Star-shaped block copolymer and preparation method thereof

Abstract

The application relates to the field of polymer preparation and discloses a star-shaped block copolymer and a preparation method thereof. The soft segment of the star-shaped block copolymer is a fully saturated polyisoolefin, the hard segment of the star-shaped block copolymer is polystyrene, the content of the styrene homopolymer is 1-10 wt% based on the total weight of the star-shaped block copolymer, and the content of the biphenyl copolymer is 1-10 wt%. The star-shaped block copolymer has a regular structure, a narrow molecular weight distribution, and a low content of the biphenyl copolymer in the copolymer. Meanwhile, in the preparation method of the star-shaped block copolymer, a diluent containing a fluoroalkane is used to replace traditional methyl chloride, so that the regularity of the structure of the star-shaped block copolymer is improved, and the pollution to the environment is significantly reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of polymer preparation, in particular, to a star block copolymer and a preparation method thereof. BACKGROUND

[0002] The synthesis of thermoplastic elastomers generally involves the preparation of triblock copolymers having soft segments in a rubbery state and hard segments in a plastic state. The hard segments in a plastic state are usually vinyl aromatic compounds (such as polystyrene), and the soft segments in a rubbery state are usually polybutadiene or polyisoprene. The most important styrene-based thermoplastic elastomer is polystyrene-butadiene-styrene triblock copolymer (SBS). The preparation of SBS by active anion technology has been widely used in industry, but the SBS prepared by this technology also has many shortcomings: for example, the polybutadiene in the soft segment structure contains high unsaturation of double bonds, resulting in poor heat resistance, weather resistance and aging resistance of SBS. Although the performance of SBS can be improved and the thermal oxidative stability and use temperature of SBS can be improved by hydrogenation, hydrogenation often requires noble metals as catalysts, and the process is complex and costly. In addition, the hydrogenation of polyisobutylene segments easily forms polyethylene segments, losing the original elasticity.

[0003] The polystyrene-isobutylene-styrene (SIBS) synthesized by active cation technology overcomes the above-mentioned shortcomings. Compared with SBS, the advantages of SIBS mainly lie in: (1) the intermediate rubbery soft segment is a fully saturated structure of polyisobutylene, which makes SIBS have more excellent air tightness and thermal oxidative stability. (2) Because the two sides of isobutylene are closely arranged with side methyl groups, SIBS has more excellent shock absorbing performance.

[0004] CN1502639A discloses a method for synthesizing SIBS triblock copolymer by single-end initiation: using a tertiary alkyl halide as an initiator and a Lewis acid as a co-initiator, first performing single-end initiation to synthesize a styrene-based macroinitiator, then adding isobutylene monomer to perform copolymerization to obtain a two-block copolymer, and then adding styrene monomer after adding a part of Lewis acid to obtain a triblock copolymer.

[0005] CN1982350A discloses a method for synthesizing SIBS triblock copolymer by single-end initiation: using styrene monomer as a first monomer, using inexpensive water as an initiator and a Lewis acid as a co-initiator to perform controlled cationic polymerization in a polymerization system containing a solvent and an additive, then adding an isobutylene monomer containing an additive to perform a second stage polymerization to obtain a two-block copolymer, and then adding the first monomer to perform polymerization to obtain a triblock copolymer SIBS.

[0006] US5428111 discloses a method for preparing polyisobutylene segment block copolymer, i.e. in a complex solvent, using a bifunctional organic tertiary alkyl chloride as an initiator, titanium tetrachloride as a co-initiator, and a steric hindering pyridine as a proton capturing agent, to initiate isobutylene for active cationic polymerization to form a polyisobutylene with a predetermined molecular weight, then adding a capping agent for capping reaction to form a relatively stable cationic active center, and then adding styrene for further polymerization.

