WO1999051433A1 - Polymeric adhesive composition for polyvinylidene chloride interpolymers - Google Patents

Abstract

The present invention is directed to an adhesive composition suitable for coextrusions with polyvinylidene chloride interpolymers and to a multilayer film structure made with the composition. The novel composition comprises less than or equal to 22 weight percent of at least one polar adhesive component polymer and greater than or equal to 78 weight percent of at least one homogeneously branched ethylene polymer. The preferred homogeneously branched ethylene polymer is a substantially linear ethylene polymer. The composition exhibits surprising, even synergistic adhesiveness to PVdC and is thought to be useful in hot-fill and cook-in applications.

Description

Polymeric Adhesive Composition for Polyvinylidene Chloride Interpolymers

The present invention relates to polymeric adhesive compositions and multilayer films containing the same. In particular, the invention relates to polymeric adhesive layers having substantial interlayer adhesion to polyvinylidene chloride (PVdC) interpolymers and to multilayer structures comprising adhesive film layers, especially blown coextruded flexible packaging film structures. The polymeric adhesive composition comprises a host polyolefin blend component, which comprises at least one homogeneously branched ethylene polymer, and an adhesive blend component, which comprises at least one polar polymer. PVdC is currently used successfully in a variety of multilayer film structures. Predominantly, for flexible packaging applications, the use of PVdC is directed to multilayer cast film structures where an adhesive tie layer is employed to provide interlayer adhesion and ensure structure integrity. Ethylene vinyl acetate (EVA) copolymers are most commonly used as the adhesive tie layer adjacent to PVdC layers or coatings. A typical multilayer structure where oxygen and moisture barrier are critical performance requirement is HDPE/EVA/PVdC/EVA. In such structures, EVA performs as both an adhesive tie layer and as an outer sealant layer. However, because EVA copolymers are known to contribute off taste and odor to packaged food items, it desirous to provide an alternative adhesive material with improved taste and odor characteristics. It is also desirous to provide an alternative adhesive material suitable for multilayer PVdC-containing film structures fabricated using a blown coextrusion technique. Similar to EVA copolymers, there are a variety of thermoplastic materials which allegedly exhibit substantial interlayer adhesion to PVdC. For example, Lustig et al. in US Patent No. 4,988,465 and Parnell et al. in US Patent No. 5,041,316 each disclose that ultra (or very) low density polyethylene resins, exemplified as heterogeneously branched linear ethylene polymers having densities less than 0.92 g/cc, exhibit substantial adhesion to PVdC in coextruded structures. At Col. 2, line 66, Parnell et al. indicates that a measure of good interlayer adhesion is greater than 40 grams/millimeter .

US Patent Nos. 4,909,881; 4,842,952; and 4,778,715 disclose that the addition of an ethylene butyl acrylate copolymer to a heterogeneously branched linear ethylene polymer can provide improved interlayer adhesion to PVdC. US Patent No. 4,755,402 to Oberle discloses that a polyamide (nylon) can be used in multilayer film structures directly adhered to PVdC and further contemplates blending the polyamide with a minor amount of an adhesive. Similarly, US Patent No. 4,888,249 to Flores et al. teach blending PVdC with a nonpolar polyolefin and a compatibilizing amount of a polar polyolefin (e.g. an ethylene acrylic acid interpolymer) to provide an adhesive for bonding PVdC layers or coatings to polyamide layers .

US Patent No. 5,272,016 to Ralph discloses a multilayer film which comprises a first outer layer, a second outer layer, and a core polyolefin layer between the first and second outer layers wherein first and second outer layers each comprise a blend of 20-35 wt . % of a homogeneously branched linear ethylene polymer and 65-80 wt . % of a ultra (or very) low density polyethylene (VLDPE) and the core polyolefin layer comprises an ethylene alpha-olefin copolymer and is comprised of at least one VLDPE, linear low density polyethylene (LLDPE) and polypropylene, or is comprised of a blend of two different ethylene alpha-olefin copolymers. Ralph does not disclose that either his first or second outer layers have substantial adhesion to PVdC.

Although a variety of polymer compositions are known that allegedly have substantial adhesion to PVdC, there are no known thermoplastic compositions that provide the property balance of good sealant properties, good taste and odor characteristics and substantial adhesion to PVdC such that the composition is suitable for use in flexible packaging multilayer film structures.

Further PVdC is known to require extra care during film fabrication to avoid extruder hot spots which can cause degradation of the PVdC and lose of its barrier characteristics. As such, fabrication of PVdC is typically performed at relatively mild melt temperatures and

- 3 - coextrusions with high melting polymers as additional film layers is generally not possible. Further, the high temperature sensitivity of PVdC complicates the desire to provide multilayer film structures with retort capabilities. Because of the unique characteristics of PVdC and the lack of PVdC adhesive tie materials with the property balance of good sealant properties and good taste and odor characteristics, it is an object of the present invention to provide novel adhesive compositions suitable for in multilayer flexible packaging film structures.

We have discovered that blending low levels of a polar polymer into at least one homogeneously branched ethylene polymer can provide a thermoplastic composition which exhibits substantial adhesion (i.e. equal to or greater than 40 grams/mm) to polyvinylidene chloride interpolymers.

The broad aspect of the invention is a thermoplastic composition suitable for coextrusions with polyvinylidene chloride interpolymers and having interlayer adhesion to polyvinylidene chloride interpolymers comprising: a) as an adhesive blend component, less than or equal to 22 weight percent, based on the total weight of the composition, of at least one adhesive polymer comprising at least one polymerized, reacted or grafted polar moiety or comonomer selected from the group consisting of lactic acid, amide, chlorine, imide, alkyl acrylate, vinyl acetate, carboxylic acid, caroboxylix ester, carbon monoxide,

- 4 terephthalatic acid, adipic, caprolactone, aldehyde, epoxy, maleic anhydride and succinnic anhydride, and b) as a host blend component, greater than or equal to 78 weight percent, based on the total weight of the composition, of at least one homogeneously branched ethylene polymer characterized as having: i. a density less than or equal to 0.91 gram/centimeter (g/cc) and ii. a short chain branching distribution index (SCBDI) greater than 50 percent.

In a preferred embodiment of the present invention, the b) host blend component comprises

(A) from 5 to 95 weight percent, based on the total weight of the polymer mixture, of at least one first ethylene polymer which is a homogeneously branched substantially linear ethylene polymer or a homogeneously branched linear ethylene polymer, wherein the first ethylene polymer is characterized as having: i. an I₂ melt index in the range of from greater than 0.14 g/10 minutes to less than 0.67 g/10 minutes, as measured by ASTM D-1238 Condition 190°C/2.16 kg, ii. a density in the range of 0.85 to 0.92 g/cc, as measured in accordance with ASTM D-792, iii. a molecular weight distribution, M_w/M_n as determined by gel permeation chromatography of less than 3.5, iv. a single differential scanning calorimerry, DSC, melting peak between -30 and 150°C, and v. a short chain branching distribution index (SCBDI) greater than 50 percent, and (B) from 5 to 95 weight percent, based on the total weight of the polymer mixture, of at least one second ethylene polymer which is a homogeneously branched ethylene polymer or a heterogeneously branched linear ethylene polymer wherein the second ethylene polymer is characterized as having a density in the range of 0.89 g/cc to 0.965 g/cc, wherein the polymer mixture is characterized as having a density of from 0.89 g/cc to 0.93 g/cc, as measured in accordance with ASTM D-792, and an I₂ melt index in the range of from 1 g/10 minutes to 5 g/10 minutes, as measured by ASTM D-1238 Condition 190°C/2.16 kg, and wherein the molecular weight of the at least one first polymer is higher than the molecular weight of the at least one second polymer.

Another aspect of the invention is a multilayer film structure having a barrier film layer and an adhesive layer adjacent to the barrier film layer, the adhesive layer comprising: a) less than or equal to 22 weight percent, based on the total weight of the composition, of at least one adhesive polymer comprising at least one polymerized, reacted or grafted polar moiety or comonomer selected from the group consisting of lactic acid, amide, chlorine, imide, alkyl acrylate, vinyl acetate, carboxylic acid, carboxylic ester, carbon monoxide, terephthalatic acid, adipic, caprolactone, aldehyde, epoxy, maleic anhydride and succinnic anhydride, and b) greater than or equal to 78 weight percent, based on the total weight of the composition, of at least one homogeneously branched ethylene polymer characterized as having : i. a density less than or equal to 0.91 gram/centimeter (g/cc) and ii. a short chain branching distribution index (SCBDI) greater than 50 percent.

