In-chain chain end functionalized solution polymerized styrene-butadiene rubber and preparation method thereof

Abstract

The invention discloses solution polymerized styrene-butadiene rubber with a functionalized chain end in a chain and a preparation method of the solution polymerized styrene-butadiene rubber. The multifunctional additive is introduced to serve as an in-chain modifier and a chain end modifier at the same time, the in-chain and chain end functionalized solution polymerized styrene-butadiene rubber is obtained through nucleophilic substitution reaction and silicon-hydrogen reaction, and the product performance can be effectively improved. Compared with unmodified or end group modified SSBR, the solution polymerized styrene-butadiene rubber provided by the invention has good processability, lower rolling resistance, good wet skid resistance and excellent physical and mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of synthetic rubber technology and relates to a solution-polymerized styrene-butadiene rubber with in-chain and chain-end functionalization. Background Technology

[0002] Solution-polymerized styrene-butadiene rubber (SSBR) has a wide range of applications (such as tires, retreaded and molded products, injection molded and extruded products, medical devices, footwear, and automotive parts), with tires being its primary application. In recent years, the demand for manufacturing high-performance tires, such as green tires, anti-skid tires, ultra-lightweight tires, and energy-saving tires, has been increasing. Therefore, the preparation of functionalized SSBR with low rolling resistance, strong wet skid resistance, and excellent wear resistance is crucial.

[0003] Currently, functionalized SSBR involves introducing heteroatom (N / O / S / Si) groups into the chain ends or middle of SSBR to improve its performance. Chain end functionalization is a relatively traditional modification method, mainly including functionalized initiator-initiated polymerization and reactive polymer end-termination methods. Functionalized initiators mainly include amine-based organolithium initiators, ether-based organolithium initiators, and multifunctional organolithium initiators. End-modification techniques mainly include tin coupling modification and halosilane / alkoxysilane modification. End-functionalization can enhance the affinity between rubber and reactive fillers to some extent. However, since polymer chains only have two chain ends, the functional group content is still very limited, and the filler dosage is generally high. Therefore, end-functionalization cannot effectively solve the filler dispersion problem in rubber, thus affecting its reinforcing effect.

[0004] In-chain functionalization is a novel modification method with the advantage of introducing more polar groups into the molecular chain, promoting filler dispersion and improving the interaction between rubber and filler. Current rubber functionalization methods include epoxidation modification, thiol-ene click reaction, and the introduction of a third functionalizing monomer, but each of these technologies has its own advantages and disadvantages. Epoxidation modification of rubber is a mature process; however, the widely used peroxy acid catalysis method uses small molecule acids as catalysts, leading to the generation of acidic wastewater during production, increasing post-treatment costs. The thiol-ene click reaction is precise and rapid, but the substrate thiol has an unpleasant odor and is toxic, and the click reaction has many side reactions that are difficult to control. US6818710B2 reports the synthesis of in-chain functionalized styrene-butadiene copolymers using a monoamine DPE derivative (1-[4-(N,N-dimethylamino)phenyl]-1-phenylethylene) as a comonomer. This effectively increases the number of functionalized groups in solution-polymerized styrene-butadiene rubber, further improving the dispersion of carbon black; on the other hand, the functionalized groups are more evenly distributed in the polymer chain, significantly improving the functionalization efficiency. However, the comonomers are expensive and there are no large-scale industrial products yet, making it difficult to industrialize functionalized solution-polymerized styrene-butadiene rubber.

[0005] Simultaneous functionalization of the chain midstream and chain ends is highly beneficial for improving the properties of solution-polymerized styrene-butadiene rubber. Unfortunately, the modification methods reported so far all involve modifying the chain ends or midstream through different reagents or multi-step methods, resulting in high production costs and difficulties in industrialization. Summary of the Invention

[0006] This invention provides a solution-polymerized styrene-butadiene rubber (SSBR) with in-chain and chain-end functionalization and its preparation method. The core of this method involves introducing a multifunctional additive that acts as both a mid-chain and chain-end modifier, utilizing nucleophilic substitution and hydrosilylation reactions to obtain the in-chain and chain-end functionalized SSBR, effectively improving product performance. Compared to unmodified or end-group modified SSBR, the solution-polymerized SSBR of this invention exhibits superior processing properties, lower rolling resistance, better wet skid resistance, and excellent physical and mechanical properties.

