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WO2025193488A1 - Film de copolyester rétractable à cavitation présentant une réduction de densité et une ténacité améliorées - Google Patents

Film de copolyester rétractable à cavitation présentant une réduction de densité et une ténacité améliorées

Info

Publication number
WO2025193488A1
WO2025193488A1 PCT/US2025/018512 US2025018512W WO2025193488A1 WO 2025193488 A1 WO2025193488 A1 WO 2025193488A1 US 2025018512 W US2025018512 W US 2025018512W WO 2025193488 A1 WO2025193488 A1 WO 2025193488A1
Authority
WO
WIPO (PCT)
Prior art keywords
film
film according
mole percent
less
heat
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/US2025/018512
Other languages
English (en)
Inventor
Michael Gage Armstrong
Mark Allen Peters
Sara Elizabeth KUHN
James Carl Williams
Andrew Dennis BURTON
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Eastman Chemical Co
Original Assignee
Eastman Chemical Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Eastman Chemical Co filed Critical Eastman Chemical Co
Publication of WO2025193488A1 publication Critical patent/WO2025193488A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/18—Manufacture of films or sheets
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/36—Layered products comprising a layer of synthetic resin comprising polyesters
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
    • C08J2367/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2423/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2423/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
    • C08J2423/10—Homopolymers or copolymers of propene
    • C08J2423/14—Copolymers of propene

