Synthesis method of SEBS (styrene-ethylene-butylene-styrene) with uniformly distributed side chains

Abstract

The invention discloses a synthesis method of SEBS (Styrene-Ethylene-Butylene-Styrene) with uniformly distributed side chains. According to the method, an SBS glue solution is obtained through three-stage polymerization by adopting an anionic polymerization method, and then a hydrogenation reaction is performed to obtain SEBS. The method is characterized in that in the two-stage polymerization reaction process, 80-90% of the theoretical molar amount of the structure regulator is added at a time, and the rest 10-20% of the theoretical molar amount of the structure regulator is correspondingly added according to the temperature rising range; the time for starting to add the structure regulator is when the temperature of the second-stage polymerization reaction begins to rise, and the time for ending to add the structure regulator is when the temperature rises to the highest. According to the method, more uniform SEBS side chain distribution is realized, the polymerization temperature can be allowed to rise to a higher temperature, polymerization heat is fully utilized to meet the initial temperature requirement of hydrogenation reaction, and energy conservation, consumption reduction and improvement of production efficiency are facilitated.

Description

Technical Field

[0001] The invention relates to a method for synthesizing SEBS, in particular to a method for synthesizing SEBS with uniformly distributed side chains, and belongs to the technical field of synthesis of styrene-based thermoplastic elastomers. Background Art

[0002] SEBS is a linear triblock copolymer with polystyrene as the terminal block and hydrogenated polybutadiene as the middle elastic block. This type of polymer does not contain unsaturated double bonds and has good light aging resistance and stability. It can be blended with filler oil, polypropylene, additives and inorganic fillers and is widely used in the coating of tool handles, shoe materials, headphone cables, wires and cables, medical infusion equipment, etc.

[0003] The structure of polymer materials determines the performance. The main influencing factor of the structure of SEBS block copolymers is the content and distribution of the side chain structure. Theoretical calculations and experimental data show that 20 methylene sequences can produce polyethylene-like crystals at room temperature. Crystallization reduces the volume of the amorphous region in the polymer and increases the tensile strength of the elastomer. Therefore, the content of the side chain structure cannot be very low. When the content of 1,2 structure polybutadiene in SBS reaches 50%, its crystallization is basically inhibited after hydrogenation, but the glass transition temperature Tg rises greatly and the resilience decreases. Therefore, in order to prevent the methylene sequence in SEBS from growing long enough to crystallize, and to ensure that the E in the EB segment has enough amount to maintain its elasticity, the content of polybutadiene 1,2 structure needs to be controlled and have good uniformity. Experiments show that when the 1,2 structure in polybutadiene has good uniformity and the content is about 38%, the increase in crystallization and the rise in Tg can achieve a good balance, and the performance can reach an ideal level, such as Kraton's SEBS best-selling product G1651.

[0004] The main factors affecting the 1,2 structure content in the polybutadiene chain segment are the amount of structure regulator added and the polymerization temperature of butadiene. A large number of literatures show that the more structure regulator is added, the higher the 1,2 structure content in the polybutadiene chain segment; at the same amount of structure regulator added, the higher the polymerization temperature, the lower the 1,2 structure content in the polybutadiene chain segment. In addition, with the increase of polymerization temperature, the 1,2-addition rate of butadiene gradually decreases, and the corresponding 1,4-addition rate of butadiene gradually increases. The 1,2 structure content in the polybutadiene segment of the synthesized SBS shows a gradually shrinking distribution. There is a certain amount of slightly longer long-chain polyethylene chain segments in the hydrogenated SEBS molecular chain, which has no adsorption capacity or compatibility with mineral oil (such as white oil, cycloalkane oil, paraffin oil, etc.). When this SEBS is filled with mineral oil to make products, the mineral oil in the product will slowly migrate out of the product over time, and the oil will separate from the product, causing a significant decline in product performance. Existing domestic manufacturers mostly use this control method, so the product quality is far behind that of foreign competitors. Some manufacturers have adopted the method of forced heat removal to narrow the control temperature of butadiene addition from 60℃~90℃ to 63℃~73℃, so as to improve the distribution uniformity of 1,2 structure content in butadiene segment. However, there is still a difference of 3%~5% between low temperature and high temperature, which cannot achieve the expected effect. In addition, the temperature of the final polymerized glue obtained by this method will be lower than 70℃, while the starting temperature of the subsequent hydrogenation reaction is higher than 70℃, which means that the glue needs to be heated by a heat source, which is not conducive to energy saving. If the polymerization temperature is further narrowed, it can only be done by extending the feeding time by 30min~60min, which will seriously affect the production efficiency.