[0007] This invention provides a chain-terminal functionalized solution-polymerized styrene-butadiene rubber, having the following structural schematic:

[0008]

[0009] Where l represents the number of polybutadiene 1,4 polymer chain segments, m represents the number of polybutadiene 1,2 polymer chain segments, n represents the number of polystyrene chain segments, and p represents the number of polysiloxane chain segments.

[0010] R1, R2, and R3 are independent of each other and are alkyl, alkoxy, or halogen atoms containing 1 to 12 carbon atoms. Suitable examples include, but are not limited to, methyl, ethyl, methoxy, ethoxy, chlorine, and bromine atoms.

[0011] This invention also provides a method for preparing in-chain and chain-end functionalized solution-polymerized styrene-butadiene rubber, comprising the following steps:

[0012] (1) Under inert gas protection, styrene monomer and butadiene monomer are added to a hydrocarbon solvent, with organolithium as an initiator and a structure regulator added. The reaction is carried out at 20-100℃ for 30-120 min to carry out random copolymerization of butadiene and styrene. The monomer conversion rate reaches more than 98%, and solution-polymerized styrene-butadiene rubber is prepared.

[0013] (2) Add a multifunctional additive to the product of step (1). reaction;

[0014] (3) Add a multifunctional auxiliary agent and a hydrosilylation catalyst to the product of step (2) and react.

[0015] In step (1), the hydrocarbon solvent includes one or more of straight-chain alkanes, aromatics and cycloalkanes, such as one or more of pentane, hexane, octane, heptane, cyclopentane, cyclohexane, benzene, toluene and ethylbenzene.

[0016] In step (1), the mass fraction of the monomer is 10wt%-20wt% of the total weight of all raw materials.

[0017] All the raw materials include styrene, butadiene, solvent, structure modifier, organolithium, multifunctional additives, and hydrosilylation catalyst.

[0018] In step (1), the monomer ratio of butadiene and styrene is 90 / 10 to 60 / 40 (wt).

[0019] In step (1), the amount of the initiator is 0.2-2 mmol per 100 grams of total monomer.

[0020] In step (1), the organic lithium is one or more of the following: n-butyllithium, piperidinium lithium, hexamethyleneimine lithium, piperidinylpiperidine lithium, etc.

[0021] In step (1), the structure modifier mainly adjusts the reactivity ratio of styrene and butadiene to make them copolymerize randomly. At the same time, it can cause the initiator to produce polarization or solvation effects, reduce its degree of association, and increase the initiation reaction rate of the initiator.

[0022] The structure modifier comprises one or more of ethers and amines; preferably one or more of tetrahydrofuran (THF), tetrahydrofurfuryl ether, diethylene glycol dimethyl ether (2G), diethyl ether, ethyl methyl ether, anisole, diphenyl ether, tetramethyldivinyl diamine, and pentamethyldivinyltriamine.

[0023] The amount of the structure modifier added is 0.1-100 times (molar ratio) of the initiator.

[0024] The styrene-butadiene molecular chains synthesized in step (1) can be linear or star-shaped. The number-average molecular weight of the polymer is 100,000-500,000, and the molecular weight distribution index is 1.0-2.0.

[0025] The general formula of the multifunctional additive is: Where R1, R2, and R3 are independent of each other and are alkyl, alkoxy, or halogen atoms containing 1 to 12 carbon atoms, suitable examples including but not limited to methyl, ethyl, methoxy, ethoxy, chlorine, and bromine atoms; p is 1-13. Suitable examples include but are not limited to one or more of the following compounds:

[0026]

[0027] In step (2), the amount of multifunctional additive added is 0.1 to 1 mmol per 100 grams of total monomer, wherein the total monomer contains styrene and butadiene.

