KR20180116294A - Polyester film containing silicone for the discharge of canned meat products - Google Patents

Abstract

Polyester multilayer films containing butylene terephthalate, such as biaxially oriented polyester (BOPET) films for lamination on metal sheets, can be used for food containers. The polyester film has an outer discharge layer to aid in the discharge of food, such as a high protein food source, when the food is cooked and sterilized by direct contact with the outer discharge layer. The polyester film may be laminated to the metal used in the manufacture of the food container and the outer drain layer is exposed to allow direct food contact between the surface of the outer drain layer and the food. The outer discharge layer comprises an ultra high molecular weight siloxane polymer, a polyethylene terephthalate resin, an alkali metal phosphate and phosphoric acid.

Description

Polyester film containing silicone for the discharge of canned meat products

The present invention relates to a butylene terephthalate-containing multilayer film, such as a biaxially oriented polyester (BOPET) film, preferably without bisphenol A, for lamination on metal sheets, which can be used for food containers. More specifically, the multilayer film has an outer discharge layer that helps release food, such as a high protein food source, when the food is cooked and sterilized by direct contact with the outer discharge layer.

The principle of food canning

Unlike pasteurized " cooked " meat products where the survival of thermostable microorganisms is allowed, the purpose of sterilization of meat products is the destruction of all contaminating bacteria including spores. The heat treatment of these products can be strong enough to deactivate / kill the most thermostable bacterial microorganisms that are spores of Bacillus and Clostridium. In fact, the meat product filled in the sealed container is exposed to a temperature in excess of 100 DEG C in a pressurized container. Depending on the product type, temperatures in the range of 110-130 ° C, in excess of 100 ° C, can be reached inside the product. The product is maintained for a period of time at the temperature level required for sterilization, depending on the product type and container size.

If the spore is not completely inactivated in the can, the plant microorganism will grow from the spore as soon as the condition is good. In the case of heat-treated processed meat, favorable conditions will exist when the heat treatment is completed and the product is stored at room temperature. Surviving microorganisms can produce toxins that destroy preserved meat products or cause food poisoning in consumers.

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

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

From the microbial point of view, it may be ideal to use a very strong heat treatment that can eliminate the risk of any viable microorganisms. However, most canned meat products have such a strong heat without suffering from a deterioration in sensory quality, such as very soft texture, jelly and fat separation, discoloration, undesired heat treatment taste and loss of nutritional value (destruction of vitamins and protein components) It can not be exposed to stress.

To comply with this aspect, compromises must be reached in order to maintain heat sterilization sufficiently strong for the microbiological safety of the product and to maintain thermal sterilization as moderately as possible for reasons of product quality.

Meat products suitable for canning

All processed meat products that require heat treatment during preparation for ingestion are suitable for warming. Meat products that are not subjected to any heat treatment prior to ingestion, such as dried meat, raw ham, or dried sausages, are of course unsuitable for canning because they are preserved at low pH and / or low water activity.

The following groups of meat products are often made from canned products: cooked ham or pork shoulder; Sausages with brine type Frankfurter; Sausage mixes of bologna or liver sausage types; Meat dishes such as salted beef, chopped pork; And ready-to-eat dishes such as chicken with rice soup with meat ingredients such as gravy, beef or chicken soup.

Can lining

Metal food and beverage containers, such as cans, are lined with a coating on the inner surface. This coating is essential to prevent corrosion of containers and contamination of food and beverages due to dissolved metal. In addition, the coating prevents canned food from being spoiled or damaged by bacterial contamination. The main types of interior coatings for food containers are made of epoxy resins, which are widely used as protective coatings due to their excellent combination of toughness, adhesion, formability and chemical resistance. These coatings are inherently inert and have been in use for over 40 years. In addition to protecting the contents from rot, this coating can extend the shelf life while maintaining the quality and taste of the food.

However, such epoxy polymers may contain a residual amount of chemical building blocks called BPA that are subject to much investigation from consumer support groups. Based on Prop. 65, California suggested that BPA be the second cause of reproductive toxicity. Therefore, it is necessary to remove the BPA-based epoxy resin as a protective coating.

Over the past decade, consumers and health professionals have raised concerns about the use of BPA in food packaging. Molecules are similar to estrogen and can act as endocrine disruptors.

Therefore, food companies are eager to escape from BPA-based food packaging. Coating manufacturers and suppliers have been working for many hours to find ubiquitous epoxy substitutes made by reacting BPA with epichlorohydrin. In summary, a coating without BPA for food containers is urgently needed. The BPA-free BOPET film of the present invention meets this need.

Lamination of the polyester film to the metal prior to forming the container is one solution for replacing the container lined with epoxy coating. Biaxially oriented polyester (BOPET) films are used in many applications such as food packaging, decoration and labels.

The food packaging industry uses BOPET films in many thermally sealable tray applications where foods can be in direct contact with BOPET, but food exudation from the BOPET film surface is inadequate.

Food discharge

One problem caused by the cooking and sterilization of foods inside the containers, especially for foods containing significant amounts of solids such as meat products, is the adherence of solid food particles to the inner container surface, . Various methods have been proposed to address this phenomenon, including the inclusion of waxes (U.S. Patent No. 6,652,979, U.S. Patent No. 6,905,774, U.S. Patent No. 7,198,856, U.S. Patent No. 7,435,465) or silicone compounds (U.S. Patent No. 6,905,774) Are disclosed in patent documents.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems.

