Patent Publication Number: US-2005129885-A1

Title: Paired bags and method of making same

Description:
FIELD OF THE INVENTION  
      The present invention relates to sets of bags made from a heat-shrinkable flexible packaging film.  
     BACKGROUND OF THE INVENTION  
      Heat-shrinkable bags made from flexible thermoplastic film have for some time been used for the packaging of various products, such as food products, especially meat. An “end-seal” bag is one such bag. In the making of heat-shrinkable end-seal bags, thermoplastic material is extruded from an annular die, in the form of a seamless tubing, with the extrudate (known as a “tape”) being relatively thick and relatively narrow. The annular extrudate is then quenched. Optionally, the tape can then be irradiated and/or coated with one or more additional layers containing thermoplastic polymer. The tape is then reheated to its softening point by exposure to hot water or steam (or other heating means) and is stretched in its longitudinal and transverse directions while the polymer remains in the solid state, resulting in heat-shrinkable film in the form of a seamless tubing. The heat-shrinkable film tubing is then converted into end-seal bags by placing the tubing into a lay-flat configuration and heat-sealing across the tubing to heat-seal the inside surface of the tubing to itself. The seals across the tubing are made at intervals along the length of the tubing, these intervals corresponding with the desired bag length(s). The resulting sealed tubing is then converted into a plurality of heat-shrinkable bags by cutting across the tubing a short distance downstream of each of the transverse heat-seals, resulting in a plurality of lay-flat bags having an open top, two seamless side edges, a heat seal across the bag near the bottom edge of the bag, and a short section of tubing (commonly referred to as a “skirt”) below the transverse heat seal.  
      Because end-seal bags extend across the entire width of the lay-flat tubing, end-seal bags come off of the production line one at a time, with each bag requiring a separate sealing cycle, a separate printing cycle, and with each bag coming off the line as a single bag. It would be desirable to reduce the number of sealing cycles, printing cycles, and cutting cycles, to increase throughput of the process, and in some cases to provide bags of reduced width.  
      In addition, most meat processing plants have packaging equipment with large vacuum chambers for the evacuation of atmosphere and sealing of a bag containing a meat product. If two small bags are loaded into the same vacuum chamber at the same time, they may overlap and have weak seals. However, if a single small bag is loaded into the large chamber, capacity is under-utilized and additional labor is required. It would be desirable to be able to place more than one small bag into the chamber without having weak seals from bag overlap.  
      Side seal bags are also made by sealing across a seamless tubing. Whereas end-seal bags have a width corresponding with the lay-flat width of the seamless tubing, side-seal bags have a length corresponding to the width of the seamless tubing, and have a width corresponding to the selected distance between transverse seals which run along the side edges of side-seal bags. In the production of side-seal bags, two or more side-seal bags have been kept together and cut free of the remainder of the tubing, and used as a bag pair. However, side-seal bags have a disadvantage of having a free shrink along the length of the side-seal bag (i.e., in the transverse direction of the length of the seamless tubing) which is higher than the free shrink across the width of the side-seal bag (i.e., corresponding with the length of the tubing). Having a higher shrink across the tubing is detrimental to the packaging of relatively long, flat, flexible products in side-seal bags, as during subsequent bag-length shrinkage of a side-seal bag, the product can become distorted, i.e., “curved”, which lowers the appearance of the package to a consumer, and which is more difficult to box because of the curve in the package. Moreover, paired side-seal bags cannot be provided as a continuous string of connected pairs, as to make the “pair” requires that the pair be separated from the remainder of side-seal bags formed from the tubing.  
     SUMMARY OF THE INVENTION  
      The present invention provides a set of heat-shrinkable bags and a process for making sets of such bags. In the process, the number of printing cycles, as well as the number of cycles used to make the transverse seals, can be cut in half, thirds, etc., while making the same total number of bags, thereby enabling a doubling, tripling, etc., of the number of bags per extrusion die, as well as per print cycle and per transverse seal cycle. In addition, the sets of heat-shrinkable bags have a lengthwise free shrink (i.e., shrink in the machine direction) which is less than the transverse free shrink (i.e., shrink across the width of the bags), so that during shrinking the heat-shrinkable bags have less tendency to distort flat, flexible, elongate products packaged in the bag.  
      The process can be used to produce sets of bags in which the bags of each set are connected with one another across the machine direction of the film being used to make the bags. Optionally, each set of bags can be provided with an appropriate number of longitudinal tear lines (i.e., tear lines running the length of the bags, i.e., in the machine direction) for ease in separating the bags from one another. In addition, because the bags are connected to one another, like a single bag the connected series of bags can be stretched out across the opening of a vacuum chamber without risk of overlap during sealing.  
      Moreover, the invention can be carried out so that each set of bags is connected to at least one other set of bags in a line of succession, e.g., resulting in a strand of paired bags, which can be of indeterminate length as it comes off of a production line. Optionally, this strand of sets of bags can be provided with transverse tear lines (i.e., a weakened region between the sets of bags, such as a line of perforations, etc.) so that each set of bags can be easily torn free of the strand of bags, as well as lengthwise (i.e., machine direction) tear lines between the bags of each set, so that the packaged product can be offered as singlets or any subset of the original set of bags.  
