Orientable ethylene-vinyl alcohol blends

Abstract

Disclosed is a blend, a multilayer film and a method for making a multilayer film having improved processability and lower crystallization temperature. The blend is at least 90.0% of an ethylene-vinyl alcohol copolymer having a first crystallization temperature; and (i) a process aid relative to the barrier layer. The blend has a second crystallization temperature that is at least lower than the first crystallization temperature.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Patent Application Serial No. 63 / 158,496, filed March 9, 2021, entitled “Orientable Ethylene Vinyl Alcohol Blend,” the entire contents of which are incorporated herein by reference. Background Technology

[0003] The subject matter disclosed herein relates to oriented ethylene-vinyl alcohol blends. More particularly, it relates to blends of orientation aids with ethylene-vinyl alcohol that improve the processability of ethylene-vinyl alcohol while retaining the fundamental benefits of ethylene-vinyl alcohol.

[0004] Ethylene-vinyl alcohol copolymers (EVA) are semi-crystalline polymers used in many industries, including food packaging. EVA provides good barrier properties and can be processed within the temperature range of other polymers. In addition to barrier properties, EVA is also typically transparent, oil and solvent resistant, flexible, moldable, weather-resistant, recyclable, and printable. EVA is transparent, rigid, and highly crystalline, providing good gas barrier properties and exhibiting relatively high moisture permeability. EVA is used in co-extruded structures for both rigid and flexible packaging. Due to its high crystallinity, it can be difficult to thermoform or orient.

[0005] The properties of ethylene-vinyl alcohol copolymers can vary based on the ethylene content. For example, increasing the ethylene content of an ethylene-vinyl alcohol copolymer generally improves its processability, flexibility, and transparency. However, increasing the ethylene content generally reduces the gas barrier properties of the ethylene-vinyl alcohol copolymer.

[0006] The above discussion provides only general background information and is not intended to be used to help determine the scope of the subject matter for which protection is sought. Summary of the Invention

[0007] A blend, a multilayer film, and a method for manufacturing the multilayer film are disclosed, the multilayer film having improved processability and a lower crystallization temperature. The blend comprises at least 90.0% of an ethylene-vinyl alcohol copolymer having a first crystallization temperature; and a processing aid relative to a barrier layer (i). The blend has a second crystallization temperature at least below the first crystallization temperature.

[0008] In practice, some publicly disclosed embodiments of multilayer films offer advantages such as improved processability, flexibility, and transparency without substantially impairing gas-barrier properties.

[0009] In one exemplary embodiment, a multilayer film is disclosed. The multilayer film includes a first outer layer, a second outer layer, and a barrier layer disposed between the first and second outer layers. The barrier layer comprises a blend of: at least 90.0% of an ethylene-vinyl alcohol copolymer having a first crystallization temperature; and (i) 2.0% to 15.0% by weight, (ii) 2.5% to 10.0% by weight, or (iii) 3.0% to 5.0% by weight of a processing aid relative to the barrier layer. The blend has a second crystallization temperature that is at least 5%, 6%, 7%, 8%, 9%, or 10% lower than the first crystallization temperature, as measured by DSC with the following parameters: a) holding at 30°C for 1.0 minute; b) heating from 30.0°C to 230.0°C at 10.0°C / min; c) holding at 230.0°C for 1.0 minute; d) cooling from 230.0°C to 10.0°C / min; e) holding at 30.0°C for 1.0 minute; f) heating from 30.0°C to 230.0°C at 10.0°C / min.

[0010] In another exemplary embodiment, a blend is disclosed comprising at least 90.0% of an ethylene-vinyl alcohol copolymer having a first crystallization temperature; and (i) 2.0 wt% to 15.0 wt%, (ii) 2.5 wt% to 10.0 wt%, or (iii) 3.0 wt% to 5.0 wt% of a processing aid relative to the barrier layer. The blend has a second crystallization temperature at least 5%, 6%, 7%, 8%, 9%, or 10% lower than the first crystallization temperature, as measured by DSC with the following parameters: a) held at 30°C for 1.0 minute; b) heated from 30.0°C to 230.0°C at 10.0°C / min; c) held at 230.0°C for 1.0 minute; d) cooled from 230.0°C at 10.0°C / min; e) held at 30.0°C for 1.0 minute; f) heated from 30.0°C to 230.0°C at 10.0°C / min.

[0011] In another exemplary embodiment, a method for manufacturing a multilayer film is disclosed. The method includes the step of providing a barrier blend comprising: at least 90.0% of an ethylene-vinyl alcohol copolymer having a first crystallization temperature; and (i) 2.0 wt% to 15.0 wt%, (ii) 2.5 wt% to 10.0 wt%, or (iii) 3.0 wt% to 5.0 wt% of a processing aid relative to the barrier layer. The blend has a second crystallization temperature at least 5%, 6%, 7%, 8%, 9%, or 10% lower than the first crystallization temperature, as measured by DSC with the following parameters: a) holding at 30°C for 1.0 minute; b) heating from 30.0°C to 230.0°C at 10.0°C / min; c) holding at 230.0°C for 1.0 minute; d) cooling from 230.0°C to 10.0°C / min; e) holding at 30.0°C for 1.0 minute; f) heating from 30.0°C to 230.0°C at 10.0°C / min. The barrier blend is co-extruded to form a multilayer film of the barrier blend having a first outer layer, a second outer layer, and a layer disposed between the first outer layer and the second outer layer.

[0012] This brief description of the invention is intended only to provide a concise overview of the subject matter disclosed herein according to one or more exemplary embodiments, and is not intended to serve as a guide for interpreting the claims or defining or limiting the scope of the invention, which is defined only by the appended claims. This brief description is provided to introduce exemplary alternatives of the concepts in a simplified form, which will be further described in detail below. This brief description is not intended to identify key or essential features of the claimed subject matter, nor is it intended to aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to embodiments that address any or all the disadvantages pointed out in the background art. Attached Figure Description

[0013] As a way to understand the features of the invention, detailed description of the invention can be made with reference to certain embodiments, some of which are illustrated in the accompanying drawings. However, it should be noted that the drawings only illustrate certain embodiments of the invention and should therefore not be considered as limiting its scope, as the scope of the invention covers other equally effective embodiments. The drawings are not necessarily drawn to scale; the focus is usually on illustrating the features of certain embodiments of the invention. In the drawings, the same reference numerals are used to indicate the same parts throughout the various views. Therefore, for a further understanding of the invention, reference can be made to the following detailed description, read in conjunction with the accompanying drawings, wherein:

[0014] Figure 1 This is a schematic diagram of a method for manufacturing multilayer films; and

[0015] Figure 2 This is a schematic diagram of the hot blown film method used to manufacture films. Detailed Implementation

[0016] Ethylene-vinyl alcohol is a copolymer of ethylene and vinyl alcohol. It is prepared by polymerizing ethylene and vinyl acetate to obtain ethylene-vinyl acetate copolymer, followed by hydrolysis. Ethylene-vinyl alcohol copolymers are highly crystalline and prepared with various molar percentages of ethylene. Ethylene-vinyl alcohol is a random copolymer with a chemical structure derived from the combination of ethylene and vinyl alcohol units.

[0017] Ethylene-vinyl alcohol copolymers have many beneficial properties.

[0018] Ethylene-vinyl alcohol copolymers are antistatic, thus reducing dust accumulation when used as a surface layer.

[0019] Ethylene-vinyl alcohol copolymer resins produce high gloss and low haze, resulting in good optical properties.

[0020] The -OH groups in the molecular chain of ethylene-vinyl alcohol copolymers enable printing on the surface.

[0021] Ethylene-vinyl alcohol copolymers are resistant to oil and organic solvents.

[0022] Ethylene-vinyl alcohol copolymers are weather-resistant and retain their color. They are resistant to yellowing or opacification.

[0023] Ethylene-vinyl alcohol copolymers exhibit good gas barrier properties. However, these properties are dependent on relative humidity (RH); increased humidity reduces gas barrier properties. Both barrier properties and humidity sensitivity vary depending on the ethylene content.

