Polyethylene polymer composition and article made therefrom

Abstract

The polymer composition comprises a polyethylene polymer having a melt relaxation ratio of 1.5 or greater, and a salt of a branched alkylphosphonic acid. A method for molding a thermoplastic polymer composition includes the steps of: (a) providing an apparatus including a die and a mold cavity; (b) providing the polymer composition described above; (c) heating the polymer composition to melt the polymer composition; (d) extruding the molten polymer composition through the die to form a parison; (e) capturing the parison in the mold cavity; (f) blowing a pressurized fluid into the parison to expand it and conform to the interior surface of the mold cavity; (g) allowing the molded article to cool so that it retains its shape; and (h) removing the molded article from the mold cavity.

Description

Technical Field of the Invention

[0001]

[0001] This application relates to polymer compositions containing salts of branched alkylphosphonic acids, such as polyethylene polymer compositions, and articles made from such polymer compositions (e.g., blown films). The salts of branched alkylphosphonic acids are thought to function as nucleating agents for the polymer. Background

[0002]

[0002] Some nucleating agents for thermoplastic polymers are known in the art. These nucleating agents generally function by forming nuclei or providing sites for crystal formation and / or growth when the thermoplastic polymer solidifies from the molten state. The nuclei or sites provided by the nucleating agent allow crystals to form at a higher temperature and / or at a faster rate in the cooled polymer than in a new non-nucleating thermoplastic polymer. When present, such an effect can enable the processing of nucleating thermoplastic polymer compositions in a shorter cycle time than a new non-nucleating thermoplastic polymer. Alternatively, the controlled nucleation induced by the nucleating agent can result in a polymer having a crystal structure different from that resulting from the purely self-nucleated crystallization of the polymer (i.e., polymer crystallization occurring in the absence of a heterogeneous nucleating agent). Such differences in crystal structure can result in polymers having different physical properties that may be desirable for certain applications.

[0003]

[0003] Polymer nucleating agents may function in a similar manner, but not all nucleating agents are created equal. For example, nucleating agents for polyethylene polymers are known in the art, but relatively few of these nucleating agents have been shown to improve the physical properties of polyethylene polymers to a commercially significant extent. In particular, there are few nucleating agents that can improve the barrier properties of articles made from polyethylene polymers (e.g., reduce water vapor and / or oxygen permeability).

[0004]

[0004] Due to its excellent shelf life, product protection, product display, and low cost, polyethylene film has established a major position in the food packaging industry. The characteristics of the food to be packaged determine the optimal barrier performance of the packaging material. While some foods require a high-barrier material for optimal barrier, others require a low-barrier material. For example, dry foods such as cereals, crackers, cookies, and powder products require packaging materials with a high barrier against water vapor or moisture, while poultry products require packaging materials with a high barrier against oxygen. Thus, by identifying additives that can be used to improve the barrier properties of polyethylene-based films, manufacturers can produce various polyethylene films that meet the barrier requirements imposed by various packaged goods. Such additives are even more desirable if the manufacturer can produce films with desirable optical properties such as low haze, high transparency, and / or high gloss.

[0005]

[0005] Furthermore, in high-barrier applications, polyethylene films often incorporate barrier layers of different materials (such as ethylene vinyl alcohol copolymers or polyamides). These barrier layers further complicate the manufacturing operation, increase the cost and expense of the film, and compromise the recyclability of the film. Thus, by improving the barrier of polyethylene, "monomaterial" packaging can be enabled that provides good barrier levels without incorporating these different barrier layers.

[0006]

[0006] From the foregoing perspectives, there remains a need for additives (such as nucleating agents) that can produce polyethylene polymer compositions that exhibit a more desirable combination of physical properties, such as high barriers against water vapor and / or oxygen, low haze, high transparency, and / or high gloss. The additives and polymer compositions described herein are intended to address such needs. Brief Summary of the Invention

[0007]

[0007] In a first aspect, the present invention provides a polymer composition comprising (a) a polyethylene polymer composition having a melt relaxation ratio of 1.5 or more; and (b) a salt of a branched alkylphosphonic acid.

[0008]

[0008] In a second aspect, the present invention provides a method for molding a thermoplastic polymer composition. The method comprises (a) preparing an apparatus comprising a die and a mold cavity, the mold cavity having an inner surface that defines the shape of the molded article; (b) preparing a polymer composition comprising (i) a polyethylene polymer composition having a melt relaxation ratio of 1.5 or more; and (ii) a salt of a branched alkylphosphonic acid; (c) heating the polymer composition to a temperature sufficient to melt the polymer composition so that the polymer composition can be extruded through the die; (d) extruding the molten polymer composition through the die to form a parison; (e) capturing the parison within the mold cavity; (f) blowing a pressurized fluid into the parison under a pressure sufficient to expand the parison so that the parison conforms to the inner surface of the mold cavity and produces a molded article; (g) cooling the molded article to a temperature at which the thermoplastic polymer composition at least partially solidifies so that the molded article retains its shape; and (h) removing the molded article from the mold cavity and includes. Detailed description of the invention

[0009]

[0009] In a first aspect, the present invention provides a polymer composition comprising (a) a polyethylene polymer composition; and (b) a salt of a branched alkylphosphonic acid. The polyethylene polymer composition preferably has a melt relaxation ratio of 1.5 or more (as described and defined below).

[0010] As described above, the polymer composition includes a polyethylene polymer. The polymer composition may include one type of polyethylene polymer or a mixture of two or more different polyethylene polymers, and the term "polyethylene polymer composition" is used herein to broadly refer to a composition containing one type of polyethylene polymer or a mixture of two or more different polyethylene polymers. Suitable polyethylene polymers include, but are not limited to, low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene, and combinations thereof. In certain embodiments, the thermoplastic polymer is selected from the group consisting of linear low density polyethylene, high density polyethylene, and mixtures thereof. In another preferred embodiment, the thermoplastic polymer is high density polyethylene.

[0011]

[0011] Suitable high density polyethylene polymers for use in the present invention generally have a density greater than about 930 kg / m 3 (e.g., greater than about 940 kg / m 3 greater than, about 941 kg / m 3 or more, about 950 kg / m 3 or more, or about 955 kg / m 3 or more). There is no upper limit to the suitable density of the polymer, but high density polyethylene polymers typically have a density less than about 980 kg / m 3 (e.g., less than about 975 kg / m 3 less than or about 970 kg / m 3 less than). Thus, in a preferred embodiment, the high density polyethylene polymer has a density of about 930 kg / m 3 to about 980 kg / m 3 (e.g., about 940 kg / m 3 to about 980 kg / m 3 , about 941 kg / m 3 to about 980 kg / m 3 , about 950 kg / m 3 to about 980 kg / m 3 , or about 955 kg / m 3 to about 980 kg / m 3 ), about 930 kg / m 3 to about 975 kg / m3 (e.g., about 940 kg / m 3 ~ about 975 kg / m 3 , about 941 kg / m 3 ~ about 975 kg / m 3 , about 950 kg / m 3 ~ about 975 kg / m 3 , or about 955 kg / m 3 ~ about 975 kg / m 3 ), or about 930 - about 970 kg / m 3 (e.g., about 940 kg / m 3 ~ about 970 kg / m 3 , about 941 kg / m 3 ~ about 970 kg / m 3 , about 950 kg / m 3 ~ about 970 kg / m 3 , or about 955 kg / m 3 ~ about 970 kg / m 3 ) and has a density of

[0012]

[0012] The high-density polyethylene polymer suitable for use in the present invention can be either a homopolymer of ethylene or a copolymer with one or more α-olefins. Suitable α-olefins include, but are not limited to, 1-butene, 1-hexene, 1-octene, 1-decene, and 4-methyl-1-pentene. The comonomer can be present in the copolymer in any suitable amount, e.g., in an amount of about 5 wt% or less (e.g., about 3 mol% or less). As will be understood by those skilled in the art, the amount of comonomer suitable for the copolymer depends greatly on the end use of the copolymer and the required or desired polymer properties indicated by that end use.

[0013]

[0013] The high-density polyethylene polymers suitable for use in the present invention can be produced by any suitable method. For example, the polymers can be produced by a free radical process using very high pressures, as described, for example, in U.S. Patent No. 2,816,883 (Larchar et al.), but the polymers are typically produced by a "low pressure" catalyst process. In this context, the term "low pressure" is used to describe a process carried out at a pressure of less than 6.9 MPa (e.g., 1,000 psig), for example 1.4 to 6.9 MPa (200 to 1,000 psig). Examples of suitable low pressure catalyst processes include solution polymerization (i.e., a process in which polymerization is carried out using a solvent for the polymer), slurry polymerization (i.e., a process in which polymerization is carried out using a hydrocarbon liquid in which the polymer does not dissolve or swell), gas phase polymerization (e.g., a process in which polymerization is carried out without using a liquid medium or diluent), or staged reactor polymerization, but are not limited thereto. Suitable gas phase polymerization processes also include so-called "condensation mode" or "supercondensation mode" processes in which a liquid hydrocarbon is introduced into the fluidized bed to increase the absorption of heat generated during the polymerization process. In these condensation mode and supercondensation mode processes, the liquid hydrocarbon is typically condensed in the recycle stream and reused in the reactor. The staged reactor process can utilize a combination of slurry process reactors (tanks or loops) connected in series, parallel, or a combination of series or parallel, such that the catalyst (e.g., a chromium catalyst) is exposed to two or more sets of reaction conditions. The staged reactor process can also be carried out by combining two loops in series, combining one or more tanks and loops in series, or using a plurality of gas phase reactors in series or in a loop gas phase configuration. Because of its ability to expose the catalyst to different sets of reactor conditions, the staged reactor process is often used to produce multimodal polymers, such as those discussed below. Suitable methods also include those in which a prepolymerization step is carried out. In this prepolymerization step, the catalyst is typically exposed to a cocatalyst and ethylene under mild conditions in a separate, smaller reactor and the polymerization reaction is allowed to proceed until the catalyst contains a relatively small amount (e.g., about 5% to about 30% of the total weight) of the resulting composition.Next, this prepolymerization catalyst is introduced into a large-scale reactor in which polymerization is to be carried out.

[0014]

[0014] The high-density polyethylene polymers suitable for use in the present invention can be produced using any suitable catalyst or combination of catalysts. Suitable catalysts include transition metal catalysts such as supported reduced molybdenum oxide, cobalt molybdate supported on alumina, chromium oxide and transition metal halides. Chromium oxide catalysts are typically produced by impregnating a chromium compound into a porous high surface area oxide support such as silica and then calcining it at 500-900 °C in dry air. Thereby, chromium is converted into a hexavalent surface chromium ester or dichromic acid ester. Chromium oxide catalysts can be used in combination with metal alkyl cocatalysts such as alkyl boron, alkyl aluminum, alkyl zinc and alkyl lithium. Examples of supports for chromium oxide include silica, silica-titania, silica-alumina, alumina and aluminophosphate. Further examples of chromium oxide catalysts include low-valent organic chromium compounds such as bis(allylene)Cr 0 , allyl Cr 2+ and Cr 3+ , Cr 2+ and Cr 4+ beta-stabilized alkyls, as well as bis(cyclopentadienyl)Cr 2+Examples of catalysts produced by depositing on a chromium oxide catalyst, such as those described above. Suitable transition metal catalysts also include supported chromium catalysts, such as those based on chromocene or silyl chromates (e.g., bis(trisphenylsilyl) chromate). These chromium catalysts can be supported on any suitable high surface area carrier, such as those described above for chromium oxide catalysts, and typically silica is used. Supported chromium catalysts can also be used in combination with a cocatalyst, such as the metal alkyl cocatalysts listed above for chromium oxide catalysts. Suitable transition metal halide catalysts include titanium(III) halides (e.g., titanium(III) chloride), titanium(IV) halides (e.g., titanium(IV) chloride), vanadium halides, zirconium halides, and combinations thereof. These transition metal halides are often supported on a high surface area solid, such as magnesium chloride. Transition metal halide catalysts are typically used in combination with an aluminum alkyl cocatalyst, such as trimethylaluminum (i.e., Al(CH3)3) or triethylaluminum (i.e., Al(C2H5)3). These transition metal halides can also be used in a staged reactor process. Suitable catalysts also include metallocene catalysts, such as cyclopentadienyl titanium halides (e.g., cyclopentadienyl titanium chloride), cyclopentadienyl zirconium halides (e.g., cyclopentadienyl zirconium chloride), cyclopentadienyl hafnium halides (e.g., cyclopentadienyl hafnium chloride), and combinations thereof. Transition metal-based metallocene catalysts complexed with indenyl or fluorenyl ligands are also known and can be used to produce high density polyethylene polymers suitable for use in the present invention. The catalyst typically contains a plurality of ligands, which may be substituted with various groups (e.g., n-butyl groups) or linked with a bridging group, such as -CH2CH2- or >SiPh2. Metallocene catalysts are typically used in combination with a cocatalyst, such as methylaluminoxane (i.e., (Al(CH3) x O y )n It is used in combination with. Other cocatalysts include those described in U.S. Patent No. 5,919,983 (Rosen et al.), U.S. Patent No. 6,107,230 (McDaniel et al.), U.S. Patent No. 6,632,894 (McDaniel et al.) and U.S. Patent No. 6,300,271 (McDaniel et al.). Other "single-site" catalysts suitable for use in the production of high-density polyethylene include diimine complexes, such as those described in U.S. Patent No. 5,891,963 (Brookhart et al.).

[0015]

[0015] The high-density polyethylene polymers suitable for use in the present invention can have any suitable molecular weight (e.g., weight-average molecular weight). For example, the weight-average molecular weight of high-density polyethylene can be from 20,000 g / mol to about 1,000,000 g / mol or more. As will be understood by those skilled in the art, the suitable weight-average molecular weight of high-density polyethylene will depend, at least in part, on the specific use or end use for which the polymer is intended. For example, high-density polyethylene polymers intended for blow molding applications can have a weight-average molecular weight of from about 100,000 g / mol to about 1,000,000 g / mol. High-density polyethylene polymers intended for pipe or film applications can have a weight-average molecular weight of from about 100,000 g / mol to about 500,000 g / mol. High-density polyethylene polymers intended for injection molding applications can have a weight-average molecular weight of from about 20,000 g / mol to about 80,000 g / mol. High-density polyethylene polymers intended for wire insulation, cable insulation, tape or filament applications can have a weight-average molecular weight of from about 80,000 g / mol to about 400,000 g / mol. High-density polyethylene polymers intended for rotational molding applications can have a weight-average molecular weight of from about 50,000 g / mol to about 150,000 g / mol.

