Use of an amorphous sulfonated copolyester resin to prepare an antifog film

Abstract

This invention relates to the use of an amorphous sulfonated copolyester resin to prepare an antifog film, especially useful for packaging food, and more particularly antifog films that can be used either as a single layer lidding film or the inner layer of a multi-layer lidding film (also referred to herein as a lidding laminate) for trays containing food or other products. The antifog film is clear by no longer than 25 hours after subjected to a test in which the film is used to contain water under refrigeration and the antifog film comprises less than an effective amount of an antifog additive. The antifog film is suitable for use as a single layer lidding film or the inner layer of a multi-layer lidding laminate for trays containing food. It may be extruded or applied after solvating. The lidding film is heat sealable.

Description

TITLE: USE OF AN AMORPHOUS SULFONATED COPOLYESTER RESIN TO PREPARE AN ANTIFOG FILMFIELD OF THE INVENTION

[0001] This invention relates to the use of an amorphous sulfonated copolyester resin to prepare an antifog film, especially useful for packaging food, and more particularly antifog films that can be used either as a single layer lidding film or the inner layer of a multi-layer lidding film (also referred to herein as a lidding laminate) for trays containing food or other products. The films may be made by extrusion or coextrusion or by solvating a copolyester in water and / or a co-solvent, applying that mixture to a web, then heating to volatilize the solvent and / or water. The antifog films are heat sealable. Such films and laminates are suitable for serving as lidding films for containers of a variety of materials, including polyethylene terephthalate (PET) (including amorphous polyethylene terephthalate (APET)), polylactic acid (PLA), polyhydroxyalkanoates (PHAs), polybutylene succinate (PBS), and recycled polyethylene terephthalate (rPET).BACKGROUND OF THE INVENTION

[0002] When a food product containing water is packed in a tray and displayed at a store front or the like at low temperature with a surface of the tray wrapped with a plastic film, fog often forms on the plastic film on the side facing the food product. This is particularly the case when the food product has a high water content. The fog on the inner surface of the wrapping film facing the food product results from the aggregation of tiny water vapors. Obstructing the visibility of the contents of the wrapped products through the wrapping film is disfavored by consumers.

[0003] A refrigerated food tray will have a perimeter lip extending above the stored food item so that the plastic film covering the top of the tray does not touch most of or any of the packaged food. In this arrangement, the consumer may see clearly through the plastic wrap to view the food item stored in the package.

[0004] Accordingly, various attempts have been proposed to prevent fog generation on a plastic film on the side facing a food product. One approach involves dispersing one or more antifog agents in the plastic film resin during processing of the film. Once in the film resin, the antifog agent tends to migrate to the surface of the film and raise the surface tension of the film. As a result, water on the inner side of the film tends to form a relatively continuous film- like, transparent sheet of water rather than a fog.

[0005] US 2014 / 0329015 discloses the use of an antifog, peelable film. The film includes an antifog layer containing an effective amount of one or more antifog agents. The layer may be applied to a surface of a heat seal layer. The antifog layer is typically applied to the food side of the film on a surface of the heat seal layer not only to save cost in coating material, but also to avoid coating the non-food side of the film with an agent that may reduce the adhesion of the ink that may be printed on the non-food side. The antifog agent is preferably applied to an amorphous polyester layer of a coextruded polyester film. The antifog agent may adhere more strongly to an amorphous polyester layer than to a plain polyester film, thereby permitting the film to be peelable from the container.

[0006] As with US 2014 / 0329015, many current antifog coatings require additional (often hydrophilic) additives to the coating composition that can impart the antifog capability. Such additives are typically not chemically reacted into the polymer backbone, utilized instead by functional end groups of the polymer or as a surface-active agent. This can cause issues for insufficient blooming of the additive or lessened durability of the antifog ability. These additives can also lessen the heat seal strength of the coating in question when their loading becomes too high.

[0007] US 2009 / 123767 Al (DU PONT) describes a sulfonated aliphatic-aromatic copolyester, which can be used in food packaging, especially for fast food packaging. The films of the sulfonated aliphatic-aromatic copolyesters used as wraps are presented as providing a good balance of physical properties, including paper-like stiffness combined with sufficient toughness, good deadfold characteristics, grease resistance, and a moisture barrier while not allowing for moisture to condense onto a food item wrapped therein, for example toavoid for moisture to condense onto the food. The copolyester is presented as having a set of properties, including the ability to prevent moisture from forming on the food, inside the wrap, or on the outside surface of a cup or container. However, the document does not describe the use of the material for its antifogging properties, i.e., properties that prevent the formation of visible droplets (fog) on the transparent or semi-transparent surface of the film.

[0008] US 2023 / 383154 Al (BOSTIK) describes a method of adhering substrate surfaces together in the absence of heat, using a cold seal adhesive which is based on an amorphous copolyester resin comprising the reaction product of (a) at least two diols comprising ethylene glycol and (b) at least three diacids or diesters comprising: (i) at least one sulfomonomer, (ii) at least one aromatic diacid or diester and (iii) at least one aliphatic diacid or diester. However, the document does not describe the use of such copolyester resin as a material having antifog properties.SUMMARY OF THE INVENTION

[0009] In order to meet at least some of the needs described herein, the present invention provides the use of an amorphous sulfonated copolyester resin to prepare an antifog film, wherein the copolyester resin comprises the reaction product of:(i) a first diacid or diester comprising at least one sulfomonomer at a mole fraction of at least about 0.02, preferably at least about 0.03, more preferably at least about 0.05, more preferably at least about 0.06, more preferably at least about 0.08, and most preferably at least about 0.09, based on the total moles of diacids and diesters;(ii) a second diacid or diester comprising at least one aromatic diacid or diester at a mole fraction at least about 0.25, preferably at least about 0.30, more preferably at least about 0.35, and most preferably at least about 0.4 based on the total moles of diacids and diesters; and(iii) at least one diol comprising at least one aliphatic diol, wherein the antifog film comprises less than an effective amount of an antifog additive, preferably less than 1 wt.% of the antifog additive, more preferably less than 0.5 wt.% of the antifog additive, morepreferably less than 0.1 wt.% of the antifog additive, based on the total weight of the film, more preferably no more than trace amounts of the antifog additive, more preferably essentially no antifog additive, and most preferably no antifog additive.

[0010] The present invention also provides a process for reducing fog on a film wherein the film comprises the amorphous copolyester resin described herein or the composition described herein.

[0011] The present invention also provides a process for sealing a container (and simultaneously imparting antifog properties to a lidding film), wherein the container has a rim defining an opening, the process comprising the step of applying the lidding film obtained by the processes described herein to the rim of the container to seal the container, thereby providing antifog properties to the lidding film.

[0012] It has been found that utilizing sulfonated copolyester eliminates the need for additional additives to exhibit antifog ability, as the manufactured coating is inherently sufficiently hydrophilic in nature. This approach also allows the sealing function of the copolyester heat seal resin to remain unaffected. Several of the above prior art examples require coextrusion or multi-layer films to make an antifog coating that also is capable of being used as a heat seal, whereas products utilizing the present invention may consist of only a single layer coating with similar capabilities as the multi-layer films of the prior art. In other words, the single layer of the invention may serve as both a heat seal layer and an antifog layer; no separate antifog layer needs to be bonded to or no antifog agent needs to be coated on the layer of the invention; the single layer is sufficient to provide the expected antifog properties.BRIEF DESCRIPTION OF THE DRAWING

[0013] FIG. 1-4: Charts showing 180-degree peel force between various substrates heat sealed by copolyester resins at 107°C, 135°C, 163°C, and 177°C.

[0014] FIG. 1 shows the results for resin of Example 1A, FIG. 2 shows the results for resin of Example 2, FIG. 3 shows the results for resin of Example 3, and FIG. 4 shows the results for resin of Example CE1.DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention may be understood more readily by reference to the following detailed description of certain embodiments of the invention and the working examples.Definitions

[0016] As used herein, "comprising" is synonymous with "including," "containing," or "characterized by," and is inclusive or open-ended and does not exclude additional, unrecited elements or process steps. As used herein, "consisting of" excludes any element, step, or ingredient not specified in the claim element. As used herein, "consisting essentially of" does not exclude materials or steps that do not materially affect the basic and novel characteristics of the claim. In each instance herein any of the terms "comprising", "consisting essentially of" and "consisting of" may be replaced with either of the other two terms.

