阅读说明：本技术 金属化的、取向的及薄线性低密度聚乙烯膜 (Metallized, oriented and thin linear low density polyethylene film ) 是由 B·安布鲁瓦兹 于 2018-05-21 设计创作，主要内容包括：本公开内容提供了用于取向膜的组合物和方法,所述取向膜可以包括基本上由双轴取向的线性低密度聚乙烯组成的芯层,其中所述芯层具有第一侧和第二侧。此外,该膜可在第一侧上包括基本上由双轴取向的线性低密度聚乙烯组成的第一密封剂层,以及在第一侧上包括基本上由双轴取向的线性低密度聚乙烯组成的第二密封剂层,其中每个膜层中的线性低密度聚乙烯可以是一种以上的类型/等级、具有相同或不同的密度,或两者。更进一步,该膜的厚度为30μm或更小,具有在38℃和90％的相对湿度下<1g/m<Sup>2</Sup>/d的水蒸气透过率,和具有在23℃和0％相对湿度下<100cm<Sup>3</Sup>/m<Sup>2</Sup>/d的氧气透过率。(The present disclosure provides compositions and methods for oriented films that may include a core layer consisting essentially of biaxially oriented linear low density polyethylene, wherein the core layer has a first side and a second side. Further, the film may comprise on the first side a first film consisting essentially of a biaxially oriented linear low density polyethyleneA sealant layer, and a second sealant layer consisting essentially of biaxially oriented linear low density polyethylene on the first side, wherein the linear low density polyethylene in each film layer may be of more than one type/grade, of the same or different density, or both. Further, the film has a thickness of 30 μm or less, and has a relative humidity of 90% at 38 ℃<1g/m 2 A water vapor transmission rate of/d, and has a relative humidity of 0% at 23 DEG C<100cm 3 /m 2 Oxygen transmission rate/d.)

1. A film, comprising:

a core layer consisting essentially of biaxially oriented linear low density polyethylene, wherein the core layer has a first side and a second side;

a first sealant layer consisting essentially of biaxially oriented linear low density polyethylene on a first side; and

a second sealant layer consisting essentially of biaxially oriented linear low density polyethylene on a first side,

wherein the film has a thickness of 30 μm or less and has a thickness of 1g/m or less at 38 ℃ and 90% relative humidity²A water vapor transmission rate of 100cm or less at 23 ℃ and 0% relative humidity³/m²Oxygen transmission rate/d.

2. The film of claim 1, further consisting essentially of one or more additives in the core layer, the first sealant layer, the second sealant layer, or a combination thereof.

3. The film of claim 1, further consisting essentially of ≦ 5 wt.% silicone rubber in the first sealant layer, the second sealant layer, or both.

4. The film of claim 1, wherein the film further comprises one or more tie layers, wherein each of the one or more tie layers is between the core layer and the first sealant layer or the second sealant layer.

5. The film of claim 1, wherein the first sealant layer, the second sealant layer, or both are metallized.

6. The film of claim 1, wherein the film further comprises one or more primers.

7. The film of claim 1, wherein the density of the biaxially oriented linear low density polyethylene in the core layer, the first sealant layer, the second sealant layer, or a combination thereof is the same or different.

8. The film of claim 1, wherein the melting peak of linear low density polyethylene of the first sealant layer, the second sealant layer, or each of the two is lower than the melting peak of linear low density polyethylene in the core layer.

9. The film of claim 1, wherein the melting peak of linear low density polyethylene in each of the first sealant layer and the second sealant layer is lower than the melting peak of linear low density polyethylene in the core layer.

10. The film of claim 1, wherein the linear low density polyethylene in the core layer, the first sealant layer, the second sealant layer, or a combination thereof has a density from 0.90 to ≦ 0.93g/cm³Within the range of (1).

11. The film of claim 1, wherein the linear low density polyethylene in the core layer, the first sealant layer, the second sealant layer, or a combination thereof is one or more grades of maleic anhydride grafted polyethylene, acrylic acid copolymers, or a combination thereof.

12. The film of claim 1, wherein the film is uniaxially or biaxially oriented.

13. The film of claim 1, wherein the first sealant layer, the second sealant layer, or both are treated at least once.

14. The film of claim 1, wherein the adhesive strength of the metallized first sealant layer or the metallized second sealant layer is at least 170g/in when pressed to a 12 μ ι η polyester film.

15. The film of claim 1, wherein the metallized first sealant layer or the metallized second sealant layer, when laminated to a 12 μ ι η polyester film, has a dwell time of 0.75s at 130 ℃ and a pressure of 41N/cm²The seal strength at (A) is at least 1800 g/in.

16. The film of claim 1, wherein the metallized first sealant layer or the metallized second sealant layer, when laminated to a 12 μ ι η polyester film, has a dwell time of 0.75s and 41N/cm at 140 ℃²Has a seal strength of at least 2400 g/in.

