CN108641026B - Application of benzyl imine pyridine iron complex in preparation of isoprene rubber - Google Patents

Application of benzyl imine pyridine iron complex in preparation of isoprene rubber Download PDF

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CN108641026B
CN108641026B CN201810399947.2A CN201810399947A CN108641026B CN 108641026 B CN108641026 B CN 108641026B CN 201810399947 A CN201810399947 A CN 201810399947A CN 108641026 B CN108641026 B CN 108641026B
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isoprene
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王庆刚
赵梦梦
王晓武
王亮
咸漠
荆楚杨
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Qingdao Institute of Bioenergy and Bioprocess Technology of CAS
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    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F136/00—Homopolymers of compounds having one or more unsaturated aliphatic radicals, at least one having two or more carbon-to-carbon double bonds
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Abstract

The invention discloses a benzyl imine pyridine iron complex, a preparation method thereof and application thereof in isoprene rubber preparation. The method comprises the following steps: adding a main catalyst, a solvent and a cocatalyst, and then adding an isoprene monomer for polymerization reaction to obtain polyisoprene. The microstructure of the obtained polyisoprene can be regulated and controlled by regulating the steric hindrance of the main catalyst, the trans-1,4 structure of the polyisoprene accounts for 30-62%, the cis-1,4 structure accounts for 21-30%, and the 3,4 structure accounts for 17-42%, and the polymer has high molecular weight and narrow molecular weight distribution. The preparation method of isoprene rubber provided by the invention can effectively improve the use efficiency and industrial application value of the iron catalyst.

Description

Application of benzyl imine pyridine iron complex in preparation of isoprene rubber
Technical Field
The present invention relates to the field of chemically synthesized macromolecules.
Background
The increasing demand in the rubber market and the insufficient productivity of natural rubber highlight the importance of synthetic rubber, which is rapidly developing as an integral part of petrochemicals. The isoprene rubber not only has certain similar characteristics to natural rubber and excellent comprehensive performance, but also has the characteristics of wide resources, good processability and the like, and is gradually developed into a pillar variety in the rubber industry. Since 1860 Williams separated isoprene from natural rubber decomposition products, more and more scientists have devoted themselves to the study of isoprene to synthesize natural rubber. There are four different microstructures for polyisoprene: cis-1, 4-polyisoprene; trans-1, 4-polyisoprene; 3, 4-polyisoprene and 1, 2-polyisoprene. Because of the differences in structural units and the manner in which the units are linked, there are large differences in performance between different polyisoprene species. In the process of synthesizing the isoprene rubber, different catalytic systems and synthesis processes are adopted to realize the structural adjustability of the polyisoprene so as to obtain the polyisoprene with different molecular weights, different structural units and different forms. It can be said that the catalyst is the core of the polyisoprene production process, and the technical progress of the isoprene rubber industry is mainly attributed to the progress of the catalyst.
In 1988, the Wangfang Poisson topic group adopted an iron-containing three-way catalytic system (Fe (acac)3/Al(i-Bu)3Nitrogen-containing electron donor) to obtain high molecular weight, high melting point and crystalline polyisoprene with 3,4 structure up to 70%. The experimental results show that Fe (acac)3/Al(i-Bu)3The binary catalytic system cannot cause isoprene polymerization, and the catalytic activity is remarkably improved when a small amount of nitrogen-containing donor is added. The disadvantage is that the system gives polyisoprene with a high gel content. In addition to using a nitrogen-containing electron donor as an additive, dialkyl phosphites may also be used as an electron donor to promote iron-catalyzed isoprene polymerization. The nitrogen or phosphorus containing electron donor is independently used as a third component to be added into a catalytic system, so that the active center of the catalyst can be stabilized, and the polymerization reaction can be promoted. With the gradual development of the ligand, the nitrogen-containing electron donor is improved to form a complex with iron element in a ligand mode to catalyze isoprene polymerization.
In 2002, Porri topic group studied (Bipy)2FeEt2And isoprene is subjected to polymerization reaction catalyzed by MAO system to obtain the crystalline polyisoprene with 3,4 structure content as high as 85%. In 2012, the Ritter topic combines an iron/imine pyridine complex, combines an aluminum alkyl and a boron salt to form a ternary system to catalyze isoprene polymerization, and shows high activity and regioselectivity. The polyisoprene prepared by the complex containing alkyl substituent is mainly of trans-1,4 structure, while the polyisoprene prepared by the complex containing aryl substituent is mainly of cis-1,4 structure. On the basis, the Chengyngle task group designs and synthesizes a series of iron/pyridine alkyl imine and iron/pyridine aryl imine complexes. The influence of ligands containing different substituents on reactivity and stereoselectivity was investigated with MAO as a cocatalyst.
