WO1999006476A1

WO1999006476A1 - Pouch for packaging flowable materials

Info

Publication number: WO1999006476A1
Application number: PCT/US1998/016057
Authority: WO
Inventors: Daniel James Falla
Original assignee: The Dow Chemical Company
Priority date: 1997-08-04
Filing date: 1998-07-28
Publication date: 1999-02-11
Also published as: TW403709B; AR016585A1; AU8605798A

Abstract

An environmentally friendly polymer film pouch made from a homogeneously branched linear ethylene interpolymer film structure for the packaging of flowable materials such as milk, is disclosed. A pouch made from a multilayer film structure such as a two-layer or a three-layer coextruded film containing at least one seal layer of a homogeneously branched linear polyethylene is also disclosed. A process for making a pouch for packaging flowable materials using a homogeneously branched linear ethylene interpolymer film structure is also disclosed.

Description

POUCH FOR PACKAGING FLOWABLE MATERIALS

This invention relates to a pouch used in consumer packaging useful for packaging flowable materials, (for example, liquids such as milk). The pouch is made from certain film structures comprising at least one homogeneously branched linear ethylene interpolymer.

U.S. Patent Nos. 4,503,102, 4,521,437, 5,288,531, and 5,360,648 disclose the preparation of a polyethylene film for use in the manufacture of a disposable pouch for packaging of liquids such as milk. U.S. Patent No. 4,503,102 discloses pouches made from a blend of a linear ethylene copolymer copolymerized from ethylene and an alpha- olefin at the C4-C10 range and an ethylene- vinyl acetate polymer copolymerized from ethylene and vinyl acetate. The linear polyethylene copolymer has a density of from

0.916 to 0.930 grams/cubic centimeter (g/cm^) and a melt index of from 0.3 to 2.0 grams/ 10 minutes (g/10 min). The ethylene-vinyl acetate polymer has a weight ratio of ethylene to vinyl acetate from 2.2: 1 to 24: 1 and a melt index of from 0.2 to 10 g/10 min. The blend disclosed in U.S. Patent No. 4,503,102 has a weight ratio of linear low density polyethylene to ethylene-vinyl acetate polymer of from 1.2: 1 to 4: 1. U.S. Patent No. 4,503,102 also discloses laminates having as a sealant film the aforementioned blend.

U.S. Patent No. 4,521,437 describes pouches made from a sealant film which is from 50 to 100 parts of a linear copolymer of ethylene and octene- 1 having a density of from 0.916 to 0.930 g/cm^ and a melt index of 0.3 to 2.0 g/10 min and from 0 to 50 parts by weight of at least one polymer selected from the group consisting of a linear copolymer of ethylene and a Cj-Cio alpha-olefin having a density of from 0.916 to 0.930 g/cm-' and a melt index of from 0.3 to 2.0 g/10 min, a high-pressure polyethylene having a density of from 0.916 to 0.924 g/crn-^ and a melt index of from 1 to 10 g/10 min and blends thereof. The sealant film disclosed in the U.S. Patent No. 4,521,437 is selected on the basis of providing (a) pouches with an M-test value substantially smaller, at the same film thickness, than that obtained for pouches made with film of a blend of 85 parts of a linear ethylene/butene- 1 copolymer having a density of about 0.919 g/crc and a melt index of about 0.75 g/10 min and 15 parts of a high pressure polyethylene having a density of about 0.918 g/crn-^ and a melt index of 8.5 g/10 min, or (b) an M(2)-test value of less than about 12 percent, for pouches having a volume of from greater than 1.3 to 5 liters, or (c) an M(1.3)-test value of less than about 5 percent for pouches having a volume of from 0.1 to 1.3 liters. The M, M(2) and M(1.3)-tests are defined pouch drop tests in U.S. Patent No. 4,521,437. The pouches may also be made from composite films in which the sealant film forms at least the inner layer.

U.S. Patent No. 5,288,531 discloses pouches made from a film structure having a blend of (a) from 10 to 100 percent by weight of at least one polymeric seal layer of an ultra low density linear ethylene copolymer interpolymerized from ethylene and at least one alpha-olefin in the range of C3-C10 with a density of from 0.89 g/cm³ to less than 0.915 g/cm³ and (b) from 0 to 90 percent by weight of at least one polymer selected from the group consisting of a linear copolymer of ethylene and a C3-C 18-alpha-olefin having a density of greater than 0.916 g/cm and a melt index of from 0.1 to 10 g/10 minutes, a high-pressure low density polyethylene having a density of from 0.916 to 0.930 g/cm^' and a melt index of from 0.1 to 10 g/10 minutes, or ethylene-vinyl acetate copolymer having a weight ratio of ethylene to vinyl acetate from 2.2: 1 to 24: 1 and a melt index of from 0.2 to 10 g/10 minutes. The heat seal layer in the U.S. Patent No. 5,288,531 provides improved hot tack strength and lower heat seal initiation temperature to a two-layer or three-layer coextruded multilayer film structure described therein.

U.S. Patent No. 5,360,648 discloses pouches made from a film structure having a blend of (a) from 10 to 100 percent by weight of at least one homogeneously branched substantially linear ethylene/α-olefin interpolymer having certain characterizing properties described therein, and (b) from 0 to 90 percent by weight of at least one polymer selected from the group consisting of a heterogeneously branched linear ethylene/C3-C 18 α-olefin copolymer, a high-pressure low density polyethylene, and an ethylene-vinyl acetate copolymer. The film structure of the U.S. Patent No. 5,360,648 provides, among other things, a broad heat sealing range.

The polyethylene pouches known in the prior art have some deficiencies. The problems associated with films known in the prior art relate to the sealing properties and performance properties of the film for preparing pouches. In particular, prior art films made into pouches have a high incident of "leakers", that is, seal defects such as pinholes which develop at or near the seal in which flowable material, for example milk, escapes from the pouch. Although the seal and performance properties of the prior art films have been satisfactory, there is still a need in the industry for better seal and performance properties in films for manufacture of hermetically sealed pouches containing flowable materials More particularly, there is a need for improved sealing properties of the film such as higher hot tack strength and lower hot tack and heat seal initiation temperature in order to improve the processabihty of the film and to improve pouches made from the films For example, the line speed of known packaging equipment used for manufacturing pouches such as form, fill and seal machines, is currently limited by the sealing properties of the film used in the machines Prior art polyethylene films generally have relatively low hot tack strength, high hot tack seal initiation temperatures and a narrow sealing range Therefore, the rate at which a form, fill and seal machine can produce pouches is limited If the hot tack strength could be increased and the heat seal temperature range where one could obtain strong seals is broadened, then the speed of a form, fill and seal machine can be increased and, thus, the rate at which pouches can be produced can be increased Until the present invention, many have attempted to broaden the heat seal temperature range of pouch film with varying degrees of success It is desired to provide a polymer film structure for a pouch container having a higher hot tack strength over a broader range than prior art films, or a suitable alternative thereto

It is desired to provide a polyethylene film structure for a pouch having a broad heat sealing range with performance properties as good or better than the known pπor art pouch films

It is also desired to provide a film structure for a pouch container having a heat seal layer such that the film structure has a broader sealing range for pouch conversion and has acceptable physical properties in the finished product

It is further desired to provide a pouch made from the aforementioned film structures such that the pouch has a reduced failure rate

It has now been discovered that homogeneously branched linear ethylene/α-olefin mterpolymers offer significant advantages m film structures of pouches The homogeneously branched linear ethylene/α-olefin mterpolymers, when used as a seal layer, have higher hot tack strength than homogeneously branched subtantially linear ethylene/α-olefin mterpolymers They have good heat sealabihty at temperatures lower than those necessary for heterogeneously branched linear ethylene/α-olefin mterpolymers and are also easily processed on conventional film and heat seal equipment Pouches made from film structures comprising the homogeneously branched linear ethylene/α- olefin interpolymers, when used as a seal layer or a combination thereof as a core layer, also have surprisingly good bursting performance.