[0005] Chinese patent CN109206568A discloses an SBS containing a butadiene block with a uniform distribution of 1,2 structures and its hydride SEBS and a preparation and application method. The preparation process of SBS is that styrene is polymerized with an initiator under the action of an activator in a first stage, and the second stage polymerization process is to dissolve the 1,2 structure regulator in butadiene and uniformly add it to the polymerization kettle within 16 to 18 minutes. After the addition is completed, the reaction is continued for 8 to 12 minutes. This method takes into account that the increase in the polymerization temperature of butadiene will cause a decrease in the 1,2 structure content. However, when a mixture of 1,2 structure regulator and butadiene is added in the second stage, the amount of the structure regulator added is too low at the beginning of the reaction, so the 1,2 structure content of the butadiene chain segment in the initial stage will be far lower than the design value. As the mixed material is continuously added, the structure content will tend to a normal value. After the mixed material is added, there is still a temperature rise process of 5°C to 10°C, which will also cause a decrease in the structure content, and it is difficult to achieve a more ideal random distribution. Chinese patent CN100497406C adopts the method of adding the main regulator and the auxiliary regulator in batches. The main regulator is added in the first stage, and the auxiliary regulator is continuously added after the addition of butadiene in the second stage to compensate for the reduction of 1,2 structure content caused by temperature rise. The auxiliary regulator is added for 15 minutes and the second stage reaction time is 35 minutes. This method does not correspond the addition speed of the auxiliary regulator to the temperature rise. There is a situation where the reaction temperature has not reached a high temperature after the auxiliary regulator is added. Then, the amount of the structure regulator in the reaction system remains unchanged, while the polymerization temperature continues to rise, which may cause the 1,2 structure content of the polybutadiene segment to decrease and be unevenly distributed. Summary of the invention

[0006] In view of the technical problem that it is difficult to achieve uniform distribution of 1,2 structure content in polybutadiene segments in the synthesis of SEBS base glue in the prior art, resulting in uneven distribution of SEBS side chains, the purpose of the present invention is to provide a method for synthesizing SEBS with uniform side chain distribution. The method utilizes the characteristic that the regulating ability of a structure regulator decreases continuously with increasing polymerization temperature, and adds the structure regulator in batches or continuously according to the variation law of polymerization temperature to achieve a more uniform distribution of SEBS side chains. The method can eliminate the influence of the continuous decrease of the 1,2 structure content of polybutadiene due to the increase of polymerization temperature during the polymerization process. At the same time, the method can allow the polymerization temperature to rise to a higher temperature, and make full use of the polymerization heat to meet the starting temperature requirement of the hydrogenation reaction, which is beneficial to energy saving and consumption reduction and improving production efficiency.

[0007] In order to achieve the above technical purpose, the present invention provides a method for synthesizing SEBS with uniformly distributed side chains. The method comprises the following steps: adding styrene monomer, activator and initiator to an anionic polymerization solution system to initiate and carry out a first stage polymerization reaction; after the first stage polymerization reaction is completed, adding a structure regulator, and continuously and uniformly adding butadiene monomer to carry out a second stage polymerization reaction; after the second stage polymerization reaction is completed, adding styrene monomer to carry out a third stage polymerization reaction, and after the third stage polymerization reaction is completed, obtaining an SBS glue, and the SBS glue is subjected to a hydrogenation reaction to obtain an SEBS with uniformly distributed side chains; the improvement is that: the structure regulator is added in a manner that: taking the theoretical molar amount of the structure regulator as 100%, 80-90% of the theoretical molar amount of the structure regulator is added at one time, and the remaining 10-20% of the theoretical molar amount of the structure regulator is added accordingly according to the temperature rise amplitude, and the time for starting to add the structure regulator is when the temperature of the second stage polymerization reaction starts to rise, and the time for ending to add the structure regulator is when the temperature rises to the highest.

