Conjugated diene polymer with multi-arm star-shaped structure as well as preparation method and application of conjugated diene polymer

Abstract

The invention relates to the field of polymer synthesis, and discloses a conjugated diene polymer with a multi-arm star-shaped structure as well as a preparation method and application thereof. The preparation method comprises the following steps: (1) in the presence of an inert solvent and a lithium-containing initiator, carrying out polymerization reaction on a conjugated diene monomer and a monovinyl aromatic hydrocarbon monomer to obtain a product system; and (2) carrying out coupling reaction on the product system and an additive containing a mixed coupling agent to obtain the conjugated diene polymer with a multi-arm star-shaped structure, wherein the mixed coupling agent comprises a star-shaped coupling agent and a linear coupling agent. The prepared conjugated diene polymer is high in molecular weight and wide in molecular weight distribution, the number-average molecular weight of the solution polymerized styrene-butadiene rubber prepared by the method is 150,000-24,000 g / mol, the molecular weight is in trimodal distribution, the molecular weight distribution is 1.6-2, and the solution polymerized styrene-butadiene rubber has improved processability and higher vulcanized rubber strength.

Description

Technical Field

[0001] This invention relates to the field of polymer synthesis, specifically to a conjugated diene polymer with a multi-arm star structure, its preparation method, and its applications. Background Technology

[0002] Styrene-butadiene rubber (SBR) is a random copolymer of butadiene and styrene, and can be divided into two main categories: emulsion SBR and solution SBR. Emulsion SBR is mostly synthesized using free radical polymerization, while solution SBR is mostly synthesized using anionic polymerization. Solution SBR exhibits good wet skid resistance, low rolling resistance, and good wear resistance, making it a promising candidate for applications in high-performance green tires and other fields.

[0003] One method for synthesizing star-shaped solution-polymerized styrene-butadiene rubber is to utilize the characteristics of anionic active polymerization. After polymerization, a coupling agent that can react with the active center is added to carry out a coupling reaction to generate a star-shaped polymer. Another method is to use a multifunctional initiator system to initiate monomer polymerization. However, the synthesis of multifunctional initiators is relatively difficult, and it is also difficult to ensure that the initiation efficiency of each initiation site remains consistent. Therefore, this method has poor control over parameters such as the molecular weight and molecular weight distribution of the polymer arm.

[0004] Solution-polymerized styrene-butadiene rubber (SBR) prepared using coupling technology can effectively reduce the number of "free ends," lower rolling resistance, and improve the material's processing properties, thereby further enhancing the various properties of solution-polymerized SBR. Currently, tin tetrachloride is commonly used as the coupling agent, but it has a relatively small number of coupling arms. Summary of the Invention

[0005] This invention addresses the problems of narrow molecular weight distribution and unsatisfactory post-processing properties in existing conjugated diene polymers, especially solution-polymerized styrene-butadiene rubber. It provides a conjugated diene polymer with a multi-arm star structure, its preparation method, and its applications.

[0006] To achieve the above objectives, a first aspect of the present invention provides a method for preparing a conjugated diene polymer having a multi-arm star structure, comprising:

[0007] (1) In the presence of an inert solvent and a lithium-containing initiator, a conjugated diene monomer and a monovinyl aromatic monomer are polymerized to obtain the product system;

[0008] (2) The product system is coupled with an additive containing a mixed coupling agent to obtain a conjugated diene polymer with a multi-arm star structure.

[0009] The mixed coupling agent includes a star-shaped coupling agent and a linear coupling agent;

[0010] The star-shaped coupling agent has the structure shown in formula (Ⅰ).

[0011] (A) a -[SiO 3 / 2 ] m -(X) b Equation (Ⅰ);

[0012] In equation (Ⅰ), m is an even number not less than 6;

[0013] In formula (Ⅰ), A is an epoxy-terminated group connected to Si, a is an integer, and 3≤a≤m;

[0014] In formula (Ⅰ), X is any non-reactive end-capping group connected to Si, and b = ma;

[0015] The linear coupling agent has the structure shown in formula (II).

[0016] Z-[(D)2SiO] n -Si(D)2-Z formula (Ⅱ);

[0017] In equation (II), n is an integer and n≥1;

[0018] In formula (II), D is any non-reactive end-capping group connected to Si;

[0019] In formula (II), Z is an epoxy-terminated group connected to Si.

[0020] The second aspect of the present invention provides a conjugated diene polymer having a multi-armed star structure prepared by the method described in the first aspect above.

[0021] The third aspect of this invention provides the application of the conjugated diene polymer with a multi-arm star structure described in the second aspect above in tire manufacturing.

[0022] Through the above technical solution, the method provided by this invention can prepare conjugated diene polymers with multi-arm star structures. Compared with traditional two-arm or four-arm coupled conjugated diene polymers, under the premise that the molecular weight of the pre-coupling polymerization product (the product after polymerization of the conjugated diene monomer and the monovinyl aromatic monomer) is comparable, the conjugated diene polymer prepared by the method of this invention has a higher molecular weight, a wider molecular weight distribution, and a trimodal molecular weight distribution. Furthermore, the method provided by this invention is particularly suitable for preparing solution-polymerized styrene-butadiene rubber with a multi-arm star structure. The number-average molecular weight of the obtained solution-polymerized styrene-butadiene rubber is 150,000-240,000 g / mol, which is significantly higher than that of traditional two-arm or four-arm coupled solution-polymerized styrene-butadiene rubber. The molecular weight distribution is trimodal, with a molecular weight distribution of 1.6-2, resulting in significantly improved processing performance and vulcanized rubber strength. Detailed Implementation

[0023] 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.

