BR112019014293B1 - ANTI-FOG AND EXTRUDIBLE COPOLYESTER HEAT SEALING RESINS - Google Patents

Abstract

A semicrystalline copolyester resin composition, formed by twin screw extrusion of various ingredients, includes copolyester resins, anti-block, slip and anti-fog additives. This semicrystalline copolyester resin can be extruded onto PET film or co-extruded with PET resin to form clear PET films with anti-fog properties. These films with anti-fog properties are produced in a single step without the use of solvent and do not involve any secondary step of coating a separate anti-fog layer. This minimizes the cost and time required by a converter to make such clear anti-fog films. These films containing the heat seal copolyester resin can be heat sealed to clear APET trays. The contents inside the trays, such as food, can be seen without fogging the inside of the film used to seal the tray. Seals are strong and removal is smooth, providing very good packing performance.

Description

CROSS REFERENCE TO RELATED ORDER

[0001] This application claims benefit under 35 U.S.C. § 119 of U.S. Patent Application Number 62/444,971, filed January 11, 2017.

FIELD OF THE INVENTION

[0002] This invention relates to copolyester resin compositions capable of forming clear heat-seal coatings used for polyester films and having anti-fog, anti-blocking and gliding capabilities. The invention also relates to methods of applying such compositions to polyester films.

BACKGROUND OF THE INVENTION

[0003] Polyester films coated with heat sealing layers are used to package food products and consumer goods. In a common application, heat seal polyester (PET) films are made on high speed food packaging machines. The film is typically coated or co-extruded with the heat seal resin/film onto one surface of the web. This web is fed through the machine to pack food and other consumer goods. The film is heat sealed onto different packaging substrates such as food containers. This is done with pressure and heat using heated plates. Sealing performance in terms of strength and package integrity is largely a function of the characteristics of the film, the heat seal layer, the tray stocks it is sealed to, and machine operating conditions such as plate temperature, pressure and lenght of stay. Since these films are used in food packaging, it is desirable that the heat seal coating, as well as the packaging film and tray stocks, be FDA direct food contact compliant (21 CFR §175.300 and above).

[0004] Current technology for PET heat seal films with anti-fog performance includes films with water-based or solvent-based anti-fog coatings. This involves several steps in the manufacture of the PET anti-fog film. The PET film is formed by extrusion or co-extrusion with the heat seal layer in the film. This film is then rolled up and supplied to the next level or processing location. The rolls are unwound, undergo expensive treatment, including corona treatment (as described in US Patent No. 5,520,764) or chemical treatment, and then the anti-fog coating is applied as a solvent-based coating or water-based coating. This step involves application using expensive equipment, drying, followed by film winding to be supplied to the next level.

[0005] Various efforts have been made to provide a heat seal coating for polyester film. WO patent application No. 2014006205 A1 describes an anti-fog coated polyester film for fresh red meat and fish packaging. The patent application explains film formation by coating the polyester film with an anti-fog additive, which is a cationic polysaccharide with suitable diluents including a solvent. The polyester film with anti-fog properties is produced in two steps using solvent.

[0006] WO patent application No. 2015046132 describes a multilaminate structure with anti-fog properties. The patent application describes the formation of a multilaminate structure using four layers, layer A being a polyolefin layer, layer B being a polyolefin intermediate layer with anti-fog additive mixed in, layer C being an acid-modified polyolefin layer and layer D being a heat-seal polyester layer kneaded with anti-fog additive. Layers A and D are treated using expensive treatment techniques to provide final properties, including printing and adhesion. This patent application describes the formation of a heat sealable laminate structure in which the anti-fog additive is used in two different layers to achieve the final performance.

[0007] China Patent Application No. CN 102558978 describes forming a transparent anti-fog PET film by spray coating an anti-fog solution onto the PET film. The anti-fog coating comprises PVA mixed with a water-soluble solvent followed by the addition of hydroxyl-group fatty acid ester in the presence of water. This solution is then sprayed onto the PET film to provide the clear anti-fog film. This patent application describes the formation of the anti-fog coating as a secondary process in the manufacture of anti-fog PET film.

[0008] Document JP 2015218211 teaches a polyester-modified polyvinyl chloride resin composition based on aliphatic polybasic acid with an average molecular weight of 1,600-3,600 derived from adipic acid, 1,2-propanediol and noctanol as a capping agent and an ester based on aliphatic polybasic acid with plasticizing efficiency <0.90, epoxidized vegetable oil and an anti-fogging agent based on glycerin. This composition is claimed to produce low shrinkage film for food packaging applications.

[0009] JP 2010001384 discloses an additive package that can be used with various plastics, including polyethylene, polypropylene, ethylene-vinyl acetate copolymer, vinyl chloride and polylactic acid to improve anti-fog and anti-static properties. The additive added to the resin contains a polyglycerine alkyl ether compound and an anionic surfactant.

[0010] KR 2009076233 explains the formation of a biodegradable and anti-fog sheet having better scratch resistance while maintaining sufficient flexibility and transparency and continuously exhibiting an anti-fog property. This is formed by melting and extruding the resin and discharging the molten resin through a slip-type die to prepare a sheet, the resin comprising a mixture of polylactic resin and aliphatic polyester or aromatic-aliphatic polyester resin. The sheet is then corona treated. An anti-fogging agent consisting of surfactant, tetrafluoroethylene as a fluorine resin and water is applied to one surface or both surfaces of the corona discharge treated sheet and the applied coating is dried at 60-100 degrees centigrade hot wind for 10-30 seconds . This patent teaches the formation of anti-fog sheet by a secondary coating process.

[0011] CN 1884371 and JP 2006055029 explain that a biodegradable resin composition that has good transparency, flexibility and weather resistance, is free from deterioration of transparency by the running off of an anti-fogging agent over time. In other words, the composition has excellent anti-fog durability. The film or foil is suitable for agriculture and food packaging. This resin composition comprises a biodegradable polyester resin, an ester of a fatty acid with an alcohol selected from sorbitol, sorbitan and polyglycerol (including dehydration-condensed alcohols, and polyhydric alcohol alkylene oxide adduct) as the anti-fog agent, and a sulfonate-based surfactant.

[0012] KR 2006109623 teaches the formation of a polyester film with a surface capable of preventing the formation of droplets on the surface of the film by applying a polyurethane resin dispersed in water on at least one surface of the uniaxially oriented polyester film. The film is kept cool by forming this thin water screen using water-dispersed polyurethane resin.

[0013] JP 2007031545 explains forming an anti-fog coating on a PET film using a water-soluble solution of anti-fog compounds like sucrose octadecanoate and sodium octadecanoate. The coating was applied on a corona-treated polyester film, dried at 70° to give an anti-fog sheet, and it demonstrates good anti-fog property at high temperature, anti-fog property retention, and non-stickiness. The process of producing an anti-fog film comprises two steps.

[0014] WO patent application No. 2005103160 discloses a composition for a biodegradable film with anti-fogging properties incorporating the following in a polylactic acid resin. A surfactant and a compatibilizer obtained from the reaction of a surfactant (R1R2R3R4N+)mX1 with a polyhydric alcohol (modified) and boric acid, where R2, R2, R3, R4 = C130 linear or independently branched alkyl, alkenyl, hydroxyalkyl , alkylaryl, arylalkyl, (AlO)fRa; A1 = C2-4 alkylene; f = 1-50; Ra = C1-30 straight or branched alkyl, alkenyl, hydroxyalkyl or alkylaryl; X1 = structure having ^1 SO3 and ^1 COOR7; m = ^ integer 1; R7 = straight or branched C1-30 alkyl, alkenyl, hydroxyalkyl, alkylaryl or (A2O)Rb; and Rb = C1-30 alkylene. Thus, Lacea H 100 and 1.0% trimethyloctylammonium 1,4-dioctyl sulfobutanedioate were kneaded at 200° and pressed to give a test piece, which shows good molecular weight retention, antistatic, and antifogging properties, and haze of 1 .5%. The heat sealability of the film is not disclosed.

[0015] Min Nie et al., Nano/Micro Engineered and Molecular Systems, 2009. NEMS 2009. 4th International IEEE Conference, January 5-8, 2009, pages 1017-1020, explains the formation of a super polyester film -hydrophilic formed by plasma treatment. The superhydrophilic polyester film was obtained by oxygen plasma treatment to maintain optical clarity under high relative humidity. The original and treated films are simultaneously exposed to steam from the hot water. The latter maintains its optical clarity because the condensed water formed a thin film instead of drops for the former. Compared with the widely used coating method, plasma treatment to obtain anti-fog polymer film has the potential of mass production, lower cost, better compatibility with hot extrusion process, and safer for food packaging. Heat sealability of the film was not explained by the authors.

[0016] Patent No. US5520764A does not teach forming a laminated structure having an anti-fog layer as one of the laminated layers. The laminate comprises a first substrate which is a blend of a polyolefin and an antifogging agent, and is co-extruded with another polyolefin, preferably an unsaturated ethylene ester copolymer or low density polyethylene. Once coextruded, this layer is corona treated and then bonded to a second substrate comprising polyester or nylon, which may also be corona treated on the bonding side. The formation of this multilaminate structure involves several steps.

[0017] US 20030148113 A1 explains the formation of an anti-fog film on several different substrates, including polyester. The anti-fog film is formed using an anti-fog coating composition comprising a silicone polymer or oligomer, a water dispersible polyurethane polymer or oligomer, and water or a co-solvent. The anti-fog film is formed by applying the anti-fog coating composition to a substrate such as polyester and coalescing or cross-linking the silicone and polyurethane compounds to form the film. The applied coating is then suitably heated for a certain period of time to form the anti-fog mesh film on the surface of the substrate. This anti-fog film is formed using polyurethane and water dispersions. The use of isocyanates as well as the removal of water during the process is somewhat challenging. Also, depending on the extent of crosslinking, the coated film can be too brittle or low crosslinking can result in flaking, i.e., a powdery film is produced that breaks down or disperses on contact with an aqueous solution or water.

[0018] Machida et.al, JOURNAL OF MATERIALS SCIENCE 34 (1999) 2569 - 2574, describes the formation of a hydrophilic surface by the photocatalytic activity of TiO2 with the addition of SiO2. The process helps the TiO2 retain more water during the UV irradiation process.

