Preparation method of ethylene-styrene isotactic polymer

Abstract

The invention relates to a preparation method of a polymer, in particular to a preparation method of an ethylene-styrene isotactic polymer, which is prepared by carrying out polymerization reaction on styrene and ethylene under the action of a composite catalyst, the composite catalyst comprises a main catalyst and a cocatalyst; the main catalyst is a [OSSO] type bridged diphenoxy titanium complex with a structure as shown in a formula (I): # imgabs0 #, in the formula (I), R1, R2, R3 and R4 are respectively alkylaryl, aryl or alkyl; and the cocatalyst is alkylaluminoxane. Compared with the prior art, the method solves the problem that in the prior art, only a mixture of multiple substances can be prepared by catalyzing ethylene and styrene through a metallocene catalyst, and separation is difficult. According to the scheme, under the composite catalysis of the [OSSO] type bridged diphenoxy titanium complex substituted by isopropyl phenyl with large steric hindrance at the ortho-position and the cocatalyst, the active isotactic polymerization of ethylene and styrene can be efficiently catalyzed.

Description

Technical Field

[0001] The invention relates to a method for preparing a polymer, in particular to a method for preparing an ethylene-styrene isotactic polymer. Background Art

[0002] Atactic polystyrene (aPS) and polyethylene (PE) are now widely used in daily life. Polystyrene has a high glass transition temperature due to its conjugated benzene ring side groups, making it a rigid and brittle material. The mechanical properties of polyethylene are average, with low tensile strength but good impact resistance. Ethylene-styrene copolymers have the excellent properties of both. After the introduction of styrene chain segments, the viscoelasticity and thermomechanical properties of the polymer material will change dramatically. Depending on the content of styrene introduced, the copolymer changes from semi-crystalline to amorphous material. Therefore, ethylene-styrene copolymers have broad application prospects in foams, films, etc.

[0003] More than 95% of the polymerization products of ethylene (E) and styrene (S) are alternating copolymers, and the stereo configuration of the styrene chain segments is an isotactic structure. Compared with ethylene homopolymer (melting temperature 100°C), the synthesized alternating copolymer (melting temperature 150°C) has significantly improved heat resistance, and compared with isotactic polystyrene (melting temperature 230°C), its processing performance has been improved to a certain extent, making it easier to process and shape.

[0004] However, ethylene-styrene copolymers cannot be synthesized by free radical polymerization and traditional Ziegler-Natta catalysts. Although metallocene catalysts can catalyze the synthesis of ethylene-styrene copolymers with different monomer compositions, the catalytic activity is low, and the obtained product is a blend of polyethylene, syndiotactic polystyrene and copolymers. The product separation is difficult and the cost is high. In addition, polyethylene is a crystalline resin (EEEE structure) and polystyrene is a non-crystalline resin (SSSS structure). The polymer structure obtained by the general polymerization method is more similar to a blend (SSSEEESSSEESS), which is prone to stress concentration when subjected to force and has poor mechanical properties.

[0005] For example, Chinese patent CN105801621A discloses a bridged bisphenoxy [OSNO] type titanium catalyst for synthesizing syndiotactic polystyrene and its application. Titanium metal complexes of [OSN'O] type and [OSNO] type with different structures are designed. Under the condition of MMAO as a cocatalyst, the activity of this type of catalyst on the syndiotactic polymerization of styrene is studied. However, this catalyst is only applicable to the syndiotactic polymerization of styrene and cannot be used for the catalytic copolymerization of styrene and ethylene. Moreover, its catalytic efficiency is only 1.9 kg polymer / g Ti / h (about 0.09×10 6g polymer / mol Ti / h), which shows that although the catalyst can achieve syndiotactic polymerization of styrene, it is still difficult to achieve better production efficiency.

[0006] Therefore, it is necessary to propose a method for stably and efficiently preparing ethylene-styrene isotactic polymers. Summary of the invention

[0007] The purpose of the present invention is to provide a method for preparing an isotactic polymer of ethylene and styrene in order to solve at least one of the above problems, and solve the problem that in the prior art, ethylene and styrene can only be prepared as a mixture of multiple substances and are difficult to separate by catalyzing ethylene and styrene with metallocene catalysts. The present invention can efficiently catalyze the active isotactic polymerization of ethylene and styrene under the composite catalysis of an [OSSO]-type bridged bisphenoxy titanium complex substituted with a large sterically hindered isopropylphenyl group at the ortho position and a co-catalyst.