[0028] In step (2), the reaction time is 30-60 min.

[0029] In step (3), the hydrosilylation catalyst is one or more of the compounds or complexes of group VIII metals, such as platinum, palladium, rhodium, ruthenium, copper, iron, manganese, nickel, cobalt, tungsten, molybdenum, actinides or lanthanides, such as Speier catalyst (chloroplatinic acid hydrate), Karstedt catalyst (platinum complex), Wilkinson catalyst (rhodium complex), iron catalyst, etc.

[0030] In step (2), chain-end modification and / or coupling are achieved through nucleophilic substitution reactions.

[0031] In step (3), a hydrosilylation reaction is carried out to obtain solution-polymerized styrene-butadiene rubber with in-chain and chain-end functionalization.

[0032] In step (3), the amount of hydrosilylation catalyst added is 0.1 wt% to 25 wt% of the multifunctional auxiliary agent.

[0033] In step (3), the reaction temperature is 60-100℃ and the reaction time is 30-120min.

[0034] In step (3), the amount of multifunctional additive added is 0.1wt% to 8wt% of the weight of solution-polymerized styrene-butadiene rubber.

[0035] As a preferred embodiment, the solution-polymerized styrene-butadiene rubber of the present invention contains an anti-aging agent.

[0036] The present invention has the following effects:

[0037] 1) Multifunctionality: It can perform both in-chain and chain-end modification functions using only one multifunctional additive;

[0038] 2) High efficiency: The preparation method of this functionalized solution-polymerized styrene-butadiene rubber is a one-pot method, which can significantly improve production efficiency and reduce production costs, which is especially important for large-scale industrial production;

[0039] 3) Improved rubber properties: The chain-terminal functionalized solution-polymerized styrene-butadiene rubber of the present invention contains siloxane functional groups with good compatibility with silica, and the content of functional groups is relatively high, which improves the compatibility between solution-polymerized styrene-butadiene rubber and silica, greatly reduces the Payne effect, and improves the strength and wear resistance of rubber; it has higher wet slip resistance and lower rolling resistance. Detailed Implementation

[0040] To facilitate understanding of the present invention, the following description, in conjunction with embodiments, will further illustrate the invention. It should be understood that the following embodiments are merely for a better understanding of the invention and do not imply that the invention is limited to these embodiments.

[0041] Main analytical methods:

[0042] In the examples, the functional groups of the rubber were determined by nuclear magnetic resonance (¹H NMR) as follows: a VARIAN UNITY 400MHz NMR spectrometer was used, CDCl3 was used as the solvent, and tetramethylsilane (TMS) was used as the internal standard. Based on the peak area of ​​the ¹H NMR spectrum and the polymer molecular formula, the content of each functional group in the copolymer could be calculated. In the examples, the signal peaks at 4.98 ppm and 5.41 ppm represent 1,2-unsaturated olefin groups and 1,4-unsaturated olefin groups, respectively. After the reaction, the characteristic peaks at 4.98 ppm and 5.41 ppm decreased significantly, indicating that the double bond content decreased and a chemical reaction occurred. At the same time, the characteristic peak of siloxane was generated at a chemical shift of 3.5 ppm to 3.6 ppm, indicating that the double bonds were consumed during the branching modification process, and siloxane groups were generated.