[0024] Ethylene-vinyl alcohol copolymers are commercially available, having an ethylene content of 24 to 48 mol%. Ethylene-vinyl alcohol copolymers with higher ethylene content tend to have better processing properties. This includes, but is not limited to, orientation, flexibility, thermoformability, elongation, stretching, and shrinkage. However, higher ethylene content also leads to reduced gas barrier properties against gases such as oxygen, carbon dioxide, carbon monoxide, and nitrogen.

[0025] On the other hand, ethylene-vinyl alcohol copolymers with lower ethylene content tend to have improved gas barrier properties compared to grades with higher ethylene content. As a trade-off, lower ethylene content ethylene-vinyl alcohol copolymers are more difficult to process and may not function properly in some applications. Conversion methods requiring a stretching stage of the material, such as thermoforming or film orientation, generally prefer ethylene-vinyl alcohol copolymer grades with higher ethylene content, thus requiring a sacrifice of barrier properties at practical film gauges. Processability is important in film processing methods such as single-layer film extrusion (blow molding or casting), co-extrusion film extrusion (blow molding or casting), co-extrusion blow molding, profile co-extrusion, and coating.

[0026] In the embodiments described herein, improved processability is achieved by mixing the ethylene-vinyl alcohol copolymer with a processing aid. By utilizing the processing aid, good barrier properties are maintained while the processability of the ethylene-vinyl alcohol copolymer is improved.

[0027] Processing aids typically have at least one ester, carboxylic acid, or carbonate functional group and at least one hydroxyl functional group. Processing aids are selected from triacetin, diacetin, lactic acid, triethyl citrate, glycerol, and glyceryl carbonate. The processing aid is blended with the ethylene-vinyl alcohol copolymer in an amount of at least 2.0, 2.5, 3.0, 3.5, or 4.0% by weight. The processing aid is blended with the ethylene-vinyl alcohol copolymer in an amount of up to 15.0, 14.0, 13.0, 12.0, 11.0, 10.0, 9.0, 8.0, 7.0, 6.0, or 5.0% by weight. The processing aid can be added as a pure substance or incorporated into the masterbatch to make the weight percentage consistent with the range described in this paragraph. In an embodiment, the processing aid is prepared as a masterbatch in a first-stage ethylene-vinyl alcohol copolymer. In an embodiment, the masterbatch is used with a second-stage ethylene-vinyl alcohol copolymer.

[0028] Processing aids can lower the crystallization temperature (T) of ethylene-vinyl alcohol copolymers. c This slows down crystallization kinetics, but has a limited impact on the final crystallinity. Therefore, as T... c Processing aids reduce the amount of ethylene-vinyl alcohol (EVA) in the amorphous state before the stretching stage of the conversion process. This leads to improved processability of the material while retaining the beneficial properties of the EVA copolymer. Furthermore, processing aids enable the formation of different crystalline forms that are easier to process, such as orientation and thermoforming.

[0029] Typically, additives are not blended with ethylene-vinyl alcohol copolymers because the added materials tend to reduce the beneficial properties of ethylene-vinyl alcohol. For example, polyamides and ionomers are known to improve processability but also reduce gas barrier properties. Therefore, in embodiments, the blend is relatively pure. In embodiments, the blend is at least 99.0 wt%, 99.1 wt%, 99.2 wt%, 99.3 wt%, 99.4 wt%, 99.5 wt%, 99.6 wt%, 99.6 wt%, 99.8 wt%, 99.9 wt%, or substantially all of ethylene-vinyl alcohol and processing aids.

[0030] Once the ethylene-vinyl alcohol copolymer and processing aids are blended, the blend can be used in applications where the ethylene-vinyl alcohol copolymer is typically used. Applications include, but are not limited to, flexible films, bags, capsules, food packaging, pharmaceutical packaging, heating elements, and automotive plastics. The blend can be further used as one or more layers in a multilayer film.

[0031] A blend of an ethylene-vinyl alcohol copolymer and a processing aid is blended to form a homogeneous mixture. An ethylene-vinyl alcohol copolymer, or a blend of ethylene-vinyl alcohol copolymers, is provided, wherein a processing aid is blended with the ethylene-vinyl alcohol copolymer to form a homogeneous blend. The formation of a homogeneous blend can be achieved by any suitable method, such as by mixing chamber, single-screw extrusion, twin-screw extrusion, grinding, granulation, melt compounding, screw blending, stirring, etc.

[0032] Suitable ethylene-vinyl alcohol copolymers include, in some embodiments, saponified or hydrolyzed ethylene / vinyl acetate copolymers, such as those with a degree of hydrolysis of at least about any of the following values: 50%, 85%, 95%, 99%.

[0033] Suitable processing aids, in some embodiments, have at least one ester, carboxylic acid, or carbonate functional group and at least one hydroxyl functional group. In embodiments, the processing aid is selected from triacetin, diacetin, lactic acid, triethyl citrate, and glyceryl carbonate. The processing aid is blended with the ethylene-vinyl alcohol copolymer in an amount of at least 2.0, 2.5, 3.0, 3.5, or 4.0% by weight. The processing aid is blended with the ethylene-vinyl alcohol copolymer in an amount of up to 15.0, 14.0, 13.0, 12.0, 11.0, 10.0, 9.0, 8.0, 7.0, 6.0, or 5.0% by weight. The processing aid may be added as a pure substance or incorporated into the masterbatch to ensure that the weight percentage is consistent with the range described in this paragraph. In the embodiments, the homogeneous blend is at least 99.0% by weight, 99.1% by weight, 99.2% by weight, 99.3% by weight, 99.4% by weight, 99.5% by weight, 99.6% by weight, 99.7% by weight, 99.8% by weight, 99.9% by weight, or substantially all of it is ethylene-vinyl alcohol and processing aids.

[0034] Adding processing aids to ethylene-vinyl alcohol copolymers lowers the crystallization temperature (T) of the ethylene-vinyl alcohol copolymer. c Decreased T c This allows a sufficient percentage of ethylene-vinyl alcohol to be retained in the amorphous state before the stretching stage of the conversion process. The slower crystallization kinetics compared to pure ethylene-vinyl alcohol copolymers and the limited effect on the final crystallinity of the blend extend the usefulness of ethylene-vinyl alcohol copolymers.

[0035] In the implementation scheme, the T of the homogeneous blend c T compared to pure ethylene-vinyl alcohol copolymer c At least 5%, 6%, 7%, 8%, 9%, or 10% lower, as measured by DSC with the following parameters: 1) Hold at 30°C for 1.0 minute; 2) Heat from 30.0°C to 230.0°C at 10.0°C / min; 3) Hold at 230.0°C for 1.0 minute; 4) Cool from 230.0°C at 10.0°C / min; 5) Hold at 30.0°C for 1.0 minute; 6) Heat from 30.0°C to 230.0°C at 10.0°C / min; 7) T m Taken from the second heating.

[0036] The crystallinity of the sample was estimated by measuring the enthalpy of the sample using DSC. In the embodiment, the ΔH of the blend of ethylene-vinyl alcohol copolymer and processing aid is... c ΔH of ethylene-vinyl alcohol copolymer c At least 70%, 75%, 80%, 85%, 90%, 95%, 100%, 105%, 110%, 115%, or 120% of the ethylene-vinyl alcohol copolymer blend with the processing aid. In the embodiments, the ΔH of the blend of ethylene-vinyl alcohol copolymer with the processing aid... m ΔH of ethylene-vinyl alcohol copolymer m At least 70%, 75%, 80%, 85%, 90%, 95%, 100%, 105%, 110%, 115%, or 120%.

[0037] In the embodiments, as indicated by the melting and / or crystallization enthalpy, the crystallinity of the homogeneous blend is at least 95% of the crystallinity of the pure ethylene-vinyl alcohol copolymer.

[0038] Multilayer film

[0039] In the embodiments, the blends described herein are used as one or more layers of a multilayer film. As used herein, the term "film" includes plastic web, whether it is a membrane or a sheet. The film may have a thickness of 0.25 mm or less, or a thickness of 0.5 to 30 mils, or 0.5 to 15 mils, or 1 to 10 mils, or 1 to 8 mils, or 1.1 to 7 mils, or 1.2 to 6 mils, or 1.3 to 5 mils, or 1.5 to 4 mils, or 1.6 to 3.5 mils, or 1.8 to 3.3 mils, or 2 to 3 mils, or 1.5 to 4 mils, or 0.5 to 1.5 mils, or 1 to 1.5 mils, or 0.7 to 1.3 mils, or 0.8 to 1.2 mils, or 0.9 to 1.1 mils.

