RU2561921C1 - Method of producing reactor powder of ultrahigh molecular weight polyethylene by polymerisation of ethylene - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to synthesis of reactor powder of ultrahigh molecular weight polyethylene. Described is a method of polymerising ethylene in a medium of aliphatic solvents using a catalyst based on functionalised bis-phenoxy-imine complexes of titanium chloride, activated with methylaluminoxane MAO. The catalyst is prepared in advance in toluene solution. The catalyst system is loaded in toluene solution with two-step loading of a MAO co-catalyst. Half of the calculated amount of MAO is added first without a catalyst. A second portion of MAO is then added with a catalytic complex while stirring intensely. The speed of the mixer increased to 1300 rpm. The catalyst used is one of three functionalised phenoxy-imine titanium halide complexes of the general structure

, where (I) R¹=isopropylbenzyl, R²=H; (II) R¹=isopropylbenzyl, R²=Me; (III) R¹=t-Bu, R²=OCH₃.

EFFECT: obtaining reactor powder of ultrahigh molecular weight polyethylene with improved morphology, which enables to process the reactor powder into ultrahigh-modulus and ultrahigh-strength bands and fibres via solvent-free cold moulding.

8 cl, 1 tbl, 12 ex

Description

The invention relates to a technology for the synthesis of reactor powders of ultra-high molecular weight polyethylene RP UHMWPE with improved morphology using phenoxyimine catalytic systems in an aliphatic solvent environment, which makes it possible to process the resulting RP reactor powder by the solid-phase method into ribbons or fibers with superstrong and ultra-modular properties.

Known technologies for the synthesis of UHMWPE by ethylene polymerization using Ziegler catalytic systems [1. US 4,983,693, 1988; 2. RU. 2064936, 1993; 3. RU. 2,176,649,200; 4. RU. 2303608, 2006; 5. RU. 2346006, 2007; 6. RU. 2471552, 2011] in an aliphatic solvent environment. However, the multicenter nature of the used catalytic systems does not make it possible to obtain RP UHMWPE with the necessary morphology, which makes it possible to realize solid-phase processing of RP into high-strength and high-modulus products. Such UHMWPE can be processed into products with particularly strong and modular properties only from solution by gel-molding, which is distinguished by complex hardware design, low productivity and high cost.

A known method of obtaining RP UHMWPE [7. RU 2459835, C08F 4/642, C07F 7/28, C08F 110/02, 08/27/2012] polymerization of ethylene in aromatic solvents using new postmetallocene catalytic systems, providing RP UHMWPE with improved morphology and the ability to process from solid phase by cold molding at a temperature lower than the melting temperature of UHMWPE, without the use of solvents, into tapes and fibers with ultra-strong and ultra-modular characteristics. However, this method, due to the specificity of the catalyst system formulation, requires the use of aromatic solvents at the polymerization stage, which is currently unacceptable by environmental requirements.

Close in technical essence to the proposed solution is a method for producing UHMWPE, described in the application US [8. US 2013/0260624 A1, B29C 47/00, C08F 4/52, D01D 5/00 ,. 10/03/2013]. This application shows the possibility of using aliphatic solvents for the polymerization, and as a polymerization catalyst, a wide range of one-center catalysts (metallocene, postmetallocene) based on Ti, Zr, Hf and activators (various aluminoxanes, including their mixtures with aluminum alkyls). The necessity of limiting the polymerization conditions was emphasized - the temperature during polymerization is not higher than 25 ° C, the ethylene pressure is not higher than 0.11 MPa, the low concentration of the catalytic system (limitation of the polymerization rate), and additional restrictions on MMη and ММв and MMη / ММв. The given polymerization conditions cannot be considered technological, because they significantly reduce productivity, complicate the process and make it uneconomical.

The invention solves the problem of developing a fundamentally new method of ethylene polymerization in an aliphatic solvent with the production of RP UHMWPE with improved morphology and the possibility of solid-phase processing of the obtained RP UHMWPE into high-strength and high-modulus films and fibers.

To solve the problem, a method is proposed for producing reactor powder of ultra-high molecular weight polyethylene RP UHMWPE by ethylene polymerization in aliphatic solvents using a catalyst based on functionalized titanium chloride bisphenoxyimine complexes activated with MAO methylaluminoxane cocatalyst. The polymerization catalyst is prepared in advance in a toluene solution and the catalyst system is charged in a toluene solution with a two-stage loading of the MAO cocatalyst: half of the calculated amount of MAO is introduced at the beginning without a catalyst, the second part of the MAO with the catalytic complex is introduced with vigorous stirring, increasing the stirrer speed to a speed of 1300 rpm min As catalysts, one of the three functionalized phenoxyimine titanium halide complexes of a general structure is used.

at concentrations not higher than 2 · 10 ^-5 mol / l of toluene, MAO methylaluminoxane is used as a cocatalyst at an MAO: Ti ratio of from 400: 1 to 500: 1.

