BR122023002709B1 - METHOD OF MANUFACTURING A LAMINATE AND METHOD OF MANUFACTURING A PACKAGE TO CONTAIN AN ITEM - Google Patents

Abstract

A semi-crystalline copolyester resin composition, formed by twin-screw extrusion of various ingredients, includes copolyester resins, anti-blocking, slip and anti-fogging additives. This semi-crystalline copolyester resin can be extruded onto PET film or co-extruded with PET resin to form clear PET films with anti-fogging properties. These anti-fogging films are produced in a single step without the use of solvent and do not involve any secondary step for coating a separate anti-fogging layer. This minimizes the cost and time required by a converter to make such clear anti-fogging films. These films containing the heat-sealable 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 peel is smooth, providing very good packaging performance.

Description

CROSS-REFERENCE TO RELATED REQUEST

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

FIELD OF INVENTION

[0002] This invention relates to copolyester resin compositions capable of forming clear heat seal coatings for use on polyester films and having antifog, antiblocking and slip capabilities. The invention also relates to methods for applying such compositions to polyester films.

BACKGROUND OF THE INVENTION

[0003] Polyester films coated with heat seal 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 coextruded with the heat seal resin/film onto a web surface. This web is fed through the machine to package food and other consumer goods. The film is heat sealed to various packaging substrates, such as food containers. This is done with pressure and heat using heated plates. Seal 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 to which it is sealed, and the machine operating conditions, such as plate temperature, pressure, and dwell time. Since these films are used in food packaging, it is desirable that the heat seal liner, 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 either 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 on the film. This film is then rolled and supplied to the next level or processing location. The rolls are unwound, undergo expensive treatment including corona treatment (as described in U.S. Patent No. 5,520,764) or chemical treatment, and then the anti-fog coating is applied as either a solvent-based coating or a water-based coating. This step involves application using expensive equipment, drying, followed by rolling the film 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 packaging fresh red meat and fish. The patent application explains the formation of the film 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 multi-laminate structure with anti-fog properties. The patent application describes the formation of a multi-laminate structure using four layers, layer A being a polyolefin layer, layer B being a polyolefin interlayer with anti-fog additive kneaded, layer C being an acid-modified polyolefin layer and layer D being a heat-sealable polyester layer kneaded with anti-fog additive. Layers A and D are treated using expensive treatment techniques to provide the 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 the formation of 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 fatty acid ester having hydroxyl group in the presence of water. This solution is then sprayed onto the PET film to provide the transparent 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] JP 2015218211 teaches a polyester modified polyvinyl chloride resin composition based on aliphatic polybasic acid having an average molecular weight of 1,600-3,600 derived from adipic acid, 1,2-propanediol and n-octanol as final capping agent and an aliphatic polybasic acid based ester having plasticization efficiency ^0.90, epoxidized vegetable oil and a glycerin based anti-fogging agent. 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 antifogging and antistatic properties. The additive added to the resin contains a polyglycerin alkyl ether compound and an anionic surfactant.

[0010]KR 2009076233 teaches the formation of a biodegradable and anti-fog sheet having improved scratch resistance while maintaining sufficient flexibility and transparency and continuously exhibiting 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, wherein the resin comprises a mixture of polylactic resin and aliphatic polyester or aromatic-aliphatic polyester resin. The sheet is then corona treated. An anti-fog 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 degree 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 leaching of an antifogging agent over time. In other words, the composition has excellent antifogging durability. The film or sheet 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 antifogging agent, and a sulfonate-based surfactant.

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

[0013] JP 2007031545 discloses the formation of an anti-fog coating on a PET film using a water-soluble solution of anti-fog compounds such as sucrose octadecanoate and sodium octadecanoate. The coating was applied to a corona-treated polyester film, dried at 70° to give an anti-fog sheet, and demonstrated good high-temperature anti-fog property, retention of anti-fog property, 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 (modified) polyhydric alcohol and boric acid, wherein R2, R2, R3, R4 = independently linear or branched C1-30 alkyl, alkenyl, hydroxyalkyl, alkylaryl, arylalkyl, (A1O)fRa; A1 = C2-4 alkylene; f = 1-50; Ra = C130 linear or branched alkyl, alkenyl, hydroxyalkyl or alkylaryl; X1 = structure having >1 SO3 and >1 COOR7; m = > integer 1; R7 = C1-30 linear or branched alkyl, alkenyl, hydroxyalkyl, alkylaryl or (A2O)Rb; and Rb = C130 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 1.5% haze. The heat sealability of the film is not disclosed.

[0015]Min Nie et al., Nano/Micro Engineered and Molecular Systems, 2009. NEMS 2009. 4th IEEE International Conference on, January 5-8, 2009, pages 1017-1020, explains the formation of a superhydrophilic polyester film 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 hot water vapor. The latter maintains its optical clarity because the condensed water forms a thin film instead of droplets for the former. Compared with the widely used coating method, plasma treatment to obtain antifogging polymer film has the potential for 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] US Patent No. 5,520,764A does not teach the formation of 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 anti-fog agent, and is coextruded with another polyolefin, preferably an ethylene unsaturated 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 bond side. The formation of this multi-laminate 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 crosslinking 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 may be very brittle or low crosslinking may result in flaking, i.e., a powdery film is produced that degrades or disperses upon 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 TiO2 to 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 composition of the anti-fog coating 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, an ethylene oxide-propylene oxide block polymer, a polyoxyethylene alkyl ether 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 hanger type die to produce a polyester film through an extrusion and lamination process to create a polyester film with anti-fogging properties on both sides of the film. Although the invention claims the anti-fogging 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. The peelable anti-fog films can be used as covering 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 by a coextrusion 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 (gli). 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 multilayer anti-fog film, wherein the peelable anti-fog layer is added to the inner layer of the multilayer structure as a secondary process.

