Reclosable Package Using Low Tack Adhesive

A package configured to reclose after an initial opening and reduce head space in the package includes a plurality of walls with a pair of opposing wall segments, where each of the opposing wall segments have top and bottom edge portions, a width, a height, and facing inner surfaces. The plurality of walls are sealed to form an interior cavity to receive items therein, the cavity bounded by a bottom wall segment and an initially removably sealed upper mouth. The package further includes a low tack adhesive zone disposed across the entire width and extending from adjacent the mouth toward the bottom wall segment along at least a majority of the height of the facing inner surfaces. The adhesive zones have a greater affinity for adhesion to each other than to the items and permit the package to be repeatedly reopened and reclosed at a plurality of different heights to minimize headspace.

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Description
CROSS-REFERENCE To RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser. No. 61/308,540 filed Feb. 26, 2010; U.S. Provisional Application Ser. No. 61/317,592 filed Mar. 25, 2010; U.S. Provisional Application Ser. No. 61/407,406 filed Oct. 27, 2010; and U.S. Provisional Application Ser. No. 61/407,409 filed Oct. 27, 2010, all of which are incorporated herein by reference in their entirety.

FIELD

A reclosable package is described herein and, in particular, a reclosable package using a low tack adhesive to reclose the package.

BACKGROUND

A package, such as a package made of flexible material, is commonly used to store items during transportation, storage, and consumption by a user. A common type of prior package is mass-produced from a web of film material. The web is formed into a continuous tube by sealing the longitudinal edges of the web together. This continuous tubular package can then be singulated into smaller packages by sealing and cutting transversely across the tubular package in the region of the transverse seals.

Commonly, prior packages initially store the items within a sealed interior cavity prior to purchase by a consumer. The consumer can then break one of the seals or remove a corner of the package to access the interior cavity and the items therein. One issue that arises after the initial breaking is how to effectively reclose the package. Reclosing can be achieved by using interlocking zipper strips, including those with a slider mechanism, such as discussed in U.S. Pat. No. 5,007,143. This solution, however, is limited to reclosing the package along the zipper strips at the top of the package, which results in headspace created as the items are removed. Furthermore, the cost of adding the zipper strips can increase the cost of the package.

If a package is provided without a reclose feature, a common practice is to fold the edges of the package over to reduce the headspace above the items and close the broken seal. A clip can then be applied over the folded material to hold the package in this closed state. This practice, however, often does not sufficiently close the package and if the consumer does not have a clip, the package can unfold and fully expose the items.

SUMMARY

A package is described herein that is configured to reclose at a plurality of different locations progressively closer to the bottom of the package after initial opening and subsequent removals of items from within the package in order to reduce headspace in the package above the items. The package includes a pair of opposing walls each having at least one adhesive zone at least partially containing a low tack adhesive extending substantially across the entirety of the width of an interior of the package. When the opposing walls are pressed together, the adhesive zones reclose the package. The low tack adhesive is particularly effective in reclosing the package by having a greater affinity for itself than for the items stored therein, allowing the low tack adhesive to adhere to itself even if the low tack adhesive comes into contact with the items. As the items are sequentially removed from the package and the package reclosed, headspace is created above the items. The size of the adhesive zones can permit the opposing walls to be pressed together at a height closely adjacent to the items to reclose the package at that location, thereby minimizing the headspace in the package. The package can further include one or more separable areas of weakness that allow an upper portion of the package to be removed above a reclosed portion of the package.

This package can provide a number of advantages. For example, as a result of reducing headspace in the package, air in the reclosed package can be reduced. Additionally, if the adhesive zone is disposed along a plurality of heights of the package, the package can be reclosed at the plurality of heights, allowing the package to reclose closely adjacent the items stored therein as it is being sequentially removed at discrete times. Finally, the optional areas of weakness can allow excess packaging to be removed which provides easier access to the items.

In one aspect, the package can include a plurality of walls with a pair of opposing wall segments, where each of the opposing wall segments has top and bottom edge portions, a width, a height, and facing inner surfaces. The plurality of walls are sealed to form an interior cavity to receive the items. The cavity is bounded below by a bottom wall segment and above by an upper mouth that is initially sealed, but is removable to permit initial access to the items. The package further includes a low tack adhesive zone disposed on and substantially across the entire width of the opposing inner surfaces. The adhesive zone can extend from adjacent the mouth toward the bottom wall segment along at least a majority of the height of the opposing wall segments. The adhesive zones can have a greater affinity for adhesion to each other than to the items and permit the package to be reclosed using the adhesive zones at a plurality of different heights of the opposing wall segments. Reclosing the package at the plurality of different heights can allow the head space in the package above the items to be minimized as the items are sequentially removed from the package at discrete times.

In another aspect, the package can include at least two walls having facing inner surfaces, where the at least two walls are sealed to each other along longitudinal edge portions thereof to form a tubular pre-package. The tubular pre-package is initially sealed on top and bottom edge portions thereof, forming an initially sealed package having an interior cavity storing the items. The package can further include a low tack adhesive disposed in a pattern substantially spanning the circumference of the tubular package on aligned portions of the facing inner surfaces of the at least two walls. Preferably, the pattern is disposed intermediate of the top and bottom edge portions. Further, the low tack adhesive has a greater affinity for adhesion to itself than to the items, which effectively permits the package to be reclosed adjacent to the items after the items are sequentially removed by pressure of the low tack adhesive disposed on the facing inner surfaces together.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a reclosable package showing the mouth in its initial, closed configuration and the items at a filled level;

FIG. 2 is a cross-sectional side elevational view of the reclosable package of FIG. 1 taken along line 2-2 in FIG. 1 and showing the items at the filled level;

FIG. 2A is an enlarged portion of the cross-sectional side elevation view of FIG. 2 showing layers of the film wall of the reclosable package;

FIG. 3 is a perspective view of the reclosable package of FIG. 1 showing the mouth in an open configuration with the items at the filled level, and showing a partial sectional view of a portion of the package;

FIG. 4 is a perspective view of the reclosable package of FIG. 1 following initial opening of the mouth and removal of some of the items therethrough, and showing the items at an intermediate level and sealed opposing walls above the items;

FIG. 5 is a cross-sectional view of the reclosable package of FIG. 4 showing the items at the intermediate level and the sealed opposing walls above the items;

FIG. 6 is a perspective view of the reclosable package of FIG. 1 following initial opening of the mouth and removal of even more of the items therethrough, and showing the items at a low level and the sealed opposing walls above the items;

FIG. 7 is a cross-sectional view of the reclosable package of FIG. 6 showing the items at the low level and the sealed opposing walls above the items;

FIG. 8 is a perspective view of the reclosable package of FIG. 1 showing a removed portion above the sealed opposing walls above the items at the intermediate level;

FIG. 9 is a top plan view of a single web of flexible material showing a pattern of low tack adhesive; and

FIG. 10 is a top plan view of a single web of flexible materials showing a pattern of low tack adhesive.

 DETAILED DESCRIPTION

A reclosable package 10 is provided to allow a user to reclose the package 10, while also reducing headspace above items 12 stored inside of the package 10 while the items 12 are sequentially removed from the reclosable package 10. The items 12 can be any product suitable for the package 10, such as a food product, including, without limitation, crackers, cookies, cheese, meat, coffee, nuts, dried fruits, spices, etc., or other products that are sequentially removed, such as compacts discs, batteries, or office supplies, to name a few. In the exemplary embodiment described herein, the items are described with regard to a foodstuff.

The reclosable package described herein is achieved at least in part through the use of a low tack adhesive 14 disposed on opposing inner surfaces 16 of the reclosable package 10, where the low tack adhesive 14 has a greater affinity for adhesion to itself than to the foodstuff 12. This allows the low tack adhesive 14 on the opposing inner surfaces 16 to be sealed together, such as by a user pressing the opposing inner surfaces 16 together, even when the foodstuff 12 has come into contact with the low tack adhesive 14 during removal of the foodstuff 12. The reclosable package 10 can optionally include an area of weakness 18 disposed around a perimeter of the reclosable package 10 to allow a user to remove a portion of the reclosable package 10 above the foodstuff 12 and adjacent a sealed area of the opposing inner surfaces 16, thereby decreasing the size of the package 10.