[0008] The purpose of the present invention is achieved through the following technical solutions:

[0009] A method for preparing an ethylene-styrene isotactic polymer, which is prepared by polymerization reaction of styrene and ethylene under the action of a composite catalyst;

[0010] The composite catalyst comprises a main catalyst and a co-catalyst;

[0011] The main catalyst is an [OSSO]-type bridged bisphenoxy titanium complex ([OSSO]-TiCl2) having a structure shown in formula (I):

[0012]

[0013] In formula (I), R1, R2, R3 and R4 are each an alkaryl group, an aryl group or an alkyl group;

[0014] The co-catalyst is alkylaluminoxane.

[0015] Preferably, in formula (I), R1, R2, R3 and R4 are each an alkylaryl group, an aryl group having 6 to 20 carbon atoms or an alkyl group having 1 to 20 carbon atoms.

[0016] Preferably, the co-catalyst is an alkylaluminoxane having a structure represented by formula (II) or formula (III):

[0017] In formula (II), R5 is an alkyl, alkenyl or aryl group having 1 to 15 carbon atoms;

[0018] In formula (III), R5 is an alkyl group, alkenyl group or aryl group having 1 to 15 carbon atoms.

[0019] Preferably, in the main catalyst, R1 and R3 are isopropylbenzene, R2 and R4 are methyl groups; and the co-catalyst is methylaluminoxane.

[0020] Preferably, the molar ratio of the aluminum content in the co-catalyst to the titanium content in the main catalyst is 100 to 1500:1.

[0021] Preferably, the composite catalyst further contains an organic aluminum compound with the structural formula Al(R6)3, wherein R6 is an alkyl group with 1 to 4 carbon atoms.

[0022] Take methylaluminoxane (MAO) as the co-catalyst for example: MAO is a partial hydrolysis product of trimethylaluminum (TMA), and the TMA content must be within a certain range (about 10wt%) so that MAO can exist relatively stably. Therefore, in addition to the main catalyst [OSSO]-TiCl2 and the co-catalyst alkylaluminoxane, the composite catalyst also contains a certain organic aluminum compound with the structural formula Al(R6)3. This organic aluminum compound, as a strong reducing agent, can further remove the chain terminators of coordination polymerization such as water and oxygen remaining in the reaction system, which is beneficial to the polymerization reaction.

[0023] Preferably, R6 is methyl, ethyl or isobutyl.

[0024] Preferably, the preparation method comprises the following steps:

[0025] S1: heating the polymerization reactor to the reaction temperature, introducing ethylene into the polymerization reactor, and then adding styrene, anhydrous toluene and a composite catalyst into the polymerization reactor, adjusting the pressure in the reactor to the reaction pressure, stirring and causing a polymerization reaction;

[0026] S2: The polymer generated by the reaction is transferred to a hydrochloric acid ethanol solution for immersion, and then filtered, washed and dried to obtain an ethylene-styrene isotactic polymer.

[0027] Preferably, the concentration of styrene is 0.5-6 mol / L, the concentration of the composite catalyst is 0.1-0.5 mmol / L, the reaction temperature is 20-90° C., and the reaction pressure is 0.1-1.5 MPa.

[0028] Preferably, the molar feed ratio of styrene to ethylene is 11 to 58:1, and the ethylene-styrene polymers polymerized within this range are mainly alternating copolymers.

[0029] Preferably, the catalytic activity of the composite catalyst is 0.15 to 16×10 6 g polymer·(mol Ti) -1 ·h -1; The monomer conversion rate of styrene is 30-90%.

[0030] Preferably, the molecular weight of the ethylene-styrene isotactic polymer is 7000-100000, including EEE, SEE, SEES, SES and SS sequences (E represents ethylene, S represents styrene), wherein the molar proportion of styrene units in the polymer chain segment is 15-90%, and the styrene units in the polymer chain segment are isotactic.

[0031] The working principle of the present invention is:

[0032] First, the co-catalyst undergoes alkylation with [OSSO]-TiCl2 to generate [OSSO]-Ti(CH3)2. Then, due to the strong reducing properties of the remaining co-catalyst (and Al(R6)3), Ti(IV) is reduced to (III) and [OSSO]-TiCH3 is promoted to form a complex.

