Method of forming recloseable packages, profiles used therein and packages produced thereby

Abstract: The disclosure relates to a method of forming a recloseable package (10) using special profile strips (20, 30); the strips themselves and a resulting package are disclosed. The profile strips have a flange element (22, 32) and a recloseable means element (24, 34), and two mated profile strips are provided with a heat barrier means (23, 33). The method comprises the steps of providing mated top and bottom profile strips (20, 30) providing top and bottom package films (12, 14) on opposite sides of the mated strips and applying heat and pressure to the films adjacent the flanges (22, 32) sufficient to simultaneously form heat seals respectively between the top film (12) and the top profile strip flange (22) and between the bottom film (14) and bottom profile strip flange (32). The heat barrier means may comprise a thickened flange element (23, 33) buffer strip or a coextrusion of high temperature resin on the inside layer of the flange element. The heat barrier means prevents the flanges from fusing together during the formation of flange-film seals.

Description: This invention relates to a method of forming recloseable packages, profile strips used in the method and packages produced thereby. More particularly, the invention relates to recloseable packages which are made from two film layers hermetically sealed at the periphery of the package and sealed to profile strips having recloseable means elements formed thereon. A common method of packaging foods such as sliced luncheon meats and the like is by use of horizontal from, fill and seal procedures. In that procedure, a bottom film is placed horizontally over a piece of equipment having a cavity the general size and shape of the article to be packaged. Heat is applied and a vacuum is drawn in the cavity, forcing the bottom film into the cavity. The food article is placed inside the film-lined cavity, and a top film is placed over the article. Heat seals are made between the top and bottom films, often while the resulting package is being evacuated to produce vacuum packed food products. There has been a recent interest in providing food packages of the type thus produced with recloseable seals. In this regard, see U.S. Patent No. 4,782,951, which is incorporated herein by reference. Recloseable food packages are generally made from separate films and extruded profile strips, though some suggestion of films with integral recloseable means may be found in the art. In the more common practice, the separate profile strips each comprises a flange and an integral interlocking member. The profile strips are formed by two separate extrusions or through two separate openings of a common extrusion die. One profile strip may have a rib or male member and the other a mating groove or female member. The male or female member extends from the front face of the flange member. The rib and groove form a pressure fastenable and releasable closure mechanism. The back side, or sometimes an extended portion of the front face of the flange, is sealed to the package film so that the closure mechanism is disposed between the package walls adjacent the openable side of the package. Though there has been some suggestion for applying the profile to the film as soon as the profile is extruded, the more common practice is to wait to apply the profile strips to the film at the time the film is made into packages. In that case, the profile strips are extruded, mated, and rolled up for storage. When used on a horizontal from, fill and seal machine, the profile strips are unwound from storage rolls and sealed to the films used to make the packages. There have been two procedures for applying the profile strips to the films. In the less common procedure, the profile strips are unwound from storage spools and unmated. Each strip is then independently sealed to the package film. One procedure of doing this is to blow hot air on the back of the profile to heat it to its softening point. It then has to be immediately pressed into contact with the film. The primary difficulty encountered with this procedure is getting the combined film/profile strips in proper alignment after the cavity is formed in the bottom film, a product is placed therein and it is time to join the two films. Due to the difficulty in remating the interlocking members once the profile strips are attached to the film, another more complicated process used is to seal the mated profile straps to the film one flange at a time. In this regard, the equipment manufacturers have developed form, fill and seal machines in which a plow element is used to separate the flange segments of the mated profile strips without disengaging the rib and groove. A heat seal is then made between the bottom film and the back side of the flange of the bottom profile strip. After the food product is inserted into the film-lined cavity and the top film put in place, a plow arrangement is again used to separate the flanges so that the flange of the top profile strip can be sealed to the top film. Heat seals are also made around the rest of the package edges. The primary problem with this procedure is that the equipment is more complicated and a sealing step has to be performed in at least two different places in the process. However, machine manufacturers Klockner-Hooper of Itasca, Illinois and T.W. Kutter of Avon, Massachusetts, have produced machines with the plow