Field of the Invention

[0001] The present invention relates to re-sealable and reclosable packaging made from flexible packaging film. More particularly, it relates to packaging that is 100% recyclable and has a resealable or reclosable opening that resists curling after repetitive removal by pealing and re-adhesion of a closure tape.

Background of the Invention

[0002] Flexible packages made from composite film on form, fill and seal (“FFS”) packaging equipment are well known in the prior art. The seals that form the package, including the top seal (relative to the consumers intended observation of the package), may comprise heat seals, cold seals, or ultrasonic seals, which are typically permanent and do not allow the consumer to non-destructively open and reclose the package along that seal. These packages are inexpensive and durable, and are therefore prevalently used in a wide range of industries including the food, chemical, medical, agricultural, and mining industries.

[0003] In some cases, the package is formed with a resealable opening so that the user can access and remove a portion of the package contents, and then reseal the package so that the remaining contents stay fresh or are simply encapsulated. One known method of forming a resealable opening is by using pressure-sensitive adhesion tape (“PSA tape”) that covers an opening, such as a slit or elongate hole, in the package. The tape usually has an adhesive-free grip edge that can be grasped to pull (peel) a portion of the tape (“reseal zone”) backward (or sideward as the case may be) to expose the opening in the package, while the remaining portion (“anchor zone”) of the tape remains affixed to the package. To reseal the opening, the reseal zone of the tape is re-applied over the opening and pressed in contact with the surrounding packaging material. Typically, 1/3 of the PSA tape surface is on one side of the opening and functions as the anchor, whereas the remaining 2/3 of the PSA tape reseals the slit.

[0004] The grip edge is typically formed by applying a grip strip of polymer material in parallel along the adhesive side of the base strip of tape (“tape base”). The grip strip and tape base need not be made from the same material. For example, tape base could be a dry substrate selected from one of the group of bi-axially oriented polypropylene, mono-axially oriented polypropylene, polyvinylchloride, and polyester, while the grip strip could be single or multiple-layer, bi-axially-oriented polypropylene or high density polypropylene (“HDPE”). The tape base could be coated with a pressure sensitive adhesive selected from the group of rubber solvent, acrylic solvent, acrylic emulsion, or hot melt.

[0005] Other known solutions for forming a resealable opening in a flexible package include zippers, slides, labels, and Velcro-like hook and loop fasteners. However, the pressuresensitive tape solution has several advantages over these other solutions including lower capital cost to install in-line equipment, greater productivity in use, and lower final package cost. Despite these advantages, a successful pressure-sensitive tape solution must take into account the package’s overall use, intended contents, surface-printed graphics, and properties such as surface energy, surface chemistry, and bulk chemistry.

[0006] The PSA tape may be applied in either the lengthwise or widthwise direction on the package such as shown in U.S. patent no. 9,090,383 (application over the widthwiseextending opening) and U.S. patent no. 8,794,834 (application along the length of the bag to hold the folded or rolled end of bag closed), both of which are incorporated herein by reference and collectively referred to as the Forman patents. Commercially available examples of flexible packaging having PSA tape applied widthwise and lengthwise are sold under the trademarks FreshPak® and Peel&Seal®, respectively, which are owned by Sealstrip Corporation. In both examples, the PSA tape is either “pre-applied” or applied “inline” to the base film from which the package is form (“package base film”) as shown and described in the Forman patents.

[0007] Like most others, the packaging industry strives to be ever-more environmentally friendly by improving the overall recyclability of plastic flexible packaging. In order to develop sustainable recyclable solutions, the plastics industry has developed new grades of polyethylene film, which are both functional for the overall package requirements but also sustainable (compatible in a polyethylene recycle stream). Examples of such films include Berry Plastics Entour™ and CharterNex Gen’s family of GreenArrow™ recyclable films for use in monomaterial polyethylene packages. However, many known PSA tapes are made of polymers that have poor recycle properties, or are incompatibly recyclable with HDPE. For example, the Forman patents describe a dry tape base that could be a substrate from one of the group of biaxially oriented polypropylene, mono-axially oriented polypropylene, polyvinylchloride, and polyester, all of which have poor recycle properties. If the package is recycled without removing these non-compatible PSA tapes, the resulting recycled material yields gels, pinholes and mechanical points of weakness. As a result, these packages could not be accepted at, for example, retail store drop-off recycle stations. Therefore, it would be desirable to provide an improved PSA tape based entirely on (tape base and grip strip) polyethylene which can be compatibly recycled with the package base film so that the entire flexible package can be accepted in retail store and community recycle streams.

[0008] These new polyethylene-based films will be utilized in a broad set of packaging applications including room temperature, freezer, and refrigerated conditions. Depending on the design and intended use, the surface properties of the package will vary greatly. For example, the surface may comprise untreated polyethylene of low surface energy, treated polyethylene of higher surface energy, or surface printed or even matte coated films. These packages will therefore require a new pressure sensitive reseal solution, such as a reseal tape or label, which compliments their widely-varying properties. For example, these new reseal solutions may require strong (>150 grams/inch of peel adhesion (180 degree peel PSTC Method 1) or moderate (50-150 grams/inch of peel adhesion 180 degree peel PSTC method 1) adhesion to the packaging. These new solutions will ultimately be subjected to a wide range of induced strain loads discussed below.