17. The film of claim 1, wherein the film is transparent or opaque.

18. A process comprising extruding, casting or blowing the core layer, the first sealant layer and the second sealant layer of claim 1 and subsequently orienting them, wherein the film has a thickness of 30 μm or less and has ≦ 1g/m at 38 ℃ and 90% relative humidity²A water vapor transmission rate of 100cm or less at 23 ℃ and 0% relative humidity³/m²Oxygen transmission rate/d.

19. The method of claim 18, further comprising treating the first sealant layer, the second sealant layer, or both at least once.

20. Use of the film according to claim 1 in packaging, labeling, bagging or labeling applications.

Technical Field

The present disclosure relates to compositions, structures and methods for metallized, oriented, multilayer, linear low density polyethylene ("LLDPE") films that include both barrier protection and enhanced sealing performance with reduced thickness in packaging, packaging and labeling applications as compared to the prior art.

Background

Polyethylene films are widely used as seals in packaging. Unoriented films typically have moderate physical properties that require bonding to other webs, such as paper, PET, BOPP, etc. to provide mechanical strength, or such as metallized PET, metallized BOPP, nylon, or aluminum foil to provide barrier protection. In addition, conventional cast or blown polyethylene sealant films are typically not metallized because metal adhesion does not adhere well to maintain integrity when laminated to a rigid web.

However, there is a need for new multilayer films that have barrier protection and enhance sealing performance to packages with reduced thickness. For the customer, the advantage is a reduced number of packages with the same performance. Furthermore, there is a need for new multilayer films that can withstand metallization and provide good metal adhesion and metallized barrier properties.

Disclosure of Invention

The present disclosure provides compositions and methods for oriented films that may include a core layer consisting essentially of biaxially oriented linear low density polyethylene, wherein the core layer has a first side and a second side. Further, the film may comprise on the first side a substantially biaxially oriented linear low density polyethyleneA first sealant layer comprising on the first side a second sealant layer consisting essentially of biaxially oriented linear low density polyethylene, wherein the linear low density polyethylene in each film layer may be of more than one type/grade, of the same or different density, or both. Further, the film has a thickness of 30 μm or less and has a thickness of 1g/m or less at 38 ℃ and 90% relative humidity²Water vapor transmission rate, < 100cm at 23 ℃ and 0% relative humidity³/m²Oxygen transmission rate/d.

Detailed Description

In general, metallized, oriented, multilayer, linear low density polyethylene ("LLDPE") films are disclosed that include both barrier protection and enhanced sealing properties in packaging, and labeling applications, and have reduced thickness as compared to the prior art. The advantage of such a film to the end user is that it reduces the amount of material compared to thicker films of the prior art, while still providing the same, similar or even better performance.

In the following, directional terminology, such as "above," "below," "over," "below," "front," "back," "top," "bottom," etc., is used for convenience. Reference is made to the accompanying drawings. In general, "above," "upper," "top," and similar terms refer to a direction away from the surface of the earth, and "below," "down," "bottom," and like terms refer to a direction toward the surface of the earth, although this is for purposes of illustration only and these terms are not intended to limit the disclosure.

Various specific embodiments, versions and examples are described herein, including exemplary embodiments and definitions employed herein for purposes of understanding. While the following detailed description gives certain preferred embodiments, those skilled in the art will appreciate that these embodiments are merely exemplary, and that the present disclosure may be practiced in other ways. For infringement purposes, the scope of the invention will refer to any claims, including their equivalents and elements or limitations that are equivalent to those that are recited.

As used herein, "polymer" may be used to refer to homopolymers, copolymers, interpolymers, terpolymers, etc. Likewise, "copolymer" may refer to a polymer comprising two monomers or a polymer comprising three or more monomers.

As used herein, "intermediate" is defined as the position of one layer of a multilayer film, wherein the layer is located between two other identified layers. In some embodiments, the intermediate layer may be in direct contact with one or both of the two identified layers. In other embodiments, additional layers may also be present between the intermediate layer and one or both of the two identified layers.

As used herein, "elastomer" is defined as a propylene-based or ethylene-based copolymer that can be extended or stretched with force to at least 100% of its original length and returns to its original dimensions quickly (e.g., within 5 seconds) after the force is removed.

As used herein, "plastomer" is defined as a propylene-based or ethylene-based copolymer having a density in the range of 0.850g/cm3 to 0.920g/cm3 and a DSC melting point of at least 40 ℃.

As used herein, "substantially free" is defined to mean that the referenced film layer is largely, but not entirely, absent the particular component. In some embodiments, as a result of standard manufacturing methods, small amounts of components may be present in the reference layer, including film debris recovery and edge trimming during processing.

