A primary amino-modified solution-polymerized styrene-butadiene rubber and its preparation method

Abstract

This invention provides a primary amine-modified solution-polymerized styrene-butadiene rubber (SBR) and its preparation method. The preparation method includes the following steps: in a polymerization system, using n-butyllithium as an initiator and tetrahydrofuran as a polymerization activator, butadiene monomers and styrene monomers are polymerized to obtain active SBR chains; a diisocyanate compound is added to the polymerization system to terminate the polymerization, and isocyanate groups are introduced at the ends of the active SBR chains to obtain a SBR solution; a terminator is added to the SBR solution, and the mixture is stirred, a precipitate is formed, and dried to obtain the primary amine-modified solution-polymerized SBR. The primary amine-modified solution-polymerized SBR prepared by this method exhibits high polarity and strong bonding with silica fillers, promoting the formation of a more stable and structurally complete filler-polymer network, and significantly improving the dynamic properties of the rubber material.

Description

Technical Field

[0001] This invention relates to the field of solution polymerized styrene-butadiene rubber (SBR), and more specifically, to a primary amine-modified solution polymerized SBR and its preparation method. Background Technology

[0002] Styrene-butadiene rubber (SBR) is one of the earliest and largest-capacity synthetic rubbers to achieve industrial production. It is a random copolymer of styrene and butadiene, and its main production processes include emulsion polymerization and solution polymerization. Among them, solution-polymerized SBR has a narrow molecular weight distribution, and its sequence distribution and microstructure can be precisely controlled. It has excellent heat resistance, abrasion resistance, and aging resistance. Its processing performance and product performance are close to those of natural rubber, and its vulcanization performance is superior to that of natural rubber. Therefore, it is widely used in vulcanized rubber products such as tires, modified plastics, and footwear materials.

[0003] In recent years, to improve the fuel economy of automobiles and to meet higher environmental and safety requirements, it is necessary to further reduce the rolling resistance of tires while improving their wear resistance and wet skid resistance. Solution-polymerized styrene-butadiene rubber (SBR), as a crucial component of tire tread compounds that come into direct contact with the ground, is required to possess excellent dynamic performance. From a safety perspective, the tread compound must exhibit excellent braking performance (wet skid resistance) on wet roads; from an energy consumption perspective, it is necessary to minimize the rolling resistance of the tread compound during driving; and from an environmental perspective, the tread compound must have excellent wear resistance to prevent excessive tire wear from generating debris that pollutes water bodies.

[0004] Previously, carbon black and silica were widely used as reinforcing fillers for tire treads. However, using silica as a filler can produce rubber compositions with excellent hysteresis properties, achieving a superior balance between high wet grip and low rolling resistance in tire treads. However, compared to the hydrophobicity of carbon black, silica has a high hydrophilicity due to the abundance of silanol groups, making it difficult to disperse uniformly in non-polar solution-polymerized styrene-butadiene rubber (SBR). Its dispersibility is worse than that of carbon black, which is detrimental to the performance of the final tire product. Therefore, modification techniques are needed to effectively combine hydrophilic silica with hydrophobic solution-polymerized SBR and ensure uniform dispersion and mixing.

[0005] To improve the affinity between silica and solution-polymerized styrene-butadiene rubber (SBR), previous researchers have attempted methods such as adding silane coupling agents during rubber compounding and surface modification of silica using silane coupling agents. However, the pretreatment process for surface modification of silica using silane coupling agents is complex, and the modification effect is not high. Researchers have also tried introducing polar functional groups at the ends of the SBR molecular chains to enhance the interfacial interaction between rubber and filler, thereby ensuring uniform dispersion of the filler in the rubber. However, only tertiary amino groups and siloxane groups can be introduced at the molecular chain ends. These groups can only pair with the silanol groups on the surface of silica filler using the lone pairs of electrons from nitrogen and / or oxygen atoms, resulting in a limited number of hydrogen bonds and weak bonding. Summary of the Invention

[0006] The present invention aims to solve the above-mentioned problems. In view of the defects of solution-polymerized styrene-butadiene rubber (SSBR) in the prior art as tire tread, the present invention aims to provide a primary amine-modified solution-polymerized styrene-butadiene rubber and its preparation method. The primary amine-modified solution-polymerized styrene-butadiene rubber prepared by the method has high polarity and strong bonding force with silica filler, which can promote the formation of a more stable and structurally complete filler-polymer network and significantly improve the dynamic performance of rubber materials.

