Patent Description:
<CIT> relates to a polyethylene cap/closure for a bottle that contains a carbonated beverage.

<CIT> describes polymer articles and processes of forming the same. The processes generally include providing a bimodal ethylene based polymer, blending the bimodal ethylene based polymer with a nucleator to form modified polyethylene and forming the modified polyethylene into a polymer article, wherein the polymer article is selected from pipe articles and blown films.

Films made from polyethylene are generally known in the art and inter alia used in packaging applications. Especially in the latter applications good optical, mechanical and barrier properties are required. Furthermore, as packaging applications frequently require heat sealing, such films should simultaneously have good sealing properties, e.g. thermal stability etc..

Thus, a specific property profile is required meeting all the afore-mentioned requirements.

It has now been found that such a property profile can be obtained by the combination of a specific bi- or multimodal polyethylene and a specific nucleating agent.

Therefore, the present invention relates to the use of a polymer composition comprising.

It has surprisingly been found that the composition of the invention has improved stiffness and optical properties while tear strength and dart impact properties were not affected or not affected in a relevant manner compared with the non-nucleated polymer. Moreover, the heat stability is maintained.

The polymer (P) used in the present invention is bimodal or multimodal, i.e. its molecular weight profile does not comprise a single peak but instead comprises the combination of two or more peaks centered about different average molecular weights as a result of the fact that the polymer comprises two or more separately produced components. Such bi- or multimodal polymers may be prepared for example by two or more stage polymerization or by the use of two or more different polymerization catalysts in a one stage polymerization. Preferably, however, they are produced by a two-or more stage polymerization process using the same catalyst, in particular a slurry polymerization in a loop reactor followed by gas phase polymerization in one or more gas phase reactor(s). Preferably the polymer (P) is produced using a two-stage polymerization process, wherein a slurry polymerization in a loop reactor followed by a gas phase polymerization in a gas phase reactor.

Such a bimodal ethylene polymer (P) consists of a low molecular weight (LMW) fraction and a high molecular weight (HMW) fraction, the HMW fraction has a higher weight average molecular weight Mw than the LMW fraction.

As outlined above, preferably the bimodal ethylene polymer (P) is produced using a two-stage polymerization process with a slurry polymerization in a loop reactor followed by a gas phase polymerization in a gas phase reactor. Preferably the LMW fraction is produced in the loop reactor and the HMW fraction in the subsequent gas phase reactor in the presence of the LMW fraction using the same catalyst.

It is preferred to continuously or intermittently introduce the procatalyst, cocatalyst, ethylene, hydrogen, optionally comonomer and diluent (typically an inert aliphatic hydrocarbon, preferably isobutane or propane) into the loop reactor, withdraw the slurry continuously or intermittently from the loop reactor, pass it into a separation stage to remove at least part of the hydrocarbons, and direct the first polymer component into the gas phase reactor, together with additional ethylene, comonomer and optionally hydrogen and an eventual inert gas to produce the second copolymer component. The resulting copolymer composition is then withdrawn from the gas phase reactor, either continuously or intermittently.

It should be understood that the multi-step process described above may include additional precontacting or prepolymerization stages, where the catalyst is pretreated or prepolymerized before it is introduced into the first polymerization stage. A process including a prepolymerization stage has been described in <CIT>. The temperature in the prepolymerization step is typically from <NUM> to <NUM>, preferably from <NUM> to <NUM> and more preferably from <NUM> to <NUM>.

Preferably, the bi- or multimodal ethylene polymer (P) is a bi- or multimodal linear low density polyethylene, more preferably a bimodal linear low density polyethylene.

The total amount of comonomers present in the bi- or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene, is preferably <NUM> to <NUM> mol%, more preferably <NUM> to <NUM> mol%, even more preferably <NUM> to <NUM> mol% and most preferably <NUM> to <NUM> mol%.

The comonomer(s) of the bi- or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene, is/are preferably selected from C<NUM> to C<NUM> alpha olefins, more preferably from C<NUM> to C<NUM> alpha olefins, e.g. <NUM>-butene and/or <NUM>-hexene.

More preferably, the bi- or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene, comprises at least two different comonomers selected from C<NUM> to C<NUM> alpha olefins, more preferably from C<NUM> to C<NUM> alpha olefins, e.g. <NUM>-butene and <NUM>-hexene. Usually not more than three different comonomers are present in the bi- or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene.

The bi- or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene, preferably has an MFR<NUM>, determined according to ISO <NUM> at a temperature of <NUM> and under a load of <NUM>, of from <NUM> to <NUM>/<NUM>, more preferably <NUM> to <NUM>/<NUM>.

The ratio of the MFR<NUM>, determined according to ISO <NUM> at a temperature of <NUM> and under a load of <NUM>, to the MFR<NUM>, determined according to ISO <NUM> at a temperature of <NUM> and under a load of <NUM>, MFR<NUM>/MFR<NUM>, of the bi- or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene is preferably <NUM> to <NUM>, more preferably <NUM> to <NUM>, even more preferably <NUM> to <NUM> and most preferably <NUM> to <NUM>.

The bi- or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene preferably has a molecular weight distribution (MWD) of below <NUM>, more preferably <NUM> or below, and most preferably of <NUM> or below.

The density of the bi- or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene, is <NUM> to <NUM>/m<NUM>, preferably <NUM> to <NUM>/m<NUM>.

The bi- or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene, preferably has a shear thinning index SHI<NUM>/<NUM> of <NUM> to <NUM>, preferably <NUM> to <NUM>.

The bi- or multimodal ethylene polymer (P) usually comprises at least.

whereby the MFR<NUM> of the ethylene polymer component (A) is different from the MFR<NUM> of the ethylene polymer component (B), the MFR<NUM> of both (A) and (B) being determined according to ISO <NUM> at a temperature of <NUM> and under a load of <NUM>.

In case of the bi- or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene, used according to the present invention a difference in MFR<NUM> denotes a difference in the molecular weight as well.

The ethylene polymer component (A) and the ethylene polymer component (B), when both are mentioned, are also be referred as "ethylene polymer component (A) and (B)".

Preferably, the ethylene polymer component (A) has a MFR<NUM>, determined according to ISO <NUM> at a temperature of <NUM> and under a load of <NUM>, of <NUM> to <NUM>/<NUM>, preferably of <NUM> to <NUM>, more preferably of <NUM> to <NUM>, more preferably of <NUM> to <NUM>, more preferably of <NUM> to <NUM>, even more preferably of <NUM> to <NUM>, g/<NUM>. More preferably, the ethylene polymer component (A) has higher MFR<NUM> than ethylene polymer component (B).

Even more preferably, the ratio of the MFR<NUM> of ethylene polymer component (A) to the MFR<NUM> of the final the bi- or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene is of <NUM> to <NUM>, preferably of <NUM> to <NUM>, preferably of <NUM> to <NUM>, <NUM> more preferably of <NUM> to <NUM>, more preferably of <NUM> to <NUM>.

If the MFR<NUM> of ethylene polymer components, e.g. ethylene polymer component (B), cannot be measured because it cannot be isolated from the mixture of the ethylene polymer components (A) and (B), then it can be calculated using so called Hagström equation (<NPL>). In the formula "MI" is used to denote the MFR<NUM>.

According to Hagström, in said equation, a=<NUM> and b=<NUM> for MFR<NUM>. Furthermore, w is the weight fraction of the other ethylene polymer component, e.g. component (A), having higher MFR. The ethylene polymer component (A) can thus be taken as the component <NUM> and the ethylene polymer component (B) as the component <NUM>. MIb is the MFR<NUM> of the final bi- or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene.

