In-chain functionalized solution polymerized styrene-butadiene rubber and in-chain modification method thereof

Abstract

The invention provides an in-chain functionalized solution polymerized styrene-butadiene rubber and an in-chain modification method thereof. The 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 terminator into the polymerization system to terminate the polymerization reaction to obtain a styrene butadiene rubber solution; the method comprises the following steps: adding a thiol compound and a free radical initiator into a styrene-butadiene rubber solution, heating and stirring the styrene-butadiene rubber solution, after a modification reaction is finished, adding alcohol to separate out and precipitate the styrene-butadiene rubber, and drying to obtain the chain-functionalized solution polymerized styrene-butadiene rubber. The in-chain functionalized solution polymerized styrene-butadiene rubber is prepared by the preparation method, and the interface bonding force between the white carbon black and the styrene-butadiene rubber can be enhanced, so that the hysteresis loss of a final tire rubber product is reduced, and the tire rubber product is endowed with high wear resistance, fatigue resistance and excellent wet skid-rolling resistance balance.

Description

Technical Field

[0001] The invention relates to the technical field of in-chain functionalized solution-polymerized styrene-butadiene rubber, in particular to an in-chain functionalized solution-polymerized styrene-butadiene rubber and an in-chain modification method thereof. Background Art

[0002] Solution polystyrene butadiene rubber (SSBR) is a random copolymer of styrene and butadiene. Its sequence distribution and microstructure can be precisely controlled. It has the characteristics of narrow molecular weight distribution and excellent heat resistance, wear resistance and aging resistance. Moreover, the vulcanization performance, processing performance and product performance of solution polystyrene butadiene rubber are better than those of natural rubber, so it is widely used in tires, shoes and other vulcanized rubber products.

[0003] At present, the "solution polymerized styrene butadiene rubber + white carbon black" system is the standard for low rolling resistance tread rubber. It has become an industry consensus to prepare tread rubber by reinforcing SSBR with white carbon black to solve the "magic triangle" problem. However, as a commonly used rubber reinforcing agent, white carbon black carries a large number of silanol groups on its surface, resulting in poor dispersion in non-polar rubber substrates. The key problem to be overcome is to achieve good interface bonding between the two through rubber material structure design and white carbon black interface property regulation, thereby achieving uniform dispersion of polar white carbon black in the rubber substrate.

[0004] In order to promote the affinity between white carbon black and solution polymerized styrene butadiene rubber, a silane coupling agent can be added during the rubber mixing process, and a method of surface modification of silicon dioxide using a silane coupling agent can be used. In addition, people also use technologies such as star coupling and end-capping modification to improve the processing performance and dynamic properties of styrene butadiene rubber. The above methods can all introduce polar functional groups such as amino groups and siloxane groups at the ends of the molecular chains 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. However, the above methods can only introduce polar functional groups at the ends of the molecular chains. Since the number of macromolecular chain ends of solution polymerized styrene butadiene rubber is very limited, the chain-end modification technology has a very limited effect on improving the interfacial bonding force between fillers and polymers. Summary of the invention

[0005] The present invention aims to solve the above problems by adopting the "thiol-ene" click chemistry reaction mechanism and utilizing thiol compounds carrying various polar functional groups to chemically modify the residual double bonds in the solution polymerized styrene-butadiene rubber, thereby introducing polar functional groups into the molecular chain of the solution polymerized styrene-butadiene rubber to enhance the interfacial bonding force between silica and styrene-butadiene rubber.

[0006] To achieve the above-mentioned purpose, the present invention provides a method for chain-in functionalized 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 terminator to the polymerization system to terminate the polymerization reaction to obtain a styrene-butadiene rubber glue solution; adding a thiol compound and a free radical initiator to the styrene-butadiene rubber glue solution, heating and stirring the styrene-butadiene rubber glue solution, and after the modification reaction is completed, adding alcohol to precipitate the styrene-butadiene rubber, and drying to obtain the chain-in functionalized solution-polymerized styrene-butadiene rubber.

[0007] Furthermore, the thiol compound includes any one or more of mercaptopropionic acid, mercaptoethanol, aminopropyl mercaptan, N,N-dimethylaminopropyl mercaptan, piperidinylpropyl mercaptan, hexamethyleneiminopropyl mercaptan, pyrrolidinopropyl mercaptan, ethyl mercaptopropionate, mercaptopropyltrimethoxysilane, mercaptopropyl ethylene oxide, mercaptopropyl glycidyl ether, and dodecyl mercaptan.