[0007] To achieve the above objectives, the present invention provides a method for preparing primary amine-modified solution-polymerized styrene-butadiene rubber (SBR). The method includes the following steps: in a polymerization system, using n-butyllithium as an initiator and tetrahydrofuran as a polymerization activator, polymerization of butadiene monomer and styrene monomer is initiated to obtain active SBR chains; a diisocyanate compound is added to the polymerization system to terminate the polymerization, and isocyanate groups are introduced at the ends of the active SBR chains to obtain a SBR solution; a terminator is added to the SBR solution, and the mixture is stirred, a precipitate is formed, and the mixture is dried to obtain primary amine-modified solution-polymerized SBR.

[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-butyllithium added is 100-750 mg / kg monomer; and the amount of tetrahydrofuran added is 50-50000 mg / kg monomer.

[0009] Furthermore, 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 a -NH2 primary amino functional group at the end of the molecular chain, three hydrogen bonds can be generated simultaneously at one end group, significantly enhancing the bonding force between the filler and the polymer chain segment.

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

[0012] Furthermore, in step S20, the polymerization is terminated at a time of 5 to 15 minutes, and the molar ratio of the diisocyanate compound to n-butyllithium 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 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 amine-modified solution-polymerized styrene-butadiene rubber, which is prepared by the preparation method described above.

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

[0016] Furthermore, the glass transition temperature of the primary amine-modified solution-polymerized styrene-butadiene rubber is -90~20℃; the Mooney viscosity of the primary amine-modified solution-polymerized styrene-butadiene rubber is (ML1+4 / 100℃) 20~110; the molecular weight of the primary amine-modified solution-polymerized styrene-butadiene rubber is 100,000~1,200,000 g / mol; the molecular weight distribution of the primary amine-modified solution-polymerized styrene-butadiene rubber is unimodal, with MDI=1.0~3.0; the amino end-capping rate or modification rate of the primary amine-modified solution-polymerized styrene-butadiene rubber is ≥95%; and the nitrogen content of the primary amine-modified solution-polymerized styrene-butadiene rubber is 50~70 mg / kg.

[0017] SSBR modified by diisocyanate end-capping has a high modification rate, therefore the diisocyanate end-capping agent has high modification reactivity.

[0018] Furthermore, the terminal modifying groups of the primary amine-modified solution-polymerized styrene-butadiene rubber contain imino, carbonyl, and primary amine structures; the primary amine-modified solution-polymerized styrene-butadiene rubber undergoes further chain extension reaction with polyurethane components through reactive extrusion technology, resulting in the formation of polyurethane block structures at the ends of the styrene-butadiene rubber molecular chains.

[0019] By adopting the technical solution of the present invention, the following technical effects can be achieved:

[0020] (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, the amount added is low, and there are no side reactions;

[0021] (2) The terminal groups formed by this SSBR have three heteroatom structures: imino-NH-, carbonyl>C=O and primary amino-NH2. Theoretically, there are 6 hydrogen bond generation sites. It has high polarity and strong binding force with silica filler, which promotes the formation of a more stable and structurally complete filler-polymer network and significantly improves the dynamic properties of rubber materials.

[0022] (3) The primary amino terminus is an active functional group, which can be used by styrene-butadiene rubber as the basis for further functional group modification reactions. For example, it can be reacted with polyurethane components using reactive extrusion technology to generate polyurethane block chain structure at the end of the styrene-butadiene rubber molecular chain. This special structure of polymer combines the excellent properties of styrene-butadiene rubber and polyurethane resin. Attached Figure Description

[0023] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0024] Figure 1 The reaction mechanism of solution-polymerized styrene-butadiene rubber end-capped with polyisocyanate compounds;

[0025] Figure 2 The chemical structural formula of solution-polymerized styrene-butadiene rubber is given. Detailed Implementation

[0026] To make the above-mentioned objectives, features, and advantages of the present invention more apparent and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] In recent years, to improve the fuel economy of automobiles and to meet higher environmental and safety requirements, it is necessary to further reduce the rolling resistance of tires while improving their wear resistance and wet skid resistance. Solution-polymerized styrene-butadiene rubber (SBR), as a crucial component of tire tread compounds that directly contact the ground, requires excellent dynamic performance. Previously, carbon black and silica were widely used as reinforcing fillers for tire treads. However, using silica as a filler can prepare rubber compositions with excellent hysteresis properties, achieving a superior balance between high wet skid resistance and low rolling resistance in tire treads. However, compared to the hydrophobicity of carbon black, silica has a high hydrophilicity due to the large number of silanol groups on its surface, making it difficult to disperse uniformly in non-polar solution-polymerized SBR. Its dispersibility is worse than that of carbon black, which is detrimental to the performance of the final tire product. Therefore, modification techniques are needed to effectively combine hydrophilic silica with hydrophobic solution-polymerized SBR and ensure its uniform dispersion and mixing.

