Composition

Abstract

The present invention provides a polymer composition comprising: a) from 99.8 to 95.0 wt%, relative to the total weight of the polymer composition, of a high density polyethylene (HDPE) having a density measured according to ISO 1183 of from 940 to 980 kg / m3 and an MFR2 measured according to ISO 1133 at 190 DEG C under a load of 2.16 kg of from 0.1 to 5.0 g / 10 min; b) 0.05 to 0.5 wt%, relative to the total weight of the polymer composition, of at least one amide slip agent; and c) 0.1 to 1.0 wt% of a wax, relative to the total weight of the polymer composition.

Description

Technical Field

[0001] The present invention relates to a polymer composition comprising high density polyethylene (HDPE), an amide slip agent, and a wax, which is suitable for manufacturing molded articles. The present invention also relates to articles comprising the polymer composition and the use of the composition for the manufacture of articles. Background Art

[0002] High density polyethylene (HDPE) is widely used in molding applications due to its combination of excellent processing properties and mechanical properties. It is well known that the properties of polyethylene are related to its density. The higher the density, the better the stiffness, however, the impact properties tend to decrease.

[0003] The present invention relates to a composition comprising an HDPE resin suitable for preparing injection molded articles, in particular caps and closures. Specifically, the caps and closures of the present invention can be used to close bottles, such as bottles for carbonated beverages and non-carbonated beverages.

[0004] Caps and closures are typically prepared using HDPE resins because they provide attractive mechanical properties, such as stiffness. However, it should be understood that compositions designed for such applications also require other user-friendly properties. In some cases, a lower coefficient of friction is required to facilitate the screwing on or off of the cap or closure. Typically, this is achieved by adding a slip agent. However, this introduces well-known critical problems to the final article. Some commonly used slip agents, such as erucamide, although they can provide the desired properties, are susceptible to oxidation, which can impart unpleasant flavors and odors to the food or beverage inside the container. Therefore, alternative solutions are sought.

[0005] A solution was proposed in EP 1278797, which is to use saturated amides as slip agents because they do not suffer from oxidation problems. However, the slip effect of such saturated amides tends to be poor. In addition, the slip effect is typically time-dependent and usually takes a long time to reach the desired low coefficient of friction.

[0006] An alternative solution is to use a permanent slip agent, which is typically a solution based on polydimethylsiloxane (PDMS), capable of immediately achieving a slip effect and not changing over time. However, in order to achieve a sufficiently good slip effect, a large amount of PDMS is usually required, which has several disadvantages, including having a negative impact on other properties of the composition. Using PDMS together with HDPE also makes the recycling of the material more challenging.

[0007] There is still a need to provide new compositions that can overcome at least some of the above problems. The inventors have unexpectedly found that by using a combination of amide slip agents and waxes, especially in combination with HDPE, an attractive balance of properties can be achieved. In particular, the composition allows for an attractive low coefficient of friction that is independent of time. Unexpectedly, the coefficient of friction may even be lower compared to using wax alone. In addition, the composition is suitable for direct use in forming injection-molded articles such as lids or closures. Summary of the Invention

[0008] In one aspect, the present invention provides a polymer composition comprising:

[0009] a) 99.8 to 95.0% by weight of high-density polyethylene (HDPE), based on the total weight of the polymer composition, having a density measured according to ISO 1183 of 940 to 980 kg / m 3 and an MFR2 measured according to ISO 1133 at 190 °C under a load of 2.16 kg of 0.1 to 5.0 g / 10 min;

[0010] b) 0.05 to 0.5% by weight of at least one amide slip agent, based on the total weight of the polymer composition; and

[0011] c) 0.1 to 1.0% by weight of wax, based on the total weight of the polymer composition.

[0012] In another aspect, the present invention provides an article comprising the polymer composition as defined above.

[0013] In yet another aspect, the present invention provides the use of the polymer composition as defined above in the manufacture of articles, preferably injection or compression molded articles such as lids or closures. Detailed Description

[0014] High-Density Polyethylene (HDPE)

[0015] The polymer of the present invention is a high-density ethylene polymer (HDPE). The HDPE can be a homopolymer or a copolymer, but is preferably an ethylene copolymer. An ethylene copolymer is a polymer in which most of its weight is derived from ethylene monomer units (i.e., at least 50% by weight of ethylene relative to the total weight of the copolymer). The comonomer contribution is preferably at most 10 mol%, more preferably at most 5 mol%. However, ideally, there is a very low level of comonomer present in the polymer of the present invention, such as 0.1 to 2.0 mol%, for example 0.1 to 1.0 mol%.

[0016] One or more other comonomers are preferably C3-12, especially C3-10 α-olefin comonomers, particularly mono- or poly-ethylenically unsaturated comonomers, especially C3-10-α-olefins such as propylene, 1-butene, 1-hexene, 1-octene and 4-methyl-pent-1-ene. 1-Hexene, 1-octene and 1-butene, or mixtures thereof, especially 1-hexene and 1-butene are particularly preferably used. Ideally, only one comonomer is present.

[0017] The polymers of the present invention can be unimodal or multimodal.

[0018] The polymers of the present invention are preferably multimodal, i.e., comprise at least two fractions. The polymer is most preferably bimodal.

[0019] Generally, polyethylene compositions comprising at least two polyethylene fractions are referred to as "multimodal", with the at least two polyethylene fractions being produced under different polymerization conditions, resulting in the fractions having different (weight average) molecular weights and molecular weight distributions. Thus, in this sense, the HDPE polymers of the present invention are preferably multimodal polyethylene. The prefix "multi" refers to the number of different polymer fractions making up the composition. With respect to comonomer content, polyethylene can also be multimodal.