One aspect of the present invention is directed to a pouch made from a film structure in tubular form and having transversely heat sealed ends, the film structure having at least one film layer comprising:

(I) from 10 to 100 percent by weight of at least one layer comprising at least one homogeneously branched linear ethylene/α-olefin interpolymer characterized as having:

(a) a composition distribution branching or breadth index (CDBI) greater than 50 percent, and

(b) a molecular weight distribution, M_w/M_n, < from 1.5 to 2.5; and

(II) from 0 to 90 percent by weight of at least one polymer selected from the group consisting of a heterogeneously branched linear ethylene/C3-Cι 8 α-olefin copolymer, a high-pressure low density polyethylene, and an ethylene-vinyl acetate copolymer.

One embodiment of the present invention is a pouch made from a two-layer (that is, A/B) coextruded film containing an outer layer of a heterogeneously branched linear low density polyethylene and an inner seal layer of the aforementioned homogeneously branched linear ethylene interpolymer.

Another embodiment of the present invention is a pouch made from a three-layer (that is, A/B/A or A/B/C) coextruded film containing an outer layer and a core layer comprising heterogeneously branched linear low density polyethylene (either the same or different heterogeneously branched linear low density polyethylenes) or a high pressure low density polyethylene and an inner seal layer comprising the aforementioned homogeneously branched linear ethylene interpolymer.

Another aspect of the present invention is a process for preparing the aforementioned pouch.

Another aspect of the present invention is directed to a pouch made from a film structure in tubular form and having transversely heat sealed ends, the film structure having at least one film layer comprising:

(I) from 10 to 100 percent by weight of at least one layer comprising at least one homogeneously branched linear ethylene polymer, wherein the homogeneously branched linear ethylene polymer is characterized as having (a) a density from 090 g/cc to 094 g/cc,

(b) a CBDI greater than 50 percent, and

(c )a single differential scanning caloπmetry (DSC) melting peak between -30 and 150 C, and (II) from 0 to 90 percent by weight of at least one polymer selected from the group consisting of a heterogeneously branched linear ethylene/C3-Ci8 α-olefin copolymer, a high-pressure low density polyethylene, and an ethylene-vinyl acetate copolymer

Another embodiment of the present invention is a pouch made from a two-layer (that is, A/B) coextruded film containing an outer layer of a heterogeneously branched linear low density polyethylene and an inner seal layer of the aforementioned homogeneously branched linear ethylene polymer

Yet another embodiment of the present invention is a pouch made from a three-layer (that is, A B/A or A/B/C) coextruded film containing an outer layer and a core layer comprising heterogeneously branched linear low density polyethylene (either the same or different heterogeneously branched linear low density polyethylenes) or a high pressure low density polyethylene and an inner seal layer comprising the aforementioned homogeneously branched linear ethylene polymer

Another aspect of the present invention is a process for preparing the aforementioned pouch

Film structures for the pouches of the present invention have a better seal at lower sealing temperatures and greater hot tack strength than currently obtainable with commercially available film Use of the films for making pouches of the present invention in form, fill and seal machines leads to machine speeds higher than currently obtainable with the use of commercially available film

Figure 1 shows a perspective view of a pouch package of the present invention

Figure 2 shows a perspective view of another pouch package of the present invention

Figure 3 shows a partial, enlarged cross-sectional view of the film structure of a pouch of the present invention Figure 4 shows another partial, enlarged cross-sectional view of another embodiment of the film structure of a pouch of the present invention

Figure 5 shows yet another partial, enlarged cross-sectional view of another embodiment of the film structure of a pouch of the present invention

Firgure 6 is a graphical illustration of maximum film hot tack strength versus resin density for a pouch of the present invention, based on resms 9-1 1 and comparative res s 1 -3 of Table 3

The pouch of the present invention, for example as shown in Figures 1 and 2, for packaging flowable materials is manufactured from a monolayer film structure of a polymeric seal layer which is a homogeneously branched linear ethylene/α-olefin interpolymer (referred to hereinafter as "HBLEP")

The HBLEP of the present invention is generally an interpolymer of ethylene with at least one α-olefin having from 3 to 20 carbon atoms The term

"interpolymer" is used herein to indicate a copolymer, or a terpolymer, or the like That is, at least one other comonomer is polymerized with ethylene to make the interpolymer For example, a HBLEP terpolymer comprising ethylene/ 1 -octene/ 1-hexene may be employed m the film structure as the polymeric seal layer Copolymers of ethylene and a C3-C20 α-olefin are especially preferred, for example, the HBLEP may be selected from ethylene/propene, ethylene/ 1-butene, ethylene/ 1-pentene, ethylene/4-methyl- 1-pentene, ethvlene/ 1-hexene, ethylene/ 1-heptene, ethylene/ 1 -octene and ethylene/ 1 -decene copolymers, preferably ethylene/ 1 -octene copolymer For the preferred polymers used in the instant invention, the term

"homogeneously branched linear ethylene polymer" means that the olefin polymer has a homogeneous short branching distribution but does not have long chain branching That is, the linear ethylene polymer has an absence of long chain branching Such polymers include linear low density polyethylene polymers and linear high density polyethylene polymers and can be made using polymenzation processes (for example, as described by Elston in USP 3,645,992) which provide uniform branching (that is, homogeneously branched) distribution Uniform branching distributions are those in which the comonomer is randomly distributed withm a given interpolymer molecule and wherein substantially all of the interpolymer molecules have the same ethylene/comonomer ratio within that interpolymer In his polymerization process, Elston uses soluble vanadium catalyst system to make such polymers, however others such as Mitsui Petrochemical Corporation and Exxon Chemical Company have used so-called single site catalyst systems to make linear ethylene polymers having a similar homogeneous structure Examples of such linear homogeneously branched ethylene polymers include TAFMER^®, a trademark of and made by Mitsui Petrochemical Company, and both EXACT^® and EXCEED^®, trademarks of and made by Exxon Chemical Company