[0007] Traditional polymerization process usually uses methyl chloride and aliphatic alkane such as n-hexane to form a mixed solvent to synthesize SIBS, but methyl chloride can consume ozone in the atmosphere, and because the polarity of methyl chloride solvent is low, the growing macromolecular chain cannot be well dissolved in the solvent to form a biphenyl copolymer, and a structurally regular triblock copolymer SIBS cannot be obtained. SUMMARY

[0008] The purpose of the present application is to overcome the problems of the prior art that the star block copolymer has an irregular structure and the content of biphenyl copolymer in the copolymer is high, and to provide a star block copolymer and a preparation method thereof, the star block copolymer has a regular structure, a narrow molecular weight distribution, and a low content of biphenyl copolymer in the copolymer; at the same time, in the preparation method of the star block copolymer, a diluent containing a fluorinated alkane is used instead of traditional methyl chloride, which can improve the regularity of the structure of the star block copolymer while significantly reducing the pollution to the environment.

[0009] In order to achieve the above-mentioned purpose, the present application provides a star block copolymer, characterized in that the soft segment of the star block copolymer is a fully saturated polyisobutylene, and the hard segment of the star block copolymer is a polystyrene.

[0010] The content of the styrene homopolymer is 1-10wt%, and the content of the biphenyl copolymer is 1-10wt%, based on the total weight of the star block copolymer.

[0011] The present application provides a preparation method of a star block copolymer, characterized in that the method comprises the following steps:

[0012] (1) contacting isobutylene with an initiator in the presence of a diluent to perform a first cationic polymerization reaction, to obtain a polyisobutylene containing a reactive group at the end;

[0013] (2) when the conversion rate of the isobutylene reaches 90% or more, adding styrene to the polymerization system to perform a second cationic polymerization reaction, to obtain the star block copolymer;

[0014] The diluent comprises a first diluent selected from aliphatic alkane and / or cycloaliphatic alkane and a second diluent which is fluoroalkane.

[0015] The third aspect of the present application provides a star-shaped block copolymer prepared by the above preparation method.

[0016] The star-shaped block copolymer and the preparation method thereof have the following beneficial effects:

[0017] The star-shaped block copolymer has a regular structure, a narrow molecular weight distribution, and a low content of biphenyl copolymer in the copolymer.

[0018] Further, in the preparation method of the star-shaped block copolymer, the diluent comprising fluoroalkane is used to replace the traditional methyl chloride, which can improve the regularity of the structure of the star-shaped block copolymer and significantly reduce the pollution to the environment. DETAILED DESCRIPTION

[0019] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The ranges and values should be interpreted as approximations. The endpoints of the ranges and values are provided as a separate point for the convenience of the reader. The ranges and values are approximate values and are intended to be rounded off to the nearest value. The endpoints of the ranges and values are not provided with a degree of accuracy to the nearest one-hundredth of the unit of measure of the lower value of the range, unless otherwise indicated in this disclosure.

[0020] The first aspect of the present application provides a star-shaped block copolymer, characterized in that the soft segment of the star-shaped block copolymer is a fully saturated polyisoolefin, and the hard segment of the star-shaped block copolymer is polystyrene.

[0021] The content of the styrene homopolymer is 1-10 wt%, and the content of the biphenyl copolymer is 1-10 wt% based on the total weight of the star-shaped block copolymer.

[0022] In the present application, the soft segment of the star-shaped block copolymer is a fully saturated polyisoolefin, the hard segment is polystyrene, and the star-shaped block copolymer contains a low content of biphenyl copolymer, which can significantly improve the tensile strength of the star-shaped block copolymer.

[0023] In the present application, the biphenyl copolymer refers to a substance generated by intermolecular electrophilic substitution reaction due to the poor solubility of the growing polystyrene growing chain during the preparation of the star-shaped block copolymer. A high content of the biphenyl copolymer will widen the molecular weight distribution of the copolymer.

[0024] According to the present application, the content of the styrene homopolymer is 2-5 wt% based on the total weight of the star-shaped block copolymer, and the content of the biphenyl copolymer is 1-7 wt%.

[0025] According to the present application, the content of the soft segment is 50-90 wt%, preferably 60-80 wt%, and the content of the hard segment is 10-50 wt%, preferably 20-40 wt%, based on the total weight of the star-shaped block copolymer.

[0026] According to the present application, the number average molecular weight of the star-shaped block copolymer is 50,000-500,000, preferably 100,000-300,000, and the molecular weight distribution of the star-shaped block copolymer is 1-4, preferably 1.2-2.5.

