CN108467443B - Novel linear low-density polyethylene for urea box and preparation method thereof - Google Patents

Novel linear low-density polyethylene for urea box and preparation method thereof Download PDF

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CN108467443B
CN108467443B CN201810178309.8A CN201810178309A CN108467443B CN 108467443 B CN108467443 B CN 108467443B CN 201810178309 A CN201810178309 A CN 201810178309A CN 108467443 B CN108467443 B CN 108467443B
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张子杰
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NANJING GRACIOUS NEW MATERIAL CO.,LTD.
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刘俊
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Abstract

The invention provides a novel linear low-density polyethylene for a urea box and a preparation method thereof, wherein the linear low-density polyethylene is obtained by in-situ polymerization of ethylene under the catalysis of an oligomerization catalyst, a copolymerization catalyst and a cocatalyst, wherein the oligomerization catalyst is a supported iron catalyst, the copolymerization catalyst is a supported zirconium catalyst, and the cocatalyst is methylaluminoxane MAO. Thereby having the characteristics of low melting point, low density and excellent mechanical property.

Description

Novel linear low-density polyethylene for urea box and preparation method thereof
Technical Field
The invention relates to the technical field of high polymer materials, in particular to novel linear low-density polyethylene for a urea box and a preparation method thereof.
Background
The emission of vehicle exhaust gases not only pollutes the environment but also is harmful to human health, and therefore, a selective catalytic system is installed on the vehicle, and the selective catalytic system uses urea aqueous solution as a reducing agent to convert nitrogen oxides in the exhaust gas of the diesel engine into nitrogen. While the stored aqueous urea solution must be used in the urea tank, which is typically made from Linear Low Density Polyethylene (LLDPE) by a rotational molding process, the quality of the LLDPE affects the performance of the urea tank.
The catalyst plays an important role in the preparation of LLDPE, which determines its polymerization behavior, polymer particle morphology, and polymer structure and properties. The invention patent of application No. CN201010515021.9 introduces a linear low-density polyethylene, which takes ethylene as raw material, pyridine diimine iron and cobalt complex as oligomerization catalyst main catalyst, beta-diimine titanium complex as copolymerization catalyst main catalyst, main group metal organic compound as only cocatalyst to form a dual-function catalyst system, and the linear low-density polyethylene is obtained by in-situ copolymerization by a one-pot method, and has the advantages that the expensive alpha-olefin is not required to be added, and the production flow is simplified; the preparation method of the main catalyst is simple, the reaction condition is mild, and the catalyst cost is low; a single cocatalyst is used, mutual interference does not exist among the bifunctional catalysts, and the consumption of the cocatalyst is small; high catalytic activity for ethylene polymerization, however, the catalyst has high activity at the initial stage of reaction and is difficult to control, and has a serious kettle adhesion phenomenon, which is not favorable for industrial application. The invention patent of application No. CN200510086486.6 describes a catalyst system for preparing linear low density polyethylene by in-situ copolymerization, the catalyst system comprises oligomerization catalyst (homogeneous or supported alpha-diimine pyridine iron series catalyst and alkyl aluminoxane cocatalyst) and copolymerization catalyst (titanium series catalyst and alkyl aluminum or alkyl aluminoxane cocatalyst), the linear low density polyethylene produced by catalysis has the characteristics of low melting point, low density, higher comonomer insertion rate, branched chains with different lengths and the like, however, LLDPE prepared by the catalyst system does not have excellent mechanical property, thereby influencing the practical application of the LLDPE.
Disclosure of Invention
The invention mainly aims to provide novel linear low-density polyethylene for a urea box and a preparation method thereof, aiming at the defects of the prior art, and the novel linear low-density polyethylene has the characteristics of low melting point, low density and excellent mechanical property.
In order to achieve the above purposes, the invention adopts the technical scheme that the novel linear low-density polyethylene material for the urea box is obtained by in-situ polymerization of ethylene under the catalysis of an oligomerization catalyst, a copolymerization catalyst and a cocatalyst, wherein the oligomerization catalyst is a supported iron catalyst, the copolymerization catalyst is a supported zirconium catalyst, and the cocatalyst is methylaluminoxane MAO.