[0008] Furthermore, the amount of the thiol compound added is 1-10% of the total mass of the monomers.

[0009] Furthermore, the free radical initiator includes any one or more of tert-butyl hydroperoxide, azobisisobutyronitrile, azobisisoheptanenitrile, dilauroyl peroxide, diisopropylbenzene peroxide, and dibenzoyl peroxide.

[0010] Furthermore, the amount of the free radical initiator added is 1-5% of the amount of the thiol compound added.

[0011] Furthermore, the concentration of the monomer is 5-30%; 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.

[0012] Further, in step S10, the terminator includes any one or more of deionized water, methanol, ethanol, isooctyl alcohol, isooctyl acid, 2,4,6-tri-tert-butylphenol, trimethylchlorosilane, 1-bromooctane, stearic acid, stearyl alcohol, acids, phenols, and halogenated hydrocarbon compounds; the added amount of the terminator is 0.9 to 2.0 times the molar amount of the initiator.

[0013] Furthermore, in step S20, the heating temperature is above 60°C, and the stirring time is 10 to 60 minutes.

[0014] The present invention also provides a chain-functionalized solution-polymerized styrene-butadiene rubber, which is prepared by the chain-functionalized solution-polymerized styrene-butadiene rubber through the above-mentioned chain-modification method.

[0015] Furthermore, the chain-functionalized solution-polymerized styrene-butadiene rubber is a random copolymer of butadiene monomer and styrene monomer; the styrene content in the chain-functionalized solution-polymerized styrene-butadiene rubber is 5-95%; the content of vinyl structural units in the chain-functionalized solution-polymerized styrene-butadiene rubber is 6-90%; the grafting rate of thiol compounds in the chain-functionalized solution-polymerized styrene-butadiene rubber is 1-60%; the Mooney viscosity of the chain-functionalized solution-polymerized styrene-butadiene rubber is 30-80; the number average molecular weight of the chain-functionalized solution-polymerized styrene-butadiene rubber is 100,000-1,000,000 g / mol; the molecular weight distribution of the chain-functionalized solution-polymerized styrene-butadiene rubber is 1.0-2.0; the glass transition temperature of the chain-functionalized solution-polymerized styrene-butadiene rubber is -50~0°C; and the modification rate of the chain-functionalized solution-polymerized styrene-butadiene rubber is greater than 90%.

[0016] After adopting the technical solution of the present invention, the following technical effects can be achieved: (1) The thiol compound and free radical initiator used in the present invention are commonly used industrial chemicals, which have the advantages of being cheap, readily available, and low in toxicity; (2) The chain modification technology adopted by the present invention, also known as mercapto-ene click chemistry modification technology, uses mercaptan compounds carrying various polar functional groups to chemically modify the residual double bonds in the solution polymerized styrene butadiene rubber, and can introduce polar functional groups such as carboxyl, hydroxyl, siloxane, tertiary amine, ester, epoxy, etc. into the molecular chain of the solution polymerized styrene butadiene rubber, which can significantly enhance the interfacial bonding force between silica and styrene butadiene rubber, thereby reducing the hysteresis loss of the final tire rubber product and giving it high wear resistance, fatigue resistance and excellent wet skid-rolling resistance balance; (3) The chain modification technology adopted in the present invention has the characteristics of low amount of modifier added, high functional group grafting rate, high polymer modification rate, etc., and has obvious modification effect, and has the advantage of controllable adjustment of functional group grafting rate; it has the advantages of mild reaction conditions, simple operation process, and few side reactions. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] 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 This is the reaction principle of chain modification of chain-functionalized solution-polymerized styrene-butadiene rubber. DETAILED DESCRIPTION

[0018] 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.

[0019] Solution-polymerized styrene-butadiene rubber is a random copolymer of styrene and butadiene. Its sequence distribution and microstructure can be precisely controlled. It has the characteristics of narrow molecular weight distribution and excellent heat resistance, wear resistance and aging resistance. Moreover, the vulcanization performance, processing performance and product performance of solution-polymerized styrene-butadiene rubber are better than those of natural rubber, so it is widely used in tires, shoes and other vulcanized rubber products.

