EXTENSIBLE HIGH PUNCTURE-RESISTANT RECYCLABLE PAPER-BASED PACKAGING STRUCTURES

Description

CROSS REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of U.S. Provisional Patent Application No. 63/664,325 filed Jun. 26, 2024. The aforementioned application is incorporated herein by reference in its entirety.

BACKGROUND

The present disclosure relates generally to the field of packaging and, more specifically, to extensible, high puncture-resistant recyclable paper-based packaging structures and articles and methods for making the extensible high puncture-resistant recyclable paper-based packaging structures and articles.

Economics of scale in product packaging allow for less general waste. The packaging required for a single portion of a set amount of product is likely less than the packaging required for several smaller portions that aggregate to the same set amount of product. As the leftover packaging is generally considered to be waste, reducing the amount of waste by providing packaging suitable to these larger amounts of product is desirable. Packaging for larger quantities or amounts of product must be robust enough to account for higher product weights and larger product dimensions, however. Similar considerations of robustness, including thermal insulating properties, must be made for packaging for frozen products, especially frozen products with higher weights.

Therefore, what is needed is a paper-based structure and/or packaging article with superior elongation and puncture resistance properties that is also recyclable through curbside recycling programs or other paper recycling streams. The present disclosure contemplates new and improved recyclable paper-based structures that overcome the above-referenced problems and others.

SUMMARY

In one aspect, a paper-based recyclable packaging structure is provided for use in applications with high product weight. The paper-based recyclable packaging structure comprises a paper substrate layer having a first surface and a second surface opposite the first surface, wherein the paper layer is formed of a paper having an anisotropy ratio in the range of 0.67 to 1.5. A first polymer extrusion coating layer is disposed on the second surface of the paper layer. The paper fiber content of the paper-based recyclable structure is in the range of 60% to 99% by weight. In further aspects, methods for producing paper based packaging structures are provided. In still further aspects, packaging articles are provided.

Advantages and benefits of the present disclosure will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may take form in various components and arrangements of components, and in various steps and arrangements of steps. The drawings, which are not necessarily to scale, are only for purposes of illustrating preferred embodiments and are not to be construed as limiting the invention.

FIGS. 1A and 1B are cross-sectional diagrams of exemplary packaging structures according to first and second embodiments of the present invention.

FIGS. 2A and 2B are cross-sectional diagrams of exemplary packaging structures according to third and fourth embodiments of the present invention.

FIG. 3 is an isometric view of an exemplary packaging article of the present invention.

FIG. 4 is a table indicating the results of mechanical strength tests of the structure using paper layers of varying basis weights.

FIG. 5 is a flow chart illustrating the steps of the methods of the present invention.

FIG. 6A is a schematic drawing of an exemplary process line for the basic steps of the method for producing a paper-based structure.

FIG. 6B is a schematic drawing of an exemplary process line for the basic steps of the method for producing a paper-based structure, where the polymer extrusion coating layer is a coextrusion coating.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The terms “a” or “an,” as used herein, are intended to encompass one or more than one. The term “another,” as used herein, is defined as at least a second or more. The terms “including” and/or “having” as used herein, are defined as comprising (i.e., open transition). As used herein, the terms “joined,” “coupled,” “operatively coupled,” and the like, are defined as indirectly or directly connected, unless specifically stated otherwise.

As used herein, “paper-based” means a material or structure primarily comprising cellulosic fibers, e.g., derived from wood pulp, and wherein the amount of plastic materials, such as polyethylene, nylon, polypropylene, polyester, and others, are sufficiently low so as not to impede recyclability in paper recycling streams.

As used herein, “recyclable” may refer to a product that is eligible for acceptance into paper recycling programs, including curbside collection programs and recycling programs that use drop-off locations, including products that comply with one or more promulgated standards or guidelines for recyclability, and including materials that are sufficiently free of plastic materials, such as polyethylene, nylon, polypropylene, polyester, and others which would impede recyclability.

