Highly branched polyethylene and solution polymerization method and application thereof

Abstract

The invention discloses highly branched polyethylene and a solution polymerization method and application thereof, and belongs to the technical field of polyolefin products and olefin polymerization, in a catalytic system containing a late transition metal complex catalyst, under the conditions that an inert solvent is lacked and the polymerization temperature Tp is greater than or equal to Tm-50 DEG C (Tm represents the melting point of the highly branched polyethylene), the polymerization temperature Tp is greater than or equal to Tm-50 DEG C; according to the present invention, one or more C2-C30 olefins are polymerized or copolymerized in the medium (the C2-C30 olefins at least comprise one or more C4-C30 olefins, and the C4-C30 olefins are concurrently used as polymerization solvents) according to the chain walking mechanism to form the target polymer highly branched polyethylene, such that the branching degree is improved, the branched chain distribution is improved, and the excellent physical property and the excellent processing property are provided; meanwhile, the preparation process is simplified, the gas-phase heat removal capability can be remarkably improved, liquid-liquid phase separation is realized at relatively low temperature and pressure, the energy consumption of post-treatment is further reduced, and industrial production is facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of polyolefin products and olefin polymerization, and specifically relates to a highly branched polyethylene and a solution polymerization method and application thereof. Background Art

[0002] Olefin solution polymerization usually needs to be carried out in a solvent, and the selection of liquid reaction medium usually depends on the inert hydrocarbon solvent of the specific olefin to be polymerized and the olefin monomer dissolved therein, and this inert hydrocarbon solvent helps to promote the dissolving of the product polymer in the liquid medium. As known in the art, the polymerization of 1-butene can be carried out without an inert solvent, because poly-1-butene is completely dissolved in the liquid monomer under common polymerization conditions, and a polymer solution can be formed. However, other olefins (for example ethylene, propylene or higher alpha-olefins) are currently all polymerized in solution in the presence of a suitable inert solvent (for example cyclohexane, normal hexane, normal heptane, 2-methylpentane or Isopar TME (isoparaffin)), because the resulting polyolefin is insoluble in the liquid monomer under common polymerization conditions. The presence of an inert solvent means that a solvent-related process section is required, such as a solvent storage system and a complex solvent recovery section, thereby removing the inert solvent from the resulting polymer, and then collecting the resulting polymer in an available form.

[0003] Therefore, it is of great significance to find a solution to allow simplification of solvent-related process sections and thus reduce CAPEX expenditures for industrial plants. Patent CN202080076460 found that olefins other than 1-butene can be solution polymerized in a liquid monomer medium in the absence of an inert solvent under the condition of a polymerization temperature Tp ≥ Tm + 20 ° C (where Tm is the melting temperature of the resulting polymer), but the polymerization temperature range is narrow. Therefore, how to enable solution polymerization in the absence of an inert solvent in a larger polymerization temperature range remains to be explored. Summary of the invention

[0004] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0005] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0006] Therefore, the object of the present invention is to overcome the deficiencies in the prior art and provide a solution polymerization method for highly branched polyethylene.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions: comprising:

[0008] In a system containing a late transition metal complex as a main catalyst and lacking an inert solvent, one or more C2-C30 olefins are polymerized or copolymerized in their own medium at a polymerization temperature Tp≥Tm-50°C and not lower than the melting point of the medium itself to form a target polymer, highly branched polyethylene, by a chain walking mechanism;

[0009] Preferably, the polymerization temperature Tp ≥ Tm-25°C, most preferably, the polymerization temperature Tp ≥ Tm-5°C.

[0010] Wherein, Tm represents the melting point of the highly branched polyethylene, and the C2-C30 olefins contain at least one or more C4-C30 olefins, and the C4-C30 olefins also serve as polymerization solvents.

