Styrene-butylene polymers, methods for making the same, toughener compositions, and ABS resins

Abstract

The present application relates to the field of toughening agent for ABS resin, and discloses a butadiene-styrene polymer, a preparation method thereof, a toughening agent composition and an ABS resin.The butadiene-styrene polymer has a structure as shown in PS-SSBR, wherein PS is a polystyrene block; SSBR is a butadiene-styrene copolymer, comprising a polybutadiene microblock, a butadiene-styrene random polymer block and a polystyrene microblock; the content of the polystyrene block in the butadiene-styrene polymer is 2-10 wt%, and the content of the butadiene-styrene copolymer is 90-98 wt% based on the total weight of the butadiene-styrene polymer; the 25 DEG C viscosity of a 5 wt% styrene solution of the butadiene-styrene polymer is 20-40 centipoise.The butadiene-styrene polymer is easy to be shaped in the condensation and drying process, has low gel content and low APHA color, and has moderate solution viscosity; and the ABS resin obtained by toughening has excellent comprehensive performance.

Description

Technical Field

[0001] This invention relates to the field of toughening agents for ABS resin, specifically to styrene-butadiene polymers and their preparation methods, toughening agent compositions, and ABS resins prepared from the toughening agent compositions. Background Technology

[0002] With the development of continuous bulk ABS resin modification technology, it has been found that a single rubber toughening agent cannot maximize the toughening effect of rubber, while a toughening rubber system with a bimodal or multimodal particle size distribution can significantly improve the impact resistance of the toughened resin. To broaden the particle size distribution of the toughening rubber, two rubbers with different particle sizes are generally used in combination. The large-particle-size rubber induces crazes and inhibits crack propagation, while the small-particle-size rubber forms cavities and shear bands to terminate crazes. The combined effect of the two particle sizes effectively improves the impact resistance of ABS resin. Studies have shown that using a combination of low-cis polybutadiene and block styrene-butadiene polymers is the optimal toughening system. Low-cis polybutadiene generates large-particle-size rubber particles, while block styrene-butadiene polymers generate small-particle-size rubber particles. For continuous bulk ABS resin, the solution viscosity of styrene-butadiene polymers in styrene has a significant impact on the reaction process. It is essential to minimize the solution viscosity of the toughening rubber in styrene to form small-particle-size rubber particles and improve the gloss of the ABS resin.

[0003] To minimize the viscosity of toughened rubber in styrene solution, the common practice is to reduce the molecular weight of the toughened rubber and increase the content of styrene structural units. However, the molecular weight cannot be reduced indefinitely, and there is also an upper limit to the content of styrene structural units; otherwise, the Mooney viscosity of the product will be too high, making it difficult to form during the coagulation and drying stages, thus resulting in a loss of the elasticity and processing properties of the toughened rubber.

[0004] CN104558455A discloses a styrene-butadiene polymer with a Mooney viscosity of 30-200 and a viscosity of 5-30 centipoise in a 5% styrene solution, as well as its preparation method. However, the polymer molecular chain is terminated with butadiene at one end, and the excessively high styrene content results in a product with too high Mooney viscosity, which makes the product more prone to pulverization, bridging during extrusion dehydration and expansion drying, and molding difficulties.

[0005] CN107722402A discloses a linear styrene-butadiene block copolymer with a single-peak distribution and a number-average molecular weight of 7-200,000. This technology uses butadiene and styrene for copolymerization, and the polymer molecular chain obtained is also ended by butadiene. However, it cannot solve the problems of high Mooney viscosity and difficult molding of styrene-butadiene polymers with high styrene content.

[0006] CN109503900A discloses a toughening agent composition and its preparation method, which uses a blending method of low cis polybutadiene rubber and styrene-butadiene block copolymer to solve the post-processing molding problem, but still does not solve the problem of difficult molding of high styrene-butadiene polymer alone. Summary of the Invention

[0007] The purpose of this invention is to overcome the problems of high styrene content styrene-butadiene polymers having difficulty in feeding and molding during the extrusion dehydration and expansion drying processes, and to provide styrene-butadiene polymers, their preparation methods, toughening agent compositions, and ABS resins.

[0008] To achieve the above objectives, the first aspect of the present invention provides a styrene-butadiene polymer having a structure shown in PS-SSBR; wherein PS is a polystyrene block; and SSBR is a butadiene-styrene copolymer comprising polybutadiene microblocks, styrene-butadiene random polymer blocks, and polystyrene microblocks.

[0009] Based on the total weight of the styrene-butadiene polymer, the content of the polystyrene block in the styrene-butadiene polymer is 2-10% by weight; and the content of the butadiene-styrene copolymer is 90-98% by weight.

[0010] The viscosity of the 5% by weight styrene solution of the styrene-butadiene polymer at 25°C is 20-40 centipoise.

[0011] The inventors of this invention have discovered that when butadiene and styrene undergo anionic copolymerization, butadiene always polymerizes first because its polymerization rate is greater than that of styrene, followed by copolymerization of butadiene and styrene to form a styrene-butadiene polymer with butadiene blocks at the head end.

[0012] The inventors of this invention further discovered that styrene-butadiene polymers with high styrene content and butadiene block structures at one end of the molecular chain exhibit severe pulverization after water washing and agglomeration, making feeding difficult during extrusion dehydration and expansion drying. Introducing an appropriate amount of polystyrene blocks into the first end of the styrene-butadiene polymer to form a structure similar to SBS can avoid this pulverization problem.

[0013] Through further in-depth research, the inventors of this invention discovered that the ABS resin prepared from the two-component toughening system composed of a styrene-butadiene polymer with the structure shown in PS-SSBR and low-cis polybutadiene rubber has good comprehensive properties.

[0014] A second aspect of the present invention provides a method for preparing a styrene-butadiene polymer, the method comprising the following steps:

[0015] (1) In the presence of an initiator and a structure modifier, the first part of styrene is subjected to a first polymerization reaction in a non-polar solvent to obtain a polymer solution I containing polystyrene blocks PS;

[0016] (2) Butadiene and the second portion of styrene are contacted with the polymer solution I to carry out a second polymerization reaction to obtain a polymer solution II containing PS-SSBR;

[0017] (3) The polymer solution II is contacted with a terminating agent to terminate the reaction;

[0018] Wherein, the first polymerization reaction and the second polymerization reaction are each anionic solution polymerization reactions independently; the weight ratio of the amount of the first portion of styrene in step (1) to the amount of the second portion of styrene in step (2) is 0.05-0.5:1; the weight ratio of the amount of butadiene to the total amount of the first portion of styrene and the second portion of styrene is 1.8-3:1; based on the total amount of the butadiene, the first portion of styrene and the second portion of styrene, the amount of the initiator is 0.5-0.8 mmol / 100g.

[0019] A third aspect of the present invention provides a styrene-butadiene polymer prepared by the preparation method described in the second aspect.

[0020] A fourth aspect of the present invention provides a toughening agent composition comprising a styrene-butadiene polymer and low-cis polybutadiene rubber, wherein the styrene-butadiene polymer is the styrene-butadiene polymer described in the first or third aspect.

