A hydrogenated asymmetric long-chain branched polystyrene-conjugated diene copolymer, and a preparation method and application thereof

Abstract

The application discloses a hydrogenated asymmetric long-chain branched polystyrene-conjugated diene copolymer and a preparation method and application thereof. The hydrogenated asymmetric long-chain branched polystyrene-conjugated diene copolymer is obtained by hydrogenating conjugated diene units of asymmetric long-chain branched polystyrene-conjugated diene copolymer (S-D / Y n ), wherein S is a styrene homopolymer block, D / Y n is a random copolymer block of conjugated diene and divinylbenzene, and n is a branching degree of the random copolymer block. The hydrogenated asymmetric long-chain branched polystyrene-conjugated diene copolymer is used as a viscosity index improver (VII) of lubricating oil, has good solubility and reversible thixotropy in oil products, has large low high-temperature thickening capacity, a shear stability index (SSI) is less than 22, and has excellent comprehensive performance.

Description

Technical Field

[0001] This invention relates to a hydrogenated styrene-conjugated diene copolymer, specifically a hydrogenated asymmetric long-chain branched polystyrene-conjugated diene copolymer, and also to its preparation method and its application as a lubricating oil viscosity index improver, belonging to the field of lubricating oil viscosity index improver synthesis technology. Background Technology

[0002] Lubricating oil viscosity index improvers (referred to as viscosity index improver VII) are usually high molecular weight compounds such as polymethyl methacrylate, ethylene propylene copolymer, and polyisobutylene. At room temperature, they are generally rubbery or solid, with molecular weights ranging from tens of thousands to hundreds of thousands. Usually, 0.5% to 1.5% of these high molecular weight polymers are added to neutral oils. The polymers form coil structures in the oil, and their volume is much larger than that of the base oil with a smaller molecular weight. Therefore, the viscosity of the oil is much greater than that of the solvent, which is why it can thicken the oil. At low temperatures, polymers in a static state contract into a dense molecular conformation called a coil, exhibiting low thickening capacity and minimal impact on oil viscosity. However, under the friction, shearing, traction, and stretching effects of the reciprocating motion of the engine oil pump and piston, the composite oil generates heat. In this high-temperature environment, the polymer molecules extend in a directional manner, increasing their hydrodynamic volume and thus increasing oil viscosity. This increases the resistance to oil flow, leading to a significant increase in viscosity. When the engine stops operating and the composite oil cools to room temperature, its viscosity returns to its original state; this process is known as reversible thixotropy. VII-blended thickened internal combustion engine oils, hydraulic oils, and gear oils exhibit excellent viscosity-temperature properties, with a smooth viscosity-temperature curve, meaning they possess good low-temperature starting performance and high-temperature lubrication capabilities, making them suitable for all seasons. Compared to single-grade oils of the same viscosity level, lubricant consumption can be reduced by 30%, while fuel consumption can be reduced by 3-5%. In recent years, with the advent of hydrogenated styrene conjugated diene copolymers, represented by Shell's SV series, formulated lubricants can achieve low-temperature starting performance while maintaining appropriate viscosity at high temperatures, i.e., good viscosity-temperature properties. However, the molecular structure of these polymers is not publicly disclosed and is considered proprietary technology.

[0003] In the prior art, Chinese patent (CN107793542A) discloses a method for synthesizing hydrogenated styrene / isoprene block copolymers. This method involves synthesizing diblock copolymers or multiblock copolymers containing styrene and isoprene blocks in an anionic polymerization system using nonpolar alkanes and toluene as polymerization solvents. The diblock copolymers or multiblock copolymers are then hydrogenated to obtain the hydrogenated styrene / isoprene block copolymer. This method utilizes a mixed solvent of nonpolar alkanes and toluene, which effectively increases the reaction probability between the active PS-Li end groups and isoprene, thereby reducing or eliminating the content of small-molecule polystyrene in the hydrogenated styrene / isoprene block copolymer and improving the dropping point when the diblock or multiblock hydrogenated styrene / isoprene block copolymer is applied to optical fiber and cable filling grease. Chinese patent (CN104342231B) discloses a viscosity index improver for lubricating oil and its preparation method. This viscosity index improver is obtained by hydrogenation modification of a polyisoprene-b-polybutadiene-b-polystyrene triblock copolymer. The preparation method involves adding a regulator to a polymerization reactor at a temperature of 60–70°C and a pressure of 0.1–0.5 MPa, followed by the sequential addition of isoprene, butadiene, and styrene monomers for polymerization. After polymerization, the resulting triblock copolymer is hydrogenated to obtain the final product. The polymer molecules are long-chain linear molecules with low intermolecular entanglement and unsatisfactory thixotropic behavior, but it exhibits a thickening effect when added to mineral oil.