The MFR<NUM> of the ethylene polymer component (B) (MI<NUM>) can then be solved from the equation when the MFR<NUM> of the ethylene polymer component (A) (MI<NUM>) and the final bi- or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene (MIb) are known.

Even more preferably the bi- or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene, is further multimodal with respect to difference in density between the ethylene polymer component (A) and ethylene polymer component (B). Preferably, the density of ethylene polymer component (A) is different, preferably higher, than the density of the ethylene polymer component (B). Preferably the density of the ethylene polymer component (A) is of <NUM> to <NUM>/m<NUM>, preferably of <NUM> to <NUM>/m<NUM>.

Naturally, in addition to multimodality with respect to, i.e. difference between, the MFR of the ethylene polymer components (A) and (B), the bi- or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene, can also be multimodal e.g. with respect to one or both of the two further properties:
multimodality with respect to, i.e. difference between,.

Preferably, the bi- or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene, is further multimodal with respect to comonomer type and/or comonomer content (mol%), preferably wherein the C<NUM> to C<NUM> alpha-olefin comonomer of ethylene polymer component (A) is different from the C<NUM> to C<NUM> alpha-olefin comonomer of ethylene polymer component (B), preferably wherein the C<NUM> to C<NUM> alpha-olefin comonomer of ethylene polymer component (A) is <NUM>-butene and the C<NUM> to C<NUM> alpha-olefin comonomer of ethylene polymer component (B) is <NUM>-hexene.

Preferably, the ratio of [the amount (mol%) of C<NUM> to C<NUM> alpha-olefin comonomer present in ethylene polymer component (A)] to [the amount (mol%) of at least two C<NUM> to C<NUM> alpha-olefin comonomers of the final the bi- or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene] is of <NUM> to <NUM>, preferably of <NUM> to <NUM>, more preferably the ethylene polymer component (A) has lower amount (mol%) of comonomer than the ethylene polymer component (B).

The comonomer content of component (A) and (B) can be measured, or, in case, and preferably, one of the components is produced first and the other thereafter in the presence of the first produced in so called multistage process, then the comonomer content of the first produced component, e.g. component (A), can be measured and the comonomer content of the other component, e.g. component (B), can be calculated according to following formula: <MAT>.

Preferably, the amount (mol%) of the C<NUM> to C<NUM> alpha-olefin comonomer(s) present in the ethylene polymer component (A) is of <NUM> to <NUM> mol%, preferably of <NUM> to <NUM> mol%, more preferably of <NUM> to <NUM> mol%, even more preferably of <NUM> to <NUM> mol%, more preferably of <NUM> to <NUM> mol%, even more preferably of <NUM> to <NUM> mol%.

Even more preferably the bi- or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene, is further multimodal with respect to difference in density between the ethylene polymer component (A) and ethylene polymer component (B). Preferably, the density of ethylene polymer component (A) is different, preferably higher, than the density of the ethylene polymer component (B). More preferably the density of the ethylene polymer component (A) is of <NUM> to <NUM>/m<NUM>, preferably of <NUM> to <NUM>/m<NUM>.

More preferably the bi- or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene, is multimodal at least with respect to, i.e. has a difference between, the MFR<NUM>, the comonomer type and the comonomer content (mol%), as well as with respect to, i.e. has a difference between, the density of the ethylene polymer component (A) and ethylene polymer component (B), as defined above, below or claims including any of the preferable ranges or embodiments of the polymer composition.

Most preferably the bi- or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene, comprises, preferably consists of, an ethylene polymer component (A) and an ethylene polymer component (B), wherein.

Preferably, the bi- or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene, comprises the ethylene polymer component (A) in an amount of <NUM> to <NUM> wt. %, preferably of <NUM> to <NUM> wt. %, more preferably of <NUM> to <NUM> wt. %, more preferably <NUM> to <NUM> wt. % and the ethylene polymer component (B) in an amount of <NUM> to <NUM> wt. %, preferably of <NUM> to <NUM> wt. %, more preferably of <NUM> to <NUM> wt. %, more preferably <NUM> to <NUM> wt. %, based on the total amount (<NUM> wt. %) of the bi- or multimodal ethylene polymer (P). Most preferably, the bi- or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene, consists of the ethylene polymer components (A) and (B) as the sole polymer components. Accordingly, the split (weight/weight) between ethylene polymer component (A) to ethylene polymer component (B) is of (<NUM> to <NUM>):(<NUM> to <NUM>) preferably of (<NUM> to <NUM>):(<NUM> to <NUM>), more preferably of (<NUM> to <NUM>):(<NUM> to <NUM>), more preferably of (<NUM> to <NUM>):(<NUM> to <NUM>).

It is noted herein, that the bi- or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene, may optionally comprise a prepolymer component in an amount up to <NUM> wt. % which has a well-known meaning in the art. In such case the prepolymer component is calculated in one of the ethylene polymer components (A) or (B), preferably in an amount of the ethylene polymer component (A), based on the total amount of the polymer of the bi- or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene.

Accordingly, the bi- or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene, is preferably produced using a coordination catalyst. More preferably, the ethylene polymer components (A) and (B) of the bi- or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene, are preferably produced using a single site catalyst, which includes metallocene catalyst and non- metallocene catalyst, which all terms have a well-known meaning in the art. The term "single site catalyst" means herein the catalytically active metallocene compound or complex combined with a cocatalyst. The metallocene compound or complex is referred herein also as organometallic compound (C).

The organometallic compound (C) comprises a transition metal (M) of Group <NUM> to <NUM> of the Periodic Table (IUPAC <NUM>) or of an actinide or lanthanide.

The term "an organometallic compound (C)" in accordance with the present invention includes any metallocene or non-metallocene compound of a transition metal which bears at least one organic (coordination) ligand and exhibits the catalytic activity alone or together with a cocatalyst. The transition metal compounds are well known in the art and the present invention covers compounds of metals from Group <NUM> to <NUM>, e.g. Group <NUM> to <NUM>, or <NUM> to <NUM>, such as Group <NUM> to <NUM> of the Periodic Table, (IUPAC <NUM>), as well lanthanides or actinides.

In an embodiment the organometallic compound (C) has the following formula (II):.

Most preferably the organometallic compound (C) is a metallocene complex which comprises a transition metal compound, as defined above, which contains a cyclopentadienyl, indenyl or fluorenyl ligand as the substituent "L". Further, the ligands "L" may have substituents, such as alkyl groups, aryl groups, arylalkyl groups, alkylaryl groups, silyl groups, siloxy groups, alkoxy groups or other heteroatom groups or the like. Suitable metallocene catalysts are known in the art and are disclosed, among others, in <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT>.

Most preferred single site catalyst is a metallocene catalyst which means the catalytically active metallocene complex, as defined above, together with a cocatalyst, which is also known as an activator. Suitable activators are metal alkyl compounds and especially aluminium alkyl compounds known in the art. Especially suitable activators used with metallocene catalysts are alkylaluminium oxy-compounds, such as methylalumoxane (MAO), tetraisobutylalumoxane (TIBAO) or hexaisobutylalumoxane (HIBAO).

More preferably the ethylene polymer components (A) and (B) of the bi- or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene, are produced in the presence of the same metallocene catalyst.