[0023] US 5614297 A- relates to a thermoplastic multilayer polymeric flexible 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 a 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-fogging agents, slip agents, nonionic surfactants, oleamides and/or fluoroelastomers in the core layer. The invention may be used as an industrial wrapper or for wrapping, covering or enclosing various non-food or food articles, but has particular utility as a food wrapper stretch or cling film. This invention does not relate to the heat sealing capability of the film for APET trays.

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

[0025]US 6,923,997 B2 explains various antifogging compositions that can be prepared and sprayed with solvent onto food containers to render the container nonfoggable. Here again, the use of solvent is imperative to the process.

[0026] US 7,700,187 B2 discloses the formation of 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 gravure application 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 where polyvinylpyrrolidone is used instead of the sulfopolyester.

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

[0028] US Patent Application No. 20050249906A1 describes the formation of a thermoset PET film by the extrusion process, but one that does not incorporate any antifog into the film composition. The application discloses the formation of a heat seal layer (0.005 Pa.s to 50 Pa.s viscosity during the process) 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 to the biaxially oriented PET film to improve adhesion of the heat seal layer during the in-line process.

[0029] As can be appreciated from a review of the above, various attempts have been proposed to produce packaging that helps the consumer to see the food clearly through the covering film. A refrigerated food tray will have a lid that extends over the stored food item so that the covering film covering the top of the tray does not touch the bulk of the packaged food. In this arrangement, the consumer preferably can see clearly through the plastic wrapper to see the food item stored in the package. If the covering 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 propagation of light from the regular direction, scattering during transmission or reflection while viewing 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 onto the tray. The package must be opened destroying all the plastic film, which undesirably reduces the shelf life of the food. Furthermore, any opening in the wrap can also reduce the shelf life of the food 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 assess the quality of the food and therefore the clarity of the lid becomes very important in the eyes of the consumer. In the past, attempts have been made to provide 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 manufacturing an anti-fog coating material that could be sealed onto APET trays. The method involved creating a PET lid material by co-extrusion, extrusion coating or solvent coating. The heat seal layer could be co-extruded together with PET to form the heat seal PET film or the heat seal layer could 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 production process of the anti-fog heat seal PET film. It involved the use of solvent or water, depending on the chemistry of the anti-fog product. The overall process involved 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 prior attempts, the present invention is directed to a solvent-free, extrudable or coextrudable heat seal coating containing an anti-fog additive and its use by film converters. The heat seal coating may be extruded into various PET film gauges or may be coextruded together with polyester or copolyester resins to form a converted PET film that exhibits good clarity, anti-fog, anti-blocking and good bond strength over a wide range of processing temperatures for different tray stocks. Once sealed, the bonds may be opened as a soft peel without being a weld seal.

[0034] According to one 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 mixture of a semicrystalline copolyester resin and an amorphous copolyester resin; an anti-fog additive; and an anti-blocking 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 consists essentially of or consists of a copolyester resin component comprising a mixture of a semicrystalline copolyester resin and an amorphous copolyester resin; an anti-fog additive; and an anti-blocking 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, consists essentially 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 anti-block 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 heat seal resin composition prior to or during the application step. A method consisting essentially of the listed steps is made in the absence of certain other steps, such as a priming step.

[0037] According to another embodiment of the invention, a method of making a package for containing 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-blocking 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 film-forming compound, such as polyester, to form the laminate, wherein the solvent is not added to the heat seal resin composition prior to 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 seal resin composition can be used as an extrudable or coextrudable copolyester resin in the production of heat sealable polyester films capable of use as food packaging closures. 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 coextruded with polyester resin to form a biaxially oriented clear anti-fog heat seal layer with good anti-blocking and slip properties. The coated films can be wound onto rolls without blocking (i.e., laminate adhesion after winding) and have good adhesion to many different packaging substrates at medium to high activation temperatures. The film coated with anti-fog properties is peelable when heat sealed onto polyester films or onto polyester tray stocks used for packaging food. Such heat seal films are conventionally sold in roll form. The rolls are then supplied in roll form for use on form, fill and seal packaging machines. This may include horizontal form fill seal (HFFS) packaging, bag or pouch manufacturing by vertical form fill seal (VFFS) technology or as a flexible packaging film such as 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-blocking 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 a heat seal copolyester. Thus, this reduces the need for two separate steps involved in manufacturing the final heat seal anti-fog PET film. The heat seal layer has anti-fog and anti-blocking and slip additives added in the proper proportion to provide adequate sealability and ease of removal, good clarity and good anti-fog properties. Furthermore, the heat seal layer has minimal blocking so that the film can be wound and unwound after production. The film can be cut for later application in a minimum amount of time. Since the resin does not involve any solvents, there is a reduction in environmental impact, as well as an increase in the safety of workers involved in the use of the resin.

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

DETAILED DESCRIPTION OF THE INVENTION

[0041] One embodiment of the invention relates to a copolyester heat seal resin capable of being extruded onto PET films or co-extruded with PET resins to produce a clear heat-sealable PET lidding film. This lidding film is then used to package fresh produce or food products or other items that could potentially contain water. The usual container for such food products is clear amorphous PET trays. The overall concept of the packaging is to help the consumer see the food in the tray. If there are water droplets or haze on the surface of the film, the overall effect of the packaging is lost and consumer satisfaction will be impaired. Haze 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 settles, it leads to water accumulating and having to go somewhere, resulting in fogging. The principle behind using anti-fog 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 a non-dispersible or thin layer of water film without obstructing vision.

