Butylbenzene block polymers, methods of making and using the same

Abstract

The application relates to the technical field of high polymer material synthesis and preparation, and discloses a butadiene-styrene block polymer and a preparation method and application thereof. The polymer has a structure represented by S1-B1-(BS)1-S2-B2-S3; S1, S2 and S3 are polystyrene blocks, B1 and B2 are polybutadiene blocks, and (BS)1 is a butadiene-styrene copolymer; the total weight of the styrene segment and the total weight of the butadiene segment are in a ratio of 2.3-9:1 based on the total weight of the polymer. The butadiene-styrene block polymer has a specific structure, specifically, the length of a single butadiene block segment is shortened, and a certain proportion of butadiene and styrene copolymer is introduced into the molecular segment, so that the butadiene-styrene block polymer has improved transparency, excellent mechanical properties and bending flexibility, and the comprehensive improvement of the mechanical properties, bending flexibility and transparency of the butadiene-styrene block polymer is realized.

Description

Technical Field

[0001] This invention relates to the field of polymer material synthesis and preparation technology, specifically to a styrene-butadiene block polymer and its preparation method and application. Background Technology

[0002] Plastic optical materials require polymers to possess superior transparency and low optical loss, good thermal stability, and flexibility. Polymethyl methacrylate (PMMA) has excellent optical properties, but PMMA is highly hygroscopic, and its strength decreases and optical loss increases significantly above 85°C.

[0003] Styrene-butadiene-styrene fully (or nearly fully) hydrogenated hard block polymers are widely used in films, profiles, sheets, and pultruded products, and are also excellent optical materials. The relative content of butadiene and styrene in the polymer before hydrogenation has a significant impact on product performance. When the butadiene content is low, the polybutadiene block molecular chains are short, resulting in poor bending flexibility of the end product. When the butadiene content is high, the polybutadiene block molecular chains are long, and overly regular polybutadiene molecular chains can lead to a tendency for crystallization in the hydrogenated product, resulting in poor optical properties of the end product.

[0004] Therefore, there is an urgent need to develop a styrene-butadiene block copolymer that can significantly improve mechanical strength and bending flexibility while maintaining excellent transparency, and can serve as a precursor for high-end optical materials. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem that existing styrene-butadiene block polymers cannot simultaneously achieve good mechanical properties, bending flexibility, and transparency. This invention provides a styrene-butadiene block polymer, its preparation method, and its applications. This styrene-butadiene block polymer has a specific structure. Specifically, by shortening the length of the single butadiene block molecular chain segment and introducing a certain proportion of butadiene and styrene copolymers into the molecular chain segment, the styrene-butadiene block polymer achieves significantly improved mechanical properties and bending flexibility while maintaining improved transparency.

[0006] To achieve the above objectives, the first aspect of the present invention provides a block styrene-butadiene block polymer, characterized in that the polymer has a structure as shown in S1-B1-(BS)1-S2-B2-S3;

[0007] Among them, S1, S2, and S3 are polystyrene blocks, B1 and B2 are polybutadiene blocks, and (BS)1 is a butadiene-styrene copolymer.

[0008] Based on the total weight of the polymer, the ratio of the total weight of the styrene segments to the total weight of the butadiene segments is 2.3-9:1.

[0009] A second aspect of the present invention provides a method for preparing a block styrene-butadiene polymer, characterized in that the preparation method includes the following steps:

[0010] (1) In a solvent, in the presence of an initiator and a regulator, styrene I undergoes a first polymerization reaction to obtain a first polymer solution containing polystyrene blocks S1;

[0011] (2) Butadiene I and styrene II are contacted with the first polymer solution to carry out a second polymerization reaction, thereby obtaining a second polymer solution containing S1-B1-(BS)1-S2.

[0012] (3) Butadiene II is contacted with the second polymer solution to carry out a third polymerization reaction to obtain a third polymer solution containing S1-B1-(BS)1-S2-B2;

[0013] (4) Styrene III is contacted with the third polymer solution to carry out the fourth polymerization reaction, and a fourth polymer solution containing S1-B1-(BS)1-S2-B2-S3 is obtained.