[0024] The first aspect of this invention provides a method for preparing a conjugated diene polymer having a multi-arm star structure, comprising:

[0025] (1) In the presence of an inert solvent and a lithium-containing initiator, a conjugated diene monomer and a monovinyl aromatic monomer are polymerized to obtain the product system;

[0026] (2) The product system is coupled with an additive containing a mixed coupling agent to obtain a conjugated diene polymer with a multi-arm star structure.

[0027] The mixed coupling agent includes a star-shaped coupling agent and a linear coupling agent;

[0028] The star-shaped coupling agent has the structure shown in formula (Ⅰ).

[0029] (A) a -[SiO 3 / 2 ] m -(X) b Equation (Ⅰ);

[0030] In equation (Ⅰ), m is an even number not less than 6;

[0031] In formula (Ⅰ), A is an epoxy-terminated group connected to Si, a is an integer, and 3≤a≤m;

[0032] In formula (Ⅰ), X is any non-reactive end-capping group connected to Si, and b = ma;

[0033] The linear coupling agent has the structure shown in formula (II).

[0034] Z-[(D)2SiO] n -Si(D)2-Z formula (Ⅱ);

[0035] In equation (II), n is an integer and n≥1;

[0036] In formula (II), D is any non-reactive end-capping group connected to Si;

[0037] In formula (II), Z is an epoxy-terminated group connected to Si.

[0038] This invention involves first subjecting a conjugated diene monomer and a monovinyl aromatic monomer to a living anionic polymerization reaction, and then coupling the polymerization product with a specific mixed coupling agent to obtain a conjugated diene polymer with a multi-arm star structure. The obtained conjugated diene polymer has the characteristics of high molecular weight, wide molecular weight distribution, and a three-peak molecular weight distribution.

[0039] According to the present invention, in the method for preparing a conjugated diene polymer having a multi-arm star structure, the conjugated diene monomer is broadly defined and may be selected from butadiene, isoprene, 1,3-pentadiene, 1,3-hexadiene, or 2,3-dimethylbutadiene, etc.

[0040] According to the present invention, in the method for preparing a conjugated diene polymer having a multi-arm star structure, the limitation on the monovinyl aromatic monomer is relatively broad, and it can be selected from, but is not limited to, styrene, p-vinyltoluene, o-vinyltoluene, m-vinyltoluene, α-methylstyrene, 4-tert-butylstyrene, 3,5-diethylstyrene, 3,5-di-n-butylstyrene, 4-n-propylstyrene, or 4-dodecylstyrene.

[0041] According to the present invention, the method provided by the present invention can be used to prepare solution-polymerized styrene-butadiene rubber with a multi-arm star structure using butadiene monomer, styrene monomer and the above-mentioned mixed coupling agent. The solution-polymerized styrene-butadiene rubber obtained has a number-average molecular weight of 150,000-240,000 g / mol and a three-peak molecular weight distribution with a molecular weight distribution of 1.6-2, which has significantly improved processing performance and vulcanized rubber strength.

[0042] According to the present invention, in the method for preparing a conjugated diene polymer with a multi-arm star structure, the molar ratio of the star-shaped coupling agent to the linear coupling agent in the mixed coupling agent is 1:(1-40), preferably 1:(1-20), which allows the prepared conjugated diene polymer to have a higher molecular weight and a wider molecular weight distribution. For solution-polymerized styrene-butadiene rubber with a multi-arm star structure prepared using this method, the above-mentioned coupling agent ratio allows the prepared solution-polymerized styrene-butadiene rubber to have a higher molecular weight and a wider molecular weight distribution, resulting in better processing performance and higher vulcanized rubber strength.

[0043] According to the present invention, in the method for preparing a conjugated diene polymer having a multi-arm star structure, the star coupling agent is a stereopolysilsesquioxane having the structure shown in formula (I), in formula (I), [SiO 3 / 2 [] represents the molar ratio of silicon atoms to oxygen atoms in the stereopolysilsesquioxane. In this invention, when m is an even number not greater than 12, the star-shaped coupling agent is a cage-type polysilsesquioxane.

[0044] According to the present invention, in the method for preparing a conjugated diene polymer having a multi-arm star structure, the star coupling agent, in addition to satisfying the structure shown in formula (I) above, preferably, in formula (I), m is selected from 8, 10 or 12; preferably, A is selected from epoxy alkyl or glycidyl ether alkyl, and a is selected from 7 or 8; preferably, X is selected from C1-C8 alkyl, C3-C8 cycloalkyl or C6-C 10 Aryl. The star-shaped coupling agent with the above-mentioned preferred structure can significantly increase the molecular weight of the polymer, resulting in a conjugated diene polymer with a wider molecular weight distribution. For solution-polymerized styrene-butadiene rubber (SBR) with a multi-arm star structure prepared by this method, the star-shaped coupling agent with the above-mentioned preferred structure can significantly increase the molecular weight of the solution-polymerized SBR, resulting in a wider molecular weight distribution and better dispersion of silica in the rubber, thus improving the processing properties of the solution-polymerized SBR.

