Linear medium-low density ethylene-based polymers with polar groups

Abstract

The present application provides a linear medium-low density ethylene-based polymer with polar groups. The polymer has a side chain end group as shown in formula (I) in the molecular chain, and has a side chain as shown in formula (II) B chain segment group, and has or does not have a side chain as shown in formula (III) C chain segment group, and has a D chain segment group as shown in formula (IV), wherein R is a linear alkyl group with ≥6 carbon atoms. The present application introduces an ester group into the polyethylene molecular chain, and obtains a linear medium-low density polyethylene with a new structure.

Description

Technical Field

[0001] This invention relates to a linear low-density vinyl polymer with polar groups, belonging to the field of polyethylene technology. Background Technology

[0002] Linear low-density polyethylene (LDPE) is a high-molecular-weight resin material with short carbon-based branches in its molecular chain, obtained by polymerization of ethylene as the main raw material. It is non-toxic, odorless, has a high softening temperature and melting temperature, and good resistance to environmental stress cracking, impact strength, and tear strength. It has been widely used in industry, agriculture, medicine and health, and daily necessities.

[0003] However, existing linear low-density polyethylene products lack polar groups in their structure, resulting in poor compatibility with polar engineering resins such as polycarbonate (PC) and acrylonitrile-styrene-butadiene copolymer (ABS), poor adhesion to non-resin materials such as metals and paper, and poor printability, dyeability, and wettability, which limits their applications.

[0004] To broaden its application scope, existing technologies mainly employ post-functionalization methods to introduce polar groups into linear low-density polyethylene. CN101698691A discloses a method for grafting glycidyl methacrylate, methyl acrylate, and an anti-crosslinking agent onto linear low-density polyethylene using melt blending technology. However, this method can only modify a portion of the material and suffers from drawbacks such as low methyl acrylate grafting rate and easy crosslinking, resulting in less than ideal effects.

[0005] In addition, existing technologies also employ high-pressure free radical polymerization to produce polar monomers such as ethylene-vinyl acetate copolymer (EVA), ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-butyl acrylate copolymer (EBA), ethylene-acrylic acid copolymer (EAA), and their ionomers, which are copolymers of ethylene and polar monomers. CN107001524A discloses a vinyl polymer and its application as a phase change heat storage material with excellent deformation properties, which can achieve the purpose of energy saving and carbon reduction. However, it adopts a high-pressure method, which requires reaction pressure of 150-300 MPa and reaction temperature of 150-300℃. The process conditions are harsh and the safety requirements are high. Its molecular structure is a dendritic random polymer with high randomness, and there is currently no means to control it.

[0006] Therefore, developing structurally controllable ethylene polar copolymers and their production methods has always been a research hotspot. Low-pressure coordination polymerization using post-transition metal catalysts offers a possibility for this. Brookhart et al. reported on diimine-type post-transition metal catalysts, where polar groups such as ester groups are randomly distributed at the ends of branched chains via a chain-walking mechanism, yielding branched ethylene polymers containing polar groups. CN101186660A, CN111362838A, CN107474077A, CN105968027A, CN105152970A, CN113651909A, CN113603611A, and others disclose a series of diimine-type nickel and palladium catalysts used for the polymerization of ethylene with polar monomers such as methyl acrylate, yielding polyethylene products with a branching degree of 10–150 branches / 1000C, with branches including methyl, ethyl, butyl, and C6 groups. + The alkyl and ester content is between 0.1 mol% and 15 mol%. Grubbs et al. reported salicylaldehyde imine-type post-transition metal catalysts. CN109021009A, CN113773211A, and others disclosed a series of salicylaldehyde imine post-transition metal catalysts. The characteristic of this type of catalyst for copolymerization of ethylene and methyl acrylate is that the ester content in the polymer can be as high as 70 mol%.

[0007] However, the main content disclosed in the aforementioned literature concerns the structure and preparation methods of catalysts, with limited information on vinyl polymer products. Analysis of the literature shows that different precursor structures of catalysts result in different structures and properties of the products. By modulating the precursor structure of the catalyst, new structures and properties can be imparted to the products, leading to new performance characteristics and applications. Therefore, based on post-transition metal catalysts and coordination polymerization methods, controlling the precursor structure of catalysts to regulate the structure and properties of polymers at the molecular level, and developing new polar linear low-density polyethylene, has significant practical implications. Summary of the Invention

[0008] To address the aforementioned technical problems, the present invention aims to provide a linear low-density vinyl polymer with polar groups. The present invention introduces ester groups into the polyethylene molecular chain, and ensures that the polyethylene molecule contains only methyl and ester groups, with or without trace amounts of long branches (the number of branched carbon atoms ≥ 6), thus obtaining a linear low-density polyethylene with a novel structure.