[0014] (5) A terminator is added to the fourth polymer solution to obtain the styrene-butadiene block polymer.

[0015] A third aspect of the present invention provides a styrene-butadiene block polymer prepared by the above-described preparation method.

[0016] The fourth aspect of the present invention provides an application of the above-mentioned styrene-butadiene block polymer in the preparation of optical material precursors.

[0017] Through the above technical solutions, the styrene-butadiene block polymer, its preparation method, and its application provided by the present invention achieve the following beneficial effects:

[0018] The styrene-butadiene block polymer provided by this invention has a specific structure. Specifically, by shortening the length of the single butadiene block molecular chain segment and introducing a certain proportion of butadiene and styrene copolymer into the molecular chain segment, the styrene-butadiene block polymer has excellent mechanical properties and bending flexibility while improving transparency, thus achieving a comprehensive improvement in the mechanical properties, bending flexibility and transparency of the styrene-butadiene block polymer.

[0019] The method for preparing styrene-butadiene block polymers provided by this invention reduces the feeding steps of multi-block polymers, is simple to operate, and allows for controllable monomer sequence distribution of the block polymers. Detailed Implementation

[0020] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0021] The first aspect of the present invention provides a styrene-butadiene block polymer, characterized in that the polymer has the structure shown in S1-B1-(BS)1-S2-B2-S3;

[0022] Among them, S1, S2, and S3 are polystyrene blocks, B1 and B2 are polybutadiene blocks, and (BS)1 is a butadiene-styrene copolymer.

[0023] Based on the total weight of the polymer, the ratio of the total weight of the styrene segments to the total weight of the butadiene segments is 2.3-9:1.

[0024] In this invention, the styrene-butadiene block polymer having the above-mentioned specific structure specifically introduces the chain segment structure of butadiene and styrene copolymer into the molecular chain of the polymer, so that the styrene-butadiene block polymer has excellent mechanical properties and bending flexibility while having improved transparency, thus achieving a comprehensive improvement in the mechanical properties, bending flexibility and transparency of the styrene-butadiene block polymer.

[0025] In this invention, the styrene-butadiene block polymer is an S1-B1-(BS)1-S2-B2-S3 block polymer, wherein S1, S2, and S3 are polystyrene blocks, and S1, S2, and S3 may be the same or different; B1 and B2 are polybutadiene blocks, and B1 and B2 may be the same or different; (BS)1 is a butadiene-styrene copolymer; and based on the total weight of the styrene-butadiene block polymer, the ratio of the total weight of the styrene segments to the total weight of the butadiene segments is 2.3-9:1.

[0026] In this invention, by controlling the ratio of the total weight of styrene segments to the total weight of butadiene segments to meet the above-mentioned range, it is possible to make the molecular chain length of the single polybutadiene block (B1 or B2) in the block polymer having the above-illustrated structure shorter, while the total content of butadiene segments in the polymer increases, thereby improving the transparency and bending flexibility of the polymer and its hydrogenation products.

[0027] When the ratio of the total weight of styrene segments to the total weight of butadiene segments exceeds 9:1, the flexibility of the polymer and its hydrogenated products will deteriorate. When the ratio of the total weight of styrene segments to the total weight of butadiene segments is less than 2.3, the transparency of the polymer and its hydrogenated products will be adversely deteriorated because the molecular chains of the single polybutadiene blocks (B1 or B2) in the block polymer are too long.

[0028] Furthermore, based on the total weight of the polymer, the ratio of the total weight of the styrene segments to the total weight of the butadiene segments is 3-5.7:1.

[0029] According to the present invention, the number-average molecular weight of the styrene-butadiene block polymer is 6 × 10⁻⁶. 4 -12×10 4 .

[0030] In this invention, to ensure the processing performance of the styrene-butadiene block polymer, the number-average molecular weight of the styrene-butadiene block polymer should not exceed 12 × 10⁻⁶. 4 .