[0028] To promote the affinity between silica and solution-polymerized styrene-butadiene rubber (SBR), previous researchers have attempted to add silane coupling agents (such as silane 69, also known as bis(triethoxysilane)tetrasulfide; γ-mercaptopropyltrimethoxysilane; etc.) during the rubber compounding process, and to use the aforementioned silane coupling agents to modify the surface of silica. However, these methods have several problems: adding silane coupling agents during compounding not only requires large quantities but also causes "migration," leading to deterioration of rubber properties; adding silane coupling agents during compounding has a limited effect on promoting the affinity between fillers and rubber; the pretreatment process for surface modification of silica using silane coupling agents is complex, and the modification effect is not high, with little improvement in the interfacial interaction between fillers and rubber.

[0029] Therefore, researchers have begun to explore the introduction of polar functional groups at the ends of solution-polymerized styrene-butadiene rubber (SBR) molecular chains. This enhances the interfacial interaction between the rubber and filler, resulting in uniform dispersion of the filler within the rubber. Furthermore, the polar functional groups carried at the ends of the SBR molecular chains effectively bind with the silica filler, significantly reducing the number of self-terminal groups and forming a well-structured filler-polymer network, thereby significantly reducing the hysteresis loss of the rubber material. LG Chem Corporation of South Korea, in its patent CN107810209B, describes: 1. Cycloheximine reacts immediately with a conjugated diene (e.g., butadiene) after contact with n-butyllithium to prepare an amino-functionalized initiator, which can be used to initiate the random copolymerization of butadiene and styrene to prepare chain-end amino-functionalized solution-polymerized SBR; 2. This invention primarily uses a vinyl-N,N-dimethylbenzylamine compound to react with butyllithium to prepare an amino-functionalized anionic initiator, which can also be used to prepare chain-end amino-functionalized solution-polymerized SBR. Asahi Kasei Corporation of Japan, in its patent CN105175582B, describes a method for random copolymerization of butadiene and styrene using alkyl lithium initiators. Finally, 1-[3-(triethoxysilyl)propyl]-4-methylpiperazine, 1-[3-(triethoxysilyl)propyl]-4-(trimethylsilyl)piperazine, tetraglycidyl-1,3-diaminomethylcyclohexane, 2-[3-(trimethoxysilyl)propyl]-1,3-dimethylimidazolane, [3-(dimethylamino)propyl]trimethoxysilane, and 1,3-dimethyl-2-imidazolinone are added as end-capping agents. All of these methods introduce amino and / or siloxane groups at the end of the styrene-butadiene rubber, achieving an end-capping modification rate of over 80%. In addition, CN102482359A also uses piperazine compounds containing siloxane substituents as end-capping agents for styrene-butadiene rubber (SBR); CN107250172B and CN109476778B use silazane compounds as end-capping agents for SBR; CN107835752A uses 3-isocyanate-propyltrimethoxysilane to react with hydroxyl-terminated polybutadiene to prepare silane-modified polybutadiene rubber for tire components. All of the above methods can introduce amino and / or siloxane groups into the chain ends of solution-polymerized SBR molecules, achieving an end-capping rate of over 80%, thus realizing chain-end modification of solution-polymerized SBR.

[0030] However, the above methods can only introduce tertiary amino groups and siloxane groups at the molecular chain ends. These groups can only pair with the silanol groups on the surface of silica fillers using the lone pairs of electrons from nitrogen and / or oxygen atoms, resulting in a limited number of hydrogen bonds and weak bonding. If a -NH2 primary amino functional group can be introduced at the molecular chain ends, three hydrogen bonds can be formed simultaneously at one end group, significantly enhancing the bonding between the filler and the polymer chain ends.

[0031] In addition, the above-mentioned capping agents have the following problems: complex structure and difficult to obtain; high price; obvious odor and strong toxicity; low reactivity and long reaction time; large addition amount and many side reactions.

[0032] The present invention aims to solve the above-mentioned problems. In view of the defects of solution-polymerized styrene-butadiene rubber (SSBR) in the prior art as tire tread, the present invention aims to provide a primary amine-modified solution-polymerized styrene-butadiene rubber and its preparation method. The primary amine-modified solution-polymerized styrene-butadiene rubber prepared by the method has high polarity and strong bonding force with silica filler, which can promote the formation of a more stable and structurally complete filler-polymer network and significantly improve the dynamic performance of rubber materials.

[0033] To achieve the above objectives, the present invention provides a method for preparing primary amine-modified solution-polymerized styrene-butadiene rubber (SBR). The method includes the following steps: in a polymerization system, using n-butyllithium as an initiator and tetrahydrofuran as a polymerization activator, initiating the polymerization of butadiene monomers and styrene monomers to obtain active SBR chains; adding a diisocyanate compound to the polymerization system to terminate the polymerization, and simultaneously introducing isocyanate groups at the ends of the active SBR chains to obtain a SBR solution; adding a terminator to the SBR solution, stirring, precipitating, and drying to obtain the primary amine-modified solution-polymerized SBR.

