KR102660324B1 - Polyester film with silicone incorporation for release of canned meat products - Google Patents

Abstract

Embodiments herein relate to bisphenol A-free, multilayer biaxially oriented polyester (BOPET) films. BOPET films have a release layer that assists the release of food. BOPET films can be laminated to metals used in the manufacture of food containers, leaving the outer release layer exposed, allowing direct food contact between the surface of the outer release layer and the food. More specifically, the present invention provides a catalyst/additive package to the components forming an external release layer resin composition, comprising: alkali-metal phosphate and phosphoric acid added during polymerization of the external release layer resin composition; and novel outer release layer resin compositions comprising ultra-high molecular weight siloxane polymers and polyethylene terephthalate resin. A wax component is added to the outer release layer for stronger release performance.

Description

Silicone-incorporated polyester film for release of canned meat products

The present invention relates to bisphenol A (“BPA”)-free multilayer films, such as biaxially oriented polyester (BOPET) films, for lamination onto metal sheets, which can be used for food containers. will be. More specifically, the multilayer film has an outer release layer, which prevents the release of food, such as high protein food sources, when the food is cooked and sterilized in direct contact with the outer release layer. Helping.

Cross-reference to related applications

This application claims the benefit of U.S. Patent Application No. 15/663,142, filed July 28, 2017, which is incorporated herein by reference in its entirety.

Principles of Food Canning

Unlike pasteurized "cooked" meat products in which heat-resistant microorganisms are allowed to survive, the goal of sterilization of meat products is the destruction of all contaminating bacteria, including their spores. The heat treatment of these products can be strong enough to inactivate/kill the most heat-resistant bacterial microorganisms, which are spores of Bacillus and Clostridium. In practice, meat products filled in closed containers are exposed to temperatures exceeding 100°C in pressure cookers. Depending on the product type, temperatures exceeding 100°C can be reached inside the product, typically in the range of 110-130°C. Depending on the product type and container size, the product is maintained for a specified period of time at the temperature level required for sterilization.

If the spores in the canned product are not completely inactivated, vegetative microorganisms will grow from the spores as soon as conditions become favorable again. In the case of heat-treated processed meat, favorable conditions will exist when the heat treatment is completed and the product is stored at ambient temperature. Surviving microorganisms can produce toxins that can damage preservative meat products or cause food poisoning in consumers.

Among the two groups of spore-producing microorganisms, Clostridium is more heat-resistant than Bacillus. A temperature of 110°C will kill most Bacillus spores within a short period of time. In the case of Clostridium, a temperature of up to 121°C is required to kill spores in a relatively short period of time.

The sterilization temperature is required for short-term inactivation (within a few seconds) of Bacillus or Clostridium spores. These spores can also be killed at slightly lower temperatures, but in this case a longer heat treatment period can be applied to reach the same level of heat treatment.

From a microbial point of view, it would be ideal to use a very strong heat treatment, eliminating the risk of any surviving microorganisms. However, most canned meat products do not suffer from any loss of their organoleptic quality, such as very soft texture, separation of jelly and fat, discoloration, undesirable heat treatment taste and loss of nutritional value (destruction of vitamins and protein components). Therefore, it cannot be exposed to such strong heat stress.

In order to follow the above-described embodiments, a compromise must be reached to keep the heat sterilization sufficient for the microbiological safety of the product, but as moderate as possible for product quality reasons.

Meat products suitable for canning

Virtually all processed meat products that require heat treatment during manufacture for consumption are suitable for heat preservation. Meat products that have not undergone any form of heat treatment before consumption, such as dried meat, raw ham or dried sausages, are naturally unsuitable for canning, as they are preserved by low pH and/or low water activity.

Without being limiting, the following groups of meat products are often prepared as canned products: cooked ham or pork shoulder; salty sausage of the frankfurter type; sausage mix of bologna or liver sausage type; Meat preparations, such as corned beef, minced pork; and ready-to-eat dishes containing meat ingredients, such as beef, rice and chicken in broth, soups containing meat ingredients, such as chicken soup or oxtail soup.

can lining

Metal food and beverage containers, such as cans, are lined on the inside with a coating. This coating is essential to prevent corrosion of containers and contamination of food and beverages by molten metals. Additionally, the coating helps prevent canned food from becoming contaminated or damaged due to bacterial contamination. The main type of interior coating for food containers consists of epoxy resins, which have achieved wide acceptance for use as protective coatings due to their excellent combination of toughness, adhesion, formability and chemical resistance. These coatings are essentially inert and have been used for over 40 years. In addition to protecting the contents from spoilage, these coatings make it possible to extend the shelf life of food while maintaining its quality and taste.

However, these epoxy polymers can contain residual amounts of a chemical building block referred to as BPA, which has faced much scrutiny from consumer advocacy groups. Under Proposition 65, California proposed for the second time to list BPA as a cause of reproductive toxicity. Therefore, there is a desire to exclude BPA-based epoxy resins as protective coatings.

Over the past decade, consumers and health experts have been raising concerns about the use of BPA in food packaging. This molecule has a form similar to estrogen and can therefore act as an endocrine disruptor.

Therefore, food companies are eager to move away from BPA-based food packaging. Coating manufacturers and their suppliers are working overtime to find replacements for the all-too-common epoxy, which is made by reacting BPA with epichlorohydrin. In short, the need for BPA-free coatings for food containers is urgent. The BPA-free BOPET film of the present invention satisfies these needs.

Laminating a polyester film to metal prior to forming the container part is one solution to replace containers lined with epoxy coatings. Biaxially oriented polyethylene terephthalate (BOPET) films are used in many applications, such as food packaging, decoration and, for example, as labels.

The food packaging industry uses BOPET film in many heat-sealable tray applications where food is in direct contact with the BOPET, but food release from the BOPET film surface is inadequate.

food release

One problem that arises from the cooking and sterilization of food in containers, especially those containing significant amounts of solids such as meat products, is the adhesion of solid food particles to the inner container surface, making discharge of the entire canned contents difficult. To solve this phenomenon, various methods have been proposed in the patent literature, and these methods include wax (US Patent No. 6,652,979, US Patent No. 6,905,774, US Patent No. 7,198,856, US Patent No. 7,435,465) or silicone compound (US Patent No. 7,435,465). Includes the introduction of Patent No. 6,905,774).