[0031] Furthermore, the number-average molecular weight of the styrene-butadiene block polymer is 7 × 10⁻⁶. 4 -11×10 4 Preferably 8×10 4 -10×10 4 .

[0032] In this invention, to obtain a styrene-butadiene block polymer with a uniform block structure, the molecular weight distribution index of the styrene-butadiene block polymer is required to be ≤1.2, for example, 1-1.2. When the molecular weight distribution index of the styrene-butadiene block polymer exceeds 1.2, the molecular weight distribution of the polymer becomes wider, which means that the styrene-butadiene block polymer simultaneously contains block polymers such as S1-B1, S1-B1-(BS)1, S1-B1-(BS)1-S2, and S1-B1-(BS)1-S2-B2.

[0033] In this invention, the above-mentioned styrene-butadiene block polymers with narrow molecular weight distribution and their hydrogenation products all have excellent mechanical properties.

[0034] Furthermore, the molecular weight distribution index of the styrene-butadiene block polymer is 1.01-1.1.

[0035] According to the present invention, based on the total weight (Bd%) of butadiene segments in the styrene-butadiene block polymer, the content (Bv%) of 1,2-butadiene structural units is 6-30% by weight.

[0036] In this invention, when the total weight of butadiene segments in the styrene-butadiene block polymer is used as a basis, and the content of 1,2-butadiene structural units meets the above-mentioned range, not only can the molecular chain length in the polybutadiene segments be effectively shortened, but the regularity of the polybutadiene block molecular chains can also be effectively disrupted. This results in a significant improvement in the mechanical properties and bending flexibility of the polymer and its hydrogenation products, while maintaining improved transparency. When the content of 1,2-butadiene structural units is too high, the bending flexibility of the styrene-butadiene block polymer decreases.

[0037] In this invention, the butadiene segments include polybutadiene block B1, polybutadiene block B2, and butadiene segments in butadiene-styrene copolymer (BS) 1.

[0038] Furthermore, based on the total weight of butadiene segments in the styrene-butadiene block polymer, the content of 1,2-butadiene structural units is 10-18% by weight.

[0039] According to the present invention, the content of non-block styrene (St-non-block%) is 3-15% by weight, based on the total weight of the styrene-butadiene block polymer.

[0040] In this invention, non-block styrene refers to styrene microblocks formed by ≤4 styrene monomers in the molecular chain.

[0041] In this invention, non-block styrene can effectively disrupt the regularity of the molecular chain and inhibit crystallization. When the content of non-block styrene meets the above-mentioned range, it can ensure that the polymer and its hydrogenation products have excellent mechanical properties. When the content of non-block styrene is too high, the high content of non-block styrene will destroy the physical crosslinking points and two-phase separation structure of the styrene-butadiene block polymer, resulting in an unfavorable reduction in the mechanical properties of the polymer and its hydrogenation products.

[0042] Furthermore, based on the total weight of the styrene-butadiene block polymer, the content of non-block styrene is 5-12% by weight.

[0043] In this invention, in order to ensure the mechanical properties of the styrene-butadiene block polymer and its hydrogenation products, the content of polystyrene segments S1, S2, and S3 in the styrene-butadiene block polymer should not differ too much, and a symmetrical structure is preferred. For example, based on the total weight of styrene segments in the styrene-butadiene block polymer, the content of polystyrene segment S1 is 25-35% by weight, the content of polystyrene segment S2 is 25-35% by weight, and the content of polystyrene segment S3 is 25-35% by weight.

[0044] Furthermore, based on the total weight of styrene segments in the styrene-butadiene block polymer, the content of polystyrene block S1 is 27-33% by weight, the content of polystyrene block S2 is 27-33% by weight, and the content of polystyrene block S3 is 27-33% by weight.

[0045] In this invention, in the styrene-butadiene block polymer (S1-B1-(BS)1-S2-B2-S3), to ensure the mechanical properties of the block polymer, the number average molecular weight of the styrene blocks (S1 and S3) is generally required to be ≥1.5 × 10⁻⁶. 4 .