[0027] In the present application, the star-shaped block copolymer has a narrow molecular weight distribution, and the star-shaped block copolymer has a structural regularity.

[0028] According to the present application, the number average molecular weight of the soft segment is 10,000-200,000, preferably 40,000-100,000, and the molecular weight distribution of the soft segment is 1-2, preferably 1-1.5.

[0029] According to the present application, the number average molecular weight of the hard segment is 5,000-200,000, preferably 10,000-100,000, and the molecular weight distribution of the hard segment is 1-2, preferably 1-1.5.

[0030] The second aspect of the present application provides a preparation method of a star-shaped block copolymer, characterized in that the method comprises the following steps:

[0031] (1) contacting an isoolefin and an initiator in the presence of a diluent to perform a first cationic polymerization reaction to obtain a polyisoolefin containing a reactive group at the terminal;

[0032] (2) when the conversion rate of the isoolefin reaches 90% or more, adding styrene to the polymerization system to perform a second cationic polymerization reaction to obtain the star-shaped block copolymer;

[0033] wherein the diluent comprises a first diluent and a second diluent, the first diluent is selected from aliphatic alkanes and / or alicyclic alkanes, and the second diluent is a fluoroalkane.

[0034] In the present application, the isoolefin and the styrene are subjected to cationic polymerization in the presence of a diluent containing a fluoroalkane, which can significantly improve the solubility of the macromolecular chain of the copolymer in the polymerization system, thereby inhibiting the generation of the biphenyl copolymer, and further obtaining a star-shaped block copolymer with structural regularity, and the copolymer has a narrow molecular weight distribution.

[0035] In the present application, the method further comprises being carried out in the presence of a nucleophile, which can be a nucleophile conventional in the art, such as N, N-dimethylacetamide, and a proton trap, which can be a proton trap conventional in the art, such as 2, 6-di-tert-butylpyridine. The amount of the nucleophile and the proton trap can be the amount conventional in the art.

[0036] According to the present application, the diluent comprises a first diluent selected from aliphatic alkane and / or alicyclic alkane and a second diluent which is fluoroalkane.

[0037] In the present application, the amount of the first diluent and the second diluent in the diluent can be selected according to the specific polymerization conditions. Specifically, the content of the first diluent is 1-99 vol% based on the total volume of the diluent; the content of the second diluent is 1-99 vol% based on the total volume of the diluent.

[0038] Further, the content of the first diluent is 60-90 vol% based on the total volume of the diluent; the content of the second diluent is 10-40 vol% based on the total volume of the diluent.

[0039] Further, the first diluent is selected from n-hexane and / or methylcyclopentane; the second diluent is selected from 1, 1, 1, 2-tetrafluoroethane. In the present application, 1, 1, 1, 2-tetrafluoroethane does not contain chlorine, does not consume ozone in the atmosphere and is not flammable, which can significantly reduce pollution to the environment.

[0040] In the present application, the amount of the diluent can be selected according to the amount of the isoolefin. Generally, the volume ratio of the diluent to the isoolefin is 2-20:1.

[0041] According to the present application, the initiator comprises at least one compound comprising a structural unit represented by formula (I) and at least one Lewis acid;

[0042]

[0043] R1, R2, R3, R4, R5, R6, R7and R8are each independently hydrogen, linear or branched C1-C 10 X is halogen; the weight average molecular weight of the compound is 1,000-200,000, and the molecular weight distribution is 1-5.

[0044] According to the present application, the isoolefin is selected from isobutylene and / or 2-methyl-1-butene, preferably isobutylene.

[0045] According to the present application, in formula (I), R1, R2, R3, R4, R5, R6, R7 and R8 are C1-C4 alkyl; X is halogen; the weight average molecular weight of the compound is 10,000-100,000, and the molecular weight distribution is 1-3.

[0046] Further, when the compound containing the structural unit shown in formula (I) is selected from polystyrene containing benzyl chloride (R1, R2, R3, R4, R5, R6, R7 and R8 are H, and X is Cl) and / or polystyrene containing benzyl bromide group (R1, R2, R3, R4, R5, R6, R7 and R8 are H, and X is Br), the prepared star-shaped block copolymer has more excellent comprehensive performance.