[0009] To achieve the above objectives, the present invention provides a linear low-to-medium density vinyl polymer with polar groups, wherein the molecular chain has an A-type repeating group as shown in formula (I) introduced by methyl acrylate monomers and having ester-terminated side chains; a B-type repeating group as shown in formula (II) introduced by ethylene monomers and having methyl side chains; a C-type repeating group as shown in formula (III) introduced by ethylene monomers and having non-methyl side chains; and a D-type repeating group as shown in formula (IV) introduced by ethylene monomers.

[0010]

[0011]

[0012] In formula (III), R is a straight-chain alkyl group with ≥6 C atoms;

[0013] Based on a total molar percentage of 100 mol% for the A-chain and D-chain groups, the molar percentage of the A-chain group is 1 mol%-30 mol%, and the molar percentage of the D-chain group is 70 mol%-99 mol%.

[0014] Based on a total molar amount of 100 mol% for the A-chain group, the B-chain group, and the C-chain group, the molar amount of the A-chain group is 50 mol%-90 mol%, and the total molar amount of the B-chain group and the C-chain group (when the C-chain group is present) is 10 mol%-50 mol%.

[0015] According to a specific embodiment of the present invention, preferably, the above-mentioned linear low-density vinyl polymer with polar groups does not contain any groups other than the A-joint group, the B-joint group, the C-joint group, and the D-joint group.

[0016] In the aforementioned linear low-density vinyl polymers with polar groups, preferably, in formula (III), R does not contain heteroatoms (i.e., O, S, N, etc.), nor does it contain the groups shown in formula (V), the groups shown in formula (VI), or cyclic molecular structures.

[0017]

[0018] In the aforementioned linear low-density vinyl polymers with polar groups, preferably, the D-chain segment group is located in the main chain and branches of the linear low-density vinyl polymer with polar groups, the A-chain segment group and the B-chain segment group are located in the branches of the linear low-density vinyl polymer with polar groups, and when the polymer has the C-chain segment group, the C-chain segment group is also located in the branches of the linear low-density vinyl polymer with polar groups.

[0019] In the aforementioned linear low-density vinyl polymers with polar groups, preferably, the molar ratio of the A-chain group, the B-chain group, and the C-chain group is (50–90):(5–50):(0–10). More preferably, the molar ratio of the A-chain group, the B-chain group, and the C-chain group is (70–90):(5–30):(0–10). Particularly preferably, the molar ratio of the A-chain group, the B-chain group, and the C-chain group is (70–90):(5–30):(0–5).

[0020] In the above-mentioned linear low-density vinyl polymers with polar groups, preferably, based on a total molar amount of 100 mol% for the A-chain group and the D-chain group, the molar amount of the A-chain group is 5 mol%-17 mol% and the molar amount of the D-chain group is 83 mol%-95 mol%.

[0021] In the above-mentioned linear low-density vinyl polymers with polar groups, preferably, based on the total molar amount of the A-chain group, the B-chain group and the C-chain group being 100 mol%, the molar amount of the A-chain group is 70 mol%-90 mol%, and the total molar amount of the B-chain group and the C-chain group (when the C-chain group is present) is 10 mol%-30 mol%.

[0022] According to a specific embodiment of the present invention, preferably, the total branching degree of the linear low-density vinyl polymer with polar groups is 6 to 177 branches / 1000C, more preferably 20 to 150 branches / 1000C.

[0023] According to a specific embodiment of the present invention, preferably, the methyl acrylate insertion rate of the linear low-density vinyl polymer with polar groups is 1 to 30 ω% (based on the total weight of the polymer being 100%).

[0024] According to a specific embodiment of the present invention, preferably, the weight-average molecular weight of the linear low-density vinyl polymer with polar groups is 0.07 × 10⁻⁶. 5 g / mol~2.1×105 The molecular weight distribution index is 1–3, and the weight-average molecular weight is 1 × 10⁻³ g / mol. More preferably, the linear low-density vinyl polymer with polar groups has a weight-average molecular weight of 1 × 10⁻³ g / mol. 5 g / mol~2.1×10 5 g / mol, with a molecular weight distribution index of 1–2.

[0025] According to a specific embodiment of the present invention, preferably, the density of the linear low-density vinyl polymer with polar groups is 0.920–0.940 kg / m³. 3 The melt flow index is ≥5 g / 10 min, the melting point is 70–110 °C, the haze is ≤12%, and the water contact angle is ≤52°. More preferably, the linear low-density vinyl polymer with polar groups has a density of 0.930–0.940 kg / m³. 3 Melt flow index ≥10g / 10min, melting point 70~80℃, haze ≤5%, water contact angle ≤45°.

[0026] According to a specific embodiment of the present invention, preferably, the above-mentioned linear low-density vinyl polymer with polar groups can be prepared by the following steps; however, the polymer of the present invention is not limited to being prepared by the following steps, which include:

[0027] An alkyldiimide nickel or palladium complex is used as the main catalyst (i.e., the catalyst precursor) and an organoaluminum compound is used as the co-catalyst to form a catalyst system; ethylene and methyl acrylate monomers are polymerized in a solvent and in the presence of the catalyst system. After the reaction is completed, the linear low-density vinyl polymer with polar groups is obtained.