[0020] The form of the molecular weight distribution curve of such multimodal polyethylene, i.e., the appearance of a plot of the polymer weight fraction as a function of its molecular weight, will show two or more maxima, or at least be significantly broadened compared to the curves of the individual fractions.

[0021] For example, if a polymer is produced by a sequential multi-stage process, using reactors connected in series and different conditions in each reactor, the polymer fractions produced in the different reactors will each have their own molecular weight distribution and weight average molecular weight. When recording the molecular weight distribution curve of such a polymer, the individual curves of these fractions are superimposed into the molecular weight distribution curve of the total resulting polymer product, usually resulting in a curve with two or more different maxima.

[0022] The HDPE of the present invention has an MFR2 measured according to ISO 1133 at 190 °C under a load of 2.16 kg of 0.1 to 5.0 g / 10 min. The preferred range of MFR2 is 0.3 to 3.0 g / 10 min, more preferably 0.4 to 2.5 g / 10 min, such as 0.5 to 2.0 g / 10 min.

[0023] The HDPE of the present invention preferably has an MFR measured according to ISO 1133 at 190 °C under a load of 21.6 kg of 15 to 80 g / 10 min, such as 20 to 75 g / 10 min, most preferably 30 to 65 g / 10 min 21 .

[0024] The HDPE of the present invention preferably has an MFR of at least 25.0, such as at least 35.0, more preferably at least 45.0 21 / MFR2 flow rate ratio (FRR). In addition, the HDPE of the present invention preferably has an MFR 21 / MFR2 flow rate ratio (FRR) of at most 80.0, such as at most 75.0, more preferably at most 70.0.

[0025] The density of the polymer measured according to ISO 1183 is in the range of 940 to 980 kg / m 3 range. Thus, the polymer of the present invention is high density polyethylene (HDPE). Preferably, the polymer has a density of 950 to 970 kg / m 3 , more preferably 951 to 965 kg / m 3 , even more preferably 952 to 963 kg / m 3 , such as 953 to 961 kg / m 3 of density.

[0026] The HDPE of the present invention preferably has a molecular weight distribution (MWD) in the range of 7 to 30, more preferably in the range of 9 to 25, such as in the range of 10 to 20.

[0027] The HDPE of the present invention typically comprises at least a lower molecular weight component (A) and a higher molecular weight component (B). The terms "higher" and "lower" herein should be understood as relative terms with respect to each other. Thus, component (A) has a lower molecular weight than component (B), and component (B) has a higher molecular weight than component (A).

[0028] In a particularly preferred embodiment, the HDPE consists of components (A) and (B). The weight ratio of fraction (A) to fraction (B) in the composition is desirably in the range of 30:70 to 70:30, more preferably in the range of 35:65 to 65:35, most preferably in the range of 40:60 to 60:40. In some embodiments, the ratio can be 35 to 55 wt% of fraction (A) and 45 to 65 wt% of fraction (B), such as 45 to 52 wt% of fraction (A) and 48 to 55 wt% of fraction (B), where the wt% values are relative to the total weight of the multimodal HDPE.

[0029] In a particularly preferred embodiment, the weight % of fractions (A) and (B) totals 100 wt%.

[0030] Each of fraction (A) and fraction (B) can be an ethylene homopolymer or an ethylene copolymer. An ethylene homopolymer refers to a polymer comprising at least 97 mol% (such as at least 98 mol%, especially at least 99.5 mol%) of ethylene monomer units. The term "ethylene copolymer" has been defined above. Most preferably, fraction (A) is an ethylene homopolymer and fraction (B) is an ethylene copolymer.

[0031] The HDPE of the present invention is typically produced by a multi-stage process, in which fractions (A) and (B) are produced in subsequent stages. In this case, the properties of the fractions produced in the second step (or additional steps) of the multi-stage process can be inferred from the polymers produced separately in a single stage, that is, by applying the same polymerization conditions (such as the same temperature, partial pressure of reactants / diluents, suspension medium, reaction time) for the stage of the multi-stage process in which the fractions are produced, and by using a catalyst in which the previously produced polymer is absent. Optionally, it is also possible, for example, according to Polymer Processing Conference (Polymer Processing Society), Extended Abstracts and Final Programme, Gothenburg, August 19 - 21, 1997, 4:13, to calculate the properties of the fractions produced in higher stages of the multi-stage process.

[0032] Therefore, although it is not possible to directly measure the multi-stage process product, the properties of the fractions produced in higher stages of such multi-stage processes can be determined by applying any one or both of the above methods. Those skilled in the art will be able to select an appropriate method.

[0033] The HDPE produced in a multi-stage process is also designated as an "in-situ" blend. The resulting final product consists of a homogeneous mixture of polymers from two or more reactors, and the different molecular weight distribution curves of these polymers together form a molecular weight distribution curve with a broad maximum or two or more maxima, that is, the final product is a multimodal polymer mixture.

[0034] The lower molecular weight fraction (A) typically has an MFR2 of 100 to 2000 g / 10 min, preferably 125 to 1500 g / 10 min, more preferably 150 to 1000 g / 10 min, such as 200 to 750 g / 10 min.

[0035] Fraction (A) can have a density of 955 to 980 kg / m 3 , preferably 960 to 978 kg / m 3 , such as 965 to 975 kg / m 3 .

[0036] Fraction (A) may be a homopolymer or copolymer of ethylene. Preferably, fraction (A) is a homopolymer of ethylene.