Although iron-catalyzed isoprene polymerization has been reported, the reactivity and selectivity of the existing iron-catalyzed systems are relatively low, and have a great gap from industrial application. Therefore, the development of more efficient catalysts that can control polymer properties, especially the development of new, highly active, highly selective, well-defined catalysts with good functional group compatibility, has been an important but challenging task.
Disclosure of Invention
In order to solve the problems of low reaction activity and selectivity of the iron catalytic system and the like, the invention provides an iron complex, a preparation method thereof and a method for preparing polyisoprene by using the iron complex catalyst. The method can adjust the microstructure of the polyisoprene under a mild condition by changing the steric hindrance of the iron complex, and meanwhile, the isoprene rubber has a large molecular weight and a narrow molecular weight distribution.
The invention is realized by the following technical scheme:
a benzyl imine pyridine iron complex, the structure is shown in formula I,
Figure GDA0002358240360000021
in the formula, R is one or more than two of bromo, methyl, ethyl, isopropyl, phenyl or methoxy; preferably R is methyl and the formula is III:
Figure GDA0002358240360000022
an iron-based catalyst system comprises a main catalyst and a cocatalyst,
the main catalyst is an iron complex, and the structural general formula of the main catalyst is as follows:
Figure GDA0002358240360000023
the cocatalyst is methylaluminoxane, trimethylaluminum, triethylaluminum, triisobutylaluminum, diethylaluminum monochloride and ethylaluminum dichloride, preferably methylaluminoxane, and the structural general formula is
Figure GDA0002358240360000024
Wherein n is a natural number of 4 to 40;
the molar ratio of the iron element in the main catalyst to the aluminum element in the cocatalyst is 1 (100-1000), preferably 1: 500;
the preparation method of the benzyl imine pyridine iron complex comprises the steps of mixing imine pyridine ligand and ferrous chloride in an equimolar ratio in dichloromethane at the temperature of 25 ℃, and carrying out aftertreatment to obtain the iron complex.
The structural general formula of the imine pyridine ligand is as follows:
Figure GDA0002358240360000025
specifically, the structural formula is one or more than two of the following structural formulas:
Figure GDA0002358240360000031
the invention also provides an application of the benzyl imine pyridine iron complex in isoprene rubber preparation. The benzyl imine pyridine iron complex is used as a main catalyst, and the cocatalyst is one or more than two of methylaluminoxane, trimethylaluminum, triethylaluminum, triisobutylaluminum, diethylaluminum monochloride and ethylaluminum dichloride; the general structural formula of the Methylaluminoxane (MAO) is
Figure GDA0002358240360000032
Wherein n is a natural number of 4 to 40; the molar ratio of the aluminum element in the cocatalyst to the iron element in the main catalyst is (100-1000): 1.
The method comprises the following steps: adding a main catalyst, a solvent and a cocatalyst, and then adding an isoprene monomer for polymerization reaction to obtain polyisoprene.
The polymerization solvent is toluene, p-xylene, n-hexane, cyclohexane, pentane, dichloromethane and tetrahydrofuran, and toluene is preferred; the amount of the solvent is as follows: the volume ratio of the solvent to the isoprene is (1-10): 1.
In the application, the feeding sequence can be as follows: sequentially adding a main catalyst/solvent/cocatalyst/isoprene and sequentially adding a cocatalyst/solvent, isoprene and a dichloromethane solution of the main catalyst, preferably sequentially adding the main catalyst/solvent/cocatalyst/isoprene to obtain polyisoprene, i.e. isoprene rubber;
in the application, the molar ratio of the isoprene monomer to the iron element in the main catalyst is preferably (2000) -5000: 1, and preferably 2000: 1;
the application is that the temperature of the polymerization reaction is-30-50 ℃, preferably 25 ℃;
the polymerization time is 10min-16h, preferably 2 h;
the polyisoprene, i.e. the isoprene rubber obtained by the application has the number average molecular weight of 5.2 multiplied by 104-5.7×105The molecular weight distribution is 1.8-4.6;
according to the application, the micro structure of polyisoprene, namely isoprene rubber, can be adjusted according to different structures of the added main catalyst, the proportion range of the obtained polyisoprene, namely isoprene rubber trans-1,4 structure is 0-84%, the proportion range of cis-1,4 structure is 10-53%, and the proportion of 3,4 structure is 6-47%.
