Thermoplastic polymer compositions and methods for preparing articles and films therefrom

Abstract

A thermoplastic polymer composition comprising a polyethylene polymer composition and a bicyclic [2.2.1]heptane-2,3-dicarboxylate. The polyethylene polymer composition may have a melt relaxation product of 50,000 or less. A method for preparing an injection-molded article includes the steps of: (a) providing the thermoplastic polymer composition as described above, (b) melting the thermoplastic polymer composition, (c) injecting the molten thermoplastic polymer composition into a mold cavity, (d) cooling the molten thermoplastic polymer composition, and (e) removing the injection-molded article from the mold cavity. A method for preparing a film includes the steps of: (a) providing the thermoplastic polymer composition as described above, (b) melting the thermoplastic polymer composition, (c) extruding the molten thermoplastic polymer composition through a slit die to form a film, (d) cooling the film, and (e) collecting the film.

Description

Technical Field

[0001] The present invention relates to thermoplastic polymer compositions and methods for preparing articles (e.g., injection-molded articles) and films (e.g., cast films) from the same. Background Technology

[0002] Several nucleating agents for thermoplastic polymers are known in the art. These nucleating agents typically function by forming nuclei or providing sites for crystal formation and / or growth in the thermoplastic polymer as it solidifies from a molten state. The nuclei or sites provided by the nucleating agent allow crystals to form in the cooled polymer at higher temperatures and / or faster rates than in the original, unnucleated thermoplastic polymer. These effects can then allow the nucleated thermoplastic polymer composition to be processed in a shorter cycle time than the original, unnucleated thermoplastic polymer. Nucleating agents can also induce the orientation of crystalline lamellae in the polymer, which does not lead to self-nucleation crystallization. Depending on the orientation of the lamellae produced by the nucleating agent, the physical properties of articles made from the polymer can be improved relative to polymers undergoing self-nucleation crystallization.

[0003] Furthermore, the effectiveness of a nucleating agent can depend on certain physical properties of the polymer being nucleated. In other words, a given nucleating agent can nucleate a polyethylene polymer with a set of physical properties more effectively than another polyethylene polymer with a different set of physical properties. The effectiveness of a nucleating agent typically depends on several physical properties of the polymer. The interrelationships between various physical properties and their effects on the nucleating agent make it difficult to easily determine the pairing of nucleating agent and polymer to produce a polymer composition with the desired properties.

[0004] Therefore, there remains a need for combinations of polymers and nucleating agents that exhibit favorable nucleation effects and produce polymer compositions with desired physical properties, such as low water vapor and oxygen permeability. Methods utilizing this advantageous combination of polymers and nucleating agents, such as injection molding and cast film methods, are also needed. The polymer compositions and methods described in this application attempt to meet these needs. Summary of the Invention

[0005] In a first embodiment, the present invention provides a thermoplastic polymer composition comprising:

[0006] (a) A polyethylene polymer composition with a melt relaxation product of 50,000 or less; and

[0007] (b) Bicyclic [2.2.1]heptane-2,3-dicarboxylate.

[0008] In a second embodiment, the present invention provides a method for producing injection-molded articles from a thermoplastic polymer composition. The method includes the following steps:

[0009] (a) Providing a thermoplastic polymer composition comprising (i) a polyethylene polymer composition having a melt relaxation product of 50,000 or less; and (ii) a bicyclo[2.2.1]heptane-2,3-dicarboxylate;

[0010] (b) Heating the thermoplastic polymer composition to a temperature sufficient to melt the thermoplastic polymer composition so that it can be injected into a mold having a cavity defining the size of the article;

[0011] (c) Injecting the molten thermoplastic polymer composition into the mold cavity;

[0012] (d) Cooling and solidifying the molten thermoplastic polymer composition in the mold cavity to form an injection-molded article; and

[0013] (e) Open the mold and remove the product from the mold cavity.

[0014] In a third embodiment, the present invention provides a method for preparing a film from a thermoplastic polymer composition. The method includes the following steps:

[0015] (a) Providing a thermoplastic polymer composition comprising (i) a polyethylene polymer composition having a melt relaxation product of 50,000 or less; and (ii) a bicyclo[2.2.1]heptane-2,3-dicarboxylate;

[0016] (b) Heating the thermoplastic polymer composition to a temperature sufficient to melt it so that it can be extruded through a die;

[0017] (c) Extruding a molten thermoplastic polymer composition through a die with a slit-shaped orifice to form a thin film exiting the orifice;

[0018] (d) Passing the film exiting the die through a cooling surface to solidify the thermoplastic polymer composition; and

[0019] (e) Collect the film. Detailed Implementation

[0020] In a first embodiment, the present invention provides a thermoplastic polymer composition comprising a polyethylene polymer composition and a bicyclo[2.2.1]heptane-2,3-dicarboxylate.

[0021] The polyethylene polymer composition used in the composition may contain any suitable polyethylene polymer or mixture of polyethylene polymers. However, it is believed that bicyclo[2.2.1]heptane-2,3-dicarboxylate is more effective in nucleation of polyethylene polymer compositions exhibiting a greater degree of melt relaxation. In some melt processing of polymers (e.g., injection molding or cast film manufacturing), the polymer melt is stretched or strained as it is extruded through a die. The strain applied to the polymer melt causes the flow direction orientation of the extended polymer chains in the polymer melt. When the processed polymer melt cools, these oriented extended polymer chains can return to a less ordered state before the polymer melt crystallizes. This process is referred to herein as “melt relaxation”. Alternatively, the oriented extended polymer chains can remain oriented in the melt and crystallize to form fibrils. These fibrils provide sites capable of initiating polymer self-nucleation. When the polymer solidifies from the melt, if enough of these fibrils are formed in the polymer, the resulting strain-induced self-nucleation can become the dominant mode of nucleation in the polymer. While self-nucleation of polymers may seem beneficial, the resulting polymer structures are often less favorable for certain desired physical properties. For example, self-nucleated polyethylene typically exhibits higher water vapor and oxygen permeability than polyethylene with heterogeneous nucleation using bicyclo[2.2.1]heptane-2,3-dicarboxylate. Therefore, to maximize the degree of nucleation induced by bicyclo[2.2.1]heptane-2,3-dicarboxylate, thermoplastic polymer compositions preferably comprise polyethylene polymer compositions exhibiting sufficient melt relaxation to ensure that strain-induced self-nucleation does not dominate.

[0022] The degree of melt relaxation exhibited by polymers is not easily quantified directly. Furthermore, melt relaxation is believed to be influenced by numerous factors, such as molecular weight, the width of the molecular weight distribution, the relative amount of the high molecular weight fraction within the distribution, and branched or nonlinear chains in the polymer. The number of factors involved and the complex relationships between them make it difficult to determine a range of values ​​for each sufficient to define polyethylene polymers exhibiting adequate melt relaxation. In other words, one might attempt to define the molecular weight distribution of a polymer exhibiting adequate melt relaxation, but the appropriate range will vary with the “shape” of the distribution (i.e., the relative amount of the high molecular weight fraction). Therefore, while these factors can be considered when attempting to identify polyethylene polymers exhibiting adequate melt relaxation, more direct and accurate melt relaxation measurements are needed.

[0023] The applicant discovered that the complex viscosity (η*) of a polyethylene polymer melt can at least partially lead to a more accurate measurement of melt relaxation. Complex viscosity (η*) depends on a complex number and consists of a real part called dynamic viscosity (η′) and an imaginary part called heterogeneous viscosity (η″). These values ​​are typically obtained through parallel-plate rheological experiments, which are well-known in industry and are described more fully below. The complex viscosity results obtained through this measurement can be plotted using heterogeneous viscosity as the y-axis and dynamic viscosity as the x-axis. Such a plot is commonly referred to as a Cole-Cole plot. For the essentially linear polyethylene polymer compositions of interest here, the Cole-Cole plot curves into an arc, and this arc approximates the circumference of a circle whose Cartesian coordinates follow the equation:

[0024] r 2 =(xh) 2 +(yk) 2 .

