GB2328673A

GB2328673A - Patch bag comprising homogeneous ethylene/alpha-olefin copolymer

Info

Publication number: GB2328673A
Application number: GB9828623A
Authority: GB
Inventors: Blaine Clemons Childress; Ronald Dean Moffitt; Timothy Theodore Oberle
Original assignee: Cryovac LLC
Current assignee: Cryovac LLC
Priority date: 1994-12-12
Filing date: 1995-12-12
Publication date: 1999-03-03
Anticipated expiration: 2015-12-12
Also published as: GB2328674A; GB9828630D0; GB2328675A; GB2328674B; GB9828623D0; GB2328673B; GB2328676B; GB9828627D0; GB9828634D0; GB2328676A; GB2328677B; GB9828637D0; GB2328672B; GB9828636D0; GB2328675B; GB2328677A; GB2328672A; GB2328930A; GB2328930B; GB9828617D0

Abstract

A patch bag has a heat-shrinkable patch 24 adhered to a heat-shrinkable bag 22, the patch comprising a heat-shrinkable monolayer patch film of from about 2 to 8 mils thickness which comprises homogeneous ethylene/alpha-olefin copolymer in an amount of from about 5 to 100% (preferably 15 to 85%) by weight. The patch film has a total free shrink at 85 degrees C of from about 10 to 100%. The homogeneous ethylene/alpha-olefin copolymer may be linear or long chain branched and may be blended with heterogeneous ethylene/alpha-olefin copolymer.

Description

1 2328673 PATCH BAG COMPRISING HOMOGENEOUS ETHYLENE /ALTPF-A-OLEFIN

COPOLYMER -.

1. Field of the Invention

The cresent invention relates to packages for the packaging of bone-in meat products. More particularly, the present invention relates to a bag having a protective catch adhered directly thereto, the protective patch preventing, or reducing, puncture of the bag by exposed bone from a meat product within the bag.

2. Background of the Invention

Heat-shr-inkable thermoplastics are known to be useful as flexible packaging materials for vacuum packaging various f oodstuf fs, including meat. Such plas tic materials, however, while is generally suitable for packaging meat, understandably have difficulties in successfully packaging sharp or bony products. For example, attempts to package bone-in primal cuts of meat usually result in an unsatisfactorily large number of bag failures due to exposed bone puncturing the bag.

The use of cushioning materials such as paper, paper lam.inates, wax impregnated cloth,- and various types of plastic inserts have proved to be less than totally satisfactory in solving the problem, as they require large expenditure of materials and labor, and are subject to shifting off of protruding bones. The preparation of special cuts of meat or close bone trim with removal of protruding bones has also been attempted. However, this is at best only a limited solution to the problem since it does not offer the positive protection necessary for a wide variety of commercial bone-in types of meat. Furthermore, removal of the bone is a relatively expensive and time-consuming procedure.

Some time ago, the use of a bag having a patch thereion, i.e., Opatch baaw, became a commercially-pref erred manner of packaging number of bone-in meat products. One of the first commercially- 2 uti-lized Patch -bags utilized a heat shrinkable bag and a patch commosed of two laminated VALERON (M) high density polyethylene ("EDPE") -Films., each film having been highly oriented in tile machine direction. In the laminated patch, the machine direction of a first HDPE lamina was oriented about 90 degrees with respect to the machine direction of a second patch lamina.

The VALE.RON (M) HDPE patch performed well in preventing punctures from exposed bone. However, upon packaging a meat product in a heat-shrinkable bag having such a patch thereon, the corners of the natch delaminated from the bag upon shrinkage of the bag, due to the ifact that the patch would not shrink as the bag shrunk. Customers perceived the delamination of the patch corners from the bac to be highly undesirable. Furthermore, the highly oriented EMPE films were opaque white due to the formation of voids is during the orientation process.

Thus, the need arose for a patch which would provide the patch bag with a desired level of puncture-resistance, while at the same time being heatshrinkable so that there would be no substantial delamination at the corners of the patch. Furthermore, although for some use s it was desirable to use an opaque patch, f or other uses it. was desirable to provide a substantially translucent or transparent patch.

Although ethylenelvinyl acetate copolymer (OEVAm) was known to have the desired heat shrink properties for use in patches. it was discovered to lack the desired level' of punctureresistance obtainablemsing the VALERON (TM) EDPE patch. That is, EVA patches had to be much thicker than an EDPE patch in order to provide the same level of puncture-resistance. Furthermore, in addition to lacking the desired puncture-resistant character, EVA lacked abrasion-resistance, further diminishing its utility as-the bulk polymer in the patch.

Surprisingly, linear low density polyethylene (LLDPE) was found to provide the combination of puncture-resistance, heat- 3 shrinkability, abrasion-res-istance, and even transparency, desired for use in a patch for patch bags. Within the last 10 years, patch bags having patches commosed of LLDPE have come into widespread COMMercial use in the united States.

However, LLDPE has several drawbacks. For examnle, LLDPE is not easily processable as it causes hi-gh extruder back pressure if extrusion is attemzted at relatively high speeds. Furthermore, because of its stiffness, LLDPE is d4fficult to orient, which necessitates that another polymer be blended with the LLDPE ill order to permit the desired orientation of the LLDPE to provide a shrinkable patch. Furthermore, LLDPE will not heat-seal to itself, necessitating the use of another type of polymer if the patch is to be formed from a collapsed film tube, as is one of the most desirable processes for manufacturing patches.

Thus, it would be desirable to locate another polymer which can provide the combination of puncture-resistance and heatshrinkability. Furthermore, it would be desirable that this other polymer also be capable of being manufactured as a substantially transparent film. Furthermore, it would be desirable if this other polymer was easier to extrude than LLDPE, had a stiffness lowenough to avoid the need to blend a stiffness -reducing- -polymer therewith, and had the ability to be heat-sealed to itself. SUMMARY OF THE INVENTION

The present invention is directed to the use of homogeneous ethylene/alpha-olefin copolymer in a patch for a patch bag. This homogeneous polymer has surprisingly been found to provide a combination of puncture-res istance and heat-shrinkability which is at least the eaulvalent of LLDPE. Furthermore, it has also surprisingly been found that this homogeneous polymer has about the same abrasion-resistance as LLDPE,, and can be used to form a substantially transparent heat shrinkable patch. Thus, this homogeneous polymer has been discovered to provide an alternative to the use of LLDPE in patches for patch bags. At least some Species of this homogeneous polymer are considerably easier to extrude than LLDPE. Furthermore, some species have a stiffness low enough to avoid the need to blend a stiffness reducing polymer therewith. Finally, at least some species of the polymer, when extruded into a tubular film, offer the further advantage of substantially better sealing to itself, relative to LLDPE.

The present invention provides a patch bag comprising a heat-shrinkable monolayer patch film having a thickness of from about 2 to 8 mils, wherein the monolayer patch film comprises homogeneous ethylene/ alpha- olef in copolymer in an amount of from about 5 to 100 weight percent, and wherein the monclayer patch film is a first heat-shrinkable film which has a total free shrink at 850C (1850F) of from about 10 to 100 percent.

Preferably, the meat product comprises at least one member selected from the group consisting of ham, spareribs, picnic, back rib, short loin, short rib, whole turkey, pork loin.

BRIEF DESCRIPTION OF THE W.AWINGS

Figure 1 illustrates a schematic view of a preferred end-seal patch bag according to the present invention, in a lay-flat view.

Figure 2 illustrates a cross-sectional view of the end-seal patch bag illustrated in Figure 1, taken through section 2-2 of Figure 1 - Figure 3A illustrates a cross-sectional view of a preferred multilayer film suitable for use as the patch in the patch-bag according to Figure 1.

Figure 3B illustrates an enlarged cross-sectional view of the multilayer film of Figure 3A.

Figure 3C illustrates a schematic cross-sectional view of a multilayer film described in Patch Film No. 19.

Figure 4 illustrates a schematic view of a preferred process for.making the multilayer film of Figure 3.

Figure 5 illustrates a cross-sectional view of a preferred multilayer film suitable f or use as the bag in the patch-bag according to Figure 1.

Figure 6 illustrates a schematic view of a preferred process for making the multilayer film of Figure 5.

Figure 7 illustrates a schematic view of a preferred process for making'the patch bag of Figure 1, using the films of Figures 3 and 5, as respectively produced by the processes of Figures 4 and 6.

Figure 8 illustrates a perspective view of a shrunken patch bag containing a pair of fresh, bone-in whole pork loins, each viewed from the ham end.

4 6 Figure 9 illust-iates a cross -sec tional view taken throuch section 9-9 of Figure 8, with the addition of a patch bag within which the pair of bone-in pork loins are packaged.

DETAILED DESCRIPTIOM OF THE IWIEXTIOM

A film seal layer, i.e., sealing layer or heat seal layer, is an outer film layer, or layers, involved in the sealing of the film to itself, another film layer of the same or another film, and/or another article which is not a film. In ceneral, up to the outer 3 mils of a film can be involved in the sealing of the film to itself or another layer. With respect to packages having only fin type seals, as opposed to lac-type seals, the sealant layer includes the inside film layer of a package, as well as supporting layers adjacent this sealant layer, the inside layer frequently is also serving as a food contact layer in the packaging of foods.

In general, a sealant layer to be sealed by heat-sealing can comprise any thermoplastic polymer; preferably, the heat-sealing layer comprises, for example, thermoplastic polyolefin, thermoplastic polyamide, thermoplastic polyester, and thermoplastic polyvinyl chloride; more preferably, thermoplastic polyolefin; still more preferably, thermoplastic polyolef in having less than 60 weight percent crystallinity. Preferred sealant compositions are the same as the compositions for the abuse layer, as set forth below.

A bag. seal is a seal of a first region of a film surface to a second region of a film surface, wherein the seal is formed by heating the recrions to at least. their respective seal initiation ---:temperatures. The heating can be performed by any one or more of a wide variety of manners, such as using a heated bar, hot air.

infrared radiation, ultrasonic sealing, etc.

A f ilm barrier layer is a layer which serves as a barrier to one or more gases. Oxygen (i.e., 02) barrier layers can comprise, for examnle, ethylene/vinyl alcohol copolymer, polyvinyl chloride, 7 polyvinylidene chloride, polyamide, polyester, polyacrYlOuitrile, etc., as known to those of skill in the art; preferably, the oxygen b a i e r layer comprises ethylene/vinyl alcohol copolymer, polyvinyl idene: chloride, and polyamide; more pref erablyr vinyl; dene chloride/methyl acrylate copolymer, as kno%m to those of skill in the art.

As used herein, uEVOH" refers to ethylene/vinyl alcohol copolymer. EVOE includes saponified or hydrolyzed ethylene/v-4nyl acetate copolymers, and refers to a vinyl alcohol copolymer having an ethylene comonomer, and prepared by, for example, hydrolysis of -vinyl acetate copolymers, or by chemical reactions with polyvinyl alcohol. The degree of hydrolysis is preferably at least 50% and more preferably at least 85%.

