Method of producing a sealing system foe a reclosable film wall package, and system made by such a method

Abstract: The disclosure relates to a closure system for a film wall package including profile strips (2,4) having a reclosable seal (6,8) of the interlocking type, flange elements (10,12) and, adjacent the reclosable seal, an adhered strip of peelable material (22,24). The peelable material (22,24) and the profile strip (2,4) may be co-extruded. With packaging film attached to the profile strips, typically to the flange elements, the resulting product may be used in a horizontal form, fill and seal operation, at which time the reclosable elements are mated and a peel seal is formed. The peel seal may be disposed on either side of the reclosable seal with respect to the interior of the package. The benefits of both peel seals and reclosable seals may be obtained by using optimum materials for those elements while, at the same time, allowing the use of a different material for the walls of the package.

Description: The current invention relates to methods of forming a sealing system for a reclosable package, and the package made. In particular, it relates to a system for a package having walls of film or the like, typically formed from one or two webs sealed at the edges, the package having a reclosable seal and a peel seal. There has been recent interest in expanding the use of reclosable seals of the interlocking type, which typically are of the rib and groove type often informally called a zipper. Seals of this type are disclosed in U.S. Patents 2,978,769 of Harrah, 3,198,228 of Naito and 4,212,337 of Kamp. Zipper seals may be manufactured in advance as elements that may be called "profile strips" and later attached to webbing, as shown in U.S. Patent 3,948,705 of Ausnit. In the alternative, the seals may be co-extruded together with one or more film members that will form the walls of the package. It is presently preferred for such profile strips to be manufactured of polyethylene. Not only is polyethylene less expensive than many other materials typically used in this technology, but it does not take a strong set. That is, when manufactured in advance the profile strips may be wound on a spool or the like and, when unwound later, do not strongly tend to resume the wound shape. This provides a significant advantage. Also in the past, packages have been provided having additional seals to complement interlocking seals. Such packages are shown in U.S. Patents 3,181,583 of Lingenfelter (rupturable tear line) and 4,246,288 of Sanborn, Jr. (hermetic seal). Second seals specifically made of peelable material are shown in U.S. Patents 4,782,951 of Griesbach et al. (used in connection with interlock closure strips 14) and 4,786,190 of Van Erden et al. (used in combination with reclosable pressure sensitive adhesive 29). Especially in the case where peelable material is used to provide a seal, it is desirable to minimize the amount of such material used. It is costly in comparison to other seal materials used in this technology. As known in the art, the so-called "peelable material" referenced above is used to make a non- reclosable seal called a "peel seal". Certain materials, typically of resinous composition, are known to react in such a manner that they can be used in combination either with a dissimilar material or with additional material of the same composition to produce such seals. Therefore, whether or not a seal is peelable depends upon the materials used. This specification uses the term "peelable material" to describe a single element of such material, but it will be understood by those skilled in the art that the term refers to such a material when used together with additional material of the same or different composition in order to produce a peel seal. EP-A-0302144 discloses a bag having wall panels defining a receptacle space and providing a bag mouth arrangement between upper end portions of the panels. A tamper evident non-reclosable closure adjacent to a reclosable zipper is located below upper end portions of the wall panels and is accessible to be opened when the zipper is open. The zipper is arranged for intermittent opening and closing of the bag. The non-reclosable closure may be a peel seal or a rupturable connection. EP-A-0384588 published after the priority date of the application discloses a reclosable, hermetically-sealed flexible package which has interlocking reclosure strips bonded to the walls of the package at a location which is parallel to and spaced apart from a seal area. Positioned between the lips of the package and spaced from the reclosure strips is a tamper-evident feature which is bonded to the inner face of the lips. The tamper-evident feature is a tear element such as a paper or plastic-tape, a strip of adhesive which will form a one time bond, or a peel seal. US-A-4617683 discloses complementary profiled fastener strips secured to the mouth and portions of a reclosable bag and with closed cell elastomer sealing strip ribs carried by the fastener strips to press against one another in the closed fastener condition of the assembly. This invention provides a method of producing a sealing system for a package comprising the steps of forming first and second profile strips for attachment to the walls of the package, each strip comprising longitudinally-extending matching reclosable seal means of the interlocking type, and providing a peel seal for the package to one side of the reclosable seal means; wherein the profile strips are formed by extrusion and in that a strip of peelable material having a resinous composition is co-extruded with at least one of the profile strips substantially parallel to and proximate the reclosable