A method for preparing branched SBS using a micro-mixed continuous flow reactor

Abstract

The present invention discloses a method for preparing branched SBS by using a micro-mixing continuous flow reactor. Through living anionic polymerization technology and capping method, the present invention first prepares a polystyrene macromonomer with styryl end groups by using a micro-mixing continuous flow reactor, then copolymerizes the macromonomer with butadiene by using the micro-mixing continuous flow reactor, and finally prepares branched SBS with polystyrene as side chains. The present invention overcomes the deficiency in the prior art that a continuous flow reactor cannot be used to prepare branched SBS. The prepared branched SBS has the advantages of low viscosity, good fluidity and being easy to mix with other polymer materials. The branched SBS has broad application prospects in the fields of asphalt modification, plastic toughening, adhesive preparation, etc.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and relates to a preparation method of a polystyrene-polybutadiene-polystyrene thermoplastic elastomer (SBS) having a branched molecular structure. This branched SBS refers to a branched structure copolymer with polystyrene as the side chain and polybutadiene as the main chain. Background Art

[0002] Polystyrene-polybutadiene-polystyrene thermoplastic elastomer (SBS) combines the physical and mechanical properties of rubber and the processing properties of plastics, and is one of the thermoplastic elastomers with the largest production in the world at present. SBS is polymerized from styrene and butadiene monomers. By using living anionic polymerization technology to sequentially polymerize styrene, butadiene, and styrene monomers, SBS with a linear molecular structure can be prepared after termination reaction. And by using living anionic polymerization technology to sequentially polymerize styrene and butadiene, and then carrying out a coupling reaction with a coupling agent such as silicon tetrachloride, SBS with a star-shaped molecular structure can be prepared.

[0003] There are mainly three methods for synthesizing branched polymers: growing side chains type, grafting side chains type, and macromonomer graft copolymerization. The first two grafting methods generally need to synthesize the main chain first and then carry out grafting reaction on the main chain. The operation is relatively complex, and the length and distribution of the obtained product side chains are difficult to control. The use of macromonomer graft copolymerization technology has the advantages of easy process control, strong designability of the main chain and side chains, high polymerization efficiency, etc., and can prepare branched polymers with uniform side chain lengths by a one-pot method. Therefore, this method has certain advantages in the synthesis of branched polymers.

[0004] In the synthesis of branched SBS, macromonomer graft copolymerization technology is usually used to prepare related branched structure SBS. The literature (Fine Chemicals, 2019, 36(8): 1702-1707) discloses a preparation method of a branched polystyrene-polyisoprene-polystyrene (SIS) with polystyrene as a regular side chain. First, using n-butyllithium as an initiator and cyclohexane as a solvent for anionic polymerization of styrene, and using an excessive amount of p-chloromethylstyrene as a terminator to terminate the living polystyrene. After post-treatment and purification, a polystyrene macromonomer containing styryl terminals is obtained; then, using n-butyllithium as an initiator, tetrahydrofuran as a regulator, and cyclohexane as a solvent for anionic copolymerization of isoprene and polystyrene macromonomer. After termination reaction and post-treatment, a branched SIS with polystyrene as a regular side chain is finally prepared. If isoprene in the above method is replaced by butadiene, a branched SBS with polystyrene as a regular side chain can be prepared. The method disclosed in it does not disclose the method of preparing branched SIS using a continuous flow reactor.

[0005] The literature (Journal of Polymer Science, Part A: Polymer Chemistry, 2002, 40(10): 1519 - 1526) discloses a method for preparing a branched - structured polystyrene - polyisoprene. First, using n - butyllithium as an initiator and cyclohexane as a solvent, anionic polymerization of styrene is carried out. Using 4 - chloro(dimethyl)silylstyrene with an equimolar amount to the living polystyrene as a capping agent to cap the living polystyrene, a polystyrene macromonomer with a styryl end is obtained. Then, in this polystyrene macromonomer solution, living polyisoprene lithium is added to react with the styryl end, and then isoprene monomer is added to synthesize a living hetero - arm star - shaped polystyrene - polyisoprene. After coupling with trichloromethylsilane, a branched - structured polystyrene - polyisoprene is finally prepared. The method disclosed in it is a batch method for preparing a branched - structured polystyrene - polyisoprene, and does not disclose a method for preparing branched SIS using a continuous - flow reactor.

