A process for the preparation of an olefin block copolymer

Abstract

The application discloses a preparation method of an olefin block copolymer and belongs to the field of olefin polymerization. The application adopts a reactive very cold comonomer in a solution polymerization process to prepare the olefin block copolymer, specifically introducing a polymerization reaction medium, an olefin monomer, a reactive very cold comonomer, a catalyst and a cocatalyst into a reactor to perform a polymerization reaction, wherein when the reactive very cold comonomer is introduced into the reactor, the volume fraction of the comonomer micro-bubbles and / or the very cold comonomer solution accounts for 50% to 99.9% of the reactor, and the introduction mode can adopt a micro-bubble generator or a multi-point liquid phase spraying, so that the olefin block copolymer can be efficiently prepared. The method is simple in process, and different property characteristics of the olefin block copolymer can be prepared by controlling the introduction frequency, the introduction temperature, the introduction mode and the introduction amount of the reactive very cold comonomer.

Description

Technical Field

[0001] This invention belongs to the field of olefin polymerization process and polymer material technology. Specifically, this invention relates to a method for preparing olefin block copolymers. More specifically, this invention relates to a method for efficiently preparing olefin block copolymers in a single reactor using reactive ultracold comonomers in a solution polymerization process. Background Technology

[0002] Olefin block copolymers (OBCs) and polyolefin elastomers (POEs) both use ethylene and α-olefins as raw materials, but OBCs exhibit a distinct multi-block structure with alternating soft and hard segments, demonstrating thermal stability and superior mechanical properties unmatched by traditional random copolymers. In the paper "Catalytic production of olefin block copolymers via chain shuttling polymerization," Dow Chemical developed a "chain shuttle" polymerization technology using a tridentate pyridine-amino-hafnium catalyst and solution polymerization process, combined with Mitsui Chemicals' FI-Zr catalyst and chain shuttle agent (CSA). This technology, combined with high-throughput screening, enables the industrial-scale production of a novel polyolefin elastomer material, olefin block copolymer (OBC), using a high-temperature solution process in a single reactor. By changing the concentration of CSA, the block length and number of OBCs can be controlled, resulting in elastomers with varying structures and properties. However, the chain shuttle technology employed by Dow has extremely high technical barriers; it is difficult to prepare polyolefin materials with high strength, high toughness, and high hardness simultaneously using a single catalyst. In their paper, "Preparation of ultrahigh molecular weight ethylene / 1-octene block copolymers using ethylene pressure pulse feeding policies," Zhu et al. employed an ethylene pressure pulse feeding strategy (simulating a two- or three-reactor series process). Utilizing the difference in the reactivity ratios of ethylene and 1-octene under different polymerization pressures using the FI catalyst, they prepared diblock and triblock olefin copolymers. The hard blocks exhibited good crystallinity, while the soft blocks demonstrated good low-temperature flexibility, making the block copolymers highly promising for applications in the thermoplastic elastomer field. However, the polymerization conditions of the FI catalyst in this study were stringent, and it could only produce diblock and triblock copolymers, limiting the number of block structures and the improvement of performance.

[0003] Existing high-temperature solution polymerization processes, through macroscopic optimization of the polymerization process and adjustment of the polymerization rates of ethylene and comonomers in two / multi-reactor systems, can only produce POE materials with a mixture of two different chain segment structures or bi / triblock elastomer materials. They cannot produce multi-block polyolefin elastomers. Their single-chain structure is significantly different from the single-chain multi-block structure of OBC, and their performance is far inferior to that of OBC materials. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention aims to provide a method for preparing olefin block copolymers. This method utilizes reactive cryogenic comonomers in a solution polymerization process to prepare olefin block copolymers, and prepares olefin block copolymers with different physical properties by controlling the introduction frequency, introduction temperature, introduction method, and introduction amount of reactive cryogenic comonomers.

[0005] According to one aspect of the present invention, the present invention provides a method for preparing olefin multiblock copolymers (OBCs) using reactive ultracold comonomers.

