Application method of composite external electron donor for controlling ethylene polymerization hydrogen regulation and comonomer distribution

Abstract

The invention discloses an application method of a composite external electron donor for controlling ethylene polymerization hydrogen regulation and comonomer distribution, and belongs to the field of ethylene polymerization catalysis. The composite external electron donor comprises halogenated ether with the molar percentage of 70-90 mol% and succinic acid ester with the molar percentage of 10-30 mol%. By means of the synergistic effect of the composite electron body, the catalyst composition improves the hydrogen regulation performance, increases the comonomer content and regulates and controls the distribution of comonomers at the same time. Therefore, the high-melt-index polyethylene resin with higher mechanical property and processability is prepared, and fibers prepared from the high-melt-index polyethylene resin as a raw material through hot air spinning have better spinnability.

Description

Technical Field

[0001] The present invention belongs to the field of ethylene polymerization catalysis, and particularly relates to an application method of a composite external electron donor for controlling hydrogen regulation and comonomer distribution in ethylene polymerization. Background Art

[0002] In existing polyethylene production processes and products, Ziegler-Natta catalysts are the most mature catalyst systems in industrial applications and the most practically valuable. After five generations of development, a catalyst system has been formed with MgCl 2 supported TiCl 4 as the main catalyst and an electron donor of AlEt 3 added. To meet various subsequent hot processing requirements of polyethylene resins, it is usually necessary for polyethylene resins to have a relatively high melt flow rate, i.e., melt index (MFR). Industrially, the method of increasing hydrogen is usually used to increase the MFR of polyethylene, but the amount of hydrogen added is limited by the reactor. Therefore, the hydrogen regulation sensitivity of the catalyst is particularly important. The addition of a compounded external electron donor can effectively improve the hydrogen regulation sensitivity of the catalyst. At the same time, in order to improve the mechanical and processing properties of polyethylene resins and their processed products, such as the elongation at break of polyethylene and the definite elongation strength of polyethylene fibers, it is necessary to regulate the comonomer content and distribution of polyethylene resins, and the addition of a compounded external electron donor is also required.

[0003] The mechanism of action of the external electron donor is as follows: Adsorbing on the Ti active center to deactivate the random active center, increasing the proportion of isotactic active centers, and thus improving the stereospecificity of catalytic polymerization and the isotacticity of synthesized polyolefins; Adsorbing on the carrier around the Ti active center to stabilize the Ti active center, improving the catalytic activity and the stability of its stereospecificity; Adsorbing on the carrier around the random active center and converting some random active centers into isotactic active centers; Reacting with the cocatalyst alkyl complex to prevent the titanium active center from being overly reduced by alkylaluminum to inactive Ti 2+ so as to increase the number of active centers.

[0004] Patent Composite Internal Electron Donor, Catalyst and Application in the Synthesis of High-Melt-Index Polypropylene (CN115785311 A) obtains higher hydrogen regulation sensitivity by regulating the molecular weight and isotacticity. A composite internal electron donor is provided, and its structure is as shown below. The composite internal electron donor can interact with the active center of the catalyst, thereby regulating the molecular weight, molecular weight distribution, and isotacticity of the polypropylene obtained by polymerization, and thus having better hydrogen regulation sensitivity and a higher melt index of the synthesized polypropylene product. However, it cannot simultaneously increase the comonomer content and regulate the comonomer distribution, which is not conducive to the regulation of product density and mechanical properties and the research and development of high-performance products.

[0005] Patent: Catalyst Component for Ethylene Polymerization, Its Preparation Method, Catalyst and Application (CN112707979 A). At least one titanium compound, electron donor compound I (unit carboxylic acid ester compound) and electron donor compound II (diol ester compound) are supported on a solid substance containing magnesium and titanium. This method requires a special preparation process to load the titanium compound and two electron donor compounds, namely unit carboxylic acid ester and polyol ester, to prepare the catalyst. It is also necessary to adjust the component contents of titanium, magnesium elements and electron donor compounds in the catalyst simultaneously. The process is too complex and the cost is relatively high during the preparation and application processes.

[0006] Patent: External Electron Donor Composition, Propylene Polymerization Catalytic Composition and Propylene Polymerization Method (CN 115873155B) relates to an external electron donor composition, a propylene polymerization catalytic composition and a propylene polymerization method. The external electron donor composition includes an ether compound in a molar percentage of 1-98 mol%, an alkoxysilane in a molar percentage of 1-98 mol% and an ester compound in a molar percentage of 1-98 mol%. This catalyst composition can not only improve the polymerization activity at the conventional polymerization temperature of polypropylene, but also inhibit the high-temperature reaction activity, and can also improve the hydrogen response sensitivity of the catalyst. More importantly, the odor grade of the propylene polymerization product prepared is relatively low. The propylene polymer prepared by this method affects the distribution of comonomers while improving the hydrogen response performance, resulting in a decline in its mechanical processing performance.