[0020] As environmental issues such as "carbon emissions" and oil resource shortages become increasingly prominent, the automotive industry has higher and higher energy-saving requirements for tires. Related studies also show that the energy consumption generated by overcoming the rolling resistance of tires during vehicle driving accounts for 30% of the total energy consumption. As a commonly used rubber reinforcing agent, silica carries a large number of silanol groups on its surface, resulting in poor dispersion in non-polar rubber substrates. The key problem that needs to be overcome is to achieve good interface bonding between the two through rubber material structure design and silica interface property regulation, thereby achieving uniform dispersion of polar silica in the rubber substrate.

[0021] In order to promote the affinity between silica and solution polymerized styrene-butadiene rubber, the following methods can be used: (1) adding silane coupling agents, including bis(triethoxysilylpropane) tetrasulfide, γ-mercaptopropyltrimethoxysilane, etc., during the rubber mixing process; (2) using the above silane coupling agents to modify the surface of silica, and by adjusting the interface properties of silica, achieve good interface bonding between silica and styrene-butadiene rubber. However, the above methods have the following problems: (1) adding silane coupling agents during mixing not only requires a large amount of silane coupling agents, but also causes "migration" of silane coupling agents in the final vulcanized product, resulting in poor rubber performance; and adding silane coupling agents during mixing does not significantly improve the interface bonding between silica and styrene-butadiene rubber; (2) the pretreatment process of using silane coupling agents to modify the surface of silica is complicated, and the modification effect is not good, and the effect of improving the interface bonding between silica and styrene-butadiene rubber is also very limited.

[0022] In addition, people also use star coupling, end-capping modification and other technologies to improve the processing performance and dynamic performance of styrene-butadiene rubber. LG Chemical Co., Ltd. of South Korea introduced in its patent CN107810209B: Cyclohexylimide reacts with conjugated dienes (such as butadiene) immediately after contacting n-butyl lithium to prepare amino-functionalized initiators, which are used to initiate random copolymerization of butadiene and styrene to prepare chain-end amino-functionalized solution-polymerized styrene-butadiene rubber; this 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.

[0023] 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%.

[0024] In addition, CN102482359A also uses a piperazine compound containing a siloxane substituent as a capping agent for styrene-butadiene rubber; CN107250172B and CN109476778B use silazane compounds as 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.

[0025] The above methods can introduce polar functional groups such as amino groups and siloxane groups into the molecular chain ends of solution-polymerized styrene-butadiene rubber, with an end-capping rate of more than 80%, thereby realizing the chain-end modification of solution-polymerized styrene-butadiene rubber. However, the above methods can only introduce polar functional groups into the molecular chain ends. Since the number of macromolecular chain ends of solution-polymerized styrene-butadiene rubber is very limited, the effect of chain-end modification technology on improving the interfacial bonding force between fillers and polymers is also very limited. In addition, the above end-capping agents have the following problems: the structure of the above chain-end modifiers is complex and difficult to obtain; the price of the above chain-end modifiers is high; the above chain-end modifiers have obvious odor and strong toxicity; the reaction activity of the above chain-end modifiers is not high, the addition amount is large, and there are many side reactions; the range of polar functional groups of the above chain-end modifiers is small, generally mainly tertiary amine groups and siloxane groups.

[0026] Therefore, we consider developing a chain modification technology for solution polymerized styrene butadiene rubber: adopting the "thiol-ene" click chemistry reaction mechanism and utilizing thiol compounds carrying various polar functional groups to chemically modify the residual double bonds in the solution polymerized styrene butadiene rubber, thereby introducing polar functional groups such as carboxyl, hydroxyl, siloxane, tertiary amine, ester, and epoxy groups into the molecular chain of the solution polymerized styrene butadiene rubber to enhance the interfacial bonding force between silica and styrene butadiene rubber, thereby reducing the hysteresis loss of the final tire rubber product and giving it high wear resistance, fatigue resistance, and excellent wet skid-rolling resistance balance.

[0027] To achieve the above-mentioned purpose, the present invention provides a method for in-chain modification of 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 terminator to the polymerization system to terminate the polymerization reaction to obtain a styrene-butadiene rubber glue solution; adding a thiol compound and a free radical initiator to the styrene-butadiene rubber glue solution, heating and stirring the styrene-butadiene rubber glue solution, and after the modification reaction is completed, adding alcohol to precipitate the styrene-butadiene rubber, and drying to obtain the in-chain functionalized solution-polymerized styrene-butadiene rubber.