One embodiment of the present invention relates to a process for the preparation of (a) phosphoric acid in an amount of from 0.4 to 1.5 moles of an alkali metal phosphate and an alkali metal phosphate in an amount of from 1.3 mol / ton of the polyester resin P1 to 3.0 mol / 0.1 to 99.9% by weight of polyester resin P1; And (b) at least one layer comprising from 0.1 to 2% by weight of a silicone resin comprising a polydimethylsiloxane resin; Polyester film has no 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 of ethylene terephthalate as a constituent of the aromatic polyester. In one embodiment, the at least one layer comprises an outer discharge layer having a food area range of about 10% or less as measured according to a Food Release Test. In one embodiment, at least one layer comprises (a) 0.1-100 wt.% Polyester resin P2 crystallizable and different from the polyester resin P1; (b) 0.1-100 wt% amorphous copolyester resin or polyester resin having a melting point at least 20 [deg.] C lower than polyester resin P2; And (c) 0.1 to 15% by weight of an anti-blocking layer 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 composition different from the heat-sealable layer B. In one embodiment, the polyester P2 comprises an aromatic polyester. In one embodiment, the polyester resin P2 comprises at least 50% by weight of polyethylene terephthalate as a constituent of the polyester resin P2. In one embodiment, the component (b) of the polyester resin having a melting point at least 20 캜 lower than the polyester resin P2 is a polybutylene terephthalate (PBT) resin, preferably a polybutylene terephthalate (PBT) .

Another embodiment of the laminated metal sheet comprises the polyester film of this embodiment. In one embodiment, the silicone resin has a kinematic viscosity in the range of 10-50 x 10 ⁶ centistokes at room temperature.

Are included in the scope of the present invention.

The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing (s) will be provided by the office upon request and upon payment of the required fee.
BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a photograph of the different ingredients used to prepare the food mix for food release testing.
Figure 2 shows a photograph of a BOPET laminated metal disc and a non-laminated BOPET film.
Figure 3 shows a photograph of inserting a food mix into a sealed container with a cap having a BOPET laminated metal disc in which the BOPET film is in contact with the food mix.
Figure 4 shows photographs of various sealing bottles containing a food mix in a autoclave and a pressure cooker on a heated stove.
Figure 5 shows a photograph showing the removal of a BOPET laminated metal disc from a cooked food mix.
Figure 6 shows a photograph of a BOPET laminated metal disk showing good and bad emissions of the food mix cooked from the BOPET film surface of the BOPET laminated metal disk.
Figure 7 is a photograph of a BOPET laminated metal disk (" test sample ") after a food discharge test with a grid superimposed on a BOPET laminated metal disk to calculate the percentage of the food surface area to which the cooked food mix is attached to the BOPET film Lt; / RTI >
Figure 8 shows a graph of percentage of food area coverage of the cooked food mix on a BOPET film as a function of weight percent of ultrahigh molecular weight silicon.

Embodiments of the present invention are directed to a polyester film, or BOPET film, having excellent heat resistance to withstand temperatures associated with retort sterilization temperature and barrier properties that provide corrosion resistance to metal containers by food. The BOPET film may be laminated and formed of a metal plate for the container forming process. In addition, the BOPET film can provide a sufficient exit surface for easy removal of high protein foods (meat products) from the container after high temperature sterilization. Surprisingly, the inventors have found that the discharge action imparted by including silicon containing ultra high molecular weight siloxane is greatly improved when using polyester resin carriers formulated with alkali metal phosphate and phosphoric acid during polymerization. The original purpose of the alkali metal phosphate / phosphoric acid package was to improve the hydrolysis resistance and the additional benefit of enhancing the discharge action of silicon was a surprising discovery.

The BOPET film may comprise one or more layers, preferably at least two layers. The multi-layer BOPET film may comprise one or more of a container side or an inner layer (i.e., heat seal or metal bond layer), a food or outer layer, and a food release layer, respectively. There can also be one or more core layers between the layer bound to the metal surface and the food side layer in direct contact with the food stored inside the container.

BOPET film

Films that can be laminated to metal can plates generally made of tin-free steel (TFS), electro-tinned steel (ETP) or aluminum are characterized by a dimensional change of less than 2.0% after heat treatment at 210 ° C.

The films disclosed herein include two or three layer coextruded and biaxially stretched structures. The outer discharge layer and the optional bottom " skin " layer are generally thinner than the core " main " The outer discharge layer (hereinafter referred to as " skin A ") generally contains ultra high molecular weight silicone (siloxane) resin, which premixes with the copolyester elastomer resin to form a " master batch "Lt; RTI ID = 0.0 > lower < / RTI >

The term " ultra high molecular weight silicon " or " UHMW PDMS " (where PDMS refers to polydimethylsiloxane) refers to PDMS resin and UHMW PDMS has a kinematic viscosity in the range of 10-50 x 10 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 ). The advantage of UHMW PDMS is that it forms stable droplet domains in various thermoplastic carriers, such as pellets, to facilitate the direct addition of additives to thermoplastics during processing, according to the references cited above. Another advantage of UHMW PDMS is that it does not flow out of the BOPET and, at the same time, travels to the BOPET film surface, providing the desired emission characteristics.