[0040] The multilayer membranes described herein may include at least and / or at most any of the following number of layers: 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, and 15. As used herein, the term "layer" refers to a discrete membrane assembly that extends substantially co-exists with the membrane and has a substantially uniform composition. Where two or more directly adjacent layers have substantially the same composition, these two or more adjacent layers may be considered a single layer for the purposes of this application. In one embodiment, the multilayer membrane utilizes microlayers. Each microlayer portion may comprise 10 to 1,000 microlayers.

[0041] In this embodiment, the multilayer shrink film has at least one barrier layer, at least two barrier layers, or multiple barrier layers. The barrier layers comprise an ethylene-vinyl alcohol copolymer with an ethylene content of 24-48 mol%. The multilayer shrink film has a free shrinkage rate of at least 60%, 65%, and 70% at 85°C, as measured according to ASTM D2732.

[0042] According to ASTM D-3985, the oxygen permeability of this multilayer membrane, measured at 0% relative humidity and 23°C, is no greater than: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, or 150 cubic centimeters (at standard temperature and pressure) / square meter / day / 1 atmosphere of oxygen pressure differential.

[0043] In this embodiment, the multilayer membrane has a CO2 / O2 transmittance ratio (CO2 / O2 TR ratio) between 1.0 and 3.5. CO2 transmittance is measured according to ASTM F2476, and O2 transmittance is measured according to ASTM D-3985. Both are tested at standard pressure, 73℉, and 0% relative humidity.

[0044] In the implementation, the multilayer membrane including the processing aid exhibits an increase in CO2 / O2TR ratio of at least 20%, 30%, 40%, 50%, 60%, 70%, or 80% compared to the membrane made without the processing aid. The control membrane without the processing aid is identical to the multilayer membrane containing the processing aid, except that an additional % by weight of EVOH is used instead of the amount of processing aid.

[0045] The membrane comprises at least one barrier layer. When applied to the membrane and / or membrane layer, the term “barrier” and the expression “barrier layer” as used herein refer to the ability of the membrane or membrane layer to act as a barrier against one or more gases. Oxygen permeability is one method of quantifying the effectiveness of the barrier layer. The term “oxygen permeability” as used herein refers to the amount of oxygen permeating the membrane according to ASTM D3985 “Standard Test Method for Oxygen Gas Transmission Rate Through Plastic Film and Sheeting Using a Coulometric Sensor,” the entire contents of which are incorporated herein by reference.

[0046] The barrier layer comprises at least 85 wt%, 86 wt%, 87 wt%, 88 wt%, 89 wt%, 90 wt%, 91 wt%, 92 wt%, 93 wt%, 94 wt%, 95 wt%, 96 wt%, 97 wt%, or 98 wt% of an ethylene-vinyl alcohol copolymer or a blend of ethylene-vinyl alcohol copolymers. The barrier layer further comprises at least 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, or 15 wt% of processing aids relative to the barrier layer. In one embodiment, the barrier layer is substantially entirely an ethylene-vinyl alcohol copolymer. The ethylene content of the ethylene-vinyl alcohol copolymer affects the processability of the multilayer film and also affects the oxygen permeability. Generally, a lower ethylene content results in lower orientationability of the film and may render it unprocessable at certain orientation ratios. A higher ethylene content generally improves the oxygen permeability properties.

[0047] In other embodiments, the barrier layer is substantially entirely an ethylene-vinyl alcohol copolymer or a blend of an ethylene-vinyl alcohol copolymer and processing aids. The ethylene-vinyl alcohol copolymer may have an ethylene content not exceeding any of the following values: 50%, 48%, 44%, 40%, 38%, 36%, 34%, 32%, and 30%, all in mol%. In embodiments, the ethylene-vinyl alcohol copolymer or blend of ethylene-vinyl alcohol copolymers results in an ethylene content between 24 and 48 mol%. Exemplary ethylene-vinyl alcohol copolymers include those with ethylene contents of 24, 27, 29, 32, 35, 38, 44, 48, and 50 mol%, and blends thereof.

[0048] Ethylene-vinyl alcohol copolymers may include saponified or hydrolyzed ethylene / vinyl acetate copolymers, such as those with a degree of hydrolysis of at least about any of the following values: 50%, 85%, 95%, 95%.

[0049] In one embodiment, the multilayer film includes at least two barrier layers with the same composition. In another embodiment, the multilayer film includes at least two barrier layers with different compositions. The composition, thickness, and other properties of the barrier layers may be substantially the same as or different from any other barrier layer.

[0050] The thickness of the barrier layer may be at least about and / or at most about any of the following values: 0.05, 0.1, 0.15, 0.2, 0.25, 0.5, 1, 2, 3, 4, and 5 mils. In some embodiments, the barrier layer is less than 15% by weight of the multilayer film. In other embodiments, the barrier layer is less than 10% by weight of the multilayer film. In still other embodiments, the barrier layer is less than 5% by weight of the multilayer film.

[0051] In one embodiment, the outer layers of the membrane described herein are a sealant layer and a surface layer. In another embodiment, both outer layers are surface layers. The first outer layer is a sealant layer, and the second outer layer is a surface layer. As used herein, the terms "seallayer," "sealing layer," "heat seal layer," and "sealant layer" refer to one or more outer layers relating to sealing a membrane to itself, another layer of the same or another membrane, and / or another non-membrane article. As used herein, "surface layer" refers to a membrane layer whose only one surface is directly adhered to another membrane layer while its other surface is exposed to the environment. The primary function of a surface layer is to provide puncture resistance, abuse resistance, heat resistance, and abrasion resistance.

[0052] As used herein, the terms "heat-seal" and "heat-sealing" refer to any seal between a first region of a membrane surface and a second region of a membrane surface, wherein a seal is formed by heating the regions to at least their respective sealing initiation temperatures. Heat sealing is the process of joining two or more thermoplastic films or sheets by heating the regions in contact with each other to a temperature at which fusion occurs, typically with pressure assistance. Heating can be performed in any or more of a variety of ways, such as using heating rods, hot wires, hot air, infrared radiation, ultraviolet radiation, electron beams, ultrasound, and molten beads. Heat sealing is typically a relatively narrow seal across the membrane (e.g., 0.02 inches to 1 inch wide). One particular heat-sealing method is a heat seal made using a pulse sealing machine, which uses a combination of heat and pressure to form a seal, wherein the heating means provides a brief pulse of heat while pressure is applied to the membrane via a sealing rod or sealing wire, which is then rapidly cooled.

[0053] The heat-sealing layer comprises a thermoplastic polymer, such as a thermoplastic polyolefin and an ionomer. In embodiments, the polymer used for the sealant layer includes homogeneous ethylene / α-olefin copolymers, heterogeneous ethylene / α-olefin copolymers, ethylene homopolymers, ionomers, and ethylene / vinyl acetate copolymers. In some embodiments, the heat-sealing layer may comprise a polyolefin, particularly an ethylene / α-olefin copolymer. For example, a polyolefin having a density of 0.88 g / cc to 0.917 g / cc, or 0.90 g / cc to 0.917 g / cc, or less than 0.92 g / cc. More particularly, the sealant layer may comprise at least one member selected from: high-density polyethylene, linear low-density polyethylene, medium-density polyethylene, low-density polyethylene, very low-density polyethylene, homogeneous ethylene / α-olefin copolymers, and polypropylene. "Polymer" herein refers to homopolymers, copolymers, terpolymers, etc. "Copolymer" herein includes copolymers, terpolymers, etc.

[0054] As used herein, the term "copolymer" refers to a polymer formed by the polymerization of at least two different monomers. For example, the term "copolymer" includes the copolymerization product of ethylene and an olefin (such as 1-octene). The term "copolymer" also includes copolymerizations of mixtures of, for example, ethylene, propylene, 1-propylene, 1-butene, 1-hexene, and 1-octene. As used herein, a copolymer identified by multiple monomers, such as "propylene / ethylene copolymer," refers to a copolymer in which any one monomer can be copolymerized in a higher weight or molar percentage than one or more other monomers. However, the monomers listed first are typically polymerized in a higher weight percentage than those listed second.