[0008] The technical solution of the present invention is proposed based on a large number of experimental studies on the homopolymerization process of butadiene. Studies have shown that the homopolymerization process of butadiene is an exothermic reaction, and the regulating activity of the structure regulator for regulating butadiene for 1,2-polymerization is very sensitive to the polymerization temperature. The general rule is that the higher the temperature, the lower the regulating activity. The optimal amount of the structure regulator at different temperatures is determined according to the activity of the structure regulator under different polymerization temperature conditions, so that the 1,2-polymerization ratio can be stabilized during the entire butadiene block polymerization process, thereby achieving a uniform distribution of the 1,2 polymerization units of polybutadiene in the entire butadiene block. In the butadiene polymerization process, the present invention controls the amount of the structure regulator required for the designed 1,2 structure content at the starting temperature of the polymerization reaction, and subsequently adds a certain amount of the structure regulator intermittently or continuously according to the temperature rise change to compensate for the decrease in the structure content of the butadiene 1,2-polymerization activity caused by the increase in the polymerization temperature, so that the polybutadiene segment can maintain a relatively uniform level.

[0009] As a preferred solution, the remaining 10-20% of the theoretical molar amount of the structure regulator is divided into N units according to the temperature rise during the second stage polymerization reaction, N = M / (t 1 -t 2 ), the unit is mol / ℃; where M is the remaining 10-20% theoretical molar dosage, the unit is mol; t 1 is the highest temperature during the second stage polymerization reaction, in °C; t 2is the initial temperature in the second stage polymerization process (i.e., the temperature of the polymerization system before the polymerization temperature starts to rise), in degrees Celsius; the remaining 10-20% of the theoretical molar amount of the structure regulator is added once for every 1-3 degrees Celsius rise in temperature, and the amount added each time is (1-3)N. Alternatively, the remaining 10-20% of the theoretical molar amount of the structure regulator is added continuously and evenly within the time range from the temperature of the second stage polymerization reaction starting to rise to the time when the temperature rises to the highest. The amount of the structure regulator must be added in strict accordance with the relationship between the temperature change and the activity of the structure regulator during the homopolymerization of butadiene. If the added structure regulator is excessive or too little, it is difficult to stabilize the activity of the structure regulator in the polymerization system, resulting in uneven distribution of 1,2 structural units.

[0010] The theoretical molar dosage of the structure regulator of the present invention is determined based on the molecular weight of the designed SBS polymer and the 1,2 structure content of the butadiene block contained therein. If the molecular weight of the designed SBS polymer and the 1,2 structure ratio of the butadiene block are determined, the molar dosage of the corresponding specific structure regulator is determined. This corresponding relationship is well known in the industry.

[0011] As a preferred solution, the structure regulator includes at least one of ethylene glycol dimethyl ether, ditetrahydrofurfuryl propane, ethylene glycol diethyl ether, tetrahydrofurfuryl alcohol ethyl ether, tetramethylethylenediamine, and hexamethylphosphoric triamide. These structure regulators are common structure regulators in the prior art that have a regulating effect on the 1,2-polymerization activity of butadiene. These preferred structure regulators all conform to the rule that the higher the temperature, the lower the regulating activity.

[0012] As a preferred solution, the adding time of the butadiene monomer is controlled within 40 to 80 minutes. If the butadiene monomer is added quickly at one time, the heating rate of the polymerization system will be too fast, the reaction will be violent, a large amount of gel will be formed, and the reactor will be blocked.

[0013] As a preferred solution, the initial temperature of the two-stage polymerization reaction is controlled at 62-65° C., the maximum temperature is 70-85° C., and the total reaction time is in the range of 30-80 min.

[0014] As a preferred embodiment, the activating agent includes tetrahydrofuran.

[0015] As a preferred solution, the initiator includes at least one of n-butyl lithium, sec-butyl lithium and isobutyl lithium, which are conventional anionic polymerization initiators, and n-butyl lithium is most preferred.

[0016] As a preferred solution, the temperature of the first stage polymerization reaction is 50°C to 70°C, and the time is 20 to 50 minutes.

[0017] As a preferred solution, the conditions of the hydrogenation reaction are: using a titanocene-benzoate composite catalyst system, a starting temperature of 72-80°C, a hydrogen pressure of 1.2-1.4 MPa, and a time of 2h-3h. This type of catalyst has a relatively low cost and good reaction activity, and can reach a hydrogenation degree of more than 97% in a short time.