The typical UHMW silicon concentration in the master batch is 50 wt%. The master batch addition level in the outer discharge layer is in the range of 0.2 to 4 wt%, resulting in a pure siloxane content in the range of 0.1 to 2%. The remaining components of the external discharge layer are phosphorus compounds in an amount of from 0.4 to 1.5 times (molar) of the alkali metal phosphate and the alkali metal phosphate (main component) as phosphorus compounds in an amount of from 1.3 mol / ton to 3.0 mol / And optionally a PET resin polyester resin composition comprising inorganic particles for block prevention purposes. A typical inorganic particle composition in this case is silica (silicon dioxide, SiO ₂ ) of submicron to several microns in size. The silica particles are typically added during coextrusion in the form of a thickened PET chip (" silica master chip ") made by adding silica in polymerization. Typical silica content in the silica master chip is 1-3% by weight; Typical addition levels of the silica master chip in the outer discharge layer are 1-15% by weight, resulting in a net silica content of about 0.1-3% by weight.

The remaining two layers will be named hereinafter as layer " B " for the core layer and will be named skin layer " C " for the skin layer placed on the opposite surface as against the A skin layer. The thickness distribution ranges from 5-30%, 40-95% and 0-30% for each of the A, B and C layers. Typical total film thickness after biaxial extension is 10-25 microns, preferably 12 microns-23 microns.

The two- or three-layer film structure is laminated on a metal sheet (steel or aluminum) and then formed into a container. Although both sides of the metal sheet can be laminated with a plastic film, the film of the present invention is laminated on the side of the metal sheet which will be the inner surface of the container, and the outer discharge layer containing silicon in this way is a food contact layer .

The core layer B may comprise 100% PET resin (" base resin "). In the absence of a C layer, layer B may also contain a block-preventive master batch or a low melting temperature copolyester described in more detail for optional layer C.

The optional skin layer C can be a low temperature melt (vs. PET) or amorphous polyester copolymer or a mixture of a low melt (or amorphous) polyester copolymer and a PET base resin. One example of a low melt polyester is a copolymer of butylene terephthalate repeating units such as poly (butylene terephthalate) (" PBT ") resin and a copolymer of isophthalic acid, naphthalene dicarboxylic acid, azelaic acid, sebacic acid, adipic acid, ethylene glycol, And other dicarboxylic acids such as 1,3-propanediol, 1-propanediol, neopentylglycol, 1,4-cyclohexyldimethanol, or diol and copolymers thereof. A non-limiting list of suitable examples of polybutylene terephthalate (PBT) resins may be DuPont's Chardin FG6129, Chardin FG6130, Thicone's Celanese 1600, Celanex 1700, Toray's Toraycon 1100M, Toraycon 1200M and the like. Other examples of low melting polyesters are trimethylene terephthalate repeating units such as poly (trimethylene terephthalate) PTT resins and copolymers of isophthalic acid, naphthalene dicarboxylic acid, azelaic acid, sebacic acid, adipic acid, ethylene glycol, 1,4- And other dicarboxylic acids such as 1,4-butanediol, butanediol, 1,2-propanediol, neopentyl glycol, 1,4-cyclohexyl dimethanol, and the like. A non-limiting list of suitable examples of polytrimethylene terephthalate (PTT) resins may be Sorone (DuPont), Cortera (Shell), Ecolax (SK Chemical). The purpose of adding a low melting or amorphous polyester copolymer to the layer is to facilitate easier adhesion to the metal during thermal lamination. However, the addition of such a copolymer is necessary to make the metal contact layer heat-sealable, since the temperature of the lamination and subsequent oven treatment can be adjusted to a value that makes the metal-contact surface sufficiently tacky to bond to the metal not. The PET polyester has a melting point peak at about 250 ° C, but the onset of melting occurs at about 205 ° C (400 ° F), which matches the lamination temperature conditions and promotes the initial bonding at the pressure of the lamination nip roll, And further strengthened by oven treatment of the laminate structure.

Polyester resin composition

The resin in the A layer is a polyester resin, " P1 ", which contains a substance dissolving in ethylene glycol and exhibiting ion dissociation. Such buffers are preferably salts of alkali metal salts, such as phthalic acid, citric acid, carbonic acid, lactic acid, tartaric acid, phosphoric acid, phosphorous acid, hypophosphorous acid; And alkali metal salts of polyacrylic acid compounds. More specifically, the alkali metal is potassium or sodium, and thus specific alkali metal salts are exemplified by sodium hydroxycitrate, potassium citrate, potassium hydrogen hydroxycatrate, sodium carbonate, sodium tartrate, potassium tartrate, sodium lactate, sodium carbonate, Sodium hydrogenphosphate, potassium hydrogenphosphate, potassium phosphate, sodium dihydrogenphosphate, sodium hypophosphite, sodium hypochlorite, sodium polyacrylate and the like.

In a preferred embodiment, P1 is an alkali metal phosphate in an amount of from 1.3 to 3.0 moles / ton of the polyester resin and an alkali metal phosphate in an amount of from 0.4 to 1.5 times (moles) of the alkali metal phosphate, Is a polyester resin composition containing phosphoric acid. It is preferable for the polyester resin composition that the acid component contains the dicarboxylic acid component in a molar amount of 95% or more. In particular, the terephthalic acid component is preferable from the viewpoint of mechanical properties. From the viewpoints of mechanical properties and thermal properties, it is preferable that the glycol component contains 95 mol% or more of a straight chain alkylene glycol having 2 to 4 carbon atoms.