Advantageous effects
(1) The iron complex/methylaluminoxane two-component catalytic system is used for catalyzing isoprene polymerization, and the boron salt price of the three components is lower than that of the three components in background introduction;
(2) the iron-based catalyst can realize high-activity controllable polymerization of isoprene to obtain high molecular weight (5.2 multiplied by 10)4-5.7×105) And iron-based isoprene rubber with narrow molecular weight distribution (1.8-4.6).
Drawings
FIG. 1 is a nuclear magnetic hydrogen spectrum with R being a methyl ligand;
FIG. 2 is a nuclear magnetic hydrogen spectrum with R being a phenyl ligand;
FIG. 3 is a nuclear magnetic hydrogen spectrum of polyisoprene obtained in example 1;
FIG. 4 is a nuclear magnetic carbon spectrum of the polyisoprene obtained in example 1.
Detailed Description
Preparation example 1
This example prepares an iron imine pyridine complex of formula II:
a100 mL dry reaction flask was charged with 4A molecular sieves and baked for 30 minutes. Under an argon atmosphere, dry dichloromethane (40mL), benzylamine (1.2g, 10.8mmol) and 6-bromopyridine-2-carbaldehyde (2.0g, 10.8mmol) were added in that order. The reaction was carried out overnight at room temperature and the aldehyde substrate was completely reacted as detected by TLC plate. Filtered, spin-dried, and vacuum-dried to give a yellow liquid (2.4g, yield: 82%) of the formula
Figure GDA0002358240360000041
25mL of dry reaction tube, and 15mL of redistilled dichloromethane and anhydrous FeCl with equal molar ratio are sequentially added into a glove box2(100mg, 0.8mmol) and the above prepared imidazopyridine ligand (217mg, 0.8mmol) were stirred at room temperature for 15 h. After the reaction was completed, methylene chloride was vacuum-dried, and then 10mL of dry n-hexane was added and washed 3 times, and vacuum-dried to a constant weight, whereby 285mg of red color was obtained (yield: 90%).
Mass spectrometry analysis: c13H11BrClFeN2[M-Cl]+Theoretical value: 364.9144, respectively; measured value: 364.9173.
elemental analysis: c13H11BrCl2FeN2: theoretical value: c, 38.85%; h, 2.76%; n, 6.97%; measured value: c, 38.76%; h, 2.83%; n,6.91 percent.
Preparation example 2
This example prepares an iron imine pyridine complex of formula III:
a100 mL dry reaction flask was charged with 4A molecular sieves and baked for 30 minutes. Under an argon atmosphere, dry dichloromethane (60mL), 2-methylbenzylamine (1.1g, 9.3mmol), and pyridine-2-carbaldehyde (1.0g, 9.3mmol) were added in this order. The reaction was carried out overnight at room temperature and the aldehyde substrate was completely reacted as detected by TLC plate. Filtered, spin-dried, and vacuum-dried to give a yellow liquid (2.2g, yield: 61%) of the formula
Figure GDA0002358240360000042
25mL dry reaction tube, successively added in a glove box15mL of redistilled dichloromethane, anhydrous FeCl of equimolar ratio2(100.0mg, 0.8mmol) and the imine pyridine ligand prepared above (165.9mg, 0.8mmol) were stirred at room temperature for 15 h. After the reaction was completed, methylene chloride was vacuum-dried, 10mL of dry n-hexane was added and washed 3 times, and vacuum-dried to a constant weight to obtain 155mg of brick red solid (yield: 58%).
Mass spectrometry analysis: c14H14Cl2FeN2[M-Cl]+Theoretical value: 301.0195, respectively; measured value: 301.0173.
elemental analysis: c14H14Cl2FeN2: theoretical value: c, 49.89%; h, 4.19%; n, 8.31%; measured value: c, 49.98%; h, 3.44%; and N, 8.15%.
