Primary amino modified solution polymerized styrene-butadiene rubber and preparation method thereof

Abstract

The invention provides primary amino modified solution polymerized styrene-butadiene rubber and a preparation method thereof. The preparation method comprises the following steps: in a polymerization system, initiating polymerization of a butadiene monomer and a styrene monomer by taking n-butyllithium as an initiator and tetrahydrofuran as a polymerization activator to obtain a styrene butadiene rubber active chain; adding a diisocyanate compound into the polymerization system to terminate polymerization, and introducing an isocyanate group to the end part of a styrene butadiene rubber active chain to obtain a styrene butadiene rubber solution; and adding a terminator into the styrene-butadiene rubber solution, stirring, separating out precipitate, and drying to obtain the primary amino modified solution polymerized styrene-butadiene rubber. The primary amino modified solution polymerized styrene-butadiene rubber is prepared by the preparation method, has high polarity and strong binding force with silicon dioxide filler, promotes generation of a more stable filler-polymer network with a more perfect structure, and remarkably improves the dynamic performance of a rubber material.

Description

Technical Field

[0001] The invention relates to the technical field of solution-polymerized styrene-butadiene rubber, in particular to a primary amino group-modified solution-polymerized styrene-butadiene rubber and a preparation method thereof. Background Art

[0002] Styrene butadiene rubber is one of the earliest synthetic rubber varieties to achieve industrial production and has the largest production capacity. It is a random copolymer of styrene and butadiene. The main production processes are emulsion polymerization and solution polymerization. Among them, solution styrene butadiene rubber (SSBR) has a narrow molecular weight distribution, and the sequence distribution and microstructure can be precisely controlled. It has excellent heat resistance, wear resistance and aging resistance. Its processing performance and product performance are close to natural rubber, and its vulcanization performance is better than natural rubber. Therefore, it is widely used in vulcanized rubber products such as tires, plastic modification and shoe materials.

[0003] In recent years, in order to improve the fuel economy of automobiles and put forward higher environmental protection and safety requirements, it is necessary to further reduce the rolling resistance of tires while improving their wear resistance and anti-skid performance. As an important component of the tire tread rubber that is in direct contact with the ground, solution polystyrene butadiene rubber is required to have excellent dynamic performance. From the perspective of safety performance, the tread rubber is required to have excellent braking performance (anti-skid performance) on wet roads; from the perspective of energy consumption, it is required to reduce the rolling resistance of the tread rubber during driving as much as possible; from the perspective of environmental protection, the tread rubber is required to have excellent wear resistance to avoid a large amount of tire wear to produce debris that pollutes the water body.

[0004] In the past, carbon black and white carbon black were used as reinforcing fillers for tire treads in large quantities, while silica was used as a filling material to prepare a rubber composition with excellent hysteresis performance, achieving an excellent balance between high wet skid resistance and low rolling resistance characteristics of the tire tread. However, compared with the hydrophobicity of the carbon black surface, the silica surface has a large number of silanol groups, which gives it a higher hydrophilicity, making it difficult to disperse evenly in non-polar solution-polymerized styrene-butadiene rubber. Its dispersibility is worse than that of carbon black, which is not conducive to the performance of the final tire product. Therefore, it is necessary to adopt a modification technology to effectively combine the hydrophilic silica with the hydrophobic solution-polymerized styrene-butadiene rubber and disperse and mix them evenly.

[0005] In order to promote the affinity between white carbon black and solution polymerized styrene butadiene rubber, predecessors have tried to add silane coupling agents during the rubber mixing process, and use silane coupling agents to modify the surface of silica. However, the pretreatment process of surface modification of silica using silane coupling agents is complicated, and the modification effect is not high. People have also tried to introduce polar functional groups at the ends of the molecular chains of solution polymerized styrene butadiene rubber to improve the interface between rubber and fillers, so that the fillers are evenly dispersed in the rubber. However, only tertiary amino groups and siloxane groups can be introduced at the ends of the molecular chains. These groups can only use the lone electron pairs of nitrogen atoms and / or oxygen atoms to pair with the silanol groups on the surface of the silica filler, resulting in a limited number of hydrogen bonds and weak binding force. Summary of the invention

[0006] The present invention aims to solve the above-mentioned problems. In view of the defects of solution polymerized butadiene styrene rubber (SSBR) in the prior art as a tire tread, the purpose of the present invention is to provide a primary amino-modified solution polymerized butadiene styrene rubber and a preparation method thereof. The primary amino-modified solution polymerized butadiene styrene rubber prepared by the method has high polarity and strong binding force with silica filler, can promote the formation of a more stable and more structurally perfect filler-polymer network, and significantly improves the dynamic properties of the rubber material.

[0007] To achieve the above-mentioned purpose, the present invention provides a preparation method of primary amino modified solution polymerized styrene butadiene rubber, which comprises the following steps: in a polymerization system, using n-butyl lithium as an initiator and tetrahydrofuran as a polymerization activator to initiate polymerization of butadiene monomer and styrene monomer to obtain a styrene butadiene rubber active chain; adding a diisocyanate compound to the polymerization system to terminate the polymerization, and at the same time introducing an isocyanate group at the end of the styrene butadiene rubber active chain to obtain a styrene butadiene rubber glue solution; adding a terminator to the styrene butadiene rubber glue solution, stirring, precipitating, and drying to obtain a primary amino modified solution polymerized styrene butadiene rubber.