Summary of the Invention

Embodiments herein are polyester films comprising one or more layers, wherein the one or more layers comprise (a) an alkali metal phosphate in an amount of 1.3 mol to 3.0 mol per ton of polyester resin P1, and the alkali on a molar basis; Polyester resin P1, 0.1-99.9% by weight, containing phosphoric acid in an amount 0.4 to 1.5 times that of metal phosphate; (b) silicone resin containing polydimethylsiloxane resin, 0.1 to 2% by weight; and (c) optionally a wax component, 0.001 to 0.09% by weight, wherein the polyester film is free of bisphenol A. In one embodiment, the polyester resin P1 comprises an aromatic polyester. In one embodiment, the aromatic polyester comprises at least 50% by weight ethylene terephthalate as a constituent of the aromatic polyester. In one embodiment, the one or more layers comprise an outer release layer having a food area coverage of less than or equal to about 10% as measured according to the Food Release Test.

In one embodiment, the film structure comprising at least an outer release layer A further comprises: (a) 0.1-100% by weight of polyester resin P2, which is crystallizable and different from polyester resin P1; (b) 0.1-100% by weight of an amorphous copolyester resin or polyester resin having a melting point at least 20° C. lower than the melting point of the polyester resin P2; and (c) a heat-sealable layer B comprising 0.1 to 15% by weight of antiblock comprising organic or inorganic particles. In one embodiment, the polyester film further comprises a heat-sealable layer C having the same or substantially the same composition as the heat-sealable layer B. In one embodiment, the polyester film further comprises a heat-sealable layer C having a different composition than the heat-sealable layer B. In one embodiment, polyester resin P2 comprises an aromatic polyester. In one embodiment, the polyester resin P2 includes at least 50% by weight ethylene terephthalate as a constituent of the polyester resin P2. In one embodiment, component (b) of the polyester resin having a melting point at least 20° C. lower than the melting point of polyester resin P2 is essentially a polybutylene terephthalate (PBT) resin.

Another embodiment relates to a laminated metal sheet comprising the polyester film of an embodiment herein. In one embodiment, the silicone resin has a kinematic viscosity in the range of 10-50 x10 ⁶ centistokes at room temperature.

A patent or application file contains one or more drawings in color. Copies of this patent or patent application publication, including color drawings, will be provided by the Bureau upon request and payment of the necessary fee.
Figure 1 shows photographs of different ingredients used to prepare food mixes for food release testing.
Figure 2 shows a photograph of a BOPET laminated metal disk and a non-laminated BOPET film.
Figure 3 shows a photograph of a food mix placed in a jar sealed with a cap having a BOPET laminated metal disk, with the BOPET film in contact with the food mix.
Figure 4 shows a photograph of several sealed jars containing food mix in a pressure cooker on a heated stove.
Figure 5 shows a photograph showing the removal of a BOPET laminated metal disk from a cooked food mix.
Figure 6 shows photographs of BOPET laminated metal discs showing good and poor release of cooked food mix from the BOPET film surface of the BOPET laminated metal discs.
Figure 7 shows BOPET laminated metal after food release testing with a grid superimposed on a BOPET laminated metal disk to calculate the percentage of food area coverage at which the cooked food mix remains attached to the BOPET film. Shows a picture of the disk ("test sample").
Figure 8 is a plot of the percentage of food area coverage at which the cooked food mix remains attached to the BOPET film as a function of weight percent of ultra-high molecular weight silicone.
Figure 9 shows the relative crystallinity (count/ sec) shows the plot.
Figure 10 shows the relative crystallinity (counts per second) measured by Show the plot.

Embodiments herein relate to polyester films, namely BOPET films, which have excellent heat resistance to withstand temperatures associated with retort sterilization temperatures and barrier properties that can provide corrosion resistance to metal containers by food products. . BOPET films can be formed by lamination to a metal plate during the container forming process. Additionally, BOPET films can provide sufficient release surface to facilitate the removal of high protein foods (meat products) from containers after high heat sterilization. Surprisingly, the present inventors have found that the release action imparted by incorporating silicones containing ultra-high molecular weight siloxanes is further enhanced when using a polyester resin carrier blended with alkali metal phosphate and phosphoric acid during polymerization. . The original purpose of alkali metal phosphate/phosphoric acid was to improve hydrolysis resistance, and the added advantage of improved silicon release behavior was a surprising discovery.

The BOPET film may comprise one or more layers, preferably two or more layers. The multilayered BOPET film may include one or more of a container side or interior layer (i.e., a heat seal or metal bonding layer), a food or exterior layer, and a food release layer. Additionally, there may be one or more core layers between a food side layer that is in direct contact with the food stored inside the container and a layer bonded to the metal surface.

BOPET FILM

Films that can be laminated to metal plates for canning are typically made of tin-free steel (TFS), electro-tin-plated steel (ETP), or aluminum, and the films are stored at 210°C as part of a continuous lamination process. It is characterized by a dimensional change of less than 2.0% after heat treatment.

The films disclosed herein are two- or three-layer coextruded and include a biaxially drawn structure. The outer release layer and any lower “skin” layers are generally thinner than the core “main” layer. The outer release layer (hereinafter referred to as “Skin A”) typically contains an ultra-high molecular weight silicone (siloxane-based) resin, which is pre-blended with a copolyester elastomer resin to form a ‘masterbatch’. , which is added at low levels to the outer release layer during coextrusion.

The term "ultra-high molecular weight silicone" or "UHMW PDMS" (where PDMS stands for polydimethylsiloxane) refers to a PDMS resin, wherein UHMW PDMS has a kinematic viscosity in the range of 10-50x10 ⁶ centistokes at room temperature. (G. Shearer; Silicones in the Plastics Industry, article 15 published in chapter 2: "Silicones in Industrial Applications", in Inorganic Polymers, edited by Roger de Jaeger, Nova Science Publishers, 2007). According to the literature cited above, the advantage of UHMW PDMS is that it forms stable droplet domains in various thermoplastic carriers as pellets, allowing for easy addition of additives directly to the thermoplastic during processing. Another advantage of UHMW PDMS is that it migrates to the surface of the BOPET film and does not bleed out from the BOPET, providing desirable release properties.