The term "homogeneously branched linear ethylene polymer" does not refer to high pressure branched polyethylene which is known to those skilled in the art to have numerous long chain branches Typically, the homogeneously branched linear ethylene polymer is an ethylene/OC-olefin interpolymer, wherein the °c-olefιn is at least one C3-C20 Ot-olef in (for example, 1-propylene, 1-butene, 1-pentene, 4-methyl- 1-pentene

1-hexene, 1 -octene), preferably wherein at least one of the α-olefins is 1 -octene Most preferably, the ethylene/α-olefin interpolymer is a copolymer of ethylene and a C3-C20 OC -olefin, especially an ethylene/C4-C_D α-olefin copolymer

Further, the term "homogeneously branched linear ethylene polymer" does not refer to, and differs from, homogeneously branched substantially linear polymer (referred to hereinafter as "SLEP"), such as described by Falla et al in U S Patent 5,360,648 In a SLEP, the interpolymer backbone is substituted with 0 01 to 3 long chain branches/ 1000 carbons Examples of SLEP include ENGAGE^® and AFFINITY^®, trademarks of and made by The Dow Chemical Company

The Short Chain Branch Distribution Index (SCBDI) or Composition Distribution Branch Index (CDBI) is defined as the weight percent of the polymer molecules having a comonomer content within 50 percent of the median total molar content The CDBI of a polymer is readily calculated from data obtained utilizing well known techniques, such as, for example, temperature rising elution fractionation (abbreviated herein as "TREF") as descπbed, for example, in, Journal of Polymer Science, Poly Phvs Ed , Vol 20, p 441 (1982) by Wild et al, or in U S Patent 4,798,081 The SCBDI or CDBI for the homogeneously branched linear ethylene/α-olefin interpolymers and copolymers used in the present invention is greater than about 50 percent, preferably greater than about 70 percent, more preferably greater than about 80 percent and most preferable greater than about 90 percent The linear ethylene/α-olefin mterpolymers and copolymers used in this invention essentially lack a measurable "high density" fraction as measured by the TREF technique The "high density" fraction includes linear homopolymer polyethylene. The "high density" polymer fraction can be described as a polymer fraction with a degree of branching less than or equal to about 2 methyls/1000 carbons. The terms "essentially lacks a measurable high density fraction" means that the linear interpolymers and copolymers do not contain a polymer fraction with a degree of branching less than or equal to about 2 methyls/1000 carbons.

The term "narrow short chain distribution" as applied herein refers to mterpolymers and pertains to the distribution of α-olefin monomer branches of the interpolymer as characterized by its SCBDI or CDBI. The term is defined herein as greater than about 50 weight percent of the interpolymer molecules have an α-olefin monomer content within 50 percent of the median total molar α-olefin monomer content. Techniques for calculating CDBI is generally described hereinabove. However, the preferred TREF technique does not include purge quantities in CDBI calculations More preferably, the monomer distribution of the interpolymer and CDBI are determined using ¹ C nuclear magnetic resonance analysis in accordance with techniques described in US Patent 5,292,845 and in Rev Macromol Chem Phvs , C29, pp. 201-317, by J C Randall. The homogeneously branched very low density polyethylene (hmVLDPE) and homogeneously branched linear low density polyethylene (hmLLDPE) are well known in the art, for example, Elston's disclosure in U S. Pat. No. 3,645,992. hmVLDPE and hmLLDPE can be prepared in solution, slurry or gas phase processes using hafnium, zirconium and vanadium catalyst systems In U.S. Pat No 4,937,299, Ewen, et al describe a method of preparing such polyethlenes using metallocene catalysts. hmVLDPE and hmLLDPE are linear polyethylenes which are homogeneously branched polymers, but like the Ziegler-type heterogeneous linear polyethylene, they do not have any long- chain branching. Commercial examples of these polymers are sold by Mitsui Petrochemical under the trademark TAFMER^® and by Exxon Chemical under the trademarks EXACT^® and EXCEED^®.

For the preferred homogeneously branched linear ethylene polymers the term "homogeneously branched" means that the comonomer is randomly distributed within a given interpolymer molecule and wherein substantially all of the interpolymer molecules have the same ethylene/comonomer ratio within that interpolymer. The term "linear ethylene/α-olefm interpolymer" does not refer to high pressure branched (free- radical polymerized) polyethylene which is known to those skilled in the art to have numerous long chain branches. The homogeneously branched linear ethylene/α-olefin copolymers and interpolymers of the present invention have a single melting point, as opposed to traditional Ziegler polymerized (heterogeneously branched) polymers having two or more melting points, as determined using differential scanning calorimetry (DSC) over a temperature range of from -20°C to 150°C. In addition, the novel homogeneously branched linear ethylene/α-olefin copolymers and interpolymers have melting points which correlate with the density of the copolymer or interpolymer. As the density of the polymer decreases, the peak melting decreases in a direct linear relationship. In contrast, heterogeneously branched ethylene polymers have peak melting points which do not vary substantially with the density of the polymer, primarily due to the presence of a high density polymer fraction which melts at about 122°C (the melting point of homopolymer linear polyethylene).

The density of the homogeneously branched linear ethylene/α-olefin interpolymers or copolymers (as measured in accordance with ASTM D-792) for use in the present invention is generally less than about 0.94 g/cm^> and preferably from 0.90 g/cπ to 0.94 g/cπ

Generally, the homogeneously branched linear ethylene/α-olefin polymer is used alone in the seal layer of the film or film structure. However, the homogeneously branched linear ethylene/α-olefin polymer can be blended with other polymers for use as the heat seal layer. Generally, the amount of the homogeneously branched linear ethylene/α-olefin polymer is from 10 percent to 100 percent, by weight of the polymer composition for the film structure.

The molecular weight of the homogeneously branched linear ethylene/α- olefin interpolymers and copolymers for use in the present invention is conveniently indicated 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 12)- Melt index is inversely proportional to the molecular weight of the polymer. Thus, the higher the molecular weight, the lower the melt index. The relationship, however, is not linear. The melt index for the homogeneously branched linear ethylene/α-olefin interpolymers and copolymers of the present invention is generally about 10 grams/10 minutes (ldg/10 min) or less, preferably from 0.01 g/10 min to 10 g/10 min, most preferably 0.4 g/10 minutes to 1.2 g/10 minutes.

Another measurement useful in characterizing the molecular weight of the homogeneously branched linear ethylene/α-olefin interpolymers and copolymers is conveniently indicated using a melt index measurement according to ASTM D-1238, Condition 190°C/10 kg (formerly known as "Condition (N)" and also known as Iio). The ratio of these two melt index terms is the melt flow ratio and is designated as 110^2- F°^r the homogeneously branched linear ethylene polymers, the I₁₀ I₂ ^ratιo correlates with the molecular weight distribution, i.e., as M_w/M_n increases Iιo/I₂ also increases. However, since the homogeneously branched linear ethylene polymers have a narrow M_w/M_n (from 1 5 to 2.5), the I₁0/I₂ ratio will be low (that is, about 6 5)

The molecular weight distribution (M /M_n) of the homogeneously branched linear ethylene/α-olefin mterpolymers and copolymers is analyzed by gel permeation chromatography (GPC) on a Waters 150C high temperature chromatographic unit equipped with three mixed porosity columns (Polymer Laboratories 10^, 10^, 10^, and 10"), operating at a system temperature of 140°C The solvent is 1,2,4- tπchlorobenzene, from which 0 3 percent by weight solutions of the samples are prepared for injection The flow rate is 1 0 millihters/minute and the injection size is 200 microliters.