[0021] The fifth aspect of the present invention provides an ABS resin, which is prepared from the toughening agent composition described in the fourth aspect.

[0022] The present invention has the following advantages through the above technical solution:

[0023] (1) The styrene-butadiene polymer provided by the present invention has the structure shown in PS-SSBR; wherein, PS is a polystyrene block; SSBR is a butadiene-styrene copolymer, which includes polybutadiene microblocks, styrene-butadiene random polymer blocks and polystyrene microblocks;

[0024] Based on the total weight of the styrene-butadiene polymer, the content of the polystyrene block in the styrene-butadiene polymer is 2-10% by weight; and the content of the butadiene-styrene copolymer is 90-98% by weight.

[0025] The viscosity of the 5% by weight styrene solution of the styrene-butadiene polymer at 25°C is 20-40 centipoise.

[0026] The styrene-butadiene polymer provided by this invention has molecular chains that are physically entangled, with fewer butadiene ends, making it easy to dry and mold. Therefore, the gel content during the drying process is low, which effectively avoids product pulverization. When applied to ABS resin, it has good impact resistance and ensures the improvement of the overall performance of ABS resin.

[0027] In preferred embodiments, the styrene-butadiene polymer APHA provided by the present invention has low color and high gloss; the solution has moderate viscosity and good fluidity.

[0028] (2) The preparation method of styrene-butadiene polymer provided by the present invention has a simple preparation process, mild and controllable reaction conditions, readily available raw materials, low cost, and low energy consumption throughout the preparation process.

[0029] (3) The styrene-butadiene polymer provided by the present invention has a suitable styrene content. Compared with low cis polybutadiene rubber alone, the styrene-butadiene polymer combined with low cis polybutadiene rubber has better interfacial compatibility. Therefore, its toughening composition for use as ABS resin has better mechanical strength.

[0030] In summary, the preparation method provided by this invention uses readily available raw materials, has low cost, simple process flow, and mild and controllable reaction conditions. The resulting styrene-butadiene polymer is easy to form during the coagulation and drying stages, has low gel content, low APHA color, and moderate solution viscosity. The ABS resin prepared by this method has good impact resistance, high gloss, and good flowability. Detailed Implementation

[0031] 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.

[0032] As previously described, the first aspect of the present invention provides a styrene-butadiene polymer having a structure shown in PS-SSBR; wherein PS is a polystyrene block; and SSBR is a butadiene-styrene copolymer comprising polybutadiene microblocks, styrene-butadiene random polymer blocks, and polystyrene microblocks.

[0033] Based on the total weight of the styrene-butadiene polymer, the content of the polystyrene block in the styrene-butadiene polymer is 2-10% by weight; and the content of the butadiene-styrene copolymer is 90-98% by weight.

[0034] The viscosity of the 5% by weight styrene solution of the styrene-butadiene polymer at 25°C is 20-40 centipoise.

[0035] During their research, the inventors of this invention discovered that by introducing PS blocks and butadiene-styrene copolymer segmental structures (SSBRs) into the molecular chain of the styrene-butadiene polymer (SBR), which include polybutadiene microblocks, SBR random polymer blocks, and polystyrene microblocks, the SBR molecular chain contains polystyrene blocks at both ends. This results in fewer butadiene ends, facilitating drying and molding, and thus reducing gel content during drying, effectively preventing product pulverization. Using SBRs that meet the specific content requirements of polystyrene blocks and butadiene-styrene copolymers facilitates the preparation of SBRs with appropriate styrene content. Furthermore, the 5% by weight styrene solution of the SBR has a moderate viscosity at 25°C, which improves the good interfacial compatibility between the SBR and ABS resin, resulting in ABS resin with good flowability.

[0036] According to some embodiments of the present invention, based on the total weight of the styrene-butadiene polymer (SBR), the content of the polystyrene block in the SBR is 2-10% by weight. Introducing the PS block into the SBR increases the physical entanglement between molecular chains, thereby effectively preventing product pulverization. If the PS block content is too low, the improvement in product pulverization is not significant; if the PS block content is too high, it is detrimental to improving the impact resistance of the ABS resin. Preferably, based on the total weight of the SBR, the content of the polystyrene block in the SBR is 2-8% by weight, preferably 3-6% by weight. The polystyrene block content within the above-mentioned preferred range is beneficial for further improving the impact resistance of the ABS resin.

[0037] According to some embodiments of the present invention, preferably, based on the total weight of the styrene-butadiene polymer, the content of the butadiene-styrene copolymer in the styrene-butadiene polymer is 92-98% by weight, preferably 94-97% by weight. The above preferred embodiments are beneficial for improving the overall performance of the modified ABS resin, while avoiding product pulverization.

[0038] According to some embodiments of the present invention, preferably, based on the total weight of the styrene-butadiene polymer (SBR), the content of styrene structural units in the SBR is 25-35% by weight, and the content of butadiene structural units is 65-75% by weight. Controlling the content of styrene and butadiene structural units ensures good interfacial compatibility between the SBR and ABS, while also adjusting the viscosity of a 5% by weight styrene solution of the SBR. With the same molecular weight, when the content of styrene and butadiene structural units is within the above-mentioned preferred range, both the viscosity of the 5% by weight styrene solution of the SBR and the elasticity of the SBR can be considered, thereby further improving the interfacial compatibility between the SBR and ABS resin.

[0039] According to some embodiments of the present invention, preferably, the styrene-butadiene polymer contains 18-27 wt% styrene blocks, wherein the styrene blocks are styrene structural units containing six or more consecutive styrene units in the styrene-butadiene polymer molecular chain.

[0040] According to some embodiments of the present invention, preferably, the content of non-block styrene is 5-11 wt%.

[0041] Using styrene-butadiene polymers that meet the specific content requirements of the styrene blocks mentioned above is beneficial for obtaining styrene-butadiene polymers with appropriate styrene content.

[0042] According to some embodiments of the present invention, preferably, the molecular weight of the styrene-butadiene polymer exhibits a bimodal distribution.

[0043] According to some embodiments of the present invention, preferably, the molecular weight of the first peak is 280,000-380,000, more preferably 300,000-360,000.

[0044] According to some embodiments of the present invention, preferably, the molecular weight of the second peak is 140,000-190,000, more preferably 150,000-180,000.

[0045] In this invention, the peak molecular weight of the first peak is the peak molecular weight of the high molecular weight portion; the peak molecular weight of the second peak is the peak molecular weight of the low molecular weight portion.

[0046] According to some embodiments of the present invention, preferably, the content of the first peak is 5-20% by weight, based on the total weight of the styrene-butadiene polymer.

[0047] According to some embodiments of the present invention, preferably, the content of the second peak is 80-95% by weight, based on the total weight of the styrene-butadiene polymer.

[0048] In this invention, the content of the first peak is the proportion of the high molecular weight fraction to the total polymer content; the content of the second peak is the proportion of the low molecular weight fraction to the total polymer content.

[0049] According to some embodiments of the present invention, preferably, the molecular weight distribution of the styrene-butadiene polymer is 1.05-1.3, more preferably 1.1-1.2.

