US20150274937A1 - Method to produce ultra-high molecular weight polyethylene - Google Patents
Method to produce ultra-high molecular weight polyethylene Download PDFInfo
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- US20150274937A1 US20150274937A1 US14/242,497 US201414242497A US2015274937A1 US 20150274937 A1 US20150274937 A1 US 20150274937A1 US 201414242497 A US201414242497 A US 201414242497A US 2015274937 A1 US2015274937 A1 US 2015274937A1
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- weight polyethylene
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- 239000004699 Ultra-high molecular weight polyethylene Substances 0.000 title claims abstract description 25
- 229920000785 ultra high molecular weight polyethylene Polymers 0.000 title claims abstract description 25
- 238000000034 method Methods 0.000 title claims abstract description 24
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims abstract description 69
- 238000006116 polymerization reaction Methods 0.000 claims abstract description 22
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 claims abstract description 21
- 239000005977 Ethylene Substances 0.000 claims abstract description 21
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims abstract description 21
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 claims abstract description 15
- 239000003446 ligand Substances 0.000 claims abstract description 9
- 239000000178 monomer Substances 0.000 claims abstract description 9
- 239000003426 co-catalyst Substances 0.000 claims abstract description 8
- 239000002685 polymerization catalyst Substances 0.000 claims abstract description 8
- 238000010438 heat treatment Methods 0.000 claims abstract description 5
- YSTQWZZQKCCBAY-UHFFFAOYSA-L methylaluminum(2+);dichloride Chemical compound C[Al](Cl)Cl YSTQWZZQKCCBAY-UHFFFAOYSA-L 0.000 claims abstract description 5
- KOKKJWHERHSKEB-UHFFFAOYSA-N vanadium(3+) Chemical compound [V+3] KOKKJWHERHSKEB-UHFFFAOYSA-N 0.000 claims abstract 3
- 239000004408 titanium dioxide Substances 0.000 claims description 18
- 229920000642 polymer Polymers 0.000 claims description 16
- 239000003054 catalyst Substances 0.000 claims description 12
- 239000002105 nanoparticle Substances 0.000 claims description 6
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 5
- 238000011065 in-situ storage Methods 0.000 claims description 5
- 239000002245 particle Substances 0.000 claims description 5
- 230000000379 polymerizing effect Effects 0.000 claims description 4
- 238000002156 mixing Methods 0.000 claims description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims 2
- 229910052757 nitrogen Inorganic materials 0.000 claims 2
- 238000001035 drying Methods 0.000 claims 1
- 239000003960 organic solvent Substances 0.000 claims 1
- 238000010791 quenching Methods 0.000 claims 1
- 230000000171 quenching effect Effects 0.000 claims 1
- 238000009738 saturating Methods 0.000 claims 1
- 238000005406 washing Methods 0.000 claims 1
- 229910052721 tungsten Inorganic materials 0.000 abstract description 9
- 239000010937 tungsten Substances 0.000 abstract description 9
- 229920010741 Ultra High Molecular Weight Polyethylene (UHMWPE) Polymers 0.000 abstract description 5
- 239000002904 solvent Substances 0.000 abstract description 4
- -1 polyethylene Polymers 0.000 description 15
- 239000002114 nanocomposite Substances 0.000 description 14
- 239000004698 Polyethylene Substances 0.000 description 13
- 229920000573 polyethylene Polymers 0.000 description 13
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 description 10
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 9
- 239000000945 filler Substances 0.000 description 8
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 6
- 229920001903 high density polyethylene Polymers 0.000 description 6
- 239000004700 high-density polyethylene Substances 0.000 description 6
- 238000005227 gel permeation chromatography Methods 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 5
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- 238000000113 differential scanning calorimetry Methods 0.000 description 4
- 238000002844 melting Methods 0.000 description 4
- 230000008018 melting Effects 0.000 description 4
