CN115703869A - Star block copolymer and preparation method thereof - Google Patents
Star block copolymer and preparation method thereof Download PDFInfo
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Abstract
The invention 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 fully saturated polyisoolefine, 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 the styrene homopolymer is 1 to 10 weight percent, and the content of the biphenyl copolymer is 1 to 10 weight percent. The star-shaped block copolymer has a regular structure and narrow molecular weight distribution, and the content of biphenyl copolymer in the copolymer is low; meanwhile, in the preparation method of the star-shaped block copolymer, the diluent containing the fluoroalkane is adopted to replace the traditional methane chloride, so that the pollution to the environment is obviously reduced while the structural regularity of the star-shaped block copolymer is improved.
Description
Technical Field
The invention relates to the field of polymer preparation, in particular to a star-shaped block copolymer and a preparation method thereof.
Background
The synthesis of thermoplastic elastomers generally involves the preparation of triblock copolymers having soft blocks which are rubbery and hard blocks which are plastic. The plastic hard segments are typically vinyl aromatics (e.g., polystyrene), while the rubbery soft segments are typically polybutadiene or polyisoprene. The most predominant styrenic thermoplastic elastomers are polystyrene-butadiene-styrene triblock copolymers (SBS). The preparation of SBS by using active anion technique is widely used in industry, but the SBS prepared by the technique has many disadvantages: for example, polybutadiene in the soft block structure contains double bonds with high unsaturation, resulting in poor heat resistance, weather resistance and aging resistance of SBS. Although the hydrogenation method can improve the performance of SBS and improve the thermal oxygen stability and the use temperature of SBS, the hydrogenation method needs noble metal as catalyst, and the process is complex and high in cost. In addition, hydrogenation of the polyisobutylene segment easily forms a polyethylene segment, and the original elasticity is lost.
The polystyrene-isobutylene-styrene (SIBS) synthesized by adopting the active cation technology overcomes the defects. Compared with SBS, its advantages are mainly reflected in: (1) The middle rubber soft segment is a fully saturated structure of polyisobutylene, so that the SIBS has more excellent air tightness and thermal oxygen stability. (2) Since the lateral methyl groups are closely arranged on both sides of the isobutylene, the SIBS has more excellent shock absorption performance.
CN1502639A discloses a method for the synthesis of SIBS triblock copolymers by single-ended initiation: taking tertiary alkyl halide as an initiator and Lewis acid as a coinitiator, firstly carrying out single-end initiation to synthesize a styrene macromolecular initiator, then adding an isobutene monomer for copolymerization to obtain a two-block copolymer, and then continuously adding a styrene monomer after supplementing a part of Lewis acid to obtain a three-block copolymer.
CN1982350A discloses a method for the synthesis of SIBS triblock copolymers by single-ended initiation: styrene monomer is used as a first monomer, in a polymerization system containing a solvent and an additive, cheap water is used as an initiator, lewis acid is used as a co-initiator to control cationic polymerization, then isoolefin monomer containing the additive is added to carry out second-stage polymerization to obtain a two-block copolymer, and the first monomer is added to carry out polymerization to obtain a three-block copolymer SIBS.
US5428111 discloses a process for preparing a segmented copolymer of polyisobutylene, which comprises the steps of initiating isobutylene to perform living cationic polymerization to generate polyisobutylene with a predetermined molecular weight in a composite solvent by using bifunctional organic tertiary alkyl chloride as an initiator, titanium tetrachloride as a co-initiator and sterically hindered pyridine as a proton trapping agent, adding a terminating agent to perform a terminating reaction to form a relatively stable cationic active center, and then adding styrene to continue polymerization.
The traditional polymerization process usually adopts a mixed solvent consisting of methane chloride and aliphatic alkane such as n-hexane to synthesize the SIBS, but because the methane chloride can consume ozone in the atmosphere, and because the polarity of the methane chloride solvent is low, the growing macromolecular chains can not be well dissolved in the solvent to generate a benzene copolymer, and the triblock copolymer SIBS with a regular structure can not be obtained.
