An ethylene-styrene copolymer with bimodal molecular weight and its preparation method

Abstract

The present invention relates to the technical field of olefin polymers, and specifically provides an ethylene-styrene copolymer with a bimodal molecular weight and a preparation method thereof. The ethylene-styrene copolymer of the present invention is shown as formula I. Compared with the prior art, through the catalyst system and polymerization reaction process of the present invention, a bimodal copolymer with polyethylene units and syndiotactic polystyrene units on the main chain can be obtained. The high molecular weight part of the number average molecular weight is 10,000 to 3,000,000, and the molecular weight distribution is 1 to 3; the low molecular weight part is 1,000 to 100,000, and the molecular weight distribution is 1 to 3.

Description

Technical Field

[0001] The present invention relates to the technical field of olefin polymers, and more specifically, to an ethylene-styrene copolymer having a bimodal molecular weight and a preparation method thereof. Background Art

[0002] Syndiotactic polystyrene is a semi-crystalline polymer with high heat resistance, strong chemical corrosion resistance, high dimensional stability, low density, low dielectric properties, good hydrolysis stability, crystallinity, and a melting point as high as 270 °C. Currently, it is used as a special polymer material and has broad application prospects in industry. However, due to the brittleness and difficult processing of high syndiotactic polystyrene materials, its application fields are severely restricted. Therefore, the modification of high syndiotactic polystyrene has always attracted the attention of scholars and the industrial community.

[0003] In 2004, Researcher Zhaomin Hou of the Institute of Physical and Chemical Research in Japan proposed introducing ethylene units into high syndiotactic styrene segments and using ethylene monomers to separate long continuous styrene segments to improve the brittleness of the material. They obtained an ethylene-styrene copolymer with syndiotactic styrene units on the main chain, and the relevant findings were published in the Journal of the American Chemical Society. In 2021, Researcher Dongmei Cui reported the preparation of ethylene-styrene multi-block copolymers using the concept of chain shuttling polymerization, also hoping to improve the mechanical properties of the material. In previous reports, the molecular weights of ethylene-styrene copolymers were all unimodal distributions.

[0004] For the industrially important polyethylene industry, in order to improve the processability of polyethylene, scholars and the industrial community have been committed to synthesizing polyethylene with a bimodal molecular weight. Among them, in the bimodal distribution of polyethylene, the high molecular weight part provides mechanical properties, making the material have high strength and high toughness; the low molecular weight part can improve the processing performance of the material and ensure the lubrication of the material. Therefore, applying the concept of bimodal molecular weight polymers to the polystyrene industry will also balance the mechanical strength and processability and achieve good results.

[0005] In summary, the copolymer material of ethylene and styrene with a bimodal molecular weight distribution is of great significance for academic research and industrial production. However, this bimodal ethylene-styrene copolymer needs to be synthesized in-situ and cannot be prepared by simply blending two polymers with different molecular weights. Therefore, suitable catalysts and polymerization processes are required. Summary of the Invention

[0006] In view of this, the object of the present invention is to provide an ethylene-styrene copolymer with a bimodal molecular weight and a preparation method thereof. Through the catalytic system and polymerization reaction process of the present invention, a bimodal block copolymer with polyethylene units and syndiotactic polystyrene units on the main chain can be obtained. The high molecular weight part of the number average molecular weight is 10,000 to 3,000,000, and the molecular weight distribution is 1 to 3; the low molecular weight part is 1,000 to 100,000, and the molecular weight distribution is 1 to 3.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] An ethylene-styrene copolymer as shown in formula I,

[0009]

[0010] In formula I, x is a natural number greater than 2;

[0011] y is a natural number greater than 1;

[0012] n is the degree of polymerization;

[0013] The number average molecular weight distribution of the copolymer of ethylene and styrene shows a bimodal distribution; the high molecular weight part of the number average molecular weight is 10,000 to 3,000,000, and the molecular weight distribution is 1 to 3; the low molecular weight part is 1,000 to 100,000, and the molecular weight distribution is 1 to 3; the molecular weight of the high molecular weight part is 30 to 50 times that of the low molecular weight part.

[0014] In the present invention, the high molecular weight part of the number average molecular weight of the copolymer is 100,000 to 2,000,000, and the low molecular weight part is 10,000 to 80,000.

[0015] In the present invention, for the high molecular weight part, the content of ethylene is 0 to 50 mol%, and for the low molecular weight part, the content of ethylene is 50 to 100 mol%.

[0016] In the present invention, the glass transition temperature of the ethylene-styrene copolymer is -50°C to 50°C, preferably -40°C to 30°C; the ethylene-styrene copolymer has two melting points, the first melting point is 110 to 130°C, and the second melting point is 200 to 275°C, preferably 200 to 270°C.