As used herein, the terms “grease resistant” or “grease resistance” refers to the character of the first and/or second polymer extrusion coating layer in blocking or impeding the absorption or transmission of grease or oil in any significant quantity.

All numbers herein are assumed to be modified by the term “about,” unless stated otherwise. The recitation of numerical ranges by endpoints includes all numbers subsumed within that range (e.g., 1 to 5 includes, inter alia, 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).

Accordingly, unless indicated to the contrary, the numerical parameters set forth in the present specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by the presently disclosed subject matter.

As used herein, the term “about,” when referring to a value, can encompass variations of, in some embodiments ±20%, in some embodiments ±10%, in some embodiments ±5%, in some embodiments ±1%, in some embodiments ±0.5%, in some embodiments ±0.1%, and in some embodiments to ±0.01%, from the specified amount, as such variations are appropriate in the disclosed materials and methods.

Referring now to the drawings, wherein like reference numerals are used to describe like or analogous items, FIGS. 1A, 1B, 2A, and 2B illustrate exemplary paper-based recyclable packaging structures 10a-10d, respectively. Referring to FIG. 1A, the structure 10a includes a paper substrate layer 12, which has a first, outer surface configured to face exteriorly in a packaging article formed from the web 10a. A polymer extrusion coating layer 16 is disposed between on a second surface 20 of the paper layer 12, the second surface 20 being opposite the first surface 18. The polymer extrusion coating layer 16 may be a monolayer or multilayer film, including multilayer film formed by coextrusion of the multiple layers or sequential extrusion of the multiple layers. The polymer extrusion coating layer 16 includes a heat-scalable innermost surface which is heat-scalable to itself to form a packaging article. The polymer extrusion coating layer 16 also provides grease resistance and, in certain embodiments, moisture barrier properties, oxygen barrier properties, or both.

In certain embodiments, the polymer extrusion coating layer 16a is formed of polyethylene (PE), polypropylene (PP), polyolefin blends, or polyolefin copolymers. In embodiments, polymer extrusion coating layer 16a comprises low-density polyethylene (LDPE), very low-density polyethylene (VLDPE), linear low-density polyethylene (LLDPE), medium density polyethylene (MDPE), linear medium density polyethylene (LMDPE), high-density polyethylene (HDPE), metallocene polyethylene including metallocene linear low-density polyethylene (mLLDPE), polyolefin plastomer (POP), cast polypropylene (CPP), ethylene-propylene copolymer (EPC), monoaxially- and biaxially-oriented polyolefins including without limitation biaxially oriented polypropylene (BOPP), and other polyolefin materials, including post-consumer recycled (PCR) polyolefins, as well as blends, coextrusions, and lamination of any of the foregoing, provided that at least the exterior most layer is a heat sealable polyolefin layer. In embodiments, the polymer extrusion coating layer 16a may be a copolymer of polyethylene and polypropylene, such as an ethylene-propylene copolymer. In embodiments, the polymer extrusion coating layer 16a may be a coextruded film with a barrier layer and optional tie resin layers as would be understood by persons skilled in the art. In embodiments, the barrier layer is selected from ethylene vinyl alcohol copolymer (EVOH) and polyamide (PA), such as nylon 6, nylon 66, nylon 6/66, and the like. In embodiments, the polymer extrusion coating layer 16a may be formed of ionomer resins (e.g., SURLYN™), ethylene-vinyl acetate copolymer (EVA), ethylene-methyl acrylate copolymer (EMA), ethylene-acrylic acid copolymer (EAA), ethylene-methyl methacrylate copolymer (EMMA), and polyvinyl alcohol (PVOH).

In embodiments, as shown in FIG. 1B, there appears a structure 10b comprising a polymer coextrusion coating layer 16b. In the illustrated embodiment, the coextrusion coating 16b comprises first and second polymer layers 26 and an oxygen and/or moisture barrier layer 30 therebetween. The first and second polymer layers 26 may be a composition as described above by way of reference to the polymer extrusion coating layer 16a. Optional first and second tie resin layers 28 may be provided between the barrier layer 30 and the first and second polymer layer 26, respectively.