[0042] According to one embodiment of the invention, a heat seal resin composition for providing a heat seal film over 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-blocking and slip additive. The combination of semicrystalline and amorphous copolyesters has been found to provide especially desirable performance for the end 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) of 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) of 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 to about 155°C. The fully formulated heat seal resin may also have a DSC melt temperature (Tm determined in accordance with ASTM D7138) of 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 most 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 3,000 poise determined at 215°C, preferably in the range of 1,000 poise to 2,500 poise, and most preferably in the range of about 1,500 poise to 2,000 poise (determined in accordance with ASTM D3236-15). In a preferred embodiment, the fully formulated heat seal resin has a glass transition temperature between about -15 °C to about 0 °C, a ball and ring melting point 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 and about 0.86 dL/g, and a melt viscosity of about 1500 poise to 2000 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 has at least two components, for example 1 diol and 2 diacid/diesters or 2 diols and a diacid/diester. As for the diol component, standard polyester diol monomers 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 may include any known diester used in the preparation of copolyester resins, such as dimethyl terephthalate or dimethyl isophthalate. The diacid monomers used may 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 may be used to produce either the semicrystalline copolyester resin or the amorphous copolyester resin, the monomer proportions and processing conditions being modified in a known manner to produce either the semicrystalline or the 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. The diols can be selected from ethylene glycol, diethylene glycol, butanediol (1,4-; 1,2-; and 1,3-), neopentyl glycol, 2-methyl-1,3-propanediol, hexanediol, trimethylolpropane, cyclohexanedimethanol, tricyclodecanedimethanol, and mixtures thereof. 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 suitable for use as semicrystalline copolyester resins include Vitel™ 1901NSB, Vitel™ 1904NSB, VitelTM 1801, VitelTM 1912NSB, VitelTM 1916NSB supplied by Bostik, Inc. or combinations thereof. These copolyesters provide the gentle peel required 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 Dow's Mor-ester grades. 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-arranged crystalline phase within the mostly 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 of 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 of between about 1,250 to about 3,250 poise (preferably, between about 1,600 to about 2,600 poise). (Throughout, all properties of the various constituents are determined consistently unless otherwise specified.)

[0045] In embodiments wherein the copolyester component comprises a blend of a semicrystalline copolyester resin and an amorphous copolyester resin, the approximate ratios of the two resins are in the range of from 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 the 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 most preferably between about 70% to about 80%.

[0046] Turning next to the amorphous copolyester resin of the copolyester resin component, the amorphous copolyester resin may be made from one or more diols, diesters, and diacids in a known manner. The diols may be selected from ethylene glycol, diethylene glycol, butanediol (1,4-; 1,2-; and 1,3-), neopentyl glycol, 2-methyl-1,3-propanediol, hexanediol, trimethylolpropane, cyclohexanedimethanol, tricyclodecanedimethanol, and mixtures thereof. The diesters may be selected from dimethyl terephthalate and dimethyl isophthalate, and mixtures thereof. The diacids may 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. In 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 supplied by 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 that 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 does not have any crystallinity and melting point as determined by DSC or equivalent technique and therefore has an enthalpy of fusion 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 in the range of about 0.5 to 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 1,750 to about 3,750 poise (preferably in the range of about 2,250 to about 3,250 poise). The range of the amorphous copolyester resin component present in the composition may be in an amount of about 5 to 40 weight percent of the composition, preferably in the range of about 10 to about 30 percent, and most preferably in the range of about 10 to about 25 percent.

[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-), 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. Such a resin provides consistent seal strength for sealing temperatures as low as 121°C or lower and up to 163°C or higher. The % haze of the films produced by coextrusion was found to be as low as 6.49% and as high as 10.23% at a coating weight of approximately 1.25 pounds/ream (lb/rm). The extruded films had a haze as high as 39.28% and as low as 21% at a coating weight of 5.5 lb/rm. The conditions for the extrusion process can be modified to provide low haze films that can be used for the application.

[0049] The heat seal resin composition also comprises anti-fog additives to impart the end application property of an anti-fog nature to the PET film. This additive imparts good anti-fog capability when the film is exposed to hot fogging or cold fogging conditions. Any suitable anti-fog additive may be used and preferably such additive, like the other constituents, is food safe if the item to be contained is a food item. The anti-fog 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 liquid ethoxylated sorbitan ester). Lonza anti-fog additives such as GlycolubeTM AFA-1 VEG (proprietary anti-fog which is an opaque viscous oily liquid at 25°C) and GlycolubeTM MO-O-20 (proprietary anti-fog additive with 20 to 30% alpha monoglyceride which is an opaque viscous oily liquid at 25°C) can also be used as anti-fog additives. Other anti-fog additives with similar chemistry, performance and properties can 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 the water droplets, forming a continuous and uniform transparent layer of water when the water condenses on the surface of the PET film. The anti-fog additive is present in an amount 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 more preferably about 2% to about 5%.

[0050] The heat seal resin composition also comprises an anti-blocking and slip additive. Without the anti-blocking additives, coated flexible substrates would tend to block when wound into a roll and stored prior to use on a form, fill and seal machine. Slip additives serve to impart slip to the film and help move the film smoothly through converting and packaging equipment. As used herein, the phrase "an anti-blocking and slip additive" is used to denote a single constituent that serves primarily to reduce blocking, a single constituent that serves primarily to reduce slip, or a single constituent that adequately performs both functions, or combinations thereof, provided that some level of both reductions in blocking and slip is achieved over a formulation without the constituent(s). Any suitable anti-blocking and slip additive may be used. The anti-blocking and slip additive may comprise silica, silicate, and amides, such as fatty amides or polyamides, or combinations thereof. The anti-blocking and slip additive may comprise amides, and the amides have a melting point in the range of 70°C to 180°C. In one embodiment, the anti-blocking and slip additive comprises fatty amides having a melting point in the range of 70°C to 150°C. In another embodiment, the anti-blocking 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 silica sources 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 5 to about 10 microns. In another embodiment, the anti-blocking and slip 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 anti-blocking and slip additives preferably include a mixture of silica (e.g. Sylobloc™ 47- a silica gel anti-blocking 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 of 10 microns) and fatty amides such as: Crodamide™ ER- anti-blocking and slip agent supplied by Croda Polymer Additives, a refined erucamide with a melting point of 79°C; Crodamide™ BR- anti-blocking and slip agent supplied by Croda Polymer Additives, a refined behenamide with a melting point of 108°C; Crodamide™ 212, anti-blocking and slip agent supplied by Croda Polymer Additives, a stearyl erucamide with a melting point of 72.5°C; or CrodamideTM EBS- anti-blocking and slip agent supplied by Croda Polymer Additives, an ethylene bis-stearamide with a melting point of 143°C. Fatty amides act as an anti-blocking agent or external lubricant that improves the flow and release properties of the coated PET film. These amides efflorescence on the surface and provide the anti-blocking capability required 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-blocking and slip additives.