Disclosure of Invention
The invention aims to overcome the problems of irregular structure of the star-shaped block copolymer and high biphenyl copolymer content in the copolymer in the prior art, and provides the star-shaped block copolymer and the preparation method thereof, wherein the star-shaped block copolymer has a regular structure and narrow molecular weight distribution, and the biphenyl copolymer content in the copolymer is low; meanwhile, in the preparation method of the star-shaped block copolymer, the diluent containing the fluoroalkane is adopted to replace the traditional methane chloride, so that the pollution to the environment is obviously reduced while the structural regularity of the star-shaped block copolymer is improved.
In order to achieve the above object, the present invention provides a star block copolymer, wherein the soft segment of the star block copolymer is fully saturated polyisoolefin, and the hard segment of the star block copolymer is polystyrene;
based on the total weight of the star-shaped block copolymer, the content of the styrene homopolymer is 1 to 10 weight percent, and the content of the biphenyl copolymer is 1 to 10 weight percent.
The second aspect of the present invention provides a method for preparing a star-shaped block copolymer, which is characterized by comprising the following steps:
(1) In the presence of a diluent, enabling isoolefin to be in contact with an initiator to carry out a first cationic polymerization reaction to obtain polyisoolefin containing a terminal reactive group;
(2) When the conversion rate of the isoolefin reaches more than 90%, adding styrene into a polymerization system, and carrying 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 alkane and/or alicyclic alkane, and the second diluent is fluorinated alkane.
The third aspect of the present invention provides a star block copolymer obtained by the above production method.
Through the technical scheme, the star-shaped block copolymer and the preparation method thereof provided by the invention have the following beneficial effects:
the star-shaped block copolymer provided by the invention has a regular structure and narrow molecular weight distribution, and the content of biphenyl copolymer in the copolymer is low.
Furthermore, in the preparation method of the star-shaped block copolymer, the diluent containing the fluorinated alkane is adopted to replace the traditional methane chloride, so that the pollution to the environment is obviously reduced while the structural regularity of the star-shaped block copolymer is improved.
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and these ranges or values should be understood to encompass values close to these ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
The invention provides a star-shaped block copolymer, which is characterized in that the soft segment of the star-shaped block copolymer is 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 the styrene homopolymer is 1-10wt%, and the content of the biphenyl copolymer is 1-10wt%.
In the invention, the soft segment of the star-shaped block copolymer is fully saturated polyisoolefine, the hard segment of the star-shaped block copolymer is polystyrene, and the star-shaped block copolymer contains a biphenyl copolymer with lower content, so that the tensile strength of the star-shaped block copolymer can be obviously improved.
In the present invention, the biphenyl copolymer means a substance produced by electrophilic substitution between molecules due to poor dissolution of the growing polystyrene growing chain in the process of preparing the star block copolymer, and the molecular weight distribution of the copolymer is widened due to an excessively high content of the biphenyl copolymer.
According to the invention, the styrene homopolymer is present in an amount of 2 to 5 wt.% and the biphenyl interpolymer is present in an amount of 1 to 7 wt.%, based on the total weight of the star-block copolymer.
According to the invention, the soft block content is from 50 to 90% by weight, preferably from 60 to 80% by weight, based on the total weight of the radial block copolymer; the hard segment content is 10 to 50 wt.%, preferably 20 to 40 wt.%.
According to the invention, the number average molecular weight of the radial block copolymer is from 50,000 to 500,000, preferably from 100,000 to 300,000; the molecular weight distribution of the star-shaped block copolymer is 1 to 4, preferably 1.2 to 2.5.
In the invention, the star-shaped block copolymer has narrow molecular weight distribution and has the characteristic of regular structure.
According to the invention, the number average molecular weight of the soft segment is from 10,000 to 200,000, preferably from 40,000 to 100,000; the soft segment has a molecular weight distribution of 1 to 2, preferably 1 to 1.5.
According to the invention, the number average molecular weight of the hard segments is between 5,000 and 200,000, preferably between 10,000 and 100,000; the molecular weight distribution of the hard segment is 1 to 2, preferably 1 to 1.5.
The second aspect of the present invention provides a method for preparing a star-shaped block copolymer, wherein the method comprises the following steps:
(1) In the presence of a diluent, enabling isoolefin to be in contact with an initiator to carry out a first cationic polymerization reaction to obtain polyisoolefin containing a terminal reactive group;
(2) When the conversion rate of the isoolefin reaches more than 90%, adding styrene into a polymerization system, and carrying 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 alkane and/or alicyclic alkane, and the second diluent is fluorinated alkane.