[0028] The main catalyst has a structure as shown in formula (VII).

[0029]

[0030] In formula (VII), M is nickel or palladium; R1 is selected from C6-C 30 aryl, C4-C 30 The cycloalkyl group; R2 and R3 may be the same or different, and R2 and R3 are each independently selected from H, C1-C8 straight-chain or branched alkyl groups; R4 and R5 may be the same or different, and R4 and R5 are each independently selected from C6-C8. 30 Aryl groups, or R4 and R5, together with adjacent carbon atoms, form acenaphthenic groups or C4-C groups. 30 cycloalkyl groups.

[0031] In the above preparation steps, preferably, in formula (VII), R1 is selected from phenyl, naphthyl, C4-C 30The cycloalkyl group; R2 and R3 may be the same or different, and R2 and R3 are each independently selected from H, methyl; R4 and R5 are phenyl, or R4 and R5 together with the adjacent carbon atom form an acenaphthenic group or a C4-C group. 30 The cycloalkyl group. More preferably, in formula (VII), R1 is phenyl or naphthyl; R2 and R3 are the same or different, and R2 and R3 are each independently selected from H, methyl (especially preferably, R2 is methyl, R3 is H or methyl); R4 and R5 are phenyl, or R4 and R5 together with the adjacent carbon atom form an acenaphthenic group.

[0032] The catalyst precursor used in this invention has the following characteristics: a sterically hindered group R1 and a sterically hindered group R2 are simultaneously located at the adjacent positions of the carbon atom of the benzene ring connected to N, forming an asymmetric structure; simultaneously, the framework of the same ligand contains sterically hindered groups R4 and R5. A preferred feature of the catalyst precursor of this invention is that a sterically hindered naphthyl or phenyl group and a sterically hindered methyl group are simultaneously located at the adjacent positions of the carbon atom of the benzene ring connected to N, and the framework contains a sterically hindered acenaphthenic or phenyl group.

[0033] In the above preparation steps, preferably, the polymerization reaction temperature is 0–150°C, the polymerization reaction pressure (i.e., ethylene pressure) is 0.1–10 MPa, and the polymerization reaction time is 0.1–24 h. More preferably, the polymerization reaction temperature is 20–100°C, the polymerization reaction pressure is 0.5–5 MPa, and the polymerization reaction time is 0.5–4 h.

[0034] In the above preparation steps, preferably, the organoaluminum compound includes one or a combination of several of alkylaluminum compounds, haloalkylaluminum compounds, and alkoxyaluminum compounds. More preferably, the organoaluminum compound includes one or a combination of several of methylaluminoxane (MAO), modified methylaluminoxane (MMAO), and isobutylaluminoxane (BAO).

[0035] In the above preparation steps, preferably, the solvent includes one or a combination of several of 1,2-dichloroethane, n-hexane, chlorobenzene, toluene, and xylene.

[0036] In the above preparation steps, the molar ratio of the main catalyst and the co-catalyst, as well as the molar ratio of the methyl acrylate monomer and the main catalyst, can be conventionally adjusted by those skilled in the art.

[0037] According to a specific embodiment of the present invention, preferably, the above preparation steps further include: after the reaction is completed, adding a terminator to terminate the reaction, thereby obtaining the linear low-density vinyl polymer with polar groups. More preferably, the terminator includes hydrochloric acid ethanol solution and / or hydrochloric acid methanol solution, etc.; particularly preferably, the volume concentration of the hydrochloric acid ethanol solution is 1-5%, and the volume concentration of the hydrochloric acid methanol solution is 1-5%. The amount of the terminator added can be conventionally adjusted by those skilled in the art.

[0038] In the preparation steps of the linear low-density vinyl polymer with polar groups of the present invention, after terminating the reaction by adding a terminator, the reaction product may be further subjected to steps such as washing, filtering, and drying to obtain the linear low-density vinyl polymer with polar groups. Washing, filtering, and drying are all conventional operations in the art, and the present invention does not specifically limit them.

[0039] This invention employs an alkyldiimine nickel or palladium complex catalyst with a specific structure and a coordination polymerization method to polymerize ethylene with methyl acrylate, introducing ester groups into the polyethylene molecular chain. Through the catalyst precursor, the polyethylene molecule contains only methyl and ester groups, with or without trace amounts of long branches (the number of branched C atoms is ≥6), resulting in a novel linear low-density polyethylene.

[0040] The linear low-density vinyl polymers with polar groups provided by this invention include, but are not limited to, the following technical effects.

[0041] Beneficial effect 1: By introducing polar ester groups into the linear low-density polyethylene chain, the intermolecular forces and hydrogen bonding generated by the ester groups solve the shortcomings of poor compatibility between linear low-density polyethylene and engineering resins, poor adhesion to non-resin materials such as metals and paper, and poor printability, dyeability, and wettability.