Core layer

As known to those skilled in the art, the core layer of a multilayer film is most often the thickest layer and provides the basis for a multilayer structure. In some embodiments, the core layer comprises, consists essentially of, or consists of biaxially oriented polyethylene ("BOPE"). In alternative embodiments, the core layer may further comprise, consist essentially of, or consist of biaxially oriented polypropylene ("BOPP"), biaxially oriented polyester ("BOPET"), biaxially oriented polylactic acid ("BOPLA"), or consist essentially of, or consist of combinations thereof. In yet another alternative embodiment, the core layer may further comprise a minor amount of an additional polymer selected from the group consisting of ethylene polymers, ethylene-propylene copolymers, ethylene-propylene-butene terpolymers, elastomers, plastomers, different types of metallocene-LLDPEs (m-LLDPEs) and combinations thereof.

The core layer may further comprise, consist essentially of, or consist of a hydrocarbon resin. Hydrocarbon resins can be used to enhance or modify flexural modulus, improve processability or improve barrier properties of the film. The resin may be a low molecular weight hydrocarbon compatible with the core polymer. Optionally, the resin may be hydrogenated. The number average molecular weight of the resin may be less than 5000, preferably less than 2000, most preferably in the range of 500 to 1000. The resin may be natural or synthetic and may have a softening point in the range of 60 ℃ to 180 ℃.

Suitable hydrocarbon resins include, but are not limited to, petroleum resins, terpene resins, styrene resins, and cyclopentadiene resins. In some embodiments, the hydrocarbon resin is selected from the group consisting of aliphatic hydrocarbon resins, hydrogenated aliphatic hydrocarbon resins, aliphatic/aromatic hydrocarbon resins, hydrogenated aliphatic aromatic hydrocarbon resins, cycloaliphatic hydrocarbon resins, hydrogenated cycloaliphatic resins, cycloaliphatic/aromatic hydrocarbon resins, hydrogenated aromatic hydrocarbon resins, polyterpene resins, terpene-phenol resins, rosins and rosin esters, hydrogenated rosins and rosin esters, and combinations thereof.

The amount of such hydrocarbon resins in the core layer, either alone or in combination, is preferably less than 20 wt%, more preferably in the range of from 1 wt% to 5 wt%, based on the total weight of the core layer.

The core layer may further comprise one or more additives such as opacifiers, pigments, colorants, cavitating agents, slip agents, antioxidants, antifog agents, antistatic agents, fillers, moisture barrier additives, gas barrier additives, and combinations thereof, as discussed in further detail below. A suitable antistatic agent is ARMOSTAT^TM475 (commercially available from Akzo Nobel of I11 Chicago).

The cavitating agent may be present in the core layer in an amount of less than 30 wt%, preferably less than 20 wt%, most preferably in the range of 2 wt% to 10 wt%, based on the total weight of the core layer.

Preferably, the total amount of additives in the core layer comprises up to about 20 wt% of the core layer, but some embodiments may be such that the amount of additives in the core layer comprises up to about 30 wt% of the core layer.

The thickness of the core layer is preferably about 5 μm to 100 μm, more preferably about 5 μm to 50 μm, and most preferably 5 μm to 25 μm.

Connecting (tie) layer

Tie layers of multilayer films are typically used to connect two additional layers of the multilayer film structure, such as the core layer and the sealant layer, and are located intermediate these other layers. The tie layers may be of the same or different composition than the core layer.

In some embodiments, the tie layer is in direct contact with a surface of the core layer. In other embodiments, another layer or layers may be between the core layer and the tie layer. The tie layer may comprise, consist essentially of, or consist of one or more polymers. In addition, the polymer may comprise C₂Polymer, maleic anhydride-modified polyethylene polymer, C₃Polymer, C₂C₃Random copolymer, C₂C₃C₄Random terpolymer, heterophasic random copolymer, C₄Homopolymer, C₄Copolymers, metallocene polymers, propylene-based or ethylene-based elastomers and/or plastomers, ethyl acrylate-methyl methacrylate (EMA) polymers, ethylene-vinyl acetate (EVA) polymers, polar copolymers, and combinations thereof. For example, one polymer may be VISTAMAXX^TMPolymer grades (commercially available from ExxonMobil chemical company of Baytown, texas) such as VM6100 and VM3000 grades. Alternatively, suitable polymers may include VERSIFY^TMPolymer (available from Dow chemical company, Midland, Mich.), Basell CATALLOY^TMResins, e.g. ADFLEX^TM T100F、SOFTELL^TM Q020F，CLYRELL^TMSM1340 (commercially available from Basell polyolefin Inc. of the Netherlands), PB (propylene-butene-1) random copolymers, such as Basell PB 8340 (commercially available from Basell polyolefin of the Netherlands), Borealis BORSOF^TMSD233CF (commercially available from Borealis, Denmark), EXCEED^TM1012CA and 1018CA metallocene polyethylene, EXACT^TM 5361、4049、5371、8201、4150、3132 polyethylene plastomer, EMCC 3022.32 Low Density Polyethylene (LDPE) (available from ExxonMobil chemical company of Baytown, Tex.).