The cocatalyst is methylaluminoxane MAO which is Lewis acid, and can alkylate the metallocene compound to generate a cation active center and remove impurities in the system to ensure that the cation active center exists stably.
According to an embodiment of the present invention, the oligomerization catalyst is a metal organic framework material/fe (salen) heterogeneous catalyst, and fe (salen) is immobilized on the metal organic framework material in an encapsulation method.
The oligomerization catalyst plays an important role in the preparation of novel linear low-density polyethylene materials. Salen is sealed in the pore canal of the metal organic framework material in a mode of 'shipbuilding in bottles', and then, the ferrous chloride tetrahydrate reacts with the Salen in the pore canal to form the metal organic framework material/Fe (Salen) heterogeneous catalyst.
Preferably, the copolymerization catalyst is a metal organic framework material/metallocene heterogeneous catalyst, and the metallocene compound is immobilized on the metal organic framework material by impregnation.
Preferably, the metallocene compound is Me2Si(Ind)2ZrCl2And Et (Ind)2ZrCl2One or two of them, metallocene compounds Me2Si(Ind)2ZrCl2Or Et (Ind)2ZrCl2Is carried on the metal organic framework material by an impregnation method to form the metal organic framework material/metallocene heterogeneous catalyst.
A preparation method of a novel linear low-density polyethylene material comprises the following specific steps:
s100, adding a solvent cyclohexane into a high-pressure reaction kettle with a stirrer, heating to 90-110 ℃, stirring for 10-30min, and discharging the cyclohexane;
s200, keeping 90-110 ℃, vacuumizing for 0.5-2h, introducing nitrogen for three times, performing ethylene displacement once, cooling to the required temperature, opening an ethylene valve, sequentially adding a solvent cyclohexane and a cocatalyst MAO, stirring for 10-20min under the condition of 3500r/min of 1500-5Pa, keeping the pressure of the ethylene through a buffer tank, and beginning to carry out in-situ copolymerization on the ethylene;
and S300, after reacting for 0.5-3h, closing the ethylene valve, stopping the reaction, washing the product with hydrochloric acid aqueous solution, water and ethanol respectively, and drying in vacuum to obtain the finished product.
Preferably, the addition amount of the cocatalyst MAO accounts for 0.4-0.8% of the mass of the solvent toluene, the molar ratio of the cocatalyst to the oligomerization catalyst is 200-300:1, and the molar ratio of the cocatalyst to the copolymerization catalyst is 200-300: 1.
According to an embodiment of the present invention, the preparation method of the oligomerization catalyst comprises the following steps:
s211, mixing the metal organic framework material with absolute ethyl alcohol to prepare a suspension with the mass fraction of 30-60%, adding salicylaldehyde into the suspension, and stirring the mixture for 10-30min under the condition of 2500r/min at 1000-;
s212, adding ethylenediamine into the mixed solution, heating to 60-80 ℃, and reacting for 1-3h under the condition of 1500r/min and 500-;
s213, cooling the first reaction liquid to room temperature, carrying out vacuum filtration, placing a filter cake in a drying oven, drying for 6-24h at 50-80 ℃, and crushing the dried filter cake to obtain an intermediate metal organic framework material/Salen compound;
s214, mixing the metal organic framework material/Salen compound with anhydrous methanol to prepare a suspension with the mass fraction of 20-50%, adding ferrous chloride tetrahydrate and anhydrous sodium carbonate, heating to 50-70 ℃, and reacting for 2-6h under the condition of 1500-;
s215, cooling the second reaction liquid to room temperature, carrying out vacuum filtration, placing a filter cake in a drying oven, drying for 6-24h at 50-80 ℃, and crushing the dried filter cake to obtain the metal organic framework material/Fe (Salen) heterogeneous catalyst for later use.