[0006] The literature (Macromolecules 2008, 41, 6322 - 6330) discloses a method for preparing a polystyrene macromonomer with a vinyl end using a continuous - flow reactor. Using a micro - flow reactor, first, a cyclohexane solution of sec - butyllithium is continuously injected into one inlet of the first micro - mixer by a pump, and the other inlet is continuously injected with a cyclohexane solution of styrene by a pump. The polymerization reaction is completed through a delay reaction tube with an inner diameter of 1 mm. Then, this living polystyrene solution is continuously injected into one inlet of the second micro - mixer, and the other inlet is continuously injected with a cyclohexane solution of chloro - dimethyl - vinylsilane into the other inlet of the second micro - mixer. Using an excessive amount of chloro - dimethyl - vinylsilane as a capping agent to cap the living polystyrene, after passing through a delay reaction tube with an inner diameter of 1 mm, a polystyrene macromonomer with a styryl end can be continuously obtained at the outlet. In the method disclosed in it, there is no method for continuously preparing branched SBS using this polystyrene macromonomer with a vinyl end. Summary of the Invention

[0007] The purpose of the present invention is to overcome the deficiency in the prior art that branched SBS cannot be prepared using a continuous - flow reactor, and to provide a method for preparing branched SBS using a micro - mixing continuous - flow reactor.

[0008] The technical solution of the present invention:

[0009] A method for preparing branched SBS using a micro - mixing continuous - flow reactor, adopting the route as shown in Figure 1 , continuously synthesizing branched SBS, including the following steps:

[0010] 1) Continuously inject the non-polar hydrocarbon solvent solution of styrene from the styrene solution storage tank V1 into one feed port of the micro mixer a M1 using the plunger pump a P1, and continuously inject the non-polar hydrocarbon solvent solution of the alkyl lithium initiator from the alkyl lithium solution storage tank a V2 into the other feed port of the micro mixer a M1 using the plunger pump b P2. After the materials flow out from the outlet of the micro mixer a M1, they pass through the micro reactor a R1, and after reaction in the micro reactor a R1, an active polystyrene solution is obtained;

[0011] 2) The active polystyrene solution continuously flows into one feed port of the micro mixer b M2. Continuously inject the non-polar hydrocarbon solvent solution of the end-capping agent with an equimolar amount to the active polystyrene from the end-capping agent solution storage tank V3 into the other feed port of the micro mixer b M2 using the plunger pump c P3. After the materials flow out from the outlet of the micro mixer b M2, they pass through the micro reactor b R2, and react in the micro reactor b R2 to cap the active polystyrene, obtaining a polystyrene macromonomer solution with styryl terminals;

[0012] 3) After the polystyrene macromonomer solution is mixed with the non-polar hydrocarbon solvent solution of butadiene and the polar regulator flowing out from the butadiene solution storage tank V4 through the plunger pump d P4, it flows into one feed port of the micro mixer c M3. Continuously inject the non-polar hydrocarbon solvent solution of the alkyl lithium initiator from the alkyl lithium solution storage tank b V5 into the other feed port of the micro mixer c M3 using the plunger pump e P5. After the materials flow out from the outlet of the micro mixer c M3, they pass through the micro reactor c R3, and react in the micro reactor c R3 to carry out the copolymerization of the polystyrene macromonomer and butadiene;

[0013] 4) The solution after the copolymerization reaction of the polystyrene macromonomer and butadiene flows into the product solution storage tank V6 containing the terminator. After the product solution is post-treated and refined, finally, the branched SBS with polystyrene as the side chain is obtained.

[0014] Among them, the mass percentage of the styrene unit in the branched SBS is 15% - 60%, and the mass percentage of the butadiene unit is 40% - 85%; the number-average molecular weight of the branched SBS is 1×10 4 - 80×10 4 , and the number-average molecular weight of the branched side-chain polystyrene is 1×10 3 - 2×10 4 .

[0015] Among them, the dosage of the alkyl lithium initiator is determined according to the number-average molecular weights of the polystyrene macromonomer and the branched SBS.

[0016] Among them, in the entire reaction system, the mass ratio of the total mass of the styrene and butadiene monomers to the mass of the non-polar hydrocarbon solvent is 1:4 - 1:12.

[0017] Among them, the temperatures of all the micro mixers and microreactors are controlled between 20°C and 120°C.

[0018] Among them, the non-polar hydrocarbon solvent is selected from one or a mixture of two or more of pentane, hexane, heptane, octane, cyclohexane, benzene, toluene, ethylbenzene, and xylene.