[0006] In the method of this invention, a polymerization reaction medium, an olefin monomer, a reactive cryogenic comonomer, a catalyst, and a cocatalyst are introduced into a reactor to carry out a polymerization reaction. The olefin monomer is ethylene. The reactive cryogenic comonomer is introduced by microbubble and / or multi-point liquid phase injection. The reactive cryogenic comonomer is selected from one or more of propylene, 1-butene, 2-butene, and 1-pentene. When microbubble is used for introduction, the introduction temperature should not be higher than 10°C above the boiling point of the comonomer and not lower than -30°C to ensure that the comonomer has good dispersibility and reactivity in the microbubble state. When multi-point liquid phase injection is used for introduction, the introduction temperature should not be higher than the boiling point of the comonomer, and preferably lower than the boiling point by 5 to 30°C, to maintain its liquid injection state and avoid gas phase flash evaporation.

[0007] According to a preferred embodiment of the present invention, during the preparation process, by controlling the frequency, temperature, method and amount of introduction of reactive ultracold comonomers, olefin block copolymers with different hard-to-soft-segment ratios can be obtained.

[0008] In a preferred embodiment of the present invention, when the reactive ultracold comonomer is introduced into the reactor, the volume fraction of the comonomer microbubbles and / or ultracold comonomer solution accounts for 50% to 99.9% of the reactor.

[0009] In a preferred embodiment of the present invention, when the reactive ultracold comonomer is not introduced into the reactor, the volume fraction of the comonomer microbubbles and / or ultracold comonomer solution accounts for 0.1% to 20% of the reactor.

[0010] In a preferred embodiment of the present invention, the frequency of introduction of the reactive cold comonomer is in the range of 0.0001 to 0.1 Hz.

[0011] According to some embodiments of the present invention, the reactive ultracold comonomer may be introduced by microbubbles alone, or by multi-point liquid phase injection alone, or by a combination of microbubbles and multi-point liquid phase injection.

[0012] In a preferred embodiment of the present invention, when multi-point liquid phase injection is used for introduction, the introduction temperature is preferably 5-30°C below the boiling point; the introduction position is located at a height of 10%-90% below the liquid surface, and the number of introduction positions is one or more.

[0013] In a preferred embodiment of the present invention, when microbubbles are introduced, the microbubble generator used is selected from one or more of an ultrasonic generator, a venturi tube, and an aeration head.

[0014] When multi-point liquid phase injection is used for introduction, the injection device is selected from one or more of the following: Venturi injector, static mixing nozzle, and ultrasonic atomizing nozzle, and the generated microbubble diameter is 10. -6 -10 -2 m.

[0015] In a preferred embodiment of the present invention, the microporous material of the microbubble generator is preferably one or more of the following: ceramic membrane, SPG membrane, sintered metal porous medium, polycarbonate membrane, and polystyrene membrane, and the porosity of the microporous material is 8% to 85%. The microbubbles generated by the microbubble generator have a diameter of 10 mm. -6 -10 -2 m.

[0016] When microbubble is introduced using a multi-point liquid phase injection method, it can be achieved by simultaneously arranging the aforementioned microbubble generator and injection device within the same reactor, or by using a microbubble and multi-point liquid phase injection synergistic introduction system. Optionally, the synergistic introduction system consists of several coaxial composite injection heads, with an outer layer being a Venturi-type liquid phase injection channel and an inner layer being a microbubble generation channel; when there are multiple coaxial composite injection heads, the composite injection heads are symmetrically distributed in the high-shear region below the agitator blades of the reactor. Optionally, the synergistic introduction system can also consist of staggered atomizing nozzles (as injection devices) and ceramic aerator heads (as microbubble generators).

[0017] In a preferred embodiment of the present invention, when a reactive ultracold comonomer is introduced, the instantaneous concentration of the comonomer is increased by 50% to 1000% compared with the concentration when no reactive ultracold comonomer is introduced.