[0025] In the above formula, x corresponds to the dynamic viscosity (η′) value, and y corresponds to the heterogeneous viscosity (η″) value at various strain rates. The constants h and k represent the offset of the circle's center from the Cartesian origin of the Cole-Cole diagram in the x and y directions, respectively. Due to the nature of complex viscosity, the value of h is positive, while the value of k is negative. It has been found that the radius of this circle (i.e., the circle approximated by the Cole-Cole diagram) is related to the degree of melt relaxation in the polyethylene polymer composition; a smaller radius generally indicates greater melt relaxation in the polymer, while a larger radius generally indicates less melt relaxation in the polymer.

[0026] Unfortunately, the radius of the circle typically fitted by a Cole-Cole plot cannot be reliably calculated from a single point on the Cole-Cole plot. Small natural variations in complex viscosity measurements will produce slightly different radius values ​​for each x,y pair. Therefore, to determine the radius of the circle, it is necessary to fit the measured dynamic viscosity (η′) and heterogeneous viscosity (η″) values ​​to the above equation using the least squares method. In this fitting process, the radius of each x,y pair is calculated by rearranging the circle equation, and the squared error (SE) of each x,y pair is calculated by squaring the difference between the average radius (i.e., the radius obtained by averaging the radii calculated for each x,y pair) and the radius calculated for that particular x,y pair. The sum of squared errors (SSE) is then calculated by summing the SEs of all x,y pairs in the Cole-Cole plot. The data fitting is performed by changing the values ​​of h and k until the sum of squared errors (SSE) is minimized. Since the radius calculated at any x,y pair depends on h and k, the individual radii are updated as a result of fitting h and k, and the average radius is also updated simultaneously. The resulting average radius value (i.e., the arithmetic mean of the radii of each x,y pair after least squares fitting) will be referred to below as the average radius (r) of the Cole-Cole plot. avg ).

[0027] As mentioned above, the average radius of the Cole-Cole diagram has been found to be related to the degree of melt relaxation in polyethylene polymer compositions. However, the average radius of the Cole-Cole diagram is also affected by the melt flow index (MFI) of the polyethylene polymer composition. In particular, for polymers with similar molecular weight distributions and levels of branching, the average radius of the Cole-Cole diagram tends to decrease significantly as the MFI of the polyethylene polymer composition increases and the molecular weight decreases. In this case, viscosity usually decreases, and it is well known that polymers with lower viscosity have faster average melt relaxation. However, the factors mentioned above, such as a wider molecular weight distribution, high molecular weight tails, or branching, can lead to an unexpectedly high radius for a given MFI, resulting in unexpectedly high viscosity and an unexpectedly long average melt relaxation time. Furthermore, the MFI range typically seen in polymers used for injection molding and cast film production can be quite wide. Therefore, it is necessary to predict whether resins over a wide MFI range will sufficiently relax in the melt to allow effective nucleation via heterogeneous nucleation with bicyclic [2.2.1]heptane-2,3-dicarboxylate, or whether insufficient melt relaxation will cause self-nucleation to become important or even dominant. Thus, to obtain a useful measurement tool for quantifying the melt relaxation of a range of polymers, it is necessary to correct or account for the effect of MFI on the average radius of the Cole-Cole diagram. Given the generally inverse relationship between the two, the inventors have found that by calculating the polymer's melt flow index (MFI) and the average radius (r) of the polymer's Cole-Cole diagram, a more effective method can be used. avg The product of MFI and r can best correct for or explain this effect. The resulting product is referred to below as the "Melt Relaxation Product" (MRP). Through extensive experimentation, the inventors have found that the Melt Relaxation Product (MRP) is a good measure of the degree of melt relaxation in a polymer; a higher MRP indicates a lower degree of melt relaxation, while a lower MRP indicates a higher degree of melt relaxation. Simply put, polymers with a higher MFI generally have a lower r avg This offsets the high MFI in the MRP equation and flattens the MRP values. However, for resins with such high MFI, r avg If the value is unexpectedly high, no shift will occur, and the MRP will increase significantly. This situation is typically characterized by inefficient melt relaxation.

[0028] As described above, the melt relaxation product (MRP) is defined as the average radius (r) of the Cole-Cole diagram of (i) the melt flow index (MFI) of the polyethylene polymer composition and (ii) the dynamic viscosity (η′) and heterogeneous viscosity (η″) of the polyethylene polymer composition. avg The product of )

[0029] MRP = MFI × r avg .

[0030] The melt flow index (MRP) of the polyethylene polymer composition can be expressed in decigrams per minute (dg / min) or grams per ten minutes (g / 10min), measured at 190°C using a 2.16 kg load according to ASTM standard D1238. The polyethylene polymer composition used in embodiments of the invention preferably has an MRP of 50,000 or less. More preferably, the MRP of the polyethylene polymer composition is about 45,000 or less, about 40,000 or less, or about 35,000 or less. The inventors have not determined a lower limit for the MRP of the polyethylene polymer composition applicable to the disclosed polymer compositions. However, considering the manner of calculation, the MRP will be a positive number greater than 1 and may be quite low for many polyethylene polymers with very high MRP. Preferably, the MRP is about 100 or more, about 1,000 or more, about 5,000 or more, or about 10,000 or more. Therefore, in a series of preferred embodiments, the MRP of the polyethylene polymer composition is about 1 to 50,000 (e.g., about 1 to about 45,000, about 1 to about 40,000, or about 1 to about 35,000), about 100 to 50,000 (e.g., about 100 to about 45,000, about 100 to about 40,000, or about 100 to about 35,000), about 1,000 to 50,000 (e.g., about 1,000 to about 45,000, about 1,000 to about 40,000, or about 1,000 to about 35,000), or about 10,000 to 50,000 (e.g., about 10,000 to about 45,000, about 10,000 to about 40,000, or about 10,000 to about 35,000).

[0031] The melt relaxation product can be determined by any suitable technique. Preferably, the heterogeneous viscosity (η″) and dynamic viscosity (η′) are measured using a rotational rheometer at 140°C, equipped with 25 mm parallel plates spaced 1.1 mm apart. The polymer sample for measurement is provided in the form of a compression molding disk. During the measurement, the angular distance or strain is preferably kept low to remain in the non-hysteresis region, with approximately 1% of the nominal strain being preferred. To obtain sufficient data, the oscillation frequency is preferably swept over several decibels covering a range from approximately 0.15 rad / s to approximately 150 rad / s. For example, measurements can be performed at the following angular frequencies: approximately 0.147 rad / s, approximately 0.216 rad / s, approximately 0.317 rad / s, etc. The frequencies are approximately 0.467 rad / s, 0.683 rad / s, 1.003 rad / s, 1.472 rad / s, 2.160 rad / s, 3.171 rad / s, 4.655 rad / s, 6.832 rad / s, 10.028 rad / s, 14.719 rad / s, 21.604 rad / s, 31.711 rad / s, 46.545 rad / s, 68.319 rad / s, 100.279 rad / s, and 147.198 rad / s. While using these precise frequencies is not strictly necessary, it has been observed that using similar numbers of frequencies near these values ​​and across similar ranges yields reliable results.

[0032] Once the heterogeneous viscosity (η″) and dynamic viscosity (η′) of the polymer have been measured, the average radius of the Cole-Cole plot can be determined using the least squares method as described above. To facilitate the calculation of the average radius using the least squares method, one of various software programs can be used (e.g., those with the solver add-in installed). Excel TM To fit the actual data. For example, when using In Excel, create a spreadsheet with columns containing equations for each radius (r), each heterogeneous viscosity (y), dynamic viscosity (x), and the sum of squared errors (SE) for each pair of dynamic and heterogeneous viscosities (x, y). The sum of squared errors (SSE) is then located in a workbook cell, set to the "Set Objective;" field to Minimize, while the constants h and k are located in the "By Changing Variable Cells:" field within the workbook cell. To avoid potential local minima, it is preferable to select "Use Multi-Start" under GRG Nonlinear, which requires boundaries on h and k. For h, the boundaries are preferably set to be greater than zero but less than a number larger than the maximum expected h value. Similarly, for k, the boundaries are preferably set to be less than zero but greater than a large negative number that is more negative than the expected k value.