[0019] Among them, the alkyl lithium initiator is selected from a mixture of one or a mixture of two or more monofunctional alkyl lithium initiators in RLi, where R is an alkyl group with 1 - 10 carbon atoms and Li is a lithium atom.

[0020] Among them, the capping agent is selected from one or a mixture of two of p-chloromethylstyrene and 4-chloro(dimethyl)silylstyrene.

[0021] Among them, the polar regulator is selected from one or a mixture of two or more of diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol dibutyl ether, triethylamine, N,N,N',N'-tetramethylethylenediamine, dipiperidinoethane, ethyl tetrahydrofurfuryl ether, and 2,2-bis(tetrahydrofuran)propane.

[0022] Among them, the terminator is selected from one or a mixture of two or more of water, methanol, ethanol, isopropyl alcohol, and acetic acid.

[0023] The beneficial effects of the present invention: Through the living anionic polymerization technology and capping method, the present invention first prepares a polystyrene macromonomer with a styryl end using a micro-mixing continuous flow reactor, and then copolymerizes the macromonomer with butadiene using the micro-mixing continuous flow reactor, and finally prepares a branched SBS with polystyrene as the side chain. The present invention overcomes the deficiency in the prior art that a continuous flow reactor cannot be used to prepare branched SBS. The prepared branched SBS has the advantages of low viscosity, good fluidity, and being easy to mix with other polymer materials. This branched SBS has broad application prospects in fields such as asphalt modification, plastic toughening, and adhesive preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is the process flow chart of the method of the present invention;

[0025] In the figure: V1 - styrene solution storage tank; V2 - alkyl lithium solution storage tank a; V3 - end-capping agent solution storage tank; V4 - butadiene solution storage tank; V5 - alkyl lithium solution storage tank b; V6 - product solution storage tank; P1 - plunger pump a; P2 - plunger pump b; P3 - plunger pump c; P4 - plunger pump d; P5 - plunger pump e; M1 - micro mixer a; M2 - micro mixer b; M3 - micro mixer c; R1 - micro reactor a; R2 - micro reactor b; R3 - micro reactor c. Detailed implementation mode

[0026] In the following examples, the experimental methods are conventional methods unless otherwise specified, and are carried out according to the techniques or conditions described in the literature in this field or according to the product specifications. The materials, reagents, etc. used in the following examples can be obtained from commercial sources unless otherwise specified.

[0027] In the present invention, a nuclear magnetic resonance spectrometer ( 1 1H-NMR) is used to analyze and test the bound styrene content of branched SBS and the 1,2-structure content of polybutadiene; a gel permeation chromatograph is used to test the number-average relative molecular mass of polystyrene macromonomer and branched SBS.

[0028] Example 1

[0029] First, a cyclohexane solution of styrene (styrene concentration: 0.1 g / mL) is continuously injected into one feed port of the micro mixer a M1 at a flow rate of 20 mL / min using the plunger pump a P1 from the styrene solution storage tank V1. A cyclohexane solution of n-butyllithium (n-butyllithium concentration: 0.5 mmol / mL) is continuously injected into the other feed port of the micro mixer a M1 at a flow rate of 2 mL / min using the plunger pump b P2 from the alkyl lithium solution storage tank a V2. After the materials flow out from the outlet of the micro mixer a M1, they pass through the micro reactor a R1. The solution flowing out from the micro reactor a R1 flows into one feed port of the micro mixer b M2. A toluene solution of 4-chloro(dimethyl)silylstyrene (4-chloro(dimethyl)silylstyrene concentration: 0.5 mmol / mL) is continuously injected into the other feed port of the micro mixer b M2 at a flow rate of 2 mL / min using the plunger pump c P3 from the end-capping agent solution storage tank V3. After the materials flow out from the outlet of the micro mixer b M2, they pass through the micro reactor b R2, and a polystyrene macromonomer solution with styryl end groups can be obtained at the outlet of the micro reactor b R2. The micro mixer a M1, the micro mixer b M2, the micro reactor a R1, and the micro reactor b R2 are placed in a constant temperature water bath at 20 °C.