[0018] As a preferred embodiment, the titanocene-benzoate composite catalyst system includes at least one main catalyst selected from bis(cyclopentadienyl)titanium dichloride, bis(cyclopentadienyl)titanium dibromide, bis(cyclopentadienyl)titanium diiodide, bis(cyclopentadienyl)titanium difluoride, bis(cyclopentadienyl)titanium dicarbonyl, bis(cyclopentadienyl)titanium dimethyl, bis(cyclopentadienyl)titanium diethyl, and bis(cyclopentadienyl)titanium dibutyl, and benzoic acid C 1 ~C 5 Alkyl esters, phthalic acid C 1 ~C 5 At least one promoter in the alkyl ester.

[0019] As a preferred solution, the molar ratio of the main catalyst to the co-catalyst is 2 to 5: 1. The hydrogenation catalyst is measured at 0.01% to 0.05% of the total mass of the polymerization monomers (including butadiene and styrene) of the main catalyst.

[0020] Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0021] 1) The technical solution of the present invention can achieve a more uniform distribution of SEBS side chains.

[0022] 2) The technical solution of the present invention can allow the polymerization temperature to rise to a higher temperature and make full use of the polymerization heat to meet the starting temperature requirement of the hydrogenation reaction, which is beneficial to energy saving and consumption reduction and improving production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the H-NMR spectrum of the SEBS base glue prepared in Example 1. DETAILED DESCRIPTION

[0024] The following examples are intended to further illustrate the present invention in detail and are not intended to limit the scope of protection or implementation of the present invention.

[0025] It should be noted that: in the following examples, gel permeation chromatography (mobile phase is tetrahydrofuran) is used to test the number average molecular weight (Mn) of the glue solution; H-NMR nuclear magnetic spectrum is used to analyze the 1,2 structure content of the polybutadiene segment. The attached figure is a typical SEBS polymer base glue nuclear magnetic hydrogen spectrum. The peak with a displacement of 5.3-5.6ppm is the hydrogen on the double bond of the polybutadiene 1,4 structure and the single hydrogen peak on the double bond of the 1,2 structure side chain, and the peak area is A. The peak with a displacement of about 4.96ppm is the two hydrogen peaks on the double bond of the polybutadiene 1,2 structure side chain, and the peak area is B. The calculation formula of the polybutadiene 1,2 structure content is: 2B / (2A+B)*100%; before the process sampling for the analysis of the polybutadiene 1,2 structure content, the glue solution needs to be dried to remove the unreacted butadiene and solvent.

[0026] The conventional method for synthesizing SEBS-YH-503 (conventional commodity) is used as an example to illustrate the relationship between temperature and activity of the structure regulator. The specific operation is referred to Example 1, except that the structure regulator is added once during the second-stage butadiene polymerization reaction, and the nuclear magnetic resonance samples are dried and analyzed at different temperatures. The data are shown in Table 1:

[0027] Table 1 NMR analysis data of samples taken during the butadiene polymerization process during the synthesis of SEBS-YH-503

[0028]

[0029] From the data in Table 1, it can be seen that: according to the conventional control method, the polymerization temperature control range in the process of butadiene polymerization is between 61 and 75 ° C, the 1,2 structure content of the polybutadiene chain segment is between 35.2 and 42.2%, and the difference between the low and high values ​​is 7%. The distribution of the 1,2 structure content on the polybutadiene molecular chain segment is very uneven. If a structure regulator is added to control the required 1,2 structure content at the initial temperature before the second stage reaction, a certain amount of structure regulator is added intermittently or continuously according to the temperature rise change, to compensate for the decrease in the 1,2 structure content of the butadiene chain segment caused by the increase in polymerization temperature, the polybutadiene chain segment can theoretically maintain a relatively uniform level. Take Table 1 as an example: the 1,2 structure content at 61 ° C is 42.2%, and the temperature is still rising. For this reason, a certain amount of structure regulator is added at 61 ° C, then at 63 ° C, the 1,2 structure content should be closer to 42.2%, and may be 42%.