Surprisingly, the inventive blend composition synergistically exhibits substantial interlayer adhesion to PVdC and balance properties. Also, in preferred embodiments, the inventive blend composition synergistically exhibits substantial interlayer adhesion to PVdC as well as good sealant properties and improved high temperature (heat) resistivity permitting successful use in retort end-uses such as, for example, hot-fill and cook-in applications. The adhesiveness of the inventive composition is also a surprise relative to compositions based onheterogeneously branched ethylene polymer.

The synergistic interlayer adhesion to PVdC is preferably greater than 100 g/25 mm, more preferably greater than or equal 500 g/25 mm and most preferably greater than or equal to 1000 g/25 mm as determined using an Instron T-peel test after permitting sample to age 24 hours at ambient room temperature and 70% relative humidity.

- 1 - The improved high temperature resistivity of the inventive blend composition may be expressed as having a film heat seal initiation temperature that ranges from equal to or at least 4.5°C lower than its Vicat softening temperature and,

more surprisingly, in particular embodiments, from equal to or at least 6°C lower than its Vicat softening temperature.

One advantage of the invention is now practitioners can manufacture multilayer packaging structures with consolidated layers, freeing up equipment capabilities to meet other objectives such as, for example, incorporating bulk/filler layers to reduce overall structure costs.

The term "polymer", as used herein, refers to a polymeric compound prepared by polymerizing monomers, whether of the same or a different type. As used herein, generic term "polymer" embraces the terms "homopolymer, " "copolymer, " "terpolymer" as well as "interpolymer . "

The term "interpolymer", as used herein refers to polymers prepared by the polymerization of at least two different types of monomers. As used herein the generic term "interpolymer" includes the term "copolymers" (which is usually employed to refer to polymers prepared from two different monomers) as well as the term "terpolymers" (which is usually employed to refer to polymers prepared from three different types of monomers). The term "homogeneously branched ethylene polymer" is used herein in the conventional sense to refer to an ethylene interpolymer in which the comonomer is randomly distributed within a given polymer molecule and wherein substantially all of the polymer molecules have the same ethylene to comonomer molar ratio. The term refers to an ethylene interpolymer that is characterized by a relatively high short chain branching distribution index (SCBDI) or composition distribution branching index (CDBI), i.e., a uniform short chain branching distribution.

Homogeneously branched ethylene polymers have a SCBDI greater than or equal to 50 percent, preferably greater than or equal to 70 percent, more preferably greater than or equal to 90 percent. Preferably, the homogeneously branched ethylene polymer is further characterized as having a narrow, essentially single melting TREF profile/curve and essentially lacking a measurable high density polymer portion (i.e. the polymer does not contain polymer fraction with a degree of short branching equal to or more than 30 methyls/1000 carbons or, alternatively, at densities less than 0.936 g/cc, the polymer does not contain polymer fraction eluting at temperatures greater than 95°C) . SCBDI is defined as the weight percent of the polymer molecules having a comonomer content within 50 percent of the median total molar comonomer content and represents a comparison of the monomer distribution in the interpolymer to the monomer distribution expected for a Bernoullian distribution. The SCBDI of an interpolymer can be readily calculated from TREF as described, for example, by Wild et al., Journal of Polymer Science, Poly. Phys . Ed., Vol. 20, p.

- 9 - 441 (1982), or in US Patent 4,798,081; 5,008,204; or by L. D. Cady, "The Role of Comonomer Type and Distribution in LLDPE Product Performance," SPE Regional Technical Conference, Quaker Square Hilton, Akron, Ohio, October 1-2, pp. 107-119 (1985) , the disclosures of all which are incorporated herein by reference. However, the preferred TREF technique does not include purge quantities in SCBDI calculations. More preferably, the monomer distribution of the interpolymer and SCBDI are determined using ¹³C NMR analysis in accordance with techniques described in US Patent No. 5,292,845; US Patent No. 4,798,081; U.S. Patent No. 5,089,321 and by J. C. Randall, Rev. Macromol. Chem. Phys., C29, pp. 201-317, the disclosures of all of which are incorporated herein by reference . In analytical temperature rising elution fractionation analysis (as described in US Patent No. 4,798,081 and abbreviated herein as "ATREF"), the film or composition to be analyzed is dissolved in a suitable hot solvent (e.g., trichlorobenzene) and allowed to crystallized in a column containing an inert support (stainless steel shot) by slowly reducing the temperature. The column is equipped with both a refractive index detector and a differential viscometer (DV) detector. An ATREF-DV chromatogram curve is then generated by eluting the crystallized polymer sample from the column by slowly increasing the temperature of the eluting solvent (trichlorobenzene) . The ATREF curve is also frequently called the short chain branching distribution (SCBD), since

- 10 - it indicates how evenly the comonomer (e.g., octene) is distributed throughout the sample in that as elution temperature decreases, comonomer content increases. The refractive index detector provides the short chain distribution information and the differential viscometer detector provides an estimate of the viscosity average molecular weight. The short chain branching distribution and other compositional information can also be determined using crystallization analysis fractionation such as the CRYSTAF fractionalysis package available commercially from PolymerChar, Valencia, Spain.

Preferred homogeneously branched ethylene polymers (such as, but not limited to, substantially linear ethylene polymers) have a single melring peak between -30 and 150°C, as determined using differential scanning calorimetry (DSC) , as opposed to traditional Ziegler polymerized heterogeneously branched ethylene polymers (that is, LLDPE and ULDPE or VLDPE) which have two or more melting points.

However, those polymers having a density of 0.875 g/cm³

to 0.91 g/cm , the single melt peak may show, depending on equipment sensitivity, a "shoulder" or a "hump" on the side low of the melting peak (that is, below the melting point) that constitutes less than 12 percent, typically, less than 9 percent, more typically less than 6 percent of the total heat of fusion of the polymer. This artifact is due to intra- polymer chain variations, and it is discerned on the basis of the slope of the single melting peak varying monotonically

- 11 - through the melting region of the artifact. The artifact occurs within 34°C, typically within 27°C, and more typically

within 20°C of the melting point of the single melting peak.

The single melting peak is determined using a differential scanning calorimeter standardized with indium and deionized water. The method involves 5-7 mg sample sizes,

a "first heat" to 150°C which is held for 4 minutes, a cool

down at 10°C/min. to -30°C which is held for 3 minutes, and

heat up at 10°C/min. to 150°C to provide a "second heat" heat flow vs. temperature curve. Total heat of fusion of the polymer is calculated from the area under the curve. The heat of fusion attributable to this artifact, if present, can be determined using an analytical balance and weight-percent calculations . The nomogeneously branched ethylene polymers for use in the invention are nonpolar polymers and can be either a substantially linear ethylene polymer or a homogeneously branched linear ethylene polymer. Most preferably, the homogeneously branched ethylene polymer is a substantially linear ethylene polymer due to its unique rheological properties .

The term "linear" as used herein means that the ethylene polymer does not have long chain branching. That is, the polymer chains comprising the bulk linear ethylene polymer have an absence of long chain branching, as in the case of traditional linear low density polyethylene polymers or

- 12 - linear high density polyethylene polymers made using Ziegler polymerization processes (e.g., USP 4,076,698 (Anderson et al.)), sometimes called heterogeneous polymers. The term "linear" does not refer to bulk high pressure branched polyethylene, ethylene/vinyl acetate copolymers, or ethylene/vinyl alcohol copolymers which are known to those skilled in the art to have numerous long chain branches.