During the polymerization, the temperature is maintained in the range of 20-40 ° C and the ethylene pressure is 0.2 0.4 MPa.

The duration of polymerization does not exceed 60 minutes

As aliphatic solvents, for example, n heptane, hexane, gasoline are used.

The molecular weight MM of the resulting reactor powder is maintained in the range 2 · 10 ⁶ -4.5 · 10 ⁶ dl / g. RP UHMWPE has a bulk density of 0.044-0.08 g / cm ³ , particle size <800 μkm in an amount above 60%.

The transfer of polymerization from an aromatic medium to an aliphatic solvent while maintaining acceptable UHMWPE yields and maintaining optimal MM of the obtained UHMWPE and optimal properties (dispersion, bulk density) of RP is associated with the choice of catalytic systems and the conditions for their preparation and introduction into the polymerization system.

In the present invention, to obtain RP UHMWPE, catalytic systems based on functionalized bis (phenoxy-imine) complexes of the general structure with various substituents R ¹ and R ² , previously successfully used to obtain RP UHMWPE with improved morphology according to the patent [7] in toluene solution, are used.

The polymerization conditions allowing to obtain RP UHMWPE capable of solid-phase processing into heavy-duty and ultra-modular tapes and fibers are given below.

Polymerization of ethylene is carried out at ethylene pressures in the range of 0.2-0.4 MPa, a temperature of 20-40 ° C and a reaction time of up to 60 minutes.

As the solvent used, for example, heptane, hexane, gasoline.

As a co-catalyst, methylaluminoxane (MAO).

The catalyst system is prepared in a toluene solution and introduced into the reaction system with vigorous stirring in two stages.

The synthesis of ligands of the bis (phenoxy-imine) complex is carried out as follows.

Ligands for I-III complexes

General methodology

A mixture of 3 mmol of the starting aldehyde, 0.612 g (3.3 mmol) of n-allyloxyaniline hydrochloride, 0.333 g (3.3 mmol) of triethylamine, 10 ml of methanol is refluxed for 10-12 h until the starting materials disappear by thin-layer chromatography (TLC). Methanol was distilled off on a rotary evaporator, the residue was dissolved in 20 ml of CHCl ₃ , washed with 20 ml of H ₂ O. The organic layer was dried with MgSO ₄ . Chloroform is distilled off, the residue is flash chromatographed, eluent is CHCl ₃ : 1: 2 hexane, and the first bright yellow fraction is taken. The solvents are distilled off, the residue is triturated with 5 ml of methanol, the precipitate is filtered off, washed with 3 ml of methanol, the bright yellow crystals are dried in a vacuum desiccator.

2 - [(4-allyloxyphenylimino) methyl] -6-cumylphenol (for complex I).

Yield 96%. T. pl. 48 ° C. IR spectrum (KBr), ν (C = N), cm ^-1 : 1615. ¹ H NMR spectrum (CDCl ₃ ), δ, ppm: 1.76 s (6Н, 2СН ₃ ), 4.52 dt (2Н) , OS H ₂ -CH = CH ₂ , J 5.0, 1.4 Hz), 5.28 dc (1H, OCH ₂ -CH = C H ₂ , J 10.0, 1.4 Hz), 5.40 dc (1H, OCH ₂ - CH-C H ₂ , J 17.0, 1.4 Hz), 5.94-6.15 m (1Н, ОCH ₂ -С H = СН ₂ ), 6.96 d (2Н _arom. , J 9.0 Hz), 7.03 t (1Н _arom. , J 8.0 Hz), 7.21 d (2H _arom. , J 9.0 Hz), 7.25-7.41 m (6H _arom. ), 7.64 d (N _arom. , J 8.0 Hz), 8.54 s (1H, CH = N), 14.00 s (1H, OH). Found: [Μ] ⁺ 371.1878. C ₂₅ H ₂₅ NO ₂ . Calculated: M 371.1880.

2 - [(4-allyloxyphenylimino) methyl] -6-cumyl-4-methylphenol (for complex II).