[0030] Example 1

[0031] The SEBS with a number average molecular weight (Mn) of 6±10,000 is synthesized by an anionic polymerization method known in the industry. The design requires that the 1,2 structure content of the polybutadiene segment is 38%. The theoretical concentration of the structure regulator tetramethylethylenediamine in the solvent is 93.5 mg / Kg. In a polymerization kettle replaced with dry protective gas (such as nitrogen), 40 tons of cyclohexane, 12 kg of tetrahydrofuran and 66 mol of butyl lithium are added, the temperature of the polymerization kettle is maintained at 65°C and the pressure is 0.3 MPa, 600 kg of styrene monomer is added first, and the reaction is carried out for 30 minutes. After the reaction, the polymerization temperature is lowered to 63°C, 3.2 kg of tetramethylethylenediamine is added, and then 2800 kg of butadiene monomer is continuously added until the temperature rises significantly, and tetramethylethylenediamine is added in batches, 0.06 kg of tetramethylethylenediamine is added at 65°C, and 0.06 kg of tetramethylethylenediamine is added at 67°C, that is, 0.06 kg of tetramethylethylenediamine is added for every 2°C rise, until the reaction temperature reaches 81°C (the time from the temperature rising significantly to the high temperature is 35 minutes), and samples are taken every 2 minutes after entering the second stage reaction for nuclear magnetic analysis, and the temperature is kept for 5 minutes after the high temperature to enter the third stage reaction; 600 kg of styrene monomer is added to the third stage reaction, and the reaction is carried out for 30 minutes. The prepared polymerized glue was poured into a hydrogenation kettle, 1000 g of dicyclopentadiene titanium dichloride and 273 g of methyl benzoate were added, the initial reaction temperature was controlled at 75°C, hydrogen was introduced to make the pressure in the kettle 1.2 MPa, the reaction time was 3 h, and SEBS glue was obtained.

[0032] Example 2

[0033] The difference from Example 1 is the second stage reaction. Other process controls are the same, except that the structure regulator is added continuously instead of in batches. In the second stage, the polymerization temperature is lowered to 63°C, 3.2 kg of tetramethylethylenediamine is added, and then butadiene monomer is continuously added until the temperature rises significantly, and tetramethylethylenediamine is continuously added at 0.925 kg / h until the reaction temperature reaches high.

[0034] Comparative Example 1

[0035] The difference from Example 1 is the second stage reaction, and the other process controls are the same, except that the structure regulator is added at one time. That is, after the first stage reaction is completed, the polymerization temperature is lowered to 63°C, 3.74 kg of tetramethylethylenediamine is added until the reaction temperature reaches 73°C, and after entering the second stage reaction, samples are taken every 2 minutes for nuclear magnetic resonance analysis, and the temperature is kept at high temperature for 5 minutes before entering the third stage reaction.

[0036] Example 3

[0037] The anionic polymerization method known in the industry is used to synthesize SEBS with a number average molecular weight (Mn) of 100,000±10,000. The design requires that the polybutadiene segment 1,2 structure content is 38%. Theoretically, the amount of structure regulator ethylene glycol diethyl ether in the solvent is 70 mg / Kg. 40 tons of cyclohexane, 12 kg of tetrahydrofuran and 40 mol of butyl lithium are added to the polymerization kettle replaced by dry protective gas (such as nitrogen). The temperature of the polymerization kettle is maintained at 65°C and the pressure is 0.3 MPa. First, 600 kg of styrene monomer is added to carry out a reaction for 30 minutes. After the reaction, the polymerization temperature is lowered to 63°C, 2.4 kg of ethylene glycol diethyl ether is added, and then 2800 kg of butadiene monomer is continuously added until the temperature rises significantly. Ethylene glycol diethyl ether is added in batches. Ether, add 0.045Kg of ethylene glycol diethyl ether at 65℃, add 0.045Kg of ethylene glycol diethyl ether at 67℃, that is, add 0.045Kg of ethylene glycol diethyl ether every 2℃ rise, until the reaction temperature reaches about 81℃ (the time from the temperature rising significantly to the high temperature is 35min), after entering the second stage reaction, take samples every 2 minutes for nuclear magnetic analysis, stay at high temperature for 5min to enter the third stage reaction; add 600Kg of styrene monomer in the third stage reaction, and react for 30min. Pour the obtained polymer glue into the hydrogenation kettle, add 1000g of dicyclopentadiene titanium dibromide and 300g of ethyl benzoate, control the initial reaction temperature to 73℃, introduce hydrogen to make the pressure in the kettle 1.3MPa, and react for 2.5h to obtain SEBS glue.

[0038] Example 4

[0039] The difference from Example 3 is the second stage reaction. Other process controls are the same, except that the structure regulator is added continuously instead of in batches. In the second stage, the polymerization temperature is lowered to 63°C, 2.4 kg of ethylene glycol diethyl ether is added, and then butadiene monomer is continuously added until the temperature rises significantly, and tetrahydrofurfuryl alcohol ethyl ether is continuously added at 0.694 kg / h until the reaction temperature reaches high.