In one aspect, the low tack adhesive 14 and package 10 are generally constructed or have a composition to minimize the adhesion of the adhesive 14 to undesired surfaces or foodstuffs 12 and still function at the same time as an effective reclosable fastener. That is, the adhesive 14 has a unique formulation or construction to achieve select tack and peel values so that the adhesive-based fastener can be opened and closed multiple times to seal the contents in the package 10 during use by a consumer, but at the same time not delaminate from the film substrate forming the opposing inner surfaces 16.

To this end, the adhesive 14 generally includes a UV-cured adhesive with relatively low tack levels to minimize adhesion to the unwanted surfaces, a selected bonding or opening peel strength sufficient to enable secure reclosure of the package 10, and a peel strength robust enough to enable repeated opening and reclosing of the package 10. At the same time, the adhesive 14 also has a strong bond to the film substrate so that the adhesive 14 does not delaminate upon opening of the package 10. By one approach, the adhesive 14 may include specific blends of a UV-curable acrylic oligomer and a tack control agent. In other approaches, the adhesive 14 may include specific blends of the UV-curable acrylic oligomer, the tack control agent, and an elastomer (rubber) component.

Preferably, the adhesive 14 is a UV-cured pressure sensitive adhesive (PSA) exhibiting cohesive properties and low tack, but, despite the low tack, still forms a strong bond to the film substrate forming the opposing inner surfaces 16. As generally understood, a cohesive-based material typically adheres more readily to like materials (i.e., self-adhesion) rather than to non-like materials. Suitable adhesive materials used herein generally exhibit a relatively low tack to undesired surfaces, but at the same time still exhibit a good bond strength to desired surfaces (such as no delaminating from the flexible front and back panels), and relatively good cohesive or self adhesion bond strength to like surfaces to hold a flexible package or pouch closed, but still permit the package to be openable or peelable by hand. The selected adhesive-based materials also permit debonding or peeling from such like materials so that the adhesive layers may be repeatedly peeled apart without substantial damage to the adhesive material and/or any underlying substrate. When the adhesive material is debonded or peeled apart, the selected adhesive materials has sufficient internal integrity and generally peels apart at an adhesive bonding interface substantially cleanly without substantial material picking, stringiness, delamination from the substrate, and/or other substantial disfigurations of the material (i.e., globbing, pilling, etc.). Advantageously, the adhesive-based fasteners herein maintain a peel adhesion where opposing adhesive strips contact each other with an average initial peel adhesion greater than about 200 grams per linear inch (gpli) and, preferably, between about 200 and about 900 gpli. Moreover, in some instances, the adhesive-based fasteners 14 retain greater than about 200 gpli and/or at least about 30 to about 200% of the average initial peel adhesion after five repeated seal and unseal operations.

In another aspect, the package 10 and adhesive 14 are also constructed to interact with each other so that the bond or peel strength of the adhesive 14 to the inner substrate surface 16 is generally greater than the opening peel strength between the layers of the adhesive 14 itself. In this manner, the adhesive 14 generally remains adhered to the inner surfaces 16 and does not substantially pick, string, or delaminate from the inner surfaces 16 when the package 10 is opened by a consumer as the adhesive 14 is peeled open. For example and in one approach, the bond or peel strength of the adhesive to the package film substrate is greater than about 900 gpli and is capable of withstanding multiple peel and re-seal cycles without detachment from the film substrate. In addition, the adhesive is cured so that it is capable of withstanding more than 100 double rubs with methyl ethyl ketone (MEK) solvent (ASTM D5402-06).

Referring now to FIGS. 1-10, an exemplary form of the reclosable package 10 is constructed from a single web 20 of flexible material top and bottom edge portions 22, 24, 42, and 44 and side edge portions 26. Before the web 20 is formed into the package 10, the low tack adhesive 14 may be applied or printed in a pattern 28 on a surface 29 of the web forming inner surfaces of the package 10. The low tack adhesive 14 may instead be formed on the web 20 at the time the package 10 is formed. The pattern 28 can take any suitable shape, including, for example all of the web 20, substantially all of the web 20 except for hermetic seal portions and tolerances therearound, on a majority of the web 20, such as intermediate of the top and bottom of the web 20 as shown in FIG. 9, or strips spaced along a height of the web 20 as shown in FIG. 10. The pattern 28, however, preferably at least substantially spans between the side edges 26 at desired heights, allowing for a longitudinal seal portion, so that the adhesive 14, when the package 10 is formed, can form a continuous seal.

In the illustrated form, the web 20 can be used to form the reclosable package 10, such as a typical vertical or horizontal form, fill, and seal type of pouch. In this form, the package 10 has a tubular shape sealed longitudinally by a fin seal 30 between the side edge portions 26 of the web 20. The package 10 includes a front wall 32 and a rear wall 34, each having top and bottom edge portions 36, 38 thereof. The package 10 further includes side walls 40 connecting the front and rear walls 32, 34 and having top and bottom edge portions 42, 44. In the illustrated form, a bottom seal 46 is formed between the bottom edge portions 38 of the front and rear walls 32, 34 and between the bottom edge portions 38 of the front and rear walls 32, 34 and the bottom edge portions 44 of the side walls 40. As illustrated, the side walls 40 fold inwardly at the bottom edge portions 44 to form the bottom seal 46, however, the side walls 40 could also fold outwardly to form an outwardly extending bottom seal. Folding the bottom edge portions 44 of the side walls 40 inward can create a bottom segment 48 for the package 10, upon which the package 10 can rest in a vertical orientation. In an another form, two webs with a mirrored pattern of low tack adhesive could be utilized where the webs are sealed together on opposing edge portions to create the tubular form. In yet another form, a gusset can be made along the bottom or sides of the package.

With the creation of the bottom seal 26, an interior cavity 50 is formed within the package 10 having a mouth 52 formed by the top edge portions 36, 42 of the front, rear, and side walls 32, 34, and 40. As in the typical form, fill, and seal process, after the longitudinal fin seal 30 and the bottom seal 46 are formed, the cavity 50 can then be filled with the foodstuff 12. As with the bottom seal 46, a top seal 54 can be formed between the top edge portions 36 of the front and rear walls 32, 34 and between the top edge portions 42 of the side walls 40. In the illustrated form, the top seal 54 is spaced from a top edge 53 of the package 10. This spacing creates a flange 55 which provides a grip for a user when opening the package 10, such as by breaking or removing the top seal 54. In this aspect, either one or both of the top seal 54 and the bottom seal 46 can be removable, meaning, for example, that the top seal 54 and the bottom seal 46 can be initially broken, or the entire seal 46, 54 can be removed from the package 10, such as with the aid of an area of weakness. So configured, the package 10 can be filled with the foodstuff 12 and hermetically sealed for storage, shipping, and display. The package 10 can then be opened by removing one of the seals 46, 54, the foodstuff 12 removed, and the package 10 resealed by sealing the opposing inner surfaces 16 together using the low tack adhesive 14.

As discussed previously, the package 10 can be provided to the user with the interior cavity 50 in an initially hermetically sealed condition enclosed by the bottom seal 46, the top seal 54, and the fin seal 30 storing the foodstuff 12. The user can then break or remove the top seal 54 to access the interior cavity 50 and the foodstuff 12. Following the initial breaking or opening, as the user sequentially removes the foodstuff 12 from the interior cavity 50, an increasing amount of headspace is created above the foodstuff 12. The low tack adhesive 14 can be utilized by the user to sequentially reduce this headspace.

As provided herein, the package 10 is reclosable at heights of the package 10 intermediate of the top seal 54 and the bottom wall segment 48, and specifically at heights where the pattern 28 of the low tack adhesive 14 substantially extends around a circumference of the package 10. As illustrated, the pattern 28 of the low tack adhesive 14 can cover a majority of the web 20, such as an area offset toward an upper portion of the package 10 as shown in FIG. 9, or all the web 20 except for the top and bottom edge portions 22, 24 and the side edge portions 26. Alternatively, the pattern 28 of the low tack adhesive 14 can be composed of a plurality of transversely disposed strips of low tack adhesive 14, such as those shown in FIG. 10. Accordingly, when a portion of the foodstuff 12 is removed, creating headspace in the package 10, the user can fold the side walls 40 inwardly at a height adjacent the foodstuff 12 and where the pattern 28 of the low tack adhesive 14 is disposed. After the side walls 40 have been folded inward, the user can press the front and rear walls 32, 34 together, pressing the circumferentially disposed low tack adhesive 14 together. As previously discussed, due to the low tack adhesive 14 having greater affinity for adhering to itself than to the foodstuff 12, the pressure applied by the user adheres the low tack adhesive 14 together and effectively recloses the package 10. The package 10 can then be reopened by breaking the seal between the low tack adhesive 14 disposed on the front, rear, and side walls 32, 34, 40, providing access to the foodstuff 12. As sequentially more foodstuff 12 is removed, the user can reclose the package 10 adjacent the foodstuff 12 to remove additional headspace in the package 10 by applying pressure against the low tack adhesive 14 at any of a plurality of heights as designed by the user within a zone where there is low tack adhesive 14 on the opposing walls. The zone may extend the entirety of the original interior height of the package 10, or may be at select heights only, e.g., the lower third, the upper third, the upper majority, the upper two-thirds or the upper three-quarters. Furthermore, a plurality of spaced zones can be provided, such as in fractions of 25%, 20% or 10%, and optionally can include exterior indicia on the package as to where the zones are located, such as graphics, areas of weakness or the like.