[0037] The higher molecular weight fraction (B) typically has an MFR2 of from 0.0001 to 1.0 g / 10 min, preferably from 0.0005 to 0.5 g / 10 min, more preferably from 0.0008 to 0.1 g / 10 min, such as from 0.001 to 0.05 g / 10 min.

[0038] Fraction (B) may have a density of from 925 to 970 kg / m 3 , preferably from 930 to 960 kg / m 3 , such as from 935 to 950 kg / m 3 of density.

[0039] Fraction (B) may be a homopolymer or copolymer of ethylene. Fraction (B) is preferably a copolymer. Preferred ethylene copolymers employ α-olefins (e.g., C3-12 α-olefins) as comonomers. Examples of suitable α-olefins include 1-butene, 1-hexene, and 1-octene. 1-Butene is a particularly preferred comonomer.

[0040] Preparation of HDPE

[0041] HDPE can be produced by any suitable polymerization method known in the art. In those embodiments where the HDPE is a multimodal HDPE, it can preferably be produced by polymerization using a Ziegler-Natta catalyst system under conditions that produce a multimodal (e.g., bimodal) polymer product. Typically, a two-stage or more-stage (i.e., multistage) polymerization process is utilized with different process conditions (e.g., different temperatures, pressures, polymerization media, hydrogen partial pressures, etc.) in different stages or zones. Preferably, the multimodal (e.g., bimodal) composition is produced by multistage polymerization, such as using a series of reactors, and preferably adding the optional comonomer only in one or more reactors used to produce one or more of the higher / highest molecular weight components. A multistage process is defined as a polymerization process in which two or more fractions of a polymer are produced by producing each one or at least two polymer fractions in separate reaction stages, typically using different reaction conditions in each stage, in the presence of the reaction product of the previous stage including the polymerization catalyst. The polymerization reactions used in each stage can include conventional ethylene homopolymerization or copolymerization reactions, such as gas phase, slurry phase, liquid phase polymerization, using conventional reactors, such as, loop reactors, gas phase reactors, batch reactors, etc. (e.g., see WO97 / 44371 and WO96 / 18662).

[0042] Preferably, the HDPE is a bimodal HDPE prepared by a two-stage polymerization process.

[0043] The first polymerization stage produces an ethylene homopolymer or an ethylene copolymer, typically an ethylene homopolymer, which is then fed to the second polymerization stage. The second polymerization stage can produce a further ethylene homopolymer or ethylene copolymer, preferably an ethylene copolymer.

[0044] The first polymerization stage is preferably a slurry polymerization step.

[0045] Slurry polymerization typically occurs in an inert diluent, typically a hydrocarbon diluent such as methane, ethane, propane, n-butane, isobutane, pentane, hexane, heptane, octane, etc., or mixtures thereof. Preferably, the diluent is a low-boiling hydrocarbon having 1 to 4 carbon atoms or a mixture of such hydrocarbons. A particularly preferred diluent is propane, which may contain small amounts of methane, ethane and / or butane.

[0046] The ethylene content in the fluid phase of the slurry can be 1 to 50 mol%, preferably 2 to 20 mol%, especially 2 to 10 mol%. The advantage of a high ethylene concentration is an increase in the productivity of the catalyst, but the disadvantage is that more ethylene needs to be recycled compared to a lower concentration.

[0047] The temperature in the first polymerization stage is typically 60 to 100 °C, preferably 65 to 95 °C, more preferably 70 to 95 °C. Excessively high temperatures should be avoided to prevent the polymer from partially dissolving in the diluent and causing reactor fouling. The pressure is typically 1 to 150 bar, preferably 40 to 80 bar.

[0048] Slurry polymerization can be carried out in any known reactor for slurry polymerization. Such reactors include continuous stirred tank reactors and loop reactors. Particularly preferred is to carry out slurry polymerization in a loop reactor. In such a reactor, the slurry is circulated at high speed along a closed pipeline using a circulation pump. Loop reactors are well known in the art and examples are given, for example, in US-A-4582816, US-A-3405109, US-A-3324093, EP-A-479186 and US-A-5391654. Therefore, it is preferred to carry out the first polymerization stage by slurry polymerization in a loop reactor.

[0049] The slurry can be withdrawn from the reactor continuously or intermittently. A preferred mode of intermittent withdrawal is to use a settling leg, where the slurry is allowed to concentrate before a batch of concentrated slurry is withdrawn from the reactor. The use of settling legs is disclosed, inter alia, in US-A-3374211, US-A-3242150 and EP-A-1310295. Continuous withdrawal is disclosed, inter alia, in EP-A-891990, EP-A-1415999, EP-A-1591460 and WO-A-2007 / 025640. Continuous withdrawal is advantageously combined with a suitable concentration method, as disclosed in EP-A-1310295 and EP-A-1591460. Preferably, the slurry is withdrawn continuously from the first polymerization stage.

[0050] Typically, hydrogen is introduced in the first polymerization stage to control the MFR2 of the resulting polymer. The amount of hydrogen required to achieve the desired MFR depends on the catalyst used and the polymerization conditions. The desired polymer properties can be obtained in a slurry polymerization in a loop reactor, where the molar ratio of hydrogen to ethylene is from 100 to 1000 mol / kmol (or moles / 1000 moles), preferably from 200 to 800 mol / kmol.

[0051] The average residence time in the first polymerization stage is typically from 20 to 120 minutes, preferably from 30 to 80 minutes. As is well known in the art, the average residence time τ can be calculated from Equation 1 below:

[0052] Equation 1: Residence time

[0053]

[0054] where V R is the volume of the reaction space (for a loop reactor, it is the volume of the reactor; for a fluidized bed reactor, it is the volume of the fluidized bed), Q o is the volumetric flow rate of the product stream (including the polymer product and the fluid reaction mixture).