The term "homogeneously branched linear ethylene polymer" refers to polymers having a narrow short chain branching distribution and an absence of long chain branching. Such "linear" uniformly branched or homogeneous polymers include those made as described in USP 3,645,992 (Elston) and those made using so-called single site catalysts in a batch reactor having relatively high ethylene concentrations (as described in U.S. Patent 5,026,798

(Canich) or in U.S. Patent 5,055,438 (Canich) ) or those made using constrained geometry catalysts in a batch reactor also having relatively high olefin concentrations (as described in U.S. Patent 5,064,802 (Stevens et al . ) or in EP 0 416 815 A2 (Stevens et al. ) ) .

Typically, homogeneously branched linear ethylene polymers are ethylene/α-olefin interpolymers, wherein the α-

olefin is at least one C₃-C₂o α-olefin (e.g., propylene, 1- butene, 1-pentene, 4-methyl-l-pentene, 1-hexene, 1-octene and the like) and preferably the at least one C₃-C₂o α-olefin is 1-butene, 1-hexene or 1-octene. Most preferably, the ethylene/α-olefin interpolymer is a copolymer of ethylene and

- 13 - a C₃-C₂o α-olefin, and especially an ethylene/C4-C₈ α-olefin copolymer such as an ethylene/1-octene copolymer, ethylene/1- butene copolymer, ethylene/1-pentene copolymer or ethylene/1- hexene copolymer. Suitable homogeneously branched linear ethylene polymers for use in the invention are sold under the designation of TAFMER by Mitsui Chemical Corporation and under the designations of EXACT and EXCEED resins by Exxon Chemical Corporation . The homogeneously branched ethylene polymer can optionally be blended with at least one nonpolar polymer. Suitable nonpolar polymers for blending with the at least one homogeneously branched ethylene polymer include, for example, a low density polyethylene homopolymer, substantially linear ethylene polymer, homogeneously branched linear ethylene polymers, heterogeneously branched linear ethylene polymers (i.e., linear low density polyethylene (LLDPE), ultra or very low density polyethylene (ULDPE) , medium density polyethylene (MDPE) , and high density polyethylene (HDPE) such as those manufactured using a Ziegler-Natta catalyst system) as well as polystyrene, polypropylene, ethylene propylene polymers, EPDM, ethylene propylene rubber, ethylene styrene interpolymers and the like.

The term "substantially linear ethylene polymer" as used herein means that the bulk ethylene polymer is substituted, on average, with 0.01 long chain branches/1000 total carbons to 3 long chain branches/1000 total carbons (wherein "total

- 14 - carbons" includes both backbone and branch carbons) . Preferred polymers are substituted with 0.01 long chain branches/1000 total carbons to 1 long chain branches/1000 total carbons, more preferably from 0.05 long chain branches/1000 total carbons to 1 long chain branched/1000 total carbons, and especially from 0.3 long chain branches/1000 total carbons to 1 long chain branches/1000 total carbons.

As used herein, the term "backbone" refers to a discrete molecule, and the term "polymer" or "bulk polymer" refers, in the conventional sense, to the polymer as formed in a reactor. For the polymer to be a "substantially linear ethylene polymer", the polymer must have at least enough molecules with long chain branching such that the average long chain branching in the bulk polymer is at least an average of from 0.01/1000 total carbons to 3 long chain branches/1000 total carbons.

The term "bulk polymer" as used herein means the polymer v/hich results from the polymerization process as a mixture of polymer molecules and, for substantially linear ethylene polymers, includes molecules having an absence of long chain branching as well as molecules having long chain branching. Thus a "bulk polymer" includes all molecules formed during polymerization. It is understood that, for the substantially linear polymers, not all molecules have long chain branching, but a sufficient amount do such that the average long chain branching content of the bulk polymer positively affects the

- 15 - melt rheology (i.e., the melt fracture properties) as described herein below and elsewhere in the literature.

Long chain branching (LCB) is defined herein as a chain length of at least one (1) carbon less than the number of carbons in the comonomer, whereas short chain branching (SCB) is defined herein as a chain length of the same number of carbons in the residue of the comonomer after it is incorporated into the polymer molecule backbone. For example, a substantially linear ethylene/1-octene polymer has backbones with long chain branches of at least seven (7) carbons in length, but it also has short chain branches of only six (6) carbons in length.

Long chain branching can be distinguished from short chain branching by using ¹³C nuclear magnetic resonance (NMR) spectroscopy and to a limited extent, e.g. for ethylene homopolymers, it can be quantified using the method of Randall, (Rev. Macromol . Chem. Phys., C29 (2&3), p. 285-297), the disclosure of which is incorporated herein by reference. However as a practical matter, current ¹³C nuclear magnetic resonance spectroscopy cannot determine the length of a long chain branch in excess of about six (6) carbon atoms and as such, this analytical technique cannot distinguish between a seven (7) carbon branch and a seventy (70) carbon branch. The long chain branch can be as long as about the same length as the length of the polymer backbone.

Although conventional ¹³C nuclear magnetic resonance spectroscopy cannot determine the length of a long chain

- 16 - branch in excess of six carbon atoms, there are other known techniques useful for quantifying or determining the presence of long chain branches in ethylene polymers, including ethylene/1-octene interpolymers. For example, US Patent No. 4,500,648, incorporated herein by reference, teaches that long chain branching frequency (LCB) can be represented by the equation LCB=b/M_w wherein b is the weight average number

of long chain branches per molecule and M_w is the weight

average molecular weight. The molecular weight averages and the long chain branching characteristics are determined by gel permeation chromatography and intrinsic viscosity methods, respectively.

Two other useful methods for quantifying or determining the presence of long chain branches in ethylene polymers, including ethylene/1-octene interpolymers are gel permeation chromatography coupled with a low angle laser light scattering detector (GPC-LALLS) and gel permeation chromatography coupled with a differential viscometer detector (GPC-DV) . The use of these techniques for long chain branch detection and the underlying theories have been well documented in the literature. See, e.g., Zimm, G.H. and Stockmayer, W.H., J. Chem. Phys., 17, 1301 (1949) and Rudin, A. , Modern Methods of Polymer Characterization, John Wiley & Sons, New York (1991) pp. 103-112, the disclosures of both of which are incorporated by reference.

A. Willem deGroot and P. Steve Chum, both of The Dow Chemical Company, at the October 4, 1994 conference of the

- 17 - Federation of Analytical Chemistry and Spectroscopy Society (FACSS) in St. Louis, Missouri, presented data demonstrating that GPC-DV is indeed a useful technique for quantifying the presence of long chain branches in substantially linear ethylene polymers. In particular, deGroot and Chum found that the level of long chain branches in substantially linear ethylene homopolymer samples measured using the Zimm- Stockmayer equation correlated well with the level of long chain branches measured using ¹³C NMR. Further, deGroot and Chum found that the presence of octene does not change the hydrodynamic volume of the polyethylene samples in solution and, as such, one can account for the molecular weight increase attributable to octene short chain branches by knowing the mole percent octene in the sample. By deconvoluting the contribution to molecular weight increase attributable to 1-octene short chain branches, deGroot and Chum showed that GPC-DV may be used to quantify the level of long chain branches in substantially linear ethylene/octene copolymers. DeGroot and Chum also showed that a plot of Log(I₂, melt index) as a function of Log(GPC Weight Average Molecular Weight) as determined by GPC-DV illustrates that the long chain branching aspects (but not the extent of long branching) of substantially linear ethylene polymers are comparable to that of high pressure, highly branched low density polyethylene (LDPE) and are clearly distinct from ethylene polymers produced using Ziegler-type catalysts such

- 18 - as titanium complexes and ordinary homogeneous catalysts such as hafnium and vanadium complexes.

For substantially linear ethylene polymers, the empirical effect of the presence of long chain branching is manifested as enhanced rheological properties which are quantified and expressed in terms of gas extrusion rheometry (GER) results and/or melt flow, Iιo/I₂, increases.

The substantially linear ethylene polymers used in the present invention are a unique class of compounds that are further defined in US Patent No. 5,272,236, application number 07/776,130, filed October 15, 1991; US Patent No. 5,278,272, application number 07/939,281, filed September 2, 1992; and US Patent No. 5,665,800, application number 08/730,766, filed October 16, 1996, each of which is incorporated herein by reference.