[0028] By introducing thiol compounds carrying polar functional groups, the residual double bonds of solution polymerized styrene butadiene rubber can be chemically modified, and various polar functional groups such as carboxyl, hydroxyl, siloxane, tertiary amine, ester, and epoxy groups can be introduced into the molecular chain of solution polymerized styrene butadiene rubber, thereby significantly enhancing the interfacial bonding force between silica and styrene butadiene rubber.

[0029] The reaction principle of chain-modified solution-polymerized styrene-butadiene rubber is as follows: Figure 1 shown.

[0030] In some embodiments of the present application, the chain modification method is carried out in a nitrogen atmosphere with a purity level of 99.99% or above, the polymerization temperature is 0~60°C, the polymerization time is 2 hours, and during the polymerization process, the reaction temperature reaches a maximum of 90~100°C.

[0031] For example, a terminator is added to the polymerization system to terminate the polymerization reaction and then stirred rapidly for 5 to 15 minutes, and an antioxidant is further added. The antioxidant is used to inhibit oxidation and thermal aging problems of the rubber during use and extend its service life. The antioxidant includes any one or more of 2,6-di-tert-butyl-p-cresol, antioxidant 1076, antioxidant 1520, antioxidant 168, antioxidant 626 and other hindered phenols, hindered amines, and phosphate compounds, preferably antioxidant 1076 and antioxidant 1520. The amount of the antioxidant added relative to the solution-polymerized styrene-butadiene rubber is 0.01 to 0.3%wt., preferably 0.05%wt.

[0032] For another example, after the in-chain modification process is completed, alcohol is added to the styrene butadiene rubber solution to precipitate the styrene butadiene rubber. After the mixture of solvent and alcohol is poured out, the wet rubber block of the milky white styrene butadiene rubber is placed in a stainless steel tray and placed in a vacuum oven at 70°C for vacuum drying for 24 hours to finally obtain a colorless and transparent styrene butadiene rubber product.

[0033] Furthermore, the thiol compound includes any one or more of mercaptopropionic acid, mercaptoethanol, aminopropyl mercaptan, N,N-dimethylaminopropyl mercaptan, piperidinylpropyl mercaptan, hexamethyleneiminopropyl mercaptan, pyrrolidinopropyl mercaptan, ethyl mercaptopropionate, mercaptopropyltrimethoxysilane, mercaptopropyl ethylene oxide, mercaptopropyl glycidyl ether, and dodecyl mercaptan.

[0034] By adding thiol compounds to the polymerization system, the chemical structure of the thiol compounds and the types of available functional groups are diversified, and customized design of polar groups and material properties for chain modification of styrene-butadiene rubber can be achieved.

[0035] Furthermore, the amount of the thiol compound added is 1-10% of the total weight of the monomers.

[0036] Preferably, the amount of the thiol compound added is 3-7% of the total mass of the monomers. It should be noted that the total mass of the monomers refers to the sum of the total mass of the butadiene monomer and the styrene monomer.

[0037] Furthermore, the free radical initiator includes any one or more of tert-butyl hydroperoxide, azobisisobutyronitrile, azobisisoheptanenitrile, dilauroyl peroxide, diisopropylbenzene peroxide, and dibenzoyl peroxide.

[0038] These free radical initiators are compounds that can decompose to generate free radicals at polymerization temperature. By adding free radical initiators to the styrene-butadiene rubber solution, they can decompose to generate a large number of active free radicals in a short period of time at a temperature greater than 60°C. The active free radicals can easily capture the thiol hydrogen atoms (SH) of the thiol compounds to generate thiol free radicals, which then react with the residual double bonds in the styrene-butadiene rubber to generate free radical addition reactions, thereby introducing the polar groups carried by the thiol compounds into the molecular chains of the styrene-butadiene rubber.

[0039] Furthermore, the amount of the free radical initiator added is 1-5% of the amount of the thiol compound added.

[0040] Preferably, the amount of the free radical initiator added is 2% of the amount of the thiol compound added.

[0041] Furthermore, the concentration of the monomer is 5-30%; 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.

[0042] Preferably, the concentration of the monomer is 20%; the amount of n-butyl lithium added is 240 mg / kg monomer, that is, the content of n-butyl lithium relative to the total mass of the monomer is 240 mg / kg; the amount of tetrahydrofuran added is 10000 mg / kg monomer, that is, the content of tetrahydrofuran relative to the total mass of the monomer is 10000 mg / kg.