      In the sets of bags of the invention, the bag length of each of the bags in the set runs in the machine direction of the tubing. Likewise, the bag width of each of the bags in the set runs in the transverse direction, i.e., across the tubing. A greater free shrink in the transverse direction is desirable for the packaging of a wide variety of products, particularly food products which tend to distort by bending along the length of the bag in which they are packaged. Various meat products, such as small beef and pork cuts, for example, beef and pork tenderloin, eye of round, single ribs, beef spare ribs, split beef back ribs, and various lamb cuts, tend to distort (i.e., bend) if packaged in a shrink bag having a higher shrink along the length of the bag than across the width of the bag. Such package distortion is reduced or eliminated in the sets of bags of the invention, which have have greater free shrink across the bag than along the length of the bag.  
      As a first aspect, the present invention is directed to a set of bags made from a film. The set of bags comprises a first lay-flat bag and a second lay-flat bag joined along their respective lengths, with an end seal extending across both the first bag and the second bag. The first bag has a first side seal extending the length of the first bag, and the second bag has a second side-seal extending the length of the second bag. The first bag is connected with the second bag in an area between the first side-seal and the second side-seal. Both the first bag and the second bag having a total free shrink at 185° F. of at least 10 percent, and both the first bag and the second bag have a transverse free shrink at 185° F. which is greater than a longitudinal free shrink at 185° F.  
      In one preferred embodiment, the set of bags has a first outer side edge and a second outer side edge, and at least one of the first outer side edge and the second outer side edge is a folded edge.  
      Preferably, the film has a total free shrink, at 185° F., of at least 15 percent; more preferably, at least 20 percent, more preferably, at least 25 percent; more preferably, at least 30 percent; more preferably, at least 35 percent; more preferably, at least 40 percent; more preferably, at least 45 percent. Preferably, the film has a total free shrink at 185° F. of from 15 to 150 percent; more preferably, from 20 to 140 percent; more preferably, from 25 to 130 percent; more preferably, from 30 to 120 percent; more preferably, from 35 to 110 percent; more preferably, from 40 to 100 percent; and, more preferably, from 45 to 90 percent.  
      Preferably, the end-seal, the first side-seal, and the second side-seal are heat seals. Preferably, the end seal, the first side-seal, and the second side-seal are each a seal of an inside surface of a seamless tubing to itself. The end-seal can be a straight seal or can be curved or have at least one curved region. If curved, preferably the end-seal is curved so that the bottom of the lay-flat set of bags is convex.  
      Preferably, the set of bags further comprises a line of weakness between the first bag and the second bag, the line of weakness being between the first side seal and the second side seal. Preferably, the line of weakness between the first bag and the second bag comprises perforations.  
      Optionally, a patch is adhered to the first bag and/or the second bag. Preferably, the first bag has a first patch adhered thereto, and the second bag has a second patch adhered thereto. Preferably, the first bag and the second bag are both made from a film having a total free shrink at 185° F. of at least 15 percent, and the first patch and the second patch are made from a film having a total free shrink at 185° F. of at least 15 percent.  
      Although the set of bags can be just a pair of bags, the set of bags can further comprise a third bag between the first bag and the second bag, the third bag having two side seals and an end seal. If the set of bags is a pair of bags, the first bag is preferably a mirror image of the second bag. Preferably, the first bag has a length equal to the length of the second bag. Preferably, first side-seal is parallel to the second side-seal.  
      Preferably, the film from which the set of bags is made is a multilayer film comprising a first outer film layer, a second outer film layer, and an inner O 2 -barrier layer comprising at least one polymer selected from the group consisting of vinylidene chloride/methyl acrylate copolymer, vinylidene chloride/vinyl chloride copolymer, ethylene/vinyl alcohol copolymer, polyamide, and polyethylene carbonate. Preferably, the multilayer film further comprises a fourth layer which serves as a tie layer between the barrier layer and the first outer film layer, and a fifth layer which serves as a tie layer between the barrier layer and the second outer layer.  
      Optionally, the first bag and the second bag have printing thereon.  
      As a second aspect, the present invention pertains to a plurality of sets of bags, with each set being in accordance with the first aspect of the invention (described above). The first set of bags comprises a first bag and a second bag joined along their respective lengths, the first pair of bags having a first end-seal extending across both the first bag and the second bag, the first bag having a first side-seal extending the length of the first bag, and the second bag having a second side-seal extending the length of the second bag, the first bag being connected with the second bag in an area between the first side-seal and the second side seal. The second set of bags comprises a third bag and a fourth bag, the second set of bags having a second end-seal extending across both the third bag and the fourth bag, the third bag having a third side-seal extending the length of the third bag and the fourth bag having a fourth side seal extending the length of the fourth bag. The third bag is connected with the fourth bag in an area between the third side-seal and the fourth side seal. The second set of bags is joined to the first set of bags in an area below the first end seal. Preferably, the third side seal is a continuation of the first side seal, and the fourth side seal is a continuation of the second side seal. Preferably, the second set of bags is joined to the first set of bags along a transverse line of weakness. Preferably, the line of weakness between the first set of bags and the second set of bags comprises perforations. Optionally, the set of bags further comprises a third set of bags which is joined to the second set of bags below the second end seal, and a fourth set of bags joined to the third set of bags below a third end seal, with the plurality of sets of bags being a portion of a strand of sets of bags, the strand being of indeterminate length. Unless inconsistent therewith, preferred embodiments of the second aspect of the invention correspond with preferred features of the first aspect of the present invention.  