In one form, the web 20 may be formed of several layers of flexible materials. As illustrated, the web 20 includes an interior layer 56, an intermediate layer 58, and an outer layer 60. In one example, the interior layer 56 is a coextruded film with a heat sealable functionality, made substantially of a heat-sealable polymer composition such as polyethylene, EVA, Surlyn or blends thereof; the intermediate layer 58 is a metallic foil material, such as aluminum; and the outer layer 60 may be PET, such as an oriented PET. So configured, advertisements or other alphanumeric or graphical content can be displayed on the outer layer 60, such as by printing or adhering a label. The combination of the layers 57, 58, 60 acts as a barrier to the interior cavity 50.

Preferably, the adhesive is UV-cured, and more preferably a UV-cured PSA adhesive exhibiting cohesive properties and low tack, but forms a strong bond to the film substrate forming the walls 32, 34, 40 of the package 10. As generally understood, a cohesive-based material typically adheres more readily to like materials (i.e., self-adhesion) rather than to non-like materials. Suitable cohesive materials used herein generally exhibit a relatively low tack to undesired surfaces, a good bond strength to desired surfaces (such as no delaminating from the flexible front and back panels), and relatively good cohesive or self adhesion bond strength to like surfaces to hold a flexible package or pouch closed, but still openable or peelable by hand. The selected cohesive-based materials also permit debonding or peeling from such like materials so that the cohesive layers may be repeatedly peeled apart without substantial damage to the cohesive material and/or any underlying substrate. When the cohesive material is debonded or peeled apart, the selected cohesive materials has sufficient internal integrity and generally peels apart at a cohesive bonding interface substantially cleanly without substantial material picking, stringiness, delamination from the substrate, and/or other substantial disfigurations of the material (i.e., globbing, pilling, etc.).

The first component of the adhesive is one or more UV-curable acrylate or acrylic oligomers. For instance, the UV-curable acrylic oligomer may be an acrylic or methacrylic acid ester having multiple reactive or functional groups (i.e., acrylic or methacrylic oligomers). In general, a functional group includes one UV reactive site. UV reactive sites are most commonly carbon-carbon double bonds conjugated to another unsaturated site such as an ester carbonyl group. By one approach, the UV-curable acrylic oligomer is an acrylic or methacrylic acid ester of a multifunctional alcohol, which means the oligomer has more than one acrylated or methacrylated hydroxyl group on a hydrocarbon backbone of the oligomer. By one approach, the adhesive may include about 1 to about 90% by weight of the UV-curable acrylic oligomers and with functionalities of about 1.2 to about 6.0. In another approach, the UV-curable acrylic oligomers may have a functionality of about 2.0 to about 3.0, and/or be provided in the adhesive in an amount of about 20 to about 70% by weight.

In one form, the multifunctional UV-curable acrylic acid ester is an acrylic acid ester of a vegetable oil having a reactive functionality of 2.0 or greater. In another aspect, the UV-curable acrylic oligomer can comprise an epoxidized soybean oil acrylate. In general, the amount of the UV-curable acrylic oligomers used, based on a preferred adhesive component ratio (ACR) (to be discussed herein), can impact the properties of the final adhesive. For instance, where the amount of the UV-curable acrylic oligomer is too low, based on the preferred ACR, the cure rate of the final adhesive is too slow. On the other hand, where the amount of the UV-curable acrylic oligomer is too high, based on the preferred ACR, the final adhesive may be adequately cured but can have inadequate self adhesion properties to seal and reseal.

The second component of the adhesive is a tack control agent. By one approach, the adhesive may include about 1 to about 65% by weight of the tack control agent. In another approach, the tack control agent can be present in amounts from about 20 to about 65%. The tack control agent can include a tackifying resin or a curable polymer/monomer combination that when cured can produce the desired levels of tack and self-adhering properties appropriate for the reclosable fastener. In one aspect, the tack control agent can comprise an aliphatic urethane acrylated oligomer. Many other types of tack control agents suitable for UV-curable PSA adhesives may also be used in the reclosable adhesive system.

An optional third component of the adhesive is an elastomeric or rubber component. By one approach, the elastomeric component may include at least one curable acrylated (i.e., acrylic modified) or methacrylated esters of a hydroxy-terminated elastomeric polymer (i.e., an elastomeric polyol). This elastomeric component can include acrylic-modified polybutadiene, a saturated polybutadiene and/or a flexible polyurethane. In one aspect, a methacrylated polybutadiene can be provided. The elastomeric material can be provided in amounts of about 0 to about 20% when used in the adhesive. In one aspect, the elastomeric material is provided in amounts of about 5 to about 15%. Satisfactory adhesives can be made with the desired low tack, resealable properties as described herein without the elastomer component; however, it is believed that the elastomeric component aids in achieving an optimal coating performance. The optimal adhesive performance can be defined by properties such as self-adhesion, tack, viscosity, and cure rate, just to name a few. The elastomeric component is useful for adjusting peel strength properties, substrate adhesion strength, increasing flexibility, viscosity control, and cure rate modulation.

The average initial peel strength of a properly cured adhesive can be in the range of about 200 gpli to about 900 gpli and, in particular, about 280 gpli to about 800 gpli, as measured by ASTM D3330/D3330M -04 method F. The adhesive is also designed to retain its average peel after repeated open and close operations (i.e., adhesion retention). Preferably, the cured adhesive can retain its average initial peel adhesion between about 280 and about 800 gpli up to at least five repeated peel-reseal cycles. Preferably, the adhesion retention value upon peeling-resealing-peeling can be between about 30 to about 200% retention of the initial value. Upon contaminating the adhesive with crackers, the adhesion retention value can be between about 30% to about 150% of the initial value, where the cracker contamination test method is as described herein.

In another form, the package 10 can further include one or more areas of weakness 18 spanning between the side edge portions 26 of the web 20. As illustrated, there are a plurality of areas of weakness 18 disposed within a span of the height of the package 10, such as offset from the longitudinal center of the package toward the top of the package 10. Alternatively, any number of areas of weakness 18 can be utilized, longitudinally spaced from one another when more than one, wherever separation of the package 10 is desired. Additionally, the one or more areas of weakness 18 can be disposed generally transversely across the package 10 or can be disposed at an angle or contain other combinations of linear or curvilinear segments as the area of weakness 18 spans the width of the package. The areas of weakness 18, so disposed, may be separated by the user as the foodstuff 12 is sequentially removed from the package 10 in order to reduce excess material above the foodstuff 12 and allow for easier access to the remaining foodstuff 12 and easier evacuation of the foodstuff 12. Graphics or other indicia on the exterior of the package may coincide with the one or more areas of weakness.

Because portions of the areas of weakness 18 are disposed on a portion of the package 10 that covers the hermetically sealed interior cavity 46, the areas of weakness 18 preferably only score the web 20, such as through the outer layer 60, the interior layer 56, or a combination of the outer or interior layer 60, 56 and the intermediate layer 58. In the illustrated form, the area of weakness 18 includes a series of small scores (laser or mechanical), however, other patterns, shapes, and sizes of scores, perforations, thinned die lines and the like can be utilized.

In the exemplary embodiments illustrated herein, the reclosable package 10 has a generally rectangular cross-section having four sides. In use, however, the package may take any suitable shape of sufficiently flexible material, including, for example, curvilinear shapes, such as generally circular or elliptical, or shapes with linear cross-sectional sides, such as a triangle, a quadrilateral, a hexagon, an octagon, or other regular or irregular polygons. Such shapes can be utilized with a partially flexible material that allows the sides of the reclosable package 10 to be pressed together. Further, the sides may be connected by fold lines or seals. Thus, the sides may not be discrete from each other, e.g., comprising separate webs of film, but rather may generally have the appearance of having multiple sides or walls.