[0019] US 20070077399 A1 explains the formation of anti-fog films for use on refrigerator doors. The anti-fog coating composition comprises an isocyanate, a hydrophilic polyol and a hydroxyl-containing surfactant having a hydrophilic group and a hydrophobic moiety. These components are mixed in organic solvents and applied to substrates including polyester. The coating is then cured with heat and time to form the anti-fog coating on the film. This process again involves several steps, as well as substantial time and use of hostile isocyanate.

[0020] CN 202742776 U explains the formation of polyester film with anti-fog coatings on both sides of the film. The anti-fog agent consists of two ingredients. The first ingredient consists of sorbitan fatty acid ester, polyoxyethylene nonylphenol ether, polyoxyethylene sorbitan fatty acid ester, glycerol fatty acid ester, a block polymer of ethylene oxide-propylene oxide, an alkyl ether of polyoxyethylene or a polyoxyethylene alkylphenyl ether and the second ingredient designated the synergist is selected from the group consisting of polyvinyl alcohol, polyethylene glycol or polyoxyethylene glycol, or a combination of at least two of them. These two ingredients are extruded by twin screws with a polyester base material. In a further step, this functional polyester layer is extruded together with a polyester base layer using a coat hanger die to produce a polyester film through an extrusion and lamination process to create a polyester film with anti-fog properties. on both sides of the film. Although the invention claims the antifogging performance of the film, it does not disclose the heat sealability of the film to various tray stocks. The composition of the polyester base is also not explained very well.

[0021] US 20130224411 A1 describes a process for making an anti-fog film useful for packaging food. Peelable anti-fog films can be used as cover films on amorphous polyester (APET) trays. The films can include at least a base layer or film, such as a polyester film, and a heat seal layer. This film base with an amorphous heat-seal layer is produced through a co-extrusion process. The anti-fog layer is then coated onto the heat seal layer. The heat seal layer allows the anti-fog coating to adhere more strongly to the anti-fog film. The seal strength of this anti-fog film is between 500 to 1000 grams per linear inch (gly). The film provides good anti-fog properties and good bond strength, but the process involves a secondary step of applying the anti-fog layer to the heat seal layer, which is claimed to be an amorphous polyester layer.

[0022] WO 2015051375 A1 teaches the formation of a peelable multi-layer anti-fog film, wherein the peel-off anti-fog layer is added to the inner layer of the multi-layer structure as a secondary process.

[0023] US 5614297 A- refers to a flexible thermoplastic multilayer polymeric film comprising at least one ethylene copolymer and at least one C3-C8 alpha-olefin within the multilayers. The multilayer comprises a first outer layer, a core layer and a second outer layer, wherein the core layer is between the first and second layers. The film is a slit cast film or blown film having at least three layers including a core layer disposed between the first and second outer layers. They also report the use of suitable additives such as anti-fog agents, slip agents, non-ionic surfactants, oleamides and/or fluoroelastomers in the core layer. The invention can be used as an industrial wrapper or for wrapping, covering or enclosing various non-food or food items, but has particular utility as a stretch film or food wrapper cling. This invention does not report the heat seal ability of the film for APET trays.

[0024] US 2011/0163101 A1 explains forming a heat seal coating containing anti-fog additives which can be solvent coated onto a biaxially oriented PET film to form a heat seal layer which can then be used to heat seal the PET film over the PLA cup stocks.

[0025] US 6,923,997 B2 teaches various anti-fog compositions that can be prepared and sprayed with solvent onto food containers to make the container fog-free. Here again, the use of solvent is imperative to the process.

[0026] US 7,700,187 B2 discloses forming a hydrophilic anti-fog coating on a biaxially oriented polyester film. The hydrophilic aqueous dispersion or solution consisting of a sulfopolyester, a surfactant and, optionally, an adhesion-promoting polymer in water, is applied to a corona-treated PET film by reverse etching followed by drying at 100°C. This is a secondary step in the process of making the final anti-fog film. A similar patent also exists as US 7,384,684 B2 from the same inventors in which polyvinylpyrrolidone is used instead of sulfopolyester.

[0027] US 8,557,384 B2 discloses a coating composition comprising an alkali metal silicate, a wetting agent and a hydrophilic anti-fog agent applied to the surface of a substrate from an aqueous dispersion, followed by drying to form the anti-fog coating on the surface of the film.

[0028] US patent application No. 20050249906A1 describes the formation of a thermoadhesive PET film by the extrusion process, but one that does not incorporate any anti-fog in the film composition. The application discloses forming a heat seal layer (0.005 Pa.s to 50 Pa.s in-process viscosity) by melt coating onto a biaxially oriented PET film as an in-line process during film manufacture. They also indicate the use of water to help coat the heat seal layer onto the biaxially oriented PET film to improve the adhesion of the heat seal layer during the in-line process.

[0029] As can be appreciated from a review of the above, several attempts have been proposed to produce packages that help the consumer to clearly see the food through the covering film. A refrigerated food tray will have a lid that extends over the stored food item so that the film covering covering the top of the tray will not touch most packaged foods. In this arrangement, the consumer preferably can clearly see through the plastic wrapper to see the food item stored in the package. If the cover film is fogged up, it may impair the view of the food on the tray.

[0030] Another attempt would be to reduce the depth of the tray so that the consumer can clearly see the food. This is due to the sharpness of the image caused by the deviation of the direction of light propagation from the regular direction, scattering during transmission or reflection while looking at the food on the tray. If the lid is fogged up, the view of the food will be impaired.

[0031] Another attempt is to wrap the tray containing the food with plastic film that could contain anti-fog ingredients. In this case, the tray is usually not transparent and the lid is rolled up rather than sealed to the tray. The package must be opened by destroying all the plastic film, which undesirably reduces the shelf life of the food. Additionally, any openings in the wrap can also reduce the shelf life of foods when stored on grocery store shelves or elsewhere.

[0032] More and more consumers would like to see the food on the tray and be able to judge the quality of the food, and therefore the cleanliness of the lid becomes very important in the eyes of the consumer. In the past attempts have provided anti-fog coatings that could be applied to the heat seal coating. This process involved expensive equipment as well as several steps in the process of making an anti-fog coating material that could be sealed in APET trays. The method involved creating a PET cover material by coextrusion, extrusion coating or solvent coating. The heat seal layer can be coextruded together with PET to form the heat seal PET film, or the heat seal layer can be extruded onto the PET film or solvent coated onto the PET film. This heat seal layer then acted as an anchor for the next step of applying the anti-fog gravure coating. This process was always done as a secondary step in the anti-fog heat seal PET film production process. It involved the use of solvent or water, depending on the chemistry of the anti-fog product. The overall process involves several steps, as well as expensive equipment to make the PET film in the converter.

SUMMARY OF THE INVENTION

[0033] In contrast to the above patents and previous attempts, the present invention is directed to a solvent-free, extrudable or co-extrudable heat seal coating containing an antifogging additive and its use by film converters. The heat seal coating can be extruded into various sizes of PET film or can be co-extruded together with polyester or copolyester resins to form a converted PET film which exhibits good clarity, anti-fog, anti-blocking and good bonding strength over a wide range. of processing temperatures for different tray stocks. Once sealed, the connections can be opened as a gentle removal without being a solder seal.

[0034] According to an embodiment of the invention, a heat seal resin composition for providing a heat seal film on a film, such as a polyester film, comprises: a copolyester resin component comprising a blend of a semicrystalline copolyester resin and an amorphous copolyester resin; an anti-fog additive; and an anti-block and slip additive.

[0035] According to another embodiment of the invention, a heat seal resin composition for providing a heat seal film on a polyester film essentially consists of or consists of a copolyester resin component comprising a blend of a semicrystalline copolyester resin and an amorphous copolyester resin; an anti-fog additive; and an anti-block and slip additive. A composition consisting essentially of the listed constituents excludes certain other constituents, such as a solvent.

[0036] According to another embodiment of the invention, a method for manufacturing a laminate comprises, essentially consists of, or consists of the steps of: forming a heat seal resin composition by mixing a copolyester resin component, an anti-fog additive and an antiblocking and slip additive in the absence of a solvent; and applying the heat seal resin composition to a film, such as a polyester film, or a film-forming compound, such as polyester, to form the laminate, wherein no solvent is added to the seal resin composition hot before or during the application step. A method consisting essentially of the listed steps is done in the absence of certain other steps, such as a primary step.

[0037] According to another embodiment of the invention, a method of making a package to contain an item comprises the steps of: (1) making a laminate by: (a) forming a heat seal resin composition by mixing a copolyester resin component, an anti-fog additive, and an anti-block and slip additive, in the absence of a solvent, and (b) applying the heat seal resin composition to a film, such as a polyester film, or the compound film-forming materials, such as polyester, to form the laminate, wherein the solvent is not added to the heat seal resin composition before or during the application step; and (2) contacting the laminate with a top lid of a food tray under sufficient heat, pressure and time to cause the heat seal resin composition to adhere the laminate to the food tray.

[0038] This copolyester heat sealing resin composition can be used as an extrudable or coextrudable copolyester resin in the production of heat sealable polyester films capable of use as lids of food product packaging. More specifically, the extrudable copolyester resin can be applied to PET films by converters (i.e. PET film producers) to create a clear anti-fog heat seal layer with anti-blocking and slip properties using traditional extrudable coating methods. This extrudable copolyester resin can also be co-extruded with polyester resin to form a clear biaxially oriented anti-fog heat seal layer with good anti-blocking and sliding properties. The coated films can be wound onto rolls without blocking (ie, laminate adhesion after winding) and have good adhesion to many different packaging substrates at medium to high activation temperatures. Coated film with anti-fog properties is detachable when heat-sealed onto polyester foils or polyester tray stocks used for food packaging. Such heat seal films are conventionally sold in roll form. The rolls are then supplied in roll form for use on form-filling and sealing packaging machines. This can include horizontal shape fill seal (HFFS) packaging, making bags or pouches by vertical shape fill seal (VFFS) technology or as a flexible packaging film such as a top film for vacuum skin packaging applications .

[0039] The present invention reduces the number of steps involved in manufacturing the final roll, since the copolyester resin includes anti-fog additives as well as anti-block and slip additives. Thus, the resin can be extruded or co-extruded with PET resin or other copolyester resin. The copolyester resin containing the anti-fog also acts as the heat-sealing copolyester. Thus, this reduces the need for two separate steps involved in making the final heat seal anti-fog PET film. The heat seal layer has anti-fog and anti-blocking additives and glidants added in proper proportion to provide adequate sealability and ease of removal, good clarity and good anti-fog properties. Furthermore, the heat seal layer has minimal blockage so that the film can be rolled up and unrolled after production. The film can be cut for later application in a minimum period of time. As the resin does not involve any solvent, there is a reduction in the environmental impact, as well as an increase in the safety of workers involved in using the resin.

