Cavitated copolyester shrink film with improved density reduction and toughness

Abstract

Disclosed are a cavitated, heat-shrinkable copolyester film containing an organic polymer additive and a process for producing the film. The film has a unique combination of properties, including one or more of high shrinkage, low density, inherent opaqueness, high toughness, and a non-contaminant in the PET recycle stream due to a final shrunk film density of < 1.00 g / cm3. The film is particularly useful for preparing shrink sleeve labels.

Description

CAVITATED COPOLYESTER SHRINK FILM WITH IMPROVED DENSITY REDUCTION AND TOUGHNESSNAMES OF PARTIES TO JOINT RESEARCH AGREEMENT

[0001] The inventions disclosed or claimed herein were made pursuant to a joint research agreement between Eastman Chemical Company and VOID Technologies Limited.TECHNICAL FIELD

[0002] The invention relates generally to heat-shrinkable films and, in particular, to cavitated, heat-shrinkable copolyester films; their methods of preparation; and corresponding shrunk films.BACKGROUND

[0003] Thermo-shrinkable (or heat-shrinkable) films are widely used as a full-wrap label for polyethylene terephthalate (PET) bottles and the like, where the label is shrunk to fit tightly around the bottle. These shrink-film labels are popular with brand owners as they provide a compelling marketing opportunity to attract consumers. These shrink films are made from a diverse array of polymers, such as polystyrene, polyolefin, polyvinyl chloride, and polyester, utilizing various monolayer and co-extruded structures.

[0004] There is a growing concern, however, regarding these labels in the PET recycling industry. The PET recyclers collect the PET bottles for manufacturing recycled PET (rPET) for various applications. The industry uses automated sorting techniques to separate the bottles depending on resin type. Infrared spectroscopy, color sortation, marker systems, manual sorting, etc. are some of the techniques used to separate PET containers from any contaminants, such as non-PET plastic containers, aluminum, plastic, etc.

[0005] Shrink-film labeled bottles are currently either removed as a contaminant or mixed with PET bottles through the sorting process. The PET bottles with shrink labels that make it through the sorting process are ground into small pieces and separatedusing a “sink / float” process. Depending upon their density, the shrink labels will float or sink. With the exception of polyolefin labels, other resins that are used to make the labels have a higher density than water and therefore sink along with PET flake, making them difficult to separate and are seen as a contaminant by the recycling industry.

[0006] With the shrink-label market growing, recyclers are seeing a growing percentage of their recycled PET bales being contaminated with shrink-film labels and are putting pressure on brand owners to make a change.

[0007] In addition, some products based on dairy or containing high levels of certain nutrients require light-blocking packaging to protect the quality of the product. Today, several solutions (such as TiO2-containing white PET bottles, TiO2-containing white HDPE bottles, and more sophisticated multi-layer containers) are available for the most light-sensitive products. However, some brands have chosen to move away from these types of containers and into clear PET containers, because the latter are more easily recyclable in the higher-value, clear PET recycle stream. To meet their light-blocking requirements, these brands have turned to opaque, full-body shrink sleeves. The commercial versions of these shrink sleeves today are typically based on PETG (PET glycol-modified) and can require colored pigments and / or opaque ink layers to meet the requirements of the product.

[0008] Inherently white, cavitated PETG films (with or without these additional components) exist today, but they can be a contaminant in the PET recycle stream if they are not properly removed during sorting. Due to a final shrunk film density of >1 .0 g / cm3, the resulting label flake will sink with the clean PET flake.

[0009] Thus, there is a need for heat-shrinkable films that do not contaminate PET recycle streams while at the same time have high ultimate shrinkage in the transverse (TD) direction, low to negative shrinkage (growth) in the machine direction (MD), inherent opacity for light blocking, high toughness, and / or surface properties that allow for efficient downstream conversion processes (e.g., slitting, printing, solvent seaming, application, and shrinking).

[0010] The present invention addresses this need as well as others, which will become apparent from the following description and the appended claims.SUMMARY

[0011] The invention is as set forth in the appended claims.

[0012] Briefly, in one aspect, the invention provides a void-containing, heat-shrinkable film. The film comprises (a) a polymer matrix comprising a copolyester and (b) a voiding agent dispersed in the polymer matrix. The voiding agent comprises an organic polymer. The film has (i) a machine direction (MD) elongation at break of at least 200% at a test speed of 300 mm / min and a thickness of 30-80 pm, and (ii) a film density of less than 1 g / cm3.

[0013] In another aspect, the invention provides a process for preparing a voidcontaining, heat-shrinkable film. The process comprises:(a) mixing the polymer matrix and the voiding agent together to form a dispersion of the voiding agent in the polymer matrix;(b) forming a film from the dispersion;(c) stretching the film from step (b) in at least one direction at or above the glass transition temperature of the polymer matrix; and(d) cooling the film from step (c) to obtain the void-containing, heat-shrinkable film.

[0014] In yet another aspect, the invention provides a heat-shrunk film. The film comprises (a) a polymer matrix comprising a copolyester and (b) a voiding agent dispersed in the polymer matrix. The voiding agent comprises an organic polymer. The heat-shrunk film has (i) a machine direction (MD) elongation at break of at least 200% at a test speed of 300 mm / min and a film thickness of 50-90 pm, and (ii) a film density of less than 1 g / cm3.BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 shows the typical shrinkage properties of a heat-shrinkable film made with Embrace™ LV copolyester.

[0016] Figure 2 shows the shrink curves of the films prepared in Examples 1-4.

[0017] Figure 3 shows the shrink curves of the films prepared in Examples 5-8.DETAILED DESCRIPTION

[0018] It has been surprisingly discovered that void-containing, heat-shrinkable copolyester films can be prepared which exhibit enough density reduction to float in water after shrinkage (and therefore is a non-contaminant in a PET recycle stream) and excellent shrinkage properties. The films can possess one or more additional desirable properties, including inherent opacity, high film toughness, and good surface properties.

[0019] The voided-shrink films of the invention can have high shrinkage and can maintain their low density even after exposure to temperatures typically present during recycling processes. The films may be used as roll-fed or traditional shrink-sleeve labels, can be printed easily, and seamed by traditional means. The voided-shrink films may be separated from mixtures of polymers and, thus, may be easily recovered and recycled from commercial waste by separation in water. The recyclability of the voided- shrink films in combination with their excellent physical properties make them particularly useful for labels and in other packaging applications.Definitions

[0020] To facilitate understanding the invention, several terms are defined below. Those left undefined have meanings as commonly understood by a person of ordinary skill in the technical areas relevant to the present invention.

[0021] The term “polyester” refers to a synthetic polymer prepared by the polycondensation of one or more difunctional carboxylic acids with one or more difunctional hydroxyl compounds. Typically, the difunctional carboxylic acid is a dicarboxylic acid, and the difunctional hydroxyl compound is a dihydric alcohol (such asglycols and diols). Alternatively, the difunctional carboxylic acid may be a hydroxy carboxylic acid (such as p-hydroxybenzoic acid), and the difunctional hydroxyl compound may be an aromatic nucleus bearing 2 hydroxyl substituents (such as hydroquinone).

[0022] The polyester may be prepared from dicarboxylic acids and diols, which react in substantially equal proportions and are incorporated into the polyester as their corresponding residues. The polyester, therefore, contains substantially equal molar proportions of diacid residues (100 mole %) and diol residues (100 mole %) such that the total moles of repeating units is equal to 100 mole %. The mole percentages may be reported based on the total moles of diacid residues, the total moles of diol residues, or the total moles of repeating units. For example, a polyester containing 30 mole % of isophthalic acid residues, based on the total diacid residues, means the polyester contains 30 mole % of isophthalic acid residues out of a total of 100 mole % of diacid residues. Thus, there are 30 moles of isophthalic acid residues among every 100 moles of diacid residues. In another example, a polyester containing 30 mole % of ethylene glycol residues, based on the total diol residues, means the polyester contains 30 mole % of ethylene glycol residues out of a total of 100 mole % diol residues. Thus, there are 30 moles of ethylene glycol residues among every 100 moles of diol residues.