As discussed herein, the package 10 has been described for use with the foodstuff 12. The foodstuff 12 may include any suitable food material, including solids, liquids, or combinations thereof. Additionally, the package 10 may be utilized to store other materials, such as any suitable plastic, metal, organic material, or combinations thereof.

Advantages and embodiments of the adhesive described herein are further illustrated by the following examples; however, the particular conditions, processing schemes, materials, and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this method. All percentages are by weight unless otherwise indicated.

EXAMPLES Example 1

Various blends of acrylic oligomers, tack control agents and elastomeric materials were tested for compatibility and storage stability (stability being defined as a mixture that does not form gels or visibly separate after storing for up to 3 days at room temperature). Table 1 below shows the combinations tested and the formulation levels used.

TABLE 1 Adhesive Formulations Tested for Stability % Component Provided in Final Adhesive Formulation Adhesive Component Storage Stability Acrylic Tack Tack Tack Ratio of Liquid Blend Oligomer Elastomer Agent Elastomer Agent Agent (ACR) Observation after Sample No. A B C D E F — 3 days 1 40 15 45 — — — 0.67 Stable, no visible (Inventive) gels, no phase separation 2 — 15 45 — 40 — 0 Stable - but did (Comparative) not cure because too low ACR 3 40 — 45 15 — — 0.67 Unstable, because (Comparative) phases separated; components were incompatible 4 — — 45 15 40 — 0 Unstable, because (Comparative) phases separated and ACR too low 5 40 15 25 — — 20 0.67 Stable, no visible (Inventive) gels, no phase separation 6 40 15 — — — 45 0.67 Unstable, because (Comparative) phases separated; components were incompatible 7 60 — — — — 40 1.5 Unstable, because (Comparative) phases separated 8 — — — — 60 40 0 Unstable, gel-like (Comparative) structure formed and ACR too low

The components are identified as follows:
  • A=acrylated epoxidized soybean oil (CN 111 US, Sartomer Company, Exton, Pa.).
  • B=methacrylated polybutadiene (Ricacryl® 3500, Sartomer Company).
  • C=tackified aliphatic acrylate oligomer (CN 3001, Sartomer Company). This component comprises a blend of an aliphatic urethane acrylate and hydrocarbon tackifier resins.
  • D=polybutadiene styrene copolymer (Ricon 184, Sartomer Company).
  • E=tackified aliphatic urethane acrylate oligomer (CN 3211, Sartomer Company).
  • F=tackifier concentrate made with a light colored, low odor aromatic resin (PRO 11236, Sartomer Company).

Adhesive Ratio ( ACR ) = ( wt % Acrylic Oligomer ) ( wt % Elastomer + wt % Tackifier )

Stability or compatibility of these adhesive components may be a factor for manufacture, shipping, in-plant storage, and use of the liquid coating mixture. The stability was judged visually by appearance and consistency of the observed formulation after storage over a period of 3 days (about 72 hours). It was observed that Samples 1, 2 and 5 in Table 1 provided visually satisfactory blends of the various adhesive components that after 3 days remained homogeneous, i.e., the components did not visibly separate or form gels. Although Sample 2 resulted in a stable formulation, this adhesive component had an undesired ACR and did not cure well (i.e., this can be seen from the MEK Rub Cure test in Table 3 below, for similarly formulated Sample 10). However, Samples 1 and 5 provided stable adhesive blends that cured well and also had a desired ACR in the range of 0.5 to 1.5. The other sample blends either separated, became too viscous and/or gelled (i.e., Sample 8 became gel-like after 3 days). Sample 8 formed a gel, which indicated that the composition formed by the aliphatic acrylate, or component E, combined with the tackifier component F was not compatible.

Thus, to achieve a stable adhesive that is appropriate for use as disclosed herein, the stable adhesive generally needs to have one of the following and, in some cases, more than one of the following, and in other cases, all of the following factors: compatible components, curable, desired ACR, and all three component parts present (i.e., acrylic oligomer, elastomer, and a tack control agent).

Example 2

Based on the initial adhesive compatibility results for the stable formulations from Example 1, these formulations were further refined to produce five formulations of adhesive coatings that were all stable for at least 24 hours as a blend of the components indicated in Table 2.

TABLE 2 Revised Adhesive Formulations % Component Provided in Final Adhesive Formulation Adhesive Stability Acrylic Tack Tack Tack Component after 24 Sample Oligomer Elastomer Agent Elastomer Agent Agent Ratio (ACR) hours No. A B C D E F — — 9 40 15 45 — — — 0.67 Yes 10 — 15 45 — 40 — 0 Yes 11 40 15 20 — — 25 0.67 Yes 12 50 — 45  5 — — 1 Yes 13 45 — 45 10 — — 0.82 Yes

The components A through F are as indicated above in Example 1. Samples 9 and 10 correlate to Samples 1 and 2, respectively, from Example 1. Sample 11 is a variation of Sample 5 from Example 1. The remaining sample formulations were new.

After the five adhesive formulations exhibited good compatibility for at least one day, the five samples were all combined with about 1% of a photoinitiator (Esacure® KTO 46, Lamberti Spa, Italy) and then tested further. The photoinitiator was comprised of a liquid mixture of trimethylbenzoyldiphenyl phosphine oxide, α-hydroxyketones and benzophenone derivatives. The samples were then coated onto film substrates comprising ethylene vinyl acetate copolymer (EVA), Metallocene low linear density polyethylene (LLDPE) and about 12 percent of an organoclay composition (about 57-63% organically modified clay and maleic anhydride grafted linear low density polyethylene carrier, PolyOne Corporation, McHenry, Ill.). In particular, the substrate had about 77 wt % (EVA), about 10 wt % Metallocene LLDPE, and about 13 wt % organoclay composition. The samples were then cured after being coated onto the film substrates, where the curing was effected by application of UV radiation with three passes under a “D” bulb, which is a mercury with iron halide bulb. A single pass under a D bulb was approximately equivalent to 75 mJ/cm2 to 100 mJ/cm2. After the coating was cured, the cured adhesive layer was evaluated for the degree of cure and effectiveness to bond to the film.

The degree of cure of the adhesive was tested using a solvent rub resistance test referred to as a methyl ethyl ketone (MEK) rub test, as per ASTM D5204. Good cure results were shown by an MEK rub value of 100 double rubs or more, which indicated that the adhesive was cured well and thus showed a resistance to the MEK rubbed over it. Poorly cured adhesives did not show much resistance to the MEK (e.g., 10 double rubs or less). MEK rub test results can be seen in Table 3 below.

Tack and initial peel of the adhesives were also observed, and reported subjectively. The tackiness of the adhesive layer was observed upon touching and the level of tack was evaluated on a scale of Low (L), Medium (M), and High (H). Similarly, the subjective force required to peel apart the samples by hand was also evaluated on a scale of L, M, and H. These test results can be seen in Table 3.

TABLE 3 Test Results for Cure and Preliminary Adhesion for Table 2 Formulations. MEK Rub Test Subjective Subjective Sample No. (# of double rubs) Tack Test Peel Test  9 >100 M M (Inventive) 10  ~10 M-H M-H (Comparative) 11 >100 M M (Inventive) 12  100 M M (Comparative) (Haze on surface) 13  100 M-H M-H (Comparative) (Haze on surface)

All of the samples had at least moderate tackiness and peel strength. Sample 10 had the highest subjective tack and peel but the poorest cure, as evidenced by an MEK rub test of about 10, which showed that after about 10 rubs of MEK the adhesive was removed from the substrate. Samples 12 and 13 had a haziness upon performing the MEK rub test, most likely due to component D, the polybutadiene styrene copolymer, rising to the surface when rubbed with MEK. Therefore, although Samples 12 and 13 fall within the desired adhesive ratio range, component D does not appear to be compatible with the other two components and thus is not a satisfactory adhesive compound. It was desirable to find an adhesive with a subjective tack result of medium or lower, subjective peel force of medium or higher and an MEK rub test of 100 double rubs or greater without haze formation, which at a minimum, Samples 9 and 11 exhibited.