[0046] A second aspect of the present invention provides a method for preparing a styrene-butadiene block polymer, characterized in that the preparation method includes the following steps:

[0047] (1) In a solvent, in the presence of an initiator and a regulator, styrene I undergoes a first polymerization reaction to obtain a first polymer solution containing polystyrene blocks S1;

[0048] (2) Butadiene I and styrene II are contacted with the first polymer solution to carry out a second polymerization reaction, thereby obtaining a second polymer solution containing S1-B1-(BS)1-S2.

[0049] (3) Butadiene II is contacted with the second polymer solution to carry out a third polymerization reaction to obtain a third polymer solution containing S1-B1-(BS)1-S2-B2;

[0050] (4) Styrene III is contacted with the third polymer solution to carry out the fourth polymerization reaction, and a fourth polymer solution containing S1-B1-(BS)1-S2-B2-S3 is obtained.

[0051] (5) A terminator is added to the fourth polymer solution to obtain the styrene-butadiene block polymer.

[0052] In this invention, the preparation method of the styrene-butadiene block polymer has the advantages of fewer steps, simple operation, and good parallelism. Compared with the prior art, by introducing the chain segment structure of butadiene and styrene copolymer into the polymer molecular chain, the length of butadiene chain segment in the polymer is effectively reduced, thereby making the obtained styrene-butadiene block polymer have improved transparency while having excellent mechanical properties and bending flexibility, thus achieving a comprehensive improvement in the mechanical properties, bending flexibility and transparency of the styrene-butadiene block polymer.

[0053] In this invention, there is no particular limitation on the type of solvent, which can be a conventional solvent in the art, such as an organic hydrocarbon solvent.

[0054] In this invention, the first polymerization reaction, the second polymerization reaction, the third polymerization reaction, and the fourth polymerization reaction are each independently anionic solution polymerization reactions.

[0055] In this invention, styrene I undergoes homopolymerization under the first polymer reaction conditions to obtain homopolymer polystyrene block S1. To ensure the segment length of the polystyrene block S1 molecular chain, preferably, in step (1), the ratio of the amount of styrene I to the total amount of styrene (styrene I + styrene II + styrene III) is controlled to be 0.25-0.35:1. When the amount of styrene I meets the above range, it can be ensured that the number average molecular weight of the polystyrene block S1 is 1.5 × 10⁻⁶. 4 -3×10 4 .

[0056] Furthermore, in step (1), the ratio of the amount of styrene I to the total amount of styrene (styrene I + styrene II + styrene III) is 0.3-0.35:1.

[0057] According to the present invention, the conditions for the first polymerization reaction include: a reaction temperature of 50-80°C.

[0058] In this invention, there is no particular limitation on the time of the first polymerization reaction, as long as styrene I is completely converted, that is, the conversion rate of styrene I is 100%.

[0059] According to the present invention, the initiator is at least one selected from lithium methyl, lithium ethyl, lithium propyl, lithium isopropyl, lithium n-butyl, and lithium sec-butyl.

[0060] According to the present invention, the amount of the initiator is 0.9-1.6 mmol / 100g, based on the total amount of the styrene and the butadiene.

[0061] According to the present invention, the modifier is at least one of tetrahydrofuran, bistetrahydrofurfuryl ether, ethyltetrahydrofurfuryl ether, and N,N-dimethyltetrahydrofurfurylamine.

[0062] According to the present invention, the molar ratio of the regulator to the initiator is 0.05-2:1.

[0063] According to the present invention, in step (2), butadiene I, styrene II and a first polymer solution containing polystyrene block S1 undergo anionic copolymerization reaction under the second polymerization reaction conditions. In order to ensure the segment length of the polystyrene block S2 molecular chain, preferably, the ratio of the amount of styrene II to the total amount of styrene (styrene I + styrene II + styrene III) is 0.3-0.5:1.