Definitions

  • 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.
  • 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.
  • PET polyethylene terephthalate
  • 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.
  • the PET recyclers collect the PET bottles for manufacturing recycled PET (rPET) for various applications.
  • 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.
  • 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 separated using a “sink/float” process. Depending upon their density, the shrink labels will float or sink.
  • 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.
  • 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.
  • 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/cm 3 .
  • the invention provides a process for preparing a voidcontaining, heat-shrinkable film.
  • the process comprises:
  • step (c) stretching the film from step (b) in at least one direction at or above the glass transition temperature of the polymer matrix
  • step (d) cooling the film from step (c) to obtain the void-containing, heat-shrinkable film.
  • 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/cm 3 .
  • Figure 1 shows the typical shrinkage properties of a heat-shrinkable film made with EmbraceTM LV copolyester.
  • Figure 2 shows the shrink curves of the films prepared in Examples 1-4.
  • Figure 3 shows the shrink curves of the films prepared in Examples 5-8.
  • 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.
  • 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.
  • polyester refers to a synthetic polymer prepared by the polycondensation of one or more difunctional carboxylic acids with one or more difunctional hydroxyl compounds.
  • the difunctional carboxylic acid is a dicarboxylic acid
  • the difunctional hydroxyl compound is a dihydric alcohol (such as glycols and diols).
  • 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).
  • 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.
  • a polyester containing 30 mole % of isophthalic acid 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.
  • a polyester containing 30 mole % of ethylene glycol 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.
  • copolyester refers a polyester made of two or more difunctional carboxylic acids, or two or more difunctional hydroxyl compounds, or both.
  • reduct means any organic structure incorporated into a polymer through a polycondensation reaction involving the corresponding monomer.
  • the term “repeating unit” means an organic structure having a dicarboxylic acid residue and a diol residue bonded through a carbonyloxy group.
  • the dicarboxylic acid residues may be derived from a dicarboxylic acid monomer or its associated acid halides, esters, salts, anhydrides, or mixtures thereof.
  • 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.
  • acid halides esters, half- esters, salts, half-salts
  • anhydrides mixed anhydrides, or mixtures thereof
  • 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.
  • 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.
  • 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.
  • voids are intended to be synonymous and refer to discrete areas of empty space within the polymer matrix.
  • the empty space may be occupied by a gas, such as air.
  • voided voided
  • microvoided void-containing
  • void-containing void-containing voids, microvoids, cavities, or micropores.
  • 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.
  • 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.
  • 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/cm 3 .
  • 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%.
  • the film density is 0.95 g/cm 3 or less, 0.90 g/cm 3 or less, 0.85 g/cm 3 or less, 0.80 g/cm 3 or less, 0.75 g/cm 3 or less, 0.70 g/cm 3 or less, 0.65 g/cm 3 or less, 0.60 g/cm 3 or less, 0.55 g/cm 3 or less, 0.50 g/cm 3 or less, 0.45 g/cm 3 or less, or 0.40 g/cm 3 or less.
  • 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.
  • TD transverse direction
  • 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.
  • MD machine direction
  • 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.
  • 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
  • the void-containing, heat-shrinkable film has a thickness of 30 to 80 pm, or 45 to 65 pm.
  • the void-containing, heat-shrinkable film has an average surface roughness of 4 pm or less.
  • 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.
  • 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.
  • 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.
  • the void-containing, heat-shrinkable film is monolayer.
  • 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.
  • the void-containing, heat-shrinkable film is multilayer and at least one layer does not contain voids.
  • the void-containing, heat-shrinkable film comprises 60 to 80% by weight of the polymer matrix, based on the total weight of the film.
  • the void-containing, heat-shrinkable film comprises 20 to 40% by weight of the voiding agent, based on the total weight of the film.
  • the voided-shrink film described herein represents a unique solution. It can provide a high-performing, inherently white shrink sleeve label for applications requiring the 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.
  • 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.
  • 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.
  • 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.
  • the polymer matrix comprises a copolyester.
  • the copolyester may be amorphous or semicrystalline, or blends thereof, with relatively low crystallinity.
  • the copolyester has a substantially amorphous morphology, meaning that the copolyester comprises substantially unordered regions of polymer.
  • 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-propaned
  • 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.
  • 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.
  • polyalkylene glycols examples include polytetramethylene glycol (PTMG) and polyethylene glycol (PEG) having molecular weights up to 2,000.
  • 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.
  • 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.
  • modifying dicarboxylic acids include succinic acid, glutaric acid, 1 ,3-cyclohexanedicarboxylic, adipic acid, suberic acid, sebacic acid, azelaic acid, dimer acid, and sulfoisophthalic acid.