In some embodiments, the tie layer may further comprise one or more additives such as opacifiers, pigments, colorants, cavitating agents, slip agents, antioxidants, antifogging agents, antistatic agents, antiblocking agents, fillers, moisture barrier additives, gas barrier additives, and combinations thereof, as discussed in further detail below.

The thickness of the tie layer is generally in the range of about 0.50 to 25 μm, preferably in the range of about 0.50 to 12 μm, more preferably in the range of about 0.50 to 6 μm, and most preferably about 2.5 to 5 μm. However, in some thinner films, the tie layer may have a thickness of about 0.5 μm to 4 μm, or about 0.5 μm to 2 μm, or about 0.5 μm to 1.5 μm.

Sealant layer

In some embodiments, the sealant layer is adjacent to the core layer. Further, the sealant layer may be on one or both sides of the core layer. In addition, the sealant layer may have the same or different composition as compared to the core. In other embodiments, one or more other layers may be between the core layer and the sealant layer. The sealant layer may comprise, consist essentially of, or consist of a polymer suitable for heat sealing or self-bonding when crimped between heated crimp sealing jaws. Suitable sealant layers include, consist essentially of, or consist of one or more polymers including homopolymers, copolymers of ethylene, propylene, butene, hexene, heptene, octene, and combinations thereof. Additionally and alternatively, suitable sealant layer compositions have a melting peak equal to or less than the melting peak of the core layer. More particularly, the sealant layer may comprise, consist essentially of, or consist of at least one polymer selected from the group consisting of: ethylene propylene-butene (EPB) terpolymers, Ethylene Vinyl Acetate (EVA), metallocene catalyzed ethylene, LLDPE, ionomers, polyethylene elastomers, plastomers, and combinations thereof.

The sealant layer may also contain processing aids such as antiblocking agents, antistatic agents, slip agents, and combinations thereof, as discussed in further detail below.

The thickness of each sealant layer is typically in the range of about 0.10 μm to 7.0 μm, preferably about 0.10 μm to 4 μm, and most preferably about 1 μm to 3 μm. In some film embodiments, the sealant layer may have a thickness of about 0.10 μm to 2 μm, 0.10 μm to 1 μm, or 0.10 μm to 0.50 μm. In some generally preferred film embodiments, the sealant layer 20 has a thickness in the range of about 0.5 μm to 2 μm, 0.5 μm to 3 μm, or 1 μm to 3.5 μm.

Skins, including metallizable skins

In some embodiments, the skin layer comprises, consists essentially of, or consists of at least one polymer selected from the group consisting of: selected from one or more acid-containing polyethylene copolymers or terpolymers, consisting essentially of and/or consisting of, which may be grafted or copolymerized. The acid-containing moiety itself can be acrylic-based, methacrylic-based, another organic acid, or a combination thereof. The acid-containing portion of the acid-containing polymer can be from 4 wt% to 20 wt%, or from 6 wt% to 16 wt%, or from 8 wt% to 12 wt%. For example, Exxon Mobil Escor EAA resin or Dupont Nucrel EAA resin or Dow Primacor EAA resin may be used. To obtain metallization or barrier properties, the acid-modified skin layer may comprise LLDPE or an ethylene vinyl alcohol-based polymer ("EVOH"), a suitable EVOH copolymer being EVAL^TMG176B or XEP 1300 (commercially available from Kuraray Company, Inc., Japan).

The skin layer may also include processing aids such as antiblocking agents, antistatic agents, slip agents, and combinations thereof, as discussed in more detail below.

The thickness of the cortex depends on the intended function of the cortex, but is typically in the range of about 0.20 μm to 3.5 μm or 0.30 μm to 2 μm, or in many embodiments 0.50 μm to 1.0 μm. In film embodiments, the skin layer may have a thickness in a range of about 0.20 μm to 1.5 μm or 0.50 μm to 1.0 μm.

Additive agent

Additives present in the film layer may include, but are not limited to, opacifiers, pigments, colorants, cavitating agents, slip agents, antioxidants, antifog agents, antistatic agents, antiblocking agents, fillers, moisture barrier additives, gas scavengers, and combinations thereof. These additives may be used in effective amounts, which depend on the desired properties.

Examples of suitable opacifiers, pigments or colorants are iron oxide, carbon black, aluminium, titanium dioxide (TiO)₂) Calcium carbonate (CaCO)₃) And combinations thereof.

