WO1995002630A1

WO1995002630A1 - Polymeric films with low water vapor transmission rates

Info

Publication number: WO1995002630A1
Application number: PCT/US1994/007553
Authority: WO
Inventors: Dirk Jozef Michiels; Ferdinand Christian Stehling; Barry Colin Trudell; Prasadarao Meka; Dirk Germaine Frans Van Der Sanden
Original assignee: Exxon Chemical Patents Inc.
Priority date: 1993-07-16
Filing date: 1994-07-06
Publication date: 1995-01-26

Abstract

The disclosure concerns certain classes of non-polar hydrocarbon polymers, their production and use. The polymers of the invention are well suited for use in producing films having unique combinations of properties, especially low water vapor transmission rate.

Description

TTTLE: POLYMERIC FILMS WITH LOW WATER VAPOR

TRANSMISSION RATES

FIELD OF THE INVENTION

This invention relates generally to films. More specifically this invention is directed toward films having iow vapor transmission rates, specifically a low water vapor transmission rate.

BACKGROUND OF THE INVENTION

Polymers exhibiting low permeability are generally referred to as barrier polymers. The major use of these barrier polymers is in the packaging industry, especially in packaging applications for foods and beverages. The driving force behind the increased market penetration by barrier plastics are that they are light weight, strong, easily disposed of by incineration, and of low costs.

The functional requirement of a package is to protect its contents from the environment over the normal shelf life of the product contained therein. The package may be a rigid container, a flexible container like a pouch or a non-barrier article with a barrier coating. In most food packaging applications protection from oxygen can be of great importance as can protection from the entry of moisture.

Moisture would cause dry soluble powders to cake or a loss of moisture may adversely affect the viscosity of water based liquids. Loss of moisture in food applications is especially important in keeping food fresh for an extended period of time. In order to provide a useful packaging material the polymer must also have other attributes including: sufficient strength to form a durable package, with good impact and tear strength; resistance to puncture; good clarity when desirable; packaging processability; ability to withstand heat processing such as hot filling and pasteurization; anti-static properties; general chemical resistance including resistance to environmental stress cracking, sealability and organoleptic properties. Thus, it is important that a good barrier polymer must have some of the more important of these properties such as tensile strength, toughness or impact resistance and optical properties as well as have low permeability.

The process of permeation through a polymeric barrier generally involves four steps: absorption of the permeating species into the polymer wall; solubility in the polymer matrix; diffusion through the wall along a concentration gradient; and desorption from the outer wall. There are certain molecular structures that lead to good barrier properties in polymers. A practical problem, however, is that the property might result in a good gas barrier but a poor water barrier or a good water barrier but poor strength and optical properties. For example, highly polar polymers, those having many hydroxyl groups for example, poly(vinyl alcohol) or cellophane are excellent gas barriers but are amongst the poorest water barriers. Conversely, very non-polar hydrocarbon polymers such as polyethylene have good water barrier properties but are poor gas barriers. For the purposes of this patent specification the barrier polymers of this invention are those non-polar hydrocarbon polymers.

Moisture transmission rates (MTR) or water vapor transmission rates (WVTR) depend generally on the crystallinity or density of the polymer. High density polyethylene (HDPE) usually has a density in the range of 0.945 g/cn to 0.960 g/cir HDPE is generally linear without any side chain branching and is substantially crystalline. HDPE because of its highly crystalline structure has a low water transmission rate but poor optical, tear strength and seal strength properties. At the other end of the density or crystallinity spectrum are those polymers generally known as very low density polyethylene (VLDPE). VLDPE's generally have a density below to 0.915 g/cn VLDPE's at the low end of the spectrum are substantially amorphous and thus lack the desired stiffness property necessary for making films. However, VLDPE's have high water vapor transmission rates.

In the past, fillers or additives such as impact modifiers or plasticizers were used to lower vapor transmission rates. However, this resulted in added costs and affected other important properties necessary to the packaging industry.