The bi- or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene, may be produced in any suitable polymerization process known in the art. Into the polymerization zone is also introduced ethylene, optionally an inert diluent, and optionally hydrogen and/or comonomer. The ethylene polymer component (A) is preferably produced in a first polymerization zone and the ethylene polymer component (B) is produced in a second polymerization zone. The first polymerization zone and the second polymerization zone may be connected in any order, i.e. the first polymerization zone may precede the second polymerization zone, or the second polymerization zone may precede the first polymerization zone or, alternatively, polymerization zones may be connected in parallel. However, it is preferred to operate the polymerization zones in cascaded mode. The polymerization zones may operate in slurry, solution, or gas phase conditions or their combinations. Suitable processes comprising cascaded slurry and gas phase polymerization stages are disclosed, among others, in <CIT> and <CIT>.

It is often preferred to remove the reactants of the preceding polymerization stage from the polymer before introducing it into the subsequent polymerization stage. This is preferably done when transferring the polymer from one polymerization stage to another.

The catalyst may be transferred into the polymerization zone by any means known in the art. For example, it is possible to suspend the catalyst in a diluent and maintain it as homogeneous slurry, to mix the catalyst with a viscous mixture of grease and oil and feed the resultant paste into the polymerization zone or to let the catalyst settle and introduce portions of thus obtained catalyst mud into the polymerization zone.

The polymerization, preferably of the ethylene polymer component (A), in the first polymerization zone is preferably conducted in slurry. Then the polymer particles formed in the polymerization, together with the catalyst fragmented and dispersed within the particles, are suspended in the fluid hydrocarbon. The slurry is agitated to enable the transfer of reactants from the fluid into the particles.

The polymerization usually takes place in an inert diluent, typically a hydrocarbon diluent such as methane, ethane, propane, n-butane, isobutane, pentanes, hexanes, heptanes, octanes etc., or their mixtures. Preferably the diluent is a low-boiling hydrocarbon having from <NUM> to <NUM> carbon atoms or a mixture of such hydrocarbons and preferred diluent is propane.

The ethylene content in the fluid phase of the slurry may be from <NUM> to about <NUM> % by mole, preferably from about <NUM> to about <NUM> % by mole and in particular from about <NUM> to about <NUM> % by mole.

The temperature in the slurry polymerization is typically from <NUM> to <NUM>, preferably from <NUM> to <NUM> and in particular from <NUM> to <NUM>. The pressure is from <NUM> to <NUM> bar, preferably from <NUM> to <NUM> bar.

The slurry polymerization may be conducted in any known reactor used for slurry polymerization.

Such reactors include a continuous stirred tank reactor and a loop reactor. It is especially preferred to conduct the polymerization in loop reactor. In such reactors the slurry is circulated with a high velocity along a closed pipe by using a circulation pump. Loop reactors are generally known in the art and examples are given, for instance, in <CIT>, <CIT>, <CIT>, <CIT> and <CIT>.

It is sometimes advantageous to conduct the slurry polymerization above the critical temperature and pressure of the fluid mixture. Such operation is described in <CIT>. In such operation the temperature is typically from <NUM> to <NUM>, preferably from <NUM> to <NUM> and the pressure is from <NUM> to <NUM> bar, preferably from <NUM> to <NUM> bar.

The slurry may be withdrawn from the reactor either continuously or intermittently. A preferred way of intermittent withdrawal is the use of settling legs where slurry is allowed to concentrate before withdrawing a batch of the concentrated slurry from the reactor. The continuous withdrawal is advantageously combined with a suitable concentration method, e.g. as disclosed in <CIT> and <CIT>.

Hydrogen may be fed into the reactor to control the molecular weight of the polymer as known in the art. Furthermore, one or more alpha-olefin comonomers are added into the reactor e.g. to control the density of the polymer product. The actual amount of such hydrogen and comonomer feeds depends on the catalyst that is used and the desired melt index (or molecular weight) and density (or comonomer content) of the resulting polymer.

The polymerization, preferably of the ethylene polymer component (B), in the second polymerization zone is preferably conducted in gas phase, preferably in a fluidized bed reactor, in a fast fluidized bed reactor or in a settled bed reactor or in any combination of these. The polymerization in the second polymerization zone is more preferably conducted in a fluidized bed gas phase reactor, wherein ethylene is polymerized together with at least one comonomer in the presence of a polymerization catalyst and, preferably in the presence of the reaction mixture from the first polymerization zone comprising the ethylene polymer component (A) in an upwards moving gas stream. The reactor typically contains a fluidized bed comprising the growing polymer particles containing the active catalyst located above a fluidization grid.

The polymer bed is fluidized with the help of the fluidization gas comprising the olefin monomer, eventual comonomer(s), eventual chain growth controllers or chain transfer agents, such as hydrogen, and eventual inert gas. The fluidization gas is introduced into an inlet chamber at the bottom of the reactor. One or more of the above-mentioned components may be continuously added into the fluidization gas to compensate for losses caused, among other, by reaction or product withdrawal.

The fluidization gas passes through the fluidized bed. The superficial velocity of the fluidization gas must be higher that minimum fluidization velocity of the particles contained in the fluidized bed, as otherwise no fluidization would occur. On the other hand, the velocity of the gas should be lower than the onset velocity of pneumatic tranu, as otherwise the whole bed would be entrained with the fluidization gas.

When the fluidization gas is contacted with the bed containing the active catalyst the reactive components of the gas, such as monomers and chain transfer agents, react in the presence of the catalyst to produce the polymer product. At the same time the gas is heated by the reaction heat.

The unreacted fluidization gas is removed from the top of the reactor and cooled in a heat exchanger to remove the heat of reaction. The gas is cooled to a temperature which is lower than that of the bed to prevent the bed from heating because of the reaction. It is possible to cool the gas to a temperature where a part of it condenses. When the liquid droplets enter the reaction zone they are vaporized.

The vaporization heat then contributes to the removal of the reaction heat. This kind of operation is called condensed mode and variations of it are disclosed, among others, in <CIT>, <CIT>, <CIT> and <CIT>. It is also possible to add condensing agents into the recycle gas stream, as disclosed in <CIT>. The condensing agents are non-polymerizable components, such as n-pentane, isopentane, n-butane or isobutane, which are at least partially condensed in the cooler.

The gas is then compressed and recycled into the inlet chamber of the reactor. Prior to the entry into the reactor fresh reactants are introduced into the fluidization gas stream to compensate for the losses caused by the reaction and product withdrawal. It is generally known to analyze the composition of the fluidization gas and introduce the gas components to keep the composition constant. The actual composition is determined by the desired properties of the product and the catalyst used in the polymerization.

The catalyst may be introduced into the reactor in various ways, either continuously or intermittently. Where the gas phase reactor is a part of a reactor cascade the catalyst is usually dispersed within the polymer particles from the preceding polymerization stage. The polymer particles may be introduced into the gas phase reactor as disclosed in <CIT> and <CIT>. Especially if the preceding reactor is a slurry reactor it is advantageous to feed the slurry directly into the fluidized bed of the gas phase reactor as disclosed in <CIT>, <CIT>, <CIT> and <CIT>.

The polymeric product may be withdrawn from the gas phase reactor either continuously or intermittently. Combinations of these methods may also be used. Continuous withdrawal is disclosed, among others, in <CIT>. Intermittent withdrawal is disclosed, among others, in <CIT>, <CIT>, <CIT> and <CIT>.

Also antistatic agent(s), such as water, ketones, aldehydes and alcohols, may be introduced into the gas phase reactor if needed. The reactor may also include a mechanical agitator to further facilitate mixing within the fluidized bed.

Typically the fluidized bed polymerization reactor is operated at a temperature within the range of from <NUM> to <NUM>, preferably from <NUM> to <NUM>. The pressure is suitably from <NUM> to <NUM> bar, preferably from <NUM> to <NUM> bar.