The cavitating or void-inducing additive may comprise any suitable organic or inorganic material that is incompatible with the polymeric material of the added layer at the biaxial orientation temperature to produce an opaque film. Examples of suitable void initiating particles are PBT, nylon, solid or hollow preformed glass spheres, metal beads or spheres, ceramic spheres, calcium carbonate, talc, chalk or combinations thereof. The average diameter of the void initiating particles may typically be about 0.1 to 10 μm.

Slip agents may include higher fatty amides, higher fatty acid esters, waxes, silicone oils and metal soaps. Such slip agents may be used in amounts of 0.1 wt% to 2 wt%, based on the total weight of the layer to which they are added. An example of a slip agent that may be useful is erucamide.

The non-migrating slip agent for one or more skin layers of the multilayer film may comprise, consist essentially of, or consist of polymethyl methacrylate (PMMA). Depending on the layer thickness and desired slip properties, the average particle size of the non-migrating slip agent may be in the range of about 0.5 μm to 8 μm, or 1 μm to 5 μm, or 2 μm to 4 μm. Alternatively, the particle size in a non-migrating slip agent such as PMMA may be greater than 20% of the thickness of the skin layer containing the slip agent, or greater than 40% of the thickness of the skin layer, or greater than 50% of the thickness of the skin layer. The particle size of such non-migrating slip agents may also be at least 10% greater than the thickness of the skin layer, or at least 20% greater than the thickness of the skin layer, or at least 40% greater than the thickness of the skin layer. Generally spherical, particulate non-migrating slip agents are contemplated, including PMMA resins, such as EPASTAR^TM(commercially available from Nippon Shokubai Co., Ltd., Japan). Other sources of commercially suitable materials are also known to exist. Non-migratoryMigration refers to the fact that these particles do not generally change position throughout the film layer in the manner of a migrating slip agent. Conventional polydialkylsiloxanes are also contemplated, such as silicone oils or gum additives having a viscosity of 10,000 to 2,000,000 centistokes.

Suitable antioxidants may comprise, consist essentially of, or consist of phenolic antioxidants, for example1010 (commercially available from Ciba-Geigy, Switzerland). Such antioxidants are generally used in amounts of 0.1 to 2 wt.%, based on the total weight of the layer to which the antioxidant is added.

The antistatic agent may include, consist essentially of, or consist of an alkali metal sulfonate, a polyether modified polydiorganosiloxane, a polyalkylphenylsiloxane, and a tertiary amine. Such antistatic agents may be used in an amount ranging from about 0.05 wt% to 3 wt%, based on the total weight of the layer.

Examples of suitable antiblocking agents can include, consist essentially of, or consist of silica-based products, e.g.44 (commercially available from Grace Davison Products, Md.), PMMA particles such as EPASTART (available from Nippon Shokubai, Inc., Japan), or polysiloxanes such as TOSPEARLTM (available from GE Bayer Silicones, Wilton, Connecticut). An effective amount of such antiblock agent is up to about 3000ppm by weight of the layer to which it is added.

Useful fillers may comprise, consist essentially of, or consist of: finely divided inorganic solid materials, such as silica, fumed silica, diatomaceous earth, calcium carbonate, calcium silicate, aluminum silicate, kaolin, talc, bentonite, clay and pulp.

Optionally, a non-ionic or anionic wax emulsion may be included in the coating, i.e. the sealing layer, to increase blocking resistance and/or reduce the coefficient of friction. For example, the sealant layer may include milk of Michem Lube 215 and Michem Lube 160And (3) preparing. Any conventional wax for use in thermoplastic films is contemplated, such as, but not limited to, Carnauba^TMWax (available from Michelman Corporation, cincinnati, ohio).

Metallization

The outer surface of each sealant layer (i.e., the side facing away from the core), i.e., if the multilayer film has more than one sealant layer, may be metallized after optionally treating it. The metallization may be performed by conventional methods, such as vacuum metallization by depositing a metal layer (e.g., aluminum, copper, silver, chromium, or mixtures thereof). After metallization, a coating may be applied to the outer metallization layer "outside" or "inside" the vacuum chamber to produce the following structure: metallized layer/sealant layer/core/sealant layer/metallized layer. In another embodiment, a primer may be applied to the metal surface followed by a top coat.

In certain embodiments, the metal used for metallization is a metal oxide, any other inorganic material capable of vacuum deposition, electroplating, or sputtering, or an organically modified inorganic material (e.g., SiO)_x，AlO_x，SnO_x，ZnO_x，IrO_xWhere x ═ 1 or 2), organically modified ceramics "ormocer", and the like. The thickness of the deposited layer is generally in the range of 100 to 5,000 angstroms, or preferably in the range of 300 to 3000 angstroms.