[0050] According to some embodiments of the present invention, when the content of styrene structural units in the styrene-butadiene polymer is constant, the molecular weight and its distribution of the styrene-butadiene polymer are closely related to the viscosity of a 5% by weight styrene solution of the styrene-butadiene polymer. When the molecular weight at the peak position of the first peak and the molecular weight at the peak position of the second peak in the bimodal structure are within the above-mentioned preferred range, it is beneficial to ensure that the viscosity of the 5% by weight styrene solution of the styrene-butadiene polymer meets the above-mentioned range.

[0051] Using styrene-butadiene polymers that meet the specific parameter requirements mentioned above, when used as toughening rubber compositions, can significantly improve the impact resistance of toughening resins.

[0052] According to some embodiments of the present invention, preferably, the vinyl content of the styrene-butadiene polymer is 8-16% by weight, more preferably 8-14% by weight. Herein, "vinyl content" refers to the ratio of the content of structural units formed by 1,2-polymerization of butadiene (i.e., 1,2-butadiene structural units) to the total content of butadiene structural units. Generally, the higher the vinyl content of the styrene-butadiene polymer, the higher the grafting and crosslinking activity during the polymerization process of ABS resin. The vinyl content of the styrene-butadiene polymer within the above-mentioned preferred range ensures high grafting and crosslinking activity during the polymerization process of ABS resin without affecting the impact resistance of the ABS resin.

[0053] According to some embodiments of the present invention, preferably, based on the total weight of the styrene-butadiene polymer (SBR), the gel content of the SBR is in the range of 0-200 ppm, more preferably in the range of 0-150 ppm, and even more preferably in the range of 0-100 ppm. In continuous bulk ABS resin toughening rubber, gel content is the most critical preparation technology. High gel content leads to a rapid increase in polymerization reactor filter pressure, increased filter replacement frequency, and the gel easily generates defects in the ABS resin sheet, affecting the gloss of the ABS resin. Therefore, the gel content of the SBR within the above-mentioned preferred range can ensure the long-term operation of the ABS resin polymerization reactor.

[0054] According to some embodiments of the present invention, preferably, the APHA color of the styrene-butadiene polymer is ≤10, more preferably ≤7, and even more preferably ≤5. The above-described preferred embodiments can more significantly improve the gloss of the styrene-butadiene polymer.

[0055] As mentioned above, a second aspect of the present invention provides a method for preparing a styrene-butadiene polymer, the method comprising the following steps:

[0056] (1) In the presence of an initiator and a structure modifier, the first part of styrene is subjected to a first polymerization reaction in a non-polar solvent to obtain a polymer solution I containing polystyrene blocks PS;

[0057] (2) Butadiene and the second portion of styrene are contacted with the polymer solution I to carry out a second polymerization reaction to obtain a polymer solution II containing PS-SSBR;

[0058] (3) The polymer solution II is contacted with a terminating agent to terminate the reaction;

[0059] Wherein, the first polymerization reaction and the second polymerization reaction are each anionic solution polymerization reactions independently; the weight ratio of the amount of the first portion of styrene in step (1) to the amount of the second portion of styrene in step (2) is 0.05-0.5:1; the weight ratio of the amount of butadiene to the total amount of the first portion of styrene and the second portion of styrene is 1.8-3:1; based on the total amount of the butadiene, the first portion of styrene and the second portion of styrene, the amount of the initiator is 0.5-0.8 mmol / 100g.

[0060] The preparation method of the styrene-butadiene polymer provided by the present invention has a simple preparation process, mild and controllable reaction conditions, readily available and low-cost raw materials, and low energy consumption throughout the preparation process.

[0061] According to some embodiments of the present invention, preferably, the weight ratio of the amount of the first portion of styrene in step (1) to the amount of the second portion of styrene in step (2) is 0.06-0.26:1, more preferably 0.08-0.2:1.

[0062] According to some embodiments of the present invention, preferably, the weight ratio of the butadiene to the total weight of the first portion of styrene and the second portion of styrene is 2-2.6:1.

[0063] Using the above preferred embodiments is beneficial for obtaining styrene-butadiene polymers with the above-described specific structure.

[0064] According to some embodiments of the present invention, in order to take into account the polymerization rate of styrene, preferably, in step (1), the conditions of the first polymerization reaction include: polymerization temperature of 40-80℃, preferably 40-70℃; polymerization pressure of 0.1-1MPa, preferably 0.2-0.5MPa; and reaction time of 2-20min, preferably 5-10min.

[0065] According to some embodiments of the present invention, preferably, in step (2), the conditions of the second polymerization reaction include: a polymerization temperature of 60-150°C, preferably 70-130°C, more preferably 90-130°C; a reaction pressure of 0.1-1 MPa, preferably 0.2-0.5 MPa; and a reaction time of 30-80 min, preferably 40-60 min. The polymerization temperature of the second polymerization reaction can adjust the sequence distribution of styrene in the molecular chain. Using the above preferred embodiments helps to ensure that the vinyl content and the non-block styrene content of the obtained styrene-butadiene polymer meet the above requirements.

[0066] According to some embodiments of the present invention, in step (1), the initiator can be any existing initiator capable of initiating anionic polymerization reactions, without particular limitation. The initiator is typically an organic monolithium initiator, which can be represented by RLi. R can be alkyl, cycloalkyl, or aryl. To improve the solubility of the initiator in the solvent, R is preferably C1-C1. 20 Alkyl, C3-C 20 cycloalkyl or C6-C 20 The initiator is an aryl group. Specifically, examples of the organic monolithium initiator include, but are not limited to, one or more of the following: methyllithium, isopropyllithium, sec-butyllithium, n-butyllithium, cyclohexyllithium, 4-cyclohexylbutyllithium, phenyllithium, triphenylmethyllithium, and 2-naphthyllithium. Furthermore, to improve the initiator's solubility in solvents and storage stability, the initiator is particularly preferably n-butyllithium and / or sec-butyllithium.

[0067] According to some embodiments of the present invention, the amount of the initiator can be rationally selected based on the amount of monomer and the desired molecular weight of the styrene-butadiene polymer. Preferably, the amount of the initiator is 0.5-0.8 mmol / 100g, based on the total amount of butadiene, the first portion of styrene, and the second portion of styrene.

[0068] According to some embodiments of the present invention, in step (1), the addition of the structure modifier can adjust the polymerization rate and the molecular structure of the product. Preferably, the structure modifier is one or more of ether compounds, amine compounds, and alkali metal alkoxy compounds. More preferably, the structure modifier is one or more of tetrahydrofuran, dioxane, diethyl ether, and triethylamine.

[0069] According to some embodiments of the present invention, preferably, the amount of the structure modifier is 50-500 mg / kg, based on the amount of the nonpolar solvent.