[0023] The term “copolyester” refers a polyester made of two or more difunctional carboxylic acids, or two or more difunctional hydroxyl compounds, or both.

[0024] The term “residue” means any organic structure incorporated into a polymer through a polycondensation reaction involving the corresponding monomer.

[0025] The term “repeating unit” means an organic structure having a dicarboxylic acid residue and a diol residue bonded through a carbonyloxy group. Thus, the dicarboxylic acid residues may be derived from a dicarboxylic acid monomer or its associated acid halides, esters, salts, anhydrides, or mixtures thereof. As used herein, therefore, the term “dicarboxylic acid” is intended to include dicarboxylic acids and any derivative of a dicarboxylic acid, including its associated acid halides, esters, half-esters, salts, half-salts, anhydrides, mixed anhydrides, or mixtures thereof, useful in a polycondensation process with a diol to make a high-molecular weight (co)polyester.

[0026] The terms “heat-shrinkable” and “shrink” are intended to be synonymous and refer to the ability of a film to become smaller in at least one direction upon exposure to heat near or above the glass transition temperature of the matrix polymer.

[0027] The terms “heat-shrunk,” “shrunk,” and “post-shrink” are intended to be synonymous and describe a film that has been exposed to heat near or above the glass transition temperature of the matrix polymer (e.g., 5 to 10 seconds in a hot-air or steamshrink tunnel at 80 to 95°C) and has become smaller in at least one direction.

[0028] The term “polymer matrix” is synonymous with the term “matrix polymer.” It refers to one or more polymers providing a continuous phase in which the voiding agent is dispersed such that the voiding agent is surrounded and contained by the continuous phase.

[0029] The terms “voids,” “microvoids,” “cavities,” and “micropores” are intended to be synonymous and refer to discrete areas of empty space within the polymer matrix.They are intentionally created during manufacturing of the film via stretching in at least one direction. During stretching, small cavities or voids are formed around the voiding agent. The empty space may be occupied by a gas, such as air.

[0030] Similarly, the terms “voided,” “microvoided,” “cavitated,” and “void-containing” are intended to be synonymous and mean “containing voids, microvoids, cavities, or micropores.”

[0031] The term “voiding agent” is synonymous with the terms “voiding composition,” “microvoiding agent,” and “cavitation agent.” It refers to a substance dispersed within a polymer matrix to bring about or cause the formation voids within the polymer matrix upon stretching of the polymer matrix. In general, the voiding agent can be organic or inorganic. Inorganic voiding agents are typically in particulate form. Organic or polymeric voiding agents typically have a degree of incompatibility with the matrix polymer such that the two form different phases when mixed in the melt, where the voiding agent (inclusion) forms a droplet phase within a continuous polymeric phase(matrix). The inclusion and the matrix ideally have poor or no adhesion to each other such that their bonding forces are low or non-existent.Voided-Shrink Film

[0032] In one aspect, the invention provides a void-containing, heat-shrinkable film comprising (a) a polymer matrix comprising a copolyester and (b) a voiding agent dispersed in the polymer matrix. The voiding agent comprises an organic polymer. The film has (i) a machine direction (MD) elongation at break of at least 200% at a test speed of 300 mm / min and a thickness of 30-80 p.m, and (ii) a film density of less than 1 g / cm3.

[0033] In various embodiments, the MD elongation at break is at least 250%, at least 300%, at least 350%, at least 400%, at least 450%, at least 500%, or at least 550%.

[0034] In various embodiments, the film density is 0.95 g / cm3or less, 0.90 g / cm3or less, 0.85 g / cm3or less, 0.80 g / cm3or less, 0.75 g / cm3or less, 0.70 g / cm3or less, 0.65 g / cm3or less, 0.60 g / cm3or less, 0.55 g / cm3or less, 0.50 g / cm3or less, 0.45 g / cm3or less, or 0.40 g / cm3or less.

[0035] In various embodiments, the void-containing, heat-shrinkable film has a transverse direction (TD) ultimate shrinkage of at least 60%, at least 65%, or at least 70%, after immersion in a 95°C water bath for 10 seconds.

[0036] In various embodiments, the void-containing, heat-shrinkable film has a machine direction (MD) shrinkage of 5% or less, or 0% or less, after immersion in an 85°C water bath for 10 seconds.

[0037] In various embodiments, the void-containing, heat-shrinkable film has a shrink force of 2 to 10 MPa. The shrink force may be measured with a LabThink FST-02 Thermal Shrinkage Tester in MPa at 80°C.

[0038] In various embodiments, the void-containing, heat-shrinkable film has a light transmittance of 50% or less, or 40% or less, or 30% or less, at a film thickness of 30-80 |im.

[0039] In various embodiments, the void-containing, heat-shrinkable film has a thickness of 30 to 80 pm, or 45 to 65 pm.

[0040] In various embodiments, the void-containing, heat-shrinkable film has an average surface roughness of 4 pm or less.

[0041] In various embodiments, the void-containing, heat-shrinkable film has an MD tensile modulus of at least 400 MPa, at least 500 MPa, at least 600 MPa, at least 700 MPa, at least 800 MPa, at least 900 MPa, at least 1,000 MPa, or at least 1,100 MPa.

[0042] For the avoidance of doubt, the void-containing, heat-shrinkable film according to the invention may be characterized by one or more for the foregoing properties, including MD elongation at break, film density, TD ultimate shrinkage, MD shrinkage, shrink force, light transmittance, thickness, average surface roughness, and MD tensile modulus.

[0043] The void-containing, heat-shrinkable film may be a single layer or may contain a plurality of layers in which at least one layer comprises the voiding agent. The singlelayer voided-shrink film may be incorporated as one or more layers of a multilayer structure, such as by lamination or coextrusion.

[0044] In various embodiments, the void-containing, heat-shrinkable film is monolayer.

[0045] In various embodiments, the void-containing, heat-shrinkable film is multilayer.

[0046] In various embodiments, the void-containing, heat-shrinkable film is multilayer and all layers contain voids.

[0047] In various embodiments, the void-containing, heat-shrinkable film is multilayer and at least one layer does not contain voids.

[0048] In various embodiments, the void-containing, heat-shrinkable film comprises 60 to 80% by weight of the polymer matrix, based on the total weight of the film.

[0049] In various embodiments, the void-containing, heat-shrinkable film comprises 20 to 40% by weight of the voiding agent, based on the total weight of the film.

[0050] The voided-shrink film described herein represents a unique solution. It can provide a high-performing, inherently white shrink sleeve label for applications requiringthe protection of products from light-degradation without the likely risk of contaminating clean PET flake during the PET recycling process. The end-use performance of this film can also be additionally modified to increase the light-blocking capabilities of the label, including by using colored pigments, opaque ink layers, and / or specialized coatings to decrease the overall transmittance of light wavelengths ranging from 350- 1100 nm. Additionally, this shrink sleeve label solution can be used in applications without the need for light-blocking properties to serve as a general-use, high- performance shrink sleeve label material that does not contaminate the PET recycle stream, unlike other label solutions including PETG, PVC, OPS, and others. A floatable, polyester-based shrink film could be particularly attractive in regions where a floatable label is the preferred solution to avoid PET contamination.