[0040] In one aspect, the invention is a formulated copolyester resin that can be extruded into various gauges of PET film or co-extruded with polyester resin to form a heat seal coating on the seal layer of the formed PET film. This film (also referred to here as a laminate) shows excellent clarity and good anti-fogging, so that the tray containing the food when sealed with this PET film does not show any fogging. The consumer can see the food even when the tray is placed in the refrigerator. The formulated blend can be produced in a twin screw extruder by melt blending various ingredients.

DETAILED DESCRIPTION OF THE INVENTION

[0041] One embodiment of the invention relates to a copolyester heat sealing resin capable of being extruded onto PET films or coextruded with PET resins to produce a clear heat sealed PET cover film. This cover film is then used to package fresh produce or food products or other items that could potentially contain water. The usual container for these food products is clear amorphous PET trays. The overall packaging concept is to help the consumer see the food on the tray. If there are water droplets or fogging on the surface of the film, the overall effect of the packaging is lost and consumer satisfaction will suffer. Fogging develops in a variety of ways, as a result of changing weather or varying temperature conditions, such as freezing or humidity. When warm air, which holds moisture, encounters a cooler surface, water can condense and settle on the cooler surface. When too much moisture sets in, it leads to the accumulation of water that needs to go somewhere, resulting in fog. The principle behind the use of antifog heat seal resin is to create a hydrophilic surface by changing the degree of wetting on the film surface when the heat seal coating is formed. The anti-fog heat seal layer improves the wettability of the surface, and when this surface attracts and absorbs moisture, it creates an undispersed or thin layer of water film without impeding vision.

[0042] According to an embodiment of the invention, a heat seal resin composition for providing a heat seal film on a polyester film, comprises: a copolyester resin component comprising a mixture of a copolyester resin semicrystalline and an amorphous copolyester resin; an anti-fog additive; and an anti-block and slip additive. The combination of semi-crystalline and amorphous copolyesters has been found to provide especially desirable performance for the final application. The semicrystalline resin reduces creep and imparts flexibility and elasticity to the heat seal coating, while the amorphous copolyester provides additional strength and anti-blocking properties to the overall heat seal coating. The fully formulated heat seal resin will be semicrystalline copolyester and may have a low glass transition temperature (Tg, determined in accordance with ASTM E1356-08) between about -30°C and about 15°C, preferably in the range of -20°C to 10°C and more preferably between about -15°C and about 0°C. The fully formulated heat seal resin may also have a ball and ring melting point (determined in accordance with ASTM E28-99) between about 110°C and about 170°C, preferably in the range of 120°C to 160°C and more preferably between about 130°C and about 155°C. The fully formulated heat seal resin may also have a DSC melt temperature (Tm determined in accordance with ASTM D7138) between about 100°C and about 170°C, preferably in the range of 120°C to 150°C and more preferably in the range of 125°C to 145°C. The fully formulated heat seal resin may also have an intrinsic viscosity (determined in accordance with ASTM D5225-14) of between about 0.4 and about 1.1 dL/g, preferably in the range of 0.5 to 1 .0 dL/g, and more preferably in the range of 0.6 and about 0.8 dL/g. The fully formulated heat seal resin may also have an apparent melt viscosity of between about 500 poise and about 3000 poise determined at 215°C, preferably in the range of 1000 poise to 2500 poise, and more preferably in the range of about 1500 poise to 2000 poise (determined in accordance with ASTM D3236-15). In a preferred embodiment, the fully formulated heat seal resin has a glass transition temperature of between about -15°C to about 0°C, a ball and ring melting point of between about 135°C to about 155 °C, a DSC melting temperature in the range of 130 °C to 145 °C, an intrinsic viscosity in the range of 0.72 to about 0.86 dL/g, and a melt viscosity of about 1500 poise at 2,000 poise.

[0043] In an exemplary embodiment, the heat seal copolyester resin is made from a combination of diol and diacid/diester components (with the diacid and diester components being interchangeable), wherein at least one of the diol or diacid/diester groups have at least two components, for example 1 diol and 2 diacids/diesters or 2 diols and one diacid/diester. As for the diol component, monomers of standard polyester diols such as ethylene glycol, diethylene glycol, butanediol (1,4-; 1,2-; and 1,3-), neopentyl glycol, 2-methyl-1,3-propanediol, hexanediol, trimethylolpropane, cyclohexanedimethanol and tricyclodecanedimethanol can be used. The diester monomers can include any known diester used in the preparation of copolyester resins, such as dimethyl terephthalate or dimethyl isophthalate. The diacid monomers used can include any known diacid used in the production of copolyester resins, such as terephthalic acid, isophthalic acid, adipic acid, azelaic acid, sebacic acid and cyclohexanedicarboxylic acid. These monomers can be used to produce either semicrystalline or amorphous copolyester resin, the monomer ratios and processing conditions being modified in known manner to produce either semicrystalline or amorphous copolyester resin.

[0044] More specifically for the semicrystalline copolyester resin of the copolyester resin component, the semicrystalline copolyester resin can be made from a diol and a diester and a diacid in a known manner. Diols can be selected from ethylene glycol, diethylene glycol, butanediol (1,4-; 1,2-; and 1,3-), neopentylglycol, 2-methyl-1,3-propanediol, hexanediol, trimethylolpropane, cyclohexanedimethanol, tricyclodecanedimethanol and their mixtures. The diesters can be selected from dimethyl terephthalate and dimethyl isophthalate and mixtures thereof. Finally, the diacids can be selected from terephthalic acid, isophthalic acid, adipic acid, azelaic acid, sebacic acid, cyclohexanedicarboxylic acid and mixtures thereof. Commercially available extrudable grade copolyester resins are suitable for use as semicrystalline copolyester resin, this application includes Vitel™ 1901NSB, Vitel™ 1904NSB, VitelTM 1801, VitelTM1912NSB, VitelTM 1916NSB supplied by Bostik, Inc. or combinations thereof. These copolyesters provide the gentle removal that is necessary for the consumer to open the package without tearing the lid and spilling the food. Another suitable resin includes Vylon 30P, commercially available from Toyobo. Still other suitable resins include Mor-ester grades from Dow. In another embodiment, the semicrystalline copolyester resin is made from ethylene glycol, terephthalic acid, sebacic acid and azelaic acid. In another embodiment, the semicrystalline copolyester resin is made from ethylene glycol, terephthalic acid and azelaic acid. In another embodiment, the semicrystalline copolyester resin is made from ethylene glycol, terephthalic acid and sebacic acid. Semicrystalline copolyester resins are those materials that have a well-disposed crystalline phase within the more random amorphous domain. The ordered crystalline sites impart properties such as toughness and opacity to the resin. Semicrystalline copolyester resins have a degree of crystallinity of at least 5% but 30% or less, as determined by DSC or equivalent technique, against a highly crystalline polypropylene standard. In one embodiment of the invention, the semicrystalline copolyester resin has a Tg of about -30°C to about 20°C (preferably about -15°C to about 5°C); a Tm of about 125°C to about 170°C (preferably about 135°C to about 160°C); a ball and ring melting point of about 110°C to about 170°C (preferably about 135°C to about 160°C); an intrinsic viscosity between about 0.85 and about 1.05 dL/g (preferably in the range of about 0.88 to about 1.0 dL/g); and a melt viscosity in the range of about 1250 to about 3250 poise (preferably between about 1600 to about 2600 poise). (Throughout, all properties of the various constituents are consistently determined unless otherwise specified.)

[0045] In embodiments where the copolyester component comprises a blend of semicrystalline copolyester resin and an amorphous copolyester resin, the approximate ratios of the two resins are in the range of 1.5:1 to 30:1, preferably from about 2 :1 to about 10:1 and more preferably from about 3:1 to about 8:1. The range of semicrystalline copolyester resin component that is present in the fully formulated heat seal resin composition can be in an amount between about 60% to about 99.9% by weight of the composition, preferably between about 70% to about 99.8% and more preferably from about 70% to about 80%.

[0046] Turning next to the amorphous copolyester resin of the copolyester resin component, the amorphous copolyester resin can be made from one or more diols, diesters and diacids in known manner. Diols can be selected from ethylene glycol, diethylene glycol, butanediol (1,4-; 1,2-; and 1,3-), neopentylglycol, 2-methyl-1,3-propanediol, hexanediol, trimethylolpropane, cyclohexanedimethanol, tricyclodecanedimethanol and their mixtures. The diesters can be selected from dimethyl terephthalate and dimethyl isophthalate and mixtures thereof. The diacids can be selected from terephthalic acid, isophthalic acid, adipic acid, azelaic acid, sebacic acid and cyclohexanedicarboxylic acid and mixtures thereof. In one embodiment, the amorphous copolyester resin comprises ethylene glycol, neopentyl glycol, terephthalic acid, isophthalic acid, sebacic acid and azelaic acid. In another embodiment, the amorphous copolyester resin is made from ethylene glycol, neopentyl glycol, terephthalic acid and isophthalic acid. In another embodiment, the amorphous copolyester resin is made from ethylene glycol, neopentyl glycol, terephthalic acid and isophthalic acid and sebacic acid. Yet another embodiment, the amorphous copolyester resin is made from ethylene glycol, neopentyl glycol, terephthalic acid and isophthalic acid and azelaic acid. In yet a final embodiment, the amorphous copolyester resin is made from ethylene glycol, terephthalic acid and isophthalic acid. Commercially available extrudable grade copolyester resins that are suitable for use as the amorphous copolyester resin in this application include amorphous copolyester resins with a high glass transition temperature (Tg) in the range of 45°C to 110°C, such as VitelTM 2700B, Vitel™ 2200B or Vitel™ 1200B available from Bostik, Inc. Another suitable resin includes Vylon RN9300, commercially available from Toyobo. These resins also help improve the adhesion of the heat seal coating on APET trays.