[0017] The present invention also provides a preparation method of the above ethylene-styrene copolymer, including:

[0018] Carrying out copolymerization reaction of ethylene and styrene under a catalytic system to obtain an ethylene-styrene copolymer as shown in formula (I);

[0019] The catalytic system is composed of an organic boron salt compound, an organic aluminum compound, and a rare earth metal complex as shown in formula (II);

[0020]

[0021] In formula II, L n is a rare earth element; L n is one of scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium;

[0022] L w is selected from Lewis bases;

[0023] L w has a number of 0 to 3;

[0024] C p is selected from substituted or unsubstituted cyclopentadienyl, substituted or unsubstituted indenyl, substituted or unsubstituted fluorenyl, substituted or unsubstituted fused heterocyclic cyclopentadienyl;

[0025] X1 and X2 are independently selected from one of a silicon methyl-substituted alkyl, a dimethyl nitrogen-substituted benzyl, a substituted or unsubstituted allyl;

[0026] Z is selected from C, Si or Ge;

[0027] R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 are independently selected from hydrogen, halogen, C1-C10 alkyl, substituted or unsubstituted aryl;

[0028] q is an integer from 0 to 3.

[0029] In the present invention, X1 and X2 are independently selected from -CH2SiMe3, -CH(SiMe3)2, -CH2C6H4NMe2-o, -1,3-C3H5, -1,3-C3H4(Me) or -1,3-C3H3(SiMe3)2;

[0030] The said L w is selected from tetrahydrofuran, diethyl ether, ethylene glycol dimethyl ether or pyridine.

[0031] In the present invention, the said R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 are independently selected from hydrogen, halogen, methyl, ethyl, isopropyl, tert-butyl or phenyl, 2,6-dimethylphenyl, 4-methylphenyl, mesityl, 2,6-diisopropylphenyl or 2,4,6-triisopropylbenzene.

[0032] In the present invention, the pressure of the polymerization reaction is 1 to 50 atm, preferably 3 to 25 atm, more preferably 3 atm. The pressure of the polymerization reaction is the pressure of ethylene gas.

[0033] In the present invention, the molar ratio of the organoborate compound to the rare earth metal complex is 1:10 to 10:1;

[0034] the molar ratio of the organoaluminum compound to the rare earth metal complex is (1 to 300):1.

[0035] In the present invention, the temperature of the polymerization reaction is 25 to 150 °C, preferably 25 to 100 °C.

[0036] In the present invention, the solvent for the polymerization reaction is one or more of aliphatic saturated hydrocarbons, aromatic hydrocarbons, aryl halides, and cycloalkanes.

[0037] In the present invention, the preparation method of the catalyst system includes: mixing the rare earth metal complex, the organoborate, and the organoaluminum compound in a hydrocarbon reagent according to the ratio to obtain a homogeneous catalyst system for ethylene-styrene bimodal copolymerization.

[0038] In the present invention, the molar ratio of the organoborate compound to the rare earth metal complex is 1:10 to 10:1, and the molar ratio of the organoaluminum compound to the rare earth metal complex is (1 to 300):1.

[0039] In the present invention, the organoborate compound can be an ionic compound composed of an organoborate anion and a cation; the organoborate anion is selected from tetraphenylborate ([BPh4] - ), tetrakis(monofluorophenyl)borate, tetrakis(difluorophenyl)borate, tetrakis(trifluorophenyl)borate, tetrakis(tetrafluorophenyl)borate, tetrakis(pentafluorophenyl)borate ([B(C6F5)4] - ), tetrakis(tetrafluoromethylphenyl)borate, tetrakis(tolyl)borate, tetrakis(xylenyl)borate, (triphenyl,pentafluorophenyl)borate, [tris(pentafluorophenyl),phenyl]borate, or undecahydro-7,8-dicarbaundecaborate; the cation is selected from carbocation, oxonium cation, ammonium cation, phosphonium cation, cycloheptatrienylium cation, or ferrocenium cation containing a transition metal, and the carbocation includes trisubstituted carbocations such as triphenylcarbocation ([Ph3C] + ), and tris(substituted phenyl)carbocations, and more specific examples of the tris(substituted phenyl)carbocations include tris(tolyl)carbocation; the ammonium cation includes trialkylammonium cations such as trimethylammonium cation, triethylammonium cation ([NEt3H] +) Tripropylammonium cations and tributylammonium cations; N,N-dialkylbenzenammonium cations such as N,N-dimethylbenzenammonium cation ([PhNMe2H] + ) N,N-diethylbenzenammonium cation and N,N-2,4,6-pentamethylbenzenammonium cation and dialkylammonium cations such as diisopropylammonium cation and dicyclohexylammonium cation; Phosphonium cations include triarylphosphonium cations such as triphenylphosphonium cation, tris(tolyl)phosphonium cation and tris(xylenyl)phosphonium cation.