      As a third aspect, the present invention pertains to a set of bags made from a film. The set of bags comprises a first lay-flat bag and a second lay-flat bag joined along their respective lengths, and an end seal extending across both the first bag and the second bag, with the first bag connecting with the second bag at a heat seal between the first bag and the second bag, the heat seal extending the length of the first bag and the second bag, with both the first bag and the second bag having a total free shrink at 185° F. of at least 10 percent and a transverse free shrink at 185° F. which is greater than a longitudinal free shrink at 185° F. Unless inconsistent therewith, preferred embodiments of the third aspect of the invention correspond with preferred features of the first aspect of the present invention.  
      As a fourth aspect, the present invention pertains to a process for converting a lay-flat film tubing to a plurality of sets of bags. The process comprises making a plurality of transverse seals across the lay-flat film tubing, with the transverse seals being spaced apart from one another by a distance corresponding with the length of each of the sets bags. Each of the transverse seals providing an end-seal across a bottom of each bag of each of the sets of bags. Then first and second longitudinal seals are made along the length of the lay-flat film tubing, the longitudinal seals providing a seal along an interior side edge of each of the sets of bags. The bags of each set of bags have a total free shrink at 185° F. of at least 10 percent and a transverse free shrink at 185° F. which is greater than a longitudinal free shrink at 185° F. Preferably, the lay-flat film tubing is a seamless tubing which is converted to the sets of bags by making transverse and longitudinal seals through the tubing, with each set of bags being separated from a remainder of the lay-flat tubing. Preferably, a the process further comprises making a line of weakness below each of the transverse seals. Preferably, the line of weakness is between the first and second longitudinal seals. Preferably, the line of weakness is below each of the transverse seals. Optionally, the process can be carried out by making one longitudinal seal down the length of the tubing, to produce a set of bags in accordance with the third aspect of the invention.  
      As a fifth aspect, the present invention pertains to a process for converting a flat film tubing to a plurality of sets of bags. The process is carried out by (A) center-folding the flat film along its length, to form a centerfolded film; (B) making a plurality of transverse seals across the centerfolded film, the seals being spaced apart from one another by a distance corresponding with the length of the sets of bags, each of the transverse seals serving as end-seals across the bottom of each of the sets of bags; (C) making first, second, and third longitudinal seals along the length of the centerfolded film, the first longitudinal seal providing a seal along and second longitudinal seals providing a seal along an interior side edge of each of the bags sets of bags. Unless inconsistent therewith, preferred embodiments of this fifth aspect of the invention correspond with preferred features of the fourth aspect of the present invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  illustrates a lay-flat view of a set (in this illustration, a pair) of L-seal bags made from a seamless tubing.  
       FIG. 2  illustrates a lay-flat view of a pair of L-seal bags made from a seamless tubing, with the pair of bags being connected to one another along a longitudinal line of weakness (e.g., perforations).  
       FIG. 3  illustrates a portion of a continuous string of L-seal bag pairs made from a seamless tubing with a longitudinal line of weakness between the bags of each pair, with each pair of bags being connected to the next successive pair of bags with a transverse line of weakness which is a short distance downstream of the transverse seal across the bags.  
       FIG. 4  illustrates a lay-flat view of a set (e.g., pair) of alternative L-seal bags made from a seamless tubing, each of the bags of each set having a curved end seal.  
       FIG. 5  illustrates a lay-flat view of an alternative pair of bags made by folding a flat film over on itself and sealing it to form a pair of bags.  
       FIG. 6  illustrates a lay-flat view of an alternative set of lay-flat bags which is made up of three bags across a seamless lay-flat tubing.  
       FIG. 7  illustrates a lay-flat view of a set of L-seal patch bags made from a seamless tubing to which a pair of patches are adhered.  
       FIG. 8  illustrates a schematic of a preferred process for producing the multilayer films for use in the sets of bags of the present invention.  
       FIG. 9  illustrates a lay-flat view of an alternative pair of L-seal bags in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      As used herein, the term “bag” is inclusive of L-seal bags, side-seal bags, backseamed bags, and pouches (i.e., “U-sealed” bags). An L-seal bag has an open top, a bottom seal, one side-seal along a first side edge, and a seamless (i.e., folded, unsealed) second side edge. A side-seal bag has an open top, a seamless bottom edge, with each of its two side edges having a seal therealong. Although seals along the side and/or bottom edges can be at the very edge itself, (i.e., seals of a type commonly referred to as “trim seals”), preferably the seals are spaced inward (preferably ¼ to ½ inch, more or less) from the bag side edges, and preferably are made using a impulse-type heat sealing apparatus, which utilizes a bar which is quickly heated and then quickly cooled. A backseamed bag is a bag having an open top, a seal running the length of the bag in which the bag film is either fin-sealed or lap-sealed, two seamless side edges, and a bottom seal along a bottom edge of the bag.  
      As used herein, the phrase “set of bags” refers to two or more bags which are connected with one another in a side-by-side relationship, with the bags extending across a tubing (seamed or seamless). The set of bags preferably comprises from 2 to 20 bags across the tubing, more preferably from 2 to 5 bags, more preferably 2 to 3 bags. Each bag preferably has a length of at least twice its width, more preferably three to ten times its width, with bag length and bag width being measured based on inside the bag dimensions while the bag is in a lay-flat position. The phrase “connected with”, as applied to the bags of a single set of bags, refers to the side-by-side relationship of the bags to one another, and does not require that the bags be directly adhered to one another. That is, two bags are connected with one another even if a third bag is between them or even if a section of waste film is between them. Likewise, two bags are connected with one another if they share as common side seal, as illustrated in  FIG. 9 , described below.  