  • the diacid component (A) comprises 0 mole percent of the residues of a modifying diacid.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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).
  • PET polyethylene terephthalate
  • PBT poly(butylene terephthalate)
  • PCT poly(cyclohexylenedimethylene terephthalate)
  • the polymer matrix comprises two or more copolyesters.
  • copolyesters examples include glycol-modified PET (PETG), glycol- modified poly(cyclohexylenedimethylene terephthalate) (PCTG), acid-modified poly(cyclohexylenedimethylene terephthalate) (PCTA), and diethylene glycol-modified PET.
  • PET glycol-modified PET
  • PCTG glycol-modified poly(cyclohexylenedimethylene terephthalate)
  • PCTA acid-modified poly(cyclohexylenedimethylene terephthalate)
  • diethylene glycol-modified PET examples include glycol-modified PET (PETG), glycol- modified poly(cyclohexylenedimethylene terephthalate) (PCTA), and diethylene glycol-modified PET.
  • PCTG glycol-modified poly(cyclohexylenedimethylene terephthalate)
  • PCTA acid-modified poly(cyclohexylenedimethylene terephthalate)
  • 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.
  • I.V. inherent viscosity
  • 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).
  • Tg glass transition temperature
  • the Tg may be determined using a TA DSC 2920 from Thermal Analyst Instrument at a scan rate of 20°C/min.
  • 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).
  • the copolyester may be obtained commercially from vendors such as Eastman Chemical Company (Kingsport, TN).
  • 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).
  • DMT dimethyl terephthalate
  • EG ethylene glycol
  • 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.
  • 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.
  • 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.
  • 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 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.
  • the copolyester in the polymer matrix comprises recycled content.
  • the copolyester in the polymer matrix comprises recycled ethylene glycol (rEG) residues.
  • the copolyester in the polymer matrix comprises recycled 1 ,4-cyclohexanedimethanol (rCHDM) residues.
  • the copolyester in the polymer matrix comprises recycled diethylene glycol (rDEG) residues.
  • the copolyester in the polymer matrix comprises recycled terephthalic acid (rTA) residues or recycled dimethyl terephthalate (rDMT) residues.
  • the copolyester in the polymer matrix may contain and/or may be blended with one or more conventional additives in traditional amounts.
  • 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.
  • branching agents e.g., glycerol, trimellitic acid, and anhydride
  • chain extenders e.g., multi
  • Colorants may be added to impart a desired neutral hue and/or brightness to the copolyester and the voided-shrink film.
  • 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.
  • the voiding agent comprises an organic polymer.
  • the organic polymer may be selected from propylene-based ionomers.
  • propylene-based ionomer refers to a propylene-based polymer that is an ionomer.
  • 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).
  • 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.
  • 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.
  • a metal cation e.g., zinc acrylate
  • Other methods include grafting or copolymerizing with a vinyl acid monomer and then neutralizing at least some of the monomer with a metal cation.
  • 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.
  • the propylene-based ionomer comprises a polypropylene homopolymer.
  • the polypropylene homopolymer has a density of 0.895 to 0.930 g/cm 3 , of 0.895 to 0.925 g/cm 3 , of 0.895 to 0.920 g/cm 3 , of 0.895 to 0.915 g/cm 3 , or of 0.895 to 0.910 g/cm 3 .
  • 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).
  • the propylene-based ionomer comprises a transition metal ion.
  • the propylene-based ionomer comprises zinc ions.
  • the propylene-based ionomer comprises a polypropylene homopolymer and zinc ions.
  • the propylene-based ionomer comprises a polypropylene homopolymer and zinc acrylate.
  • the propylene-based ionomer comprises the reaction product of a polypropylene homopolymer and zinc acrylate.
  • 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%.
  • the voiding agent comprises a polypropylene homopolymer, zinc acrylate, and optionally, a polyethylene (e.g., LDPE or LLDPE).
  • a polypropylene homopolymer e.g., LDPE or LLDPE.
  • the voiding agent comprises the reaction product of a polypropylene homopolymer, zinc acrylate, and optionally, a polyethylene (e.g., LDPE or LLDPE).
  • a polypropylene homopolymer e.g., LDPE or LLDPE.
  • Suitable voiding agents may be obtained from VOID Technologies (USA) Limited (Wisconsin, US).
  • the invention provides a process for preparing the voidcontaining, heat-shrinkable film.
  • the process comprises the steps of:
  • step (c) stretching the film from step (b) in at least one direction at or above the glass transition temperature of the polymer matrix
  • step (d) cooling the film from step (c) to obtain the void-containing, heat-shrinkable film.
  • the mixing step (a) may be carried out according to methods known in the art.
  • 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.
  • a suitable mixing device e.g., a single- or twin-screw extruder, a roll mill, a planetary mixer, or a Banbury mixer
  • 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 involves first 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.
  • the voiding agent is undiluted before the mixing step
  • the voiding agent is diluted with a carrier resin before the mixing step (a).
  • 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.
  • 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.
  • step (a) The dispersion from step (a) may be passed directly to the film-forming step
  • the dispersion may be formed into fully compounded compositions and then stored and/or transported for subsequent film-forming processing.
  • 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).
  • the unoriented film may have a thickness in the range of 100 to 400 pm.
  • the shape of the unoriented film is not restricted in any way.
  • it may be a flat film or in the form of a tube.