The polymerization of at least ethylene polymer component (A) and ethylene polymer component (B) in the first and second polymerization zones may be preceded by a prepolymerization step. The purpose of the prepolymerization is to polymerize a small amount of polymer onto the catalyst at a low temperature and/or a low monomer concentration. By prepolymerization it is possible to improve the performance of the catalyst in slurry and/or modify the properties of the final polymer.

The prepolymerization step may be conducted in slurry or in gas phase. Preferably, prepolymerization is conducted in slurry, preferably in a loop reactor. The prepolymerization is then preferably conducted in an inert diluent, preferably the diluent is a low-boiling hydrocarbon having from <NUM> to <NUM> carbon atoms or a mixture of such hydrocarbons.

The temperature in the prepolymerization step is typically from <NUM> to <NUM>, preferably from <NUM> to <NUM> and more preferably from <NUM> to <NUM>.

The catalyst components are preferably all introduced to the prepolymerization step. Preferably the reaction product of the prepolymerization step is then introduced to the first polymerization zone. Also preferably, as mentioned above, the prepolymer component is calculated to the amount of the ethylene polymer component (A).

It is within the knowledge of a skilled person to adapt the polymerization conditions in each step as well as feed streams and resident times to obtain the bi- or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene.

The bi- or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene, comprises at least, and preferably solely, the ethylene polymer components (A) and (B) obtained from the second polymerization zone, which is preferably a gas phase reactor as described above, is the subjected to conventional post reactor treatment to remove the unreacted components among others.

Thereafter, typically, the obtained polymer is extruded and pelletized. The extrusion may be conducted in the manner generally known in the art, preferably in a twin screw extruder. One example of suitable twin screw extruders is a co-rotating twin screw extruder. Those are manufactured, among others, by Coperion or Japan Steel Works. Another example is a counter rotating twin screw extruder. Such extruders are manufactured, among others, by Kobe Steel and Japan Steel Works. Before the extrusion at least part of the desired additives, as mentioned above, are preferably mixed with the polymer. The extruders typically include a melting section where the polymer is melted and a mixing section where the polymer melt is homogenized. Melting and homogenization are achieved by introducing energy into the polymer. Suitable level of specific energy input (SEI) is from about <NUM> to about <NUM> kWh/ton polymer, preferably from <NUM> to <NUM> kWh/ton.

In the present invention the term "hydrocarbyl" denotes a monovalent residue consisting of carbon and hydrogen atoms only.

In compound (I) each of R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM> and R<NUM> is preferably independently selected from hydrogen, C<NUM> to C<NUM> hydrocarbyl groups, hydroxyl, C<NUM> to C<NUM> alkoxy, C<NUM> to C<NUM> alkyleneoxy, amine, C<NUM> to C<NUM> alkylamine, F, Cl, Br, I and phenyl, preferably from hydrogen and a C<NUM> to C<NUM> hydrocarbyl group, more preferably from hydrogen and a C<NUM> to C<NUM> alkyl group, even more preferably from hydrogen and a C<NUM> to C<NUM> alkyl group, still more preferably from hydrogen and a C<NUM> or C<NUM> alkyl group.

Preferably, the total number of carbon atoms present in R<NUM> to R<NUM> is <NUM> or below, more preferably <NUM> or below and most preferably <NUM> or below.

In a preferred embodiment, each of R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM> and R<NUM> is hydrogen or a methyl group, and in a particularly preferred embodiment each of R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM> and R<NUM> is hydrogen.

In case in the compound according to formula (I) two of R<NUM> to R<NUM> located on adjacent carbon atoms may be fused to form a cyclic structure, preferably a cyclic hydrocarbyl structure, the cyclic hydrocarbyl structure is preferably a five to eight-membered ring, more preferably a five or six-membered ring. The cyclic hydrocarbyl structure, if present, may be an aliphatic cyclic hydrocarbyl structure or an aromatic cyclic hydrocarbyl structure, and is preferably an aliphatic cyclic hydrocarbyl structure. Usually, the cyclic hydrocarbyl structure, if present, comprises <NUM> to <NUM> carbon atoms.

However, preferably, the compound according to formula (I) does not comprise such cyclic structures.

As to n and z, both of them may be is <NUM> or <NUM>, and the sum of n+z is <NUM>. Preferably, n is <NUM> and z is <NUM>.

As outlined above, M is selected from the groups consisting of calcium, strontium, lithium, zinc, magnesium and monobasic aluminium, preferably M is selected from calcium, and magnesium. In a preferred embodiment M is calcium.

Preferably the amount of compounds according to formula (I) is within the range of <NUM> to <NUM> ppm, more preferably <NUM> to <NUM> ppm, more preferably within the range of <NUM> to <NUM> ppm, even more preferably within the range of <NUM> to <NUM> ppm, based on the total amount of the polymer composition.

The compound according to formula (I) acts as a nucleating agent in the polymer composition used according to the present invention. Nucleating agents provide nucleation sites for crystal growth during cooling of a thermoplastic molten formulation. The presence of such nucleation sites results in a larger number of crystals, which, in turn are smaller. As a result of the smaller crystals formed therein, usually clarification of the target thermoplastic may be achieved. Therefore, nucleating agents are sometimes also referred to as clarifiers. However, clarification may also be achieved without nucleation, i.e. not all clarifiers are necessarily nucleating agents.

The polymer composition used according to the invention may further comprise a fatty acid salt, usually the fatty acid salt of a metal, e.g. an alkaline metal, an alkaline earth metal and/or zinc.

Fatty acids are known to the person skilled in the art. Fatty acids having <NUM> to <NUM> carbon atoms are preferred whereby fatty acids having <NUM> to <NUM> carbon atoms are particularly preferred.

Non-limiting examples for suitable fatty acid salts are stearates of metals, e.g. alkaline metals, alkaline earth metals and/or zinc, particularly zinc stearate or calcium stearate.

The total amount of fatty acid salts, if present, is preferably within the range of <NUM> to <NUM> ppm, more preferably within the range of <NUM> to <NUM> ppm, even more preferably within the range of <NUM> to <NUM> ppm and even more preferably within the range of <NUM> to <NUM> ppm, based on the total amount of the polymer composition.

In case fatty acids are present, preferably the weight ratio of the compound according to formula (I) to the total amount of fatty acid(s) is within the range of <NUM>:<NUM> to <NUM>:<NUM>, preferably within the range of <NUM>:<NUM> to <NUM>:<NUM>.

Further nucleating agents and/or clarifiers besides the compounds according to formula (I) and the fatty acid salts, if present, may be used in the polymer composition. In case they are used, their amount is usually below <NUM> ppm based on the total amount of the polymer composition.

In one embodiment the only nucleating agents and clarifiers present in the polymer composition used according to the present invention are the compounds according to formula (I), and the fatty acid salts, if present.

Preferably, the total amount of nucleating agents and clarifiers in the composition used according to the present invention including the compounds of formula (I) and, the optional fatty acid salt(s) is <NUM> to <NUM> ppm, more preferably <NUM> to <NUM> ppm, more preferably within the range of <NUM> to <NUM> ppm, even more preferably within the range of <NUM> to <NUM> ppm based on the total amount of the polymer composition.

The amount of the bi- or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene is preferably at least <NUM> wt. %, more preferably at least <NUM> wt. %, even more preferably at least <NUM> wt. %, such as at least <NUM> wt. %, based on the total weight of the polymer composition.

The amount of the compound according to formula (I) is given above.

The polymer composition may contain further polymer components and optionally additives and/or fillers. It is noted herein that additives may be present in the bi- or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene, and/or mixed with the bi- or multimodal ethylene polymer (P) e.g. in a compounding step for producing the polymer composition. The optional additives and fillers and the used amounts thereof are conventional in the field of film applications. Examples of such additives are, among others, antioxidants, process stabilizers, UV- stabilizers, pigments, fillers, antistatic additives, antiblock agents, nucleating agents, acid scavengers as well as polymer processing agent (PPA).