In certain embodiments, the polymer coextrusion coating layer 16b has a coextruded structure, as follows, wherein optional tie resin layers (“tie”) may be provided to promote adhesion between adjacent layers:

polyolefin / barrier / polyolefin .

Exemplary polyolefins include polyethylene (PE) and polypropylene (PP). Exemplary barriers include ethylene vinyl alcohol copolymer (EVOH), polyamide (PA), and/or polyvinyl alcohol (PVOH). Exemplary polyamides include nylon, such as nylon 6, nylon 66, nylon 6/66, and the like. Examples of such multilayer structures include:

In certain embodiments, the polymer coextrusion coating layer 16b has a coextruded structure, as follows, wherein optional tie resin layers (“tie”) may be provided to promote adhesion between adjacent layers:

polyolefin / polyolefin / barrier / polyolefin / polyolefin .

Exemplary polyolefins include polyethylene (PE) and polypropylene (PP). Exemplary barriers include ethylene vinyl alcohol copolymer (EVOH) and/or polyamide (PA). Exemplary polyamides include nylon, such as nylon 6, nylon 66, nylon 6/66, and the like. Examples of such multilayer structures include:

In certain embodiments, the polymer coextrusion coating layer 16b has a coextruded structure, as follows, wherein optional tie resin layers (“tie”) may be provided to promote adhesion between adjacent layers:

cast ⁢ polypropylene / barrier / cast ⁢ polypropylene

wherein the cast polypropylene (CPP) layers may be monolayer or multilayer CPP structures. Exemplary barriers include ethylene vinyl alcohol copolymer (EVOH) and/or polyamide (PA). Exemplary polyamides include nylon, such as nylon 6, nylon 66, nylon 6/66, and the like. Examples of such multilayer structures include:

In certain embodiments, the polymer coextrusion coating layer 16b has a coextruded structure, as follows, wherein optional tie resin layers (“tie”) may be provided to promote adhesion between adjacent layers:

barrier / polyolefin

wherein the barrier layer is applied directly to the paper layer and the polyolefin layer is disposed on the barrier layer. Optional tie resin layers (“tie”) may be provided to promote adhesion between adjacent layers.

Examples of such multilayer structures include:

Referring now to FIG. 2A, there is shown a structure 10c which includes a paper layer 12 having a first polymer extrusion coating layer 16c disposed on a first side 18 thereof, and a second polymer extrusion coating layer 16c disposed on a second side 20 thereof. The first and second polymer extrusion coating layers 16c may be as described above by way of reference to the polymer extrusion coating layer 16a.

Referring now to FIG. 2B, there is shown a further embodiment structure 10d which includes a paper layer 12 having a first polymer coextrusion coating layer 16d disposed on a first side 18 thereof, and a second polymer coextrusion coating layer 16d disposed on a second side 20 thereof. The first and second polymer coextrusion coating layers 16d may be as described above by way of reference to the polymer coextrusion coating layers 16b. Relative thicknesses of the various layers shown in FIGS. 1A, 1B. 2A, and 2B are understood as being not necessarily to be to scale and are presented approximately equally for illustrative purposes only.

In embodiments, the paper layer 12 has a basis weight of about 25-70 pounds per ream (40-114 g/m²), preferably 35-55 pounds per ream (57-90 g/m²), and most preferably 40-50 pounds per ream (65-81 g/m²). Unless specified otherwise, basis weights given in pounds per ream are based on a 3000 square foot ream. In embodiments, the paper layer 12 is comprised of two or more paper plies adhered to one another, as disclosed, for example in co-owned U.S. Provisional Patent No. 63/548,327, filed Nov. 13, 2023, which is hereby incorporated in its entirety by reference. The fiber content of the paper layer 12 and to coating weight of the extrusion or coextrusion coating layer(s) is such that the overall structure 10 has a paper fiber content in the range of from 60% to 99%, by weight, e.g., 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or any subrange thereof. In certain embodiments, the structure 10 has a paper fiber content which is in the range of 80% to 99% by weight.