[0040] Comparative Example 2

[0041] The difference from Example 1 is the second stage reaction, and the other process controls are the same, except that the structure regulator is added at one time. That is, after the first stage reaction is completed, the polymerization temperature is lowered to 63°C, 2.8 kg of ethylene glycol diethyl ether is added until the reaction temperature reaches 73°C, and after entering the second stage reaction, samples are taken every 2 minutes for nuclear magnetic resonance analysis, and the temperature is kept at high temperature for 5 minutes before entering the third stage reaction.

[0042] Example 5

[0043] The SEBS with a number average molecular weight (Mn) of 200,000±10,000 is synthesized by an anionic polymerization method known in the industry. The design requires that the 1,2 structure content of the polybutadiene segment is 38%. The theoretical amount of the structure regulator hexamethylphosphoric acid triamide in the solvent is 47 mg / Kg. In a polymerization kettle replaced with dry protective gas (such as nitrogen), 40 tons of cyclohexane, 12 kg of tetrahydrofuran and 40 mol of butyl lithium are added, the temperature of the polymerization kettle is maintained at 65°C and the pressure is 0.3 MPa, 600 kg of styrene monomer is first added, and a first-stage reaction is carried out for 30 minutes. After the reaction, the polymerization temperature is lowered to 63°C, 1.6 kg of hexamethylphosphoric triamide is added, and then 2800 kg of butadiene monomer is continuously added until the temperature rises significantly, and hexamethylphosphoric triamide is added in batches, 0.03 kg of hexamethylphosphoric triamide is added at 65°C, and 0.03 kg of hexamethylphosphoric triamide is added at 67°C, that is, 0.03 kg of hexamethylphosphoric triamide is added for every 2°C rise, until the reaction temperature reaches about 81°C (the time from the temperature rising significantly to the high temperature is 35 minutes), and samples are taken every 2 minutes after entering the second-stage reaction for nuclear magnetic analysis, and the temperature is kept for 5 minutes after the high temperature to enter the third-stage reaction; 600 kg of styrene monomer is added in the third-stage reaction and the reaction is carried out for 30 minutes. The prepared polymerized glue was poured into a hydrogenation kettle, 1000 g of dicyclopentadiene titanium dibromide and 273 g of methyl benzoate were added, the initial reaction temperature was controlled at 73°C, hydrogen was introduced to make the pressure in the kettle 1.4 MPa, the reaction time was 2 h, and SEBS glue was obtained.

[0044] Example 6

[0045] The difference from Example 5 is the second stage reaction. Other process controls are the same, except that the structure regulator is added continuously instead of in batches. In the second stage, the polymerization temperature is lowered to 63°C, 1.6 kg of hexamethylphosphoric triamide is added, and then butadiene monomer is continuously added until the temperature rises significantly, and hexamethylphosphoric triamide is continuously added at 0.462 kg / h until the reaction temperature reaches high.

[0046] Comparative Example 3

[0047] The difference from Example 5 is the second stage reaction, and the other process controls are the same, except that the structure regulator is added at one time. That is, after the first stage reaction is completed, the polymerization temperature is lowered to 63°C, 1.87 kg of hexamethylphosphoric triamide is added until the reaction temperature reaches 73°C, and after entering the second stage reaction, samples are taken every 2 minutes for nuclear magnetic resonance analysis, and the temperature is kept at high temperature for 5 minutes before entering the third stage reaction.

[0048] Table 2 Test results after adopting the new process

[0049]

[0050]

[0051] It can be seen from Table 2 that: by using the conventional method (i.e., Comparative Example 1, Comparative Example 2, Comparative Example 3), although the content of polybutadiene 1,2 structure in the final product can be controlled at about 38%, from the results of process sampling nuclear magnetic resonance analysis, the distribution of polybutadiene 1,2 structure in the molecular chain is very uneven, and the difference between the maximum and minimum values ​​is more than 6%; and whether the structure regulator is added in batches or continuously, the distribution of 1,2 structure content of the polybutadiene segment is more uniform than before the process adjustment, achieving the expected effect; in addition, according to the design number average molecular weight range of 50,000 to 200,000, by adjusting the one-time addition and subsequent addition of the structure regulator, the content of polybutadiene 1,2 structure can be controlled at about 38%, and the polybutadiene 1,2 structure in the molecular chain shows a relatively uniform distribution, and the difference between the maximum and minimum values ​​is within 1%.