[0047] According to the present application, the Lewis acid is selected from one or more of boron trifluoride, titanium tetrachloride, tin tetrachloride and aluminum trichloride, and is preferably titanium tetrachloride.

[0048] In the present application, preferably, the initiator is mixed with a solvent to form an initiator solution, and then the initiator solution is added to the polymerization system, and the solvent can be various liquid substances capable of dissolving the compound containing the structural unit shown in formula (I) and the Lewis acid, for example, the solvent can be selected from at least one of the above-mentioned diluents.

[0049] According to the present application, the concentration of the compound containing the structural unit shown in formula (I) is 0.1×10 -4 mol / L-0.1 mol / L, and the concentration of the Lewis acid is 0.1×10 -3 mol / L-0.1 mol / L, based on the total volume of the diluent, isoolefin and styrene.

[0050] Further, when the concentration of the compound containing the structural unit shown in formula (I) is 0.5×10 -3 mol / L-0.01 mol / L, and the concentration of the Lewis acid is 0.1×10 -2 mol / L-0.1 mol / L, based on the total volume of the diluent, isoolefin and styrene, the comprehensive performance of the prepared star-shaped block copolymer is more excellent.

[0051] In the present application, the amount of the isoolefin and the styrene can be adjusted according to the preset molecular weight of the block copolymer, and specifically, the molar ratio of the isoolefin to the styrene is 1:0.05-1.

[0052] Further, when the molar ratio of the isoolefin to the styrene is 1:0.1-0.5, the block efficiency of the prepared copolymer can be further improved.

[0053] In the present application, the styrene is preferably mixed with a solvent to form a styrene solution before being added to the polymerization system, and the solvent can be at least one of the above-mentioned diluents, and preferably the solvent is the same as the diluent.

[0054] According to the present application, the first cationic polymerization reaction is carried out at a temperature of -120℃ to 20℃, preferably -100℃ to 0℃, and more preferably -100℃ to -40℃.

[0055] According to the present application, the second cationic polymerization reaction is carried out at a temperature of -120℃ to 20℃, preferably -100℃ to 0℃, and more preferably -100℃ to -40℃.

[0056] In the present application, the conditions of the first cationic polymerization reaction can be the same as or different from the conditions of the second cationic polymerization reaction.

[0057] In the present application, the preparation method further comprises adding a polymerization terminator (e.g. an alcohol) to the mixture obtained after the polymerization to terminate the polymerization reaction. The present application does not have specific limitations on the type and amount of the polymerization terminator, which can be selected according to the conventional practice in the art, and the polymerization terminator is capable of terminating the polymerization reaction, which will not be described herein.

[0058] In the present application, the monomers and diluents used for polymerization are preferably refined under the conditions commonly used in the art before use, which will not be described herein.

[0059] The present application provides a star-shaped block copolymer prepared by the above-mentioned preparation method.

[0060] In the present application, the soft segment of the star-shaped block copolymer is a fully saturated polyisoolefin, and the hard segment of the star-shaped block copolymer is polystyrene.

[0061] The content of the styrene homopolymer is 1-10wt% based on the total weight of the star-shaped block copolymer, and the content of the biphenyl copolymer is 1-10wt%.

[0062] In the present application, the soft segment of the star-shaped block copolymer is a fully saturated polyisoolefin, and the hard segment is polystyrene, and the star-shaped block copolymer contains a low content of biphenyl copolymer, which can significantly improve the tensile strength of the star-shaped block copolymer.

[0063] In the present application, the content of the styrene homopolymer is 2-5wt% based on the total weight of the star-shaped block copolymer, and the content of the biphenyl copolymer is 1-7wt%.

[0064] In the present application, the content of the soft segment is 50-90wt%, preferably 60-80wt%, based on the total weight of the star-shaped block copolymer; the content of the hard segment is 10-50wt%, preferably 20-40wt%.

[0065] In the present application, the number average molecular weight of the star-shaped block copolymer is 50,000-500,000, preferably 100,000-300,000; the molecular weight distribution of the star-shaped block copolymer is 1-4, preferably 1.2-2.5.