Therefore, a need exists for a barrier polymer from which a film having low transmission rates without the need for fillers or additives can be made such that the film also has a balance of desirable physical properties. SUMMARY OF THE INVENTION

It has been discovered that metallocene catalyst systems can be used to produce polymers having not only excellent strength, sealing and optical properties but having superior water vapor transmission rates. These polymers or barrier polymers of the invention are particularly well suited for use in the packaging industry, specifically in those applications in which low water vapor transmission rates are desirable.

The invention is directed toward a polymer film comprising at least one resin layer. This layer has a density less than 0.935 g/crn³, a M_w M_n less than 3, a composition distribution breadth index greater than 80%; and said resin characterized in that at a density of 0.90 g/cm³ said film has a water vapor transmission rate less than 2.25 g/mil/100 in² day. The film is either a single layer or multilayer film and can be coextruded, laminated or blended with other materials.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects, features and advantages of the invention will become clearer and more fully understood when the following detailed description is ready in conjunction with the accompanying drawings, in which Figure 1 illustrates water vapor transmission rates as a function of density comparing films of this invention made with metallocene catalysts with those films made from resins produced by Ziegler-Natta catalysts.

Figure 2 is a DSC curve for the polymers of this invention and shows a single melting peak. Figure 3 is a DSC curve for a prior art material showing multiple melting peaks.

DETATLED DESCRIPTION OF THE INVENTION Introduction This invention concerns certain classes of non-polar hydrocarbon polymers specifically polyethylene resins, their production into film and applications in which films having a low water vapor transmission rates are desirable. These resins have unique properties particularly well suited for use in producing certain classes of polymeric films. Principally, these resins are used primarily in packaging applications, specifically those applications requiring good water vapor transmission rates, for example, food and chemical packaging. The resulting films have combinations of properties rendering them superior to resins previously available. Some of these resins have been placed into commerce under the trade names EXACT 3001, 3025, 3024, 3026, 3027, 3028, 4011, 2009, 2010, 3006 and 3016 all available from Exxon Chemical Company, Houston, Texas.

Up until now it was not known or disclosed that these resins and others of this invention when converted into films would suφrisingly and unexpectedly have low water vapor transmission rates. Following is a detailed description of certain preferred resins within the scope of this invention, preferred methods of producing these resins and preferred applications of these resins. Those skilled in the art will appreciate that numerous modifications to these preferred embodiments can be made without departing from the scope of the invention.

We have discovered that certain metallocene catalyst systems produce polymer resins that are highly desirable for use in certain film applications. Generally, these resins have a very narrow molecular weight distribution and composition distribution than polymers produced from conventional Ziegler catalysts. Production of the Resins

The polymer resins of this invention are produced using metallocene catalyst systems in a polymerization or copolymerization process in gas, slurry solution or high pressure phase.

The process for polymerizing or copolymerizing involves the polymerization of one more of the alpha-olefin monomers having from 2 to 20 carbon atoms, preferably 2-15 carbon atoms. The invention is particularly well suited to the copolymerization reactions involving the polymerization of one or more of the monomers, for example alpha-olefin monomers of ethylene, propylene, butene-1, pentene-1, 4-methylpentene-l, hexene-1, octene-1, decene-1 and cyclic olefins such as styrene. Other monomers can include polar vinyl, dienes, norbornene, acetylene and aldehyde monomers. Preferably a copolymer of ethylene is produced such that the amount of ethylene and comonomer is adjusted to produce a desired polymer product. Preferably the comonomer is an alpha- olefin having from 3 to 15 carbon atoms, preferably 4 to 12 carbon atoms and most preferably 4 to 10 carbon atoms. In another embodiment ethylene is polymerized with at least two comonomers to form a teφolymer and the like. If a comonomer is used then the monomer is generally polymerized in a proportion of 70.0-99.99, preferably 70-90 and more preferably 80-95 or 90-95 mole percent of monomer with 0.01-30, preferably 3-30 and most preferably 5-20, 5-10 mole percent comonomer.

