Multi-layer heat-seal film

Abstract

A multilayer film comprising linear low density polyethylene (LLDPE) and a process for producing the same are provided herein. In some embodiments, the multilayer film comprises a primary layer comprising an extruded first LLDPE composition and a second layer comprising a polymer composition. A process for producing a multilayer film according to the embodiments disclosed herein includes melting a first LLDPE composition and a polymer composition, wherein prior to extrusion, the first LLDPE composition comprises a first LLDPE polymer and a free radical generator. As a result of the multilayer film being formed from a first LLDPE composition comprising a free radical generator that acts as a rheology modifier, it can have desirable tear, heat seal, puncture, and dirt drop characteristics.

Description

Technical Field

[0001] This application relates to a multilayer polymer film containing linear low density polyethylene.

Background Art

[0002] Introduction Polyethylene polymers and copolymers are generally classified into the group of high density polyethylene (HDPE) having a density of generally about 0.93 g / cm 3 ~0.98 g / cm 3 low density polyethylene (LDPE) having a density of generally about 0.91 g / cm 3 ~0.93 g / cm 3 and linear low density polyethylene (LLDPE) having a density of generally about 0.91 g / cm 3 ~0.94 g / cm 3 Linear low density polyethylene contains short chain branches and fewer long chain branches than LDPE, and is a substantially linear ethylene polymer further defined in U.S. Patent No. 5,272,236, U.S. Patent No. 5,278,272, U.S. Patent No. 5,582,923, and U.S. Patent No. 5,733,155, a homogeneously branched linear ethylene polymer composition such as that of U.S. Patent No. 3,645,992, a heterogeneously branched ethylene polymer prepared according to the process disclosed in U.S. Patent No. 4,076,698, and / or blends thereof (such as those disclosed in U.S. Patent No. 3,914,342 or U.S. Patent No. 5,854,045).

[0003] LLDPE is frequently coextruded with similar or dissimilar polymers to produce multilayer films. In coextrusion, two or more extruders melt different polymers and feed the polymers into a single extrusion die. The polymers are extruded together to form a film containing one or more layers of each polymer, and the layers are adhered together. The multilayer film can contain a first or primary layer that includes an LLDPE polymer selected to provide desired physical properties such as tensile strength, puncture resistance, and tear resistance. Other layers in the multilayer film can be selected to provide other desired properties such as improved heat seal performance, appearance, rigidity, adhesion between layers, and / or a barrier to the migration of water, oxygen, or flavor components.

[0004] Multilayer films are frequently used in form, fill and seal (FFS) packaging to contain articles in sealed pouches made from the film. In summary, the FFS packaging process typically includes the following steps. 1. Unroll the film from a roll and advance it in the machine direction. 2. Fold the film and bring the outer edges together, and weld the edges together with heat and pressure to form a hollow tube having a seam running in the machine direction. 3. A set of heated jaws clamp the tube with heat and pressure transverse to the machine direction to form a seal transverse to the machine direction. This forms a pouch having an open end upstream. 4. Fill the pouch with product from the open end. 5. A set of heated jaws clamp the open end of the pouch with heat and pressure transverse to the machine direction to form a second seal transverse to the machine direction, and the product is confined within the pouch between the two seals. 6. Cut the closed pouch from the end of the tube.

[0005] The forming, filling, and sealing system can be vertical (VFFS) or horizontal (HFFS). FFS packaging places strict requirements on the film used to produce it. The film must be flexible enough to be easily folded to form a pouch, but strong enough to withstand the many handling and stresses during boxing, transportation, storage, and display. The film must seal quickly and completely without gaps and voids. The seal must be strong enough to hold the product inside the pouch before the seal is fully cooled, and the pouch closure must remain strong throughout the life of the package. The film must provide effective sealing on different devices with different temperature control capabilities. Ideally, these requirements can be met by making the film as thin as possible to minimize cost, weight, and waste generated from the packaging.

[0006] Heat sealing can potentially weaken the primary layer of the film in the area adjacent to the seal. The heated jaws that form the heat seal, when softening the heat seal layer, may accidentally soften the primary layer. The process of moving the film line and filling the pouch places stress on the heated film. The stress on the heated primary layer makes it thinner in the area adjacent to the heat seal. After the film cools and the stress is released, the primary layer remains thin and weak near the seal compared to the rest of the pouch. The pouch is prone to cracking or tearing near the seal.

[0007] One solution to minimize thinning of the primary layer is to add more than 20% low-density polyethylene to the LLDPE polymer used in the primary layer. However, LDPE increases the die pressure of the primary layer polymers and reduces their processability.

[0008] It would be desirable to reduce thinning in the primary layer without reducing the processability of the polymers in other layers. SUMMARY OF THE INVENTION

[0009] One aspect of the present invention is a process for producing a multilayer film, comprising: (1) melting (a) a first LLDPE composition and (b) a polymer composition in separate extruders; and (2) co-extruding the first LLDPE composition and the polymer composition under conditions suitable for forming a multilayer film comprising a primary layer comprising an extruded LLDPE composition derived from the first LLDPE composition and a second layer comprising the polymer composition. a) Before extrusion, the first LLDPE composition comprises (i) at least 85 weight percent of a first LLDPE polymer comprising at least 0.20 vinyl groups per 1000 carbon atoms and (ii) a free radical generator at a weight ratio of 5 to 1000 parts per million by weight (ppmw). b) The process wherein the conditions in the extruder are suitable for substantially decomposing the free radical generator.

[0010] "Substantially decomposing" means that at least 80 weight percent of the free radical generator decomposes under the reaction conditions during extrusion, and in some embodiments, at least 90 weight percent, or at least 95 weight percent, or at least 99 weight percent decomposes. In some embodiments, the free radical generator is at undetectable levels after extrusion is complete. The "primary layer" in the multilayer film may also be referred to as the "first layer".

[0011] A second aspect of the present invention is a multilayer film produced by the process of the first aspect of the present invention.

[0012] A third aspect of the present invention is a multilayer film, comprising: a) a primary layer comprising an extruded first LLDPE composition comprising at least 85 weight percent of a first LLDPE polymer, wherein the extruded first LLDPE composition has a complex viscosity ratio (η0.1 / η 10 ) and a ratio (Mz Abs / Mw Abs ) of 2.9 to 4.0, and a primary layer having b) a second layer containing the polymer composition, the multilayer film comprising.

[0013] A fourth aspect of the present invention is a process using the multilayer film in the second or third aspect, the process being one in which the multilayer film is used in a forming, filling, and heat-sealing packaging process.

[0014] A fifth aspect of the present invention is a sealed package produced by the process in the fourth aspect of the present invention.

[0015] Without wishing to be bound by theory, the free radical generator in the first LLDPE composition increases the complex viscosity ratio of the extruded first LLDPE composition by inducing a slight increase in long chain branching. The increased complex viscosity ratio means that the extruded first LLDPE composition has a substantially higher viscosity under the low shear conditions that exist during heat sealing on the FFS line, but does not have a substantially higher viscosity under the high shear conditions that exist in the extrusion die. The higher viscosity on the FFS line enables the extruded first LLDPE composition to have better resistance to thinning and weakening during the heat sealing process. The lower viscosity in the extrusion die enables the first LLDPE composition to maintain good processability. In addition, in some embodiments, the multilayer film of the present invention has improved puncture resistance and dirt drop results.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

DETAILED DESCRIPTION OF THE INVENTION

[0017] First LLDPE Composition The present invention uses a first LLDPE composition comprising a first LLDPE polymer and a free radical generator. In some embodiments, the first LLDPE polymer can be a blend of LLDPE polymers that collectively meet the criteria described herein, and in some embodiments, the first LLDPE polymer is a single LLDPE polymer that meets the criteria described herein. The phrase "first LLDPE polymer" encompasses both embodiments. In some embodiments, the first LLDPE composition further comprises other polyethylene polymers, such as a carrier resin used in a masterbatch with a free radical generator, as described later.