Particularly, ethylene glycol having 2 carbon atoms is preferable from the viewpoint of moldability and crystallization of the polyester resin. In addition to terephthalic acid and ethylene glycol, additional polyester materials such as diacids such as isophthalic acid, naphthalene dicarboxylic acid, or 1,4-cyclohexyldimethanol, diethylene glycol, 1,3-propylene glycol, Diols such as 4-butylene glycol can be provided in the polyester composition polymerization mix as copolymerization components at up to 5 mole percent levels of total disac- tions or diols. If the content of the copolymerization component exceeds 5 mol%, this will result in a decrease in the heat resistance due to the lowering of the melting point and a decrease in the hydrolytic resistance due to the lowering of the crystallinity of the polyester. From the viewpoint of hydrolysis resistance, it is preferable that the polyester resin composition contains an alkali metal phosphate in an amount of 1.3 mol / ton to 3.0 mol / ton of the polyester resin. Preferably from 1.5 mol / ton to 2.0 mol / ton of polyester resin. When the content of the alkali metal phosphate is less than 1.3 mol / ton of the polyester resin, the resistance to organoleptic hydrolysis may become insufficient. On the other hand, when the alkali metal phosphate is contained in an amount exceeding 3.0 mol / ton of the polyester resin, phase separation (precipitation) of the alkali metal phosphate tends to occur.

Examples of alkali metal phosphates include sodium dihydrogenphosphate, sodium dihydrogenphosphate, trisodium phosphate, potassium dihydrogenphosphate, potassium dihydrogenphosphate, tripotassium phosphate, lithium dihydrogenphosphate, lithium dihydrogenphosphate, trilithium phosphate .

Preferred examples of alkali metal phosphates are alkali metal dihydrogen phosphates and alkali metal phosphates. Alkali metal phosphates in which the alkali metal is Na or K are preferable from the viewpoint of organohydrolysis resistance. Particularly preferred examples of alkali metal phosphates are sodium dihydrogenphosphate and potassium dihydrogenphosphate. From the viewpoint of long-term hydrolysis resistance, it is preferable that the phosphoric acid is 0.4 to 1.5 times the molar ratio of the alkali metal phosphate. Preferably 0.8 to 1.4 times. If it is less than 0.4 times, the long-term hydrolysis resistance may deteriorate. If it exceeds 1.5 times, the polymerization catalyst is inactivated by an excess of phosphoric acid, which not only leads to retardation of polymerization but also increases the amount of terminal group COOH, which will contribute to lowering the hydrolysis resistance of the polyester resin.

According to the calculations based on the contents of alkali metal phosphate and phosphoric acid, the polyester resin composition contains 1.8 mol / ton of alkali metal element and polyester resin in an amount of from 1.3 mol / ton of polyester resin to 9.0 mol / By weight of the polyester resin in an amount of 7.5 mol / ton. In view of the type of alkali metal phosphate preferred, the polyester resin composition preferably comprises from 1.8 mol / ton of alkali metal element and polyester resin in an amount of from 1.3 mol / ton of polyester resin to 6.0 mol / ton of polyester resin By weight of the polyester resin in an amount of 7.5 mol / ton.

From the viewpoint of reducing the amount of terminal group COOH and suppressing the formation of foreign matter, the total content of the phosphorus compound contained in the polyester resin composition of the present composition is preferably from 30 PPM to 150 PPM Weight. More preferably, the content is from 60 PPM to 150 PPM.

The composition of the polyester resin P1 is a metal-containing compound ("metal compound") in which the metal element is at least one member selected from the group consisting of Na, Li and K, a metal element selected from the group consisting of Mg, Ca, Wherein the metal element is at least one member selected from the group consisting of Sb, Ti and Ge, and the total amount of the metal element is not less than 30 PPM and not more than 500 PPM Lt; / RTI > By adjusting the total amount of metal elements to within this range, the amount of terminal group COOH can be reduced in the polyester to improve heat resistance. More preferably, the content is from 40 PPM to 300 PPM. The elements Na, Li and Ka are alkali metal elements. The divalent metal elements Mg, Ca, Mn, and Co elements are ester exchange catalysts, and impart electrostatic properties such as intrinsic resistance of the polyester resin. Sb, Ti and GE are metal members having an ability to catalyze polymerization of a polyester resin and serve as polymerization catalysts.

BOPET film process

Preferably, the multilayer PET film is oriented biaxially before it is laminated to a metal substrate. Typically, the raw PET resin is supplied in solid form to a melt treatment apparatus, preferably a continuous screw extruder. The heating of the melting apparatus is controlled so that the PET resin is maintained at a temperature not lower than the decomposition temperature of the polymer while keeping the PET resin at the melting point or higher. The PET molten resin is extruded from a suitably shaped die to form a thin, flat polymer melt ribbon. The polymer ribbon is quenched in air or on a cooled roll to form a firm, self-supporting film. The film is absorbed by a set of rollers rotating at different rotational speeds to stretch the film in the direction of successive advancing motions, called machine direction (" MD "). The elongation can be accompanied by heating of the film to make the crystal orientation in the MD. The unidirectionally oriented film is stretched in a transverse machine direction (" TD ") which is fixed at the opposite edge of it in a tenter oven and is laterally sideways to the MD. The tenter oven is heated to a temperature that acts to create a crystalline orientation in TD to form a biaxially oriented PET film. Preferably the biaxially oriented PET film is stretched between about 100% -400% in MD and 100% -600% in TD. The biaxially oriented film may preferably be thermoset at a temperature of from about 300 내지 to about 490,, more preferably from about 350 ℉ to about 460..

Example

The invention will be better understood with reference to the following examples, which are intended to illustrate particular embodiments within the full scope of the invention, but the scope of the invention is not limited to the examples.

Resin material

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

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

PET resin P2 (normal film grade PET resin, not containing alkali metal phosphate): Toray F21MP (IV = 0.65; Tm = 255 DEG C) manufactured by Toray Plastics America.