For the puφoses of this patent specification the term "metallocene" is defined to contain one or more cyclopentadienyl moiety in combination with a transition metal of the Periodic Table of Elements. The metallocene catalyst component is represented by the general formula (Cp)mMRnR p wherein Cp is a substituted or unsubstituted cyclopentadienyl ring; M is a Group IV, V or VI transition metal; R and R¹ are independently selected halogen, hydrocarbyl group, or hydrocarboxyl groups having 1-20 carbon atoms; m = 1-3, n = 0-3, p = 0-3, and the sum of m + n + p equals the oxidation state of M. Various forms of the catalyst system of the metallocene type may be used in the polymerization process of this invention. Exemplary of the development of these metallocene catalysts for the polymerization of ethylene is found in the disclosure of U.S. Patent No. 4,871,705 to Hoel, U.S. Patent No. 4,937,299 to Ewen, et al. and EP-A-0 129 368 published July 26, 1989, and U.S. Patent Nos. 5,324,800, 5,017,714, and 5,120,867 to

Welborn, Jr. all of which are fully incoφorated herein by reference. These publications teach the structure of the metallocene catalysts and includes alumoxane as the cocatalyst. There are a variety of methods for preparing alumoxane of which one described in U.S. Patent 4,665,208. Other cocatalysts may be used with metallocenes, such as trialkylaluminum compounds; or ionizing ionic activators or compounds such as, tri (n-butyl) ammonium tetra (pentaflurophenyl) boron, which ionize the neutral metallocene compound. Such ionizing compounds may contain an active proton, or some other cation associated with but not coordinated or only loosely coordinated to the remaining ion of the ionizing ionic compound. Such compounds are described in EP-A-0 277 003 and

EP-A-0 277 004 both published August 3, 1988 and are both herein fully incoφorated by reference. Further, the metallocene catalyst component can be a monocyclopentadienyl heteroatom containing compound. This heteroatom is activated by either an alumoxane or an ionic activator to form an active polymerization catalyst system to produce polymers useful in this present invention. These types of catalyst systems are described in, for example, PCT International Publications WO 92/00333 published January 9, 1992, U.S. Patent Nos. 5,096,867 and 5,055,438, EP-A-0420436 and WO 91/ 04257 all of which are fully incoφorated herein by reference. In addition, the metallocene catalysts useful in this invention can include non-cyclopentadienyl catalyst components, or ancillary ligands such as boroles or carbollides in combination with a transition metal. Additionally it is not beyond the scope of this invention that the catalysts and catalyst systems may be those described in U.S. Patent No. 5,064,802 and PCT pubUcations WO 93/08221 and WO 93/08199 pubUshed April 29, 1993 aU of which are herein incoφorated by reference. AU the catalyst systems described above may be, optionally, prepolymerized or used in conjunction with an additive or scavenging component to enhance catalytic productivity.

The catalyst particles in a gas phase process may be supported on a suitable paniculate material such as polymeric supports or inorganic oxide such as silica, alumina or both. Methods of supporting the catalyst of this invention are described in U.S. Patent Nos. 4,808,561, 4,897,455, 4,937,301, 4,937,217, 4,912,075,

5,008,228, 5,086,025 and 5,147,949 and U.S. Application Serial Nos. 898,255, filed June 15, 1992 and 885,170, filed May 18, 1992, all of which are herein incoφorated by reference. The preferred support method in a gas phase process is generally disclosed in U.S. Patent No. 4,937,301 and related U.S. patents which are listed above.

The preferred catalyst, catalyst system and process is described in detail in U.S. Patent No. 5,084,534 herein fully incoφorated by reference. Characteristics of the Resins

A key characteristic of the resins of the present invention is their composition distribution. As is well known to those skilled in the art, the composition distribution of a copolymer relates to the uniformity of distribution of comonomer among the molecules of the copolymer. Metallocene catalysts are known to incoφorate comonomer very evenly among the polymer molecules they produce. Thus, copolymers produced from a catalyst system having a single metallocene component have a very narrow composition distribution - most of the polymer molecules wiU have roughly the same comonomer content, and within each molecule the comonomer wiU be randomly distributed. Ziegler-Natta catalysts, on the other hand generally yield copolymers having a considerably broader composition distribution. Comonomer inclusion will vary widely among the polymer molecules.