[0040] The organic borate compound can specifically be selected from [Ph3C][B(C6F5)4], [PhNMe2H][BPh4], [NEt3H][BPh4], [PhNMe2H][B(C6F5)4], etc.; An organoboron compound with the same function as the organic borate compound can also be used, such as B(C6F5)3;

[0041] The organoaluminum compound is selected from one or more of trimethylaluminum, triethylaluminum, tripropylaluminum, tributylaluminum, triisopropylaluminum, triisobutylaluminum, tripentylaluminum, trihexylaluminum, tricyclohexylaluminum, trioctylaluminum, triphenylaluminum, tri-p-tolylaluminum, tribenzylaluminum, ethyldibenzylaluminum and ethyldi(p-tolyl)aluminum.

[0042] In the present invention, the rare earth metal complex is any one of complexes 1 to 35:

[0043] Complex 1: Cp = C5Me4, Z = Si, R1 = H, R2 = H, R3 = H, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 = H, R 11 = Me, R 12 = Me, Ln = Sc, X1 = CH2SiMe3, X2 = CH2SiMe3;

[0044] Complex 2: Cp = C5Me4, Z = Si, R1 = H, R2 = H, R3 = H, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 = H, R 11 = Me, R 12 = Me, Ln = Y, X1 = CH2SiMe3, X2 = CH2SiMe3;

[0045] Complex 3: Cp = C5Me4, Z = Si, R1 = H, R2 = H, R3 = H, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 = H, R 11 = Me, R 12=Me, Ln = Lu, X1 = CH2SiMe3, X2 = CH2SiMe3;

[0046] Complex 4: Cp = C5Me4, Z = Si, R1 = H, R2 = H, R3 = H, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 = H, R 11 = Me, R 12 = Me, Ln = Dy, X1 = CH2SiMe3, X2 = CH2SiMe3;

[0047] Complex 5: Cp = C5Me4, Z = Si, R1 = H, R2 = H, R3 = H, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 = H, R 11 = Me, R 12 = Me, Ln = Er, X1 = CH2SiMe3, X2 = CH2SiMe3;

[0048] Complex 6: Cp = C5H4, Z = Si, R1 = H, R2 = H, R3 = H, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 = H, R 11 = Me, R 12 = Me, Ln = Sc, X1 = CH2SiMe3, X2 = CH2SiMe3;

[0049] Complex 7: Cp = C5H4, Z = Si, R1 = H, R2 = H, R3 = H, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 = H, R 11 = Me, R 12 = Me, Ln = Y, X1 = CH2SiMe3, X2 = CH2SiMe3;

[0050] Complex 8: Cp = C5H4, Z = Si, R1 = H, R2 = H, R3 = H, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 = H, R 11 = Me, R 12 = Me, Ln = Lu, X1 = CH2SiMe3, X2 = CH2SiMe3;

[0051] Complex 9: Cp = C 13 H 10, Z = Si, R1 = H, R2 = H, R3 = H, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 = H, R 11 = Me, R 12 = Me, Ln = Sc, X1 = CH2SiMe3, X2 = CH2SiMe3;

[0052] Complex 10: Cp = C 13 H 10 , Z = Si, R1 = H, R2 = H, R3 = H, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 = H, R 11 = Me, R 12 = Me, Ln = Y, X1 = CH2SiMe3, X2 = CH2SiMe3;

[0053] Complex 11: Cp = C 13 H 10 , Z = Si, R1 = H, R2 = H, R3 = H, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 = H, R 11 = Me, R 12 = Me, Ln = Lu, X1 = CH2SiMe3, X2 = CH2SiMe3;

[0054] Complex 12: Cp = C5Me4, Z = Si, R1 = Me, R2 = H, R3 = H, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 = H, R 11 = Me, R 12 = Me, Ln = Sc, X1 = CH2SiMe3, X2 = CH2SiMe3;

[0055] Complex 13: Cp = C5Me4, Z = Si, R1 = Me, R2 = H, R3 = H, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 = H, R 11 = Me, R 12 = Me, Ln = Y, X1 = CH2SiMe3, X2 = CH2SiMe3;

[0056] Complex 14: Cp = C5Me4, Z = Si, R1 = Me, R2 = H, R3 = H, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 = H, R 11=Me, R 12 =Me, Ln = Lu, X1 = CH2SiMe3, X2 = CH2SiMe3;