arrangement. In addition we have sold a package closure comprising profile strips in the United States of America under the name FRESH-TRAK Style 40. The closure comprised profile strips each comprising a closable element for forming a reclosable seal and a flange element. The flange elements were thickened to provide heat barriers to enable the strips to be adhered by heat and pressure to the film walls of a package to form a heat seal therewith whilst not causing the inter-engaging flanges of the profile strips to fuse together. This invention provides a method of producing a reclosable package comprising film walls and reclosable profile strips, the method comprising the steps of: providing mated first and second profile strips, each strip comprising a reclosable means element for forming a reclosable seal and a flange element, said mated profile strips further comprising a heat barrier means associated with the flange elements; providing a first film adjacent the back side of the flange element of the first of the mated profile strips; applying heat and pressure to the film and adjacent flange element sufficient to form a heat seal between said first film and said flange element of the first profile strip, and the heat barrier means preventing said heat and pressure from fusing said flanges together; providing a second film adjacent the back side of the flange element of the second of the mated profile strips; applying heat and pressure to the second film and adjacent flange element sufficient to form a heat seal between said second film and said flange element of the second profile strip, said heat barrier means preventing said heat and pressure from fusing said flanges together; and forming seals between the films to complete the formation of the package; wherein the heat barrier means is of a material different to that of the flange elements, wherein each profile strip comprises an extruded resin, and wherein the heat barrier means comprises a resin co-extruded with the resin of at least one of the profile flanges so as to be between the flanges of the mated profile strips, the softening point of the resin comprising the heat barrier means being higher than that of the resin forming the co-extruded flange portion of the profile strip. The heat barrier serves the function of preventing the heat which seals the flange-film layers together from sealing the two flanges together. The machinery used in the process of the present invention, and its operation, are much simplified. No plows are required in the equipment to separate flange members for sealing. All sealing steps can be performed at the same time and at the same machine station. A double profile arrangements may be used to allow product filling on both sides of the center of web of film where the double profiles are sealed. The invention and its advantages will best be understood from the following detailed description of some preferred embodiments, reference being made to the accompanying drawings in which: FIG. 1 is a perspective view of a preferred embodiment package of the present invention; FIG. 2 is a sectional view taken along line 2-2 of FIG. 1; and FIG. 3 is a cross sectional view of a profile strip used in the package of FIG. 1. FIGS. 1 and 2 of the drawings show a recloseable package 10 to which the present invention is particularly applicable. As shown, package 10 contains a sliced luncheon meat product. The package can of course be used for any number of foods or even non-food items, and shaped appropriately. The package 10 is made from a top film layer 12, a bottom film layer 14, and two profile strips 20 and 30, best seen in FIG. 2. The two films are sealed around the peripheral sides by heat seals 15. Also, a peg hole 16 is formed in the package 10, with another seal 17 formed at the top edge and around the hole 16. The seal 18 between the product 11 and recloseable opening of the package is a peel seal. The seals 15 and 18 hermetically seal the package during distribution and sale. After purchase, a consumer separates the recloseable seal and the peel seal 18, leaving the peripheral seals intact. After removing a portion of the product, the profile strips 20 and 30 (described more fully below) may be used to form a recloseable seal to help maintain freshness of the unused product 11. The profile strips 20 and 30 include, respectively, flange elements 22 and 32, and recloseable means elements 24 and 34. The recloseable means elements 24 and 34 may be interlocking rib and groove members as shown, or may take other forms known in the art. A preferred shape of the interlocking rib and groove members is disclosed in U.S. Patent Nos. 3,038,225 and 3,198,228, incorporated herein by reference. The profile strips 20 and 30 each have a separate heat barrier means 23 associated with the inside face or front side of the flange elements 22 and 32. The heat barrier means ensures that films 12 and 14 may be simultaneously sealed respectively to the back sides of flange elements 22 and 32, while the interlocking elements are mated, without also fusing the flange elements 22 and 32 of the mated profile strips 20 and 30. Even though the inside faces of flange elements 22 and 32 do not fuse together, experimentation with the invention has shown that the flanges are often difficult to separate after the film-profile sealing process. It has been found that ridges 26 and 36 provided on the front face respectively of the flange elements 22 and 32 hold the flange elements 