      The phrases “lay-flat film tubing”, “lay-flat bag”, and “lay-flat width” are known to those of skill in the flexible film art. A lay-flat film tubing is extruded through an annular die, with the extrudate being cooled and gathered by converging sets of rollers and wound up in flattened form. A lay-flat bag includes end-seal, side-seal, L-seal, etc. bags which can be made by sealing the inside of a lay-flat film tubing to itself, following by cutting across the tubing to convert the tubing into, for example, an end-seal bag. A side seal bag requires slitting one side edge of the tubing in addition to cutting across the tubing. Side-seal and L-seal lay-flat bags can also be made by folding a flat film and sealing the inside surface of the folded film to itself. A pouch s often made by sealing two separate pieces of flat film to one another, with the seals extending up the sides of the pouch and across the bottom of the pouch, leaving the top of the bag open for the insertion of the product to be packaged.  
      As used herein, the phrase “line of weakness” refers to any line, whether straight or curved, whether wide or narrow, in which the film has been weakened by any means so that the film can readily be torn apart along the line. Preferably the line of weakness is formed by perforating the film.  
      As used herein, the phrases “heat-shrinkable film,” “heat-shrink film” and the like refers to a film which has been oriented while in the solid state (as opposed to a blown film, which is oriented at, above, or near the melting point of the polymer). The tension on a heat-shrinkable film increases upon the application of heat if the film is restrained from shrinking. As a corollary, the phrase “heat-contracted” refers to a heat-shrinkable film, or a portion thereof, which has been exposed to heat such that the film or portion thereof is in a heat-shrunken state, i.e., reduced in size (unrestrained) or under increased tension (restrained). Preferably, the heat shrinkable film has a total free shrink (i.e., machine direction plus transverse direction), with the free shrink in each direction (measured in accordance with ASTM D 2732) of at least as 5 percent at 185° C., more preferably at least 7 percent, still more preferably, at least 10 percent, still more preferably, at least 15 percent, and, yet still more preferably, at least 20 percent. The total free shrink at 185° F. can be from 10 to 150 percent, more preferably from 20 to 120 percent, more preferably from 40 to 100 percent.  
      As used herein, the phrases “inner layer” and “internal layer” refer to any layer, 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 of 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 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 “inside layer” refers to the outer layer of a multilayer film packaging a product, which is closest to the product, relative to the other layers of the multilayer film.  
      As used herein, the phrase “outside layer” 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. Likewise, the “outside surface” of a bag is the surface away from the product being packaged within the bag.  
      As used herein, the term “adhered” 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.  
      Although the films used in the patch bag according to the present invention can be monolayer films or multilayer films, the patch bag comprises at least two films laminated together. Preferably, the patch bag is comprised of films which together comprise a total of from 2 to 20 layers; more preferably, from 2 to 12 layers; and still more preferably, from 4 to 12 layers. In general, the multilayer film(s) used in the present invention can have any total thickness desired, so long as the film provides 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.  
       FIG. 1  is a lay-flat view of a pair of L-seal bags  10  which have been made by sealing the inside layer of a flexible, thermoplastic seamless tubing to itself. Pair of bags  10  comprises first bag  12  and second bag  14 , which in turn have open tops  16  and  18 , respectively, and transverse seal  20 , with end seal portion  22  serving as the end seal for first bag  12  and end seal portion  24  serving as the end seal for second bag  14 . First bag  12  has inner longitudinal seal  13  and second bag  14  has inner longitudinal seal  15 . Together end seal portion  22  and inner longitudinal seal  13  make up a so-called “L-seal” of first bag  12 , with the same being present for the combination of end seal portion  24  and inner longitudinal seal  15  for second bag  14 . First bag  12  and second bag  14  share central region  34 , which as illustrated has no weakened line, so that products packaged in first bag  12  and second bag  14  are paired with one another unless cut apart along the length of central region  34 . Side edge  28  of first bag  12  is a folded edge (which usually is creased during processing of the seamless tubing from which the bags are formed), as is side edge  30  of second bag  14 . Skirt region  32  is below transverse seal  20 , with skirt region  32  extending all the way across both first bag  12  and second bag  14 , i.e., from side edge  28  to side edge  30 , with skirt region  32  extending from immediately below transverse seal  20  to bottom edge  36 .  
       FIG. 2  is a lay-flat view of a L-seal bag pair  40  having features which correspond with the features of the pair of bags illustrated in  FIG. 1 , except that L-seal bag pair  40  additionally has a longitudinal line of weakness  42  running the length of central region  34 . Line of weakness  42  is preferably a set of perforations aligned along a straight line which is located in the middle of central region  34 , and which runs the entire length of central region  34 .  
       FIG. 3  illustrates continuous string  50  of L-seal bag pairs  40  having all of the feature as illustrated in  FIG. 2 . However, in continuous string  50 , immediately beneath skirt  32  of each bag pair  40 , is transverse line of weakness  52 . Line of weakness  52  is preferably a set of perforations aligned along a straight line located far enough below transverse seal  32  to provide skirt  32  with adequate width.  
       FIG. 4  is a lay-flat view of alternative L-seal bag pair  80  having features which largely correspond with the features of the pair of bags illustrated in  FIG. 2 , except that transverse seal  82  has curved sections  84  and  86 , which provide end-seals across the bottom of first bag  88  and second bag  90 , respectively. Likewise, matching curved sections are present at open top  92  and  94  of first bag  88  and second bag  90 , respectively.  