[0004] Chinese Patent (CN102731739A) discloses a star-shaped polymer for improving the viscosity index of lubricating oil, its preparation method, and its application. This star-shaped polymer has asymmetric arms composed of two different types of polymer arms. The first type of arm is a hydrogenated polyisoprene homopolymer, and the second type of arm is a copolymer with a hydrogenated polyisoprene-hydrogenated polybutadiene-polystyrene block structure. In the copolymer arms, the polystyrene segment is close to the core of the star-shaped polymer, the hydrogenated polybutadiene segment is in the middle of the arm, and the hydrogenated isoprene segment is on the outside of the arm. The star-shaped polymer structure contains 2-15% polybutadiene blocks, and both the polyisoprene and polybutadiene blocks are hydrogenated. This invention's star-shaped polymer not only exhibits excellent thickening effect and shear stability, but also has low pumping viscosity and low-temperature starting viscosity when used in the formulation of thickened engine oils, and it does not form crystals or gels in engine oils. In "Study on Hydrogenated SIBR for Viscosity Index Improvement", Dalian University of Technology, Polymer Materials, 2009, a series of SIBRs with controllable molecular weight and narrow molecular weight distribution were synthesized in cyclohexane solvent using n-butyllithium as an initiator, tetrahydrofuran as a structure modifier, and styrene, isoprene, and butadiene as monomers, employing molecular design and anionic polymerization techniques. The content of 1,2 structures of polybutadiene segments and 3,4 structures of polyisoprene segments in SIBRs was controlled using a tetrahydrofuran monoprotic system. The hydrogenation reaction of the synthesized SIBR samples was studied using nickel naphthenate / triisobutylaluminum as a homogeneous catalytic system. The results show that the nickel naphthenate / triisobutylaluminum catalytic system exhibits high catalytic activity and selectivity. At a reaction temperature of 60℃, a hydrogen pressure of 4MPa, a catalyst dosage of 2mg / g dry gel, an Al / Ni ratio of 7, and a reaction time of 3h, the degree of hydrogenation of SIBR reaches 98%. The hydrogenation reaction rates of various microstructures in SIBR, from highest to lowest, are: B1,2 > B1,4 > I3,4. The hydrogenated SIBR can be used as a viscosity index improver. The main properties of viscosity index improvers include thickening ability, shear stability, high-temperature and high-shear properties, and low-temperature performance. In the paper "Preparation and Characterization of Star-shaped Hydrogenated Random Copolymer HSIBR", Chemical Industry and Engineering, 2012, No. 4, a star-shaped styrene-isoprene-butadiene terpolymer (SIBR) was prepared by anionic polymerization using divinylbenzene (DVB) as a coupling agent and cyclohexane as a solvent. Using nickel naphthenate and triisobutylaluminum as catalysts, the reaction was carried out at 60℃ and 4.0 MPa hydrogen pressure for 4 h to prepare a 100% hydrogenated star-shaped styrene-isoprene-butadiene terpolymer (HSIBR). The effects of DVB / Li dosage and single-arm relative molecular mass on polymer coupling efficiency (CE) and hydrogenation reaction were investigated. The self-made HSIBR was also used as a lubricating oil viscosity index improver to test its performance.The results showed that SIBR achieved the highest coupling efficiency of 86.8% using DVB as a coupling agent, and the synthesized HSIBR was used as a viscosity index improver for lubricating oil. Similarly, in the paper "Molecular Structure of Viscosity Index Improver HSD", Polymer Materials Science and Engineering, November 2012, FT-IR, 1H-NMR, and DSC tests were performed on the viscosity index improver hydrogenated styrene / conjugated diene (butadiene, isoprene) copolymer (HSD). The study showed that HSD is a highly hydrogenated styrene-butadiene block copolymer with a high butadiene content, a styrene mass fraction of 18.50%, a butadiene mass fraction of 81.50%, and a butadiene hydrogenation degree of 98.20%. Gel permeation chromatography (GPC) determined that the number-average molecular weight of HSD12F was 4.59 × 10⁻⁶. 5 g / mol, single-arm number-average molecular weight is 6.47 × 10⁻⁶ g / mol. 4 The g / mol indicates that HSD is a star-shaped styrene-butadiene block copolymer with 7.10 arms and a coupling efficiency of 86.44%. That is, the polymer is a linear active polymer before coupling, and then coupled with DVB. However, in this coupling method, DVB is added to the active lithium polymer. Because divinylbenzene has high activity, DVB will quickly copolymerize with DVB monomers after binding with active lithium chains, producing a large amount of gel, while other active molecular chains are not coupled. In addition, the paper "Synthesis and Assembly Behavior of Branched Copolymers Based on Anionic Polymerization", Ju Zhenhua, Fudan University, 2013(08)) proposes that branched block copolymers are a type of multi-block hyperbranched structure with polymer chains connecting the branching points. The multi-component blocks make the properties of the whole polymer more diversified, so this type of polymer has a wide range of application prospects in biology, medicine and materials. Anionic polymerization, as a truly living polymerization process, offers unique advantages in synthesizing block copolymers with well-defined compositions and polymers with precisely controllable structures. Therefore, anionic synthesis is undoubtedly an effective method for preparing branched block copolymers.