[0016]

[0016] The high-density polyethylene polymers suitable for use in the present invention can also have any suitable polydispersity, defined as the value obtained by dividing the weight-average molecular weight of the polymer by the number-average molecular weight of the polymer. For example, the high-density polyethylene polymer can have a polydispersity of greater than 2 to about 100. As will be appreciated by those skilled in the art, the polydispersity of a polymer is greatly influenced by the catalyst system used to produce the polymer, and in the case of metallocene and other "single-site" catalysts, generally polymers with relatively low polydispersity and narrow molecular weight distribution are produced, while with other transition metal catalysts (e.g., chromium catalysts), polymers with higher polydispersity and broader molecular weight distribution are produced. The high-density polyethylene polymers suitable for use in the present invention can also have a multimodal (e.g., bimodal) molecular weight distribution. For example, the polymer can have a first fraction with a relatively low molecular weight and a second fraction with a relatively high molecular weight. The difference between the weight-average molecular weights of the fractions of the polymer can be any suitable amount. In fact, the difference between the weight-average molecular weights need not be large enough for the two distinct molecular weight portions to be resolved using gel permeation chromatography (GPC). However, in certain multimodal polymers, the difference between the weight-average molecular weights of the portions can be large enough for two or more distinct peaks to be resolved from the GPC curve of the polymer. In this context, the term "distinct" does not necessarily mean that the portions of the GPC curve corresponding to each part do not overlap, but simply means that distinct peaks (i.e., maxima) for each part can be resolved from the GPC curve of the polymer. The multimodal polymers suitable for use in the present invention can be produced using any suitable method. As described above, multimodal polymers can be produced using a stepwise reactor method. A suitable example is a stepwise solution process incorporating a series of stirred tanks. Alternatively, multimodal polymers can be produced in a single reactor using a combination of catalysts designed to produce polymers each having a different weight-average molecular weight.

[0017]

[0017] The molecular weight distribution of the polymer can also be characterized by measuring and comparing the melt flow index (or melt flow rate) of the polymer under different conditions to obtain a flow rate ratio (FRR). This method is described, for example, in Procedure D of ASTM Standard D1238 entitled "Standard Test Method for Melt Flow Rates of Thermoplastics by Extrusion Plastometer". Preferably, the FRR is calculated using the melt flow index (MFI 21.6 ) measured using a 21.6 kg load as specified in the standard, and the melt flow index (MFI 2.16 ) measured using a 2.16 kg load as specified in the standard. Both melt flow indices are measured at a temperature of 190 °C as specified in the standard. The high density polyethylene polymer used in the polymer composition can have any suitable FRR. Preferably, the high density polyethylene polymer has an FRR (MFI 21.6 / MFI 2.16 ) of about 65 or less. More preferably, the high density polyethylene polymer has an FRR (MFI 21.6 / MFI 2.16 ) of about 40 or less or about 20 or less.

[0018]

[0018] The high-density polyethylene polymers suitable for use in the present invention can have any suitable melt flow index. For example, the high-density polyethylene polymers can have a melt flow index of from about 0.01 dg / min to about 50 dg / min (e.g., from about 0.01 dg / min to about 40 dg / min). Similar to the weight average molecular weight, those skilled in the art understand that the suitable melt flow index of the high-density polyethylene polymers depends, at least in part, on the specific use or end use for which the polymer is intended. Thus, for example, high-density polyethylene polymers intended for blow molding applications can have a melt flow index of from about 0.01 dg / min to about 1 dg / min. High-density polyethylene polymers intended for blown film applications can have a melt flow index of from about 0.5 dg / min to about 50 dg / min (e.g., from about 1 dg / min to about 10 dg / min, from about 1 dg / min to about 5 dg / min, or from about 0.5 dg / min to about 3 dg / min). High-density polyethylene polymers intended for cast film applications can have a melt flow index of from about 2 dg / min to about 10 dg / min. High-density polyethylene polymers intended for pipe applications can have a melt flow index of from about 2 dg / min to about 40 dg / min (measured at 190 °C with a 21.6 kg load). High-density polyethylene polymers intended for injection molding applications can have a melt flow index of from about 2 dg / min to about 80 dg / min. High-density polyethylene polymers intended for rotational molding applications can have a melt flow index of from about 0.5 dg / min to about 10 dg / min. High-density polyethylene polymers intended for tape applications can have a melt flow index of from about 0.2 dg / min to about 4 dg / min. High-density polyethylene polymers intended for filament applications can have a melt flow index of from about 1 dg / min to about 20 dg / min. The melt flow index of the polymer is measured using ASTM standard D1238-04c.

[0019]

[0019] The high-density polyethylene polymers suitable for use in the present invention generally do not contain a large amount of long-chain branches. The term "long-chain branch" is used to refer to a branch attached to the polymer chain and is of a length sufficient to affect the rheology of the polymer (e.g., a branch having a length of about 130 or more carbon atoms). If desired for the use in which the polymer is employed, the high-density polyethylene polymer may contain a small amount of long-chain branches. However, the high-density polyethylene polymers suitable for use in the present invention typically contain very few long-chain branches (e.g., about 1 long-chain branch per 10,000 carbons, less than about 0.5 long-chain branches per 10,000 carbons, less than about 0.1 long-chain branches per 10,000 carbons or less than about 0.01 long-chain branches per 10,000 carbons).

[0020]

[0020] Also, the degree of long-chain branching in the polymer can be characterized using rheological methods (see, for example, R.N. Shroff and H. Mavridis, "Long-Chain-Branching Index for Essentially Linear Polyethylenes", Macromolecules, Vol. 32(25), pp. 8454 - 8464(1999)). In particular, the long-chain branching index (LCBI) is a rheological index used to characterize relatively low levels of long-chain branching and is defined as follows:

[0021]

Equation

[0022] In the formula, η0 is the limiting zero-shear viscosity at 190 °C (expressed in poise), and [η] is the intrinsic viscosity in trichlorobenzene at 135 °C (expressed in dL / g). LCBI is based on the observation that when the level of long-chain branching in an otherwise linear polymer is low, the melt viscosity η0 increases significantly without a change in the intrinsic viscosity [η]. The higher the LCBI, the greater the number of long-chain branches per polymer chain. Preferably, the high-density polyethylene polymer used in the polymer composition has an LCBI of about 0.5 or less, about 0.3 or less, or about 0.2 or less.

[0023]

[0021] In a preferred embodiment, the polymer composition comprises a blend of two or more high-density polyethylene polymer compositions. In a preferred embodiment comprising two high-density polyethylene polymer compositions, the first high-density polyethylene polymer composition has a density of about 950 kg / m 3 to about 975 kg / m 3 (preferably 950 kg / min 3 to 960 kg / min 3 ), and the second high-density polyethylene polymer composition has a density of about 950 kg / m 3 to about 970 kg / m 3 (preferably 955 kg / m 3 to 965 kg / m 3) has a density. The melt flow index of the first high-density polyethylene polymer composition (determined according to ASTM D 1238 at 190 °C using a 2.16 kg load) is preferably greater than 5 dg / min (more preferably about 15 dg / min to about 30 dg / min). Further, the melt flow index of the first high-density polyethylene polymer composition is preferably at least 10 times greater than the melt flow index of the second high-density polyethylene polymer composition. The melt flow index of the second high-density polyethylene polymer composition (determined according to ASTM D 1238 at 190 °C using a 2.16 kg load) is preferably about 0.1 dg / min to about 2 dg / min (more preferably about 0.8 dg / min to about 2 dg / min). The first high-density polyethylene polymer composition can have any suitable polydispersity, but the polydispersity (determined by gel permeation chromatography according to ASTM D 6474-99) is preferably about 2 to about 20, more preferably about 2 to about 4. Without wishing to be bound by theory, the low polydispersity (e.g., 2 to 4) of the first high-density polyethylene polymer composition is thought to be able to improve the nucleation rate and overall barrier performance of the blown film prepared from the polymer composition. The polydispersity of the second high-density polyethylene polymer composition is thought not to be important for achieving the desired results, but for the second high-density polyethylene polymer, a polydispersity of about 2 to about 4 is preferred. The above-described first high-density polyethylene polymer composition may consist of a single high-density polyethylene polymer providing the desired properties, or the first high-density polyethylene polymer composition may include a blend of two or more high-density polyethylene polymers having the desired properties. Similarly, the second high-density polyethylene polymer composition may consist of a single high-density polyethylene polymer or a blend of two or more high-density polyethylene polymers having the desired properties.

[0024]

[0022] In the embodiment described in the preceding paragraph, the first and second high-density polyethylene polymer compositions may be present in the polymer composition in any suitable relative amounts. Preferably, the first high-density polyethylene polymer composition is present in an amount of about 5 wt% to about 60 wt% of the total high-density polyethylene polymers present in the composition (the second high-density polyethylene polymer composition constituting the balance). In other preferred embodiments, the first high-density polyethylene polymer composition is present in an amount of about 10 wt% to about 40 wt% or about 20 wt% to about 40 wt%. In a particularly preferred embodiment, the polymer composition comprises (i) a first high-density polyethylene polymer composition having a melt flow index of about 15 to about 30 dg / min and a density of about 950 kg / m 3 to about 960 kg / m 3 and (ii) a second high-density polyethylene polymer composition having a melt flow index of about 0.8 to about 2 dg / min and a density of about 955 kg / m 3 to about 965 kg / m 3 in amounts of about 10 wt% to about 30 wt% and about 70 wt% to about 90 wt%, respectively. The blends of high-density polyethylene polymers described above can be made by any suitable process, such as (i) physical blending of particulate resins; (ii) co-feeding different high-density polyethylene resins to a common extruder; (iii) melt blending (in any conventional polymer blending apparatus); (iv) solution blending; or (v) a polymerization process using two or more reactors. A highly preferred blend of high-density polyethylene polymer compositions is prepared by a solution polymerization process using two reactors operating under different polymerization conditions. This provides a uniform in situ blend of the first and second high-density polyethylene polymer compositions. An example of this process is described in published U.S. Patent Application Publication No. 2006 / 0047078A1 (Swabey et al.), the disclosure of which is incorporated herein by reference. The overall blend of high-density polyethylene polymer compositions preferably has a polydispersity of about 3 to about 20.

[0025]

[0023] Medium-density polyethylene polymers suitable for use in the present invention generally have a density of about 926 kg / m 3~about 940 kg / m 3 It has a density of. The term "medium density polyethylene" has a density between high density polyethylene and linear low density polyethylene and is used to refer to a polymer of ethylene containing relatively short branches compared to the long branches present in low density polyethylene polymers produced at least by free radical polymerization of ethylene at high pressure.

[0026]

[0024] The medium density polyethylene polymers suitable for use in the present invention are generally copolymers of ethylene and at least one α-olefin, such as 1-butene, 1-hexene, 1-octene, 1-decene and 4-methyl-1-pentene. The α-olefin comonomer can be present in any suitable amount, but typically is present in an amount of less than about 8 wt% (e.g., less than about 5 mol%). As will be understood by those skilled in the art, the amount of comonomer suitable for the copolymer depends greatly on the end use of the copolymer and the necessary or desired polymer properties indicated by that end use.

[0027]

[0025] The medium density polyethylene polymers suitable for use in the present invention can be produced by any suitable method. Similar to high density polyethylene polymers, medium density polyethylene polymers are typically produced by "low pressure" catalyst methods, such as any of the methods described above in connection with high density polyethylene polymers suitable for use in the present invention. Examples of suitable methods include, but are not limited to, gas phase polymerization, solution polymerization, slurry polymerization and staged reactor methods. Suitable staged reactor methods can incorporate any suitable combination of the above gas phase, solution and slurry polymerization methods. Similar to high density polyethylene polymers, staged reactor methods are often used to produce multimodal polymers.

[0028]

[0026] The medium density polyethylene polymers suitable for use in the present invention can be produced using any suitable catalyst or combination of catalysts. For example, the polymers can be produced using Ziegler catalysts, such as transition metal (e.g., titanium) halides or esters (e.g., triethylaluminum) used in combination with organic aluminum compounds. These Ziegler catalysts can be supported, for example, on magnesium chloride, silica, alumina or magnesium oxide. The medium density polyethylene polymers suitable for use in the present invention can also be produced using so-called "dual Ziegler catalysts", which contain one catalyst species (e.g., a combination of titanium ester and triethylaluminum) for dimerizing ethylene to 1-butene, as well as another catalyst (e.g., titanium chloride supported on magnesium chloride) for copolymerizing ethylene and the resulting 1-butene. The medium density polyethylene polymers suitable for use in the present invention can also be produced using chromium oxide catalysts, such as those produced by depositing a chromium compound on a silica-titania support, oxidizing the resulting catalyst in a mixture of oxygen and air, and then reducing the catalyst with carbon monoxide. These chromium oxide catalysts are typically used in combination with trialkylboron or trialkylaluminum compounds. Chromium oxide catalysts can also be used in combination with Ziegler catalysts, such as titanium halide or titanium ester-based catalysts. The medium density polyethylene polymers suitable for use in the present invention can also be produced using supported chromium catalysts, for example, those described above in the discussion of catalysts suitable for making high density polyethylene. The medium density polyethylene polymers suitable for use in the present invention can also be produced using metallocene catalysts. Several different types of metallocene catalysts can be used. For example, the metallocene catalyst can contain a bis(metallocene) complex of zirconium, titanium or hafnium with two cyclopentadienyl rings and methylaluminoxane. Similar to the catalysts used for high density polyethylene production, the ligands can be substituted with various groups (e.g., n-butyl groups) or linked with bridging groups.Another class of metallocene catalysts that can be used is composed of a bis(metallocene) complex of zirconium or titanium and an anion of a perfluorinated boron aromatic compound. A third class of metallocene catalysts that can be used is called a constrained geometry catalyst and contains a monocyclopentadienyl derivative of titanium or zirconium in which one of the carbon atoms of the cyclopentadienyl ring is linked to the metal atom by a bridging group. These complexes are activated by reacting them with methylaluminoxane or by forming an ionic complex with a non-coordinating anion such as B(C6F5)4− or B(C6F5)3CH3−. A fourth class of metallocene catalysts that can be used is a metallocene-based complex of a transition metal such as titanium that contains one cyclopentadienyl ligand combined with another ligand such as a phosphine imine or -O-SiR3. This class of metallocene catalysts is also activated by methylaluminoxane or a boron compound. Other catalysts suitable for use in the production of medium density polyethylene suitable for use in the present invention include, but are not limited to, the catalysts disclosed in U.S. Patent No. 6,649,558.

[0029]

[0027] The medium density polyethylene polymers suitable for use in the present invention can have any suitable compositional uniformity, which is a term used to describe the uniformity of the branches of the copolymer molecules of the polymer. Many commercially available medium density polyethylene polymers have a relatively low compositional uniformity in which the high molecular weight fraction of the polymer contains a relatively small amount of α-olefin comonomer and has relatively few branches, while the low molecular weight fraction of the polymer contains a relatively large amount of α-olefin comonomer and has a relatively large amount of branches. Alternatively, another set of medium density polyethylene polymers has a relatively low compositional uniformity in which the molecular weight fraction of the polymer contains a relatively large amount of α-olefin comonomer, while the low molecular weight fraction of the polymer contains a relatively small amount of α-olefin comonomer. The compositional uniformity of the polymer can be measured using any suitable method, such as temperature rising elution fractionation.