It is understood herein that any of the additives and/or fillers can optionally be added in so called master batch which comprises the respective additive(s) together with a carrier polymer. In such case the carrier polymer is not calculated to the polymer components of the polymer composition, but to the amount of the respective additive(s), based on the total amount of polymer composition (<NUM> wt.

The properties of the polymer composition are mainly defined by the bi - or multimodal ethylene polymer (P), such as the bi- or multimodal linear low density polyethylene, or the bimodal linear low density polyethylene.

Hence, the polymer composition, preferably has an MFR<NUM>, determined according to ISO <NUM> at a temperature of <NUM> and under a load of <NUM>, of from <NUM> to <NUM>/<NUM>, more preferably <NUM> to <NUM> /<NUM>.

The ratio of the MFR<NUM>, determined according to ISO <NUM> at a temperature of <NUM> and under a load of <NUM>, to the MFR<NUM>, determined according to ISO <NUM> at a temperature of <NUM> and under a load of <NUM>, MFR<NUM>/MFR<NUM>, of the polymer composition is preferably <NUM> to <NUM>, more preferably <NUM> to <NUM>, even more preferably <NUM> to <NUM> and most preferably <NUM> to <NUM>.

The polymer composition preferably has a molecular weight distribution (MWD) of below <NUM>, more preferably <NUM> or below, and most preferably of <NUM> or below.

Preferably, the density of the polymer composition is in the range of <NUM> to <NUM>/m<NUM>, more preferably in the range of <NUM> to <NUM>/m<NUM>.

The polymer composition preferably has a shear thinning index SHI<NUM>/<NUM> in the range of <NUM> to <NUM>, more preferably in the range of <NUM> to <NUM>.

With regard to the properties of the bi- or multimodal ethylene polymer (P) and the compound according to the formula (I) reference is made to the definitions provided above.

The polymer composition when formed into a monolayer film having a thickness of <NUM> is further characterized by at least one of the following features.

The preparation of the film is described in the experimental part.

The present specification further describes an article comprising, preferably consisting of, the polymer composition used according to the present invention.

Preferably the article of is a film comprising one or more layer(s), wherein at least one of the layers comprises, preferably consists, of a polymer composition used according to the present invention, more preferably, the film is a monolayer film.

The total thickness of the film comprising one or more layer(s), preferably the monolayer film is preferably within the range of <NUM> to <NUM>, more preferably within the range of <NUM> to <NUM> and most preferably within the range of <NUM> to <NUM>.

The film may be prepared by methods usual in the art, e.g. casting or blow-extrusion, the latter being preferred.

The preferred blow-extrusion process is described in the following.

Films are produced by extrusion through an annular die with a pressure difference applied to blow the extruded cylinder into a film and achieve the desired orientation within the film, i.e. to build a stress into the cooled film.

The components of the film, e.g. the bi - or multimodal ethylene polymer (P), the compound according to formula (I) and the fatty acid salt, if present, are typically intimately mixed prior to extrusion and blowing of the film, as is well known in the art. It is especially preferred to thoroughly blend the components, for example using a twin screw extruder, preferably a counter-rotating extruder prior to extrusion and film blowing.

Typically, the compositions constituting the layers of the film will be blown i.e. (co)extruded at a temperature in the range <NUM> to <NUM>, and cooled by blowing gas (generally air) at a temperature of <NUM> to <NUM> to provide a frost line height of <NUM> to <NUM> times the diameter of the die, preferably <NUM> to <NUM> times the diameter of the die. The blowing up ratio should generally be in the range <NUM> to <NUM>, preferably <NUM> to <NUM>.

Suitable film-forming processes are for example described in <CIT>.

The film-forming process steps are known and may be carried out in one film line in a manner known in the art. Such film lines are commercially available.

The film, preferably the blown film has preferably not been subjected to a subsequent stretching step.

The present specification further describes the use of a compound according to the following formula (I)
<CHM>
wherein.

The present invention is directed to the use of a polymer composition as described above for providing a film maintaining an oxygen induction time within <NUM> % of the oxygen induction time of the identical polymer composition without the compound according to formula (I) and the optional fatty acid salt.

Preferably in the use according to the present invention the amount of the bi- or multimodal ethylene polymer (P) based on the film is at least <NUM> wt.

The present specification further describes the use of a polymer composition comprising.

Preferably, said formed article is a film or a molded article, more preferably a blow molded article or rotomolded article.

It is especially preferred that said formed article is a pipe, mono-or multilayered film, cap, closure, artificial grass or geomembrane.

Preferred features of the polymer composition and the article described above are also preferred features of the use according to the present invention.

Density of the materials is measured according to ISO <NUM>-<NUM>:<NUM> (method A) in Isododecane (immersion liquid) at <NUM>. Samples are prepared by compression moulding (CM) of plates at <NUM>, the average cooling rate of CM plates is appoximately <NUM>/min. Test specimens are prepared by die cutting of <NUM> pieces with a diameter of <NUM>.

The test specimens are conditioned for at least <NUM> at <NUM> and <NUM> % relative humidity before testing. Determination of density starts <NUM> (± <NUM>) hours after compression moulding.

The melt flow rate (MFR) is determined according to ISO <NUM> and is indicated in g/<NUM>. The MFR is an indication of the melt viscosity of the polymer. The MFR is determined at <NUM> for PE. The load under which the melt flow rate is determined is usually indicated as a subscript, for instance MFR<NUM> is measured under <NUM> load, MFR<NUM> is measured under <NUM> load or MFR<NUM> is measured under <NUM> load.

Molecular weight averages (Mz, Mw and Mn), Molecular weight distribution (MWD) and its broadness, described by polydispersity index, PDI= Mw/Mn (wherein Mn is the number average molecular weight and Mw is the weight average molecular weight) were determined by Gel Permeation Chromatography (GPC) according to ISO <NUM>-<NUM>:<NUM>, ISO <NUM>-<NUM>:<NUM>, ISO <NUM>-<NUM>:<NUM> and ASTM D <NUM>-<NUM> using the following formulas: <MAT> <MAT> <MAT>.

For a constant elution volume interval ΔVi, where Ai, and Mi are the chromatographic peak slice area and polyolefin molecular weight (MW), respectively associated with the elution volume, Vi, where N is equal to the number of data points obtained from the chromatogram between the integration limits.

A high temperature GPC instrument, equipped with an IR5 infrared detector from PolymerChar (Valencia, Spain), equipped with <NUM> x Agilent-PLgel Olexis and 1x Agilent-PLgel Olexis Guard columns (Church Stretton, UK) was used. As the solvent and mobile phase <NUM>,<NUM>,<NUM>-trichlorobenzene (TCB) stabilized with <NUM>/L <NUM>,<NUM>-Di tert butyl-<NUM>-methyl-phenol) was used. The chromatographic system was operated at <NUM> and at a constant flow rate of <NUM>/min. <NUM>µL of sample solution was injected per analysis. Data collection was performed using PolymerChar GPC-IR control software.

The column set was calibrated using universal calibration (according to ISO <NUM>-<NUM>:<NUM>) with <NUM> narrow MWD polystyrene (PS) standards in the range of <NUM>,<NUM>/mol to <NUM><NUM>/mol. The PS standards were dissolved at room temperature over several hours. The conversion of the polystyrene peak molecular weight to polyolefin molecular weights is accomplished by using the Mark Houwink equation and the following Mark Houwink constants: <MAT> <MAT> <MAT>.