[0017] As used herein, the terms “process” and “method” are used interchangeably.

[0018] In the present application:- the expression “comprised between ... and ...” should be understood as including the limits;- any description, even though described in relation to a specific embodiment, is applicable to and interchangeable with other embodiments of the present invention;- where an element or component is said to be included in and / or selected from a list of recited elements or components, it should be understood that in related embodiments explicitly contemplated here, the element or component can also be any one of the individual recited elements or components, or can also be selected from a group consisting of any two or more of the explicitly listed elements or components; any element or component recited in a list of elements or components may be omitted from such list; and- any recitation herein of numerical ranges by endpoints includes all numbers subsumed within the recited ranges as well as the endpoints of the range and equivalents.

[0019] The term “mole fraction” as used herein refers to the ratio of the number of moles of a component to the total number of moles of all components in the mixture. For example, in the context of a first diacid or diester comprising at least one sulfomonomer, the mole fraction is the number of moles of sulfomonomer relative to the total number of moles of diacids and diesters in the mixture. Unless otherwise noted, all references to mole fractions of particular monomers (e.g., diacids, diesters) are based on the number of moles of that particular diacid or diester charged (before any reaction) based on the total number of moles of diacids or diesters charged, and all references to mole fractions of particular diols are based on the number of moles of that particular diol charged (before any reaction) based on the total number of moles of diols charged, regardless of whether the term “reaction product” or “residue” is used to identify such monomers.

[0020] As used herein, the term “about” in reference to a number or range of numbers refers to the stated number and numbers + / - 10% thereof, or 10% below the lower listed limit and 10% above the higher listed limit for the values listed for a range. For example, "about 40 mol.%" means 36-44 mol.%, inclusive

[0021] The term “(co)polyester” as used herein refers to a synthetic polymer prepared by the reaction of one or more difunctional carboxylic acids or esters (i.e., diacids or diesters) with one or more difunctional hydroxyl compounds (i.e., diols), and is generic to both polyesters and copolyesters. The term “polyester” as used herein refers to the reaction product of one diacid or diester with one diol, whereas the term “copolyester” as used herein refers to the reaction product of multiple diacids or diesters with one diol, multiple diols with one diacid or diester, or multiple diacids or diesters with multiple diols. While the term “copolyester” refers to a polymer prepared by the reaction of the different monomers, the term “resin” or “copolyester resin” as used herein refers to the material form of the copolyester, which may be supplied in various forms (including beads, pellets or granules). The resin maythen be processed into final products, such as the antifog film of the invention. The terms “copolyester” and “copolyester resin” may be used interchangeably herein.

[0022] The term “reaction product” as used herein refers to any product of an esterification or transesterification reaction of any of the monomers used in preparing the copolyester, including an oligomer or the final copolyester, reacted to certain intrinsic and / or melt viscosities. The term “residue” as used herein includes a monomer formed in situ by the reaction of other monomers which may become part of the copolyester backbone. Typically, the relative amounts of the monomer residues in the copolyester product are the same as or very similar to the relative amounts of the monomers used in the charge to prepare the copolyester. In some conditions, however, other monomers are formed during the production of the copolyester and such formed monomers may become part of the final product. When ethylene glycol is used, for example, some amount of diethylene glycol is often formed in situ and its residue may become part of the copolyester backbone, as is known in the art. In particular, the amount of diethylene glycol formed when ethylene glycol is used as a charged monomer may vary between about 0 mol.% to about 40 mol.% or between about 2.5 mol.% to about 30 mol.%. While a higher amount of diethylene glycol versus ethylene glycol tends to reduce the copolyester resin’s heat resistance (e.g., softening point, melting point, and glass transition temperature), it has been found that the presence of diethylene glycol in the copolyester prepared herein does not significantly impact the antifog performance of the film of the invention described herein.

[0023] Unless otherwise indicated herein, the glass transition temperature values provided herein are determined in accordance with ASTM E1356-08 using DSC. As is known in the art, glass transition temperature values are obtained and reported herein as the values obtained upon the second heat of the sample.

[0024] Heat of fusion values provided herein are determined according to ASTM E793-01 “Standard Test Method for Enthalpies of Fusion and Crystallization by Differential Scanning Calorimetry,” except with one modification to the test in that a scanning temperature of 15 °C per minute instead of 10°C per minute was used. As is known in the art,heat of fusion values are obtained and reported herein as the values obtained upon the first heat of the sample.

[0025] As used herein, “amorphous” copolyester resins are those resins which are glassy and transparent. They do not have a definite molecular arrangement as the structure is very randomized and intertwined. Based on the glass transition temperature, they can be either tacky or brittle at room temperature. Amorphous copolyester resins do not have any crystallinity and melting point as determined by DSC or equivalent technique and therefore have an enthalpy of fusion of zero. The copolyester resins of the invention are stably amorphous, meaning that they do not develop any significant crystalline domains (or any at all) after storage at room temperature for a week. It should be noted that the antifog film described herein may consist solely of one or more amorphous copolyester resins or it may also contain a semicrystalline or crystalline copolyester resin in an amount such that, upon solvating or thermal setting done during extrusion, any crystalline domains are interrupted such that the blend becomes amorphous. As is well-known, crystallinity is due to the orientation of polymer chains. Upon solvating or such thermal setting, chains of a single grade may become unassociated with those same chains, thus interrupting any crystallinity and making the whole blend amorphous. Grades of copolyester resins herein that will be extruded would be made up entirely of amorphous copolyester resins.

[0026] Unless otherwise indicated herein, intrinsic viscosity values provided herein are determined in accordance with ASTM D5225-14.

[0027] Unless other indicated herein, Thermosel viscosity (which is the same as melt viscosity) is determined in accordance with ASTM method D3236-15 at 215°C.

[0028] Unless otherwise indicated herein, melt flow index values provided herein are determined in accordance with ASTM D1238-20 at a temperature of 190°C and using a weight of 2.16 kg.

[0029] Unless otherwise indicated herein, the softening point values provided herein are determined in accordance with ASTM D36 using mineral oil.

[0030] The term “antifog additive,” also known as antifog or antifogging agents and treatments, as used herein refers to chemical compounds that prevent the condensation of water in the form of small droplets on a surface which resemble fog and is not a reactant used in forming the copolyester used herein. Antifog additives known in the art that can be used as a component of an antifog layer may comprise esters of aliphatic alcohols, polyethers, polyhydric alcohols, esters of polyhydric aliphatic alcohols, polyethoxylated aromatic alcohols, nonionic ethoxylates, hydrophilic fatty acid esters, and combinations thereof. Specific antifog additives may for example comprise polyoxyethylene, sorbitan monostearate, polyoxyethylene sorbitan monolaurate, polyoxyethylene monopalmitate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan trioleate, poly (oxypropylene), polyethoxylated fatty alcohols, polyoxyethylated 4-nonylphenol, polyhydric alcohol, propylene diol, propylene triol, ethylene diol, monoglyceride esters of vegetable oil or animal fat, mono- and / or diglycerides such as glycerol mono- and dioleate, glyceryl stearate, monophenyl polyethoxylate, sorbitan monolaurate, or combinations thereof.

[0031] As used herein, the test used to assess the antifog properties of the films, also called “Antifog Test”, involves first applying the solvated coatings to 92-gauge polyethylene terephthalate (“PET”) at a coating weight of between 1.5 and 6.5 g / m2to form a lidding laminate. The antifog test is carried out by heat-sealing, using a hot press at 150°C, the lidding laminate over a PET container with a volume of approximately 236.6 mL (8-ounce) with the coating of the copolyester resin or blend of the examples at the innermost layer of the lidding laminate relative to the interior of the container. Before heat-sealing, the container was charged with 20 g of water at 20°C at ambient relative humidity. The sealed container was stored at a cooling temperature of 3°C immediately after heat-sealing. Upon sealing, the lidding laminate was typically foggy and not clear. The time after sealing when the lidding laminate sealing the PET container according to the Antifog Test first becomes clear is referred to herein as the “Antifog Time.”