[0042] ① Compared with the high-pressure free radical polymerization process currently used in industry, the medium- and low-density linear polyethylene with polar groups disclosed in this invention is obtained under low-pressure and mild process conditions, with the temperature reduced by at least 50 to 100°C and the pressure reduced by at least 10 to 100 MPa.

[0043] ② Compared with post-functionalization, such as grafting technology, the insertion rate of polar monomer ester groups in the medium-low density linear polyethylene with polar groups disclosed in this invention is increased by more than 1 times.

[0044] Beneficial Effect 2: This invention utilizes a catalyst with a specific alkyldiimide nickel or palladium complex and a coordination polymerization method to polymerize ethylene with methyl acrylate, resulting in a novel linear low-density polyethylene with only methyl and ester groups in the polyethylene molecule, and with or without trace amounts of long branches (≥6 C atoms in the branches). Besides being polar, the branched structure of this linear low-density polyethylene differs from that of existing general-purpose linear low-density polyethylene. Because it contains only methyl branches (or also trace amounts of long branches), its crystalline structure is more regular and denser, resulting in improved mechanical properties. Its light transmittance and flexibility are better than existing general-purpose linear low-density polyethylene, and the long-chain branching has a significant impact on polymer properties and material processing performance.

[0045] Through extensive research, the inventors of this invention discovered that, for alkyldiimide post-transition metal catalysts, increasing the steric hindrance of the ortho-substituents on the benzene ring connected to N in the catalyst precursor imine and / or the steric hindrance in the backbone results in a polymer branching state primarily dominated by methyl groups, with a small amount of long-chain branching above hexyl groups. This avoids the formation of ethyl, propyl, butyl, and aryl groups, unlike the branched polyethylene obtained with Brookhart catalysts. Compared to Brookhart-type α-diimide nickel catalysts with 2,6-diisopropyl substituents at the ortho position, the catalyst precursor of this invention, with its specific sterically hindered group at the ortho position on the benzene ring connected to N, effectively controls the branching state of the polymer while minimizing the influence of temperature and ethylene pressure on the branching state.

[0046] The linear low-density vinyl polymer with polar groups provided by this invention has the following uses: Compared with polyethylene, in addition to imparting polarity, its toughness, tensile properties, and other properties are improved to varying degrees, greatly expanding its application range. The main applications include: ① Extrusion-coated products for paper, metal, textiles, or plastics, formed in powder form using plasma, flame jetting, or fluidized bed technologies; ② Glass adhesives; ③ Hot melt adhesives and pressure-sensitive adhesives; ④ Flexible packaging films and stretch films with good tensile properties; ⑤ Various hoses such as automotive heating hoses; ⑥ Insulation layers and sheaths for wires and cables; ⑦ Rigid or flexible foams; ⑧ Compatibilizers and toughening agents between polar and non-polar polymers, and internal plasticizers when polymers (such as polyvinyl chloride) are mixed; ⑨ Various additives, such as reactive diluents in automotive paints, pour point depressants and viscosity index improvers for lubricating oils, and asphalt modifiers. Furthermore, it can be further modified. The functional groups on the polymer can be used to initiate the polymerization reaction of other types of monomers. For example, the prepared fluoride can reduce liquid permeation in medical polyolefin membranes. The new polymer formed after adding appropriate functional groups can be used as a curing agent for other polymers with complementary functional groups.

[0047] In summary, this invention provides a linear low-density vinyl polymer with polar groups. This polymer is a linear low-density polyethylene product with improved toughness, transparency, and other properties. It is produced by reacting ethylene with methyl acrylate through low-pressure, in-situ coordination polymerization, introducing polar ester groups into the polyethylene backbone, thereby endowing the linear low-density polyethylene with polarity. Compared with general-purpose linear low-density polyethylene obtained by existing technologies, the ethylene-methyl acrylate copolymer proposed in this invention overcomes the disadvantage of general-purpose linear low-density polyethylene lacking polarity, significantly improves compatibility with polar engineering plastics, and exhibits excellent adhesion to non-resin materials such as metals, paper, and wood. It is particularly suitable for use as a composite packaging film, simplifying the structure of existing composite packaging films and reducing their production costs. Detailed Implementation

[0048] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0049] Examples 1-1 to 1-9

[0050] Polar medium-low density linear polyethylene obtained by copolymerization of ethylene and methyl acrylate

[0051] (1) Synthesis of the main catalyst [Ar-N=C(An)-(An)C=N-Ar]NiBr2 (An=acenaphthene, Ar=2-methyl-6-naphthyl-phenyl), which has the structure shown in formula (VIII):

[0052]

[0053] The main catalyst can be prepared using 2-methyl-6-naphthylaniline and other raw materials, according to the method provided in the literature J.Am.Chem.Soc.1996,118,267-268Supporting Information Available.