[0018] In a preferred embodiment of the present invention, the polymerization reactor is a slurry stirred reactor or a slurry loop reactor.

[0019] In a preferred embodiment of the present invention, the polymerization reaction temperature is 50 ℃ to 230 ℃, and the polymerization reaction pressure is 0.1 MPa to 20 MPa.

[0020] In a preferred embodiment of the present invention, the temperature difference between the temperature when the reactive ultracold comonomer is introduced and the temperature when the reactive ultracold comonomer is not introduced is 20 °C to 100 °C.

[0021] In a preferred embodiment of the present invention, the reactive cold comonomer is preferably one or more of propylene and 1-butene.

[0022] In a preferred embodiment of the present invention, the polymerization reaction medium is selected from one or more of toluene, ethylbenzene, benzene, n-butane, n-pentane, isopentane, cyclopentane, n-hexane, 2-methylpentane, 3-methylpentane, cyclohexane, n-heptane, methylcyclohexane, 2-methylhexane, 3-methylhexane, and 3-ethylpentane, preferably n-hexane and methylcyclohexane.

[0023] In a preferred embodiment of the present invention, the catalyst is selected from one or more of non-bridged metallocene catalysts, bridged metallocene catalysts, and restricted geometry CGC catalysts.

[0024] In a preferred embodiment of the present invention, the co-catalyst is selected from one or more of methylaluminoxane, modified methylaluminoxane, tripentafluorophenylborane, trimethylaluminum, triethylaluminum, triisobutylaluminum, trihexylaluminum, and trioctylaluminum.

[0025] According to another aspect of the present invention, an olefin block copolymer prepared according to the above method is also provided. Its melting point is between 110 °C and 125 °C, and its density is 0.900 g / cm³. 3 ~0.915 g / cm 3 The melt index is between 0.1 g / 10 min and 2.0 g / 10 min.

[0026] The present invention has the following outstanding gain effects: (1) The present invention introduces reactive ultracold comonomers into the polymerization reaction by using a microbubble generator and / or multi-point liquid phase injection, which can enhance backmixing of the flow field, improve heat and mass transfer behavior, regulate the spatial distribution of temperature field and concentration field in the flow field, dynamically modulate the polymerization microenvironment around the active chain, induce the active chain to shuttle polymerization in the low temperature high comonomer reaction zone and the high temperature low comonomer reaction zone, realize the preparation of olefin block copolymers with alternating "hard segment-soft segment" in a single reactor with a single catalyst, and break through the existing "dual catalyst + chain shuttle" system required for the preparation of olefin block copolymers; (2) The coupling of temperature gradient, concentration gradient, time and modulation frequency in the two high and low temperature reaction zones in the present invention can regulate the block length, block number, branch length, branch content and distribution, and construct a "hard segment-soft segment" molecular chain growth model; (3) The preparation of olefin block copolymers with alternating "hard segment-soft segment" in a single reactor with a single catalyst has the advantages of low energy consumption, low material consumption and significantly reduced investment cost. Detailed Implementation

[0027] The embodiments of the present invention will be described in detail below with reference to examples. The following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified, specific conditions in the examples are performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, reagents or instruments used in the examples are commercially available conventional products.

[0028] The following methods are used to test the structure or properties of the polyolefins produced in the embodiments described: Characterization of weight-average molecular weight and molecular weight distribution index: high-temperature gel permeation chromatography (GPC).

[0029] Characterization of melt flow index: measured according to ISO 1133 method at 230 °C / 2.16 kg.

[0030] Determination of melting point and glass transition temperature: differential scanning calorimetry (DSC).

[0031] Tensile strength and elongation at break: Universal testing machine.

[0032] Impact strength testing: impact testing machine.

[0033] Comonomer insertion rate: Nuclear magnetic resonance spectrometer ( 13 C-NMR).

