RU2624215C2 - Method of producing a reactor powder of super-high-molecular polyethylene - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: process is carried out by polymerizing ethylene in an aliphatic solvent medium using phenoxyimine titanium-halide complexes. The polymerization catalyst is introduced into the reaction medium in dry form together with the cocatalyst under conditions of increasing stirring speed.

EFFECT: production of polyethylene of reactor powder of ultrahigh molecular weight polyethylene with improved morphology that allows processing reactor powder into ultrahigh-modulus and ultrahigh-strength tapes and fibers by cold forming without solvents.

7 cl, 12 ex, 1 tbl

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 the environment of aliphatic solvents. 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 2552636, C08F 4/642, C08F 110/02, 06/10/2015] polymerization of ethylene in aromatic solvents using new post-metallocene catalyst systems, providing RP UHMWPE with improved morphology and the ability to process from the solid phase by cold forming without using solvents temperature below the melting temperature of UHMWPE, with the production of tapes and fibers with ultra-strong and ultra-modular properties. 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 in medical technology for medical requirements.

Close in technical essence of 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 mixtures of aliphatic solvents with toluene for polymerization, and the amount of toluene is not lower than 50% vol. As polymerization catalysts, a wide range of one-center catalysts (metallocene, postmetallocene) based on Ti, Zr, Hf and activators (various aluminoxanes, including their mixtures with aluminum alkyls, which are introduced into the reaction system as a solution). The catalyst is introduced as a pre-prepared solution. 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 MMv and MMη / MMv. The given polymerization conditions cannot be considered technological, because they significantly reduce productivity and make it not economical.

The invention solves the problem of expanding the assortment and optimizing the structure of catalytic systems based on phenoxyimine titanium halide complexes and clarifying the conditions that allow the polymerization of ethylene in an aliphatic solvent to obtain 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 .

The problem is solved by the method of producing a reactor powder of ultra-high molecular weight polyethylene RP UHMWPE by polymerizing ethylene in an aliphatic solvent using phenoxyimine titanium halide complexes of structures I, II, III, capable of solid-phase processing into products with superstrong and ultra-modular properties, while the catalyst is introduced into the reaction system in dry form together with cocatalyst under conditions of additional hydrodynamic effect on the reaction system (increase in the speed of mixing niva or ultrasonic exposure).

As catalysts, one of the three fluorine substituted phenoxyimine titanium halide complexes of the general structure is used:

The polymerization catalyst is introduced into the reaction medium in dry form at concentrations not higher than 0.5⋅10 ^-5 mol / L in the system, MAO methylaluminoxane is used as a cocatalyst at an MAO: Ti ratio of from 250: 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 30 minutes

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

MM of the resulting reactor powder is maintained in the range (3.0-6.0) × 10 ⁶ g / mol. RP UHMWPE has a bulk density of 0.044-0.08 g / cm ³ , the particle size of the resulting RP is in the range of 800-600 μm with a narrow distribution.

In the present invention, to obtain RP UHMWPE, catalytic systems based on fluorine substituted bis (phenoxyimine) 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 30 minutes.

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

As a co-catalyst, methylaluminoxane (MAO).

The synthesis of ligands of the bis (phenoxyimine) complex is carried out in the following way:

Ligands for I-III complexes

General methodology

A mixture of 1 mmol of the corresponding substituted salicylic aldehyde, 10 ml of toluene, 0.18 g (1 mmol) of pentafluoroaniline, 10 mg of p-toluenesulfonic acid and 0.27 g (2 mmol) of anhydrous CaSO ₄ was boiled under stirring under reflux for 20-30 h until the starting materials disappeared ( according to TLC). After distillation of the solvent, the residue was flash chromatographed using silica gel 5-40μ, eluent 1: 1 chloroform-hexane. The solvent was evaporated, solid residues were recrystallized from methanol.

2-2- (1-Phenylethyl) -6 - [(pentafluorophenylimino) methyl] phenol (for complex I).

Yield 93%, mp. 74-75 ° C. IR spectrum, ν, cm ^-1 : 1608 (CH = N). ¹ H NMR spectrum (CCl ₄ ), δ, ppm: 1.63 d (3H, CH ₃ , J 7.2 Hz), 4.70 k (1H, CH, J 7.2 Hz), 6.92 t (1H _arom. , J 8.0 Hz), 7.18-7.36 m (7Н _arom. ), 8.79 s (1Н, CH = N), 12.53 s (1Н, ОН). Found: [M] ⁺ 399.0989. C ₂₁ H ₁₄ F ₅ NO. Calculated: M 399.0990.

