Abstract:
A multiple compartment bag is provided. The bag includes opposite walls and a seal connecting the opposite walls and dividing the bag into a first compartment extending from a first side of the seal and a second compartment extending from a second side of the seal opposite the first side. The seal includes a length and each of the first and second sides spans the length. The seal also includes a first section along the seal length that has a first peel strength and a second section along the seal length adjacent to the first section that has a second peel strength greater than the first peel strength.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is based upon and claims priority on U.S. Provisional Application No. 61/178,860, filed on May 15, 2009, the contents of which are fully incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention is directed frangible seals for dividing bags in multiple compartments, to such multiple compartment bags with such frangible seals and to methods of forming such seals, especially to frangible seals in polyethylene bags, to polyethylene bags with such seals, and to methods of forming such seals in polyethylene bags. These frangible seals connected opposite walls of the bag along a seam to define the compartments. 
         [0003]    Plastic bags  10  having two compartments  12 ,  14  separated by a frangible seal  16  interconnecting opposite walls of the bags, as for example shown in  FIG. 1 , are known for use in the pharmaceutical and biotech industries for holding the appropriate solutions or contents used to make pharmaceuticals and the like. Such bags are described in PCT Publication No. WO 2007/142887, published on Dec. 13, 2007, the contents of which are fully incorporated herein by reference. Such bags are typically formed by welding together two films, each film defining an opposite wall of the bag. The two compartments in such bags are separated by the frangible seal. The frangible seal  16  is a “soft” seal such that it can easily be broken. As can be seen in  FIG. 1 , the frangible seal defines a seam  18  diving the bag in two compartments for storing separate materials which can be mixed at an appropriate time by easily breaking the frangible seal. For example, in the first compartment may be filled with a powder and the second compartment with a liquid. When ready to use, pressure is applied in one compartment, as for example by squeezing, which causes the frangible seal to rupture and the contents of the two compartments to mix. Although not shown in  FIG. 1  the bags have ports that allow the compartments to be filled with the appropriate contents. 
         [0004]    The problem with such bags is that many times the frangible seals inadvertently or prematurely rupture on their own or are very difficult to rupture. For example, the frangible seals may prematurely rupture when the second compartment is being filled with a liquid due to the pressure created by the liquid. Typically, the frangible seals are created using a sealing bar which applies pressure and heat along the bag to form the seal. Due to the slight differences in the intensity of the heat and pressure on the sealing bar which is used to form the seal, the frangible seals have weak points. These weak points may fail prematurely by slowly creeping open, especially on larger bags (i.e., bags having a capacity greater than one liter) whose one compartment is filled with a liquid. Bags made of polyethylene are significantly more susceptible to these problems than bags made of polypropylene. When the bags are made from polyethylene, such frangible seals cannot be formed to have consistent strength and thus, consistent performance. It is for this reason that currently most bags in the industry are formed from polypropylene. Consequently, more robust seals separating the compartments in such bags, especially such as polyethylene bags are desired. 
       SUMMARY OF THE INVENTION 
       [0005]    In an exemplary embodiment a multiple compartment bag is provided. The bag includes opposite walls and a seal connecting the opposite walls and dividing the bag into a first compartment extending from a first side of the seal and a second compartment extending from a second side of the seal opposite the first side. The seal includes a length and each of the first and second sides spans the length. The seal also includes a first section along the seal length that has a first peel strength and a second section along the seal length adjacent to the first section that has a second peel strength greater than the first peel strength. In another exemplary embodiment, the opposite walls are attached together along their periphery forming another seal having the second peel strength. In yet another exemplary embodiment, the second peel strength is at least 90% of the tensile strength of a wall of the bag. In a further exemplary embodiment, the second peel strength is at least 98% of the tensile strength of a wall of the bag. In another exemplary embodiment, the second peel strength is at least as greater or greater than the tensile strength of the wall. In one exemplary embodiment, the first peel strength is not greater than 13 lbs/in. In another exemplary embodiment, the first peel strength is not less than 3 lbs/in. In yet another exemplary embodiment, the second peel strength is at least 90% of the tensile strength of a wall of the bag. In a further exemplary embodiment, the second peel strength is at least 98% of the tensile strength of a wall of the bag. In yet a further exemplary embodiment, the first peel strength is in the range of 5 lbs/in to 9 lbs/in. In an exemplary embodiment, the peel strength of the seal along the first side is greater than along the second side. In one exemplary embodiment, a third section of the seal along the seal length adjacent the second section has said first peel strength and a fourth section of the seal along the seal length adjacent the third section has the second peel strength. In yet another exemplary embodiment, each of the first and third sections have a length greater than each of the second and fourth section along each side of the seal. In an further exemplary embodiment, the first, second, third and fourth sections are each trapezoidal in plan view and each have a length along the first side and along the second side of the seal such that the length of each of the first and third sections along the first side