The molecular weight determination 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 using appropriate Mark-Houwink coefficients for polyethylene and polystyrene (as described by Williams and Ward in Journal of Polymer Science, Polymer Letters, Vol 6, (621) 1968) to derive the following equation

^polyethylene = a * (Mp₀iy_Styrene)

In this equation, a = 04316 and b = 1.0 Weight average molecular weight, M , is calculated in the usual manner according to the following formula: M = Σ w_t* Mi, where Wi and M_f are the weight fraction and molecular weight, respectively, of the ι^tn fraction eluting from the GPC column. For the homogeneously branched linear ethylene/α-olefin interpolymers and copolymers, the M_w/M_n is preferably from 1.5 to 2.5, especially 2 to 2.5.

Additives, known to those skilled in the art, such as antioxidants (for example, hindered phenohcs (for example, Irganox® 1010 or Irganox® 1076 made by Ciba Geigy Corp.), phosphites (for example, Irgafos® 168 made by Ciba Geigy Corp.), cling additives (for example, polyisobutylene (PIB)), Standostab PEPQ_ supplied by Sandoz, anti-block additives, slip additives, UV stabilizers, pigments, processing aids (especially fluoroelastomers such as Dynamar® FX 5920 made by 3M are useful to improve processabihty for the homogeneously branched linear ethylene polymers) can also be added to the polymers for film structures, from which the pouches of the present invention are made.

The films and film structures disclosed herein can be monolayer or multilayer film structures, with the proviso that the homogeneously branched linear ethylene/α-olefin copolymers and interpolymers be used as at least one layer, preferably the seal layer. The thickness of the seal layer may be from at least about 0 1 mil (2.5 microns) and greater, preferably from 0 2 mil (5 microns) to 10 mil (254 microns) and more preferably from 0 4 mil ( 10 microns) to 5 mil ( 127 microns).

A surprising feature of the film structure for pouches of the present invention is the broad heat seal range, especially in view of the narrow melting point range associated with the linear ethylene polymer (measured using differential scanning caloπmetry) Generally, the heat seal range of the film structure can be from 50°C to 160°C and preferably from 75°C to 130°C It has been found that the seal layer of the present invention has a broader heat seal range than prior art polyethylene film made from heterogeneously branched ethylene polymers, even at comparable densities. A broad heat seal range is important to allow for more flexibility in the heat sealing process used for making pouches from the film structure Generally, the melting point range of the linear ethylene polymer used to make the film structure having the heat seal ranges specified above can be from 50°C to 130°C and preferably from 55°C to 115°C Another unexpected feature of the pouch film structure of the present invention is the film's maximum hot tack strength, using the DTC Hot Tack Strength Method defined herembelow. Generally, decreasing the density of heterogeneously branched linear ethylene/α-olefin interpolymers has no effect on the maximum hot tack strength. The film of present invention achieves greater maximum hot tack strength as the density of the homogeneously branched linear ethylene/α-olefin copolymers and mterpolymers is decreased.

Yet another unexpected feature is that films of the present invention achieve greater hot tack strengths over broader region than films made from homogeneously branched substantially linear ethylene/α-olefm copolymers and interpolymers For example a film made using a heterogeneously branched linear ethylene/α-olefin interpolymer will have a maximum hot tack strength of 2 7 N/m at a density of 0 905 g/cm , a film made using a the homogeneously branched substantially linear ethylene/α-olefin copolymers will have a maximum hot tack strength of 7 0 N/m at a density of 0 902 g/cm and a film of the present invention made from a homogeneously branched linear ethylene/α-olefin copolymer having a density of 0 900 g/cm³ will have a maximum hot tack strength of 9 8 N/in

The film structure of the present invention also has a hot tack or heat seal initiation temperature of less than about 110°C at a force of at least about 1 N/inch (39 4 N/m) It has been found that a seal made with the seal layer of the present invention has a higher strength at lower sealing temperatures than seals with a pπor art polyethylene having higher densities

A high heat seal strength at low temperatures and a broad hot tack range are important to allow conventional packaging equipment such as a vertical form, fill and seal machine to run at faster rates and to produce pouches with fewer leakers

It is believed that the use of at least one homogeneously branched linear ethylene polymer m a seal layer of a film structure for pouches of the present invention provides ( 1 ) a pouch that can be fabricated at a faster rate through a form, fill and seal machine, and (2) a pouch having fewer leakers, particularly when the pouch of the present invention is compared to pouches made with linear low density polyethylene, ultra linear low density polyethylene, high pressure low density polyethylene, or a combination thereof

In one embodiment of the present invention, a pouch is made from a film structure in tubular form and having transversely heat sealed ends The film structure has at least one film layer comprising

(I) from 10 to 100 percent by weight of at least one layer comprising at least one homogeneously branched linear ethylene/α-olefin interpolymer characterized as having

(b) a molecular weight distribution, M_w/M_n, < trom 1 5 to 2 5, and

(II) from 0 to 90 percent by weight of at least one polymer selected from the group consisting of a heterogeneously branched linear ethylene/C3-C 18 α-olefin copolymer, a high-pressure low density polyethylene, and an ethylene-vmyl acetate copolymer.

The heterogeneously branched linear ethylene/C3-Cι 8 α-olefin copolymer of (II) is generally a linear low density polyethylene (such as that made using Ziegler catalysts). The linear low density polyethylene is often further divided into subsets labeled as very low density polyethylene (VLDPE) or ultra low density polyethylene (ULDPE) VLDPE and ULDPE are interchangeable terms herein and are generally used in this manner by those skilled in the art. Generally, the density of the linear low density polyethylene of (II) ranges from 0 87 g/cm^ to 0.94 g/cm^, preferably from 0 87 g/cm^ to 0.915 g/cπ Preferably, the heterogeneously branched linear low density ethylene/C3-C 18 α-olefin copolymer of (II) has a melt index from 0.1 to 10 g/10 minutes

Preferably, the high-pressure low density polyethylene of (II) has a density from 0.916 to 0 93 g/cm^ and a melt index from 0 1 to 10 g/10 minutes. Preferably, the ethylene-vinyl acetate copolymer of (II) has a weight ratio of ethylene to vinyl acetate from 2.2.1 to 24.1 and a melt index from 0.2 to 10 g/10 minutes.