According to an embodiment of the present invention, the preparation method of the copolymerization catalyst comprises the following steps:
s221, mixing a metal organic framework material with toluene to prepare a suspension with the mass fraction of 30-60%, adding a metallocene compound, heating to 50-100 ℃, and stirring at the temperature of 500-1500r/min until the solvent is completely volatilized, wherein the adding amount of the metallocene compound accounts for 50-80% of the mass of the metal organic framework material;
s222, drying the obtained solid for 2-6h in a drying oven at the temperature of 50-80 ℃, and grinding the dried solid to obtain the metal organic framework material/metallocene heterogeneous catalyst for later use.
According to an embodiment of the invention, the metal organic framework material is MIL-100, which is assembled by iron cluster compound and trimesic acid ligand, and the preparation method comprises the following steps:
s231, dissolving ferric chloride hexahydrate in corresponding parts by mass in deionized water, stirring to fully dissolve, adding trimesic acid, continuing stirring for 0.5 hour, and placing into an autoclave for reaction at 130 ℃ for 72 hours;
and after the S232 reaction is finished, cooling to room temperature, washing with hot water and methanol for three times, treating in boiling methanol for 12 hours, and carrying out vacuum drying at 150 ℃ for 12 hours to obtain the metal organic framework material MIL-100 for later use.
Wherein, the preparation of the metal organic framework material can also be prepared by a microwave-assisted method or a mechanical stirring method.
Compared with the prior art, the invention has the following advantages and beneficial effects:
(1) because the large steric hindrance substituent at the ortho position of the oligomerization catalyst has a limiting effect on the beta-H elimination reaction of the active center, the beta-H elimination is intensified along with the reduction of the steric hindrance effect of the Salen molecular configuration of the oligomerization catalyst, so that the oligomerization catalyst has higher selectivity on linear alpha-olefin; the metal organic framework material contains unsaturated metal coordination sites, so that the metal organic framework material can be used as a Lewis acid catalytic center and is cooperated with a cocatalyst MAO to promote alkylation of a metallocene compound, generate a cation active center and stabilize the cation active center; meanwhile, the specific surface area of the metal-organic framework material is large, the accessibility of active sites is large, and the ethylene takes the pore channel of the metal-organic framework material as a 'microreactor' to generate high-purity linear alpha-olefin under the action of an oligomerization catalyst active center; the copolymerization catalyst is a single-active-center metallocene compound with excellent copolymerization performance, then under the action of a carrier metal organic framework material and a cocatalyst, linear alpha-olefin and ethylene are subjected to in-situ copolymerization, and the linear alpha-olefin is directly inserted into a growing polymer chain to generate LLDPE step by step.
(2) The oligomerization catalyst and the copolymerization catalyst are both supported catalysts, so that the design not only reduces the consumption of cocatalyst, reduces the mutual interference among the catalysts and improves the catalytic activity of a catalyst system, but also effectively controls the activity at the initial stage of reaction and eliminates the serious kettle sticking phenomenon;
(3) the catalyst carrier is used for assisting a cocatalyst MAO to promote alkylation of a metallocene compound to generate a cation active center and stabilize the cation active center on one hand, and is used as a microreactor to provide more active sites for catalytic reaction on the other hand.
Detailed Description
The following description is presented to disclose the invention so as to enable any person skilled in the art to practice the invention. The preferred embodiments in the following description are given by way of example only, and other obvious variations will occur to those skilled in the art.
The chemical reagents adopted in the embodiment of the invention are all purchased from the market: cocatalyst methylaluminoxane MAO A Kehai 20% toluene solution was purchased from Nanjing Kongchen chemical Co., Ltd; metallocene compound Me2Si(Ind)2ZrCl2And Et (Ind)2ZrCl2Purchased from Sigma-Aldrich; the ethylene Yangzhi petrochemical is purchased from Nanjing Yaojiang trade company, Inc.; the Z-N catalyst was purchased from Mitsui chemical; other chemicals were purchased from the national pharmaceutical group chemicals, ltd.