       FIG. 5  is an illustration of an alternative pair of bags  60  comprising first bag  62  and second bag  64  which can be made by centerfolding a flat film (or slitting a seamless tubing). First bag  62  and second bag  64  have open tops  16  and  18 , respectively. Pair of bags  60  has transverse seal  20 , with seal sections  22  and  24  serving as the end seal for first bag  62  and second bag  64 , respectively. In addition, first bag  62  has outer folded edge  28  and inner longitudinal seal  13  (i.e., first bag  62  being an L-seal bag). In addition to end seal section  24 , second bag  64  has both inner longitudinal seal  15  and outer longitudinal seal  66  (i.e., second bag  64  being a U-seal bag). Second bag  64  also has skirt  68  running the length of the bag, between outer longitudinal seal  66  and outer edge  70 . As in  FIG. 1 , pair of bags  60  share central region  34 , which as illustrated has no weakened line, so that products packaged in first bag  62  and second bag  64  are paired with one another unless cut apart along the length of central region  34 .  
       FIG. 6  illustrates a lay-flat view of an alternative set of lay-flat bags ( 100 ) including first bag  102  along a first folded side edge of the seamless tubing, second bag  104  along a second folded side edge of the seamless tubing, and third bag  106  positioned between first bag  102  and second bag  104 . Each of bags  102 ,  104 , and  106  shares transverse end seal  108 , and first bag  102  is an L-seal bag utilizing a portion of end seal  108  in combination with first side seal  110 . Second bag  104  is also an L-seal bag, also utilizing a portion of end seal  108 , but in combination with second side seal  112 . Third bag  106  is a U-seal bag utilizing yet another portion of end seal  108 , together with third side seal  114  and fourth side seal  116 . While side seals  110 ,  112 ,  114 , and  116  are termed side seals because they each run along a side edge of respective bags  102 ,  104 , and  106 , they each run in the machine direction. First bag  102  is joined to third bag  106  along line of weakness  118  (preferably a line of perforations), and second bag  104  is joined to third bag  106  along line of weakness  120  (preferably also a line of perforations).  
       FIG. 7  illustrates a lay-flat view of a pair of bags  122  which correspond with pair of bags  40  illustrated in  FIG. 2 , except that first bag  124  has patch  128  adhered thereto, and second bag  126  has patch  130  adhered thereto.  
      Preferably, the film stock film from which the bag is formed has a total thickness of from about 1.5 to 5 mils; more preferably, 1.5 to 4 mils; more preferably, 2 to 3. mils; more preferably, 2 to 2.5 mils. Preferably the stock film from which the bag is formed is a multilayer film having from 1 to 20 layers; more preferably, 3 to 10 layers; more preferably, 4 to 8 layers.  
      Preferably, the bag film, present in the form of a seamless tubing, backseamed tubing (lap seal, fin seal, or butt sealed backseamed tubing with butt seal tape) or as a flat film, has a total (i.e., L+T) free shrink at 185° F. of from about 45 to 125 percent, with a free shrink in the longitudinal (i.e., machine) direction of from 20 to 50 percent, and a free shrink in the transverse direction of from 25 to 75 percent, with the transverse free shrink being greater than the longitudinal free shrink. More preferably, the bag film has a total free shrink at 185° F. of from about 55 to 110 percent, with a free shrink in the longitudinal direction of from 25 to 45 percent, and a free shrink in the transverse direction of from 30 to 65 percent, again with the transverse free shrink being greater than the longitudinal free shrink. More preferably, the bag film has a total free shrink at 185° F. of from about 65 to 95 percent, with a free shrink in the longitudinal direction of from 30 to 40 percent, and a free shrink in the transverse direction of from 35 to 55 percent, again with the transverse free shrink being greater than the longitudinal free shrink.  
      Preferably, the transverse free shrink at 185° F. is higher than the longitudinal free shrink at 185° F. by an amount of from about 5 to 30 percent, more preferably from 8 to 20 percent higher. Preferably, the transverse free shrink is from 1.1 times to 1.8 times as high as the longitudinal free shrink, more preferably from 1.2 to 1.7 times as high, more preferably from 1.25 to 1.65 times as high.  
      Table I, below, provides a preferred multilayer film structure for making a set of bags in accordance with the present invention, including the composition, thickness, and general function of each of the film layers. This film, extruded from an annular die and thereafter extrusion coated, was in the form of a seamless tubing and had a total thickness of approximately 2.4 mils, and exhibited a total free shrink at 185° F. of 20% in the machine direction and 33% in the transverse direction.  
                       TABLE I                               Layer Thickness       Layer Function   Layer Chemical Identity   (mils)                  Outside and abuse   90% EVA #1   0.58       layer   10% HDPE #1       O 2 -Barrier layer   96% VDC/MA #1;   0.19            2% epoxidized soybean oil; and            2% bu-A/MA/bu-MA terpolymer       Puncture-resistant   85% LLDPE #1 &amp; 15% EBA #1   1.15       Sealant and inside   80% SSPE#1   0.48       layer   20% LLDPE #2                  
 
      In Table I, LLDPE #1 was DOWLEX® 2045 linear low density polyethylene, obtained from the Dow Chemical Company of Midland, Mich. LLDPE #2 was ESCORENE® LL3003.32 linear low density polyethylene, obtained from Exxon Chemical Company of Baytown, Tex. SSPE#1 was AFFINITY® Pl1280 metallocene-catalyzed ethylene/octene copolymer, having a density of 0.900 g/cc and a melt index of 6 g/10 min, obtained from The Dow Chemical Company, of Midland, Mich. HDPE #1 was Fortiflex® T60-500-119 high density polyethylene, obtained from Solvay Polymers, of Deer Park, Tex. EVA No. 1 was ESCORENE® LD318.92 ethylene/vinyl acetate copolymer having a melt index of 2.0, a density of 0.930 g/cc, and a vinyl acetate mer content of 9 percent, this resin being obtained from the Exxon Chemical Company. EBA No. 1 was SP1802 ethylene/butyl acrylate copolymer containing 18% butyl acrylate, obtained from Chevron Chemical Company, of Houston, Tex.  