is shorter than their corresponding length along the second side, and such that the length of each of the second and fourth sections along the first side is longer than their corresponding length along the second side. In yet a further exemplary embodiment, the seal includes a plurality of first sections and a plurality of second sections, such that each of the first sections is adjacent to a second section of the plurality of second sections. In one exemplary embodiment, the seal defines a vertex along the length of the seal whereby a first portion of the seal along the seal length extends at an angle relative to a second portion of the seal along the seal length. In another exemplary embodiment, the seal further includes a third portion extending at an angle relative to the first portion and a fourth portion extending at an angle relative to the second portion and opposite the third portion. In yet another exemplary embodiment, the two walls are attached to each other at a periphery of each wall, and the third and fourth portions are aligned with each other and each extend to said periphery. In yet another exemplary embodiment, the bag is formed by attaching the two walls to each other along a periphery of each wall forming a seam, and the seam includes a first side, a second side extending from the seam first side and a third side extending from the seam first side and spaced apart from the seam second side, and at least a port between the seam second and third sides, and the seal extends from the seam second side to the seam third side. In a further exemplary embodiment, the bag is formed by attaching the two walls to each other along a periphery of each wall forming a seam, wherein the seam includes a first side, a second side extending from the seam first side and a third side extending from the seam first side and spaced apart from the seam second side, and at least a port between the seam second and third sides and the seal forms a loop in plan view beginning and ending at the seam first side such that a column is defined in the bag between the seal and the seam second side. In yet a further exemplary embodiment graduations are formed on one of the walls along the column. 
         [0006]    In another exemplary embodiment a multiple compartment bag is provided. The bag includes opposite walls, a first seal connecting the opposite walls defining a first compartment, the first seal having a first peel strength, a second seal connecting the opposite walls and extending from the first seal, the second seal having a second peel strength, and a second compartment is defined adjacent the first compartment bounded by the first and second seals, and a third compartment is defined adjacent the first and the second compartments and bounded by the first and second seals. With this embodiment, the second peel strength is lower than the first peel strength. In yet another exemplary embodiment, the first seal includes a plurality of first sections and a plurality of second sections, wherein each of the plurality of first sections is adjacent a second section of the plurality of second sections, wherein each first section has a third peel strength and wherein each of the second sections has a fourth peel strength, wherein the fourth peel strength is greater than the third peel strength. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a schematically depicted plan view of a prior art two-compartment bag. 
           [0008]      FIG. 2  is a schematically depicted plan view of an exemplary embodiment bag of the present invention. 
           [0009]      FIG. 3  is a schematically depicted plan view of another exemplary embodiment bag of the present invention. 
           [0010]      FIG. 4  is a partial plan view of an exemplary embodiment frangible seal of the present invention. 
           [0011]      FIG. 5  is a schematically depicted plan view of yet another exemplary embodiment bag of the present invention. 
           [0012]      FIG. 6  is schematically depicted plan view of yet a further exemplary embodiment bag of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0013]    Most multiple compartment bags in the industry are currently made from polypropylene. Applicants have invented a better frangible seal  20  that can be used on bags formed from polypropylene as well as from polyethylene ( FIGS. 2 and 3 ). Typically, such bags are formed by welding together two films (or layers) of polypropylene or two films (or layers) of polyethylene. Such welding forms a hard seal  21  around the perimeter  22  of the bags. These layers form opposite walls of the bag. Applicants have discovered that they can form a more robust frangible seal  20  by the “stitching” a soft seal  28  with hard seals  30  defining a seam  32  that divides the bag in a first compartment  36  and a second compartment  38 . In other words, as shown in  FIGS. 2 and 3 , hard seals  30  are placed intermittently along the seam defined by the soft seal  28 . In an exemplary embodiment, the hard seal is formed using the regular welding process which is used to form the bag. As such the hard seals have the same strength as the hard seal  21  forming the bag. In another exemplary embodiment, the hard seal has sufficient strength such that the bag will fail before the hard seal fails. Typically a soft seal has a peel strength in the range of about 3 lbs/in to about 13 lbs/in and preferably in the range of about 5 lbs/in to about 9 lbs/in. In an exemplary embodiment, a hard seal ideally has a peel strength equal to the tensile strength of the material forming the bag (i.e., the tensile strength of the film forming a wall of the bag) but preferably not less than of 98% of the tensile strength of the material forming the bag. Sometimes a hard seal has a peel strength of at least 90% of the tensile strength of the material forming bag. In many instances it is desired that the film forming the bag, and thus the bag, fails prior to the hard seal failing. The peel strength of a seal is the strength it takes to pull apart the opposite walls of the bag joined at the seal. In one exemplary embodiment, a soft seal allows the bag opposite walls to be pulled apart and to separate the soft seal without damaging the bag walls, whereas a hard seal is such that it cannot be pulled apart without the film tearing or otherwise being damaged. The peel strength of the seal is measured using a peel strength test as per ASTM D882. 