[0030] Example 2

[0031] According to the same method as in Example 1, except that the flow rate of the cyclohexane solution of n-butyllithium was adjusted to 0.8 mL / min and the flow rate of the toluene solution of 4-chloro(dimethyl)silylstyrene was adjusted to 0.8 mL / min, and the remaining conditions remained unchanged, a polystyrene macromonomer solution with a styryl end was obtained at the outlet of the microreactor b R2.

[0032] Example 3

[0033] According to the same method as in Example 1, except that the flow rate of the cyclohexane solution of n-butyllithium was adjusted to 0.5 mL / min and the flow rate of the toluene solution of 4-chloro(dimethyl)silylstyrene was adjusted to 0.5 mL / min, and the remaining conditions remained unchanged, a polystyrene macromonomer solution with a styryl end was obtained at the outlet of the microreactor b R2.

[0034] Example 4

[0035] First, a toluene solution of styrene (styrene concentration: 0.1 g / mL) was continuously injected into one inlet of the micro mixer a M1 at a flow rate of 20 mL / min from the styrene solution storage tank V1 by using the plunger pump a P1, and a hexane solution of sec-butyllithium (sec-butyllithium concentration: 0.4 mmol / mL) was continuously injected into the other inlet of the micro mixer a M1 at a flow rate of 2.5 mL / min from the alkyllithium solution storage tank a V2 by using the plunger pump b P2. After the materials flowed out from the outlet of the micro mixer a M1, they passed through the microreactor a R1. The solution flowing out from the microreactor a R1 flowed into one inlet of the micro mixer b M2, and a toluene solution of 4-chloro(dimethyl)silylstyrene (4-chloro(dimethyl)silylstyrene concentration: 0.5 mmol / mL) was continuously injected into the other inlet of the micro mixer b M2 at a flow rate of 2 mL / min from the capping agent solution storage tank V3 by using the plunger pump c P3. After the materials flowed out from the outlet of the micro mixer b M2, they passed through the microreactor b R2, and a polystyrene macromonomer solution with a styryl end was obtained at the outlet of the microreactor b R2. The micro mixer a M1, the micro mixer b M2, the microreactor a R1, and the microreactor b R2 were placed in a constant temperature water bath at 40 °C.

[0036] Comparative Example 1

[0037] According to the same method as in Example 1, except that the toluene solution of 4-chloro(dimethyl)silylstyrene was replaced with a toluene solution of p-chloromethylstyrene, and the remaining conditions remained unchanged, a polystyrene macromonomer solution was obtained at the outlet of the microreactor b R2.

[0038] Comparative Example 2

[0039] The polystyrene macromonomer with styryl end groups was prepared in an intermittent manner. The specific steps were as follows: 250 mL of cyclohexane, 250 mL of tetrahydrofuran, and 50 g of styrene were successively added into a 1 L polymerization kettle. Circulating water at 20 °C was introduced into the jacket of the polymerization kettle. After the system temperature reached stability, 25 mL of a cyclohexane solution of n-butyllithium (the concentration of n-butyllithium was 1.0 mmol / mL) was added to initiate the polymerization of styrene. After 50 minutes, 25 mL of a toluene solution of p-chloromethylstyrene (the concentration of p-chloromethylstyrene was 10.0 mmol / mL) was added to carry out the end-capping reaction of living polystyrene. After 60 minutes, 1 mL of ethanol was added. After 20 minutes, the solution was added to a 5 L stainless steel cylinder containing 2 L of ethanol to precipitate the polystyrene macromonomer. The precipitate was washed three times with 1 L of ethanol respectively, and finally dried to a constant weight in a vacuum drying oven at 30 °C to obtain 45 g of white powder of the polystyrene macromonomer with styryl end groups.

[0040] The molecular weight and distribution of the polystyrene macromonomers obtained in Examples 1-4 and Comparative Examples 1-2 were analyzed and tested using a gel permeation chromatograph, and the results are shown in Table 1.