[0047] As used herein, amorphous copolyester resins are those resins which are glassy and transparent. They do not have a defined molecular arrangement, as the structure is very random and intertwined. Based on the glass transition temperature, they can be sticky or brittle at room temperature. The amorphous copolyester resin lacks any crystallinity and melting point as determined by DSC or equivalent technique and therefore has a melting enthalpy of zero. In one embodiment of the invention, the amorphous copolyester resin has a Tg of about 45°C to about 110°C (preferably about 60°C to about 80°C); a ball and ring melting point of about 125°C to about 175°C (preferably about 140°C to about 160°C); an intrinsic viscosity between about 0.5 and about 0.7 dL/g (preferably in the range of about 0.55 to about 0.65 dL/g); and a melt viscosity in the range of about 1750 to about 3750 poise (preferably between about 2250 to about 3250 poise). The range of amorphous copolyester resin component that is present in the composition can be in an amount between about 5% and 40% by weight of the composition, preferably between about 10% to about 30% and most preferably between about 10% % to about 25%.

[0048] In an exemplary embodiment, the heat seal copolyester resin is made from a combination of conventional polyester diols, such as ethylene glycol, diethylene glycol, butanediol (1,4-; 1,2-; and 1, 3-), neopentylglycol, 2-methyl-1,3-propanediol, hexanediol, trimethylolpropane, cyclohexanedimethanol, tricyclodecanedimethanol and diesters such as dimethyl terephthalate, dimethyl isophthalate or diacids such as terephthalic acid, isophthalic acid, adipic acid , azelaic acid, sebacic acid and cyclohexanedicarboxylic acid. Such a resin provides consistent seal strength for seal temperatures as low as 121°C or lower and up to 163°C or higher. The % haze of the films produced by coextrusion were found to be as low as 6.49% and as high as 10.23% for a coating weight of approximately 1.25 pounds/ream (lb/rm). The extruded films had haze as high as 39.28% and as low as 21% for a coat weight of 5.5 lb/rm. Conditions for the extrusion process can be modified to provide low haze films that can be used for the application.

[0049] The heat sealing resin composition also comprises anti-fog additives to impart the final application property of anti-fog nature to the PET film. This additive imparts good anti-fog ability when the film is exposed to hot-fog or cold-fog conditions. Any suitable anti-fog additive can be used and preferably this additive, like the other constituents, is food safe if the item to be contained is a food item. The antifogging additive may be selected from the group consisting of sorbitan esters, glycerol esters, ethoxylated sorbitan ester and alpha monoglyceride modified compounds, and mixtures thereof. Various anti-fog additives supplied by Croda Polymer Additives can be used, such as AtmerTM 100 (a liquid sorbitan ester), AtmerTM 1440 (a liquid glycerol ester), AtmerTM 1010 (a glycerol ester paste), AtmerTM 116 (a sorbitan ester liquid ethoxylate). Lonza's anti-fog additives, such as GlycolubeTM AFA-1 VEG (proprietary anti-fog, which is a viscous oily liquid opaque at 25°C) and GlycolubeTM MO-O-20 (patented anti-fog additive with 20 to 30% alpha monoglyceride that is a viscous oily liquid opaque at 25 °C) can also be used as an anti-fog additive. Other anti-fog additives with similar chemistry, performance, and properties may also be used. Preferably, the anti-fog additive migrates to the surface of the PET film and increases the surface energy of the PET film and decreases the surface energy of water droplets, forming a continuous and uniform transparent layer of water when water condenses on the surface. of the PET film. The antifogging additive is present in an amount of between about 0.01% to about 5% by weight of the fully formulated heat seal resin composition, preferably about 0.1% to about 5% and most preferably about from 2% to about 5%.

[0050] The heat sealing resin composition also comprises an anti-blocking and slip additive. Without the anti-blocking additives, coated flexible substrates would tend to block when rolled into a roll and stored before being used in a form, fill and seal machine. Slip additives serve to give film slip and help move the film smoothly through converting and packaging equipment. As used herein, the phrase "an anti-blocking and slipping additive" is used to denote a single constituent that serves primarily to reduce blocking, a single constituent that serves primarily to reduce slippage, or a single constituent that adequately performs both functions, or their combinations, provided that some level of both reductions in blocking and slippage is achieved over a formulation without the constituent(s). Any suitable anti-blocking and sliding additive can be used. The anti-blocking and sliding additive may comprise silica, silicate and amides such as fatty amides or polyamides or combinations thereof. The antiblocking and glidant additive may comprise amides and the amides have a melting point in the range of 70°C to 180°C. In one embodiment, the antiblock and slip additive comprises fatty amides having a melting point in the range of 70°C to 150°C. In another embodiment, the antiblock and slip additive comprises polyamides having a melting point in the range of 150°C to 180°C and an average particle size in the range of about 0.5 to about 10 microns. In yet another embodiment, the anti-blocking and slip additive comprises silica, and the silica has an average particle size in the range of about 0.5 to about 10 microns. In another embodiment of the invention, the silica is a mixture of two sources of silica consisting of a first source having an average particle size of about 0.5 to about 4 microns and a second source having an average particle size of about from 5 to about 10 microns. In another embodiment, the anti-blocking and glidant additive comprises particles from a first and second source and the first source has an average particle size of about 1.5 to about 4 microns and the second source has an average particle size of about 8 to about 12 microns.

[0051] The antiblocking and slip additives preferably include a silica blend (e.g., Sylobloc™ 47 - a silica gel antiblocking agent supplied by W.R. Grace & Co. with a particle size of 5.4 to 6 .6 microns, Sylysia™ 310P- a silicate supplied by Fuji Silysia Chemical Ltd with a particle size of 1.5 to 4 microns and Lo-Vel™ 29- a synthetic amorphous precipitated silica supplied by PPG industries with an average particle size 10 micron) and fatty amides, such as: Crodamide™ ER-antiblocking and glidant available from Croda Polymer Additives, a refined erucamide with a melting point of 79 °C; Crodamide™ BR- anti-blocking and slip agent provided by Croda Polymer Additives, a refined behenamide with a melting point of 108 °C; Crodamide™ 212, anti-blocking and glidant available from Croda Polymer Additives, a stearyl erucamide with a melting point of 72.5 °C; or CrodamideTM EBS-antiblocking and glidant available from Croda Polymer Additives, an ethylene bis-stearamide with a melting point of 143 °C. Grease amides act as an anti-blocking agent or external lubricant that improves the flow and release properties of the coated PET film. These amides bloom on the surface and provide the anti-blocking capability needed when the film is stored after the coating is manufactured. Furthermore, the addition of polyamides such as OrgasolTM 2001 UD NAT 2 (melting point 177 °C, spheroidal polyamide with a particle size of 5 microns) and OrgasolTM 2002 EXD NAT 1 (melting point 177 °C, spheroidal polyamide with a particle size of 10 microns) supplied by Arkema Inc. can also be used as suitable anti-block and slip additives.

[0052] The copolyester monomers, as well as the additives used in the composition of the heat sealing resin, are desirably approved for direct contact with food. It has been found that semicrystalline copolyester heat sealing resins are easily extruded into PET films or co-extruded with polyester resins to form a heat sealing PET film. Thus, semicrystalline copolyester heat seal resin provides excellent adhesion to polyester films for use in sealing APET (Amorphous Polyester) tray stocks. The heat seal resin with a semi-crystalline structure with low glass transition temperature eliminates the tendency for the heat seal coating to slip when the coated packaging film is stored in roll form prior to use in a forming, filling machine. and sealing the package. Also provides flexibility, elasticity and resistance to coating

[0053] A mixer or extruder can be used to make the heat seal resin composition of the present invention. The additives can be extruded using a Leistritz MIC 27 6L/400 twin screw extruder to form the formulated copolyester heat seal resin which can then be coextruded with PET or extrusion coated onto PET film. It is recommended to dry Vitel® copolyester resins at 68°C for five hours prior to the twin screw extrusion process. The following parameters can be used for all compositions, but the pressures can be varied, and consequently the torque, so that both are represented as a range. Solids can be fed using three solid feeders. Two vibrating feeders, a screw feeder and a liquid port can be used for feeding into the extruder port. The feed rate can be varied to obtain the desired weight percentage of each raw material according to the formulation. A bolt dimension of 27 mm can be used and can be run at a speed of about 200 rpm with a pressure of 650 to 800 psi, giving a torque of 72%. The screw zone temperatures can be set to 130, 135, 135, 140, 140, 145, 150, 150, 150, 150 °C for the extrusion process. An extruder temperature can be controlled using a chiller (eg Aqua Poly Equipments Co. AEC chiller) which can be set to 60 °C. The thus extruded heat seal resin can be cooled using a water bath, crystallized and cut to give solid pellets. Once extruded and cut, the formulated copolyester resin can be dried and packaged in foil lined bags for use by the converter.

[0054] According to another embodiment of the invention, a method for manufacturing a laminate comprises the steps of: forming a heat seal resin composition by mixing a copolyester resin component, an anti-fog additive and an anti-blocking and slip-in-the-absence additive of a solvent; and applying the heat seal resin composition to the polyester to form the laminate, wherein no solvent is added to the heat seal resin composition before or during the application step. While other methods of applying the heat seal resin composition to the polyester may be used, co-extrusion or extrusion is preferably used.

[0055] In one aspect, the invention is directed to a heat seal coated packaging film to which the heat seal coating is applied on one side of the film by an extrusion process. The film is formed by extruding the formulated heat seal resin at a specific temperature which will help melt the formulated heat seal resin and form a stable curtain which can then adhere to a PET film. This final film has 100% coverage of the heat seal coating in some embodiments. Typically, the heat seal coating so formed should have a thickness corresponding to a coating weight of at least 1.0 lb/rm and can range as high as 5 lb/rm or 10 lb/rm. As used here, a ream ("rm") is 3,000 square feet. Coating thickness is also determined by extrusion temperature as well as line speed and screw speed. The thickness is adjusted based on these parameters to give a coating that is clear, capable of sealing tray stock with good bond strength with easy removal rather than solder sealing, as well as good anti-fog and anti-blocking ability. Any expert in the extrusion art would know how to obtain such a film coating.

[0056] In another aspect, the invention is directed to a heat seal coated packaging film which is formed by coextruding the formulated heat seal resin together with the PET resin to form the extrudate. This extrudate is biaxially oriented to give the final film which acts as a PET substrate to bond to the APET trays. In doing so, the film is very clear with the heat seal coating as one of the layers of the film which imparts heat sealability to the film as well as imparts anti-fog and anti-blocking ability to the film. Anyone skilled in the art would know how to make such a PET film for use in food packaging. This is described very well in examples like Pat. US Pat. No. 4,375,494, US Pat. US Pat. No. 7,413,800. US Pat. No. 3,371,947, US Pat. US Pat. No. 4,165,210, US Pat. US No. 6,939,584. Typically, the heat seal coating formed by this technique is less in thickness compared to the extrusion coating due to the ability to orient the film in both directions. Coating weight is at least 1.0 lb/rm. Coating weight is also determined by coextrusion temperature as well as line speed and screw speed. The coating weight is adjusted based on these parameters to give a coating that is clear, capable of sealing the tray stock with good bond strength giving easy removal when the tray is opened, as well as having good anti-fog and anti-blocking ability.