[0051] The voided-shrink film described herein can be more easily and efficiently printed, solvent seamed, and shrunk than alternative solutions attempting to fulfill the needs of a high-performing shrink sleeve that does not contaminate the PET recycle stream.

[0052] Additionally, regrind utilization techniques known to those skilled in the art can be used to repurpose scrap generated during film extrusion, thus reducing overall yield losses.Polymer Matrix

[0053] The polymer matrix comprises a copolyester.

[0054] The copolyester may be amorphous or semicrystalline, or blends thereof, with relatively low crystallinity. In various embodiments, the copolyester has a substantially amorphous morphology, meaning that the copolyester comprises substantially unordered regions of polymer.

[0055] In various embodiments, the copolyester comprises (A) a diacid component comprising at least 80 mole percent, based on the total moles of diacid residues, of the residues of one or more diacids selected from terephthalic acid, naphthalenedicarboxylic acid, 1 ,4-cyclohexanedicarboxylic acid, and isophthalic acid;and (B) a diol component comprising (i) 10 to 100 mole percent, based on the total moles of diol residues, of the residues of one or more diols selected from 1 ,4- cyclohexanedimethanol, neopentyl glycol, and diethylene glycol; and (ii) 0 to 90 mole percent, based on the total moles of diol residues, of the residues of one or more diols selected from ethylene glycol, 1 ,2-propanediol, 1 ,3-propanediol, 1 ,4-butanediol, 1 ,5- pentanediol, 1 ,6-hexanediol, 1 ,8-octanediol, 2,2,4-trimethyl-1 ,3-pentanediol, 2, 2,4,4- tetramethyl-1 ,3-cyclobutanediol, 1 ,3-cyclohexanedimethanol, bisphenol A, and polyalkylene glycol.

[0056] The 1 ,4-cyclohexanedimethanol (CHDM) and 1 ,4-cyclohexanedicarboxylic acid (CHDA) may be used as the pure cis, pure trans, or mixtures of cis / trans isomers.

[0057] Any of the naphthalenedicarboxylic acid isomers may be used, such as the 1 ,4-, 1 ,5-, 2,6-, or 2,7-isomer, or mixtures thereof.

[0058] Examples of polyalkylene glycols include polytetramethylene glycol (PTMG) and polyethylene glycol (PEG) having molecular weights up to 2,000.

[0059] The diacid component (A) may comprise up to 20 mole percent (e.g., 0 to 10 mole percent, 0 to 5 mole percent, or 0 to 1 mole percent) of the residues of one or more modifying diacids containing from 2 to 16 carbon atoms, if desired. For example, the diacid component (A) may comprise from 0 to 20 mole % of the residues of other aromatic dicarboxylic acids containing 8 to 16 carbon atoms, cycloaliphatic dicarboxylic acids containing 8 to 16 carbon atoms, aliphatic dicarboxylic acids containing 2 to 16 carbon atoms, or mixtures thereof. Examples of modifying dicarboxylic acids include succinic acid, glutaric acid, 1 ,3-cyclohexanedicarboxylic, adipic acid, suberic acid, sebacic acid, azelaic acid, dimer acid, and sulfoisophthalic acid.

[0060] In various embodiments, the diacid component (A) comprises 0 mole percent of the residues of a modifying diacid.

[0061] In various other embodiments, the diacid component (A) comprises up to 10 mole percent of the residues of a modifying diacid selected from adipic acid and / or glutaric acid.

[0062] In various embodiments, the copolyester comprises (A) a diacid component comprising at least 90 mole percent of terephthalic acid residues and (B) a diol component comprising from (i) 60 to 90 mole percent of ethylene glycol residues and (ii) from 10 to 40 mole percent of the residues of 1 ,4-cyclohexanedimethanol, neopentyl glycol, diethylene glycol, 1 ,4-butanediol, or combinations thereof. In various subembodiments, the diol component may comprise: (i) from 0 to 32 mole percent of 1 ,4- cyclohexanedimethanol residues; (ii) from 0 to 30 mole percent of neopentyl glycol residues; (iii) from 0 to 15 mole percent of diethylene glycol residues; and (iv) from 0 to 15 mole percent of 1 ,4-butanediol residues. In various other sub-embodiments, the diol component may comprise: (i) from 18 to 28 mole percent of 1 ,4-cyclohexanedimethanol residues; (ii) from 0 to 15 mole percent of neopentyl glycol residues; (iii) from 8 to 15 mole percent of diethylene glycol residues; and (iv) from 0 to 15 mole percent of 1 ,4- butanediol residues.

[0063] In various embodiments, the copolyester comprises (A) a diacid component comprising at least 95 mole percent of terephthalic acid residues and (B) a diol component comprising from 10 to 99 mole percent of 1 ,4-cyclohexanedimethanol residues, from 0 to 90 mole percent of ethylene glycol residues, and from 1 to 25 mole percent of diethylene glycol residues.

[0064] In various embodiments, the copolyester comprises (A) a diacid component comprising at least 95 mole percent of terephthalic acid residues and (B) a diol component comprising from 10 to 40 mole percent of 1 ,4-cyclohexanedimethanol residues, from 35 to 89 mole percent of ethylene glycol residues, and from 1 to 25 mole percent of diethylene glycol residues.

[0065] In various embodiments, the copolyester comprises (A) a diacid component comprising at least 90 mole percent of terephthalic acid residues and (B) a diol component comprising 52 to 88 mole percent of ethylene glycol residues, 10 to 28 mole percent of 1 ,4-cyclohexanedimethanol residues, and 2 to 20 mole percent of diethylene glycol residues.

[0066] In various embodiments, the copolyester comprises (A) a diacid component comprising at least 90 mole percent of terephthalic acid residues and (B) a diol component comprising 72 to 88 mole percent of ethylene glycol residues, 10 to 15 mole percent of 1 ,4-cyclohexanedimethanol residues, and 2 to 13 mole percent of diethylene glycol residues.

[0067] In various embodiments, the copolyester comprises (A) a diacid component comprising at least 90 mole percent of terephthalic acid residues and (B) a diol component comprising 59 to 77.5 mole percent of ethylene glycol residues, 15 to 28 mole percent of 1 ,4-cyclohexanedimethanol residues, and 7.5 to 13 mole percent of diethylene glycol residues.

[0068] The diacid component (A) is based on 100 mole percent, and the diol component (B) is based on 100 mole percent. In other words, the total mole percent of the diacid component (A) is 100, and the total mole percent of the diol component (B) is 100.

[0069] Other examples of copolyesters that may be included in the polymer matrix are those based on poly(ethylene terephthalate) containing from 15 to 55 mole percent of 1 ,3- or 1 ,4-cyclohexanedimethanol residues, and from 1 to 25 mole % of diethylene glycol residues; those based on poly(ethylene terephthalate) containing from 15 to 35 mole % of 1 ,3- or 1 ,4-cyclohexanedimethanol residues, and from 5 to 20 mole % of diethylene glycol residues; and those based on poly(ethylene terephthalate) containing from 20 to 30 mole % of 1 ,3- or 1 ,4-cyclohexanedimethanol residues, and from 10 to 20 mole % of diethylene glycol residues.

[0070] It is understood by persons skilled in the art that the final copolyester composition in the polymer matrix can be arrived at by blending various (co)polyester resins or by direct reactor copolymerization of the appropriate mixture of monomers.

[0071] In various embodiments, the polymer matrix further comprises a polyester homopolymer. Examples of polyester homopolymers include polyethylene terephthalate) (PET), poly(butylene terephthalate) (PBT), and poly(cyclohexylenedimethylene terephthalate) (PCT).