[0041] Table 1

[0042]

[0043] As can be seen from Table 1, the number-average molecular weight of the polystyrene macromonomers prepared in Examples 1-4 was consistent with the dosage of the alkyllithium initiator, and the molecular weight distribution index (Mw / Mn) was less than 1.2, indicating that the end-capping reaction of the end-capping agent 4-chloro(dimethyl)silylstyrene with living polystyrene was quantitative and did not cause the broadening of the molecular weight distribution of the polystyrene macromonomer. The molecular weight distribution index (Mw / Mn) of the polystyrene macromonomer prepared in Comparative Example 1 was 1.78, which was much larger than that of the products prepared in Examples 1-4, indicating that the end-capping reaction of the end-capping agent p-chloromethylstyrene was incomplete and coupling reaction occurred, resulting in the broadening of the molecular weight distribution of the polystyrene macromonomer. The molecular weight distribution index (Mw / Mn) of the polystyrene macromonomer prepared by the intermittent method in Comparative Example 2 was 1.18, less than 1.2, but the molar ratio of the end-capping agent p-chloromethylstyrene to n-butyllithium used in Comparative Example 2 was 10:1, much higher than the ratio of the end-capping agent to alkyllithium in Examples 1-4 (molar ratio 1:1), indicating that a large amount of end-capping agent was required to prepare the polystyrene macromonomer with styryl end groups by the intermittent method, and its economic benefit was lower than that of the continuous method of the present invention.

[0044] Example 5

[0045] First, use plunger pump a P1 to continuously inject a cyclohexane solution of styrene (styrene concentration is 0.1 g / mL) from the styrene solution storage tank V1 into one feed port of the micro mixer a M1 at a flow rate of 20 mL / min. Use plunger pump b P2 to continuously inject a cyclohexane solution of n-butyllithium (n-butyllithium concentration is 0.5 mmol / mL) from the alkyl lithium solution storage tank a V2 into the other feed port of the micro mixer a M1 at a flow rate of 2 mL / min. After the materials flow out from the outlet of M1, they pass through the micro reactor a R1. The solution flowing out from the micro reactor a R1 flows into one feed port of the micro mixer b M2. Use plunger pump c P3 to continuously inject a toluene solution of 4-chloro(dimethyl)silylstyrene (4-chloro(dimethyl)silylstyrene concentration is 0.5 mmol / mL) from the capping agent solution storage tank V3 into the other feed port of the micro mixer b M2 at a flow rate of 2 mL / min. After the materials flow out from the outlet of the micro mixer b M2, they pass through the micro reactor b R2 and are mixed with a cyclohexane solution of butadiene and tetrahydrofuran (butadiene concentration is 0.2 g / mL, tetrahydrofuran concentration is 0.01 mmol / mL, flow rate is 40 mL / min) flowing out from the butadiene solution storage tank V4 through plunger pump d P4 at the outlet of the micro reactor b R2. The mixed solution flows into one feed port of the micro mixer c M3. Use plunger pump e P5 to continuously inject a cyclohexane solution of n-butyllithium (n-butyllithium concentration is 0.02 mmol / mL) from the alkyl lithium solution storage tank b V5 into the other feed port of the micro mixer c M3 at a flow rate of 2.7 mL / min. After the materials flow out from the outlet of the micro mixer c M3, they pass through the micro reactor c R3 to carry out the copolymerization of the macromonomer and butadiene. The solution after the copolymerization reaction of the macromonomer and butadiene flows into the product solution storage tank V6 containing a 1% (wt) ethanol cyclohexane solution. The product solution is subjected to post-treatment and purification, and finally branched SBS with polystyrene as the side chain is obtained. The micro mixer a M1, the micro mixer b M2, the micro mixer c M3, and the micro reactor a R1, the micro reactor b R2, and the micro reactor c R3 are placed in a constant temperature water bath at 70 °C.

[0046] Example 6

[0047] According to the same method as in Example 4, only adjust the concentrations of the cyclohexane solution of butadiene and tetrahydrofuran in the butadiene solution storage tank V4 and the flow rate of plunger pump d P4, that is, adjust the butadiene concentration to 0.1 g / mL, the tetrahydrofuran concentration to 0.08 mmol / mL, and the flow rate to 37 mL / min, and keep the other conditions unchanged. The product solution is subjected to post-treatment and purification, and finally branched SBS with polystyrene as the side chain is obtained.

[0048] Example 7

[0049] According to the same method as in Example 4, only the concentrations of butadiene and tetrahydrofuran in the cyclohexane solution in the butadiene solution storage tank V4 and the flow rate of the plunger pump dP4 are adjusted, that is, the butadiene concentration is adjusted to 0.1 g / mL, the tetrahydrofuran concentration is adjusted to 0.2 mmol / mL, and the flow rate is adjusted to 20 mL / min. The other conditions remain unchanged. The product solution is post-treated and refined, and finally branched SBS with polystyrene as the side chain is obtained.