[0057] Importantly, no primer coating is required for this heat seal coating to adhere to the substrate commonly used in the packaging industry, used to pack fresh produce, or in general polyethylene terephthalate (PET) to be used as a coating material clear for food packaging. Proper anchoring to substrates is accomplished by including resins that have the ability to adhere to this substrate. In addition, corona treatment is useful to increase surface energy and improve anchorage if needed during the extrusion process. This treatment generally cleans the surface of the PET film most of all, as PET film has high static and tends to get dirty on the surface.

[0058] The flexible PET film thus formed is sealed to an APET container that holds items such as fresh produce and other refrigerable foods. This package prevents food leakage with good package integrity. The seal on the APET tray can be formed by placing the flexible film on top of the container and applying heat and pressure for a set period of time to melt and soften the sealable liner layer, helping it to adhere to the APET container. This allows the flexible skin to form an easily peelable seal between the flexible lid stock and the rigid tray stock. The seal is called a peel-off seal, so that the lid is strong enough to hold food without any leakage, but at the same time it is easy to open instead of tearing the flexible lid resulting from a solder seal. This type of seal is controlled by the proper selection of copolyester resin chemistry, as well as being able to adjust uniform film thickness during the manufacture of flexible PET film by extrusion or co-extrusion process.

[0059] As seen in several cases, the sealable layer coating is applied to the PET film as a secondary offline process. Pat. WO No. 2014006205 A1, CN 102558978, KR 2006109623, JP 2007031545, US 20130224411 A1, US 2011/0163101 A1 are all examples for this process. This can occur before, during or between any stretching operations to form the final flexible PET film. Coating generally uses organic solvents or water, depending on the chemistry of the coating. These solvents, if not completely evaporated, can cause sticking or blocking of the film when rolled up after film production. Furthermore, any solvent trapped in the film may be harmful to use in the next step when used for food packaging. Thus, proper heating and drying of the film, involving longer process time, along with expensive equipment, are very important to produce a good quality film for the desired final application. In certain cases, this step can impair the overall properties of the film, making it brittle and also deteriorating tensile properties. Thus, in-line coating produced without the aid of solvents and which can be processed in a single step would be beneficial to the converter in terms of reducing steps as well as reducing the use of solvents or eliminating them completely and also reducing the total time and cost to produce the film.

[0060] In practice, converters use the extrusion or co-extrusion process to produce the clear PET cover film. While this work is specific to the extrudable hot seal copolyester resin, any converter capable of handling solvents could also potentially use this product to form the heat seal PET film. Since heat seal copolyester resin dissolves in solvents such as tetrahydrofuran (THF) or 1,3-dioxolane, the resin can be solvated in these solvents and applied to PET films. This is usually done by feeding a roll of packaging film to a printer, such as a gravure or flexo printer. The converter then uses the printer to apply the solvated heat seal coating to one side of the packaging film. The converter then dries the solvent based heat seal coating to remove the solvent, for example using conventional in-line drying systems, thereby leaving a dry solid layer of heat seal coating on the packaging film. The converter then rewinds the coated and dried film into roll form for later use in a package forming, filling and sealing machine. As mentioned, it may be necessary to treat the packaging film via corona discharge prior to applying the heat seal coating through the extrusion process or during the printing process in order to ensure proper anchoring of the coating to the packaging film. . This treatment generally cleans the surface of the PET film most of all, as PET film has high static and tends to get dirty on the surface.

[0061] According to an embodiment of the invention (i.e., in a method of manufacturing a laminate or manufacturing a package to contain an item, such as a food product), the heat seal copolyester resin contains the following ingredients: a. heat seal polyester resin in an effective amount, such as about 90-95% by weight, b. anti-fog additives in an effective amount, such as about 0.01-5% by weight, and c. antiblocking and glidant additives in an effective amount, such as comprising about 0.01-2.5% by weight silica and about 0.01-2.5% by weight amides (steryl erucamide, refined erucamide, bis -stearamide or ethylene polyamide etc.).

[0062] The weight percentages can vary over a wide range to achieve the objects of the present invention. According to one embodiment of the invention, the copolyester resin component is present in an amount of between about 80% to about 99% by weight of the composition; the anti-fog additive is present in an amount of from about 0.01% to about 5% by weight of the composition; and the antiblock and slip additive is present in an amount of from about 0.01% to about 5% by weight of the composition. According to another embodiment of the invention, the semicrystalline copolyester resin component is present in an amount of between about 60% to about 99.9% by weight of the composition; and the amorphous copolyester resin is present in an amount of from about 5% to about 40% by weight of the composition. According to yet another embodiment of the invention, the semicrystalline copolyester resin component is present in an amount of between about 70% to about 99.8% by weight of the composition; the amorphous copolyester resin is present in an amount of from about 10% to about 30% by weight of the composition; the anti-fog additive is present in an amount of from about 0.1% to about 5% by weight of the composition; the antiblock and slip additive is present in an amount of from about 0.1% to about 5% by weight of the composition. According to yet another embodiment of the invention, the semicrystalline copolyester resin component is present in an amount of between about 70% to about 80% by weight of the composition; the amorphous copolyester resin is present in an amount of from about 10% to about 25% by weight of the composition; the anti-fog additive is present in an amount of from about 2% to about 5% by weight of the composition; and the antiblock and slip additive is present in an amount of from about 0.1% to about 2% by weight of the composition.

[0063] In each of the above embodiments, the heat seal resin composition may contain only the constituents identified above, namely the copolyester resin component (alone or as the sum of the semicrystalline copolyester resin component and the amorphous copolyester resin), the anti-fog additive, and the anti-block and slip additive. In this case, the sum of the weight percentages of these constituents would increase to 100%. In some embodiments, additional constituents such as a solvent, an antioxidant, a colorant, a filler and a UV fluorescent agent may be added. In such embodiments, the sum of the weight percentages of the three components (i.e., the copolyester resin component, the anti-fog additive, and the anti-block and slip additive) or the four components (i.e., the semicrystalline copolyester resin component , amorphous copolyester resin component, anti-fog additive, and anti-block and slip additive) listed above would be less than 100%.

[0064] To provide good adhesion to APET trays, this semicrystalline copolyester resin is used in conjunction with a high Tg copolyester resin in embodiments of the invention. The semi-crystalline nature of the resin is a beneficial feature in that an amorphous resin with a similar low Tg would be prone to cold flow at room temperature and would tend to creep or flow so that the integrity of the coating would be compromised when the resin coated roll heat sealing is stored. It also helps provide smooth lid removal when the PET lid is opened from the APET tray. This will prevent the seal from being a solder seal, as well as prevent the cover from being shredded.

[0065] The listed heat seal copolyester resins are semicrystalline but are not completely crystallized in time during conversion to PET films. In other words, these resins are slow crystallizers and it takes about one to six hours to completely crystallize in the presence of heat, while the skin conversion takes place in a few seconds. The film tends to block severely unless anti-blocking additives are included in the mix.

[0066] According to the invention, it is desirable that the packaging film onto which the heat seal coating is extruded or the film formed by the coextrusion process is suitable for use in the food industry and is listed as being in compliance with FDA direct food contact, 21 CFR §175.300, with a condition of use for refrigerated food packaging. For the extrusion process, the heat seal copolyester resin is melt extruded onto a PET film, which is then quenched and preferably oriented in at least one direction to obtain a heat seal coating having uniform coating as well as good clarity for the application. This heat seal coated PET film can then be used to seal the containers. When the PET film comprises more than one layer, or where the coextrusion process is beneficial, the different polyesters or copolyesters with suitable additives are simultaneously coextruded through independent orifices of a multi-orifice die and then joining the still molten layers together. It can also be achieved by a single-channel coextrusion in which the molten streams of the respective polymers are first joined together within a channel leading to a die manifold and thereafter extruded together from the die orifice under conditions of linear flow without blend, thereby producing a multilayer polymeric film which can then be oriented and heated to form a biaxially oriented PET film with one of the layers being the heat seal layer. This layer on the PET film can then be used to heat and pressure seal containers.

[0067] The coating is preferably applied to result in a minimum coating weight of 1.00 pounds/ream and a maximum coating weight of 10 pounds/ream, depending on the process. Coextrusion processes generally have the ability to form very thin heat seal coating layers compared to extrusion coating. Higher coating weights generally increase turbidity and decrease the removal force on the vessel. Furthermore, if not required, it results in higher costs for the converter. After the coating film is produced by extrusion or co-extrusion process, the coated web is wound onto a roll of heat seal coated film. Once produced, the roll can be cut and used for further processing or packaging.

[0068] The heat-sealing copolyester resin is packaged and shipped to converters in aluminum-lined bags. The only handling part is drying the resin well enough to allow for gentle processing of the resin so that it doesn't degrade with heat and moisture. A good level for moisture in the formulated heat seal resin would be 0.05% by weight or less.

[0069] The heat seal copolyester resin is preferably a combination of conventional polyester diols such as ethylene glycol, diethylene glycol, butanediol (1,4-; 1,2-; and 1,3-), neopentyl glycol, 2- methyl-1,3-propanediol, hexanediol, trimethylolpropane, cyclohexanedimethanol, tricyclodecanedimethanol and diesters such as dimethyl terephthalate, dimethyl isophthalate or diacids such as terephthalic acid, isophthalic acid, adipic acid, azelaic acid, sebacic acid and cyclohexanedicarboxylic acid. The overall composition of the heat seal copolyester resin provides excellent anchorage to the polyester for the extrusion process. It can also be co-extruded together with commercial polyester resin to form the final heat seal film without any incompatibility or in-line processing problems, this is due to the chemical identity of the resins being extruded. No primer coating is required to anchor the heat seal coating to a high surface energy PET film during the extrusion process. This anchoring to high surface energy substrates is easily achieved due to the polar nature of the copolyester resin. Corona treatment of the substrate will also improve anchorage if needed. This treatment generally cleans the surface of the PET film more than anything else, as PET film has high static and tends to get dirty on the surface.