[0007] Under normal circumstances, improving the hydrogen response performance often sacrifices the distribution performance of comonomers. Therefore, it is necessary to find the best balance point between the hydrogen response performance and the comonomer distribution performance to achieve the coordinated development of both. Summary of the Invention

[0008] In order to solve the above problems, the purpose of the present invention is to provide a method for applying a composite external electron donor to control the hydrogen response and comonomer distribution in ethylene polymerization.

[0009] In order to achieve the above purpose, the present invention adopts the following technical solutions: A composite external electron donor composition. Calculated based on the sum of molar percentages being 100%, the composite external electron donor composition includes a halogenated ether in a molar percentage of 70-90 mol% and a succinate in a molar percentage of 10-30 mol%; the halogenated ether is a cyclic halogenated ether or a chain halogenated ether having 1-10 carbon atoms, 1-2 oxygen atoms and 1-3 halogen atoms in its chemical structure.

[0010] Further, the chain halohydrin ether is one of bis(1-chloroethyl) ether, bis(2-chloroethyl) ether, bis(1-bromoethyl) ether, bromoethyl ethyl ether, bis(2-chloroethyl) ether, bis(1-chloropropyl) ether, bis(2-bromoisopropyl) ether; the cyclic halohydrin ether is one of 2,3-dichlorotetrahydrofuran, 1,3-dibromotetrahydrofuran, 2-chloro-2-bromopyran, 2,5-dichloro-1,4-dioxane.

[0011] Further, the succinate is diisopropyl 2,3-diisopropylsuccinate or diisobutyl 2,3-diisopropylsuccinate.

[0012] The present invention also provides the application of the above composite external electron donor composition in the preparation of a polyethylene catalyst composition.

[0013] A polyethylene catalyst composition, the polyethylene catalyst composition comprising MgCl 2 supported titanium tetrachloride, triethylaluminum and a composite external electron donor composition; the molar ratio of the triethylaluminum to the titanium element in the MgCl 2 supported titanium tetrachloride is 10.

[0014] Further, the mass fraction of titanium in the MgCl 2 supported titanium tetrachloride is 10%; the molar ratio of the composite external electron donor composition to the titanium element in the MgCl 2 supported titanium tetrachloride is 2.5 - 7.5:1.

[0015] The present invention also provides the application of the above polyethylene catalyst composition in the copolymerization reaction of ethylene and α-olefin.

[0016] Further, the polyethylene composition is added to the reaction system all at once at the start of the reaction.

[0017] Further, the α-olefin is one of 1-hexene, 1-butene, 1-octene.

[0018] The beneficial effects of the present invention are as follows: (1) By compounding halohydrin ether compounds and succinate compounds to prepare an external electron donor, the synergistic effect of the halohydrin ether compounds and the succinate compounds can improve the hydrogen regulation performance while increasing the comonomer content and regulating the comonomer distribution, thereby preparing a high melt index polyethylene resin with strong mechanical properties and good processing properties.

[0019] (2) Compared with loading an electron donor compound on the catalyst, it is necessary to adjust the component contents of titanium and magnesium elements and compounds at the same time, and the loading requires a special process. The present invention can optimize the existing catalytic polymerization system by compounding external electron donors, without replacing the main catalyst and the cocatalyst, and the addition method is simpler, greatly reducing the use cost.

[0020] (3) While maintaining high activity and not affecting production efficiency, the present invention improves the hydrogen regulation sensitivity of the catalytic system to produce high melt index polyethylene products. At the same time, due to the synergistic effect of the compound external donor on the increase in the content and regulation of the distribution of the comonomer, the polyethylene product also has excellent processing performance, and the fiber prepared from it has excellent spinnability. Specific Embodiments

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. The illustrative embodiments and descriptions thereof of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0022] Example 1 Test raw materials: MgCl 2 A catalyst loaded with titanium tetrachloride, wherein the mass fraction of titanium element is 10%; triethylaluminum (the molar ratio of triethylaluminum to titanium tetrachloride loaded on MgCl 2 is 10 in terms of titanium element); hydrogen; ethylene; hexene; the molar ratio of the composite external electron donor composition to the catalyst (in terms of titanium element) is 5.0. The composite external electron donor includes: 90 mol% of dibromoethyl ethyl ether and 10 mol% of diisopropyl diethyl succinate.

[0023] The ethylene polymerization reaction was carried out in a 1 L glass reaction kettle (0.4 Mpa) equipped with a mechanical stirrer and a temperature control device. The reaction kettle was heated to 65 °C, evacuated to remove air and water vapor, and replaced with nitrogen 3 times. The composite external electron donor composition (the molar ratio of the composite external electron donor to MgCl 2 loaded with titanium tetrachloride is 5.0), triethylaluminum, MgCl 2 loaded with titanium tetrachloride (25 mg), 1 ml of comonomer (hexene) were added in sequence. The mechanical stirrer was started at a rotational speed of 200 r / min, hydrogen was added, and ethylene was introduced until the reaction ended. The hydrogen partial pressure was 20%. The temperature was raised to 95 °C. After reacting for 1 h, the stirring was stopped, the temperature was lowered, the pressure was released to discharge the unreacted raw materials, and the product was discharged to obtain polyethylene particles.