- 229910052720 vanadium Inorganic materials 0.000 description 4
- PBKONEOXTCPAFI-UHFFFAOYSA-N 1,2,4-trichlorobenzene Chemical compound ClC1=CC=C(Cl)C(Cl)=C1 PBKONEOXTCPAFI-UHFFFAOYSA-N 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 239000002131 composite material Substances 0.000 description 3
- 230000003247 decreasing effect Effects 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 239000011159 matrix material Substances 0.000 description 3
- COCAUCFPFHUGAA-MGNBDDOMSA-N n-[3-[(1s,7s)-5-amino-4-thia-6-azabicyclo[5.1.0]oct-5-en-7-yl]-4-fluorophenyl]-5-chloropyridine-2-carboxamide Chemical compound C=1C=C(F)C([C@@]23N=C(SCC[C@@H]2C3)N)=CC=1NC(=O)C1=CC=C(Cl)C=N1 COCAUCFPFHUGAA-MGNBDDOMSA-N 0.000 description 3
- 238000003786 synthesis reaction Methods 0.000 description 3
- PNEYBMLMFCGWSK-UHFFFAOYSA-N Alumina Chemical compound [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 2
- FENRYBRSJXUNBC-SXUBXDNWSA-K CC(C)(C)C1=CC2=C(O[V](Cl)(Cl)(O3CCCC3)(O3CCCC3)/N(C3=CC=CC=C3)=C\2)C(C(C)(C)C)=C1 Chemical compound CC(C)(C)C1=CC2=C(O[V](Cl)(Cl)(O3CCCC3)(O3CCCC3)/N(C3=CC=CC=C3)=C\2)C(C(C)(C)C)=C1 FENRYBRSJXUNBC-SXUBXDNWSA-K 0.000 description 2
- ZMANZCXQSJIPKH-UHFFFAOYSA-N Triethylamine Chemical compound CCN(CC)CC ZMANZCXQSJIPKH-UHFFFAOYSA-N 0.000 description 2
- 229910021549 Vanadium(II) chloride Inorganic materials 0.000 description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
- 239000000654 additive Substances 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 2
- 239000003921 oil Substances 0.000 description 2
- 230000000704 physical effect Effects 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- 238000000527 sonication Methods 0.000 description 2
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 2
- ITAKKORXEUJTBC-UHFFFAOYSA-L vanadium(ii) chloride Chemical compound Cl[V]Cl ITAKKORXEUJTBC-UHFFFAOYSA-L 0.000 description 2
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 1
- 239000004809 Teflon Substances 0.000 description 1
- 229920006362 Teflon® Polymers 0.000 description 1
- 229910003074 TiCl4 Inorganic materials 0.000 description 1
- 229910021551 Vanadium(III) chloride Inorganic materials 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- 229910021486 amorphous silicon dioxide Inorganic materials 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- OVHDZBAFUMEXCX-UHFFFAOYSA-N benzyl 4-methylbenzenesulfonate Chemical compound C1=CC(C)=CC=C1S(=O)(=O)OCC1=CC=CC=C1 OVHDZBAFUMEXCX-UHFFFAOYSA-N 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 238000013329 compounding Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 239000007970 homogeneous dispersion Substances 0.000 description 1
- DLINORNFHVEIFE-UHFFFAOYSA-N hydrogen peroxide;zinc Chemical compound [Zn].OO DLINORNFHVEIFE-UHFFFAOYSA-N 0.000 description 1
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 239000012968 metallocene catalyst Substances 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 238000006384 oligomerization reaction Methods 0.000 description 1
- 125000002524 organometallic group Chemical group 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920000098 polyolefin Polymers 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 239000011541 reaction mixture Substances 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 238000003980 solgel method Methods 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- XJDNKRIXUMDJCW-UHFFFAOYSA-J titanium tetrachloride Chemical compound Cl[Ti](Cl)(Cl)Cl XJDNKRIXUMDJCW-UHFFFAOYSA-J 0.000 description 1
- ZNOKGRXACCSDPY-UHFFFAOYSA-N tungsten(VI) oxide Inorganic materials O=[W](=O)=O ZNOKGRXACCSDPY-UHFFFAOYSA-N 0.000 description 1
- HQYCOEXWFMFWLR-UHFFFAOYSA-K vanadium(iii) chloride Chemical compound [Cl-].[Cl-].[Cl-].[V+3] HQYCOEXWFMFWLR-UHFFFAOYSA-K 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K9/00—Use of pretreated ingredients
- C08K9/02—Ingredients treated with inorganic substances
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F110/00—Homopolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
- C08F110/02—Ethene
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F2500/00—Characteristics or properties of obtained polyolefins; Use thereof
- C08F2500/01—High molecular weight, e.g. >800,000 Da.