[0043] Further, in step S10, the terminator includes any one or more of deionized water, methanol, ethanol, isooctyl alcohol, isooctyl acid, 2,4,6-tri-tert-butylphenol, trimethylchlorosilane, 1-bromooctane, stearic acid, stearyl alcohol, acids, phenols, and halogenated hydrocarbon compounds; the added amount of the terminator is 0.9 to 2.0 times the molar amount of the initiator.

[0044] By adding a terminator such as deionized water, the terminator can react with the active center of the carbon anion to make it lose its reactivity, thereby terminating the polymerization and ensuring that the polymerization reaction no longer continues, thereby obtaining a styrene-butadiene rubber product with a narrow molecular weight distribution and controllable molecular structure.

[0045] Preferably, the terminator is deionized water, and the molar ratio of the terminator to the n-butyl lithium initiator is 1.2.

[0046] Furthermore, in step S20, the heating temperature is above 60°C, and the stirring time is 10 to 60 minutes.

[0047] Preferably, the heating temperature is above 80° C. and the stirring time is 30 min.

[0048] The present invention also provides a chain-functionalized solution-polymerized styrene-butadiene rubber, which is prepared by the chain-functionalized solution-polymerized styrene-butadiene rubber through the above-mentioned chain-modification method.

[0049] Furthermore, the chain-functionalized solution polymerized styrene butadiene rubber is a random copolymer of butadiene monomer and styrene monomer; the styrene content in the chain-functionalized solution polymerized styrene butadiene rubber is 5-95%; the content of vinyl structural units in the butadiene structural units in the chain-functionalized solution polymerized styrene butadiene rubber is 6-90%; the grafting rate of thiol compounds in the chain-functionalized solution polymerized styrene butadiene rubber is 1-60%; the Mooney viscosity of the chain-functionalized solution polymerized styrene butadiene rubber is 30-80; the number average molecular weight of the chain-functionalized solution polymerized styrene butadiene rubber is 100,000-1,000,000 g / mol; the molecular weight distribution of the chain-functionalized solution polymerized styrene butadiene rubber is 1.0-2.0; the glass transition temperature of the chain-functionalized solution polymerized styrene butadiene rubber is -50-0°C; and the modification rate of the chain-functionalized solution polymerized styrene butadiene rubber is greater than 90%.

[0050] Preferably, the content of styrene in the chain-functionalized solution-polymerized styrene-butadiene rubber is 25-30%, preferably 30%; the content of vinyl structure in the butadiene structural unit in the chain-functionalized solution-polymerized styrene-butadiene rubber is 13-60%, preferably 40%; the grafting rate of thiol compounds in the chain-functionalized solution-polymerized styrene-butadiene rubber is 2-6%, preferably 2.5%; the Mooney viscosity of the chain-functionalized solution-polymerized styrene-butadiene rubber is 63; the number average molecular weight of the chain-functionalized solution-polymerized styrene-butadiene rubber is 400,000-500,000 g / mol, preferably 450,000 g / mol; the molecular weight distribution of the chain-functionalized solution-polymerized styrene-butadiene rubber is 1.4; the glass transition temperature of the chain-functionalized solution-polymerized styrene-butadiene rubber is -20~-15°C, preferably -15°C; the modification rate of the chain-functionalized solution-polymerized styrene-butadiene rubber is greater than 97%.

[0051] In some embodiments of the present application, the polar functional groups carried by the thiol compound can be selected from the following ranges: carboxyl, hydroxyl, primary amino, N,N-dimethylamino, piperidinyl, pyrrolidinyl, hexamethyleneimine, ester, trimethoxysilyl, epoxy, glycidyl, and dodecacarbon aliphatic hydrocarbon.

[0052] The embodiments and comparative examples of the present invention are mainly tested and characterized by the following methods.

[0053] 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.

[0054] 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.

[0055] 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 NMR 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 and the grafting rate of thiol compounds. The grafting rate refers to the molar fraction of the residual double bonds that undergo grafting reactions with thiol in all butadiene structural units.

[0056] 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.