A typical UHMW silicon concentration in the masterbatch is 50% by weight. The masterbatch addition level in the outer release layer ranges from 0.2 to 4% by weight, resulting in a net silicon content in the range of 0.1-2%. The remaining components of the outer release layer are an alkali metal phosphate as a phosphorus compound in an amount of 1.3 mol/ton to 3.0 mol/ton, and another phosphorus compound in an amount of 0.4 to 1.5 times (on a molar basis) the alkali metal phosphate. It is a polyethylene terephthalate (PET) resin composition containing phosphoric acid (main ingredient) and optionally inorganic particles for anti-blocking purposes. A typical inorganic particle composition in this case is silica (silicon dioxide, SiO ₂ ) with sizes ranging from a few submicrons to several microns. Silica particles are typically added during coextrusion in the form of concentrate PET chips (“silica masterchips”), which are typically prepared by adding silica to the polymerization. Typical silica content in silica masterchips is 1-3% by weight; Typical addition levels of silica masterchips in the outer release layer are 1-15% by weight, resulting in a net silica content of approximately 0.1-3% by weight.

Release layer A may additionally contain a wax component for more robust release performance. The term “wax component” refers to a component containing wax or wax-like substances. Waxes are a broad class of organic compounds that are hydrophobic, malleable solids around room temperature. These typically include higher alkanes and lipids, which have melting points above about 40° C. (104° F.), so that when melted they form a low-viscosity liquid. Wax is insoluble in water but soluble in organic, non-polar solvents. Different types of natural waxes are manufactured by plants and animals and originate from petroleum (Source: https://en.wikipedia.org/wiki/Wax ). “Wax-like material” refers to a material that has the properties of wax but is not a wax.

The amount of added wax component is 0.001 to 0.090% by weight. Examples of such waxes are mentioned in U.S. Patent No. 6,905,774, which is incorporated herein by reference in its entirety. Specifically, examples of wax compounds that can be used herein are esters of aliphatic carboxylic acid compounds and aliphatic alcohol compounds, and amides of aliphatic carboxylic acid compounds and aliphatic amine compounds, preferably the wax has a total number of carbons of 30 to 120, More preferably, it is composed of 40 to 100 compounds. Examples of such compounds include stearyl stearate, carnauba wax, candelilla wax, rice wax, pentaerythritol full ester, behenyl behenate, palmityl myristate and stearyl triglyceride. Synthetic or natural waxes containing aliphatic esters such as are preferred in terms of compatibility with polyester.

Carnauba wax, especially purified wax, in particular in view of its excellent release properties after repeated use, use after manufacture and use in aqueous environments, and because it is non-adsorbent and improves hygiene in food packaging applications. Addition of carnauba wax is preferred.

The term "robust performance" relates specifically to commercial metal lamination facilities where, due to process limitations, there is variability across the web width, both in terms of thermal history and correspondingly in terms of the final form of the laminated film. do. Such equipment is described in U.S. Patent No. 9,358,766. Commercial metal laminating lines have two main factors that influence this morphology: one is the preheating temperature of the steel sheet just before contact with the polyester film at the time of laminating (one or both of the pair of nip rolls are preheated); ). For biaxially oriented PET-based films, this temperature is 320-430°F, preferably 360-430°F. The second is the temperature set in the post-heating station (e.g., an infrared (IR)-heated oven), which serves to stabilize the initial bond between the plastic film and the steel that occurs during the lamination step. For biaxially-oriented PET films, this temperature is 350-500°F, preferably 420-460°F. As the laminated sheets exit the post-processing (“post-bake”) station, variability in the form of the laminated polyester film can occur, for example, at different points across the width of the laminate. As indicated by crystallinity (as measured, for example, by X-ray diffraction-XRD), crystallinity is affected by both the preheating temperature and the post-heating temperature. Profiles of relative crystallinity (counts per second) determined by XRD for films containing no wax are shown in Figure 9 and for films containing wax are shown in Figure 10. As shown in Figure 10, the addition of wax increases the relative crystallinity (count) measured by /sec) is surprisingly found to be lower than that of the film of Figure 9, which does not contain any wax component. Additionally, it was surprisingly found that the film of Figure 10 had superior food release than the film of Figure 9. When combining siloxane with PET resin P1 (PET resin containing alkali metal phosphate and phosphoric acid), the amount of wax required for meat release is comparable to that of films that use wax alone for release properties (e.g. Toray Industries Lumirror(TM) grade FN8 polyester film from Toray Industries at the level in U.S. Patent No. 6,652,979 (0.1 - 2% by weight) or at the level in U.S. Patent No. 6,905,774 (0.1 - 5% by weight). ) is impregnated with carnauba wax formulated with ).

The remaining two layers will hereafter be referred to as layer “B” for the core layer and skin layer “C” for the skin layer lying opposite to the A skin layer. Thickness distribution ranges from 5-30%, 40-95%, and 0-30% for layers A, B, and C, respectively, based on total film thickness. Typical total film thickness after biaxial stretching is 10-25 microns, preferably 12-23 microns.

The two- or three-layer film structure is laminated onto a metal sheet (steel or aluminum), which is then made into a container. Although both sides of the metal sheet may be laminated with a plastic film, the film of the present invention will be the inner surface of the container, such that the outer release layer containing silicone is the food-contact layer (i.e., the layer away from the metal substrate of the can). It is intended to be laminated on top of a metal sheet.

Core layer B may include 100% PET resin (“base resin”) by weight. If there is no C layer, layer B may also contain an anti-block-containing masterbatch or low-melting copolyester described in more detail below for optional layer C.