In the present invention, isoolefin and styrene are cationically polymerized in the presence of a diluent containing fluoroalkane, so that the solubility of the macromolecular chain of the copolymer in the polymerization system can be significantly improved, the formation of biphenyl copolymers can be suppressed, and a star-shaped block copolymer with a regular structure can be obtained, and the copolymer has a narrow molecular weight distribution.
In the present invention, the method further comprises performing in the presence of a nucleophile, which may be a nucleophile conventional in the art, such as N, N-dimethylacetamide, a proton scavenger, which may be a proton scavenger conventional in the art, such as 2, 6-di-tert-butylpyridine, and the like. For the amount of the nucleophile and proton scavenger, the amounts conventional in the art may be used.
According to the invention, the diluent comprises a first diluent selected from aliphatic alkanes and/or alicyclic alkanes and a second diluent which is a fluorinated alkane.
In the present invention, the amount of the first diluent and the second diluent in the diluent may be selected according to specific polymerization conditions, and specifically, based on the total volume of the diluent, the content of the first diluent is 1 to 99vol%; the content of the second diluent is 1-99vol%.
Further, the content of the first diluent is 60-90vol% and the content of the second diluent is 10-40vol% based on the total volume of the diluents.
Further, the first diluent is selected from n-hexane and/or methylcyclopentane; the second diluent is selected from 1, 2-tetrafluoroethane. In the invention, the 1, 2-tetrafluoroethane does not contain chlorine, does not consume ozone in the atmosphere, is non-flammable and can obviously reduce the pollution to the environment.
In the present invention, the amount of the diluent may be selected according to the amount of the isoolefin. Typically, the volume ratio of the diluent to the isoolefin is from 2 to 20:1.
according to the invention, the initiator comprises at least one compound comprising structural units of formula (I) and at least one Lewis acid;
R 1 、R 2 、R 3 、R 4 、R 5 、R 6 、R 7 and R 8 Each independently hydrogen, straight or branched C 1 -C 10 An alkyl group; x is halogen; the weight average molecular weight of the compound is 1,000-200,000, and the molecular weight distribution is 1-5.
According to the invention, the isoolefin is selected from isobutene and/or 2-methyl-1-butene, preferably isobutene.
According to the invention, in the formula (I), R 1 、R 2 、R 3 、R 4 、R 5 、R 6 、R 7 And R 8 Is C 1 -C 4 Alkyl groups of (a); x is halogen; the weight average molecular weight of the compound is 10,000-100,000, and the molecular weight distribution is 1-3.
Further, when the compound comprising the structural unit represented by the formula (I) is selected from polystyrene (R) containing benzyl chloride 1 、R 2 、R 3 、R 4 、R 5 、R 6 、R 7 And R 8 Is H, X is Cl) and/or polystyrene containing benzyl bromide groups (R) 1 、R 2 、R 3 、R 4 、R 5 、R 6 、R 7 And R 8 H, and X is Br), the prepared star-shaped block copolymer has more excellent comprehensive performance.
According to the invention, the Lewis acid is selected from one or more of boron trifluoride, titanium tetrachloride, tin tetrachloride and aluminium trichloride, preferably titanium tetrachloride.
In the present invention, it is preferable that the initiator is added to the polymerization system in the form of an initiator solution after mixing the initiator with a solvent, and the solvent may be various liquid materials capable of dissolving the compound comprising the structural unit represented by formula (I) and the lewis acid, for example, the solvent may be selected from at least one of the above-mentioned diluents.
According to the invention, the concentration of the compound comprising the structural unit of formula (I) is 0.1X 10, based on the total volume of the diluent, isoolefin and styrene -4 mol/L is 0.1mol/L or less; the concentration of the Lewis acid is 0.1X 10 -3 mol/L-0.1mol/L。
Further, the concentration of the compound comprising the structural unit represented by the formula (I) is 0.5X 10 when the total volume of the diluent, the isoolefin and the styrene is taken as a reference -3 mol/L-0.01mol/L; the concentration of the Lewis acid is 0.1 x 10 -2 When the mol/L is 0.1mol/L to 0.1mol/L, the prepared star-shaped block copolymer has more excellent comprehensive performance.