With reference to Figures 3 to 5, the film structure of the pouch of the present invention also includes a multilayer or composite film structure 30, preferably containing the above-described polymeπc seal layer being the inner layer of the pouch. As will be understood by those skilled in the art, the multilayer film structure for the pouch of the present invention may contain various combination of film layers as long as the seal layer forms part of the ultimate film structure. The multilayer film structure for the pouch of the present invention may be a coextruded film, a coated film or a laminated film. The film structure also includes the seal layer m combination with a barrier film such as polyester, nylon, EVOH, polyvinyhdene dichloπde (PVDC) such as Saran^®- (Trademark of The Dow Chemical Company) and metallized films. The end use for the pouch tends to dictate, in a large degree, the selection of the other material or matenals used in combination with the seal layer film. The pouches descπbed herein will refer to seal layers used at least on the inside of the pouch.

One embodiment of the film structure 30 for the pouch of the present invention, shown in Figure 3, compπses a homogeneously branched linear ethylene polymer seal layer 31 and at least one polymeric outer layer 32. The polymeric outer layer 32 is preferably a polyethylene film layer, more preferably a heterogeneously branched linear polyethylene referred to hereinafter as 'linear low density polyethylene" ("LLDPE") or a combination thereof "ultra linear low density polyethylene" ("ULDPE") or a combination thereof "very low density polyethylene ("VLDPE") or a combination thereof "homogeneously branched substantially linear ethylene polymer"(SLEP) An example of a commercially available LLDPE is DOWLEX^® 2045 (Trademark of and commercially available from The Dow Chemical Company) An example of a commercially available ULDPE is ATTANE^® 4201 (Trademark of and commercially available from The Dow Chemical Company) An example of a commercially available SLEP is AFFINITY^® PL 1880 (Trademark of and commercially available from The Dow Chemical Company)

The LLDPE (including both the VLDPE and ULDPE) useful herein are heterogeneously branched linear copolymers of ethylene and a minor amount of an alpha-olefin having from 3 to 18 carbon atoms, preferably from 4 to 10 carbon atoms (for example, 1-butene, 4-methyl- 1 -pentene 1-hexene, 1 -octene, and 1-decene) and most preferably 8 carbon atoms (for example, 1 -octene) Generally, the heterogeneously branched LLDPE are made using Ziegler catalysts (for example, using the method described in U S Patent No 4,076,698 (Anderson et al )

The LLDPE for the outer layer 32 generally has a density greater than 0 87 g/cm-', more preferably from 0 9 to 0 93 g/cm^, generally has a melt index (I2) from 0 1 to 10 g/10 min, preferably from 0 5 to 2 g/10 min, and generally has an l\θ/l2 ^ratl° from 5 to 20, preferably from 7 to 20

For the heterogeneously branched LLDPE (including both VLDPE and UDLPE), the I10 I2 ratio tends to increase as the molecular weight (M /M_n) of the

LLDPE increases, in surprising contradistinction to the novel homogeneously branched linear ethylene/α-olefm mterpolymers and copolymers discussed herein

The homogeneously branched substantially linear ethylene/α-olefin interpolymer (SLEP) for the outer layer 32 made using the method described in U S Patent Nos 5,272,236 and 5,278,272, has a melt index, I2, from 0 01 grams/10 minutes to

10 grams/10 minutes, preferably 0 5 to 2 grams / 10 minutes, and a density from 0 85grams/cm to 0 94 grams/cm^, preferably from 0 900 to 0 925 grams/10 minutes, and a molecular weight distribution, M_w/M_n, from 1 5 to 2 5, and a melt flow ratio, I10/I2. °f at least about 7, preferably from 7 to 20

The thickness of the outer layer 32 may be any thickness so long as the seal layer 31 has a minimum thickness of about 0 1 mil (2 5 microns) Another embodiment of the film structure 30 for the pouch of the present invention, shown in Figure 4, comprises the polymeric layer 32 sandwiched between two polymeric seal layers 31

Still another embodiment of the film structure 30 for the pouch of the present invention, shown in Figure 5, compπses at least one polymeπc core layer 33 between at least one polymeπc outer layer 32 and at least one polymeric seal layer 31 The polymeric layer 33 may be the same LLDPE or a combination thereof SLEP film layer as the outer layer 32 or preferably a different LLDPE or a combination thereof SLEP, and more preferably an LLDPE or a combination thereof SLEP that has a higher density than the outer layer 32 The thickness of the core layer 33 may be any thickness so long as the seal layer 31 has a minimum thickness of about 0 1 mil (2 5 microns)

Yet another embodiment (not shown) of the film structure for the pouch of the present invention can be a structure including a seal layer 31 and another polyethylene film layer referred to hereinafter as "high pressure low-density polyethylene" ("LDPE") The LDPE layer generally has a density from 0 916 to 0 930 g/cιτH and has a melt index from 0 1 to 10 g/10 mm The thickness of the LDPE layer may be any thickness so long as the seal layer 31 has a minimum thickness of about 0 1 mil (2 5 microns)

Still another embodiment (not shown) of the film structure for the pouch of the present invention can be a structure including a seal layer 31 and a layer of EVA copolymer having a weight ratio of ethylene to vinyl acetate from 2 2 1 to 24 1 and a melt index of from 0 2 to 20 g/10 min The thickness of the EVA layer may be any thickness so long as the seal layer 31 has a minimum thickness of about 0 1 mil (2 5 microns) The thickness of the film structure used for making the pouch of the present invention is from 0 5 mil (12 7 microns) to 10 mils (254 microns), preferably from 1 mil (25 4 microns) to 5 mils (127 microns)

As can be seen from the different embodiments of the present invention shown in Figures 3-5, the film structure for the pouches of the present invention has design flexibility Different LLDPEs (for example, VLDPE and ULDPE) or SLEPs can be used in the outer and core layers to optimize specific film properties such as film stiffness and film physical properties Thus, the film can be optimized for specific applications such as for a form, film and seal machine

The polyethylene film structure used to make a pouch of the present invention is made by either the blown tube extrusion method or the cast extrusion method, methods well known m the art. The blown tube extrusion method is descnbed, for example, in Modern Plastics Mid-October 1989 Encyclopedia Issue, Volume 66, Number 1 1, pages 264 to 266. The cast extrusion method is descnbed, for example, in Modern Plastics Mid-October 1989 Encyclopedia Issue, Volume 66, Number 11, pages 256 to 257.