[0030]

[0028] The medium-density polyethylene polymers suitable for use in the present invention can have any suitable molecular weight. For example, the polymers can have a weight average molecular weight of from about 50,000 g / mol to about 200,000 g / mol. As will be understood by those skilled in the art, the suitable weight average molecular weight of medium-density polyethylene will depend, at least in part, on the specific application or end use for which the polymer is intended.

[0031]

[0029] The medium-density polyethylene polymers suitable for use in the present invention can also have any suitable polydispersity. Many commercially available medium-density polyethylene polymers have a polydispersity of from about 2 to about 30. The medium-density polyethylene polymers suitable for use in the present invention can also have a multimodal (e.g., bimodal) molecular weight distribution. For example, the polymer can have a first fraction with a relatively low molecular weight and a second fraction with a relatively high molecular weight. Similar to the high-density polyethylene polymers suitable for use in the present invention, the difference between the weight average molecular weights of the fractions of the multimodal medium-density polyethylene polymer can be any suitable amount. In fact, the difference between the weight average molecular weights need not be large enough for the two distinct molecular weight fractions to be resolved using gel permeation chromatography (GPC). However, in certain multimodal polymers, the difference between the weight average molecular weights of the parts can be large enough for two or more distinct peaks to be resolved from the GPC curve of the polymer. In this context, the term "distinct" does not necessarily mean that the portions of the GPC curve corresponding to each part do not overlap, but simply means that distinct peaks for each part can be resolved from the GPC curve of the polymer. The multimodal polymers suitable for use in the present invention can be produced using any suitable method. As described above, the multimodal polymers can be produced using a stepwise reactor process. A suitable example is a stepwise solution process incorporating a series of stirred tanks. Alternatively, the multimodal polymers can be produced in a single reactor using a combination of catalysts designed to produce polymers each having a different weight average molecular weight.

[0032]

[0030] The medium density polyethylene polymers suitable for use in the present invention can have any suitable melt flow index. For example, the medium density polyethylene polymers can have a melt flow index of from about 0.01 dg / min to about 200 dg / min. Similar to the weight average molecular weight, those skilled in the art understand that the suitable melt flow index of the medium density polyethylene polymer depends at least in part on the specific application or end use for which the polymer is intended. Thus, for example, medium density polyethylene polymers intended for blow molding applications or pipe applications can have a melt flow index of from about 0.01 dg / min to about 1 dg / min. Medium density polyethylene polymers intended for blown film applications can have a melt flow index of from about 0.5 dg / min to about 3 dg / min. Medium density polyethylene polymers intended for cast film applications can have a melt flow index of from about 2 dg / min to about 10 dg / min. Medium density polyethylene polymers intended for injection molding applications can have a melt flow index of from about 6 dg / min to about 200 dg / min. Medium density polyethylene polymers intended for rotational molding applications can have a melt flow index of from about 4 dg / min to about 7 dg / min. Medium density polyethylene polymers intended for wire and cable insulation applications can have a melt flow index of from about 0.5 dg / min to about 3 dg / min. The melt flow index of the polymer is measured using ASTM standard D1238-04c.

[0033]

[0031] The medium density polyethylene polymers suitable for use in the present invention generally do not contain a large amount of long chain branches. For example, the medium density polyethylene polymers suitable for use in the present invention generally contain less than about 0.1 long chain branches per 10,000 carbon atoms (e.g., less than about 0.002 long chain branches per 100 ethylene units) or less than about 0.01 long chain branches per 10,000 carbon atoms.

[0034]

[0032] The linear low density polyethylene polymers suitable for use in the present invention generally have a density of 925 kg / m 3 or less (e.g., about 910 kg / m3 ~about 925 kg / m 3 has a density of. The term "linear low density polyethylene" is used to refer to a lower density polymer of ethylene having relatively short branches as compared to the long branches present in at least the low density polyethylene produced by free radical polymerization of ethylene at high pressure.

[0035]

[0033] Linear low density polyethylene polymers suitable for use in the present invention are generally copolymers of ethylene and at least one α-olefin, such as 1-butene, 1-hexene, 1-octene, 1-decene and 4-methyl-1-pentene. The α-olefin comonomer can be present in any suitable amount, but is typically present in an amount of less than about 6 mol% (e.g., about 2 mol% to about 5 mol%). As will be understood by those skilled in the art, the amount of comonomer suitable for the copolymer is highly dependent on the end use of the copolymer and the required or desired polymer properties indicated by that end use.

[0036]

[0034] Linear low density polyethylene polymers suitable for use in the present invention can be produced by any suitable method. Similar to high density polyethylene polymers, linear low density polyethylene polymers are typically produced by "low pressure" catalyst methods, such as any of the methods described above in connection with high density polyethylene polymers suitable for use in the present invention. Suitable methods include, but are not limited to, gas phase polymerization, solution polymerization, slurry polymerization and staged reactor methods. Suitable staged reactor methods can incorporate any suitable combination of the above gas phase, solution and slurry polymerization methods. Similar to high density polyethylene polymers, staged reactor methods are often used to produce multimodal polymers.

[0037]

[0035] The linear low density polyethylene polymers suitable for use in the present invention can be produced using any suitable catalyst or combination of catalysts. For example, the polymers can be produced using Ziegler catalysts, such as transition metal (e.g., titanium) halides or esters (e.g., triethylaluminum) used in combination with organic aluminum compounds. These Ziegler catalysts can be supported on, for example, magnesium chloride, silica, alumina or magnesium oxide. The linear low density polyethylene polymers suitable for use in the present invention can also be produced using so-called "dual Ziegler catalysts", which contain one catalyst species (e.g., a combination of titanium ester and triethylaluminum) for dimerizing ethylene to 1-butene, as well as another catalyst (e.g., titanium chloride supported on magnesium chloride) for copolymerizing ethylene and the produced 1-butene. The linear low density polyethylene polymers suitable for use in the present invention can also be produced using chromium oxide catalysts, such as those produced by depositing a chromium compound on a silica-titania support, oxidizing the resulting catalyst in a mixture of oxygen and air, and then reducing the catalyst with carbon monoxide. These chromium oxide catalysts are typically used in combination with a trialkylboron or trialkylaluminum compound. Chromium oxide catalysts can also be used in combination with Ziegler catalysts, such as titanium halide or titanium ester-based catalysts. The linear low density polyethylene polymers suitable for use in the present invention can also be produced using supported chromium catalysts, such as those described above in the discussion of catalysts suitable for making high density polyethylene. The linear low density polyethylene suitable for use in the present invention can also be produced using metallocene catalysts. Several different types of metallocene catalysts can be used. For example, the metallocene catalyst can contain a bis(metallocene) complex of two cyclopentadienyl rings of zirconium, titanium or hafnium and methylaluminoxane. Similar to the catalysts used for high density polyethylene production, the ligands can be substituted with various groups (e.g., n-butyl groups) or linked with crosslinking groups.Another class of metallocene catalysts that can be used is composed of bis(metallocene) complexes of zirconium or titanium and anions of perfluorinated boron aromatic compounds. A third class of metallocene catalysts that can be used is called constrained geometry catalysts and contains monocyclopentadienyl derivatives of titanium or zirconium in which one of the carbon atoms of the cyclopentadienyl ring is linked to the metal atom by a bridging group. These complexes are activated by reacting them with methylaluminoxane or by forming an ionic complex with a non-coordinating anion such as B(C6F5)4- or B(C6F5)3CH3-. A fourth class of metallocene catalysts that can be used is a metallocene-based complex of a transition metal such as titanium that contains one cyclopentadienyl ligand combined with another ligand such as a phosphine imine or -O-SiR3. This class of metallocene catalysts is also activated by methylaluminoxane or a boron compound. Other catalysts suitable for use in the production of linear low density polyethylene suitable for use in the present invention include, but are not limited to, the catalysts disclosed in U.S. Patent No. 6,649,558.

[0038]

[0036] The linear low density polyethylene polymers suitable for use in the present invention can have any suitable compositional uniformity, which is a term used to describe the uniformity of the branching of the copolymer molecules of the polymer. Many commercially available linear low density polyethylene polymers have a relatively low compositional uniformity in which the high molecular weight fraction of the polymer contains a relatively small amount of α-olefin comonomer and has relatively few branches, while the low molecular weight fraction of the polymer contains a relatively large amount of α-olefin comonomer and has a relatively large amount of branches. Alternatively, another set of linear low density polyethylene polymers has a relatively low compositional uniformity in which the high molecular weight fraction of the polymer contains a relatively large amount of α-olefin comonomer while the low molecular weight fraction of the polymer contains a relatively small amount of α-olefin comonomer. The compositional uniformity of the polymer can be measured using any suitable method, such as temperature rising elution fractionation.

[0039]

[0037] The linear low density polyethylene polymers suitable for use in the present invention can have any suitable molecular weight. For example, the polymer can have a weight average molecular weight of from about 20,000 g / mol to about 250,000 g / mol. As will be understood by those skilled in the art, the suitable weight average molecular weight of linear low density polyethylene will depend, at least in part, on the particular use or end use for which the polymer is intended.

[0040]

[0038] The linear low density polyethylene polymers suitable for use in the present invention can also have any suitable polydispersity. Many commercially available linear low density polyethylene polymers have a relatively narrow molecular weight distribution and thus a relatively low polydispersity, for example, from about 2 to about 5 (e.g., from about 2.5 to about 4.5 or from about 3.5 to about 4.5). The linear low density polyethylene polymers suitable for use in the present invention can also have a multimodal (e.g., bimodal) molecular weight distribution. For example, the polymer can have a first fraction having a relatively low molecular weight and a second fraction having a relatively high molecular weight. Similar to the high density polyethylene polymers suitable for use in the present invention, the difference between the weight average molecular weights of the fractions of the multimodal low density polyethylene polymer can be any suitable amount. In fact, the difference between the weight average molecular weights need not be large enough such that the two distinct molecular weight fractions can be resolved using gel permeation chromatography (GPC). However, in certain multimodal polymers, the difference between the weight average molecular weights of the fractions can be large enough such that two or more distinct peaks can be resolved from the GPC curve of the polymer. In this context, the term "distinct" does not necessarily mean that the portions of the GPC curve corresponding to each part do not overlap, but rather simply means that distinct peaks for each fraction can be resolved from the GPC curve of the polymer. The multimodal polymers suitable for use in the present invention can be produced using any suitable method. As described above, the multimodal polymers can be produced using a stepwise reactor process. A suitable example is a stepwise solution process incorporating a series of stirred tanks. Alternatively, the multimodal polymers can be produced in a single reactor using a combination of catalysts designed to produce polymers each having a different weight average molecular weight.

[0041]

[0039] The linear low density polyethylene polymer suitable for use in the present invention can have any suitable melt flow index. For example, the linear low density polyethylene polymer can have a melt flow index of from about 0.01 dg / min to about 200 dg / min. Similar to the weight average molecular weight, those skilled in the art understand that the suitable melt flow index of the linear low density polyethylene polymer depends, at least in part, on the specific application or end use for which the polymer is intended. Thus, for example, a linear low density polyethylene polymer intended for blow molding applications or pipe applications can have a melt flow index of from about 0.01 dg / min to about 1 dg / min. A linear low density polyethylene polymer intended for blown film applications can have a melt flow index of from about 0.5 dg / min to about 3 dg / min. A linear low density polyethylene polymer intended for cast film applications can have a melt flow index of from about 2 dg / min to about 10 dg / min. A linear low density polyethylene polymer intended for injection molding can have a melt flow index of from about 6 dg / min to about 200 dg / min. A linear low density polyethylene polymer intended for rotational molding applications can have a melt flow index of from about 4 dg / min to about 7 dg / min. A linear low density polyethylene polymer intended for wire and cable insulation applications can have a melt flow index of from about 0.5 dg / min to about 3 dg / min. The melt flow index of the polymer is measured using ASTM standard D1238-04c.

[0042]

[0040] The linear low density polyethylene polymer suitable for use in the present invention generally does not contain a large number of long chain branches. For example, the linear low density polyethylene polymer suitable for use in the present invention generally contains less than about 0.1 long chain branches per 10,000 carbon atoms (e.g., less than about 0.002 long chain branches per 100 ethylene units) or less than about 0.01 long chain branches per 10,000 carbon atoms.

[0043]

[0041] The low density polyethylene polymers suitable for use in the present invention generally have a density of less than 935 kg / m 3 and, in contrast to high density polyethylene, medium density polyethylene and linear low density polyethylene, have a relatively large amount of long chain branching in the polymer.

[0044]

[0042] The low density polyethylene polymers suitable for use in the present invention can be either ethylene homopolymers or copolymers of ethylene and polar comonomers. Suitable polar comonomers include, but are not limited to, vinyl acetate, methyl acrylate, ethyl acrylate and acrylic acid. These comonomers can be present in any suitable amount and a comonomer content of up to 20% by weight is used for certain applications. As will be understood by those skilled in the art, the amount of comonomer suitable for the polymer will depend largely on the end use of the polymer and the necessary or desired polymer properties indicated by that end use.

[0045]

[0043] The low density polyethylene polymers suitable for use in the present invention can be produced using any suitable method, but typically the polymer is produced by free radical initiated polymerization of ethylene at high pressure (e.g., about 81 to about 276 MPa) and high temperature (e.g., about 130 to about 330 °C). Any suitable free radical initiator can be used in such a process, with peroxides and oxygen being the most common. The mechanism of free radical polymerization results in short chain branching and also a relatively high degree of long chain branching in the polymer, which distinguishes low density polyethylene from other ethylene polymers (e.g., high density polyethylene and linear low density polyethylene). The polymerization reaction is typically carried out in an autoclave reactor (e.g., a stirred autoclave reactor), a tubular reactor or a combination of such reactors arranged in series.

[0046]

[0044] The low-density polyethylene polymers suitable for use in the present invention can have any suitable molecular weight. For example, the polymers can have a weight-average molecular weight of from about 30,000 g / mol to about 500,000 g / mol. As will be understood by those skilled in the art, the suitable weight-average molecular weight of low-density polyethylene will depend, at least in part, on the particular use or end use for which the polymer is intended. For example, a low-density polyethylene polymer intended for blow molding applications can have a weight-average molecular weight of from about 80,000 g / mol to about 200,000 g / mol. A low-density polyethylene polymer intended for pipe applications can have a weight-average molecular weight of from about 80,000 g / mol to about 200,000 g / mol. A low-density polyethylene polymer intended for injection molding applications can have a weight-average molecular weight of from about 30,000 g / mol to about 80,000 g / mol. A low-density polyethylene polymer intended for film applications can have a weight-average molecular weight of from about 60,000 g / mol to about 500,000 g / mol.