A film abuse layer is a film layer which serves to resist abrasion, puncture, and other potential causes of reduction of package integrity, as well as potential causes of reduction of package appearance quality. Abuse layers can comprise any polymerr so long as the polymer contributes to achieving an integrity goal and/or an appearance. goal; preferably, the abuse layer comprises polymer comprising at least one member selected from the group consisting. of ethylene/alpha-olefin copolymer having a density of from about 0.85 to 0.95. propylenelethylene copolymer, polyamide, ethylene/vinyl acetate copolymer, ethylene/methyl acrylate copolymer, and ethylenelbutyl acrylate copolymer. etc. as known to those of skill in the art; more preferably, in the patch bag of the present invention the abuse layer of the patch comprises homogeneous ethylenelalpha olefin copolymer.

A film core layer is an inner film layer, i.e., internal fil= layer, which has a primary function other than serving as _an adhesive or compatibilizer for adhering.two layers to one another. Usually, the core layer, or layers, provides the multilayer film with a desired level of strength, 'i.e., modulus, and/or optics,, and/or added abuse resistance, and/or specific impermeability.

8 A film skin layer is an outside film layer, in a mul-l-ilayer film used in the mackaging of a product. The skin layer is subject to abuse. Accordingly, the preferred polymers for the skin layer are the same as the preferred polymers for the abuse layer.

A film tielayer is an inner layer of a multilayer film, this inner layer having the primary purpose of adhering two layers of the film to one another. Tie layers generally comprise any polymer having a polar group grafted thereon, so that the polyme r is canable of covalent bonding to polar polymers such as polyamide and ethylene /viny 1 alcohol copolymer; preferably, tie layers comprise at least one member selected from the group consisting of polyolefin, modified polyolefin, ethylene/vinyl acetate copolymer, modified ethylene/vinyl acetate copolymer, and homogeneous ethylene/alpha-olefin copolymer; more preferably, tie layers comnrise at least one member selected from the group consisting of anhydride modified grafted linear low density polyethylene, anhydride grafted low density polyethylene, homogeneous ethylenelalpha-olefin copolymer, and anhydride grafted ethylenelvinyl acetate copolymer.

A film laminate is a film made by bonding together two or more layers of film or other materials. LATni nation can be accomplished by joining layers with adhesives. joining with heat and pressure, and even spread coating and extrusion coating. Film laminates also include coextruded multilayer films comprising one or more tie layers.

A heat-shrinkable f ilm is typically made by f irs-L'.. being stretched at an elevated temperature (the orientation temperature) which is below the melt temperature of at least ' one polymer present in the film. During the orientation process, the film is generally.

biaxially oriented by being stretchedw in the transverse direction, and "drawnO in the machine direction. Preferably, the application of substantial cooling occurs at some point downstream of the upstream roller, the point of cooling being dependent upon 9 material orooerties and cooling rates. Ultimately, this type of process results in a film which is heat-shrinkable in both the transverse and longitudinal directions. Upon subsequently heating unrestrained, unannealed, oriented polymer-containing material to its orientation temperature, heat shrinkage is produced almost to the oricinal. unstretched, i.e., pre-oriented dimensions. The orientation in oriented films can be produced in one or more of a variety of manners.

The orientation ratio of a film is the multiplication product of the extent to which the plastic film material is expanded in several directions, usually two directions perpendicular to one another. "Drawing" is orientation in the machine direction, while "stretch-!ng" is orientation in the transverse direction. For films extruded throuah an annular die, stretching is obtained by "blowing" the film to produce a bubble. Drawing is obtalned by passing the film through two sets of powered nip rolls, with the downstream set having a higher surface speed than the upstream set, with the resulting draw ratio being the surface speed of the downstream set of nip rolls divided by the surface speed of the upstream set of nip rolls. The degree of orientation is also referred to as th- orientation ratio, or sometimes as the 0 racking ratio'.

As used herein, the term polymer refers to the product of a polymerization reaction, and is inclusive of homopolymers, copolymers., terpolymers, etc. In general, the layers of a film can consist essentially of a single polymer, or can have still additional polymers together therewith, i.e., blended therewith.

As used herein, the term "copolymero refers to polymers formed by the polymerization reaction 6f at least two different monomers. For example, the term copolymero includes the copolymerization reaction product of ethylene and an alpha-olefin, such as 1-hexene. However, the term copolymero is also inclusive of, for examplet the copclymerization of a mixture of ethylene, propylene, 1-hexenef and 1-oczene.

As used herein, the term "polymer-4zation" is inclusive Of homonolymerizat;%ons, copolymerizations, terpolymerizations, etc., and includes alltypes of copolymerizations such as random, graft, block, etc. In general, the polymers in the films used in accordance with the present invention, can be prepared in accordance with any suitable polymerization process, including slurry polymer -5zation, gas phase polymerization, and high pressure polymerization processes.

is polymerization processes generally use superatmospheric: pressures and temperatures in the range of 400-1000C. In a slu ry polymerization, a suspension of solid, particulate polymer is f ormed in a liquid polymerization medium to which are added ethylene and comonomers. and often hydrogen along with catalyst. The liquid employed in the polymerization medium can be an alkane, cycloalkane, or an aromatic hydrocarbon such as toluene, ethylbenzene or. xylene. The medium employed should be liquid under the conditions of" polymerization, and relatively inert. Preferably, hexane or toluene is employed.

Alternatively, gas-phase polymerization processes utilize s uperatmo spheric pressure and temperature in the range of about 500-1200C. Gas phase polymerization can be performed in a stirred or fluidized bed of catalyst and product particles, in a pressure vessel adapted to permit the separation of product particles from unreacted gases. Ethylene, 'comonomer, hydrogen and an inert-. diluent gas such as nitrogen can be introduced or recirculated so as to maintain the particles at temperatures of SC-120'C. Triethylaluminum may be added as needed as a scavenger of water, oxygen, and other impurities. Polymer product can be withdrawn continuously or semicontinuously, at a rate such as to maintain a constant product inventory in the reactor. After polymerization and deactivation of the catalyst, the product polymer can be recovered by any suitable means. In commercial practice, the 11 polymer product can be recovered directly from the cas phase reactor, freed of residual monomer with a nitrogen purge, and used without further deactivation or catalyst removal.

High pressure polymerization processes utilize a catalyst system comprising a cyclopentadienyl-transition metal compound and an alumoxane compound. It is important, in the high-pressure process, that the polymerization temperature be above about 1200C., but below the decompositlion temperature of the polymer product. It is also _i=ortant that the polymerization pressure be above about 500 bar (kc/cm). In those situations wherein the molecular weight of the polymer product that would be produced at a given set of operating conditions is higher than desired, any of the techniques known in the art for control of molecular weight, such as the use of hydrogen or reactor temperature, may be used in the process of this invention.

A heterogeneous polymer is a polymerization reaction product having a relatively wide variation in molecular weight and relatively wide variation in composition distribution, i.e., typical polymers prepared, for example, using conventional Ziegler Natta catalysts. Although there are a few exceptions (such as Zlecler-Natta catalyzed TAFMER (TM) linear homogeneous ethylenelaipha-olefin copolymers produced by Mitsui Petrochemical Corporation), heterogeneous polymers typically contain a relatively wide variety of chain lengths and comonomer percentages.

In contrast to heterogeneous polymers, homogeneous polymers are polymerization reaction products of relatively narrow molecular weight distribution and relatively narrow composition distribution.

Homogeneous polymers are useful in various layers of the patch bag of the present invention. Homogeneous polymers are structurally cUf f erent from heterogeneous polymers, in that homogeneous polymers exhibit a relatively even sequencing of comonomers within a chain, a mirrorina of secruence distribution in all chains, and a similarity of length of all chains, i.e., a narrower molecular 12 weight dist=ibution. Furthermore, homogeneous polymers are typically prepared using metallocene, or other single-site type catalysis, rather than using Ziegler bTa-$-.ta catalysts.

More p articularly, homogeneous ethylene/alpha-olei'--4n copolymers may be characterized by one or more methods known to those of skill in the art, such as molecular weight distribution (M,jMJ, commosition distribution breadth index (CDBI), and narrow melting point range and single melt pc-Int behavior. The molecular weight distribution (MjMJ, also known as polydispersity, may be determined by gel permeation chromatography.The homoceneous ethylene/alpha-olef in copolymers useful in this invention generally has of less than 2.7; preferably from about 1.9 to 2.5; more preferably, from about 1.9 to 2.3. The cozzosition distribution breadth index (CDBI) of such homogeneous is ethyl ene/alpha-o lef in copolymers will generally be greater than about 70 percent. The CDBI is defined as the weight percent of the copolymer molecules having a comonomer content within 50 percent (i.e., plus or minus 50%) of the median total molar comonomer content. The CDBI of linear polyethylene, which does not contain a comonomer, is defined to be 100%. The Composition Distribution Breadth Index (CDBI) is determined via the technique of Temperature Rising Elution Fractionation (TREF). CDBI determination clearly distinguishes the homogeneous copolymers used in the present invention (narrow composition distribution as assessed by CDBI ts values generally above 70%) from VLDPEs available commercially which generally have a broad composition distribution as assessed by CDBI values generally less than 55%. The CDBI of a copolymer is readily calculated from data obtained from techniques known in the art, such as, for example, temperature rising elution fractionation as described, for example, in Wild et. al., J. Poly. Sci. P01X. Phys. Ed-, -, Vol. 20, p.441 (1982). Preferably, the homogeneous ethylene /alpha-o lef in copolymers have a CDBI greater than about 70%, i.e., a CDBI of from about 70% to 99%. In general, the 13 homogeneous ethylene/ainha-clefin copolymers in the mul-tilayer films of the 'present invention also exhibit a relatively narrow meltingpoint range, inccmr)ar-4sonw-4-Lh "heteroceneous copolymers", i.e., polymers having a CD3-7 of less than 55%. Pref erably, the homogeneous ethyl ene/almha-o lef in copolymers exhibit an essdatially singular melting point characteristic, with a peak melting point (T.), as determined by Differential Scanning Colorimetry (DSC), of from a_baut 600C to 1100C. Preferably the hcmogeriecus copolymer has a DSC peak T. O- J-' from about 800C to 1000C. As used herein, the phrase "essentially single melting point" means that at least about 80%, by weight, of the material corresponds to a single T. peak at a temperature within the range of from about 60C to 110'C, and essentially no substantial fractlon of the material has a peak melting point in excess of about 1150C., as determined by DSC analysis. DSC measurements are made on a Perkin Elmer System 7 Thermal Analysis System. Melting information reported are second melting data, i.e., the sample is heated at a programmed rate of 100C.1min. to a temperature below its critical r ange. The sample is then reheated (2nd melting) at a programmed rate of 101C/min.

The presence of higher melting peaks is detrimental to film properties such as haze, and compromises the chances for meaningful reduction in the seal initiation temmerature of the final film.

A homogeneous ethylenelalpha-o 1 e fin copolymer can, in general, be prepared by the copolymerization of ethylene and any one or more alpha-olefin. Preferably, the alpha-olefin is a (:-C.. alphamonoolefin, more preferably, a C,-C 1. alpha-monoolefin, still more preferably, a C,-C, alpha-monoole.-F-,n. Still more preferably, the alpha-olefin comprises at least one member selected from the group consisting of butene-1, hexene-l. and octene-1, i. e., 1-butene,. 1- hexene, and 1-octene, respectively. Most preferably, the alphaolef in comr)rises octene-1, and/or a blend of hexene-1 and butene-1 - Processes for preparing and using homogeneous polymers are disclosed in U. S. Patent No. 5.206.075, U.S. Patent No. 5,241,031, 14 is and PCT International Application WO 93/03093, each of which is hereby incorporated bv reference thereto, in its entirety. Further details regarding the production and use of homogeneous ethyl ene/alpha-a lef in copolymers are disclosed in PCT International Publication Number WO 90/03414, and PCT International Publication Number WO 93/03093, both of which designate Exxon Chemical Patents, Inc. as $the Applicant, and both of which are hereby incorporated by reference thereto, in their respective entireties.