[0052] The copolyester monomers, as well as the additives used in the heat seal resin composition, are desirably approved for direct food contact. Semi-crystalline copolyester heat seal resins have been found to be readily extruded into PET films or co-extruded with polyester resins to form a heat sealable PET film. Thus, the semi-crystalline copolyester heat seal resin provides excellent adhesion to polyester films for use in sealing APET (amorphous polyester) tray stocks. The heat seal resin having a semi-crystalline structure with low glass transition temperature eliminates the tendency of the heat seal coating to slip when the coated packaging film is stored in roll form prior to use in a package form, fill and seal machine. It also provides flexibility, elasticity and strength to the coating

[0053] A mixer or extruder may be used to make the heat seal resin composition of the present invention. The additives may be extruded using a Leistritz MIC 27 6L/400 twin screw extruder to form the formulated copolyester heat seal resin which may 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 may be used for all compositions, but pressures may be varied and consequently torque so that both are represented as a range. Solids may be fed using three solid feeders. Two vibrating feeders, one screw feeder and one liquid port may be used for feeding into the extruder port. The feed rate may be varied to obtain the desired weight percentage of each raw material according to the formulation. A screw size 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%. Screw zone temperatures can be adjusted 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 (e.g. AEC chiller from Aqua Poly Equipments Co.) which can be adjusted to 60 °C. The heat seal resin thus extruded 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 packed in aluminum 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 additive in the absence 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 prior to or during the application step. Although other methods for applying the heat seal resin composition to the polyester may be used, coextrusion 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 to one face of the film by an extrusion process. The film is formed by extruding the formulated heat seal resin at a specific temperature that will help melt the formulated heat seal resin and form a stable curtain that 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 thus formed will have a thickness corresponding to a coating weight of at least 1.0 lb/m and may go as high as 5 lb/m or 10 lb/m. As used herein, a ream ("rm") is 3,000 square feet. The coating thickness is also determined by the extrusion temperature, as well as the 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 peeling rather than solder sealing, as well as good anti-fogging and anti-blocking capabilities. Anyone skilled in the art of extrusion would know how to obtain such a coating film.

[0056] In another aspect, the invention is directed to a heat seal coated packaging film that 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 that acts as the PET substrate for bonding 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 that imparts heat sealability to the film as well as imparting anti-fog and anti-blocking capabilities to the film. One skilled in the art will know how to manufacture such a PET film for use in food packaging. This is very well described in examples such as U.S. Pat. No. 4,375,494 , U.S. Pat. No. 7,413,800 , U.S. Pat. No. 3,371,947 , U.S. Pat. No. 4,165,210 , U.S. Pat. US No. 6,939,584. Typically, the heat seal coating formed by this technique is thinner in thickness compared to extrusion coating due to the ability to orient the film in both directions. The coating weight is at least 1.0 lb/m. The coating weight is also determined by the coextrusion temperature as well as the line speed and screw speed. The coating weight is adjusted based on these parameters to give a coating that is clear, capable of sealing to tray stock with good bond strength for easy removal when the tray is opened, as well as having good anti-fogging and anti-blocking capabilities.

[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 package fresh produce, or in general polyethylene terephthalate (PET) to be used as a clear coating material for food packaging. Proper anchoring to the substrates is accomplished by the inclusion of resins that have the ability to adhere to this substrate. In addition, corona treatment is useful to increase surface energy and improve anchoring if required during the extrusion process. This treatment generally cleans the surface of the PET film more than anything else, since PET film has high static and tends to have dirt on the surface.

[0058]The flexible PET film thus formed is sealed to an APET container containing items such as fresh produce and other refrigerable foods. This package prevents leakage of food with good packaging 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 period of time to melt and soften the sealable coating layer, helping it adhere to the APET container. This allows the flexible film to form an easy-peel seal between the flexible lid stock and the rigid tray stock. The seal is termed easy-peel because the lid is strong enough to retain the food without any leakage, but at the same time is easy to open rather than tearing the flexible lid resulting from a weld seal. This type of seal is controlled by the proper selection of the copolyester resin chemistry, as well as being able to adjust a uniform film thickness during the manufacture of the flexible PET film by extrusion or coextrusion process.

[0059] As seen in several instances, the sealable layer coating is applied to the PET film as an off-line secondary process. WO Pat. 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 PET flexible film. The coating typically uses organic solvents or water, depending on the chemistry of the coating. These solvents, if not completely evaporated, can cause the film to stick or block when rolled after the film is produced. Additionally, any solvent retained in the film can be detrimental 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, is very important to produce a good quality film for the desired end application. In certain cases, this step can degrade the overall properties of the film by making it brittle and also deteriorating the 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 altogether and also reducing the overall time and cost to produce the film.