[0055] The production rate is appropriately controlled using the catalyst feed rate. The production rate can also be influenced by appropriately selecting the monomer concentration. The desired monomer concentration can then be achieved by appropriately adjusting the ethylene feed rate.

[0056] In the second polymerization stage, ethylene is optionally polymerized in the presence of a catalyst and the ethylene polymer produced in the first polymerization stage, together with at least one α-olefin comonomer. It should thus be understood that the second polymerization stage produces an ethylene polymer which combines with the ethylene polymer from the first polymerization stage to form the multimodal HDPE of the present invention. Preferred comonomers have been discussed above, however it is noted that it is particularly preferred if at least one α-olefin is 1-butene.

[0057] The second polymerization stage is preferably a gas phase polymerization step, i.e., it is carried out in a gas phase reactor. Any suitable gas phase reactor known in the art can be used, such as a fluidized bed gas phase reactor.

[0058] For a gas phase reactor, the reaction temperature used is generally in the range of 60 to 115 °C (e.g., 70 to 110 °C), the reactor pressure is generally in the range of 10 to 25 bar, and the residence time is generally 1 to 8 hours. The gas used is typically a non-reactive gas such as nitrogen or a low-boiling hydrocarbon, such as propane together with the monomer (e.g., ethylene).

[0059] Typically a chain transfer agent (e.g., hydrogen) is added to the second polymerization stage, preferably in an amount of 50 to 500 mol of H2 / kmol of ethylene.

[0060] The split between the first polymerization stage and the second polymerization stage (i.e., between slurry polymerization and gas phase polymerization) is typically 30:70 to 70:30, more preferably 35:65 to 65:35, and most preferably 40:60 to 60:40.

[0061] Pre-polymerization

[0062] A prepolymerization step can be carried out prior to the polymerization steps discussed above. The purpose of prepolymerization is to polymerize a small amount of polymer onto the catalyst at low temperature and / or low monomer concentration. By prepolymerization, the performance of the catalyst in the slurry can be improved and / or the properties of the final polymer can be altered. The prepolymerization step is carried out in a slurry.

[0063] Thus, the prepolymerization step can be carried out in a loop reactor. Then the prepolymerization is preferably carried out in an inert diluent, typically a hydrocarbon diluent such as methane, ethane, propane, n-butane, isobutane, pentane, hexane, heptane, octane, etc. or a mixture thereof. Preferably, the diluent is a low-boiling hydrocarbon having 1 to 4 carbon atoms or a mixture of such hydrocarbons.

[0064] The temperature in the prepolymerization step is typically 0 to 90 °C, preferably 20 to 80 °C, and more preferably 55 to 75 °C.

[0065] The pressure is not critical and is typically from 1 to 150 bar, preferably from 40 to 80 bar.

[0066] The amount of monomer is typically from 0.1 to 1000 grams of monomer polymerized per gram of solid catalyst component in the prepolymerization step. As is known to those skilled in the art, the catalyst particles recovered from the continuous prepolymerization reactor do not all contain the same amount of prepolymer. Instead, each particle has its own characteristic amount, which depends on the residence time of the particle in the prepolymerization reactor. Since some particles have resided in the reactor for a relatively long time while some particles have resided for a relatively short time, the amount of prepolymer on different particles will also be different, and some individual particles may contain an amount of prepolymer that exceeds the above limits. However, the average amount of prepolymer on the catalyst is typically within the above-specified limits.

[0067] As is known in the art, the molecular weight of the prepolymer can be controlled by hydrogen. Further, antistatic additives can be used to prevent the particles from adhering to each other or to the walls of the reactor, as disclosed in WO-A-96 / 19503 and WO-A-96 / 32420.

[0068] When a prepolymerization step is present, it is preferred to introduce all of the catalyst components into the prepolymerization step. However, when the solid catalyst component and the cocatalyst can be fed separately, only a part of the cocatalyst can be introduced into the prepolymerization stage and the remaining part can be introduced into the subsequent polymerization stage. Also in this case, it is necessary to introduce a large amount of cocatalyst in the prepolymerization stage in order to obtain a sufficient polymerization reaction therein.

[0069] It should be understood that within the scope of the present invention, the amount of polymer produced in the prepolymerization is typically in the range of 1 to 5% by weight relative to the final HDPE.

[0070] Catalyst

[0071] The polymerization is typically carried out in the presence of a Ziegler-Natta polymerization catalyst. Suitable Ziegler-Natta (ZN) catalysts generally comprise at least a catalyst component formed from a transition metal compound of Groups 4 to 6 of the Periodic Table (IUPAC, Nomenclature of Inorganic Chemistry, 1989), a metal compound of Groups 1 to 3 of the Periodic Table (IUPAC), optionally a compound of Group 13 of the Periodic Table (IUPAC), and optionally an internal organic compound (such as an internal electron donor). The ZN catalyst can also comprise one or more additional catalyst components, such as a cocatalyst and optionally external additives.

[0072] Suitable ZN catalysts preferably contain a magnesium compound, an aluminum compound, and a titanium compound supported on a particulate support.

[0073] The particulate support can be an inorganic oxide support such as silica, alumina, titanium dioxide, silica - alumina, silica - titanium dioxide or a MgCl2 - based support. Preferably, the support is a silica or MgCl2 - based support.

[0074] Particularly preferred Ziegler - Natta catalysts are those described, for example, in EP 1378528 A1 and EP 2994506.