Yield 92%. T. pl. 134 ° C. IR spectrum (KBr), ν (C = N), cm ^-1 : 1619. ¹ H NMR spectrum (CDCl ₃ ), δ, ppm: 1.78 s (6H, 2CH ₃ ), 2.40 s (3H, CH ₃ ), 4.54 dt (2H, OS H ₂ -CH = CH ₂ , J 5.0, 1.4 Hz), 5.31 dc (1H, OSH ₂ -CH = C H ₂ , J 10.0, 1.4 Hz), 5.43 d.c. (1H, OCH ₂ -CH = С Н ₂ , J ₁ 17.0, J ₂ 1.4), 6.02-6.11 m (1Н, OCH ₂ -C H = CH ₂ ), 6.91 d (2Н _arom. , J 8.5 Hz), 7.09 s (2H _arom. ), 7.16 s (2H _arom. , J 8.5 Hz), 7.38 s (2H _arom. ,), 8.51 s (1H, CH = N), 13.30 s (1H, OH). Found: [M] ⁺ 385.2046. C ₂₆ H ₂₇ NO ₂ . Calculated: Μ 385.2036.

2 - [(4-allyloxyphenylimino) methyl] -6-tert-butyl-4-methoxyphenol (for complex III).

Yield 98%. T. pl. 60 ° C. IR spectrum (KBr), ν (C = N), cm ^-1 : 1607. ¹ H NMR spectrum (CDCl ₃ ), δ, ppm: 1.46 s (9H, C (CH ₃ ) ₃ ), 3.78 s (3H, OCH ₃ ), 4.54 dt (2H, OS H ₂ -CH = CH ₂ , J 5.3, 1.4 Hz), 5.29 d.k (1H, OCH ₂ -CH = C H ₂ , J 10.5, 1.4 Hz), 5.41 dc (1H, OCH ₂ -CH = C H ₂ , J 17.5, 1.4 Hz), 5.99-6.09 m (1H, OCH _2- C H = CH ₂ ), 6.67 d (1H _arom. , J 2.9 Hz), 6.92 d (1 H _arom , J 8.8 Hz), 6.99 d (1 H _arom , J 2.9 Hz), 7.23 d (1 H _arom , J 8.8 Hz), 8.54 s (1 H, CH = N) 13.57 s (1H, OH). Found: [M] ⁺ 339.1824. C ₂₁ H ₂₅ NO ₃ . Calculated: M 339.1829.

Complexes (I-III).

General technique. A mixture of 2.3 mmol of the corresponding ligands, 10 ml of absolute methylene chloride, 4.25 g of a toluene solution containing 0.273 g (1.15 mmol) of TiCl ₂ (O ⁱ Pr) _{2 was} stirred at room temperature under argon for 24 hours. The solvent was distilled off from the resulting dark red solution in a vacuum of a water-jet pump, the residue was washed on the filter with hexane (2 × 2 ml), dried in a vacuum of an oil pump at 95 ° C for 1 h. The corresponding complexes were obtained in the form of a brilliant dark red-brown powder.

Bis {2 - [(4-allyloxyphenylimino) methyl] -6-cumylphenoxy} titanium (IV) dichloride (complex I).

Yield 87%. IR spectrum (KBr), ν, cm ^-1 : 437 (Ti-N), 524 (Ti-O), 1610 (C = N). Found,%: C 69.07; H 5.80; Cl 8.20; N 3.12. C ₅₀ H ₄₈ Cl ₂ N ₂ O ₄ Ti. Calculated,%: C 69.85; H 5.63; Cl 8.25; N 3.26.

Bis {2 - [(4-allyloxyphenylimino) methyl] -6-cumyl-4-methyl-phenoxy-si} titanium (IV) dichloride (complex II).

Yield 92%. IR spectrum (KBr), ν, cm ^-1 : 451 (Ti-N), 565 (Ti-O), 1607 (C = N). Found,%: C 70.25; H 5.94; Cl 8.24; N 3.15. C ₅₂ H ₅₂ Cl ₂ N ₂ O ₄ Ti. Calculated,%: C 70.35; H 5.86; Cl 8.00; N 3.16.

Bis {2 - [(4-allyloxyphenylimino) methyl] -6-tert-butyl-4-methoxy-phenoxy} titanium (IV) dichloride (complex III).

Yield 93%. IR spectrum (KBr), ν, cm ^-1 : 442 (Ti-N), 576 (Ti-O), 1608 (C = N). Found,%: C 63.30; H 6.30; Cl 8.50; N, 3.49. C ₄₂ H ₄₈ Cl ₂ N ₂ O ₆ Ti. Calculated,%: C 63.40; H 6.08; Cl 8.91; N, 3.52.