[0024] After the polymerization reaction ended, the melt index of the obtained polyethylene particles was tested to be 35.2 g / 10 min, the comonomer content was 0.95 mol%, the elongation at break was 88%, the impact strength was 3.0 KJ / m 2 and the fixed elongation strength of the fiber after hot air spinning (fiber spinnability) was 2.42 Cn / dtex.

[0025] Example 2 Test raw materials: MgCl 2A catalyst loaded with titanium tetrachloride, in which the mass fraction of titanium element is 10%; triethylaluminum; hydrogen; ethylene; butene; the molar ratio of the composite external electron donor composition to the catalyst (calculated based on titanium element) is 5.0. The external electron donor composition includes: 80 mol% of dibromoethyl ethyl ether and 20 mol% of diisopropyl 2,3 - diisopropylsuccinate.

[0026] The ethylene polymerization reaction was carried out in a 1L glass reactor (0.4 Mpa) equipped with a mechanical stirrer and a temperature control device. The reactor was heated to 65 °C, evacuated to remove air and water vapor, and replaced with nitrogen three times. Then, the composite external electron donor composition, triethylaluminum, and MgCl 2 The catalyst loaded with titanium tetrachloride (25 mg), 1 ml of the comonomer (butene) were added in sequence. The mechanical stirrer was started at a speed of 200 r / min, hydrogen was added, and ethylene was introduced until the reaction ended. The partial pressure of hydrogen was 20%. The temperature was raised to 95 °C. After reacting for 1 h, the stirring was stopped, the temperature was lowered, the pressure was released to discharge the unreacted raw materials, and the product was discharged to obtain polyethylene particles.

[0027] After the polymerization reaction ended, the melt index of the obtained polyethylene particles was tested to be 32.7 g / 10 min, the comonomer content was 0.94 mol%, the elongation at break was 82%, and the impact strength was 3.1 KJ / m 2 And the constant elongation strength of the fiber after hot air spinning (spinnability of the fiber) was 2.33 Cn / dtex.

[0028] Example 3 Test raw materials: MgCl 2 A catalyst loaded with titanium tetrachloride, in which the mass fraction of titanium element is 10%; triethylaluminum (the molar ratio of triethylaluminum to the titanium tetrachloride loaded on MgCl 2 calculated based on titanium element is 10); hydrogen; ethylene; octene; the molar ratio of the composite external electron donor composition to the catalyst (calculated based on titanium element) is 2.5. The external electron donor composition includes: 70 mol% of dibromoethyl ethyl ether and 30 mol% of diisopropyl 2,3 - diisopropylsuccinate.

[0029] The ethylene polymerization reaction was carried out in a 1L glass reactor (0.4 Mpa) equipped with a mechanical stirrer and a temperature control device. The reactor was heated to 65 °C, evacuated to remove air and water vapor, and replaced with nitrogen three times. Then, the composite external electron donor composition, triethylaluminum, and MgCl 2Load titanium tetrachloride (25 mg), 1 ml of comonomer (1-octene), start mechanical stirring at a speed of 200 r / min, add a certain amount of hydrogen (the amount of hydrogen added is calculated based on the pressure drop of the 500 mL gas storage tank) and introduce ethylene until the reaction ends. Among them, the hydrogen partial pressure is 20%, heat up to 95 °C, after reacting for 1 h, stop stirring, cool down, relieve pressure to discharge the unreacted raw materials, and discharge the material to obtain polyethylene particles.

[0030] After the polymerization reaction ends, the melt index of the obtained polyethylene particles is 26.5 g / 10 min, the comonomer content is 0.82 mol%, the elongation at break is 72%, and the impact strength is 2.8 KJ / m 2 And the constant elongation strength (spinnability of the fiber) of the fiber after hot air spinning is 1.95 cN / dtex.

[0031] Example 4 Except that diisobutyl 2,3-diisopropyl succinate is used instead of diisooctyl 2,3-diisopropyl succinate, the rest of the test procedures are the same as in Example 1, and the test results are shown in Table 1.

[0032] Example 5 Test raw materials: MgCl 2 Catalyst loaded with titanium tetrachloride, in which the mass fraction of titanium element is 10%; triethylaluminum (the molar ratio of triethylaluminum to titanium tetrachloride loaded on MgCl 2 is 10 in terms of titanium element); hydrogen; ethylene; hexene; the molar ratio of the composite external electron donor composition to the catalyst (in terms of titanium element) is 5.0. Among them, the external electron donor composition includes: 80 mol% of bis(2-chloroethyl) ether and 20 mol% of diisooctyl 2,3-diisopropyl succinate.