[0009] In many applications, the consumer does not open and dispense the entire contents of the flexible package at one time. In the case of resealable flexible packages, the consumer may pull back and re-adhere the PSA tape a dozen or more times before the contents of the package are depleted. The strain induced in the PSA tape by pulling and re-adhering can induce curling, which will make the tape difficult to re-adhere, especially if it winds back up on itself, and can cause the tape to de-adhere from the surface of the package, thereby compromising the integrity of its sealing function. In the packaging industry, curled reclosing tapes can be viewed as a defective product. The level of induced curl from strain depends on the material from which the PSA tape is formed. For example, multilayer polyethylene films are known to have good recycle properties but a propensity to curl when strained. Many machine direction oriented polyethylene films, such as disclosed in U.S. Patent 11,214,047, Dow Chemical Global Technologies LLC, incorporated herein by reference, also have a propensity to curl when strained.

[0010] Some prior art patents discuss methods of overcoming curl during production of the film itself. For example, W02008 039822, incorporated herein by reference, teaches a method of controlling production curl by applying a coating during manufacture of the film itself. This patent also discloses the use of machine stretching of the film to achieve both flatness of the final film to achieve overall structure compatibility. It also highlights the observation that the observed curl occurs in the direction of the coated side due to the retraction of the coating. This patent discusses that the maximum curvature generally occurs when the coating-to-web thickness ratio (i.e., the ratio of the coating thickness to the web thickness) is between about 0.5 and about 1.0. Additionally, U.S. Patent 8,709,611 discusses the use of nucleated high density polyethylene within multilayer structures to not only improve the modulus of the film but also to impart improved water vapor transmission rates in packaging films. These patents do not however highlight the need or a potential solution to how to use multilayer polyethylene films with a non-sealant layer such as in a label or tape film packaging application wherein a coating is applied, in this case a pressure sensitive adhesive coating but used in packaging applications.

[0011] U.S. Patent 9,724,901 discloses production methods for the use of mono and multilayer films which can be biaxially oriented to achieve flatness and reduced curl and is herein incorporated as a reference. The solution developed in this patent describes the use of film core resin blends based on selected combinations of more than one mLLDPE or mLDPE resins having particular melt indices result in a blend of polymers having a broad molecular weight distribution, including the possibility of bimodal and trimodal distributions.

Typically, single site metallocene catalysts generally produce polymers with a narrow molecular weight distribution, i.e., Mw/Mn to be around 2 (weight-average molecular weight divided by number-average molecular weight, wherein Mw and Mn both can be measured by gel permeation chromatography (GPC)). Narrow molecular weight distributions deliver limited molecular chain entanglements in order to provide needed melt elasticity. The enhanced melt elasticity can be desired during film orientation or stretching at elevated temperature in order to assist in maintaining film integrity without breakage. When Mw/Mn reaches around 4 or >4, i.e., a broad molecular weight distribution, the polymer melt or blend may have enhanced polymer chain entanglement, and, thus, improved melt elasticity at elevated temperatures. This improved melt elasticity enables improved TD stretch at high temperatures, as well as reduced melt fracture during extrusion. When molecular weight distribution^ by blending together three m-LLDPE resins, the three-component blends showed greatly improved melt elasticity and film orientation through tenter orientation as compared to narrow molecular weight distribution components and blends. Through this polyethylene blending methodology method it is reasonable to assume a print layer film that is both recyclable but curl resistant and does not contain a sealant layer can be produced. Such a product, Ethyl-Lite tm 25HDCSR a clear print film for example is offered by Jindal Films and can be corona treated on a single side in order to receive a print coating or film to film lamination. The inventors of this patent do not contemplate the need or use of a recyclable biaxially oriented polyethylene recyclable film with minimal curl for use with adhesive coatings in the resealable packaging space where minimal curl from strain induced use can create an undesirable reseal packaging tape or label feature.

[0012] None of the above-referenced patent teach a product, or method, for preventing strain-induced curl from consumer use of a package during the repeated unsealing (opening) and resealing (closing) cycles typically encountered in resealable consumer packaging of pressure sensitive reseal tape and label features.. Therefore, it would also be desirable to provide an improved PSA tape or label structure that minimally curls when repeatedly strained, such as when the tape is being pulled from and re-adhered to the package. Moreover, it would be even more desirable if the improved PSA tape was also compatibly recyclable with the package base film so that the entire package can be recycled.