PET resin P3: Bottle grade PET resin 8712A of INVISTA having an IV of 0.75.

PET resin P4: PET resin block blocking master batch type F18M (IV = 0.62, Tm = 255 占 폚) containing 2% silica particles (Fuji Silysia 310P) with an average size of 2 占 퐉 made by Toray Plastics America.

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

Slow-crystallized copolyester resin CoP2: IPET F55M resin (IV = 0.69; manufactured by Toray Plastics America) based on a 19:81 mole (= in this case weight) subcombination of isophthalic acid / terephthalic acid reacted with ethylene glycol. Tm = 205 [deg.] C).

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

Low melting point polyester resin P5: 223 占 폚 EI having a melting point. DuPont Dinemoor's polybutylene terephthalate (PBT) resin Crustine FG6130.

Test method

In the above examples, various properties were measured in the following manner:

The intrinsic viscosity (IV) of the film and resin was tested according to ASTM D 4603. This test method is for IV measurements of soluble poly (ethylene terephthalate) (PET) at 0.50% concentration in a 60/40 phenol / 1,1,2,2-tetrachloroethane solution with a glass capillary viscometer .

The melting point of the copolyester resin is measured using a TA Instruments differential scanning calorimeter Model 2920. 0.007 g Resin sample is tested substantially in accordance with ASTM D3418-03. Preliminary thermal cycling is not used in accordance with Note 6 of the ASTM standard. The sample is then heated to a temperature of 300 DEG C at a rate of 10 DEG C / min while recording thermal flaw and temperature data. The melting point is reported as the temperature at the endothermic peak.

General film making procedure

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

The multilayer coextruded laminated sheet is co-extruded with one or two coextruders to melt the core extruder and skin blend and deliver it to the die to melt the core blend and transport it to the die. The extrusion through the main extruder takes place at a treatment temperature of about 270 ° to 285 ° C. Extrusion through a secondary extruder takes place at a treatment temperature of about 270 ° to 280 ° C. The primary and secondary streams pass through the die to form a laminated coextruded structure and cast onto a cooling drum whose surface temperature is controlled at about 21 占 폚 to solidify the non-oriented laminated sheet at a casting speed of about 9 mpm. The unstretched laminated sheet is stretched in the longitudinal direction at about 75 DEG C to 85 DEG C about 3 times its original length, and the obtained stretched sheet is annealed at about 70 DEG C to obtain a uniaxial stretch laminated sheet.

The uniaxially stretched laminated sheet was injected into a tenter preheated to 80 DEG C at a linear velocity of about 27 mpm, stretched in the transverse direction at about four times its original length at about 90 DEG C, and then thermally cured or annealed at about 210 DEG C Provides a biaxially oriented sheet that reduces internal stress, minimizes shrinkage, and is relatively thermally stable.

Film thermal lamination procedure on metal sheet

Lead-free steel having a thickness of 0.0075 " was preheated to 400 F (unless otherwise stated) .The steel and film were passed through a set of nip rolls to form the initial bond of the film to the steel. Is passed through a secondary heating operation (" post-baking ") for 20 seconds at 460F and then cooled to room temperature.

The film surface laminated on the steel was the opposite side of the silicon-containing side (food contact side; A side in the example), i.e. the side of the laminate was B side or C side in the examples.

Food Discharge Test

The food surface area on the food contact surface of the polyester film laminated to the steel is measured according to the food release test referred to herein as the " food release test ". The procedures for food release testing are described below.

A food mixture prepared by mixing chicken eggs / ground beef / flour at a ratio of 3/2/1 was prepared as follows:

A. The food waste mix manufacturing step shown in Fig. 1

● For 8-10 bottle tests: 1 pound of ground beef in a mixing bowl like a plastic bottle

● Add 5 A grade large egg contents into the mix container and mix manually with a spatula or metal rod

● Add 8 ounces of multipurpose white flour slowly and mix until thoroughly mixed

B. Place the sample in a glass test bottle as in Figures 2 and 3

The disc was cut sufficiently small to fit the bottom of the bottle using scissors from the film / metal laminate as described above (Figure 2): In the example, a disc of 47 mm diameter was used to place the half- Lt; RTI ID = 0.0 >

● Cut the BOPET film to a large enough sheet size to fit the bottle and keep the food mix as described in the next step

● Place a piece of film on top of the bottle can (top of the meat discharge surface) and place the metal disc on the container with the food contact side facing up

● Place a few spoonfuls of the food waste mix on the sample disc

● The film wrapped around the disc below the food discharge mix and the food discharge mix.

● Place the wrapped food mix (with sample disc on the bottom) in the bottle and cover the bottle cover.

C. Retorting and Testing (Figures 4 and 5)

The "retort" (pressure cooker shown in FIG. 4) was filled with water to the bottom of the perforated steam plate to 0.5 "

● Place the test bottle on top of the plate and secure the retort cover.

● The retort was placed on a hot plate set at medium-high pressure and the pressure valve started to vibrate and retorted for 90 minutes (internal pressure 14.7 psig, temperature about 260 ° F).

● Remove the autoclave from the heat and cool until the valve, which is safe to open, comes down.

● The autoclave was opened and the bottle was removed with a forceps and left overnight.

● The film was unwound from the food mix (the food mix was still attached to the metal disk).

The disc was peeled off from the food mix at right angles to evaluate the discharge performance. See Figure 6 for a good and bad example of food distribution.