Embodiments of the pouches of the present invention, shown m Figures 1 and 2, are hermetically sealed containers filled with "flowable matenals". By "flowable materials" it is meant matenals which are flowable under gravity or which may be pumped, but the term "flowable matenals" does not include gaseous materials The flowable materials include noncarbonated liquids (for example, milk, water, fruit juice, wine) and carbonated liquids (for example, soda, beer, water), emulsions (for example, ice cream mix, soft margarine), pastes (for example, meat pastes, peanut butter); preserves (for example, jams, pie fillings, marmalade), jellies; doughs; ground meat (for example, sausage meat); powders (for example, gelatin powders, detergents), granular solids (for example, nuts, sugar, cereal); and like materials. The pouch of the present invention is particularly useful for packaging liquids (for example, milk). The flowable material may also include oleaginous liquids (for example, cooking oil or motor oil)

Once the film structure for the pouch of the present invention is made, the film structure is cut to the desired width for use in conventional pouch-forming machines. The embodiments of the pouch of the present invention shown in Figures 1 and 2 are made in so-called form, fill and seal machines well known in the art With regard to Figure 1, there is shown a pouch 10 being a tubular member 1 1 having a longitudinal lap seal 12 and transverse seals 13 such that, a "pillow-shaped" pouch is formed when the pouch is filled with flowable mateπal With regard to Figure 2, there is shown a pouch 20 being a tubular member 21 having a penpheral fin seal 22 along three sides of the tubular member 1 1, that is, the top seal 22a and the longitudinal side seals 22b and 22c, and having a bottom substantially concave or "bowl-shaped" member 23 sealed to the bottom portion of the tubular seal 21 such that when viewed in cross-section, longitudinally, substantially a semi-circular or "bowed-shaped" bottom portion is formed when the pouch is filled with flowable material. The pouch shown in Figure 2 is the so-called "Enviro-Pak" pouch known in the art.

The pouch manufactured according to the present invention is preferably the pouch shown m Figure 1 made on so-called vertical form, fill and seal (VFFS) machines well known in the art Examples of commercially available VFFS machines include those manufactured by Hayssen or Prepac A VFFS machine is descnbed in the following reference F C Lewis, "Form-Fill-Seal," Packaging Encyclopedia, page 180, 1980 In a VFFS packaging process, a sheet of the plastic film structure descnbed herein is fed into a VFFS machine where the sheet is formed into a continuous tube in a tube-forming section The tubular member is formed by sealing the longitudinal edges of the film together — either by lapping the plastic film and sealing the film using an inside/outside seal or by fin sealing the plastic film using an inside/inside seal Next, a sealing bar seals the tube transversely at one end being the bottom of the "pouch", and then the fill material, for example milk, is added to the "pouch " The sealing bar then seals the top end of the pouch and either burns through the plastic film or cuts the film, thus, separating the formed completed pouch from the tube The process of making a pouch with a VFFS machine is generally described in U S Patent Nos 4,503,102 and 4,521,437

The capacity of the pouches of the present invention may vary Generally, the pouches may contain from 5 milliliters to 10 liters, preferably from 10 millihters to 8 liters, and more preferably from 1 liter to 5 liters of flowable matenal The use of the homogeneously branched linear ethylene/α-olefin interpolymer seal layer of the present invention in a two or three-layer coextruded film product will provide a film structure that can be used for making pouches at a faster rate in the VFFS and such pouches produced will contain fewer leakers

The pouches of the present invention can also be printed by using techniques known in the art, e g , use of corona discharge or flame treatment before pnntmg

Use of the pouch for packaging consumer liquids such as milk has its advantages over containers used in the past the glass bottle, paper carton, and high density polyethylene jug The previously used containers consumed large amounts of natural resources in their manufacture, required a significant amount of space in landfill, used a large amount of storage space and used more energy in temperature control of the product (due to the heat transfer properties of the container)

The pouches of the present invention made of thin film, used for liquid packaging, offers many advantages over the containers used in the past The pouches ( 1 ) consume less natural resources, (2) require less space in a landfill, (3) can be recycled, (4) can be processed easily, (5) require less storage space, (6) use less energy for storage (heat transfer properties of package), (7) can be safely incinerated and (8) can be reused (for example, the empty pouches can be used for other applications such as freezer bags, sandwich bags, and general purpose storage bags).

Experimental"

Coextruded blown film samples having an A/B/A structure were made using layer ratios of: A=15 percent (by weight of the total structure) and B= 70 percent (by weight of the total structure) However, m film samples containing resin samples 9, 10, and 11 in Table 1, the layer ratio's were. A=20 percent and B=60 percent. Layer B was an ethylene/ 1 -octene LLDPE having a melt index (I2) of about 1 g/10 minute and a density of about 0 92 g/cm-' and does not contain additives In the examples, resins 1-3 were all heterogeneously branched ethylene/ 1 -octene copolymers resins 4-7 were all homogeneously branched substantially linear ethylene/ 1 -octene copolymers, resins 9 -1 1 were all homogeneously branched linear ethylene polymer (HBLEP),. Table 1 summarizes physical properties of the resins used to make A B/A coextruded blown film samples descnbed in the examples and comparative examples.

Legend (*)Comparatιve example, NM - not measured

Resins 1, 2, 5, 6, and 7 were dry blended to contain 4,000 ppm S1O2 and 1 ,200 ppm Erucamide. Resin 3 was dry blended to contain 6,000 ppm S1O2 and 1,200 ppm Erucamide. Resin 4 was dry blended to contain 14,000 ppm S1O2 and 1,200 ppm Erucamide. Resin 8 was a monolayer milk pouch film designated "SM3" made by and available from DuPont Canada and was believed to be a blend of about 8 percent (by weight) of a low density polyethylene having a density of about 0.92 g/cm^ and about 92 percent (by weight) of a heterogeneously branched linear low density Resin 9, 10 and 11 were dry blended to contain 4,000 PPM Sι0₂ and 1,000 ppm Erucamide. The SM3 film has a final film density reported by DuPont as 0.918 g/cirA

Film samples were produced on an Egan three layer extruder system Extruder A has a 2.5 inch diameter screw (Barr2 type) equipped with a Maddox mixer, L/D of 24 1 , 60 HP drive Extruder B has a 2 5 inch diameter screw (DSB II type) equipped with a Maddox mixer, L/D of 24 1 , 75 HP drive Extruder C has a 2 inch diameter screw (Modified MHD (Johnson) type) equipped with a Maddox mixer, L/D of 24 1, 20 HP drive The blown film line was also equipped with an 8 inch 3-layer coextruding die body, a Gloucester Tower, a Sano collapsing frame, a Sano bubble sizing cage, and a Sano bubble enclosure

Each of the film samples was made at 3 mil target thickness using a blowup ratio (BUR) of 2 5 1

Each film was tested according to the following test methods Puncture Puncture was measured by using an Instron Tensile Tester with an integrator, a specimen holder, and a puncturing device The Instron was set to obtain a crosshead speed of 10 inches/minute and a chart speed (if used) of 10 inches/minute Load range of 50 percent of the load cell capacity ( 100 lb load for these tests) should be used The puncturing device was installed to the Instron such that the clamping unit was attached to the lower mount and the ball was attached to the upper mount on the crosshead Five film specimens were used (each 6 inches square) The specimen was clamped in the film holder and the film holder was secured to the mounting bracket The crosshead travel was set and continues until the specimen breaks Puncture resistance was defined as the energy to puncture divided by the volume of the film under test Puncture resistance (PR) was calculated as follows

PR = E/(( 12)(T)(A))

where PR = puncture resistance (ft-lbs/in-³),

E = energy (inch-lbs) = area under the load displacement curve, 12 = inches/foot,