[0034] Example 1 This embodiment uses a metallocene catalyst, n-hexane as the solvent, and 1-butene as the comonomer. A microbubble and multi-point liquid-phase injection synergistic introduction system is employed, consisting of a coaxial composite nozzle: an outer Venturi-type liquid-phase injection channel and an inner microbubble generation channel. The two composite nozzles are symmetrically distributed in the high-shear region below the agitator blades of the reactor. The polymerization reactor is purged with high-purity nitrogen to remove moisture and oxygen from the reactor interior.

[0035] First, 2 μmol of metallocene catalyst was dissolved in 1 mL of toluene and set aside. The polymerization reactor temperature was adjusted to 130 °C, and 800 mL of n-hexane was added sequentially, followed by 1.6 mmol of co-catalyst methylaluminoxane and 2 μmol of metallocene catalyst CGC. Ethylene was introduced at a pressure of 30 bar, and then 1-butene pre-cooled to -10 °C was intermittently introduced using the aforementioned synergistic introduction system at a copolymer introduction / interval time of 5 min / 10 min. During introduction, liquid 1-butene was atomized through the outer nozzle, while microbubbles were generated through the inner nozzle. The two formed a "gas-liquid micro-dispersion system" at the moment of spraying, which was rapidly dispersed in the solvent. Polymerization was carried out for 30 min, and the relevant characterization and performance test results of the obtained product are shown in Table 1.

[0036] Example 2 This embodiment uses a metallocene catalyst, n-hexane as the solvent, and 2-butene as the comonomer. A microbubble and multi-point liquid-phase injection synergistic introduction system is employed, consisting of staggered atomizing nozzles and ceramic aerators. The polymerization reactor is purged with high-purity nitrogen to remove moisture and oxygen from its interior.

[0037] First, 2 μmol of metallocene catalyst was dissolved in 1 mL of toluene and set aside. The temperature of the polymerization reactor was adjusted to 160 °C, and 800 mL of n-hexane was added sequentially, followed by 1.6 mmol of co-catalyst methylaluminoxane and 2 μmol of metallocene catalyst CGC. Ethylene was introduced at a pressure of 20 bar. Using the aforementioned synergistic introduction system, 2-butene pre-cooled to 0 °C was intermittently introduced at a time interval of 10 min / 10 min. During introduction, 2-butene was ultrasonically atomized to form microdroplets, while the aeration head generated a large number of microbubbles, synergistically enhancing dispersion and mixing. Polymerization was carried out for 40 min. The relevant characterization and performance test results of the obtained product are shown in Table 1.

[0038] Example 3 This embodiment uses a non-bridged metallocene catalyst, n-hexane as the solvent, and propylene as the comonomer. A sequential injection-enhanced dispersion system is employed: first, annular microporous ceramic aerators are arranged at the bottom of the reactor to continuously introduce ethylene microbubbles; then, two static mixing liquid-phase nozzles are installed at 50% below the liquid level. The polymerization reactor is purged with high-purity nitrogen to remove moisture and oxygen from the reactor.

[0039] First, dissolve 2 μmol of the non-bridged metallocene catalyst in 1 mL of toluene and set aside. Adjust the polymerization reactor temperature to 210 °C, then add 800 mL of n-hexane, followed by 2 mmol of the co-catalyst-modified methylaluminoxane and 2 μmol of the non-bridged metallocene catalyst. Introduce ethylene at a pressure of 15 bar, maintaining a bottom ethylene microbubble flow (10 μm in diameter). -3 Using a static mixing liquid phase nozzle, pre-cooled liquid propylene (pre-cooled to 15 °C below boiling point -62.6 °C) was intermittently introduced at a copolymer introduction / interval time of 10 min / 5 min, and sprayed into a rising microbubble cloud. The bubbles were used to achieve secondary breakage and rapid dispersion of the droplets, and polymerization was carried out for 30 min. The relevant characterization and performance test results of the obtained product are shown in Table 1.