With a fiber content in the range of 60% to 99% by weight, the structure 10 and any packaging article 46 (as discussed below) formed therefrom are recyclable in paper recycling streams. In embodiments, the paper layer 12 is made of extensible or semi-extensible paper. While not intending to be bound by any particular theory, it is believed that the relatively uniform fiber sizes of the extensible and semi-extensible paper substrates result in a relatively uniform percentage of elongation at break when comparing the transverse direction (TD) and machine direction (MD), thereby allowing for uniform stress distribution and increased puncture resistance.

In embodiments, the first and/or second polymer extrusion coating layers 16a, 16c, and the polymer coextrusion coating layers 26, which may be the same or different, provide scalability, grease resistance, and in certain embodiments, moisture and oxygen resistance. Embodiments such as those shown in FIGS. 1B and 2B, where one or both of first and second polymer coextrusion coating layers 16b, 16d include a barrier layer provide increased moisture and oxygen resistance.

Now referring to FIG. 3, an isometric view of an exemplary packaging article 46 is provided. Although an open-ended bag is shown, the packaging article 46 may come in many forms, including bags, pouches, and overwraps. Exemplary packaging articles include pillow packs, self-opening sack (SOS) bag, pinch bottom pouch, pinch bottom open mouth (PBOM) bag, stand up pouches, and quad seal side gusseted bags, and others. The packaging article 46 has an interior 48 in which the product will be disposed. The first polymer extrusion coating layer 16 is the inner surface of the packaging article 46 which will face the product. As shown, the paper layer 12 is shown on the exterior of the packaging article 46. Given the superior mechanical strength properties of the structure 10 out of which the packaging article 46 is formed, as detailed below with reference to FIG. 3, the packaging article 46 is capable of packaging high weight products without compromising the integrity of the structure 10 and the packaging article 46.

Now referring to FIG. 4, a table is provided indicating the results of extensibility and mechanical strength tests of paper layers 12 of varying basis weights. It has been found in reducing the present invention to practice that packaging structures utilizing a paper substrate having an anisotropy ratio in the range of 0.67 to 1.5 and a puncture resistance greater than or equal to 3 pound-force (lbf) (13.3 N) exhibit superior elongation and puncture resistance. The paper substrates exhibiting these properties appear bolded in FIG. 4.

The anisotropy ratio of the paper substrate as used herein is defined as the ratio of the percentage of elongation of the paper substrate at break in the transverse direction (TD) to the percentage of elongation of the paper substrate at break in the machine direction (MD). Percentage of elongation is expressed herein as a percentage of the original, unstretched length. The percentage of elongation at break is measured during tensile testing under ASTM D882-18.

In embodiments, the paper substrate 12 also has puncture resistance greater than or equal to 3 lbf (13.3 N), preferably in the range of 3 lbf (13.3 N) to 13.5 lbf (60 N). As used herein, “puncture resistance” means the penetration resistance of the structure 10 as measured by ASTM F1306-21 with a standard probe of 3.2 mm diameter moving at standard speed of 25 mm/minute. The bolded rows of the table shown in FIG. 4 indicate the paper layers 12 that meet the criteria of both an anisotropy ratio in the range of 0.67 to 1.5 and a puncture resistance in the range of 3 lbf (13.3 N) to 13.5 lbf (60 N). As shown in the left column, of the papers tested, only the extensible paper layers 12 met these criteria.

Now referring to FIG. 5, the steps of the methods for forming a paper-based structure and packaging article, as described above, are provided. Method 100a for producing the paper-based structure 10a includes a step 102 of providing the paper layer 12 having a paper exterior surface 18 and an interior surface 20. The polymer extrusion coating layer 16a is brought onto the interior surface 20 of the paper substrate 10a at step 104a. A packaging article is formed at a step 114.

