HEAT-SHRINKABLE FILM AND RELATED SYSTEMS AND METHODS

Abstract

In various examples, the subject matter of the present disclosure relates to multilayer heat-shrinkable films having improved recyclability, low shrink initiation temperatures, and low shrink tensions. The films have shrink initiation temperatures of 60° C. or less and low shrink tensions of 9 N / mm 2 It may have the following shrink tension: The film is configured to prevent the formation of lumps during the recycling process.

Description

[Technical Field]

[0001] The following disclosure relates to heat shrinkable films, and in particular examples to heat shrinkable films for shrink-fit labeling of packaging such as food and beverage containers. [Background technology]

[0002]

[0002] Generally, heat shrinkable films are films that tend to shrink when heated or exposed to high temperatures. Heat shrinkable films are used to cover and protect items, hold items together, label items, and provide tamper-evident protection.

[0003]

[0003] To manufacture and utilize heat-shrinkable films, a polymeric material is prepared, extruded into a film, biaxially and / or uniaxially stretched, and formed into a roll. In a packaging facility, the film is unwound, printed, and seamed to form a tube that can be applied around an article such as a container. The film is then heated to a shrink initiation temperature so that it shrinks to a tight fit around the container. The container can be filled with a desired product (e.g., a beverage) and sold to a consumer.

[0004] After use, containers and labels can be subjected to a recycling process in which the containers and labels are crushed, cut, and / or shredded into flakes or particles. The particles can be washed or de-inked by subjecting them to a high-temperature washing process. The washed particles can be subjected to a drying and solidification process in which the particles are heated to remove water and crystallize and / or increase the molecular weight of the particles. The treated particles can be reused to form new containers, new heat-shrinkable films, or other products. [Summary of the Invention]

[0005]

[0006] In general, the subject matter of the present disclosure relates to heat-shrinkable films having a low shrink initiation temperature, low shrink tension, and improved recyclability. A low shrink initiation temperature is desirable because it allows for lower temperatures or less heat to be used to apply the film to a container or other article. This results in reduced thermal expansion of the container during the shrinking process and / or reduced damage to the container or its contents. A low shrink force is desirable because it reduces the likelihood that the film will crush the container, especially when the container is empty. Improved recyclability can allow the film and container to be recycled and blended to form new products. In comparison, previous heat-shrinkable films with low shrink initiation temperatures and low shrink tensions may not be recyclable because such films tend to form clumps during the drying and / or solidification stages of the recycling process. The clumps can interfere with the proper flow of material through the recycling process, as described herein.

[0006]

[0007] In one embodiment, the presently disclosed subject matter relates to a multilayer heat-shrinkable film. The film includes a first layer having a first blend of a first copolyester including a first diol component having diethylene glycol (DEG) and 1,4-cyclohexanedimethanol (CHDM), an amorphous polyethylene terephthalate (APET), and optionally a second copolyester including a second diol component having 2-dimethylpropane-1,3-diol (NPG) (and optionally DEG), a second layer including the first blend, and a core layer disposed between the first and second layers and including a second blend of a third copolyester including a third diol component having 2-methyl-1,3-propanediol (MPO) and DEG, an APET, and optionally a fourth copolyester including a fourth diol component having NPG (and optionally DEG), the multilayer heat-shrinkable film having a shrink initiation temperature of 60° C. or less and a shrink strength of 9 N / mm 2 It has the following shrinkage tension:

[0007]

[0008] In a particular example, the film has a shrinkage onset temperature of at least 50° C. The film has a shrinkage onset temperature of 6 N / mm 2 The first layer and / or second layer may have a glass transition temperature of about 70°C to about 80°C. The core layer may have a glass transition temperature of about 60°C to about 70°C. The first layer, second layer, and / or core layer may have an intrinsic viscosity of about 0.65 dL / g to about 0.85 dL / g. The core layer may occupy about 50% to about 90% of the total thickness of the film, and the first layer and second layer may each occupy about 5% to about 25% of the total thickness of the film.

[0008]

[0009] In various embodiments, the first blend may comprise about 18% to about 78% by weight of a first copolyester, about 10% to about 30% by weight of APET, and optionally up to about 90% by weight of a second copolyester. The first blend may include an antiblocking additive. The second blend may comprise about 55% to about 85% by weight of a third copolyester, about 10% to about 35% by weight of APET, and optionally up to about 10% by weight of a fourth copolyester. The second blend may include the first copolyester. The first diol component may contain about 60 mol% to about 70 mol% ethylene glycol (EG), about 5 mol% to about 15 mol% DEG, and about 20 mol% to about 30 mol% CHDM; the second diol component may contain about 65 mol% to about 75 mol% EG and about 23 mol% to about 33 mol% NPG; the third diol component may contain about 56 mol% to about 66 mol% EG, about 14 mol% to about 24 mol% MPO, and about 1 mol% to about 15 mol% DEG; and the fourth diol component may contain about 65 mol% to about 75 mol% EG and about 23 mol% to about 33 mol% NPG. The first blend may contain a second copolyester, and the second blend may contain a fourth copolyester, and the second and fourth copolyesters may be the same. The multilayer heat shrinkable film may be formulated to resist bonding to other materials when heated to a temperature of about 210°C.

[0009]

[0010] In another aspect, the presently disclosed subject matter relates to a method for producing a multilayer heat-shrinkable film, the method comprising the steps of obtaining a first blend including a first copolyester having a first diol component comprising diethylene glycol (DEG) and 1,4-cyclohexanedimethanol (CHDM), amorphous polyethylene terephthalate (APET), and, optionally, a second copolyester having a second diol component comprising 2-dimethylpropane-1,3-diol (NPG), and a third copolyester having a third diol component comprising 2-methyl-1,3-propanediol (MPO) and DEG. obtaining a second blend comprising a fourth copolyester having a fourth diol component comprising NPG, APET, and optionally, NPG; and co-extruding the first blend and the second blend to form a heat-shrinkable film comprising a first layer having the first blend, a second layer having the first blend, and a core layer having the second blend and disposed between the first layer and the second layer, wherein the multilayer heat-shrinkable film has a shrink initiation temperature of 60° C. or less and a shrink tension of 9 N / mm 2 The following is the result.