Example 1
The specific preparation method of the metal organic framework material MIL-100 is as follows:
dissolving 2.7g of ferric chloride hexahydrate in 50mL of deionized water, stirring for full dissolution, adding 1.39g of trimesic acid, and continuing stirring for 0.5 h; then the solution is put into a high-pressure kettle to react for 72 hours at the temperature of 130 ℃; and after the reaction is finished, cooling to room temperature, washing with hot water and methanol for three times, boiling in boiling methanol for 12 hours, and vacuum-drying at 150 ℃ for 12 hours to obtain the metal organic framework material MIL-100.
The oligomerization catalyst is a metal organic framework material/Fe (Salen) heterogeneous catalyst, and the preparation method comprises the following steps:
mixing a metal organic framework material with absolute ethyl alcohol to prepare a suspension with the mass fraction of 30%, adding salicylaldehyde into the suspension, and stirring the mixture for 30min at the speed of 1000r/min, wherein the adding amount of the salicylaldehyde accounts for 50% of the mass of the metal organic framework material;
adding ethylenediamine into the mixed solution, heating to 60 ℃, and reacting for 3 hours at the speed of 500r/min, wherein the molar ratio of the salicylaldehyde to the ethylenediamine is 1: 1;
cooling the obtained reaction liquid to room temperature, carrying out vacuum filtration, placing a filter cake in a drying oven, drying for 24 hours at 50 ℃, and crushing the dried filter cake to obtain an intermediate metal organic framework material/Salen compound;
mixing the obtained metal organic framework material/Salen compound with anhydrous methanol to prepare a suspension with the mass fraction of 20%, adding ferrous chloride tetrahydrate and anhydrous sodium carbonate, heating to 50 ℃, and reacting for 6 hours at the speed of 500r/min, wherein the adding amount of the ferrous chloride tetrahydrate accounts for 20% of the mass of the metal organic framework material/Salen compound, and the adding amount of the anhydrous sodium carbonate accounts for 0.2% of the mass of the metal organic framework material/Salen compound;
and cooling the obtained reaction liquid to room temperature, carrying out vacuum filtration, placing the filter cake in a drying oven, drying for 24h at 50 ℃, and crushing the dried filter cake to obtain the metal organic framework material/Fe (Salen) heterogeneous catalyst for later use.
The copolymerization catalyst is a metal organic framework material/metallocene heterogeneous catalyst, and the specific preparation method is as follows:
mixing a metal organic framework material with toluene to prepare a suspension with the mass fraction of 30%, and adding a metallocene compound Me into the suspension2Si(Ind)2ZrCl2Heating to 50 ℃ and stirring at 500r/min until the solvent is completely volatilized, wherein the addition amount of the metallocene compound accounts for 50% of the mass of the metal organic framework material;
and (3) drying the obtained solid for 6 hours in a drying oven at the temperature of 50 ℃, and grinding the dried solid to obtain the metal organic framework material/metallocene heterogeneous catalyst for later use.
The specific preparation method of the novel linear low-density polyethylene for the urea box comprises the following steps:
adding a solvent cyclohexane into a high-pressure reaction kettle with a stirrer, heating to 90 ℃, stirring for 30min, discharging the cyclohexane, keeping the temperature at 90 ℃, and vacuumizing for 2 h; introducing nitrogen for replacement for three times, and introducing ethylene for replacement for one time; cooling to required temperature, opening ethylene valve, sequentially adding cyclohexane solvent and MAO catalyst, stirring at 1500r/min for 20min, adding oligomerization catalyst and copolymerization catalyst, and rapidly increasing ethylene pressure to 1 × 105Pa, keeping the pressure of the ethylene through a buffer tank, and beginning to carry out in-situ copolymerization on the ethylene; after 3h of reaction, the reaction is closedClosing an ethylene valve, and stopping reaction, wherein the addition amount of a cocatalyst MAO accounts for 0.4 percent of the mass of the solvent toluene, the molar ratio of the cocatalyst to the oligomerization catalyst is 200:1, and the molar ratio of the cocatalyst to the copolymerization catalyst is 200: 1; and washing the product with hydrochloric acid aqueous solution, water and ethanol respectively, and drying in vacuum to obtain the novel linear low-density polyethylene material.