[0032] The term “lidding laminate” as used herein refers to the film structure designed for sealing trays or containers, often used in packaging applications such as food storage. Ittypically consists of an inner layer, which provides specific functional properties (e.g., antifogging), and additional layers that may enhance mechanical strength, barrier properties, or printability. In the context of the provided example, the antifog film serves as the inner layer of the lidding laminate, ensuring clear visibility of the packaged contents while maintaining a secure seal over the tray. The lidding laminate may be a single layer lidding laminate or a multi-layer lidding laminate.

[0033] The container was observed until the film became visually clear or, simply referred to as “clear” herein. A “visually clear” film as used herein refers to a film having a diffuse transmittance value of 40% or greater. An "opaque film’” or a "cloudy film” as used herein refers to a film having a diffuse transmittance value of less than 40%. The films prepared from the copolyesters described herein are characterized by a novel combination of properties which preferably include having a visual clearness or clarity and having a diffuse transmittance value of greater than 40%, preferably, greater than 60%, or even more preferably, greater than 80%, as determined by ASTM Method D1003. These observations were done in daylight with a human eye having normal (i.e., 20 / 20) vision (or corrected to normal vision) but with no magnification.Use of the copolyester resin

[0034] The present invention relates to the use of an amorphous sulfonated copolyester resin to prepare an antifog film, or in other words, it relates to the use of such copolyester resin to prepare a film with antifog properties.

[0035] The copolyester resin used herein comprises at least one amorphous copolyester resin comprising the reaction product of:(i) a first diacid or diester comprising at least one sulfomonomer at a mole fraction of at least about 0.02, preferably at least about 0.03, more preferably at least about 0.05, more preferably at least about 0.06, more preferably at least about 0.08, and most preferably at least about 0.09, based on the total number of moles of diacids and diesters;(ii) a second diacid or diester comprising at least one aromatic diacid or diester at a mole fraction at least about 0.25, preferably at least about 0.30, more preferably at least about 0.35,and most preferably at least about 0.4, based on the total number of moles of diacids and diesters; and(iii) at least one diol comprising at least one aliphatic diol.

[0036] According to the present invention, the antifog film comprises less than an effective amount of an antifog additive, preferably less than 1 wt.% of the antifog additive, more preferably less than 0.5 wt.% of the antifog additive, more preferably less than 0.1 wt.% of the antifog additive, based on total weight of the film, more preferably no more than trace amounts of the antifog additive, more preferably essentially no antifog additive, and most preferably no antifog additive.

[0037] The antifog film described herein may preferably have an Antifog Time of no longer than 25 hours, preferably at no longer than 15 hours, preferably no longer than 10 hours, and most preferably no longer than about 7 hours of storage. The Antifog Time is determined by the Antifog Test, described herein. In short, the test involves heat-sealing (using a hot press at 150°C) a container with a film to be tested, wherein the container is made of polyethylene terephthalate (PET), has a volume of approximately 236.6 mF (8-ounce), and contains 20 g of water filled at 20°C at ambient relative humidity, then storing the sealed contained at a cooling temperature of 3°C immediately after heat-sealing.

[0038] The sulfomonomer (i) is difunctional and is a dicarboxylic acid or ester thereof containing a metal sulfonate group or a glycol containing a metal sulfonate group or a hydroxy acid containing a metal sulfonate group. The cation of the sulfonate salt may be NH4, or a metal ion, such as Li+, Na+, K+, Mg++, Ca++, Cu++, Ni++, Fe++, or Fe+++. Preferred are monovalent cations, such as NH4+, Ei+, Na+, and K+, when stability in water is desired. Preferably, the sulfomonomer contains a -SO3M group attached to an aromatic nucleus, wherein M is hydrogen, NH4, or a metal ion. The difunctional monomer component may be either a dicarboxylic acid or a diol adduct containing a -SO3M group. In preferred embodiments, the sulfomonomer is aromatic. Preferably, the sulfomonomer comprises at least one of dimethyl 5-sulfoisophthalate sodium, 5-sulfoisophthalic acid, or sodium sulfo succinate. Preferably, the sulfomonomer is selected from the group consisting of dimethyl 5-sulfoisophthalate sodium, 5- sulfoisophthalic acid, sodium sulfo succinate and combinations thereof. Preferably, the sulfomonomer is dimethyl-5-sulfoisophthalate.

[0039] The at least one aromatic diacid or diester (ii) may comprise at least one of dimethyl terephthalate, terephthalic acid, isophthalic acid, dimethyl isophthalate or dimethyl 2,6-naphthalene dicarboxylate. Preferably, it is selected from the group consisting of dimethyl terephthalate, terephthalic acid, isophthalic acid, dimethyl isophthalate, dimethyl 2,6- naphthalene dicarboxylate, and combinations thereof.

[0040] The amorphous copolyester resin may further comprise residues of a third diacid or diester comprising at least one aliphatic diacid or diester at a mole fraction of at least about 0.25, preferably at least about 0.30, more preferably at least about 0.35, and most preferably at least about 0.4, based on the total number of moles of diacids and diesters. As noted above, even though in some places herein, certain monomers are referred to as “residues,” the mole fraction is based on the number of moles of the monomer charged (i.e., the number of moles of the third diacid or diester charged divided by the total number of moles of diacids and diesters charged); it is not intended to refer to the bound ratios of the monomer residues. Preferably, the third aliphatic diacid or diester comprises at least one of azelaic acid or sebacic acid. Preferably, it is selected from the group consisting of azelaic acid, sebacic acid, and combinations thereof.

[0041] The aliphatic diol (iii) may be present at a mole fraction of at least about 0.7, more preferably at least about 0.8, and most preferably at least about 0.9, and at most 1, more preferably at most about 0.98, and most preferably at most about 0.95, based on the total number of moles of diacids or diesters. The aliphatic diol may comprise at least one of ethylene glycol, diethylene glycol, neopentyl glycol or 1,4-cyclohexanedimethanol. The aliphatic diol may be selected from the group consisting of ethylene glycol, diethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol, and combinations thereof. The aliphatic diol may consist of ethylene glycol, diethylene glycol, neopentyl glycol, and, optionally, 1,4- cyclohexanedimethanol. The aliphatic diol may comprise ethylene glycol and diethylene glycol, or it may consist solely of either ethylene glycol or diethylene glycol. Preferably,ethylene glycol may be present at a mole fraction of at least about 0.2, more preferably at least about 0.4, and most preferably at least about 0.6, and at most about 0.85, preferably at most about 0.8, and most preferably at most about 0.75, based on the total number of moles of ethylene glycol. Also preferably, diethylene glycol may be present at a mole fraction of at least about 0.05, more preferably at least about 0.1, and most preferably at least about 0.15, and at most about 0.5, preferably at most about 0.4, and most preferably at most about 0.35, based on the total number of moles of diols.

[0042] The hydroxyl-functional monomers used to make amorphous copolyester resin of the invention may primarily be diols, with diols being the major type of monomers used, or they may exclusively be diols, with diols being the only monomers used.

[0043] The amorphous copolyester resin may comprise residues of triols or higher hydroxyl functional monomers at a mole fraction of at most about 0.20, preferably at most about 0.15, more preferably at most about 0.1, and most preferably at most about 0.05, based on the total number of moles of hydroxyl-functional monomers (i.e., including diols, triols, and higher hydroxyl-functional monomers).

[0044] The amorphous copolyester resin may be such that, based on the total number of moles of diacids or diesters:- the at least one sulfomonomer (i) is present at a mole fraction of at least about 0.05, preferably at least about 0.06, and more preferably at least about 0.08, and at most about 0.2, preferably at most about 0.18, and more preferably at most about 0.15 based on the total number of moles of diacids or diesters;- the at least one aromatic diacid or diester (ii) is present at a mole fraction of at least about 0.25, preferably at least about 0.3, and more preferably at least about 0.33, and at most about 0.6, preferably at most about 0.55, and more preferably at most about 0.5 based on the total number of moles of diacids or diesters;- it further comprise residues of a third diacid or diester comprising at least one aliphatic diacid or diester at a mole fraction of at least about 0.25, preferably at least about 0.30, andmore preferably at least about 0.35, and at most about 0.65, preferably at most about 0.6, and more preferably at most about 0.57, based on the total number of moles of diacids or diesters.