[0018] The first LLDPE polymer has a density of 0.91 g / cm 3 ~0.94 g / cm 3 Before extrusion, it has at least 0.20 vinyl groups per 1000 carbon atoms.

[0019] In some embodiments, the first LLDPE polymer is a copolymer in which at least 70 weight percent of the polymer is derived from ethylene monomer and at least 2 weight percent of the polymer is derived from one or more comonomers. Examples of suitable comonomers can include α-olefins. Suitable α-olefins can include those containing 3 to 20 carbon atoms (C3~C 20 ) can be mentioned. For example, the α-olefin is C4~C 20 α-olefin, C4~C 12 α-olefin, C3~C 10It can be an α-olefin, a C3-C8 α-olefin, a C4-C8 α-olefin, or a C6-C8 α-olefin. In some embodiments, the α-olefin is selected from the group consisting of propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-nonene, and 1-decene. In other embodiments, the α-olefin is selected from the group consisting of propylene, 1-butene, 1-hexene, and 1-octene. In further embodiments, the α-olefin is selected from the group consisting of 1-hexene and 1-octene.

[0020] In some embodiments, the repeating units derived from ethylene constitute at least 80 wt%, or at least 90 wt%, or at least 92 wt% of the first LLDPE polymer. In some embodiments, the repeating units derived from ethylene constitute up to 98 wt%, or up to 96 wt%, or up to 94 wt%, or up to 93 wt% of the first LLDPE polymer. In some embodiments, the repeating units derived from the α-olefin constitute up to 20 wt%, or up to 18%, or up to 15%, or up to 12%, or up to 10%, or up to 8% of the first LLDPE polymer. In some embodiments, the repeating units derived from the α-olefin comonomer constitute at least 2 wt%, or at least 4%, or at least 6%, or at least 7% of the first LLDPE polymer.

[0021] The comonomer content may be expressed in terms of short-chain branches per 1000 carbon atoms, where the short-chain branches are residues of the comonomer and contain 18 or fewer carbon atoms, or 10 or fewer carbon atoms, or 6 or fewer carbon atoms. In some embodiments, the first LLDPE polymer has at least 2 short-chain branches, or at least 5, or at least 7, or at least 9 per 1000 carbon atoms. In some embodiments, the first LLDPE polymer has up to 20 short-chain branches, or up to 18, or up to 15, or up to 13, or up to 11 per 1000 carbon atoms.

[0022] In some embodiments, the first LLDPE polymer may be homogeneously branched or heterogeneously branched. The long-chain branches contain at least 20 carbon atoms. In some embodiments, the first LLDPE polymer contains 3 or fewer long-chain branches per 1000 carbon atoms, or 2 or fewer, or 1 or fewer. In some embodiments, the first LLDPE polymer is substantially linear (essentially 0 long-chain branches per 1000 carbon atoms) except for short-chain branches obtained from comonomers.

[0023] The first LLDPE polymer has a density of 0.90 g / cm 3 ~0.94 g / cm 3 All individual values and subranges from 0.90 g / cm 3 ~0.94 g / cm 3 are included and disclosed herein. For example, in some embodiments, the density ranges from a lower limit of 0.900, 0.905, 0.910, 0.915, 0.920, 0.925, 0.930, or 0.935 g / cm 3 to an upper limit of 0.940, 0.935, 0.930, 0.925, or 0.920 g / cm 3

[0024] ​Before co-extrusion molding, the first LLDPE polymer has at least 0.20 vinyl groups per 1000 carbon atoms. All individual values and sub-ranges of at least 0.20 vinyl groups per 1000 carbon atoms are included and disclosed herein. For example, in some embodiments, the first LLDPE polymer has at least 0.20, 0.25, 0.30, or 0.35 vinyl groups per 1000 carbon atoms. In other embodiments, the first LLDPE polymer has at most 1.00 vinyl groups per 1000 carbon atoms, or 0.70 vinyl groups per 1000 carbon atoms, or 0.65 vinyl groups per 1000 carbon atoms, or 0.60 vinyl groups per 1000 carbon atoms, or 0.55 vinyl groups per 1000 carbon atoms, or 0.50 vinyl groups per 1000 carbon atoms, or 0.45 vinyl groups per 1000 carbon atoms.

[0025] In some embodiments, the melt index (I2) of the first LLDPE polymer ranges from 0.01 g / 10 min to 30 g / 10 min. All individual values and sub-ranges from 0.01 g / 10 min to 30 g / 10 min are included and disclosed herein. For example, in some embodiments, the melt index (I2) ranges from a lower limit of 0.01, 0.05, 0.1, 0.25, 0.5, 1, 3, 5, 7, 10, 12, 15, 18, 20, 23, or 25 to an upper limit of 30, 27, 25, 22, 20, 17, 15, 12, 10, 8, 5, 2, 1, 0.9, 0.7, or 0.5.

[0026] In some embodiments, the first LLDPE polymer has a weight average molecular weight (Mw Abs ) of at least 80,000 Da, or at least 100,000 Da, or at least 120,000 Da before extrusion molding. (All molecular weights are based on absolute molecular weight measurements.) In some embodiments, the first LLDPE polymer has a weight average molecular weight (Mw Abs ) of at most 200,000 Da, or at most 160,000 Da, or at most 130,000 Da before extrusion molding.

[0027] In some embodiments, the first LLDPE polymer has a melt mass-flow rate (MFR) of at least 3, or at least 3.5, or at least 4 before extrusion. Abs / Mn Abs ) before extrusion. In some embodiments, the first LLDPE polymer has a melt mass-flow rate (MFR) of at most 6, or at most 5, or at most 4.5 before extrusion.

[0028] In some embodiments, before extrusion, the ratio of Mz Abs / Mw Abs of the first LLDPE polymer is at least 2, or at least 2.5, or at least 2.75. In some embodiments, before extrusion, the ratio of Mz Abs / Mw Abs of the first LLDPE polymer is at most 4, or at most 3.5, or at most 3.25, or at most 3, or at most 2.9.

[0029] In some embodiments, before extrusion, the first LLDPE polymer has a complex viscosity (η 10 ) of 6000 Pa·s or less, or 5000 Pa·s or less, or 4900 Pa·s or less, or 4800 Pa·s or less, or 4700 Pa·s or less at a temperature of 190 °C and an angular frequency of 10 rad / s. In some embodiments, before extrusion, the first LLDPE polymer has a complex viscosity (η 10 ) of at least 4000 Pa·s, or at least 4250 Pa·s, or at least 4500 Pa·s at a temperature of 190 °C and an angular frequency of 10 rad / s.

[0030] In some embodiments, before extrusion, the first LLDPE polymer has a complex viscosity (η 0.1) has. In some embodiments, prior to extrusion, the first LLDPE polymer has a complex viscosity (η 0.1 ) of at least 5000 Pa·s, or at least 6000 Pa·s, or at least 7000 Pa·s at a temperature of 190 °C and an angular frequency of 0.1 rad / s.