In the present invention, the amount of the isoolefin and the styrene may be adjusted according to a preset molecular weight of the block copolymer, specifically, the molar ratio of the isoolefin to the styrene is 1:0.05-1.
Further, when the molar ratio of the isoolefin to the styrene is 1: when the amount is 0.1 to 0.5, the block efficiency of the copolymer to be produced can be further improved.
In the present invention, it is preferable that the styrene is added to the polymerization system in the form of a styrene solution after mixing the styrene with a solvent, which may be at least one of the above-mentioned diluents, and preferably, the solvent is the same as the kind of the diluent.
According to the invention, the conditions of the first cationic polymerization reaction comprise: the reaction temperature is from-120 ℃ to 20 ℃, preferably from-100 ℃ to 0 ℃, more preferably from-100 ℃ to-40 ℃.
According to the invention, the conditions of the second cationic polymerization reaction comprise: the reaction temperature is-120 ℃ to 20 ℃, preferably-100 ℃ to 0 ℃, more preferably-100 ℃ to-40 ℃.
In the present invention, the conditions for the first cationic polymerization reaction and the conditions for the second cationic polymerization reaction may be the same or different.
In the present invention, the preparation method further comprises adding a polymerization terminator (e.g., alcohol) to the mixture obtained by polymerization after completion of the polymerization to terminate the polymerization reaction. The type and amount of the polymerization terminator in the present invention are not particularly limited, and may be selected conventionally in the art, so as to terminate the polymerization reaction, and are not described herein again.
In the present invention, the monomers and diluents used for polymerization are preferably purified under conditions commonly used in the art before use, and are not described herein in detail.
The third aspect of the present invention provides a star-shaped block copolymer obtained by the above-mentioned production method.
In the invention, the soft segment of the star-shaped block copolymer is 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 the styrene homopolymer is 1-10wt%, and the content of the biphenyl copolymer is 1-10wt%.
In the invention, the soft segment of the star-shaped block copolymer is fully saturated polyisoolefine, the hard segment of the star-shaped block copolymer is polystyrene, and the star-shaped block copolymer contains a biphenyl copolymer with lower content, so that the tensile strength of the star-shaped block copolymer can be obviously improved.
In the invention, 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%.
In the present invention, the content of the soft segment is 50 to 90wt%, preferably 60 to 80wt%, based on the total weight of the star block copolymer; the hard segment content is 10 to 50 wt.%, preferably 20 to 40 wt.%.
In the present invention, the number average molecular weight of the star block copolymer is 50,000 to 500,000, preferably 100,000 to 300,000; the molecular weight distribution of the star-shaped block copolymer is 1 to 4, preferably 1.2 to 2.5.
In the present invention, the number average molecular weight of the soft segment is 10,000 to 200,000, preferably 40,000 to 100,000; the soft segment has a molecular weight distribution of 1 to 2, preferably 1 to 1.5.
In the present invention, the number average molecular weight of the hard segment is 5,000 to 200,000, preferably 10,000 to 100,000; the molecular weight distribution of the hard segment is 1 to 2, preferably 1 to 1.5.
The present invention will be described in detail below by way of examples.
In the following examples and comparative examples, the conversion of monomer was measured by a weighing method.
Conversion (%) = (weight of obtained polymer/total weight of monomer added) × 100%; wherein, after the step (1) is finished, the conversion rate of isobutene is obtained.
In the following examples and comparative examples, the molecular weight and molecular weight distribution index (M) of the polymer w /M n Recorded as MWD) is determined by LC-20A liquid gel permeation chromatograph manufactured by Shimadzu corporation of Japan, and single-pore chromatographic column is adopted
And
the four columns are used together. The mobile phase is tetrahydrofuran, and the flow rate is 0.7mL/min; the concentration of the sample solution is 2mg/mL, and the sample injection amount is 200 mu L; the test temperature is 35 ℃; monodispersed polystyrene was used as a standard.
In the following examples and comparative examples, the contents of styrene homopolymer and biphenyl interpolymer in the polymerization product were measured by nuclear magnetic resonance hydrogen spectroscopy. The hydrogen nuclear magnetic resonance spectroscopy test employed an AVANCE400 nuclear magnetic resonance apparatus commercially available from Bruker, switzerland, with deuterated chloroform as the solvent and Tetramethylsilicon (TMS) as the internal standard.