[0047]

[0045] The low-density polyethylene polymers suitable for use in the present invention can have any suitable melt flow index. For example, the low-density polyethylene polymers can have a melt flow index of from about 0.2 dg / min to about 100 dg / min. As described above, the melt flow index of the polymer is measured using ASTM standard D1238-04c.

[0048] As noted above, one of the main distinctions between low density polyethylene and other ethylene polymers is the relatively high degree of long chain branching within the polymer. Low density polyethylene polymers suitable for use in the present invention may have any suitable amount of long chain branching, such as about 0.01 or more long chain branches per 10,000 carbon atoms, about 0.1 or more long chain branches per 10,000 carbon atoms, about 0.5 or more long chain branches per 10,000 carbon atoms, about 1 or more long chain branches per 10,000 carbon atoms, or about 4 or more long chain branches per 10,000 carbon atoms. There is no strict maximum limit to the degree of long chain branching that may be present in low density polyethylene polymers suitable for use in the present invention, although long chain branching in many low density polyethylene polymers is less than about 100 long chain branches per 10,000 carbon atoms.

[0049]

[0047] The polyethylene polymer composition used in the polymer composition may include any suitable polyethylene polymer or a mixture of polyethylene polymers. However, the salts of branched alkylphosphonic acids are considered to be more effective in the nucleation of polyethylene polymer compositions that exhibit a greater degree of melt relaxation. During a particular melt processing of the polymer (e.g., blow molding), when the polymer melt is extruded through a die, it is subjected to extensional thinning or strain. The polymer melt may be further subjected to additional extensional thinning or strain when the extruded polymer melt is further processed, e.g., drawn and / or blown. The strain applied to the polymer melt causes the extended polymer chains in the polymer melt to orient in the flow direction. As the processed polymer melt cools, these directionally oriented extended polymer chains can return to a less ordered state prior to the crystallization of the polymer melt. This process is herein referred to as "melt relaxation". Alternatively, the directionally oriented extended polymer chains can crystallize while remaining oriented in the melt to form fibrils. These fibrils provide sites that can initiate the self-nucleation of the polymer. When such fibrils are sufficiently formed in the polymer as the polymer solidifies from the melt, the resulting strain-induced self-nucleation can become the dominant mode of nucleation of the polymer. Although the self-nucleation of the polymer may seem beneficial, the polymer structures generated by such self-nucleation are generally not very favorable for certain desired physical properties. For example, self-nucleated polyethylene generally exhibits higher water vapor and oxygen permeabilities than polyethylene heterogeneously nucleated with salts of branched alkylphosphonic acids. Therefore, in order to maximize the degree of nucleation induced by the salts of branched alkylphosphonic acids, the polymer composition preferably contains a polyethylene polymer composition that exhibits sufficient melt relaxation to ensure that strain-induced self-nucleation is not dominant.

[0050]

[0048] The degree of melt relaxation exhibited by a polymer or polymer composition cannot be easily directly quantified. Furthermore, melt relaxation is thought to be affected by many factors such as molecular weight, breadth of molecular weight distribution, relative amount of high molecular weight fraction in the molecular weight distribution, and branching or non-linear chains in the polymer or polymer composition. Due to the number of factors involved and the complex relationships between those factors, it is difficult to specify the range of each value sufficient to define a polyethylene polymer composition exhibiting sufficient melt relaxation. In other words, an attempt may be made to define the molecular weight distribution of a polymer exhibiting sufficient melt relaxation, but the appropriate range may vary depending on the “shape” of the distribution (i.e., the relative amount of the high molecular weight fraction). Therefore, when attempting to identify a polyethylene polymer composition exhibiting sufficient melt relaxation, these factors can be considered, but a more direct and accurate measurement of melt relaxation may be desired.

[0051]

[0049] The shear storage modulus (G’) of a viscoelastic material (e.g., a polymer melt) is related to the stored energy (stress), such as that stored in the above-described directionally oriented extended polymer chains. The shear loss modulus (G’’) of a viscoelastic material is related to the energy loss or dissipation, such as that released by the relaxation of the directionally oriented extended polymer chains in a polymer melt. The ratio of the shear loss modulus to the shear storage modulus (G’’ / G’), defined as tanδ, is proportional to the loss of energy versus storage at a given strain rate. For materials where tanδ is less than 1, energy storage is dominant at the measured strain rate. For materials where tanδ is greater than 1, energy loss (dissipation) is dominant at the measured strain rate. Furthermore, by using a comparison of tanδ measured at different strain rates (e.g., the ratio of tanδ), it is possible to quantify the degree to which the predominance of energy loss and energy storage in the material changes with changes in the strain rate.

[0052]

[0050] The shear storage modulus and the shear loss modulus can be measured at various strain rates by various techniques. However, when the modulus is used for the accurate measurement of the polymer's melt relaxation, both moduli should be measured at the strain rate to which the polymer melt is subjected during melt processing or at a rate close thereto. For this purpose, the inventors believe that the measurement of the shear storage modulus and the shear loss modulus by a parallel plate rheometer at angular frequencies of about 0.1 rad / s and about 10 rad / s provides a fair approximation of the strain rate to which the polyethylene polymer composition melt is subjected during processing. As described above, the ratio of tan δ at these two strain rates can be used to show the changes in energy loss and energy storage with the change in strain rate. After extensive experiments with various polymers and polymer compositions, it is considered that a polyethylene polymer composition in which the energy loss increases significantly (i.e., tan δ increases significantly) as the strain rate decreases (i.e., the angular frequency decreases) exhibits sufficient melt relaxation for heterogeneous nucleation by salts of branched alkylphosphonic acids. In particular, the ratio of tan δ at about 0.1 rad / s to tan δ at about 10 rad / s, hereinafter referred to as the "melt relaxation ratio", is considered to be 1.5 or more. In other words, the polyethylene polymer composition preferably has a melt relaxation ratio of 1.5 or more, more preferably 1.55 or more.

[0053]

[0051] As described above, the melt relaxation ratio (MRR) is defined as the ratio of tan δ at about 0.1 rad / s to tan δ at about 10 rad / s:

[0054]

Equation

[0055] In this definition, two angular frequencies are defined to be approximately equal to a predetermined value. Thus, tanδ at approximately 0.1 rad / s can be measured at any angular frequency from 0.095 to 0.105 rad / s, and tanδ at approximately 10 rad / s can be measured at any angular frequency from 9.5 rad / s to 10.5 rad / s. The exact angular frequencies used for the determination of MRR can vary within the above range, but the ratio of the two angular frequencies must be 1:100 (i.e., there must be a 100-fold difference between the two angular frequencies).

[0056]

[0052] The melt relaxation ratio can be measured by any suitable technique. Preferably, the shear loss modulus (G’’), the shear storage modulus (G’), and tanδ are determined by parallel plate rheometry at a temperature of 190 °C using a rotational rheometer equipped with 25 mm parallel plates set at a 1.1 mm gap. The polymer sample used for the measurement is provided in the form of a compression molded disk. During the measurement, the angular distance or strain is preferably kept low so as to remain in the non-hysteresis region, and a nominal strain of about 1 percent is preferred. Since these parameters are determined from the polymer melt, the presence of a nucleating agent does not significantly affect the shear loss modulus (G’’), the shear storage modulus (G’), and tanδ measured from the polyethylene polymer. Thus, these parameters (and the melt relaxation ratio) can be measured from the polyethylene polymer composition before being combined with the salt of the branched alkylphosphonic acid, or the parameters can be measured from a polymer composition comprising the polyethylene polymer composition and the salt of the branched alkylphosphonic acid.

[0057] As described above, the polyethylene polymer composition can include any suitable polyethylene polymer or mixture of polyethylene polymers that exhibits a desired melt relaxation ratio. Thus, the polyethylene polymer composition can include a single polyethylene polymer that exhibits a desired melt relaxation ratio. Alternatively, the polyethylene polymer composition can include a mixture of two or more polyethylene polymers where the mixture exhibits a desired melt relaxation ratio. In such a mixture, each polyethylene polymer can exhibit a melt relaxation ratio that falls within a desired range, although this is not essential. For example, a polyethylene polymer that exhibits a relatively low melt relaxation ratio (e.g., less than 1.5) can be mixed with another polyethylene polymer having a higher melt relaxation ratio (e.g., 1.55 or greater) in an appropriate amount to obtain a polyethylene polymer composition that exhibits a desired melt relaxation ratio.

[0058] As described above, the polymer composition also includes a salt of a branched alkylphosphonic acid. When used herein, the term "branched alkylphosphonic acid" refers to a phosphonic acid of the following formula (C).

[0059]

Chemical formula

[0060] In formula (C), R 101 is a branched alkyl group. The salt of the branched alkylphosphonic acid can include any suitable cation. In a preferred embodiment, the salt of the branched alkylphosphonic acid includes one or more cations selected from the group consisting of Group 1 element cations, Group 2 element cations, and Group 12 element cations. In a preferred embodiment, the salt of the branched alkylphosphonic acid includes a Group 1 element cation, preferably two sodium cations. In another preferred embodiment, the salt of the branched alkylphosphonic acid includes a Group 2 element cation. In a particularly preferred embodiment, the salt of the branched alkylphosphonic acid includes a calcium cation.

[0061]

[0055] The branched alkylphosphonic acid can contain any suitable branched alkyl group (i.e., R 101 can be any suitable branched alkyl group). In a preferred embodiment, the branched alkylphosphonic acid contains a branched alkyl group selected from the group consisting of isopropyl, sec-butyl, isobutyl, tert-butyl, tert-pentyl, neopentyl, isopentyl, sec-pentyl, sec-isopentyl, pentan-3-yl, and 2-methylbutyl. In another preferred embodiment, the branched alkylphosphonic acid contains an alkyl group having a branch point located at the alpha-carbon or beta-carbon relative to the phosphorus atom, with a branch point at the alpha-carbon being particularly preferred. In a preferred embodiment, the branched alkylphosphonic acid contains a tertiary alkyl group (i.e., an alkyl group containing 4 non-hydrogen substituents, such as 3 alkyl groups and at least 1 carbon atom bonded to the phosphorus atom). In a preferred embodiment, the branched alkylphosphonic acid contains a branched alkyl group selected from the group consisting of tert-butyl, tert-pentyl, and neopentyl. In a particularly preferred embodiment, the branched alkylphosphonic acid contains a tert-butyl group (i.e., R 101 is tert-butyl). Thus, in a preferred embodiment, the salt of the branched alkylphosphonic acid is selected from the group consisting of the disodium salt of tert-butylphosphonic acid, the calcium salt of tert-butylphosphonic acid (i.e., calcium t-butylphosphonate or calcium t-butylphosphonate monohydrate), and mixtures thereof. In another particularly preferred embodiment, the salt of the branched alkylphosphonic acid is the calcium salt of tert-butylphosphonic acid (i.e., calcium t-butylphosphonate or calcium t-butylphosphonate monohydrate).

[0062]

[0056] The salt of the branched alkylphosphonic acid can have any suitable specific surface area (e.g., BET specific surface area). In a preferred embodiment, the salt of the branched alkylphosphonic acid has a BET specific surface area of about 20 m 2 / g or more. In another preferred embodiment, the salt of the branched alkylphosphonic acid has a BET specific surface area of about 30 m 2It has a BET specific surface area of / g or more. The BET specific surface area of the salt of the branched alkylphosphonic acid can be measured by any suitable technique. Preferably, the BET specific surface area of the salt of the branched alkylphosphonic acid is measured in accordance with ISO standard 9277:2010 entitled "Determination of the Specific Surface Area of Solids by Gas Adsorption - BET method" using nitrogen as the adsorption gas. The salts of the branched alkylphosphonic acids disclosed herein generally have a delaminable layered structure using techniques known in the art. Delamination of such a layered structure increases the BET specific surface area of the salt of the branched alkylphosphonic acid, thereby assisting dispersion. Physical methods for increasing the BET specific surface area of the salt of the branched alkylphosphonic acid include air jet milling, pin milling, hammer milling, grinding mills, and the like. Improved dispersion and surface area can also be achieved by more sophisticated mixing and extrusion methods, such as high-intensity mixing and twin-screw extrusion. Thus, salts of branched alkylphosphonic acids that do not have the desired BET specific surface area can be delaminated using these and other known techniques until the desired BET specific surface area is achieved.

[0063]

[0057] The polymer composition can contain any suitable amount of a salt of a branched alkylphosphonic acid. In a preferred embodiment, the salt of the branched alkylphosphonic acid is present in the polymer composition in an amount of about 50 parts per million (ppm) or more, based on the total weight of the polymer composition. In another preferred embodiment, the salt of the branched alkylphosphonic acid is present in the polymer composition in an amount of about 75 ppm or more, about 100 ppm or more, about 150 ppm or more, about 200 ppm or more, or about 250 ppm or more, based on the total weight of the polymer composition. The salt of the branched alkylphosphonic acid is preferably present in the polymer composition in an amount of about 5,000 ppm or less, based on the total weight of the polymer composition. In a preferred embodiment, the salt of the branched alkylphosphonic acid is preferably present in the polymer composition in an amount of about 4,000 ppm or less, about 3,000 ppm or less, about 2,000 ppm or less, about 1,500 ppm or less, about 1,250 ppm or less, or about 1,000 ppm or less, based on the total weight of the polymer composition.Accordingly, in a series of preferred embodiments, the salt of the branched alkylphosphonic acid is present in the polymer composition in an amount of about 50 ppm to about 5,000 ppm (e.g., about 50 ppm to about 4,000 ppm, about 50 ppm to about 3,000 ppm, about 50 ppm to about 2,000 ppm, about 50 ppm to about 1,500 ppm, about 50 ppm to about 1,250 ppm, or about 50 ppm to about 1,000 ppm), about 75 ppm to about 5,000 ppm (e.g., about 75 ppm to about 4,000 ppm, about 75 ppm to about 3,000 ppm, about 75 ppm to about 2,000 ppm, about 75 ppm to about 1,500 ppm, about 75 ppm to about 1,250 ppm, or about 75 ppm to about 1,000 ppm), about 100 ppm to about 5,000 ppm (e.g., about 100 ppm to about 4,000 ppm, about 100 ppm to about 3,000 ppm, about 100 ppm to about 2,000 ppm, about 100 ppm to about 1,500 ppm, about 100 ppm to about 1,250 ppm, or about 100 ppm to about 1,000 ppm), about 150 ppm to about 5,000 ppm (e.g., about 150 ppm to about 4,000 ppm, about 150 ppm to about 3,000 ppm, about 150 ppm to about 2,000 ppm, about 150 ppm to about 1,500 ppm, about 150 ppm to about 1,250 ppm, or about 150 ppm to about 1,000 ppm), about 200 ppm to about 5,000 ppm (e.g., about 200 ppm to about 4,000 ppm, about 200 ppm to about 3,000 ppm, about 200 ppm to about 2,000 ppm, about 200 ppm to about 1,500 ppm, about 200 ppm to about 1,250 ppm, or about 200 ppm to about 1,000 ppm), about 250 ppm to about 5,000 ppm (e.g., about 250 ppm to about 4,000 ppm, about 250 ppm to about 3,000 ppm, about 250 ppm to about 2,000 ppm, about 250 ppm to about 1,500 ppm, about 250 ppm to about 1,250 ppm, or about 250 ppm to about 1,000 ppm). When the polymer composition contains more than one salt of the branched alkylphosphonic acid, each salt of the branched alkylphosphonic acid can be present in the polymer composition in one of the amounts described above, or the total amount of all salts of the branched alkylphosphonic acid present in the polymer composition can fall within one of the ranges described above.Preferably, when the polymer composition contains more than one salt of a branched alkylphosphonic acid, the total amount of all salts of the branched alkylphosphonic acid present in the polymer composition falls within one of the above ranges.