[0031] The polyethylene polymer can be characterized by a complex viscosity ratio (η 0.1 / η 10 ), which is the ratio of the complex viscosities measured at angular frequencies of 0.1 rad / s and 10 rad / s and a temperature of 190 °C. In some embodiments, prior to extrusion, the first LLDPE polymer has a complex viscosity ratio (η 0.1 / η 10 ) of 2.5 or less, or 2.25 or less, or 2 or less, or 1.9 or less, or 1.8 or less, or 1.75 or less, or 1.7 or less. In some embodiments, the first LLDPE polymer has a complex viscosity ratio (η 0.1 / η 10 ) of at least 1.5.

[0032] Examples of suitable LLDPE polymers commercially available from The Dow Chemical Company include polymers sold under the trademarks DOWLEX™ TG2085B, DOWLEX™ GM8051, ELITE™ 5401G, ELITE™ NG5401B, ELITE™ XB 81844.38, and ELITE™ AT 6501.

[0033] The first LLDPE polymer can be produced via a gas phase, solution phase, or slurry polymerization process, or any combination thereof, using any type of reactor or reactor configuration known in the art, such as a fluidized bed gas phase reactor, a loop reactor, a stirred tank reactor, or a batch reactor, in parallel, in series, and / or in any combination thereof. In some embodiments, a gas phase or slurry phase reactor is used. Suitable first LLDPE polymers can be produced according to the processes described on pages 15 - 17 and 20 - 22 in International Publication No. WO 2005 / 111291 (A1). Catalysts that can be used to produce the first LLDPE polymers described herein can include Ziegler - Natta, chromium, metallocene, constrained geometry, or single - site catalysts. In some embodiments, the first polyethylene polymer can be a unimodal LLDPE prepared using single - stage polymerization, such as slurry polymerization, solution polymerization, or gas phase polymerization. In other embodiments, the first LLDPE polymer can be a unimodal LLDPE prepared in a loop reactor, for example, in a single - stage loop polymerization process. The loop reactor process is further described in International Publication No. WO 2006 / 045501 or International Publication No. WO 2008 / 104371. Multimodal (e.g., bimodal) polymers can be produced by mechanical blending of two or more separately prepared polymer components, or can be prepared in - situ in a multi - stage polymerization process, or both. In some embodiments, the first LLDPE polymer can be a multimodal LLDPE prepared in - situ by the use of one or more different polymerization catalysts, including single, multiple, or dual - site catalysts, in a multi - stage, i.e., two or more - stage, polymerization or in a single - stage polymerization. For example, the first LLDPE polymer can be a multimodal LLDPE produced by at least two - stage polymerization using the same catalyst, such as a single - site or Ziegler - Natta catalyst, as disclosed in U.S. Patent No. 8,372,931.Thus, as disclosed in U.S. Patent No. 4,352,915 (two slurry reactors), No. 5,925,448 (two fluidized bed reactors), and No. 6,445,642 (a loop reactor followed by a gas phase reactor), for example, two solution reactors, two slurry reactors, two gas phase reactors, or any combination thereof can be used in any order. However, in other embodiments, the first LLDPE polymer can be a multimodal polymer, for example, an LLDPE produced using slurry polymerization in a loop reactor followed by gas phase polymerization in a gas phase reactor, as disclosed in European Patent No. 2653392 (A1).

[0034] Prior to coextrusion, the first LLDPE composition further comprises a free radical generator. Examples of free radical generators include organic peroxides and organic azo compounds. In some embodiments, the free radical generator is an organic peroxide compound.

[0035] In some embodiments, the free radical generator has a half-life of 200 seconds or less at 220 °C. For example, some embodiments of the free radical generator can have a half-life of 175 seconds or less, 150 seconds or less, or 125 seconds or less at 220 °C. Some embodiments of the free radical generator can have a half-life of at least 30 seconds, or at least 45 seconds, or at least 60 seconds at 220 °C.

[0036] In some embodiments, the free radical generator can have a molecular weight of 200 to 1000 Daltons (Da). All individual values and subranges from 200 to 1000 Daltons are included and disclosed herein. For example, in some embodiments, the free radical generator can have a molecular weight of at least 225 Da or 250 Da. In some embodiments, the free radical generator can have a molecular weight of up to 1000 Da or up to 700 Da.

[0037] In some embodiments, the free radical generator can be a cyclic peroxide. Examples of suitable cyclic peroxides can be represented by the following formula:

[0038] [Chemical Formula] wherein R1 to R6 are each independently hydrogen, or an inert substituted or unsubstituted C1-C 20 alkyl, C3-C 20 cycloalkyl, C6-C 20 aryl, C7-C 20 aralkyl, or C7-C 20 alkaryl. Representative examples of the inert substituents included in R1 to R6 are hydroxyl, C1-C 20 alkoxy, linear or branched C1-C 20 alkyl, C6-C 20 aryloxy, halogen, ester, carboxyl, nitrile, and amide. In some embodiments, R1 to R6 are each independently, for example, C1-C 10 alkyl, or a lower alkyl containing C1-C4 alkyl.

[0039] Some of the cyclic peroxides as described herein are commercially available, but if not, U.S. Patent No. 3,003,000, Uhlmann, 3 rdAs described in Ed., Vol. 13, pp. 256 - 57 (1962), the paper "Studies in Organic Peroxides XXV Preparation, Separation and Identification of Peroxides Derived from Methyl Ethyl Ketone and Hydrogen Peroxide", Milas, N. A. and Golubovic, A., J. Am. Chem., Soc, Vol. 81, pp. 5824 - 26 (1959), "Organic Peroxides", Swern, D. editor, Wiley - Interscience, New York (1970), and Houben - Weyl Methoden der Organische Chemie, El 3, Volume 1, page 736, it can be prepared by contacting a ketone with hydrogen peroxide.

[0040] In some embodiments, the cyclic peroxide can be 3,6,9 - triethyl - 3,6,9 - trimethyl - 1,4,7 - triperoxonan, commercially available from AkzoNobel under the trade name TRIGONOX 301. The cyclic peroxide used herein can be a liquid, solid, or paste, depending on the melting points of the peroxide and the diluent (if present) carried therein.

[0041] The free radical generator should be present in an amount suitable for increasing the low shear viscosity of the first LLDPE composition. In some embodiments, the ratio of the free radical generator to the first LLDPE composition is from 5 ppmw to 1000 ppmw. All individual values and subranges from 5 to 1000 ppmw are included herein and disclosed herein. For example, the ratio of the free radical generator to the first LLDPE composition can range from a lower limit of 5, 10, 20, 30, 40, or 50 ppmw to an upper limit of 40, 50, 60, 65, 75, 100, 150, 250, 350, 450, 550, 650, 750, 850, 950, or 1000 ppmw. In some embodiments, the weight ratio of the free radical generator to the first LLDPE composition can range from 5 to 100 ppmw, or 5 to 75 ppmw, or 10 to 75 ppmw, or 5 to 50 ppmw, or 10 ppmw to 50 ppmw, or 15 to 35 ppmw, or 20 to 40 ppmw, based on the total amount of the polymer.

[0042] In some embodiments, the first LLDPE composition optionally includes other polyethylene polymers. In some embodiments, any other polymer is an LLDPE polymer. In some embodiments, another polymer is low density polyethylene.