[0060]In practice, converters use either the extrusion or coextrusion process to produce the clear PET cover film. Although this work is specific to the extrudable heat seal copolyester resin, any converter capable of handling solvents could also potentially use this product to form the heat seal PET film. Since the 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 flexographic 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 solid dry layer of heat seal coating on the packaging film. The converter then rewinds the coated and dried film into a roll for later use in a package form, fill and seal machine. As mentioned, it may be necessary to treat the packaging film by corona discharge prior to applying the heat seal coating via the extrusion process or during the printing process in order to ensure proper bonding of the coating to the packaging film. This treatment generally cleans the surface of the PET film more than anything else, since PET film has high static and is prone to surface dirt.

[0061] According to one embodiment of the invention (i.e., in a method of manufacturing a laminate or manufacturing a package for containing 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. anti-blocking and slip additives in an effective amount, such as comprising about 0.01-2.5% by weight of silica and about 0.01-2.5% by weight of amides (steryl erucamide, refined erucamide, bis-stearamide or ethylene polyamide etc.).

[0062] The weight percentages may vary over a wide range to achieve the objectives of the present invention. According to one embodiment of the invention, the copolyester resin component is present in an amount between about 80% to about 99% by weight of the composition; the anti-fog additive is present in an amount of about 0.01% to about 5% by weight of the composition; and the anti-block and slip additive is present in an amount of 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 between about 60% to about 99.9% by weight of the composition; and the amorphous copolyester resin is present in an amount of 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 between about 10% to about 30% by weight of the composition; the anti-fog additive is present in an amount of between about 0.1% to about 5% by weight of the composition; the anti-blocking and slip additive is present in an amount of between 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 between 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 anti-block 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 component), the anti-fog additive, and the anti-blocking and slip additive. In such a case, the sum of the weight percentages of these constituents would increase to 100%. In some embodiments, additional constituents may be added, such as a solvent, an antioxidant, a colorant, a filler, and a UV fluorescent agent. 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-blocking and slip additive) or the four components (i.e., the semicrystalline copolyester resin component, the amorphous copolyester resin component, the anti-fog additive, and the anti-blocking and slip additive) listed above would be less than 100%.

[0064] To provide good adhesion to APET trays, this semi-crystalline 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 characteristic in that an amorphous resin with a similarly low Tg would be prone to cold flow at room temperature and would tend to creep or flow such that the integrity of the coating would be compromised when the heat seal coated roll is stored. It also helps to provide smooth removal of the lid when the PET lid is opened from the APET tray. This will prevent the seal from being a weld seal, as well as prevent the lid from being shredded.

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

[0066] In accordance with 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 be suitable for use in the food industry and be listed as complying 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 into a PET film, which is then tempered and preferably oriented in at least one direction to obtain a heat seal coating having uniform coating as well as good clarity for application. This heat seal coated PET film can then be used to seal the containers. Where the PET film comprises more than one layer, or where a 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 the layers are joined together while still molten. This can also be achieved by a single channel coextrusion in which the melt 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 linear flow conditions without mixing, thus producing a multilayer polymer 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 in the PET film can then be used to seal containers with heat and pressure.

[0067] The coating is preferably applied to result in a minimum coating weight of 1.00 lbs./ream and a maximum coating weight of 10 lbs./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 haze and decrease peel strength at the container. Additionally, if not required, it results in higher costs to the converter. After the coating film is produced by extrusion or coextrusion 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 seal copolyester resin is packaged and shipped to converters in aluminum lined bags. The only handling part is drying the resin well enough to allow gentle processing of the resin so that it does not suffer degradation from 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 anchoring to the polyester for the extrusion process. It can also be co-extruded with commercial polyester resin to form the final heat seal film without any incompatibility or in-line processing issues, 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 the anchoring if required. This treatment generally cleans the surface of the PET film more than anything else, as PET film has high static and is prone to surface dirt.

[0070] The heat seal coating on the PET film provides excellent sealability for APET trays over a wide range of temperatures. Bond strength in excess of 200 grams per linear inch (gli) is provided at bond seal temperatures of 121°C. The bond strength is very consistent throughout the application temperature window. This consistent bond strength allows for the formation of reliable seals at various bond temperatures during the form, fill and seal packaging 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 blend of semi-crystalline and amorphous copolyester resins. A good example is the use of Vitel™ 1901 copolyester resin, which is semi-crystalline. 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 highly compatible and easy to melt and mix in a twin screw extruder along with other additives, by those skilled in the art of copolyester resin extrusion. Thus, the final base copolyester resin has a combination of semi-crystalline and amorphous nature with a low enough glass transition temperature to make it flexible without cold flow, elastic, resistant to deformation and sufficient strength to form a very stable bond to an APET tray. The coating, together with the other additives, is non-blocking and has sufficient slip 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 produce a PET film that is clear, has anti-fog capabilities and provides smooth and consistent removals. The anti-fog capability of the film does not decrease with storage of the film in roll form.