      Table II, below, provides another preferred multilayer film structure for making the sets of bags in accordance with the present invention, the film having a total thickness of 3 mils and a free shrink at 185° F. of 28 percent in the machine direction and 36 percent in the transverse direction.  
                       TABLE II                               Layer               Thickness       Layer Function   Layer Chemical Identity   (mils)                                            Outside and abuse    80% SSPE2   0.21       layer    20% LLDPE3       Core Layer   100% LLDPE2   0.32       Tie Layer   100% EMA   0.11       O 2 -Barrier layer    96% VDC/MA #1;   0.21            2% epoxidized soybean oil; and            2% bu-A/MA/bu-MA terpolymer       Tie Layer   100% EVA1   0.11       Substrate Core Layer    60% LLDPE2   1.5            40% LLDPE3       Seal Layer    60% SSPE1   0.56            40% LLDPE 1                  
 
      Table III, below, provides another preferred multilayer film structure for making the sets of bags in accordance with the present invention, the film having a total thickness of about 2.2 mils and a free shrink at 185° F. of about 31% in the machine direction and about 44% in the transverse direction.  
                       TABLE III                               Layer               Thickness       Layer Function   Layer Chemical Identity   (mils)                                            Outside and abuse    85% SSPE2   0.19       layer    15% LLDPE3       Core Layer   100% LLDPE2   0.29       Tie Layer   100% EMA   0.1       O 2 -Barrier layer    96% VDC/MA;   0.19            2% epoxidized soybean oil; and            2% bu-A/MA/bu-MA terpolymer       Tie Layer   100% EVA1   0.1       Substrate Core Layer    80% LLDPE2   0.86            20% LLDPE3       Seal Layer    80% SSPE1   0.48            20% LLDPE 1                  
 
      Table IV, below, provides another preferred multilayer film structure for making the sets of bags in accordance with the present invention, the film having a total thickness of 2.3 mils and a free shrink at 185° F. of 25 in the machine direction and 41 in the transverse direction.  
                       TABLE IV                               Layer               Thickness       Layer Function   Layer Chemical Identity   (mils)                                            Outside and abuse   100% EVA4   0.6       layer       O2-Barrier layer    96% VDC/MA #1;   0.17            2% epoxidized soybean oil; and            2% bu-A/MA/bu-MA terpolymer       Substrate Core Layer   100% EVA4   1.28       Seal Layer   100% LDPE   0.26                  
 
      Table V, below, provides another preferred multilayer film structure for making the sets of bags in accordance with the present invention, the film having a total thickness of 2 mils and a free shrink at 185° F. of 31 in the machine direction and 46 in the transverse direction.  
                       TABLE V                               Layer               Thickness       Layer Function   Layer Chemical Identity   (mils)                                            Outside and abuse    85% SSPE2   0.18       layer    15% LLDPE3       Core Layer   100% LLDPE2   0.27       Tie Layer   100% EMA   0.09       O2-Barrier layer    96% VDC/MA #1;   0.18            2% epoxidized soybean oil; and            2% bu-A/MA/bu-MA terpolymer       Tie Layer   100% EVA1   0.09       Substrate Core Layer    80% LLDPE2   0.73            20% LLDPE3       Seal Layer    90% SSPE1   0.45            10% MB1                  
 
      Table VI, below, provides another preferred multilayer film structure for making the sets of bags in accordance with the present invention, the film having a total thickness of 2 mils and a free shrink at 185° F. of 26 in the machine direction and 42 in the transverse direction.  
                               TABLE VI                                           Layer                   Thickness           Layer Function   Layer Chemical Identity   (mils)                                                        Outside and abuse    85% EVA3   0.27           layer    15% LLDPE3           Core Layer   100% LLDPE2   0.4           Core Layer   100% EVA3   .13           Core Layer   100% EVA3   0.09           Substrate Core Layer    76% LLDPE2   0.8                24% MB2           Seal Layer   100% LLDPE4   0.31                      
 
      Table VII, below, provides another preferred multilayer film structure for making the sets of bags in accordance with the present invention, the film having a total thickness of 2.2 mils and a free shrink at 185° F. of 36 in the machine direction and 51 in the transverse direction.  