[0066] In the present application, the number average molecular weight of the soft segment is 10,000-200,000, preferably 40,000-100,000; the molecular weight distribution of the soft segment is 1-2, preferably 1-1.5.

[0067] In the present application, the number average molecular weight of the hard segment is 5,000-200,000, preferably 10,000-100,000; the molecular weight distribution of the hard segment is 1-2, preferably 1-1.5.

[0068] The present application will be described in detail below through examples.

[0069] In the following examples and comparative examples, the conversion rate of monomers is determined by weighing method.

[0070] Conversion rate (%) = (weight of obtained polymer / total weight of added monomers) x 100%; wherein the conversion rate of isobutene is determined after step (1) is completed.

[0071] In the following examples and comparative examples, the molecular weight and molecular weight distribution index (M w / M n of the polymers are determined by using LC-20A liquid gel permeation chromatograph produced by Shimadzu Corporation of Japan, using single-aperture chromatographic column and four columns in combination. The mobile phase is tetrahydrofuran, the flow rate is 0.7mL / min; the sample solution concentration is 2mg / mL, the sample injection amount is 200μL; the testing temperature is 35℃; and monodispersed polystyrene is used as standard sample.

[0072] In the following examples and comparative examples, the content of styrene homopolymer and biphenyl copolymer in the polymerization product is determined by using nuclear magnetic resonance hydrogen spectrum. The nuclear magnetic resonance hydrogen spectrum test uses AVANCE400 nuclear magnetic resonance instrument commercially available from Bruker Corporation of Switzerland, deuterated chloroform is used as solvent, and tetramethylsilane (TMS) is used as internal standard.

[0073] The solvents and monomers used in the following examples and comparative examples were purified by methods commonly used in the art before use. The polymerization reactions and the preparation of initiator solutions were carried out in a dry box from MBRAUN, Germany, equipped with a low-temperature cooling bath.

[0074] The macromolecular grafting agent CM-PS is a compound comprising structural units of formula (I), wherein R1, R2, R3, R4, R5, R6, R7 and R8 are H, and X is Cl, which can be obtained by free radical polymerization of styrene and 4-vinylbenzyl chloride according to methods commonly used in the art, or by free radical polymerization of styrene and p-methylstyrene, followed by chlorination of the resulting random copolymer of styrene and p-methylstyrene.

[0075] Example 1

[0076] Firstly, 1 ml of N,N-dimethylacetamide was dissolved in 5 ml of dichloromethane, and 1 ml of 2,6-di-tert-butylpyridine was dissolved in 20 ml of dichloromethane.

[0077] In a glass reactor equipped with a strong constant speed stirrer, 80 ml of 1,1,1,2-tetrafluoroethane, 120 ml of n-hexane, 0.80 x 10 -3 mol of titanium tetrachloride (concentration of 0.004 mol / L), 1.5 ml of N,N-dimethylacetamide solution in dichloromethane, 1 ml of 2,6-di-tert-butylpyridine / dichloromethane solution, and 1.6 x 10 -3 mol (0.008 mol / L) of macromolecular grafting agent CM-PS (Mw = 113,000, MWD = 1.68) were sequentially added, and then 16.8 g of isobutene was added to start the polymerization. After 60 minutes of polymerization, the conversion of isobutene was as shown in Table 1, and 6 g of styrene was added to continue the polymerization for 50 minutes to obtain SIBS-A1 with a star structure. The molar ratio of isobutene to styrene was 1:0.192, the content of the first diluent n-hexane was 60 vol%, and the content of the second diluent 1,1,1,2-tetrafluoroethane was 40 vol%.

[0078] It was tested that the number average molecular weight and the molecular weight distribution of the block copolymer, the polyisobutylene soft segment and the polystyrene hard segment, and the content of the styrene homopolymer and the biphenyl copolymer in the block copolymer were as shown in Table 1.

[0079] Comparative Example 1

[0080] The polymerization was carried out in the same way as in Example 1, except that the polymerization of isobutylene was 30 minutes, and the conversion of isobutylene was shown in Table 1, to produce SIBS-D1 with star structure. The number average molecular weight and molecular weight distribution of the block copolymer, polyisobutylene soft segment and polystyrene hard segment, and the content of styrene homopolymer and biphenyl copolymer in the block copolymer were tested and shown in Table 1.