[0070] According to some embodiments of the present invention, in step (1), the type of nonpolar solvent is not particularly limited, and can be any existing substance used as a reaction medium. For example, the nonpolar solvent is a cycloalkanes or a mixture of cycloalkanes and aliphatic hydrocarbons. Preferably, the cycloalkanes are one or more of cyclohexane, methylcyclopentane, and methylcyclohexane; the aliphatic hydrocarbons are one or more of methylpentane, n-hexane, n-heptane, and isooctane. Furthermore, the inventors of the present invention have found that using a mixture of aliphatic hydrocarbons and cycloalkanes as the nonpolar solvent, and wherein the content of the aliphatic hydrocarbons in the mixture does not exceed 30% by weight, can avoid heterogeneous polymerization and result in a smaller fluctuation in the molecular weight of the obtained styrene-butadiene polymer. Preferably, based on the total weight of 100 parts by weight of the reaction monomers, the amount of the nonpolar solvent is 400-900 parts by weight; wherein the total weight of the reaction monomers is the total amount of butadiene, the first portion of styrene, and the second portion of styrene.

[0071] According to some embodiments of the present invention, in step (3), the polymer solution II is contacted with a terminating agent to terminate the reaction. The terminating agent serves three purposes: first, to terminate the active chain; second, to adjust the pH value of the condensate; and third, to remove metal ions from the styrene-butadiene polymer. The above operations not only remove metal ions from the styrene-butadiene polymer, reducing its color, but also achieve the purpose of terminating the polymerization reaction.

[0072] Preferably, in step (3), the terminating agent is an aqueous solution of carbon dioxide or a fatty acid, preferably an aqueous solution of carbon dioxide. There are no particular limitations on the type and amount of the fatty acid used; both can achieve the inventive objective of this invention to a certain extent.

[0073] According to some embodiments of the present invention, preferably, the fatty acid is one or more selected from adipic acid, sebacic acid, stearic acid, malic acid, citric acid, and tartaric acid, with citric acid being particularly preferred. The above-described preferred embodiments facilitate control of the final product color, and the fatty acid can be provided in the form of a fatty acid solution. The solvent in the fatty acid solution is water and / or an inert solvent, wherein the inert solvent is cyclohexane, n-hexane, or a mixture of both in any proportion. Using the aqueous carbon dioxide solution as a terminator facilitates the formation of a weakly acidic environment. There are no particular limitations on the formation of the aqueous carbon dioxide solution; for example, carbon dioxide (such as carbon dioxide gas or dry ice) can be dissolved in water to form an acidic aqueous carbon dioxide solution. The above-described preferred embodiments facilitate further reduction of the color of the resulting styrene-butadiene polymer while terminating the polymerization reaction.

[0074] According to some embodiments of the present invention, preferably, the amount of fatty acid used is 0.1-1 parts by weight, more preferably 0.2-0.5 parts by weight, based on the total weight of 100 parts by weight of the reaction monomers; wherein, the total weight of the reaction monomers is the total amount of butadiene, the first portion of styrene and the second portion of styrene.

[0075] According to some embodiments of the present invention, preferably, the amount of the aqueous carbon dioxide solution, calculated as carbon dioxide, is 0.5-1.5 mol, based on 1 mol of the initiator.

[0076] The above-described preferred embodiments facilitate the removal of metal ions from the styrene-butadiene polymer, thereby improving the polymer's color.

[0077] According to some embodiments of the present invention, there are no particular restrictions on the manner of contact in step (3). Preferably, the terminating agent is added to the polymer solution II to make the contact.

[0078] According to some embodiments of the present invention, the contact conditions in step (3) are not particularly limited. Preferably, the contact conditions include: a contact temperature of 10-100°C, preferably 40-60°C; a contact pressure of 0.1-1 MPa, preferably 0.2-0.5 MPa; and a contact time of 0.1-0.5 hours, preferably 0.2-0.4 hours.

[0079] According to some embodiments of the present invention, preferably, step (3) further includes: removing the solvent from the styrene-butadiene polymer solution obtained from the termination reaction.

[0080] According to some embodiments of the present invention, preferably, step (3) further includes: contacting the styrene-butadiene polymer solution obtained from the termination reaction with an antioxidant.

[0081] According to some embodiments of the present invention, preferably, the antioxidant is a mixture of antioxidant 1520 and antioxidant 1076.

[0082] According to some embodiments of the present invention, preferably, the weight ratio of antioxidant 1520 to antioxidant 1076 in the mixture is 0.5-2:1.

[0083] According to some embodiments of the present invention, preferably, the weight ratio of the amount of antioxidant to the amount of styrene-butadiene polymer is 0.2-0.4:100.

[0084] The above-described preferred embodiments are beneficial for the storage and transportation of styrene-butadiene polymers.

[0085] As previously described, a third aspect of the present invention provides a styrene-butadiene polymer prepared by the preparation method described in the second aspect. The styrene-butadiene polymer is the same as or similar to the styrene-butadiene polymer provided in the first aspect of the present invention, and will not be described again here.

[0086] According to some embodiments of the present invention, the styrene-butadiene polymer APHA has low color and high gloss; the solution has moderate viscosity and good fluidity.

[0087] As previously stated, a fourth aspect of the present invention provides a toughening composition comprising a styrene-butadiene polymer and low-cis polybutadiene rubber, wherein the styrene-butadiene polymer is the styrene-butadiene polymer described in the first or third aspect.

[0088] According to some embodiments of the present invention, preferably, the Mooney viscosity of the low-cis polybutadiene rubber is 32-52; and the viscosity of a 5% by weight styrene solution of the low-cis polybutadiene rubber at 25°C is 20-40 centipoise. The low-cis polybutadiene rubber using the above-described preferred embodiments is beneficial for controlling the particle size of the rubber phase in ABS resin.

[0089] According to some embodiments of the present invention, preferably, the weight ratio of the low-cis polybutadiene rubber to the styrene-butadiene polymer is 0.4-5:1, more preferably 0.4-4:1, more preferably 0.43-2.3:1, and even more preferably 0.67-1.5:1. When the toughening agent composition of the above preferred embodiments is used as a toughening agent for ABS resin, the resulting ABS resin exhibits excellent comprehensive properties.

[0090] As previously described, the fifth aspect of the present invention provides an ABS resin prepared from the toughening agent composition described in the fourth aspect.

[0091] According to some embodiments of the present invention, the ABS resin has good impact resistance, high gloss, and good flowability.

[0092] The present invention will be described in detail below through embodiments.

[0093] In the following examples and comparative examples, unless otherwise specified, the pressure of carbon dioxide is gauge pressure, and all raw materials used are commercially available products. Among the raw materials used:

[0094] Cyclohexane (CYH) was purchased from Sinopharm Reagent Company, with a purity >99.9%, and was soaked in a molecular weight sieve for 30 days, with a water content of less than 5 ppm;

[0095] Styrene (St) was purchased from Yanshan Petrochemical Company; it is polymer grade.

[0096] Butadiene (Bd) was purchased from Yanshan Petrochemical Company; it is of polymer grade.

[0097] Butyllithium (Li) was purchased from Bailingwei Reagent Company, 1.6 mol·L⁻¹ -1 Hexane solution;

[0098] Tetrahydrofuran (THF) was purchased from Inokai Reagent Company, analytical grade, soaked for 30 days using a molecular weight sieve, with a water content of less than 5 ppm;

[0099] Dioxane (DOX) was purchased from Inocare Reagents, analytical grade, soaked for 30 days on a molecular weight sieve, with a water content of less than 5 ppm.

[0100] Antioxidant 1520 and Antioxidant 1076 were purchased from Sinopharm Reagent Company.