[0045] According to the present invention, more preferably, in formula (Ⅰ), m is 8; A is glycidyl ether oxyalkyl, a is selected from 7 or 8; X is selected from methyl or phenyl.

[0046] According to the present invention, more preferably, the star-shaped coupling agent is selected from octaglycidyl etheroxypropyl polysilsesquioxane (structural formula...). ) or methyl heptahydrate oxypropyl polysilsesquioxane (structural formula) ).

[0047] According to the present invention, in the method for preparing a conjugated diene polymer having a multi-arm star structure, the linear coupling agent, in addition to satisfying the structure shown in formula (II) above, preferably, in formula (II), D is selected from C1-C8 alkyl, C3-C8 cycloalkyl, C6-C8 cycloalkyl, C7-C8 cycloalkyl, C8-C8 cycloalkyl, C9-C ... 10 aryl, C1-C8 alkoxy, C3-C8 cycloalkoxy, or C6-C 10 The aryloxy group has 1 ≤ n ≤ 10; preferably, Z is selected from epoxy alkyl or glycidyl ether alkyl. For solution-polymerized styrene-butadiene rubber with a multi-arm star structure prepared by this method, the use of the linear coupling agent with the above-mentioned preferred structure can improve the dispersion of silica in the rubber and enhance the processing performance of the solution-polymerized styrene-butadiene rubber.

[0048] According to the present invention, more preferably, in formula (II), D is selected from C1-C8 alkyl or C1-C8 alkoxy, n is 1; Z is glycidyl etheroxypropyl.

[0049] According to the present invention, more preferably, the linear coupling agent is glycidyl etheroxypropyl-terminated polydimethylsiloxane (C... 16 H 34 O5Si2, CAS: 102782-97-8).

[0050] According to a particularly preferred embodiment of the present invention, in the method for preparing a conjugated diene polymer with a multi-arm star structure, the molar ratio of the star coupling agent to the linear coupling agent is 1:(1-8), wherein the star coupling agent is octaglycidoxypropyl polysilsesquioxane, and the linear coupling agent is glycidoxypropyl-terminated polydimethylsiloxane. Using a mixed coupling agent with this particularly preferred composition allows the prepared conjugated diene polymer to have a further increased molecular weight and a wider molecular weight distribution. For the preparation of solution-polymerized styrene-butadiene rubber with a multi-arm star structure using this preferred embodiment, the prepared solution-polymerized styrene-butadiene rubber can have a further increased molecular weight and a wider molecular weight distribution, resulting in further improved processing properties and vulcanizate strength.

[0051] According to the present invention, in the method for preparing a conjugated diene polymer having a multi-arm star structure, in step (1), the polymerization reaction can be carried out in an environment and under conditions conventional in the art for the living anionic polymerization of conjugated diene monomers (e.g., butadiene) and monovinyl aromatic monomers (e.g., styrene), and the present invention has a wide range of limitations.

[0052] According to the present invention, in step (1), the inert solvent is broadly defined and can be selected from at least one of C5-C7 cycloalkanes, aromatics, and isoalkanes. Preferably, the inert solvent can be selected from at least one of n-hexane, cyclohexane, and cycloheptane. More preferably, the inert solvent is a mixed solvent formed by cyclohexane and n-hexane in a weight ratio of (0.1-10):1.

[0053] According to the present invention, in step (1), the lithium-containing initiator is broadly defined, and various organolithium initiators in the art capable of initiating living anionic polymerization reactions of conjugated diene monomers (e.g., butadiene) and monovinyl aromatic monomers (e.g., styrene) can be used. Specifically, the organolithium initiator can be selected from at least one of methyllithium, isopropyllithium, sec-butyllithium, n-butyllithium, cyclohexyllithium, 4-cyclohexylbutyllithium, phenyllithium, triphenylmethyllithium, and 2-naphthyllithium. Considering the solubility and storage stability of the organolithium initiator in solvents, preferably, the organolithium initiator is n-butyllithium and / or sec-butyllithium.

[0054] According to the present invention, in step (1), the amount of lithium-containing initiator is not particularly limited and can be the conventional amount in the art.

[0055] According to the present invention, in step (1), preferably, the weight ratio of the conjugated diene monomer to the monovinyl aromatic hydrocarbon is (1.5-9):1.

[0056] According to the present invention, in step (1), preferably, the polymerization reaction is carried out under a protective atmosphere.

[0057] According to the present invention, in step (1), the initiation temperature of the polymerization reaction can be selected in a conventional manner in the art. Preferably, the initiation temperature of the polymerization reaction is 20-60°C, which is beneficial for controlling the structure of the polymer chain during the polymerization reaction.

[0058] According to the present invention, in step (1), the polymerization reaction can also be carried out in the presence of a structure modifier. In the present invention, there are no particular limitations on the type and amount of the structure modifier; various conventional structure modifiers in the art and conventional amounts can be used, preferably ethyl tetrahydrofurfuryl ether.