[0043] The first LLDPE polymer constitutes at least 85 weight percent of the first LLDPE composition. In some embodiments, the first LLDPE polymer constitutes at least 90 weight percent, or at least 95 weight percent, or at least 99 weight percent of the first LLDPE composition. In some embodiments, the LDPE polymer constitutes at least 1 weight percent, or at least 2 weight percent, or at least 3 weight percent of the first LLDPE composition. In some embodiments, the LDPE polymer constitutes from 0 to 15 weight percent, or 0 to 10 weight percent, or 0 to 5 weight percent, or 0 to 3 weight percent, or 0 to 1 weight percent, or essentially 0 weight percent of the first LLDPE composition.

[0044] One way to introduce other polymers into the first LLDPE composition is to blend a free radical generator with a carrier polymer to form a masterbatch, as described in PCT Patent Publication No. 2017 / 172273 (A1). The masterbatch can be blended with the first LLDPE polymer to form the first LLDPE composition, and the free radical generator can be dispersed throughout the first LLDPE polymer. The masterbatch provides better control of the free radical generator concentration and better dispersion.

[0045] The carrier polymer can be low density polyethylene (LDPE), linear low density polyethylene (LLDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), or combinations thereof. In some embodiments, the carrier polymer is an LLDPE polymer. When the carrier polymer is an LLDPE polymer, it can have the same description, embodiments, and examples as those recited for the first LLDPE polymer, except that the presence of vinyl end groups is more optional rather than required. In some embodiments, the carrier polymer is an LDPE polymer.

[0046] In some embodiments, the masterbatch composition contains at least 100 ppmw of the free radical generator, or at least 200 ppmw, or at least 300 ppmw, or at least 400 ppmw, or at least 500 ppmw. In some embodiments, the masterbatch composition contains up to 4000 ppmw of the free radical generator, or up to 3000 ppmw, or up to 2000 ppmw, or up to 1500 ppmw, or up to 1000 ppmw.

[0047] Depending on the concentration of the free radical generator in the masterbatch composition, the first LLDPE polymer and the masterbatch can be blended in a ratio of 60:40 to 99.9:0.1. All individual values and sub-ranges are included and disclosed herein. For example, in some embodiments, the first LLDPE polymer and the masterbatch are blended in a ratio of 65:35 to 99.9:0.1, 65:35 to 99.9:0.1, 70:30 to 99.9:0.1, 75:25 to 99.9:0.1, 80:20 to 99.9:0.1, 85:15 to 99.9:0.1, 90:10 to 99.9:0.1, 95:5 to 99.9:0.1, 97:3 to 99.9:0.1, 95:5 to 99:1, or 97:3 to 99:1. The first LLDPE polymer and the masterbatch can also be blended such that the amount of the masterbatch in the first LLDPE composition ranges from 0.1 to 40 wt%. All individual values and sub-ranges are included and disclosed herein. For example, in some embodiments, the first LLDPE polymer and the masterbatch can be blended such that the amount of the masterbatch in the first LLDPE composition is at least 0.1 wt%, or at least 0.2 wt%, or at least 0.5 wt%, or at least 1 wt%, or at least 2 wt%, and in some embodiments, the first LLDPE polymer and the masterbatch can be blended such that the amount of the masterbatch in the first LLDPE composition is 15 wt% or less, or 10 wt% or less, or 5 wt% or less, or 3 wt% or less.

[0048] In some embodiments, the first LLDPE composition may contain other additives common to LLDPE films, such as plasticizers, flame retardants, antioxidants, acid scavengers, light and heat stabilizers, lubricants, pigments, antistatic agents, slip compounds, and heat stabilizers. In some embodiments, the other additives constitute 5 weight percent or less, or 4 weight percent or less, or 3 weight percent or less, or 2 weight percent or less, or 1 weight percent or less of the first LLDPE composition. In some embodiments, the other additives constitute essentially 0 weight percent of the first LLDPE composition.

[0049] In some embodiments herein, the first LLDPE composition comprises a primary antioxidant in an amount of 2,000 ppmw or less. All individual values and subranges of from 0 to 2,000 ppmw of the primary antioxidant are included and disclosed herein. For example, in some embodiments, the first LLDPE composition can comprise a primary antioxidant in an amount from a lower limit of 0, 10, 25, 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, or 1900 ppmw to an upper limit of 15, 30, 50, 75, 100, 150, 250, 350, 450, 550, 650, 750, 850, 950, 1000, 1050, 1150, 1250, 1350, 1450, 1500, 1550, 1650, 1750, 1850, 1950, or 2000 ppmw. In other embodiments herein, the first LLDPE composition can comprise a primary antioxidant in an amount up to 250 ppmw, up to 200 ppmw, up to 150 ppmw, up to 100 ppmw, up to 50 ppmw, up to 25 ppmw, or 0 ppmw. In further embodiments, the first LLDPE composition can comprise a primary antioxidant in an amount from 10 to 1000 ppmw, from 10 to 500 ppmw, from 500 to 1000 ppmw, from 10 to 300 ppmw, or from 20 to 100 ppmw. The primary antioxidant is generally a radical scavenger which is an organic molecule consisting of a hindered phenol or a hindered amine derivative. Examples of primary antioxidants include pentaerythrityl tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), which is commercially available from BASF under the name IRGANOX™ 101, or octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, which is commercially available from BASF under the name IRGANOX™ 1076, and other primary antioxidants well known in the polyolefin industry. The secondary antioxidant decomposes hydroperoxides and is generally an organic molecule consisting of a phosphite, phosphonite, or thio compound.Examples of exemplary secondary antioxidants include tris(2,4-di-tert-butylphenyl) phosphite, commercially available from BASF under the name IRGAFOS™ 168, or tris(nonylphenyl) phosphite.

[0050] Other polymer layer materials In some embodiments, the first LLDPE composition is coextruded with the polymer composition to form a multilayer film containing a primary layer derived from the first LLDPE composition and a second layer derived from the polymer composition. The two layers are adhesively bonded to each other either directly or indirectly.

[0051] The selection of the polymer composition depends on the purpose of the layer it forms. Common layers in multilayer LLDPE films include heat-seal layers, printing layers, rigid layers, barrier layers, and tie layers.

[0052] Polymers for heat-seal layers are generally thermoplastic polymers that can be easily melted and adhered under heat-seal conditions in forming, filling, and seal-packaging processes. These are often referred to as heat-seal polymers by those skilled in the art. Examples of common heat-seal polymers include LLDPE (produced using either a Ziegler-Natta catalyst or a metallocene catalyst), ethylene-vinyl acetate copolymers, and blends of these polymers. In many embodiments, the heat-seal polymer contains metallocene LLDPE.

[0053] In some embodiments, the heat-seal polymer has an average density of at least 0.90 g / cm 3 or at least 0.91 g / cm 3 . In some embodiments, the heat-seal polymer has an average density of at most 0.94 g / cm 3 , or at most 0.93 g / cm 3 , or at most 0.92 g / cm 3 .

[0054] In some embodiments, the heat-sealing polymer has a melt index (I2) of at least 0.2 g / 10 min, or at least 0.5 g / 10 min, or at least 0.7 g / 10 min, or at least 1 g / 10 min, or at least 2 g / 10 min. In some embodiments, the heat-sealing polymer has a melt index (I2) of at most 10 g / 10 min, or at most 5 g / 10 min, or at most 3 g / 10 min.