Example 2
The preparation method of the metal organic framework material MIL-100 is the same as that of example 1.
The oligomerization catalyst is a metal organic framework material/Fe (Salen) heterogeneous catalyst, and the preparation method comprises the following steps:
mixing a metal organic framework material with absolute ethyl alcohol to prepare a suspension with the mass fraction of 60%, adding salicylaldehyde into the suspension, and stirring the mixture for 10min at the speed of 2500r/min, wherein the adding amount of the salicylaldehyde accounts for 80% of the mass of the metal organic framework material;
adding ethylenediamine into the mixed solution, heating to 80 ℃, and reacting for 1h under the condition of 1500r/min, wherein the molar ratio of the salicylaldehyde to the ethylenediamine is 3: 1;
cooling the obtained reaction liquid to room temperature, carrying out vacuum filtration, placing a filter cake in a drying oven, drying for 6 hours at the temperature of 80 ℃, and crushing the dried filter cake to obtain an intermediate metal organic framework material/Salen compound;
mixing the obtained metal organic framework material/Salen compound with anhydrous methanol to prepare a suspension with the mass fraction of 250%, adding ferrous chloride tetrahydrate and anhydrous sodium carbonate, heating to 70 ℃, and reacting for 2 hours at 1500r/min, wherein the adding amount of the ferrous chloride tetrahydrate accounts for 60% of the mass of the metal organic framework material/Salen compound, and the adding amount of the anhydrous sodium carbonate accounts for 0.2% of the mass of the metal organic framework material/Salen compound;
and cooling the obtained reaction liquid to room temperature, carrying out vacuum filtration, placing the filter cake in a drying oven, drying for 6h at the temperature of 80 ℃, and crushing the dried filter cake to obtain the metal organic framework material/Fe (Salen) heterogeneous catalyst for later use.
The copolymerization catalyst is a metal organic framework material/metallocene heterogeneous catalyst, and the specific preparation method is as follows:
mixing a metal organic framework material with toluene to prepare a suspension with the mass fraction of 60%, and adding a metallocene compound Me into the suspension2Si(Ind)2ZrCl2Heating to 80 ℃ and stirring at 1500r/min until the solvent is completely volatilized, wherein the adding amount of the metallocene compound accounts for 80% of the mass of the metal organic framework material;
and (3) drying the obtained solid for 2 hours in a drying oven at the temperature of 80 ℃, and grinding the dried solid to obtain the metal organic framework material/metallocene heterogeneous catalyst for later use.
The specific preparation method of the novel urea tank linear low-density polyethylene comprises the following steps:
adding a solvent cyclohexane into a high-pressure reaction kettle with a stirrer, heating to 100 ℃, stirring for 30min, discharging the cyclohexane, keeping the temperature at 100 ℃, and vacuumizing for 0.5 h; introducing nitrogen for three times, performing ethylene displacement once, cooling to a required temperature, opening an ethylene valve, sequentially adding cyclohexane solvent and MAO cocatalyst, stirring for 10min at 3500r/min, adding oligomerization catalyst and copolymerization catalyst, and rapidly increasing ethylene pressure to 1 x 105Pa, keeping the pressure of the ethylene through a buffer tank, and beginning to carry out in-situ copolymerization on the ethylene; after reacting for 2h, the ethylene valve is closed, and the reaction is stopped. Wherein the addition amount of the catalyst promoter MAO accounts for 0.4 percent of the mass of the solvent toluene, the molar ratio of the catalyst promoter to the oligomerization catalyst is 200:1, and the molar ratio of the catalyst promoter to the copolymerization catalyst is 200: 1. And washing the product with hydrochloric acid aqueous solution, water and ethanol respectively, and drying in vacuum to obtain the novel linear low-density polyethylene material for the urea box.
Example 3
The preparation method of the metal organic framework material MIL-100 is the same as that of example 1.