Example 3

The curing effectiveness of three different variations of an adhesive formulation were tested by applying the adhesive to the same film substrate as described in Example 2 and then curing in three different manners; a UV-curing step (“UV Cure”) performed on commercial equipment, an electron beam (EB) curing step (“EB Cure”) performed on a similar commercial system as the UV-cure but utilizing electron beam technology, and an EB cure performed on laboratory equipment (“EB Lab Cure”). Table 4 below shows the formulation of the three adhesives tested. The commercial EB system and lab EB system are both compared due to the varying energy levels supplied by each. The acrylic oligomer is CN 111 US, the elastomer is Ricacryl® 3500 and the tackifier is CN 3001 as described in Example 1.

TABLE 4 Sample Adhesive Formulation % Provided in Final Adhesive Formulation Adhesive Acrylic Tack Component Ratio Sample No. Oligomer Elastomer Agent (ACR) 14 69.2 7.7 23.1 2.2 (Comparative) 15 45 15 40 0.81 (Inventive) 16 35 15 50 0.53 (Inventive)

The “UV Cure” comprised passing the coated sample under a UV-lamp at about 25 ft/min in air and with about 2 to 4 passes, such that the sample was passed under the length of the UV-lamps 2 to 4 times. The energy provided by 1-pass of the UV lamp at 25 ft/min was equivalent to about 100 mJ/cm2. The “EB Cure” on a commercial system (Faustel Corporation, Germantown, Wis.) was performed under nitrogen gas at about 125 ft/min to about 250 ft/min with only one pass and at about 2 Mrad to about 2.4 Mrad, and the “EB Lab Cure” was also performed under nitrogen requiring about 6 to 8 passes under the lab EB system, which operated at about 10 ft/min. Total cumulative dose for 6-8 passes through the lab EB unit was about 2 Mrad to about 4 Mrad. It is appreciated that a smooth surface finish of the adhesive fastener 12 is desired in some cases for a good adhesive to adhesive peel strength. If the surface of the adhesives 12 is lumpy, such as having a consistency of an orange peel, the adhesive fasteners 12 tend not to adhere together well. It was observed that all cured coating samples had comparably smooth and level surface finishes. After curing all of the samples, the peel strengths were tested per ASTM D3330/D3330M-04 method F, these results are shown in Table 5 below.

TABLE 5 Peel Strength Results for Different Cure Processes (UV vs. E-beam) Peel Strength Results Inventive Comparative Peel Peel Peel Strength Strength Strength under UV under EB Under EB Cure No. UV Cure No. EB Lab Cure No. EB Sample No. Condition Passes Condition Passes Conditions Lab Passes 14 200 gpli 2 0 gpli 1 100 gpli 6-8 passes (Comparative) 15 480 gpli 3.5 0 gpli 1 200 gpli 6-8 passes (Inventive) 16 680 gpli 4 0 gpli 1 200 gpli 6-8 passes (Inventive)

Surprisingly, it was found that an ultraviolet curing treatment (UV Cure) outperformed both of the EB cures. The EB Cure performed on the commercial line had no adhesion at all, i.e., peel strength of 0 gpli. The EB Lab Cure had some adhesion, but the UV-cured samples had the best adhesion overall.

In terms of the UV Cure results, Samples 15 and 16 had acceptable ranges of peel strengths (i.e., 480 gpli and 680 gpli, respectively) whereas Sample 14 had a lower peel strength (i.e., 200 gpli). The lower peel strength seen in Sample 14 is likely due to the adhesive formulation used with Sample 14, which did not fall within the desired range of 0.5 to 1.5 (i.e., it had a ratio of 2.2).

While not wishing to be limited by theory, it is believed that a UV-radiation cure in ambient air (about 21% oxygen) provides a cure from the bottom of the sample up toward its surface due to the oxygen inhibition of free radical curing in adhesive portions adjacent or near the surface. The tacky components are more aliphatic in nature and therefore are lower in surface energy than, for example, the ester or urethane components. In some cases, chemical systems self-organize to the lowest possible energy state if allowed sufficient time. In the present case, it is believed that the slower cure rate of the UV process allows sufficient time for the tacky components of the coating to migrate toward the surface. In contrast, the EB curing process results in a much faster reaction cure rate, thus providing a more random arrangement of the polymer where it sets up cross-links within the growing polymer network too quickly for significant surface-energy driven self-ordering to develop. Thus, the EB cure may have an opposite cure pattern than the UV-radiation process, where EB curing commonly takes place in a nitrogen-purged environment and may cure faster at the surface and slower near the substrate. This can result in a completely different adhesive behavior based solely on the different cure methods. Ordinarily, such a rapid cure would be desirable, however, when curing the coating disclosed herein, such a fast cure is a disadvantage because it does not allow sufficient time to transpire in the process for the adhesive components to become fully organized.

While not wishing to be limited by theory, it is further believed that the slower cure time of the UV radiation curing allows for the growing polymer units to arrange themselves, such that polar units of the polymer favor the substrate and non-polar units favor the surface, where having the non-polar units near the surface of the substrate allows the adhesive coating to bond and stick to itself. This allows the adhesive components that are most compatible with the film substrate to congregate at the adhesive/substrate interface, thus enhancing the substrate adhesion, which may be one factor that aids in the absence of delamination from the substrate film.

Example 4

Two inventive adhesive-based reclosable fasteners, Samples 17 and 18, were prepared as indicated in Table 6. The two sample adhesives were compared to a standard pressure sensitive adhesive fastener (PSA-control, Sample 19) obtained from a commercial Nabisco Chips Ahoy Snack'n Seal® package using a standard PSA (Fasson 5700, Avery Dennison Corp., Pasadena, Calif.).

TABLE 6 Adhesive-based Fastener Formulations % Component Provided in Final Adhesive Formulation CN 111 US Esacure ® Adhesive (Acrylic Ricacryl ® 3500 CN 3211 KTO46 Component Samples Oligomer) (Elastomer) (Tack Agent) (Photoinitiator) Ratio (ACR) 17 35 12 50 3 0.56 (Inventive) 18 35 0 62 3 0.56 (Inventive)

The substrate that was coated comprised about 77.2% EVA, about 10% metallocene LLDPE, and about 12.8% organoclay filler composition PolyOne 231-615 masterbatch. The masterbatch comprises about 57% to about 63% organically modified clay and a carrier that contains MA-LLDPE and polyethylene. Sample 17 was cured at a UV-curing station having an average light energy of about 730 mJ/cm2 and an average line speed of about 100 ft/min at an average oven temperature of 130° F. Sample 18 was cured at the UV-curing station having a light energy of about 700 mJ/cm2 with a line speed of about 100 ft/min at an oven temperature of 160° F. The standard adhesive, PSA-control, was already provided in a final form adhered to a cookie package (Kraft Foods).

A crumb contamination test was performed on all three packages to see if the food particles would negatively impact the sealing of its respective adhesive. The crumb test procedure comprised the following steps: first, Triscuit® crackers were obtained and crushed using a bottom of a glass jar. The breaking of the crackers in this fashion created small particles that would be consistent with what would be found in the bottom of a bag. Next, a 2 inch diameter ring fixture was placed onto the adhesive of the sample to be tested. Approximately 5 grams of crumbs were placed into the ring on the sample. The sample and ring were gently agitated back and forth to settle the crumbs onto the adhesive surface of the reclosable fastener. The ring was removed from the sample and the crumbs were gently shaken off of the sample and disposed. The ring was replaced back on the substrate in its original position and the area exposed to the crumbs was visually rated for the quantity of crumbs retained. A visual rating scale of zero to 100 was used, where zero meant no visible retained crumbs and 100 meant the total surface was covered with adhering crumbs. The results of the cracker crumb test are shown in Table 7.

Additionally, the peel strength of the adhesives was tested after contaminating with cracker crumbs. The peel strength was measured using a standard testing procedure, ASTM D3330/D3330M-04 method F, where the strength of the adhesive bond was tested by peeling one side away from the other and measuring the peel strength that was required. An initial peel strength, a subsequent peel strength after an initial contamination with cracker crumbs, and a second peel strength after a second round of contamination with cracker crumbs, where the sample was contaminated using the same procedure as the initial contamination, were measured. The results for the samples are presented in Table 7.

TABLE 7 Crumb Contamination Test Results Initial peel Peel strength Peel strength % Peel strength strength (no after first % Peel strength after second retained after contamination) contamination retained after first contamination second Contamination Samples (gpli) (gpli) contamination (gpli) contamination rating 17 315 167 53% 128 41% 0-10 18 116 161 138% 155 133% 0-10 19 499 196 39% 25 5% 60-80  (PSA- Control)

It can be seen from the results that the adhesivity (i.e., peel strength) of the PSA-control, as measured per ASTM test D3330/D3330M-04 method F, dropped to about 5% of its initial peel force value (i.e., from about 500 gpli to about 25 gpli) after only two cracker crumb exposures. In contrast, both of the adhesive-based Samples 17 and 18 retained at least about 41% of its initial peel force value after two exposures to the cracker crumbs, with Sample 18 actually showing an increase in peel force after contamination and after repeated closures and openings. Additionally, the visual crumb contamination ratings for the adhesive-based samples were 0 to 10, compared to values of 60 to 80 for the PSA-control.