[0034] The reaction mechanism of solution-polymerized styrene-butadiene rubber end-capped with polyisocyanate compounds is as follows: Figure 1 As shown.

[0035] For example, a solvent is added to the polymerization system. 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 solution, an antioxidant can be added. The antioxidant can be one or more of butylated hydroxytoluene (BHT), antioxidant 1076, and antioxidant 1520, and the amount of antioxidant added is 0.1~1.0%wt of the solution-polymerized styrene-butadiene rubber, preferably 0.6%wt. In addition, by adding the terminator deionized water after stirring, the isocyanate groups can be converted into primary amino groups. Then, by adding polar solvents such as alcohol or methanol, the SSBR modified with primary amino groups at the chain ends can be precipitated.

[0036] 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-butyllithium added is 100-750 mg / kg monomer; and the amount of tetrahydrofuran added is 50-50000 mg / kg monomer.

[0037] 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 of monomer, where the monomer refers to butadiene monomer and styrene monomer, and the amount of tetrahydrofuran added per kilogram of monomer is 500 mg.

[0038] Furthermore, the diisocyanate compound includes at least one of diphenylmethane diisocyanate, hydrogenated phenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, naphthalene diisocyanate, and hexamethylene diisocyanate.

[0039] By introducing a -NH2 primary amino functional group at the end of the molecular chain, three hydrogen bonds can be generated simultaneously at one end group, significantly enhancing the bonding force between the filler and the polymer chain segment.

[0040] Furthermore, in step S10, the polymerization temperature is 0~100℃ and the polymerization time is 20~180min.

[0041] Further, in step S20, the polymerization is terminated at a time of 5 to 15 minutes, and the molar ratio of the diisocyanate compound to the n-butyllithium is 0.9 to 1.5.

[0042] Preferably, the molar ratio of the diisocyanate compound to n-butyllithium is 1.1 to 1.2.

[0043] 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 terminator added is 0.9 to 5.0 times the molar amount of the initiator; and the stirring time is 5 to 15 minutes.

[0044] Preferably, the terminator is deionized water, and the amount of terminator added is 3.0 times the molar amount of the initiator.

[0045] The present invention also provides a primary amine-modified solution-polymerized styrene-butadiene rubber, which is prepared by the preparation method described above.

[0046] Furthermore, the styrene content of the primary amine-modified solution-polymerized styrene-butadiene rubber is 5-70%; the vinyl content of the primary amine-modified solution-polymerized styrene-butadiene rubber is 6-90%.

[0047] Furthermore, the glass transition temperature of the primary amine-modified solution-polymerized styrene-butadiene rubber is -90~20℃; the Mooney viscosity of the primary amine-modified solution-polymerized styrene-butadiene rubber is (ML1+4 / 100℃) 20~110; the molecular weight of the primary amine-modified solution-polymerized styrene-butadiene rubber is 100,000-1,200,000 g / mol; the molecular weight distribution of the primary amine-modified solution-polymerized styrene-butadiene rubber is unimodal, with MDI=1.0~3.0; the amino end-capping rate or modification rate of the primary amine-modified solution-polymerized styrene-butadiene rubber is ≥95%; and the nitrogen content of the primary amine-modified solution-polymerized styrene-butadiene rubber is 50~70 mg / kg.

[0048] SSBR modified by diisocyanate end-capping has a high modification rate, therefore the diisocyanate end-capping agent has high modification reactivity.

[0049] Furthermore, the terminal modifying groups of the primary amine-modified solution-polymerized styrene-butadiene rubber contain imino, carbonyl, and primary amine structures; the primary amine-modified solution-polymerized styrene-butadiene rubber undergoes further chain extension reaction with polyurethane components through reactive extrusion technology, resulting in the formation of polyurethane block structures at the ends of the styrene-butadiene rubber molecular chains.

[0050] By generating the "SSBR-N-TPU" amphiphilic elastomer, it can be used as a blending modifier and solubilizer for polar resins such as polycarbonate (PC), polyethylene terephthalate (PET), polyetheretherketone (PEEK), etc., as well as non-polar polymers such as cis-butadiene rubber, styrene-butadiene rubber, styrene-butadiene-styrene block copolymer (SBS), polymer elastomer-olefin-styrene-olefin copolymer (SEBS), polyethylene (PE), polypropylene (PP), etc.

[0051] This invention mainly compares the modification effects of diisocyanate end-capping agents on SSBR. Therefore, the embodiments and comparative examples of this invention are mainly tested and characterized using the following methods.