[0057] Complex 15: Cp = C5Me4, Z = Si, R1 = H, R2 = Me, R3 = H, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 =H, R 11 =Me, R 12 =Me, Ln = Sc, X1 = CH2SiMe3, X2 = CH2SiMe3;

[0058] Complex 16: Cp = C5Me4, Z = Si, R1 = H, R2 = Me, R3 = H, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 =H, R 11 =Me, R 12 =Me, Ln = Y, X1 = CH2SiMe3, X2 = CH2SiMe3;

[0059] Complex 17: Cp = C5Me4, Z = Si, R1 = H, R2 = Me, R3 = H, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 =H, R 11 =Me, R 12 =Me, Ln = Lu, X1 = CH2SiMe3, X2 = CH2SiMe3;

[0060] Complex 18: Cp = C5Me4, Z = Si, R1 = H, R2 = -OMe, R3 = H, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 =H, R 11 =Me, R 12 =Me, Ln = Sc, X1 = CH2SiMe3, X2 = CH2SiMe3;

[0061] Complex 19: Cp = C5Me4, Z = Si, R1 = H, R2 = -OMe, R3 = H, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 =H, R 11 =Me, R 12 =Me, Ln = Y, X1 = CH2SiMe3, X2 = CH2SiMe3;

[0062] Complex 20: Cp = C5Me4, Z = Si, R1 = H, R2 = -OMe, R3 = H, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 = H, R 11 = Me, R 12 = Me, Ln = Lu, X1 = CH2SiMe3, X2 = CH2SiMe3;

[0063] Complex 21: Cp = C5Me4, Z = Si, R1 = H, R2 = H, R3 = CF3, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 = H, R 11 = Me, R 12 = Me, Ln = Sc, X1 = CH2SiMe3, X2 = CH2SiMe3;

[0064] Complex 22: Cp = C5Me4, Z = Si, R1 = H, R2 = H, R3 = CF3, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 = H, R 11 = Me, R 12 = Me, Ln = Y, X1 = CH2SiMe3, X2 = CH2SiMe3;

[0065] Complex 23: Cp = C5Me4, Z = Si, R1 = H, R2 = H, R3 = CF3, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 = H, R 11 = Me, R 12 = Me, Ln = Lu, X1 = CH2SiMe3, X2 = CH2SiMe3;

[0066] Complex 24: Cp = C5Me4, Z = Si, R1 = H, R2 = H, R3 = H, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 = H, R 11 = Me, R 12 = Me, Ln = Sc, X1 = CH2C6H4NMe2-o, X2 = CH2C6H4NMe2-o;

[0067] Complex 25: Cp = C5Me4, Z = Si, R1 = H, R2 = H, R3 = H, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 = H, R 11 = Me, R 12=Me, Ln = Y, X1 = CH2C6H4NMe2-o, X2 = CH2C6H4NMe2-o;

[0068] Complex 26: Cp = C5Me4, Z = Si, R1 = H, R2 = H, R3 = H, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 =H, R 11 =Me, R 12 =Me, Ln = Lu, X1 = CH2C6H4NMe2-o, X2 = CH2C6H4NMe2-o;

[0069] Complex 27: Cp = C5H4, Z = Si, R1 = H, R2 = H, R3 = H, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 =H, R 11 =Me, R 12 =Me, Ln = Sc, X1 = CH2C6H4NMe2-o, X2 = CH2C6H4NMe2-o;

[0070] Complex 28: Cp = C5H4, Z = Si, R1 = H, R2 = H, R3 = H, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 =H, R 11 =Me, R 12 =Me, Ln = Y, X1 = CH2C6H4NMe2-o, X2 = CH2C6H4NMe2-o;

[0071] Complex 29: Cp = C5H4, Z = Si, R1 = H, R2 = H, R3 = H, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 =H, R 11 =Me, R 12 =Me, Ln = Lu, X1 = CH2C6H4NMe2-o, X2 = CH2C6H4NMe2-o;

[0072] Complex 30: Cp = C 13 H 10 , Z = Si, R1 = H, R2 = H, R3 = H, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 =H, R 11 =Me, R 12 =Me, Ln = Sc, X1 = CH2C6H4NMe2-o, X2 = CH2C6H4NMe2-o;

[0073] Complex 31: Cp = C 13 H 10 , Z = Si, R1 = H, R2 = H, R3 = H, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 = H, R 11 = Me, R 12 = Me, Ln = Y, X1 = CH2C6H4NMe2 - o, X2 = CH2C6H4NMe2 - o;