[0033] Since these parameters are determined by the polymer melt, the presence of the nucleating agent will not have any significant effect on the heterogeneous viscosity (η″), dynamic viscosity (η′), or melt flow index measured by the polyethylene polymer composition. Therefore, these parameters (and the melt relaxation product) can be measured by the polyethylene polymer composition before being combined with the bicyclo[2.2.1]heptane-2,3-dicarboxylate, or these parameters can be measured by a thermoplastic polymer composition containing the polyethylene polymer composition and the bicyclo[2.2.1]heptane-2,3-dicarboxylate.

[0034] As described above, a polyethylene polymer composition may comprise any suitable polyethylene polymer or mixture of polyethylene polymers exhibiting the desired melt relaxation product. Thus, a polyethylene polymer composition may comprise a single polyethylene polymer exhibiting the desired melt relaxation product. Alternatively, a polyethylene polymer composition may comprise a mixture of two or more polyethylene polymers exhibiting the desired melt relaxation product. In such a mixture, each polyethylene polymer may exhibit a melt relaxation product falling within the desired range, but this is not required. For example, a polyethylene polymer exhibiting a relatively high melt relaxation product (e.g., greater than 50,000) may be mixed with an appropriate amount of another polyethylene polymer having a lower melt relaxation product (e.g., less than 50,000) to produce a polyethylene polymer composition exhibiting the desired melt relaxation product.

[0035] Polyethylene polymers suitable for polyethylene polymer compositions include polyethylene homopolymers and polyethylene copolymers. Suitable polyethylene copolymers include copolymers of ethylene 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. Comonomers may be present in the copolymer in any suitable amount, for example, about 8% by weight or less (e.g., less than about 5 mol%) or more preferably about 5% by weight 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 polyethylene copolymers depends largely on the end use of the copolymer and the desired or expected polymer properties specified by that end use.

[0036] Polyethylene polymers suitable for thermoplastic polymer compositions can be produced by any suitable method. For example, as described in, for instance, U.S. Patent No. 2,816,883 (Larchar et al.), the polymer can be produced by a free radical process using very high pressures, but the polymer is typically produced in a “low-pressure” catalytic process. Herein, the term “low-pressure” is used to refer to a process carried out at pressures less than 6.9 MPa (e.g., 1000 psig), such as 1.4–6.9 MPa (200–1000 psig). Examples of suitable low-pressure catalytic processes include, but are not limited to, 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 liquid hydrocarbon in which the polymer is not dissolved or swollen), gas-phase polymerization (e.g., a process in which polymerization is carried out without the use of a liquid medium or diluent), or staged reactor polymerization. Suitable gas-phase polymerization processes also include so-called “condensation mode” or “ultra-condensation mode” methods, in which liquid hydrocarbons are introduced into a fluidized bed to increase the absorption of heat generated during polymerization. In these condensation and ultracondensation methods, liquid hydrocarbons are typically condensed in a circulating stream and reused in the reactor. Staged reactor methods can utilize combinations of slurry process reactors (tanks or loops) connected in series, parallel, or a combination of series and parallel connections, such that the catalyst (e.g., a chromium catalyst) is exposed to more than one set of reaction conditions. Staged reactor processes can also be carried out by combining two loops in series, combining one or more tanks and loops in series, using multiple gas-phase reactors in series, or loop-gas-phase arrangements. Because they can expose the catalyst to different sets of reactor conditions, staged reactor methods are commonly used for the production of multi-peak polymers, such as those discussed below. Suitable methods also include those in which a prepolymerization step is performed. In this prepolymerization step, the catalyst is typically exposed to a co-catalyst and ethylene under mild conditions in a smaller, separate reactor, and the polymerization reaction is carried out until the catalyst constitutes a relatively small amount of the resulting composition (e.g., about 5% to about 30% of the total weight). This prepolymerized catalyst is then introduced into a larger reactor where polymerization takes place.

[0037] Polyethylene polymers suitable for thermoplastic polymer compositions 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 on alumina, chromium oxide, and transition metal halides. Chromium oxide catalysts are typically prepared by impregnating a chromium compound onto a porous, high-surface-area oxide support, such as silica, followed by calcination in dry air at 500–900 °C. This converts chromium to hexavalent surface chromates or dichromates. Chromium oxide catalysts can be used in combination with alkylating metal co-catalysts such as alkylboron, alkylaluminum, alkylzinc, and alkyllithium. Supports for chromium oxide include silica, silica-titanium dioxide, silica-alumina, alumina, and phosphoaluminates. Other examples of chromium oxide catalysts include those produced by using lower-valent organochromium compounds, such as bis(aromatic)Cr 0 Allyl Cr 2+ and Cr 3+ Cr 2+ and Cr 4+ β-Stable Alkyl and Bis(Cyclopentadienyl)Cr 2+ Catalysts prepared by deposition onto chromium oxide catalysts, such as those described above. Suitable transition metal catalysts also include supported chromium catalysts, such as those based on chromium diacene or silyl chromates (e.g., bis(triphenylsilyl)chromate). These chromium catalysts can be supported on any suitable high surface area support, such as those described above for chromium oxide catalysts, typically silica. Supported chromium catalysts can also be used in combination with co-catalysts, such as the alkylated metal co-catalysts described 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 typically supported on high surface area solids such as magnesium chloride. Transition metal halide catalysts are typically used in combination with alkylaluminum co-catalysts such as trimethylaluminum (i.e., Al(CH3)3) or triethylaluminum (i.e., Al(C2H5)3). These transition metal halides can also be used in staged reactor processes. 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. Metallocene catalysts based on transition metals complexed with indene or fluorene ligands are also known and can be used to prepare high-density polyethylene polymers suitable for the present invention. The catalysts typically contain multiple ligands, and these ligands can be substituted with various groups (e.g., n-butyl) or linked to bridging groups such as -CH2CH2- or >SiPh2. Metallocene catalysts are typically used with co-catalysts such as methylaluminoxane (i.e., (Al(CH3)2)). xO y ) n Other cocatalysts include those described in U.S. Patent Nos. 5,919,983 (Rosen et al.), 6,107,230 (McDaniel et al.), 6,632,894 (McDaniel et al.), and 6,300,271 (McDaniel et al.). Other “unit-point” catalysts suitable for the production of polyethylene polymers include diimine complexes, such as those described in U.S. Patent No. 5,891,963 (Brookhart et al.).

[0038] The polyethylene polymer composition (and the polyethylene polymer present in the composition) can have any suitable density. A suitable density range is about 880 kg / m³. 3 Approximately 970 kg / m 3 Preferably, the density of the polyethylene polymer composition is about 940 kg / m³. 3 Or higher (e.g., approximately 940 kg / m²) 3 Approximately 970 kg / m 3 More preferably, the density of the polyethylene polymer composition is about 945 kg / m³. 3 Approximately 967 kg / m 3 In another preferred embodiment, the density of the polyethylene polymer composition is about 955 kg / m³. 3 Approximately 965 kg / m 3 .

[0039] The polyethylene polymer composition (and the polyethylene polymer present in the composition) can have any suitable melt flow index (MFI). Preferably, the MFI of the polyethylene polymer composition is about 1 dg / min or higher (e.g., about 2 dg / min or higher). In another preferred embodiment, the MFI of the polyethylene polymer composition is about 4 dg / min or higher. Preferably, the MFI of the polyethylene polymer composition is about 80 dg / min or lower. In another preferred embodiment, the MFI of the polyethylene polymer composition is about 60 dg / min or lower. In another preferred embodiment, the MFI of the polyethylene polymer composition is about 40 dg / min or lower. Therefore, in a series of preferred embodiments, the MFI of the polyethylene polymer composition is about 1 dg / min to about 80 dg / min (e.g., about 1 dg / min to about 60 dg / min or about 1 dg / min to about 40 dg / min), about 2 dg / min to about 80 dg / min (e.g., about 2 dg / min to about 60 dg / min or about 2 dg / min to about 40 dg / min), or about 4 dg / min to about 80 dg / min (e.g., about 4 dg / min to about 60 dg / min or about 4 dg / min to about 40 dg / min). The melt flow index of the polyethylene polymer composition is preferably measured according to ASTM standard D1238 at 190°C using a 2.16 kg load.