[0005] The polymers obtained by coupling reactive styrene / conjugated diene copolymers with divinylbenzene (DVB) in the aforementioned literature all have a core-radialized, short-branched multi-arm molecular structure, with a coupling efficiency of only 86%. They still contain a relatively low linear polymer with a mass fraction of 14%, and these oligomers are not shear-resistant in oils. Furthermore, DVB readily self-polymerizes or cyclizes to form hyperbranched polymers, producing large molecules or gels. Polymers containing gels and linear polymers are unsuitable as viscosity index improvers for lubricating oils. Gels easily cause fluid blockage, and low-molecular-weight linear polymers are prone to chain breakage and poor viscosity-temperature properties under shear stress. However, hydrogenated polymers of asymmetric branched polystyrene-conjugated diene with low linear oligomer content and narrow molecular weight distribution have not yet been reported as viscosity index modifiers. Summary of the Invention

[0006] The existing technology for coupling reactive styrene / conjugated diene copolymers using divinylbenzene (DVB) suffers from drawbacks such as low coupling efficiency, high linear oligomer content leading to low thickening ability, and the presence of some macromolecules and gels in the coupled polymer, resulting in poor viscosity-temperature properties and shear stability as a viscosity index modifier. The first objective of this invention is to provide a hydrogenated polystyrene-conjugated diene polymer (ABHSD) with high thickening ability, good viscosity-temperature properties and shear stability, low oligomer content, no gel, narrow molecular weight distribution, and asymmetric long-chain branched structure.

[0007] The second objective of this invention is to provide a simple and low-cost method for preparing the ABHSD.

[0008] A third objective of this invention is to provide an application of ABHSD as a viscosity index improver for lubricating oils. When added to base oils, it exhibits a shear stability index (SSI) below 22 and a thickening capacity >8.4 mm. 2 Advantages include a smooth viscosity-temperature curve that changes with temperature ( / s).

[0009] To achieve the above-mentioned technical objectives, the present invention provides a hydrogenated asymmetric long-chain branched polystyrene-conjugated diene copolymer, which is obtained by hydrogenating the conjugated diene units of the asymmetric long-chain branched polystyrene-conjugated diene copolymer; the asymmetric long-chain branched polystyrene-conjugated diene copolymer has the following expression: SD / Y n Where S represents a styrene homopolymer block, and D / Y n S is a random copolymer block of conjugated diene and divinylbenzene, where n is the degree of branching of the random copolymer block; the number average molecular weight of S is 4 × 10⁻⁶. 4 ~6×10 4 D / Y n The number average molecular weight is 20 × 10⁻⁶.4 ~26×10 4 n is 2 to 6. The present invention controls the number average molecular weight of polystyrene blocks preferably in the range of Mn = 40,000 to 60,000. The purpose is to control ABHSD to have suitable stiffness and sufficient melt strength, so as to ensure that the finished product made from the hydrogenated polymer in the extrusion, drying and grinding units has good powder stability and will not agglomerate when stored at medium and low temperatures.

[0010] As a preferred embodiment, the degree of hydrogenation of the conjugated diene unit in the asymmetric long-chain branched polystyrene-conjugated diene copolymer is >98%.

[0011] As a preferred embodiment, the mass ratio of styrene units to conjugated diene units in the asymmetric long-chain branched polystyrene-conjugated diene copolymer is (15-25) / (85-75); the mass of divinylbenzene units in the random copolymer block of conjugated diene and divinylbenzene is 0.05-0.10% of the mass of conjugated diene units. Introducing trace amounts of divinylbenzene units into the random copolymer block of conjugated diene and divinylbenzene has a significant impact on the performance of ABHSD. Although DVB has a higher polymerization rate than conjugated diene, when trace amounts of DVB copolymerize with a high concentration of conjugated diene monomer, the probability of collision between the conjugated diene and active lithium is much higher in this polymerization environment than the probability of collision between trace amounts of DVB and active lithium. Therefore, the copolymerization of the two exhibits random asymmetric branched copolymerization. In the polymerization of the polyconjugated diene units in the ABHSD copolymer of this invention, the reason for selecting DVB containing trace amounts of bifunctionality is to randomly and asymmetrically branch the polyconjugated diene units, thereby reducing the homopolymerization of DVB and decreasing the formation of large molecules and aggregated insolubles. Under shear traction, the branched molecular chains of this ABHSD copolymer extend and orient themselves outward. Adding it to oils increases the viscosity of the oil at high temperatures, while also improving the shear resistance of the polymer and reducing molecular chain breakage. Furthermore, when the shear traction force disappears and the temperature decreases, the branched long molecular chains shrink, coil, and entangle, reducing the oil's thickening ability and benefiting engine starting, i.e., exhibiting good low-temperature performance. The aforementioned viscosity-temperature properties exhibited by the ABHSD copolymer are essential behavior of VII.

