RU2179560C2 - Polyethylene, film and other products comprising polyethylene - Google Patents

Abstract

FIELD: chemistry of polymers. SUBSTANCE: described are polyethylenes having narrow molecular weight distribution and narrow composition distribution. Ethylene polymer has polydispersity index of about to 4, distribution index from about 1.0 to 9 along length of crystallizable chains L_W/L_N and turbidity index of less than 370 p- 330 in which p is density in manufacturing films, index of ethylene polymer relaxation time spectrum and melt index for said polymer having the following relationship: about 2,5 < (ПСВР)(ИР⁰¹⁶)] < about 6,5, wherein MI is index of ethylene polymer relaxation time spectrum and IEPR is melt index. Ethylene polymer have preferably combination of high transparency and shock resistance with low content of extractable agent and improved processibility in manufacturing products such as film. EFFECT: improved properties of the title products. 8 cl, 1 tbl

Description

 This invention relates to polyethylenes having a narrow molecular weight distribution and a narrow composition distribution, which are also easy to process with a relatively narrow distribution of relaxation times. Products made from these ethylene polymers have superior transparency and impact strength, as well as low extractables.

 The background of the invention.

Much attention was paid to metallocene catalysts because of their ability to produce ethylene polymers having a relatively narrow molecular weight and comonomer distribution at high polymerization rates. Such narrow molecular weight and comonomer distributions contribute to improving the transparency, toughness and levels of extractable substances in ethylene polymers having a density much lower than 0.95 g / cm ³ . However, for some applications requiring processability, such as extrudability, these ethylene polymers may not be suitable due to their narrow molecular weight distribution. For example, US Pat. Nos. 5,420,220 and 5,324,800 disclose linear low density polyethylenes obtained using metallocenes having characteristic narrow molecular weight and comonomer distributions along with associated processing limitations.

Unfortunately, if the molecular weight distribution of the ethylene polymer is expanded in order to improve processability, the transparency and impact strength of the polymer are reduced. In addition, the content of extractable substances increases, especially for ethylene polymers having a density much lower than 0.93 g / cm ³ . To improve the processability of the ethylene polymer while maintaining a narrow molecular weight distribution, long chain branching may be introduced into the polymer. For example, US Pat. Nos. 5,272,236 and 5,278,272 and PCT Applications WO 94/07930 describe metallocene-produced ultra-low and low density polyethylenes having long chain branched structures that have improved processability. However, long chain branched structures sometimes promote directional orientation during the manufacturing process, leading to an imbalance in mechanical properties and reduced impact resistance and tear resistance. The transparency of manufactured products, such as blown film, may also be less than optimal for long chain branched polyethylene with narrow molecular weight and comonomer distributions.

 Applicants have identified a family of ethylene polymers having a narrow molecular weight distribution and a narrow composition distribution compared to traditional linear low density polyethylene obtained using Ziegler-Natta catalysts. However, unexpectedly, ethylene polymers also have a relatively narrow distribution of relaxation times, determined by their index of relaxation time spectrum (PSVR), so that the processability of ethylene polymers is comparable, with an equal melt index, to the processability of traditional linear low density polyethylenes obtained using catalysts Ziegler-Natta, which have a wider molecular weight distribution, and better than many serial polyethylene obtained using metallocenes.

 Film products made from real ethylene polymers are characterized by high transparency, higher impact strength (for example, when piercing) and a low content of extractable substances. Similarly, injection molded articles made from real ethylene polymers have improved transparency and impact strength (e.g., low temperature and environmental stress cracking (SRNOS)), since they have a higher impact strength compared to the known linear low-density polyethylene density. The increased impact resistance associated with the ethylene polymers of the applicants makes it possible to more finely calibrate the film and "thin" the molded part while maintaining sufficient strength. In addition, ethylene polymers give the best performance in large-scale film applications such as stretch, high transparency and other packaging films. And due to the low content of extractable substances of these ethylene polymers, film and molding products made from them are promising for use in the food packaging market.

 A brief description of the invention.