[0070] The heat seal coating on the PET film provides excellent sealability for APET trays in a wide range of temperatures. Bond strength in excess of 200 grams per linear inch (gly) is provided at bond seal temperatures of 121°C. Bond strength is very consistent throughout the application temperature window. This consistent bond strength allows for reliable seals to form at various bond temperatures during the form-wrap, fill and seal process. This property is highly desirable within the packaging industry.

[0071] As mentioned above in embodiments of the invention, the copolyester resins used in this invention are a mixture of semicrystalline and amorphous copolyester resins. A good example is the use of Vitel™ 1901 copolyester resin, which is semicrystalline. It has a glass transition temperature of -4 °C and a broad melting peak at 125 °C (ASTM D7138). It has a ball and ring melting point of about 150 °C. The amorphous copolyester used in the invention is VitelTM1200B with a glass transition temperature of 70°C and a ball and ring melting point of 145°C. Since it is amorphous, it does not impart any crystallinity to the overall heat seal coating. The two copolyester resins are very compatible and easy to melt and are mixed in a twin screw extruder together with other additives, which are skilled in the technique of copolyester resin extrusion. Thus, the final base copolyester resin has a combination of semicrystalline and amorphous nature with low enough glass transition temperature to make it flexible without cold flow, elastic, resistant to deformation and enough strength to form a very stable bond to a APET tray. The coating, together with the other additives, is non-blocking and has sufficient sliding properties to be easily handled unrolled once produced and stored in roll form. It also contains the anti-fog additives in a suitable combination to impart a PET film that is clear, has anti-fog capabilities and provides smooth, consistent removals. The film's anti-fog ability does not decrease with roll film storage.

[0072] Vitel™1901NSB together with Vitel™1200B was identified as a desirable combination to form the base heat seal copolyester resin. The blend generally consists of about 70-90% VitelTM 1901 and 10 to 30% VitelTM 1200B by weight of the binary blend to give the desired properties. While this combination has been identified as a preferred embodiment, this cannot be restrictive as other combinations and other Vitel® copolyester resins can be used to form the base of the anti-fog heat seal copolyester resin. Other copolyester blends with similar hot properties may be suitable for the manufacture of the invention including resins containing the following polyester monomers: conventional polyester diols such as ethylene glycol, diethylene glycol, butanediol (1,4-; 1,2-; and 1,3-), neopentylglycol, 2-methyl-1,3-propanediol, hexanediol, trimethylolpropane, cyclohexanedimethanol, tricyclodecanedimethanol and diesters such as dimethyl terephthalate and dimethyl isophthalate and diacids such as terephthalic acid, isophthalic acid, adipic acid, azelaic acid, sebacic acid and cyclohexanedicarboxylic acid. Semicrystalline copolyester resins will have Tg between -30°C and 0°C, Tm from 100°C to 160°C, and ball and ring melting point from 70°C to 160°C. Amorphous copolyesters would have a Tg of 45°C to 110°C and a ball and ring melting point of 130°C to 200°C. The intrinsic viscosity of these copolyester resins can range from 0.5 to 1.0 dl/g.

[0073] The heat seal coating formulation described herein is an extrudable copolyester resin intended for sale to film converters, for example, as a fully formulated dry resin in bags or drums. As copolyesters have a tendency to absorb moisture over time, the converter is expected to dry the fully formulated copolyester resin before extruding or co-extruding it. Vacuum or air drying at 60 °C (140 °F) for a minimum of four hours should reduce moisture to 0.05% by weight or less for the next step.

[0074] A suitable combination of additives is desirable for good processability of the resin, as well as having the desired final properties, including good adhesion strength, clarity and anti-fog ability. This was achieved by a combination of anti-lock, glide and anti-fog additives. A combination of antiblock and slip additives of a suitable particle size is desirable to provide the antiblock and slip nature to the film. It also helped the additives properly efflorescence to the surface of the film without competition between the anti-blocking and anti-fogging ingredients. The clarity of the film was not compromised in doing so either. A combination of silica such as SyloblocTM47 and SylisiaTM 310P as well as fatty amides such as Crodamide 212, Crodamide ER, or polyamide such as Orgasol 2001 UD NAT2 has been found to provide a smooth and consistent coating. A combination of anti-fog additives such as Atmer 1010 and Atmer 116 is also preferred for good anti-fog properties. These additives have been chosen so that they do not undergo any degradation during the twin screw extrusion process for manufacturing the heat seal copolyester resin, as this is carried out at temperatures as high as 150°C or more.

[0075] In summary, the disclosed heat seal copolyester resin composition provides extrusion or co-extrusion coating to obtain a clear PET film, which can be used for packaging food, to be stored in the refrigerator. The PET film containing the food contact side heat seal coating is clear, non-blocking and is capable of condensing water droplets to provide a clear window for the consumer to view the quality of packaged food without any fogging . The shelf life of food packaged in APET trays is not compromised as the package is well sealed with the heat seal coated PET film. The processing window for the packaging industry is also good, as the package can be sealed at 121°C to about 163°C with consistent bond strength using 35 psi pressure and a dwell time of about 0.5 seconds . These conditions can be modified depending on the application window of the packaging industry. It can be primed free extrusion coated onto the PET film and provide good bonding strength to APET trays. For applications requiring direct food contact, all components of the selected fully formulated heat seal copolyester resin need to comply with FDA regulations as well as EU food contact compliance.

[0076] The predominant film used in these applications is a polyester, such as Mylar®. However, the base film can include any plastic material that is suitable for packaging food products. Useful plastics include homopolymers, copolymers, terpolymers and heteropolymers of one or more of polyolefins, polyamides, polyesters, polyvinyls, polystyrenes, polyurethanes, polycarbonates, including polymers such as ethylene/vinyl alcohol copolymers (EVOH), polyvinylidene chlorides, polyalkylene, and starch-containing polymers. Ionomer films could also be considered, such as SURLYN® sold by DuPont Teijin Films. Plant-based or other renewable materials can also be used, for example PEF (polyethylene furanoate), PLA (polylactic acid) or polycaprolactone based polymers. Thus, whenever "polyester film" is used here, it can be replaced by any of these other films.

[0077] Films can, for example, be cast, extruded, co-extruded, laminated, and the like, including orientation (uniaxial or biaxially) by various methodologies (e.g., blown film, mechanical stretching, or the like). Various additives known to those skilled in the art may be present in the respective film layers including the presence of tie layers and the like. Additives include antioxidants and heat stabilizers, ultraviolet (UV) light stabilizers, pigments and dyes, fillers, delusters, anti-slip agents, plasticizers, anti-blocking agents, other processing aids, and the like.