[0050] Example 8

[0051] First, use the plunger pump aP1 to continuously inject the xylene solution of styrene (styrene concentration is 0.1 g / mL) from the styrene solution storage tank V1 into one feed port of the micro mixer aM1 at a flow rate of 20 mL / min. Use the plunger pump bP2 to continuously inject the cyclohexane solution of sec-butyl lithium (sec-butyl lithium concentration is 0.5 mmol / mL) from the alkyl lithium solution storage tank aV2 into the other feed port of the micro mixer aM1 at a flow rate of 0.8 mL / min. After the materials flow out from the outlet of the micro mixer aM1, they pass through the micro reactor aR1. The solution flowing out from the micro reactor aR1 flows into one feed port of the micro mixer bM2. Use the plunger pump cP3 to continuously inject the ethylbenzene solution of 4-chloro(dimethyl)silylstyrene (4-chloro(dimethyl)silylstyrene concentration is 0.5 mmol / mL) from the capping agent solution storage tank V3 into the other feed port of the micro mixer bM2 at a flow rate of 0.8 mL / min. After the materials flow out from the outlet of the micro mixer bM2, they pass through the micro reactor bR2 and are mixed with the xylene solution of butadiene and ethyltetrahydrofurfuryl ether (butadiene concentration is 0.2 g / mL, ethyltetrahydrofurfuryl ether concentration is 0.002 mmol / mL, flow rate is 30 mL / min) flowing out from the butadiene solution storage tank V4 through the plunger pump dP4 at the outlet of the micro reactor bR2. The mixed solution flows into one feed port of the micro mixer cM3. Use the plunger pump eP5 to continuously inject the cyclohexane solution of sec-butyl lithium (sec-butyl lithium concentration is 0.02 mmol / mL) from the alkyl lithium solution storage tank bV5 into the other feed port of the micro mixer cM3 at a flow rate of 2.8 mL / min. After the materials flow out from the outlet of the micro mixer cM3, they pass through the micro reactor cR3 for the copolymerization of the macromonomer and butadiene. The solution after the copolymerization reaction of the macromonomer and butadiene flows into the product solution storage tank V6 containing a 1% (wt) ethanol xylene solution. The product solution is post-treated and refined, and finally branched SBS with polystyrene as the side chain is obtained. The micro mixer aM1, the micro mixer bM2, the micro mixer cM3 and the micro reactor aR1, the micro reactor bR2, the micro reactor cR3 are placed in a constant temperature oil bath at 120 °C.

[0052] Example 9

[0053] According to the same method as in Example 7, only the concentrations of butadiene and ethyl tetrahydrofurfuryl ether in the xylene solution in the butadiene solution storage tank V4 and the flow rate of the plunger pump eP5 are adjusted, that is, the butadiene concentration is adjusted to 0.1 g / mL, the ethyl tetrahydrofurfuryl ether concentration is adjusted to 0.01 mmol / mL, and the flow rate of the plunger pump eP5 is adjusted to 3.4 mL / min. The remaining conditions remain unchanged. The product solution is post-treated and refined, and finally branched SBS with polystyrene as the side chain is obtained.

[0054] Example 10

[0055] First, use plunger pump a P1 to continuously inject a hexane solution of styrene (styrene concentration is 0.1 g / mL) from styrene solution storage tank V1 into one feed port of micro mixer a M1 at a flow rate of 20 mL / min. Use plunger pump b P2 to continuously inject a hexane solution of n-butyllithium (n-butyllithium concentration is 0.5 mmol / mL) from alkyl lithium solution storage tank a V2 into the other feed port of micro mixer a M1 at a flow rate of 0.5 mL / min. After the materials flow out from the outlet of micro mixer a M1, they pass through micro reactor a R1. The solution flowing out from micro reactor a R1 flows into one feed port of micro mixer b M2. Use plunger pump c P3 to continuously inject a hexane solution of 4-chloro(dimethyl)silylstyrene (4-chloro(dimethyl)silylstyrene concentration is 0.5 mmol / mL) from capping agent solution storage tank V3 into the other feed port of micro mixer b M2 at a flow rate of 0.5 mL / min. After the materials flow out from the outlet of micro mixer b M2, they pass through micro reactor b R2 and are mixed with a hexane solution of butadiene and 2,2-bis(tetrahydrofuran)propane (butadiene concentration is 0.1 g / mL, 2,2-bis(tetrahydrofuran)propane concentration is 0.01 mmol / mL, flow rate is 16 mL / min) flowing out from butadiene solution storage tank V4 through plunger pump d P4 at the outlet of micro reactor b R2. The mixed solution flows into one feed port of micro mixer c M3. Use plunger pump e P5 to continuously inject a cyclohexane solution of n-butyllithium (n-butyllithium concentration is 0.02 mmol / mL) from alkyl lithium solution storage tank b V5 into the other feed port of micro mixer c M3 at a flow rate of 3.3 mL / min. After the materials flow out from the outlet of micro mixer c M3, they pass through micro reactor c R3 to carry out the copolymerization of the macromonomer and butadiene. The solution after the copolymerization reaction of the macromonomer and butadiene flows into product solution storage tank V6 containing a 0.02% (wt) hexane solution of water. The product solution is post-treated and refined, and finally branched SBS with polystyrene as the side chain is obtained. Micro mixer a M1, micro mixer b M2, micro mixer c M3 and micro reactor a R1, micro reactor b R2, micro reactor c R3 are placed in a constant temperature water bath at 50 °C.