Still another cenus of homogeneous ethyl ene/alpha-olef in coMolymers is disclosed in U.S. Patent No. 5,272,236, to LAI, et.

al. and U.S. Patent No. 5,278,272, to LAI, et. al., both of which are hereby incorporated by reference thereto, in their respective entireties.

The term "polyolefin" refers to any polymerized olefin, which can be linear, branched, cyclic, aliphatic, aromatic, substituted, or unsubstituted. More specifically, included in the term polyolefin are homopolymers of olefin, copolymers of olefin, copolymers of an olefin and an non-olefinic comonomer copolymerizable with the olefin, such as vinyl monomers, modified polymers thereof, and the like. Specific examples include polyethylene homopolymer, polypropylene homopolymer, polybutene, ethyl enelalp ha-o lef in copolymer, propylenelalpha-olef in copolymer, butene/alpha-olefin copolymer, ethylenelvinyl acetate copolymer, ethylene/ethyl acrylate copolymer, ethylenelbutyl acrylate copolymer,ethylenelmethyl acrylate copolymet, ethylenelacrylic acid copolymer, ethylenelmethacrylic acid copolymerf modified polyolefin resin, ionomer resin, polymethylpentene, etc. Modified polyolefin resin is inclusive of modified polymer prepared by copolymerizing the homopolymer of the olefin or copolymer thereof with an unsaturated carboxylic acid, e.g., acrylic acid,' methacrylic acid, isobutyl acrylate, or the like, or a derivative thereof such as the anhydride, ester, metal salt, or the like. It could also be obtained by incor-porating into the olefin homopolymer is or copolymer, an unsaturated carboxylic acid, e.g./ maleic' acid, fumaric acid' or the like, or a derivative thereof such as the anhvdride, ester or metal salt or the like.

As used herein, terms identifying polymers, such as Methylene/alphaolefin coDolymerl, Mpolyamidem, "polyester#.

polyurethane', etc. are inclusive of not only polymers comprising repeating units derived from monomers known to polymerize to fa= a polymer of the named type, but are also inclusive of comanomers, derivatives, etc. which can copolymerize with monomers known to polymerize to produce the named polymer. For example, the term "polyamide" encompasses both polymers comprising repeating units derived from monomers, such as caprolactam, which polymerize to form a polyamide, as well as copolymers derived from the capolymerization of caprolactam with a comonomer which when polymerized alone does not result in the formation of a polyamide. Furthermore, terms identifying polymers are also inclusive of mIxtures, blends, etc, of such polymers with other polymers of a different type.

Modified polymers, such as modified ethylene/vinyl acetate copolymer', and "modified polyolefinw include such polymers having an anhydrid&' functionaliy grafted thereon and/or copolymerized therewith and/or blended therewith. Preferably, such modified polymers have the anhydride functionality grafted on or polymerized therewith, as opposed to merely blended. therewith.

The homogene ous ethylene Jalpha-o 1 ef in copolymers useful in the bag f ilm. and patch f ilm. of the patch bag of the present invention include, f or example, metallocene catalyzed polymers such as EXACT (TX) linearhomogeneous ethyl enelalpha-o lef in copolymers obtainable from the Exxon Chem-ical Company, and TAFMER (TM) linear homogeneous ethylene/alpha-olefin resin obtainable from the Mitsul Petrochemical CorporatioL. All these homogeneous copolymers generally include copolymers of ethylene with one or more comonomers selected from C4 to Cl. alpha-olefin such as butene-1 16 (i.e., 1._butene), hexene-1, octene-1, etc. in which the molecules of the copolymers comprise long chains with relatively few side chain branches or cross-linked structures. This molecular structure is to be contrasted with conventional low or medium density polyethylenes which are more highly branched than their respective counterparts. For example, LLDPE has a density usually in the range of from about 0.91 grams per cubic centimeter to about 0.94 grams per cubic centimeter.

Another group of homogeneous ethylene/alpha-olefin copolymers are available from The Dow Chemical Company, and are known as AFFINITY. (M) long chain branched homogeneous ethyl:ene/alpha-olef in copolymers. It has been discovered that AFFINITY (M) long chain branch homogeneous ethylene/alpha-olefin copolymers are easier to pro cess into films, relative to'other homogeneous ethylene/alpha olefin copolymer.s, such as EXACT (TY.). linear h omogeneous ethylene/alpha-olefin copolymers obtained from the Exxon Chemical Company. For this reason, among others, AFFINITY (M) long chain branched homogeneous ethylene /alpha-olef in copolymers are preferred over EXACT (M) linear homogeneous ethylenelalpha-olefin copolymers. Preferred long chain branched homogeneous ethylene /alpha-o 1 ef in copolymers have are those having a density of from about 0.87 to 0. 94 g/cc, more preferably 0.89 to 0.92 g/cc. Long chain branched homogeneous ethylene /alpha-o lefin copolymers are preferably produced using polymerization reaction.

a metallocene-catalyzed Although in the patch bag of the present invention the patch comprises homogeneous ethylenelalpha-olefin copolymer, the patch and/or the bag may further comprise heterogeneous ethylene/alphaolefin copolymer. Several preferred heterogeneous.ethylenelalpha olefin copolymer include: linear low density polyethylene (LLDPE), very low density polyethylene (VLDPE), and ultra low density polyethylene (=PE).

17 In general, both homogeneous and heterogeneous ethylen.,-:/alDhaolefin copolymers result from the copolymerization of from about 8. to 99 weight percent ethylene and from 1 to 20 weight -percent alpha-olefin; preferably, frora the copolymerization of from about 85 to 95 weight percent ethylene with 5 to 15 weight percent alDhaolefin.

As used herein, the phrases inner layer" and "internal layer" refer to any laver, of a multilayer film, having both of its principal surfaces directly adhered to another. layer of the film.

As used herein, the phrase outer layer" refers to any film layer of film having less than two its principal surfaces directly adhered to another layer of the film. The phrase is inclusive of monolayer and multilayer films. In multilayer films, there are two outer layers, each of which has a principal surface adhered to only is one other layer of the multilayer film. In monolayer films, there is only one layer, which, of course, is an outer layer in that neither of its two principal surfaces are adhered to another layer of the film. - AS used herein, the phrase winsIde layeru refers to the outer layer, of a multilayer film packaging a product, which is closest to the product.,- relativ: to the other layers of the multilayer film.

As used herein, the phrase outside layern refers to the outer layer, of a multilayer film packaging a product. which is furthest from the product relative to the other layers of the multilayer film.

As used herein, the term wadheredw is inclusive of films which are directly adhered to one another using a heat seal -or other means, as well as films which are adhered to one another using an adhesive which is between the two films.

As used herein, the phrase udirectly adheredo, as applied to film layers, is defined as adhesion of the subject film layer to the object film layer, without a tie layer, adhesive, or other 18 layer.. therebetween. In contrast, as used herein, the word "between", as applied to a film layer expressed as being between two ot-her specified layers, includes both direct adherence of the subject layer between to the two other layers it is between, as well as including a lack of direct adherence to either or both of the two other layers the subject layer is between, i.e., one or more additional layers can be imposed between the subject layer and one or more of the layers the subject layer is between.

Extrusion is the process of forming continuous shames by forcing a molten plastic material through a die, followed by cooling or chemical hardening. Immediately prior"to extrusion through the die, the relatively high-viscosity polymeric material is fed into a rotating screw of variable pitch, i.e., an extruder, which forces the polymeric material through the die.

Coextrusion is the process of extruding two or more materials through a single die with two or more orifices arranged so that the extrudates merge and weld together into a laminar structure before chilling, i.e., quenching. Coextrusion can be em-cloyed in film blowing, free film extrusion, and extrusion coating processes.

The "machine direction of a film is a direction along the length of the film, i.e., the direction in which the film is f ormed during extrusion and coating. In contrast, the Otransverse direction' of a film is a direction across the film. perpendicular to the machine or longitudinal direction.

As used herein, the phrase of ree shrinkm refers to the percent dimensional change in a 10 cm, x 10 cm specimen of film, when subjected to selected heat, as measured by ASTM D 2732, as known to those of skill in the art. ASTM D 2732 is described in the 1990 Annual Book of ASTYStandards, Section 8, Plastics, Vol. 08.02, pp.368-371, which is hereby incorporated by reference thereto, in its entirety.

Althouch the films used in the patch bag according to the present invention can be monolayer films or multilayer films, the 19 patch bag comprises at least two films laminated together. Preferably, the patch bag is comprised of films which together comz)rise a total of from. 2 to 20 layers; more preferably, from 2 to 12 layers; and still more preferably, from 4 to 9 layers.

In general, the monalayer or multilayer films used in the patch bag of the present invention can have any total thickness desired, so long as the films provide the desired properties for the particular packaging operation in which the film is used, e.g. abuse-resistance (especially puncture-resistance), modulus, seal strength, optics, etc. However, for efficiency and conservatlon of resources, it is desirable to obtain the necessary punctureresistance using the minimum patch thickness. Preferably, the film stock from which the patches are cut has a total. thickness of from about 2 to 8 mils; more pref erably, from about 3 to 6 mils.

is Furthermore, the patch film can be a monolayer film or a multilayer f ilm. Several patch f -51ms described in detail below contain a total of 4, 6, and 14 layers.

Figure 1 is. a side-view illustration of a preferred end-seal patch bag 20, in a lay-flat position, this patch bag being in accord with the present invention; Figure 2 is a cross-sectional view of patch bag 2.0 taken tin=ough section 2-2 of Figure 1.

Viewing Figures 1 and 2 together. patch bag 20 comprises bag 22. front patch 24 (i.e., first patch 24), and rear patch 26 (i.e., second patch 26), open top 28, and end-seal 30. The designations of Ofront'. and Oback"/rear" are merely with respect to that side of patch bag 20 which is up when patch bag 20 is in its lay-flat position.

Figure 3A illustrates a crosssectional view of preferred 3layer film 36 for use as the stock material from which patches 24 and 2 6 can be cut. First layer 38 serves as an outside and puncture- resistant layer; second layer 40 serves as a tie layer and is preferably made up of two identical layers bonded to one azother; third layer 42 serves as an inside layer and a puncture resistant layer.

F-Scrure 3B illustrates an enlarged cross-sectional view of the film of Figure 3A, including second layer 40 illustrated as beina comiDosed of identical film inner layers 44 and 46 adhering to one another. Inner layers 44 and 46 are preferably formed by collapsing a multilayer film tube having an inside layer which can be adhered to itself, resulting in what can be considered to be either a single central film layer, or a pair of identical fild layers which are adhering to one another. Hence Figure 3A illustrates petch film 3 6 as a three layer f ilm, whereas Figure '33 illustrates the same film as a four layer film, with the two inner layers being adhered to one another as represented by dotted line 48 because layers 44 and 46 can be considered to form a single is layer since they are identical in thickness and chemical composition, due to the process used to make the film. The process illustrated in Figure 4, described in detail below, can be used to produce the fil Tn of Figure 3B.