[0011] As a preferred solution polymerization method of highly branched polyethylene of the present invention, wherein: the C4-C30 olefin monomer is selected according to the branching degree of the target polymer;

[0012] When the branching degree of the target polymer is ≥200 / 1000C, the C4-C30 olefin monomer is any one or more of C4-C30 olefins;

[0013] When the branching degree of the target polymer is 150 to 200 / 1000C, the monomer of the C4 to C30 olefin is any one or more of the C5 to C30 olefins;

[0014] When the branching degree of the target polymer is 100 to 150 / 1000C, the monomer of the C4 to C30 olefin is any one or more of the C6 to C30 olefins;

[0015] When the branching degree of the target polymer is 80 to 100 / 1000C, the monomer of the C4 to C30 olefin is any one or more of the C8 to C30 olefins;

[0016] When the branching degree of the target polymer is 50 to 80 / 1000C, the monomer of the C4 to C30 olefin is any one or more of the C10 to C30 olefins.

[0017] As a preferred solution polymerization method of highly branched polyethylene described in the present invention, the content of C4-C30 olefin monomers in the polymerization system is 50-100 mol%.

[0018] As a preferred embodiment of the solution polymerization method of the highly branched polyethylene described in the present invention, wherein: among the C2-C30 olefins, the monomers of the C2-C3 olefins are selected from one of ethylene or propylene, and the monomers of the C4-C30 olefins include one or more of the C4-C18 olefins.

[0019] As a preferred embodiment of the solution polymerization method of highly branched polyethylene described in the present invention, the C4-C30 olefins are selected from one or more of butene, pentene, hexene, heptene, octene, nonene, deoxyene and dodecene.

[0020] As a preferred embodiment of the solution polymerization method of the highly branched polyethylene described in the present invention, the C4-C30 olefins include C4-C6 olefins.

[0021] As a preferred embodiment of the solution polymerization method of highly branched polyethylene described in the present invention, the late transition metal complex catalyst includes one or more complexes of nickel, palladium and iron.

[0022] As a preferred embodiment of the solution polymerization method of highly branched polyethylene described in the present invention, the late transition metal complex catalyst includes one or more of α-diimine nickel complex and α-diimine palladium complex.

[0023] As a preferred scheme of the solution polymerization method of highly branched polyethylene described in the present invention, the catalytic system also includes a co-catalyst, wherein the co-catalyst includes one or more of aluminoxane, modified aluminoxane, alkylaluminum, alkylaluminum chloride or B(C6F5)3.

[0024] As a preferred embodiment of the solution polymerization method of the highly branched polyethylene described in the present invention, the aluminoxane comprises methylaluminoxane or methylaluminoxane modified with triisobutylaluminum.

[0025] As a preferred embodiment of the solution polymerization method of highly branched polyethylene described in the present invention, the alkylaluminum chloride is selected from at least one of trimethylaluminum chloride, diethylaluminum chloride, triethylaluminum trichloride, triisobutylaluminum chloride, triethylaluminum chloride, monoethylaluminum chloride and diethylzinc chloride.

[0026] As a preferred embodiment of the solution polymerization method of highly branched polyethylene described in the present invention, the polymerization system further comprises a diene monomer selected from one or more of ethylidene norbornene, dicyclopentadiene, 1,4-hexadiene, 1,7-octadiene, 6,10-dimethyl-1,5,9-undecatriene, 3,7-dimethyl-1,6-octadiene, 5,7-dimethyl-1,6-octadiene and 7-methyl-1,6-octadiene.

[0027] As a preferred embodiment of the solution polymerization method of the highly branched polyethylene described in the present invention, the polymerization system further comprises a molecular weight regulator selected from one or more of diethyl zinc and hydrogen.

[0028] As a preferred embodiment of the solution polymerization method of the highly branched polyethylene of the present invention, the polymerization or copolymerization temperature is 30 to 150° C. and the pressure is 0.1 to 5 MPa.