[0081] Comparative Example 2

[0082] The polymerization was carried out in the same way as in Example 1, except that the second diluent was chloromethane, to produce SIBS-D2 with star structure. The number average molecular weight and molecular weight distribution of the block copolymer, polyisobutylene soft segment and polystyrene hard segment, and the content of styrene homopolymer and biphenyl copolymer in the block copolymer were tested and shown in Table 1.

[0083] Example 2

[0084] First, 1 ml of N,N-dimethylacetamide was dissolved in 5 ml of dichloromethane, and 1 ml of 2,6-di-tert-butylpyridine was dissolved in 20 ml of dichloromethane.

[0085] In a glass reactor equipped with strong constant speed stirring, 80 ml of 1,1,1,2-tetrafluoroethane pre-cooled to -80°C, 120 ml of n-hexane, 0.80 x 10 -3 mol of titanium tetrachloride (concentration of 0.004 mol / L), 1.5 ml of N,N-dimethylacetamide dichloromethane solution, 1 ml of 2,6-di-tert-butylpyridine / dichloromethane solution, and 1.6 x 10 -3 mol (0.008 mol / L) of macromolecular grafting agent CM-PS (Mw = 113,000, MWD = 1.68) were sequentially added, and then 16.8 g of isobutylene was added to start the polymerization. After 60 minutes of polymerization, the conversion of isobutylene was shown in Table 1, and 8 g of styrene was added to continue the polymerization for 50 minutes to produce SIBS-A2 with star structure. Among them, the molar ratio of isobutylene to styrene was 1:0.258, and in the diluent, the content of the first diluent n-hexane was 60 vol%, and the content of the second diluent 1,1,1,2-tetrafluoroethane was 40 vol%.

[0086] The number average molecular weight and molecular weight distribution of the block copolymer, polyisobutylene soft segment and polystyrene hard segment, and the content of styrene homopolymer and biphenyl copolymer in the block copolymer were tested and shown in Table 1.

[0087] Example 3

[0088] Firstly, 1 ml of N, N-dimethylacetamide was dissolved in 5 ml of dichloromethane, and 1 ml of 2, 6-di-tert-butylpyridine was dissolved in 20 ml of dichloromethane.

[0089] In a glass reactor equipped with strong constant speed stirring, 80 ml of 1, 1, 1, 2-tetrafluoroethane, 120 ml of n-hexane, 0.80 x 10 -3 mol of titanium tetrachloride (concentration of 0.004 mol / L), 1.5 ml of N, N-dimethylacetamide dichloromethane solution, 1 ml of 2, 6-di-tert-butylpyridine / dichloromethane solution, and 1.9 x 10 -3 mol (0.008 mol / L) of macromolecular grafting agent CM-PS (Mw = 113,000, MWD = 1.68) were sequentially added, and then 16.8 g of isobutene was added to start the polymerization. After 60 minutes of polymerization, the conversion rate of isobutene was as shown in Table 1, and 8 g of styrene was added to continue the polymerization for 50 minutes to obtain SIBS-A3 with a star structure. Among them, the molar ratio of isobutene to styrene was 1:0.258, the content of the first diluent n-hexane in the diluent was 60 vol%, and the content of the second diluent 1, 1, 1, 2-tetrafluoroethane was 40 vol%.

[0090] It was tested that the number average molecular weight and the molecular weight distribution of the block copolymer, the polyisobutylene soft segment and the polystyrene hard segment, and the content of the styrene homopolymer and the biphenyl copolymer in the block copolymer were as shown in Table 1.

[0091] Example 4

[0092] Firstly, 1 ml of N, N-dimethylacetamide was dissolved in 5 ml of dichloromethane, and 1 ml of 2, 6-di-tert-butylpyridine was dissolved in 20 ml of dichloromethane.