&Quot; Retort process " refers to a process for treating a metal container having a wall composed of a composite of a metal substrate having a polymer film laminated on the inside, outside, or both sides of the substrate with active vapor or superheated water for a certain period of time .

&Quot; Active steam " means that the steam is in direct contact with the surface of the vessel. Vapor is generally overheated, that is, above the boiling point of water. The nominal retort process requires exposure to steam at a temperature of 260 < 0 > F for 90 minutes. The temperature and duration of the retort process can be varied to provide approximately equivalent sterilization and food pasteurization effects. For example, the temperature may be lower for a shorter period of time or longer.

The discharge performance was evaluated by creating photographic images of test laminated discs after discharge and superimposing the rectangular grid images using MS paint software. Then the number of grid rectangles occupied by the remaining food attached is calculated and expressed as a percentage of the total number of grid squares. The lower the percentage, the better the food discharge performance (Fig. 7).

Food Moving Test

The tests were carried out in accordance with the provisions of Title 21 CFR 177.1630, Conditions (f), (g) and (h) under Qualified Laboratories (National Food Lab, Livermore, Renamed as follows: formerly: Covance Laboratories, Madison, Wis.). The test consists in determining the level of chloroform-soluble extract present in the exposed medium after exposure of the food contact surface (in this case layer A) under the following provisions for each use condition.

Condition (f): Allowed for foods other than alcoholic beverages at temperatures not exceeding 250 ° F. - Extract limit: 0.5 mg / in ² after 2 hours of exposure to n-heptane at 150 ° F and distilled water at 250 ° F.

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

Condition (h): Food can be baked during baking or oven cooking at temperatures in excess of 250 ℉. Extract limit: 0.02 mg / in ² after 2 hours exposure to 150 의 n-heptane.

Examples 1 and 1a

The three layer BOPET film structure was prepared by melt extrusion from three extruders feeding the resin blends corresponding to layers A, B and C shown in Tables 1, 2 and 3, respectively. The silicon masterbatch content in layer A was 0.5%, which corresponds to a silicon content of 0.25% by weight. The difference between compositions 1 and 1a was for the Block Prevention Masterbatch (P4) content in Layer A and the Amorphous Copolyester (CoP1) content in Layer C (and the major resin balance P1 and P2 Of final content). The cast film was stretched three times along the machine direction at a temperature of 82 DEG C and then stretched 4 times in the transverse direction through an oven maintained at 85-93 DEG C in the stretching zone and 204 DEG C in the annealing zone to produce a biaxially oriented film And collected in roll form by a rotary winder at a linear velocity of 32 m / min.

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

Examples 2 and 2a

Using the A / B / C three-layer structure as shown in Tables 1, 2 and 3, the only significant difference was that the silicon master batch content of layer A corresponding to 0.5 wt% silicon was 1.0% 1a was repeated. The results of the food release test are listed in Table 4.

Example 3

Example 1 was repeated with the only significant difference that the silicon master batch content of layer A corresponding to a silicon content of 1.0 wt% was 2.0%, resulting in an A / B / C three layer structure as shown in Tables 1, . The results of the food release test are listed in Table 4.

Example 4

The two-layer BOPET film structure was prepared by melt extrusion through two extruders feeding the resin blends corresponding to layers A and B, respectively, as shown in Tables 1 and 2. Layer B contains 15% PBT. The two-layer BOPET film structure was prepared by melt extrusion through two extruders feeding a resin blend corresponding to Layers A and B, cast onto a cooling drum maintained at 21 占 폚 and rotated at a linear speed, Stretched three times along the machine direction at the temperature and then stretched four times along the transverse direction through an oven maintained at 85-93 占 폚 in the elongation zone and at 204 占 폚 in the annealing zone and fed by a rotary winder at a linear velocity of 32 m / And collected in a roll form. The final A / B biaxially oriented two-layer structures are shown in Tables 1 and 2, respectively. The silicon masterbatch content in layer A is 0.5%, which corresponds to a silicon content of 0.25% by weight.

Example 5

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

Example 6

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

Comparative Example 1

Example 1a was repeated with the only difference that no silicon masterbatch was added to layer A to produce an A / B / C 3 layer structure as shown in Tables 1, 2 and 3, respectively. The results of the food release test are listed in Table 4.

Comparative Example 2

For this comparative example, a commercial biaxial film was used which is available in two layers available as Toray Plastics Americas grade " Lumirror 48G PA66 " (Layers A and B are the same except that layer B contains internal regeneration). The film product is based on P2 as the base resin and P4 as the block prevention masterbatch, respectively. The A / B structure is shown in Table 1 and Table 2, and the results of the food discharge test are listed in Table 4. Table 4:

Comparative Example 3

Example 1a was repeated with the only major difference that the main polyester resin (base resin) was P2 (standard film grade PET) and that no PET resin containing alkali metal phosphate and phosphoric acid (like P1) was used, , 2 and 3 as shown in Fig. As in Example 1, this comparative example included a 0.5% silicon master batch. The results of the food release test are listed in Table 4.

Comparative Example 4

Example 2a was repeated with the only major difference that the main polyester resin (base resin) was P2 (standard film grade PET) and that no PET resin containing alkali metal phosphate and phosphoric acid (like P1) was used, , 2 and 3 as shown in Fig. As in Example 2, this comparative example contained 1.0% silicon master batch in layer A. The results of the food release test are listed in Table 4.