A rolling ball tack test was also performed on uncontaminated Samples 17, 18, and 19, which was a modified version of ASTM D3121 and followed the test method parameters of ASTM D3121, unless otherwise specified. The modified test measured how strong the surface of the coating adhered to non-like materials, such as the polar surface of a rolling glass ball.

The rolling ball method included: releasing a glass ball which was placed two inches up the standard incline specified in the ASTM method and allowing the ball to accelerate down the incline and roll across a horizontal surface of the pressure sensitive adhesive sample. The modified test version included using a glass ball instead of a metal ball, the glass ball having a diameter of about ⅛ inch, and using a shortened release point off of the incline (i.e., as indicated above, two inches up the incline). The relative tack was determined by measuring the distance the ball traveled across the adhesive before stopping, beginning from the end of the ramp. A longer rolling ball travel distance indicated lower tack to the polar surface of the glass ball, and indicated that the coating has a lower tendency to stick to rollers and metal surfaces on packaging machines, compared to coatings with a shorter rolling ball travel distance which indicated a higher tack level. A longer rolling ball travel distance may also correlate to a lower tendency to adhere to food crumbs. In this measurement, the measurement was limited to a maximum of 4 inches because the maximum sample size available for testing was 4.0 inches×4.0 inches. Results from the rolling ball tack test are shown at Table 8.

TABLE 8 Rolling Ball Tack Test Results Samples Rolling Ball Distance (Inches) 17 >4 18 >4 19 ⅛ (PSA-Control)

From the results, it can be seen that the two inventive Samples 17 and 18 had lower surface tack than the control, as evidenced by the glass ball easily rolling across the surface of the reclosable fastener and off of the 4 inch long sample. On the contrary, the glass ball stuck to the PSA-control almost immediately upon contacting the PSA-control surface, which was indicative of a high tack surface of the coating.

Example 5

A peel repetition test was performed to test the reseal and peel ability over multiple repetitions. Approximately twenty samples were made; Samples 20 to 35 were made using the adhesive formulation of Sample 17 from Example 4, and Samples 36 to 38 were made using the adhesive formulation of Sample 18 from Example 4. Samples were produced on a commercial scale pilot coating line via the flexographic coating process. The liquid adhesive coating system was preheated to 160° F. (71° C.) and circulated through a chambered doctor blade which was mounted to an engraved chromium oxide ceramic roll. The engraved roll (which was also temperature-controlled to 160° F. (71° C.)) transferred the liquid adhesive coating to a patterned rubber roll. The patterned rubber roll in turn transferred the patterned coating to the moving substrate film (i.e., the process illustrated in FIG. 6). After exiting the coating station, the film traveled through a 60 ft. long oven section. A UV treater, consisting of 3 banks of UV lamps, was located at the oven exit. The line configuration with the UV zone located at the exit end of the oven resulted in the maximum path length between the coating station where the material was applied and the UV curing station, which maximized the amount of time available for the liquid adhesive coating to flow-out and level, prior to being cured into a cross-linked polymer network. It is believed that, in some cases, a smooth and level coating surface helps to achieve the desired adhesive to adhesive peel force in the fully cured adhesive.

A series of experimental coating runs were performed. Line speed, oven temperature, and the number of UV lamp banks were varied. The experimental design and experimental observations are summarized in Table 9 below. Visual surface roughness, MEK resistance, and separation of adhesive along the adhesive-to-adhesive bond line of the sample prior to testing were determined. In general, samples produced at 300 ft./min. to 500 ft./min. line speed had a rough surface appearance and low or no subjective peel force. Instrumented peel force measurement of these samples was for the most part not possible because the joined samples separated on their own accord before further tests could be carried out. Samples produced at 100 ft./min. had a smooth surface appearance and moderate adhesive to adhesive peel force. These samples were further characterized using instrumented peel force testing as summarized in Tables 10 and 11 to follow. Only the samples that did not separate on their own, as shown in Table 9, were tested in the repeated peel-reseal tests. These were Samples, 21, 22, 29, 30, 31, 32, 35, 36 and 38.

TABLE 9 Experimental Design Used to Produce Samples for Peel Repetition Testing Visual MEK Rub Adhesive- Line Oven adhesive Test (# of Joined Sample Based Speed Temperature No. of UV surface double samples No. Sample No. (ft/min) (° F.) lamp banks appearance rubs) separated 20 17 (Ex. 4) 500 100 3 Very 15 Yes Rough 21 17 (Ex. 4) 100 100 1 Smooth 100+ No 22 17 (Ex. 4) 100 100 3 Smooth 100+ No 23 17 (Ex. 4) 500 100 1 Very  5 Yes Rough 24 17 (Ex. 4) 300 100 2 Very 100+ Yes Rough 25 17 (Ex. 4) 500 130 2 Very 60 Yes Rough 26 17 (Ex. 4) 300 130 2 Very 100  Yes Rough 27 17 (Ex. 4) 300 130 3 Very 100  Yes Rough 28 17 (Ex. 4) 300 130 1 Very 20 Yes Rough 29 17 (Ex. 4) 100 160 1 Smooth 100+ No 30 17 (Ex. 4) 300 160 2 Slightly 100+ No Rough 31 17 (Ex. 4) 100 160 2 Smooth 100+ No 32 17 (Ex. 4) 100 160 3 Smooth 100+ No 33 17 (Ex. 4) 500 160 1 Very  5 Yes Rough 34 17 (Ex. 4) 500 160 3 Very 100  No Rough 35 17 (Ex. 4) 100 130 2 Smooth 100+ No 36 18 (Ex. 4) 100 160 3 Smooth 100  No 37 18 (Ex. 4) 500 160 3 Rough 100  Yes 38 18 (Ex. 4) 300 160 3 Rough 100  No

The first set of peel tests were performed using short intervals between peels, i.e., about three minutes between a peel-reseal cycle. Table 10 includes results for this test, where the averages of two samples tested per condition are provided. These results are compared to Sample 19, the PSA-control from Example 4.

TABLE 10 3-Minute Delay Peel-Reseal Test Results Sample 19 Peel Strength Value (gpli) Peel PSA- Sample Sample Sample Sample Sample Sample Sample Sample Sample No. Control 21 22 29 30 31 32 35 36 38 1 459.8 291.8 461.8 273.3 148.0 266.7 417.4 418.3 273.9 136.9 2 320.8 74.0 242.1 131.6 32.5 129.7 206.3 195.8 527.2 43.0 3 275.0 52.4 204.4 111.5 27.1 112.9 180.8 171.9 452.9 44.8 4 254.7 51.8 183.2 107.6 24.2 104.1 158.6 141.6 424.7 41.1 5 256.9 48.7 161.8 99.2 23.7 102.3 140.5 128.8 404.6 41.8

The second set of peel tests were performed using a longer duration interval between peels, i.e., about 24 hours between peel-reseal cycles, in order to understand the impact of longer adhesive-adhesive contact time, with the first peel taking place about one week after the samples were prepared. The test results for the extended delay peel-reseal samples are shown at Table 11.

TABLE 11 24-Hour Delay Peel-Reseal Test Results Peel Strength Value (gpli) Sample 19 Peel PSA- Sample Sample Sample Sample Sample Sample Sample Sample Sample No. Control 21 22 29 30 31 32 35 36 38 1 539.8 271.1 441.7 288.8 149.2 301.9 434.7 432.5 277.3 124 2 521.6 202 362.1 238.5 116.2 147 327.6 338.7 447.4 107.3 3 514.6 233.1 349.6 248.3 115.8 226.3 297.6 321.6 478.5 106.5 4 550.3 218.2 314.8 222.2 95.5 239 286.5 289 493.9 116.8 5 567 231.9 285.9 236.9 95.9 224 299.9 280.4 487.5 125.1

The results show that the samples including adhesive formulation of Sample 17 from Example 4 do not exhibit as pronounced of a decrease in peel force that typically occur with repeated peels when the duration between peels was 24 hours (i.e., Samples 21, 22, 29, 30, 31, 32, and 35 in this example). When the adhesive Sample 17 was allowed to remain in contact with itself for about 24 hours between peels, the adhesive recovered up to about 85% of its original peel force value, even after five peel-reseal cycles. Sample 30 had significantly lower average peel force values compared to the other test samples. Even though the joined samples did not separate on their own accord, it had poor surface smoothness due to the higher line speed of 300 ft/min.