Preparation example 3
This example prepares an iron imine pyridine complex of formula IV:
a100 mL dry reaction flask was charged with 4A molecular sieves and baked for 30 minutes. Under an argon atmosphere, dry dichloromethane (60mL), 2-methylbenzylamine (1.9g, 14.0mmol), and pyridine-2-carbaldehyde (1.5g, 14.0mmol) were added in this order. The reaction was carried out overnight at room temperature and the aldehyde substrate was completely reacted as detected by TLC plate. Filtered, spin-dried, and vacuum-dried to give a yellow liquid (2.6g, yield: 84%) of the formula
Figure GDA0002358240360000051
25mL of dry reaction tube, and 15mL of redistilled dichloromethane and anhydrous FeCl with equal molar ratio are sequentially added into a glove box2(100.0mg, 0.8mmol) and the imine pyridine ligand prepared above (177.0mg, 0.8mmol) were stirred at room temperature for 15 h. After the reaction was completed, methylene chloride was vacuum-dried, and then 10mL of dry n-hexane was added and washed 3 times, and vacuum-dried to a constant weight to obtain 244mg of a red solid (yield: 88%).
Mass spectrometry analysis: c14H14Cl2FeN2[M-Cl]+Theoretical value: 315.0351, respectively; measured value: 315.0342.
elemental analysis: c15H16Cl2FeN2: theoretical value: c, 51.32%; h, 4.59%; n, 7.98%(ii) a Measured value: c, 51.11%; h, 4.32%; n,8.14 percent.
Preparation example 4
This example prepares an iron imine pyridine complex of formula V:
a100 mL dry reaction flask was charged with 4A molecular sieves and baked for 30 minutes. Under an argon atmosphere, dry dichloromethane (60mL), 2,4, 6-trimethylbenzylamine (1.4g, 9.4mmol) and pyridine-2-carbaldehyde (1.0g, 9.3mmol) were added in this order. The reaction was carried out overnight at room temperature and the aldehyde substrate was completely reacted as detected by TLC plate. Filtered, spin-dried, and vacuum-dried to give a yellow solid (1.2g, yield: 55%) of formula
Figure GDA0002358240360000052
25mL of dry reaction tube, and 15mL of redistilled dichloromethane and anhydrous FeCl with equal molar ratio are sequentially added into a glove box2(100.0mg, 0.8mmol) and the imine pyridine ligand prepared above (188.0mg, 0.8mmol) were stirred at room temperature for 12 h. After the reaction was completed, a clear liquid was obtained, methylene chloride was vacuum-drained, 10mL of dry n-hexane was added and washed 3 times, and vacuum-drained to constant weight to obtain 178mg of brick-red flaky solid (yield: 62%).
Mass spectrometry analysis: c16H18ClFeN2[M-Cl]+Theoretical value: 329.0508, respectively; measured value: 329.0521.
elemental analysis: c16H18Cl2FeN2: theoretical value: c, 52.64%; h, 4.97%; n, 7.67%; measured value: c, 52.51%; h, 5.12%; and N, 7.89%.
Preparation example 5
This example prepares an iron imine pyridine complex of formula VI:
a100 mL dry reaction flask was charged with 4A molecular sieves and baked for 30 minutes. Under an argon atmosphere, dry dichloromethane (60mL), 2,4, 6-trimethylbenzylamine (1.7g, 9.3mmol) and pyridine-2-carbaldehyde (1.0g, 9.3mmol) were added in this order. The reaction was carried out overnight at room temperature and the aldehyde substrate was completely reacted as detected by TLC plate. Filtration, spin-drying, and vacuum suction-drying gave a yellow solid (1.6g, yield: 63%) of formula
Figure GDA0002358240360000061
25mL of dry reaction tube, and 15mL of redistilled dichloromethane and anhydrous FeCl with equal molar ratio are sequentially added into a glove box2(50.0mg, 0.4mmol) and the above prepared imidazopyridine ligand (107.4mg, 0.4mmol) were stirred at room temperature for 24 h. After the reaction was completed, a red suspension was obtained, methylene chloride was vacuum-drained, 10mL of dry n-hexane was added and washed 3 times, and vacuum-drained to a constant weight to obtain 98mg of a violet solid (yield: 62%).
Mass spectrometry analysis: c19H16ClFeN2[M-Cl]+Theoretical value: 363.0351, respectively; measured value: 363.0372.
elemental analysis: c19H16Cl2FeN2: theoretical value: c, 57.18%; h, 4.04%; n, 7.02%; measured value: c, 57.01%; h, 4.28%; and 6.89 percent of N.