[0033] At the beginning of the polymerization reaction, the monomer (styrene monomer is more sensitive to the III-valent titanium active center, so the first monomer to be inserted is generally styrene) first coordinates to the vacant site of the transition metal active center to form an α-π coordination complex ([OSSO]-Ti-SCH3); due to the steric effect of the ortho-isopropylphenyl group of the catalyst and the electron-withdrawing effect of the sulfur atom, the second monomer to be inserted preferentially is the ethylene monomer ([OSSO]-Ti-SECH3); subsequently, styrene and ethylene monomers continuously insert into the transition metal-carbon bond to carry out chain growth ([OSSO]-Ti-SESESE···CH3), and finally a large molecular ethylene-styrene isotactic polymer is generated.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The invention adopts an [OSSO] type bridged bisphenoxy titanium complex substituted with a large sterically hindered cumene group at the ortho position, which can efficiently catalyze the isotactic polymerization of ethylene and styrene in the presence of a cocatalyst methylaluminoxane.

[0036] Under the catalytic action of the composite catalyst of the present invention, the catalytic efficiency of the polymerization reaction can reach up to 16×10 6 g polymer·(mol Ti) -1 ·h -1 , the monomer conversion rate of styrene is above 80%; the molecular weight of the isotactic polymer is M WThe molecular chain segments contain EEE, SEE, SEES, SES, and SS sequences, wherein the molar proportion of styrene units in the polymer chain segments is adjustable between 15% and 90%, and the configuration of the styrene units is isotactic. In addition, the composite catalyst of the present invention can also be used for isotactic polymerization of styrene (catalytic efficiency is not less than 7.83×10 6 g polymer / mol Ti / h) and ethylene homopolymerization (catalytic efficiency not less than 9.38×10 6 g polymer / mol Ti / h), and can also be used as a replacement for existing catalysts for isotactic polymerization of styrene and homopolymerization of ethylene (such as the bridged bisphenoxy [OSNO] type titanium catalyst disclosed in CN105801621A).

[0037] Compared with mono-titaniumocene catalysts CP*TiCl3, CP*TiF3, and CP*Ti(OMe)3 (CP*=C5Me5), the catalyst used in this scheme shows high catalytic activity, and the product has high stereoregularity and is relatively pure (the products obtained under a wider monomer feed ratio are mainly alternating copolymers); the prepared polymer (SESESESESE structure) has high structural regularity and is a semi-crystalline material with good mechanical properties.

[0038] The catalyst used in this scheme is simple to prepare, has low sensitivity to water and oxygen, is easy to store, and has readily available raw materials, is environmentally friendly, and has low preparation costs. The amount of cocatalyst MAO used in the composite catalyst is small (MAO is expensive, accounting for more than 80% of the single polymerization cost), and reducing the amount of MAO used can further reduce the polymerization cost. DETAILED DESCRIPTION

[0039] The present invention is described in detail below with reference to specific embodiments, but this is by no means a limitation of the present invention.

[0040] In the following description, unless otherwise specified, the reagents used are conventional commercially available products, and the methods used are well known in the art.

[0041] Any matters not covered in the following description may adopt existing technologies.

[0042] A method for preparing an ethylene-styrene isotactic polymer, which is prepared by polymerization reaction of styrene and ethylene under the action of a composite catalyst;

[0043] The composite catalyst comprises a main catalyst and a co-catalyst;

[0044] The main catalyst is an [OSSO]-type bridged bisphenoxy titanium complex having a structure shown in formula (I):

[0045]

[0046] In formula (I), R1, R2, R3 and R4 are each an alkaryl group, an aryl group or an alkyl group;

[0047] The co-catalyst is alkylaluminoxane.

[0048] The main catalyst is prepared by the following method:

[0049] Add 4-methylphenol (1 mol) and catalyst p-toluenesulfonic acid (0.1 mol) into a dry and clean two-necked polymerization reaction bottle. After the two are fully stirred and heated to 45°C, add 2-phenyl-1-propylene (1 mol) dropwise. After reacting for 1 hour, add 100 ml of ice water dropwise to quench. Collect the organic layer and recrystallize it using a mixed solution of toluene / acetonitrile to obtain intermediate L1.