[0054] (2) Polymerization of ethylene and methyl acrylate

[0055] The polymerization reaction was carried out in a 300 mL stainless steel pressure vessel equipped with a mechanical stirrer and a pressure-resistant liquid feed pipe on the vessel lid. The vessel was purged three times with nitrogen to remove air. The vessel was heated to 150 °C under a vacuum of -0.1 MPa and held at that temperature for 2 hours, then cooled to room temperature. The vessel was then purged three more times with nitrogen, followed by three purgings with ethylene at a certain pressure. Under an ethylene atmosphere at room temperature, 200 mL of toluene, 0.2 mmol of the main catalyst, and 5 mL of 4 M MAO were injected into the vessel through the feed pipe and stirred for 30 min. Then, 5 mL of methyl acrylate was added and stirred for 10 min. Under an ethylene atmosphere at room temperature, 40 mL of a toluene solution of the main catalyst was added to the vessel through the feed pipe, maintaining a total reaction volume of 250 mL. The reaction temperature was raised to a specific temperature using an electric heater. The reaction temperature was controlled by deionized water circulating through an internal coil and the electric heater, monitored by an internal thermocouple, with a temperature control accuracy of ±1 °C. After reaching the reaction temperature, ethylene was introduced, and the pressure in the reactor was kept constant at a certain reaction pressure. The reaction was continued for a certain time. After releasing the ethylene pressure, 20 mL of 5% (v / v) acidic methanol was added to terminate the polymerization. The resulting precipitated polymer was collected, filtered, washed several times with methanol, and then dried to constant weight under vacuum at 60°C. The reaction temperature, reaction pressure, and reaction time are shown in Table 1.

[0056] Large-scale polymerization is carried out in a 10L high-pressure reactor. The reactor lid is equipped with a pressure-resistant liquid feed pipe. The amounts of ethylene and nitrogen are measured using an online mass flow meter. The reaction temperature is uniformly raised by electrically heating the heat transfer oil in the reactor's outer jacket. The outer jacket contains coils through which deionized water or other cooling media can be circulated. The reaction temperature is controlled within the desired range by online adjustment of the cooling water flow rate and by heating the heat transfer oil via the electric heater. Temperature is monitored by thermocouples inside the reactor, providing feedback to the temperature controller with a temperature control accuracy of ±1℃. The reactor is purged with nitrogen three times to remove air. The reactor is then heated to 150℃ under a vacuum of -0.1MPa and held at that temperature for 2 hours, then cooled to room temperature. The reactor is then purged with nitrogen three more times, followed by pressurization with ethylene at a certain pressure, and this process is repeated three times. Under an ethylene atmosphere at room temperature, 2L of toluene and 50mL of a 4M MAO toluene solution were injected into the reactor through a feed pipe. Under the same ethylene atmosphere at room temperature, 1L of a 0.2mmol main catalyst toluene solution was added to the reactor through the feed pipe, and the mixture was stirred for 30 minutes. 100mL of methyl acrylate was then added. The reactor temperature was raised to a specific reaction temperature using an electric heater. Once the reaction temperature was reached, ethylene was introduced, and the reactor pressure was maintained at a constant reaction pressure. The reaction was continued for a certain time. After releasing the ethylene pressure, 1L of 5% (v / v) acidic methanol was added to terminate the polymerization. The reactants were then discharged from the bottom of the reactor into a separator through a discharge valve. The separator had a two-layer structure; the upper layer was equipped with a stirring device suitable for solid-liquid systems, and a filter screen was installed between the upper and lower layers. Upon starting the separator's stirring, the liquid in the reactants automatically fell into the lower part of the separator and was then transferred to another sealed container for recycling. A stream of hot, dry nitrogen or air is introduced into the lower part of the separator to dry the remaining solid reactants on the upper part of the separator screen. The gas is discharged from the top of the separator. The organic matter content in the gas is monitored periodically. When the organic matter content is ≤100ppm, the solid reactants in the separator are collected, washed with methanol, filtered, and dried several times. Finally, they are dried to constant weight under vacuum at 60℃. The reaction temperature, reaction pressure, and reaction time are shown in Table 1.

[0057] The experimental results of the polymerization of ethylene and methyl acrylate are shown in Table 1.

[0058] (3) Structural analysis and performance testing of polymers

[0059] The structural analysis results of the polymer are shown in Tables 2, 3-1, and 3-2, and the performance analysis data of the polymer are shown in Table 4.

[0060] (4) Sources of raw materials and equipment:

[0061] Ethylene, polymerization grade, purity 99.9%, PetroChina Daqing Branch;

[0062] Methyl acrylate, analytical grade, 98.5%, containing 0.05% MEHQ stabilizer, Shanghai Aladdin Biochemical Technology Co., Ltd.

[0063] 2-Methyl-6-naphthylaniline, purity 99.0%, prepared in-house;

[0064] MAO, 2M hexane solution, Chengdu Boruit Chemical Technology Co., Ltd.;

[0065] Acenathoquinone, 98%, Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0066] (DME)NiBr2, 96%, Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0067] Toluene, analytical grade, 99.5%, Nanjing Chemical Reagent Co., Ltd.