[0055] In some embodiments, the heat-sealing polymer has a melting temperature of at least 80 °C, or at least 85 °C, or at least 90 °C, or at least 100 °C. In some embodiments, the heat-sealing polymer has a melting temperature of at most 130 °C, or at most 125 °C, or at most 120 °C.

[0056] In some embodiments, the heat-sealing polymer has a seal start temperature (for a seal strength of 4 N / 15 mm) of at least 80 °C, or at least 85 °C, or at least 90 °C, or at least 95 °C. In some embodiments, the heat-sealing polymer has a seal start temperature (for a seal strength of 4 N / 15 mm) of at most 130 °C, or at most 120 °C, or at most 110 °C, or at most 105 °C.

[0057] In some cases, Ziegler-Natta polyethylene may have a higher density, a higher seal start temperature, and a lower melt index within the above ranges, while metallocene polyethylene may have a lower density, a lower seal start temperature, and a higher melt index within the above ranges.

[0058] In some embodiments, the heat-sealing polymer has a hot tack strength at 110 °C of at least 0.6 N / 15 mm, or at least 0.8 N / 15 mm, or at least 1 N / 15 mm, or at least 1.5 N / 15 mm. There is no desired maximum hot tack strength, but in some embodiments, a hot tack strength at 110 °C greater than 10 N / 15 mm or greater than 5 N / 15 mm is not required.

[0059] Examples of suitable heat-seal polymers include reinforced polyethylene polymers marketed under the trademark ELITE™, and certain LLDPE polymers marketed under the trademark DOWLEX™.

[0060] The printing layer will typically be on the surface of the multilayer film opposite the heat-seal layer. The polymer can be selected to have a good appearance, such as high gloss, and to provide a good surface for ink adhesion. Examples of common polymers in the printing layer include LLDPE derived from Ziegler-Natta or metallocene catalysts. Common printing layer polymers are marketed under the trademarks DOWLEX™ GM8051, DOWLEX™ TG2085B, DOWLEX™ GM8070, DOWLEX™ 2049, ELITE™ AT6501, and INNATE™ ST50.

[0061] The barrier layer can reduce the movement of gases, moisture, and / or flavor components through the multilayer film. Examples of common barrier polymers include ethylene vinyl alcohol, ethylene vinyl acetate, polyvinylidene chloride, polypropylene, polyamide, polyethylene terephthalate, and polyvinyl chloride. Polymers for the barrier layer are marketed under trademarks such as SARAN™, Eval, Ube Nylon-6, and Miramid.

[0062] The tie layer can improve the adhesion of different layers in the multilayer film, particularly when the different layers contain incompatible polymers. Examples of common tie layer polymers include ethylene acrylic acid copolymers and ethylene vinyl acetate copolymers. Examples of common tie layers are marketed under the trademarks BYNEL™, Plexar, EMAC, Surpass, and Novapol.

[0063] Coextrusion and Multilayer Films: The materials of the above name can be co-extruded by processes known for forming multilayer films. The materials can be melted in separate extruders. The molten materials are fed into an extrusion die. The die is designed to extrude each material as one or more separate continuous layers in the multilayer film.

[0064] In cast film extrusion, the die is a slot die, and the film is extruded onto a cooling roll, quenched, and wound up on the roll.

[0065] In blown film extrusion, the die is a circular die. Bubbles (such as air or nitrogen) are trapped inside the circular film between the die and a pair of downstream nip rollers. The film passes over the bubbles and is biaxially stretched before solidifying. The film is cooled, flattened, and wound onto a roll.

[0066] Examples of co-extrusion processes are LyondellBasell, A Guide to Polyolefin Film Extrusion, Publication 6047 / 1004 (available at lyb.com), LyondellBasell, How to Solve Blown Film Problems, Publication 6483 / 0559 (available at www.lyondellbasell.com), Qenos Pty, Ltd., Film Extrusion and Conversion - Technical Guide (July 2015) (available at qenos.com), Golghate et al., Adopting Best Practices in Blown Film Extrusion Process: Need of the Hour to Control Environmental Burdens, 3(1) International Journal of Industrial Engineering & Technology 63 - 80 (2013), and Goff et al., The Dynisco Extrusion Processors Handbook, 2nd Edition (available at www.dynisco.com).

[0067] In the process of the present invention, the conditions in the extruder (including the extrusion die) for the first LLDPE composition should be suitable to substantially decompose the free radical generator. The necessary conditions may depend on the free radical generator selected and the effectiveness of mixing in the extruder. In some embodiments, the first LLDPE composition achieves a temperature of at least 180°C, or at least 190°C, or at least 200°C, or at least 210°C, or at least 215°C. Generally, the temperature is low enough that the first LLDPE composition is not substantially decomposed. In some embodiments, the temperature does not exceed 250°C, or 240°C, or 230°C. In some embodiments, the first LLDPE composition maintains the selected temperature for at least 30 seconds, or at least 45 seconds, or at least 60 seconds; in some embodiments, the first LLDPE composition maintains the selected temperature for 15 minutes or less, or 10 minutes or less, or 5 minutes or less, or 3 minutes or less, or 2 minutes or less. Suitable conditions for decomposing the free radical generator are often achieved in extruders used in conventional multilayer film extrusion, and in some embodiments, no changes in existing procedures are required.

[0068] The product of the coextrusion process is a multilayer film that includes at least (1) a primary layer derived from a first LLDPE composition and (2) a second layer derived from a polymer composition and adhered directly and indirectly to the primary layer. In some embodiments, the second layer is a heat-seal layer containing a heat-seal polymer, as previously described. The heat-seal layer, if present, will generally form one surface of the multilayer film.

[0069] In some embodiments, the multilayer film further comprises a third polymer layer adhesively bonded directly or indirectly to the primary layer on the side opposite the second layer. For example, the multilayer film can include at least three layers including (1) a primary layer, (2) a heat seal layer adhesively bonded directly and indirectly to one side of the primary layer that forms one surface of the multilayer film, and (3) another surface layer adhesively bonded directly and indirectly to the primary layer on the side opposite the heat seal layer that forms the other surface of the multilayer film. In some embodiments, the other surface layer is a printed layer as described above.

[0070] In a structure of three or more layers, the primary layer is frequently an inner layer rather than a surface layer and is often referred to as the "core" layer.

[0071] In some embodiments, the multilayer film includes more layers, such as 5, 6, 7, 8, or 9 layers. For example, in addition to the three layers described above, the multilayer film can contain a barrier layer and one or more tie layers for promoting adhesion between the barrier layer and the surrounding layers. In some embodiments, the barrier layer and the tie layer are inner layers rather than surface layers.

[0072] In some embodiments, the multilayer film has a thickness of at least 10 μm, or at least 20 μm, or at least 30 μm. In some embodiments, the multilayer film has a thickness of up to 200 μm, or up to 150 μm, or up to 120 μm, or up to 100 μm.

[0073] In some embodiments, the primary layer constitutes at least 30%, or at least 40%, or at least 50%, or at least 60%, or at least 70%, or at least 80%, or at least 90% of the thickness of the multilayer film. In some embodiments, the layers other than the primary layer constitute at least 5%, or at least 10%, or at least 20%, or at least 30% of the thickness of the multilayer film. In some embodiments, the second layer constitutes at least 5%, or at least 10%, or at least 20% of the thickness of the multilayer film. In some embodiments, the third layer constitutes at least 5%, or at least 10%, or at least 20% of the thickness of the multilayer film.