Summary of the Invention

[0013] The present invention comprises a PSA tape that can be used in combination with a film of polymer packaging material to form a flexible package having a resealable opening. The PSA tape is intended to be pre-applied to the film stock of the package (“package base film”), or applied to the package base film during an initial stage of a form, fill and seal process. The PSA tape has high tensile strength, high resistance to tear propagation, good transparency, and limited elongation at break. Unlike prior art tapes, the PSA tape is made from a curl-resistant, polyethylene material that is compatibly recyclable with the package base film to which it is applied, thereby making the final consumer package fully recyclable. In this context, compatibly recyclable means that the entire final consumer package is certified by third parties as being acceptable for store drop off stations for later repurpose/recycle into other polyethylene-based materials such as decking materials and trim fascia.

[0014] Many multilayer, polyethylene films are known to curl under strain. Therefore, only certain blends of polyethylene can be used. In one preferred embodiment, the PSA tape comprises a base made of 2 mil thick film, item no. GAP-2501, and a grip strip made of 0.9 mil thick film, item no. GAP-1001, both of which are machine-direction-oriented films manufactured by Charter Next Generation (“CNG”). These films are marketed as recyclable films as determined by compatibility testing by third parties such as Trex and additionally through established Association of Plastics Recyclers(APR) Protocol (FPE-CG-01) guidelines. [0015] These film structures can be produced through various production methods that include blown and cast production processes. The film may be oriented in the machine direction or bi-axially oriented.

[0016] In one preferred embodiment, the invention comprises a flexible package formed from a film of polymer packaging material having first and second panels sealed at a top portion and a bottom portion, an elongate slit in the first panel, and an elongate strip of pressure-sensitive-adhesion, re-closing tape (“PSA tape strip”) applied to the surface of the first panel over the slit. The PSA tape strip has an adhesive edge portion abridging and releasably sealing the slit and a non-adhesive edge portion arranged on one side of the slit and lying against the first panel. The PSA tape strip is adapted so that the slit can be unsealed by gripping the non-adhesive edge portion and pulling the PSA tape strip away from the first panel until the adhesive edge portion no longer abridges the slit. The PSA tape strip comprises a base material of polymer film that is compatibly recyclable with the packaging material. The PSA tape strip also resists curling when it is strained by pulling it away from the first panel to unseal the slit.

[0017] In another preferred embodiment, the PSA tape strip comprises a base material of polymer film, a pressure-sensitive adhesive applied to a first side of the base material, and a non-adhesive grip strip of polymer film applied to the adhesive along one edge of the first side of the base material to form a non-adhesive edge portion, and the remainder of the first side forming an adhesive edge portion. The grip strip is preferably compatibly recyclable with the packaging material.

[0018] In a further embodiment of the invention, the PSA tape strip comprises a base material of polymer film, a pressure-sensitive adhesive applied to a first side of the base along one edge in a pattern less than the width of said tape strip to form an adhesive edge portion. The remainder of the first side has no adhesive applied thereto and forms a non- adhesive edge portion.

[0019] Compared to prior art packaging and pressure sensitive adhesive tapes, the PSA tape strip has a substantially reduced tendency to curl when strained. In one preferred embodiment, the PSA tape has a percentage curl less than about 10%, more preferably less than 7%, and even more preferably less than about 5% as measured on 1 in. wide test samples using ASTM Method 3330 for peel adhesion. The degree of curl was determined by measuring the change of width of the 1 inch wide tape at 2.5 in. down the 6 in. test strip that was applied to the test panel. In preferred embodiments, the base material comprises machine-direction-oriented polyethylene film produced from a blown film process having a multilayer film structure of at least 3 but less than 8 layers. The base material may have a stretch ratio of 1:3 but no greater than 1:10. The base material may contain 25 to 65 percent by weight of HDPE, combined with a blend of metallocene LLDPEs and higher alpha olefin LLDPE utilizing butene, hexene, or octane, said blend comprising 10 to 90 percent by weight of metallocene LLDPE. The base material preferably has a thickness of at least 1.6 mils but less than 2.5 mils. The haze value of the base material is preferably less than 10%. In preferred embodiments, at least one side of said base has been corona treated to a surface tension of at least 36 dynes/cm but less than 46 dynes/cm. Preferably, the base material has a secant modulus between 130,000 to 250,000 p.s.i. in the machine direction and 100,000 to 225,000 p.s.i. in the cross direction. More preferably, the base material has a secant modulus between 200,000 to 250,000 p.s.i. in the machine direction and 175,000 to 225,000 p.s.i. in the cross direction. In a preferred embodiment, the secant modulus ratio (machine direction to cross direction) is greater than 90%.

[0020] The pressure sensitive adhesive is selected from known, VOC-compliant adhesives for flexible webs and film. The adhesive preferably should be low foaming and have high optical clarity. If a grip strip is not incorporated into the tape, as taught in the prior art, the adhesive can be applied in a defined pattern or a broad pattern with a defined pattern of deadener, to create the grip edge. Preferably, the adhesive coating has a thickness from 0.6 to 1.1 mils and is selected from the group consisting of: solvent based acrylic or rubber based, aqueous based, formulated styrenic isoprene or formulated styrenic butadiene block copolymer hot melt adhesive or Ultra Violet Light (UV C) hot melt acrylics.