[0050] 0.4 mol of L1 was added to the reaction flask and dissolved with 100 ml of toluene. 0.4 mol of disulfur dichloride was added dropwise at -10°C, and the reaction temperature was raised to 50°C for two hours. Then 80 g of zinc particles and 80 ml of hydrochloric acid were added in batches and the temperature was raised to 80°C for 5 hours. The organic layer was collected and recrystallized with acetonitrile and pentane to obtain intermediate L2.

[0051] Add 0.2 mol of L2, 40 ml of methanol, and 0.2 mol of sodium hydroxide to the reaction flask, stir until the solid is completely dissolved, then heat to 65°C, add 10 ml of toluene solution containing 0.1 mol of 1,2-dibromoethane dropwise, react for 2 hours, rinse the solid product with acetone, and then drain the solvent to obtain intermediate L3.

[0052] Add 0.1 mol of intermediate L3 and 40 ml of anhydrous toluene to a polymerization reaction bottle filled with nitrogen, add 0.1 mol of titanium tetrachloride toluene solution dropwise at -10°C, react for 2 hours, raise the temperature to room temperature and react for 12 hours, filter with a sand core funnel to remove insoluble matter, and then use n-hexane for recrystallization to obtain a red product, which is [OSSO]-TiCl2 catalyst (main catalyst).

[0053] More specifically,

[0054] In formula (I), R1, R2, R3 and R4 are each an alkaryl group, an aryl group having 6 to 20 carbon atoms or an alkyl group having 1 to 20 carbon atoms;

[0055] The co-catalyst is an alkylaluminoxane having a structure represented by formula (II) or formula (III):

[0056] In formula (II), R5 is an alkyl, alkenyl or aryl group having 1 to 15 carbon atoms;

[0057] In formula (III), R5 is an alkyl group, alkenyl group or aryl group having 1 to 15 carbon atoms.

[0058] Preferably, in the main catalyst, R1 and R3 are isopropylphenyl groups, R2 and R4 are methyl groups, and their structural formula is shown in formula (IV); the co-catalyst is methylaluminoxane.

[0059]

[0060] The molar ratio of the aluminum content in the co-catalyst to the titanium content in the main catalyst is 100-1500:1.

[0061] In addition, in the composite catalyst, an organic aluminum compound with the structural formula Al(R6)3 is formed by the main catalyst and the co-catalyst, wherein R6 is an alkyl group with 1 to 4 carbon atoms, such as methyl, ethyl and isobutyl.

[0062] A method for preparing an ethylene-styrene isotactic polymer comprises the following steps:

[0063] S1: heating the polymerization reactor to the reaction temperature, introducing ethylene into the polymerization reactor, and then adding styrene, anhydrous toluene and a composite catalyst into the polymerization reactor, adjusting the pressure in the reactor to the reaction pressure, stirring and causing a polymerization reaction;

[0064] S2: The polymer generated by the reaction is transferred to a hydrochloric acid ethanol solution for immersion, and then filtered, washed and dried to obtain an ethylene-styrene isotactic polymer.

[0065] in:

[0066] The concentration of styrene is 0.5-6 mol / L, the concentration of the composite catalyst is 0.1-0.5 mmol / L, the reaction temperature is 20-90° C., and the reaction pressure is 0.1-1.5 MPa.

[0067] The molar feed ratio of styrene to ethylene is 11-58:1, and the ethylene-styrene polymers polymerized within this range are mainly alternating copolymers.

[0068] The catalytic activity of the composite catalyst is 0.15 to 16×10 6 g polymer·(mol Ti) -1 ·h -1 ; The monomer conversion rate of styrene is 30-90%.

[0069] The molecular weight of the ethylene-styrene isotactic polymer is 7000-100000, including EEE, SEE, SEES, SES and SS sequences (E represents ethylene, S represents styrene), wherein the molar proportion of the styrene unit in the polymer chain segment is adjustable from 15 to 90%, and the styrene unit in the polymer chain segment is isotactic.

[0070] In the following examples, the [OSSO]-type bridged bisphenoxy titanium complex with the structure shown in formula (IV) is used as the main catalyst, and methylaluminoxane is used as the co-catalyst.

