Recyclable film for thermoforming

Abstract

A recyclable film having at least a first layer, a second layer, and a third layer can be used in a thermoformed packaging assembly, the first layer comprising high density polyethylene and a nucleating agent, the second layer comprising high density polyethylene, the third layer comprising high density polyethylene and a nucleating agent. This film structure is advantageous because it can be more easily thermoformed than traditional high density polyethylene films and can maintain the shape taken during the thermoforming process, exhibiting minimal warping or shrinking.

Description

[0001] This case is a divisional application of patent application number 201980095040.X, filed on August 21, 2019, entitled “Recyclable film for thermoforming”, the parent application of which is incorporated by reference in its entirety into this divisional application. TECHNICAL FIELD

[0002] The present disclosure relates to film structures suitable for thermoforming into packaging assemblies, in particular high performance recyclable films. BACKGROUND

[0003] High performance packaging films are used to package many products, such as food, pharmaceutical, consumer or industrial goods. Particularly designed packaging is used for products that are environmentally sensitive to help protect the product and extend the shelf life to the point in time when the consumer can use the product. These packages are often made from various types of polymers and additives that provide the properties needed to achieve “high performance”. The materials chosen for the packaging can enhance barrier properties, physical properties or aesthetics, among others. Often, the design of the package includes multiple materials to achieve multiple properties.

[0004] Combining materials in a single packaging material can create difficulties in determining how to dispose of the package after use. Recycling is often the most efficient, or only possible, when the materials in the package are of the same polymer type. Efforts to use recyclable packaging materials, especially those of a single polymer type, result in lower performance and / or significantly higher cost. As a few examples, lower performance characteristics encountered can be visual defects, less barrier and shorter shelf life, slower speed on packaging equipment.

[0005] One polymer type that is particularly suitable for recycling is high density polyethylene. This material has been used for many years for milk jugs or other bottles. These bottles are 100% high density polyethylene and provide suitable barrier properties due to the wall thickness. In many countries, there are processes in place to collect, sort and recycle these packages.

[0006] However, the use of high density polyethylene as a primary component has not translated into the form of most flexible packaging. In addition to injection molding or blow molding, high density polyethylene suffers from low efficiency of use. For example, in thermoforming flexible packaging, such as trays or cups, high density polyethylene has been found to not form as easily or consistently as other materials, such as polystyrene or PVC. Forming of high density polyethylene can be slow and result in poorly formed parts. In addition, secondary crystallization of high density polyethylene can cause formed parts to warp and curl within hours and days after forming. For this reason, thermoformed packaging often uses other materials, such as multi-layer films with a combination of materials, to obtain good parts at acceptable speeds. Due to the variety of materials in these films, they are not recyclable. SUMMARY

[0007] The structure and material components of the thermoformed base assembly are configured to provide moisture barrier, excellent formability characteristics, and recyclability options. The thermoformable base film forming the base has a high level of high density polyethylene, making it readily recyclable. Surprisingly, the thermoformable films described herein have an acceptable operating window in the thermoforming process. It is also advantageous that the final thermoformed base assembly retains the original thermoformed shape, resisting warping and shrinking.

[0008] In various embodiments of the disclosure, a thermoformable base film is described. The thermoformable base film has a first layer having high density polyethylene and a nucleating agent, a second layer having high density polyethylene, and a third layer having high density polyethylene and a nucleating agent. The second layer is between the first layer and the third layer. The first and third layers can each form a surface of the thermoformable base film. The first layer can additionally include a metallocene linear low density polyethylene. The second layer can additionally include a hydrocarbon resin and / or a nucleating agent.

[0009] Additionally, the film can have a fourth layer between the first layer and the third layer, the fourth layer having high density polyethylene and inorganic particles. The inorganic particles can be calcium carbonate and / or can be present at a level of 10% by weight relative to the entire fourth layer.

[0010] The film can also have various other layers, including but not limited to an oxygen barrier layer or a center layer including an ethylene vinyl alcohol copolymer. If the film has a center layer, the center layer includes an ethylene vinyl acetate copolymer, and the film is palindromic. The film can be formulated to have a total composition suitable for recycling. To facilitate recycling, the film can be formulated to be essentially free of polyester, ethylene vinyl alcohol copolymer, and polyamide.

[0011] In various embodiments of the disclosure, a thermoformed base is described. The thermoformed base is formed from the thermoformable base film and includes at least one cavity and a flange (i.e., unformed area) around each of the cavities. It is advantageous for the films described herein that the thermoformed bases retain the shape taken during the thermoforming process.

[0012] In various embodiments of the disclosure, the thermoformed base described herein is combined with a product and a lid packaging assembly to produce a packaged product. The lid is hermetically sealed over the flange of the base, enclosing the product in the cavity. The lid can include metal or paper. The lid can be peelably sealed to the base, such that it can be removed by hand.

[0013] In some embodiments, the lid is a "push through" lid. In other words, the cavity of the thermoformed base can be manually depressed and the product pushed through the lid for dispensing. In preferred embodiments of the packaged product, the lid has a first outer layer having high density polyethylene and inorganic particles, a second outer layer having a polyethylene-based material, and a first inner layer having high density polyethylene, a nucleating agent, and optionally a hydrocarbon resin. In some embodiments of the packaged product, both the base and lid assembly are recyclable in the same recycling process.