The oligomerization catalyst is a metal organic framework material/Fe (Salen) heterogeneous catalyst, and the preparation method comprises the following steps:
mixing a metal organic framework material with absolute ethyl alcohol to prepare a suspension with the mass fraction of 60%, adding salicylaldehyde into the suspension, and stirring the mixture for 130min at the speed of 2500r/min, wherein the adding amount of the salicylaldehyde accounts for 80% of the mass of the metal organic framework material;
adding ethylenediamine into the mixed solution, heating to 80 ℃, and reacting for 1h under the condition of 1500r/min, wherein the molar ratio of the salicylaldehyde to the ethylenediamine is 3: 1;
cooling the obtained reaction liquid to room temperature, carrying out vacuum filtration, placing a filter cake in a drying oven, drying for 6 hours at the temperature of 80 ℃, and crushing the dried filter cake to obtain an intermediate metal organic framework material/Salen compound;
mixing the obtained metal organic framework material/Salen compound with anhydrous methanol to prepare a suspension with the mass fraction of 50%, adding ferrous chloride tetrahydrate and anhydrous sodium carbonate, heating to 70 ℃, and reacting for 6 hours at the speed of 500r/min, wherein the adding amount of the ferrous chloride tetrahydrate accounts for 60% of the mass of the metal organic framework material/Salen compound, and the adding amount of the anhydrous sodium carbonate accounts for 1.5% of the mass of the metal organic framework material/Salen compound;
and cooling the obtained reaction liquid to room temperature, carrying out vacuum filtration, placing the filter cake in a drying oven, drying for 24h at 50 ℃, and crushing the dried filter cake to obtain the metal organic framework material/Fe (Salen) heterogeneous catalyst for later use.
The copolymerization catalyst is a metal organic framework material/metallocene heterogeneous catalyst, and the specific preparation method is as follows:
mixing the metal organic framework material with toluene to prepare a suspension with the mass fraction of 60%, and adding a metallocene compound Et (Ind)2ZrCl2Heating to 100 ℃, and stirring at 1500r/min until the solvent is completely volatilized, wherein the addition amount of the metallocene compound accounts for 80% of the mass of the metal organic framework material;
and (3) drying the obtained solid for 6 hours in a drying oven at the temperature of 50 ℃, and grinding the dried solid to obtain the metal organic framework material/metallocene heterogeneous catalyst for later use.
The specific preparation method of the linear low-density polyethylene material for the novel urea box comprises the following steps:
adding solvent cyclohexane into a high-pressure reaction kettle with stirringHeating to 110 deg.C, stirring for 10min, discharging cyclohexane, maintaining at 110 deg.C, and vacuumizing for 0.5; introducing nitrogen for three times, performing ethylene displacement once, cooling to a required temperature, opening an ethylene valve, sequentially adding cyclohexane solvent and MAO cocatalyst, stirring for 10min at 3500r/min, adding oligomerization catalyst and copolymerization catalyst, and rapidly increasing ethylene pressure to 1 x 105Pa, and maintaining the ethylene pressure through a buffer tank, and starting ethylene in-situ copolymerization. After the reaction time of 0.5h, the ethylene valve is closed, and the reaction is stopped. Wherein the addition amount of the cocatalyst MAO accounts for 0.8 percent of the mass of the solvent toluene, the molar ratio of the cocatalyst to the oligomerization catalyst is 400:1, and the molar ratio of the cocatalyst to the copolymerization catalyst is 300: 1. And washing the product with hydrochloric acid aqueous solution, water and ethanol respectively, and drying in vacuum to obtain the novel linear low-density polyethylene material.
Example 4
The preparation method of the novel linear low-density polyethylene material for the urea box is the same as that in example 2, except that the oligomerization catalyst is Salen only, and the copolymerization catalyst is metallocene compound Me only2Si(Ind)2ZrCl2。
Example 5
A novel linear low density polyethylene material for urea tanks was prepared as in example 2, except that a commercially available Z-N catalyst system was used.