The invention relates to an ethylene polymer having: a) a polydispersity index of about 2-4; C) the melt index of the IR and the index of the spectrum of relaxation times, HRMS, such that [(HRMS) (IR ^0.6 )] is from about 2.5 to about 6.5; c) a distribution index along the length of the crystallizable chains, L _w / L _n, from about 1 to 9; and d) a density ρ and a percentage of turbidity in the manufacture of the film, such that the percentage of turbidity is less (370ρ - 330).

 The invention also relates to an ethylene polymer obtained by reacting ethylene and, optionally, a higher α-olefin under polymerization conditions with a non-supported catalyst composition in liquid form, the catalytic composition comprising a transition metal catalyst that produces substantially short chain branching.

 DETAILED DESCRIPTION OF THE INVENTION

 The ethylene polymers of the invention include ethylene homopolymers and copolymers of ethylene and a linear or branched higher α-olefin containing from 3 to about 20 carbon atoms, with a density in the range from about 0.9 to about 0.95 and a melt index from about 0.1 to 200. Suitable higher α-olefins include, for example, propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene and 3,5,5-trimethyl-1-hexene. Cyclic olefins, such as vinylcyclohexane or norbornene, can also be copolymerized with ethylene. Aromatic compounds having vinyl unsaturation, such as styrene and substituted styrenes, can also be introduced as comonomers. Particularly preferred ethylene polymers contain ethylene and from about 1 to about 40 wt.% One or more of these comonomers.

Ethylene polymers have a polydispersity index, uncorrected for long chain branching, from about 2.0 to about 4.0, preferably about 2.5-3.5. The polymer polydispersity index (PPD) is defined as the ratio of the weight average molecular weight of the polymer to the number average molecular weight of the polymer (M _w / M _n ). PPD, uncorrected for long chain branching, is determined using size exclusion chromatography (BXPM) using a WATERS 150 C GPC (gel permeation chromatography) at 140 ^° C with 1,2,4-trichlorobenzene at a flow rate of 1 ml / min. A set of column pore sizes provides molecular weight separation spanning from 200 to 10,000,000 Daltons. The NBS 1475 or 1496 polyethylene standard, developed by the National Institute of Standards Technology, is used as a calibration standard to obtain an uncorrected (estimated linear polymer) molecular weight distribution.

These ethylene polymers have unique rheological properties that imply a special molecular structure and give high impact resistance in the manufactured products. These unique rheological properties also contribute to the relative ease of manufacturing of finished products, especially during film extrusion. In particular, ethylene polymers have a melt index, IR, an index of the spectrum of relaxation times, PSVR, such that for a given polyethylene:
about 2.5 <[(PSVR) (TS ^0.6 )] <about 6.5.

Preferably,
about 3.0 <[(PSVR) (IR ^0.6 )] <about 5.0.

In the latest formulas, IR is the polymer melt index, expressed in grams per 10 minutes, determined in accordance with ASTM D-1238, paragraph E, at 190 ^o C, and PSVR is an indicator of the spectrum of polymer relaxation times in dimensionless units.

где N - число видов, а di и λi - вес и время для каждого из видов (см. работу J. D. Ferry, Viscoelastic Properties of Polymers, John Wiley & Sons, 1980, стр. 224-263). Релаксационный спектр может быть определен для полимера с использованием программы, такой как реологическая IRIS - программа, которая является коммерчески доступной от IRIS Development. Как только распределение видов в релаксационном спектре является рассчитанным, первый и второй моменты распределения, которые являются аналогами М_n и М_w первого и второго моментов молекулярно-массового распределения, рассчитываются следующим образом:

ПСВР определяется как g_II/g_I.The PSVR of an ethylene polymer is defined as follows: the polymer is first subjected to shear strain, and then its reaction to deformation is determined using a viscometer (plastometer). As is known in the art, based on the polymer reaction and the mechanics and geometry of the used viscometer, the relaxation module G (ω) or the dynamic modules G ′ (ω) and G ″ (ω) can be determined as functions of time t or frequency ω, respectively (see (JM Dealy and KF Wissbrun. Melt Rhedogy and Jts Role in Plastics Processing. Van Nostrand Reinhold. 1990, pp. 269-297). The mathematical relationship between the dynamic modulus and the storage modulus is the Fourier integral, but the data system can also be calculated using another well-known relaxation spectrum (see SH Wasserman, J. Rheology, vol. 39, pp. 601-625 (1995) ) Using the classical mechanical model, a discrete relaxation spectrum can be determined, consisting of a series of relaxations or “species”, each with characteristic intensity or “weight” and relaxation time. Using this spectrum, the modules are expressed as:

where N is the number of species, and di and λi are the weight and time for each species (see JD Ferry, Viscoelastic Properties of Polymers, John Wiley & Sons, 1980, pp. 224-263). The relaxation spectrum can be determined for the polymer using a program such as rheological IRIS — a program that is commercially available from IRIS Development. As soon as the distribution of species in the relaxation spectrum is calculated, the first and second moments of the distribution, which are analogues of M _n and M _{w of the} first and second moments of the molecular weight distribution, are calculated as follows:

PSVR is defined as g _II / g _I.

 Since PSVR is sensitive to indicators such as molecular weight distribution of the polymer, molecular weight of the polymer, and long chain branching, it is a sensitive and reliable indicator of polymer stress relaxation. The higher the PSVR value, the wider the distribution of polymer relaxation times and therefore the polymer processability is better.

In addition, polyethylenes have a distribution index along the length of crystallized chains, L _w / L _n , from about 1 to about 9, preferably about 1-6, indicating that they have a relatively narrow distribution of comonomers and therefore relative uniformity of composition. The distribution index along the length of crystallizable chains is determined using fractionation by washing with increasing temperature (PSF), as described in Wild et al. J. Polymer Seci., Poly. Phys. Ed. t, 20, p. 441 (1982). A diluted solution of polyethylene in a solvent such as 1,2,4-trichlorobenzene is loaded at 1-4 mg / L at high temperature into a packed column. The column is then slowly cooled at a rate of 0.1 ^° C./min to room temperature in a controlled manner so that the polyethylene crystallizes on the packing in order to increase branching (or reduce crystallinity) with decreasing temperature. The column is then heated in a controlled manner at a rate of 0.7 ^o C / min to a temperature above 140 ^o C at a constant solvent flow rate of 2 ml / min through the column. The polymer fractions, when they are washed out, have a decrease in branching (or an increase in crystallinity) with increasing temperature. An infrared concentration detector is used to monitor the concentration of the effluent. From the temperature data of the low-voltage filter, the branching frequency of this comonomer can be obtained. Therefore, the lengths of the sections of the main chain between the branches, expressed as L _w and L _n , can be calculated as follows. L _w is the weight average chain length between the branches:
L _W = Σ _i W _i L _i
and L _n is the number average chain length between the branches:
L _n = I / Σ _i (W _i / L _i ),
where W _i is the weight fraction of the polymer component i having an average length of the main chain portion L _i between two adjacent branch points.

These polymers have a low turbidity when forming into films, showing the highest transparency at a given polymer density. In particular, ethylene polymers have a percentage turbidity during film formation and a given density such that for a given ethylene polymer:
% turbidity <(370ρ-330),
where ρ is the polymer density.

Preferably,
% turbidity <(370ρ-335).

Density is determined in accordance with ASTM D 1505 (G-101). The determination of the turbidity percentage is carried out in accordance with the ASTM D 1003 test method, which measures transmitted light, which, when passing through the sample, deviates from the incident beam by direct scattering. According to this test method, only the luminous flux deviating on average by more than 2.5 ^o is considered cloudy.

 The catalyst compositions that can be used to produce the polyethylenes of the invention have no carrier, are in liquid form and contain transition metal catalysts that produce substantially short chain branching, preferably short chain branching. Such transition metal catalysts include compounds containing transition metal complexes, substituted and unsubstituted ligands with a π bond, and heteroallyl residues.