[0029] As a preferred embodiment of the solution polymerization method of the highly branched polyethylene of the present invention, the polymerization or copolymerization temperature is preferably 50 to 90° C., and the pressure is preferably 0.5 to 2.0 MPa.

[0030] As a preferred embodiment of the solution polymerization method of highly branched polyethylene described in the present invention, the situation of lacking inert solvent includes one of the situations of no inert solvent or unavoidably using a small amount of inert solvent or diluent to meet the needs of the main catalyst or co-catalyst.

[0031] As a preferred embodiment of the solution polymerization method of the highly branched polyethylene described in the present invention, the solution polymerization method includes one or more of intermittent operation, semi-continuous operation or continuous operation.

[0032] As a preferred embodiment of the solution polymerization method of highly branched polyethylene described in the present invention, the continuously operated solution polymerization method can adopt one or more reactors of the same or different types connected in series or in parallel, and the types of reactors include but are not limited to continuous stirred tank reactors, tubular reactors, tower reactors, microchannel reactors, ultra-gravity reactors, micro-interface enhanced reactors or static mixer reactors.

[0033] As a preferred embodiment of the solution polymerization method of highly branched polyethylene described in the present invention, the temperature in the reactor is usually controlled by cold feed, gas phase evaporation heat removal, jacket heat removal, external circulation heat exchanger heat removal and other means.

[0034] As a preferred embodiment of the solution polymerization method of highly branched polyethylene described in the present invention, the solution polymerization method further includes a post-treatment step, and the post-treatment step includes achieving a liquid-liquid phase separation operation of a polymer-rich phase-polymer-poor phase by changing the system temperature and / or pressure, thereby obtaining the target polymer highly branched polyethylene.

[0035] As a preferred embodiment of the solution polymerization method of highly branched polyethylene described in the present invention, in which: in the continuous operation mode of the method, the residence time of the liquid reaction medium in the polymerization device is usually 15 to 90 minutes.

[0036] As a preferred embodiment of the solution polymerization method of highly branched polyethylene described in the present invention, in which: in the continuous operation mode of the method, the residence time of the liquid reaction medium in the polymerization device is 30 to 60 minutes.

[0037] As a preferred embodiment of the solution polymerization method of highly branched polyethylene described in the present invention, the monomer or comonomer of the target polymer highly branched polyethylene obtained by the solution polymerization method is C4-C6 olefin.

[0038] As a preferred embodiment of the solution polymerization method of the highly branched polyethylene described in the present invention, the C4-C6 olefin is 1-pentene.

[0039] Another object of the present invention is to provide a highly branched polyethylene obtained by a solution polymerization method of highly branched polyethylene.

[0040] As a preferred embodiment of the highly branched polyethylene of the present invention, the number average molecular weight of the highly branched polyethylene is 1000 to 1500000; and the molecular weight distribution index is 1.2 to 2.5.

[0041] As a preferred embodiment of the highly branched polyethylene of the present invention, the content of C4-C30 olefin monomers in the highly branched polyethylene is usually 0.1-30 mol%.

[0042] As a preferred embodiment of the highly branched polyethylene of the present invention, the content of C4-C30 olefin monomers in the highly branched polyethylene is 5-20 mol%.

[0043] Another object of the present invention is to provide a solution polymerization method for highly branched polyethylene and its application in the fields of photovoltaic film, rubber and polymer modifier.

[0044] Beneficial effects of the present invention:

[0045] (1) The branching degree of the highly branched polyethylene obtained by polymerization according to the present invention is increased, and the branch chain distribution is improved, so that the product has better physical properties and processing properties.

[0046] (2) The scheme of the present invention allows the process sections of solvent logistics, solvent storage and pumping, and solvent purification to be removed, while also simplifying the recovery section. Compared with the conventional scheme of a polymerization system using hexane as a solvent and no comonomer is added or a small amount of C4-C5 olefin is added as a comonomer, the gas phase heat removal capacity can be significantly improved, liquid-liquid phase separation can be achieved at a relatively low temperature and pressure, and the energy consumption of post-processing can be further reduced, which is beneficial to industrial production. DETAILED DESCRIPTION

[0047] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0048] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0049] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0050] Unless otherwise specified, the raw materials and equipment used in the present invention are commercially available in the art.