[0072] In various embodiments, the polymer matrix comprises two or more copolyesters. Examples of copolyesters include glycol-modified PET (PETG), glycol- modified poly(cyclohexylenedimethylene terephthalate) (PCTG), acid-modified poly(cyclohexylenedimethylene terephthalate) (PCTA), and diethylene glycol-modified PET.

[0073] In various embodiments, the copolyester may have an inherent viscosity (I.V.) from 0.5 dL / g to 1.4 dL / g, from 0.65 dL / g to 1.0 dL / g, or from 0.65 dL / g to 0.85 dL / g, as determined in 60 / 40 (wt / wt) phenol / tetrachloroethane at a concentration of 0.25 g / 50 mL at 25°C.

[0074] In various embodiments, the copolyester may have a glass transition temperature (Tg) of at least 50°C (e.g., from 80°C to 105°C, from 80°C to 100°C, from 80°C to less than 100°C, from 80° C to 99° C, or from 80°C to 98°C). The Tg may be determined using a TA DSC 2920 from Thermal Analyst Instrument at a scan rate of 20°C / min.

[0075] The copolyester may be made by various methods known in the literature, for example, by a direct esterification reaction of the diol with the dicarboxylic acid or by an ester interchange reaction of the diol with the dicarboxylic acid ester, followed by polycondensation of the reaction product (see, e.g., US 2,720,507).

[0076] Alternatively, the copolyester may be obtained commercially from vendors such as Eastman Chemical Company (Kingsport, TN).

[0077] The copolyester may also be produced from chemically recycled monomers (i.e., those produced by any known method of depolymerization). (Co)polyesters can be depolymerized to form the monomer units originally used in their manufacture. One commercially practiced method for (co)polyester depolymerization is methanolysis. In methanolysis, the (co)polyester is reacted with methanol to produce a depolymerized (co)polyester mixture comprising (co)polyester oligomers, dimethyl terephthalate (DMT), and ethylene glycol (EG). Other monomers, such as 1 ,4-cyclohexanedimethanol (CHDM) and diethylene glycol (DEG), may also be present depending on the composition of the (co)polyester in the methanolysis feed stream.

[0078] Some representative methods for the methanolysis of polyethylene terephthalate) (PET) are described in U.S. Patent Nos. 3,037,050; 3,321 ,510; 3,776,945; 5,051,528; 5,298,530; 5,414,022; 5,432,203; 5,576,456; and 6,262,294, the contents of which are incorporated herein by reference. The ’530 patent, for example, describes a process for recovering EG and DMT from scrap polyester. The process includes the steps of dissolving scrap polyester in oligomers of EG and terephthalic acid or DMT and passing super-heated methanol through this mixture. The oligomers can comprise any low molecular weight polyester polymer of the same composition as that of the scrap material being employed as the starting component such that the scrap polymer will dissolve in the low molecular weight oligomer. The DMT and the EG are recovered from the methanol vapor stream that issues from depolymerization reactor.

[0079] Another approach to depolymerize (co)polyesters is glycolysis. It involves reacting the (co)polyester with a glycol, such as EG or CHDM, to produce a depolymerized polyester mixture. For example, US 4,259,478 discloses a process comprising heating a polyester in the presence of CHDM to glycolize the polymer, distilling out EG from the glycolysis mixture, and polycondensing the glycolysis mixture to form a copolyester in which at least a portion of the EG units are replaced by CHDM units. Similarly, US 5,635,584 discloses reacting post-consumer or scrap polyester with glycol to produce a monomer or low molecular weight oligomer by depolymerizing the polyester. The monomer or oligomer, as the case may be, is then purified using one or more steps including filtration, crystallization, and optionally adsorbent treatment or evaporation. The monomer or oligomer thus obtained is particularly suitable as a raw material for producing packaging-grade polyester material. Because the process includes purification steps, purity specifications for the previously-used polyester material need not be strict.

[0080] Thus, in various embodiments, the copolyester in the polymer matrix comprises recycled content.

[0081] In various embodiments, the copolyester in the polymer matrix comprises recycled ethylene glycol (rEG) residues.

[0082] In various embodiments, the copolyester in the polymer matrix comprises recycled 1 ,4-cyclohexanedimethanol (rCHDM) residues.

[0083] In various embodiments, the copolyester in the polymer matrix comprises recycled diethylene glycol (rDEG) residues.

[0084] In various embodiments, the copolyester in the polymer matrix comprises recycled terephthalic acid (rTA) residues or recycled dimethyl terephthalate (rDMT) residues.

[0085] The copolyester in the polymer matrix may contain and / or may be blended with one or more conventional additives in traditional amounts. Examples of additives include antioxidants, melt-strength enhancers, branching agents (e.g., glycerol, trimellitic acid, and anhydride), chain extenders (e.g., multifunctional isocyanates, multifunctional epoxides, and phenoxy resins), flame retardants, fillers, acid scavengers, dyes, colorants, pigments, antiblocking agents, flow enhancers, impact modifiers, antistatic agents, processing aids, mold release additives, plasticizers, slips, stabilizers, waxes, UV absorbers, optical brighteners, lubricants, pinning additives, foaming agents, nucleators, carbon black, crosslinked polystyrene beads, and the like. Colorants, sometimes referred to as toners, may be added to impart a desired neutral hue and / or brightness to the copolyester and the voided-shrink film. Examples of processing aids include calcium carbonate, talc, clay, mica, zeolites, wollastonite, kaolin, diatomaceous earth, TiO2, NH4CI, silica, calcium oxide, sodium sulfate, and calcium phosphate. Use of titanium dioxide and other pigments or dyes, may be included, for example, to control whiteness of the film or to make a colored film. An antistatic agent or other coating may also be applied to one or both sides of the film. Corona and / or flame treatment is also an option although not typically necessary because of the high surface tension of the voided-shrink film. The presence of voids and / or any additives may serve to block the transmission of UV light for applications with UV-sensitive products.Voiding Agent

[0086] The voiding agent comprises an organic polymer.

[0087] The organic polymer may be selected from propylene-based ionomers.

[0088] The term “propylene-based ionomer” refers to a propylene-based polymer that is an ionomer.

[0089] The terms “propylene-based polymer” and “polypropylene” are used interchangeably. They refer to a polymer that contains more than 50 mole percent of polymerized propylene monomer (based on the total amount of polymerizable monomers) and, optionally, may contain at least one comonomer. Propylene-based polymer includes propylene homopolymer and propylene copolymer (meaning units derived from propylene and one or more comonomers).

[0090] The term “ionomer” refers to a polymer having a combination of electrically neutral and neutralizable repeating units where the neutralizable component is a pendant group covalently bonded to the polymer backbone, and at least partially neutralized (“ionized”) with a cation. The neutralizable component typically contains a carboxylic acid group. Usually, no more than 15 mole percent (e.g., 1 to 15 mole%) of the repeating units are ionized or can be ionized.

[0091] The ionomer can be formed by methods known in the art, such as by grafting a neutralized monomer comprising a vinyl acid neutralized by a metal cation (e.g., zinc acrylate) to a polymer or copolymerizing the neutralized monomer with another monomer. Other methods include grafting or copolymerizing with a vinyl acid monomer and then neutralizing at least some of the monomer with a metal cation. Whether the ionomer is formed from grafting or copolymerizing with a neutralized monomer or with a vinyl acid monomer that is subsequently neutralized, the metal cation may comprise one or more of zinc, sodium, potassium, calcium, and aluminum; and the vinyl acid component may comprise acrylic acid or methacrylic acid. The vinyl monomer may also be a non-ionic vinyl ester, but this route would include additional reaction steps and would generate more byproducts to be removed. The grafting, copolymerization, and neutralization reactions can be carried out in an extruder, in solution, or in the solid state. Additional components such as initiators and / or catalysts may be added to facilitate the reactions.