The optional skin layer C may be a low-melting (relative to crystalline PET) or amorphous polyester copolymer or a blend of a low-melting (or amorphous) polyester copolymer with a PET base resin. One example of a cold-melt polyester is butylene terephthalate repeat units, such as poly(butylene terephthalate) ("PBT") resins and their other dicarboxylic acids or diols, such as isophthalic acid, naphthalene diols, etc. It is a resin containing copolymers with carboxylic acid, azelaic acid, sebacic acid, adipic acid, ethylene glycol, 1,3-propanediol, 1,2-propanediol, neopentyl glycol, and 1,4-cyclohexyldimethanol. . A non-exclusive list of suitable examples of polybutylene terephthalate (PBT) may be: Crastin® FG6129, Crastin® FG6130 from Dupont, Celanese from Ticona. 1600, Celanex (trademark) 1700, Toraycon (trademark) 1100M, Toraycon (trademark) 1200M from Toray Industries. Other examples of cold melt polyesters include resins containing trimethylene terephthalate repeat units, such as poly(trimethylene terephthalate) (PTT) resin and dicarboxylic acids or diols other than these, such as isophthalic acid, Resins containing copolymers with naphthalene dicarboxylic acid, azelaic acid, sebacic acid, adipic acid, ethylene glycol, 1,4-butanediol, 1,2-propanediol, neopentyl glycol, 1,4-cyclohexyldimethanol, etc. am. A non-exclusive list of suitable examples of polytrimethylene terephthalate (PTT) resins may be as follows: Sorona (registered trademark) (DuPont), Corterra (registered trademark) (Shell), Ecoriex (registered trademark) (SK Chemicals) ). The purpose of adding a cold melt or amorphous polyester copolymer to the layer is to facilitate easier adhesion to the metal during thermal lamination. However, the addition of these copolymers is not necessary to make the metal contact layer heat-sealable, since the lamination temperature and subsequent oven temperature are such that the metal-contacting side becomes sticky enough to bond to the metal. This is because the temperature of the treatment can be adjusted. While PET polyester has a melting peak around 250°C, melt onset occurs at around 205°C (400F), which is consistent with the lamination temperature requirements and facilitates initial bonding at the pressure of the lamination nip roll, which Additional strengthening is achieved by oven treatment of the laminated structures at approximately 460°F.

polyester resin composition

The resin of layer A is a polyester resin, “P1”, containing a buffering agent that is soluble in ethylene glycol and contains a material that exhibits ionic dissociation. Such buffering agents are preferably alkali metal salts, for example salts of phthalic acid, citric acid, carboxylic acid, lactic acid, tartaric acid, phosphoric acid, phosphorous acid, hypophosphorous acid; Alkali metal salts such as polyacrylic acid compounds, etc. More specifically, the alkali metal is potassium or sodium, and therefore specific alkali metal salts are for example sodium dihydrogen hydroxycitrate, potassium citrate, potassium hydrogen hydroxycitrate, sodium carbonate, sodium tartrate, potassium Tartrate, sodium lactate, sodium carbonate, sodium hydrogen phosphate, potassium hydrogen phosphate, potassium phosphate, sodium dihydrogen phosphate, sodium hypophosphite, sodium hypochlorite, sodium polyacrylate, etc.

In a preferred embodiment, P1 is an alkali metal phosphate as the first phosphorus compound in an amount of 1.3 to 3.0 mol per tonne of polyester resin, and 0.4 to 1.5 mole of said alkali metal phosphate as the second phosphorus compound. It is a polyester resin composition containing a cultured amount of phosphoric acid. In the case of a polyester resin composition, it is preferable that its acid component contains a dicarboxylic acid component in a molar amount of 95% or more. In particular, the terephthalic acid component is preferred from the viewpoint of mechanical properties. Additionally, from the viewpoint of mechanical and thermal properties, it is preferred that the glycol component contains straight-chain alkylene glycol having 2 to 4 carbon atoms in an amount of 95% or more on a molar basis.

In particular, ethylene glycol having two carbon atoms is preferable from the viewpoint of moldability and crystallization of the polyester resin. In addition to terephthalic acid and ethylene glycol addition polyester raw materials, for example diacids such as isophthalic acid, naphthalene dicarboxylic acid, or diols such as 1,4-cyclohexyldimethanol, diethylene glycol, 1,3- Propylene glycol, 1,4-butylene glycol, may be present as a copolymerized component in the polymerization mix of the polyester composition at a level of up to 5 mole percent of the total diacid or diol. If the content of the copolymerized component exceeds 5 mol%, this will cause a decrease in heat resistance due to a decrease in melting point and a decrease in hydrolysis resistance due to a decrease in the crystallinity of the polyester. From the viewpoint of hydrolysis resistance, it is preferable that the polyester resin composition contains alkali metal phosphate in an amount of 1.3 mol to 3.0 mol per ton of polyester resin. Preferably it is 1.5 mol to 2.0 mol per ton of polyester resin. If the content of alkali metal phosphate is less than 1.3 mol per ton of polyester resin, long-term hydrolysis resistance may be insufficient. On the other hand, if the alkali metal phosphate is contained in an amount exceeding 3.0 mol per ton of polyester resin, this is likely to cause phase separation (precipitation) of the alkali metal phosphate.

Examples of alkali metal phosphates include sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, lithium dihydrogen phosphate, dilithium hydrogen phosphate, Contains trilithium phosphate.

Preferred examples of alkali metal phosphates are alkali metal dihydrogen phosphate and alkali metal phosphate. Alkali metal phosphates where the alkali metal is Na or K are preferred from the viewpoint of long-term hydrolysis resistance. Particularly preferred examples of alkali metal phosphates are sodium dihydrogen phosphate and potassium dihydrogen phosphate. From the viewpoint of long-term hydrolysis resistance, it is preferable that phosphoric acid is 0.4 to 1.5 times that of alkali metal phosphate in molar ratio. Preferably it is 0.8 to 1.4 times. If it is less than 0.4 times, the long-term hydrolysis resistance may be worse. If this exceeds 1.5 times, the polymerization catalyst is deactivated by excess phosphoric acid; This will not only cause a delay in polymerization but also cause an increase in the amount of end group COOH, which will contribute to a decrease in the hydrolysis resistance of the polyester resin.

According to calculations based on the contents of alkali metal phosphate and phosphoric acid, the polyester resin composition contains an alkali metal element in an amount of 1.3 mol to 9.0 mol per ton of polyester resin, and 1.8 mol to 7.5 mol per ton of polyester resin. Contains an amount of phosphorus. In terms of the type of alkali metal phosphate preferred, the polyester resin composition preferably contains an alkali metal element in an amount of 1.3 mol to 6.0 mol per ton of polyester resin and an amount of 1.8 mol to 7.5 mol per ton of polyester resin. Contains phosphorus.

From the viewpoint of reducing the amount of end group COOH and suppressing the formation of foreign substances, the total content of the phosphorus compound contained in the polyester resin composition of the present composition is 30PPM to 30PPM based on the weight of the polyester resin composition in terms of the amount of elemental phosphorus. It is preferable that it is 150PPM. It is more preferable that this content is 60PPM to 150PPM.