[0033] The ethylene polymerization reaction is carried out in a 1 L glass reaction kettle (0.4 Mpa) equipped with a mechanical stirrer and a temperature control device. Heat the reaction kettle to 65 °C, evacuate to remove air and water vapor, replace with nitrogen 3 times, and sequentially add the composite external electron donor composition, triethylaluminum, MgCl 2 Load titanium tetrachloride (25 mg), 1 ml of comonomer (hexene), start mechanical stirring at a speed of 200 r / min, add hydrogen and introduce ethylene until the reaction ends. Among them, the hydrogen partial pressure is 20%, heat up to 95 °C, after reacting for 1 h, stop stirring, cool down, relieve pressure to discharge the unreacted raw materials, and discharge the material to obtain polyethylene particles.

[0034] After the polymerization reaction ends, the melt index of the obtained polyethylene particles is 28.9 g / 10 min, the comonomer content is 0.91 mol%, the elongation at break is 78%, and the impact strength is 2.8 KJ / m 2And the fixed elongation strength of the fiber after hot air spinning (fiber spinnability) is 2.20 Cn / dtex.

[0035] Example 6 Test raw materials: MgCl 2 Catalyst loaded with titanium tetrachloride, in which the mass fraction of titanium element is 10%; triethylaluminum (the molar ratio of triethylaluminum to titanium tetrachloride loaded on MgCl 2 is 10 in terms of titanium element); hydrogen; ethylene; butene; the molar ratio of the composite external electron donor composition to the catalyst (in terms of titanium element) is 7.5. Among them, the external electron donor composition includes: 80 mol% of bis(2-chloroethyl) ether and 20 mol% of diisopropyl 2,3-diisopropylsuccinate.

[0036] The ethylene polymerization reaction was carried out in a 1L glass reactor (0.4 Mpa) equipped with a mechanical stirrer and a temperature control device. The reactor was heated to 65 °C, evacuated to remove air and water vapor, and replaced with nitrogen 3 times. Then, the composite external electron donor composition, triethylaluminum, MgCl 2 loaded with titanium tetrachloride (25 mg), 1 ml of comonomer (butene) were added in sequence. The mechanical stirrer was started at a speed of 200 r / min, hydrogen was added, and ethylene was introduced until the reaction ended. Among them, the hydrogen partial pressure was 20%. The temperature was raised to 95 °C, and after reacting for 1 h, the stirring was stopped, the temperature was lowered, the pressure was released to discharge the unreacted raw materials, and the product was discharged to obtain polyethylene particles.

[0037] After the polymerization reaction ended, the melt index of the obtained polyethylene particles was tested to be 26.7 g / 10 min, the comonomer content was 0.88 mol%, the elongation at break was 75%, and the impact strength was 2.6 KJ / m 2 And the fixed elongation strength of the fiber after hot air spinning (fiber spinnability) is 2.06 Cn / dtex.

[0038] Example 7 Test raw materials: MgCl 2 Catalyst loaded with titanium tetrachloride, in which the mass fraction of titanium element is 10%; triethylaluminum (the molar ratio of triethylaluminum to titanium tetrachloride loaded on MgCl 2 is 10 in terms of titanium element); hydrogen; ethylene; butene; the molar ratio of the composite external electron donor composition to the catalyst (in terms of titanium element) is 5.0. Among them, the external electron donor composition includes: 90 mol% of bis(2-chloroethyl) ether and 10 mol% of diisobutyl 2,3-diisopropylsuccinate.

[0039] The ethylene polymerization reaction was carried out in a 1L glass reactor (0.4 Mpa) equipped with mechanical stirring and temperature control devices. The reactor was heated to 65 °C, evacuated to remove air and water vapor, replaced with nitrogen three times, and the composite external electron donor composition, triethylaluminum, and MgCl 2 supported titanium tetrachloride (25 mg), 1 ml of comonomer (butene) were added successively. The mechanical stirring was started at a speed of 200 r / min, hydrogen was added, and ethylene was introduced until the reaction ended. The hydrogen partial pressure was 20%. The temperature was raised to 95 °C. After reacting for 1 h, the stirring was stopped, the temperature was lowered, the pressure was released to discharge the unreacted raw materials, and the product was discharged to obtain polyethylene particles.

[0040] After the polymerization reaction ended, the melt index of the obtained polyethylene was tested to be 27.1 g / 10 min, the comonomer content was 0.89 mol%, the elongation at break was 76%, and the impact strength was 2.7 KJ / m 2 and the constant elongation strength of the fiber after hot air spinning (fiber spinnability) was 2.06 Cn / dtex.

[0041] Example 8 Test raw materials: MgCl 2 catalyst supported with titanium tetrachloride, in which the mass fraction of titanium element was 10%; triethylaluminum (the molar ratio of triethylaluminum to titanium tetrachloride supported by MgCl 2 was 10 in terms of titanium element); hydrogen; ethylene; octene; the molar ratio of the composite external electron donor composition to the catalyst (in terms of titanium element) was 5.0. The external electron donor composition included: 70 mol% of bis(2-chloroethyl) ether and 30 mol% of diisobutyl 2,3-diisopropyl succinate.