[0075] If used, the magnesium compound is preferably the reaction product of a dialkylmagnesium and an alcohol. The alcohol is a straight - chain or branched - chain aliphatic monohydric alcohol. Preferably, the alcohol has 6 to 16 carbon atoms. Branched - chain alcohols are particularly preferred, and 2 - ethyl - 1 - hexanol is an example of a preferred alcohol. The dialkylmagnesium can be any compound in which magnesium is bonded to two alkyl groups, which may be the same or different. Butyloctylmagnesium is an example of a preferred dialkylmagnesium.

[0076] The aluminum compound is a chlorine - containing alkylaluminum. Particularly preferred compounds are dialkylaluminum dichloride and sesquialkylaluminum chloride.

[0077] The Group 4 to 6 transition metal compound is preferably a titanium or vanadium compound, more preferably a halogen - containing titanium compound, and most preferably a chlorine - containing titanium compound. A particularly preferred titanium compound is titanium tetrachloride.

[0078] The catalyst can be prepared by contacting the support with the above - mentioned compounds in sequence, as described in EP 688794 or WO 99 / 51646. Alternatively, the catalyst can be prepared by first preparing a solution from the components and then contacting the solution with the support, as described in WO 01 / 55230.

[0079] Another suitable ZN catalyst contains a titanium compound and a magnesium halide compound acting as a support. Thus, the catalyst contains a titanium compound and optionally a Group 13 compound, such as an aluminum compound on magnesium dihalide (such as magnesium dichloride). Such catalysts are disclosed, for example, in WO 2005 / 118655, EP 810235, WO 2014 / 096296 and WO 2016 / 097193.

[0080] Suitable activators are Group 13 metal compounds, typically Group 13 alkyl compounds, especially alkylaluminum compounds, where the alkyl group contains 1 to 16 carbon atoms. These compounds include trialkylaluminum compounds such as trimethylaluminum, triethylaluminum, triisobutylaluminum, trihexylaluminum, and tri-n-octylaluminum, alkylaluminum halides such as diethylaluminum chloride, ethylaluminum dichloride, ethylaluminum sesquichloride, dimethylaluminum chloride, etc. Particularly preferred activators are trialkylaluminums, among which triethylaluminum, trimethylaluminum, and triisobutylaluminum are especially used.

[0081] The amount of activator used depends on the specific catalyst and activator. Typically, the amount of triethylaluminum used is such that the molar ratio of aluminum to transition metal (e.g., Al / Ti) is 1 to 1000, preferably 3 to 100, especially about 5 to about 30 mol / mol.

[0082] Optional internal organic compounds can be selected from the following categories: ethers, esters, amines, ketones, alcohols, acid anhydrides, or nitriles or mixtures thereof. Preferably, the optional internal organic compounds are selected from ethers and esters, and most preferably from ethers. Preferred ethers have 2 to 20 carbon atoms and especially include monocyclic, bicyclic, or polycyclic saturated or unsaturated ethers with 3 to 6 ring atoms. If used, typical cyclic ethers applicable to the present invention are tetrahydrofuran (THF), substituted THF such as 2-methyl THF, bicyclic ethers such as 2,2-bis(2-tetrahydrofuranyl)propane, 2,2-bis-(2-furyl)-propane, or their isomers or mixtures thereof. Internal organic compounds are also often referred to as internal electron donors.

[0083] In the production of the HDPE of the present invention, a compounding step is preferably applied, where the composition of the base resin (i.e., the blend, which is typically obtained as a base resin powder from the reactor) is extruded in an extruder and then granulated into polymer pellets in a manner known in the art.

[0084] HDPE can also contain small amounts of additives such as pigments, nucleating agents, antistatic agents, fillers, antioxidants, etc., generally in an amount of up to 10 wt%, preferably up to 5 wt%.

[0085] Optionally, additives or other polymer components can be added to the HDPE in the above-mentioned amounts during the compounding step. Preferably, the HDPE of the present invention obtained from the reactor is compounded with additives in an extruder in a manner known in the art.

[0086] Composition

[0087] The present invention relates to a composition comprising HDPE as defined above and at least one amide slip agent and wax.

[0088] The polymer composition comprises 95.0 to 99.8% by weight of HDPE, relative to the total weight of the polymer composition. Preferably, the HDPE is present in an amount of 96.0 to 99.75% by weight, more preferably 98.0 to 99.75% by weight, relative to the total weight of the polymer composition.

[0089] At least one amide slip agent is present in an amount of 0.05 to 0.5% by weight, relative to the total weight of the polymer composition. Preferably, at least one amide slip agent is present in an amount of 0.08 to 0.4% by weight, more preferably 0.1 to 0.3% by weight, relative to the total weight of the polymer composition.

[0090] The wax is present in an amount of 0.1 to 1.0% by weight, relative to the total weight of the polymer composition. Preferably, the wax is present in an amount of 0.12 to 0.8% by weight, more preferably 0.15 to 0.5% by weight, relative to the total weight of the polymer composition.

[0091] Although polymers other than HDPE are present in the polymer composition within the scope of the present invention, preferably HDPE is the only polymer component present.

[0092] The polymer composition preferably consists of HDPE, at least one amide slip agent and wax. For the avoidance of doubt, even when the polymer composition "consists of" HDPE, at least one amide slip agent and wax, it is contemplated that normal polymer additives such as pigments, nucleating agents, antistatic agents, fillers and antioxidants may be present. Thus, the term "consisting of" does not mean the exclusion of the presence of polymer additives. However, it excludes the presence of other polymer components for blending with HDPE, at least one amide slip agent and wax. However, this is not excluded if the carrier polymer is used as part of a masterbatch. The composition may be free of any other blended polymers but may still include a small amount of the carrier polymer for the masterbatch.