[0064]

[0058] Salts of branched alkylphosphonic acids suitable for use in the compositions of the present invention can be prepared by any suitable process. For example, the salt can be prepared by reacting a branched alkylphosphonic acid with a metal base such as a metal hydroxide (e.g., calcium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide) or a metal oxide (e.g., calcium oxide or zinc oxide) in an aqueous medium. Salts of branched alkylphosphonic acids prepared by such processes can be hydrates (e.g., calcium t-butylphosphonate monohydrate). Such hydrated salts can be dehydrated by heating the salt to a sufficiently high temperature, but many of such dehydrated salts (e.g., calcium t-butylphosphonate) are not sufficiently stable to rehydrate when exposed to moisture in the atmosphere.

[0065]

[0059] In addition to the salts of the branched alkylphosphonic acids described above, the polymer composition of the present invention can contain other polymer additives. Suitable additional polymer additives include antioxidants (e.g., phenolic antioxidants, phosphite antioxidants, and combinations thereof), antiblocking agents (e.g., amorphous silica and diatomaceous earth), pigments (e.g., organic pigments and inorganic pigments) and other colorants (e.g., dyes and polymeric colorants), fillers and reinforcing agents (e.g., glass, glass fibers, talc, calcium carbonate, and magnesium oxysulfate whiskers), nucleating agents, clarifying agents, acid scavengers (e.g., metal salts of fatty acids, such as metal salts of stearic acid, and hydrotalcite-like materials), polymer processing additives (e.g., fluoropolymer processing additives), polymer crosslinking agents, slip agents (e.g., fatty acid amide compounds obtained from the reaction of fatty acids with ammonia or amine-containing compounds), fatty acid ester compounds (e.g., fatty acid ester compounds obtained from the reaction of fatty acids with hydroxyl-containing compounds, such as glycerol, diglycerol, and combinations thereof), polymer modifiers (e.g., hydrocarbon resin modifiers, such as those sold under the trade name Oppera(™) by Exxon Mobil Corporation), and combinations of the foregoing, but are not limited thereto.

[0066]

[0060] In a preferred embodiment, the polymer composition further comprises one or more acid scavengers. As described above, suitable acid scavengers include metal salts of fatty acids and hydrotalcite-like materials (e.g., synthetic hydrotalcite). Suitable metal salts of fatty acids include C 12 ~C 22 fatty acids (e.g., saturated C 12 ~C 22Metal salts of fatty acids), such as zinc stearate, are included, but not limited thereto. In a preferred embodiment, the acid scavenger is selected from the group consisting of zinc, potassium, and lanthanum salts of stearic acid, and zinc stearate is particularly preferred. Suitable hydrotalcite-like materials for use as acid scavengers include synthetic hydrotalcite materials (CAS No. 11097-59-9) sold by Kisuma Chemicals under the trade names "DHT-4A" and "DHT-4V", but are not limited thereto.

[0067]

[0061] The salts of branched alkylphosphonic acids and the acid scavenger can be present in the polymer composition in any suitable relative amounts. For example, the salts of branched alkylphosphonic acids and the acid scavenger can be present in the polymer composition in a ratio of about 10:1 to about 1:10 (salt of branched alkylphosphonic acid to acid scavenger) based on the weight of the salt of branched alkylphosphonic acid and the acid scavenger in the polymer composition. More preferably, the salts of branched alkylphosphonic acids and the acid scavenger are present in the polymer composition in a ratio of about 4:1 to about 1:4, about 3:1 to about 1:3 (e.g., about 3:1 to about 1:1 or about 3:1 to about 2:1), about 1:1 to about 1:4, or about 1:1 to about 1:3 based on the weight of the salt of branched alkylphosphonic acid and the acid scavenger in the polymer composition. In a particularly preferred embodiment, the salts of branched alkylphosphonic acids and the acid scavenger are present in the polymer composition in a ratio of about 2:1 based on the weight of the salt of branched alkylphosphonic acid and the acid scavenger in the polymer composition (e.g., about 2 parts by weight of calcium t-butylphosphonate monohydrate per 1 part by weight of zinc stearate). In another particularly preferred embodiment, the salts of branched alkylphosphonic acids and the acid scavenger are present in the polymer composition in a ratio of about 3:1 based on the weight of the salt of branched alkylphosphonic acid and the acid scavenger in the polymer composition (e.g., about 3 parts by weight of calcium t-butylphosphonate monohydrate per 1 part by weight of zinc stearate).

[0068]

[0062] As described above, in addition to the salts of the branched alkylphosphonic acids of the present invention, the polymer composition of the present invention can contain other nucleating agents. Suitable nucleating agents include 2,2'-methylene-bis-(4,6-di-tert-butylphenyl) phosphate (for example, sodium 2,2'-methylene-bis-(4,6-di-tert-butylphenyl) phosphate or hydroxyaluminum bis(2,2'-methylene-bis-(4,6-di-tert-butylphenyl) phosphate), bicyclo[2.2.1]heptane-2,3-dicarboxylate (for example, disodium bicyclo[2.2.1]heptane-2,3-dicarboxylate or calcium bicyclo[2.2.1]heptane-2,3-dicarboxylate), cyclohexane-1,2-dicarboxylate (for example, calcium cyclohexane-1,2-dicarboxylate, aluminum monobasic cyclohexane-1,2-dicarboxylate, dilithium cyclohexane-1,2-dicarboxylate, or strontium cyclohexane-1,2-dicarboxylate), glycerolate (for example, zinc glycerolate), phthalate (for example, calcium phthalate), phenylphosphonate (for example, calcium phenylphosphonate), and combinations thereof, but are not limited thereto. In the case of bicyclo[2.2.1]heptane-2,3-dicarboxylate and cyclohexane-1,2-dicarboxylate, the carboxylate moiety may be arranged in either the cis or trans configuration, and the cis configuration is preferred.

[0069] As described above, the polymer composition of the present invention may also contain a clarifying agent. Suitable clarifying agents include, but are not limited to, trisamides and acetal compounds which are condensation products of polyhydric alcohols and aromatic aldehydes. Suitable trisamide clarifying agents include amide derivatives of benzene-1,3,5-tricarboxylic acid, derivatives of N-(3,5-bis-formylamino-phenyl)-formamide (e.g., N-[3,5-bis-(2,2-dimethyl-propionylamino)-phenyl]-2,2-dimethyl-propionamide), derivatives of 2-carbamoyl-malonamide (e.g., N,N'-bis-(2-methyl-cyclohexyl)-2-(2-methyl-cyclohexylcarbamoyl)-malonamide), and combinations thereof, but are not limited thereto. As described above, the clarifying agent may be an acetal compound which is a condensation product of a polyhydric alcohol and an aromatic aldehyde. Suitable polyhydric alcohols include acyclic polyols such as xylitol and sorbitol, and acyclic deoxypolyols (e.g., 1,2,3-trideoxynonitol or 1,2,3-trideoxynon-1-enitol). Suitable aromatic aldehydes typically contain a single aldehyde group where the remaining positions on the aromatic ring are either unsubstituted or substituted. Thus, suitable aromatic aldehydes include benzaldehyde and substituted benzaldehydes (e.g., 3,4-dimethyl-benzaldehyde or 4-propyl-benzaldehyde). The acetal compound produced by the aforementioned reaction may be a monoacetal, diacetal, or triacetal compound (i.e., a compound containing 1, 2, or 3 acetal groups, respectively), with diacetal compounds being preferred. Suitable acetal-based clarifying agents include, but are not limited to, the clarifying agents disclosed in U.S. Patent Nos. 5,049,605; 7,157,510; and 7,262,236.

[0070]

[0064] The polymer composition of the present invention can be produced by any suitable method or process. For example, the polymer composition can be produced by simply mixing the individual components of the polymer composition (e.g., the polymer, the salt of the branched alkylphosphonic acid, and other additives if present). The polymer composition can also be produced by mixing the individual components under high shear or high intensity mixing conditions. The polymer composition of the present invention may be provided in any form suitable for further processing to produce manufactured articles from the thermoplastic polymer composition. For example, the thermoplastic polymer composition may be provided in the form of a powder (e.g., a free-flowing powder), flakes, pellets, prills, tablets, aggregates, etc.

[0071] The polymer composition of the invention of the first aspect can take the form of a masterbatch composition designed for addition or dropwise addition to a new polymer (e.g., a non-nucleating high-density polyethylene polymer). In such an aspect, the polymer composition generally contains a greater amount of the salt of a branched alkylphosphonic acid compared to a thermoplastic polymer composition intended for use in forming a manufactured article without further dilution or addition to a new thermoplastic polymer. For example, the salt of the branched alkylphosphonic acid can be present in such a polymer composition in an amount of about 0.5 wt% or more (e.g., about 1 wt% or more or about 2 wt% or more). The maximum amount of the salt in the masterbatch is limited only by manufacturing and processing considerations, but the amount is typically about 50 wt% or less. Thus, in a series of preferred aspects, the salt of the branched alkylphosphonic acid is about 0.5 wt% to about 50 wt% (e.g., about 0.5 wt% to about 40 wt%, about 0.5 wt% to about 30 wt%, about 0.5 wt% to about 25 wt%, about 0.5 wt% to about 20 wt%, about 0.5 wt% to about 15 wt%, about 0.5 wt% to about 10 wt%, about 0.5 wt% to about 5 wt%, or about 0.5 wt% to about 4 wt%), about 1 wt% to about 50 wt% (e.g., about 1 wt% to about 40 wt%, about 1 wt% to about 30 wt%, about 1 wt% to about 25 wt%, about 1 wt% to about 20 wt%, about 1 wt% to about 15 wt%, about 1 wt% to about 10 wt%, about 1 wt% to about 5 wt%, or about 1 wt% to about 4 wt%), or about 2 wt% to about 50 wt% (e.g., about 2 wt% to about 40 wt%, about 2 wt% to about 30 wt%, about 2 wt% to about 25 wt%, about 2 wt% to about 20 wt%, about 2 wt% to about 15 wt%, about 2 wt% to about 10 wt%, about 2 wt% to about 5 wt%, or about 2 wt% to about 4 wt%) based on the total weight of the polymer composition and can be present in the masterbatch. In such a masterbatch composition, additional additives contained in the composition are also present in higher amounts intended to provide the desired concentration when the masterbatch composition is dropped into a new polymer.

[0072]

[0066] The polymer composition of the present invention is considered useful for the production of thermoplastic polymer manufactured articles. The polymer composition of the present invention can be formed into a desired thermoplastic polymer manufactured article by any suitable technique, such as injection molding (e.g., thin-wall injection molding, multi-component molding, overmolding, or 2K molding), blow molding (e.g., extrusion blow molding, injection blow molding, or injection stretch blow molding), extrusion (e.g., fiber extrusion, tape (e.g., slit tape) extrusion, sheet extrusion, film extrusion, cast film extrusion, pipe extrusion, extrusion coating, or foam extrusion), thermoforming, rotational molding, film blowing (blown film), film casting (cast film), compression molding, extrusion compression molding, extrusion compression blow molding, etc. The thermoplastic polymer article produced using the polymer composition of the present invention may consist of multiple layers (e.g., multilayer blown or cast film, or multilayer injection molded article), and one or any suitable number of the multiple layers contain the polymer composition of the present invention.

[0073]

[0067] The polymer composition of the present invention can be used to produce any suitable manufactured article. Suitable manufactured articles include, but are not limited to, medical devices (e.g., prefilled syringes for retort use, intravenous supply containers, and blood collection devices), food packaging, liquid containers (e.g., containers for beverages, drugs, personal care compositions, shampoos, etc.), garment cases, microwave-compatible articles, shelves, cabinet doors, machine parts, automotive parts, seats, pipes, tubes, rotational molding parts, blow molding parts, films, fibers, etc.

[0074]

[0068] The polymer composition of the present disclosure has a particularly improved (i.e., lower) water vapor and oxygen permeability compared to a non-nucleating polymer and a nucleating polymer that does not exhibit the described physical properties (e.g., density, melt relaxation ratio, melt flow index, etc.), and is thus considered suitable for use in extrusion blow molding and film blowing processes. For example, it has been observed that an extrusion blow molded bottle made from the thermoplastic polymer composition of the present disclosure exhibits a significantly lower water vapor permeability than a similar extrusion blow molded bottle made from a nucleating polymer that does not exhibit the desired melt relaxation ratio. As described above, this result is believed to be due to the selection of a polyethylene polymer composition that exhibits sufficient melt relaxation to maximize the nucleating effect of the salt of the branched alkylphosphonic acid.

[0075]

[0069] Accordingly, in a second aspect, the present invention provides a method for molding a thermoplastic polymer composition. The method comprises (a) providing an apparatus including a die and a mold cavity, the mold cavity having an inner surface that defines the shape of the molded article; (b) providing a polymer composition comprising (i) a polyethylene polymer composition having a melt relaxation ratio of 1.5 or greater; and (ii) a salt of a branched alkylphosphonic acid; (c) heating the polymer composition to a temperature sufficient to melt the polymer composition such that the polymer composition can be extruded through the die; (d) extruding the molten polymer composition through the die to form a parison; (e) capturing the parison within the mold cavity; (f) blowing a pressurized fluid into the parison under a pressure sufficient to expand the parison to conform to the inner surface of the mold cavity and produce the molded article; (g) cooling the molded article to a temperature at which the thermoplastic polymer composition at least partially solidifies such that the molded article retains its shape; and (h) removing the molded article from the mold cavity and includes.

[0076]

[0070] The polymer composition used in the method of this second aspect may be any of the polymer compositions described above. The apparatus used to carry out the method of the present invention can be any suitable extrusion blow molding apparatus. Suitable extrusion blow molding apparatuses include continuous extrusion blow molding apparatuses, such as rotary wheel extrusion blow molding apparatuses and shuttle extrusion blow molding apparatuses, and intermittent extrusion blow molding apparatuses, such as reciprocating screw extrusion blow molding apparatuses, and accumulator head extrusion blow molding apparatuses. As described above, the apparatus includes a die through which a plasticized (melted) polymer composition is extruded to form a parison. The apparatus also includes a mold having a mold cavity. The mold cavity or the inner surface of the mold cavity defines the shape of the molded article produced by the apparatus. More specifically, the inner surface of the mold cavity defines the outer surface of the molded article produced by the apparatus.