Claims

1. A method for synthesizing SEBS with uniformly distributed side chains, comprising: adding styrene monomer, activator and initiator to an anionic polymerization solution system, initiating and carrying out a first stage polymerization reaction; after the first stage polymerization reaction is completed, adding a structure regulator, and simultaneously continuously and uniformly adding butadiene monomer to carry out a second stage polymerization reaction; after the second stage polymerization reaction is completed, adding styrene monomer to carry out a third stage polymerization reaction, after the third stage polymerization reaction is completed, obtaining SBS glue, and obtaining SEBS by hydrogenation reaction of the SBS glue; characterized in that: The structure regulator is added in the following manner: taking the theoretical molar amount of the structure regulator as 100%, 80-90% of the theoretical molar amount of the structure regulator is added at one time; and then the remaining 10-20% of the theoretical molar amount of the structure regulator is added accordingly according to the temperature rise amplitude, and the time for starting to add the structure regulator is when the temperature of the second-stage polymerization reaction starts to rise, and the time for ending to add the structure regulator is when the temperature rises to the highest.

2. The method for synthesizing SEBS with uniform side chain distribution according to claim 1, characterized in that: The remaining 10-20% of the theoretical molar amount of the structure regulator is equally divided into N units according to the temperature rise during the second stage polymerization reaction, N = M / (t1-t2), the unit is mol / °C; wherein M is the remaining 10-20% of the theoretical molar amount, the unit is mol; t1 is the highest temperature during the second stage polymerization reaction, the unit is °C; t2 is the initial temperature during the second stage polymerization reaction, the unit is °C; The remaining 10-20% of the theoretical molar amount of the structure regulator is added once for each 1-3°C rise in temperature, and the amount added each time is (1-3)N; or, The remaining 10-20% of the theoretical molar amount of the structure regulator is added continuously and uniformly within the time range from when the temperature of the second-stage polymerization reaction starts to rise to when the temperature rises to the maximum.

3. A method for synthesizing SEBS with uniform side chain distribution according to claim 1 or 2, characterized in that: The structure regulator includes at least one of ethylene glycol dimethyl ether, ditetrahydrofurfuryl propane, ethylene glycol diethyl ether, tetrahydrofurfuryl alcohol ethyl ether, tetramethylethylenediamine, and hexamethylphosphoric triamide.

4. The method for synthesizing SEBS with uniform side chain distribution according to claim 1, characterized in that: The total time for continuously and uniformly adding the butadiene monomer is 40 to 60 minutes.

5. A method for synthesizing SEBS with uniform side chain distribution according to claim 1, 2 or 4, characterized in that: The initial temperature of the two-stage polymerization reaction is controlled at 62-65° C., the maximum temperature is controlled at 70-85° C., and the total reaction time is controlled at 30-80 minutes.

6. The method for synthesizing SEBS with uniform side chain distribution according to claim 1, characterized in that: The activating agent includes tetrahydrofuran; The initiator includes at least one of n-butyl lithium, sec-butyl lithium and isobutyl lithium.

7. A method for synthesizing SEBS with uniform side chain distribution according to claim 1 or 6, characterized in that: The temperature of the first stage polymerization reaction is 50° C. to 70° C., and the time is 20 to 50 minutes.

8. A method for synthesizing SEBS with uniform side chain distribution according to claim 1 or 6, characterized in that: The conditions of the hydrogenation reaction are: using a titanocene-benzoate composite catalyst system, a starting temperature of 72-80° C., a hydrogen pressure of 1.2-1.4 MPa, and a time of 2 h to 3 h.

9. The method for synthesizing SEBS with uniform side chain distribution according to claim 8, characterized in that: The titanocene-benzoate composite catalyst system comprises at least one main catalyst selected from the group consisting of bis(cyclopentadienyl)titanium dichloride, bis(cyclopentadienyl)titanium dibromide, bis(cyclopentadienyl)titanium diiodide, bis(cyclopentadienyl)titanium difluoride, bis(cyclopentadienyl)titanium dicarbonyl, bis(cyclopentadienyl)titanium dimethyl, bis(cyclopentadienyl)titanium diethyl and bis(cyclopentadienyl)titanium dibutyl, and at least one co-catalyst selected from the group consisting of C1-C5 alkyl benzoate and C1-C5 alkyl phthalate.

10. The method for synthesizing SEBS with uniform side chain distribution according to claim 9, characterized in that: The molar ratio of the main catalyst to the co-catalyst is 2 to 5:1.

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