Figure 3C illustrates a cross-sectional view cLan.alternative -20 multilayer film 200 which can be used as stock material for preparing a patch for the patch bag of the present invention.

multilayer film 200 is a 7-layer film, and is described in detail in Patch Film"No. 19, below. Multilayer film 200 is composed of outer layer 202, bulk layer 204, tie layer 206, 02-barrier layer 208, tie layer 210, bulk layer 2.12, and outer layer 214.

Figure 4 illustrates a schematic of a preferred process for producing the multilayer films of Figures 3A, 3B, and 3C. In the process illustrated in Figure 4, solid polymer beads (not illustrated) are fed to a plurality of extruders 52 (for simplicity, only one extruder is illustrated). Inside extruders 52, the polymer beads are forwarded, melted, and degassed, following which the resulting bubble-free melt is forwarded into die head 54, and extruded through annular die, resulting in tubing 21 56 which is 5-40 mils thick, more preferably 20-30 mils thick, sti-11 more preferably, about 25 mils thick.

A-fter cooling or quenching by water spray from cooling ring 58, tubing 56 is collapsed by pinch rolls 60, and ik thereafter fed throuah irradiation vault 62 surrounded by shielding 64, where tubing 56 is irradiated with hiah energy electrons (i.e., ionizing radiation) from iron core transformer accelerator 66. Tubing 56 is guided through i-rradiation vault 62 on rolls 68. Preferably, the irradiation of tubing 56 is at a level of from about 2 to 10 mecarads (hereinafter MIR").

After irradiation, irradiated tubing 70 is directed over guide roll 72, after which i=radiated tubing 70 passes into hot water bath tank 74 containina water 76. The now collapsed irradiated tubina 70 is submersed in the hot water for a retention time of at is least about 5 seconds, i.e., for a time period in order to bring the film up to the desired temperature, following which supplemental heating means (not illustrated) includ-ing a plurality of steam rolls around which irradiated tubing 70 is partially wound, and optional hot air blowers, elevate the temperature of irradiated tubing 70 to a desired orientation temperature of from abmkt -1 tr-af'C (2 4o -2!C0 Thereafter, -:.irradiated film 70 is directed through nip rolls 78, and.bubble 80 is blown, thereby transversely stretching irradiated tubing 70. Furthermore, while being blown, i.e., transversely stretched, irradiated film 70 is drawn (i.e., in the longitudinal direction) between nip rolls 78 and nip rolls 86, as nip rolls 86 have a higher surface speed than the surface speed of nip rolls 78. As a result of the transverse stretching and longitudinal drawing, irradiated, biaxial ly-oriented, blown tubing film 82 is produced, this blown tubing preferably having been both stretched at a ratio of from about 1: 1. 5 1: 6, and drawn at a ratio of from about 1:1.5-1:6. More preferably, the stretching and drawing are each performed at a ratio of from about 1:2 1:4. The 22 io is result is a biaxial Orientation of from about 1:2.25 1:36, more preferably, 1:4 - 1:16.

While bubble 80 is maintained between pinch rolls 78 and 86, blown tubing 82 is collapsed by rolls 84, and thereafter conveyed through pinch rolls 86 and across guide roll 88, and then rolled onto wind-up roller 90. Idler roll 92 assures a good wind-up.

The invention is illustrated by the following examples, i.e., patch films, which are provided for the purpose of representation, and are not to be construed as limiting the scope of the invention." Unless stated otherwise, all percentages, parts, etc. are by weight.

Patch Film Nos. 1, 2, 5', and 6-14, 16-17, and 19 are patch films which can be used to make a patch for a patch bag according to the present invention. Patch Film Nos. 3, 4., 15, and 18 are comparative patch films to be contrasted to patch films which can be used to make the patch bag of the present invention.

Patch Film No. 1 A coextruded, two-ply tubular tape was cast, the tape having a thickness of 29 mils, the tape having an A layer making up 85 percent of the tape thickness, and a B layer making up 15 percent of the tape thickness.. The A Layer was composed of: (a) 87 weight percent DOWLEX 2045 (TM) linear low density polyethylene having a density of 0.920 g/.cc, obtained from The Dow Chemical Companyr of Midland, Michigan (hereinafter LLDPE flu), (b) 10 weight percent ELVAX 3128 (TM) ethylene/vinyl acetate copolymer having a vinyl acetate content of 10 percent, obtained from DuPontf Of Willn J ngtOn, Delaware, hereinafter 'EVA flu, and (c) 3 weight percent TEKNOR EPE-9621C (TM) antiblock agent, obtained from Teknor Apex Plastics Division, of Pawtucket, R.I., hereinafter 'Antiblock flu. The B Layer contained 100 weight percent EXACT SLP 4008 linear homogeneous ethyl enelalpha-o 1 ef in plastomer having a density of 23 0.885 a/cc, obtained from the Exxon Chemical- Company, of Baytown, Texas (hereinafter, "linear homogeneous ethyle. ne/alpha olef in '1") The two-ply tubing was cooled to a solid.phase in a water bath and then electronically crosslinked with a 50b Kev beam to a level of from about 2 to 10 MR. The resulting crosslinked two-ply tubing was heated by steam cans and hot air at about 99'104C (210-220OF), and was subsequently oriented by being drawn and stretched approximately 350%, in each of the machine and transverse directions, resnectively, using a trapped bubble of air held between two nip rolls. The orientation produced a 2.25 mil two-ply film in the fo= of a tube.

Aft.er drawing, the resulting tube of hot-water-shrinkable flat film was passed through a pair of nip rolls, causing the inside B layer to bond to itself upon tube collapse, rendering a final four- is ply film, with the "middlew plies being the inside B layer bonded to itself (i.e., resulting in a "4-ply" film having a thickness of 4.5 mils), as follows:

A Blend A SLP 4008 SLP 4008 Blend A B B A Table I, i=ediately below, includes the chemical composition and thickness of each of the layers, together with the function which the layer serves in the patch.

24 1 TABLE I

Fig. 3 layer layer desig- thickness nation laver function- -chemical ident-i'k-v (Mils) 38 outside layer 87% LLDPE Awl; 10% EVA:zrl; 2.0 & puncture- 3% Antiblock Arl 0 resistant layer tie layer homogeneous ethylene/ 0.7 alpha-ole-f-;-- E_ is 42 inside layer 87% LLDPE #rl; 10% EVA 'rl; 2.0 & puncture- 3% Antiblock '71 res istant layer Patch Film No. 1 was composed of the above three layers, the middle layer being composed of the inside tube layer adhered to itself. Patch Film No. 1 was determined to have a free shrink at 185OF (via ASTY- 2732), and an instrumented impact, as set forth below in Table II, below. Instrumented i=act was measured by a procedure substantially equivalent to ASTM D 3763. ASTM D 3763 is described in the 1990 Annual Book of ASTM Standards. Section 8, Plastics, Vol. 08.03, pp. 174-178, which is hereby incorporated by reference thereto, in its entirety.

An alternative to Patch Film No. 1 is a two-layer film having a thickness.of about 4.5 mIls, with about 85 weight percent of this film having a composition corresponding to layer 38 described in Table I above, and with 15 weight percent of this f ilm, having a composition corresponding to layer 40 above. This film could be produced using a flat die, rather than a circular die.

Patch Film No. 2 Patch Film No. 2 was prepared by the same process employed to produce Patch Film No. 1, with the exception that in Patch Film No.

2, the A Layer was composed of a blend o---: (a) 87 weight percent LLDPE ='l, (b) 10 we-Jaht percent EXACT 3032 (!M) linear homogeneous ethylene /alDha-o 1 ef in plastomer having a.density of 0.900 g/cc, also obtained from the Exxon Chemical Company (hereinafter, linear homogeneous ethyl ene/alpha-olef in coDolymdr IT2), and (c) 3 weight percent Antiblock #1. In Patch Film No. 2, the B Layer remained identical to the B Layer of Patch Film No. 1. Furthermore, as with Patch Film No. 1, in Patch Film No. 2 the A Layer made up 85 r)ercent of the tape thickness, and a B layer made up 15 percent of the tape thickness. The Patch Fil.m No. 2 free shrink and instrumented impact are provided in Table 11, below.

Patch Film No. 3 (Comparat,.ve) Patch Film No. 3 was prepared by the same process employed to produce Patch Film No. 1, except that in Patch Film No. 3, the A Layer was composed of a blend of: (a) 87 weight percent LLDPE 'rl, (b) 10 weight percent ELVAX 3128 (M) ethylene/vinyl acetate copolymer having a vinyl acetate content of 9 percent and a density of 0.928 glcc, and a melt index of 2.0, obtained from the DuPont Chemical Co., of Wilmington, Delaware (hereinafter referred to as EVA izr2), and (c) 3 weight percent Antiblbck =11. In Patch Film No.

3. the B Layer was composed of 100 weight percent ELVAX 3175 (M) ethylene/vinyl acetate copolymer having a vinyl acetate content of 28 percent and a density of 0.950 g/cc, and a melt index of 6.0, obtained from the DuPont Chemical Co., of Wilmington, Delaware (hereinafter referred to as EVA 1Ar2). Furthermore, as with Patch Film No. 1, in Patch Film No. 3 the A Layer made up 85 percent of the tape thickness, and A B layer made up 15 percent of the tape thickness.

The Patch Film No. 3 free shrink and instrumented imDact are provided in Table II, below. Patch Film No. 3 is a comparative patch film because it does not comprise any homogeneous ethylene/alpha-olefin copolymer.

26 is Patch Film No. 4 (Comparative) Patch Film No. 4 was prepared by the same process employed to produce Patch Film No. 1, except that in Patch Film No. 4, the A Layer was composed of a blend of: (a) 82 weight percent LLDPE al, (b) 15 weight percent EVA rll, and (c) 3 weight percent Antiblock jr, 1. In Patch Film No. 4, the B Layer was composed of 100 weight percent EVA #2. Furtherm, ore, as with Patch Film No 1, in Patch Film No. 4 the A Layer made up 85 percent of the tape thickness, and a B layer made up 15 percent of the tape thickness.

The Patch Film No. 4 free shrink and instrumented imDac-l- are provided in Table II, below. Patch Film No - 4 is a comparative patch film because it does not comprise any homogeneous ethylene/alpha-clefin copolymer.

Patch Film No. 5 Patch Film No. 5 was prepared by the same proc ess employed to produce Patch Film No. 1, except that in Patch Film No. 5. the A Layer was composed of a blend of: (a) 67 weight percent LLDPE 'rl; (b) 30 weight percent XUS9220.01, a proprietary experimental long chain branched homogeneous ethylenelalpha-olefin copolymer (hereinaf ter referred toas "homogeneous ethylene/ alpha-o lef in 'r3") having a density of 0.901 glcc and a melt index of 0.9, obtained under a development agreement with The Dow Chemical company of Midland, Michigan; and, (c) 3 weight percent Antiblock 11. The information concerning XUS9220.01 and the evaluation results of f ilm/bag containing the experimental polymer which are set forth. in this examDle have been approved for release by Dow.

In Patch Film No. 5, the B Layer was composed of 100 weight percent EVA #2. Furthermore, as with Patch Film NO. 1, in Patch Film No. 5 the A Layer made up 85 percent of the tape thickness, and a B layer made up 15 percent of the tape thickness..