The solvents and monomers used in the following examples and comparative examples were refined by methods commonly used in the art before use, and the polymerization reaction and the preparation of the initiator solution were carried out in a dry box commercially available from MBRAUN, germany, equipped with a low temperature cooling bath.
The macromolecular grafting agent CM-PS is a compound containing a structural unit shown as a formula (I), wherein R is 1 、R 2 、R 3 、R 4 、R 5 、R 6 、R 7 And R 8 H and X is Cl, and can be obtained by free radical polymerization of styrene and 4-vinylbenzyl chloride or by free radical polymerization of styrene and p-methylstyrene to obtain a random copolymer of styrene and p-methylstyrene, and then chlorinating the random copolymer.
Example 1
1 ml of N, N-dimethylacetamide was first dissolved in 5 ml of dichloromethane and 1 ml of 2, 6-di-tert-butylpyridine was dissolved in 20 ml of dichloromethane and used.
80 ml of 1, 2-tetrafluoroethane precooled to minus 80 ℃, 120 ml of n-hexane and 0.80 multiplied by 10 are sequentially added into a glass reactor with strong constant stirring -3 mol titanium tetrachloride (concentration 0.004 mol/L), 1.5 ml of a solution of N, N-dimethylacetamide in methylene chloride, 1 ml of a solution of 2, 6-di-tert-butylpyridine in methylene chloride, and 1.6X 10 -3 mol (0.008 mol/L) of a macromolecular grafting agent CM-PS (Mw =113,000, MWD = 1.68), then 16.8 g of isobutene was added to start polymerization, the conversion rate of isobutene was shown in Table 1 after 60 minutes of polymerization reaction, and 6 g of styrene was added to continue the polymerization reaction for 50 minutes to obtain the SIBS-A1 with a star structure. Wherein the molar ratio of isobutene to styrene is 1:0.192, the content of the first diluent n-hexane in the diluent is 60vol% of the second diluent 1, 2-tetrafluoroethane was 40vol%.
The number average molecular weights and molecular weight distributions of the block copolymer, polyisobutylene soft segment and polystyrene hard segment, and the contents of styrene homopolymer and biphenyl interpolymer in the block copolymer were measured as shown in table 1.
Comparative example 1
The polymerization process was the same as in example 1, except that the polymerization reaction of isobutylene was carried out for 30 minutes and the conversion of isobutylene was as shown in Table 1, to obtain SIBS-D1 having a star-shaped structure. The number average molecular weights and molecular weight distributions of the block copolymer, polyisobutylene soft segment and polystyrene hard segment, and the contents of styrene homopolymer and biphenyl copolymer in the block copolymer were measured as shown in Table 1.
Comparative example 2
Polymerization was carried out in the same manner as in example 1 except that the second diluent was methyl chloride to obtain SIBS-D2 having a star structure. The number average molecular weights and molecular weight distributions of the block copolymer, polyisobutylene soft segment and polystyrene hard segment, and the contents of styrene homopolymer and biphenyl copolymer in the block copolymer were measured as shown in Table 1.
Example 2
1 ml of N, N-dimethylacetamide was first dissolved in 5 ml of dichloromethane and 1 ml of 2, 6-di-tert-butylpyridine was dissolved in 20 ml of dichloromethane and used.
80 ml of 1, 2-tetrafluoroethane precooled to minus 80 ℃, 120 ml of n-hexane and 0.80 multiplied by 10 are sequentially added into a glass reactor with strong constant stirring -3 mol titanium tetrachloride (concentration 0.004 mol/L), 1.5 ml of a solution of N, N-dimethylacetamide in methylene chloride, 1 ml of a solution of 2, 6-di-tert-butylpyridine in methylene chloride, and 1.6X 10 -3 mol (0.008 mol/L) of macromolecular grafting agent CM-PS (Mw =113,000, MWD = 1.68), then 16.8 g of isobutene is added to start the polymerization, after 60 minutes of polymerization reaction, the conversion rate of the isobutene is shown in Table 1, 8 g of styrene is added to continue the polymerization reaction for 50 minutes to obtain the SIBS-A2 with a star structure. Wherein the molar ratio of isobutene to styrene is 1:0.258, the content of n-hexane in the first diluent is 60vol%, and the content of 1, 2-tetrafluoroethane in the second diluent is 40vol%.