Integration in the low molecular weight part was done either from the first rise of the polymer peak or if this is before the first calibration point from the first calibration point.

All samples were prepared in the concentration range of <NUM> -<NUM>/ml and dissolved at <NUM> for <NUM> hours for PE under continuous gentle shaking.

The reduced viscosity (also known as viscosity number), ηred, and intrinsic viscosity, [η], of polyethylenes (PE) are determined according to ISO <NUM>-<NUM>: "Determination of the viscosity of polymers in dilute solution using capillary viscometers".

Relative viscosities of a diluted polymer solution with concentration of <NUM>/ml and of the pure solvent (decahydronaphthalene stabilized with <NUM> ppm <NUM>,<NUM>-bis(<NUM>,<NUM>-dimethylethyl)-<NUM>-methylphenol) are determined in an automated capillary viscometer (Lauda PVS1) equipped with <NUM> Ubbelohde capillaries placed in a thermostatic bath filled with silicone oil. The bath temperature is maintained at <NUM>. The sample is dissolved with constant stirring until complete dissolution is achieved (typically within <NUM>).

The efflux time of the polymer solution as well as of the pure solvent are measured several times until three consecutive readings do not differ for more than <NUM> (standard deviation).

The relative viscosity of the polymer solution is determined as the ratio of averaged efflux times in seconds obtained for both, polymer solution and solvent: <MAT> [dimensionless].

Reduced viscosity (ηred) is calculated using the equation: <MAT> where C is the polymer solution concentration at <NUM>: <MAT>, and m is the polymer mass, V is the solvent volume, and γ is the ratio of solvent densities at <NUM> and <NUM> (γ=ρ<NUM>/ρ<NUM>=<NUM>).

The calculation of intrinsic viscosity [η] is performed by using the Schulz-Blaschke equation from the single concentration measurement: <MAT> where K is a coefficient depending on the polymer structure and concentration. For calculation of the approximate value for [η], K=<NUM>.

The corresponded Mv values for the PE are calculated by using the following Mark Houwink equation: <MAT>.

Comonomer Content (%wt and %mol) was determined quantitative nuclear-magnetic resonance (NMR) spectroscopy.

Quantitative <NUM>C{<NUM>H} NMR spectra recorded in the molten-state using a Bruker Avance III <NUM> NMR spectrometer operating at <NUM> and <NUM> for <NUM>H and <NUM>C respectively. All spectra were recorded using a <NUM>C optimised <NUM> magic-angle spinning (MAS) probehead at <NUM> using nitrogen gas for all pneumatics. Approximately <NUM> of material was packed into a <NUM> outer diameter zirconia MAS rotor and spun at <NUM>. This setup was chosen primarily for the high sensitivity needed for rapid identification and accurate quantification (<NPL>, <NPL>, <NPL>). Standard single-pulse excitation was employed utilising the NOE at short recycle delays of <NUM> (<NPL>, <NPL>) and the RS-HEPT decoupling scheme (<NPL>,<NPL>). A total of <NUM> (<NUM>) transients were acquired per spectra. Quantitative <NUM>C{<NUM>H} NMR spectra were processed, integrated and relevant quantitative properties determined from the integrals. All chemical shifts are internally referenced to the bulk methylene signal (δ+) at <NUM> ppm (<NPL>).

Characteristic signals corresponding to the incorporation of <NUM>-butene were observed (<NPL>) and the comonomer fraction calculated as the fraction of <NUM>-butene in the polymer with respect to all monomer in the polymer.

The amount of isolated <NUM>-butene incorporated in EEBEE sequences was quantified using the integral of the *B2 sites at <NUM> ppm accounting for the number of reporting sites per comonomer: <MAT>.

With no other signals indicative of other comonomer sequences, i.e. consecutive comonomer incorporation, observed the total <NUM>-butene comonomer content was calculated based solely on the amount of isolated <NUM>-butene sequences: <MAT>.

Characteristic signals corresponding to the incorporation of <NUM>-hexene were observed (<NPL>) and the comonomer fraction calculated as the fraction of <NUM>-hexene in the polymer with respect to all monomer in the polymer.

The amount isolated <NUM>-hexene incorporated in EEHEE sequences was quantified using the integral of the *B4 sites at <NUM> ppm accounting for the number of reporting sites per comonomer: <MAT>.

The amount consecutively incorporated <NUM>-hexene in EEHHEE sequences was quantified using the integral of the ααB4B4 site at <NUM> ppm accounting for the number of reporting sites per comonomer: <MAT>.

The amount non-consecutively incorporated <NUM>-hexene in EEHEHEE sequences was quantified using the integral of the ββB4B4 site at <NUM> ppm accounting for the number of reporting sites per comonomer: <MAT>.

Due to the overlap of the signals from the *B4 and *βB4B4 sites from isolated (EEHEE) and non-consecutively (EEHEHEE) incorporated <NUM>-hexene respectively the total amount of isolated <NUM>-hexene incorporation is corrected based on the amount of non-consecutive <NUM>-hexene present: <MAT>.

The total <NUM>-hexene content was calculated based on the sum of isolated, consecutive and non-consecutively incorporated <NUM>-hexene: <MAT>.

The total mole fraction of <NUM>-hexene in the polymer was then calculated as: <MAT>.

The amount of ethylene was quantified using the integral of the bulk methylene (δ+) sites at <NUM> ppm. This integral included the γ site as well as the 3B4 sites from <NUM>-hexene. The total ethylene content was calculated based on the bulk integral and compensating for the observed <NUM>-butene and <NUM>-hexene sequences and end-groups: <MAT>.

Characteristic signals resulting from saturated end-groups were observed. The content of such saturated end-groups was quantified using the average of the integral of the signals at <NUM> and <NUM> ppm assigned to the <NUM> and <NUM> sites respectively: <MAT>.

The presence of isolated comonomer units is corrected for based on the number of comonomer units and saturated end-groups present: <MAT>.

The mole percent comonomer incorporation is calculated from the mole fraction: <MAT> <MAT>.

The weight percent comonomer incorporation is calculated from the mole fraction: <MAT> <MAT>.

The chemical composition distribution was determined by analytical Temperature Rising Elution fractionation as described by <NPL>. The separation of the polymer in TREF is according to their crystallinity in solution. The TREF profiles were generated using a CRYSTAF-TREF <NUM>+ instrument manufactured by PolymerChar S. (Valencia, Spain).

The polymer sample was dissolved in <NUM>,<NUM>,<NUM>-trichlorobenzene (TCB, stabilized with <NUM>/L <NUM>,<NUM>-Di tert butyl-<NUM>-methyl-phenol) at a concentration between <NUM>,<NUM> and <NUM>,<NUM>/ml at <NUM> for <NUM> and <NUM> of the sample solution was injected into the column (<NUM> inner diameter, <NUM> length, filled with inert e.g. glass beads). The column oven was then rapidly cooled to <NUM> and held at <NUM> for <NUM> for stabilization purpose and it was later slowly cooled to <NUM> under a constant cooling rate (<NUM>/min). The polymer was subsequently eluted from the column with <NUM>,<NUM>,<NUM>-trichlorobenzene (stabilized with <NUM>/L <NUM>,<NUM>-Di tert butyl-<NUM>-methyl-phenol) at a flow rate of <NUM>,<NUM>/min at <NUM> for a period of <NUM> followed by a temperature increase from <NUM> to <NUM> at a constant heating rate of <NUM>/min with a flow rate of <NUM>,<NUM>/min. The concentration of the polymer during elution was recorded by an infrared detector (measuring the C-H absorption at <NUM> micrometer wavelength). The detector response was plotted as a function of the temperature. The normalized concentration plot was presented as fractogram together with the cumulative concentration signal normalized to <NUM>.