[0072] Vitel™ 1901NSB in conjunction with Vitel™ 1200B has been identified as a desirable combination to form the base heat seal copolyester resin. The combination generally consists of about 70-90% Vitel™ 1901 and 10 to 30% Vitel™ 1200B by weight of the binary combination to give the desired properties. Although this combination has been identified as a preferred embodiment, this cannot be restrictive, as other combinations and other Vitel® copolyester resins may be used to form the base 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-), neopentyl glycol, 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 a Tg between -30°C and 0°C, a Tm of 100°C to 160°C, and a ball-and-ring melting point of 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 to be sold to film converters, for example, as a fully formulated dry resin in bags or drums. Since copolyesters have a tendency to absorb moisture over time, it is expected that the converter will dry the fully formulated copolyester resin prior to subjecting it to the extrusion or coextrusion process. Vacuum or air drying at 60 °C (140 °F) for at least four hours should reduce the moisture to 0.05 wt % 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-fogging ability. This was achieved by a combination of anti-blocking, slip and anti-fogging additives. A combination of anti-blocking and slip additives with a suitable particle size is desirable to provide the anti-blocking and slipping nature to the film. It also helped in proper efflorescence of the additives to the surface of the film without competition between the anti-blocking and anti-fogging ingredients. The clarity of the film was also not compromised in doing so. A combination of silica such as SyloblocTM 47 and SylisiaTM 310P as well as fatty amides such as Crodamide 212, Crodamide ER, or polyamide such as Orgasol 2001 UD NAT2 was found to provide a smooth and consistent coating. A combination of anti-fogging additives such as Atmer 1010 and Atmer 116 is also preferred to achieve good anti-fogging properties. These additives have been selected 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 an 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 heat seal coating on the food contact side is clear, non-blocking and is capable of condensing water droplets so as to provide a clear window for the consumer to see the quality of the packaged food without any fogging. The shelf life of the food packaged in the APET trays is not compromised since the package is well sealed with the heat seal coated PET film. The processing window for the packaging industry is also good since the package can be sealed at 121°C to about 163°C with consistent bond strength using 35 psi pressure and dwell time of about 0.5 seconds. These conditions can be modified depending on the application window of the packaging industry. It can be primer-free coating by extrusion on 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 may 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 (EVOH) copolymers, polyvinylidene chlorides, polyalkylene carbonates, and starch-containing polymers. Ionomer films could also be considered, such as SURLYN® sold by DuPont Teijin Films. Plant-based or other renewable materials may also be used, for example, polymers based on PEF (polyethylene furanoate), PLA (polylactic acid), or polycaprolactone. Therefore, whenever "polyester film" is used here, it can be replaced by any of these other films.

[0077] Films may, for example, be molded, extruded, coextruded, laminated, and the like, including orientation (uniaxially 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 binder layers and the like. Additives include antioxidants and thermal stabilizers, ultraviolet (UV) light stabilizers, pigments and dyes, fillers, delusterants, anti-slip agents, plasticizers, anti-blocking agents, other processing aids, and the like.

[0078]In addition, 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 multilayer film. For packaging films such as these, it is common to use films that have several different layers for various reasons. A three or four layer structure is possible, where the top layer is easy to print on, the middle layer is an oxygen barrier, the third layer provides high strength, and the fourth layer is our adhesive.

ASPECTS OF THE INVENTION

[0079] 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 mixture of a semicrystalline copolyester resin and an amorphous copolyester resin; an anti-fog additive; and an anti-blocking and slip additive.

[0080] Aspect 2. The composition of aspect 1, wherein: the copolyester resin component is present in an amount of from 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 anti-block and slip additive is present in an amount of from about 0.01% to about 5% by weight of the composition.

[0081] Aspect 3. The composition of aspect 2, wherein: the semicrystalline copolyester resin component is present in an amount of from 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.

[0082] Aspect 4. The composition of aspect 3, wherein: the semicrystalline copolyester resin component is present in an amount of from 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 anti-block and slip additive is present in an amount of from about 0.1% to about 5% by weight of the composition.

[0083] Aspect 5. The composition of aspect 4, wherein: the semicrystalline copolyester resin component is present in an amount of from 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 anti-block and slip additive is present in an amount of from about 0.1% to about 2% by weight of the composition.

[0084]Aspect 6. The composition of any one of aspects 1-5, wherein the anti-blocking and slip additive comprises silica and amides.

[0085]Aspect 7. The composition of aspect 6, wherein the anti-block and slip additive comprises amides and the amides comprise fatty amides and polyamides.

[0086]Aspect 8. The composition of aspect 7, wherein: the fatty amides are present in an amount between about 0.01% to about 1.5% by weight of the composition; and the polyamides are present in an amount between about 0.001% to about 1.0% by weight of the composition.

[0087]Aspect 9. The composition of aspect 7, wherein the anti-blocking and glide additive comprises amides and the amides have a melting point in the range of 70°C to 180°C.

[0088]Aspect 10. The composition of aspect 9, wherein the anti-blocking and slip additive comprises fatty amides having a melting point in the range of 70°C to 150°C.

[0089]Aspect 11. The composition of aspect 9, wherein the anti-blocking 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.

[0090]Aspect 12. The composition of aspect 6, wherein the anti-block and slip additive comprises silica and the silica has an average particle size in the range of about 0.5 to about 10 microns.

[0091]Aspect 13. The composition of aspect 12, wherein the silica is a mixture of two silica sources 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 5 to about 10 microns.

[0092]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.

[0093]Aspect 15. The composition of any one of aspects 1-14, wherein the anti-fog additive is selected from the group consisting of sorbitan esters, glycerol esters, ethoxylated sorbitan ester and alpha monoglyceride modified compounds, and mixtures thereof.

[0094]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) of 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) of 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) of 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) 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 to 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 most preferably in the range of 15,000 poise to 20,000 poise.

[0095]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 a 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.

[0096] Aspect 18. A method of manufacturing 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 prior to or during the application step.

[0097] Aspect 19. The method of aspect 18, wherein the application step comprises coextruding the heat seal resin composition with the film forming compound or the polyester, which is in the form of a resin prior to the coextrusion step.

[0098] Aspect 20. The method of aspect 18, wherein the polyester is in the form of a polyester film and the applying step comprises extruding the heat seal resin composition onto the polyester film.

[0099] Aspect 21. The method of aspect 20, further comprising extruding the polyester to provide the polyester film.

[00100] 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.

[00101] Aspect 23. The method of any one of aspects 18-22, further comprising winding the laminate into a roll form.

[00102] Aspect 24. A method of manufacturing a laminate consisting essentially of 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 to a film, such as a polyester film, to form the laminate, wherein no solvent is added to the heat seal resin composition prior to or during the application step.

[00103] Aspect 25. A method of manufacturing a package for containing 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 anti-blocking and slip additive, 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 prior to 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.