¹ H NMR spectra of the complexes were recorded on a Bruker AV-400 instrument with an operating frequency of 400.13 MHz. IR spectra were recorded on a Vector 22 spectrometer for samples in KBr tablets. The reaction progress and the purity of the synthesized compounds were monitored by TLC on Silufol UV-254 plates, chloroform was used as an eluent. Elemental analysis was performed on a Euro EA 3000 CHNS analyzer. The gross formulas of the obtained compounds were calculated from high resolution mass spectra recorded on a DFS Thermo Electron Corporation spectrometer. Melting points were determined on a Mettler Toledo FP90 instrument in a capillary when heated at a rate of 1 deg / min.

UHMWPE reactor powders were compacted in a mold at room temperature, pressure Р _к = 100 MPa for 30 minutes. The used scheme for the preparation of monolithic UHMWPE samples simulates the continuous process described in [9. Joo Y.K., Zhou H., Lee S.-G., Lee H.-K., Song J.-K., Journ. Applied Polym. Sci. 2005. V. 98. p. 718]. The uniaxial orientation hood of monolithic samples of RP UHMWPE in the form of double-sided blades with a working part size of 3.45 × 10 mm ² was carried out in a thermostat in a silicone oil medium in the temperature range 130-136 ° C. The values of the elastic modulus E, tensile strength σ and tensile elongation ε were measured under uniaxial tension of samples with a working part length of 100 mm on a Shimadzu AGS-10 universal testing machine. Tests of the samples were carried out in air at room temperature and a moving clamp moving speed of 2 mm / min. For each type of initial RP, measurements of the mechanical characteristics were performed for at least 8 samples, after which the obtained values of the characteristics were averaged.

The invention is illustrated by the following examples and table.

The examples summarize the conditions for the preparation and conduct of polymerization and its termination, isolation and washing of the obtained RP UHMWPE. The properties of the obtained UHMWPE RP (dispersion, bulk density, MM characteristics and strength and modular properties) are determined by standard methods.

Example 1

Ethylene is polymerized in a steel reactor with a capacity of 150 ml (in the case of developments for the study of strength and modular properties, a 1.5 liter reactor was used) equipped with a removable jacket and a propeller stirrer with a magnetic drive. The pressure in the reactors is maintained automatically, and the temperature is controlled by supplying water of the appropriate temperature from the ultrathermostat to the reactor jacket. Before starting the polymerization, the reactor is vacuumized to a residual pressure of 1 · 10 ^-1 mm Hg, at T = 150-170 ° C (heating with a mantle heater) for 1 h with three times washing with dry argon. After the reactor is cooled to room temperature, 45 ml of heptane are loaded into the syringe with argon counterflow using medical syringes (heptane is pre-dried with calcined alumina and purged with argon for 30 minutes), heating to 40 ° C and a stirrer with a rotation speed of 300 rpm and injected into the reactor 0.12 ml of MAO (1.75 · 10 ^-4 mol). After 3 minutes, a mixture of 5 ml of a solution of 5 ml of a solution of bis {{- - ((4-allyloxyphenylimino) methyl] -6-cumyl-phenyloxy} titanium (IV) dichloride (0.7 · 10 ^{- 6} mol) in toluene with 0.12 ml of MAO (1.75 · 10 ^-4 mol). Argon is blown off, ethylene is saturated twice; then ethylene is fed to a pressure of 0.2 MPa and the stirring speed is increased to 1300 rpm. The process is carried out no more than 60 minutes The polymerization is stopped by adding 2% Hcl in isopropanol to the reactor. The resulting suspension is filtered on a Buchner funnel, washed from Hcl with a mixture of water and alcohol (until there is no acid on litmus paper). Dry the polymer in vacuo at 60 ° C until constant weight.

The yield of PE 3.038 g, MM, measured at 135 ° C in decalin in a Ubbelode viscometer is 4.0 · 10 ⁶ dl / g. Activity = 460 gk _PE / g _Ti · MPa · h. The multiplicity of drawing a transparent UHMWPE film is λo = 230, elastic modulus E = 144 GPa, tensile strength σ = 2.4 GPa, tensile elongation of 2.15%, bulk density of RP is 0.065 g / cm ³ .

Examples 2-8

Similar by the method of example 1, subject to the conditions presented in the table; the exception is Example 4, where MAO and complex I are charged separately to the reactor.

Example 9 (comparative)

Similar to example 2, but the polymerization temperature was 60 ° C, which led to a decrease in the yield of PE to 2.642 g and an increase in MM to 5.1 · 10 ⁶ dl / g. At the same time, the percentage of the optimal fraction (by bulk density) decreased to 50%, which indicates a violation of ordering in the process of crystallite formation with increasing polymerization temperature.