[0077]

[0071] In the above method, the polymer composition can be heated to any suitable temperature that enables melting the polymer composition and extruding it through the die. The temperature at which the polymer composition is heated does not significantly affect the nucleation performance of the salt of the branched alkylphosphonic acid, but a higher temperature may promote a larger and faster melt relaxation, thereby potentially improving the nucleation performance to some extent. However, the temperature at which the polymer composition is heated should not be excessively high, as an excessively high temperature may reduce the viscosity of the molten polymer composition to the point where the parison sags excessively and there is improper variation in the wall thickness of the molded article. Preferably, the polymer composition is heated to a temperature of about 170 °C to about 205 °C. The polymer composition is preferably maintained within this range until it is formed into the final molded article.

[0078]

[0072] Once the polymer composition is heated to the desired temperature, the polymer composition is extruded through the die of the apparatus to form a parison. The resulting parison is then captured within the mold cavity of the apparatus. The mold typically includes a single opening that allows access to the mold cavity. The parison is captured within the mold such that the open end of the parison is aligned with the opening of the mold. Once the parison is captured within the mold, pressurized fluid (e.g., air) is blown into the open end of the parison under sufficient pressure such that the parison conforms to the inner surface of the mold cavity and forms the desired molded article. Once the parison is blown to form the desired molded article, the article is held within the mold for a sufficient time such that the thermoplastic polymer composition solidifies to the extent that the article maintains its shape when removed from the mold. The mold of the apparatus is typically cooled such that cooling occurs more rapidly and the cycle time is reduced.

[0079]

[0073] Once captured within the mold, the parison can be inflated using any suitable pressure. The pressure required depends on several factors, but the parison is generally inflated at a pressure of from about 135 kPa to about 830 kPa. In certain embodiments, the parison can be inflated in multiple stages, for example, following an initial pressurization at from about 135 kPa to about 280 kPa with a second pressurization at from about 550 kPa to about 830 kPa.

[0080]

[0074] As noted above, it has been observed that certain polyethylene articles containing one of the salts of the branched alkylphosphonic acids described above exhibit significantly lower water vapor and oxygen permeabilities. For example, such improvements in the barrier to water vapor and oxygen have been observed for high density polyethylene films containing one of the salts of the branched alkylphosphonic acids described above. Thus, in another aspect, the present invention provides a polyethylene film having an improved barrier to water vapor and oxygen. The film has a (i) density of from about 930 kg / m 3 to about 970 kg / m 3It comprises a high-density polyethylene polymer having a density, and (ii) a salt of a branched alkylphosphonic acid. The high-density polyethylene polymer present in the film may be any of the high-density polyethylene polymers described above in connection with the embodiments of the polymer composition of the present invention. In a preferred embodiment, the high-density polyethylene polymer has a multimodal molecular weight distribution having two or more maxima. The salt of the branched alkylphosphonic acid present in the film can be any of the salts of the branched alkylphosphonic acids described above in connection with the embodiments of the polymer composition of the present invention. In a preferred embodiment, the salt of the branched alkylphosphonic acid is the calcium salt of tert-butylphosphonic acid (for example, calcium t-butylphosphonate monohydrate).

[0081]

[0075] As described above, the polyethylene film has an improved barrier to water vapor and oxygen, as evidenced by a significantly improved water vapor and oxygen permeability. In a preferred embodiment, the film has a normalized oxygen transmission rate (nOTR) of about 300 cm 3 ·mil m -2 / day -1 (0.209 atm) -1 or less, about 275 cm 3 ·mil m -2 / day -1 (0.209 atm) or less, about 250 cm 3 ·mil m -2 / day -1 (0.209 atm) -1 or less, about 225 cm 3 ·mil m -2 / day -1 (0.209 atm) -1 or less, or about 200 cm 3 ·mil m -2 / day -1 (0.209 atm) -1 or less. In another preferred embodiment, the film has a water vapor transmission rate of about 3 g mil m -2 / day -1 or less, about 2.5 g mil m -2 / day -1 or less, about 2 g mil m -2 / day -1 or less, or about 1.75 g mil m -2Day -1 It has the following normalized water vapor transmission rate (nWVTR). In addition to these barrier improvements, polyethylene films generally have a desirable combination of low haze, high transparency, and high gloss. For example, a polyethylene film of the present invention having a thickness of about 3 mils can exhibit a haze of about 20% or less (e.g., about 15% or less) and / or a transparency of about 90% or more (e.g., about 95% or more). In a preferred embodiment, the polyethylene film has a gloss of about 80% or more (e.g., about 90% or more).

[0082]

[0076] The following examples further illustrate the above subject matter, but should of course not be construed as limiting its scope in any way.

[0083] Example 1

[0077] This example demonstrates the production of a polymer composition according to the present invention and the improved properties exhibited by a cast film made from such a polymer composition.

[0084]

[0078] The cast film was made using a high density polyethylene polymer (HDPE), specifically Sclair 2908 manufactured by Nova Chemicals. The polymer was reported to have a density of 961 kg / m 3 and a melt flow index of 7.0 dg / min. The granular resin was ground into a powder and then compounded with the additives described below.

[0085]

[0079] The sample was prepared by mixing the ground HDPE resin with 638 ppm of the specified phosphonate, 319 ppm of zinc stearate, 300 ppm of Irganox® 1010 antioxidant, and 600 ppm of Irgafos® 168 antioxidant. The control sample was prepared by mixing the ground HDPE resin with 300 ppm of Irganox® 1010 antioxidant and 600 ppm of Irgafos® 168 antioxidant. The combined components were mixed in a 10 L Henschel high-intensity mixer at 2,000 rpm for approximately 2.5 minutes.

[0086]

[0080] Each of the obtained mixtures was compounded through a Deltaplast single-screw extruder equipped with a 1-inch diameter screw with an L / D of 30 and having a Maddock mixing section. The temperature profile of the four barrel zones from the front to the end was 160 °C, 175 °C, 190 °C, and 190 °C. A short cylindrical strand die with a temperature set at 190 °C was connected to the end. The polymer strands were water-cooled and cut into pellet size with a standard pelletizer. The extruder was purged with HDPE resin between each sample.

[0087]

[0081] Before making the film, each compounded sample was bag-mixed with 6 wt% of linear low-density polyethylene (LLDPE) resin. The LLDPE resin used was Dowlex 2035 with a reported density of 919 kg / m 3 and a melt flow index of 6.0 dg / min. The LLDPE resin was added to facilitate a constant feed rate during film extrusion.

[0088]

[0082] The film was extruded with a Killion lab system. The system was equipped with a single-screw extruder having a screw diameter of 1 inch and an L / D of 24 with an Egan mixing section. During processing, the first zone of the extruder was set at 180 °C and the remaining zones and transfer line were set at 205 °C. The polymer melt from the extruder was spread onto a 12-inch laboratory-scale chill roll through an adjustable die lip set at 0.5 mm intervals and a 205 °C 150 mm film die having a T-shaped coat hanger spreading profile, followed by a tensile winding take-up system. The chill roll temperature was maintained at 85 °C with a coolant. The screw speed of the extruder was set at 60 rpm so as to obtain a line output of 3.6 kg / hour. The chill roll surface rolling speed was set at 19 feet / minute. With the above settings, a target film thickness of about 3 mils was obtained.

[0089]

[0083] The haze and transparency of the obtained film were measured according to ASTM D1003 using a BYK Haze Guard Transparency Transmission haze meter. The gloss was measured using a BYK single-angle 45° micro gloss meter with the film placed on a matte finish vacuum table to avoid backside reflection. The crystallization temperature of the film was measured using a Mettler Toledo differential scanning calorimetry (DSC) unit in the temperature range of 60 to 200 °C at a heating / cooling rate of 20 °C / minute.

[0090]

[0084] The oxygen transmission rate (OTR) of the extruded film was measured using a Mocon film permeation cell (surface area 50 cm 2 ; cell volume on the sensor side of the film 12.0 cm 3) Measured in accordance with ASTM F3136 using a MOCON OpTech®-O2 Model P unit. The unit (sensor and cell) was placed in a laboratory with controlled temperature and humidity (23 °C and 50% relative humidity in accordance with ASTM D618-08). The sensor side of the cell (under the film) was pre-purged with dry low-oxygen nitrogen for 10 minutes, while the top or “insult” side of the film was purged with low dew point in-house compressed air, resulting in an oxygen exposure of 0.209 atm. To account for slight film thickness variations, the results were normalized to a thickness of 1.0 mil for more direct comparison. The results are in units of cm 3 ·mil·m -2 ·day -1 ·(0.209 atm) -1 of normalized oxygen transmission rate (nOTR).

[0091]

Table 1

[0092]

[0085] As can be seen from the data in Table 1, films made using salts of branched alkylphosphonic acids have desirably low nOTR (600 cm 3 ·mil·m -2 ·day -1 ·(0.209 atm) -1showed less than), and some films also showed low haze and high gloss. These data suggest that such salts are effective nucleating agents for polyethylene polymers. Among these salts, the data indicate that calcium t-butylphosphonate (specifically, calcium t-butylphosphonate monohydrate) is particularly effective in improving the physical properties of the film. In fact, films made with calcium t-butylphosphonate show an nOTR that is approximately 68% lower than that of the control film. Such a dramatically low nOTR makes such films particularly useful for products that must be protected from oxygen, such as meat packaging. Further, this dramatic increase in nOTR was accompanied by a significant decrease in haze (about 75%) and an increase in gloss compared to the control film. Thus, films made with calcium t-butylphosphonate not only exhibit highly desirable barrier properties but also optical properties that make them an attractive option for product packaging.

[0093] Example 2

[0086] This example demonstrates the production of a polymer composition according to the present invention and the improved properties exhibited by blown films made from such polymer compositions.

[0094]

[0087] Blown films were made using a blend of high molecular weight HDPE and low molecular weight HDPE. In particular, Sclair 19C (manufactured by Nova Chemicals) functioned as the high molecular weight HDPE. This HDPE resin has been reported to have a density of 958 kg / m 3 and a melt flow index of 0.95 dg / min. The low molecular weight resin has a density of 965 kg / m 3And it was DMDA8007 (manufactured by Dow Chemical) which was reported to have a melt flow index of 8.3 dg / min. Two kinds of HDPE resins were blended at a ratio of 7.5 parts by weight of Sclair19C to 2.5 parts by weight of DMDA8007. Specifically, 75 kg of 19C pellets and 25 kg of 8007 pellets were weighed separately and combined, and uniformly mixed with a Munson mixer. The obtained resin blend was compounded using an MPM single-screw extruder. The temperature settings from zone 1 to zone 3 were 162 °C, 176 °C and 190 °C, and the die temperature was 190 °C. After extruding the first 1 kg of material, the polymer strands coming out of the die were transferred to a water bath. The polymer strands were cut into pellet sizes with a standard pelletizer. The compounded HDPE blend was passed through the Munson mixer again to ensure a uniform distribution. The granular compounded HDPE resin blend was pulverized into powder before subsequent use described below. This pulverized compounded HDPE resin blend is hereinafter referred to as "HDPE resin blend 1".

[0095]

[0088] The samples used for making blown films were prepared by mixing HDPE resin blend 1 with 600 ppm of the specified phosphonate, 300 ppm of zinc stearate, 300 ppm of Irganox® 1010 antioxidant, and 600 ppm of Irgafos® 168 antioxidant. The control sample was prepared by mixing HDPE resin blend 1 with 300 ppm of Irganox® 1010 antioxidant and 600 ppm of Irgafos® 168 antioxidant. The combined components were mixed at 2,000 rpm for about 2.5 minutes with a 10 L Henschel high-intensity mixer.

[0096]

[0089] After mixing, each blend of HDPE and the additive was compounded using a Prism twin-screw extruder. The temperature profiles of zones 1 to 4 from the front to the end were 170 °C, 175 °C, 185 °C, and 190 °C; the die temperature was 160 °C. The screw speed of the extruder was set at 400 rpm. After extruding the first 200 g of material, the polymer strand was transferred to a water bath. The cooled polymer strand was cut into pellet size using a standard pelletizer.

[0097]

[0090] Prior to film fabrication, each sample was bag mixed with 3 wt% of processing agent 10476 - 11, a masterbatch provided by Colortech, Inc., containing 3.0% active fluorinated resin polymer processing aid in a linear low-density polyethylene (LLDPE) carrier resin having an MFI of 2 dg / min.

[0098]

[0091] The film was extruded into a Labtech Engineering single-layer blown film line equipped with a 25 mm barrel extruder (L / D 30) having a Maddock mixer section and a pineapple chip, a single-layer spiral mandrel die with a 40 mm die lip setting and a die gap of 1.2 mm, a dual lip air ring, a guide cage, a guide plate, and a take-up system for winding the film roll. The feed throat zone was 180 °C and all other extruder and die zones were 210 °C. The screw speed was 110 rpm, resulting in a feed rate of 5.0 kg / hour. The speeds of the take-up and air ring blowers were adjusted to produce a film at a frost line height of 13 cm and approximately 2.0 mils.

[0099]

[0092] The optical properties, crystallization temperature, and nOTR of the film were measured as described above. The water vapor transmission rate (WVTR) of the selected film was measured according to ASTM F1249 (100 °F, 90% RH) using an Illinois Instruments Model 7011 water vapor permeation analyzer. The results were normalized to 1.0 mil to account for minor thickness variations and to facilitate direct comparison, g·mil·m -2·day -1 The unit was obtained.

[0100]

Table 2

[0101]

[0093] As can be seen from the data in Table 2, the blown film made using the salt of branched alkylphosphonic acid has a desirably low nOTR (600 cm 3 ·mil·m -2 ·day -1 ·(0.209 atm) -1 less than), and some films also showed low haze and high transparency. These data suggest that such salts are effective nucleating agents for polyethylene polymers. Among these salts, the data show that calcium t-butylphosphonate (specifically, calcium t-butylphosphonate monohydrate) is particularly effective in improving the physical properties of the film. In fact, the film made using calcium t-butylphosphonate shows an nOTR that is about 72% lower than that of the control film. Furthermore, the film made using calcium t-butylphosphonate had an nWVTR that was about 66% lower than that of the control film. These improvements in barrier properties were accompanied by a significant reduction in haze (about 66%) compared to the control film. Therefore, the film made using calcium t-butylphosphonate not only provides highly desirable barrier properties but also shows optical properties that make it an attractive option for product packaging.