[0052] Mooney viscosity test: Preheat two samples with a weight of more than 15 grams for 1 minute, then measure at 100°C for 4 minutes using an MV-2000 manufactured by ALPHA Technologies.

[0053] Molecular weight determination (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 was used as the standard sample for molecular weight calculation; THF was used as the mobile phase at a flow rate of 1 ml / min.

[0054] Modification rate analysis method: Using primary amino-modified styrene-butadiene rubber as the sample, the amino modification rate was determined by utilizing the characteristic that the modified component adsorbs onto a GPC column packed with silica-based gel. The adsorption amount of the modified rubber component on the silica column was determined by the difference in chromatograms (the difference between the chromatogram obtained by measuring the sample solution containing the sample and the low molecular weight polystyrene internal standard using a polystyrene-based gel column and the chromatogram obtained by measuring using a silica-based column). GPC analysis sample preparation method: 10 mg of sample and 5 mg of standard low molecular weight polystyrene internal standard were dissolved in 20 ml of tetrahydrofuran. Polystyrene-based column GPC determination conditions: THF was used as the eluent, and 200 μL of sample was injected into the device for measurement. A guard column (TSK guard column HHR-H manufactured by Tosoh Corporation) and three columns (TSK gel Super Multipore HZ-H manufactured by Tosoh Corporation) were connected together. The chromatogram was obtained using an RI detector (HLC8020, manufactured by Tosoh Corporation) at a column oven temperature of 40°C and a THF flow rate of 1.0 mL / min. For silica-based column GPC assays, THF was used as the eluent, and 200 μL of the sample was injected into the apparatus for analysis. Three silica-based columns (Zorbax PSM-1000S, PSM-300S, and PSM-60S) were connected together, with a DIOL 4.6 × 12.5 mm 5 micron guard column connected to the front. The chromatogram was obtained using an RI detector (HLC8020, manufactured by Tosoh Corporation) at a column oven temperature of 40°C and a THF flow rate of 0.5 mL / min. Method for calculating the modification rate: Set the peak area of ​​the chromatogram using a polystyrene column to 100, and designate the peak area of ​​the sample as P1 and the peak area of ​​standard polystyrene as P2; set the peak area of ​​the chromatogram using a silica column to 100, and designate the peak area of ​​the sample as P3 and the peak area of ​​standard polystyrene as P4, where P1 + P2 = P3 + P4 = 100. Calculate the modification rate (%) using the following formula:

[0055] Modification rate (%) = [1 - (P2 × P3) / (P1 × P4)] × 100

[0056] Nuclear magnetic resonance (NMR) analysis: The microstructure of the sample was analyzed using a Brucker 600 MHz superconducting Fourier transform NMR spectrometer. The ¹H spectrum was observed at 600 MHz, and the ¹³C spectrum at 150.9 MHz. The solvent was CDCl₃, TMS was used as an internal standard, and the test temperature was 20℃. This method can be used to analyze the styrene and vinyl content of styrene-butadiene rubber (SBR).

[0057] DSC thermal property analysis method: Take a sample of 15-20 mg, and test the temperature range from -120℃ to 120℃. Before the formal test, eliminate the thermal history. The heating and cooling rate is 10℃ / min, and the dwell time at the highest and lowest temperatures is 5 min. This method can be used to analyze the glass transition temperature of styrene-butadiene rubber.

[0058] Conversion rate test method: A small portion of the polymer solution was removed from the reactor using a specially designed cylindrical container. The total weight of the cylindrical container containing the polymer solution was then measured (A). The polymer solution in the cylindrical container was then transferred to an aluminum tray, and the weight of the cylindrical container without the polymer solution was measured (B). The aluminum tray containing the polymer solution was dried in a vacuum oven at 100°C for at least 180 minutes until the polymer was completely dry and transparent. Finally, the weight of the dried polymer was measured (C), and the polymer conversion rate was calculated using the following mathematical formula:

[0059]

[0060] Nitrogen content analysis method: N content was measured using the NSX analytical method with a trace nitrogen quantitative analyzer (NSX-2100H). Specifically, the trace nitrogen quantitative analyzer (autosampler, horizontal furnace, PMT & Nitrogen detector) was turned on, the carrier gas flow rate was set to 250 ml / min for Ar, 350 ml / min for oxygen, and 300 ml / min for ozone generator, and the heater was set to 800°C. The analyzer was left to stabilize for approximately 3 hours. After stabilization, calibration curves were prepared using nitrogen standards (AccuStandard S-22750-01 to 5 ml) at concentrations of 5 ppm, 10 ppm, 50 ppm, 100 ppm, and 500 ppm, and the area corresponding to each concentration was obtained. Then, a ceramic boat containing 20 mg of sample was placed in the analyzer's autosampler and measured to obtain the area. The N content was calculated using the thus obtained sample area and calibration curves.