[0008] Furthermore, the concentration of the monomer is 5-30%; the mass ratio of butadiene monomer to styrene monomer is (3-133):57; the amount of n-butyl lithium added is 100-750 mg / kg monomer; and the amount of tetrahydrofuran added is 50-50000 mg / kg monomer.

[0009] Further, the diisocyanate compound includes at least one of diphenylmethane diisocyanate, hydrogenated phenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, naphthalene diisocyanate and hexamethylene diisocyanate.

[0010] By introducing -NH2 primary amino functional groups at the ends of the molecular chains, three hydrogen bonds can be generated simultaneously at one end group, and the binding force between the filler and the polymer chain segments is significantly enhanced.

[0011] Furthermore, in step S10, the polymerization temperature is 0-100°C, and the polymerization time is 20-180 min.

[0012] Further, in step S20, the time for terminating the polymerization is 5 to 15 minutes, and the molar ratio of the diisocyanate compound to n-butyl lithium is 0.9 to 1.5.

[0013] Further, in step S30, the terminator includes at least one of deionized water, ethanol, methanol, isooctanoic acid, isooctyl alcohol, menthol, carbon dioxide, and trimethylchlorosilane; the amount of the terminator added is 0.9 to 5.0 times the molar amount of the initiator; and the stirring time is 5 to 15 minutes.

[0014] The present invention also provides a primary amino group-modified solution polymerized styrene butadiene rubber, which is prepared by the above-mentioned preparation method.

[0015] Furthermore, the styrene content of the primary amino group-modified solution polymerized styrene butadiene rubber is 5-70%; the vinyl content of the primary amino group-modified solution polymerized styrene butadiene rubber is 6-90%.

[0016] Furthermore, the glass transition temperature of the primary amino group modified solution polymerized styrene butadiene rubber is -90~20℃; the Mooney viscosity of the primary amino group modified solution polymerized styrene butadiene rubber is (ML1+4 / 100℃) 20~110; the molecular weight of the primary amino group modified solution polymerized styrene butadiene rubber is 100,000~1.2 million g / mol; the molecular weight distribution of the primary amino group modified solution polymerized styrene butadiene rubber is a unimodal distribution, MDI=1.0~3.0; the amino termination rate or modification rate of the primary amino group modified solution polymerized styrene butadiene rubber is ≥95%; the nitrogen content of the primary amino group modified solution polymerized styrene butadiene rubber is 50~70 mg / kg.

[0017] The modification rate of SSBR modified by diisocyanate blocking is high, and therefore the modification reaction activity of the diisocyanate blocking agent is high.

[0018] Furthermore, the terminal modification groups of the primary amino-modified solution polymerized styrene butadiene rubber contain imino, carbonyl and primary amino structures; the primary amino-modified solution polymerized styrene butadiene rubber further undergoes chain extension reaction with the polyurethane component through reactive extrusion technology, so that the polyurethane block structure is generated at the end of the styrene butadiene rubber molecular chain.

[0019] After adopting the technical solution of the present invention, the following technical effects can be achieved: (1) Compared with the prior art, the diisocyanate compound used in this technical solution has extremely high reactivity with active lithium terminals and water molecules, has a low addition amount, and has no side reactions; (2) The terminal groups formed by the SSBR include three heteroatom structures: imino-NH-, carbonyl>C=O and primary amino-NH2. Theoretically, there are 6 hydrogen bond formation sites, which are highly polar and have strong binding force with silica fillers, promoting the formation of a more stable and more structurally perfect filler-polymer network, significantly improving the dynamic properties of rubber materials; (3) The primary amino terminal is an active functional group and can be used by SBR as the basis for further functional group modification reactions. For example, reactive extrusion technology can be used to react with polyurethane components to generate a polyurethane block chain structure at the end of the SBR molecular chain. This special structured polymer combines the excellent properties of SBR and polyurethane resin. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which: Figure 1 The reaction mechanism of polyisocyanate-terminated solution-polymerized styrene-butadiene rubber; Figure 2 It is the chemical structure formula of solution-polymerized styrene-butadiene rubber. DETAILED DESCRIPTION

[0021] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] In recent years, in order to improve the fuel economy of automobiles, and to put forward higher environmental protection and safety requirements, it is necessary to further reduce the rolling resistance of tires while improving their wear resistance and anti-skid properties. As an important component of the tire tread rubber material that is in direct contact with the ground, solution-polymerized styrene butadiene rubber is required to have excellent dynamic performance. In the past, carbon black and white carbon black were used in large quantities as reinforcing fillers for tire treads, and the use of silica as a filling material can prepare a rubber composition with excellent hysteresis performance, achieving an excellent balance between the high anti-skid properties and low rolling resistance properties of the tire tread. However, relative to the hydrophobicity of the carbon black surface, the silica surface has a large number of silanol groups, which gives it a higher hydrophilicity, making it difficult to disperse evenly in non-polar solution-polymerized styrene butadiene rubber, and its dispersibility is worse than that of carbon black, which is unfavorable to the performance of the final tire product. Therefore, it is necessary to adopt a modification technology to effectively combine the hydrophilic silica with the hydrophobic solution-polymerized styrene butadiene rubber and disperse and mix them evenly.