[0057] 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: Example 1 The embodiment of the present invention provides a method for in-chain modification of solution-polymerized styrene-butadiene rubber, which specifically comprises the following steps: S1. Using cyclohexane as solvent, n-butyl lithium as initiator, and tetrahydrofuran as polymerization activator, butadiene monomer and styrene monomer are polymerized at 0-60°C for 2h to obtain styrene-butadiene rubber active chains, and the temperature during the reaction reaches 90-100°C at the highest. In this step: the monomer concentration is 20%; the amount of 2 mol / L n-butyl lithium initiator added is 2.1 ml; the amount of tetrahydrofuran added is 10000 mg / kg monomer; the mass ratio of styrene monomer to butadiene monomer is 30 / 70; the total weight of monomers is 1000 grams; and the amount of solvent added is 4000 grams.

[0058] S2. Add deionized water to the styrene-butadiene rubber solution to terminate the polymerization reaction, stir rapidly for 5-15 minutes, and then add antioxidants 1076 and 1520. In this step: the molar ratio of the terminator to n-butyl lithium is 1.2; the amount of the antioxidant added to the solution-polymerized styrene-butadiene rubber is 0.05%wt.

[0059] S3. Add the modifier mercaptopropionic acid and the free radical initiator dilauroyl peroxide to the styrene-butadiene rubber glue, heat the glue to raise the temperature to above 80°C, and stir for 30 minutes. The amount of thiol compound added is 3.4% of the total mass of the monomer, and the amount of free radical initiator added is 2% of the amount of modifier added. Finally, add alcohol to the glue to precipitate the styrene-butadiene rubber. After pouring 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 for vacuum drying for 24 hours, and finally obtain a colorless and transparent styrene-butadiene rubber product.

[0060] In this embodiment, the measured monomer conversion rate is 100%, the Mooney viscosity is 63, and the number average molecular weight is 45×10 4 g / mol, weight average molecular weight is 63.0×10 4 g / mol, molecular weight distribution is 1.4, styrene content is 30.00%, 1,2-polybutadiene structural unit content is 40.00%, glass transition temperature is -15℃, modification rate is 97.10%, and grafting rate is 2.50%.

[0061] Example 2 The relevant polymerization process conditions in Example 1 remain unchanged, except that in S3, the modifier is hexamethyleneiminopropyl mercaptan, and the amount of the modifier added is 5.7% of the total weight of the monomer. The measured monomer conversion rate is 100.00%, the Mooney viscosity is 63, and the number average molecular weight is 45×10 4 g / mol, weight average molecular weight is 63.0×10 4 g / mol, molecular weight distribution is 1.4, styrene content is 30.00%, 1,2-polybutadiene structural unit content is 40.00%, glass transition temperature is -15℃, modification rate is 97.80%, and grafting rate is 2.50%.

[0062] Example 3 The relevant polymerization process conditions in Example 1 remain unchanged, except that in S3, the modifier is trimethoxy silane, and the amount of the modifier added is 6.4% of the total weight of the monomer. The measured monomer conversion rate is 100.00%, the Mooney viscosity is 63, and the number average molecular weight is 44×10 4 g / mol, weight average molecular weight is 61.6×10 4 g / mol, molecular weight distribution is 1.4, styrene content is 30.00%, 1,2-polybutadiene structural unit content is 41.00%, glass transition temperature is -15℃, modification rate is 98.20%, and grafting rate is 2.50%.

[0063] Comparative Example 1 The relevant polymerization process conditions in Example 1 remain unchanged, except that no modifier is added in S3. The measured monomer conversion rate is 100.00%, the Mooney viscosity is 50, and the number average molecular weight is 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℃, modification rate is 0%, and grafting rate is 0%.

[0064] Comparative Example 2 The relevant polymerization process conditions in Example 1 remain unchanged, except that in S3, the modifier is 3-chloropropyltrimethoxysilane. The measured monomer conversion rate is 100%, the Mooney viscosity is 56, and the number average molecular weight is 41.2×10 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 the measured end group number is lower than the lower limit of NMR analysis capability.

[0065] Comparative Example 3 The relevant polymerization process conditions in Example 1 remain unchanged, except that in S3, the modifier is N,N-dimethylaminopropyltrimethoxysilane. The measured monomer conversion rate is 100%, the Mooney viscosity is 55, and the number average molecular weight is 42.01×10 4 g / mol, and the weight average molecular weight is 63.02×10 4 g / mol, molecular weight distribution is 1.5, 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 the measured end group number is lower than the lower limit of NMR analysis capability.