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
- C08K3/20—Oxides; Hydroxides
- C08K3/22—Oxides; Hydroxides of metals
- C08K2003/2237—Oxides; Hydroxides of metals of titanium
- C08K2003/2241—Titanium dioxide
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
- C08K3/20—Oxides; Hydroxides
- C08K3/22—Oxides; Hydroxides of metals
- C08K2003/2258—Oxides; Hydroxides of metals of tungsten
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K2201/00—Specific properties of additives
- C08K2201/011—Nanostructured additives
Definitions
- the present invention relates to polymers, and particularly to a method to produce ultra-high molecular weight polyethylene (UHMWPE) using a tungsten-doped titania (TiO 2 /W) nanofiller.
- UHMWPE ultra-high molecular weight polyethylene
- TiO 2 /W tungsten-doped titania
- Ultra-high molecular weight polyethylene is an exceptional polymer with unique mechanical and physical properties such as chemical resistance, impact resistance, abrasion resistance, lubricity and thermal stability. These properties are directly related to the molecular and super molecular structure of the polyethylene polymer.
- Ultra-high molecular weight polyethylene is obtained by polymerizing ethylene at low pressure using Zeigler-Natta catalyst supported by fixing TiCl 4 or VOCl 3 onto amorphous SiO 2 . Recently methyl aluminum dichloride (MADC) was found to be a potential cocatalyst in the polymerization/oligomerization process.
- MADC methyl aluminum dichloride
- nanocomposites are of great interest in industry because they possess exceptional mechanical properties, flammability, gas barrier properties and thermal stability depending on their shape, loading, particles size, dispersion of the fillers and bonding.
- Polymer composites have been made by (a) solution mixing, (b) melt compounding and (3) in situ polymerization. Among these methods, in-situ polymerization is considered to be more promising since it leads to a homogeneous dispersion of filler in the polymer matrix.
- nanoparticle fillers have been developed and used as additives in polymer matrices.
- various inorganic nanoparticles have been used as nanofillers such as titanium dioxide (TiO 2 ), silicon dioxide (SiO 2 ), aluminum trioxide (Al 2 O 3 ) and zinc dioxide (ZrO 2 ) to improve polymer properties.
- TiO 2 titanium dioxide
- SiO 2 silicon dioxide
- Al 2 O 3 aluminum trioxide
- ZrO 2 zinc dioxide
- Polymer-based TiO 2 composites have been extensively studied in the literature to improve mechanical and thermal properties of the polymer. Although TiO 2 -filled polymers are known, the properties of such composite materials are fixed.
- Ultra-high molecular weight polyethylene UHMWPE
- TiO 2 /W tungsten doped titania nanofiller material
- the reactor is charged with a solvent (e.g., toluene) and heated to a temperature suitable for polymerization, e.g., about 30° C. Following heating, the ethylene monomer is fed into the reactor and allowed to saturate for at least 10 minutes and a methyl aluminum dichloride co-catalyst (MADC) is added to initiate polymerization of ethylene. Polymerization is quenched by adding methanol containing HCl, which is then washed and dried to yield UHMWPE incorporated with titania-tungsten nanofillers.
- a solvent e.g., toluene
- MADC methyl aluminum dichloride co-catalyst
- FIG. 1 shows the structural formula of the catalyst composed of vanadium (III) complex with bidentate salicylaldiminato ligands used in the method of making high-density polyethylene with titania-iron nanofillers.
- FIG. 2 is a graph illustrating the molecular weight distribution of the high-density polyethylene nanocomposites using gel permeation chromatography.
- a method to produce ultra-high molecular weight polyethylene with improved mechanical and thermal properties using metallocene catalyst with tungsten-doped titanium dioxide as nanofiller is disclosed.
- high-density polyethylene with titania-tungsten nanofillers permits control over and variation of the overall polymeric properties, such as molecular weight and the associated thermal properties.
- the molecular weight, the crystallinity and the melting temperature of high-density polyethylene are all increased, while the polydispersity index (PDI) is decreased.