The high crystalline fraction (HCF) is the amount in wt. % of the polymer fraction with will elute between <NUM> and <NUM> elution temperature, which mainly contains the homo-polyethylene chains or chains with a very low branching content.

The low crystalline fraction (LCF) is than the amount in wt. % of the polymer fraction with elutes between <NUM> and <NUM>.

The characterization of melt of polymer composition or polymer as given above or below in the context by dynamic shear measurements complies with ISO standards <NUM>-<NUM> and <NUM>-<NUM>. The measurements were performed on an Anton Paar MCR501 stress controlled rotational rheometer, equipped with a <NUM> parallel plate geometry. Measurements were undertaken on compression moulded plates, using nitrogen atmosphere and setting a strain within the linear viscoelastic regime. The oscillatory shear tests were done at <NUM> applying a frequency range between <NUM> and <NUM> rad/s and setting a gap of <NUM>.

In a dynamic shear experiment the probe is subjected to a homogeneous deformation at a sinusoidal varying shear strain or shear stress (strain and stress controlled mode, respectively). On a controlled strain experiment, the probe is subjected to a sinusoidal strain that can be expressed by <MAT>.

If the applied strain is within the linear viscoelastic regime, the resulting sinusoidal stress response can be given by <MAT> where.

Dynamic test results are typically expressed by means of several different rheological functions, namely the shear storage modulus G', the shear loss modulus, G", the complex shear modulus, G*, the complex shear viscosity, η*, the dynamic shear viscosity, η', the out-of-phase component of the complex shear viscosity η" and the loss tangent, tan δ which can be expressed as follows: <MAT> <MAT> <MAT> <MAT> <MAT> <MAT>.

Besides the above mentioned rheological functions one can also determine other rheological parameters such as the so-called elasticity index EI(x). The elasticity index EI(x) is the value of the storage modulus, G' determined for a value of the loss modulus, G" of x kPa and can be described by equation (<NUM>).

For example, the EI(5kPa) is the defined by the value of the storage modulus G', determined for a value of G" equal to <NUM> kPa.

Shear Thinning Index (SHI<NUM>/<NUM>) is defined as a ratio of two viscosities measured at frequencies <NUM> rad/s and <NUM> rad/s, µ<NUM>/ µ<NUM>.

The chemical composition distribution as well as the determination of the molecular weight distribution and the corresponded molecular weight averages (Mn, Mw and Mv) at a certain elution temperature (polymer crystallinity in solution) were determined by a fully automated Cross Fractionation Chromatography (CFC) as described by <NPL>.

A CFC instrument (PolymerChar, Valencia, Spain) was used to perform the cross-fractionation chromatography (TREF x SEC). A four-band IR5 infrared detector (PolymerChar, Valencia, Spain) was used to monitor the concentration. Around <NUM> of the polymer sample was dissolved in <NUM> TCB in the stainless steel vessel for <NUM> at <NUM>. Once the sample was completely dissolved an aliquot of <NUM>,<NUM> was loaded into the TREF column and stabilized for a while at <NUM>. The polymer was crystallized and precipitated to a temperature of <NUM> by applying a constant cooling rate of <NUM>/min. A discontinuous elution process was performed using the following temperature steps: (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>).

In the second dimension, the GPC analysis, <NUM> PL Olexis columns and 1x Olexis Guard columns from Agilent (Church Stretton, UK) were used as stationary phase. As eluent <NUM>,<NUM>,<NUM>-trichlorobenzene (TCB, stabilized with <NUM>/L <NUM>,<NUM>-Di tert butyl-<NUM>-methylphenol) at <NUM> and a constant flow rate of <NUM>/min were applied. The column set was calibrated using universal calibration (according to ISO <NUM>-<NUM>:<NUM>) with at least <NUM> narrow MWD polystyrene (PS) standards in the range of <NUM>,<NUM>/mol to <NUM><NUM>/mol. Following Mark Houwink constants were used to convert PS molecular weights into the PE molecular weight equivalents (ASTM D6474). <MAT> <MAT>.

Data processing was performed using the software provided from PolymerChar with the CFC instrument.

Heterogeneity factor (HF) describes both, variation in the comonomer content or density and in the molecular weight between high crystalline (HC) and low crystalline (LC) fraction. The HC fraction is defined as the polymer fraction eluting above <NUM>, where the LC fraction is the fraction eluting between <NUM> and <NUM> in CFC. From the elution temperatures and their corresponded molecular weight fractions obtained by CFC analysis, the HF is calculated in the following way: <MAT>.

The peaks maxima are obtained from the TREF curve extracted from the CFC results. TP(HC) is the peak maximum of the HC fraction where TP(LC) is the peak maximum from the LC fraction. If there is no peak maximum for the low crystalline fraction, the assigned Tp is <NUM>. The Mw (at Tp) is the weight average molecular weight of the polymer fraction eluting at Tp or if the Tp is between two CFC fractions, the Mw is calculated by a linear regression. The HF is negative if the Mw for the low crystalline fraction is smaller than the high crystalline fraction. Generally, a high HF indicates high variation in comonomer content and molecular weight combined with well-separated low and high crystalline peaks in the TREF profile.

The angle α is the angle between the adjacent leg B and the hypotenuse in a right-angled triangle. The length of the adjacent leg B can be described by the difference of the peak maxima of the high and low crystalline peak (TP(HC) - TP(LC)) where the length of opposite leg A (log (Mw(atTp(LC)) - log(Mw(atTp(HC)) * <NUM>) is the difference between the Mw values at the corresponded peak maxima.

<FIG> shows the relation between the angle α and the heterogeneity factor (HF).

Determined according to ISO <NUM>-<NUM>.

Determined according to ISO <NUM>-<NUM>: <NUM>.

Determined according to ASTM D <NUM> using a pressure sensor method (standard conditions <NUM>, <NUM>% humidity).

The oxidation induction time (OIT) at <NUM> was determined with a TA Instrument Q20 according to ISO <NUM>-<NUM>. Calibration of the instrument was performed with Indium and Tin, according to ISO <NUM>-<NUM>. The maximum error in temperature from calibration was less than <NUM>. Each polymer sample (cylindrical geometry with a diameter of <NUM> and thickness of <NUM>±<NUM>) was placed in an open aluminium crucible, heated from <NUM> to <NUM> at a rate of <NUM> min-<NUM> in nitrogen (><NUM> vol. % N<NUM>, < <NUM> ppm O<NUM>) with a gas flow rate of <NUM> min-<NUM>, and allowed to rest for <NUM> before the atmosphere was switched to pure oxygen (><NUM> vol. % O<NUM>), also at a flow rate of <NUM> min-<NUM>. The samples were maintained at constant temperature, and the exothermal heat associated with oxidation was recorded. The oxidation induction time was the time interval between the initiation of oxygen flow and the onset of the oxidative reaction. Each presented data point was the average of three independent measurements.

The seal initiation temperature (at <NUM> N) was determined in accordance with ASTM F <NUM> and ASTM F <NUM> with a seal with of <NUM>, a seal pressure of <NUM> psi and a dwell time of <NUM>. The SIT was determined when the seal force reached <NUM> N.

The hot tack temperature (at <NUM> N) was determined in accordance with ASTM F <NUM> (inside-inside) at a sealing pressure of <NUM> N/mm<NUM>, a dwell/sealing time of <NUM>, a delay time of <NUM> and a test/peel speed of <NUM>/s.