[0061] Example 1

[0062] Cyclohexane was used as the solvent, n-butyllithium as the initiator, and tetrahydrofuran as the polymerization activator. Butadiene and styrene were polymerized at 20-100℃ for 2 hours. The monomer concentration was 20%, the amount of cyclohexane added was 4000g, the mass ratio of butadiene to styrene was 30 / 70, the amount of 2.0mol / L n-butyllithium solution added was 2.10ml, and the amount of 100g / L tetrahydrofuran added was 5ml. Then, diphenylmethane diisocyanate (MDI) was added at the same polymerization temperature, with 8.5ml of 0.5mol / L diisocyanate compound solution added. The polymerization was terminated for 5-15 minutes, simultaneously introducing isocyanates into the ends of the styrene-butadiene rubber molecular chains. The cyanate ester group was added to the styrene-butadiene rubber (SBR) solution at the polymerization temperature. Deionized water (the amount of the terminator was three times the molar equivalent of the initiator) was added as a terminator, and the mixture was stirred rapidly for 5-15 minutes. Then, butylated hydroxytoluene (BHT) antioxidant (0.6% wt) was added. Alcohol was added to the solution to precipitate the SBR. After discarding the solvent and alcohol mixture, the wet, milky-white SBR block was placed in a stainless steel tray and then vacuum-dried in a 70°C vacuum oven for 24 hours. A colorless and transparent SBR product was finally obtained. The monomer conversion rate was measured to be 99.80%, the Mooney viscosity to be 65, and the number-average molecular weight to be 43.44 × 10⁻⁶. 4 g / mol, weight-average molecular weight is 62.99 × 10 4 The composition of styrene-butadiene rubber is as follows: 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 60 mg / kg.

[0063] Example 2

[0064] With the polymerization conditions in Example 1 unchanged, except that the modifier was replaced with hexamethylene diisocyanate (HDI), the monomer conversion rate was measured to be 100.00%, the Mooney viscosity to be 63, and the number-average molecular weight to be 45.67 × 10⁻⁶. 4 g / mol, 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-polymerized styrene-butadiene rubber is 60 mg.

[0065] Example 3

[0066] With the polymerization conditions in Example 1 unchanged, except that the modifier was replaced with isophorone diisocyanate (IPDI), the monomer conversion rate was measured to be 99.70%, the Mooney viscosity was 65, and the number-average molecular weight was 44.8 × 10⁻⁶.4 g / mol, 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-polymerized styrene-butadiene rubber is 60 mg.

[0067] Comparative Example 1

[0068] With the polymerization conditions in Example 1 unchanged and no modifier added, the monomer conversion rate was measured to be 99.80%, the Mooney viscosity to be 50, and the number-average molecular weight to be 39.67 × 10⁻⁶. 4 g / mol, weight-average molecular weight is 57.12 × 10⁻⁶ g / mol. 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℃, modification rate is 0%, and nitrogen content per kilogram of solution-polymerized styrene-butadiene rubber is 60 mg.

[0069] Comparative Example 2

[0070] With the polymerization conditions in Example 1 unchanged, except that the modifier was replaced with ethylene oxide, the monomer conversion rate was measured to be 100%, the Mooney viscosity to be 57, and the number-average molecular weight to be 42.88 × 10⁻⁶. 4 g / mol, weight-average molecular weight is 62.60 × 10⁻⁶ g / mol. 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-polymerized styrene-butadiene rubber is 0 mg.

[0071] Comparative Example 3

[0072] The polymerization conditions in Example 1 were kept unchanged, except that the modifier was replaced with 3-chloropropyltrimethoxysilane. The monomer conversion rate was measured to be 99.90%, the Mooney viscosity was 56, and the number-average molecular weight was 41.20 × 10⁻⁶. 4 g / mol, 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-polymerized styrene-butadiene rubber is 0 mg.

[0073] Comparative Example 4

[0074] The polymerization conditions in Example 1 were kept unchanged, except that the modifier was replaced with N,N-dimethylaminopropyltrimethoxysilane. The monomer conversion rate was measured to be 100%, the Mooney viscosity to be 55, and the number-average molecular weight to be 42.01 × 10⁻⁶. 4 g / mol, weight-average molecular weight is 63.02 × 10⁻⁶ g / mol. 4 g / mol, molecular weight distribution of 1.50, styrene content of 30.33%, 1,2-polybutadiene structural unit content of 40.50%, glass transition temperature of -30℃, modification rate of 78.50%, and nitrogen content of 0 mg per kilogram of solution-polymerized styrene-butadiene rubber.