- a polymerization catalyst is first prepared.
- the catalyst is a vanadium (III) complex bearing salicylaldiminato ligands of the general class [RN ⁇ CH(2,4-(Bu 2 C 6 H 12 O))]VCl 2 (THF) 2 , and more particularly, having the formula shown in FIG. 1 .
- the vanadium catalyst was synthesized by conventional methods, such as that taught in Wu, J.-Q., et al., “Synthesis, Structural Characterization, and Ethylene Polymerization Behavior of the Vanadium(III) Complexes Bearing Salicylaldiminato Ligands”, Organometallics, 2008, 27(15): p. 3840-3848 (in particular, the catalyst is designated catalyst 2a in the Wu article, shown in Scheme 1 at p. 3841), which is hereby incorporated by reference in its entirety.
- VCl 3 (THF) 3 (0.75 g) was dissolved in dried tetrahydrofuran (20 mL) and added slowly to a solution of salicylaldiminato ligand, [RN ⁇ CH(2,4- t Bu 2 C 6 H 12 O))]VCl 2 (THF) 2 , (0.40 g) in tetrahydrofuran (20 mL) to form a red mixture.
- This mixture was stirred for 10 min, after which Et 3 N (0.3 mL, 216 mg) was added and stirred for 4 hours at room temperature. Finally, the solution was concentrated to about 10 mL, and then the mixture was filtered to remove NH 4 Cl.
- undoped titania nanofillers were synthesized, in addition to nanofillers formed from titania doped with tungsten.
- undoped titania nanofillers were synthesized by a modified sol-gel process under constant sonication. Titanium (IV) alkoxide precursor (1 ml) in 5 ml ethanol was hydrolyzed in the presence of 1 ml of water at room temperature to form a white solution of hydrolyzed titania particles.
- tungsten (VI) oxide were dissolved in 25 ml of ethanol and then added to the hydrolyzed titania solution under constant sonication.
- the reaction mixture was sonicated for 30 minutes. After this duration, the precipitate was washed with ethanol many times to remove excess NO 3 ⁇ . The precipitate was dried overnight at 100° C. and then heated for 5 hours to convert the amorphous titania into the crystalline anatase form. Finally, the product was ground into a fine powder. The samples were denoted as TiO 2 /W for titania doped with tungsten. The average particle size of the nanofiller that was produced was 10 nm.
- Ethylene polymerization was conducted in a 250 mL round-bottom flask equipped with a magnetic stirrer. A portion of the catalyst (prepared in advance, as described above) and a required amount of the TiO 2 /W nanofiller were added to the flask, and the reactor was charged with toluene (80 mL). Then, the flask was immersed in oil bath and when reactor temperature was equilibrated with bath oil temperature (30° C.), nitrogen gas was removed by vacuum pump. Then ethylene was fed into the reactor. After 10 minutes of saturation of ethylene in toluene, polymerization was initiated with the introduction of 1 mL of the cocatalyst (MADC) into the reactor. Polymerization reaction was quenched by adding 250 mL of methanol containing HCl (5 vol. %). Finally, the polymer was washed with an excess amount of methanol and dried inside an oven at 50° C. for 24 hours.
- MADC cocatalyst
- GPC Analysis Molecular weight of polyethylene composites was determined by Triple Detection High Temperature Gel Permeation Chromatography (GPC) using 1,2,4-trichlorobenzene as a solvent. 25 mg of the material was placed into a 40 mL glass vial and accurately weighed and 10 mL of the solvent was added using a clean 10 mL glass pipette. The vial was capped with a Teflon coated cap and the samples were placed into the Vortex Auto Sampler and left to dissolve for 3hrs at 160° C. while stirring gently.
- GPC Triple Detection High Temperature Gel Permeation Chromatography
- DSC Analysis Crystallinity of ethylene, ethylene nano-composites (Xc %) and melting temperature (T m ) were measured by differential scanning calorimetry (DSC) from TA instruments Q1000. Heating and cooling for both first and second cycles were done in nitrogen atmosphere at the rate of 10° C. min ⁇ 1 from a temperature of 30° C. to 160° C.