[0074] Complex 32: Cp = C 13 H 10 , Z = Si, R1 = H, R2 = H, R3 = H, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 = H, R 11 = Me, R 12 = Me, Ln = Lu, X1 = CH2C6H4NMe2 - o, X2 = CH2C6H4NMe2 - o;

[0075] Complex 33: Cp = C5Me4, Z = Si, R1 = H, R2 = -OMe, R3 = H, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 = H, R 11 = Me, R 12 = Me, Ln = Sc, X1 = CH2C6H4NMe2 - o, X2 = CH2C6H4NMe2 - o;

[0076] Complex 34: Cp = C5Me4, Z = Si, R1 = H, R2 = -OMe, R3 = H, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 = H, R 11 = Me, R 12 = Me, Ln = Y, X1 = CH2C6H4NMe2 - o, X2 = CH2C6H4NMe2 - o;

[0077] Complex 35: Cp = C5Me4, Z = Si, R1 = H, R2 = -OMe, R3 = H, R4 = H, R5 = H, R6 = H, R7 = H, R8 = H, R9 = H, R 10 = H, R 11 = Me, R 12 = Me, Ln = Lu, X1 = CH2C6H4NMe2 - o, X2 = CH2C6H4NMe2 - o.

[0078] In an embodiment of the present invention, the structure of the rare earth metal complex is as follows:

[0079]

[0080] The present invention has no special requirements for the source of the rare earth metal complex shown in formula (II), and it is preferably prepared by the following method: (1) Mix the compound shown in formula III with a lithiating reagent and L n Cl3 to obtain an intermediate; (2) Mix the intermediate with an alkylating reagent to obtain a rare earth metal complex;

[0081]

[0082] L n is a rare earth element; L n is one of scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium;

[0083] In formula III, q is an integer from 0 to 3;

[0084] Z is selected from C, Si or Ge;

[0085] C p is selected from substituted or unsubstituted cyclopentadienyl, substituted or unsubstituted indenyl, substituted or unsubstituted fluorenyl, substituted or unsubstituted fused heterocyclic cyclopentadienyl;

[0086] R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 are independently selected from hydrogen, halogen, C1-C10 alkyl, substituted or unsubstituted aryl.

[0087] In the present invention, the synthesis route of the rare earth metal complex is as follows:

[0088]

[0089] In the present invention, the raw materials for preparing the intermediate further include a Lewis base; the specific step (1) is: first mix the compound shown in formula III, the Lewis base and the lithiating reagent, and then mix with L n Cl3 to obtain an intermediate;

[0090] The molar ratio of the compound shown in formula III to the lithiating reagent is 1:(1-5), preferably 1:1;

[0091] The molar ratio of the compound shown in formula III to L n Cl3 is 1:(1-5), preferably 1:1;

[0092] The molar ratio of the intermediate product to the alkylating agent is 1:(2 - 10), preferably 1:2.

[0093] In the present invention, in step (1), the mixing time is 5 - 15 h and the temperature is -78 - 0 °C; in step (2), the mixing time is 1 - 10 h and the temperature is -78 - 0 °C.

[0094] The reaction of the present invention is preferably carried out in a nitrogen atmosphere; the alkylating agent is preferably LiCH2SiMe3 or LiCH2C6H4NMe2 - o; the lithiating agent is preferably n - butyllithium.

[0095] In one embodiment of the present invention, the preparation method of the rare earth metal complex includes:

[0096] Under a nitrogen atmosphere and at -78 °C to 0 °C, the compound (ligand) shown in formula III and a Lewis base are mixed, a hexane solution of n - butyllithium (concentration 2.5 M) in an amount equal to the number of moles of the ligand is added, and the reaction is carried out for 1 h. Then, L n Cl3 in an amount equal to the number of moles of the ligand is added, and the reaction is carried out for 4 h. Then, an alkylating agent in an amount twice the number of moles of the ligand is added and the reaction is carried out for 4 h. The solvent is removed, extracted with hexane, and concentrated to obtain a rare earth complex modified with an aromatic group.

[0097] The preparation method of the ethylene - styrene bimodal copolymer of the present invention preferably includes: mixing a styrene monomer and a solvent to obtain a mixed solution; introducing an ethylene monomer into the mixed solution, and finally adding a catalyst composition to obtain an ethylene - styrene copolymer; the time for introducing ethylene is 10 - 20 min; the solvent is preferably toluene.

[0098] In the present invention, the preparation method of the ethylene - styrene bimodal copolymer further includes: terminating the polymerization reaction with hydrochloric acid and an ethanol solution, then pouring the polymerization reaction solution into ethanol for precipitation, filtering, and drying in vacuo at 40 °C for 24 h to obtain a polymer of ethylene and styrene.