Preparation example 6
This example prepares an iron imine pyridine complex of formula VII:
a100 mL dry reaction flask was charged with 4A molecular sieves and baked for 30 minutes. Under an argon atmosphere, dry dichloromethane (60mL), 2,4, 6-trimethylbenzylamine (1.3g, 9.4mmol) and pyridine-2-carbaldehyde (1.0g, 9.3mmol) were added in this order. The reaction was carried out overnight at room temperature and the aldehyde substrate was completely reacted as detected by TLC plate. Filtered, spin-dried, and vacuum-dried to give a yellow liquid (1.4g, yield: 66%) of the formula
Figure GDA0002358240360000062
25mL of dry reaction tube, and 15mL of redistilled dichloromethane and anhydrous FeCl with equal molar ratio are sequentially added into a glove box2(100mg, 0.79mmol) and the imine pyridine ligand prepared above (178.5mg, 0.8mmol) were stirred at room temperature for 24 h. After the reaction was completed, methylene chloride was vacuum-dried, and then 10mL of dry n-hexane was added and washed 3 times, and vacuum-dried to a constant weight to obtain 134mg of a purple solid (yield: 48%).
Mass spectrometry analysis: c14H14ClFeN2O[M-Cl]+Theoretical value: 317.0144, respectively; measured in factThe value: 317.0166.
elemental analysis: c14H14Cl2FeN2O: theoretical value: c, 47.63%; h, 4.00%; n, 7.94%; measured value: c, 47.41%; h, 4.12%; and N,7.83 percent.
Example 1
A 25mL dry reaction tube is transferred to a glove box, 4.0mg (10 mu mol) of a weighed main catalyst shown in formula II is added, the glove box is transferred to the outside, 5mL of anhydrous toluene and 3.33mL (1.5M) of methylaluminoxane are added under the argon atmosphere, 2mL (20mmol) of isoprene monomer is added, the reaction is carried out for 10min at room temperature, methanol dilute hydrochloric acid solution (1:50, V/V) is used for stopping the reaction, a large amount of white solid is separated out and filtered, the solid is washed by a large amount of ethanol, and the vacuum pumping is carried out at room temperature until the weight is constant, wherein the yield is 52 percent, the number average molecular weight is 325567, the molecular weight distribution is 2.0, the proportion of trans-1,4 structures is 52 percent, the proportion range of cis-1,4 structures is 22 percent, and the proportion of 3,4 structures is.
Example 2
A 25mL dry reaction tube is transferred to a glove box, 3.4mg (10 mu mol) of the weighed catalyst in the formula III is added, the mixture is transferred to the outside of the glove box, 5mL of anhydrous toluene and 3.33mL (1.5M) of methylaluminoxane are added under the argon atmosphere, 2mL (20mmol) of isoprene monomer is added, the mixture reacts for 10min at room temperature, methanol dilute hydrochloric acid solution (1:50, V/V) is used for stopping the reaction, a large amount of white solid is separated out and filtered, the solid is washed by a large amount of ethanol, and is vacuumized to constant weight at room temperature, the yield is 75%, the number average molecular weight is 573947, the molecular weight distribution is 1.8, the proportion of trans-1,4 structures is 80%, the proportion range of cis-1,4 structures is 13%, and the proportion of 3,4 structures is 7%.
Example 3
A 25mL dry reaction tube is transferred to a glove box, 3.5mg (10 mu mol) of the weighed catalyst in the formula IV is added, the glove box is transferred to the outside, 5mL of anhydrous toluene and 3.33mL (1.5M) of methylaluminoxane are added under the argon atmosphere, 2mL (20mmol) of isoprene monomer is added, the reaction is carried out for 10min at room temperature, methanol dilute hydrochloric acid solution (1:50, V/V) is used for terminating the reaction, a large amount of white solid is separated out and filtered, the solid is washed by a large amount of ethanol, and is vacuumized to constant weight at room temperature, the yield is 60%, the number average molecular weight is 332142, the molecular weight distribution is 2.0, the proportion of trans-1,4 structures is 49%, the proportion range of cis-1,4 structures is 23%, and the proportion of 3,4 structures is 28%.