[0010]

[0011] In some examples, co-extruding the first blend and the second blend can include heating the first blend and the second blend to a temperature of about 200°C to about 300°C. Co-extruding the first blend and the second blend can include casting a heat-shrinkable film through a die onto a chill roll. The method can include stretching the heat-shrinkable film in a tenter frame to a draw ratio of about 1.5 to about 7. The heat-shrinkable film can have a glass transition temperature, and the stretching can be performed at a temperature of about the glass transition temperature to about the glass transition temperature plus 20°C.

[0011]

[0012] In another aspect, the presently disclosed subject matter relates to a method of using a multilayer heat-shrinkable film, the method comprising the steps of providing a multilayer heat-shrinkable film comprising: a first layer comprising a first blend of a first copolyester comprising a first diol component having diethylene glycol (DEG) and 1,4-cyclohexanedimethanol (CHDM), amorphous polyethylene terephthalate (APET), and optionally a second copolyester comprising a second diol component having 2-dimethylpropane-1,3-diol (NPG) (and optionally DEG); a second layer comprising the first blend; and a core layer disposed between the first and second layers and comprising a second blend of a third copolyester comprising a third diol component having 2-methyl-1,3-propanediol (MPO) and DEG, APET, and optionally a fourth copolyester comprising a fourth diol component having NPG (and optionally DEG), wherein the multilayer heat-shrinkable film has a shrink initiation temperature of 60° C. or less and a shrink strength of 9 N / mm 2 The method includes the steps of: applying a shrink tension to the multilayer heat shrinkable film, forming the multilayer heat shrinkable film into a sleeve, placing the sleeve around an object, and applying heat to the sleeve to shrink the sleeve onto the object. In a particular example, the object is or includes a container or bottle.

[0012]

[0013] In another aspect, the presently disclosed subject matter relates to a method for recycling a multilayer heat-shrinkable film, the method comprising: (i) flakes formed from polyethylene terephthalate (PET) bottles; and (ii) a shrinkage initiation temperature of 60° C. or less, 9 N / mm 2 The method includes obtaining a mixture of particles and a heat-shrinkable film having a shrink tension of:

[0013]

[0014] In various instances, the solidification step in the recycling process can increase the molecular weight of the heat-shrinkable film. The particles can meet the requirement of less than 1% weight loss during PET flake clumping evaluation, as specified in PET Flake Clumping Evaluation, document PET-S-08, published November 16, 2018, by the ASSOCIATION OF PLASTIC RECYCLERS.

[0014]

[0015] These and other objects, together with advantages and features of the embodiments of the present invention disclosed herein, will become more apparent with reference to the following description, drawings, and claims. Furthermore, it should be understood that the features of the various embodiments described herein are not mutually exclusive and can exist in various combinations and permutations.

[0015]

[0016] The foregoing summary of the invention, including a description of some embodiments, its motivation, and / or its advantages, is intended to aid the reader in understanding the present disclosure and is not intended to limit the scope of any of the claims in any way.

[0016]

[0017] In the drawings, like reference numbers generally refer to the same parts throughout the different views. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various embodiments of the invention are described with reference to the following drawings: [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic perspective view of a heat shrinkable film, in accordance with certain examples; [Figure 2] 1 is a schematic perspective view of a shrink sleeve formed from a heat-shrinkable film, in accordance with certain examples. [Figure 3] 1 is a schematic diagram of a process for manufacturing a heat shrinkable film, in accordance with certain examples. [Figure 4]FIG. 1 is a schematic diagram of a process for recycling heat shrinkable film, in accordance with certain examples. [Figure 5] 1 is a plot of shrink tension versus temperature for a heat shrinkable film, in accordance with certain examples. DETAILED DESCRIPTION OF THE INVENTION

[0018]

[0023] The claimed devices, compositions, systems, and methods of the present invention are intended to encompass variations and adaptations developed using information from the embodiments described herein. Adaptations and / or modifications of the devices, compositions, systems, and methods described herein may be made by one skilled in the art.

[0019]

[0024] It should be understood that the order of steps or order for performing certain actions is immaterial so long as the invention remains operable. Moreover, two or more steps or actions may be conducted simultaneously.

[0020]

[0025] In various examples, "shrink tension" (alternatively referred to as "shrink force") is the tension, force, or stress (e.g., force per area) exerted by the heat-shrinkable film during the shrinking step. While high-shrink tension films may be suitable for rigid articles, lower shrink tensions may be desirable for flexible, easily deformed, and / or empty articles. Furthermore, printed low-shrink tension films have been observed to exhibit improved shrink performance (e.g., lower risk of discoloration, color concentration, distortion of printed images, and label defects). Shrink tension may be measured using ASTM D2838, DIN 53369:1076-02, or similar techniques. In one example, shrink tension may be the maximum tension exerted by the heat-shrinkable film over a temperature range.

[0021]

[0026] In various examples, the "shrinkage initiation temperature" is the temperature at which the heat-shrinkable film begins to shrink. A lower shrinkage initiation temperature may be desirable to minimize deformation or damage to the article in which the film is used. For plastic articles such as polyethylene terephthalate (PET) bottles, the shrinkage initiation temperature of the heat-shrinkable film is preferably substantially lower than the glass transition temperature of the article to avoid or minimize any deformation of the article. Furthermore, the shrinkage initiation temperature of the film is preferably low enough so as not to damage or destroy any contents in the article. The shrinkage initiation temperature may be measured using ASTM-D-2732 or a similar technique.

[0022]

[0027] In certain instances, "intrinsic viscosity" (IV) is a property of the polymer that makes up the shrink film. IV can depend on the average molecular weight of the polymer, for example, a higher molecular weight results in a higher IV. In some cases, a lower IV can be associated with a lower shrink tension. IV can be measured using ASTM D4603-03 or a similar technique.