[0092] In various embodiments, the propylene-based ionomer comprises a polypropylene homopolymer.

[0093] In various embodiments, the polypropylene homopolymer has a density of 0.895 to 0.930 g / cm3, of 0.895 to 0.925 g / cm3, of 0.895 to 0.920 g / cm3, of 0.895 to 0.915 g / cm3, or of 0.895 to 0.910 g / cm3.

[0094] In various embodiments, the polypropylene ionomer has a melt flow rate (MFR) of 0.1 to 10 g / 10 min, of 0.1 to 5 g / 10 min, or of 0.1 to 3 g / 10 min (230°C / 5 kg).

[0095] In various embodiments, the propylene-based ionomer comprises a transition metal ion.

[0096] In various embodiments, the propylene-based ionomer comprises zinc ions.

[0097] In various embodiments, the propylene-based ionomer comprises a polypropylene homopolymer and zinc ions.

[0098] In various embodiments, the propylene-based ionomer comprises a polypropylene homopolymer and zinc acrylate.

[0099] In various embodiments, the propylene-based ionomer comprises the reaction product of a polypropylene homopolymer and zinc acrylate.

[0100] In various embodiments, the ionomer has a molar ratio of acid equivalents to monomer units of 0.1 % to 5%, and a neutralization of acid equivalents of 10% to 100%.

[0101] In various embodiments, the voiding agent comprises a propylene-based polymer, zinc acrylate, and optionally, a polyethylene.

[0102] In various embodiments, the voiding agent comprises a polypropylene homopolymer, zinc acrylate, and optionally, a polyethylene (e.g., LDPE or LLDPE).

[0103] In various embodiments, the voiding agent comprises the reaction product of a polypropylene homopolymer, zinc acrylate, and optionally, a polyethylene (e.g., LDPE or LLDPE).

[0104] In various embodiments, the voiding agent comprises a melt-blended composition comprising a polypropylene homopolymer, zinc acrylate, and optionally, a polyethylene (e.g., LDPE or LLDPE).

[0105] In various embodiments, the polyethylene may be present in amounts up to 1 wt%, based on the weight of the voided-shrink film.

[0106] Suitable voiding agents may be obtained from VOID Technologies (USA) Limited (Wisconsin, US).

[0107] In various embodiments, the voiding agent is free of inorganic particles. Examples of inorganic particles as voiding agents include solid glass beads, metal spheres, ceramic beads, calcium carbonate, talc, silica, and hollow glass microspheres. Hollow microspheres may also be referred to as spheres, balls, bubbles, or microballoons.Process for Preparing Voided-Shrink Film

[0108] In another aspect, the invention provides a process for preparing the voidcontaining, heat-shrinkable film. The process comprises the steps of:(a) mixing the polymer matrix and the voiding agent together to form a dispersion of the voiding agent in the polymer matrix;(b) forming a film from the dispersion;(c) stretching the film from step (b) in at least one direction at or above the glass transition temperature of the polymer matrix; and(d) cooling the film from step (c) to obtain the void-containing, heat-shrinkable film.

[0109] The mixing step (a) may be carried out according to methods known in the art. For example, the voiding agent and the matrix copolyester may be dry-blended or melt- blended at a temperature at or above the Tg of the copolyester in a suitable mixing device (e.g., a single- or twin-screw extruder, a roll mill, a planetary mixer, or a Banbury mixer) to form a uniform dispersion of the voiding agent in the matrix copolyester.

[0110] The voiding agent may be introduced into the matrix copolyester in various ways, such as by direct addition or by masterbatch addition. Direct addition involves adding the voiding agent in undiluted form to the matrix copolyester followed by the filmforming step (b) without any intervening unit operations. Masterbatch addition involvesfirst diluting the voiding agent with a carrier resin to form a masterbatch (or concentrate). The masterbatch is then added to the matrix copolyester before the filmforming step (b). The carrier resin may be the same or different from the matrix copolyester.

[0111] In various embodiments, the voiding agent is undiluted before the mixing step(a).

[0112] In various other embodiments, the voiding agent is diluted with a carrier resin before the mixing step (a).

[0113] In the case of a masterbatch, the concentration of the voiding agent may be in the range of 40 to 80% by weight, or 50 to 70% by weight, based on the weight of the masterbatch.

[0114] The voiding agent may be in a solid, semi-solid, or molten form. It may be advantageous to add the voiding agent as a solid or a semi-solid to allow for rapid and uniform dispersion within the copolyester upon mixing.

[0115] The dispersion from step (a) may be passed directly to the film-forming step(b).

[0116] Alternatively, the dispersion may be formed into fully compounded compositions and then stored and / or transported for subsequent film-forming processing.

[0117] The film-forming step (b) may be carried out by any suitable method known in the art, such as extrusion, calendering, casting, and blowing. These methods initially create an unoriented film (or partially oriented in the case of blowing).

[0118] The unoriented film may have a thickness in the range of 100 to 400 pm.

[0119] The shape of the unoriented film is not restricted in any way. For example, it may be a flat film or in the form of a tube.

[0120] The unoriented film is subsequently stretched in at least one direction to impart orientation and to create the voids. Methods of unilateral or bilateral film orientation are well known in the art, such as the roll stretching method, the long-gap stretching method, the tenter-stretching method, and the tubular stretching method. Biaxiallyoriented films may be stretched sequentially, simultaneously, or some combination of simultaneous and sequential stretching.

[0121] Generally, the unoriented film may be stretched in the machine direction (MD) (i.e., the direction in which the film is produced on a film-making machine), the transverse direction (TD) (i.e., the direction perpendicular to the MD), or both at stretch ratios of 2X to 7X to create an oriented / stretched film. More typical stretch ratios include 4X to 6X.

[0122] The stretching step (c) can be performed using various devices known in the art, such as a double-bubble blown-film tower, a tenter frame, or a machine direction drafter.

[0123] The stretching step (c) is preferably performed at or above the glass transition temperature (Tg) of the polymer matrix. For example, the stretching temperature can range from Tg to Tg + 25°C, although this may vary slightly depending on the additives used.

[0124] The stretch rate may vary, for example, from 10 to 60 cm per second.

[0125] The stretching step (c) may be carried out in-line with the film-forming step (b) or in a subsequent operation.

[0126] The unoriented film can be stretched as a single film layer or can be coextruded with another polymer, such as PET, polyethylene, or polypropylene, as a multilayer film and then stretched.

[0127] The voids are formed around the voiding agent as the copolyester matrix is stretched at or above the Tg of the copolyester. Because of the incompatibility and other factors between the voiding agent and the copolyester matrix, the copolyester matrix separates from and slides over the voiding agent as it is stretched, causing voids to be formed in the direction or directions of stretch. The final size and shape of the voids depend on the direction(s) and amount of stretching. For example, if stretching is only in one direction, voids will form at the sides of the voiding agent in the direction of stretching. Typically, the stretching operation simultaneously forms the voids and orients the copolyester.

[0128] After stretching, the film may have a thickness in the range of 30 to 80 pm or 45 to 65 pm.

[0129] Following stretching, the oriented film is cooled to obtain the void-containing, heat-shrinkable film. The cooling step (d) may be carried out by any known manner, e.g., by contacting the film with cooled surfaces or with a cooling fluid, such as air and / or in a liquid bath.Sleeve or Roll-Fed Label

[0130] The voided-shrink films according to the invention are particularly useful as sleeves or roll-fed labels. These sleeves and labels may be applied to plastic bottles, such as those made of PET.

[0131] Thus, in another aspect, the invention provides a sleeve or roll-fed label comprising the voided-shrink films described herein.