                       TABLE VII                               Layer               Thickness       Layer Function   Layer Chemical Identity   (mils)                                            Outside and abuse   100% SSPE2   0.19       layer       Core Layer   100% SSCPE3   0.29       Tie Layer   100% EVA2   0.10       O2-Barrier layer    96% VDC/MA #1;   0.19            2% epoxidized soybean oil; and            2% bu-A/MA/bu-MA terpolymer       Tie Layer   100% EVA1   0.10       Substrate Core Layer    90% SSCPE3   0.86            10% EPD       Seal Layer   100% SSPE1   0.48                  
 
      In Tables II through VII, SSPE1 was Dow Affinity® PL 1280 ethylene/octene copolymer, having a density of 0.900 g/cc and a melt index of 6 g/10min. SSPE2 was Dow Affinity® PL 1850, having a density of 0.902 g/cc and a melt index of 3 g/10 min. SSCPE3 was DPF 1150.01 single site catalyzed ethylene/octene copolymer having a density of 0.901 g/cc and a melt index of 0.9 g/10 min, obtained from Dow. LLDPE1 was Exxon Escorene® LL3003.32 linear low density polyethylene having a density of 0.9175 g/cc and a melt index of 3.2 g/10 min. LLDPE2 was Dow Attane® 4203, having a density of 0.905 g/cc and a melt index of 0.8 g/10 min. LLDPE3 is Dow Dowlex® 2045.03 linear low density polyethylene, having a density of 0.92 g/cc and a melt index of 1.1 g/10 min. LLDPE4 was Exceed® 4518PA ethylene/hexene copolymer having a density of 0.918 and a melt index of 4.5 g/10 min. LDPE was Ruxell® V3401 ethylene/octene copolymer having a density of 0.911 g/cc and a melt index of 5.7 to 7.5 g/10 min, obtained from Huntsman. EVA1 was LD-713.93 ethylene/vinyl acetate copolymer, having a vinyl acetate content of 15 percent, a density of 0.933 g/cc and a melt index of 3.5 g/10 min, and was obtained from Exxon. EVA2 was Escorene® LD 761.36 ethylene/vinyl acetate copolymer having a density of 0.95 g/cc, a melt index of 5.7 g/10 min, and a vinyl acetate content of 28 percent, obtained from ExxonMobil. EVA3 was Escorene® LD 318.92 ethylene/vinyl acetate copolymer having a density of 0.93 g/cc, a melt index of 2 g/10 min, and a vinyl acetate content of 9 percent, obtained from ExxonMobil. EVA4 was Elvax® 3128 ethylene/vinyl acetate copolymer having a density of 0.928 g/cc, a melt index of 2 g/10 min, and a vinyl acetate content of 8.9%, obtained from DuPont. EMA was EMAC SP 1305 ethylene/methyl acrylate copolymer, having a methyl acrylate content of 20 percent, a density of 0.944 g/cc and a melt index of 2 g/10 min, also obtained from Exxon. EPD was Vistalon® 7800 ethylene/propylene/diene terpolymer, having a density of 0.87 g/cc and a melt index of 1.5 g/10 min, obtained from Exxon. VDC/MA was SARAN® MA-134 vinylidene chloride/methyl acrylate copolymer, obtained from the Dow Chemical Company. The epoxidized soybean oil was PLAS-CHEK® 775 epoxidized soybean oil, obtained from the Bedford Chemical Division of Ferro Corporation, of Walton Hills, Ohio. Bu-A/MA/bu-MA terpolymer was METABLEN® L-1000 butyl acrylate/methyl methacrylate/butyl methacrylate terpolymer, obtained from Elf Atochem North America, Inc., of 2000 Market Street, Philadelphia, Pa. 19103. MB1 was FSU 93E polyethylene masterbatch with slip and antiblock, having a density of 0.975 g/cc and a melt index of 7.5 g/10 min, obtained from A. Schulman. MB2 was 180637 light cream masterbatch having a density of 1.25 g/cc, obtained from Ampacet.  
       FIG. 8  illustrates a schematic of a preferred process for producing the multilayer films described in Tables I, II, and III, above. In the process illustrated in  FIG. 8 , solid polymer beads (not illustrated) are fed to a plurality of extruders  140  (for simplicity, only one extruder is illustrated). Inside extruders  140 , the polymer beads are forwarded, melted, and degassed, following which the resulting bubble-free melt is forwarded into die head  142 , and extruded through an annular die, resulting in tubing  144  which is 10 to 30 mils thick, more preferably 15 to 25 mils thick.  
      After cooling or quenching by water spray from cooling ring  146 , tubing  144  is collapsed by pinch rolls  148 , and is thereafter fed through irradiation vault  150  surrounded by shielding  152 , where tubing  144  is irradiated with high energy electrons (i.e., ionizing radiation) from iron core transformer accelerator  154 . Tubing  144  is guided through irradiation vault  150  on rolls  156 . Preferably, tubing  144  is irradiated to a level of about 4.5 MR.  
      After irradiation, irradiated tubing  158  is directed through nip rolls  160 , following which tubing  158  is slightly inflated, resulting in trapped bubble  162 . However, at trapped bubble  162 , the tubing is not significantly drawn longitudinally, as the surface speed of nip rolls  164  are about the same speed as nip rolls  160 . Furthermore, irradiated tubing  158  is inflated only enough to provide a substantially circular tubing without significant transverse orientation, i.e., without stretching.  
      Slightly inflated, irradiated tubing  158  is passed through vacuum chamber  166 , and thereafter forwarded through coating die  168 . Second tubular film  170  is melt extruded from coating die  168  and coated onto slightly inflated, irradiated tube  158 , to form two-ply tubular film  172 . Second tubular film  170  preferably comprises an O 2 -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. Pat. 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  172  is wound up onto windup roll  174 . Thereafter, windup roll  174  is removed and installed as unwind roll  176 , on a second stage in the process of making the tubing film as ultimately desired. Two-ply tubular film  172 , from unwind roll  176 , is unwound and passed over guide roll  178 , after which two-ply tubular film  172  passes into hot water bath tank  180  containing hot water  182 . The now collapsed, irradiated, coated tubular film  172  is submersed in hot water  182  (having a temperature of about 210° F.) for a retention time of at least about 5 seconds, i.e., for a time period in order to bring the film up to the desired temperature for biaxial orientation. Thereafter, irradiated tubular film  172  is directed through nip rolls  184 , and bubble  186  is blown, thereby transversely stretching tubular film  172 . Furthermore, while being blown, i.e., transversely stretched, nip rolls  188  draw tubular film  172  in the longitudinal direction, as nip rolls  188  have a surface speed higher than the surface speed of nip rolls  184 . As a result of the transverse stretching and longitudinal drawing, irradiated, coated biaxially-oriented blown tubing film  190  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  186  is maintained between pinch rolls  184  and  188 , blown tubing film  190  is collapsed by rolls  192 , and thereafter conveyed through nip rolls  188  and across guide roll  194 , and then rolled onto wind-up roll  196 . Idler roll  198  assures a good wind-up.  