[0014] It has been discovered that a thermoformable base film having at least a first layer, a second layer, and a third layer as described herein can be used to produce thermoformed base packaging assemblies with superior results. This is unexpected because the thermoformable base film contains a significant amount of high density polyethylene which has previously been shown not to have an acceptable combination of properties for high performance thermoformed packaging applications. The thermoformable base film described herein produces a key and previously unachieved combination of 1) ease of thermoforming, 2) high moisture barrier, and 3) recyclability. BRIEF DESCRIPTION OF DRAWINGS

[0015] The present disclosure can be more fully understood with reference to the following detailed description of the embodiments of the present disclosure when considered in conjunction with the accompanying drawings, in which:

[0016] Figure 1 is a cross-sectional schematic of an embodiment of a thermoformable base film including a first layer, a second layer, and a third layer;

[0017] Figure 2 is a cross-sectional schematic of an embodiment of a thermoformable base film including a first layer, a separate second layer, a third layer, and a center layer;

[0018] Figure 3 is a cross-sectional schematic of an embodiment of a thermoformable base film including a first layer, a second layer, a third layer, a center layer, and an oxygen barrier layer;

[0019] Figure 4 is a cross-sectional schematic of an embodiment of a thermoformable base film including a first layer, a second layer, a third layer, and a fourth layer;

[0020] Figure 5 is a perspective view of a thermoformed base assembly including 10 cavities;

[0021] Figure 6 is a top view of a thermoformed base assembly showing 12 cavities and one flange;

[0022] Figure 7 is a cross-sectional schematic of a package including a thermoformed base assembly, a product, and a lid assembly;

[0023] Figure 8is a cross-sectional schematic of an embodiment of a lid assembly for packaging a product; and

[0024] Figure 9 is a graph showing data from a USP 671 (40°C, 75% RH) weight gain / cavity / day study.

[0025] The drawings illustrate only some embodiments and are not therefore mutually exclusive. The elements depicted in the drawings are illustrative and not necessarily drawn to scale, and the same (or similar) reference numerals in the figures represent the same (or similar) features throughout the figures. DETAILED DESCRIPTION

[0026] Described herein is a high-density polyethylene-based thermoformable base film suitable for packaging products that can be sensitive to oxygen and / or moisture. A lid film can be heat sealed to a thermoformed base packaging assembly made from the thermoformable base film, resulting in a package that can be accepted in a high-density polyethylene recycling process. The high-performance package can be suitable for products such as, but not limited to, pharmaceuticals, nutraceuticals, medical products, fresh food, refrigerated food, shelf-stable food, consumer goods, cosmetics, and chemicals.

[0027] The structure and material composition of the thermoformed base assembly are uniquely configured to provide moisture barrier, good clarity, and recyclability options. Unexpectedly, the thermoformable films described herein have an acceptable operating window in the thermoforming process, such that the final thermoformed base assembly is easily thermoformable. Also unexpectedly, the thermoformable base material described herein is able to maintain the original thermoformed shape upon thermoforming, thereby resisting warping and shrinking.

[0028] The package described herein includes at least two packaging assemblies. The first is a thermoformed base assembly made from a high-density polyethylene-based film. The thermoformed cavity can be deep or shallow and is generally shaped to hold the intended product therein. The thermoformable base film should have a thickness to provide the rigidity (i.e., stiffness), durability, and barrier properties needed upon thermoforming. The second is a lid packaging assembly. The lid is configured from a film that is capable of being heat sealed hermetically to the thermoformed base assembly, thereby creating a protective package for the product.

[0029] In some embodiments of the package, a high-performance lid assembly having a composition rich in high-density polyethylene can be used in conjunction with a thermoformed base. The combination of the thermoformed base assembly and the lid packaging assembly provides superior packaging features while maintaining a highly uniform polymer composition (consisting essentially of polyethylene, mostly high-density polyethylene) to provide the opportunity to recycle the entire package in a single stream, such as a high-density polyethylene bottle stream.

[0030] The packaging assemblies described herein are unique in that they are produced using high levels of high density polyethylene, but still retain the high performance features required for demanding packaging applications. The hermetically sealed packages provide excellent product protection (i.e., moisture barrier), good appearance, good forming precision and consistency, good heat resistance, and good seal strength. The use of materials that can be readily recycled in high density recycle streams has not previously provided packaging with these levels of performance.

[0031] Substrate packaging assemblies

[0032] The thermoformed substrate packaging assemblies are formed from a thermoformable base film 10 having at least a first layer 20, a second layer 30, and a third layer 40, with the second layer positioned between the first and third layers, as shown. Figure 1 The first and third layers can have similar or identical compositions and together make up from about 10% to about 35% of the total thickness (or volume) of the thermoformable base film. The second layer makes up from about 25% to about 90% of the thermoformable base film. In some embodiments of the thermoformable base film, the second layer makes up from about 50% to about 90% of the thermoformable base film. Additional layers can also be present in the thermoformable base film.

[0033] As used herein, the term“layer” refers to a building block of a film that is a structure of a single material type or a uniform blend of materials. A film contains one or more layers that are connected to each other. A layer can contain a single polymer, a blend of materials within a single polymer type (i.e., polyethylene), or a blend of different polymer types, can contain metallic or other non-polymeric materials and can have additives. A layer can be continuous with the film or can be discontinuous or patterned as compared to the film. A film has two surfaces that are opposite each other. A layer at a surface of the film is not connected to another layer of the film at that surface.

[0034] The first and third layers of the thermoformable base film each contain high density polyethylene and a nucleating agent. The high density polyethylene should be present in each of the first and third layers in an amount greater than 80% by weight, greater than 85% or about 90% or more. Two or more different high density polyethylene materials can be used in each of the first and third layers. As used throughout this application, the term“high density polyethylene” or“HDPE” refers to both (a) homopolymers of ethylene having a density from about 0.960 g / cm3to about 0.970 g / cm3, and (b) copolymers of ethylene and an alpha-olefin (typically 1-butene or 1-hexene) having a density from about 0.940 g / cm3to about 0.958 g / cm3. High density polyethylene includes polymers made with Ziegler or Phillips type catalysts and polymers made with single-site metallocene catalysts. The high density polyethylene can be bimodal and can be pre-nucleated.

[0035] As used throughout this application, the term "nucleating agent" refers to an additive that forms nuclei in a polymer melt to control the growth of the catalyst. The nucleating agent can be of any type that is capable of nucleating high density polyethylene, and can be added at the time of high density polyethylene polymerization or at a later point in time by adding and melt blending a masterbatch containing the nucleating agent. Examples of nucleating additives include minerals such as chalk, talc, clay, kaolin, silicates, and the like, and organic agents such as aliphatic or aromatic carboxylates, aromatic salts, metal salts of aromatic phosphorous compounds, quinacridone, and aromatic amides. Further examples of nucleating agents include zinc glycerate, calcium glycerate, calcium hexahydrophthalate, zinc hexahydrophthalate, salts and the like, and mixtures thereof. The nucleating agent can be present in the first and third layers of the thermoformable base film at levels from about 0.2% to about 3.5% by weight of the layer.