[0042] The ethylene polymerization reaction was carried out in a 1L glass reactor (0.4 Mpa) equipped with mechanical stirring and temperature control devices. The reactor was heated to 65 °C, evacuated to remove air and water vapor, replaced with nitrogen three times, and the composite external electron donor composition, triethylaluminum, and MgCl 2 supported titanium tetrachloride (25 mg), 1 ml of comonomer (octene) were added successively. The mechanical stirring was started at a speed of 200 r / min, hydrogen was added, and ethylene was introduced until the reaction ended. The hydrogen partial pressure was 20%. The temperature was raised to 95 °C. After reacting for 1 h, the stirring was stopped, the temperature was lowered, the pressure was released to discharge the unreacted raw materials, and the product was discharged to obtain polyethylene particles.

[0043] After the polymerization reaction ended, the melt index of the obtained polyethylene particles was tested to be 24.2 g / 10 min, the comonomer content was 0.85 mol%, the elongation at break was 72%, and the impact strength was 2.5 KJ / m 2 and the constant elongation strength of the fiber after hot air spinning (fiber spinnability) was 2.02 Cn / dtex.

[0044] Example 9 Test raw materials: MgCl 2 Titanium tetrachloride supported catalyst, wherein the mass fraction of titanium element is 10%; triethylaluminum (the molar ratio of triethylaluminum to titanium tetrachloride supported by MgCl 2 is 10); hydrogen; ethylene; hexene; the molar ratio of the composite external electron donor composition to the catalyst (calculated based on titanium element) is 5.0. Among them, the external electron donor composition includes: 90 mol% of 2,3-dichlorotetrahydrofuran and 10 mol% of diisopropyl 2,3-diisopropylsuccinate.

[0045] The ethylene polymerization reaction was carried out in a 1 L glass reactor (0.4 Mpa) equipped with a mechanical stirrer and a temperature control device. The reactor was heated to 65 °C, evacuated to remove air and water vapor, and purged with nitrogen three times. The composite external electron donor composition, triethylaluminum, and MgCl 2 supported titanium tetrachloride (25 mg), 1 ml of comonomer (hexene) were added in sequence. The mechanical stirrer was started at a speed of 200 r / min, hydrogen was added, and ethylene was introduced until the reaction ended. The hydrogen partial pressure was 20%. The temperature was raised to 95 °C. After reacting for 1 h, the stirring was stopped, the temperature was lowered, the pressure was released to discharge the unreacted raw materials, and the product was discharged to obtain polyethylene particles. After the polymerization reaction ended, the melt index of the obtained polyethylene particles was measured to be 31.2 g / 10 min, the comonomer content was 0.93 mol%, the elongation at break was 83%, the impact strength was 3.0 KJ / m 2 and the constant elongation strength (fiber spinnability) of the fiber after hot air spinning was 2.24 Cn / dtex.

[0046] Example 10 Test raw materials: MgCl 2 Titanium tetrachloride supported catalyst, wherein the mass fraction of titanium element is 10%; triethylaluminum (the molar ratio of triethylaluminum to titanium tetrachloride supported by MgCl 2 is 10); hydrogen; ethylene; butene; the molar ratio of the composite external electron donor composition to the catalyst (calculated based on titanium element) is 2.5. Among them, the external electron donor composition includes: 90 mol% of 2,3-dichlorotetrahydrofuran and 10 mol% of diisopropyl 2,3-diisopropylsuccinate.

[0047] The ethylene polymerization reaction was carried out in a 1 L glass reactor (0.4 Mpa) equipped with a mechanical stirrer and a temperature control device. The reactor was heated to 65 °C, evacuated to remove air and water vapor, and purged with nitrogen three times. The composite external electron donor composition, triethylaluminum, and MgCl 2Load titanium tetrachloride (25 mg), comonomer (butene) 1 ml, start mechanical stirring at 200 r / min, add hydrogen and introduce ethylene until the reaction ends. Among them, the hydrogen partial pressure is 20%, heat up to 95 °C, after reacting for 1 h, stop stirring, cool down, relieve pressure to discharge unreacted raw materials, and discharge to obtain polyethylene particles. After the polymerization reaction ends, the melt index of the obtained polyethylene particles is tested to be 25.6 g / 10 min, the comonomer content is 0.80 mol%, the elongation at break is 70%, and the impact strength is 2.6 KJ / m 2 And the constant elongation strength (spinnability of the fiber) of the fiber after hot air spinning is 1.89 Cn / dtex.

[0048] Example 11 Test raw materials: MgCl 2 Catalyst loaded with titanium tetrachloride, in which the mass fraction of titanium element is 10%; triethylaluminum (the molar ratio of triethylaluminum to titanium tetrachloride loaded on MgCl 2 is 10); hydrogen; ethylene; octene; the molar ratio of the composite external electron donor composition to the catalyst (calculated based on titanium element) is 5.0. Among them, the external electron donor composition includes: 80 mol% of 2,3-dichlorotetrahydrofuran and 20 mol% of diisopropyl diethyl succinate.