The composition of polyester resin P1 is a metal-containing compound (“metal compound”) wherein the metal element is one or more members selected from the group consisting of Na, Li, and K, and the metal element is Mg, Ca, Mn, and Co. A metal compound in which the metal element is one or more members selected from the group consisting of Sb, Ti, and Ge, wherein the total amount of these metal elements is based on the entire polyester resin composition. Therefore, it is desirable to adjust it to 30PPM or more and 500PPM or less. By adjusting the total amount of metal elements within this range, the amount of end group COOH can be reduced in the polyester resin to improve its heat resistance. It is more preferable that this content is 40PPM to 300PPM. The elements Na, Li and Ka are alkali metal elements. The divalent metal elements Mg, Ca, Mn, and Co are transesterification catalysts and impart electrostatic properties, such as resistance, to the polyester resin. Sb, Ti and Ge are metal members that have the ability to catalyze the polymerization of polyester resin and act as a polymerization catalyst.

BOPET Film Processing

Preferably, the multilayer PET film is biaxially oriented prior to lamination thereof to a metal substrate. Typically, the raw material PET resin is fed in solid form to a melt processing device, preferably a continuous screw extruder. Heating in the melt processor is controlled so that the PET resin remains above its melting point but below the polymer degradation temperature. Molten PET resin is extruded from an appropriately shaped die to form a thin, flat ribbon of polymer melt. The polymer ribbon is quenched in air and/or on a chilled roll to form a solid, self-supporting film. The film is taken up by a set of rollers rotating at different rotational speeds, stretching the film in a continuous forward direction, referred to as the machine direction (“MD”). Stretching may be accompanied by heating the film to achieve crystal orientation in MD. A unidirectional film is clamped at its opposite edges and stretched in a tenter oven in the transverse machine direction (“TD”) laterally perpendicular to the MD. The tenter oven is heated to a temperature operating to achieve crystal orientation in TD, forming a biaxially oriented PET film. Preferably, the biaxially oriented PET film is stretched about 100%-400% in MD and 100%-600% in TD. The biaxially oriented film can be heat-cured at a temperature preferably between about 300°F and about 490°F, more preferably between about 350°F and about 460°F.

Example

The present invention will be better understood by reference to the following examples, which are intended to illustrate specific embodiments within the overall scope of the invention, but the scope of the invention is not limited to the following examples.

resin material

The resin materials for the films mentioned in the examples are as follows:

PET resin P1 (PET resin containing alkali metal phosphate and phosphoric acid): Toray F1CCS64 (IV = 0.65; Tm = 255° C.) supplied by Toray Films Europe.

PET resin P2 (conventional film-grade PET resin, free of alkali metal phosphates): Toray F21MP (IV = 0.65; Tm = 255° C.) manufactured by Toray Plastics America.

PET Resin P3: Bottle-grade PET resin 8712A from Invista, with an IV of 0.75.

PET Resin P4:

PET resin anti-block masterbatch type F18M (IV = 0.62; Tm = 255° C.) containing 2% silica particles (Fuji Silysia 310P) with an average size of 2 μm, manufactured by Toray Plastics America.

Amorphous copolyester resin CoP1: Eastar (registered) supplied by Eastman Chemical (based on terephthalic acid reacted with a 33:67 mole parts combination of 1,4-cyclohexyldimethanol (CHDM)/ethylene glycol) trademark) 6763 PETG; IV = 0.76.

Slow-crystallization copolyester resin CoP2: IPET F55M resin (IV=0.69 ;Tm=205℃).

Silicone Resin Masterbatch: Dow Corning MB50-010 containing 50% ultra-high molecular weight polymerized siloxane (“silicone resin”) and 50% polyester elastomer carrier resin.

Low-melting point polyester resin P5: Polybutylene terephthalate (PBT) resin Crastin® FG6130 from E.I. DuPont De Nemours, with a melting point of 223°C.

The carnauba wax component was added in the form of a masterbatch containing 2% wax by weight (“Wax MB”), commercially available under the trade name WO30 from Toray Industries.

General film manufacturing procedure

Multilayer coextruded BOPET films were prepared using a 1.5 m wide pilot-line sequential orientation process. The coextruded film is cast on a cooling drum using an electrostatic pinner, heated and oriented in the machine direction through a series of differently moving rolls, and then transversely stretched in a tenter oven.

The multilayer coextruded laminate sheet is coextruded by a main extruder to melt and transport the core blend to the die and by one or two sub-extruders to melt and transport the skin blend to the die. Extrusion via the main extruder is carried out at a processing temperature of 270°C to 285°C. Extrusion through the sub-extruder is carried out at a processing temperature of about 270°C to 280°C. Both the main polymer melt stream and the subpolymer melt stream flow through a die to form a layered coextruded structure, which is then cast in a cooling drum with a surface temperature controlled to about 21° C., non-oriented at a casting speed of about 9 mpm. The laminate sheet is solidified. The non-oriented laminate sheet was stretched in the longitudinal direction at about 75°C to 85°C to an elongation rate of about 3 times the original length, and the resulting stretched sheet was annealed at about 70°C to obtain a uniaxially oriented laminate sheet. .

The uniaxially oriented laminate sheet is introduced into the tenter at a linear speed of about 27 mpm, previously heated to 80°C, stretched transversely at about 90°C to a stretch of about 4 times the original width, and then at about 210°C. Heat-curing or annealing reduced internal stresses due to orientation, minimized shrinkage, and provided biaxially oriented sheets that were relatively thermally stable.

Thermal lamination procedure of film to metal sheet

Tin-free steel (TFS), 0.0075" thick, was preheated to 400°F (except where otherwise noted). The steel and film were passed through a set of nipped rolls, allowing the film to adhere to the steel. An initial bond was formed and the film and steel laminate structure was then passed through a second heating operation (“post-bake”) at 460 F for 20 seconds and then cooled to room temperature.

The side of the film laminated to the steel was opposite the silicone-containing side (the side in contact with food; side A in the example). That is, the side to be laminated was side B or side C in the example.

How to test

Various properties in the above-described examples were measured by the following method:

Intrinsic viscosity (IV) of films and resins was tested according to ASTM D 4603. This test method involves the IV determination of soluble poly(ethylene terephthalate) (PET) at a concentration of 0.50% in a 60/40 ratio of phenol/1,1,2,2-tetrachloroethane solution by a glass capillary viscometer. It is for.

The melting point of the copolester resin is measured using a differential scanning calorimeter model 2920 from TA Instruments. A 0.007 g resin sample was tested substantially according to ASTM D3418-03. Consistent with Note 6 of the ASTM standard, prethermal cycles are not used. The sample is then heated at a rate of 10°C/min to a temperature of up to 300°C, while recording heat flow and temperature data. The melting point is reported as the temperature at the endothermic peak.