Furthermore, it was surprising to find that the samples including adhesive formulations of Sample 18 from Example 4 actually increased in peel force value (i.e., Sample 36 in this example) with repeated peels at both the short and long time intervals between peel test cycles, similar to its contamination peel test results in Table 7, evidence of a full recovery of peel force after resealing. Only Sample 36 showed an increase in peel force value. Sample 36 was the sample cured using the slower line speed, which may have helped to provide a level and smooth sample surface (see Table 9). Sample 38 was made at a higher line speed than Sample 36 resulting in a rougher surface, which may be why there was a decrease in peel force value, as well as a low initial peel force value.

In comparison, the PSA-control showed recovery behavior only when the interval between peels was long, i.e., 24 hours. At the shorter time interval, the control actually dropped in peel force, by about 40%.

Overall, for both peel-reseal tests, the best performers were Samples 22, 32, 35 and 36. These four samples all correlated to adhesives made with similar processing conditions. For example, all four samples had slow line speeds of 100 ft/min, with at least two or more banks of UV lamps turned on. The adhesives that failed the peel-reseal tests likely did not have sufficient time to flow out and level prior to UV curing.

Example 6

An aging study was conducted using the adhesive Samples 17 and 18 of Example 4, Table 6 in order to understand the effects of longer adhesive to adhesive contact time on peel performance. Various properties of the adhesive were tested over a seven-week period including subjective initial peel force (i.e., low, medium, high), visual appearance after peeling, subjective tack or tendency to stick to fingers (i.e., none, low, medium, high), coating durability (i.e., MEK solvent resistance test ASTM D5204), and instrumented peel (i.e., 5 consecutive peels repeated on same sample at intervals of about 3 minutes using ASTM D3330/D3330M-04 method F; two samples were tested and averaged together) all at various adhesive to adhesive contact times. The adhesives were coated onto the same film substrates that were used in Example 2. Table 12 below shows the aging results for Sample 17. Table 13 below shows the aging results for Sample 18.

TABLE 12 Summary of Aging Study of Sample 17 Test Performed Day 0 Day 3 Week 1 Week 2 Week 3 Week 4 Week 5 Week 6 Week 7 Subjective H H H H H H H H H Initial Peel Force Change in No change No change No change No change Spotty Spotty Spotty Spotty Spotty appearance to adhesive to adhesive to adhesive to adhesive surface surface surface surface surface after appearance appearance appearance appearance whitening whitening whitening whitening whitening peeling Subjective Low Low Low Low None None None None None Tack MEK Rub >100 >100 >100 >100 >100 >100 >100 >100 >100 (# of double rubs) 1st Peel 553 567 559 553 463 600 323 505 592 Avg. g/in 2nd Peel 370 381 377 382 343 375 241 311 348 Avg. g/in 3rd Peel 339 354 347 361 333 352 228 300 335 Avg. g/in 4th Peel 318 342 340 338 330 326 232 292 326 Avg. g/in 5th Peel 311 322 326 323 311 297 226 277 317 Avg. g/in Avg. Peel 378 393 390 391 356 390 250 337 384 Strength g/in of 5 peels

TABLE 13 Effect of Adhesive/Adhesive Contact Time on Repeat Peel Performance (Sample 18) Test Performed Day 0 Day 3 Week 1 Week 2 Week 3 Week 4 Week 5 Week 6 Week 7 Subjective H+ H H H H H H+ H+ H+ Initial Peel Force Appearance No change No change No change No change Surface Surface Surface Surface Surface change to adhesive to adhesive to adhesive to adhesive Damage Damage Damage Damage Damage after appearance appearance appearance appearance peeling Subjective Low Low Low Low None None None None None Tack MEK Rub >100 >100 >100 >100 >100 >100 >100 >100 >100 (# of double rubs) 1st Peel 781 819 788 800 944 833 819 846 963 Avg. g/in 2nd Peel 519 586 567 590 668 377 576 622 556 Avg. g/in 3rd Peel 438 485 510 519 428 234 437 485 218 Avg. g/in 4th Peel 399 396 407 409 102 107 322 229 105 Avg. g/in 5th Peel 386 358 343 361 64 66 251 134 73 Avg. g/in Avg. Peel 505 529 523 536 441 323 481 463 383 Strength g/in of 5 peels

It should be noted that the average peel strength value was an average of five repeated peels on the same sample that were consecutively peeled at intervals of approximately three minutes. Therefore, the first peel was determined and the peel strength value recorded, and the reclosable fastener sample was resealed. After three minutes had passed, the reclosable fastener was peeled apart again and the peel force strength was recorded. The process was repeated until five peels were performed.

The subjective peel force, subjective tack and MEK rub test results were all good for both Samples 17 and 18 regardless of the duration of the adhesive to adhesive contact. The peel force values (i.e., initial and subsequent peels on the same sample) remained consistent for Sample 17 regardless of the duration of adhesive to adhesive contact for the range of zero days to 7 weeks. Sample 17 showed a much more consistent peel-reseal cycle than Sample 18. After the initial peel of Sample 17, the loss in adhesive to adhesive bond strength as represented by the loss in peel force upon subsequent peels was generally less than about 10% per subsequent peel, and was consistent regardless of the adhesive to adhesive contact time.

Beginning in week 3, there was a visible change in both Samples 17 and 18 (i.e., noticeable whitening and increase in opacity) upon peeling the aged samples. It is believed that this visible change is evidence of microscopic surface deformation of the adhesive due to forces acting on the adhesive surface during manual or instrumented peeling. The surface deformation did not affect the critical performance attributes of the adhesive (i.e., tack or peel strength). In the end, Sample 17 held up slightly better, with its peel strength either increasing over time, i.e., recovering peel strength, or generally maintaining about a 10% peel loss between subsequent peels.

Example 7

The inventive adhesive-based reclosable fastener Sample 17, from Example 4, was compared to three other inventive adhesive-based reclosable fasteners, Samples 39 to 41, having the formulations as indicated in Table 14.

TABLE 14 Adhesive-based Fastener Formulations % Component Provided in Final Adhesive Formulation Adhesive CN 111 US Ricacryl ® CN 3211 BR 144 CN 2302 Esacure ® Component (Acrylic 3500 (Tack (Acrylic (Acrylic KTO46 Ratio Samples Oligomer) (Elastomer) Agent) Oligomer) Oligomer) (Photoinitiator) (ACR) 17 35 12 50 0 0 3 0.56 (Inventive) 39 27 0 50 20 0 3 0.94 (Inventive) 40 35 3 39 20 0 3 1.31 (Inventive) 41 15 0 45 20 17 3 1.16 (Inventive)

Component BR 144 is identified as an acrylic oligomer (BR 144, Bomar Specialties Company, Torrington, Conn.). Component CN 2302 is also identified as an acrylic oligomer (CN 2302, Sartomer Company). All three Samples, 39 to 41, have incorporated the acrylic oligomer BR 144, with Samples 39 and 40 having two acrylic oligomers and Sample 41 having three acrylic oligomers present in the formulation.

The adhesives were coated onto the same film substrates that were used in Example 2. Samples 39 to 41 were cured at a UV-curing station having an average line speed of about 25 ft/min and three passes under the UV lamps totaling about 400 mJ/cm2 to about 600 mJ/cm2.

Coating durability of the four adhesives was tested (i.e., MEK solvent resistance test ASTM D5204) as well as initial peel strength using ASTM D3330/ D3330M-04 method F. A rolling ball tack test was also performed, which was a modified version of ASTM D3121 as described in Example 4, except the sample size available for testing was about 2.5 inches wide by about 7 inches long. These results are indicated in Table 15.

TABLE 15 Test Results for Cure and Adhesion using Table 14 Formulations. Average Rolling MEK Rub Test Initial Peel Initial Peel Initial Peel Ball (# of double Strength - Strength - Strength Distance Samples rubs) 1 (gpli) 2 (gpli) (gpli) (inches) 17 >100 184 191 188 1.5 39 >100 698 733 716 6.0 40 >100 341 333 337 >7.0 41 >100 336 289 313 >7.0

The initial peel strength, i.e., initial peel performed under laboratory conditions, increased for the new formulations by about 30%-300% compared to Sample 17, having only one acrylic oligomer component. The rolling ball tack distance increased for the new formulations by more than 300% compared to Sample 17.