[0102] Example 3

[0094] This example demonstrates the production of the polymer composition according to the present invention and the improved properties shown by injection molded articles made from such polymer compositions.

[0103]

[0095] The injection molded article was made using Sclair 2908 HDPE manufactured by Nova Chemicals. The polymer has a density of 961 kg / m 3and is reported to have a melt flow index of 7.0 dg / min. The granular resin was ground into powder before being compounded with the additives described below.

[0104]

[0096] Samples were prepared by mixing the ground HDPE resin with 600 ppm of the specified phosphonate, 300 ppm of zinc stearate, 300 ppm of Irganox® 1010 antioxidant, and 600 ppm of Irgafos® 168 antioxidant. Control samples were prepared by mixing the ground HDPE resin with 300 ppm of Irganox® 1010 antioxidant and 600 ppm of Irgafos® 168 antioxidant. The combined components were mixed in a 30 L Henschel high-intensity mixer at 2000 rpm for about 3 minutes.

[0105]

[0097] Each of the resulting mixtures was compounded using a Leistritz ZSE-18 twin-screw extruder. Prior to each sample, the extruder was purged with Sclair2908 HDPE resin. The temperature profile of all zones was set at 155 °C to 165 °C; the die temperature was 155 °C. The screw speed was set at 500 rpm and the feed rate was 3.5 kg / hour. After extruding the first 200 g of material, the polymer strand was transferred to a water bath. The cooled polymer strand was cut into pellet size using a standard pelletizer.

[0106]

[0098] Each compounded sample was molded into ISO shrinkage plaques according to ISO 294 using a 55-ton Arburg injection molding machine. The mold had a dual cavity and the plaque dimensions were 60.0 mm in length, 60.0 mm in width, and 2.0 mm in height. The throat temperature was 40 °C. The first four zones of the barrel were set at 210 °C and the last zone was set at 230 °C. The mold temperature was set at 40 °C. The total cycle time was 40 - 45 seconds. The resulting ISO shrinkage plaques were subjected to measurement of the crystallization temperature and plaque shrinkage in the machine direction (MD) and transverse direction (TD).

[0107]

[0099] Further, each compounded sample was molded into plaques for use in OTR and WVTR measurements. Specifically, each compounded sample was molded into a plaque using a Husly 90-ton injection molding machine connected to a custom end gate die having dimensions of 4.0 inches in length, 4.0 inches in width, and 1.0 mm in height. The temperature profiles from zone 1 to zone 3 of the extruder from the front to the end were set at 230 °C, 230 °C, and 230 °C. The nozzle was set at 250 °C, and the mold was set at 35 °C. The cycle time was 22.3 seconds, and the cooling time was 10 seconds. The maximum injection pressure was 1,140 psi. The resulting square plaques could be directly attached to an oxygen permeation analyzer and a water vapor transmission analyzer, and are herein referred to as "barrier plaques". The barrier plaques were subjected to measurements of optical properties, OTR, and WVTR using the same apparatus and ISO or ASTM methods as described above.

[0108]

Table 3

[0109]

Table 4

[0110] As can be seen from the data in Tables 3 and 4, the salt of branched alkylphosphonic acid (specifically, calcium t-butylphosphonate monohydrate) is a particularly effective nucleating agent for HDPE resin. Analysis of the ISO shrinkage plaques shows an increase in the crystallization temperature of the polymer indicating nucleation of HDPE by calcium t-butylphosphonate. Further, the transverse shrinkage of the plaques was dramatically reduced by calcium t-butylphosphonate. This very low TD shrinkage indicates very strong lamellar growth in the transverse direction of the plaque. Such in-plane lamellar growth is thought to lead to a decrease in the permeability of the plaque as the crystalline lamellae create a more tortuous path perpendicular to their growth direction. Indeed, this decrease in permeability was supported by the differences in nOTR and nWVTR observed in the barrier plaques. Plaques made using HDPE resin nucleated by calcium t-butylphosphonate showed nOTR and nWVTR values that were approximately 53% and 59% lower, respectively, than the control film. This dramatic decrease in the barrier was also accompanied here by a significant reduction in haze and an increase in transparency. This combination of improved barrier and optical properties makes the polymer nucleated by the salt of branched alkylphosphonic acid particularly attractive as a packaging material.

[0111] Example 4

[0101] This example demonstrates the production of a polymer composition according to the invention and the improved properties demonstrated by blown films made from such polymer compositions.

[0112]

[0102] 48.0 g of calcium t-butylphosphonate monohydrate (“CaTBP”), 24.0 g of zinc stearate, 8.0 g of DHT-4V, 0.60 g of Irganox® 1010 primary antioxidant, 1.4 g of Irgafos® 168 secondary antioxidant, and 1918 g of granular Sclair2908 HDPE (density 961 kg / m 3A masterbatch composition was prepared by combining [specific components] and MFI 7.0 dg / min. The above components were combined and intensively mixed at 2,000 rpm for 2.5 minutes in a 10-liter Henschel mixer. Then, the mixture was twin-screw compounded in a Leistritz 18 mm co-rotating twin-screw extruder equipped with a strand pelletizer. The barrel temperature zone was set at 145 - 155 °C, the screw speed was 500 rpm, and the feed rate was 3.0 kg / hour. The resulting masterbatch contained 2.4 weight percent of calcium t-butylphosphonate monohydrate and was designated as the "CaTBP masterbatch".

[0113]

[0103] A hydrocarbon resin masterbatch composition was prepared by combining 2400 g of OPPERA PR100A hydrocarbon resin, 1.2 g of DHT-4V, 1.2 g of Irganox® 1010 primary antioxidant, 3.6 g of Irgafos® 168 secondary antioxidant, and 3594 g of granular Nova Sclair 2908 HDPE as a polymer carrier. The components were compounded and intensively mixed at 1,200 rpm for 2.0 minutes in a 30-liter Henschel mixer. Next, the mixture was twin-screw compounded in a Leistritz 27 mm co-rotating twin-screw extruder equipped with a strand pelletizer. The barrel temperature zone was set at 140 - 150 °C, the screw speed was 400 rpm, and the feed rate was 15.0 kg / hour. The resulting masterbatch contained 40.0 weight percent of PR100A and was hereinafter referred to as the "PR100A masterbatch". The technical data sheet of the PR100A hydrocarbon resin states that the softening point is 137.7 °C. The glass transition temperature was determined to be approximately 85 °C by differential scanning calorimetry.

[0114]

[0104] A single-layer blown film was made from Nova Sclair 19C (density 958 kg / m 3And having an MFI of 0.95 dg / min), Sclair 2908, the above processing aid 10476-11 (“PPA MB”), and other components shown in Table 5 below were prepared by dry blending. The dry blend was fed directly into the hopper of the Labtech Engineering single-layer blown film line described in Example 2 above. The temperature of the extruder zone was raised to 200 °C, and the transfer zone and die zone were at the same temperature. The film was produced with a nominal thickness of 2 mils, a feed rate of 5.0 kg / hour, and a frost line height of 13 cm.

[0115]

[0105] The WVTR and OTR of the obtained film were measured as described above in Examples 1 and 2. These results were also normalized here with respect to the measured film thickness to allow for a more direct comparison taking into account minor thickness variations.

[0116]

Table 5

[0117]

Table 6

[0118]

[0106] As can be seen from the data in Tables 5 and 6, the addition of 600 ppm of calcium t-butylphosphonate monohydrate (CaTBP) resulted in a film showing a 56% decrease in both nWVTR and nOTR compared to the control film. As described above, this reduction in nWVTR and nOTR is significant. However, the data shows that the addition of hydrocarbon resin can further reduce nWVTR and nOTR. In fact, the improvement in barrier properties by the addition of hydrocarbon resin is particularly significant for oxygen permeability, which was further reduced by 13% when only 6 wt% of hydrocarbon resin was added.

[0119] Example 5

[0107] This example demonstrates the manufacture of a polymer composition according to the present invention and the improved properties demonstrated by blown films made from such polymer compositions.

[0120]

[0108] A total of 2,000 grams of a mixture containing 1.0% calcium t-butylphosphonate monohydrate and 0.50% zinc stearate in granular ExxonMobil LL 1002.09 LLDPE resin (density 918 kg / m 3 and MI 2.0 dg / min) was mixed in a 10 liter Henschel high intensity mixer at 2,000 rpm for 2.5 minutes. The mixture was compounded on an 18 mm co-rotating twin screw extruder with a barrel temperature set point of 155 - 165 °C. The resulting nucleating agent masterbatch was then dry blended at 6.0% with ExxonMobil LL 1001X31 (butene LLDPE having a density of 918 kg / m 3 and MFI 1.0 dg / min) along with 3.0% of the processing aid 10476 - 11 described above. This dry blend was compounded on the same extruder and profile as the masterbatch.

[0121]

[0109] The compounded resin manufactured above was converted into a 1.9 mil blown film using the Labtech Engineering lab single layer unit described in Example 2 above. The extruder zone was heated to 200 °C and all transfer lines / die zones were also at 200 °C. The blow up ratio was 2.5, the operating speed was 4.1 kg / hour, and the frost line height was 14 cm.

[0122]

[0110] A control sample was produced using a "blank" masterbatch (identical to the nucleating agent masterbatch except that calcium t-butylphosphonate monohydrate or zinc stearate was not added). This blank MB was subjected to all of the other preparations described above and a 1.9 mil film was also produced.

[0123]

[0111] The OTR of the obtained film was measured at 100% oxygen exposure using a Systech Illinois Model 8001 oxygen permeation analyzer in accordance with ASTM D 3985 (dry, 23°C). The results were normalized to a thickness of 1.0 mil to account for the slight differences in film thickness. Thus, the unit of normalized OTR (nOTR) is cm 3 ·mil m -2 day -1 (atmO2 -1 ) is.

[0124]

[0112] The nOTR of the film made using the "blank" masterbatch (containing no salt of branched alkylphosphonic acid) was 8,067 cm 3 ·mil m -2 day -1 (atmO2) -1 . The nOTR of the film made using branched alkylphosphonic acid was 5,025 cm 3 ·mil m -2 day -1 (atmO2) -1 . This approximately 38% reduction in nOTR is significant and indicates that the salt of branched alkylphosphonic acid (especially calcium t-butylphosphonate monohydrate) also nucleates the linear low-density polyethylene polymer.

[0125] Example 6

[0113] This example demonstrates the production of the polymer composition according to the present invention and the improved properties demonstrated by the blown film made from such a polymer composition. Specifically, this example demonstrates the effect of BET specific surface area on the nucleation performance of the salt of branched alkylphosphonic acid.

[0126]

[0114] Six samples (Samples 6-1 to 6-6) of calcium t-butylphosphonate monohydrate having different BET specific surface areas were evaluated as nucleating agents for blends of HDPE resin. Specifically, using 600 ppm of each sample, a blend of Sclair 19C (manufactured by Nova Chemicals) and DMDA 8007 (manufactured by Dow Chemical) similar to that described in Example 2 above was nucleated. Further, the nucleated HDPE blend was converted into a monolayer blown film in the same manner as described in Example 2 above.

[0127]

[0115] The BET specific surface area of the nucleating agent samples was measured in accordance with ISO standard 9277:2010 entitled "Determination of the Specific Surface Area of Solids by Gas Adsorption - BET method" using nitrogen as the adsorbing gas. The nOTR and nWVTR of the selected films were measured as described above in Examples 1 and 2.

[0128]

Table 7

[0129]

[0116] As can be seen from the data in Table 7, all films containing salts of branched alkylphosphonic acids (specifically, calcium t-butylphosphonate monohydrate) showed dramatically improved barriers compared to the control HDPE film. The data demonstrate that all of these salts were very effective nucleating agents for HDPE resin blends. However, the data also show that as the BET specific surface area of the salt increases, the salt nucleates the HDPE resin blend better. This is evident from the inverse correlation between the BET specific surface area of the salt and the nOTR of the film made using the salt.

[0130] Example 7

[0117] This example demonstrates the manufacture of a polymer composition according to the present invention and the improved barrier properties demonstrated by an extrusion blow molded article made from such a polymer composition. Specifically, this example demonstrates a reduction in water vapor transmission rate demonstrated by an extrusion blow molded bottle made using a polymer composition containing a salt of a branched alkylphosphonic acid and a polyethylene polymer composition having a melt relaxation ratio of 1.5 or greater.

[0131]

[0118] The extrusion blow molded article was made using Sclair® 58A HDPE resin sold by Nova Chemical. The reported density of 58A is 957 kg / m 3 and the reported melt flow index is 0.41 dg / min. The tanδ of 58A at 0.1 rad / s and 10 rad / s was measured (as described above) and determined to be 1.504 and 0.896, respectively. Thus, Sclair 58A HDPE had a melt relaxation ratio (MRR) of 1.679.

[0132]

[0119] Sclair 58A HDPE was nucleated using a masterbatch containing calcium t-butylphosphonate monohydrate (CaTBP). Specifically, the masterbatch contained 0.9 wt% CaTBP, 0.4 wt% DHT-4V, and 0.4 wt% zinc stearate in DMDA 8007 HDPE (manufactured by Dow Chemical) as the carrier resin. The masterbatch was added to Sclair 58A HDPE to obtain CaTBP loadings of 300 ppm (sample 7-2) and 1,000 ppm (sample 7-3). The masterbatch pellets and 58A pellets were first mixed at low intensity for about 5 minutes and compounded through a MPM single screw extruder. The temperature profile of the extruder barrel was raised from 149 °C (300 °F) to 210 °C (410 °F).

[0133] With a Bekum H121s single-station injection blow molding unit, extrusion blow molded bottles were produced from Sample 7-2, Sample 7-3, and non-nucleating Sclair 58A (Sample 7-1). A shampoo-shaped mold was installed on a carriage. The target shampoo bottle had a volume of 500 mL and a weight of 32 g (±0.5 g). The barrel temperature profile from the front to the end was set at 180 °C. The die gap was set at 33%. The mold was set at 18 °C (65 °F). The machine cycle time was 14 seconds.

[0134]

[0121] Next, the obtained bottles were tested and the water vapor transmission rate (WVTR) was determined according to the following procedure. WVTR was measured using an Illinois Instruments Model 7011 water vapor transmission analyzer with modifications to the moving line connected to an ESPEC LHU-113 oven. The oven was maintained at 37.7 °C and a relative humidity (RH) of 90% in accordance with ASTM F 1249. The bottles were attached to a platform designed for water vapor transmission rate measurement and sealed. Since the bottles had the same weight and volume (32 g and 500 mL), the WVTR unit was reported as mg / (bottle·day). The results of the WVTR measurement are shown in Table 8 below.