[0074] The decomposition of the free radical generator during extrusion can change the properties of the first LLDPE composition in the primary layer. Without wishing to be bound by theory, the inventors hypothesize that this change results from the small amount of long chain branching introduced by the free radical generator. The resulting first LLDPE composition may be referred to as the extruded first LLDPE composition. · In some embodiments, the extruded first LLDPE composition has a weight average molecular weight (Mw Abs ) of at least 90,000 Da, or at least 110,000 Da, or at least 122,000 Da, or at least 125,000 Da, or at least 130,000 Da. In some embodiments, the extruded first LLDPE composition has a weight average molecular weight (Mw Abs ) of up to 200,000 Da, or up to 160,000 Da. · In some embodiments, the extruded first LLDPE composition has a molecular weight distribution (Mw Abs / Mn Abs ) of at least 4, or at least 4.5, or at least 5. In some embodiments, the extruded first LLDPE composition has a molecular weight distribution (Mw Abs / Mn Abs ) of up to 7, or up to 6, or up to 5.5. · In some embodiments, Mz for the extruded first LLDPE composition Abs / Mw Abs The ratio is at least 2.5, or at least 2.9, or at least 3.1, or at least 3.2. In some embodiments, Mz of the extruded first LLDPE composition Abs / Mw Abs The ratio is at most 5.0, or at most 4.0, or at most 3.5. · In some embodiments, Mz of the extruded first LLDPE composition Abs / Mw Abs The ratio is at least 5%, or at least 8%, or at least 10%, or at least 12%, or at least 15%, or at least 17% higher than the Mz / Mw ratio of the first LLDPE polymer before extrusion. In some embodiments, the Mz / Mw ratio of the extruded first LLDPE composition is at most 30%, or at most 25%, or at most 20% higher than the Mz / Mw ratio of the first LLDPE polymer before extrusion. · In some embodiments, the extruded first LLDPE composition has a complex viscosity (η 10 ) of 6000 Pa·s or less, or 5000 Pa·s or less, or 4900 Pa·s or less, or 4800 Pa·s or less, or 4700 Pa·s or less at a temperature of 190 °C and an angular frequency of 10 rad / s. In some embodiments, the extruded first LLDPE composition has a complex viscosity (η 10 ) of at least 4500 Pa·s or at least 4700 Pa·s at a temperature of 190 °C and an angular frequency of 10 rad / s. · In some embodiments, the extruded first LLDPE composition has a complex viscosity (η 0.1) has. In some embodiments, the extruded first LLDPE composition has a complex viscosity (η 0.1 ) of 15,000 Pa·s or less, or 12,000 Pa·s or less, or 11,000 Pa·s or less at a temperature of 190 °C and an angular frequency of 0.1 rad / s. · In some embodiments, the extruded first LLDPE composition has a complex viscosity ratio (η 0.1 / η 10 ) of at least 1.6, or at least 1.7, or greater than 1.7, or at least 1.75, or at least 1.8, or at least 1.85, or at least 1.9, or at least 1.95. In some embodiments, the extruded first LLDPE composition has a complex viscosity ratio (η 0.1 / η 10 ) of 4 or less, or 3 or less, or 2.5 or less. · In some embodiments, the complex viscosity (η 0.1 ) of the extruded first LLDPE composition (at a temperature of 190 °C and an angular frequency of 0.1 rad / s) is at least 5%, or at least 10%, or at least 15%, or at least 20%, or at least 25%, or at least 30%, or at least 35%, or at least 40% higher than the complex viscosity of the first LLDPE polymer before extrusion. In some embodiments, the complex viscosity (η 0.1 ) of the extruded first LLDPE composition (at a temperature of 190 °C and an angular frequency of 0.1 rad / s) is at most 100%, or at most 60% higher than the complex viscosity of the first LLDPE polymer before extrusion. · In some embodiments, the complex viscosity ratio (η 0.1 / η 10 ) of the extruded first LLDPE composition is at least 5%, or at least 10%, or at least 15%, or at least 20% higher than the complex viscosity ratio of the first LLDPE polymer before extrusion. There is no maximum value for the desired increase in the complex viscosity ratio, but in some embodiments, an increase exceeding 50% is unnecessary.

[0075] In some embodiments, the multilayer film of the present invention has a 2% secant modulus of at least 140 MPa, or at least 150 MPa, or at least 160 MPa, or at least 170 MPa. In some embodiments, the multilayer film of the present invention has a 2% secant modulus of at most 250 MPa, or at most 200 MPa, or at most 180 MPa.

[0076] In some embodiments, the multilayer film of the present invention has a puncture force of at least 1.5 N, or at least 1.55 N / μm, or at least 1.60 N / μm, or at least 1.65 N / μm per 1 μm of film thickness. In some embodiments, the multilayer film of the present invention has a puncture force of at most 5 N / μm or at most 3 N / μm. In some embodiments, the puncture force of the multilayer film of the present invention is at least 5%, or at least 10%, or at least 12% higher than the puncture force of a comparable film containing a comparable polymer extruded without a free radical generator in the primary layer.

[0077] In some embodiments, the multilayer film of the present invention has a dirt drop resistance of at least 5 g, or at least 6 g / μm, or at least 6.2 g / μm, or at least 6.5 g / μm, or at least 7 g / μm, or at least 7.5 g / μm per 1 μm of film thickness. In some embodiments, the multilayer film of the present invention has a dirt drop resistance of at most 20 g / μm or at most 10 g / μm. In some embodiments, the dirt drop resistance of the multilayer film of the present invention is at least 5%, or at least 10%, or at least 15%, or at least 20%, or at least 25% higher than the dirt drop resistance of a comparable film containing a comparable polymer extruded without a free radical generator in the primary layer.

[0078] In some embodiments, the multilayer film of the present invention has a haze of at most 25%, or at most 22%, or at most 20%, or at most 18%. There is no desired minimum level of haze (0%), but in many embodiments, a haze of less than 10% is not necessary.

[0079] Use of Multilayer Film The multilayer film of the present invention can be used in conventional form, fill, and seal processes such as vertical form, fill and seal (VFFS) processes or horizontal form, fill and seal (HFFS) processes. Examples of suitable processes are U.S. Patent Nos. 4,757,668, 4,807,420, 5,279,098, 5,540,035, and 5,533,322, and publications described in Vertical Form Fill and Seal, available on their website (www.rockwellautomation.com) published by Rockwell Automation Inc. Suitable equipment is commercially available.

[0080] The multilayer film of the present invention having an extruded primary layer can have improved packaging properties compared to similar packages containing unextruded polymers. In some embodiments, the modification substantially increases the bag drop strength of packages made using the multilayer film. In some embodiments, the modification substantially increases the heat seal strength of packages made using the multilayer film at elevated temperatures. In some embodiments, the film, when sealed and tested as described in the test method, can provide a seal strength within 10% (or 5%) of the maximum strength over a range of 5°C, or 10°C, or 15°C, or 20°C. A wide range of effective sealing temperatures is beneficial because a single film can provide strong seals for various devices operating at different temperatures.

[0081] The present invention is further illustrated by the following examples, which illustrate specific embodiments of the invention but do not limit the broad scope of the invention.