[0012] As a preferred embodiment, the conjugated diene unit in the random copolymer block of the conjugated diene and divinylbenzene is at least one of isoprene, isoprene, and butadiene.

[0013] As a preferred embodiment, the mass fraction of the 1,2-addition units and / or 3,4-addition units of the random copolymer block of the conjugated diene and divinylbenzene is 30-50%. To prevent the conjugated diene units in ABHSD from containing long polyethylene chains after hydrogenation, which would cause the polymer to crystallize and become a polyolefin resin insoluble in base oils, a sufficient number of 1,2- or 3,4-chain segments are required in the polyconjugated diene segment. Furthermore, the presence of some side-branched structural units in the polymer is also beneficial for the hydrogenated ABHSD to exhibit a viscosity-temperature effect in oil products.

[0014] As a preferred embodiment, the number-average molecular weight Mn of the asymmetric long-chain branched polystyrene-conjugated diene copolymer is 24 × 10⁻⁶. 4 ~32×10 4 Molecular weight distribution index M w / M n =1.05~1.17. The weight-average molecular weight Mw of the asymmetric long-chain branched polystyrene-conjugated diene copolymer is 250,000~300,000, and the mass fraction of oligomers in the polymer is <0.6%.

[0015] The chemical formula for the ABHSD polymer provided by this invention is: SD / Y n .

[0016] Where S represents the block formed by homopolymerization of styrene, with a degree of polymerization between 400 and 600 (an integer), and a number-average molecular weight Mn = 4 × 10⁻⁶. 4 ~6×10 4 D / Y n D represents the asymmetric long chain segment formed by the random copolymerization of conjugated diene and divinylbenzene, where D is the conjugated diene polymerization unit, Y is the divinylbenzene linking unit, and n is the number of unevenly distributed or asymmetric branched chains (nodes) formed by divinylbenzene in the random copolymer segment. n is a positive integer between 2 and 6, and its derived physical meaning is the degree of branching or branching factor; D / Y n The number-average molecular weight Mn = 20 × 10 4 ~26×10 4 ;SD / Y n The number-average molecular weight Mn is 24 × 10⁻⁶. 4 ~32×10 4 .

[0017] The present invention provides the following molecular conformation of the ABHSD polymer:

[0018]

[0019] Where S represents a polystyrene block with an asymmetric long chain segment in the middle (D / Y) n) is a random copolymer of conjugated diene and divinylbenzene, and Y is a branched junction in an asymmetric long chain segment.

[0020] This invention also provides a method for preparing hydrogenated asymmetric long-chain branched polystyrene-conjugated diene copolymer. The method involves first adding styrene monomer to an anionic polymerization system containing a structure modifier for homopolymerization, then adding a mixture of divinylbenzene and conjugated diene monomers for copolymerization to obtain an asymmetric long-chain branched polystyrene-conjugated diene copolymer solution. A nickel / aluminum catalyst is then added to the asymmetric long-chain branched polystyrene-conjugated diene copolymer solution, and hydrogen is introduced to carry out a hydrogenation reaction, thus obtaining the final product.

[0021] As a preferred embodiment, the structure modifier is at least one of tetrahydrofurfuryl ethyl ether, bis(tetrahydrofurfuryl propane), tetrahydrofurfuryl ethyl ether, and tertiary amine compounds; the amount of the structure modifier relative to the conjugated diene monomer is 0.06–0.10 g / 100 g. To ensure that the polydiene segments of ABHSD have a sufficient number of 1,2- or 3,4-units, it is essential to add a suitable structure modifier to the conjugated diene during polymerization. Preferred structure modifiers are tetrahydrofurfuryl ethyl ether, bis(tetrahydrofurfuryl propane), tetrahydrofurfuryl ethyl ether, and tertiary amine compounds, with at least one of tetrahydrofurfuryl ethyl ether, bis(tetrahydrofurfuryl propane), and tetrahydrofurfuryl ethyl ether being preferred. The amount used is 0.06–0.10 g / 100 g of diene monomer, and the controlled mass fraction of 1,2-addition and / or 3,4-addition units in the polyconjugated diene segment is 30–50%.

[0022] As a preferred embodiment, the homopolymerization reaction is carried out at a temperature of 50–70°C for a time of 20–25 min.

[0023] As a preferred embodiment, the temperature during the copolymerization reaction is controlled within the range of 50–70°C, and the mixed monomers of divinylbenzene and conjugated diene are uniformly added to the reaction system within 15–20 minutes. After the mixed monomers of divinylbenzene and conjugated diene are completely added, the reaction continues for another 15–25 minutes. Controlling the feeding time of the mixed monomers of divinylbenzene and conjugated diene to 15–20 minutes aims to ensure that DVB (divinylbenzene monomer) undergoes simultaneous random random branching as the diene monomer molecular chain grows. The further reaction time of 15–25 minutes aims to improve the monomer conversion rate.