[0040] The thermoplastic polymer composition comprises a bicyclic [2.2.1]heptane-2,3-dicarboxylate. The two carboxylate moieties of the bicyclic [2.2.1]heptane-2,3-dicarboxylate anion are preferably located in the cis position relative to each other. Furthermore, the two carboxylate moieties of the bicyclic [2.2.1]heptane-2,3-dicarboxylate anion are preferably located in the inner position relative to the longest bridge of the anion. Therefore, in a preferred embodiment, the thermoplastic polymer composition comprises a salt of cis-intra-bicyclic [2.2.1]heptane-2,3-dicarboxylate (i.e., (1R,2R,3S,4S)-bicyclic [2.2.1]heptane-2,3-dicarboxylate). The bicyclic [2.2.1]heptane-2,3-dicarboxylate may comprise any suitable counterion of the bicyclic [2.2.1]heptane-2,3-dicarboxylate anion. Preferably, the counterion is selected from alkali metal cations and alkaline earth metal cations. In another preferred embodiment, the counter ion is selected from alkaline earth metal cations. Most preferably, the counter ion is a calcium cation (i.e., Ca). 2+(Cation). Therefore, in a particularly preferred embodiment, the salt is bicyclic [2.2.1]heptane-2,3-dicarboxylic acid calcium, especially cis-endo-bicyclic [2.2.1]heptane-2,3-dicarboxylic acid calcium (i.e., (1R,2R,3S,4S)-bicyclic [2.2.1]heptane-2,3-dicarboxylic acid calcium).

[0041] The bicyclic [2.2.1]heptane-2,3-dicarboxylate can be a hydrate (i.e., a crystalline solid with water of crystallization) or a dehydrate (i.e., a crystalline solid without water of crystallization). Those skilled in the art will understand that the bicyclic [2.2.1]heptane-2,3-dicarboxylate can also be a physical mixture of hydrate and dehydrate. In a preferred embodiment, the bicyclic [2.2.1]heptane-2,3-dicarboxylate is a dehydrate. In another preferred embodiment, the bicyclic [2.2.1]heptane-2,3-dicarboxylate is a hydrate, more preferably a monohydrate. Those skilled in the art will recognize that when started as a monohydrate, melt processing of the polymer composition can remove at least some of the water of crystallization from the bicyclic [2.2.1]heptane-2,3-dicarboxylate, resulting in a mixture of monohydrate and dehydrate. Therefore, in one preferred embodiment described above, the bicyclic [2.2.1]heptane-2,3-dicarboxylate is a dehydrate prior to melt processing of the thermoplastic polymer composition. Therefore, the corresponding thermoplastic polymer composition is prepared by adding the desired amount of the dehydrated bicyclo[2.2.1]heptane-2,3-dicarboxylate to the above-described polyethylene polymer composition. In another preferred embodiment, the bicyclo[2.2.1]heptane-2,3-dicarboxylate is a hydrate (preferably a monohydrate) before melt processing the thermoplastic polymer composition. Therefore, the corresponding thermoplastic polymer composition is prepared by adding the desired amount of the hydrated bicyclo[2.2.1]heptane-2,3-dicarboxylate to the above-described polyethylene polymer composition. The addition of the bicyclo[2.2.1]heptane-2,3-dicarboxylate can be carried out by dry mixing the salt and the polyethylene polymer composition before melt mixing, or the salt can be added to the polyethylene polymer composition while it is being melt-processed, for example, through a side feeder connected to an extruder.

[0042] The thermoplastic polymer composition may contain any suitable amount of bicyclic [2.2.1]heptane-2,3-dicarboxylate. In a preferred embodiment, the thermoplastic polymer composition contains about 50 ppm or more of bicyclic [2.2.1]heptane-2,3-dicarboxylate. In another preferred embodiment, the thermoplastic polymer composition contains about 100 ppm or more of bicyclic [2.2.1]heptane-2,3-dicarboxylate. In another preferred embodiment, the thermoplastic polymer composition contains about 200 ppm or more of bicyclic [2.2.1]heptane-2,3-dicarboxylate. In a preferred embodiment, the thermoplastic polymer composition contains about 5000 ppm or less of bicyclic [2.2.1]heptane-2,3-dicarboxylate. In another preferred embodiment, the thermoplastic polymer composition contains about 3000 ppm or less of bicyclic [2.2.1]heptane-2,3-dicarboxylate. In another preferred embodiment, the thermoplastic polymer composition comprises about 2500 ppm or less of bicyclic [2.2.1]heptane-2,3-dicarboxylate. Thus, in a range of preferred embodiments, the thermoplastic polymer composition comprises about 50 ppm to about 5000 ppm (e.g., about 50 ppm to about 3000 ppm, about 50 ppm to about 2500 ppm, or about 50 to about 2000 ppm), about 100 ppm to about 5000 ppm (e.g., about 100 ppm to about 3000 ppm, about 100 ppm to about 2500 ppm, or about 100 to about 2000 ppm), or about 200 to about 5000 ppm (e.g., about 200 ppm to about 3000 ppm, about 200 ppm to about 2500 ppm, or about 200 to about 2000 ppm) of bicyclic [2.2.1]heptane-2,3-dicarboxylate.

[0043] In a preferred embodiment, in addition to the polyethylene polymer composition and the bicyclo[2.2.1]heptane-2,3-dicarboxylate, the thermoplastic polymer composition also contains an acid scavenger. Suitable acid scavengers include, but are not limited to, fatty acid salts, hydrotalcite compounds, and mixtures thereof.

[0044] Therefore, in a preferred embodiment, in addition to the polyethylene polymer composition and the bicyclo[2.2.1]heptane-2,3-dicarboxylate, the thermoplastic polymer composition also comprises a fatty acid salt. In a preferred embodiment, the fatty acid salt is C 12 -C 22 Fatty acid salts, preferably C 14 -C 20 Fatty acid salts or C 16 -C 18 Fatty acid salts. In another preferred embodiment, the fatty acid is a saturated fatty acid (e.g., saturated C450). 12-C 22 Fatty acids, saturated C 14 -C 20 Fatty acids or saturated C 16 -C 18 (Fatty acids). In a particularly preferred embodiment, the fatty acid salt is a stearate. The fatty acid salt may contain any suitable counterion of the fatty acid anion. Preferably, the counterion is selected from the group consisting of alkali metal cations (e.g., sodium or potassium cations), alkaline earth metal cations (e.g., magnesium or calcium cations), and Group 12 cations (e.g., zinc cations). In a preferred embodiment, the counterion of the fatty acid salt is a zinc cation. Therefore, in a particularly preferred embodiment, the fatty acid salt is zinc stearate (i.e., the polymer composition also contains zinc stearate).

[0045] When present in a thermoplastic polymer composition, fatty acid salts can be present in any suitable amount. In a preferred embodiment, the thermoplastic polymer composition contains about 50 ppm or more of fatty acid salts. In another preferred embodiment, the thermoplastic polymer composition contains about 100 ppm or more of fatty acid salts. In another preferred embodiment, the thermoplastic polymer composition contains about 200 ppm or more of fatty acid salts. In a preferred embodiment, the thermoplastic polymer composition contains about 5000 ppm or less of fatty acid salts. In another preferred embodiment, the thermoplastic polymer composition contains about 3000 ppm or less of fatty acid salts. In another preferred embodiment, the thermoplastic polymer composition contains about 2500 ppm or less of fatty acid salts. Therefore, in a series of preferred embodiments, the thermoplastic polymer composition comprises about 50 ppm to about 5000 ppm (e.g., about 50 ppm to about 3000 ppm, about 50 ppm to about 2500 ppm, or about 50 to about 2000 ppm), about 100 ppm to about 5000 ppm (e.g., about 100 ppm to about 3000 ppm, about 100 ppm to about 2500 ppm, or about 100 to about 2000 ppm), or about 200 to about 5000 ppm (e.g., about 200 ppm to about 3000 ppm, about 200 ppm to about 2500 ppm, or about 200 to about 2000 ppm) of fatty acid salts.