[0132] The sleeves and labels may be prepared from the voided-shrink film according to methods known in the art.

[0133] Generally, to produce a commercial shrink label, the stretched film may be converted further into rolls of labels ready to be applied and shrunk onto a packaging container. These conversion steps include slitting, printing, seaming, perforating, sleeving, and shrinking.

[0134] The sleeves and labels may be conveniently seamed by methods known in the art, such as solvent bonding, adhesive bonding, pressure-sensitive adhesive bonding, hot-melt glue bonding, UV-curable adhesive bonding, radio frequency sealing, heat sealing, ultrasonic bonding, air-curable adhesive bonding, and dry-liquid adhesive bonding.

[0135] For traditional shrink sleeves involving transverse oriented film (via tentering or double bubble), the label may be first printed and then seamed along one edge to make a tube. Solvent seaming can be performed using any of a number of solvents or solvent combinations known in the art, such as THF, dioxylane, acetone, cyclohexanone, methylene chloride, n-methylpyrrilidone, and MEK. These solvents have solubilityparameters close to that of the film and serve to dissolve the film surface sufficiently for welding.

[0136] Other methods such as RF sealing, adhesive gluing, UV curable adhesive bonding, and ultrasonic bonding can also be used.

[0137] The resulting seamed tube is then cut and applied over the bottle prior to shrinking in a steam, infrared, or hot-air tunnel.

[0138] For roll-fed labels, the voided film is traditionally oriented in the machine direction using, for example, a drafter. These labels are wrapped around the bottle and typically glued in place in-line.Shrunk Film

[0139] In yet another aspect, the invention provides a heat-shrunk film.Compositionally, the heat-shrunk film is the same as the voided-shrink film of the invention. It contains (a) a polymer matrix comprising a copolyester and (b) a voiding agent dispersed in the polymer matrix, wherein the voiding agent comprises an organic polymer. The polymer matrix (a) and the voiding agent (b) are as described herein. But as its name suggests, the heat-shrunk film has been exposed to heat at or near the Tg of the polymer matrix and has reduced in size in at least one direction.

[0140] The heat-shrunk film has (i) a machine direction (MD) elongation at break of at least 200% at a test speed of 300 mm / min and a film thickness of 50-90 pm, and (ii) a film density of less than 1 g / cm3.

[0141] In various embodiments, the heat-shrunk film has an MD elongation at break of at least 250%, at least 300%, at least 350%, at least 400%, at least 450%, or at least 500%.

[0142] In various embodiments, the heat-shrunk film has a film density of 0.95 g / cm3or less, 0.90 g / cm3or less, 0.85 g / cm3or less, 0.80 g / cm3or less, 0.75 g / cm3or less, 0.70 g / cm3or less, or 0.65 g / cm3or less.

[0143] In various embodiments, the heat-shrunk film has a thickness of 50 to 90 pm.

[0144] In various embodiments, the heat-shrunk film has an MD tensile modulus of at least 400 MPa, at least 500 MPa, at least 600 MPa, at least 700 MPa, at least 800 MPa, at least 900 MPa, or at least 1 ,000 MPa.

[0145] For the avoidance of doubt, the heat-shrunk film according to the invention may be characterized by one or more of the foregoing properties, including MD elongation at break, film density, thickness, and MD tensile modulus.

[0146] In various embodiments, the voiding agent in the heat-shrunk film is free of inorganic particles.

[0147] In various embodiments, the heat-shrunk film is monolayer.

[0148] In various embodiments, the heat-shrunk film is multilayer.

[0149] In various embodiments, the heat-shrunk film comprises 20 to 40% by weight of the voiding agent, based on the total weight of the heat-shrunk film.

[0150] In various embodiments, the heat-shrunk film is in the form of a sleeve or roll- fed label.General Provisions

[0151] To remove any doubt, the present invention includes and expressly contemplates and discloses any and all combinations of embodiments, features, characteristics, parameters, and / or ranges mentioned herein. That is, the subject matter of the present invention may be defined by any combination of embodiments, features, characteristics, parameters, and / or ranges mentioned herein.

[0152] It is contemplated that any ingredient, component, or step that is not specifically named or identified as part of the present invention may be explicitly excluded.

[0153] Any process / method, apparatus, compound, composition, embodiment, or component of the present invention may be modified by the transitional terms “comprising,” “consisting essentially of,” or “consisting of,” or variations of those terms.

[0154] As used herein, the indefinite articles “a” and “an” mean one or more, unless the context clearly suggests otherwise. Similarly, the singular form of nouns includes their plural form, and vice versa, unless the context clearly suggests otherwise.

[0155] While attempts have been made to be precise, the numerical values and ranges described herein may be considered approximations. These values and ranges may vary from their stated numbers depending upon the desired properties sought to be obtained by the present disclosure as well as the variations resulting from the standard deviation found in the measuring techniques. Moreover, the ranges described herein are intended and specifically contemplated to include the endpoints, all sub-ranges, and discrete values within the stated ranges. For example, a range of 50 to 100 is intended to include all values within the range including sub-ranges such as 60 to 90, 70 to 80, etc.

[0156] Any two numbers of the same property or parameter reported in the working examples may define a range. Those numbers may be rounded off to the nearest thousandth, hundredth, tenth, whole number, ten, hundred, or thousand to define the range.

[0157] The content of all documents cited herein, including patents as well as nonpatent literature, is hereby incorporated by reference in their entirety. To the extent that any incorporated subject matter contradicts with any disclosure herein, the disclosure herein shall take precedence over the incorporated content.

[0158] This invention can be further illustrated by the following working examples, although these examples are included merely for purposes of illustration and are not intended to limit the scope of the invention.EXAMPLESMaterials

[0159] Embrace™ LV copolyester is a commercially available copolyester shrink film resin from Eastman Chemical Company. This resin has a density of 1 .30 g / cm3, a glass transition temperature (Tg) of 69°C, and an inherent viscosity of 0.70 dL / g. Table 1 andFigure 1 detail the typical property profile of shrink films produced with Embrace™ LV copolyester. The shrink film properties of this resin were generated as a control alongside the other examples and fall within typical ranges. This is comparative Example 1 .Table 1 - Typical Properties of Film Made of Embrace™ LV Cooolvester

[0160] The typical shrinkage properties of a shrink film made of Embrace™ LV resin are shown in Figure 2 where shrinkage was measured in the main shrinkage direction (TD direction) and in the direction orthogonal to the main shrinkage direction (MD direction) at temperatures ranging from 60 to 95°C.

[0161] VOID Technologies (USA) provided two concentrates containing a voiding agent. Concentrate 1 (C1 ) contained 60% by weight of an ionomer 1 (11 ) as the voiding agent and 40% by weight of Embrace™ LV resin as a carrier resin. 11 was a melt blend of 1.25% by weight of a 60 / 40 zinc acrylate / polyethylene masterbatch blend (wt / wt) and 98.75% by weight of a polypropylene homopolymer (density = 0.900 g / cm3, MFR = 1.8 g / 10 min (230°C / 2.16 kg)) (PP1 ). Concentrate 2 (C2) contained 60% by weight of an ionomer 2 (I2) as the voiding agent and 40% by weight of Embrace™ LV resin as a carrier resin. I2 was a melt blend of 2.5% by weight of a 60 / 40 zinc acrylate / polyethylene masterbatch blend (wt / wt) and 97.5% by weight of PP1 . The zinc acrylate / polyethylene masterbatch blend was obtained commercially.

[0162] 11 was prepared by melt blending the zinc acrylate / polyethylene masterbatch blend with PP1 in the reported amounts in an extruder at an extrusion temperature of 220°C. The melt blend was extruded through a die to obtain strands at a throughput rate of 80 Ibs / hr. Strands of 11 were then cooled and pelletized with a Gala underwater pelletizer to form 11 pellets.