[0021] In one preferred embodiment, the pressure sensitive adhesive comprises a waterbased, acrylic emulsion such as Robond PS-90 (From Dow Chemical) formulated with a low level of isocyanate coreactant such as Dow Chemical CR 9-101. In this embodiment, the adhesive is formulated with less than 1% CR 9-101 per solid part of acrylic emulsion. The package base film may be corona treated prior to application of the PSA adhesive to increase adhesive anchorage of the PSA adhesive to the package base film. Adhesive anchorage can be achieved in numerous other ways such as adding external crosslinkers such as isocyanate chemistries, aziridines, carbodiimides, multi-layer coatings in addition to optimal levels of corona treatment.

[0022] In another preferred embodiment, the invention comprises a resealable, pressure- sensitive-adhesion tape (“PSA tape”) for use in combination with a flexible package formed from a film of polymer packaging material. The PSA tape comprises a base material of polyethylene film that is compatibly recyclable with the packaging material, and a pressure sensitive adhesive applied to one side of the base material along one at least a lengthwiseextending edge to form an adhesive edge portion and a non-adhesive edge portion. The PSA tape strip preferably comprises a base material of polymer film that is compatibly recyclable with said packaging material. The PSA tape resists curling when it removed from a surface to which it has been adhered by pulling on the non-adhesive edge portion. The PSA tape may be formed as a continuous roll or a series of segmented labels.

[0023] In another embodiment, the PSA tape has pressure-sensitive adhesive applied to the entirety of one side of the base material, and a grip strip of polymer film applied to the pressure-sensitive adhesive along one edge of the first side of the base material to form the non-adhesive edge portion. The remainder of the first side forms the adhesive edge portion. In this embodiment, the grip strip and the pressure-sensitive adhesive are preferably compatibly recyclable with the packaging material. In preferred embodiments, the PSA tape has the properties described above with respect to the flexible package.

[0024] The grip strip preferably comprises either polyethylene or polypropylene film. In other preferred embodiments, instead of applying a grip strip, the pressure-sensitive adhesive is applied to the entirety of one side of the base material, and a water based or UV cure deadener used in the label industry is applied to the pressure-sensitive adhesive along one edge of the first side of the base material to form a non-adhesive edge portion. The remainder of the first side forms the adhesive edge portion. In preferred embodiments, the width of the non-adhesive edge portion is at least !4 in.

[0025] In a further embodiment, the base material of the PSA tape comprises a multilayer biaxially-oriented, polyethylene-based film. The film has a core layer formed of a core resin composition comprising a blend of 50 to 90% by weight of a first metallocene linear low density polyethylene (mLLDPE) resin having a melt index from about 0.8 dg/s to about 2 dg/s, about 5-25% by weight of a second mLLDPE resin having melt index from about 0.1 dg/s to about 0.8 dg/s, and about 5-25% by weight of a third mLLDPE resin having a melt index from about 2 dg/s to about 10 dg/s. The film also has a skin layer having a skin resin composition comprising one or more polyolefin plastomers, wherein said skin layer has a thickness of approximately 3% to 20% as compared to a total thickness of the extruded, oriented, multilayer, film structure.

[0026] In one embodiment, the PSA tape is applied to the package film by an applicator arranged upstream in a FFS packaging line. As the film enters the PSA tape applicator, a rotary blade initially slits the film in a lengthwise-extending (travel direction) pattern, and then immediately applies the PSA tape over the slits. Because the tape is thin and flexible, no modification of the FFS machine’s former or seal jaws is needed. No heat is used to apply the tape and the PSA tape has no effect on line speed.

[0027] WO 2017/003773 published January 5, 2017 is incorporated herein by reference.

Brief Description of the Drawings

Fig. 1 is a flexible package in accordance with a preferred embodiment of the invention; Fig. 2 is an enlarged section of the package shown in Fig. 1, which illustrates opening the package by pealing back an elongate stripe of pressure-sensitive-adhesion tape in accordance with an embodiment of the invention;

Fig. 3 is a top plan view (not to scale) of a section of schematic illustration of a pressure- sensitive-adhesion tape in accordance with an embodiment of the invention;

Fig. 4 is a cross-sectional view (not to scale) of a pressure-sensitive-adhesion tape in accordance with an embodiment of the invention;

Fig. 5 is a fragmented perspective view of a pressure-sensitive-adhesion tape applied to a film of packaging material during in accordance with an embodiment of the invention;

Fig 6 is a schematic illustration of a pressure-sensitive-adhesion tape in accordance with an embodiment of the invention illustrating the width of the seal zone and anchor zone;

Figs. 7 and 8 are perspective views of a flexible package in accordance with an embodiment of the invention in the closed and open configuration, respectively;

Figs. 9 and 10 are perspective views of a flexible package in accordance with an embodiment of the invention in the re-closed configuration; and,

Fig. 11 is a schematic illustration of a method of producing a flexible package in accordance with a preferred embodiment of the invention.