  • 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.
  • Biaxially oriented films may be stretched sequentially, simultaneously, or some combination of simultaneous and sequential stretching.
  • 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.
  • MD machine direction
  • TD transverse direction
  • More typical stretch ratios include 4X to 6X.
  • 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.
  • the stretching step (c) is preferably performed at or above the glass transition temperature (Tg) of the polymer matrix.
  • Tg glass transition temperature
  • the stretching temperature can range from Tg to Tg + 25°C, although this may vary slightly depending on the additives used.
  • the stretch rate may vary, for example, from 10 to 60 cm per second.
  • the stretching step (c) may be carried out in-line with the film-forming step (b) or in a subsequent operation.
  • 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.
  • another polymer such as PET, polyethylene, or polypropylene
  • 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.
  • 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.
  • the invention provides a sleeve or roll-fed label comprising the voided-shrink films described herein.
  • the sleeves and labels may be prepared from the voided-shrink film according to methods known in the art.
  • 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.
  • 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.
  • 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 solubility parameters close to that of the film and serve to dissolve the film surface sufficiently for welding.
  • the resulting seamed tube is then cut and applied over the bottle prior to shrinking in a steam, infrared, or hot-air tunnel.
  • the invention provides a heat-shrunk film.
  • 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.
  • 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/cm 3 .
  • MD machine direction
  • 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%.
  • the heat-shrunk film has a film density of 0.95 g/cm 3 or less, 0.90 g/cm 3 or less, 0.85 g/cm 3 or less, 0.80 g/cm 3 or less, 0.75 g/cm 3 or less, 0.70 g/cm 3 or less, or 0.65 g/cm 3 or less.
  • 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.
  • 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.
  • the voiding agent in the heat-shrunk film is free of inorganic particles.
  • the heat-shrunk film is monolayer.
  • the heat-shrunk film is multilayer.
  • the heat-shrunk film comprises 20 to 40% by weight of the voiding agent, based on the total weight of the heat-shrunk film.
  • the heat-shrunk film is in the form of a sleeve or roll- fed label.
  • 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.
  • 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.
  • EmbraceTM LV copolyester is a commercially available copolyester shrink film resin from Eastman Chemical Company. This resin has a density of 1 .30 g/cm 3 , a glass transition temperature (T g ) of 69°C, and an inherent viscosity of 0.70 dL/g. Table 1 and Figure 1 detail the typical property profile of shrink films produced with EmbraceTM 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 .
  • 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 EmbraceTM LV resin as a carrier resin.
  • Concentrate 2 contained 60% by weight of an ionomer 2 (I2) as the voiding agent and 40% by weight of EmbraceTM 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.
  • 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.
  • C1 was prepared by melt blending 11 pellets with EmbraceTM 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.
  • C2 was prepared by melt blending I2 pellets with EmbraceTM 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.
  • 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.
  • 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/cm 3 or isopropyl alcohol and distilled water for densities ⁇ 1 .0 g/cm 3 . 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.
  • 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.
  • Shrink force was measured with a LabThink FST-02 Thermal Shrinkage Tester in MPa at 80°C. Film Making Procedure
  • 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 EmbraceTM LV copolyester content. The percentages stated for the EmbraceTM 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.
  • Films 1-8 were prepared following the procedures described above.
  • Film 1 was an EmbraceTM LV control film with no voiding additives.
  • Film 2 was made from a blend of C1 diluted with additional EmbraceTM LV copolyester as a letdown resin.
  • Films 3-5 were made from blends of C2 diluted with additional EmbraceTM LV copolyester as a letdown resin.
  • Film 6 was made from a blend of C2 diluted with an alternative copolyester (EmbraceTM Encore), which is typically classified as a crystallizable PET (cPET) shrink film resin.
  • EmbraceTM Encore an alternative copolyester
  • cPET crystallizable PET
  • Film 7 was made from EmbraceTM LV HY1000 resin, which is a blend of HY1000 concentrate and EmbraceTM 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.
  • Film 8 was made from EmbraceTM 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.
  • 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 (EmbraceTM Float technology), suggesting better printability. The average surface roughness of Examples 2-5 is on par with Example 7 (EmbraceTM LV HY1000 technology). Furthermore, for films with skin layers, Examples 4-5 have higher MD tensile modulus values than Example 8, indicating greater stiffness.

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Abstract

L'invention concerne un film de copolyester thermorétractable à cavitation contenant un additif polymère organique et un procédé de production du film. Le film présente une combinaison unique de propriétés, comprenant une ou plusieurs caractéristiques parmi un retrait élevé, une faible densité, une opacité inhérente, une ténacité élevée et une teneur en non-contaminants dans le flux de recyclage de PET due à une densité de film rétracté finale de < 1,00 g/cm3. Le film est particulièrement utile pour préparer des étiquettes à manchon rétractable.
PCT/US2025/018512 2024-03-13 2025-03-05 Film de copolyester rétractable à cavitation présentant une réduction de densité et une ténacité améliorées Pending WO2025193488A1 (fr)

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