[0056] Comparative Example 3

[0057] According to the same method as in Example 5, only replacing the toluene solution of 4-chloro(dimethyl)silylstyrene with the toluene solution of p-chloromethylstyrene, and keeping the other conditions unchanged, a comparative sample of branched SBS can be obtained.

[0058] Comparative Example 4

[0059] The branched SBS is prepared in an intermittent manner. The specific steps are as follows: 500 mL of cyclohexane, 10 g of the polystyrene macromonomer prepared in Comparative Example 2, 40 g of butadiene, and 0.2 mL of tetrahydrofuran are sequentially added into a 1 L polymerization kettle. Circulating water at 50 °C is introduced into the jacket of the polymerization kettle. After the system temperature reaches stability, 2.5 mL of a cyclohexane solution of n-butyllithium (the concentration of n-butyllithium is 0.1 mmol / mL) is added to initiate polymerization. After 90 minutes, 1 mL of ethanol is added. After 20 minutes, the solution is added to a 5 L stainless steel cylinder containing 2 L of ethanol to precipitate the polymer. The precipitate is washed three times with 1 L of ethanol respectively, and finally dried to a constant weight in a vacuum drying oven at 30 °C to obtain 47 g of a branched SBS jelly.

[0060] The combined styrene content and the 1,2-structure content of polybutadiene of the polymers obtained in Examples 5-10 and Comparative Examples 3-4 are analyzed and tested by using a nuclear magnetic resonance spectrometer ( 1 1H-NMR); the number-average relative molecular mass and molecular weight distribution of the polymers obtained in Examples 5-10 and Comparative Examples 3-4 are tested by using a gel permeation chromatograph. The results are shown in Table 2.

[0061] Table 2

[0062]

[0063] Note 1: Based on the total mass of butadiene structural units in the copolymer being 100 wt%.

[0064] As can be seen from Table 2, the method provided by the present invention can continuously prepare a polystyrene macromonomer with styryl terminals and branched SBS. Specifically, for Examples 5-10, by adjusting the amounts of the polystyrene macromonomer molecular weight, alkyllithium initiator, butadiene, etc., branched SBS with different lengths of polystyrene side chains, different styrene segment contents, and different molecular weights can be prepared. The styrene segment content in the branched SBS prepared in Comparative Example 3 is lower compared with the amount of the polystyrene macromonomer used, because there is a coupling reaction during the preparation of the polystyrene macromonomer in this example, and the end-capping reaction is incomplete, resulting in some polystyrene macromonomer terminals not containing styrene groups, so that some polystyrene macromonomers cannot be incorporated into the molecular chain in the finally obtained branched SBS. Branched SBS can be prepared by using the intermittent method in Comparative Example 4, but in this example, an excessive amount of end-capping agent is used to prepare a polystyrene macromonomer with styryl terminals by the intermittent method. After refining and drying, the polystyrene macromonomer and butadiene are copolymerized by the intermittent method, and finally branched SBS can be prepared, but its economic benefit is lower than that of the method for preparing branched SBS by using a micro-mixing continuous flow reactor of the present invention.