Detailed Description of the Preferred Embodiments

[0028] For the purpose of illustrating the invention, several embodiments of the invention are shown in the accompanying drawings. However, it should be understood by those of ordinary skill in the art that the invention is not limited to the precise arrangements and instrumentalities shown therein and described below. Throughout the specification, like reference numerals are used to designate like elements.

[0029] Throughout the drawings, the various embodiments are illustrated using transparent materials so that the package contents can be seen. However, it should be appreciated by those of ordinary skill in the art that the embodiments may be made from opaque or printed material without departing from the intended scope of the invention.

[0030] Throughout the specification, as used in connection with various elements and portions of elements, the following definitions apply.

[0031] The terms “Polyethylene” or “ethylene-based polymer” shall mean polymers comprising greater than 50% by weight of units which have been derived from ethylene monomer as described in U.S. Pat. No. 11,214,047. This includes polyethylene homopolymers or copolymers (meaning units derived from two or more comonomers). Common forms of polyethylene known in the art include Low Density Polyethylene (LDPE); Linear Low Density Polyethylene (LLDPE); Ultra Low Density Polyethylene (ULDPE); Very Low Density Polyethylene (VLDPE); single-site catalyzed Linear Low Density Polyethylene, including both linear and substantially linear low density resins (m-LLDPE); Medium Density Polyethylene (MDPE); and High Density Polyethylene (HDPE). These polyethylene materials are generally known in the art; however the following descriptions may be helpful in understanding the differences between some of these different polyethylene resins.

[0032] The term “LLDPE”, includes both resin made using the traditional Ziegler-Natta catalyst systems as well as single-site catalysts, including, but not limited to, bis-metallocene catalysts (sometimes referred to as “m-LLDPE”) and constrained geometry catalysts, and includes linear, substantially linear or heterogeneous polyethylene copolymers or homopolymers. LLDPEs contain less long chain branching than LDPEs and includes the substantially linear ethylene polymers, which are further defined in U.S. Pat. Nos. 5,272,236, 5,278,272, 5,582,923 and 5,733,155; the homogeneously branched linear ethylene polymer compositions such as those in U.S. Pat. No. 3,645,992; the heterogeneously branched ethylene polymers such as those prepared according to the process disclosed in U.S. Pat. No. 4,076,698; and/or blends thereof (such as those disclosed in U.S. Pat. Nos. 3,914,342 and 5,854,045). The LLDPEs can be made via gas-phase, solution-phase or slurry polymerization or any combination thereof, using any type of reactor or reactor configuration known in the art, with gas and slurry phase reactors being most preferred. Similarly the Ziegler-Natta catalyst used in higher alpha olefin LLDPE are commonly based on butene, hexene, or octene copolymerized in the presence of ethylene.

[0033] The term “HDPE” refers to polyethylenes having densities greater than about 0.935 g/cm ³ , which are generally prepared with Ziegler-Natta catalysts, chrome catalysts or single- site catalysts including, but not limited to, bis-metallocene catalysts and constrained geometry catalysts.

[0034] The term “curl” means the tendency of a web (or multi-layer web) of material to deviate from a generally flat or planar orientation when there are no external forces on the web. “Curl percentage” or “curl %” shall mean the percentage change in width of a 1 in. wide by 6 in. long test sample using the testing procedure described below in ASTM Method for peel adhesion. The degree of curl is determined by measuring the change of width of the 1 inch wide tape at 2.5 in. down the 6 in. test strip that was applied to the test panel.

[0035] A package in accordance with an embodiment of the invention is shown in Fig. 1 and is designated generally by reference numeral 10. The package 10 has a conventional construction and was formed on an FFS machine by folding flexible packaging film 8 into a tube with lateral edges of the film being heat welded along a longitudinal seam 14 at the rear of the package as shown, for example, in Fig. 1. Heat seal welds 15 at the top and bottom of the package complete its construction.

[0036] The package 10 has a front panel 11 that was formed with a lateral (width wiseextending) slit 13 that functions as the resealable opening for the package 10. The slit 13 is covered by a strip of resealable PSA seal tape 12. In this embodiment, the slit 13 extends the entire width of the package while the seal tape spans the entire width of the package and wraps around the sides edges of the package and adheres to the rear panel. In other preferred embodiments the opening may have a different configuration, such as an elongated hole, so long as its dimensions are proportioned so that PSA seal tape adheres to a sufficient amount of surrounding package material to create the sealing force for the package’s intended application. In further preferred embodiments, the PSA tape 12 need not wrap around the sides or even extend along the entire width of the package so long as the tape is proportioned to cover the entire slit 13.

[0037] The construction of the PSA seal tape 12 comprises a base material 23, a pressure sensitive adhesive 25, and a grip strip 27, and is schematically illustrated in Figs. 3-4, which are not to scale. In one preferred embodiment, the adhesive 25 is applied to the entire surface of one side of the base material 23. The grip strip 27 is adhered to the base material 23 by the pressure-sensitive adhesive 25. When used in common consumer food packaging, the PSA seal tape may be about 1 to 1.25 in. wide, and the grip strip 27 is about 0.3 to 0.5 the width of the tape base. In other applications, the width of the PSA seal tape 12 may vary in proportion to the size of the package and the force needed to seal the opening. In preferred embodiments of all sizes, the grip strip extends along the entire length of the PSA seal tape. The slit of the package is unsealed and opened by peeling the PSA seal tape off the package by pulling the grip strip 27 as shown in Fig. 2.