Example 6
The preparation method of the novel linear low-density polyethylene material for the urea box is the same as that in example 2, except that the oligomerization catalyst is only a metal organic framework material, and the copolymerization catalyst is only a metal organic framework material.
EXAMPLES Properties of the materials prepared
Weighing a certain amount of polymer, testing on a differential scanning calorimeter, wherein the heating rate is 10 ℃/min, the heating interval is 40-180 ℃, the heat history of the polymer is eliminated by first heating, and the melting point value of a sample is recorded during second heating; pressing a film on a hot press at 150 ℃, rapidly quenching, drying the film, and measuring the density of the sample by using a density gradient tube method; and (3) measuring and filtering a reaction product, performing qualitative and quantitative analysis on a liquid-phase product by GC-MS, drying a solid product at 40 ℃ in vacuum to constant weight, and obtaining the catalytic activity through the weight change before and after the reaction. The tensile property test refers to the national standard GB/T1040-2006, and the test speed is as follows: 100 mm/min; the impact performance test is carried out according to the national standard GB/T1843-2008.
TABLE 1 ethylene materials made in examples 1-6 for property testing
Figure BDA0001587987670000081
Examples 7 to 13
The preparation methods of the linear low-density polyethylene materials for the novel urea tanks in examples 7 to 13 are the same as those in example 2, except that the molar ratios of the cocatalyst to the oligomerization catalyst are respectively 50:1, 100:1, 150:1, 250:1, 300:1, 400:1 and 500:1, and the performance tests are shown in table 2
TABLE 2 Main Properties of LLDPE specimens from examples 7-13
Figure BDA0001587987670000082
Example 14 to example 20
The preparation methods of the linear low-density polyethylenes for the novel urea tanks in examples 14 to 20 are the same as those in example 2, except that the co-catalyst accounts for the mass of the solvent toluene, the molar ratio of the co-catalyst to the oligomerization catalyst is 200:1, the molar ratio of the co-catalyst to the copolymerization catalyst is 200:1, and the co-catalyst accounts for 0.1%, 0.3%, 0.5%, 0.6%, 0.8%, 1.0%, and 1.2% of the mass of the solvent toluene in examples 14 to 20, and the performance tests are shown in table 3.
TABLE 3 Main Properties of LLDPE specimens from examples 14-20
Figure BDA0001587987670000091
The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are merely illustrative of the principles of the invention, but that various changes and modifications may be made without departing from the spirit and scope of the invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims (6)

1. The linear low-density polyethylene for the urea box is characterized by being obtained by in-situ polymerization of ethylene under the catalysis of an oligomerization catalyst, a copolymerization catalyst and a cocatalyst, wherein the oligomerization catalyst is a metal organic framework material/Fe (Salen) heterogeneous catalyst, Fe (Salen) is immobilized on the metal organic framework material by an encapsulation method, the copolymerization catalyst is a metal organic framework material/metallocene heterogeneous catalyst, a metallocene compound is immobilized on the metal organic framework material by an impregnation method, the cocatalyst is methylaluminoxane MAO, the molar ratio of the cocatalyst to the oligomerization catalyst is 200-250:1, and the molar ratio of the cocatalyst to the copolymerization catalyst is 200:1, the oligomerization catalyst is prepared by the following preparation method and comprises the following steps:
s211, mixing the metal organic framework material with absolute ethyl alcohol to prepare a suspension with the mass fraction of 30-60%, adding salicylaldehyde into the suspension, and stirring the mixture for 10-30min under the condition of 2500r/min at 1000-;
s212, adding ethylenediamine into the mixed solution, heating to 60-80 ℃, and reacting for 1-3h under the condition of 1500r/min and 500-;
s213, cooling the first reaction liquid to room temperature, carrying out vacuum filtration, placing a filter cake in a drying oven, drying for 6-24h at 50-80 ℃, and crushing the dried filter cake to obtain an intermediate metal organic framework material/Salen compound;
s214, mixing the metal organic framework material/Salen compound with anhydrous methanol to prepare a suspension with the mass fraction of 20-50%, adding ferrous chloride tetrahydrate and anhydrous sodium carbonate, heating to 50-70 ℃, and reacting for 2-6h under the condition of 1500r/min to prepare a second reaction solution, wherein the adding amount of the ferrous chloride tetrahydrate accounts for 20-60% of the mass of the metal organic framework material/Salen compound, and the adding amount of the anhydrous sodium carbonate accounts for 0.2-1.5% of the mass of the metal organic framework material/Salen compound;
s215, cooling the second reaction solution to room temperature, carrying out vacuum filtration, and placing a filter cake in a drying oven at 50-80 DEG C
Drying for 6-24h, and crushing the dried filter cake to obtain the metal organic framework material/Fe (Salen) heterogeneous catalyst.