[0036] Examples of pre-nucleated high density polyethylene materials that can be suitable for use in the thermoformable base film are Grade M6020SB available from Equistar and HPS167AB available from Nova Chemicals. An example of a non-nucleated high density polyethylene material that can be suitable for use in the thermoformable base film is Grade M6020 available from Equistar. An example of a nucleating agent masterbatch material that can be suitable for use in the thermoformable base film is HPN nucleating agent available from Milliken. HPN nucleating agent.

[0037] The first and third layers can have other components in addition to the high density polyethylene and the nucleating agent. For example, the first or third layer can include a metallocene linear low density polyethylene material. If the nucleating agent is added to the first and / or third layer by a masterbatch, a carrier polymer, typically a low density polyethylene or a linear low density polyethylene, is also a component of the layer.

[0038] The first and third layers can have the same, similar, or different compositions with respect to the type of high density polyethylene, the type of nucleating agent, the presence of other components, and the blending ratio of the materials. The first and third layers can have the same, similar, or different thicknesses.

[0039] The second layer of the thermoformable base film includes a high density polyethylene. In some embodiments, the second layer of the thermoformable base film includes a high density polyethylene, a hydrocarbon resin, and a nucleating agent. In some embodiments, the second layer of the thermoformable base film includes a high density polyethylene and a hydrocarbon resin, or a high density polyethylene and a nucleating agent. The second layer can be divided into multiple "second layers" that can be separated by other layers. The single or multiple second layers must be between the first and third layers.

[0040] The high density polyethylene should be present in the second layer in an amount of from about 60% to about 90% by weight. The high density polyethylene can be present in the second layer in an amount greater than 80% or in an amount greater than 85%. Two or more different high density polyethylene materials can be present in the second layer. A nucleating agent can be present in the second layer of the thermoformable base film at a level of from about 0.2% to about 3.5% by weight of the layer.

[0041] As used herein, the phrase "hydrocarbon resin" refers to low molecular weight products (molecular weight less than about 10,000 Daltons) produced by polymerization of coal tar, petroleum, and turpentine feedstocks. The hydrocarbon resins can include any of those disclosed in U.S. Patent No. 6,432,496, published August 13, 2002, or in U.S. Patent Application 2008 / 0286547, published November 20, 2008, which two applications are incorporated by reference in their entirety into the present application. More specifically, the hydrocarbon resins can include, by way of non-limiting example, petroleum resins, terpene resins, styrene resins, cyclopentadiene resins, saturated alicyclic resins, or mixtures of such resins. Additionally, the hydrocarbon resins can include, by way of non-limiting example, hydrocarbon resins derived from polymerization of dicyclopentadiene (DCPD)-rich olefin feed, polymerization of olefin feed produced in a petroleum cracking process, such as a crude C9 feed stream, polymerization of pure monomers such as styrene, alpha-methyl styrene, 4-methyl styrene, vinyl toluene, or any combination of these or similar pure monomer feedstocks, polymerization of terpene olefins such as alpha-pinene, beta-pinene, or d-limonene, or combinations of these. The hydrocarbon resins can be fully or partially hydrogenated. Specific examples of hydrocarbon resins include, but are not limited to, Norpol® R1140 hydrocarbon resin, available from Eastman Chemical Company (Kingsport, Tenn.), Eastobond® T1140, available from Arakawa Chemical Industries, Limited (Osaka, Japan), Eastobond® P-140, available from Hercules Incorporated (Wilmington, Del.), Eastobond® S135 polyterpene resin, and Eastobond® S135 polyterpene resin. Norpol® R1140 hydrocarbon resin, available from Eastman Chemical Company (Kingsport, Tenn.), Eastobond® T1140, available from Arakawa Chemical Industries, Limited (Osaka, Japan), Eastobond® P-140, available from Hercules Incorporated (Wilmington, Del.), Eastobond® S135 polyterpene resin.

[0042] The hydrocarbon resin can be present in the second layer in an amount between 0% and 50% by weight. The upper limit of the hydrocarbon resin used can be dictated by processing issues (i.e. insufficient melt strength during extrusion) or film properties. For example, high levels of hydrocarbon resin can result in interlayer adhesion issues or film brittleness. The amount of hydrocarbon used in the second layer will also depend on the type of hydrocarbon resin used and the thickness of the second layer. For example, thinner second layers can be able to handle higher levels of hydrocarbon resin before issues are encountered.

[0043] In some embodiments of the thermoformable base film, the hydrocarbon resin can be present at levels up to 30% by weight relative to the second layer. The hydrocarbon resin can be loaded into the second layer at levels between 2.5% and 30%. Some embodiments of the thermoformable film will have a hydrocarbon resin level in the second layer between 5% and 20%. In exemplary embodiments, the hydrocarbon resin is present in an amount of about 15% or about 7.5% by weight. The level of hydrocarbon resin can be adjusted to control the moisture barrier properties of the film and the thermoforming temperature window. Increasing the level of hydrocarbon resin increases the moisture barrier properties of the film. Increasing the level of hydrocarbon resin increases the thermoforming temperature window of the thermoformable base film.

[0044] Any additional materials present in the first, second, or third layers of the thermoformable base film or present in other layers of the thermoformable base film should be acceptable to a high density recycling process. The additional materials can be present at low levels such that they do not disrupt or otherwise hinder the recycling process. The additional materials can be of a type that is acceptable to the recycling process, such as other types of polyethylene based materials. The additional materials can be present with a compatibilizer system.

[0045] Other layers can be present in the thermoformable base film so long as the layers do not compromise the properties of the film (i.e. the materials must be acceptable to the high density recycling process). The other layers can be present anywhere in the thermoformable base film.