Film crystallinity was measured by the X-ray diffraction method on a PANalytical X'Pert PRO system with a Cu X-ray source (40 kV, 20 mA) and a Xe gas proportional type detector. The incident X-ray beam is directed to the sample over a spectrum of angles and the intensity of the diffracted beam is measured at each angle as counts of pulses per second. A measure of crystallinity, specified as “counts per second” (cps), is reported based on the count of the number of pulses at the peak intensity of the diffracted beam. The sample was scanned from 18° to 32° to cover both the PBT and PET maximum diffraction angles, 2θ=23.38° and 2θ=25.8°, relative to the [100] crystal phase plane (angle of peak intensity). A desirable cps value before lamination is 1500 or higher, and after lamination, it is 900 or higher.

Food release testing:

The food area coverage of the polyester film laminated to steel on the food-contacting side is measured according to the food release test, referred to herein as the "food release test". The procedure for food release testing is described below.

A 3/2/1 ratio egg/ground beef/flour food mixture was prepared as follows:

A. Food release mix preparation steps shown in Figure 1

* 8-10 jar test: 1 lb of ground beef was placed in a mix container, such as a plastic jar.

* The contents, which were 5 large grade A eggs, were placed in the above mixing container and mixed manually using a spatula or metal bar.

* Slowly add 8 oz of all-purpose white flour, mixing until combined.

B. Sample placement into glass test jar as shown in Figures 2 and 3

* Disks were cut from the film/metal laminate as described above, small enough to fit into the bottom of the jar, using a shear (Figure 2): in the examples, 47 mm diameter disks were used. It was fitted inside a Ball(registered trademark) jar with a 1/2 pint wide opening.

* BOPET film was cut into sheets of a size large enough to fit into the jar and hold the food mix as described in the steps below.

* The film sheet was simply placed on top of the can (meat releasing side upward) and then the metal disk was placed on top of it, with the side in contact with the food facing up.

* Two soup-spoon sized dollops of food release mix were placed on top of the sample disk.

* A film was wrapped around the food release mix and the disc was placed underneath the food release mix.

* The surrounding food mix (including the sample disk at the bottom) was placed in the jar and the jar was capped.

C. Retortation and Testing (Figures 4 and 5)

A "retort" (pressure cooker as shown in Figure 4) was filled with water to 0.5" below the perforated steam plate.

* The test jar was placed on the steam plate and the retort (pressure cooker) lid was tightly closed.

* The retort was placed on a hot plate set to medium-high temperature and retorted for 90 minutes after the pressure valve began to oscillate (internal pressure 14.7 psig, temperature approximately 260°F).

* Remove the pressure cooker from the heat and allow it to cool until the valve lowers, indicating that it is safe to open.

* Open the pressure cooker, remove the jar with tongs, and let it sit overnight.

* Release the film from the food mix (the food mix was still attached to the metal disc).

* The disc was peeled from the food mix in an orthogonal motion and evaluated for release performance. See Figure 6 for good and bad examples of food release.

“Retort process” is a procedure in which the inside or outside of a metal container having walls consisting of a composite of a metal substrate with a polymer film laminated on the inside, outside or both of the metal substrate is treated for a certain period of time with live steam or superheated water. means.

“Live vapor” means that the vapor is in direct contact with the surface of the container. Steam is generally superheated, i.e. above the boiling point of water. Nominally, the retort process refers to exposure to steam at a temperature of 260°F for 90 minutes. The duration of exposure and temperature of the retort process can be varied as appropriate to provide equivalent sterilization and food pasteurization effects. For example, temperatures may be high for short periods of time or low for long periods of time.

Release performance was rated by taking photographs of the test stacked disks after release and superimposing a rectangular grid image using Microsoft Paint(TM) software. The number of grid squares occupied by attached residual food was then counted and expressed as a percentage of the total number of grid squares. The lower the percentage, the better the food release performance (Figure 7). On a percentage basis, the acceptance ratings are as follows (based on U.S. Patent No. 6,905,774):

Grade A (“Excellent”): 0-5%

Grade B (“Good”): 5-10%

Grade C (“Acceptable”): 10-20%

Grade D (“Poor”): 20-50%

Grade E (“Very Poor”): 50-100%

food transfer test

A qualified laboratory (named as follows at the time of testing; Covance, Madison, Wis.) under the conditions prescribed by Code of Federal Regulations, Title 21CFR177.1630, Conditions (f), (g), and (h). Tested by Covance Laboratories. The test consists of exposing the food-contact surface (in this case layer A) under the following specifications for each use condition and then determining the level of chloroform-soluble extractables present in the exposure medium:

Condition (f): Acceptable for food excluding alcoholic beverages at a temperature not exceeding 250°F - Extractable limit: 0.5 mg/in ² after 2 hours exposure to n-heptane at 150°F and distilled water at 250°F.

Condition (g): Acceptable for alcoholic beverages not exceeding 50% alcohol - Extractable limit: 0.5 mg/in ² after 24 hours exposure in 50% ethanol at 120°F.

Condition (h): Permitted to hold food during baking or oven cooking at temperatures exceeding 250°F - Extractable Limit: 0.02 mg/in ² after 2 hours exposure to n-heptane at 150°F.

Examples 1 and 1a

Three-layer BOPET film structures were prepared by melt extrusion from three extruders feeding resin blends corresponding to layers A, B, and C shown in Tables 1, 2, and 3, respectively. The silicone masterbatch content in layer A was 0.5%, which corresponds to a silicone content of 0.25% by weight. The difference between composition 1 and composition 1a concerns the content of antiblock masterbatch (P4) in layer A and the content of amorphous copolyester (CoP1) in layer C (and the main The resulting difference in the contents of the resin balance P1 and P2 is caused). The cast film is biaxially oriented by stretching 3 times along the machine direction at a temperature of 82°C and 4 times along the transverse direction through an oven held at a temperature of 85-93°C in the stretching zone and 204°C in the annealing zone. was made and collected in roll form by a winder rotating at a linear speed of 32 m/min.

The film was subsequently laminated onto the tin-free metal sheet with the C side adhered to the metal sheet surface. Side A of the film was then tested for food release according to the procedure described above. The scores, expressed as a percentage of the total area occupied by remaining food, are listed in Table 4.