[0051] The catalysts Ni1, Ni3, and Ni4 used in the specific embodiments or comparative examples of the present invention are synthesized by referring to the method of patent CN116239494A "ligand compound and preparation method, catalyst composition and application, catalyst and polyethylene elastomer and preparation method and application"; the catalyst Ni4 is synthesized by referring to the method of patent CN116462715A "an acenaphthene-based α-diimine nickel complex, catalyst and application thereof".

[0052] The performance test of the target polymer highly branched polyethylene in the present invention refers to the following method:

[0053] Degree of branching and branch distribution:

[0054] Degree of branching 13 C NMR determination: the product highly branched polyethylene was dissolved in 1,2-o-dichlorobenzene, TMS was used as the internal standard, and the measurement was performed on a Bruker AVANCE III 500 MHz, the temperature was set to 100 °C, the number of scans was 3000, the spectrum width was 18.8324 kHz, the data acquisition time was 0.87 s, and the delay time was 2 s.

[0055] Melting Point:

[0056] The melting point is tested by DSC, the temperature range is -60~150℃, and the temperature change process is:

[0057] The first stage: from room temperature (25°C) to 150°C, the heating rate is 10°C / min, and the temperature is maintained at 150°C for 2 minutes;

[0058] The second stage: from 150℃ to -60℃, the cooling rate is 10℃ / min, and the temperature is kept at -60℃ for 2min;

[0059] The third stage: heating from -60℃ to 150℃ at a rate of 10℃ / min; then dropping to 40℃.

[0060] The cooling rate is 10℃ / min, and the test ends;

[0061] The melting point was obtained from the melting peak of the third stage heating curve.

[0062] Melt flow rate:

[0063] The melt flow rate (melt index) was tested according to the standard ASTM D1238 test method (190°C and 2.16 kg).

[0064] Catalytic activity ratio:

[0065] The catalytic activity ratio is the ratio of the yield of highly branched polyethylene to the weight of the catalyst used, and the weight of the catalyst used is the weight of the late transition metal catalyst.

[0066] Molecular weight and molecular weight distribution index:

[0067] The weight average molecular weight and molecular weight distribution index were determined by high temperature gel permeation chromatography (PL-GPC220) at 150 °C with 1,2,4-trichlorobenzene as mobile phase and polystyrene as standard;

[0068] Lamination transparency and haze:

[0069] The transparency and haze of the film of highly branched polyethylene were measured according to GBT 2410-2008 Test method for light transmittance and haze of transparent plastics.

[0070] Example 1

[0071] This embodiment provides a solution polymerization method for highly branched polyethylene lacking an inert solvent, specifically:

[0072] A 5L polymerization kettle was treated to be anhydrous and oxygen-free and then evacuated, 3L 1-hexene (comonomer C4-C30 olefin, also serving as polymerization solvent) was added into the polymerization kettle, the temperature was raised to 80°C, ethylene (C2-C3 olefin) was introduced, the pressure in the polymerization kettle was raised to 1.0 MPa, 0.02g of a toluene solution (concentration 2mg / mL) of a late transition metal complex (main catalyst) Ni3 and 1M hexane solution (4.0mL) of triethylaluminum trichloride (co-catalyst) were added, the reaction was started, ethylene was continuously introduced into the polymerization kettle to control the feed rate so that the pressure in the polymerization kettle was maintained at 1.0 MPa, the polymerization temperature was 80°C, and the polymerization time was 30min;

[0073] After the reaction is completed, the rubber liquid in the polymerization kettle is released, washed with ethanol aqueous solution, and finally devolatilized and dried to obtain the highly branched polyethylene P1.