[0055] As used in this article, "high-density polyethylene" (HDPE) has a density of at least 0.950 g / cm³.

[0056] As used in this article, "medium-density polyethylene" (MDPE) has a density of 0.930 to 0.950 g / cm³.

[0057] As used in this article, “low-density polyethylene” (LDPE) has a density of 0.910 to 0.930 g / cm³.

[0058] As used in this article, “linear low-density polyethylene” (LLDPE) has a density of 0.910 to 0.930 g / cm³.

[0059] As used in this article, “Very Low Density Polyethylene” (VLDPE) has a density of less than 0.915 g / cm³.

[0060] Unless otherwise stated, all densities in this document are measured according to ASTM D-1505.

[0061] As used herein, the term "polyolefin" refers to any polymerized olefin, which may be linear, branched, cyclic, aliphatic, substituted, or unsubstituted. More specifically, the term polyolefin includes homopolymers of olefins, copolymers of olefins, copolymers of olefins and non-olefin comonomers that can copolymerize with olefins, such as unsaturated esters, unsaturated acids (especially α-β monocarboxylic acids), unsaturated acid anhydrides, and metal neutral salts of unsaturated acids. Specific examples include polyethylene homopolymers, polypropylene homopolymers, polybutene, ethylene / α-olefin copolymers, propylene / α-olefin copolymers, butene / α-olefin copolymers, ethylene / vinyl acetate copolymers, ethylene / ethyl acrylate copolymers, ethylene / butyl acrylate copolymers, ethylene / methyl acrylate copolymers, ethylene / acrylic acid copolymers, ethylene / methacrylic acid copolymers, modified polyolefin resins, ionomer resins, polymethylpentene, etc. Modified polyolefin resins include modified polymers prepared by copolymerizing olefin homopolymers or copolymers thereof with unsaturated carboxylic acids (e.g., maleic acid, fumaric acid, etc.) or their derivatives (e.g., acid anhydrides, esters, or metal salts). It can also be obtained by incorporating unsaturated carboxylic acids (such as maleic acid, fumaric acid, etc.) or their derivatives (such as acid anhydrides, esters or metal salts, etc.) into olefin homopolymers or copolymers.

[0062] As used herein, the terms "modified polymer" and more specific expressions such as "modified ethylene / vinyl acetate copolymer" and "modified polyolefin" refer to such polymers having anhydride functional groups as defined above grafted thereon and / or copolymerized and / or blended therewith. Preferably, such modified polymers have anhydride functional groups grafted thereon or polymerized therewith rather than merely blended therewith.

[0063] Typically, ethylene / α-olefin copolymers comprise copolymers obtained by copolymerizing about 80 to 99 wt% ethylene and 1 to 20 wt% α-olefins. Preferably, ethylene / α-olefin copolymers comprise copolymers obtained by copolymerizing about 85 to 95 wt% ethylene and 5 to 15 wt% α-olefins.

[0064] As used herein, the term "homogeneous polymer" refers to a polymerization product exhibiting a relatively wide range of molecular weight variations and a relatively wide range of compositional distributions, i.e., a typical polymer prepared using a conventional Ziegler-Natta catalyst. Homogeneous copolymers typically contain relatively wide variations in chain length and comonomer percentages. Homogeneous copolymers have a molecular weight distribution (Mw / Mn) greater than 3.0.

[0065] As used herein, the term "homogeneous polymer" refers to a polymerization product having a relatively narrow molecular weight distribution and a relatively narrow compositional distribution. Homogeneous polymers can be used in the various layers of multilayer heat-shrinkable films. Structurally, homogeneous polymers differ from heterogeneous polymers in that they exhibit a relatively uniform arrangement of comonomers within the chain, a mirror-like sequence distribution across all chains, and a similarity in chain length, i.e., a narrower molecular weight distribution. Furthermore, homogeneous polymers are typically prepared using metallocene or other single-point catalysis rather than Ziegler-Natta catalysts. Homogeneous polymers have a molecular weight distribution (Mw / Mn) of less than 3.0. More specifically, homogeneous ethylene / α-olefin copolymers can be characterized by one or more methods known to those skilled in the art, such as molecular weight distribution (Mw / Mn). w / M n Compositional distribution width index (CDBI), narrow melting point range, and single melting point behavior. Molecular weight distribution (M w / M n The polydispersity, also known as "polydispersity," can be determined by gel permeation chromatography. In some embodiments, the homogeneous ethylene / α-olefin copolymer has an M of less than 2.7; in another embodiment, it is about 1.9 to 2.5; and in yet another embodiment, it is about 1.9 to 2.3. w / M nThe compositional distribution width index (CDBI) of such homogeneous ethylene / α-olefin copolymers is typically greater than about 70%. CDBI is defined as the weight percentage of copolymer molecules with a comonomer content within 50% (i.e., ±50%) of the median total molar comonomer content. The CDBI of comonomer-free linear polyethylene is defined as 100%. The compositional distribution width index (CDBI) is determined by temperature elution fractionation (TREF) technology. CDBI determination clearly distinguishes homogeneous copolymers (i.e., narrow compositional distributions as assessed by CDBI values ​​typically greater than 70%) from commercially available very low-density polyethylene (typically having wide compositional distributions as assessed by CDBI values ​​typically less than 55%). TREF data for determining the CDBI of copolymers and the calculations performed therefrom are readily available from techniques known in the art, such as temperature elution fractionation (e.g., Wild et al.). J.Poly.Sci.Poly.Phys.Ed. The data calculations are as described in Vol. 20, page 441 (1982). In some embodiments, the homogeneous ethylene / α-olefin copolymer has a CDBI greater than about 70%, i.e., about 70% to 99%. Generally, the homogeneous ethylene / α-olefin copolymers used in this invention also exhibit a relatively narrow melting point range compared to "heterogeneous copolymers," i.e., polymers with a CDBI less than 55%. In one embodiment, the homogeneous ethylene / α-olefin copolymer exhibits essentially a single melting point characteristic, such as the peak melting point (T0) determined by differential scanning calorimetry (DSC). m The DSC peak temperature is approximately 60°C to 105°C. In one embodiment, the homogeneous copolymer has a DSC peak temperature of approximately 80°C to 100°C. m The term "basic single melting point" as used in this article refers to a single melting point (T) at least approximately 80% by weight of the material, as determined by DSC analysis, corresponding to a temperature range of approximately 60°C to 105°C. m The material exhibits a peak melting point exceeding approximately 115 °C, with virtually no significant portion of the material. DSC measurements were performed on a Perkin Elmer System 7 Thermal Analysis System. The reported melting information is from the second melting, i.e., the sample was heated to a temperature below its critical range at a programmed rate of 10 °C / min. The sample was then reheated at a programmed rate of 10 °C / min (second melting).

[0066] Homogeneous ethylene / α-olefin copolymers can typically be prepared by copolymerizing ethylene with any one or more α-olefins. In some embodiments, the α-olefin is C3-C. 20 α-Monoolefin, C4-C 12α-Monoolefins, C4-C8 α-monoolefins. In one embodiment, the α-olefin copolymer comprises at least one member selected from: butene-1, hexene-1, and octene-1, namely 1-butene, 1-hexene, and 1-octene, respectively. In one embodiment, the α-olefin copolymer comprises octene-1, and / or a blend of hexene-1 and butene-1. In another embodiment, the α-olefin copolymer comprises a blend of at least two of octene-1, hexene-1, and butene-1.

[0067] In one embodiment, the heat-sealing layer is primarily composed of polyolefins. In another embodiment, the heat-sealing layer has a total polyolefin content of 90 to 99% by weight, based on its overall composition. In still other embodiments, the heat-sealing layer consists solely of polyolefins.