[0043] Example 1:

[0044] The experiment was conducted in a 1L stainless steel polymerization reactor. Under a nitrogen atmosphere, 10g of styrene, 37g of 1,3-butadiene, 400g of cyclohexane, and 0.79g of THF were added sequentially to the reactor. After heating the system to 30℃, 0.2ml (1.6M) of n-butyllithium was added to the reactor using a syringe to initiate the copolymerization reaction. The reaction pressure was 0.5MPa. After 40 minutes of polymerization, the monomer conversion rate reached over 99%. 0.08mmol of the multifunctional auxiliary agent C-1 was added to the reactor to initiate a coupling reaction. After 15 minutes, the coupling reaction ended. 0.5mmol of C-1 and 0.04mmol of Speier catalyst (chloroplatinic acid hydrate) were added again, and the reaction continued for another hour. Then, 0.48g of 2,6-di-tert-butyl-p-cresol was added, and the mixture was stirred for 10 minutes before being discharged. The product was stripped and dried under a nitrogen atmosphere to obtain functionalized solution-polymerized styrene-butadiene rubber, named S-1. The basic and performance data of the copolymer are shown in Table 1.

[0045] Example 2-15:

[0046] Using the same preparation method as in Example 1, but replacing the multifunctional additives with C-2 to C-15, functionalized styrene-butadiene rubbers S-2 to S-15 were obtained.

[0047] Comparative Examples 1-3:

[0048] Using the same preparation method and dosage as in Example 1, except that the dosage of modifier (C-1) was changed to 0.04 / 0.16 / 0.32 mmol in step (2), functionalized styrene-butadiene rubber S-1-0.04 / S-1-0.16 / S-1-0.32 was obtained.

[0049] Comparative Examples 4-7:

[0050] Using the same preparation method and dosage as in Example 1, except that the dosage of the chain modifier (C-1) was changed to 0.25 / 4 / 10 / 15 mmol in step (3), functionalized styrene-butadiene rubber S-1-0.25 / S-1-4 / S-1-10 / S-1-15 was obtained.

[0051] Comparative Examples 8-10:

[0052] The experiment was conducted in a 1L stainless steel polymerization reactor. Under a nitrogen atmosphere, 10g of styrene, 37g of 1,3-butadiene, 400g of cyclohexane, and 0.79g of THF were added sequentially to the reactor. After heating the system to 30℃, 0.2ml (1.6M) of n-butyllithium was added to the reactor using a syringe to initiate the copolymerization reaction. The reaction pressure was 0.5MPa. After 40 minutes of polymerization, the monomer conversion rate reached over 99%. Coupling agents C-16 / C-17 / C-18 (0.08mmol) were then added to the reactor to initiate the coupling reaction. After 15 minutes, the coupling reaction ended. Then, 0.5mmol of C-16 / C-17 / C-18 and 0.04mmol of Speier catalyst (chloroplatinic acid hydrate) were added, and the reaction continued for another hour. Finally, 0.48g of [unspecified ingredient] was added. 2,6-Di-tert-butyl-p-cresol was stirred for 10 minutes and then discharged. The product was stripped and dried under a nitrogen atmosphere to obtain functionalized solution-polymerized styrene-butadiene rubber, named S-16 / S-17 / S-18. The basic and performance data of the copolymers are shown in Table 1.

[0053]

[0054] Comparative Example 11

[0055] The experiment was conducted in a 1L stainless steel polymerization reactor. Under a nitrogen atmosphere, 10g of styrene, 37g of 1,3-butadiene, 400g of cyclohexane, and 0.79g of THF were added sequentially to the reactor. After heating the system to 30℃, 0.2ml (1.6M) of n-butyllithium was added to the reactor using a syringe to initiate the copolymerization reaction. The reaction pressure was 0.5MPa. After 40 minutes of polymerization, the monomer conversion rate reached over 99%. 0.08mmol of coupling agent C-2 was then added to the reactor to initiate the coupling reaction. After 15 minutes, the coupling reaction ended. 0.48g of 2,6-di-tert-butyl-p-cresol was added, and the mixture was stirred for 10 minutes before being discharged. The product was stripped and dried under a nitrogen atmosphere to obtain unmodified solution-polymerized styrene-butadiene rubber, named S-19. The basic and performance data of the copolymer are shown in Table 1.