[0023]

[0028] In various instances, the "glass transition temperature" (Tg) is the temperature at which an amorphous polymer transitions from a glassy state to a rubbery state. The Tg value can affect many physical properties of a polymer; in particular, a decrease in the glass transition temperature can result in a decrease in the shrinkage onset temperature. However, in some cases, if the Tg is too low, the film may become tacky or adhesive, making it unsuitable for packaging purposes. The glass transition temperature can be determined using thermomechanical analysis (TMA), dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), or similar techniques.

[0024]

[0029] Generally, heat-shrinkable films are films that tend to shrink when exposed to heat or elevated temperatures (e.g., above a shrinkage initiation temperature). Heat-shrinkable films can be used to form labels for various containers, such as bottles, cap seals, or bundle packaging. For example, ink can be printed on the heat-shrinkable film to produce images and / or text. The printed heat-shrinkable film can be formed into a tubular sleeve and placed over the container. When heat is applied, the sleeve can shrink to achieve a snug fit over the container. The container can be filled with a desired product (e.g., a beverage) and sold to a consumer. Heat-shrinkable films and related manufacturing methods are described in International Publication No. WO 2022 / 072477, published April 7, 2022, the entire disclosure of which is incorporated herein by reference.

[0025]

[0030] After use, the containers and labels may be subjected to a recycling process in which the containers and labels are crushed, cut, and / or shredded into flakes or particles. The particles can be washed or de-inked by subjecting them to a high-temperature washing process. The washed particles may be subjected to a drying and / or solidification process in which the particles are heated to remove water and render the particles crystallizable and / or increase their molecular weight. However, in some instances, the high temperatures of the drying and / or solidification process can make the particles sticky, which can cause the particles to form clumps. The clumps can block filters or screens and / or form bridges that prevent the proper flow of material in the recycling process.

[0026]

[0031] A wide variety of polymeric materials can be used to make heat-shrinkable films. For example, polyvinyl chloride (PVC) and polystyrene (PS), especially oriented polystyrene (OPS), are commonly used to manufacture heat-shrinkable films. PVC and OPS can provide low shrinkage initiation temperatures and low shrinkage tensions; however, PVC and OPS films are generally not easily recyclable. For example, PVC and OPS films are often used with containers made from different materials, and proper recycling may require the various material types to be separated.

[0027]

[0032] Polyethylene terephthalate (PET) is commonly used in the food and beverage packaging industry to manufacture containers and heat-shrinkable films. Amorphous polyethylene terephthalate (APET) is favored for its versatility, transparency, and recyclability and is frequently used to manufacture food and beverage containers (e.g., including food trays, bowls, cups, and bottles). However, to be suitable for shrink film applications, APET's tendency to crystallize may need to be reduced. Glycol-modified PET (commonly referred to as copolyester, "PET-G" or "PETG") can have a suitably low degree of crystallinity. However, films made from PETG can become sticky during the recycling process, particularly at low shrink initiation temperatures and shrink tensions, as described herein. This can make such films difficult or impossible to recycle.

[0028]

[0033] Advantageously, compared to previous films having low shrink initiation temperatures and low shrink tensions, the heat-shrinkable films described herein are less prone to becoming sticky and / or forming lumps during the recycling process. For example, the films can be mixed with similar materials (e.g., PET bottle flakes) and, unlike previous films, can be subjected to solidification and other recycling steps without forming lumps that could form blockages or otherwise impede the proper flow of the material.

[0029]

[0034] FIG. 1 is a schematic perspective view of a heat-shrinkable film 10 according to a particular example. The heat-shrinkable film 10 includes a top layer 12, a bottom layer 14, and a core layer 16 disposed between (e.g., bonded to) the top layer 12 and the bottom layer 14. In various examples, the top layer 12, the bottom layer 14, and the core layer 16 each include or are composed of a polyester, such as PET, APET, one or more copolyesters (also called copolyesters or PETGs), or a combination thereof. The polyesters and copolyesters each can have a diol component and a dicarboxylic acid component and can be formed by transesterifying the diol component with a dicarboxylic acid (DA) component, followed by polymerization. The diol component of certain polyesters (e.g., APET) can be or include ethylene glycol (EG).

[0030]

[0035] The diol component in the copolyester can be composed of or can include, for example, ethylene glycol (EG), diethylene glycol (DEG), neopentyl glycol (NPG, e.g., 2-dimethylpropane-1,3-diol), cyclohexanedimethanol (CHDM, e.g., 1,4-cyclohexanedimethanol), methylpropanediol (MPO or MPDIOL, e.g., 2-methyl-1,3-propanediol), or any combination thereof. Alternatively or additionally, in some examples, the diol component may be composed of or include 1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,3-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-diethyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,1-dimethyl-1,5-pentanediol, 1,2-octanediol, 1,3-octanediol, or any combination thereof. In some examples, including NPG in the diol component can result in higher shrink force, desirable shrink characteristics, and / or good anti-clumping performance (e.g., acceptable performance in the clumping performance test described herein). NPG may be less expensive than other types of diol components. Inclusion of CHDM and / or DEG in the diol component can result in lower shrink force and desirable shrink properties; however, including too much CHDM and / or DEG can result in inadequate or insufficient anti-clumping performance. Inclusion of EG in the diol component (e.g., in APET) can result in good anti-clumping performance, but high amounts can result in relatively poor shrink properties. In various examples, it may be desirable for the film to have a higher shrink rate in the cross direction compared to the machine direction.

[0031]

[0036] The dicarboxylic acid (DA) component in the polyesters or copolyesters can be composed of or include, for example, terephthalic acid (TA), dimethyl terephthalic acid, isophthalic acid (IPA), naphthalenedicarboxylic acid, orthophthalic acid, aromatic dicarboxylic acids, adipic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, aliphatic dicarboxylic acids, cycloaliphatic dicarboxylic acids, esters thereof, or any combination thereof. In one example, the dicarboxylic acid component in the polyesters and copolyesters is terephthalic acid (TA) or an ester thereof.