[0023] In order to promote the affinity between white carbon black and solution polymerized styrene butadiene rubber, predecessors have tried to add silane coupling agents (such as silicon 69, also known as: bis (triethoxysilyl propane) tetrasulfide; γ-mercaptopropyl trimethoxysilane; etc.) during the rubber mixing process, and use the above silane coupling agents to modify the surface of silica. However, the above methods have the following problems: adding silane coupling agents during mixing not only requires a large amount of silane coupling agents, but also causes "migration" phenomenon, resulting in poor rubber performance; adding silane coupling agents during mixing has a limited effect on promoting the affinity between fillers and rubber; the pretreatment process of using silane coupling agents to modify the surface of silica is complicated, and the modification effect is not high, and the improvement of the interface between fillers and rubber is not obvious.

[0024] Therefore, people began to try to introduce polar functional groups at the ends of the solution polymerized styrene butadiene rubber molecular chains, thereby improving the interface between rubber and fillers and making the fillers evenly dispersed in the rubber; and the polar functional groups carried at the ends of the solution polymerized styrene butadiene rubber molecular chains are strongly combined with the silica fillers, significantly reducing the number of self-terminals and forming a well-structured filler-polymer network, thereby significantly reducing the hysteresis loss of the rubber material. LG Chemical Co., Ltd. of South Korea introduced in its patent CN107810209B: 1. Cyclohexyl imine reacts with conjugated dienes (such as butadiene) immediately after contacting n-butyl lithium to prepare an amino-functionalized initiator, which is used to initiate random copolymerization of butadiene and styrene to prepare chain-end amino-functionalized solution polymerized styrene butadiene rubber; 2. The present invention mainly uses vinyl-N, N-dimethylbenzylamine compounds to react with butyl lithium to prepare amino-functionalized anionic initiators, which can also be used to prepare chain-end amino-functionalized solution polymerized styrene butadiene rubber. Asahi Chemical of Japan introduced in its patent CN105175582B: using alkyl lithium initiator to initiate random copolymerization of butadiene and styrene, and finally adding 1-[3-(triethoxysilyl)propyl]-4-methylpiperazine, 1-[3-(triethoxysilyl)propyl]-4-(trimethylsilyl)piperazine, tetraglycidyl-1,3-bisaminomethylcyclohexane, 2-[3-(trimethoxysilyl)propyl]-1,3-dimethylimidazolidine, [3-(dimethylamino)propyl]trimethoxysilane, 1,3-dimethyl-2-imidazolidinone as end-capping agents, which can introduce amino and / or siloxane groups at the end of styrene-butadiene rubber, and the end-capping modification rate can reach more than 80%. In addition, CN102482359A also uses piperazine compounds containing siloxane substituents as end-capping agents for styrene-butadiene rubber; CN107250172B and CN109476778B use silazane compounds as end-capping agents for styrene-butadiene rubber; CN107835752A uses 3-isocyanate propyltrimethoxysilane to react with terminal hydroxyl polybutadiene to prepare silane-modified polybutadiene rubber for tire components. The above methods can introduce amino groups and / or siloxane groups into the molecular chain ends of solution-polymerized styrene-butadiene rubber, with an end-capping rate of more than 80%, thereby achieving chain end modification of solution-polymerized styrene-butadiene rubber.

[0025] However, the above method can only introduce tertiary amino groups and siloxane groups at the ends of the molecular chains. These groups can only use the lone electron pairs of nitrogen atoms and / or oxygen atoms to pair with the silanol groups on the surface of the silica filler, resulting in a limited number of hydrogen bonds and weak binding force. If the -NH2 primary amino functional group can be introduced at the end of the molecular chain, three hydrogen bonds can be formed at one end group at the same time, and the binding force between the filler and the polymer chain end is significantly enhanced.

[0026] In addition, the above-mentioned capping agents have the following problems: complex structure and difficulty in obtaining; high price; obvious odor and strong toxicity; low reaction activity and long reaction time; large addition amount and many side reactions.

[0027] The present invention aims to solve the above-mentioned problems. In view of the defects of solution polymerized butadiene styrene rubber (SSBR) in the prior art as a tire tread, the purpose of the present invention is to provide a primary amino-modified solution polymerized butadiene styrene rubber and a preparation method thereof. The primary amino-modified solution polymerized butadiene styrene rubber prepared by the method has high polarity and strong binding force with silica filler, can promote the formation of a more stable and more structurally perfect filler-polymer network, and significantly improves the dynamic properties of the rubber material.

[0028] To achieve the above-mentioned purpose, the present invention provides a method for preparing a primary amino-modified solution-polymerized styrene-butadiene rubber. The method comprises the following steps: in a polymerization system, using n-butyl lithium as an initiator and tetrahydrofuran as a polymerization activator to initiate polymerization of butadiene monomer and styrene monomer to obtain a styrene-butadiene rubber active chain; adding a diisocyanate compound to the polymerization system to terminate the polymerization, and at the same time introducing an isocyanate group at the end of the styrene-butadiene rubber active chain to obtain a styrene-butadiene rubber glue solution; adding a terminator to the styrene-butadiene rubber glue solution, stirring, precipitating, and drying to obtain the primary amino-modified solution-polymerized styrene-butadiene rubber.

[0029] The reaction mechanism of polyisocyanate-terminated solution-polymerized styrene-butadiene rubber is as follows: Figure 1 shown.