2. The linear low density polyethylene for urea tanks according to claim 1, characterized in that the metallocene compound
Is Me2Si(Ind)2ZrCl2And Et (Ind)2ZrCl2One or two of them, metallocene compounds Me2Si(Ind)2ZrCl2Or Et (Ind)2ZrCl2Is carried on the metal organic framework material by an impregnation method to form the metal organic framework material/metallocene heterogeneous catalyst.
3. A method for preparing the linear low density polyethylene for the urea box according to any one of claims 1-2, comprising the following steps:
s100, adding a solvent cyclohexane into a high-pressure reaction kettle with a stirrer, heating to 90-110 ℃, stirring for 10-30min, and discharging the cyclohexane;
s200, keeping 90-110 ℃, vacuumizing for 0.5-2h, introducing nitrogen for three times, performing ethylene displacement once, cooling to the required temperature, opening an ethylene valve, sequentially adding a solvent cyclohexane and a cocatalyst MAO, stirring for 10-20min under the condition of 3500r/min of 1500-5Pa, keeping the pressure of the ethylene through a buffer tank, and beginning to carry out in-situ copolymerization on the ethylene;
and S300, after reacting for 0.5-3h, closing the ethylene valve, stopping the reaction, washing the product with hydrochloric acid aqueous solution, water and ethanol respectively, and drying in vacuum to obtain the finished product.
4. The method according to claim 3, wherein the copolymerization catalyst is prepared by the steps of:
s221, mixing a metal organic framework material with toluene to prepare a suspension with the mass fraction of 30-60%, adding a metallocene compound, heating to 50-100 ℃, and stirring at the temperature of 500-1500r/min until the solvent is completely volatilized, wherein the adding amount of the metallocene compound accounts for 50-80% of the mass of the metal organic framework material;
s222, drying the obtained solid for 2-6h in a drying oven at the temperature of 50-80 ℃, and grinding the dried solid to obtain the metal organic framework material/metallocene heterogeneous catalyst for later use.
5. The preparation method as claimed in claim 4, wherein the cocatalyst MAO is added in an amount of 0.4-0.8% by mass of the solvent toluene.
6. The preparation method of claim 5, wherein the metal organic framework material is MIL-100, which is assembled by iron cluster compound and trimesic acid ligand, and the preparation method comprises the following steps:
s231, dissolving ferric chloride hexahydrate in corresponding parts by mass in deionized water, stirring to fully dissolve, adding trimesic acid, continuing stirring for 0.5 hour, and placing into an autoclave for reaction at 130 ℃ for 72 hours;
and after the S232 reaction is finished, cooling to room temperature, washing with hot water and methanol for three times, treating in boiling methanol for 12 hours, and carrying out vacuum drying at 150 ℃ for 12 hours to obtain the metal organic framework material MIL-100 for later use.
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Citations (1)

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Publication number Priority date Publication date Assignee Title
CN1621423A (en) * 2003-11-28 2005-06-01 中国科学院化学研究所 Process for preparing linear low density polyethylene

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1621423A (en) * 2003-11-28 2005-06-01 中国科学院化学研究所 Process for preparing linear low density polyethylene

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Title
羧基配体金属有机骨架材料作为催化剂的研究进展;王丽苹等;《分子催化》;20150630;第29卷(第3期);第275-287页 *

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