[0071] Example 1

[0072] A polymerization reactor with an air pipe passage and a feeding port was vacuum dried at 90°C for 3h, then the reaction temperature was lowered to 70°C, and after three replacements with ethylene gas, 20ml of styrene, 20ml of anhydrous toluene, 1000umol of methylaluminoxane (co-catalyst), and 5umol of [OSSO]-Ti catalyst (main catalyst) were added in sequence under normal pressure, and then the ethylene pressure was adjusted to 0.5MPa, and the stirring blade speed was adjusted to 800r / min. After reacting for 30min, 10ml of methanol was added to terminate the polymerization; the polymer was transferred to a 5wt% hydrochloric acid ethanol solution and soaked overnight, then filtered, rinsed with ethanol several times, and dried to constant weight in a 65°C vacuum drying oven. The obtained sample was recorded as run1.

[0073] The sample-related test results are shown in run 1 of Table 1 below.

[0074] Example 2

[0075] The polymerization reactor with an air pipe passage and a feeding port was vacuum dried at 90°C for 3h, then the reaction temperature was lowered to 70°C, and after three times of replacement with ethylene gas, 20ml of styrene, 20ml of anhydrous toluene, 1500umol of methylaluminoxane, and 5umol of [OSSO]-Ti catalyst were added in sequence under normal pressure, and then the ethylene pressure was adjusted to 0.5MPa, and the stirring blade speed was adjusted to 800r / min. After reacting for 30min, 10ml of methanol was added to terminate the polymerization; the polymer was transferred to a 5wt% hydrochloric acid ethanol solution and soaked overnight, then filtered, rinsed with ethanol several times, and dried to constant weight in a 65°C vacuum drying oven. The obtained sample was recorded as run2.

[0076] The sample-related test results are shown in run 2 of Table 1 below.

[0077] Example 3

[0078] The polymerization reactor with an air pipe passage and a feeding port was vacuum dried at 90°C for 3h, then the reaction temperature was lowered to 70°C, and ethylene gas was replaced three times. Then 20ml of styrene, 20ml of anhydrous toluene, 3000umol of methylaluminoxane, and 5umol of [OSSO]-Ti catalyst were added in sequence under normal pressure, and the ethylene pressure was adjusted to 0.5MPa, and the stirring blade speed was adjusted to 800r / min. After reacting for 30min, 10ml of methanol was added to terminate the polymerization; the polymer was transferred to a 5wt% hydrochloric acid ethanol solution and soaked overnight, then filtered, rinsed with ethanol several times, and dried to constant weight in a 65°C vacuum drying oven. The obtained sample was recorded as run3.

[0079] The sample-related test results are shown in run 3 of Table 1 below.

[0080] Example 4

[0081] The polymerization reactor with an air pipe passage and a feeding port was vacuum dried at 90°C for 3h, then the reaction temperature was lowered to 70°C, and ethylene gas was replaced three times. Then 20ml of styrene, 20ml of anhydrous toluene, 1500umol of methylaluminoxane, and 5umol of [OSSO]-Ti catalyst were added in sequence under normal pressure, and the ethylene pressure was adjusted to 0.1MPa, and the stirring blade speed was adjusted to 800r / min. After reacting for 30min, 10ml of methanol was added to terminate the polymerization; the polymer was transferred to a 5wt% hydrochloric acid ethanol solution and soaked overnight, then filtered, rinsed with ethanol several times, and dried to constant weight in a 65°C vacuum drying oven. The obtained sample was recorded as run4.

[0082] The sample-related test results are shown in run 4 of Table 1 below.

[0083] Example 5

[0084] The polymerization reactor with an air pipe passage and a feeding port was vacuum dried at 90°C for 3h, then the reaction temperature was lowered to 70°C, and after three times of replacement with ethylene gas, 20ml of styrene, 20ml of anhydrous toluene, 1500umol of methylaluminoxane, and 5umol of [OSSO]-Ti catalyst were added in sequence under normal pressure, and then the ethylene pressure was adjusted to 0.2MPa, and the stirring blade speed was adjusted to 800r / min. After reacting for 30min, 10ml of methanol was added to terminate the polymerization; the polymer was transferred to a 5wt% hydrochloric acid ethanol solution and soaked overnight, then filtered, rinsed with ethanol several times, and dried to constant weight in a 65°C vacuum drying oven. The obtained sample was recorded as run5.

[0085] The sample-related test results are shown in run 5 of Table 1 below.