[0045] It has been found that certain copolyester resins of this composition range show an antifog effect immediately upon running the Antifog Test as described herein and maintain antifog effectiveness for at least three weeks.

[0046] The amorphous copolyester resin may have a Tg in accordance with ASTM E1356-08 of at least about -40°C, preferably at least about -35°C, more preferably at least about -30°C and / or at most about 100°C, preferably at most about 90°C, more preferably at most about 85°C.

[0047] The amorphous copolyester resin may have an intrinsic viscosity determined in accordance with ASTM D5225-14 of between about 0.2 dL / g to about 0.6 dL / g, preferably between about 0.25 dL / g and about 0.55 dL / g.

[0048] The amorphous copolyester resin may have a Thermosel (or melt) viscosity determined in accordance with ASTM method D3236-15 at 215°C of between about 25 Pa.s and about 1,000 Pa.s, preferably between about 50 Pa.s and about 750 Pa.s.

[0049] The amorphous copolyester resin may have a melt flow index determined in accordance with ASTM D1238-20 at a temperature of 190°C and using a weight of 2.16 kg. of between about 2 g / 10 min to about 250 g / 10 min, preferably between about 10 g / 10 min and about 150 g / 10 min.

[0050] The amorphous copolyester resin may have a softening point determined in accordance with ASTM D36 using mineral oil of between about 75°C to about 200°C, preferably between about 100°C and about 185°C.

[0051] The films or laminates describe herein have also been found to have low haze. Having a low haze is desirable so that consumers can easily see through the laminate to view the product within the sealed container. Preferably, the haze of the laminate, as determined in accordance with ASTM D1003, is less than about 1%, preferably below about 0.7%, more preferably below about 0.5%, and most preferably below about 0.2%.

[0052] The present invention also relates to the method of using the copolyester described above to prepare such a film.Process for preparing the amorphous copolyester

[0053] The process for preparing the copolyester used in the present invention is not limited. It may for example involve a transesterification or a direct esterification. The copolyesters used in the present invention typically can be prepared from diacids or diesters and diols which react in substantially equal proportions and are incorporated into the copolyester polymer as their corresponding residues. The diols may be added in excess, as unreacted diols may be more easily evaporated than unreacted diacids or diesters. Alternatively, the copolyesters described herein may contain substantially equal molar proportions of diacid or diester residues and diol residues.

[0054] Suitable processes include, but are not limited to, the steps of reacting one or more dicarboxylic acids with two or more diols at a temperature of 100°C to 315°C at a pressure of 0.1 to 760 mm Hg for a time sufficient to form a polyester. US 3,772,405, incorporated herein by reference, notably describes a process for making the copolyester resin, wherein the process comprises: (I) heating a mixture comprising the selected monomers useful in any of the copolyesters of the invention in the presence of a catalyst at a temperature of 150°C to 255°C for a time sufficient to produce an initial polyester; (II) heating the initial polyester of step (I) at a temperature of 240°C to 320° C for 1 to 4 hours; and (III) removing any unreacted glycols.

[0055] Suitable catalysts for use in this process include, but are not limited to, organo- zinc, titanium, or tin compounds, although organo-tin compounds are not preferred for food packaging applications. The use of this type of catalyst is well-known in the art. Examples of catalysts useful in the present invention include, but are not limited to, zinc acetate dihydrate, butyl tin tris-2-ethylhexanoate, dibutyltin diacetate, titanium (IV) 2-ethylhexyloxide, titanium (IV) butoxide and / or dibutyltin oxide. Other catalysts may include, but are not limited to, those based on manganese, lithium, germanium, and cobalt. Catalyst amounts may range from 10 ppm to 20,000 ppm or 10 to 10,000 ppm, or to 5,000 ppm or 10 to 1,000 ppm or 10ppm to 500 ppm, or 10 ppm to 300 ppm or 10 ppm to 250 ppm, based on the weight of the final polymer. The process may be carried out in either a batch or continuous process. In embodiments of the invention, the reaction is continued until the product has a desired viscosity, which may be determined by stopping the reaction using methods, for example by stopping the vacuum and heat.Compositions for forming the antifog film

[0056] The compositions for forming the antifog film comprise the sulfonated copolyester, or sulfonated copolyester resin, described herein. They may optionally contain one or more additives, such as additives conventionally used in the manufacture of polymeric films. Examples of such additives are pigments, lubricants, anti-oxidants, free radical scavengers, UV absorbers, thermal stabilizers, anti-blocking agents, surface active agents, slip aids, optical brighteners, gloss improvers, and viscosity modifiers, among other additives.Preferably, none of these additives adversely impact the clarity of the film.

[0057] The compositions may comprise less than an effective amount of an antifog additive, as defined herein. Preferably, they comprise less than 1 wt.% of the antifog additive, more preferably less than 0.5 wt.% of the antifog additive, more preferably less than 0.1 wt.% of the antifog additive, based on total weight of the film. Even more preferably, they comprise no more than trace amounts of the antifog additive, more preferably essentially no antifog additive, and most preferably no antifog additive.

[0058] The present invention also relates to the use of the composition as described above, comprising such sulfonated copolyester, to prepare such a film. In particular, these compositions are characterized in that they comprise less than an effective amount of an antifog additive, as defined above. In these uses, the antifog film is heat- sealable, it may additionally be used as a heat seal, as addition to its antifog properties.

[0059] The present invention also relates to the method of using the composition as described above, comprising such sulfonated copolyester, to prepare such a film.Process for reducing fog on a film

[0060] The present invention also relates to the process of reducing fog on a film, wherein the film comprises the amorphous copolyester resin described herein or the composition described herein.

[0061] The present invention also relates to the process of reducing fog on a film, comprising incorporating the amorphous copolyester resin described herein as a component of a film composition, preferably the composition described herein.

[0062] All features described herein with respect to the amorphous copolyester resin and the composition also apply to the process for reducing fog on films.Lidding film or laminate, and process for preparing them

[0063] The antifog film described herein may be used as a single layer lidding film or as the inner layer of a multi-layer lidding film or lidding laminate. For example, the antifog film may be used to prepare a tray intended to contain food.

[0064] The process for preparing a lidding film or laminate described herein may comprise the step of:- applying a mixture to a packaging web to provide a coated packaging web, wherein the mixture comprises at least one amorphous copolyester resin and at least one of water or an organic cosolvent, said copolyester resin being as defined herein.

[0065] The lidding laminate described herein is effective as an antifog layer without needing a separate antifog additive. In the prior art, antifog additives are typically incorporated either into said mixture or applied to the laminate after the mixture has been applied to the packaging web. In the present invention, the use of antifog additives is not necessary. Advantageously, the process for preparing a lidding film or laminate does not include any step to apply antifog additives, for example as an additional layer or as a coating, to the laminate described herein.

[0066] In an embodiment, the mixture comprises at least one amorphous copolyester resin and water. In another embodiment, the mixture comprises at least one amorphous copolyester resin and the organic cosolvent. In still another embodiment, the mixture comprises at least one amorphous copolyester resin, water and the organic cosolvent, such asisopropanol. The organic cosolvent may be isopropanol, acetone, methyl ethyl ketone, ethyl acetate, and combinations thereof. The evaporating step is carried out in any known way, such as by heat or forced air directed to the mixture / film.

[0067] The films described herein may be prepared by extrusion or coextrusion. The process for preparing a lidding laminate may comprise the steps of: extruding at least one amorphous copolyester resin to provide an antifog film, said copolyester resin being as defined herein. In addition, a lidding laminate may be prepared by coextruding an antifog film as described above along with a packaging web to provide a lidding laminate.

[0068] The glass transition temperatures of the copolyester resins or blends may vary over a wide range. In general, the suitability of a copolyester resin or blend for application by solubilization (i.e., in water or a solvent then driving off the solvent) versus extrusion depends on a number of factors, including the glass transition temperature of that resin or blend and its solubility in solvents or solvent mixtures. Generally, a copolyester resin or blend should have a glass transition temperature of above about 25°C-50°C to be suitable for application by extrusion. Some of the copolyester resins described herein are most suitable for extrusion. Copolyester resins that are tacky and in the form of a slab at room temperature (typically having a low Tg) are difficult to extrude. They tend to stick to the extrusion equipment. On the other hand, copolyester resins with a high glass transition temperature may still be able to be solvated in some solvent mixtures. Solubility of a material depends on a number of factors, including the relative polarities and chemical make-up of the copolyester reins and the solvent or solvent mixture. A copolyester resin’s ability to perform well in extrusion may also be reflected by its melt flow index. Copolyester resins having melt flow indices (as defined herein) below about 20 g / 10 minutes tend to be able to be processed by extrusion or coextrusion, as well as can be solvated to form a waterborne or solventbome coating.