Substantially linear ethylene polymers differ significantly from the class of polymers conventionally known as homogeneously branched linear ethylene polymers described above and, for example, by Elston in US Patent 3,645,992. As an important distinction, substantially linear ethylene polymers do not have a linear polymer backbone in the conventional sense of the term "linear" as is the case for homogeneously branched linear ethylene polymers. Substantially linear ethylene polymers also differ significantly from the class of polymers known conventionally as heterogeneously branched traditional Ziegler polymerized linear ethylene interpolymers (for example, ultra low density

- 19 - polyethylene, linear low density polyethylene or high density polyethylene made, for example, using the technique disclosed by Anderson et al. in US Patent 4,076,698, in that substantially linear ethylene interpolymers are homogeneously branched polymers; that is, substantially linear ethylene polymers have a SCBDI greater than or equal to 50 percent, preferably greater than or equal to 70 percent, more preferably greater than or equal to 90 percent. Substantially linear ethylene polymers also differ from the class of heterogeneously branched ethylene polymers in that substantially linear ethylene polymers are characterized as essentially lacking a measurable high density or crystalline polymer fraction as determined using a temperature rising elution fractionation technique. The substantially linear ethylene polymer for use in the present invention is characterized as having

(a) melt flow ratio, I10 I2 - 5.63,

(b) a molecular weight distribution, M_w/M_n, as determined by gel permeation chromatography and defined by the equation:

(M_w/M_n) < (I₁₀/I₂) - 4.63,

(c) a gas extrusion rheology such that the critical shear rate at onset of surface melt fracture for the substantially linear ethylene polymer is at least 50 percent greater than the critical shear rate at the onset of surface melt fracture for a linear ethylene polymer, wherein the substantially linear ethylene polymer and the linear ethylene polymer comprise the same comonomer or comonomers, the linear ethylene polymer has an I₂ and M_w/M_n

- 20 - within ten percent of the substantially linear ethylene polymer and wherein the respective critical shear rates of the substantially linear ethylene polymer and the linear ethylene polymer are measured at the same melt temperature using a gas extrusion rheometer, (d) a single differential scanning calorimetry, DSC, melting peak between -30° and 150°C, and (e) a short chain branching distribution index greater than 50 percent. Determination of the critical shear rate and critical shear stress in regards to melt fracture as well as other rheology properties such as "rheological processing index" (PI), is performed using a gas extrusion rheometer (GER) .. The gas extrusion rheometer is described by M. Shida, R.N. Shroff and L.V. Cancio in Polymer Engineering Science, Vol. 17, No. 11, p. 770 (1977) and in Rheometers for Molten Plastics by John Dealy, published by Van Nostrand Reinhold Co. (1982) on pp. 97-99, the disclosures of both of which are incorporated herein by reference.

The processing index (PI) is measured at a temperature of 190°C, at nitrogen pressure of 2500 psig (17.2 MPa) using a 0.0296 inch (752 micrometers) diameter (preferably a 0.0143 inch diameter die for high flow polymers, e.g. 50-100 I₂ melt index or greater), 20:1 L/D die having an entrance angle of 180°. The GER processing index is calculated in millipoise units from the following equation:

- 21 - PI = 2.15 X 10⁶ dyne/cm²/ (1000 X shear rate),

where: 2.15 X 10⁶ dyne/cm² (215 Mpa) is the shear stress at 2500 psi (17.2 Mpa), and the shear rate is the shear rate at the wall as represented by the following equation:

32 Q'/ (60 sec/min) (0.745) (Diameter X 2.54 cm/in)³, where :

Q' is the extrusion rate (gms/min) ,

0.745 is the melt density of polyethylene (in

gm/cm³) , and

Diameter is the orifice diameter of the capillary (inches) .

The PI is the apparent viscosity of a material measured

at apparent shear stress of 2.15 x 10° dyne/cm² (215 Mpa). For substantially linear ethylene polymers, the PI is less than or equal to 70 percent of that of a conventional linear ethylene polymer having an I2, M_w/M_n and density each

within ten percent of the substantially linear ethylene polymer . An apparent shear stress vs. apparent shear rate plot is used to identify the melt fracture phenomena over a range of nitrogen pressures from 5250 to 500 psig (36.2 to 3.4 Mpa) using the die or GER test apparatus previously described.

According to Ramamurthy in Journal of Rheology, 30(2), 337-357, 1986, above a certain critical flow rate, the observed extrudate irregularities may be broadly classified

- 22 - into two main types: surface melt fracture and gross melt fracture .

Surface melt fracture occurs under apparently steady flow conditions and ranges in detail from loss of specular gloss to the more severe form of "sharkskin". In this disclosure, the onset of surface melt fracture is characterized at the beginning of losing extrudate gloss at which the surface roughness of extrudate can only be detected by 40x magnification. The critical shear rate at onset of surface melt fracture for the substantially linear ethylene polymers is at least 50 percent greater than the critical shear rate at the onset of surface melt fracture of a linear ethylene polymer having about the same I2 and M_w/M_n.

Preferably, the critical shear stress at onset of surface melt fracture for the substantially linear ethylene polymers

of the invention is greater than 2.8 x 10° dyne/cm² (280 MPa)

Gross melt fracture occurs at unsteady flow conditions and ranges in detail from regular (alternating rough and smooth, helical, etc.) to random distortions. For commercial acceptability, (e.g., in blown film products), surface defects should be minimal, if not absent. The critical shear rate at onset of surface melt fracture (OSMF) and critical shear stress at onset of gross melt fracture (OGMF) will be used herein based on the changes of surface roughness and configurations of the extrudates extruded by a GER. For the substantially linear ethylene polymers used in the invention,

23 - the critical shear stress at onset of gross melt fracture is

preferably greater than 4 x 10° dyne/cm² (400 Mpa)

For the processing index determination and for the GER melt fracture determination, substantially linear ethylene polymers are tested without inorganic fillers and do not have more than 20 ppm aluminum catalyst residue. Preferably, however, for the processing index and melt fracture tests, substantially linear ethylene polymers do contain antioxidants such as phenols, hindered phenols, phosphites or phosphonites, preferably a combination of a phenol or hindered phenol and a phosphite or a phosphonite.

The molecular weight distributions of ethylene polymers are determined by gel permeation chromatography (GPC) on a Waters 150C high temperature chromatographic unit equipped with a differential refractometer and three columns of mixed porosity. The columns are supplied by Polymer Laboratories and are commonly packed with pore sizes of 10³, lύ⁴, 10⁵ and 10⁶A. The solvent is 1, 2, 4-trichlorobenzene, from which about 0.3 percent by weight solutions of the samples are prepared for injection. The flow rate is about 1.0 milliliters/minute, unit operating temperature is about 140°C and the injection size is about 100 microliters.

The molecular weight determination with respect to the polymer backbone is deduced by using narrow molecular weight distribution polystyrene standards (from Polymer

Laboratories) in conjunction with their elution volumes. The equivalent polyethylene molecular weights are determined by

- 24 - using appropriate Mark-Houwink coefficients for polyethylene and polystyrene (as described by Williams and Ward in Journal of Polymer Science, Polymer Letters, Vol. 6, p. 621, 1968, the disclosure of which is incorporated herein by reference) to derive the following equation:

M polyethylene = a * ( M polystyrene )' b

In this equation, a = 0.4316 and b = 1.0. Weight average molecular weight, M_w, is calculated in the usual manner according to the following formula: Mj = (Σ w₁(M₁ ))^:ι; where

w_x is the weight fraction of the molecules with molecular weight M_x eluting from the GPC column in fraction i and j = 1 when calculating M_w and j = -1 when calculating M_n.

For the at least one homogeneously branched ethylene polymer used in the present invention, the M_w/M_n is preferably less than 3.5, more preferably less than 3.0, most preferably less than 2.5, and especially in the range of from 1.5 to 2.5 and most especially in the range from 1.8 to 2.3.

Substantially linear ethylene polymers are known to have excellent processability, despite having a relatively narrow molecular weight distribution (that is, the M_w/M_n ratio is typically less than 3.5). Surprisingly, unlike homogeneously and heterogeneously branched linear ethylene polymers, the melt flow ratio (I₁₀/I₂) °f substantially linear ethylene polymers can be varied essentially independently of the molecular weight distribution, M_w/M_n. Accordingly, especially when good extrusion processability is desired, the preferred

- 25 - ethylene polymer for use in the present invention is a homogeneously branched substantially linear ethylene interpolymer.