[0101] Low-cis polybutadiene rubber, produced by Yanshan Branch, has a Mooney viscosity of 37, a viscosity of 24.6 centipoise at 25°C for 5% styrene solution, a vinyl content of 12.4 wt%, a gel content of 36 ppm, and an APHA color of 7.

[0102] In the following examples and comparative examples, the relevant characteristic parameters were measured using the following methods:

[0103] (1) Molecular weight and molecular weight distribution index: The molecular weight and molecular weight distribution index of the polymer were determined using an HLC-8320 gel permeation chromatograph from Tosoh Corporation, Japan. This gel permeation chromatograph is equipped with TSKgel SuperMultiporeHZ-N and TSKgel SuperMultiporeHZ standard columns. The solvent was chromatographically pure THF, and narrow-distribution polystyrene was used as the standard. The method for testing the molecular weight and molecular weight distribution index of the styrene-butadiene polymer was as follows: the solvent was chromatographically pure tetrahydrofuran, and narrow-distribution polystyrene was used as the standard. The polymer sample was prepared into a tetrahydrofuran solution with a mass concentration of 1 mg / mL. The injection volume was 10.00 μL, the flow rate was 0.35 mL / min, and the test temperature was 40.0℃.

[0104] The molecular weight distribution index of styrene-butadiene polymer is the total molecular weight distribution index of rubber, that is, the molecular weight distribution index measured based on bimodal distribution. The content of high molecular weight components refers to the percentage of the peak area of ​​the elution peak corresponding to the high molecular weight components in the bimodal distribution to the total peak area of ​​the bimodal distribution.

[0105] (2) Microstructure testing of polymers, including the content of styrene and butadiene structural units, the content of butadiene 1,2- structural units, the content of styrene blocks and the content of styrene non-blocks, etc. The microstructure was determined using a BRUKER AVANCED RX400MHz nuclear magnetic resonance spectrometer. The solvent used in the test was deuterated chloroform, and tetramethylsilane was used as an internal standard.

[0106] (3) Gel content: The gel content was determined by gravimetric method. The specific procedure was as follows: The rubber sample was added to styrene and shaken in a shaker at 25°C for 16 hours to completely dissolve the soluble substances, preparing a styrene solution containing 5% by weight of rubber. The mass of the rubber sample was recorded as C (in grams). A 360-mesh clean nickel mesh was weighed, and the mass of the clean nickel mesh was recorded as B (in grams). The solution was then filtered through the nickel mesh. After filtration, the nickel mesh was rinsed with styrene and dried at 150°C and normal pressure for 30 minutes. The mesh was then weighed, and its mass was recorded as A (in grams). The gel content was calculated according to the following formula:

[0107] Gel content % = [(AB) / C] × 100%.

[0108] (4) Viscosity of 5% rubber in styrene solution at 25℃: The viscosity was measured at 25℃ using a Finkell viscometer, following the enterprise standard Q / SH3155.SXL.C26-2019 of Beijing Yanshan Petrochemical Company. The principle of the measurement was to utilize the flow resistance of fluid through a capillary tube over a certain period of time to determine the viscosity of rubber in styrene (5% by weight solution concentration) at 25℃. The specific measurement steps were as follows: accurately prepare a styrene solution with 5% rubber content, fill the viscometer bulb with the solution, start the timer when the solution level reaches the upper mark of the bulb, stop the timer when the solution level reaches the lower mark of the bulb, and record the time taken for the solution to flow from the upper mark to the lower mark, accurate to 0.1 seconds. Measuring instruments: constant temperature water bath and viscometer; testing conditions: constant temperature 25℃.

[0109] (5) APHA colorimetry: The colorimetry of styrene-butadiene polymer and low cis polybutadiene rubber was measured using a LICO620 colorimeter with a colorimeter tube diameter of 11 mm. In particular, for styrene-butadiene polymer, it is necessary to first prepare it into a 5% styrene solution.

[0110] (6) ABS performance

[0111] The notched impact strength of simply supported beams was determined according to the method specified in GB / T1043.1-2008;

[0112] The tensile yield strength was determined according to the method specified in GB / T1040.2-2006;

[0113] The Vicat softening temperature was determined according to the method specified in GB / T1633-2000;

[0114] The melt flow index was determined according to the standard specified in GB / T3682.1-2018, with a nominal load of 10 kg and a test temperature of 220℃.

[0115] Gloss was determined according to the method specified in GB / T8807-1988.

[0116] Examples 1-7 illustrate the styrene-butadiene polymer and its preparation method provided by the present invention.

[0117] Example 1

[0118] (1) The 5L reactor was purged with high-purity argon gas multiple times until the oxygen content of the entire reaction system was below 5ppm; in the presence of an initiator and a structure modifier, the first portion of styrene underwent a first polymerization reaction in a non-polar solvent to obtain a polymer solution I containing polystyrene blocks (PS); wherein:

[0119] The types and quantities of each raw material are shown in Table 1;

[0120] The first polymerization reaction is an anionic solution polymerization reaction; the conditions for the first polymerization reaction are shown in Table 2.

[0121] (2) Butadiene and the second portion of styrene are contacted with polymer solution I to carry out a second polymerization reaction, yielding polymer solution II containing PS-SSBR; wherein:

[0122] The types and quantities of each raw material are shown in Table 1;

[0123] The second polymerization reaction is an anionic solution polymerization reaction; the conditions for the second polymerization reaction are shown in Table 2.

[0124] (3) The polymer solution II was contacted with a terminator to terminate the reaction. Then, an antioxidant was added to the styrene-butadiene polymer solution obtained from the termination reaction, and finally the solvent was removed to obtain styrene-butadiene polymer P1. The structure and properties of the obtained polymer were determined, and the results are shown in Table 3; where:

[0125] The terminating agent is an aqueous solution of carbon dioxide, and the dosage is shown in Table 2.

[0126] The antioxidant is a mixture of antioxidant 1520 and antioxidant 1076, wherein the weight ratio of antioxidant 1520 to antioxidant 1076 is 1:1; the weight ratio of the amount of antioxidant to the amount of styrene-butadiene polymer is 0.2:100.

[0127] The contact conditions were: contact temperature 60℃; contact pressure 0.2MPa; and contact time 0.25h.

[0128] Examples 2-7

[0129] Following the method of Example 1, with the differences shown in Tables 1 and 2, and the rest being the same, styrene-butadiene polymers P2 to P7 were obtained respectively. The structure and properties of the obtained polymers were determined, and the results are shown in Table 3.

[0130] Comparative Example 1

[0131] Following the method of Example 1, except that the first portion of styrene in step (1) and the second portion of styrene in step (2) were added simultaneously, while the rest were the same, a styrene-butadiene polymer DP1 was obtained. This styrene-butadiene polymer was dried into a powder and could not be granulated or molded. The structure and properties of the obtained polymer were determined, and the results are shown in Table 4.

[0132] Comparative Example 2

[0133] Following the method of Example 1, except for the amounts of styrene in the first and second portions (see Table 1), all other parameters remained the same, resulting in a styrene-butadiene polymer DP2. This styrene-butadiene polymer, after drying, was a powder and could not be granulated or molded. The structure and properties of the obtained polymer were determined, and the results are shown in Table 4.