Comparative Example 5

The extrusion conditions were the same as those listed in Example 4. The final A / B biaxially oriented two-layer structure is shown in Tables 1 and 2, respectively. As in Example 3, this comparative example included a 2.0% silicon master batch in Layer A corresponding to a silicon content of 1 wt%. The results of the food release test are listed in Table 4

Comparative Example 6

Comparative Example 5 was repeated with the only major difference that the silicon masterbatch content in the A layer was 4.0%, corresponding to a silicon content of 2.0% by weight, to produce an A / B two-layer structure as shown in Tables 1 and 2. The results of the food release test are listed in Table 4.

Comparative Example 7

Comparative Example 3 was repeated (the 0.5 wt% silicon master batch in the A layer corresponding to 0.25 wt% silicon) with the only difference that the main resin in the A layer was P3, resulting in A / B / C 3 layer structure. The results of the food release test are listed in Table 4.

Reference Example

The reference example is represented by a commercial film currently considered for an inner container liner with food discharge properties, i.e., Lu Mirror grade FN8 from Toray Industries. The film was impregnated with a carnauba wax compound at levels in the range specified by U.S. Patent No. 6,652,979 (0.1-2% by weight) or U.S. Patent No. 6,905,774 (000.1-5% by weight).

Mixture composition of layer A Suzy Example P1 P2 P3 P4 Silicon MB Layer thickness, μm Comparative Example 1 97% - - 3% 0% 1.5 Example 1 94.5% - - 5% 0.5% 1.5 Example 1a 96.5% - - 3% 0.5% 1.5 Example 2 94% - - 5% One% 1.5 Example 2a 96% - - 3% 2% 1.5 Example 3 93% - - 5% 3% 1.5 Example 4 93.9% 5.6% 0.5% 1.5 Example 5 93.9% 5.6% 0.5% 1.5 Example 6 93.9% 5.6% 0.5% 1.5 Comparative Example 2 - 95% - 5% 0% 1.8 Comparative Example 3 - 94.5% - 5% 0.5% 1.5 Comparative Example 4 - 94% - 5% One% 1.5 Comparative Example 5 - 95% - 3% 2% 1.8 Comparative Example 6 - 93% - 3% 4% 1.8 Comparative Example 7 - - 94.5% 5% 0.5% 1.5

B mixed composition Suzy Example P1 P2 P3 P4 CoP2 P5 Layer thickness, μm Comparative Example 1 - 100% - - - - 10.7 Example 1 - 100% - - - - 10.7 Example 1a - 100% - - - - 10.7 Example 2 - 100% - - - - 10.7 Example 2a - 100% - - - - 10.7 Example 3 - 100% - - - - 10.7 Example 4 - 79.4% - 5.6% - 15% 13.5 Example 5 - 64.4% - 5.6% - 30% 13.5 Example 6 - 49.4% - 5.6% - 45% 13.5 Comparative Example 2 - 95% - 5% - - 10.4 Comparative Example 3 - 100% - - - - 10.7 Comparative Example 4 - 100% - - - - 10.7 Comparative Example 5 - 92% - 3% 5% - 13.5 Comparative Example 6 - 92% - 3% 5% - 13.5 Comparative Example 7 - 100% - - - - 10.7

C mixed composition Suzy Example P1 P2 P3 P4 CoP1 Layer thickness, μm Comparative Example 1 - 67% - 3% 30% 1.5 Example 1 - 85% - - 15% 1.5 Example 1a - 67% - 3% 30% 1.5 Example 2 - 85% - - 15% 1.5 Example 2a - 67% - 3% 30% 1.5 Example 3 - 85% - - 15% 1.5 Example 4 - - - - - - Example 5 - - - - - - Example 6 - - - - - - Comparative Example 2 - - - - - - Comparative Example 3 - 85% - - 15% 1.5 Comparative Example 4 - 85% - - 15% 1.5 Comparative Example 5 - - - - - - Comparative Example 6 - - - - - - Comparative Example 7 - 85% - - 15% 1.5

Results of steel lamination temperature and food discharge test Metal lamination condition Food Discharge Test Example The major PET resin (A layer) of the food-contact outer discharge layer % Of food-contact external discharge layer silicone resin Lamination temperature ℉ Post bake temperature ℉ Percentage of area where non-discharged food remains Comparative Example 1 P1 0.00% 400 460 14% Example 1 P1 0.25% 400 460 11% Example 1a P1 0.25% 400 460 7% Example 2 P1 0.50% 400 460 9% Example 2a P1 0.50% 400 460 8% Example 3 P1 1.00% 400 460 7% Example 4 P1 0.50% 370 440 2% Example 5 P1 0.50% 370 440 One% Example 6 P1 0.50% 370 440 2% Comparative Example 2 P2 0.00% 400 460 96% Comparative Example 3 P2 0.25% 400 460 55% Comparative Example 4 P2 0.50% 400 460 59% Comparative Example 5 P2 1.00% 400 460 27% Comparative Example 6 P2 2.00% 400 460 25% Comparative Example 7 P3 0.25% 400 460 76% Reference Example n / a none; Instead of carnauba wax 400 460 10%

These results indicate that the film containing polyester P1 (alkali metal phosphate / phosphate containing polyester) in the food discharge layer has the same silicon level in the food discharge layer but contains a standard (without alkali metal phosphates / phosphates) polyester Indicating that the performance is much better than the comparative composition.

For a more in-depth analysis, Figure 2 shows this result for the silicon content in layer A in the following way: One data series is the data corresponding to the film comprising resin P1 as the main PET resin in layer A Comparative Example 1 and Examples 1, 1a, 2, 2a, and 3) are grouped; The other data series groups data (Comparative Examples 2, 4, 5, and 6) including the resin P2 as the main resin in the A layer. The single data point shows the data for the film of Comparative Example 7 (including resin P3 and 0.25% silicon).