[0038] The tape base 23 and grip strip 27 are made from a flexible, polymer material that is compatibly -recyclable with polyethylene packaging, including HDPE, and has good resistance to curling under strain. In preferred embodiments, the tape base material has a thickness range between 1.5 and 3 mils, preferably 1.6 to 2.0 mils. In preferred embodiments, the grip strip has a thickness range between 0.5 and 2.0 mils, more preferably 0.9 to 1.4. The pressure-sensitive adhesive is applied in a thickness of range between and 0.6 and 1.0 mils. To insure good recycle compatibility, in a preferred embodiment, the overall adhesive content from the PSA tape is less than about 5% of the total weight of the package to which the PSA tape is adhered.

[0039] Materials suitable for use in the PSA tapes of the invention are machine-direction- oriented polyethylene film produced from a blown film process. The orientation ratio is between 1 :4 and 1:10, meaning that the length of the film has been increased by between a factor of 4 and

10. The resins may be blends of metallocene LLDPEs, higher alphaolefin LLDPEs, and HDPEs. The materials should have good thermal stability with minimal film shrinkage at 120°C, and surface energy of about 38-44 dynes. The secant modulus is preferably approximately 3x higher than traditional PE films used at similar gauges. The tape materials should preferably have the additional properties recited in Table 1:

Table 1

In one exemplary preferred embodiment, the tape base was formed from 2.0 mil GAP -2501 machine-direction-oriented polyethylene film (formerly GAP-1501) and the grip strip was formed from GAP 1001, both of which are manufactured by Charter Next Generation, Inc., Milton, Wisconsin.

Example 1

[0040] An acrylic emulsion pressure-sensitive adhesive formulated with a low level of Dow Chemical CR 9-101, an isocyanate coreactant (formulated at a level less than 1% CR 9-101 per solid part of acrylic emulsion), was applied directly to a 2 mil film of machine-direction- oriented polyethylene sold by Chart Next Generation, Inc., Milton, Wisconsin, under catalog GAP-1001 (“Film A”), and for comparison, to a 2 mil film of GAP-2501 formerly sold under the name GAP-1501 (“Film B”). The isocyanate was used to improve the anchorage of the adhesive to the corona treated polyethylene films. Both films were also corona treated to raise the surface energy to greater than 40 dynes/cm to help increase anchorage of the adhesive to the film. The adhesive was dried in a coating process. To achieve a residual retained moisture less than 0.5% in the adhesive film using, oven conditions in a ramped profile from 150-220°F in a multi-zoned forced air drying process were used. The films were then wound into a master roll of self-wound adhesive tape. The thickness of the adhesive coat on both films was 0.9 mils (24 g/m ² ). Those skilled in the arts understand that adhesive anchorage of pressure sensitive adhesives can be achieved in numerous way including the addition of external crosslinkers such as isocyanate chemistries, aziridines, carbodiimides, multi-layer coatings in addition to optimal levels of corona treatment. A standard 2 mil polypropylene tape, Amtopp TT-50 (“Film C”), manufactured by Inteplast Group, Livingston, New Jersey, treated with a similar acrylic emulsion from Dow Chemical sold under the trademarks Robond™ PS-90, Robond™ PS-2000 type, was used as a control. The typical properties of the films are described in Table 1. Table 2

[0041] The two tapes created from Films A and B and Reference Tape C were evaluated for peel adhesion and curl behavior. Specifically, peel was measured by applying 1 in. wide samples of each tape to a Chemsultants™ stainless steel test panel using the procedures outlined in ASTM Method 3330 for peel adhesion. These panels are stainless steel, 50 by 125 mm (2 by 5 in) no less than 1.1 mm (0.043 in.) thick, conform to Type 302 or 304 of Specification ASTM A666, and have a bright annealed finish. The surface roughness height shall be 50 ± 25 nm (2.0 ± 1.0 i/in.) arithmetical average deviations from the mean line. A smooth, 4.5 lb. stainless steel roller was used to apply the test tapes to the panel. A one minute dwell time was used prior to measuring the peel force and curl behavior of each sample. The peel force was measured using an SP-2100 Slip Peel Tester from Imass Inc., Accord, Massachusetts. Those skilled in the art of pressure sensitive adhesives will understand that the use of a stainless-steel surface represents a standardized method to measure adhesion and the tapes response to deformation for an applied force. This methodology is the basis to reproducibly mimic the forces that a consumer may apply to a reseal tape feature which may be applied on to a film surface ranging for 32 dynes/cm (Untreated Polyethylene or Polypropylene packaging films) to > 40 dynes/cm for a Polyester film, printed or matte coated film, or treated film. The degree of curl was determined by measuring the change of width of the 1 inch wide tape at 2.5 in. down the 6 in. test strip that was applied to the test panel. This way the measurement for film thickness change was determined at the same spot between samples. The reduction in width was recorded for each sample. The results of this evaluation are recorded in table 3. Curl % was recorded as the change of width of the 1 in. test strip divided by the original width multiplied by 100%.