[0069] The lidding laminate described herein may comprise a substrate and the antifog film described herein, wherein the film is adhered to the substrate. The substrate is not limited whatsoever, and may be polyethylene terephthalate (PET) (including amorphous polyethylene terephthalate (APET)), polylactic acid (PLA), polyhydroxyalkanoates (PHAs), polybutylenesuccinate (PBS), and recycled polyethylene terephthalate (rPET). This may form a bag that seals onto itself to contain an object, such as food.

[0070] The lidding film described herein is suitable for use on a container, such as for food.

[0071] Advantageously, the lidding film described herein does not include a supplemental antifog layer or an antifog coating applied to the antifog film described herein, which serves as the heat seal layer for the lidding film. The lidding film may be a single film or it may be a multi-layer film (referred to herein as a lidding laminate), which includes an outer layer and optional intermediate layers. The outer layer may bear a label or printed matter. The optional intermediate layers may include a pressure sensitive adhesive layer which is adhered to and in direct contact with the antifog film (also the heat seal layer) described herein and, when no other intermediate layers are present, adhered to and in direct contact with the outer layer.Sealed container, and associated processes

[0072] Also described herein is a sealed container comprising a container having a rim defining an opening and a lidding laminate as described herein, wherein the antifog film is bonded to the rim. The antifog film may be bonded to the rim by heat seal, namely heating the antifog film prepared by solvating, extrusion, or coextrusion, and then applying it to the rim of the container.

[0073] The process for sealing a container having a rim defining an opening may comprise the step of applying the lidding film obtained by the processes described above to the rim of the container to seal the container in an orientation such that the antifog film is the innermost layer of the lidding film relative to the opening (in cases where the lidding film is multi-layer).Composting process

[0074] The sulfonated copolyester resin used for the antifog coating may be capable of being composted in an industrial composting facility.

[0075] Also described herein is a process for composting the amorphous sulfonated copolyester resin as described herein, comprising: a) mixing the resin with compost; and b) subjecting the mixture obtained in a) to conditions effective to decompose the resin, wherein the conditions effective to decompose the resin may comprise a temperature range, a humidity content and a residence time.ASPECTS OF THE INVENTIONAspect 1. Use of an amorphous sulfonated copolyester resin to prepare an antifog film, wherein the copolyester resin comprises the reaction product of:(i) a first diacid or diester comprising at least one sulfomonomer at a mole fraction of at least about 0.02, preferably at least about 0.03, more preferably at least about 0.05, more preferably at least about 0.06, more preferably at least about 0.08, and most preferably at least about 0.09, based on the total number of moles of diacids or diesters;(ii) a second diacid or diester comprising at least one aromatic diacid or diester at a mole fraction of at least about 0.25, preferably at least about 0.30, more preferably at least about 0.35, and most preferably at least about 0.4, based on the total number of moles of diacids or diesters; and(iii) at least one diol comprising at least one aliphatic diol, wherein the antifog film comprises less than an effective amount of an antifog additive.Aspect 2. The use of aspect 1, wherein the antifog film has an Antifog Time of longer than 25 hours, preferably at no longer than 15 hours, preferably no longer than 10 hours, and most preferably no longer than about 7 hours of storage.Aspect 3. The use of any of aspects 1-2, comprising less than 1 wt.% of the antifog additive, more preferably less than 0.5 wt.% of the antifog additive, more preferably less than 0.1 wt.% of the antifog additive, more preferably no more than trace amounts of the antifog additive, more preferably essentially no antifog additive, and most preferably no antifog additive.Aspect 4. The use of any of aspects 1-3, wherein the sulfomonomer is aromatic.Aspect 5. The use of any of aspects 1-4, wherein the sulfomonomer comprises at least one of dimethyl-5-sulfoisophthalate, 5-sulfoisophthalic acid, or sodium sulfosuccinate.Aspect 6. The use of any of aspects 1-5, wherein the sulfomonomer is selected from the group consisting of dimethyl-5-sulfoisophthalate, 5-sulfoisophthalic acid, and sodium sulfosuccinate and combinations thereof.Aspect 7. The use of any of aspects 1-6, wherein the sulfomonomer is dimethyl-5- sulfoisophthalate.Aspect 8. The use of any of aspects 1-7, wherein the aromatic diacid or diester (i) comprises at least one of dimethyl terephthalate, terephthalic acid, isophthalic acid, dimethyl isophthalate, or dimethyl 2,6-naphthalene dicarboxylate.Aspect 9. The use of any of aspects 1-8, wherein the aromatic diacid or diester is selected from the group consisting of dimethyl terephthalate, terephthalic acid, isophthalic acid, dimethyl isophthalate, dimethyl 2,6-naphthalene dicarboxylate, and combinations thereof.Aspect 10. The use of any of aspects 1-9, wherein the amorphous copolyester resin further comprises residues of a third diacid or diester comprising at least one aliphatic diacid or diester at a mole fraction of at least about 0.25, preferably at least about 0.30, more preferably at least about 0.35, and most preferably at least about 0.4, based on the total number of moles of diacids or diesters.Aspect 11. The use of aspect 10, wherein the aliphatic diacid or diester comprises at least azelaic acid or sebacic acid.Aspect 12. The use of aspects 10 or 11, wherein the aliphatic diacid or diester is selected from the group consisting of azelaic acid, sebacic acid, and combinations thereof.Aspect 13. The use of any of aspects 1-12, wherein the aliphatic diol is present at a mole fraction of at least about 0.7, preferably at least about 0.8, and more preferably at least about 0.9, and at most 1, preferably at most about 0.98, and more preferably at most about 0.95, based on the total number of moles of diols.Aspect 14. The use of any of aspects 1-13, wherein the aliphatic diol comprises at least one of ethylene glycol, diethylene glycol, neopentyl glycol, or 1,4-cyclohexanedimethanol. Aspect 15. The use of any of aspects 1-14, wherein the aliphatic diol is selected from the group consisting of ethylene glycol, diethylene glycol, neopentyl glycol, 1,4- cyclohexanedimethanol, and combinations thereof.Aspect 16. The use of any of aspects 1-15, wherein the at least one aliphatic diol consists of ethylene glycol, diethylene glycol, neopentyl glycol, and, optionally, 1,4- cyclohexanedimethanol .Aspect 17. The use of any of aspects 1-16, wherein the at least one aliphatic diol comprises, based on the total moles of diols: ethylene glycol at a mole fraction of at least about 0.2, preferably at least about 0.4, and morepreferably at least about 0.6, and at most about 0.85, preferably at most about 0.8, and more preferably at most about 0.75; and diethylene glycol at a mole fraction of at least about 0.05, preferably at least about 0.1, and more preferably at least about 0.15, and at most about 0.5, preferably at most about 0.4, and more preferably at most about 0.35.Aspect 18. The use of any of aspects 1-17, wherein the at least one diol consists of diethylene glycol.Aspect 19. The use of any of aspects 1-18, wherein the amorphous copolyester resin has a Tg in accordance with ASTM E1356-08 of at least about -40°C, preferably at least about - 35°C, more preferably at least about -30°C, and / or at most about 100°C, preferably at most about 90°C, more preferably at most about 85°C.Aspect 20. The use of any of aspects 1-9 or 12-19, wherein: the amorphous copolyester resin further comprises residues of a third diacid or diester comprising at least one aliphatic diacid or diester at a mole fraction of at least about 0.25, preferably at least about 0.30, and more preferably at least about 0.35, and at most about 0.65, preferably at most about 0.6, and more preferably at most about 0.57, based on the total number of moles of diacids or diesters;the sulfomonomer (i) is present at a mole fraction of at least about 0.05, preferably at least about 0.06, and more preferably at least about 0.08, and at most about 0.2, preferably at most about 0.18, and more preferably at most about 0.15, based on the total number of moles of diacids or diesters; and the aromatic diacid or diester (ii) is present at a mole fraction of at least about 0.25, preferably at least about 0.3, and more preferably at least about 0.33, and at most about 0.6, preferably at most about 0.55, and more preferably at most about 0.5, based on the total number of moles of diacids or diesters.Aspect 21. The use of any of aspects 1-20, wherein the film has a haze % as determined in accordance with ASTM D1003, is less than about 1%, preferably below about 0.7%, more preferably below about 0.5%, and most preferably below about 0.2 %.Aspect 22. The use of any of aspects 1-21, wherein the amorphous copolyester resin comprises residues of triols or higher hydroxyl functional monomers at a mole fraction of at most about 0.20, preferably at most about 0.15, more preferably at most about 0.1, and most preferably at most about 0.05, based on the total number of moles of hydroxyl-functional monomers.Aspect 23. The use of any of aspects 1-22, wherein the amorphous copolyester resin does not comprise any residues of triols or higher hydroxyl functional monomers.Aspect 24. The use of any of aspects 1-23, wherein the amorphous copolyester resin has an intrinsic viscosity determined in accordance with ASTM D5225-14 of between about 0.2 dL / g to about 0.6 dL / g, preferably between about 0.25 dL / g and about 0.55 dL / g.Aspect 25. The use of any of aspects 1-24, wherein the amorphous copolyester resin has a Thermosel (or melt) viscosity determined in accordance with ASTM method D3236-15 at 215°C of between about 25 Pa.s and about 1,000 Pa.s, preferably between about 50 Pa.s and about 750 Pa.s..Aspect 26. The use of any of aspects 1-25, wherein the amorphous copolyester resin has a melt flow index determined in accordance with ASTM D1238-20 at a temperature of 190°Cand using a weight of 2.16 kg of between about 2 g / 10 min to about 250 g / 10 min, preferably between about 10 g / 10 min and about 150 g / 10 min.Aspect 27. The use of any aspects 1-26, wherein the amorphous copolyester resin has a softening point determined in accordance with ASTM D36 using mineral oil of between about 75°C to about 200°C, preferably between about 100°C and about 185°C.Aspect 34. Use of a composition for forming an antifog film comprising an amorphous sulfonated copolyester resin, wherein the copolyester resin comprises a reaction product of::(i) a first diacid or diester comprising at least one sulfomonomer at a mole fraction of at least about 0.02, preferably at least about 0.03, more preferably at least about 0.05, more preferably at least about 0.06, more preferably at least about 0.08, and most preferably at least about 0.09, based on the total number of moles of diacids or diesters;(ii) a second diacid or diester comprising at least one aromatic diacid or diester at a mole fraction of at least about 0.25, preferably at least about 0.30, more preferably at least about 0.35, and most preferably at least about 0.4, based on the total number of moles of diacids or diesters; and(iii) at least one diol comprising at least one aliphatic diol, wherein the antifog film comprises less than an effective amount of an antifog additive, preferably comprising less than 1 wt.% of the antifog additive, more preferably less than 0.5 wt.% of the antifog additive, more preferably less than 0.1 wt.% of the antifog additive, based on total weight of the film, even more preferably, comprising no more than trace amounts of the antifog additive, more preferably essentially no antifog additive, and most preferably no antifog additive.Aspect 35. The use of aspect 34, further comprising one or more additives, preferably comprising at least one of pigments, lubricants, anti-oxidants, free radical scavengers, UV absorbers, thermal stabilizers, anti-blocking agents, surface active agents, slip aids, optical brighteners, gloss improvers, or viscosity modifiers, among other additives.Aspect 36. The use of aspects 34 or 35, wherein the composition comprises less than an effective amount of an antifog additive, preferably comprising less than 1 wt.% of the antifogadditive, more preferably less than 0.5 wt.% of the antifog additive, more preferably less than 0.1 wt.% of the antifog additive, based on total weight of the film, even more preferably, comprising no more than trace amounts of the antifog additive, more preferably essentially no antifog additive, and most preferably no antifog additive.Aspect 40. The use of any of aspects 1-39, wherein the antifog film is additionally used as a heat seal.Aspect 41. The use of any aspects 1-27, wherein the antifog film is used as a single layer lidding film or as the inner layer of a multi-layer lidding film or lidding laminate.Aspect 42. The use of any aspects 1-27, wherein the antifog film is used to prepare a tray intended to contain food.Aspect 43. Process for reducing fog on a film, wherein the film comprises the amorphous copolyester resin described herein or the composition described herein.Aspect 44. Process for reducing fog on a film, comprising incorporating the amorphous copolyester resin described herein as a component of a film composition, preferably the composition described herein.Aspect 45. Process for sealing a container having a rim defining an opening comprising the step of applying the lidding film obtained by the processes described above to the rim of the container to seal the container, thereby providing antifog properties to the lidding film. Aspect 46. The process of aspect 45, wherein the lidding film consists of the antifog film.Aspect 47. The process of aspect 45, wherein the lidding film is a multi-layer film and the step of applying comprises applying the lidding film in an orientation such that the antifog film is the innermost layer of the lidding film relative to the opening.