From the results, it can be seen that the new formulations having two or more acrylic oligomers had an overall improved performance compared to Sample 17, as evidenced by the rolling ball test and the peel strength test. All samples had excellent cure rates, evidenced by the MEK rub test. In particular, all of the new sample formulations, i.e., Samples 39 to 41, had lower surface tack than Sample 17 and, in particular, Samples 40 and 41 had an even better low surface tack as evidenced by the glass ball easily rolling across the surface of the reclosable fastener and off of the 7 inch long sample.

Example 8

The four inventive adhesive-based reclosable fasteners of Example 7 were tested for various repeat peel tests. The samples were initially peeled apart and opened, the peel force was measured in grams per linear inch (gpli) using ASTM test method D3330/D3330M-04 method F, then resealed for three minutes, and the peel repeated. This seal-reseal was repeated every three minutes until ten data points were obtained. The results are presented below in Table 16.

TABLE 16 Three Minute Peel Delay Test Average Peel Strength (gpli) Peel 17 39 40 41 Repetition (Inventive) (Inventive) (Inventive) (Inventive) 1 721.4 371 710 388.6 2 525.5 492.4 501.8 517.2 3 477.8 477.1 485.8 442.5 4 443.6 474.2 459.1 386.7 5 423 478.1 449.6 346.3 6 392.9 480.0 430.2 313.7 7 374.5 482.5 411.5 295.4 8 352.6 504.7 397.4 255.9 9 332.6 491.8 381.2 224.3 10 326.6 490.3 380.9 204.3

Example 9

A 24-hour delay repeat test was performed using the same four inventive samples from Example 7. The samples were initially peeled apart and opened, the peel force required being measured. Then the samples are resealed and allowed to sit for 24 hours in a controlled environment, i.e., 72F and 50% relative humidity (RH), until they were repeeled and opened again. This is repeated until a total of five data points have been gathered, or for a period of five days. The results are presented below in Table 17.

TABLE 17 24-Hour Peel Delay Test Peel Force (gpli) Initial Peel, Samples Day 1 Day 2 Day 3 Day 4 Day 5 17 708.1 616.1 582.3 579.4 653.6 (Inventive) 39 555.5 641.6 690 752.4 653 (Inventive) 40 811.7 748.6 666 614.7 546.9 (Inventive) 41 469.2 513.6 516.8 503.2 479 (Inventive)

All four of the samples maintain their peel performance throughout the five day test period, without any sample falling below 400 gpli on any of the test days. Samples 39 and 41 actually increase in peel force and recover the initial peel force or increase in peel force during the test period. Thus, allowing these samples to remain sealed for a period of at least 24 hours allows these samples to recover or increase in adhesivity.

Example 10

In Example 10, a similar test to Example 9 was performed using the four samples described in Example 7; however, after each peel opening the adhesive area was contacted with whole coffee beans, resealed, and allowed to remain closed for 24 hours, and repeeled.

After each peel opening, whole coffee beans were placed on the adhesive surface and removed in less than five minutes. The samples were resealed and allowed to sit for 24 hours in a controlled environment, i.e., 72° F. and 50% RH, until they were repeeled and opened again. This is repeated until a total of five data points have been gathered, or for a period of five days. The results are presented below in Table 18.

TABLE 18 24-Hour Peel Delay Test After Coffee Bean Contamination Average Peel Force (gpli) Initial Peel, Samples Day 1 Day 2 Day 3 Day 4 Day 5 17 695 507 422.1 344.3 271.5 (Inventive) 39 627.3 647 571.2 458.6 294.9 (Inventive) 40 770.4 548.3 412.1 327.3 230.4 (Inventive) 41 506.9 476.1 382 298.3 211.1 (Inventive)

Although the data shows a slight decrease in peel strength, the peel values still exceed 200 gpli after five peel/contamination cycles with whole coffee beans.

Example 11

A rolling ball tack test as described in Example 4 was performed on film with no adhesive for comparison to the tack values of the low tack adhesive. The results are provided below in Table 18. Roll #3 from Sample 1 took a fairly sharp turn shortly after contacting the film.

TABLE 18 Rolling Ball Tack Test On Uncoated Film Sample 1 2 Roll #1 16.75 15.875 Roll #2 18 18 Roll #3 10.875 14.25 Roll #4 17.25 18.125 Roll #5 20.25 19.875 Roll #6 15 AVERAGE 16.35 17.23

It will be understood that various changes in the details, materials, and arrangements of the package and process of formation thereof, which have been herein described and illustrated in order to explain the nature of the described package, may be made by those skilled in the art within the principle and scope of the embodied method as expressed in the appended claims.

Claims

1. A reclosable package for items, the package comprising:

a plurality of walls sealed to form an interior cavity for receiving the items, the cavity being bounded by a bottom wall segment and an upper mouth initially sealed, the seal of the mouth being peelably openable to permit initial access to the items in the interior cavity, the plurality of walls including a pair of opposing wall segments each having top and bottom edge portions, a width, a height and facing inner surfaces; and
a low tack adhesive zone disposed on the inner surfaces of each of the opposing wall segments across the entire width of each of the opposing wall segments and extending from adjacent the mouth toward the bottom wall segment along at least a majority of the height of the opposing wall segments, the adhesive zones having a greater affinity for adhesion to each other than to the items and permitting the package to be reclosed using the adhesive zones at a plurality of different heights of the opposing wall segments after initial opening of the upper mouth to progressively decrease the size of the cavity so as to minimize head space in the reclosed package above the items as the items are sequentially removed from the package.

2. The reclosable package of claim 1, further comprising at least one area of weakness extending laterally across a circumference of the package configured to allow a portion of the package adjacent the upper mouth to be removed and thereby reduce extraneous packaging material above at least one of the plurality of different heights.

3. The reclosable package of claim 1, wherein the package further comprises opposing side wall segments having facing inner surfaces, and wherein a low tack adhesive zone is disposed on the inner surfaces of each of the opposing side wall segments.

4. A reclosable package for items, the package comprising:

at least two walls having facing inner surfaces, the at least two walls sealed to form a tubular package having a circumference, the tubular package initially sealed on top and bottom edge portions thereof to form an interior cavity for storing the items;
a low tack adhesive disposed in a pattern spanning the circumference of the tubular package on aligned portions of the facing inner surfaces of the at least two walls intermediate of the top and bottom edge portions; and
wherein the low tack adhesive has a greater affinity for adhesion to itself than to the items effectively permitting the package to be reclosed adjacent to the items after sequential reduction thereof by pressure of the low tack adhesive on the facing inner surfaces together.

5. The reclosable package of claim 4, wherein the low tack adhesive is disposed on a majority of the facing inner surfaces.

6. The reclosable package of claim 4, wherein the pattern of the low tack adhesive comprises a plurality of strips spaced along the height of the at least two walls and disposed generally transversely to a longitudinal axis of the package along a circumference of the package.

7. The reclosable package of claim 4, further comprising at least one area of weakness extending laterally across the circumference of the package configured to allow a portion of the package adjacent the items to be removed and thereby reduce extraneous packaging material above a reclosed portion of the package.

8. The reclosable package of claim 6, further comprising a plurality of areas of weakness extending generally transversely to the longitudinal axis of the package along the circumference of the package and disposed above and adjacent to the plurality of strips of the low tack adhesive.

9. A method of reclosing a package for items, the method comprising:

opening the package at a peelably openable seal thereof;
sequentially removing the items from the package, thereby creating headspace in the package;
reclosing a portion of the package adjacent the items using a low tack adhesive disposed on opposing inner surfaces, thereby decreasing the headspace in the package.

10. The method of claim 9, further comprising removing a portion of the package adjacent the adhered opposing inner surfaces by separating an area of weakness extending circumferentially around the package adjacent the reclosed portion of the package.

Patent History
Publication number: 20110211773
Type: Application
Filed: Feb 25, 2011
Publication Date: Sep 1, 2011
Inventors: Derek J. Romeo (Ridgewood, NJ), Lynn S. Mann (Danbury, CT), Paul Anthony Zerfas (Verona, WI)
Application Number: 13/035,269
Classifications
Current U.S. Class: Selectively Adjustable Volume (383/2)
International Classification: B65D 30/10 (20060101);