- the molecular weight (Mw) of the polyethylene was found to increase by adding TiO 2 /W filler with vanadium complex during polymerization.
- the optimum value for the filler was 10 mg (Entry 2, Table 1) which molecular weight (Mw) was 1.2 ⁇ 10 6 (g mol ⁇ 1 ).
- An increase in the filler concentration 15 mg resulted in a decrease in the molecular weight (Mw) when compared to the 10 mg of filler concentration but still showed a significant increase compared to the control.
- Polydispersity index (PDI) was decreased by adding TiO 2 /W nanofiller and decreased with increasing the amount of the TiO 2 /W nanofiller as shown in Table 1. This decrease in PDI improved the thermal properties of polyethylene nano-composites.
- FIG. 2 illustrates the molecular weight distribution of the polyethylene nanocomposites using gel permeation chromatography.
- the thermal characteristics of the polyethylene nanocomposites were determined by differential scanning calorimetry (DSC).
- the melting temperatures of polyethylene and polyethylene nanocomposites samples were determined by DSC from the second heating cycle.
- the results of the in situ polymerization using vanadium complex catalyst of FIG. 1 and MADC co-catalyst system at 1.3 bar and the resulting polymer nanocomposite characteristics of the UHMWPE are summarized in Table 1.
- the polyethylene nanocomposites showed that the melting temperature (T m ) was slightly higher (Entry 2 and 3, Table 1) than that of the control (Entry 1, Table 1) due to the presence of the nanofiller and the increase in the molecular weight of polyethylene nanocomposites.
Abstract
Description
- 1. Field of the Invention
- The present invention relates to polymers, and particularly to a method to produce ultra-high molecular weight polyethylene (UHMWPE) using a tungsten-doped titania (TiO2/W) nanofiller.
- 2. Description of the Related Art
- Ultra-high molecular weight polyethylene (UHMWPE) is an exceptional polymer with unique mechanical and physical properties such as chemical resistance, impact resistance, abrasion resistance, lubricity and thermal stability. These properties are directly related to the molecular and super molecular structure of the polyethylene polymer. Ultra-high molecular weight polyethylene is obtained by polymerizing ethylene at low pressure using Zeigler-Natta catalyst supported by fixing TiCl4 or VOCl3 onto amorphous SiO2. Recently methyl aluminum dichloride (MADC) was found to be a potential cocatalyst in the polymerization/oligomerization process.
- It is common in the plastics industry to blend various additives with a matrix polymer for the purpose of improving one or more polymer physical properties. Such compositions that contain nanofillers dispersed in a polymer matrix are referred to as nanocomposites. Polyolefin nanocomposites are of great interest in industry because they possess exceptional mechanical properties, flammability, gas barrier properties and thermal stability depending on their shape, loading, particles size, dispersion of the fillers and bonding. Polymer composites have been made by (a) solution mixing, (b) melt compounding and (3) in situ polymerization. Among these methods, in-situ polymerization is considered to be more promising since it leads to a homogeneous dispersion of filler in the polymer matrix.
- In recent years, highly effective nanoparticle fillers have been developed and used as additives in polymer matrices. For example, various inorganic nanoparticles have been used as nanofillers such as titanium dioxide (TiO2), silicon dioxide (SiO2), aluminum trioxide (Al2O3) and zinc dioxide (ZrO2) to improve polymer properties. Polymer-based TiO2 composites have been extensively studied in the literature to improve mechanical and thermal properties of the polymer. Although TiO2-filled polymers are known, the properties of such composite materials are fixed.
- It would be desirable to provide a method for producing ultra-high molecular weight polyethylene (UHMWPE) with tungsten doped titania nanofiller material (TiO2/W) that permits control over and variation of the overall polymeric properties, such as molecular weight and the associated thermal properties.
- Thus, a method to produce ultra-high molecular weight polyethylene solving the aforementioned problems is desired.