[0068] In one embodiment, the melting point of the heat-sealing layer is less than any of the following values: 220°C, 210°C, 200°C, 190°C, 180°C, 170°C, 160°C, 150°C, 140°C, and 130°C; and the melting point of the heat-sealing layer may be at least any of the following values: 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, and 150°C. In one embodiment, the heat-sealing layer comprises 80 to 99% by weight of a linear low-density polyethylene copolymer with a melting point between 90 and 130°C. In one embodiment, the heat-sealing layer comprises 80 to 99% by weight of an extremely low-density polyethylene copolymer with a melting point between 85 and 125°C. All references to the melting point of the polymer, resin, or film layer in this application refer to the peak melting temperature of the major molten phase of the polymer, resin, or layer as determined by differential scanning calorimetry according to ASTM D-3418.

[0069] In embodiments where the heat-sealing layer comprises an amorphous material, the heat-sealing layer may not clearly exhibit a melting point. The glass transition temperature of the heat-sealing layer can be less than any of the following values, and can be within the range of any of the following values: 125°C, 120°C, 110°C, 100°C, 90°C, 80°C, 70°C, 60°C, and 50°C; measured with relative humidity that can be any of the following values: 100%, 75%, 50%, 25%, and 0%. The glass transition temperature (Tg) of all mentioned polymers is... g The specific heat was determined by the Perkin Elmer "half Cp extrapolated" method according to ASTM D3418 "Standard Test Method of Transition Temperatures of Polymers by Thermal Analysis" (the entire contents of which are incorporated herein by reference). "Half Cp extrapolated" refers to the point on the curve where the specific heat change is half of the change in the complete transition.

[0070] In one embodiment, the heat seal layer has a melt index or composite melt index of at least 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5 and 5.0 g / 10min as measured according to ASTM D 1238 at 190°C and 2.16 kg.

[0071] The thickness of the heat-sealing layer can be selected to provide sufficient material to produce a strong heat-sealed bond, but not so thick that it negatively affects the film properties to an unacceptable level. The thickness of the heat-sealing layer can be at least any of the following values: 0.05 mil, 0.1 mil, 0.15 mil, 0.2 mil, 0.25 mil, 0.3 mil, 0.35 mil, 0.4 mil, 0.45 mil, 0.5 mil, and 0.6 mil. The thickness of the heat-sealing layer can be less than any of the following values: 5 mil, 4 mil, 3 mil, 2 mil, 1 mil, 0.7 mil, 0.5 mil, and 0.3 mil. The thickness of the heat-sealing layer as a percentage of the total film thickness can be less than any of the following values: 50%, 40%, 30%, 25%, 20%, 15%, 10%, and 5%; and can be within any range between the foregoing values ​​(e.g., 10% to 30%).

[0072] The surface layer is a membrane layer on which only one surface is directly adhered to another membrane layer, while the other surface is exposed to the environment. The main functions of the surface layer are to provide puncture resistance, abuse resistance, heat resistance, and abrasion resistance.

[0073] As used herein, the term "direct adhesion" applied to a membrane layer is defined as the host membrane layer adhering to the guest membrane layer without any adhesive, bonding agent, or other layer between them. Conversely, as used herein, the term "between" applied to a membrane layer indicating it is between two other specified layers includes both the host layer being directly adhered to the two other layers sandwiching it, and the host layer not being directly adhered to either or both of the two other layers sandwiching it, i.e., one or more additional layers may be applied between the host layer and one or more of the layers sandwiching it.

[0074] The thickness of the surface layer can be selected to provide sufficient resistance to abuse. The surface layer thickness can be at least any of the following values: 0.05 mil, 0.1 mil, 0.15 mil, 0.2 mil, 0.25 mil, 0.3 mil, 0.35 mil, 0.4 mil, 0.45 mil, 0.5 mil, and 0.6 mil. The surface layer thickness can be less than any of the following values: 5 mil, 4 mil, 3 mil, 2 mil, 1 mil, 0.7 mil, 0.5 mil, and 0.3 mil. The surface layer thickness as a percentage of the total membrane thickness can be less than any of the following values: 50%, 40%, 30%, 25%, 20%, 15%, 10%, and 5%; and can be within any range of the foregoing values ​​(e.g., 10% to 30%).

[0075] In some embodiments, the surface layer comprises a polyolefin, a polypropylene copolymer, a polyolefin block copolymer, or a blend thereof. In some embodiments, the surface layer is primarily a polypropylene copolymer. In some embodiments, the surface layer comprises at least 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, 95 wt%, or substantially all of a polypropylene copolymer. In some embodiments, the surface layer comprises at least 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, 95 wt%, or substantially all of linear low-density polyethylene, very low-density polyethylene, or a blend thereof.

[0076] The membrane may contain one or more intermediate layers, such as adhesive layers, bulk layers, or abuse layers. In addition to the first intermediate layer, the membrane may also contain a second intermediate layer. "Intermediate" herein refers to a layer of a multilayer membrane located between the outer and inner layers. "Inner layer" herein refers to a layer that is not an outer or surface layer, and whose two main surfaces are directly adhered to another layer of the membrane. "Outer layer" herein refers to any membrane layer of the membrane whose main surfaces are directly adhered to fewer than two other layers of the membrane. All multilayer membranes have two and only two outer layers, each with a main surface adhered to only one other layer of the multilayer membrane. In a single-layer membrane, there is only one layer, which is, of course, the outer layer, because neither of its two main surfaces is adhered to another layer of the membrane. "Outer layer" is also used to refer to the outermost layer of a plurality of concentrically arranged layers in a seamless tube or the outermost layer of a seamless membrane tube.

[0077] The thickness of the interlayer may be at least about and / or at most about any of the following values: 0.05, 0.1, 0.15, 0.2, 0.25, 0.5, 1, 2, 3, 4, and 5 mils. The thickness of the interlayer as a percentage of the total membrane thickness may be at least about and / or at most about any of the following values: 1, 3, 5, 7, 10, 15, 20, 25, 30, 35, 40, 45, and 50%.

[0078] Thermoplastic film

[0079] This blend can be used to manufacture films produced by thermoplastic film-forming methods known in the art. The film can be prepared by extrusion or co-extrusion using methods such as tubular trapped bubble film, double bubble or triple bubble orientation, or flat film (i.e., cast film or slot die) methods. The film can also be prepared by applying one or more layers using extrusion coating, adhesive lamination, extrusion lamination, solvent coating, or latex coating (e.g., spreading and drying on a substrate). Combinations of these methods can also be used.

[0080] heat shrink film

[0081] In this embodiment, the film is a heat-shrinkable film. The film can be prepared by uniaxial orientation alone or by biaxial orientation. As used herein, the term "heat-shrinkable" refers to a film exhibiting a total free shrinkage rate (i.e., the sum of free shrinkage rates in the longitudinal and transverse directions) of at least 10% at 185℉ as measured by ASTM D 2732 (the entire contents of which are incorporated herein by reference). All films exhibiting a total free shrinkage rate of less than 10% at 185℉ are designated herein as non-heat-shrinkable. A heat-shrinkable film may have a total free shrinkage rate of at least 15%, or at least 20%, or at least 30%, or at least 40%, or at least 45%, or at least 50%, or at least 55%, or at least 60%, or at least 65%, or at least 70% at 185℉ as measured by ASTM D 2732. Heat shrinkability can be achieved by orientation in the solid state (i.e., at a temperature below the melting temperature of the polymer). The film can be oriented, for example, in the machine direction (i.e., longitudinal), transverse, or both directions (i.e., biaxial orientation) to enhance its strength, optical properties, and durability. The film roll or tube can be uniaxially or biaxially oriented by applying tension at a temperature that softens the film (e.g., above the Vicat softening point; see ASTM 1525) but below its melting point. The film can then be rapidly cooled to retain the physical properties developed during the orientation process and to provide the film with heat-shrinkable properties. The film can be oriented using, for example, tenter frame methods or bubble methods (double-bubble, triple-bubble, etc.). These methods are known to those skilled in the art and are therefore not discussed in detail here. The total orientation factor used (i.e., stretching in the transverse direction and pulling in the longitudinal direction) can be any desired factor, such as at least 2×, at least 3×, at least 4×, at least 5×, at least 6×, at least 7×, at least 8×, at least 9×, at least 10×, at least 16×, at least 22×, at least 30×, or 1.5× to 20×, 2× to 16×, 3× to 12×, or 4× to 9×.