[0049] The ethylene polymerization reaction is carried out in a 1 L glass reaction kettle (0.4 Mpa) with mechanical stirring and temperature control device. Heat the reaction kettle to 65 °C, evacuate to remove air and water vapor, replace with nitrogen 3 times, and sequentially add the composite external electron donor composition, triethylaluminum, MgCl 2 Load titanium tetrachloride (25 mg), comonomer (octene) 1 ml, start mechanical stirring at 200 r / min, add hydrogen and introduce ethylene until the reaction ends. Among them, the hydrogen partial pressure is 20%, heat up to 95 °C, after reacting for 1 h, stop stirring, cool down, relieve pressure to discharge unreacted raw materials, and discharge to obtain polyethylene particles. After the polymerization reaction ends, the melt index of the obtained polyethylene particles is tested to be 28.8 g / 10 min, the comonomer content is 0.89 mol%, the elongation at break is 79%, and the impact strength is 2.9 KJ / m 2 And the constant elongation strength (spinnability of the fiber) of the fiber after hot air spinning is 2.07 Cn / dtex.

[0050] Example 12 Test raw materials: MgCl 2 Catalyst loaded with titanium tetrachloride, in which the mass fraction of titanium element is 10%; triethylaluminum (the molar ratio of triethylaluminum to MgCl 2The molar ratio of the supported titanium tetrachloride based on titanium element is 10); hydrogen; ethylene; hexene; the molar ratio of the composite external electron donor composition to the catalyst (based on titanium element) is 5.0. The external electron donor composition includes: 90 mol% of 1,3-dibromotetrahydrofuran and 10 mol% of diisopropyl 2,3-diisopropylsuccinate.

[0051] The ethylene polymerization reaction was carried out in a 1 L glass reactor (0.4 Mpa) equipped with a mechanical stirrer and a temperature control device. The reactor was heated to 65 °C, evacuated to remove air and water vapor, and purged with nitrogen three times. Then, the composite external electron donor composition, triethylaluminum, and MgCl 2 supported titanium tetrachloride (25 mg), comonomer (hexene) 1 ml were added in sequence. The mechanical stirrer was started at a speed of 200 r / min, hydrogen was added, and ethylene was introduced until the reaction ended. The partial pressure of hydrogen was 20%. The temperature was raised to 95 °C, and after reacting for 1 h, the stirring was stopped, the temperature was lowered, the pressure was released to discharge the unreacted raw materials, and the product was discharged to obtain polyethylene particles.

[0052] After the polymerization reaction ended, the melt index of the obtained polyethylene particles was tested to be 25.6 g / 10 min, the comonomer content was 0.86 mol%, the elongation at break was 73%, and the impact strength was 2.7 KJ / m 2 and the constant elongation strength of the fiber after hot air spinning (spinnability of the fiber) was 2.05 Cn / dtex.

[0053] Example 13 Test raw materials: MgCl 2 The catalyst of supported titanium tetrachloride, in which the mass fraction of titanium element is 10%; triethylaluminum (the molar ratio of triethylaluminum to MgCl 2 The molar ratio of the supported titanium tetrachloride based on titanium element is 10); hydrogen; ethylene; butene; the molar ratio of the composite external electron donor composition to the catalyst (based on titanium element) is 5.0. Among them, the external electron donor composition includes: 80 mol% of 1,3-dibromotetrahydrofuran and 20 mol% of diisopropyl 2,3-diisopropylsuccinate.

[0054] The ethylene polymerization reaction was carried out in a 1 L glass reactor (0.4 Mpa) equipped with a mechanical stirrer and a temperature control device. The reactor was heated to 65 °C, evacuated to remove air and water vapor, and purged with nitrogen three times. Then, the composite external electron donor composition, triethylaluminum, and MgCl 2Load titanium tetrachloride (25 mg), comonomer (butene) 1 ml, start mechanical stirring at 200 r / min, add hydrogen and introduce ethylene until the reaction ends. Among them, the hydrogen partial pressure is 20%, heat up to 95 °C, after reacting for 1 h, stop stirring, cool down, relieve pressure to discharge unreacted raw materials, and discharge to obtain polyethylene particles. After the polymerization reaction ends, the melt index of the obtained polyethylene particles is tested to be 24.9 g / 10 min, the comonomer content is 0.84 mol%, the elongation at break is 73%, and the impact strength is 2.6 KJ / m 2 And the constant elongation strength of the fiber after hot air spinning (fiber spinnability) is 2.05 Cn / dtex.

[0055] Example 14 Test raw materials: MgCl 2 Catalyst loaded with titanium tetrachloride, in which the mass fraction of titanium element is 10%; triethylaluminum (the molar ratio of triethylaluminum to titanium tetrachloride loaded on MgCl 2 is 10); hydrogen; ethylene; octene; the molar ratio of the composite external electron donor composition to the catalyst (calculated by titanium element) is 2.5. Among them, the external electron donor composition includes: 80 mol% of 1,3-dibromotetrahydrofuran and 20 mol% of diisobutyl 2,3-diisopropyl succinate.