[0030] For example, a solvent is also added to the polymerization system, and the solvent can be one of n-pentane, cyclopentane, n-hexane, cyclohexane, n-heptane, benzene, toluene, xylene, and tetrahydrofuran, preferably cyclohexane, and the amount of solvent added is 4000g. After adding the terminator to the styrene-butadiene rubber glue, an antioxidant can be added, and the antioxidant can be one or more of butylated hydroxytoluene (BHT), antioxidant 1076, and antioxidant 1520. The amount of the antioxidant added is 0.1-1.0%wt of the styrene-butadiene rubber solution, preferably 0.6%wt. In addition, after stirring, the isocyanate group can be converted into a primary amino group by adding a terminator deionized water, and the addition of polar solvents such as alcohol and methanol can precipitate the SSBR modified with the primary amino group at the chain end.

[0031] Furthermore, the concentration of the monomer is 5-30%; the mass ratio of the butadiene monomer to the styrene monomer is (3-133):57; the amount of n-butyl lithium added is 100-750 mg / kg monomer; and the amount of tetrahydrofuran added is 50-50000 mg / kg monomer.

[0032] For example, the concentration of the monomer is preferably 20%; the mass ratio of butadiene monomer to styrene monomer is preferably 7:3; the amount of tetrahydrofuran added is preferably 500 mg / kg monomer, where the monomers refer to butadiene monomer and styrene monomer, and the amount of tetrahydrofuran added per kilogram of monomer is 500 mg.

[0033] Further, the diisocyanate compound includes at least one of diphenylmethane diisocyanate, hydrogenated phenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, naphthalene diisocyanate and hexamethylene diisocyanate.

[0034] By introducing -NH2 primary amino functional groups at the ends of the molecular chains, three hydrogen bonds can be generated simultaneously at one end group, and the binding force between the filler and the polymer chain segments is significantly enhanced.

[0035] Furthermore, in step S10, the polymerization temperature is 0-100°C, and the polymerization time is 20-180 min.

[0036] Further, in step S20, the time for terminating the polymerization is 5 to 15 minutes, and the molar ratio of the diisocyanate compound to the n-butyl lithium is 0.9 to 1.5.

[0037] Preferably, the molar ratio of the diisocyanate compound to n-butyl lithium is 1.1 to 1.2.

[0038] Further, in step S30, the terminator includes at least one of deionized water, ethanol, methanol, isooctanoic acid, isooctyl alcohol, menthol, carbon dioxide, and trimethylchlorosilane; the amount of the terminator added is 0.9 to 5.0 times the molar amount of the initiator; and the stirring time is 5 to 15 minutes.

[0039] Preferably, the terminator is deionized water, and the amount of the terminator added is 3.0 times the molar amount of the initiator.

[0040] The present invention also provides a primary amino group-modified solution polymerized styrene butadiene rubber, which is prepared by the above-mentioned preparation method.

[0041] Furthermore, the styrene content of the primary amino group-modified solution polymerized styrene butadiene rubber is 5-70%; the vinyl content of the primary amino group-modified solution polymerized styrene butadiene rubber is 6-90%.

[0042] Furthermore, the glass transition temperature of the primary amino group modified solution polymerized styrene butadiene rubber is -90~20℃; the Mooney viscosity of the primary amino group modified solution polymerized styrene butadiene rubber is (ML1+4 / 100℃) 20~110; the molecular weight of the primary amino group modified solution polymerized styrene butadiene rubber is 100,000-1.2 million g / mol; the molecular weight distribution of the primary amino group modified solution polymerized styrene butadiene rubber is a unimodal distribution, MDI=1.0~3.0; the amino termination rate or modification rate of the primary amino group modified solution polymerized styrene butadiene rubber is ≥95%; the nitrogen content of the primary amino group modified solution polymerized styrene butadiene rubber is 50~70 mg / kg.

[0043] The modification rate of SSBR modified by diisocyanate blocking is high, and therefore the modification reaction activity of the diisocyanate blocking agent is high.

[0044] Furthermore, the terminal modification group of the primary amino-modified solution polymerized styrene butadiene rubber contains an imino group, a carbonyl group and a primary amino group structure; the primary amino-modified solution polymerized styrene butadiene rubber further undergoes a chain extension reaction with a polyurethane component through a reactive extrusion technique, so that a polyurethane block structure is generated at the end of the styrene butadiene rubber molecular chain.

[0045] By generating "SSBR-N-TPU" amphiphilic elastomer, it can be used as a blending and modified solubilizer for polar resins such as polycarbonate (PC), polyethylene terephthalate (PET), polyetheretherketone (PEEK), etc., as well as non-polar polymers such as butadiene rubber, styrene-butadiene rubber, styrene-butadiene-styrene block copolymer (SBS), polymer elastomer-olefin-styrene-olefin copolymer (SEBS), polyethylene (PE), polypropylene (PP), etc.

[0046] The present invention mainly compares the modification effects of diisocyanate-based blocking agents on SSBR, so the embodiments and comparative examples of the present invention are mainly tested and characterized by the following methods.

[0047] Mooney viscosity test: Two samples having a weight of 15 g or more were preheated for 1 minute and then measured at 100° C. for 4 minutes using MV-2000 manufactured by ALPHA Technologies.

[0048] Molecular weight test (including number average molecular weight, weight average molecular weight and molecular weight distribution index): measured by gel permeation chromatography (GPC) at 40°C. Polystyrene monodisperse standard is used as the standard sample to calculate the molecular weight; THF is used as the mobile phase with a flow rate of 1 ml / min.