[0082] Crosslinking

[0083] One or more layers of the membrane—or at least a portion of the entire membrane—may be cross-linked, for example, to improve the membrane's strength or alter its melting or softening properties. Cross-linking can be achieved by using chemical additives or by subjecting one or more membrane layers to one or more energy-based irradiation treatments—such as ultraviolet radiation or ionizing radiation, such as X-rays, gamma rays, beta rays, and high-energy electron beam treatments—to induce cross-linking between molecules of the irradiated material. Available ionizing radiation doses include at least about and / or at most about any of the following values: 5, 7, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 90, 100, 110, 120, 130, and 150 kGy (kilogray). In an embodiment, the membrane is not cross-linked. Cross-linking may occur prior to the orientation process, for example, to enhance membrane strength before orientation, or cross-linking may occur after the orientation process.

[0084] It may be desirable to avoid irradiating one or more film layers. For this purpose, one or more layers can be extruded and irradiated, and then subsequent layers can be applied to the irradiated substrate, for example, by an extrusion coating method. This will produce an extruded coating interface in which at least one layer is substantially uncrosslinked.

[0085] Optical properties

[0086] The transparency of the film (also referred to herein as film clarity) is measured according to ASTM D 1746-97 "Standard Test Method for Transparency of Plastic Sheeting" (the entire contents of which are incorporated herein by reference), published in April 1998. The results are reported herein as "transparency percentage". The multilayer heat-shrinkable film can exhibit a transparency of at least 15%, or at least 20%, or at least 25%, or at least 30% as measured using ASTM D 1746-97.

[0087] The haze value of the film was measured according to ASTM D 1003-00, "Standard Test Method for Haze and Luminous Transmittance of Transparent Plastics" (the entire contents of which are incorporated herein by reference), published in July 2000. The results are reported as "haze percentage" in this document. The multilayer heat-shrinkable film can exhibit a haze of less than 7.5%, less than 7%, or less than 6% as measured using ASTM D 1003-00.

[0088] The gloss value of the film is measured according to ASTM D 2457-97 "Standard Test Method for Specular Gloss of Plastic Films and Solid Plastics" published on January 10, 1997 (the entire contents of which are incorporated herein by reference). The results are reported as "gloss percentage" in this document. The film may exhibit a gloss of 60% to 100%, or 70% to 90%, as measured using ASTM D 2457–97.

[0089] Figure 1 A diagram illustrating the method of membrane manufacturing. Figure 1 In the method shown, various polymer formulations of solid polymer beads (not shown) are fed into multiple extruders (only one extruder is shown for simplicity). Inside extruder 10, the polymer beads are degassed, and the resulting bubble-free melt is then fed into die 12 and extruded through an annular die to obtain a strip 14 that is about 15 to 30 mils thick and has a lay-up width of about 2 to 10 inches.

[0090] After being cooled or quenched by a water spray from cooling ring 16, the tubing 14 is collapsed by pinch rollers 18 and then fed through an irradiation vault 20 surrounded by shielding hood 22, where it is irradiated with high-energy electrons (i.e., ionizing radiation) from the core transformer accelerator 24. The tubing 14 is guided over the irradiation vault 20 on rollers 26. In one embodiment, the tubing 14 is irradiated to a level of approximately 20–100 kGy to obtain irradiated tubing 28. The irradiated tubing 28 is wound onto winding rollers 30 as it exits the irradiation vault 20 to form an irradiated tubing roll 32.

[0091] After irradiation and winding, in the second stage of the method for manufacturing the tubular film, as needed, the winding roller 30 and the irradiated tubular strip roll 32 are removed and installed as the unwinding roller 34 and the unwinding tubular strip roll 36. The irradiated tubular material 28, unwound from the unwinding tubular strip roll 36, is then passed through the guide roller 38, and subsequently through a hot water bath 40 containing hot water 42. The irradiated tubular material 28 is then immersed in the hot water 42 (preferably at a temperature of about 85°C to 99°C) for about 20 to 60 seconds, a sufficient time to allow the film to reach the temperature required for biaxial orientation. Thereafter, the hot irradiated tubular strip 44 is guided through the roller 46 and bubbled 48, thereby laterally stretching the hot irradiated tubular strip 44 to form the oriented film tube 50. Furthermore, during the bubbling, i.e., the lateral stretching, the surface speed of the roller 52 is higher than that of the roller 46, thereby resulting in longitudinal orientation. As a result of transverse stretching and longitudinal drawing, an oriented film tube 50 is produced. This blown tube is preferably both stretched and drawn at a ratio of about 1:1.5 to 1:6. More preferably, the stretching and drawing are each performed at a ratio of about 1:2 to 1:4. The result is a biaxial orientation of about 1:2.25 to 1:36, more preferably 1:4 to 1:16. While the bubble 48 is held between rolls 46 and 52, the blown film tube 50 is collapsed by converging pairs of parallel rolls 54, then conveyed through rolls 52 and over guide rolls 56, and then wound onto winding rolls 58. Driven roll 60 ensures good winding.

[0092] The resulting multilayer film can be used to form bags, casings, thermoformed products, and lids, which can then be used to package food-containing products. While various embodiments are illustrated and described herein, other packaging structures are considered, such as resealable bags, side-sealed bags, stand-up pouches, stand-up capsules, end-seal bags, and lap-seal bags.

[0093] In the implementation plan, through Figure 2 The blown film method shown in the figure produces the film. Figure 2 The diagram illustrates a method for manufacturing "thermally blown" films, which are oriented in a molten state and therefore cannot be heat-shrinked. Although in Figure 2 Only one extruder 139 is shown, but it should be understood that more than one extruder can be used to manufacture films.

[0094] exist Figure 2In this method, extruder 530 supplies molten polymer to an annular die 531 to form a film, which can be single-layered or multi-layered, as known to those skilled in the art, depending on the design of the die and the arrangement of the extruder relative to the die. Polymer granules suitable for forming the film are supplied to extruder 530. Extruder 530 applies sufficient heat and pressure to the polymer granules to melt the polymer and allow the molten material to flow through the annular die 531.

[0095] The extruder 530 is equipped with a screen pack 532, a breaker plate 533, and a heater 534. The film is extruded between a mandrel 535 and a die 531, and the resulting extrudate is cooled by cold air from an air ring 536. The molten extrudate is immediately blown into blown bubbles 537 to form a molten-oriented film. As the molten-oriented film is fed upwards along the length of the bubble 537, it cools and solidifies. After solidification, the film tube is passed through guide rollers 538 and slumped into a flattened form by rolls 539. The slumped film tube optionally passes through a treater bar 540, then through a driven roller 541, and then around a tension control roller 542, which applies tension control to the slumped film tube 543, which is then wound into a roll 544 via a winder 545.

[0096] Unless otherwise stated, all references to ASTM procedures (and are incorporated herein by reference) refer to the most recently published ASTM procedure up to the priority (i.e., original) filing date of this patent application filed with the U.S. Patent and Trademark Office.

[0097] Example

[0098] Table 1 - Characteristics of the resins used in the examples (Identity)

[0099]

[0100]

[0101] Processing aids were selected and blended into the ethylene-vinyl alcohol copolymer using the Intelli-Torque mixing chamber to create a homogeneous mixture. DSC measurements of the blended sample were obtained. The ability to determine transition temperatures and enthalpies makes DSC a valuable tool for generating phase diagrams for a wide range of chemical systems. The transition from an amorphous solid to a crystalline solid is an exothermic process and results in a peak in the DSC signal. As the temperature increases, the sample eventually reaches its melting temperature (T0). m The melting process results in an endothermic peak in the DSC curve. ΔH is the enthalpy, and the crystallization temperature (T) is recorded. c All measurements were obtained through the following methods:

[0102] Keep at 30℃ for 1.0 minute.

[0103] Heating from 30.0℃ to 230.0℃ at a rate of 10.0℃ / min.

[0104] Hold at 230.0℃ for 1.0 minute.

[0105] Cooled from 230.0℃ at a rate of 10.0℃ / min.

[0106] Keep at 30.0℃ for 1.0 minute.

[0107] Heating from 30.0℃ to 230.0℃ at a rate of 10.0℃ / min.

[0108] T m Taken from the second heating.