A measure of composition distribution is the "Composition Distribution Breadth Index" ("CDBI"). CDBI is defined as the weight percent of the copolymer molecules having a comonomer content within 50% (that is, 25% on each side) of the median total molar comonomer content. The CDBI of a copolymer is readily determined utilizing well known techniques for isolating individual fractions of a sample of the copolymer. One such technique is Temperature Rising Elution Fraction (TREF), as described in Wild, et al., J. Poly. ScL, Polv. Phvs. Ed., vol. 20, p. 441 (1982) and U.S. Patent No. 5,008,204, which are incoφorated herein by reference.

To determine CDBI, a solubility distribution curve is first generated for the copolymer. This may be accompUshed using data acquired from the TREF technique described above. This solubihty distribution curve is a plot of the weight fraction of the copolymer that is solubilized as a function of temperature. This is converted to a weight fraction versus composition distribution curve. For the puφose of simplifying the correlation of composition with elution temperature the weight fractions less than 15,000 are ignored. These low weight fractions generally represent a trivial portion of the resin of the present invention. The remainder of this description and the appended claims maintain this convention of ignoring weight fractions below 15,000 in the CDBI measurement.

From the weight fraction versus composition distribution curve the CDBI is determined by estabUshing what weight percent of the sample has a comonomer content within 25% each side of the median comonomer content. Further details of determining the CDBI of a copolymer are known to those skiUed in the art. See, for example, PCT Patent Application WO 93/03093, pubUshed February 18, 1993. The resins of the present invention have CDBI's generally in the range of

80-98%, usuaUy in the range of 85-98% and most typically in the range of 90-95%. Obviously, higher or lower CDBI's may be obtained using other catalyst systems with changes in the operating conditions of the process employed.

The films of this invention are also distinguishable from known films made from Ziegler-Natta based resins on the basis of their molecular weight distribution

(MWD). The MWD of the present resins is materially narrower than that of resins produced using traditional Ziegler-Natta catalysts. The polydispersity index (M_w Mn) of our resins is typically in the range of 1.5-3, compared to a range of 3 and above for most known Ziegler catalyzed resins. In this regard the present resins are very different from many commercially available resins produced using Ziegler-Natta catalysts. In addition, the tails of the molecular weight distribution curve for the present resin are considerably smaUer than those of known Ziegler- Natta LLDPEs. This distinction is readily apparent by comparing the ratio of Mz Mw (the ratio of the third moment to the second moment) and Mz+l/Mw (ratio of the fourth moment to the second moment). Utilizing the present invention, resins can be produced with an Mz M less than 2.5, usuaUy less than 2.0 and most typically in the range of 1.4 - 1.9. In contrast, the ratio of Mz/Mw for Ziegler-Natta resins is typically above 2.5. Similarly, the value of Mz+l/Mw for the present resins is less than 4.0, usually less than 3.0 and most typically in the range of 2.0-3.0. For Ziegler-Natta resins Mz+l/Mw is generally much higher - typically above 4.0. Table I provides further data regarding Mz, Mw, Mz+1 for the resins of this invention and also for some commercially available resins.

Those skiUed in the art wiU appreciate that there are several methods avaUable for deterrriining the molecular weight distribution of a polyethylene sample. For the puφose of Table I and other reference to Mw, Mz and Mz+1 given in this application and the appended claims, molecular weight distribution is determined with a Waters Gel Permeation Chromatograph equipped with ultrastyro gel columns operated at 145°C. Trichlorobenzene is used as the eluting solvent. The calibration standards are sixteen polystyrenes of precisely known molecular weight, ranging from a molecular weight of 500 to a molecular weight of 5.2 miUion. NBS 1475 polystyrene was also used as a calibration standard.

The melt index of the resins of the invention are generaUy in the range of 0.1 to 1000 dg/min, preferably 0.1 to 100 dg/min, more preferably 0.1 to 20 dg/min and even more preferably 0.1 to 10 dg/min and most preferably 0.1 to 5 dg/min. Properties of films produced from the resins

The resins produced using the metallocene catalyst described above are in many appUcations markedly superior to commercially available products. These resins are particularly useful in film appUcations. Tables I and π set forth the properties of films of this invention (resin A-J) of the present invention and compares these properties to the corresponding properties of films produced several commerciaUy avaUable resins derived from conventional Ziegler-Natta catalysts.