Surface treatment

One or both outer surfaces of the multilayer film may be surface treated to increase the surface energy to render the film receptive to metallization, coatings, printing inks, adhesives, and/or lamination. The surface treatment may be carried out according to one of the methods known in the art, including corona discharge, flame, plasma, chemical treatment or treatment by means of a polarized flame.

Primer coating(priming)

An intermediate primer coating may be applied to the multilayer film. In this case, the film may first be treated by one of the aforementioned methods to provide increased active adhesive sites thereon, and then a continuous coating of primer material may be subsequently applied to the so-treated film surface. Such primer materials are well known in the art and include, for example, epoxy, poly (ethylenimine) (PEI), and polyurethane materials, U.S. Pat. No. 3,753,769, U.S. Pat. No. 4,058,645, and U.S. Pat. No. 4,439,493, each of which is incorporated herein by reference, disclose the use and application of such primers. The primer provides an overall adhesive active surface that is sufficiently strong to bond to the entire subsequent coating composition and can be applied to the film by conventional solution coating methods, such as by roll coating.

Orientation of

In certain embodiments, the films herein are further characterized by biaxial orientation. The film may be made by any suitable technique known in the art, such as tenter or blow molding process, LISIM^TMAnd the like. In addition, operating conditions, temperature settings, line speeds, etc. will vary depending on the type and size of equipment used. Nonetheless, generally described herein is a method of making the films described throughout this specification. In a particular embodiment, a film is formed and biaxially oriented using a tenter frame process. In the tentering process, a line speed of more than 100m/min to 400m/min or more and a throughput of more than 2000kg/h to 4000kg/h or more can be achieved. In the tentering process, sheets/films of various materials are melt blended and coextruded, for example through 3, 4, 5, 7 layer dies, into the desired film structure. An extruder having a diameter in the range of 100mm to 300mm or 400mm and a length to diameter ratio in the range of 10/1 to 50/1 can be used to melt blend the molten layer material and then meter the melt stream into a die having a die gap of 0.5 or 1 to an upper limit of 3 or 4 or 5 or 6 mm. The extruded film is then cooled using air, water, or both. Generally, a single large diameter roll immersed in a water bath or two large chilled rolls set at 20 or30 to 40 or 50 or 60 or 70 ℃ are suitable cooling means. When extruding the film, an air knife and edge pinning were used to provide intimate contact between the melt and the chill roll.

Downstream of the first cooling step in this embodiment of the tenter frame process, the unoriented film is reheated to a temperature of 80 to 100 or 120 or 150 ℃, in one embodiment by any suitable means, such as heated S-wrap rollers, and then passed between closely spaced differential rollers to achieve machine direction orientation. It will be appreciated by those skilled in the art that this temperature range may vary from device to device, particularly depending on the nature and composition of the components making up the membrane. Ideally, the temperature should be below the temperature at which the film melts, but high enough to facilitate the machine direction orientation process. Such temperatures referred to herein refer to the film temperature itself. The film temperature can be measured by using, for example, infrared spectroscopy, where an infrared source is directed at the film as it is processed; those skilled in the art will appreciate that for transparent films, measuring the actual film temperature will be less accurate. The heating means of the film production line may be set at any suitable heating level, depending on the instrument, to achieve a specified film temperature.

The elongated and thinned film is sent to the tenter section of the production line for TD orientation. At this point, the edges of the sheet are gripped by mechanical grippers on the continuous chain and pulled into a long, precisely controlled hot air oven for the preheating step. In the preheating step, the film temperature is 100 or 110 to 150 or 170 or 180 ℃. Likewise, the temperature will be below the temperature at which the film will melt, but the temperature should be high enough to facilitate the step of transverse orientation. Next, the edges of the sheet are gripped by mechanical grippers on a continuous chain and pulled into a precisely controlled hot air oven for transverse stretching. When the tenter chain diverges by the amount required to stretch the film in the transverse direction, the process temperature is reduced by at least 2 ℃, but typically not more than 20 ℃, relative to the preheat temperature to maintain the film temperature so that it does not melt the film. After stretching to achieve film cross direction orientation, the film is annealed at a temperature below the melting point, then the film is cooled from below the stretching temperature to 5 to 10 or 15 or 20 or30 or 40 ℃, then the clips are released prior to trimming, and then optional corona (coronal), printing and/or other processing may be performed, followed by winding.

Thus, TD orientation is achieved by: the machine-oriented film is preheated and then stretched and annealed at a temperature below the melting point of the film, followed by a cooling step at a lower temperature. In one embodiment, the film described herein is formed by the following method: the film is annealed by first preheating the film to impart cross-direction orientation and then reducing the process temperature by 2 or3 to 5 to 10 or 15 or 20 ℃ relative to the preheat temperature, while simultaneously effecting cross-direction orientation of the film, then reducing the temperature by 5 to 10 or 15 or 20 or30 or 40 ℃ relative to the melting point temperature, maintaining or slightly reducing (over 5%) the amount of stretching. The latter step imparts low TD shrink characteristics to the films described herein. Thus, for example, where the preheat temperature is 120 ℃, the draw temperature may be 114 ℃ and the cooling step may be 98 ℃, or any temperature within the disclosed ranges. As will be understood by those skilled in the art, the steps are performed for a sufficient time to affect the desired film properties.