[0099] The present invention uses a single - cyclopentadienyl rare earth metal complex with a special structure, combined with an organoboron salt compound and an organoaluminum compound to form a catalytic system. Through the catalytic system and polymerization reaction process of the present invention, a multi - block copolymer with a bimodal molecular weight distribution composed of syndiotactic polystyrene sequences and polyethylene sequences on the main chain can be obtained. The high - molecular - weight part of the number - average molecular weight is 10,000 - 3,000,000, and the molecular weight distribution is 1 - 3; the low - molecular - weight part is 1,000 - 100,000, and the molecular weight distribution is 1 - 3. BRIEF DESCRIPTION OF THE DRAWINGS

[0100] Figure 1 1H NMR spectrum of the copolymer sample prepared in Example 1 of the present invention 1 1H NMR spectrum;

[0101] Figure 2 13C NMR spectrum of the copolymer sample prepared in Example 1 of the present invention 13 13C NMR spectrum;

[0102] Figure 3 DSC diagram of the copolymer sample prepared in Example 1 of the present invention;

[0103] Figure 4 GPC diagram of the copolymer sample prepared in Example 3 of the present invention. Detailed implementation mode

[0104] Next, in combination with the embodiments of the present invention, the technical solutions of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work shall fall within the scope of protection of the present invention.

[0105] To further illustrate the present invention, the following examples are used for detailed description. The raw materials used in the following examples of the present invention are all commercially available products.

[0106] The relevant test processes adopted in the embodiments of the present invention are as follows:

[0107] 1) Determination of styrene content: The content of styrene in the copolymer is calculated according to the 1H NMR spectrum of the copolymer measured in C2D4Cl4 at 110 °C, 1 1H NMR spectrum, f St = 4A ar / (5A al + A ar ) * 100%;

[0108] 2) Determination of the stereoselectivity of styrene structural units in the copolymer and the sequence structure of the copolymer: The syndiotactic selectivity of styrene structural units in the copolymer and the arrangement of syndiotactic polystyrene sequences and ethylene sequences are obtained according to the 1H NMR and 1 1H NMR and 13 13C NMR spectra of the polymer;

[0109] 3) Determination of the glass transition temperature (Tg) and melting point (Tm) of the copolymer: The glass transition temperature and melting point of the copolymer are measured by differential scanning calorimetry (DSC); g ) and melting point (Tm m ) of the copolymer: The glass transition temperature and melting point of the copolymer are measured by differential scanning calorimetry (DSC);

[0110] 4) Determination of the number average molecular weight (Mn) and molecular weight distribution (Mw / Mn) of the copolymer: The number average molecular weight (Mn) and molecular weight distribution (Mw / Mn) of the copolymer n ) and molecular weight distribution (Mw / Mn w / Mn n ) of the copolymer: The number average molecular weight (Mn) of the copolymer n ) and molecular weight distribution (Mw / Mnw / M n ) Determined by gel permeation chromatography (GPC) using polystyrene as the standard substance at 150 °C with 1,2,4-trichlorobenzene as the mobile phase.

[0111] For the complex 1 used in the examples of the present invention, its preparation method includes the following steps:

[0112]

[0113] Under -78 °C and nitrogen conditions, a solution of 2.5 M n-butyllithium in n-hexane (0.3 mmol, 0.12 ml) was added dropwise to a solution of tetramethylcyclopentadienyl ligand (0.3 mmol, 0.1 g) in tetrahydrofuran (10 ml). After reacting for 1 h, ScCl3 (0.3 mmol, 0.1 g) was added to the above reaction solution, and the reaction was carried out for 4 h. Then LiCH2SiMe3 (0.6 mmol, 0.06 g) was added and the reaction was carried out for 4 h. The reaction solution was concentrated and recrystallized to obtain 0.10 g of pale yellow cyclopentadienyl scandium complex 1, with a yield of 50%.

[0114] Example 1

[0115] The ethylene-styrene copolymer and its preparation method in this example include the following steps:

[0116] In a glove box, 20 mL of toluene and 10 mmol of styrene monomer were added to a 100 mL high-pressure reactor and mixed and stirred. The temperature inside the reactor was 25 °C. The reactor was taken out of the glove box and connected to a Schlenk tube, and ethylene was filled into it to make it reach a saturated state in the toluene solution; Complex 1 (6.4 mg, 10 μmol), Al i Bu3 (0.2 ml, 100 μmol, 0.5 M toluene solvent) and triphenylcarbenium tetrakis(pentafluorophenyl)borate [Ph3C][B(C6F5)4] (9.2 mg, 10 μmol) were dissolved in toluene to prepare a catalyst composition; the catalyst composition was quickly injected into the flask through a syringe to initiate polymerization. The polymerization reaction was carried out for 15 min under the introduction of 3.0 atm of ethylene, and then 2 ml of hydrochloric acid ethanol solution (v / v, 1:10) was added to terminate the polymerization reaction. Then the polymerization reaction solution was poured into 200 ml of ethanol for precipitation, filtered, and vacuum dried at 40 °C for 24 h to obtain an ethylene-styrene polymer with a net weight of 1.34 g. For the high molecular weight part, the ethylene content is 27%, and for the low molecular weight part, the ethylene content is 90%; the conditions and result data of ethylene-styrene copolymerization are shown in Table 1 in detail.