seal means to form the peel seal. Preferably strips of peelable material of resinous composition are co-extruded with both profile strips parallel to and proximate the reclosable seal means to form, together, the peel seal. It is also preferred that said forming step comprises forming said first and second profile strips each with a flange element and adhering webbing to the respective flange elements to form opposite sides of a package. In the latter method said forming and adhering steps may comprise co-extruding a profile strip, an adhered strip of resinous peelable material and webbing. A package having such a sealing system will enjoy the benefits of two separate seals: a reclosable seal offering the benefits of a standard profile seal and a non-reclosable peel seal offering the benefits of such seals. Typically, the peelable material would be heat-sealed together at a time later than the time of manufacture of the sealing system, and most typically following the introduction of contents to a packaging web during a horizontal form, fill and seal operation. However, variations are possible. Also typically, the two interlocking seals would be joined together shortly after manufacture and the resulting zipper rolled on a spool. At a later time, the two profile strips will be joined to one or two webs of film to form the walls of the package. (In known manner, whether one or two webs of film are used to form the walls of the package will depend upon whether a single web is folded over to form two walls.) However, if desired the profile strips and the container walls may be co-extruded together. The invention also provides a sealing system for a package comprising first and second profile strips for attachment to the walls of the package each strip having longitudinally-extending reclosable seal means of the interlocking type and a peel seal for the package formed to one side of the reclosable seal means; characterised in that the profile strips are extruded and in that the strip of peelable material is of a resinous composition and is co-extruded with at least one of the strips substantially parallel to and proximate the reclosable seal means. The sealing system may comprise first and second profile strips each comprising longitudinally-extending matching reclosable seal means of the interlocking type and at least one of the profile strips being as defined above. More specifically said first and second profile strips may respectively comprise flange members and a webbing adhered to the respective flange members of said sealing system, the webbing comprising at least one wall of a package. The strip of resinous peelable material may beco-extruded with the profile strip. The flanges disclosed herein take the form of flange elements having thickened sections to form a heat barrier as disclosed and claimed in EP-A-0395362 the disclosure of which is hereby incorporated by reference. An advantage of using separate strips for the reclosable seal means is that one is not as limited by the composition of the materials used, and may somtimes use a less expensive material for the seal while attaining superior performance. For example, a preferred material for use in packing meat is an iononomer resin from Du Pont marketed under the trademark SURLYN. Yet, as explained above, it is presently preferred to manufacture a profile strip from polyethylene. An advantage of using a reclosable profile strip is that it provides a durable reclosable seal that is more desirable for certain applications than other reclosable seals such as adhesive seals. A further advantage of the current invention is that in certain cases, package size may be reduced. Figure 1 is a cross-sectional elevation of a first embodiment of profile strips according to the current invention, shortly after manufacture and before being joined together; Figure 2 is a cross-section of a second embodiment of profile strips according to the current invention, before being joined together; and Figure 3 is a fragmentary cross-section of a package according to the current invention and showing a seal made from the second embodiment described above, before being opened for the first time. Shown in Figure 1 are cross-sections of profile strips 2, 4 respectively having formed thereon interlocking reclosable seal means elements 6, 8. To the left of the elements 6, 8 in Figure 1 are flange elements 10, 12 having distal ends in the form of thickened sections 14, 16. Preferably, the sections 14, 16 have formed thereon ridges 18, 20. The functions of the elements 14-20 will be described briefly later and is described in greater detail in the above-mentioned EP-A-0395362. The interlocking seal means 6, 8 extend longitudinally of the profile strips 2, 4. First and second strips 22, 24 of peelable material also extend longitudinally of the profile strips, substantially parallel to and proximate the reclosable seal means 6, 8. It will be understood that, at some point before a package embodying the sealing system is completed, the strips of peelable material 22, 24 will be heat-sealed together to form a peel seal 26 as shown in Figure 3. It is preferred that the adherence of the strips 22, 24 to the profile strips 2, 4 be attained by co-extrusion of the profile strip with adhered peelable material. The material of the profile strips 2, 4 is preferably polyethylene but may be another known material for such use. Typically, the peel seal material may be made using SURLYN®. In particular, the peelable material may be made from one hundred percent virgin SURLYN® ionomer resin with additives blended-in or a product presently commercially known as SURLYN® 8414-1. In the alternative, a non-SURLYN® peelable material may be made by blending