[0163] C1 was prepared by melt blending 11 pellets with Embrace™ LV resin in the reported amounts in a twin-screw Coperion ZSK-26 extruder at an extrusion temperature of 200°C. The melt blend was extruded through a die to obtain strands at a throughput rate of 120 Ibs / hr. Strands of C1 were then cooled and pelletized with a Gala underwater pelletizer to form C1 pellets.

[0164] I2 was prepared by melt blending the zinc acrylate / polyethylene masterbatch blend with PP1 in the reported amounts in an extruder at an extrusion temperature of 250°C. The melt blend was extruded through a die to obtain strands at a throughput rate of 90 Ibs / hr. Strands of I2 were then cooled and pelletized with a Gala underwater pelletizer to form I2 pellets.

[0165] C2 was prepared by melt blending I2 pellets with Embrace™ LV resin in the reported amounts in a twin-screw Coperion ZSK-26 extruder at an extrusion temperature of 210°C. The melt blend was extruded through a die to obtain strands at a throughput rate of 80 Ibs / hr. Strands of C2 were then cooled and pelletized with a Gala underwater pelletizer to form C2 pellets.Testing Methods

[0166] Shrinkage was measured by placing a 50-mm by 50-mm square film sample in water at temperatures ranging from 65°C to 95°C for 10 seconds without restricting shrinkage in any direction. The percent shrinkage was then calculated by the following equation: % shrinkage = [(50 mm - length after shrinkage) / 50 mm] x 100. Shrinkage was measured in the direction orthogonal to the main shrinkage direction (machine direction, MD) and was also measured in the main shrinkage direction (transverse direction, TD). Negative shrinkage indicated growth.

[0167] Molecular weight (Mw) data was generated using gel permeation chromatography (GPC) following standard practices.

[0168] MD elongation at break and tensile modulus were measured using a method similar to ASTM D882-12. A test speed of 300 mm / min was used for the reported value. Shrunk film tensile data (modulus and MD elongation at break) were captured using the same method. Before the analysis, a stretched film was shrunk around a PET bottle with a typical shape to represent the shrunk labels from commercial applications. The film was shrunk using a heat gun.

[0169] Light transmittance values reported in Table 3 were generated using a BYK Haze-gard plus in transmission mode per standard protocols.

[0170] The reported density values were obtained using solvent blends and calibrated beads in a 1000-mL gradient tube. This density measurement technique was modeled after ASTM D1505-18. Similar values can be obtained by cutting samples of the produced film and placing it in a container filled with a solution of either NaCI and distilled water for densities >1 .0 g / cm3or isopropyl alcohol and distilled water for densities <1 .0 g / cm3. The solutions were prepared with a known amount of each component, and the final density was calculated using the standard practice of calculating density in these mixtures.

[0171] The density of the film sample can be inferred by observing whether the film floats on top, sinks to the bottom, or suspends in the middle of the mixture. Care should be taken to ensure that the film does not produce a false reading due to the presence of air bubbles. This method can be used in real-time to measure the density of the mixture during film production.

[0172] Surface roughness values were generated using optical profilometry. Optical profilometry was used to extract full three-dimensional topographical data from the surface. Surface roughness of films was analyzed using a Bruker Contour GT Optical Profilometer at three spots different spots in the respective film.

[0173] Shrink force was measured with a LabThink FST-02 Thermal Shrinkage Tester in MPa at 80°C.Film Making Procedure

[0174] To produce film, all of the resins were dried in a desiccant drier at 60°C overnight before extrusion. Film samples were produced using a 30:1 L / D air cooled extruder with 64-mm barrier screw. For multilayer samples, two 24:1 L / D air cooled satellite extruders (each with a 31 ,75-mm barrier screw) were used in combination with an ABC three-layer die. The skin layers of the multilayer samples were made of Embrace™ LV resin alone.

[0175] After extrusion, all films were uniaxially stretched by a factor of 1 .1x to 10x using a tenter frame (e.g., 4.5X-5.5X in the transverse direction in relation to the film extrusion). The films could also include a low level of orientation in the orthogonal direction of the main stretching direction. The production conditions are reported in Table 2.

[0176] After extrusion and tentering, typical properties related to the performance of a shrink label film were measured. TD and MD shrinkage, MD elongation at break, light transmittance, and density are the most common performance parameters for commercial applications of this invention. The methods for evaluating each are described above.

[0177] It should be noted that the density of the films changed rapidly within the first 3-4 hours after production due to the relaxation of the film. Changes in density within 4 hours have been measured at about 0.2 g / cm3and will vary slightly between films.More gradual changes to the density of the film has been observed over a 24-hour period, but film density remained relatively consistent after this point. All of the film density values reported below were generated 48 hours after production.

[0178] Table 2 below details the production conditions for each of the examples. All samples were blended with 0.5 wt% of a PETG-based anti-block additive in either a single skin layer of a multilayer film construction, or throughout the entire film in the case of the monolayer samples. That addition was not factored into the compositions below and was instead represented by the Embrace™ LV copolyester content. Thepercentages stated for the Embrace™ LV copolyester, the additive, and the final voiding agent represent the content in only the core layer in films that included skin layers. The annealing temperature, which was the third zone in the tenter oven, was always set slightly lower than the preceding preheat and stretch temperatures, but is not described below.Examples 1-8

[0179] Films 1-8 were prepared following the procedures described above.

[0180] Film 1 was an Embrace™ LV control film with no voiding additives.

[0181] Film 2 was made from a blend of C1 diluted with additional Embrace™ LV copolyester as a letdown resin.

[0182] Films 3-5 were made from blends of C2 diluted with additional Embrace™ LV copolyester as a letdown resin.

[0183] Film 6 was made from a blend of C2 diluted with an alternative copolyester (Embrace™ Encore), which is typically classified as a crystallizable PET (cPET) shrink film resin.

[0184] Film 7 was made from Embrace™ LV HY1000 resin, which is a blend of HY1000 concentrate and Embrace™ LV copolyester. This resin represents a commercially available light-blocking, white PETG shrink film sleeve solution. It has a different voiding agent than Films 2-6.

[0185] Film 8 was made from Embrace™ Float resin. This resin is a non-commercial PETG-based material that also targeted the production of a floatable, light-blocking white PETG film. It has a different voiding agent than Films 2-6.

[0186] Each film was tested for the most common performance parameters. The results are reported in Tables 3 and 4 below.Table 2 - Film Production Conditions= ComparativeTable 3 - Resulting Film Properties= ComparativeTable 4 - Additional Film Properties= Comparative

[0187] As seen in Table 4, inventive Examples 2-5 have much higher shrunk film MD elongation at break values than comparative Examples 6-8, indicating greater toughness. Additionally, Examples 2-5 have lower average surface roughness than Example 8 (Embrace™ Float technology), suggesting better printability. The average surface roughness of Examples 2-5 is on par with Example 7 (Embrace™ LV HY1000 technology). Furthermore, for films with skin layers, Examples 4-5 have higher MD tensile modulus values than Example 8, indicating greater stiffness.

[0188] The invention has been described in detail with particular reference to specific embodiments thereof, but it will be understood that variations and modifications can be made within the spirit and scope of the invention.

Claims

CLAIMS\Ne claim:1 . A void-containing, heat-shrinkable film comprising:(a) a polymer matrix comprising a copolyester; and(b) a voiding agent dispersed in the polymer matrix, wherein the voiding agent comprises an organic polymer, and wherein the film has:(i) a machine direction (MD) elongation at break of at least 200% at a test speed of 300 mm / min and a thickness of 30-80 pm; and(ii) a film density of less than 1 g / cm3.