[0117] The ethylene-styrene copolymer obtained in Example 1 was analyzed by nuclear magnetic resonance to obtain 1 1H NMR and 1313C NMR spectra, such as Figure 1 and Figure 2 shown. Figure 1 In Figure 1 , the triplet - quintet peaks in the alkyl region indicate that the styrene segments in the ethylene / styrene copolymer are syndiotactic structures; Figure 2 In Figure 2 , the peaks in the alkyl region prove the existence of ethylene / styrene copolymers with a high styrene insertion rate and ethylene / styrene copolymers with a high ethylene insertion rate. Using differential scanning calorimetry for its test and analysis, the DSC diagram is obtained, such as Figure 3 shown. Figure 3 The DSC curve of Figure 3 indicates that there is a T g , two T m . Using size - exclusion chromatography for its analysis, the GPC diagram is obtained, such as Figure 4 shown. Figure 4 The GPC curve of Figure 4 is bimodal distribution, and the molecular weight distribution is relatively wide.

[0118] Example 2

[0119] The ethylene - styrene copolymer and its preparation method of this example include the following steps:

[0120] In a glove box, 20 mL of toluene and 40 mmol of styrene monomer are added to a 100 mL high - pressure reactor and mixed and stirred. The temperature in the reactor is 25 °C. The reactor is taken out of the glove box and connected to a Schlenk tube, and ethylene is filled into it to reach a saturated state in the toluene solution; Complex 1 (6.4 mg, 10 μmol), Al i Bu3 (0.2 ml, 100 μmol, 0.5 M toluene solvent) and triphenylcarbenium tetrakis(pentafluorophenyl)borate [Ph3C][B(C6F5)4] (9.2 mg, 10 μmol) are dissolved in toluene to prepare a catalyst composition; The catalyst composition is quickly injected into the flask by a syringe to initiate polymerization. After the polymerization reaction is carried out for 15 min under the introduction of 3.0 atm of ethylene, 2 ml of hydrochloric acid - ethanol solution (v / v, 1:10) is added to terminate the polymerization reaction. Then the polymerization reaction solution is poured into 200 ml of ethanol for precipitation, filtration, and vacuum - dried at 40 °C for 24 h to obtain an ethylene - styrene polymer with a net weight of 2.03 g. For the high - molecular - weight part, the ethylene content is 33%, and for the low - molecular - weight part, the ethylene content is 85%; The conditions and result data of ethylene - styrene copolymerization are shown in Table 1 in detail.

[0121] Example 3

[0122] The ethylene - styrene copolymer and its preparation method of this example include the following steps:

[0123] In the glove box, 20 mL of toluene and 50 mmol of styrene monomer were added to a 100 mL high-pressure reactor and mixed with stirring. The temperature inside the reactor was 25 °C. The reactor was taken out of the glove box and connected to a Schlenk tube, and ethylene was introduced into it to reach a saturated state in the toluene solution; Complex 1 (6.4 mg, 10 μmol), Al i Bu3 (0.2 ml, 100 μmol, 0.5 M toluene solvent) and triphenylcarbenium tetrakis(pentafluorophenyl)borate [Ph3C][B(C6F5)4] (9.2 mg, 10 μmol) were dissolved in toluene to prepare a catalyst composition; the catalyst composition was quickly injected into the flask through a syringe to initiate polymerization. After the polymerization reaction was carried out for 30 min under a 1.0 atm ethylene feed, 2 ml of hydrochloric acid ethanol solution (v / v, 1:10) was added to terminate the polymerization reaction. Then the polymerization reaction solution was poured into 200 ml of ethanol for precipitation, filtered, and vacuum dried at 40 °C for 24 h to obtain an ethylene-styrene polymer with a net weight of 2.34 g. For the high molecular weight part, the ethylene content was 37%, and for the low molecular weight part, the ethylene content was 83%; the conditions and result data of the ethylene-styrene copolymerization are shown in Table 1 in detail.