[0056] Comparative Example 12

[0057] The experiment was conducted in a 1L stainless steel polymerization reactor. Under a nitrogen atmosphere, 10g of styrene, 37g of 1,3-butadiene, 400g of cyclohexane, and 0.79g of THF were added sequentially to the reactor. After heating the system to 30℃, 0.2ml (1.6M) of n-butyllithium was added to the reactor using a syringe to initiate the copolymerization reaction. The reaction pressure was 0.5MPa. After 40 minutes of polymerization, the monomer conversion rate reached over 99%. 0.32mmol of isopropanol was added to the polymerization reactor to quench the reaction. After 15 minutes, 0.5mmol of C-2 and 0.04mmol of Speier catalyst (chloroplatinic acid hydrate) were added, and the reaction was continued for another hour. Then, 0.48g of 2,6-di-tert-butyl-p-cresol was added, and the mixture was stirred for 10 minutes before being discharged. The product was stripped and dried under a nitrogen atmosphere to obtain uncoupled, in-chain functionalized solution-polymerized styrene-butadiene rubber, named S-20. The basic and performance data of the copolymer are shown in Table 1.

[0058] Table 1 Test data for solution-polymerized styrene-butadiene rubber products

[0059] serial number Relative elongation (%) Tensile strength (MPa) Tanδ(0℃) Tanδ (60℃) S-1 401.9 20.3 0.0842 0.5101 S-1-0.04 422 20.1 0.0102 0.4888 S-1-0.16 421 19.9 0.0860 0.5232 S-1-0.32 400.3 19.1 0.0832 0.5022 S-1-0.25 432.1 18.7 0.0902 0.4932 S-1-4 394.3 22.2 0.0832 0.5216 S-1-10 390.6 22.8 0.0861 0.5245 S-1-15 388.6 22.6 0.0877 0.5443 S-2 477.2 24.1 0.0710 0.5555 S-3 398.1 20.1 0.0851 0.5050 S-4 482.0 24.3 0.0704 0.5806 S-5 442.0 22.3 0.0767 0.5603 S-6 419.8 21.2 0.0807 0.5327 S-7 392.0 19.8 0.0864 0.4975 S-8 437.5 22.1 0.0774 0.5553 S-9 495.2 25.0 0.0684 0.5881 S-10 419.0 21.1 0.0810 0.5302 S-11 388.1 19.5 0.0877 0.4899 S-12 498.9 25.2 0.0679 0.6032 S-13 435.6 22.0 0.0777 0.5528 S-14 502.9 25.4 0.0673 0.6182 S-15 421.7 21.3 0.0803 0.5352 S-16 374.2 18.9 0.0905 0.4749 S-17 364.3 18.4 0.0929 0.4623 S-18 368.2 18.6 0.0919 0.4673 S-19 391.2 20 0.0855 0.5025 S-20 382.1 19.3 0.0886 0.4849

[0060] Note: Vulcanization conditions:

[0061] SSBR raw rubber: 500g, sulfur: 1.5 phr, antioxidant (antioxidant 4020, i.e., N-(1,3-dimethylbutyl)-N'-phenylhydroquinone): 1 phr, stearic acid: 2 phr, vulcanization accelerator (tetramethylthiuram disulfide): 1 phr, silica: 50 phr, aromatic oil (TDAE, environmentally friendly aromatic oil): 5 phr. Except for the SSBR raw rubber, all other materials are commercially available industrial products commonly used in the rubber industry. The polymer samples obtained in Examples 1-15 and Comparative Examples 1-12 were vulcanized to prepare their respective corresponding vulcanized rubbers. The vulcanization conditions were: roller temperature 50°C; vulcanization temperature 145°C; pressure maintained at 10-15 MPa; vulcanization time 35 min. Akron abrasion was measured using an indoor abrasion testing machine, LAT100. The smaller the value, the better the abrasion resistance. Tanδ (0℃) characterizes the rubber's resistance to wet skids, and the larger the value, the better the resistance to wet skids. Tanδ (60℃) is the loss factor at 60℃, and the smaller the value, the lower the rolling resistance.