T = film thickness (inches), and

A = area of the film sample in the clamp = 12 56 ιn^,

Dart Impact ASTM D1709, method A, Elmendorf Tear ASTM D1922,

Tensile Properties ASTM D882 using an Instron tensile tester (cross- head speed of 500 mm/mm, full scale load of 5 kg, threshold of 1 percent of full scale load, break criterion of 80 percent, 2 inch gauge length and 1 inch sample width). Coefficient of Friction: ASTM D1894. Coefficient of friction range was important in order for the film to properly move over the forming collars in a vertical- form-fill and seal machine (for example, a Hayssen form-fill-seal machine): if the coefficient of friction was too low, the film may be too slippery for the pull belts to grip the film and if the coefficient of friction was too high, the film may be too tacky for the machine to pull the film over the forming collar; typical targets for the Hayssen form-fill- seal machine were:

(i) inside/outside coefficient of friction from 0.10 - 0.30 and (ii) outside/outside coefficient of friction from 0.10 - 040; 1 percent and 2 percent Secant Modulus: ASTM D882. Film stiffness was important, especially for "free-standing" pouches like that shown in Figure 2. The 1 percent and 2 percent secant modulus tests provide an indication of the stiffness of the film;

Heat Seal Strength: This test measures the force required to separate a seal after the seal has been allowed to cool. Seals were made using the DTC Hot Tack Tester but only the heat seal portion of the unit was used. Conditions used were: Specimen width: 24.4 mm Sealing time: 0.5 seconds Sealing pressure: 0.27 N/mm/mm No. samples/time: 5

Temperature increments: 5°C.

Seal strength was determined using an Instron Tensile Tester Model No. 1 122. The film samples were exposed to relative humidity of 50 percent and a temperature of 23°C for 24-48 hours prior to testing. Instron test conditions were as follows:

Direction of pull: 90° to seal

Crosshead speed: 500 mm/minute

Full scale load (FSL): 5 kg Threshold: 1 percent of FSL

Break Criterion: 80 percent

Gauge length: 2.0 inches and

Sample width: 1.0 inch; Hot Tack Performance: The hot tack test measures the force required to separate a heat seal before the seal has had a chance to cool. This test simulates filling a pouch with material just after the seal was made. The hot tack strength was typically the limiting factor in increasing line speeds of a pouch manufacturing and filling operation. In this test, the films were tested using a DTC Hot Tack Tester Model No.

52D. Conditions used were:

Specimen width: 24.4 mm Sealing Time: 0.5 seconds Sealing Pressure: 0.27 N/mm/mm Delay Time: 0.5 seconds

Peel Speed: 150 mm/sec Number of samples/temperature: 5 Temperature Increments: 5°C Temperature Range: 70°C - 130°C Hot tack failure of the seals generally occurs in three stages: no seal; seals which pull apart (peeling); and film failure (where the molten film pulls apart with no apparent effect on the seal). Film failure region begins where the hot tack strength reaches a maximum level. In each case, film failure occurs just in front of the seal. A force of 1 N/inch was arbitrarily selected to determine the seal initiation temperature.

Water Filled Pouch Performance: Pouches were manufactured using a Hayssen Ultima VFFS unit and contain 2L of water. The following conditions were used on the Hayssen:

Model No.: RCMB@-PRA M.A. No. U 19644

Mass of water = 2,000 grams Bag size = 7 inches by 12.5 inches Film width = 15.25 inches Registration Rolls: on from 5° to 135° Pull Belts: on from 10° to 140°

Knife: on from 146° to 265° Jaw close: from 136° to 275° Platen: on from 136° to 265° Stager: off Auxiliary: on from 137° to 355°

Quah-seal: on from 140° to 265°

Start Delay: 50 ms

Bag eject: on End air seal: 200 ms

Empty bags/minute: 60

Filled bags/minute: 15

Seal bar pressure: 150 psi

Type of side seal: lap, and Seam seal temperature: 260°F.

A Pro/Fill 3000 liquid filler was attached to the VFFS The settings on the Pro/Fill 3000 were: P.S = 35, volume = 0903, and C.O.A. = 70;

(0 End Heat Seal Strength: Water filled pouches were made using sealing bar temperatures starting at 280°F. Approximately 20 pouches were made at this temperature, then the sealing bar temperature was reduced in 5°F increments until the pouches no longer hold water. Five pouches from the 20 made at each temperature were randomly chosen, the water drained, and the empty pouch tested for seal strength using an Instron Tensile Tester Model No. 1 122 using the conditions described in the Heat seal Strength test. At the seal bar temperature where the pouch no longer holds water, the force of the water being pumped into the pouch was believed to be too great for the hot, semi-molten seal. As a result, the seal separates and it appears that the pouch experiences hot tack failure at this temperature,

Table 2

*NM = Not measured ^Comparative Example Only

*NM = Not measured

''Comparative Example Only

The data in Tables 2 and 2A show that films made using both the heterogeneously branched ethylene/α-olefin copolymers and those made using the novel homogeneously branched linear ethylene/α-olefin inteφolymer have higher puncture resistance than the commercially available SM3 film.

Similarly, the data also show that films made using both the heterogeneously branched ethylene/α-olefin copolymers and those made using the novel homogeneously branched linear ethylene/α-olefin inteφolymer have higher dart impact strength than the commercially available SM3 film. Furthermore, films made using the homogeneously branched linear ethylene/α-olefin inteφolymer having higher dart impact strength than either the SM3 film or film made using heterogeneously branched ethylene/α-olefin copolymers.

Elmendorf tear also was higher for films made from both the heterogeneously branched ethylene/α-olefin copolymers and those made using the novel homogeneously branched linear ethylene/α-olefin inteφolymer, as compared with the commercially available SM3 film. Table 3 Hot Tack Strength (N/inch; N/25 mm))

**Comparative Example Only NA = Not Applicable; NM = Not Measured

The data in Table 3 shows that films made using the novel homogeneously branched linear ethylene/α-olefin inteφolymer have higher hot tack strength than film made from homogeneously branched substantially linear ethylene /α- olefin inteφolymer or heterogeneously branched ethylene/α-olefin copolymers and higher

10 hot tack strength than commercially available SM3 film.

Table 4

^♦♦Comparative Example Only 5 NA = Not Applicable

NM= Not Measured

The data in Table 4 shows that films made using the novel homogeneously branched linear ethylene/α-olefin inteφolymer have higher heat seal 10 strength than film made from heterogeneously branched ethylene/α-olefin copolymers and lower heat seal initiation temperatures than both the commercially available SM3 film and film made using heterogeneously branched ethylene/α-olefm copolymers Table 5

Hayssen Heat Seal Strength of 2 L Water Filled Pouches lbf/inch (N/m)

^♦Comparative Example Only The data in Table 5 shows that films made using the novel homogeneously branched linear ethylene/α-olefin inteφolymer have broader sealing ranges and higher Hayssen heat seal strengths than film made from heterogeneously branched ethylene/α-olefin copolymers having similar densities.