[0134] Comparative Example 3

[0135] Following the method of Example 1, except for the amount of styrene in the first and second portions (see Table 1), the rest were the same, and styrene-butadiene polymer DP3 was obtained. The structure and properties of the obtained polymer were determined, and the results are shown in Table 4.

[0136] Comparative Example 4

[0137] Following the method of Example 1, except for the amount of styrene and butadiene added in the second part (see Table 1), all other parameters were the same, and styrene-butadiene polymer DP4 was obtained. The structure and properties of the obtained polymer were determined, and the results are shown in Table 4.

[0138] Comparative Example 5

[0139] Following the method of Example 1, except for the amount of initiator added (see Table 1), all other parameters were the same, and styrene-butadiene polymer DP5 was obtained. The structure and properties of the obtained polymer were determined, and the results are shown in Table 4.

[0140] Table 1 (All amounts listed in the table are based on pure compounds)

[0141]

[0142] Note: CYH is cyclohexane, THF is tetrahydrofuran, DOX is dioxane, Li is n-butyllithium, St1 is part 1 styrene, St2 is part 2 styrene, and Bd is butadiene.

[0143] Table 2

[0144] project T1 T2 P1 P2 t1 t2 <![CDATA[CO2]]> unit ℃ ℃ MPa MPa min min mmol Example 1 50 120 0.3 0.3 8 50 2.1 Example 2 50 120 0.3 0.3 10 50 2.1 Example 3 60 110 0.4 0.4 5 55 2.1 Example 4 70 100 0.3 0.3 5 60 2.2 Example 5 50 120 0.3 0.3 8 50 1.9 Example 6 50 120 0.3 0.3 8 50 2.2 Example 7 80 150 0.3 0.3 8 50 2.1 Comparative Example 1 120 / 0.3 / 60 / 2.1 Comparative Example 2 50 120 0.3 0.3 8 50 2.1 Comparative Example 3 50 120 0.3 0.3 8 50 2.1 Comparative Example 4 50 120 0.3 0.3 8 50 2.1 Comparative Example 5 50 120 0.3 0.3 8 50 2.1

[0145] Note: T1 is the polymerization temperature of the first polymerization reaction, T2 is the polymerization temperature of the second polymerization reaction, P1 is the polymerization pressure of the first polymerization reaction, P2 is the polymerization pressure of the second polymerization reaction, t1 is the polymerization time of the first polymerization reaction, and t2 is the polymerization time of the second polymerization reaction.

[0146] Table 3

[0147] project P1 P2 P3 P4 P5 P6 P7 St,% 31.2 31.2 31.1 30.1 25.6 34.6 31.3 St-block, % 23.1 23.6 22.7 23.6 20.2 26.3 20.6 St-non-block, % 8.1 7.6 8.4 6.5 5.4 8.3 10.7 PS, % 4.8 4.0 3.2 5.9 4.1 3.2 4.8 SSBR, % 95.2 96.0 96.8 94.1 95.9 96.8 95.2 Bd, % 68.8 68.8 68.9 69.9 74.4 65.4 68.7 Bv, % 11.8 10.2 11.3 10.8 11.6 11.0 14.4 <![CDATA[MP1 / 10 4 ]]> 32.7 32.4 32.8 30.2 32.3 30.7 36.5 A1，％ 8.4 8.8 6.6 5.1 8.6 8.2 18.9 <![CDATA[MP2 / 10 4 ]]> 16.3 16.2 16.4 15.1 16.1 15.3 18.1 A2，％ 91.6 91.2 95.4 94.9 91.4 91.8 81.1 Mw / Mn 1.14 1.13 1.11 1.08 1.14 1.12 1.28 gel, ppm 32 28 46 34 42 37 133 Sv, cp 30.2 30.4 29.1 31.8 36.7 21.2 37.8 APHA 5 5 5 5 7 5 10

[0148] Note: St represents the content of styrene structural units in the styrene-butadiene polymer (SBR), St-block represents the content of styrene blocks, St-non-block represents the content of styrene non-blocks, PS represents the content of polystyrene blocks, SSBR represents the content of butadiene-styrene copolymer, Bd represents the content of butadiene structural units in the SBR, Bv represents the vinyl content, MP1 represents the peak molecular weight of the high molecular weight fraction, MP2 represents the peak molecular weight of the low molecular weight fraction, A1 represents the proportion of the high molecular weight fraction to the total polymer, A2 represents the proportion of the low molecular weight fraction to the total polymer, Mw / Mn represents the molecular weight distribution of the SBR, gel represents the gel content of the SBR, Sv represents the viscosity of a 5% by weight styrene solution of the SBR at 25°C, and APHA represents the color of the SBR.

[0149] Table 4

[0150] DP1 DP2 DP3 DP4 DP5 St,% 31.2 31.2 31.3 20.1 31.2 St-block, % 21.7 22.2 25.9 16.1 21.7 St-non-block, % 9.5 9.0 5.4 5.0 9.5 PS, % 0 1.1 10.7 4.8 4.8 SSBR, % 100 98.9 89.3 95.2 95.2 Bd, % 68.8 68.8 68.7 79.9 68.8 Bv, % 11.6 11.5 11.6 11.9 9.8 <![CDATA[MP1 / 10 4 ]]> 32.2 32.4 32.6 32.1 20.6 A1，％ 8.8 8.5 8.6 9.2 9.5 <![CDATA[MP2 / 10 4 ]]> 16.1 16.2 16.3 16.0 10.3 A2，％ 91.2 91.5 91.4 90.8 90.5 Mw / Mn 1.15 1.14 1.14 1.15 1.15 gel, ppm 226 214 48 68 44 Sv, cp 26.8 27.3 34.6 42.8 12.8 APHA 10 10 7 10 15

[0151] Note: The definitions of each item are the same as in Table 3.

[0152] Preparation Examples 1-7 (for illustrating the toughening agent compositions provided by the present invention)

[0153] The styrene-butadiene polymers prepared in Examples 1-7 were used to form toughening agent compositions with low-cis polybutadiene rubber in a 1:1 weight ratio, and these compositions were designated as Z1-Z7.

[0154] Comparative preparation examples 1-5

[0155] Styrene-butadiene polymers prepared using Comparative Examples 1-5 were combined with low-cis polybutadiene rubber at a weight ratio of 1:1 to form toughening agent compositions, denoted as DZ1-DZ5 respectively.

[0156] Application Examples 1-7 are used to illustrate the ABS resin and its preparation method provided by the present invention.

[0157] Application Example 1

[0158] 100g of toughening agent composition Z1, 150g of ethylbenzene, 650g of styrene, and 250g of acrylonitrile were mixed and fully dissolved. 40g of mineral oil (provided by Beijing Yanshan Petrochemical Company Chemical Plant No. 1, density 0.86g / mL, the same below) and 0.3g of peroxy-2-ethylhexyl tert-butyl carbonate were added and mixed. The mixture was polymerized at a stirring rate of 400rpm and a polymerization temperature of 105℃ for 2h, and then the temperature was raised to 120℃ for 2h. The mixture was then polymerized at a stirring rate of 150rpm and a temperature of 150℃ for 4h. The reaction product was then subjected to vacuum flash evaporation to remove unreacted monomers and solvents, yielding ABS resin A1. The structural and performance analysis results are shown in Table 5.