22 and 32 apart from each other, making it easier to separate the flange elements when opening the package 10. It is also speculated that the thickness added to the flange by the ridges helps prevent sealing of the flanges. The package 10 is formed in a horizontal form, fill and seal machine. The machine is similar to those produced by Klockner-Hooper and T.W. Kutter. Another machine manufacturer, Multivac or Kansas City, Missouri, has been developing simplified equipment to take advantage of the benefits of the present invention. Such a machine is sold by Multivac as their RT5200 packaging machine. The machine operation is similar to that described above, except simplfied. The profile strips 20 and 30 are provided with their respective recloseable means elements 24 and 34 mated. After the product 11 is in place, on the bottom film 14, the mated profile strips, 20 and 30, and the top film 12 are supplied, the mated profile strips of course being sandwiched between films 12 and 14. Heat and pressure are applied to the films 12 and 14 adjacent the profile flange elements 22 and 32 sufficient to simultaneously form heat seals 27 and 28 respectively between the top film 12 and back side of flange element 22 and between the bottom film 14 and back side of flange element 32. In the preferred process, these heat seals are made at the same time and in the same machine position that seals 15, 17 and 18 are made and the package 10 is evacuated (in the case of vacuum packaged food products). FIG. 3 shows one of a pair of profile strips 220 embodying the present invention (matching profile strips as shown in FIG. 2 are provided). Profile strip 220 is very similar to the profile strip 20 of FIG.2. In the FIG. 3 embodiment, heat barrier means comprising a heat resistant resin 226 is coextruded on a section of the front side of one or preferably both of the flange elements 222 and its unshown counterpart. The heat resistant resin has a higher softening point than the remainder of the flange element so that when the flange elements are heated during the film-flange sealing operation, the inside surfaces of the flange elements do not fuse together. For example, if the flanges are extruded from low density polyethylene, the heat resistant resin may be a polyester. The temperature and pressures used to seal the profile strips to the top and bottom films 12 and 14 will of course depend on the types of films used, their thicknesses, the resin used to make the profile strips, etc. These factors are commonly considered when appropriate process parameters are developed by those of ordinary skill in the art. The profile strips 20 and 30 are preferably made of low density polyethylene (LDPE) containing a blend of 0-10%, preferably 2%, EVA. The LDPE will have a density of from .900-.970 g/cm³. The preferred LDPE had a density of .920-.929 g/cm³. Other heat sealable resins may also be used. The preferred packaging films for use in processed meat application are Curwood Forming Web #579 for bottom film 14 and Curwood Nonforming Web #2580K for top film 12, both from Curwood, Inc. of Oshkosh, Wisconsin. The overall film composition may of course vary with the application, and can either be monolayer, coextrusion or a laminate. The sealant layer is the layer important to the present invention. The preferred sealant layer is LDPE with 2-6% EVA blended in. For this preferred embodiment, the sealing dwell time is from 0.5-5 sec., preferably 2 sec. Sealing temperatures are typically 200°F - 500°F, (approx. 100-250°C), preferably 260°F - 300°F (approx. 120-150°C). Sealing pressure are typically 40-110 psi (approx. 2.7-7.5 bar) preferably 80-100 psi (approx. 5.5-6.9 bar). In the embodiment of FIG. 3, the heat resistant resin will preferably by polyester, polyproplyene, polybutylene, SURLYN (Trade Mark) or other resin with a higher softening point than the softening point of the preferred LDPE-EVA resin blend used for the rest of the profile strip. The heat resistant layer will be from about 2-6 mils (approx. 0.05-0.15mm), preferably 2-4 mils (approx. 0.05-0.10mm) thick. Though the remainder of the flange need be only thick enough to seal to the package film, as a practical matter it is preferred to have the LDPE/EVA portion of the flange element 5-6 mils (approx. 0.12-0.15mm) thick, which is the minimum thickness of the profile. This makes it easier to have uniform coextrusion, since the die forming the profile strip must be machined in such a way as to also form the interlocking members. The invention has been described in its use with a horizontal form, fill and seal process. However, the method of the invention could also be practiced in vertical form, fill and seal procedures, overwrapping, and adapted for other packaging equipment processes. The package could be formed from a folded sheet instead of two separate films. In that case the fold between the two film halves would replace one of seals 15. Also, the peel seal 18 could be outside the recloseable seal. In the preferred process of the invention, the heat seals 27 and 28 are made simultaneously on both sides of the package. However, using the profiles of the present invention makes it possible to form the heat seals while the flanges are together, regardless of whether they are formed simultaneously. It may be advantageous, where existing equipment can be used with simple modification, to seal the top film 12 to profile strip 20 at one point and seal film 14 to profile strip 30 at a subsequent point.