Examples

[0082] Test Method The parameters described in this application can be measured using the following measurement methods.

[0083] [Table 1]

[0084] Molecular weight Molecular weight / molecular weight distribution and Mark-Houwink plots for branched structure analysis are measured using triple detector gel permeation chromatography. The processes and equations utilized are described in U.S. Patent No. 8,871,887, which is incorporated by reference. For gel permeation chromatography (GPC) processes (conventional GPC, light scattering (LS) GPC, viscosity measurement GPC, and gpcBR), a triple detector gel permeation chromatography (3D-GPC or TDGPC) system is utilized. As this system, a Robotic Assistant Delivery (RAD) high temperature GPC system can be mentioned [Other suitable high temperature GPC equipment includes Waters (Milford, Mass.) model 150C high temperature chromatograph, Polymer Laboratories (Shropshire, UK) models 210 and 220, and Polymer Char GPC-IR (Valencia, Spain)], which is equipped with a Precision Detectors (Amherst, Mass.) 2-angle laser light scattering (LS) detector model 2040, an IR4 infrared detector from Polymer ChAR (Valencia, Spain), and a 4-capillary solution viscometer (DP) [Other suitable viscometers include the Viscotek (Houston, Tex.) 150R 4-capillary solution viscometer (DP)]. GPC having at least one of these latter two independent detectors and the former detector can be referred to as "3D-GPC" or "TDGPC", but the term "GPC" generally refers to conventional GPC only. Data collection is performed using software, for example, Polymer Char GPC-IR. This system also includes, for example, an online solvent degassing device from Polymer Laboratories.

[0085] The eluate from the GPC column set flows through each detector arranged in series in the order of an LS detector, an IR4 detector, and then a DP detector. A systematic method for determining the multiple detector offset is carried out in a manner consistent with that published by Balke, Mourey, et.al. (Mourey and Balke, Chromatography Polym. Chapter 12, (1992)) (Balke, Thitiratsakul, Lew, Cheung, Mourey, Chromatography Polym. Chapter 13, (1992)). Use an Olexis LS column. Operate the carousel section of the sample at 140 °C and the column section at 150 °C. Prepare the sample at a concentration of 0.1 gram of polymer in 50 milliliters of solvent. The chromatography solvent and the sample preparation solvent are 1,2,4-trichlorobenzene (TCB) containing 200 ppmw of 2,6-di-tert-butyl-4-methylphenol (BHT). Sparge the solvent with nitrogen. Gently stir the polymer sample at 160 °C for 4 hours. The injection volume is 200 microliters. Set the flow rate through the GPC to 1 mL / min.

[0086] In conventional GPC, an IR4 detector is used and the GPC column set is calibrated by measuring 21 narrow molecular weight distribution polystyrene standards. The molecular weights of the standards range from 580 g / mol to 8,400,000 g / mol and the standards are contained in six "cocktail" mixtures. Each standard mixture had at least an order of magnitude interval between individual molecular weights. Prepare the polystyrene standards at 0.025 g in 50 mL of solvent for molecular weights above 1,000,000 g / mol and 0.05 g in 50 mL of solvent for molecular weights below 1,000,000 g / mol. Dissolve the polystyrene standards by gently stirring at 80 °C for 30 minutes. Calculate the number average molecular weight, weight average molecular weight, and z average molecular weight from the formula as described, for example, in U.S. Patent No. 8,871,887.

[0087] For LS GPC, the PDI2040 detector model 2040 of the precision detector is used. For 3D-GPC, the absolute weight-average molecular weight is calculated from the formula as described, for example, in U.S. Patent No. 8,871,887. The gpcBR branching index is determined by calibrating the light scattering, viscosity, and concentration detectors and subtracting the baseline. Then, an integration window is set for the integration of the low molecular weight retention volume range in the light scattering and viscometer chromatograms indicating the presence of the detectable polymer from the refractive index chromatogram. Linear polyethylene standards are used to establish the Mark-Houwink constants for polyethylene and polystyrene. For example, as described in U.S. Patent No. 8,871,887, the constants are used to construct two linear references for the conventional calibration of polyethylene molecular weight and polyethylene intrinsic viscosity as a function of elution volume. To determine the gpcBR branching index, the molecular weight of the sample is determined using the light scattering elution area of the sample polymer. For example, the analysis is performed using the final Mark-Houwink constants as described in U.S. Patent No. 8,871,887.

[0088] Vinyl unsaturation The sample is prepared by adding approximately 130 mg of the sample to 3.25 g of 50 / 50 tetrachloroethane-d2 / perchloroethylene in a 10 mm NMR tube of Norell 1001-7 together with 0.001 M Cr(AcAc)3. The sample is purged by passing nitrogen through the solvent for approximately 5 minutes via a pipette inserted into the tube, capped, sealed with Teflon tape, and then soaked overnight at room temperature to facilitate dissolution of the sample. The sample is heated at 115 °C and vortexed to ensure homogeneity.

[0089] 1H NMR is performed on a Bruker AVANCE 400 MHz spectrometer equipped with a Bruker Dual DUL high-temperature CryoProbe at a sample temperature of 120 °C. Two experiments are carried out to obtain spectra: a control spectrum for quantifying total polymer protons and a double presaturation experiment, which suppresses strong polymer backbone peaks and enables a highly sensitive spectrum for end-group quantification. This control is carried out with a ZG pulse, 4 scans, AQ 1.64 s, D1 (relaxation delay) 14 s. The double presaturation experiment is carried out with a modified pulse sequence, 100 scans, DS 4, AQ 1.64 s, D1 (presaturation time) 1 s, D13 (relaxation delay) 13 s. The region from 4.95 to 5.15 ppmw is integrated to determine the vinyl content.

[0090] Polymer viscosity The sample is compression molded in air at 190 °C and a pressure of 25,000 pounds for 6.5 minutes, and then the plaque is cooled on an experimental bench. The thickness of the plaque is approximately 3 mm. Constant temperature frequency sweep measurements are performed with an ARES strain-controlled parallel plate rheometer (TA Instruments) equipped with 25 mm parallel plates under a nitrogen purge. For each measurement, the rheometer is thermally equilibrated for at least 30 minutes before setting the gap to zero. The sample is placed on the plate and melted at 190 °C for 5 minutes. Then the plate is closed to 2 mm, the sample is trimmed, and then the test is started. This method incorporates an additional 5-minute delay to allow for temperature equilibration. This experiment is carried out at 190 °C, at 5 points per decade, over a frequency range of 0.1 to 100 rad / s. The strain amplitude is constant at 10%. The stress response is analyzed with respect to the amplitude and phase, from which the storage modulus (G’), loss modulus (G”), complex modulus (G * *), dynamic complex viscosity (η * *), and tan(δ) or tandelta are calculated.

[0091] Masterbatch: A masterbatch (MB-1) containing 1000 ppmw of Trigonox 301 free radical generator dispersed in DOW (trademark) LDPE 4016 is prepared. The masterbatch is produced on a ZSK-26 mm Coperian co-rotating twin screw extruder (TSE) under a nitrogen atmosphere. The extruder is an 11-barrel, 44 L / D electrically heated water-cooled machine with a maximum RPM of 1200. The LDPE is fed into barrel 1 at a rate of 60 pounds per hour via a K-Tron KQX gravimetric feeder. A 1:1 solution of the free radical generator and mineral oil is injected into barrel 9 via a 1000D ISCO syringe pump and a backpressure injection valve to obtain an active free radical generator with a target concentration of 1000 ppmw. The polymer melt is then fed through a transfer piece and a polymer diverter valve to a two-hole, 0.110-inch diameter die in water to produce pellets at approximately 37 counts / g.