[0064] In this invention, the polymerization rate of butadiene is greater than that of styrene. During the copolymerization reaction of styrene II and butadiene I, most of the butadiene I preferentially undergoes homopolymerization of butadiene to generate polybutadiene block B1. As the reaction proceeds, the amount of styrene II is much greater than that of butadiene I due to the consumption of butadiene I. Some of the butadiene I undergoes copolymerization with styrene II to generate butadiene-styrene random copolymer (BS)1. When all the butadiene I is consumed, the remaining styrene II undergoes homopolymerization to generate polystyrene block S2.

[0065] Furthermore, the ratio of the amount of styrene II to the total amount of styrene (styrene I + styrene II + styrene III) is 0.35-0.45:1.

[0066] According to the present invention, in step (2), the ratio of the amount of butadiene I to the total amount of butadiene (butadiene I + butadiene II) is 0.5-0.7:1, preferably 0.55-0.65:1.

[0067] According to the present invention, the conditions for the second polymerization reaction include: a reaction temperature of 50-80°C.

[0068] In this invention, when the temperature of the second polymerization reaction meets the above-mentioned range, the proportion of butadiene-styrene copolymer (BS)1 can be controlled, and the polymerization rate can be made suitable.

[0069] In this invention, there is no particular limitation on the reaction time of the second polymerization reaction, as long as styrene II and butadiene I are completely converted, that is, the conversion rate of styrene II and butadiene I is 100%.

[0070] According to the present invention, in step (3), butadiene II is contacted with a second polymer solution containing S1-B1-(BS)1-S2 to undergo an anionic copolymerization reaction. In order to ensure that polybutadiene block B1 and polybutadiene block B2 have similar molecular chain lengths, thereby improving the overall performance of the block polymer, preferably, the ratio of the amount of butadiene II to the total amount of butadiene is 0.3-0.5:1, more preferably 0.35-0.45:1.

[0071] According to the present invention, the conditions for the third polymerization reaction include a reaction temperature of 50-80°C.

[0072] In this invention, when the temperature of the third polymerization reaction meets the above-mentioned range, the polymerization reaction can have a suitable reaction rate, and the styrene-butadiene block polymer described in the first aspect of this invention can be obtained.

[0073] In this invention, there is no particular limitation on the reaction time of the third polymerization reaction, as long as butadiene II is completely converted, that is, the conversion rate of butadiene II is 100%.

[0074] According to the present invention, in step (4), styrene III is contacted with a third polymer solution containing S1-B1-(BS)1-S2-B2 to undergo an anionic copolymerization reaction. Preferably, to ensure the segment length of the polystyrene block S3 molecular chain, the ratio of the amount of styrene III to the total weight of styrene (styrene I + styrene II + styrene III) is 0.25-0.35:1. When the amount of styrene III meets the above range, the number average molecular weight of the polystyrene block S3 can be ensured to be 1.5 × 10⁻⁶. 4 -3×10 4 .

[0075] Furthermore, the ratio of the amount of styrene III to the total weight of styrene (styrene I + styrene II + styrene III) is 0.3-0.35:1.

[0076] According to the present invention, the conditions for the fourth polymerization reaction include a reaction temperature of 50-80°C.

[0077] In this invention, there is no particular limitation on the reaction time of the fourth polymerization reaction, as long as styrene III is completely converted, that is, the conversion rate of styrene III is 100%.

[0078] According to the present invention, the ratio of the total amount of styrene (styrene I + styrene II + styrene III) to the total amount of butadiene (butadiene I + butadiene II) is 2.3-9:1.

[0079] In this invention, when the ratio of the total amount of styrene to the total amount of butadiene meets the above-mentioned range, it can be ensured that the obtained styrene-butadiene block polymer has excellent mechanical properties and bending flexibility while having improved transparency, thus achieving a comprehensive improvement in the mechanical properties, bending flexibility and transparency of the styrene-butadiene block polymer.

[0080] Furthermore, the ratio of the total amount of styrene to the total amount of butadiene is 3-5.7:1.

[0081] A third aspect of the present invention provides a styrene-butadiene block polymer prepared by the above-described preparation method.