[0049] Modification rate analysis method: Using primary amino-modified styrene-butadiene rubber as a sample, the amino modification rate is determined by utilizing the characteristic that the modified component will be adsorbed on a GPC column with silica gel as a filler. The amount of modified rubber component adsorbed on the silica column is determined by the difference in chromatograms (the difference in the chromatogram is the difference between the chromatogram obtained by measuring the sample solution containing the sample and the low molecular weight internal standard polystyrene using a polystyrene gel column and the chromatogram obtained by measuring the sample solution using a silica column). GPC analysis sample preparation method: 10 mg of sample and 5 mg of standard low molecular weight polystyrene internal standard are dissolved in 20 ml of tetrahydrofuran. Polystyrene column GPC measurement conditions: THF is used as an eluent, and 200 μL of the sample is injected into the device for measurement. A guard column (trade name "TSK guard column HHR-H" manufactured by Tosoh Corporation) and three columns (trade name "TSKgel Super Multipore HZ-H" manufactured by Tosoh Corporation) are connected and used. Under the conditions of a column box temperature of 40°C and a THF solution flow rate of 1.0 mL / min, an RI detector (trade name "HLC8020" manufactured by Tosoh Corporation) was used for measurement to obtain a chromatogram. Silica column GPC measurement conditions: THF was used as an eluent, and 200 μL of the sample was injected into the device for measurement. Three silica columns with the trade names "Zorbax PSM-1000S", "PSM-300S" and "PSM-60S" were connected and used, and a trade name "DIOL 4.6×12.5mm5micron" was connected to the front section as a protective column for use. Under the conditions of a column box temperature of 40°C and a THF flow rate of 0.5 mL / min, an RI detector (trade name "HLC8020" manufactured by Tosoh Corporation) was used for measurement to obtain a chromatogram. The calculation method of the modification rate is as follows: the peak area of ​​the chromatogram using the polystyrene column is set as 100, the peak area of ​​the sample is set as P1, and the peak area of ​​the standard polystyrene is set as P2; the peak area of ​​the chromatogram using the silica column is set as 100, the area of ​​the sample is set as P3, and the peak area of ​​the standard polystyrene is set as P4, wherein P1+P2=P3+P4=100, and the modification rate (%) is calculated by the following formula: Modification rate (%) = [1-(P2×P3) / (P1×P4)]×100 Nuclear magnetic resonance analysis method: The microstructure of the sample was analyzed using a 600 MHz superconducting Fourier transform nuclear magnetic resonance spectrometer from Brucker. The 1H spectrum observation frequency was 600 MHz, and the 13C spectrum observation frequency was 150.9 MHz. The solvent was CDCl3, TMS was the internal standard, and the test temperature was 20°C. This method can be used to analyze the styrene content and vinyl content of styrene-butadiene rubber.

[0050] DSC thermal performance analysis method: sample 15-20mg, temperature test range -120℃ to 120℃, eliminate thermal history before formal testing, heating and cooling rate is 10℃ / min, and the dwell time of the highest and lowest temperatures is 5min. This method can be used to analyze the glass transition temperature of styrene-butadiene rubber.

[0051] Conversion rate test method: Use a special cylindrical container to take out a small amount of glue from the reactor, then measure the total weight of the cylindrical container containing the polymer solution (A), then transfer the polymer solution in the cylindrical container to an aluminum pan, measure the weight of the cylindrical container after removing the polymer solution (B), dry the aluminum pan containing the polymer solution in a vacuum oven at 100°C for more than 180 minutes until the polymer is completely dry and transparent, finally measure the weight of the dry polymer (C), and calculate the polymer conversion rate according to the following mathematical formula: Nitrogen content analysis method: N content is measured by NSX analysis method using a trace nitrogen quantitative analyzer (NSX-2100H). Specifically, the trace nitrogen quantitative analyzer (autosampler, horizontal furnace, PMT & Nitrogen detector) is turned on, the carrier gas flow rate is set to 250ml / min for Ar, 350ml / min for oxygen, 300ml / min for the ozone generator, the heater is set to 800°C, and the analyzer is placed for about 3 hours to stabilize. After stabilizing the analyzer, a calibration curve with a calibration curve range of 5ppm, 10ppm, 50ppm, 100ppm and 500ppm is made using a nitrogen standard (AccuStandard S-22750-01 to 5ml), and the area corresponding to each concentration is obtained. Afterwards, a ceramic boat containing 20mg of sample is placed in the autosampler of the analyzer and measured to obtain the area. The N content is calculated by using the sample area and calibration curve thus obtained.

[0052] Example 1 Cyclohexane is used as solvent, n-butyl lithium is used as initiator, tetrahydrofuran is added as polymerization activator, butadiene and styrene polymerization is initiated at 20-100°C for 2h, wherein the monomer concentration is 20%, the amount of cyclohexane added is 4000g, the mass ratio of butadiene and styrene is 30 / 70, the amount of 2.0mol / L n-butyl lithium solution added is 2.10ml, and the amount of 100g / L tetrahydrofuran added is 5ml; then diphenylmethane diisocyanate (MDI) is added at the polymerization temperature, and the amount of 0.5mol / L diisocyanate compound solution added is 8.5ml, the polymerization is terminated for 5-15min, and at the same time, isocyanate is introduced into the molecular chain end of styrene-butadiene rubber. Cyanate group; add deionized water as terminator to the styrene-butadiene rubber solution at the polymerization temperature (the amount of terminator added is 3 times the molar equivalent of the initiator), and stir rapidly for 5-15 minutes, then add butylated hydroxytoluene (BHT), an antioxidant, and the amount of antioxidant added is 0.6%wt; add alcohol to the solution to precipitate the styrene-butadiene rubber, pour off the mixture of solvent and alcohol, put the wet rubber block of milky white styrene-butadiene rubber into a stainless steel tray, and then put it into a vacuum oven at 70°C and dry it in vacuum for 24 hours, and finally obtain a colorless and transparent styrene-butadiene rubber product, and the measured monomer conversion rate is 99.80%, the Mooney viscosity is 65, and the number average molecular weight is 43.44×10 4 g / mol, weight average molecular weight is 62.99×10 4 g / mol, molecular weight distribution is 1.45, styrene content is 30.33%, 1,2-polybutadiene structural unit content is 40.50%, glass transition temperature is -30℃, modification rate is 91.70%, and nitrogen content is 60mg / kg solution polystyrene butadiene rubber.