The Patch Film No. 5 free shrink and instrumented impact are provided in Table II, below.

27 TAB LE 11 Film NO - Free Shr-J--kat Free ShrinkJ Impact Energy to Wc t8 s o F) g.CC (2 0 5 OF) Strength Break MD, %TD %Y_D, %TD (1bs) (ft-lbs) 1 11 16 20 30 97 4.8 2 1 18 21 32 109 5.7 3 io 17 20 30 100 5.0 (comparative) 4 13 18 25 3 2 87 3.1 (comparative) 14 20 88 3.2 As can be seen from Table II, the Imoact strength of various patch films according to the present invention, e.a., Patch Film Nos. 1, 2, and 5, were f ound to be comparable to the impact strength exhibited by comparative Patch Film No. 3 and comparative Patch Film No. 4, both of which utilize LLDPE as the polymer which. provides the patch film with high impact strength. Thus, it has been found that the use of homogeneous ethyl ene/alpha-o 1 ef in copolymers, in accordance with the present invention, can result in a patch film having an impact strength substantially equivalent to, and in some instances even better than, the impact strength of LLDPE- based patch films.

Patch Film No. 6 A coextruded, two-ply, tubular tape was cast, the tape having a thickness of 9 mils, the tape having an A layer making up 85 percent of the tape thickness, and a B layer making up 15 percent of the tape thickness. The A Layer was composed of a blend of: (a) 50 weight percent of a resin composition referred to as ECD 103 linear homogeneous ethylene/hexene copolymer, also obtained from the Exxon Chemical Company (hereinafter referred to as alinear homogeneous ethyl ene/alpha-a lef in (b) 37 weight percent ECD 28 106 linear homogeneous ethylene/hexene copolymer, havina a density of about 0.917g/cc, and a melt index of about 3, also obtained from the Exxon Chemical Co. (hereinafter referred to as linear homogeneous ethylene /alpha-o lef in IrS"), (c) 10 weight percent LD 200.48 (TV.) low density polyethylene having a density of 0.917 g/cc and a melt index of 6.7, this low density polyethylene also obtained from the Exxon Chemical Co., and (d) 3 weight percent Antiblock #1. In Patch _Frilm No. 6, the B Laver was composed of 100 weight percent EVA #2.

The two-ply sheet was cooled to a solid lphase using a chilled roll, and then electronically crosslinked with a 500 Kev beam to a level of approximately 2 to 10 MR. The resulting crosslinked two ply sheet was heated with hot air o11710&r'-.k(il-10-220 F) 1 and was subsequently oriented by drawing and stretching approximately 300 is percent in each of the machine and transverse directions, respectively, using a tenter frame, to -produce a biaxially oriented film having a thickness of about 1 mil. The impact strength of the resulting Film No. 6 is provided in Table III, below.

Patch Film No. 7 A coextruded, two-ply sheet is cast, the sheet having a thickness of 18 mIls, the sheet having an A layer making up 85 percent of the sheet thickness, and a B layer making up 15 percent of the sheet thickness. The A. Layer is composed of a blend of: (a) 97 weight percent linear homogeneous ethylene jalpha-o lef in #4, and (b) 3 weight percent Antiblock #l. In Patch Film No. 7, the B Laver is composed of 100 weight percent EVA '72.

The twoply sheet is cooled to a solid phase using a chilled roll, and then electronically cross linked with a 500 Kev beam to a level of approximately 2 to 10 MR. The resulting crosslinked two ply sheet is heated with hot air a91-M,k(210-220-F), and is subsequently oriented by drawing and stretching approximately 300 percent in each of the machine and transverse directions, 29 respectively, using a tenter frame, to produce a biaxially-oriented IL-4- 1.m having a thickness of about 2 mils.

Patch Film No. 8 A single ply sheet"is cast, the sheet having a thickness of is mils, the sheet being composed of a blend of: (a) 97 weight percent linear homogeneous ethyl ene/alpha-o lef in 11r4, and (b) 3 weight percent Antiblock #1. Af ter the sheet is cast, the tape is cooled to a solid phase using a chilled roll, and then electronically crosslInked with a 500 Rev beam to a level of approximately 2 to 10 YR. The "res. ulting crosslinked two-ply sheet is heated with hot a-;ratiot-10k10-220OF), and is subsequently or.L.ented, using a tenter frame, to impart longitudinal orientation in an amount of about 300 percent, and transverse orientation in an is amount of about 300 percent, to result in a biaxially oriented film having a thickness of about 2 mils.

Patch Film No. 9 A single ply tubular tape is cast, the tape having a thickness of 27 mils, the tape being composed of a blend of: (a) 97 weight percent linear homogeneous ethylenelalpha-olifin-- 114, and (b) 3 weight percent Antiblock #l. After the tape is cast, the tape is cooled to a solid phase using chilled air or chilled water, and then electronically crosslinked with a 500 Rev beam to a level of approximately 2 to 10 MR. The resulting crosslinked tape is then heated with hot air tat:.1210-220OF), and is subsequently oriented by drawing a_nd stretching approximately 300 percent in each of the machine and transverse directions, respectively, using a trapped bubble process, to produce a biaxial ly-oriented film having a thickness of about 3 mils. The tubular film is thereafter slit to f orm a f!at f ilm suitable f or use as a patch on a patch bag.

Patch Film go. 10 Patch Fil.m No. 10 was prepared by he same process employed to produce Patch Film No. 6, except that in Patch Film No. 10, the A Layer was composed of a blend of: (a) 67 weight percent LLDPE r'l, (b) 30 weight percent ENGAGE EG 8100 (M) lona chain branched homogeneous ethylene /alpha-o 1 ef in copolymer, also obtained from The Dow Chemical Company (hereinafter referred to as "homogeneous ethyl ene/alpha-olef in 11r6), and (c) 3 weight percent Antiblock Irl.

In Patch Film No. 10, the B Layer was commosed of 100 weiaht percent EVA #2. Furthermore, as with Patch Film No. 6, in Patch Film No. 10 the A Layer made up 85 percent of the tape thickness.

and a B layer made up 15 percent of the tame thickness.

The Patch Film No. 10 instr=ented impact is provided in Table III, below.

Patch Film No. 11 Patch Film No. 11 was prepared by the same process employed to produce Patch Film No. 6, except that in Patch Film No. 11, the A Layer was composed of a blend of: (a) 67 weight percent.LI&DPE 11, (b) 30 weight percent ENGAGE EG 8150 (M) long chain branched homogeneous ethyl enelalpha-o lef in copolymer, also obtained from The Dow Chemical Company (hereinafter referred to as ehomogeneous ethyl ene/alpha-c 1 ef in 11r7), and (c) 3 weight percent Antiblock #1. In Patch Film No. 11,., the B Layer was composed of 100 weight percent EVA #2. Furthermore, as with Patch Film No. 6. in Patch Film No. 11 the A Layer made up 85 percent of the tape thickness, and a B layer made up 15 percent of the tape thickness.

The Patch Film No. 11 instrumented impact is provided in Table III, below.

Patch Film No. 12 Patch Film No. 12 was prepared by the same process employed to produce Patch Film No. 6, except that in Patch Film No. 12, the A Layer was composed of a blend of: (a) 50 weight percent of a resin 31 is referred to as SW.9042 linear homogeneous ethylene /alDha-olefil copolymer, obtained from the Exxon Chemical Company (hereinafter referred to as "linear homogeneous ethylene/alpha olefin Z'8"), (b) 47 weight percent LLiDPE Irl, and (c) 3 weight percent Antiblock ral. In Patch Film No. the B Layer was composed of 100 weight percent EVA #2. Furthermore, as with Patch Film No. 6, in Patch Film No. 12 the A Layer made up 85 percent of the tape thickness, and a B layer made up 15 percent of L-he tape thickness.

The Patch Film No. 12 instrumented imoact is provided in Table ii---, below.

Patch Film No. 13 Patch Film No. 13 was prepared by the same processemployed to produce Patch Film No. 6, except Film No. 13 was a three-ply.tubular film in which the A Layer made up 35 percent of the thickness of the film, the B Layer made up 50 percent of the th-ickness of the f 11m, and the C Layer made up 15 percent of the thickness of the film. The A Layer was composed of a blend of: (a) 94 weight percent AFFINITY EF 1031 (M) long chain branched homogeneous ethylenelalpha-olefin also obtained from The Dow Chemical Company (hereinafter referred to as---long chain branched homogeneous ethylene/alpha-olefin copolymer 'W), and (b) 6 percent Antiblock #1. The B Layer was composed of 100 percent AFFINITY 1570 (M) long chain branched homogeneous ethyl ene/alpha-o le f in copolymer, obtained from The Dow Chemical Company (hereinafter, ethylene /alpha-o lef in tlOw). The C Layer was composed of 100 weight percent EVA #2.

The Patch Film No. 13 instrumented impact is provided in Table Ill, below.

Patch Film No. 14 Patch Film No. 14 was a three-ply film prepared by the same process employed to produce Patch Film No. 13, except that in Patch 32 Film No. 14, the A Layer was composed of a blend of: (a) 67 weight percent LLDPE -rll, (b) 30 weight percent homcceneous ethylene/alphaolefin r'7, and (c) 3 percent Antiblock ti. The B Layer was composed of 100 percent homogeneous ethylene/alpha olefin #7, the C Layer was composed of 100 weight percent EVA #2.

The Patch Film No. 14 instr-umented impact is provided in Table Ill, below.

Patch Film No. 15 (Commarative) 10. Patch Film No. 15 was a two-ply film prepared by the same process employed to produce Patch Film No. 6, except that in Patch Film No. 15. the A Layer was composed of a blend of: (a) 87 weight percent LLDPE 'W1, (b) 10 weight percent EVA 1-1, and (c) 3 percent Antiblock #1. The B Layer was composed of 100 weight percent EVA l#2. Patch Film No. 15 is a comparative patch film because it does not comprise any homogeneous ethylene/alpha-olefin copolymer.

The Patch Film No. 15 instrumented impact is provided in Table Ill, below.

TABLE Ill

Film NO Impact Strength (lbs) 6 19 16 11 17 12 13 14 (comparative) is 14 13 19 As can be seen from Table Ill, the impact strength of various patch films according to the present invention, e.g., Patch Film Nos. 6 and 10-15, range from a low of 13 lbs to a high of 20 pounds, whereas comparative Patch Film No. 1.5 had an impact strength of 19 pounds.

33 is Patch Film No. 16 Patch Film No. 16 was prepared by a process similar to the process employed in the production of Patch Film No. 1. Patch Film No. 16 was made by coextruding a tubular film which had an A/3/C structure in the thickness ratio of 15170/15, respectively. The A Layer was an outside layer composed of: (a) 87 weight percent LLDPE -='l; (b) 10 weight percent EVA Arl; and (c) 3 weight percent Anti-block #1. The B Layer was a core layer composed of (a) 97 weight percent homogeneous ethylene/alpha- olefin copolymer 7110; and, (b) 3 weight percent Antiblock Arl. The C Layer was an inside layer composed of 100 weight percent EVA #2.

The coextruded, three-ply tubular tame was cast, the tape havina a thickness of 20 mils. The two-ply tubing was cooled to a solid phase in a water bath and then electronically crosslinked with a 500 Kev beam to a level of approximately 12 VIR.