[0024] As a preferred embodiment, the nickel / aluminum catalyst is a complex of nickel isooctanoate-diisobutylaluminum hydride and / or triisobutylaluminum hydride, wherein the Ni / Al molar ratio of the nickel / aluminum catalyst is 3 to 6.

[0025] As a preferred embodiment, the amount of the nickel / aluminum catalyst relative to the amount of the asymmetric long-chain branched polystyrene-conjugated diene copolymer solution is 0.5 to 0.9 mmol / 100g, wherein the nickel / aluminum catalyst is measured by the mass of nickel, and the asymmetric long-chain branched polystyrene-conjugated diene copolymer solution is measured by the dry basis mass.

[0026] As a preferred embodiment, the conditions for the hydrogenation reaction are: a temperature of 70–80°C, a hydrogen pressure of 1.2–1.5 MPa, and a reaction time of 1.5–3.0 h.

[0027] As a preferred embodiment, the solvent used in the anionic polymerization system is cyclohexane or n-hexane and mixtures thereof, wherein the suitable monomer mass concentration is 10-15%; and the initiator used is n-butyllithium.

[0028] As a preferred embodiment, the conjugated diene monomer may be at least one of isoprene, isoprene, and butadiene, or a mixture thereof, with isoprene being the most preferred. Isoprene itself contains a short-branched structure, which is beneficial for improving the viscosity-temperature effect of ABHSD.

[0029] The ABHSD preparation method provided by this invention is carried out in two steps:

[0030] Step 1, SD / Y n Polymer preparation: In a cyclohexane-hexane solvent system containing a structure modifier, styrene monomer is first subjected to anionic polymerization initiated by n-butyllithium at a temperature of 50–70 °C for 20–25 min. Then, a mixed monomer consisting of conjugated dienes containing dissolved DVB is continuously and uniformly added to the active solution that has formed lithium polystyrene in the first stage for random copolymerization over 15–20 min. After the diene monomer is added, the reaction continues for another 15–25 min to obtain SD / Y. n In polymer solutions, the molecular weight, molecular weight distribution index, and microstructure of the polymer in the polymer solution can be determined.

[0031] The second step is the preparation of ABHSD:

[0032] A measured amount of nickel isooctanoate-diisobutylaluminum hydride or triisobutylaluminum complex (commonly known as Ni / Al catalyst) is added to the polymer solution after polymerization to carry out a hydrogenation reaction. When the degree of hydrogenation of the conjugated diene segment in the polymer molecule reaches the set requirement, the hydrogenation reaction can be stopped. After the hydride is washed with an aqueous solution of citric acid, the residual catalyst dissolved in the aqueous phase is removed by centrifugation. The hydrogenated liquid is then subjected to water vapor condensation, extrusion, and drying to obtain ABHSD. The Mooney viscosity of the ABHSD polymer is ML(1+4)100℃=55~65.

[0033] The present invention also provides an application of hydrogenated asymmetric long-chain branched polystyrene-conjugated diene copolymer as a viscosity index improver for lubricating oils.

[0034] As a preferred embodiment, the ABHSD is a diblock copolymer, which does not exhibit the behavior of thermoplastic elastomers and vulcanized rubber. The polymer has no modulus or strength at low temperatures and cannot be used as vulcanized rubber. It is most suitable for use as VII. The hydrogenated asymmetric long-chain branched polystyrene-conjugated diene copolymer base oil is added at a mass percentage of 0.8-1.5%; most preferably 0.95-1.15%.

[0035] Compared with existing technologies, the beneficial effects of the technical solution of this invention are as follows:

[0036] Compared to existing DVB-coupled core multi-arm short linear polystyrene / conjugated diene hydrides (HSDs) as viscosity index modifiers, which suffer from drawbacks such as lack of reversible thixotropy, low thickening capacity, poor high-temperature performance, and the tendency of large molecules and gels to clog oil pumps and pistons (rings), as well as poor viscosity-temperature properties and shear stability, this invention provides a gel-free ABHSD polymer with a narrow molecular weight distribution, easy solubility in base oils, and strong thickening capacity. Its molecular structure features random, asymmetric branched long chains and side chains, allowing the coiled molecular chains to extend and orient themselves outward under shear forces in oil, increasing the oil's viscosity at high temperatures. At low temperatures (when the engine is stopped or started), the branched molecular chains contract, coil, and entangle, reducing the oil's viscosity and facilitating engine starting. This demonstrates both viscosity-temperature effect and reversible thixotropy. Compared to other commercially available polymers, ABHSD, when added to base oil at 1.0% (by weight), exhibits a shear stability index (SSI) below 22 and a thickening capacity >8.4 mm. 2 The ABHSD polymer exhibits advantages such as a smooth viscosity-temperature curve that changes with temperature. Based on these characteristics, the ABHSD polymer of this invention is particularly suitable for use as VII.

[0037] The ABHSD polymer preparation technology of the present invention is simple, can be completed using existing mature processes, and is easy to control and industrialize. Attached Figure Description

[0038] Figure 1 The GPC pattern of the asymmetric long-chain branched polystyrene-conjugated diene copolymer prepared in Example 1 is shown.