[0046] When present in the thermoplastic polymer composition, the fatty acid salt may be present in any suitable relative amount to the amount of the bicyclo[2.2.1]heptane-2,3-dicarboxylate. In a preferred embodiment, the bicyclo[2.2.1]heptane-2,3-dicarboxylate and the fatty acid salt are present in the thermoplastic polymer composition in a mass ratio of about 5:1 to about 1:5 based on their respective masses. In another preferred embodiment, the bicyclo[2.2.1]heptane-2,3-dicarboxylate and the fatty acid salt are present in the thermoplastic polymer composition in a mass ratio of about 3:1 to about 1:3 based on their respective masses. In yet another preferred embodiment, the bicyclo[2.2.1]heptane-2,3-dicarboxylate and the fatty acid salt are present in the thermoplastic polymer composition in a mass ratio of about 2:1 to about 1:2 based on their respective masses. More preferably, the bicyclo[2.2.1]heptane-2,3-dicarboxylate and the fatty acid salt are present in the thermoplastic polymer composition in a mass ratio of about 2:1 to about 1:1 based on their respective masses. Most preferably, the bicyclo[2.2.1]heptane-2,3-dicarboxylate salt and the fatty acid salt are present in the thermoplastic polymer composition in a mass ratio of about 2:1.

[0047] In another preferred embodiment, in addition to the polyethylene polymer composition and the bicyclo[2.2.1]heptane-2,3-dicarboxylate, the thermoplastic polymer composition also comprises a hydrotalcite compound. Suitable hydrotalcite compounds can be naturally occurring or synthetically produced, although synthetically produced materials are generally preferred. Suitable synthetic hydrotalcite compounds include, but are not limited to, the series of materials marketed by Kyowa Chemical Industry Co., Ltd. under the name "DHT," for example... Hydrotalcite-based materials. When present in a thermoplastic polymer composition, the hydrotalcite compound can be present in any suitable amount, including any amount and / or proportion of the aforementioned fatty acid salts. Furthermore, in some embodiments, the thermoplastic polymer composition may simultaneously contain both fatty acid salts and hydrotalcite compounds.

[0048] The thermoplastic polymer compositions described herein can be used to produce any suitable articles or products. Suitable products include, but are not limited to, medical devices (e.g., pre-filled syringes for retort applications, intravenous supply containers, and blood collection devices), food packaging, liquid containers (e.g., containers for beverages, pharmaceuticals, personal care compositions, shampoos, etc.), garment boxes, microwaveable articles, shelves, cabinet doors, mechanical parts, automotive parts, sheets, pipes, tubes, rotationally formed parts, blow-formed parts, films, fibers, etc. The thermoplastic polymer compositions can be formed into the desired articles by any suitable technique, such as injection molding, injection rotational molding, blow molding (e.g., injection blow molding or injection stretch blow molding), extrusion (e.g., sheet extrusion, film extrusion, cast film extrusion, or foam extrusion), extrusion blow molding, thermoforming, rotational molding, film blow molding (blown film), film casting (cast film), etc. The thermoplastic polymer compositions disclosed herein are considered particularly suitable for injection molding and cast film processes, with injection molding being particularly preferred.

[0049] It is believed that the disclosed thermoplastic polymer compositions are highly suitable for injection molding and cast film processes because they exhibit significantly improved (i.e., lower) water vapor and oxygen permeability compared to unnucleated polymers and nucleated polymers that do not exhibit the aforementioned physical properties (e.g., density, melt relaxation product, melt flow index, etc.). For example, cast films made from the disclosed thermoplastic polymer compositions have been observed to exhibit significantly lower water vapor and oxygen permeability than similar cast films made from nucleated polymers that do not exhibit the desired melt relaxation product. Furthermore, injection molded articles made from the disclosed thermoplastic polymer compositions have been observed to exhibit significantly lower water vapor and oxygen permeability compared to similar injection molded articles made from nucleated polymers that do not have the desired melt relaxation product. As stated above, this result is attributed to the selection of polyethylene polymer compositions that exhibit sufficient melt relaxation to maximize the nucleation effect of bicyclo[2.2.1]heptane-2,3-dicarboxylate.

[0050] Therefore, in a second embodiment, the present invention provides a method for producing injection-molded articles from a thermoplastic polymer composition. The method includes the following steps:

[0051] (a) Providing a thermoplastic polymer composition comprising (i) a polyethylene polymer composition having a melt relaxation product of 50,000 or less; and (ii) a bicyclo[2.2.1]heptane-2,3-dicarboxylate;

[0052] (b) Heating the thermoplastic polymer composition to a temperature sufficient to melt the thermoplastic polymer composition so that it can be injected into a mold having a cavity defining the size of the article;

[0053] (c) Injecting the molten thermoplastic polymer composition into the mold cavity;

[0054] (d) Cooling and solidifying the molten thermoplastic polymer composition in the mold cavity to form an injection-molded article; and

[0055] (e) Open the mold and remove the article from the mold cavity.

[0056] The thermoplastic polymer composition used in the method of this second embodiment can be any of the thermoplastic polymer compositions described above. The apparatus for carrying out the method of the present invention can be any suitable injection molding apparatus.

[0057] In the above method, the thermoplastic polymer composition can be heated to any suitable temperature for molten thermoplastic polymer composition and injected into the mold cavity. The temperature to which the thermoplastic polymer composition is heated has no significant effect on the nucleation properties of bicyclo[2.2.1]heptane-2,3-dicarboxylate, but higher temperatures can promote larger and faster melt relaxation, which can improve nucleation properties to some extent. However, the temperature to which the thermoplastic polymer composition is heated should not be too high to avoid excessive "flash" (i.e., melt leakage from the mold seam). Preferably, the thermoplastic polymer composition is heated to a temperature of about 150°C to about 220°C. The thermoplastic polymer composition can be first heated to a temperature of about 150°C to about 170°C in the feed port of the extruder, and then heated to a temperature of about 180°C to about 220°C in the final zone of the extruder. Once heated to the desired temperature, the molten thermoplastic polymer composition is preferably held at the desired temperature until it is injected into the mold cavity.

[0058] In a third embodiment, the present invention also provides a method for preparing a film from a thermoplastic polymer composition. The method includes the following steps:

[0059] (a) Providing a thermoplastic polymer composition comprising (i) a polyethylene polymer composition having a melt relaxation product of 50,000 or less; and (ii) a bicyclo[2.2.1]heptane-2,3-dicarboxylate;

[0060] (b) Heating the thermoplastic polymer composition to a temperature sufficient to melt it so that it can be extruded through a die;

[0061] (c) Extruding a molten thermoplastic polymer composition through a die with a slit-shaped orifice to form a thin film exiting the orifice;

[0062] (d) Passing the film exiting the die through a cooling surface to cure the thermoplastic polymer composition; and

[0063] (e) Collect the film.

[0064] The thermoplastic polymer composition used in the method of this second embodiment can be any of the thermoplastic polymer compositions described above. The apparatus for carrying out the method of the present invention can be any suitable casting film apparatus. For example, a casting film machine can be equipped with a single extruder and die for producing a single-layer film. Alternatively, a casting film machine can be equipped with one or more extruders and a suitable die feed block suitable for producing multiple individual layers in the melt and combining them into a single film. The film produced by such a casting film machine will be a multilayer film. When preparing a multilayer film, the thermoplastic polymer composition of the present invention can be used to prepare any one or more layers of the multilayer film. In other words, the above-described method includes a method for preparing a multilayer film in which all layers of the film are prepared using the thermoplastic polymer composition, and a method for preparing a multilayer film in which at least one layer of the multilayer film is prepared using the thermoplastic polymer composition, and the remaining layers of the multilayer film are prepared using one or more additional polymer compositions.