Example 10 (comparative)

The polymerization is carried out in a solution of an aromatic solvent - toluene. The loading of the reaction components is similar to Example 1. The output of UHMWPE = 3.478 g, the activity of 527 kg _PE / g _Ti · MPa · h, the exception is lower values of MM = 2.7 · 10 ⁶ dl / g, the required fraction in bulk density up to 67% .

Example 11 (comparative)

The polymerization is carried out analogously to example 1, but the ethylene pressure is 0.4 MPa. The results: yield PE = 6.455 g, activity 490 kg _PE / g _Ti · MPa · h, bulk density = 0.15 g / cm ³ , fraction <800 = 77%, i.e. with increasing ethylene pressure, the bulk density sharply increases, which impairs the ability of RP to be processed by cold forming into ribbons and fibers.

Example 12 (comparative)

Ethylene polymerization is carried out in 150 ml steel autoclaves equipped with a removable jacket and magnetically driven propeller stirrers. The pressure in the reactors is maintained automatically, and the temperature is controlled by supplying water of the appropriate temperature from the ultrathermostat to the reactor jacket. Before the polymerization begins, the reactor is vacuumized to a residual pressure of 1 · 10 ^-1 mm Hg, at T = 150-170 ° C for 1 h with three times washing with dry argon. After the reactor is cooled, V = 150 ml to room temperature, the loading is carried out in the following order through a loading nozzle in countercurrent with argon: 44.75 ml of heptane are loaded with medical syringes, heating is included at 40 ° C, 0.25 ml of MAO (3.8 · 10 ^-4 mol), 7 6 · 10 ^-7 mol (0.000036 g Ti) of complex I, MAO / Ti = 500/1 mol / mol. The complex is washed with 5 ml of toluene in a stream of argon in a reactor, stirring is started at 1300 rpm, argon is blown off, and ethylene is saturated twice at 0.3 MPa; then ethylene is fed up to 0.4 MPa. The process is completed after 60 minutes by adding 2% HCl in isopropanol to the reaction mixture. The resulting suspension is filtered on a Buchner funnel, washed from HCl with a mixture of water and alcohol (until there is no acid on litmus paper). Dry the polymer in vacuo at 60 ° C.

The yield of PE is 2.307 g; MM, measured at 135 ° C in decalin in a Ubbelode viscometer, is 5.5 · 10 ⁶ dl / g. Activity = 160 kg _PE / g _Ti · MPa · h.

When a dry catalyst is introduced into heptane instead of a catalyst solution, without preliminary dissolving the catalyst in toluene, the yield of the prepared RP of UHMWPE decreases. Residues of the unworked catalyst in the form of orange colored inclusions are included in the resulting RP, which indicates the insufficient solubility of the complex in an aliphatic solvent, which leads to a sharp decrease in its activity.

The main results, which allow us to illustrate the conditions under which it is possible to obtain RPM UHMWPE with improved morphology and the ability to solid-phase processing of RP into tapes and fibers with ultra-modular and ultra-strong properties, are summarized in the table.

Claims (8)

1. A method of producing a reactor powder of ultra-high molecular weight polyethylene RP UHMWPE by ethylene polymerization in aliphatic solvents using a catalyst based on functionalized bisphenoxyimine titanium chloride complexes activated with MAO methylaluminoxane cocatalyst, characterized in that the polymerization catalyst is prepared in advance in a toluene solution and the catalyst system is charged toluene with a two-stage loading of MAO cocatalyst: half the estimated amount of MA administered initially without catalyst, a second part with a MAO catalyst complex introduced with vigorous stirring and the stirrer speed increased to 1300 rev / min. 2. The method according to p. 1, characterized in that as the catalysts use one of the three functionalized phenoxyimine titanium halide complexes of the General structure

at concentrations not higher than 2 · 10 ^-5 mol / l of toluene, MAO methylaluminoxane is used as a cocatalyst at an MAO: Ti ratio of from 400: 1 to 500: 1. 3. The method according to p. 1, characterized in that during the polymerization withstand the temperature regime in the range of 20-40 ° C and ethylene pressure of 0.2-0.4 MPa. 4. The method according to p. 1, characterized in that the polymerization duration does not exceed 60 minutes 5. The method according to p. 1, characterized in that as aliphatic solvents use, for example, n heptane, hexane, gasoline. 6. The method according to p. 1, characterized in that the molecular weight of the obtained RP UHMWPE is kept within 2 · 10 ⁶ -4,5 · 10 ⁶ dl / g 7. The method according to p. 1, characterized in that the resulting reactor powder has a bulk density in the range of 0.044-0.08 g / cm ³ . 8. The method according to p. 1, characterized in that the resulting reactor powder has a yield of more than 60% at a size of <800 μkm.