[0068] 300mL pressure-resistant reactor, 10L reactor, Yantai Keli Chemical Equipment Co., Ltd.

[0069] (5) Evaluation and analysis methods:

[0070] The structural analysis of the ligands in the main catalyst was performed using a Varian Mercury-Plus nuclear magnetic resonance spectrometer. ¹H NMR testing conditions: tetramethylsilane (TMS) as the reference solution and CDCl₃ as the solvent. 13 C NMR testing conditions:

[0071] Elemental analysis of the ligands of the main catalyst was performed using a Vario EL trace element analyzer.

[0072] Mass spectrometry analysis of the main catalyst was performed using electrospray ionization (ESI) LCMS-2010A. Bromide analysis of the main catalyst was performed using matrix-assisted laser desorption / ionization time-of-flight mass spectrometry (MALDI-TOF-MS) on a Bruker ultrafleXtreme instrument.

[0073] The structural analysis of the polymer was performed using a Bruker-500 nuclear magnetic resonance spectrometer. The 1H NMR testing conditions were: frequency 300 Hz, 120 °C, with CDCl3 as the solvent. 13 C NMR testing conditions: frequency 75 Hz, CDCl3 as solvent, tilt angle 74°, delay time 4 s, sampling time 1.5 s, measurement method: proton decoupling method.

[0074] Polymer molecular weight and molecular weight distribution were determined using a PE CR-7 gel permeation chromatograph. Conditions: 135℃, 1,2,4-trichlorobenzene as eluent, flow rate 1.0 mL / min.

[0075] The melting point of the polymer was determined using a TE Q2000 differential scanning calorimeter. The temperature was increased to 170°C at a rate of 10°C / min, held for 5 min, and then decreased to 50°C at a rate of 10°C / min. The heating and cooling curves were recorded.

[0076] The density of the polymer was analyzed using the method in GB / T10332-2010, using a CEAST 6001 density meter.

[0077] The melt flow index of the polymer was analyzed using the method in GB / T 3682-2018, with a CEAST 6542 melt flow rate meter, a die diameter of 2.095 μm, a temperature of 190 °C, an accuracy of 0.1 °C, and a load of 2.16 kg.

[0078] The haze and transmittance of the polymer were analyzed according to GB / T 2410-2008.

[0079] The water contact angle of the polymer was measured using a Kyowa G-1 contact angle meter. Deionized water was dropped onto the film surface and tested 1 minute later. For each sample, three points with a 5mm gap between the droplets were measured, for a total of six readings, and the arithmetic mean was taken. The droplet volume was controlled between 1 and 5 microliters.

[0080] (6) Calculation method:

[0081] The ester content in the polymer was calculated according to the method provided in CN107001524A.

[0082] Examples 2-1 to 2-9

[0083] Polar medium-low density linear polyethylene obtained by copolymerization of ethylene and methyl acrylate

[0084] (1) Synthesis of the main catalyst [Ar-N=C(An)-(An)C=N-Ar]NiBr2 (An=phenyl, Ar=2,4-dimethyl-6-phenyl-phenyl), which has the structure shown in formula (IX):

[0085]

[0086] The main catalyst can be prepared using 2,4-dimethyl-6-phenyl-aniline and other similar raw materials, through a method similar to that in Example 1.

[0087] (2) Polymerization of ethylene and methyl acrylate

[0088] The polymerization reaction method and conditions are the same as those in the foregoing examples.

[0089] (3) Structural analysis and performance testing of polymers

[0090] The specific methods for polymer structure analysis and performance testing are the same as those in the aforementioned examples.

[0091] The experimental results of the polymerization of ethylene and methyl acrylate are shown in Table 1, the structural analysis results of the polymer are shown in Tables 2, 3-1 and 3-2, and the performance analysis data of the polymer are shown in Table 4.

[0092] Comparative Example 1

[0093] (1) Synthesis of the catalyst precursor [Ar-N=C(An)-(An)C=N-Ar]NiBr2 (An=acenaphthene, Ar=2,6-diisopropyl-phenyl), which has the structure shown in formula (X):

[0094]

[0095] The catalyst precursor can be prepared using 2,6-diisopropylaniline or similar raw materials, and the method is similar to that in Example 1.

[0096] (2) Polymerization of ethylene and methyl acrylate

[0097] The polymerization reaction method and conditions are the same as those in the foregoing examples.

[0098] (3) Structural analysis and performance testing of polymers

[0099] The specific methods for polymer structural analysis and performance testing are the same as those in the aforementioned examples. Reaction temperature, reaction pressure, and reaction time are shown in Table 1.

[0100] The experimental results of the polymerization of ethylene and methyl acrylate are shown in Table 1, the structural analysis results of the polymer are shown in Tables 2, 3-1 and 3-2, and the performance analysis data of the polymer are shown in Table 4.