[0040] Example 4 This embodiment uses a non-bridged metallocene catalyst, n-hexane as solvent, and 1-pentene as comonomer. An integrated coupled injector system (with a built-in Venturi tube microbubble generator) is employed, with four injectors arranged in layers along the axial direction of the reactor. The polymerization reactor is purged with high-purity nitrogen to remove moisture and oxygen from its interior.

[0041] First, 2 μmol of non-bridged metallocene catalyst was dissolved in 1 mL of toluene and set aside. The temperature of the polymerization reactor was adjusted to 180 °C, and 800 mL of n-hexane was added sequentially, followed by 2 mmol of trimethylaluminum co-catalyst and 2 μmol of non-bridged metallocene catalyst. Ethylene was introduced at a pressure of 40 bar. Then, using the aforementioned coupled injector, 1-pentene pre-cooled to -5 °C was intermittently introduced at a time interval of 20 min / 20 min. During the introduction, the high-speed flowing 1-pentene generated negative pressure at the throat of the venturi tube, drawing in ethylene gas and shearing it to generate microbubbles. After forming a gas-liquid two-phase flow, it was ejected. Polymerization was carried out for 40 min. The relevant characterization and performance test results of the obtained product are shown in Table 1.

[0042] Example 5 This embodiment employs a bridged metallocene catalyst, using n-hexane as the solvent and propylene as the comonomer. A parallel coordinated injection system is used, with two injection point groups set in the straight section of the loop reactor. Each point group includes an ultrasonic generator (for generating microbubbles) and a Venturi liquid-phase injector. The polymerization reactor is purged with high-purity nitrogen to remove moisture and oxygen from the reactor.

[0043] First, 2 μmol of the bridged metallocene catalyst was dissolved in 1 mL of toluene and set aside. The temperature of the polymerization reactor was adjusted to 90 °C, and 800 mL of n-hexane was added sequentially, followed by 1.6 mmol of triethylaluminum co-catalyst and 2 μmol of the bridged metallocene catalyst. Ethylene was introduced at a pressure of 20 bar, and then propylene pre-cooled to -47.6 °C was intermittently introduced using the aforementioned synergistic injection system at a time interval of 10 min / 30 min. The liquid propylene and ethylene microbubbles were dispersed in the solvent by a stirrer. Polymerization was carried out for 40 min, and the relevant characterization and performance test results of the obtained product are shown in Table 1.

[0044] Comparative Example 1 This embodiment uses a metallocene catalyst, n-hexane as a solvent, and 1-butene as a comonomer. The polymerization reactor is purged with high-purity nitrogen to remove moisture and oxygen from the reactor.

[0045] First, 2 μmol of metallocene catalyst was dissolved in 1 mL of toluene and set aside. The temperature of the polymerization reactor was adjusted to 120 °C, and 800 mL of n-hexane and 200 mL of 2-butene were added sequentially. Then, 1.6 mmol of methylaluminoxane co-catalyst and 2 μmol of metallocene catalyst CGC were added sequentially. Ethylene was introduced and the ethylene pressure was 30 bar. Polymerization was carried out for 20 min. The relevant characterization and performance test results of the obtained product are shown in Table 1.

[0046] Table 1 As shown in the table above, the characterization results of the block copolymers prepared in Examples 1-5 and Comparative Example 1 show that the block copolymer products prepared in Examples 1-5 have a narrower molecular weight distribution index, a higher weight-average molecular weight, a higher melting temperature, and a lower melt index compared to the copolymer product of Comparative Example 1, exhibiting a more regular chain structure and better crystallinity. The obtained olefin block copolymers have melting points of 110 ℃~125 ℃ and densities of 0.900 g / cm³. 3 ~0.915 g / cm 3The melt index ranged from 0.1 g / 10 min to 2.0 g / 10 min, and the various properties were well-matched and conformed to the structure-property correlation law of olefin block copolymers, verifying the significant effect of this preparation method in improving the regularity and comprehensive performance of copolymer segments.