[0093] The polymer composition is typically prepared by blending and uniformly mixing the components (e.g., HDPE, at least one amide slip agent and wax), for example, by melt mixing in an extruder.

[0094] The polymer composition of the present invention can be characterized by a constant or stable coefficient of friction (COF). In particular, when measured according to ISO 8295 on an injection-molded specimen prepared according to ISO 17855-2, the composition can have a coefficient of friction of at most 0.35 or lower, preferably 0.30 or lower, after 1 day. Optionally or additionally, when measured according to ISO 8295 on an injection-molded specimen prepared according to ISO 17855-2, the composition can have a coefficient of friction of at most 0.35 or lower, preferably 0.30 or lower, after 14 days. Optionally or additionally, when measured according to ISO 8295 on an injection-molded specimen prepared according to ISO 17855-2, the composition can have a coefficient of friction of at most 0.35 or lower, preferably 0.30 or lower, after 37 days.

[0095] Amide slip agent

[0096] At least one amide slip agent can be any suitable amide slip agent known in the art. The term "slip agent" is known to those skilled in the art, and thus it should be understood that the amide slip agent can be any slip agent that includes at least one amide group. Slip aids are used to reduce the force required to remove the closure from a bottle or package.

[0097] In a preferred embodiment, the amide slip agent is a fatty acid amide derivative. The fatty acid amide derivative can be an unsaturated or saturated fatty acid amide derivative, preferably a saturated fatty acid amide derivative.

[0098] Thus, in one embodiment, the amide slip agent is an unsaturated fatty acid amide, preferably monounsaturated, i.e., a fatty acid amide derivative containing only one vinyl group.

[0099] Thus, in one embodiment, the unsaturated fatty acid amide can be one of the following formulas:

[0100] CH3(CH2) x CH=CH(CH2) y CONH2

[0101] Where x and y are independent of each other and are positive integers.

[0102] In a particularly preferred embodiment, x is a positive integer between 4 and 10 and / or y is a positive integer between 8 and 14, preferably x = 7 and y = 11.

[0103] Thus, it is particularly preferred that the unsaturated fatty acid amide is:

[0104] CH3(CH2)7CH=CH(CH2) 11 CONH2, i.e., erucamide.

[0105] Optionally, the amide slip agent may be a saturated fatty acid amide. The saturated fatty acid amide may include 8 to 30 carbon atoms. The saturated fatty acid amide is preferably a straight-chain fatty acid amide represented by the formula CH3(CH2)nCONH2, where n is 6 to 28. Particularly preferred are straight-chain saturated fatty acid amides containing at least 12 carbon atoms and mixtures thereof. Most preferably, the saturated fatty acid amide is selected from the group consisting of behenamide, arachidamide, stearamide, palmitamide, myristamide, and lauramide.

[0106] Within the scope of the present invention, the composition includes a single amide slip agent or a mixture of two or more different amide slip agents. Herein, when a mixture is present, the mixture may contain only saturated fatty acid amides, only unsaturated fatty acid amides, or both saturated fatty acid amides and unsaturated fatty acid amides. Most preferably, a single amide slip agent is employed.

[0107] Wax

[0108] The wax can be any suitable wax. Herein, it should be understood that by "wax" we mean an organic compound that is a lipophilic, malleable solid at near ambient temperature. They include higher alkanes and lipids, typically having a melting point above about 40 °C (104 °F), thus giving a low viscosity liquid. Waxes are insoluble in water but soluble in organic non-polar solvents.

[0109] If the wax is a natural wax, it is particularly preferred. It should be understood that by "natural wax" we mean a wax produced by plants or animals or a wax present in petroleum. For the purposes of the present invention, the definition of "natural wax" is defined as a wax of natural origin or a mixture of waxes of natural origin, which can be a plant wax, an animal wax, or a mineral wax, or can be a chemically modified derivative thereof; or a combination of at least one wax of natural origin with other types of waxes or components. The natural waxes of the present invention can be of plant origin, animal origin, or mineral origin.

[0110] In an even further preferred embodiment, the natural wax is a modified natural wax, particularly a polar modified natural wax. A modified wax is a natural wax that has been chemically treated to alter its properties and performance. Thus, a polar modified natural wax is a wax that has been modified to include one or more polar functional groups. Examples of such functional groups include hydroxyl, carboxyl, amino, and phosphate groups.

[0111] When measured at 100 °C according to DIN 53019, the wax may have a viscosity in the range of 10 to 100 mPas -1 preferably in the range of 20 to 80 mPas -1 range.

[0112] Preferably, when measured according to ISO 2176, the wax has a dropping point of 70 to 110 °C, more preferably 75 to 105 °C.

[0113] When measured according to ISO 2114, the wax may have an acid value of 5 to 65 mg KOH / g, such as 6 to 55 mg KOH / g.

[0114] Ideally, when measured according to ISO 3681, the wax has a saponification value of 50 to 150 mg KOH / g, such as 60 to 130 mg KOH / g.

[0115] Suitable waxes are commercially available, for example from Clariant under the trade name Licocare.

[0116] Article

[0117] Still further, the present invention relates to an article comprising the composition as described above. The present invention also relates to the use of such a composition in the manufacture of an article.

[0118] In one embodiment, relative to the total weight of the article, the article comprises at least 90.0% by weight, more preferably at least 95.0% by weight, still more preferably at least 98.0% by weight, such as at least 99.9% by weight of the composition of the present invention. Particularly preferably, the article consists of the composition.