[0062] As shown in Table 1, compared with the control sample, the wet skid resistance and tensile strength of styrene-butadiene rubber modified with this multifunctional additive (the molar ratio of hydrosiloxane to organolithium initiator for chain end modification is 1:(1.5-5); while the amount of hydrosiloxane added for chain mid-chain modification is 2-30 mmol per 37 g butadiene) were significantly improved. At the same time, low rolling resistance and low abrasion performance were also guaranteed. The reason is that the appropriate content of multifunctional additive can not only reduce the free-moving SSBR chain ends by acting as a coupling agent, but also act as a chain mid-chain modifier and improve the dispersibility with silica through siloxane groups, which greatly improves the performance of rubber.

[0063] Finally, it should be noted that the above embodiments are only used to describe preferred embodiments of the present invention, and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that various modifications and improvements made to the technical solutions of the present invention by means of modifications or equivalent substitutions should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A chain-in-chain end-functionalized solution styrene-butadiene rubber having the following structural formula: ###0001### l is the number of polybutadiene 1,4 polymerized chain segments, m is the number of polybutadiene 1,2 polymerized chain segments, n is the number of polystyrene chain segments; p is the number of polysiloxane chain segments; R1, R2, R3 are independently alkyl, alkoxy or halogen atoms containing 1 to 12 carbon atoms, preferably methyl, ethyl, methoxy, ethoxy, chlorine, bromine atoms. wherein 2. A method for preparing a chain-in-chain end-functionalized solution styrene-butadiene rubber, comprising the following steps: (1) under inert gas protection, in a hydrocarbon solvent, adding styrene monomers, butadiene monomers, using organic lithium as an initiator, adding a structure regulator, reacting at 20 to 100°C for 30 to 120 minutes to perform random copolymerization of butadiene and styrene, with a monomer conversion rate of 98% or more, to prepare a solution styrene-butadiene rubber; (2) adding a multifunctional additive to the product of step (1) and reacting; (3) adding a hydrosilylation catalyst to the product of step (2) and reacting. In the step (1), the weight ratio of butadiene and styrene monomers is 90 / 10 to 60 / 40. The structure regulator comprises one or more of ethers, amines; preferably one or more of tetrahydrofuran, tetrahydrofurfuryl ether, diethylene glycol dimethyl ether, ethyl ether, ethyl methyl ether, anisole, diphenyl ether, tetramethyl divinyl diamine, pentamethyl divinyl triamine. The multifunctional additive is selected from one or more of the following compounds: (2) adding a multifunctional adjuvant to the product of step (1) reaction; In the step (2), the multifunctional additive is added in an amount of 0.1 to 1 mmol per 100 grams of total monomers, the total monomers comprising styrene and butadiene.

3. The method of claim 2, wherein, In the step (3), the hydrosilylation catalyst is one or more of compounds or complexes of Group VIII metals, preferably one or more of compounds or complexes of platinum, palladium, rhodium, ruthenium, copper, iron, manganese, nickel, cobalt, tungsten, molybdenum, actinide or lanthanide series metals.

4. The method of claim 2, wherein, In the step (1), the organolithium is n-butyllithium, lithium piperidide Lithium hexamethyleneimide Lithium piperidide one or more of the following:

5. The method of claim 2, wherein, In the step (3), the multifunctional additive is added in an amount of 0.1 wt% to 8 wt% of the weight of the solution styrene-butadiene rubber.

6. The method of claim 2, wherein, The multifunctional auxiliary agent has a general formula wherein R1, R2, R3 are independently alkyl, alkoxy or halogen atom containing 1-12 carbon atoms, preferably methyl, ethyl, methoxy, ethoxy, chlorine atom, bromine atom; p is 1-13.

7. The method of claim 2, wherein, ​ 8. The method of claim 2, wherein, ​ 9. The method of claim 2, wherein, ​ 10. The method of claim 2, wherein, ​

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