[0076] The following examples demonstrate several aspects of certain preferred embodiments of the present invention and are not to be construed as limitations thereof.

[0077] Raw materials

[0078] The following components were used in the examples.Table 1: Raw materials

[0079] Certain copolyester resins or blends of copolyester resins were prepared.Table 2 below shows the charge ratio of Examples 1A, IB, 2, 3, 4A - 4C, and 5-15 and Comparative Example (“CE”) 1. Example 9 is a 75 / 25 weight ratio blend of Examples 2 and IB. Example 10 is a 50 / 25 / 25 weight ratio blend of Example 2, Example IB, and CE1.Example 11 is a 10 / 75 / 15 weight ratio blend of Example 2, Example IB, and CE1. The percentages of monomers shown in Table 2 for these three examples are weighted averages of the examples used in the blends. It should be noted that CE1 is a comparative example because it developed crystalline domains upon storage over several days, demonstrated by cloudiness. It had these crystalline domains when subjected to the tests described below. However, it was used in Examples 10 and 11 in such low amounts that, when these blends were solvated, any crystallinity was interrupted such that the entire solvated blend was amorphous.Table 2: Monomer charge mole % ratios

[0080] To make Examples 1A, IB, 2, 3, 4A - 4C, and 5-15 and CE 1, appropriate amounts of monomers were charged into a 2L flask. For example, for Example 1A, 293.23 g of ethylene glycol (EG), 76.21 g of neopentyl glycol (NPG), 145.96 g of diethylene glycol (DEG), 527.84 g of dimethyl terephthalate (DMT), 97.01 g of dimethyl 5-sulfoisophthalate sodium salt (DMSIP), 0.56g of zinc acetate dihydrate, and 5.20 g of Irganox® 1010 were charged into a 2L flask. For Example IB, the amount of dimethyl 5-sulfoisophthalate sodium salt (DMSIP) was increased to 189.69 g and the amount of dimethyl terephthalate (DMT) was decreased to 323.99 g. The flask was fitted with a mechanical stirrer, thermocouple, distillation head, and nitrogen inlet port. The reaction mixture was stirred and heated to 204°C in a Glas-Col heating mantle under a slow nitrogen purge. After reaching 204°C, the reaction mixture was stirred for about 1.5 hours with a slight nitrogen purge, until the distillation temperature at the top of the column dropped below 60°C. About 200 g of a colorless distillate was collected over this heating cycle. At this point to the flask was added 132.76 g of isophthalic acid (IPA), 547.09 g of sebacic acid (sebacic), 125.67 g of ethylene glycol (EG), 32.66 g of neopentyl glycol (NPG), and 0.28 g of germanium dioxide. For Example IB, the amount of isophthalic acid (IPA) was reduced to 13.20 g. The reaction mixture was then heated to 200°C over 0.4 hours with stirring under a slow nitrogen purge. The resulting reaction mixture was held at 200°C under a slight nitrogen purge for about 2 hours, or until the distillation temperature at the top of the column dropped below 90°C. The reaction mixture was then heated to 255 °C over 1.5 hours with stirring under a slight nitrogenpurge. About 126 g of a colorless distillate was collected over this heating cycle. The reaction mixture was then staged to full vacuum with stirring at 255 °C. The resulting reaction mixture was stirred for 4 hours under full vacuum, (pressure less than 5 torr). The vacuum was then released with nitrogen and the reaction mass was transferred to a PTFE tray and allowed to cool to room temperature. About an additional 120 g of distillate was recovered and 1.30 kg of a solid product was recovered. The end point was determined by agitator rotational speed (rpm) change, which would correspond to the desirable viscosity of the copolyester melt.