[0032]

[0037] In various examples, the top layer 12 and / or the bottom layer 14 can include a blend of a first copolyester, a second copolyester, and APET. The diol component in the first copolyester can be or include, for example, a combination of EG, DEG, and CHDM. The diol component in the second copolyester can be or include, for example, a combination of EG, DEG, and NPG. The diol component in APET can be or include EG. The dicarboxylic acid component in the first copolyester, the second copolyester, and APET can be or include terephthalic acid and / or isophthalic acid. In some examples, the top layer 12 and / or the bottom layer 14 can further include one or more additives, such as an antiblocking agent. The antiblocking agent can include, for example, inorganic particles (e.g., SiO2 particles) dispersed in the PET and / or PETG matrix. The antiblocking agent can prevent film 10 from sticking to itself, for example, when stacked in sheets or rolls. Top layer 12 and bottom layer 14 can include the same ingredients and / or have the same composition. In various examples, at least a portion of the APET can include or be replaced with recycled APET and / or recycled PET (RPET) material, such as PET bottle flakes.

[0033]

[0038] Table 1 includes minimum, maximum, and representative values ​​for the amounts of first copolyester, second copolyester, APET, and antiblocking agent present in top layer 12 and / or bottom layer 15, according to specific examples. Each listed value can be a minimum, maximum, or average value (e.g., within a range of values). Various embodiments include any parameter value (e.g., integer or decimal value) within the stated range. For example, the amount of first copolyester in top layer 12 and / or bottom layer 14 can be greater than, less than, or equal to 18, 19, ..., or 78 percent by weight (wt%). Explicit support and written explanations of these values ​​for each parameter are provided herein.

[0034] [Table 1]

[0035]

[0039] Table 1. Composition of top layer 12 and / or bottom layer 14.

[0040] Table 2 includes minimum, maximum, and representative values ​​for the composition of the first copolyester, second copolyester, and APET present in the top layer 12 and / or bottom layer 14, according to specific examples. Each listed value is a mole percent of the total moles of diol components or a mole percent of the total moles of dicarboxylic acid (DA) components. Each listed value can be a minimum, maximum, or average value (e.g., within a range of values). Various embodiments include any parameter value (e.g., integer or decimal value) within the stated range. For example, the amount of ethylene glycol (EG) in the first copolyester can be greater than, less than, or equal to 60, 61, ..., or 70 (% of the total moles of diol components). Explicit support and written explanations of these values ​​for each parameter are provided herein.

[0036] [Table 2]

[0037]

[0041] Table 2. Composition of the components of the top layer 12 and / or bottom layer 14.

[0042] In various examples, the core layer 16 may include a blend of a third copolyester, a fourth copolyester, and APET. The diol component in the third copolyester may be or include, for example, a combination of EG, MPO, DEG, and NPG. The diol component in the fourth copolyester may be or include, for example, a combination of EG, DEG, and NPG. The dicarboxylic acid component in the third copolyester and the fourth copolyester may be or include terephthalic acid (TA) and / or isophthalic acid (IPA). In various examples, the fourth copolyester and the second copolyester may be the same. At least a portion of the APET may include or be replaced with recycled APET and / or recycled PET material, such as PET bottle flakes.

[0038]

[0043] Table 3 includes minimum, maximum, and representative values ​​for the amounts of third copolyester, second copolyester, and APET present in core layer 16, according to specific examples. Each listed value can be a minimum, maximum, or average value (e.g., within a range of values). Various embodiments include any parameter value (e.g., integer or decimal value) within the stated range. For example, the amount of third copolyester in core layer 16 can be greater than, less than, or equal to 55, 66, ..., or 85 percent by weight (wt%). Explicit support and written explanations of these values ​​for each parameter are provided herein.

[0039] [Table 3]

[0040]

[0044] Table 3. Composition of core layer 16.

[0045] In some examples, the first copolyester can replace at least a portion of the fourth copolyester in core layer 16. For example, core layer 16 can include the first copolyester in an amount of about 0% to about 10%, or about 5%, by weight.

[0041]

[0046] Table 4 includes minimum, maximum, and representative values ​​for the compositions of the third copolyester, fourth copolyester, and APET present in the core layer 16, according to specific examples. Each listed value is a mole percent of the total moles of diol components or a mole percent of the total moles of dicarboxylic acid (DA) components. Each listed value can be a minimum, maximum, or average value (e.g., within a range of values). Various embodiments include any parameter value (e.g., integer or decimal value) within the stated range. For example, the amount of ethylene glycol (EG) in the third copolyester can be greater than, less than, or equal to 56, 57, ..., or 66 (% of the total moles of diol components). Explicit support and written explanations of these values ​​for each parameter are provided herein.

[0042] [Table 4]

[0043]

[0047] Table 4. Composition of components in the core layer 16.

[0048] While Tables 1 and 3 above indicate that top layer 12, bottom layer 14, and core layer 16 can be formed from or include a blend of polymers (e.g., a blend of a copolyester and APET), in other examples, any of these layers can be formed from a single type of polymer (e.g., a single copolyester). For example, the blend of a first copolyester, a second copolyester, and APET in top layer 12 and / or bottom layer 14 can be replaced with a single copolyester having a similar or equivalent composition to the blend (e.g., similar or equivalent mole percentages of the diol and dicarboxylic acid components). Considering the representative values ​​in Tables 1 and 2, for example, the diol component of the single copolyester can include about 75 mol% EG, about 0 mol% MPO, about 5 mol% DEG, about 7 mol% NPG, and about 12 mol% CHDM. The properties (eg, shrink onset temperature, shrink tension, glass transition temperature, melting point temperature, intrinsic viscosity, clumping ability, etc.) of a single copolyester can be similar or identical to those of the blend.