The resulting crosslinked two-ply tubing was heated by immersion in a hot water bath having a temperature of aboullif2100 E), and was subsequently oriented by beina drawn and stretched approximately 370%, in each of the machine and transverse directions, respectively, using a trapped bubble of air held between two nip rolls, resulting in a three-ply"film having thickness of about 1.46 mils, in the form of a tube.

After drawing, the resulting tube of hot -water- shrinkable flat film was passed through a pair of nip rolls, causing the inside C layer to bond to itself upon tube collapse, rendering a final sixply patch film having a thickness of about 2.9 mils. Patch Film 0C No. 16 was determined to have a free shrink a-,-1(1850F) (deter=lned using ASTM 2732) of about 48 percent, and the instrumented impact of Patch Film No. 16 (determined using ASTM D 3763), was determined to be about 110 pounds.

34 Patch Film No. 17 Patch Film No. 17 was prepared by a process similar to the process employed in the production of Patch Film No. 16. Patch Film No - 17 was made by coextruding a tubular f ilm which had an A/B/C structure in the thickness ratio of 35150/15 respectively.

The A Layer was an outside layer composed of: (a) 87 weight percent LLDPE #1; (b) 10 weight percent EVA 1Arl; and (c) 3 weight percent Antiblock #1. The B Layer was a core layer composed of (a) 97 weight percent long chain branched homogeneous ethylene/alpha olefin copolymer #3; and, (b) 3 weight percent Antiblock.711. The -C Layer was an inside layer composed of 100 weight percent EVA =-2.

The coextruded, three-ply tubular tape was cast, the tape having a thickness of 20 mils. The two-ply tubing was cooled to a solid phase in a water bath and then electronically crosslinked is with a 500 Kev beam to a level of from about 2 to 10 MR.

The resulting crosslinked two-ply tubing was heated by immersion in a hot water bath having a temperature of abou.tY.(208 F), and was subsequently oriented by being drawn approximately 340% in the machine direction and stretched approximately 370%, in the transverse direction, using a trapped bubble of air held between ---twonip rolls, resulting in a three-ply film having a thickness of about 1.6 mils, in the form of a tube.

After drawing, the resulting tube of hot-water-shrinkable flat film was passed through a pair of nip rolls, causing the inside C layer to bond to itself upon tube collapse, rendering a final six ply patch film having a thickness of about 3.2 iails. Patch Film No. 17 was determined to have a free shrink at(185OF) (determined using ASTM 2732) of about 57 percent, and the instrumented impact of Patch Film No. 17 (determined using ASTM D 3763), was determined to be about 63 pounds. It is believed that Patch Film No. 17 would have been considerably greater if the orientation had been carried out at a temnerature of abour-l(.L95"F), as the homogeneous polymer's density of 0.9016 permitted the lower orientation temperature.

Patch Film No. 18 (Comparative) Patch Film No. 18 was a comparative with respect to Patch Film Nos. 16 and 17. Patch Film No. 18 was prepared by a process S.Lmilar to the mrocess employed in the production of Patch Film Nos. 16 and 17. Patch Film No. 18 was made by coextruding a tubular film which had an A/B/C structure in the thickness ratio of 15/70/15, respectively. The A Layer was an outside layer composed OZ: (a) 87 weight percent LLDPE #11; (b) 10 weight percent EVA fl; and (c) 3 weight percent Antiblock #1. The B Layer was identical.

in chemical composition, to the A Layer. The C Layer was an inside layer composed of 100 weight percent EVA #2.

The coextruded, three-1ply tubular tame was cast, the tape having a thickness of 20 mils. The two-ply tubing was cooled to a solid phase in a water bath and then electronically crosslinked is with a 500 Kev beam to a level of from about 2 to 10 MR.

The resulting crosslinked two-ply tubing was heated by i=ersion in a hot water bath having a temperature of about210OF), and was subseauently oriented by being drawn approximately 360% in the machine direction and stretched approximately 370%, in the transverse direction, using a trapped bubble of air held between two nip rolls, resulting in a three-ply film having a thickness of about 1.5 mils. in the form of a tube.

After drawing, the resulting tube of hot-water-shrinkable flat film was passed through a pair of nip rolls, causing the inside C layer to bond to itself upon tube collapse, rendering a final sixply patch film having a thickness of about..1.0 mils. Patch Film No. 18 was determIned to have a free shrink. atla8soF) (determined using ASTM 2732) of about 50 percent, and the instr=ented impact of Patch Film No. 18 (determined using ASTM D 3763), was determined to be about 100 pounds.

A comparison of Patch Film No. 16 with Patch Film No. 18 reveals that the use of the homogeneous ethylene /alpha-o 1 ef in copolymer in the core layer of Patch Film No. 16 produces a patch 1 36 film having an impact strength of about 10 perce-at greater than the control. The control is the substantial ecuivalent of patch films which have been used commercially. The 10 percent increase in the impact strength, which is directly attributabli to the use of a homogeneous ethylene/ alpha-o 1 ef in copolymer, is'considered to be a substantial increase over the impact strength of Comparative Patch Film NO - 18.

Patch Film No. 19 A coextruded, severi-ply tubular tape was cast, the taiDe having a thickness of 18. 6 m ils, the tape having an A layer making up 85 percent of the tape th-,c.kness, and a B layer making up 15 percent of the tape thickness. The three-ply tubing was cooled to a solid phase in a water bath and then electronically crosslinked with a 500 Kev beam to a level of from about 2. to 10 VIR. The resulting is crosslinked three-ply tubing was extrusion coated with four additional polymer layers extruded through an annular die, in a process as illustrated in Figure 6. The resulting 26.5 mil extrusion-coated tape was thereafter immersed in a hot water bath have a temperature of aboutX(19 2 01, and was subsequently. oriented by being drawn approximately 300% in the machine direction, and stret7Ched approximately 325% in the transverse direction, using a trapped bubble of air held between two nip rolls. The orientation produced an approximately 2.7 m11 two-ply film in the form of a tube. Figure 3C is a schematic cross-sectional view of Patch Film No.

Table IV, below, includes the chemical composition and thickness of each of the layers, together with the function which the layer serves in the patch.

3 7 1 TABLE IV

Fig. 3C layer layer thickness desig nation laver function chemical-ident-jtv (mils) 202 inside layer 90% EVA #3 0.36 10% LLDPE #1 204 bulk homogeneous ethylene/ 1.39 alcha-olet:in copolymer 111 206 tie EVA #4 0.15 208 0,-barrier PVDC Blend l#1 0.18 210 tie 100% EVA #2 0.15 212 bulk homogeneous ethylene/ 0.30 alpha-olefin copolymer rIll 214 outside layer 92.5% EVA ATS 0.17 7.5% LLDPE rAl EVA- 11r13 was PE 3507-2 (TM) ethylene/vinyl acetate copolymer having a vinyl acetate content of 6.2%, a melt index of 2.5, and a density of 0.93, g/cc, and was obtained from DuPont. EVA '74 was EP 4062-2 (TM) ethylene/vinyl acetate copolymer having a vinyl acetate content of 15%, a melt index of 2.5, and a density of 0.938 g/cc., and was also obtained from DuPont. EVA IV.5 was LD-318.92 (TM) ethylene/vinyl acetate copolymer having a vinyl acetate content of 9%, a melt index of 2.0, and a density of 0.93 g/cc, and was obtained from Exxon. PVDC Blend #1 was a composition comprising:

(a) about 9 6 weight percent DOW MA1 3 4 (m) vinylidene chloridelmethyl acrylate copolymer having a methyl acrylate content of 8.5%, obtained from The Dow Chemical Company, of Midland, Michigan; (b) about 2 weight percent PLAS CEEK 775 (TM) epoxidized soybean oil, obtained from Ferro Chemicals, of Bedford, Ohio; and, (c) about 2 weight percent ISETABLEIT L1000 (TM) acrylate blend, obtained Elf Atochern, of- Philadelphia, Pennsylvania. METABLEN 38 L1000 (M) comprises about 53 weight percent methyl methacrylate 29 weight percent butyl methacry late ("BY-A"), and 19 weight percent butyl acrylate ("BA").

For Patch Film No. 19, which was commosed of two films each of which had a thickness of about 2.7 mils (i.e., a total thickness of about 5.4 mils) and each of which waz composed of the abovedescribed seven layers, the free shrink it(1 850 (deter=ned using ASTY1 2732) was about 75 percent, and the instrumented impact was about 112 pounds of force, and an energy to break of about 5 ft- lbs.

Preferably, the stock film from which the bag is formed has a total thickness of from about 1.5 to 5 mils; more preferably, about 2.5 mils. Although the film stock from which the bag is formed can be a monalayer film, preferably the film stock from which the bag i s f o=ed is a multilayer f ilm having f rom 3 to 7 layers; more preferably, 4 layers. Preferably, the bag film comprises an 02barrier layer, preferably as a core layer.

in a preferred patch bag according to the present invention, the bag film, i.e., the second heat-shrinkable film, comprises:

(A) an outside layer comprising at least one member selected from the gi:oup consisting of ethyl ene/alpha-ol ef in copolymer having -a density of from about 0.85 to 0.95, propylene/ethylene copolymer, polyamide, ethylene/vinyl acetate copolymer, ethylenelmethyl acrylate copolymert and ethylene/butyl acrylate copolymer,.

(B) a core 0. barrier layer comprising at least one member selected from the group consisting of ethylene/vinyl alcohol copolymer, polyvinyl chloride, polyvinylidene chloride, polyamide, polyester, polyacrylonitrile; and (C) an inside layer comprising at least one memb er selected from the group consisting of thermoplastic polyolefin, thermoplastic polyamide, thermoolastic polyester, and the=oplastic polyvinyl chloride.

Figure 5 illustrates a cross-sectional view of. preferred fourlayer film 51 for use as the tubing film stock from which, from 39 which, for example, bag portion 22 of preferred end-seal patch bag 20 (illustrated in Figures 1 and 2), can be formed. Multilayer film 51 can have, for example, a physical structure, in terms of number of layers, layer thickness, and layer arrangement and orientation in the patch bag, and a chemical composition in terms of the various polymers, etc. present in each of the layers, as set forth in Table V, below.

TJAB LE V F ig. 5 layer desig nation laver function chem;cal identity layer. thickness - (Mils) is 53 outside layer E VA #r 1 0.56 & abuse layer barrier layer.96% VDC/MA, Axl; 0.2 2% epoxicUzed soybean oil; 2% buty! acrylate/methyl acrylate/butyl methacrylate terpolymer 57 puncture-re- 80% LLDPE #1 1.25 sistant layer 20% EBA #1 59 sealant layer EVA #1 0.53 & inside layer EVA #1 was the same ethylenelvinyl acetate copolymer described above. VDC/MA 4T1 was SARAN MA-134 (TM) vinylidene chloride/methyl acrylate copolymer, obtained from The Dow Chemical Company. The epoxidized soybean oil was PLAS-CEEK 775 (TM) epoxidized soybean oil, obtained from the Bedf ord Chemical Division of Ferro Corporation, of Walton Hills, Ohio. Bu-AIMA/bu-MA, terpolymer was METABLEN L-1000 (TM) butyl acrylate/methyl methacrylate/butyl methacrylate terpolymer, obtained from Elf Atochem North America, Inc., of 2000 Market Street, Philadelphia, Pennsylvania 19103. EBA Arl- was EA 705-009 (TV-) ethylene/butyl acrylate copolymer containing 5% butyl acrylate, obtained from the Quantum Chemical Company of Cincinnati, Ohio. Alternatively, EBA '1 can be EA 719-009 (TV ethylene/butyl acryl ' ate copolymer, having butyl acrylate content of 18.5%, also obtained from Quantum Chemical Company. Optionally, the linear low' density polyethylene of the bag f ilm, can be replaced with a homogeneous ethylene /alpha-o lef in copolymer.