[0081] Certain properties of the various formulations were measured and are reported below in Table 3.Table 3: Formulations properties

[0082] To make a film, the copolyester resin or blend of the examples was dispersed in water and / or an organic solvent. This is done by either heating water to 96 - 98°C and mixing at high speed while adding resin in small amounts, or mixing resin into a blend of 3: 1 DI water:organic solvent without heat. The solvated coatings were applied to 92 ga polyethylene terephthalate (“PET”) between 1.5 and 6.5 g / m2. The antifog test was carried out by heat-sealing, using a hot press at 150°C, a film of the copolyester resin or blend of the examples over a polyethylene terephthalate container with a volume of approximately 236.6 mL (8-ounce), containing 20 g of water filled at 20°C at ambient relative humidity and storing the sealed container at a cooling temperature of 3°C immediately after heat-sealing. The film was positioned such that the antifog coating was the innermost layer on the film relative to the interior of the container.

[0083] To make extrudates (as was done for Examples 12-15), copolyester granules or pellets were fed into an extrusion coating line equipped with slot die or blown film, or cast film extrusion line to produce a clear heat sealable lidding laminate with anti-fogging properties. In the process of extrusion coating, the copolyester is directly extruded onto PET film, whereas in the case of blown and cast film, copolyester is coextruded with PET or PE resins to form a laminate. Other layers, such as tie layer and PSA layer may be needed depending on the structure of laminate. The typical extrusion temperature of these copolyesterresins ranges from 180 to 225°C. In all cases, copolyester resins were dried to less than 0.1% moisture level prior to extrusion. Returning to the data reported in Table 3, intrinsic viscosity is not as reliable because these products are water-dispersible, which impacts the test for intrinsic viscosity. Therefore, Thermosel viscosity was also tested and that is a better measure of viscosity. As can be seen, an example’s melt flow index was found to be generally inversely related to Thermosel viscosity, as is expected. “N / A” means that for these examples, there was no melt peak when the DSC was run, meaning that these examples are amorphous or essentially amorphous.

[0084] The column “Antifog Time” in Table 3 represents the time after sealing when the film sealing the PET container according to the Antifog Test became clear. Thus, the best performers showed an “Immediate” effect, or an antifog time of zero, and these are Examples IB, 4A - 4C, and 5. Even Example 9, which achieved a clear film after 25-30 hours, could be beneficial in a commercial application because a sealed container of food often does not reach its final display area to be viewed by consumers until after many hours (even 30 hours or above) have elapsed. For example, the sealed food product might need to be transported to its point-of-sale destination to a final consumer. In all cases, the examples show antifog ability to continue for at least three weeks after a clear film was attained. The antifog film does not appear to be affected by the carrier solution, whether it is water, water / co-solvent, or only solvent. The antifog function performed equally well across a range of coating weights.

[0085] The heats of fusion of the Examples were measured in accordance with ASTM E-793-01 using DSC except with one modification to the test in that a scanning temperature of 15°C per minute instead of 10°C per minute was used. The heats of fusion generally correspond to the degree of crystallinity of a copolyester resin or a blend of copolyester resins, with a low heat of fusion indicating an amorphous or essentially amorphous resin or blend and a high heat of fusion indicating a crystalline resin or blend. CE 1 had a heat of fusion, measured after several days of storage of 15.3 J / g. At this point, the film demonstrated a lack of clarity and would not be acceptable for applications requiring a clear film. All of the Examples 1A, IB, 2, 3, 4A - 4C, and 5-11 showed no melt peak, so wereamorphous or essentially amorphous, which would allow them to be used in applications requiring a clear film.

[0086] The glass transition temperatures of Examples 1A, IB, 2, 3, 4A - 4C, and 5-11 ranged from a low of -23°C (Example 4C) to a high of 81°C (Example 6). In general, the suitability of the copolyester resin or blend for application by solubilization (i.e., in water or a solvent then driving off the water / solvent) versus extrusion depends primarily on the glass transition temperature of that resin or blend. Generally, a copolyester resin or blend should have a glass transition temperature of above 25°C-50°C to be suitable for application by extrusion. Therefore, the copolyester resins of Examples 2 and 6-8 are the most suitable ones for extrusion. On the other hand, the copolyester resins or blends of Examples 1 A, IB, 3, 4A- 4C, 5, and 9-11 are more suitable for application by solubilization.

[0087] Some of the films produced from Examples 1 - 11 and CE1 as described above were tested for adhesive properties by undergoing a 180° peel force on PET, rPET, and PLA after having been applied at heat seal temperatures ranging from 107 °C to 192°C to coat weights of about 2 - 2.5 gsm (about 1 - 1.4 Ib / ream ). For all formulations tested, at least one set of conditions (heat seal temperature, substrate chosen) demonstrated a peel force suitable for a range of commercial applications. Increasing the amount of sulfomonomer in the blends from 5 wt.% to 12.5 wt.% did not significantly adversely affect bond performance and, in many cases, improved bond performance.

[0088] In particular, Figures 1-4 show the results of peel force values of heat seal laminates for respectively Examples 1A, 2, 3 and CE1, prepared via hand drawdown with a #10 Mayer rod onto 92 ga PET. Coatings were dried for 5 minutes at 70°C to flash off solvent. The coated samples were then cut into 3.8 cm by 2.5 cm (1.5” by 1”) peels and sealed for 0.5 seconds to rigid substrates of PVDC (Polyvinylidene chloride), HIPS (High impact polystyrene), RPET (recycled PET) and APET (amorphous PET) at 107°C, 135°C, 163°C, and 177°C (225°F, 275°F, 325°F, and 350°F). Once cooled, the samples were tested via 180-degree peel at a rate of 30.5 cm / min (12’7min).

[0089] It is believed that some embodiments of the present invention are compostable. The composting process uses microorganisms such as bacteria or fungi to break down the organic materials, the latter producing carbon dioxide, water, heat, and compost. It is important that microorganisms have a continuous supply of organics, water, and oxygen. The standard methods for compostability testing are EN 13432 for packaging and ASTM 6400, which is a standard specification for compostable plastics. To be considered compostable, the product must demonstrate the three following items: (1) disintegration - after starting with the product cut to 2 cm lengths, in 12 weeks of composting under laboratory controlled composting compositions 90% of the product must pass a 2 mm sieve; (2) biodegradation - sixty percent of the organic carbon must be converted to carbon dioxide by the end of the test period when compared to the positive control (cellulose); and no adverse effect on the quality of the compost - the germination rate and the plant biomass of the sample composts shall be no less than 90% and levels of heavy metals shall be less than certain standards, which vary by regions.

[0090] Special conditions are required to perform this test. First, a temperature- controlled incubator is used to maintain a temperature of 58°C, and the composting vessel (7.5 liters capacity) is split into two parts by use of a porous pad. The bottom part contains 1 liter of water and carbon dioxide is bubbled through this water to saturate the gas with water. Inoculum: A 3-month-old compost is used; it is sieved through a 9.5 mm sieve and mixed. Ammonium chloride is added such that the C / N ratio is less than 15 and water volume is adjusted so that the moisture content is 50%.

[0091] Disintegration test: The test starts with 200 g of 2 cm x 2cm squares of the product, which are added to 1.2 kg of compost and put into the 7.5 liters vessel. The mixture is composted for 12 weeks; the vessel is shaken weekly to mix samples and compost and to prevent channeling. After 12 weeks, material is screened through a 2mm sieve. No more than 10% of the original dry weight of the product can be retained on the sieve.

[0092] Biodegradation: This test is made with four mixes: Sample (10 g of the product and 600 g of compost), positive control (replacing the product by cellulose), a negative control (100 g of PET and 600 g of compost), and a blank (600 g of compost only).