3-2- (1-Phenylethyl) -4-methyl-6 - [(pentafluorophenylimino) methyl] phenol (for complex II).

Yield 89%, mp. 103-104 ° C. IR spectrum, ν, cm ^-1: 1612 (CH = N). ¹ H NMR spectrum (CCl ₄ ), δ, ppm: 1.66 d (3H, CH ₃ , J 7.2 Hz), 2.32 s (3H, CH ₃ ), 4.71 k (1H, CH, J 7.2 Hz), 7.12 d (2H _arom. , J 8.0 Hz), 7.25-7.35 m (5H _arom. ), 8.78 s (1H, N = CH), 12.41 s (1H, OH). Found: [M] ⁺ 405.1160. C ₂₂ H ₁₆ F ₅ NO. Calculated: M 405.1146.

1-2- [1- (4-tert-Butylphenyl) ethyl] -6 - [(pentafluorophenylimino) methyl] phenol (for complex III).

Yield 95%, mp. 101-102 ° C. IR spectrum, ν, cm ^-1 : 1603 (N = CH). ¹ H NMR (CCl _4), δ, ppm .: 1.29 s [9H, C _{(CH3) 3],} 1.63 d (3H, _CH3, J 7.2 Hz), 4.69 for (1H, CH, J 7.2 Hz), 6.91 t (1H _arom. , J 8.0 Hz), 7.21-7.37 m (6H _arom. ), 8.79 s (1H, CH = N), 12.53 s (1H, OH). Found: [M] ⁺ M 447.1584. C ₂₅ H ₂₂ F ₅ NO. Calculated: M 447.1616.

Complexes (I-III).

General technique. A mixture of 1 mmol of the corresponding ligand, 40 ml of absolute methylene chloride, 1 mmol of TiCl ₂ (OPr-i) ₂ in the form of a solution (0.350 mmol / g) in absolute toluene was stirred under argon for 24 hours. The solvents from the resulting dark red solution were distilled off in vacuum of a water-jet pump, the residue was washed on the filter with hexane (2 × 2 ml), kept for 1 h in a vacuum of an oil pump at 100 ° С. The corresponding complexes of brilliant dark red-brown powder were obtained.

Bis {2- (1-phenylethyl) -6 - [(pentafluorophenylimino) methyl] phenoxy} titanium (IV) dichloride (complex I).

Yield 85%. % IR spectrum (KBr), ν, cm ^-1 : 1598 (CH = N), 540 (Ti-O), 455 (Ti-N). ¹ H NMR spectrum, CDCl ₃ , δ, ppm: 1.57-1.69 m (6H, 2CH ₃ ), 4.69-4.75 m (2H, 2CH), 7.07-7.46 m (16H _arom. ), 8.05-8.21 m (2H, 2CH = N). Found,%: C 57.13; H 3.02; Cl 7.93; N, 2.89. C ₄₂ H ₂₆ Cl ₂ F ₁₀ N ₂ O ₂ Ti Calculated,%: C 56.09; H 2.91; Cl 7.88; N 3.11.

Bis {2- (1-phenylethyl) -4-methyl-6 - [(pentafluorophenylimino) methyl] phenoxy} titanium (IV) dichloride (complex II).

Yield 95%. IR spectrum (KBr), ν, cm ^-1 : 1596 (CH = N), 551 (Ti-O), 449 (Ti-N). ¹ H NMR (CDCl _3), δ, ppm .: 1.57-1.68 m (6H, 2CH _3), 2.29-2.35 m (6H, 2CH _3), 4.65-4.80 m (2H, 2CH), 7.02- 7.48 m (14H _arom. ), 8.28-8.36 m (2H, 2CH = N). Found,%: C 57.15; H 3.40; Cl 7.58; N, 2.89. C ₄₄ H ₃₀ Cl ₂ F ₁₀ N ₂ O ₂ Ti. Calculated,%: C 56.98; H 3.28; Cl 7.65; N 3.02.

Bis {2- [1- (4-tert-butylphenyl) ethyl] -6 - [(pentafluorophenylimino) methyl] phenoxy} titanium (IV) dichloride (complex III).