The number average molecular weights and molecular weight distributions of the block copolymer, polyisobutylene soft segment and polystyrene hard segment, and the contents of styrene homopolymer and biphenyl interpolymer in the block copolymer were measured as shown in table 1.
Example 3
1 ml of N, N-dimethylacetamide was first dissolved in 5 ml of dichloromethane and 1 ml of 2, 6-di-tert-butylpyridine was dissolved in 20 ml of dichloromethane and used.
80 ml of 1, 2-tetrafluoroethane precooled to minus 80 ℃, 120 ml of n-hexane and 0.80 multiplied by 10 are sequentially added into a glass reactor with strong constant stirring -3 mol titanium tetrachloride (concentration 0.004 mol/L), 1.5 ml of a solution of N, N-dimethylacetamide in methylene chloride, 1 ml of a solution of 2, 6-di-tert-butylpyridine in methylene chloride, and 1.9X 10 -3 mol (0.008 mol/L) of macromolecular grafting agent CM-PS (Mw =113,000, MWD = 1.68), then 16.8 g of isobutene is added to start the polymerization, after 60 minutes of polymerization reaction, the conversion rate of the isobutene is shown in Table 1, 8 g of styrene is added to continue the polymerization reaction for 50 minutes to obtain the SIBS-A3 with a star structure. Wherein the molar ratio of isobutene to styrene is 1:0.258, the content of n-hexane in the first diluent is 60vol%, and the content of 1, 2-tetrafluoroethane in the second diluent is 40vol%.
The number average molecular weights and molecular weight distributions of the block copolymer, polyisobutylene soft segment and polystyrene hard segment, and the contents of styrene homopolymer and biphenyl interpolymer in the block copolymer were measured as shown in table 1.
Example 4
1 ml of N, N-dimethylacetamide was first dissolved in 5 ml of dichloromethane and 1 ml of 2, 6-di-tert-butylpyridine was dissolved in 20 ml of dichloromethane and used.
80 ml of 1, 2-tetrafluoroethane precooled to minus 80 ℃, 120 ml of n-hexane and 0.8 ml of n-hexane are sequentially added into a glass reactor with powerful constant-speed stirring0×10 -3 mol of titanium tetrachloride (concentration 0.004 mol/L), 1.5 ml of a solution of N, N-dimethylacetamide in methylene chloride, 1 ml of a solution of 2, 6-di-tert-butylpyridine in methylene chloride, and 0.6X 10 -3 mol (0.008 mol/L) of a macromolecular grafting agent CM-PS (Mw =113,000, MWD = 1.68), then 16.8 g of isobutene was added to start polymerization, the conversion rate of isobutene was shown in Table 1 after 60 minutes of polymerization reaction, and 6 g of styrene was added to continue the polymerization reaction for 50 minutes to obtain the SIBS-A5 with a star structure. Wherein the molar ratio of isobutene to styrene is 1:0.192, the content of n-hexane in the first diluent was 60vol%, and the content of 1, 2-tetrafluoroethane in the second diluent was 40vol%.
The number average molecular weights and molecular weight distributions of the block copolymer, polyisobutylene soft segment and polystyrene hard segment, and the contents of styrene homopolymer and biphenyl interpolymer in the block copolymer were measured as shown in table 1.
Example 5
Polymerization was carried out in the same manner as in example 1, except that: the content of the first diluent in the diluent is different from that in example 1, and specifically, the content of the first diluent is 70vol%. But in the range of 60-90 vol%.
TABLE 1
As can be seen from the results of Table 1, the star block copolymers prepared in examples 1 to 5 according to the preparation method provided by the present invention not only have narrow molecular weight distribution, but also biphenyl interpolymer is significantly reduced in the copolymer.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including various technical features being combined in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.
Claims (12)
1. The star-shaped block copolymer is characterized in that the soft segment of the star-shaped block copolymer is 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 the styrene homopolymer is 1-10wt%, and the content of the biphenyl copolymer is 1-10wt%.
2. The star block copolymer of claim 1, wherein the styrene homopolymer is present in an amount of 2 to 5wt% and the biphenyl interpolymer is present in an amount of 1 to 7wt%, based on the total weight of the star block copolymer.