Figure 6 illustrates a schematic of a preferred process for producing the multilayer film of Figure 'S. In the process illustrated in Figure 6, solid polymer beads (not illustrated) are fed to a plurality of extruders 52 (for simplicity, only one extruder is illustrated). Inside extruders 52, the polymer beads are f orwarded, melted, and degassed, f ollow:;.ng which the resulting bubble-free melt is forwarded into die head 54, and extruded throuah an annular die, resulting in tubing 94 which is 10-30 mils thick, more preferably 15-25 mils thick.

After cooling or quenching by water spray from cooling ring 58, tubing 94 is collapsed by pinch rolls 60, and is thereafter fed throuah irradiation vault 62 surrounded by shielding 64, where tubing 94 is irradiated with high energy electrons (i.e., ionizing radiation) from iron core transformer accelerator 66. Tubing 94 is guided through. irradiation vault 62 on rolls 68. Preferably, tubing 94 is irradiated to a level of from about 2 to 10 MR.

After irradiation, irradiated tubing 96 is directed through pinch rolls 98, following which tubing 96 is slightly inflated, resulting in trapped bubble 100. However, at trapped bubble 100, the tubing is not significantly drawn longitudinally, as the surf ace speed of nip rolls 102 are about the same speed as nip rolls 98. Furthermore, irradiated tubing 96 is inflated only enough to provide a- substantially circular tubing without significant transverse orientation, i.e., without stretching.

Slightly inflated, irradiated tubing 96 is passed through vacuum, chamber 104, and thereafter forwarded through coating die 106. Second tubular -Eilm, 108 is melt extruded from coating die 106 41 and coated onto slJahtly inflated, irradiated tube 96, to form two ply tubular film 110. Second tubular film 108 preferably comprises an 0. barrier layer, which does not pass through the ionizing radiation. Further details of the above-described coating step are generally as set forth in U.S. Patent No. 4,278,738, to BRAX et.

al., which is hereby incorporated by reference thereto, in its entirety.

After irradiation and coating, two-ply tubing film 110 is wound up onto windup roll 112. Thereafter, winduD roll 112 is removed and instal-led as unwind roll 114, on a second stage in the process of making the tubing film as ultimately desired. Two-ply tubular film 110, from unwind roll 114, is unwound and passed over guide roll 72, af ter which two-ply tubular film 110 passes into hot water bath tank 74 containing water 76. The now collamsed, is irradiated, coated tubular film 110 is submersed in hot water 76 (having a temperature of aboutl210OF) for a retention time of at least about 5 seconds, i.e., for a time period in order to bring the film uD to the desired temperature for biaxial orientation.

Thereafter, irradiated tubular film 110 is directed through.ni_p rolls 78, and bubble 80 is blown. thereby transversely stretching tubular film 110. Furth76r=ore, while being blown, i.e.;" transversely stretched, nip rolls 86 draw tubular film 110 in the longitudinal direction, as nip rolls 86 have a surface speed higher than the surface speed of nip rolls 78. As a result of the transverse stretching and longitudinal drawing, irradiated, coated biaxially-driented blown tubing film 112 is produced, this blown tubing preferably having been both stretched in a ratio of from about 1:1.5 - 1:6, and drawn in a ratio of from about 1:1.5-1:6.

More preferably, the stretching and drawing are each performed a ratio of from about 1:2 - 1:4. The result is a biaxial orientation of from about 1:2.25 - 1:36, more preferably, 1:4 - 1:16. While bubble 80 is maintained between pinch rolls 78 and 86, blown tubing 112 is collapsed by rolls 84, and thereafter conveyed through pinch 1 42 rolls 86 and across. guide roll 88, and then- rolled onto windup roller 90. Idler roll 92 assures a good wind-up.

The polymer components used to fabricate multilayer films according to the present invention may also. contain appropriate amounts of other additives normally included in such compositions. These include slip agents such as talc, antioxidants, fillers, dyes, pigments and dyes, radiation stabilizers, antistatic agents, elastomers, and the like additives known to those of skill in the art of packaging films.

The multilayer films used to make the patch bag of the present invention are preferably irradiated to induce crosslinking, as well as corona treated to roughen the surface of the films which are to be adhered to one another. In the irradiation process, the film is subjected to an energetic radiation treatment, such as corona discharge, plasma, flame, ultraviolet, X-ray, gamma ray, beta ray, and high energy electron treatment, which induce cross-link-ing between molecules of the irradiated material. The irradiation of polymeric films is disclosed in U.S. Patent '. NO. 4,064,296, to BORNSTEIN, et. al., which is hereby incorporated in Its entirety, by reference thereto. BORNSTEIN,, et. al. discloses the use ' of ionizing radiation for crosslinking the polymer present in the film.

To produce crosslinking, a suitable radiation dosage of high energy electrons is applied to the film. Preferably, irradiation is carried out by an electron accelerator and the dosage level is determined by standard dosimetry methods. other accelerators such as a Vander Graff or resonating transformer may be used. The radiation is not limited to electrons from an accelerator since any ionizing radiation may be used. The ionizing radiation crosslinks the polymers in the film. Preferably, the film is irradiated at a level of from 2-15 MR, more preferably 2-10 MR. As can be seen from the descriptions of preferred films for use in the present

43 1 1 invention, the most pref erred amount of radiation is dependent upon the film and its end use.

The corona treatment of a film is pre.,;:or,-aed by subjecting the surfaces of the film to corona discharge, i.e., the ionization of a gas such as air in close proximity to a film surface, the ionization initiated by a high voltage passed through a nearby electrode, and causing oxidation and other changes to the film surface, such as surface roughness. Corona treatment of polymeric materials is disclosed in U.S. Patent No. 4,120,716, to BONETt issued October 17, 1978, herein incorporated in its entirety by reference thereto, discloses improved adherence characteristics of the surface of polyethylene by corona treatment, to oxiCze the polyethylene sur..;.:ace. U.S. Patent No. 4,879, 430, to HOFFY-AN, also hereby incorporated in its entirety by reference thereto, discloses is the use of corona discharge for the treatment of plastic webs for use in meat cook-in packaging, with the corona treatment of the inside surface of the web to increase the adhesion of the meat to the adhesion of the meat to the proteinaceous material.

Although corona treatment is a preferred treatment of the multilayer films used to make the patch bag of the present invention, plasma treatment of the firm may also be used.

A preferred patch bag of the present invention, as illustrated for example in Figures 1 and 2, can be manufactured by a preferred process as illustrated in Figure 7. The process of Figure 7 can be summarized as follows.

in general, a patch bag can be manufactured by carrying out the following process. First, a thermoplastic film is extruded, and thereafter oriented in a machine direction and a transverse direction, so that a first biaxially-oriented, heat- s hrinkabl e, thermoplastic patch film is produced. Then, the patch film is cut into a plurality of patches which are then adhered to a tubingr following which the tubing, having the patch adhered thereto, is 44 formed into a bag. Alternatively, but less preferably, the patch can be adhered to a pre-form, ed bag.

A preferred process for producing the patch bag of the present invention is as follows. First, a heat-shrinkable patch is produced by a process comprising the steps of: (i) coextruding a multilayer, thermoplastic patch tubing, comprising an outside layer and an inside layer, the outside layer comprising homogeneous ethyl ene/alpha-o 1 ef in copolymer and the inside layer comprising a polymer capable of sealing to itself; (ii) applying a sufficient amount of at least one member selected from the group consisting of an inert dust and an inert powder, to an inside surface of the patch tubing, so that upon collapsing the tubing after extrusion, the tubing does not self -adhere; (iii) collapsing the patch tubing; (iv) irradiating'the collapsed patch tubing so that polymers making up the patch tubing are crosslinked by the irradiation; (v) opening, inflating, heating, and stretching the patch tubing so that a biaxially- oriented, heat-shrinkable patch tubing is formed; (vi) simultaneously cooling, collapsing, and flattening the biaxially-oriented, heat- shrinkable patch tubing, -whereupon the inside layer of the biaxial ly- oriented, heat-shrinkable patch tubing adheres to itself, resulting in patch film s.tock. Secondly, a heat-shrinkable bag tubing is prepared in a manner as known to those of skill in the art, for example, by the method illustrated in Figure 6, described above. Third, adhesive is applied to one side of the patch film stock, and the resulting adhesive- coated patch film stock is cut into a plurality of patches, following which the resulting adhes ive -coated patch is adhered to the heatshrinkable bag tubing. Fourth, the heat-shrinkable bag tubing, having the patch adhered thereto, is cut and sealed, so that a patch bag is f ormed bag is formed f rom a portion of the heat shrinkable bag film tubing having the patch adhered thereto.

In this process, preferably the patch tubing is irradiated at a level of from about 2 to 15 lR. The adhesive can comprise any suitable adhesive as known to those of skill in the art. Preferably, two patches are adhered to the heat-shrinkable bag tubing.

Preferably, the tubing having the first and second patches adhered thereto is produced by the process illustrated in Figure 6, discussed above. In Ficmre 7, patch film roll 116 supplies patch film 118. Patch film 118 is directed, by idler roll 120, to corona treatment devices 131 which subject the upper surface of patch film 118 to corona treatment as 1Datch filM, 1-1-8 passes over corona treatment roll 122. After corona treatment, patch film 118 is directed, by idler rolls 124 and 126, into (optional) printing roll 128.

Patch film 118 is thereafter directed over idler rolls 130, 132, 134, and 136, after which patch film118 is passed through a small gap (i.e., a gap wide enough to- accommodate patch film 118 passing therethrough while receiving an amount of adhesive which corresponds with a dry coating, i.e. .,.weight after drying, of about milligrams per 10 square inches of patch film) between adhesive application. roll 138 and adhesive metering roll 140. Adhesive application roll 138 is partially immersed in adhesive 142 supplied to trough 144. As adhe.sive roll 138 rotates -"counter-clociwise, adhesive 142, picked up by the immersed surface of adhesive roll 138. moves upward, contacts, and is metered onto, the full width of one side of patch f ilm 118, moving in the same direction as the surface of' adhesive roll 138. [Examples of suitable types of adhesives include thermoplastic acrylic emulsions, solvent based adhesives and high solids adhesives, ultraviolet-cured adhesive, and electron-beam cured adhesive, as known to those of skill in the art.- A preferred adhesive is RHOPLEX N619 (TM) thermoplastic acrylic emulsion, obtained from the Rohm & Haas Company, at Dominion Plaza Suite 545, 17304 Preston Rd., Dallas, Texas 75252, Rohm & Eaas having headquar-ters at 7th floor, Independence Mall West, Philadelphia, Penn. 19105 -]Patch film 118 thereafter passes 46 so far around adhesive metering roll 140 (rotating clockwise) that the adhesive-coated side of patch film 118 is in an orientation wherein the adhesive is on the top surface of patch film 118, as adhesive-coated patch film 118 moves betweerr adhesive metering roll and idler roll 146 Thereafter, adhesive-coated patch film 118 is directed over drying oven entrance. idler roll 146, and passed through oven 148 within which patch film 118 is dried to a decree that adhesive 142 on match film 118 becomes tacky. Upon exiting oven 148, patch film 118 is directed partially around oven-exit idler roll 150, following which patch. film 118 is cooled on chill rolls 152 and 154, each of which has a surface temperature of c-ibout(40-45"F), and a diameter of about 12 inches. The cooling of patch film 118 is carried out in order to stabilize patch film 118 from further is shrinkage.