certain grades of polybutylene with ethylene vinyl acetate copolymer, or polyethylene, or both. An example of such polybutylenes are various grades marketed as DURAFLEX® by Shell Chemical Company, Polybutylene Business Center, Houston, Texas. The use of other peelable materials may be possible. Those set forth above are presently thought to be the most common. Nevertheless, the current invention is applicable to any extrudable peel seal material. The embodiment of Figure 1 is a sealing system in which the peel seal that is to be formed will be disposed on that side of the reclosable seal that is toward the interior of the package. Figure 2 shows a second embodiment according to the current invention in which the peel seal will be disposed on the exterior side of the reclosable seal. For purposes of the current invention, the two embodiments are otherwise thought to be substantially equivalent. However, users may have reasons for preferring one embodiment over the other. For example, the embodiment of Figure 2 may be more compact, and the embodiment of Figure 1 may prove easier to seal in connection with a step of applying top and bottom film layers 30, 32. According to either embodiment, there will result a single peel seal 26. The type of equipment used in forming the final package also may dictate the embodiment preferred. As an alternative to the embodiments shown in Figures 1 and 2, one may provide that only one of the two profile strips has a strip of peelable material. The current invention applies to two generic types of peel seals, both of which are known in the art. According to one type, the peel seal 26 will fail during opening at some point across its thickness. According to the second type, the peel seal 26 may remain intact when the package is opened, one of the two profile strips simply being peeled away from the peel seat. For purposes of the present invention, this distinction is not important. As stated above, the profile strips according to the current invention may be co-extruded together with the walls of the package. In the alternative, as shown in Figure 3, a package 28 may comprise a top film layer 30 and bottom film layer 32 joined by heat seals 34 and 36 to the profile strips 2, 4. During manufacture, dual profile strips may be formed by making tandem pairs of profile strips, as disclosed in the said EP-A-0395362. Also within the scope of the current invention is the option of expanding the strips of peelable material 22,24 so that they cover substantial portions of the profile strip surfaces on which they are disposed. While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and described herein in detail preferred embodiments of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention as defined in the claims to the embodiments illustrated.

Claims: A method of producing a sealing system for a package (28) comprising the steps of forming first and second profile strips (2,4) for attachment to the walls of the package, each strip comprising longitudinally-extending matching reclosable seal means (6,8) of the interlocking type, and providing a peel seal for the package to one side of the reclosable seal means; characterised in that the profile strips are formed by extrusion and in that a strip of peelable material (22) having a resinous composition is co-extruded with at least one of the profile strips (2) substantially parallel to and proximate the reclosable seal means (6,8) to form the peel seal. A method as claimed in Claim 1, characterised in that strips of peelable material (22,24) of resinous composition are co-extruded with both profile strips parallel to and proximate the reclosable seal means (6,8) to form, together, the peel seal. A method as claimed in Claim 1 or Claim 2, characterised in that said forming step comprises forming said first and second profile strips (2,4) each with a flange element (10,12) and adhering webbing (30,32) to the respective flange elements (10, 12) to form opposite sides of a package (28). A method as claimed in Claim 3, characterised in that said forming and adhering steps comprise co-extruding a profile strip (2,4), an adhered strip of resinous peelable material (22,24), and webbing (30,32). A sealing system for a package comprising first and second profile strips (2,4) for attachment to the walls of the package each strip having longitudinally-extending reclosable seal means (6) of the interlocking type and a peel seal for the package formed to one side of the reclosable seal means; characterised in that the profile strips are extruded and in that the strip of peelable material is of a resinous composition and is co-extruded with at least one of the strips substantially parallel to and proximate the reclosable seal means (6). A sealing system for a package (28) comprising first and second profile strips (2, 4) each comprising longitudinally-extending matching reclosable seal means (6, 8) of the interlocking type , at least one of the profile strips being as defined in Claim 5. A sealing system as claimed in Claim 6, characterized in that said first and second profile strips (2,4) respectively comprising flange members (10,12), and a webbing (30,32) adhered to the respective flange members (10,12) of said sealing system, the webbing comprising at least one wall of a package (28). A sealing system as claimed in Claim 6 or Claim 7, characterized in that the strip of resinous peelable material (22,24) is co-extruded with the profile strip (2,4).

Inventors: HEINTZ DAVID A, SIMONSEN STEVEN H, WEGNER WAYNE M, HEINTZ, DAVID A., SIMONSEN, STEVEN H., WEGNER, WAYNE M.
Applicants: REYNOLDS CONSUMER PROD, REYNOLDS CONSUMER PRODUCTS, INC.
Application year: 1990
Main classification: B65D33
IPC codes: B31B19, B65D33