[0078] Furthermore, although the single-film layer is primarily discussed here, the "film" to which the heat seal resin composition is applied can be any type of multi-layer film. For packaging films like these, it is common to use films that have several different layers for different reasons. A three- or four-layer structure is possible, where the top layer is easy to print, the middle layer is an oxygen barrier, the third layer gives high strength, and the fourth layer is our adhesive. ASPECTS OF THE INVENTION Aspect 1. A heat seal resin composition for providing a heat seal film on a film such as a polyester film comprising: a copolyester resin component comprising a blend of a semicrystalline copolyester resin and an amorphous copolyester resin; an anti-fog additive; and an anti-block and slip additive. Aspect 2. The composition of aspect 1, wherein: the copolyester resin component is present in an amount of between about 80% to about 99% by weight of the composition; the anti-fog additive is present in an amount of from about 0.01% to about 5% by weight of the composition; and the antiblock and slip additive is present in an amount of from about 0.01% to about 5% by weight of the composition. Aspect 3. The composition of aspect 2, wherein: the semicrystalline copolyester resin component is present in an amount of between about 60% to about 99.9% by weight of the composition; the amorphous copolyester resin is present in an amount of from about 5% to about 40% by weight of the composition. Aspect 4. The composition of aspect 3, wherein: the semicrystalline copolyester resin component is present in an amount of between about 70% to about 99.8% by weight of the composition; the amorphous copolyester resin is present in an amount of from about 10% to about 30% by weight of the composition; the anti-fog additive is present in an amount of from about 0.1% to about 5% by weight of the composition; and the antiblock and slip additive is present in an amount of from about 0.1% to about 5% by weight of the composition. Aspect 5. The composition of aspect 4, wherein: the semicrystalline copolyester resin component is present in an amount of between about 70% to about 80% by weight of the composition; the amorphous copolyester resin is present in an amount of from about 10% to about 25% by weight of the composition; the anti-fog additive is present in an amount of from about 2% to about 5% by weight of the composition; and the antiblock and slip additive is present in an amount of from about 0.1% to about 2% by weight of the composition. Aspect 6. The composition of any one of Aspects 1-5, wherein the antiblock and slip additive comprises silica and amides. Aspect 7. The composition of aspect 6, wherein the anti-blocking and glidant additive comprises amides and the amides comprise fatty amides and polyamides. Aspect 8. The composition of aspect 7, wherein: the fatty amides are present in an amount of between about 0.01% to about 1.5% by weight of the composition; and the polyamides are present in an amount of between about 0.001% to about 1.0% by weight of the composition. Aspect 9. The composition of aspect 7, wherein the antiblock and slip additive comprises amides and the amides have a melting point in the range of 70°C to 180°C. Aspect 10. The composition of aspect 9, wherein the anti-blocking and glidant additive comprises fatty amides having a melting point in the range of 70°C to 150°C. Aspect 11. The composition of aspect 9, wherein the anti-block and slip additive comprises polyamides having a melting point in the range of 150°C to 180°C and an average particle size in the range of about 0.5 to about 10 microns. Aspect 12. The composition of aspect 6, wherein the anti-blocking and slip additive comprises silica and the silica has an average particle size in the range of about 0.5 to about 10 microns. Aspect 13. The composition of aspect 12, wherein the silica is a mixture of two sources of silica consisting of a first source having an average particle size of about 0.5 to about 4 microns and a second source having a size average particle size from about 5 to about 10 microns. Aspect 14. The composition of aspect 12, wherein the first source has an average particle size of about 1.5 to about 4 microns and the second source has an average particle size of about 8 to about 12 microns . Aspect 15. The composition of any one of Aspects 1-14, wherein the antifog additive is selected from the group consisting of sorbitan esters, glycerol esters, ethoxylated sorbitan ester and alpha monoglyceride modified compounds, and mixtures thereof. Aspect 16. The composition of any one of Aspects 1-15, wherein the heat seal resin composition has: a low glass transition temperature (Tg, ASTM E1356-08) between about -30°C and about 15°C, preferably in the range of -20°C to 10°C, and more preferably between about -15°C to about 0°C; a ball and ring melting point (ASTM E28-99) between about 110°C and about 170°C, preferably in the range of 120°C to 160°C and most preferably between about 130°C and about 145 °C; a DSC melting temperature (Tm ASTM D7138) between about 100°C and about 170°C, preferably in the range of 120°C to 150°C, and more preferably in the range of 125°C to 145°C; an intrinsic viscosity (ASTM D5225-14) between about 0.4 and about 1.1 dL/g, preferably in the range of 0.5 to 1.0 dL/g and most preferably in the range of 0.6 and about 0.8 dL/g; and an apparent melt viscosity of between about 5,000 poise and about 30,000 poise determined at 215°C, preferably in the range of 10,000 poise to 25,000 poise and more preferably in the range of 15,000 poise to 20,000 poise. Aspect 17. The composition of any one of Aspects 1-16, wherein: the semicrystalline copolyester resin has a Tg of about -30°C to about 0°C, a Tm of about 100°C to about 160°C and a ball and ring melting point of about 70°C to about 160°C; the amorphous copolyester has a glass transition temperature (Tg) of between about 45°C to about 110°C and ball and ring melting point of about 130°C to about 200°C; the anti-fog additive has a Tg in the range of about -64 °C to about 0 °C the anti-block and slip additive has a Tm between about 70 °C and about 180 °C and an average particle size between about 0.5 and about 10 microns. Aspect 18. A method of making a laminate comprising the steps of: forming a heat seal resin composition by mixing a copolyester resin component, an anti-fog additive, and an anti-block and slip additive, in the absence of a solvent; applying the heat seal resin composition to a film-forming compound, such as polyester, or a film, such as a polyester film, to form the laminate, wherein no solvent is added to the heat seal resin composition before or during the application step. Aspect 19. The method of aspect 18, wherein the application step comprises coextruding the heat seal resin composition with the film-forming compound or polyester, which is in the form of a resin prior to the coextrusion step. Aspect 20. The method of aspect 18, wherein the polyester is in the form of a polyester film and the application step comprises extruding the heat seal resin composition onto the polyester film. Aspect 21. The method of aspect 20, further comprising extruding the polyester to provide the polyester film. Aspect 22. The method of aspect 20, wherein no primer is applied to the polyester film before the heat seal resin composition is applied to the polyester film. Aspect 23. The method of any one of aspects 18-22, further comprising winding the laminate into a roll form. Aspect 24. A method for making a laminate consisting essentially of the steps of: forming a heat seal resin composition by mixing a copolyester resin component, an antifog additive, and an antiblock and slip additive, in the absence of a solvent ; applying the heat seal resin composition to a film-forming compound, such as polyester, or to a film, such as a polyester film, to form the laminate, wherein no solvent is added to the heat seal resin composition warm before or during the application step. Aspect 25. A method of manufacturing a package to contain an item comprising the steps of: making a laminate by: forming a heat seal resin composition by mixing a copolyester resin component, an anti-fog additive, and an additive antiblocking and sliding, in the absence of a solvent; and applying the heat seal resin composition to a film-forming compound, such as polyester, or a film, such as a polyester film, to form the laminate, wherein no solvent is added to the heat seal resin composition. hot before or during the application step; and contacting the laminate with a top lid of a food tray under sufficient heat and pressure to cause the heat seal resin composition to adhere the laminate to the food tray. The following definitions are provided below: DEFINITIONS 1. High Tg copolyester resins are those resins that have a glass transition temperature of 30°C or greater as determined by Differential Scanning Calorimetry (DSC). 2. Low Tg copolyester resins are those resins that have a glass transition temperature of less than 30°C and below as determined by DSC. 3. The glass transition temperature (abbreviated Tg) is defined as a second order phase transition where an amorphous material becomes glassy and brittle on cooling below and becomes soft and pliable on heating. 4. The seal is called easy peel off or soft peel off, so that the lid is strong enough to hold food without any leakage, but at the same time it is easy to open instead of tearing the flexible lid resulting from a seal. soldering. 5. Weld sealing is the inverse of peel sealing where opening the flexible film from the tray can result in lidstock film tearing 6. Converter is a film manufacturer that can make PET lidstock film by extrusion, co-extrusion or by solvent coating process.

EXAMPLES

[0079] The following examples demonstrate various aspects of certain preferred embodiments of the present invention and should not be construed as limitations thereof.

[0080] Example 1

[0081] Composition 1 of the copolyester heat seal coating: Vitel 1901NSB (or V1901NSB) manufactured by Bostik, Inc is a semi-crystalline copolyester resin with a Tg of - 4 °C, Tm of 125 °C and a melting point ball and ring of about 150 °C. Vitel 1200B (or V1200B) manufactured by Bostik, Inc is an amorphous copolyester resin with a Tg of 70°C and a ball and ring melting point of about 145°C. The heat seal copolyester comprises 76.96% by weight of copolyester V1901NSB, 19.24% by weight of copolyester V1200B, 0.63% by weight of Sylisia 310P from Fuji Sylisia with an average particle size of 2.7 µm , 0.29% by weight of Orgasol 2001 UD Nat 2 from Arkema, Inc. with an average particle size of 5μm, 1.44% by weight of Atmer 1010 and 1.44% by weight of Atmer 116, both Atmers supplied by Croda. The components were mixed using an extruder and pelletized. The thus extruded heat seal resin was cooled using a water bath, crystallized and cut to give solid pellets. The pellets are then dried and packaged to be used for extrusion or co-extrusion. The physical properties of heat seal copolyester resin 1 are given in Table 1. All of the examples cited in the invention were co-extruded and some of them were extrusion coated onto 48 gauge PET film. The properties of the film produced using the examples are given in Table 2 and 3. As can be seen from the examples, the co-extrusion process gave better clarity as well as good anti-fog properties compared to the extrusion process. There was better coating weight control using the co-extrusion process than the extrusion process. The coat weight of the heat seal coating containing the antifog produced by coextrusion could be as low as 1.0 to 2 lb/rm, while the coat weight through the extrusion process was mostly close to 5 to 9 lb. /rm. It was found that by modifying the extrusion temperature, the clarity of the film was improved. It can also be understood that by using a smooth printing roller, as well as controlling the pressure as well as the screw speed of the extruder, the weight of the coating can be controlled and therefore the clarity can be improved. By simplifying the extrusion process by one skilled in the art, it is possible that we can achieve good clarity for the extruded film. The anti-fog properties were very good for the co-extrusion process and good for the extrusion process. Again, higher heat seal coat weights are not needed for this application and this really detracted from the final properties of the film including clarity, adhesion strength as well as anti-fog ability. Again, producing uniform films with good coating weight control is very important to achieve good clarity and good anti-fog properties.

[0082] Example 2.

[0083] Composition 2 of the copolyester heat seal coating: The heat seal copolyester comprises 76.79% by weight of copolyester V1901NSB, 19.22% by weight of copolyester V1200B, 0.84% by weight of Sylobloc 47 from W.R. Grace & Co with an average particle size of 6 µm, 0.28% by weight of Orgasol 2001 UD Nat 2 from Arkema, Inc., 1.43% by weight of Atmer 1010 and 1.43% by weight of Atmer 116, both Atmers supplied by Croda. Components are twin screw extruded using Leistritz MIC 27 6L/400 equipment as described above. The physical properties of heat seal copolyester resin 2 are given in table 1.

[0084] Example 3.

[0085] Composition 3 of the copolyester heat seal coating: The heat seal copolyester comprises 76.69% by weight of copolyester V1901NSB, 19.18% by weight of copolyester V1200B, 0.37% by weight of Sylobloc 47 from W.R. Grace & Co, 0.36% by weight of Sylisia 310P from Fuji Sylisia, 0.44% by weight of Crodamide ER from Croda, 1.48% by weight of Atmer 1010 and 1.48% by weight of Atmer 116 , both Atmers supplied by Croda. Components are twin screw extruded using Leistritz MIC 27 6L/400 equipment as described above. The physical properties of heat seal copolyester resin 3 are given in table 1.

[0086] Example 4.

[0087] Composition 4 of the copolyester heat seal coating: The heat seal copolyester comprises 75.7% by weight of copolyester V1901NSB, 18.92% by weight of copolyester V1200B, 0.66% by weight of Sylobloc 47 from W.R. Grace & Co, 0.52% by weight of Sylisia 310P from Fuji Sylisia, 1.2% by weight of Crodamide ER from Croda, 1.5% by weight of Atmer 1010 and 1.5% by weight of Atmer 116 , both Atmers supplied by Croda. Components are twin screw extruded using Leistritz MIC 27 6L/400 equipment as described above. The physical properties of heat seal copolyester resin 4 are given in table 1.

[0088] Example 5.

[0089] Composition 5 of the copolyester heat seal coating: The heat seal copolyester comprises 75.65% by weight of copolyester V1901NSB, 18.91% by weight of copolyester V1200B, 0.65% by weight of Sylobloc 47 from W.R. Grace & Co, 0.51% by weight of Sylisia 310P from Fuji Sylisia, 0.88% by weight of Crodamide ER and 0.4% by weight of Crodamide 212 from Croda, 1.5% by weight of Atmer 1010 and 1.5% by weight Atmer 116, both Atmers supplied by Croda. Components are twin screw extruded using Leistritz MIC 27 6L/400 equipment as described above. The physical properties of heat seal copolyester resin 5 are given in Table 1.

[0090] Example 6

[0091] Composition 6 of the copolyester heat seal coating: The heat seal copolyester comprises 75.65% by weight of copolyester V1901NSB, 18.91% by weight of copolyester V1200B, 0.65% by weight of Sylobloc 47 from W.R. Grace & Co, 0.51% by weight of Sylisia 310P from Fuji Sylisia, 0.4% by weight of Crodamide ER and 0.88% by weight of Crodamide 212 from Croda, 1.5% by weight of Atmer 1010 and 1.5% by weight Atmer 116, both Atmers supplied by Croda. Components are twin screw extruded using Leistritz MIC 27 6L/400 equipment as described above. The physical properties of heat seal copolyester resin 6 are given in Table 1.

[0092] Example 7 is a commercial grade VitelTM 1916NSB which does not contain any antifog within the formulation. This was used as a comparison product to determine the anti-fog properties of films produced using the above examples which contained anti-fog (1-6).