Table 6 summarizes data for the five foot drop test

Table 6

*Comρarative Example Only

Although resin 1 1 and comparative resin 1 have similar densities, pouches made from resin 11 have a much lower percent failure than pouches made from comparative resin 1.

Similarly, resin 10 and comparative resin 2 have similar densities, but pouches made from resin 10 have a lower percent failure than pouches made from comparative resin 2. Pouches made using resin 1 1 also have lower percent failure than do pouches made using comparative resin 3, even though the resins have similar density.

Claims

1. A pouch made from a film structure in tubular form and having transversely heat sealed ends, the film structure having at least one film layer comprising:

(I) from 10 to 100 percent by weight of at least one homogeneously branched linear ethylene/╬▒-olefin inte╧åolymer characterized as having: (a) a CDBI of greater than 50 percent, and

(b) a molecular weight distribution, M_w/M_n, in the range of 1.5 to

2.5; and

(II) from 0 to 90 percent by weight of at least one polymer selected from the group consisting of a homogeneously branched substantially linear ethyelene/ C3-C20 ╬▒-olefin inte╧åolymer, a heterogeneously branched linear ethylene/C╬▓-C 18 ╬▒-olefin copolymer, a high-pressure low density polyethylene, and an ethylene-vinyl acetate copolymer.

2. The pouch of Claim 1 wherein the film layer comprising (I) and (II) is a seal layer.

3. The pouch of Claim 2 wherein the film structure has an outer layer comprising at least one polymer selected from the group consisting of a homogeneously branched substantially linear ethyelene/ ╬▒-olefin inte╧åolymer, a heterogeneously branched linear ethylene/C3-C] 8 ╬▒-olefin copolymer, a high-pressure low density polyethylene, and an ethylene-vinyl acetate copolymer.

4. The pouch of Claim 3 wherein the film structure has a core layer comprising a high-pressure low density polyethylene.

5. The pouch of claim 1 wherein the homogeneously branched linear ethylene/╬▒- olefin inte╧åolymer is a copolymer of ethylene and a C3-C20 ╬▒-olefin.

6. The pouch of claim 1 wherein the homogeneously branched linear ethylene/╬▒- olefin inte╧åolymer is a copolymer of ethylene and 1 -octene.

7. The pouch of claim 1 wherein the homogeneously branched linear ethylene/╬▒- olefin inte╧åolymer is a te╧åolymer of ethylene and at least one C3-C20 ╬▒-olefin.

8. The pouch of claim 1 wherein the homogeneously branched linear ethylene/╬▒- olefin inte╧åolymer has less than 0.01 long chain branches/1000 carbons.

9. The pouch of claim 1 wherein the molecular weight distribution, Mw/M_n, of the homogeneously branched linear ethylene/╬▒-olefin inte╧åolymer of (I) is from 1.5 to 2.5.

10. The pouch of claim 1 wherein the melt flow ratio, L₀/I₂ of the a homogeneously branched linear ethyelene/ ╬▒-olefin inte╧åolymer of (I) is at least about 7.

11. The pouch of claim 1 wherein the homogeneously branched linear ethylene/╬▒- olefin inte╧åolymer of (I) has a melt index, I2, from 0.01 grams/10 minutes to 10 grams/10 minutes, and a density from 0.90 grams/cm^ to 0.94 grams/cm^, a molecular weight distribution, M_w/M_n, from 1.5 to 2.5, and a melt flow ratio, Il╬╕/l2_> ┬░f ^at l^east about 7.

12. The pouch of claim 1 where in the homogeneously branched substantially linear ethyelene/ C3-C20 ╬▒-olefin inte╧åolymer of (II) has a melt index, I2, from 0.01 grams/ 10 minutes to

10 grams/10 minutes, and a density from 0.85 grams/cm^ to 0.94 grams/cm^, a molecular weight distribution, M_w/M_n, from 1.5 to 2.5, and a melt flow ratio, Ii╬╕/l2_> of at least about 7.

13. The pouch of claim 1 where in the homogeneously branched substantially linear ethyelene/C3-C20 ╬▒-olefin inte╧åolymer of (II) is further characterized as having: a) a density from 0.870 g/cm3 to 0.940 g/cm3 b) a melt index from 0.01 g/10 minutes to 10 g/10 minutes. c) from 0.01 long chain branches/1000 carbons to 3 long chain branches/1000 carbons.

14. The pouch of claim 1 wherein the heterogeneously branched linear ethylene/C3-C] 8-ct-olefin copolymer of (II) has a density greater than about 0.87 g/cm^ and a melt index from 0.1 to 10 g/10 minutes.

15. The pouch of claim 1 wherein the high-pressure low density polyethylene of (II) has a density from 0.916 to 0.93 g/cm^ and a melt index from 0.1 to 10 g/10 minutes.

16. The pouch of claim 1 wherein the ethylene-vinyl acetate copolymer of (II) has a weight ratio of ethylene to vinyl acetate from 2.2: 1 to 24: 1 and a melt index from 0.2 to 10 g/10 minutes.

17. The pouch of Claim 1 wherein the pouch holds from 5 mL to 5000 mL.

18. The pouch of claim 1 wherein the pouch contains a flowable material.

19. The pouch of Claim 15 wherein the flowable material is milk.

20. In a process for preparing a pouch containing a flowable material, wherein the pouch is prepared from a film structure using a form fill seal technique, the improvement comprising using a film structure having at least one film layer comprising:

(a) from 10 to 100 percent by weight of at least one homogeneously branched linear ethylene/╬▒-olefin inte╧åolymer, and

(b) from 0 to 90 percent by weight of at least one polymer selected from the group consisting of a heterogeneously branched linear ethylene/C3-Ci8 ╬▒-olefin copolymer, a high-pressure low density polyethylene and an ethylene/vinyl acetate copolymer.

21. In a process for preparing a pouch containing a flowable material, wherein the pouch is prepared from a film structure using a form fill seal technique, the improvement comprising using a film structure having at least one film layer comprising:

(I) (a) from 10 to 100 percent by weight of at least one homogeneously branched linear ethylene/╬▒-olefin inte╧åolymer, and (b) from 0 to 90 percent by weight of at least one polymer selected from the group consisting of a homogeneously branched substantially linear ethyelene/ C3-C20 ╬▒-olefin inte╧åolymer, a heterogeneously branched linear ethylene/C3-C 18 ╬▒-olefin copolymer, a high-pressure low density polyethylene and an ethylene-vinyl acetate copolymer; and at least one layer comprising: (II) a heterogeneously branched linear low density ethylene/C3-C╬╣ 8 ╬▒-olefin copolymer having a density greater than about 0.87 g/cm-^> and a melt index from 0.1 to 10 g/10 minutes.

22. The process of Claim 21 wherein the film structure includes at least one other layer comprising:

(III) a high-pressure low density polyethylene having a density from 0.916 to 0.93 g/c╧Ç and a melt index from 0.1 to 10 g/10 minutes.