[0053] Example 2 The relevant polymerization process conditions in Example 1 remain unchanged, and only the modifier is replaced with hexamethylene diisocyanate (HDI). The measured monomer conversion rate is 100.00%, the Mooney viscosity is 63, and the number average molecular weight is 45.67×10 4 g / mol, and the weight average molecular weight is 65.76×10 4 g / mol, molecular weight distribution is 1.44, styrene content is 31.10%, 1,2-polybutadiene structural unit content is 42.50%, glass transition temperature is -30℃, modification rate is 97.80%, and nitrogen content per kilogram of solution polystyrene butadiene rubber is 60 mg.

[0054] Example 3 The relevant polymerization process conditions in Example 1 remain unchanged, and only the modifier is replaced with isophorone diisocyanate (IPDI). The measured monomer conversion rate is 99.70%, the Mooney viscosity is 65, and the number average molecular weight is 44.8×10 4g / mol, and the weight average molecular weight is 64.51×10 4 g / mol, molecular weight distribution is 1.44, styrene content is 29.98%, 1,2-polybutadiene structural unit content is 39.48%, glass transition temperature is -30℃, modification rate is 96.90%, and nitrogen content per kilogram of solution polystyrene butadiene rubber is 60 mg.

[0055] Comparative Example 1 The relevant polymerization process conditions in Example 1 were kept unchanged, and no modifier was added. The monomer conversion rate was measured to be 99.80%, the Mooney viscosity was 50, and the number average molecular weight was 39.67×10 4 g / mol, weight average molecular weight is 57.12×10 4 g / mol, molecular weight distribution is 1.44, styrene content is 29.90%, 1,2-polybutadiene structural unit content is 41.50%, glass transition temperature is -30°C, modification rate is 0%, and nitrogen content per kilogram of solution polystyrene butadiene rubber is 60 mg.

[0056] Comparative Example 2 The relevant polymerization process conditions in Example 1 remain unchanged, and only the modifier is replaced by ethylene oxide. The measured monomer conversion rate is 100%, the Mooney viscosity is 57, and the number average molecular weight is 42.88×10 4 g / mol, weight average molecular weight is 62.60×10 4 g / mol, molecular weight distribution is 1.46, styrene content is 30.20%, 1,2-polybutadiene structural unit content is 39.70%, glass transition temperature is -30℃, modification rate is 92.33%, and nitrogen content per kilogram of solution polystyrene butadiene rubber is 0 mg.

[0057] Comparative Example 3 The relevant polymerization process conditions in Example 1 remain unchanged, and only the modifier is replaced with 3-chloropropyltrimethoxysilane. The measured monomer conversion rate is 99.90%, the Mooney viscosity is 56, and the number average molecular weight is 41.20×10 4 g / mol, and the weight average molecular weight is 60.56×10 4 g / mol, molecular weight distribution is 1.47, styrene content is 30.40%, 1,2-polybutadiene structural unit content is 41.50%, glass transition temperature is -30℃, modification rate is 80.40%, and nitrogen content per kilogram of solution polystyrene butadiene rubber is 0 mg.

[0058] Comparative Example 4 The relevant polymerization process conditions in Example 1 remain unchanged, and only the modifier is replaced with N, N-dimethylaminopropyltrimethoxysilane. The measured monomer conversion rate is 100%, the Mooney viscosity is 55, and the number average molecular weight is 42.01×104 g / mol, and the weight average molecular weight is 63.02×10 4 g / mol, molecular weight distribution is 1.50, styrene content is 30.33%, 1,2-polybutadiene structural unit content is 40.50%, glass transition temperature is -30℃, modification rate is 78.50%, and nitrogen content per kilogram of solution polystyrene butadiene rubber is 0 mg.

[0059] Comparative Example 5 The relevant polymerization process conditions in Example 1 remain unchanged, and only the modifier is replaced with 4-vinyl-N, N-dimethylbenzylamine. The monomer conversion rate is measured to be 99.60%, the Mooney viscosity is 59, and the number average molecular weight is 42.30×10 4 g / mol, and the weight average molecular weight is 62.18×10 4 g / mol, molecular weight distribution is 1.47, styrene content is 29.78%, 1,2-polybutadiene structural unit content is 40.13%, glass transition temperature is -30℃, modification rate is 89.90%, and nitrogen content per kilogram of solution polystyrene butadiene rubber is 31.5 mg.