[0044]

[0049] Additionally or alternatively, the blend of the third copolyester, the fourth copolyester, and APET in the core layer 16 can be replaced with a single copolyester having a similar or equivalent composition to the blend (e.g., similar or equivalent mole percentages of the diol and dicarboxylic acid components). Considering the representative values ​​in Tables 3 and 4, for example, the diol component of the single copolyester can include about 71 mol% EG, about 13 mol% MPO, about 7 mol% DEG, about 8 mol% NPG, and about 0 mol% CHDM. The properties of the single copolyester (e.g., shrink onset temperature, shrink tension, glass transition temperature, melting point temperature, intrinsic viscosity, clumping ability, etc.) can be similar or identical to those of the blend.

[0045]

[0050] Referring again to FIG. 1 , the heat-shrinkable film 10 can have a thickness T, a length L, and a width W. The thickness T can be, for example, about 15 microns to about 100 microns, or about 40 microns. In various examples, the core layer 16 can account for about 50% to about 90%, or about 80% of the total thickness T. The top layer 12 and the bottom layer 14 can account for the remainder of the total thickness T and / or have equal thicknesses. For example, the top layer 12 and the bottom layer 14 can each account for about 5% to about 25%, or about 10% of the total thickness T. The length L and width W can vary depending on the manufacturing process, packaging process, and / or application of the film 10. For example, a web of heat-shrinkable film 10 in a manufacturing process can have a width W of up to about 20 m, and the web can be slit into narrower ribbons having widths W as small as about 0.01 m. Alternatively, as described herein, for particles of heat shrinkable film 10 in a recycling process, the length L and / or width W (or diameter in the case of circular particles) can be from about 1 mm to about 50 mm, or from about 3 mm to about 15 mm.

[0046]

[0051] In various examples, one or more layers or materials may be disposed on the top layer 12 or bottom layer, between the top layer 12 and core layer 16, or between the bottom layer 14 and core layer 16. The film 10 may be coated with, for example, paint, primer, or ink (e.g., a printed image or text). The top layer 12 and / or bottom layer 14 may serve as a contact medium printed with a washable primer and / or washable ink that can be removed during the recycling process as described herein. The top layer 12 and bottom layer 14 may be formulated to avoid agglomerating with the PET flakes when exposed to high temperatures in the recycling process. The core layer 16 may provide desirable shrinkage properties, such as low shrinkage force and low shrinkage onset temperature.

[0047]

[0052] Table 5 includes minimum, maximum, and representative values ​​for properties of film 10, top and bottom layers 12 and 14, and core layer 16, according to specific examples. The properties of top and bottom layers 12 and 14 can be the same or different in these examples. Each listed value can be a minimum, maximum, or average value (e.g., within a range of values). Various embodiments include any parameter value (e.g., integer or decimal value) within the stated range. For example, the shrink onset temperature of film 10 can be greater than, less than, or equal to 50, 51, ..., or 60°C. Explicit support and written explanations of these values ​​for each parameter are provided herein.

[0048] [Table 5]

[0049]

[0053] Table 5. Properties of film 10, top layer 12 and bottom layer 14, and core layer 16.

[0054] The heat shrinkable film 10 can have any shape and need not be flat and rectangular, as shown in Figure 1. For example, with reference to Figure 2, the heat shrinkable film 10 can be formed (e.g., by creating a seam using a solvent) into a shrink sleeve 20 having a tubular shape. The shrink sleeve 20 can be placed over a bottle (or other container) and, upon application of heat (e.g., using steam, hot air, microwave energy, or infrared radiation), can shrink to fit snugly around the bottle.

[0050]

[0055] FIG. 3 is a schematic diagram of a manufacturing process 30 that can be used to produce a heat-shrinkable film (e.g., heat-shrinkable film 10), according to a particular example. One or more extruders 32 can be used to co-extrude three layers (e.g., top layer 12, bottom layer 14, and core layer 16) for the heat-shrinkable film. The processing temperature of the extruder 32 can be from about 200°C to about 300°C. The three layers are cast onto a chill roll 34, which cools and solidifies the film. A web of film 36 is inspected by one or more quality control sensors 38 and fed to a tenter frame 40. The tenter frame 40 can stretch the film in the transverse direction (perpendicular to the machine direction) to a stretch ratio of about 1.5 to about 7, or about 5. Additionally or alternatively, one or more downstream rollers can stretch the film in the machine direction by pulling the web at a faster speed compared to the speed of the upstream rollers. Stretching can be performed to increase the glass transition temperature T of the heat-shrinkable film or one or more layers of the film. g For example, approximately T g ~About T g Stretching can be performed at a temperature of +20°C (e.g., about 65°C to about 105°C). One or more quality control sensors 42 can inspect the stretched film, which can be wound to form a roll 44.

[0051]

[0056] In a subsequent step (not shown), the heat-shrinkable film may be unwound from the roll 44 and subjected to a printing process in which ink is applied to the heat-shrinkable film. In some examples, one or more intermediate layers may be applied between the heat-shrinkable film and the ink. For example, a caustic soda-dissolvable or strippable primer may be applied to the heat-shrinkable film before the ink is applied. The primer may facilitate ink removal during a subsequent high-temperature washing process, as described herein. Additionally or alternatively, the heat-shrinkable film may be formed into a tubular shape (e.g., to form the sleeve 20) and / or cut to a desired size.

[0052]

[0057] 4 is a schematic diagram of a recycling process 50 that can be used to recycle heat shrinkable films (e.g., heat shrinkable film 10). Process 50 can begin by obtaining used or leftover packaging material 52, including heat shrinkable film and other recyclable materials, such as PET containers or bottles. The leftover packaging material 52 is fed to a shredder 54, which crushes, cuts, and / or shreds the packaging material 52 to obtain particles 56 of these materials. In various examples, particles 56 can include particles of heat shrinkable film at least partially covered with ink.