[0109] Table 2 - DSC of various additives

[0110]

[0111] (C) = Comparison

[0112] Samples 1-4 show that this additive leads to a crystallization temperature (Tc). c This reduces, while maintaining or enhancing, the overall crystallinity. This is unexpected, as similar additives have not shown any effect on T... c Similar effects to overall crystallinity. For example, as shown in Sample 6, propylene glycol, although structurally similar to glycerol carbonate, exhibits a similar effect to T... c No effect. Similarly, as shown in sample 7, 2-acetyl triethyl citrate, despite being structurally very similar to triethyl citrate, showed no effect on T. c It also had no effect. Furthermore, the various molecular weights of polyethylene glycol used in samples 8-10 had no effect on T. c It had virtually no effect. Although racemic lactide is structurally very similar to lactic acid, sample 9 showed no effect on T... c While effective, it also has a negative impact on the overall crystallinity of the structure.

[0113] Table 3 - DSC values ​​for various additive loadings

[0114]

[0115] Various EVOH resins were used as control samples 12-15. Samples 16-20 showed reduced T values ​​at various additive loadings. c The crystallinity of the sample was estimated by measuring the enthalpy of the sample using DSC. In the embodiment, the ΔH of the blend of EVOH and processing aids... c ΔH for EVOH cAt least 70%, 75%, 80%, 85%, 90%, 95%, 100%, 105%, 110%, 115%, or 120% of the EVOH blend with the processing aid. In the embodiments, the ΔH of the blend of EVOH and the processing aid... m ΔH for EVOH m At least 70%, 75%, 80%, 85%, 90%, 95%, 100%, 105%, 110%, 115%, or 120%.

[0116] Multilayer film examples

[0117] To demonstrate the improved membrane properties, two membranes with the same composition and layer thickness, excluding the barrier layer, were fabricated using a two-bubble method. Table 4 lists the membranes, where all % are by weight within the layers. Layer 4 of membrane 2 was made using 50% EVOH1 and 50% of a masterbatch containing 16% triacetyl ester and 84% EVOH1.

[0118] Table 4

[0119]

[0120] The free shrinkage rates of membranes 1 and 2 were obtained according to ASTM D2732. The results are reported in Table 5 below.

[0121] Table 5

[0122] sample Preheating / bath temperature (℉) Free shrinkage rate (%) Membrane 1 200 / 200 78 / 84 195 / 195 84 / 88 190 / 190 87 / 86 Membrane 2 200 / 200 74 / 72 195 / 195 81 / 78 190 / 190 87 / 87

[0123] As shown in Table 5, membrane 2 has almost the same free shrinkage rate as the control membrane 1. Therefore, the processing aids have no adverse effect on the free shrinkage rate.

[0124] The oxygen permeability of the membrane was also compared. All data were collected according to ASTM D3985 and are shown in Table 6.

[0125] Table 6

[0126]

[0127] As shown in Table 6, the processing aids have only a small effect on the oxygen permeability of the membrane.

[0128] To manufacture additional membranes, see Table 7.

[0129] Table 7

[0130]

[0131] The oxygen permeability (OTR) of membranes 3 and 4 was tested under standard temperature and pressure according to ASTM D-3985.

[0132] Table 8

[0133] Avg.OTR0%RH Avg. OTR 90% RH (cc / m2·d·atm) (cc / m2·d·atm) Membrane 3(C) 3.46+0.14 45.4+5.8 Membrane 4 2.97+1.23 40.1+4.5

[0134] As shown in Table 8, the processing aids have only a small effect on the oxygen permeability of the membrane under various relative humidity conditions.

[0135] To manufacture additional membranes, see Table 9.

[0136] Table 9

[0137]

[0138] Test the CO2 and O2 transmittance of membranes 5-8. Tests were conducted at 73℉ and 0% relative humidity. CO2 transmittance was measured according to ASTM F2476, and O2 transmittance was measured according to ASTM D-3985.

[0139] Table 10

[0140]

[0141] As shown in Table 10, compared to membranes 5 and 8, membranes 6 and 8 have little effect on CO2 and O2 permeability, respectively. Surprisingly, the processing aid improves the CO2 / O2 permeability ratio (CO2 / O2TR ratio). The CO2 / O2TR ratio is calculated using the following formula:

[0142] CO2 transmittance ÷ O2 transmittance = CO2 / O2TR ratio

[0143] A series of 9-layer cast film structures were prepared as shown in Table 11.

[0144] Table 11

[0145]

[0146]

[0147] Oxygen permeability (OTR) and permeability were determined under two conditions, 0% RH in and out (0 / 0) and 90% RH in and out (90 / 90) and reported in Table 12 below. Oxygen permeability was measured according to ASTM D3985, the entire contents of which are incorporated herein by reference. Permeability was measured according to ASTM F1927, the entire contents of which are incorporated herein by reference.

[0148] Table 12

[0149]

[0150]

[0151] The impact properties of the membrane were measured on an Instron 9340, and the results are reported in Table 13. Instrumental impact was measured using a dart test according to ASTM D 3763 (the entire contents of which are incorporated herein by reference). Slow puncture was measured using a crosshead velocity of 1 inch / minute according to ASTM F1306.

[0152] Table 13

[0153]

[0154] Measure the optical properties and report them in Table 14. Measure the film clarity according to ASTM D 1746-97 "Standard Test Method for Transparency of Plastic Sheeting" published in April 1998 (the entire contents of which are incorporated herein by reference). Measure the film haze value according to ASTM D 1003-00 "Standard Test Method for Haze and Luminous Transmittance of Transparent Plastics" published in July 2000 (the entire contents of which are incorporated herein by reference).

[0155] Table 14

[0156]

[0157] This written description discloses the invention using examples, including the best mode, and also enables any person skilled in the art to practice the invention, including making and using any apparatus or system and performing any of the included methods. The patentable scope of the invention is defined by the claims, but may include other examples that would occur to a person skilled in the art. Such other examples are intended to fall within the scope of the claims if they have structural elements that are not different from the literal language of the claims, or if they include equivalent structural elements that are not substantially different from the literal language of the claims.

[0158] Parts list:

[0159] 10 Extruder

[0160] 11 Polyamide

[0161] 12. Head

[0162] 14 Pipes

[0163] 16 Cooling ring

[0164] 18 pinch rollers

[0165] 20 Irradiated vaults

[0166] 22 Shielding Cover

[0167] 24 Iron-core transformer accelerator

[0168] 26 rolls

[0169] 28 Pipes

[0170] 30 winding rollers

[0171] 32 Irradiated tube rolls

[0172] 34 Unwinding Rollers

[0173] 36 Unwinding of tubular strip coils

[0174] 38 guide rollers

[0175] 40 Hot water bath

[0176] 42 Hot water

[0177] 44 pipe strip

[0178] 46 rolls

[0179] 46 Pinch Rollers

[0180] 48 bubbles

[0181] 50 membrane tubes

[0182] 52 rolls

[0183] 54 parallel rollers

[0184] 56 guide rollers

[0185] 58 winding rollers

[0186] 60 driven rollers

[0187] 62 bags

[0188] 64 membrane

[0189] 66. Top opening

[0190] 68 Bottom

[0191] 70 end seal

[0192] 72 Packaged meat products

[0193] 74 Packaged Products

[0194] 76. Clips

[0195] 78. Casing film

[0196] 80 Inner Surface

[0197] 81 Sealing

[0198] 82 Outer surface

[0199] 84 heat seal

[0200] 86 Inner Surface

[0201] 88 Butt Sealing Tape

[0202] 90 Outer surface

[0203] 92 Inner Surface

[0204] 94 Sealing

[0205] 139 Extruder

[0206] 530 Extruder

[0207] 531 mold head

[0208] 531 Ring-shaped die head

[0209] 532 Filter Assembly

[0210] 533 Circuit Breaker Board

[0211] 534 heater

[0212] 535 mandrel

[0213] 536 Air Ring

[0214] 537 Bubbles

[0215] 538 guide roller

[0216] 539 Rolls

[0217] 540 Treaterbar

[0218] 541 Driven Roller

[0219] 542 Tension Adjustment Roller

[0220] 543 Membrane tube

[0221] Volume 544

[0222] 545 Winder

Claims

1. A multilayer film comprising a first outer layer, a second outer layer, and a barrier layer disposed between the first outer layer and the second outer layer, the barrier layer comprising a blend of the following materials: a. At least 90.0% of an ethylene-vinyl alcohol copolymer having a first crystallization temperature; and b. 2.0% to 10.0% by weight of a processing aid relative to the barrier layer, wherein the processing aid is selected from glyceryl triacetate, glyceryl diacetate, lactic acid, triethyl citrate, and glyceryl carbonate. The blend has a second crystallization temperature that is at least 5% lower than the first crystallization temperature, as measured by DSC using the following parameters: a) Keep at 30°C for 1.0 minute; b) Heat from 30.0℃ to 230.0℃ at a rate of 10.0℃ / min; c) Hold at 230.0℃ for 1.0 minute; d) Cool from 230.0℃ at a rate of 10.0℃ / min; e) Hold at 30.0℃ for 1.0 minute; f) Heat from 30.0℃ to 230.0℃ at a rate of 10.0℃ / min.