[0046] For example, the thermoformable base film can have a center layer. As used herein, a “center” layer is a layer that has the same number of layers on either side of the center layer of a given film. Figure 2 An embodiment of a thermoformable base film is shown having a first layer 10 forming a surface of the thermoformable base film, a third layer 40 forming an opposing surface of the thermoformable base film, two second layers 30 separated and divided by a center layer 60. In this example, the center layer has two layers on either side and thus it is in the center of the thermoformable base film. The center layer can have any composition as described herein, such as having an oxygen barrier material or a tie material.

[0047] The center layer 60 is particularly useful when the thermoformable base film is produced by a "collapsed bubble" process. During this process, a multi-layer film is produced by an annular co-extrusion process and then the tube is collapsed, merging the two sides into one final film. This process creates a palindromic layer structure and the center layer contains a material that will bond to itself under warm conditions, such as ethylene vinyl acetate copolymer. The thermoformable base film made from this process must have first and third layers that are identical in thickness and composition. The thermoformable base film made from this process must have a center layer. The thermoformable base film made from this process must have at least two second layers.

[0048] In some thermoformable base films, such as Figure 3 In the embodiment shown, there can be one or more oxygen barrier layers. The oxygen barrier layer should be between the first layer and the third layer. The oxygen barrier layer contains a material known to limit the transmission of oxygen through a film. One option for the oxygen barrier material is EVOH. In some cases, the EVOH can be present with a compatibilizer that allows the EVOH to be incorporated into a high density polyethylene recycle stream.

[0049] As used herein, "EVOH" refers to an ethylene vinyl alcohol copolymer. EVOH is also known as saponified or hydrolyzed ethylene vinyl acetate copolymer and refers to an ethylene vinyl alcohol copolymer with an ethylene comonomer. EVOH is prepared by hydrolysis (or saponification) of an ethylene vinyl acetate copolymer. EVOH is commercially available in the form of resins with different percentages of ethylene. Preferably, the ethylene / ethylene vinyl alcohol copolymer comprises from about 27-38 mole percent ethylene or even 27-29 mole percent ethylene.

[0050] Figure 3 An embodiment of a thermoformable base film 10 is shown with a variety of selected combinations, including a first layer 20, a third layer 40, four second layers 30, a center layer 60, two oxygen barrier layers 70, and four tie layers 80. This embodiment can be produced by a collapsed bubble process, in which case the film is palindromic. Alternatively, the film can be produced by a different process and then the film is not necessarily palindromic. Tie layers 80 are used in this embodiment and can be introduced into any other embodiment of a thermoformable base film. Tie layers are layers that are intended to tie non-similar layers (in this case, an oxygen barrier layer and a second layer). The need for a tie layer depends on the materials in the adjacent layers. For the embodiments of thermoformable base films described herein, a tie layer based on a polyethylene copolymer is typically suitable.

[0051] As Figure 4As shown, the thermoformable base film 10 may have a fourth layer 50, which is high-density polyethylene with inorganic particles such as calcium carbonate or talc. Adding one or more fourth layers can help achieve clean cutting of the material after thermoforming. One or more of the fourth layers 50 should be located between the first layer 20 and the third layer 40 of the thermoformable base film 10. The inorganic particles should be present in the fourth layer in an amount of at least 10% by weight or between 10% and 30%.

[0052] In some embodiments of the thermoformable base film, the first or third layer forms the surface of the film. This surface can be the surface on which the cover assembly is heat-sealed. In this arrangement, the cover is heat-sealed to the first or third layer comprising high-density polyethylene.

[0053] Thermoformable base film can be fully co-extruded or produced through other processes such as lamination or coating.

[0054] In general, thermoformable base films can have a thickness from about 4 mils (102 micrometers) to about 80 mils (2,032 micrometers). Some packaging applications will benefit from thermoformable base films with a thickness from about 8 mils (203 micrometers) to about 50 mils (1,270 micrometers). In some embodiments, the thermoformable base film has a thickness from about 8 mils (203 micrometers) to about 25 mils (635 micrometers).

[0055] Thermoformable base film should have an overall composition suitable for recycling. Thermoformable base film should have an overall composition suitable for recycling in processes that typically accept polyethylene-based materials. The overall composition may also be suitable for recycling in processes that accept high-density polyethylene materials.

[0056] The thermoformable base films described herein can be recycled after their primary use is complete. As used herein, the term "suitable for recycling" is intended to indicate that the film can be transformed into new, useful articles through reprocessing in a polyolefin recycling stream (i.e., a polyethylene-based recycling stream). Reprocessing may require washing, separation, melting, and molding, among many other steps. Typically, when recycling plastic packaging through reprocessing, the material is mechanically cut into small pieces, melted, mixed, and reshaped into new products. If multiple incompatible materials are present in the packaging, interactions can occur during reprocessing, resulting in gels, brittle materials, undesirable appearance, and products that are generally unusable or of poor quality. The term "recyclable" is used to indicate that these defects are generally absent. Qualification as recyclable material is not regulated by any particular agency but can be determined by specific groups such as the Association for Plastic Recycling (APR) and How2Recycle. TM The recyclable membrane disclosed herein is applicable to high-density polyethylene-based recycling streams. Introducing the recyclable membrane into any of these recycling pathways via reprocessing should not require additional compatibilizers.

[0057] Suitable recyclability can be obtained by keeping the total amount of high density polyethylene in the total composition of the thermoformable base film at a high level. Any additives used should be kept at a minimum amount. Any non-polyethylene based polymers present can be accompanied by a compatibilizer to obtain a composition suitable for recycling.

[0058] To further strive for a total composition suitable for recycling, some embodiments of the thermoformable base film do not contain a polyester material. Polyester materials are typically used in films due to ease of thermoforming, stiffness, and clarity. However, the presence of polyester can greatly hinder the recyclability of the film.

[0059] To further strive for a total composition suitable for recycling, some embodiments of the thermoformable base film do not contain an EVOH material. EVOH is typically used in films because it is a thermoformable oxygen barrier material. However, the presence of EVOH can greatly hinder the recyclability of the film.

[0060] To further strive for a total composition suitable for recycling, some embodiments of the thermoformable base film do not contain a polyamide material. Polyamide materials are typically used due to ease of thermoforming, durability, and stiffness. However, the presence of polyamide can greatly hinder the recyclability of the film.