[0119] The article according to the present invention can be an injection-molded or compression-molded article, preferably an injection-molded article, more preferably a lid or closure. Such articles can be prepared by conventional methods known in the art.

[0120] It should be understood that any of the above parameters are measured according to the detailed tests given below. In any parameter, if narrower and broader embodiments are disclosed, these embodiments are disclosed in combination with the narrower and broader embodiments of the other parameters.

[0121] The present invention will now be described with reference to the following non-limiting examples.

[0122] Test methods:

[0123] Melt flow rate (MFR)

[0124] The melt flow rate is measured according to ISO 1133 at 190 °C under a load of 2.16 kg (MFR2) or 21.6 kg (MFR 21 ).

[0125] Calculate the MFR2 of fractions (A) and (B)

[0126] log A = x · log B + (1 - x) · log C

[0127]

[0128] B = MFR2 of fraction (A)

[0129] C = MFR2 of fraction (B)

[0130] A = final MFR2 (mixture) of multimodal HDPE

[0131] X = weight fraction of fraction (A)

[0132] Flow rate ratio (FRR21 / 2))

[0133] FRR is determined as the ratio between MFR 21 and MFR2.

[0134] GPC

[0135] The number average molecular weight (Mz, Mw and Mn), molecular weight distribution (MWD) and its width described by the polydispersity index PDI = Mw / Mn (where Mn is the number average molecular weight and Mw is the weight average molecular weight) are determined by gel permeation chromatography (GPC) according to ISO 16014-1:2003, ISO 16014-2:2003, ISO 16014-4:2003 and ASTM D 6474-12 using the following formula

[0136]

[0137]

[0138] For a constant elution volume interval ΔV i , where A i and M i are the chromatographic peak slice area and the polyolefin molecular weight (MW) related to the elution volume V i respectively, and N equals the number of data points obtained from the chromatogram between the integration limits.

[0139] A high-temperature GPC instrument is used, which is equipped with an infrared (IR) detector (IR4 or IR5) from PolymerChar (Valencia, Spain), and is equipped with 3 x Agilent-PLgel Olexis and 1 x Agilent-PLgel Olexis Guard columns. As the solvent and mobile phase, 1,2,4-trichlorobenzene (TCB) stabilized with 250 mg / L 2,6-di-tert-butyl-4-methylphenol is used. The chromatographic system operates at 160 °C and at a constant flow rate of 1 mL / min. 200 μL of the sample solution is injected for each analysis. Data collection is carried out using Agilent Cirrus software version 3.3 or PolymerChar GPC-IR control software.

[0140] The column set is calibrated using universal calibration (according to ISO 16014-2:2003) with 19 narrow MWD polystyrene (PS) standards in the range of 0.5 kg / mol to 11,500 kg / mol. The PS standards are dissolved at room temperature for several hours. The conversion of the polystyrene peak molecular weight to the polyolefin molecular weight is done by using the Mark Houwink equation and the following Mark Houwink constants:

[0141] K PS = 19×10 -3 mL / g, α PS = 0.655

[0142] K PE = 39×10 -3 mL / g, α PE = 0.725

[0143] K PP = 19×10 -3 mL / g, α PP = 0.725

[0144] A third-order polynomial fit is used to fit the calibration data.

[0145] All samples are prepared in the concentration range of 0.5 to 1 mg / ml and dissolved at 160 °C for 2.5 hours (for PP) or 3 hours (for PE) with continuous gentle shaking.

[0146] Density

[0147] Density is measured according to ISO 1183 and ISO 1872-2 for sample preparation.

[0148] Coefficient of friction (CoF)

[0149] Based on ISO 8295 in 150×80×1mm 3 CoF was measured on thick injection molded specimens. Injection molding was done according to ISO17855-2. CoF testing was performed on a Zwick Z1.0 S machine. The following conditions were used:

[0150] Test speed: 100mm / min±10mm / min

[0151] Measuring distance: 56mm

[0152] Load weight: 200g±2g

[0153] Prior to measurement, the specimens were stored at 23° C. and RH 50% for a desired period of time, such as 1 day, 3 days, 7 days, etc.

[0154] experiment

[0155] Material:

[0156] Polysiloxane MB: MULTIBASE TM MB25-235 masterbatch is commercially available from Multibase (masterbatch containing 25 wt% polysiloxane).

[0157] Slip agent: Finawax S, a stearic acid amide commercially available from Fine Organics.

[0158] wax: RBW 102 Powder VITA is a polar modified wax based on renewable resources, commercially available from Clariant. It has a viscosity measured at 100° C. according to DIN 53019 of 20 mPa.s.

[0159] HDPE: Bimodal HDPE produced in a pilot plant using ZN catalyst (as disclosed in EP 2994506) with a prepolymerization-loop-gas phase reactor configuration, having an MFR of 0.8 g / 10 min, 955.5 kg / m 3 density.

[0160] Table 1 shows typical polymerization parameters and final polymer properties of HDPE.