3. The radial block copolymer according to claim 1 or 2, wherein the soft block content is from 50 to 90 wt. -%, preferably from 60 to 80 wt. -%, based on the total weight of the radial block copolymer; the hard segment content is 10 to 50 wt.%, preferably 20 to 40 wt.%.
4. The radial block copolymer according to any one of claims 1 to 3, wherein the radial block copolymer has a number average molecular weight of 50,000 to 500,000, preferably 100,000 to 300,000; the molecular weight distribution of the star-shaped block copolymer is 1-4, preferably 1.2-2.5;
preferably, the number average molecular weight of the soft segment is 10,000 to 200,000, preferably 40,000 to 100,000; the molecular weight distribution of the soft segment is 1-2, preferably 1-1.5;
preferably, the number average molecular weight of the hard segment is 5,000 to 200,000, preferably 10,000 to 100,000; the molecular weight distribution of the hard segment is 1 to 2, preferably 1 to 1.5.
5. A method for preparing a star-shaped block copolymer, which is characterized by comprising the following steps:
(1) In the presence of a diluent, enabling isoolefin to be in contact with an initiator to carry out a first cationic polymerization reaction to obtain polyisoolefin containing a terminal reactive group;
(2) When the conversion rate of the isoolefin reaches more than 90%, adding styrene into a polymerization system, and carrying 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 alkane and/or alicyclic alkane, and the second diluent is fluorinated alkane.
6. The preparation method according to claim 5, wherein the first diluent is contained in an amount of 1 to 99vol%, preferably 60 to 90vol%, based on the total volume of the diluent; the content of the second diluent is 1-99vol%, preferably 10-40vol%;
preferably, the first diluent is selected from n-hexane and/or methylcyclopentane; the second diluent is selected from 1, 2-tetrafluoroethane.
7. The production method according to claim 5 or 6, wherein the initiator comprises at least one compound comprising a structural unit represented by formula (I) and at least one Lewis acid;
R 1 、R 2 、R 3 、R 4 、R 5 、R 6 、R 7 and R 8 Each independently hydrogen, linear or branched C 1 -C 10 An alkyl group; x is halogen; the weight average molecular weight of the compound is 1,000-200,000, and the molecular weight distribution is 1-5;
preferably, the isoolefin is selected from isobutylene and/or 2-methyl-1-butene, preferably isobutylene.
8. The process according to claim 7, wherein R in the formula (I) 1 、R 2 、R 3 、R 4 、R 5 、R 6 、R 7 And R 8 Is C 1 -C 4 Alkyl groups of (a); x is halogen; the weight average molecular weight of the compound is 10,000-100,000, and the molecular weight distribution is 1-3;
preferably, the compound comprising the structural unit represented by formula (I) is selected from polystyrene containing benzyl chloride and/or polystyrene containing benzyl bromide groups;
preferably, the lewis acid is selected from one or more of boron trifluoride, titanium tetrachloride, tin tetrachloride and aluminum trichloride, preferably titanium tetrachloride.
9. The production method according to claim 7 or 8, wherein the concentration of the compound comprising the structural unit represented by the formula (I) is 0.1X 10 based on the total volume of the diluent, the isoolefin and the styrene -4 mol/L to 0.1mol/L, preferably 0.5X 10 -3 mol/L-0.01mol/L; the concentration of the Lewis acid is 0.1 x 10 -3 mol/L to 0.1mol/L, preferably 0.1X 10 -2 mol/L-0.1mol/L。
10. The production method according to any one of claims 5 to 9, wherein the molar ratio of the isoolefin to the styrene is 1:0.05 to 1, preferably 1:0.1-0.5.
11. The production method according to any one of claims 5 to 10, wherein the conditions of the first cationic polymerization reaction include: the reaction temperature is-120 ℃ to 20 ℃, preferably-100 ℃ to 0 ℃, and more preferably-100 ℃ to-40 ℃;
preferably, the conditions of the second cationic polymerization reaction include: the reaction temperature is from-120 ℃ to 20 ℃, preferably from-100 ℃ to 0 ℃, more preferably from-100 ℃ to-40 ℃.
12. A radial block copolymer obtained by the production method according to any one of claims 5 to 11.
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