[0061] The thermoformable base film can not contain a polyester, EVOH, and polyamide.

[0062] It has been found that the thermoformable base film having at least a first layer, a second layer, and a third layer as described herein can be used to produce a thermoformed substrate packaging assembly with superior results. This is surprising because the thermoformable base film contains a high amount of high density polyethylene which has previously been shown to not have an acceptable combination of properties for high performance thermoformed packaging applications. The thermoformable base film described herein produces a key and previously unachieved combination of 1) ease of thermoforming, 2) high moisture barrier, and 3) recyclability.

[0063] Most surprising is the thermoforming characteristics of the thermoformable base film described herein. Thermoforming is a process by which a film is heated to a minimum temperature above which the polymers soften to the point that they can be physically shaped into a desired shape and below a maximum temperature at which the film melts and cannot be web handled. It is well known that high density polyethylene materials have a very narrow temperature window (difference between the minimum and maximum processing temperatures). The thermoformable base film comprising a second layer using a hydrocarbon resin as described herein can increase the thermoforming temperature window by up to 100% or even 200% compared to a film without a hydrocarbon resin in the second layer. Due to the wider range of forming temperatures, even a small amount of hydrocarbon resin (i.e. 2.5%) in the second layer of the thermoformable film can have a significant impact on how easily the film can be thermoformed.

[0064] Surprisingly, the thermoformable base films described herein, while having a high level of high density polyethylene, maintain the shape taken during the thermoforming process. In other words, the thermoformed substrates produced from the thermoformable base films can be thermoformed without experiencing post-thermoforming warping or curling. In addition, any shrinkage that can occur after thermoforming is also greatly reduced or eliminated. This result is in contrast to previously thermoformed high density polyethylene films.

[0065] The thermoformable base films advantageously have excellent moisture barrier. The moisture barrier properties depend on the layer composition. One way to increase the moisture barrier is to increase the amount of hydrocarbon resin or nucleating agent in the second layer. Another way to increase the moisture barrier is to use bimodal high density polyethylene. The moisture barrier performance of the thermoformable base films is important because it allows this material to replace other standard formed films, such as PVC, which are not easily recyclable, for packaging moisture sensitive products.

[0066] Packaging products

[0067] The thermoformable base films can be formed into packaging assemblies (thermoformed substrates) and used in combination with other packaging assemblies (such as a lid) to produce a package. The thermoformed substrates can be produced from the thermoformable base films by a thermoforming process using heat and pressure (mechanical and / or vacuum). The thermoformed substrates can be highly rigid and non-flexible, or the thermoformed substrates can be flexible while still maintaining the thermoformed shape. The thermoformed substrates described herein have at least one cavity that houses a product and a flange that surrounds each of these cavities. The flange is typically an unformed area of the film and acts as a location to connect the thermoformed substrate to other packaging assemblies, which can be a lid, another thermoformed substrate assembly, or some other packaging assembly.

[0068] Figures 5-7 Examples of thermoformed substrates are shown in FIGS. 12-14. In these embodiments, the thermoformed substrate 100 has a plurality (10 or 12) of small cavities 110 surrounded by a flange 120. The cavities, such as these, can be specifically designed to hold a single pharmaceutical tablet or capsule. Alternatively, the cavities of the thermoformed substrate can be large and hold multiple product tablets. All numbers, sizes, and shapes of cavities are contemplated by this application.

[0069] As Figure 7As shown in the packaged product embodiment of FIG. 1 1 10, each cavity 1 10 present is surrounded by a flange 120. The flange 120 of the thermoformed substrate 100 should be a region free of bends for attachment to another packaging component, such as a lid packaging component 200. Product 1 100 is present, encapsulated in each of the cavities. In this embodiment, the lid component is hermetically sealed to the flange in a region surrounding each of the cavities of the thermoformed substrate. Alternatively, the lid can be attached to the thermoformed substrate at the flange in a region that includes the entire perimeter surrounding all of the cavities, rather than between each of the cavities.

[0070] The thermoformed substrate can be attached to another packaging component by a seal, preferably a hermetic seal. In this way, the product within the package is fully encapsulated in the cavities and protected by the thermoformed substrate and one or more other packaging components. Exchange of gases, liquids, microorganisms, or other materials is limited to those capable of passing through the packaging components, as the hermetic seal does not allow passage in the space between the components.

[0071] The product contained in the cavities of the thermoformed substrate is not limited. The product can be environmentally sensitive, such as a pharmaceutical or food product. The product can require physical protection, such as a delicate medical device. To protect the consumer, the product can require packaging, such as a pharmaceutical or cleaning agent, should employ a child-resistant package. The product can be suitable for easy dispensing, such as a piece of gum or candy.

[0072] If a lid packaging component is included in the packaged product, the lid can have any composition suitable for the application. The lid should have a heat sealable outer layer formulated such that it can be easily attached to the thermoformed substrate by heat sealing. The seal between the lid packaging component and the thermoformed substrate can be peelable (i.e., easily manually separated, peel strength less than about 2,500 g / in) or fused.

[0073] If the lid is fused to the thermoformed substrate, the lid can be formulated and / or designed such that the product can be pushed through the lid for dispensing. Particularly for applications including a packaged product of pharmaceutical tablets, pieces of gum, etc., the cavities of the thermoformed substrate can be flexible enough that a consumer can manually depress the cavity, forcing the product through the lid component for dispensing.

[0074] The lid packaging component should have a moisture and / or oxygen barrier similar to that of the thermoformed substrate. Materials commonly used for high performance lids include, but are not limited to, metal or paper layers. The metal and / or paper layers can be laminated or otherwise connected to a polymer layer, including a heat sealable layer. The lid can be printed, scored, or otherwise modified for specific properties.

[0075] One example of a lid component that can be sealed to a thermoformed substrate to provide a packaged product is shown in FIG. 1 1 10. Figure 8The lid can have a first outer layer 210 that includes high density polyethylene and inorganic particles such as talc or calcium carbonate. This type of outer layer provides high heat resistance during the process of sealing the lid assembly to the thermoformed base assembly to enclose the product. The lid can have a second outer layer 220 that includes a polyethylene based material formulated to heat seal to the thermoformed base at relatively low temperatures. An example of a material blend that works well with a moisture barrier layer is high density polyethylene, hydrocarbon resin, and nucleating agent. This blend is similar to the second layer of the thermoformable base assembly. As Figure 8 One advantage of the lid shown is that it has similar recyclability as compared to the thermoformable base film described herein, such that the entire package can be recycled together without separation.