[0074] Comparative Example 1

[0075] The difference between this comparative example and Example 1 is that n-hexane is used as the polymerization solvent, no comonomer is added, and the rest of the preparation process is the same as that of Example 1 to obtain the highly branched polyethylene D1 of this comparative example.

[0076] Example 2

[0077] The difference between this embodiment and embodiment 1 is that the comonomer 1-hexene is adjusted to 1-octene, and the rest of the preparation process is the same as that of embodiment 1 to obtain the highly branched polyethylene P2 of this embodiment.

[0078] Comparative Example 2

[0079] The difference between this comparative example and Example 2 is that the comonomer 1-octene is adjusted to n-hexane and 1-octene, specifically:

[0080] 1.7 L of n-hexane and 1.3 L of 1-octene were added to the polymerization kettle. After the reaction started, ethylene and 1-octene were continuously introduced into the polymerization kettle at a molar ratio of 14:1. The rest of the preparation process was the same as that in Example 2 to obtain the highly branched polyethylene D2 of this comparative example.

[0081] Example 3

[0082] The difference between this embodiment and embodiment 1 is that the comonomer 1-hexene is adjusted to 1-decene, the late transition metal complex (main catalyst) Ni3 is adjusted to Ni1, the polymerization temperature is 70°C, and the rest of the preparation process is the same as that of embodiment 1 to obtain the highly branched polyethylene P3 of this embodiment.

[0083] Comparative Example 3

[0084] The difference between this comparative example and Example 3 is that the comonomer 1-decene is adjusted to 1-pentene, and the rest of the preparation process is the same as Example 3. During the polymerization process, the polymer precipitates and sticks to the wall, and the highly branched polyethylene D3 of this comparative example is obtained.

[0085] Comparative Example 4

[0086] The difference between this comparative example and Example 3 is that the transition metal complex (main catalyst) Ni3 is adjusted to Ni4, and the rest of the preparation process is the same as Example 3. During the polymerization process, the polymer precipitates and sticks to the wall. The highly branched polyethylene D4 of this comparative example is obtained.

[0087] Example 4

[0088] This embodiment provides a solution polymerization method for highly branched polyethylene lacking an inert solvent, which is different from Embodiment 1 in that the type of polymerization monomer is adjusted and a molecular weight regulator is added, specifically:

[0089] A 5L polymerization kettle was treated to be anhydrous and oxygen-free and then evacuated, 3L 1-pentene (C4-C30) and 720g ethylidene norbornene (ENB) were added into the polymerization kettle, the temperature was raised to 85°C, the pressure in the polymerization kettle was raised to 0.5Mpa, 0.02g of a toluene solution (concentration 2mg / mL) of a late transition metal complex (main catalyst) Ni4, 4.0mL of a hexane solution of 1M triethylaluminum trichloride (co-catalyst) and 1.0ml of a hexane solution of 1M diethylzinc (molecular weight regulator) were added, the reaction was started, ethylene was continuously introduced into the polymerization kettle to control the feed rate so that the pressure in the polymerization kettle was maintained at 0.5MPa, the polymerization temperature was 85°C, and the polymerization time was 30min;

[0090] After the reaction is completed, the rubber liquid in the polymerization kettle is released, washed with ethanol aqueous solution, and finally devolatilized and dried to obtain the highly branched polyethylene P4.

[0091] The reaction conditions and polymer properties of Examples 1 to 4 and Comparative Examples 1 to 4 for preparing highly branched polyethylene are shown in Table 1.

[0092] Table 1 Reaction conditions and polymer properties

[0093]

[0094] The relevant performance test results of the highly branched polyethylene obtained in Examples 1 to 4 and Comparative Examples 1 to 4 are shown in Table 2 and Table 3.