[0053]

[0058] The particles 56 are fed to a washer 58, which can clean the particles 56 using a high-temperature cleaning process involving soaking, mixing, and / or scrubbing the particles 56 in a warm liquid bath. The liquid bath can contain water, caustic soda (e.g., in an amount of about 0.1% to about 5% by weight), detergent (e.g., in an amount of about 0.1% to about 3% by weight), and other ingredients (e.g., antifoaming or defoaming agents). The liquid bath can have a temperature of about 55°C to about 95°C, or about 85°C. The washer 58 can have a mixing device (e.g., a rotating blade operating at 500 rpm) for mixing or agitating the particles 56 in the liquid bath. The output from the washer 58 can include washed particles 60 (e.g., with little or no ink) on a heat-shrinkable film and a stream of ink, dirt, or other contaminants 62.

[0054]

[0059] The washed particles 60 are fed into an oven or reactor 64, where the particles are heated (e.g., under reduced pressure) to a temperature of about 170°C to about 230°C for a drying and solidification process. The drying and solidification process can remove water, crystallize the particles 60, and / or increase the molecular weight of the particles 60. The reactor 64 can produce treated particles 66, which can be used to form recycled products such as new heat-shrinkable films, containers, etc. In certain embodiments, the oven or reactor 64 can include multiple ovens or reactors and / or process the washed particles 60 in more than one stage, which can include, for example, (i) a drying and crystallization stage and (ii) a solidification stage. The drying and crystallization stage can be performed at a temperature of about 130°C to about 190°C for up to about 180 minutes. The drying and crystallization stage can be performed at atmospheric pressure or under reduced pressure. The solidification stage can be performed at a temperature of about 170°C to about 230°C for about 90 minutes or longer to achieve the desired molecular weight. The solidification step can be carried out under reduced pressure (eg, below atmospheric) and / or in a nitrogen environment to avoid oxidation.

[0055]

[0060] As described herein, in some examples, the high temperatures in reactor 64 can cause particles 60 to become sticky, which can cause particles 60 to bond to each other or to other materials (e.g., PET bottle flakes) and form clumps. The formation of clumps can result in blocking of filters or screens and / or the formation of bridges that prevent proper flow of material through recycling process 50. Preferably, compared to previous low-shrinkage heat-shrinkable films, the heat-shrinkable films described herein (e.g., film 10) are less prone to becoming sticky and / or forming clumps during recycling process 50, thereby improving the recyclability of the film. For example, the particles of the heat-shrinkable films described herein can not melt and / or become adhesive or tacky when exposed to the temperatures and pressures in oven or reactor 64. In various examples, the heat-shrinkable films described herein are formulated to resist bonding with other materials when heated to temperatures of about 170°C to about 230°C, or about 210°C.

[0056]

[0061] Lump formation performance test

[0062] A clumping performance test was conducted to evaluate the tendency of heat-shrinkable films described herein (e.g., Film 10) to form clumps during the recycling process (e.g., due to high temperatures in the solidification process). The test procedure was similar to that outlined in document PET-S-08, "PET Flake Clumping Evaluation," published November 16, 2018, by the Association of Plastic Recyclers (APR). The films used in the test had thicknesses ranging from 30 to 80 microns and compositions matching the "Typical" values ​​shown in Tables 1 through 4 above.

[0057]

[0063] To conduct the test, the film was cut into 10 mm x 10 mm particles and mixed with PET bottle flakes (ranging in size from 3 to 20 mm) in a ratio of 3% to 97% (e.g., 3 g of film particles to 97 g of bottle flakes). The mixture was placed in a baking dish and placed in a 165°C oven for 30 minutes. The baking dish was removed from the oven and allowed to cool to room temperature. The baking dish was then placed back in a 210°C oven for 90 minutes. The baking dish was then removed from the oven and allowed to cool to room temperature. The contents of the baking dish (film particles and flakes) were transferred to an 11.2 mm screen (e.g., a sieve with approximately 11.2 mm square openings). The screen was shaken by hand to allow individual flakes to fall through. Any individual flakes too large to pass through the screen were removed by hand and placed with the flakes that passed through. Agglomerated flakes that broke up during the sorting process were not considered problematic. Any agglomerates that did not pass through the screen were weighed and the weight recorded. Any film particles, flakes, or residue that melted and adhered to the baking dish were weighed separately and recorded.

[0058]

[0064] Test results show that approximately 99.05% of the film particles and flakes were able to pass through the screen and / or did not form unacceptable agglomerates. This means that less than 0.95% of the film particles and flakes did not pass through the screen and / or did not form unacceptable agglomerates. This 0.95% value is consistent with acceptable agglomeration prevention performance and meets APR guidelines for PET flake recycling. For example, the film can meet APR guidelines for achieving less than 1% weight loss due to agglomerates not passing through a 12mm screen and / or loss due to adhesion to a baking dish.

[0059]

[0065] For comparison, other heat-shrinkable films with different structures and formulations were tested for clumping performance. In one example, a film consisting of a single layer of the first copolyester (e.g., pertaining to Table 2) exhibited a clumping performance of about 7 N / mm 2and did not meet APR guidelines for clumping performance testing (e.g., the film had a weight loss of more than 1% due to clumps that did not pass through a 12 mm screen). In another example, a film made from a single layer of the formulation used for top layer 12 and bottom layer 14 as described herein had acceptable clumping performance, but had a shrink tension of about 12 N / mm 2 The resulting film had an unacceptably high shrink tension of 1000 kJ / cm.

[0060]

[0066] Evaluation of contractile tension

[0067] Tests were conducted to evaluate the shrink tension of heat-shrinkable films described herein (e.g., Film 10). The films used in the tests had thicknesses ranging from 35 to 80 microns and compositions conforming to the "Typical" values ​​shown in Tables 1 through 4 above. Shrink tension was measured in accordance with DIN 53369:1076-02, "Testing of Plastic Films; Determination of the Shrinking Stress."

[0061]

[0068] To conduct the test, the film was cut into 100 mm x 10 mm strips and fixed in a measurement holder with a force sensor. The sample and holder were moved into a heating chamber where the temperature was increased from 40°C to 100°C at a rate of 102°C / hour (1.7°C / min). The force sensor was used to measure the tension of the film as the temperature increased. Measurements were taken on three separate samples to ensure repeatability. Figure 5 contains a plot of tension versus temperature from the test. The maximum shrink tension in this example was 7.9 N / mm 2 which occurred at a temperature of about 84°C.