Table 3

[0042] The results in Table 3 show that the preferred inventive Tape B possesses approximately equivalent peel adhesion to Tape A but has much improved curl resistance. While Tape C had the best adhesion and curl resistance, it is not compatibly recyclable with HDPE packaging.

[0043] The typical property values for Film B are listed in Table 4.

Table 4 One of ordinary skill in the art should appreciate that the intended application of the PSA tape is to a flexible polymer packaging material, not a stainless steel sheet such as described above. However, it should also be appreciated that the inventive PSA tape may be applied to numerous different polymer surfaces with different surface properties, such has polyethylene and polyester. For example, polyethylene may have a typical base surface energy of 30 dyne, which would yield lower adhesion an introduce less strain and ultimately less curl to the tape when you use it, compared to one that is corona treated to 42 dynes, which would introduce a higher grab and then ultimately more strain and then curl when you peel the tape off of a higher energy surface. By comparison, the adhesive has a greater inherent ability to adhere to polyester because of the surface energy and the chemistry of the surface itself (more polar than PE). ASTM Method 3330 for peel adhesion provides one test method for measuring and thus quantifying the low curl percentage of the invention.

Example 2:

[0044] An acrylic UV cure, hot melt, pressure sensitive adhesive was applied directly to two machine-direction-oriented polyethylene films at 2mil thickness sold by Chart Next Generation, Inc., Milton, Wisconsin, under catalog no. GAP-1001 (“Film A”), and catalog no. GAP 2501 formerly known as GAP-1501 (“Film B”). Both films were corona treated to raise the surface energy to greater than 40 dynes/cm to help increase anchorage of the adhesive to the film. The adhesive was cured at 20 mJ/cm ² UV-C Dosage in a coating process and wound into a master roll of self-wound adhesive tape. The thickness of the adhesive coat on both films was 0.9 mils (24 g/m ² ). Each of the roll stocks were then slit into 1.125 in. narrow tapes and had a 0.9 mil grip strip of XCC-18167 (“Film C”), manufactured by Charger Next Generation, Inc., laminated to create a dry edge onto the tape.

[0045] The properties of the untreated PE films are listed below.

Table 5

[0046] The two tapes created from the films, were evaluated for reseal performance in a resealable package application. Tapes 1 and 2 comprise the combination of Films A+C and Films B+C, respectively. Specifically, a 5 in. by 8 in. package of the configuration shown in Figs. 1 and 2 was formed using a three-layer packaging film schematically illustrated below: exterior side of bag interior (contents) side of bag

[0047] The inward facing side of Film 1 was corona treated to greater than 40 dynes/cm for print receptivity. The outside layer of Film 1 was not corona treated and was at 32 dynes/cm surface tension for this specific testing.

[0048] The peel and reseal test protocol involves opening and then resealing Tape 1 and Tape 2 over the package slit. When the seal tape is initially applied to the package, the entire width of the adhesive portion of the tape, i.e., excluding the grip strip, is adhered to the package and straddles the slit as best seen in Figs. 1 and 6. The width of the tape on the top side of the slit that re-adheres to the package is illustrated in Fig. 6, identified by reference letters “WRZ”, and is hereinafter referred to as the seal zone width. The width of the tape on the bottom side of the slit that stays adhered (anchored) to the package is identified by reference letters “WAZ” and is referred to as the anchor zone width. Both tapes had a 6 mm anchor zone width, a 12 mm reseal zone width, and a 12.7 mm wide grip strip. Note that the reduction in the WAZ is observed to be curl in direction up opposite from the adhesive coated side (i.e. curling away from the surface the tape is applied to). Each tape is rated on a scale of Pass Plus (P+), Pass (P) and Pass minus (P-) or complete failure (F) as defined below:

1. P+ : Good adhesion to the package film - peel force of 150 grams/inch and higher peel after 1 minute dwell (applied to the package film),

2. P: Moderate adhesion to the package film peel of 75-150 grams/inch after a 1 minute dwell (applied to the package film)

3. P-: Low but acceptable Adhesion to the package film peel of 75 grams-40 grams/inch after a 1 minute dwell (applied to the package film)

4. Failure F: Very light adhesion to the package film; like a 3M post it note peel of less than 40 grams/inch after a 1 minute dwell (applied to the package film), Tape fracture/break, Package film destruct, full adhesive transfer to the packaging film from the tape.

[0049] The failure mode of the PSA tape should be an adhesive failure, more specifically, a clean peel of the tape from the package where no adhesive is transferred to the package film. The subjective peel ratings are defined based on previous package testing results from industry testing.