Suitable constrained geometry catalysts for use manufacturing substantially linear ethylene polymers include constrained geometry catalysts as disclosed in U.S. application number 07/545,403, filed July 3, 1990; U.S. application number 07/758,654, filed September 12, 1991; U.S.

Patent No. 5,132,380 (application number 07/758,654); U.S. Patent No. 5,064,802 (application number 07/547,728); U.S.

Patent No. 5,470,993 (application number 08/241,523); U.S.

Patent No. 5,453,410 (application number 08/108,693); U.S.

Patent No. 5,374,696 (application number 08/08,003); U.S.

Patent No. 5,532,394 (application number 08/295,768); U.S. Patent No. 5,494,874 (application number 08/294,469); and

U.S. Patent No. 5,189,192 (application number 07/647,111. Suitable catalyst complexes may also be prepared according to the teachings of WO 93/08199, and the patents issuing therefrom, all of which are incorporated herein by reference. Further, the monocyclopentadienyl transition metal olefin polymerization catalysts taught in USP

5,026,798, which is incorporated herein by reference, are also believed to be suitable for use in preparing the polymers of the present invention, so long as the polymerization conditions substantially conform to those described in US Patent No. 5,272,236; US Patent No. 5,278,272 and US Patent No. 5,665,800, especially with strict attention

- 26 - to the requirement of continuous polymerization. Such polymerization methods are also described in PCT/US 92/08812 (filed October 15, 1992) .

The foregoing catalysts may be further described as comprising a metal coordination complex comprising a metal of groups 3-10 or the Lanthanide series of the Periodic Table of the Elements and a delocalize β-bonded moiety substituted with a constrain-inducing moiety, said complex having a constrained geometry about the metal atom such that the angle at the metal between the centroid of the delocalized, substituted pi-bonded moiety and the center of at least one remaining substituent is less than such angle in a similar complex containing a similar pi-bonded moiety lacking in such constrain-inducing substituent, and provided further that for such complexes comprising more than one delocalized, substituted pi-bonded moiety, only one thereof for each metal atom of the complex is a cyclic, delocalized, substituted pi- bonded moiety. The catalyst further comprises an activating cocatalyst . Suitable cocatalysts for use herein include polymeric or oligomeric aluminoxanes, especially methyl aluminoxane, as well as inert, compatible, noncoordinating, ion forming compounds. So called modified methyl aluminoxane (MMAO) is also suitable for use as a cocatalyst. One technique for preparing such modified aluminoxane is disclosed in US PATENT No. 5,041,584. Aluminoxanes can also be made as disclosed in US Patent No. 5,218,071; US Patent No. 5,086,024; US Patent

- 27 - No. 5,041,585; US Patent No. 5,041,583; US Patent No. 5,015,749; US Patent No. 4,960,878; and US Patent No. 4,544,762.

Aluminoxanes, including modified methyl aluminoxanes, when used in the polymerization, are preferably used such that the catalyst residue remaining in the (finished) polymer is preferably in the range of from 0 to 20 ppm aluminum, especially from 0 to 10 ppm aluminum, and more preferably from 0 to 5 ppm aluminum. In order to measure the bulk polymer properties (e.g. PI or melt fracture), aqueous HCl is used to extract the aluminoxane from the polymer. Preferred cocatalysts, however, are inert, noncoordinating, boron compounds such as those described in EP 520732.

Substantially linear ethylene are produced via a continuous (as opposed to a batch) controlled polymerization process using at least one reactor (e.g., as disclosed in WO 93/07187, WO 93/07188, and WO 93/07189), but can also be produced using multiple reactors (e.g., using a multiple reactor configuration as described in USP 3,914,342) at a polymerization temperature and pressure sufficient to produce the interpolymers having the desired properties. The multiple reactors can be operated in series or in parallel, with at least one constrained geometry catalyst employed in at least one of the reactors. Substantially linear ethylene polymers can be prepared via the continuous solution, slurry, or gas phase polymerization in the presence of a constrained geometry

- 28 - catalyst, such as the method disclosed in EP 416,815-A. The polymerization can generally be performed in any reactor system known in the art including, but not limited to, a tank reactor (s), a sphere reactor (s), a recycling loop reactor (s) or combinations thereof and the like, any reactor or all reactors operated partially or completely adiabatically, nonadiabatically or a combination of both and the like. Preferably, a continuous loop-reactor solution polymerization process is used to manufacture the substantially linear ethylene polymer used in the present invention.

In general, the continuous polymerization required to manufacture substantially linear ethylene polymers may be accomplished at conditions well known in the prior art for Ziegler-Natta or Kaminsky-Sinn type polymerization reactions, that is, temperatures from 0 to 250°C and pressures from atmospheric to 1000 atmospheres (100 MPa) . Suspension, solution, slurry, gas phase or other process conditions may be employed if desired.

A support may be employed in the polymerization, but preferably the catalysts are used in a homogeneous (i.e., soluble) manner. It will, of course, be appreciated that the active catalyst system forms in si tu if the catalyst and the cocatalyst components thereof are added directly to the polymerization process and a suitable solvent or diluent, including condensed monomer, is used in said polymerization process. It is, however, preferred to form the active

29 - catalyst in a separate step in a suitable solvent prior to adding the same to the polymerization mixture.

The substantially linear ethylene polymers used in the present invention are interpolymers of ethylene with at least one C₃-C₂₀ α-olefin and/or C₄-C₁₈ diolefin. Copolymers of

ethylene and an α-olefin of C₃-C₂₀ carbon atoms are especially

preferred. The term "interpolymer" as discussed above is used herein to indicate a copolymer, or a terpolymer, or the like, where, at least one other comonomer is polymerized with ethylene or propylene to make the interpolymer.

Suitable unsaturated comonomers useful for polymerizing with ethylene include, for example, ethylenically unsaturated monomers, conjugated or non-conjugated dienes, polyenes, etc. Examples of such comonomers include C₃-C₂o α-olefins such as

propylene, isobutylene, 1-butene, 1-hexene, 1-pentene, 4- methyl-1-pentene, 1-heptene, 1-octene, 1-nonene, 1-decene, and the like. Preferred comonomers include propylene, 1- butene, 1-pentene, 1-hexene, 4-methyl-l-pentene and 1-octene, and 1-octene is especially preferred. Other suitable monomers include styrene, halo- or alkyl-substituted styrenes, vinylbenzocyclobutane, 1, 4-hexadiene, 1,7- octadiene, and naphthenics (e.g., cyclopentene, cyclohexene and cyclooctene) .

The density of the homogeneously branched ethylene polymer used in the invention is preferably less than 0.93 grams/centimeter (g/cc) , more preferably in the range from

0.85 g/cc to 0.92 g/cc, and most preferably in the range from

- 30 - 0.89 g/cc to 0.917 g/cc, as measured in accordance with ASTM D-792.

The molecular weight of the least one homogeneously branched ethylene polymer and the inventive blend composition can be conveniently determined using a melt index measurement according to ASTM D-1238, Condition 190°C/2.16 kg (formerly known as "Condition E" and also known as I₂) ■ Melt index is inversely proportional to the molecular weight of the polymer. Thus, the higher the molecular weight, the lower the melt index, although the relationship is not linear.

Also, practitioners will recognized that the melt index of the composition itself can affect performance properties. That is, in generally and although the relationship is not necessarily linear, a lower melt index (i.e., higher molecular weight) can yield a higher defined heat seal strength.

Preferably, the I₂ melt index of the at least one homogeneously branched ethylene polymer and the inventive blend composition is in the range of from 0.01 to 50 g/10 minutes, more preferably from 0.1 to 20, and most preferably from 0.4 to 12 g/10 minutes.