Method 100b for producing the paper-based structure 10b includes a step 102 of providing the paper layer 12 having a paper exterior surface 18 and an interior surface 20. The polymer coextrusion coating layer 16b is brought onto the interior surface 20 at step 104b. A packaging article is formed at a step 114.

In embodiments, the methods 100a, 100b may include providing a second polymer extrusion coating layer 16b or a second polymer coextrusion coating layer 16d, respectively, on the exterior surface 18 of the paper layer 12.

In the methods, 100a, 100b, the paper layer 12 comprises paper fiber content which is in the range of 60% to 99% by weight based on the weight of the packaging structure 10a, 10b, respectively. In certain embodiments, in the methods, 100a, 100b, the paper layer 12 comprises paper fiber content which is in the range of 80% to 99% by weight based on the weight of the packaging structure 10a, 10b, respectively.

Now referring to FIG. 6A, there is shown an exemplary process line suitable for forming the packaging structure 10a as shown in FIG. 1A. A paper substrate layer 12 is unrolled from a feed roll 1140 and fed toward an extrusion coating station 1180. Optionally, on the way to the extrusion coating station 1180, the paper layer 12 is fed past a surface treater 1144, such as a flame treater, corona treater, plasma treater, or ozone treater, which treats the interior surface 20 surface of the paper layer 12 to improve adhesion.

The extrusion coating station 1180 includes a hopper 1182 containing a polymer, e.g., polyolefin pellets. The hopper 1182 feeds the polymer into the barrel of an extruder 1184, which includes heating elements and means for conveying the polymer resin through the extruder barrel. Molten polymer exits a die 1186 as a uniform curtain of molten polymer 1138 at a point just before the paper layer 12 approaches the nip between a pressure roller 1188 and a chill roller 1190. The first polymer extrusion coating layer 16 is thereby applied to the paper layer 12. The resultant paper-based structure 10a is rolled up onto a take up roll 1158.

To form the packaging structure 10c as shown in FIG. 2A, the roll 1158 is then fed through a second extrusion coating line or the same line configured to coat the opposite side 18 of the paper substrate 12 with the second polymer extrusion coating layer 16c.

Now referring to FIG. 6B, there is shown an exemplary process line suitable for forming the packaging structure 10b as described with reference to FIG. 1B, wherein the polymer extrusion coating layer is a coextrusion coating layer 16b. The paper layer 12 is unrolled from the feed roll 1140 and fed toward a coextrusion coating station 1192. Optionally, on the way to the coextrusion coating station 1192, the paper layer 12 is fed past a surface treater 1162, such as a flame treater, corona treater, plasma treater, or ozone treater that treats the surface of the paper layer 12 to improve adhesion.

The coextrusion coating station 1192 includes hoppers 1194a, 1194b, and 1194c, etc., containing the resins to be coextruded, e.g., polymer, EVOH, and tic resin in the depicted embodiment. It will be recognized that other coextrusion structures are contemplated. The hoppers 1194a-1194c feed the resins into the barrels of respective extruders (not shown). The molten materials from the extruders are combined in a feed block 1196 which arranges the molten resins in the desired layered arrangement and are directed to a coextrusion die 1198. The molten resins exit the die 1198 as a uniform, layered melt curtain at a point just before the paper layer 12 approaches the nip between a pressure roller 1193 and a chill roller 1195. The resultant paper-based structure 10b is rolled up onto a take up roll 1176.

To form the packaging structure 10d as shown in FIG. 2B, the roll 1158 is then fed through a second extrusion coating line or the same line configured to coat the opposite side 18 of the paper substrate 12 with the second polymer coextrusion coating layer 16d.

It will be recognized that the process lines appearing in FIGS. 6A and 6B are exemplary only and that the order and manner of performing the steps of method 100 can be modified.

The invention has been described with reference to the preferred embodiment. Modifications and alterations will occur to others upon a reading and understanding of the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.