<NUM> grams of a metallocene complex bis(<NUM>-methyl-<NUM>-n-butylcyclopentadienyl) zirconium (IV) dichloride (<NPL>), and <NUM> of a <NUM>% solution of commercial methylalumoxane (MAO) in toluene were combined and <NUM> dry, purified toluene was added. The thus obtained complex solution was added onto <NUM> silica carrier Sylopol <NUM> SJ (supplied by Grace) by very slow uniform spraying over <NUM> hours. The temperature was kept below <NUM>. The mixture was allowed to react for <NUM> hours after complex addition at <NUM>.

A multimodal polymer was prepared in a multistage reactor system containing a loop reactor and a gas phase reactor. A prepolymerization step preceded the actual polymerization step. The prepolymerization stage was carried out in slurry in a <NUM> dm<NUM> loop reactor at about <NUM> in a pressure of about <NUM> bar using the polymerization catalyst prepared above. Ethylene was fed in a ratio of (<NUM> of C<NUM>)/(<NUM>/catalyst). Propane was used as the diluent, <NUM>-butene was fed in amounts of (<NUM> of C<NUM>)/(<NUM> of C<NUM>) and hydrogen was fed in amount to adjust the MFR<NUM> of the prepolymer to about <NUM>/<NUM>.

The obtained slurry together with prepolymerized catalyst were introduced into a <NUM> dm<NUM> loop reactor operated at <NUM> and <NUM> bar pressure, wherein also continuous feeds of propane, ethylene hydrogen and <NUM>-butene were introduced such that ethylene content in the reaction mixture was <NUM> mol%. The molar ratio of H<NUM>/C<NUM> in the reactor was <NUM> mol/kmol and the mole ratio of <NUM>-butene to ethylene was <NUM> mol/kmol when the process conditions were adjusted to form a polymer having an MFR<NUM> of <NUM>/<NUM> and a density of about <NUM>/m<NUM>.

The polymer was withdrawn from the loop reactor and introduced into a flash tank operated at <NUM> bar pressure and <NUM> temperature.

From the flash tank the polymer was introduced into a fluidized bed gas phase reactor, where also additional ethylene, <NUM>-hexene comonomer and hydrogen were added, together with nitrogen as an inert gas to produce the HMW component in the presence of the LMW component such that ethylene content in the reactor gas was <NUM> mol%. The gas phase reactor was operated at a temperature of <NUM> and a pressure of <NUM> bar and the ratio of H<NUM>/C<NUM>, was <NUM> mol/kmol and C<NUM>/C<NUM> <NUM> mol/kmol in the reactor when the process conditions were adjusted to form a final polymer which, after collecting the polymer, blending with additives and extruding into pellets in a counter-rotating twin-screw extruder JSW CIM90P, resulted in a polymer having an MFR<NUM> of <NUM>/<NUM> and density of <NUM>/m<NUM>. The split between the polymer produced in the loop reactor and the polymer produced in the gas phase reactor was <NUM>/<NUM>. The polymer produced in the prepolymerization amounted to about <NUM> to <NUM> % of the total polymer and was calculated to the amount of the Loop product.

Following the above procedure, three multimodal polymers (A), (B) and (C) were produced using the same polymerization conditions. The polymers had an average Mn of <NUM>/mol, an average Mw of <NUM>/mol, an average Mz of <NUM>/mol, an average molecular weight distribution, MWD (Mw/Mn) of <NUM>. The average C<NUM>-content was <NUM> mol% and the average C<NUM>-content was <NUM> mol%. The average SHI<NUM>/<NUM> was <NUM>.

The heterogeneity factor (HF) determined by Cross fraction chromatography (CFC) and the molecular weight determined by GPC as described above are summarized in Tables <NUM> and <NUM>.

The ethylene copolymer (polymers (A), (B) and (C) compounded together) was mixed with HPN-20E, a mixture of <NUM> wt. % Calcium (1R, <NUM>)-cyclohexanedicarboxylate and <NUM> wt. % Zinc stearate, obtainable from Milliken, to obtain a final amount of HPN-20E of <NUM> ppm based on the resulting composition and films were produced on a coextrusion film blowing line (obtained from DR. COLLIN GMBH). The parameters were as follows:.

The procedure of inventive example <NUM> was repeated except that HPN-20E was not used. Hence, the corresponding mixing step was neither carried out.

The optical, mechanical and barrier properties of the compositions according to inventive example IE1 and comparative example CE1 are summarized in Table <NUM>.

The results in the above table shows that the tensile modulus, i.e. the stiffness, is significantly increased (by <NUM>%) using <NUM> ppm HPN-20E. Furthermore, the tear strength is not affected. The dart drop impact was reduced by <NUM>% but this is not significant.

Moreover, the haze is reduced significantly by <NUM>% and gloss values are increased significantly using HPN-20E. The Gloss at <NUM>° was even increased by <NUM>%.

The usage of HPN-20E did not lead to yellowing of the polymer.

In addition, the barrier properties are improved significantly. The oxygen transmission rate (OTR) is reduced by almost <NUM>% and the water vapour transmission (WVR) is reduced by almost <NUM>%.

The SIT using HPN-20E film is almost the same of the pure polymer while the hot tack is improved (by almost <NUM>%.

Thus, the above results show that the inventive composition provides film having better mechanical strength, optical properties, barrier properties and hot tack without having high negative impact on the sealing performance and toughness performance.

The ethylene copolymer (polymers (A), (B) and (C) compounded together) was melt-blended with HPN-20E, a mixture of <NUM> wt. % Calcium (1R, <NUM>)-cyclohexanedicarboxylate and <NUM> wt. % Zinc stearate, obtainable from Milliken, to obtain a final amount of HPN-20E of <NUM> ppm based on the resulting composition and extruded using a ZSK-<NUM> melt extruder, the melt processing conditions are summarized in Table <NUM>.

The procedure of inventive example IE2 was repeated except that no HPN-20E was added, i.e. the neat polymer was subjected to the same compounding process as used in inventive example IE2.

Exceed 1018HA, a unimodal ethylene-hexene copolymer obtainable from ExxonMobil, was melt-blended with HPN-20E in the same manner as inventive example IE2 to obtain a final amount of HPN-20E of <NUM> ppm based on the resulting composition.

The procedure of comparative example <NUM> was repeated except that no HPN-20E was added, i.e. the neat polymer was subjected to the same compounding process as used in comparative example CE4.

The oxygen induction times (OIT) of examples IE2, CE3, CE4 and CE5 were measured and compared, the results are as follows. <MAT> <MAT>.

Claim 1:
Use of a polymer composition comprising
a) a bi- or multimodal ethylene polymer (P) having a molecular weight distribution (MWD) of below <NUM> and a heterogeneity factor (HF) determined by Cross fraction chromatography (CFC) in the range of <NUM> to <NUM> and a density in the range of <NUM> to <NUM>/m<NUM>;
b) a compound according to the following formula (I)
<CHM>
wherein
each R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM> and R<NUM> is independently selected from hydrogen, C<NUM>, to C<NUM> hydrocarbyl groups, hydroxyl, C<NUM> to C<NUM> alkoxy, C<NUM> to C<NUM> alkyleneoxy, amine, C<NUM> to C<NUM> alkylamine, F, Cl, Br, I and phenyl;
whereby two of R<NUM> to R<NUM> located on adjacent carbon atoms may be fused to form a cyclic structure;
M is selected from the groups consisting of calcium, strontium, lithium, zinc, magnesium and monobasic aluminium;
n is <NUM> or <NUM>;
z is <NUM> or <NUM>;
the sum of n+z is <NUM>; and
c) optionally a fatty acid salt
for providing a film maintaining an oxygen induction time within <NUM> % of the oxygen induction time of the identical polymer composition without the compound according to formula (I) and the optional fatty acid salt.