Other measurements useful in characterizing the molecular weight of ethylene polymers involve melt index determinations with higher weights, such as, for common example, ASTM D-1238, Condition 190°C/10 kg (formerly known as

"Condition N" and also known as Iχo) • The ratio of a higher weight melt index determination to a lower weight

- 31 - determination is known as a melt flow ratio, and for measured I_lO and the I₂ melt index values the melt flow ratio is conveniently designated as Iχo/1₂- Preferably, the substantially linear ethylene polymer when employed in the invention as the at least one homogeneously branched ethylene polymer has an I₁0/I₂ melt flow ratio greater than or equal to 6.8, more preferably greater than or equal to 8 and most preferably in the range of from 8.5 to 20 and especially in the range of 9 to 15. In the present invention, at least one homogeneously branched ethylene polymer is blended with less than or equal to 22, preferably less than or equal to 17, more preferably less than or equal to 12 weight percent, based on the total weight of the composition, of at least one thermoplastics resin having polymerized, reacted or grafted polar moieties. Suitable polar moieties (or comonomers; are selected from the group consisting of lactic acid, amide, chlorine, imide, alkyl acrylate, vinyl acetate, carboxylic acid, carboxylic ester, carbon monoxide, terephthalatic acid, adipic, caprolactone, aldehyde, epoxy, maleic anhydride and succinnic anhydride .

Suitable thermoplastic polar polymers for use as the adhesive component polymer include, but are not limited to, anhydride modified polyethylenes (for example, succinnic anhydride and maleic anhydride grafted to LDPE, ULDPE, LLDPE, MDPE, HDPE, ethylene-propylene interpolymer, ethylene-styrene interpolymer, homogeneously branched linear ethylene polymer

- 32 - and especially substantially linear ethylene polymer such as described, for example, in US Patent No. 5,346,963; chlorinated polyolefin (for example, chlorinated LDPE, ULDPE, LLDPE, MDPE, HOPE, ethylene-propylene interpolymer, ethylene- styrene interpolymer, homogeneously branched linear ethylene polymer and especially substantially linear ethylene polymer) ; free-radical initiated high pressure carbonyl- containing polyethylenes (for example, ethylene/acrylic acid (EAA) interpolymers, ethylene/methacrylic acid (EMAA) interpolymers ethylene/vinyl acetate (EVA) interpolymers, ethylene/methacrylate (EMA) interpolymers, ethylene/methyl methacrylate (EMMA) interpolymers, ethylene/ethyl acrylate (EEA) interpolymers, and ethylene/n-butyl acrylate (EnBA) ; especially those manufactured in accordance with the teachings described in US Patent No. 4,599,392 and US Patent No. 4,988,781); polyamide; polyolefin carbon monoxide interpolymer (for example, ethylene/carbon monoxide (ECO), copolymer, ethylene/acrylic acid/carbon monoxide (EAACO) terpolymer, ethylene/methacrylic acid/carbon monoxide (EMAACO) terpolymer, ethylene/vinyl acetate/carbon monoxide (EVACO) terpolymer and styrene/carbon monoxide (SCO) ) ; polyethylene terephthalate (PET); polyester urethane; chlorinated polyethylene; polylactic acid (PLA); polyether (for example, PEBAX); polyester/polyether block polymers (for example, HYTEL) ; and combinations thereof.

Especially preferred for use as the adhesive component polymer are ethylene methyl acrylate copolymers (supplied,

- 33 - for example, under the designation EMAC SP 2268T by Chevron) ; ethylene-vinyl acetate copolymers (supplied, for example, under the designation Elvax 3175LG by Dupont) ; ethylene n- butyl acrylate maleic anhydride terpolymers (supplied, for example, under the designation Lotader 341o by Elf Atochem) ; and ethylene-acrylic ester copolymers (supplied, for example, under the designation Lotryl 28MA07 by Elf Atochem) . The most especailly preferred adhesive component polymer is ethylene-vinyl acetate copolymers. When relatively high melting polymers are employed such as, for examples, some grades of polyamides and polyethers, a substantially low melting polar polymer (that is, DSC melting point less than 105°C such as, for example, an EAA copolymer containing 6.5-10% AA) or a plasticizer should also be blended with the homogeneously branched ethylene polymer. In one preferred embodiment, a polyamide is blended with a homogeneously branched ethylene polymer and an ethylene acrylic acid interpolymer. For such ternary blends with the substantially low melting polar polymer, the relatively high melting polar polymer should constitute no more than 5 to 20 weight percent of the total weight of the two polar polymers. Two suitable ternary blend compositions comprise Nylon 6 (or Nylon 66) and EAA and the other comprises PLA and EVA. Other preferred polymeric combination of more than one polar moiety or comonomer as the adhesive blend component is PLA-g- MAH; that is, a poly lactic acid and maleic anhydride grafted polymer such as described, for example, by Ma et al.,

- 34 - Polymeric Materials Science and Engineering, Proceedings of the ACS Division of Polymeric Materials Science and Engineering, v. 76, pp. 527-528, Washington, DC (1997), the disclosure of which is incorporated herein by reference. Suitable poly lactic acid (PLA) polymers for use in the invention are well known in the literature (e.g., see D. M. Bigg et al., "Effect of Copolymer Ratio on the Crystallinity and Properties of Polylactic Acid Copolymers", ANTEC '96, pp. 2028-2039; WO 90/01521; EP 0 515203A; and EP 0 748846A2, the disclosures of each of which are incorporated herein by reference) . Suitable poly lactic acid polymers are supplied commercially by Cargill Dow under the designation EcoPLA.

A high molecular weight wax may be added to the composition to improve the retortability of the composition. That is, for example, permit successful use in hot-fill and cook-in applications.

Suitable thermoplastic polyurethane for use in the invention are commercially available from The Dow Chemical Company under the designation PELLATHANE and also from another supplier under the designation ESTANE.

Suitable polyolefin carbon monoxide interpolymers can be manufactured using well known high pressure free-radical polymerization methods. However, they may also be manufactured using traditional Ziegler-Natta catalysis and even with the use of so-called homogeneous catalyst systems such as those described and referenced herein above.

35 - For superior adhesion to polyvinylidene chloride interpolymers, the carbon monoxide content of the polyolefin carbon monoxide interpolymer (as well as for the free-radical initiated high pressure carbonyl-containing polyethylenes) should preferably be in the range of from 7 to 16 weight percent, based on the total weight of the polymer and especially from 9 to 12 weight percent, based on the total weight of the polymer.

Suitable free-radical initiated high pressure carbonyl- containing ethylene polymers can be manufactured by any technique known in the art including the methods taught by Thomson and Waples in US Patent No. 3,520,861. Suitable ethylene vinyl acetate interpolymers for use in the invention are commercially available from various suppliers, including Exxon Chemical Company and Du Pont Chemical Company . Suitable ethylene/alkyl acrylate interpolymers are commercially available from various suppliers. Suitable ethylene/acrylic acid interpolymers are commercially available from The Dow Chemical Company under the designation PRIMACOR. Suitable ethylene/methacrylic acid interpolymers are commercially available from Du Pont Chemical Company under the designation NUCREL .

Preferred free-radical initiated high pressure carbonyl- containing ethylene polymers (especially EVA copolymers) are characterized as having improved thermal stability by having effective additive packages incorporated therein or, preferably by possessing inherently improved

- 36 - thermal/extrusion stability such as by being characterized by more favorable long chain branching characteristics. Such polymers with improved thermal/extrusion stability may be manufactured in accordance with the teachings in US. Patent No. 4,988,781. For example, ethylene vinyl acetate interpolymers with improved thermal/extrusion stability relative to ordinary ethylene vinyl acetate interpolymers are supplied Exxon Chemical Company.

Chlorinated polyethylene (CPE) , especially chlorinated substantially linear ethylene polymers, can be prepared by chlorinating polyethylene in accordance with well known techniques. Preferably, chlorinated polyethylene comprises equal tc or greater than 30 weight percent chlorine. Suitable chlorinated polyethylenes for use in the invention are commercially supplied by The Dow Chemical Company under the designation TYRIN.

Suitable anhydride grafted polyolefins for use in the invention may be manufactured by any technique known in the art, including those taught in US Patent No. 4,087,587; US Patent No. 4,087,588; US Patent No. 5,346,963; and US Patent No. 5,705,565.

