,
`5,006,500, 5,001,205, 4,937,301, 4,925,821, 4,871,523,
`4,871,705, and 4,808,561, each of Which is incorporated
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`herein by reference in its entirety. These catalyst systems
`and their use to prepare such copolymer materials are also
`set forth in EP 0 600 425 A1 and PCT applications WO
`94/25271 and 94/26816. The loW polydispersity polymers
`thus produced generally have a crystalline content in eXcess
`of at least 10 Weight percent, generally in eXcess of at least
`15 Weight percent.
`The above patents and publications generally report that
`these catalysts contain one or more cyclopentadienyl moi
`eties in combination With a transition metal. The metal
`locene catalyst may be represented by the general formula
`CCMAaBb Wherein C is a substituted or unsubstituted cyclo
`pentadienyl ring; M is a Group 3—10 metal or Lanthanide
`series element, generally a Group IVB, VB, or VIB metal;
`A and B are independently halogen, hydrocarbyl group, or
`hydrocarboXyl groups having 1—20 carbon atoms; a=0-3,
`b=0-3, and c=1-3. The reactions can take place in either gas
`phase, high pressure, slurry, or solution polymeriZation
`schemes.
`At least one of the inner polymeric layers of the present
`invention is preferably constructed entirely With a loW
`polydispersity polyethylene polymer, preferably produced
`by metallocene catalyst technology. HoWever, the inner
`polymeric layer may also comprise a blend of the loW
`polydispersity polymer With a second resin material. The
`second material may be an ole?n polymer resin. For
`example, this may include, but is not limited to, LLDPE,
`LDPE, HPLDPE, VLDPE, propylene resins or combinations
`thereof. The second resin material is preferably a LLDPE
`resin having a density of from about 0.89 to about 0.94
`g/cm3, a LDPE resin having a density of from about 0.90 to
`about 0.935 g/cm3, a VLDPE resin having a density of from
`about 0.88 to about 0.91 g/cm3. The comonomer for the
`second resin material preferably has from about 4 to about
`10, more preferably about 6 to about 8 carbon atoms. If the
`second resin material is to be incorporated With the
`metallocene-catalyZed resin, it is preferred to maintain the
`level of the metallocene-catalyZed resin to at least about 60
`Wt. % of the inner polymeric layer. The resultant blended
`polymer resin maintains the desired properties of the
`metallocene-catalyZed resin material and may be more eco
`nomical for certain applications.
`Additionally interior layers are also contemplated in the
`present invention to provide barrier properties or cost reduc
`tions.
`NON-CLING LAYER
`The multilayer roll Wrap ?lms of the present invention
`contains at least one outer non-cling layer Which is located
`adjacent to the inner polymeric layer. The non-cling layer
`provides tensile strength, better stretched optics, and resis
`tance to tiger striping.
`The non-cling layer is preferably comprised of a high
`pressure, loW density polyethylene (HPLDPE) having a
`density of from about 0.88 to about 0.935 g/cm3 and
`preferably from about 0.90 to about 0.935 g/cm3. The LDPE
`has a melt indeX of from about 0.5 to about 6, and preferably
`from about 1 to about 3 g/10 min. as measured by ASTM
`D1238.
`It is also contemplated that polypropylenes may comprise
`the non-cling layer of the present invention. The
`polypropylene, Which is generally isotatic polypropylene,
`has a density from about 0.89 to about 0.91 g/cm3. The
`polypropylene has a melt ?oW ratio, de?ned as 120/12 and as
`determined in accordance to ASTM D-1238, of from about
`2 to about 25 and preferably from about 5 to about 15 g/10
`mm.
`It is also contemplated that the non-cling layer may be
`comprised of random copolymers of propylene and ethylene
`
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`With an ethylene content in the range of from about 2 to
`about 6 Wt. %, preferably from about 2.5 to about 5.0 Wt. %
`and most preferably from about 3.0 to about 4.5 Wt. % of the
`non-cling layer. The random ethylene-propylene copolymers
`have a melt ?oW ratio of from about 2 to about 15, preferably
`from about 3 to about 11, and more preferably from about 4
`to about 7.
`Alternatively, the non-cling layer may be prepared With
`heterophasic copolymers of propylene and ethylene. These
`heterophasic copolymers comprise a propylene material
`With domains of ethylene interspersed. Useful heterophasic
`copolymers of propylene and ethylene are available from,
`among others, Himont, Inc. The heterophasic copolymers of
`propylene and ethylene have a melt ?oW ratio, de?ned as
`120/12 and as determined in accordance to ASTM D-1238, of
`from about 10 to about 18, preferably from about 11 to about
`16 and more preferably from about 12 to about 15. The
`ethylene content is in a range from about 12 to about 30 Wt.