в которой
М - переходный металл, предпочтительно, Z_r или Н_f;
L - замещенный или незамещенный лиганд с π-связью, координационно соединенный с М, предпочтительно, циклоалкадиенильный лиганд;
каждый Q независимо выбирается из группы, состоящей из -О-, -NR-, -CR₂- и -S-, предпочтительно, кислород;
Y - С или S, предпочтительно, углерод;
Z - выбирается из группы, состоящей из -OR, -NR₂, -СR₃, -SR, -SiR₃, -PR₂ и -H, при условии, что, когда Q - -NR-, тогда Z выбирается из группы, состоящей из -OR, -NR₂, -SR, -SiR₃, -PR₂ и - Н, предпочтительно, Z выбирается из группы, состоящей из -OR, -CR₃ и -NR₂;
n - 1 или 2;
А - одновалентная анионная группа при n=2 или двухвалентная анионная группа при n= 1, предпочтительно, А - карбамат, карбоксилат или другой гетероаллильный остаток, описанный комбинацией Q, Y или Z; и
каждый R - независимо, группа, cодержащая С, Si, N, O и/или P, где одна или более R -групп могут быть присоединены к L -заместителю, предпочтительно, R -углеводородная группа, содержащая от 1 до 20 углеродных атомов, наиболее предпочтительно, алкильная, циклоалкильиая или арильная группа, и одна или более из них могут быть присоединены к L - заместителю.Preferably, such compounds have one of the following general formulas I or II:

wherein
M is a transition metal, preferably Z _r or H _f ;
L is a substituted or unsubstituted π-linked ligand coordinated to M, preferably a cycloalkadienyl ligand;
each Q is independently selected from the group consisting of —O—, —NR—, —CR ₂ - and —S—, preferably oxygen;
Y is C or S, preferably carbon;
Z is selected from the group consisting of -OR, -NR ₂ , -CR ₃ , -SR, -SiR ₃ , -PR ₂ and -H, provided that when Q is -NR-, then Z is selected from the group consisting of —OR, —NR ₂ , —SR, —SiR ₃ , —PR ₂ and — H, preferably Z is selected from the group consisting of —OR, —CR ₃ and —NR ₂ ;
n is 1 or 2;
A is a monovalent anionic group at n = 2 or a divalent anionic group at n = 1, preferably A is a carbamate, carboxylate or other heteroallyl residue described by a combination of Q, Y or Z; and
each R is independently a group containing C, Si, N, O and / or P, where one or more R groups can be attached to an L-substituent, preferably an R-hydrocarbon group containing from 1 to 20 carbon atoms, most preferably an alkyl, cycloalkyl or aryl group, and one or more of them may be attached to the L - substituent.

в которой:
М - переходный металл, предпочтительно, Z_r или Н_f;
L - замещенный или незамещенный лиганд с π-связью, координационно соединенный с М, предпочтительно, циклоалкадиенильный лиганд;
каждый Q независимо выбирается из группы, состоящей из -О-, -NR-, -CR₂- и -S-, предпочтительно, кислород;
Y - С или S, предпочтительно, углерод;
Z - выбирается из группы, состоящей из -OR, -NR₂, -CR₃, - SR, -SiR₃, -PR₂ и -Н, при условии, что, когда Q- -NR -, тогда Z выбирается из группы -OR, -NR₂, -SR, -SiR₃,
-PR₂ и -Н, предпочтительно, Z выбирается из группы, состоящей из -OR, -CR₃ и - NR₂;
n - 1 или 2;
A - одновалентная анионная группа при n=2 и двухвалентная анионная группа при n=1, предпочтительно, А - карбамат, карбоксилат или другой гетероаллильный остаток, описанный комбинацией Q, Y и Z;
каждый R - независимо, группа, содержащая С, Si, N, О и/или Р,
где одна или более R-групп могут быть присоединены к L -заместителю, предпочтительно, R - углеводородная группа, содержащая от 1 до 20 углеродных атомов, наиболее предпочтительно, алкильная, циклоалкильная или арильная группа, и одна или более групп могут быть присоединены к L - заместителю,
Т - мостиковая группа, выбираемая из группы, состоящей из алкиленовых или ариленовых групп, содержащих от 1 до 10 углеродных атомов, необязательно, замещенная углеродом или гетероатомами, германием, кремнием и алкилфосфином; и
m=1-7, предпочтительно, 2 - 6, наиболее предпочтительно, 2 или 3.

wherein:
M is a transition metal, preferably Z _r or H _f ;
L is a substituted or unsubstituted π-linked ligand coordinated to M, preferably a cycloalkadienyl ligand;
each Q is independently selected from the group consisting of —O—, —NR—, —CR ₂ - and —S—, preferably oxygen;
Y is C or S, preferably carbon;
Z - is selected from the group consisting of -OR, -NR ₂ , -CR ₃ , - SR, -SiR ₃ , -PR ₂ and -H, provided that when Q- -NR -, then Z is selected from the group -OR, -NR ₂ , -SR, -SiR ₃ ,
—PR ₂ and —H, preferably Z is selected from the group consisting of —OR, —CR ₃ and —NR ₂ ;
n is 1 or 2;
A is a monovalent anionic group at n = 2 and a divalent anionic group at n = 1, preferably A is a carbamate, carboxylate or other heteroallyl residue described by a combination of Q, Y and Z;
each R is independently a group containing C, Si, N, O and / or P,
where one or more R groups can be attached to the L-substituent, preferably R is a hydrocarbon group containing from 1 to 20 carbon atoms, most preferably an alkyl, cycloalkyl or aryl group, and one or more groups can be attached to L - Deputy
T is a bridging group selected from the group consisting of alkylene or arylene groups containing from 1 to 10 carbon atoms, optionally substituted with carbon or heteroatoms, germanium, silicon and alkylphosphine; and
m = 1-7, preferably 2-6, most preferably 2 or 3.

 Particularly preferred compounds containing transition metal complexes, substituted and unsubstituted π-linked ligands and heteroalkyl residues are indenyl zirconium tris (diethyl carbamate) and indenyl zirconium tris (pivalate).

 Other transition metal catalysts that can be used to produce ethylene polymers are derivatives of mono- and non-bridged bis and tricyclopentadienyl coordination complexes with a transition metal, such as those described in US Pat. Nos. 4,542,199, 5,324,800 and European Patent No. 25061-BI, give almost non-long chain, preferably non-long chain branches in polyethylene. Examples of such catalysts are bis (cyclopentadienyl) zirconium dichloride and bis (cyclopentadienyl) zirconium diphenoxide.

 The catalysts are used in combination with activating cocatalysts, such as aluminoxanes, for example methylaluminoxane (MAO) or modified methylaluminoxane (MMAO) or boralkyls, to form catalyst compositions without carriers in liquid form to produce polyethylene. Alumoxanes are preferred cocatalysts, and the process for their preparation and use is well known in the art.

 The catalyst compositions used to prepare ethylene polymers must be introduced into the reaction zone in liquid form without a carrier, as described in US Pat. No. 5,371,036. As used herein, the term "carrierless form" includes a liquid catalyst, liquid cocatalyst, catalyst solution (s) and cocatalyst in the same or different solvent (s) and combinations thereof. In addition to their ability to produce real ethylene polymers having excellent properties, soluble catalyst compositions have a number of additional practical advantages. The carrier-free catalyst compositions can avoid the costs associated with the carrier material and its preparation, and provide a very high ratio of catalytic specific surface to volume. In addition, carrier-free catalyst compositions provide polymers having a much lower residual ash content than polymers prepared using supported catalyst compositions.

 Ethylene polymers can be obtained by conventional methods of emulsion, solution, suspension or gas phase polymerization using reaction conditions well known in the art. A single reactor or several reactors installed in series can be used. Gas phase polymerization using one or more fluidized bed reactors is preferred.

The polymerization is preferably carried out in the gas phase in a mixing reactor or in a fluidized bed using well-known equipment and technology. Preferably, excess pressure is used in the processes 1 to 1000 lbs / ⁱⁿ² (6,9-6900 kPa), preferably 50-400 lb / ⁱⁿ² (345-2760 kPa), and most preferably 100-300 lbs / inch ² (690-1440 kPa) and temperatures ranging from 30 to 130 ^° C., preferably 65-110 ^° C. Ethylene and other monomers, if used, are contacted with an effective amount of the catalyst composition at a temperature and pressure sufficient to initiate polymerization.

 Suitable gas phase polymerization reaction systems include a reactor into which monomer (s) and catalyst composition are loaded, and which contains a layer of formed polyethylene particles. The invention is not limited to any particular type of gas phase reaction system. As an example, a conventional fluidized bed process is conducted by passing a gaseous stream containing one or more monomers continuously through a fluidized bed reactor and in the presence of a catalyst composition at a rate sufficient to maintain the particulate layer in suspension. A gaseous stream containing unreacted gaseous monomer is continuously discharged from the reactor, compressed, cooled, optionally partially or completely condensed, and recycled to the reactor. The product is removed from the reactor, and fresh monomer is added to the recycled stream.

 Conventional additives may be introduced into the process, provided that they do not interfere with the action of the catalyst composition.

 When hydrogen is used in the method as a regulator of the degree of polymerization, it is used in amounts ranging from about 0.001 to about 10 moles of hydrogen per mole of total monomer feed. In addition, as desired for temperature control, any gas inert to the catalyst composition and reactants may also be present in the gas stream.

 Organometallic compounds can be used as agents that purify poisonous impurities to increase catalytic activity. Examples of these compounds are metal amines, preferably aluminum alkyls, most preferably triisobutylaluminum, tri-β-hexylaluminum. The use of such cleaning agents is well known in the art.

 Ethylene polymers can be mixed with other polymers and resins, if necessary, using techniques known in the art. In addition, various additives and reagents can be mixed with ethylene polymers. In particular, additional thermal and light oxidation stabilizers can be introduced, including hindered amine light stabilizers, thioethers or disulfide and arylphosphites or phosphonites. In order to meet the specific product requirements, crosslinking agents, including dicumyl peroxide, dyes, including carbon black and titanium dioxide, lubricants, including metal stearates, processability enhancers, including fluoroelastomers, can be mixed with the ethylene polymer of the invention, if necessary. friction reducing agents, including oleamide or erucamide, anti-sticking additives, or mold release agents, including stearamide, ethylene bis stearamide, variable pore size zeolite, calcium carbonate , talc or silicon dioxide, blowing agents, flame retardants and other traditional materials.

 The ethylene polymers of the invention are suitable for the manufacture of a variety of finished products, such as film, including transparent films and shrink films, extrusion coatings, insulation and sheaths of wires and cables, crosslinked insulation of power cables, injection molded products, injection molded, extruded pipes, hoses, profiles and sheets, insulating or semi-conductive cladding and / or screens. Methods for manufacturing such products are well known in the art.

 The contents of the above patents are given here for comparison.

 The following non-limiting examples further illustrate the invention.

 EXAMPLES

 Measurements.

, с последующими тремя Shodex А 80 М/S (Shava) колонками длиной 25 см для воздействия на молекулярно-массовое разделение линейного полиэтилена от примерно 200 до 10000000 Дальтон. В обоих типах колонок содержится пористая набивка полистиролдивинилбензола. Для получения растворов полимера и хроматографического элемента в качестве растворителя используется 1,2,4-трихлорбензол. Все измерения выполняются при температуре 140±0,2^oС. Аналоговые сигналы от детекторов массы и вязкости собираются в вычислительной системе. Собранные данные затем обрабатываются с использованием стандартной программы, коммерчески доступной из нескольких источников (Waters Corporation и Viskotek Corporation), для молекулярно-массового распределения, неоткорректированного для длинноцепочечного разветвления. При калибровке используется калибровочный метод широкого молекулярно-массового распределения и линейный полимер в качестве эталона (cм. работу W.W. Jau, J.J. Kirkland and D.D. Bly, Modern Sige-Exclusion Jiduid Chromatography, Wiley, стр. 289-313), Для последнего для полимерного эталона должны быть известны две молекулярно-массовые относительные статистики, такие как значения среднечисленной молекулярной массы и значения средневесовой молекулярной массы. На основе молекулярно-массовой калибровки объем вымывания превращается в молекулярную массу предполагаемого линейного полимера этилена.The molecular weight and molecular weight distribution are determined as follows. A WATERS 150 C GPC chromatograph is used, equipped with mixed pore columns for molecular weight measurements. For size exclusion chromatography (VCRM), a 25 cm long pre-column from Polymer Jabs is used, with a nominal pore size of 50

, followed by three Shodex A 80 M / S (Shava) columns 25 cm long to influence the molecular weight separation of linear polyethylene from about 200 to 10,000,000 Daltons. Both types of columns contain a porous packing of polystyrene divinylbenzene. To obtain polymer solutions and a chromatographic element, 1,2,4-trichlorobenzene is used as a solvent. All measurements are performed at a temperature of 140 ± 0.2 ^o C. Analog signals from mass and viscosity detectors are collected in a computer system. The collected data is then processed using a standard program commercially available from several sources (Waters Corporation and Viskotek Corporation) for molecular weight distribution, uncorrected for long chain branching. Calibration uses the calibration method of wide molecular weight distribution and a linear polymer as a reference (see WW Jau, JJ Kirkland and DD Bly, Modern Sige-Exclusion Jiduid Chromatography, Wiley, pp. 289-313), for the latter for a polymer reference two molecular weight relative statistics should be known, such as number average molecular weights and weight average molecular weights. Based on molecular weight calibration, the leaching volume is converted to the molecular weight of the proposed linear ethylene polymer.

Rheological measurements are performed during dynamic shear tests using the new Weissenberg rheogoniometer model supplied by TA Instrument. The experiments were carried out by the method of parallel plates in a nitrogen atmosphere at 190 ^o C. The samples had a size of approximately 1100-1500 microns and a diameter of 4 cm. The oscillation frequency in the experiments is covered by a frequency interval from 0.1 to 100 s ^-1 with 2% strain amplitude. Using the TA Instrument rheometer program, the response torque is converted into data by dynamic modules and dynamic viscosity at each frequency. Discrete relaxation spectra are fitted to the data on the dynamic modules for each sample using a package of serial IRIS programs.

 PVHT measurements are performed as described previously. The polymer melt index, expressed in grams over 10 minutes, is determined in accordance with ASTM D 1238, condition E. Density measurements are carried out in accordance with ASTM D 1505 (G - 101). Turbidity is determined in accordance with ASTM D 1003 test method.

 Examples 1-19 and A-N.

A number of ethylene polymers according to the invention (examples 1-19) are compared with samples of known polyethylene in a number of properties, including polydispersity index (PPD), distribution index along the length of crystallized chains (L _w / L _n ), melt index (IR), indicator relaxation time spectrum (PSVR), percent turbidity and density. The results are given in the table.

 The ethylene polymers in Examples 1-19 are prepared using a gas phase fluidized bed reactor having a nominal diameter of 14 inches (355 mm) and a bed height of 10 feet (305 mm). Each of the catalyst compositions in Examples 1-19 is in liquid form without a carrier.

 The catalyst composition used in Examples 1-12 contains indenyl zirconiumtris (diethyl carbamate) catalyst and a modified activating methylaluminoxane cocatalyst.

 In the catalyst composition used in each of Examples 13-17, indenyl zirconiumtris (pivalate) and modified methylaluminoxane as an activating cocatalyst are contained.

 The catalyst composition used in Examples 18 and 19 contains, respectively, bis (cyclopentadienyl) zirconium dichloride and bis (cyclopentadienyl) zirconium diphenoxide and modified methylaluminoxane as an activating cocatalyst.

 Examples 9-12 are linear copolymers of ethylene and 1-butene, while examples 1-8 and 13-19 are linear copolymers of ethylene and 1-hexene.

 Comparative Examples A and B are AFFI 1 TU industrial polyolefin plastics supplied by The Dow Chemical Company, as indicated in the table.

 Comparative Examples C to H are the industrial linear ethylene polymers EXCEED and EXACT, supplied by Exxon Chemical, as indicated in the table.

 Comparative Example I is an industrial linear ethylene polymer supplied by BASF as indicated in the table.

Comparative Example J is a linear copolymer of ethylene and 1-hexene, also prepared using a gaseous fluidized bed reactor having a nominal diameter of 14 inches (355 mm) and a bed height of 10 feet (305 mm). The catalyst composition used in Comparative Example J contains bis (n-butylcyclopentadienyl) zirconium dichloride as a catalyst and modified methylaluminoxane with SiO ₂ as a support as an activating cocatalyst.

 Comparative Examples K-N are industrial linear low density ethylene polymers produced by the UNIPOL method (Union Carbide Corp.) using a gaseous fluidized bed reactor. They are copolymers of ethylene and 1-butene or 1-hexene and are commercially available under the brands HS 7093, HS 7037, HS 7028 and DFDA 9064.

Comparative Example O is a linear copolymer of ethylene and 1-hexene, obtained analogously to Example 18, except that bis (cyclopentadienyl) zirconium dichloride is used as a catalytic composition and modified methylaluminoxane on an SiO ₂ carrier is an activating cocatalyst.

 Each ethylene polymer of the invention is dry blended with about 1,500 ppm Irganox B-900 (Ciba-Jeigy Copration) and blended in an I 1/2 inch (38 mm) extruder with a standard LLDPE screw (length: diameter = 30: 1 ) at a speed of 40 lb / h (≈98 rpm).

 The granular ethylene polymers of the invention and the polyethylenes of the comparative examples are blown into films using typical operating conditions with a mouthpiece temperature and a blowing rate shown in the table. The degree of blowing is defined as the ratio of the final diameter of the stocking (pipe) to the diameter of the mouthpiece. Blown film extrusion equipment is Sterling - an extruder with a diameter of 1 1/2 inches (38 mm) equipped with a screw for conventional processing of LLDPE with L / D = 24: 1 (constant step, reduced depth, mixing MoIdex - head) and spiral needle mouthpiece. Blown film extrusion equipment operated at a speed of 45 lbs / h (≈98 rpm).

Claims (8)

1. The ethylene polymer having a) a polydispersity index of about 2 to 4; c) the IT melt index and the PSRR relaxation time spectrum index such that [(PSVR) (TS ^0.6 )] is about 2.5-6.5; c) a distribution index along the length of the crystallized chains L _w / L _{n of} about 1 - 9; and d) a density ρ and a percentage of turbidity in the manufacture of the film such that the percentage of turbidity is less than (370ρ - 330).  2. The ethylene polymer according to claim 1, containing about 1 to 40 wt. % linear or branched α-olefin having from 3 to about 20 carbon atoms.  3. The ethylene polymer according to claim 1, containing about 1 to 40 wt. % comonomer selected from propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene and mixtures thereof.  4. A product from an ethylene polymer, characterized in that it is obtained from an ethylene polymer according to claim 1.  5. The product according to claim 4, which is a film. 6. The ethylene polymer obtained by contacting ethylene and, optionally, a higher α-olefin under gas phase polymerization conditions with a catalyst composition in liquid form without a carrier, said catalyst composition comprising a transition metal catalyst that gives substantially short chain branching, and the polymer has the following characteristics: a) a polydispersity index of about 2 to 4; b) the IT melt index and the PSRR relaxation time spectrum index such that [(PSVR) (TS ^0.6 )] is about 2.5-6.5; c) a distribution index along the length of the crystallized chains L _w / L _{n of} about 1 - 9; and d) a density ρ and a percentage of turbidity in the manufacture of the film such that the percentage of turbidity is less than (370ρ-330).  7. The ethylene polymer according to claim 6, wherein the transition metal catalyst is idenyl zirconiumtris (diethylcarbamate) or idenyl zirconiumtris (pivalate).  8. The ethylene polymer according to claim 6, obtained by gas-phase polymerization.

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