Additives, for example, Irgafos® 168 made by Ciba Geigy Corp.)), are preferably added to protect the inventive blend composition from degradation during thermal processing steps such as pelletization, molding, extrusion, and characterization methods. Other additives to serve special functional needs include cling additives, for example, PIB,

- 37 - antiblocks, antislips, pigments, fillers and crosslinkers, may also be added to the inventive blend composition. In- process additives, for example, calcium stearate, or water, may also be used for other purposes, for instance, to deactivate residual catalyst.

Preferred polyvinylidene vinyl chloride interpolymers for use in the invention comprises from 5 to 30, more preferably 10 to 25, and most preferably from 15 to 20 weight percent vinyl chloride and, optionally at least one other copolymerizable ethylenically unsaturated monomer (s) such as, for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, acrylonitrile, methacrylonitrile, all combinations thereof and the like. Polyvinylidene vinyl chloride methyl acrylate are especially preferred for use in the invention. Suitable PVdC for use in the invention is commercially available from The Dow Chemical Company under the designations SARAN and SARAN-MA.

The compositions can be made via any known technique, including, but not limited, dry blending and extrusion melt mixing of component polymers, in si tu polymerizations and interpolymerizations that involve multiple reactors and/or multiple catalyst systems, and aqueous dispersion preparation (for example, as described in US Patent No. 5,574,091). In general, practitioners will recognize that melt mixing and high shear extrusion during fabrication can improve the homogeneity of compositions prepared by dry blending. The inventive multilayer structure made using

- 38 - conventional fabrication techniques known in the art. Another embodiments of the invention include fabricating the inventive composition into the form of a film, sheet (that is, a film having a thickness greater than 20 mils (0.51 mm)), coating, and a thermoformed or molded article. As such, fabrication can include a lamination and coextrusion technique or combinations thereof, or using the inventive composition alone to provide a monolayer sealant film, and can also specifically include blown film, cast film, extrusion coating, injection molding, blow molding, thermoformmg, profile extrusion, pultrusion, compression molding, rotomoldmg, or injection blow molding operations or combinations thereof. Fabrication of multilayer structure of the invention can also include elaborate orientation techniques such as "tenter framing" or a "double bubble," "tape bubble," "trapped bubble" process or combinations thereof and the like. However, the preferred fabrication technique is a blown film coextrusion.

Packaging Foods With Plastics, by Wilmer A. Jenkins and James P. Harrington (1991); "Coextrusion For Barrier Packaging" by W.J. Schrenk and C.R. Finch, Society of Plastics Engineers RETEC Proceedings, June 15-17 (1981), pp. 211-229; K.R. Osborn and W.A. Jenkins in "Plastic Films, Technology and Packaging Applications" (Technomic Publishing Co., Inc. (1992)); and "Laminations Vs. Coextrusion" by D. Dumbleton (Converting Magazine (September 1992) describe blown or cast fabrication including lamination and

- 39 - coextrusion techniques.

The double bubble technique is described by Pahkle in US Patent 3,456,044.

The composition or film of the invention has utility in a variety of applications. Suitable applications include, for example, but are not limited to, monolayer packaging films; multilayer packaging structures consisting of other materials or layers such as, for example, high density polyethylene, biaxially oriented polypropylene or biaxially oriented ethylene polymer for shrink film and barrier shrink applications; packages formed via form/fill/seal machinery; packaging structures; cook-in food packages; hot-fill packages; compression filled packages; heat sealable stretch wrap packaging film such as, for example, fresh produce packaging and fresh red meat retail packaging; as well as in packages, containers, bags and lidding stock for uses such as, for example, but not limited, cereal box liners, cake mix packages, cracker tubes, medical device and item packaging, snack food convenience packages and containers, and gaskets. Multilayer structures may further include additional structural layers such as AFFINITY™ polyolefin plastomers, available from The Dow Chemical Company, ENGAGE™ polyolefin elastomers, available from Dupont Dow Elastomers, DOWLEX™

LLDPE, available from The Dow Chemical Company, ATTANE™

ULDPE, available from The Dow Chemical Company, EXACT and EXCEED resins from The Exxon Chemical Corporation, TAFMER resins from Mitsui Chemical Corporation or blends of any of

- 40 - these polymers with each other or with another polymer, such as a low density polyethylene (LDPE) resin or a high density polyethylene resin.

In general, multilayer structures of the present invention (whether biaxially or monoaxially oriented or not) can include, but are not limited to, more than one barrier layers, tie layers, and/or structural layers. Various materials can be used for these layers, with some of them being used as more than one layer in the same multilayer structure. Some of these materials include: paper, glassine, foil, nylon, ethylene/vinyl alcohol (EVOH) copolymers, polyethylene terepthalate (PET) , and polypropylene, especially, oriented polypropylene (OPP) .

Generally, the multilayer structure of the present invention can comprise any number of layers or materials or polymers deemed required for a targeted application, including more than one inventive film layer as well as only one layer (monolayer film) . However, typically, the multilayer structure of the invention comprises from 2 to 7 layers.

Practitioners will recognize that higher film thicknesses will generally tend to affect performance properties. In general, film structure can be of any thickness demanded by a particular target application. The thickness of the multilayer structure can range from 0.3 to 20 mils (0.008 to 0.51 mm), preferably from 0.4 to 12 mils (0.01 to 0.3 mm). For packaging or containing high-sugar

- 41 - content food and moisture or flavor sensitive items, structure thicknesses will generally be higher. The thickness of the inventive adhesive layer will preferably be in the range of from 0.1 to 1 mil (0.0025 to 0.025 mm), and even thinner where dispersions are employed

EXAMPLES

In evaluation to determine the adhesiveness of various polymers to a PVdC, less than 10 weight percent of an ethylene vinyl acetate copolymer containing 9 weight percent vinyl acetate and supplied by Exxon Chemical Company under the designation ESCORENE 409.09 was admixed with a substantially linear ethylene polymer supplied by The Dow Chemical Company. The substantially linear ethylene polymer was AFFINITY Plastomer 1280 and had a 0.900 g/cm³ density and a 6.0 12 melt index. This blend (Inventive Example 1) was coextruded into blown film with a layer of SARAN resin film interpose between two layers of the blend film. The interlayer adhesion at the blend/SARAN interface was determined using an Instron and a T-peel test. The interlayer adhesion at the interface was measured to be 2,100 g/25 mm.

Example 1 was repeated except the substantially linear ethylene polymer was blown coextruded with SARAN without the addition the EVA or any other polymer (comparative example

2). Interlayer adhesion for this comparative example was found to be substantially non-existent; that is, less than 40 g/25 mm.

- 42 - In another evaluation, several resins were tested for their usefulness as adhesive component polymers in AFFINITY Plastomer 1280. The evaluation included AFFINITY Plastomer 1280 and a poly lactic acid polymer as controls and two instances of a ternary polymer blend. In this evaluation, 1.5 to 2 inch (3.8 to 5.1 cm) wide, 0.125 to 0.25 inch (0.3 to 6 cm) thick coextruded ribbon for each sample was fabricated with PVdC as the core layer and the adhesive polymer blend (that is, the AFFINITY Plastomer 1280 plus the adhesive component polymer) as the encapsulating outer layer. The ribbons were fabricated on a 64 mm diameter Egan extrusion line equipped with a 25 mm diameter side arm extruder. The PVdC flow was through the main 64 mm extruder and the adhesive polymer blend flowed through the 25 mm side arm extruder. The PVdC used in this evaluation was supplied by The Dow Chemical Company under the designation XU- 32046.31. The various polymers used as the adhesive component polymer are listed in Table 1. The adhesive component polymers were used at both 10 and 20 weight percent, based on the total weight of the adhesive polymer blend.

Within 30 minutes of fabrication, each coextruded ribbon sample was cut into one inch (2.5 cm) wide strips, scored and its two layers were partially separated. Each sample was then rated for its interlayer adhesiveness at 180 degree using a relatively constant manual pull. A rating of 0 was an indication of substantially nonexistent adhesiveness and a rating of 4 was an indication of nearly inseparable adhesiveness. Table 1 provides the adhesive ratings for the various samples.