`%, preferably about 15 to about 26 Wt. % and more prefer
`ably about 17 to about 24 Wt. % of the non-cling layer.
`The non-cling layer of the ?lm can be treated by such
`knoWn and conventional post-forming operations as corona
`discharge, chemical treatment, ?ame treatment, etc., to
`modify the printability or ink receptivity of the surface(s) or
`to impart other desirable characteristics thereto.
`It is contemplated that the non-cling layer may include
`any of several anticling, slip or antiblock additives to
`promote slip characteristics in the non-cling layer. Such
`additives include silicas, talcs, diatomaceous earth, silicates,
`lubricants, etc. These additives are generally blended With
`the resin material in an amount of from about 100—20,000
`ppm
`The roll Wrap ?lms of the present invention can be
`constructed to contain a plurality of layers in various com
`binations. According to one embodiment, the roll Wrap ?lm
`Will be of an A\B\C construction as depicted in FIG. 1
`Wherein the ?lm layer (10) is the outer cling layer (layer A),
`?lm layer (20) is the inner polymeric layer (layer B), and
`?lm layer (30) is the outer non-cling layer (layer C).
`According to other embodiments, the roll Wrap ?lm may
`be of an A\B\B\B\C construction such as depicted in FIG. 2
`Where the ?lm layers (10), (20), (30), are the cling, inner
`polymeric, and non-cling layers, respectively, as previously
`described With respect to FIG. 1. Alternatively, roll Wrap
`?lms may be of an A\B\B\C or an A/B/A/B/C With other
`types of multi-layered constructions being contemplated.
`ROLL WRAP PROPERTIES
`The roll Wrap ?lm of the present invention has relatively
`high puncture resistance, as measured by the F-50 dart drop
`test procedure (ASTM D1709). It is the experience of those
`skilled in the art that the F-50 dart drop test is Well correlated
`to the end-use puncture resistance of roll Wrap ?lms. The
`F-50 dart drop value of the ?lms is at least about 600 grams,
`preferably at least about 800 grams, and more preferably
`from at least about 1,000 grams.
`The roll Wrap ?lm has a cling force of at least about 150,
`preferably at least about 175, more preferably at least about
`200, and in some cases as high as about 250 grams/inch as
`determined by ASTM D5458-94. Generally, the cling force
`of the roll Wrap ?lm betWeen the outer layers (measured
`from inside to outside [I/O]) is from about 160 to about 260
`grams/inch. The cling force as measured from outside to
`outside (O/O) does not have a cling value.
`The roll Wrap ?lm of this invention can, if desired, be
`provided in the non-stretched, i.e., unoriented, or at most
`only modestly stretched state prior to use. The ?lms of the
`present invention are capable of being stretched from at least
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`about 50, preferably at least about 150 and most preferably
`at least about 250 linear percent.
`The roll Wrap ?lms of the present invention are preferably
`constructed so that the transverse direction tear resistance
`(TD tear), as determined by ASTM D1922, is at least about
`400 g/mil, preferably at least about 450 g/mil, more prefer
`ably at least about 500 g/mil. The machine direction tear
`resistance (MD tear) as determined by ASTM D1922, of the
`?lm is generally at least about 150 g/mil, preferably at least
`about 200 g/mil, and more preferably at least about 250
`g/mil.
`The roll Wrap ?lms of the present invention are preferably
`constructed so that the stretch force as measured by the MD
`force at 200% is at least about 1,200 psi and preferably is at
`least about 1,400 psi. The roll Wrap ?lms of the present
`invention have very little or no tiger striping at 250%
`stretching on a prestretched roll Wrap machine and have
`excellent stretched optics.
`The roll Wrap ?lm con?gurations are constructed accord
`ing to conventional practices. Generally, the preferred pro
`cessing technique is to coextrude and cast the ?lms in a
`simultaneous fashion, hoWever in some cases it may be
`appropriate to ?rst coextrude at least tWo ?lm layers and
`thereafter extrusion coat the remaining ?lm layers. It is
`preferred to employ knoWn and conventional techniques of
`coextrusion to assemble the composite structures of the ?lms
`of this invention. Reference may be made to US. Pat. No.
`3,748,962, the contents of Which are incorporated herein by
`reference for details of a coextrusion procedure Which can
`be employed in the fabrication of a multilayer ?lm in
`accordance With this invention. Generally, the resin materi
`als are heated to their molten state and their viscosities are
`coordinated to prepare multilayer ?lms in a uniform manner.
`The molten materials are conveyed to a coextrusion adapter
`that combines the molten materials to form a multilayer
`coextruded structure. The layered polymeric material is
`transferred through an extrusion die is opened to a prede
`termined gap commonly in the range of betWeen from 0.05
`in. (0.13 cm) to about 0.012 in. (0.03 cm). The material is
`the