[0082] The fourth aspect of the present invention provides an application of the above-mentioned styrene-butadiene block polymer in the preparation of optical material precursors.

[0083] The present invention will be described in detail below through embodiments.

[0084] The butadiene content (Bd%), 1,2-structural unit content (Bv%), styrene content (St%), block styrene content (St-block%), and non-block styrene content (St-non-block%) of styrene-butadiene block polymers were determined using a Bruker AVANCE 400 superconducting nuclear magnetic resonance spectrometer. 1 H-NMR test, 1 The resonance frequency of the H nucleus was 300.13 MHz, the spectral width was 2747.253 Hz, the pulse width was 5 μs, the data point was 16 K, the sample tube diameter was 5 mm, the solvent was deuterated chloroform (CDCl3), the sample concentration was 15% (W / V), the test temperature was room temperature, the number of scans was 16, and the calibration was performed with a tetramethylsilane chemical shift of 0 ppm.

[0085] The molecular weight and molecular weight distribution of the styrene-butadiene block polymer were determined using an HLC-8320 gel permeation chromatograph from Tosoh Corporation, Japan. The test conditions included: TSKgel SuperMultipore HZ-N column, TSKgel SuperMultipore HZ standard column, chromatographic grade THF solvent, polystyrene as calibration standard, sample concentration of 1 mg / mL, injection volume of 10 μL, flow rate of 0.35 mL / min, and test temperature of 40 °C.

[0086] Transmittance and haze were tested using a Japanese NDH-1001DP turbidimeter, according to ASTM D1003-2000.

[0087] Mechanical properties were tested using an INSTRON 5567 electronic tensile testing machine manufactured by Instron Corporation, USA.

[0088] Tensile properties were tested according to GB / T 1040.1-2018, and flexural properties were tested according to GB / T 9341-2008.

[0089] Impact strength was tested using a pendulum impact testing machine, Ceast ResilImpactor 6957, manufactured by CEAST, Italy, according to GB / T 1843-2008.

[0090] Experimental setup and process: The experiment was conducted in a 5L polymerization reactor. Solvent, butadiene and styrene monomer were added from the polymerization pipeline, while initiator, structure modifier and terminator were added from the top of the polymerization reactor using a syringe.

[0091] Cyclohexane was purchased from Sinopharm Reagent Company, with a purity >99.9%. It was soaked in a molecular weight sieve for 15 days, and the water content was less than 5 ppm.

[0092] Styrene, polymer grade, sourced from Yanshan Petrochemical;

[0093] Butadiene, polymer grade, sourced from Yanshan Petrochemical;

[0094] Butyllithium (Li) was purchased from Bailingwei Reagent Company, 100ml specification, 1.6mol·L⁻¹. -1 Cyclohexane solution, diluted to 0.4 mol·L⁻¹ -1 Cyclohexane solution;

[0095] Tetrahydrofuran (THF) was purchased from Bailingwei Reagent Company, 500g specification, chromatographic grade, with a relative molecular mass of 72.1g / mol.

[0096] Example 1

[0097] This embodiment is used to illustrate the styrene-butadiene block polymer and its preparation method of the present invention.

[0098] (1) Under nitrogen protection, solvent (cyclohexane), structure modifier (tetrahydrofuran), and styrene I (types and amounts are shown in Table 1, and the amounts listed in the table are all measured by pure compounds) were added to a 5L reactor. The polymerization temperature was controlled within the range of 50-80℃. The designed amount of n-butyllithium (the amount is shown in Table 1, and the amounts listed in the table are all measured by pure compounds) was added to the 5L reactor to prepare polystyrene block S1, and the analysis and testing were carried out. The results are shown in Table 2.

[0099] (2) After the complete conversion of styrene I, the designed amount of butadiene I and styrene II (the types and amounts are shown in Table 1, and the amounts listed in the table are all measured by pure compounds) were added to the reactor to prepare block polymer S1-B1-(BS)1-S2, and the analysis and testing were carried out. The results are shown in Table 2.