[0059] Furthermore, as is known to those skilled in the art, trace amounts of water may be present in the inert solvent, conjugated diene monomer, and monovinyl aromatic hydrocarbon. Water is a terminator in anionic polymerization, capable of terminating chain growth reactions through proton transfer. Therefore, in this invention, to ensure the smooth progress of the polymerization reaction, it is preferable to remove water from the inert solvent, conjugated diene monomer, and monovinyl aromatic hydrocarbon monomer before the polymerization reaction. This dehydration can be achieved by adding a dehydrating agent. In this invention, the types of dehydrating agents are known to those skilled in the art, such as γ-alumina or 5A molecular sieves.

[0060] According to the present invention, in step (2), the molar ratio of the mixed coupling agent (based on the epoxy groups in the star-shaped coupling agent) to the lithium-containing initiator (based on the elemental lithium) is (0.8-1):1, preferably (0.9-1):1, which is more conducive to the formation of a multi-arm star structure.

[0061] According to the present invention, in step (2), preferably, the temperature of the coupling reaction is 40-70°C and the time is 15-40 min, which is more conducive to obtaining a higher coupling rate and coupling efficiency.

[0062] According to the present invention, in the method for preparing a conjugated diene polymer with a multi-arm star structure, for the preparation of solution-polymerized styrene-butadiene rubber with a multi-arm star structure, the additive may contain, in addition to the star-shaped coupling agent and the linear coupling agent, other conventional reagents used in the art for preparing solution-polymerized styrene-butadiene rubber, including but not limited to terminators, antioxidants, etc., and the selection and amount of these reagents can be conventionally selected in the art. Preferably, the terminator may be selected from alcohol and / or water; preferably, the antioxidant may be selected from at least one of antioxidant 1520, antioxidant 1076, antioxidant 1010 and antioxidant 264.

[0063] According to the present invention, in the method for preparing a conjugated diene polymer having a multi-arm star structure, the conversion rates of the conjugated diene monomer and the monovinyl aromatic hydrocarbon can be obtained by nuclear magnetic resonance (NMR) testing and calculation.

[0064] According to the present invention, in the method for preparing a conjugated diene polymer with a multi-arm star structure, after the coupling reaction is completed, the conjugated diene polymer product can be precipitated from the product system by purification precipitation, centrifugation, filtration, decantation or hot water coagulation, or the solvent in the product system can be removed by air stripping. All of the above treatments can be carried out by conventional means in the art, and will not be described in detail here.

[0065] The second aspect of the present invention provides a conjugated diene polymer having a multi-armed star structure prepared by the method described in the first aspect above.

[0066] According to the present invention, the conjugated diene polymer prepared by the method has a multi-arm star structure and is characterized by high molecular weight, wide molecular weight distribution and trimodal molecular weight distribution.

[0067] According to the present invention, preferably, the conjugated diene polymer is a solution-polymerized styrene-butadiene rubber (SBR) having a multi-arm star structure. Based on the total weight of the solution-polymerized SBR, the content of styrene structural units in the solution-polymerized SBR is 10-40%, and the content of vinyl structural units is 60-90%.

[0068] According to the present invention, the solution-polymerized styrene-butadiene rubber with a multi-arm star structure has a number-average molecular weight of 150,000-240,000 g / mol and a three-peak molecular weight distribution of 1.6-2, exhibiting excellent processing performance and high vulcanized rubber strength.

[0069] The third aspect of this invention provides the application of the conjugated diene polymer with a multi-arm star structure described in the second aspect above in tire manufacturing.

[0070] The conjugated diene polymer provided by this invention, particularly solution-polymerized styrene-butadiene rubber with a multi-arm star structure, has significantly improved processing performance and vulcanized rubber strength. As a raw material, it can be better used in the production of high-performance tires, improving the mechanical properties and wear resistance of tires.

[0071] The present invention will be described in detail below through examples. Unless otherwise specified, all raw materials used in the following embodiments and comparative examples are commercially available products.

[0072] In the following examples and comparative examples, peak temperature refers to the highest temperature measured during the polymerization reaction.

[0073] In the following examples and comparative examples, the monomer conversion rate is calculated using the formula: (initially added monomer weight - remaining monomer weight after reaction) / initially added monomer weight, where monomer refers to styrene monomer or butadiene monomer.

[0074] In the following examples and comparative examples, the number-average molecular weight and molecular weight distribution of the polymer (specifically solution rubber) were determined using a Shimadzu LC-10AT gel permeation chromatography (GPC) instrument, with tetrahydrofuran as the mobile phase, narrow-distribution PS as the standard, and the test temperature at 40°C.

[0075] In the following examples and comparative examples, the inert solvent, butadiene monomer, and styrene monomer were all soaked in 5A molecular sieve (molecular sieve balls φ3-5mm, purchased from Dalian Kangyu Chemical Co., Ltd., and pre-dried at 500℃ for 5h) for one week before feeding.

[0076] Example 1

[0077] Under nitrogen protection, 2500g of mixed solvent (cyclohexane to n-hexane weight ratio of 88:12), 70g of styrene, 210g of butadiene, and 1.5mL of structure modifier ethyl tetrahydrofurfuryl ether were added to a 5L polymerization reactor. The system was heated to 40℃, and 40mL of n-butyllithium solution (concentration of n-butyllithium was 0.1437mol / L) was added. The reaction reached a peak temperature of 71℃ after 15min, and the conversion rate was measured to be 100% 5min after reaching the peak temperature. After the system temperature reached 45℃, a mixed coupling agent was added to the reactor: 0.2043g of octaglycidoxypropyl polysilsesquioxane (molecular weight of 1337.9g / mol) and 0.4429g of glycidoxypropyl-terminated polydimethylsiloxane (molecular weight of 362.6g / mol). The coupling reaction was carried out at 45℃ for 30min, and then 0.5mL of isopropanol was added to terminate the reaction. After stirring for 10 minutes, add 2.24g of antioxidant 264. After the rubber solution is condensed by water vapor, it is dried on a two-roll mill to obtain solution-polymerized styrene-butadiene rubber (denoted as P1).