[0056] The ethylene polymerization reaction is carried out in a 1 L glass reaction kettle (0.4 Mpa) with mechanical stirring and temperature control device. Heat the reaction kettle to 65 °C, evacuate to remove air and water vapor, displace with nitrogen 3 times, and sequentially add the composite external electron donor composition, triethylaluminum, MgCl 2 Load titanium tetrachloride (25 mg), comonomer (octene) 1 ml, start mechanical stirring at 200 r / min, add hydrogen and introduce ethylene until the reaction ends. Among them, the hydrogen partial pressure is 20%, heat up to 95 °C, after reacting for 1 h, stop stirring, cool down, relieve pressure to discharge unreacted raw materials, and discharge to obtain polyethylene particles.

[0057] After the polymerization reaction ends, the melt index of the obtained polyethylene particles is tested to be 22.4 g / 10 min, the comonomer content is 0.82 mol%, the elongation at break is 71%, and the impact strength is 2.5 KJ / m 2 And the constant elongation strength of the fiber after hot air spinning (fiber spinnability) is 1.98 Cn / dtex.

[0058] Comparative Example 1 Test raw materials: MgCl 2 Catalyst loaded with titanium tetrachloride, in which the mass fraction of titanium element is 10%; triethylaluminum (the molar ratio of triethylaluminum to MgCl 2The molar ratio of the supported titanium tetrachloride based on titanium element is 10); hydrogen; ethylene; hexene.

[0059] The ethylene polymerization reaction was carried out in a 1 L glass reactor (0.4 Mpa) equipped with a mechanical stirrer and a temperature control device. The reactor was heated to 65 °C, evacuated to remove air and water vapor, and purged with nitrogen three times. Then, the composite external electron donor composition, triethylaluminum, and MgCl 2 supported titanium tetrachloride (25 mg), comonomer (hexene) 1 ml were added successively. The mechanical stirrer was started at a speed of 200 r / min, hydrogen was added, and ethylene was introduced until the reaction ended. The partial pressure of hydrogen was 20%. The temperature was raised to 95 °C, and after reacting for 1 h, the stirring was stopped, the temperature was lowered, the pressure was released to discharge the unreacted raw materials, and the product was discharged to obtain polyethylene particles.

[0060] After the polymerization reaction ended, the melt index of the obtained polyethylene particles was tested to be 15.0 g / 10 min, the comonomer content was 0.48 mol%, the elongation at break was 65%, and the impact strength was 2.2 KJ / m 2 And the constant elongation strength of the fiber after hot air spinning (fiber spinnability) was 0.85 Cn / dtex.

[0061] Comparative Example 2 Test raw materials: MgCl 2 The catalyst of supported titanium tetrachloride, in which the mass fraction of titanium element is 10%; triethylaluminum (the molar ratio of triethylaluminum to MgCl 2 The molar ratio of the supported titanium tetrachloride based on titanium element is 10); hydrogen; ethylene; hexene; the molar ratio of the external electron donor to the catalyst (based on titanium element) is 5.0, and the external electron donor is dibromoethyl ethyl ether.

[0062] The ethylene polymerization reaction was carried out in a 1 L glass reactor (0.4 Mpa) equipped with a mechanical stirrer and a temperature control device. The reactor was heated to 65 °C, evacuated to remove air and water vapor, and purged with nitrogen three times. Then, the composite external electron donor composition, triethylaluminum, and MgCl 2 supported titanium tetrachloride (25 mg), comonomer (hexene) 1 ml were added successively. The mechanical stirrer was started at a speed of 200 r / min, hydrogen was added, and ethylene was introduced until the reaction ended. The partial pressure of hydrogen was 20%. The temperature was raised to 95 °C, and after reacting for 1 h, the stirring was stopped, the temperature was lowered, the pressure was released to discharge the unreacted raw materials, and the product was discharged to obtain polyethylene particles. After the polymerization reaction ended, the melt index of the obtained polyethylene was tested to be 22 g / 10 min, the comonomer content was 0.63 mol%, the elongation at break was 72%, and the impact strength was 2.5 KJ / m 2 And the constant elongation strength of the fiber after hot air spinning (fiber spinnability) was 1.36 Cn / dtex.

[0063] Comparative Example 3 Test raw materials: MgCl 2 Catalyst loaded with titanium tetrachloride, where the mass fraction of titanium element is 10%; triethylaluminum (the molar ratio of triethylaluminum to titanium tetrachloride loaded on MgCl 2 is 10 in terms of titanium element); hydrogen; ethylene; hexene; the molar ratio of external electron donor to catalyst (in terms of titanium element) is 5.0, and the external electron donor is diisopropyl ethyl 2,3 - diisopropyl succinate.

[0064] The ethylene polymerization reaction was carried out in a 1L glass reactor (0.4 Mpa) equipped with a mechanical stirrer and a temperature control device. The reactor was heated to 65 °C, evacuated to remove air and water vapor, and replaced with nitrogen 3 times. Then, the composite external electron donor composition, triethylaluminum, MgCl 2 loaded titanium tetrachloride (25 mg), and 1 ml of comonomer (hexene) were added in sequence. The mechanical stirrer was started at a rotational speed of 200 r / min, hydrogen was added, and ethylene was introduced until the reaction ended. Among them, the hydrogen partial pressure was 20%. The temperature was raised to 95 °C, and after reacting for 1 h, the stirring was stopped, the temperature was lowered, the pressure was released to discharge the unreacted raw materials, and the product was discharged to obtain polyethylene particles.