[0060] From the test results of SBBR of Examples 1 to 3 and Comparative Examples 1 to 5, it can be seen that: 1. The modification rate of SSBR modified by diisocyanate end-capping is higher, so the modification reaction activity of diisocyanate end-capping agent is higher; 2. The nitrogen content of diisocyanate-terminated SSBR is higher, so the modification rate of diisocyanate-terminated SSBR is higher, the polarity is higher, and there is a stronger interaction between it and the rubber filler; 3. The molecular weight and Mooney viscosity of diisocyanate-terminated SSBR are higher, so the strong polar terminal groups of diisocyanate-terminated SSBR have stronger interactions.

[0061] In order to evaluate the application performance of the solution-polymerized styrene-butadiene rubber after being made into vulcanized rubber, in an embodiment of the present invention, the vulcanized rubber is prepared by first-stage mixing and second-stage mixing. In the first-stage mixing, rubber, silica, organic silane coupling agent (X50S, Evonik), processing oil (TDAE), zinc oxide (zinc white), stearic acid, antioxidant (TMQ (RD)) (2,2,4-trimethyl-1,2-dihydroquinoline polymer), anti-aging agent (6PPD (dimethylbutyl-N-phenyl-phenylenediamine) and microcrystalline wax) are added, and mixed using a Banbury mixer equipped with a temperature control device. In this case, the initial temperature of the mixing device is controlled at 70°C, and after the mixing is completed, the first mixed rubber is obtained at a discharge temperature of 145°C. In the second stage of mixing, the first rubber mix was cooled to room temperature, and the first rubber mix, sulfur, rubber accelerator (DPD (diphenylguanidine)) and vulcanization accelerator (CZ (N-cyclohexyl-2-benzothiazolylsulfenamide)) were added to the mixer and mixed at a temperature below 100°C to obtain the second rubber mix. Finally, the vulcanized rubber sample was prepared by vulcanization crosslinking in a flat vulcanizer at 160°C for 20 minutes.

[0062] Table 1 shows the mixing formula of vulcanized rubber.

[0063] Note: The raw material amounts in Table 1 are expressed in parts by weight based on 100 parts by weight of styrene-butadiene rubber.

[0064] The vulcanized rubbers obtained after mixing the SSBR prepared in Examples 1 to 3 and Comparative Examples 1 to 5 were tested and characterized by the following methods.

[0065] Vulcanized rubber tensile test: The tensile strength when the test sample is cut and the tensile stress at 300% elongation (300% tensile strength) are measured according to the tensile test method of ASTM 412. For this purpose, a Universal Test Machine 4204 manufactured by Instron is used, and the tensile strength, modulus and elongation are measured at room temperature at a tensile rate of 50 cm / min.

[0066] Vulcanized rubber dynamic mechanical properties test: A dynamic mechanical analyzer manufactured by TA was used. The loss factor Tanδ of each sample was measured when deformed under the conditions of a 10Hz frequency of the deformation mode and a measurement temperature ranging from -60°C to 80°C. The Payne effect is represented by the difference between the minimum and maximum values ​​in the deformation range of 0.28% to 40%. The lower the Payne effect, the higher the filler dispersion. When the loss factor at 0°C increases, the anti-skid property is better, and when the loss factor at 60°C decreases, the hysteresis loss decreases and the rolling resistance decreases, that is, the fuel economy is increased. When the loss modulus at 60°C decreases, the internal heat generation of the rubber decreases, the hysteresis loss decreases, and the dynamic performance improves.

[0067] DIN abrasion resistance test of vulcanized rubber: For each vulcanized rubber sample, a DIN abrasion test was performed based on ASTM D5963 and displayed by the DIN loss index (volume index: ARIA (Abrasion Resistance Index, Method A)).

[0068] Application Example 1 Application Example 1 is the physical properties of the vulcanized rubber samples prepared from the primary amino-terminated modified SSBR in Examples 1 to 3 and Comparative Examples 1 to 5. The results are shown in Table 2.

[0069] Table 2 shows the physical properties of the vulcanized rubber samples prepared from the SSBR modified with primary amino groups in Examples 1 to 3 and Comparative Examples 1 to 5.

[0070] From the test data in Table 2, we can know that: The 300% tensile strength and elongation at break of Examples 1 to 3 and Comparative Examples 1 to 5 are not much different, but the tensile strength of Examples 1 to 3 is significantly higher than that of Comparative Examples 1 to 5, among which, although the tensile strength of Comparative Examples 2 to 5 is slightly higher than that of Comparative Example 1, it is significantly lower than that of Examples 1 to 3. This shows that the mixing and dispersion performance of primary amino-terminated SSBR and rubber filler is the best, and the filler-polymer network of the prepared vulcanized rubber is the most complete and has the best mechanical properties. Diisocyanate end-capping modification technology is more advantageous than tertiary amine group, siloxane group and hydroxyl end-capping modification technology.

[0071] The higher the wear resistance index, the better the wear resistance of the vulcanized rubber. The wear resistance index of Examples 1 to 3 is significantly higher than that of Comparative Examples 1 to 5, indicating that the primary amino group end-capping modification improves the wear resistance of SSBR.

[0072] The higher the 0℃ loss factor, the higher the anti-slip property or grip of the vulcanized rubber. The 0℃ loss factors of Examples 1 to 3 are all greater than 0.2, which are higher than that of Comparative Example 1. Therefore, the primary amino group modification technology gives SSBR excellent grip performance and anti-slip property on ice. Comparative Examples 2 to 5 are not much different from Examples 1 to 3, and are all higher than Comparative Example 1, indicating that tertiary amine groups, siloxane groups, and hydroxyl end-capping modification technologies can also improve the grip performance of SSBR.