[0066] Comparative Example 4 The relevant polymerization process conditions in Example 1 remain unchanged, except that in S3, the modifier is 4-vinyl-N, N-dimethylbenzylamine. The measured monomer conversion rate is 100%, the Mooney viscosity is 59, and the number average molecular weight is 42.3×10 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 the measured end group number is lower than the lower limit of NMR analysis capability.

[0067] This invention mainly compares the differences between the mid-chain modification technology and the chain end modification technology of SSBR: 1. From the result that the modification rate of the mid-chain modified SSBR is higher, it can be seen that the mid-chain modification technology of the present invention has higher reaction activity; 2. From the result that the grafting rate of polar functional groups of chain-modified SSBR is higher, it can be seen that the chain-modification technology can give SSBR a higher degree of functionalization, thus significantly improving the interfacial bonding strength between SSBR and white carbon black; 3. From the results of higher molecular weight and Mooney viscosity of mid-chain modified SSBR, it can be seen that the interaction force between molecular chains of mid-chain modified SSBR is significantly higher than that of chain end modification technology.

[0068] In order to evaluate the application performance of the vulcanized rubber made of the functionalized solution-polymerized styrene-butadiene rubber in the chain, 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.

[0069] Table 1 shows the mixing formula of vulcanized rubber.

[0070] Note: The raw material amounts in Table 1 are expressed in parts by weight based on 100 parts by weight of styrene-butadiene rubber.

[0071] The vulcanized rubber obtained after mixing the SSBR prepared in Examples 1 to 3 and Comparative Examples 1 to 4 was tested and characterized by the following methods.

[0072] 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.

[0073] 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.

[0074] 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)).

[0075] Application Example 1 Application Example 1 is the physical properties of the vulcanized rubber samples prepared from the SSBR in Examples 1 to 3 and Comparative Examples 1 to 4. The results are shown in Table 2.

[0076] Table 2 shows the physical properties of the vulcanized rubber samples prepared from the SSBR in Examples 1 to 3 and Comparative Examples 1 to 4.

[0077] From the comparison of the Mooney viscosity of the rubber mixes, the Mooney viscosity of all the rubber mixes has increased compared to the raw rubber, but the Mooney viscosity of the rubber mixes of Examples 1 to 3 has not increased significantly compared to the raw rubber, and is much lower than that of Comparative Examples 1 to 4. It can be seen that compared with the chain end modification technology, the SSBR modified in the chain has the best mixing and dispersion performance with the rubber filler, is easy to eat, and the heat generation during the mixing process is not high, so the pre-vulcanization degree of its rubber mix is ​​the lowest. The data characteristics reflected are: the Mooney viscosity of the rubber mix is ​​not significantly increased compared to the raw rubber Mooney. Compared with Comparative Example 1, the Mooney of the rubber mixes of Comparative Examples 2 to 4 is lower, but significantly higher than that of Examples 1 to 3.

[0078] The 300% tensile strength and elongation at break of the embodiments and the comparative examples are not much different, but the tensile strength of embodiments 1 to 3 is significantly higher than that of comparative examples 1 to 4. Among them, although the tensile strength of comparative examples 2 to 4 is slightly higher than that of comparative example 1, it is significantly lower than that of embodiments 1 to 3. This shows that compared with the chain end modification technology, the mid-chain modified SSBR has the best mixing and dispersion performance with the rubber filler, the filler-polymer network of the prepared vulcanized rubber is the most complete, the mechanical properties are the best, and the mid-chain modification technology has more advantages.

[0079] 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 4, indicating that the chain modification technology improves the wear resistance of SSBR.

[0080] The higher the 0℃ loss factor, the higher the anti-slip and grip of the vulcanized rubber. The 0℃ loss factors of Examples 1 to 3 are all greater than 0.3, which are higher than Comparative Examples 1 to 4, so the mid-chain modification technology gives SSBR excellent grip and anti-slip properties on ice. Comparative Examples 2 to 4 are not much different from the examples, and are all higher than Comparative Example 1, indicating that the chain end modification technology can also improve the grip performance of SSBR, but it is much worse than the mid-chain modification technology.

[0081] 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 0.1000, slightly lower than Comparative Example 1, and not much different from Comparative Examples 2 to 4. This shows that the chain modification technology mainly affects the 0°C loss factor, but has little effect on the 60°C loss factor, indicating that the chain modification technology gives SSBR a more excellent wet skid-rolling resistance balance performance.