[0093] The moisture content of the mixtures is adjusted to 50%. The composting vessels are placed in the incubator at 58°C ± 2°C. The CO2 free air is then connected and adjusted so that the flow rate is between 150 and 200 ml per minute. The gases exiting the test chambers are plumbed to a solenoid valve, which is controlled to divert air for 2 minutes out of every 2 hours. These diverted gases flow into 1 -liter adsorption units containing a known volume of IN sodium hydroxide to adsorb the carbon dioxide being produced in the vessels (for the remainder to the 2 hours the exhaust is simply vented to the room). The sodium hydroxide is periodically titrated to measure the CO2 production; the standard days for the titration are 3, 7, 14, and every 7 days after that. Titration is made to pH 8.5 with 0.5N HC1 after adding BaCh to precipitate the carbonates formed by the CO2. Fresh IN sodium hydroxide is placed in the absorption units and the whole process is repeated. The testing is carried out until the CO2 production from both the sample and the positive control have plateaued up to a maximum of 180 days.Table 4: Disintegration Testing

Claims

CLAIMS1. Use of an amorphous sulfonated copolyester resin to prepare an antifog film, wherein the copolyester resin comprises a reaction product of:(i) a first diacid or diester comprising at least one sulfomonomer at a mole fraction of at least about 0.02, preferably at least about 0.03, more preferably at least about 0.05, more preferably at least about 0.06, more preferably at least about 0.08, and most preferably at least about 0.09, based on the total number of moles of diacids and diesters;(ii) a second diacid or diester comprising at least one aromatic diacid or diester at a mole fraction of at least about 0.25, preferably at least about 0.30, more preferably at least about 0.35, and most preferably at least about 0.4, based on the total number of moles of diacids and diesters; and(iii) at least one diol comprising at least one aliphatic diol.

2. Use of the resin of claim 1, wherein the antifog film comprises less than an effective amount of an antifog additive, preferably less than 1 wt.% of the antifog additive, more preferably less than 0.5 wt.% of the antifog additive, more preferably less than 0.1 wt.% of the antifog additive, based on the total weigh of the antifog film more preferably no more than trace amounts of the antifog additive, more preferably essentially no antifog additive, and most preferably no antifog additive.

3. Use of the resin of claims 1 or 2, wherein the sulfomonomer is aromatic, preferably the sulfomonomer comprises at least one of dimethyl-5-sulfoisophthalate, 5- sulfoisophthalic acid or sodium sulfosuccinate, more preferably the sulfomonomer is selected from the group consisting of dimethyl-5-sulfoisophthalate, 5-sulfoisophthalic acid, sodium sulfosuccinate and combinations thereof, and most preferably the sulfomonomer is dimethyl-5- sulfoisophthalate.

4. Use of the resin of any one of the preceding claims, wherein the aromatic diacid or diester comprises at least one of dimethyl terephthalate, terephthalic acid,isophthalic acid, dimethyl isophthalate or dimethyl 2,6-naphthalene dicarboxylate, preferably the aromatic diacid or diester is selected from the group consisting of dimethyl terephthalate, terephthalic acid, isophthalic acid, dimethyl isophthalate, dimethyl 2,6-naphthalene dicarboxylate and combinations thereof.

5. Use of the resin of any one of the preceding claims, wherein the amorphous copolyester resin further comprises residues of a third diacid or diester comprising at least one aliphatic diacid or diester at a mole fraction of at least about 0.25, preferably at least about 0.30, more preferably at least about 0.35, and most preferably at least about 0.4, based on the total number of moles of diacids and diesters.

6. Use of the resin of any one of the preceding claims, wherein the aliphatic diol is present at a mole fraction of at least about 0.7, preferably at least about 0.8, and more preferably at least about 0.9, and at most 1, preferably at most about 0.98, and more preferably at most about 0.95, based on the total number of moles of diols.

7. Use of the resin of any one of the preceding claims, wherein the aliphatic diol comprises at least one of ethylene glycol, diethylene glycol, neopentyl glycol or 1,4- cyclohexanedimethanol, preferably the aliphatic diol is selected from the group consisting of ethylene glycol, diethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol, and combinations thereof, more preferably the aliphatic diol consists of ethylene glycol, diethylene glycol, neopentyl glycol, and, optionally, 1,4-cyclohexanedimethanol.

8. Use of the resin of any one of the preceding claims, wherein the aliphatic diol comprises, based on the total number of moles of diols: ethylene glycol at a mole fraction of at least about 0.2, preferably at least about 0.4, and more preferably at least about 0.6, and / or at most about 0.85, preferably at most about 0.8, and more preferably at most about 0.75; and diethylene glycol at a mole fraction of at least about 0.05, more preferably at least about 0.1, and more preferably at least about 0.15, and / or at most about 0.5, preferably at most about 0.4, and more preferably at most about 0.35.

9. Use of the resin of any one of the preceding claims, wherein the aliphatic diol consists of diethylene glycol.

10. Use of the resin of any one of the preceding claims, wherein the amorphous copolyester resin further comprises residues of a third diacid or diester comprising at least one aliphatic diacid or diester at a mole fraction of at least about 0.25, preferably at least about 0.30, more preferably at least about 0.35, and most preferably at least about 0.4, based on the total number of moles of diacids or diesters, wherein the aliphatic diacid or diester preferably comprises at least azelaic acid or sebacic acid.

11. Use of the resin of claim 10, wherein the aliphatic diacid or diester is selected from the group consisting of azelaic acid, sebacic acid, and combinations thereof.

12. Use of the resin of any one of the preceding claims, wherein the resin has a Tg in accordance with ASTM E1356-08 of:- at least about -40°C, preferably at least about -35°C, more preferably at least about - 30°C, and / or- at most about 100°C, preferably at most about 90°C, more preferably at most about 85°C.

13. Use of the resin of any one of the preceding claims, wherein the antifog film has an Antifog Time of no longer than 25 hours, preferably at no longer than 15 hours, more preferably no longer than 10 hours, and most preferably no longer than about 7 hours of storage.

14. Use of a composition for forming an antifog film comprising an amorphous sulfonated copolyester resin, wherein the copolyester resin comprises a reaction product of::(i) a first diacid or diester comprising at least one sulfomonomer at a mole fraction of at least about 0.02, preferably at least about 0.03, more preferably at least about 0.05, more preferably at least about 0.06, more preferably at least about 0.08, and most preferably at least about 0.09, based on the total number of moles of diacids or diesters;(ii) a second diacid or diester comprising at least one aromatic diacid or diester at a mole fraction of at least about 0.25, preferably at least about 0.30, more preferably at least about 0.35,and most preferably at least about 0.4, based on the total number of moles of diacids or diesters; and(iii) at least one diol comprising at least one aliphatic diol, wherein the antifog film comprises less than an effective amount of an antifog additive, preferably comprising less than 1 wt.% of the antifog additive, more preferably less than 0.5 wt.% of the antifog additive, more preferably less than 0.1 wt.% of the antifog additive, based on total weight of the film, even more preferably, comprising no more than trace amounts of the antifog additive, more preferably essentially no antifog additive, and most preferably no antifog additive.

15. The use of claim 14, further the composition comprises one or more additives, preferably comprising at least one of pigments, lubricants, anti-oxidants, free radical scavengers, UV absorbers, thermal stabilizers, anti-blocking agents, surface active agents, slip aids, optical brighteners, gloss improvers, or viscosity modifiers, among other additives.

16. The use of claim 14 or 15, wherein the composition comprises less than an effective amount of an antifog additive, preferably comprising less than 1 wt.% of the antifog additive, more preferably less than 0.5 wt.% of the antifog additive, more preferably less than 0.1 wt.% of the antifog additive, based on total weight of the film, even more preferably, comprising no more than trace amounts of the antifog additive, more preferably essentially no antifog additive, and most preferably no antifog additive.

17. The use of any of claims 1-16, wherein the antifog film is additionally used as a heat seal.

18. The use of any of claims 1-17, wherein the antifog film is used as a single layer lidding film or as the inner layer of a multi-layer lidding film or lidding laminate.

19. The use of any of claims 1-17, wherein the antifog film is used to prepare a tray intended to contain food.

20. A process of reducing fog on a film, wherein the film comprises the amorphous copolyester resin of any of claims 1-12 or the composition of any of claims 14-16.

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