[0039] Figure 2 H is the asymmetric long-chain branched polystyrene-conjugated diene copolymer prepared in Example 1. 1 -NMR spectrum.

[0040] Figure 3The hydrogenated asymmetric long-chain branched polystyrene-conjugated diene copolymer prepared in Example 1 has H 1 -NMR. Detailed Implementation

[0041] The following examples are intended to further illustrate the content of this invention and do not constitute a limitation on the scope of protection of the claims or the implementation methods of this invention.

[0042] In the following examples, the number-average molecular weight and molecular weight distribution index of the polymers were determined using gel permeation chromatography (GPC); H2 was used. 1 - The microstructure of the polymer was quantitatively determined by NMR spectroscopy; the viscosity ML of the polymer (ML100℃1+4) was determined by Mooney viscometer; the thickening ability of the polymer was tested by SH / T0566-93 method; the shear stability index (SSI) of VII was tested by SH / T0103-2007 method; the fluidity of the thickened oil was tested at 25℃ by the Forte-4 cup method.

[0043] Example 1

[0044] In a clean 5-liter polymerization reactor, 3000 mL of cyclohexane, 0.5 mL of ETE, and 67 mL of styrene were first added. The temperature was raised to 50–60 °C, and then 3.0 mL of 0.40 mol / L n-butyllithium (NBL) was added to initiate the polymerization of styrene. After polymerization for 24 min, polystyrene active lithium (Sm-Li) was obtained. + Then, a mixed monomer consisting of 353 mL of isoprene and 2.6 mL of 0.70 mol / L DVB cyclohexane solution is continuously and uniformly added to the polystyrene active lithium solution over 18 min to randomly copolymerize with the solution that has already formed polystyrene lithium. After the addition of the diene monomer is complete, the reaction continues for another 20 min to obtain SD / Y. n Polymer stock solution. Sampling revealed that the polymer Mn = 26.83 × 10⁻⁶. 4 The molecular weight distribution index is 1.16, the mass fraction of oligomers in the polymer is 0.56%, and the content of 3,4-addition units is 39.5%.

[0045] The original polymer solution was introduced into a 5L hydrogenation reactor, and 9 mL of a cyclohexane solution containing 0.2 mol / L nickel [where n(nickel isooctanoate) / n(triisobutylaluminum) = 4.3] was added. The mixture was stirred for 2.5 h at 70–80 °C and a hydrogen pressure of 1.2–1.4 MPa. The degree of hydrogenation of the polyisodiene unit was measured to be 98.4%. The hydrogenated liquid was then drained, and 120 g of a 10% (by weight) citric acid aqueous solution was added to the hydrogenated liquid and stirred for 30 min. Finally, the aqueous phase was separated by centrifugation, and the oil phase was condensed and dried with steam to obtain the ABHSD polymer (labeled as ABHSD-1#). The ML100℃ 1+4 of the ABHSD-1# polymer was 62.6. GPC analysis of the original polymer is shown below. Figure 1 H 1 -NMR spectrum see Figure 2 ; ABHSD-1# of H 1 -NMR spectrum see Figure 3 .

[0046] Example 2

[0047] The relevant processes and conditions in Example 1 were kept unchanged, except that the amount of styrene added was changed to 48 mL, NBL to 2.6 mL, ETE to 0.7 mL, and DVB cyclohexane solution to 2.8 mL.

[0048] As a result, the polymer Mn was measured to be 29.64 × 10⁻⁶. 4 The molecular weight distribution index is 1.17, the mass fraction of oligomers in the polymer is 0.53%, and the content of 3,4-addition units is 45.7%. The degree of hydrogenation of the ABHSD polymer (labeled as ABHSD-2#) after hydrogenation is 98.6%, and the ML100℃1+4 is 64.7.

[0049] Example 3

[0050] The relevant processes and conditions in Example 1 were kept unchanged, except that the amount of styrene added was changed to 88 mL, NBL to 3.4 mL, ETE to 0.4 mL, and DVB cyclohexane solution to 2.4 mL.

[0051] As a result, the polymer Mn was measured to be 25.34 × 10⁻⁶. 4 The molecular weight distribution index is 1.14, the mass fraction of oligomers in the polymer is 0.32%, and the content of 3,4-addition units is 34.6%. The degree of hydrogenation of the ABHSD polymer (labeled as ABHSD-3#) after hydrogenation is 98.7%, and the ML100℃1+4 is 56.7.

[0052] Example 4

[0053] The relevant processes and conditions in Example 1 were kept unchanged, except that the added isoprene was 250 mL, butadiene was 130 mL, NBL was 3.3 mL, ETE was 0.8 mL, and DVB cyclohexane solution was 3.4 mL.