- The invention provides a method for polymerizing ethylene monomer to produce ultra-high-molecular-weight polyethylene (UHMWPE) by incorporating tungsten (W) doped titania (TiO2/W) nanofiller during the ethylene polymerization process, which produces UHMWPE with improved thermal properties. Specifically, the process for producing the (UHMWPE) comprises contacting ethylene under polymerization conditions with a catalyst composition comprising a polymerization catalyst (vanadium (III) complex bearing bidentate salicylaldiminato ligands in the presence of TiO2/W nanofiller and a co-catalyst in a reactor. The reactor is charged with a solvent (e.g., toluene) and heated to a temperature suitable for polymerization, e.g., about 30° C. Following heating, the ethylene monomer is fed into the reactor and allowed to saturate for at least 10 minutes and a methyl aluminum dichloride co-catalyst (MADC) is added to initiate polymerization of ethylene. Polymerization is quenched by adding methanol containing HCl, which is then washed and dried to yield UHMWPE incorporated with titania-tungsten nanofillers.
- These and other features of the present invention will become readily apparent upon further review of the following specification and drawings.
-
FIG. 1 shows the structural formula of the catalyst composed of vanadium (III) complex with bidentate salicylaldiminato ligands used in the method of making high-density polyethylene with titania-iron nanofillers. -
FIG. 2 is a graph illustrating the molecular weight distribution of the high-density polyethylene nanocomposites using gel permeation chromatography. - Similar reference characters denote corresponding features consistently throughout the attached drawings.
- A method to produce ultra-high molecular weight polyethylene with improved mechanical and thermal properties using metallocene catalyst with tungsten-doped titanium dioxide as nanofiller is disclosed.
- The method of making high-density polyethylene (HDPE) with titania-tungsten nanofillers permits control over and variation of the overall polymeric properties, such as molecular weight and the associated thermal properties. As will be shown below, through the addition of TiO2/W nanofiller, the molecular weight, the crystallinity and the melting temperature of high-density polyethylene are all increased, while the polydispersity index (PDI) is decreased. In order to make the high-density polyethylene with titania-tungsten nanofillers, a polymerization catalyst is first prepared. The catalyst is a vanadium (III) complex bearing salicylaldiminato ligands of the general class [RN═CH(2,4-(Bu2C6H12O))]VCl2(THF)2, and more particularly, having the formula shown in
FIG. 1 . - The vanadium catalyst was synthesized by conventional methods, such as that taught in Wu, J.-Q., et al., “Synthesis, Structural Characterization, and Ethylene Polymerization Behavior of the Vanadium(III) Complexes Bearing Salicylaldiminato Ligands”, Organometallics, 2008, 27(15): p. 3840-3848 (in particular, the catalyst is designated catalyst 2a in the Wu article, shown in
Scheme 1 at p. 3841), which is hereby incorporated by reference in its entirety. In this procedure, VCl3(THF)3 (0.75 g) was dissolved in dried tetrahydrofuran (20 mL) and added slowly to a solution of salicylaldiminato ligand, [RN═CH(2,4-tBu2C6H12O))]VCl2(THF)2, (0.40 g) in tetrahydrofuran (20 mL) to form a red mixture. This mixture was stirred for 10 min, after which Et3N (0.3 mL, 216 mg) was added and stirred for 4 hours at room temperature. Finally, the solution was concentrated to about 10 mL, and then the mixture was filtered to remove NH4Cl. Red-black crystals formed by diffusion of n-hexane (20 mL) into the solution, thus producing the vanadium (III) complex bearing salicylaldiminato ligands shown inFIG. 1 that is used as the polymerization catalyst. - As a control, undoped titania nanofillers were synthesized, in addition to nanofillers formed from titania doped with tungsten. Basically, undoped titania nanofillers were synthesized by a modified sol-gel process under constant sonication. Titanium (IV) alkoxide precursor (1 ml) in 5 ml ethanol was hydrolyzed in the presence of 1 ml of water at room temperature to form a white solution of hydrolyzed titania particles. For titania nanofillers doped with tungsten, 1.2 g of tungsten (VI) oxide were dissolved in 25 ml of ethanol and then added to the hydrolyzed titania solution under constant sonication. The reaction mixture was sonicated for 30 minutes. After this duration, the precipitate was washed with ethanol many times to remove excess NO3 −. The precipitate was dried overnight at 100° C. and then heated for 5 hours to convert the amorphous titania into the crystalline anatase form. Finally, the product was ground into a fine powder. The samples were denoted as TiO2/W for titania doped with tungsten. The average particle size of the nanofiller that was produced was 10 nm.