[0159] Application Example 2-7

[0160] Following the method of Application Example 1, except that toughening agent compositions Z2-Z7 were used instead of Z1, and the reaction products were subjected to vacuum flash evaporation to remove unreacted monomers and solvents, respectively, to obtain ABS resins A2-A7. The structural and performance analysis test results are shown in Table 5.

[0161] Compare and contrast examples 1-5

[0162] Following the method of Application Example 1, except that toughening agent compositions DZ1-DZ5 were used instead of Z1, and the reaction products were subjected to vacuum flash evaporation to remove unreacted monomers and solvents, respectively, to obtain ABS resins DA1-DA5. The structural and performance analysis test results are shown in Table 5.

[0163] Table 5

[0164] ABS number MI, g / 10min VST, ℃ TYS, MPa <![CDATA[CIS,KJ / m 2 ]]> Gloss (60°) A1 25.7 94.5 43.1 18.8 96 A2 25.5 94.7 43.1 18.9 94 A3 25.7 94.5 42.7 18.2 93 A4 25.6 94.5 43.0 17.8 94 A5 22.4 94.2 42.6 19.2 82 A6 27.4 94.1 42.4 17.5 97 A7 21.7 94.0 42.5 18.2 80 DA1 24.8 93.2 42.4 18.1 74 DA2 25.1 93.8 42.6 17.9 76 DA3 22.6 94.0 43.1 16.4 77 DA4 18.7 94.1 42.9 18.4 68 DA5 29.8 93.4 41.8 15.9 88

[0165] Note: MI is melt flow index, VST is Vicat softening point, TYS is tensile yield strength, CIS is notched impact strength of simply supported beam, and Gloss is gloss.

[0166] As can be seen from the results in Table 3, the styrene-butadiene polymers prepared in Examples 1-7 have low gel content, low APHA color, and suitable solution viscosity.

[0167] As can be seen from the data in Table 5, the styrene-butadiene polymers prepared in Examples 1-7, when combined with low-cis polybutadiene rubber to form a toughening agent composition, result in ABS resins with better overall performance after being toughened by the toughening agent composition.

[0168] 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.

[0169] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0170] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A styrene-butadiene polymer, characterized in that, The styrene-butadiene polymer has the structure shown in PS-SSBR; wherein PS is a polystyrene block; SSBR is a butadiene-styrene copolymer, comprising polybutadiene microblocks, styrene-butadiene random polymer blocks and polystyrene microblocks; Based on the total weight of the styrene-butadiene polymer, the content of the polystyrene block in the styrene-butadiene polymer is 2-10% by weight; the content of the butadiene-styrene copolymer is 90-98% by weight. The viscosity of the 5% by weight styrene solution of the styrene-butadiene polymer at 25°C is 20-40 centipoise. The styrene-butadiene polymer is prepared by a method comprising the following steps: (1) In the presence of an initiator and a structure modifier, the first part of styrene is subjected to a first polymerization reaction in a non-polar solvent to obtain a polymer solution I containing polystyrene blocks PS; (2) Butadiene and the second portion of styrene are contacted with the polymer solution I to carry out a second polymerization reaction to obtain a polymer solution II containing PS-SSBR; (3) The polymer solution II is contacted with a terminating agent to terminate the reaction; Wherein, the first polymerization reaction and the second polymerization reaction are each anionic solution polymerization reaction independently; the weight ratio of the amount of the first part of styrene in step (1) to the amount of the second part of styrene in step (2) is 0.05-0.5:1; the weight ratio of the amount of butadiene to the total amount of the first part of styrene and the second part of styrene is 1.8-3:1; based on the total amount of the butadiene, the first part of styrene and the second part of styrene, the amount of the initiator is 0.5-0.8 mmol / 100g.

2. The styrene-butadiene polymer according to claim 1, wherein, Based on the total weight of the styrene-butadiene polymer, the content of the polystyrene block in the styrene-butadiene polymer is 2-8% by weight; and the content of the butadiene-styrene copolymer is 92-98% by weight.

3. The styrene-butadiene polymer according to claim 2, wherein, Based on the total weight of the styrene-butadiene polymer, the content of the polystyrene block in the styrene-butadiene polymer is 3-6% by weight; and the content of the butadiene-styrene copolymer is 94-97% by weight.

4. The styrene-butadiene polymer according to claim 1, wherein, Based on the total weight of the styrene-butadiene polymer, the styrene structural unit content in the styrene-butadiene polymer is 25-35% by weight, and the butadiene structural unit content is 65-75% by weight.

5. The styrene-butadiene polymer according to any one of claims 1-4, wherein, The styrene-butadiene polymer contains 18-27 wt% styrene blocks, wherein the styrene blocks are styrene structural units consisting of six or more consecutive styrene units in the styrene-butadiene polymer molecular chain.

6. The styrene-butadiene polymer according to any one of claims 1-4, wherein, The styrene-butadiene polymer contains 5-11 wt% non-block styrene.

7. The styrene-butadiene polymer according to any one of claims 1-4, wherein, The molecular weight of the styrene-butadiene polymer exhibits a bimodal distribution.

8. The styrene-butadiene polymer according to claim 7, wherein, The molecular weight of the first peak is 280,000-380,000.

9. The styrene-butadiene polymer according to claim 8, wherein, The molecular weight of the first peak is 300,000-360,000.

10. The styrene-butadiene polymer according to claim 7, wherein, The molecular weight of the second peak is 140,000-190,000.

11. The styrene-butadiene polymer according to claim 10, wherein, The molecular weight of the second peak is 150,000-180,000.

12. The styrene-butadiene polymer according to claim 7, wherein, Based on the total weight of the styrene-butadiene polymer, the content of the first peak is 5-20% by weight.

13. The styrene-butadiene polymer according to claim 7, wherein, Based on the total weight of the styrene-butadiene polymer, the content of the second peak is 80-95% by weight.

14. The styrene-butadiene polymer according to claim 7, wherein, The molecular weight distribution of the styrene-butadiene polymer is 1.05-1.

3.

15. The styrene-butadiene polymer according to claim 14, wherein, The molecular weight distribution of the styrene-butadiene polymer is 1.1-1.

2.

16. The styrene-butadiene polymer according to any one of claims 1-4, wherein, The vinyl content of the styrene-butadiene polymer is 8-16% by weight.

17. The styrene-butadiene polymer according to claim 16, wherein, The vinyl content of the styrene-butadiene polymer is 8-14% by weight.

18. The styrene-butadiene polymer according to any one of claims 1-4, wherein, Based on the total weight of the styrene-butadiene polymer, the gel content of the styrene-butadiene polymer is in the range of 0-200 ppm.

19. The styrene-butadiene polymer according to claim 18, wherein, Based on the total weight of the styrene-butadiene polymer, the gel content of the styrene-butadiene polymer is in the range of 0-150 ppm.