Claims: A method of producing a reclosable package (10) comprising film walls (12 and 14) and reclosable profile strips (20 and 30), the method comprising the steps of: a) providing mated first and second profile strips (20 and 30), each strip comprising a reclosable means element (24,34) for forming a reclosable seal and a flange element (22,32), said mated profile strips further comprising a heat barrier means (226) associated with the flange elements (22,32); b) providing a first film (12) adjacent the back side of the flange element (22) of the first of the mated profile strips (20); c) applying heat and pressure to the film and adjacent flange element (22) sufficient to form a heat seal between said first film and said flange element of the first profile strip (20), the heat barrier means preventing said heat and pressure from fusing said flanges (22,32) together; d) providing a second film (14) adjacent the back side of the flange element (32) of the second of the mated profile strips (30); e) applying heat and pressure to the second film and adjacent flange element sufficient to form a heat seal between said second film and said flange element of the second profile strip (30), said heat barrier means again preventing said heat and pressure from fusing said flanges together; and f) forming seals (15) between the films to complete the formation of the package, g) characterised in that the heat barrier means (226) is of a material different to that of the flange elements, in that each profile strip (20,30) comprises an extruded resin, and in that the heat barrier means (226) comprises a resin co-extruded with the resin of at least one of the profile flanges (22) so as to be between the flanges (22,32) of the mated profile strips, the softening point of the resin comprising the heat barrier means being higher than that of the resin forming the co-extruded flange portion of the profile strip. A method as claimed in Claim 1, characterised in that the flange element (22) comprises a blend of low density polyethylene and 0-10% EVA, and the heat resistant resin (226) is selected from the group consisting of polyester, polypropylene, polybutylene and ionomer. A method as claimed in any Claim 1 or Claim 2, characterised in that the first film (12) and second film (14) are sealed to their respective flange elements (22,32) simultaneously. A method as claimed in any of Claims 1 to 3, characterised in that the heat barrier means (226) is sufficiently effective that the film wall (12) may be heat sealed to the profile strip (20) by the application of heat and pressure. A reclosable package comprising: a) film walls (12 and 14) sealed to each other and to reclosable profile strips (20 and 30) located along one side of said film walls to form the package, b) the reclosable profile strips each comprising: i) a flange element (22,32) having a front and back side; and ii) a reclosable means element (24,34) on the front side of the flange element; and c) a heat barrier means (226) associated with the front side of at least one of the flange elements sufficient so that one of the film walls may be heat sealed to the respective back side of the pair of reclosable profile strips while the reclosable means elements of the profile strips are mated, without also fusing the flange elements (22,32) of the reclosable profile strips, due to the presence of said heat barrier means (226); characterised in that the heat barrier means is of a material different to that of the flange element, in that the reclosable profile strips (20,30) each comprise an extruded resin and in that said heat barrier means (226) comprises a resin co-extruded with the resin of at least one of the profile flanges (22,32) so as to be between the flanges of the mated profile strips, the softening point of the resin comprising the heat barrier means being higher than that of the resin forming the co-extruded flange portion of the profile strip. A reclosable package as claimed in Claim 5, characterised in that the flange element (22) comprises a blend of low density polyethylene and 0-10% EVA and the heat resistant resin (226) is selected from the group consisting of polyester, polypropylene, polybutylene and ionomer. A reclosable package as claimed in Claim 5 or Claim 6, characterised in that the heat barrier means (226) is sufficiently effective that both of the film walls (12,14) may be simultaneously heat sealed to the respective back sides of the pair of strips (20,30) while the strips are mated without also fusing the flange elements (22,32) of the strips to each other. A reclosable package as claimed in any of Claims 5 to 7, characterised in that the heat barrier means (226) is sufficiently effective that the film wall (12) may be heat sealed to the profile strip (20) by the application of heat and pressure. A profile strip for use in making a reclosable package (10), the profile strip comprising: a) a flange element (22) having a front and back side; b) a reclosable means element (24) on the front side of the flange element (22); and c) a heat barrier means (226) associated with the front side of the flange element (22), said heat barrier means (226) being functional so that a film (12) may be heat sealed to the back side of the profile strip (20) while the profile strip is mated to a corresponding profile strip (30) without also fusing the flange elements (22,32) of the two mated profile strips (20,30), due to the presence of said heat barrier means (226); characterised in that said heat barrier means is of a material different to that of the flange element (22), in that the profile strip (20) comprises an extruded resin and in that said heat barrier means (226) comprises a resin co-extruded with the resin of the front side of the flange element (22), wherein the softening point of the resin comprising the heat barrier means being higher than the softening point of the resin of the co-extruded flange element. A profile strip as claimed in Claim 9, characterised in that the flange element (22) comprises a blend of low density polyethylene and 0-10% EVA and the heat resistant resin (226) is selected from the group consisting of polyester, polypropylene, polybutylene and ionomer. A profile strip as claimed in Claim 9 or Claim 10, characterised in that the heat barrier means (226) is functional so that a film (12) may be heat sealed to the back side of the profile strip (20) simultaneous to another film (14) being heat sealed to the back side of a mated, corresponding profile strip (30) without also fusing the flange elements (22,32) of the two mated profile strips (20,30) to each other. A profile strip as claimed in any of Claims 9 to 11, characterised in that the heat barrier means (226) is sufficient so that the film wall (12) may be heat sealed to the profile strip (20) by the application of heat and pressure.

Inventors: BUCHKO RAYMOND, TOMIC MLADOMIR, WEGNER WAYNE M, WIRTH LAWRENCE W, BUCHKO, RAYMOND, TOMIC, MLADOMIR, WEGNER, WAYNE M, WIRTH, LAWRENCE W
Applicants: REYNOLDS CONSUMER PROD, REYNOLDS CONSUMER PRODUCTS, INC.
Application year: 1990
Main classification: B65D33
IPC codes: B65D33, B31B19, B65B61, B65D75