[0086] Example 6

[0087] The polymerization reactor with an air pipe passage and a feeding port was vacuum dried at 90°C for 3 hours, then the reaction temperature was lowered to 70°C, and after three replacements with ethylene gas, 20 ml of styrene, 20 ml of anhydrous toluene, 1500 umol of methylaluminoxane, and 5 umol of [OSSO]-Ti catalyst were added in sequence under normal pressure, and then the ethylene pressure was adjusted to 1.1 MPa, and the stirring blade speed was adjusted to 800 r / min. After reacting for 30 minutes, 10 ml of methanol was added to terminate the polymerization; the polymer was transferred to a 5 wt% hydrochloric acid ethanol solution and soaked overnight, then filtered, rinsed with ethanol several times, and dried to constant weight in a 65°C vacuum drying oven. The obtained sample was recorded as run 6.

[0088] The sample-related test results are shown in run 6 of Table 1 below.

[0089] Example 7

[0090] The polymerization reactor with an air pipe passage and a feeding port was vacuum dried at 90°C for 3h, then the reaction temperature was lowered to 50°C, and after three replacements with ethylene gas, 20ml of styrene, 20ml of anhydrous toluene, 1500umol of methylaluminoxane, and 5umol of [OSSO]-Ti catalyst were added in sequence under normal pressure, and then the ethylene pressure was adjusted to 0.5MPa, and the stirring blade speed was adjusted to 800r / min. After reacting for 30min, 10ml of methanol was added to terminate the polymerization; the polymer was transferred to a 5wt% hydrochloric acid ethanol solution and soaked overnight, then filtered, rinsed with ethanol several times, and dried to constant weight in a 65°C vacuum drying oven. The obtained sample was recorded as run7.

[0091] The sample-related test results are shown in run 7 of Table 1 below.

[0092] Example 8

[0093] The polymerization reactor with an air pipe passage and a feeding port was vacuum dried at 90°C for 3h, then the reaction temperature was lowered to 80°C, and after three replacements with ethylene gas, 20ml of styrene, 20ml of anhydrous toluene, 1500umol of methylaluminoxane, and 5umol of [OSSO]-Ti catalyst were added in sequence under normal pressure, and then the ethylene pressure was adjusted to 0.5MPa, and the stirring blade speed was adjusted to 800r / min. After reacting for 30min, 10ml of methanol was added to terminate the polymerization; the polymer was transferred to a 5wt% hydrochloric acid ethanol solution and soaked overnight, then filtered, rinsed with ethanol several times, and dried to constant weight in a 65°C vacuum drying oven. The obtained sample was recorded as run8.

[0094] The sample-related test results are shown in run 8 of Table 1 below.

[0095] Example 9

[0096] The polymerization reactor with an air pipe passage and a feeding port was vacuum dried at 90°C for 3 hours, then the reaction temperature was lowered to 80°C, and after three replacements with ethylene gas, 20ml of styrene, 20ml of anhydrous toluene, 1500umol of methylaluminoxane, and 2umol of [OSSO]-Ti catalyst were added in sequence under normal pressure, and then the ethylene pressure was adjusted to 0.5MPa, and the stirring blade speed was adjusted to 800r / min. After reacting for 60 minutes, 10ml of methanol was added to terminate the polymerization; the polymer was transferred to a 5wt% hydrochloric acid ethanol solution and soaked overnight, then filtered, rinsed with ethanol several times, and dried to constant weight in a 65°C vacuum drying oven. The obtained sample was recorded as run9.

[0097] The sample-related test results are shown in run 9 of Table 1 below.

[0098] Comparative Example 1

[0099] The polymerization reactor with an air pipe passage and a feeding port was vacuum dried at 90°C for 3h, then the reaction temperature was lowered to 50°C, and after three times of replacement with ethylene gas, 40ml of anhydrous toluene, 1500umol of methylaluminoxane, and 5umol of [OSSO]-Ti catalyst were added in sequence under normal pressure, and then the ethylene pressure was adjusted to 0.5MPa, and the stirring blade speed was adjusted to 800r / min. After reacting for 30min, 10ml of methanol was added to terminate the polymerization; the polymer was transferred to a 5wt% hydrochloric acid ethanol solution and soaked overnight, then filtered, rinsed with ethanol several times, and dried to constant weight in a 65°C vacuum drying oven. The obtained sample was recorded as run10.

[0100] The sample-related test results are shown in run 10 of Table 1 below.