[0076] Examples and Data

[0077] Improvements in the Temperature Window for Thermoforming

[0078] The structures discussed herein have a distinct advantage in the ease of thermoforming as compared to previously known high density polyethylene based films. The base packaging assemblies formed from the disclosed base packaging films disclosed herein retain the shape in which they are formed without warping due to crystallization of the polymer. The thermoformed part retains the same dimensions and shape for minutes, hours, days, and weeks after thermoforming. In addition, the thermoforming of the material is easier because the operating window (i.e., temperature) for forming is wider.

[0079] Generally, the best performance of a thermoforming process occurs when the film is heated to a temperature between the softening temperature and the melting temperature of the polymer. In the case of high density polyethylene, this temperature window for thermoforming is typically very small - a few degrees. This makes the thermoforming process of standard high density polyethylene films very difficult to control. It has been found that the base packaging films described herein have a much wider operating window for thermoforming temperatures, enabling softening at lower temperatures and without exhibiting sagging.

[0080] In addition, it is known that high density polyethylene based films exhibit secondary crystallization, resulting in significant part shrinkage and warping over a period of minutes, hours, or days after thermoforming. The thermoformable base packaging films described herein do not exhibit this secondary crystallization phenomenon, thus allowing the use of these materials in the thermoforming of critical parts such as packaging blisters.

[0081] The thermoformable base film Example 1, Example 2, and Comparative Example 1 were manufactured using a standard blown film co-extrusion process, collapsing the bubble into a single, palindromic film. The details of these films are shown in Table 1, and the structures are shown in Figure 2Example 1 includes a first layer having high density polyethylene and a nucleating agent, a second layer including high density polyethylene, a hydrocarbon resin, and a nucleating agent, and a third layer including high density polyethylene and a nucleating agent. The second layer is divided into two layers, separated by a center layer including an ethylene vinyl acetate copolymer, due to the collapsed bubble process used to make the film. In addition, the first and third layers must have the same composition. Example 2 and Comparative Example 1 are processed similarly. The second layer of Comparative Example 1 contains no hydrocarbon resin, the second layer of Example 1 includes about 7.5% by weight of hydrocarbon resin (18.75% loading of a 40% masterbatch), and the second layer of Example 2 includes about 15% by weight of hydrocarbon resin (37.5% loading of a 40% masterbatch).

[0082] The thermoformable base films Example 1, Example 2, and Comparative Example 1 were run on a Uhlmann Blister machine B1240 as a forming web. The Uhlmann was used to thermoform ten cavities in the thermoformable base film (as shown in Figure 5 The tooling used produced cavities sized to fit a zero (0) capsule. The material was cycled through the thermoforming process at a rate of 35 cycles / minute. Prior to forming, the Uhlmann used top and bottom contact heating in three indices.

[0083] To evaluate the temperature window for forming proper cavities, the contact heating temperature was slowly increased and the formed pouches were evaluated at each temperature. It was found that the minimum heating temperature required to achieve a fully formed pouch for Comparative Example 1 was 112°C. The tester considered a cavity to be fully formed when there was evidence of a vacuum port on the surface of the cavity. For Comparative Example 1, a maximum heating temperature of 115°C was determined when the material began to melt, deform, and was aesthetically poor. Thus, this material had a temperature window of about 3°C for thermoforming good cavities.

[0084] The thermoformable base of Example 1 was tested in the same manner as Comparative Example 1. The minimum temperature was found to be 109°C and the maximum temperature was 115°C. This was a temperature operating window of 6°C, a 100% improvement over the thermoformable base of Comparative Example 1. The thermoformable base of Example 2 was tested in the same manner as Comparative Example 1. The minimum temperature was found to be 106°C and the maximum temperature was 115°C. This was a temperature operating window of 9°C, a 200% improvement over the thermoformable base of Comparative Example 1.

[0085] Table 1: Details of thermoformable base films

[0086]

[0087]

[0088] HDPE1 = high density polyethylene, melt index = 2.0 g / 10 min (190C, 2160 g), density = 0.96 g / cc

[0089] HDPE3 = high density polyethylene, melt index = 1.2 g / 10 min (190C, 2160 g), density = 0.967 g / cc

[0090] HC MB = hydrocarbon masterbatch containing 40% hydrocarbon and 60% high density polyethylene

[0091] Nuc MB = nucleator masterbatch containing 4% nucleator in low density polyethylene

[0092] EVA1 = ethylene vinyl acetate copolymer, vinyl acetate content = 12%, density 0.93 g / cc

[0093] EVA2 = ethylene vinyl acetate copolymer, vinyl acetate content = 26%, density 0.95 g / cc

[0094] 2 MVTR test conditions: ASTM 1249, conditions of 100°F and 90% Rh

[0095] High oxygen barrier version

[0096] Thermoformable base film example 3 was manufactured using a standard blown film co-extrusion process, collapsing the bubble into a single, palindromic film. The details of these films are shown in Table 2, and the structure is shown in Figure 3 Example 3 contains a first layer having high density polyethylene and nucleator, a second layer containing high density polyethylene, hydrocarbon resin, and nucleator, a third layer containing high density polyethylene and nucleator, and an oxygen barrier layer containing EVOH and tie layers. The second layer is divided into four different layers, separated by other layers. The oxygen barrier layer is divided into two different layers, separated by other layers. The first and third layers have the same composition.