(1) The trend line of the series P1 is much lower than the trend line of the series P2, suggesting an improvement to a resin having improved hydrolytic stability achieved by including an alkali metal phosphate / catalyst phosphoric acid / additive package in a standard resin .

(2) A single data point corresponding to Example 7, namely the other main resin having hydrolytic stability (achieved by solid state versus higher IV), i.e. resin P3, generally corresponds to the trend line of series P2. That is, this resin was not improved by the addition of the standard resin.

(3) Further improvements in food waste performance are found in both series by incorporating siloxane ultra high molecular weight silicon. However, after about 1 wt.% Silicon incorporation, the stabilizer is reached.

(4) In the case of Series P1, the ballast is placed below the benchmark set by the commercial BOPET film of the reference example (film type FN8) once the silicon content exceeds approximately 0.1 wt%.

(5) On the other hand, series P2 maintains stability well above the benchmark line set by FN8, indicating that the benchmark value can not be reached at any silicon addition level.

In addition to the ballast, from a practical point of view, another factor in setting the upper silicon level of the food contact layer is that the silicon movement into the food reaches a level above the allowed level to pass through a particular section of FDA regulation 21 CFR 177.1630, .

Move test result After exposure 21 CFR 177.1630 methanol extract (mg / in ² ) Passed 21 CFR 177.1630 Conditions: Example Main PET resin of outer contact layer (A layer) % Of food contact outer discharge layer% silicone resin ethanol Heptane water Example 1 P1 0.25% n / a <0.01 n / a (f), (g), (h) Example 2 P1 0.50% n / a <0.01 n / a (f), (g) Example 3 P1 1.00% n / a <0.01 n / a (f), (g) Comparative Example 6 P2 2.00% 0.05 0.15 0.05 (f), (g)

The results indicate that a silicon content of at least 2 wt.% In the food contact layer prevents the film from passing through the most critical condition (h) for use as a container liner of a container that has undergone a food sterilization process, generally above 250 DEG F.

The lower temperature required for successful lamination and post-processing in the case of an embodiment comprising PBT in the layer (in this case B layer) that is in contact with the metal during lamination is that the PBT is blended with the blend component (having a melting point at least 20 캜 lower than the melting point of the polyester P2 Polyester resin &quot;).

Claims (21)

(a) from 0.1 to 99.9 wt% of an alkali metal phosphate and from 0.4 to 1.5 times molar amount of phosphoric acid in an amount of from 1.3 mol / ton of the polyester resin P1 to 3.0 mol / ton of the polyester resin P1, Of polyester resin P1; And (b) 0.1-2 wt% of a silicone resin comprising a polydimethylsiloxane resin, wherein the polyester film comprises butylene terephthalate. The method according to claim 1,
Polyester resin P1 is a polyester film containing an aromatic polyester. 3. The method of claim 2,
Wherein the aromatic polyester comprises at least 50% by weight of ethylene terephthalate as a constituent of the aromatic polyester. The method according to claim 1,
Wherein the at least one layer comprises an outer exit layer having a food area range of less than or equal to about 10% when measured according to a Food Release Test. The method according to claim 1,
The polyester film is free of bisphenol A, and at least one of the layers comprises (a) 0.1 to 100% by weight of a polyester resin P2 crystallizable and different from the polyester resin P1; (b) 0.1-100 wt% amorphous copolyester resin or polyester resin having a melting point at least 20 [deg.] C lower than polyester resin P2; And (c) 0.1 to 15% by weight of an anti-blocking layer comprising organic or inorganic particles. 6. The method of claim 5,
A polyester film further comprising a heat-sealable layer (C) having the same or substantially the same composition as the heat-sealable layer (B). 6. The method of claim 5,
A polyester film further comprising a heat-sealable layer (C) having a composition different from the heat-sealable layer (B). 6. The method of claim 5,
Polyester P2 A polyester film comprising an aromatic polyester. The method according to claim 6,
Polyester P2 A polyester film comprising an aromatic polyester. 6. The method of claim 5,
The polyester resin P2 contains at least 50% by weight of polyethylene terephthalate as a constituent component of the polyester resin P2. The method according to claim 6,
The polyester resin P2 contains at least 50% by weight of polyethylene terephthalate as a constituent component of the polyester resin P2. 6. The method of claim 5,
Wherein the polyester resin having a melting point lower than that of the polyester resin P2 by at least 20 DEG C is polybutylene terephthalate. 6. The method of claim 5,
Wherein the at least one layer comprises an outer exit layer having a food area range of less than or equal to about 10% measured according to a food release test. The method according to claim 6,
Wherein the at least one layer comprises an outer exit layer having a food area range of less than or equal to about 10% measured according to a food release test. A laminated metal sheet comprising the polyester film of claim 1. A laminated metal sheet comprising the polyester film of claim 5. A laminated metal sheet comprising the polyester film of claim 6. 15. The method of claim 14,
Wherein the at least one layer comprises an outer exit layer having a food area range of less than or equal to about 10% measured according to a food release test. 16. The method of claim 15,
Wherein the outer discharge layer has a food area range of less than about 10% measured according to a food discharge test. 17. The method of claim 16,
Wherein the outer discharge layer has a food area range of less than about 10% measured according to a food discharge test. The method according to claim 1,
Wherein the silicone resin has a kinematic viscosity in the range of 10-50 x 10 ⁶ centistokes at room temperature.

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