[0100] (3) After the complete conversion of butadiene I and styrene II, the designed amount of butadiene II (the types and amounts are shown in Table 1, and the amounts listed in the table are all measured by pure compounds) is added to the reactor to prepare block polymer S1-B1-(BS)1-S2-B2.

[0101] (4) After the complete conversion of butadiene II, the designed amount of styrene III (the types and amounts are shown in Table 1, and the amounts listed in the table are all measured by pure compounds) is added to the reactor to prepare block polymer S1-B1-(BS)1-S2-B2-S3.

[0102] (5) After the complete conversion of styrene III, the designed amount of terminator (isopropanol) was added to the reactor (the types and amounts are shown in Table 1, and the amounts listed in the table are all measured by pure compounds) to obtain S1-B1-(BS)1-S2-B2-S3 styrene-butadiene block polymer P1, and the structural analysis test was performed. The results are shown in Table 2. The physical properties of the sample were tested. The results are shown in Table 3.

[0103] Examples 2-8

[0104] This embodiment is used to illustrate the styrene-butadiene block polymer and its preparation method of the present invention.

[0105] According to the method described in Example 1, except that the parameters shown in Table 1 were used to prepare styrene-butadiene block polymers, thereby obtaining styrene-butadiene block polymers P2-P8 respectively, and structural analysis tests were performed, the results of which are shown in Table 2; physical property tests were performed on the samples, the results of which are shown in Table 3.

[0106] Table 1

[0107]

[0108]

[0109] Table 1 (continued)

[0110]

[0111]

[0112] Table 2

[0113]

[0114]

[0115] Note: St% / Bd%, is the ratio of the total weight of styrene segments to the total weight of butadiene segments.

[0116] Table 2 (continued)

[0117]

[0118] Note: St% / Bd%, is the ratio of the total weight of styrene segments to the total weight of butadiene segments.

[0119] Table 3

[0120]

[0121] As can be seen from the results in Table 3, the styrene-butadiene block polymer prepared by the present invention shortens the molecular chain length of the single butadiene block and introduces a certain proportion of butadiene and styrene copolymer into the molecular chain segment, so that the styrene-butadiene block polymer has improved transparency while having excellent mechanical properties and bending flexibility, thus achieving a comprehensive improvement in the mechanical properties, bending flexibility and transparency of the styrene-butadiene block polymer.

[0122] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A styrene-butadiene block polymer, characterized in that, The polymer has a structure as shown in S1-B1-(BS)1-S2-B2-S3; Among them, S1, S2, and S3 are polystyrene blocks, B1 and B2 are polybutadiene blocks, and (BS)1 is a butadiene-styrene copolymer. Based on the total weight of the polymer, the ratio of the total weight of the styrene segments to the total weight of the butadiene segments is 2.3-9:1; Based on the total weight of the styrene-butadiene block polymer, the content of non-block styrene is 3-15% by weight. Specifically, based on the total weight of styrene segments in the styrene-butadiene block polymer, the content of polystyrene block S1 is 25-35% by weight. Based on the total weight of styrene segments in the styrene-butadiene block polymer, the content of polystyrene block S2 is 25-35% by weight. Based on the total weight of styrene segments in the styrene-butadiene block polymer, the content of polystyrene block S3 is 25-35% by weight.

2. The styrene-butadiene block polymer according to claim 1, wherein, Based on the total weight of the polymer, the ratio of the total weight of the styrene segments to the total weight of the butadiene segments is 3-5.7:

1.

3. The styrene-butadiene block polymer according to claim 1 or 2, wherein, The number-average molecular weight of the styrene-butadiene block polymer is 6 × 10⁻⁶. 4 -12×10 4 .

4. The styrene-butadiene block polymer according to claim 1 or 2, wherein, The number-average molecular weight of the styrene-butadiene block polymer is 7 × 10⁻⁶. 4 -11×10 4 .

5. The styrene-butadiene block polymer according to claim 1 or 2, wherein, The number-average molecular weight of the styrene-butadiene block polymer is 8 × 10⁻⁶. 4 -10×10 4 .