[0161] Table 1

[0162] HDPE Pre-polymerization Temperature (°C) 70 Pressure (kPa) 5700 H2 (g / h) 5.0 Loop reactor Temperature (°C) 95 Pressure (kPa) 5500 C2 Concentration (mol%) 3.5 H2 / C2 (mol / kmol) 430.0 Density 970.0 Split ratio % 49.0 MFR2 (g / 10min) 350.00 GPR Temperature (°C) 85 Pressure (kPa) 2000 H2 / C2 (mol / kmol) 110 C4 / C2 (mol / kmol) 25.0 Split ratio % 51.0 <![CDATA[Density (kg / m 3 )]]> 955.5 MFR2 (g / 10min) 0.80 MFR in GPR 0.002 Density in GPR 941.6 Pellets <![CDATA[Density (kg / m 3 )]]> 955.5 MFR2 (g / 10min) 0.8 MFR21 (g / 10min) 47.35 MFR21 / MFR2 59.2 MWD 12-14

[0163] Composition and Test Specimen Formation

[0164] The desired amount of HDPE powder and additives are premixed in a high-intensity mixer and then compounded on a ZSK 57 twin-screw extruder. The melt temperature is 210 °C and the production rate is 200 kg / h. The following additives are added: 0.05 wt% of Irganox 1010 (BASF), 0.2 wt% of Irgafos 168 (BASF) and 0.05 wt% of CEASIT FI, where wt% is relative to the total weight of the composition (sum of HDPE powder + additives = 100%).

[0165] Three compositions as shown in Table 2 were prepared via blending. The blending was done on a ZSK 18 twin-screw extruder with a melt temperature of 210 °C and an output rate of 7 kg / h. The coefficient of friction was measured on injection-molded specimens of 150×80×1 mm 3 over a series of time periods and the results are shown in Table 2.

[0166] It can be seen that when compared to CE2, the examples of the present invention show improved (lower) CoF values which are consistent over time. The combination of slip agent and wax in IE1 results in a constant CoF (advantageous in terms of short storage times for production efficiency) which is advantageously low. The advantage that IE1 offers over CE1 is that it is far more suitable for recycling. The presence of two different materials, PE and polysiloxane, in CE1 would make the recycling of this composition challenging.

[0167] Table 2: Composition and properties of the molded articles.

[0168] CE1 IE1 CE2 HDPE (wt%) 97 99.75 99.75 Slip agent (wt%) 0.1 Wax (wt%) 0.15 0.25 Polysiloxane MB (wt%) * 3 <![CDATA[MFR2 (g / 10 min) of the blend]]> 0.76 0.9 0.79 Coefficient of friction 1 day 0.18 0.29 0.4 3 days 0.2 0.26 0.42 7 days 0.23 0.25 0.39 14 days 0.2 0.21 0.44 37 days 0.22 0.20 0.40

[0169] *Added as masterbatch.

Claims

1. A polymer composition, comprising: a) 99.8 to 95.0% by weight of high density polyethylene (HDPE), relative to the total weight of the polymer composition, having a density measured according to ISO 1183 of 940 to 980 kg / m 3 and an MFR2 measured according to ISO 1133 at 190 °C under a load of 2.16 kg of 0.1 to 5.0 g / 10 min; b) from 0.05 to 0.5% by weight, based on the total weight of the polymer composition, of at least one amide slip agent; and c) from 0.1 to 1.0% by weight, based on the total weight of the polymer composition, of a wax.

2. The polymer composition according to claim 1, wherein the HDPE has an MFR2 measured according to ISO 1133 at 190 °C under a load of 2.16 kg of from 0.3 to 3.0 g / 10 min, preferably from 0.4 to 2.5 g / 10 min, more preferably from 0.5 to 2.0 g / 10 min.

3. The polymer composition according to claim 1 or 2, wherein the HDPE has a density of 950 to 970 kg / m 3 , preferably 951 to 965 kg / m 3 , more preferably 952 to 963 kg / m 3 , even more preferably 953 to 961 kg / m 3 measured according to ISO 1183.

4. The polymer composition according to any one of claims 1 to 3, wherein the HDPE is a multimodal polyethylene polymer, the multimodal polyethylene polymer comprising a lower molecular weight (LMW) component (A) and a higher molecular weight (HMW) component (B).

5. The polymer composition according to claim 4, wherein the HDPE comprises a lower molecular weight (LMW) homopolymer component (A) and a higher molecular weight (HMW) ethylene copolymer component (B), preferably, wherein the HMW copolymer component (B) comprises at least one C3-12 α-olefin, preferably 1-butene, 1-hexene and 1-octene, more preferably 1-butene.

6. The polymer composition according to claim 4 or 5, wherein the HDPE comprises from 48 to 55% by weight of the HMW component (B) and from 52 to 45% by weight of the LMW component (A).

7. The polymer composition according to any one of claims 1 to 6, wherein the amide slip agent is a saturated or unsaturated fatty acid amide.

8. The polymer composition according to claim 7, wherein the amide slip agent is a saturated fatty acid amide, preferably selected from the group consisting of behenamide, arachidamide, stearamide, palmitamide, myristamide and lauramide.

9. The polymer composition according to any one of claims 1 to 8, wherein the wax is a natural wax, preferably a polar-modified natural wax.

10. The polymer composition according to any one of claims 1 to 9, wherein the wax has a viscosity in the range of 10 mPas -1 to 100 mPas -1 measured at 100 °C in accordance with DIN 53019.

11. The polymer composition according to any one of claims 1 to 10, wherein the composition comprises from 0.08 to 0.4% by weight, preferably from 0.1 to 0.3% by weight, of the amide slip agent, based on the total weight of the composition as a whole.

12. The polymer composition according to any one of claims 1 to 11, wherein the composition comprises from 0.12 to 0.8% by weight, more preferably from 0.15 to 0.5% by weight, of the wax, based on the total weight of the polymer composition as a whole.

13. An article comprising the polymer composition according to any one of claims 1 to 12.

14. The article according to claim 13, wherein the article is an injection-molded or compression-molded article, preferably an injection-molded article, such as a lid or closure.

15. Use of the polymer composition according to any one of claims 1 to 12 in the manufacture of an article, preferably an injection-molded or compression-molded article, such as a lid or closure.

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