[0062]

[0069] term

[0070] The phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

[0063]

[0071] As used in this specification and claims, the terms "approximately," "approximately equal," and other similar phrases (e.g., "X has a value of approximately Y" or "X is approximately equal to Y") should be understood to mean that one value (X) is within a predetermined range of another value (Y). The predetermined range can be plus or minus 20%, 10%, 5%, 3%, 1%, 0.1%, or less than 0.1%, unless otherwise specified.

[0064]

[0072] As used herein and in the claims, the indefinite articles "a" and "an" should be understood to mean "at least one" unless expressly indicated otherwise. The term "and / or" as used herein and in the claims should be understood to mean "either or both" of the elements so conjoined, i.e., the elements are present conjunctively in some cases and disjunctively in other cases. Multiple elements listed with "and / or" should be construed in the same manner, i.e., "one or more" of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the "and / or" clause, whether related to those elements specifically identified or not. Thus, as a non-limiting example, a reference to "A and / or B," when used in combination with an open-ended term such as "comprising," can refer in one embodiment to A only (optionally including elements other than B), in another embodiment to B only (optionally including elements other than A), in yet another embodiment to both A and B (optionally including other elements), etc.

[0065]

[0073] As used in this specification and in the claims, "or" should be understood to have the same meaning as "and / or" as defined above. For example, when separating items in a list, "or" or "and / or" should be interpreted as inclusive, i.e., including at least one, but also including more than one, of a number or list of elements, and optionally including additional, unlisted items. Only terms clearly indicated to the contrary, such as "only one of," or "exactly one of," or, when used in the claims, "consisting of," refer to the inclusion of exactly one element of a number or list of elements. In general, the term "or" when used when preceded by terms of exclusivity, such as "either," "one of," "only one of," or "exactly one of," shall be interpreted only as indicating exclusive alternatives (i.e., "one or the other, but not both"). As used in the claims, "consisting essentially of" shall have its ordinary meaning as used in the field of patent law.

[0066]

[0074] As used in this specification and claims, the phrase "at least one" in connection with a list of one or more elements should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed in the list of elements, and not excluding any combination of elements in the list of elements. This definition also allows for the optional presence of elements other than those specifically identified in the list of elements to which the phrase "at least one" refers, whether related to the specifically identified elements or not. Thus, as a non-limiting example, "at least one of A and B" (or, equivalently, "at least one of A or B," or, equivalently, "at least one of A and / or B") can refer in one embodiment to at least one, optionally two or more, A, and no B (and optionally including elements other than B); in another embodiment to at least one, optionally two or more, B, and no A (and optionally including elements other than A); in yet another embodiment to at least one, optionally two or more, A, and at least one, optionally two or more, B (and optionally including other elements); etc.

[0067]

[0075] The use of "including," "comprising," "having," "containing," "involving," and variations thereof, is meant to encompass the items listed thereafter and additional items.

[0068]

[0076] The use of ordinal terms such as "first," "second," "third," etc. in the claims to modify claim elements does not, in itself, imply any importance, priority, or order of one claim element relative to another claim element, or the chronological order in which method actions are performed. Ordinal terms are used merely as labels to distinguish claim elements, distinguishing one claim element having a certain name from another element having the same name (but using ordinal terms).

[0069]

[0077] Each numerical value set forth herein, for example in a table, chart, or graph, is considered to represent the minimum or maximum value within the range of the corresponding parameter. Thus, when added to a claim, the numerical value provides explicit support for claiming a range that may lie above or below the numerical value, in accordance with the teachings of this specification. For numerical ranges recited herein, various embodiments include any parameter value (e.g., integer or decimal value) within the recited range. For example, if the recited range is 1 to 10, the value of each parameter can be greater than, less than, or equal to 1, 2, 3, ..., 9, or 10. Unless included in the claims, each numerical value presented herein should not be considered limiting in any respect.

[0070]

[0078] The terms and expressions used herein are used as terms and expressions of description rather than of limitation, and the use of such terms and expressions is not intended to exclude any equivalents of the features shown and described, or portions thereof. Moreover, while specific embodiments of the present invention have been described, it will be apparent to those skilled in the art that other embodiments incorporating the concepts disclosed herein may be used without departing from the spirit and scope of the present invention. The features and functions of the various embodiments may be arranged in various combinations and permutations, all of which are considered to be within the scope of the disclosed invention. Therefore, the described embodiments are to be considered in all respects as illustrative only and not restrictive. Furthermore, the configurations, materials, and dimensions set forth herein are intended to be illustrative and in no way limiting. Similarly, while physical descriptions are provided for illustrative purposes, they are not intended to be bound by any particular theory or mechanism or to limit the scope of the claims accordingly.

Claims

1. A multilayer heat-shrinkable film comprising: a first copolyester comprising a first diol component comprising diethylene glycol (DEG) and 1,4-cyclohexanedimethanol (CHDM); amorphous polyethylene terephthalate (APET), and a second copolyester optionally comprising a second diol component comprising 2-dimethylpropane-1,3-diol (NPG); a first layer comprising a first blend of a second layer comprising the first blend; and disposed between the first layer and the second layer; a third copolyester comprising a third diol component comprising 2-methyl-1,3-propanediol (MPO) and DEG; APET, and optionally, a fourth copolyester comprising a fourth diol component comprising NPG; and a core layer comprising a second blend of the above, wherein the multilayer heat-shrinkable film has a shrink initiation temperature of 60° C. or less and a shrink strength of 9 N / mm ２ A multilayer heat shrinkable film having a shrink tension of:

2. 10. The multilayer heat shrinkable film of claim 1, wherein the film has a shrink initiation temperature of at least 50°C.

3. The film has a resistance of 6 N / mm ２ The multilayer heat shrinkable film of claim 1 , which has a higher shrink tension.