[0093] In a glass reactor equipped with strong constant speed stirring, 80 ml of 1, 1, 1, 2-tetrafluoroethane, 120 ml of n-hexane, 0.80 x 10 -3 mol of titanium tetrachloride (concentration of 0.004 mol / L), 1.5 ml of N, N-dimethylacetamide dichloromethane solution, 1 ml of 2, 6-di-tert-butylpyridine / dichloromethane solution, and 0.6 x 10 -3mol (0.008 mol / L) macromolecular grafting agent CM-PS (Mw = 113,000, MWD = 1.68) was added, and then 16.8 grams of isobutene was added to start the polymerization. After 60 minutes of polymerization, the conversion rate of isobutene was as shown in Table 1, and 6 grams of styrene was added to continue the polymerization for 50 minutes to obtain the star-shaped SIBS-A5. Among them, the molar ratio of isobutene to styrene was 1:0.192, and in the diluent, the content of the first diluent n-hexane was 60 vol%, and the content of the second diluent 1,1,1,2-tetrafluoroethane was 40 vol%.

[0094] It was tested that the number average molecular weight and the molecular weight distribution of the block copolymer, the polyisobutylene soft segment and the polystyrene hard segment, and the content of the styrene homopolymer and the biphenyl copolymer in the block copolymer were as shown in Table 1.

[0095] Example 5

[0096] The same method as in Example 1 was used for polymerization, except that in the diluent, the content of the first diluent was different from that in Example 1, specifically, the content of the first diluent was 70 vol%. However, it was within the range of 60-90 vol%.

[0097] Table 1

[0098]

[0099] As can be seen from the results in Table 1, the star-shaped block copolymer prepared according to the preparation method of Examples 1-5 provided by the present application not only has a narrow molecular weight distribution, but also significantly reduces the content of the biphenyl copolymer in the copolymer.

[0100] The above describes the preferred embodiments of the present application in detail, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A star-shaped block copolymer, characterized in that The soft segment of the star-shaped block copolymer is a fully saturated polyisoolefin, and the hard segment of the star-shaped block copolymer is polystyrene; based on the total weight of the star-shaped block copolymer, the content of styrene homopolymer is 1-10wt%, and the content of biphenyl copolymer is 1-10wt%; the biphenyl copolymer refers to a substance generated during the preparation of the star-shaped block copolymer due to the incomplete dissolution of the growing polystyrene chain, resulting in an electrophilic substitution reaction between molecules; The preparation method of the star-shaped block copolymer comprises the following steps: (1) contacting an isoolefin with an initiator in the presence of a diluent to perform a first cationic polymerization reaction to obtain a polyisoolefin having a terminal reactive group; (2) When the conversion rate of the isoolefin reaches 90% or more, adding styrene to the polymerization system to carry out a second cationic polymerization reaction to obtain the star-shaped block copolymer; Wherein, the diluent comprises a first diluent and a second diluent, the first diluent is selected from aliphatic alkanes and / or alicyclic alkanes, and the second diluent is a fluoroalkane; The initiator comprises at least one compound comprising a structural unit represented by formula (I) and at least one Lewis acid; Formula (I), R1, R2, R3, R4, R5, R6, R7 and R8 are each independently hydrogen, a linear or branched C1-C 10 Alkyl; X is halogen; the weight average molecular weight of the compound is 1,000-200,000, and the molecular weight distribution is 1-5; Based on the total volume of the diluent, isoolefin and styrene, the concentration of the compound comprising the structural unit represented by formula (I) is 0.1×10 -4 mol / L-0.1mol / L; the concentration of the Lewis acid is 0.1×10 -3 mol / L -0.1mol / L; The molar ratio of the isoolefin to the styrene is 1:0.05-1.

2. The star-shaped block copolymer according to claim 1, wherein Based on the total weight of the star-shaped block copolymer, the content of the styrene homopolymer is 2-5wt%, and the content of the biphenyl copolymer is 1-7wt%.

3. The star-shaped block copolymer according to claim 1, wherein Based on the total weight of the star-shaped block copolymer, the content of the soft segment is 50-90 wt %; and the content of the hard segment is 10-50 wt %.

4. The star-shaped block copolymer according to claim 3, wherein Based on the total weight of the star-shaped block copolymer, the content of the soft segment is 60-80 wt %; and the content of the hard segment is 20-40 wt %.