Claims

1. A method for preparing branched SBS using a micro-mixing continuous flow reactor, characterized in that, it comprises the following steps: 1) Using plunger pump a (P1), continuously inject a non-polar hydrocarbon solvent solution of styrene from the styrene solution storage tank (V1) into one feed port of the micro-mixer a (M1). Using plunger pump b (P2), continuously inject a non-polar hydrocarbon solvent solution of an alkyllithium initiator from the alkyllithium solution storage tank a (V2) into the other feed port of the micro-mixer a (M1). After the materials flow out from the outlet of the micro-mixer a (M1), they pass through the micro-reactor a (R1). After reacting in the micro-reactor a (R1), an active polystyrene solution is obtained; 2) The active polystyrene solution continuously flows into one feed port of the micro-mixer b (M2). Using plunger pump c (P3), continuously inject a non-polar hydrocarbon solvent solution of a capping agent with an equimolar amount to the active polystyrene from the capping agent solution storage tank (V3) into the other feed port of the micro-mixer b (M2). After the materials flow out from the outlet of the micro-mixer b (M2), they pass through the micro-reactor b (R2). Reacting in the micro-reactor b (R2), the active polystyrene is capped to obtain a polystyrene macromonomer solution with styryl terminals; The capping agent is selected from one or a mixture of two of p-chloromethylstyrene and 4-chloro(dimethyl)silylstyrene; 3) After the polystyrene macromonomer solution is mixed with a non-polar hydrocarbon solvent solution of butadiene and a polarity regulator flowing out from the butadiene solution storage tank (V4) through plunger pump d (P4), it flows into one feed port of the micro-mixer c (M3). Using plunger pump e (P5), continuously inject a non-polar hydrocarbon solvent solution of an alkyllithium initiator from the alkyllithium solution storage tank (V5) into the other feed port of the micro-mixer c (M3). After the materials flow out from the outlet of the micro-mixer c (M3), they pass through the micro-reactor c (R3). Reacting in the micro-reactor c (R3), copolymerization of the polystyrene macromonomer and butadiene is carried out; 4) The solution after the copolymerization reaction of the polystyrene macromonomer and butadiene flows into the product solution storage tank (V6) containing a terminator. The product solution is subjected to post-treatment and purification, and finally branched SBS with polystyrene as the side chain is obtained.

2. The method for preparing branched SBS using a micro-mixing continuous flow reactor according to claim 1, characterized in that, The mass percentage of styrene units in the branched SBS is 15% - 60%, and the mass percentage of butadiene units is 40% - 85%; the number-average molecular weight of the branched SBS is 1×10 4 - 80×10 4 , and the number-average molecular weight of the branched side-chain polystyrene is 1×10 3 - 2×10 4 .

3. The method for preparing branched SBS using a micro-mixing continuous flow reactor according to claim 1 or 2, characterized in that, the dosage of the alkyllithium initiator is determined according to the number-average molecular weights of the polystyrene macromonomer and the branched SBS.

4. The method for preparing branched SBS using a micro-mixing continuous flow reactor according to claim 1 or 2, characterized in that, in the whole reaction system, the mass ratio of the total mass of the styrene and butadiene monomers to the mass of the non-polar hydrocarbon solvent is 1:4 - 1:

12.

5. The method for preparing branched SBS using a micro-mixing continuous flow reactor according to claim 1 or 2, characterized in that, The temperature of all the micro mixers and micro reactors is controlled between 20°C and 120°C.

6. A method for preparing branched SBS using a micro mixing continuous flow reactor according to claim 1 or 2, characterized in that, the non-polar hydrocarbon solvent is selected from one or a mixture of two or more of pentane, hexane, heptane, octane, cyclohexane, benzene, toluene, ethylbenzene, and xylene.

7. A method for preparing branched SBS using a micro mixing continuous flow reactor according to claim 1 or 2, characterized in that, the alkyl lithium initiator is selected from a mixture of one or two or more monofunctional alkyl lithium initiators in RLi, where R is an alkyl group with 1 to 10 carbon atoms and Li is a lithium atom.

8. A method for preparing branched SBS using a micro mixing continuous flow reactor according to claim 1 or 2, characterized in that, the polar regulator is selected from one or a mixture of two or more of diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol dibutyl ether, triethylamine, N,N,N’,N’-tetramethylethylenediamine, dipiperidinoethane, ethyl tetrahydrofurfuryl ether, and 2,2-bis(tetrahydrofuran)propane.

9. A method for preparing branched SBS using a micro mixing continuous flow reactor according to claim 1 or 2, characterized in that, the terminator is selected from one or a mixture of two or more of water, methanol, ethanol, isopropanol, and acetic acid.

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