[0073] The lower the 60°C loss factor, the lower the rolling resistance of the vulcanized rubber, and the use of tires can improve the fuel economy of automobiles. The 60°C loss factors of Examples 1 to 3 are all lower than 0.0905, much lower than Comparative Examples 1 to 5, indicating that the primary amino end-capping modification technology can significantly reduce the rolling resistance of SSBR. Among them, the 60°C loss factors of Comparative Examples 2 to 5 are all lower than Comparative Example 1, indicating that the tertiary amine group, siloxane group and hydroxyl end-capping modification technology also reduce the rolling resistance of SSBR to a certain extent, but far less than the primary amino end-capping modification technology.

[0074] The lower the 60°C loss modulus, the lower the endogenous heat of the vulcanized rubber and the better the dynamic performance. When used as a tire, it can reduce rolling resistance and improve fatigue resistance. The 60°C loss modulus of Examples 1 to 3 is lower than that of Comparative Examples 1-5, indicating that the endogenous heat of the primary amino group-terminated modified SSBR is lower, the dynamic performance is better, and the fatigue resistance is good. Similarly, the 60°C loss modulus of Comparative Examples 2 to 5 is lower than that of Comparative Example 1, indicating that tertiary amine groups, siloxane groups, and hydroxyl end-capping modification technologies can also improve the dynamic performance and fatigue resistance of SSBR, but the improvement effect is not as good as that of primary amino group-terminated modification technology.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a primary amino group-modified solution-polymerized styrene-butadiene rubber, characterized in that: The preparation method comprises the following steps: S10, in a polymerization system, using n-butyl lithium as an initiator and tetrahydrofuran as a polymerization activator to initiate polymerization of butadiene monomer and styrene monomer to obtain a styrene-butadiene rubber active chain; S20, adding a diisocyanate compound to the polymerization system to terminate the polymerization, and at the same time introducing an isocyanate group at the end of the styrene-butadiene rubber active chain to obtain a styrene-butadiene rubber glue solution; S30, adding a terminator to the styrene-butadiene rubber solution, stirring, separating out a precipitate, and drying to obtain the primary amino group-modified solution-polymerized styrene-butadiene rubber.

2. The preparation method according to claim 1, characterized in that: The concentration of the monomer is 5-30%; the mass ratio of the butadiene monomer to the styrene monomer is (3-133):57; the addition amount of the n-butyl lithium is 100-750 mg / kg monomer; and the addition amount of the tetrahydrofuran is 50-50000 mg / kg monomer.

3. The preparation method according to claim 1, characterized in that: The diisocyanate compound includes at least one of diphenylmethane diisocyanate, hydrogenated phenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, naphthalene diisocyanate and hexamethylene diisocyanate.

4. The preparation method according to claim 1, characterized in that: In the S10, the polymerization temperature is 0-100°C, and the polymerization time is 20-180 min.

5. The preparation method according to claim 1, characterized in that: In the S20, the time for terminating the polymerization is 5 to 15 minutes, and the molar ratio of the diisocyanate compound to the n-butyl lithium is 0.9 to 1.

5.

6. The preparation method according to claim 1, characterized in that: In S30, the terminator includes at least one of deionized water, ethanol, methanol, isooctanoic acid, isooctyl alcohol, menthol, carbon dioxide, and trimethylchlorosilane; the amount of the terminator added is 0.9 to 5.0 times the molar amount of the initiator; and the stirring time is 5 to 15 minutes.

7. A primary amino group-modified solution-polymerized styrene-butadiene rubber, characterized in that: The primary amino-modified solution-polymerized styrene-butadiene rubber is prepared by the preparation method according to any one of claims 1 to 6.

8. The primary amino group-modified solution-polymerized styrene-butadiene rubber according to claim 7, characterized in that: The styrene content of the primary amino group-modified solution-polymerized styrene-butadiene rubber is 5-70%; the vinyl content of the primary amino group-modified solution-polymerized styrene-butadiene rubber is 6-90%.

9. The primary amino group-modified solution-polymerized styrene-butadiene rubber according to claim 7, characterized in that: The glass transition temperature of the primary amino group-modified solution polymerized styrene butadiene rubber is -90~20°C; the Mooney viscosity of the primary amino group-modified solution polymerized styrene butadiene rubber is (ML1+4 / 100°C) 20~110; the molecular weight of the primary amino group-modified solution polymerized styrene butadiene rubber is 100,000~1.2 million g / mol; the molecular weight distribution of the primary amino group-modified solution polymerized styrene butadiene rubber is a unimodal distribution, MDI=1.0~3.0; the amino termination rate or modification rate of the primary amino group-modified solution polymerized styrene butadiene rubber is ≥95%; the nitrogen content of the primary amino group-modified solution polymerized styrene butadiene rubber is 50~70 mg / kg.

10. The primary amino group-modified solution-polymerized styrene-butadiene rubber according to claim 7, characterized in that: The terminal modification group of the primary amino-modified solution-polymerized styrene-butadiene rubber contains an imino group, a carbonyl group and a primary amino group structure; the primary amino-modified solution-polymerized styrene-butadiene rubber further undergoes a chain extension reaction with a polyurethane component through a reactive extrusion technology, so that a polyurethane block structure is generated at the end of the styrene-butadiene rubber molecular chain.

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