[0065] In the above method, the thermoplastic polymer composition can be heated to any suitable temperature to melt it and extrude it through a die. The temperature to which the thermoplastic polymer composition is heated has no significant effect on the nucleation properties of bicyclo[2.2.1]heptane-2,3-dicarboxylate, but higher temperatures can promote larger and faster melt relaxation, which can improve nucleation properties to some extent. However, the temperature to which the thermoplastic polymer composition is heated should not be too high, as this may reduce the viscosity of the molten polymer composition to a level that affects the quality of the cast film. Preferably, the thermoplastic polymer composition is heated to a temperature of about 150°C to about 220°C. The thermoplastic polymer composition can be first heated to a temperature of about 150°C to about 170°C in the feed inlet of the extruder, and then heated to a temperature of about 180°C to about 220°C in the final zone, delivery line section, and slot die of the extruder. Once heated to the desired temperature, the molten thermoplastic polymer composition is preferably held at the desired temperature until it is extruded through the die. Based on the properties of the polymer, those skilled in the art of cast film production will recognize the need for temperature regulation to maintain an appropriate trade-off between output rate, system back pressure, and film stability.

[0066] The molten polymer can be fed directly from the extruder into the die. Alternatively, the molten polymer can be fed from the extruder into a melt pump connected to the die or die feed block. A suitable melt pump is preferably a positive discharge device, which produces a consistent flow of molten polymer to the die or die feed block, regardless of the extruder discharge pressure. Compared to a standalone extruder, using a melt pump provides a more stable short-term output, which in turn minimizes longitudinal thickness variations (i.e., "surging") in the cast film.

[0067] After leaving the mold, the film is passed over a cooled surface to cure the thermoplastic polymer composition. This cooled surface is typically one or more quenching rollers, which are cooled, for example, by circulating cooling water or another coolant through the internal volume of the rollers. In some applications, a vacuum chamber can be used to remove entrained air that would otherwise be trapped between the quenching roller surface and the film. This entrained air acts as thermal insulation, so reducing or eliminating the amount of entrained air will increase the rate at which the film cools to the desired temperature.

[0068] The cooled film described above can be collected in any suitable manner. For example, the film is typically wound up by a winding machine, such as a surface winding machine, a turret or center winding machine, or a center / surface winding machine.

[0069] The following examples further illustrate the above-mentioned topics, but should not be construed as limiting their scope in any way.

[0070] Example 1

[0071] The following examples illustrate the preparation and properties of several thermoplastic polymer compositions according to the present invention.

[0072] Several commercially available high-density polyethylene resins were tested to determine their melt flow index (MFI) and the mean radius (r) of the Cole-Cole diagram. avg Then the melt relaxation product (MRP) for each resin was calculated. The results of these measurements and calculations are listed in Table 1 below.

[0073] The MFI of each polyethylene polymer is expressed in decigrams per minute (dg / min) and measured according to ASTM standard D1238 at 190°C using a 2.16 kg load. The mean radius (r) of the Cole-Cole diagram is also shown. avgThe following parameters were determined according to the general procedure described above. Specifically, the dynamic viscosity (η′) and heterogeneous viscosity (η″) were measured using a TA Instruments ARES G2 rotational rheometer equipped with 25 mm parallel plates set with a 1.1 mm gap. A compression plate of the polymer was placed on the bottom plate of the rheometer and allowed to melt at a measurement temperature of 140°C. The top and bottom plates were then set to the desired 1.1 mm gap, and any excess molten polymer protruding beyond the plate boundaries was trimmed. Then, the parameters were calculated at approximately 0.147, 0.216, 0.317, 0.467, 0.683, 1.003, 1.472, and 2.1 mm. Viscosity measurements were performed at angular frequencies of 60, 3.171, 4.655, 6.832, 10.028, 14.719, 21.604, 31.711, 46.545, 68.319, 100.279, and 147.198 rad / s. These measurements yielded dynamic viscosity (η') and heterogeneous viscosity (η″) values ​​(in the output typically available in modern rheometers), which were then plotted to generate a Cole-Cole plot, with dynamic viscosity (η') as the x-axis and heterogeneous viscosity (η″) as the y-axis.

[0074] To determine the average radius of the Cole-Cole diagram for each resin, the measured data were fitted to the following Cartesian equation for a circle using the least squares method:

[0075] r 2 =(xh) 2 +(yk) 2 .

[0076] In the above formula, x corresponds to the dynamic viscosity (η′) value, and y corresponds to the heterogeneous viscosity (η″) value. Variables h and k represent the offset of the circle center from the origin of the Cole-Cole diagram. Due to the nature of complex viscosity, the value of h is positive, while the value of k is negative. (Using a device with a Solver add-in installed...) Excel TMPerform the actual fit of the data. Columns are constructed using equations for the individual r, individual y, individual x, and squared error (SE) for each (x, y) pair generated at each strain rate. The sum of squared errors (SSE) is then placed in a workbook cell, set to the "Set Objective:" field to Minimize, while the constants h and k are placed in the "By Changing Variable Cells:" field. To avoid possible local minima, GRG Nonlinear is set to "Use Multi-Start". The boundary for h is set to be greater than zero but less than a number greater than the maximum expected h value. The boundary for k is set to be less than zero but greater than a large negative number, more negative than the expected k value. After fitting and minimizing the SSE, the radius values ​​for each x, y pair of the Cole-Cole plot are averaged, and the resulting value is reported as the average radius (r) of the Cole-Cole plot for the polymer. avg ).

[0077] Table 1. Density, melt flow index, and average radius (r) of Cole-Cole diagram for several commercial HDPE polymers avg and the product of melt relaxation

[0078]

[0079]

[0080] Several polymer compositions were prepared using the aforementioned HDPE polymers to investigate the relationship between the polymer melt relaxation product and the nucleation efficiency of bicyclo[2.2.1]heptane-2,3-dicarboxylate. To facilitate mixing of bicyclo[2.2.1]heptane-2,3-dicarboxylate with each HDPE polymer, a masterbatch was prepared by mixing 240.0 g of calcium bicyclo[2.2.1]heptane-2,3-dicarboxylate, 120.0 g of zinc stearate, 90 g of DHT-4V, 0.90 g of Irganox 1010, 2.1 g of Irgafos 168, and 5547.0 g of Nova Sclair 2908 HDPE polymer. The mixture was transferred to a 30-liter Henschel high-intensity mixer and mixed at 1200 rpm for 3.0 minutes. The resulting mixture was then blended using a Leistritz 27-mm co-rotating twin-screw extruder at a speed of 18 kg / hr, with a screw speed of 400 rpm. The first zone was set at 100°C, and the other zones at 165-175°C. The resulting masterbatch contained 4% by weight of bicyclo[2.2.1]heptane-2,3-dicarboxylic acid calcium, hereinafter referred to as "Masterbatch 1".

[0081] A polymer composition containing bicyclic [2.2.1]heptane-2,3-dicarboxylate was prepared by twin-screw compounding / granulation of a dry blend of masterbatch 1 and HDPE polymer at a screw speed of approximately 500 rpm and a screw speed of 3.5 kg / hr on a Leistritz 18-mm co-rotating twin-screw extruder. The first zone was set at 160°C, and subsequent zones varied between 145 and 155°C.

[0082] Then, according to ISO 294, using a 55-ton Arburg injection molding unit and a two-cavity mold, a portion of the unnucleated and nucleated HDPE polymers were molded into shrinkage sheets (2.0 mm x 60.0 mm x 60.0 mm). The shrinkage rate of these sheets was measured according to ISO 294. The results of the shrinkage rate measurement are shown in Table 2 below.