For the puφoses of this patent specification all tests were run on a 2 1/2" blown film line. The extruder was a 24/1 IJD and was powered by a 40 hp DC motor, the overall reduction ratio was 15.22: 1 giving a maximum screw speed of 115 φm. The cylinder and screw showed virtuaUy no wear. The screw was a dual channel barrier mixing screw with Maddock mixer at the tip designed for LLDPE extrusion. (Feed section — 4 1/2 diameters long with 0.50" depth channels, Barrier section — 13 diameters long with 0.165" wide flights and 0.050" clearance; Metering section — 4 diameters long with 0.210" deep channels; Mixer — 2 1/2 diameters long with 3 channels, 0.050" clearance and 0.375" wide barriers.) A 20/80/100/20 mesh screen pack was used for all test runs.

A state-of-the-art die system was used, including a 6" multi-ported low pressure spiral mandrel die with a 1/2" die land. Mandrel extensions for 60 mU die gaps were used, all with parallel die lands. The air ring was a duel orifice air ring employing a forming cone of 6" height and 11" top diameter.

Further details of the process above is found in the paper, Kurzbuch, "LLDPE Blown FUm Productivity: Effects of Processing Temperatures and Die

Gap on Attainable Production Rates", Journal of Plastic Film & Sheeting. Vol. 3, April, 1987, which is herein incoφorated by reference.

Blown films tend toward a lower water vapor transmission rate as compared with cast films at the same density. AU the tests herein were conducted on blown films.

The resins of this invention have lower WVTR than traditional Ziegler- Natta produced materials at the same or similar density. This can best be seen in Figure 1 which plots WVTR as a function of density. For the puφoses of this patent specification WVTR tests were performed on a MOCON permatron developed by Modern Controls, Inc. using ASTMF 372-73 at 100°F (378°C) and 100% relative humidity. The WVTR's of the films of the invention are generally in the range of 0.5 g mil/100 in²/day to 3.0 g mil/100 in²/day. Preferably are film having a WVTR in the range of 0.5 g mil/100 in²/day to 2.5 g mil 100 in²/day and more preferably in the range of 0.55 g mil/100 in /day to 2.0 g mil/100 in²/day. This particular attribute is most pronounced in films having a density less than 0.940 g/cm³, preferably less than or equal to 0.935 g/cm³ and a density greater than 0.860 g/cm³, preferably greater than 0.88 g/cm³. Most preferred are films having densities in the range of 0.865 g/cm³ to 0.940 g/cm³, preferably 0.87 g/cm³ to 0.935 g/cm³, most preferably 0.88 g/cm³ to less than 0.935 g/cm³, most preferably 0.900 g/cm³ to 0.930 g/cm³ and even most preferably .900 g/cm³ to 0.915 g/cm³.

In one embodiment where the resin of the invention is characterized in that at a density of 0.90 g/cm³ said film has a WVTR less than 2.25 gmil 100 in²/day, preferably the WVTR is less than 2.0 g mil/100 in²/day, more preferably less than 1.75 g mil 100 in²/day and most preferably less than 1.5 g mil/100 in²/day. In yet another embodiment the resin is characterized in that at a density of

0.91 g/cm³ said film has a WVTR less than 1.5 g mil/100 in²/day, most preferably less than 1.4 g mil/100 in /day.

In still another embodiment the resin is characterized in that at a density of 0.912 g/cm³ said film has a WVTR is less than 1.55 g mil/100 in²/day preferably less than 1.5 g mil 100 in²/day.

In one embodiment the WVTR for the films of this invention are represented by the following general empirical formula derived from Figure 1 :

WVTR = 314.43 - (650.45 X D) + (336.5 X D²) where D is the density. Films made from resins of traditional Ziegler-Natta materials generally follow the following empirical formula: WVTRl = 614.33 - (1285.16 XD) + (672.44 XD²) where D is the density. Thus, at a given density less than about 0.935 g/cm³ WVTR wiU be less than WVTR¹.