[0135]

Table 8

[0136] As can be seen from the data in Table 8, the extrusion blow molded articles (Samples 7-2 and 7-3) made from Sclair58A HDPE resin nucleated with calcium t-butylphosphonate all showed improved barriers compared to the bottles (Sample 7-1) made using non-nucleated Sclair58A HDPE. The bottle made from Sample 7-2 containing only 300 ppm of CaTBP showed a reduction in WVTR of about 33% compared to the bottle made from Sample 7-1. The bottle made from Sample 7-3 containing 1,000 ppm of CaTBP showed a reduction in WVTR of about 44% compared to the bottle made from Sample 7-1.

[0137] Example 8 This example demonstrates the lack of change in water vapor transmission rate shown by extrusion blow molded bottles made using a polymer composition containing a salt of a branched alkylphosphonic acid and a polyethylene polymer composition having a melt relaxation ratio of less than 1.5.

[0138] The extrusion blow molded articles were made using Formolene® HB5502B HDPE resin sold by Formosa. The reported density of HB5502B is 955 kg / m 3 and the reported melt flow index is 0.35 dg / min. The tanδ of HB5502B was measured at 0.1 rad / s and 10 rad / s (as described above) and determined to be 1.247 and 0.955, respectively. Thus, the melt relaxation ratio (MRR) of Formolene HB5502B HDPE was 1.306.

[0139]

[0125] First, Formolene HB5502B HDPE was ground into powder. Next, the ground HB5502B was combined with 600 ppm of calcium t-butylphosphonate monohydrate (CaTBP), 300 ppm of zinc stearate, 300 ppm of Irganox® 1010, and 600 ppm of Irgafos® 168. The components were highly mixed in a 30 L Henschel high-intensity mixer operating at 1,200 rpm for about 2.5 minutes. The resulting mixture (Sample 8-2) was melt compounded using a CT Leistritz twin-screw extruder. The temperature profile of the extruder barrel increased from 155 °C to 160 °C, the screw speed was set at 400 rpm, and the feed rate was 8 kg / hour. For comparison, another mixture (Sample 8-1) containing only ground HB5502B, 300 ppm of Irganox® 1010, and 600 ppm of Irgafos® 168 was also mixed and melt compounded as described above.

[0140]

[0126] The resulting pelletized polymer composition was processed into extrusion blow molded bottles as described in Example 7. The water vapor transmission rate of the bottles was also measured as described in Example 7. The results of the WVTR measurements are shown in Table 9 below.

[0141]

Table 9

[0142] As can be seen from the data in Table 9, the bottle (Sample 8-2) made using the polymer composition nucleated by calcium t-butylphosphonate monohydrate (CaTBP) did not show any significant change in the normalized water vapor transmission rate compared to the bottle (Sample 8-1) made using the non-nucleated Formolene HB5502B HDPE resin. This result is in marked contrast to the improvement in barrier (reduction in WVTR) observed with the nucleating resins in Example 7 (comparing Samples 7-2 and 7-3 to Sample 7-1). However, this difference in barrier properties is thought to be due to the difference in the melt relaxation ratio (MRR) between Sclair58A HDPE and Formolene HB5502B HDPE. As described above, Sclair58A HDPE had an MRR of 1.679. In contrast, Formolene HB5502B HDPE had an MRR of 1.306. Since the Sclair58A HDPE used in Example 7 had an MRR of 1.5 or greater, Sclair58A HDPE exhibited sufficient melt relaxation to allow nucleation of the polymer by the salt of the branched alkylphosphonic acid (CaTBP) during the processing time, and this nucleation resulted in an increase in the barrier (reduction in WVTR). In contrast, since Formolene HB5502B HDPE had an MRR of 1.49 or less, Formolene HB5502B HDPE relaxed very slowly during processing and could not be nucleated by the salt of the branched alkylphosphonic acid (CaTBP). This slow relaxation effectively prevented CaTBP from nucleating the polymer and resulted in a significant amount of strain-induced self-nucleation in the polymer. This self-nucleation of the polymer (in contrast to nucleation by CaTBP) did not result in any significant change in the barrier between the nucleated polymer (Sample 8-2) and the non-nucleated polymer (Sample 8-1) (no significant change in WVTR). Therefore, comparing the results of Examples 7 and 8 emphasizes the role that the MRR of the polyethylene polymer composition can play in the nucleation performance of the salt of the branched alkylphosphonic acid, particularly with respect to barrier improvement in the extrusion blow molding process.

[0143] All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference in their entirety as if each were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

[0144]

[0129] The terms "a", "an", and "the", as well as similar indicatives, used in the context of describing the subject matter of this application (especially in the context of the following claims) are to be construed as including both the singular and the plural, unless otherwise indicated herein or clearly contradicted by the context. The terms "comprising", "having", "including", and "containing" are to be construed as open-ended terms (i.e., meaning "including but not limited to") unless otherwise specified. The recitation of ranges of values herein is merely intended to be a shorthand method of referring individually to each separate value within the range, and each separate value is hereby incorporated into this specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or clearly contradicted by the context. The use of any and all examples or illustrative language (e.g., "such as") presented herein is merely intended to more clearly clarify the subject matter of this application and is not intended to limit the scope of the subject matter unless otherwise claimed. No language in this specification should be construed as indicating that any non-claimed element is essential to the practice of the subject matter described herein.

[0145] The preferred embodiments of the subject matter, including the best mode known to the inventors for carrying out the claimed subject matter, are described herein. Variations of the preferred embodiments may become apparent to those skilled in the art upon reading the foregoing description. The inventors expect those skilled in the art to employ such variations as appropriate, and the inventors intend the subject matter described herein to be practiced otherwise than as specifically described herein. Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Further, any combination of the above-described elements in all possible variations thereof is included in this disclosure unless otherwise specifically described herein or otherwise clearly contradicted by context. The invention described in the claims of the present application at the time of initial filing is appended below. [C1] (a) A polyethylene polymer composition having a melt relaxation ratio of 1.5 or more; and (b) a salt of a branched alkylphosphonic acid A polymer composition comprising. [C2] The polyethylene polymer composition has a density of about 930 kg / m 3 ~ about 970 kg / m 3 The polymer composition according to C1, having. [C3] The polyethylene polymer composition has a molecular weight distribution, and the molecular weight distribution has two or more maxima. The polymer composition according to C1 or C2. [C4] The polymer composition according to any one of C1 to C3, wherein the salt of the branched alkylphosphonic acid contains one or more cations selected from the group consisting of Group 1 element cations, Group 2 element cations, and Group 12 element cations. [C5] The polymer composition according to C4, wherein the salt of the branched alkylphosphonic acid contains a Group 2 element cation. [C6] The polymer composition according to C5, wherein the salt of the branched alkylphosphonic acid contains a calcium cation. [C7] The polymer composition according to any one of C1 to C6, wherein the branched alkylphosphonic acid contains a branched alkyl group selected from the group consisting of isopropyl, sec-butyl, isobutyl, tert-butyl, tert-pentyl, neopentyl, isopentyl, sec-pentyl, sec-isopentyl, pentan-3-yl, and 2-methylbutyl. [C8] The polymer composition according to any one of C1 to C7, wherein the branched alkylphosphonic acid contains a tertiary alkyl group. [C9] The polymer composition according to C7, wherein the branched alkylphosphonic acid contains a branched alkyl group selected from the group consisting of tert-butyl, tert-pentyl, and neopentyl. [C10] The polymer composition according to any one of C1 to C9, wherein the salt of the branched alkylphosphonic acid is a salt of tert-butylphosphonic acid. [C11] The polymer composition according to any one of C1 to C10, wherein the salt of the branched alkylphosphonic acid is a calcium salt of tert-butylphosphonic acid. [C12] The salt of the branched alkylphosphonic acid has a BET specific surface area of about 20 m 2 / g or more. The polymer composition according to any one of C1 to C11. [C13] The salt of the branched alkylphosphonic acid has a BET specific surface area of about 30 m 2 / g or more. The polymer composition according to C12. [C14] The polymer composition according to any one of C1 to C13, wherein the salt of the branched alkylphosphonic acid is present in the polymer composition in an amount of about 50 parts per million to about 2,000 parts per million based on the total weight of the polymer composition. [C15] A method for molding a thermoplastic polymer composition, comprising: (a) preparing an apparatus including a die and a mold cavity, the mold cavity having an inner surface defining the shape of the molded article; (b) preparing (i) a polyethylene polymer composition having a melt relaxation ratio of 1.5 or more; and (ii) a polymer composition containing a salt of a branched alkylphosphonic acid; (c) heating the polymer composition to a temperature sufficient to melt the polymer composition so that the polymer composition can be extruded through the die; (d) extruding the molten polymer composition through the die to form a parison; (e) capturing the parison within the mold cavity; (f) blowing a pressurized fluid into the parison under a pressure sufficient to expand the parison so that the parison conforms to the inner surface of the mold cavity to produce a molded article; (g) cooling the molded article to a temperature at which the polymer composition at least partially solidifies so that the molded article retains its shape; and (h) removing the molded article from the mold cavity A method comprising the steps of: [C16] The method according to C15, wherein the polyethylene polymer composition has a melt relaxation ratio of 1.55 or more. [C17] The polyethylene polymer composition has a density of about 930 kg / m 3 ~ about 970 kg / m 3 The method according to C15 or C16. [C18] The method according to any one of C15 to C17, wherein the polyethylene polymer composition has a melt flow index of 1 dg / min or less at 190 °C. [C19] The method according to any one of C15 to C18, wherein the polyethylene polymer composition has a molecular weight distribution, and the molecular weight distribution has two or more maxima. [C20] The molded article has a normalized oxygen transmission rate (nOTR) of about 300 cm 3 ·mil m -2 ·day -1 (0.209 atm) -1 or less. The method according to any one of C15 to C19. [C21] The molded article has a normalized water vapor transmission rate (nWVTR) of about 3 g mil m -2·day -1 or less. The method according to any one of C15 to C20.

Claims

1. A polymer composition comprising: (a) a polyethylene polymer composition having a melt relaxation ratio of 1.5 or more, wherein the melt relaxation ratio (MRR) is calculated using the following formula: 【Equation 1】 (wherein tan δ is the ratio of the shear loss modulus to the shear storage modulus (G″ / G′) of the polyethylene polymer composition, tan δ 0.1 rad / s is the value of tan δ measured at an angular frequency of 0.1 rad / s, and tan δ 10 rad / s is the value of tan δ measured at an angular frequency of 10 rad / s), and (b) a salt of a branched alkylphosphonic acid present in the polymer composition in an amount of 50 parts per million to 2,000 parts per million based on the total weight of the polymer composition. A polymer composition comprising the same.

2. The polyethylene polymer composition has a density of 930 kg / m ３ to 970 kg / m ３ The polymer composition according to claim 1.

3. The polyethylene polymer composition has a molecular weight distribution, and the molecular weight distribution has two or more maxima. The polymer composition according to claim 1.

4. The salt of the branched alkylphosphonic acid comprises one or more cations selected from the group consisting of Group 1 element cations, Group 2 element cations, and Group 12 element cations. The polymer composition according to claim 1.

5. The salt of the branched alkylphosphonic acid comprises a Group 2 element cation. The polymer composition according to claim 4.

6. The salt of the branched alkylphosphonic acid comprises a calcium cation. The polymer composition according to claim 5.

7. The polymer composition according to claim 1, wherein the branched alkylphosphonic acid contains a branched alkyl group selected from the group consisting of isopropyl, sec-butyl, isobutyl, tert-butyl, tert-pentyl, neopentyl, isopentyl, sec-pentyl, sec-isopentyl, pentan-3-yl, and 2-methylbutyl.

8. The polymer composition according to claim 1, wherein the branched alkylphosphonic acid contains a tertiary alkyl group.

9. The polymer composition according to claim 7, wherein the branched alkylphosphonic acid contains a branched alkyl group selected from the group consisting of tert-butyl, tert-pentyl, and neopentyl.

10. The polymer composition according to claim 1, wherein the salt of the branched alkylphosphonic acid is a salt of tert-butylphosphonic acid.

11. The polymer composition according to claim 1, wherein the salt of the branched alkylphosphonic acid is a calcium salt of tert-butylphosphonic acid.

12. The polymer composition according to claim 1, wherein the salt of the branched alkylphosphonic acid has a BET specific surface area of 20 m ２ / g or more.

13. The polymer composition according to claim 12, wherein the salt of the branched alkylphosphonic acid has a BET specific surface area of 30 m ２ / g or more.

14. The polymer composition according to claim 1, wherein the salt of the branched alkylphosphonic acid is present in the polymer composition in an amount of 100 ppm to 1,000 ppm based on the total weight of the polymer composition.

15. A method for molding a thermoplastic polymer composition, comprising: (a) preparing an apparatus including a die and a mold cavity, the mold cavity having an inner surface defining the shape of the molded article; (b) A step of preparing a polymer composition, wherein the polymer composition is (i) a polyethylene polymer composition having a melt relaxation ratio of 1.5 or more, and the melt relaxation ratio (MRR) is represented by the following formula: [Equation 2] (wherein, tan δ is the ratio (G″ / G′) of the shear loss elastic modulus and the shear storage elastic modulus of the polyethylene polymer composition, tan δ 0.1 rad / s is the value of tan δ measured at an angular frequency of 0.1 rad / s, and tan δ 10 rad / s is the value of tan δ measured at an angular frequency of 10 rad / s), a polyethylene polymer composition calculated using the formula; and (ii) a salt of a branched alkylphosphonic acid, wherein the salt of the branched alkylphosphonic acid is present in the polymer composition in an amount of 50 ppm to 2,000 ppm based on the total weight of the polymer composition; (c) A step of heating the polymer composition to a temperature sufficient to melt the polymer composition so that the polymer composition can be extruded through a die; (d) A step of extruding the molten polymer composition through the die to form a parison; (e) A step of capturing the parison in the mold cavity; (f) A step of blowing a pressurized fluid into the parison under a pressure sufficient to expand the parison so that the parison conforms to the inner surface of the mold cavity to produce a molded article; (g) A step of cooling the molded article to a temperature at which the polymer composition is at least partially solidified so that the molded article retains its shape; and (h) A step of removing the molded article from the mold cavity A method comprising the steps of.

16. The method according to claim 15, wherein the polyethylene polymer composition has a melt relaxation ratio of 1.55 or more.

17. The polyethylene polymer composition is 930 kg / m ３ to 970 kg / m ３The method according to claim 15, having the density of **Claim 18** The method according to claim 15, wherein the polyethylene polymer composition has a melt flow index of 1 dg / min or less at 190 °C. **Claim 19** The method according to claim 15, wherein the polyethylene polymer composition has a molecular weight distribution, and the molecular weight distribution has two or more maxima. **Claim 20** The molded article has a normalized oxygen transmission rate (nOTR) of ３ · 300 cm －２ · per day －１ (0.209 atm) or less, according to the method of claim 15. －１ The method according to claim 15, having the following normalized oxygen transmission rate (nOTR). **Claim 21** The molded article has a normalized water vapor transmission rate (nWVTR) of －２ · 3 g per day －１ or less, according to the method of claim 15.

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