Yield 96%. IR spectrum (KBr), ν, cm ^-1 : 1602 (CH = N), 562 (Ti-O), 450 (Ti-N). ¹ H NMR spectrum, CDCl ₃ , δ, ppm: 1.25-1.39 m [18Н, 2С (СН ₃ ) ₃ ], 1.56-1.70 m (6Н, 2СН ₃ ), 4.53-4.72 m (2Н, 2СН) ), 6.84-7.45 m (14Н _arom. ), 8.24-8.37 m (2Н, 2CH = N). Found,%: C 59.56; H 4.26; Cl 6.87; N, 2.71. C ₅₀ H ₄₂ Cl ₂ F ₁₀ N ₂ O ₂ Ti. Calculated,%: C 59.36; H 4.18; Cl 7.01; N, 2.77.

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 KBr pellet samples. 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.

Reactor UHMWPE powders compacted in the mold at room temperature _to a pressure P = 100 MPa for 30 min. The used scheme for the preparation of monolithic UHMWPE samples simulates the continuous process described in [9. Joo YK, Zhou N., 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 ° С. 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 ultra-thermostat to the reactor jacket. Before the start of the polymerization reactor was evacuated to a residual pressure 1⋅10 ^-1 mm Hg, at T = 150-170 ° C (heating using a heating mantle) over 1 hour, three times washing with dry argon. After the reactor is cooled to room temperature, 45 ml of heptane are loaded in syringes with argon counterflow using medical syringes (heptane is preliminarily dried with calcined aluminum oxide and purged with argon for 30 min), heating to 30 ° C and a stirrer with a rotation speed of 300 rpm and in dry form is introduced into the reactor, 0.33 ml of MAO (5,08⋅10 ^-4 mol), 2,03⋅10 ^-6 mol (0.000097 g Ti) complex I in dry form, MAO / Ti = 250/1 mol / the mole. Argon is blown off, ethylene is saturated twice; then ethylene is fed to a pressure of 0.25 MPa and the stirring speed is increased to 1300 rpm. The process is carried out no more than 30 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 2.53 g, MM, measured at 135 ° C in decalin in a Ubbelode viscometer, is 4.8 × 10 ⁶ dl / g. Catalyst activity = 205 kg _pe / g _Ti ⋅MPa⋅h. The multiplicity of drawing a transparent UHMWPE film was λo = 200, elastic modulus E = 123 GPa, tensile strength σ = 3.14 GPa, tensile elongation 3.2%, bulk density RP equal to 0.065 g / cm ³ , particle size 700 μm.

Examples 2-10

Similar by the method of example 1, subject to the conditions presented in the table

Example 11 (comparative)

Similar to example 2, but the ratio of MAO / Ti increased to 500: 1, which led to an increase in activity to 238 kg _pe / g _Ti ⋅ MPa⋅h. At the same time, the percentage of the optimal fraction (by bulk density) decreased to 45%, which indicates a violation of ordering in the process of crystallite formation with an increase in the polymerization rate.

Example 12 (comparative)

Similar to example 2, but the polymerization temperature was 40 ° C, which led to some decrease in the yield of PE to 2.506 g and an increase in MM to 6.5 610 ⁶ dl / g. At the same time, the percentage of the optimal fraction (by bulk density) decreased to 44%, which indicates a violation of ordering in the process of crystallite formation with increasing polymerization temperature.

The main results, which allow us to illustrate the conditions under which it is possible to obtain RP 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 (12)

1. A method of producing a reactor powder of ultra-high molecular weight polyethylene RP UHMWPE by polymerizing ethylene in an aliphatic solvent using phenoxyimine titanium halide complexes, characterized in that the polymerization catalyst is introduced into the reaction medium in dry form together with cocatalyst under conditions of increasing mixing speed. 2. The method according to claim 1, characterized in that as the catalysts use one of the three fluorine-substituted phenoxyimine titanium halide complexes of a general structure

where (I) R ¹ = ethyl phenyl, R ² = H; (II) R ¹ = ethyl phenyl, R ² = Me; (III) R ¹ = tert-butylethylphenyl, R ² = H at concentrations not higher than 0.5⋅10 ^-5 mol / L in the system, MAO methylaluminoxane is used as a cocatalyst at an MAO: Ti ratio of from 250: 1 to 500: 1. 3. The method according to claim 1, characterized in that during the polymerization the temperature is maintained in the range of 20-40 ° C and the ethylene pressure is not higher than 0.25 MPa. 4. The method according to claim 1, characterized in that the polymerization duration does not exceed 30 minutes 5. The method according to claim 1, characterized in that, for example, n-heptane, n-hexane, gasoline are used as aliphatic solvents. 6. The method according to claim 1, characterized in that the resulting reactor powder has a bulk density in the range of 0.044-0.08 g / cm ³ . 7. The method according to claim 1, characterized in that a reactor powder with a particle size <800 μm with a narrow size distribution is obtained.