         [0014]    In a polyethylene bag, Applicants have discovered that there is a small window where the soft seam of the frangible seal can be broken by hand without simply falling apart. Applicants have discovered that there are four variables that affect the “softness” of the polyethylene soft seal. The four factors are temperature, time, pressure and geometry. The temperature of which the seam is created is critical as is the amount of time the seam is subjected to heat and pressure. The soft seals are created using a temperature and time roughly about ⅓ the temperature required to create a hard seal. While temperatures and times for creating a soft seal are lower than those required to create a hard seal, the pressure required to form the soft seal in an exemplary embodiment is about double the pressure required to form the hard seal. Applicants have discovered that higher pressure helps reduce creep which Applicants have also discovered is vital to the success of creating a soft seal with polyethylene film. In an exemplary embodiment, the temperature to which the polyethylene films are subjected to for forming the soft seal in polyethylene bags in the range of about 175° F. to about 225° F., the pressure is in the range of about 58 psi to about 80 psi, and the time for which the temperature and pressure is applied is in the range of about 8 to about 18 seconds. 
         [0015]    Applicants have also discovered that they can create a frangible seal having sufficient strength so as to be resistant to premature rupturing by creating a soft seal defining a seam for separating the compartments, and by stitching the soft seal with hard seals at intervals in the range of 1 to 3 inches, although these interval may be greater than 3 inches or smaller than 1 inch depending on the size of the bags. With larger bags which will hold more liquid which will subject the seal to larger hydraulic pressures, the intervals should be on the smaller side. In an exemplary embodiment, the hard seals have a length  40  that is about one third to one-half the length  42  of the soft seal portion between consecutive hard seals. 
         [0016]    Applicants have discovered that the strength of the frangible seals may also be affected by the geometry of the seal. i.e., the length and the shape of the seal. The longer the seal, i.e., the seam defining the seal, the more prone to premature failure. Furthermore, Applicants have discovered that they can control the function of the frangible seal by changing the overall shape of the frangible seal and its geometry. For example, Applicants have discovered that the overall shape of the frangible seal seam  32  shown in  FIG. 2 , which has two generally horizontal portions  44  and two oblique portions  46  defining a vertex  48 , works best with larger bags such as bags having the capacity of 10 liters or more, and the shape shown in  FIG. 3 , which includes two obliquely extending portions  50  defining a vertex  52 , works best with smaller bags such as bags having of 5 liters or less. Applicants have discovered that by incorporating a vertex in the seam, the bags are least likely to pinch closed. A bag pinches closed when one film forming the bag collapses and creates a temporary seal against an opposite film forming the bag. If a portion of the bag pinches closed, it may cause the operator to unintentionally over-pressurize the bag when filling it with a liquid or other material as the pinched portion of the bag will not accept any such liquid or material, which may cause premature rupture of the frangible seal. The angle of the between the obliquely extending sides defining the vertex may by optimized and may be different for each sized bag. 
         [0017]    Moreover, it is desirable to have a frangible seal that not only separates two or more chambers but also provides a geometry that makes it easy to fill the compartments with a consistent quantity of liquid or other material. A straight seal perpendicular to the sides of the bag works well for separating components but is difficult to visually see when the proper fill volume is reached. A straight seal extending from the sides of the bag at an angle, instead of perpendicular, increases sensitivity but requires the bag be kept upright and with its bottom edge perfectly level when filling. A desired frangible seal shape will both increase sensitivity and provide guidance for maintaining the bag in an upright orientation with its bottom edge being horizontal. 
         [0018]    It is difficult to find a shape that will not crease when the bag is filled. Such creases or folds create a pressure differential across the fold or crease, and consequently the bag compartments can not be filled to consistent levels because the pressure differential caused by the fold or crease varies with how the user supports the bag. Applicants have discovered that with the exemplary embodiments shown in  FIGS. 2 and 3 , the shapes of the frangible seal seams are such that fold or pinch points should not occur during filling. Moreover with these exemplary embodiments, the liquid or other material can uniformly fill the vertex which acts as a measuring region of the bag which may or may not have graduation marks indicating volume. In an exemplary embodiment, the measuring marks are laser etched onto the outside of the film. The vertex also provides increased sensitivity to visually measure the fill volume. In addition, the vertex will provide a gauge on both of its sides (i.e., the oblique portions  46  or  50 ) for determining if the bag is being held in an proper upright position. If it is, the liquid or other material will intersect each side of the vertex at the same level. Another advantage of the hard seals is that they create regions where such marking can occur without risk of damage to the film. 