       FIG. 9  illustrates a lay-flat view of an alternative set of lay-flat L-seal bags  200 , also in accordance with the present invention. Set of bags  200  has been made by sealing the inside layer of a flexible, thermoplastic seamless tubing to itself. Pair of bags  200  comprises first bag  202  and second bag  204 , which in turn have open tops  206  and  208 , respectively, and transverse seal  210 , with end seal portion  212  serving as the end seal for first bag  202  and end seal portion  214  serving as the end seal for second bag  204 . First bag  202  is connected with second bag  204  longitudinal seal  216 . First bag  202  and second bag  204  share seal  216 , so that products packaged in first bag  12  and second bag  14  are paired with one another. Side edge  218  of first bag  202  is a folded edge (which usually is creased during processing of the seamless tubing from which the bags are formed), as is side edge  220  of second bag  204 . Skirt region  222  is below transverse seal  210 , with skirt region  222  extending all the way across both first bag  202  and second bag  204 , i.e., from side edge  218  to side edge  220 , with skirt region  222  extending from immediately below transverse seal  210  to bottom edge  224 .  
      The polymer components used to fabricate multilayer films for use in making the bags of the present invention may also contain appropriate amounts of other additives normally included in such compositions. These include antiblocking agents (such as talc), slip agents (such as fatty acid amides), fillers, pigments and dyes, radiation stabilizers (including antioxidants), fluorescence additives (including a material which fluoresces under ultraviolet radiation), antistatic agents, elastomers, viscosity-modifying substances (such as fluoropolymer processing aids) and the like additives known to those of skill in the art of packaging films.  
      The multilayer films used to make the bags 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-linking between molecules of the irradiated material. The irradiation of polymeric films is disclosed in U.S. Pat. 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.  
      Radiation dosages are referred to herein in terms of the radiation unit “RAD”, with one million RADS, also known as a megarad, being designated as “MR”, or, in terms of the radiation unit kiloGray (kGy), with 10 kiloGray representing 1 MR, as is known to those of skill in the art. A suitable radiation dosage of high energy electrons is in the range of up to about 16 to 166 kGy, more preferably about 40 to 90 kGy, and still more preferably, 55 to 75 kGy. Preferably, irradiation is carried out by an electron accelerator and the dosage level is determined by standard dosimetry processes. Other accelerators such as a van der Graaf or resonating transformer may be used. The radiation is not limited to electrons from an accelerator since any ionizing radiation may be used.  
      As used herein, the phrases “corona treatment” and “corona discharge treatment” refer to subjecting the surfaces of thermoplastic materials, such as polyolefins, 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. Pat. No. 4,120,716, to BONET, issued Oct. 17, 1978, herein incorporated in its entirety by reference thereto, discloses improved adherence characteristics of the surface of polyethylene by corona treatment, to oxidize the polyethylene surface. U.S. Pat. No. 4,879,430, to HOFFMAN, also hereby incorporated in its entirety by reference thereto, discloses 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 film may also be used.  
      A multilayer film is preferably converted to the bags of the present invention by heat sealing both across the film (i.e., a transverse heat seal) as well as heat sealing in the machine direction along the length of the film (i.e., a machine direction seal). The transverse seal is preferably made using a heat sealing method known as “impulse sealing”, which is carried out by placing a seal bar across the film and thereafter momentarily passing current through a heat seal wire on the seal bar. The seal wire heats up, transferring heat through a first side of the film tubing (or folded film) to the other side, causing the film to be sealed to itself. This sealing method is well known to those of skill in the art.  
      The lengthwise heat sealing (i.e., machine direction heat sealing) can be carried out using a seal bar and impulse sealing, i.e., in the same manner that the transverse seals are made. However, impulse heat sealing is generally carried out by forwarding the film intermittently in a direction along the length of the film tubing or sheet. If continuous forwarding of the film is desired during lengthwise heat sealing, a continuous band sealer can be used. Such continuous band heat sealers are described in U.S. Pat. No. 5,858,153, to Mack, entitled “Method for Making Tubular Containers”, as well as U.S. Pat. No. 6,344,258 B1, to Rasmussen, entitled “Heat-Sealing Polymer Films”, and U.S. Pat. No. 5,034,088, to Denker, entitled “Band Wheel and Tension Control”, each of which is hereby incorporated, in its entirety, by reference thereto. Continuous band sealers are available from, for example, Lamination Plus, 1142 West Flint Meadow Drive, P.O. Box 121, Kaysville, Utah, 84037, and Pierce Packaging Equipment, Inc., 217 South Claremont Street, San Mateo, Calif., 94401.  
      Although the present invention has been described in connection with the preferred embodiments, it is to be understood that modifications and variations may be utilized without departing from the principles and scope of the invention, as those skilled in the art will readily understand. Accordingly, such modifications may be practiced within the scope of the following claims.