4. 10. The multilayer heat shrinkable film of claim 1, wherein the first layer and the second layer each have a glass transition temperature of from about 70°C to about 80°C.

5. 10. The multilayer heat shrinkable film of claim 1, wherein the core layer has a glass transition temperature of from about 60°C to about 70°C.

6. 10. The multilayer heat shrinkable film of claim 1, wherein the first layer, the second layer, and the core layer each have an intrinsic viscosity of from about 0.65 dl / g to about 0.85 dl / g.

7. 10. The multilayer heat shrinkable film of claim 1, wherein the core layer comprises from about 50% to about 90% of the total thickness of the film, and the first layer and the second layer each comprise from about 5% to about 25% of the total thickness of the film.

8. the first blend comprising: about 18% to about 78% by weight of said first copolyester; about 10% to about 30% by weight of said APET, and 10. The multilayer heat shrinkable film of claim 1, optionally comprising up to about 90% by weight of said second copolyester.

9. 10. The multilayer heat shrinkable film of claim 8, wherein the first blend further comprises an anti-blocking additive.

10. the second blend comprising: about 55% to about 85% by weight of said third copolyester; about 10% to about 35% by weight of said APET, and 10. The multilayer heat shrinkable film of claim 1, optionally comprising up to about 10% by weight of said fourth copolyester.

11. 10. The multilayer heat shrinkable film of claim 1, wherein said second blend further comprises said first copolyester.

12. the first diol component comprises about 60 mol% to about 70 mol% ethylene glycol (EG), about 5 mol% to about 15 mol% DEG, and about 20 mol% to about 30 mol% CHDM; the second diol component comprises about 65 mol% to about 75 mol% EG, and about 23 mol% to about 33 mol% NPG; the third diol component comprises about 56 mol% to about 66 mol% EG, about 14 mol% to about 24 mol% MPO, and about 1 mol% to about 15 mol% DEG; and 10. The multilayer heat shrinkable film of claim 1, wherein the fourth diol component comprises from about 65 mol % to about 75 mol % EG and from about 23 mol % to about 33 mol % NPG.

13. 2. The multilayer heat shrinkable film of claim 1, wherein the first blend comprises the second copolyester, the second blend comprises the fourth copolyester, and the second copolyester and the fourth copolyester are the same.

14. 10. The multilayer heat shrinkable film of claim 1, wherein the film is formulated to resist bonding to other materials when heated to a temperature of about 210°C.

15. 1. A method for making a multilayer heat shrinkable film, said method comprising: a first copolyester comprising a first diol component comprising diethylene glycol (DEG) and 1,4-cyclohexanedimethanol (CHDM); amorphous polyethylene terephthalate (APET), and optionally, a second copolyester comprising a second diol component comprising DEG and 2-dimethylpropane-1,3-diol (NPG); obtaining a first blend comprising: a third copolyester comprising a third diol component comprising 2-methyl-1,3-propanediol (MPO) and DEG; APET, and optionally, a fourth copolyester comprising a fourth diol component comprising NPG; obtaining a second blend comprising: co-extruding the first blend and the second blend; a first layer comprising said first blend; a second layer comprising the first blend; and a core layer comprising the second blend and disposed between the first layer and the second layer; forming a heat shrinkable film comprising: The multilayer heat-shrinkable film has a shrinkage initiation temperature of 60° C. or less and a shrinkage strength of 9 N / mm ２ The method comprises the following contraction tension:

16. 16. The method of claim 15, wherein co-extruding the first blend and the second blend comprises heating the first blend and the second blend to a temperature of from about 200°C to about 300°C.

17. 16. The method of claim 15, wherein co-extruding the first blend and the second blend comprises casting the heat shrinkable film through a die onto a chill roll.

18. 16. The method of claim 15, further comprising stretching the heat shrinkable film in a tenter frame to a draw ratio of about 1.5 to about 7.

19. 20. The method of claim 18, wherein the heat shrinkable film has a glass transition temperature and the stretching step is performed at a temperature of from about the glass transition temperature to about the glass transition temperature plus 20°C.

20. 1. A method of using a multilayer heat shrinkable film, said method comprising: a first copolyester comprising a first diol component comprising diethylene glycol (DEG) and 1,4-cyclohexanedimethanol (CHDM); amorphous polyethylene terephthalate (APET), and a second copolyester optionally comprising a second diol component comprising 2-dimethylpropane-1,3-diol (NPG); a first layer comprising a first blend of a second layer comprising the first blend; and disposed between the first layer and the second layer; a third copolyester comprising a third diol component comprising 2-methyl-1,3-propanediol (MPO) and DEG; APET, and optionally, a fourth copolyester comprising a fourth diol component comprising NPG; a core layer comprising a second blend of obtaining a multilayer heat shrinkable film comprising: The multilayer heat-shrinkable film has a shrinkage initiation temperature of 60° C. or less and a shrinkage strength of 9 N / mm ２ providing a contraction tension of: forming the multilayer heat shrinkable film into a sleeve; placing the sleeve around an object; and applying heat to the sleeve to cause the sleeve to shrink onto the object.

21. 21. The method of claim 20, wherein the object comprises at least one of a container or a bottle.

22. 1. A method for recycling a multilayer heat shrinkable film, said method comprising: (i) flakes formed from polyethylene terephthalate (PET) bottles; and (ii) a shrinkage initiation temperature of 60°C or less and a shrinkage strength of 9 N / mm ２ obtaining a mixture of particles of a heat shrinkable film having a shrink tension of: heating the flakes and particles to a temperature of about 170°C to about 230°C in a recycling process; The method wherein the particles are formulated to prevent bonding to the flakes during the recycling process.

23. 23. The method of claim 22, wherein the recycling process includes a solidification step that increases the molecular weight of the heat shrinkable film.

24. 23. The method of claim 22, wherein the particles meet the requirement of less than 1% weight loss during PET flake clumping evaluation as specified in PET Flake Clumping Evaluation, document PET-S-08, published November 16, 2018 by the ASSOCIATION OF PLASTIC RECYCLERS.

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