[0095] Table 2 Degree of branching and branch distribution

[0096]

[0097] Table 3 Other properties

[0098]

[0099] From the comparison of the branching degree and branch distribution data of P1 and D1 in Table 2, it can be seen that using 1-hexene instead of n-hexane as a solvent can also stabilize the polymerization, and the branching degree is greatly improved, the branch distribution is improved, and the proportion of C2-C5 branches is significantly increased;

[0100] From the comparison of the branching degree and branch distribution data of P2 and D2, it can be seen that using 1-octene to completely replace n-hexane can also achieve stable polymerization, and the branching degree is increased, the branch distribution is improved, and the proportion of long branches of C6 and above is further increased;

[0101] From the comparison of the branching degree and branch chain distribution data of P3 and D3, it can be seen that when the branching degree is low, using 1-pentene instead of 1-decene, although the branching degree is improved, it still cannot be stably polymerized and precipitation occurs;

[0102] From the comparison of the branching degree and branch chain distribution data of P3 and D4, it can be seen that when other conditions remain unchanged, adjusting the catalyst alone will also greatly reduce the branching degree, thus failing to stabilize the polymerization;

[0103] This shows that, when the catalyst is a suitable late transition metal catalyst and the degree of branching of the polymer is high enough, olefins other than 1-butene can also be solution polymerized in a suitable C4 and above liquid monomer medium in the absence of an inert solvent and at a polymerization temperature that is even slightly lower than the melting point of the resulting polymer.

[0104] In summary, it can be seen from the data in the above table that the degree of branching of the highly branched polyethylene obtained by polymerization in the scheme of the present invention is improved, the branch distribution is improved, the weight average molecular weight of the highly branched polyethylene is 69000-110000; the molecular weight distribution index is 2.0-2.3, so that the product has better physical properties and processing performance, and the transparency and haze of the film pressing of the highly branched polyethylene P1-P4 are on par with the photovoltaic-grade POE indicators on the market, and can be applied to photovoltaic films, rubbers, polymer modifiers and other fields, among which P4 has a cross-linkable double bond, which is more conducive to the occurrence of cross-linking reactions.

[0105] Example 5

[0106] In this example, highly branched polyethylene is prepared in a pilot plant with an annual capacity of 10,000 tons. The pilot plant is a polyethylene process plant with a continuous polymerization reaction in kettle type, and is equipped with two series-connected 10m 3 The polymerization kettle has a height-to-diameter ratio H / D=1.50, a reaction temperature of 85°C, and a reaction pressure of 1.0 MPa;

[0107] 1-pentene (comonomer C4-C30 olefin, also serving as polymerization solvent) at a flow rate of 14.7 t / h, ethylene (C2-C3 olefin) at a flow rate of 1.24 t / h, a toluene solution of a late transition metal complex (main catalyst) Ni4 (concentration of 2 mg / mL, flow rate of 100 L / h, and an addition amount of pure catalyst of 200 g / h) and a 1M hexane solution of triethylaluminum trichloride (co-catalyst) at a flow rate of 40 L / h were continuously introduced into the polymerization kettle. The charging factor of both kettles was 60%, the residence time was 30 min, the polymerization rate was 1.6 t / h, the solid content of the glue was 12.8 wt%, and the glue discharged from the polymerization kettle was added. A trace amount of ethanol is injected into the catalyst to deactivate it. After ethylene is separated by an ethylene separator, the rubber liquid is pressurized and transported by a booster pump. After being heated by a two-stage heat exchanger, it enters a liquid-liquid separation decanter with a temperature of 150°C and a pressure of 2.5 MPa. Phase separation occurs in the liquid-liquid separator decanter. The polymer-poor phase (containing polymer <0.1%) flows out from the upper outlet of the separator, is cooled by a heat exchanger, and is directly returned to the polymerization reactor after dealcoholization by a molecular sieve drying tower; the polymer-rich phase (containing 30-40% of polymer) flows out from the bottom of the separator, and the rubber liquid passes through a silica gel adsorption tower to remove catalyst residues. The highly branched polyethylene P5 is obtained by dry devolatilization and extrusion granulation.