[0101] Linear low-density polyethylene samples collected from the market were analyzed. The results of the polymer structural analysis are shown in Tables 2, 3-1, and 3-2, and the polymer performance analysis data are shown in Table 4.

[0102] Reference: Zhang Qingyi, “Comparison of structure and properties of mLLDPE and LLDPE”, Synthetic Resins and Plastics, 2020, 37(6):55.

[0103] Comparative Example 2

[0104] DFDA7042, 1-Butene Copolymer LLDPE, manufactured by PetroChina Company Limited.

[0105] Comparative Example 3

[0106] 7042, 1-Butene copolymer LLDPE, grafted with methyl acrylate, provided by Changchun Institute of Applied Chemistry, Chinese Academy of Sciences.

[0107] Table 1 Results of ethylene-methyl acrylate polymerization

[0108]

[0109]

[0110] Note: a, 1×10 5 g / molcat, b, 1×10 5 g / mol.

[0111] Table 2 Results of polymer alkyl branched chain structure analysis

[0112]

[0113]

[0114] Note: a. Mole percentage (based on a total alkyl branch count of 100%)

[0115] Table 3-1 Results of polymer structure analysis

[0116]

[0117] Note: a. Weight percentage (based on the total weight of the polymer as 100%).

[0118] b moles, number of ester units = Mw × ester content (ω%) ÷ 59.

[0119] c-ethyl unit number = Mw × (1-ester content (ω%)) ÷ 28.

[0120] d Total number of units = Number of ester units + Number of ethyl units

[0121] e-ester branching = 500 * 2 * number of ester units / total number of units.

[0122] Table 3-2 Results of polymer structure analysis

[0123]

[0124] Note a: Alkyl branching is... 13 Calculation of C NMR spectral data.

[0125] Table 4. Results of polymer performance analysis

[0126]

[0127]

[0128] As can be seen from the above data, this invention uses an alkyldiimine nickel or palladium complex catalyst with a specific structure and a coordination polymerization method to polymerize ethylene and methyl acrylate, introducing ester groups into the polyethylene molecular chain. Through this specific catalyst precursor, the polyethylene molecule contains only methyl and ester groups, with or without trace amounts of long branches (the number of C atoms in the branches is ≥6), and without other branches such as ethyl, propyl, butyl, pentyl, and aryl, resulting in a new type of linear low-density polyethylene.

Claims

1. A linear low-density vinyl polymer with polar groups, wherein the molecular chain has an A-type repeating group as shown in formula (I) introduced by methyl acrylate monomer and having ester-terminated side chains, and a B-type repeating group as shown in formula (II) introduced by ethylene monomer and having methyl side chains, and the molecular chain has or does not have a C-type repeating group as shown in formula (III) introduced by ethylene monomer and having non-methyl side chains, and the molecular chain has a D-type repeating group as shown in formula (IV) introduced by ethylene monomer. Formula (I) Equation (II) Equation (III) Formula (IV) in, In formula (III), R is a straight-chain alkyl group with ≥6 C atoms; Based on a total molar percentage of 100 mol% for the A-chain and D-chain groups, the molar percentage of the A-chain group is 1 mol%-30 mol%; and Based on a total molar amount of 100 mol% for the A-chain group, the B-chain group, and the C-chain group, the molar amount of the A-chain group is 50 mol%-90 mol, and the total molar amount of the B-chain group and the C-chain group is 10 mol%-50 mol.

2. The linear low-density vinyl polymer with polar groups according to claim 1, wherein, In formula (III), R does not contain heteroatoms, nor does it contain the groups shown in formula (V), the groups shown in formula (VI), or cyclic molecular structures. Equation (V) Formula (VI).

3. The linear low-density vinyl polymer with polar groups according to claim 1, wherein, The D-chain repeating group is located in the main chain and branches of the linear low-density vinyl polymer with polar groups, the A-chain repeating group and the B-chain repeating group are located in the branches of the linear low-density vinyl polymer with polar groups, and when the polymer has the C-chain repeating group, the C-chain repeating group is also located in the branches of the linear low-density vinyl polymer with polar groups.

4. The linear low-to-medium density vinyl polymer with polar groups according to claim 1, wherein, The molar ratio of the A-chain group, the B-chain group, and the C-chain group is (50-90):(5-50):(0-10).

5. The linear low-to-medium density vinyl polymer with polar groups according to claim 4, wherein, The molar ratio of the A-chain group, the B-chain group, and the C-chain group is (70-90):(5-30):(0-10).

6. The linear low-to-medium density vinyl polymer with polar groups according to claim 5, wherein, The molar ratio of the A-chain group, the B-chain group, and the C-chain group is (70-90):(5-30):(0-5).

7. The linear low-to-medium density vinyl polymer with polar groups according to claim 1, wherein, Based on a total molar percentage of 100 mol% for the A-chain group and the D-chain group, the molar percentage of the A-chain group is 5 mol% to 17 mol%.