[0078] The number-average molecular weight and molecular weight distribution of P1 are shown in Table 1.

[0079] Example 2

[0080] Under nitrogen protection, 2500g of mixed solvent (cyclohexane to n-hexane weight ratio of 88:12), 70g of styrene, 210g of butadiene, and 1.5mL of structure modifier ethyl tetrahydrofurfuryl ether were added to a 5L polymerization reactor. The system was heated to 40℃, and 40mL of n-butyllithium solution (concentration of n-butyllithium was 0.1437mol / L) was added. The reaction reached a peak temperature of 68℃ after 16 minutes, and the conversion rate was measured to be 100% 5 minutes after reaching the peak temperature. After the system temperature reached 45℃, a mixed coupling agent was added to the reactor: 0.4903g ​​of octaglycidoxypropyl polysilsesquioxane (molecular weight of 1337.9g / mol) and 0.1329g of glycidoxypropyl-terminated polydimethylsiloxane (molecular weight of 362.6g / mol). The coupling reaction was carried out at 45℃ for 30 minutes, and then 0.5mL of isopropanol was added to terminate the reaction. After stirring for 10 minutes, add 2.24g of antioxidant 264. After the rubber solution is condensed by water vapor, it is dried on a two-roll mill to obtain solution-polymerized styrene-butadiene rubber (denoted as P2).

[0081] The number-average molecular weight and molecular weight distribution of P2 are shown in Table 1.

[0082] Example 3

[0083] Under nitrogen protection, 2500g of mixed solvent (cyclohexane to n-hexane weight ratio of 88:12), 70g of styrene, 210g of butadiene, and 1.5mL of structure modifier ethyl tetrahydrofurfuryl ether were added to a 5L polymerization reactor. The system was heated to 40℃, and 40mL of n-butyllithium solution (concentration of n-butyllithium was 0.1437mol / L) was added. The reaction reached a peak temperature of 75℃ after 13 minutes, and the conversion rate was measured to be 100% 5 minutes after reaching the peak temperature. After the system temperature reached 45℃, a mixed coupling agent was added to the reactor: 0.0557g of octaglycidoxypropyl polysilsesquioxane (molecular weight of 1337.9g / mol) and 0.6040g of glycidoxypropyl-terminated polydimethylsiloxane (molecular weight of 362.6g / mol). The coupling reaction was carried out at 45℃ for 30 minutes, and then 0.5mL of isopropanol was added to terminate the reaction. After stirring for 10 minutes, add 2.24g of antioxidant 264. The rubber solution is then condensed by steam and dried on a two-roll mill to obtain solution-polymerized styrene-butadiene rubber (denoted as P3).

[0084] The number-average molecular weight and molecular weight distribution of P3 are shown in Table 1.

[0085] Example 4

[0086] Under nitrogen protection, 2500g of mixed solvent (cyclohexane and n-hexane weight ratio of 88:12), 112g of styrene, 168g of butadiene, and 1.5mL of structure modifier ethyl tetrahydrofurfuryl ether were added to a 5L polymerization reactor. The system was heated to 40℃, and 40mL of n-butyllithium solution (concentration of n-butyllithium was 0.1437mol / L) was added. The reaction reached a peak temperature of 67℃ after 16 minutes, and the conversion rate was measured to be 100% 5 minutes after reaching the peak temperature. After the system temperature reached 45℃, a mixed coupling agent was added to the reactor: 0.2043g of octaglycidoxypropyl polysilsesquioxane (molecular weight of 1337.9g / mol) and 0.4429g of glycidoxypropyl-terminated polydimethylsiloxane (molecular weight of 362.6g / mol). The coupling reaction was carried out at 45℃ for 30 minutes, and then 0.5mL of isopropanol was added to terminate the reaction. After stirring for 10 minutes, add 2.24g of antioxidant 264. The rubber solution is then condensed by steam and dried on a two-roll mill to obtain solution-polymerized styrene-butadiene rubber (denoted as P4).

[0087] The number-average molecular weight and molecular weight distribution of P4 are shown in Table 1.

[0088] Example 5

[0089] Under nitrogen protection, 2500g of mixed solvent (cyclohexane and n-hexane weight ratio of 88:12), 28g of styrene, 252g of butadiene, and 1.5mL of structure modifier ethyl tetrahydrofurfuryl ether were added to a 5L polymerization reactor. The system was heated to 40℃, and 40mL of n-butyllithium solution (concentration of n-butyllithium was 0.1437mol / L) was added. The reaction reached a peak temperature of 70℃ after 15min, and the conversion rate was measured to be 100% 5min after the reaction reached the peak temperature. After the system temperature reached 45℃, a mixed coupling agent was added to the reactor: 0.2043g of octaglycidoxypropyl polysilsesquioxane (molecular weight of 1337.9g / mol) and 0.4429g of glycidoxypropyl-terminated polydimethylsiloxane (molecular weight of 362.6g / mol). The coupling reaction was carried out at 45℃ for 30min, and then 0.5mL of isopropanol was added to terminate the reaction. After stirring for 10 minutes, add 2.24g of antioxidant 264. The rubber solution is then condensed by steam and dried on a two-roll mill to obtain solution-polymerized styrene-butadiene rubber (denoted as P5).