[0108] Comparative Example 5

[0109] The difference between this comparative example and Example 5 is that, in this comparative example, hexane is added as solvent, no comonomer is added, the flow rate of hexane is 14.4 t / h, the flow rate of ethylene is 1.84 t / h, the hexane solution of late transition metal complex (main catalyst) Ni4 (concentration is 2 mg / mL, flow rate is 90 L / h, the addition amount of pure catalyst is 180 g / h) and 1M trichlorotriethyldialuminum toluene solution (flow rate is 36 L / h), the polymerization rate is 1.25 t / h, and the solid content of the glue is 8 wt%. The rest of the preparation process is the same as that of Example 5, that is, the highly branched polyethylene D5 of this comparative example is obtained.

[0110] The reaction conditions and related performance test results of highly branched polyethylene obtained in Example 5 and Comparative Example 5 are shown in Tables 4 to 6, and the heat transfer data are shown in Table 7, wherein the gas phase heat removal is determined and controlled based on the calculation of the entrainment velocity of the mist.

[0111] Table 4

[0112]

[0113] Table 5

[0114]

[0115]

[0116] Table 6

[0117]

[0118] Table 7

[0119]

[0120]

[0121] As can be seen from the above table, in Example 5, 1-pentene is used as a comonomer and polymerization solvent, and the polymerization control is greatly simplified: since there is no inert solvent, as long as the polymerization temperature and pressure are well controlled, the concentration of the comonomer is always uniform and stable, and the key ethylene / comonomer concentration ratio remains stable; in contrast, in a copolymerization system with an inert solvent, not only the polymerization temperature and pressure must be controlled, but also the concentration of the comonomer must be additionally controlled in order to control the ethylene / comonomer concentration ratio.

[0122] At the same time, it can be seen from the data in Table 7 that, compared with Comparative Example 5, the evaporation and heat removal capacity of the system is greatly improved, and the production capacity of the device is greatly improved; because there is no inert solvent, compared with the copolymerization system with an inert solvent, the purification and recovery of the comonomer can cancel the distillation process, thereby simplifying the steps; and because liquid-liquid phase separation can be achieved at relatively low temperature and pressure, the energy consumption of post-treatment is further reduced, which is beneficial to industrial production.

[0123] In summary, the present invention provides a highly branched polyethylene synthesized by solution polymerization in the absence of an inert solvent, wherein the degree of branching is increased and the branch distribution is improved, thereby making the product have better physical properties and processing properties;

[0124] In addition, the scheme of the present invention allows the process sections of solvent logistics, solvent storage and pumping, and solvent purification to be removed, while also simplifying the recovery section. Compared with the conventional scheme of a polymerization system using hexane as a solvent and no comonomer is added or a small amount of C4-C5 olefin is added as a comonomer, the gas phase heat removal capacity can be significantly improved, liquid-liquid phase separation can be achieved at a relatively low temperature and pressure, and the energy consumption of post-processing can be further reduced, which is beneficial to industrial production.

[0125] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A solution polymerization method for highly branched polyethylene, characterized in that: include, In a system containing a late transition metal complex as a main catalyst and lacking an inert solvent, one or more C2-C30 olefins are polymerized or copolymerized in their own medium at a polymerization temperature Tp≥Tm-50°C and not lower than the melting point of the medium itself to form a target polymer, highly branched polyethylene, by a chain walking mechanism; Wherein, Tm represents the melting point of the highly branched polyethylene, and the C2-C30 olefins contain at least one or more C4-C30 olefins, and the C4-C30 olefins also serve as polymerization solvents.