[0092] Multilayer film Example 1: A 5-layer film is co-extruded on a Reifenhauser extruder having a blow-up ratio (B.U.R.) of 2.5, a temperature range of 185 °C to 200 °C, a thickness of 32 μm, and an output rate of approximately 450 kg / h. The film contains DOWLEX (trademark) TG 2085B linear low density polyethylene, the MB-1 masterbatch, and the MB901250BX processing aid from Ampacet. Each layer constitutes 20% by volume of the film. The content of each layer is shown in Table 2.

[0093]

Table 2

[0094] Example 2: A 3-layer film is co-extruded using a Collin medical line extruder having an 80 mm die, a 1.8 mm die gap, a B.U.R. of 2.5:1, a thickness of 100 μm, and an output rate of approximately 1.50 kg / h. The temperature inside the die is 230 °C. The film contains DOWLEX™ GM8051 linear low density polyethylene, MB-1, and the processing aid MB901250BX from Ampacet. The content of each layer is shown in Table 3.

[0095] Example 3: As described in Example 2, a 3-layer film is co-extruded using a higher level of MB-1 masterbatch. The content of each layer is shown in Table 3.

[0096] [Table 3]

[0097] Comparative Example 1: A 5-layer film is co-extruded as described in Example 1, except that the film contains the EB853 / 72 LDPE polymer (commercially available from Braskem) in the proportions shown in Table 4 instead of the MB-1 masterbatch.

[0098] [Table 4]

[0099] Comparative Example 2: A 3-layer film is co-extruded as described in Example 2, except that no MB-1 masterbatch is used and the die temperature is 235 °C. The proportion of the components is shown in Table 5.

[0100] [Table 5]

[0101] Test The mechanical properties of the 5-layer film from Example 1 and the 5-layer film from Comparative Example 1 are measured using the procedures in the test method. The results are shown in Table 6.

[0102]

Table 6

[0103] The properties of the three - layer films and their compositions from Examples 2 and 3, and the three - layer film and its composition from Comparative Example 2 are measured using the procedures in the test method. The results are shown in Table 7.

[0104]

Table 7

[0105] Using the multilayer films prepared in Example 2 of the present invention, Example 3 of the present invention, and Comparative Example 2, and using the sealing procedure in ASTM F2029, a number of heat seals are performed while raising the temperature. The seals are cooled for 40 hours and then the seal strength is tested using the procedure in the test method. The results are shown in Table 8 and Figure 1. (In Figure 1, Example 2 of the present invention is referred to as "the present invention 2.1", and Example 3 of the present invention is referred to as "the present invention 2.2". The results show that the film of the present invention maintains strong seals over a wide range of seal temperatures, while the seals using the comparative film are strong only in a narrow temperature range and the seal strength decreases when the temperature exceeds the optimum temperature.

[0106]

Table 8

[0107] The hot - tack strength of the seals is tested at increasing temperatures using the multilayer films prepared in Example 2 of the present invention, Example 3 of the present invention, and Comparative Example 2 and using the hot - tack test described in the test method. The results are shown in Table 9 and Figure 2. (In Figure 2, Example 2 of the present invention is referred to as "the present invention 2.1", and Example 3 of the present invention is referred to as "the present invention 2.2".

[0108]

Table 9

Claims

1. It is a multilayer film, (a) A primary layer comprising an extruded first LLDPE composition comprising at least 85 weight percent of the first LLDPE polymer, wherein the extruded first LLDPE composition has a complex viscosity ratio (η) of at least 1.7 with respect to the complex viscosity measured at 190°C and angular frequencies of 0.1 rad / s and 10 rad / s. ０．１ / η １０ (2) the ratio of 2.9 to 4.0 (Mz Ａｂｓ / Mw Ａｂｓ A primary layer having, (b) A multilayer film comprising a second layer containing a polymer composition.

2. The multilayer film according to claim 1, wherein the second layer comprises a heat-seal polymer.

3. (c) The multilayer film according to claim 1, further comprising a third layer of polymer directly or indirectly bonded to the primary layer opposite the second layer.

4. The extruded first LLDPE composition has a complex viscosity ratio (η) of at least 1.8 for the complex viscosity measured at 190°C and angular frequencies of 0.1 rad / s and 10 rad / s. ０．１ / η １０ A multilayer film according to claim 1, having the following characteristics:

5. The extruded first LLDPE composition has a complex viscosity ratio (η) of at least 1.9, with respect to the complex viscosity measured at 190°C and angular frequencies of 0.1 rad / s and 10 rad / s. ０．１ / η １０ A multilayer film according to claim 1, having the following characteristics:

6. The extruded first LLDPE composition has a complex viscosity (η ０．１ ), measured at 190 ° C. and an angular frequency of 0.1 rad / s, of at least 8000 Pa · s, The multilayer film according to claim 1.

7. The extruded first LLDPE composition has a complex viscosity of at least 9000 Pa·s (η) measured at 190°C and an angular frequency of 0.1 rad / s. ０．１ A multilayer film according to claim 1, having the following characteristics:

8. The extruded first LLDPE composition exhibits a complex viscosity of up to 5000 Pa·s (η) as measured at 190°C and an angular frequency of 10 rad / s. １０ A multilayer film according to claim 1, having the following characteristics:

9. The multilayer film according to claim 1, wherein the film has a puncture force of at least 1.60 N per 1 μm of film thickness when measured by ASTM D5748 at 250 mm / min.

10. The multilayer film according to claim 1, wherein the film has a dirt drop resistance of at least 6 g per 1 μm of film thickness, as measured by ASTM 17-9 - Method A.

11. A process for producing a multilayer film according to any one of claims 1 to 10, comprising: (1) a step of melting (a) a first LLDPE composition and (b) a polymer composition in a separate extruder; and (2) a step of co-extruding the first LLDPE composition and the polymer composition under conditions suitable for forming a multilayer film comprising a primary layer containing an extruded first LLDPE composition derived from the first LLDPE composition and a second layer containing the polymer composition, (a) Before extrusion molding, the first LLDPE composition comprises (i) at least 85 weight percent of a first LLDPE polymer containing at least 0.20 vinyl groups per 1000 carbon atoms, and (ii) 5 ppmw to 1000 ppmw of a free radical generator. (b) A process in which the conditions inside the extruder are suitable for substantially decomposing the free radical generator.

12. The process according to claim 11, wherein the free radical generating agent is a cyclic peroxide.

13. The process according to claim 11, wherein the first LLDPE composition contains 10 to 100 ppmw of a free radical generator before extrusion molding.

14. The process according to claim 11, wherein, before extrusion molding, the first LLDPE composition comprises (1) a first LLDPE polymer, and (2) a masterbatch containing a carrier polymer which is an LLDPE polymer or an LDPE polymer, and 10 ppmw to 1000 ppmw of the free radical generator.

15. The extruded first LLDPE composition in the multilayer film has a complex viscosity ratio (η) that is at least 10 percent higher than the complex viscosity ratio of the first LLDPE polymer before extrusion. ０．１ / η １０ The process according to claim 11, comprising:

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