Catalyst composition and method for preparing the same

Abstract

The invention relates to linear low density polyethylene having a density in the range from about 900 kg/m.sup.3 to less than about 940 kg/m.sup.3 as determined using IS01872-2, having a molecular weight distribution (M.sub.w/M.sub.n) in the range from 2.5 to 3.5, having an area under the peak in the temperature range from 20 to 40 C. determined using an analytical temperature rising elution fractionation analysis using 1,2-dichlorobenzene and a heating rate of 1 C./min, wherein the area is in the range from 5 to 20% of the sum of the areas under all peaks determined with the analytical temperature rising elution fractionation analysis.

Claims

1. A linear low density polyethylene, comprising: a density in the range from about 900 kg/m.sup.3 to less than about 940 kg/m.sup.3 as determined using ISO1872-2; a molecular weight distribution (Mw/Mn) in the range from 2.5 to 3.5; a peak in the temperature range from 20 to 40 C. determined using an analytical temperature rising elution fractionation analysis using 1,2-dichlorobenzene and a heating rate of 1 C./min; and an area under the peak, wherein the area is in the range from 5 to 20% of the sum of the areas under all peaks determined with the analytical temperature rising elution fractionation analysis.

2. The linear low density polyethylene according to claim 1, wherein zirconium is present in the linear low density polyethylene in an amount in the range from 0.01 to 10 ppm based on the linear low density polyethylene.

3. The linear low density polyethylene according to claim 1, wherein a total CH.sub.3 per 1000 carbon atoms as determined using 13 C NMR is at least 15.

4. The linear low density polyethylene according to claim 1, wherein the linear low density polyethylene is substantially free of long chain branching.

5. The linear low density polyethylene according to claim 1, wherein the linear low density polyethylene has a melt flow rate as determined using ASTM D-1238-10, condition E (190 C., 2.16 kg) in the range from 0.5 to 100 dg/10 min.

6. The linear low density polyethylene according to claim 1, wherein the linear low density polyethylene has a high load melt index as determined using ASTM D-1238-10, condition F (190 C., 21.6 kg) in the range from 10 to 100 dg/min.

7. The linear low density polyethylene according to claim 1, wherein the linear low density polyethylene has a solubility in hexane as measured using ASTM D5227-01(2008) of less than 5 wt %.

8. The linear low density polyethylene according to claim 1, wherein the linear low density polyethylene has a crystallization temperature (Tc) in the range from 100 to 140 C. as determined using Differential Scanning calorimetry according to ASTM D 3418-08 using a scan rate of 10 C./min on a sample of 10 mg and using the second heating cycle.

9. A composition comprising the linear low density polyethylene of claim 1 and further comprising additives.

10. A film comprising the linear low density polyethylene of claim 1.

11. The film according to claim 10, wherein a gloss 45 angle as determined using ASTM D-2457-08 is at least 50.

12. The film according to claim 10, comprising a haze as determined using ASTM D-1003-11 of less than 10.

13. The film according to claim 10, wherein a seal strength as determined using ASTM F88-06 in the temperature range from 105 to 140 C. is on average at least 10N/24 mm.

14. The film according to claim 10, wherein a hot tack strength as determined using ASTM F1912-98 in the temperature range from 105 to 120 C. is on average at least 1.5N/15 mm.

15. An article comprising the linear low density polyethylene of claim 1.

16. The linear low density polyethylene according to claim 1, wherein zirconium is present in the linear low density polyethylene in an amount in the range from 0.01 to 10 ppm based on the linear low density polyethylene; and wherein a total CH.sub.3 per 1000 carbon atoms as determined using 13 C NMR is at least 15.

17. The linear low density polyethylene according to claim 16, wherein the linear low density polyethylene is substantially free of long chain branching.

18. The linear low density polyethylene according to claim 1, wherein the linear low density polyethylene has a melt flow rate as determined using ASTM D-1238-10, condition E (190 C., 2.16 kg) in the range from 0.5 to 100 dg/10 min; wherein the linear low density polyethylene has a high load melt index as determined using ASTM D-1238-10, condition F (190 C., 21.6 kg) in the range from 10 to 100 dg/min; wherein the linear low density polyethylene has a solubility in hexane as measured using ASTM D5227-01(2008) of less than 5 wt %; and wherein the linear low density polyethylene has a crystallization temperature (Tc) in the range from 100 to 140 C. as determined using Differential Scanning calorimetry according to ASTM D 3418-08 using a scan rate of 10 C./min on a sample of 10 mg and using the second heating cycle.

19. A method of making the linear low density polyethylene of claim 1, the method comprising: adding ethylene and an alpha-olefin having 3 to 10 carbon atoms to a reactor; and adding a catalyst composition to the reactor, wherein the catalyst composition comprises a support containing a single site catalyst component, a catalyst activator, and a modifier, wherein the modifier is the product of reacting an aluminum compound of general formula (1) ##STR00021## with an amine compound of general formula (2) ##STR00022## wherein, R1 is hydrogen or a branched or straight, substituted or unsubstituted hydrocarbon group having 1-30 carbon atoms, R2 and R3 are the same or different and selected from branched or straight, substituted or unsubstituted hydrocarbon groups having 1-30 carbon atoms and R4 is hydrogen or a functional group with at least one active hydrogen R5 is hydrogen or a branched, straight or cyclic, substituted or unsubstituted hydrocarbon group having 1-30 carbon atoms, R6 is a branched, straight or cyclic, substituted or unsubstituted hydrocarbon group having 1-30 carbon atoms.

20. A linear low density polyethylene produced by the method of claim 19.

Description

SHORT DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows the aTREF of the LLDPE of comparative example A, wherein T stands for the temperature in C. and wherein DD stands for the differential distribution dC/dT.

(2) FIG. 2 shows the aTREF of the LLDPE of comparative example B. In FIG. 2, T stands for the temperature in C. and wherein DD stands for the differential distribution dC/dT.

(3) FIG. 3 shows the aTREF of the LLDPE of comparative example C. In FIG. 3, T stands for the temperature in C. and wherein DD stands for the differential distribution dC/dT.

(4) FIG. 4 shows the aTREF of the LLDPE of example 11. In FIG. 4, T stands for the temperature in C. and wherein DD stands for the differential distribution dC/dT.

(5) FIG. 5 shows the seal force SF (N/24 mm) of the LLDPE of comparative example A as a function of the temperature T ( C.).

(6) FIG. 6 shows the seal force SF (N/24 mm) of the LLDPE of comparative example B as a function of the temperature T ( C.).

(7) FIG. 7 shows the seal force SF (N/24 mm) of the LLDPE of comparative example C as a function of the temperature T ( C.).

(8) FIG. 8 shows the seal force SF (N/24 mm) of the LLDPE of example 11 as a function of the temperature T ( C.).

(9) FIG. 9 shows the hot tack strength HTS (N/15 mm) of the LLDPE of comparative example A as a function of the temperature T ( C.).

(10) FIG. 10 shows the hot tack strength HTS (N/15 mm) of the LLDPE of comparative example B as a function of the temperature T ( C.).

(11) FIG. 11 shows the hot tack strength HTS (N/15 mm) of the LLDPE of comparative example C as a function of the temperature T ( C.).

(12) FIG. 12 shows the hot tack strength HTS (N/15 mm) of the LLDPE of example 11 as a function of the temperature T ( C.).

EXAMPLES

Experimental Conditions

(13) All materials were handled in a nitrogen atmosphere using either Schlenk techniques or a nitrogen filled glove box. Nitrogen and isopentane were supplied from a plant source and were dried through an additional bed of molecular sieves, if necessary. All other solvents were first dried over molecular sieves and if necessary sodium/potassium amalgam. The catalysts were prepared using temperature controlled to within 0.5 C. in a silicon oil bath with stirring. Most reagents were used as received from the manufacturer or supplier.

Example 1

Preparation of Modifiers

(14) Several modifiers according to the invention were prepared as indicated in Table 1 below.

(15) TABLE-US-00001 TABLE 1 AL:N* Modifier molar ratio Description A 1:1 At room temperature, add slowly neat 2.47 gram of triisobutylaluminum to a solution of octadecylamine (3.35 gram in 25 ml of isopentane). Remove isopentane under vacuum. The product is high boiling point liquid. B 1.6:1 At room temperature, add slowly neat 4.04 gram triisobutylaluminum to a solution of octadecylamine (3.35 gram in 25 ml of isopentane). Remove isopentane under vacuum. The product is high boiling point liquid. C 3:1 At room temperature, add slowly neat 7.41 gram triisobutylaluminum to a solution of octadecylamine (3.3490 gram in 25 ml of isopentane). Remove isopentane under vacuum. The product is high boiling point liquid. D 1:1 At room temperature, add slowly neat 2.53 gram triisobutylaluminum to a solution of 2-ethylhexylamine (1.54 gram in 50 ml of toluene). E 1:1 At room temperature, add slowly neat 0.11 ml triisobutylaluminum to a solution of Atmer 163 (0.130 g of Atmer 163 in 5 ml of toluene). Atmer 163 is a synthetic ethoxylated amine. *AL:N means molar ratio of aluminum (Al) to nitrogen (N)

Examples 2-4

(16) In Examples 2-4 several catalyst compositions were tested.

(17) 0.0880 gram of metallocene catalyst component biphenyl(2-indenyl).sub.2ZrCl.sub.2 was activated separately by adding to the catalyst component 10.7 ml of MAO (10 wt % solution in toluene). In a reaction flask, 10 ml of toluene was added to 5 gram of silica (Grace 955 obtained from Aldrich Chemical Co.) as a support. The activated catalyst component was then transferred to the silica support and the mixture was allowed to react at a temperature of about 50 C. for 1 hour.

(18) A modifier was then added to the reaction mixture, after which reaction was allowed to continue for 30 minutes followed by vacuum drying of the catalyst composition. The catalyst compositions contained 0.244 wt % of Zr and 7.2 wt % of Al (originating from the MAO; additional Al content originating from the modifier not included). This resulted in a molar ratio of Al/Zr of about 100.

(19) Flow properties of the dry catalyst composition were judged visually.

(20) The catalyst composition was tested in an ethylene slurry homopolymerisation process. Productivity in terms of gram PE per gram catalyst composition was determined and after the reaction the reactor was inspected for fouling and/or sheeting.

(21) The results can be found in Table 2 below.

(22) TABLE-US-00002 TABLE 2 Productivity Fouling/ [gram Ex. Modifier Flowability sheeting PE/gram Cat.] 2 Modifier A Excellent None 6500 0.195 gram in 5 ml toluene 3 Modifier B Excellent None 3783 0.195 gram in 5 ml toluene 4 Modifier C Excellent None 2967 0.195 gram in 5 ml toluene

Example 5

(23) Example 5 is similar to Examples 2-4.

(24) 4.380 gram of metallocene catalyst component biphenyl(2-indenyl).sub.2ZrCl.sub.2 was activated separately by adding to the catalyst component 531 ml of MAO (10 wt % solution in toluene). In a reaction vessel, 600 ml of toluene was added to 250 gram of silica (Grace 955 obtained from Aldrich Chemical Co.) as a support. The activated catalyst component was then transferred to the silica support and the mixture was allowed to react while being stirred at a temperature of about 50 C. for 1 hour.

(25) The solution of modifier D above was then added to the reaction mixture, after which reaction was allowed to continue for 30 minutes followed by vacuum drying of the catalyst composition. The catalyst composition contained 0.24 wt % of Zr and 7.2 wt % of Al (originating from the MAO; additional Al content originating from the modifier not included). This resulted in a molar ratio of Al/Zr of about 100. The flowability of this catalyst was excellent. No reactor sheeting or fouling was observed and the productivity was 2050 gram PE/gram catalyst.

Examples 6-8

Fluid-Bed Polymerisation

(26) The supported catalyst of Examples 2-4 of Table 4 were tested in a continuous gas phase fluidized bed reactor having an internal diameter of 45 cm and a reaction zone height of 140 cm. The bed of polymer particles in the reaction zone is kept in a fluidized state by a recycle stream that works as a fluidizing medium as well as a heat dissipating agent for absorbing the exothermal heat generated within reaction zone. The reactor was kept at a constant temperature of about 87 C. and at a constant pressure of about 21.7 bar. Ethylene and hexene were used as the raw materials for polymerisation. These materials form a make-up stream. A Continuity Aid Agent (CAA) was mixed with the make-up stream as a 2% by weight solution in isopentane carrier solvent. The catalyst composition contained biphenyl(2-indenyl).sub.2ZrCl.sub.2 as the catalyst component.

(27) The solid catalyst composition was injected directly in the reaction zone of the fluidized bed using purified nitrogen as a carrier gas. The injection rate was adjusted to maintain a constant production rate of about 12 kg/hr. The produced polymer was discharged from the reaction zone semi-continuously via a series of valves into a fixed volume chamber. The so obtained product was purged to remove any volatile hydrocarbons and was then treated with humidified nitrogen to deactivate any trace quantities of residual catalyst composition. The properties of the polymer were determined by the following test methods:

(28) TABLE-US-00003 TABLE 3 Melt Index ASTM D-1238 - 10 Condition E (190 C., 2.16 kg) Melt Index ASTM D-1238 - 10 Condition F (190 C., 21.6 kg) Density ISO1872-2. The samples were prepared and pressed according to ISO1872-2 and annealed by boiling in water for half an hour, then left to cool for 16 hours in the same water after which the samples were measured. Bulk The resin is poured in a fixed volume cylinder of 400 cc. The bulk Density density is measured as the weight of resin divided by 400 cc to give a value in g/cc. Average The particle size is measured by determining the weight of material Particle collected on a series of U.S. Standard sieves and determining the weight Size average particle size based on the sieve series used. Fines fines are defined as the percentage of the total distribution passing through a 120 mesh standard sieve. This has a particle size equivalent of 120 microns. Tm Tm is determined according to ASTM D3418-08 as follows: Samples weighing approximately 5-10 mg are sealed in aluminum sample pans. The DSC data is recorded by first cooling the sample to 50 C. and then gradually heating it to 200 C. at a rate of 10 C./min. The sample is kept at 200 C. for 5 minutes before a second cooling-heating cycle is applied. Both the first and second cycle thermal events are recorded. The melting temperature is measured and reported during the second heating cycle (or second melt). Solubility ASTM D5227-01(2008). Film samples are extracted with hexane for 2 in hexane hours at 49.5 C. 0.5 C., dried and weighed. The loss in weight of the film is the solubility in hexane. Molecular Sample preparation weight The polymer samples were dissolved (0.1 w %) in 1,2,4-trichlorobenzene distribution (TCB), which was distilled prior to use, over a period of 4 h at 150 C. (Mw/Mn) under nitrogen and stabilized with di-tertbutylparacresol (DBPC) at a concentration of 1 g/L. The solutions were filtered at high temperature (150 C.) using a millipore filtration setup (1.2 m) positioned in a Hereous LUT oven operating at 150 C. SEC-DV measurement The separation of the polymer according to molar mass is performed with a PL-GPC220 equipped with PL BV-400 viscosimeter and refractive index detector. This SEC system is operated at high temperature (column compartment at 150 C., injector compartment at 150 C., and solvent reservoir at 60 C.) and a flow of 1.0 mL/min. Four Polymer Laboratories GPC columns (PL 13 m mixed Olexis columns) were used. Calculations were performed with Viscotek TriSEC 2.7 software. The eluent used was 1,2,4-trichlorobenzene. The columns were calibrated using linear polyethylene standards.

(29) TABLE-US-00004 TABLE 4 Example 6 7 8 Zr (wt %) 0.18 0.20 0.24 Ethylene (mole %) 46.0 46.0 46.0 Hexene (mole %) 5.29 5.25 5.22 Continuity Aid Agent (ppm) 50 50 50 Catalyst Productivity (kg/kg) 5,870 6,050 6,700 Residual Ash (ppm) 155 150 140 Melt Index - MI (dg/min) 1.03 1.02 0.99 Density (g/cc) 0.9190 0.9187 0.9183 Bulk Density (g/cc) 0.372 0.375 0.377 Average Particle Size 860 895 938 (microns) Fines (%) 0.1 0.1 0.1

(30) As can be seen from the results presented in Table 4, polyolefins such as LLDPE can be produced with the catalyst composition of the invention with a minimal amount of fines, which means that fouling and/or sheeting in gas phase and slurry polymerization processes will also be minimal.

Example 9

Large Scale Preparation of the Catalyst Composition of the Invention

(31) At room temperature, 0.595 kg of diphenyl(2-indenyl).sub.2ZrCl.sub.2 was added to 36.968 kg of a 30% methylaluminoxane solution (Al content 13.58 wt %) and stirred for 30 minutes to form activated metallocene. About 172 kg of dry toluene was added to 43 kg of silica 955 to form a silica slurry. At about 30 C., the activated metallocene was added to the silica slurry under agitation. After the activated metallocene was added, the temperature was increased to 50 C. After 2 hours at 50 C., all of modifier F (Table 5) was added. After addition the mixture was kept at 50 C. for 1 hour. The reaction temperature was then reduced to 30 C. The toluene was removed by filtration and the obtained catalysts composition was dried by raising the temperature to 55 C. and using a flow of warm nitrogen. The Al/Zr ratio used in this experiment was approximately 150.

(32) TABLE-US-00005 TABLE 5 Modifier F At room temperature, add slowly 0.114 kg of neat triisobutylaluminum to a solution of 0.057 kg of cyclohexylamine in 9.7 kg of dry toluene.

(33) The catalyst composition obtained had an excellent flow as judged visually.

Example 10

(34) The catalyst composition was tested in an ethylene slurry polymerisation process. After the reaction, the reactor was inspected for fouling and/or sheeting and no fouling/sheeting was observed.

Example 11

(35) Also, the properties of the polymer prepared were tested using the methods as indicated herein.

(36) The properties were compared to the properties of other linear low density polyethylenes.

(37) Comparative example A: LLDPE 6118NE from Saudi Basic Industries Corporation

(38) Comparative example B: LLDPE Exceed 1018CA (Lot: M07120316C (USA)) from Exxon Mobile

(39) Comparative example C: LLDPE Eltex PF6212LA from Ineos polyolefins

Example 11: LLDPE Produced in Example 10; Example According to the Invention

(40) The properties of the materials are indicated in Table 6 below:

(41) TABLE-US-00006 TABLE 6 LLDPEs used and their properties. Ex MI.sub.2.16 D Cat. LCB Comonomer incorporation A 0.84 921.4 ZN No 1-hexene Ziegler Natta B 0.9 920.1 M No 1-hexene homogeneous C 1.34 919.5 M Yes 1-hexene reverse 11 0.99 920.5 M No 1-hexene homogeneous MI.sub.2.16: melt flow index, measured according to ASTM D-1238 - 10 Condition E (190 C., 2.16 kg) in dg/min D: density (kg/m.sup.3) Cat: catalyst LCB: long chain branching ZN: Ziegler Natta M: Metallocene incorporation: the comonomer composition distribution, that is the distribution of the short chain branching (butyl branches due to incorporation of the 1-hexene comonomer) as a function of the molecular weight.

(42) TABLE-US-00007 TABLE 7 Properties of LLDPE produced in example 11 (modifier F) compared to comparative examples Example property A B C 11 Density (kg/m.sup.3) 921.4 920.1 919.5 920.5 M.sub.w/M.sub.n 4.6 2.6 4.2 3.2 Zr <0.01 <0.01 0.1-1 Total CH.sub.3 16.7 12.5 16.1 16.8 per 1000 carbon atoms Butyl branches (hexane) 16.0 12.0 15.2 16.1 per 1000 C (wt %) (9.6) (7.3) (8.3) (9.4) Melt flow rate (190 C., 2.16 kg) 0.84 0.9 1.34 0.99 Solubility in hexane (wt %) <0.6 <1.0 Crystallization temp. ( C.) 66 67 64 68 (main peak at higher 111.2 106.0 104.8 109.7 temperature)

(43) An analytical temperature rising elution fractionation (aTREF) was performed on the examples of comparative examples A-C and of example 11.

(44) Analytical temperature rising elution fractionation (ATREF) analysis was conducted according to the method described in U.S. Pat. No. 4,798,081 and Wilde, L.; Ryle, T. R.; Knobeloch, D. C.; Peat, L R.; Determination of Branching Distributions in Polyethylene and Ethylene Copolymers, J. Polym. ScL, 20, 441-455 (1982), which are incorporated by reference herein in their entirety. The composition to be analyzed was dissolved in 1,2-dichlorobenzene of analytical quality filtrated via 0.2 m filter and allowed to crystallize in a column containing an inert support (Column filled with 150 m stainless steel beans (volume 2500 L) by slowly reducing the temperature to 20 C. at a cooling rate of 0.1 C./min. The column was equipped with an infrared detector. An ATREF chromatogram curve was then generated by eluting the crystallized polymer sample from the column by slowly increasing the temperature of the eluting solvent (1,2-dichlorobenzene) from 20 to 130 C. at a rate of 1 C./min.

(45) The instrument used was Polymer Char Crystaf-TREF 300.

(46) Stabilizers: 1 g/L Topanol+1 g/L Irgafos 168

(47) Sample: approx. 70 mg in 20 mL

(48) Sample volume: 0.3 mL

(49) Pump flow: 0.50 mL/min

(50) The software from the Polymer Char Crystaf-TREF-300 was used to generate the spectra.

(51) The results are presented in FIGS. 1-4 and in Table 8 below. In Table 8, the peak temperature of the peaks is indicated with the area as a percentage of the sum of the areas under all peaks determined with aTREF.

(52) TABLE-US-00008 TABLE 8 Ex. Peak 1: Peak 2: Peak 3: A 97.8 C./51.4% 79.9 C./35.4% 35 C./13.1% B 94.4 C./24.5% 84.5/75.1% 35 C./~0.5% C 95.1/20.9% 78.1/77.7% 35 C./1.4% 11 96.8 C./46.5% 83.3 C./46.0% 35 C./7.5%

(53) As can be seen from Table 8, the LLDPE according to the invention has an area under the peak in the temperature range from 20 to 40 C., for example in the temperature range from 25 to 35 C., determined using an analytical temperature rising elution fractionation analysis using 1,2-dichlorobenzene and a heating rate of 1 C./min, wherein the area is in the range from 5 to 20% of the sum of the areas under all peaks determined with the analytical temperature rising elution fractionation analysis

Example 11

(54) Preparation of Film

(55) The LLDPE powder produced in example 10 was melt-mixed with suitable additives in a twin screw extruder to produce LLDPE pellets. It was found that the LLDPE powder had a very good processability.

(56) Single layer films of 25 m were produced from the LLDPE pellets on a Brabender blown film line, having a frost line height of 30 cm using a blow up ratio of 2.5 and a die throughput of 3.0 kg/hr/cm. (output 60 kg/h)

(57) The line was equipped with a 200 mm die, a die gap of 2.3 mm, reversing haul-off, chilled cooling air, thickness profile measurement and back to back winder. The overall throughput was kept constant. Barrel temperature profiles were ramped from 170 C. at the feed section to 200 C. at the die.

(58) The properties of the film were measured according to the methods mentioned in Table 9.

(59) TABLE-US-00009 TABLE 9 Property Measurement method Gloss 45 angle and Gloss 60 angle ASTM D-2457 - 08 Haze ASTM D-1003 - 11 Hot tack strength ASTM F1912-98 Seal force ASTM F88-06

(60) The example was repeated for the LLDPEs of comparative examples A-C.

(61) It was found that the LLDPE of the invention showed a better processability in the extruder as compared to comparative examples A-C.

(62) The results for the gloss and haze are given in Table 10 below.

(63) TABLE-US-00010 TABLE 10 Gloss and haze of single layer films of 25 m of comparative examples A-C and of example 11. Example property A B C 11 Gloss 45 angle 38.9 67 64.7 76.3 Gloss 60 angle 76.2 122.4 Haze 12.9 5.1

(64) As can be seen from Table 10, film comprising LLDPE of the invention has excellent optical properties (high gloss and low haze). The results for the seal force and hot tack strength of the films are given in FIG. 5-FIG. 12.

(65) As can be seen by comparing FIG. 8 with FIG. 5-7, film of the invention shows a considerably higher average seal force (also referred to herein as seal strength) in the temperature range from 105 to 140 C. as compared to the films comprising the LLDPE of the comparative examples A-C.

(66) As can be seen by comparing FIG. 12 with FIG. 9-11, film of the invention shows a considerably higher average hot tack strength in the temperature range from 105 to 120 C. as compared to the films comprising the LLDPE of the comparative examples.