Thus, in certain embodiments, the films described herein are biaxially oriented with at least 5 or 6 or 7 or 8 weight TD orientation and at least 2 or3 or 4 weight MD orientation. So formed, in certain embodiments, at least three layers (one core, two skin layers, thickness 18-21 μm) have an ultimate tensile strength in the range of TD from 100 or 110 to 80 or 90 or 200 MPa; in other embodiments, the ultimate tensile strength in the MD is in the range of 30 or 40 to 150 or 130 MPa. Further, in certain embodiments, the SCS films described herein have an MD Elmendorf tear of greater than 10 or 15g, while in other embodiments the 25TD Elmendorf tear is greater than 15 or 20 g.

INDUSTRIAL APPLICABILITY

The disclosed multilayer films may be stand-alone films, laminates, or webs. Alternatively, the multilayer film may be sealed, coated, metallized and/or laminated to other film structures. The disclosed multilayer films may be prepared by any suitable method, including the steps of: co-extruding a multilayer film according to the description and claims of the present description; orienting and preparing the film for the intended use, for example by coating, printing, slitting, or other converting methods.

For certain applications, it may be desirable to laminate the multilayer film to other polymeric films or paper products for packaging decoration, including printing and metallization. These activities are typically performed by the end user or the film maker who processes the film for supply to the end user.

The prepared multilayer film can be used as a flexible packaging film for packaging articles or goods, such as food or other products. In some applications, the film may be formed into a pouch-type package, such as may be used for packaging beverages, liquids, granular or dry powder products.

Example embodiments

Typically, cast or blown polyethylene sealant films are not metallized because the metal does not adhere well to maintain integrity when laminated to a rigid web.

However, disclosed is a new thin BOPE multilayer film that can withstand metallization and also provides good metal adhesion and metallized barrier properties.

The following BOPE transparent films have been produced on a biaxially oriented polypropylene ("BOPP") line:

example 1

Flame treatment

1.0μm	m-LLDPE1
		23μm	m-LLDPE1
1.0μm	50％m-LLDPE1+50％m-LLDPE2+10,000ppm silicate 6 μm

Example 2

Flame treatment

1.0μm	50％m-LLDPE1+50％m-LLDPE2
		23μm	m-LLDPE1
1.0μm	50％m-LLDPE1+50％m-LLDPE2+10,000ppm silicate 6 μm

Example 3

Flame treatment

1.0μm	100% maleic anhydride grafted polyethylene
		23μm	m-LLDPE1
1.0μm	50％m-LLDPE1+50％m-LLDPE2+10,000ppm silicate 6 μm

Example 4

Flame treatment

1.0μm	100％Escor 5100
		23μm	50％m-LLDPE1+50％m-LLDPE2+10,000ppm silicate 6 μm
1.0μm	50％m-LLDPE1+50％m-LLDPE2+10,000ppm silicate 6 μm

In these examples, a metallocene LLDPE ("m-LLDPE") was used, i.e., having a melt flow index of 1.9g/10min, 0.927g/cm³Has a density of 3.8g/10min and a melting peak at 127 ℃ of m-LLDPEi, a melt flow index of 0.913g/cm³The melting peak is m-LLDPE2 at 113 ℃. Other types of LLDPE, whether formed under non-metallocene chemical conditions or not, may be used, for example, those having a melt flow index of 1 to 3 and a density of 0.915 to 0.930g/cm, using lanthanide or actinide or metallocene catalysis³The melting peak is 115 ℃ to 135 ℃. However, it is noteworthy that the LLDPE resin used for the sealant layer must have a lower melting peak than the LLDPE resin used for the core layer. Preferably, the viscosity also follows this requirement.

In example 3, maleic anhydride-grafted polyethylene having a density of 0.91g/cm was used³And a melting peak of 118 ℃. For example, in an alternative embodiment, one or more grades of maleic anhydride grafted polyethylene may be used alone, i.e., having a density in the range of 0.900 to 0.930g/cm³Density in the range, or blending into one or more LLDPE based resins.

In example 4, Escor 5100 is abbreviated ExxonMobil Escor 5100, which is an ethylene acrylic acid ("EAA") copolymer containing 11% acrylic acid, having a melt flow index of 8.5g/10min and a density of 0.940g/cm³And a melting peak at 95 ℃. In an exemplary embodiment, Escor 5100 may be substituted with other acrylic ("AA") copolymers (e.g., Primacor3002) comprising 8% AA copolymer available from Dow having a melting peak at 100 ℃, and/or used in combination with ExxonMobil Escor 5100 and/or other acrylic copolymers.