2. The film according to claim 1 , wherein the MD elongation at break is at least 250%, at least 300%, at least 350%, at least 400%, at least 450%, at least 500%, or at least 550%.

3. The film according to any one of the preceding claims, wherein the film density is 0.95 g / cm3or less, 0.90 g / cm3or less, 0.85 g / cm3or less, 0.80 g / cm3or less, 0.75 g / cm3or less, 0.70 g / cm3or less, 0.65 g / cm3or less, 0.60 g / cm3or less, 0.55 g / cm3or less, 0.50 g / cm3or less, 0.45 g / cm3or less, or 0.40 g / cm3or less.

4. The film according to any one of the preceding claims, which has a transverse direction (TD) ultimate shrinkage of at least 60%, at least 65%, or at least 70%, after immersion in a 95°C water bath for 10 seconds.

5. The film according to any one of the preceding claims, which has a machine direction (MD) shrinkage of 5% or less, or 0% or less, after immersion in an 85°C water bath for 10 seconds.

6. The film according to any one of the preceding claims, which has a shrink force of 2 to 10 MPa.

7. The film according to any one of the preceding claims, which has a light transmittance of 50% or less, or 40% or less, or 30% or less, at a film thickness of 30-80 pm.

8. The film according to any one of the preceding claims, which has a thickness of 30 to 80 pm, or 45 to 65 pm.

9. The film according to any one of the preceding claims, which has an average surface roughness of 4 pm or less.

10. The film according to any one of the preceding claims, which has an MD tensile modulus of at least 400 MPa, at least 500 MPa, at least 600 MPa, at least 700 MPa, at least 800 MPa, at least 900 MPa, at least 1,000 MPa, or at least 1,100 MPa.11 . The film according to any one of the preceding claims, wherein the voiding agent is free of inorganic particles.

12. The film according to any one of the preceding claims, which is monolayer.

13. The film according to any one of claims 1-11 , which is multilayer.

14. The film according to claim 13, wherein at least one layer does not contain voids.

15. The film according to any one of the preceding claims, which comprises 20 to 40% by weight of the voiding agent, based on the total weight of the film.

16. The film according to any one of the preceding claims, wherein the polymer matrix further comprises a polyester homopolymer.

17. The film according to any one of the preceding claims, wherein the polymer matrix comprises two or more copolyesters.

18. The film according to any one of the preceding claims, wherein the polymer matrix comprises a copolyester comprising:(a) a diacid component comprising at least 90 mole percent of terephthalic acid residues; and(b) a diol component comprising (i) 60 to 90 mole percent of ethylene glycol residues and (ii) 10 to 40 mole percent of the residues of 1 ,4-cyclohexanedimethanol, neopentyl glycol, diethylene glycol, 1 ,4-butanediol, or combinations thereof, wherein the diacid component is based on 100 mole percent and the diol component is based on 100 mole percent.

19. The film according to claim 18, wherein the diol component comprises:(i) 0 to 32 mole percent of 1 ,4-cyclohexanedimethanol residues;(ii) 0 to 30 mole percent of neopentyl glycol residues;(iii) 0 to 15 mole percent of diethylene glycol residues; and(iv) 0 to 15 mole percent of 1 ,4-butanediol residues.

20. The film according to claim 19, wherein the diol component comprises:(i) 18 to 28 mole percent of 1 ,4-cyclohexanedimethanol residues;(ii) 0 to 15 mole percent of neopentyl glycol residues;(iii) 8 to 15 mole percent of diethylene glycol residues; and(iv) 0 to 15 mole percent of 1 ,4-butanediol residues.21 . The film according to any one of the preceding claims, wherein the organic polymer comprises a propylene-based ionomer.

22. A sleeve or roll-fed label which comprises the film according to any one of the preceding claims.

23. A process for preparing the film according to any one of claims 1-21 , the process comprising:(a) mixing the polymer matrix and the voiding agent together to form a dispersion of the voiding agent in the polymer matrix;(b) forming a film from the dispersion;(c) stretching the film from step (b) in at least one direction at or above the glass transition temperature of the polymer matrix; and(d) cooling the film from step (c) to obtain the void-containing, heat-shrinkable film.

24. The process according to claim 23, wherein the voiding agent is undiluted before the mixing step (a).

25. A heat-shrunk film comprising: a) a polymer matrix comprising a copolyester; and b) a voiding agent dispersed in the polymer matrix, wherein the voiding agent comprises an organic polymer, and wherein the heat-shrunk film has:(i) a machine direction (MD) elongation at break of at least 200% at a test speed of 300 mm / min and a film thickness of 50-90 g.m; and(ii) a film density of less than 1 g / cm3.

26. The heat-shrunk film according to claim 25, wherein the MD elongation at break is at least 250%, at least 300%, at least 350%, at least 400%, at least 450%, or at least 500%.

27. The heat-shrunk film according to any one of claims 25-26, wherein the film density is 0.95 g / cm3or less, 0.90 g / cm3or less, 0.85 g / cm3or less, 0.80 g / cm3or less, 0.75 g / cm3or less, 0.70 g / cm3or less, or 0.65 g / cm3or less.

28. The heat-shrunk film according to any one of claims 25-27, which has a thickness of 50 to 90 pm.

29. The heat-shrunk film according to any one of claims 25-28, which has an MD tensile modulus of at least 400 MPa, at least 500 MPa, at least 600 MPa, at least 700 MPa, at least 800 MPa, at least 900 MPa, or at least 1 ,000 MPa.

30. The heat-shrunk film according to any one of claims 25-29, wherein the voiding agent is free of inorganic particles.31 . The heat-shrunk film according to any one of claims 25-30, which is monolayer.

32. The heat-shrunk film according to any one of claims 25-30, which is multilayer.

33. The heat-shrunk film according to any one of claims 25-32, which comprises 20 to 40% by weight of the voiding agent, based on the total weight of the heat-shrunk film.

34. The heat-shrunk film according to any one of claims 25-33, wherein the polymer matrix further comprises a polyester homopolymer.

35. The heat-shrunk film according to any one of claims 25-34, wherein the polymer matrix comprises two or more copolyesters.

36. The heat-shrunk film according to any one of claims 25-35, wherein the polymer matrix comprises a copolyester comprising:(a) a diacid component comprising at least 90 mole percent of terephthalic acid residues; and(b) a diol component comprising (i) 60 to 90 mole percent of ethylene glycol residues and (ii) 10 to 40 mole percent of the residues of 1 ,4-cyclohexanedimethanol, neopentyl glycol, diethylene glycol, 1 ,4-butanediol, or combinations thereof, wherein the diacid component is based on 100 mole percent and the diol component is based on 100 mole percent.

37. The heat-shrunk film according to claim 36, wherein the diol component comprises:(i) 0 to 32 mole percent of 1 ,4-cyclohexanedimethanol residues;(ii) 0 to 30 mole percent of neopentyl glycol residues;(iii) 0 to 15 mole percent of diethylene glycol residues; and(iv) 0 to 15 mole percent of 1 ,4-butanediol residues.

38. The heat-shrunk film according to claim 37, wherein the diol component comprises:(i) 18 to 28 mole percent of 1 ,4-cyclohexanedimethanol residues;(ii) 0 to 15 mole percent of neopentyl glycol residues;(iii) 8 to 15 mole percent of diethylene glycol residues; and(iv) 0 to 15 mole percent of 1 ,4-butanediol residues.

39. The heat-shrunk film according to any one of claims 25-38, wherein the organic polymer comprises a propylene-based ionomer.

40. A sleeve or roll-fed label which comprises the heat-shrunk film according to any one of claims 25-39.

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