[0047] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing olefin block copolymers using reactive ultracold comonomers in a solution polymerization process, characterized in that, A polymerization reaction medium, olefin monomer, reactive cryogenic comonomer, catalyst, and cocatalyst are introduced into a reactor to carry out a polymerization reaction. The reactive cryogenic comonomer is introduced by microbubble and / or multi-point liquid phase injection. The olefin monomer is ethylene. The reactive cryogenic comonomer is selected from one or more of propylene, 1-butene, 2-butene, and 1-pentene. When microbubble introduction is used, the introduction temperature is not higher than 10 °C above the boiling point of the comonomer and not lower than -30 °C. When multi-point liquid phase injection is used, the introduction temperature is not higher than the boiling point of the comonomer.

2. The method according to claim 1, characterized in that, During the polymerization process, by controlling the frequency, temperature, method, and amount of introduction of reactive ultracold comonomers, it is possible to obtain olefin block copolymers with different lengths and proportions of hard and soft segments in the molecular chain.

3. The method according to claim 1, characterized in that, When reactive ultracold comonomers are introduced into the reactor, the volume fraction of comonomer microbubbles and / or ultracold comonomer solutions accounts for 50% to 99.9% of the reactor volume; when reactive ultracold comonomers are not introduced into the reactor, the volume fraction of comonomer microbubbles and / or ultracold comonomer solutions accounts for 0.1% to 20% of the reactor volume.

4. The method according to claim 1, characterized in that, The microbubble generator used for microbubble introduction is selected from one or more of ultrasonic generators, venturi tubes, and aeration heads. The microporous material of the microbubble generator is selected from one or more of ceramic membranes and SPG membranes. The generated microbubbles have a diameter of 10 mm. -6 -10 -2 m; The multi-point liquid phase jetting uses a jetting device selected from one or more of the following: a Venturi jetter, a static mixing nozzle, and an ultrasonic atomizing nozzle. The average droplet size produced by the jetting device is 10 mm. -6 -10 -4 Within the range of m.

5. The method according to claim 1, characterized in that, When introducing liquid phase through multi-point injection, the introduction temperature is 5–30 °C below the boiling point; the introduction position is located at a height of 10%–90% below the liquid surface, and there are one or more introduction positions.

6. The method according to claim 1 or 4, characterized in that, The polymerization reaction temperature is 50 ℃~230 ℃, the polymerization reaction pressure is 0.1 MPa~20 MPa, and the temperature difference between the polymerization reaction temperature when a reactive ultracold comonomer is introduced and the temperature when no reactive ultracold comonomer is introduced is 20 ℃~100 ℃.

7. The method according to claim 1, characterized in that, The frequency of introducing reactive ultracold comonomers is in the range of 0.0001~0.1 Hz. When reactive ultracold comonomers are introduced, the instantaneous concentration of the comonomer increases by 50%~1000% compared with the concentration when reactive ultracold comonomers are not introduced.

8. The method according to claim 1, characterized in that, The polymerization reaction medium is selected from one or more of toluene, ethylbenzene, benzene, n-butane, n-pentane, isopentane, cyclopentane, n-hexane, 2-methylpentane, 3-methylpentane, cyclohexane, n-heptane, methylcyclohexane, 2-methylhexane, 3-methylhexane, and 3-ethylpentane.

9. The method according to claim 1, characterized in that, The catalyst is selected from one or more of non-bridged metallocene catalysts, bridged metallocene catalysts, and restricted geometry CGC catalysts; the co-catalyst is selected from one or more of methylaluminoxane, modified methylaluminoxane, tripentafluorophenylborane, trimethylaluminum, triethylaluminum, triisobutylaluminum, trihexylaluminum, and trioctylaluminum.

10. An olefin block copolymer prepared by the method according to any one of claims 1 to 9, characterized in that, The olefin block copolymer has a melting point of 110 °C to 125 °C and a density of 0.900 g / cm³. 3 ~0.915 g / cm 3 The melt index is between 0.1 g / 10 min and 2.0 g / 10 min.

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