5. The star-shaped block copolymer according to any one of claims 1 to 4, wherein The number average molecular weight of the star-shaped block copolymer is 50,000-500,000; and the molecular weight distribution of the star-shaped block copolymer is 1-4.

6. The star-shaped block copolymer according to claim 5, wherein The number average molecular weight of the star-shaped block copolymer is 100,000-300,000; and the molecular weight distribution of the star-shaped block copolymer is 1.2-2.

5.

7. The star-shaped block copolymer according to claim 5, wherein The number average molecular weight of the soft segment is 10,000-200,000; and the molecular weight distribution of the soft segment is 1-2.

8. The star-shaped block copolymer according to claim 7, wherein The number average molecular weight of the soft segment is 40,000-100,000; and the molecular weight distribution of the soft segment is 1-1.

5.

9. The star-shaped block copolymer according to claim 5, wherein The number average molecular weight of the hard segment is 5,000-200,000; and the molecular weight distribution of the hard segment is 1-2.

10. The star-shaped block copolymer according to claim 9, wherein The number average molecular weight of the hard segment is 10,000-100,000; and the molecular weight distribution of the hard segment is 1-1.

5.

11. The star-shaped block copolymer according to claim 1, wherein Based on the total volume of the diluent, the content of the first diluent is 1-99 vol%; the content of the second diluent is 1-99 vol%.

12. The star-shaped block copolymer according to claim 11, wherein Based on the total volume of the diluent, the content of the first diluent is 60-90 vol%; the content of the second diluent is 10-40 vol%.

13. The star-shaped block copolymer according to claim 11, wherein The first diluent is selected from n-hexane and / or methylcyclopentane; the second diluent is selected from 1,1,1,2-tetrafluoroethane.

14. The star-shaped block copolymer according to claim 1, wherein The isoolefin is selected from isobutylene and / or 2-methyl-1-butene.

15. The star-shaped block copolymer according to claim 14, wherein The isoolefin is isobutylene.

16. The star-shaped block copolymer according to claim 14, wherein In formula (I), R1, R2, R3, R4, R5, R6, R7 and R8 are C1-C4 alkyl groups; X is a halogen; and the weight average molecular weight of the compound is 10,000-100,000, with a molecular weight distribution of 1-3.

17. The star-shaped block copolymer according to claim 14, wherein The compound comprising the structural unit represented by formula (I) is selected from polystyrene containing benzyl chloride and / or polystyrene containing benzyl bromide groups.

18. The star-shaped block copolymer according to claim 14, wherein The Lewis acid is selected from one or more of boron trifluoride, titanium tetrachloride, tin tetrachloride and aluminum trichloride.

19. The star-shaped block copolymer according to claim 18, wherein The Lewis acid is titanium tetrachloride.

20. The star-shaped block copolymer according to claim 1, wherein Based on the total volume of the diluent, isoolefin and styrene, the concentration of the compound comprising the structural unit represented by formula (I) is 0.5×10 -3 mol / L-0.01mol / L; the concentration of the Lewis acid is 0.1×10 -2 mol / L -0.1mol / L.

21. The star-shaped block copolymer according to claim 1, wherein The molar ratio of the isoolefin to the styrene is 1:0.1-0.

5.

22. The star-shaped block copolymer according to claim 1, wherein The conditions of the first cationic polymerization reaction include: a reaction temperature of -120°C to 20°C.

23. The star-shaped block copolymer according to claim 22, wherein The conditions of the first cationic polymerization reaction include: a reaction temperature of -100°C to 0°C.

24. The star-shaped block copolymer according to claim 23, wherein The conditions of the first cationic polymerization reaction include: a reaction temperature of -100°C to -40°C.

25. The star-shaped block copolymer according to claim 1, wherein The conditions for the second cationic polymerization reaction include: a reaction temperature of -120°C to 20°C.

26. The star-shaped block copolymer according to claim 25, wherein The conditions for the second cationic polymerization reaction include: a reaction temperature of -100°C to 0°C.

27. The star-shaped block copolymer according to claim 26, wherein The conditions for the second cationic polymerization reaction include: a reaction temperature of -100°C to -40°C.

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