2. The solution polymerization method of highly branched polyethylene as claimed in claim 1, characterized in that: The C4-C30 olefin monomers are selected according to the branching degree of the target polymer; When the branching degree of the target polymer is ≥200 / 1000C, the C4-C30 olefin monomer is any one or more of C4-C30 olefins; When the branching degree of the target polymer is 150 to 200 / 1000C, the monomer of the C4 to C30 olefin is any one or more of the C5 to C30 olefins; When the branching degree of the target polymer is 100 to 150 / 1000C, the monomer of the C4 to C30 olefin is any one or more of the C6 to C30 olefins; When the branching degree of the target polymer is 80 to 100 / 1000C, the monomer of the C4 to C30 olefin is any one or more of the C8 to C30 olefins; When the branching degree of the target polymer is 50 to 80 / 1000C, the monomer of the C4 to C30 olefin is any one or more of the C10 to C30 olefins.

3. The solution polymerization method of highly branched polyethylene as claimed in claim 1, characterized in that: The content of C4-C30 olefin monomers in the polymerization system is 50-100 mol%.

4. The solution polymerization method of highly branched polyethylene as claimed in claim 1, characterized in that: The late transition metal complex catalyst includes one or more complexes of nickel, palladium and iron.

5. The solution polymerization method of highly branched polyethylene as claimed in claim 4, characterized in that: The late transition metal complex catalyst includes one or more of α-diimine nickel complex and α-diimine palladium complex.

6. The solution polymerization method of highly branched polyethylene according to claim 1, characterized in that: The catalytic system also includes a co-catalyst, wherein the co-catalyst includes one or more of aluminoxane, modified aluminoxane, alkylaluminum, alkylaluminum chloride or B(C6F5)3.

7. The solution polymerization method of highly branched polyethylene as claimed in any one of claims 1 or 3, characterized in that: The polymerization system also includes a diene monomer selected from one or more of ethylidene norbornene, dicyclopentadiene, 1,4-hexadiene, 1,7-octadiene, 6,10-dimethyl-1,5,9-undecadiene, 3,7-dimethyl-1,6-octadiene, 5,7-dimethyl-1,6-octadiene, and 7-methyl-1,6-octadiene.

8. The solution polymerization method of highly branched polyethylene as claimed in any one of claims 1, 3 or 7, characterized in that: The polymerization system further comprises a molecular weight regulator selected from one or more of diethyl zinc and hydrogen.

9. The solution polymerization method of highly branched polyethylene according to claim 1, characterized in that: The polymerization or copolymerization temperature is 30-150° C. and the pressure is 0.1-5 MPa.

10. The solution polymerization method of highly branched polyethylene according to claim 9, characterized in that: The polymerization or copolymerization temperature is 50-90° C. and the pressure is 0.5-2.0 MPa.

11. The solution polymerization method of highly branched polyethylene according to claim 1, characterized in that: The case of lacking an inert solvent includes one of the cases of no inert solvent or the case of using a small amount of an inert solvent or a diluent inevitably to meet the needs of the main catalyst or the co-catalyst.

12. The solution polymerization method of highly branched polyethylene according to any one of claims 1 to 11, characterized in that: The solution polymerization method includes one or more of batch operation, semi-continuous operation or continuous operation.

13. The solution polymerization method of highly branched polyethylene according to claim 12, characterized in that: The solution polymerization method further comprises a post-treatment step, wherein the post-treatment step comprises achieving a polymer-rich phase-polymer-poor phase liquid-liquid phase separation operation by changing the system temperature and / or pressure, thereby obtaining the target polymer highly branched polyethylene.

14. The solution polymerization method of highly branched polyethylene according to claim 13, characterized in that: The monomer or comonomer of the target polymer high-branched polyethylene obtained by the solution polymerization method is C4-C6 olefin.

15. The highly branched polyethylene obtained by the solution polymerization method of highly branched polyethylene according to any one of claims 1 to 11 or 14, characterized in that: The number average molecular weight of the highly branched polyethylene is 1000-1500000, and the molecular weight distribution index is 1.2-2.

5.

16. The use of the highly branched polyethylene according to claim 15, characterized in that: The applications include applications in the fields of photovoltaic films, rubber, and polymer modifiers.

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