[0075] Comparative Example 5

[0076] The polymerization conditions in Example 1 were kept unchanged, except that the modifier was replaced with 4-vinyl-N,N-dimethylbenzylamine. The monomer conversion rate was measured to be 99.60%, the Mooney viscosity was 59, and the number-average molecular weight was 42.30 × 10⁻⁶. 4 g / mol, weight-average molecular weight is 62.18 × 10⁻⁶ g / mol. 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-polymerized styrene-butadiene rubber is 31.5 mg.

[0077] The test results of SBBR in Examples 1-3 and Comparative Examples 1-5 show that:

[0078] 1. SSBR modified with diisocyanate end caps has a higher modification rate, therefore the modification reactivity of diisocyanate end capping agents is higher;

[0079] 2. SSBRs with diisocyanate end-capping have a higher nitrogen content, resulting in a higher modification rate, higher polarity, and stronger interaction with rubber fillers.

[0080] 3. The SSBR with diisocyanate end-capping has a higher molecular weight and Mooney viscosity, thus the strong polar end groups of the SSBR with diisocyanate end-capping have stronger interactions.

[0081] To evaluate the application performance of solution-polymerized styrene-butadiene rubber (SBR) after vulcanization, in embodiments of the present invention, the vulcanized rubber is prepared through a first-stage mixing and a second-stage mixing process. In the first-stage mixing, rubber, silica, organosilane 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 mixing is performed using a Banbury mixer equipped with a temperature control device. In this case, the initial temperature of the mixing apparatus is controlled at 70°C, and after mixing, the first compound is obtained at a discharge temperature of 145°C. In the second stage of compounding, the first compound was cooled to room temperature, and then the first compound, sulfur, rubber accelerator (DPD (diphenylguanidine)), and vulcanization accelerator (CZ (N-cyclohexyl-2-benzothiazolylsulfinamide)) were added to the mixer and mixed at a temperature below 100°C to obtain the second compound. Finally, vulcanized rubber samples were prepared by crosslinking in a flat vulcanizing machine at 160°C for 20 minutes.

[0082] Table 1 shows the compounding formulas for vulcanized rubber.

[0083] Note: The raw material quantities in Table 1 are expressed as parts by weight based on 100 parts by weight of styrene-butadiene rubber.

[0084] The vulcanized rubbers obtained after compounding the SSBR prepared in Examples 1-3 and Comparative Examples 1-5 were tested and characterized by the following methods.

[0085] Tensile testing of vulcanizates: Tensile strength and tensile stress at 300% elongation (300% tensile strength) were measured according to ASTM 412 tensile testing method when the test specimens were cut. For this purpose, a Universal Test Machine 4204 manufactured by Instron was used, and tensile strength, modulus and elongation were measured at room temperature at a tensile rate of 50 cm / min.

[0086] Dynamic mechanical property testing of vulcanizates: A dynamic mechanical analyzer manufactured by TA was used. The loss factor Tanδ was measured for each sample after deformation at a frequency of 10 Hz in deformation mode and a measurement temperature range of -60°C to 80°C. The Payne effect is represented by the difference between the minimum and maximum values ​​within the deformation range of 0.28% to 40%. A lower Payne effect indicates higher filler dispersibility. Increasing the loss factor at 0°C improves wet skid resistance, and decreasing it at 60°C reduces hysteresis loss and rolling resistance, thus increasing fuel economy. A decrease in the loss modulus at 60°C reduces internal heat generation in the rubber, reduces hysteresis loss, and improves dynamic performance.

[0087] 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)).

[0088] Application Example 1

[0089] Application Example 1 shows the physical properties of vulcanized rubber samples prepared from primary amine-terminated SSBR in Examples 1-3 and Comparative Examples 1-5. The results are shown in Table 2.

[0090] Table 2 shows the physical properties of the vulcanized rubber samples prepared by primary amine-modified SSBR in Examples 1-3 and Comparative Examples 1-5.

[0091]

[0092] From the test data in Table 2, we can see that:

[0093] The 300% tensile strength and elongation at break of Examples 1-3 were not significantly different from those of Comparative Examples 1-5. However, the tensile strength of Examples 1-3 was significantly higher than that of Comparative Examples 1-5. While the tensile strength of Comparative Examples 2-5 was slightly higher than that of Comparative Example 1, it was significantly lower than that of Examples 1-3. This indicates that the primary amine-terminated SSBR exhibits the best mixing and dispersion properties with the rubber filler, resulting in the most complete filler-polymer network and the best mechanical properties in the prepared vulcanized rubber. Diisocyanate end-capping modification technology has advantages over tertiary amine group, siloxane group, and hydroxyl group end-capping modification technologies.

[0094] A higher abrasion resistance index indicates better abrasion resistance of the vulcanized rubber. The abrasion resistance indices of Examples 1-3 are significantly higher than those of Comparative Examples 1-5, indicating that primary amine end-capping modification improves the abrasion resistance of SSBR.