- Ethylene polymerization was conducted in a 250 mL round-bottom flask equipped with a magnetic stirrer. A portion of the catalyst (prepared in advance, as described above) and a required amount of the TiO2/W nanofiller were added to the flask, and the reactor was charged with toluene (80 mL). Then, the flask was immersed in oil bath and when reactor temperature was equilibrated with bath oil temperature (30° C.), nitrogen gas was removed by vacuum pump. Then ethylene was fed into the reactor. After 10 minutes of saturation of ethylene in toluene, polymerization was initiated with the introduction of 1 mL of the cocatalyst (MADC) into the reactor. Polymerization reaction was quenched by adding 250 mL of methanol containing HCl (5 vol. %). Finally, the polymer was washed with an excess amount of methanol and dried inside an oven at 50° C. for 24 hours.
- GPC Analysis: Molecular weight of polyethylene composites was determined by Triple Detection High Temperature Gel Permeation Chromatography (GPC) using 1,2,4-trichlorobenzene as a solvent. 25 mg of the material was placed into a 40 mL glass vial and accurately weighed and 10 mL of the solvent was added using a clean 10 mL glass pipette. The vial was capped with a Teflon coated cap and the samples were placed into the Vortex Auto Sampler and left to dissolve for 3hrs at 160° C. while stirring gently.
- DSC Analysis: Crystallinity of ethylene, ethylene nano-composites (Xc %) and melting temperature (Tm) were measured by differential scanning calorimetry (DSC) from TA instruments Q1000. Heating and cooling for both first and second cycles were done in nitrogen atmosphere at the rate of 10° C. min−1 from a temperature of 30° C. to 160° C.
- As shown below in Table 1, the molecular weight (Mw) of the polyethylene was found to increase by adding TiO2/W filler with vanadium complex during polymerization. The optimum value for the filler was 10 mg (Entry 2, Table 1) which molecular weight (Mw) was 1.2×106 (g mol−1). An increase in the
filler concentration 15 mg resulted in a decrease in the molecular weight (Mw) when compared to the 10 mg of filler concentration but still showed a significant increase compared to the control. Polydispersity index (PDI) was decreased by adding TiO2/W nanofiller and decreased with increasing the amount of the TiO2/W nanofiller as shown in Table 1. This decrease in PDI improved the thermal properties of polyethylene nano-composites.FIG. 2 illustrates the molecular weight distribution of the polyethylene nanocomposites using gel permeation chromatography. - The thermal characteristics of the polyethylene nanocomposites were determined by differential scanning calorimetry (DSC). The melting temperatures of polyethylene and polyethylene nanocomposites samples were determined by DSC from the second heating cycle. The results of the in situ polymerization using vanadium complex catalyst of
FIG. 1 and MADC co-catalyst system at 1.3 bar and the resulting polymer nanocomposite characteristics of the UHMWPE are summarized in Table 1. -
TABLE 1 UHMWPE Properties as a Function of Nanofiller Content Mw % of TiO2/W (Daltons) Tm Crystallinity Entry No. (mg) ×10−4 PDI (° C.) (Xc) 1 0 19.5 3.7 135 50 2 5 86.2 2.5 136 52 3 10 120 2.1 137 51 4 15 78.6 2.6 135.5 49 - The polyethylene nanocomposites showed that the melting temperature (Tm) was slightly higher (Entry 2 and 3, Table 1) than that of the control (
Entry 1, Table 1) due to the presence of the nanofiller and the increase in the molecular weight of polyethylene nanocomposites. The percentage of crystallinity in polyethylene nanocomposites samples was determined and showed that the percentage of crystallinity in polyethylene nanocomposites increased slightly to 52% using 5 mg of TiO2/W (Entry 2, Table 1) as compared to the control (Xc=50%) (Entry 1, Table 1). When the amount of the filler increased, the crystallinity increased to 49%, using 15 mg of TiO2/W nanofiller with Tm =135.5° C. (Entry 4, Table 1). - The above-described process unexpectedly produces polyethylene nanocomposites (UHMWPE) with improved thermal properties and impact resistance.
- It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.
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