Thereafter, patch film 118 is directed, by idler rolls 156 and 158, onto a belt of pre-cutting vacuum conveyor assembly 160, and thereafter forwarded to a rotary scissor-type knife having upper rotary blade assembly 162 and lower blade 164, the. knife -cutting across the width of patch film 118 in order to form patches 166. Patches 166 are forwarded and held on top of a belt of post-cutting vacuum

conveyor assembly 168. While patches 166 are held on the belt of post-cutting vacuum conveyor assembly 168, tubing-supply roll 170 supplies biaxially oriented, lay-flat film tubing 172 which is directed. by idler roll 174, to corona treatment devices 176 which subject the upper surface of lay-flat tubing film 172 to corona treatment as lay-flat tubing f-;lm 172 passes over corona treatment roll 178. After corona treatment, lay-flat tubing film 172 is directed, by idler roll 180, partially around the surface of upper pre-lamination nip roll 182, and through the nip between upper prelaminating nip roll 182 and lower prelaminating nip roll 184, the pre-laminating nip rolls being above and below the post- cutting vacuum conveyor belt. Prelaminating nip rolls 182 and 184 47 position patches 166 onzo the now lower, corcria-treated outside surface of lay-flat film tubing 172. After passing through the nip between prelaminatinc niz rolls 182 and 184, lay-flat tubing 172, having patches 166 laninated intermittently thereon, exits off the downstream end of the past-cutting vacuum conveyor assembly 168, and is directed through the nip between upper laminating nip roll 186 and lower laminat.:,.-nc nip roll 188, these rolls exerting pressure (about 75 psi) -;-- order to secure patches 166 to lay-flat tubJncr 172, to result in patch- laminated lay-flat tubing 190.

0 Thereafter, patc-,,--'a=,.nar-ed lay-flat tubIng 190 is wound up to form rewind roller 192, with rewind roll 192 having the laminated patches thereon oriented [--awards the outer-facing surface of rewind roll 192.

in a subsequent pirocess not separately illustrated, rewind roll 192 is removed from its winder and is positioned in the place of tubing supply roll 170, and the process of Figure 7, described immediately above, is repeated, wherein a second set of patches is la=inated to patch-laminated lay-flat tubing' 192, this second set of patches being applied to the other side of patch-laminated lay- 0 flat tub;na 192. Of course, the second set of patches are accurately aligned and registered so that they are substantially aligned with the positioning of the first set of patches laminated to lay-flat tubing film 172. In order to achieve accurate alignment, photosensors (i.e., photoeyes, etc.), not illustrated, are used to detect the location of the patch. An appropriate location f or such a photosensor is upstream of upper pre-lamination roll 182, below the patch-laminated lay-flat tubing.

Throughout the process described above, patches 166 can have a width less thanafecual to the width of lay-flat tubing film 172, so that the patches respectively: leave uncovered regions along the sides of the baq, go to the edae of the lay-f lat tubing.

48 Once both sets of patches have been applied to lay-flat tubina film 172, the resulting two-patch tubing is directed into a bagmaking machine, in a process not illust-rated.

In general, sealing of film to produce' a bag can be performed using a hot bar (heat seal) or a nichrome 'wire fixed to a chilled metal bar (impulse seal), as is known to those of skill in the art, or any other sealing means l=own to those of skill in the art, such as ultrasonic radiation, radio freauency radiation, and laser.

The prefferred sealing means is an impulse sealer. Films which are predominantly polyethylene are generally sealed using impulse sealina orhot bar sealing. Both linear and shaped seals can be formed, as is known to those of skill in the art.

in general, sealing and cutting of tubing to produce bags is disclosed in U.S. Patent No. 3,552,090, U.S. Patent No. 3,383,746, is and U S-A-3625P6, ' - '. filed July 25, 1969, to OWEEN, each of these two U.S. Patents as well as the U.S. Patent application, hereby being incorporated by reference thereto, in their entireties.

Another alternative patch bag which can be used in the present inven tion is dis clos ed in u, s - A -L 5'jl-o 6.6,. in the names of G.K. WILLIAMS and S.A.-BRADY, fúled April 21, 1993,, which is hereby incorporated by reference thereto, in its entirety. This application discloses an end-seal patch bag having at least one patch thereon, preferably two patches thereon, wherein the patches are in a -rotated. position when the patch bag is in its lay-flat position. In accordance with the present invention, one or more supplemental seals are made inward of the pri=ary seal in the patch bag disclosed in the WILLIAMS, et. al. US-A-s4c6.

The catch bag according to the present invention can also comprise a plurality of overhanging bonded patches, as disclosed in copending U.S.S. N. 08/268,087, filed June 28, 1994, entitled 0PATCE BAG HAVING OVERIE1UNGING BONDED PATCHES-, filed June 28, 1994, in the 49 name of S. BRADY, et. al., the entirety of which is hereby incorporazed by reference thereto.

The patch bag according to the present invention can further comprise a primary seal across a portion of the bag which is not covered by a patch, and a secondary seal inward of the primary seal, as disclosed in copending U.S. Pc,tn entitled "PATCH BAG WITH SUPPLEMENTAL SEAL", filed July 21, 1994, in.the name of S. BRADY, et. al., the entirety of which is hereby incorporated by reference thereto.

A more detailed disclosure of this patch bag can be found in coperiding U. S. Patent Application to OBEIRLE et. al... entitl'ed "PATCH BAG HAVING CONTINUOUS PATCH". Of course, this feature is useful reaardless of whether the patches are overhanging and bonded to one another.

Although in general the bag according to the present invention can be used in the packaging of. any product, the bag of the present invention is especially advantageous for the packaging of food products, especially fresh meat products comprising bone. Among the meat products which can be packaged in the films and packages accorcLna to the present invention are poultry, pork, beef, lamb, goat, horse, and fish. More specifically, preferred meat products to be packaged in the patch bag of the present invention include ham, spareribs, picnic, back rib, short loin, short rib, whole turkey, and pork loin. The patch bag of the present invention is especially..useful for the packaging of a pair of bone-in whole pork loins.

Ficure 8 illustrates a perspective view of a pair of bone-in whole pork loins 244, each viewed from the ham end, aligned together in a preferred position for packaging in a preferred patch bag as illustrated in Figures 1 and 2, as described in detail above. The pair of pork loins as illustrated in Figure 8 are placed in the patch bag illustrated in Figures 1 and 2, with the -5=PT:) SulmOTIO; 9qZ;0 adOOS ORZ UMT Daz)TZDpad;Rq A-em SUOT-4RnT;TPOM ROns -AT5u-rPac:)OV -'Pzr-G-45aaPun AT-FP-eaa TT-Lm -.aR GW4 UT P9TTT:s 9SORZ SP 'UOTZUG.&UT 9R:;0 adOOS PU.2 5GIdTDU-Iad GR.4 MO.I; 5uT:apdap ZnogzTm paz-r-LTzn aq Apm sno-r Z12T2P.A PUR SUOTZ-R:)T;TPOW -4-9-q-4 p004SaapUn aC[ OZ ST ZT 'szuaurTpoc[ma paaia;gad 9.qz RzTm zo-,DaiiuoD UT P9C[T205GP Ua9q "R UOT-4UGAUT -4uasaad aq-4 Rf>noqlTy - saan-4Dund euoq asnR:) oi zsZ auoct pire '05Z guoq auTR: lsz E?uoq crra go Gaom ao quo ftoTTR 15pq Gq.4 go 05pa anz nioa; RnUT =TPR-GUO -4n0CER 01 o-4 dn ATuo pra:lxa a;aqzpz znq 15-pq Gq.4 go s95pa gpTs pq, ol pua-4xa ZOU op 5Gp:)ZRd GRZ RDTUM UT 5Pq nD:-gd R 5UTSn ZVqZ pnno; UGGq SPR z 1 -ZSZ auoq aagzRa; pu-e OSZ auoq G11TRD '9:7E GU0q C[TZ SUTPZ=On :..t,Z SUTOT xiod go -GAOC[R Pac[Taos;ap Z pr-2 1 saarL5Til 1IT pa:pazsnTTT F5pq ROZRcl aqz /.-9'T 'OE SPC[ ROZPd R;0 MGTA TRUOT:OGS -SSOaO R;0 UOTZTPPR gnZ RZTX Zgq.4950 19 9-zrL5T.R;0 6-6 UOT-4naS -q5no-znz Ua3[-e: MaTA TRI2OT-4z)'as-5502:) le 6 G-Tn5TA IIOTZugAzrT ZUaSaad GRZ 0Z BUT aoz)t, P ZnnPOZd PG5RX:)?d -2 TIT ZTnSaa 0Z IuaXurans pii-e "'P9T'Pas 5-aq q:)z-ad

Claims

C L A I M S

C 1. A patch bag comprising a heat-shrinkable monolayer patch film having a thickness of from about 2 to 8 mils, wherein the monolayer patch film comprises homogeneous ethylene/ alpha-olef in copolymer in an amount of from about 5 to 100 weight percent, and wherein the monolayer patch film is a first heat-shrinkable film which has a total free shrink at 850C (1850F) of from about 10 to 100 percent.
2. A patch bag according to claim 1, wherein the monolayer patch film comprises homogeneous ethylene/alphaolefin copolymer in an amount of from about 5 to 97 weight percent.
3. A patch bag according to claim 2, wherein the monolayer patch film comprises homogeneous ethylene/alphaolefin copolymer in an amount of from about 15 to 85 weight percent.
4. A patch bag according to claim 1, wherein the monolayer patch film comprises homogeneous ethylene/alpha- olefin copolymer and heterogeneous ethylene/ alpha-o le fin copolymer.
5. A patch bag according to any one of claims 1 to 4, wherein the monolayer patch film has a thickness of from about 3 to 6 mils.
6. A patch bag according to claim 11 wherein the heatshrinkable monolayer patch film comprises a blend of linear homogeneous ethylene/alpha-olefin copolymer and heterogeneous ethylene/alpha-olefin copolymer.
7. A patch bag according to claim 6, wherein the blend comprises from about 10 to 50 percent linear homogeneous ethylene/ alpha-olef in copolymer and from about 90 to 50 percent heterogeneous ethylene/alphaclefin copolymer.
8. A patch bag according to any one of claims 1 to 5, wherein the heatshrinkable monolayer patch film comprises long chain branched homogeneous ethylene/alpha- olefin copolymer and heterogeneous ethylene/ alpha-olef in copolymer.
9. A patch bag according to claim 8, wherein the heat-shrinkable monolayer patch film comprises a blend of long chain branched homogeneous ethylene/alphaolefin copolymer and heterogeneous ethylene/alpha-olefin copolymer.