         [0019]    In another exemplary embodiment, the geometry of the hard seals relative to the soft seal portions between the hard seals is varied. In one exemplary embodiment as shown in  FIG. 4 , the hard seals  30  are trapezoidal in shape when viewed in plan view. A benefit of using different geometries between the hard seal and the soft seal is that it makes such seals easy to visually distinguish from each other. The shape of the seal in an exemplary embodiment is created by using a different shape dye in the sealing apparatus that is used to form the seal. Such apparatuses known in the art. 
         [0020]    In an exemplary embodiment, when viewing the bag in plan view and thus, the seal along its length, the hard seals have a trapezoidal shape and so do the soft seals. Applicants have discovered that giving the hard seals a trapezoidal shape a frangible seal is formed having a softer side  31  and a harder side  33 . As can be seen due to the trapezoidal shapes of the soft seal and hard seals, the softer side has a greater portion of its length occupied by the soft seals  28  than the hard seals  30  as compared to the harder side. In this regard the frangible seal may tailored for specific needs. For example in case where the bag will house a powder and a liquid, the frangible seal may be designed such that the softer side is faces the compartment that will house the liquid so that it may rupture easier at the appropriate time. Other shaped hard and/or soft seals may be used to tailor the performance of the inventive frangible seals. 
         [0021]    Applicants have discovered that their inventive frangible seal works consistently on larger bags, such as bags capable of holding more than one liter, even more than 5 liters or even more than 10 liters of liquid. For example, the exemplary frangible seals may be successfully employed in ten-liter bags. The inventive frangible seals are more robust and much more resistant to leakage and premature rapture due to the large capacity of the bag or due to accidental dropping or pressing of the bag. By “stitching” the softer seal with hard seals, Applicants have discovered that they can create a frangible seal in larger bags behaves much like a soft frangible seal in a smaller bag which is much less vulnerable to leaking because of the smaller hydraulic pressures provided by the liquid in the bags and because of the shorter length of such seal. 
         [0022]    As discussed, the exemplary bags may contain either powder or liquid to eventually be mixed with another substance. The powder or liquid may be added via separate inlets (not shown in the drawings). The exemplary embodiment seals may be formed by forming each soft seal portion and each hard seal portion individually or may be formed by first forming a soft seal which defines the seal seam and then stitches the soft seal intermittently with hard seals. In yet a further exemplary embodiment hard seals are formed first and the soft seals are formed over the entire prospective seam (including over the hard seals) to define the frangible seal seam. 
         [0023]    Other exemplary embodiment frangible seal seam  32  designs are shown in  FIGS. 5 and 6 , respectively. In the embodiment shown in  FIG. 5 , a column  61  is created in the second compartment which connects a first portion  38 A of the second compartment with a second portion  38 B of the second compartment. In an exemplary embodiment, the column has a width  65  that is in the range of about 10% to about 20% of the width of the bag. The column  61  may be provided with graduations  63  that will allow the person filling the bag to know when the bag has been filled with an appropriate amount of liquid or other material. The frangible seal seam  32  in an exemplary embodiment is formed according to the principals of the present invention. In the embodiment shown in  FIG. 6 , the frangible seal forming seam  62  forming the first compartment  36  will be formed in accordance with the present invention such that it includes a soft seam stitched with hard seals. A further seam  64  is formed from a soft seal  66  to serve as a relief valve, defining a temporary compartment  68 . In this regard, when the second compartment  38  is filled with a liquid or other material, the soft seal seam  66  will break when enough pressure is created by the liquid or other material in the first compartment. When the seam  66  breaks it would give the operator an indication that the second compartment has been properly filled. In yet another exemplary embodiment, a pressure relief valve is incorporated in any or all of the compartments that provides relief from pressure and notice to the operator that a compartment has been filled with an appropriate amount of liquid or other material. An exemplary pressure relief valve will have Luer connectivity. 
         [0024]    As this invention has been described herein by way of exemplary embodiments, many modifications and variations will be apparent to those skilled in the art. Accordingly, it is to be understood that the invention described herein may be embodied other than as specifically described herein. For example, it should be understood that while the present invention especially applies to bags made from polyethylene, and while it also applies to bags made of polypropylene, it should be understood that it also equally applies to other material type plastic bags.