[0097] Table 2: Details of thermoformable base films

[0098]

[0099]

[0100] HDPE1 = high density polyethylene, melt index = 2.0 g / 10 min (190C, 2160 g), density = 0.96 g / cc

[0101] HDPE3 = high density polyethylene, melt index = 1.2 g / 10 min (190C, 2160 g), density = 0.967 g / cc

[0102] HC MB = Hydrocarbon masterbatch containing 40% hydrocarbon and 60% high density polyethylene

[0103] Nuc MB = Nucleating agent masterbatch containing 4% nucleating agent in low density polyethylene

[0104] EVA1 = Ethylene vinyl acetate copolymer, vinyl acetate content = 12%, density 0.93 g / cc

[0105] EVA2 = Ethylene vinyl acetate copolymer, vinyl acetate content = 26%, density 0.95 g / cc

[0106] MAg PE = Maleic anhydride grafted polyethylene

[0107] EVOH = Ethylene vinyl alcohol copolymer, 38 mol% ethylene

[0108] 1 OTR test conditions: ASTM F1927, conditions of 73 °F and 0% Rh

[0109] Weight gain study

[0110] The weight gain study was performed according to Method B of ASTM D7709-12, which compares the weight gain of each cavity of a package including thermoformed substrates according to the present disclosure as well as other blister packaging industry standard materials. The blister card contained ten cavities formed as zero blister. A test unit of five blister cards was used to calculate the weight gain. The blisters were filled with desiccant (previously stored in vacuum packaged foil packets) and sealed on the Uhlman B1240 packaging equipment described above. The storage conditions used were 40 °C and 75% RH.

[0111] The weight gain study included thermoformed substrates from two different heat formable base films. The first was Example 2 described in Table 1 above. The second was Example 4 further described in Table 3, which was a 10 mil white heat formable base film.

[0112] Table 3: Details of heat formable base films

[0113]

[0114]

[0115] HDPE1 = High density polyethylene, melt index = 2.0 g / 10 min (190 C, 2160 g), density = 0.96 g / cc

[0116] HDPE3 = High density polyethylene, melt index = 1.2 g / 10 min (190 C, 2160 g), density = 0.967 g / cc

[0117] HC MB = hydrocarbon masterbatch comprising 40% hydrocarbon and 60% high density polyethylene

[0118] Nuc MB = nucleating agent masterbatch comprising 4% nucleating agent in low density polyethylene

[0119] CaC03MB = calcium carbonate masterbatch comprising polyethylene, inorganic content greater than 30%

[0120] White MB = white masterbatch comprising polyethylene and titanium dioxide

[0121] EVA1 = ethylene vinyl acetate copolymer, vinyl acetate content = 12%, density 0.93 g / cc

[0122] EVA2 = ethylene vinyl acetate copolymer, vinyl acetate content = 26%, density 0.95 g / cc

[0123] Two thermoformed substrates formed into a blister were filled with desiccant and sealed with Lid A. Lid A had a heat resistant outer layer with high density polyethylene and inorganic particles (calcium carbonate), an inner layer with high density polyethylene and nucleating agent, and a heat seal outer layer comprising a polyethylene based plastomer.

[0124] Results of the weight gain study can be found in Figure 9 Example 2 substrate and Lid A combination resulted in a single cavity transmission of about 0.34 mg / cavity.day. Example 4 substrate and Lid A combination resulted in a single cavity transmission of about 0.45 mg / cavity.day. For comparison, a similar test run using a thermoformed film of 10 mil PVC / 90 gsm PVDC / 1 mil PE and a 1 mil soft temper foil lid resulted in a transmission rate of about 0.54 mg / cavity.day, and a thermoformed film of 7.5 mil PVC / 2 mil Aclar and a 1 mil soft temper foil lid resulted in a transmission rate of about 0.16 mg / cavity.day. The thermoformed substrates described herein result in moisture transmission rates suitable for pharmaceutical packaging while achieving single stream recyclability.

[0125] Improvements in cutting

[0126] The cut performance of the thermoformable base film can also be evaluated while producing the package on the Uhlman B1240 packaging equipment. After the package is sealed, the blister card is cut from the web. It is observed that the thermoformable film of Example 4 cuts much cleaner without abrading the edges of the blister card compared to other thermoformable base films that do not contain a layer with inorganic particles (calcium carbonate).

[0127] Examples

[0128] Examples of thermoformable base films:

[0129] A. A thermoformable base film, comprising:

[0130] a first layer comprising high density polyethylene and a nucleating agent,

[0131] a second layer comprising high density polyethylene, and

[0132] a third layer comprising high density polyethylene and a nucleating agent,

[0133] wherein the second layer is positioned between the first layer and the third layer, and wherein after thermoforming, the thermoformable base film retains the shape taken during thermoforming.

[0134] B. The thermoformable base film of any other embodiment, further comprising a fourth layer comprising high density polyethylene and inorganic particles, wherein the inorganic particles are present in the fourth layer at a level of at least 10% by weight, and wherein the fourth layer is between the first layer and the third layer.

[0135] C. The thermoformable base film of embodiment B, wherein the inorganic particles are calcium carbonate.

[0136] D. The thermoformable base film of any other embodiment, wherein the first layer further comprises metallocene linear low density polyethylene.

[0137] E. The thermoformable base film of any other embodiment, wherein the first layer and the third layer each form a surface of the thermoformable base film.

[0138] F. The thermoformable base film of any other embodiment, further comprising an oxygen barrier layer comprising an ethylene vinyl alcohol copolymer, wherein the oxygen barrier layer is positioned between the first layer and the third layer.

[0139] G. The thermoformable base film of any other embodiment, further comprising a center layer comprising an ethylene vinyl acetate copolymer, and wherein the thermoformable base film is palindromic.

[0140] H. The thermoformable base film of embodiments A-G or I, wherein the second layer further comprises a hydrocarbon resin.

[0141] I. The thermoformable base film of any other embodiment, wherein the second layer further comprises a nucleating agent.

[0142] J. A thermoformable base film, comprising:

[0143] a first layer comprising high density polyethylene and a nucleating agent,

[0144] a second layer comprising from 60% to 90% by weight of high density polyethylene and from 2.5% to 30% by weight of a hydrocarbon resin, and

[0145] a third layer comprising high density polyethylene and a nucleating agent,

[0146] wherein the second layer is positioned between the first layer and the third layer,

[0147] wherein the second layer has a thickness of from 25% to 90% of the total thickness of the heat formable base film, wherein the high density polyethylene is present in the first layer at a level of at least 90% by weight relative to the first layer, and wherein the high density polyethylene is present in the third layer at a level of at least 90% by weight relative to the third layer.