[0090] The number-average molecular weight and molecular weight distribution of P5 are shown in Table 1.

[0091] Example 6

[0092] Under nitrogen protection, 2500g of mixed solvent (cyclohexane and n-hexane weight ratio of 88:12), 70g of styrene, 210g of butadiene, and 1.5mL of structure modifier ethyl tetrahydrofurfuryl ether were added to a 5L polymerization reactor. The system was heated to 40℃, and 40mL of n-butyllithium solution (concentration of n-butyllithium was 0.1437mol / L) was added. The reaction reached a peak temperature of 69℃ after 15min, and the conversion rate was measured to be 100% 5min after the reaction reached the peak temperature. After the system temperature reached 40℃, a mixed coupling agent was added to the reactor: 0.2043g of octaglycidoxypropyl polysilsesquioxane (molecular weight of 1337.9g / mol) and 0.4429g of glycidoxypropyl-terminated polydimethylsiloxane (molecular weight of 362.6g / mol). The coupling reaction was carried out at 40℃ for 15min, and then 0.5mL of isopropanol was added to terminate the reaction. After stirring for 10 minutes, add 2.24g of antioxidant 264. After the rubber solution is condensed by water vapor, it is dried on a two-roll mill to obtain solution-polymerized styrene-butadiene rubber (denoted as P6).

[0093] The number-average molecular weight and molecular weight distribution of P6 are shown in Table 1.

[0094] Example 7

[0095] Under nitrogen protection, 2500g of mixed solvent (cyclohexane and n-hexane weight ratio of 88:12), 70g of styrene, 210g of butadiene, and 1.5mL of structure modifier ethyl tetrahydrofurfuryl ether were added to a 5L polymerization reactor. The system was heated to 40℃, and 40mL of n-butyllithium solution (concentration of n-butyllithium was 0.1437mol / L) was added. The reaction reached a peak temperature of 68℃ after 15min, and the conversion rate was measured to be 100% 5min after the reaction reached the peak temperature. After the system temperature reached 70℃, a mixed coupling agent was added to the reactor: 0.2043g of octaglycidoxypropyl polysilsesquioxane (molecular weight of 1337.9g / mol) and 0.4429g of glycidoxypropyl-terminated polydimethylsiloxane (molecular weight of 362.6g / mol). The coupling reaction was carried out at 70℃ for 40min, and then 0.5mL of isopropanol was added to terminate the reaction. After stirring for 10 minutes, add 2.24g of antioxidant 264. The rubber solution is then condensed by steam and dried on a two-roll mill to obtain solution-polymerized styrene-butadiene rubber (denoted as P7).

[0096] The number-average molecular weight and molecular weight distribution of P7 are shown in Table 1.

[0097] Example 8

[0098] Under nitrogen protection, 2500g of mixed solvent (cyclohexane and n-hexane weight ratio of 88:12), 70g of styrene, 210g of butadiene, and 1.5mL of structure modifier ethyl tetrahydrofurfuryl ether were added to a 5L polymerization reactor. The system was heated to 40℃, and 40mL of n-butyllithium solution (concentration of n-butyllithium was 0.1437mol / L) was added. The reaction reached a peak temperature of 67℃ after 17min, and the conversion rate was measured to be 100% 5min after reaching the peak temperature. After the system temperature reached 45℃, a mixed coupling agent was added to the reactor: 0.2160g of methyl hepta-glycidyl oxypropyl polysilsesquioxane (molecular weight of 1237.8g / mol) and 0.4429g of glycidyl oxypropyl-terminated polydimethylsiloxane (molecular weight of 362.6g / mol). The coupling reaction was carried out at 45℃ for 30min, and then 0.5mL of isopropanol was added to terminate the reaction. After stirring for 10 minutes, add 2.24g of antioxidant 264. After the rubber solution is condensed by water vapor, it is dried on a two-roll mill to obtain solution-polymerized styrene-butadiene rubber (denoted as P8).

[0099] The number-average molecular weight and molecular weight distribution of P8 are shown in Table 1.

[0100] Example 9

[0101] The method of Example 8 is followed, except that methyl heptaglycidyl etheroxypropyl polysilsesquioxane is replaced with an equimolar amount of phenyl heptaglycidyl etheroxypropyl polysilsesquioxane (structural formula...). ), replacing glycidyl etheroxypropyl-terminated polydimethylsiloxane with an equimolar amount of glycidyl etheroxypropyl-terminated polydiethylsiloxane (i.e., C8H). 20 OSi2(C6H 11 O2)2), other steps and conditions are the same as in Example 8. Solution-polymerized styrene-butadiene rubber (denoted as P9) is obtained.

[0102] The number-average molecular weight and molecular weight distribution of P9 are shown in Table 1.