[00104] The following definitions are given below: DEFINITIONS 1. High Tg copolyester resins are those resins that have a glass transition temperature of 30 °C or higher 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 lower as determined by DSC. 3. Glass transition temperature (abbreviated as Tg) is defined as a second-order phase transition where an amorphous material becomes glassy and brittle upon cooling below and becomes soft and flexible upon heating. 4. The seal is called easy peel or soft peel so that the lid is strong enough to retain the food without any leakage but at the same time is easy to open rather than tearing the flexible lid resulting from a weld seal. 5. Weld sealing is the reverse of peel sealing, where opening the flexible film from the tray may result in rupture of the lidstock film. 6. Converter is a film manufacturer that can make PET lidstock film by extrusion, coextrusion or solvent coating process.

EXAMPLES

[00105] The following examples demonstrate various aspects of certain preferred embodiments of the present invention and should not be construed as limitations thereof.

Example 1

[00106] Copolyester Heat Seal Coating Composition 1: Vitel 1901NSB (or V1901NSB) manufactured by Bostik, Inc is a semicrystalline copolyester resin with a Tg of -4°C, Tm of 125°C, and a ball and ring melting point 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 wt% V1901NSB copolyester, 19.24 wt% V1200B copolyester, 0.63 wt% Sylisia 310P from Fuji Sylisia with an average particle size of 2.7 μm, 0.29 wt% Orgasol 2001 UD Nat 2 from Arkema, Inc. with an average particle size of 5 μm, 1.44 wt% Atmer 1010 and 1.44 wt% 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 sheared to give solid pellets. The pellets are then dried and packaged for use in extrusion or coextrusion. The physical properties of the heat seal copolyester resin 1 are given in Table 1. All of the examples cited in the invention were coextruded and some of them were extrusion coated onto 48 gauge PET film. The properties of the film produced using the examples are given in Tables 2 and 3. As can be seen from the examples, the coextrusion process gave better clarity as well as good antifogging properties compared to the extrusion process. There was better control of the coating weight using the coextrusion process than the extrusion process. The coating weight of the heat seal coating containing the antifogging produced by coextrusion could be as low as 1.0 to 2 lb/m, while the coating weight through the extrusion process was mostly in the region of 5 to 9 lb/m. 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 roll, as well as by controlling the pressure as well as the screw speed of the extruder, the coating weight 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 good clarity for the extruded film can be achieved. The anti-fogging properties were very good for the co-extrusion process and good for the extrusion process. Again, higher heat seal coating weights are not required for this application and this actually degraded the final film properties including clarity, adhesion strength as well as anti-fogging ability. Again, producing uniform films with good control of the coating weight is very important to achieve good clarity and good anti-fogging properties.

Example 2

[00107] Copolyester Heat Seal Coating Composition 2: The heat seal copolyester comprises 76.79 wt. % V1901NSB copolyester, 19.22 wt. % V1200B copolyester, 0.84 wt. % Sylobloc 47 from W. R. Grace & Co with an average particle size of 6 μm, 0.28 wt. % Orgasol 2001 UD Nat 2 from Arkema, Inc., 1.43 wt. % Atmer 1010 and 1.43 wt. % Atmer 116, both Atmers supplied by Croda. The 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.

Example 3

[00108] Copolyester Heat Seal Coating Composition 3: The heat seal copolyester comprises 76.69 wt% V1901NSB copolyester, 19.18 wt% V1200B copolyester, 0.37 wt% Sylobloc 47 from W. R. Grace & Co, 0.36 wt% Sylisia 310P from Fuji Sylisia, 0.44 wt% Crodamide ER from Croda, 1.48 wt% Atmer 1010 and 1.48 wt% Atmer 116, both Atmers supplied by Croda. The components are twin screw extruded using Leistritz MIC 27 6L/400 equipment as described above. The physical properties of the heat seal copolyester resin 3 are given in Table 1.

Example 4

[00109] Copolyester Heat Seal Coating Composition 4: The heat seal copolyester comprises 75.7 wt% V1901NSB copolyester, 18.92 wt% V1200B copolyester, 0.66 wt% Sylobloc 47 from W. R. Grace & Co, 0.52 wt% Sylisia 310P from Fuji Sylisia, 1.2 wt% Crodamide ER from Croda, 1.5 wt% Atmer 1010 and 1.5 wt% Atmer 116, both Atmers supplied by Croda. The components are twin screw extruded using Leistritz MIC 27 6L/400 equipment as described above. The physical properties of the heat seal copolyester resin 4 are given in Table 1.

Example 5

[00110] Copolyester Heat Seal Coating Composition 5: The heat seal copolyester comprises 75.65 wt% V1901NSB copolyester, 18.91 wt% V1200B copolyester, 0.65 wt% Sylobloc 47 from W. R. Grace & Co, 0.51 wt% Sylisia 310P from Fuji Sylisia, 0.88 wt% Crodamide ER and 0.4 wt% Crodamide 212 from Croda, 1.5 wt% Atmer 1010 and 1.5 wt% Atmer 116, both Atmers supplied by Croda. The 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.

Example 6

[00111] Copolyester Heat Seal Coating Composition 6: The heat seal copolyester comprises 75.65 wt% V1901NSB copolyester, 18.91 wt% V1200B copolyester, 0.65 wt% Sylobloc 47 from W. R. Grace & Co, 0.51 wt% Sylisia 310P from Fuji Sylisia, 0.4 wt% Crodamide ER and 0.88 wt% Crodamide 212 from Croda, 1.5 wt% Atmer 1010 and 1.5 wt% Atmer 116, both Atmers supplied by Croda. The 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.

[00112] Example 7 is a commercial grade VitelTM 1916NSB that does not contain any antifog within the formulation. This was used as a comparison product to determine the antifog properties of films produced using the above examples that contained antifog (1-6).

[00113] Coefficient of Friction (COF) Test: To maintain good winding performance, a heat seal packaging film was tested for COF on an Instron Model 5982 tester following ASTM method D1894. The COF is recorded in Table 2. The data suggests good sliding property or ease of winding onto a roll.