[0148] K. The heat formable base film according to any other embodiment, wherein the heat formable base film has a total composition suitable for recycling.

[0149] L. The heat formable base film according to any other embodiment, wherein the heat formable base film is substantially free of polyester, ethylene vinyl alcohol copolymer, and polyamide.

[0150] Heat formed base embodiments:

[0151] M. A heat formed base comprising:

[0152] a heat formable base film according to any embodiment A-L,

[0153] at least one cavity, and

[0154] a flange surrounding each of the cavities.

[0155] N. The heat formed base according to embodiment M, wherein the heat formed base retains a shape taken during a heat forming process.

[0156] Packaged product embodiments:

[0157] O. A packaged product comprising:

[0158] a heat formed base according to embodiment M or N,

[0159] a lid packaging assembly, and

[0160] a product,

[0161] wherein the lid packaging assembly is hermetically sealed to the flange of the heat formed base and the product is enclosed in the at least one cavity of the heat formed base.

[0162] P. The packaged product of embodiment O, wherein the lidding packaging assembly comprises a heat seal layer and a layer comprising at least one of metal or paper.

[0163] Q. The packaged product of any other embodiment, wherein the lidding packaging assembly is peelably sealed to the flange of the thermoformed base.

[0164] R. The packaged product of embodiments O, Q, S, or T, wherein both the thermoformed base and the lidding packaging assembly are recyclable in the same recycling process.

[0165] S. The packaged product of any other embodiment, wherein at least one cavity of the thermoformed base can be manually depressed and the product can be pushed through the lidding packaging assembly for product dispensing.

[0166] T. The packaged product of embodiments O, Q, R, or S, wherein the lidding packaging assembly comprises

[0167] a first outer layer comprising high density polyethylene and inorganic particles,

[0168] a first inner layer comprising high density polyethylene, a nucleating agent, and optionally a hydrocarbon resin, and

[0169] a second outer layer comprising a polyethylene-based material.

Claims

1. A thermoformable base film comprising: a first layer comprising high density polyethylene, a nucleating agent, and a metallocene linear low density polyethylene, a second layer comprising high density polyethylene and from 15% to 20% by weight of a hydrocarbon resin relative to the second layer, and a third layer comprising high density polyethylene and a nucleating agent, wherein the second layer is located between the first layer and the third layer, and wherein the thermoformable base film retains the shape taken during thermoforming after thermoforming; and further comprising a fourth layer comprising high density polyethylene and inorganic particles, wherein the inorganic particles are present in the fourth layer in an amount of between 10% and 30% by weight, and wherein the fourth layer is between the first layer and the third layer, and wherein the inorganic particles are calcium carbonate or talc.

2. The thermoformable base film of claim 1, wherein, The inorganic particles are calcium carbonate.

3. The thermoformable base film of claim 1, further comprising an oxygen barrier layer comprising an ethylene vinyl alcohol copolymer, wherein the oxygen barrier layer is located between the first layer and the third layer.

4. The thermoformable base film of claim 1, further comprising a center layer comprising an ethylene vinyl acetate copolymer, and wherein the thermoformable base film is palindromic.

5. The thermoformable base film of claim 1, wherein, The second layer further comprises a nucleating agent.

6. A thermoformed base comprising: the thermoformable base film of claim 1, at least one cavity, and a flange surrounding each of the cavities.

7. The thermoformed substrate of claim 6, wherein, The thermoformed base retains the shape taken during thermoforming.

8. A packaged product comprising: the thermoformed base of claim 6, a lid packaging assembly, and a product, wherein the lid packaging assembly is hermetically sealed to the flange of the thermoformed base, and the product is enclosed in at least one cavity of the thermoformed base.

9. The packaged product of claim 8, wherein, The lid packaging assembly comprises a heat seal layer and a layer comprising at least one of a metal and paper.

10. The packaged product of claim 8, wherein, The lid packaging assembly is peelably sealed to the flange of the thermoformed base.

11. The packaged product of claim 8, wherein, The thermoformed base and the lid packaging assembly are recyclable in the same recycling process.

12. The packaged product of claim 8, wherein, At least one cavity of the thermoformed base can be manually depressed, and the product can be pushed through the lid packaging assembly for product dispensing.

13. The packaged product of claim 8, wherein, The lid packaging assembly comprises: a first outer layer comprising high density polyethylene and inorganic particles, a first inner layer comprising high density polyethylene, a nucleating agent, and optionally a hydrocarbon resin, and a second outer layer comprising a polyethylene-based material. The inorganic particles are calcium carbonate.

3. The thermoformable base film of claim 1, further comprising an oxygen barrier layer comprising an ethylene vinyl alcohol copolymer, wherein the oxygen barrier layer is located between the first layer and the third layer.

4. The thermoformable base film of claim 1, further comprising a center layer comprising an ethylene vinyl acetate copolymer, and wherein the thermoformable base film is palindromic. The second layer further comprises a nucleating agent.

6. A thermoformed base comprising: the thermoformable base film of claim 1, at least one cavity, and a flange surrounding each of the cavities. The thermoformed base retains the shape taken during thermoforming.

8. A packaged product comprising: the thermoformed base of claim 6, a lid packaging assembly, and a product, wherein the lid packaging assembly is hermetically sealed to the flange of the thermoformed base, and the product is enclosed in at least one cavity of the thermoformed base. The lid packaging assembly comprises a heat seal layer and a layer comprising at least one of a metal and paper. The lid packaging assembly is peelably sealed to the flange of the thermoformed base. The thermoformed base and the lid packaging assembly are recyclable in the same recycling process. At least one cavity of the thermoformed base can be manually depressed, and the product can be pushed through the lid packaging assembly for product dispensing. The lid packaging assembly comprises: a first outer layer comprising high density polyethylene and inorganic particles, a first inner layer comprising high density polyethylene, a nucleating agent, and optionally a hydrocarbon resin, and a second outer layer comprising a polyethylene-based material. The inorganic particles are calcium carbonate.

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