[0103] Example 10

[0104] The method of Example 8 is followed, except that methyl heptaglycidyl etheroxypropyl polysilsesquioxane is replaced with an equimolar amount of ethyl heptaglycidyl etheroxypropyl polysilsesquioxane (structural formula...). Replace glycidyl etheroxypropyl-terminated polydimethylsiloxane with an equimolar amount of C 16 H 34 O5Si2(C2H6OSi)6 (CAS: 130167-23-6), with other steps and conditions the same as in Example 8. Solution-polymerized styrene-butadiene rubber (denoted as P10) was obtained.

[0105] The number-average molecular weight and molecular weight distribution of P10 are shown in Table 1.

[0106] Comparative Example 1

[0107] Under nitrogen protection, 2500g of mixed solvent (cyclohexane and n-hexane weight ratio of 88:12), 70g of styrene, 210g of butadiene, and 1.5mL of structure modifier ethyl tetrahydrofurfuryl ether were added to a 5L polymerization reactor. The system was heated to 40℃, and 40mL of n-butyllithium solution (concentration of n-butyllithium was 0.1437mol / L) was added. The reaction reached a peak temperature of 72℃ after 17min, and the conversion rate reached 100% 5min after reaching the peak temperature. After the system temperature reached 45℃, 0.6644g of linear coupling agent glycidyl etheroxypropyl-terminated polydimethylsiloxane (molecular weight of 362.6g / mol) was added to the reactor. The coupling reaction was carried out at 45℃ for 30min, and then 0.5mL of isopropanol was added to terminate the reaction. After stirring for 10min, 2.24g of antioxidant 264 was added. After the adhesive solution is condensed by water vapor, it is dried by an open mill to obtain solution-polymerized styrene-butadiene rubber (denoted as DP1).

[0108] The number-average molecular weight and molecular weight distribution of DP1 are shown in Table 1.

[0109] Comparative Example 2

[0110] Under nitrogen protection, 2500g of mixed solvent (cyclohexane and n-hexane weight ratio of 88:12), 70g of styrene, 1.5mL of structure modifier ethyl tetrahydrofurfuryl ether, and 210g of butadiene were added to a 5L polymerization reactor. The system was heated to 40℃, and 40mL of n-butyllithium solution (concentration of n-butyllithium was 0.1437mol / L) was added. The reaction reached a peak temperature of 69℃ after 16 minutes, and the conversion rate reached 100% after 5 minutes of reaching the peak temperature. After the system temperature reached 45℃, 0.2387g of tin tetrachloride (molecular weight of 260.5g / mol) was added to the reactor for coupling reaction. The reaction was carried out at 45℃ for 30 minutes, and then 0.5mL of isopropanol was added to terminate the reaction. After stirring for 10 minutes, 2.24g of antioxidant 264 was added. After the solution was condensed by steam, it was dried on a two-roll mill to obtain solution-polymerized styrene-butadiene rubber (denoted as DP2).

[0111] The number-average molecular weight and molecular weight distribution of DP2 are shown in Table 1.

[0112] Table 1

[0113]

[0114] Note: S1, S2, and S3 represent the proportions of the peak areas occupied by each molecular weight peak in the GPC spectrum of the polymer product.

[0115] As can be seen from the results in Table 1, the solution-polymerized styrene-butadiene rubber obtained by the method provided in this invention has a high number-average molecular weight, a wide molecular weight distribution, and a three-peak molecular weight distribution, thus exhibiting superior processing performance.

[0116] Test case

[0117] Rubber compositions containing solution-polymerized styrene-butadiene rubber P1-P10 and DP1-DP2 prepared in Examples 1-10 and Comparative Examples 1-2 were respectively compounded to prepare vulcanized rubbers (denoted as M1-M10 and DM1-DM2, respectively).

[0118] Rubber composition: 100 parts by weight of solution-polymerized styrene-butadiene rubber, 15.0 parts by weight of treated aromatic oil (TDAE), 60 parts by weight of silica 165N, 10 parts by weight of No. 9 industrial reference carbon black, 4.8 parts by weight of Si-69 silane coupling agent, 3.0 parts by weight of zinc oxide, 2.0 parts by weight of stearic acid (SA), 2.0 parts by weight of antioxidant (antioxidant 4010), 1.5 parts by weight of sulfur, 1.5 parts by weight of accelerator D (diphenylguanidine), and 1.5 parts by weight of accelerator TBBS.

[0119] Mixing process: Using the above rubber composition, a two-stage mixing process was adopted. The initial temperature of the first stage was set at 80℃, and the rotor speed was set at 90 rpm. First, all the solution-polymerized styrene-butadiene rubber was added to the internal mixer (BR1600, British Farrar) and plasticized for 30 seconds. Then, 3 / 4 of the amount of silica 165N, Si-69 silane coupling agent and zinc oxide were added and mixed for 150 seconds. Finally, the remaining 1 / 4 of the amount of silica 165N, No. 9 industrial reference carbon black and stearic acid (S) were added. A) Antioxidant 4010: After the rubber compound reaches 150℃ for 5 minutes, discharge it; let it stand for 4 hours; for the second stage mixing, set the initial temperature to 40℃ and the rotor speed to 60 rpm. Add the first stage compound to the internal mixer and mix for 30 seconds, then add sulfur, accelerator D, and accelerator TBBS and mix for 240 seconds before discharging; pass the second stage compound through a two-roll mill (X(S)K-160 type, Shanghai Shuangyi Rubber & Plastics Machinery Factory) three times longitudinally to produce sheets. The two-roll mill rollers are at room temperature. The compound must stand for at least 8 hours before vulcanization. Vulcanization is carried out using a flat vulcanizing machine at a vulcanization temperature of 160℃ and a vulcanization time of 35 minutes to obtain vulcanized rubber.