6. The styrene-butadiene block polymer according to claim 1 or 2, wherein, The molecular weight distribution index of the styrene-butadiene block polymer is 1-1.

2.

7. The styrene-butadiene block polymer according to claim 6, wherein, The molecular weight distribution index of the styrene-butadiene block polymer is 1.01-1.

1.

8. The styrene-butadiene block polymer according to claim 1 or 2, wherein, Based on the total weight of butadiene segments in the styrene-butadiene block polymer, the content of 1,2-butadiene structural units is 6-30% by weight.

9. The styrene-butadiene block polymer according to claim 8, wherein, Based on the total weight of butadiene segments in the styrene-butadiene block polymer, the content of 1,2-butadiene structural units is 10-18 by weight.

10. The styrene-butadiene block polymer according to claim 1 or 2, wherein, Based on the total weight of the styrene-butadiene block polymer, the content of non-block styrene is 5-12% by weight.

11. The styrene-butadiene block polymer according to claim 1 or 2, wherein, Based on the total weight of styrene segments in the styrene-butadiene block polymer, the content of polystyrene block S1 is 27-33% by weight. And / or, based on the total weight of styrene segments in the styrene-butadiene block polymer, the content of polystyrene block S2 is 27-33% by weight. And / or, based on the total weight of styrene segments in the styrene-butadiene block polymer, the content of polystyrene block S3 is 27-33% by weight.

12. A method for preparing the styrene-butadiene block polymer according to any one of claims 1-11, characterized in that, The preparation method includes the following steps: (1) In a solvent, in the presence of an initiator and a regulator, styrene I undergoes a first polymerization reaction to obtain a first polymer solution containing polystyrene blocks S1; (2) Butadiene I and styrene II are contacted with the first polymer solution to carry out a second polymerization reaction to obtain a second polymer solution containing S1-B1-(BS)1-S2; (3) Butadiene II is contacted with the second polymer solution to carry out a third polymerization reaction to obtain a third polymer solution containing S1-B1-(BS)1-S2-B2; (4) Styrene III is contacted with the third polymer solution to carry out the fourth polymerization reaction, and a fourth polymer solution containing S1-B1-(BS)1-S2-B2-S3 is obtained; (5) A terminator is added to the fourth polymer solution to obtain the styrene-butadiene block polymer.

13. The preparation method according to claim 12, wherein, In step (1), the ratio of the amount of styrene I to the total amount of styrene is 0.25-0.35:1; And / or, the conditions for the first polymerization reaction include: a reaction temperature of 50-80°C; And / or, the initiator is selected from at least one of methyl lithium, ethyl lithium, propyl lithium, isopropyl lithium, n-butyl lithium, and sec-butyl lithium; And / or, based on the total amount of the styrene and the butadiene, the amount of the initiator is 0.9-1.6 mmol / 100g; And / or, the modifier is selected from at least one of tetrahydrofuran, bistetrahydrofurfuryl ether, ethyltetrahydrofurfuryl ether and N,N-dimethyltetrahydrofurfurylamine; And / or, the molar ratio of the regulator to the initiator is 0.05-2:

1.

14. The preparation method according to claim 12 or 13, wherein, In step (2), the ratio of the amount of styrene II to the total amount of styrene is 0.3-0.5:1; And / or, the ratio of the amount of butadiene I to the total amount of butadiene is 0.5-0.7:1; And / or, the conditions for the second polymerization reaction include: a reaction temperature of 50-80°C.

15. The preparation method according to claim 12 or 13, wherein, In step (3), the ratio of the amount of butadiene II to the total amount of butadiene is 0.3-0.5:1; And / or, the conditions for the third polymerization reaction include: a reaction temperature of 50-80°C.

16. The preparation method according to claim 12 or 13, wherein, In step (4), the ratio of the amount of styrene III to the total amount of styrene is 0.25-0.35:1; And / or, the conditions for the fourth polymerization reaction include: a reaction temperature of 50-80°C.

17. The use of the styrene-butadiene block polymer according to any one of claims 1-11 in the preparation of optical material precursors.

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