[0054] As a result, the polymer Mn was measured to be 28.65 × 10⁻⁶. 4 The molecular weight distribution index is 1.16, the mass fraction of oligomers in the polymer is 0.48%, the content of isoprene 3,4-addition units is 48.7%, and the content of butadiene 1,2-addition units is 46.8%. The degree of hydrogenation of the ABHSD polymer (labeled as ABHSD-4#) after hydrogenation is 98.8%, and the ML100℃1+4 is 64.3.

[0055] Example 5

[0056] The relevant processes and conditions in Example 1 were kept unchanged, except that 14 mL of hydrogenation catalyst was added.

[0057] As a result, the degree of hydrogenation of the ABHSD polymer (labeled as ABHSD-5#) after hydrogenation was measured to be 99.3%, the mass fraction of oligomers in the polymer was 0.47%, and the ML100℃1+4 was 62.9.

[0058] Comparative Example 1

[0059] The relevant processes and conditions in Example 1 were kept unchanged, except for the addition of 5 mL of hydrogenation catalyst. As a result, the degree of hydrogenation of the ABHSD (labeled as ABHSD-6#) polymer after hydrogenation was measured to be 87.6%, the mass fraction of oligomers in the polymer was 0.38%, and the ML100℃1+4 was 62.9.

[0060] Comparative Example 2

[0061] The relevant processes and conditions in Example 2 were kept unchanged, except that the amount of styrene added was 42 mL, NBL was 2.4 mL, and DVB cyclohexane solution was 2.7 mL.

[0062] As a result, the polymer Mn was measured to be 26.23 × 10⁻⁶. 4 The molecular weight distribution index is 1.15, and the content of 3,4-addition units is 44.6%. After hydrogenation, the degree of hydrogenation of the ABHSD polymer is 98.1%, the ML100℃1+4 is 62.6, and the mass fraction of oligomers in the polymer is 0.43%. The ABHSD polymer exhibits cold flow and agglomeration, making it difficult to form into powder.

[0063] Comparative Example 3

[0064] The relevant processes and conditions in Example 3 were kept unchanged, except that the amount of styrene added was changed to 94 mL.

[0065] As a result, the polymer Mn was measured to be 25.72 × 10⁻⁶. 4 The molecular weight distribution index is 1.15, the content of 3,4-addition units is 33.9%, the degree of hydrogenation of the ABHSD polymer after hydrogenation is 98.5%, the ML100℃1+4 is 59.4, and the mass fraction of oligomers in the polymer is 0.45%. After adding 1.0% (by weight) of ABHSD polymer to base oil (150N) and stirring at 50-80℃ for 60 min, part of the polymer is still in a swollen state.

[0066] Comparative Example 4

[0067] The relevant processes and conditions in Example 1 were kept unchanged, except that the mixed monomers composed of isoprene and DVB were added to the polymerization reactor at one time for copolymerization.

[0068] As a result, the polymer Mn was measured to be 22.32 × 10⁻⁶. 4 The molecular weight distribution index is 1.12, the content of 3,4-addition units is 38.6%, the degree of hydrogenation of polyisodiene units is 98.6%, the mass fraction of oligomers in the polymer is 0.56%, the polymer ML100℃1+4 is 59.4, and the hydrogenated polymer is labeled as ABHSD-7#.

[0069] Comparative Example 5

[0070] The relevant processes and conditions in Example 1 were kept unchanged, except that 3.0 mL of DVB was added after the second stage of isoprene polymerization was completed for coupling for 25 min.

[0071] As a result, the polymer Mn was measured to be 23.68 × 10⁻⁶. 4 The molecular weight distribution index is 1.18, the mass fraction of oligomers in the polymer is 6.87%, the content of 3,4-addition units is 38.6%, the degree of hydrogenation of polyisodiene units is 98.6%, the polymer ML100℃1+4 is 59.4, and the hydrogenated polymer is labeled as ABHSD-8#.

[0072] Application Example 1

[0073] 1.0% (by weight) of ABHSD prepared in this invention and Shell SV-260 were added to 150N base oil containing an appropriate amount of antioxidant 1076. After stirring at 60-80°C for 40 min, VII behavior analysis was performed. The results are shown in Table 1.

[0074] Table 1 Behavior of Aggregate VII

[0075]

[0076] Note: "SSI" is the shear stability index of polymer VII. The larger the value, the worse the shear stability.

[0077] As can be seen from Table 1, the ABHSD designed and prepared according to the present invention, as VII, exhibits good solubility and viscosity-temperature properties in oils; at the same time, the SSI value is less than 22, which shows good shear stability.

Claims

1. A hydrogenated asymmetric long-chain branched polystyrene-conjugated diene copolymer, characterized in that: It is obtained by hydrogenating the conjugated diene units of an asymmetric long-chain branched polystyrene-conjugated diene copolymer; The asymmetric long-chain branched polystyrene-conjugated diene copolymer has the following expression: SD / Y n ; Where S represents the homopolymer block of styrene, and D / Y n is a random copolymer block of conjugated diene and divinylbenzene, where n is the degree of branching of the random copolymer block; The number-average molecular weight of S is 4 × 10⁻⁶. 4 ~6×10 4 ; D / Y n The number average molecular weight is 20 × 10⁻⁶. 4 ~26×10 4 ; n is 2 to 6; The degree of hydrogenation of the conjugated diene unit in the asymmetric long-chain branched polystyrene-conjugated diene copolymer is >98%; The number-average molecular weight Mn of the asymmetric long-chain branched polystyrene-conjugated diene copolymer is 24 × 10⁻⁶. 4 ~32×10 4 Molecular weight distribution index M w / M n =1.05~1.