20. The styrene-butadiene polymer according to claim 19, wherein, Based on the total weight of the styrene-butadiene polymer, the gel content of the styrene-butadiene polymer is in the range of 0-100 ppm.

21. The styrene-butadiene polymer according to any one of claims 1-4, wherein, The APHA color of the styrene-butadiene polymer is ≤10.

22. The styrene-butadiene polymer according to claim 21, wherein, The APHA color of the styrene-butadiene polymer is ≤7.

23. The styrene-butadiene polymer according to claim 22, wherein, The APHA color of the styrene-butadiene polymer is ≤5.

24. A method for preparing the styrene-butadiene polymer according to any one of claims 1-23, characterized in that, The preparation method includes the following steps: (1) In the presence of an initiator and a structure modifier, the first part of styrene is subjected to a first polymerization reaction in a non-polar solvent to obtain a polymer solution I containing polystyrene blocks PS; (2) Butadiene and the second portion of styrene are contacted with the polymer solution I to carry out a second polymerization reaction to obtain a polymer solution II containing PS-SSBR; (3) The polymer solution II is contacted with a terminating agent to terminate the reaction; Wherein, the first polymerization reaction and the second polymerization reaction are each anionic solution polymerization reaction independently; the weight ratio of the amount of the first part of styrene in step (1) to the amount of the second part of styrene in step (2) is 0.05-0.5:1; the weight ratio of the amount of butadiene to the total amount of the first part of styrene and the second part of styrene is 1.8-3:1; based on the total amount of the butadiene, the first part of styrene and the second part of styrene, the amount of the initiator is 0.5-0.8 mmol / 100g.

25. The method according to claim 24, wherein, The weight ratio of the amount of styrene used in the first part in step (1) to the amount of styrene used in the second part in step (2) is 0.06-0.26:

1.

26. The method of claim 25, wherein, The weight ratio of the amount of styrene used in the first part in step (1) to the amount of styrene used in the second part in step (2) is 0.08-0.2:

1.

27. The preparation according to claim 24, wherein, The weight ratio of the butadiene used to the total weight of the first and second portions of styrene is 2-2.6:

1.

28. The method according to any one of claims 24-27, wherein, In step (1), the conditions for the first polymerization reaction include: polymerization temperature of 40-80℃; polymerization pressure of 0.1-1MPa; and polymerization time of 2-20min.

29. The method according to claim 28, wherein, The conditions for the first polymerization reaction include: polymerization temperature of 40-70℃; polymerization pressure of 0.2-0.5MPa; and polymerization time of 5-10min.

30. The method according to any one of claims 24-27, wherein, In step (2), the conditions for the second polymerization reaction include: polymerization temperature of 60-150℃; polymerization pressure of 0.1-1MPa; and polymerization time of 30-80min.

31. The method according to claim 30, wherein, The conditions for the second polymerization reaction include: polymerization temperature of 70-130℃; polymerization pressure of 0.2-0.5MPa; and polymerization time of 40-60min.

32. The method according to claim 31, wherein, The conditions for the second polymerization reaction include a polymerization temperature of 90-130℃.

33. The method according to any one of claims 24-27, wherein, In step (1), the initiator is one or more of methyl lithium, isopropyl lithium, sec-butyl lithium, n-butyl lithium, cyclohexyl lithium, 4-cyclohexylbutyl lithium, phenyl lithium, triphenylmethyl lithium and 2-naphthyl lithium.

34. The method according to claim 33, wherein, The initiator is n-butyllithium and / or sec-butyllithium.

35. The method according to any one of claims 24-27, wherein, In step (1), the amount of the initiator is 0.5-0.8 mmol / 100g, based on the total amount of butadiene, the first portion of styrene and the second portion of styrene.

36. The method according to any one of claims 24-27, wherein, In step (1), the structure modifier is one or more of ether compounds, amine compounds and alkali metal alkoxy compounds.

37. The method of claim 36, wherein, The structure modifier is one or more of tetrahydrofuran, dioxane, diethyl ether, and triethylamine.

38. The method according to any one of claims 24-27, wherein, In step (1), the amount of the structure modifier is 50-500 mg / kg, based on the amount of the nonpolar solvent.

39. The method according to any one of claims 24-27, wherein, In step (3), the terminating agent is an aqueous solution of carbon dioxide or a fatty acid.

40. The method according to claim 39, wherein, The terminating agent is an aqueous solution of carbon dioxide.

41. The method according to claim 39, wherein, Based on the total weight of 100 parts by weight of the reaction monomers, the amount of fatty acid used is 0.1-1 parts by weight; wherein, the total weight of the reaction monomers is the total amount of butadiene, the first portion of styrene and the second portion of styrene.

42. The method according to claim 39, wherein, Based on the total weight of 100 parts by weight of the reactants, the amount of fatty acids used is 0.2-0.5 parts by weight.

43. The method according to claim 40, wherein, Based on 1 mol of the initiator, the amount of the aqueous carbon dioxide solution used is 0.5-1.5 mol.

44. The method according to claim 39, wherein, The fatty acid is one or more of adipic acid, sebacic acid, stearic acid, malic acid, citric acid, and tartaric acid.

45. The method according to claim 44, wherein, The fatty acid is citric acid.

46. ​​The method according to any one of claims 24-27, wherein, Step (3) further includes: removing the solvent from the styrene-butadiene polymer solution obtained from the termination reaction.

47. The method according to any one of claims 24-27, wherein, Step (3) further includes contacting the styrene-butadiene polymer solution obtained from the termination reaction with an antioxidant.

48. The method according to claim 47, wherein, The antioxidant is a mixture of antioxidant 1520 and antioxidant 1076.

49. The method according to claim 48, wherein, In the mixture, the weight ratio of antioxidant 1520 to antioxidant 1076 is 0.5-2:

1.

50. The method of claim 47, wherein, The weight ratio of the antioxidant to the styrene-butadiene polymer is 0.2-0.4:

100.

51. A toughening agent composition, characterized in that, The toughening agent composition contains a styrene-butadiene polymer and low-cis polybutadiene rubber, wherein the styrene-butadiene polymer is the styrene-butadiene polymer according to any one of claims 1-23.

52. The toughening agent composition according to claim 51, wherein, The Mooney viscosity of the low-cis polybutadiene rubber is 32-52; the viscosity of the low-cis polybutadiene rubber in a 5% by weight styrene solution at 25°C is 20-40 centipoise.

53. The toughening agent composition according to claim 51 or 52, wherein, The weight ratio of the low-cis polybutadiene rubber to the styrene-butadiene polymer is 0.4-5:

1.

54. The toughening agent composition according to claim 53, wherein, The weight ratio of the low-cis polybutadiene rubber to the styrene-butadiene polymer is 0.4-4:

1.

55. The toughening agent composition according to claim 54, wherein, The weight ratio of the low-cis polybutadiene rubber to the styrene-butadiene polymer is 0.43-2.3:

1.

56. The toughening agent composition according to claim 55, wherein, The weight ratio of the low-cis polybutadiene rubber to the styrene-butadiene polymer is 0.67-1.5:

1.

57. An ABS resin, characterized in that, The ABS resin is prepared from the toughening agent composition according to any one of claims 51-56.

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