[0095] A higher 0°C loss factor indicates better wet grip or traction of the vulcanized rubber. The 0°C loss factors of Examples 1-3 are all >0.2, higher than Comparative Example 1, indicating that primary amine modification technology endows SSBR with excellent grip and wet grip on ice. Comparative Examples 2-5 show little difference from Examples 1-3, and are all higher than Comparative Example 1, suggesting that tertiary amine groups, siloxane groups, and hydroxyl end-capping modification technologies can also improve the grip performance of SSBR.

[0096] A lower 60°C loss factor indicates lower rolling resistance of the vulcanized rubber, which can improve fuel economy when used in tires. The 60°C loss factors of Examples 1-3 are all below 0.0905, significantly lower than Comparative Examples 1-5, indicating that primary amine end-capping modification technology can significantly reduce the rolling resistance of SSBR. Among them, the 60°C loss factors of Comparative Examples 2-5 are all lower than Comparative Example 1, indicating that tertiary amine groups, siloxane groups, and hydroxyl end-capping modification technologies also reduce the rolling resistance of SSBR to some extent, but far less than the primary amine end-capping modification technology.

[0097] A lower loss modulus at 60°C indicates lower internal heat generation and better dynamic performance in vulcanized rubber. When used in tires, this can reduce rolling resistance and improve fatigue resistance. The loss moduli at 60°C in Examples 1-3 are all lower than those in Comparative Examples 1-5, indicating that the primary amine-terminated SSBR has lower internal heat generation, superior dynamic performance, and better fatigue resistance. Similarly, the loss moduli at 60°C in Comparative Examples 2-5 are all lower than those in Comparative Example 1, indicating that tertiary amine groups, siloxane groups, and hydroxyl-terminated modification techniques can also improve the dynamic performance and fatigue resistance of SSBR, but the improvement effect is not as good as that of primary amine-terminated modification techniques.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A process for the preparation of a primary amino group-modified solution- polymerized styrene-butadiene rubber, characterized in that, The preparation method comprises the following steps: S10, initiating polymerization of butadiene monomers and styrene monomers in a polymerization system by using n-butyllithium as an initiator and tetrahydrofuran as a polymerization activator to obtain butadiene styrene rubber active chains; S20, adding a diisocyanate compound to the polymerization system to terminate polymerization and introduce isocyanate groups at the ends of the butadiene styrene rubber active chains to obtain butadiene styrene rubber glue; S30, adding a termination agent to the butadiene styrene rubber glue, stirring, precipitating, and drying to obtain the primary amino group modified solution polymerized butadiene styrene rubber; The termination agent comprises deionized water.

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

3. The preparation method according to claim 1, characterized in that, The diisocyanate compound comprises at least one of diphenyl methane diisocyanate, hydrogenated phenyl methane diisocyanate, toluene diisocyanate, isophorone diisocyanate, naphthalene diisocyanate, and hexamethylene diisocyanate.

4. The method of claim 1, wherein, In the S10, the temperature of the polymerization is 0-100 ℃, and the time of the polymerization is 20-180 min.

5. The preparation method according to claim 1, characterized in that, In the S20, the time of the polymerization termination is 5-15 min, and the molar ratio of the diisocyanate compound to the n-butyllithium is 0.9-1.

5.

6. The method of claim 1, wherein, In the S30, the addition amount of the termination agent is 0.9-5.0 times the molar amount of the initiator; and the time of the stirring is 5-15 min.

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

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

9. The primary amino-modified solution styrene-butadiene rubber of claim 7, wherein The glass transition temperature of the primary amino group modified solution polymerized butadiene styrene rubber is -90-20 ℃; the Mooney viscosity ML1+4 / 100 ℃ of the primary amino group modified solution polymerized butadiene styrene rubber is 20-110; the molecular weight of the primary amino group modified solution polymerized butadiene styrene rubber is 100-1200 kg / mol; the molecular weight distribution of the primary amino group modified solution polymerized butadiene styrene rubber is unimodal distribution, MDI=1.0-3.0; the amino group capping rate or modification rate of the primary amino group modified solution polymerized butadiene styrene rubber is ≥95%; and the nitrogen content of the primary amino group modified solution polymerized butadiene styrene rubber is 50-70 mg / kg.

10. The primary amino-modified solution styrene-butadiene rubber of claim 7, wherein The terminal modification group of the primary amino group modified solution polymerized butadiene styrene rubber contains imino, carbonyl, and primary amino structures; and the primary amino group modified solution polymerized butadiene styrene rubber is further subjected to chain extension reaction by reaction extrusion technology to generate polyurethane block structure at the ends of butadiene styrene rubber molecular chains.

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