Examples 2 and 2a

Examples 1 and 1a were repeated, with the only major difference being that the A/B/C three-layer structure was used as shown in Tables 1, 2, and 3, respectively, but the silicon masterbatch content in layer A was 1.0%, and the content was equivalent to a silicon content of 0.5% by weight. The results of the food release tests are listed in Table 4.

Example 3

Example 1 was repeated, with the only major difference being that an A/B/C three-layer structure was made as shown in Tables 1, 2, and 3, respectively, but the silicon masterbatch content of layer A was 2.0%, which was The content was equivalent to 1.0% by weight. The results of the food release tests are listed in Table 4.

Example 4

Two-layer BOPET film structures were prepared by melt extrusion from two extruders feeding resin blends corresponding to layer A and layer B, as shown in Tables 1 and 2, respectively. Layer B contains 15% PBT. The extrusion conditions were the same as those listed in Comparative Example 5. The silicone masterbatch content of layer A was 0.5%, which corresponds to a silicone content of 0.25% by weight.

Example 5

Example 4 was repeated, with the only difference being that the weight fraction of PBT in layer B was increased to 30%.

Example 6

Example 5 was repeated, with the only difference being that the weight fraction of PBT in layer B was increased to 45%.

Comparative Example 1

Example 1a was repeated, with the only major difference being that the A/B/C three-layer structure was prepared as shown in Tables 1, 2, and 3, respectively, but no silicone masterbatch was added to layer A. The results of the food release tests are listed in Table 4.

Comparative Example 2

For this comparative example, grade "Lumirror", a commercially available biaxial film with two layers (layer A and layer B are identical except that layer B contains internal recycling) available from Toray Plastics America. (Trademark) 48G PA66" was used. The film products are based on P2 as the base resin and P4 as the antiblock masterbatch, respectively. The A/B structures are shown in Tables 1 and 2, and the results of the food release tests are listed in Table 4.

Comparative Example 3

Example 1a is repeated, except that the A/B/C three-layer structure is prepared as shown in Tables 1, 2, and 3, respectively, but the main polyester resin (base resin) is P2 (standard film-grade PET). and that no PET resin (eg, P1) containing alkali metal phosphate and phosphoric acid was used. Like Example 1, this comparative example consisted of 0.5% by weight silicone masterbatch. The results of the food release tests are listed in Table 4.

Comparative Example 4

Example 2a is repeated, except that the A/B/C three-layer structure is prepared as shown in Tables 1, 2, and 3, respectively, but the main polyester resin (base resin) is P2 (standard film-grade PET). and that no PET resin (eg, P1) containing alkali metal phosphate and phosphoric acid was used. Like Example 2, this comparative example consisted of 1.0% by weight silicone masterbatch in layer A. The results of the food release tests are listed in Table 4.

Comparative Example 5

The two-layer BOPET film structure was manufactured by melt extrusion through two extruders feeding the resin blends corresponding to layer A and layer B and then casting on a cooling drum maintained at 21°C and machine direction at a temperature of 82°C. It was formed into a biaxially oriented film by stretching 3 times along the transverse direction and stretching 4 times along the transverse direction through an oven maintained at a temperature of 85-93°C in the stretching zone and 204°C in the annealing zone, at 32 m/min. It was collected in roll form by a rotating winder at a linear speed of . The final A/B biaxially-oriented two-layer structure is shown in Tables 1 and 2, respectively. Similar to Example 3, this comparative example consists of 2.0% by weight silicone masterbatch in layer A, which corresponds to a silicon content of 1% by weight. The results of the food release tests are listed in Table 4.

Comparative Example 6

Comparative Example 5 was repeated, with the only difference being that A/B two-layer structures were prepared as shown in Tables 1 and 2, respectively, but the silicon masterbatch content of layer A was 4.0% by weight, which corresponds to a silicon content of 2.0% by weight. The point was to do it. The results of the food release tests are listed in Table 4.

Comparative Example 7

Comparative Example 3 was repeated (0.5 wt% silicon masterbatch in layer A corresponds to 0.25 wt% silicon), with the only difference being that A/B/C three-layer structures were fabricated as shown in Tables 1 and 2, respectively. However, the main resin of layer A was P3. The results of the food release tests are listed in Table 4.

Reference example

The reference example was represented by a commercially available film currently considered suitable for inner container liners with food release properties, namely Lumirror® grade FN8 polyester film from Toray Industries. The film is impregnated with carnauba wax formulated at levels in the range described by U.S. Patent No. 6,652,979 (0.1 - 2% by weight) or U.S. Patent No. 6,905,774 (0.1 - 5% by weight).

[Table 1]

[Table 2]

[Table 3]

[Table 4]

These results show that films comprising polyester P1 (alkali metal phosphate/phosphoric acid-containing polyester) in the food release layer are identical to those of a standard (i.e. alkali metal phosphate/phosphoric acid-free) polyester in the food release layer. It is shown to perform better than comparative compositions containing silicone levels.

For a more thorough analysis, Figure 8 shows these results for the silicone content in layer A in the following manner: one data series corresponds to a film containing resin P1 as the main PET resin in layer A (compare Example 1 and Examples 1, 1a, 2, 2a, and 3) are collected; Another data series collects data containing resin P2 as the main resin in layer A (Comparative Examples 2, 4, 5, 6). A single data point plots data for the film of Comparative Example 7 (containing Resin P3 and 0.25% silicone). The following points are clear:

(1) The trend line for series P1 lies much lower than that for series P2, which shows the improved hydrolytic stability of the present invention, achieved by introducing alkali metal phosphate/phosphoric acid into the catalyst/additive packaging, from standard resins. It is implied that it is improved with a resin having .

(2) Example 7, i.e. a single data point corresponding to a different main resin with hydrolytic stability (achieved by the solid referred to as high IV), i.e. resin P3, is generally inside the trend line for series P2. In other words, this resin does not show any improvement over the standard resin.

(3) Further improvement in food release performance in both series is noted by introducing siloxane-based ultra-high molecular weight silicones; However, a plateau is reached after incorporation of about 1% by weight of silicon.

(4) For series P1, if the silicone content exceeds approximately 0.1% by weight, this plateau lies below the benchmark set by the reference example, a commercially available BOPET film (film type FN8).