17.

2. The hydrogenated asymmetric long-chain branched polystyrene-conjugated diene copolymer according to claim 1, characterized in that: The mass ratio of styrene units to conjugated diene units in the asymmetric long-chain branched polystyrene-conjugated diene copolymer is (15~25) / (85~75); the mass of divinylbenzene units in the random copolymer block of conjugated diene and divinylbenzene is 0.05~0.10% of the mass of conjugated diene units.

3. The hydrogenated asymmetric long-chain branched polystyrene-conjugated diene copolymer according to claim 1, characterized in that: The conjugated diene unit in the random copolymer block of the conjugated diene and divinylbenzene is at least one of isoprene, isoprene and butadiene.

4. The hydrogenated asymmetric long-chain branched polystyrene-conjugated diene copolymer according to claim 1, characterized in that: The mass fraction of the 1,2-addition unit and / or 3,4-addition unit of the random copolymer block of the conjugated diene and divinylbenzene is 30-50%.

5. A method for preparing a hydrogenated asymmetric long-chain branched polystyrene-conjugated diene copolymer according to any one of claims 1 to 4, characterized in that: In an anionic polymerization system containing a structure modifier, styrene monomer is first added for homopolymerization, followed by copolymerization of a mixture of divinylbenzene and conjugated diene monomers to obtain an asymmetric long-chain branched polystyrene-conjugated diene copolymer solution. A nickel / aluminum catalyst is added to the asymmetric long-chain branched polystyrene-conjugated diene copolymer solution and hydrogen is introduced for hydrogenation reaction to obtain the final product.

6. The method for preparing a hydrogenated asymmetric long-chain branched polystyrene-conjugated diene copolymer according to claim 5, characterized in that: The structure modifier is at least one of tetrahydrofurfuryl ethyl ether, bistetrahydrofurfuryl propane, tetrahydrofurfuryl ethyl ether, and tertiary amine compounds; the amount of the structure modifier relative to the conjugated diene monomer is 0.06~0.10g / 100g.

7. The method for preparing a hydrogenated asymmetric long-chain branched polystyrene-conjugated diene copolymer according to claim 5, characterized in that: The homopolymerization reaction is carried out at a temperature of 50-70°C for 20-25 minutes. During the copolymerization process, the temperature is controlled within the range of 50~70°C, and the mixed monomers of divinylbenzene and conjugated diene are uniformly added to the reaction system within 15~20 minutes. After the mixed monomers of divinylbenzene and conjugated diene are added, the reaction is further carried out for 15~25 minutes.

8. The method for preparing a hydrogenated asymmetric long-chain branched polystyrene-conjugated diene copolymer according to claim 5, characterized in that: The nickel / aluminum catalyst is a complex of nickel isooctanoate-diisobutylaluminum hydride and / or triisobutylaluminum hydride, and the Ni / Al molar ratio of the nickel / aluminum catalyst is 3~6.

9. A method for preparing a hydrogenated asymmetric long-chain branched polystyrene-conjugated diene copolymer according to claim 5 or 8, characterized in that: The amount of the nickel / aluminum catalyst relative to the amount of the asymmetric long-chain branched polystyrene-conjugated diene copolymer solution is 0.5~0.9 mmol / 100g, wherein the nickel / aluminum catalyst is measured by the mass of nickel, and the asymmetric long-chain branched polystyrene-conjugated diene copolymer solution is measured by the dry basis mass.

10. A method for preparing a hydrogenated asymmetric long-chain branched polystyrene-conjugated diene copolymer according to claim 5, characterized in that: The conditions for the hydrogenation reaction are: temperature of 70~80°C, hydrogen pressure of 1.2~1.5MPa, and reaction time of 1.5~3.0h.

11. The application of the hydrogenated asymmetric long-chain branched polystyrene-conjugated diene copolymer according to any one of claims 1 to 4, characterized in that: It is used as a viscosity index improver for lubricating oils.

12. The application of the hydrogenated asymmetric long-chain branched polystyrene-conjugated diene copolymer according to claim 11, characterized in that: The hydrogenated asymmetric long-chain branched polystyrene-conjugated diene copolymer base oil is added at a mass percentage of 0.8-1.5%.

13. The application of the hydrogenated asymmetric long-chain branched polystyrene-conjugated diene copolymer according to claim 12, characterized in that: The hydrogenated asymmetric long-chain branched polystyrene-conjugated diene copolymer base oil is added at a mass percentage of 0.95~1.15%.

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