Examples of BOPE are disclosed herein and are biaxially oriented according to U.S. patent No. 8,080,294.

In addition to flame treatment after orienting the BOPE film, the film was then further processed in a vacuum, 80: 20Ar-O₂The examples were plasma treated in an atmosphere on the flame treated surface of the dual seal thin BOPE film and the measured values are listed in table 1.

TABLE 1

From this value it can be seen that when the sealant layer comprises maleic anhydride grafted polyethylene or ethylene acrylic acid copolymer, then there is good barrier properties, i.e. low WVTR and OTR values result.

The method used to determine the steady state transmission rate of oxygen through a film sample is in accordance with ASTM D-3985. Pressure 760mmHg, in cm³/m²And/day. The analysis was performed at atmospheric pressure. Then, the data was pressure-compensated by a computer to normalize the data to 760mmHg (sea level). Since most materials are heterogeneous and their shielding layers can be very thin relative to the total thickness, the thickness cannot be measured. This means that the material structure is provided with a transmission rate as such. The shield is oriented toward the carrier gas. No special condition exists in the prior test. The sample was not placed in the desiccator. The conditioning time refers to the time between the insertion of the sample from the diffusion cell and the beginning of the measurement cycle. The total conditioning time is the time between the insertion of the sample from the diffusion cell and the end of the test, i.e., the total elapsed time. Standard test conditions are 23 degrees celsius and dry oxygen, i.e., 0% Relative Humidity (RH).

The method for determining the transmission rate of water vapor through a film sample is in accordance with ASTM F-1249. The units used are grams per square meter per day. The shield is oriented toward the carrier gas. No special condition exists in the prior test. The sample was not placed in the desiccator. Since most materials are heterogeneous and their shielding layers can be very thin relative to the total thickness, the overall structure thickness cannot be measured. This means that the material structure is provided with a Water Vapour Transmission Rate (WVTR) as such. The conditioning time set on the instrument refers to the time between the insertion of the sample from the diffusion cell into the sample and the start of the first measurement cycle. During this time, the carrier gas does not pass through the water vapor sensor and therefore does not measure WVTR. The total conditioning time is the total elapsed time, i.e., the time between insertion of the sample into the diffusion cell and the end of the test. The test conditions were 37.8 ℃ and the actual relative humidity was 90%.

Further experiments confirmed that the metallized side of the exemplary BOPE film was laminated to a 12 μm polyester ("PET") film using a two-component polyurethane-based adhesive. The adhesive strength of the laminate is shown in table 2. The bond strength can be measured by cutting a 1 inch wide strip of the laminate and then peeling the main and auxiliary webs apart on an Instron tensile tester at 12 inches/minute and 90 degree peel angles (commercially available from Instron global headquarters, norwood, ma). The adhesive strength is the maximum peel force measured by the test.

TABLE 2

From this value, it is shown that when the sealant layer comprises an ethylene acrylic acid copolymer, the laminated BOPE film exhibits excellent metal adhesion, i.e., the film tears without metal transfer to the PET-based substrate. In contrast, however, when the sealant layer comprised maleic anhydride grafted polyethylene, the results were not satisfactory, i.e., the metal was transferred from the metallized layer to the PET based substrate at a rate of 170 g/inch.

Using an Otto Brugger capper with crimping jaws, at a dwell time of 0.75s and 41N/cm²The sealing values of the above laminated BOPE films were measured at ten degree intervals of 100 ℃ to 150 ℃ under the pressure of (c), as shown in table 3.

TABLE 3

Biaxially oriented LLDPE films with a sealant layer comprising an ethylene-acrylic acid copolymer, metallized and PET laminated, exhibited high seal strengths of 4390 g/inch. Other examples show that the seal strength is lower due to weaker metal bonding on LLDPE films; that is, as previously discussed in terms of bond strength, the transfer from the sealant BOPE metalized web to the PET web occurred during the seal opening.

In the MET-PET example 4 example, additional improvements were achieved by adding silicone rubber (silicone gum) to the sealant layer to reduce the coefficient of friction on the sealant side without sacrificing the metallized barrier layer and metal adhesion strength. Up to 5% of silicone rubber masterbatch can be added to reduce the coefficient from 0.40 (no silicone rubber) to 0.30. Exemplary silicone masterbatches that can be used are Dow Corning 50-313, Dow Corning HMB-1103, and Constab SL05093 LD.

While the foregoing is directed to exemplary embodiments of the disclosed invention, other and further embodiments of the disclosed compositions, systems, and methods may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.