[0083] Table 2. Transverse (TD) shrinkage rate results for samples 1-16

[0084]

[0085]

[0086] For the bicyclic [2.2.1]heptane-2,3-dicarboxylate used as a nucleating agent in these samples, the low lateral shrinkage compared to the control unnucleated polymers is an indicator of good polymer nucleation efficiency. As can be seen from the data in Table 2, calcium bicyclic [2.2.1]heptane-2,3-dicarboxylate was able to nucleate all HDPE polymers, as evidenced by the reduction in lateral shrinkage. However, the reduction in shrinkage for sample 16 was significantly lower than that for samples 2-6, 8, 10, 12, and 14. This data suggests that calcium bicyclic [2.2.1]heptane-2,3-dicarboxylate did not nucleate this particular HDPE polymer (i.e., Dowlex IP 40 used in sample 16) as well as other HDPE polymers. As shown in Tables 1 and 2, the MRP of the Dowlex IP40 polymer used to prepare sample 16 was greater than 50,000, while the MRP of the polymers used to prepare samples 2-6, 8, 10, 12 and 14 was less than 50,000 (e.g., less than 35,000).

[0087] A portion of the unnucleated and nucleated HDPE polymers were also molded into barrier plates on a Husky 90-ton injection unit using a square mold with an end gate measuring 1.0 mm thick × 4.0 inches (101.6 mm) wide × 4.0 inches (101.6 mm) wide. The extruder zone temperature from feed to end was 230 / 250 / 230°C, the nozzle temperature was 250°C, and the mold coolant temperature was 45°C. The injection linear speed was 60 mm / s. The total cycle time was 19.7 seconds, the cooling time was 10.0 seconds, and the pressure was 900 psi. The water vapor transmission rate (WVTR) of the resulting barrier plates was measured according to ASTM F 1249, and the results were normalized to thickness (yielding nWVTR). Conventional oxygen transmission rate (OTR) measurements were also performed on some plates according to ASTM D 3985 (dry, 23°C), but using indoor low dew point air instead of 100% oxygen contamination. Measurements were performed using an Illinois Instruments Model 8001 oxygen permeation analyzer. Initial OTR measurements were normalized to thickness. Normalized OTR (nOTR) was expressed as cc*mil / m. 2 / 24-hr / 0.209atm O2 is reported in units. The results of nWVTR and nOTR measurements are listed in Table 3 below.

[0088] Table 3. Normalized water vapor transmission rate (nWVTR), percentage change in nWVTR (%Δ), normalized oxygen transmission rate (nOTR), and percentage change in nOTR (%Δ) for samples 1-16

[0089]

[0090]

[0091] The data in Table 3 show that bicyclic [2.2.1]heptane-2,3-dicarboxylate calcium can nucleate all HDPE polymers, as evidenced by the measured decrease in nWVTR. However, the decrease in nWVTR for sample 16 is significantly less than that observed in samples 2-6, 8, 10, 12, and 14. In fact, the decrease in nWVTR for sample 16 is only about one-third of that for the other samples. This data indicates that bicyclic [2.2.1]heptane-2,3-dicarboxylate calcium does not nucleate the Dowlex IP 40 used in sample 16 as well as the other HDPE polymers. As mentioned above, the MRP of the Dowlex IP 40 polymer used to prepare sample 16 is greater than 50,000, while the MRP of the polymers used to prepare samples 2-6, 8, 10, 12, and 14 is less than 50,000 (less than 35,000).

[0092] The reduction in transverse shrinkage and WVTR is directly related to the nucleation of the polyethylene polymer composition via bicyclic [2.2.1]heptane-2,3-dicarboxylate. Therefore, the difference between these two sets of results suggests that bicyclic [2.2.1]heptane-2,3-dicarboxylate is more effective in nucleating polymers and polymer blends with melt relaxation products of 50,000 or less. This is surprising, as there is no known evidence in the art that nucleation of bicyclic [2.2.1]heptane-2,3-dicarboxylate depends on these polymer properties. However, as stated above, the inventors believe this difference is due to the lower degree of melt relaxation exhibited by polymers with melt relaxation products greater than 50,000. In such polymers, the polymer melt relaxes slowly, resulting in significant strain-induced self-nucleation rather than nucleation by bicyclic [2.2.1]heptane-2,3-dicarboxylate.

[0093] Example 2

[0094] The following examples illustrate the production and properties of several thermoplastic polymer compositions.

[0095] By varying amounts of Dow Several polymer compositions were prepared by mixing DMDH-6400NT 7HDPE polymer with the ExxonMobil HD 6719.17HDPE polymer used in Example 1. An unnucleated control was prepared by mixing the required amounts of DMDH-6400 polymer and HD 6719.17 polymer with 2% Sclair 2908HDPE resin (the carrier used in the masterbatch preparation described in Example 1). Nucleated samples were prepared by mixing the required amounts of DMDH-6400 polymer and HD 6719.17 polymer with 2% masterbatch 1 described in Example 1. The percentages of DMDH-6400 polymer and HD 6719.17 polymer in each sample are listed in Table 4 below. The polymer blends were compounded using a Leistritz 18-mm co-rotating twin-screw extruder at a screw speed of 500 rpm, a feed rate of 4.0 kg / hr, and a barrel temperature of 155-165°C.

[0096] As described in Example 1, the polymer compositions were molded into barrier plates. Also as described in Example 1, the normalized oxygen permeability (nOTR) of each plate was measured. The results of these measurements are listed in Table 4 below.

[0097] Table 4. Melt Flow Index (MFI) and Mean Radius of Cole-Cole Diagram (r) for Samples 17-22 avg Melt relaxation product (MRP) and normalized oxygen permeability (nOTR), and the percentage change in nOTR (%Δ).

[0098]

[0099] As can be seen from the data in Table 4, the reduction in nOTR is relatively moderate for all polymer blends. In fact, the nOTR reduction observed in samples 18, 20, and 22 is only about half that observed in samples 2-6, 12, and 14 of Example 1. Furthermore, the data in Table 4 show that the MRP of samples 17-22 is significantly higher than 50,000. These high MRP values ​​indicate insufficient melt relaxation in the polymer, which, as mentioned above, hinders the nucleation of the polymer via the bicyclic [2.2.1]heptane-2,3-dicarboxylate.

[0100] Example 3

[0101] The following examples illustrate the production and properties of several thermoplastic polymer compositions.

[0102] Several polymer compositions were prepared using the HD 6719.17 HDPE polymer described above. These compositions were prepared by adding an increased amount of a peroxide, specifically 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane (…). Polymer compositions were prepared by mixing (DBPH) polymers. It is generally believed that treating HDPE copolymers with peroxides increases long-chain branching (LCB), but some short-chain branching (SCB) may also occur. Branching contributes to at least some increase in molecular weight (and decrease in molecular weight index), and generally contributes to at least some broadening of the molecular weight distribution. Both of these effects should increase the average radius of the Cole-Cole diagram, which should also increase the melt relaxation product (MRP). Therefore, this series of experiments explored the effect of increasing MRP for a given polyethylene polymer composition.

[0103] A polymer composition was prepared by adding the required amount of peroxide (DBPH) to 4 kg of HD 6719.17 powder, which was ground from commercially available granules in a mill. Specifically, the polymer powder was loaded into a Hobart mixer and mixing was initiated. DBPH, which is liquid at room temperature, was slowly added dropwise until the required amount was reached, and mixing continued for 5 minutes. The resulting mixture was then extruded and granulated using a Deltaplast single-screw extruder (1 inch (2.54 cm) diameter, L / D 30, Maddock mixing section, 210°C flat barrel profile), connected to a wire pelletizer. A 150-mesh sieve assembly was also used to increase back pressure and induce more slip / mixing in the extruder, ensuring complete incorporation of the peroxide into the polymer. The collected granules were tumbled and mixed to more thoroughly homogenize the sample before further processing. The amounts of peroxide (DBPH) and calcium bicyclo[2.2.1]heptane-2,3-dicarboxylate used to prepare the various polymer compositions are listed in Table 5 below.

[0104] As described in Example 1, a portion of the resulting granular polymer composition was molded into a barrier plate. The remaining portion of the composition was dry-blended with 2.2% of the masterbatch 1 described in Example 1 to obtain a nucleating composition containing 880 ppm of nucleating agent. This nucleating composition was also molded into a barrier plate as described in Example 1. The barrier plate was then analyzed using the procedure described in Example 1 to determine the normalized oxygen permeability (nOTR). The results of these analyses are listed in Table 5 below.