2. The multilayer film according to claim 1, wherein the ethylene-vinyl alcohol copolymer has a first ΔH c And the blend has a second ΔH c The second ΔHc is the first ΔH c At least 70%.

3. The multilayer film according to claim 1 or 2, wherein the ethylene-vinyl alcohol copolymer has an ethylene content of not more than 40 mol%.

4. The multilayer film according to claim 1 or 2, wherein the multilayer film is a heat-shrinkable multilayer film having a total free shrinkage rate of at least 30% at 185℉ as measured by ASTM D 2732.

5. The multilayer film according to claim 1 or 2, comprising at least two barrier layers.

6. The multilayer film according to claim 5, wherein the multilayer film comprises a layer disposed between the at least two barrier layers.

7. The multilayer film according to claim 1 or 2, wherein the processing aid comprises: a. At least one ester, b. At least one carboxylic acid or carbonate functional group, and c. At least one hydroxyl functional group.

8. The multilayer film according to claim 1 or 2, wherein the barrier layer comprises less than 1.0% by weight of salt based on the composition of the barrier layer.

9. The multilayer film according to claim 1 or 2, wherein the barrier layer comprises 0.0–1.0% by weight of a material different from the ethylene-vinyl alcohol copolymer and the processing aids.

10. The multilayer membrane according to claim 1 or 2, wherein the oxygen permeability of the membrane at standard temperature and pressure, as measured according to ASTM D-3985 at 0% relative humidity and 23°C, is not greater than 5 cubic centimeters / square meter / day / 1 atmosphere of oxygen pressure difference.

11. The multilayer film according to claim 1 or 2, wherein the processing aid is in the form of a masterbatch.

12. The multilayer film according to claim 1 or 2, wherein the processing aid is 2.0% to 10.0% by weight of triethyl citrate or glyceryl triacetate relative to the barrier layer.

13. The multilayer film according to claim 1 or 2, wherein at least a portion of the film is cross-linked.

14. The multilayer film according to claim 1 or 2, wherein the ethylene-vinyl alcohol copolymer has a first ΔH m And the blend has a second ΔH m The second ΔHm is the first ΔH m At least 70%.

15. The multilayer film according to claim 1 or 2, wherein the film has a transparency of at least 15% as measured using ASTM D 1746-97.

16. The multilayer film according to claim 1 or 2, wherein the film has a haze of less than 7.5% as measured using ASTM D 1003-00.

17. The multilayer film according to claim 1 or 2, wherein the film has a gloss level of 60% to 100% as measured using ASTM D 2457–97.

18. The multilayer membrane according to claim 1 or 2, wherein the membrane has a CO2 / O2 transmittance ratio between 1.5 and 3.0, wherein the CO2 transmittance is measured according to ASTM F2476 and the O2 transmittance is measured according to ASTM D-3985 at standard pressure, 73℉ and 0% relative humidity.

19. A blend of ethylene-vinyl alcohol copolymer and processing aid, comprising: a. At least 90.0% of an ethylene-vinyl alcohol copolymer having a first crystallization temperature; and b. 2.0% to 10.0% by weight of a processing aid relative to the blend, wherein the processing aid is selected from glyceryl triacetate, glyceryl diacetate, lactic acid, triethyl citrate, and glyceryl carbonate. The blend has a second crystallization temperature that is at least 5% lower than the first crystallization temperature, as measured by DSC using the following parameters: a) Keep at 30°C for 1.0 minute; b) Heat from 30.0℃ to 230.0℃ at a rate of 10.0℃ / min; c) Hold at 230.0℃ for 1.0 minute; d) Cool from 230.0℃ at a rate of 10.0℃ / min; e) Hold at 30.0℃ for 1.0 minute; f) Heat from 30.0℃ to 230.0℃ at a rate of 10.0℃ / min.

20. The blend of claim 19, wherein the ethylene-vinyl alcohol copolymer has a first ΔH c And the blend has a second ΔH c The second ΔHc is the first ΔH c At least 70%.

21. The blend according to claim 19 or 20, wherein the ethylene-vinyl alcohol copolymer has an ethylene content of not more than 40 mol%.

22. The blend according to claim 19 or 20, wherein the processing aid comprises: a. At least one ester, b. At least one carboxylic acid or carbonate functional group, and c. At least one hydroxyl functional group.

23. The blend according to claim 19 or 20, wherein the blend comprises less than 1.0% by weight of salt based on the composition of the blend.

24. The blend according to claim 19 or 20, wherein the blend comprises 0.0–1.0% by weight of a material different from the ethylene-vinyl alcohol copolymer and the processing aid.

25. The blend according to claim 19 or 20, wherein the processing aid is 2.0% to 10.0% by weight of triethyl citrate or glyceryl triacetate.

26. The blend according to claim 19 or 20, wherein the processing aid is 2.0% to 10.0% by weight of glyceryl diacetate or glyceryl carbonate.

27. The blend according to claim 19 or 20, wherein the ethylene-vinyl alcohol copolymer has a first ΔH m And the blend has a second ΔH m The second ΔHm is the first ΔH m At least 70%.

28. A method for manufacturing a multilayer film, comprising the following steps: a. Providing a barrier blend comprising: i. At least 90.0% of an ethylene-vinyl alcohol copolymer having a first crystallization temperature; and ii. A processing aid of 2.0% to 10.0% by weight relative to the barrier blend, wherein the processing aid is selected from glyceryl triacetate, glyceryl diacetate, lactic acid, triethyl citrate, and glyceryl carbonate. The blend has a second crystallization temperature that is at least 5% lower than the first crystallization temperature, as measured by DSC using the following parameters: a) Keep at 30°C for 1.0 minute; b) Heat from 30.0℃ to 230.0℃ at a rate of 10.0℃ / min; c) Hold at 230.0℃ for 1.0 minute; d) Cool from 230.0℃ at a rate of 10.0℃ / min; e) Hold at 30.0℃ for 1.0 minute; f) Heat from 30.0℃ to 230.0℃ at a rate of 10.0℃ / min. b. The barrier blend is co-extruded to form a multilayer film having a first outer layer, a second outer layer, and the barrier blend disposed as a layer between the first outer layer and the second outer layer.

29. The method of claim 28, wherein the ethylene-vinyl alcohol copolymer has a first ΔH c And the blend has a second ΔH c The second ΔHc is the first ΔH c At least 70%.

30. The method according to claim 28 or 29, wherein at least one layer of the membrane is cross-linked by a radiation dose of 20-150 kGy.

31. The method according to claim 28 or 29, wherein the multilayer film is a heat-shrinkable multilayer film having a total free shrinkage rate of at least 30% at 185℉ as measured according to ASTM D 2732.

32. The method according to claim 28 or 29, wherein the processing aid comprises: a. At least one ester, b. At least one carboxylic acid or carbonate functional group, and c. At least one hydroxyl functional group.

33. The method of claim 28 or 29, wherein the barrier blend comprises less than 1.0% by weight of salt based on the composition of the barrier blend.

34. The method of claim 28 or 29, wherein the barrier blend comprises 0.0–1.0% by weight of a material different from the ethylene-vinyl alcohol copolymer and the processing aid.

35. The method according to claim 28 or 29, wherein the ethylene-vinyl alcohol copolymer has a first ΔH m And the blend has a second ΔH m The second ΔHm is the first ΔH m At least 70%.

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