(5) On the other hand, series P2 shows a plateau significantly above the benchmark line set by FN8, indicating that the benchmark value cannot be reached at any silicon addition level.

Besides ballast, from a practical standpoint, another factor that determines the upper silicone level in the food contact layer is silicone migration into the food, as shown in Table 5 below: The point is that you have to reach a higher level than what makes passing possible:

[Table 5]

The results indicate that a silicone level greater than 2% by weight in the food contact layer will ensure that the film passes the most critical condition (h) for use as a container liner for containers subjected to food sterilization processes typically exceeding 250°F. It indicates that it prevents something from being done.

The lower temperatures required for successful lamination and post-processing in the case of embodiments comprising PBT in the layer (in this case Layer B) that will be in contact with the metal during lamination are the lower temperatures required for the PBT as a blend component (20°C lower than the polyester resin P2). The effects of using it as a (representing a category of polyester resin with a low melting point) are described above.

In the previous examples, samples of laminated disks were taken from random locations on the metal-coated web. In the examples that follow, the influence of crystallinity and location on food release is evaluated: these examples help to demonstrate the advantage of introducing wax in improving the shift in influence of crystallinity.

Comparative Example 8: (This is a comparative example {no wax} to Example 7 with added wax that follows). Two-layer biaxially oriented polyester films, with layer compositions as shown in Tables 1 and 2, were prepared by film production consisting of a main extruder and a sub-extruder, a casting drum, machine-direction stretching and transverse stretching (tenter oven). Manufactured on line. The elongation was 4.8 in the MD direction and 3.7 in the TD direction. The maximum stretching temperature was 121°C in MD and 104°C in TD. Depending on the TD orientation, there was a 5% relaxation section at 233°C. The final linear speed was 288 m/min. The final film product was subsequently laminated onto a sheet of tin-free metal sheet on the B-layer side under the following conditions: lamination temperature 370-380°F (188-193°C); Post bake 430-440°F (221-227°C). Food release was tested according to the procedure described above at six different locations across the width of the laminate, depending on the following locations within the laminate device: drive side (DS), midway between the drive side and the center. ("DSC"), two points centered on either side of the true center, i.e. center-left ("C-L") and center-right ("C-R"), midway between the tending side and the center. (distance) (“TSC”), and tenting side (“TS”). The scores, expressed as percent of total area occupied by remaining food, are listed in Table 4.

Additional laminations were performed at different lamination and post-bake temperatures to evaluate the effect on the crystallinity remaining in the film after the still-lamination process. The results are plotted in Figure 9.

Example 7: Comparative Example 8 was repeated except that 4.5% wax masterbatch (resulting in 0.9% wax by weight) was added to Layer A, as shown in Table 1. The PBT level in layer B (resin “P5”) was increased to 35% by weight for reasons not relevant to the scope of the invention and should not affect the release results. The process changes compared to Example 7 are a lower MD ratio (4.5), and small adjustments in MD and TD maximum temperatures (116°C and 123°C, respectively); Additionally, the TD relaxation temperature was 216°C. The final film product was then laminated onto a sheet of tin-free metal sheet on the B-layer side under the following conditions: lamination temperature 370-380°C (188-193°C), post-bake 430-440°F (221-227°C). ℃). Food release was tested according to the procedure described above at five different locations across the width of the stack, depending on the following locations within the laminate device: drive side (DS), midway between the drive side and center (“DSC”); center, midway between the tenting side and the center (“TSC”), and the tenting side (“TS”). The scores, expressed as percent of total area occupied by remaining food, are listed in Table 6.

Additional laminations were performed under different lamination and post-bake temperature conditions to evaluate the effect on the crystallinity remaining in the film after the still-lamination process. The results are plotted in Figure 10.

[Table 6]

The results of the food release tests in Example 7 and Comparative Example 8, along with the crystallinity tests, show that the addition of wax does not improve crystallization, but nonetheless mitigates the effect of loss of crystallinity on food release properties. It supports the fact that it is assisting. This has, for example, a food release score around the center that is better for the wax-containing sample (Example 7) compared to the control (Comparative Example 8), where crystallinity is almost gone in both Examples and Comparative Examples. It is clear by this. Overall, these examples demonstrate that the addition of wax to the original design (food-contact skin A comprising polyester and silicone using alkali metal phosphates in catalytic packaging) may result in meat release, which may not be appropriate under certain lamination situations. It demonstrates that goodness is added to the characteristics.

All U.S. patents and publications cited herein are incorporated by reference in their entirety.

Claims (32)

A polyester film comprising an outer release layer (layer A) and a core layer (layer B),
The outer emitting layer is
(a) A polyester resin comprising (i) an alkali metal phosphate in an amount of 1.3 mol to 3.0 mol per ton of polyester resin P1 and (ii) phosphoric acid in an amount of 0.4 to 1.5 times the alkali metal phosphate on a molar basis. P1 93-99.9% by weight
(b) wax component and
(c) 0.1-3% by weight of silica
Includes;
wherein the core layer includes polyester resin P2 and 15 to 45% by weight of polybutylene terephthalate (PBT);
wherein the polyester film is free of bisphenol A and the weight percentages of (a), (b), (c) and any optional one or more additional components in the outer release layer total 100% by weight;
The outer release layer has a food area coverage of 10% or less as measured according to a food release test,
Polyester film. According to paragraph 1,
A polyester film, wherein the core layer comprises 30 to 45% by weight PBT. According to paragraph 1,
(a) 67-85% by weight of polyester resin P2, which is crystallizable and different from polyester resin P1;
(b) 15-30% by weight of an amorphous copolyester resin or polyester resin having a melting point at least 20° C. lower than the melting point of the polyester resin P2; and
(c) Antiblock containing organic or inorganic particles, 0-3% by weight.
It further comprises a heat-sealable layer (layer C) comprising,
having an outer release layer, a core layer and a heat-sealing layer in this order,
Polyester film. According to paragraph 3,
A polyester film, wherein polyester P2 comprises an aromatic polyester. According to paragraph 3,
A polyester film, wherein the polyester resin P2 contains 50% by weight or more of ethylene terephthalate as a component of the polyester resin P2. According to paragraph 3,
A polyester film, wherein the polyester resin having a melting point at least 20° C. lower than that of polyester resin P2 includes butylene terephthalate repeating units. A laminated metal sheet comprising the polyester film according to claim 1. A laminated metal sheet comprising the polyester film according to claim 3. delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete