POLYETHYLENE COMPOSITION COMPRISING TWO TYPES OF LINEAR LOW DENSITY POLYETHYLENE

Abstract

The invention is directed to a polyethylene composition comprising 20-90 wt % of a LLDPE A and 80-10 wt % of a LLDPE B, wherein i) LLDPE A is obtainable by a process for producing a copolymer of ethylene and another α-olefin in the presence of an Advanced Ziegler-Natta catalyst, ii) LLDPE B is obtainable by a process for producing a copolymer of ethylene and another α-olefin in the presence of a metallocene catalyst.

Claims

1. A polyethylene composition comprising 20-90 wt % of a LLDPE A and 80-10 wt % of a LLDPE B, wherein i) LLDPE A is obtained by a process for producing a copolymer of ethylene and another α-olefin in the presence of an Advanced Ziegler-Natta catalyst, wherein the Ziegler-Natta catalyst is produced in a process comprising the steps of: (a) contacting a dehydrated support having hydroxyl groups with a magnesium compound having the general formula MgR′R″, wherein R′ and R″ are the same or different and are independently selected from the group comprising an alkyl group, alkenyl group, alkadienyl group, aryl group, alkaryl group, alkenylaryl group and alkadienylaryl group; (b) contacting the product obtained in step (a) with modifying compounds (A), (B) and (C), wherein: compound (A) is at least one compound selected from the group consisting of carboxylic acid, carboxylic acid ester, ketone, acyl halide, aldehyde and alcohol; compound (B) is a compound having the general formula R.sup.1.sub.a(R.sup.2O).sub.bSiY.sup.1.sub.c, wherein a, b and c are each integers from 0 to 4 and the sum of a, b and c is equal to 4 with a proviso that when c is equal to 4 then modifying compound (A) is not an alcohol, Si is a silicon atom, O is an oxygen atom, Y.sup.1 is a halide atom and R.sup.1 and R.sup.2 are the same or different and are independently selected from the group comprising an alkyl group, alkenyl group, alkadienyl group, aryl group, alkaryl group, alkenylaryl group and alkadienylaryl group; compound (C) is a compound having the general formula (R.sup.11O).sub.4M.sup.1, wherein M.sup.1 is a titanium atom, a zirconium atom or a vanadium atom, O is an oxygen atom and R.sup.11 is selected from the group comprising an alkyl group, alkenyl group, alkadienyl group, aryl group, alkaryl group, alkenylaryl group and alkadienylaryl group; and (c) contacting the product obtained in step (b) with a titanium halide compound having the general formula TiY.sub.4, wherein Ti is a titanium atom and Y is a halide atom, ii) LLDPE B is obtained by a process for producing a copolymer of ethylene and another α-olefin in the presence of a metallocene catalyst.

2. The polyethylene composition according to claim 1, wherein the polyethylene composition comprises 45-88 wt % of LLDPE A and 55-12 wt % of LLDPE B.

3. The polyethylene composition according to claim 1, wherein the metallocene catalyst comprises a supported metallocene catalyst component, a catalyst activator and a modifier.

4. The polyethylene composition according to claim 1, wherein the support for the Ziegler-Natta catalyst is silica, alumina, magnesia, thoria, zirconia or mixtures thereof.

5. The polyethylene composition according to claim 1, wherein compound (A) is methyl n-propyl ketone, ethyl acetate, n-butyl acetate, acetic acid, isobutyric acid, isobutyraldehyde, ethanoyl chloride, ethanol or sec-butanol.

6. The polyethylene composition according to claim 1, wherein compound (B) is tetraethoxysilane, n-propyltriethoxysilane, isobutyltrimethoxysilane, dimethyldichlorosilane, n-butyltrichlorosilane or silicon tetrachloride.

7. The polyethylene composition according to claim 1, wherein compound (C) is titanium tetraethoxide, titanium tetra-n-butoxide or zirconium tetra-n-butoxide.

8. The polyethylene composition according to claim 1, wherein the metallocene catalyst comprises a metallocene component of the formula I ##STR00013## wherein M is a transition metal selected from the group consisting of lanthanides and metals from group 3, 4, 5 or 6 of the Periodic System of Elements; Q is an anionic ligand to M; k represents the number of anionic ligands Q and equals the valence of M minus two divided by the valence of the anionic Q ligand; R is a hydrocarbon bridging group; and Z and X are substituents.

9. The polyethylene composition according to claim 3, wherein the catalyst activator is an alumoxane, a perfluorophenylborane and/or a perfluorophenylborate.

10. The polyethylene composition according to claim 3, wherein the modifier is the product of reacting an aluminum compound of general formula (1) ##STR00014## with an amine compound of general formula (2) ##STR00015## wherein R.sup.31 is hydrogen or a branched or straight, substituted or unsubstituted hydrocarbon group having 1-30 carbon atoms, R.sup.32 and R.sup.33 are the same or different and selected from branched or straight, substituted or unsubstituted hydrocarbon groups having 1-30 carbon atoms R.sup.34 is hydrogen or a functional group with at least one active hydrogen R.sup.35 is hydrogen or a branched, straight or cyclic, substituted or unsubstituted hydrocarbon group having 1-30 carbon atoms, and R.sup.36 is a branched, straight or cyclic, substituted or unsubstituted hydrocarbon group having 1-30 carbon atoms.

11. The polyethylene composition according to claim 10, wherein the amine compound is octadecylamine, ethylhexylamine, cyclohexylamine, bis(4-aminocyclohexyl)methane, hexamethylenediamine, 1,3-benzenedimethanamine, 1-amino-3-aminomethyl-3,5, 5-trimethylcyclohexane or 6-amino-1,3-dimethyluracil.

12. The polyethylene composition according to claim 10, wherein the aluminum compound is a tri-alkylaluminum compound or a dialkylaluminumhydride.

13. The polyethylene composition according to claim 1, wherein during the process for producing a copolymer of ethylene and another α-olefin in the presence of a metallocene catalyst system a continuity aid agent is added, wherein said continuity aid agent is prepared separately prior to introduction into the process by reacting: at least one metal alkyl or metal alkyl hydride compound of a metal from group IIA or IIIA of the Periodic System of the Elements, and at least one compound of general formula R.sup.21.sub.mY.sup.4R.sup.22.sub.p′ wherein R.sup.21 is a branched, straight, or cyclic, substituted or unsubstituted hydrocarbon group having 1 to 50, R.sup.22 is hydrogen or a functional group with at least one active hydrogen, Y.sup.4 is O, N, P or S, p and m are each at least 1 and are such that the formula has no net charge, the molar ratio of the metal of the metal alkyl compound and Y.sup.4 is 2:1 to 10:1.

14. A process comprising forming the polyethylene composition according to claim 1 to prepare an article.

15. An article comprising the polyethylene composition according to claim 1.

16. The polyethylene composition according to claim 1, wherein compound (A) is methyl n-propyl ketone, ethyl acetate, n-butyl acetate, acetic acid, isobutyric acid, isobutyraldehyde, ethanoyl chloride, ethanol or sec-butanol; compound (B) is tetraethoxysilane, n-propyltriethoxysilane, isobutyltrimethoxysilane, dimethyldichlorosilane, n-butyltrichlorosilane or silicon tetrachloride; and compound (C) is titanium tetraethoxide, titanium tetra-n-butoxide or zirconium tetra-n-butoxide.

17. The polyethylene composition according to claim 16, wherein the metallocene catalyst comprises a metallocene component of the formula I ##STR00016## wherein M is a transition metal selected from the group consisting of lanthanides and metals from group 3, 4, 5 or 6 of the Periodic System of Elements; Q is an anionic ligand to M; k represents the number of anionic ligands Q and equals the valence of M minus two divided by the valence of the anionic Q ligand; R is a hydrocarbon bridging group; and Z and X are substituents; a catalyst activator comprising alumoxane, a perfluorophenylborane and/or a perfluorophenylborate; and a catalyst modifier that is the product of reacting an aluminum compound of general formula (1) ##STR00017## with an amine compound of general formula (2) ##STR00018## wherein R.sup.31 is hydrogen or a branched or straight, substituted or unsubstituted hydrocarbon group having 1-30 carbon atoms, R.sup.32 and R.sup.33 are the same or different and selected from branched or straight, substituted or unsubstituted hydrocarbon groups having 1-30 carbon atoms R.sup.34 is hydrogen or a functional group with at least one active hydrogen R.sup.35 is hydrogen or a branched, straight or cyclic, substituted or unsubstituted hydrocarbon group having 1-30 carbon atoms, and R.sup.36 is a branched, straight or cyclic, substituted or unsubstituted hydrocarbon group having 1-30 carbon atoms;

18. The polyethylene composition according to claim 17, wherein the amine compound octadecylamine, ethylhexylamine, cyclohexylamine, bis(4-aminocyclohexyl)methane, hexamethylenediamine, 1,3-benzenedimethanamine, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane or 6-amino-1,3-dimethyluracil; and the aluminum compound is a tri-alkylaluminum compound or a dialkylaluminumhydride.

19. A process comprising blowing a film from the polyethylene composition of claim 18.

20. The article of claim 19, wherein the article is a blown film.

Description

EXAMPLES

[0180] The polyethylene compositions 1-5 were prepared by mixing AZ LLDPE and metallocene LLDPE followed by extrusion of the mixture. Composition 1 is a composition consisting of 100% AZ LLDPE and composition 5 is a composition consisting of 100% metallocene LLDPE. The other compositions are polyethylene compositions with different amounts of AZ LLDPE and metallocene LLDPE.

[0181] Mixing

[0182] For each composition 2 kg of pilot plant reactor base resin in granular form was used mixed with additives, as shown in table 1. The additives mixing was carried out in a small Henschel mixer (3 kg capacity) at slow speed for 3 minutes.

[0183] Compounding

[0184] Compounding was carried out in an extruder; Thermo Fischer/twin T-Fischer PTW24.

[0185] The extrusion conditions are shown in Table 1. The melt pressure and the torque were determined during extrusion.

[0186] The compounding conditions were kept similar for all 5 different compositions.

TABLE-US-00001 Melt TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS8 TS9 TS10 pressure Torque ° C. ° C. ° C. ° C. ° C. ° C. ° C. ° C. ° C. ° C. (bar) (Nm) Composition 1 100% AZ - C6-LLDPE. Irganox 1076 = 200 ppm. Irgafos 168 = 800 ppm. ZnSt = 500 ppm 107.2 179.9 180.0 185.0 189.9 190.0 195.0 194.6 199.8 178.5 10.1 100.0 Composition 2 75% AZ -C6 LLDPE + 25% C6 mLLDPE. Irganox 1076 = 500 ppm. Irgafos = 2000 ppm 105.2 180.0 185.0 190.0 190.0 194.9 195.0 194.8 200.1 177.1 15.0 103.7 Composition 3 50% AZ -C6 LLDPE + 50% C6 mLLDPE. Irganox 1076 = 500 ppm. Irgafos = 2000 ppm. 105.5 179.9 185.0 189.8 190.1 194.9 195.0 195.1 199.2 175.6 18.1 108.6 Composition 4 25% AZ -C6 LLDPE + 75% C6 mLLDPE. Irganox 1076 = 500 ppm. Irgafos = 2000 ppm. 104.3 179.9 185.1 189.8 190.0 195.0 194.0 194.8 200.5 173.1 24.6 125.2 Composition 5 100% C6 mLLDPE. Irganox 1076 = 500 ppm. Irganox 1076 = 500 ppm. Irgafos = 2000 ppm. PPA Dynamar 5920A = 800 ppm 106.0 179.9 185.0 189.9 190.0 194.8 194.2 194.2 200.1 178.6 27.7 127.7

[0187] In Table 1 it is shown that the melt pressure was trending up going from 100 wt. % AZ LLDPE to 100 wt. % mLLDPE. 100 wt. % AZ LLDPE yielded 10.1 bar whereas 100 wt. % mLLDPE yielded 27.7 bar.

[0188] In Table 1 it is also shown that also the torque was trending up going from 100 wt. % AZ LLDPE to 100 wt. % mLLDPE. 100 wt. % AZ LLDPE yielded 100 Nm whereas 100 wt. % mLLDPE yielded 127.7 Nm.

[0189] 100 wt. % AZ LLDPE was the polyethylene composition that was the easiest to process whereas, 100 wt. % mLLDPE was the most difficult to process.

[0190] Table 1 shows that the polyethylene compositions comprising 25 wt. % mLLDPE and 50 wt. % mLLDPE have a surprisingly low melt pressure and low torque.

[0191] Properties

[0192] The properties of the polyethylene compositions 1, 2, 3, 4 and 5 are shown in Table 2 and Table 3.

[0193] The melt index (MI) was determined according to ASTM D1238-13 with a load of 2.16 kg at a temperature of 190° C.

[0194] The high load melt index (HMLI) was determined according to ASTM D1238-13 with a load of 21.6 kg at a temperature of 190° C.

[0195] The melt flow ratio (MFR) was determined according to ASTM D1238-13 at a temperature of 190° C. as the ratio of HMLI/MI.

[0196] The density was determined according to ASTM D 792-13.

[0197] The zero shear viscosity η.sup.0 was determined according to ASTM D 4440-08 using an advanced rheological expansion system (ARES).

[0198] The complex viscosity η* was determined according to ASTM D 4440-08 using an advanced rheological expansion system (ARES).

[0199] The storage modulus G′ was determined according to ASTM D 4440-08 using an advanced rheological expansion system (ARES).

[0200] The cole-cole graph was made according to ASTM D 4440-08 using an advanced rheological expansion system (ARES).

[0201] The crystalline melting temperature was determined with differential scanning calorimetry (DSC) according to ASTM D 3418-08.

[0202] The crystallization temperature was determined with differential scanning calorimetry (DSC) according to ASTM D 3418-08.

[0203] The crystallinity was determined with differential scanning calorimetry (DSC) according to ASTM D 3418-08. DSC heating/cooling rate is 10° C./minute.

[0204] The crystalline melting temperature was determined in the second heating curve whereas, the % crystallinity was determined after the first heating and during the cooling process.

[0205] The weight average molecular weight distribution (MWD) was determined with gel permeation chromatography (GPC) according to ASTM D 6474-99. Polystyrene was used for the standardization of the GPC.

[0206] The Mz+1 value was determined with gel permeation chromatography (GPC) according to ASTM D 6474-99.

[0207] The die swell was determined with a capillary rheometer according to ASTM D 3835-08.

[0208] The color of the pellets of compositions 1-5 was determined with a Hunter ColorFlex according to ASTM D 6290-13. The results are given in Table 3.

TABLE-US-00002 TABLE 2 Results Polyethylene composition 1 2 3 4 5 MI g/10 min 0.966 0.993 0.993 1.023 1.15 HLMI g/10 min 27.66 25.46 22.76 21.8 21.86 MFR 28.62 25.63 22.92 21.307 19.065 Density kg/m.sup.3 920.4 921.2 921.1 921.3 921.9 ARES Zero Pas 1.6 × 10.sup.4 1.38 × 10.sup.4 9003 7933 6689 shear viscosity η0 DSC ° C. 124.6 123.90 123.24 122.63 122.71 Crystalline melting temperature DSC ° C. 112.5 111.2 111.17 110.26 109.64 Crystallization temperature DSC % 43.2 44.88 42.93 40.93 40.5 Crystallinity GPC MWD 4.64 4.26 3.93 3.41 3.03 GPC Mz + 1 g/mol 1040205 987631 897788 622014 443061

TABLE-US-00003 TABLE 3 Hunter - ColorFlex - color L, a & b Composition L a B 1 78.693 −0.910 −0.460 2 79.743 −1.000 −0.553 3 78.503 −0.707 −0.753 4 77.580 −0.670 −0.533 5 76.077 −1.093 —

[0209] The melt index (MI) of all the polyethylene compositions was similar, with a slight trending down when going from a 100 wt. % mLLDPE to a 100 wt. % AZ LLDPE.

[0210] The MWD was trending down going from 100 wt. % AZ LLDPE to 100 wt. % mLLDPE. The MWD was 4.64 for 100 wt. % AZ LLDPE and 3.03 for 100 wt. % mLLDPE. The broader the MWD, the easier the processability of the polyethylene composition and the narrower the MWD the most difficult to process. The broader the MWD the better the bubble stability and the narrower the MWD the poorer the bubble stability. For blown film extrusion, the better bubble stability is desired for higher throughput and a wider Blow UP Ratio (BUR).

[0211] The Mz+1 was trending down going from 100 wt. % AZ LLDPE to 100 wt. % mLLDPE.

[0212] The mechanical properties will trend down as we go from 100% mLLDPE to 100% AZ LLDPE.

[0213] The crystalline melt temperature was trending down going from 100 wt. % AZ LLDPE to 100 wt. % mLLDPE. 100 wt. % AZ LLDPE yielded 124.6° C. and 100 wt. % mLLDPE yielded 122.71° C. The crystallinity temperature was trending down going from 100 wt. % AZ LLDPE to 100 wt. % mLLDPE. 100 wt. % AZ LLDPE yielded 112.5 and 100 wt. % mLLDPE yielded 109.64° C. AZ LLDPE coo Is faster than mLLDPE.

[0214] The % crystallinity was trending down going from 100 wt. % AZ LLDPE to 100 wt. % mLLDPE. There is an optimum of 44.88% crystallinity at 75 wt % AZ LLDPE. This difference in % crystallinity is the reason behind the difference in the crystalline melt and crystallinity temperatures between 100 wt. % AZ LLDPE and 100 wt. % mLLDPE and the other polyethylene compositions.

[0215] The zero shear viscosity was trending down going from 100 wt. % AZ LLDPE to 100 wt. % mLLDPE. The difference between 100 wt. % AZ LLDPE and 100 wt. % mLLDPE was significant as shown in Table 2.

[0216] The complex viscosity η* versus frequency, as shown in FIG. 1, showed that 100 wt. % AZ LLDPE was more viscous than 100 wt. % mLLDPE, at lower frequency but, 100 wt. % AZ LLDPE was more shear thinning than 100 wt. % mLLDPE. 100 wt. % mLLDPE exhibited a more Newtonian flow than 100 wt. % AZ LLDPE.

[0217] The storage modulus G′ at lower frequency of 100 wt. % AZ LLDPE was higher than 100 wt. % mLLDPE i.e. 100 wt. % AZ LLDPE was behaving more elastically than 100 wt. % mLLDPE. At higher frequency, all the lines for the different polyethylene compositions were coincided, as shown in FIG. 2.

[0218] The cole-cole graph, as illustrated in FIG. 3, show that both AZ LLDPE and mLLDPE were miscible and will form a homogeneous blend for the polyethylene compositions that were tested. It turns out that the mixture having 75% AZ LLDPE and 25% mLLDPE shows almost the same cole-cole graph as the 100% AZ LLDPE.

[0219] The die swell graph, as illustrated in FIG. 4, shows that the 100 wt. % AZ LLDPE exhibited a higher die swell than 100 wt. % mLLDPE. All other polyethylene compositions 2 to 4 showed values surprisingly close to the 100 wt % mLLDPE values.

[0220] Comparison of all graphs shows that the addition of a small amount of mLLDPE to AZ LLDPE improves the dies well to the preferred level of the mLLDPE, but also keeps a number of preferred properties of the AZ LLDPE, especially at lower amounts of added mLLDPE.