[0050] The tapes were applied after a continuous slit was introduced to the packaging film in the direction that the film travels (machine direction) as shown in Fig. 5. The package measured 8 in. in the machine direction and a 5 in. in the cross width direction. The packages underwent 5 peel-reseal cycles at room temperature conditions (22°C/50% relative humidity per ASTM peel method specifications). The peel force was measured using an SP- 2100 Slip Peel Tester from Imass Inc., Accord, Massachusetts. The cycling followed these steps:

Cycle 1 - peel back the reseal strip from a new package; re-adhere the strip over the slit; wait 1 hour; measure WRZ;

Cycle 2 - peel back and re-adhere the reseal strip immediately after completion of cycle 1; wait 24 hours; measure WRZ;

Cycle 3-5 - peel back and re-adhere the reseal strip immediately after completion of the previous cycle; wait 72 hours; measure WRZ.

The results are shown in Table 6. Table 6

[0051] Table 6 shows an increasing loss of adhesion (contact amount) for both tapes after each cycle, which is primarily caused when the film curls and peels away from the surface of the packaging film. In the first three cycles, degradation of the adhesive is not believed to significantly degrade adhesion.

[0052] Table 6 shows that the amount of curl and adhesion reduction of Tape 2 is small enough to make the package acceptable as a resealable consumer package. The amount of curl and adhesion reduction of Tape 1 is unacceptable as a resealable consumer package. The overall performance of each tape could be further improved by corona or flame treatment, or coating of the packaging film surface to raise the surface tension from that of untreated polyethylene 30-32 dynes/cm to greater than 36 dynes/cm but a broad range of surface treatments are common in the packaging industry and the benchmarking of an untreated surface film demonstrates the invention with its preferred properties.

[0053] Table 6 also shows how the amount of strain-induced curl reduces dramatically after the third cycle. After the third cycle, subsequent cycles induce very little strain-induced curl. Therefore, any further reduction in adhesion is more likely associated with a degradation of the adhesive.

[0054] In a preferred embodiment, the reduction in the width of the reseal zone after the first cycle is preferably less than 15%, after the second cycle is preferably less than 35%, and after the third cycle is preferably less than 50%. Preferably, the reduction in the width of the reseal zone remains less than 50% in any subsequent cycles. [0055] In the embodiment shown in Figs. 1-2, the PSA reseal tape 12 is constructed and arranged to “reseal” the slit when the consumer presses the tape down over the slit. When properly re-adhered, the package will not leak through the slit over an extended period of time. In another preferred embodiment, a PSA tape is constructed and arranged to “reclose” the package when the consumer folds or rolls the open end of the package and re-adheres the PSA tape over the folded or rolled end of the package to keep the package from unfolding or unrolling. In this embodiment, the fold or roll retards air exchange to the package interior, and retards spillage and contamination. However, it is not a hermetic/tight seal against leaking or spoilage due to compromise from the original, interior packaging conditions. [0056] A preferred embodiment of the invention having a reclosable opening is shown in Figs. 7-10 and is designated generally by reference numeral 110. In this embodiment, a PSA reclose tape is applied along the length-wise (and machine direction) dimension of the package. The package 110 has a conventional construction and was formed on an FFS machine by folding flexible packaging film into a tube with lateral edges of the film being heat welded along a longitudinal seam 114 at the rear of the package 110. Heat seal welds 114, 115 at the top and bottom, respectively, of the package complete its construction.

[0057] Referring to Figs. 7 and 8, the package 110 has a PSA reclose tape 12 extending from the top seal 124 to the bottom seal 125. The reclose tape may be shorter than this length so long as it provides sufficient length to close the bag as described below. The reclose tape 12 preferably has the same construction as the reseal tape described above including a base material 23, a pressure-sensitive adhesive 25, and a grip strip 27.

[0058] A preferred method of reclosing a package is shown in Figs. 9-10. Referring to Fig. 9, the reclose tape is first released from the package by grasping the grip strip near the top of the package and pulling it away from the package. Referring to Fig. 10, only portion of the reclose strip should be released from the package and a sufficient length should remain adhered to the bottom portion of the package. The top of the package is then folded down or rolled down as shown in Fig. 10. The released portion of the reclose tape is then re-adhered to the folded or rolled portion. The next time it is desired to remove some of the contents of the package, the reclose strip is peeled down again so that the top of the package may be unrolled to dispense its contents.

[0059] A machine for producing a package in accordance with a preferred embodiment of the invention is schematically illustrated in Fig. 11. In this embodiment, a roll 41 of PSA tape 12 as described above is fed into an applicator 45, which cuts and applies a predetermined length of the PSA tape 12 onto a film of packaging material 42. The film 42 then travels through a series of additional processing stations 44 and 46. From there, the film travels to further forming stations including, for example, a form-fill -seal machine (“FFS”), thereby producing the flexible packaging such as described in the Forman patents.

[0060] The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described herein, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention. For example, novel resealable package can be achieved by applying a label instead of a tape. It would use a different applicator set up but one could achieve a very similar resealable package.