[0101] Comparative Example 2

[0102] The polymerization reactor with an air pipe passage and a feeding port was vacuum dried at 90°C for 3h, then the reaction temperature was lowered to 50°C, and after replacing with nitrogen gas three times, 20ml of anhydrous toluene, 20ml of styrene, 1500umol of methylaluminoxane, and 5umol of [OSSO]-Ti catalyst were added in sequence under normal pressure, and then the nitrogen pressure was adjusted to 0.5MPa, and the stirring blade speed was adjusted to 800r / min. After reacting for 30min, 10ml of methanol was added to terminate the polymerization; the polymer was transferred to a 5wt% hydrochloric acid ethanol solution and soaked overnight, then filtered, rinsed with ethanol several times, and dried to constant weight in a 65°C vacuum drying oven. The obtained sample was recorded as run11.

[0103] The sample related test results are shown in run 11 of Table 1 below.

[0104] Comparative Example 3

[0105] The polymerization reactor with a gas pipe and a feed port was vacuum dried at 90°C for 3 hours, then the reaction temperature was lowered to 70°C, and ethylene gas was replaced three times. Then 20 ml of styrene, 20 ml of anhydrous toluene, 6000 umol of methylaluminoxane, 10 umol of CP were added in sequence under normal pressure. * TiCl3 catalyst, then adjust the ethylene pressure to 0.5MPa, adjust the stirring blade speed to 800r / min, and add 10ml of methanol to terminate the polymerization after reacting for 60min; transfer the polymer to 5wt% hydrochloric acid ethanol solution and soak overnight, then filter, rinse with ethanol several times, and dry in a vacuum drying oven at 65℃ to constant weight. The obtained sample is recorded as run12.

[0106] The sample-related test results are shown in run 12 of Table 1 below.

[0107] Table 1 Test results of copolymer samples prepared in Examples 1 to 9 and Comparative Examples 1 to 3

[0108]

[0109] Note: “—” indicates that no test result can be obtained under the specified test method.

[0110] The performance test methods in Table 1 are as follows:

[0111] 1) H NMR 1 H NMR (400 MHz) and 13 C NMR (101MHz): measured by Varian Unity Inova400 NMR instrument, using deuterated chloroform as reagent, at 25°C. Styrene content (C st ).

[0112] 2) Differential Scanning Calorimeter (DSC): The instrument model is PerkinElmer DSC-4000. Heat from 30°C to 300°C at 10°C / min, hold for 5 min; then cool to -50°C at 10°C / min; keep at -50°C for 5 min, and heat to 300°C at 10°C / min. Record the secondary heating curve and calculate the glass transition temperature (T g ) and melting temperature (T m ).

[0113] 3) Gel Permeation Chromatography (GPC) The molecular weight and molecular weight distribution of the polymer were determined using a Varian PL-220HTGPC high temperature gel permeation chromatograph, with standard polystyrene as the standard sample and 1,2,4-trichlorobenzene as the mobile phase at a flow rate of 1.0 ml / min and a test temperature of 150°C.

[0114] It can be seen from Table 1 that:

[0115] From run 1 to run 3, it can be seen that the aluminum-titanium ratio (co-catalyst: main catalyst) has a certain influence on the catalytic activity. The insertion rate of the styrene monomer unit is higher at a lower aluminum-titanium ratio. When the aluminum-titanium ratio is 300, the composition of the polymer product is closer to 1:1, indicating that the product is mainly an alternating copolymer.

[0116] It can be seen from run 4, run 5, run 2, and run 6 that with the increase of ethylene pressure, that is, the decrease of the monomer feed ratio of styrene / ethylene, the insertion rate of styrene units shows an obvious downward trend. In the polymers with 40-60% styrene, the proportion of alternating copolymers reaches more than 80%, and it can be considered that the product is mainly alternating copolymers. It can be concluded that when the ethylene pressure is between run 5 (0.2MPa) and run 6 (1.1MPa), the product obtained is mainly alternating copolymers.