[0082] The lower the 60°C loss modulus, the lower the endogenous heat of the vulcanized rubber, the better the dynamic performance, and the better the fatigue resistance when used as a tire. The 60°C loss modulus of Examples 1 to 3 are all lower than those of Comparative Examples 1 to 4, indicating that the chain-modified SSBR has lower endogenous heat, better dynamic performance, and better fatigue resistance. Similarly, the 60°C loss modulus of Comparative Examples 2 to 4 are all lower than that of Comparative Example 1, indicating that the chain-end modification technology of tertiary amine groups and siloxane groups can also improve the dynamic performance and fatigue resistance of SSBR, but the improvement effect is slightly lower than that of the chain-modified technology.

[0083] 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 in-chain modification of in-chain functionalized solution-polymerized styrene-butadiene rubber, characterized in that: The chain modification 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; adding a terminator to the polymerization system to terminate the polymerization reaction to obtain a styrene-butadiene rubber solution; S20, adding a thiol compound and a free radical initiator to the styrene-butadiene rubber solution, heating and stirring the styrene-butadiene rubber solution, and adding alcohol to precipitate the styrene-butadiene rubber after the modification reaction is completed, and obtaining the in-chain functionalized solution-polymerized styrene-butadiene rubber after drying.

2. The chain modification method according to claim 1, characterized in that The thiol compound includes any one or more of mercaptopropionic acid, mercaptoethanol, aminopropyl mercaptan, N,N-dimethylaminopropyl mercaptan, piperidinylpropyl mercaptan, hexamethyleneiminopropyl mercaptan, pyrrolidinylpropyl mercaptan, ethyl mercaptopropionate, mercaptopropyltrimethoxysilane, mercaptopropyl ethylene oxide, mercaptopropyl glycidyl ether, and dodecyl mercaptan.

3. The chain modification method according to claim 1, characterized in that The added amount of the thiol compound is 1-10% of the total mass of the monomer.

4. The chain modification method according to claim 1, characterized in that The free radical initiator includes any one or more of tert-butyl hydroperoxide, azobisisobutyronitrile, azobisisoheptanenitrile, dilauroyl peroxide, dicumyl peroxide, and dibenzoyl peroxide.

5. The chain modification method according to claim 1, characterized in that: The amount of the free radical initiator added is 1-5% of the amount of the thiol compound added.

6. The in-chain modification method according to claim 1, characterized in that: The concentration of the monomer is 5-30%; 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.

7. The in-chain modification method according to claim 1, characterized in that: In S10, the terminator includes any one or more of deionized water, methanol, ethanol, isooctyl alcohol, isooctyl acid, 2,4,6-tri-tert-butylphenol, trimethylchlorosilane, 1-bromooctane, stearic acid, stearyl alcohol, acids, phenols, and halogenated hydrocarbon compounds; the added amount of the terminator is 0.9 to 2.0 times the molar amount of the initiator.

8. The in-chain modification method according to claim 1, characterized in that In S20, the heating temperature is above 60°C, and the stirring time is 10 to 60 minutes.

9. A chain-functionalized solution-polymerized styrene-butadiene rubber, characterized in that: The in-chain functionalized solution-polymerized styrene-butadiene rubber is prepared by the in-chain modification method described in any one of claims 1 to 8.

10. The in-chain functionalized solution-polymerized styrene-butadiene rubber according to claim 9, characterized in that: The chain-functionalized solution-polymerized styrene-butadiene rubber is a random copolymer of the butadiene monomer and the styrene monomer; the styrene content in the chain-functionalized solution-polymerized styrene-butadiene rubber is 5-95%; the vinyl structural unit content in the chain-functionalized solution-polymerized styrene-butadiene rubber is 6-90%; the grafting rate of the thiol compound in the chain-functionalized solution-polymerized styrene-butadiene rubber is 1-60%; the Mooney viscosity of the chain-functionalized solution-polymerized styrene-butadiene rubber is 30-80; the number average molecular weight of the chain-functionalized solution-polymerized styrene-butadiene rubber is 100,000-1,000,000 g / mol; the molecular weight distribution of the chain-functionalized solution-polymerized styrene-butadiene rubber is 1.0-2.0; the glass transition temperature of the chain-functionalized solution-polymerized styrene-butadiene rubber is -50~0°C; and the modification rate of the chain-functionalized solution-polymerized styrene-butadiene rubber is greater than 90%.

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