[0120] Tensile properties were tested on the vulcanized rubber prepared above. Tensile properties were characterized using a material testing machine (SHIMADZU, AG-20KNG). The force sensor used in the material testing machine was 1KN. The tensile rate was 500 mm / min, the test temperature was 23±2℃, and the effective part length of the sample was 25 mm, the width was 6 mm, and the thickness was 2 mm, according to the method specified in GB / T 528-2008. Five parallel experiments were performed for each group of samples, and the average value was taken. The Mooney viscosity increase of the compound was the difference between the Mooney viscosity of the compound and the Mooney viscosity of the raw rubber (rubber before compounding). The Mooney viscosity was determined using a Mooney viscometer according to the method specified in GB / T 1232. The results are shown in Table 2. In Table 2, X represents the dispersion degree of the filler in the rubber compound, and Y represents the distribution index of large particles in the filler. The larger the X and Y values, the better the dispersion of the surface filler.

[0121] Table 2

[0122]

[0123] As can be seen from the results in Table 2, the solution-polymerized styrene-butadiene rubber obtained by the method provided in this invention has a lower Mooney value, better filler dispersion, and better processing performance, while also exhibiting significantly improved vulcanized rubber strength.

[0124] 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 method for preparing a conjugated diene polymer having a multi-arm star structure, comprising: (1) In the presence of an inert solvent and a lithium-containing initiator, a conjugated diene monomer and a monovinyl aromatic monomer are polymerized to obtain the product system; (2) The product system is coupled with an additive containing a mixed coupling agent to obtain a conjugated diene polymer with a multi-arm star structure. The mixed coupling agent includes a star-shaped coupling agent and a linear coupling agent; The star-shaped coupling agent has the structure shown in formula (Ⅰ). (A) a -[SiO 3 / 2 ] m -(X) b Equation (Ⅰ); In equation (Ⅰ), m is an even number not less than 6; In formula (Ⅰ), A is an epoxy-terminated group connected to Si, a is an integer, and 3≤a≤m; In formula (Ⅰ), X is any non-reactive end-capping group connected to Si, and b = ma; The linear coupling agent has the structure shown in formula (II). Z-[(D)2SiO] n -Si(D)2-Z formula (Ⅱ); In equation (II), n is an integer and n≥1; In formula (II), D is any non-reactive end-capping group connected to Si; In formula (II), Z is an epoxy-terminated group connected to Si.

2. The method according to claim 1, wherein, In the mixed coupling agent, the molar ratio of the star-shaped coupling agent to the linear coupling agent is 1:(1-40); Preferably, the molar ratio of the star-shaped coupling agent to the linear coupling agent is 1:(1-20).

3. The method according to claim 1 or 2, wherein, In formula (Ⅰ), m is selected from 8, 10 or 12; A is selected from epoxy alkyl or glycidyl ether alkyl, and a is selected from 7 or 8; X is selected from C1-C8 alkyl, C3-C8 cycloalkyl, or C6-C 10 Aryl.

4. The method according to claim 3, wherein, In equation (Ⅰ), m is 8; A is a glycidyl ether alkyl group, and a is selected from 7 or 8; X is selected from methyl or phenyl.

5. The method according to claim 4, wherein, The star-shaped coupling agent is selected from octaglycidyl oxypropyl polysilsesquioxane or methyl heptaglycidyl oxypropyl polysilsesquioxane.

6. The method according to any one of claims 1-5, wherein, In formula (II), D is selected from C1-C8 alkyl, C3-C8 cycloalkyl, C6-C 10 aryl, C1-C8 alkoxy, C3-C8 cycloalkoxy, or C6-C 10 Aryloxy group, 1≤n≤10; Z is selected from epoxy alkyl or glycidyl ether alkyl.

7. The method according to claim 6, wherein, In formula (II), D is selected from C1-C8 alkyl or C1-C8 alkoxy, and n is 1; Z stands for glycidyl etheroxypropyl.

8. The method according to claim 7, wherein, The linear coupling agent is glycidyl etheroxypropyl-terminated polydimethylsiloxane.

9. The method according to any one of claims 1-8, wherein, The molar ratio of the mixed coupling agent, calculated based on the epoxy groups in the star-shaped coupling agent, to the lithium-containing initiator, calculated based on the elemental lithium, is (0.8-1):1, preferably (0.9-1):1; And / or, the weight ratio of the conjugated diene monomer to the monovinyl aromatic hydrocarbon is (1.5-9):1; And / or, the initiation temperature of the polymerization reaction is 20-60°C; And / or, the coupling reaction is carried out at a temperature of 40-70°C for a time of 15-40 min.

10. A conjugated diene polymer having a multi-armed star structure prepared by the method according to any one of claims 1-9.

11. The application of the conjugated diene polymer with a multi-arm star structure as described in claim 10 in tire manufacturing.

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