A particular attribute of the present resins is their very low level of extractable components. The extractables level for most grades of resins are in the range of between 5.5% to below 0.1%, preferably below 2.6%, more preferably below 1.0%, even more preferably below 0.8% and most preferably below 0.5%. The extractables level of our resins generally increases with decreasing molecular weight and decreasing density. At any given molecular weight and density (or side chain branching) our resins have an extractables level significantly below that of the coutiteφart Ziegler-Natta grade. For the puφoses of this specification and the appended claims, the extractables level is measured by exposing film produced from the resin to n-hexane at 50°C for 2 hours. This process is further detaUed in 21 CFR 177.1520 (d)(3)(ϋ) an FDA requirement. It will be appreciated by those skilled in the art, that the extractables test is subject to substantial variation. The variations may be due to film thickness (4 mils maximum) or any other variable that changes the surface to volume ratio. FUm fabrication type (e.g. blown, cast) and processing conditions may also change the extractable amount. The low extractables of films produced from these resins makes them weU suited for food appUcations. Films produced from the present resins also have excellent optical properties. The exceUent optics can be seen from Table LI.

The exceUent tensile strength, impact strength and puncture properties of the present resins permit resin density to be raised as required to achieve the desired film stiffness and/or yield strength without reducing toughness below acceptable levels for most appUcations. This superior toughness/stiffness balance has significant benefit by permitting simplified film formulations for applications requiring yield strength as weU as exceUent water vapor transmission rates.

Another important property of the films produced in accordance with this invention is their very high impact strength. Dart impact strengths above 1000 g/mil may be easily obtained. Indeed, many grades have dart impact strengths above 1500 g/mU.^" Dart impact strengths for the films of this invention are in the range of about 100 g/mU to greater than 1500 g/mil, preferably greater than 400 g/mU to more preferably greater than 900 g/mil and most preferably greater than 1000 g/mU. It is not beyond the scope of the invention to blend the resins of the films of the invention with other materials such as LLDPE, LDPE, HDPE, PP, PB, EVA, SBS and the Uke. The films of the invention include blown or cast films in mono- layer or multUayer construction formed by coextrusion or lamination.

The resin and product properties recited in this specification were determined in accordance with the foUowing test procedures. Where any of these properties is referenced in the appended claims, it is to be measured in accordance with the specified test procedure.

Property Units Procedure

Melt Index dg/min ASTMD-1238(E)

Density g/cc ASTMD-1505

Haze % ASTMD-1003

Gloss φj.45° % ASTMD-2457

Tensile @ Yield psi ASTMD-882

Elongation (3> Yield % ASTMD-882

Tensile @ Break psi ASTMD-882

Elongation @, Break % ASTMD-882

1% Secant Modulus kpsi ASTMD-882

Dart Impact Strength g/mil ASTMD-1709

Elmendorf Tear Resistance g mil ASTMD-1922

Puncture Force lb/mil ASTMD-3763

Puncture Energy in-lb/mil ASTMD-3763

Puncture Propagation Tear Resistance (PPT) kgf ASTMD-2582

Total Energy Impact it-lb ASTMD-4272

Reblock g ASTMD-3354

Water Vapor Transmission Rate g mil 100 in²/day ASTMF 372-73

While the present invention has been described and illustrated by reference to particular embodiments thereof, it wiU be appreciated by those of ordinary skill in the art that the invention lends itself to variations not necessarily Ulustrated herein. For example, it is not beyond the scope of this invention to include additives with the claimed films or to blend or coextrude the claimed films with other polymers or even laminate the claimed films to other materials such as metal foUs, paper, other polymer films and the Uke. For this reason, then, reference should be made solely to the appended claims for puφoses of determining the true scope of the present invention.