[0093] Coefficient of Friction (COF) Testing: To maintain good winding performance, a heat seal packaging film was tested for COF on an Instron Model 5982 tester following ASTM D1894 method. The COF is recorded in Table 2. The data suggest good sliding property or ease of winding into a roll.

[0094] Blocking test: The blocking test was conducted on a Block Tester I.C. made by Koehler. Test samples (triplicates) were prepared by placing 2 inch x 2 inch samples in the blockage tester. The samples were aligned such that one sample had the heat seal coated side of the PET film facing up and against the uncoated side of the second PET film which was on top of it. 3 of these sets from each example were placed in the lock tester. A pressure of 10 psi (pounds per square inch) was applied to the film samples. The blocking tester containing the samples was placed in an oven at 50 °C for 16 hours. The blockage tester was removed from the oven and conditioned to the environment. A peel test was conducted on the compressed samples and peel strength values of 50 gly or below are considered passing or non-blocking. All samples had less than 50 gly for the blocking test.

[0095] Haze test: The % haze of the film was measured using the Konica Minolta CM-3700A spectrophotometer in transmittance mode. OnColor software was used for testing. Values were recorded as % haze using the CIELab color spectrum. A standard was used which was a clear PET film without any coating on the film. Test samples were run after instrument calibration and standardization.

[0096] Heat Seal: The heat seal was conducted in a Gradient heat seal tester, model GHS-03, manufactured by Labthink International, Inc., Medford, MA. The heat seal pressure was 35 psi and the dwell time was 0.5 second (ASTM F88). The heat seals were made with heat seal liner facing the APET tray stock. The APET tray stock selected for this study was a silicone-treated 0.025-inch-thick tray stock. Two sealing temperatures were selected for the current study. Sealing temperatures were 121 °C and 163 °C. This does not limit sealing conditions, and should not be construed as limiting them. Once sealed, the samples were conditioned at room temperature (25 °C and 32% RH) for 24 hours. Test data under the two different sealing conditions are reported in table 2.

[0097] Bond strength test: The adhesion test or bond strength test is conducted on Instron 5543 following ASTM D903. The test was performed at room temperature (25 °C and 32% RH). The removal speed is 12 in/minutes. Peel force values are listed in table 2.

[0098] Coating weight test: The coating weight of the coated film was tested using ASTM F2217. The solvent used for complete removal of the coating was tetrahydrofuran.

[0099] Anti-fog test: The anti-fog effectiveness of the PET film produced using the heat seal coating was evaluated by the following method. Cold Haze: 2 inch high clear APET trays were used for the test. A white paper towel was placed inside the tray and filled with 30 mL of distilled water at room temperature. The paper towel would hold the water and prevent water from spilling out when the tray is sealed or moved to be placed in the fridge. The tray lid was about M inches. The APET tray was placed inside a silicone mold for proper alignment during sealing. The about 4 inch diameter PET film containing the heat seal liner was then placed face down in the tray, meaning the heat seal liner was facing the inside of the tray. The PET film was then sealed onto the tray using a low temperature press at 150°C to obtain a very good seal. The pressure in the press was about 40 psi. The dwell time was 1 sec. A photo of the tray after sealing was taken to represent zero time. See Figure 1. The sealed tray is placed in a refrigerator at 6°C (43°F). The anti-fog property of the film is then evaluated after 30 min, 1 hour, 2 hours, up to 24 (1 day) to 96 hours (4 days) and about 20 days. Each time, pictures were taken for comparison. Representative photos are shown in figure 2 for samples tested at 24 hours. All samples containing anti-fog coating remain clear compared to sample 7 which did not contain anti-fog additives. Hot Fog: Glass vial containing 50% internal volume of water was covered with the PET film containing the heat seal anti-fog coating face down on top of the vial. Rubber bands were used to secure the film to the vial. The water in the flask was then heated to 70°C using a water bath for 2 minutes and up to 30 minutes. The anti-fog ability of the films was then evaluated by visual inspection. The hot fogging ability of the films appeared to be very good, especially with medium-sized droplets. The PET film without anti-fog heat seal coating immediately fogs up with hazy fine droplets. Photos are not included for the hot fog test.

[00100] This application discloses various ranges and numerical values in the text. The disclosed numerical ranges and values inherently support any range or value within the disclosed numerical ranges, although a precise range limitation is not literally stated in the specification, because this invention may be practiced over the disclosed numerical ranges.

[00101] The above description is presented to enable a person skilled in the art to make and use the invention, and is provided in the context of a particular application and its requirements. Various modifications to preferred embodiments will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments and applications without departing from the scope and spirit of the invention. Thus, this invention is not intended to be limited to the embodiments shown, but is to be accorded the broadest scope consistent with the principles and features described herein. Finally, the full disclosure patents and publications referred to in this application are incorporated herein by reference. Table 1 The. Glass transition temperature as determined by ASTM E1356-08 b. Ball and ring softening point determined by ASTM E28-99 c. Melting point determined by ASTM D7138 using DSC d. Intrinsic viscosity determined by ASTM D5225-14 e. % moisture by weight, determined using Computrac moisture determination equipment, heating solid pellets to 110 °C to constant weight Table 2: Properties of coextruded PET film using above samples f. Dynamic friction reported based on tests performed referencing ASTM D1894 g. % turbidity tested as described in text h. Bond strength performed per ASTM D903 at 121°C and 163°C and reported as grams per linear inch (gly) i. Coating weight tested using ASTM F2217 and reported as pounds per ream (lb/rm) Table 3: Properties of Extrusion Coated PET Films

Claims (18)

1. A heat sealing resin composition for providing a heat sealing film on a film such as a polyester film, comprising: a copolyester resin component comprising a mixture of a semicrystalline copolyester resin and a resin amorphous copolyester; an anti-fog additive; and an anti-block and slip additive; and wherein at least one heat seal resin composition has: a low glass transition temperature (Tg, ASTM E1356-08) between -30°C and 15°C, a ball and ring melting point (ASTM E28- 99) between 110°C and 170°C, a DSC melting temperature (Tm ASTM D7138) between 100°C and 170°C, an intrinsic viscosity (ASTM D5225-14) between 0.4 and 1.1 dL/g , and an apparent melt viscosity between 5,000 poise and 30,000 poise determined at 215°C. 2. Composition according to claim 1, characterized in that the anti-fog additive is selected from the group consisting of sorbitan esters, glycerol esters, ethoxylated sorbitan ester and compounds modified with alpha monoglyceride, and mixtures thereof. 3. Composition according to claim 1, characterized in that it comprises: a low glass transition temperature (Tg, ASTM E1356-08) between -20°C and 10°C, and more preferably between -15°C to 0° W; ball and ring melting point (ASTM E28-99) between 120°C and 160°C; DSC melting temperature (Tm ASTM D7138) between 120°C and 150°C; the intrinsic viscosity (ASTM D5225-14) between 0.5 and 1.0 dL/g, and the apparent melting viscosity between 10,000 poise and 25,000 poise determined at 215°C. 4. Composition according to claim 1, characterized in that the semicrystalline copolyester resin has a Tg of -30°C to 0°C, a Tm of 100°C to 160°C and a melting point of ball and 70°C to 160°C ring; the amorphous copolyester having a glass transition temperature (Tg) of between 45°C to 110°C and ball and ring melting point of 130°C to 200°C; the anti-fog additive having a Tg in the range of -64°C to 0°C; the anti-blocking and sliding additive having a Tm between 70°C and 180°C and an average particle size between 0.5 and 10 microns. Composition according to claim 1, characterized by: the low glass transition temperature (Tg, ASTM E1356-08) between -15°C and 0°C; ball and ring melting point (ASTM E28-99) between 130°C and 145°C; DSC melting temperature (Tm ASTM D7138) between 125°C and 145°C; the intrinsic viscosity (ASTM D5225-14) between 0.6 and 0.8 dL/g, and the apparent melting viscosity between 15,000 poise and 20,000 poise determined at 215°C. 6. Composition according to claim 1, characterized in that: the copolyester resin component is present in an amount between 80% and 99% by weight of the composition; the anti-fog additive is present in an amount of 0.01% to 5% by weight of the composition; and the antiblock and slip additive is present in an amount of from 0.01% to 5% by weight of the composition. Composition according to claim 6, characterized in that: the semicrystalline copolyester resin component is present in an amount between 60% and 99.9% by weight of the composition; the amorphous copolyester resin being present in an amount of from 5% to 40% by weight of the composition. Composition according to claim 7, characterized in that: the semi-crystalline copolyester resin component is present in an amount between 70% and 99.8% by weight of the composition; the amorphous copolyester resin is present in an amount of from 10% to 30% by weight of the composition; the anti-fog additive is present in an amount of 0.1% to 5% by weight of the composition; and the antiblock and slip additive is present in an amount of from 0.1% to 5% by weight of the composition. Composition according to claim 8, characterized in that: the semi-crystalline copolyester resin component is present in an amount between 70% and 80% by weight of the composition; the amorphous copolyester resin is present in an amount of from 10% to 25% by weight of the composition; the anti-fog additive is present in an amount of 2% to 5% by weight of the composition; and the antiblock and slip additive is present in an amount of from 0.1% to 2% by weight of the composition. Composition according to claim 1, characterized in that the antiblocking and sliding additive comprises silica and amides. Composition according to claim 10, characterized in that the antiblocking and sliding additive comprises amides and the amides comprise fatty amides and polyamides. 12. Composition according to claim 11, characterized in that: the fatty amides are present in an amount of 0.01% to 1.5% by weight of the composition; and the polyamides are present in an amount between 0.001% to 1.0% by weight of the composition. Composition according to claim 11, characterized in that the antiblocking and sliding additive comprises amides and the amides have a melting point in the range of 70°C to 180°C. Composition according to claim 13, characterized in that the anti-blocking and sliding additive comprises fatty amides having a melting point in the range of 70°C to 150°C. Composition according to claim 13, characterized in that the anti-blocking and sliding additive comprises polyamides having a melting point in the range of 150°C to 180°C and an average particle size in the range of 0.5 to 10 microns . Composition according to claim 10, characterized in that the anti-blocking and sliding additive comprises silica and the silica has an average particle size in the range of 0.5 to 10 microns. 17. Composition according to claim 16, characterized in that the silica is a mixture of two sources of silica consisting of a first source having an average particle size of 0.5 to 4 microns and a second source having an average size of particle size of 5 to 10 microns. Composition according to Claim 17, characterized in that the first source has an average particle size of 1.5 to 4 microns and a second source has an average particle size of 8 to 12 microns.