Example 4
A 25mL dry reaction tube is transferred to a glove box, 3.7mg (10 mu mol) of the weighed catalyst in the formula V is added, the glove box is transferred to the outside, 5mL of anhydrous toluene and 3.33mL (1.5M) of methylaluminoxane are added under the argon atmosphere, 2mL (20mmol) of isoprene monomer is added, the reaction is carried out for 10min at room temperature, methanol dilute hydrochloric acid solution (1:50, V/V) is used for terminating the reaction, a large amount of white solid is separated out and filtered, the solid is washed by a large amount of ethanol, and is vacuumized to constant weight at room temperature, the yield is 35%, the number average molecular weight is 219952, the molecular weight distribution is 2.1, the proportion of trans-1,4 structures is 38%, the proportion range of cis-1,4 structures is 21%, and the proportion of 3,4 structures is 41%.
Example 5
A 25mL dry reaction tube is transferred to a glove box, 4.0mg (10 mu mol) of the weighed catalyst in the formula VI is added, the glove box is transferred to the outside, 5mL of anhydrous toluene and 3.33mL (1.5M) of methylaluminoxane are added under the argon atmosphere, 2mL (20mmol) of isoprene monomer is added, the reaction is carried out for 16h at room temperature, methanol dilute hydrochloric acid solution (1:50, V/V) is used for terminating the reaction, a large amount of white solid is separated out and filtered, the solid is washed by a large amount of ethanol, and the solid is vacuumized to constant weight at room temperature, wherein the yield is 81%, the number average molecular weight is 198655, the molecular weight distribution is 2.4, the proportion of trans-1,4 structures is 0%, the proportion range of cis-1,4 structures is 50%, and the proportion of 3,4 structures is 50%.
Example 6
A 25mL dry reaction tube is transferred to a glove box, 3.5mg (10 mu mol) of the weighed catalyst in the formula VII is added, the glove box is transferred to the outside, 5mL of anhydrous toluene and 3.33mL (1.5M) of methylaluminoxane are added under the argon atmosphere, 2mL (20mmol) of isoprene monomer is added, the reaction is carried out for 10min at room temperature, methanol dilute hydrochloric acid solution (1:50, V/V) is used for terminating the reaction, a large amount of white solid is separated out and filtered, the solid is washed by a large amount of ethanol, and is vacuumized to constant weight at room temperature, the yield is 35%, the number average molecular weight is 219952, the molecular weight distribution is 2.1, the proportion of trans-1,4 structures is 38%, the proportion range of cis-1,4 structures is 32%, and the proportion of 3,4 structures is 30%.
Example 7
The method of example 2 was used to polymerize isoprene, except that the reaction time was extended to 2h, a large amount of white solid precipitated after quenching, the yield was 100%, the number average molecular weight was 513369, the molecular weight distribution was 1.8, the proportion of trans-1,4 structure was 81%, the proportion of cis-1,4 structure was 12%, and the proportion of 3,4 structure was 7%.
Example 8
Isoprene polymerization was carried out by the method of example 7, except that methylaluminoxane (0.67 mL, 1.5M) was quenched to precipitate a large amount of white solid, the yield was 78%, the number average molecular weight was 336528, the molecular weight distribution was 2.0, the proportion of trans-1,4 structure was 80%, the proportion of cis-1,4 structure was 12%, and the proportion of 3,4 structure was 8%.
Example 9
Isoprene polymerization was carried out by the method of example 7, except that 6.7mL (1.5M) of methylaluminoxane was quenched to precipitate a large amount of white solid with a yield of 100%, a number average molecular weight of 502179, a molecular weight distribution of 2.0, a proportion of trans-1,4 structure of 80%, a proportion of cis-1,4 structure of 12%, and a proportion of 3,4 structure of 8%.
Example 10
Isoprene polymerization was carried out by the method of example 7, except that 5.0mL (1.0M) of trimethylaluminum was used as the cocatalyst, and no solid was precipitated after quenching, with a yield of 0%.
Example 11
Isoprene was polymerized by the method of example 7, except that the cocatalyst was changed to triethylaluminum (5.0 mL) (1.0M), no solid was precipitated after quenching, and the yield was 0%.
Example 12
Isoprene was polymerized by the method of example 7, except that 5.0mL (1.0M) of triisobutylaluminum was used as the cocatalyst, and no solid was precipitated after quenching, resulting in a yield of 0%.