[0124] Table 1 Conditions and result data of ethylene-styrene copolymerization

[0125]

[0126] Example 4

[0127] The ethylene-styrene copolymer and its preparation method in this example are different from those in Example 1 in that Al i Bu3 was omitted from the catalyst composition in this example, and the polymerization activity decreased slightly. The specific steps are as follows:

[0128] In the glove box, 20 mL of toluene and 10 mmol of styrene monomer were added to a 100 mL high-pressure reactor and mixed with stirring. The temperature inside the reactor was 25 °C. The reactor was taken out of the glove box and connected to a Schlenk tube, and ethylene was introduced into it to reach a saturated state in the toluene solution; Complex 1 (6.4 mg, 10 μmol), triphenylcarbenium tetrakis(pentafluorophenyl)borate [Ph3C][B(C6F5)4] (9.2 mg, 10 μmol) were dissolved in toluene to prepare a catalyst composition; the catalyst composition was quickly injected into the flask through a syringe to initiate polymerization. After the polymerization reaction was carried out for 15 min under a 3.0 atm ethylene feed, 2 ml of hydrochloric acid ethanol solution (v / v, 1:10) was added to terminate the polymerization reaction. Then the polymerization reaction solution was poured into 200 ml of ethanol for precipitation, filtered, and vacuum dried at 40 °C for 24 h to obtain a bimodal distribution ethylene-styrene polymer with a net weight of 0.68 g.

[0129] The foregoing description of the disclosed embodiments enables those skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing an ethylene-styrene copolymer represented by Formula I, characterized in that, Including: Ethylene and styrene are copolymerized under a catalytic system to obtain a copolymer of ethylene-styrene represented by formula (I); The catalytic system is composed of an organic borate compound, an organoaluminum compound, and a rare earth metal complex represented by formula (II); （I）； (II); In formula I, x is a natural number greater than 2; y is a natural number greater than 1; n is the degree of polymerization; The number average molecular weight distribution of the copolymer of ethylene-styrene is bimodal; the high molecular weight part of the number average molecular weight is 10,000 to 3,000,000, and the molecular weight distribution is 1 to 3; the low molecular weight part is 1,000 to 100,000, and the molecular weight distribution is 1 to 3; the molecular weight of the high molecular weight part is 30 to 50 times that of the low molecular weight part; In formula II, L n is a rare earth element; L w selected from Lewis bases; The number of L w is from 0 to 3; C p Selected from substituted or unsubstituted cyclopentadienyl, substituted or unsubstituted indenyl, substituted or unsubstituted fluorenyl, substituted or unsubstituted fused heterocyclic cyclopentadienyl; X1 and X2 are independently selected from one of alkyl substituted with silicon methyl, benzyl substituted with dimethyl nitrogen, and substituted or unsubstituted allyl; Z is selected from C, Si or Ge; R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 are independently selected from hydrogen, halogen, C1-C10 alkyl, substituted or unsubstituted aryl; q is an integer from 0 to 3.

2. The preparation method of the ethylene-styrene copolymer according to claim 1, characterized in that, The glass transition temperature of the copolymer of ethylene-styrene represented by formula (I) is -50 °C to 50 °C; The ethylene-styrene copolymer has two melting points, the first melting point is 110 to 130 °C, and the second melting point is 200 to 275 °C.

3. The preparation method of the ethylene-styrene copolymer according to claim 1, characterized in that, The L w is selected from tetrahydrofuran, diethyl ether, ethylene glycol dimethyl ether or pyridine.

4. The preparation method of the ethylene-styrene copolymer according to claim 1, characterized in that, The R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 are independently selected from hydrogen, halogen, methyl, ethyl, isopropyl, tert-butyl or phenyl, 2,6-dimethylphenyl, 4-methylphenyl, mesityl, 2,6-diisopropylphenyl or 2,4,6-triisopropylbenzene.

5. The preparation method of the ethylene-styrene copolymer according to claim 1, characterized in that, The pressure of the polymerization reaction is 1 to 50 atm.

6. The preparation method of the ethylene-styrene copolymer according to claim 1, characterized in that, The molar ratio of the organic borate compound to the rare earth metal complex is 1:10 to 10:1; The molar ratio of the organoaluminum compound to the rare earth metal complex is (1 to 300):

1.

7. The preparation method of the ethylene-styrene copolymer according to claim 1, characterized in that, The temperature of the polymerization reaction is 25 to 150 °C.

8. The preparation method of the ethylene-styrene copolymer according to claim 1, characterized in that, The solvent for the polymerization reaction is one or more of aliphatic saturated hydrocarbons, aromatic hydrocarbons, aryl halides, and cycloalkanes.

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