[0105] Table 5. DBPH concentration, nucleating agent concentration, melt flow index (MFI), and mean radius (r) of the Cole-Cole diagram for samples 23-34 avg Melt relaxation product (MRP), normalized oxygen permeability (nOTR), and percentage change in nOTR (%Δ)

[0106]

[0107] The data in Table 5 show that increasing the amount of peroxide leads to a decrease in the melt flow index (MFI) and the average radius of the Cole-Cole diagram (r). avg The increase of ). avgThe increase in nOTR was greater than the decrease in MFI, leading to an increase in the melt relaxation product (MRP). Examination of the nOTR data for samples 24, 26, 28, 30, 32, and 34 showed that the decrease in nOTR relative to the unnucleated control generally decreased with increasing MRP. However, even at an MRP of 44,900, sample 34 still showed a 38% decrease in nOTR relative to the control, indicating that the polymer still exhibited sufficient melt relaxation for nucleation via the bicyclic [2.2.1]heptane-2,3-dicarboxylate to be predominant over any strain-induced self-nucleation.

[0108] All references cited in this article, including publications, patent applications and patents, are incorporated herein by reference to the same extent that each reference is individually and specifically indicated to be incorporated herein by reference and elaborated in its entirety.

[0109] In the context of describing the subject matter of this application (particularly in the context of the following claims), the use of the terms “a” and “the”, and similar indicators, should be interpreted as encompassing both singular and plural, unless otherwise stated herein or obviously contradicted by the context. Unless otherwise stated, the terms “comprising,” “having,” “including,” and “containing” should be interpreted as open-ended terms (i.e., meaning “including, but not limited to”). Unless otherwise stated herein, the enumeration of numerical ranges herein is intended only as a shorthand method for individually referencing each individual numerical value falling within that range, and each individual numerical value is incorporated into the specification as if it were individually referenced herein. All methods described herein may be performed in any suitable order unless otherwise stated herein or obviously contradicted by the context. The use of any and all instances or exemplary language (e.g., “for example”) provided herein is intended only to better illustrate the subject matter of this application and does not constitute a limitation on the scope of the subject matter unless otherwise required. No language in the specification should be construed as indicating that any unclaimed element is necessary for the practice of the subject matter described herein.

[0110] This document describes preferred embodiments of the subject matter of this application, including the best modes known to the inventors for implementing the claimed subject matter. Variations of these preferred embodiments will be apparent to those skilled in the art after reading the foregoing description. The inventors expect those skilled in the art to appropriately adopt such variations, and the inventors wish to practice the subject matter described herein in ways different from those specifically described herein. Therefore, this disclosure includes all modifications and equivalents of the subject matter described in the appended claims, as permitted by applicable law. Furthermore, any combination of the foregoing elements in all possible variations is covered by this disclosure unless otherwise stated herein or clearly contradicted by the context.

Claims

1. A thermoplastic polymer composition comprising: (a) A polyethylene polymer composition with a melt relaxation product of 50,000 or less; and (b) Bicyclic [2.2.1]heptane-2,3-dicarboxylate, wherein the bicyclic [2.2.1]heptane-2,3-dicarboxylate is calcium bicyclic [2.2.1]heptane-2,3-dicarboxylate. The melt relaxation product (MRP) is defined as the average radius (r) of the Cole-Cole diagram of (i) the melt flow index (MFI) of the polyethylene polymer composition and (ii) the dynamic viscosity (η′) and heterogeneous viscosity (η″) of the polyethylene polymer composition. avg The product of ) 。 2. The thermoplastic polymer composition according to claim 1, wherein the melt relaxation product of the polyethylene polymer composition is 45000 or less.

3. The thermoplastic polymer composition according to claim 1 or 2, wherein the polyethylene polymer composition has a melt flow index of 1 dg / min to 80 dg / min at 190°C.

4. The thermoplastic polymer composition according to claim 1 or 2, wherein the bicyclo[2.2.1]heptane-2,3-dicarboxylate is cis-endo-bicyclo[2.2.1]heptane-2,3-dicarboxylate calcium.

5. The thermoplastic polymer composition according to claim 1 or 2, wherein the thermoplastic polymer composition comprises 100 ppm to 3000 ppm of the bicyclo[2.2.1]heptane-2,3-dicarboxylate.

6. The thermoplastic polymer composition according to claim 1 or 2, wherein the thermoplastic polymer composition further comprises a component selected from C 12 -C 22 Acid scavengers of fatty acid salts, hydrotalcite compounds, and mixtures thereof.

7. The thermoplastic polymer composition of claim 6, wherein the thermoplastic polymer composition comprises 100 ppm to 3000 ppm of the salt of the acid scavenger.

8. A method for producing injection-molded articles, the method comprising the following steps: (a) A thermoplastic polymer composition comprising (i) a polyethylene polymer composition having a melt relaxation product of 50,000 or less; and (ii) a bicyclic [2.2.1]heptane-2,3-dicarboxylate, said bicyclic [2.2.1]heptane-2,3-dicarboxylate being calcium bicyclic [2.2.1]heptane-2,3-dicarboxylate. The melt relaxation product (MRP) is defined as the average radius (r) of the Cole-Cole diagram of (i) the melt flow index (MFI) of the polyethylene polymer composition and (ii) the dynamic viscosity (η′) and heterogeneous viscosity (η″) of the polyethylene polymer composition. avg The product of ) ； (b) Heating the thermoplastic polymer composition to a temperature sufficient to melt the thermoplastic polymer composition so that it can be injected into a mold having a cavity defining the size of the article; (c) Injecting the molten thermoplastic polymer composition into the mold cavity; (d) Cooling and solidifying the molten thermoplastic polymer composition in the mold cavity to form an injection molded article; as well as (e) Open the mold and allow the article to leave the mold cavity.

9. A method for preparing a thin film, the method comprising the following steps: (a) A thermoplastic polymer composition comprising (i) a polyethylene polymer composition having a melt relaxation product of 50,000 or less; and (ii) a bicyclic [2.2.1]heptane-2,3-dicarboxylate, said bicyclic [2.2.1]heptane-2,3-dicarboxylate being calcium bicyclic [2.2.1]heptane-2,3-dicarboxylate. The melt relaxation product (MRP) is defined as the average radius (r) of the Cole-Cole diagram of (i) the melt flow index (MFI) of the polyethylene polymer composition and (ii) the dynamic viscosity (η′) and heterogeneous viscosity (η″) of the polyethylene polymer composition. avg The product of ) ； (b) Heating the thermoplastic polymer composition to a temperature sufficient to melt it so that it can be extruded through a die; (c) Extruding the molten thermoplastic polymer composition through a die with a slit-shaped orifice to form a film exiting the orifice; (d) Allowing the film exiting the die to pass over a cooling surface to cure the thermoplastic polymer composition; and (e) Collect the film.

10. The method according to claim 8 or 9, wherein the melt relaxation product of the polyethylene polymer composition is 45,000 or less.

11. The method according to claim 8 or 9, wherein the polyethylene polymer composition has a melt flow index of 1 dg / min to 80 dg / min at 190°C.

12. The method according to claim 8 or 9, wherein the bicyclic [2.2.1]heptane-2,3-dicarboxylate is cis-endo-bicyclic [2.2.1]heptane-2,3-dicarboxylate calcium.

13. The method according to claim 8 or 9, wherein the thermoplastic polymer composition comprises 100 ppm to 3000 ppm of the bicyclo[2.2.1]heptane-2,3-dicarboxylate.

14. The method according to claim 8 or 9, wherein the thermoplastic polymer composition further comprises a material selected from C 12 -C 22 Acid scavengers of fatty acid salts, hydrotalcite compounds, and mixtures thereof.

15. The method of claim 14, wherein the polymer composition comprises 100 ppm to 3000 ppm of the salt of the acid scavenger.

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