8. The linear low-to-medium density vinyl polymer with polar groups according to claim 1, wherein, Based on a total molar amount of 100 mol% for the A-chain group, the B-chain group, and the C-chain group, the molar amount of the A-chain group is 70 mol% to 90 mol%, and the total molar amount of the B-chain group and the C-chain group is 10 mol% to 30 mol%.

9. The linear low-to-medium density vinyl polymer with polar groups according to claim 1, wherein, The total branching degree of the linear low-density vinyl polymer with polar groups is 6~177 branches / 1000C.

10. The linear low-to-medium density vinyl polymer with polar groups according to claim 9, wherein, The total branching degree of the linear low-density vinyl polymer with polar groups is 20~150 branches / 1000C.

11. The linear low-to-medium density vinyl polymer with polar groups according to claim 1, wherein, The linear low-density vinyl polymer with polar groups has a weight-average molecular weight of 0.07 × 10⁻⁶. 5 g / mol ~2.1×10 5 g / mol, with a molecular weight distribution index of 1~3.

12. The linear low-to-medium density vinyl polymer with polar groups according to claim 11, wherein, The linear low-density vinyl polymer with polar groups has a weight-average molecular weight of 1×10⁻⁶. 5 g / mol ~2.1×10 5 g / mol, with a molecular weight distribution index of 1~2.

13. The linear low-to-medium density vinyl polymer with polar groups according to claim 1, wherein, The linear low-to-medium density vinyl polymer with polar groups has a density of 0.920~0.940 kg / m³. 3 Melt flow index ≥5g / 10min, melting point 70~110℃, haze ≤12%, water contact angle ≤52°.

14. The linear low-to-medium density vinyl polymer with polar groups according to claim 13, wherein, The linear low-density vinyl polymer with polar groups has a density of 0.930~0.940 kg / m³. 3 Melt flow index ≥10g / 10min, melting point 70~80℃, haze ≤5%, water contact angle ≤45°.

15. The linear low-to-medium density vinyl polymer with polar groups according to claim 1, wherein, The methyl acrylate insertion rate of the linear low-density vinyl polymer with polar groups is 1-30w.

16. The linear low-to-medium density vinyl polymer with polar groups according to claim 1, wherein, The polymer is prepared by the following steps: An alkyldiimide nickel or palladium complex is used as the main catalyst and an organoaluminum compound is used as the co-catalyst to form a catalyst system. Ethylene and methyl acrylate monomers are polymerized in a solvent and in the presence of the catalyst system. After the reaction is completed, the linear low-density vinyl polymer with polar groups is obtained. The main catalyst has a structure as shown in formula (VII). Equation (VII) In formula (VII), M is nickel or palladium; R1 is selected from C6-C 30 aryl, C4-C 30 The cycloalkyl group; R2 and R3 may be the same or different, and R2 and R3 are each independently selected from H, C1-C8 straight-chain or branched alkyl groups; R4 and R5 may be the same or different, and R4 and R5 are each independently selected from C6-C8. 30 Aryl groups, or R4 and R5, together with adjacent carbon atoms, form acenaphthenic groups or C4-C groups. 30 cycloalkyl groups.

17. The linear low-to-medium density vinyl polymer with polar groups according to claim 16, wherein, In formula (VII), R1 is selected from phenyl, naphthyl, C4-C 30 The cycloalkyl group; R2 and R3 may be the same or different, and R2 and R3 are each independently selected from H, methyl; R4 and R5 are phenyl, or R4 and R5 together with the adjacent carbon atom form an acenaphthenic group or a C4-C group. 30 cycloalkyl groups.

18. The linear low-to-medium density vinyl polymer with polar groups according to claim 17, wherein, In formula (VII), R1 is phenyl or naphthyl; R2 and R3 are the same or different, and R2 and R3 are each independently selected from H and methyl; R4 and R5 are phenyl, or R4 and R5 together with the adjacent carbon atom form acenaphthenic.

19. The linear low-to-medium density vinyl polymer with polar groups according to claim 16, wherein, The polymerization reaction is carried out at a temperature of 0~150℃, at a pressure of 0.1~10MPa, and for a time of 0.1~24h.

20. The linear low-to-medium density vinyl polymer with polar groups according to claim 19, wherein, The polymerization reaction is carried out at a temperature of 20-100℃, at a pressure of 0.5-5MPa, and for a time of 0.5-4h.

21. The linear low-to-medium density vinyl polymer with polar groups according to claim 16, wherein, The organoaluminum compounds include one or a combination of several of alkylaluminum compounds, haloalkylaluminum compounds, and alkoxyaluminum compounds.

22. The linear low-to-medium density vinyl polymer with polar groups according to claim 21, wherein, The organoaluminum compounds include one or more of methylaluminoxane, modified methylaluminoxane, and isobutylaluminoxane.

Images