[0117] According to the relationship between the Henry constant (H) and absolute temperature (T) of the ethylene-toluene system, the Henry constant of ethylene in toluene can be calculated:

[0118] log H=3.6901-544.21 / T

[0119] Among them, H is in atm, T is in K;

[0120] Then, according to the relationship between Henry's constant and solubility, the solubility of ethylene in toluene under the corresponding conditions is calculated:

[0121] P E =H·X E

[0122] Where X E The unit is mol / mol;

[0123] The polymerization temperature was 70°C (343.15K), the polymerization pressure was 0.2MPa (1.97atm) and 1.1MPa (10.86atm), the amount of toluene was 20ml (0.189mol), and the amount of styrene was 20ml (0.173mol);

[0124] Substituting the above data into the calculation, we can get: at 0.2MPa, the amount of ethylene dissolved in toluene is 0.003mol, and at 1.1MPa, the amount of ethylene dissolved in toluene is 0.016mol. That is, the products obtained when the monomer feed ratio of styrene / ethylene is between 11 and 58 are mainly alternating copolymers.

[0125] It can be seen from run 7 (50°C), run 2 (70°C) and run 8 (80°C) that increasing the temperature is obviously helpful for improving the catalytic activity and is beneficial to the insertion of ethylene units, but overall the product is still mainly an alternating copolymer.

[0126] From run 10 and run 11, it can be seen that the catalyst can also be used for the homopolymerization of ethylene and styrene.

[0127] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for preparing an ethylene-styrene isotactic polymer, characterized in that: It is prepared by polymerization of styrene and ethylene under the action of a composite catalyst; The composite catalyst comprises a main catalyst and a co-catalyst; The main catalyst is an [OSSO]-type bridged bisphenoxy titanium complex having a structure shown in formula (I): In formula (I), R1, R2, R3 and R4 are each an alkaryl group, an aryl group or an alkyl group; The co-catalyst is alkylaluminoxane.

2. The method for preparing an ethylene-styrene isotactic polymer according to claim 1, characterized in that: In formula (I), R1, R2, R3 and R4 are independently an alkaryl group, an aryl group having 6 to 20 carbon atoms or an alkyl group having 1 to 20 carbon atoms.

3. The method for preparing an ethylene-styrene isotactic polymer according to claim 1, characterized in that: The co-catalyst is an alkylaluminoxane having a structure represented by formula (II) or formula (III): In formula (II), R5 is an alkyl, alkenyl or aryl group having 1 to 15 carbon atoms; In formula (III), R5 is an alkyl group, alkenyl group or aryl group having 1 to 15 carbon atoms.

4. The method for preparing an ethylene-styrene isotactic polymer according to claim 1, characterized in that: In the main catalyst, R1 and R3 are isopropylbenzene, R2 and R4 are methyl groups; and the co-catalyst is methylaluminoxane.

5. The method for preparing an ethylene-styrene isotactic polymer according to claim 1, characterized in that: The molar ratio of the aluminum content in the co-catalyst to the titanium content in the main catalyst is 100-1500:

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6. The method for preparing an ethylene-styrene isotactic polymer according to claim 1, characterized in that: The composite catalyst also contains an organic aluminum compound with the structural formula of Al(R6)3, wherein R6 is an alkyl group with 1 to 4 carbon atoms.

7. The method for preparing an ethylene-styrene isotactic polymer according to claim 6, characterized in that: The R6 is methyl, ethyl or isobutyl.

8. The method for preparing an ethylene-styrene isotactic polymer according to claim 1, characterized in that: The preparation method comprises the following steps: S1: heating the polymerization reactor to the reaction temperature, introducing ethylene into the polymerization reactor, and then adding styrene, anhydrous toluene and a composite catalyst into the polymerization reactor, adjusting the pressure in the reactor to the reaction pressure, stirring and causing a polymerization reaction; S2: The polymer generated by the reaction is transferred to a hydrochloric acid ethanol solution for immersion, and then filtered, washed and dried to obtain an ethylene-styrene isotactic polymer.

9. The method for preparing an ethylene-styrene isotactic polymer according to claim 8, characterized in that: The concentration of styrene is 0.5-6 mol / L, the concentration of the composite catalyst is 0.1-0.5 mmol / L, the reaction temperature is 20-90° C., and the reaction pressure is 0.1-1.5 MPa.

10. The method for preparing an ethylene-styrene isotactic polymer according to claim 8, characterized in that: The molecular weight of the ethylene-styrene isotactic polymer is 7000-100000, including EEE, SEE, SEES, SES and SS sequences, wherein the molar proportion of styrene units in the polymer chain segment is 15-90%, and the styrene units in the polymer chain segment are isotactic.

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