TABLE π TYPICAL BLOWN FILM PROPERTIES (2.5" EGAN/60 MIL DIE GAP)

Attane 4201 LL-1001 LL-3001

Grade Units D VLDPE LLDPE LLDPE Resin E Resin A Resin B

Comonomer — Octene Butene Hexene Butene Butene Hexene

Density G/CC .912 0.918 0.918 0.9102 0.9012 0.9001

Melt Index G/10° 1 1 1 1.16 1.17 0.93

Gauge Average MIL 1.21 1.42 1.24 1.35 1.34 1.36

1% Secand Modulus PSI MD 23150 30140 33370 16940 10630 11930

PSI TD 27320 35550 40650 18050 10800 12900

Tensile @ Yield PSI MD 1134.2 1305.5 1381.3 984.8 663.3 707

PSI TD 1112.4 1407.4 1571.2 929.2 613.8 654

Elongation @ Yield % MD 6.07 6.06 5.91 6.91 8.37 7.6

% TD 5.46 5.81 5.74 6.85 7.69 7.35

Elongation @ Break % MD 488.3 598.3 565.3 645 593 442

% TD 687.8 769 721.8 665.3 679.2 542

Ultimate Tensile PSI MD 8514 6831 8228.3 8140.8 8669.3 10748

PSI TD 7107.8 4816 6253.3 5675.5 7245 9606

Shrink % MD 57 49 36 57 33 40

% TD -6 -15 -6 -12 4 -1

ElmendorfTear g/mil MD 379 118.5 244.2 111.4 122.7 152 g/mil TD 659.4 412.3 641.1 236.7 176.9 250

Dart Impact g/mil 803.8 92.9 114.5 >1050 >1057.5 >1042

Puncture Force lbs/mil 7.44 5.7 5.75 5.94 7 8.52

Puncture Energy in"lbs/mil 22.57 10.97 13.83 14.33 21.1 27.26

Haze % 8.4 13.6 15.5 3.7 3.1 0.6

Gloss % 59.1 45.8 38.4 78.9 82.6 94.6

Total Energy Impact Mbs 23C 4.2 1.085 1.784 2.137 >6.16 >6.16

Mbs -34C — 0.685 0.734 1.736 2.16 3.49

WVTR g mil/100 in²/day 1.58 1.19 1.26 1.24 1.73 ' 1.86

Claims

CLAΓMSI Claim:

1. A polymeric film having improved water vapor transmission rate comprising at least one resin layer, said layer having a density in the range of 0.860 g/cm³ to 0.935 g/cm³, a Mw Mn less than 3, a Mz Mw less than 2.0, a CDBI greater than 80% and said resin layer is characterized in that at a density of about 0.90 g/cm³ said film has a WVTR less than 2.25 g mil/100 in²/day.

2. A polymeric film comprising at least one layer, said layer having a density less than 0.935 g/cm³ and said film having a WVTR such that the following formula is generally satisfied:

WVTR = 314.54 - (650.45 x D) + (336.5 x D²) where D represents density of said layer.

3. A polymeric film comprising at least one layer comprising a density less than 0.935 g/cm³ and said film having a WVTR less than the WVTR¹ using the following formula:

WVTR¹ = 614.33 - (1285.16 xD) + (672.44 xD²) where D represents density of said layer.

4. The polymeric film of any preceding claim wherein said layer has a CDBI greater than about 90%.

5. The polymeric film of any preceding claim wherein said layer has a density in the range of less than about 0.88 g/cm³ to about 0.92 g/cm³.

6. The polymeric film of any preceding claim wherein said layer has a single melting peak.

7. The polymeric film of any preceding claim wherein said film has a WVTR less than about 2.0 g mil/100in /day, preferably less than 1.75 g mil/100 in²/day.

8. The polymeric film of any preceding claim wherein said film has a dart impact strength greater than 900 g/mil,preferably greater than 1000 g/mil.

9. The polymeric film of any preceding claim wherein said film is blended with laminated to or coextruded with at least one other polymer.

10. The film of any preceding claim wherein said layer has a Mz/Mw less than 1.9.

11. The film of claim 3 wherein said WVTR is 80% of WVTR¹.

12. An article of manufacture comprising the polymeric film of any preceding claim.

13. The article of claim 12 wherein said article is selected from one of the group consisting of bags, pouches, packages and containers.