[0065] After the polymerization reaction ended, the melt index of the obtained polyethylene particles was tested to be 15.9 g / 10 min, the comonomer content was 0.83 mol%, the elongation at break was 79%, the impact strength was 2.8 KJ / m 2 and the constant elongation strength (spinnability of fiber) of the fiber after hot air spinning was 1.98 Cn / dtex.

[0066] Table 1 Properties of Polyethylene Particles Obtained in Examples 1 - 14 and Comparative Examples 1 - 3 Table 1 - 1 Table 1 - 2 *Ethyl ester: Diisopropyl ethyl 2,3 - diisopropyl succinate; Butyl ester: Diisopropyl butyl 2,3 - diisopropyl succinate In Comparative Example 1, except that the compounded external electron donor composition was not added, the other conditions were the same as those in Example 1. The melt index of the obtained polymerization product was 15.0 g / 10 min, and the comonomer content was 0.48, only about 1 / 2 of that in Example 1. Moreover, there were obvious differences in the mechanical properties and the constant elongation strength of the fiber compared with Example 1. It can be seen that the addition of the compounded external electron donor during the polymerization process can effectively improve the hydrogen response sensitivity of the polymerization product and the mechanical properties of the polymer.

[0067] In Comparative Example 2, when the external electron donor dibromoethyl ethyl ether was added alone, the melt index increased relatively significantly, while the improvement in the comonomer content and distribution was relatively limited. Therefore, the improvement in the mechanical properties of the polymerization product and the modulus at a specified elongation of the processed fiber was relatively small.

[0068] In Comparative Example 3, when the external electron donor diisopropyl diethyl 2,3 - disuccinate was added alone, there was basically no improvement in the melt index, i.e., the hydrogen regulation sensitivity, but the increase in the comonomer content and the improvement in the comonomer distribution were relatively obvious, and the mechanical properties of the polymerization product and the modulus at a specified elongation of the processed fiber increased significantly.

[0069] In Example 1, a compound external electron donor composition was added: 90 mol% of dibromoethyl ethyl ether and 10 mol% of diisopropyl diethyl 2,3 - disuccinate. By utilizing the synergistic effect of the haloether compound and the succinate compound, the hydrogen regulation performance can be improved while increasing the comonomer content and regulating the comonomer distribution. The melt index, mechanical properties of the polymerization product, and the modulus at a specified elongation of the processed fiber all increased significantly.

[0070] The above are only the preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope covered by the present invention.

Claims

1. A composite external electron donor composition, characterized in that: The composite external electron donor composition comprises 70-90 mol % of halogenated ether and 10-30 mol % of succinate ester, based on the molar percentage of 100%; the halogenated ether is a cyclic halogenated ether or a chain halogenated ether having 1-10 carbon atoms, 1-2 oxygen atoms and 1-3 halogen atoms in its chemical structure.

2. The composite external electron donor composition according to claim 1, characterized in that: The chain halogenated ether is one of di(1-chloroethyl) ether, di(2-chloroethyl) ether, di(1-bromoethyl) ether, dibromoethylethyl ether, di(2-chloroethyl) ether, di(1-chloropropyl) ether, and di(2-bromoisopropyl) ether; the cyclic halogenated ether is one of 2,3-dichlorotetrahydrofuran, 1,3-dibromotetrahydrofuran, 2-chloro-2-bromopyran, and 2,5-dichloro-1,4-dioxane.

3. The composite external electron donor composition according to claim 1, characterized in that: The succinate is diisoethyl 2,3-diisopropylsuccinate or diisobutyl 2,3-diisopropylsuccinate.

4. Use of the composite external electron donor composition as claimed in any one of claims 1 to 3 in the preparation of a polyethylene catalyst composition.

5. A polyethylene catalyst composition, characterized in that: The polyethylene catalyst composition comprises titanium tetrachloride supported by MgCl2, triethylaluminum and a composite external electron donor composition; the molar ratio of the triethylaluminum to the titanium element in the titanium tetrachloride supported by MgCl2 is 10.

6. The polyethylene catalyst according to claim 5, characterized in that: The mass fraction of titanium in the titanium tetrachloride loaded with MgCl2 is 10%; the molar ratio of the composite external electron donor composition to the titanium element in the titanium tetrachloride loaded with MgCl2 is 2.5-7.5:

1.

7. Use of the polyethylene catalyst composition according to any one of claims 5 to 6 in the copolymerization of ethylene and α-olefins.

8. The use according to claim 7, characterized in that: The polyethylene composition is added entirely into the reaction system at the beginning of the reaction.

9. The use according to claim 7, characterized in that: The α-olefin is one of 1-hexene, 1-butene and 1-octene.

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