- 43 - Table 1

Example Ribbon Outer Layer Adhesive Rating

3 10 wt% Tyrin 3611 P - AFFINITY PL 1280

4 20 wt% Tyrin 3611 P - AFFINITY PL 1280

5 10 wt% PLA 4040D - AFFINITY PL 1280

6 20 wt% PLA 4040D - AFFINITY PL 1280

7 PLA 4040D

8 20 wt% KR05 K-resin - AFFINITY PL 1280

9 10 wt% KR05 K-resin - AFFINITY PL 1280

10 20 wt% Estane 58224 - AFFINITY PL 1280

11 10 wt% Estane 58224 - AFFINITY PL 1280

12 10 wt% Catalloy KS089P - AFFINITY PL 1280

13 20 wt% Catalloy KS089P - AFFINITY PL 1280

14 10 wt% Elvaloy HP-441 - AFFINITY PL 1280

15 20 wt% Elvaloy HP-441 - AFFINITY PL 1280

16 20 wt% EMAC SP 2268T - AFFINITY PL 1280 3

17 10 wt% EMAC SP 2268T - AFFINITY PL 1280 3

18 10 wt% Elvax 3175LG - AFFINITY PL 1280 4

19 20 wt% Elvax 3175LG - AFFINITY PL 1280 4

20 10 wt% Lotader 3410 - AFFINITY PL 1280 3

21 20 wt% Lotader 3410 - AFFINITY PL 1280 3

22 20 wt% Lotryl 28MA07 - AFFINITY PL 1280 3

23 10 wt% Lotryl 28MA07 - AFFINITY PL 1280 3

24 20 wt% Kraton FG 1901 - AFFINITY PL 1280

25 10 wt% Kraton FG 1901 - AFFINITY PL 1280

26 10 wt% Ultramid C35/Primacor 3330 - AFFINITY PL

1280

27 20 wt% Ultramid C35/Primacor 3330 - AFFINITY PL

1280

28 10 wt% Ultramid C35 - AFFINITY PL 1280

29 20 wt% Ultramid C35 - AFFINITY PL 1280

30 AFFINITY PL 1280

44 -

Claims

We Claim

1. A composition suitable for coextrusions with polyvinylidene chloride interpolymers and having interlayer adhesion to polyvinylidene chloride interpolymers comprising: a) less than or equal to 22 weight percent, based on the total weight of the composition, of at least one adhesive polymer comprising at least one polymerized, reacted or grafted polar moiety or comonomer selected from the group consisting of lactic acid, amide, chlorine, imide, alkyl acrylate, vinyl acetate, carboxylic acid, carboxylic ester, carbon monoxide, terephthalatic acid, adipic, caprolactone, aldehyde, epoxy, maleic anhydride and succinnic anhydride, and b) greater than or equal to 78 weight percent, based on the total weight of the composition, of at least one homogeneously branched ethylene polymer characterized as having: i. a density less than or equal to 0.91 gram/centimeter (g/cc) and ii. a short chain branching distribution index (SCBDI) greater than 50 percent.

2. The composition of Claim 1 wherein the b) component comprises

(A) from 5 to 95 weight percent, based on the total weight of the polymer mixture, of at least one first ethylene polymer which is a homogeneously branched

- 45 - substantially linear ethylene polymer or a homogeneously branched linear ethylene polymer, wherein the first ethylene polymer is characterized as having:

i. an I₂ melt index in the range of from greater than 0.14 g/10 minutes to less than 0.67 g/10 minutes, as measured by ASTM D- 1238 Condition 190┬░C/2.16 kg, ii. a density in the range of 0.85 to 0.92 g/cc, as measured in accordance with ASTM D-792, iii. a molecular weight distribution, M_w/M_n as determined by gel permeation chromatography of less than 3.5, iv. a single differential scanning calorimetry, DSC, melting peak between -30 and 150┬░C, and v. a short chain branching distribution index

(SCBDI) greater than 50 percent, and

(B) from 5 to 95 weight percent, based on the total weight of the polymer mixture, of at least one second ethylene polymer which is a homogeneously branched ethylene polymer or a heterogeneously branched linear ethylene polymer wherein the second ethylene polymer is characterized as having a density in the range of 0.89 g/cc to 0.965 g/cc, wherein the polymer mixture is characterized as having a density of from 0.89 g/cc to 0.93 g/cc, as measured in accordance with ASTM D-792, and an I₂ melt index in the range of from 1 g/10 minutes to 5 g/10 minutes, as measured by ASTM

D-1238 Condition 190┬░C/2.16 kg, and wherein the molecular

weight of the at least one first polymer is higher than the molecular weight of the at least one second polymer.

- 46 -

3. The composition of Claim 1 wherein the at least one adhesive polymer is selected from the group consisting of ethylene alkyl acrylate copolymers, ethylene-vinyl acetate copolymers, ethylene/alkyl acrylate/maleic anhydride terpolymers, and ethylene/carboxylic ester copolymers.

4. The composition of Claim 1 wherein the at least one adhesive polymer is an ethylene methyl acrylate copolymer.

5. The composition of Claim 1 wherein the at least one adhesive polymer is an ethylene-vinyl actetate copolymer.

6. The composition of Claim 1 wherein the at least one adhesive polymer comprises is an ethylene/n-butyl acrylate/maleic anhydride terpolymer.

7. The composition of Claim 1 wherein the at least one adhesive polymer is an ethylene/acrylic ester copolymer.

8. The composition of Claim 1 wherein the at least one adhesive polymer comprises vinyl acetate.

9. The composition of Claim 1 wherein the at least one adhesive polymer comprises at least one carboxylic acid.

10. The composition of Claim 1 wherein the at least one

- 47 - adhesive polymer comprises at least one carboxylic ester.

11. The composition of Claim 1 wherein the at least one adhesive polymer comprises terephthalatic acid.

12. The composition of Claim 1 wherein the at least one adhesive polymer comprises adipic.

13. The composition of Claim 1 wherein the at least one adhesive polymer comprises caprolactone.

14. The composition of Claim 1 wherein the at least one adhesive polymer comprises an aldehyde.

15. The composition of Claim 1 wherein the at least one adhesive polymer comprises an epoxy end group.

16. The composition of Claim 1 wherein the at least one adhesive polymer comprises maleic anhydride.

17. The composition of Claim 1 wherein the at least one adhesive polymer comprises succinnic anhydride.

18. A multilayer film structure having a barrier film layer and an adhesive layer adjacent to the barrier film layer, the adhesive layer comprising:

- 48 a) less than or equal to 22 weight percent, based on the total weight of the composition, of at least one adhesive polymer comprising at least one polymerized, reacted or grafted polar moiety or comonomer selected from the group consisting of lactic acid, amide, chlorine, imide, alkyl acrylate, vinyl acetate, carboxylic acid, carboxylic ester, carbon monoxide, terephthalatic acid, adipic, caprolactone, aldehyde, epoxy, maleic anhydride and succinnic anhydride, and

b) greater than or equal to 78 weight percent, based on the total weight of the composition, of at least one homogeneously branched ethylene polymer characterized as having: i. a density less than or equal to 0.91 gram/centimeter (g/cc) and ii. a short chain branching distribution index (SCBDI) greater than 50 percent.

19. The multilayer structure of Claim 18 wherein the structure is fabricated using a coextrusion technique.

20. The multilayer structure of Claim 19 wherein the coextrusion technique is a blown film technique.

21. The multilayer structure of Claim 18 wherein the structure comprises at least 3 layers.

22. The multilayer structure of Claim 18 wherein the structure comprises at least 3 thermoplastic film layers

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23. The multilayer structure of Claim 18 wherein the structure comprises at least 5 layers.

24. The multilayer structure of Claim 18 wherein the structure comprises at least 7 layers.

25. The multilayer structure of Claim 18 wherein the structure is a balanced structure having an odd of number of layers with at least one barrier film core layer at the center of the structure.

26. The composition of Claim 1 wherein the weight percent of component A is less than or equal to 17 and the weight percent of component B is greater than or equal to 73.

27. The composition of Claim 1 wherein the weight percent of component A is less than or equal 12 and the weight percent of component B is greater than or equal to 88.

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