[00114] Block Test: The block test was conducted on an I.C. Block Tester made by Koehler. Test specimens (triplicates) were prepared by placing 2 inch x 2 inch specimens in the block tester. The specimens were aligned such that one specimen had the heat seal coated side of the PET film facing up and against the uncoated side of the second PET film that was on top of it. 3 such sets of each specimen were placed in the block tester. A pressure of 10 psi (pounds per square inch) was applied to the film specimens. The block tester containing the specimens was placed in an oven at 50°C for 16 hours. The block tester was removed from the oven and conditioned to room temperature. A peel test was conducted on the compressed specimens and peel force values of 50 gli or below were considered as passing or non-blocking. All specimens were less than 50 gli for the block test.

[00115] Haze Test: The % haze of the film was measured using Konica Minolta CM-3700A spectrophotometer in transmittance mode. OnColor software was used for the test. The values were recorded as % haze using CIELab color spectrum. A standard was used which was a clear PET film without any coating on the film. The test samples were run after calibration and standardization of the instrument.

[00116] Heat Sealing: Heat sealing was conducted on a Gradient Heat Seal Test Apparatus, 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). Heat seals were made with heat seal liner facing APET tray stock. The APET tray stock selected for this study was a 0.025 inch thick silicone treated tray stock. Two sealing temperatures were selected for the current study. The sealing temperatures were 121 °C and 163 °C. This does not limit the sealing conditions, and should not be construed as their limitations. Once sealed, the specimens were conditioned at room temperature (25 °C and 32% RH) for 24 hours. The test data under the two different sealing conditions are reported in Table 2.

[00117] Bond Strength Test: The adhesion test or bond strength test is conducted on the Instron 5543 following ASTM D903. The test was performed at room temperature (25 °C and 32% RH). The peel rate is 12 in/minutes. Peel force values are listed in Table 2.

[00118] 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.

[00119] Anti-fogging Test: The anti-fogging effectiveness of the PET film produced using the heat seal coating was evaluated by the following method. Cold fogging: Clear 2-inch-high APET trays were used for the test. A white paper towel was placed inside the tray and was filled with 30 mL of distilled water at room temperature. The paper towel would hold the water and prevent water from spilling when the tray was sealed or moved to be placed in the refrigerator. The lid of the tray was about U inches. The APET tray was placed inside a silicone mold for proper alignment during sealing. The approximately 4-inch diameter PET film containing the heat seal coating was then placed face down on the tray, meaning that the heat seal coating was facing the inside of the tray. The PET film was then sealed to the tray using a low temperature press at 150°C to obtain a very good seal. The pressure in the press was approximately 40 psi. The dwell time was 1 sec. A photograph of the tray after sealing was taken to represent time zero. See Figure 1. The sealed tray was placed in a refrigerator at 6°C (43°F). The antifog property of the film was then evaluated after 30 min, 1 hour, 2 hours, up to 24 hours (1 day) to 96 hours (4 days) and approximately 20 days. Photographs were taken for comparison each time. Representative photographs are shown in Figure 2 for samples tested at 24 hours. All samples containing antifog coating remained clear compared to sample 7 which contained no antifog additives. Hot fogging: A glass bottle containing 50% internal volume water was covered with the PET film containing the heat seal antifog coating face down on top of the bottle. Rubber bands were used to secure the film to the bottle. 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-fogging ability of the films was then assessed 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 fogged immediately with fine, hazy droplets. Photos are not included for the hot fogging test.

[00120] This application discloses various numerical ranges and 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 stated verbatim in the specification, because this invention may be practiced throughout the disclosed numerical ranges.

[00121] 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 the preferred embodiments will be readily apparent to those skilled in the art, and the generic principles set forth herein may be applied to other embodiments and applications without departing from the scope and spirit of the invention. Accordingly, this invention is not intended to be limited to the embodiments shown, but is intended to conform to the broadest scope consistent with the principles and features described herein. Finally, the full disclosure of the patents and publications referred to in this application are incorporated herein by reference. Table 1 a. Glass transition temperature 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 D522514 e. % moisture by weight determined using a Computrac moisture determination equipment by heating the solid pellets at 110 °C to constant weight Table 2: Properties of coextruded PET film using the above samples f. Dynamic friction reported based on tests performed referencing ASTM D1894 g. % haze 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 (gli) i. Coating weight tested using ASTM F2217 and reported as pounds per ream (lb/rm) Table 3: Properties of Extrusion Coated PET Films

Claims (8)

1. A method for manufacturing a laminate comprising the steps of: forming a heat seal resin composition by mixing a copolyester resin component comprising a mixture of a semi-crystalline copolyester resin and an amorphous copolyester resin, an anti-fog additive, and an anti-blocking 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 prior to or during the application step. 2. The method of claim 1, wherein the application step comprises coextruding the heat seal resin composition with the film forming compound or the polyester, which is in the form of a resin prior to the coextrusion step. 3. The method of claim 1, 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. 4. The method of claim 3, further comprising extruding the polyester to provide the polyester film. 5. The method of claim 3, wherein no primer is applied to the polyester film before the heat seal resin composition is applied to the polyester film. 6. The method of claim 1, further comprising winding the laminate into a roll form. 7. A method for manufacturing a laminate comprising the steps of: forming a heat seal resin composition by mixing a copolyester resin component comprising a mixture of a semi-crystalline copolyester resin and an amorphous copolyester resin, an anti-fog additive, and an anti-blocking 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 prior to or during the application step. 8. A method of manufacturing a package for containing an item comprising the steps of: making a laminate by: forming a heat seal resin composition by mixing a copolyester resin component comprising a mixture of a semi-crystalline copolyester resin and an amorphous copolyester resin, an anti-fog additive, and an anti-blocking and slip additive, 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 prior to 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.