Example 13
Isoprene was polymerized by the method of example 7, except that the cocatalyst was changed to 5.0mL (1.0M) of diethylaluminum chloride, and no solid was precipitated after quenching, and the yield was 0%.
Example 14
Isoprene was polymerized by the method of example 7, except that the order of addition was changed: a25 mL dry reaction tube was transferred to a glove box, and 3.4mg (10. mu. mol) of the weighed main catalyst represented by formula III was added thereto, and then transferred to the outside of the glove box, and 5mL of anhydrous toluene and 2mL (20mmol) of isoprene were added thereto under an argon atmosphere, and 3.33mL (1.5M) of methylaluminoxane was further added thereto. After quenching, a large amount of white solid is separated out, the yield is 100%, the number average molecular weight is 236994, the molecular weight distribution is 2.0, the proportion of trans-1,4 structures is 73%, the proportion range of cis-1,4 structures is 12%, and the proportion of 3,4 structures is 15%.
Example 15
Isoprene was polymerized by the method of example 11, except that the order of addition was changed: a25 mL dry reaction tube was charged with 5mL of dry toluene, 2mL (20mmol) of isoprene, 3.33mL (1.5M) of methylaluminoxane under an argon atmosphere and finally a solution of 3.4mg (10. mu. mol) of catalyst (R is 4-methyl) in dichloromethane (1mL) was added. After quenching, a large amount of white solid is precipitated, the yield is 33%, the number average molecular weight is 765, the molecular weight distribution is 4.6, the proportion of trans-1,4 structures is 62%, the proportion of cis-1,4 structures is 21%, and the proportion of 3,4 structures is 17%.
Example 16
The method of example 7 was used to polymerize isoprene, except that the polymerization reaction was carried out at-30 ℃, a large amount of white solid was precipitated after quenching, the yield was 78%, the number average molecular weight was 52061, the molecular weight distribution was 1.8, the proportion of trans-1,4 structure was 10%, the proportion of cis-1,4 structure was 48%, and the proportion of 3,4 structure was 42%.
Example 17
Isoprene was polymerized by the method of example 7, except that the polymerization was carried out at-78 ℃ and no solid precipitated after 16h of quenching, the yield being 0%.
Example 18
Isoprene was polymerized by the method of example 7, except that the polymerization was carried out at 50 ℃, and after quenching, a large amount of white solid was precipitated, with a yield of 13%, a number average molecular weight of 113280, a molecular weight distribution of 3.8, a proportion of trans-1,4 structure of 23%, a proportion of cis-1,4 structure of 35%, and a proportion of 3,4 structure of 42%.

Claims (4)

1. The application of the benzyl imine pyridine iron complex in the preparation of isoprene rubber is characterized in that the benzyl imine pyridine iron complex is used as a main catalyst, a cocatalyst is methylaluminoxane, and the structural general formula of Methylaluminoxane (MAO) is shown in the specification
Figure FDA0002350184770000011
Wherein n is a natural number of 4 to 40; the molar ratio of the aluminum element in the cocatalyst to the iron element in the main catalyst is (100-;
the preparation steps of the isoprene rubber are as follows: adding a main catalyst, a solvent and a cocatalyst, adding an isoprene monomer, and carrying out polymerization reaction at room temperature to obtain polyisoprene;
the structure of the benzyl imine pyridine iron complex is shown as a formula I,
Figure FDA0002350184770000012
in the formula, R is methyl;
the preparation method of the benzyl imine pyridine iron complex comprises the steps of mixing imine pyridine ligand and ferrous chloride in an equimolar ratio in dichloromethane at the temperature of 25 ℃, and carrying out aftertreatment to obtain the iron complex; the structural formula of the imine pyridine ligand is as follows:
Figure FDA0002350184770000013
2. the use according to claim 1, wherein the solvent is one or more of toluene, p-xylene, n-hexane, cyclohexane, pentane, dichloromethane and tetrahydrofuran; the molar ratio of the isoprene monomer to the iron element in the main catalyst is (2000) -5000) 1.
3. Use according to claim 1, wherein the polymerization time is from 10min to 16 h.
4. Use according to claim 1, characterized in that the polyisoprene obtained has a number-average molecular weight of 5.2X 104-5.7×105The molecular weight distribution is 1.8-4.6; the obtained polyisoprene trans-1,4 structure accounts for 0-84%, the cis-1,4 structure accounts for 10-53%, and the 3,4 structure accounts for 6-47%.
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